GOVERNMENT OF INDIA MINISTRY OF RAILWAYS TECHNICAL

SPECIFICATION NO. TI/SPC/PSI/CT/0515(05/2015) Page 1 of 27

TRACTION INSTALLATION DIRECTORATE

GOVERNMENT OF INDIA

MINISTRY OF RAILWAYS

TECHNICAL SPECIFICATION

FOR

CURRENT TRANSFORMERS

i. 220 kV, 200 - 100/5A

ii. 132 kV, 400 - 200/5A

iii. 110 kV, 400 - 200/5A

iv. 66 kV, 800 – 400/5A

for

RAILWAY AC TRACTION SUBSTATIONS

(MAY 2015)

SPECIFICATION NO. TI/SPC/PSI/CT/0515(05/2015)

ISSUED BY

Traction Installation Directorate Research Designs & Standards Organisation,

Manak Nagar, Lucknow-226011.


SPECIFICATION: TECHNICAL SPECIFICATION FOR

CURRENT TRANSFORMER FOR RAILWAY AC

TRACTION SUBSTATIONS.

SPECIFICATION No. TI/SPC/PSI/CT/0515(05/2015)

Amendment

Number

Amendment /Revision Total pages

including drawings

Date of

Issue

Prepared By Checked By Approved By

Signature

Date

Désignation SSE(TR) DDTI(PSI) DTI(PSI)


INDEX

ITEM

NO

HEADING PAGE

1.0 Scope 4

2.0 Governing Specification 4

3.0 Service Conditions 5

4.0 Traction Power Supply System 5

5.0 Rating and other Particulars 6

6.0 Type & General Construction 8

7.0 Bushing and Terminal Arrangement 9

8.0 Parts Fittings and Accessories 10

9.0 Painting 10

10.0 Testing 10

11.0 Technical data and drawings 14

12.0 Spares 16

13.0 Erection Testing and Commissioning 16

14.0 Training of Indian Railway‟s Engineers 16

15.0 Warranty 16

16.0 Packing and Shipment 17

APPENDIXES

APPENDIX- A General Arrangement at the Traction

Transformer at Traction Sub-station

18

APPENDIX- B Schematic Diagram showing the protection scheme

19

APPENDIX- C Schedule of Guaranteed Performance, Technical and Other Particulars

20

ANNEXURES

ANNEXURE- A Drawing & Details of Terminal Connectors 23

ANNEXURE- B Format for Title of Drawings 24

ANNEXURE- C Details of 132 kV CT to be used in Mumbai 25


area

1.0 SCOPE

1.1 This specification applies to outdoor electrically exposed type Current

Transformer for a nominal system voltage of 220 kV or 132 kV or 110 kV or 66 kV for use in unattended Railway Traction Sub-station

in any part of India together with associated. Electrical/Electronic measuring/indicating instrument and protective devices. It supersedes Specification No. ETI/PSI/117(07/88),

ETI/PSI/102(08/87), ETI/PSI/40(08/83), ETI/PSI/22(09/82) and ETI/PSI/55(09/79).

1 .2 The Current Transformer shall be complete with all parts, fittings and accessories including mounting frame work of steel, necessary for its efficient operation. All such parts, fittings and accessories shall be

deemed to be within the scope of this Specification, whether specifically mentioned herein or not. The Current Transformer shall

be of proven design.

2.0 GOVERNING SPECIFICATION:

2.1 Assistance has been derived from the following Standards,

specifications/codes of practices (latest version) in the preparation of this specification.

S.

No.

Standards & Codes of

Practices

Applicable Rules.

1. IS:5 – 1978

(3rdRevisin)

Colours for ready mixed paints and

enamels.

2. IEC: 185-1966 Current Transformer.

3. IS:335-1983 Specification for new insulating oil

4. IS:1271-1958 Classification of insulating material for electrical machinery and apparatus in relation to their thermal stability in service.

5. IS:1570 (Pt.V) Specification of bolt, nut and spring washer.

6. IS:1576-1967 Solid press-board for electrical purposes.

7. IS:2074-1979 Ready mixed paint, air drying red oxide

zinc chrome priming.

8. IS:2099-1985 Bushing for alternating voltages above

1000 volts.

9. IS:2705-1981 Specification for Current Transformers: -

Part–I: General requirement. Part–II: Measuring Current Transformer.

Part-III: Protective Current Transformer.

10. IS:2932-1974 Enamel synthetic interior

(a) Under coating (b) Finishing

11. IS:3024-1965 Electrical steel sheets (oriented with amendment No. 1&2)

12. IS:4201-1988 Application guide for Current Transformer.

13 IS:4253 (Part-II)-1980 Cork and rubber.

14. IS:5561-1970 Electrical power connectors.

15. IS:11322-1955 Method for partial discharge measurement


in in Instrument Transformers.

16 RDSO‟s Spec No. ETI/OHE/18(04/84)

with correction Slip No.6 (09/87)

Steel and stainless steel fasteners.

17 RDSO‟s Spec No. ETI/PSI/70(11/84)

Specification for hollow porcelain insulator and bushings.

2.2 Any deviation from this specification proposed by the tenderer

calculated to improve upon the performance, utility and efficiency

of the equipment will be given due consideration, provided full particulars of the deviation with justification thereof are furnished.

