SIEMENS
CABLE BOOK
POWER CABLES
& THEIR APPLICATIONS
PART 1 VOLUME
I
I
-t
Power Cables and th eirApplication Part
1
Materials . Construction Criteria for Selection Prniont r I vJvvr Ple n nin n Laying and Installation . Accessories Measuring and Testing
Editor: Lothar Heinhold
i
3rd revised edition. 1990
Siemens Aktiengesellschaft
Observations on the German terms and the VDE Specifications
'
'Kabel' and oLeitungen'
Kabel' and 'Leitungen'
Porrer cables are used for rhe transmission of elecrrical energy or as control cables lor the purpuses of
measurement, control and monitorin-s in electric pouer installations. In German usage. a disrinction rs made rraditionally benr.een 'Kabel' and .Leitungen'.
'Leituneen' (literally'leads') are used. generally speaking. for wiring in equipment. in u.inng installations and for connections to moving or mobile cquipments and units. The terrn can thus be rranslated as 'insulatcd wires' or 'l.iring' or .flerible cables'
or'cords'. 'Kabel' (cables) are used principally for power rransmission and distribution in electricity supply-aurhoritv sys[ems. in indusrry and in mines etc.
$'ith the use of modern insulating and
sheathin_s materials rhe constructional differences between .Kabel' and 'Leirungen' are in many cases no longer discernl
ole.
The disrinction is therelore observed purelv in terms of rhe area of applicarion. as desiribed in DIN lDE 0:98 Part I for pouer cables and part 3 for s.iring and flexible cables, and in the desien specifica_ tions referred to lherein. e.g. DIN VDE Oij0for wiring and flexible cables and DIN VDE 0271 for pVC insulated cables.
Further factors in the choice between .Kabel' and 'Leitungen' are the equipment Specifications (e.g. DIN VDE 0700), the installation Specifications (e.g. DIN VDE 0100) or the operating stresses to be expected.
It can be taken as a rule of thumb that .Leirungen' must not be laid in the ground, and that cables of
flexible construction are classified as .Leituneen'. even if their rared voltase is higher rhan 0.6I kV - e.g. trailing cables. This apart, there are also types of 'Kabel' that are nor inrended for laying in the _eround (e.g. halogen-free cables with improved performance in condirions of fire to DIN VDE 0266. or ship lirin! cibles to DfN VDE 0261).r - .."
In the present translation the ierms 'cable' an,
'porver cable' have been used to include flexible anr_ u iring cables where there is no risk of confusion.
\-DE
Specifications
v
From considerations of consistencv in references an, for greater clrrity, the VDE Specificarions applicabl_ to po$er cables are eeneralll' quoted in accorcancc rvith the new pracrice as 'DIN VDE . . . .'.
This applies equalll ro rhe older specificationr ri hich still retain the designarion , VDE . . . ' or
'DIN
57
..
./VDE
..
.' in their tirles. Furrhermore
since these specifications are of lundamental significancc, the practice of quoring rhe date of publication has been dispensed wirh.
Insulated Wires and Flexible Cables
Constructional Elements
of Insulated Cables Conductors
ll
l.l l.:
Wiring Cables and Flexible Cables
l2
Porver Crbles
IJ
Insulation
l)
l5
3.1
l'7
3.1. r
tr.)
Poll mers Thermoplastics (Plastomers) Copolymers F)uoroplastics. Polvr rni l Chloridc {PVC) Pohcthylenc tPE) Cross- Linked Pol.vethylene (XLPE) Elastomers Thcrmoplastic Elastomers lTPE).Conducting Rubber.Natural R ubber (NR). Stl rene Butadienc Rubbcr (SBR).Nirrile Butadiene Rubber (NBR1. Butyl Rubber ( IIR ). E thylene- Pro py lene Rubber (EPR). Silicone Rubber (SiR).Ethl lene Vin;-i Acerrre (EVA) Thermosetting Polymers (Duromers) Chemicel Aging of Poh nrcrs Thc Intluence of Moisrure on Polyolefi ne Insulating !larerials Impregnatcd Paper Lirerature Referred to in Secrion 2
J
Protective She:lths
J.l 3.2 J.J
Thermoplastic Sheaths Elastomer Sheaths Sheathing Materials for Special
3'l
Purposes
lvletal Shearh
39 39
Protection against Corrosion
.ll
Cable rvith Lead Sheath Aluminium-Sheathed Cables
4l
Armour
43
Concentric Conductors
41
) 1.1
l.l.t l.
l.l
)t
2.) !.)
1t
-
8 3.1
I
3.!t
6
1
8.1.1 8.1.2 3.1.3 8.1.1 3.1.1 3.1.
::)
3.i
-r
3.1
io
J_1
t.1 '1 a
45
Conducting Layers Metallic Componen!s of Electrical
45
Screening
46
Longitudinally Water proof Screens.
47
.19
Core ldentificrrion of Clblcs
3l
ll lt.l I l.:
Application tnd Installxtion of Cablcs Rated Voltagc. Opcraring Volrilge Selcction of Conductor Cross-Sectional Area
.19 .19
54
)) 55 56
6: 1l
/)
86 33
89
Power Cables
lZ
National and Intcrnational Standards
0t
t2.l
VDE Specifications Standards oI Other Countries IEC and CENELEC Standards
01
12.2 12.3
94 94
l3
Tlpes of Construction of LowHigh-Voltage Cables
IJ.-t 13.2
General Type Designation Selection of Cables and Accessories
100
Power Cables for Special Applicatiom
124
t.)..)
Electrical Screening
National and International Standards VDESpecifications HarmonizedSrandards National Types IEC Standards Selection of Flcxible Cables Clbles ibr Fircd I nsrallations Fiexible Cablcs FLEXO Cords Flcxiblc Ceblcs lbr \lining and Industrv Halosen-Free SIENOPYR Wiring rnd Flexible Ca bles rritlt Improvco Perlormrnce in thc Evenr of Frrc
Dcfinition of Locltions to DIN !'DE 0100
3'7
38
.+9
t0
?7 30 J)
TJpes of Wires and Cables
14.1 14.2
and
Cable wirh Elastomer Insulation Shipboard Power Cable 14.2.L Constructionand Characteristics
102
t:+ 124 124
1.1.2.2 Application and Installation 1.1.3 Halogen-Free Cables with Improved Characteristics in the Case of Fire 1.1.3.1 Testing Performance under Conditions of Fire Spread of Fire.Corrosivity of Combusrion Gases. Smoke Density. Insulation Retention under Conditions of Fire Construction and Characteristics l+,_).J L:r1ing end I nsralla rion t.1.4 Cables for Mine Shafts and Galleries 14.5 R ivcr and Sea Crbles
125
l:)
18.4
ll5
18.4.1 18.4.2
l:8 129
Airport Cablcs
lJl
11.7
131
1{8
Cable ',vith Polymer Insulation and Lead Sheath I nsulated Overhead Line Cables
l5
High- and Extra-High-\roltage Cables
lJ+
1i.1
Cable with Polymcr Insulation
I
5.2
1
5.3
l
i.3.1
15.1.2 15.3.3
Lo*.Pressure Oil-Filled Cable wirh Leld or Aluminium Sheath Thermally Stable Cable in Stcel Pipe High-Pressure Oil-Filled Cable lnternai Gas-Prcssu re Crble External Gas-Pressure Cablc (Pressure Cable)
18.4.3
1i0
1r.6
1
18.2.4 Use of Tables 18.3 Calculation of Load Capacity
t.)!
18.-1..:l
J+
1i5
Ca b les
18.4.6
139
Planning of Cable Installations
16 17 17.1 17.2 17.3
Guide for Planning of Cable Installations
t4l
18.5 8.5.1
1
Cable Rated Voltages
t+o
18.5.2
.Allocation of Cable Rated Voltages Rated Lightning Impulse Withstand Voltage Voltage Stresses in the Event of Earth Fault
l+o
18.5.3 18.6
Current-Carrving Capacity in Normal Operation 18.1 Terms, Definitions and Regulations 18.2 Operating Conditions and Design Tables 18.2.1 Operating Conditions forlnstallations in Ground 18.2.2 Operating Conditions, Installation in
'| .11
147
1E
air 18.2.3 Project Design Tables
Load Capacity Installed in Ground/Air. Rating Factors for Installation in
Ground, lor Differing Air Temperatures and for Groups in Air
150 150
152
t52 157 159
Pipcs
Thernral Resisrances I{ and ?'i.Load Capacity for an Installarion of Pipes in Ground or Air or in Ducts Banks
1i8 139
18.6.1 18.6.2
18.6.3 18.6.4 18.6.5 18.6.6 18.7 18.8 19 19.1
19.2 19.2.1
l8t
ThermalResistances 184 Thermal Resistance of the Cable 18.1 Thermal Rcsistance of Air 186 Horizontal I nstallation . Vertical Installation . Atmospheric Pressure. .\mbicnt Temperature. Solar Radiarion. Arr;r n-genrent of Cables Thermal Resistance of the Soil . lgi Temperature Field of a Cable.Definition of Soil-Thermal Resistance . Daily Load Curve and Characteristic Diameter 'Drying-Out of the Soil and Boundary Isorherm d. Fictitious Soil-Thermal Resistance 7"j and ?"j".Load Capacirv v Grouping in the Ground . 107 Fictitious Additional Thennal Rcsistanccs AIj and AIi- duc to Grouping.Loud Capacity. Extension of the Dn .\rea.Current-C:rrrying Cupacity ol Dissimilar
18.-1.5 Installation in Ducts and
138
180
Soil-Thermal-Resisrivity
. l1-i -
. ll
{J
Cable in thc Ground. Phi'sical and Thermal Characteristics of Soil. Influcnce of Moisture Content.Msasurins. Basic Quantities for Calculation Bedding Matcrial.Sand.Gravel Mixtures. Sand-Ccmcnt Mixtures Calculation of Loud Caplcity Installation in Channcls and Tunncls ?-10 Unventilatcd Channels and Tunncls .,.0 Arransemcnt of Cablcs in Tunncls . 133
.
Channcls u'ith Forced Venrilation Load Capacity of a Cablc for ShortTime and Intermittcnt Operatron
General
.
215
. .
239
Calculation with Minimum Time Value Adiabatic Heat Rise . Root-Mean-Square Value of Current . Short-Time Operation Intermittent Operation . Symbols Used in Formulae in Section l8 Literature Referred to in Section 18. .
239
-
239
241
_
241
242
243
_
245
250
1<1 Short-Circuit Conditions General Temperature Rise of Conductor under 1<'l Line-To-Earth Short Circuit Conductor and Sheat Currents under Line-To-Earth Short Circuit 257 Load Capacity under Line-To-Earth Short-Circuit /J9
i I
l9.i l9.l.
t
Short-Circuit Thcrntal Rating Guidc tbr Projcct Dcsrgn .
r65
"
l6J
'
Pcrlornrrncc undcr Short'CircuiL Condirions Short-Circuit Dut).' Short-Circuit Crplcity ol' Conductor. Scrccns- Shclths
ll.l ll.l
end.\rmour Criculutions of Short-Circuit Capacity ..\dirbltic und Non- \rlilbrrtic Tcmpcrl-
185
19.3.+ 19..r 19..1. I
r
v.+.1
ing Short-Circuit Thermo-N{echanic;rl Forccs and . 292 Erpansion Gcnerll EtTcct of Thermal Explnsion in Crblcs Mounting ot' Singlc-Core Cables 296 Accessones . . C"p".iry Short-Circuit \fechanical 19'7 Elecrromlgnetic Forccs Eilccr of Electromagnctic Forccs LineTo-Elrth. Linc-To-Line und Balanced Thrcc-Phlsc Short Circuit i00 \lulti-Corc Crrblc Tcnsilc Force fi Surlucc Prcssure fi' Clble Construction Erperience and Calcuhtion Quantities Firing Elements Single-Core Cables and Fixing
\[cthods Bcnding Stress Surluce Prcssure Srrcssing ol' C)amps
l9.l.,l
lnd
fi
.\cccssories Sl mbols used
19.6
in Scction l9 Litcrature Rcfcrrcd to in Section l9
in Formulae
Resistance and Resistance per Unit Lcngth of Conductor
20
20. r
20.2 20.1
ir
Resistance per Unit Length on d.c. Resistance pcr Unit Lcngth on a.c. Currcnt Reiatcd Losses Inductance and lnductance per Unit Length
-l.t i.2 21.2.1
21.2.2 21.2.3 11 1,1
tt
?
21.4
.
_r05
Inductance per Unit Length of a Conductor System Single-Core Cables Earthed at Both Ends Arrangement of Cables Earthing from Either One or Both Ends of Metal Sheath or Screen Cross-Bonding of the Sheaths, Transposition of the Cables
Multi-Core Cables Zero-Sequence Impedance and ZeroSequence Impedance per Unit Length Literature Referred to in Section 21
23
Clp:rcitlnce :tnd C:lpacitancc per Lnit
Lcngth ccncnrl
. -ili . ll6 . 319 .
J-U
.
.
320 321
.
3?2
.
322
-ri l
l-l1
. li't . il6
InsulationResistance,Insulation Resistrnce per Unit Length rnd Leakage
)) I
. 21 Determination of Voltage Drop . i40 ll.l General . l-+.1 Short Cable Runs . ll0 l+.i Long Cable Runs 25 Economic Optimization of Cable Size i'll l-i.l S;-mbols used in Formulae in i47 Section 25 . i-17 25 in Section to Relerred 15.: Lircrature Porver Cables nith 26 Interference of -f -1'+0
-1-10
ud
elecommunication
Crbles
lntcrtcrcncc 16.1.1 \lutual Inductancc 16.1.1 Inducing Currcnts 16.l.i Current Rcduction Fcctor of the Intlucncing Powcr Cable 16.l
lnductivc
16.1.-l Voltagc Reduction Factor of i20
.
.lil
Operating Capacitance per Unit Lcngth Ci Clpacitivc Currcnt /i and Earth'Fault Currcnt ,fi of a Cable Dielcctric Losses
Control
Binders
19.5
:1.-.1
ll.+
rurc Risc ivtethod Tcmperature Rise dur-
19.1.3
27
Z7
. -151 . ]51 . -lil . i52
the
.
355
.
357
Noise Voltage in Symmetrical Circuits . Ohmic Intert'crence . Interference Inductive and Ohmic . Details Required for Planning . Crlculated Example
358
lnl'lucnccd Telccommunication Cable 16.1-5 Rcduction Factors of Compensating
26). 16.3 26.1 l6.j :6.6
l'19
Conductors
i58 359
i59 160
Design and Calculation of Distribution
- J-:O
.362 Systems . 362 27.1 Introduction Requirement Determination of Power 27 .Z
.
27
. 32f . 322 328
. 328 . 329 329
.
JJU
as a Basis for Planning .?..1 Load Requirement of Dwellings 27 -2.2 Load Requirements of Special
JOJ
363 365
Consumers 27.2.3 27.3
Total Load Planning of Distribution
Systems
366
27.3.t z't.3.2
General Selection of Distribution Voltase
JOO
JOO
JO/
'^^' .-' and lypes ol up-
17.3.3 Low-Voltage Systems
368
Ststcm Configuratron ciation in the Public Supply Extension of a Low-Voltage System Systems of Buildings lndustrial SupPly Systems Location oisubstations Component Parts of the
Calculation ol Inlestigations of Protective Measures Asainst Excessive Touch Voltage 27.4.,1 In" estigation of Short-Circuit Protection and Discrimination 17.+.5 Computer-Aided Systenr Calculation 27.5 Literature Referred to in Section 27
Cable ldentification Marking
385
)9.1 29.2 29.3
29.4 29.4.1
29.4.1 29.5 29.5.1
29.5.2 29.6 29.6.1
29.6.1 30 30.1
Jl.t
Outer Sheath of Polyvinylchloride lPVC) and PolyethYlene tPE) Jute Servines on Cables s'ith Lead
420
i1.2
189
Manufacturers,VDE-Marking Colours of Outer Sheaths and Prolective Coverings Core Identification for Power Cables up to Uql U:0.6/ I kV Core Identification for Cables for
Lal ing the Cables Transporting Preparation for LaYing the Cable Differences in Level of the Cable Route Laying of Cables in the Ground Cable Route Laying of the Cables Laying of Cables Indoors Cables on Walls, Ceilings or Racks ' Cable Tunnels and Ducts Cable Clamps Types of Clamps Arrangements and Dimensions Installation Guide Preparation of Cable Ends
416
Sheath 32
Cable Accessories
)J.l
Fundament::l Objectit es Requirements Stress Control Fundamental PrinciPles for the Construction and Installation of
31.2
il.3 i2.4
rl-)
Compound Filling Tc'chnique Cast-Resin Techniques Shrink-On Technique Lapping Tcchnique Push-On Technrque Plug Tcchniquc Literaturc Referred to in Section
33
Cable Plan
-:1 .i
1
J-,+,+ 32.4.5 12.4.6
,11i .124
r
Acccssones
32..1.3
..395 ..395
Rated Voltages Exceeding L:o,U =0.611 kV 29
410
-r_:.+,I
Laying and Installation
28.4
Repair of Damage to Outer Sheath
t8i
! | .+.)
?8.3
31
)61
Basics
a Lorv-Voltage S1'stem
28 28.1 28.2
418
J
JU.
Lo$.Voltage SYstem i75 17.i.-1 \f edium-Voltage SYsrems Mediumthe of Expansion upply' S Public voltage System' Distribution Systems tn Large Buildings lndustrial Supply Systems Standby Power Supply Component Parts of the Medium-Voltage System Charge Current Compensation and Star Point Treatment The Superimposed High-Voltage SYstem i81 Svstem Calculation 1? 1 I
Earthine of Metallic Sheaths and Coverings Conductor Jointing
30.2
J't
tl7 lt9 4ll +J{ 135 437
32 . 137 .138
Measuring and Testing of Power lnstallations
34
Elcctrical l'Ieasurements in thc Cablc Installation, as Installed
Jtr
Voltage Tests
39'7
General
439
440
J).-: 35.3
Testing with d.c. Voltage Tesring rvith a.c. Voltage
399
36
400
J
401 401 401
JO.
Locating Faults 443 Preliminary Measurements Location Measurements bY the Conventional Method Locating of Faults by Pulse Reflection Method Preparation of Fa ult Point by Bum-
398 399
403 408 408 408 410
415 415
O.1
J
JO.+ Jb.
)
JO.O
M7_
Through Locating Using Audio FrequencY Testing of ThermoPlastic Shealhs
449
450
452
37
Construction and Resistance of Conductors
454
38
Conversion Table
457 458
-
iuonstrucilonal ElgtllgtILS ul
ll l5ulclLE\l vc|utso
I
-
1 Conductors for aluminium.
The conductors in wiring cables and flerible cables consis! norvada.vs of copper (Cu). The use of aluminium (Al), as well as copper, is also common in power cables. The cross-sectional area of the conductor ls quoted brsically not Js the geonterritul but as the electrical!1' eJfectiL'e cross'sectional area. i.e the cross-scctiontl rrcl as dctermined by e rcsistance , -rasurement.
rvith the tempcrature
standard tor copper. IEC 28 'lnternational Stendard ot' Resis(ilnce tor Copper'. n standrrd value for the resistivity at ?0'C
page 310):
In the international
.- given as g,o=$=g.0l7l1l Omm:im The
temperature coefficienI e:o at ]0'C for this copper is rro:3.93 x 10-riK. This value increases or de' creases approximatcly in proportion to thc conductivity. Investigations have sho$n that the product of the temperature coefficient and the resistivity rvith different conductivities is neariy constant a! 0.6776 x 10-a O mm'?/m K.
Similar relationships exist for aluminium. In this case, IEC 1 11 'Resistivity of Commercial Hard Drawn Aluminium Conductor Wire' gives the resistivity at a temperature of 20 "C as azo:0.028264 Q mm2/m and the temperature coefficient as e.o:4.93 x 10- r/K. This coefficient is pro-ortional to the degree of purity of the aluminium. z{d decreases with increasing impurity in the same .y as the electrical conductivity. Here again, the product of resistivity and temperature coefficient remains approximately constant, in rhis case at .139 x 10 -a f) mm27m K. The temperature dependence ofthe resistivity is given in general by
Qc.: Qr,[l + a3,(3, - 9,)] Thus
(1.0)
x 10-r(9-20) Q mm:im (1 2)
1.1
J)
expressed in "C.
ln the planning of
cable installations. horvever. in vierv of the unavoidable uncertaincies in the given intbrmation. it is quite sut'ficient to calculate rvith the conventional temperature coefficients lsee
for copper.
1:o:393xl0-17K 7.o :126 x l0-r;K 1
On:-1-:234 5 6
(1.3) (1 4)
[or aluminium. 1:o
:4
03
x 10-
ri
K
zo :4.38 x 10 - 31K O
o
I ::-:2)8
K
(1.5) (1.6)
6(|
In general. 1
aJ
= ----------: VOf
l/N.
(
1.7)
O
To convert a measured conductor resistance to the reference conditions of 20 "C and 1000 m length, the following expressions are applicable, according to rEC 228, 1966:
for copper,
:
for copper,
q"=g.o*0.68 x 10-a(3-20) O mm2/m
Qr:Q:o*
(1.1)
254.5 1000 ottm n,o=R"ri#frx:,
(1.8)
11
I
Conductors
lor aluminium, R:o = Ra-
,. lloo 97t #L 248+3 I
{
t.9)
accepted so far.
s here
i] R, 1
conductor temperature (oC) measured conductor resislance at 3'C (Q) length of cable (m) R.o conductor resistance at l0'C (Q,'km)
To permit the economicai construction oIcables rrirh a small numbcr of rvire -eauges. the conduclor desiqn has been siightly altered in accordance uith IEC ll8 (for details see IEC ll8. 1966) and rhe resisrancc determined lccording ro Ihc e\pression IJ .\.:o = --------; /\ I A: At !Z Llll 1l'ft rl'
n d K
If the conductors are insulated rvirh a material $ hicL provokes an adverse chemical reacrion s,ith the copper. a metallic protective laver round rhe coppcr $ irc is necessary. e.g. of tin or some other barrier (scr page 27).
l.I
resisrivity at 20'C for copper. .4 = l'1 .211 Qmmr; km lor aluminium, ,1 :)8.264 f)mm?,,km number of wires in the conductor diameter of individual wires (mm) factor to allow for the cffects of manulacruring processes:
K, K. K.
The minimum number and the diameter of the wirc and the resistance of the conductor are laid dowr in IEC 228 and DIN VDE 0295 (see also pages 45i to 457). Cables used abroad embody conductors ir accordance wirh the rcspectile national specifica tions. in the case rhar rhesc differ from IEC.
(1.10)
\\ here
.1
minium for conductors in wiring cables for fixcd installations. These types. also mentioned in the ncu IEC specification, have not, however, been gencrall.
for u,ire diameter and surface trcatment for conductor stranding for core stranding
Because of improved manufacturing techniqucs. par-
trcularll lhe compaction of stranded circular and sector-shaped conductors, the basic principles shich had underlain the establishmcnt of conductor resistances had lost something in validity. so that a revision of the existing IEC and VDE specifications became necessary. In particular the differences in rhe resistance values lor solid and stranded conductors. and for single- and multicore cables, in the former
It was thus possible 1978 edition of iEC 228 to achieve greater consistency of resistance value and a reduction in ranges were no longer applicable.
in the
Wiring Cables and Flexible Cables
Tlpes of Conductor For flcxible and uiring cablcs in the Federal Republic of Germany. rvith fcw cxceprions. circular copper conductors arc uscd. Thcsc are aimed at two arear of application: For Fi.rc/ lnstullut iorr The cables are subjcct to nrechanical stresses due to bending only during installation. Accordingiy, solid conductors are preferably uscd up to cross-sectionalarea of 10 mm: and strandcd conductors i' -\vc l0 mm2 For the Connection
o-f
ll'lobile Equipnrcnl
These cables. since they have to be flexible. embody_ fine-stranded conductors for all cross-sectional areas. Where a particularly high degree of flexibility is necessary, e.g. in the leads to welding-electrode holders,_
the number of conductor classifications from six to four. In 1980 this international agreemenl. rras incorporated into the standards for power cables,
u'ires, and wiring cables and flexible
cables account in the tables and planning sheets in the presenr
(DIN VDE 0295). The new values are raken inlo
book.
As well as plain aluminium conductors, the use has been tried in some countries of nickel-olated or tinned aluminium, and the so-called coppei-clad alu-
1l
Fig. l.t Multiple stranded, circular fl exible conductor
Coppcr Conductors .
Solid conductors lrc prctcrrcd up to l(r mm- crossscctional srea. strondcd conductors lbr 25 rnm: and J
Tinscl strxnds
Tinscl cond uctor Fig,
1.2
Tinse I conductor
Fllt
coppcr wire
Thrcad oi svnthetic Ilbres
Fie.
1.3 Construction of tinsel strund
boVc.
Givcn lnd adcquatc lbility to rvithstand bcnding. thc conductors should have a space tlctor rvhich. together with rhe chosen conductor scction. results in good utilization of the cross-sectional urea of the cable. Accordingly, where possible, compacted circular conductors. or. if the cable construction permits. compacted sector-shaped conductors. are used. The space flctor defines the percentage of the geometrical crosssectional area of a conductor that is occupied by the individual wires. The construction of single-core cable and three-core separately-leaded (S.L.) cable rcquircs the use of circular conductors. Aluminium Conductors
--\e conductor strands are madc up ot'c number. ilpopriate to the cross-sectionul urer of the conductor. oi errra tlnc substrands (multiple srrunded. circular tlerible conductors. Fig. l.l). For very llexible connccting cords of vcry small cross-scctional arcir. c.g. 0. 1 mmr lbr clcctric shavcrs. tinscl conductors ( Figs. l.L and l.i):tre uscd.
IIultiple strunded cirtulur JIe.rible <'onluttors (Fig. 1.1) consist of strands whose individual rvircs are themselves stranded or bunched. The ability of the conductor to wirhstand mechanical stresses and its fle.ribility depcnd particularly on rhc stranding arrangement. as well as on the quality and diamctcr of the wires. The shorter the lay of the strands and substrands, the greater the flexibility and the ability r withstand bending. The srrands may be laid in ne same direction in all layers (uniform-lay strand.,rg) or the direction may alternate from layer to la,'-er (reversed-lay stranding). Conducrors with uniformlay stranding are preferred in llexible cables for hoists ' ,ecause of their better runnins behaviour rvhen changing direction over rollers. Tinsel conductors (Fig. 1.2) are made up ofa number of tinsel threads stranded rogether. Each thread (Fig. 1.3) consists of a textile core with a helical wire strip (copper strip 0.1 ro 0.3 mm wide and 0.01 to 0.02 mm
thick).
DIN VDE 0295 pcrmits the use of circular solid and stranded aluminium conductors lionr 25 nrmr uprvlrds lnd scctor-shapcd conductors Irom 50 mm: upwrrds. Solid conductors ure prcterrcd in cables rvith pol.v''nrer insulation and sector-shlped conductors in the rangc of cross-sectional urcas tiom 50 to 185 mnrr. Singlecorc cablcs normally have strandcd circular conductors: solid conductors are usuirlly uscd only in laid-up single-corc cablcs in cases of high thermal loading. because of thc problems of thcrm:rl expansion (see page 192).
If cables with polymcr insulation and aluminium protcctive (P) or ncutral (PEN) conductors are laid in the ground or in an agrcssive atmosphere. in the evcnt of damagc to the sheath and thc insulation these conductors may be open-circuited in the course of time through corrosion. The possibiiity of damage must therefore be taken into account. rvhen such cables are installed. by the selection of appropriate protecuve measures.
llilliken
Conductors
For high-power transmission with conductor crosssectional areas of 1200 mm2 or more. special measures are necessary to keep additional losses due to skir effect within tolerable limits. To this end, either the individual conductor stlands are provided with an insulating layer (e.g. enamel) and so laid-up that 13
l
Conductors
\ormal lay-up
Compacted
their position within the cross-section of the conductor changes periodically along the lenght of rhe conductor, or the conductors are made up of separate stranded, sector-shaped elements which are rrrapped in conducting paper (Fig. 1.4). This latter type is also known as the milliken conductor. Single-core oil-filled cables require a hollorv conductor, rvhile external-gas-pressure pipe llpe cables require oval conductors. Superconductors
Lou -loss conductor for oil-lillcd cables ( \liiliken conductor)
Circular holloq conouclof
Fig. l..l Construction of multi-core circu lar conductors
x1
ffi
@
Oval conductor
Solid
Stranded
shaped
shaped conductor.
conductor
Fig. 1.5 Construction of sector shaped conductors
Fig. 1.6
Model of a flexible superconducting cable core. Constructed of aluminium wires each with a lhin coaring of Niobium laid-up over a PE carrying tube. Above this an insulation of polymeric plastic loil is applied followed b1r the concentric retum conductor and a profiled PE rape as proleclive layer t-
tl
The most suitable conductor materials for superconducting cables are pure niobium and niobium-tin. those critical temperatures are around 9.5 K .. _. 18.4 K respecrively. Since the current llorls onhlin a very thin surface layer (0.1gm). lhere is no need for the u,hole conductor to consist ol this rclatively expensive superconducting material. It is sufficicnt if a thin layer (10 to 100 pm) is dcposited on a carricr naterial, e.g. high-purity copper or aluminium. The carrier metals must be so disposed that they are not traversed by rhe magnetic field of the conductor, and the generation of eddy-current losses is avoided
(Fig. 1.6). The development of superconducting cables is as yet in rhe early stages, although 110 kV cables capable of transmitting 2500 MVA have already been produced for experimental purposes.
--l
For the insulariorl of rviring cables and llexible cables. s-vnthetic nraterials and naturll rubber are used. and for porver cables. as rvell as these' tmpreg-
nated paper. As a result of the development which has taien place in recent years. these materials can be produced rvith various electrical- thermal and mechanical properties according to their intended purpose. It is thus possible to manufacture cables lbr specific requirements and tields of application.
2.1 Pol-vmers A poll-mer is I macromolecule composed oi r hrqe number of basic units. the monomers. If tlte mlcromolecule is s-"-nthesized using onl."- one kind of rD{,pomer. the producr is a homopolymcr. If the poi- .er chains are made up of nro diffcrent tvpes of monomer. the result is a copoll-mer. and of three different t)-Pes a terpolYmer'
\lost of the important insulating matcrials are today produced s).'nthetically. Only in the case of clastomers rre partly narural products still oi technical signil-i-
Technically important polymers are classified (Tlble 3.1.1 .rccording to their physical properties as
tr F tr
thermoplastics (Plastomers), elastomers and thermosetringpolymers(duromers).
The polymers principally used in cabie engineering are listed in Table 2.2.
is rvorth noting that materials rvhich do not fit lnto rhls clussification oi thermoplastics. elastomerics and thermosetting materials are finding increasing application in cable engineering. These include the
It
cross-linked polyolefines (e.g. cross-linked polyethl-lene), rvhich behave as elastomers above the criticel melting point. as manifested particularly in the heat-pressure characteristics :lt iligh letnperatures
(Fig.2.1). Also in this crteeorv ure the so-cllled thermophstic elastomers rvith their chdracterislic thermoplastic behlviour at processing temperatures and elastomeric cltlrlctcristics ltt thc temperatures at r''hich thev are used.
cance.
Trblc
2.1
Technically important polymers chssilied according to thcir physical properties Polymers
Sy.'ntheti, mate rials
^r,,rtu,ior,ill lrstomers
Highly molecular materials which after cross-linking (vulcanizing) develop elastic characteristics i.e. a large reversible elongation in resPonse to low tensile stress
Thermoplaslic (Plastomers)
Thermosetting pol,vmers (Duromers)
Macromolecular materials lvhich are. at higher temperatures. Plastically formable and are teverslbly plastifiable, i.e. theY harden on cooling but become Plastifi-
Polymers which harden when heated above a critical temPera-
able when reheated
ture and are no longer reversiblY formable. In this condition these
materials are normallY crosslinked
15
2lnsulation Table
2.2
Summary of the most important polymers used in the manufacture of cables
Thermoplastics (Plastomers)
Duroplastic (Duromers)
Elastomers Cross-
Thermoplastic
linked Thermo-
Elastomers
plastics Pol.vvinl lchloride Polyethl lene Ethylene Vinyl-Acetate Copoll mer (v.{ < 30%)
Cross-
Blends
PE
linked
XLPE
Polyfines and Natural Rubber I nree btocK -' Polymer
Cross-
Styrene-
linked
Alkylene-
Ethylene
styrene
Polyethylene
EVA
Ethylene-.Acrl,late-
Copolymer, e.g.:
Erhl'lene-Ethyl-Acrylate EEA Elh)'lene-Butyl-Acrylate EBA
Poll'propylene Poll'amide
of
PVC
PP
Copoiymer
tha ne
Resin
Styrene- Butadien
Rubber
and Poll,ester
SBR
NBR EPR
"
Ethylcnc-Propylenc
ETFE
Dienc Monomer Rubber
EPD M
Polychloroprenc
CR
Chlorsulphonyl
FEP
Polycthy Ienc
CSM
Chlorinated Polycthylenc
CM
Silicone Rubber
SiK
Epichlorohydrin Rubber
ECO
Ethylene-VinylAcetatc-Copolymer (vA > l0%)
EVA
The gencral tcrm for EPR and EPDM is EPR
:'tslockpollmcr:acopol)mcruhosachainiscomposcdofaltcrnatingscqucnccsofjdcnticalmonomcrunits
lndenr deprh LDPE 10
I
,/-
,,r/
70 80
90
(70r)
..1"')
I
XIPE minenl
Heat-pressure test to DIN VDE 0472 Test sample: conductor 1.5 mmr with insulation
filled
I
0.8 mm thick,
EPR
I
Test duration: 4 h
{cross-linked]r
<;
EVA'
Determination of load using the formula: I
lo
conren
>30%
F:0.6.y'2-D-6-6'
(cross.linked) I
120 150
140
"c
150
F
D
Temperar!re Ll
llvA
Fig. 2.1 Heat-pressure characteristics of polyolefi nes.
.1:":^::y-
,t
,r.i 4:
PVC
-
d
EP
Pol)'ure-
llR
Ethylene-Propylene
rnropthr'leneHexafluoropropylcncCopoll'mer ( Fluorinated Ethylene
l
Rubber)
Rubber
Ter rr fl
Propllene)
Epoxy
Resin
N itri lc- Bu tad ien
Eth.vlen e-Tetrafl uoro-
eth) lene
NR
(lsoprene Isobutylene
Rubber
Copolymer Thermoplastic Polyurethane (PUR)
P.A
Natural Rubber Buryl Rubber
Load in N Diameter of core in mm lvlean wall thickness of insulation in rnm
PI PL
2.1.1 Thermoplastics
(
Plastome rs)
Thermoplastics are madc up of linear or branchcd macromolcculcs. and unlike the elastomers and thcrmosetting pol;-mers hlvc rcvcrsible forming charlcteristics. Thc combinltion of propertics of thcmoplastics are dctcrmincd by their structural tnd molecular arrangcment. Thc thermopiastic polyethylene (PE) has the simplest structure oi all plastics
trls. i.i
t.
HH tl HH Fig.
2.2
Structural torm of Poll.'ethelene {PE)
In the so-called high-pressure polymerization of ethchein molecules with liltcral JIkyl groups ilre $ne. '.ne''l bv redicll initiation {LDPE los-Densitv PO. Ionic polr mcriz:rLion lt lorv prcssurc. on thc othcr hxnd. lcads to lincar. very lirtie brlnched chains (HDPE - ffigh-Dcnsity Pfl. Thc less branchcd the chain molecules of a polyeth-vlene are. the greater is its possible cr-vstallinity. With increesing crystallinity, melting temperature, tcnsile strength. Youn-g's modulus (stiffness), hardness and resistancc to solvents increase. while impact strength. rcsistancc to stress crackins and transparenc.v decrease. Like ail thermoplastics, the polyolcfines - as in the case of e.g. polyethylene and polypropyiene - also consist of a mixture of macromolecules of dilferent sizes. and it is possible to control the mean molecular weight and the molecular weight distribution within tain Iimits through the choice of suitable polymerization conditions. . the
technical data sheets of the raw material manufacturers, instead of the mean molecular rveight, the It florv indexr)(for polyolefines) or the so-called K value (for polyvinyl chloride, PVC) is quoted (see page 18).
The mean molecular weight and the molecular weight distribution have a considerable effect on the mechanical properties. Thus, as a rule, tensile strength,
elongation at tear and (notched) impact strength in-
::-" The rncl!-llow iO
lr""""r:r""
index tMFI) is thc quanrity of matcrial in g uhich undcr
is exrruded rhrough a givc'l sizcd jcr in a pcriod of
creasc rvith incrcasing chain lcngth. as :rlso thc viscos-
ity oi the plasticized material. It should be borne in mind. however. that with
incre:rsing mclting visrnaterial more difficuit to rvork. cosity the becomcs
The molecuiar chains (polyethylcnc. polvvinl-l chloridet rcsulting from the synthcsizing rclctions. c.g. the polymcrization of suitable monomers (ethylene. vinyl chloride) are tormed by atomic forces (primary bonds). The cohesion of the molecular chains is due to secondary forces. In the polyolefines, for erample, the dispersion or vxn der Waal forces predominate. In this case the forces of attraction betrveen the molecules are unpolarized. In plastics rvith polarized groups. besides the dispersion forces. dipole orientation furces betrveen the chains are also eifective (e.9. in PVC). Strong forces of attraction betrveen the chain molecules are also represented by the hydro,een bridges. as. for example. in poly-amides. poll-urethancs :lnd iluoroplastics. With sy-mmetrical structures the thermoplastics bonded by dispersion. dipole or hy-drogen bonds tend towards crvs(rllization. The_"- are thcn hard and tough. lnd of high strength. and the sotjening range is smail. To the e\tent that the macromolecular structure is asymmetrical (e.g. in PVC). thc tendencv ro crystallization is reduced and the sollening ranse extended. Arvareness of thcse rclationships norv makcs
it
possi-
ble to manul'acture plastics tailored ro their application requirements. In addition to standard thermoplastic PVC and PE. thermoplastics and elastomers produced by specifically directed copoll-merization of ethylenes rvith other copolymerable monomers har e assumed significancc in cable engineering.
Copolvmers
The thermoplastic copolymers most frequentlv used in cable engineering are based on ethvlene and are produced by copolymerization with vinvl acetate (EVA copolymer) or with alkyl acrylates (EEA and EBA copolymers). EVA copolymers with a vinyl acetate content up to 30% contain methylene units in crysralline formation and are therefore workable as thermoplastics. With a further increase in the vinyl acetate (VA) content the product becomes rubbery. Polyethylenes and the ethylene copolymers, such as e.g. EVA, are of special significance in cable engineering because these thermoplastics can be cross-
t7
rl 2lnsulation
tl
ll n
cI
ll
Polyvinyl Chloride (PVC)
n I
Among rhe insulating materials used for flexible anr wiring cables, plastic compounds based on polyvinr chloride (PVC) have assumed particular significance
I
:
H
tl
-co-cH
:
Fig.2.3 Structural form of EVA
il ll
il
ll
Fluoroplastics
n,
il
ll' :
,
The various mechanical propcrties of the polymers (e.g. tensile strenglh, extension, elasticity and cold resistance). the various resistances to external influences (e.g. acids, aikalies. oil) and their electrical and lhcrmal characteristics determine the areas of application of the cables in s hich they are used for insuladon and sheathine.
lli It; i
ti
I
-+-
i-i-r-i+ I it Y-r L
T
^1r
l
I
---l-L
tr
tt
rr
I
I
-
rEF
CF3Jy
Fig.2.4 Structural form of ETFE and FEP
I 18
2.5
Structural form of PVL
For insulating and sheathing mixtures in cable engi necring, PVC obtained by the suspension method i usually used. These types of PVC, offered by th chemical industry as S-PVC. are distinguished b' thcir grain structure and K value. The K value. ac cording to Fikentscher (DIN53726), characterize the mean molecular weight of the PVC. The grai: structurc is significant from the point of view of th processing of the compound. For the manufactur. of soft PVC compounds for the cable industrl'. a; S-PVC uith porous grain (plasticizer sorption) an( a K value of about 70 has bccome generally acceptcd PVC and additives like plasticizers, mineral fillers antioxidants. coulering pigment a.s.o. are preparel in a mixing and gelling process, under heat, to pro duce the working compound. The compound, usually in granular form, is pressec onto the conductor as insulation, or onto the cori as a sheath, by means of extruders.
r
:
ii-i-i+ Fig.
Fluoroplastics are characterized by an outsrandint combination of properties. such as good thcrmal stabilit.v, excellent electrical characteristics and high rcsistance to chemical attack and flame rcsistance. Thc best known fluoropol-vmers in cable engineering are the thermoplasrically workable copolymers of ethylene and tetrafluoroethylene (ETFE) and of tetrafluoroethylene and hexafluoropropylene (FEP) (Fie. 2.a).
lli
:
The starring material, the vinyl chloride, is nowadal produced mainly by the chlorination of eth-vlen. (Fig. 2.5). It can be converted to polyvinylchlorid. by the emulsion (E-PVC), suspension (S-PVC) o: mass pol),merization (M-PVC) method.
)inked b1' means of orsanic peroxides or high-energy radiation. Cross-linking increases the thermomechanical stability - i.e.. rvith a temperature loading beyond the crystallite melting point of the crosslinked thermoplastics the material no longer exhibits themroplastic. but rather thcrmoelastic characteristlcs.
il
ll
3
Pure PVC resulting from polymerization is unsuitable for use as an insulating and sheathing materia for flexible and wiring cables, because at its servic temperature it is hard and brittle, and also thermali' unstable. It is only through the incorporation of ad ditives that the mechanical/thermal and electricr characteristics necessary in such materials, togerhe: with good processing properties, are obtained.
The most import:rnt additivcs arc:
tici:ers The plasticizcrs normllly usecl are cstcrs ol'or3lnic acids. such as DOP (Di-1-crhyiherylphthaiate) or DIDP ( Di-isodecy-lphthalatc). Estcrs of lzelnin or scbacic acid tre used for compounds rvith especillly good cold resistance, while those for higher servtce temperxtures contain trimellith ccid esters or poll ester plcsticizers. P
las
Stabili:ers These confer thermal and thermal oxidization stabili-
ty on rhe PVC compound during processing and in service. Principally used as stabilizers are leld salts such as basic lead sulphate or lead phthalate Antioxidunts tre necesslry in addition. to prevent. ibr c. ,rplc. dcterioration of the plasticizcr through oridatlon. Fillcr s
-f
;e are used to obtain a specitied combination of char:rcteristics. In addition thev contribute to reduce thc cost. The most uscd llllcrs for PVC compounds
lrc culcium carbonate and kaolin.
Pol-veth-'.'lene (PE)
j
-
Polyethylenc is a macromolcculur hydrocarbon rvith a structurc sirnilar to thut of thc parat'fins (tbr thc structural tbrnrula see page l7). This matcrial. rvith its excellcnt dielcctric properties. is used ls an insulating matcrial in porver cable enginecring in both noncross-linked (thermoplastic PE) and cross-linked (XLPE) form. The power cables produced by Siemens with thcrmoplastic polyethylene insulation are knorvn by the protected trlde name PROTOTHEN'Y and those with cross-linked polyethelene insulation by the trade name PROTOTHEN-X. Of the wide range of ty'pes of polyethelene offered by the chemical industry, only specially prepared, purified and stabi' lized tlpes rrc uscd in cablc cngincering.
Thcse improve the
workebility Stclrltcs urc usually
used. P
ROTO D
U
For installations with especially stringent requirements as to burning behaviour, compounds for cables have been developed which satisfy the bunched cable burning test, Test Category 3, of DIN VDE 0472,
Pari 804, lead to a lower emission of smoke and gas and do not release hydrogen chloride (see pages 79 and 125).
i I
!r 't
r :
' :
I
I
la-vers over and under the insulation. The inner lal er
T
both thermoplastic and cross-linked poilethelene lre sensitive to ionization dischargcs. it is necessar-v- ior clbles rvith r:rtcd voltages from L 6, L = 3.5 6 kV upwards to incorporlre conducting
usually consists ol a weakly conducting alkyl copo' l1,mer. Various mcthods rvere tbrmerly used to provide the outer conducting laYer:
>
grlphitizing or conducting lacqucr or
I
tr
T
conduct-
ing adhesivc rvith weakly conducting tape applied cxtruded conducting luyers. lvhich serc either applied in a scparxte process or extruded in the sante process with the insulation.
R Flexible antl lYiritg Cables
Cables with PVC insulation manufactured by Siemens arc known by the trade name PROTODUR' They can be laid without special precautions in ambicnt temperatures above -5'C. If the cables are colder than this, they must be carefully warmed be, e installation. Flexible and wiring cables are generally of smaller diameter than porver cables' and are therefore subject to lower stresses in installation. so that with careful handling they can be laid at lorver .' lperatures. For countries such as Norway. Srveden or Finland. PVC compounds are available which afford the necessary bending capability down to low temperatures.
t
Because
to it: Lubric tut ts
I
T
I T T T
co[]pounds
T
Conduclor
T
Conducltng
I
I
Insulalinq compound
I
I Fig.2.6
Schematic arrangement of triple extrusion 19
1 -!I
2Insulation
According to the new specifications of only outer conducting layers perextruded rvith and bonded to the insulation are
DIN VDE
02731 . .87,
mitted.
The extruded conducting layers are very thin, and so firmly bonded to the insulation that they can be separated from it only with a scraper' In some counrries conducting layers are used whose adhesion is somervhat lower, so that - if necessary after scoring rvith a tool - they can be stripped by hand (cables rvith strippable conducting layers). Because of the force required in the stripping operation' such laycrs are made somewhat thicker. L
To ensure operational reiiability in medium' and highvoltage porver cables. it is particularly important' apart from using high-purity material and observing appropriate cleanliness in the nranulacturing processcs. that thc insulation and the conducting layers should be free of bubbles, and that therc should be good adhesion bctwecn the conducting laycr and the insulation. According to DiN VDE 0273 this must be checked on every manufactured length by means
of an ionization test. comparison with high polymers with polarized structures, such as PVC. high polymcrs with unpolariscd structures, such as PE and XLPE' are characterized by outstanding electrical charactcristics. They have, horvever, poor adhesion properties in relation to other materials, e.g. moulding compounds. This characteristic has to be takcn into account in the design of accessories.
In :
L
L Ui
li ll ll
I 1 n
For the lorv-voltage range a polycthylenc insulation compound has been successfully developed which bonds s'ell to accessory materials and thus ensures the water-tightness of joints.
PROTOTHEN.Y is not usual to use thermoplastic polyethylene in power cables for lJolIJ=0.611 kV, because of the high conductor temperatures to be expected under short-circuit conditions. For higber rated voltages' while it offers advantages in comparison with PVC and paper insulation because of its satisfactory dielectdc properties, it has declined in significance as power cable insulation, beceuse of its poor heat/presiure characteristics (Fig.2.1), in comparison with cross-linked polyethylene, and has been omitted from the new specification VDE DIN 0273/..87.
It
t0
Cross-Linked Polyethylene (XLPE)
PROTOTHEN.X The linear chain molecules of the polyethylene are knirted by the cross-linking into a three-dimensional network. There is thus obtained from the thermoplastic a material uhich at temperatures above the crlstallite mclting point cxhibits elastomcric propcrties By this mcans the dirnensional stability under heat As it and the mechanical properties are improved oC can be result, conductor temperltures up to 90 to 250 "C up and opcralion normal pcrmitted in ns. under short-circuit conditio There are thrce principal methods for cross-linking poll'cthylenc insulation matcrials :
Cross-linking bY Pcro.x idcs
Organic radical componcnts. in particular spccilic organic pcroxidcs. are incorporated. Thesc dccomposc at temperaturcs above thc cxtruding lemperaturc' into highly rcactive radicals. These radicals interlink rhe initially isolated polymer chains in the thermoplastic in such a rvay that i] spxce netuork results (Fig. 2.7). 'o'as crossFormerly, polyethylcne cable insulation
linkcd mainly by 'continuous vulcanization in
a
steam tube', in the so-called CV!)method (Fig.2.8)'
In this methoti the polycthylcne. mixcd u ith the pcroxide as a cross-linking initiator. is pressed onto thc conductor. by means of an extruder, at about 130 "C (below the temperature at rvhich the pcroxide dccomposes). Follouing this. in the same process, the insuiated core is passed through a tube, about 125 m long, Iilled with saturated steam at high pressure' At a pressure of 16 to 22 bar and a temperature ol aboui 200 to 220 "C, the organic peroxide decomposes into reactive primary radicals, which effect the cross-linking. The crosslinking process is followed immediately by a cooling stage. This must similarll take place under pressure in tubes 25 to 50 m long' to privent the formation of bubbles in the wlcanizec maierial through the presence of gaseous products
of the peroxide reaction' An alternatives to this 'classical' crossJinking pro cess, methods have been developed in which gase' or liquids, e.g. silicone oil or molten salrs (salt bath cross-linking) are used as media for the heat transfer I' Cv:
continuouJ nrlcanisation
f".
R-?-o-o-f?"'-R
Peroxide
CH,
CH.
cH.
Primary radical
t-R-9-9'
+ CH.
o
I
cH.
tR-C:O
CH"
+
+
- cH2-CH2-cH2-cH2-
cHr-cHr-cHz-cHr-
Po
I t
I
Lr|.
R-c-oH + I
cH4
I
+
- cH2-cH a -cHz-cH2O
CH.
- CHz-CH -CH2-CH2-
Polymer radrcal
-t
I
I
- cH,-tH-cH2-cH2- cH2-cH-cH2-cH2 -
Barliial combination during network formalion
Fig.2.7
i
I
Cross linked Pol'Tethylene
T
Cross-linking of Polyethylene by organrc perortdcs
T
I I
lnterml enl drive unil
T I
I
Tension
conlrcl unit
b
I."
Cooling
tit
l0ne
or
'f t
T Tube length approx 125 m
Fig.2.8
I
Continuous cross-linking in a steam tube (CV process) I
Y I I
2Insulation Compared to vulcanisalion with steam, these methods permit crossJinking at higher temperatures and lower pressures. Cross-linking by Electron Beants
The polymer chains are crosslinked directly by means of high-energy electron beams, without thc necessity for the heating stage which is essential with peroxides. It will be clear from consideration of the
reaction sequence in the cross-linking of polyethylene by electron irradiation, as illustrated in simplified form in Fig.2.9, that in this case also gaseous reacrion products are formed (mainly hydrogen). Cross-linking by Siloxane Bridges
Polyolefines can also be cross-linked by means of siloxane bridges, u hcreby suitable alkoxysilancs are radically grafted into the poll,mer chains. In the presence of moisture and a condcnsation catalt st. hvdro-
"- CH z-CHz-CH2-C H, *CHz-CHz-CHr-CH.^^,
lysis takes place to form silanol groups, which then condense to the interlinking siloxane bonds (Fig. 2.10). Because the grafted silane can contain up to three reactive alkoxy groups, this offers the possibility that bundled linking locations can be formed.
Although as regards the chemical structure of
the
cross-linking bridges the cross-linked polymer matrix appears to be quite different from those produced by the methods previously described, a combination of characteristics is nevertheless obtaincd which essentially corresponds to that of the crosslinked PE produced by the classical methods.
Like all polyolefines, crosslinked polyethylene is subject to a time and tenrperature-dependent oxidative decomposition, and it. has to be protected against this by the addition of anti-oxidants, so that il can uithstand continuous service at 90 "C over a lonq period of time (see page 27).
Polyethylene
t
leo I
Y
H.
+
-CHz-CH-CH2-CHr^ a
,
*cHz-cHz-cH2-cH.^, J
lao
Formation of polymer radicals
lI
Y
* C Hz-CH-CH2-CH.^,., H.*
a
a
-, CHz-CH-CH2-CH"I
Y
l
Eadical combination during nework lormarion
1)
* CH:-FH-CH2-CH, ^I
^^,CHz-CH-CH2-CH"-,
Cross.linked Polyethylene
Fig. 2.9 Cross-linking of Polyethylene by electron beams
Elastomers 2.1
HrC. H.C.
\
-CHr
+
2
/
cH,
OR
Hrc:cH-si-oR \
HrC.
Polyerhylene
cH,
OR
H.L
HrlGrairing
{Radical initiation)
/o^ "."a'cH-c{2-cq2-si-oR oR *"a.
RO
"tta. r, i'i2
Rojsi-cH,-cHr-c H cH,
cH"
+
Hydrolysis
H2O
(caralysrl
-2ROH
H.C CH. H
CHz
Fis.
2.10
Cross-linked Polyerhylene
Cross-linking of Polyethylene by Siloxane bridge method
2.1.2 Elastomers In contrast to the thermoplastics. the molecule chains l[ elastomers form an extensive meshed networli' This cross-linking, or vulcanization, gives rise to the elastic nature oIthe material: a large reversible extension in response to low tensile stressElastomeric materials are used lor insulation and for sheaths. They are applied mainly where the product has to be particularly flexible.
A wide range of
elastomers is nowadays available to the cable industry. This makes possible the manufacture of compounds with specif-rc properties, such as high abrasion and oil resistance, weather and heat resistance and flame resistance, combined with good overall elecrrical and mechanical chlracteristics.
The classical elastomeric material. natural rubber' hls declined in signific:.rnce in recent yerrs' In its place. the synthetic elastomers. produced by the copolymerization of ethylene and propylene, are conitantly finding new areas of application in cable engineering. These ethylene-propylene copolymers' known under the general term EPR, contaln no dou'
by ble bonds, and cannot, therefore, be crossJinked unsathe to rhe vulcanization methods appropriate turated rubbers (e.g. natural rubber, styrene butarubber). On ihe other hand, because of the
diene absence of iouble bonds in the main molecular greater chains, these elastomers have a significantly to resislance to thermooxidative decomposition and heat' and ozone rhe effect of ultra-violet radiation'
2 Insuladon IJ
Fig. 2.11
I
i-i*
I
H
Structural form of EPR and EpD
EPR
HH
tl
EP0i\il
with Erhylidiene
Y_Y tl
as Iercomp0nent
HH
With the incorporation of a dienet), EPDM elas-
ene butylene blocks, which are so struct.ured that etl
tomers are obtained (Fig. 2.1 1), in which the doublebond active in cross-linking is arranged not in rhe main chain but in a side -eroup.
ylene butylene chains contain styrene units as en blocks. Polyesters and polyurethanes wirh TPE prol' erties are also known.
Thermoplastic Elastomers (TPE)
:'
Technically interestine combinations of propcrtics can be obtained through thc admixture of rhermoplastic olefines. e._1. poll propylene rvith ethl lene propylene elaston.rers, or bl rhe direct production of socalled pollolciine block poll'nrers. Such copolvmers of ethl'lene and propllene *'ith a block structure consist of an EP elastomer phase uith crlstalline homopoll mer end blocks. *'hich represent the unstable reversible cross-linking centres. At temperatures above the cr]'stallite melting point. rhese materials have thermoplastic propcrties: belou thc cr1'stallite melting point the),behave as elastomers. Polymers of this kind are therefore called thermoplastic clastomers
(TPE):'. Another class of thcrmoplastic clastomers is represented by three-block polvmers o[ styrene and ethl l-
Other types of elastomers used in cable engineerir are polychloroprene, chlorosulphonated polyethl enc and chlorinated polycthylcne, which. because t thcir advantaceous properties in relation to enviror mental influences. are prcfcrably uscd as shearhin matcrials. Conducting Rubber
Through the addition of conducting fillers, e.g. ca. bon black. natural rubber and syntheric elastom. compounds riirh a resistivity of from a few Qcm u to several thousand C2cm can be produced. Conduc ine rubber compounds are generally used in the mor itoring of flexible and riiring cables in mines. an also for inner semiconductin-s layers and held limi ing in s,"-nthetic elastomer insulated high-r,ohag cables (Ozonex principle).
Natural Rubber (NR)
Natural rubber is obrained in various counrries i rhe equatorial belt from rhe rubber tree (hevea bras: The drencs used as tercomponenls are spccial hydrare mrlcrials *ilh double iinks tahich arc non{onjugatcd ln ror:re Fublicerions for thcmoFllsric cllslomcrs rh. !bbrclia(ion TPR
rj u*d
as prcviousl]
liensis). This tree contains in the cambium cells unde
its bark a milkl juice (latex), which flous our whe the bark is cut. The rubber is obtained from th through coagulation with chemicals, electro coagL
Elastomers 2.1 {
lation or by other methods. The resulting rubber is supplied to the manufacturer in smoked form as 'r*ok"d sheets' and in chemically bleached form as 'crepe'. Rubber is a hydrocarbon of high molecular weight with the monomer unit 1,4-polyisoprene' with the addition of vulcanization and aging-protection additives, specially selected fillers, and where appropriate by blending with synthetic elastomers, insuiating compounds for cables and compounds for the sheathing of flexible and wiring cables can be manufactured.
Unlike synthetic elastomers, natural rubber has to be subjected to a so-called mastication process during
rnufacture. to make it receptive to the additives a,rd to obtain the required plasticity in the compound. The significance ofnatural rubber in the cable industry has declined sharply in recent years in favour of synthetic eiastomers.
hand, i lower isoprene content lowers lhe rate of vulcanization and makes the product less elastic' The relatively smali number of double bonds makes butyl rubber less susceptible to the effects of oxygen and ozone. The main advantages are very low water absorption and low gas permeability. The good heat resistance permits operating temperatures uP to 90 "C with suitable compound structures. The mechanical properties can be improved by the addition of special active fillers; plasticizers, for example, im' prove the elastic properties, particularly aI low temperatures. Since EPR and EPDfvt synthetic elastomers have become available, butyl rubber ist used onl;' in special cases. Ethylene-Propylene Rubber (EPR)
EPR is uscd su
Styrene Butadiene Rubber (SBR)
SBR is a copolymer of styrene and butadiene' referred to as either a hot or a cold polymer according to the method of manufacture. Cold polymers. rvith the normal st)rene contcnt ol 2'lol, (by rveight) arc characterized in comparison rvith the so-called hotrubber t-vpes by higher tensilc and tclrr strength rnd bctter rvorking c h arac teristics : thel irrc thercfore prcferrcd as admixtures used in thc production of SBRNR compounds. SBR and SBR-NR mixturcs trc suit:rble for usc ts insulation in lorv-voltagc fleriblt' and,,r'irins cubles for operxting tenlpcrlltlres up to 60 "c. Nitrile Butadiene Rubber (NBR) Through the copolymerization of acryl nitrile nith hutadiene. ellstomers are obtained rvhich are distin.,-rishcd in comparison rvith the SBR types b-u" high oil rcsistance and good rveather resistance. For this rc:lson thev are preferably used for sheathing compo u nds.
By mixing rvith PVC, NBR-PVC blends are produced rvhich have better flame resistance.
Butyl Rubber (IIR)
Butyl rubber is a copolymer of isobutylene and lsoprene. To permit vulcanization, an unsaturated componcnr of 1.5 to 4.5% (by rveight) is introduced. Thc lorier the isoprcne content. thc less is the ertent to rvhich thc rubbcr lgcs under hc:.rt i on thc othcr
ls:r
general designation for the tr"o
b-types
ethylene-propylene rubber (EPR) and erhylene-propylene terpolymer rubber (EPDM).
Ethylene-propylene rubber (EPR) is a copolymer of lorv density rvithout C-C double bonds. i.e. it rs a completely saturatcd polymer rvhich. likc polyethylene. can only be cross-linked radically The further dcvelopment of this saturated rubber to EPDM (Fi-s. 2.11) through the incorporation of dienes rvith hrcral doublc bonds pcrmits a conventional sttlphur vulcanization as ',vell as radical cross-linking. e.g u irh pcroxidcs.
There is litrle ditterencc bcnvccn cross-linked EPR and EPDivl as regards mechanicll and electrical properties. Peroxide - i.e. radical - cross-linking. ho$ever. gives better long-term hext resistance and better heat pressure charucteristics than sulphur vul-.*caniza lio n.
Outstanding characteristics of these elastomers are resistance to ozone. oxtgen and ionization. good flexibility at low temperatures and high resistance to $eather and light. Because of their good dielectric properties EPR and EPDVI. depending on the struc' ture of the compound. are suitable for insulation at voltages up to 100 kV, rvith a maximum permissible oC. Such insuservice temperature between 80 and 90 Iating materials will wirhstand temperatures up to 250 "C without damage under short-circuit conditions. Cables rvith ethylene propylene rubber (EPR) manu-
rlcturcC by Siemens are knorvn by thc protected tradc name PROTOLON. 25
i
2lesulation Blending EPR with PE enables the mechanical strength and hardness to be increased significantly ('hard grade'). The insulating materials so produced closely resemble the elasticized polyethylenes in their combination of characteristics, i.e. they exhibit, as well as the improved mechanical characteristics, improved electrical characteristics, similar to those of polyethylene. They are known by the abbreviation HEPR.
Silicone Rubber (SiR)
Silicone rubber is produced by the polycondensation of hydrolyzed dimethyldichlorosilane and methylphenyldichlorosilane. The macromolecules in this case consist not of carbon chains, as in most other polymers, but of silicon-oxygen chains (Fig.2.1?), uhich is the reason for the rcmarkably high heat resistance.
During processing, fillers are added to the silicone rubber, together with organic peroxides for the purpose of crossJinking (vulcanization). The end product is characterized by a high heat resistance. Because
of the excellent insulation properties and the practically unvarying flexibility over the temperature range from -50 to +180"C, flexible and wiring cables insulated *irh siliconc rubber crn bc uscd contin'180'C (up uously at conductor tempctatutes up to to 250 "C for short periods).
Thc
silicone-rubber-bascd SInNOTHERM compounds manufactured by Siemens have outstanding eiectrical charactcristics r.vith good resistance to ozone. They are inscnsitivc to moisture and exhibit good rveather resistance. The-v are thus suitable for both insulation and sheathing. Another preferred arel of application is that of accessorics.
Ethylene Vinyl Acetate (EVA)
EVA is a copolymer which is used either as a t. moplastic (vinyl acetate content < 30%) or, with s able crossJinking, as an elastomer (see Fig.2.,l structural formula). The properties of an EVA cc lymer are in the main determined by the ratir vinyl to acetate content. Cross-linked EVA e tomers are characterised by good heat resistance permit conductor temperatures up to 120'C- T also exhibit excellent resistance to aging in hot and superheated steam, together with very satisfa ry heat/pressure characteristics (see page 16), part larly at high temperatures. In addition, EVA c, pounds have outstanding resistance to ozone and ygen, weather resistance and colour stability. The namic freezing point is in the region of -2{ - 30 "C. The application of EVA as an insula material is limited by its electrical characteristic the low-vohage range. The compounds are used heat-resistant non-sheathed cables and flexible co and for heating cables.
.
2.
1.3 Thermosetting Polymers (Duromers)
Unlike the elastomers, thcrmosetting polymers usually closely crosslinked and in general have be t. ',vear resistance and dimensional stability than moplastics and elastomers.
Thc application of the thermosetting pollmers as sulating materials is limited to the use of epo: and polyurethane rcsins for thc {iiling of cable ac sorics. Filling resins bascd on epoxides are preferr converted to the thermosetting state bv heat-cur Poll'urethane resin materials, on the other hil harden at room temperature, and so offer advanti. in application techniques. Both types o[ resin are : able for outstanding adhesive strength. particulr to metals.
A suitable choice of
resins and hardeners enabl uell balanced combination of thermomechanical
electrical pfoperties
to be obtained, together r
good chemical resistance.
ftttl QH" 9H. I
-Fo-gi-o-qi-o-fttrl I CH3 R L (R
Fig. _:o
=
CH, or C,H,)
2.12 Structural form of SiK
-Duroplastics ' Chemical Aging 2'2
2.2 Chemical Aging of PolYmers is understood lhe change in the Bv the term'aging' -maierial with time Polymers are subof a "ioo.it'i., iect'in use to chemical changes which have an adverse ,e-i;;;;; their mechanical and electrical characterisncs.
with The chemical aging processes are accelerated to necessary increasing temperature. It is therefore temperap.ot..t pily..tt which are exposed to high iur.t Uy means o[ stabilizers' in order to ensure an from adequare service life for the products made them.
t
particularly.'. sheaths tha( are exposed proto direct sunlight (UV radiation) must be further rected ag;rinst this effect by the addition of so-called lieht stalilizers to the compounds' Carbon black has
rlrtion lnd.
'.
vc-d
to be an excellent light stabilizer,
especialll"
lbr polyoleiines; an addition ol2 to 3% (by $cigh[) rineiu divided carbon black, well distributed' tords an effective Protectlon.
oi
al--
In the prescnce of atmospheric oxygen, thc chcmical aging of many polymers' e.g. the polyolefines' arises from oxidation processes rvhich are provoked' or accelerated. by heat and light' For thc purpose of stabilization. anti-oxidants are added to thc polymcrs ln a proportion, normally' oi 0.1 to 0 5% (b1" neight) Asins relcrions. espcciulll oxidution. itrc ltccclcrl(r'd cltall-ticall.v by the presence of some metals This is parricularl; marked in thc case of contact bct\\'cen coppcr and polyolefines. in this situation anti-oxii rnts oftcr no apprecicble proccction' tn practice. to avoid direct contact betlveen pollolchnc insulation and copper conductors. separators are otien introduced. e.g. plastic hlms rvith sufficient stahilitl in cont:-rct sith copper. or tinncd coppcr con-!.lctors itre used. In mediunl and high'voltage cable the tield-limitrng conducting layers act as separltors' Conductins compounds xre protected against the eft'ect of direct contact lvith copper by their high carbon black content. Where there is direct contact betrveen polyoleFtne insulating materials and copper conductors. metal deactivators are added to the insulating compounds to counl.eract the catalytic effect. It has been possible to demonstrate by practical aging tests that by this means a sen'ice life can be achier.ed which is compa-
Evaluation of the aging properties of polymer cable life' materials is based on two quantities: the sertice a material which for time *ii.h d"oot.t the period of up to remains serviceable' and the temPerature /imi'' ;hich a material can be used subject to given boundary conditions. These two quantities are interrelated' so that an increase in the temperature limit results in a reduction in the service [ife' In determining the corresponding pair of values for the service life and the temperature limit, the changes in the signihcant characleristics lvhich are necessary for the iunction of the material must be examined as functions of temperature and time up to point rvhere an end criterion is reached. The choice of characteristics and of the end criterion determine the re-
It
f i
I
sults.
In clble engineering the terr strength is in most clses adopted as the essential characteristic, and as an end criterion, on practical reasons' the attainmenl of a .."particular elongltion value, e.g. en=50% (residual elongation).
Tf f
T
DtN VDE 0304 contains guidclines for the dctermrnrtion of the thermal stability oI electrical insulating
i
mlrerials. the revised edition of December 1980 being a rcproduction oi IEC 216 (1974).
:
According to DIN VDE 030'1. under the designauon ' tcmpcraturc indcx ' (Tt ). a te mperaturc limit for a scrvicc liic ot'20000 h is stipulated Tli l6J' for example. signifies that the material for which it is quoted rcmains scrviccablc for 20000 h under lnl thermal strcJs a! tcmperaturcs up to l6'l 'C' To obtain the tempercture index (TI). expcrimentalll' determined pairs oI values for a rirnge of temperatures - the test temperaturc l' and the service life r5 - lre plotted on a grlph trith time on a loecrithmic horizonial aris and the reciprocal of the absolute temperature on the verticai axis. A straight line is drawn through the plotted points and bv- ertrapolation gives the required temperature index' ln the grrphs of Figs. 1.13 to I I6 the temperrture.values on the horizontal axis h:rve been converted to oegrees Celsius ("C) for erse of resdtng.
F
--
rrble riith that obtained in compounds not subjecr to contact $.ith coooer.
21
Chemical Aging 2.2
rc6.
h. 301 20
2
1
rcl o> Yeats
10s
b
4l
,l,I
2
1J
100
8l Months
2 101
1
6 4
?0 10
2
\
6
02 6
Days
2
\\. 2
10'
6 4 2
I
4b dc $
20
0.6 0.4
do120{0160 2oo 25o"c3so
40 60 8b 100 120140160 200 250 "C J50 TemPeralute-
Temperatute
Curvc
I
Curvc
2
..to.
Normll peroxide crosslinked compound for mcdium-voltage cablc Compound with metal dcactivator for lo$volrage clble with copper conductor
Fig. 2.15 Service life
of EVA insulation comPounds
2.1.1
,{vice
liie of XLPE insulation compounds
Fig. 2.15 shows thc temperature dependence of thc service life of an EVA insulating compound' Aging took place in contact with tinned conductors; the end crirerion was eq: JQo/o and the temperxture index (Ir) was 117 "C.
29
I
lDSUlaUOn
2.3 The Influence of Moisture on Polyolefine Insulating Materials
rc5 h
4 30 20
2
rcs
10
6
b
2
2
10"
6 4 ?
l.Months
2
l0j
,|
6 20
1 2
\
10
6 101
0ays
6 2 1
2
,
Practical experience and long-term tests on mod^, cables have shown that water has an adverse effer on polyolefine insulating materials such as pE anT XLPE. Using appropriate dyeing techniques, it;. possible to observe tree-like structures in such mater als subjected to electrical stresses. These originatd from practically unavoidable microscopically smalr fault locations and run in the direction of the electr field. This phenomenon, known as 'water treeing (WT) is quite distinct from 'eiecrrical' tree formatio=n (electrical treeing, ET) caused, for example, by ior izarion.
1o'
The mechanism whereby WT structures arise has nc so far been clearly explained. Because the WT growr is influenced by many lactors besides water and elecl tric flelds, and these processes rake a long time, inve: tigation is very difficulr and time-consuming. t-no
ing the finer points, WT structures can be c*ded into two groups (Fig.2.17):
6 1 2
D
1
tr
0.6
TemPeralute.....--..-.-
Fig. 2.I6 Service life of EPR insulation compounds
Fig. 2.16 shows the scrvice lifc characreristic for an EPR insulating compound for 0.6,/l kV cables. The values uere obtained from insulating coverings in direct contact rvith copper (l0yo elon-eated conduclors); the end criterion $as cR:100% and the rempirature index ( I/1 rres I I3 'C
'bow-tie trees' in rhe interior of the insulation _ 'vented trees' originaring from rhe boundaries of the insulation.
