Maintenance Handbook on Transformer of 3 Phase Electric Locomotive

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GOVERNMENT OF INDIA MINISTRY OF RAILWAYS

M a H a ai i n nt te e n na an n c c e e H an n d db o oo o k k o n n T r a o 3 3 P P h L o an n s s o r rm m e e r r o ha a s s e e E E l le c ct tr r i ic c L oc co om m o ot ti i v ve e END USER: USER: Loco Maintenance Maintenance Staff

CAMTECH/E/14-15/3 Loco Transformer/1.0

March, 2015

,

Maharajpur, GWALIOR - 474 005

M a H a ai i n nt te en na an n c ce e H an n d db o oo o k k o n n T r a 3 P P h E l L o an n s s f o r rm m e er r o o f 3 ha as s e e E le c ct tr ri i c c L oc c o om m o o t ti iv ve e

QUALITY POLICY

“To develop safe, modern and cost effective Railway Technology complying with Statutory and Regulatory requirements, through excellence excellence in Research, Designs and Standards and Continual improvements in Quality Management System to cater to growing demand of passenger and freight traffic on the railways”.

M a H a ai i n nt te en na an n c ce e H an n d db o oo o k k o n n T r a 3 P P h E l L o an n s s f o r rm m e er r o o f 3 ha as s e e E le c ct tr ri i c c L oc c o om m o o t ti iv ve e

QUALITY POLICY

“To develop safe, modern and cost effective Railway Technology complying with Statutory and Regulatory requirements, through excellence excellence in Research, Designs and Standards and Continual improvements in Quality Management System to cater to growing demand of passenger and freight traffic on the railways”.

FOREWORD

Emerging technological changes require dissemination of new technology and induction of new maintenance practices. The three phase electric locos were inducted quite some time back in Railway system but still there is no maintenance handbook on transformer. The transformer is an important equipment of electric loco (like heart in human body). The transformer needs proper maintenance for trouble free and reliable operation of locomotives. CAMTECH has prepared this handbook on “Maintenance “Maintenance of Transformer of Three Phase Electric Locomotives” with an objective to provide comprehensive information on the technical as well as maintenance maintenance aspects of the transformer. I hope this handbook prove to be useful for the field staff engaged in the maintenance of three phase electric locomotives locomotives and its transformer.

CAMTECH, Gwalior th Date: 26 March, 2015

A.R.Tupe Executive Director

PREFACE

Transformer is an important equipment of three phase electric locomotives. Proper upkeep of transformer is necessary to ensure trouble free operation of three phase electric locomotives. locomotives. This handbook on “Maintenance of Transformer” of 3 phase electric locomotive has been prepared by CAMTECH with the objective of making our maintenance personnel aware of correct maintenance and overhaul techniques to be adopted in the field. This handbook covers brief technical details, maintenance practices, testing along a long with w ith testing instruments required. req uired. This also covers condition monitoring of transformer oil and model questions on the subject. It is clarified that this handbook does not supersede any existing provisions/guidelines laid down by Railway Board, RDSO or o r OEM. The handbook is only for guidance and it is not a statutory document. I am sincerely thankful to all field personnel who helped us in preparing this handbook. Technology up-gradation learning is a continuous process. Please feel free to write tour for any addition/ modification modification in this handbook. We shall s hall highly appreciate your contribution in this direction.

CAMTECH, Gwalior Date: 26 th March, 2015

Peeyoosh Gupta Director/ Electrical

CONTENTS Chapter No.

1.

Page No.

Foreword Preface Contents Correction Slip

iii iv v vii

GENERAL

01

1.1

Introductions

01

1.2

Transformer Working Principle

03

1.2.1 EMF Equation of Transformer

04

Description of Three Phase Loco Transformer

04

1.3.1 Transformer Cooling

04

1.4

Different Parts of Transformer

07

1.5

Technical Data of Electric Loco Transformer

10

1.6

Transport of Transformer

11

1.6.1 Lifting of the Transformer

11

1.6.2 Supporting the Transformer on a Point

12

Storage of Transformer

12

1.7.1 Maintenance During Storage

13

Factors Affecting Life of Transformer

13

1.3

1.7

1.9 2.

Description

MAINTENANCE

15

2.1

Periodic Maintenance Schedules

15

2.2

Trip Inspection

16

2.3

Oil Circulating Pumps (SR & TFP) IA, IB

17

2.4

Main Transformer IC Schedule

18

2.5

Main Transformer (AOH) Schedule

19

2.6

Main Transformer (IOH) Schedule

20

2.7

Main Transformer POH Schedule

21

2.7.1 Painting Procedure

22

2.8

Procedure for Replacement of Bushings

22

2.9

Transformer Oil Check

23

Chapter No.

2.10

3.

Description

Page No.

Testing of Loco Transformer

24

2.10.1 Tests

24

2.11

Testing Equipment

25

2.12

Installation of the Transformer on Locomotive

26

2.13

Check Points While Maintenance

29

2.14

Transformer Oil

31

2.14.1

Oil Specification

31

2.14.2

Purification of Transformer Oil

32

2.12.3

Condition monitoring of Transformer by Dissolved Gas Analysis

34

MODEL QUESTION

39

ANSWERS

45

An Approach to Equipment Failure Investigation

46

ANNEXURE – I

47

-

Reliability Action Plan (RAP)

ISSUE OF CORRECTION SLIPS The correction slips to be issued in future for this handbook will be numbered as follows : CAMTECH/E/14-15/3 Loco Transformer/C.S. # XX date--------Where “XX” is the serial number of the concerned correction slip (starting from 01 onwards).

CORRECTION SLIPS ISSUED Sr. No.

Date of issue

Page no. and Item no. modified

Remarks

1


CHAPTER 1

GENERAL 1.1

INTRODUCTION

Figure 1.1

Three Phase Loco Transformer

The transformer is a static device, which transforms power from one AC circuit to another AC circuit at same frequency but having different characteristics. These circuits are conductively disjointed but magnetically coupled by a common time varying magnetic field. It can raise or lower the voltage with a corresponding decrease or increase in current. In all the electric locomotives, limiting the value of current during starting, speed control is achieved by supply of variable voltage to the traction motors. This variation of applied voltage can be carried out easily by the use of transformer along with Static Convertor provided in the locomotive. The windings which form the electrical circuit must fulfill certain basic requirements, particularly the di-electric, thermal and mechanical stresses imposed on it during testing as well as in service and cater for over loads under adverse conditions. The WAG9 transformer unit consists of the main transformer active part and two different types of reactors, hosed in a tank. The main transformer converts the overhead line voltage (25 kV) to the lower operating voltages for: 

traction power supply 1268V



auxiliary 1kV

The main transformer is integrated into the traction circuit between overhead line and rail return line. The primary current line flows from the pantograph via roof line, vacuum circuit breaker, the roof bushing into the primary winding of the main transformer. It then flows back to the rail via the earth return brushes on four of the six axles. And WAP5, WAP7 transformer has total load winding in addition toWAG9 transformer.

Maintenance Handbook on Transformer of 3 Phase Electric Locom

March, 2015

2


Figure 1.2

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Schematic Diagram of Power Circuit of 3 Phase Loco (WAG 9 , WAG 7)

Maintenance Handbook on Transformer of 3 Phase Electric Locomo

3


1.2

TRANSFORMER WORKING PRINCIPLE In general principle of working of a transformer can be expressed on the basis of law of electromagnetic induction as following: a. b.

When a conductor cuts the magnetic flux or magnetic flux cut the conductor, an emf is induced in the conductor. The magnitude of this emf is proportional to the rate of change of flux.

Where,

E

=

-d/dt

E 

= =

emf flux

Kinds of emf

The emf may be induced by two ways i.

Dynamically induced emf

ii.

Statically induced emf. a.

Mutually induced emf

b.

Self induced emf

An emf induced in a coil due to variation of flux in another coil placed near to first is called mutually induced emf. The emf induced in a coil due to change of its own flux linked with it is called selfinduced emf. (In case of autotransformer) In its simplest form, a transformer consists of two conducting coils. The primary is the winding which receives electric power, and the secondary is one which delivers the electric power. These coils are wound on a laminated cor e of magnetic material. The physical basis of a transformer is mutual induction between two circuits linked by a common magnetic flux through a path of low reluctance as shown in fig.1.2 LAMINATED CORE

PRIMARY

SECONDARY

Figure 1.3

Ideal Transformer

The two coils possesses high mutual inductance. If one coil is connected to a source of alternating voltage, an alternating flux is set up in the laminated core, most of which is linked up with the other coil in which it produces mutually induced emf i.e. E = M di/dt If the second circuit is closed, a current flows in it and so electric energy is transferred (entirely magnetically) from first coil (primary winding) to the second coil (secondary winding). Maintenance Handbook on Transformer of 3 Phase Electric Locom

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4 1.2.1


EMF Equation of Transformer

Let,

N1 =

Number of turns in primary.

