Technical Specification for 20 MVA Transformer.pdf

TS-1 A TECHNICAL SPECIFICATIONS OF 20 MVA 132/33 KV POWER TRANSFORMER 3.1

SCOPE This specification covers the design, manufacture, shop testing, delivery and, if desired by the purchaser supervision of commissioning of 20MVA, 132/33 KV power transformers as detailed in these specification.

3.2 STANDARDS 3.2.1 The transformers shall conform in all respects to IS-2026 / 1977 or latest amendment thereof, and CBIP specification except where specified other wise. Equipment meeting any other authoritative standard, which ensure an equal or better quality than the standard mentioned above could also be considered. 3.3

CLIMATIC CONDITIONS The transformer shall be suitable for operation under climatic conditions given in “Instructions to tenderer”

3.4

TYPE RATING AND QUANTITY The transformers shall have core type construction, ONAN, ONAF cooled and shall be suitable for outdoor service The salient rating and electrical characteristics of the transformer shall be as follows:-

3.5

3.5.1 PARTICULRS (i) (a) Continuous capacity (ONAF Cooling) (b) Continuous capacity (ONAN Cooling) (ii) Rated HT voltage (KV) (iii) Rated LT voltage (KV) (iv) Frequency (C/S) (v) No. of phases (vi) Percentage impedance at 75°C (vii) Connections a) HV winding b) (viii) (ix) (x) (xi) (xii)

LV winding Vector Group On Load Tap Changer Type of cooling Quantity Earthing

20 MVA 16 MVA 132 33 50 Three 13.75% Star Star YNyn0 Later in specification ONAN/ONAF Both sides earthed.

effectively

3.5.2 All the transformers shall be oil immersed weather proof and suitable for outdoor installation in lightning areas. 3.5.3 The transformers shall be capable of withstanding thermal, transient and mechanical effects of a short circuit on the terminals of any winding with full voltage maintained on all other windings for a duration of 2 seconds as per IS:2026-1977. 266

3.5.4 Technical and guaranteed particulars of the transformers offered shall be furnished as per ‘SCHEDULE-R’ enclosed. 3.6 INSULATION 3.6.1 The dielectric strength of the winding insulation of the bushings shall conform to the values given in IS:2026 3.6.2 For rated system voltage of 132 KV and 33 KV following minimum impulse test voltages of 1.2/50 micro second full wave will be offered:System voltage Impulse test voltage 132 KV 550 KVP 33 KV 170 KVP 3.6.3 The HV winding shall have graded insulation, the neutral end insulation being of 95 KVP (impulse) and 38 KV (power frequency) withstand value. The LV windings of the transformer shall have uniform insulation. 3.7

TEMPERATURE RISE

3.7.1 Each transformer shall be capable of operating continuously at their normal rating without exceeding temperature rise limits as specified below:TEMPERATURE RISE i) Winding

ii)

3.8

55°C by measurement 50°C by the measurement

Oil (hottest layer)

resistance thermometer

FREQUENCY

3.8.1 The transformer shall be suitable for continuous operation with a frequency variation of plus-minus 5% from normal of 50 Hz without exceeding the specified temperature rise. 3.9

PARALLEL OPERATION

3.9.1 The 20MVA, 132/33 kV transformers procured against this specification shall operate satisfactorily in parallel among themselves and with similar 40MVA transformer units already acquired by the purchaser. 3.9.2 The new 20MVA, 132/33 KV transformers may also be required to operate in parallel with the 63MVA & 40 MVA, 132/33 KV transformers presently installed at various substation. It shall therefore be ensured that the transformers to be purchased against this specification shall operate satisfactorily with the above existing units. 3.10

IMPEDANCE The guaranteed impedance with tolerance shall be as required for parallel operation as per details given in cl.3.9. Impedances shall include positive and zero sequence and shall be expressed in terms of the branches of the star connected equivalent diagram, all on the same MVA basis. Impedance percentage volts at

267

normal tap, and 75°C winding temp. shall be subject to I.S. tolerances, and as indicated in cl.3.5.1(vi) 3.11

MAXIMUM FLUX DENSITY The maximum flux density in any part of the core and yoke at normal voltage and frequency, on normal tap shall not exceed 1.5 Tesla (15,000 lines per sq.cm).

3.12 TRANSFORMER LOSSES The no load loss in kilowatt at rated voltage and rated frequency and the copper losses in kilowatts at rated output, rated voltage, rated frequency and at 75°C and auxiliary losses shall be guaranteed as under for each transformer.

i. ii.

iii.