Because of the low concentration of moisture in rhF intcrior of the insularion, the growth of .bow-ti. trees' is slorved do*n. so that they usually remai
small (Figs. ?.18a and 2.18b). The serviceability oTcablcs is thcrcfore only rarch impaired b1..bo*,-tr. trces'.
'\'cntcd rrccs' (Figs.2.l9a ro :.190 r"quirc .norl
critical asscssmcnt. Thcsc can cxtcnd right rhrougi the insulation if sulficicnt rvatcr is available. In rhi \\a) thc clecrrical srability of rhe cablc is gradualll: rcduccd. until a breakdorvn of the cable is in, te,'
ourer conducting layel
Point oi
)K. Inner conducting layer
A\N
,,80w'tie
Conducror
Fig.2.11 Diasramatic example of WT structures
l0
Influence of Moisture 2'3
Fig. 2.194
" Vented tree ". grorving from the outer graphited conducting lay-er o[ a PE cable
Fis. 2.18
r
'' 6o*-tie rress" in a cable rvith XLPE insuhLion (magnihcation 1 : 100)
, t
Fig.2.l9b PE cable from the earll dlls of PE technLquc. " \'enrcd trcc". grosing from thc outer uraPhitcd conducring
la1-cr
,
8.
Fig. 2.18 b PE cablc' from the
'' B()\\-.!ic trccs" of
clrlv days of PE techniquc rvith hiei dcnsity (magniiiclrtion I : !60)
ll
Fig. 2.19d " Vented tree " (lcncrh approx. 700 pm) on rhe\.der extruded conducting layer of a 20 kV XLPE cable afler several years operation $ith water inside the cable (magnification I :135)
Fig.2.19c PE cabl: fronr rhc elrlr. davs of PE technique.
'\:nted rree" srorring from the outcr srlphited .-onductinc It\cr. {Thc picture ',r,rs constructed fronr i\\ o photociaphs
)
Fig. 2.19e " \/ented tree" (length approx. 50 pm) at rhe outer extruded conducting layer of a 20 kv XLPE cable after se\eral vears of operarion (maenification: 1 :1i5)
:r
Influence of Moisture 2.3
by the conversion of the water tree into an electrical tree (Fig. 2.19l). for Experiments on cables that had been in service of lack of a result as which' oUout.igttt years. in con' to the penetrated care in iristaliation, water had ductors and the screen regions, have confirmed the deterioresults of accelerated laboratory tests on the of insustrength ralion to be expected in the electrical lation. In this lonnection. Fi-s' 2'20 shows, by means of Weibull statistics (a method of evaluation speciall)" developed for the physics of breakdown mechanismsl, the determinid residual strength as dependent on the nature of the applied voluge' which by linear probresression of the measured values plotted in the ratec rhe of 2oh abilit-v diagram is established as 63 lvatet value. lt cin be seen from this illustration that in the conductor has a particularly unfavourable el'fect on the insulation [2. 1]. This knorvledge has given rise to the follo"vin-e measures for rhe construction. manufacture and installation of cables with PE or XLPE insulation:
a) minimization of fault locations in insulation
and
al the boundaries of the conducting layers' i'e': tr optimization of the purity of the insulating and conducting-layer materials and the cleanliness of the manuf;rcturing process:
D
extrudcd conductins lavers to bc preferred'
conrcnt and prcvcntion of ln' gress of moisture. i.c.:
b; rcduction of sltlcr
tr
tr
prevention of ingress of water into the conduc' tors and the screen region in mlnutacture' storage' transport and installation and in service (e.g. through subsequent damagc to the sheath). use
of mechanicitlll resistant outer sheath' e g'
of PE.
Fig.2.l9f Structure change from WT to ET at the top of a " Vented rree", XLPE cable aiter 6000h "Water treeing test" with 5 kV/mm and water in the conductor and following short-time stressing with approximately nine times operational field sfength. (The picture was construcred from trvo photographs)
D
provision of lcngthsise rvirtcr-tisht screen tegion to limit the ingress oI rvater in the event of damage to the sheath.
tr
in high-voltlge cable. for > 36i60 kV' the use
of a Iaminated aluminium sheath and a lengthrvise water-tight screen region' In addition to this. intensivc development is in progress to increase the resistance of XLPE insulating iompounds to WTt) bv means of additives [2 3]' r, In lFr hlc:trurc lLo rcicrrc,.l t..) r "WJtcr trcc rctrrdcnt
compouno
r\\ TP. rcmoourd)
-rJ
Probabiliry of failure P
aoa
/_"$_____
I 24
,rf:t I
ll
JI
Test series Percenr rared
kV/nn 7t )
varue %
12
100 157
0.1
100
lor
kV/mm
Vollaqe qradienr
rc2
a) a.c. \'oltage
I
102
f.-..........-
kvimm Voilage gradienl 6
b) Impulse voltage
Nerv condit.ion, dry. not prcstrcsscd
Water in the conductor and bclow thc shcath of thc cable after eight years in opcration Water under the sheath of thc cablc aftcr so.en )ears ln oPeratron
oJl 50
Ware..at the undxmt{:cd sherth aftcr ninc lcars in
operatron
t0
23 Jestseres Fig.2.20 Breakdosn stren,sth
1i 2)3|
eel:elr iared kV/mm. 150
varLe vo
of t0 kV pE cables.
\\'eibull-Disrribution : Probabilirv of lailure p relarir e to mcan voltage sradrent f (break-doun rolragc dir.ided bl thickncss of insulation)
.rl
4
100
,, i0 , 47
i
4
g9 | 116 59 I 78
0.r
tc
102
hV/mm
Voltage gradrenr F
c) d.c. r'oltale
-
Impregnated Paper ' Bibliography 2'5
_2.4 lmpregnated PaPer impregnated paper was used for conductor insulaoi th" last century' It made possible tion ai ttre "ni of cables for higher voltages' Be-the manufacture pirper lnsulilcause of its good dielectric properties' to lne tion is still indispensible for cables used al up -hiehest operating voltages customary today ln the loiv- and medium-voltage ranges' however - up to polymers to an ever30 kV - it has been replaced by development - increasing eKtent in recent decades' This to the highalso increasingly is noru bJing extended voltage range.
I G '. papcr consists of the purest possible -
long*ta-
It is oled ccilulos". obclincd from northcrn timbers' pro,lso knort n ls sudium ccllulosc papcr' lrom the insuarc ."ss by rrhr;h it is prepared. The conductors Ln ivith this special high-quality paper to the thick' n!-. required tbr the ratcd volta-ee In the casc ol prothc higher'voltagc cables, it is advantageous to scrcen I vide conducting pilpers on the conductor and of metallized paper on the core. rvhose thickness' up to ir certain iimit' according to DIN VDE 0225' is counred as part of the insulation thickness' The single- or multi-core clble asscmbly' accordins to the cable construclion. is dricd in an imprcgnltLtng txnk and then impregnatcd rvith a degasscd and dried impregnating medium f impregnrting compound') appropriate to lhe intended purpose of thc cablc' Papcr-insulated c:.rblcs arc dividcd according to thc ncthod of imprcgnation into mirss-tmpregniltco clblcs and oil-llllcd c0blcs. Cables lvhosc lnsulatlon I rillcd aftcr instlllation *ith nitrogen undcr pressltre crtblc 2q; knorr n its internrtl gls pressure
tion from the liquid to the semi-solid state' and are prevented from flowing in the permissible service temperalure range by the microwax structure'
- like all dielectric polybutene compounds - have outstanding propenies, even after long periods of service
In addition,
these non-draining compounds
For extra-high-voltage low-pressure oil-frlled cable'
a lorv-viscosity gas-absorbing impregnant is This may be e mineral oil rich in aromatic
used'
combenwith alkyl pounds. a naphtha-based mineral oil good )ene additivei or an alkyl benzene, ensuring gas absorption in an electric field at all service temOther i.r",ur.t. especially in regard to hydrogen' recharacteristics oI these impregnants are adequate in srvell to tendenc.v little sistance to oxidation and used' the presence o[ the sealing materials
2.5 Literature Referred to in Section
2
Krmmel, C : Sunderhauf. H: Lringswasserdichte Kunststoffkabel (Lengthrvise watertight clbles)' Elektrotechn. Z. (1952) No 4, pp' 173-176 f2.ll Kulkner, W: Miiller. U; Peschke' E F: Henkel' H.J.: Olshausen' R.v.: Water treeing in PE and XLPE insulated medium and high'voltage cables' Elektr.-Wirlsch. 8l (1932) No' 26, pp 9l l-9?2 VPE[1.i] Pcschke. E : Wicdenmann. R': Ein neues Water-tree-retardiermit \littclspannungskabel cndcr ilTR-)isolierung (A nerr XLPE mcdium(WTR) inr oltage cable wilh water-tree-retardant (19S7) No 6' 36 .uhtilon). Elektr.-Wirlsch
Il.ll
uou -r ollitgc. mcdium-r oltlge lnd urternitl gits prcssure cebles are impregnated rvith high-viscosity pol!-
'
'|tcnc compounds. r'hich have very lorv dielectrtc ,.sscs and erccllcnt irging charucteristics' trom .low to vcrl high opcrating tempcfatures. ln compilrtson ri ith thc oil-resin compounds produced tiom natural or svnrhetic hldrocirrbon restns.
The viscositl of the impregnating compound is chosen in such a way that small differences in level do not cause the compound to migrate.
For special cables to be installed on steep slopes. 'non-draining cables' and internal gas pressure cables. special compounds are used, known as nondraining or nd compounds. These consist oi polybutenc modificd by the addition ot' selected microcrys-
tallinc'r',lxcs: thcv shrink onlv slishtlv in thc transi-
i5
Experimental installation for the investigation of the influence of water on polymer insulating materials in medium- and high-voltage cables
,.:
;.i;:' ;;
i
\ '\
Protective Sheaths ' Thermoplastic Sheaths 3'1
3 Protective Sheaths
A distinction is made in the DIN-VDE specifications between sheaths and protective coverings or outer of thermoplastics or elastomers' -coverings Protective coverings and outer coverlngs serve as corrosion protection over a metal sheath or as light me-ct"nical protection for flexible and wiring cables' !i..*rexs shetths are dimensioned for greater mechanrc l stresses. Since the Droperties of these components ltre slmllcr 1 ior dimensions' only rhe collective term "'s..cxth' is uscd in rclation to cablcs in the follo* ing
-
section.
3.1 ThermoPlastic Sherths Pol-vvinyl Chloride (PVC)
PVC-based compounds arc uscd prcdomintntly as n sheathing material for po',ver clblcs and for llcxiblc lnd rriring cables becausc ol thc mlnl ad\'ltntil{cs
thcl ol'ilr. The thermoplastic sheath is extruded onto the c:Lblc corc assembly in a proccss providin-t a seamless sheaths havc a cleln. '"cr. Cablcs rvith PVC outer
iroth
surface.
The PVC compounds combine high tensile strength lnd elonr:arion. pressure stability even in high-tem' . .rrturc reglons. resistlnce to prlctic lly lll chenriclls in soils and most chemic:rls encountered in chemicll plants. and especially flame resistance and reslstlncc to aeing. The sheaths used in PROTODUR cablcs are characterized by their comparative hxrd' ncss. toughness rnd adequirte pliabiliry from the point of vierv of bending at low temperatures (see page 18).
The PVC outer sheath proved over many years for por"er and wiring cables in fired installations is also used. in a suitably softer form, for flexible cables. Llshr and medium PVC-sheathed flexible cords have bL'en introduced satisfactorily for household equipmcn! bccrusc ot'thcir cicar irnd durable colours and
smooth surlaces. PVC-shearhed flexible cords are nor suitlble for use at low temPeratures. in the open atr
or in heating appliances (e.g smoothing irons)' in rvhich the cable can come into contact with hot parts:
elasromer-sheathed cords should be used
in
these
cases.
Poll ethl lene (PE) Practical experience in supply'authority systems has shorvn rhat in many cases medium-voltage cables laid in the ground are subjected to considerably higher mechanical stresses than was originally assumed' Be' cause of rhe danger presented to cables by the pene' tration of moisture. an undamaged impervious outer sheath has a decisive effect on the life expectancl" of PE and XLPE insulation (see page 30). A mechanicalll resistant PE sheath is therefore increasinglvprelerre,i. especially' for medium- and high-voltage cables *ith XLPE insulation. A PE shearh is recommcndcd in thc ncrv spccification DIN VDE 0271 37 rbr XLPE cablcs laid in thc ground
Thc disadvantagcs of thcse mlterials. such as llamm.rbility. greater ditticulty of handling in instailatton' interior adhesion to the miltericls normally used in rueccsories lnd greater longitudinal shrinkagc' are lcccpted in vierv of their grei'tter hardness and abrasion ."ria,rnaa. From considerations of resistance to UV r;.-rdiltion and environmcntitl strcss cr:rcking' onl; black PE sheaths arc permitted. Thc mosl significant fuctor in the choice of the base poly-mers is the temperature to be expected in normal service. The screen temperature to be expected under fault condirions (see page 286) should be allowed for by suitable constructional measures.
Particularly advantageous is the combination of a PE sheath with the measures described in Section 7 3 tbr the sealing of the screen region of the cable againsr the ingress of moisture. ln connection with the leading-in or laying of cables in intcrior locations. ir must be rem!'mbcred th;lt PE 37
:
J
l'rotecrrve Sheaths
sheaths are not flame retardant. Where necessarv. appropriate fire protection measures should be adopted at the site, e.g. spraying or painting the cable with a flame retardant protective coating.
to weathering, chemicals and heat Siemens have developed special synthetic elastomer compounds for use as an outer sheath material.
_
Polychloroprene (PCP)
Poll'amide (PA) and Polyurethane (PUR) Polyamides are polycondensarion products with linear chain structures made up of dicarbon acids and diamines or aminocarbon acids. Polyurethanes are polyaddition products with a chain-formation to spatial structure of di-isocyanates or polyisocyanates and dialcohols or polyalcoholes respecrively. Flexible and wiring cables subjecred ro parricularly high mechanical stresses or to chemical influences, e.g. from benzene or agressive, mostly aromatic oils (e.g. coaltar oils), are provided with a protective layer of polyamide or polyurerhane or/er the sheath or the insulation. These two materials are distinguished mainly b1 outstanding mechanical propcrties and good resistance to oils, fats, ketones, esters and chlorinated hldrocurbons. Pollamide protective covcrings arc applied to, among others. flexible and wiring cables for use in mineral oil extraction and in aircraft. Poll'amides are not suitable lor use as insulating materials, on account of their poor dielectric characteristics. but because of their high abrasion rcsistance and touqhness, together with their good resistance to organic solvents and fuels thc! are used as sheathins materials for special flcrible and rviring cirblcs. Polvurerhane sheaths har.e high inrpact rcsistancc. high fleribility at low rentperarures and,sood abraslon rcslstance.
A polymer of 2-chlorine-butadien shows a good resis_ tance against the influences ol light, oxygen and ozone and a very good resistance against cold, heat and flames. Its excellent resistance against chemicals, which is very high for a elastomer deserves special mention.
It
has, therefore, particular advantages for use as
a basic material for sheathing compounds.
The cables and flexible cables manufactured b1,Siemens uith a sheath based on polychloroprene are kno* n under rhe rrade mark PROTOFIRM. The mechanical srrength of the vulcanized compound is very hi-lh. therefore. these cables have an increased service life under mechanical stresses of any \_J. PROTOFI RM sheaths also offer advantages u.hire good resistance to seathering. flame rctardance and a certain ammount of resistance to oil is reo uired. furthcrmore where a clastomer is preferred to pVC compounds bccausc of its higher flexibility, rcsistancc to abrasion and tear cxtension.
-
Thcsc shcaths, thercfore. arc particularly suited for flcxiblc cablcs in undcrground mining applicarions and loc:rtions rrith fire hlzard Chlorosulphonl
I Potvethllenc (CSII)
is produccd bl,chlorosulphonation of pol),crh1lc'nc. The parrly cr)srallinc polycthylcnc is in rhis CS i\'1
Poll propl lene (PP)
is of lcss importance because of its brittleness ar lo\\' tempcrature and its special sensitir._ itr to t hermo-oxida tir e deteriorltion. eipecilllv rvhen in contrcr uirh coppcr. can onll bc emploved undcr Poly'prop1.'lene
limired conditions.
3.2 Elastomer Sheaths
ln
the Federal Republic of Germany, apart from use in * iring and halogen-free coblei *ith im.ships proveo propertres under fire conditions, elastomer sheaths are only used for rviring and f,lexible cables. Because natural rubber has only limittcd rcsistancc -1O
process transferrcd into an anrorphous clastonter. The cross-linkins can be established by using eirt-^r radical or conventiontl special sulphur compounu-. CSNI is alailublc:rs an industrial prodtrct undcr the tradc mark HYPALON (N4anulacturer: Dupont de Nemours International S.A.). Both. propertics and the ranqc of applicarion corrcspond to thosc of polvchloroprc-nc (PCP). hos,cver. CSlvl has improved properties as regards colour lastness and resistance to heat.
-
-
Chlorinated Polyethl.lene (CM)
CM is a new sheath compound with characteristics virtualll identical wirh those of HYPALON but u,ith rcduced flcxibility at lou' temperirtures. When blcndc'd g ith oth!.r !'lastontcrs soccial comoounds
-
Sheaths of Rubber for Special Purposes'
_
-
-
EPR or EPDM can be produced, e.g. by the use of tl" at low temperarure is improved' 9r',by t'lexibility '"i'tiiur-i",adien rubber the oil and fuel resis-
"t" tance is imProved'
Nitril-ButNdien Rubber (NBR) immersed in oil Cables which are ro be permanently on o.. o-tia"a with an oil resistant sheath based predominantlv is rubber ttti", (NBR)' Nitril "iitii il"a"a'with and is known for its good "r.i ,..ir,on". to oil. This resistance to oil is based on ii. o"i".i,v of the nitril rubber molecule' Nitril ruboils U", it ,ft.t.f"re highl.v resistive to non'polarised highlv,olt.nt, but docs sri'eil considerably in "i. polarised solvents'
ivc
rylh*!::l
sheath NYBUY and PVC'insulated cables with lead as locutions with ;;;;J r- ntting stations as well cables also have' i"" ona explosion hazard: these mechanical damas protectio; against corrosion and ogi. uo oot.. sheath ol PVC' 17640 For the lead sheath a cable lead Kb-Pb to DIN vrthe agatnst is used which is sufficiently resistant materi bration whictr are normally present' The base at for this cable lead is pig lead Pb 99'94. tots DIN 1719. To avoid a coarce grain structure thts of copper blended with 0.03 to 0 05% (by weight) { I tole J, r,.
_ 3.3 Sheathing Nlaterials for Special Purposes cables Sicmcns have devclopcd cablcs and llexiblc (FlamcunO". ,ft" trade mark SIENOPYR FRNC n"i"tO.n,, Non Corrosive) which hlve particulirrly: namell importanr characteristics in the evcnt of tire'
>
reduced support
ol
combustion cvcn
rvhen
bunched
Trble 3.1 Cable lead to DIN 17640' A base metal of Pb 99.94 to DtN 1719 with an additional 0.001% lvlg must bc uscd
nation
bl thc usc ol'spccial shcathing mrtcrials
base matcrials are olelincopol-vmcrc such.:ls flamc-retardent qualities' - VA or EEA. To achicve thcsc mctcrii.tls being normally combustiblc' ccrtaln hvdratc containing mineral tlllers are used' Thcrefore - satisfl the aboic requirements itll other additivcs such as lnriitging a!:ents are halogen-frce'
Ahe
3.4 Nletal Sheath Lead Sheath
Insulation materials. sensitive to humidity' e'g tmprcgnated, paper are protected by a metal sheath' Since the bcginning of cable mlnufacturing leud, s hich is crsl io hlnJlc. hls bccn the proven mrtterill tbr this pLrrDosc. Lcud covc'rcd PVC'shelthed cablcs
Kb-Pb Te 0.0+
Abbreviation Uscd lbr
Cablc sheaths rvhich tre subjected to l high dcgrcc
Wcak ullol cable shcuths: busc metal
> tirmes do not contlin corrosivc sttbstanccs > grcrtlv rcduced snrokc dcvclopmcnt > rctcntion of instltiltion r', hicvcd
Tellurium lead
D.sig-
lbr manufacturc of liloy clblc shci.I
of vibrution
ths
Componenls in % (b! rveightt Cu
0.03
5b
L
Sn
0.0i to 0.05
-0.05
o.orto remlindcr to
rcmtindcr to t 00?6
Pb
\{lximum umount of rddiLi\cs in
70
Ag
0.001 0.001
I[
0.050
Fe
0.001
\tg Sb
0.001 0.005
Sn Zn
0.005 0.001
: Thir
"
lcrd smeLlers Cu uddi(ion crn bc omi(lcd by irgrconrcnt bct!\r'cn
rnd cablc m:rnuilcturlrl
uprol)05'; ' iirt-*"i".rrr riupumx\ rlso hrlc :rn so conicn( ol
l9
Table
3,2
Features of Lead and Aluminium
Features
Cable lead Kb-Pb
to DIN Density
Aluminium for
640
cable sheaths
g/cm3
Ten
2.7
N/mm2
Elongation
!o 18 40 to 50
lo to zo z) to J)
4to5
5.0 to 6.5
13
%
Brincll Hardness to DIN 50351
HB 5131,2s130 HB 2.sl3t, 2s130
Melting point Specific resistance at 20
17
'c 'C
Thermal conductivity Specific heat capacity
327
55 to 65
z) to J)
roirr 658
Om
2t.4.10-8
K.
34.8
218
I m-l\
1.45.106
2.5 . 106
--i-;
2.84.
10
-
E
For cables u hich are to bc subjccred to hcavier vibration, e.g. cables for installation on bridges, rail*.ay, cables or aerial cables, Siemens prelerably use a leadtellurium-alloy to DIN 17640 (Kb-pb Te 0.04). The basis for rhis alloy is pig lead pb 99.94 ro DIN 1719. to u'hich at leasr 0.035% of tellurium is added.
To ensure these cables correspond to the normal ^, ,, core paper-insulated cables, the thickness of the >ro_ minium sheath is dimensioned such that the conduc_ tivity of the sheath has a value equal to or greater than that of the corresponding standardized neutral conductor.
The main characteristics of lead and aluminium for use as cable shcaths arc shorvn in Table i.2.
The good electrical conductivity of the aluminium sheath ensures a eood screening factor; the interfer_ cncc u,irh control cables and communication cables is therefore lower than that of lead-sheathed cables
Aluminium Shcath In the 1 940's Siemens AG rr.erc thc first manufacturcr to succced in pressing aluminium. *.ith its high stability and good conductivity. arouno a corc asscmblr.. u hich prcviously could only be done rvith lead. Afrer haling provcn their rvorth, cables rvith aluminium shc:rth wcrc included ar firsr in VDE 02g6,,10.56 "Spccifications for Metal-Sheathed power Cables on Triai " since 1964 for aluminium_sheathed cables. DIN VDE 0255 '.Specification for Cables s.irh Mass.lm pregnatcd papcr Insulation and MeralShearh in Powcr Plants'. applies. A. rcliable. corrosion prorccrion ensures
that the alu_ minium sheath is not threatencd even under unfa_
vourable conditions. Aluminium_shcathed cables arc installed in the same manner as paper lead cables. The.smooth soft aluminium sheattr-atio*s surncienitu small bending radii (see page 400). The good electrical conductivity of aluminium makes po-ssible
it
10 use the sheath as neutral conductor IPEN) in thee-pbase systems wtrh earrhed neutral point (three-phase four_wire sysrems). 40
(see page 352).
Normally cables *.ith aluminium sheath do not have to be armoured. due to the mechanical stabilitv of aluminium. This is of parricular imporrance in rhe
of single-core cables ivhere *,ith lead_sheathed l)'pes the mechanical protection could onlv be achieved by a relarilely expensive non-magnetic r"case
mour
Aluminium is not susceptible to vibration and does not tend to re-crr.stallize even at higher ambient temperatures. These facts make aluminium-sheathed cables particularly useful for installations u,here sub_ lection to heavy Vibration is to be expected. e.q. on bridges, alongside rails av tracks etc.
Conosion Protection 4.1
4 Protection against Corrosion
depending upon the requirements, a bedding o[ imprignated jute (NEKEBA) is applied' If for practical reasons, a polymeric sheath was not laid over selecte-d a layer of polymeric foil must be electroor chemical of the armour if there is danger
po"ver cables Meial-sheathed as rvell as armoured corroslon' agalnst protection must be provided wirh
4.1 Cable rvith Lead Sheath
F-
lytic corrosion (NEKEBEA)'
.ius \laterials in Bituminous Compounds
Pollmeric Outer Sherth
(J rutrntouretl C ubles
1^protection against corrosion consists of several tt- -rs oi bituminized paper and one layer of pre-
neuimpregnated jute, rvith intermediate coatings oI tr"i biiurninout coatings (Asphal0 The outer surface is white-rvashed to Prevent sticking of the cables rvhilsr on the drum. Norvadays this type o[ protecuon aqainst corrosion is onl.v rarely uscd lt is increasingiloieferred to use a plastic sheath bondcd to thc lead sheeth b1 a suitable comPound
Annoured
The PE outer sheaths of medium- or high-tenston cables are alrvays coloured black (see page 395)'
of
Table4.1 shors the colour DrN VDE 0206.
outer sheaths to
C ables
Beked cables are provided with a protectlve lnner covering over the lead shelth consisting of several layers oi bituminized tlbrous materiai rvith intermediatc lalers of bituminous compound This protecttve rer covering serves also as bedding for the armour' a lal er -\e armour is prorected lsainst corrosion by surtace outer The ., jute in bituminous compound. is *hite-rvashed. This tlpe of protection agalnst cor''-rsion is sufficient under normal conditions' heav,v chemical or electroll-.ttc corrosion at least one la-ver of elastomer type or pot)meric foii hxs to bc provided in addition to the tapes
tf there is a danger of
oi tlbrous m:rLeri:ll. unless the clble is protecred c.n
reliable corrosion protection is provided by a flame sheath of PVC which is chemically stable and abnorto retardent. Cables which are to be subjected mal stresses. either in operation or during installation a PE-sheath or a reinforced PVC sheath to DIN VDE 0225 can be Provided'
A
b1
outer polymeric sheath.
Table
4.1
Colour of outer sheath
PE outer sheath
\ledium and high-voltage cable PVC outer sheath
Separate Lead-Sheathed
(
S.L.)
Cables
Separate lead-sheathed (S.L.) cables have, over each lead sheath. a bitumen layer and a layer of polymenc tape rvhich is lollorved by a further layer of bitumen
compound and one layer of bituminized tibre tape. Ol'er the touch protected and laid-up cores an inner protecii'.'e shearh of puper- or textile tape. and (or).
Lorv-voltage cable
0.6/1
Black
Low-voltage cable [or mining applications below ground
0.6/
Yellow
lvledium- and high' vokase cable
1
> 0.6iI
4.2 Aluminium-Sheathed Cables Whilst being exceedingly durable when installed in free air, aluminium has to be protected by a water and ion-resistant anti-corrosive covering, if the cable is to be installed in the ground. In order to achieve a high degree of salety and mechanical strensth a multiJayer corrosion protection is required. According to DIN VDE 0255 Type A5 it consists of a plastic foil applied overlapped and bonded to the aluminium sheath and to the outer pVC sheath bv means of bitumen compound. Special tests show that the corrosion protection adheres well to the aluminium sheath and that in the event of a locally limired damage to the cable eventual corrosion on the outside of the aluminium sheath is practically limited to the exposed area.
.11
Armour
5
Armour
5
-fh.
orrnou, protects the cable against mechanical for rated stresses. In ,h. a"r" of polymeric cables above Lfo/U:0'611 kV it normally serves -voltages llso as an electrical screenlng' arPaper-insuhted lead-sheathed cables are normally apeacn tapes' steel *'ith trvo compounded -rnorrred in ol'. ln open helir in such a mlnner thill the ."cond tapc corers the g:rp left b;- thc firsc' -High-r'oh,rge crbles wirh polymer insulrrtion having
sysSingle-core cables in single'or three-phase a'c' **-, ur" not armoured as a rule, in order to avoid addirional losses. An armour of non-magnetic material. however, has to be provided wherever mecnanle'tcal demage or higher tensile srresses are to be pected du-ring or after laying of the clble Occasionaliy rntr.-itpr-.gnated or oil-filled cables are manuflactured sith an open armour of steel wires' inste:rd of a non-magnetic armour. tor reasons ot economlcs'
iallic a-opp". ,"ta.n as rvell as low-voltage cables s: PVC or XLPE insulation and alumintum-if a
-sheathed clbles do not require to be armoured they are sufficiently protected against damage and noi.uUj..t.a to tensiie stresses' The permissible pull - during ia1-ing of cablcs is shorvn on p'rge 406' An armour of flat-steel wires may also scrvc as a screen in multi-corc cablcs r"irh polymcr insullttion
-
not having a screen ofcopper' This design is common for PVC ilbles ior 3.5 6 kV. *here ;t scrccn lrounll each core separately is not rcquircd' irnd illso fLrr cubles to be installed in nenvorks rvhcre doubic carth-
earth-faults in earthcd ncutral s)sterns rcnticr ltn :lrmour ot'stccl rrircs ltdvltnt;tgcoLts in its firncrion as a commoll mctallic screen (scc also
Iiruits
-
or
^" ltc -n i
-
(;$les
!..,
).
lre to b!' itlbjectcd to highcr mcchlnl(especialll tensilc stress) must be 1r'
\\ hich
stresscs mourcd rrith salvanized stcel uircs' The right protilc I'g. tllt. round or "2"-rvire). dimensions lnd ...icnsth ol'thc $ires hits to bc choscn according to thc size :rnrl applicarion ot'thc clble' e g as rirer cable. submarine citble or shati cable (see pages 129 rrnd ll0t. A stccl t:tpc hclir prercnts bird-cageing of the * ires.
.+-)
o Loncentnc conductors
6
Concentric Conductors
The concentric conductors in low-voltage cables such as NYCY, 2XCY, NYCWY and 2XCWy are used as PE or PEN conductors (see page 397) and at the same time form touch protecdon. Accordine to the VDE specificarions these must be of copp-er. The cross-sectional area included in the type desienation. houever, relates only to the material used for the phase (main) conducrors.
in a cable
u.ith copper conductors. for cxamole. NYC\\'\' 3 x 95 SM,50 0.6. I kV. the value of diiecr currcnt reslsttnce of the conccntric copper conductor. to comph * ith thc abovc rc-,qulation nust not be greater than the maximum value of that of a cooper conduclor of 50 mmr. Similarly in a cable wiih aluminium conducrors NAyCWy 3 x 95 SM,,9i 0.6/l kV lhe value old.c. rcsisrance of rhe concenrric
copper conductor, to comply u,ith thc above recula_ tion, must not be greater than the maximum of that of an aluminium conductor of 95 mmr. ""alre The concentric conductor compriscs cirhcr
I hclicallr applied layer of copper sires or a ulve form llrcr of copper uires r CEAN DE R-crblr., ) c.g. NYCrif:
or 2XCWY. In addition a copper tapc is applicd
hclicalll to interconnect thc \\.ircs (transvcrse helical tapc). In rhe Fedcral Republic of Gcrmlnl. alumin_ runr rs not permitted for use as it concentric conduc_ tor.
tll
Concentric conductors are arranged under the outer polymer sheath to ensure they are protected against corrosron. ll armour is arranged above the concentric conducror a separarion sheaih limperviou, sh.eath) of PVC musr beapplied Uer*..n ttern. "*,.uJLJ (iyp. relerence desisnations for concentric conductor sLe page 101.)
Electrical Screening- Conducting Layers 7'1
7 Electrical Screening
with Electrical screening is necessary only for cables functions: Uo>0.6/1 kV and fulfils the following Potential grading and limiting of the electrical
>
I
> p
lelo
Conduction of charge and discharge currents .
ouch Pro tectlon
To satisfy these functions the screening normally" comorises a combination of conducting lay-ers rvith
,1lic
elements. One differentiates between cables ru-r non-radial characteristic fields (e'g' belted cables) and radial field cables. The rldial charactertstics of lines of held between conductor and screen is achieved by placing a conducting layer' I metal screen or a metal sheath over each individual core' Insulation is stressed only perpendicullr to the rvall (papcr thickness. In cables with laminated dielectric elcctriinsulation) this is the direction of the highest cal withstand. Interstices of the corcs in thcsc cablcs remain field-free (see Page 97). t) 7.1 Conducting LaYers
Thc magnirudc of clcct.ric strcss rnd thc dcgrcc of .sitivitl of thc insr-rlation mtterinl ilg lnst pilrtlal govern the tvpe of screening of the insulit-chrrrge !ron with conducting la]ers (Table 7.1). rble
(H-foil), if necessary in combination wirh conducting pop"t. it can also consist of a combination of aluminium tape with conducting Paper tapes' Cable with PVC Insulation
The "inner conducting layer" consists of a PVC
compound having a high carbon-black content' This is normally applied togerher with the insulation in a single production process so that both layers are bonded firmly without gcps or cavities'
For the " outer conducring layer" elastic conducting adhesives with a cover o[ conducting tapes (textile or carbon black paper) is a preflerred mcthod' Cable rvith PE or XLPE Insulation Bec::use
of the higher sensitivity of PE and XLPE
insulation to partial discharge the reliable ''lell adheilolc /. I Arrangement of conducting Layers above and beiorv lhc cable insulation I
belorv the in
conducting
laler over the conductor)
The "outer conducting layer" normaly consists of merallized paper. also known as H6chstidter Folie
I
mpregnated PlPer
t) belted cable radial field cable
Pvc
insulation (outer conductlng lir!'erl
kV
KV
3.7 l0 3.7 15
3.6i6
Lio,'L'
6i 10
EPR
6i10
PE
3.616
XLPE
3.6i6
r' tn thri boot rh\: rn]plcr rcrm .onducring h)_cr' hrs bccr ujcil ini(crd ol rcmrconllucrrng trt!r chosc in rh\: r\s0cct.i!c IEC jtinJrrJt
above the
rlted voltages excecding
Thc "inncr conducting la.ver" consists of scleral ielcrs ol'semi-conducting paper (llso kno"r'n as cat-
it
sulrtion
(inner
rrith Paper Insulation
bon black paper). This is often retlrred to as conductor smoothing because is used to smooth local peaks in the electric field rvhich could otherrvise oq' cur. e.g. because of irregularities in the surftrce of stranded conductors.
Conducting la;-ers required
Tl pe of insulution
wilh non_rldill tictd: p"missiblc only for rlled toit,rg.. Lo Ci<3.? l0 kV. In C..mrny bellcd cabl's irrc nodnrll/ useo tbr voitilgcr 1,, C'<6,10 kv l*c prge l'l$) Paper-insul:rted cablc
45
7 Electrical
Screenins
> A layer of copper wires with a helix of copper tape or tapes aborc thc laid-up individuattv
sive eap and cavity-free bonding to conducting Iayers
is of greatest significance for the life expectancy of the cable. DIN VDE 0273 requires proof of non-partial discharge for each individual cable length for a voltase range up to 2 Uo and with a measuring sensitivity of <5 pC.
screened cores (transverse helical tape) which mav be each screened with conducting layers or;
DA
layer of copper wires with a helix of copper tape or tapes or a layer of copper tape oter-each indiuidual core which may be each screened with conducting layers; or they are
The "inner conducring layer" normally consists of a polvmer compound which is made conductive bv adding carbon black and is, together with the insulation. applied ro rhe cable in a single manufacturing process and in the case of XLPE cable, cross-linked
>
Metal sheaths (e.g. paper-insulated cables) aboue each inditidual core or above the laitl-up cores which may be each individually screened ty mer_ alized paper; or
>
Steel-wire armourins (e. g. in cables ,,vith polymer sheath) ouer the laid-up individually screened cores; each screened by conducting layers
r,r'ith the insulation.
The "outer conducrin_e layer" is formed by rhe insulation and a laver of conductive polymer compound bein-e simultaneously applied to the cable and in rhe case of XLPE cable. cross-linked. This from a technical viovpoint is rhe most favourable solution *,here rhe conducting layer is firmly bonded to rhc insulation and rcquires a special tool to remove it durine cablc. installltion. In anorher variant rhis l.r_ver cai bc rcmoved bl hand after picrcing ri ith a tool.
In thc Fedcral Republic of Germanl, it u,as previous practicc to use cabics in rvhich thc outcr conducting Iaycr consisted of graphitc rubbed on rhe outer surface of the core *'ith a conducring tape applied ovcr it. This graphite required a special solvcnr to rcmovc it during installation. Thc nov regulation DIN VDE 0273'..87 does no morc include this r.ariant. Cablc
rr
t
In contrast to lhe rules for concentric conducto)./ for copper screens ir is not the elecrrical effective cross section which is the important factor because
*'hen considering earrh fault or short-circuit stresses (see page 287) the geometric cross secrion is the morc significant (Tablc 7.2). Screens are arrangcd belorv the outer poiymcr sheath to providc protection against corrosion.
If armouring is provided above the copper scrcen thrs must alwavs bc separatcd from thc scrcen b\' ln inrpcrr ious sep;.rr:llion shelth of pVC,
ith EPR Insulation
EPR is lcss sensitivc'to partial discharse in comoarj\\ith PE and XpLE bLrr hcrc ulso irincr lnd outer ',()n conducting larers of poll.mer compound must bc providcd und firmh.bonded ro thc insuhtion.
t
Other materials (e. _s. aluminium) are not acceptable. parricularll in Germanl .
Table 7.2
\'linimum cross-sectional areas of screens to VDE (geometric cross scction )
\ominal cross-sectional of main cond uctor mm:
l}::llft.omponents
of Etectricar
ti i-j
e. q.
ovcr the circumlerthe transmission of these currcnls ln the loneitudinJl dircction ol rhe clble ro_ $ aros.the.earthed point. additional elemenrs having a suDstantially los.er specific resistance n...rr..1i "r. This function is performed by metallic screens u.hich are ln ,,r.ith the conducring lalers. contrct relectrical L.rependlng on cablc tr pc thcse are: 46
Nominal cross-sectioni
arel of ntm I t6 16
70
16
1?0
to to
150 185
_)
240
i) -
300
t)
,:100
I '
screen
l6
50
The resis.tance ol'conductinc lavers is sufficienr ro ,n. rerl small parrial charge and dischrrge ::l-.:-"] currents ovcr small distances. cncc ol the corc. For
area
i) "
''
3_i
r u.orj scclion of t6 mm: rs pcimrrrrrl Forsincle-corc crblcs lrid in canh !cro\r sccrion of t6 nm, ij ircrmitlcd For cabies luid in c:rrlb
Metallic Components ' Screens Resistant to Water Penetration 7'3
-
Type designations of screens see page 101; details curreni carrying capacity of screens in the event -foi of earth fault. double earth fault and earth short cirsce pagc 281.
_cuit
5
7.3 Longitudinally Water Proof
-
Screens
conditions are to be considered (e' g subruns with great height differential' damage to outer sheath) additional measures can be - taken. To avoid rvater penetrating the cable through damage to the outer sheath rvhich could, in the area the screen. spread over a large distance it is pru-''] of ' ,ir to use cables which are protected against $ater peuetration in the screen irreas. To achieve this proiection thcrc are scverll constructional possibilities' ] e.g. in the screen arer absorbent porvders or lapes clbe added *hich srvell in the event of moisturc in-:s so thirt all c:lvities and g:rps are filled and the - longitudinal spread of moisture is limited'
If
"*rr"." cables, marine
I
In ir construction devclopcd by Siemcns thc scrcenlng embedded in unvulc:rnised rubbcr. Thc gap '.vires are sealing betrveen screen wires :rnd thc extrudcd outer conducting layer is irchievcd by a bolster of lor"-con' ducting moisture srvelling ltbres or a cotnbinlttion of low-conducting crepe pxper r"ith a tlpc of nonconducting moisture srvelling fibrcs. This bolstcr also cnsures electricll contac! ol'the scr.'en rvircs lith thc outcr conducting lirycr abovc the- insttlittitln. Outcr nrcchunicul protcction is proridcri in cach clsc b1 lr tough PE shcath (Fig. 7.1).
This t! pc o[' construction has signiticlnt advilntlgcs \ -r thc simplc longitudrnrtlll $;ttcr prool rltriltnt lclling tapc or srrcllins poldcr) irnd c"cn thottgh ^...' marginlll'more costly has rcccived good murket acccptancc. The special advantages of thc inncr cover, ol' unvr.rlcanized rubber irrc:
>
good adhesion to thc PE shcath rvhich limits the unavoidable shrinking of PE shelth to a negligible dcgrec:
>
protcction of the othcr component pilrts of the cable when. in the event of shorr-circuit or double earth short-circuit, the screcn cln attilin a relotive' ly high temperature;
>
additional barrier against ingress of moisture from minor damage to the sheath when in such an cvent thc moisture is prevented from re:rchtng
l
Conductor
2 Inner-conducting IaYer 3 XLPE insulation 4 Outer extruded conducting layer 5 Semi-conducting crePe PaPer 6 Swelling tape 7 Copper wire screen 8 Helix of copper tape 9 Inner covering of unvulcanized rubber
l0
t' l I
i
PE outer sheath
j
Fig. 7.1 Single-core cable rvirh XLPE insulation. longitudinall;.' waGr proof screens and PE sheath Type NA2XS(F)
lY
Ix
150
Rill 15 6. l0 kV
If transverse sealing of the sheath against diffusion of moisture is required as e.g. rvith high-voltage
cables r',ith rated voltage UolU>36160 kV, an aluminium tape. plastic coatcd on one side only' is applied in a longitudal direction bctrvecn the PE sheath and the coppcr scrcen. This is closcll- bondcd to the PE sheath at the overlapping arca (AI pcth-shcath). Thc area surrounding thc scrccn is tillcd u ith swclling porvdcr. A further possibiiity *'hich is plrticulari)" suitable tbr submlrinc c:rblc is it mctal sheath 1e. g. Pb. Al) * hich normalll' mlkes a coppcr screen unnecessar\'.
ttlc inner core and the longitudinal sealing (ssell'I
',) n...i
.t1
Ths power-supply cable to a mobile container crane is subJscted to frequent reeling and unreeling and also to nt-sh-mechanical stresses. PROTOLON trailins cables which are service-free
o{Ier safety in operaiion and long service life even under such extreme conditions
Types o[ Wires and Cables 8'1
Insulated Wires and Flexible Cables li I I
I
l.
- 8 Types of lVires and Cables -
8.1 National and International Standards porver lnsulated wires and flexible cables for electrtc installations must be capable of rvithstanding the st. -ses experienced during both installation and in operrrion. ln a typical normal plant. containing fi'red^ .ubl. run, and itirh provision lbr the connection of nAile loads, this cln bc bcst ensured by using cables r'1 'h comply *ith the relevant nationsl or international srandards, not only rvith regard to construcrion irnd testing but also to the parlmeters and limitrtions lbr the iype ol applicrtion For spccial applic:rtions only cables which comply, in thcir conslruction and ciaracte.istics, as close as possible to VDE or IEC specitications should be uscd'
Intbrmation for the sciecrion of cablcs is given on
8.1.1 VDE SPecifications
The mlin VDE specificutrons govcrning c()rlstruction. tcsting and applicltion of ilcxiblc cablcs arc: DIN VDE 0107 Insulating and shetth cornpounds for cabl':s and tlexiblc cords DIN VDE 0150 Cables. rvircs and flt'xiblc cords tbr Pou er inst;.rlia cion
^:t
voE 0lS I PvC
61$1g5.
rr
ircs rrntl ilcxiblt'
cords for Porver installl tion DIN VDE 0lSl Rubber cables. wires and flcxible cords tbr Po*er installnlion l)lN VDE 0139 Detlnitions tbr cables. lvlrcs ilnd flexible cords for porver installution DI\ \'DE 0l9l Idcntificetion ofcores in clbles and tlerible cords used in porver installations with nominal voltages up to 1000
v
DIN VDE 0295 Conductors
of clbles. wires
and
flexible cords for power installation DIN VDE 0198 Application of cables, wires and Purts 3 and 4 flexible cords in porver installations DIN VDE 0171 Testing of clbles. rvircs lnd l'lc'xible c..-:::
When the VDE Approvat Organization verihes that a flexible cable complies with the relevant VDE specifications it authorises the use of a black-red printed identification thread. A second identification thread is used as a manufacturers mark which shorvs for the products of Siemens AG the colours green-rvhite' red-rvhire. As an alternative to the identification threads or in addition to these the mark dVDE ) and the manufacturers lrade mark may be printed or embossed on the cable or sheath ln special cases the clbles are marked *irh r rvord lrldc murk or by r protected trirde merk such:rs. in the case of Siemens. a coloured line over the full length of the sheath. At the prcsent limc therc are no VDE specificalions to covir the cables shorvn in Sections 8 21 to 8.4 horvever, in producing thcse cablcs' the su[et1' technical requiremenls laid dorvn in VDE are ad' hercd to such that all types of construction compll' with thc principles of these rules. ouge 55.
8.1.2 Harmonized Standards''
It is thc rask ol the Europenn Committec tbr Elcctro' tcchnictl Standardisation (CENELEC) to rcmovc rcchnicirl bJrricrs to trldc bctr"ccn mcmbcr countries
*herc diflering standrrds. nittional resulirtions or approvll proceedurcs crist. \\'ithin thc committee ecch ioun,tj it represented bl its national delegates (representatives of consumers. mtnufltcturers and standrtrds org:rnislrtions) $ho prcpirrc I b;rstc hlrmonization document rvhich. after a pcriod for public commcnt. is used as a basis tor a final harmonized document rvhich is then issued and brought into force' The relevant nationrl committees are then obliged to ilccept the contents ol these documents without deviation or addition and introduce them into their relevant national standards system.
if..liiiiu"int,or,t. i:",tr:."-i"",tf
"n,f
L. r
Rcrzhil. E.: \\'drncr. A.. Hlrmoniricrung dc. Boolilct ll. vDe-Vcrhg cmbH
-leilunr.n
+9
ii i I
6
r yPes
or E'lres and cables
CENELEC harmonized documents cables are:
for
flexible
HD
21
Pollvinyl chloride-insulated cables of rated volrages up to and including 4501750V _ Part 1 up to Parr 5
HD
22
Rubber-insulated cables ofrated voltages up to and including 4501750V part 1 up ro Part 4.
-
These documents together with the associated amendments are aimed to achieve world-wide approval of rhe relevanr IEC srandards (see page 55.y.
In the Federal Republic of Germany they are published and in force as:
DIN VDE 0281 PVC cables, wires and flexible DIN VDE
0l8l
cords for porver installation Rubber cables. *,ires and flexible cords for polver installation
The national standards DIN VDE 0150 for rvDes of construcrion. rvhich are replaced by rhe above har_ monized standards, have meanwhile been with_ drawn.
The harmonized standards relate firstly to the most commonly used cables such as insulated u,ires and flexible cords. For these a special marking was a-greed containing rhe letrers
or ahernarivel;; harmonization thread coloured black-red-yello*.. This marking rogerher $,ith VDE mark. authorized by thc approval organization. and the manufacturcrs nrark is sho*.n on the insulation or sheath. hcnce products of Siemens AC are marked e. g.
SIEMENS
lf identification threrds are used the nationalirv of thc ap-proval organization can be dererminea fiom' thc lengths of colours on rhe thread (Ta^differing ble' 8.I ).
Thc marking is approved b1,the CENELEC member countnes ln accepting the HAR approval proceedure. The use. of wires, cables and cords marked in this manner ts accepted by these countries without further approval:
(B)
Belgium pederal Repu.blic oiGermany
Denmark (DK)
(F)
Unired kingdorn Ireland
QRtl
_i0
ognise the harmonized standards but their use in
these countries requires individual approval.
Type Designation
In order to avoid confusion due to language a new common system of type designations has been agreed. Inirially this system will be used only for harmotized cables and approved supplementary types. This consists of three parts (Table g.2). The first parr identifies the regulations to which the cable has been manufactured and the rated volta_ee. The letter " H " indicates that rhe cable in all respelts complies u'ith the harmonized standard. A lettei .e, is used ro indicate that the cable complies basically uith the harmonized standard but is only "pprou.d for use in a specific country (approved national supplementary rype). vohage is expressed by tu,o a.c.
Ln:,:,:O uo,' u wngrg: Uo
volra,*
is the r.m.s. value between any insulated conduc_
tor and earth and
Marking
France
The countries Finland, portugal and Switzerland rec-
qgg) \'r\.'
/r, (D) ii.irr,Jril"a, tNI_l r
,. r,,
NorwaY (N) Austria (A) SPain (E)
Ss eden (S)
U
is the r.m.s. value between any two phase con_ ductors in a multic-core cable or in a svstem of single core cables.
The second part contains the abbreviations for component parts. The third part contains information on the number of cores and rated cross-section as u'ell as indication uhen a protective conductor (green-lellorr) is included. For harmonized flexible
cables the presence of a grcen-1,ellou core is nb.loneer indicated b1 rhe letrcr ..1" or s.hich previou-slv rr as uscd as a suffix ro the tvpe designation.
..O
National and International Standards 8'1
Table
8.1
Approval authorities and harmonization marking Harmouization marking either printed or embossed
Country and approval authority
Harmonization marking by black red yellow identihcation threads (colour length in cm)
black lred CEBEC
Beleium
lYellow 1
Coirite Electrotechnique Belge (CEBEC) Federal Republic of Germany and West Berlin v.iU"na Deutscher E lektrotech niker (VDE) e' V ' Priifstelle Denmark
f
.arks
I
3
Elektriske Materielkonrroll (DEMKO) USE
France
il
1
I
Union Technique de I'Electricite (UTE)
L
,nd
5
lEtvlNlEQU
5
KElvlA-KEUR
3
NElvlKO
7
5
5
institute for Industrial Research and Srandards (llRS) Italv tstiiuro del Marchio Qualita (lMQ) Netherlands
N.V. tot Keuring van Elektrotechnische Materialien (KEMA) Norwey Norees Elektriske M ateriellko
nrroio Orr"rr.l.ttir.t
".
nt ro
ll (NENIKO)
Verband fiir Elektrotechnik (OVE)
Sweden
SENIKO
s' enska Elektriska Nllterielkontrollanstalter
. ivrKo) -Jilln Asocilcion Electrotichica v Electronica Esp'rnola (AEE) rited Kingdom British Approvals Service for Electric Cables
OUNEO BASEC
.I
3
5l
-us v.rulgs Table
8.2
System for cable designation for flexible cables to harmonzed standards
EIemen6 of the description
Part I
ffi
Standffds Harmonized type Recognized national type
tl
Rated voltage UolU 300i300 v 300i500 v 4s017 s0 v
I
---J
07
Insulation PVC
Natural andror styrene-butadiene Silicone rubber
v
aubba. -
Sheathing PVC Natural and or styrene-butadiene rubber
Poll'chloroprene GIass-fibre braid Texrile braid Textile braid u ith flame-retardaru qompound Special constructions FIar. divisible
Flar, non-divisible Cen rral he:rrt { non-strain_be:rring
R
N
_
)
D5
Circular solid (risid) Circular stranded (rigid.y
oi rec::sr roiil"o *,,"rr,,ro* oi IEC l:8i ior. n.riUt" crblc> _ Highlr flerible rCles 6 of tEC I jti) tbr s
j
Itc\lblc cables
-\'
Ntt. of corcs
l'rotcctile conductor \\'il hout green vellorr corc rlrtn grecn, r,ellorr core Sizc of conductor
cxrntptcs of t).pe desicnations
,i;i,T:"il:l-:heathed
clbre ror -ccncrar purposcs
r", r'llll;Y l;iil] 3::'t l1':^l **..-,n*,n.. *irh green vellou.core
;,_::::,i.-,
-R -K -F -IJ
Tinsel conductor
i,,1f; .... . .s,u 5uuq conductor
T T2 H H2
Conductors
!l:^i:1. lgi"', Flexible_(Clas
R S
H07RN_F 3c2.s
;:ii'il;:":lliiledcircurarcord.,-'l;;rl:llJlft1.;
rJ
Part 2
Part
3
Harmonized Standards 8.1
8.3
Table
Summary of cables to harmonized standards
Cables
to DIN VDE
0281
Type abbreviation
Rated voltage
No. of
Nominal
cores
cross-
Superseded types to VDE 0250
sectional area
UolU
mmz Single-core non-sheathed cables
for internal wiring - with solid conductur - with flexible conductor
H05V-U H05V-K
300/500
with rigid solid conductur wirh rigid stranded conductor with flexible conductor
H07V-U H07V-R H07V-K
45017 50
rat linsel cords
H03VH-Y
300,'300
H03VH-H
Single-core non'sheathed cables for general PurPoses
F
Flut non-sheathed cords
;
',r PVC-sheathed cords
-,,rcular
-
lli.r
t
Ordinary PVC'sheathed cords - circular
Flat PVC-sheathed flexible cables lo lilts and simihr aPPlication
0.5 to
NYFA, NYA NYFAF, NYAF
1
1.5 to l0 6 to 400 1.5 to 240
NYA NYA NYAF
1
-
NLYZ
300'300
1
0.5 and 0.75
NYZ
H03VV-F H03VVH2-F
3001300
2ro4 2
0.5 and 0.75 0.5 and 0.7i
NYLHY rd NYLHY fl
H05VV-F
300i 500
Ito)
0-75 to 4
1
H05VVH2-F
300/500
)
1
0.7 5
NYMHY rd NYMHY rd NYMHY N
HO5YVH6-F H07VvH6-F
300i 500
3to24
0.75 and
I 1 1
0.1
to
to
16
0.5 to
16
1.5
450r7i0
2.5
1
NY FLY NY FLY
Cuhles
to DIit' l/DE 0)31 llcut-resistant silicone
:tlili'b9_;.rided cords
HO5S.'-K
j00
500
H03RT-F l:oo':oo H05RR.F
300'500
narl- po I vchlo ropreneshclthcd cords
H05RN-F
300r500
v;- po lvchloroprencsheathed flexible cables
HOTRN-F
,..,
rd i nlr-v.. to
u
gh-rubber-
shcathed cords 'd
i
H ca
450,',750
I
I
l2and3 Ito)
0.7
i
to
1.5
0.75 to 2.5
N]GAFU NSA
NLH. NVIH
3and4
4and6
I
fandJ
0.75 and I 0.75 and I
Nivl Hdu Nlvl Hdu
4
0.7 5
N Nl Hou
.5 to 500
I
1
2and5 3and4
1to25 1to 300
4ro24 4to24
0.7 5
4to24 4to24
0.75
NNIH. NMH6U and NSHou
Rubber-insulated Iift cables for normal use
-
braided cables
armoured cables
HOsRT2D5-F HO7RT2D5-F
H05RND5-F HOTRND5-F
3o0i soo
450/750 300/5oo
45017i0
1
1
NFLG NFLG NFLCC N FLGC
5i
Table 8.4
Comparison of flexible cabres to harmonized shndards DIN vDE 02gr and Type of cable
Cables to
DIN VDE c:- -r^ ^-_-s rrux-snca[osq caDles Ior lnternal wiring ',r-yrE-!ur - with solid conductor - x'ith flexible conductor
*'irh rigid solid conductor
r'ith rigid stranded conductor uith flexible conductor
Flat tinsel cords
-----_.-.-
-.......--.........."o.d. ..---=-....."=.Light PVC-sheath.d "o.d, - circular flat Ordinarl' PvC-sheathed ;-d;- circular - flat Flat non-sheathed
Flat pvc-shearheo fl "*ibl. lifr and similar application
"ullill.-_.._.-
02g2 with IEC
Superseded 0281
Comparable construction
types to
DIN VDE
O25O
H05V-U H05V-K
NYFA, NYA NYFAF, NYAF
H()TY-U H07V-R H07V-K
NYA...e NYA...m NYAF NLYZ NYZ
Jrrrsrs-Lurs u(.)n-sncatneq caDtes lor general purposes
-
DIN vDE
H03VH-Y HO3VH-H
tough_rubbcr_sheathcd cords
c:rblcs
H05VVH6-F HOTVVHGF
NYMHY NYMHY NYFLY NYFLY
f'I
exist. nrmelr.
a number
' li';;,::i:i;J!:j:;:: na,iona, ,vpes which approvgd narional rypes u.hich are an addition ro the
I" ::HT ",
p..,.
;
f3fl l?' "# ;i', i"r;';A,ffi :.T h
:,
--
:
i: ." i!;.1;1 o, n.,
::,i: ::,:,,
1r<
NSA
245 rEC 5l
H05RN-F HOTRN-F
l.-t National Tl.pes ,.r
<,)
245 IEC
HO5RND;F
::i{"
Fa
HO3RT-F
HOTRNDs-F
approved hirmor
I
N2GA FU
H05RT2D5-F
rhose cabtes shou,n rn Tabtc 6 or natlonal t1.pes
^1
HOsSJ-K
HOTRT2D;F
rmourcd cables
a)
))1 lE t-
Comparable consl.ruction
0282
NLH
l.
0i
NM II
245 IEC
5i
245 IEC
53
NMHciu
14i tFa il
NMHou NSHriu
braided cables
A.
,)7
truoncr rnsuluted Iift cilbles for normal usc
:ff::,lr-"T
))1 rEt-
H05\'1'-F H05\'1'H2-F
H05RR-F
vr(lrnar)' polychloroprcnc-sheathcd fl exiblc cublcs rr sr\ \ porlchloroprcne-shcathed flcrible
d.
227 IEC 02
l^ I tra
Heat-resistan! silicone-insulated cables Drstoeo cords
a
227 IEC 0l 227 IEC 0l
l)? lFa i1
Cables to
-
227 rEC 05 227 IEC 06
H03\'\'-F I nvr pv,,r Ho3\'\'H2-F I Nil;jy ii
DIN VDE
vrqlnilrl
to IEC 227
245 IEC
6i
245 I EC 66
N FLC NFLG N FLGC N FLCC
o1 a.pproved national tvpes tne harmonized tvDes: 'ho.,"
----.-.-uhich deviure lrom
natiolal types which not yer bcen embraced by,rhe .harmonizarion procedurc. e.g. flexible caDles wtth a rated volta-se > I kV as wellas muhi_ core cables for fixed u.iring for which harmoniza_ rlon ls not yet finalised.
All tables mentioned in 1 and 2 are however covered b1'VDE specificarions, carry the VDE ."**;;;; are only approved for use in the Federal n"juUIi.
of Germanl'.
National and Internationat Standards ' Selection 6f Flexible Cables 8.2
8.1.4 IEC Standards The following IEC publications are current in respect of cables:
rEC227: "Polyvinylchloride-insulated flexible cables and cords with circular conductors and a rated voltage not exceeding 750 V
"
1 Sheathed cables for fixed wiring. 10 Light polyvinyl chloride'sheated cable cables for light duty. 41 Flat tinsel cord 42 Flat non-sheathed cord 43 Cord for decorative chains
4 Non-sheathed flexible
5 Flerible cords for normal
51 Braided cord 52 Light polyvinyl chloride'sheathed cord 53 Ordinary polyvinyl chloride or tough'rubbersheathed cord 57 Ordinary polychloroprene or other equivalent synthetic elastomer-shearhed cord
tEC 245: " Rubber-insulated flexible cables and cords with circular conductors and a rated voltage not exceeding 750
'
V".
to IEC correspond in construction lvith rhe rypes listed in Table 8.4 to DIN VDE 0281 and DIN VDE 0282. They differ in some cases in dimenre cables
Ans
and test requiremenis.
r
the IEC standards cables are identificated by trvo numbers preceded by the abbreviated title of the relevant IEC standard. The first number designates the basic class of cable, the second the specific type rvithin the basic class. The class separation of 'medium' and 'light' does not comply with the classiflcations
in DIN VDE.
dutY.
6
Flexible cables for he'.rvy duty.
66 Heavy polychloroprene or other equivalent synthetic elastomer-sheathed flexible cable
7
Sheated flerible cables for special duty.
70 Braided lift cable 7l Flat polyvinyl chloridc-sheethed lift cables and cables for flexible connections 74 Though-rubber-sheathed lift cable 75 Polychloroprene or other equivalent synthetic elas' tomer-sheathed lift cable
8
Flexible cables for special appiication
3l
To ugh-rubber-sheathed
arc
r.r'elding electrode
cable
82 Poly-chloroprenc or other equivalent s;"nthetic elastomer-shcathcd arc $ clding elcctrode cllble
0
Non-sheathed cables for lixed rviring. Single-core non-shcrlhed ctblc rvith rigid conductor lbr general purposes 01 Singlc-core non-shcathed cable rvith llexible cond uctor for general purposes He:rt-resistant silicone-insulated cable for a con-
0l
' ^03
ductor temperature of maximum 180 'C 05 Single-core non-sheathed ccble rvith solid conduclor for internal for a conducior temperalule "viring oi 70 'C 06 Single-core non-sheathed cable with flexible conductor for internal rviring for a conductor temperIrure of 70.C 07 Single-core non-sheathcd cable rvith solid conductor for internal wiring for a conductor temperature oi l0i .C 08 Single-core non-sheathed cable wirh flexible conductor for internal wiring [or a conductor temperarure of 105 .C
8.2 Selection of Flexible Cables When selecting the type required the relevant VDE specifications and thc VDE specifications for the erection of power installations and also the special regulations issued by electricity supply authorities or others (factory inspeclorate. mines and quarries inspectorate) rvhere applicable. must be observed. In countries other than Germany, in addition to the harmonized types, cables made to the VDE specifications may be used provided their characteristics meet the requirements for the function and the relevant regulations for that country. Tables 8.5 and 8.6 show the most commonly used types and areas of application.
))
8.2.1 Cabtes for Fixed In]tanation Table
8.5
Cables
for fixed installarion
Typc
Single
300i 500
v
To facilirare large-scale inrernal wrnng. additional colours and two-colour combinations are allowed. Green and yellow may
inrernal *iring
onl) by I
I I I Single-core non-sheathed cables for
<, r_ -_:!,Jt:. --*,t:i_
H07V-K is flexible, becruse of ils DIN
rl l.
lrncl) stranded conductor. and so oflers advanraqes
morr'ing parrs
troi
I : i 4
PRoToDUR insuhtion
Copfcr conductor. solid Conper conducror. srr.rndcd Copper conducror. flcriblc
1.8'ltv
Cables rvith a nominli \oltt!e ( ,, L' of at lcrsr L8 I tV rrJ considqred to bc short-circuit
crblc for spccii!l
I'ol\chloronrcni shc lh PRr)r('Lo\ iniuhrion Conpcr conducror fi c\iht
nurPoscs
ll!
t
ru
ild
::0
:rtio
con-
rilid
prcllc-she!thed
SlFLr\
- e,g. hinged
panel.s.
As equiporenrial bonding conductors, these wires can be Iuid directly on. in or undcr pluster, or on racks etc.
'l
tn
Pollchloro-
\'[
0:81
for inslallation in conduit in confined spaces or for connections to
purposes
Single-core
individually, ho*-
ever. rt rt rs permirred by lhe applicable safety requiremenrs.
PRorot)uR insulation Copper conductor. solid Copper conducror. flexible
,1i0 750 V *:-ili.r,
used
DIN 028r
I)
lN
\'t'
0:50
und earth-fault-proof in su itchboards und disrribution bolrds ralcd ur up lo I 000 V.
j
v
LA building arc indispensible h.n slot chasing is not possible rn buildings of prc-strcsscd or SIF
il!
$
\flrc\
DI\ \'I,? 0:i0
Poured concrete. or on li!:ht
building boards.
I
I
Rubhcr sheath PR0r()r)uR insuhrion Coppcr conducror. sotrd
LiSht PVC. thcd cable shea
1 PRoDoruR
I
i
ci
sheath
Exrruded fitler
3 PRoroDuR insulnrion 4 Copper conducror. solid or strrnded
:
lt
l4
For applications \ri(h more srrin- e.g. in ugriculrurirl installations, dairies. gent requirements
cheese-making plants. laundries.
industrial and administrative buildings.
DIN..
0t50
vD.
Fixed Installation 8.2
Standard colourS
Applications
Crosss€ctional area mm_
of insulation
Io dry locations
0.5 to I
Green-yellow Black Light blue
.lilucto15
In op€rating
ln
areas and store rooms subject to fire hazard
with explosion
Not permitted
Noi permitted
Not permitted
Open instullutioo on insulators beyond
Installation'in
ln s$irchboards
plastic conduit on and under
and distribution bourds to
In damp and wet locations, and outdoors
or sheath
Brown
For intemal wiring of equipment and protected installation in and on luminaires. Also for installation in conduil on and under plaster, but only for signalling sys-
violer
tem5.
areas
hazard
Grey Whire Red
1,5
lo 400
Crcen-yellow
ln conduit on or under plitster (only in
Black
plastic conduit in bathrooms and shower compartmcnts in drvellings and hotels) and for opeo instrlllrtion on insula(ors over plaster beyood arm's relch. ln cquipment. switchborLrds and dislribution bolrds and in or on luminaires rvith J rirtcd volt:rgc of up ao 1000 V a.c. or 750 v d.c. to earth. For use rn rlil vehicles the d.c. opcrating voltage may be up ro 900 v to elrth.
Light blue Brorvn
Violct Grey
Whirc 1.5
to 240
Red
1.5
to 100
Bluck
for ir:rction rchiclr:s und busscs to $cll ls in drv rooms
l)llj
plaster
Dl\
Not permittcd
\ot
Not pcrmittcd
On, in and
On. in and under plaster to
On. in und under plaster,
DIN VDE
depending on
arm's reach. but not outooors
\'DE
0165
VDE 0l l5
as
,,tal
to
)lo.l1 tllrnd-:)
Naturul
In or under phstcr. including instalhtions in bJthrooms xnd sho\-er compxrtmcn(s in
p,irmitted
drvellings and hotcls. without plilster co\'ering in cavities of ceilings and rvalls of non-flammable mirterials. Not permitted in
lr.sudt.5 I
*ooden houses or buildingj uJed for lgricultural purposes. or in adjLrcent scctions of buildings not separatcd from them by fireproof *irlls.
1.5
to
16
1.5 ro 10 1.5
ro l0
1.5 ro 15
r.) ro
16
Grey
Oo, in and under plaster
under plaster
OlOO
specialchemical and rhermal fcctors (see
DIN VDE OI65)
57
Table
8.5
T]'pe
Cablcs for fixed installarion (continucd) Type designarion
Rated vottage
Construclion
Rcmarks
Stan631,
UoiU
Lead covcred
NYBUY
--
300/500
PVC.
v
shearhed cable
This typc is preferred for use *here high safery is demanded _
I
g. in chemical r\'orks, heavy in_ dusrr]' and mining installarions. e.
I
I -l__-_, PRoroouR outer shcarh : Lcad shcath I Errrudcd filtcr
1 PRoroola
DIN V5 0250
insularion
5 Coppcr conducror. solid or slrandcd PVC-shearhed metalclad
NHYRU Z' t' 300;i00
\
Used in place of liehr pVCsheathed cables
iaole
I : i
\\'nere tlxtngs on plaster are more $ideiy spaced. \HyRUZy has an eiasric rubber illler and a
^\_eon
\YLY
kV
Erlmded fillc.
src x t
x!i ,r/rtv
Cables
l
\YLRZY
.1,',8
kV
sheath. The shearh \{ire nust not be used as an eanhing or protec-
ln'e conductor.
'll-
Applicalion accordine to DIN
\;DE 0t:3.
-rj
stcxExt.6liv
DIN VI 0150
Thc discharge wire consisrs of unl|ed copper slrands of 0.3 mm dia. and has a cross-secrional
I
I
I ProrcDrR shqth : Foldcd mctal (zinc) shcarh I Dischargc *irc
4
V
l.i
Shcath uirc i PRoroD(a insularion 6 Coppcr conduclor. solid or srrlndcd
Lighrins
DIN 0250
tinned-copper shearh wire 0.5 or mm: s.irh one, rrr.o or three strands) under the iolded-meral
PRoroola oulcr shaarh Foidcd rn.tal (zinc) shcalh
:l
.li 3
tbr fixed u.iring
area of 1.5 mm:.
PRoroouR insulalion
5 Copp€r conducror. Ilcxiblc
'NOTHERM. rnsulated
SIA
300i 500
v
l\,laximum
operating I I temperarure 180.C.
he!tresistant
For use in high-ambienr lemper_ - e.g. in hearing appliI I ances. hrgh.po\r'er luminaires. foundries and boiler rooms. I rxposure to superheated steam 1 and flue gases should be I
caotes
SI.AF
I
.ondu.r*
Silicone rubbcr insularion
atures
Cr
ruc
cld.-
to-
DIN VDE 0t50
avoided-
2 Coppcr conductor, rolid
3 Heat. rlslSlant silicone.
insulatcd{ablc
5E
HO5SJ.K
AO5SJ.K
300/500
v
Coppcr conductor. llcxible
DIN VDI 0282
Fixed Installation 8.2
Standard
Applicxtions
colours of insulatioo
l^LrossI
ln operatlrlg areas
or shea!h
secLlonSl
rooms sublect to fire hazard
area
mm-
| .L
On, in and uoder plastet' but not in bath' rooms and shower compartments in dweilings and ho!els,
1.5 to l5 1.5 to i5 1.5 ro 35 1.5 to 6
tnd store
On. in and under Plaster
On, in and under plastcr pefinrtted
In ilrets with e:(plosion hazrrd
On, in and under plaster, depcnding on specialchcmical and thermirl factors (see
DIN VDE
Grey
1.5 ro 15 1.5 to :5 1.5 to 25
1.5
to
0.75
On, in and under plaster and ln rooms coll' taining high-frequency equipment. but not in buthrooms and shower comparlments ln drvellings and hotels.