N2 =

Number of turns in secondary.

m =

Maximum flux in the core in webres.

f =

Frequency of AC input in Hz.

v1 =

Instantaneous value of applied voltage in primary winding in volts.

The instantaneous value of counter electromotive force e1, can be expressed as e1 = - N1 d/dt volt The counter emf e 1 is equal and opposite to applied voltage v 1 i.e. v1 = N1 d/dt volt rms value of emf induced in primary E1 = 4.44 f N 1 m Similarly, rms value of emf induced in secondary E2 = 4.44 f N 2 m In an ideal transformer V1 = E1 & V2 = E2 Where V2 is the secondary terminal voltage With the above expressions we get E2/ E1 = N2/ N1 = K Where K is known as voltage transformation ratio. (a) If N2 > N1 i.e. K > 1 then the transformer is called step up transformer. (b) If N2 < N1 i.e. K < 1 then the transformer is called step down transformer.

1.3

DESCRIPTION OF THREE PHASE LOCO TRANSFORMER & ITS PARTS Each loco requires one transformer for feeding supply to traction converters/ traction motors, to auxiliary converter for supplying to auxiliary machines and to supply Hotel load of train. This transformer will consist of Primary winding, 04 Traction windings, Auxiliary winding (BUR) and Hotel Load winding. In addition, it has a FILTER winding which is connected on locomotive to passive filter. The transformer tank also contains 02 series resonant chokes (one for each converter) & 03 Auxiliary Converter double chokes (one for each of the 03 auxiliary converters).

1.3.1

Transformer cooling Transformer is oil cooled and external cooling of the oil is designed with two independent oil circuits with cooling units located within the machine room of locomotives. However, the cooling units / circuit component do not form part of transformer supply.

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5


Figure 1.4

Figure 1.5

Cooling Arrangement

Layout of Winding in Transformer Tank


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6


Figure 1.6

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Three phase loco transformer winding diagram


7


1.4

DIFFERENT PARTS OF TRANSFORMER i.

Transformer tank fastening Material Colour Weight Identity No.

: : : :

Aluminium RAL-7009stain 966 kg with lid HSTN 424007

Figure 1.7 Transformer Tank Fastening ii.

Transformer main winding Identity No. : HSTN 424337 Make

: ABB Badodara, BHEL Jhansi, CGL Mandideep Bhopal, EMCO Thane Mumbai, High volt electrical Ltd Mumbai,

Figure 1.8 Transformer main Winding

iii.

SOD Winding Identity No. Make

: HSTN 424005  ABB Badodara, BHEL Jhansi, CGL Mandideep Bhopal, EMCO Thane Mumbai, High volt electrical Ltd Mumbai,

Figure 1.9 SOD Winding iv.

GOD Winding Identity No. Make

: HSTN 424006  ABB Badodara, BHEL Jhansi, CGL Mandideep Bhopal, EMCO Thane Mumbai, High volt electrical Ltd Mumbai,

Figure 1.10 GOD Winding Maintenance Handbook on Transformer of 3 Phase Electric Locom

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8


v.

Transformer Bushing Identity No. DT 1/250 : HSTN 310500 DT 1/630 : HSTN 310501 DT 1/1000 : HSTN 310502 DT 1/2000 : HSTN 310503 DT 1/3150 : HSTN 310504

Figure 1.11 Transformer Bushing

vi.

High Voltage Bushing Identity No.

: HSTN 420783P0001

Technical Data: 18/30 kV, 800A Supplier : Elasti mold or RDSO approved

Figure 1.12 High Voltage Bushing

vii.

Temperature Sensor (Thermometer) Identity No. : HSTN 424136P0001 Technical Data : PT-100 Supplier : JUMO Stafa or RDSO approved

Figure 1.13 Temperature Sensor

viii.

Overflow Valve Identity No. : HSTN 4/12/0144R Pressure setting : 0.8 bar Supplier : Millen Engineer or RDSO approved

Figure 1.14 Overflow Valve ix.

Transformer Main Valve Identity No. : Technical Data : Supplier :

HSTN 4274037P0001 NW80 ND6 Fatco or RDSO approved

Figure 1.15 Transformer main Valve March, 2015


9


Slide of oil intake and drainage

x.

Identity No. : Pressure setting : Supplier :

HSTN 422368P0001 NW32/25 Hofiman or RDSO approved

Figure 1.16 Slide of oil intake and drainage

xi

Two conservator tanks including - Air dehumidifier including valve -Oil level gauge Identity No. Material Colour Volume

: : : :

HSTN Aluminium RAl 7030 stain 137DMQ

Figure 1.17 Conservation Tanks

xii.

Breather Identity No. : Technical Data : Supplier :

HSTN 422029P0001 EM3MA Yogya or RDSO approved

Figure 1.18 Breather The special features of the transformer are :-

•

Transformer is mounted under slung on under frame

•

Transformer is designed for feeding GTO/IGBT based Power and Auxiliary converter load.

•

Very high impedance between primary & traction windings

•

100% de-couplings between windings

•

Use of continuous transposed conductor for windings

•

Use of disc construction of windings

•

Transformer and conservator t ank of Aluminum Alloy

•

Rapid action coupling between transformer and conservators in oil circuit


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10

1.4


TECHNICAL DATA OF 3 PHASE ELECTRIC LOCO TRANSFORMERS (WAP5, WAP7 & WAG9) Common Ratings for WAG9, WAP5 & WAP7 Loco Transformers

Rated voltage Normal 25.0 kV Maximum 30.0 kV Minimum 17.5 kV Frequency 50Hz ± 6 % Cooling medium Inhibited transformer oil to IEC – 296/ IS-12463 Series Resonant Choke (2SOD 240) Inductance 0.551 mH (± 15 %), Liner to I peak = 1391A Thermal current Ith 984A Resonant frequency 100Hz Voltage stress between terminals to earth Nominal 482 Vac , Max. 3471 V

Auxiliary Converter Choke (6GOD 120) Inductance per PUR - choke

0A

30 mH

120A

30 mH

155A

26 mH

190A

20 mH

Frequency

100 hz

Current

Rated 155A,

Ripple

Nominal 38.6%, Max. 50.2%

Voltage to earth

Rated 1153 V, Max. 2000 V

Max. 190A

Ratings f or WAG9 loco tr ansf ormer

Winding

Power (kVA)

Voltage

Current

HV

6531

25000

261.25

Traction

4 x 1449

4 x 1269

4 x 1142

BUR

334

1000

334

Filter

400

1154

347

Total weight

9450 ± 3 % kg

Ratings f or WAP5 and WAP7 L oco Tr ansf ormer

Winding HV Traction BUR Filter Hotel load Total weight

March, 2015

Power (kVA) 7475/7775 4 x 1449 334 400 945/1245 10000 ± 3 % kg

Voltage 25000 4 x 1269 1000 1154 750/960

Current 299/311 4 x 1142 334 347 1260/1296


11


Weight Unit

Quantity

Kg per unit

Kg total

Transformer active part LOT 7500/ LOT 6500

1

5780/ 5380

5780/ 5380

Series resonant circuit recator 2 SOD 240

1

590/ 590

590/ 590

Auxiliary Converter DC-Link Reactor 6 GOD 120

1

570/ 570

570/ 570

Tank and lid

1

900/ 900

900/900

Insulation oil

1

1800/1780

1800/ 1780

Equipment

1

260/ 230

260/ 230

Total transformer unit

9900/ 9450

Expansion tank (oil level at 20°C)

1.5

2

88

176

TRANSPORTATION OF TRANSFORMER The transformer is transported full with oil. Any oil volume changing (which is caused by temperature variations) during the transport or storage are taken up by the transport expansion tank which is mounted on the transformer oil. The breather is connected to the transformer’s expansion tank. The breather should only be removed during the installation of the tr ansformer in the locomotive, and rectified as soon as possible. The breather must be filled with new or dried silica ge l.

1.5.1

Lifting of the Transformer

The transformer must never be lifted without its lid. Lifting points are welded to the side of the tank for this purpose. The rope should be attached on these lifting points as described in figure shown below. The ropes should never make a smaller angle than  = 60° with the horizontal, otherwise there is a danger t hat the tank will distort.

Figure 1.19

Lifting of the Transformer


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12 1.5.2


Supporting the Transformer on a Point

If for any reason the transformer needs to be supported on a point, then it should only be supported on the indicated areas shown by the arrows in the figure given below.

Figure 1.20

1.6

Support Point of Transformer

STORAGE OF TRANSFORMER The transformer can be stored as long as required, if the maintenance is carried out as required if it is under maintenance or ready to use. The various points for storage of transformer is described below. a.