Guaranteed No load loss at normal ratio, rated frequency and without any plus tolerance should not be more than 9.5 KW. Guaranteed Copper loss (Load Loss) at normal ratio, rated output rated voltage and rated frequency at 75°C average winding temperature without plus tolerance should not be more than 75.0 KW. Guaranteed Auxiliary loss at normal ratio, rated frequency and without any plus tolerance should not be more than 2.0 KW.

Firm should quote losses as mentioned above only. However firm may quote less loss as per their design which will be appreciated. Computation of capitalization will be done on the basis of losses fixed by UPPTCL as mentioned above. The offer of those firms, whose losses are more than the losses mentioned by UPPTCL, is likely to be rejected. The rates of computation shall be :i) Rs. 2,12,500.00 per KW of guaranteed no load loss ii) Rs. 86,700.00 per KW of guaranteed copper loss iii) Rs. 85,000.00 per KW of guaranteed auxiliary losses. The rates mentioned above may be revised as per current provision in CBIP and REC manual. 3.12.2 The penalties shall be separately evaluated from (i) the excess of the test figures of the no load loss over the corresponding guaranteed values @ Rs. 2,12,500.00 per KW, (ii) the excess of the test values of copper loss, over the corresponding guaranteed values @ Rs. 86700.00 per KW, (iii) the excess of test value of guaranteed auxiliary loss @ Rs. 85000.00 per KW. It shall be at the discretion of purchaser to reject the transformers having losses in excess of guaranteed quoted value or accept them after having penalty as the above. 3.12.3 The contractor shall submit calculations along with relevant documents for no load losses, load losses and auxiliary losses. 3.13 3.13.1

COOLING The transformers shall have ONAN and ONAF cooling. The transformers shall be capable of giving a continuous output of at least 80% of their rating with only natural air (ONAN) cooling without exceeding the specified temperature rise limits.

3.13.2 The cooling arrangement shall consist of detachable radiators which should be directly mounted on the transformers. Connections between the radiators and tank shall be made with flanges provided with gaskets and an indicating shutoff valve provided at both 268

connection ends, which can be fastened in open or closed position. Separate oil tight blank flange shall be provided for each tank connection for use when the radiator unit is detached. All radiators shall be completely interchangeable. Bottom of the radiators should be supported on angle frame also to reduce the oil leakage from radiators joints and distribute and mechanical load uniformly. 3.13.3 The radiators shall be so arranged that these can be detached from tank without disturbing the oil in the transformer. These shall be designed to withstand the vacuum and pressure specified for the tank. Radiators shall be so designed as to be accessible for cleaning & painting & to prevent accumulation of water on the outer surface to completely drain oil from the tank or bank & to ensure against formation of pockets when the tank is being filled. All connections between the radiators and tank shall be provided with blank flange when the particular item is dispatched. Each radiator shall have a lifting eye and oil drain valve and vent at top.

3.13.4 Number of cooling fans for forced air cooling purposes must not be less than 8 running and 2 standby i.e. 4+1 in each group. Which shall be mounted on the frame connected with tank in such a manner, that no separate foundation work shall be required for the fans or the radiators or for the marshalling kiosk. Fans should be of High quality noise less and durable. These shall be readily accessible for inspection, maintenance or repairs. All the radiators shall be completely interchangeable. One No. standby cooling fan is to be required in both HV&LV side. 3.13.5 The fans for air blast cooling shall be so mounted that no damage to the coolers can arise from the vibration due to the operation of fans. Galvanized wire mesh screens shall be fitted to prevent accidental contact with the blades. The mesh being not greater than 2.5 cm.

3.14

COOLER CONTROL

3.14.1 Cooler scheme shall be suitable to operate with 440 volts 3 phase, 4 wire, 50 Hz external power supply with a voltage variation of + 10%. 3.14.2 A marshalling box cum cooler control cabinet of weather proof construction shall be provided for housing the control equipment of cooler scheme. This unit shall be provided with doors in the front as well as on the back. All the fittings, switches fuses and contactors etc. would be mounted on the front side of the marshalling box and the wiring shall be done from the back side. The terminal blocks shall be provided in the side. The marshalling box shall be mounted on the transformers tank in such a manner that both the doors could be opened for operation or repairs etc. without any difficulty. 3.14.3 The cables between this unit and fans, W.T.I, O.T.I., buchholz relay etc. shall be provided by the tenderer. Cables should be of copper and 1.1 KV grade. It shall be complete with hinged doors, padlock arrangement, thermostatically controlled space heaters to prevent condensation, cubicle light and the terminal glands for the cables. 3.14.4