10
to
contxining
On. in and under plas{er permitted irno to
high-lrequencY equlpment.
in rooms con_
On. in and under plaster. in rooms
DIN VDE
0165)
Not permitted
0293
but not
trining hi!h-
outdoors
lrcquency cquipmenr
cqulvrlcnl Onlv in ventilared steel pipes to DIN '19010 or in signs neon metallic also in under and on flastcr. -iitrlrt and reliefs as well as cable conduits of mctal'
Not pcrmissible
Not permissible
On rnd under plaster
Not permissible
Not pcrmissible
Not permttted
,'-ot permitred
In prorected installations in equipment and in or on luminaires
Not permi(ed
120
0.75 ro 95
ln conduit on and under Plaster and in or on luminaires
Not permitted
lnstallation in plastic conduit on and under plaster
In switchboards and distribution boards to
DIN vDE
0165
59
d
l\.pes
Table
ol wtres and Lilbles
8.5
T) pe
Cables for fircd insrallation (conrinucd) Tl'pe dcsignatio
Hcatresistant synthetic elastomerinsulated
N4CA
cables
N4GAF
Ratcd
Constructron
\'oltacc
.;
r'
.150i
750 V
Maximum operating conductor tempcrature 120 'C. For wiring subject ro highmechanical s(resses.
I I I
60
Rcmurts
S\nrhetic clirstomcr insularion Copper conduc!or. solid or slr.rnded. tinned Copp.r conduclor. lle\iblc. linned
Stirndarc
DIN VE 0250
Fixed Installation 8.2
Slfndard
.ors
.{pplicxtions
colours Cross-
of insulation
In dry locarions
-sectional area
ln dcmp and
In operlting
ln
wet Iocallons.
arcas and store
with e:(plosion
and outdoors
rooms subjec! to tire hazard
hazard
Not permitled
lnstailation in phstic conduit on irnc unocr
In switchboards and distribution
plaster
DIN VDE
rmm-
-0.5
ro 95
L5 and 1.5 L5 and f.5
-L
Black Creen-Yellow Blue
1.5 and 2.5
Brown
0.5 to 95
Black
In conduit on and under plaster. in or on iuminaires and in protected installillions ln equipmenl.
i.rreas
boirrds to OI65
I
(
.l t, ,l-1 I
6L
tJ I)
pes
ol \\rires and Cables
8.2.2 Flexible Cables Table
8.6
Ttp.
Flat
FIe
xible cables
T) pe
Rared
dcsignation
voltage L'o' U
HO3VH.Y
300i 300
Construction
Rcmarks
v
To avoid overloads. these
unset
cords may be used for permanent connection to appliances, or in conjuncrion
cord
I PRoToouR inlul!tion 2 Tinselconduclor lat non-
HOSVH.H
100 i00
v
cord I
lunda_
DIN Vr, 0281
\\'ith appliance conneclors, only if the current does not exceed 1A. Not suirtble for cooking or heatlng appliances.
Not suirable for connecting cooking and heating appli-
shearbed
S
DIN
V
0:81
ances,
PRoToDuR insuhlion
Copper conduclor. highl! t'le\ jblc
Light
HO]\TV.F
PVC.
HOJVVHz-F
100 100
v
sheathed corcl
I
I : i Ordinary
HO5VV.F
PVC-
HOJVVH2.F
300 i00
Not suilable for connecring cooking rnd hertinu appliAs \rcll as thc round t)pe. thcre is also a Oat version
PRorooL,r insuhlron Coppcr conduclor. ftc\iblc
0.5 and 0.7i mmr.
H03VVH2-F, tqin-core,
Pcrmitted for connecting cooking and hearing appli
shcathcd corcl
only if there is no possibility of contact beances
1 PRoroDuR
2
J
shcarh
PnoroDUR insularion Copper conduclor. llcxiblc
I
I
ances.
PRoTot)LR shc!lh
v
t)t\ \ 0:s
tween the cable and hot parts of the appliance or other sourccs of hcat. As well as the round t!pe. there is also a flat \.ersion H05VVH:-F, r\rin-core. u,
/) mm'
DIN VLrr 0281
Flexib le Crbies 8.1
rctors
JET
Cross-
sectional arer
Srandard colours
Applications
of insulation or sheath
Loca(ion
Black Whire Grey
ln drv locarions -
B lack Whire
In dry locations and otfices
Permissible strcss
mm: 0.1
0.5 rnc 0.75
e.
e. in homes and offices
-
e.g. in homes. kitchens
0.i and 0.?i 0.5 rnd 0.15
Black Whire
2 3
0.75 to 2.5 0.75 to 2.5 u.
/) to i.)
0.75 to 1.5
7
I
to:.5
BIack
whire
-
e.
g. rudios. table
lamps etc.
In dry locations
lnd
-
.. g- in homes. kitchens
offices.
Not in rndus(riirl or agriculturrl premires.
0.i and 0.75
For light electricll equipmenr uith rer;" lorv mechanical stresscs
Brown
3
For connecting extremely light hand appir - e. g. elecrric shavers. The curren! loading must not exceed I A and the length must not exceed 2 m.
ances
In dry locations: for domesric xnd cooking appliances also in damp and uet locattons. Not in industrial or agricultural premises. but permitted in taiiors shops and similar premises.
For lighr electrical equipment !r i!h lo$ stresses - e. g. otllce rtachinej. table lamps. kitchen appliunces erc.
mcchlnicrl
For connecting electrical appliances wi!h medium mechanical stresses - e.g. washrlrg machines. spin driers. refrigerators etc. The cables may be installed permanenll! e. g. in fumiture. decorative panelling,
8
T1'pes of Wircs and Cubles
Table
8.6
T) r,e
Flcxiblc cablcs (continucd) Ttpe desiSnation
Rrled \oltage
Rcmarks
C(rnstructr(rn
Sldnd.rr,{,
L'o L
Braidcd
HO3RT-F
100/i00
v
corcl
:31
l I I
Brrid Te\rile
fill.r
S\ nrhelrc
The braid consists of polished rayon yarn. Further development led to the de-
Dt\ \.t_
0l8l
sign of rubber-sheathed cables suitable to withsrand the high-mcchanical and thcrmai stresses Nhen uscd rr ith dorncstic irons (scc
Secrion FLEXO-cables).
.L:lomer insuhlion
.1 Copper condu.t!rr. fle\rble. tinned
Crdinarytough rubber-
HO-iRR-F
,i00 500
v
Thcse cubles irre not suil-
rble lbr continuous usc ou
I
t)tN \'r 0:8:
ldoors.
sheathed
cord
I \!rurrl rubher \h$th : S\nlheric el!\tomcr insulation 3 CDppcr condu.ror. fl€\ible. tinned
Ordinarv poll chloro-
HOJRN-F
,i00 500
v
For use u hcrc thcrc is
.l
possibilitl of crposurc ttr I
prcne-
I
l)lN Yt_ 0:sl
l'rts and oils.
sheuthed Pol)chloronrcne shcrrh nth.uc !lrsbnrrr insulut'on Cof'pcr conduclor. llc\iblc. linncd
cord
S)
HOTRN-F
.150r750 V
Pcrmittcd for permanent protccted installation in conduit or in equipment. and for rotor connecting cablcs for motors rvith ratcd voltagcs of up to I 000 V a.c. or 750 V d.c. to carth.
polychloroprcncshcathed
flcxiblc cublcs
ln rail vehiclcs
DIN Y[
0t8t -
i
the d.c.
-+!
opcrating volta!c may bc up ro 900 V to earth. The dcsign ot thc
,l I
\/i
OZOFLEX-H07RN-F highll
I I
Pol-rchloroprcnc outh€r sb€ath Pol,Ychloroprenc inncr shealh
3 S!nlhelic elaslomer insulation
4
Copper conductor. flexibl.. tinned
ncxiblc cuble is similar to thar of the H07RN-F. but with a short lay. textile filler and extremely finely stranded conductors.
T
r.
5 Teitile fillcr
PROTO-
NSSH6U
0.6/1
kv
This type ofcable is suitable for forced guiding and feeling only to a limited extent. For this kind of use,
FIRM. sheathed cable
1 PRorofrnM tpol\'chloroprene) outcr shcath
2
Polychloroprcnc inncr sheafi
3 Syn$eric .lasromer insularion
4
64
Coppcr conductor. flexible. tinncd
CORDAFLEX cables (NSHT0U) are recommended (sce page ?2).
DINIff o25Z
r
Flexible Cables 8.2
'rductors
Stlndard
Applic.rtions
nber
Cross-
colours of insulation
Location
sectional afeil
or shesth
Pcrmissiblc strcss
mm:
l.i l.i
0.75 ro 0.75 to
Bluc-white
ln dry locations and offices.
-
e.g. in homes. kitchens
Not in industrial or rericullural premiscs. but permitted in tailors'shops and similar
For lighl eleclricrl appliances wirh lo\r mechanicul strciscs - e. g. elecrric blankers
premises.
0.;-i to
0.;i
l.i
Black
ro 6
In dry locations und offices.
-
e.
-r.
in homes. kirchens
Not in industriul or lgricultur:rl prcmiscs. but permitted in railors shops Nnd similar
0.7i !o 6 0.75 to l-5
premises.
F-or conncc!ing electricul uppiilnccs rrith low mcchilDicrl strcsses - c.:. \'Jcuun:
clclrncrs, irons. kitchen cquipmenr. solderlng lrons ctc. Thcsc clblcs miry also be insr:riled permilncntly - c.g. in lurniture. d!'cori!ri\e
pJncllint. scrccns ctc. 0.;-i lnd 1.0 {).7i irnd I 0.75 and 0.;
Bhck
In drv, damp lnd *ct locations lnd outdoors
1
i
0.7 5
1.5
',) l$
oi6
1 I I I
1.5
to
In dry, damp and rvct locations and ourdoors. In agricultural operating arcxs and thosc
to
c"hi-r
500
300
ro 25
to 4
and 1.5
I and 1
r^ fi-- l'.."..1
In operating areas and storerooms ta DIN VDE 0165 subjecr to explosion ha-
l.) anq z.)
1
and
1.5 1.5 1.5 1.5 1.5
to ro
to
185 185 185
to 70 to 4
For connccting electrical appiiirnces and tools. including industrial equipmenr $irh mcdium-mechanical stresses - e. g. large wirtcr herters, hot-plates. pouer drills. cir. cular saws and mobile motors or machines on buildinq sites. For permanent installa. tion - e.g, in temporary buildings - and for dircct instlllltion in componenrs of hoisting equipment. machines erc.
Where cables are subject to kinking and rwisting - c.g. lbr hcnd grindtrs and porver
1.5 1.5
2.5 to 400
ro 36
Black
to 25 to 300
For connecting clcctrical lppiilncrs lnd tools rvith lorv-nrcchunicirl stresses - e. g. dccp-l'at lriers. kitchcn equipmenr. soldering irons. hcdgc clippcrs clc. Thesc cables mr-'- ulso bc insrallcd pcrmanently - e.g. in cxvities in pretabricated building secrions.
drills.
Yellow
ln dry, damp and wet locarions ard outdoors. Irr agricultural operating arcas and those subject to fire hazard. In operating arcas and storerooms to DIN VDE 0165 subject to explosion
For heavy equipment and tools wirh highmechanical stresses on buildiog sites, io industry, in quarries and in open-cast and ulderground mines.
hazad.
b)
8
Tvoes of Wires and Cables
Table
8.6
Flexible cablcs (continued)
Type
Type
designalion
Constructron
Rated voltage
Remxrks
StandarLl
Suitable for operation in water at depths up to
Constrt
500 m.
rclales to
The ability to operate con-
DIN
rinuously in water has been proved by tests. Design and dimensions are as for H0?RI.--F.
0?82
UoiU
HYDRO.
TGK
FIRM
TGKT
cables
TGW
450/750 V
:l
tlon
cle*
V'
Cables lo meet special rcquirements on request.
TGFLW
I
I
I
Polychloroprcnc sheath
2 S-lnrhclic clasiomcr insulaoon 3 Copp€r conductor flciiblc
:t Heat-
{CMH.IG
300/500
lflsulation cross-linkcd polyolcfinc
v
resrstanl
flexible cable Heal-resistant !! nthctic claslomer sheath
Maximum operatlne con_ oC. ductor tcmperature 120
Const
These cables also remain
relates
flexible at low remperarures - down to about -10"C.
0282
Maxlmum opemtlng con_ oC. ductor temperature 180
0250
rL-r.
lion cl(
_
DIN VI]
Hcat-rcsistanl sl_nthctic clastomcr insulrlion Copp€r conduclor. flcxrblc, linned
Heat-
N:GMH]C
300/500
v
resistant
\''
Exposure to superheated steam and flue gases is
siliconeinsulated
harmful.
and sheathed cablc
lf air is excluded at temPer1 Siliconc-rubber shcath
2 Siliconc-rubtlcr insulation J Copp€r conductor. flexiblc ARCO.
DIN
NSLFFOU
200
atures above 100'C the mechanical properties of the silicone rubber are imparred. These cables have a PRO-
v
TOFIRM sheath which
FLEX welding cable
I :
PRoIoF|RM (polychloropr.nc) shcath
is
DIN vt-'
l
oil-resistant, flame retardant and resistant to abrasion and indentation. Maxtmum oPerating conducror temperature 80'C.
Scparator
3 Copp.r conductor. flcxiblc
FLEXI-
NSLFFOU
100
v
PREN cable 1
PRoToFIRM
(polychlo.oprcnc) shcath
2 Scparator 3 Coppcr conduclor, hiShly ncxiblc
66
DIN
cables have an extremelY
0250
fi ncly-strandcd
weldiog (hand held)
FLEXIPREN hand-welding conductor,
with thinner strands thall arc required bY VDE 0250. This makes them excePtlooally flexible.
\_
Flexible Cables 8.2
Cross-
icctronal arcir
Stcndxrd
Applicrtions
colouts of insulation or 5neirlh
Locltion
Pcrmissrble srress
Blue
fn water, in d4,, damp and wer locations and outdoors
For connecting electrical equipmcnt wnh medium-mechanical stresses. especiall) cquipmenr which opcrates continuousl)- in water - e. g. submerged pumps and underwater Iloodliehrs. TGK tbr rlaler temperarures up ro 10.C TCKT tbr continuous immersion in cclking water up to -10'C TGW and TCFLW lor rvate11g111p.r","rat up ro 60'C.
C rev
ln dry. damp and Ner !oc!rions 3nd outdoors
For connecting cooking rnd he:rrinu rcciiJnces with medium-mechanical stresl.J -rnd increuscd embient tcmpcrJtures - e. g
mml
l
I I I I
5
to
-<00
ro 15 to i00 !o -:00 ro
li
lo -0
lo;0 I
{
u:to-.J u :lo__) 0.li lo l.-i
0.75 io 0.i5 to 0.75 to 0.75 to
.l
i0
Brown
1
.l .l
lo lo r35
25 !o
cookers. €lect c stortse hqlters etc.
Black
Black
In dry, damp and wer loclrions and outdoorS
For Iow-mechanical srresses and ambient lemperatureS.
In dry, damp and rver locations and outCloo15
For very high-mechanical stresses as machine aDd hund-rvelding cables.
In dry, damp and wer locarions and outooors
Highly-flexible hand.welding cable for very high-mechaniclrl stresses.
hi_eh-
o/
8
T1pe5 ofJVires and Cables
Table
8.6
T! pe
Fiexible cablcs (continucd) T.vpe
dcsignation
L
PVC
SYSL
Construction
Rated voltage
Rcmarks
Stand;rr.
For llxcd installation but not rr'ith free movement and forced guidance orl rollers or reeling dury.
Constr
oiU
300/500
v
control cable I
I 2
I
tlOn Clo(.
related l.
DIN
\
0250
PRoroDuR shcarh Separator I >l: core) PRoroDL'R insularion
.{ Coppcr conducror lle\ible
PROTO-
\YSLYO
-1001500
v
\ - r-
FLEX
I
PVC.
I
control
I
The outer sheath is substan-
PRoroouR shcalh
2 T€J(ilc la)c.
tially unaffectcd by mois-
PRoroDuR insulslion .1 Copper conductor. fle\ible
ca ls.
I }.YSLYCYO
i00 i00 v
;riii 4i. ifli :1jt 1
FLEX
1\l'n('.i9-
screened
PVC-
control cablc
I : I I
PRoToDUR shcath
Tinned-coppcr brsid
PRorooriR innlr shcath PRoroDuR insulation 5 Copper conductor. flcrible
Lifr
YSLTKJZ
300/500
v
ture. oils. fats and chemi-
These cables meet rhe re-
quirements for " Elcctrical equipmcnl of indusrrial machines" in accordance \\ilh IEC :04 and DIN
VDE
01
ll.
The screening
braid of rhe NYSLYCYO. by virtue of its design, has a very low coupling of 150 O/km. Insulation lnd sheath are made from a cold-resistant PVC compound (flexible
control cable
do,,\'n to -10'C) Cables with up to l8 cores have a tertile strain bearing element: with 24 or more cores the strain bearing elcment is a steel rope. This
I
PRoroDuR shcath
I
Separalor
4
PRoToDUR
insllalion
5 Copper conductor. Bcxible
6 Sheathcd strain bcaring clcment
68
DI\ \'I
0li0
reels.
cable
PROTO.
For arrcngements affording fre--dom of movement: not for lorced guiding over rollers or operation on
$ill support
the maximum suspension Iength with a factor of safety of five. The
manufacturer's installation instructions musl b€ adhered to.
Constr tion cl(rclatcs tc
DIN \r) 0250
_
Flexrble Crbles 8.2
rductoas
inber
Crosssectional areS
Standard colours
Applications
of sheath
Location
Crey
In dry damp und wct locrtions
Permissible stress
mm: r60
0.5 ro 6
For control equipmenr, production lines muchine tools as connecring lnd inter-
lnd
conlecting cxbles with medium-mechanical srresses.
o6L
0.5 to 1.5
Crev
ln dry. danrp lnd rrct locrtions
For control equipment. production lines and machine tools as connecting and interconnr:cting cablcs with medium-mcchanicll slrcsscs,
:
L) _,\
0.i ro:.i
Grev
In dry. damp and
*ct locltions
For controi rooms, production lines lnd datl-proccssing equipmcnt with mcdiumrncchrnicdl stresses. rvhere interferencc
Black
ln dry, damp and wet location
i( rFd,'ire,l
A sclf-supporting flexible control cable with mediurn-mechanical strcss - e.g. for lifts rnd conveyor systemsl suspension lengths up to -s0 m. cage relocity r.rp to 1.5 m.'s.
69
8 Tl pes of Wires and Cables Table T.
8.6
--
Flexible cablcs (continucd) T! Pe
Rated
designation
voltage
Construction
Remarks
Stanrr
Insulatioo and sheath are made from a cold-resislant compound (flexible dorvn to
Con-
UolU
Lifr llerible
YSLYTK.JZ YSLYCYTK-JZ
300/500
v
control
I
cabies
8
-
i0 'c).
The strain bearing element is a steel rope with reduced rs isting
uhich
*ill
tion
c
r' DI\
rela
0l5G-
support
rhe maximum suspension lengrh !rith a factor of
I PRO1oDUR shearh : Te\til. b.!id I PRoroDuR in ner shealh I Sepiiraror i Te\rile filler 6
PRoroDuR insuhuon
7 Coppei conductor. nerible
3
Shealhed nrain bcanng clemcnl
safer) of fi\'e. ln equipment for which interference suppression to YDE 0875 is required. type
\'SLYCYTK-JZ nust
be
used. The manufaclurer's
installa(ion instructions must be ldhered to.
Flat PVC'insulated cables
DI)
Pvc-
are nol intended for use
0ts,
shea!hed
ouldoors.
Flat
H05VVH6-F
i00
500
v
lle\ible cables
for lifis
HO?VVH6.F
500/700
v
and
similar applicarion
PL,{NO. FLEX
NGFLGOU
1
PRoToDUR rhcarh
: i
PRoIoDUR insulalion
Copf'er conduclor. flexible
A cold-resistani chloroprene rubber is used for rhe
300/500 V
sheath. enabling the crblcs to remain sufficientiy flexible doqn to - 35 'C. Thc insulation consists of an ozone and \r'ealher-resistant
flat flexible cables
1 Pollchlaroprcnc shcalh
I
Synthctic .laslomcr insulation
3 Copper conductor. highly nexibl€
70
PROTOLON synthcticelastomcr. Maximum o;rr_ aring conductor temPera-
ture 90 "C.
DII' 025(
Flexible Cables 8.2
nductors umber
Crosssecuonal area
Standard colours
Applicrtions
of sheath
Location
Permissible strcss
Black
ln dry, damp and wet iocation
Self-supporting flexible control cables with medium-mechanical stress - e. g. for lifts rnd conveyor syslems; suspension iength5 up to 150 m, cage velocity up to l0 m.s.
mm:
i+
I
rdi-
0.5 for rhe
.ually-
communi-
ireencd
cation cores
lfnmunilon
:
t 0.75 and I
ro l'1
o14 '.o
I
nd+
1.5
Black
In dry, damp and wel locatlons
caole.
to l6
to 2.5 1ro.1 1
Fle:
Black
In dry, damp and wet locations and oulooors
1roi5 1to95
71
8 Types of Wires and Table
Cables
E.6 Flcrible cablcs
-f! pe
CORDA-
(continucd)
Tlpe
Rated
dcsignation
\
NSHTOU
0.6/1
Construction
Rcmarks
Srandart
Maximum operating conductor temperature 90 "C.
02i0
oltage L'oiU
kv
FLEX cable
DIN VDE
Shca(h ol' pol) chloroprene. 0erible dorr n lo - l0 "C.
I :
Polvchloroprene ourer :he!rh
Polvchloroprene inncr shealh
3 S!nlhetic claslomer insulation
I CORDA.
\SHTOU
0.6,1
Copper conductor. Ile\ible. linned
kv
I1arimum operuting conductor temperature 90 oC. Sherth of pollchloroprenc. 0eriblc doqn ro - 15.C.
FLEX(K) cable
I I
Dh* vl) 0150
PolYchloroprene lrulcr rhe3lh
Suppo ing braid
-1 Pol)"chloronrene Inncr sherlh
I i
Texljle Lrlcr Slnllictic elasromer insubtion
6 Coppcr conducror. Uc\ihtc. COR DA.
FLEX
\SHTOU
0.6
tinncd
1kv
l\1
cable
I : I
Pol)chloroprenc oursr shcuth Suppo.ring braid Polvchloroprene inne. she!rh
Ll Svnlheric elaslomer insulation
5 Foil 6 Coppcr conduc(or. Ilcxiblc.
72
axi m r.:m opcrarin g
con-
ductor temperature 90.C. Sheath of poll'chloroprene, flcxiblc do$ n ro -:0.C
(sM)
tinned
DIN VI: 0t_r0
Flexible Cables 8.2
.
nducrors Crosssectional area
Standard
Applicltions
colours ofsheath
Locauon
Permissible stress
tslrcx
In dry, damp und we! localions and
For high-mcchanical stresses on rcels without guide rollers fbr apparJtus with realing speedy up to 60 m,iminule.
mm: 1.5
2.5 .1
to
outdoors
50
''
::o
l0
Li
.rnd 1.5
1.5 to
Bhck
ll0
In dry, drnp ind \\et locallons xnd outrloors
I
l0
For high-mechanical stresses prel-.rably for lorced guiding - c,g. rccls or guide rollers. lbr high Jccelerirtion and tra\el speeds in hoists, trunsportltlon xnd qolevor cqulp_ mcnt. For tru\'al spccds up to l:0 m mlnLIIC,
L5 and 1.5 10
to
50
Yellow
In dry. damp and $et locations nd out
For very high-dy-namic stresses as e. g. opcrution of clcctro-hydraulic grab cranes' ciane Iifting mrgnets etc. as well as mobile cublc carrien. For travel speeds up to
ll0
mtminutc.
S Tl pcs
qrf \\ij1g5
and Cublcs
8.2.-l FLE\O Cords
FLE\O cords comprisc clastomcr- or
PVC-shcathcd
cables iraving either vulcanized or nroulded. non-scp-
arable connectors. such as plues connectors or appliance plugs, factory attached at on or both cnds. If cables and connectors are of elastomers these are vulcanized in the press. With PVC sheathed cables the
Fig. 8.1 European flat plug up to 2.5 A to
DIN 49464-F/CEE 7 sheet XVI
connectors are also of PVC injection moulded to form one unit. Frequently plastic plugs are also moulded on to elastomer-sheathed cables. Prefabricated FLEXO cables save time and cost during instlllation. have a high deeree of electrical sufetl. and offer the user practical advantages.
Due to the additional requirements for connecring :ables tor hearing applicanccs, especiall_v- domestic rrons. a cable sas developed u,hich u'iil u,ithstand the high bending stresses and remperature. This cord is available under rhe trade name THER\4OSTABIL rnd is desiened closely to rhe r),pe of construction 05RR and fulil,compiies rvith rhe harmonized standard. Thc pin support bridge is of mouldcd Duroplast and supports other contacts such as the protecrivc conductor contact. it is not permitted to use thermoplastic materials for the manufacture of the pin support bridee. All component parts of the conneclor are firmly embedded and secured on ail sides in cither the elastomer or rhe plastic during moulding and therefore are electrically insulated and mechanically protected. The conductors are either soldcred or rvcided to the contact pieces. The attachment. of thc cord to the support bridge is formed by a tapered sleeve rvhich prevents sharp bending and improvcs resisrance to kinking. The arrangement of cord entry into the conneclor can be either central (Figs. 8.1 or 8.2) or angled (Fig. 8.3). Cables with central cable cnrry arc suitable for appliances \\,here the plug is frequently disconnecred and connecled. Connectors with aneled cable entry are generally more suirable *here sp-ace is limiued. The relevant standards iay down rhe profile and d! for the pin end of the connector. However the overal shape of the body of rhe supporr bridge is lefr to the designer providing rhat all test requirements are fulfilled. A Siemens design, generally favoured by users, is protected under the trade name PROTOFORM. mensions
Connectors of different constructions could also be manulactured, bul because ofthe high cost of mould'1,1
Fig.8.2
SCHUKO plug for 10 A to DIN 19.1.11-Rl CEE \:ll \r'irh two protecrive contacr s)stems. nainlv for use in Belgium and France
7
sheet
Fig.8.3
SCHUKO plug for 10 A ro DIN 49.1.11-Rl/CEE IV
7
sheet
ing and tooling this is only pracrical where
laree
quantities are required.
The free cable end, used for the fixed connection, can be finished by the customer as desired and can be stripped, fitted wir.h boot-lace slee.r'es, sDade connectors or others. As part of an elaborate quality control system all features relevant to safety are tested both during and immediately after manufacture. Safety features related to personel safety are routine tested. Furthermore, during approval type testing rhe relevant national approval authorities carry out extensive elecrrical and mechanical tests.
lndustrl S'3 Flcxiblc Cablcs lbr i!lining and Heavy PROTOITONT Polychloroprenc-She:rthed Cebles NSSHOU These cables are used lbr the connection of motors. l'ixed and movable heavy apparatus as weil as indus-
trial tools. This type of construction aiso For factory made approvals conncction cords. special
il::;:;';X""":L':,i:',i1,';::l'iiiil,:"*l;t:
harmonized ri.;;;. il" rpprovels rre brsed on ,tt. I..quir"rn"n-ir-" r oix I'dE regulations ls rvell as CEE publications 7 rnd ll respectlvelv'
8.3 Flexiblc Cables for )Iining
-.
and IndustrY
replaces
type NSHOU. which was not covered by the harmonized standard. tor cables subjected to hrgh-mechanical strcsses having cross-scctional lrcas up to 6 mmr and up to 5 cores. In mining belorv ground rvhere cebles ere subjected to gls J construction type nust be used which has l concentric protectlve conductor surrounding either all main phase conductors or is equaly divided arranged around e:rch individual phase conductor. The iater typc is prelerred in rhe mining industry (Fig. 3.5). Thc inrcrsticcs of the corcs mly:rlso be used to incorporate pilot cores.
,re high-mechanical stresses met in mining and he:rvf industry require tough cebles with a type of construction suited to the relevlnt application. These cabies must have a particularly stronq outer shcrth. For clastomer-shcathctl clbles Siemens huvc
developed the impacr rcsistant. tcar-abrasion reslslant PROTOFIRIvI sheath (sce pagc 38). Sheath colours see Table 8.7.
't.rtrlc ti.7 Shc;rth colours
.tnd
DIN VDE
tl I
l l
PROTOFIRM outcr sherth
Polychloroprene inner sheath Textile layer + Numbered PROTOLON-insulated cores 5 Copper conductors, flexible. tinned
to DIN VDE 0:06
Fig. 8.-l
0118
NSSHoU l9 x 2.5
Heavy PROTOivlONT polychloroprene'shelthed cables 0.61 1 kV
Sheath colo ur
Rltcd voitage L/o/U<0.6. 1 kV Rrtcd voltage Uo/ U> 0.6r I kV Intrinsically safc cquipment
Poll chloroprene-sheathed Cables
for Heavv\ lechanicai Stresses Pollchloroprene-sheathed cables for heavy-mecnanical stresses for rated voltases uo to 1000 V are
;'i[{ill
3i,'.,
Tl."
ii,*T.,il?il;
JJ*: !,, caotes.forminingi. 1;: rhe-regulations DIN vDE 0118 and ;;:: ""E0168 as well as anv special regulations mining authoriry must be observed. annltcations DIN VDE 0100 is similarlr- ,.1.i.'i''n
i'"lllrl:]::1,
1 PROTOFIRM outer shexth 2 Polychloroprene inner sheath 3 Textile layer 4 Layer of tinned copper wires 5 PROTOLON insulation 6 Copper conductors, flexible, tinned Fig. 8.5
Heavy PROTOMONT polychloroprene'sheathed c:ble NSSHoU I x 95+50/3 E 0.6i 1 kV
/)
8 Tlpcs of \\rircs and Cables PROTOLON trailing cables (Fig.8.10) are constructed in line rvith DIN VDE 0250. For thc currcnrcarr) ing capacities to DIN VDE 0250 o{' 3 loaded conductors in free air at 30'C thc valucs sho$n in Table 8.8 apply. For ambient tcmperatures orher than 30 "C rhese values require to be adjusted using the factors given in Table 8.9.
I
The cores for high-voltage cables lrom 6 kV uprvards
PROTOFIRM outer sheath
2 Polychloroprene 3 Extruded filler
are constructed
sheath
4
Conducting rubber PROTOLON insulation 5 6 Copper conductor. flexible
principle
(see
proved over several decades i.e. to avoid harmful partial discharge conducting rubber layers are placed over the conductors and above the PROTOLON insulation. The earth conductor, sheathed in conducting rubber. is divided and laid into the interstices
Fig. 8.10
PROTOLON trailing cable NTSCGEWoU I x 25+l xtj
to the OZONEX
page 24) developed by Siemens and which has been
I
betrveen the cores.
6i10 kV
In high-tension cables the conductins rubber
lar.er
also acts as touch protection. It is therefore necessarv
for the conductivity to be such rhat thc rcsistlr.,., betsecn the protective conduclor and any poinr on the outcr conducting )ayer not to ercccd i00 O,
Table 8.8
ing clpaciries of PROTOLON i0'C ambient
Current-carrr cables at
Nominal cross-
Currcnt-carrving capacitics
sectional area
mm-
rrailins
ra(cd voltase
up ro 10 kv
above l0 kV
./..)
I
6 10
IO 25
'
110
146
i5
t71
50 70
21 3
For motor connection boxes, transformer station!
and gate-end boxcs and similar equipme)-
336
PROTOLON indoor terminations are used.
r50
450
185
514
For cables laid on the ground etc. a correction factor of 0.95 has ro be applied Table 8.9
Correction factors for ambient air temDeratures other than 30 'C. To be applied ro the current-;arrying capacities shown in Table 8.8
78
Trailing cables must be provided wirh terminations to protect against ingress of moisture. With rated voltages greater than 6 kV the termination also provides an electrical function. The individual rerminatjon constructions are dependant on operating and installation conditions.
279 391
oC
strensth and provides torsion protection.
181
95 120
Ambient temperature Correction factor
For particularly hieh stresses and travel speeds erceeding 60 n min PROTOLON cables are fitted u.irh an additionll rextile braid incorporated in rhe outer sheath. The textile braid increases mechanical
For rated voltages up to 10 kV a simple dir.iding box termination is sufficient (Fi-q.8.11). From l5 kV upwards a dividing box rvith core sleeves is required (Fig.8.12). Where space is severely limited a smaller divider with core sleeves over the cable tails is available (Fig. 8.13). For use on ourdoor trailing cables up to 35 kV a rn:lcanised water shed termination is available which may be directly connected to overhead supply wires (Fig.8.1a). These are mainly used in Electriciry Board networks during network alterations, for the supply to floating dredgers, or open cast mining, or
ll'3 Flcriblc Cablcs tbr ivlining lnd Industrl Heavy PROTOIIONT Polychloroprene-Sheethed C;rbles NSSHOU These cables are used lbr the connection of motors. l'ixed and movable heavv apparatus as well as indus-
triel rools. This type of construction also For lactory made rpprovals connccdon cords. special are necessary lor tnougn cven indiridual countrics lhe cord itself complics in llmost ull clscs wltn tne harmonized stanaaiJ- rnc lpprovals are based on the requiremenis-or-p r x vDE regulations ls rvell as CEE publications 7 and 11 rcspectively'
)lining
8.3 Flexiblc Cables for and Industry
repiaces
NSHOU. which was noc covered by the harmonized srandard. tbr cubles subjected to high-mechanical siresses having cross-sectional arexs up to 6 mmr and up to i cores. In mining beloiv ground rvhere cebles are subjccted to g:rs J construction ttpe rrust cype
be used rvhich has
l
concentric protective conducror surrounding either all main phase conductors or is equaly divided arranged around elch individual phase conductor. The Iutcr ty-pe is prel'errcd in rhe mining industry (Fig. 3.,s). Thc intcrsticcs of rhe corcs mlv also be used to incorporate pilot cores.
-,re high-rnechanical strcsses met in mining and heavv induslry require tour:h cubles with u type of construcrion suited to the rclcv3nt application. These cables must have a particularly stronq outer shr'oth. For clastomcr-shca thcci cablcs Siemens havc
developed the impacl rcsistan!. tclr-abrasion rcsistant PROTOFIRIvI sheath (see page 38). Shcath colours see Table 8.7.
I PROTOFI 2
l
RlI
outer sheath
Polvchloroprene inner sheath
Textile laver Numbered P ROTO LON-insulated cores j Copper conductors, flexible. tinned
"l
'trblc ll.7 Slrc:rth colours
and
DIN VDE
Fig. 8.{ Heavy .P ROTO ivlO NT polychloroprene-sherrhed cables NSSHOU l9 x 1.5 0.6, 1 kV
to DIN VDE 0106 0118 Sheath colo ur
Rutcd eoltage UolU< 0.6 I kV Kutcd vohage UolC;>0.6 1 kV ' ntrrnsically safe cquipmcnt
Pol;-chloroprene-Sheathed
.\lechanical Stresses
Cables
for Heavv-
P.ol:-chloroprene-sheathed
cables tbr heavv-melor rated vohaees up to LOOO v aie ffilT":':YTd by Siemens under the trade name and 8.5). when serecting ;;;:y-.lt"Ir (Figs.8.4 rhe regularions DrN vDE 0118 and iirl:'rlflllyS of rt . -L-- ", od as well as any special regulations
cnanical stresses
F..';:,..:l:t.ul, mining aurhority must be observed.
-
','qustnal applications ,., rrrEvant
DIN VDE 0100
is
similar-
1 PROTOFIRM outer sheath
2
Polychloroprene inner sheath
3 Textile layer 4 Layer of tinned copper wires 5 PROTOLON insulation
6
Copper conductors, flexible, tinned
Fig. 8.5
Heavy.PROTOMONT polychloroprene-sheathed crble NSSHOU 3 x 95+50i3 E 0.6/1 kV 15
- 8 Tlpes of \\ ircs and Clbics Cables for Coal-Cuttcrs for Operation
bclow Ground
\'loving corl-cultcrs in rnining below ground are connected with coal-cuttcr cablc (Fig.8.6). These cables are subjected to the hcavicst mechanical stresses.
Depending on the type of cable arrangement: free dragging, forced guiding by protective cable drag chains or forced guiding with a cable roller system, three different cable constructions were developed particularly for rhe supply of power to coal-cutters. The drag cable must be capable of withstanding the operational pulling forces with a high lactor of safet.v. For this purpose a steel-copper braid is embedded in the outer sheath which performs additionally the function of concentric protective conductor.
In the drag chain system
cables are guided rvithout siqnificant tensile stress. Thc cutter cable in this ar-
ranqencnt, howcvcr, must bc particularly flcrible to allow casicr installation and to achicve frce ntovcmcnt of thc chain. To achieve this the concentric protcctivc conductor consisting of stecl-copper braid is arranged between the inner and outer sheaths. A later development for forced guiding ofcoal-cutter cable is the protected installation in an enclosed duct via a moving roller system. For this purpose a specially flexible range of coal-cutter cables, having a braid of strands of polymeric yarn embedded in rhe outer sheath, rvere developed. All cutter cables have control and monitoring cores laid into the interstices bets cen lhe cores. For mechanical reasons these control and monitoring cores are constructed in concentric form. The monitoring conductor is electrically connected to the conductive rubber layers lr hich surround the cores of the phase conductors. This connection is used together with a monitoring device to detect damage to the cable and initiate disconnec tion.
With increasing cross-scctional areas thc problenr of both mcchanical handling and service Iile incrcase and because of this Siemens do not manufacture PROTOMONT coal-cutter cablcs larger than 150 mmr lor Us1'L:0.6i1kY. Poll chloroprene-Sheathed Cables for Hoists
In interconnecting shafts between coal seams of different lcvels. hoists mav be installed.
I
PROTOFIRM outcr shcarh
2 Armour (protective conductor) of steel-copper braid
, i
I nncr sheath Control monitoring conductor: control conductor 1.5 mm2 flexible tinned copoer conducror under a PROTOLON insulation colouied blue and monitoring conductor 1.5 mmz tinned concentric copper conductor and conducting layer 5 Phase conductor: copper cooductor, fldxible tinned under a coloured pROTOLON insulation and conducting layer
.1
|
2 3 4
56
1 PROTOFIRM sheath
2 3 4 5 6 7
Wide mesh textile braid Textile braid Screened communication cores PROTOLON insulation Sheathed strain bearing element Copper conductors, flexible, tinned.
Fig. 8.7
PROTOMONT rubber-shearhed cables for hoists. NTMTWOU 8 x 1.5 ST+2 x I FM(C) 0.6iI kv td
I ndustr-v 8.3 for Mining and
Fqr thL' con(r.l1. of hoist cages, c:rblc NT\ITWOU is uscd.
J ,:!i
,\
rorslon-trce centrally arranged tiee hanging of rhis cable up to 200 car.ion purposes. two of the ten
screened.
-
polychloroprene-Sheathed Cables
Lighting Frr. ,^h. .:lT:'tfn cotl rtce
,
.\JJnuu
i ii.t
.fl.ameproof
lishii,iffi
cabtes are used in whiih' r idual core screenins is used as o prototivi,ciiiil-ffiar
or. Whcre rhe corl face lighting installation iidiri. porttes relecommunicarions, then the coal face ligbt. ing cable musr also conrain a screencd conmuniee. rions Dair 1Fie.3.3).
.
loth cable rvpes are connccted to monitodng 6ppa. r:rrus. In the case of NSSHOU cablcs onc phtsc i;n. ductor is used as a conductor in thc monitoring rys. rcnr. In cables incorporating tclccomnunicxtions onc n:onitoring corc is providcd shc:rthcd with conduc. rivc rubber rvhich in turn is conncclcd to thc cotrduc. tivc rubber layers over thc phasc con(luctor$ itnd thc control cores.
67
.{ 5
8
S
PROTOFIR\t o uter she:rth Textile layer Polychloroprene sheath Conducting rubber sheath Protective conductor PROTOLON insularion Communication cores Copper conductor, flexible, tinned
Fig.8.8 ROTO MONT-polychloroprene sheathed cable lor coal face liehtins NSSHKCGEF-MOil 3 x 6 + 2 x 2.5 ST+2 x 0.5 FM +2.5 UL 0.6/1 kv P
llining
UolU>0.6ll
l9es SUPROMONT
for rated kV under the trade
cabie (Fig 8.9).
7
39
r0
1 Monitoring conductor 5 Conducting laYcr 6 Extrudcd fillcr ProtcctiYc conductor 8
Control corc
Il
insulrtron t0 Coppcr conductor. llcxiblc 9 PROTODU
Fle. 8.9
SJPROIVIOIT C.TbIC NYHSSYCY J x.15+l x l(y'3 E+3 x l.i ST+UL i.6 6 kV
SUPROivIONT cables of cither thermoplastic or clustomcric construction are used to bring the high tcnsion nctwork of 6 kV or 10 kV direct to the load ccntrcs. These cables are used, lor example. for the incomrng feed to transformers in mining work laces bclow ground and in lunnel operations for roads or underground rail systems. This avoids having lowvoltase cables with lar-ee cross-sectional areas. For rersons of safety thcse cables are provided with a protectivc conductor, a monitoring conductor and stcei-wire braid as armouring below the outer shexth. In addition control cores are incorporated in rhe intcrslices of cores. SUPROMONT cables are supplied. mostly, in lengths of either 100 m or 200 m with factory-fitted end terminations. The form of termination being arranged to suit the type of connecting or interconnecting boxes. Trailing Cables and their Terminations
Trailing cables are used to transmit large amounts of energy in the voltage range of 1 to 35 kV and are subjected to high-mechanical stresses. These cables are used on large mobile machinery such as
Cables above 0.6/1 kV
Siemens provide mining cables
o
bDuR out"' th""th
for'b :
of
s t
voltname
excavators, dredgers coal face equipment and hasting
gear in the form of drum wound or trailed power supplies. 77
8 Tlpes of \\rires and
Cables
PROTOLON trailing cables (Fig.8.l0) are consrructcd in linc rvith DIN VDE 0250. For thc currcntcarr) ing capacitics to DIN VDE 0250 ol' -1 loaded conductors in frce air at 30'C the valucs shorvn in Table 8.8 apply. For ambient tcmperaturcs orher than 30 "C these values require to be adjusted using the factors given in Table 8.9.
I
The cores for high-voltage cables from 6 kV uprvards
PROTOFIRM outer sheath
2 Polychloroprene 3 Extruded filler
to the OZONEX
principle (see by Siemens and which has been proved over several decades i.e. to avoid harmful partial discharge conducting rubber layers are placed over the conductors and above the PROTOLON insulation. The earth conductor. sheathed in conducting rubber. is divided and laid into the interstices
are constructed
sheath
page 24) developed
,l /-^-.1,,^ri-I uvvvr uLrrrrs r',hhpr ' !vrrs
5 PROTOLON insulation 6 Copper conductor. flexible Fig. 8.10
PROTOLON trailing cable NTSCGE\\'oU 3 x ?5+3 x 15 I6i10 kV
bet*,een the cores.
ln high-tension
cables the conducting rubber laler
also acts as touch protection. It is therelore necessarv
for the conductivity to be such that the Table 8.8 C urrenr-carr1 cables at
ing capacities
oC ambient -.i0
Nominal crosssectional area
mm-
oi
betseen the protective conductor and any point rhe outcr conducting layer not to escced 500 Q.
For particularly high
Currcnt-carrf ing capacities in A ratcd voltai:e up to l0 kV abovc I0 kV
6
43 56
10 16
r04
110
25
138
146
35
171 213
:zo
zo)
279
95
3t7
JJO
120 150
170
391
50 '70
78
stresses and travel speeds erPROTOLON cables are fitted rvith ceeding 60 m min ln additionll textile braid incorporated in the outer shcath. The terlile braid increases mechanical strength and provides torsion protection.
Trailing cables must be provided with terminations to protect against ingress of moisture. With rated voltages greater than 6 kV the termination also provides an clectrical function. The individual termination constructions are dependant on operating and installation conditions.
18r
450
185
di
PROTOLON trriling
2.5
1
rcsistar^
514
For cables laid on the ground etc. a correction factor of 0.95 has to be applied
For motor connection boxes, lransformer station. and -eate-end boxes and similar equipme.-PROTOLON indoor terminations are
used.
For rated voltaees up to 10 kV a simple dividing box termination is sufficient (Fig. 8.11). From 15 kV upwards a divrding box with core sleeves is required (Fig.8.12). Where space is severely limited a smaller divider with core sleeves over the cable tails is available (Fig. 8.13).
Table 8.9
Correction factors for ambient air temperatures other than 30 "C. To be applied to the currenl-carrying capacities shown in Table 8.8 Ambient temperature Correction factor
78
oC
cables up to 35 kV a wlcanised water shed termination is available which may be directly connected to overhead supply wires
For use on outdoor trailing
(Fig.8.1a). These are mainly used in Electricity Board networks during network alterations, for the supply to floating dredgers, or open cast mining, or
Haloucn Frcc Cablcs 8.3
Fig. 8.1 I
Dividing box termrnatton lor
trailing cebles NTSWOU and NTSCCEWOU wi(h rrted voltages from I to 10 kV
tbr rhe po',ver supply to building sitcs. This outdoor tcrminiltion is dcsigncd to withstand thc strcsscs to be expected
during tiequcnt rcirrrangement ofcables.
8.4 Halogen-Fre€ SIENOPYR Wiring and Flexible Cables with Improved Performance in the Event of Fire
Fig. 8.12
Dividing box termination with for trailing cables NTSCGEWOU with rated voltages from l5 to l5 kV
stress cone
Fig.8.13 Low-space dividing box with stress cone for trailing cables NTSCGEwoU with rated voltages from 6 to 10 kV
-vi + -t
T
Experience gained from a number oi large fires has shorvn that. particularly in buildings rvith a high density of installed cables and rvires, e. g. hospitals. horels etc.. considerable consequential damage can be caused when the cable insulation is PVC based. In such conditions during the combustion of PVC matcrials chlorine and hydrogen is released rvhich in the presence of moisture combine to form the highl-v corrosive hydrochloric acid. The consequential damage caused by this is often more eKtensive than thc prima' r-v damage. ln addition such materials in the event of tlre lead to such a strong smoke dcvclopmcnr thlt rescue rvork and tire fighting is signiticantly hampered.
To reduce rhe risk. espccially in buiidings with a high concentration of people and/or high value contents. Siemens has developed halogen-free insulution materials having special profile characteristics to suit their applications und employ these on the most important basic types of cables and wires. These new products bear the trade name SIENOPYR and l'ulfil the general requirements for cables and wircs in respect of electrical mechanical and chcmicll pirramctcrs and in addition have the following spccial cha ractcristics :
tr tr >
very little support of combustion no corrosive combustion gasscs from halogcns much reduced smoke dcnsitY
The testing relating to combustion cher:rctcristics of cables and wires are laid down in DIN VDE 0472 for rhe combuslion characteristics in Part 804 gasses in Part 813 the corrosiveness ofcombustion the smoke
Fig.8.14 Vulcanized outdoor water shed termination with clamP on terminal
density
in PreParation
For further details see also page 125 " Halogen-Free Cables with Improved Performance in the Event of Fire." The oreferred areas of application for SIENOPYR cablei are in installations having increased safety reouirements, e.g- hospitals' .high-risc buildings' theatres, industrial buildings' Po\Yer stations' hotels, 79
8 Ti pcs of Wircs and Crrtrlcs schools. dcpartnlent storcs. clectrontc ing plants and the trausporl lnoustry'
d ta
proccss-
Hcat-Rcsistant Non-Shealhcd Singlc-Core
SIENOPYR Cables
For thc application of thcsc cablcs thc rulcs givcn in DIN vDE 0198 Part 3 " Application of cablcs. *ires and flcxrblc cords for porver installations. Cen'
eral rules for cables". must be observed. In particular the data for the relevant basic types of cables, from which the SIENOPYR t!pes were derived' must be noted. In addition also rhe relevent installation and
apparatus standards as \\'eil as standards and directives of the relevant authoritics or institutions must be observed.
In line uirh current market requircments the folloriing cable t)':pes are readily availablc: r-ight sheathed SIEr.\OPYR cables. Heat resistant non-sheathed singie-core cables Single-core sl nrhetic clastomer-sheathed SIENOPYR cables for special purPoses Sy nrhetic elastomer-sh ea t hed llexible SI ENOPYR (X )
For ssitchgcar and distribution boards in drl rooms as rviring cablcs. u'ith incrcascd pcrformance in thc event of firc, cables 4i0t750 V with solid conductor (N)HX4CA or with flexible conductor (N)HX4GAF are used. These cables are also suitable for internal rviring of apparatus having rated voltages up to 1000 V a.c. or 750 V d.c. to earth. The maximum conductor operating temperature is 110 "C. These insulated rvires also remain flexiblc at low temperatures and can be used dorvn to - 30'C.
The construcrion complics riith the rcgulations for heat-resistant s]'nthetic clastomer-insulated cabies (N.ICA respectively N4GAF) DIN VDE 0150 Part 501.
l.v
cables.
I
Apart frorn thc above special tl pes arc mlnufactured c. g. control cabics. Light-Sheathed
SIENOP\R
;;..,".,, -. . . ,.1
Cables
I
As installation cables in buildings u'ith high dcnsitl ol'
people andror valuable conlents for fixed installation above, on as rvell as in and under plaster SI ENOPYR sheathed cables type NHXMH 300i 500 V are recommended. These cannot only be used in dry but also in humid and wel rooms. The cable corresPonds to DIN VDE 0150 Part 214. It is based. as regards dimensions and basic characteristics on the NYM type of construction and is designed for the same maximum conductor opcratine (emperature of 70'C.
I
Insulation of s,r'nthctic elastomer based on Ethl'leneVinl lacetatc-CopoJlmer 2 Copper conductor. solid. tinned 3 Coppcr conductor. Ilexible. tinned Fig. 8.16
Heat-resistant non-sheathed single-core SIENOPYR cable. (N)HX.lGA. (N)HXlGAF'1507750 V
\..Single-Core 51'nthetic ElastomerSheated SIENOPYR Cable for Special Purposes
These cables
1 Sheath of non-crosslinked polyolefine compound 2 Core insulation of non-crosslinked special compound 3 Insulation of crosslinked polyolefine compound 4 Copper conductor, soiid or stranded Fig.8.l5 Light sheathed SIENOPYR 80
cable
NHXMH
300/500 V
kV can be used for fixed traction vehicles and buses to
for
1.8i3
installations in DIN VDE 0115 Section 2 as well as in dry rooms. DiN VDE 0100 permits lhese to be used as shortcircuit fault proof and earth fault proof connections. The maximum conductor operating temperature is 90 'C. The sheath is oil resistant to DiN VDE 0472 Part 803 test type A.
The construction is in line with DIN VDE 0250 Part 602 for special rubber-insulated cables NSGAFOU.
Halogen-Free Cablcs 8.3
I
Shelth ot'cross-linked synthetic elastomer based on Ethl
lene- V in
y
lacetrte-Co poly mer
Insulution of cross-linked synthetic elastomcr based on Ethy lene-ProPYlene- Rubber 3 Copper conductor, flexible. tinned
I
Fig. 8.17
Single-corc s)ntheric elastomer-sheathed SIENOPYR
clble lbr sPccial PrlrPoses r\)HXSCAFHXO 1.8;l kV
SIE\OPYR(X) Synthetic Elastomer-Sheathed ,-(lesible Ceble (N)HXSHXO ' :or tlexible connection c:lbles irnd interconnecting cubles in buildings with high conccntration of people ;rnd or vulueble contents with medium-high mechanicul strcss s1 nthetic elilstomer-sheathed SIE\OPYR(X) c;rbles are used. tYPe
(N)HXSHXO (Fig.3.18). Thcsc can bc use-d in dry. tllmp and wet rooms as rvell as outdoors. They may lrlso be used in fixed installations The cables are constructed closely to DIN VDE 0250 Prrt 81 2 (NSSHOU). The ma.rimum conductor operrting temperature is 90 "C. The sheath is oil resistant
ro DIN VDE 0472 Part 803, test type A. Furtherrnore the cable is KMVr) fault resistant which means Lhey are also suited to meet the special conditions ol rpplication in nucleer power stations.
,-i-iiFliL'
.e.oolant
medium
ry-rffi' I
Outer sheath ofcrossJinked syntheiic elastomer based
on Ethylene-Vynilacetate-Copolymer
2 Inner sheath ofcrosslinked synthetic elastomer
based
on Ethylene-Vynilacetate-Copolymer 3 Insulation of cross-linked synthetic elastomer based on Ethylene-Propylene-Rubber 4 Copper conductor, flexible, tinned
Fig.8.lE SIENOPYR(X) Synthetic elastomer-sheathed flexible cable (N)HXSHXO 81
9 Core Idenrification of Cables
9
Core Identification of Cables
The identiflcation of cores for insulated cables has been agreed internationallY and is incorporatcd in DIN VDE 0293 (Table 9.1 ).
Table
9.1
cables have one core with a smaller cross then this core must be marked green-yellow scction in cablcs with protective conductor or blue in cables without protective conductor.
If flexible
Core idcntilicrtion Cablcs s ith grecn, yellorv core
(markcd J' to DtN VDE 0l-i0 rcspcctivr-ly'G to DIN VDE 0?81.0:31)
Ciblcs u'ithout grccn /1'cllorv corc (markcd'0'to DIN VDE 0250 rcspcctivciv 'X' to DIN VDE 0131i 0:81)
Cablls for fi\!'d instirlliltion I
green !cllo\\
black (othcr colours
)
grecn l ellorv. black r'
brorvn, bluc
3
greeni ycllorv. black. blue
black, blue. brol n
grecni yellorv. black, blue, brown
black, blue. brou n, black
5
greeniycllorv. black. blue, brown, black
black. blue. brou'n. black. black
6 and over
grecn/yellow,
black and numbcrcd
'')
additional cores black and numbered Flerible cables 3)
1
black
1
brown, blue
3
ereenlyellow. brown. blue
black, blue, brown "l
4
green/yellorv, black, blue, brown
black, blue, brown. black')
5
greeniyellow, black, blue, brown, black
black, blue, brown, black, blacka)
6 and over
green/yellow,
black and numbered
additional cores black and numbered r) Ti3 individual colours lreco or
:'
rr
'r 82
yellow or any othd colour combinalion except grecn/y.llow is no! pcrmi(rcd. Cabtes for wiring Panially Typc Tcsted Factory-Buih Asscmbles may hoq,cver bc marlcd grecn or ycllow as w.ll as with dual colouri. This 2-core variant is !o DIN vDE otOO Part 540 and is only pcrmissibtc for qoss secrions equal or grcaler rhan 10 mrtl'l coppcr Tire corc coiour for illumination and lightirlg is brown i to 5-corc cablcs without grccntyclloq corc arc no! yc! harmonizcd
of appararus and
Identification 9
-
Tr;c;mn^rr.ni
rhrt
tn.
core marked greeniyellow must be used exclusivell- for protective conductor (PE or PEN) This must not be used tor any other purpose'
-
The core marked blue is used for neutral conductor (N). This core can be used as required (i e also as phase conductor) but not as protective conductor (PE) or combined neutral and protectlve conductor (PEN). porver supply cables are used in telecomunication installations ro VDE 0800 the green/yellow core must also be used exclusively as conductor with protective l( :tlon.
If
-
I
dJ
l0
Deilnitions of Locations
10 Definition of Locations to DIN VDE 0100
The definition of locations in accordance with the follo*ing categories often requires exact knowledge of the condrrions at site as $ell as of the operating conditions. If. for exampie. tn a location high humidiry occurs only at one definite place but the rest of the location is dry because of proper ventilation. the whole iocation need not be ciassified as damp.
Humid and Wet Areas and Locations are rreas in which electrical equipment must be at Ieast drip protected (lP X1 to DIN 10050).
In areas and locations in rvhich $ater jets are used fbr cleaning but uhere the elecrrical equipment is not normaly directly subjected to rvater jets the
Electrical Operating Areas
.quipment must be at least spiash protected 1lP XJ to DIN .10 0i0).
are rooms or locations used essentially for the opera-
In
tion of eiectrical equipment and eenerally ro qualified personnel onll'.
accessible
These include. ior example. suirch houses. conrrol rooms. distribution installations in separtte rool.lls. separate electrical test depanments and laboratories. machine rooms in pou.er stations and rhe like u here the machines are artended solely by qualified pcrsons. Closed Electrical Operating .{reas are rooms or locations used exclusively for the opera-
in rvhich uater.jets are used and where the eiectrical equipment is directly suh areas and Iocations
jected to the q ater jers than the cquipment must ha\v a sufficient tvpe of protection or suitable additionll protection u hich does not impair rhe proper operation oi' that equipment.
Notc: Protection class lP X5 to DIN -10050 does protecr the equipment against cleanine with high pressure water jets e. g. hosins dou,n or hieh pressure cleanin g.
tion of electrical equipment and kept locked.
The Iocks may be opened by authorized persons onll- and onl_""
qualilied persons are permitted to enter
these
areas.
for example. closed su itchboards and disrribution boards, lranslormer cubicles, switcheear cubicies. distribution boards in sheet-steel housings or in other forms of enclosure. pole-mounted substaThese include,
tlons.
Locations )Yith Fire Hazard
are rooms or locations or sections in rooms or in the open where, owing to local conditions and the nature of the work. there is a risk that easily ignitable materials in dangerous quanrities mav come so close to electrical apparatus that high temperatures on tl.' \v/ apparatus or arcs may cause fire. These may include working. drying, storaqe rooms
Dry Locations
or sections of such rooms as well as locations of
are rooms or locations in which condensation of moisture does not usually occur or in which the air is not saturated with moisture. These include, for example, dwelling rooms (also hotel rooms), ofljces; they may also include: business premises, sales rooms, lofts, staircases and cellars with heatine and
When classifying rooms as locations with fire hazard the relevant regulations must be observed.
venrilation. Kitchens and bathrooms in dwellings and hotels are considered as dry rooms as regards the wiring insrallation, as moisture is present in them only tempo-
rarily. 84
this nature outdoors, e.g. paper, textile and woodworking lactories. hay, straw. jute, flax stores.
Easily ignitable is applied to combustible solid marerials which when exposed to the flame of a march for 10 s continue to burn or to glow after the source of ignition has been removed.
These may include hay, straw. straw dust, wood shavings, loose excelsior, magnesium turnings, brushwood, Ioose paper, cotton waste or cellulose fibre.
Location Types l0
)lobile Buildings
-"...onrtru.tions
which arc suitable lbr anrJ designed for repeated crrection and dismantling such as fair equipment e. g. round-abouts' slides, are:lna -ground stantls. sales kiosks. tents, also buildings for travelling erhibitions, apparatus for artistic displays in the and similar. Wagons which can be largely modi-air fied and used operationaly in a fixed location (e'g' Shorvman rvaqons) are also classified as mobile build'
_
horse. cattle. slreep and pigs. In lddition duc to the prescnce of casily ignitable materials an increased danger of tire may be present. Further dangcrs arc present in rooms for intensive farming and also for small animals e. g. failure of life sustaining systems.
Depending on the form of danger existing in the agriculture operating area. in addition DIN VDE 0100 Parts 720 and 737, covering humid and wet areas and rooms as well as outdoor installations' musr be observed.
ings.
Aress with ExPlosion Hazard
- r.^ arexs in rvhich because of local and operational _
-
L..,rci:rons:rn explosive utmosphere c:ln occur in r danUerous quantity (explosion hazard). Ap.qrplosire atmosphere is u mixture of combustible 1- )r. t"pou.t. mist or dust with air. which contains i,.c usual additional substances (e. g' moisture). under atmospheric conditions such that atter ignition a burning reaction extends unaided.
-
Opcrarional equipment for areas with explosion hazard are selected in respect of zones. temperature class and the explosion group of the combustible material:
-
see
_
Installations on Building Sites
-
DIN VDE
0165.
comprise the electrical equipment for carrying out struitural rvork above or below ground on building sites as rvell as with structural steelwork' Building sites also include constructional work and parts of '"ch which is extended, modified. put into service .,,-{emolished.
at rvhich merely handlamps, soldering irons' welding equipments. electric tools to DIN VDE 0740. ^ g. drilling machines, grinding wheels. polishers and ulner appliances used individually are not regarded as building sites.
Ptaces
-
Agricultural Operating Areas are rooms, locations or areas which are used for agri-
culture or similar purposes e.g. horticulture.
Note: In agricultural areas because of special ambient con' ditions e. g. ingress of moisture, dust' highly chem! cally agreisive vapours acids or salts' to which lhe electricil equipmint is subjected there is an increased risli oi accident both to persons and to farm animals (large animals). Large farm animals include 85
.r
l
l
ryp,,!d U .rllu lnrtillt:ltlOn Ol L:lblCs
Application and Installation of Cables
Cables must be selected and applied in line wirh ruies laid dorvn in DIN VDE 029& and *," .,unauiirl._ ferred.to therein. They must be installed ;; ing suitable installation fixing marerials. ",ili; Th;y;;;
prorecred against mechaniial. thermal cll damase by location or protective means.
;;:i;-
be.
)Iechanical protection rvhich is generally accepted
include:
' >
Insulared u,ires in condurt u.hich bear the identifi_
carion mark A ro DIN VDE 0605.
Such dangerous locations or near floor level.
g
UV
Light
l'C-sheathctl t.ables may be insralled in brick_ cmbedding l;;;;.;;";, nor pernlilted where rhe concrere ts tamped, vibrated or rammed.
pofyr.ria
iri".ui"iy
lan exist io.
fi""a.
"";;p;;-;;
under pl.aster must be insralted verrically parailel to the room corners. In ceil_ :_r^:::r-zontally rngs rhe may be installed using the di;"; ;;;;; :e atso DIN VDE 18015). 'norr o.r cabre nxing :"1:: shape must be considered. W
9:1,:
ll ::
;;il','i;
b.i;g.J ;;;
;;il;
;; ;$..i
::;:l::,l|: ?I;
i"".Tl"rT?i: .cted movement does not cause damage to the elec_ u Ical equlpment.
:::
Apan fro.m the cable oubide diameter and the cable construction also the rype of insrallation tion wilt affect rhe smaijisr ""d ";;;;:
"l""."ui" fi"aj"g.""!lli.
are raid doq,n rn DrN vDE 02e8 Il:',.1:::* :",,"es rarr J (see Table I l.l ).
Metal sheathing as well as any unrnsulated sheath not be used as operitional Itj":-yr, tng conductors nor must "r;;;;r;;;;': tiey oe used lor neutral
or protecdve conduclor. 86
"i;'i".;f;,;d
s ashers.
P
*ork and cemenr. Direcl
A^t_locarions which are parricularly hazardous additlonal protec_tion must be provided" sreel conduit or cladding .. fri"f,
FIar underplasrcr cable musr only be installed bv rr,^ means and pro..rr", ,fr., a" i", a.ioi'l ::.,:!,":h oama,ce rhe cable. Approvcd means of n*ing .r. :r lor rnsrance use of pads of gypsum plur,., o, ,h.up-.j ce.ble clips of plasric or insulcrion .our.d ,"r"1. ,i.l,i adhesive or nailing u.irh spccial n*;"g,
Flat underplaster cable can be installed under plasrerboard.sheets only when the boards ur. ,.aur.a'l rhe \r,all \\,irh pads of_e1,psum plaster. \_
> Sheathed cables. i > Porr er cabies. > Installarion in or undcr plaster, > lnstaliation in cavities. > Installation in rrunkin_s ro DIN VDE 060.1. or
Ir.is not permitted to bury flexible insulated power in the ground.
cables
Lig.lu Pt'C-sheathed cables P l,',C -s he
a
r
hc
d
ca b
t
es,y y B (t
,yyl.t and lead coceretl y r"y h;";;;.," ;; i;:
underground conduit providinc ;" ;;;j; ill,l l"accessible and replacabl. lemarns ;. strong, protected ""d ing;J ";;;;;;;i il^Tlfri:"ilv lrqurds. and venrilared. This type "guinrt
should be rhe exceprion and only used \\'here rrallr)rg drunt and ,?11." urtn
.::l_"ir".:.
minin
g
of insialatioi
i".,h;;;;;.
drug cablcs areused on mo_ ma-chinery
;;J";;;;;;;;
well as convcying _accessorics.as a oove eround and "quip;;;; open_cast opera-.-. uons DrN vDE 0r68 n,"r, olitl"llJoomilar r
In rpecia!
g. u,ith flexible cable for fast moveforced guiding over rollers speciaily con_ :)-::l: i"dcables, e. g. strucrecl CORDAFLe X ' p"f rcii"r"_ prene-sheathed cable NSHTOU must be usel. ca.ses, e.
/oads musr be relieved of purr or 3:!P.!:: :'.1,!: at their connecring
rh" p.ot;iiu.
f^r:l :tl.r..,core conductor "nar. ,h";;i;-;;l;; must be left longer ca.rrying cores, such that iailure tf," ,irui" :lfrent retreving,device the protective conductor.or" "i i, lniy srress rhe currenr carryrng cores. :r,-.j:::":-.roundingafte-r off of the cabte entry p"iii :11e,v:: ". the power cables against sharp "r"
$:i,:"#;::",
bends
Pcrnrissiblc Bcndine
Table l
l.l
Radii
ll
\lininrum pcrmissiblc bcnding radii Rated voltage up to 0.6/
Cablc tl pc
1
kV
Rrted votrilgc above 0.6, I kV
Cables
for pernwnent inslallatiotl
Outer diameter r/ o[ the cable or thickness d of llat cable up to 10 mm
over l0 to 15 mm I over 25 mm
Permanent installation
+d
4d
Formed bend
l(
2d
Fletible cublcs
Outer diamcter r/ of the cablcs or thickncss up
to
I oYer
3mm
I to ll
Fixed installation
3d
3d
Fqp movine
)u
1d
e--.;able entry
3d 5d
Forced guiding
"
e.g.
drum operatton cabie waeon operation
mm
-
'
7.5d
Jd
/
of lht clblc
o\er lo\er ll to l0 mm I l0 mm
1t
6d
ir/
5d
l0 {/
+u
5J
5l
l0 r/
5t
i,/
6t
tzd
1d
5r/
drag chain operation
roller guides
6d
l.) .I
l0 (i
i11
5d
1.5d
l.J
10 r/ Ll
t5 d
t'Thet-rpcofconsrruclionmustbccheckcdlocnsurcsuirabilityforlhisl)peoIopcrrlion
The application and installation of neon Iighting cables is covered in DIN VDE 0128. In addition to this the following must also be observed:
-
Where neon lighting cables enter enclosures they must be covered with sleeving or enter through a gland. In ouldoor installations the cable en!ry must be sealed by sheaths or covers of insulating material to prevent surface creepage.
In respec! of cable constructions which are used for several different types of application it may be advisable to discus the application with the manufacturer. 87
-
I
I
Appiication and Insrallation of Cablcs
I
I.
I
Rated Voltage, Operaring Voltage
The definitions of ratcd voltace and operating voltage of wiring cables and flerible cables is given in DIN VDE 0198 Part 3. Rated Voltage
The rated voltage of an insulated cable is the voltage on rvhich the construction and testing of the cable, in respect of electrical characreristics, is based. The rated voltase is expressed bv ls.o a.c. voltage values Llol U expressed in V: LIo rms value between one-phase
r/
conductor and earth (non insulated surrounding). rms value between t$'o-phase conductors of a multi-core cable or a system of single-core cables.
In a s,ystem rr.ith a.c. voltase the ratcd voltage of the cabie must be at least equal lo the rated voltase ''f the system ro ',r.hich it is connected. This condiriJn .rpplies to the value Uo as rvell as ro rhe value U. In a svstem $.ith d.c. voltage the rated svstem voltace musr not ercced 1.5 timcs rhe rared a.c. voltage of the cabic.
Operating \roltage The opcrating voltaee is thc voltage bet\r.ecn conduc-
tors or bctrvccn conductors and carth pr"aan,; ., * porvcr installarion undcr hcaltht,stablc conditions. Cables y,ith Raled Voltage
uolu <0.61 I
kv
These cables are suitable for application on 3_phase.
sinlle-phase and d.c. installations *h.r" th.'mu*i_ mum permanently permissible operating voltage docs not erceed the rated voltagc of rhe cable by morc tharl 109i' for u,iring cables and fle_rible cables u,jrh ratcd Vollage Lr6i
1096
U<
-1501750
V
for wiring cablcs and llexiblc
volta se L'o.
cablcs
sirh
rared
U:0.611 kV
lf iring Cohle:; unl Fta.rih!e Cuhlt,.r \t.irh Rott,l l.olrugc L:o U >0.611 ky' Thc'se cables are suirable
for application in
3_phase
and single-phase installations having a maximum opcrarrng voltaee not e.\ceeding l0yo above the rated voltage ol the cable. Table I 1.2 Typical rated voltages of various cable types Rated voltage
Cabie type
r00/i00 v 300/500 450/750
single-phase installations where rhe star point is eflectiveiy earthed:
v v v
single-phase installations where rhe star point is not effecrively earrhed providing
Tinsel cords and flat non-sheathed cords FJat building u.ires
Light PVC-shearhed cables Heavy polychloroprene-sheathed flexible
cables
0.6/ 1kv | .8/ 3 kv
4 i 8kv 6 /10 kv
kv 12 120 kv l4 /25 kv 18 i30 kv :0 /35 kv
PROTOFI RM-sheathed cables Single-core poli chloroprene-sheathed
lor special purposes Neon lighting cables cables
8.7i t s
8E
a) in 3-phase and b) in 3-phase and
UolU
220i 380
The cable may be used:
Trailing cables
that any individual earrh laulr is not susrain.j
Ionger than 8 hours and the rotal ofall earth laulr._. tlmes per vear does not cxceed 125 hours. If this
situation can not be ensured than. ,o anru." u life of rhe cable. a cable having a higher
service
rated voltage should be selected.
for Direct Current Installatiotts For cables in d-c. installations the permanent perCables
missible operadng d.c- voltage between conductors must not exceed 1.5 times the rated a.c. voltage of the cable. In 2-wire earthed d.c. installationsthis value must be multiplied by a factor of 0.5.