Storing place

The oil-filled transformer should be stored in covered area. The storing place must be dry and the transformer must be covered with a lose taped plastic sheet. Figure 1.21

b.

Storing Place

Connecting flanges

All pipes, pumps and blocking valves should be closed off using blanking flanges.

Figure 1.22 Connecting Flange

c.

Expansion tank

Fix the expansion tanks in vertical position on a higher level than the transformer’s lid. Join then with flexible pipes with transformer in the same way as they are installed in the locomotive. The oil level in the expansion tank should correspond with the temperature mark. Figure 1.23 ExpansionTank March, 2015


13


d.

Labels

Covering the transformer with stickers is forbidden. If stickers need to be added then they should be stuck on separate plates. The plates should then be tied to the transformer using strings (no wire).

TFPG No. : 2027453 Make : BHEL Date of O/H : 11.05.2014

Figure 1.24 Labels e.

Checks

After transport and installation at the storing place the transformer should be checked for any signs of oil leakage. 1.6.1

Maintenance During Storage a.

Checks

According to the atmospheric conditions the oil level and the silica gel in the breather should be checked every 6 months. b.

Oil level

If the oil level is lower than the equivalent temperature mark, oil can be added by the filling cap on the expansion tank with the oil of the same quality. Mixing with oils which have significantly different parameters should be avoided. If the oil level is not visible at the expansion tank, the reason for the low oil level must be found. Oil should not be added by the filling cap of the expansion tank as long as reason has not been found. c.

Breather

If more than half of the silica gel is saturated (moisturized), then it must be completely replaced. The old silica gel may be regenerated. The transformer must not stay longer than 3 hours without functional breather.

1.7

FACTORS AFFECTING LIFE OF TRANSFORMER Life of transformer is affected by the following factors: 1. 2. 3. 4. 5.

Moisture Oxygen Solid Impurities Varnishes Slackness of winding

a.

Effect of moisture on transformer life

Presence of moisture in oil is highly undesirable as it affects adversely the dielectric properties of oil. The moisture present in oil also affects the solid insulation of transformer. As paper insulation is highly hygroscopic in nature, when transformer is filled with oil, it absorbs the moisture from oil which affects its insulation properties as well as reduces its life. Solubility of moisture in oil increases with increase in temperature and oxidation products of oil. When the oil in service Maintenance Handbook on Transformer of 3 Phase Electric Locom

March, 2015

14


oxidizes, acids are formed. These acids increase moisture solubility of oil. Acids coupled with moisture further decompose the oil forming more acids and moisture. Thus the rate of deterioration of oil increases. Check the colour of silica gel in each inspection and if found pink, replace or reactivate crystals at 150 degree C. Test transformer oil for electric strength and water content in IC schedule & POH and carry out purification with high vacuum type transformer oil filtration plant if required. Arrest the oil leakage if any. b.

Effect of Oxygen

Oxygen may be present inside the transformer due to air remaining in oil. The oxygen reacts and decomposes the cellulose of insulation. This forms an organic acid soluble in oil and sludge, which blocks the free circulation of the oil. The adverse effect of oxygen, which may be aggravated by catalytic action between hot oil and bare copper, increase the operating te mperature. Carry out oil purification with high vacuum type transformer oil purification plant periodically to remove atmospheric gases (air) and sludge. c.

Effect of Solid Impurities

The solid impurity present in the oil reduces its dielectric strength considerably. A good remedy is to filter the oil periodically. d.

Effect of Varnishes

Some varnishes having oxidizing effect, react with transformer oil and precipitate sludge on windings. Synthetic varnishes having acid inhibiting properties, generally delay the natural formation of acid and sludge in the oil. e.

Effect of slackness of winding

After few months of service, the transformer coils may suffer natural setting. This may wear the conductor insulation at some places and lead to an inter-turn failure. The coils may also get displaced under load conditions or momentary short circuit conditions, which may result in electrical and magnetic unbalance and produce even greater displacement. A good practice is, therefore to lift the core and windings to take up any slackness present at the first major schedule. Periodic maintenance of transformer is essential to ensure safety, reliability and trouble free operation of electric locomotive over a long time period.

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15


CHAPTER 2

MAINTENANCE

2.1

PERIODIC MAINTENANCE SCHEDULES 3-Phase (ABB) locomotives

Ref. :

Rly. Bd. Letter No. 97/Elect(TRS)/440/18/44(3-Phase), dt. 23.02.07

Coaching Locos - WAP5/WAP7 locos Maintenance Schedule

Trip inspection (TI)

Periodicity

3000 kms or one trip, whichever is later

Duration

2 hrs

IA

90 days

4 hrs

IB

180 days

6 hrs

IC

270 days

8 hrs

MOH

18 months

6 working days

4.5 years + 6 months or IOH

12 lakh kms. whichever is earlier.

WAP-7 - 11 working days WAP-5 - 20 working days

9 years + 6 months or POH

24 lakh kms. whichever is

28 working days

earlier. Freight Locos - WAG9/WAG9H locos Ref. : Rly. Bd. Letter No. 97/Elect(TRS)/440/18/44(3-Phase), dt. 23.02.07 Maintenance Schedule

Periodicity

Trip inspection (TI)

45 days

IA

90 days

IB

180 days

IC

270 days

MOH

18 months

IOH POH

6 years + 6 months or 12 lakh kms. whichever is earlier. 12 years + 6 months or 24 lakh kms. whichever is earlier.


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16

2.2


TRIP INSPECTION 1.

OIL CIRCULATING PUMPS (SR & TFP)

Visually examine all SR & TFP oil pumps for any oil leakage /any abnormal sound and take needful action

No leakage

2.

MAIN TRANSFORMER

i

Inspect the color of the silica gel. I f it is pink, remove the filter from the locomotive

Blue

ii

Dry the silica gel in oven at 150 degree C and replace

Blue Middle strip

iii

Read off the oil level on the gauge situated on the conservator. Top up the oil as necessary and Check for any signs of leakage

No leakage

iv

Prismatic level gauge-clean the gauge with a dr y cloth and check for leaks

Cleaned & No leakage

v

Examine the flanges of the pipe couplings and flexible hose that link the transformer and conservator and check the holding clamps.

Checked & Found intact

vi

Check/attend the condition of earthing shunts of transformer body (As per RDSO/SMI/0248)

Intact

vii

Check the main TFP and its protection cover of drain cock for damage/crack & oil leakage


viii

Check visually the foundation bolts of transformer and nylock nuts for proper locking


ix

Check/attend stoochi coupling pipes of conservator for proper layout and fitment and attend for any leakage

Intact/ No leakage

x

Check VPTFP and VPSR for oil leakage on RH.

No leakage

xi

Examine the HV bushing for sings of damage, burning etc. Replace if defective. Ensure RTV on base.

Checked / Replaced

xii

Check the oil leakage from TFP bushing

No leakage

3.

OIL COOLING UNIT CASING WITH RADIATOR

i

Examine flange joint for sign of cracks, oil leakage and loose/missing screws

Checked/ intact

ii

Remove all dust, dirt and debris from the radiator chamber via the machine room access cover (using vacuum cleaner) in case of less air flow booking

Cleaned

iii

Visually check the oil cooler radiator for any oil leakage / external damage from top and bottom

No leakage/No damage

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+/- 6”,


17


2.3

IA, IB SCHEDULE. 1

OIL CIRCULATING PUMPS (SR & TFP) IA,IB.

i

Visually examine all SR & TFP oil pumps for any oil leakage Normal /any abnormal sound and take needful action

ii

Check the mechanical support fasteners of all four oil pumps

2.

MAIN TRANSFORMER

Normal

i ii

Inspect the colour of the silica gel. If it is pink, remove the filter Blue from the locomotive

iii


Blue

iv

Read off the oil level on the gauge situated on the conservator. Top up the oil as necessary and

Middle strip

Check for any signs of leakage

No leakage

v

Prismatic level gauge-clean the gauge with a dry cloth and check/attend for leaks


vi

Examine/attend the flanges of the pipe couplings and flexible hose that link the transformer and conservator


vii

Check visually the foundation bolts of transformer and Nylock nuts, for proper locking

Intact

viii

Check the condition of earthing shunts of transformer body ( As Intact per RDSO/SMI/0248)

ix

Visually inspect & clean the electrical connection to the Intact insulator and condition of insulator for crack

x

Visually inspect the condition of oil cooling metallic pipes, check/attend for leakage / damage & check all fixing clamps

+/- 6”

Intact / No leakage

xi

Check/attend stuchi coupling pipes of conservator for proper Intact/ layout and fitment and attend for any leakage leakage

xii

Examine the HV bushing for signs of damage, burning etc. Replace if defective. (Ensure RTV on base)

xiii

Check the availability compensator.

xiv

Check the main TFP and its protection cover for damage / crack No crack / No & oil leakage. (RDSO/TC/076) leakage

xv

Check the oil leakage from TFP bushing.

of

hosepipe


over

the

oil

No

Examined

pipe Checked

No leakage

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18 2.4


IC SCHEDULE. 1

OIL CIRCULATING PUMPS (SR & TFP)

i.

