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HV Cable Sizing Calculation (MOL) - Fahahil
2006-4851 Rev. 1
A Input Input Data Data as per per Spe Specif cifica icatio tions ns 1 2 3 4 5 6
Nominal System Voltage Highest System Voltage Short Circuit capacity Ground temperature Soil thermal resistivity Maximum depth of laying
: : : : : :
3.3 kV 3.6 kV 25 kA for 1 second 40 °C 2.5 °C m/W 1.0 m
B Calculation B1 Required cross cross section section of cable cable for short circuit circuit withstanding withstanding capability capability The new cable shall withstand a Fault level of 25 kA for 1 sec. Cable cross section of 300 of 300 sq.mm is able to withstand the fault level level = 42.9 kA for 1 sec. ( Refer cable catalogue in Attachment-1, sheet 3 ) For adequacy check of continuous current capacity & voltage drops, following steps are utilised ( Refer attached sheet for calculation ) B2 Dera Derate ted d curre current nt
: Ic x TDF
HV CABLE SIZING CALCULATION A
B
Sl.
C
No. From
1
D
E
F
Feeder details
14SB-3003
To
VSDS Input
Full load Load
Cable
current
Length
in Amps.
(L)
(Iflc)
kVA
metres
1600
150
G
H
Starting Cable type current
(CU/XLPE/
I
J
K
L
No. of
Type
Total
Min. reqd.
of
Derating
cable
installation
factor
current
TDF
rating
runs
in Amps. SWA/PVC) (Ist) Iflcx6.5
279.9
-
YES
1
Ground
0.6208
M
N
O
P
Q
R
S
Current
Result
Voltage
%
Voltage
%
for proposed
drop
Volt-drop
drop
Volt-drop
cable size
during
during
during
during
cable
running
running
starting
starting
volts
%
volts
%
8.15
0.25
-
-
Proposed rating of the cable size proposed
(F/K)
(Sq.mm.)
(amps.)
450.9
300
481
SAFE
transformer
Manufacturer data ( refer attached DUCAB catalogue copies ) Derating Factors for cables laid in ground Derating factor for ground temperature
Cable data =
1.07
Derating factor for variation in thermal resistivity of soil 2.5 °C M/W (Multicore)
Cable
Resistance Reactance Current rating
size
in Ground
=
0.74
(Sq.mm)
(ohms/km)
(ohms/km)
(amps.)
=
0.98
300
0.08
0.08
481
laid in horizontal formation touching
=
0.8
TDF for cables laid in ground
=
0.6208
Derating factor for depth of laying ( upto 300 sq.mm. ) Derating factor for grouping two cables
Notes:
2006-4851, rev 1 Attachment-1, Sheet 2
LV CABLE SIZING Derating factors : The following De-rating factors are considered for LV cable sizing.: Laid In Ground
Ground Temperature @ 40 0C =
0.82
A
(refer Table 3 of Ducab catalogue in Attachment-2, sheet 3)
Soil Thermal resistivity = 2.5 deg.C m/W
0.74
B
(refer Table 4 of Ducab catalogue in Attachment-2, sheet 3)
Depth of installation @ 700 mm=
0.96
C
(refer Table 5 of Ducab catalogue in Attachment-2, sheet 4)
Grouping of cables for 5 circuits
0.59
D
(refer Table 7 of Ducab catalogue in Attachment-2, sheet 5)
Hence Total De-rating factor for Cables =
AxBxCxD 0.344
Voltage Drop at steady State Voltage drop = mV x I x L/1000 in volts
LV CABLE SIZING CALCULATION TABLE Equipment Description / Tag Number To
f d o a g o n L i t a R
From (A)
(B) in kVA
VSDS Trfe Secondary-1&2
VSDS Panel Incomer Unit
800
VSDS Inverter-1/2&3
VSDS Motor
g n i t a R r o t o M
(C) in kW
g n i t a R r e d e e F
g e n g i a t t l a r o e V p O
(D) (E) in in Amps Volts
r r e t o w c o a P F
(F)
t d n a e o r L r l g r u l l l o n t y u C a r i c c F e t n v a r a e O e F i c D i f f E
e d f e o l r y b i a i C u t q c e a R p m A
(G)
415 741
415
0.80
0.90
y t g t n i n i c e r y a r r p u r a a C C C e l b a C
e e l z b i a S C d e t c e l e S
(H) in Amps
(I)
(J) in Amps
(K) (L) in Runs Sq.mm. per Ph
1113.00
0.344
3235.46
1C x 630
741.00
0.344
2154.07
300
h t g n e L e l b a C
(M) in Amps
(N) in Mtrs
4
1000
155
4
590
140
Voltage Drop Steady State d e e l t c b e a l e C S r o F
(O) in
g n i t r a t d S e r w o o t l o l A M
Voltage Drop During Motor Starting t n e r r u C
e d l e b t c a e C l e S
d e w o l l A
mV/A/m
(P) in %
(Q) in %
(R) in x FL
(S) in %
(T) in %
0.195
2.03
5.0
NA
NA
N.A
0.190
1.19
5.0
NA
NA
N.A
NOTES: H = B/(1.732xE) or (C/G)/(1.732xExF) or D; J = H/I; P = HxNxOx100/(Ex1000xL); S = PxR
