Technical Specification-Power Transformer

49 

Full text

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POWER TRANSFORMER

POWER TRANSFORMER

(With Provision for Installation/Adaptation of Sergi System) (With Provision for Installation/Adaptation of Sergi System)

Specificati

Specificati on on No. No. Version Version Date Date of of Issuance Issuance Total Total Pages Pages Issuing Issuing Section Section / / DepartmentDepartment

PID/TS/PTR/1.0

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CONTENTS

CONTENTS

1.

1. SCOPE SCOPE ... . 55 2.

2. SYSTEM SYSTEM PARAMETERS PARAMETERS ... 5... 5 3.

3. SERVICE SERVICE CONDITIONS CONDITIONS ... 5... 5 4.

4. GENERAL GENERAL ... ... 55 5.

5. EQUIPMENT EQUIPMENT IDENTIFICATION AND IDENTIFICATION AND COLOR COLOR CODES ...CODES ... . 66 6.

6. TECHNICAL TECHNICAL DESCRIPTION DESCRIPTION ... 6... 6

6.1

6.1 General General Design Design ... ... 6 6  6.2

6.2 Windings ...Windings ... ... 7 7  6.3

6.3  Magnetic Core ... Magnetic Core ... 8... 8 6.4

6.4 Transformer Transformer Tank ...Tank ... ... 88 6.5

6.5 Terminals ...Terminals ... ... 1010 6.6 

6.6  Current Current TransformerTransformers .s ... ... 1212 6.7 

6.7  Cooling ...Cooling ... ... 1313 6.8

6.8 Control of Control of Cooling Units ...Cooling Units ... 16 ... 16 

7.

7. TAP TAP CHANGERS ...CHANGERS ... 17... 17 8.

8. PARALLEL PARALLEL OPERATION OPERATION AND VOLTAND VOLTAGE AGE REGULATION ...REGULATION ... ... 2121 9.

9. PERFORMANCE PERFORMANCE CHARACTERISTICS OF CHARACTERISTICS OF MOTORS MOTORS ... ... 2121 10.

10. TRANSFORMER TRANSFORMER OIL ...OIL ... 21... 21 11.

11. OIL OIL CONSERVATOR CONSERVATOR ... 21.. 21 12.

12. PIPING PIPING AND AND VALVES VALVES ... ... 2222 13.

13. MEASURING MEASURING AND AND MONITORING MONITORING EQUIPMENT ...EQUIPMENT ... ... 2323 14.

14. CONTROL CUBICLES, CONTROL CUBICLES, MARSHALLING BOXES, MARSHALLING BOXES, WIRING AND WIRING AND CONDUITS ...CONDUITS ... ... 2525 15.

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16.

16. DRAWINGS DRAWINGS AND AND DOCUMENTS ...DOCUMENTS ... 27... 27 17.

17. TESTING TESTING AND AND INSPECTION INSPECTION ... 27... 27

17.1

17.1  Factory Tests  Factory Tests ... 28... 28 17.1.1

17.1.1 Routine Routine Tests ...Tests ... ... 2828 17.2

17.2 Type Tests Type Tests and Special and Special Tests ...Tests ... 29... 29 17.3

17.3 Tests on Tests on Transformer Tank and Transformer Tank and AccessoAccessories ries ... 31... 31 17.4

17.4 Site Tests Site Tests (minimum requirements) ...(minimum requirements) ... 31... 31

18.

18. CORROSION CORROSION PROTECTION PROTECTION ... 32... 32

18.1

18.1  Responsibility and Guarantees  Responsibility and Guarantees ... 32... 32 18.2

18.2 Test Test Instruments...Instruments... 32... 32 18.3

18.3  Materials... Materials... 33... 33 18.4

18.4 Galvanized Steel Galvanized Steel Surfaces ...Surfaces ... 34... 34 18.4.1

18.4.1 General Requirements ...General Requirements ... ... 3434 18.4.2

18.4.2 Cleaning and Cleaning and Surface Preparation ...Surface Preparation ... 34... 34 18.5

18.5  Painting at Manufacturer's Pre Painting at Manufacturer's Premises mises ... 35... 35 18.5.1

18.5.1 Painting ...Painting ... ... 3535

19.

19. CAPITALISATION CAPITALISATION OF OF LOSSES ...LOSSES ... 36... 36 20.

20. GUARANTEED GUARANTEED VALUES VALUES AND AND PENALTIES ...PENALTIES ... ... 3636 21.

21. LOSSES LOSSES ... ... 3636 22.

22. RATED RATED POWER POWER AND AND OUTPUT ...OUTPUT ... ... 3737 23.

23. NOISE NOISE LEVEL...LEVEL... ... 3737 24.

24. REJECTION REJECTION ... ... 3737 25.

25. TRANSPORT TRANSPORT ... ... 3737 26.

26. IMPACT IMPACT RECORDERS ...RECORDERS ... 38... 38 27.

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1.

1. SCOPESCOPE

This part of the Specifications covers the design, manufacture, factory testing, transport, marking, This part of the Specifications covers the design, manufacture, factory testing, transport, marking, packing, shipping, delivery to site, unloading and storage at site

packing, shipping, delivery to site, unloading and storage at site of power transformers with provision forof power transformers with provision for installation/ada

installation/adaptation of ptation of Sergi system.Sergi system.

2.

2. SYSTEM PARAMETERSSYSTEM PARAMETERS

Highest Highest System System Voltage Voltage : : 145 145 kVkV

System System Frequency Frequency : : 50 50 HzHz

Nominal Nominal Voltage Voltage : : 132 132 kVkV

Short Short Circuit Circuit Level Level : : 40kA 40kA for for 3.0 3.0 secondsseconds

BIL BIL : : 650kV 650kV (peak)(peak)

3.

3. SERVICE CONDITIONSSERVICE CONDITIONS

a.

a. Peak Peak ambient ambient air air temperaturetemperature 5050ooCC

b.

b. Mean Mean maximumaximum m temperature temperature during during 24 24 hourshours 4040ooCC

c.

c. Minimum Minimum temperature temperature 00ooCC

d.

d. Maximum Maximum relative relative humidityhumidity 95% at dry bulb95% at dry bulb Temperature of 45 Temperature of 45ooCC

e.

e. AltitudAltitude e Does Does not not exceed exceed 1000m1000m

f. Location

f. Location Sea-coastSea-coast

g.

g. Wind Wind speedspeed 160 KM/hr.160 KM/hr.

h.

h. Rain, Rain, condensation condensation and and heavy heavy pollution pollution shall shall be be considered considered while while designingdesigning

4.

4. GENERALGENERAL

The power transformers shall be designed and arranged in full compliance with all applicable Sections, The power transformers shall be designed and arranged in full compliance with all applicable Sections, Articles, and Specific Works Data Sheets of these Specifications and no deviation would be

Articles, and Specific Works Data Sheets of these Specifications and no deviation would be acceptable.acceptable. The supplier/Tenderer/Contractor shall submit with his offer a list of similar transformers already The supplier/Tenderer/Contractor shall submit with his offer a list of similar transformers already delivered by the manufacturer proposed. Past supply records of similar ratings of transformers for 15 delivered by the manufacturer proposed. Past supply records of similar ratings of transformers for 15 years shall be submitted in detail with the offer.

years shall be submitted in detail with the offer.

