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of 26 Issued on 29.09.2016 Report No. RDSO/2016/EL/IR/173, Rev.0

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GOVERNMENT OF INDIA MINISTRY OF RAILWAYS

Report on Reliability of

Transformer of Three Phase Electric Locomotive

Report No.: RDSO/2016/EL/IR/173. Rev ‘0’

Issue Date: September’ 2016

Approved by

EDSE(CO-ORD) Signature

Issued by

Electrical Directorate Research, Designs and Standards Organisation

Manak Nagar, Lucknow-226011



Status of Revision

S. No. Date of Revision Page No. Revision Reason of Revision



Table of contents

S. No. Description Page No.

1. Introduction 4

2. Rating of Three phase Loco transformer 5

3. Different Parts of Three phase Loco transformer 6

4. Background 7

5. General steps to improve reliability of transformer: 7

6. Condition monitoring of traction transformers by Dissolved Gas Analysis (DGA)

11

7. Specific Steps to improve reliability of Transformer 13

8. Failure mode & Modifications to be carried out by Manufacturers.

13

9. Oil leakage from the transformer bushings and covers in 3-phase locomotives

20

10. Conclusion and Recommendations 24

11. Annexure-I 26



1.0 Introduction:

Initially, 33 Nos. of 3-phase drive (11-WAP5, 22-WAG9) locomotives were imported

from M/s ABB/Switzerland (now M/s. Bombardier Transportation) with transfer of

technology. These locomotives had Secheron make main 7500 / 6500 KVA

transformers. When these locomotives were taken up for indigenous production at

CLW, main transformer was got developed through M/s. BHEL, M/s CGL, M/s

BT/India, M/s NGEF & M/s EMCO based on Transfer of Technology (TOT). Later

on, few more sources obtained TOT from CLW. So far, CLW have manufactured

about 89 WAP-5, 700 WAG-9/WAG9H and 279 WAP-7 (passenger version of WAG9)

locomotives; majority of which have been provided with indigenously manufactured

traction transformers supplied by TOT partners.

A three phase Electric locomotive Traction Transformer consists of one Primary

winding, four Traction windings, one Auxiliary winding (BUR) and two Hotel Load

windings (Originally the transformer of WAP5 loco was provided with only one 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 traction converter) & 03 Auxiliary Converter double chokes (one for each of

the 03 auxiliary converters). The 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.

Unlike the transformer provided in conventional electric locomotives the

transformer provided in three phase locomotives is equipped with special features

as follows:

• Transformer is mounted under slung on under frame

• Transformer is designed for feeding GTO/IGBT based Power and Auxiliary

converter load.

• It has very high impedance between primary & traction windings to satisfy

operational requirements

• 100% de-couplings between windings

• Use of continuous transposed conductor (CTC) for windings

• Use of disc construction of windings

• Transformer and conservator tank made of Aluminum Alloy.



2.0 Rating of three phase Locomotive Transformers:

Table1: Rating of Transformer

SN Parameters Values

1 Type LOT-6500/LOT-7500*/LOT-7775**

2 Original Design Secheron SA

3 Windings: Nos.

Traction

Auxiliary

Filter

Hotel Load*

4

1

1

1*/2**

4 Frequency (f nom) 50 Hz

5 Primary Voltage:

Maximum

Nominal

Minimum

30.0 kV

25.0 kV

17.5 kV

6 Voltage Ratings (at 25.0 kV Catenary):

Traction

Auxiliary

Filter

Hotel Load*

1269V

1000V

1154V

750V*/960**V

7 Current Ratings:

HT

Traction

Auxiliary

Filter

Hotel Load*

261A/299A/311 A

4 x 1142A

334A

347A

1X1260A*/2X648A**

8 Thermal Ratings:

Primary

Traction

Filter

Hotel Load*

6531 kVA/7500 kVA/7775 kVA

4 x 1449 kVA

400 kVA

945 kVA*/2X622.5kVA**

9 Winding Data:

Traction

Auxiliary

Filter

Hotel Load*

37.0 mΩ, 2.1 mH ± 15%

60.0 mΩ, 0.43 mH

19.0 mΩ, 0.29 mH

11.0mΩ, 0.37 mH*



3.0 Different parts of Transformer: The LOT 6500/7500/7775 transformer has following main parts:

1. Transformer tank: Transformer tank : Material : Aluminium Colour : RAL-7009 Weight : 966 kg

Figure1: Transformer Tank

2. Transformer main winding: Power (kVA)= 6531/7500/7775 Voltage: 25000 V Current: 261.25/299/311 Amp Winding Resistance 489.5 to 585.9 mOhm

