33 kV Potential Transformer

8/6/2019 33 kV Potential Transformer

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UTTAR & DAKSHIN HARYANA BIJLI VITRAN NIGAM

Specification No. CSC- XXXIX/DH/UH/P&D/2009-2010

Technical Specification

FOR

33 kV Potential Transformer

IIssue of the Month: Jan. 2010 Common Specifications Committee

UHBVN & DHBVN

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1. Scope:

1.1. This specification provides for design, engineering, manufacture

testing of Outdoor Potential Transformer along with Terminal

connectors for Projection and metering services in different 33 KV Sub-

Stations in Haryana.

1.2. It is not the intent to specify completely here in all the details of design

and construction of equipment. However, the equipment shall conform

in all respects to high standard of engineering, design & workmanship

and shall be acceptable to the purchaser who will interpret the

meanings of drawings and specification and shall have the power to

reject any work or material which in his judgment is not in accordance

there with. The offered equipment shall be complete with all

components necessary for their effective and trouble free operation.

Such components shall be deemed to be with in the scope of bidders

supply irrespective of whether those are specifically brought out in the

specification and or the commercial order or not.

2. STANDARDS :

2.1. Unless otherwise specified elsewhere in this specification the rating as

well as performance and testing of the instrument transformers shallconform but not limited to the latest revision available at the time of

placement of order of the relevant standards as listed hereunder :-

Sr.No.

Standard No. Title

1. IS:3156(Part-I toPart-III)

Voltage Transformer

2. IS:3156(Part-IV) Capacitor voltage porcelain bushing

3. IS:2099 High voltage porcelain bushing

4. IS:3347 Dirnensions of porcelain T/F bushing

5. IS:2071 Method of high voltage testing

6. IS:335 Insulating oil for T/Fs & Switchgears.

7. IS:2165 Insulation Co-ordination of highest voltages forequipments.

8. IS:2147 Degree of protection provided by enclosuresfor low voltage switchgears and control.

9. IEC:186 Voltage Transformer.

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Maximum wind pressure 195 Kg./m Sq.10.

Note: Moderately hot and humid tropical climate conducive to rust and

fungus growth. The climatic conditions are also prone to wide variations in

ambient conditions. Smoke is also present in the atmosphere. Heavylightening also occur during June to October.

4. Principal Parameters:The capacitor voltage transformers and potential transformers covered in

this specification shall meet the technical requirements listed hereunder.

Principal Technical Parameters:Sr. No. Item Specification

Type Installation Single phase, oil filled, self

cooled, hermetically sealed,outdoor type.

4.1.

Type of Mounting Steel Structure4.2.

Highest System Voltage (KV rms) 364.3.

Suitable for system frequency 50 Hz4.4.

Voltage Ratioa) Rated primary voltage (kV rms)b) Secondary voltage (volts)i. CVTii. PT

33/3

110/3Core-I, 110/3

4.5.

Method of earthing the system Solidly earthed4.6.

1.2/50 microsecond lightning impulsewithstand voltage (kVp)

1704.7.

1 Minute dry & wet power frequencywithstand voltage primary (kV rms)

704.8.

Min. creepage distance of porcelain housing(mm)

9004.9.

Creepage factor (Max.) 4.04.10.

Rated voltage factor 1.2 continuous and 1.5 for 30seconds

4.11.

One minute power frequency withstandvoltage for secondary winding (kV rms)

3.04.12.

4.13.Max. temperature rise over ambient of 60oC As per IS: 3156 or equivalent

IEC.

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5. General Technical Requirements:

5.1. Common for PTs:

5.1.1. The insulation of the instrument transformers shall be so that the

internal insulation shall have higher electrical withstand capabilitythan the external insulation. The designed dielectrics withstandvalues of external and internal insulations shall be clearly broughtout in the guaranteed technical particulars. The dielectric withstandvalues specified in this specification are meant for fully assembledinstrument transformer.

5.1.2. Porcelain Housing :

5.1.2.1. The details of location and type joint, if provided on theporcelain shall be furnished by the Supplier along with the offer.The housing shall be made of homogeneous vitreous porcelainof high mechanical and dielectric strength. Glazing of porcelainshall be of uniform brown or dark brown colour with a smoothsurface arranged to shed away rain water particles (fog).

5.1.2.2. Details of attachment of metallic flanges to the porcelainshall be brought out in the offer.

5.1.3. The metal tanks shall have bare minimum number of welded jointsso as to minimize possible locations of oil leakage. The metal tanksshall be made out of mild steel / stainless steel /aluminum alloy,depending on the requirement. Welding in horizontal plane is to be

avoided as welding at this location may give way due to vibrationsduring transport resulting in oil leakage. Supplier has to obtainspecific approval from Purchaser for any horizontal welding used inthe bottom tank.