The following engineering data shall be submitted with the The following engineering data shall be submitted with the offer:offer: (a)

(a) Technical schedules, all drawings with Technical schedules, all drawings with all informationall information (b)

(b) Type test Type test certificates, for similar transformers as offeredcertificates, for similar transformers as offered (c)

(c) Type test certificates for different bushings, surge arresters and tap Type test certificates for different bushings, surge arresters and tap changerschangers (d)

(d) Certificates for short circuit tests Certificates for short circuit tests and temperature rise tests performed on and temperature rise tests performed on transformers with similartransformers with similar transformer as offered.

transformer as offered. (e)

(e) Quality system certificateQuality system certificate (f)

(f) General arrangement of transformer showing all dimensionsGeneral arrangement of transformer showing all dimensions (g)

(g) Details of all cable boxes and bushingsDetails of all cable boxes and bushings (h)

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(i)

(i) Deviations from Tender Specifications, brochures etc.Deviations from Tender Specifications, brochures etc. (j)

(j) Foundation drawingsFoundation drawings (k)

(k) Necessary drawings of provision for Necessary drawings of provision for installation/ainstallation/adaptation of Sergi systemdaptation of Sergi system (l)

(l) Reference list and Reference list and Customer certificate of successful operation from major utilities.Customer certificate of successful operation from major utilities.

Please note following: Please note following:

(i)

(i) In case, the Tenderer/Contractor/Supplier is not able to produce Type Test/Special Test CertificatesIn case, the Tenderer/Contractor/Supplier is not able to produce Type Test/Special Test Certificates for similar rating equipment certified from independent international accredited laboratory to the for similar rating equipment certified from independent international accredited laboratory to the satisfaction of Engineer/Co

satisfaction of Engineer/Company then, he has to mpany then, he has to make arrangement for conductinmake arrangement for conducting such g such tests at antests at an independent international accredited laboratory in the presence of KE Engineer, as per latest IEC independent international accredited laboratory in the presence of KE Engineer, as per latest IEC Publications of IEC-60076 and its relevant/applicable parts on various tests. The total cost of such Publications of IEC-60076 and its relevant/applicable parts on various tests. The total cost of such tests along with full expenditure of K-ELECTRIC engineer(s) alongwith Third Party inspector for tests along with full expenditure of K-ELECTRIC engineer(s) alongwith Third Party inspector for witnessing these tests has to be

witnessing these tests has to be borne by the Supplier/Contractor.borne by the Supplier/Contractor. The latest issues

The latest issues of Recommendatiof Recommendations of the ons of the international Electrotechnicinternational Electrotechnical Commission (IEC) in particularal Commission (IEC) in particular the IEC 60076,IEC 60137, IEC 60214, IEC 60296 and IEC

the IEC 60076,IEC 60137, IEC 60214, IEC 60296 and IEC 60354 shall apply.60354 shall apply.

For applicable technical standards, tests and general requirements refer to applicable sections of these For applicable technical standards, tests and general requirements refer to applicable sections of these Specification

Specification Documents.Documents.

5.

5. EQUIPMENT IDENTIFICATION AND COLOR CODESEQUIPMENT IDENTIFICATION AND COLOR CODES

The color of the transformers shall be

The color of the transformers shall be RAL7035 and shall be painted to C4 RAL7035 and shall be painted to C4 specification for 5-15yearsspecification for 5-15years..

6.

6. TECHNICAL DESCRIPTIONTECHNICAL DESCRIPTION 6.1

6.1 General DesignGeneral Design

The design of the

The design of the power transformers shall be based on the following requirements:power transformers shall be based on the following requirements: a)

a) The transformers shall be designed for operation at ambient shade temperatures up to a maximumThe transformers shall be designed for operation at ambient shade temperatures up to a maximum of 50

of 50ooC.C.

 b)

 b) The maximum permissible temperature rise of the transformer oil (top oil) shall not exceed 45 K,The maximum permissible temperature rise of the transformer oil (top oil) shall not exceed 45 K, the average temperature rise of the winding is to be limited to 50 K, and the winding hot spot the average temperature rise of the winding is to be limited to 50 K, and the winding hot spot temperature rise shall not exceed 63 K. The hot spot factor (H) for power transformers with core temperature rise shall not exceed 63 K. The hot spot factor (H) for power transformers with core form type of core shall be

form type of core shall be 1.3.1.3. c)

c) The transformers shall be capable of operating continuously within The transformers shall be capable of operating continuously within the specified temperature risethe specified temperature rise limits at their full rated power (full nameplate ratings) at all tap changer settings and under all limits at their full rated power (full nameplate ratings) at all tap changer settings and under all specified site and

specified site and installation conditions.installation conditions. d)

d) The transformers, completely assembled with bushings, cable boxes and/or flange connections,The transformers, completely assembled with bushings, cable boxes and/or flange connections, shall be designed and

shall be designed and constructed to withstand without damages the effects of short constructed to withstand without damages the effects of short circuits as percircuits as per IEC 60076-5 for at

IEC 60076-5 for at least 3 seconds least 3 seconds after long-time emergency cyclic loading conditions as specifiedafter long-time emergency cyclic loading conditions as specified in IEC 60354 at 30

in IEC 60354 at 30ooC ambient temperature under thermal steady state conditions (to be C ambient temperature under thermal steady state conditions (to be verified byverified by

thermal short-circuit calculation and steady state heat-run test). thermal short-circuit calculation and steady state heat-run test).

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e)

e) The transformers shall be designed with particular attention to the suppression of harmonicThe transformers shall be designed with particular attention to the suppression of harmonic voltages to eliminate wave form distortion and from

voltages to eliminate wave form distortion and from any possibility of high any possibility of high frequency disturbancesfrequency disturbances reaching such a magnitude to

reaching such a magnitude to cause interference with communication circuits.cause interference with communication circuits. f)

f) Neutral points shall be brought out Neutral points shall be brought out and grounded as specified.and grounded as specified. g)

g) The open delta of stabilising winding, if any, shall be bThe open delta of stabilising winding, if any, shall be brought out by outdoor bushings and shall berought out by outdoor bushings and shall be shortened and grounded by solid copper bars

shortened and grounded by solid copper bars rigidly supported and fastened.rigidly supported and fastened. h)

h) Provision for installation/adaptation of Sergi system to be made at transformer necessary drawingProvision for installation/adaptation of Sergi system to be made at transformer necessary drawing to be submitted by

to be submitted by supplier for approval.supplier for approval. i)

i) Furthermore, each transforFurthermore, each transformer shall comply with the stipulations of mer shall comply with the stipulations of the following Articles.the following Articles.