Figure 2: Transformer main winding

3. SOD Winding (Series Resonant Choke): Inductance per choke : 2 x 0.551 mH (±15%) Linear to I peak = 1391A ii) Thermal current ITh : 2 x 984A iii) Resonant frequency : 100 Hz iv) Voltage stress between a. terminals max. : 482 VAC b. to earth max. : 3471 V v) Separate voltage withstand capability : 10 KV

Figure 3: SOD Winding

4. GOD Winding (Auxiliary Converter Choke): Current (Amp) Inductance (mH) 0 30 120 30 155 26 190 20 Frequency 100 Hz Ripple 38% (Nom) 50.2 max Voltage to earth 1153V (Rated) 2000V

(Max) Separate voltage withstand capability

10 kV

Figure 4: GOD Winding



4.0 Background:

Zonal Railways had been reporting increased number of failures/problems in the

indigenously manufactured transformers for 3-phase electric locomotives. Based on

the failure analysis and study of different types of failures, various corrective

actions have been suggested by RDSO to manufacturers and Zonal Railways vide

different letters and MOMs. The general measures required to improve reliability

and other modifications suggested by RDSO from time to time has been compiled in

this report. These measures are divided in two parts i.e. general measures and

special measures. The general measures include condition monitoring of

transformers by various methods such as Dissolved Gas Analysis (DGA) and

benchmarking of abnormal DGA values. The special measure includes the steps to

be taken based on the specific failures reported. Such types of failures includes

core heating, circulating current in earthing shunt or overheating of clamping

structure leading to abnormal DGA. Also, cases of oil leakages had been reported in

transformers and special steps had been suggested by RDSO based on the

discussion with manufacturers.

5.0 General steps to improve reliability of transformer:

In order to ensure reliable performance of a transformer, there are several steps

required from transportation to storage of transformer. These small steps as

detailed below should be taken by Electric Loco sheds/manufacturers to enhance

the reliability of a transformer.

5.1 Transportation of transformer:

The transformer is to be transported duly filled with oil. The conservator is

transported along with the transformer without oil and oil is supplied in separate

drums. The breather should be removed during the installation of the transformer

in the locomotive, and put back as soon as possible. The breather must be filled

with new or dried silica gel.

5.2 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 that the tank

will distort.

(a) Correct Method (b) Incorrect Method

Figure 5: Lifting of a Transformer

5.3 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 6: Supporting of Transformer

5.4 Storage of Transformer:

The transformer can be stored as long as required. However, following points

should be given proper attention while storing a transformer.

Support points of transformer



5.4.1 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 loose taped plastic sheet.

Figure 7: Stored TFP

5.4.2 Connecting flanges

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

Figure 8: Connecting Flange

5.4.3 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

between the minimum and maximum temperature mark.

Figure 9: Expansion Tank



5.4.4 Labels:

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).

Figure 10: Labeling

5.4.5 Checks:

After transport and installation at the storing place the transformer should be

checked for any signs of oil leakage.

5.5 Maintenance during Storage: 5.5.1Checks

According to the atmospheric conditions, the oil level and the silica gel in the

breather should be checked every 6 months.

5.5.2 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.

5.5.3 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.

TFP No. 2042130 Make: BHEL Date of O/H:20/8/16



6.0 Condition monitoring of traction transformers by Dissolved Gas

Analysis (DGA):

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. The complete details of method of measurement are given in RDSO

SMI No. RDSO/ELRS/SMI/138. However basic details are given below for ready

reference.