In such a case, the tenderer shall quote according to this specification and the deviations, if any, proposed by him shall be quoted as an alternative/alternatives. In case of any contradiction

between the provisions of the Indian Standards Specification/Recommendation of IEC and this Specification the

letter shall prevail. 3.0 SERVICE CONDITIONS:

3.1 The Current Transformer is intended for use in humid tropical climate in any part of India with the following atmospheric

conditions:

1. Maximum ambient temperature of

air in the shed 45C

2. Minimum temperature air in the

shed 0 C

3. Maximum relative humidity 100%

4. Maximum wind pressure 200 kg/m2

5. Number of thunderstorm days per annum

85 days (Approx.)

6. Maximum no of dust storm days/annum

35 days

7. Average annual rainfall 1750 to 6250 mm.

8. Altitude Not exceeding 1000 m

3.2 The Current Transformer shall be subjected to vibrations on account of trains running on nearby railway tracks. The amplitude of these vibrations which occur with rapidly varying time period in the range of 15 to

70 ms lies in the range of 30 to 150 microns at present with the instantaneous peak going up to 350 microns.

4.0 TRACTION POWER SUPPLY SYSTEM: 4.1 General scheme: The single phase, 50 Hz power supply for Railway

Traction at 25 kV is obtained from 220kV/132kV/110kV/66kV three phase grid system through a step down single phase Traction Power Transformer,

The primary winding of which is connected to two phases of the three phase effectively earthed transmission line network of the of the State Electricity Board. In order to reduce the impedance on the three-phase grid

system, the two phases of three-phase transmission line are tapped in a cyclic order for feeding the successive substations. The distance between

adjacent Sub-stations is normally 40 km and 80 km depending upon the density of traffic, gradients in the section, etc.


4.1.1 One terminal of the 25 kV secondary winding of the Traction Transformer is connected to the Overhead Equipment (OHE) and the other

equipment is solidly earthed and connected to the appropriate running rails. The load current flow through the OHE to the locomotives and returns

through the rail(s) and earth to the Sub-station. Where Booster transformers and Return conductors are used the Return current flows through these and partly through the earth in the vicinity of the Sub-

station. Approximately midway between two adjacent Sub-stations, a dead zone known as the “Neutral Section” or „Phase Break‟ is provided to

separate the different phases. The power to the OHE on one side of the sub-station is controlled by a feeder circuit breaker while that for each track is controlled by an interrupter. In case of a fault on the OHE, the feeder

circuit breaker isolates it. The incoming 220/132/110/66 kV supply voltage may vary between 10% to -12.5% as per I.E. Rule No. 54. A schematic

diagram No. ETI/PSI/702-1 MOD „D‟ showing the general arrangement at the Traction Transformer at the Traction Sub-station is at „Appendix-A‟.

4.2 The Current Transformer shall be on the Primary side of the single

phase Traction Power Transformer for use with the following Electrical/Electronic measuring/indicating instruments/meters and

protective devices/Relays: -

a) Instantaneous Overcurrent Relay,

b) Inverse Definite Minimum Time Lag Over Current Relay,

c) Restricted Earth Fault Relay.

A panel/Digital type indicating Ammeters will also be connected to these

Current Transformers.

4.3 Operation of any of the protective devices/relays which serve as the

backup protective system for that on the 25 kV side of the Traction Power Transformer shall trip the circuit breaker on the primary side of the Transformer. A schematic diagram showing the protection scheme is at

Appendix – B. 5.0 RATING AND OTHER PARTICULARS

5.1(a) For other tan Mumbai area: The rating and other particulars of the Current Transformer shall be as follows:-

i)Type: Single phase, oil filled natural

air cooled, One core for other than Mumbai area.

ii) No. of windings: Primary – Two Secondary - One iii) System voltage:

a. Nominal system voltage, kV 220 132 110 66

b. Highest system voltage, kV 245 145 123 72.5

iv) Rated primary/secondary Currents:



c. Primary Current, Amp. 200-

100

400-

200

400-

200

800-

400

d. Secondary Current, Amp. 5 5 5 5

v. Rated Frequency, Hz 50 Hz, +/- 3%

vi Class of Insulation A

vii Rated Burden 30 VA


viii Accuracy Class Other than Mumbai area -

5P to IS: 2705-1981(Part-III)

ix Accuracy limit factor 15

x. Rated short time current:

Nominal

system voltage, kV

Transformation

ratio

Short – time

current rating (thermal) for one second, kA

Short time current

rating (Dynamic) kA.

220 200-100/5 31.5 78.75

132 400-200/5 31.5 78.75

110 400-200/5 31.5 78.75

66 800-400/5 31.5 78.75

xi. Rated Insulation Level:

a. Nominal system voltage, kV

220 132 110 66

b. Rated one minute power frequency withstand

voltage, kV(rms)

460 275 230 140

c. Impulse withstand

voltage (1.2/50 micro, sec. wave shape),

kV (peak)

1050 650 550 325

xii. Terminal Bushing:


220 132 110 66

b. Rated current, Amps. 800 800 800 800

c. Minimum creepage

distance, mm

6125 3625 2075 1813

xiii. Temperature rise: See clause 10.1.2

xiv. Rated overload: 150% of full load for 15 minutes.

xv. Secondary winding resistance at 75 0C (Max.) 0.3 Ohms.