Cooler control scheme shall consist of the following equipments. i) A miniature circuit breaker for the incoming A.C. supply with thermal 269

ii)

iii)

iv) v) vi) vii)

overload and short circuit protections which will also initiate an alarm when this breaker trips A three phase motor starter with each fan (Max. 10 nos.) to start the fans manually, as well as in the auto mode. Auto operation of fans will be initiated through 2 nos. of W.T.I, contacts, such that the starting of fan is through a contactset on a higher temperature and the switching off of fans is through another W.T.I. contact set on a temperature lower than required for the starting of fans. Individual fan starting in manual operation on the transformer is also required. However a remote emergency manual starting switch for fans shall also be provided on the RTCC panel. Only cam operated rotary switches shall be used wherever required. Cartridge fuse units for each fan motor Provision for an alarm be made in case, the WTI contact has operated, and any one or more fan(s) have not started. All the terminal nos. and device code to be adopted will be as finalized by this office. The marshalling box cum cooler control cubicle shall be mounted on the transformer and no separate foundation shall be required for the same.

3.14.5 The terminal blocks to be provided with the marshalling box shall be rated for 15 amps and will be suitable for uninterrupted duty. The terminal blocks shall be of 440 volts grade complete with insulated barriers, terminal studs, washers, nuts, lock nuts and identification, strips and shall also have disconnecting and shorting links. These should be suitable to receive at least two cores of 2.5 mm sq.copper conductor cables. The terminal blocks should be preferably of Kirloskar make catalogue No. TK-45 Elmex make or equivalent reputed make. Similar terminal blocks shall also be provided for RTCC and driving mechanism units. 3.14.6 Provision for the fan working remote indication on OLTC panel shall be made. Fan trip annunciation for each fan shall also be provided through the contacts of starters. 3.14.7 The fan motors shall be automatically controlled by the winding temperature indicator (WTI), which shall have at least four sets of contacts, which could be set independently for desired temperatures. The first two contacts will be used for starting the fans. The third contact will be used to initiate an alarm and the last contact will be used for tripping the transformer. 3.14.7.1 The WTI and OTI shall be suitable for local as well as remote indication (on RTCC panel) of temperature. 3.14.8

3.14.9

A manual auto changeover switch shall be provided in the marshalling box for operation of cooler fans, for testing as and when needed. An indication for manual / auto mode be provided on RTCC panel. Engraved single line diagram on non rusting steel plate will be provided on RTCC/Marshalling Box on back of front door.

3.15 CORE 3.15.1 The core shall be built up with high-grade cold rolled non-aging, low loss, and high permeability grain oriented silicon steel laminations specially suitable, for transformer 270

cores. The successful bidder shall have to produce the relevant documents towards use of proposed input materials of prime quality of CRGO as per the following details: (a) Invoice of supplier; (b) Mills test certificate: (c) Packing list; (d) Certificate of origin: (e) Bill of lading; (f) Bill of entry certified by Custom Department; Further, these materials shall be directly procured either from the mill or through their accredited marketing organization of repute and not through any agent. 3.15.2 After being sheared the lamination shall be treated to remove all burrs and shall be re- annealed to remove all residual stresses. At least one side of each lamination shall be coated with an insulating coating as may be approved by the ISS and as per the modern manufacturing practice, which shall be inert to the action of hot transformer oil. The nature of insulation on core should be specified, in the tender. 3.15.3.1 The core shall be rigidly clamped or bolted to ensure adequate mechanical strength and to prevent vibration during operation. The bolts used in the assembly of core shall be suitably insulated and clamping structure shall be so constructed that eddy currents will be minimum. 3.15.4 The core shall be provided with lugs suitable for lifting the complete core and coil assembly of the transformer. 3.15.5 The core and the coil shall be so fixed in the tank that shifting does not occur when the transformer is moved or during a short circuit. 3.16 WINDING 3.16.1 The winding shall be so designed that all coil assemblies of identical voltage ratings shall be interchangeable and field repairs to the windings can be made readily without special equipment. The coil shall be supported between adjacent sections by insulating spacers and the barriers/ bracings etc. Insulation used in the assembly of the windings shall be arranged to ensure a free circulation of the oil and to reduce hot spot in the windings.