Visually examine all SR & TFP oil pumps for any oil Normal leakage / any abnormal sound and take needful action

ii

Check the electrical connections of all four oil pumps

iii

Check the mechanical support fasteners of all four oil Normal pumps.

2.

MAIN TRANSFORMER

i

Perform the sample test on transformer oil.

ii

Normal

Check specific value of BDV, DGA, moisture and acidity.

30 kV (serviceable oil)

If BDV value falls below 30KV/ DGA gases more,

Done

oil centrifuging to be done iii

Inspect the color of the silica gel. If it is pink, remove the filter from the locomotive

Blue

iv


Blue

v

Read off the oil level on the gauge situated on the Middle strip +/- 6” conservator. Top up the oil as necessary and No leakage Check for any signs of leakage

vi

Prismatic level gauge-clean the gauge with a dry cloth and check for leaks


vii

Examine the flanges of the pipe couplings and flexible hose that link the transformer and conservator


viii

Visually inspect & clean the electrical connection to the Intact insulator and condition of insulator for cracked, flashed mark & ensure red marking.

ix

Check visually condition of foundation bolts of transformer and Nylock nuts for proper locking

Intact

x

Check / attend the condition of earthing shunts of transformer body ( As per RDSO/SMI/0248)

Intact

xi

Visually inspect the condition of oil cooling metallic pipes, check for leakage / damage & check all fixing c lamps

Checked Intact found no leakage

xii

Examine the HV bushing for sings of damage, burning etc. Replace if defective. Ensure RTV on base.

Checked / Replaced

xiii

Check the availability of hosepipe over the oil pipe compensator

OK

xiv

Check the main TFP and its protection cover for damage/crack & oil leakage. (RDSO/TC/076)


xv


No leakage

xvi

Check/attend stoochi coupling pipes of conservator for proper layout and fitment and attend for any leakage

Intact/ No leakage

xvii

Check the deformity of TFP drain cock cover guard, if deformed, replace it.

Checked / Replaced

March, 2015


19


2.5

MAIN TRANSFORMER (AOH) SCHEDULE 1.

MAIN TRANSFORMER (AOH)

i

Perform the sample test on transformer oil. Check specific value of BDV and moisture, acidity & DGA.

OK

ii

Oil centrifuging to be done. And used separate plant for different transformer oil. & check oil as per SMI 158.

72 Hrs.

iii

Replace the silica gel with new crystals

Blue

iv

Read off the oil level on the gauge situated on the Middle strip +/conservator. Top up the oil as necessary and 6” check for any signs of leakage No leakage

v

Prismatic level gauge-clean the gauge with a dry cloth and Cleaned & check for leaks No leakage

vi

Visually inspect the high voltage cable at the main transformer connection for damage or oil contamination. Replace the cable if damaged or if contaminated with oil

OK

vii

Examine the flanges of the pipe couplings and flexible hose that link the transformer and conservator


viii

Visually inspect & clean the electrical connection to the insulator and condition of insulator for crack & Red marking to be done.

Intact

ix

Check visually condition of foundation bolts of transformer and Nylock nuts for proper locking

Intact

x

Check / attend the condition of earthing shunts of transformer body (RDSO/SMI/0248 dated 22.11.2007 )

Intact

xi

Visually inspect the condition of oil cooling metallic pipes, Checked / check for leakage / damage & check all fixing clamps and Intact / also check the drain cock, isolating cock for oil leakage & No leakage/ clean it. cleaned

xii

Examine the HV bushing for sings of damage, burning etc. Replace, if defective.

Checked Cleaned

xiii

Check the availability of hosepipe over the oil pipe compensator.

OK

xiv

Check the main TFP and its protection damage/crack & oil leakage. (RDSO/TC/076)


xv


No Leakage

xvi

Examine the bushing for signs of damage, burning etc. Renew if defective. Clean off all deposits and dirt from the insulators

Checked Cleaned

xvii

Check conservator foundation welding and conservator stand bolts for tightness & ensure provision of double nut

Intact

xviii Check / attend Stoochi coupling pipes of conservator for proper layout and fitment and attend for any leakage

Intact


cover

for

&

&

March, 2015

20

2.6


MAIN TRANSFORMER (IOH) SCHEDULE 1.

MAIN TRANSFORMER (IOH)

i

Perform the sample test on transformer oil. Check specific value of BDV and moisture, acidity & DGA.

OK

ii

Oil centrifuging to be done. And used separate plant for different transformer oil. & Maintenance oil as per SMI 158.

72 Hrs.

iii

Replace the silica gel with new crystals.

Blue.

iv

Read off the oil level on the gauge situated on the Middle strip +/- 6”. conservator. Top up the oil as necessary and check for any No leakage. signs of leakage.

v

Prismatic levels gauge-clean the gauge with a dry cloth and check for leaks.

Cleaned leakage.

vi

Visually inspect the high voltage cable at the main transformer connection for damage or oil contamination. Replace the cable if damaged or if contaminated with oil.

OK.

vii

Examine the flanges of the pipe couplings and flexible hose that link the transformer and conservator.

Checked & Found intact.

viii

Visually inspect & clean the electrical connection to the insulator and condition of insulator for crack.

Intact.

ix

Check foundation bolts of transformer with proper torque and Nylock nuts for proper locking.

Intact.

x

Check / attend the condition of earthing shunts of transformer body ( RDSO/SMI/0248 dated 22.11.2007 )

Intact.

xi

Visually inspect the condition of oil cooling metallic pipes, check for leakage / damage & check all fixing clamps. And also check the drain cock, isolating cock for oil leakage & clean it.

Checked Intact found no leakage.

xii

Examine the HV bushing for sings of damage, burning etc. Replace if defective & ensure red marking.

Checked & Cleaned.

xiii

Check the availability of hosepipe over the oil pipe compensator.

OK.

xiv

Check the main TFP and its protection cover for damage / crack & oil leakage. (RDSO/TC/076)

Checked & Found intact.

xv

Check the oil leakage from TFP bushing.

No Leakage

xvi

Examine the bushing for signs of damage, burning etc. Renew if defective. Clean off all deposits and dirt from the insulators.

Checked & Cleaned.

xvii

Check conservator foundation welding and conservator stand bolts for tightness & ensure provision of double nut.

Intact.

xviii

Check/ Attend Stoochi pipes of conservator for proper layout and fitment and attend for any leakage.

Intact.

xix

Replace all rubberized cork sheet and bushing oil seal & gasket as per TC-76.

Done

March, 2015

&


No

21


2.7

MAIN TRANSFORMER POH SCHEDULE

Figure 2.1

01

02 03 04

Lifting of Transformer Winding

Visually inspect the electrical connections, earthing cable, bushing and insulators on the main transformer for cracks, chips and evidence of impact damage. Renew if defective. Clean the connectors and replace any damaged chipped or cracked insulators. Test oil sample for BDV, DGA, acidity and other lab tests. DGA to be done as per RDSO SMI (RDSO/SMI/138 & OEM Doc. Dt. 27th Nov. 1995).Incoming oil test. Check any leakage sign of oil from bushing, tank, pipe line, oil gauge If any attend the same/replased. Visually inspect the condition of oil cooling metallic pipes, check for leakage / damage & check all fixing clamps. Ensure instructions contained in RDSO s letter no. EL/3.2.1/3-Ph dated 30.07.09 for arresting oil leakages ca ses.” Examine the flanges of the pipe couplings and flexible hose that link the transformer and conservator. Maintenance of assembly of electrical terminal of traction winding bushing 2U12V1, 2U2-2V2, 2U3-2V3 & 2U4-2V4 in indigenously manufactured transformers type LOT 6500/7500 used in 3-phase drive locomotives type WAG9/WAP5 .( RDSO/ELRS/SMI/0228 dt. 13.08.02) Replace all sealing gaskets including tank cover gasket. Replace all rubberized cork sheet. Replace all TFP bushings rubber seals Cleaned the transformer winding & tank with filtered transformer oil. Fit the tank & bushing cover with new gasket Fit the all bushings, safety valve, temperature censer, gate valve, drain cock with new gasket. Dry out the windings moisture in vacuumed drying plant & fill the filtered oil. Carry out Insulation Resistance test and Tan delta test. Check the winding resistance, inductance and continuity test , ratio test of the windings. Replace Transformer foundation bolts and bushing nuts.& Tighten with proper torque. Prismatic level gauge – Clean the gauge with dry cloth to check for leaks. If any attend it. Replace the silica gel , in clean & attended breather assembly. Replace the transformer oil. . Conduct centrifuging of the oil (Use separate plant, the shell DIALA-DX oil should not be mixed with any other type of transformer Oil). Check the oil level on the gauge situated on the conservator. Top up if required and any sign of leakage. Finally cleaned & paint the transformer with accessories. ‟