Basic diagnosis of DGA is based upon the quantity of gases generated. Types of

gases in excess norms produced by oil decomposition/cellulosic material

depends upon the hot spot temperature produced by faults. Characteristics

gases associated with various faults are as under:-

Table: 2

S. No. Dissolved gases. Associated faults.

i. Methane (CH4) Low temperature hot spot.

ii. Ethane (C2H6) High temperature hot spot.

iii. Ethylene (C2H4) Strong over-heating.

iv. Acetylene (C2H2) Arcing

v. Hydrogen (H2) Partial discharge

vi. Carbon dioxide(CO2) & Carbon monoxide (CO)

Thermal decomposition of paper insulation

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:



6.1Permissible concentrations of dissolved gases in the oil of a healthy

transformer:

Table: 3 Gas Less than 4 years

in service (ppm)

4-10 years in

service (ppm)

More than 10 years

in service (ppm)

Hydrogen (H2) 100/150 200/300 200/300

Methane (CH4) 50/70 100/150 200/300

Acetylene(C2H2) 20/30 30/50 100/150

Ethylene (C2H4) 100/150 150/200 200/400

Ethane (C2H6) 30/50 100/150 800/1000

Carbon dioxide (CO2)

3000/3500 4000/5000 9000/12000

6.2 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 (50 kv for in service oil and 60 kV for new oil ).

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 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.



7.0 Specific Steps to improve reliability of Transformer:

7.1 Failure of transformers on account of abnormal DGA- Design issues:

In spite of predictive maintenance actions taken by electric Loco sheds, the

problems in 3-Ph locomotive transformers on account of abnormal DGA which

was reported high due to one or more reasons of has been observed. The failed

transformers were opened at the works of M/s BHEL and M/s ABB in presence

of RDSO representatives and found overheating/flashing marks observed on

the guide pin of the clamping fixture of centre tie rod. 01 No. LOT 7500 KVA

transformer of M/s CGL was also reported with abnormal DGA. The

transformer was opened at CGL‟s Works at Mandideep in presence of RDSO

representative where overheating marks observed on the centre tie rod.

Based on the failure analysis and discussion with M/s ABB and M/s BHEL, it

was concluded that DGA was found high due to reasons of core heating,

circulating current in earthing shunt or overheating of clamping structure. In

order to eliminate these failures, following modifications had been identified for

implementation. Further based on the positive results of these modifications, it

was decided to implement these modifications in all the transformers

supplied/repaired by the manufacturers. The details of modifications are given

below:

7.2 Failure mode and modifications to be carried out by manufacturers:

7.2.1 Due to less cooling of outer (last) core packet, heating marks had been observed as shown in figure-11 leading to abnormal DGA cases.

Figure 11: Heating mark observed on the core due to less cooling.



In order to improve cooling, it was decided to remove the side wedges of outer

(last) core packet in all the transformers to be manufactured/repaired.

Following Figure-12 shows the details of modification to be carried out. After

implementing this modification, such type of cases has not been reported.

Wedges provided

Figure 12: Removal of side wedge of outer (last) core packet

7.2.2 In addition to above, it was decided to introduce (2 x 15 mm) slot in the

existing 5 x 30 mm rectangular outer core wedge as per details given in

Figure-13 for improving the core cooling. Earlier, RDSO had permitted M/s

BHEL to use existing rectangular wedge 5 x 30 mm with slot dimension as 2

x 10 mm.

Figure 13: Introduction of slot (2 x 15 mm) in the existing 5

x 30 mm rectangular outer core wedge



7.2.3 In order to block the circulating current between reactive active part and

tank it was decided to use of insulating washer as per details given in Figure

14 in the fixation of reactor and tank to improve isolation between reactor

active part & tank.

Figure 14: Use of insulating washer

7.2.4 The circulation of induced current in the centre tie rod had resulted into heating of the centre tie rod as well as centering pin of the transformer leading to abnormal DGA cases. The failure mode is shown in following figure-15.

Sign of overheating

Figure15: Circulating path of induced currents in centre tie rod and overheated centre tie rod.



In order to eliminate such cases following modification has been suggested.

(a) Use of 2 mm fibre glass insulating tube on the centering pin and 2 mm

insulation sheet of pre-compressed board/Nomex board between the

centering pin and tank bottom as per details given in figure 16. For this,

existing diameter of centering pin is to be reduced from 45 mm to 41 mm.