6.2

6.2 WindingsWindings

All transformer windings for LI: 650 kV / AC: 275 kV and below shall have uniform insulation. Transformer All transformer windings for LI: 650 kV / AC: 275 kV and below shall have uniform insulation. Transformer windings designed for higher insulation levels may

windings designed for higher insulation levels may have non-uniform insulation. In these cases the have non-uniform insulation. In these cases the ratedrated insulation level for neutral points shall be LI: 650 kV / AC: 275 k,

insulation level for neutral points shall be LI: 650 kV / AC: 275 k, Vector group is YNyn0 (d11).Vector group is YNyn0 (d11). Due to the

Due to the possibility of high transferred over-voltages LV windings with a rated possibility of high transferred over-voltages LV windings with a rated voltage of 12 kV in voltage of 12 kV in powerpower transformers having HV windings of U

transformers having HV windings of Umm= 110 kV and above shall be = 110 kV and above shall be designed for not less than LI: 125 kV /designed for not less than LI: 125 kV /

AC: 50 kV, and the same in transformers not having HV windings of U

AC: 50 kV, and the same in transformers not having HV windings of Umm= 110 kV and above shall be= 110 kV and above shall be

designed for a rated insulation level of not less than LI: 95 kV / AC: 38 kV. Particular values for all insulation designed for a rated insulation level of not less than LI: 95 kV / AC: 38 kV. Particular values for all insulation and test levels shall be obtained from the description of the Scope of Work / Scope of Supply and the Specific and test levels shall be obtained from the description of the Scope of Work / Scope of Supply and the Specific Works Data Sheets of these Specifications.

Works Data Sheets of these Specifications.

All windings and their leads shall be designed and arranged such as to withstand all kinds of transferred All windings and their leads shall be designed and arranged such as to withstand all kinds of transferred over-voltages. Protective capacitors shall not be provided for any of the windings. Non-linear ZnO protective voltages. Protective capacitors shall not be provided for any of the windings. Non-linear ZnO protective elements in any windings other

elements in any windings other than regulation windings will not than regulation windings will not be accepted.be accepted.

Windings shall be of best modern design with conductors having constant cross-section along the whole Windings shall be of best modern design with conductors having constant cross-section along the whole windings, and the current densities shall not exceed 2.62 A/mm

windings, and the current densities shall not exceed 2.62 A/mm22 in any part of the windings. Electrolytic in any part of the windings. Electrolytic

copper of a high conductivity and insulation material of high quality (class A, in accordance with IEC

copper of a high conductivity and insulation material of high quality (class A, in accordance with IEC6008560085)) shall be used. The insulation material of windings and connections shall be free from insulation compounds shall be used. The insulation material of windings and connections shall be free from insulation compounds subject to softening, shrinking or collapsing during service. Moreover, none of the material used shall subject to softening, shrinking or collapsing during service. Moreover, none of the material used shall disintegrate, carbonise or become brittle under the action of hot oil, under all specified load conditions. disintegrate, carbonise or become brittle under the action of hot oil, under all specified load conditions. The coils must be capable of withstanding movement and distortion caused by all operating conditions as The coils must be capable of withstanding movement and distortion caused by all operating conditions as specified in

specified in IEC 60354IEC 60354. Adequate barriers shall be provided between windings and core and between the. Adequate barriers shall be provided between windings and core and between the windings. All leads or bars from the windings to the terminal boxes and bushings shall be rigidly supported. windings. All leads or bars from the windings to the terminal boxes and bushings shall be rigidly supported. Stresses on coils and connections must be avoided. To increase the capability of the transformers of Stresses on coils and connections must be avoided. To increase the capability of the transformers of withstanding the stresses under short-circuit conditions modern technology in design and construction shall withstanding the stresses under short-circuit conditions modern technology in design and construction shall be applied (e.g. low current densities as above, and pre-drying and pre-compressing of the windings before be applied (e.g. low current densities as above, and pre-drying and pre-compressing of the windings before mounting onto the core, etc.).

mounting onto the core, etc.).

The values for impedance voltages on extreme tappings shall not deviate from those for principal tappings by The values for impedance voltages on extreme tappings shall not deviate from those for principal tappings by a percentage value of more than two third of the difference in percentage tapping factor between the a percentage value of more than two third of the difference in percentage tapping factor between the concerned tappings and the principal tappings, and the transformers shall have the highest losses at the concerned tappings and the principal tappings, and the transformers shall have the highest losses at the highest current taps (lowest voltage taps). At the time of inspection, FAT supplier would

highest current taps (lowest voltage taps). At the time of inspection, FAT supplier would need to provide theneed to provide the certificate of origin/supplie

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6.3

6.3 Magnetic CoreMagnetic Core

The magnetic core shall be made of

The magnetic core shall be made of laminations of non-agelaminations of non-ageing, cold-rolled, grain-oriented, silicon steel ofing, cold-rolled, grain-oriented, silicon steel of high permeability (Hi-B-type; W17/50: max. 1.05 W/kg) without burrs. The maximum magnetic flux high permeability (Hi-B-type; W17/50: max. 1.05 W/kg) without burrs. The maximum magnetic flux density in the

density in the legs and yokes of the core legs and yokes of the core shall not exceed 1.6 Tesla at rshall not exceed 1.6 Tesla at rated voltage and frequency.ated voltage and frequency.

Each lamination shall be insulated with high quality insulation coating. The joints of limbs and yokes shall Each lamination shall be insulated with high quality insulation coating. The joints of limbs and yokes shall be designed and constructed to keep the no-load losses and the hot spot temperature in the magnetic core be designed and constructed to keep the no-load losses and the hot spot temperature in the magnetic core as well as the noise level as low as possible by application of the step-lap core stacking method.

as well as the noise level as low as possible by application of the step-lap core stacking method. The core and its clamping plates shall form a rigid unit

The core and its clamping plates shall form a rigid unit structure, which shall maintain its form and positionstructure, which shall maintain its form and position under the severe

under the severe stresses encountered during shipment, installation and short circuits. Care shall stresses encountered during shipment, installation and short circuits. Care shall also bealso be taken to secure uniformly distributed mechanical pressure over all the laminations to prevent setting of taken to secure uniformly distributed mechanical pressure over all the laminations to prevent setting of the core and to

the core and to limit noise and vibrations to a limit noise and vibrations to a minimum under service conditions.minimum under service conditions.

In order to prevent closed magnetic circuit via the tank, the top main core clamping structure shall not be In order to prevent closed magnetic circuit via the tank, the top main core clamping structure shall not be connected to the tank cover. The magnetic core shall be earthed to the tank cover at one point only through connected to the tank cover. The magnetic core shall be earthed to the tank cover at one point only through removable links in an appropriate terminal box, placed in an accessible position on the tank cover and which, removable links in an appropriate terminal box, placed in an accessible position on the tank cover and which, by disconnection, will enable the insulation between the core and transformer tank, etc., to be tested at by disconnection, will enable the insulation between the core and transformer tank, etc., to be tested at voltages up to 2.5 kV for the purpose of checking deterioration during service.

voltages up to 2.5 kV for the purpose of checking deterioration during service.