5.1(b) For ABT Metering: The rating and other particulars of the Current Transformer shall be as follows:-

i)Type: Single phase, oil filled natural air cooled, One core for ABT Metering.

ii) No. of windings: Primary – Two Secondary - One

iii) System voltage:



iv) Rated primary/secondary Currents:




c. Primary Current, Amp. 200-100

400-200

400-200

800-400

d. Secondary Current, Amp. 1 1 1 1

v. Rated Frequency, Hz 50 Hz, +/- 3%

vi Class of Insulation A

vii Rated Burden 30 VA

viii Accuracy Class For ABT Metering – 0.2S to IS: 2705-1981(Part-III)

x. Rated short time current:

Nominal system

voltage, kV

Transformation ratio

Short – time current rating

(thermal) for one second, kA

Short time current rating (Dynamic)

kA.

220 200-100/5 31.5 78.75

132 400-200/5 31.5 78.75

110 400-200/5 31.5 78.75

66 800-400/5 31.5 78.75

xi. Rated Insulation Level:


220 132 110 66

b. Rated one minute power frequency withstand

voltage, kV(rms)

460 275 230 140

c. Impulse withstand

voltage (1.2/50 micro, sec. wave shape), kV (peak)

1050 650 550 325

xii. Terminal Bushing:


220 132 110 66

b. Rated current, Amps. 800 800 800 800

c. Minimum creepage distance, mm

6125 3625 2075 1813

xiii. Temperature rise: See clause 10.1.2

xiv. Rated overload: 150% of full load for 15 minutes.

xv. Secondary winding resistance at 75 0C (Max.) 0.3 Ohms

5.1(c) For Mumbai area: The rating and other particulars of the

Current Transformer shall be as refer Annexure -C:-

6.0 TYPE AND GENERAL CONSTRUCTION:

6.1 The current Transformer shall be suitable for mounting on steel structures embedded in concrete foundations close to the circuit

breakers.

6.2 The Current Transformer shall be of sealed type either filled

with inert gas or provided with metallic bellows above the cooling and insulating oil. In case of inert gas filling, a pressure relief device shall be provided.


6.3 The core shall be built up of high permeability Cold Rolled Grain Oriented (CRGO) silicon steel laminations conforming to IS: 3024, the

laminations being coated on both sides with suitable insulations capable of withstanding stress relief annealing.

6.4 Class „A‟ insulation immersed in oil shall be used. The Current

Transformer shall be supplied complete with insulating oil conforming to IS:335 required for first filling.

6.5 The current transformer shall have a Single Core with wound primary. The primary winding shall be split in two sections insulated from

each other and connected to terminals P1, P2, C1 & C2. It shall be possible to change the transformation ratio by connecting C1 with C2 for series configuration or P1 with C1 & P2 with C2 for parallel configuration. For

connecting these terminals in series or parallel configuration, suitable links of adequate section made of copper flat shall be provided. The nuts and

checknuts used for connecting these links shall be made of copper. Only copper conductor shall be used for primary and secondary windings.

6.5.1 Normally no joints in the winding shall be allowed. Joints if

unavoidable shall be brazed with high silver alloy grade Ba Cu Ag6 of IS: 2927-1975 or electrically butt-welded.

6.6 The secondary terminals of the Current Transformer shall be housed in a weather proof terminal box of mild steel of thickness not less

than 1.6mm. The connection/disconnection of external cable to/from the terminals shall be easy and convenient. The cables shall be of 4 sq. mm, sections 2 core PVC insulated and PVC

sheathed and their entry into the terminal box shall be through proper cable glands fitted on the bottom of the terminal box. The cable glands

shall be supplied with the Current Transformer.

6.6.1 Facilities for short–circuiting the secondary terminal shall be provided within the terminal box. The Current Transformer shall be

provided with a standard IOA test winding.

6.7 All the bolted mechanical and electrical connections in the

Current Transformer will be tightened properly to prevent loosening in service due to vibrations.

7.0 BUSHING AND TERMINAL ARRANGEMENT:

7.1 Out door type bushing shall conform to IS: 5621.The basic insulation level shall have the appropriate value as given in clause 5.1(xi) of this specification. The porcelain housing shall be capable of withstanding

all electrical and mechanical stresses that might be produced during the operation of the Current Transformer under normal and short-circuit

conditions.

7.2 The profile of porcelain shed shall be simple and free from the ribs on the underside so as to avoid accumulation of dust and pollutants

and permit easy cleaning. The porcelain housing shall be of single piece construction i.e. without joint in the porcelain body. The material of

clamping rings/ flanges used shall conform to MCI Grade BM-340 of IS: 2108 or to SGCI Grade: 400/12 of IS:1865 or to Aluminium alloy Grade:4450 of IS:617. The mass of Zinc coating shall not be less that 1000

gm/mm2.


7.3 Porcelain housing/support insulator used shall have creepage distance as given in Clause 5.1(xii)-C.

7.4 The bushing/housing terminal shall be provided with rigid type connectors as per Research Designs & Standards Organisation (RDSO)

drawing No. ETI/PSI/11010 in Annexure – „A‟ suitable for connecting to „ZEBRA‟ 28.62 mm ACSR conductor. The connector shall conform to IS: 5561 and its design shall be such so as to be connected to the equipment

terminal pad with a minimum of four 12 mm dia bolts, nuts and lock nuts which shall all be of stainless steel conforming to IS: 1570(Pt. V) Grade 04

Cr. 17 Ni 12 Mo2. Each of these bolts shall also have a flat washer and spring washer.

7.5 The connectors and porcelain housing shall be procured only

from approved manufacturers.