Detail procedure is explained as follows:

Step 1 Reduce the diameter of the insert pin to 41mm by machining the

existing pin:

Figure 16

Step2: Insulating tube to be introduced at bottom pin

Figure 17



Step3: Nomex paper introduced to insulate the bottom part of the pin in addition

to fibre glass tube to insulate the pin.

Figure 18

Figure19 Complete figure showing the modification



7.3 Clamping studs fitted in the bottom side of transformer (GOD/SOD Reactor

side) has two earthing leads going from the clamps - one to bottom side tie-

rod and the other to top side tie-rod. It was noticed that overheating of the

stud (M16 x 160) due to circulating current passing through the stud.

Hence, it was decided to change the location of both the earthings to one

(single) clamp only. This had ensured proper earthing and avoid chances of

current flowing through the stud.

Figure 20: Single clamp earthing

All the earthing connection shall have provision of crimping along with brazing for jointing of cable lugs with earthing cables.

Figure 21: Crimping along with brazing for jointing of cable lugs with earthing cables.



7.4 Additional issues: It has also been found that abnormal DGA is caused

due to looseness of earthing connected to the centre tie rod of the clamping arrangement. Hence care should be taken to properly tighten the earthing connection.

Figure 22

Figure 23

7.5 It has also been noticed that if proper earthing externally to the tank (see below) is not ensured then circulating current inside the transformer will find a path and shall lead to failure hence proper earthing external to the transformer also needs to be ensured. Also, it may be noted that where ever any paint is applied at the point of earthing, same should be removed by proper cleaning before making earth connection because it acts as insulation while flowing earth current.

Figure 24



7.6 Oil leakage from the transformer bushings and covers in 3-phase

locomotives

While the traction transformers imported from OEM had given satisfactory

service, the indigenous transformers supplied by ToT partners had given

problem of oil leakage from the transformer bushings and cover. Problem

was studied and it was noted to be due to non-standard type of gaskets / „O‟

rings used by manufacturers in assembly. To prevent the problem, a

Technical Circular No. ELRS/TC/0076, Rev’0’ was issued by RDSO

specifying the manufactures and type of gaskets to be provided on bushings,

, top cover and bushing plates of transformers.

However, the problem of oil leakage had been again reported by Railways.

The matter was investigated by RDSO and the majority cases of oil leakage

reported were due to

1. Use of non specified gaskets/‟O‟ rings by the manufactures. Quality of

gasket / „O‟ ring is important and therefore specification and vendors of

these was examined; and

2. Also, oil leakage cases were on account of bushing gaskets at location* „B‟

& „C‟ (SKEL-4663) which was of NEBAR and supplied by M/s James

Walker, UK. NEBAR gaskets were made of a blend of rubber and cork

material. Equivalent material of NEBAR developed by M/s Nu-Cork and

supplied by M/s CGL had also reported failed by some of the Railways.

Based on above following remedial action suggested:

7.6.1 Oil Leakage from bushing Gasket:

On the subject issue, RDSO had interacted with M/s ABB, India and M/s

ABB/Secheron, the OEM of these transformers who had conducted a quality

audit of their unit at Vadodara. Based on their global experience, ABB

Secheron had recommended the use of NBR (Nitrile) gaskets at location* B &

C (SKEL-4663, Alt.1 placed at page 22 of this report) in place of NEBAR

gaskets. RDSO had further discussed the matter with all the transformer

manufacturers including M/s ABB and it had been considered to use NBR

(Nitrile) gasket for bushing gaskets at location „B‟ and HNBR gasket for

bushing gaskets at location „C‟ with high temperature withstand capacity in

place of existing NEBAR gaskets. Accordingly, the requisite changes have



been incorporated in Technical Circular No. ELRS/TC/0076, Rev‟0‟ and Rev

„1‟ had been issued. The salient technical details of Technical Circular are as

follows:

The bushings used for different applications in the transformers for 3-phase

locomotives are given in Table-4 as follows:-

Table 4 TYPE OF BUSHING APPLICATION TERMINALS

DT 3/2000 Traction Bushings

SOD Bushings

2u1-2v1, 2u2-2v2, 2u3-2v3, 2u4-2v4, X11-X12, X21-X22

DT 1/250 GOD Bushings XB11-XB12, XB13-XB14,XB21-XB22, XB23-XB24, XB31-XB32, XB33-XB34.