5.1.4. Surface Finish:

The ferrous parts exposed to atmosphere shall be hot dipgalvanized or shall be coated with at least two coats of zinc rich epoxypainting. All nuts, bolts and washer shall be made out of stainless steel.

5.1.5. Insulating Oil:

Insulation oil required for first filling of the instrument transformershall be covered in suppliers scope of supply. The oil shall meetthe requirement of latest edition IS: 335 or equivalent IEC.

5.1.6. Prevention Of Oil Leakages And Entry Of Moisture:

5.1.6.1. The Supplier shall ensure that the sealing of instrumenttransformer is properly achieved. In this connection the

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arrangement provided by the Supplier at various locationsincluding the following ones shall be described, supported bysectional drawings.

i. Locations of emergence of primary and secondary terminals.

ii. Interface between porcelain housing and metal tanks.

iii. Cover of the secondary terminal box.

5.1.6.2. Nuts and bolts or screws used for fixation of the interfacingporcelain bushings for taking out terminal shall be provided onflanges cemented to the bushings and not on the porcelain.

5.1.6.3. For gasketed joints. Wherever used nitrilc butyl rubbergaskets shall be used. The gasket shall be fitted in properlymachined groove with adequate space for accommodating the

gasket under compression.

5.1.7. Oil Level Indicators:

Instrument transformer shall be provided with oil sight window atsuitable location so that the oil level is clearly visible with naked eyeto an observer standing at ground level.

5.1.8. Earthing:

Metal tank of the instrument transformer shall be provided with twoseparate earthing terminals for bolted connection to 50x8mm MSFlat to be provided by the Purchaser for connection to station earth-mat.

5.1.9. Instrument transformer shall be provided with suitable liftingarrangement to lift the entire unit. The lifting arrangement shall beclearly shown in the general arrangement drawings. Liftingarrangement (Lifting eye) shall be positioned in such a way so as toavoid any damage to the porcelain housing or the tanks duringlifting for installation transport. If necessary string guides shall beoffered which shall be of removable type.

5.1.10. NAME PLATE:

The instrument transformer shall be provided with non-corrosive,legible name plate with the information specified in relevantstandards, duly engraved punched on it. In addition to these P.O.No. with date, item No. of P.O. & connection diagram shall also bemarked in rating plate.

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5.1.11. Suitable terminal connection for connecting ACSR conductor

of size 0.2 Sq. inch (Panther) shall be supplied. Suitable terminalearth connectors for earthing connections shall also be provided.

5.1.11.1. The terminal connectors shall meet the following

requirement:-1. Terminal connectors shall be manufactured and tested as per IS:

556 or equivalent IEC.

2. All castings shall be free from blow holes, surface blisters, cracksand cavities. All sharp edges and corners shall be blurred androunded off.

3. No part of a clamp shall be less than 10mm thick.

4. All ferrous parts shall be not dip galvanized conforming to IS:2633or equivalent IEC.

5. For bimetallic connectors, copper alloy liner of minimum 2 mmthickness shall be cast integral with aluminum body.

6. Flexible connectors shall be made from tinned copper / aluminumbody.

7. All current carrying parts shall be designed and manufactured tohave minimum contact resistance.

8. Connectors shall be designed to be corona free in accordance withthe requirements stipulated in IS: 5561 or equivalent IEC.

5.1.12. Enamel If used for conductor insulation, shall be polyvinyl

acetate type and shall meet the requirements of IS:4800 or equivalentIEC. Polyester shall not be used. Double cotton cover, if used, shallbe suitably covered to ensure that it does not come in contact with oil.

5.1.13. The temperature rise on any part of equipment shall notexceed maximum temperature rise specified in IS-3156 or equivalentIEC. However, the permissible temperature rise indicated is for amaximum ambient temperature of 60 0C.

5.1.14. The instrument transformer shall be so constructed that itcan be easily transported to site within the allowable transportlimitation and in horizontal position, if the transport Limitations sodemand.

5.1.15. The instrument transformers shall be vacuum filled with oilafter processing and thereafter hermetically sealed to eliminatebreathing and to prevent air and moisture from entering the tanks.Sealing Type oil filling and or oil sampling cocks shall be providedwith facility to reseal the same. The method adopted for hermeticscaling shall be described in the offer.

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5.1.16. Suitable arrangement shall be made to accommodate the

expansion and contraction of oil due to temperature variation. Thepressure variation shall be kept within limits which do not impair thetightness of the instrument transformer. A pressure relief devicecapable of releasing abnormal internal pressure shall be provided.