7.6 For equipment earthing, the steel supporting frame shall be provided with two earthing terminals of adequate capacity to carry the rated shot-circuit current safely. The earthing terminal shall be connected

to 50mm x 8 mm MS flat. The earthing terminal shall be provided with 17.5 +0.5mm dia. hole for fixing the earthing flat 0.4

7.7 The approved source of porcelain housings are as under:

(i) M/s Aditya Birla Insulator, Hallol & Rishra.

(ii) M/s Insulators & Electricals Co. Mandideep, Bhopal.

(iii) M/s Modern Insulators Ltd., Abu Road,

(iv) M/s WSI, Chennai.

8.0 PARTS FITTINGS & ACCESSORIES:

8.1 Apart from the parts, fittings & accessories specifically detailed in the

foregoing clauses, the following shall be supplied with each Current Transformer.

(i) Rating plate with diagram of connections and terminal

markings. (ii) Weather–proof terminal box.

(iii) Lifting lugs. (iv) Pressure Release Device. (v) Nitrogen gas filling valve and oil filling port.

(vi) Oil level gauge of prismatic glass. (vii) Adjustable arcing horns.

(viii) Cable Gland (Brass Nickel plated). 9.0 PAINTING

9.1 All the steel surfaces which are in contact with insulating oil shall be painted with heat resistant oil insoluble insulating warmish. All

steel surfaces exposed to weather shall be given on primer coat of zinc chromate and two coats of gray paint to shade No. 631 of IS: 5. One coat of additional paint shall be given at site by the manufacturer.

9.2 Fasteners.

All fasteners of 12 mm diameter and less exposed to atmosphere

shall be stainless steel and those above 12 mm diameter shall be preferably


be of stainless steel or of mild hot dip galvanized to RDSO‟s specification No. TI/SPC/OHE/FASTNERS/0120(03/2013).

10.0 TESTING

10.1 Once a purchase order is placed for supply of a Current Transformer

the designs and drawings shall be furnished to the purchaser/ Director General (Traction Installation), Reseach Designs and Standards Organisation, [DG(TI), RDSO] Lucknow, as the case may be, within the

period stipulated in the order. Only after all the designs and drawings have been approved for prototype tests and a written advice given to that

affect, shall be successful tenderer/manufactuer take up manufacture of the prototype of the transformer. It is to be clearly understood that any change or modification required by the above authorities to be done in the

prototype shall be done expeditiously, not withstand approval having already been given for the designs and drawings. Such change or

modification shall be incorporated in the drawings as indicated in clause 14.4.

(ii) Prior to giving a call to the purchaser/DG(TI), RDSO, Lucknow, for

inspection and testing of the prototype, the successful tenderer/ manufacturer shall submit a detailed test schedule consisting of schematic

circuit diagrams for each of the tests and the number of days required to complete all the tests at one stretch. Once the schedule is approved, the

tests shall invariably be done accordingly. However, during the process of type testing or even later, the purchaser reserves the right to conduct any additional test(s), besides those specified herein, on any equipment/ items

so as to test the equipment/item to his satisfaction or for gaining additional information and knowledge. In case any dispute or disagreement arises

between the successful tenderer/manufactuerer and representative of the purchaser/DG(TI) RDSO, Lucknow, during the process of testing as regards the procedure for type tests and/or the interpretation and acceptability of

the results of type tests, it shall be brought to the notice of the purchaser/DG(TI), RDSO, Lucknow as the case may be, whose decision

shall be final and binding. Only after the prototype transformer is completed and ready in each and every respect, shall the successful tenderer/manufacturer give the actual call for the inspection and testing

with at least 15 days notice for the purpose.

iii) In the event of the tests not being carried through the completion at

the one stretch for any reason attributable to the successful tenderer/ manufacturer and it is required for the representative of the purchaser/Director General (Traction Installation), Research Designs &

Standard Organisation, [DG(TI) RDSO], Lucknow, to go again or more number of times to the works of the successful tenderer/manufacturer or

other place(s) for continuing and/or completing the tests on the prototype(s) of the equipment, the successful tenderer/manufacturer shall reimburse to the purchaser/DG(TI), RDSO, Lucknow, the costs for the

representative having to visit the works or other place(s) for the tests more than once. The costs as claimed by the purchaser/DG(TI), RDSO, Lucknow,

shall be paid through a demand draft to the concerned Accounts Officer of the Purchaser/DG(TI), RDSO, Lucknow, as shall be advised to the successful tenderer/manufacturer.”

iv) The following type tests shall be carried out on the prototype current transformer art the works of the successful tenderer/ manufacturer or at

the reputed testing laboratory in the presence of the representative of the


Purchaser/DG(TI), RDSO, Lcuknow, in accordance with the relevant specifications and as modified or amplified as under:

10.1.1 Visual inspections: It shall comprises

(a) Checking of the layout, terminal markings, mounting

arrangement, labeling and any other items.

(b) Quality of painting and anti-rust treatment.

(c) Quality of workmanship and finish as well as provision of all

parts, fittings and accessories.

10.1.2 TEMPERATURE-RISE TEST:

This test shall be carried out on the Current Transformer for the higher rating fitted with approved terminal connector for full–load and for overload specified in clause 5.1(xiv). The temperature rise under

specified overload shall not exceed the following values.:

(a) Winding : 500C (Temperature rise measurement

by the resistance method).