Magnetic circuits with an insulated sectional construction shall be provided with a separate link for each Magnetic circuits with an insulated sectional construction shall be provided with a separate link for each individual section. Where oil ducts or insulating barriers parallel to the plane of the laminations divide the individual section. Where oil ducts or insulating barriers parallel to the plane of the laminations divide the magnetic circuit into two or more electrically separate parts, the ducts or barriers shall be bridged and the magnetic circuit into two or more electrically separate parts, the ducts or barriers shall be bridged and the magnetic circuit shall not be regarded as being of sectional construction.

magnetic circuit shall not be regarded as being of sectional construction.

The main earthing connection shall have a cross-sectional area of not less than 80 mm

The main earthing connection shall have a cross-sectional area of not less than 80 mm22  but connections  but connections

inserted between laminations may have cross-sectional area reduced to a minimum of 20 mm inserted between laminations may have cross-sectional area reduced to a minimum of 20 mm22..

6.4

6.4 Transformer TankTransformer Tank

The transformer tank shall be of the upper flange type with reinforced cover. The completely assembled tank The transformer tank shall be of the upper flange type with reinforced cover. The completely assembled tank including radiators, conservators, and associated oil piping shall be fully vacuum proof. The construction shall including radiators, conservators, and associated oil piping shall be fully vacuum proof. The construction shall be of mild steel and shall be of sufficient strength and rigidity to withstand moving, shipping and handling be of mild steel and shall be of sufficient strength and rigidity to withstand moving, shipping and handling without any de-formation. All seams and joints other than those of such tank covers, which may be jointed without any de-formation. All seams and joints other than those of such tank covers, which may be jointed to the upper flange of the tank by welding, shall be welded both inside and outside of the tank to secure to the upper flange of the tank by welding, shall be welded both inside and outside of the tank to secure strong, leak-proof joints.

strong, leak-proof joints.

The construction shall employ weldable structural steel of an approved grade to BS 7613 and BS EN 10029 or The construction shall employ weldable structural steel of an approved grade to BS 7613 and BS EN 10029 or equivalent.

equivalent.

The minimum thickness of tank walls shall be 6 mm for transformer lengths of less than 2500 mm and 9 mm The minimum thickness of tank walls shall be 6 mm for transformer lengths of less than 2500 mm and 9 mm for transformer le

for transformer length of 2500 mm and above, and that for tank cover sngth of 2500 mm and above, and that for tank cover shall be at least 20 mm for transhall be at least 20 mm for transformersformers up to 80 MVA per unit and not less than 25 mm for transformers of 100 MVA per unit and above. Any kind of up to 80 MVA per unit and not less than 25 mm for transformers of 100 MVA per unit and above. Any kind of laminated tank covers are not acceptable.

laminated tank covers are not acceptable.

The tank bottom shall be of one plane and shall be a heavy rigid base structure. The four tank walls shall be The tank bottom shall be of one plane and shall be a heavy rigid base structure. The four tank walls shall be plane and of one piece each and shall be welded directly onto the tank bottom without steps. Any kind of plane and of one piece each and shall be welded directly onto the tank bottom without steps. Any kind of bell-type tanks are not acceptable.

bell-type tanks are not acceptable.

If heavy steel cross beams are provided as a rigid base structure the thickness of tank bottom shall not be less If heavy steel cross beams are provided as a rigid base structure the thickness of tank bottom shall not be less than 12 mm. In case of self-supporting tank bottom without heavy steel cross beams the bottom plate shall than 12 mm. In case of self-supporting tank bottom without heavy steel cross beams the bottom plate shall

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have a minimum thickness of 25 mm for transformers up to 30 MVA per unit, min. 30 mm for transformers have a minimum thickness of 25 mm for transformers up to 30 MVA per unit, min. 30 mm for transformers up to 63 MVA per unit, min. 40 mm for transformers up to 100 MVA per unit and at least 50 mm for up to 63 MVA per unit, min. 40 mm for transformers up to 100 MVA per unit and at least 50 mm for transformers above 100 MVA per unit. Laminated tank bottom will not be accepted.

transformers above 100 MVA per unit. Laminated tank bottom will not be accepted.

The completely assembled transformer shall be oil and gas tight and shall be capable of withstanding without The completely assembled transformer shall be oil and gas tight and shall be capable of withstanding without damage, under service conditions, the forces arising under pressure conditions of at least 1.0 bar (>14 PSI) damage, under service conditions, the forces arising under pressure conditions of at least 1.0 bar (>14 PSI) and/or exceeding 25% over the maximum operating pressure, resulting from the system of oil preservation and/or exceeding 25% over the maximum operating pressure, resulting from the system of oil preservation used (whatever is higher). Tank stiffeners shall be provided as required, and these shall

used (whatever is higher). Tank stiffeners shall be provided as required, and these shall be designed to avoidbe designed to avoid water penetration.

water penetration.

The complete tank and its cover shall be designed in such a manner as to leave no external pockets in which The complete tank and its cover shall be designed in such a manner as to leave no external pockets in which water can accumulate no internal pockets in which oil can remain when draining the tank and/or in which air water can accumulate no internal pockets in which oil can remain when draining the tank and/or in which air can be trapped when filling the tank.

can be trapped when filling the tank.

Wherever possible, the transformer tank and its accessories shall be designed without pockets wherein gas Wherever possible, the transformer tank and its accessories shall be designed without pockets wherein gas may collect. For this purpose the tank cover shall be especially designed. Where pockets cannot be avoided, may collect. For this purpose the tank cover shall be especially designed. Where pockets cannot be avoided, pipes shall be provided to vent any gas into the main expansion pipe.

pipes shall be provided to vent any gas into the main expansion pipe.

Vent pipes shall have minimum inside diameter of 25 mm. Both ends of the tank cover shall be connected to Vent pipes shall have minimum inside diameter of 25 mm. Both ends of the tank cover shall be connected to the main expansion pipe.

the main expansion pipe.

All connections bolted to the tank shall be fitted with suitable gas and oil resistant gaskets made of such a All connections bolted to the tank shall be fitted with suitable gas and oil resistant gaskets made of such a material that no serious deterioration occurs under service conditions & must be

material that no serious deterioration occurs under service conditions & must be heat and oil resistant rubber.heat and oil resistant rubber. All gaskets shall be of closed design (without open ends) and shall be of one piece only.

All gaskets shall be of closed design (without open ends) and shall be of one piece only. Rubber gaskets usedRubber gaskets used for flange connections of the various oil compartments shall be laid in grooves or in groove-equivalent for flange connections of the various oil compartments shall be laid in grooves or in groove-equivalent retainers on both sides of the gaskets throughout their total length. Care shall be taken to secure uniformly retainers on both sides of the gaskets throughout their total length. Care shall be taken to secure uniformly distributed mechanica

distributed mechanical pressure over the l pressure over the gaskets and retainers throughout the total length.gaskets and retainers throughout the total length.

Gaskets of neoprene and/or such material which can be easily damaged by over-pressing (e.g. any kind of Gaskets of neoprene and/or such material which can be easily damaged by over-pressing (e.g. any kind of impregnated/bonded or other kind of cork) are not acceptable for any of the equipment. Use of hemp as impregnated/bonded or other kind of cork) are not acceptable for any of the equipment. Use of hemp as gasket material is also

gasket material is also prohibited.prohibited.