5.2. VOLTAGE TRANSFORMER (PT):

5.2.1. The voltage transformer shall be oil immersed, sealed type and selfcooled suitable for the services indicated and conforming to themodern practices of design and construction. the core shall be of highgrade, non ageing. Electrical silicon laminated steel of low hysteresisloss and high permeability to ensure high accuracy at both normaland over voltages.

5.2.2. The primary winding of voltage transformers will be connectedphase to ground.

5.2.3. All the fuses and the links shall be provided at the V.T terminalboxes.

5.2.4. The design of PT shall be based on following requirements:-

i. They must transmit sudden drops of primary voltages.

ii. They must have sufficiently low short circuit impedance as seenfrom secondary.

5.2.5. The secondary terminals of the PTs shall be brought out in aweather proof terminal box and it shall be provided with a removablegland plate.

6. TESTS:

6.1. TYPE TESTS:

6.1.1. TYPE TESTS OF POTENTIAL TRANSFORMERS (PTs):

The equipment offered should be fully type tested. In case, the equipmentof the type and designing offered has already been type tested, thesupplier shall furnish 4 sets of type test report along with the offer. Thetype test report should not be more than 5 years old, reckoned from thedate of Bid opening and type test should have been carried out in

accordance with ISS-3156 (1992) / equivalent IEC from Govt. Govtapproved test House.

However temperature rise test although covered under type tests will begot conducted by the Supplier on one piece of total ordered quantity ofeach type at his premises in the presence of the Inspecting Officer of thepurchaser, without any extra charges. The Purchaser reserves the right todemand repetition of some or all the type tests in the presence ofPurchasers representation.

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6.2. ACCEPTANCE AND ROUTINE TESTS :

i. All acceptance and routine tests as stipulated in the relevantstandards shall be carried out by the Supplier in presence ofpurchasers representative unless dispensed with in writing by thePurchaser.

ii. Immediately after finalization of the programme of routine /acceptance testing, the Supplier shall give sufficient advanceintimation to the Purchaser to enable him to depute hisrepresentative for witnessing the testing.

7.0 DOCUMENTATION

i. All drawings shall conform to international standards (ISO) Aseries of drawings sheet / Indian Standard Specification IS:11065. All drawings shall be in ink. All dimensions and data shallbe in S.I.Units.

ii. List of Drawings :a. General outline and assembly drawings of the equipment.

b. Graphs showing the performance of equipment in regard tomagnetization characteristics.

c. Sectional view showing :

i. General Constructional Features.

ii. Materials/Gaskets/Sealing used.

iii. The Insulation & the winding arrangements, methodof connection of the primary / secondary terminals

etc.

iv. Porcelain used and its dimensions.

d. Arrangement of terminals and details of connection studsprovided.

e. Name plate.

f. Schematic drawings.

iii. The successful Supplier shall submit four sets of final versions of allthe drawings mentioned under clause 7.II except 7.II(b) above.within 15 days of date of receipt of acceptance of offer from thepurchaser. The Purchaser shall communicate hiscomments/approval on the drawings to the Supplier within onemonth of date of receipt of above drawings. The Supplier shall, ifnecessary, modify the drawings and resubmit four copies of themodified drawings for Purchasers approval within two weeks fromthe date of Purchasers comments. Actual graphs as per clause7.II(b) generated at the time of inspection shall be submitted forpurchasers approval.

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iv. The manufacturing of the equipment shall be strictly in accordance

with the approved drawings and no deviation shall be permittedwithout the written approval of the Purchaser. All manufacturingand fabrication work in connection with the equipment prior to theapproval of the drawings shall be at the Suppliers ask.

v. After receipt of Purchasers approval the Supplier shall submitfollowing drawings /documents along with a soft copy in suitablemedia, within two weeks :

Sr.No.

Equipment No. of Sets ofDrawings

No. of nicely printed andbound volumes of operation,maintenance and erectionmanuals in English.

1 33KV PTs 1 Set per PT 1 Set per PT

vi. Approval of drawings work by Purchaser shall not relieve thesupplier of his responsibility and liability for ensuring correctness &correct interpretation of the latest revisions of applicable standards,rules and codes of practices. The equipment shall conform in allrespects to high standards of engineering, design workmanship andlatest revisions of relevant standards at the time of ordering.

vii. GTPs: The technical & Guaranteed technical parameters shall besupplied in the format as per Annexure-A. The tenders without/blank GTPs sheet shall be liable for rejection.