05 06

07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22


March, 2015

22 2.7.1


Painting Procedure Cleaning the affected area

Using sand paper or a sander to smooth down and clean the affected area, a smooth transition to the intact paintwork must be made. Cover the area with primer by including the intact paint work out side. Top coating (Painting of transformer)

Once the primer has been applied, wait at least 6 hours to apply the top coating. It can be applied by painting, rolling or spraying. The drying time at room temperature of about 20°C is 6 hours; at temperatre of 60°C it is 1 hour. Primer Coating

2.8

Two component epoxy resin Two component polyurethane paint

PROCEDURE FOR REPLACEMENT OF BUSHINGS Removal of bushings

The gaskets and the washers outside of the transformer can be replaced without removing the transformer lid. The oil level has to be decreased to 50mm from the lower side of the lid. Once the electrical terminals has been removed, the fixing nut can be untightened. Assembly

Clan the contact surface before assembling, No oil or glue must be applied on the gaskets. Fit the gaskets with the insulator and the corresponding washers on the bolt. Before tightening the fixing nut make sure that the inner insulator mates on the positioning wedge. Once the bushing has been assembled, tighten the fixing nut with a dynamometer (tightening torque). To ensure the tightness of the gasket, retighten the nut a few hours later . The oil level must be topped off to normal level, Use the filling system for this reason. The transformer has to be vented after oil filling. Gaskets of lid

In order to avoid leakages between the upper frame of the tank and the lid, the fixing bolts must be tightened with the following tightening torque. It has to be applied on the nut where accessible.

Figure 2.2 March, 2015

Gaskets of Lid


23


2.9

TRANSFORMER OIL CHECK Taking oil samples

Only clean and dry sample containers should be used. These containers must not contain any traces of cleaning fluids. Before taking oil samples, clean the draining valve on the transformer; 5 litres of oil should then be drained off; after that the sample container should be rinsed using roughly ½ litre of oil. The oil sample must be protected from light. The following are recommended as sample containers: -

glass bottles made out of dark-coloured glass, with a polished glass stopper.

-

Tinned steel cans with a screw top.

-

Clear glass bottle which should be covered with an o paque cover after the sample has been taken.

The oil sample should be at least 2 litres. For laboratory tests, 5 litres are required. If an oil sample is required to determine the amount of water gas or air content, then special vacuum bottles should be used. In such a case we recommend that we should be notified about the preparation of bottles and suction equipment. Checking for any solid impurities in the oil. A test tube should be filled with the oil sample and held up against a light source. If there are any solid impurities in the oil, then the oil from which the sample comes should be filtered. Simple test for water content

This is done using the so-called ‘Spatter -test”, i.e. the oil sample heated in the test tube up to 105-110°C. If there is any water in the oil then this will be noticeable if the oil cracles, snaps or bubbles. If the oil is overheated then the presence of water is falsely indicated; the upper temperature should therefore not be exceeded. Dielectric strength (IEC test)

In accordance with the IEC standard 156 (which also complies with the Swiss standard), this test should be performed using 12.5mm ball electrodes with a diameter of 2.5mm or with the half – ball electrodes (so-called VDE Kalloten) also with a diameter of 2.5mm. The oil sample (temperature 15-25°C) should be slowly poured (to avoid air bubbles) into the clean test container; the test should be carried out immediately. The voltage should be increased evenly up to break down at a rate of 2 kV/second; this should be carried out 6 consecutive times. After each time the space between the electrodes must be free of traces of breakdown; use a clean and dry glass rod (diameter  2mm) and move it slowly in-between the two electrodes. All six break down voltages should be noted and the arithmetic average calculated (i.e. the sum of the individual values divided by six). None of the individual values should lie more than 15% below the average value, otherwise the test must be repeated using a new oil sample.


March, 2015

24

2.10


TESTING OF LOCO TRANSFORMER

2.10.1 Tests

Following common tests to be carried out in the transformer either in case of failure or during overhauling in oil filled conditions. a. b. c. d. e. a.

Insulation resistance test.(Meggering) Continuity test Winding resistance test Ratio test Winding inductance test Meggering

Check the insulation resistance of windings. It should be minimum 2100 M ohms.        

b.

Primary to earth by 2.5 kV megger. Secondary to earth by 1 kV megger. Primary to secondary by 2.5 kV megger. Primary to BUR. by 2.5 kV megger. BUR. to earth by 1 kV megger. Secondary to BUR. by 1 kV megger. Primary to H.L. by 2.5 kV megger. H.L. to earth. by 1 kV megger. GOD Terminal. to earth. by 1 kV megger. SOD Terminal. to earth. by 1 kV megger.

Continuity Test

Check the continuity of the following windings with the multimeter:      

c.

Winding Resistance Test SN

WINDING

1 2

Primary winding Secondary windings BUR winding H.L. winding. SOD. winding GOD. winding

3 4 5 6 March, 2015

Primary winding Secondary windings BUR winding H.L. winding. SOD. winding. GOD. winding.

RESISTANCE VALUE LOT-6500 LOT 7500


25


d.

Ratio Test / Polarity Test.

Apply 230V a.c. supply to the primary winding of the transformer across 1U – 1V and check the voltage appearing at the following t erminals. 1 4 5 6 e.

2.11

And 2V1 2U3 & 2U4. 2U1 & 2U2 2U3 & 2U4

2V1 & 2U2 Sorted 2V3 & 2U4 Sorted 2V1 & 2V2 Sorted 2V3 & 2V4 Sorted

23.35 V 23.35 V 0V 0V

Winding inductance test SN

WINDING

INDUCTANCE VALUE LOT-6500 LOT 7500

1

Primary winding

2 3 4 5 6

Secondary windings BUR winding H.L. winding. SOD. winding GOD. winding

TESTING EQUIPMENT LIST OF TESTING INSTRUMENTS Sr.No.

Instrument

Make / Model No.

Range/Capacity

Yokogawa / WT 330 or similar

As per manual

1

Power Analyzer

2

100 KV HV Test set

SEV or similar

100 KV, 100 mA

3

100 KV Motorised Oil Test Set

SEV or similar

0-100 KV

4

Ratio meter (TR100)

Fifty Hertz / TR100 or similar

--

5

Digital Micro ohm meter

Prestige / PE-17RP or similar

As per manual

6

Digital Megger

Megger Co. or similar

5KV

7

Digital Frequency meter

Prestige or similar

200 HZ

Power analisor

Megger

Oil BDV Tester

100 kV HV SET


Voltage Ratio Meter

Micro Ohm Meter

March, 2015

26

2.12


INSTALLATION OF THE TRANSFORMER ON LOCOMOTIVE During assembly in the locomotive, the main valves of the transformer stay closed. Lift the transformer slowly under the under frame of the locomotive. Make sure that the two centering pins fit in the corresponding hole. The transformer has 4 fixing points each with 4 bolts. So that the bolts are relived of any strains caused by share forces in the horizontal and vertical directions, a centering pin is provided on two diagonally opposite fixing points. The fixing plates are covered with a layer of paint to prevent corrosion which could between aluminium and steel. The mounting surfaces are made in such a way that the exchange of the transformer is guaranteed; tolerances have been taken into account. Assemble the hot dip galvanized washers under the supports when assembling the bolts. Tighten the fixing bolts with 675 Nm. a.

Fitting of Oil Piping Before removing the blanking flanges make sure that all blocking valves are closed. They stay closed during the whole installation. Special care must be taken to ensure that all pipes, pumps and coolers have been thoroughly cleaned and flushed with insulation oil before one proceeds with assembling.

b.

Fitting of the angled connector Before the angled connector can be fitted onto the bushing, the bushing must be properly cleaned. No dirt should be trapped in the connection. To allow easy fitting, the bushing should be slightly greased with silicon. When mounting the angled connector care should be taken that no air is trapped inside. The connector can be vented using a nylon thread on the bushing, which is pulled out when the angled connector is fitted.

c.

Electrical Connections

The electrical terminations of the bushings have to be carried out in a way, that the nut 11.1 stay accessible to be re-tightened. Electrical connections must not be numb. They should be made flexible so that the bushing isn’t stained. Cable connections should be made with a loop, for bars use flexible ribbon to connect them on the bushing. When assembling the electrical connections, make sure that the nut 11.1 does not become loose. Keep a distance of min. 3 mm between the 2nuts. After assembling of the connection re-tighten the nut 11.1. The tightening torque for each type of bushing is indicated in the table given below

Figure 2.3

March, 2015

Electrical Connection


27


DIN type DT 1/250 DT 1/ 630 DT 1/1000 DT 1/2000

d.