Power transformers shall be equipped with manholes and hand-holes of suitable size to facilitate installation Power transformers shall be equipped with manholes and hand-holes of suitable size to facilitate installation and maintenance (i.e. tap changers, current transformers, bushings etc.). Manholes for tap changers shall and maintenance (i.e. tap changers, current transformers, bushings etc.). Manholes for tap changers shall have size of minimum 800 mm in height and 350 mm in width, and shall be arranged in a convenient floor have size of minimum 800 mm in height and 350 mm in width, and shall be arranged in a convenient floor height. All openings in the cover of the transformer tank for bushings, manholes and terminal boxes shall be height. All openings in the cover of the transformer tank for bushings, manholes and terminal boxes shall be provided with adequate flanges. Covers for inspection openings, hand-holes etc. located on the tank cover provided with adequate flanges. Covers for inspection openings, hand-holes etc. located on the tank cover shall be provided with adequate gas stoppers. Tap selector shall be equipped with one inspection window for shall be provided with adequate gas stoppers. Tap selector shall be equipped with one inspection window for observation. All inspection covers etc. shall be provided with

observation. All inspection covers etc. shall be provided with two lifting handles each.two lifting handles each.

It must be possible to remove any bushing completely without removing the tank cover. Easy access shall be It must be possible to remove any bushing completely without removing the tank cover. Easy access shall be also provided for internal connection of bushings without extensive dismantling any external mounting such also provided for internal connection of bushings without extensive dismantling any external mounting such as radiators etc.

as radiators etc.

The tank cover and all covers for mounting, cleaning, manholes, handholes and inspection openings on tank The tank cover and all covers for mounting, cleaning, manholes, handholes and inspection openings on tank and cable boxes etc. shall be earthed by suitable grounding conductors of the flexible type having a cross and cable boxes etc. shall be earthed by suitable grounding conductors of the flexible type having a cross section of minimum 95 mm

section of minimum 95 mm22. Appropriate earthing studs with bolts and washers of stainless steel shall be. Appropriate earthing studs with bolts and washers of stainless steel shall be

provided. provided.

In order to prevent tank deformation during operation, spring-loaded pressure relief devices / explosion vents In order to prevent tank deformation during operation, spring-loaded pressure relief devices / explosion vents with trip contact of an approved type shall be mounted through approved elbow turrets onto the tank cover with trip contact of an approved type shall be mounted through approved elbow turrets onto the tank cover

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for rapid release of any pressure that might be generated within the tank and cause damage to the for rapid release of any pressure that might be generated within the tank and cause damage to the equipment. The devices shall operate at a static pressure which shall be less than the test

equipment. The devices shall operate at a static pressure which shall be less than the test pressure on tank.pressure on tank. The nominal operating pressure of the devices shall not exceed 0.7 bar (or 10 PSI). The related elbow turrets The nominal operating pressure of the devices shall not exceed 0.7 bar (or 10 PSI). The related elbow turrets shall be connected through vent pipes as above to Buchholz relay.

shall be connected through vent pipes as above to Buchholz relay. All transformer tanks and radiators with fins shall be

All transformer tanks and radiators with fins shall be subject to oil leak tests as subject to oil leak tests as specified in the relevant Articlesspecified in the relevant Articles for Inspections and Tests.

for Inspections and Tests.

The following moving and handling facilities shall be provided for each transformer: The following moving and handling facilities shall be provided for each transformer: a)

a) 4 (four) jacking lugs for raising or lowering the transformers (completely filled with oil) by means of4 (four) jacking lugs for raising or lowering the transformers (completely filled with oil) by means of hydraulic jacks.

hydraulic jacks.  b)

 b) Lugs for lifting the complete transformer. The minimum length of the base of the lugs shall be 300 mmLugs for lifting the complete transformer. The minimum length of the base of the lugs shall be 300 mm for transformers of a weight up to and including 10 tons, and 500 mm for transformers of a weight for transformers of a weight up to and including 10 tons, and 500 mm for transformers of a weight above 10 tons.

above 10 tons. c)

c) Eyes for lifting the core, coils, tank and/or tank cover.Eyes for lifting the core, coils, tank and/or tank cover. d)

d) Pulling eyes for moving the trPulling eyes for moving the transformansformers in ers in any direction.any direction. e)

e) Bi-directional wheels with blocking facilities for transformers up to 125 MVA per unit. The distanceBi-directional wheels with blocking facilities for transformers up to 125 MVA per unit. The distance between the centres of wheels shall be 1746 mm (Standard Railway guage).

between the centres of wheels shall be 1746 mm (Standard Railway guage). f)

f) 1 (one) tank access ladder of zinc-powder coated mild steel with lockable hinged door securely fixed1 (one) tank access ladder of zinc-powder coated mild steel with lockable hinged door securely fixed onto the tank cover and lower parts of the tank (applicable for transformers with ratings of 20 MVA onto the tank cover and lower parts of the tank (applicable for transformers with ratings of 20 MVA and above). Ladders shall be provided with hand-rails of min. 100 cm length at the upper end. and above). Ladders shall be provided with hand-rails of min. 100 cm length at the upper end. Hand- Hand-rails shall be rigidly fixed on the ladders and onto the transformer tank. If the distance between the rails shall be rigidly fixed on the ladders and onto the transformer tank. If the distance between the ladder and tank cover exceeds 4 cm an appropriate platform (e.g. grating securely fixed in a rigid ladder and tank cover exceeds 4 cm an appropriate platform (e.g. grating securely fixed in a rigid mounting frame) with hand-rails as specified above shall be provided. Surface preparation and painting mounting frame) with hand-rails as specified above shall be provided. Surface preparation and painting in accordance with relevant article of these Specifications.

in accordance with relevant article of these Specifications. g)

g) Filter valves of the slide valve type for oil Filter valves of the slide valve type for oil inlet and outlet arranged diagonally on lower part of tank. Ainlet and outlet arranged diagonally on lower part of tank. A suitable valve for vacuum application shall also be provided in a convenient floor height. All of these suitable valve for vacuum application shall also be provided in a convenient floor height. All of these valves shall have minimum 50 mm inside diameter and shall be equipped

valves shall have minimum 50 mm inside diameter and shall be equipped with flanges having adapterswith flanges having adapters with R 1 ½"

with R 1 ½" male thread fitted with screwed cap.male thread fitted with screwed cap. h)

h) Oil sampling valves (top and bottom) with suitable adapters of R ¾" male thread fitted with screwedOil sampling valves (top and bottom) with suitable adapters of R ¾" male thread fitted with screwed cap for direct connection of oil sampling facilities shall be provided and shall be arranged diagonally on cap for direct connection of oil sampling facilities shall be provided and shall be arranged diagonally on one tank wall at

one tank wall at a convenient floor height.a convenient floor height. i)

i) Padlocking facilities for all valves including radiator butterfly valves.Padlocking facilities for all valves including radiator butterfly valves.  j)

 j) Two adequate earthing terminals completely made of stainless steel capable of carrying for 5 secondsTwo adequate earthing terminals completely made of stainless steel capable of carrying for 5 seconds the full lower voltage short circuit current of t

the full lower voltage short circuit current of the transformer shall be provided and installed diagonallyhe transformer shall be provided and installed diagonally at the bottom of the transformer tank.

at the bottom of the transformer tank.