3.16.2 The coil shall be dried under vacuum and submerged in dried insulating oil to develop the full electrical strength of the windings. All materials used in the insulation and assembly of the windings shall be insoluble, non catalytic, chemically inactive in the hot transformer oil, and shall not soften or otherwise be adversely affected under the operating conditions. 3.16.3 All threaded connections shall be provided with locking facilities. All leads from the winding to the terminal board and bushings shall be rigidly supported to prevent injury from vibration. Guide tubes shall be used where practical. 3.16.4 The winding shall be clamped securely in place so that they will not be displaced or deformed during short circuits. The copper conductor used in the construction shall be best suited to the requirements and all permanent current carrying joints in the windings and the leads, shall be welded, or brazed as far as possible. 3.17

INSULATION OIL

3.17.1 Oil for first filling together with ten percent extra oil shall be supplied with each transformer. The oil shall comply in all respects with the insulations of IS:335. Particular attention shall be paid to deliver the oil free from moisture having uniform quality through out in non-returnable steel drums. One number oil sampling bottle is to be provided alongwith the Transformer. 271

3.17.2

The quantity of oil for first filling of each transformer shall be stated in the tender and in G.A. drawing. The cost of the oil shall also be given separately.

3.17.3

Following tests will be required to be performed on a sample of oil from each transformer and witnessed by UPPTCL’s representative and the test certificates shall be furnished with the routine test reports of the transformer. a) b) c) d) e) f) g) h) i)

3.17.3.1

Density at 29.5°C Kinematic viscosity at 27°C Interfacial tension Flash point Neutralization value (total acidity) Dielectric strength (Break down voltage) Dielectric dissipation factor (Tan delta) Specific resistance ohm-cm Water content, PPM (Karit Fisher Method)

The test certificates of oil suppliers shall not be accepted in this respect. Dissolved gas analysis of the oil for the transformer in respect of the gases named below shall be performed on the one transformer on which impulse and heat run test have been performed. 1. Hydrogen (H2) 2. Carbon di-oxide (CO2) 3. Carbon Monoxide (CO) 4. Methane (CH4) 5. Ehylene (C2 H4) 6. Acetylene (C2 H2) 7. Ethane (C2 H6)

3.18 3.18.1

TANK The transformer tank and cover shall be fabricated from good commercial grade low carbon steel suitable for welding and of adequate thickness. The tank and the cover / shall be of welded construction. All seams shall be welded and where practicable they shall be double welded. The tank shall have sufficient strength to withstand without permanent distortion (i) filling by vacuum and (ii) continuous internal gas pressure of 0.7 atmospheres with oil at operating level. The tank cover shall be bolted to the tank and the transformer design shall be such that the tank will not be splitted between the lower and upper cooler connection for untanking.

3.18.2

A manhole with a welded flange and a bolted cover shall be provided on the tank cover. The manhole shall be of sufficient size to afford easy access to the lower ends of the bushings terminals etc.

3.18.3

All bolted connection to the tank shall be fitted with suitable oil tight gaskets which shall give satisfactory service under the operating conditions. Special attention shall be given to the methods of making the hot oil tight joints between the tank and the cover as also between the cover and the bushings. All other outlets to ensure that the joints can be remade satisfactorily and with ease, with the help of semi-skilled labour. Where-ever compressible gaskets are used stoppers shall be provided to prevent over compression. 272

3.18.4

Suitable guides shall be provided for positioning the various parts during assembly or dismantling. Adequate space shall be provided between the core and winding and the bottom of tank for collection of any sediment or sludge.

3.18.5

Lifting eyes or lugs shall be provided on all parts of the transformer, requiring independent handling during assembly or dismantling. In addition, the transformer tank shall be provided with lifting lugs and bosses properly secured to the sides of the tank, for lifting the transformer either by crane or by jacks.

3.18.6

The design of the tank, the lifting lugs and bosses shall be such that the complete transformer assembly filled with oil can be lifted with the use of these lugs without any damage or distortions.

3.18.7

The tank shall be provided with two suitable copper alloy pads for the purpose of grounding, where the G.I. earthing strip of size 75x10 mm shall be clamped either in horizontal direction or in vertical direction with 4 no. studs without drilling any hole in the G.I. earthing strip.