Tightening torque and max. horizontal load for DIN bushings Drawing no. D Section (mm2) Bolt Extern. HSTN 310 500 M12 74.5 84.3 HSTN 310 501 M 20 220 245 HSTN 310 502 M 30 x 2 596 621 HSTN 310 503 M 42 x 3 1150 1210

M

F

10 30 65 150

50 60 80 100

Earthing Terminal Fitting

In order to avoid discharges and unwanted failures, all metallic parts inside and outside the transformer are earthed. The earthings of the transformer active part and the reactors are connected with each other via the tank. The marked earthing terminals have to be connected to the locomotive’s earthing terminals.

Figure 2.4 e.

Inside Earthing

Figure 2.5

Outside Earthing

Filling the remaining oil

Once the transformer has been installed in the locomotive and all piping connections to the heat exchanger and the pump have been made, it is necessary to fill the remainder of the cooling system with oil. The oil used must comply with the relevant specifications. Casting doubt on, an oil test has to be carr ied out. The transformer main valves should only be opened when all pipes and the heat exchanger have been filled with oil and vented. No air should enter the transformer assembly from the piping or the heat exchanger. f.

Filling with oil barrel

The barrel with the insulation oil has to be brought on a higher level than the lid of the transformer, join the oil barrel with a flexible pipe to the draining tap (13.1/ 13.3). All apparatus must be cleaned and free of dirt and moisture . Fit a silica breather to the barrel’s breather port. g.

Filling with pump

The oil filling system, which should be suitable to a standard oil barrel standing vertically, must not exceed a flow of 5litre/min and it must contain a no return valve. All apparatus must be cleaned and free of dirt and moisture. Fit a silica gel breather to the barrel’s breather port. Fit the filling system with a flexible pipe to the draining tap (13.1/13.3). Start pumping and drive any air out of the filling system. Maintenance Handbook on Transformer of 3 Phase Electric Locom

March, 2015

28


h.

Venting the pipe work and heat exchangers

Make sure that there isno air in the filling hose. Crack open the drawing tap (13.1/13.3). Open the venting tap (13.2) on the heat exchanger until oil runs out. Close venting tap (13.2) and draining tap (13.1/ 13.3). Repeat this procedure on the opposite side. Connect the filling hose to the draining tap (13.4/ 13.6) and vent the pipe with venting screw (13.5) on the heat exchanger. If during the filling process a change of barrel is required, stop pumping before air is drawn into the system. Close the venting and the filling tap, change the barrel, run the pump and drive any air out of the filling system. Continue filling.

Figure 2.6 Transformer Layout in the Loco i.

Oil pumping

Before the pump is put up into action, make sure that the pumps, piping and heat exchanger are filled with oil. Never start the pump without oil. j.

Checking the direction of rotation

Remove the screw plug (14.1) and push the head face on the shaft of the rotation indicator (14.2). The rotation direction of the pump is correct when the rotation indicator turns in the same direction as the arrow. After completing the check, refit the screw plug (14.1)

Figure 2.7 Transformer Layout in the Loco March, 2015



k.

29

Venting

Once all pumps, pipes and heat exchangers are filled up with oil, the transformer main valves can be opened. Secure the valves in open position. To drive any remaining air out of the system, put the two oil pumps in operation for 30 seconds. Let the whole system resting during 30 minutes. Connect the filling system to one of the draining taps, put it into action and crack open all vent plugs (15.1) on the transformers lid until oil leaks out. Repeat this procedure until the total breathing of the system. Adjust the oil level in the expansion tank a fter.

Figure 2.8

2.13

Transformer Assembly Venting Layout

CHECK POIINTS WHILE MAINTENANCE a.

Oil Level Check

The oil level in the expansion tank has to be checked each time beore switching on the transformer and in case of non use at least every 6 months. The oil level in the expansion tank must be equal to the corresponding temperature mark on the sight glass (17.3) b.

Oil Level beneath the corresponding temperature mark

In case of the oil level is under the corresponding temperature mark, oil can be added directly by the filling plug on the expansion tank. The oil used must comply with the relevant specification. c.

Oil level not visible on the sight glass

If the oil level isn’t visible on the sight glass (17.3), the transformer must not be switched on. The oil must not be toped off by the filling plug on the expansion tank. One have to control the distance between the lid and the oil level in the transformer. For this reason open one of the vent plug on the transformer lid and measure the distance between the upper side of the plug and the oil level. If the distance is lower than 100mm the oil can be topped off by the draining valve of the transformer or the pipes between transformer and heat exchanger. The transformer has to be vented after. Maintenance Handbook on Transformer of 3 Phase Electric Locom

March, 2015

30


If the distance between upper side of the plug and the oil level is more than 100mm then the level can only be topped off under vacuum conditions. For this reason the transformer must be removed from the locomotive and put in a vacuum oven. d.

Oil level above the corresponding temperature mark.

If the oil level is above the corresponding temperature mark, oil can be drained by the draining valve on the transformer.

Figure 2.9 e.

Expansion Tank

Silica Gel Breather

According to the atmospheric conditions, the colour of the silica gel should be checked roughly every six months. When more than half of it is pink (saturated with water), then it should be replaced. The saturated silica gel can then be dried out. Put it in an oven and increase the temperature slowly min 115°C to max. 150°C. Keep the temperature until the silica gel turns blue again. Silica gel should not be dried-up in sun light as because of insufficient heat only the outer layer gets dried up. However, this process should not be repeated too many times; after a while the silica gel appears to be not so effective, probably due to the ingress of dirt.

Good Condition

Bad Condition

Figure 2.10 f.

Silica Gel

Leakage of expansion tank

Whenever breather, silica gel colour more than half got pink (saturated with water)

March, 2015


31


2.14

TRANSFORMER OIL The transformer unit is filled with 2000 kg of mineral oil. The oil serves as a cooling and insulating agent.

2.14.1

Oil Specification Ref. no Characteristic

Unit

Value

00001

Ident. Text

--

Insulation oil T1

00002

Ident no.

--

NBT 402614P0201

01000

Description

--

The insulation oil T1 is a pure mineral product without any additive; it is used in transformer and switch gear.

01120

Density at 20°C

g/ml

 0.895

01500

Delivery instructions

--

ZN 02125

01800

Documentation

--

ZLC – documentation HSTC 419458

05100

Colour

--

Pale yellow to yellow

07900

Special properties

--

The oil is not cloudy and is free of solid particles and water

26350

Pour point IEC class IA IEC class IIA

°C

 - 30  - 45

Test method

ISO 3675 DIN 51757 and

QZ

ISO 3016 ASTM D 97-66 DIN 51597

29300

Flash point in enclosed crucible

a

°C

 130

22500

Thermal expansion coefficient

K -1

Standard NB 214200

31300

Dielectric loss factor -tan  at 90°C 50 Hz

 0.005

IEC publ. 247-1978 VDE 0370/ 12.78

35300

Break-down voltage

kV

 50

IEC publ. 156

43700

Interface tension

mN/m

 40

ASTM D 971-50

45100

Cinematic viscosity At + 20°C At + 40°C At – 15°C class IEC IA At – 30°C class IIA

mm /s

 25

ISO 3104

51370

Corrosive content

--

55100

Neutralisation value

55350

Aniline point

sulphur

2

ISO2719 ASTM D 93 – 66 DIN 51758

 11  800  1800

None

mgKOH/g  0.03 °C


 80

DIN 51353 IEC Publ. 296-1978 ISO 2977 DIN 51775 March, 2015

32


2.14.2 Purification of Transformer Oil

Figure 2.11

Purification of Transformer Oil

The object of oil purification is to remove all contaminants such as water, carbon deposits, dirt, sludge, dissolved moisture and gases. The most important quality to be preserved is the di-electric strength, which is affected by the presence of moisture. The insulating materials used in the winding are hygroscopic by nature and therefore moisture is absorbed through defective breathers, gaskets and addition of untreated make up oil. It is essential to remove these impurities by purifying the oil when the dielectric strength goes below the permissible limits. The purification plant should be capable of removing dissolved air/ moisture in the form of free and finely dispersed water vapour and moisture in solution, sludge and fibers, gases, carbonaceous products formed due to arcing and drum scale or any other solid particles from insulating oil. The plant should be capable of purifying the rated capacity of transformer oil to the following parameters in maximum three phases. a. Suspended impurities – maximum 1 micron particle size. b. Water content – from 100 ppm to less than 5 ppm c. Gas removal – from fully saturated i.e. 10 to 12% by volume with air/gas down to less than 0.25% d. Acidity correction – with addition of clay filters the neutralization index should go down from 0.5 to 0.05 mg KOH/ gm of oil. e. Dielectric strength – Minimum 60 kV f. Dissipation factor of oil/ tan delta at 90°C – 0.002 The switching ON & OFF of the heater groups should be thermostatically controlled so that the temperature of the oil during treatment is not be permitted to rise above 60°C. Operating vacuum should be better than 1 torr. March, 2015


33


Filtration of EHV grade oil to be carried out at a vacuum level of 98% at a temperature of 60 degree C and of inhibited oil at a pressure of 0.15 torcillie at a temperature of 60 degree C, provided the specific resistance is within limits. Filtration should continue till such time the oil is completely dried. Check the filtered oil sample for electrical strength and water content and if these parameters are within the limits, the oil is fit for use and if not, repeat filtration till electric strength and water content are within limits. Water content in Oil

Test Test method Periodicity Permissible limit Requirement of new oil

: : : : :

Water content (PPM) As per IS:335-1983 IC/ AOH/ IOH/ POH 35 PPM (Max.) 25 PPM (max.)