6.5

6.5 TerminalsTerminals

a)

a) Out door BushingsOut door Bushings

Where specified, outdoor bushings shall be provided.

Where specified, outdoor bushings shall be provided. Uncovered bushings other than those to be Uncovered bushings other than those to be solidlysolidly

grounded shall be designed for pollution level “IV” (very heavy) in accordance with IEC 60815, unless grounded shall be designed for pollution level “IV” (very heavy) in accordance with IEC 60815, unless

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specified otherwise in the Specific Works Data Sheets. They shall correspond to IEC 60137, shall be free specified otherwise in the Specific Works Data Sheets. They shall correspond to IEC 60137, shall be free from defects

from defects and shall and shall be thoroube thoroughly vitrghly vitrified. KE ified. KE requires requires Trench (FraTrench (France mance make) or Pake) or Passoni Villa (ssoni Villa (Italy maItaly make)ke) Bushings, for any other manufacturer prior approval will be required by contractor.

Bushings, for any other manufacturer prior approval will be required by contractor. Insulators shall be of

Insulators shall be of top quality electrical grade porcelain, homogenous and non-porous, and shall be intop quality electrical grade porcelain, homogenous and non-porous, and shall be in one piece. If insulators are composed of several parts jointed together by synthetic resin, this shall be one piece. If insulators are composed of several parts jointed together by synthetic resin, this shall be brought to the attention of K-ELECTRIC. The glaze shall not be

brought to the attention of K-ELECTRIC. The glaze shall not be depended upon for insulation and shall bedepended upon for insulation and shall be of a uniform shade of brown, completely covering all exposed parts of

of a uniform shade of brown, completely covering all exposed parts of the insulator.the insulator. Bushings for power windings of U

Bushings for power windings of Umm= 72.5 kV and above shall be of the condenser type equipped with test= 72.5 kV and above shall be of the condenser type equipped with test

tap at the

tap at the bushing flange. Bushings for windings below Ubushing flange. Bushings for windings below Umm= 72.5 kV shall = 72.5 kV shall be preferably oil-filled as per DINbe preferably oil-filled as per DIN

standard or equivalent equipped with

standard or equivalent equipped with rigidly fixed solid gas rigidly fixed solid gas stoppers. DIN equivalent bushings for powerstoppers. DIN equivalent bushings for power windings of rated voltage: 33 kV and above shall be provided with metallised lower part. All bushing windings of rated voltage: 33 kV and above shall be provided with metallised lower part. All bushing connecting nuts, bolts, washers, rings, caps on the

connecting nuts, bolts, washers, rings, caps on the top shall be of top shall be of non-magnetinon-magnetic material.c material.

Each condenser bushing shall have marked upon it, the manufacturers name or identification mark and Each condenser bushing shall have marked upon it, the manufacturers name or identification mark and year of manufacture as well as serial number. These marks shall be clearly legible and visible after year of manufacture as well as serial number. These marks shall be clearly legible and visible after assembly of fittings and shall be

assembly of fittings and shall be imprinted and not impressed.imprinted and not impressed.

All bushings shall be designed for operation and storage in a horizontal position without any restriction. All bushings shall be designed for operation and storage in a horizontal position without any restriction. All bushings shall be

All bushings shall be designed for the highest over-current that can flow through the designed for the highest over-current that can flow through the windings.windings.

The bushings shall be arranged on the tank cover in such a manner, that removal of the same is possible The bushings shall be arranged on the tank cover in such a manner, that removal of the same is possible without lowering of the oil to

without lowering of the oil to such a level where such a level where the windings are exposed to the the windings are exposed to the atmospheatmosphere. Bushingsre. Bushings up to U

up to Umm= 52 kV shall be arranged in an upright position.= 52 kV shall be arranged in an upright position.

Bushing turrets with removable flanged-on covers on the bushing side shall be provided for all bushings. Bushing turrets with removable flanged-on covers on the bushing side shall be provided for all bushings. Removable bushing turrets bolted onto appropriate flanges on the tank cover are also acceptable. Removable bushing turrets bolted onto appropriate flanges on the tank cover are also acceptable. Common bushing turrets of an approved design may be provided for bushings up t

Common bushing turrets of an approved design may be provided for bushings up t o Uo Umm= 52 kV. Common= 52 kV. Common

bushing turrets shall be provided with two vent plugs each to be arranged at an approved location. bushing turrets shall be provided with two vent plugs each to be arranged at an approved location. Removable bushing turrets shall be provided with four adequate lifting lugs each. All

Removable bushing turrets shall be provided with four adequate lifting lugs each. All bushing turrets shallbushing turrets shall be equipped with vent

be equipped with vent pipes on their highest points which shall be connected to main expansion pipe topipes on their highest points which shall be connected to main expansion pipe to route any gas collection through Buchholz relay.

route any gas collection through Buchholz relay.

Easy access shall be provided for internal connection of bushings without extensive dismantling any Easy access shall be provided for internal connection of bushings without extensive dismantling any external mounting such as radiators etc.

external mounting such as radiators etc.

b)

b) Cable Cable Termination Termination BoxesBoxes

Where specified air insulated terminal boxes on the LV side shall be

Where specified air insulated terminal boxes on the LV side shall be provided suitable for the connectionprovided suitable for the connection by busduct(s).

by busduct(s).

The transformer Tenderer/Contractor shall co-ordinate with the bus-duct Tenderer/Contractor for the The transformer Tenderer/Contractor shall co-ordinate with the bus-duct Tenderer/Contractor for the requirements of the mechanical and electrical transition from the

requirements of the mechanical and electrical transition from the bus-duct to the bus-duct to the transformetransformer terminationr termination box.

box.

As far as the bus-duct connection is concerned the scope of supply/works for the transformer As far as the bus-duct connection is concerned the scope of supply/works for the transformer Tenderer/Contractor shall be limited to the termination box incorporated with suitable flanges and Tenderer/Contractor shall be limited to the termination box incorporated with suitable flanges and gaskets (as determined by the

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bus-bars, if required. Suitable grounding studs with bolts and washers made of stainless steel shall be bus-bars, if required. Suitable grounding studs with bolts and washers made of stainless steel shall be provided as determined by

provided as determined by the bus-duct Tenderer/Contractor.the bus-duct Tenderer/Contractor.

The supply of the bus-duct Tenderer/Contractor shall include the transition from bus-duct housing to The supply of the bus-duct Tenderer/Contractor shall include the transition from bus-duct housing to transformer terminal box and the electrical connections (by braided links) between the bus-duct transformer terminal box and the electrical connections (by braided links) between the bus-duct conductors and the transformer bushings. The bus-duct(s), neither their housing nor their electrical conductors and the transformer bushings. The bus-duct(s), neither their housing nor their electrical connections, shall exert any forces on the terminal box or

connections, shall exert any forces on the terminal box or the bushings of the the bushings of the transformer.transformer.