Rated Opcrating Voltagc Conductor Cross Section I l '2
11.2 Selection of Conductor Cross-Sectional .{rex General
The temperature rise. respectively current-carrytngcaoacitv. of a cable is dependent upon the type ol construction. the characteristics ol the materials used and also operating conditions' In order to achieve a sat-e design and a full service life of a cable the
conductor cross-sectional area must be chosen such th:rt the requlrenent current-carry ing capacity
i
tr tr 1
thc
co
/"> loading
/o
nditions of
normal oPeration and shorr circuit
satistled. This rvill ensure that no part of the '-rble at any point in time is heated above the rated maximum permissible operating [empcrlturc rcspcctively short-circuit tcmperature. Current-CarrYing CaPacitY in r'r*ormal OPeration
The design of installation projecrs is simplified by using esrablished data collected over several decades in respect of current-carrt ing capacitl: undcr practlcal aoolications rvhich has now been incorporated in var'
ious regulations governing apparatus and installation. For electrical installations in buildings the standards for electrical installation of buildings DIN vDE 0100 apply for power installations up to '000V. In this standard. up to the present day' in /-ilrt 523 the types of installation rvere divided into ,-rree groups:
Group 1: insulated conductors and single-core cables in a conduit ,-iroup 2: multi-core cables for fixed installation Group 3: single-core cables for fixed installations and power cables. The xssociated values for current-carrying capacity had been determined originally for rubber insulated cables.
By todays standards, these groupings of types of installation appear extremely rough but have, however,
proved to be adequate for the methods practised at that time. Meanwhile, however, different installation practises have developed and modern, more sophisticated materials have become available. These developments have necessitated the evolution of more detaiied project planning.
In Februrry
1988. the specilication
DIN VDE 0:93
Part .1 " Recommended values for current-cilrr]-ing capacity lbr sheathed and non-sheathed cables tor tixed wirings. tlexible cabies and cords"' wus published. This pubiication contains comprehensive and detailed information on the relevant terms and regularions required to determine the cross-sectional area of conductors for normal operation and for shortcircuit conditions. Firstly the Precise operating condi' tions on rvhich this data was based were detlned and specilicd. Blscd on rhcsc rtferent'e !)perdtlttg conclirrr.,rs. rvhich teke into lcount thc rrpe oJ' operdtiotl as rlcll as iutullutiort tncf ttnbient c c'rtrtlilir'trls, tabu' lated data rvas prepared ol ratatl lalrrr's of currentcarr,ving clpacity | (rlted value). To clter tor conditions rvhich der iate from the ilgrced opcr:lting condirions. convcrsion fuctors were prepared. The relarionship:
I,:l,nf applics riherc fl/ is rhe product of ull conlerston tlctors rvhich arc aPPlicable. As J basls tbr ty.'pe of operation. t t.rttllrtti'.ltis ttperutitttr *as sclectcd. rvhich is operation at constant current lbr a durction sufficicnt for the cable to reach thermal equilibrium but otherwise not limited in time'
Short-tinc tnd' intermittentl operatiort e'g' for
the crane starting currents of motors or the operatlon or installations are described in Section 13 6'
The spec(ied untbient !empcratLrre for all applications is :O iC ind it is required that the room is sufficiently large and ventilated such that the ambient tcmperatu.. i. not noticexbly increased by the cable losses
The in.stallation conditions, in comparison to the pre' viously used groups I to 3. are more precisely defined and enlarged. One differentiates norv between:
\tethod of Installation
tYPe
A:
lnstallation in walls having low thermal conductivity' lvlethod of installation tYPe B I : Installation of single-core insulated cables in conduit or duct on or in a wall, Method of installation tYPe B 2 : Installation of multi
Method of installation tYPe E: Insrallation oi cable in free atr. 89
. ^ r !l,Hu!Arrwrr dllu lltstil
ilUon oI LaDjcs
Table I 1.3
Currenr-carrf ing capacit-"-. Cabrcs for fired instatarion. Mcthod of instatation A.
I
nsularing material
Br, B
l
and
c
PVC
Type designation t)
NYM. NYBUY, NHYRUZY, NYiF, NYIFY, HOTV-U, HOTV;,HO7V-K, NHXMH
Maximum permissible operating temperature
70
8;
"c
No. of loaded conductors Method of installation
ln thermally
.
insulated $,ails
&& PF I
nsulated conductors
in conduit r) 5r
&ffi RR M ulri-core cable in
conduit
s'
Multi-core cable in the wall
.9n or in rvalls
In condurl or
Insuiated conducrors rn conduit on the
uallrr
1-r j--r
4d
4@)
Insuiated conductors rn trunking on the wall //./,/,/,/)
or undcr plaster I direcr installation
trunking
Mulri-core cable in conduiI on the \r'a ll or on the lloor
i--t
4@
bb
Multi-core
blc on
ca
thc rvall or on
the \v
J----,
1@J
\4ulLi-corc cablc in
trunking on rhc u,all or on the floor
Singlc-core shearhed cable on the u,ail or on the floor
.//rtrt
?n'/.Fi ryt'n Insulated conductors, srngle-core sheathed cablcs. m ulti-core cable in conduit in masonry 6)
Multi-core cable, flat wcbbed building wrrcs ln the wall or under plaster 7)
-opper conductor Nominal cross-sectional area tn mm:
Current-carrying capacity in A
1.5 IJ
I /.)
18
6
t0
JI
l6
42
.i)
56
)0
89
70 95
t20
90
I*
I
2l
19
28
28
lo
41
36
)t
50
5.5
19.5
tt.)
LO
24
35
46
41
57
46
68
50 68
61
l)a
89 111
63 85
90
77
112
110
96
r08
95
138
151
r 19
rJo
134
164
192 'r1a
188
269
101
€
l ).-) 21
171
207
239
-
/o
Conductor Cross Scction I1.2
Table I l.-l
Currcnt-carrl ing clpacity. Crblcs for llxcd installation. \lethod of instlllation in ftee 3ir
-
PVC
Insulating material Type designation
NY\,t. NY)vlZ, NYMT, NYBUY, NHYRUZY. NHXMH :), NYHSSYCY ])
"
70
)la.rimum permissible operatlng temperature
'c
No. of loaded conductors Method of installation
Ae ''i l>03d CoDper conductor ainal-cross sectional afel rn mm-
Current-carrying caprcity in A 18.i l)
r.5 2.5 + 6 10 10
60 30
z) i5
1?6
101
50') 70')
153
"'
JJJ
95
I'
196
Typc designation and fur(hcr dctails
:r Not included in DIN VDE 0:98 I' Ratcd voltag. 1.6i6 kv
"'
Part
iI Secdon E.l l. Insuladon
ofc.oss-linkcd polyolcfine compound
Not included in DIN VDE 029E Part,t
r ur each of these reference operatittg corlditions the recommended rated values of current-carrying capacitv /. are shorvn in Tables I 1.3 and I 1 .4. The headings r ,.he tables include diagramatic representations of the installations for ease of understanding which, togelher with the footnotes, provide a detailed description. The current
> ( tr
two-core cables with two conductors loaded as well as for two loaded singletore insulated con-
ductors or two loaded single-core sheathed cables given in Table 1 1.3 columns 2. 4. 6 and 3 45 rvell as Table 1 1.4 columns 2 and lor
>
three-core cables with three conductors loaded as well as for three loaded single-core insulated con' ductors or three loaded single-core sheathed cables given in Tablell.3 columns 3. 5' 7 and 9 as well as Table 11.4 column 3.
Typc designadoo and furlher dcrrilr in seclioo 8.1 corducroG i! conduit ia cnclosed floor trcnch Also appliG lo iosulalcd coDducro6 io coDdui! i! ecatilatcd 0oor u.dcb Also appliG to ouili-corc cabl. iD opc! or vcotilatcd trench Also applies to idsulalcd co[duc!o.s, siogle-corc shothcd cablc, rnulti
''_' Also appliG (o iosularcd _'
" : r'
91
r
r
.'riri)rrcauon and tnstilllalron ol cables
Whc::. for cxample, in a multi-cerrc cablc all conductors are not loadcd at tlte samc tinlc. the I'alue of
curreni-carr\,ing capacity is possibll. r:reatcr than that given in Tables l l .3 and 1 1..1. Thc rclo,ant r.alues depend on the type of construcrioll of thc cable and thc insrallation conditions such that common conver_ sion factors cannot be prepared. For reasons of safety it is recommended to consider only the number of loaded conducrors, disregarding rhe rotal number of cores. rvhen allocating a value of current_carrvin s capacitl. from Tables I 1.j and I 1.1. Only in rhis wai cen olerloadinq be safely aloided.
The current-carrying capacit.i' at ambient temDera_ tures other rhan i0 "C can be esrlblished usine rhe conve:;ion facrors given in Table l.l.l0 in paril of t
his u ork.
I he currenl-carrvrng capacitv quantirics ,eiven in Ta_
t,
bles 11.3 and 11.-1 appiy *irh rhe proviso rhar only eirher one multi-core cable or ru o iespectivelr. three -ringte_
insulared conductors. alternatir.elr siLeathca cre cable. are installed. Ifser.eral cables are arran-eed ne\t to one another. Jbo\'e one .tnolher or adiucinr to or :bo!e porrer cables thcn the clrrrr'ins clpecirl. is rcduced corresponding ro rhe hindefcd hear'dissipation. respecrively rhe addirional hear eenerared. Cl)nveision factors rlhich clter for rhis g,:ouforg oi cables for fixed installarion (possiblr. ,vith'po'*,cr cables). are given in Tables 1.l.ll and l.l.12 in Sectron 1.1.1 of part 2 of rhis worx.
AIso included in part 2 rvill be found informations on flexrble cables and merhods of insrallation uhich could not be_incjuded in part 1 for reasons ofspace.
Lonversron lactors are also incorporated for lrcat re_ .tistant cables, for ntulti-core cabks rr.ith ntore thart {irc
Currcnt-Carr.r.ing Capacity under Short Circuit
,c^rtrermall) permissiblc short-circuir currenr /,r. .rs.oetermined from the rated short_tine current den.v/ r-./,h. Irom Table I .1.16 in Section 1 .1.3 of parr 3 ot tnrs work from: l,o.=
I,r,l/llli
/,u. = /,r,, S.
n here
/'r' Thenmally permissible short-crrcurr current-carcapacirv ,rrb! rylng I uermally efectiue short_circuit currenr
92
tr, r*
Rarcd short-circuit duration (rr,= I s) Short-circuit duration in s -/,n, Rated short-circuit current densit\. S" Nominal cross-sectional area ofconductor
Determination of Voltage Drop Especially in low-voltage networks. apart lrom rhe current-carrytng capacity, the conductor cross_sec_ tional area must also be considered in respect of volta,ee drop Arl ro ensure this does not exceed the per_ missible value. For the calcularion of this. .ornpr.hensive aids for desi-sn are included in Secrion 1.1.,{ of part I of rhis u,ork. Protection against Excessire Temperature Rise it is possible to heat cables above rhe permissible limit bv an operarional overcurrenr as s,eil as bv short circuit-current. prorective der.ices must be in. corporated. therefore. for protection against ovcrcur._ rent as lisred in e.g. DIN VDE 06j6. DIN VDE 06, and DIN VDE 0660. The co-ordination oI these ovcrcurrent protection vrces to the conductor cross_sectional
dc_
area is made bv refcrcncc ro DIN VDE 0100 part -130. Details lbr this arc also includcd in Section t.:.S in part 2 oi this work.
National and International Standards l2.l
Power Cables
12 National and International Standards 12.1 VDE Specifications
DIN VDE
0273 Cross-linked polyethylene-insulated
cables, nominal voltrses : UolU 6i10, l2120 and l8i 30
In
respect of construction, testing and applicatioo d 2orver cables. the relevant valid editions of the lollowing VDE specitications and DIN standards applv:
[
DIN VDE O]7] Cross-linked polyethylene-insul:rred conductors for overhead transmlssion lines. nominal voltage:
uolu 0.6lt kv ,..i VDE 0]06 Recommendations on coiours for polymeric sheaths and coverings with polymeric and rubber insulation for cables and flexible cords
DIN VDE 0207 Insulating
and
DIN VDE
0239
DIN VDE 0255 Regulations for
mass-impregnated metal-sheathed
power cables (except external gaspressure and oil-filled cables)
DIN VDE
I \
oil-filled cables and their accessories for nominal voltages up to uolu 2301400 kv
tions rvith nominal voltages up to
DIN VDE
0258 Internal-gas-pressure cables and accessories for alternating voltages up
to
l/)
DIN VDE
_
DIN vDE 0266 Halogen-free cables with improved characteristics in the case of flre; nominal voltages: UolU 0.611 kV DIN vDE 0271 PVC-insulated cables with nominal voltages up to and including
Conductors
DIN VDE
0298
Application
DIN VDE 0272 Crosslinked polyethylene-insulated cables ; nominal uoiu 0.611 kv
voltage:
of cables, wires and flexible cords in power installations
Part I : Ceneral for cables rvith rated voltages UolU up to 18/30 kV Part 2: Recommended values for currentcarrying capacity of cables for fixed
installation
with rated
voltages
U,;lU up to 18/30 kV
DIN VDE
of fictitious diameters for determination of dimensions of protective coverings for cables and flexible cords for power installations.
0299 Calculation method on the basis
with plastic insulation and lead sheath for power installation
kv
of
cables, wires and flexible cords for power installation
0295
0265 Cables
6/10
v
DIN VDE
KV
-
-
1000
0256 Low-pressure
VDE 0257 E.\ternal-gas-pressure pipe type cables and their accessories for alternating voltages up to 275 kV
and
l'le.rible cords used in power installa-
sheathing com-
paper-insulated
Definitions for cables. rvires and Ilexible cords for power instrllation
DIN VDE 029] Identification of cores in cables
pounds for cables and flexible cords
_
kv
Part
DIN VDE
1:
O3O4
Power cables
Thermal properties of electrical insulating materials
Part 27: Ceneral procedures for the determinatiod of thermal endurance properties, temperature indices and thermal endurance profiles Part 22: Lisi r:f materials enC available tests 93
12 National and Intcrnational Srandards
DIN VDE 0472 Tcsting of cablcs. rvires and flcxiblc cords
DIN \rDE 0100 Ercction of powcr insrallations wirh ratcd voltages up to 1000 V DIN VDE 0l0l Erection of power insrallarions wirh rated voltages above 1 kV
DIN VDE 0103 Mechanical and thermal short_circuit strength of electrical power installations
DIN VDE 0105 Operation ofl power installations DIN \rDE 0111 Insulation co-ordination to equipment for three-phase a.c. systems above 1 kV
,lN YDE 0115 Rail-borne and trackless vehicles DIN VDE 0l 1E Specilications for rhe crecrion of elecrrical insrallations in mines be_ low ground
DIN VDE 0168 Spccification for the erection and operation of elecrrical insrallations in open-cast mines, quarries and similar ri,orks
DINVDE 0211 Planning and design of
overhead pou'er lines with rated voltages up ro 1000 v
DIN VDE 0228 Proceedings in rhe
case of inrerference on telecommunication installa-
rions by electric power installations
DIN
17640
Lead and iead alloys for
cable
I2.2
Standards of Other Countries
Cables manufactured to standards of orhcr countries e.g-. British standards (BS). French srandards (NF). Italian standards (CEI), Swedish standards (SEN),
comply normaly
in their
basic construction witi
cables manufactured to VDE.standards but deviate in dimensions and test requirements. Where required
AG can also supply cables to meet rh;se or other standards. Certain rypes are already approved. by the relevant standards institures. Siemens
12.3 IEC and CENELEC Standards The international commissions IEC and CENELEC have the responsibility to unify the r.ar;-ing srandards which exist within the E.E.C. Ar rhe piesent rime lt cannot be forseen by u hat date full harmonization v will be achieved. In deference ro IEC. CENELEC does not normally prepare independant specifica_ tions. The " final harmonized documcnts.. aic issued by CENELEC and after a short introductory period, enforced to be incorporated in the narional specincations of the relevani standards institutions without any change of content. In certain circumstances CENELEC also issues European Norms (EN norms) which must bc acceprcd by the mcmber counrriei unchanged in form and contenr. The following IEC publications are relevant to power cables:
sheaths
DIN
89150
Cables and flexible cords for instalIation on ships; survey, current rat-
lngs, overcurrent protection, direc_ rion for Iaying
.DIN
89158
Power cables wirh copper braid; MGCG
t1..pe
DIN
89
159
Communication cables,
type
FMGCG; nominal cross-sectionil
DIN
89t60
area 0.5 mm2 and 0.75 mm2 Power cables without copper braid;
type MCG
IEC 28 (1925) Revised ed. International standard of resistance for copper IEC 55 Paper-insulated metal-sheathed cables for rated voltages up to l8/30 kV (wirh copper or aluminium conductors and excluding gas-pressure and oilfilled cables) 55-1 (1978) Fourth ed. Part 1 : Tests 55-2 (1981) First ed. Part 2: General and construction requirements
Electrical installation in shiDs 92-3 (1965') Second ed. Part 3: Cables (construction, testing and installations)
\J
Narional and Intcrnationil Standards
IEC lll (19S,1) Sccond cdRcsistivitl t't' conrnrcrcial hlrtt-.jrarvn alunrinium clcctricll cond uctLr r rvirc IEC
1.+I
Tests on oil-t-rlled
lnd
acccssones
-uas-prcssure
cables and their
141-l (1976) Second ed. Part 1: Oil-tllled. paper-insulated. mctul-sheathed cables and accessories tbr liternating loltaees up to and including -100 kV
'
ll I -l ( I 96-1) First cd. Pl rt l: .rcrnal qas-prcssurc clbles ancl lccessories tbr alternating voltar:es up to 175 kV
lll-3 ..IT
(
196-1)
First cd.
J:
12.3
IEC l.l0 ( 1966) First cd. Irnpu)sc tcsts on cablcs and thcir:rcccssorics IEC 137 (1931) Second cd. Calculation of the continuous current r:rrins of cables ( 100920 load factor) IEC 3ll (1970) First ed. Fire-resisting charlcteristics of electric cablcs IEL JJ-:
Test on electric cables under fire condirions l-12- 1 (1979) Second ed.
Part l: Test on a sinsle vertical insulared crble
lirc
or
i-r:--.i (1982) First cd. Parr -i: Tcsts on bunchcd rvires or cablcs
'-.iternal cas-prcssurc (gas comprcssion) cables and acccssories lbr rltcrnttins volrlues up to 175 kV
IEC 501 (1931) Third ed. Extruded solid dir-lc.ctric insulatcd porvcr cablcs ibr rrted voltages tionr I kV up to 30 kV
l-tl--+ ( l9lt0) Firsr cd. Part -l: Oil-impregnatcd papcr-insulatc.d high prcssure oillilled pipe-type crblcs and their lccessorics lbr alternatins voltagcs up to and including.l00 kV
IEC -i'+0 ( l93l) Sccond cd. Test methods lor insLrilrions and shearhs of electric cubles and cords (chsromcric and thcrmopllsric compounds)
IEC 167 (196.1) First ed. ivlcthods of tcst for the derermindtion of rhc insulation resistance of solid insuhring milterials
IEC 754-1 (1982) First ed. Test on gases cvolvcd during combustion of electric cables. Part 1: Determination of the amount of halogen acid gas evolved durins the combustion of polymeric materials taken from cablcs
IEC 133 (198.1) Sccond ed. Guide to the selcction of high-voltage cables
rF'216 zluide for .
the determination of thermal endurance
operties of electrical insulatins materials
261-l (1974) Second ed.
'rrt
1:
IEC 311 Common tcst mcthods lor insulating and sheathing matcrials of clectric cablcs 31 1-1 Part I \ [ethods for seneral lpplicarion
veneral procedures for the delerminirtion of ther-
3l1-1-I (1985) First
mal endurance properties, temperature indices and thermal endurance profiles (s. DIN IEC 216 Teil 1 / VDE 0304 Teil 2l)
Section One: - lv{easurement of thickness and overall dimensions Tests for determining the mechanical properties -
216-2 (197 4) Second ed. Part 2: List of materials and available tests G. DIN IEC 216 Teil 1 / vDE 0304 Teil 21)
IEC 228 (1978) Second ed. Conductors of insulated cables iEC 229 (1982) Second ed. Tests on cable oversheal.hs which have a special protective function and are applied by extrusion
ed.
811-1-2 ( 1985) First ed. Section Two : - Thermal ageing methods E11-1-3 (1985)
First ed.
Section Three:
-
Method for determining the densiry Water absorption test Shrinkage test
9)
l2
National rnd Intcrnirrional Standards
8l 1- l-4 ( l9Si) First cd. Sccti(ln Four: - Tcst rt lo\ tcrlpcrlturc
3l I-l Part l Methods specific to elastomcric compounds
811-l-l (1986) First
cd.
Section One: - Ozone resistance test
-
Hot set test \lineral oil imnrersion test
81 I --i
Part
l
lvlethods sp.ciiic to PVC compounds 1-l- l (19Ei) Fjrst ed. Section One: 31
-
Pr:ssure resr at high tcmperature Test lor resistance to crackin!:
8l I -l-2 ( 19ti5) First ed. Scction Trvo: Loss of mass Lcst Thcrntal stability tcst 8l 1 -.1 Parr 4 \4ethods specific ro polyethylene and poll.propr. lene compounds 81 1-4- 1
(1985) First ed.
Section One: Resistance to environmenlal strcss crackins
-
\Vrapping tcst afrer thermal ageing in air \{clsurcmcnt of the rnclt llou inder Carbon black and'or minerrl conrcnt mclsurcnrent in PE
IEC 310 (1980) Firsr ed. T!.sts for porver cables rvith crtruded insulation lbr rrred lolrages abor.e 30 k\t (Lr.:-.j[ li\'.y up ro I j0 kv (Li-: 170 kV)
\-
Tlpcs of Construction of Lorv- lnd High-Voltagc Cubles l3.l
l3
T-v.'pes
13.l
of Construction of Lorv- and High-Voltage Cables
General
When designing cables it is necessarv to take itccounr oI both ambient conditions and the electrical stresses rvhich ma-v- occur. Whcre:rs the ambient conditions arc important rvhen selecting the right tvpe ot'protecrive covering and armour. the electrical stresses are ' : decisive tuctor tbr. rmonsst orhers. the thickness of rhe insulltion and the right rvpe of screen. A distinction is made betrreen cabies ha,,ing a non-rldial .-r\ctric fleld (e.9. belted cables) and radial field
,
bles.
,\[ulti-core cubles vith nort-ntLliul ./ielr/ have only onc screen tbove the Iaid-up cores, They are. as cun be sccn frorn Table 7.I (see page .{5) dcpending on the material useci for insulation only permissible up to cable rarcd t oltage of nruximum L'or L :3.7r10 kV. Paper insulated cables rvith nonradial tleld are also knorvn as belted cubles. as abovc the laid-up cores an addirional rhin layer of insulation is added, namely the belt insulation. High-tension cables manufitctured to VDE are normally used for nctworks rvhich have a non-earthed star point. The insulation " conductor,lmetal sheath " is therefore dimensioned such that the cable can aiso. '- the event of an earrh fault. remain in operation z-{r several hours wirhout incurring any damaee (see rge l-17).
'
To meet the requirements of standards effective in -rher countries for nelrvorks with non-eanhed star ,,oint (e.g. nerworks wirh earth-fault compensarion or insulated star poinr) belted cables wirh increased
In the Federal Repubiic of Germanv. rvith cables having PVC insulation on rated voltases of l0 kV, normally multi-core cables are used. For medium-voltlge cables with XLPE insulorion L'e L'=
6r
hos ever single-core t) pes are mostly prelerred. Three
laid up single-corc XLPE cables have advanragcs rr hcrc instlilution spece is Jt J prcmium. The senicc
lili
ot' r:redium-voltase cables wirh
insuhtion is influcnccd
b_v.,
\LPE
ingress ol' moisture (sce
page 30). Thc'retbre turther developm!'nr has rhe rxr-
gct to limit and loculise the insress of rvurer rr hcn the cable sheath is tlamagc'd. T_"-pes oi construcrion riith PE sheath (sce plge 37) .rnd longirudinll *lrertrqht scrccns
lrc
thL'rclbrc ot'incrcascd sieniilcancg.
Dimensions and tcst spccilicutions of cables as rrcll lbr thcir installution are laid do*n in national VDE spccilicarions and international IEC standards (see pagc 93). Apar! from these a larse number ol othcr types of constructions erist for special applicirtions (sce page 12.1). as rcsulations
The cables must be sclected depending on rated voltage. the requircmcnts in opcration and also economic considerations. Table 13.1 shows the various basic t.vpes of construction of cables. On pages 102 to I 23 the cable typcs together rvith tcrminations and jointing methods commonly used in Germany are illustrated. For the selection of cables the chapter " Planning of cable installations ' (page 141) should be observeo.
belt insulation are often used. Radial field cables have a screen above the insulation of each individual phase conductor which directs the field lines in a radial formation. Radial freld cables tnclude all single-core cables having a concentric conductor and screen as well as multi-core cables havins a.conducting layer above the insulation of each indil vldual core: the interstices are field_free.
The metallic components of the screen (see page 46) can be arranged also either above each individual core or above the laid-up cores. 97
l-1
Trrc. (rl'(
-l'ublc
l-1.
Clrlrics
I
()n51rucli()n
oi L,,rr-
lrrrcl
ilrr:lr-\ olril!l ('Jbl-s
Ilusic corrsllucrions rrl clri.lcs
*itlt insullliotr ol P\'(
Dill_rlrnr rr l' clcclnc ficld
Rltcd ollrscs
rrr
\LPt: T] n(-,\l- ctrn(tl
rrcl trrrl
Erlnrplcs ol'
\
(,,
t) pc dcsi!nu rion
L
KV ,\'
rn-r udi u I li c ld
cu hle,.t
Cl blcs rrithLrut rrrctal cr.rc'ring
N\ \'. \.\\'Y l\\':'. \.{l\\'
\lLrlti-corc cablcs
\flth
conccnl nc con.:uctcrr N
\'C\\ \'. \..\ \'c
\
\'
]\C\\ \' :,. \A:\C\\ \ Up t() -r.6 6
!\1tlt llilt \lcel rrire u;:Iout
.wliul t it ll c,ti!ct Sinrl('-core eirblcs ir tth coneclttric cLrIl!j!.i!i(rr
\\ rth e()irnf[ :.!rccD
-r.6 6
liom i.(r (.l ] rr itlr copfrcr :crccn
lor X LPE Thrcc-corc cablcs uith frorn 3.61 6 coppcr scrccn abovc crch indir idual crr re
P:rrtirrl discirargc-licc coI.15tructt()ti b\ !r5c ol- I cond ucting lal cr trctrr ccn conO ucl()r and lnsu
i\-
l\
N
YS\"
S:
\'. \,\ l\S: \'
\,\\
SY
Iillion {inncr
cond ucting llr cr) us rr cll as llt outcr
N]XSE]\'. N/\]XSE]\'
h\ cr ly bondcd 10 thc in su lt rion c()nd ucting li rnr
IOT ,\ LPE
from
98
-1.6 6
Three-corc. cables q ith a conduclins inner larer ubor e the laid-up cores and a coDcenlric copper screen or flat steel \4ire armo ur
N]XS:\" NA:XS:\' N:XF]}'. \ A]X F]\' NY
F\'. NAYFY
[]rrsic
lc
\ ith plrpc:- iir5ulilti(rn unti
trtcl,tl .i:cltth
C
onstrLrcti
l-1.
I
" (tttlt:s inlprcr:natctl cltblct
T1 pc rrl' constructttrn
Errmplcs oltrpc dcsir:nalitrn
Bcltcci cablcr: Thc Il id-u p corcs Jra surroundcd b\ ] colnntolt instrlatiorr - l-.clt irtsulat irrn - lolle\\\cd b\ thc nrctlrl shctrtlr
\KLEY
irges
L'
rr
6 l0
\,.\
K L EY
\KI]A \.-\ K U.\
t
-1o I ii
-r
()
Singlc-ct.rrc clrblcs
:
Cond uctor s ith in:ulu tion.
xnd protccri\c lr\ crs
tq
I,l8
t0
l-or r oltagcs ( ,, a : -1.6 (r kV untl :itror c :r llr,, cr ,rl trrct.rili:eLl frirlcr tr iI]clLtdcd lbtrr c thc insullrtitlrr. to cnsurc run;- caritics in thc diclcctric rcnrlin licld l-rcc und ltcncc corr)n:l-trcc. CJ\ it tc\ rnlr-'" r:ccur bcIorv thc nlctitIshcuth duc to chi.lngcs in volurnc ol'thc inrprcunat.ing nrass causcd through vltri tions rn Ioird.
Scparatc lcud-sherrhcd (S. L.) ctblcs: TIrree single-core clbles each u,ith lcad shcath and corrosion protcction. laidup and provided \\'ith rire ncccssarv olerxl protecri\ e Ia) !-rs. S. L. cirblcs Ibr I 1.6 l0 kV and I 7.1 -:0 kV
NKLEY
\,\
K L EY'
NKY NAKY
N
EK
E
N.\ EK
I],\ E
B,\
are commonl.v" used in Gennuny.
0 ro
18,
i0
H-Cable
:
Paper-insulated cores covered by H-loil are laid-up and are surrounded by textile webbing rvhich contains aluminium wires interrvoven. A common metal sheath and protecti\.e layer is then added overal. This type ofconstructron is now used in Cermany only for special applications.
t ilh l"od ,h""rh (puper-lcrd
-q"bl"t
clrblc) and cables
NHKRGY NAHKRGY
$irh iriuminiurn shc*h
qo
I3
Tlpcs of Consrruction of Low- and Hir:h-\-ol13ng
l3.2 Tr pe designation
C'n61c-5
RF
R\{ V Cables arc dcsigna led \\'ith:
>
,\bbrcr,iltcd dcscnptlon of thc cable desicn and its component materials
tr > > >
H
Number of cores by nominal cross-sectional arca of conductor in mml Indications of shape type of conductor Where applicable nominal cross-sectional area of scrcen or concentric conductor in mm: Rared voltage in kV (sce Section 17).
The description of type of construction is derived by adding a combination of letters after the firsr letter
'N'
building the order ofconstruction out*ards from 'he conductor. The letter ' N ' indrcates " Norm 11 pe ' and designates cable tlpes uhich comply uith rhe VDE specilicarions nrentioncd in Sections ll and 1,1. The follo*'ing are not indicated: _, > >
> > >
Additional S1'mbols for Cables with lmproled Characteristics in the Case of Fire
HX 'l FE
Insulation of crosslinked Halogen-free poIymer compound Shcath of cross-linked Halogen-free poll.mer compound Sheath of non-cross-linked Halogen-frce po-
lymer compound
Insulation retention (symbol appears after the designation of conducror)
;iymbols for Ships Cable
\{ G \J
Power supply ships cable ro Dsutatron of EpR Sbeath of CR Screen of copper braid
HNA standard
l
Slubols for Conrtuctor DF
RM SE
SM 100
The rated cross-sectional area of copper screens is given after an oblique sign 'i ' locared aftcr the symbols for the phase conductors e.g. NYSEY I x95 RMi 16 6 10 kV. The rated cross-sectional lrea of the concentric conductor is also rndicated folloriing I ' sign afrer the sl nrbols for the phase conductors c.g. NYCWY i x 95 SMi50 0.6 I k\/. Further Commonlv Used Sr mbots
Copper conduclor lnsulatron ol- impresnut!'d papcr (core. bclr ) Inner and outer conductins lavers in cables rrirh pollnrer insulation Inncr coverings Fillcrs of the interstices Inner beddings of fibreous materiais.
HX
OM
Flcxible circular conducror Stranded circular conductor conrpacted br cither squeezing through rollcrs or lhe us; of shaped wires (for thermall-"- stable cablc\ * ith paper insulation) Circular hollow conductor, lhe diamerer of the oil channei given in mm preceds the Jerter 'H' e. g. RMiV 14H Stranded conductor of oval cross-section
Solid circular conductor stranded circular conductor Jotrd sector shaped conductor stranded sector shaDed conducror
YV IYV O AA
Rcinlbrccd PVC shearh Reinforccd PE sheath Opcn armour (FO or RO) Double outcr pro(ccrive la1,cr ol'fibrous matcria
Tc sv
I
Lead sheath ol'lead Tellur alloy Special inrprcgnation for cable with paper insulation for steeply sloping cable runs
(sr':
nd
: non-draining compound
pagc 35)
see
Lctter Designation 13.2
Table
l-1.2
Summary ol'the main lcttcrs uscd for the typc dcsignation of cable
Construclion clenren(
r-
027 | . 0272. 02'7 3
High- and crtra high-voltaee ceblcs DIN VDE 0:56. 0257,0258
N
N
no le!ter
no lelter
Paper-insuhtcd
Poll"me
cables
insulated cables
DIN VDE O]5J Norm tl pc
DIN VDE
0265,
Conductor no letter of aluminium Insulation Paper rvirh mass impregnation Pcper oil impregnated - lvi!h high-pressure oil cables in jleel prpe Paper rvith mass impregnation
no lelter
o OI
-
Ibr external gr.s pressurised cable lor internJl g3s pressuriscd cablc \:C. polyvinylchloride PE. polrethylene XLPE. cross-linked pollcth-vlene
P
-
I
]Y 2X
Concentric copper conduclor longitu
-irhirh *are form iay
c cw
Coppcr screen - lor single-core crbles or for multi-core cables rvith common mctallic scrccn
S
-
mclallic screen on e:rch core in multi-corc cxblcs
SE
Screening in multi-corc cirbles trirh p!pcr insulation
rnd common mcral sherth {H-clblc)
-
single-corc screening !r'irh metalliscd pdper (Hdchsrddrer Folie)
Metal shearh of lead - for single.core cables and multi-core cables with common sheath - for three-core cables with corrosion protection on each sheuth - non-magnetic pressure protection bandage on the lcld shearh of aiuminium
-
H
K
EK
:
KL
smooth corrugated
KL KLD
.ron laid-up corcs
u
-laid-up coics Thermoplastic sheath and inner protective covering
- rYL
-
UD
SneaLn
PE shearh
'app€d bcdding with addirional laler or plasttc tapc
I
Y
Y
2Y
2Y
E
E
Armour
-
steel tape
flar steil wire round steel wire spiral binder taDe skid. wire (non-magnetic)
F
F p
F R
G
GL
steet tubc
ST
Outer protection
_
-
iliE",Aflf,"n"
0ute) in compound
Cable wirh IJoIU=O.6ll
-
Y
PE sheath
I
2Y
kv wirhout concentnc conductor
wr(h grecn/ycllow core wltnout grecn/yellow corc
-r
-l
-o
101
rJ
I Jpcs ur
\-onsrrucuon ol Low_ and Hrgh-voltage Cables
13.3 Selection of Cables and Accessories Tablc 13.3 Cables and associate accessories Construction
Dcsignation,
Preferrcd applicarion
Limited applicarion
Power cable: lndoors. cable trunking. outdoors and buried in the ground, for power stations. industrl and switcheear as well as for urban supply networks, if mechanical damage
It may
standards
NY IPROTODUR-insllation
(PVC)
l'
NYY
2PROTODUR-sheaih
NAYY
{PVC)
+ '|
:
is
DIN \'DE
I Cu'condLrcbr
4 Tanc or c:(trudcd filcr
lEc 50:
N\ I
\'
N\'Y
P R
OTO DU
IPVCI
R-ioJulrlion :
N,\
c\\
\
Conrrolccblc: as for power cables
(P|C)
,l Tirn. or c\trudcd
t)IN VDE O:7I tEc it)l
fillcr
\
L\1. : PROI()- I Concrnrric. I pR()Tocondr,;tor DUR. prorccu\. or I)UIIrn\uli[ron PE\ corrducro. sh.rrh rl'\'Ct t( u $lrL.r irnd (l\(l
NYC\'\'" \.{ \'c\\'\'
,l
((rrlt\ar\L hcjrr!t (ln.)
\\ c\ :' :
Dl\
5 [\rru(lcd Iilt.r
I
P.I{OT{
).
lEc
t
:
(; Fli,r
il
\r,i\.t
:r Srcct rrt)c
rP!c)
561 j Cu
I
Con,.crrrc mnductor in $r!c
l0l
For installation in the ground. indoors. cablc trunking and outdoors if subscqucnt mcchanical damugc is likcl\. For
urbrn nct\rorks. houschold fccdcrs and srrc.l Iishring.
rlii lttl
\
unlikelv
O27I
PROTODUR-shcrrh
I Cu-conducror
l
PROT()-
DUR.
Thc c,.rnccntric conductor in $'r\e forfi is not cut Jt brrnch poln(s.
\'DE 0t?l 501
\\'FG\'
For installarion in rh. {round.
\..), \'FG \.
rndoors. coblc trunkin! and ouldoors i f incrcilscd ntcch!n-
rcrl protection is rcquircd or hich-pulling sl.csscs
(PlCl
\\ hcrc
ml)
occur durinq insrullltion or opcrution
DIN VDE O]7I
? Lapf,cd inncr co|'crin!
formllton
be necessary to 9r..
relevant local regulation installing in countrics ot_ than Germany.
IEC JO:
:':,a,,^..,-,-.. ConcL:nLrrc
, ' rnolrcd ,hcire!ii\ -, condurror
\\'here high-mechlnical
m )'occur dunn slilllllrion and opcrilrion.-r s(icsscs
conccntric conductor shoui rlot bc considcrcd irs irrnr
Comprehensive solutions can be provided quickly for complex planning tasks with the aid of a data processing system
7ri:z ;
Thermally Stable Cable in Steel Pipe 15.3
tion. The a.c. voltage rvithstand is approximately 60 kVimm and the peak voltage 130
withstand
kv/mm.
These valucs are higher than those of low-pressure oil cables. Without sacrificing the safety in operation it is possible therefore to reduce the thickness of insularion. Because ol this particularly economical t-vpe ofconst:uction cables can be produced for rated voltages oi i o't/:1211710 kV and greater.
15.3.2 Internal Gas-Pressure Cable
The paper insulation over each core is impregnated with a non-migrating humidity proof mass. Because of thus no additional proteccive cover is necessary during transport and installation. This cable, in contrast to external gas-pressure cable does not have a sheath (Fig. 15.11). Above the outer layer of paper insulation copper tapes are applied overlapped rvith conducting paper which lorms a screen for field limiting. Either individual non-laid-up cores each prorected by a gliding rvire or laid-up multi+ore cables ,,vith flat steel-wire armour are fed into the steel pipe rvhich. on completion. is then filled rvith Nitrogen' The operating pressure is set at 15 to l6 bar for rated voltages of IJltJo:61 I l0 kV The gas can penctrate the insulation and Illl all voids such [hi]t. even in the event oI earth t'ault. ionisation is prevented' The vohage withstand of this cable core arransement. the construction of which closely resembles that of massimpregnated cable, is so improved by the gas pressure that the c:tble is suitable for higher operating voltage (see page 134).
Fig. l5.l I lniernal gas-pressure cable in steel pipe NtvFSl l\' I x 120 RMiV 6'+i 110 kV
15.3.3 Extern:ll Gas-Pressure Cable (Pressure Cable) The paper-insulated cores are each ivrapped rvith Htbil and impregnated rvith a high viscosity synthetic oil..\bovc thc tbil is I leld sheirth. rvhich acts as a diaphragm. and rhis is strcngthened by trvo lalers of helic.rlll rvound copper tape (Fig l5l3) Above rhc luid-up corcs is lr tllt steel-*irc itrmtrttr' \itcr fccding cablcs into thc pipc'and the installation is completed. thc pipe is iilied rvith nitroscn lt a pressure ol 15 to 16 bar. Thc girs prcssure tlloss the mrss impregnation to erplnd under helt but' \t'ltn thc g:rs tighilc:rd shcath Lre t ine rts a mcmbrlne' lbrces it birck to thc originil position *hcn it cools To eusc this ilction of the shertth membrltnc the conductors lre of ov:.rl cross-section instead of round'
Fig. t5.12 Outdoor sculing ends u ith sprcader box tbr intcrnai g:ts:-...:,1-r I t^r,, :n si,t.'r :\rI\'-r
Fig. 15.13 Externul gls-pressure cilble in steel pipe \..P\:D!FS! lY 3 x l-to o\1 \" 5'!'t 10 \\' 139
15 High- and Extra-High-Voltage Cables
15.3 Thermally Stable Cable in Steel Pipe Occasionally special requirements regarding mechanical strengths ofcables are to be met. In areas subject to subsidence, e.g. movement of ground and also of the surface cables laid in the ground are subjected to pressure and tensile stresses. In long cable runs on bridges or scaffolding with long distances between support points it is necessary to have special mechanical protection or mechanical reinforcement. For these applications cables laid in steel pipe have advanlages over other methods, furthermore it should be noted that steel pipe provides good screening rvhere neighbouring control and telecommunication cablcs could other\r'ise be affected.
Thc pipe used to accommodate the cable can be installed independanr ol rhe cable installation. For this onll parts of the underground cablc run nced to be accessible or opened at man holes other$ ise the pipe can be sealed afrer being installed and tested. To catcr for later extcnsions additional pirres can bc laid in rescrve.
The direction o[ cable runs in srecl pipc must bc planned in great derail such that sharp bands arc avoided wherevcr possible. Thc insrallcd lcnsth of cable cores is dependent upon thc tlpe ofcablc. the cross-sectional area of conductor and thc tvpe of tcrrain. Depending on circumstances elery 300 to 800
mcters lointinl points arc requircd and at these points zr nlo to thr!.e mctcr lcngth of largcr diametcr pipe is r clded to r.hc main pipc via srecl adaptors. This consrruction makes it possible to rcopcn this joint at a iatcr datc and rcclosc it $.ithout endangcring thc cable or cuu.inc rhc pipc. Ar rhc end of the cable pipe a sprcuder box is uscd t'ronr *hich the cable tails are lcad to sealing cnds: thesc cable tails bcing protected bl non-magncric flcxible pipcs. The stcr'l pipe must haYc good corrosion protection because \!ater tightness and mechanical \r'ithstand of the steel pipe are viral facrors in this form of cable installation. The pipes are therelore protected by a layer of extruded PE coverinc.
earthed steel pipe forms a cathode. Material transfer cannot occur. The operating pressure and hence the air/oil tightness of the installation is monitored by contact manome-
15.3.1 High-Pressure Oil-Filled Cable
The paper insulated cores which are screened with H foil are impregnated with low viscosity synrhetic oil. A layer of copper tape in which the helix gap is closed with a plastic tape prevents the impregnation leaking and also prevents ingress of moisture during transporrarion and installation. Above this, a protection against damage during feeding into the pipes. a slow wound helix of non-magnetic gliding rvire is added (Fig. 15.10). On conpletion of final installation the pipe is then evaculted before filling r.r'irh a lorv viscosity insglqring oil and via a prcssure rcgularing detice, .a under a working pressure of 16 bar. As the oil expands due to temperature rise caused by electrical load the cxcess florvs into a storage container *hcn a set operating pressure is reachcd. Converscly as the cable cools and oil pressure falls the rcquired quantity is automatically rerurncd, via a pump s1,stem. to maintain the set operating pressure. The vital componcnt parts of the pressure regulating apparatus. such as pressure monitors. pumps and valves. are duplicated in the installation. Faiiure ofanl one item automaticalll initiatcs rhc sriitching in of thc rcscrvc itcm. The pos cr suppll lor this sr.srcm is normalll takcn from the nctwork bur a standbl gcnr'raaor is also installed to carcr for suppll, failure. The opcrating prcssure oI l6 bar ntaintains the cable insulation void-free during anl condirion of op-rr-
It is possible to improve this corrosion protection by the use of "electric corrosion protcciion". To achiele this protection graphite electrodes are installed close to the pipe. Pipe and elcctrodes are connccted to the output of a lo*.-pou er rectifier set such that the graphire elecrrodes are anodes and the
Fig. 15.10 High pressure oil filled cablc in steel pipe
Low-Pressure Oil Cable 15.2
j
of small leakages, e.g. at pressure switches, merering links or valves any oil loss is replaced over a long period by the oil present in expansion vessels. Operation can therefore be continued until a suitable
Single-core cables are provided with a longitudinal channel via a hollow conductor. Depending on the diameter of the oil channel, the viscosity of the oil used and the loading of the cable with double-sided feeding, cable runs of approximately 4000 m can be adequately supplied with oil. If only one end is connected to a vessel the relative length is halved.
In
For oil-fiiled cable runs where great differences in
Three-core oil-filled cables are sealed off rvith spreader joints. The individual cores are carried through corrugated flexible copper pipes to single' conductor sealing ends. The oil expansion vessels are connected to the splitter dividing bos. With singlecore oil-filled cables the pressure expansion vessels are connected to the individual sealing ends.
level occur and also for very long cable runs, sealed stop joints are fitted to divide the static pressures and also to allorv the connection of expansion vessels along the cable run. With this system one achieves locked sections which with respect to oil content are completell independent of one anolher. For Iong rble runs. depending upon height differentials. the number of locked sections is reduced compared to those required for a level run.
The operlting pressure of an oil-filled cable is nor:--.ally bctrveen 1.5 and 6 bar. Since the strength of the lead sheath only permits lorv internal pressures, thcsc cables have a pressure protecrion tape in the form of a helix rvound directly over the lead. [n 3-core oil-hlled cables this tape is of steel but in single-core cables it is of non-magnatic material. For cables with aluminium sheath the tape is omirted
case
time occurs to make a repair.
For all voltage ranges outdoor sealing ends with porcelain insulators are available (Fig. 15.9).
AII lorv-pressure oil-filled cables can be
connected
via connecting sealing ends direct to transformers or s*.itchgear (see page 394). Especially for the highest voltages the rvide spaced through-bushings can be replaced by sealing ends shorving particular advanrage where space is limited, e. g. in caverns, enclosed srr itchgear etc.
Oil expansion vessels consist of cylindrical steel containers rvhich contain oil-hlled comprcssiblc cclls The cells are soldered air tight. All remaining spacc in the container is hllcd rvith oil. Depcnding on the exoansion of the oil which results from load Iariations and seasonal lemperolures of the ground. the rrumbcr ol'rcsseis is cillcuhted irnLl thus thc operilting orcssure is maintaincd ivithin desired limits. Vessels .,l thc samc construction arc built into the cable drum ')r the purpose of controlling the pressure inside thc -table. rrithin prescribed limits. during trrnsport storiLge and installation thus catering for nornlal temperture lluctuations.
The operaring pressure of an oil-filled cable. or an1 onc of the several locking sections within an installation, is monitored by means of contact mirking manometers. lI an excessive temperature rise occurs rvithin the full length of the cable, the high-pressure contact is operated similarly and if damage or oil loss occures, the low pressure contact is operated. The functioning of the cable can thus be monitored from one central point and any fault can be signalled by either visual or audible alarm. Lorv-pressure oilfilled cables have the advantage over other high-voltagc cable thal this constcnt monitoring is possible l, t r! ra!:r.!i',.elv iorv oo,,.rating oressure.
Fig. 15.9
Ouldoor se'rlins enris lbr single-corc oil-ililed clbles
t3'l
l! lllgn- anq Exlra-l.llgn- vollagE \'aulcs Oil content
y
1.0
r0
0.5
Conduclor cross'secllon
a oil-filled cable b
4-_
mass-impreenated cable
Fig. 15.5
Relationship of current-carryine capacity with respecr to cross-sectional area
Oil pressute
p
*
Fig. 15.7 Characteristic of an oil expansion vessel Dielecllic loss factof lan
{)
r.c Iage q:ad:enl F
a oil-filled cable b
-.._
mass-intprcgnared cablc
Fig. 15.6
Dielectric loss factor (typical relationship)
in
rcspcct
to \'oltugc
sradient
voltage at which the cavitics start to ionise the loss factor often rises r,erv considerably (ionisation knee). The dielectric loss factor tan d for oil-fllled cables (Fig. 15.6) is considerably lower and is little influenced by temperature and voltage; foimation of voids and ionisation do nor occur. Oil-filled cabies are, without having to increase the operating pressure, the only cable which can be used for the highest currentll, used a.c. operating vokage (up to Ci. :420 kV).
l -)o
Fig. 15.8 Oil expansion vessel rvith
g:$
Oil-{llled cables are manufactured as 3-core cabies for cabie rated voitage of U:60 ro 132 kV and as sin-cle-core cables up to the highest currently used operating voltages. The longitudinal channels for oil movement are achieled in 3-core cables by omitting the filler from the inrersrices between the laid-up cores and the metal sheath. The oil channels are therefore situated directly below the metal shearh *'hich facilitates rhe connection of oil expansion vesseis at anv given srraight joint. shouid this be necess.rr), as on long cable runs (Figs. 15.7 and 15.8).
Cable with Polymer Insulation ' Low-Pressure Oil-Filled Cables 15.2
cent. developments it is recommended' for the increase of safety of operation and in service life to
The voltage withstand is: For mass-
build these high-voltage cables with protection ingres of moisture in both longitudinal and radial direction (Fig. l5.l).
For rated voltages up to UolU:64lll0 kV cables with pollmer insulation are already in use to a large extent. The development of this cable for higher voltages is continuing.
15.2 Lorv-Pressure Oil-Filled Cable with Lead or Aluminium Sheath
,
:or the oil-fillcd cables (Figs. 15.2 and l5.l)
thc ir thin oil. \\'hcn
paper insuhtion is impregnarcd "vith heated the expanding oil can florv through longitudi-
nll
channcls to oil expansion vessels which receive :.-.le oil under increasing presstlre, conversely $ hen ' lche load is rcduccd and cooling occurs, the oil is lbrced back into the crble.
In oil-impregnated cablcs cltvities cirn nc!ct occur' These cables are therefore insensitivc to tcmpcraturc cycles and are therefore thermally stablc. Thc voltage withstand of oil-filled cables during opcration is markedly higher than that of mass-imp regnated cables (Fi-q. 15.4).
impregnated cables
Short-time withstand kv,'mm Limiting continuous withstand kV/mm Working stress kV/mm
50 12 to 15 max.5
The insulation of oil-filled cables therefore onll requires to be half the thickncss ofrhat of mass-impreunated cables for a given rated voltage. With the higher thcrmal stability of thc oil-filled cable also a higher operating temperature can be used. Since. because of thc reduced insulation thickness on oil-filled cables and thus the thermal resistance is less, these clbles have a higher current carrying capacity by approximately 50% highcr for a givcn cross-scctional i.rrea (Fi-s. l5.s). Thc higher the operating voitage of a cable the morc important becomes the dielectric loss factor tan d. With mass-impregnated cable the loss factor laries considcrably r', ith vuriltions in rcmpcrature. At thc
0rl :illed cable
15.2 Oil-tllled cable NOKUDEY l x 3oo Rlt.'v 1l H
Fig.
64i 110
kv
JO
20
llme-..-*
Fig. 15.3
oil-rilled crbl.j NoKDEFOY I x Ii0 sNt
36r'6{) kV
Fig. 15.{ Time-voluge rvithstand ol oil-fillcd cablc in compurison rvith mass-impregneted cable
li5
15 High- and Extra-High-Voltage Cables
15 High- and Extra-High-Voltage Cables
All cables are subjected to changes in load and therefore to temperature cycling during operation. The changes due
to thermal expansion and contraction
of both the conductors and insulation materials under the metal sheath, in mass-impregnated cables, produces small cavities (voids) in the insulation which u,hen of a certain size start to produce partial discharge due to the influence of the dielectric field rvhen this field is of a certain srrengrh. At this stage not only the dielectric losses are increased but also uhere high volta_ges are concerned the service life of the mass-impregnated cable may be reduced. For this rcason this type of cablc to DIN VDE 0255 is permitted only for rated volrages of up ro UotU:18130 kV. For higher rared volrages thermally stable cables wirh papcr insulation (Table 15.1) or cables with polymer insulation must bc uscd.
15.1 Cable rvith Polymer Insulation In the past for rated voltascs from Lro,U=36160 kV almost rvithout exception thermalll srable cablcs rvirh
]'ablc
l5.l
Fig. t5.l High voltage cable wirh XLPE insulation
Tl pe 2XS(FL)2Y
1
x 2a0 RM/35 64/'1 10 kv
paper insulation were uscd but these are now increasingly superseded by' cables with insulation of XLPE and in somc countries also of EPR. The special advantasc of the cables is tbat thcy are maintenancelree. The construction of the cables complics, except
ibr dimensions. rvith the standard construction for rated rolta,ees up to [',, U:18'i]0 kV. Bascd on re-
Summarl'of trpc ol'construction and arca ofapplicarion for thcrnrallr stablc cablcs rvith papcr insularion Cahlt, .rith natul shtath
Basic
Normalll
construction
rated voltages U
used
C'ahlt, in .tracl pipc
Standards
Basic cons
lruction
Normalll
used
Standards
rated voltagcs L'
kY Oil_fillcd cablc.r
Lou.pressure
60 to -llio
oil-fi1led cablcs u ith lead or
(
t - :410)
DIN VDE 0]56, IEC 141-1
Hirh-pressure oil-filled cable
1
10 to
(t;
iti0
IEC 141-4
= 110)
aluminium sheath Gas prcssura cablcs
Internal gas pressure cables
External gas pressure cablcs
l -l+
110
(t;
to 150 = 170)
DIN VDE 0258, IEC 141-l DIN VDE O]57. I EC 141-l
Insuleted Overhead Line Cables 14.8
Table
14.2
Recommendations for installations Recommendation for
Type of proximity ot crossing
installation
On pole
No gap necessary
In woodland or near
No distance specified,
single trees
mechanical damage must be avoided
From roof areas
Touching when swinging and under maximum sag to be prevented
From chimney stacks
lvlechanical damage when swinging must be prevented, the distance above opening of chimney stack 2.5 m
'rom anlenna and
Touching when swinging also with maximum sag must be
\-irens
ports, insulated suspension clamps are used which also accommodate a change of route direction of up to 30o. For branch points, insulated branch point clamps are used which allow connection without removing insulation from the cores. The electrical connection is made through a toothed contact plate.
When selecting suspension clamps, the maximum allowable rope tension (normally between 30 and 40 N/mm2 of rope diameter) with a maximum support load not exceeding 6000 N must be observed. The suspension spans are selected depending on the terrain to be between 300 to 500 meters. This span also depends on the height of the mast which may be up to 150 m, however for pole heights ol 8 to 10 m the span is approximately 40 to 60 m.
prevented
From accessable parts
not
less than 0.6 m
of buildings e.g. flat
roofs From bridges or similar
No distance specified. mechanical damage must be prevented
From telecommunication overhead lines: Bare wires
Acrial cables Fixing points of telecommunication equipment
vTable
Distance at crossing
:,:l
rrbove or bclow
14.3
C urren t-carrying capacity ofinsulated overhead line cablcs
Jross-sectional area of aluminium
conductor
mm:
Operating frequency up to 60 Hz
Wind speed 0.6 m/s Ambient temperature 35 'C Direct sunlight lvlaximum conductor temperature 80 oC
T
JJ
l4
Power Cables for Special Applications
solvents and fuel oils. The lead sheath must not be used as neutral conductor (N). If a sheath wire is incorporated it can be used to earth the lead sheath e. g. in explosion proof installations (DIN VDE 0165). Because of the good coupling resistance of the closed lead sheath these cables have advantages where electromagnetic compatibility (EMC) is important.
14.8 Insulated Overhead Line Cables Insulared overhead cables are not strictly power cables. Based on their application and construction they ha1'e become classified as overhead line cables. Because the same insulation materials are used as for po*cr cables these overhead line cables are corered bl the VDE regulations for cable. Construction and Characteristics
lnsulated overhead line cables for medium voltage are not standardized. The construction is largell in line u ith cable to DIN VDE 02.73. For the construction and testing of overhead line cable lor 0.6,11 kV rated voltage the standard DIN VDE 02.74 is applicable. The stranded rope conductors (15 to 70 mm:t are made of drawn pure aluminium * ires. These wires compll uith DIN 4E200 parts prior to being manufactured into the conductor rop!-. For th!- construction and characteristics of the conductor rope DIN 48201 Part 5 applies rvith thc'erception of thc values for numbcr of strands. ciiamctcr and elcctrical resistance of the rope rrhich is laid dorvn in DIN YDE 0174. The insulation of individual conductor ropes consists of biack XLPE t1'pe 2XI1 to DIN VDE 0107 Part 12 u,hich. to improve resistance to sunlight and u'eather. has an addition of at l9i, carbon black. In addition to single-core overhead line cables. bundles of 4 cabies are also standardized (4-core insulated overhcad line cables). in this 4-core
cable the phase conductors are marked by l, 2 or 3 longitudinal ribs along the lengrh of the cable. The neulral conductor (N) being the fourth core has the same cross-sectional area as the phase conductors. The neutral does not bear an identifying mark. Bundles of four cores each with a conductor cross section of 70 mm2 are also available combined with either one or two additional cores of smaller cross secrion (35 mm2;. These additional conductors carry identification markings of four and five ribs respectively. Application and lnstallation Insulated overhead line cables have advantages particularly over difficult terrain. They are frequentll used in woodland (narrow avenues are possible) and are also used for the extension or refurbishment of existing urban netuorks. In these areas four-core overhead line cables are predominant for systemsA three phase * ith PEN. Bundles of four-cores wrr.,. one or two additional cores of reduced cross section are used where street lighting is feed from the same main line. Single-corc overhead line cables are frcquently used ior the suppll of single-phase loads. Suspension and support ol the cables is possible b-v rhe use of \ ooden or concrete poles as well as from
roof supports. For this
s1'stem
DIt.\ VDE 0211 ap-
plies and for domestic iecds DIN VDE 0100 Part 7ll applies. The specific characteristics of insulated over-
head line cables provides full insulation qithout breaks both in opcn terrain as uell as in buildings rr here mechanicai damage to the insulation is most unlikcly to occur. Rccommendations for installarion in differcnt situations is given in Tablc 14.2.
For thc current carrling capacitl ol overhead line cables (see Table 14.1) instead of thc values in DIN YDE 019E. houcrer. Table 4 of DIN YDE 017.1 applies. The conductor temperature. in the event of short-circuit for mcchanical reasons must not exceed 1i0 "c. For the suspension of insulated overhead line cables special supporting equipments are required. In the suspension clamps each individual core of the bundle of four is securely wedged in a polymer chock thus transmitting a friction grip of the rope core indirectll' via the insulation. \\rhere the cable incorporates cores
Fig. t4.15 nsulated overhead line cables \-FA:X :l x 70 R\,1 0.6'1 kv I
of smaller cross-section these are not held b] the clamp. For the suspension from poles or roof sup-
River and Sea Cable . Airr'ort Cable . Cable with Polvmer Insulation 14.7
Fig. t4.t3 Airport cable FLYCY I x 6 REl2.5 ll2kV
Application and Installation
Single-core airport cables supply airport lighring equipments connected in serries. Normally singlephase transformers are used to feed special liehts. For this duty joints or plug connectors are used to connect the equipment via flexible tails of NSGAF.
14.7 Cable rvith Polymer Insulation and Lead Sheath Fig. 14.12 Installation operation at sel: running off from cuble stack over rollers to laving head at stcrn of vesscl
in the bed using a scavenging kecl rvirh high pressurc
Cables with polymer insulation and lead sheath are used in Germany for spccial operating condirions whereas. in thc main. PVC-insulated cables are used for rated voltages of 0.6/1 kV. In special circumstances lead-sheathed cables are also used for higher rated voltaecs (e. -q. 3.6'6 kV) or with a different insuIation of c. g. XLPE.
water Jets.
For river crossings srandard cablcs could also be used ii laid in thermoplastic piping or luid in rrenchcs cur in thc bcd.
14.6 Airport Cables Airport cables suppll energy to aifport lighting appa-
Construction rnd Charucteristics
Cablc u ith poll.mer insulation and lcad shearh for 0.6 I kV ratcd voltauc arc govcrncd by DIN VDE 0265. Thcsc are constructcd as multi-corc cable and conrain either solid or stranded copper conductors. The lead sh!':rth is arranged ovcr the inner covering. Below this an additional tinned conductor may be arranged as sheath rvire- Above the lead sheath a PVC sheath is provided.
ftrtLls.
Application and Installation Construction and Characteristics The cables are single corc and have a copper conduc-
tor of 6 mm: and a concentric conductor of 2.5. 4 or 6 mm? cross-section. Insularion and outer sheath are of PVC. The consrruction is in line with iEC 502 and DIN VDE 0271. Prelerred rated voltages are 1/2 and 5/10 kV- Other rhan this standard consrruction tr hich is used in Germuny there are construcrions having EPR insulation and CR sheath e.g. ro the American standards of rhe Federal Aviation Administralion (FAA L 8l+).
Cables rvith polvmer insulation and lead sheath are applir'd especiallv rvhere there is danger ofeffect from
Fig. l{.1-l Cable rvith PVC insulation and lead shearh NYKY 0.6,'I KV tJl
r{
ro\}er
LaDles
lor Speclal Applrcatrons
In order to avoid mctallic contact bctween construction elements having different electrolytic potenrials a protective extruded covering of PVC (separation sheath) is always included between a concentric con-
ductor and the round steel-wire R or the flat steelwire armour F. In addition, a protective PVC sheath is included above the armour. This sheath is coloured yello* in underground mining cables with rated volt-
age of 0.6/l kV. For both construction and tesr.ing of these cables generally DIN VDE 0271 applies for PVC insulated cables and DIN VDE 0273 for XLPE insulated cables. In addition, where no other national standard exists, IEC 502 is relevant.
Installation and Fixing
In mining installations rvith slopes up to 50'rhe cable must be supported at dislances of no more than 5 meters and must bc hung rrith suitable sas betueen supports. This applies for armoured as well as unarmoured gallerl' cablcs.
In mining
locations rvhere the slopes excecd 50' cables must be tear rcsistant u ith a degrcc of safcty factor 3. For the calculation ol' tear rcsistancc of cables the armour is the deciding lactor. Thesc cablcs must. afier hanging in, be fixed by clamps at disunces not exceedin-q 6 meters. Whcrc longcr distances betr,,een supports is unavoidablc the armour must withstand the tensile srress',r'ith a llctor ols:rfcty of 5. Accessories for mining lpplications bclo*' cround nrust. in Gcrman1,. apart lrorn VDE approval. also have the special approval of rhc Obcrbcrg:imtcr (minlng lnspecloral.e ).
PVC insulated and for medium voltage XLpE is more commonly used. For this application a cable with both longitudinal and radial water tightness is generally selected (see page 47). Cables having polymer insulation are particularly suited especially if a combination of communication cores as well as optical fibre cores are required. With paper lead cables the lead sheath must be thicker than those in DIN VDE 0255 to cater for the mechanical srresses to be expected. If the cable is to be subjected continuous vibration, e.g. by heavy surf, the lead sheath is then strengthened by alloy additions as prorecrion against metal fatigue fractures. The armour of river and sea cables consists of tinned steel wires uhich are, depending on local conditions, either of round or flat profilc. The shapc and thickness are depcndent upon the expected tensile stresses and any prevailing danger (bl punting poles, anchors. movement of sea bed etc.). In particularly unfavourable conditions a double armour may bc necessary. To provide safe prol.ection against corrosion of thc lrmour thc c' 'r serving comprises two layers of compounded special jute or a polymcr shcath (PVC or PE). Lal ing and lnstallation
The method of lal,ing sea cables is dependent upon iocal conditions and on the tlpe of equipment available (loading facilirics and typc of ship). The dclivery iength is oftcn onll limired by transportation capacirr'. If necessarv individual lcngrhs arc spliccd to achieve the total required length. Should it be nccessary to joint crbles at sea. cable joints can be provided n hich are also safe in operation under difficult installation conditions. Rivcr cablc-s and cablcs laid in tidal insliorc \\'aters arc olten laid in trcnches cut
14.5 Rirer and Sea Cables Cables used for crossing rirers or for ltvinc in sea \\'ater. e.g. for the conncction ol island net\\orks to the mainland. for the supply of cnergl' to ol'f-shorc plant or for rhe operation of lighthouscs or nar.igational aids. are usuallt fitred sith a subsrantiai armour to \\ ithstand the high-mechanical srresses during installarion and u hcn in opcrrLrion.
T)'pe of Construction River and sea cables normalll have polvmer or paper tnsulation. Poh'mer-iusulared cables havc the ad\.ant:L,se
I
i0
ol lo\\'$eight. Normxll)
lorr.-volra-!:e cables are
Fig. l4.t I XLPE-insulated sea crble u'ith round steel.uire armour for I I'10 kV
Halogen Free Cable 14.3
14.3.3 Laying and Installation
with improved characteristics in the event of fire are used in indoor installations and outdoors in a similar manner to NYY cables. They can be arranged on racks or fixed to walls and ceilings in either vertical or horizontal directions by means of cable clips. The bending radius of the cable is 12 D (singlecore 15D). Installation directly in the ground is not recommended for these cables. When terminating these cables both inner and outer sheaths should be cut at ihe same point. When the insulation has been removed a silicone covering which may be included must also be removed. In addition the instructions [or installation and transportation given in DIN VDE 0298 Part I must be observed. For joint,ng eirher flame retardant cast-resin joints or flame retardanc shrink-on sleeves may be used. If insulation retention is required tbr the joints special measures nus! be taken. '!Cables to DIN VDE 0266 (type NHXHX and NHXCHX) are designed for a maximum conducror operating temperature oi 70 "C with a maximum permissible short-circuit temperature o[ 160 'C. For cables (type (N)2XH and (N)2XCH) rvith VDE Register Nr. 11099109'110 the maximum permissiblcconductor operating temperature is 90 "C and the maximum permissible short-circuir remperlrure is 250 "C. The current ccrrvins capacity- must be taken from the relevant trbles in DIN VDE 0293 Parr l (see Section l8). Cables
The cablcs rith spccial characteristics in thc event ,ri firc lrc ,.-mplolcri rr hcrc spcciul mcesrrrcs. tbr thc protection of high-rllue cquipmcnt or pcrsons. musr 'rc takcn. In these circumstlnces aplrrt from the re'iLrccd spreltl ol firc. in sonle cuses priorirl is -eiven !-,ro the characteristics as reeards corrosiveness of tlmes rnd smoke densitl rvhcrels in other ctses insulirtion rctcntron mlv be ot'primc importlnce.
14.4 Cables for Mine Shafts and Galleries
In mining installations below ground
cables with polymer insulation are commonly used as mine shaft and gallery cables. These cables for rated voltages 0.6/1 kV always contain a protective conductor and most of them are armoured. Construction and Characteristics Cables used in mining applications normally have copper conductors. For plant with rated voltages up to 10 kV PVC insulation to DIN VDE 0118 is used. In areas subject to mining gas, however, only installations with rated voltaees up to 6 kV are permitted. Installations having a rated voltage of 10 kV and rvith cable having XLPE insulation have been approved bl Oberbergamt (OBA) (mining aurhoriry) Nordrhein-Westlalen. The protecrive conductor is incorpomted in the follo',ving types:
>
as sepirmtc
insuhtcd conductor marked green yelNYFCY-J 4 x 50 S lvl 0.6/1 kV
lo"v e.g. as in
>
conccntric conductor above inner covering e.e. as in NYCYRGY 3 x 50 SVI/25 3.616 kV
p
equally split. concentric conductor over individurl corc's c. g. irs in NYCEYRGY 3 x 50 R\1i25 6',10
kv.
Fig. t4.9 Gallerv cablc NYCYFGY
Fig.
I x 110 SNIr'70 i.6i 6 k\'
1.1.10
\tine shaft cable NYCYRGY
i x l:0 SVI 70 1.616 kV t29
14 Power Cables for Special Applications elastomer, halogen-free, material compound HI base EPR to DIN VDE 0207 Partz3.
1,
The laid-up cores are surround by a core cover of halogen-free elastomer compound with low flammability. The sheath consists of halogen-free, low flammability elastomer compound HM 1 to DIN VDE 0207 Part 24 (base EVA). If necessary a concentric conductor is arranged below the sheath (type NHXCHX). to DIN VDE 0266 normally have insulation retention (see page 127) of more than 20 minutes (designation FE). For this the conductors of smaller cross sections require additional silicone covers.
Cables Fig. 14.6 Arrangement testing of insulation retention under conditions of fire
1.{.3.2 Construction and Characteristics
To improve the characteristics of cables in ltre there are rwo courses of action. Firstly one can increase the halogen content of the materials or one can add components which together with halogen have a synergistic effect. By this means cable can be manufactured having a very good characteristic in regard to rhe limitation of spreading of fire. Corrosive and toxic gases are hou'ever developed during combustion. By special compounding it is possible to reduce, at least, the high smoke emission of the halogen con' taining materials. Such cablcs as FR-PVC-cable (flame-retardant lorv smoke) arc used in some Europeaa countries c. g. lor installation in po"r'er sta(ionsAnothcr possibilit) for the improvement of the characteiistics in firc is to prevent the formation of toNic or corrosivc gases: here pure polyolefines are used as materials for insulation and sheaths. These materials are relativell'easill flammable. An improvement of rhe characteristics of such pollmers is possible b1 the use of special compounds (see page 39 "sheathing \4aterials for Special Purposes"). One possrbilitl' for this is the addition of aluminiumoxl ' hydrate. In the case of fire \\'ater is than released *'hich vapourises. This endotherm process leads to quicker exringuishing of the ltre.
Cables with Improved Characteristics in Fire to DIN \rDE 0266
SIENOPYR-FRNC-cabIe to DIN VDE 0266 type NHXHX 0.6,'1 k\t (Fig. 1.1.7) have an insuiation of 1'rt
Fig. 14.7 SIENOPYR-FRNC-cabIe NHXHX 4 x 1.5 FE 0.6,'l kV with insulation retention
Fig. 14.8 STENOPYR-FRNC-cable (rr-)2XH 4 x 1.5 0.6'1 k\/ q ithout insulation retention
Cable with lmprored Characteristics in the Event of Fire According to YDE Register Nr. 11099109/ll0
SIENOPYR-FRNC-cabIe Type (N)2XH (Fig. 1a.8) have an insulation of special cross-linked polyethylene compound 2XI I to DIN VDE 0207/Part 22 with the laid-up cores surrounded by a cover of halogen free, low flammabiiity thermoplastic filler. The sheath consists of a low flammability thermoplastic compound with increased heat resistance HM2 to DIN VDE 0207 (base EYA). if required a concentric conductor can be arranged below the sheath (type (N)2XCH).