3.18.8

Each tank shall be equipped with the following valves with standard flange connection for external piping. i) One drain and lower filter valve placed to completely drain the tank. At the opinion of the contractor a large valve may be furnished with an accentric reducer. This valve shall be equipped with a small sampling cock. ii) One upper filter valve located at the top of the tank. The opening of this valve shall be baffled to prevent aeration of the oil. Alternatively, this valve can be located at any convenient position to suit connection, to the filter machine but may be connected to upper part of the tank by means of internal piping. The upper filter valve shall be on the side opposite to the side of lower filter valve. iii) Pressure relief valve should operate at a pressure below the test pressure for the tank. This device shall be mounted so that oil from the device should fall on the ground. iv) One oil filling cum filter valve in the oil conservator.

3.18.9.1.1 Engraving of Transformer serial No. and month of manufacturing on transformer tank & core frame shall be done before offering for inspection. 3.18.9.1.2 There should be provision on PRV with dome on top on tank with tripping arrangement instead of explosion vent. 3.18.9.1.3

Air cell of best quality rubber (having no reaction with T/F oil) should be provided inside conservator tank to avoid oil contamination. 3.18.9.1.4 Supporting plate-form is to be provided for attending the Buchholz Relay, for its easy accessibility. 3.19 3.19.1

UNDERCARRIAGE The transformer tank shall be supported on a structural steel base equipment with forged steel or cast steel single flanged wheels suitable for moving the transformer completely filled with oil.

273

3.19.2

Jacking steps shall be provided. It shall be possible to change the direction of the wheels through 90° when transformer is lifted on jacks to permit movement of the transformer both in longitudinal and transverse directions. All the transformers shall have rail gauge of 1676.4 mm in both the directions.

3.19.3

Pulling eyes shall be provided to facilitate moving the transformer and they shall be suitably braced in a vertical direction so that bending does not occur when the pull has a vertical component.

3.20

TAP CHANGING MECHANISM (20 MVA; 132/33 KV Transformer)

3.20.1

The transformer shall be provided with full capacity speed non inductive transition resistance type On load pattern taps on HV neutral end to vary voltage on LV side from –5% to + 15% in equal steps of 1.25% each i.e. 17 taps including one normal tap position. The tested ratios shall not have more than + 0.50% error from rated ratios on any of the 17 nos. of taps.

3.20.2

Tap changing mechanism shall be suitable for remote operation from RTCC panel in the control room in addition to being capable of local manual as well as local electrical operation. OLTC gear shall be suitable for bi-directional flow of full power. Once the tap changing operation has been initiated it must be completed even if the supply to the driving mechanism interrupts. A 440 volt 3phase 50 cycles external supply will be available for the operation of the changer. The supplier will provide an auxiliary 440 volts/55-0-55 volts transformer in the driving mechanism of the OLTC to operate the control scheme for the OLTC. Suitable audio as well as visual alarm shall be provided in case of failure of A.C. supply to OLTC cubicle.

3.20.3

The OLTC shall include the following:i) An oil immersed tap selector switch, which shall not interrupt the load current during tap change. ii) Diverter switch with transition resistance iii) Separate compartment for diverter switch with independent oil conservator and oil surge protective device iv) Motor driven mechanism v) Control & protection devices vi) Local tap changer position indicator. vii) Manual operating device.

3.20.3.1

The OLTC shall be properly type tested and OLTC of such vendors who have got done type test on OLTC be accepted within five years. Reports of type/ Routine tests carried out on OLTC at vendor’s works has to be enclosed with final test report.

3.20.4

The on load tap changer shall be so designed that the contacts of tap selector switch do not interrupt the arc. The diverter switch shall be located on separate oil filled compartment. The compartment shall be provided with means of releasing the gas produced by the arcing. It shall be designed so as to prevent the oil in the diverter switch compartment from mixing with the oil in the main tank or the tap selector.

274

3.20.5

The tap changer shall be capable of permitting parallel operation with other transformers of the same type covered by this specification, as well as, these already acquired by the purchaser (cl.3.9)

3.20.6

The transformers shall give full load output on all taps. The manual operating device shall be so located on the transformer that it can be operated by a man standing at the level of the transformer track. It shall be strong and robust in construction, and all rotating parts and shafts shall be covered by protective caging or covering. The control scheme for the tap changer shall be provided independent control of the tap changer when the transformers are in independent service. In addition, provision shall be made to enable parallel control also so that the tap changer will be operated simultaneously when one or more units are in parallel, so that under normal conditions the tap changer will not become out of step. For this each of the seventeen taps shall be matched with the taps of the follower transformer, and the odd and even tap matching scheme shall not be acceptable. Additional feature like master and follower as well as an audio visual indication during the operation of motor shall also be incorporated.