The terminal box shall accommodate outdoor bushings as above, and the design shall comply with The terminal box shall accommodate outdoor bushings as above, and the design shall comply with protection category IP55. Access openings shall be foreseen for checking of the bushings as well as for protection category IP55. Access openings shall be foreseen for checking of the bushings as well as for making and checking of

making and checking of the electrical connections.the electrical connections. Ingress of dust

Ingress of dust and formation of condensate in the termination boxes must be and formation of condensate in the termination boxes must be prevented by two prevented by two parallelparallel silica gel breathers of min. 2 kg silica gel filling capacity controlled by two-position three-way valves as silica gel breathers of min. 2 kg silica gel filling capacity controlled by two-position three-way valves as specified in Article below.

specified in Article below.

c) General c) General

All bushings shall be

All bushings shall be at least of the same insulation level as that at least of the same insulation level as that for the related windings and/or neutral.for the related windings and/or neutral. For all terminals of windings undergoing switching impulse tests the clearances in air between life parts For all terminals of windings undergoing switching impulse tests the clearances in air between life parts shall exceed those specified in IEC

shall exceed those specified in IEC 60076-3 by at least 5 percent.60076-3 by at least 5 percent. Each of the bushings shall be designed for a

Each of the bushings shall be designed for a rated current corresponding at least to the current for long-rated current corresponding at least to the current for long-time emergency cyclic loading of the transformers as specified in IEC

time emergency cyclic loading of the transformers as specified in IEC 60354.60354.

Support insulators shall be of top quality electrical grade porcelain or cast resin and shall be of a

Support insulators shall be of top quality electrical grade porcelain or cast resin and shall be of a uniformuniform shade of brown. Insulators shall

shade of brown. Insulators shall have the same minimum creepage distances as the rhave the same minimum creepage distances as the related bushings, andelated bushings, and the creepage distances of cable

the creepage distances of cable sealing ends shall sealing ends shall be co-ordinated accordingly.be co-ordinated accordingly.

All main flange connections, cable boxes and related covers etc. shall be earthed by suitable grounding All main flange connections, cable boxes and related covers etc. shall be earthed by suitable grounding conductors of the flexible type each having a cross section of minimum 95 mm

conductors of the flexible type each having a cross section of minimum 95 mm22or as per detail or as per detail design ofdesign of

the earthing system. the earthing system.

In case of different Tenderer/Contractor for transformers and HV connections etc. all parties are to In case of different Tenderer/Contractor for transformers and HV connections etc. all parties are to co-operate in order to ensure a proper and complete boundary between these sectors, i.e. the operate in order to ensure a proper and complete boundary between these sectors, i.e. the Tenderer/Contrac

Tenderer/Contractor for tor for transformetransformers shall rs shall provide the provide the specified bushings and/or connection boxes andspecified bushings and/or connection boxes and all connection parts at the

all connection parts at the transformetransformer side r side and/or the complete sealed cable terminating boxes includingand/or the complete sealed cable terminating boxes including the stress cones and all parts for

the stress cones and all parts for proper connection of the sealing ends, and suitable flanges with oil-/SFproper connection of the sealing ends, and suitable flanges with oil-/SF66

--bushings (double-flange --bushings) for GIS-type surge arresters, if required. bushings (double-flange bushings) for GIS-type surge arresters, if required. On the

On the other hand, the other hand, the Tenderer/CoTenderer/Contractor for cables, switchgear and all ntractor for cables, switchgear and all other connections shall provideother connections shall provide the complete pot heads and cable sealing ends, bus-duct and/or SF

the complete pot heads and cable sealing ends, bus-duct and/or SF66 connection boxes i connection boxes including metallicncluding metallic

bellows (if required), surge arresters, adapter pieces and all other equipment required for proper bellows (if required), surge arresters, adapter pieces and all other equipment required for proper completion and function of the related work.

completion and function of the related work.

It is hereby understood that responsibility of the transformer Tenderer/Contractor covers the It is hereby understood that responsibility of the transformer Tenderer/Contractor covers the oil-tightness.

tightness.

6.6

6.6 Current TransformersCurrent Transformers

Where required, current transformers shall be provided in accordance with the requirements of these Where required, current transformers shall be provided in accordance with the requirements of these Specifications

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and connected in such a manner that easy

and connected in such a manner that easy removal of the same is possible without cutting or removal ofremoval of the same is possible without cutting or removal of any insulation material of the leads to the bushings required and without lowering of the oil to such a any insulation material of the leads to the bushings required and without lowering of the oil to such a level where the wi

level where the windings are exposed to the atmosphere.ndings are exposed to the atmosphere. All of the

All of the concerned bushing turrets shall be equipped with concerned bushing turrets shall be equipped with appropriate current transformer terminaappropriate current transformer terminationtion boxes for direct connection of the related CTs. Separate termination boxes shall be provided for current boxes for direct connection of the related CTs. Separate termination boxes shall be provided for current transformers for protection and those for used for thermal replica.

transformers for protection and those for used for thermal replica.

The technical data shall also be co-ordinated with the protection requirements and the related

The technical data shall also be co-ordinated with the protection requirements and the related switchgearswitchgear CTs. If the requirements of protection show that a higher rated output and/or ratio than specified is CTs. If the requirements of protection show that a higher rated output and/or ratio than specified is necessary, the Tenderer/Contractors shall provide the current transformers for the required ratings necessary, the Tenderer/Contractors shall provide the current transformers for the required ratings without extra price. Reference is made to the relevant Articles for protection relay and stability with without extra price. Reference is made to the relevant Articles for protection relay and stability with regard to current

regard to current transformer's design. The Specifcations of the current transformer's design. The Specifcations of the current transformetransformers including rs including excitationexcitation curves shall be submitted with the offer to K-ELECTRIC for approval. All current transformers shall be curves shall be submitted with the offer to K-ELECTRIC for approval. All current transformers shall be designed for an extended rated current of

designed for an extended rated current of at leastat least 150% to cover cyclic loading duties as 150% to cover cyclic loading duties as per IEC 60354.per IEC 60354. Where built-in current transformers are provided, the related bushings, SF

Where built-in current transformers are provided, the related bushings, SF66 connection boxes and cable connection boxes and cable

terminal boxes shall be arranged to be removed without interfering with the pertinent current terminal boxes shall be arranged to be removed without interfering with the pertinent current transformer. Removal of any CT must be possible without lowering of the oil to such a level where the transformer. Removal of any CT must be possible without lowering of the oil to such a level where the windings are exposed to

windings are exposed to the atmosphere.the atmosphere.

6.7

6.7 CoolingCooling a)

a) ONAN ONAN Cooled Cooled TransformersTransformers

Transformers of a rated power up to 15 MVA

Transformers of a rated power up to 15 MVA per unit shall be per unit shall be provided with a self-cooled type of coolingprovided with a self-cooled type of cooling system (ONAN) provided by at least two groups of detachable radiators flanged directly onto the tank system (ONAN) provided by at least two groups of detachable radiators flanged directly onto the tank and/or external headers at the transformer tank, mainly in the vicinity of the core-/coil-arrangement at and/or external headers at the transformer tank, mainly in the vicinity of the core-/coil-arrangement at the two along sides of

the two along sides of the transformer.the transformer.