Figure 2.12

Water content test set

Acidity in Oil


: : : : :

Total Acidity As per IS:1448-67 IC/ AOH/ IOH/ POH 0.5mg KOH/gm (Max.) 0.03mg KOH/gm (Max.)

Figure 2.13

Acidity Test Set

Oil breakdown voltage


: : : : :

Electrical Strength (Break down voltage) As per IS:6792-72 IC/ AOH/ IOH/ POH 30KV (rms)(min.) 60 KV (rms)

: : : : :

Flash point As per IS: 1448-1970 IOH/ POH 125 deg. C (Min) 140 deg. C (Min)

Flash point



March, 2015

34


INSULATION RESISTANCE DURING DRYING OUT Readings of temperature and insulation resistance should be recorded every two hours, from commencement until the full operation is completed. If these readings are plotted on a graph, the appearance will be as shown in fig.

S M H O G E M N I E C N A T S I S E R N O I T A L U S N I

E R U T A R E P M E T

Fi ure 2.14

Insulation Resistance Gra h

It is observed that there are four distinct stages: A.

Initially the insulation resistance drops down to a low value because of rise in temperature of the oil up to about 60 degree C.

B.

Insulation resistance will continue to remain at a low level despite temperature being maintained at a high level until most of the moisture from the windings and oil has been driven out.

C.

The insulation resistance will thereafter rise gradually and level off, indicating that all moisture has been driven out and the drying out operation has been completed. At this point oil circulation should be discontinued.

D.

As the oil cools off, the insulation resistance will rise much above the leveling off point at the end stage (C). This is because the insulation resistance value doubles for a fall in temperature of about 10°C to 15°C.

2.14.3 Condition Monitoring Of Transformer by Dissolved Gas Analysis


: : : : :

Dissolve gas analysis As per SMI 138 IC/ AOH/ IOH/ POH As per SMI 138 --

Figure 2.15 March, 2015

DGA Analysis Set (A)


35


A.

Introduction

In order to detect incipient faults in the transformer and to arrest deterioration/ damage to the transformer insulation, gases dissolved in the transformer oil are detected, analysed and preventive measures adopted. Gas Chromatography method is used for detection of the dissolved gases and identification of incipient faults. The most significant gases generated by decomposition of oil and deterioration of paper insulation on the conductor are hydrogen, methane, ethane, ethylene and acetylene. The quantities of these gases dissolved in transformer oil vary depending upon the type and severity of the fault conditions. B.

Sensitivity Limits

Gas Chromatography apparatus should be able to detect the following minimum concentration of dissolved gases: Hydrogen : Hydrocarbon : Carbon oxides :

5 ppm 1 ppm 25 ppm


March, 2015

36


Figure 2.16

March, 2015

DGA Gas Extraction System


37


C.

Establishment of Reference Values/ Bench Marks

To establish a reference value/ bench mark, gas as generated from initial sample of oil from each healthy transformer should be collected. Results of the analysis are taken as a reference value/ benchmark. Results of later periodic analysis are compared with the benchmark for each transfor mer. D.

Establishment of Norms

The contents of various dissolved gases in the transformer oil vary with design and operating conditions. It is desirable that the values of concentration of gases of healthy transformers of different age groups are to be gathered by the Railways concerned to evolve suitable norms. However, as a starting point, the permissible concentrations of dissolved gases in the oil of a healthy transformer are given below as guidelines: Gas

E.

Less than 4 years in service (ppm) Hydrogen (H2) 100/150 Methane (CH4) 50/70 Acetylene (C2 H2) 20/30 Ethylene (C2 H4) 100/150 Ethane (C2 H6) 30/50 Carbon dioxide (CO 2) 3000/3500 Diagnosis of Fault

4-10 years in More than 10 years service (ppm) in service (ppm) 200/300 200/300 100/150 200/300 30/50 100/150 150/200 200/400 100/150 800/1000 4000/5000 9000/12000

Basic Diagnosis of DGA is based upon the quantities of gases generated. Types of gases in excess of norms produced by oil decomposition/ cellulosic material depend upon the hot spot temperature produced by faults. Characteristics of gases associated with various faults are as under: Methane (CH4) Ethane (C2 H6) Ethylene (C2 H4) Acetylene (C2 H2) Hydrogen (H2) Carbon dioxide (CO 2) Carbon monoxide (CO) F.

Low temperature hot spot High temperature hot spot Strong over heating Arcing Partial discharge Thermal decomposition of paper insulation

Word of Caution

To start with the diagnosis, it is necessary to be satisfied that measured gas concentrations are significant and high enough to warrant diagnosis, because some amount of gases will always be there due to normal operating conditions without any fault but it can be sufficient to be misleading. The reasons for the situation are: 



Gases formed during the refining processes and not completely removed by oil degassing. Gases formed during drying and impregnating the transformer in sheds/ workshops.


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38

CAMTECH/E/14-15/3 Loco Transformer/1.0 



G.

Gases formed in the event of previous faults and not completely removed from the oil-impregnated insulation before being refilled with degassed o il. Gases formed during repairs by brazing, welding, etc.

Procedure for Fault Diagnosis 















Obtain the results of concentration of various gases in ter ms of microlitre (ppm). Compare the concentrations with sensitivity limits. These should be at least ten times the sensitivity. If it exceeds sensitivity limits, compare with benchmarks. If it exceeds benchmarks, compare concentrations with norms depending upon age and design of transformer. If one or more gases are above norms, compare with the last sample results; if increase is sufficient, obtain a check sample. If the check sample confirms the results, calculate the rate of increase of gas. If rate of increase is more than 10% per month, it is considered rapid and warrants immediate further investigations including lifting of core and internal inspect ion. If the gas production rate is medium, i.e., less than 10% per month, sampling frequency to be increased from quarterly to monthly. Take a planned shut down for further investigation. *****

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Figure 2.17

39

Typical Arrangement in a Gas Chromotograph


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40


Figure 2.18

Sample Strip Chart

Dissolve Gas Analysis (DGA) Do’s

1. Give sufficient time for stabilization. 2. Replaced the saptan after every 15 injection 3. Check sapton before start the equipment. 4. Keep standby colomn. 5. Use stabilization electricity with proper earthing. 6. Flush the syringe after each injection. 7. While fire use proper fire extinguisher. 8. Check all leakage before testing. Don’ts

1. Don’t start TCD before opening of gas. 2. Don’t increase filament current out of safe limit. 3. Don’t excess gas flow in column.

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41


CHAPTER 3

MODEL QUESTIONS 3.1

OBJECTIVE 1.

2.

3.

4.

5.

6.

Before starting work on faulty circuit it should be ensured that a.

The faulty circuit has been isolated from power supply and earthed.

b.

The worker is capable to do the work.

c.

The connections are not approachable.

d.

None of the above.

One can protect himself from electric shock by wearing hand gloves of good. a.

Conducting material

b.

Insulating material

c.

Semiconductor material

d.

Any of the above.

Which of the following are safety precautions? a.

Don’t touch live wire or equipment with bare hands.

d.

Before switching on DJ, see no one is working inside loco.

c.

Use insulated melting and hand gloves.

d.

All of the above.

Which material is recommended as fire extinguisher in electrical cases? a.

Carbon tetra chloride

b.

Carbon dioxide

c.

Sulphur hexafluoride

d.

Any of the above.

The BDV of transformer oil should be a.

20kV

b.

30kV

c.

40kV

d.

50kV

The colour of moisturized silica gel is a.

Pink

b.

Blue

c.

Yellow

d.

Green


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March, 2015


7.

The material filled in breather of transformer is a. Silicagel b. Sulphuric acid c. SF6 d. Mineral oil

8.