DT 3/630

Filter/BUR/Earth Bushings

2UF-2VF, 2UB-2VB, 1V

DT 1/2000 Hotel Load Bushings 2UH -2VH

In order to prevent oil leakage from the bushing gaskets, it is necessary to

use gaskets at different locations in the bushings as per details given in the

Table-5 below:-

Table 5

Bushing Type

Location

A B C D E

DT 1/250

NITRILE Ø 22/12x11

NITRILE Ø 29/14x3

HNBR Ø 50/28x4

NBC Ø 50/28x2

NBC Ø 45/25x2

DT 1/2000

NITRILE Ø 59/42x18

NITRILE Ø 76/44x3

HNBR Ø 104/70x4

NBC Ø 104/70x3

NBC Ø 90/63x3

DT 3/630

NITRILE Ø 32/20x13

NITRILE Ø 41/22x3

HNBR Ø 70/45x4

NBC Ø 70/45x2

NBC Ø 63/40x2

DT 3/2000

NITRILE Ø 59/42x18

NITRILE Ø 76/44x3

HNBR Ø 104/70x4

NBC Ø 104/70x3

NBC Ø 90/63x3

The Locations A, B, C, D & E of the gaskets are indicated in the RDSO

drawing SKEL No.4663, Alt.1 (Figure 25 on page 22) which is given below for

ready reference. The details of the above gasket material, the governing

Specifications and Source of supply has been given in Technical Circular No.

ELRS/TC/0076, Rev‟1‟ . It may be noted that HNBR is a hydrogenated nitrile

compound of standard quality for use in the transformer gaskets. This

exhibits good chemical and mechanical properties at high temperature.



RDSO Drawing No. SKEL 4663, Alt-1 Figure 25: Location of various gaskets



7.6.2 Oil Leakage from Cover Gaskets:

In order to prevent oil leakage from transformer cover gaskets as well as from the

two bushing plate gaskets, it is necessary to use joint less gaskets as per details

given in Table-6 Below. The sources of supply are indicated in Technical Circular

No. ELRS/TC/0076, Rev‟1‟.

Table: 6

Location Qty. Material Single piece

With overlap joint

Dia. ‘S’

Ref. IS / BS

Tank Cover

01 Nitrile (nitrile rubber vulcanized butadiene)

8035 ± 10 mm

8035 ± 10 + „C’ (44) mm = 8079 ± 10 mm

16mm BS : 2751-2001

Bushing Covers

02 Nitrile (nitrile rubber vulcanized butadiene)

3930 ± 10 mm

3930 ± 10 + „C’ (20) mm = 3950 ± 10 mm

07mm BS : 2751-2001

7.6.3 Crushing of oil Compartment gaskets

The crushing of oil compartment gaskets leads to less cooling of core and winding

as given in figure 25 below:

Figure 27: Crushing of oil compartment gasket.



In order to avoid crushing of oil compartment gasket, the material of gasket has

been specified and shall be used as per details given in Table-7 below. The sources

of supply are also indicated in Technical Circular No. ELRS/TC/0076, Rev‟1‟.

Table 7: Oil Compartment gaskets

SN Description of gasket

Drg. No. Ref. IS/BS/ Material

Unit Qty Per set

1. 450 x 1744 x 6 HSTN104275P0001 FPM (Viton) Ref. IS:3400

No. 4

2. 80 x 421 x 6 HSTN424015P0001 No. 4

3. 100 x 290 x 6 HSTN423988P0001 No. 4

4. 80 x 409 x 6 HSTN423987P0001 No. 4

5. 80 x 414 x 6 HSTN423986P0001 No. 4

6. 10 mm Dia. Round cord

HSTN003296P0010 mm 8150

8.0 Conclusion and Recommendations:

(i) The transformer of a three phase electric Locomotive is a very vital

component. The failures of a transformer cause detention of locomotive for

considerable time and all the care should be taken to avoid failures. Though,

all the topics related with reliability of three phase transformer such as its

schedule maintenance part and other maintenance aspect has not been

covered in this report due to focus of the report being on the specific steps

taken by RDSO. In this connection, a “Maintenance Handbook on

Transformer of 3 Phase Electric Locomotives has already been issued by

CAMTECH, Gwalior” covering the relevant details. Some of the important

points have been included in this report from this maintenance handbook.