(b) Insulating oil : 400C (temperature rise measurement by thermometer)

(c) Terminal connector : 400C (temperature rise measurement by thermometer)

The above values are with reference to an ambient temperature of 450C.

10.1.3 Impulse Voltage Test:

The lightening impulse voltage withstand test shall be done on the primary windings with test voltages specified in clause 5.1(xi).

10.1.4 Short-time current test:

The short time thermal (rms) and dynamic (peak) current withstand

tests shall be done to verify the ability of the Current Transformer and the terminal connectors fitted there to withstand the rated short-time current specified in clause 5.1(x). The Current Transformer shall be deemed to

have passed the test if the conditions laid down in clause 7.6.3 of IS: 2705 (Pt. I) are satisfied.

10.1.5 Excitation test and plotting of magnetizing characteristics curves.

The curve shall be drawn at least up to that point, where an increase

of 100% in voltage results in an increase of 50% in current.

10.2 TYPE TEST ON ACCESSORIES:

10.2.1 Porcelain Bushing

The following tests shall be carried out on prototype unit of 52 kV or

72.5 kV or 123 kV or 145 kV or 245 kV (as the case may be) class bushings in accordance with IS: 2099 and IS: 5621.

(i) Dry power-frequency withstand voltage test.

(ii) Wet power-frequency withstand voltage test.

(iii) Dry-lightening impulse voltage withstand test.

(iv) Thermal stability test.


(v) Temperature-rise test.

(vi) Thermal short time current withstand test.

(vii) Dynamic current withstand test.

(viii) Cantilever load withstand test.

(ix) Measurement of partial discharge quantity (as per IS:6209)

(x) Tightness test at flange or other fixing devices.

(xi) Temperature cycle test.

10.2.2 Test on terminal connectors:

The terminal connector shall be from the approved supplier of RDSO. In case these are not from the approved suppliers of RDSO,

the following tests shall be carried out:

(i) Visual inspections and verification of dimensions.

(ii) Tensile test.

(iii) Resistance Test.

(iv) Temperature-rise test at normal and specified overload.

(v) Short- time current test.

(vi) Chemical analysis of materials used.

10.3 In addition to the above tests, all routine tests detailed in clause 10.7 shall be carried out on the test unit.

10.4 If the prototype of a Current Transformer conforming to this

Specification has been approved for earlier supplies to Indian Railways, the testing of prototype again may be waived provided that

no change in the design or material(s) used have been made.

10.5 Manufacturers type test certificates in respect of the tests carried out on (a) porcelain housing and (b) terminal connector, as

per relevant IEC recommendations/IS specifications shall be submitted by the successful tenderer for approval.

10.6 The tenderer may quote separately his charges for conducting short-time current (thermal) and dynamic current withstand tests

described in clause 10.1.4, hereof. No charges shall be payable for any other type and routine/acceptance test.

10.7 Routine tests/Acceptance tests.

Every Current Transformer shall be subject to the following tests at the manufacturer‟s works as per IS: 2705 (Pt.I) and IS:

4322.

10.7.1 Verification of Terminal markings and polarity.

10.7.2 High voltage power-frequency tests on primary winding.

The windings shall be subject to the following tests voltages:


220 132 110 66


b. Voltage to be

applied between winding & earth, kV (rms)

460 275 230 140

c. Voltage to be applied between

two sections of primary winding,

kV (rms)

2 2 2 2

10.7.3 High voltage power-frequency withstand test on the secondary winding: 3 kV (rms) for one minute.

10.7.4 ACCURACY TESTS:

The accuracy test shall comprise the following:-

a) Current error & phase displacement at the rated primary current.

b) Composite error at rated accuracy limits primary current.

10.7.5 Measurement of insulation resistance between primary winding and secondary winding with a 2500 V Megger; and that

between secondary winding & earth with a 500 V Megger.

10.7.6 Measurement of secondary winding resistance and its

computation at 750C.

10.7.7 Measurement of partial discharge of windings.

10.8 Only after clear written approval of the results of the tests on

the prototype unit is communicated by RDSO/purchaser to the manufacturer, shall be taken up bulk manufacture of the ordered

Current Transformers which shall be strictly with the same material and process as adopted for the prototype. In no circumstances shall material, other than those approved in the designs/drawings and /or

the prototype, be used for bulk manufacture on the plea that they had been obtained prior to the approval of the prototype.

11.0 TECHNICAL DATA AND DRAWINGS:

11.1 The information furnished in “Schedule of Guaranteed Performance, Technical & other particulars‟ (Appendix –„C‟) shall be

complete in all respects. If there is entry like‟ shall be furnished later‟ or blanks are left against any item, the tenderer is not likely to be

considered such as omissions causes delay in finalising the tender. Evidence in the form of type test reports for basic insulation level, i.e. rated impulse withstand voltage test, rated power frequency

(wet) withstand test, rated power frequency (dry) withstand test, temperature rise test and short time current withstand test on the

current transformer offered shall be furnished”.

11.2 The tenderer shall specifically indicate in a statement attached with his offer, his compliance with each clause and sub-clause of this

specification. A separate statement shall be attached with the offer indicating reference to the clauses where the tenderer deviates

therefrom together with detailed remarks/justification. If either the


statement of compliance or statement of deviation is not attached with the offer, it is not likely to be considered. If there are no

deviations, a „NIL‟ statement shall be attached.