The protective device to internal fault in a transformer is a. Current relay b. Bucholz c .Lead d. Silicon steel

9.

Three phase Loco Transformer Tank & Lid made of material. a. Iron b. Copper c. Stainless Steel d. Aluminium

10.

Which of the following is not the function of transformer oil a. Cooling of winding and core. b. Providing additional insulation c. Media for are quenching d. Provides inducting coupling

11.

Transformer oil should be free from a. Odour b. Gases c. Temperature d. Moisture

12.

The short circuit test of a transformer gives a. Copper loss at full load b. Copper loss at half load c. Iron loss at any load. d. Sum of iron loss and copper loss.

13.

The type of oil, which is suitable as transformer oil is a. Crude oil b. Organic oil c. Mineral oil d. Animal oil

14.

Transformer is an example of a.

Current transformer

b.

Potential transformer

c.

Auto transformer

d.

All of the above Maintenance Handbook on Transformer of 3 Phase Electric Locomo


15.

16.

17.

18.

19.

20.

43

The colour of fresh transformer oil is a.

Pale yellow

b.

Dark brown

c.

Blue

d.

Colourless

The purpose of conservator tank in a transformer is to a.

Monitor oil level

b.

Top up the oil

c.

Both a & b above

d.

None of the above.

The saturated silica gel can be dried out in the oven at the max temperature until silica gel turn blue again. a.

60°C

b.

160°C

c.

150°C

d.

115°C

The oil sample container should be rinsed sample oil quantity a.

½ Ltrs.

b.

1 Ltrs.

c.

2 Ltrs.

d.

1½ Ltrs.

The oil sample are require to test. a.

2 Ltrs.

b.

3 Ltrs.

c.

4 Ltrs.

d.

5 Ltrs.

Dielectric strength of oil should be performed using 12.5 mm ball electrodes with a gap ofa.

04mm

b.

05mm

c.

2.5mm

d.

03mm


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3.2.


FILL IN THE BLANKS 1. Transformer is a ………….device 2. G-9 Loco transformer has…………….windings 3. G-9 Loco transformer has………………..tank 4. G-9 Loco Required variable voltage is achieved by the use of ……….…………. 5. An emf induced in a coil due to variation of flux in another coil is called…… 6. The coils of a transformer are wound on a …………core of ………….material 7. The conductors used in HV and LV windings of loco transformer are………… 8.

In G-9 Loco The primary side is protected from the voltage surges by means of ………….placed on the roof of the locomotive.

9.

The auxiliary winding is protected from sudden rises in voltage by means of ………………connected across the winding.

10. Ingress of moisture is prevented by means of ……………. 11. The complete cooling arrangement includes……….., ………..and………….. 12. The oil pump and the cooler are connected to the conservator by………………… 13. The breather is attached to ………………and contains…………… 14. Pink colour of silica gel indicates…………….. 15.

The colour of transformer oil become dark brown, it indicates presence of …… ……

16. Operating vacuum of transformer oil purification plant shoul be …………. 17. DGA stands for ………………….. 18. Transformer must never be lift without its………………. 19. Oil BDV Test six consecutive reading should not lie more then…… 20. The lifting ropes should not make a smaller angle then….with the horizontal.

3.3

SAY ‘TRUE’ OR ‘FALSE’

1. Transformer transforms power from one AC circuit to another AC circuit, at same frequency. 2. Transformer can raise or lower the voltage. 3. Transformer can raise or lower the frequency. 4. Two circuits in a transformer linked by a common magnetic flux through a path of low reluctance. 5. In case of step up transformer, the transformation ratio will be more than one. March, 2015


45


6.

Constructional features of a loco transformer are more or less same other power transformer.

7.

25 kV condenser/ cable head bushing is mounted on the top of the tank cover.

8.

The cooling arrangement of the loco transformer is force oil forced air t ype.

9.

In G-9 Loco the complete cooling equipment is mounted on the cover of the loco transformer.

10.

In G-9 Loco spring-loaded safety valve is fitted to t he top of the conservator.

11.

Presence of moisture in transformer oil is highly desirable.

12.

The oxygen present in transformer reacts with insulation and forms an organic acid.

13.

The solid impurities present in insulation oil strengthen its dielectric strength as well as insulation of windings.

14.

The slackness of winding is desirable factor to create electrical and magnetic unbalance of the coils.

15.

Meggering is done to check the insulation resistance of t he windings.

16.

The tightening torque of the bolts of tank and lid must be 70 Nm.

17.

To arrest the oil leakage from bushing RDSO has recommended to use ISI make gaskets.

18.

Bushing gaskets to be replaced as per TC- 076.

19.

New M.S. hardware may be used in transformer flange joints fitting.

20.

Periodic maintenance of transformer is essential to ensure safety, reliability and trouble free operation of Locomotives.

ANSWERS

3.1-

1 (a), 2 (b), 3 (d), 4 (b), 5 (d), 6 (a), 7 (a), 8 (a), 9 (d), 10 (d), 11 (a), 12 (a), 13 (c), 14 (d),

3.2-

1- Static,

2- 04,

15 (a), 16 (c), 17 (c), 18 (a), 19 (d), 20 (c).

3-Aluminium Alloy, 4-GTO or IGBT, 5-Metual Induction,

6- Leminated, Silicon Steel, 7-Continuous Transposed Cu Conductor, 8- Lightening arrester, 9-RCL Damping, 11- Radiator & Blower,

12-oil Pipe, 13-Conservator, Silicagel, 14-Humid

15- Acid & Impurties, 16-1Torr,

3.3-

1-T,

2-T,

3-F,

4-T,

10-Air dehumidifire,

5-T,

12-T, 13-F, 14-T, 15-T, 16-T,

17-Incipien fault,

6-T, 17-F,


7-T, 18-T,

18-Lid, 19-15%, 20-60°.

8-T, 19-F,

9-F,

10-T, 11-F,

20-T.

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AN APPROACH TO EQUIPMENT FAILURE INVESTIGATION A.

On Failure Aspects 1. Occurrence 2. Date of occurrence 3. Past similar occurrences if any 4. Analysis of failure i.e. why did it happen? 5. Whether the rate of failure is worse than other installations?

B.

On Maintenance Aspects

C.

D.

E.

F.

1.

Whether schedule maintenance & required testing have been carried out on the failed equipment as per norms stipulated?

2.

Does the frequency of maintenance require change?

3.

Was the work properly supervised?

4.

Was any RDSO modification required to be done?

5.

Is any modification possible to avoid failure?

About Staff

1.

Is the quality of work done satisfactorily?

2.

Is the skilled staff properly trained to carry out the work?

3.

Is the SMI available with them?

4.

Are proper tools available with the staff?

About Material

1.

Is the material received from approved source?

2.

Whether the material is as per approved specification?

3.

Can a better material be used?

About Testing

1.

Is the testing equipment available?

2.

Could testing procedure be improved to weed out the failures?

3.

Whether testing equipment are calibrated?

General Points

Whether following points were checked / performed properly?

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1.

Proper contact

2.

Clearances

3.

Capacity

4.

Proper contact pressure

5.

Crack detections

6.

Cleaning

7.

Proper connections/alignment

8.

Cross checks/super checks


47


ANNEXURE – ‘I’

Reliability Action Plan (RAP) Condition monitoring of loco transformer by Dissolve Gas Analysis. ( RDSO/SMI/138 & OEM Doc. Dt. 27th Nov. 1995). Replacement of bushing gaskets during IOH inspection.( ELRS/TC/0076 dt. 17.09.2002). Maintenance of transformer oil in service .(RDSO/ELRS/SMI/158 dtd. 19.01.95). Maintenance of assembly of electrical terminal of traction winding bushing 2U1-2V1, 2U22V2, 2U3-2V3 & 2U4-2V4 in indigenously manufactured transformers type LOT 6500/7500 used in 3-phase drive locomotives type WAG9/WAP5 .( RDSO/ELRS/SMI/0228 dt. 13.08.02) Ensuring tightness of stuchi coupling, base plate and conservator tank foundation bolt during overhauling. As per OEM guidelines & present practices followed by shed. “Ensure instructtions contained in RDSO’s letter no. EL/3.2.1/3-Ph dated 30.07.09 for arresting oil leakages cases.”


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REFERENCE

1.

ABB Maintenance manual.

2.

Electrical Technology Books.

3.

RDSO SMI 138, 158

4.

RDSO MS 0228.

5.

RDSO TC - 076

6.

Details collected from various field units (Shed and workshop).

7.

Details collected from M/s High voltage Electrical Ltd. , Mumbai

6.

Suggestions received during the seminar held on 30.10.2014 organised by CAMTECH/ Gwalior.

March, 2015


Maintenance Handbook on Transformer of 3 Phase Electric Locomotive

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