3.20.7

3.20.8

Necessary interlock blocking independent control when the units are in parallel shall be provided.

3.20.9

Under abnormal conditions such as may occur if the contactor controlling one tap changer gets stuck, the arrangement must be such as to switch off supply to the motor so that an out of step condition is limited to one tap difference only. Details of out of step protection provided for the taps should be furnished in the tender.

3.20.10

The contactors and associated gear for the tap change driving motors shall be housed in a local kiosk mounted on the transformer. All devices except the OLTC motor shall operate on 55-0-55 volts A.C. supply only.

3.20.11

Complete particulars of the tap changing gear including capacity of the motor shall be stated in the tender.

3.20.12

Tap changers are not required to be suitable for automatic voltage sensed operation.

3.20.13

The rated current of the tap changer shall not be less than 300 Amps for 20MVA transformers

3.21 3.21.1

REMOTE TAP CHANGER CONTROL PANEL (RTCC) All tap changing control equipments shall be mounted on a separate panel for each transformer which will also be quoted separately. This panel shall be complete with all necessary fittings, instrument wiring terminal blocks, cable glands, internal light etc. The panel should be self-supporting, made of sheet steel. It shall be completely vermin proof and arrangements to prevent ingress of vermin through cable entry holes or ventilation slots shall be provided. The panel shall be provided with doors opening at the centre on which nothing shall be mounted. The panel is required to be matched with 275

existing panels of the purchaser of height 2250 mm and depth, which can be 500-700mm. The OLTC panel shall be of light grey colour corresponding to I.S. 631. 3.21.2

The tap changing scheme shall be such as to operate the steps of two or more transformers in parallel simultaneously as well as independently as and when desired.

3.21.3

A sequence selector switch comprising of four positions shall be provided which will indicate whether the transformer is in independent, master, follower or in off position. The scheme will give step by step, tap changing operation. In the independent position it shall be possible to change the taps of any transformer independently. Any one transformer can be made ‘Master’ and on changing the taps of this transformer, the taps of all other follower units will change automatically with the master and it will not be possible to change the taps of the follower transformers, independently.

3.21.4

The OLTC control scheme shall be designed for 55-0-55 volts A.C. Necessary auxiliary transformers of 440/55-0-55 volts A.C. shall be supplied by the contractors. This auxiliary transformer shall be installed in the driving mechanism as per latest practice to ensure that no 440 or 230 V A.C. supply is taken into the RTCC panel except for the purpose of light and heater. The OLTC control scheme and the Master follower parallel operation shall be identical to the standard control scheme based on the recommendations of C.B.I.P codes and which has been adopted by the purchaser, in respect of the existing transformers of various other makes. The contractor shall ensure that terminal nos. and the device codes as adopted by the Purchaser shall be followed by the supplier.

3.21.5

Following indications shall be provided on RTCC panel i) Fan running indication (red colour) one for each fan ii) Auto / manual indication for fan controls switch iii) 55-0-55 volts A.C. supply on (red colour) iv) Fault on indication lamp v) OLTC motor protection switch open indication (green colour) vi) Tap change in progress(Amber colour with one independent buzzer) vii) Tap position of transformer (digital indication) viii) Winding temp. indicator ix) Oil temp. indicator

3.21.5.1

Following non trip flag indications with alarm shall be provided i) Fan trip (separate flag for each fan) ii) M.C.B. for cooler control trip iii) A.C. supply to fans and tap changer fail iv) Main conservator oil level low v) OLTC conservator oil level low vi) W.T.I. operated fans not started vii) Tap changer motor stuck viii) Taps not in synchronism (out of step) ix) 55-0-55 A.C. voltage low.

3.21.5.2

Annunciations required on purchaser’s transformer control panel 276

The following flag indications are required to be passed on to the purchaser’s transformer control panel. The required terminal blocks for them shall be provided on the transformer marshalling box as per the attached drg. (Annexure VII). a) i) ii) iii) iv) v) b) i)

TRIP ALARM Buchholz alarm W.T.I. alarm O.T.I. trip Tap changer oil surge relay trip Pressure release device trip NON TRIP ALARM W.T.I. temp. high ii) O.T.I. temp. high iii) Buchholz alarm

3.21.6.1

The alarm scheme should be such that it will be possible to silence the alarm after its receipt and immediately after receipt, it shall be available for next operation. It should not however be possible to reset the flag unless the cause of the fault is removed.