11.3 The tenderer shall furnish the following drawings as per Indian

Railways standards in sizes of 210mm x 297 mm or any integral multiplies thereof. A format of the title sheet is attached at Appendix „D‟.

a) Outline general arrangement giving the overall dimensions of current transformer.

b) Internal arrangement of Current Transformer including cross–sectional views.

11.4 The tenderer shall also furnish the following information

along with his offer-

a) Excitation characteristic curve.

b) Manufacturer‟s test certificates of :-

(i) Winding wire (ii) Oil seal/gaskets (iii) insulating oil

(iv) pressure release device.

c) The tenderer shall furnish the detailed calculation and basis in support of the minimum knee point voltage.

For calculations purpose the lead resistance may be presumed as 0.4 ohms.

11.5 The successful tenderer shall be required to submit for approval the following detailed dimensioned drawings as per Indian Railways standard in Annexure –„B‟ (Title of

Drawing) in sizes of 210mm x297mm or any integral multiples thereof-

a) General outlines drawings showing mounting arrangement, relative position of primary and secondary terminals, CT earthing and position of various parts, fittings

and accessories.

b) Cross-sectional view along with its internal details.

c) Porcelain housing/bushing including its clamping arrangement.

d) Name and rating plate with the diagram of connections

(both in English and Hindi).

e) Details of primary terminals and links used for changing

the transformation ratio.

f) Secondary terminals and terminal box.

g) Details of metallic bellow, if provided as well as its

operation.

h) Detailed part drawings for:-

(i) Oil level gauge(ii) Nitrogen Gas filling valve(iii) Pressure release device(iv) Cable gland (v) Terminal connector (vi) Earthing terminals and (vii) Oil draining pipe with plug.


11.6 After approval, six copies of approved drawings along with two sets of reproducible prints shall be supplied to each

consignee(s). Besides, two copies of drawings along with one set of reproducible prints shall be supplied to the

Director General (Traction Installation), Research Designs & Standards Organisation, Lucknow (India).

11.7 The successful tenderer shall supply five copies of the

instruction/maintenance manual for the Current Transformer to each consignee(s) and two copies to the

Director General (Traction Installation), Research Designs and Standards Organisation, Lucknow (India).

12.0 SPARES:

The tenderer shall furnish along with his offer a list of spare (with cost) recommended by him for maintenance of

Current Transformer for a period of two year.

13.0 ERECTION TESTING AND COMMISSIONING:

13.1 The transformer shall be erected by the purchaser under

the supervision of a competent engineer of the successful tenderer/manufacturer/supplier. The Current Transformer

shall be subjected to the specified proving/pre-commissioning tests by the Railways‟s Engineer at site and

with which the successful tenderer/supplier/ manufacturer shall also be fully associated. For this purpose, prior intimation regarding the date and location of tests shall be

given by the purchaser to the supplier/ manufacturer/successful tenderer.

14.0 TRAINING OF INDIAN RAILWAY‟S ENGINEERS

14.1 The offer shall include the training of two Engineers of the Indian Railways free of cost at the manufacturer‟s in India

or abroad and at the maintenance depots/workshop on a railway system or other public utility where Current

Transformers of similar/identical design are in operation. The total duration of training for each engineer shall be for 12 weeks of which approximately 6 weeks will be at

manufacturer‟s works and 6 weeks on Railway system or other public utility. The cost of travel to the country of the

manufacturer and back will be borne by the Indian Railways. Other details shall be settled at the time of finalizing the contract of the purchase order.

15.0 WARRANTY:

15.1 Each Current Transformer supplied against a purchase

order/contract in which this specification is quoted, irrespective of origin (imported or indigenous), shall be guaranteed for trouble-free and satisfactory performance

for a period of 24 months from the date of supply of or 18 months from the date of commissioning at the sub-station

on Indian Railways, whichever period is shorter. Details of warranty clause, the extant of responsibility and other relevant aspects shall be included in the purchase order or

contract. The tenderer shall furnish detailed terms and conditions in this regard in his offer.


The successful tenderer shall make necessary arrangements for closely monitoring the performance of the

Current Transformer through periodical (preferably once in two months during the warranty period) visits to the sub-

station for on the spot detailed observations. Arrangement shall also be made for spare parts to be kept readily available with the manufacturer/supplier/ successful

tenderer to meet exigencies warranting replacement so as to put back the Current Transformer in service without

unduly long interruption of traction power supply.

16.0 PACKING AND SHIPMENT:

16.1 The Current Transformer shall be transported from the manufacturer‟s works to the destination by rail, road or sea

as determined in the contract/purchase order. The parts, fittings and accessories which are liable to damage during transit shall be separately packaged/crated and dispatched

so as to reach destination along with the Transformer tanks. Any opening crated on the Current Transformer tank

by the removal of any parts, fittings and accessories shall be closed by suitable blanking plates.

A general packing list, for the various components of each Current Transformer shall be furnished. The packing has to be done properly so that no damage may be done during

transit.

APPENDIX – ‘A’


APPENDIX – ‘B’

Schematic Diagram Showing the Protection Scheme:


SUB-SECTOR SUB-SECTOR SUB-SECTOR

SECTOR


APPENDIX-C

SCHEDULE OF GUARANTEED PERFORMANCE, TECHNICAL AND

OTHER PARTICULARS.