.
Halogen Free Cable 14.3
resistant to the spread of fire (Fig. 14.3); type designation in SIENOPYR cables: FR (flame retardant). Similar tests are also included in other national test specifications for cables. The current international concept is laid down in IEC report 332-3 and an IEC Srandard is under preparation.
As an aid for the selection of materials for cables wirh improved perlormance in fire oxygen index testing is also used. In this test a sample of the relevant material is combusted and it is recorded what degree of oxygen content, in a nitrogen/oxygen mirture, is necesssary to sustain combustion. The higher the recorded oxygen index OI " the more resistant the ma-
I
terial is to supporting combustion under normal conitions r sure assessment of the characteristics and performance in fire for the complete cable can horvever only be made by testing in the chimney rig. The orygcn index test however is most useful for material ualitv assurance testin c.
\-/
Fig.
l{.5
Testing for smoke densiry (cube rest)
Smoke Density
Corrosivity of Combustion Gases Halogens contained in cable marerials such as chiorine in PVC, but also fluorine and bromine in other polymer insulation materials, raise rhcir ignition tcmpcratures and hence their rcsistance to thc spread o | fire along the cable. I I however the cable insulation is burnt lbr example by external heat inpur corrosive of combustion are formed rvhich. togethcr * irh -sases
humidity from the air or rvith *lter front fire exinguishers. form acids (e.g. HCL). This acid can lcad ro corrosion damage to electrotechnical equipment \-..nd to parts of buildings. A test method $'as therefore devised to measure the amount of corrosive gas oroduced during combusrion (Fig. I4.4). [n rhe tesr proceedure laid dorvn in DIN VDE 0471 Part 813 material samples are combusted and the gases produced passed through water while measurements are made of elecrrical conductivitv and oH value of rhe water. Cables containing only materials rvhich comply rvith
prescribed values of conductivity and pH level are classed as halogen-free and non-corrosive in the event
oi fire (designation in SIENOPYR cables: NC, noncorroslve).
:-'' in iotcrnr!!()nil rirndrnir LOI
If cables rvith insulation or sheaths containing chlorrne are combusted dense black smoke is produced. This smoke hampers fire fighting and also evacuarion of anv premises used by the public. To assess cables usrn-u spccial materials rr ith lesser smoke densiry in the case of tjre I EC TC 20 recommends an oprical test procedure in an enclosed cube (Fig. 14.5). The FRNC cables described on page 128 have. under comparable conditions of fire. a ten times lolver smoke densitl than PVC-insuiated and shearhed ' cables of similar construction.
Insulation Retention under Conditions of Firc In certain installations it is also required under conditions of flre for the cable to remain functional for a certain period of time i.e. to continue to supply electrical energv. To ensure this characteristic is satisfied cables are subjected to a test of insulation retention under condirions of fire (type test) (Fig. 14.6). In the type test laid down in DIN VDE 0472Part814 a single cable in horizontal position is subjected to flame from a long gas burner. A voltage of 380 V is applied to the core of the cable (rated voirage 0.6 1 kV) via a fuse and the test result is satisfacrory ii the tise remains inract durins the test. t27
14 Power Cables for Special Applications
Fig. 14.2 Burning PVC during combusr.ion resting
Fig. 14.3
Burning SIENOPYR-FRNC cable during combustion tesL I n-q
[igasur]nq eleclrode Ces
l',,?-i-.i! boll]9s
;r eoi.:_:
fvl
etncj
C:: t!3sn ng ccitigs ii -'lf ans'metioi
Comb,,,ls:ron o,;gr
a0ru3i3t
v. l1 d slLlled vlate
pfi
3
elecrfoc: L
i\
Porcgiar: i:a. coN;a
iri';
36n;r€
uuo9i I9::
r--:
Cond!criviry
pH ma3suring
measuring
devri:
0evrce
Fig. I1.4 Tesl airansemgnr to assess corrosivitl of combustion gasses 116
Srction pump
Shipboard Power Cable'Halogen Free Cable
t4.2.2 Application and Installation Cables of the type MGCC (Fig. 14.1a) can be insralled in line wirh DIN 89150 and close to IEC Publication 92-352 as a permanent installation in any room and on open decks. Cable
lvlcG (Fig. la.1b) should only be installed be-
low the upper metal deck.
Due to the good electrical screening of the
r'
type
MGCG, having a copper wire braid, radio interference and the disturbance of the operation of electronic equipment is reduced. The copper wire braid also acts as mechanical protection and in the event of a fault provides touch protection. For this purpose 5oth ends must be securely earthed by screlvs. The load c:rpacities o[ shipboard cables is laid down in IEC 92-201 (values: see Part 2).
,v. 3asically rhe cables type MGCG to DIN 89 158 and rllcc
to DIN 89 160 are recognized by the follorving classificarion bodies. However for the individual manufacturer approval may be requiredr)
> American Bureau of Shipping (ABS) > Bureau Veritas (BV) > Det Norske Veritas (DNY) > Germanischer LloYd (GL) > Lloy'ds Register of Shipping (LRS) > Polski Rejestr Statkorv (PRS) > USSR Register oI Shipping (RSU)
l4:3 - -
14.3 Halogen-Free Cables 2) with Improved Characteristics in the Case of Fire The standard low-volnge cables (0.6i1 kV) for indoor installations (Section 13) and the standardized installation cables (Section 8) are flame retardant in rhe sense of IEC 332-l and the identical regulation DIN VDE 0472 Part 804, type test B. These require a single test on the cable using a gas burner. PVCinsulated cables and flexible wires as well as the cable commonly used in some countries with XLPE insulation and a suitable sheath satisfy IEC test requirements. These cables have proved themselves over many years in service and will continue to be used in the future mainly in industrial installations.
For buildings or plant rvith a high concentralion of either persons or high-value contents however very ofren more stringent safety requirements apply. To meet these requirements cables with improved performance in the event of fire are available. 1.1.3.1 Testing Performance under Conditions of Fire
The follorving characteristics of cables are relevant under conditions of f-tre:
> Spread of fi re p Corrosivity of combustion gases > Smoke density > Insulation retention during fire Spread of Fire
Practical experience has shorvn that a single PVCinsulated and PVC-sheathed cable rihcn installed in the normally vertical plane does not aid the spread of fire. horvever this does not appll- rvhen cables are bunched such as installation in parallel or in bundles (Fig. 14.2). An arrangement [or comparative testlng rrls developed to determine the burning characteristics of bunched cables (DlN VDE 0471 Part 804 type rest c). For this test the cables are fired to a ladder rack side by side in a vertical chimney. at the bottom of rvhich a gas burner subjects the cables to flame for a given period of 20 minutes.
Afier turning off the burner the flames must not continue to spread to the upper end of the test arrangement. Cables which pass this test can be classed as
r'
Dcpcnding on cl:rssriexti.)n aulho.ity
thii could
mcirn cith€r approvrl
r'
Sc,: p.rgc
*irh
79. 'Fhloged-Frce SIENOPYR wiring rod Flerible Crblcs
improved Performrncc in th. Ev€nr of Fire
'
I
i)
14 Power Cables for
S_pecial
Applications
14 Power Cables for Special Applications
14.1 Cable with Elastomer Insulation
tions in engine rooms under tropical conditions or when used outdoors in u'inter conditions.
These cables have been superseded in Germany by cables with PVC insulation. Only on shipboard installarions are cables with elastomer insulation still used to any great extent.
The core designation for shipboard cables is shown in Table 14.1 and this differs from DIN VDE 0293.
In a iew countries low- and medium-voltase cables u,ith an insulation of Ethylene-Propylene-Rubber
Table
(EPR) have major significance. The operating characteristics of these cables compl;' as to their permissible conductor operating temperature of 90 .C in normal operation and 250 "C in the event of shorr-circuir with rhose of XLPE cables. However ir must be nored thar in the medium-voltage range EPR offers a higher resisrance to parrial discharge but on the other hand has
slightli higher dielectric
losses.
l4.l
Core identification ofshipboard cables
No. of cores
Colo u r
I
Light gre1, Light grcl -black Light grel -black-red Light grey-biack-red-blue
l 3
4
j
Li ght gre.v'-black-red-blue-black
Light grer'. e3ch \^ith a number designation in black commencing from the
6 and a
bove
centre u ith number I
14.2 Shipboard Power Cable In cables to IEC 92 for merchant marine vesscls elastomei insulation materials and normalll.also eias_ tomef sheathin,q materials are used. pVC shcaths are also permitted in various combinarions but. because of their thermoplastic characreristics and because of the insrallarion conditions prevailing on shipboard. are not recommended.
t:l.ljJ
a) MGCG
0.6.11
kV ltirh scrsen
l:1.2.1 Construction and Characteristics
In Germanv shipboard cables are manufactured. compll in-e *'ith the relevant DIN norms. s.ith EpR insulation and CR sheath. This insularion is suirable for the normal conditions of operating temperatures in ship building of up to 85 .C. The pROTOLON compounds used by Siemens have a particularly hi_eh reslsta-nce to high temperature and have a long service life under the influence of ozone and partial dis_ charges. The PROTOFIRM sheath is highiy resistant to notch impact and tearing as well as being oil resistant and flame retardant. It mainrains irs elasticitr, at both high and lou temperarures. e.g. in insrella_ 1'1,1
b) MGC 0.6,/1 kV without screen
I I
Tinned stranded conductors EPR insulation (PROTOLON) Inner covering
3 4 Separating foil 5 Copper wire braid 6 Polychloroprene-sh.ath (pROTOFI RM) Fig.
l4.l
Shipboard po*r--r cables MCCC und
\lCG
Cables and Associated Accessories 133
uolu>6110 kv (u_> Indoor sealing ends (examples)
Outdoor sealing cnds
Cablejoints
(cxamples)
(examples)
Straight
12
kv)
joint WP
Push-on sealing end FAE $ ith core sp.eading
Push-on scxling end IAES lvirh corc sprcirding
Srraight transition joint ctnncct paper insullted \\
ith i-core XLPE
5\l-wP to S.
L.
cablcs
Secling end FEP with porcelain insulators and core spreuding
l2l
lJ
I )?es
Tabte
ol uonstructlon ol Low- and Hlgn-voltage uables
13.3
Cables and associated accessories (continued)
Construction
N
2'l S(F) A 2X I -Al- 2 PROTO- 3 Copper scrcen 4 PROTOcoo- THEN-X- (longirudinal THENducror insulaiion (XLPE) wa|cr dght) shcalh (PE)
+ 's rtl
Prcferrcd application
Limircd applicarion
N2XS(R2Y
In unfavourablc insrallation conditions cspccially if, after mcchanical damagc ingress of water in longitudinal dircction musl be avoidcd longitudinally watertight cables with extrudcd fi lling compound and gap scaling in thc scrcen area offer advantage.
In cablc trunking and indo( It must bc noted that the pI sh,eath.is no-t.flamc retardar wnsn rnsta rng single-cors c:IOIeS ln arr adcquate fixin( must bc providcd bccause odlmamic effect of short-ci rc currcnts (s€e pagc 297). For lhe selection ofscreen cross-section the earth-faul rcspectively double ea h-p. condirions of the nerrvorl n be considcred.
Typcs used in countries where 3-core cables are rsquired
Thcse cablcs wirh sheu previously used in u..ran no works are in Gcrmany incrr ingly superscded by mech:Lr. cally superior rypcs wirh Pl shcuth.
NA2XS(F)2Y
4
5 Inn:r irnd
ourer Ialer
6 Gap sealing
(conducdng t:lpe q.ilh s*clling rapc)
cooductin_e
7 E{ruded fillcr
I
Designation, standards
IEC 502
sa I Cu*crecn over
PROTOTHE\--Xrnsulatior (XLPE)
DIN VDE O]7] N2XSEY
PROIODUR.
each individual
n*A2XSEY
shcath {PVC)
ffi .ri
56
.l Cu-conducror 5 Inncr rnd ourcr conducrinc
6 Conduclin! tapc
llrcr
7 Ertrudcd filler
-ffi \:\ I
SE \ F \ : Cu- I PROTO- I Flar srcel- 5 PROTO_ ;i{EN-X- scrccn DUR- $irc DURrntulstton ovcr cach shcath irrrnour shcrth ,\LPE) indilidual rpvc) lpYC) PROTO-
1
6 i 18
I
3{
IEC 502
N]XSEYFY NA2XSEYFY
N:XSEYRY
NA]XSE\'RY
5
8 Conducting 9 Trpc
lapc
Tl pes used in othercountrics with Bat steel-uire armour F or armour ofsteel round-\rire R $ hsre dilfi cult installarion and operating conditions exist. Preferred \r'ith PE sheath instead of PVC sheath for laling in
ground.
910
6 Cu-conducloa 7 Inr:i and ourer co:du.!ing hlc.
ll:
DIN VDE O]7]
10 Errruded llller
DIN VDE IL E )UI
O:73
A
Cables and Associated Accessories 133
U o; I U Indoor scaling cnds
Outdbor sealing cnds
(examplcs)
(examples)
2 l2
kV (U^>
24
kV)
Cablcjoints (cxrmplcs)
Brass straight
\-.
120
joint
EoD wirh transparent irst-rcsin insulttor
PLr;h-on strright
joint Ai!lS
Srrrighr joint wP
Plue-in termination WS
Srraight transition joint Sivl-wP for connccnng a papcr insulated S.L.-cable to i single-core X LPE cables
t2l
13 Types of Construction of Low- and High-Voltage Cables
Table
13.3
Cables and associated accessories (continued)
Construction
NA 1Al-
2 AluEridium- 3 Plasric
shcalh
coo-
mass
apc
4 PROTODUR-
cmbcdded
Dcsignation, standards
Prefcrrcd application
NKLEY NAKLEY
Cablcs prcviously used
for
urban nctworks; now bcing
rcioforc-cd
supcrscdcd by XLPE cablcs.
shcau
cluctor
Limitcd applica!ion
(Pvc)
Not suitablc for mcchanical strcsses and areas subjcct to subsidcncc; whcrc diffcrcnssl in lcvcl occur (e.g. stecp sloDe
cables wirh polymcr insulaiio must be used.
561 5 Conducting papcr 6 Insulatioo (irnprcgnaled papcr)
N2\
(conducting pap€r and
S
1 PROTOTHEN-X- 2
insuiation
Cu-scrccn
Al foil)
DIN VDE
0255
\
N2XSY
Thesc
3 PROTODUR-
NA]XSY
previously used in urban networks are in Gcrmany incrcasingly superseded by mechanically superior type
shcaft (PVC)
CXLPE)
:E
cablcswirh PVC shearh
with PE shearh.
ii
45
.1
I
conditions ol'the network ml
5 6
Cui conducror
\:\
7
lDoer and ourer
aooductinglayer
]\
I Al.
2 PROTOTHEN-XinsulalioD
duc!or
be
6 Conducliog 7
Tape
I
S :\ I Cu- a PROTOTHET'-
(XLPE) screen
EL )UI
N2XS2Y
ln ground for urban networks because ofextremely low di-
NA]XS]Y
shearh (PE)
electric losscs. To ease installation 3 cables can be layed up and supplied on a single drum.
4ffi and
ourcr
120
6 Conducdng
upe
7 Tape
If after mechanical da,nage i; gress
ofuater
is likely cable
having longiludinal water tightness in the scrcen area h,, hr
advanlages.
\\'hen used indoors it must b. b observed that the PE shealh r not flame retardant. \\'hen installing single.core cables in air adequate fixing must be provided because of the dynamic effecr ofshort-c: cuit currents (see pagc 297).
5561
conouctlng layer
considcred.
DIN VDE O]7]
l:14
5 lnn.i
ln ground ifbecause ofmcchanical stresses damagc to i. PVC sheath is likely. When instailing singlc-core cablcs in air adequare llxing must be providcd becausc of the dynamic effect ofshort-ci cuit currents (see pagc 297;. For the selection olscrcen cross sections. the e:trth-faui respectively double earth.fau
DIN VDE tEc 502
0273
Cables and Associated Accessories 133
url u>12 Indoor scaling ends (cxamples)
120
kv (u_ > 24 kv)
Cablc joints (examplcs)
Srraighr
joint with individual
lead inner casing
EoD wi(h rransparent cast.resin insulators
EoD wirh transparent cast-rcsrn insulators wlth lncreased short-circuir
withstand
Straight joint with steel inner casing for connecting H-cables to S.L.
'_ r ro
13 Types of Construction ofLow- and High-Voltage Cables
Table
13.3
Cables and associated accessories (continued) Dcsignation,
Construction
Prcferrcd application
Limitcd application
In ground ifno panicular
Indoors and in cablc trunkin only with flamc retardant ou shcath alternarively with our shcath rcmoved;
standards
NEK
I
B
E
I
ffi Inditidually
4 Jutc
Stccl-lapc
rape
screcncd lcad5hca!hcd core
NEKEBA NAEKEBA
strcsscs arc Prescnt
scrving
whcrc thcre is danger ofcorr, sion additional corrosion prc
1234
tcction is rcquiled; whcre differenccs in level occ (c.9. sreep slop€s) cables
wilf
polymer insulation must be uscd.
61
i Cu-
6 Conducting 7
conduc-
\,\ I
papcr
Insula(ion
8
Layers ofmass-
(imprcgnatcdpapcr) imprcgnaled
fibrous rnar.rial
E[EB\ lape
ffi shcarbed lcadshcrtbed core
0255
NEKEBY
2 Individually 3 Plaslic
Al-
DIN VDE
.1
Sreel-tapc 5 PROTOa[nour DUR-
ln ground increased corrosion protection is required; also suitable for indoors
NAEKEBY
shcalh
Wherc differenccs in tevel occur (e.g. steep slopes) cabl
uith polymer insuiation mu. be used
(Pvc)
1234t
s;
s
6 Conducrin! ; lnsulalion
r|lp3r
E Lavcrs ofmass-
lrmpregnarcd papcr)
imp.cena(ed
fibrous materiaii
\u
I
ti
I
of : Lead I mar3lliscd rhcrth Scr€-_ning
.\
sreel qirc armour FIar
4
--fl l:lr
5 6;
8
NHKF-A NAH KFA
$ ith flat srccl-wire armour
NHK RA
NAHKRA
hi
scr\lnq
gh-mechanical stresses can
provide in-
NHKBA
creased
,\-AHKBA
corrosion a red PROTODUR sheath (PVC) rcplaced thejure
protection against
ierYing (Dcsignation: s'HKRY respectively
NHKFY)
E Fillcr
a Lryers
F
or amour of round steel-$,ircs R as river or sea cable: in ground where particularl) be expected: {o
ofmass_
rmtrcSnatcd tlbrous rnate.ials
118
j
i
Cu-conducror ? Insula(ion (imprcgn3reJ o lonor:rrns pJn3' p.rlerl 5
Jure
Dh.- VDE Olj
DIN VDE O:5J
H-cables wi(h steel-t-.,.", armour are rarell used. S.L.cirbles are preferred: \ 'here i lerences in level occur (e.g. sleep slopes) cables with pol\ mer insulation must be used
Cables and Associated Accessories 13.3
uolu-6110 kv Indoor scaling ends
Cablcjoints
(cxamplcs)
(examplcs)
(u-:12 kv)
Streightjoint WP
Push-on sealing end
Push-on sealing end
IAES
FAE
IO
IO
Straigh( rransirionjoinr UMP for connecting a ]-core mass impregnated cable to a 3-core XLPE cable
r.rer.
Table
13.3
r vrBS!
v4urvJ
Cables and associated accessories (continued)
Construction
Dcsignation,
Prcfcrrcd application
Limited application
In ground for urban nctworks
Largcr termination spac€ th" tor stngte-corc cable is re_ quircd. For installation in trunkins
standards
NA 1
S2Y
?x
Al-
3 Cu-scrcen 4 PROTO-
2 PROTOcooductor THEN-X-
shcath (PE)
(XLPE)
ffi I
5 Inn::
and
ourcr
lapc 7 Tapc
su
I
PROTOTHEN-X-
rnsulatron (NLPE)
:
#
Cables with PVC shcath
4
6 Conducling
condu.!in8layer
\l\
because of cxtremely low dielectric losscs.
THEN-
insuladon
12
N2XS2Y NA2XS2Y
:\
I over cach indivudal core Coppcr-screen
prcviousiy used in urban nctworks are in Ccrmany incrcasingly supcrscded by thc mcchanical supcrior type
and indoors ir musr be norid rhat thc PE shearh is not flan
with PE shearh.
lnsutatlon are not available i Iongitudinal warer tighr forr
retaroant-
Multi.corc cables with Polyr polyn
DIN VDE O?7] IEC i02 N2XSE2Y
PROTOTHEiT-she th
NA2XSE2Y
(PE)
It
lll
{:
56
I Cu. i .onJJJlor
\ t\ I
PROTO-
oulcr 6 Conductint - 7 Errruded (ntc Ia)cr fillcr
st: I Copo!'r
TtlE\-X. titiutauon r\LPE)
I
lnncr and
condu.lrn!
1
screcn orct each
indii idurl
I
l.l
t-\
Fht 5 PROTODUR- srccl-*irc DURsheaLh armour sheath {PvC) (pvc) PROTO-.1
DIN VDE
O]73
IEC 50: nvIXSEYFY
\\/ith flat steel-wire armour F
^-A2XSEYFY
or armour ofround sleel-xire R for underground mining.
i.*IXSEYRY NA2XSEYRY
arc difficulr.
llli-l
6 Cu. cobduator
lr6
910
and outcr concluctrng lryer
7 Inn€r
6 Conducring 9 Exrrudcd
rape
PE sheath insread of PVC shearh also for insrallation in ground where in5tallil-
tion and operating conditions
5
==_il 67 78
with
filler 10 lape
DIN VDE IEC 50:
0273
The prer-iousl; used cables u ith PVC sheath areiGer, manr' rncreasinely ..sedc br superior types with PE
s.
sheuth.
Cables and Associated Accessoriis 133
Uql Indoor sealing ends
Cablcjoints
(Examples)
(Examples)
U:6110 kV ( U-
-
12
kV)
Push-on straight joint AiltS
iPush-on scaling end
FAE
Strright joint wP
Push-on se3ling cnd IAES
Srraightjoint WPS *ith shrink-on
sleeve
Sealing end with
porcelain insulator FEP
,q*\ "{:;1'],,
Straight transition join! UMP for connecting a 3-core mass impregnated cable
to 3-single-core XLPE
cables
PLug-in tcrminrtion WS
rti
13 Types ol Construction of Low- and High-Voltage Cables
Table
13.3
Cables and associated accessories (continued) Designation,
Construction
Prefcrred application
Limitcd applicarion
Thes€ cables with PVC sheath prcviously used in urban neG
In ground ifbecause ofme. chanical strcsses damase ro rr ' PVC shearh is likely. When installing single_core cablcs in air adequare fixins must be provided bccausc o-f thc dynamic cfTecr ofshon-ci; cult currents (see page 297). For lhc sclection ofscrcen cross sections, the ca.th-faulr respecrively double car!h-fauL
standards
\ S 2 Cu-screen 3 PROTODUR-
N2I I PROTOTHEN.XiDsulalion
N2XSY NA2XSY
shcarh
works arc in Germany increasingly supeneded by mechanically superior type
(PVC)
O(LPE)
with PE shearh.
t2i
ffi .l 5
i5
4 Cu-
i
conduiror
\ \ l '1,-
'
conditions ofrhe network mu be considered. 1
Inncr and outcr conducung Iltef
l\ : PROTO-
6 Conduclinc 7
S
Conductor THEr--X-
TaDe
r.rpc
3 Cu-scrccn
:\ I PROTO-
DIN VDE
O2?3
IEC 501
N:XS:Y
ln ground for urban networks
NA]XS2Y
becausc ofextremely low electrical losses. To case installation 3 cables can be layed up
THEN.
insulation (XLPE)
sncaut {
pE)
and supplied on a single
ir
having longirudinal water tighlness in the screen area h.. advantagesWhcn used indoors it must bl obse.ved thar lhe PE shearh i
drum.
not flame retardant. When installing single-core cables in air adequare fixing must be provided because of dynamic effect of shorr-circu:
_'E l:1.1
i56
I I afre r mechanicald^ge gress ofwater is Iikely uable
currents (sec page 297). For rhe selection ofscrecn cross-scctions. earth-[ault rcspectivcl) double carrh-faulr
1
conditions ofthc nct*ork ml bc considered.
Inrr: and outcr
6 Conducting
uf'j
? Trpc
DIN VDE
O]73
IEC JO]
I f,, :'rf r :\ : PROTO- I Coppcr scrccn .{ PROTO.onciuclor THEN-X- lonqirudincll\ THENin,;ul:rtron $ulcr ushr ,hl.rrh
A:-
N]XS(F)]Y N.{:XS(F)lY
In unfavourable inJalliltion conditions especial l-'.' if aftcr mechanical damase ingress
{PE)
!tt 5 56 5 InD:r and ouler
t1t
la\cr
1
6 Gap
sealing
(conducting upe
,*ith srelli!rg trpr)
7
Exrruded filler
DIN vDE
lEc 50:
O2?3
shear
is not flame retardant.
\\'hen installing single-corc
mu5t bc avoided. longitudi-
cables in air adequate lixing must be pror-ided because of
tages.
--:==
anaoor
*ater in longitudinal direcrion nall]'water tight cables !\'ith extruded filler and sap sculing in the screen area offer advan-
l?il
conducrjnc
of
In crble trunking
il musl be noled the I L
dl namic effccr ofshort-circu currents (see page 29?). For the selection ofscrcen cross section the ear(h-fault r spectilely double earth-far.rlr conditions ofthe network mr be considered.
Cables and Associated Accessories 13.3
uolu-6110 kv (u-:12 kv) Indoor scaling cnds
Outdoor sealing cnds
Cablejoints
(examples)
(cxamples)
(examples)
-, €:?
f,
:fl HI HI Push-on
Sealing cnd with
Push-on
s€rling cnd rAES r0
porcclain insulator FEP
sealing end
FAE
Straight joint WP
10
- ''l-
et'rKq. Plug-in terminrtion WS
Straight joint UI{P for connccting a 3 core mass impregnatcd cabie to 3-single core or one 3-corc
PROTODUR cable
Push-on
Push-on sealing end FAE 10
Srraightjoint WP
scaliirg end
IAES
1O
1r3
13 Tlpes of Construction of Low- aod High-Voltage Cables
Table
13.3
Cables and associated accessories (continued)
Consrruction
NY I
S
PROTODUR- 2
3 PROTODUR.
Cu-sclccn
Dqsignation, standards
Preferred application
Limitcd applicarior
NYSY NAYSY
For powcr stations and
::---:--:------wncn s€lectlng screen
switchgear as well as stadons becausc of small bending radii
56ctrons canh_faulth rq5p€c-
in confincd spaccs indoors. As underground b€cause of light weight where installation conditions a.c difficult (c.g.
h
shcat
iD5ula!ioo
("vc)
(Pvc)
steep slopcs)
cross_
rrvcly ooubtc canh-faulI conc uons ot tnc network must consrocrcd-
Whsn installing single-co1q caotes ln atr adcquate fixins musr bc providcd becaux iJ
dynamic cffect of shorr-circui currcnts (see page 297).
t2l
{
=H ti
5
6
I 5 lnner and out3r o Conducling ? Tape DIN VDE O27I
4 Cu-.ooductoa
coaduclrng
]\..,\ I A:-
\'
la,ar
(apes
S[
'\
2 PROTODUR- 3 Cu-screen
cooductor
iDsulation (PVC)
#
{
cach individual abovc
rEc
502
NYSEY PROTODUR-
Indoors, cable crunking, ourdoors and in ground; for power stations, industr) and switchgear
NAYSEY
shcath
(pVC)
113.r ttJl
ttl
j Inn::andout:r con6uauog tater
\\
6 Conducrins lape 7 Exlruded llljcr
r'
I PROTODUR- I rij,rllrion tPvC)
steet qire itrmour Ft.{
\ I
PROTODUR_ shealh (pVC)
DIN VDE
O27I
IEC 502
N\'FY NA\'FY
With flat steel-\r'ire armour F or armour ofround steel-* ire R in difficult installation or operaling conditions
,.-1'R\'
NAYRY
,l
: j i 6 Cu-cooductor 5lnnerandourcr
6
conducringltyer
111
Exrrlrded
conductiog{iller
DIN VDE
lEc
502
0271
When selecting screen crosssections the earth fault respe.tively double earth fauh conL tions ofthe nctwork must be considcred
Cables and Associated Accessories 13.3
UnlU:3.616 kV
(U-:7.2kY);
Indoor sealing end
Outdoor selling end
(examplcs)
(ex!mples)
UnlU-6110 kV (U-:12 kV) Cable joint (examples)
av
Strxighr loint
(spcciri \\irh lcld inncr clstng)
:caling end
IK\l
Encxscd serling end FF I0 ith porcehin insulators
u
I3
T5pes ofConstruction
13.3
Table
ofLow- and High-Voltage Cables
Cables and associated accessories (continued) Designation. standards
Construction
iA K B I .41- 2 Lcad shcath 3 Srceltapc adnour conductor
4
Jute serving
NKBA NAKBA
Preferrcd application
Limired application
ln thc ground. ifno particular
lndoors.tnd in cablc trunI\i
onty wtth ltamc retardanl o sncatn, tt need be outcr scn musl be removed: $here dil ences rn levcl occur (e.,. sler slopes).cables $ ith pol!,mcr rnsutatlon musl t€ uscd
Stresses arc present
#|ffi 12)4
lllt
r 6/
6
i i
7
In'u::rLron
llnilragnxtcd pJncr,
BclL
inruh(ion
lrmprcgnrlco pcpcr)
6 Fiil.r
8 \1Jrs imprcgnrted
\.\
B\
I
A!: Lcad shcrth 3 Stccl ranc ionductor
paper
4 PROTODUR-
DIN VDE
0255
NKBY
ln ground ifincreased corro-
\\'hcrc diffcrcnces r,, tc\cl
NAK BY
sion prorection is rquired: ulso suit:rblc indoors
cur (e.g. srcep slopes) cirblc
shcalh I PvCJ
#
with pol;"mcr insulation
(.
nrL
bc uscd
l:14
i 6r
s
7 llclt insulrtion
,,- ^,^nn.,r,l ^,n,.r
6 F,i.r:
S i\hss rmpr.snrtcd pspcr
R,\ I :\rmour of
I i.-rd shr'.|th
+-
$irc
K FA
\\'ith flat
steel-* irc- F and round stecl-l ire armour l{.
NKRA NAKRA
purticul r mechitnicul strcsscs shcrth rrc to b. c\pect.d e-q. pullins. tilpc \\'ith doublc ou(cr.iutL scrvins as
I
li
I Cu-.ooductor 6 Fillc. 8 l{rssiF^n..n,,,,,1 -"{ ln,.i:r,on 7 HJ,r In.ulruon ;l;:;Lrii::ign:rtcdprfcr) lrnrprcgxrtcdpi'pcfl
llt)
O:55
NAKFA
r.\
-i Jurs \cr\'ing
I:
.i j6r-
DIN vDE
DIN vDE O]5J
ri!cr or seiL cnblc
Indoors and in
if
cab\Iunki
rc. ,anl o ilh sleel spiral bin(l
onl] uirh flamc $
Cables and Associated Accessories 13.3
Uol U -3.6 | 6 Indoor sealing ends (cxalnplcs)
Outdoor sealing ends (examplcs)
kV (U-
- 7.2 1iY;
Cable joina (examplcs)
I
H
PROTOLIN-srlaighr joinr
T PROTOLIN-sealing end
l-PEB
Encased sealing end FF l0
with porcelain insulators
Straight joint \\'P
Push-on seaiing end
IAES
1O
Sealing end FEP
with porcclain insulator
109
13 Types of Construction ofLow- and High-Voltage Cables
Table
13.3
Cables and associated accessories (continued)
Construction
Dcsignation, standards
NI' t PROTODUR. iosulatioD
TYFY
3 PROTODUR.
slcel
wirc armour
(Pvc)
NAYFY
shcalh
(Pvc)
4 Culosulalion
j
\\
S
I
]'
F
2 Fla!
PROTODURinsulation {PVC)
2
Indoor, cablc trunking, outdoors and in ground for power stations, industry and switchgcar
3 PROTODUR.
NYSY NAYSY
sheath
(PVC)
Because of small bending .adii indoors in confined spaccs, for power stations and switchgearas wcllas in stations, as
undcrground cablc, because weighr favoured in situations whcre installation is
ofits light
dimculr e.g. srcep slopes
?ffi t7l
ttl
4i
4
Cu-
108
5 6
i
1
Inner and outcr conducrins li'ller
6 Conducling 7 Tape lape
Limitcd appticadon
DIN VDE O:7I
Lappcd inncr colcring
Ctr-screen
Prcfcrrcd application
Dh.{ VDE 0l7l
When selecting screen cros sections the carth fault rcsn tively double earth fauk $1r the network must be consid ered. When installing singlc core cables in airadequetc: ing must be provided becau
of dynamic cffect of short-c cuit currents (see page :91)
Cables and Associated Accessories 13.3
Uol U :0.611 lndoor sealing end
Cable joints
lciamples)
(examples)
kV (U-
: 1.2 kV)
T-join I
Thc connection of lhc neulrtl conductors in clblcs $ith aluminium shc th is mirde by slitting helicirlly and opcning up rhc shcxth
Cylindrical seaiing end
Polc mountcd scilling cnd
:
StrJi.rltt Jornt rrithour lcud inncr clsirrn
l0l
Table
I3.3
Cables and associared accessories (continued)
Construction Limired applicarion r\-
A I Al-
cooductor
EY
IiL
:
Aluminiumshealh
I Mqsr.. 4 PROTODUR. crhDedded shcath prasrrc (pVC)
NKLEY NAKLEY
tapc
-r
Insuhtron
(rmnrc':n3rcd ptp3r)
NK I Lcld shcrlh
6 Filtcr t] Srccl-trpc
I
.lutc scr\ing
Dt^- \'DE
0255
NKBA NAKBA
Cable prer.iouslr uscd for
urban nctrrorks g hcre addiIronal-carthing rhrour:h rhe lcud sheilh
(iinducror
6 Fincr
urnnrtSorlcd pirncr) 7 Belr insuhLion l|nrprcgn!trd prnerl
106
il::trllitr,ffi[T:
Sclr insul!lion
lrmprcgnatcd Papcr)
:
Cablc prcviously used for urban nct*,orks. aluminium sheath used as neuaral conducror (N) respecrively as PEN conducror
DIN \ DE 0:,i5
\us
req
uired.
Indoor and in cablc trunlin:l only u ith llume rctardanr ou-r corcr or aftcr rcmoval oflhl Jutc seruns. Where there ij danqer oIcorrosion addition. corrosron protcction is requrrcd e.g. PVC outcr shcirih (dcsi!nurion NKBy. NA K tl\'). l hcrr rdditionlt earthing ria lcad shclrh ir n,, t ncccsslr\.
Cables and Associated Accissotes 13'3
uol u :0.611 kv indoor sealing cnds
Outdoor sealing cnd
Cable joints
eramplcs)
(cxamplcs)
(cxamplcs)
.
(u-:
1.2
kv)
Shrink-on straight joint
l-core cablc , irh ncd tails
PROTOLIN-straight joint
P
icr
ROTO LIN-brxnch Y-joint
.able
'!1th-dnccntric conduclor rnd parallcl rails
V
PROTOLIN-transition joint for cable with pol!mer insuiation to mass impregnated cable
*".*r,n ;'ll.l":":i:.'
wirc armour and
105
Table
13.3
Cables and associated accessories (continued)
Construction
Dcsignarion, lPrefercdaoolication "
Limircd application
standards | NA I AI.
2\
\'
2 PROTOTHEN.X. 3 PROTODUR.
cotrductoa idsulation
shcath
(Pvc)
CXLPE)
I
PROTOTHE.\--Xrosuttuon
{xLpE)
n,h.
rn countrics othcr (nan Lrermany.
:
:xl'',
Conrrolcable:
PROTODUR_
(hc.ih
as
iifpir
for power cable
ll
.r
,i
Cu{onducror
----_-_.._-
4 Tapc
or filler
:\
IEC 50:
c\\ --
\ : J Conccnrrrc. J pROTo. cotrdu.-ror !l-9IO_ THE\-X. prorcculc or DUR_ Insutation tpE\r conJucror ;;ri; r\LpE' ,Cu srrcs rnd ii;VC;
IAI-,
:XC\\'\'I ' NA]XC\\'Y
h.lical t:locl
r:tr
fl tl
5 Erlrud.C fiiier
for-
Where high-mcchanical stresses may occur
durins installalion and operation.-The conccntnc cond!ctor should not be considcrcC as armoua
\\ here subsequent mechanical
damage is likely. For srreer
lighting and household feedrrs in urban networks.
DI\
I
j
\'DE
0172
ICL ]U]
IPROTOiHE\.X. (XLPE,
i\ I Flal stctl qrrc arrnour
I
:XF\'" PROTODUR_ sheath
(pVC)
@ q
{ Cu
I k\
For installarion in rhe ground. rnooors. cable trunking and ourdoors where higher-mechanical protection is required or * here high pulling srresses mal occur during insrallalion or oPeration.
j:l
LaDlc for L-
For urban networks wi(h concentaic conductor ofwave mdtion which is not cul al
branch points. For inslallaiion in the ground, indoors. cable rrunking and outdoors
raansr.erJc
104
lnsra rng
l2
ffi \{
It may be neccssary to ob5er_r= rcrevant tocal rcgulations
DIN VDE 0272 IEC 502
4 Exrruded filler
3
Power cables for urban nct. wo.ks, for installation in the ground, cable trunking. inand outdoors. Cable with copper conducror also forpower stations. industry and swilchgcar.
NA2XY
IEL )U]
\arth NLPE Insuhlion rnd coppcr conciucLors as
qji:
3s irrmoureC
.ijblcs rrc nor !ct rnclud.d rn
DI\
\,DE 0:?:
Cablei and Associated Accessories 13.3
usl'u -0.611 kv (utdoor scaling ends
Ourdoor sealing ends
Cablejoints
r:(umptes)
(examples)
(eramples)
: 1.2 kv)
Shrink-on strairht joinr
)rc cirble h fr d tails
PROTOLIN-cablc cnd
PROTOLIN-straighr joinr
PEA
PROTOLIN-brunch \'-joinL
.il concuntnc conductor .l plrxll.l rriis
V
T-joinr HNI
Shrink-on cable end
n
:ore cable lh lli!( ste(l-\\ ir(rncd tlrrL
lrmour
end
PROTOLIN-tr.rnsirion joint for cablc with polymet insulltion lo mass-imoregnlted cublc
l0l
Guiderfor Plannine of Cable Installations l6
Planning of Cable Installations
Table
Cable Installations
Actron
Section
Selection of type of construction lor cables and accessories
IJ
Consideration of conditions lor transporration. installation and mounring
29.
In planning an installation Table
' -
16.1 may act as a
guide.
-
tlpe ofconstruction o[the cable is to be selected to meet ambient conditions and to withstand thc me' chanical and thermal stresses. The installation re' ar{irements of both VDE and those of local regulato-
I
;re
authorities must be observed.
- Th. short-circuit withstand of accessories must be
For the installation of sealing ends in either indoor or outdoor, the atmospheric conditions such as humidity, saline and dirt content as well as altitude above see level (if exceeding
checked accordingly.
-
1000 m) are relevant. Special mechanical' chemical
and moisture content
of the soil are criteriar to
be
considered rvhen selecting cable joints.
-
-
16.1 Guide for planning ofcable
16 Guide for Planning of
Recommendations for trilnsportation. instnllation and mounting methods can be found in Scctions 29 and i0. Sections 17 to 25, of the part dealing rvith planning. contain instructions tbr thc selcction of rrted roltagc. conductor lnd screen cross-scctionirl -eas and for the determination of key electrical data ,r-i1her considerations $hich may have an influence , olannine are dealt rr ith in Seccion 26 and distribution nett,, oiks are dealt rvith in Section 27.
-rr
heip in the solution of special problems Siemens AC mckes available their experience to assist in selecting the most suitable type ofconstruction on technical and economic grounds together rvith the crosssectional area of conductor. With the aid of special
installations
l0
Selection of cable rated voltage Selcction ofconductor cross section to the follorving criteria when by the largest ol lhe resultinq values are to be used
Current loading during normal operl' tion Fi.rult current in case of short-circurt (mainly in netrvorks with rated voltages
greltcr than I kV) Voltilge drop
(mtinll
in nctworks rvith
rated voltages up to 1 kV) Economics (Calculrttions appropnatc
for instlllations rvhere large irmor.rnts of power xrc lo be transmitted)
l0 to
Electrical key data
23
Characteristics during operarion Interference cables I
"vith
communication
ndustrial and urban networks
computer softtvare. a solution can invariably be arrived at very quickly.
In the selection of a cable for a particular application the data listed in Table 16.2 (planning aid) are necessar.v. The more accurate and detailed this information the more accurate rvill be the result. The project engineer should have to reiy as little as possible on DUri .rssumptlons or estlmlrtlons
l4l
16 Guide for Planning of Cable Installations
Table
15.2
Planning aid for cable installations.
For the selection of cable and determination of conductor and screen cross-sectional area the following data necessary. To ease the handling of inquiries a check list is available on request. 1 T)'pe ofcable construction
1.1 Type designation 1.2 Material for insularion (PVC, XLPE, mass-impregnated paper) 1.3 Number of cores (single- or multi-core) 1.4 Cross-seclional area ofconductor qn 1.5 Conductor marerial (copper; aluminium)
I
2.1 2.2 2.3 2.4 2.5
Vohage
Earthing conditions, treat-
Nominal voltase of network U.
Maximum operating vohage Ub_.. System frequency/
Type ofcurrent (3 ph,
I
ph, d.c.)
Rated lighrning impulse withstand vohage L',"
3.1
Insulated or u.irh arc-suppression-coil earrhed star Doint. Ifindividual earth faults exceed 8 h lnd rhe rotal ofall earrh faults is sreat than 125 h per Year, the duration of the indir'idual earth fauh and duiationv of all earth faults per vear must be stated.
3.2 3.3
Direct earthin-s
4.1
Typc of operation
ment of star point (see Sections 17 and 19.1)
Load capacin r) in normal operation, operating condiltons
are
Earthing via additional impcdance
4.1.1 Lotd factorlr.daill, load fluctual.ion (in po*.crsupply sysremsapprox. 0.7 ro 0.8 : in ind ustrial ncr$ orks 0.7 to 1 .0 t. For intcrmiircnt operarion a lord diagram agtinsr time is required. 4. | .l Transmitrcd porrcr (max. Ioad to Fig. Ig.1 t 4.1.1 Is a securc Lransmission cssential ( u,hich mclns a minim um of tu.o cablcs per conncction)l I
nstallation condirions
Lcnsth of run in cround in pipe in eround in air ( free air) in duct or tunnel
4.2.1 I nstallarion in ground depth of la1 /r co",er ofconcrere riles. plastic tiles. earth:n$.are cover or Iavin_s in troushs rvith or rr ithout sand dimensions of trouehs \a,ith drawines arransement ofsinele-core cables bundled or side by side dimensional drau.ings for massed group ofcables
I
D:;'inirion scs par:: l5{l
Planning
Table
Aid
16
16.2 Continued
4 continued
4.2.3 Installation in pipe in ground depth of lay fr pipe material PVC, PE, steel, concrete or earl.hen ware pipe diameter and thickness (of wall) Arrangement
\"n/
kOIa,
@@6
Dirgram of groups of cables 4.2.4 Installation in air (e. g. indoors in large spaces such that the air tempertture does not increase due to heat loss from the cables). Installation on the floor, wall, open duct or racking, dimensional drawins ofgroups (compare Tables 18.23 and 18.24). 4.2.5 Installation in covered channels, tunnels The uir temperarure in the channel is increased by heat loss from the cirble
D:rta ofchannel in line wirh Section 18.5: inside rvidth b1
inside height /rt covering ri dimensional drarving of overall arrangement and answer to q uestions in 4.3.1 rvherc forced ventilation is used the temperature of the outlet alr or for the calculation of the cooiin-e required air quantity - the temperature of thc ineoine air must be given (normirlly max. value of ambient temperaturc). 4.3
Anrbient conditions
+.-). t
I
nstl
llltion in ground
ground
le
mpcrature 3.
thermal resistivity of soil for moist area gu for dried-out area g,
4.J.2 I nstallation in air air temperalure 3"
4.4
Externitl heat input 4.4.1 Heating b;- direct sunlight must be considered ifsun protection is not provided (see Section 18.4.2) 4.4.2 Hclting by district heating pipes rvhere laid in sround dimensional drarving to Fig. 16.'l and answers to questions in -1.J.1 4.4.3 Heating by other cables which run parallel or across typc designation with data on cross-sectional area and rated voltage load current
1b
distances and depths of lay with dimensional drawing
t+J
l6
Cuide for Planning of Cable Installations
Table
16.2
Continued
5 Load-capacity in case of
5.t
Calculation with rhe use ofvalues from network calculation treatment ofstar point and indication ofcritical short-circuit currents (one, two or three pole) initial symmetrical short-circuit current.Il' peak short-circuit current 1. continuous short-circuit current Ii shon-circuit duration rr
5.2
Calculation with values from protective device (ifvalues in 5.1 are not known) treatment ofstar point and indication ofcritical short-circuit current (one, two or three pole)
short-circuits (thermal and mechanical stress)
breaking capacity S.
short-circuit duration t"
-
6
Voltage drop
System frequenc.v/
Transmitted power S or loading current /o Power factor cos p Length of run /
Typeofcurrent:3 ph, 1 ph a.c. ord-c. Allosable voltage drop AU or Au
7 Calculation of economy
I lt
Transmitted power S Length ofrun / Depreciation durarion r Annual rate of interest p Amortization rate I Addition to amortization to covcr maintainance and repair Electricity price t" Utilization lime of power losses l', Opcration pcriod f6
Is
Planning
'
Aid
16
! ipe of construction Depth of lay' h
rytricr heatiry
r
:pth of
ducr
lay
m m m m
hF
Distance
AF
Widrh Heisht
ur hr Return
Feed prpe
Inner diameter
of ...
m
... m
,/. ...
m
...
l.
...
W/Km
... W/Km
'rt
...
insulation Outef diameter of insulation Heat conductivity u latio n
of
ins
Tempe rature of
prpe
m
herting
'edium
24; far as Possible dePenIt on amblent temperature)
\-
'rR...
L
g. 16.1 lemperature rise of cable caused by district heating: data for calculation
145
I
/
LaDle Kaleo
v
oltages
ble 17.1 . These are derived from the values for lhreephase installations by using the following formulae:
17 Cable Rated Voltages
Uv-^':23t:,
vt
U0...:+,
where neither conductor is earthed,
where one conductor is earthed.
v3
17.1 Allocation of Cable Rated Voltages The voltages for which a cable has been designed forms the basis of certain operating characteristics and rest conditions and are termed the rated voltages.
To avoid confusion in installations having one conductor earthed e.g. in traction feed cables it must be observed that the highest voltage ofsystem Uo.oo, for these cables must not be greater than the permissible voltaee YS to the metal cover. l/ { f-
As opposed to other electrical machinery or equipment cables have rated voltages stated as UolU where
according to VDE
:
L/o the cable rated r.m.s. poser-frequency voltage bet$'een each conductor and metallic cover or earth
U
rhe cable rated r.m.s. pos'er-frequency voltage between pharse conductors in a three-phase network (U --y' 3 Us).
standards for cable an additional valuc lor highest permissible voltage L/. is stated in brackets. The voltage designation is uritten as UoiU(U^).
ln IEC
U. is also the " highcst r.m.s. powcr-frequcncl'
voltage for equipment" DIN VDE 0111a.
to DIN VDE 0101 and
*ith
rated voltagcs Lq U arc uccording to use on three-phase installation u ith l nonrinal vollagc
Cables
DIN VDE 0198 and IEC I S3 suitablc for
in uhich the highest voltase ofa s)'stem U6.n,. does not !'\ceed the Values given in DIN VDE 011I and IEC 71-1 (see Tablc 17.1). Since the insulation of cables rvith polynrcr insulation hrrr inq a rated voltage Usl {-; :0.6i1 kV and all radial
D
these
in sinsle-phase a.c. systems uhere both conductors are insulated from earth. rvith a sl,stem nominal voltage U^<)Uo,
tr
in single-phase a.c. systems where one conductor is earthed, with a system nominal voltage
t.
The hi-qhesr voltage of u s1'stenr L6... for cables for sinrle-phase alternating current rrc shorvn in Ta-
l.l6
In Gcrmany the voltage rating of 3 kV has been made obsolete and is no longer included in VDE speciF 'tions. If in individual cascs, e.g. in circuits for:re srarring of large slipring motors, operating voltages Ub are encountered which are higher than that allorvcd lor cables with a rated voltage Ue1 U= 0.6/1 kV it is acceptable according to DIN VDE 0271, to use PVC cables with concentric conductor or armour (e. g. NYCWY, NYFGY) having a cable rated voltlge Uo. U:0.6i1 kV. However rvith cable cross-sectional areas of 240 mm2 and above. the insulation rvall thickness is thc samc as is required to IEC 501 for cablc \\'ith Uo,'U= 1.E/'3 kV. The pcrmissible quantit) of L/.:3.6 kV must. ho',r'eler. not bc cxcccd.
A comparison of cablc rated voltaues to VDE
1."<1.=1 iL,o
ficld cables are designed lor the voltage Uo, are also suitable for installations
In direct current systems having a maximum operating voltage of up to Ur.,,=1.8 kV conductor/conductor and conductor/earth VDE permits the use of cable with Uo = 0.6 kV.
and
IEC togcthcr sith thc permissible continuous "highest voltages for elcctrical equipmcnt and machines" rvith relevant data to BS 77 shos's that for these s dards. apart from differing ratcd voltages the srir e highest permissible voltages app)y (Table 17.2).
Rated Impulse (Lightning) Withstand Voltage ' Voltage Stresses in the Event of Eanh Fault 17.3
Table 17.1
Allocation of cable rated voltages U_olU(U^) and highest voltages for equipment and the highest voltages of a system Cable rated voltages
Systems
y.
to the nominal voltages Un
for
uolu (u^) Three-phase current
Single-phase current
Nominal voltage
Highest voltage
Non-earthed system
One conductor earthed
of a system
Nominal voltase
Highest voltage
Nominal voltage
Highest voltage
u,<2Lto
of a system Uu.o"
U;3
of a system
KV
kv
Ur^ KV
a
.6
l
.3,'3 3.6i6 l
6/10
l5 ll /20 l8i 30
(.7i
(1.1) (3.6) r'
3
(i .2)
o
t.2
1.1
3.6 7.2
't.2
L'u-",
1.4
KV
0.6
8.3
0.7
3.6
t2
12
15
7.5 ?4 36
36
)2
Not applicable in these
Not applicable in
voltage ranges
voltaee ranges
(52) (72.s) 64/110 (123)
110
76132 (r45)
I
72.5 123
J!
'145
150
170
871150 (170) t27,t220 (245)
220
220;380 (420)
380
l4
6
28
t2
l.l
18
21
7
1
45 60
I
kv
Uo
l0 20 30
2614s 36160
DIN VDE 0298 part IEC I8J
KV
1
(12) (17,5) r) (11) (36)
*
these
410
DIN VDE OIOI DIN VDE OIII
DIN VDE
0198
part
I
IEC 7I-1 Thr\ \ oitrgc rrnsc to IEC t
_i.
l-l rnd
IEC I3,i ir no l)nger conltlincd in rhc vDe rp\:!irjc]rions for cublc
17.2 Rated Lightning Impulse Withstand Voltage
17.3 Voltage Stresses in the Event of Earth Fault
The rered lighrning impulse riirhsrand voltages U,u trhich must be considered for electrical equipment and machines in three-phase nenvorks are listed in Table 17.2 as exrracred from DIN VDE 01 1 1 and IEC 71-1. Cables and accessories which comply with VDE or IEC standards are designed and tlsied to withstand these stresses. In the calculation of the insulation design for high-vokage cables the impulse withstand and switching overvoltages are very impor-
In the event of an earth lault. the cable insulation is subjected to voltage stresses of shorrer or longer duration dependant upon both the trearment of the star point and the design of the network protection (see also page 380). When applying cables different considerations must be given to the rhree types of stress A, B and C :
tant and are simulated by a test impulse voltage wave . g I .2/50 ps respecriveiv 250/:500 ps (1.? and lo_!1. berng -:)U the wave front rime ivirh 50 and 2500 bcing the decav time to half varue;.
A
Systems which in case
ofan earth fauit are disconnected instantaneously i.e. within 1 s: these are mainly networks with a low-resistance earthed star point. For this stress type all cables are suitable.
17 Cable Rated Voltages
17.2 Allocation of voltages to VDE, IEC
Table
DIN VDE 0298, part DIN VDE 01I1,
1
and British Standard (BS)
Three-ohase networks to BS 77
DIN vDE DIN VDE lEc 71-1
Nominal
Rated lightning impulse withstand voltage U,B
IEC 183 Cable rated voltage
Highest voltage
UolU
for equipment
kv
KV
voltage U
U. kv
Highest voltage
0111, list 2 0298, part 1
of a system
Ut^.' kv
kv
Radial field cables 0.6i
1.2
1
I.8t3
"
3.616 6, 10 r) 8.7. 15
J.O
J.J
'1.2
6.6 1t
t2
3.6 1.2
t2
1'7.5
18i 30
36
JJ
JO
26 45
)f, I !.)
66
|
64i110 tot | ): 8?/150 121 1220
220i 380
75
ll5
22
.^: tlt
60 95
rl1n
36160
40
170
88
100
At rated voltages from UqlU= 26/45 k'._ the wall thickn€ss of the insulation is selected and tested to mee! the specified
110
123
requlrements
132
14i
110 1i<
220
420
380
!.)
410
Cables with non-radial field
0.6 I
1.1
r a ': Ll
i.6 t.6
3.6 6
7.? 1.2
6161'
6 l0 8.7r 1 0
:)
11
ll
0.0
ll
1.6
.10
1.2
60
1l
In Ccrmanl no longcr uscd irnd thercforc not includ.d In VDE sLrndJrdi :'" Onil fo( paper-insuhlrd cablcs (e.g. !o IEC i5). Not commonl].' us€d in Csrmlrn!
B
7i
and b-'ncc nol includcd in
Dlr" \'DE 0:i-i
oper- C Systems which in the event of a fault remain in earthed: operation for a longer period than described under B. with one phase earthed. these are networks with an insulated star point Systems, which. under fault conditions, are ated for a short time only with one phase
or alternatively having earth fault compensation. According !o iEC 183 this duration should not exceed one hour unless longer durations are speci-
in the relevant cable standards dependent upon the t\ pc of cable construction.
fied
l rlE
Voftages Stresses in the Event of Earth
Table
17.3
Fault
17.3
Selection of medium-voltage cables according to stress types B and C under earth'fault conditions
Cable rated voltage
Cable type
Operation with single earth fault to Stress type B
Stress type C
Single earth fault 8 h Sum of earth fault durations per year 125 h
Cable must be selected have rating voltage Uo/U
UJU KV
Non-radial field cables with PVC or EPR insulation Belted cables with paper insulation
permissible 3.616
6/10
8.7lls" .{adial field clbles with insulation of paper, PVC. PE, XLPE or EPR
3.6t6 6/ 10 8,7/1 5 ' ) 12120
18/30
!'
kv
permissible permissible permissible
616tt
or 6i10
8,7/10 ')
permissible permissible permissible permissible permissible
6,110
8.7i 15 12 r20
" or 12.'20
18i 30
Cables with correspondingly reinforced insulation are required (not covered by IEC- and VDE standards)
VDE slxndards -_o Ionger uscd in Ce.many and thcrcforc no longcr includcd in
e
Selection of Cable
iVI e clitn t- V o tt ag
Stress type A: All cables rre suitablc Stress type B and C: See Table 17.3
which comply rvith VDE or IEC standards are suitable for stress type B providing any individual earthfauh duration does not exceed approximatel.v- 8 h and the total sum of all earth-tault times in one -"-ear docs not ekceed approximatel)- 125 h. If earth-fauh durations are to exceed these values substantially, cables of the next highest voitage grirde must be used (e. g. instead of L;olLr=6i10 kV use L'o'1.':12120 kV) or. in the case of belted cirbles, a cable rvith higher belt
H
iglrl'oItage
Cab|a.s v'irh Papt'r Insulutinrt
(Uo'U>liJ,30kr'), rvhich have been tested to VDE or IEC stlndards a.are suituble lbr stress tl pe B providing any individual :arth fault does not exceed a duration of approximately 8 h and the total sum of all earth-fault durations per year does not erceed 125 h approximately'. fhese cables. however, are not designed for operation under stress type C. When it is required to install cabies in a network oF plant where longer earth't'ault durations are to be expected. the cable insulation lvill require to be appropriately dimensioned and tested. High-Voltage Cables *ith PE, XLPE or EPR Insulation ( UolU> 18130 kV) are normally dimensioned and tested for use in netrvorks or planc with stress type A. If it is required that these cables will be opercted lor a limited time or longer rvith an errth fault on one phase. this must be taken into account rvhen dimensioning and testing the cable.
Ca
b Ie s,
insulation must be used (e. g. instead ol tis|L':6t10 kV use cable UolL-:8.7710 kV) (see Table 17.3). This type of belted cable is not used in Germany and there for no provision is made for it in VDE standards. For cables having rated volrages greater lhan lLolU:13'30 kV the insulation rvall thickness must be dimensioned appropriately. For medium- and high-voltage cables it must be noted that their service life is affected if for frequenr short periods and/or for longer periods the cables are operated with an earth fault on one phase. Low.l/oltage Cables, rvhich comply rvith the VDE and IEC standards are suitable for stress type C rvithout limitation. 149
l8
Current-Carrying Capacity in Normal Operation
18 Current-Carrying Capacity in Normal Operation
18.1 Terms, Delinitions and Regulations Basically the terms definitions and regulations laid down in DIN VDE 0298 Part 2 and DIN VDE 0289 Part 8 apply. Load Capacity is the short term to express current-carryins capacity. With load capacity the permissible current f. is being
pregnated cables, in addition, the remperature lise is limited to avoid the formation of voids in the insulation (Table 18.1).
Conduc tor C ross- Se c tional Areu must be selected such that in normal operation the loading 16 does nor exceed the load capacity 1. -eiven
t'lR 1e\
Ihs 1,.
defined under certain operaring conditions.
In addition to compliance with the above reeularions the following is also relevant: The lalues of current-carrying capacity for the reference operating conditions which are given in Tables 18.2 and 18.4 are rated values. These reference operaring conditions (in DIN VDE 0298 Part 2 named
as "normal" operating conditions) are in the same sense rated data to DIN IEC 50 (1 51). The followine equarion applies
1,=
I,nf,
(18.1)
*,here fI/ is the producr of all factors ',r'hich must be considered. For electricity utility operarion or other cyclic rypes of operarion the maximum load corresponds to load capacity which is defined as /, or 1..
ls the short term for current loadinc. Loading relates to lhe currents uhich a cable be required to mav carrl under specific operational conditions.
In normal operation loading is lhe operating currutt /0. in electricity utility operations or other cyclic types of operation the max. value of the loading is the operating current.
le O p era t ing
Te mp
er
atur e
is the maximum permissible temperature at the con-
ductor under normal operation. This value is used in the calculation ol load capacity for normal operation. This is included in DIN VDE 0298 pari 2 in respect of load duration (load factor). For mass-im-
li0
Tentperature Rise
of a cable is dependant upon construction, characteristics of materials used and operaring conditions. An additional temperature rise must be considered where grouping u ith other cables or heat input from heating pipes. solar radiation etc. occurs.
.\'onntl
O pcratiott
Normal operation includes all
t1.pes
of
operation.
such as. continuous operarion, short-time operation.
Loadirg
P ernt iss ib
Decisive for this are the most unfavourable operaring conditions at any point along the whole cable ' '' durine operation. This ensures that the conducosr is not heated at any time and at any point above the permissible operating temperature.
intermittent operation. clclic operation. utility s, plv operation, providing the permissible operatiig temperature is not exceeded.
OL'eruIran!s include both overload currents and short-circuit currents (DIN VDE 0100 Part 430 and Parr 200). These can cause, for a limited period, conductor temperatures u hich are higher than the permissible operating temperature. The cable in these cases must be protected against detremental temperature rise by overcurrent protection devices. If necessary the conductor cross-sectional area may have to be dimensioned to satisf)' the conditions of short-circuit stresses as discussed in Secrion 19.3.
-
_
Terms Deflnitions and-Regulations
Table
l8.l
l8.l
Permissible operating temperatutss and thermal resistivities
Type of construction
Standard
Permissible
Permissible temperature rise
Thermal
operating
installed in
resistivities
'c
Ground
Air
l\
l\
KmiW
XLPE cable
DIN VDE DIN VDE
0272, 0273
90
J.)
PE cable
DIN VDE
0273
70
3.5,'
PVC cable
DIN VDE DIN VDE
0265,
70
6.0:'
DIN VDE
O]55
Iass-impregnated cablc
0271
Belred cable
I kv
80 80 65
'3.6 6 kV rl^0.6 , 6l0kv
of
insulation
temperature
65 65
))
45
55 35
6i
))
65
55
6.0 6.0 6.0
Single-core cable, S.
L.
and H cablc 0.6 1 kv 61
10
80 80 10
kv
3.6.6
kV
kv 18, i0 kv l
6i
2,20
" Aiio roDlics
:r .\lso
60
45 35
.10
JI,,
for rll ou(cr rh\:rths ot PE
applics fo.
!ll
outcr shc:rrhs of PVC irnd proLcerirc co\crs ol jurc rcr!inS
lterloa
turrelrtr ciln occur bv operational overloadhat is otherrvise a fault-free circuit. For these conditions permissible temperatures have not yet reen defincd. These rvill be dependent on borh duration and frequencv of the overload occurances: these again at-fect the heat deformation characteristics and ing in
j-i
6.0 6.0 6.0 6.0 6.0
rr
accclerate a-seing.
Short-cirait currents flow when a fault of neglegible tmpedance occurs betrveen active conductors which in normal circumstances have different potentials. The permitted short-circuit temperatures are acceptable only for a duration of up to 5 seconds. In systems *ith an insulated neutral and in compensated networks, a line-to-earth short-circuit current is tcrmed earth-fault current. Such earth-fault current
c:ruse voltage stresses
in the fault-lree conductors (see Secrion l7). to an ertent thirt temperatures erceedins
\irh
bitunrinous compound
the permissible operating lemperltures cannot
be
permitted. Entergent'v Operation
is a type of operation quire common in USA and some other countries. Here currents are permitted which are higher than the load capacity in normal operation. The conductor "emergencv operating temperature" which may on some occasions signihcantly exceed the permissible operaring remperarure are limited in duration for the individual faults both during any one year and during the service life of the cable. A definition and the question of what values of emergency operating temperature are acceptable for the differenr tvpes of cable and also rvhat reCuction in service lit'e is to be agreed is currently under discussion in the relevant IEC rvorking sroups.
l5l
IE Current-Carrying Capacity in Normal Operation Type of Operation describes the temporal characteristics of the load capacity and the loading. Continuous Operation
is an operation with constant current for a duration sufficient for the cable to reach a thermally stable condition but is otherwise not limited in time.
18.2 Operating Conditions and Design Tables To assist in preparing a clear basis for design, regulatory and operating conditions are discussed under
tr type of operation, tr conditions of installation, tr ambient conditions.
Utility Supply Operation is described in Section 18.2.1.
Short Time and Intermittent Loadinp
18.2.1 Operating Conditions for Installations in Ground
is described in Section 18.6.
Type of Operation
The values included in rhe tables for installation in ground are based on the type of operation commonly experienced in electricity supply networks (supply utility loads). This load is defined by a 24 hour lc^4 diagram which illustrates maximum load and lu.-a factor (see Fig. 18. t ).
Load,har load 100
en --1
0.6
I
---Fig.
12
16
20 hours
24
Time-......*
Relation of load to maximum load in % Relation of average load to maximum load
l8.l
Daily load plot and determination of load factor rr (Example) I
-sl
Operating Condirions installed in Ground 18.2
Ivlaximum load and load lactor of the given load are determined from the daily load plot or reflerence load plot. The daily load plot (24 hour load plot) is the shape of the load over 24 hours under normal operation. The reference load plot is the average load shape of selected, similar daily load plots. The highest value of the maximum load read from the daily load plot is taken as operating current .Ib. If the load fluctuates within time bands which are less than 15 minutes, then the mean value ofthe load peak over a 15 minutes period is taken as maximum load, i.e. a mean value must be determined over the range of time which contains the peak, this being then termed maximum load.
'
he load factor nr is determined by plotring the load erpressed as percent of maximum load on squared ^
paper (see Fig. 18.1). The load facror nr results in total area belorv the curve which is equal to the '-\e;er of the rectansular shape. By counting squares belorv the load curve the area can be determined reasonably accurltely. This arca should be entered on the diagram. thus enabling direcr reading of rhe relationship between average load and ma.rimum load and hence load factor rn provided thar, as in Fi_q. 18.1, the scale is selected such thar 100% load is equal to unity on the load lactor sclle (see example 18.1, page 180).
The average load is the mean valuc ol'rhc daily load plot; the load factor being the quotienr from the avcrage load divided b-"" the maximum load.
For this calculated load factor the given maximum load /o must not excced thc Ioad capLrcity 1..
the commonly used depth of lay for low-voltage and medium-voltage cables (0.7 to 1.2 m) it is therefore assumed that the necessary slight reduction in load capacity is compensated for by the slightly more favourable conditions.
For these reasons when the depth of lay varies within that range any variation in load capacity is ignored.
The quantities for cable load capacity are for the arrangements shown in Table 18.2 for one multi-core or one single-core cable in a d.c. system or for three single-core cables in a 3-phase system. With larger numbers of cables a reduction factor from Tables 18.15 to 18.21 must be applied. These reduction factors were derived for cables of equal size arranged side by side in one plane and loaded identically with the same maximum load and load factor. For cables of different construcrions and,/or operaring with different load factor it is necessary to form appropriate reduction factors for erch form of construction and/ or load lactor for the toral number of cables in the trench and thus establish the lactors most unfavourable for all cables. Crossing of cable runs can cause difficulties especially rvhen these are denselv packed. At such points the cables must be laid rvith a sufficiently rvide vertical and horizontal spacing. In addition !o this the heat dissipation musr be assisted by using the mosr far ourable bedding material. A calcularion ol conductor heat output and temperaLure rise is adlisable
ll
8.11.
In situations of great grouping and rvhere there is limited space, a sufficientll large bricked pit can eleviate heat build-up. This pit can enable the cables to cross in air and the resultant temperature rise of the air in the pit and also the temperature rise of conductors can be calculated as indicated in Section 18.5.
Installation Conditions
The depth oJ luv ol a cable in ground is generally taken as 0.7 m rvhich is the distance below the eround surface to the axis of the cable or the centie o[ a bunch oI cables. If one calculares the load caoacitv of a cable laid in the ground it is found this reduces as depth increases. assuming the same temperature and soil-rhermal-resistivity. With increasing depth of lav horvever, the ambient temDerature is reduced and so. normally. is the soil-rhermal-resistivity since the deeper regions of the ground are more moist and remrtin morc- consistant thirn the surtirce llvers. For
The load caytcitt, oJ' tnuki-core PVC cfules is calculated by multiplying rhe load capacity for 3-core cables in Table 18.5 by the rating factors for laying in the ground given in Table 18.25.
In the -eround, cables are normally embedded in
a
layer of sand or a layer ol sieved soil and are covered with either bricks or tiles of concrete or plastic. Tbese bedding and covering arrangemenrs (see Table 18.2) do not affect the load capacity. When inverted 'U'-shaped cover plates are installed, air may be trapped and therefore it is advisable to use a reduction trctor of 0.9 in the c:rse. I
)J
18 Current-Carrying Capacity in Normal Operation Table
18.2
Operating conditions, installation in ground r) S ite operating conditions
Refe r e nc e op er ating c on dit ions
to evaluate the rated currents
and calculation of current-carrying capacity
.f.
L-r,nr Type of operation
Load factor of0.7 and maximum Ioad from tables for insrallation in sround
Rating factors /, to Table 18.1 5 or 18.1 6 , to Table 18.17 to 18.21
I ns t a I lat ion conditions Depth of lay 0.7 m
For depth of lay up to 1.2 m no conversion necessary
Arrangement:
I
/n \v
multi-core cable
1 single-core cable in d.c. system
Rating lactors for multi-core cables to Table 18.25 for grouping or bunched
t.l
3 single-core
cables in 3-phase system side by side rvith clearance
ol/cm
/, /,
to Table 18.15 or 18.16 to Table 18.17 to 18.21
Calculation refer Section 18.4.4
3
single-core cables in 3-phase system bunched 2)
Rating factors for
Embedded in sand or soil backfill and if necessary with a cover of bricks, concrete plates or flat to slightly curved thin plastic plates
' U '-shaped cover rvith trapped I
air/=
0.9
nstalled in pipes/= 0.85
Calculation refcr Scction 18.4.6 .4nbient conclitiorrs Ground temperature at installation depth ?0 "C
Rating factors
Soil-thermal resistivitl of moist area
1Km'W
./, to Table
18.1-5
./r to Table
18.1 7
or I 8.1 6 to 18.21
Cclculation refer to Section 18.J.3 Soil-thermal resistivitv of dry area 1.5
Km W
Protection from external heating
e.
g. from heating ducts
See
Section
16.
Table 16.1
Jointhg and earthnrg of metal sheaths or screens at both ends (see Section 21) t'
Sire operarin8 coDdirions
for installarion in ground musl alwlys be calculrred using the two rating fcclors
thc specific grouDd thermrl resislivity nnd on thc .aring factor: '?' Cabl.s touchiog io lrianSular
1<1
formation are classed
as
n/=r.4
"bunched"
/,
aod
I
since both faclors dcpeod on
Operating Conditions insulled in Ground 18.2 When laying cables in pipes the heat insulation effect of the air layer be[ween cable and pipe must be especially considered [18.2]. For installations in pipe systems a reduction of load capacity by a lactor of 0.85 is recommended where an accurate calculation is not justifiable (see Section 18.4.5).