8. INSPECTION:

All tests and inspection shall be made at the place of the manufacturerunless otherwise especially agreed upon by the manufacturer and thepurchaser at the time of purchase. The manufacturer shall afford theinspector representing the purchaser, all reasonable facilities, withoutcharge, to satisfy him that the material being supplied is in accordancewith the specification.

The purchaser has the right to get the tests carried out at his own costby an independent agency, whenever there is a dispute regarding thequality of the supply.

The manufacturer shall be responsible to pay penalty of Rs20,000/- for each occasion at which the fake inspection call has beenmade or the material is rejected during testing/inspection by theauthorized agency/representative of the Nigam. This penalty would be inaddition to the expenses incurred by the Nigam in deputing theInspecting Officer, carrying out such inspection

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CORE WISE DETAILS OF 36KV POTENTAIL TRANSFORMER (PT) OF3 CORES

Sr.

No.

Particulars Requirements

1. Rated primary voltage 33/3 KV

2. Type Single phase

3. No. of secondaries One

4. Rated voltage factor 1.2 continuous

5. Rated voltage (volts) Secondary-I 110/3

6. Application Main metering

7. Accuracy 0.5

8. Output burden (VA) 10

9. Percentage voltage error & phasedisplacement (minutes) forrespective specified accuracyclasses

As per ISS/IEC

NOTE: Each winding shall fulfill its respective specified accuracy

requirement within its specified output range whilst at the same time the

other winding has an output of any value from 0 to 100% of the outputrange specified for the other winding in line with cause.

9. Challenge Clause:-

The material offered/received after the inspection by the authorized

inspecting officer may again be subjected to the test for or any parameter

from any testing house/in-house technique of the Nigam & the results if

found deviating un-acceptable or not complying to approved GTPs the

bidder shall arrange to supply the replacement within thirty (30) days of

such detection at his cost including to & fro transportation. In addition

penalty @10% of cost of the inspected lot of material shall be imposed.

10. Warranty Period:-

The supplier shall be responsible to replace, free of cost, with no

transportation or insurance cost to the purchaser, up to destination, the

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whole or any part to the material which in normal and proper use proves

the defective in quality or workmanship, subject to the condition that the

defect is noticed within 18 months from the date of receipt of material in

stores or 12 months from the date of commissioning whichever period

may expire earlier. The consignee or nay other officer of Nigam actually

using the material will give prompt notice of each such defect to the

supplier. The replacement shall be effected by the supplier within a

reasonable time, but not, in any case, exceeding 45 days/ The supplier

shall, also, arrange to remove the defective within a reasonable period,

but not exceeding 45 days from the date of issue of notice in respect

thereof, failing which, the purchaser reserve the right to dispose of

defective material in any manner considered fit by him (purchaser), at the

sole risk and cost of the supplier. Any sale proceeds of the defective

material after meeting the expenses incurred on its custody, disposal

handling etc., shall however be credited to the suppliers account and set

off against any outstanding dues of the purchaser against the supplier.

The warranty for 12/18 months shall be one time.

Director/Technical-I,

UHBNV, Panchkula

Director/Project,

DHBVN, Hisar

CGM/PD&C,

UHBVN, Panchkula

CGM/P&D,

DHBVN, Hisar.

FA & CAO/MM,

UHBNV, Panchkula

FA & CAO/MM,

DHBVN, Hisar

GM/P&D,

UHBNV, Panchkula

GM/P&D,

DHBVN, Hisar

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ANNEXURE-A

GUARANTED TECHNICAL PARTICULARS

POTENTIAL TRANSFORMER

1. Manufacturers type and designation.

2. Type.

3. Rated frequency.

4. Rated Primary voltage.

5. Number of Secondary windings.

6. Rated secondary voltage.

7. Class of Accuracy.

8. Limits of errors:

i.) Percentage voltage ratio error.

ii.) Phase displacement (Minutes).

9. Rated burden.

10. Rated voltage factor & time:

11. Temperature rise at 1.2 times rated voltage when applied

continuously with rated burden (0C).

12. Insulation class of

i. Primary windings

ii. Secondary windings

13. One minute power frequency (dry) withstands test voltage (kv).

14. One minute power frequency (wet) withstands test voltage.

15. 50 micro second impulse withstand test voltage (kv peak).

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16. One minute power frequency withstands voltage on secondary

(Volts).

17. a) Creepage distance.

b) Creepage factor.

18. Standard to which the equipment conforms.

19. Standard to which the oil conforms.

20. Total weight of the PT.

21. Over-all dimensions.

22. Mounting details.

23. Weight of the oil.

24. Total shipping weight.

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33 kV Potential Transformer

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