S. No.

Description Unit of measurement

1. Name of the manufacturer

2. Country of origin

3. Standard governing specification

4. Manufacturer‟s type designation

5. (a) Nominal system voltage

(b) Highest system voltage

kV

kV

6. (a) Rated primary current

(b) Rated secondary current

(c) Rated transformation ratio

Amp

Amp

7 Rated burden VA

8 Accuracy class

9 Rated accuracy limit factor

10 Current error at rated primary current Percent

11 Phase displacement at rated primary current

Minutes

12 Complete error at rated accuracy limit primary current

percent

13 Rated short-time current and duration

(a) Thermal (Ith)

(b) Dynamic (Idyn)

kA (RMS)for one sec.

kA (peak)

14 Temperature–rise of the windings

(by resistance method) over an ambient temperature of 45 0C

(a) At rated current

(b) At 100% overload for 5 minutes

0C

0C

15. Partial discharge level pC

16. Particulars windings

a) Primary winding

i) Type

ii) No. of turns

iii) Current density at rated current

Amp/mm2


iv) Size of conductor

v) Class of insulation

b) Secondary windings:

i) Type

ii) No. of turns

iii) Current density at rated

current

iv) Size of conductor

v) Class of insulation

vi) Resistance computed to 75 0C

vii) Insulating material used

c) Rated insulation levels:

i) One minute power frequency withstand voltage

ii) Inter-section withstand voltage of primary windings.

iii) Impulse withstand voltage

Amp/mm2

Ohm

kV (rms)

kV (rms)

kV (peak)

17 Particulars of core:

i) Type

ii) Flux density.

a) At rated primary current

b) At 15 times rated primary current

iii) Thickness of steel laminations

iv) Whether CRGO steel stampings are used ?

v) Knee point e.m.f.

vi) Exciting current to knee point

Tesla

Tesla

mm

18. Particulars of porcelain housing/bushing:

(i) Specification to which it conforms

(ii) Name of manufacturer

(iii) Power frequency withstand voltage for one minute.

(a) Dry

(b) Wet

iv) Dry lightning impulse withstand

voltage, 1.2/50 micro-second wave shape.

v) Visible power frequency discharge voltage.

vi) Creepage distance in air

kV (rms)

kV (rms)

kV (peak)

kV (rms)


a. Protected

b. Total

vii) Weight of porcelain housing /bushing

mm

mm

Kgs.

19 Overall dimensions:

i) Length

ii) Width

iii) Height

mm

mm

mm

20 Weights:

(i) Total weight of copper used

a) Primary winding

b) Secondary winding

(ii) Weight of core

(iii)(a) Quantity of insulating oil

b) Weight of insulating oil

iv) Total weight

Kgs.

Kgs.

Kgs.

Liter

Kgs.

Kgs.

21 Particulars of terminal connector:

(i) Name of manufacturer

(ii) Rated current

(iii) Temperature rise above an

ambient temperature of 45 0C

a) At rated current

b) At 150 percent of rated current for 15 minutes.

Amp.


ANNEXURE- „A‟

Details of Terminal Connector:


ANNEXURE- „B‟

Format of Title Drawing:


ANNEXURE- „C‟

1.0 SCOPE

This part of specification cover design, manufacture, testing,

inspection, packing and supply of 145 kV class outdoor, Current Transformer with CT ratio of 1200-800-400/5A to the Specification given below to be used in Mumbai area on 110

kV side at Traction Sub-station with 30 MVA Transformers and required to be operated in parallel with adjacent Traction Sub-

stations.

2.0 RATING AND OTHER PARTICULARS:

i) Type Single phase, oil filled natural air cooled outdoor.

ii) No. of cores 4

iii) System voltage

a) Nominal system voltage , kV

b) Highest system

voltage, kV

132

145

iv) Rated

primary/secondary currents

a) Primary current, Amp

b) Secondary

current, Amp

1200

5

v) CT ratio 1200-800-400/5A

vi) Rated frequency 50 Hz,+/-3%

vii) Class of insulation A

viii) a) Short time current rating

(thermal) for 3 second, kA

b) Short circuit withstand current

(3 sec.), kA

c) Short time current rating

(dynamic), kA (peak)

40

40

100

ix) Rated insulation level

a) One minute 50

Hz withstand voltage/induced over-voltage, kV

275


(rms)

b) Impulse withstand voltage, positive

and negative polarity (1.2/50

microseconds wave), kV (peak)

650

x) Minimum creepage distance of insulator (31 mm/kV), mm

4495

xi) Temperature rise Maximum temperature

rise of windings immersed in oil

50 0C over an ambient temp. 50 0C

xii) Rated Overload 150% of full load for 15 minutes

xiii) Rated Burden & Class of Accuracy of different

cores

Core-1 Core-3

Core-2&4

Protection R met Protection

Burden in VA 40 40 -

Accuracy Class 5P20 0.2 PS

Instrument Security

factor

- <5 -

Knee point voltage - - >750V

Iex (max) at Vk/2 - - <100 mA

Rct (max) - - <1.0 Ohm at max. tap.

2.1

a) multi ratio specified shall be obtained by taps on secondary side.

b) The values specified above for metering & protection core shall be met for the lowest tap. (except) Rct and knee point voltage for PS core which is at the highest

tap).

c) P1 and P2 markings to be permanently riveted.

d) CT shall be of dead tank design.

e) Power factor terminal (test tap) shall be provided inside the secondary terminal box.

f) The disposition of various CT cores and detailed drawings along with SOGP shall be furnished for RDSO‟s approval

before manufacture is taken up.

3.0 Construction:


The current transformers shall be hermitically sealed. They shall be suitable for upright mounting on steel structures.