Ambient Conditions The ground temperature SE is taken as the temperature at installation depth with the cable under no load condidons.
Figs. 18.2 and I 8.3 a indicate mean values of meaI red ground temperatuces belo',v a surface containing vegetation. The temperature at a depth of one meter belorv a concrete or asphalt surface which is s_ubjected to solar radiation (Fig. 18.3 b) may, during . ) summer months, achieve a level 5 'C higher than -rese measured values. Calculations rvith lower temperatures than 20'C as given in the tables should not be made unless such a quantity is proved by mcirsurements during thc summer months. In dcscrt areas the temperatures can be somervhat higher than those as shown in Fig. 18.4. The soil-thermal-resistit,itv is largely dependant on density and water content of the rclcvant typc of
[iIMXI
'c
:-;:';i:;:
UXUXXqI
c) Below grass roots
[ &[ xs
xv xwuu
b) Belorv asphalt surface f ig. 18.3
Ground tcmperature in Erlungen 1966 (months I to XII)
6fcufd lemoerarure
Grcurl ,n
V
iJE
l)a
--
Extreme value Mean value over 10 years
Fig. 18.2 Ground temperalurc at a depth of I m, extrente values irnd mern value measured in Stuttgart-Hohenheim. .lS0 m lbor e sea lcvel, rncdium soil
fu1ar.
April llla,r June July Aug Sept. 0cr.
Nov
Fig. 18.4 Ground temperatures ar virrious depths in Kurvlit 155
l8
Current-Carrying Capacity in Normal Operation
soil. With differing types of soil and the effect of climatic conditions on water content (precipitation, ground temperature) the level of the water table as well as variations in cover of the surface and vegetation, both local and seasonal must be considered (see Fie. 18.s) [18.3]. Due ro heat loss from the cable neighbouring cables and other heat dissipating items the soil may dry our. For the calculation of quantities in the tables and to simplify tabulation the region surrounding the cable has been distinguished between a moist area and a dry area.
The reference value of 1.0 Km/W was selected for the soil-thermal resistiuity qs of the moist region. This quantily applies for normally sandy soil in a warm moderate climate (see DIN 50019) with a maximum ground temperature of 25 oC. Lower values are experienced in the colder seasons with sufficiently high precipitation and more favourable types of soil. Higher values must be selected for zones u'ith higher ground temperatures, extensive dry periods or with almost zero precipitation. If detailed data are not available IEC 287 recommends quantitics which should be used and these are reproduced in Table 18.3. Lower values of ambient can. where desircd,
Sci
i iir:rnal.resisiivit,i l1
10
09: 0.8
be used for the calculation of load carrying capacity for the winter period or during seasons of high rainIall.
_
Tables 18.15 to 18.21 provide rating factors for the individual soil-thermal resistivity of the moist region. In ground which has a content of rubble, slag, ash, organic material or waste etc. one must expect very much higher values of soil-thermal resistivity. In such instances it may be necessary to take measurements or to replace the soil in the vicinity ol the cable.
For areas of built-up ground of normal types of soil which are not compacted and where increase of density is not to be expected for a considerable time the next higher value of soil-thermal resistivity from Tables 18.15 to 18.21 should be selected. The same applies where a cable run is situated in the rooting area of hedges or trees.
A
soil-thermal resistit'it'of 2.5 KmllI' \,as selected .[or the dr;'region taking into consideration that. d is frequently used as a bedding material. For ceFain types of soil or thermally stable bedding material with compacted dense soil lower quantities can be achieved. For individual cases quantities of resistivity and the resulting current-carrying capacity must be calculated separately (see Section 18.4.6).
Prointitl' to or the crossing of district heating Iines often results in a dangerously high temperature rise in the cable. especially if the heating pipes are insufficiently insulated [18.4 to 18.5]. The continuous heat loss from the heating pipcrvork can causc drying out of the soil. Because of this. sufficiently larqe clcarances must be maintained betrveen cables and pipes
_ _
and also between cables.
District heating lines situated near to cables should be insulated on all sides. Minimum clearances u-., h are given in [18.6] are estimated on the basis that * rhe cable is loaded to approximately 60 to 70% of the load capacity and there is little grouping as is common practice in utility suppll net$ orks. At crossovers or at areas of parallel runs rvith district heating iines the current-carrying capacity will be reduced. lnstalling the cables in sufficiently large pits at these areas will increase their load capacity.
If insulation is arranged between the district heating lines and the cable, this is not fully elfective and
* -
tends to reduce the heat dissipation of the cable.
Fig. 18.5 Soil-thermal resistivity of virgin soil showing seasonal varittion (mcasured at various locations) [18.5] 1_56
To arrive at the measures required it is necessarl ro refer to the questions in Table 16.1, Section 4.4.2 as *eil as to Fig. 16.1.
-
Operating Conditions, Installation in
Air
18.2
18,2.2 Operating Conditions, Installation in Air
Table 18.3 Recommended calculation quantities to IEC 287 [18.2] a) Ambient temperatures at sea level
Climate
Ambient temperature of ground at 1 m depth
oI air
troplcal subtropical temperale
Type of Operation
Mini-
Max!
Mini-
Maxi-
mum
mum "C
mum
mum
'c
25 10
55
25
40
0
25
15 10
.C 40 30 20
The quantities given in the table for installation in air apply for continuous operation. Because of the significantly shorter heating and cooling times compared with installations in ground in a public utility type o[ operation the highest load must not exceed the load capacity at continuous operation.
The load capacity in intermittent operation with shorter duty cycle times can be calculated by reference to Section 18.6. Installation Conditions
b) Soil-thermal resistivities
Soilthermal resistivities
Km/W continuously moist regular rainfall seldom rains Lirtle or no rains
0.7 1.0
2.0
The quantities one obtains for the rated load capacitl1. apply for the arrangements shown in Table 18.4 for multicore cables and lor systems o[ three single-
core cables installed in free air. The quantities are based on installation in free air with unhindered hear dissipation by radiation and convection and with the exclusion of external heat sources in an ambient air temperature rvhich does not rise significantly. The requisite practical conditions lor this are illustrared in Table 18.4. Rating facrors for other installation conditions and for grouping of cables are given in Tables 18.2i and 18.24.
Thc load capaciries of multicore PVC cables can be calculated by taking the quantities lor three core cables from Table 18.6 and applying the rating factors iiom Table 18.25. Where a cable is installed directly on a wall or on the floor. the load capacity.. must be reduced using a factor of 0.95. Factors for grouping are given in T.rbles 18.11 and 18.11. Where applicable in these tables the reduction factor ol 0.95 for installation directl,'- on a rvall has rlready been taken into account. The thermal resistance of the air in respect of a cable installed in free air can be calculated by ret'erence to Section 18.4.2. 81' using the design data to Section 18.2 it is not necessarl,to know the air-themalresistance. Ambient Conditions
The quantities given in the tables for installation in air are based on an air (emperature of 30 "C. For other air temperatures the raiing factors in Table
t57
l8
Currcnt-Carrying Capacitf in Normal Opcration
Table
18.{
Opcrating conditions. installed in air
Rcfcrcnce opcrating condit iotts lo elaluate the rated currcnt /,
Sit
c opcroting cottrJitiorts
and calculation of current-carrying capacit)'
I.: I,nf
Type of operation
Continuous operation from tables for installalion in air
I us ta I lo
t
iott condit ions
Arrangement:
o e
singie-core d.c. cable
3 single-core cables in
3-phase system side
by side u'ith clearance equal to cable dia.
3 single-core bunched
cables
Rating factors for
/n \9
1 multi-core cable
I
Load capacity in intermittent operal.lon to Section 18.6
multi-core cable to Table 18.25 grouping to Tables 18.2i and
18.2-1
YM tdldl
in 3-phase sl"stcm
"
Installation in frec air i.e. unhindcrcd heal dissipation by: cable spaced arvay from u all. floor or ceiling cables side by side with spacing minimum twice diamcter, cable runs above one another \'ertical spacing twice cable diamcter. minimum between layers of cablcs 30 cm Arnhient conditions
Air temperature
30
Rating factors for
'C
Sufficiently large and ventilated rooms in which the ambient temperature is not noticeably increased by losses from the cables
differing ambient tcmperatures to Table 18.21 grouping to Tables 18.13 and 18.24 Load capacity whcn installed in channcls or tunnels to Seclion 18.5 Load caoacitv to Section 18.4.2
Protected from direct solar radiatron etc.
Jointing and earthirrg of metal sheath or screens at both ends (see Section 21) rr Cablcs touching in triangular formalion arc classcd
158
as
"bunched"
'
it is neccssary to assumc an ltnbicnt dir temperirture for installing cables in air. provided that Where
18.2.3 Project Design Tables
no higher valucs are known tiom expcricnce or fiom mcasurcment. the tbllorvins are uscd:
The Tables 18.2 and 13.4 with the reference operill.ing condirions and other diflcring conditions can be uscd as a guide lor project design.
"c
Unheated cellar rooms
20
Normal climate rooms (unheated in summer)
25'C
Factorv bavs- work rooms ctc.
30'c
The above ambient temperatures are typical tor mid Europeln locations.
-
Pr6ject Design Tablcs 18.2
Tables 18.5 to 18.14 give quantities o[ load capacity ofcables, i.e. rated currents f, based on specific operating conditions.
For conditions other than these specific operaring conditions the rating factors for these are included in Tables
1
8.1
5 to 18.25.
Temperaturcs exceeding the relerence calculation o'antity of l0 "C may well be experienced in rooms :,. -.h inadequate protection tiom solar radiation, insut'ficient ventil3tion or rooms contlining machincs or plant having a high heat dissipation erc.
-
1er
_ ^ -
certain conditions the heat loss from clbles i..oy itself lead to an increase in ambient air temperature. This applies mainly to cable trenches. ducts. channcls or tunnels (see Section 13.5).
If the air temperature in encloscd rooms is incrcuscd by the heat loss from the cables (e.g. in cable trenches, cable trays etc.) the rating llctors in Table 18.22 for different air temperatures, together with the factors for grouping must be applied.
Other heat inouts. e. s. solar radiation. must be considered or prevented by the use of covers (sce Scction 18.4.2). Ifcovers are used, however. the air circulation must not be hindered. A calculation of load capacity under conditions of solar radiation can be made by reference to Section 18.4.2.
159
l8
Currcn t-Carrying Capacity in Nornral Opcration
Table
18.5
uolu:0.6lt k\'
Load capacity, installcd in grorrrrl
Insulation material
l\{ass-imprc!natcd papcr
Metal sheath
Lead
Designation
N(A) KBA
Standard
DIN VDE
Pvc
XI-PE
Aluminium
Lead
N(A)KLEY
N(.4.)K.A.
N(A)YY N(A)YCWY
N(A)YY
DIN VDE O]7I
O:Js
NYKY
N(A)2XY
DIN VDE
DIN VDE
0272
0265 30
Pcrmissible conductor temperature
'c
70 I'
Arrangement
t_7\,
\1r., ir\:,r9
.o- J\:,)(' (:,(.
'c
:)
o
"c
90
o
f_7\e
&
o
an z':\
l1
11 35
:l
t-/t, o
q7\:r'
&
c)(
Copper conduc!or nominal crosssectional area
nml
Load capacitl in A
il
t6
70
5l
1.1 .++
90
68
56
1.5 l.l
I
-
6
t0 t6
l5 l5
50 70
95
;.-
:,,
161
175
191
201
ll0
110
t0l 3.15
rtl
. t
:0i
t5r
150
t8J
199
i_r1
t9
-167
379 .1:6
.10:
115 533
r168
468
603
6r 0
571
665
603
i9i 194
507
567
400
602
6-s4
500
Alu
til
237
387
571
:00
162
:94
43'l 533
169
r06
r85 300
i*o
192
150
:40
i:s
i2
160
.t
364
111 ?81
t8l
l6 68
7i
90
ll6
9?
1)'l
1]l
11'l
l _'17
r6l
57
165
t95
137
:96
l3i t:8
195
:i0
222
19:
l-:9 ts7
?32 136
)72
l-i6
t82
175
428 483
4t9
J99
l5l
561
6i7
lt6
166
199
143
529 986 1125
{64
18l
561
514
542
6i2
600
621 698
730 823
il3
l3l
t6l :31
ili
-161
lq
30
5',
55
6
6l
]]7
1ts
l7i
)l
ls
t06 :J9 :i65
s2
101
107
r
.10
53
98
151
l8 6l
:te
86
ed
ll1
I 1,i
r.1l
1.19
t7s
175
:05 :51
-'i:7
.r02
t0i
J8l
ll
I
2i9 i10
109
rl 11
r:il l1
l0 -16
i50
-i.16
l-il
618
i90
i96
.16
701
141
419 521 587
61,-
175
,109
Ito
sl9
5
-i-13
931
i80
60i
1073
663
t123
669 748
i
689
78r 38'
inium conductor
nominal crosssectional arca Load capacity in A
mm2 25
103
35 50
124
135
'70
1.18
l6t
182
197
95 r20
?18
150 185
281
249 320
240 300
400
48r
500
Table for rating factors
" tt
17'l
lll
118
\27
r5r
:12
112
151
r79
r53
r32 t51
16J
:82
176
r86
218
r9t
t0l
l3r
:1r
::i
t6r
1.10
325
339 388 435
361
494
308
406 446
5?8
363
412
178 421
49r
654 165
4't 5
196
529
873
104
99
1gz
r25
r35
155
I9
119 184
160
::9
r95
r84 222
236 268
2t'3
22r
213
ioJ
i09
252
265
301 141
345
283
389
322
297 335
398 449 520 58?
119 503 573
313
388
421
435 496 552
r,
158 188
4E3
2't0
562
18.15 18.10
18.17 18.18
r8.19
18.20
:54 :85
:8r 3l
332 316
479 543
299 340
308 350
.108
637
40t
408
41€
494
72r
162
53
512 @9
832
455 526
531
61
601
699
949
18.18
18.19
18.20
18.21
18.20
18.17 18.18
36
r-
18.r5 1E.19
Cablc ia 3-phas. oDcratron Load capaciry in d.c. sysrerns
Reference operaring conditions and guide for site operating conditions see Table 18.2.
r60
271
18.15
't8.t7
19
r66
311
297
l6
r8.21
18.20
| 8.20
18.17
t8.t8 l8.l
Load Capacity Installcd in GroundiAir 18.2
18.6 Load capucity.
installed in air' PvC I'
.ttion material
\llss-i
rl shefth
Lcad
Aluminium
Inallon
N(A) N(A)K,\ KBA
N(A)KLEY
prcgnirtcd pirpcr
Jiard
DIN VDE O:5J
rissible con_ortempcfirturt:
s0
XLPE Leud
N(A)YY
N(A)YY
NYKY
N(A)2XY
DIN VDE
DIN VDE
N(.{)YCwY DIN VDE (]:7I
O]72
0265
"c
ngemqnr
t\e .nat
=0.61t kv
L'ol U
r-0 "C
.,I
&
:r
^,,-\| @
\9\:,/\:
o
o
"c
90 ,:I
t-v\e
\:
/n/iL (, A/.n \-7\-r' \, \_7\e \: :./
\,
\119\'
)ss-
.onal areir Loxd cirFrci!y in A
t6
i5
t0
t; _i;
I
i't tl0
t;s
169
203
:ll
t59 :99
;., ;,,
r68
t55 3r2
io:
{3
i9
00
l.l0
ltJ
l0i
li9
166
r99
r68
:00
ti9
251
199
:69
306
36r
l
ll0 tl i 173
JT
.li9
i0+
i
5.1
.ll2
,:.13
415
500
.103
.163
397
1t'9
57i
150 +02
570 654
6i8
.r7.1
533 611
/JJ
912 10:3
893
53
712 628
522 5.r5
594
6r9
o)/
126
134
309
786
lrl ji
S9
l;6 :;l {61
l
61:
i0'l
Jt
60 s0 r06
l
Irr
359 1000
:0
t5
t0
I
27
3.1
2'1
t5
.17
3'7
.ls
51
66
7S
l0i
s9 r13
:06 :61
il.1
)il
i6l
19.l
+l jj
.l-+
51
7l
1)
1i
96
l;l :ll
72
96
l-r0
l0l li9
160
r70
166
r9i
i38
211 305
108 265
159 202
361
.ll2
lr3 .11
6
ll
ll
111
2ll
i6
t53
::3 ;0{
132
.137
i5i
381
3:l
559
J07
438
6.13
+69
_\07
779 902
551
606 697
7.19
1070 t2.16
116
816 933
10r8
131 163
l]]
13r
r63
106
l.r7
t6l
:00
139
:05
li.l
323
231
t5l
ilJ
3'7'7
210
196
308
34r
366 :1:0
395
-136
.ri 6
-t3-l 5.19
590 673
+i6
181
560
657
3r7
563
7J9
940
492
-
57
til
211
t:3
t5
ll
r06
l.l5
1t-6
-ll
:.1
t3
169
t:.1
ll
l2
60 50
I
159
S.5
oo s9
D7
:01
tsl
i36
il
13.5
:i i1 ll
6.i8
ill 364
inium conductor inal cross-
ioru
t'
-
rea
Load capacity in A 39 103
lJl 165
130 157 193
120 488
33
I tJ
136
t.l0
t66
r95
231
I r-6 221
ri8
102
2'7
|
ll0
294
l7l
:0:
190 221
210
119 291 333 384
153
238
lE4
2'1'1
323
390 450
272
116
328 370
361
23r
252
131
Jl+
363
112
3:0
239
320
5i5
3i2
489
.184
5r5
733
194 589
548 627
548
623
428 503
ltt
3i9
613
669
06/
for
666
't'16
18.22
tl 18.24
18.23
18.24
iablc id 3-phas4 opemaion capacily in d.c. syslcms -)ad tlucs up to 2l() mrnr harmonizcd
160
I -.18
23'7
718
)les nq
l7-l
3
343
366 I
9l
1.15
283
201
233 267 310
l]3 113 155
| 5.r
191
33 107 130
157
377
433 523 603
t00
502
460
605
{35
530
699 830
501
642
592
966
749
t8.22 1E.23
18.24
r8.23
548 647
i35 6i5 798
916
18.22
18.24
18.24
18.23
'r f^'.i. r.--.--,.tr for grouping io CENELEC
lerence operating conditions and guide for site operating conditions see Table 18.4"
161
l8
Currcn t-Carrying Capacitl,in Normal Opcration
Table I
18.7 Load capacity. installcd
nsulation matcrial
in ground
uol u =3.616
Mass-impregnated paper
kv
PVC
\,1etal sheath
N(A)KA
Designation
DIN VDE
Standard
N(A)K
L
N(A)YFcY,J N(A)YSY,)
EY
DIN VDE
0255
70
Permissible
0271
"c
conductor temPerature Artansement Copper cortductor
nominal crossiectional area (mm:)
Load cupacity in A
l5 l5
140
,\0
198 :.13
to/
'70
)91
95
175 ?01
t< I
170
1J+
239
162 191
191
)37
l0l
)u+
184 123
t45
120 150 185
371
13'7
438
192
1.10
.+90
i08
561
300 400 500
550
5
7'l
oJl
655 732
6t9 i09
705
t6i
ji2 600
to/
106
;;;
t26
1i9
158 187
::l
]79
130
lo
ll9
16,1
3 t'9
,r00
275 JIJ J)!
5
137
391
.188
,18
7
541
i2:
60'l
56-1
666
603
"12
11A
780
lwttinium cottduct or nominal crosssectional area (mm2)
1.16
-'r
190
r89 t28 166
i6.+ 396
460
rl78
505
518 587
536 605
560 610
,1
Load capacity in A 108
25 35 50 70
103
182
189
95
118 250
-JO
270
221
)51
301
307 343
J+l
385
398 449 520 588
447
388
501
434 495 552
129
156
125
85
149 184
t
185
320
226 256 291 329
240
312
384
300
4t9
400
481
110 150
281
500
503
570
226
:68
)t! 638
283 321
135 160 196
1
5.1
11't
147
178
174 213
18: 220 260
165 297 335
292
243
337
310
Tables for
225 256 286 324
287 116 355
409
425 488
457
509
18.1 5
raung factors
"
three
corc
18.19
tr
single corc
Reference operating conditions and guide for site operating conditions see Table 18.2.
to/
Load Capacity Installcd in Ground/Air
Table
-
18.8 Load clpacity,
Insulation material
18.2
LtnlU=3.616 kY
installcd in arr
ivlass-impregnated paper
Metal she'.lth
N(A)K.\
Designation
-
Standard
DIN VDE
N
(A)K LEY
N(A)YFGY N(A)YSY:'
DIN VDE
0255
70
Permissible
"
O27I
"c
conductor temperature Arrxngement
l' .per conductor nomlnal crosssecrio nal arel 1mm:)
2\
Loud caprLcity in A 5
1ll
I +_)
157
173
ll0
297
t97
222
toJ
-i55 +06 +56
271
Ji
217
3rl
170
i
+lJ
l5
1i9
164
r33
r6l
105
t52
170
t00
t67
196
tJl
l0l
tJo
153 03
I
)0
169
132
20.1
70
212
22'l
257
95
259
!to
173
_t
301
lr0
lt-i
_o+
l:0
i 6.r
+31 491
t0i
_.t,i6
_r49
10.1
565
100
163
-5ll
150 185
240 300 400 500
1t1
305
J++
3
l9.r
:+15
465
.191
570
669
>rl
554 653
654
i63
+/J 5i9
5+5 611
731
900
622
7)3
-122
740
892
1016
308
783
608
6.1
|i9
Alutninium conductor nominal crosssectional area (mm:) 5
Ib)
q5
1ll
i6l
588
127
480
6.15
,13
7
)+/
565
643
109 133
t29
152
158
157
t
8.l
t22
176
t99
t67
t97
23'l
153
249 283
183
205 737 27?
240 278
215
3t7
280 323 365
324
373
JIJ
364
414
283
384
432 494 587
483 539 618
335
520
447 514 619
597
7t7
668
684
290
201
.)
234
150 185
268 308
240
365
300 400 500
5.r
.r06
))J bi)
1tl
97
t17
131
70
Jlo
I
Load capacity in A 89 109
,{
I 7.1
436 485
385 413 529
372
tU)
!') \
723 828
498
Tables for
101
187
246
384 450
135
lo+
1i8
205 210
25r 290
217 318
327
315 444
319 434 )l /
505 587
18.22
rating factors
18.23
"
lltcc
coae lr singlc core
!r
tcapcraturc 'l for grouping Reference operating conditions and guide for site operating conditions for air
see
Table 18.4. 163
lo \-ulrcrlL-\_ilIIy
Table
lg \-<11-,dLrL-\ t i\uIllldr \./l,utdLloIl
18.9 Load capacity.
uolu = 6lt0 kv
installcd in grorrrrrl
lnsulation matcriul Metal sheath N(A)YSEY
Designation
''
N(A)2XSY
N(A)2XSrY
N(A)YHSY,'
Standard
DIN VDE
DIN VDE
0255
O27I
DIN VDE
0273
DIN VDE
0273
Permissible concluctoa temperature
Arraneement
Coppcr conductor nominal crosssectional area
Load c!prcir) in A
mm:
.
:i li
15r 166
1
I7._
]l
195
tt0
70
lt3
169
-t0.
95
ls6
110 150
-il5
161
-1ln .10J
164
JO5
50
:.1()
.19-.-
r8i 155 512 581
140 300 ,100
528 593
:,,
665
56i 62( 61(
7i9
500
,lluninium conductor nominal crosssecttonal arca
Load capacity in A
mml 25
91
l5
110
50 70
r32
130 155
150 178
174
r50
r69
181
165
r90
1r7
211
183
:07
2:0
v)
100
727
259
)49
19
229 259 295
259
291
2't9
:-18
146 173
16l
r20
296
l8l
308
217
i06
125
i6i
316 358
420 468 514 572
116 469 532 599
150 185
240 300 400 500
Tables ratrng factors
190
329
370
343 389
384 433
428
449
50r 566
546
179 610
107 ?37 166 302 350 395 451
3.r3 395
387 464
408 465
490
501
for
rr thrcc core 2' singlc core
Reference operating conditions and guide for site operating conditions see Table 18.2.
164
t6l
151
177
111
19.1
:19
l3F 313 35( 394 .15
_ i
50?
55!
62:-
18.15 '18.1
!'
Load Capacity Installed in Cround/Air 18.2
',c
t8.10
uolu=6lt0kv
Load clpacity, installed in oir'
aoon malen:rl
\lass-imprcgnated papcr
.rl sheath
N(A)KLEY
3natron
N(A)2YSY
N(A)2XSY N(A)2XS2Y
DIN VDE O:7J
DIN VDE O:73
N(A)YHSY:' DIN VDE
DIN VDE O]7I
O]55
nissible con-
lr
temperature
lngemenl
ninal cross-
.!onal
area
Lord capacity in A
t9l r70
:7'l
tl
_r.15
l-ss
lt3
29"1
J31
j
.130
l
ilt
-i
6ll
l5i
'116
+90
811 901
571
)
37
ls6
)
1006
ninium conaluctor
Illinal cros5-
.tional area Load capacity in A
0
lcs
ll3
l17
168
141
l
i5
irt
211
t71
168
2
190
2-s
8
:16
219 249
i00
l-19 28.1
205 231 268
286
394
326
307
334
.169
386
382
536 639 729
522 592
336
365
385
418 196
156
173
178
lr
165
222
:69
:00
:69
:31 162
ll0
l0r
398
1ru
for
5
31'l 3 t-7
3.18 .135
469
513
53.1
652
603 680
'141
838 18.22
ung
Lhtcc
ll3
corc
singlc corc
tmperaturc -t rr ai! grouping
efe:ence operacing coodirions and guide for site opcratrng condtnons
rc!
aadte
id.r. 165
l8
Curren t-Carrying Capacity in Normal Operation
Table l8.l
I
Load capacity. inst:rllcd in groattrl
Insulation material
url
Mass-impregnated paper
X
u:
t2120
kv
LPE
Metal shearh
Standard
N(A)KLEY
N(A)KA
Designation
DIN VDE
N(A)2YSY
DIN VDE
0255
N(A)2XSY N(A)2XS2Y O:73
DIN VDE
0273
90'c
Permissible
conductor temperature Arrangement Copper conductor
rominal crosssectional area lmmr) ,t) 35
50 70 95 110 150
Load capacity in A 123 148
126
r39 166
151
151
r84
118 165
I /O
175
180
196
119
191
108
?:0
221
264
168
:98
10.1
JJO
143
185
380
388
240 300 400 500
140 496 559
t
<:
169
287
i6i i66 1
r8l
179
519
156
511 591
5i9
i78
618
650
661
689
505 563 615
lutniniuttt cotlduct or nominal crosssectional area (mmz)
102
119 155 399
_1S
22.3
liO
273
104
3t5
t?5
i73
368
-10I .107
410 .160
463
,r9 8
196
534
569
556
601
692
674 750
633 686
520
556
189
ia_1
I
.1t0 478
198
156
A
Load capacity in
25
97
35 50
tr7 140
70 95 120 150 185
205 233
:o1 298
240
346
300 400 500
391
448
208 237 267 304 355 403 471 534
,{
r28 152
127
139
151
loo
I
Ol
181
.." I t.t
irt
186
185
203
197
??1
211
231
250
221
240
tJ)
trtJ
252
28.1
250 280
270
_o/
182 3?0
291
198
358
Jl)
):>
365
373 406 450 489
223 185
323 377
425
463
407
491 555
529 588
462 513
JOZ
l5l
196
391
123
421
440 499 567
473
474
521
538
566
579
606
630
Tables for
rating factors
Reference operating conditions and guide for site operating conditions see Table 18.2.
166
327 369
287 320
511
18.15
18.19
-
Load Capacity lnstalled in Ground/Air 18.2
T.rble
uolu=t7l20kv
18.12 Load c:rplcity. installcd in trir Nlass-impregnated paper
lnsulation material
X LPE
Metal sheath
.\luminium
Designation
N(A)KLEY DIN VDE
Standard
0255
N(A)2YSY
N(A)2XSY N(A)2XS2Y
DIN VDE 027]
DIN VDE O]73
Permissible
-
90
"c
conductortemperature Arransement
\
pper condltL'tor nominal cross-
-
sectional area (rnm:)
Load capacity in A 106
109
119
ll6
t):
l+5
165
JU
ll8 l5l
1i8
I
/)
199
70
t9?
196
218
l-19
I5
2-+0
95 120 150
232
li8
16l
ls9
272
l5r
299
i09
:66 i08 i50
10.1
_or+
66
l8l
185
3.+0
152
.101
+i6
i00 3i9 i87
+11
438
240
397
5i6
4,\ 3
.+70
300 400 500
149
171
5.13
608
515
513
552 623
645
510 592
517 627
671
J
733
198
199
I
l9
172
661
lJ+ 161
16.1
193
199
19.1
t91
ti0
li8
,,:;
137
t96
-i.17
58
.+:0
tl9 _t
295 3.10
-]
J3i
198 .166
5.r0
504
)Jl
6ll
5r5
589
627
718
586
665
715
dlJ 904
817
319 921
757
101
1
Ahuniniutn conductor nominal crosssectional area (mm:)
Load capacitv in A
J)
,J
l0l :0 70
123 153
136
2 170
118 155 194
l]6 152 189
tt, 189
179 223
it, 210
ll0
185
207
237
230
271
2t2
239
274
2b:
tb)
3l?
150 185
273
.)
l:.
295 JJ+
299
351
275
.5+2.
400
485
248
sz)
)/J
300 400 500
371 440
5t2
)
503
589
654
5
lll
358
425 484
/)
360 410 483 546
388 495 547
128 378
406
471
.+oJ
535
652
536
604
740
olL
683
838
Tables for
18.22
ratlng factors
18.23
It for
afu
EmFcralurc .r
for groupiog
Reference operating conditions and guide for site operating conditions see Table 18.4.
167
l8
Currcnt-Cqrrying Capacitl in Normal Opcration
Table
uolu:
18.13 Load capacity. installed in ground
8/.30
kv
XLPE
M rss-rmprcgnatcd paper
Insulation material
r
Metal sheath
N(A)KLEY
Desisnation
DIN VDE
Standard
N(A)]YSY
DIN VDE
0255
N(A)2XSY N(A)2xSrY 0273
DIN VDE 90
Permissible conductor temperature
0273
"c
Arrangement
.--opper contluctor
nominal crosssectional area
Load capacity in A
mm'
i
207
112 169 109
li2
11'l
152
35 50
138
i0 9i
16-1
156 187
168
155
1
t0l
18i
196
150
tl9
140
180
l0l
2i1
18.1
:
1tl
:
120
28r
187
il9
1i0
Jlo Jfo
3?4 -10 /
i58
-18
-104
,1t5
'168
501
516 603 612
557
185
.128
210 162
300 400 500 A
luntittiurtt
521
483 ,i
58
otrJ con ducl
,.1
i
627
686
t88
6.1
ll0
-: -1+
l:6
151
257 106
18.1
116
tl9
-i06
_r37
319
341
-j81
i53
t86
+lo
366
135
4i0
503
_t
6,.j
.11
0
-1.19
165
415 468
532
54'l
576
-i03
.r90
463
56-1
546 594
50i
608 684
641
o-1j
541
703
toz
768
697
or
nominal crosssectional area
Load capacity in A
mm:
110
128 182
178
154 19t
163
r80
110 157 195
199
)22
211
lJ)
215
226
238
264
t56
219
r68
256
270
299
290
130 371
1)t
355
366
400
426
161
394
4'19
516
438 476
545
)l-!
614
638
121 145
35 50 70
107 127
110
lol
95
193
163 196
120 150 185
219
252
279
302
240
J..t
287 336
Jlo
J9J 399
308 355
285 319 JOI
300 400 500
366
380 445 504
415 480
448
396
510
541
)b/
)
419
131
368
274
449 498
341 396
Tables for
factors
Reference operaring conciitions and guicie for site operating conditions see Table 18.2 168
527 587
t75
196
ll8
1.,
322
18.1 5
18.19
Load Capacity lnstallcd in Cround'.\ir 18.2
Table
l8.l{
LInlL'= l8/30 kv
Load Capacity. installcd in atl'
lnsulation material
XLPE
N{ass-imprcgnatcd plpcr
ivletal sheath
N(A)K LEY
Designation
DIN VDE
Standard
0255
N(A)2YSY
N(A)]XSY N(A):XS2Y
DIN VDE 027]
DIN VDE 90
Permissible
O]73
"c
conductor lemperature Arrangemcnt
Copper contluctor
-
nominal cross-
*\tional
area
Lord crpucity in A
.l_
_
119
35 _i0
li5
150
I
161
132
16t 100
199
ll2
t"l3
lttS
to-)
100
j.18
1la
199
J++
+00
.)t+
I i.+
i88
+o
+:) .169
640
,<.ll
t6
603
t79
183
l0l
213
95
216
721
-:+o
2'77
120 150 185
246
t< i
?78
188
115 366
313
370
+lJ
i85
437
48.1
199
543
591
610
7
300 400 500
470
512 576
1+tt
ll0
70
240
-\+
ll8 i6l
t17
2
t'9
199 362
il3 .18i
510
507 590
416 469 516 630
161
590
666
71'7
526 572
b/)
823
812 904
929
1011
763
821
t't
r
5-10
615 713
Aluminiunt conductor
nominal crossctional area
Ain'
Load capacity in A 95
35 50
110
v)
140 168
1't2
120 150 185
192 217
224
240
289
9?.
'0
300 400 500
I
lo
115
ll5
r39
177
1i6
Lt)
llo
139
209
249
218 747
-t) I
221 252 289
239 269 303
302
343
384
393 469 538
517 588
198
283
t32
351 377
392
501
450 499
137
iu
232
2 t'0
111
281
rt8
268
JIJ
)!)
378
302
351
365
346 408
.101
418 494
485 577
535 605 ooJ
564
649
180
654 835
Tables for
18.22
rating factors
18.23
'r
for air
tcmpcalurc r, for grouping
Reference operating conditions and guide for site operating conditions see Table 18.4
t69
l8
C
urrcnt-Carrl,ing Capaciti in Nornlal Opcration
Table
18.15 Rating factor.^ for installation in ground (nor applicable to PVC cablcs with {.;n'U:6/10 kV)
Pcrmissible
Cround
con-
alulc
Soil-thcrmal rcsistivity
tcmpcr-
Kn
0.7 Km,W
1.0
Load factor
Load factor
W
1.5 Kmi \V
?.5 KmTW
Load factor
Load factor
ductor tsmper-
aturc
'c
'c
0.50
)
1.24
r0
1.23
l5
1.21
:0
|
90
.19
0.60 0.70 1.11 I .19
1.17 1.15
0.85
0.50 0.60 0.70
1.13
Lt6
1.1 I
l
1.08 1.06
1.l l
1.03
1.09 1.07
1.09 1.07 1.05
r.00
r.05
r.0l
1.01
1.00
1.07 1.05
25
i0 i5 t0 1.!'7
i0 10
1.li
t0
1.13 1.10
li
0.85
0.50 0.60 0.70
0.35
1.00
'.00
l.l8 l.1
1.00
r.07
| .03
1.00
1.05 1.01 1.00
L0l
0.98
0.99 0.96
0.9 5
0.9s 0.95
0.9.1
0.91
0.90 0. s8
0.90 0.ss 0.s7 0.8i 0.3.1 0. s7 0. s6 0. s.1 0.81 0.8l 0.3: 0.30 0.7s
0.78 0.75 0.12 0.68
1.00
0.99
0.83 0.85
l.:3 1.:0 1.14 1.0s t.1l t.t0 1.07 l.l 7 1 .11 1.06 I .10 L07 1.0i t.t9 1.1 5 1 .09 1.0i 1.07 r.05 1.01 t.l7 l.l 3 L07 1.01 1.05 1.0_'i 1.00 1.11
t.0l L00
:5
l0
ti
0.97 0.95
1.0-l
0.9i
0.99 0.98 0.97 0.96 0.97 0.96 0.95 0.93 0.95 0.93 0.92 0.91 0.92 0.91 0.90 0.88
0.89 0. s6
0.99 0.96
0.9 5
0.94
0.9:
0.91
0.93
0.39 0.s6
0.
ti8
0.8 7
0.
s6 0.8.1 0.32
sJ
0.
s-l
0.
s0
.01
0.91
0.9'l 0.97
0.s5
0.
0.95
0.89
0.86 0.84
0.98 0.95 0.91 0.90
1
0.97
0.94 0.91
0.91
0.91 0.91 0.91 0.92 0.90 0.33 0.s9 0.37 0.85 0.31 0.'17
0.7s 0.75
5
I
.t9
Ll:
10
1
.2'1
I
15
r.25
:0
1.18
.19 1.17 I .1.1
r.09
1.rl
l
I
1.03
t.0J
t.00 0.99 0.98 0.97 0.95
1.06
t.
1.08
t.06
t.0l
0.97
1.10
I .0_'l
1.08
1.06
1
1.0r
r.06
l.0l
1
0.99 .00 0.96
0.9.1
1.08
t.0l
1.00
0.91
0.9i 0.38 0.it7
0.9-1
0.89
1.t5
:5
l
i0
.0-l
0.91
0.35
0.85
0.61
0.84 0.81 0.80 0.77
35
1.:3
5
1.21
10
1.:9 114 t.:0
r5
1.26
l0
1.r6
l.1l
1.09
1.09
l.
l.09 1.06
1.02
1.09 r .06
1.06
0.98
r.03
1.03 1.00
r.03
1.00
0.97
1.22
1.18
1.1 I
06 1.04
l.:0
r.1 5
1.08
1.01
l0
0.9
i
0.82 0.79 0.78 0.76 0.7 4 0.72
25
l0 l5
\-
0.68
0.
ti6
0.1). 0.68 0.63 0.59
0.96 0.95
0.91
0.89
0,82
0.38
0.8 5
0,78
0.9 5
0.91 0.90 0.86
0.84 0.82
0.74
0.92
0.37
0.86 0.8.4 0.83 0.It2 0.1{ I 0.79
0.30 0.71
0.73
0.70
0.75
0.12.
0.70
0.9J 0.s9
0..s
l
0.93
0.91
0.90 0.88
0.65
40
20
0.71
0.97 0.94 0.90
35
5 10 15
0.75
t.04 r.00 0.99 0.98 0.96 0.94 0.92 0.85
l
25
60
0.s2 0.7s
0.96 0.9i 0.9l 0.9l 0.E9 0.83 0.93 0.9: 0.9l 0.38 0.s6 0.79 0.90 0.s9 0.s7 0.s5 0.s3 0.76
40 65
0.8 r
0.6-l
JO
70
0.5 ro 1.00
0.60 0.55
1.30 1.28 1.25
l.:8 t.:4 1.26 l.l1
1.1'l
l.:J 1.2r
1.19
t.l
2
1.0,1
t_to
r.09
1.01
r
.l0 l.t5 1.r2
L07
1.12 1.09 1.06
| .09
l 0l
1.09 1.06 1.03 1.00
1.03
1.00
0.9'l 0.92 0.s6 0.85
1.06
0.93
1.05 1.02
0.9'1
0.98 0.95
0.93 0.90
0.88
1.00
0.82
0.99 0.96 0.92 0.89
0.81
0.98 0.96 0.94 0.91 0.91
0.87 0.83 0.19
0.39 0.86 0.82 0.78 0.71
40
0.94 0.92 0.90 0.88 0.87 0.8.1 0.83
0.80
0.19 0.75 0.70
0.76 0.72 0.67
0.8.1
0.80 0.7 6 0.72 0.67
0.62 0.57 0.51
For mass-impregnated cables in line with Section 18.1 for temperatures below 20oC, an increase of load capacity is only permitted under certain conditions in line with the quantities for the permissible temperature rise in Table 18.1 . The radng
170
factor,
must only be used together with factor
f,
in Tables 18.17 to 18.21.
Rating Factor
Table 13.16 Raring
llctor/,
round
Arrxn,.lemcnt
C
a lb
!cmpcrature
lc
Numbcr of
^t^., )ys(ems L 3ores I
I
I
'c )
l
l0
li
t0
ll
for Installation in Cround
for installation in sround (rrrrt applicablc to PVC cablcs with L'oi Li=
6;
18.2
l0 kV)
Soil-thermill rcsistivity
w
0.7 Km W
1.0 Km.
Load fac(or
Lord facror
1.5 Km
Load factor
Load factor
to l.0
0.3 5
1.00 0.50
0.60 0.70
0.35
1.00 0.5
1.17 1.23 1. t6 1.09 1 . 1.+ l.l l r.09 r.0i l.:9 l.t5 t.2l 1.07 1.12 L09 1.06 r.0l 1.17 l.2l l.l8 l.l I 1.0.1 r.09 r .06 1.0i 0.93 | .:.r l.:0 1.15 1.03 l.0l 1.06 1.01 1.00 0.95
1.00 0.99 0.97 0.96 0.9,1 0.93 0.90 0.39
0.98 0.95 0.91
0.96
0.94
0.9: 0.35
0.s7 0.36
0.3'l 0.33 0.30
0.50 0.60
0.70 0.3 5
1.00 0.50
0.60 0.70
l.lt
t.0-:
1.00
J; i5 l0
0.97 0.9l 0.9.1 0.s9
w
1.5 KmTW
0.91
0.39 0.31 0.37 0.8 5 0.7'1 0.38 0.3 6 0.3+ 0.31 0.73 0.9 3
0.90
0.71
0.69
0.3i 0.82 0.30 0.79 0.76 0.7i 0.6-l 0.i5 0.11 0.t0 0.i9 0.51
I
l.tl l.:l
t0
l.:9 l.:6
t0
l.l9 t.:l Ll7
)
-l
ti
.20
I
1.17 1.15 l
1.11
l.l
I
1.08
.1l r.05
r.06 Lll 1.0i l.03
1.03
r.05
l.01
0.96
1.0i
r.0l
0.93
0.91
1.0i
L 0-j
0.9 5
0.97 r.03
0.99
0.99 0.96
0.99
0.96
0.91
0.
1.00
:5 t0
0.91 s3
0.90 0.3l
i
0.9i
0.9-l 0.9 0.92 0.91 0.39 0.90 0.s9 0.s? 0.36 0.36 0.8 5 0.8{ 0.3l
i
0.32 0.79 0.78 0.3
0.90
0.
0.3 7
0.3J 0.1
0.3l
0.31
s3 0.31
0.79
0.30 0.73
0.76
0.7l 0.61
0. ?6
0.7.1
0.71
0.70
0.67
0.68 0. i9 0.61 0.-ij
.15
0.r7
.10
l0
)
6
)
1.16
L:1
l0
l.l.l
r
l.l3
1.1J
t5
t0
l.ll l
.19
l6
r.0s
1.05
l.0l
0.9 7
1.00 r.05 0.96 L02 0.91 0.99
l.0l
0.99
0.9.1
l.l7 Ll0 t.0i
l.t{
1.07
1.11 1.09
1.01
1.0.1
0.96 0.9 r 0.96 0.9,t 0.lt7 0.99
0.96 0.9i
t5
i0
0.s9 0.31 0.36 0.30
0.91 0.39 0.33 0.36 0.3 5 0.9.1
0.90 0.39 0.87 0. s5
0.36 0.3 3
0.3+ 0.76 0.30 0. /-l
0.33
0.31
0.'79
0.7 6
0.31
0.79
0.17
0.75
0.71 0.6.1
0.78 o.'t'1 0.11 o.13
0.75
0.71 0.69
0.70 0.66
0.68 0_53 0.61 0.52 0.53 0.J6
0.3 2
0.71
0.64 0.61
35 .1{)
8
r0
r.l9
5
1.21
t5
1.
t3
t.lo r.
r3
l.l5 l lt
| .07
0.99 1.05
t.0:
0.99 0.9+ 0.89 0.33 0.36
0.35
0.32
0.80 0.72
l.1 l
L04 0.96 r.02 0.99 0.96 0.91 0.85 0.34 0.83 0.31 0.78 0.'t6 0.67 1.09 r.0l 0.9i 0.99 0.96 0.9: 0.37 0.32 0.31 0.79 0.71 0.74 0.12 0.63 1.06 0.98 0.90 0.96 0.9: 0.89 0.3.1 0.78 0.1'l 0.7 5 0.73 0.70 0.67 0.57
:5
0.92
0.39
30
0.35 0.30 0.71 0.73 0.32 0.76 0.70 0.68
35
0.71
0.69 0.66 0.66 0.64 0.61 0.60 0.56
0.61 0.52 0.5 7
5 10 15
0.:9 t.22
1.17
1.19
r.l5 1.10 l.l2 l.07
1.17
:0
r.09
l.l_t
r.05 0.98 L03 1.02
0.99 1.04 0.96
25
t.00 0.91 0.97 0.9.1 0.9.1 0.90 0.E8 0.94 0.90 0.87 0.94 1.00 0.9r 0.91
0.92 0.37 0.86 0.89 0.33 0.32 0.35 0.79 0.78 0.81 0.7 6 0.74
0.90 0.37 0.33 0.73 0.79 0.?3
30
0.71
0.8,1
0.3
i
0.79 0.71 0.75 0.73 0.11 0.81
0.70 0.68 0.66 0.63
35
0.66 0.61
0.56
0.80
0.73 0.69
0.'16
o.'t3 0.65
0.72 0.68
0.69 0.60
0.63 0.58 0.52
0.60
40
0.65 0.54 0_.18
0.5.1
0.48 0.22
Arrangemcnt a
Arrungcment
- :e'"ooo or e*te All
0..15
0.51 0.i3
.10
r0
0.68
0.38
t0 20
t-
0.71 0.71 0.63
@@
Arrangcment c
/:\ /n
/'a\ \, N' \-/
I
lTcm
clearances 7 cm
The rating
factor/, must only
be used together wirh rating
factor, in Tables 18.17 to 18.21.
t7l
l8
C
urrent-Carryrng Capacitl in Normal Opcration
18.17 Rating factor.t for installatiorr in ground. Single-core cables in three-phasc systcm. bunched
Tabte
of
T-vpc
N unrbc
construction
r
0.7 Kmi
w
1.0
0.5
0.6i 1 ro
l8
30 kV
0.7
1.09
1.04
0.99
1.1
0.97 0.88 0.83
0.90 0.80
0.84
I
0.98 0.89
0.7 5
0.69
0.3J
5
0.19
0.71
0.65
6
0.7 6
0.6:
0.80 0.11
8 10
0.12 0.69
0.68 0.64
)
1.5 Km,
0.'l
1
r .05 0.91
1.13 1.00
2.5
Load factor
r.06
0.S.1
0.'t1
0.98 0.89
0.75
0.69
0.8.1
o.i 6
1.05 0.91
0.82
0.79
0.7l
0.6i
0.s0
0.1)
6
0.7 6
0.63
0.61
8
0.12 0.69
0.6.1
0.53
0.6 r
0.,i6
0.11 0.71 0.69
0.69 0.65 0.61
1.09
L03
r.02
0.90
0.t6
0.1'l
0.70
0.92 0.32
0.87 0.76
0.8i
0.94 0.81 0.78
0.7 3
0.66 0.61 0.59
0.81 0.78
0.56
0.70
0.56
0.70
0.73 0.70 0.66 0.63
0.67
0.i9
0.80 0.11 0.73
0.70 0.65 0.62
0.11
t.07
1.01
1.11
1.09
r.0l
l.00
0.s6
L02
0.94
0.87
0.75 0.70
0.90
0.91 0.82 0.17
0.76 0.70
0.92
0.33
0.76
0.s6
0.78
0.71
0.66 0.63 0.59 0.56
0.30 0.71
0.71 0.70 0.65 0.62
0.66
0.s2
0.71
0.67
0.6l
0.78
0.6J
i9
0.7.1
0.56
0.70
0.70 0.66 0.61
0.si
0.7i 0.70
0.
1.01
r.02
0.99
1.0.1
r.05
1.00
1.07
r.06
1.01
1.1 I
0.89 0.79 0.75
0.s4
0.97 0.89 0.84
0.91 0.81
0.s5
0.99
0.
0.90
s6 0.76
1.01
0.7 5
0.91 0.83
0.91
0.76
0.70
0.&5
0.1'l
0.71
0.86
5
0.73
0.71
0.65
0.61
0.71
0.58
0.^12
0.59
0.78 0.73
t0
0.68
0.61
0.5-i
0.69
0.71 0.70 0.65 0.62
0.64
8
0.66 0.63 0.59 0.56
0.81
0.68 0.64
0.11 0.69 0.65 0.62
0.66
0.7 5
0.80 0.77
0.s0
6
0.56
0.70
Mass-impreg4ated
1
0.94
r.00
1.06
0.91
0.85
0.6/l lo 18r30 kV
3
0.8.1
0.8r
0.7 5
0.97 0.90
1.04 0.92 0.82
r.01
0.88
0.99 0.93 0.87 0.84
0.99
2
0.95 0.88 0.79
0.97
cables
0.86 0.76
0.76
0.70
0.85
0.7'l
0.71
0.79 0.76 0.72 0.69
o.'12 0.69
0.6i
0.80
0.63 0.58 0.56
0.'11
0.73 0.70 0.65 0.62
0.69
0.82
0.65
0.71
0.70 0.68 0.64
0.68
0.6 r
0.5 5
5
0.78
6
0.7i
10
Load factor
All
0.8.1 0.7.1
0.62 0.58
0.64 0.61
Load fac(or
0.85
1.0
0.8 5
1.0
0.17 0.73
0.69
0.72 0.69
Load factor
0.94
0.87
0.?
0;t'l
3
0.67 0.62
0.56
0.67 0.62
0.6r 0.55
0.68 0.62
0.11 0.61
0.52 0.50 0.46 0.44
0.58 0.55 0.52 0.49
0.52 0.50 0.46
0.58
0.52
0.56 0.52 0.49
0.50 0.46 0.44
172
0.51
0.49
0.44
1.02 0.67
0.91
0.93 0.83
0.86
0.78
0.11
0.66
0.31
0.63
0.78 0.73 0.70
0.73 0.70 0.66 0.62
0.61 0.64
0. -i9
0.56
Load factor
0.52 0.50 0.46 0.44
0.87
0.7'l
8 10
r.08
r.01
0.59 0.56
0.93
0.71 0.61
0.58 0.55
r.l5
0.87
0.87
0.'71
5
0.64 0.60 0.57
0.94 0.78 0.68 0.63
0.93
0.56
l.0l 0.87
0.70 0.66 0.63
1.0
I
i9
0.57
0.7'l
0.85
2
0.
0.83 0.78
1.0
of
l
1.08 0.93
0.85
construclron
types
0.59 0.57
Lt0
0.9-l 0.86 0.82
0.69
0.6J
1.00
I
0.7.1
0.71
0.8 5
2 3
PVC cables 0.6/1 to 6 10 kV
0.7
1.1'l
0.61
0.99
0.6
1.01
0.66
r.02
0.5
0.86
0.69 0.65 0.61
0.90 0.80
0.7
1.07
o.'72
1.01
0,6
Km/w
0.91 0.82
0.70
5
10
r.00
0.'t 6
0.9 5
0.88 0.81
0.5
0.82
0.61
0.69
0.'l
0.8 5 0.7 5
0.i8 0.i6
0.7 2
w
Load factor
0.6
0.5
I
I
i0 kv
0.6
2 3
PE cables 6/10 ro 18
Km/W
Load factor
Load factor
XLPE cables
/cm
Soil-thcrmal resisli\ it]-
of systcms
--
0.52 0.49
0.?r 0.61
0.56
0.7'l
0.76
0.59
0.56
Ratine Factor
/. tbr lnstallation in Ground lli.2
Table 18.18 Rating llctor/. for installation in ground. Sinsle-core cables in three-phase s1-stem. bunched T;"pe
of
Numbcr systems
Soil-thcrmal rcsisnritv 0.7 KmlW
1.0
Load factor
Load factor
0.5
XLPE cables
!o i3ij0 kV
PE cables
i-
PVC cables
I to 6i 10 kv
Loird factor
0.7
0.5
0.6
0.7
0.5
0.6
0.7
1.09 0.98
0.91
1.0.+
1.05
1.00
l.l
3
t.0'1
l.0l
| .17
0.9.1
0.99 0.39
l.tI
.01
r.02
0.9i
t.0.1
l.06
0.9,1 0.91
0.37
0.31
0.9
0.3s
0.97
0.3:
0.31
0.73
0.91
0.
0.79
0.99 0.95
0.90
0.31
0.97 0.39 0.s5
0.90
.l
0.39 0.31 0.73
0.36
0.;9
5
0.33
0.39
0.s
0.75
0.90
0.91
0.3i
0.:6
0.1?
0.3 7
0.7 3
0.
0.;0
0.
0.70
0.s5
0.31
0.7-l
0.63
i.l
0.63
0.31
0.7
0.18 0.76
0.:l
t0
0.39 0.8fi 0.31
0.tl
0.s.1
0.71 0.70 0.68
0.s I
3
0.19 0.76
0.32 0.30 0.11
0.7 5
0.36
0.30 0.79 0.76
0.7J
6
0.99 0.89 0.s l 0.73
l
l
1.01
1.0?
0.97
0.91
5
s-l 0.31
0.
s.l 1
0.91
s8
i
r.0l
0.69
1.06
1.0i
l. t0
|.01
r.0l
0.97
r.01 0.90
t.09
0.39
L0l
l.li
0.9
i
1.00
r.00
t.06
0.93
0.91
0.9
0.3.1
5
0.3s
0.3l
0.97
0.
s9
0.sl
0.99
0.91
0.s.1
0.r3
0.9i
0.3 5
0.79
0.9 5
0.90 0.s6
0.39 0.37
0.sr
0.;5
0.75
0.91
0.3
i
0.;6
0.89 0.36
0.3 |
0.:.1
0.3 5
0.s0 0.7'l
0.7i
0.3.1
0.7l 0.;0
0.90 0.33
0.32
0.;9 0.;6
0.tI
0.63
0.32
0.71
0.68
0.31
0.75
0.73 0.7 6
0.99 0.39
1.0.1
r.05
I.00
1.07
t.06
1.01
l.t1
r.03
l.0l
0.96 0.33
0.90
r.0.1
0.91
1.06
0.98
0.91
0.3l
1.00 0.9?
0.3:
0.El
0.98 0.95
0.90 0.37
0.sJ
0.76 0.74 0.7 | 0.69
0.91
0.83
0.17
0.89 0.36 0.8+
0.31
0.i5
0.78 0.76
0.12 0.70
3
0.91
0.37
-l
0.9t
0.3.1
5
0.33 0.36
3
0.
si
0.30 0.79 0.76
0.7J
6
0.31
0.7.1
0.7: 0.;0
0.70 0.63
0.sl
0.:9
0.69
l.0l
1.02
0.97 0.94 0.9r
0.95 0.33
0.31
0.
r3
0.92
0.s5
0.79
0.97 0.93
0.91 0.39 0. s6
0.38 0.36
0.81
0.7 5
0.16
0.90
0.32
0.7.1
0.83
0.3.1
0_17
0.71
0.32
0.8:
0.75
0.69
0.38 0.35 0.83
0.81 0.73
r0
0.73 0.70 0.69
0.30
8
0.79 0.76 0.15
0.39 0.37
0.82
6
I 2
0.9,1
0.95
0.99
r.00
l.06
1.0.1
t.0l
1
.15
t.03
r.02
0.91
0.9i
0.9.1
0.39
r.00
r.05
0.91
0.91
0.37
0.3l
0.95
0.96 0.33
0.39
:l
0.91 0.33 0.30 0.76
0.99
0.90 0.37 0.36
0.3r
0.83
0.77
0.91
0.33
0.77
0.97 0.92
0.39
0.39
0.90 0.32 0.73
0.79 0.71 0.71
0.73
0.86 0.34
0.79
0.73 0.7 r
0.39 0.86
0.11
0.79
0.71
0.68 0.65
0.30 0.78 0.7 4 0.'12
0.7 r
0.81
0.37 0.35 0.82 0.80
0.73
0.i7
0.68 0.66
0.33 0.31
0.31 0.73 0.75 0.73
I 2
5
kV
0.6
Load fJctor
1
3
'les tre 1 ro 18i30
0.5
2.5 KrnTW
L09
4
Mass-impreenated
0.7
I.5 KmTW
l
1
ro 13,30 kV
0.6
Km W
2
r0
0.6i
I
oI
construction
0.611
25cm
3
5
0.84
6
0.8 3
8 10
0.30 0.78
0.36 0.32
0.71
0.71
0.67 0.65
Load lactor
Load factor
Load lactor
0.85
1.0
0.85
l_0
0.85
1.0
0.85
1.0
0.37 0.75 0.67
0.94 0.82
0.94 0.83 0.14
0.87
0."14
0.87 0.75 0.67
0.64
0.70
0.64
0.71
0.&
0.60 0.59 0.56 0.54
0.67 0.65 0.62
0.60 0.59 0.56
0.67 0.65 0.62
0.60 0.59 0.56
0.61
0.54
0.61
0.54
I
constructiou
0.93 0.32
0.87
0.93
2
0.15
3
0.74
0.67 o.64
0.82 o.74 0.70
0.70 5 8
10
0.3.1
Load factor
Alle typcs of
o
0.76
0-79
0.67 0.65 0.62 0.60
0.60 0.59 0.56
0.54
o.67 0.65 0.62 0.60
0.30
0.7.1
0.72 0.68 0.66
u.t) o.67
tt)
18 Currcnt-Carrying Capacrty in Normal Opcration
oooooo Table
18.19 Rating factor/r for installation in eround.
--?g' All Clcaranccs 7 cm
Single-core cables in three-phase systems side by side Type of
Number of Soil-(hermal rcsisti\it!
con5truction
s,vstcms
0.7
Km/w
1.0
XLPE cables 0.6/ 1 to 18130 kv
0.7
0.6
0.1
0.5
1.01
1.00 0.87
I .18
0.94 0.85 0.80
1.05
0.'17
0.9i
0.73
0.90 0.87 0.34
1.08
r.05
0.99
1.01
0.9 3
0.86
r.03
0.92
0.34 0.80
0.i1
0.93
0.73
0.89
0.76 0.71 0.69
0.69 0.67 0.64 0.61
0.3
t0
0.84 0.82 0.79 0.7'l
1.04 0.98 0.93 0.89
5
8
0.7l
i
0.71 0.75
0.70
0.80
0.7 |
0.81
0.73
0.69
0.6i 0.6i
1.01
r.00
l.l
0.9.1
r.02
0.85
0.37 0.71
0.s0
0.7l
0.87
0.78
0.t1
0.68 0.65
0.3i
0.16
0.3
r
0.7 2
0.69 0.65
0.6.1
0.i9
0.70
0.6i
0.3i
0.1'l
0.33 0.30 0.73
0.7 5
0.91
0.8l
0
0.70
0.s6
o.'t'l
0.r0
0.
s7
0.s.1
0.7 5
0.6s
0.3
i
0.78 0.76
0.7
0.68 0.65 0.63
0.8 r
0.7l
0.7:
0.6i
0.70
0.65 0.63
0.31
0.78
0.79
0.70
0.61
1.01
1.00
t.07
r
.05
1.01
1.01
0.3 7
1.00
0.9 5
0.97
0.85
0.78
0.8 r
0.11
0.95 0.90
0.86 0.82
0.88 0.19 0.74
1.16 1.05
Lt0
0.94
0.96 0.91
0.8 7 0.8 2
0.39 0.79 0.75
0.85
0.11
0.?0
0.87
0.87
0.7 5
0.84
0.19 0.76
0.70
0.69 0.65 0.63
0.8
0, ?8
0.68 0.65 0.63
0.78 0.76 0.72 0.70
0.71
0.83 0.80
0.95 0.E6
1.00 0.95
1.00 0.8?
1.09
1.06
0.1'l
0.95
0.96
0.73
0.90 0.88
0.78
0.80
0.7,1
0.9r
0.95 0.86 0.82
r.01 0.88 0.19
1.
1.01
0.84
1.00 0.93 0.85 0.81
0.7.1
0.91
0.8 2
o.71
0.70
0.86 0.83
0.78 0.77
0.71
0.68 0.65 0.63
0.87 0.85
0.7 r
0.'l4
0.80
0.71 0.75 0.'12
0.70
0.81
0.78
0.70
0.87 0.85 0.82 0.79
0.96 0.91 0.88 0.86
0.9'l
0.98
1.01
0.89 0.84 0.80
0.
s6
0.96
0. t'7
0.91
0.7i
0.89
0.16 o.74
0.;0
8
0.84 0.82 0.19
t0
0.'l'l
0.69
0.68 0.65 0.63
Mass.impregnated
I
cables
2
0.94 0.89
0.6/1 to 18/30 kV
3
0.93 0.89 0.86 0.84
5
6 8 10
0.7 t
0.69
0.t3
0.71
0.69
0.7 2
0.68
0.65 0.63
I
0.81
0.19
0.3 r
0.79
0.78 0.16 0.?3 0.70
0.69 0.66 0.64
i
i3
0.81
0.
0.79
0.7
t9
1.05
|
0.19 0.76
0.71
0.73 0.71
0.85
1.0
0.85
1.0
0.85
1.0
0.85
1.0
1
0.91
0.85
0.93
0.85
0.71
0.71
0.'19
0.71
0.62
0.69
0.65
0.58
0.65
0.62 0.58
0.92 0.78 0.69 0.65
0.85
0.77 0.69
0.92 0.78
0.85
2 3
o.62 0.58
0.69 0.65
0.62 0.58
5
0.61
0.62 0.50
0.55 0.53
0.57 0.55
0.51
0.62 0.60 0.57 0.55
0.55
0.59 0.57 0.55
0.55 0.53
0.6 r
6
l0
0.51
0.49
0.55
0.49
0.49
0.69 0.66 0.61
r.03
Load factor
0.55 0.53 0.51
0.'71
0.89 0.79 0.75
Load factor
0.60 0.57
r
0.69
.10
r
Load factor
0.11
7._
0.91 0.87 0.81
Load fac(or
8
174
0.,'-0
0.7.1
0.61
constnrction
0.78 0.75 0.71 0.70
r
0.61
AII typcs of
0.8:
0.8
0.69
5
0.91
0.90
0.71
6
0.7-l
0.9 5
0.69 0.67
3
0.96
0.81
1.01
0.76 0.71
I
0.86
0.38 0.79 0.?1
0.s8 0.70
0.84 0.81 0.79 0.77
l
1.03
0.96 0.36
t.r1
0.34 0.30
PVC cablcs 0.6/1 ro 6, 10 kV
l.1l
r.06
0.96 0.86
0.89 0. s7
6
Ll9
1.06 0.96
3
t0
1.01
0.88 0.78
1.19
0.s6 0.77
6
1.09 0.9 5
0.6
s7 0.73
0.99
0_92
5
0.5
1.01
0.93
0.9 3
.1
0.78
0.'l
0.7
0.
0.98
to 13,30 kV
0.68
Load lactor
1.0'l 0.95 0.86
I
6110
1.5 KmlW
0.6
0.81
2
PE cables
w
Load factor
0.5
1
6
I
0.6
2
0.8 8
1.5 Kmi
Load factor
Load factor 0.5
Km/w
0.53 0.51
0.49
0.6. 0.6.+
-Ratinrr Factor
Table
L for
lnstallation in Ground 18.2
18,20 Rating factor/r lbr installation in -sround.
Type
Numbe r
of construction
oI cables
0.6i
I and 6110 kV
PE cirbles I
PVC cubles r' 0.6i
I and 3.616 kv
Mass-impregnated cables: ted cables
U{l;3.6i6kv . caoles
3.6i6; 6i 10 kv
0.7 Km,W
1.0
Load lactor
Load factor
types
of
3 phasc
0.7
0.5
r.06
l.0t
t.tI
1.07
0.92
1.01
0.94
0.
0.31
0.86 0.71 0.7 r
0.92 0.36
0.8.r 0.73
0.i1
0.73
0.31
0.7 3
0.7l
0.67
i
0.70 0.66
0.79 0.11
0.71
0.6i
0.61
0.71
0.66 0.61
0.60
0.70
0.61 0.6.r 0.60 0.57
0.31
0.73
0.7
0.5 1 .09 0.99 0.90 0.85
1.03
0.99
1.06
1.0i
r.00
0.3J
0.98 0.39
0.9r
0.35
0.s1
0.7 5
0.3.1
0.;6
0.70
0.7:
0.66 0.63
0.6
0.6
0.7 1.02 s7
+
0.3l
5
0.73
0.71
0.6
6
0.7i
0.68
8
0.71
0.6.1
0.6i 0.i9
0.30 0.77 0.71
l0
0.63
0.61
0.56
0.69
I 2
0.99
r.00
0.99 0.3+
l.0l
r.0l
r.00
1.08
:.06
1.01
1.03
l.0l
0.91
0.96
0.91
0.3 5
0.92
0.36
l.0l
0.9.1
0.3 7
0.7.1
0.39
0.3 r
0.7 5
0.33
0.1'l
0.9:
0.31
0.i'7
0.69
0.3J
0.;6
0.t0
0.99 0.90 0.35
0. /-3
0.71
0.36
0.73
0.
0.65 0.63
0.80
0.l:
0.66
0.31
0_61
0.3:
0. ?.1
0.67
0.7'l
0.6-l
0.73
0.i9
0.7
i
0.71
0.71 0.69
0.71
0.66
0.6,i 0.60
0.61
0.56
0.70
0.63
0.61 0.60 0.57
0.79
0.i9
0.69 0.65
0.71 0.70 0.66
0.71
0.6i
0.-i7
0.97
1.00
l 0+ 0.97
r.0l
1.01
t.tJ
1.07
1.0:
0.36
0.93
1.01
0.76
0.91
0.El
0.94 0.34
0.71
0.36
0.7s
0.87 0.77 0.72
0.38 0.73 0.71
l
0.
s6
0.71 0.69 5
3
0.3 5
4
0.8:
0.39 0.30 0.75
j
0.78
0.7 r
6
0.7 5
3 10
0.71
0.63 0.6.r
0.63
0.61
0.-<6
I 2
0.91
0.92 0.87 0.30 0.76
0.9.1 0.3 5
4
0.36 0.32 0.30
5
0.78
6 8
0.'t 6
l
10
0.12 0.69
0.69 0.65 0.61
i9
0.56
0.7
0.7i 0.70
0.3.1
0.90 0.31 0.11
0.'t2
0.66
0.31
0.73
0.67
0.31
0.71
0.69 0.65 0.62
0.6{
0.77 0.73
0.70 0.66
0.6.1
0.73
0.7 |
0.68 0.65
0.60
0.74
0.67
0.61
0.70
0.63
0.5 7
0.71
0.6.+
0.53
0.95 0.89
1.00 0.39 0.35
1.00 0.92 0.31 0.73
0.59 0.57
0.92 0.37
0.19
0.32 0.79 0.75 0.7 r
0.75
0.72 0.67 0.64
/
i:
0.68 0.65 0.61
0.i3
1.06
1.05
l.0l
I.07
1.02
1.01
0.94
0.38
0.12
0.36
0.93 0.31 0.19
0.87
0.7'7
0.99 0.9r
0.73 0.73
0.92 0.37
0.35 0.E0
0.79 0.71
0.63 0.65
0.76
0.69
0.6'l
0.61
0.30 0.75
0.73 0.68
0.66 0.62
0.71
0.64
0.58
0.69 0.66 0.62 0.59
0.83
0.74
0.82 0.19 0.75 0.72
0.75
0.7 |
0.72
u.o)
0.59
0.89
I
3
0.84 0.82
0.31
0.97 0.35 0.76
0.'t'l
0.71
5
0.30
0.67 0.65
0.7.r
0.1'7
0.79
8
0.73 0.70
0.73 0.70 0.66 0.63
0.E1
6
0.61
0.53
0.94
0.12 0.68 0.65
Load factor
Load factor
Load factor
Load facror
0-85
1.0
0.85
1.0
0.85
1.0
0.85
1.0
0.94 0.71 0.68
0.89 o.72 o.62 0.57
0.94 0.78
0.89
0.94
0.89
0.72 0.62 0.57
0.78 0.69 0.63
0.'72
0.95 o.79
0.62 0.57
0.69 0.64
0.89 0.72 0.62 0.57
0.53 0.51
0.59 0.56 0.52 0.50
0.53 0.51
0.59 0.57 0.52
0.53
0.60
0.51
0.47
0.57 0.53
0.50
0.44
0.50
o.47 0.44
u._
1.00
0.94
0.59 0.56 0.52 0.49
0.;:
0.86
1
0.68 0.63
.]'' 1;.j i_.r.3bl:s ,).6/1 k./ ri! : J or qu:rouues aiso rppry for singleiorc cabla fo! 0.6/ t kV
srstsn: .he:e :,,anrilie5
0.
0.97 0.91 0.E6
2
2
Lnc
0.6
Load facror
0.39 0.80 0.75
5 o 8 10
Io d.c. systehs
0.5
1.02
0.63
tr [u
7cn
2.5 Km,W
Km,W
Load factor
0.9 5
3
''
0.7
1.5
1
I
construction:)
0.6
Krn.W
2
t0
All
I
Soil-thermal resisti\ it)'
0.5
XLPE cables:)
\-/
v
Three-corc rr cablcs in three-phase s!stems
5
0.47 0.44
0.53 0.51
0.47 0.44
ccDductcil
175
l8
Cu
Table
rrcnt-Cerrying Capacity in Normal Opcration
A /\ !. t, t. .,
18.21 Rating factort for installation in ground.
7cm
Three-core cables in three-phase systems Tl pe of
Number
con5trucl,on
of cables
PVC cables 0.6/1 kV PVC cablcs 6/10 kV Mass-imprcgnated-
D
H-cables 6/10 to
Km W
0.7 KmlW
1.0
Load factor
Load factor
0.6
0.7
0.5
0.6
I
0.90
0.91
2
0.85 0.80 0.77
0.85
0.79
0.93 0.85 0.78
0.99 0.92 0.36
0.71
0.14
0.98 0.93 0.87 0.35
0.70 0.67 0.63 0.60
0.84
5
0.75
0.75
kV and
6
0.71
0.'t3
Mass-impreganated S.L. cables
3
0_73
0.69
l0
0.71
0.66
18730
I
Soil-thermal resislivit!