Radiators shall be of the DIN type or equivalent provided with six cooling channels in each radiator fin. Radiators shall be of the DIN type or equivalent provided with six cooling channels in each radiator fin. Accumulation of air in the radiator heads must be avoided. Radiators of the multi-tube type or similar Accumulation of air in the radiator heads must be avoided. Radiators of the multi-tube type or similar arrangements are not acceptable.

arrangements are not acceptable.

The cooling fins of the radiators shall have nominal width of 470 - 520 mm, and their height shall not The cooling fins of the radiators shall have nominal width of 470 - 520 mm, and their height shall not exceed 3.0 m. The nominal sheet steel t

exceed 3.0 m. The nominal sheet steel thickness of the radiator walls shall be hickness of the radiator walls shall be not less than 1.2 mm.not less than 1.2 mm. The radiator fins shall be welded with approved stiffening rods (horizontally and diagonally) to prevent The radiator fins shall be welded with approved stiffening rods (horizontally and diagonally) to prevent vibration during operation of the

vibration during operation of the transformetransformers. The rs. The distance between horizontally arranged bracing strapsdistance between horizontally arranged bracing straps shall not exceed 100 cm. Radiators shall be fully vacuum proof and pressure tested and shall be liquid shall not exceed 100 cm. Radiators shall be fully vacuum proof and pressure tested and shall be liquid tight.

tight.

The radiators shall be fitted with suitable drain and vent plugs so that they can be completely drained and The radiators shall be fitted with suitable drain and vent plugs so that they can be completely drained and vented. No radiators shall be fitted underneath of

vented. No radiators shall be fitted underneath of air-filled cable boxes.air-filled cable boxes. The radiators shall be connected to the tank or

The radiators shall be connected to the tank or external headers by butterfly valves in such a manner thatexternal headers by butterfly valves in such a manner that each radiator can be removed without taking

each radiator can be removed without taking the transformer out of service, and without the transformer out of service, and without draining any oildraining any oil from the tank and/or common headers (if any). The mechanical tolerance of the arrangement shall be from the tank and/or common headers (if any). The mechanical tolerance of the arrangement shall be minimised to allow the exchange of all radiators of the same type without additional fitting. The lower minimised to allow the exchange of all radiators of the same type without additional fitting. The lower radiator headers shall be connected to the transformer tank or common headers in a height of not less radiator headers shall be connected to the transformer tank or common headers in a height of not less than 80 cm above floor level.

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All butterfly valves shall be arranged in a vertical position and in such a manner that their position All butterfly valves shall be arranged in a vertical position and in such a manner that their position indications are clearly and freely visible

indications are clearly and freely visible and legible directly from tank cover and and legible directly from tank cover and from ground level. Valvefrom ground level. Valve position indicators must not be arranged underneath the flange of t

position indicators must not be arranged underneath the flange of the tank cover.he tank cover. Flanged on common headers, if any shall be connected each to the tank via

Flanged on common headers, if any shall be connected each to the tank via slide valves mounted directlyslide valves mounted directly onto the transformer tank or cover. Common headers shall not be connected to bushing turrets.

onto the transformer tank or cover. Common headers shall not be connected to bushing turrets.

Accumulation of air within the radiators and headers must be avoided. Upper common headers for Accumulation of air within the radiators and headers must be avoided. Upper common headers for connection of radiators shall be connected through isolation valves and vent pipes to

connection of radiators shall be connected through isolation valves and vent pipes to the main expansionthe main expansion pipe. Radiator banks mounted onto the tank or

pipe. Radiator banks mounted onto the tank or separately shall not be provided.separately shall not be provided.

The radiators shall be assembled and fitted to the tank in such a manner as to provide mechanical The radiators shall be assembled and fitted to the tank in such a manner as to provide mechanical protection to themselves and to prevent vibrations. Suitable

protection to themselves and to prevent vibrations. Suitable stiffening bars of stainless steel stiffening bars of stainless steel shall be fittedshall be fitted along the radiators on top and bottom. Stiffening bars shall not be arranged cross-wise on top and bottom along the radiators on top and bottom. Stiffening bars shall not be arranged cross-wise on top and bottom of the radiator groups.

of the radiator groups.

All parts of the equipment shall be accessible for inspection and cleaning. Hot-dip galvanised radiators All parts of the equipment shall be accessible for inspection and cleaning. Hot-dip galvanised radiators shall not be

shall not be provided.provided.

Where applicable, the following accessories shall

Where applicable, the following accessories shall be provided:be provided:

 1 (one) butterfly valve each for inlet and outlet for each radiator, directly accessible from ground1 (one) butterfly valve each for inlet and outlet for each radiator, directly accessible from ground

level and tank cover level and tank cover

 2 (two) isolation valves for connecting of each common header (if any) with the transformer tank2 (two) isolation valves for connecting of each common header (if any) with the transformer tank

and/or cover and/or cover

 1 (one) drain plug with 1 (one) drain plug with screwed cap at the outlets of screwed cap at the outlets of each lower common header (min. two lowereach lower common header (min. two lower

common headers, if provided) suitable for temporary installation of temperature sensors directly common headers, if provided) suitable for temporary installation of temperature sensors directly in the oil-flow during

in the oil-flow during heat-run testsheat-run tests

1 (one) air vent plug with screwed cap at the inlets of each upper 1 (one) air vent plug with screwed cap at the inlets of each upper common headcommon header (min. two air forer (min. two air for

upper common headers, if provided) suitable for temporary installation of temperature sensors upper common headers, if provided) suitable for temporary installation of temperature sensors directly in the

directly in the oil-flow during heat-run testsoil-flow during heat-run tests

Additional air vent plugs and drain Additional air vent plugs and drain plugs on common headers, as requiredplugs on common headers, as required

 1 (one) drain plug for each radiator at the outlet of each radiator suitable for temporary installation1 (one) drain plug for each radiator at the outlet of each radiator suitable for temporary installation

of temperature sensors directly in the oil-flow during heat-run tests in case of radiators directly of temperature sensors directly in the oil-flow during heat-run tests in case of radiators directly flanged onto the tank

flanged onto the tank

1 (one) air vent plugs each at the inlet of each radiator header suitable for temporary installation1 (one) air vent plugs each at the inlet of each radiator header suitable for temporary installation

of temperature sensors directly in the oil-flow during heat-run tests in case of radiators directly of temperature sensors directly in the oil-flow during heat-run tests in case of radiators directly flanged onto the tank. For radiators with upper headers of the elbow type ("swan-neck" type) air flanged onto the tank. For radiators with upper headers of the elbow type ("swan-neck" type) air release plugs shall be provided at

release plugs shall be provided at both ends of these headersboth ends of these headers

Numbered identification plates for all butterfly valves and other valves, so as to comply with theNumbered identification plates for all butterfly valves and other valves, so as to comply with the

plate for valve arrangement and piping. Particular details for all plates

Figure

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References

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