Zonal Railways are requested to go through this maintenance handbook.

(ii) All the failed transformers, whether under warranty or not, should be

inspected jointly by manufacturer and the concerned Railways and joint

note made in each case. This will help in analyzing the type wise failures

leading to identification of remedial measures.

(iii) The instructions elaborated in clause 7.0 have already been issued by RDSO

to manufacturers, however, Zonal Railways should closely monitor the

progress of implementation and the performance of the modified



transformers. Zonal Railways should ensure that these steps are being taken

by manufacturers during repair of transformers as well. This may be verified

during consignee inspection.

(iv) These modification needs to be implemented during POH of transformers of

three phase locomotives. Workshops are required to plan accordingly.

(v) Proper records regarding cut in serial no. of a transformer with certain

improvement measures, affect of change in manufacturing process etc.

should be maintained to ensure traceability.

(vi) Performance of NBR/HNBR/Viton based gaskets of M/s Nu-Cork & M/s

BOSCO to be monitored closely and any abnormality observed in the same

should be reported to RDSO so that further corrective action can be taken.

(vii) Performance of NBC gaskets of different suppliers shall also be monitored

and any abnormality observed in the same should be reported to RDSO for

taking further corrective action.

(viii) It may be noted that special facilities are required to be developed for

storage of the nitrile gaskets by manufacturers in consultation with M/s

Nu-cork/M/s Bosco, the supplier of gaskets/‟O‟ rings of 3-ph transformers.

It shall also be ensured by manufacturers that the gaskets/‟0‟ rings

procured should be used well within the expiry date of these gaskets so that

their properties do not change with the passage of time.

(ix) In order to improve quality, it is recommended that CLW should verify the

availability of M&P and Testing facilities as stipulated in Schedule of

Technical Requirement (STR). At the same time Quality Assurance Plan may

also be verified ensuring that the actions suggested in this report have been

included in the QAP.

(x) It should be ensured that the manufacturing area of 3-phase locomotive

transformer is segregated from other activities and it should be dust free

and under air conditioned/temperature controlled environment to prevent

any foreign ingress of material.

(xi) All the materials/sub-component used in manufacturing of the

transformer should be as approved in Bill of Material (BOM) or as

specified/stipulated by competent authority from time to time.



Annexure-I 1. Special Maintenance Instructions:

S. No. SMI No. Title Date of issue

1. ELRS/SMI/0228 Assembly of electrical terminations of traction winding bushings 2u1_2v1, 2u2_2v2, 2u2_2v3, 2u4_2v4 in indigenously manufactured transformers type lot_6500/lot_7500 used in 3phase drive locomotives type WAG9/WAP5

06.08.02

2. SMI/249 Rev ‟0‟ Test procedure, Lower limit and process of adding inhibitor in transformer oil of

inservice traction transformer

28.11.07

2. Modification Sheets:

S. No. MS No. Title Date of issue

1. RDSO/2014/EL/MS/0432/Rev‟0‟

Removal of shorting link provided at c-d terminal of over current relay of 3-ph locomotives.

12.03.14

3. Technical Circulars:

S. No. TC No. Title Date of

issue

1. ELRS/TC-0076-2002 Rev.‟0‟,

Oil leakage from the transformer bushings and covers in 3 phase locomotive

17.9.02,

2. ELRS/TC-0076 Rev‟1‟ Oil leakage from the transformer bushings and covers in 3 phase locomotive

22.02.13

REFERENCES:

1. “Maintenance Handbook on Transformer of 3 Phase Electric Locomotives issued by CAMTECH, Gwalior”

2. Quality Audit of manufacturing of 6500/7500 LOT transformers for 3- phase electric locomotives produced by M/s BHEL, Jhansi on 18.05.2012.

3. MOM conducted at various forums with manufacturers by RDSO on 26-3-

14, 22-4-14, 11-6-14, 5-9-14, 3-2-15 & 3-5-16 and Presentations given by manufacturers.

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government of india ministry of railways...page 1 of 26 issued on 29.09.2016 report no....

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