0.5
belted cables 6/10 kV
0.7
1.5 Km,W
2.5
Load factor
Load factor
0.5
0.6
0.7
1.04 0.95
0.90
1.01
0.86 0.82
0.80 0.75
0.95 0.90
0.71
0.36 0.81 0.73 0.75
1.00
1.05
0.89 0.80 0.75
0.98 0.93 0.89
0.71
0.8 5 0.8 2
0.i7
0.68
0.11
0.71 0.71 0.70
0.6.1
0.77
0.14
0.67
0.61
0.74
0.70 0.67
0.81
0.81
Km;W
0.5
0.6
1.01
0.63 0.6.1
0.61
1.09 0.96 0.87 0.32
Load facror
0.8 5
1.0
0.8
i
1.0
0.s5
1.0
0.s
0.91
0.61
0.97 0.32 0.73 0.68
I
0.96
0.91
0.96
0.91
0.97
0.91
constfuction
2
0.31
0.3:
0.76 0.66
0.8:
0.76 0.66
4
0.12 0.61
0.76 0.66
l
0.61
5
0.63
0.57
6
0.60
0.55
8
0.56 0.51
0.51
0.61 0.60 0.56
0.,18
0.54
10
'r Tuo- and lhrec{ore PVC cabics for L'o,U=0.6t1kV in singlc-phasc
.l
/o
0.71 0.67
1.0
0.76 0.66
0.61
0.73 0.68
0.i7
0.63
0.
i7
0.64
0.55
0.61
0.55
0.61
0.5? 0.55
0.51
0.i 7 0.54
0.51
0.57
0.51
0.r3
0.48
0.,s4
0.48
a.c. and in d.c. slstcms
0.76
0.6.1 0.61
0.67
Load lactor
All t)pes of
0.81
0.11
Load faclor
i
1.04
0.90
0.7:
kv Load factor
0.7
0.78 0.75
12r20 and
13j30
,,-n (. .,
0.61
0.69
Rating Factors for Differing Air Temperrturcs 18.2 Tabelle 18.22
Rxting facrors T1-pe
/;
of
construction
for differing
temperatures
Pcrmissible
Pcrmissible
Arr temperatuae
conductor
temperature
tempcrature
rise K
ro"c I 15.c l:0"c l?s"c
'c XLPE cables
lir
ljo.c ll5.c l10"c I rs.c
l_.0"c
Ratins factor
90
l.t5
1.1:
1.03
1.04
1.0
0.96
0.91
0.3 7
0.32
70
r.tl
Ll;
l.l2
1.06
t.0
0.9.1
0.37
0.19
0.71
0.31 0.76
D.65
PE- and
PvC cables I{ass-rmpregnated cable5
Belted cablcs 'r.6,1 to 1.6,6 kV
,
r0
kv
Singlc-core. S.L. and H-cables \0.6i I ro 3.6,6 kV
.,10 kv
-.:,:0 kv 13,30
kv
80
))
r.05
r.0i
r.05
1.0_i
65
1.0
0.95
0.39
.15
1.0
1.0
1.0
1.0
1.0
0.93
0.3 5
80
l)
1.0-i
1.0i
1.0
r.06 t.0
r.05 r.06
o.i9
0.;l
1.0
l0
r.0
|.0
t.0 t.0
0.89 0.37
0. t''l
r.06
0.95 0.91
0.31
l5
1.05 1.06 1.0
0.35
t.0
0.76
0.5i
1.0
1.0
1.0
0.93 0.91
0.3l
0.71
0.-r s
'70
65 60
0.;7
171
l8
C
urrcn t-Carryi4g Capacrtf in Nornral Opcration
Table
t
8.23 Rating factors.[1 for
groups in air
'
).
Singie-core cabies in three-phase syslems
Arrangement
of cables
Numbcr of cablc fays or cable racks
Inst allation irt huncltcs
Inst allcd in one planc
:
distance from wall > 2 cm
Clcarancc = 2rl distance from wall > 2 cm
Number of systems
Number of systems
Clcarance
)
I
cable diamctcr r/
l
On the
fioor
)
I
.zcrn d d t^ ^ ^ ^ ^ ^ L!Z--9--2-t:--Sl-Sl-
3
22ctn 0.9 5
0.90
0.
0.9l 0.89 0.88
0.95
0.90
0.88
0.90
0.8 5
0.83
0.91
0.39
0.88
1
r.r 6\ loa 3n
22.!t1 2d
0 87
0.84
0.83
0.8.1
0 81
0.81
0.88
0.8 3
0.E1
o
0.8l 0.80 0.79
0.s6
0.s1
0.19
1
r
1.00
0.98
0.96
-:91
,l
I
On cable
racks
.00
0.97
0.96
)
0.91
0.94
0.93
I .00
0.95
0.93
l
0.96
0.93
0.92
1
.00
0.94
0.92
6
0.94
0.91
0.90
1
.00
0.91
0.90
l6ir ni
0.89
(9_!L
zd
,a
rfi! sl
1 "|&__e__e-Ei IAA-o.
_,r*?_ _r1,9J
'lo
.ltrJ
.11
0.91
_2d
6a)
lra 6\ lnii rlai
:2-, 1Lr 0.94
rn
*it\ -+r /:vl ;r
F:rl_
On supporls or on the wall
r:\
6ri
20
lcr /i r---T
tra\s 1
Zd
I
s8
On cable
2d
0.89
0.86
sr
0.84
^l
:1
I r:\
,EO
Arrangement for which a reduction is not required r)
ln installations in one plane $'ith increased clearance the increased sheath or screen losses counteract the otherwise reduced temperature rise. Therefore indications as to reduction-free arranqements cannot be made here.
t'
-ll;
=2cm
.4d
2d
^r-l;l-
,€o____@____ap,:
1,rt
r.r
r.r €l 1@____@____mdr
):L !l-!}\: :/_ _ _-\:1r:, __ __sagJ 4
Io cotrfined spaccs cr \{hcrc much grouoing occurs the iosscJ of thc cabies increasc the aia tcmp€raLure snd thtrcforc addiaional raling fictors for diffcriog air lcmprrarures tiom Tablc lE-:: mus! bc applicd
178
Rating Factors for Croups in
Table
Air
18.2
18.2{ Rating factors/11 for groups in air "'
cubles in d.c. sy"stcms
\lulti-core cables and single-core Arrrnge-
-vumbcr
menl
ol
of cables
cable
cables
I
Side by side rvithout clcarancc
Clcilrlnce: cable diamcter r/ distance from rvcll > 2 cm
lnd touching wall
rll-s
or
Number of
Number of
cable mck5
cables
caoles
l
I
l
6
6
9
On the
IIoor 0.9 5
0.90 0.s3 0.3
0.9i
0.90
5
lr.v\,n N-^.U-Z-
0.90 0.3:1 0.30 0.75 0.71
0.31
{' On
:ry I
0. s3
0.35 0.3-l
0.9-i
0.sl
0.80
0.9 5
0.30 0.16 0.7l 0.69
0.90 0.s5 0.31 0.31
0.30 0.75 0_73
!1-w.v\-rv:v--v:
F
Ri
-?\.:rs-?\.:s-:N.:s.:r-1rl
I
J
0.3s 0.3l 0.s
6
0.36 0.31 0.;9 0.7'1 0.76
r
0.f-i 0.7s 0.71
0.79 0.78
0.70
0.63 {
On cable
r.00 0.98 0.96 0.91 0.92
racks
) 3
6
1.00 0.95 0.93 0.90 0.39
L00
0.9.1 0.91
0.39 0.88
1.00 0.93 0.90 0.87 0.86
dd :Jy ,ti I ,liA cr i3l
r; i:-^-i
-i
He_rsr_\.2._J
0.76 0.72 0.68 0.66
-
0.95 0.8.1 0.s0 0.75 0_71
0.90 0.87 0.86
26; |--l 6-\
Yry.rv.'v.vn,?vi',7n
i
4
0.95 0.7s 0.74 0.70 0.68
F-&S:-\JSA2. :)
-- - J
0.95 0.76 0.7l 0.68 0.66
,l^ :|)K 0,95 0.78 0.7.1 0.68 0.66
:tx 'l2i
:)
.r"
.l\-t Arrangemcnt for which a reduction is not requircd r)
f**
0.30 0.76 0.71 0.69
]'(1 i 1.00 0.91
*g
l-,'v.vrv-..vrr.rvrvryi k
0.9 5
-.l:sr
supports or on the
.,all
0.9 5
Number ofcables
Number of cables
arrang€d abo$e each other is nol .estricted
arranged side by side is not restricted
>2cm
T. -r-E+Yr---v'---Fr--.=l. .22d
d
fe---e---e--51 +a__-@---@--.
::-.rna:idspaccs.:?hcr.nuchgroupingoccuGlhe:osscsofthEc.tblca:ncrcas.lhcairrcmpemturclodlhereforcddirional olllenog air tcmpcrarurcs faor! Iublc 18.22 musr bc applied
r3dDg fac(o6 for
179
l8
Current-Carrying Capacity in Norn:al Operation
Table 18.25 Rating factorsr), multi-core cables with conductor cross-sectional area of 1.5 to l0 mm2. Installation in eround or in air
18.2.4 Use of Tables
If the transmitted power is knorvn the operalinq current
1b
(loading) can be calculated using the equations
from Table 18.26 where Uo is the operating voltage Number of Ioaded
lnstalled in
of the network and cos
the oower factor.
co
cores
Air 5
7 10
t9 1A
0.70 0.60 0.50
0.75 0.65 0.55
0.45
0.50
0.40 0.35
0..15
0..10
0.30
0.35
0.25
0.i0
5'Thcse facrors arc to bc applied to ratings in Tablc 18.5. multi-corc cables in rhc ground and to ratings in Tablc 18.6. multicore cabl€s in air. bolh in 3-phasc operation
Table 18.25 Equations for the calculation of operating current /o from the transmitted power Type of
Apparen t
Active
Network
Power S
Power P
P II
Direct current
s tl
Single-phase a.c.
Reactive Power Q var
P
a
U" cos,/
Uo sin
r
s Three phase
I
V3un
g
=o-
J L hsln
q4
From the 24 hour day load diagram and as referred to in Sections 18.1 and 18.2.3 the maximum load is also the operating current /0. Where the installation is to be in ground the 24 hour load diagram is to be used to determine the load factor nr. Where the installation is to be in air this is not required.
\/ Example
l8.l
. In a three-phase network with Ub= l0 kV an apparent power of l0 MVA is to be transmitted. The operating current /b is determined from f-
s
10
x
106
vA
V)vt fxl0x103V
=
577
A.
From the 24 hour load diagram (Fig. 18.6) with the maximum load equal to operating current I6-- 577 A, the average load is first calculated. This is done by taking the area below the load curve plotted from current and time values and calculating an average value over the 24 hour period: 180
Calculation of Load CapacitY 18.3
+h
-100
-\ + 160 A
+-l
h
260A+577A
577
A+400 A
l
.100
+-+ h
A +450 A
450
A+300 A = +01 .{.
From this the load lactor becomes ,' =
9= J/l
o
O.t.
The load capacity of two cables
NA2XSzY
3
x
185
SE/25 6i l0 kV
Load
is required to be determined when installed in ducts under the following operating conditions:
577
500
Load factor m= 1.0 Soil-thermal resistivity
400 300
Ground temperature
Qs
9E
:
=
1.5
Km/W.
30 oC.
-10
The rating factors for these conditions: r00
4
12
8
16
20
Hours 24
Time-=_
Schematic daily load diagram
Fig. 18.6
The load capacity per cable becomes
o
The calculated operlring current /o:577 A rvith the load factor nr:0.7 is to be transmitted using XLPE cables type
NA2XS2Y
3
x .../...
6110
KmAV and nr:0.7, the rating factor r.om Table 18.15:/, = 1.6, rating factor from Ta_.'lr 2 cables, the group -
t
1g.20,
1.0
f.:0.85.
In order ,o rnut. a direct comparison with the tabur"ted currents I. the calculation is made with a Iicti.-.rus value of operating current /br. With N:2 parallel connected cables
'br
(where tors).
- .,\i n/ fI/
Jt/ 2x1.0x0.85
fac-
From Part 2, Table 5.6.5 two cables with A.luminium conductors and a cross-sectional area of 185 mm2 will be adequate. The load capacity for one cable is:
x
1.0 x
,= I ,nJ'=
1.17 x 0.8
I x 0.72 x 0.3 5:
172 A.
0.85-
295 A.
18.3 Calculation of Load Capacity
A cable is heated by
losses generated by current in the conductors and, when on a,c., by losses generated
in the metal coverings as well as by dielectric losses in the insulation. The dielectric losses can be ignored, however, in PVC cables up to Uo/[.r = 3.5i6 kv, in mass-impregnated cables up to Uolu = 18i30 kV and in cables with PE or XLPE insulation up to U olU = 6ai 1 10 kV. Under steady-state conditions the dissipated heat is equal to the sum of all losses in the cable. Heat losses are conducted to the surface of a cable and thence, when a cable is in air, transmitted to the ambient by convection and radiation (Sec-
= 339 A per cable
is the product of all relevant rating
I.: I,ttf:347
I
kv
under the specified operating conditions in Table 18.2. From Part 2, Table 5.6:5 it is found that the largest cross-sectional area is not sufficient to carry 577 A: therefore 2 cables in parallel are required:
For gr=
from Table 18.15 li =0.81. and for trvo cables from Table 18.20 l:.=0.72. for laying in pipe from Table I 8.2 /R = 0.35.
tion 18.4.2). Where a cable is installed in the ground, the heat loss is conducted from the cable surface through the surrounding soil to the atmosphere (Section 18.4.3). The difference between conductor temperature and ambient temperature is approximately proportional to the total losses. The law of heat flow is analogous to Ohm's law, where the heat flow @ corresponds to electric current I, the temperature dif' ':ce 4 ^ --rresr.."'1" to ''-llrge dit::ene lr ^ the lotal thermal resistance 2. ./ corresponds ao elestn181
l8
Current-Carry ing Capacitl in Normal Operarion
in the analogy by currents ied in at
cal resistance R thus:
U: IR
fro m
A3.=rP1;r
the analog)'
(
18.r)
The heat florv @ (losses) is the sum of the heat losses Pi attributed to load current and the losses Pi related to the supply voltage. For heat to be transferred from its place of origin to the ambient it must overcome the thermal resistance ( of the cable and the thermal resistance d to the ambienr. In considering heat transfer from a cable surface to the ambient 7l may be the thermal resistance of the air 7i' or the thermal resistance of the ground 7i. Using the analogy between the florv of heat and the flo*' of electric current (Equation 18.2) an aquivalent . , :ircuit dia.gram can be dra*n (Fig. 18.7) for heat from a cable and the resulting temoerature rises produced. Heat transfer by radiation and convecrion from a cable installed in free air is represented by two resistors connected in parallel u'ith ,.'each other but in series rvith the thermal resistances of the cable. When installed in the ground the tl'o resistors are replaced by a single resistor being the soil-thermal resistance. losses flou inq
The heat losses Pj which are related to load current arise in the conductor, in the metal parts and in the armour, rvhereas the dielectric heat losses P! are generated in the insulation. These losses are reoresented
Conductor ienperature
appropriate points. Due to these losses the conductor temperature 3'- is increased by A3. and the surface temperature of the cable So is increased by A3o relative to the ambient temperature 9u.
For a cable with current flowins in n conductors the to current are
losses due
P'i: n I2 R*, and the dielectric losses (see Section 22) are / II \:
P;=nuc'b\f3)
equatron
R*. = Ri, + A R' =
R.:,(
I
+r',-:i
o)( I
+i.
r
+i,:) ( 3V I
rvhilst the d.c. resistance at permissible operating tenrperatu re 3.. is
R'"= R':o
Il
+ r.o (J1. _ l0)].
and the additional resistance
AR',:R;.-R;
(
r8.6)
is
(18.7)
Conductor lempetature
Thermal resistance
ol insularion
Condunor losses Thernral resislance
lr'l,
of insulation
Sheath losses
Iiin
Sheath losses
Ihermal resislancc oi
Thermal resistance ol
inner Iayers
inner layers
Il
Ar,'rour iosses Thermal resistance oi ourer shearhs
du
Thelmal resistance, of the ground
Ij
I;
Toral losses
Amour iosses
fj
Thermal resistances corresponding ro convecfl0n ano
radiation
fj
Thermal resistance oi outer shearhs
Ij
P,'+ PJ
Toral losses
Ambient lemperature
Ambienl temperalure
a) Cable in free air
b) Cable in ground
182
(l 8.1)
tan a.
The effective resistance (a.c. resistance) R! (see Section 20) is practically constant at the permissible operating temperature and can be expressed by the
Conductor losses
0ielecrric
(18.3)
P,'+ Pj
Fig. 18.7 Equivalent circuit for heat flow in a cable
Calculation of Load Capacity 18.3 measurable rise in conductor resistance caused by current dependant a.c. losses. These losses lrise in each conductor due to skin effect and proximity eifect (-v. and.r,,) and by induction and eddy currents in the metal sheath (,i,) as well as by eddy currents and mxgnetic reversal in the armour (1..). If these factors are incorporated in equation 18.2 for rhe temperature rise of each conductor the following .^"" rinn r nnlicc'
giving
a
LlL=lrz Rr+ejlf ri+ +urR;(l +)-,)+Pol + U'r R;( I + ). | +
).2)
rrlj+
+
P',r)n( Tj
{13.3)
+ 7l).
:lne
actual thermal resistance of the cable (see also Section 18.4.1)is given by:
^
TK=(Tiltr)+I!+1r:.
(t8.9)
The partial resistances of the insulation are represented by I/ and for the inner and outer protective covers as ?j and Tj respectivelv. (The tliermal resistances of the metallic elements are small enoush to be ignored).
To make the equations clearer and to simplify their application in design work, fictitious thermal resistances are introduced. The fictitious thermal resistance lii for heat losses due to the current. resuits from equation 18.2 and equation 18.8 with
lL+r rKi-
tl
+ ).,) Ti
l+i.r+).-
+T:
Where the individual thermal resistances. Ioss lactors. or effective resistances are not given. tlrey can be derived using the methods provided in the literarure referred to later It8.2, 13.7 and 13.3].
In the following the effective resistances are calculated or derived for the permissible operating temperature 91,.
If the operating voltage Uo is liable to deviate significantly from the rated voltage U of the cable then the dielectric losses must be calculated usinu Li. rather than [.I in equation 13.-1. The thermal resistance of the surroundings Ti is governed by operating conditions described in Secrion 13.2. For ittstallution in J)'ee air the thermal resistlnce of the air T,- is calculated as shown in Section i3.J.2 lnd has been used to determine the load capacity in air under specilied conditions rvirh an ambient temperature of j0'C. as can be seen in the tebles and text in Section 13.2: I-
31,-i0-A3,r r R",(7ir+
(13.11)
TL")
The load capacity for installation arrangements other than in free air or lor groups, is calculated using the rating lactors (Table 18.23 and 18.24). Rating factors /for ambient temperatures I, other than 30"C are calculated by using equations 18.2 and 18.14, assuming constant effective resistance and. thermal resistance (see also Table 18.22) with
(18.r0)
3. -ln-43.
-,d the lictitious thermal resistance fKd relating to the dielectric losses from equation 18.4, assumes that these originate at a mid point in the insulation. with
(1s.r5)
.
r,i":ft+r;+r!.
(r8.ll)
From these relationships the load capacity 1" can be found for a permissible operating temperature 3Lr and an ambient temperature 3u
Normally the dieletric temperature rise A3o in cables up to U: 30 kV is neglegible apart from PVC cables rvith rated voltages of U>10 kV. For these cables however it is common practice when calculating rating factors in air to neglect the dielectric heat rise which with the exception of a few cases is little more than 2 K.
For installations in the grountl Ij represents the thermal resistance of the soil. As indicated in Section 18.4.3 the equation 18.12 has to be extended because
In
R'*,(7-r, + Ij.)
with the temperature rise due to dielectric
Aid:4(7id+I4).
(18. r 2)
losses (18.13)
of drying out of the soil and cyclic loading Values for load capacity can be taken from the tables in Section 18.2. The load capacity for non-specified operating conditions must be calculated according to Sections 13.4.3 to 18.4.5 or alternarively by the use of conversion facrors in Tables 18.15 ro 18.2t. 183
l8
Curren t-Carry ing Capacirl in
Normll Opcnrtion
18..{ Thermal Resistances
0uter shearh
fj
lvletal shealh or screen
18.4.1 Thermal Resistance of the Cable
The thermal resistance of the cable ft takes into consideration the thermal insulating effect of electrical insulation and cable sheaths (Fig. 18.8) and must be calculated by using construction data and thermal resistivities [18.2, 18.7, 18.8].
For single-core cables with a metal sheath for example:
ri= =
Qt O: dL _ lr d, d
T;+
l':j
jrr"**9r"* :n aL :it
dtr
(18.r6)
thermal resistivity of insulation thermal resistivity of outer sheath material cond uctor diameter diameter over insulation or under metal sheath or screen diameter over metal sheath or screen overall diameter
The thermal insulating effect of metal covers is very small and can be ignored. Values for the thermal resistivity of materials used in cables can be found in Table 18.1. These values are assumed to be constant over the temperature range up to the permissible conductor operating temperature and so is the resulting thermal resistance.
The fictitious thermal resisiances 7ii to equation 18.10 and Qo to equation l8.l I for commonly used - cable types of constructions are shown in Fig. 18.9.
184
Fig. 18.8 Thermal resistances
Iianddofa
single-core cable
Thermal Resistance of the Cable 18.'l
Example 18.2 The cable data mentioned in the examples are taken from Part 2 (English version is in preparation). These values were calculated on the basis of the latest constructional design of the relevant cables and there[ore they may slightly deviate from the data indicated in the Tables 18.5 to 18.14 in resDect of the currentcarrying capacities.
0.6 0.5 0.4 0.3
0.7
Ibble
-
05
The conductor resistances for the cable selected for lhe example
04
NAIXS2Y I x
0.1
rre taken from Part
PVC
:
150 Rlvl/25 12/20 kV 2. Table 5.6.6 a and b:
Direct current resistance ol conductor ar 20
'c
Rlo=0.106Qkm
Eflective resistance at 90'C - bunched installed in ground or air - side by side installed in sround
A 02
Rl".=0.169 a km
R",=0.185Okm
The specific details of construction are: -,1 qL
Diameter of aluminium conductor
r-.J< rrrlr -- r.t --
Thickness of inner conducting layer
0.7 mm
Thickness oI insulation of XLPE
5.5 mm
Thickness of outer conducting layer including the protective cover under the screen
0.8 mm
Diameter under the screen
r/r = 28.5 mm
Diameter of single screen wire
0.-i mm
Increase in length due to helically wound construc:=OOS tiY" t tion of screen wire
:0.2 mm b:5.0 mm
Thickness of transverse helical tape ?5
70
95
120 150
185 240 500 400 500 mmz
Conductot cross'sectional araa
q--
Cables with or without common screen Cables with individual core screens Single-core cables
Fig. 18.9
-
Fictitious thermal resistances of commonly used cable constructions. 7ii, from equation 18.10 and ?xo for PVC-cable tor U6lU:6110 kV from equation 18.11. Cables with XLPE insulation have been calculated with PVC sheaths
rJ
Width of transrerse helical tape Increase in length due to helically wound construc::0.30 (i0%) tion of transverse tape Geometric cross-sectional area of screen4r:25 mm2 Electrical conductivity of screen, mean value
Diameter over screen
z:56.
106
dv= 299 mm
Thickness of protective layers and separating layer above the screen
sheath Outer overall diameter
I Qm
0.-1
Thickness ofouter PE
mm
2.5 mm
d:
35.7 mm
185
l8
Curren t-Carrying Capacttl in Normal Opcration
Using the thermal resistivities given in Table I 8.1
rve
18.4.2 Thermal Resistance of Arr
Horizontal Installation in Free Air
-" "._=0.176'i':', {lg.16) _ " - In I,, = sr ln "' "r W dt 2n "- 14.5 2n
/,
15
157
Km
ri=irlni=iln]=0099 - ./7t dM Jlt /9.9 T
K= ri + lrj =
*-, W
0.376 + 0.099 = 0.475
(18.t6)
Km/w.
Heat from cables installed in air is dissipated by convection and radiation. In the equivalent circuit, Fig. 18.7, the thermal resistance Tt" ofair is indicated by trvo thermal resistances in parallel representing convection and radiation. The thermal resistance of air can be expressed by [18.7; 18.9]:
(18.16)
For the calculation of the fictitious thermal resistance l'*, of rhe cable, the sheath loss factor /., must be used in the calculation according to [18.7]. zl., and T', are zero since armour and protective cover beirveen screen and armour are missing. For a trefoil installation in the ground this gives:
A+(l +r.,)?l ,l (1+i.r + /-:)
+
rj
0 176
(18.10)
= r-::;0.01 60 - -0.099--0.{69 -
tt
-
Consider a cable which is not influenced by other sources of heat (solar radiation) and rvhich does not increase the temperature of its surroundings. If such a cable is arranged horizontally in free air, so that it dissipates its losses into its surroundings by natural conlection and unhindered radiation, the coefficient of heat transfer z*, in dry air at an atmospheric p sure of l01J hPa. is:
0.0185 ,,, 1l: /i,, + ri kij
Km.w. u
These values. together with values for other types of insrallation, are shown for comparison in Table 18.27. Values for the fictitious thermal resistance of the cables l'i, differ from one another due to their dependance on the magnitude of the sheath loss factor i-r.
(18.17)
dlftz*+ f,t,)
108(*)r
ith
k':0.919
3
+J. JOv
30+3u
.
k"=1.033-#, A3o=
3o-3,
/tR rq\
(18.20)
and the rhermal transfer coefficient:. for radiation co a[(273 + 3o)a
Table 18.27
Comparison of fictitious thermal resistances ?ii between calculated lalues from equation 18.10 and graphical results from Fig. 18.9
Arrangement
)-\ to
I8.71
7ii to equation 18.10
In ground,
0.0160
0.469
0.0163
0.601 ,)
0.0116
0.448
Tiii to Fig. 18.9 l)
bunched
In free air, bunched
In ground, side by side "
1r
valucs for cabks with PVC shlath Calcularcd to Scciion 18.4.2
186
:0.545
-(273 + 3u)*] ,
A9o
(t8.ll) -
where o:5.67 x l0-E W/m2 Ka (Stephan-BolzmaYn constant) and eo the emissivity of the cable surface. With the factors k' and k" for the mean temperature account is taken to tbe variable quantities of the air.
Fig. 18.10 [18.10; l8.ll] facilitates the selection of auxiliary values forf,/* and k for the arrangements selected as specified operating conditions (Table 18.4) [18.7; 18.10].
-
-
The cable shown in Fig. 18.10a radiates freely in all directions. The heat is transferred by radiation from the cable surface to the walls of the room in which the cable is situated. A decisive factor in the temperature rise of the cable surface at a constant rate of loss is the temperature of these walls which normally one would expect to be at ambient temperature.
{hermal
/,=1
Resistance of
Air l8'{
Fig. 13.l0d illustrates free heat dissipation by conlection. The heatcd air initially florvs around the cable (laminar limiting layer) then rises uprvards in laminar form mixing with cooler air from the surroundings in an area of turbulence. A decisive factor in the temperature rise of the cable surface is, in this instance. apart from the cable diameter and amount of losses, the temperature of the surrounding air. The selected clearances shown in Fig. 18.10e which are equal to the cable diameter do not obstruct the heat flow since the thickness of the {lowing lir stream is comparatively small.
for one outel cable: /.=t arc sin {d/2a}/180", ior the cenlle cable: [=1-2 arc sin ldl| ali180'
-
Heat dissipation by radiation
In the bunched arrangement the cooling area of the cable is reduced to approximately t$o thirds. Bi/ reducing the cooling surface area the thermal flow rvithin the cable is also hindered and because of this the thermal resistance of the cable is effectively increased [13.10]. This restriction in heat florv was taken lnto account rvhen calculating the \tlues shorvn in
OJ
itr v{fir
6 6665 uf f -1t'l
Fi-s. 18.9.
The temperature rise of the cable surface is:
,-'l
tLrLr-rU-rrt,d, -----;;---;irl(if ,Lu
a ,to
Heat dissipation by convection
rLu
, -1-
D'
'r'
(l 3.12)
and the temperature rise A3o of the conductor caused by dielectric losses is:
Fig. 18.10 Heat dissipation, installed in free air
A 3d
= P;{7id + Ti,).
(18.23)
The thermal resistance of the cable Tiu can be calculated e.g.:
'- -e emissivitv of a cable surface can be taken €^0.95.
as
The same considerations also apply for the arrange.-ents 18.10b and 18.i0c. However any obstruction .- the thermal transfer must be considered. In Fig. 18.10b three single-core cables of a three-phase system are shown where only the thermal radiation from the centre cable is indicated. It is seen that the neighbouring cables obstruct heat transfer to the surroundings in the areas shown shaded. The reduction in heat dissipation is approximately directly proportional to the part of the cable surface embraced by the shaded angles.
In
Fig. 18.10c three single-core cables are shown bunched in trefoil. The obstruction in this arrangement is greater than that ofFig. 18.10b since approximately one third of the cable surface considered does not radiate heat to the surroundines.
tr
Calculation of temperature rise A36 to equation 18.22 and 18.23 with Tr_"=0.5 KmrW;
tr
Calculation of thermal resistance l"r, to equation 13.17
D
to
18.21
the calculations must be repeated n times until the difference between (?f,)" and (7t.)"-t is suffiently small.
For a multi-core cable without dielectric losses and with a 30'C ambient temperature, the external thermal resistance can be reasonably accurately obtained from the curves shown in Fig. 18.11a. Where the dielectric loss can be ignored one obtains from equation 18.22
AgL,_
?ii+?i.
A3o ri"
(18.22a)
By a graphical method, assuming a cable having a fictitious thermal resi":: '! " . . i KmAM with 187
18 Currcnt-Carrying Capacity in Normal Operation
0uter diamerer d
)ter
dr-
i\m
-24 26. 28
l0
45 50
80Temperature iise of cable 40
20 20
30
J0
40 Temperature rise of
-i-
a9" .c60 +
50
60
5U
t
0ri i
'l
0
02-l
\___________ Temperaturd rrse
ol
cable surlace
ior 20 Jo 30
50 510
50
Temperature tise of conduclot
odJ
\
061
700
r50 __
A3o-
"c
60
d8gl-_ |
\^
081
, Km
|(m
I
lwl 12'
1.0
r;-rili0us Thermal resislance 0f cable
Fig. 18.1I
/ii
a
Thermal resistance of air for a cable instailed horizontally in free air (3u= 30'C; €o = 0.95)
188
|
lFicririous Thermal resistance oi cable I'i,
\v' Fig. 18.11b Thermal resistance of air for three cables bunched in free air installed horizontally (9u=30'C;
so
= 0.95)
-
Thermal Resistance of
--.1:-.--_ ';i a ir
$_" "
ii,
Air
18..1
l8
a permissible temperature rise of A3.. = $Q K. entering these values as coordinates in Fig. 13.lla gives the point P. Through point P a straight line must be drawn such that point P', rvith the thermal resistance oI air Tt" and the temperature difference value A3o as coordinates, lies on the curve corresponding to the cable diameter d=32 mm.
20
The following values are obtained from the graph:
0uter drametet
0l I
mm to
22.
t":0.7
24 26
KmrW,
A30:40 K
28
For bunchetl single-core cables [18.10] the thermal resistance of the insulation and the outer sherth is increased due to obstructed heat dissipation. For cables to Fig. 18.8 without a thermally conducting metal sheath one derives:
Temperature
5r0
20
510
20
i0
t), :n dt
tl , L' = f i-L ln l-L ' '-
rise ol cable surface
40
50
f,,
rise oi conducror A $L
02
-
,/rr
_:_+_
0.6
us15)
(18.26)
T'r-f*tf-t-,. Jtt'l 'l
JlltM
^.1 rl:+ln+, :JT AL
0.8
(
13.27)
I
r\t
1.0
-fiorlr{s
'..
( 13.2.1)
.
:ft
For cables rvith metallic covering and hence improved heat dissiparion the follorving applies rvith additional reference to Table 13.29:
0.4
rm
,). :-Ltn ,l
*S,.''"(f) ':f
40
J0 Temperature
T: = f ' "'
lhermal fesislance of cable
Il,
Fig. 18.1I c Tr"ermal resistance of air for three single-core cables .-.-talled side by side in free air
-
914 o 11.otr, 'vv
gtt dt 'i f,n
+X
L
0 3.28)
"ry1
The thermal resistance of the outer protective covering Ij is calculated using equation 18.24 with equa-
tion
18.25.
The thermal resistivity gM of the metallic covering has to be taken into account and mav be selected from Table 18.28. Table 18.28 Thermal resistivity
Material
g'
Thermal resistivity
9,,,
KmAv Copper
Aluminium
l04.8 . l02.7.
28.7. 10-
3 3
l
19.1 '1-3
t89
l8
Current-Carrying Capacityjn Normal Operation
Table 18.29 Valucs required for the calculation of the effcctive thermal thickness of a sheath or screen Sheath-. screen factor
Thermal effective thickness of sheath or screen
Mean diame ter of metal shcath or screen
Metal sheath
du-du
,)r, 7r
n Tapes with spacing
dn. +:)
d"-J
nb(1
Wire screen with a 570 increase tn length due to the helix and with n transverse helical taPes Tape overlapped (as roof tiles)
tdu.
l-
nb(l +:)
t1-7
{=
,i)t'
dn-
6
I
-.t
dM-l(t
I
-t ---ubtr + =t 0ll f.| ------:
d"
applied rvith:=0.05
Two tapes aPPlied without 3pacing.
I
I
+:'
rT,,/r'
- l,)
-
rr Ar approximatc consideralion hcal dissipation lhrough thc \\'ires
Expression:
r.lq
b rr z d 6"
Diameter over the metal sheath or screcn (lransversc hclical tapc) ,){ : <) Width of tape (transverse helical tape) Number of tapes (transverse helical tape) Increase in length, due to the helical wound construction of tape {transverse helical tape) Thickness of each tape (transverse helical tape) Thickness of metal sheath
Example 18.3
For three single-core cables NA2XS2Y I x 150 RM/25 12i?0 kV bunched in free air, the lollowing app'fiEi (Dimensions see example 18.2, page 185):
it tt /d,\ ft 1r / 14.5 \ *==-=)=arcsin{--l=--p-2rcsinl-l=0.7:8. -'--"'\2x35.7J ' ' 6 l8f 6 l8CP
(18.15)
-
y.= ft = !^rr =1.392, ft-E 7t-V.t.:6
(18.25)
-
(18'16)
-
\2d)
Tr=gr l"
dr
' 2n"'dy-
3.5
2,r
di:6=0.2(Table
.
rM: 190
-
ndu-
---:-:_------: =
nb\L
+:)
t,. "'
28J
K.
-., "". 14;=0376;'
18.29)
*r'oo-o1\
z(dv - dl ---:----+ = i'''J;i i:^=,:14.35 (Table n0\t +:) I x )(l 1-u.JU,
18.19),
Thermal Resistance of
Air
1E.J
(
2.7x10-rx28.5x10-r 4x0.2x 10- l
2.7
x 10- r x 23.5 x l0-
rr
; T* J,)tl
-+-:
u.J
/ol
-l
: ,l.o+oT_, ',.Km lll 1'' -= 'Ir
tl
3
4x0.2x 10- l
13.13)
t- T'
J.\l ' sI
i.302 x 0.376
+
I 14.35
x
(13.:6)
0.480'
1.646
K.
^ ,.,^ lr=u.+duT-.
( l^
i57=n,.,oK'
-tt=J"r_ln -,Q,,^'l I
l.JUj -,',..,-.,-t-]',. = \.r agg=v.r-7T:-.
r', 0:+10 Ti,:, IT. - l-i0.Ul6i-o.r:s=o.oor """'W' ''' l+).t -rr=,
(rs.ro)
For the three single-core cables bunched in free air one arrives after several iterations
- 9u) T',L, _ (?0 - i0) 1..06 = 38.1 K. Tii+ f'1, 0.601+ 1.06
(31.
A rto
(
3o= A$o4 $,= 38.3 + i0= 63.3 K,
( 18.22
^ 3o+Ju A3o-l3u i3.3+2 x 30 2 2 2 r Jq rs
/<':0.919
+fr= r
k":1.033-ffi:
O.etl1
p' 99185 .''.;." r.o8
kd
e^
,
o r!
^ li9\'= /e f
\ rri4 /
'":--=----3o-
,
-, f
l.-||-.--=-.=:-.=:----
-.' ::iic
(r 8.1e)
(
213, fk: =')/
z")
_
0.0r8s r nsi-III9XY -
zx )).t x tu
\l
:ri
3i8.3
x J:=': lx ). =-
rlw
5'366
'b-J-=
+ 68.3)a -(273 + 30))n'l :7.229
"106
:,no , tu -{.i G5.366+17.229)
9t,-9u icsses
1.08 | ^
-
0.95 x 5.67 [(273 _0 =--------
I
x n:. ?fJ)./
18.19)
zl3
3sJ
I
nd(|, ar+f,
(13.20)
Jg r5
oll273 + 3^lt -(27 273+3u)'l
Ir__=-=-
a)
JOv
f rrding to Fig. l8.l0c and1f.b=) f
,.=
"--'
-#:oss'
r.033-
13.r2)
Kn='
(18.13)
(
A.m-
18.21)
-, Km
w'
(18.17)
(18.14)
ienored.. see Section 18.3. 191
l8
Current-Carrying Capacirf in Normal Operarion
Vertical Installation
Atmospheric Pressure
All knoln melhods of calculation and descriptions
The heat dissipation by convection decreases rvith decrease in atmospheric pressure [18.9]. For high al-
of values for load capacity relate to cables installed in the horizontal plane. For lertically installed cables neither theoretical nor experimental investigation is
titudes the thermal heat transfer constant for convection must be modified as follows:
known.
Whether the mounting is verrical or horizontal has, in principle, no influence on the heat dissipated by radiation.
.
The heat dissipated by convection from a vertical cylinder oi length / and diameter d is, with all other conditions equal, more favourable than that of the cylinder in horizontal position. provided that
-> d
2.'17
refer [18.12; 18.13]. Since this relationship is always ;atisfied in respecl of cables installed in a vertical plane it follows that they can normally \\'ithstand heavier loads than when they are installed horizontally. Thus the same load capacity can be applied to both conditions.
10t
'.
=
r'
o'?f
5
+
t"'," (S, (-#-J*, Jt (l8.l8a)
*ith k'and k" to equation 18.19 and k to Fig 18.10.
.{rritude ml 011000120001i00011000 _ Armosphericlllll pressure
p
hPal l0l3
|
899
|
795
|
701
|
614
Altitudes up to 1000 m create a negligible reduction in Ioad capacity.
-
Thermal Resistance ol'
Air
18.{
Example I $.J
Ar alritudes of j000 m above sea level an atmospheric pressure of 701 hPl is used for the calculation. For the cable
NA2XSIY I x
150
RlvV25 l2l20kv
this gives. after several iterations and, using dimensions from example 18.2 (page t85) and 7*, from example 18.3 (page 190)
Ti, IKt + Tr,
{31,-3u)
30 = A 30
+
3.:
(90-30) 0.601+
39.22 +
1.131 (
l.li.t
i0 = 69.22 K.
(
1s.22)
l3.ll
a)
*,irh P; = 0
i9.21+lxl0 ^ Ato+23u )1 *
=o.r'r*$=o.srs+ JOv
a' =
r.033-#=
a:11 JOv
-#
r.o::
(
= r osl+.
(ls.l9)
:o.s;s+.
(ls.r9)
\i *, / \d"J-=
o _+k,',.,.^^/a36\i/ ,(k:(,0.0135 *|, w
r
o5il
0.01 35
0.973-l x -+
iX-)l./^ltl
r08(---i9!'?
(l8.l8a)
+ 3o)r A
-
(273 +
J,
9r)1] _ 0.95 x 5.67[(273 +69.22)]-{273 +10)*l
l9.ll lo! x
I
T:
.
r d(f, zn+f"2.)
n
\i )'( l0li/ 701
-l
irR =J '--Km: ' eo o [(273
13.:0)
R;, (Ti$ +
7t
Ii")
35.7
x l0-r
(3 4.,s?8
+3
7.26
...
1.134)
W
K;:
(13.21)
Km
l)
I x0.269x l0-r (0.601+
_",., i :o I
:159 A.
(I
3.17)
(r3. r2)
The load capacity at this altitude is therefore reduced by a factor
/
I= j:'J:o.gsr. t. Joo 1SO
ltt
l8
Currcn t-Carrying Cxpacit! in Normal Operation
Table 18.30
Ambient Temperature
The thermal resistance of air around a cable varies only to 3 smallextent 3t conslant conductor temperature and rising ambient temperature. Normally it is suflicient therefore to use equation 18.15 for the cal' culation of load capacity for other ambient temperatures. This formula was used to obtain the values ln I able l6.li. Example 18.5
Absorotivitv of cable surfaces to solar radiation
Material of the outer protective cover
Absorptivity
Asphalted jute PVC PE Polychloroprene Lead
0.8 0.6 0.4 0.8 0.6
For an ambient temperature deviating from 30'C e.c. 3, =.1i'C the conversion factor ts
'- 90-i0 =oR7
r-T-
(13.r5)
and the load capacity
I,=f I,=0.87
x 366= 318 A.
Solar Radiation Cables subjected to solar radiation are subject to an
addirional temperature rise
A3r=
1o,igt'
(18.19)
and the cable surface temperature rise in relation to ambient temperature is ll
(3.,
-
3u
'-tOS
+ ro d E]'ii) Ti(i + Ia
-A
3a
Tl.. ot
! d 'r' rs. (r8.30)
The load capacity 1, is found from /i^--------;;-j-
AJd-Alts /0t,'oUr,, _-t - |y/ -------;----.-=-' ,l^wr{r1;tr5l
(18.31)
and the thermal resistance { of air, taking into account rhe solar radiation, by iteration using the equations 18.17 to 18.21. For this the term 7i" in equation 18.17 must be replaced by I and in equations 18.18 to 18.20 the calculation is made using A9or from equation 18.30 instead of A9e and 9es instead of 3q.
The absorption coefficient zo of solar radiation for the cable surface can be found in Table 18.30 fl8.2l.
194
The intensity of solar radiation E on a horizontal plane is 1.35 kW7'm: maximum (solar constant). Normally the actual values are less and depend on the degree of lattitude, season, weather conditions, time of day etc. [8.1a; 18.15]. Should local values not be available tbe value of E: I kW,'m: can be used in calculations ! 8.21. \v.
Thermal Rcsistrnce of
i\ir
18.{
Example 18.6 Three single-core cables bunched in free air
NA2XSIY I x 150 Rlvt/25
l2120 kV
are exposed to solar radiation with intensity
The calculation of thermal resistance
I(
E: I kWim:.
is made by iteration:
{31,-9u+aodETki)T! (90-30+0.4x -rtt'r' ! Ki-T''
3o: .\ llor;3, :
-13.39
S
i5.7 x l0-3 x l.0 x 10-r x 0.601) 1.035 :13.39 K. (13.22) 0.601+ 1.035
+ 30:73.39 K,
,. J3e5.-2ilu 13.39+2xi0
(18.20)
,rd = -------
A',=oele-5:se1e*i!] Jdv Jov {
ft" = 1.03r z. =
= 1 65e1.
(r8.l9)
3 Sr7 -ffi : r.033 -ffi =0.e761.
(18.19)
0.01s5 ,,, , ^^ /A30r\' (',, II-11 a 1" I 0s
(-j!I)':
| 05el
,
.++:^=..o
e76r
x'
or
(;j#m-)::
r
r*
S (
- (27] + i0)"1 : ,*'_ co a [1273 + 9o)+ -(273 + 3r)'] _ 0.95 x 5.67 [(273 + 73.39)' x
A9o,
| T:: t t: i,tf, o, +f. t):@ LSr:
7o 4
p
I(:0.4
x 35.7 x l0-3 x
lOs
'11.39
I 1.0
::to'r-K' u:) V'
x iOr x
1.035
7.408
1
:
14.3
K,
;--. K.m-
l 3.13)
(l3.ll) (18.17)
(18.2e)
(18.r2)
e load capacity
/
with solar radiation intensity E:1.0 kW/m: is reduced by the factor
lrn
f:]:3=o.st. rr Joo
195
l8
Current-Carrying Capacit) in Nornal Operation
In Fig.
Arrangement of Cables
Heat dissipation of cables is affected rvhen they are in contact with surfaces (rvalls, floors, ceilings). At the point of contact the flow of air is hindered and therefore the heat dissipation by convection is reduced. Heat dissipation by radiation is influenced by the emissivity and the temperature of the adjacent area in contact, should this differ from ambient. In direct contact heat may also be transmitted by conducrion, so that the thermal conductivity of the adjacent area is important (Fig. 18.12).
i-
Quanrities of load capacity for cables in contact u'ith surfaces established by experiment are normally less than for installations in free air. in the VDE specifications this t) pe of installation is taken into considerarion by use of a reduction factor of 0.95.
,.
Grouping cables can also hinder heat dissipation as has been shown in the calculations of thermal resistance of air for three single-core cables (Fig. I 8.10).
.
I
18.13 various arrangements ofcables and rhe relel ant rating factors to DIN VDE 0298 are shorvn. On the left hand side it can be seen that by arranging cables close together or by mounting on a solid surface the convection reduction is made worse. Similar
comments apply to the vertical arrangement of cables. The reduction is however relatively greater than that for the horizontal arrangement since the upper cable lies in the path of warm air flow from lower cables. The chimney effect (improvement of heat dissipation by convection through moving air flons) is somewhat reduced. The greatest reduction occurs in densely lilled trouqhs or racks as can be lrequently found in cable trenches of large power installations (Table 18.23 and Section 18.5).
2d .]-f ')':i :1-o---r--ti d,
.l
10
o_ a-
l^ lto
,
1.0
z 2cm
i
leat dissipation by radiarion
c)
,M
0.96
z2cm
082
)l
0.73
Heat dissipalion by conveuion
Fig. 18.12
Fig. 18.13 Reduction factors for various arransements of
Obstruction of heat dissipation by adjacent surfaces
multi-core cables in air
196
Thermal ResGtance of the Soil 18.4
18.4.3 Thermal Resistance of the Soil
Temperature Field of a Cable in the Ground
The heat loss P' generated in a cable flows through the surrounding soil to the surface of the ground where it is then dissipated into the atmosphere. To depict the temperature field of the cable in ground one normally assumes a constant ground temperature 36 and a soil-thermal resistivity gr rvith a negligicie rhermal transfer resistance at the ground surface. .\lso ir is assumed that the total heat loss generated in the cable (source) is directed to zero in an imaginary cable situated as a mirror image in relation to the ground surface- The temperature rise at the point i- :lative to the temperature of the ground 96, speciflically the surface of the ground (Fig. 18.14), is obtained from [18.16] (18.32)
The isothermal lines are determined by the condition A3p:ssn51.., and therefore the relation ci,'c" must also be constant.
,cp
(18.33) Cp
Fig. l8.l{ Temperature field of a cable of diameter
11=
I
r lnd
dcpth of lay /r. Furthcr cxplanations in the text
For a given heat loss P'and temperature rise A9o one obtains from (18.32) and (18.33) the geometric constant for the isotherms (
l 8.34)
expressions for determining the isothermal line ^e tnrough point P for a cable with a diameter d:2r
cable) run parallel to the cable axis. The depth of this line source is ho and the isothermal lines are eccentric to this by a distance e".
For the deoth of the line source
and a depth of lay h (Fig. 18.14) are as follows:
lo -
lius of the isotherm
(
13.38)
and the eccentricity of the cable ,
2hokP
P
- ;-;---, r(F_t
(
18.35)
+\l&i_\:ho+ - \=
6-y' 1rz -rz.
(13.39)
",,
(
18.36)
the depth lro and the radius r, of the isotherms are known, their geometric constant can be found from
eccentricity of the isotherm eP= zhol(ki
1to=
If
depth of the isorherm hP= ho(k?
t = 6-
h?-ho.
,. _hs* hp-rp "P- h"- hp+ rp
(18.40)
ho=
(18.41)
(18.37)
One can visualise a temDerature field comprising a series of lines which at distance e (eccentricity of the
with
197
l8
Current-Caryi4g Capacitl in Normal Operation
For a point P on the surface of the ground becomes the temperature rise by definition is ci,,''c, = I
"n6
If a point A at a distance a from the cable axis and ir from the surface of the ground is imagined the tem-
perature rise at this point can be determined from equation 18.32 and equation 18.38:
A{t!: r t
ln
/ia
18.41
with the geometric constant for mutual heating
\h+Vh2-r2)2+a2. th
-l/
h2
-
b) Isothermal line through point P, i'i. to equation 18.46
a) Cable, l"i to equation
r2)2
+
(18.11)
a2
Definition of Soil-Thermal Resistancc The temperature rise of the cable surface is obtarned by putting a:r in equation 18.42 and, after some manipularion as well as putting d = 2 r, to
ase=r'ftnt
Fig. 18.15 Soil-thermal resistance (the range considered in formula is shaded in each case)
t"l lnl
ll i;-lr /i\
----l a a.l .."l
(18.13) (18.47)
rvith the geometric constant for rhe cable
(18.44)
/2
i,\'
^=#* \7/
(r8.r4)
or
,=#
(18.49)
This also defines the soil-thermal resistance of a cable, that is the thermal resistance between the cable surface and earth (Fig. 18.15a): a)
1E=:-ln,i !ft
%,
lzh
:ft
\
4
t2h\2
\a -')
(1 8.45.1
r gp
= ;-
III d9,
(18.46)
,/.7t
where the geometric constant of this isothermal line is determined using equation 18.32 and equation 18.40. 198
b) Single-core
c)
Single-core
cables,
cables,
bunched
side by side
'-'
Fig. 18.16 Soil-thermal resistance for continuous operation rn
Correspondingly the soil-thermal resistance between the ground surface and the isotherm through a point P is established (Fig. 18.15b):
Multi-core
cable
= 1.0 without drying out, qE:constant
For three single-core cables in a three-phase system - producing equal losses in all three cables -:
rr=fi$"*+zt"t
(18.47) "),
with the geometric constant k of one cable as in Fig. 18.16. In bunched installations - arranged in tre-
Thermal Resistance of the Soil 18..1
foil
-
the geometric const:rnt kr for grouping can be found approximatelv from k"
=
ll
ri.
(
r3.18)
Normally the depth of lay is very large in relation to the radius of the cable. The eccentricity of the cable then becomes neglegible and one obtains simplifications of the equation in Fig. 18.16 for continuous operation rvithout drying out of the ground. This means the load is constant in time and also the soilthermal resistivitv is constan t.
For a relationship rvhere hltl>5 the value found by calculation using equation 18.-19 deviates by less than ; ',0 from the value given by equation 13.44.
{aily
Load Curre and Characteristic Diameter
r./,
, . ith cyclic opcrurion rhe lord capaciry is grelrer than for continuous operation.
ln continuous operation (Fig. 18.17) one obtains. after a warm-up period iollorving rhe switch on, a constant temperature distribution in the ground which falls in a near logarirhmic manner from rhe
Continuous operation
cable surfacc to the ambient temperxture. For a cyclicly changing load over a long period. after the switch on period one sees - between fixed temperature limits - r temperature curve va.rying aeainst time. Near to the cable the temperature change is most extreme but this decreases with increase of distance from the cable.
If one considers the thermal field of a cable in rhe ground (Fig. 18.18) the areas within rhe isothermal Iines can be depicted, for calculation purposes. by partial heat resislances and capacitors so that a chain of RC components is developed. A calcularion of temperature rise and also of the load capacity is possible utilising this equivalent diagram. Accurare results. however, can only be achieved bv very involved calculation. For dcily load curves including the partern for urban
utilily supply nerworks, a merhod is used which provides a sufficiently accurate result wirh a reduced amount of calculation and is suitable for the load factors ransinq nl :0.5 to 1.0. This t.v-pe of operation is described in more detail in Section 13.2.3.
To simplify calculations rhe so called characreristic diameter ri, is inrroduced (Fig. 18.19). The tempera-
Cyclic operation
l"* \
100%
Time._
Tite-.-..........-
Time-
Titt
lealrnq
J00%
Fig. 18.17 Heating of the ground
by continuous operation and cyclic operation 199
'
l8
Currcnt-Carrying Capacitl in Normal Operation
the daily load cbaracteristic curve. Ourside the characteristic diameter a conslanl temperature exists (i.e. the thermal capacitors are cbarged up during rhe warm-up phase and do not enter into the calculation for the steady state condition). The loss factor p for the determination of the mean current heat loss is
p=0.3 m+0.7
(18.s1)
m2.
The characteristic diameter d. is dependant upon the thermal characteristics of the ground, the frequency of rv equal fluctuations over 24 hour period and on the loss factor p. Fig. 18.18 -Theoretical development of isothermal lines in the
-round and substitution of lalers between the individual lines by a chain of R, C components
For the characteristic diameter d" in irr rvith a load factor to satisfy 0.5 <,r < 1.0 and for a sinusoidal load variation: 0.205 n gE
,/ -t I
"
\0..1' I
\Kmfvi
[or rectalinear load variation
,: '
'r "
0..19i
1/
ni
V\!
-:-------------=_:.
I
O"
(18.53)
\"'
\Kmlw/ for an average shape of load variation which is neither sin usoidal nor rectalinear O.lO3+0.246VG (
i U idv -ig.
Distance itom
Lc(#)"'
cable-_
18.19
rleating of the ground in cyclic operation
Table 18.31 Loss lactors and characteristic diameters for a soil-thermal resistivity of 1.0 KmiW and daily Ioad curve wi!h maximum load Load factor
Loss factor
m
p from equation 18.51
ture dse outside the characteristic diameter is determined by the average loss with dependance on the load factor however, the highest degree of temperature rise within the area embraced by the characteristic diameter is dependant on the maximum value of load. Within the characteristic diameter the temperature varies with rime to a curve which closely follows 200
18.s4)
Characteristic diameter d, in m Sinusoidal Rectalinear load from load from equation equation
Mixed load from cquation
18.52
18.53
18.54
0.5
0.325
0.205
0.281
0.243
0.6
0.432
o.1 0.8 0.9
0.553
0.105 0.205
0.:05
0.324 o.367 0.409
0.205
0.451
0.265 0.286 0.307 0.318
0.688 0.837
Thermal Resistance of the Soil
The geometric c()nstant k" of the circle rvith the characteristic diametcr ,i, is obtained from the an:rlogY oI equation I 3.-l-l:
, lh *r:7]*
.+
i
Ir
18.'1
Temperatute
.T1
Cable suriace remperature
80:ll
(18.55)
Dr-ving-Out of the Soil and Boundary Isotherm d.
40
By reference to Fig. 13.10 it rvill be seen that at a certain load. rvhich is limited only by the maximum permissible operating temperature, the surface of cables of different types of construction rvill assume d'o:renr surface temperatures. While the surface tempj,ature of a mass-impregnated cable may be approximately .+5 "C, the surface of an XLPE cable can reach 7i "C (at 20'C ground temperature, degree of l^{ing 1.0 and assuming the soil does dry-out). The c _jrence is significant. It is knorvn that sandy soiis tend to dry-out rvhen the cable surface temperature is approximarely 30"C installed in a 20oC ground temperature. The danger oI drying-out is higher rvhere XLPE cables are used than where mass-impregnated cables are installed. This danger also increases rvith increasing load lactor.
JO
20
r0
0.J
0.4
0.5
0.6
0i 0.8 0.9 m axis-*
1.0
Disrance ifom cable
a b
Three XLPE cables
\A2XS2Y I x 150125 Rll I 2,':0 One mass-impre gnated clble' NAEKEBY
3
x
150
R!{
kV
12/20 kV
Fig. 18.20
!laximum heating of the ground by different
cables
This drying-out area (Fig. 13.2t) is indicated by an isothermal line excentric to the cable - the boundary isotherm - having a diameter d,.
on the stipulations given in DIN vDE 0298 Part 2 the limiting temperature rise A3, can be deBased
rived from the equation
^
ar - 15-(l-nr) 100 -'' l
(r
s.56)
and this results in
'
A3,= l5 K forcontinuous operanon with
rn:
1.0,
A 3.
:
A 9,
= 32 K for daily load curve with
.
25 K for utility load operation with rn = 0.7, m
= 0.5.
Within the boundary isothermal line the soil-thermal resistivity can be taken as 0!= 2.5 KmfV representlng the almost completely dried-out sandy soil or the sand used as bedding material. Outside of the boundary isotherm rhe value ae= 1.0 Km/W is used which rePresents almost all natural types of soil in European
Fig
18.21
Heating. of. the grour
.
20r
l8
Current-Carrying Capacitf in Normal Operation
'2., li,r'/ / /, /.//
Fictitious Soil-Thermal Resistanccs T', and Ti"
/./////./. "
6.fr
trnr+{p-r) tni,l 0av)
r=9tni " tJt a)
0s.5s)
Muiti-core cable
a>.
6=fr trnr+{p-r) rn*r+p2lnk
l 0&59)
r,!#(lnr+2tnt")
(18.60)
b)
18.63.
Single-core cables side
bl
side rvith d.<2a
,'. ., y,/./,/././,/,,.,,/,/./,//.///
Load Capacity
///,/,//
* iln i+3 (p-1) l,-2In tal 08.61) (1s62) i,'*(tnt*ztni") c) Single-core cables d) Single-core cablcs sidc by side rvith d, >24 bunched I,y-
t
.
The fictitious soil-thermal resistances T'. and Ii, take into account the cyclic performance of a daily load curve and drling-out of the soil. These can be calculated using the equations in Fig. 18.22 but can also be taken, for some arrangements, from Fig. 18.23. For the calculation of load capacity these resistances are to be incorporated into equation
ln
and k" to Fig. 18.16, k, to equation 18.55
Fig. 18.22 Formulae for calculation of the fictitious soil-thermal resistances 7,, and T', with daily load cycle nr< 1.0 and drying-out of the soil
Previously the values for load capacity in the ground rvere calculated using the rules for continuous operarion but did not take account o[ drying-out of the soil, which rvas permitted only for defined public utiliry load type of operation. For continuous operation the recommendation was to use either the factor 0'5 or a factor which corresponded to a sufficiently \a selected soil-thcrmrl resistivity.
Load capacity is norv - as explained in the previous section - (DIN VDE 0298 Part 2) calculated using a method which takes into account drying-out of the soil together rvith maximum Ioad and load factor, $ hich is derived from a daily load curve. Load capacity can be found from
,
Fu-gr- PitT'** T'.\ *[(qJoE)- l]43.
'":/@ ,
l
l6.oJl
q,ith the individual terms or values determined follows
as
:
Load factor nr to Fig. 18.1, loss factor I to equation 18.51, \r, characteristic diameter d, to equation 18.54 or Table 18.2 for the thermal resistivity (,e: I Kmllv, limiting temperature rise A3, to equation 18.56, geometric factors A', k" and k, to Fig. 18.16 and equa-
tion
18.55,
thermal resistances Ti and I',, to Fig. 18.22 providing it is established, where necessary, that d">24 or
dr<2a. The diameter of the dry area d, is not essential for the calculation but it must be verified whether the assumption that the soil is drying-out does apply, that means d, > d respectively 96 > 9. : 9o=
9r'-Pi Tit-
9.=3e+A9'. )n)
PiTi.d,
(18.64) (18.65)
Thermal Resistance of the Soil 18.'l
Fig. 18.23 Fictitious soil-thermal resistance f. at nr= 1.0, l'ly at nr=0.7 relative to outer diameter d of cable and depth of iay /r for a soil-thermal resistivity of s. = 2.5 Km/w and pE = 1.0 Kmiw
1.0
I
.
---70mm.
6.0
(9 q/ i9
5,J 4.0 3.0
1.5
1.0
2.5 2.0
ta
1.0
08 0.6 0.5
40 50 50 80 100 150 Outet diameter
200mm
oi cable d
-
The ohmic losses in equation 18.64 must be determined using the load capacity calculated for dryingout the soil. If the surface temDerature is found to be less than the temperarure of the boundary isotherm, the calculation for load capacity must be rePeated but under the assumption that the soil does not dry-out. The calculation routine described above
To simplify this calculation the characteristic diameter is to be determined using the thermal resistivity of the moist area. A comparison of diameters is therefore avoided and the result is on the safe side since the lower thermal resistivity results in a maximum value for the characteristic diameter.
ior capaclly Jo < J! must be satlslied. 203
l8
urrent-Carry ing Capacitl'in Normal Operation
C
Example 18.7 Three single-core cables
\A2XS2Y I x
150
RM/25 12/20 kV
are installed in ground under different oPerating conditions. Dimensions and thermal resistane of the cable can be taken from example 18.2 on page 185
or from Part 2, Table 5.6.6a. Bntched installatiotr for the speciJied operatittg conditions to Table 18.2.
Type of operation: Supply utility operation with nr=0.7 or any equivalent load variation (Fig. 18.6) rvith a frequency of load cycles x: 1. u
= 0.3
rrr
+0.7 rnr: 0.J x 0.7+0.7 x 0.7tr = 0.553,
r/i n o\o '
,'
:0.186
(18.51) m
(18.51)
,
Krn
2x0.7 35.7x 10-3
(13..14)
-l
(
, )h 2x0.7 JT "^".Kt ir ft-' ^" = 7= lstlo.l: T:,=
*[lnk+ ts
=f
3(p-
ttn 78.42+3
^ r',: h]nk*z
1)
(1
lnk"+2 lnk,]
15
fr
[n
8.18)
(18.61)
l tn q 6q+) ln ta ttt= -.. I aas .- Kt (0.553-1/... w
tn,t"J =
13.55)
78.+2+2ln
,
Km
39.:3]:4.656;.
(18.62)
{l-07) 100-25K. t3_:tr, (l-rn)3 100=15 '- r
(18.56)
.
is made with t ,: specilied operating conditions to Table gives in equation 18.63 the rated value ,f the load capacity /. with P: = 0. f'Kt = 0 469 KmTw as in Sectio 18.4.1 and R*.:0.269 Q/km as in Part 2, Ta : 5.6.6a. Since the calculation
18.2, this
o3-. A, ,,:t,/ry4+''r '' V nR*,(T'11;+r',,) t@= / txo.z6ex l0-3(0.469+3.445) '--"' 320
30=91.-Prfli: St,-n Il R-,- =90-1
(18.63)
x3202 x0.269 x10-3 x0.469=77'1 "C' (18 64)
with
P:: 3,:
0 and Pi to equation 18.3 Se
+ A9, = 20 +25 =
45'C.
The assumption that 90> 9, is 204
there:
(18.65)
verified.
Thermal Resistance of the Soil 18.'l
Btutchetl tnstulltrtiort
For
rn: I
then
4:
rlitlt lr =
The same vrlue is obtained using the rating factors of Table 18.15 (/i =0.93) andTable 18.19(/::0.3,i)
I
I and T'." = 1'
l'=i
rl-lllon
A3.:t5-" ;""":15K. ao, . - F*-Wfr.,tsll____;r*tr,.,*nrl _ ,,=
(18.s6)
(18.63)
For nr: 0.7 3o=
The current-carrying capacity 1.:120A is identical to rhe ouantitv siven in DIN VDE 0298 Part 2 as ti )e seen in Table 18.11From the quantities for /, and I. the rating factor is
90- I x 353r
:74.1"C.
V
90-10+[(].5,1]-11 l5 _1(q l _r/ !1' = [/ lro%9.10=l{0..t69+4556)--ra
xf 2= 0.93 x 0.35 = 0.79.
i = lOr- ?5 = 45 oa and for
rrr:
1.0
3o= 90- I x 277: x 0.285 x = 80.2 'C, .'l =1n-! I\= ltoa 3o
l0-r
x0.'l-18 (
13.64)
> 3, .
159
The same value is obtained Table 18.l5 Ur
:
f: f, f.: x
by using
factors from
0.93) and Table 18.171/,=6.371 t";,1t
Calttltttiotr of diunterer d, untl tlepth of lay h, of the tlrr areu Jbr u bunclrcd installatiott und lor m= 1.0 Assuming: r/, > d,
0.93 x 0.87 = 0.8
1.
ho=tn
The individual thermal resistance can also, in this case, be calculated using the equations in Fig. 18.16 and Fig. 18.22. It is however easier to take these from the graphs in Fig. 18.23 and 18.9 or Part 2, Table 5.6.6 b giving
= 0.448 KmAV.
ls
-"r =.I/rn
h. = ho
For R;.:9.235Q/km (according to Part 2, Table nr
x
l0-i l)i
, | 2rA3, l k,:expl;_r*l
r/,
T',:3.794Kmlw, T'.r: 2.583 Km7-W,
",'.6 b) and
ltl-r::VO;,-(:S.l
=0.7 m,
(18.41)
Insrallatiott in Ground Side by Side
'l'kr
x l0-3 x 0.448 (13.64)
In both cases therelore
.1 . l, ,t1,3:o
. '.
x 0.285
with
= 0.7 is
dy
Qr.
l3 x
lx
1.0x1592 x0.269x l0-r_l
/. 570 ;'' , = 4x0.7 ;i=la;-l )./u--l ;
(Fig. l s.la)
I r;)
= 0.51 m, (13.66)
t,2-Ll < -nz Ll ^4J,M:--:-_-:0.7 0.74 = ;:i ; K;-t ).iu--l =
m.
(
13.67)
= 0.286 m the assumption d, > d, is proven.
go-20+[(2.trt-lJx _.r,.r ,__r/ ' t* 0.285 x l0-r10.4-+3+2.583) ^ v
and for
rz:
t.o
_,1 eo-2GtdtD-lJts
,-
/
r x0.285x t0-r(0.lt48+3.794)
(18'63)
^--. (18.63)
The two quantities give a resulting rating factor of
I
277 )i!
205
l8
Curren t-Carry ing Capacity in Normal Operation
Diameter of the Dry Area
tI-:/+ll^-
The diameter of the dry area rvith respect to the characteristic diameter can be determined once the load capacity is knou'n. For this calculation the necessary'
the depth of the boundary isotherm is given by
/',:ro#
geometric factors k, for a multi-core cable as well as for three single-core cables are shown in Fig. 18.24. The diameter for the dry area is obtained from
G^,
d.,dv
',,="'pl::*l
t'
k,=exp
d,'dy
- d,.dy ,-
1"9
[(?
i,=exp
d|.dr.2a
d..22'd, k,=exp
lzrat
/5aE
r o\ Pov 0t>0,>G \//o \ lJ._', t,=e,o
{tff
v/
-tr-r, ) (tn
k,) /
lFJfl))
+(r-p
1'tn
t,)rf 4+g)]
) P,tn kt)
/
lil
lP'+
€Fi
{pPJP;)l
2a-d^t
d,t
r,,=",p
t(ff
?a-d,r-da
dr.\a-d,1
-(t-r,)
@r t({p
r,="'olffii)
'
d,t
- (p4 = P)
/
2 tn k
"l
tpl! ftll
t@{::,
d,1
rv- (P,+{) 2ln
n J$, ;+3 Gpl 4ln rrl=expL-----:--+E-r ,
2
/p
t.,
.,2r!t|,/pp+(1-p)frlnit-(pPJff)2lnt.' k1=ex9t_________FE-|
Fig. 18.24 Geometric constants of the dry area for one three-core cable and three single-core cabies 206
(18.67)
and the depth of the line source /to is derived from equation 18.38.
/6\--4
d,
(r 8.66)
Croupirlg in Ground 18.{ The cable ly-ing in the centre is heated most and is the reference cable designated l. In most instances the eccentricity of the cable is neglegible. For trvo cables (Fig. 18.25a) the grouping factor is
18.{..1 Grouping in the Ground Fictitious .{dditional Thermal Resistances -\
Ij
and A
Ii,
due to Grouping
Cables grouped in a common cable trench or installed with insufficient spacing from one another result in mutual heating. Thus the load capacity is subsequently reduced. Reduction lactors for the normally used spacings are shown in Tables 18.17 to 18.21. The load capacity for large spacings, lor groups of cable etc. must be calculated for the individual situa-
rt. , L ,2 l/ \tt|'r ttl) 'ru -:
''
-.
t/ trt.
(13.73)
- h,t' + a'
independant of rvhich cable is heating the other. If
trvo cables are arranged at the same
depth
(Fig. 18.25b) then according to equation 18.50:
rio ns.
For the calculation of load capacity the superposirion of-temperature fields is considered here also. Interferd : with ground heat conductivity, due to variations in homogeneiry caused by the cables, is neglected. Because of the commonly used ciearance of 7 cm bet'ryeqn cables this can be done rvirhout introducing $ .ficant error.
For the fictitious additional thermal resistances ATj and dTi" of multi-core cables (calculated rvith g,) due to grouping, the follorving are applicable rvhen considering daily load variations
6 T_,
:flfir,*u -" L:
rr
rn
r"].
Y".l
(l 8.68)
Considering dielectric losses and continuous operation with rn = 1 in equation 18.68 4 must be made equal to I and this gives
ar;:fri;, -'"
(
\a I
V
13.7+)
For six cables as in Fig l8.2ic then
f ; =r,n1,{t'f,*,*2'n
MuI
-ln
fi'',
': l/(r) *'* (18.75)
In groups of bunched single-core cables the distance betrveen centres of bunches b can be used to simplily
:
l r'*,.u. - r)rr -
y;=1,ftlf*,=1n*.
(
18.69)
calculation. Since in equation 13.77 the number of loaded cores per cable is considered with n= l. to take account ol all losses the ligure 3 must be introduced into the group factor. If in Fig. 18.25c for example the six cables are replaced by six three-phase systems each comprising three bunched single-core cables this {:ives.
lE r ) d,=Jli I
2.