They shall be provided with Nitrogen cushions/stainless steel bellows. CTs shall be suitable for hot line washing.

The Current Transformer winding shall be housed in a galvanized tank suitable for outdoor duty. Earthing arrangement shall be provided for CT tank.

3.1 Tank Fabrication

The tank shall be fabricated from tested quality low carbon

steel suitable for welding and of adequate thickness. The tank shall be designed to withstand mechanical shocks during transportation, vacuum filling of oil and continuous

internal pressure over normal hydrostatic pressure of oil and short circuit forces.

The construction of the tank shall be designed to prevent ingress of water into or leakage of oil from the tank. All bolted connections shall be fitted with weather proof, hot

oil resistant gasket in between (Butile Nitrile/Neoprene Rubber), for complete oil tightness. If gasket is

compressible, metallic stops shall be provided to prevent over compression.

Tank fabrication drawings shall be submitted for approval before the manufacturing is taken up.

3.2 SPECIAL CONSTRUCTION NOTE:

After the internal elements such as primary & secondary windings are sealed in the tank with porcelain shell, the

assembled CTs shall be subjected to vacuum & heat treatment and finally filled with degasified oil in vacuum.

4.0 General

4.1 Current Transformers shall be provided with unthreaded stud terminals at top for connections to 110 kV, 50 mm

OD aluminium busbar. The primary current terminals shall be of tinned copper.

4.2 The current transfer area of the terminals shall be

adequate to meet the temperature rise requirements as per IEC: 44-1/IS: 2705 for CTs. The cross-section area of

the terminal shall be indicated in the drawings.

4.3 Mechanical load test on primary terminals: Test reports are to be submitted as per IEC 44-1.

4.4 The Burdens specified for different cores refer exclusively to connected burden and should exclude the bleeder

resistance if any. Current transformer‟s guaranteed burdens and accuracy class are to be intended as simultaneous for all cores.

4.5 CTs shall be provided with a capacitance test tap in the HV lead to enable future monitoring of conditions of HV

insulation.

4.6 Earthing terminals shall be provided in the secondary junction box for earthing of secondary winding of CT.


4.7 The alignment and centre line of CT primary terminals shall be correct so as to avoid bending of connections.

4.8 The CT secondary terminal box shall be of GI (IP 55) and shall be provided with collar to prevent entry of moisture &

good neoprene gaskets designed to prevent entry of foreign particles. Junction box shall be sufficiently large to connect 1100 V upgrade, 4C x 6 sq. mm cables through

cable glands for all the secondary cores.

4.9 CT secondary terminals shall be terminated to stud type

non disconnecting terminal blocks inside the terminal box. CT secondary terminals shall be provided with lock nuts.

4.10 All ferrous parts exposed to atmosphere including main

tank, secondary terminal box & top metallic should be hot dip galvanized.

4.11 The current transformer shall be supplied complete with insulating oil conforming to IS: 12463 and Railway requirements. The insulating oil shall be procured from the

manufacturers approved by RDSO. The successful tenderer/manufacturer shall submit test certificates as per

IS: 12463 for oil.

4.12 The tenderer shall furnish their compliance or otherwise

against each clause/sub-clause of the technical specification. If the tenderer wishes to deviate from the provision of any clause/sub-clause, he shall furnish the full

details with justification for such deviations.

4.13 Detailed drawings of CT along with SOGP shall be

furnished for RDSO‟s approval before manufacture is taken up.

4.14 The CT shall be used for following additional protective

devices/relays.

i) Fibre optic line differential protection

ii) Directional over current relay.

iii) LBBU relay (LBB- breaker failure relay)

iv) Bus bar differential low impedance type protection

relay

v) Energy metering

5.0 The following Type and Routine Tests as per IEC:44-1, IS:270-5 and RDSO specification No. ETI/PSI/117(07/88) with A&C slip No. 1 to 6 shall be conducted on the Current Transformer

required for Mumbai area under DC-AC conversion.

5.1 Type Tests

1. Visual inspection

2. Temperature rise test

3. Impulse voltage test

4. Short time current test


5. Excitation test and plotting of magnetizing characteristic curves.

6. Radio interference test

7. Seismic withstand test.

8. Thermal stability test.

9. Thermal co-efficient test i.e. Measurement of tan delta as a function of temperature.

10. The CTs shall be subjected to special i.e. Multiple chopped impulse test on primary winding as per clause 6.3 (C)

and Annexure - (B) of IEC 60044-1 in order to evaluate the ageing characteristics of the CT insulation. This test is to be done to assess the CT performance in service to withstand the

high frequency over voltage generated due to closing and opening operations of isolators.

5.2 Routine Tests

1. Dimensional check

2. Verification of terminal marking and polarity

3. Power frequency voltage withstand test on primary winding.

4. Power frequency voltage withstand test on secondary

winding.

5. Accuracy tests.

a) Current error and phase displacement at the rated primary current.

b) Composite error at rated accuracy limit primary current.

6. Measurement of knee point voltage, exciting current and ISF test (only for metering core).

7. Measurement of winding resistance test.

8. Insulation resistance measurement test.

9. Inter turn over-voltage test.

10. Partial discharge test (PI) value shall be less than 5pC).

11. Capacitance and tan delta value measurement than delta value should be less than ….5%

12. Oil leakage test.

Documents

GOVERNMENT OF INDIA MINISTRY OF RAILWAYS TECHNICAL