^ Similarly for three single-core cables in a three-phase system:
fi) A, rn
/(-6)*'*t'"
tffi;* (
18.76)
AT:":
Values for grouping factors for a cable laying at the
A.::*Tr,
end of the group may be taken also from Fig. 18.26. For a cable on the inside the group factors for the number of cables laying to the right and to the left must be summated.
(
i 8.71)
N, is the number ofcables within the circle ofcharacteristic diameter dy.
With the aid of equation 18.64 and equation i8.65 it must be verified whether the soil actually dries out.
The grouping factor Ed, is for a number of cables 1,2, 3 ..., i, ...N (Figs. 18.14 and 18.25):
I6t:Th::
(18.72)
207
l8
Currcnt-Carrying Capacity in Normal Operarion
Load Capacity
For N cables of the same t.vpe. having the same ioading and the same losses installed in the same trench the load capacity is
, _-, I or,- Ju-e;1r;o "-/
+
ri +a r;+ (p2r1-
r1
aq -
(18.77)
Extension of the Dry Area
.{s described in Section 18.41 the dry area mal be represented in special cases by a circular or nearly circular area with a diameter. equal to the diameter d,. More accurately the boundary of the dry area can be determed by calculating the temperature rise in all points P (.x, y) which accurately correspond \\'i'\ rhe temperature rise of the boundary isotherm This is effected by inserting to the relationships gilen
l\n
in Fig. 18.27 in the formula
}
43,= I(riPii+P:i) x
ln ]: zn
x
- x)2 (.v - h' + eJz + (-r' -.r):
11'+ /r,
-
e,): +
1.r,
(18.78)
e. g. y and .r is altered continuously given values for losses Pi; and P;i the until, with the calculated value of temperature rise at the point P(-r, _r') exactly corresponds with the given value of A9,. In most instances the eccenlricity e can be neglected (see Section 18.4.3).
a fixed coordinate
In Fig. 18.27 the cables 1,2.,... i... N are shown u their mirror images to the ground surface. The .r aX is located at the ground surface. It is assumed that the circles with the characteristic diameter lay u ithin the dry area. Since the characteristic diameter based on the lower value of thermal resistivity of the moist region will be somewhat too large, the results will be on the safe side, The same applies if the extent of the dry area becomes smaller than the circle with the characteristic diameter.
With the aid of equation 18.78 the isotherms in the moist area can also be determined (Fig. 18.28).
Fig. 18.25
For this A9, must be replaced by the temperature rise of the selected isothermal line. The isotherms in the dry area can not be established using this relative-
Groups of cables referred to in the text
ly simple method.
208
Crouping in Cround Massing faclor
E,i
Number
of
cables
18...1
og=1.0 KmM
r0
I
20
8
7 b
15
5
---s,=2.5
KmM
j
Qe
=
1,0 Km; W
3u=10'C
Ail.=li
-2
J 4 56 8 t0 t5 20 25J0 Rario j-_
rrr
K
Fig. 18.28 Temperature ficld of trvo cablcs
= 0.7
Nyy I x l j0 0.611 kV
Fig. 18.26 Crouping factor Id relative ro depth of lay fi and to spacing distlnce .r. and rhc numbJr o[ cabies in rhe trench in relation to a cable on the end of the rorv
Example 18.8
Four circuits t)pe
of bunched single-core
NA2XS2Y are arranged
1
x
150
in the
cables
of
the
RMi25 t2l20kv
same trench. The clearance is
cm. The cables are to operate to the specified conditrons in Table 18.3. 7
The centre spacing of two bunches is (Fig. 1g.29)
b:2 d+70 mm:2
x 35.7 mm+70 mm= I41.4 mm.
The electrical and thermal data for a single bunch was calculated in example 18.7 (see page 204, Section 18.4.3). The calculation for a group of such cables is made in respect of a bunch laying in the centre (cables 1, 2 and 3): Fig, I8.27 Heating of a point p(.r, y) by cabte
i:
l, 2,3, ..., N
a, +1iv,- tl1s- t; tnt,]. # -" fir'.r"t, 12 rv+ t
(lE.6g)
l8
Current-Carrying Capacity in Normal Operation
/7/////777.. t, r.,.//,, //////////./,
///L ////////z z//,' /.
12.
the outermost bunch. The factors for the cables,{ to 6 as u,ell as the factors for cables 7 to 12, in each case relative to cables I to 3. must be determined and then summated. For bunches of three single-core cables the value established in this way must be multiplied by 3.
h 0.7m -'-'b Fa\r-:-:1 0.14 m 9
) di :JXjxiJ:lJ.J, l:
l:
:-"t
:-'
lo
9
.-Ti.:. l r1qi - 1il=Jqi | -' 1--t
+
rr
Fig. 18.29 Arrangement of installation for cxample
18.8
R'*, (T'*, +
@
_-r/L
/
I x 0.169 x
I;,
+A
]"l')
I0 - ' t0.169
-
(18.i7)
3.+45 + -1.1r'>.
= 223 A.
\earl) The characteristic dianreter r{:0.286 nr is greater rhan 26 = 0.130 m. Therefore u ith ,V" :9 and with equation 18.72 as well as equation 18.76 one obtains 19
^ -:-t) 1rl" 1.5
I a,+(9-3)(ir-l)lnt,lJ ' +u' sTr
D
f. x.J ln
;-lJ :tt L
+p3xr
4hl
+te-3Xr-r)ln4l
+0.553 x 3ln
- l) ln:*-ql u.l86l
:fr?( [tr.as+0.s53 x 4.89-6.12] =
Two three-core cables type
NYSEY
3
x 185 RM/25
6i 10 kV
are arranged in the same trench \t ith a clearance b''. tween them of 7 cm and are to be operated to the specified conditions in Table 18.1.
The other cables in Fig. 18.30 are not loaded. The following electrical and thermal values are available from Part 2, Table 5.1.18: Ri",=0.121 O,&m, I, = 394 A, Pi = 3'7 win' = 68.8 mm, (reference diameter)
d
= 0'364 KmAM' Iica=0'253 KmAil'
The grouping factor E 61 can also be determined from
210
Example 18.9
Ih
4. 15 Km,AM.
Fig. 18.26. The factors
from Part 2 Table 5.6.6a: /,:320 A. from Table 18.1 5 : /, = t.O, from Table 18.17 : fr=Q.l , and I,: J,xf' x.[ :320 x 1.0 x 0.7 = 224 A.
(18.68)
nffi.t.
+ 6(0.553
the sarne result can be obtained by reference to Section 18.2 and Part 2 using the following:
in this figure are given for
4r
Ti
= l'071 KmAv'
=La74Km[w.
-
Crouoins in Ground 18.{
with
.\,:2
|{.2
IJt:tJr:2.31
and
)2
J
,' )i ll"j=i:fd,:i x2.31 )fr
{t8.6e)
:O.S19 rmAV;
| _ | / 10 -
20
- y
-
3.7 (0.253
J x 0.121 x
+
9)+ [(2.5 1.0]- rl :s 10.36.tt 1.071 +0.j15)
1..r74 +0.91
l0-r
:331 A.
Fig. 18.30 Arranseme nt of insrallarion for erample 18.9
Current-Carrying Capacity of Dissimilar Cables The load capacity of one cable
is
, _., /l+,-}r-P:(T;d+T.)-[(q./qJ- l] AJ,
V
nRi,(fi.,-
f',")
,lR 61r
/
_1/ ta-jo-J.7(0.251+ 1.474)+ [(].5/ 1.0)_ ll 3 x0.12[ x l0-](0.364+ 1.071) V
25
=394 A
z1=
AS,,=
70 mm +
a; 0.7 m __j.=_=504 a
Apart from the ,V cables being similar to each other (indicated by the index i), as shown in Fig. 18.29, there are orher M cables being similar to each other (indicated by the index j) accomrnodared in the same trench (Fig. 18.30). If the loading of these M cables is the same this results in mutual heating, for instance. the trefoil-arranged single-core cables indicated by 1,2.3 are heuted by:
f;,
d:70 mm+69 mm= 139 mm
+qj{*ft'r,,+pjtyij+ i
0.139 m
\-"1I
2
From Fi-e. 18.26
The grouping factor for
Irt:2.31. I
For m: 0.7 from Table 8.31 I = 0.553 and d" = 0.286 m.
ia,,
^
4,: *l
*r i a,+1ru,- l)tu;-l) rnk,l Mv'l I
;
=0.515 KrnrV.
1
f
\\.,
*
(h,-
M multicore
!')',+'i: h,)z + al,'
J) cables is
(18.80)
three-phase conditions the ratins factor becomes
J
: ) \ [2.31 +0+(2-
in
ti,+.\ryiitti-rrrnr,l} I
for N bunched single-core cables operating under
From example 18.7 kr:9.69 and hence
^ r.Y, ia, -"L2
=
(r 3.79)
frfa,,+
(i8'58) l)(0.ss3
-
1)
ln e.6e]
1u,-tir"fffi.
(18.81)
If all N
cables are loaded at the same level the current-carrying capacity of the trefoil-arrangement (or cable) in question is: 271
l8
Current-Carrying Capacity in Nonnal Operation
''
l/
n
(r 8.82)
R*,i(T;ji+ rl,,-ATl,r)
If the load capaciry of the M cables is to be investigated in respect of the heating from the group of N cables the indices in the equation above need to be interchanged.
Mr;; is the number of cables in group j, whose circle with characteristic diameter drl embraces the cable considered of the group i. Since it must be assumed that all cables N and ,'11 are situated in the same dry area the boundary isotherm must be determined by using the larger of the trvo load factors al; or
The loading of the 10 kV cables is now to be 200 A each at a Ioad factor of nt:0.7 and d":0.286 m (Table 18.27). drl2 is therefore less thin the smallest spacing /rt-ft,:0.3 m at aii:0 in Fig. 18.30 and hence ,l1r;1 :0. Using equation 18.80 in relation to the axis of the bunched cables 1, 2 and 3 with a', : 0 compared with a;1:0.14 m (example 18.9) we get
v ,4r n-,-n 7r.:-0: 't--'.. f ;.=1n17t'"-" ; ' / (1.0-0.7)'+0'
rrl (eQuation 18.56).
Using equations 18.64 and 18.65 the assumption that the soil is drying out must be verifled. Should this not be the case then in all equations g! must be re;laced by gu.
*ln
(1.0+0.7):+0.1.11 (1.0-0.7):+0.1.1:
(r8.80)
_ 1 1-7
With the quantities from erample
18.9
rle
get \-/
Pij:,r/i R;,, The cables from example 18.8 (Fig. 18.29) are installed at a depth of i': I nt 1Ot=. 18.30) but otherwise are operated under the sanre conditions.
From Fig. 18.23
it is found for li:1.0
m. nr:0.7
and d:35.1 mm
f":3.7
43,,-' = 3.7
have simplified (see example 18.8) in
6
(18.79)
6,
+
,,.\
=
ld,:3
(2.65
195
A.
(18,,_,
Additionally, it must be ascertained that the 10 kV cables are not heated excessirely by the 20 kV cables thus
P::rI?
P'
(18.3)
=1x1952x0.269x10-3 :10.23 Wm.
L2
+4.62):21.81,
Also in this example drl2 is less than the smallest 0.553 x 11.81 = 4.80
KmfV
and
,-@
1x0.269 x 10-r(0.469+3.7+4.80) (18.77)
)11
-r 14.52= 10+0.553 x 3.37+01 ln
K
V
from Fig. 18.26 the values 2.65 for two cables and 4.62 for three cables are found. For the load capacity rf N= l2 single-core cables with a depth of lay increased to I m, but still ignoring the influence of the two three-core l0 kV cables M situated above, we
V
)fi
?i
3.37
,.@txo.:69 x lo-r(0.469+3.7+4.8) =
1Il,'!ft=
:
and the load capacity
0.140 m
f
)i -
:15.7
1.0 m
16,:
14.52 Wi m.
The temperature rise caused by the trvo 10 kV cables is therefore
Km/w'
For the ratio
lr' b
(18.1)
: 3 x l00r x 0.121 x l0- r:
Example 18.10
distance
hi- ht:9.3
and therefore lr'r;; = 0'
-
Installation in Ducts and Pioes 18.4
(18.3r)
A9;;= 0+ t0.23
?<
;[0+0.553
x 19.34+0] = 43.53 K.
(r
, - 170-20-3.7(0.253+ 1.474+0.919)+[(2.5/l)- l] :5-43.53 3 x0.l2lx t0-r(0.364+1.071+0.515) v
Since the loading with 200 A is smaller than the load caoacity of 120 A, the 10 kV cables are not heated i .:ssively. The interdependance of load capacity of a group of cables on loading of the other group can be seen by reference to Fig. 18.31. At the point of \ersection of the curves the temperature of the con, tors are at their maximum values of 90 'C and 7u"C respectivelv.
1.,=331 A at
(18.82)
18.-1.5 Installation in Ducts and Pipes
As rvell as the thermal resistances descnbed earlier additional thermal resisrances are involved (Fig. 18.i2)
P
the thermal resistance ?l of the space between the cable surface and the inner rvall of the pipe and
D
.-;:--
the thermal resistance f{ of the pipe (with metal pipe ( is insignificant).
Thermal Resistance
{=0
8.79)
I(
of the pipe
The thermal resistance 1.x of the pipe is derived from the specific thermal resistance ofp" ofthe pipe material. the outer diameter d* and the thickness 6* of the pipe wall with
Qn, / R = :In -------. zIt , l)p, I
(r
8.83)
'-4
Thermal Resistance
Ii
of the Internal Space
The thermal resistance 7i of the space whether filled rvith air or gas is determined by iteration [18.42, 18.431:
(18.84)
1,,=211 Aar I,=0 (10 tV
100
A9": T' ,*
cable '
150
200
A
250
1r'
*
(18.85)
"r.
The equivalent diameter ds in m for cables with diameter d is
Currenl Ir
Fig. lSJl Load capacity interdependance o[ two groups of cables trom example lg.9
-
for for for for
one cable in a pipe
aE- ut
two cables in a pipe three cables in a pipe four sables in ri pipe
de:1.65d, de= 2-15 d ' de= 2.3Qd.
zt)
l8
Current-Carrying Capacity in Normal Operation
The mean temperature 9. of the air space for n* cables is celculated by approximation
r- =1s.. -,r, - r
s.
+($ - r)a s,l \tE/)
Conducto. lemperalure
t1-
Conduclor losses Thermal resistance
'
ol insulalion
lossesPJ
l'l, Shearh losses
"-(?*n*t:,) ]"ki +
nR
(1.; + i';r +
Ij
T; J*
r;l',"($+ rl+ r:,)
Armour losses
l.
t'-(*-')"" "l
Thermal resislance ol inner layers
Thermal resistance of ourer shearh
fj
(18.86) Thermal resislance of air space
I;
is obtained from equation 18.3. Pi is obtained
from equation 18.4 and the dielectric temperature rise lrom
A3o=P' [Ti.o+n*(Ti'+Ii + T:)].
(
Thermal resislance
oi pipe I,{
18.87)
The constants a. b, and c rvhich depend on the type of pipe and arrangement can be taken from Table 18.i2. The pressure p for cables in pipes is I bar.
For a temperature dillerence of A3"= 20 K between pipe inner wall and rhe cable surface for cables in an air filled pipe and Agp:10 K for gas pressurised cables taking account of a limited range of diameters
Thermal resislance oi qround
Ij
Ioral losses P.'-
&
PJ
Ambienr lemperalure
Fig. 18.32 Equivalcnt circuit for the thermal florv from cables installed in a pipe in the ground
de= 15 mm to 100 mm for cables in pipe
d:=
75 mm
to
125 mm
Table 18.32 Constants a, b, c,
for gas pressure cables
A,8, C for the calculation of thermal resislance di for installation in ducts or pipes "
the simplified equation [18.a2; 18.2]
I + 100
(B+Cg-)
(18.88) dE
is used with constants A, B and C to Table 18.i2. In addition iteration using equations 18.86 and 18.87 is required (d, is to be applied in m). A rough calcula,ion is possible rvith Fig. 18.33
Typc of pipe and arrangemcnt
a
h
c
Cablc in mctal pipe
11.41
15.63
0.2r96 5.2
c
.4
0.01
l0
Cable in hard iibre pipe (fibre r) duco
in air in concrete
I
l.4l
4.65 0.1163 5.1
11..11
5.5 5
I l.4l 11.41
11.11
0.r808 5.:
0.83 0.0061 0.91 0.0095
Cable in asbestos
ln atr in concrete
0.1033 10.20 0.2067 5.2
t.2 1.1
0.0055 0.0110
Cable in eanhenwarc 1.87
Prpe
Gas-pressurc cable in stcel pipe (14 bar)
I
l.4l
15.63
0.46 0.0036
0.2r96 0.95 0.00 0.0021
High-prcssurc oil-lillcd cable in stcel pipc
0.26 0.28 0.0026
r) For plastic pipcs valuc! not yal incorporalcd in IEC
rr
214
28?. It is rccom_ mcndcd to usc lhe valucs fot hard fibrc pipc as an aPProximalc calculatior|. For inslallation of thc pipcs in ground $c constanls for piPcs Hdcd in concrctc :nay bc uscd Bitumcn imprcgnatcd wood fibrc
Installation in Ducts and Pioes 18.{
1.2
1.0
08
08
(,
0.6
oz
1.5
2
3 4 5
Equivalent diametet d
7 cmt0
E-
a) Hard fibre pipe in concrete (as an approximation also for plastic pipe in concrete or in the ground)
t.t
2
3 4 5
[quivalent diameter
d
7
e-
cm10
b) Asbestos-cement pipe a
in conclete or in the ground
l_t
2
3 4 5
Equivalenr diamerer
7cmi0
d.-....-........-
Earthenware duct
in the ground
Fig. 18.33 Thermal resistance of rhe air space between a cable and a pipe
?t
5
- 18 Current-Carrying Capacir; in Nonnal Operation Load Capacitl for an Installation of Pipes in Ground or in Air
The load capacity for cables laying in the ground can be calculated from
91.-9E- P; [Tid + rR(T;+ T;i+ 4)+A 4] +[(q'iqJ- l] AS' rr R*,ITi, + rr*(?"i + ?i + I:y)+ A 71"]
(
18.8e)
The number of cables in the pipe is n* and n is the number of loaded conductors in each cable. Tlre thermal resistances of the soil Ti and Ti, are calculated as in Section 18.4.3 using the diameter of the pipe '*. The additional thermal resistances A7l and Al" taking account of grouping are calculated as in Sec-
tivity does not exceed a specified value qu in the driedout stale. Normally qo
tion
In duct banks the power cables are to be arranged only in the outer ducts as indicated in Fig. 18..'' [18.aa]. The heat dissipation from the inner piper' of a duct bank into the ground is signilicantly less
13.4.4.
If the load capacity in air is required the quantity I thermal resistance '1"., for an installation in air as in Section 18..1.2 must be inserted rvhile the ther' mal resistances I , 4,., Aq and Ad, are omitted. Load Capacitl' for an Installation in Ducts Banks
In some industrial installations the cables are installed in duct banks at 0.6 m depth or greater (Fig. 18.3a). The ducts are firstly installed in layers with the aid of distance pieces and then bedding or filler material is compacted after each layer is positioned. The clearance between ducts must be selected wide enough to ensure proper filling. If normal sand is used for this the load capacity to equation 18.89 r appropriate. Horvever a thermally stable bedding material (see Section 18.4.6), e.g. a suitable concrete mix mav be selected provided that the thermal resis-
favourable by comparison to the outer pipes because ol the obstruction caused by air in the outer pipes. If porier and control cables are to be run together the power cables. because of the better heat dissipation. are preferably arranged in the upper layers.
It
must be assumed that the soil dries out around the pipe block rvith dimensions,r and y and the equivalent diameter do to equation 18.90. In the zone em' braced by the equivalent diameter du and the diameter of the boundary isotherm d,, therefore, one must calculate the corrective thermal resistances fi- and 7f,r'. using the thermal resistivity 9.. Outside the diameter d, calculations are made using the thermal resistivity 3s for moist soil, rvhich is intrc duced through the correction term in the top line. ''-
77V 7v-/2 VZV ZVZ 7772-T l>o.sm
lool loool lool loool looool lool lo@@ol lool lo@ol loool lool lool lo@ol lo@ol looool loool leel lgSl lool @ unsuitable for power cables
-
Fig. 18.35 Fig. 18.34 Arrangemenr ofducr banks )1A
Examples of arrangement of pipes in duct banks
I
Installation in Ducts and Pipes
The equivalent diameter r/o of the duct bank with dimensions x and _u is (Fig. 13.16) [ I8.2] I I.r /+ .\\ . /. t:\ .ls=lexpl;;(;-;)ln(l+,)+ln;1,
[quivalent radius
18..1
rl
r" cm
.rl
I
60
(13.e0)
70
L- -, \,"
whereby one has to select ,r < y and I
.I
60
< 3. )u
The geometric lactor is
40
r"=]*1f$-, ds V \us/ i
(r8.9 r)
30
20
,
assumed that ./,>
/B therefore drying-out of the
soil occurs and for the corrective thermal resistances for multi-core cables and d*> dy> dB .V
a--s':qrl.vornko+ f ln L
.,
j,
(18.92)
l.
.t*, I
r
-,''. T;;:a-'u|.Volnku+4 f t.,
o,
-.V,t4-l) rn r"]; (
multi-core cables and d,> dB>
dy
['
irom equation I 8.92, tBv=IttB;
single-core cables and d,> d.!>
13.93)
(I (
20 30 40 50 60 80 100, cm 200
Fig. 18.36 Equivalent radius r, = r.lrl2 of a duct bank rvith dimensions r and _r' in Fig. 13.3.1, where ;s 4 -1' provided rhat
,r'-rSl
Lastly it must also be investigated rvherher the assumption r/, > ri u applies: J,
18.93 a)
=
.l lrs
L.
;;f-:,
(18.66a)
rvit h
dB (
'ir!,', from
(l 8.93 b)
equation 18.93;
18.92b)
k, = exp
2r /3, q, N, (p Pi+ Pi)
(18.e4)
and Pi to equation 18.3 as well as Pj ro equarion
".ngle-core cables and d,> dR> d"
18.4.
from equation 13.92.
r*: Pri
l0
8.92 a)
?'i,* from equation 13.92
Tf
r0
(I
8.92 c)
(18.93c)
.
If d,
For the load capacity an extension of equation 18.89 is used 3..
- ji
+ rR + T;)+A rB + rii] +A0, l(eJ e e) n R*. [Ti.1+ n* (I; + Ii + ?"By) + A T;.r + T'l [Ti
(ft
a (
18.95)
The thermal resistances Ti, Ti, and A!i, are calculated in line with Section 1g.4.3 and 18.4.4 with g, replaced by pg. This corresponds with'the assu#ption that rhe thermal resistivity outside the pipes has the uniform quantity qu. 217
l8
Curren t-Carrying C4pacity in Normal Operation
18.4.6 Soil-Thermal Resistilitv
Backllll
Cable in the Ground
To avoid
An accurate knowledge of the thermal resistivity of the soil and the bedding materials not only allows optimum utilisation of the cable up to the permissible operating temperature but also prevents early aging or destruction due to excessive heating [18.18 to 18.201. High soil-thermal resistivity - as a consequence of drying-out of the sround - are particularly dangerous for highly loaded cables in continuous operation in unfavourable ground conditions.
If
the slightly rvider surroundings of the cable are included in the consideration. three areas can be de(Fig. 18.37) which under certain conditions -scribed i, .nay have different thermal resisrivities. The three areas can be distinguished as follows:
damage to a cable construction good ground, free of ingredients such as building rubble. clinker, etc., should be used for backlill and should be sufliciently compacted [18.6; 18.21]. Normally the excavated soil is suitable for this purpose. The physical and thermal characteristics can be approximately equal to those of the virgin soil (Area l). Bedding Material Bedding materials. in line with the requirements discussed earlier [18.16; 18.21] should be free of stones
and should comprise sand or other compacrable type
of soil rvith a maximum particle size of l0 mm. This should be Iaid in layers of l0 cm and compacted by
Virgin Soil
' -,f this is undisturbed and is ri ithout significant inclusions of humus (moorland) the soil-thermal resistivity
is normally, for European latitudes. no more than I Km lV. Care must be taken u,here the ground is made-up and is only partially consolidated rvith a mixture of slag, ashes and the like. included. In such it is advisable to measure the thermal and ohvsical orooerties of the soil. cases
Table 18.33 Quantities of soil components
Dry density
Thermal
t ml
resistility KmrW
Cranite
2.5 to 3.0
0.32 to 0.25
Basalt
).9
0.6
Feldspar
2.5
0.43
Basic ele
mcnt or
ma t cri:L
I
Glimmer Mica
1.7
Gneiss
0.19
Limestone
2.5
0.78
Quartz
2.5 to 2.8
0.ll
Sandstone
1)
0.54
Slag
0.3 ro
Organic
l.l
1
to 3.5
4
materials,
molst Area Area Area
I I 3
Virgin soil Backfrll Bedding material
Fig. 18.37 Thermal-resistance areas surrounding a cable laid in
ground 218
Organic
1
materials,
dry Water
Au
I
1.68
40
Soil-Thermal Resistivity
18..1
hand compactors up to a cover of 30 cm above the cable. Below the cables hard parts such as rocks or boulders should be replaced by filler material. Bog, peat, ash and building rubble as well as chemically contaminated earth should be replaced to a distance' of 20 cm by liller material. Here also the previously excavated soil can be used providing it has suitable characteristics.
Physical and Thermal Characteristics of Soil
Soil comprises three basic components. It consists ot-granular particles of material rvhich differ in their d ,nical and mineral constituents. size and form of particles, parlicle size distribution, density and moisture content. Between the more or less compacted pn(ticles there are cavities, or pores, which may be , d with either rvarer or air. The air contained in
I
Soil parricie
2 Skin of water 3 Hygroscopically bound wxter 4 Pore filling water Fig. 18.38 Fine granular particles and water Iayer
the pores may itsell contain rvater vapour depending on the temperature.
Heat is transferred in such amorohous materials bv conduction.
A
comparison of the thermal resistivities in Table 18.13 indicates the extent to which the total thermal resistance is related to the constituents of the soil.
The individual soil particles have molecular like powers of adhesion and attract a layer of condensed water. This hygroscopically bound water does not move and can be removed only by changing it into vapour, for example by heating to above 105 to )'C. Fine granular soils bind in this manner more than coarse grained soils- The amount of ^Ier r/!,und water also depends on moisture content as well as pressure and the temperature of the air in "-: soil.
Ifsuflicient water is present in the soil, the hygroscopically bound water is covered with an additional concentric skin of water (Fig. 18.38) which connects neighbouring particles as pore filling water. This improves heat conduction since, in comparison with air, water is a good conductor of heat and the pores become heat bridges. The amount of skin water is subject to great variations which are caused by storage of penetrating water and its evaporation. Especially ln the temperature zone of cables a reduction of water content is to be expected even up to completely dried out. Even in this case it is important that the thermal resistivity remains sulliciently low. To meet this requlrement it is necessary that the conrent of solid
material relative to the content of pores rr is Iarge. Such mixtures with reduced caviries have a high resulting dry density 70. The thermal resisrivity reaches a minimum when all pores are filled with water i.e. at maximum water content Ie. The above mentioned values can be determined by reference to DIN 4016 or from an information sheet prepared by Forschungsgesellschaft ftr das StraBenwesen [ 18.34], e.g. using the Ddrr-Wiige-Method. The following relationships exist : Water content
,r=i-
Pore content
n:l-!
ia
I
(18.96)
(18.97)
where
73
particle density, i.e. the relationship of dry weight of solid material to the pore-free volume (in non- or weak binding soils y"=2.65 tlm3),
y6
the dry density, i.e. the weight of the dry soil relative to the unit volume.
y
the density of moist soil,
i.e. the weight of the moist soil relative to the unit volune. 219
l8
Curren t-Carrying Capacirl in Normal Operatiqn
To obtain the most densely compacted soil the pores bets een the larger particles should be filled with particles of a smaller group such that a less porous mixture is developed. Such an ideal grain distribution is shown on the distribution diagram as a parabolic cun,e (Fig. 18.39 curves I and 2) and can be treated analrricallv with equation p
= (dld-",)'.
(l 8.e8)
oniy a small variety of particle sizes (cun'e,1 in Fig. 18.39). Well graded soils, in rvhich the smaller particles fill the pores between larqer particles have a more flat or parabolic shape of curve. The relationship is expressed by U = d6sld
(
16
with du6 the particle diameter with 60%
18.99)
passing
through the sieve and d,o the particle diameter with this p represents the part of the weight of sieved material rvhich passes through a mesh u'idth of "equivalent diameter" d, ci.", the diameter of the largest ,eranule of the mixture, r=0.5 according to Fuller. .r = 0.25 to 0.4 according to Talbot and ::0.11 to 0.514 according to Jahn 18.221.
ln
The particle size distribution curve can be derived according to DIN 4016 or can be found in a paper of the Forschungsgesellschafi fiir das Stra8enrvesen _l8.ja], in $hich the sieved material is treated using a series of mesh widths. The point A in Fig. 18.39 on curve number 4 signifies that 739lo of the total mass of sieled material has a sranular diameter of < 0.63 mm.
The steeper the particle size distribution cune the more uniform is the material i.e. it is rnade up of
l0%
passing through.
Soils having U < 5 (steep curve) are classed as uniform whilst soils having U>51flat curve) are classed as
non-uniform.
From the parlicle size distribution curve the ease of compaction can also be recognised. Easily compactable grades normally comprise well graded. ueak or non-cohesive sands (also sand gravel mixtures) \vith U> 7. Soils are classified as non-cohesile rvhere !l; have a low content of silt and clay (approximately < l0%), do not tend to form clods and therefore remain loose and flowing. They permit cavitl,-free fillinu of the trench and especially in the vicinitl' of the cable. In mildly cohesive soils lhe individual particles adherc to one another and form a modular mass. they are therefore less suitable as a beddine material and
Besidue in
sieve
0
%weiqht
10-
t-1*
t*
i'i'
*l-F qn
40.i-
*t+I
4n
170
--l l-
{eo
t" I
10
^l UT
0001 0002
r10
Particle size distribution curve
to equation 18.98 with
x:0.3
Crushed limestone (residue
from splitting opelation) Probe No 6 from Table 18.35
Building sand Probe No I from Table 18.35 Sand-loam-mixture
+100 20 mm 63 100
6.3 l\4esh sire
220
Particle size distribution curve to equation 18.98 with .r = 0.5
Fig. 1839 Particle size distribution curve
Soil-Thermal Resistivity 18.4 require a more intensive compacting. Furthermore
Ory
density;o
some kinds oi soil, depending on water content, tend to srvell and shrink which can lead to the formation of cracks and cavities in the vicinity oi the cable
where rvater content alters due field of the cable.
to the temperature
The ease of densifying or compacting depends very much upon the water content during compacling. By use of rhe Proctor apparatus [18.34] the most favourable water content and the highest dry state density for compacting can be determined by sample investigation. For this test a probe is applied to several samples of soil, each having a different water content. F.ch sample is compressed in three layers in a cy,.,.dn:al test vessel of say, l0 cm diameter and 12 cm hright. The apparatus eives o. consistant compacting effort, relative ro rhe volume (60 Mpm/m3 kJ/mtr) - known as rhe Proctor effort. This ^588.4 )rt is derived from a weight of 2.5 kg falling through 30 cm with 25 blows for each of the three layers. The resulting dry density is depicted in curves shorvn in Fig. 18.40. This investigation shorvs rhe degree of compaction achievable depending on the type of soil - degree of non-uniformity - and materials. With a content of approximarely 5 ro 20% of silt this not only fills the pores between large granules, thus ensuring a higher dry density but also in conjunction with water acts as a lubricatine asent when
0510%15 Waler conlent
I I i
i,,/
+
Sand Sand and silt
Gravel, sand and powdered stone
-1 Gravel. sand and silt
Fig. 18..{0 Proctor curves ;o =fru) of various types of soil
comPacting.
The particle shape also inlluences the dry density. Round particles result in higher values in comparison to flat or crystaline shapes.
A marked influence of chemical-mineral composition on thermal resistivity is noticeable at high values of 7 density and low water content. Sands and eravels containing quarrz are, because of their reducei thermal resistivity (Table 18.33) preferred. Where soil contains, apart from large gravel and sand particles, sulficient silt, the water binding capacity and also the good adhesion of the larger parricles is noticeable. I ests have shown an improved heat conductivity for this mixture. Because oi its surface tension thi silt forms a film over the larger granules and draws itself mto the pores. Heat conducting bridges are formed lrom the solid constituents which remain present even when the soil is completety dried out. This phenomena can, however, only be readily obsenid when pnor to drying-out a certain minimum water content ls present.
A large number of
tests have been conducted to establish an analytical relationship between the physical properties ofsoil and its thermal resistivity [18.23 to 18.27]. Direct measurement of thermal characteristics is however preferred to all other methods, since this provides the most accurate values. For the interpretation of beat conductivity processes in soils, it will be inevitable even in the future to occasionally make these thermal investigations.
The relationships between thermal resistivity, density and degree of humidity for two types of soil are shcwn in Fig 18.41. 221
l8
Curren t-Carrying Capaciri in Normal Operation
llhermal conduclivrry i-l
l"url-J #:
i
llnermal conduclivily i.r
| fiiil i
I
ll,l
3.0-.--r--------r:--
2.5
I I
I I
\
t
I
l I
\
\
\
Moisture Volumelric content
in%
20
010
I
30
40 50 60 VoF% 80 PorositY....-.-..........-
2.5 tlnr 2.0 __0ensiry a)
1.5
2.0 .-2.5 r/mJ Densrty
1.0
b) Soil
Sea sand
Fig, 18.41 Thermal conductivity l"u and thermal resistivity ofsoil
g.= lli.p relati'te to density
and materials at
20'C 18.401
-lnfluence of Moisture Content
The moisture content of soil is dependant on
a
number of natural factors [18.30]:
D
F ))')
Diflerent types of soil have dillerent capacities to absorb water and to retain it. The smaller the pores the better the water retention. Loam, i.e. clay containing soils dry-out much slower than sandy soils [18.28]. Crushed stones, gravel or made-up slag have no water holding capacity. The water table can re-wet the soil where the soil has sufficient suction [8.29]. The moisture con-
tent of the upper layers is dependant upon the water table level. In large-particle poor soils the suction can be zero but in coarse sands it can be 0.03 m to i.0 m and in loam I m to 30 m. The surface contour can provide either a drainage (hill) or containment (valley) effect.
Roots of shrubs and trees dry-out the soil during periods of low precipitation. Sandy soils are affected more so than Ioam.
Road surfaces or other coverings Drevent
free
Soil-Thermal Resistrvity l8.J evi.rporation of rvater from the surface so that the moisture content below (hem mav be present higher than in the non-covered surroundings.
tr
Precipitation provides a major proportion of moisture input to the ground.
tr
Solar radiation, both duration and intensity together with wind, surface characteristics and vegetation influence evaporation.
tr
The moisture content of the soil and hence its
thermal resistivity follows an annual cycle which is controiled by the influences mentioned above and also depends on the tlpe of soil and deprh. moisture content can also result from pret -High eding $ecther conditions. Heavy rainfall or tharv can also influence deeper lavers and can cause a rapid change of moisture content parricularlv ,;in sandl soil. To predict moisl.ure content is mosl lifficult and cxn only be considered as a rough . -approximation. It requires observation and experience or er many years.
In the vicinity of a cable (area 3. Fig. 13.37) rhe temperature field influences the water holding capacity whereas in the more distant surroundings (areas 2 and l) the natural variations of water content described above are mainly related to the climate of the soil. The temperature {ield of the cable causes the vapour pressure in the vicinity of the cable to rise and the water vapour held in the air contained in the pores of the soil to move awav from the cable. This action causes the capillary suction in the soil C 'e to the cable to increase so that the water returns !p.,{he cable in liquid form. If the remperarure of rhe , ,le surface exceeds a critical value of 30"C for sandy soils or 50 "C for loam at ambients of approximately l5"C to 20'C, this circulation cycle is inrerr. - ied and the cable surroundings dry-out up to rhe critical isotherm. As tests have shown [18.18, 18.23 and 18.311 rhis cycle is mainly time dependant and can be suddenly interrupted by rainfall and may even be reversed. In some instances the dried-out zone extends only a few centimeter but can, in unfavourable conditions cover the total area of the beddinq material and beyond. The selection as well as coripaction of the bedding material is therefore of significant im-
I Precipiration
l''l
I
j50--
mm
-r---"1
50 0
.lnbie
renperal!re
?0
"c 15
i0
speciiic soii rhermal resistance p,
-..--.---
(hnffsglsd ground d1s3 within a diameter of 30 to 60 cm Area within a diameter of l0 to 30 cm Area within a diameter of l0 cm
portance for the temperature rise and the load capacity of the cable.
Fig. 18.42 illustrates how weather conditions combined with a typical cable loss of 82 Wm can influence the drying-our -:ress. F
Fig. 18.42 Load test in open country (Erlangen 1968). Influence of climate and cable heat loss on drying-out of the soil :J)
l8
Current-Carrying Capacitf in Normal Operation
The cable has a diameter of .10 mm and a depth of lay of 0.9 m. The made up soil consisted of a sand loam mixture l'ith a unilormity index U = 144 and was used as back fill as rvell as bedding material (curve 5, Fig. 18.39). The drfing-out process commenced in July as a (delayed) consequence of increasing duration of sunshine and soil temperature with reduced precipitation. The re-wetting commences approximately mid-November.
r\n equal distribution of moisture u,ithin a partly dried-out test sample can be achieved by heating for a sufliciently long period rvith the vessel closed (Fig. 18.a3 b). Apparatus which can be used on site in open country to measure thermal resistivity is commercially available with variable expenditure of measurement and time [ 18.32]. Basic Quantities for Calculation
To facilitate the calculation of soil-thermal Measuring
- Measurements [18.3. 18.30] are only truly meaningful i if next lo the lhermal resistivity the moisture content, density and erain size distribution curve are also mea-
i
sured. Measurements in open country at depth of lay need to extend over seleral years to determine the annual differences of moisture content relative - to l'eather conditions. These can be on a Iarge scale and are therefore very costly and quantities gained from experience are normally used instead. A quantity specified in DIN VDE 0198 Part 2 of 1.0 KmTw is normally used except for areas such as
f tr tr
.
suspected slag, waste or peat, continuously loaded high-voltage cabled or if basic investigations for general application are to be conducted.
The thermal resistivity can be measured e.g. by use of a needle probe. In Fig. 18.43 apparatus for laboratory measurements [18.33] is illustrated. The sample of moist sorl is compacted, using one third of the Proctor force (200 kJ/m3) (Fig. 18.43a), together with the measuring probe. The reduced Proctor force is used in order to take account of the hindered compacting which is often the case in a cable trench. The probe is heated by means of a heating element wire (Fig. I 8..13 d) while the increase in temperature is measured by means of a sensing resistance wire. Thermal resistivity is calculated from the temperature nse.
Measurements need to be conducted on a moist, partially dry as well as on a totally dried-out sample
whilst the warer content rv as well as density 7 need to be determined in each case. The graphical representation of the measured values (Figs. 18.44 and 18.46) characterises the type of soil investigated.
To dry or completely dry-out the soil sample,
the vessel must be rearranged (Fig. 18.43c) and placed open in a heating cabinet at 105 "C.
resis-
tances (Section 18..1.3) and to establish the load capacity tables (Section 18.2.3) the relevant quantities
for ambient conditions had to be aqreed as a basis. -fhe thernal resisriL'it.;,, of rhe soil wvlfected br heat fi'otn u cable -the moist area - s'as fired at 1.0 KmW. Measurements made previously in Germany rar produced quantities in excess of 1.0 KmlW u ith tH exception of very dry sandy soils, made up arels. or in areas which contained industrial wastc e.g. building rubble [ 8.3 ], 18.i5]. A large number of the quantities measured were below 1.0 KmrW due to the relatively high loam content within the soils having good water retention capacity, or due to a preYailing season of high precipitation at the time of measurement. If quantities of less than 1.0 KmAV are to be used these should be verified by sufficiently long periods of measurement and should embrace at least one dry period. It must be considered aiso that when the cable is installed the ground is disturbed. This means that the bedding material surrounding the cable and the back llll in the trench up to the ground surface is not so highly compacted as the original soil and the favourable characteristics of the und; turbed soil will not be fully achieved. Backfill ar\l bedding material can, depending on the selection made, have characteristics inferior to those of the surrounding soil.
'fhe thennal resisliuity oJ the dried-out soil was agreed as 2.5 KmfM. Laboratory measurements made on test samples which had been dried-out at 105 "C indicated, depending on the type of soil and degree of compaction, quantities between 1.5 and 3.0 KmflV. Contaminated soils have much higher quantities [18.33]. The permissible operating temperature in modern cables ranges between 60'C for 30 kV massimpregnated cable and 90 "C for cable with insulation of XLPE. The surface temperature of such cables is however less than these quantities even after taking into consideration heat from neighbouring cables or
-
Soil-Thermal Resistivity 18.4
End plare
Hearing and measuflng pr00e
Ram plare End plale
Fallinq weight
0l Vessel closed at both ends to equalise moisture distribution while in heatine cabinet Cuide iube
Thermal
Extensron cylinder
insulalion
fu1easu(inq cylinder Ram plare
Soil sample Probe
Suppon plare
Thermal
6askel
insularion
End plare
fnd pla{e
Apparatus for compacting the soii sample
c) Sample prepared for measurements
Magnesium or
Ease of cast resin
Varnish layer
Insularion (pliable resin)
h,-,stance wi
lnsulation ring
Shrink lube
Suppon ring (metal)
l\reta I rube staioless sreel
Healing wirs Heat conduclinq shealh Solder seal
d) Cross section through heating and measuring probe
Fig. 18.43 ApDaratus for Ceter:nining thermal :esistivity, water ccnrent and J:nsity 225
l8 C urrent-farrying Capacit-"- in Normal
Operation
groups. Under practical opcrational conditions the surface temperature of the cable would alNays be less rhan 105"C and drying out rvould be reduced such thar it rvould appear permissible to use 2.5 KmfV as a standard quantity for the dry area.
The boundarlt isothernt which separates the moist from rhe dry area is aflected by many influences such as type of soil, water retention capacity under local conditions. weather conditions, soil temperature as well as time related heating of the cable surface relative to soil temperature.
lf all these effects are considered it appears possible to approximately double the temperature rise limit , at nr :0.5 relative to the quantity for continuous op-
'
!
erarion and for intermediate quantities select a linear increase. The temperature rise limit A3, can therefore be represented by the equation 13.56 in Section 18.4.1 such that rvith a quantity of l5 K for continuous op:ration at rrr:1.0 this rvould relate lo 15 K for a pubiic utility load at rrr=0.7 und .ll K for a daily load cvcle rvith rr:0.5.
In Great Britain for lorv- and medium-voltage cables for both continuous operation and cyclic operation the quantities given in Table l8.3tl are used. These are extracted from an E.R.A. report 69-30 Part I "Current rating standards for distribution cables", [8.36]. Where drying-out o[ the soil is expected and where a more accurate assessment of load capacity is necessary quantities are used as, e.g. in [l8.37] for the moist region 1.2 KmflV, for the dry region 3.0 KmlW and for the boundary isotherm in loam 50 "C or sandy soil 35 "C where both these temperatures relate to a 15 'C soil temperature. In [18.38] consideration is given to the different conditions prevailing in summer and rvinter and their effect on Ioad capacity. For the rvinter months ihe quantities 0.9/3.0 Km;W aI l0 oC anibient temperature and for lhe summer months 1.2/3.0 Km,1V at l5 'C ambient temperature are recommended. The quanlity of the boundary isotherm in both instan. is 50 'C. These quantities are supported in I I 8.].J rvirh the e\ception of the soil-thermal resistir.ity of the unloaded soil s hich is given as an increased quan-
tity for the *inter period oi
1.05 Km7W.
18.34 Soil-thermal resistivities from "Elcctric Cablcs Handbook- ll8.36l (Quantities in brackets where the ground surface is impen'ious to watcr) Table
Type of soil
Soil-thermal resistivity in equally over u'hole
Km/$ at maximum loading
year, the summcr
therefore also during dry period in the
.l
I I
I
in summer (Mar.7'April to mid.-Nov.), however outside the dry periods; also fceder cables which are only used
ln wtnter (mid.-Nov. to Var.i ApriJ)
in emergency
1.5 (1.2)
l.l
1.0)
1.0 (0.8)
bog
1.2 (r.2)
r.r (1.0)
1.0 (0.8)
Clal bearing soil
1.5 (1.2)
1.2 (1.0)
0.9 (0.8)
Chalky soil with crushed sand as bedding material
1.2 (t.21
r.l
t.2 (t.21
Very stony soil or broken stone
I.)
l.J
1.2
Very dry sand
2.5
2.0
l.)
Made up soil
1.8
l.tt
1.2
All soils wirh the exception
:f
(
the following
Peat
.::o
-
(1.0)
Soil-Thermal Resiitiviiy 18.{
Bedding
)laterial
The investigation and selection of bedding material is ahva;-s recommended where the cables are to be operated under continuous load (rn= 1.0). A knolledge of the soil together with the physical and thermal characteristics of the bedding material makes it possible ro establish a more appropriate load capacity. Generally the excavated soil is more favourable than the rypes of sand used by the building industry. Artificially produced mixes are particularly suited for cable runs which are operated at high thermal srress. The use of this for longer runs of continuously loaded high-voltage cable is related to a question ofeconomy rvhereby ir must be considered that in thermal bottle r. -ks of short lengths - excessive grouping and crossing of cables or crossing of hearing ducts - the cost of the marerial could play only a secondary role. A(here building v,,ork is carried out at a later date , selected or specially mixed bedding material must neirher be replaced by material having poorer properIies nor must the volumetric rveight be changed.
Of the types of soil which occur naturally the quartz containing sandy types have the most favourable granular distribution, e.g. a high uniformity inder Li and a reduced pore content n. The thermal conductivity as well as ease of working and compacting are improved by a content of fine granules d<0.2 mm and of silt d <0.063 mm. [n Table 18.35 quanriries are given of a number of measurements.
The highest thermal resistiviry of 5.4 KmAV rvas found in household waste contained in sample number 16. Sands wirh a lorv uniformity index reached quantities of above 3.0 Km;W. The samples 7 to 10 are gravel sand mixtures containine diflerent quantities of silr (powdered limestone). The thermal resistivities of these mixtures are shorvn in Fi_e. 18..14.
The particle size distribution curves of sand samples I I to I 5 are shown in Fig. 18.45 and rhe thermal resistivities relative to moisture content are shorvn
Thern6l fes:gir!rq lri
lTirernal resisriviry o,
Kr
iff''-NT
lo
w 0.8
'
*rtrro.ontrn,
a) Relative to
dry density with various levels of silt contenr Sample
number
7
(0% SchA) yd:1.975 tlm3 ra:2.015 tlm3 9 (10% SchA) yd:2.03 tlm3 10 (15% SchA) yd=z.M tlrn3 8/1 (5% SchA)
45alol5o/06
"5-i" -6
Waler conlent
b) Relative to dry density with constant level of silt content Sample number
8/l
(5% SchA) tr=2i15 tlm3 8/2 (5% SchA) yd= 1.94 tlmt 8/3 (5% SchA) yo = 1.84 t/m3
Fig. 18.14
Relationship of thermal resistivity oE to water content w of a gravel sand mixture with a silt granular conrent
(JcnA) ol powdered limestone
227
l8
Current-Carrying Capacity in Norm3rl Operation
Table 18.35 Soil ph1'sical key data and thermal resistivitics of (ested samples Sample
2o.oor
number
%
d,o mm
mm
duo
I
Sand
0
0.13 5
0.46
la
Sample No. 1 with 4% clay
,1.0
0.1l5
0.42
Basalt wheathered = 2.75 t/m3)
)
0.1
0.75
5
0.1
+
6
5
8
2 3
(;r.
6
Crushed limestone (;'. = 1.75 t/m3)
1
Gravel, sand in
proportion
I
l:l
Gravel, sand in
proportion l: I +5% (SchA) 9
10
Gravel, sand in proportion l: I +
d
oold tc
tl
r',t
ti
m'
%
Km/w
0.34
1.7 5
0.05
1.80
0.335
l. /o
0.0
1.35
7.5
0.388
r.685
0.0
2.52
0.75
7.5
0.32
1.87
0.0
1.68
0.085
1.5
17.5
0.247
2.09
0.0
|.22
0.07
1.6
:)
0.218
2.15
0.0
l.t5
0.0t5
l.l
31.5
0.28
1.98
0.0
l.15
0.tl
0.93
0.255
1.975
0.0 6.0
0.96
3.4
0.41
l
0.:1
.1.0
1Q
0.14
2.015
0.0 6.0
0.76 0.40
7
0.1
-:.
)
tl
0.234
2.01
0.0 6.0
0.69
l0o,'o (SchA)
Gravel, sand in
proportion 1:l +
t)
U=
0.40
lt
0.06
1.0
16.6
0.13
1.04
0.0 6.0
0.67 0.39
159/" (SchA)
li
Sand
0
0.21
0.55
2.5
0.40
l.o
0.0
1.88
I2
San
d
J
0.r 8
0.7
3.9
0.37
l. oo
0.0
l.2 t
Sand
l0
0.:l
0.47
2.14
0.42
1.54
0.0
Sand
l)
0.1
0.16
l.o
0.5
14
Sandy loam
to
1)9,
0.38
l.
Waste material
in
0/o
ofgranular size d<0.063 mm {SchA) silt content of powdered limestone Particle diameter at l07o sieveJet-through
pe.e63 Cont€flt
lro " duo U n ia 7 ?" w qE
not measureo
Particle diameter at 6070 sievelet-through Degree of uniformity Pore content
Dry density Density of moist sample Density of solid material Water content Measured thermal resistivity
oJ
0.0
3.78
0.0
L77
0.0
5.4
Soil-Thermal Resistivity 18.J
Sludge
l
Fig.
Grain
Sieved
Sieve resrdue
lmarefiar
i
100:
% weiqhr
18..15
Particle size distribution curves for soil samples I I to li in Table 13_15
0
% wsiqht
I
!0r
10
20 70
30
60
40
50
50
40
60
20
l"^ iou
0-:
100
0.001 0002
20 mm 63 100 6.t
i
fulesn srze
.--.-
Thernal resisl,;rrv,r, 4
in Fig. 18.46. Sample number l5 contained almost 30% of particles d<0.063 and was found difficult to compact.
In Great Britain the sand-gravel and
sand-cement
mixtures have become known under the heading of " thermally stable bedding materials ". Sand-Gravel )Iixtures
water content
I %10 w_
Fig. 18.46
B:Xtri:'ff.tty
The mixture ratio is intended to be 50:50 but deviations of up to 45:55 are acceptable. The grain size of the sand should not exceed 2.4 mm but a 5% content of up to 5 mm is acceptable. The dry density should not be Iess than 1.6 t/m3. No organic or clay content is permitted. The grain size of gravel should be between 2.4 and 10 mm. Sharp edged particles should not be present. The mixture should be delivered with a water content of between 7 and l\yo and compacted to a dry density of 1.8 t/m3 to obtain a thermal resistivity of 1.2 Km/lrV in the dried out state.
The conditions required can also be fulfilled by a
s" for soil samples numbered 11 to
powdered stone-gravel mixture. Crushed gravel may only be used up to 50% of the total gravel content. 229
l8
Current-Carrying Capacity in Normal Operation
Sand-Cement Mixtures
rvhich is still acceptable. Thc requirement for the mixture described above is approximately fulfilled by the cun'e A | 8.411.
In the set state the bedding material must be crumbly so that it will not damage the cable in the event of subsidence and also should it become necessary to subsequently remove it. It is recommended to use sands with a pore content <0.55 which approximate the particle size distribution curve (18.47, curve D)
Calculation of Load Capacity The calculation of Ioad capacity, where thermally stable bedding material is used, is made to Section 18.4.6 using equations 18.92 to 18.95. Using the dimensions of the bedding material, designated ,r, )' and characteristic diameter du, the geometric factor kb as well as thermal resistances Ti,' and Tirl with gu the ther-
mal resistivity of the bedding material in the driedout state can be calculated. The thermal resislances Ti, and Il are not used rvhere the cable is buried directly in the bedding material and does not lay in a DiDe.
The sand-cement proportions should be l4:l by volume or 18 to 20: I by weight. To achieve compaction
1.6 tt'm3 and a relevant thermal resistility of '.2 Km7W, a water-cement ratio of approximately -2: I by weight is required.
to
18.5 Installation in Channels rnd Tunnels .-18.5.1 Unrentilated Channels and Tunnels
For the development of suitable mixtures the rules for the manufacture of concrete in DIN 1045 can be used. since a pore reduced mix and also an ability for compaction are also required for concrele. To DIN 1045 the range between particle size distribution curves A and B result in a particularly good mixture
ln unventilated and covered channels and tunnels, the heat generated in tbe cables is transmitted in the main only through the s'alls, base and top of the duct. Natural ventilation is mostly prevented by the compartmentalization rvhich are unavoidable. These form heat barriers and cause the air surroundinq the cables
whereas particles between B and C produce a mixture
Sieve resrdue
96 weiqht
10'
EO
20
10
30
60
40 50
60 70 80
90
0.001 0.002
0.02
0.1
0.063
|
0.21
0.25
065
6.31
48
100
20 mm 65100
Mesh size
230
Fig. 18.47 Particle size distribution curves A. B. C for a concrete mixture to DIN 1045 and curve D
for a sand-cement mixture
Installation in Channels and Tunnels 18.5
in the channel to incrcase itr temperal.urc such that the load capacity is reduced compared with that oI
CJnducior Iemperature Conducror losses
lree air. The temperature rise of the air in the channel depends
upon the dimensions of the channel and the magnitude of the losses of all the cables in it. The number ol cables generating losses and the locations within the channel have no influence on the temperature rise of the air contained in the channel [ 18.45].
Shearh losses
Thermal resislance of inner layers
Ij
Armour losses
The equivalent circuit for the thermal path of heat florv lrom a c:rble enclosed in a channel is shown in Fig. 13.13. Heut is rransmirted from the cable surface by radiation to the inner surfaces of the channel. Since rhese areas are large compared to the cable i-..t'ace area. the heat transmission factor for radiation can be calculated rvirh the emission lactor eo:0.95. as for a cable installed in free air. As op2rqed to installation in free air the follorving addi, :al thermal resistances must be taken into consideiation:
D
tr
Thermal resistancg oi outer sheaths
Ij
ihermal lransier iesistance oi rhe cable for radiation
Ii.
::.i fiE
Thermal transfer resistance at rhe qround surface Ilo
the thermal resistance ?}u o[ the channel rvalls
Toral losses
the thermal transfer resistance 7'-io at the ground surface. respectively channel surface.
I
o::re
Thermal transier resistance':; conveclaon on the inn€r wall of rhe channel
Thermal resistance of the channel lvalls and lhe surrounding
the thermal trrnsfer resistance Ti* for conveclion on the inner wall of the channel.
The thermal transler resistance at the channel inner wall is
Ii(
Il*
and the surro unding soil,
tr
Thermal transier resistance cable for convecrion
(*
for convection
Anarent iemperalure
Fig. 18..18 Equivalent diagram for heat flow from a cable in a channel
(l 8.100)
z.,2lb, + hr)
rqth
the dimensions h1 and b1 to Fig. 18.49. The -ermal transfer factor r, is selected to DIN .1701 with 7.7 W lKm2 (arithmetic mean from the quantities for walls, base and top cover) [18.46].
ij* is in series with Q* and both are in parallel with I,q5. The thermal resistance of air {", of a cable in the channel is calculated to eouation 18.17 and the eouations I
(18.101)
Tir TL"t
(18.102)
xdf"tr'
h1 Height of channel br Width of channel
I
(18.103)
1t
rKK-r ITK
rKS
ri
Thickness of covering
Fig. 18.49 Covered channel in ground :JI
l8
Current-Clrrf ing Capacity in Normal Operation
The thermal transfer resistance fi. is very smaJl in relation to the other thermal resistances and can be ignored in the following cases:
f tr f
for three-core cable with d<90 mm,
aginary layer with a thicknes d and a soil-rhermal resisti'r'ity 08. With a thermal transfer factor r, = 20 W/Km'z this becomes [18.48]
"l
for single-core cable with d<45 mm, in channels with a circumference 2 (br+b1)> I m.
a,
(18. 105) Qe
The thickness of covering
i
must be increased
the value d
..
,
The thermal resistance (, takes into considerarion heat conduction from the inner wall of the channel rhrough to the ground surface Ii 8.47]. This is affecred by the channel dimensions tFig. 18.a9) and the soilthermal resistivity gE (to reduce complicarion rhe hermal resistivity of the channel material is raken
and inserted in equation 18.104.
This results in T;E + i"io
T:.
l'rr, | ll/
-1- ,L
-lr+rnl-----=-* ZI LV2
trI
,,'ml]., ( I 8.
104)
The thermal transfer resistance Qo at the ground surface, or *'here applicable rhe channel surface, is approximated using the thermal resistance of an im-
rslance
[
[t,',,
lt rli,
,| +i. , I| u-;-r-l _|t-]-tnt__lQr
+{-
(18. t06)
a^ Qz
also as 0E):
I ,t
I
by _
L
V1 (18.
lN< -
With the aid of Fig. 18.50 a quick resuh can be obtained for the two thermal resistances assuminq a soil-thermal resisriviry of I Km7W. For orher quanrities of soil-thermal resistiviry rhe result from the graph must be multiplied by 9e
I K"tlV
{f;€ + fio}
n: I 2 J o 10
IJ 20 50
J 4 56
Fig. 18.50 Thermal resistance (fig + channel relative to 8
dimensions h1,b,
atO€-1Km^V 1.t
z
b'
jlJ-n
and
+
4.)
of a
The temperature of the soil is dependant on the depth oi lay, i.e. the measuring depth (see Sections 18.3 and 13.4). The remperature at a depth of approximately [0 m is constant and is equal to the mean annual temperature of the air (in Germany approximately 9'C). In smaller depths the temperature follows the variations of air temperature with a certain time delay. Various depths are affected by seasonal variations whereas close to and at the ground surface the temperature can vary depending on time of day. The mean value of these temperatures during the summer months is higher than the temperature of the deeper layers. With cables on no load the air in a channel assumes a mean temperature resulting from the temE,-'ltures of the inner surfaces and the parts of the irlrrer arers of the channel boundary faces. The base and rvalls of the channel assume approximately soil temperature at the depth of channel centre line. The ftr surface of the channel lid reaches, because of t'l ,. influence of air temperature and sunshine during summer months. a higher temperature by a value of A3, (Fig. 13.51). Thus the mean temperature of the air in the channel becomes A/) ati JTE=,rEr---;;-----i-
:{3+
(l
8.107)
r'l
\Dr /
and with loaded cables and the summation ol losses of all cables in the channel as I(Pi + P!) 3r = 3rr +
-5.2
I(4'+
P;)(TiE +
rio)
( 18.
r08)
Arrangement of Cables in Tunnels
The cables are either mounted direct to the walls with the aid of cable clips or laid on racks or trays. :. : ventilarion clearance between trays depends on _ their width; this should wherever possible be not less than 300 mm to provide for the installation of heavy cables. On trays and racks as well as where cables are fixed direct to the walls a clearance between highly loaded cables equal to the diameter of the cable should be maintained to keep heat transmission from cable to cable as low as possible. The height of tunnels should oot be less than 2.2 m. The width should be chosen such that a free passageway clearance of 60 to 80 cm is maintained. With trays installed at a vertical pitch of 30 cm their width should be limited to 50 cm to allow access for cable installation.
Installation in Channels and Tunnels
10
18.5
20 cm
Covering u
-....* J0
Fig. 18.51 Temperature rise A3, of the inner face oi channei iop rel:rtire to thickness ii oI thc covcrins
In the design of an installation the iollorving pr.rcedures can apply: initially a first approrimation is nade of the cross-sectional area for each individual :able at some,r0 to 50"'6 greater lhan the size required for installation in free air. For high currents it may be necessarv to use several cables per current path. Secondly a sketch plan is made of the tunnel shorving the required height. width. number of tral'.s and arrangement of cables following the rules mentioned above. From the proposed arrangement of cables shorvn in the sketch plan the rating factor for groups installed in air /s to Tables 13.23 or 18.24 can be selected. The total losses in the tunnel are next calculated and the resultant increase in temperature of air in the tunnel is found from equation 18.108. The temperature of the tunnel air rvith cables under no load must be increased by this amount and a revised rating factor selected relative to this increased ambient temperature /" from Table 13.22 or from equation 13.15. When the load capacity /. is multiplied by these factors the product must not be less than the load to be transmitted.
Ir< I,fnft.
(18.10e)
If this condition is not satisfied
either the number of cables, the cross-sectional area or the tunnel dimensions must be increased. If these proposals are not possible or not practical then forced ventilation must be employed. The time constant of a tunnel is great compared to the time constant of a cable, The temperature rise of the air in the tunnel can be determined therefore tJ)
!3 I
Rar
Current-Carry ing Capacir) in Normal Operation
iaclor 4,
1.0
5 678910 15 m
25
J0
40
a) Relative io arrangement and number of cables on a cable tray./1h
Numbet of multi cote cables-..............*
Baring
i
ror
/H
3 4 5678910 15 20 25 50 Numbet ol muhi.cote cables -.--_
b)
Relative to number ofequally loaded trays above one another with single layer on each/"
Fig. 1852 Rating factors for grouping of multi-core cables - or bunched single-core cables of one circuit - on cable trays
Installation in Channcls-lnd Tunnels 18.5 by using Ihe root mean square value /u of the currents producing the losses over 24 hours:
, _.,'/i,r,+Ii,r.+... *Ij1 r, '"[/ t' +h+... '',-tt
(18. l
l0)
with r,+r,+ ...t;:24 h. Where 10,, 10r... are the currents rvhich flow during the times tr. t, ... For groups of larger numbers of cables than is allowed for in the tables rating factors to Fig. 18.52 can be used. These values are also valid for singlecore cables if for each circuit instead of a multi-core cable the requisite number of single-core cables are l-rched. In these cases the raring factors for load capacity /, apply as for bunched cables. If more than six trays are installed above one another \ rating factor for six trays may be used in the . :ulation. --
An approximation of the rtring factor lor bunching in air /1r. for cables rouching one another, can be formed from the raring factor /"n (horizontal component) for groups on a cable tray to Fig. 18.52a and the rating lactor 1," (verrical component) for groups of approximately equally loaded cable trays above one another.
It
is J
ll-
JHh JHv
with
h,= 0.95
f-":0.93 , ,:0.9
for two cable trays above one another for three cable trays above one another for six and more cable trays above one another.
Where the number of cables and the loadine are not kno',vn the cross-sectional areas must be delrmined ,ng an assumed total reduction. A final review rvill then enable a decision to be made as to whether forced venrilation is required and whether or not the rating factor applied initially was adequate.
1853
through the channel rvalls is not raken into consideration. [n this rvav fans are not sized too small and thus some reserve capacity is available for future extenSlons.
The air rate required Q is dependent on rhe total heat loss generated by the cable t(P|+ 4), the channel length I and the temperature rise of the cooling air A3*u between entry and exit. This is expressed by
,(P'!P'\l
(l3.ul)
(p J rKii
co being the specific heat
of air at constant pressure but is dependent on temperature as rvell as humidity; rn approximate calculation can be made t irh c-: l.J KJ/ltm-The air velocity u is determined by raking rhe crosssectional area of rhe channel calculated from heieht and rvidth (see also Fi_s. 18.53)
f=;.o If
noise nuisance is
(ls.lll) to be avoided the air
velocity
musl. not exceed 5 m/s.
The temperature rise ol the cooling air rr{st be chosen giving consideration to the temperature at the point of entry and the temperature which is permissible at the exit. In most instances the temperature oi the input cooling air will be identical with the design ambient temperature 9u. The hottest cable is considered in respect of permissible operatin-s remperature 3r, in deciding the temperature rise of the cooling air using the formula
aSKii<31.-tu-ag
(r8.1l3)
rvith
^3:(3,.-30"q(fJ'
(18.1l4)
Since the moving air significanrly improves heat dissiChannels with Forced Ventilation
If natural ventilation
proves
to be
inadequate, i.e.
the air in the channel is overheared and the conductor temperature exceeds the permissible quantity forced
ventilation is necessary where other means are not possible e.g. enlarging the size ofchannel. Mostly the calculation is based on the total heat loss generated within the channel. Heat dissipated
pation from the cable the rating factor required for groups/" need not be applied.
l8
Current-Carrying Capacrli in Normal Operation
Example l8.l I
In a tunnel with dimensions 1.2 m x 1.5 m the cables shown in Table 18.36 are to be installed and be loaded rvith the currents given in the table. The dura-
tion of operation is first of all planned for 8 hours full load per day. It is required to operate also at full load for 16 hours per day when under this condition forced ventilation may be provided. The ambient temperature 3u of the air is 35'C and the soil temperature 3E at the depth equivalent to the tunnel cenrre, with cables unloaded, is 25 "C. The soil-thermal resistivit) is 1.2 KmflV. The planned arraneement of cables is shown in Fig. 18.53
For the 8 hour operation in respect of 24 hours the f-. oot mean square value of current in the cable NYFGY is: /
t rbtl ,,,
' y -_I/
8
-t
tr+t2
'.t'
t,./
Fig. 18.53 Arrangement of cables ior example
a^
for the losses
I 8. I
I ,_. -
Table 18.36 Cable types and loading for Example l8.l for 8 hour operation
8 //t\' ,i-,i,ttl// \: _,,.r\r/ - '' D'-
'/, /,//. / . .//2. '
D' ,'ql
205\'
=44qLl '- 14\ llsl
= 6.34
w/m-
Cable tl pe
NYFGY
u"iu
3
x
l50SM
kv 3.6i6
\YCY 4x:40 0.6: I
SN,l
I
\..EKBY NEKBY 3x70 RM 3xl20RM 17t20
12120
Number of cables
and
Loading
:
Pi
= l3 x 6.J4 = 82.4 W'm.
-The sum
ofall
losses
ofall
+ 55.0 + 27.5 +
cables to Table 18.36 gives
37.2
h-
u-
:
h_t\
:-!=
ii'
|5
))
=ii= U.I9 Z
t
"- :7
105
185
l:0
l?0
315
129
r95
211
11.9
53.4
i6.3
40.5
70
70
65
65
Jb
I
0.65
0.66
6.34
7.86 55.0
0.62
0.63
4.5E
5.31 37.2
Eight-houroperation
P: 2P:
R
0.192
= 1 KmAV to 0.078 KmflV.
w;m
Itl-r
and
the thermal resistance Tie+Tlo results for
7
Permissiblc operating temp€rature
+::--= 0.192 m, ztJ . t.,!
t'S
5
Ohmic
P'
= 202.1 \N lm.
I
ii- = il - 6:0.
7
Load capacity
From the curve, Fig. 18.50 with
-
A
/,A
losses
82.4
1b
l3
ps
wrm
WN
f.3 f,gf"
o.79 0.69
A9 A9*o
82.4
16.9
K
0.79 0.69
t1.7
I E.1
2't.5 0.76 0.66
IJ.J
0;t6 0.66 13.8
t6.2
For grouping up to 5 cabl6 on 7 trays a rating factor /6 =0.87 is to bq applied (scc Table 18.24).
Installation in Channels and Tunnels 18.5
-.1
I
I
n1
20 Sum
oi losses in clannel
I
50 lP
-
100
200
500Wm
J00
P,l
Air. iocly r/ 0.5
-
m/s
03 0.2
a u
E(Pi+ Pl) ASrr I
Air rate required in mr/s Air velocity in m/s Heat loss from all cables in W/m Temperature rise of cooling air in K Length of channel in m Cross-sectional area of channel in m2
The dotted line applies to quantities in examole l8.l I Fig.
used
l8s4
Calculation diagram: Cablechannel withforced ventilation 111
l8
Current-Carrying Capaciti. in Normal Operatiqn
With a soil-thermal resisrivity of g, :
1.2
KmflV
rhe
For the cable NYFGY
corrected thermal resistance of the soil including the lunnel becomes
t'l
Ii,+ rio-ffi
0.078 = 0.094
Km/w.
43. 'l--!----:jL=
"i
1{-
:F+t) \/_) /
r
:{-*r) \1.) I
-T4oa
vith l3i:-S.i K irom Fig. 18.51 and lhe temperature with the loaded cables is
+ )02.1 x 0.094:45
(18103)
"C.
The rating factor for the deviating ambient remperature is
f tt. -3nlr"=V'ffi=ll
r.
{rs ri}
^_r=o.ts
and the overall rating factor is
f :f H.fs:0.87
x 0.79
:0.69.
The factors IJI, are in each case smaller than the required reduction factors /, and /r, i.e. the crosssectional areas are dimensioned correctly. Wben changing
|
'c-'t
to l6 hour operation
one gets
| 1/'-TG
ll
.A-
and
t6
P' (rb\z ''P, - ''14\/./' The total losses in the tunnel are therefore doubled z.
4'
-
2
x 202.1 = 404.2 W lm
and rhe temperature of the tunnel air is raised to
%:26+404.2x 0.094:64
"C.
Therefore the tunnel must be ventilated.
.'--
{l3.lr4)
(18.l 13)
^-
:
I(4',+P,l/ co A
3*o
-104.1 x 10 1.3
x l0r x l0 =
U.Oji
m -,
S
(l8.lll) and for the air velocity
3r:3rE + E(P; + P;)(4E +'&o) ).6
r0s x.
The quantities for all remaining cables can be taken from Table 18.36. Wirh an appropriare quanrity of A9*u: 16 K, length of tunnel l0 m and profile oi the tunnel of 1.5 x 2.2:1.3 mr the air rate reouired rhen becomes
(18. 107)
=
:
ASxr(70-35-16.9 < l8.l K.
cables is
.
)O{\ r
\J r)i ^3:(i0-30)l=l
The temperature in the tunnel with no load on the
l--:
/
(18.108)
a
0.611
The same results can be obtained from Fis.
(l s.l
18.5-1.
l
l)