3.21.6.2

There should be a provision of electronic Annunciation window instead of mechanical relay for different indications at RTCC panel.

3.22

OIL PRESERVING EQUIPMENT

3.22.1

Oil preserving equipment shall be conservator.

3.22.2

The conservator shall have two filter valves, one at the bottom at one end, the other at the top at opposite end and in addition to the valves specified in the accessories for the main tank. The conservator shall also have a shut off valve and a sump with a small drain valve and sampling cock, the later so arranged as not to interfere with oil lines. The magnetic oil level gauge shall be mounted on the conservator.

3.22.3

There shall also be an oil conservator for the OLTC which could either be provided separately or a partition in the main conservator, with an independent M.O.L.G.

3.23.0

BUSHINGS The following type of bushing shall be provided on the 20MVA; 132/33 KV transformers. (i) HV 145 KV oil impregnated condenser type bushing of 800 Amps (ii) LV 36 KV plain porcelain oil communicating type bushings of 1000 Amps

3.23.1

The bushings shall be suitable for heavily polluted atmosphere (anti fog type) and shall have high factors of safety against leakage to ground and shall be so located as to provide adequate electrical clearance between bushings and between the bushings and grounded parts. Bushings of identical voltage shall be interchangeable. All bushings shall be equipped with suitable terminals of approved type and size and all external current carrying contact surface shall be silver plated, adequately. The insulation 277

i) ii)

iii)

class of the neutral bushing shall be properly coordinated with insulation class of the neutral end of the winding. Each bushing shall be so coordinated with the transformer insulation that all flashovers will occur outside the tank. The porcelain used in bushings shall be of the wet process homogenous and free from cavities or other flaws. The glazing shall be uniform in colour and free from blisters burs and other defects. All bushings shall have puncture strength greater than, the dry flashover value. Special adjustable arcing horns are also to be provided for all bushings. All bushings shall comply with I.S. 2099.

iv) The tenderers are required to give the guaranteed withstand voltages for the above bushings and also furnish a calibration curve with different settings of the coordination, gap to the purchaser to decide the actual gap setting. Tenderers recommendations are also invited in this respect. v)

vi)

vii)

The 132 KV bushings shall be condenser type and the 33 KV bushings shall be oil filled and these shall be identical to drawings attached as Annexure-V & VI. The minimum creepage distance of all the bushings shall not be less than 25 mm per KV of the max. System voltage as specified in clause 3.5 system particulars of this specification. The HV & LV bushings should be placed coinciding with the centre line of the transformer rollers.

3.24

CENTRE OF GRAVITY The center of gravity of the transformer shall be low and as near to the vertical central line as possible. The transformer shall be stable with or without oil and radiators. If the center of gravity is accentric relative to track either with or without oil, its location shall be shown on the outline drawing.

3.25 3.25.1

ACCESSORIES Each transformer shall be provided with the following accessories:i) A dial type indicating thermometer of robust pattern mounted inside the marshalling kiosk at a convenient height to read the temperature in the hottest part of the oil and fitted with the alarm and trip contacts with a repeater on RTCC panel to give oil temperature. ii) A winding temperature indicator with repeater and alarm / trip fan starting contacts (08 nos.) iii) Two magnetic type oil level gauge with low level alarm contact and a dial showing minimum; max. and normal oil level. The gauge shall be readable from the transformer base level. iv) Two oil filling valve (in let) one for main conservator tank and one for OLTC conservator tank. v) Two oil drain valves one from main conservator and other from OLTC conservator. vi) One filter valve located at the top of the tank on one side

278

vii) viii) ix) ix)

One filter valve located near the bottom of the tank on the other side of transformer Oil sampling valves for top, middle and bottom oil sample Pressure release device of a safety valve of the chimney type with an equalizer pipe interconnecting the top of the conservator and upper most part of the safety valve should be provided to permit rise of oil in the pipe. A stop cock should also be provided in the interconnecting pipe. An air release cock shall also be fitted in a convenient position. The safety valve pipe shall preferably take off from the side of the transformer tank near to the tank cover and not from the top of tank cover. In case if the pipe is taking off from the top of tank cover, arrangements shall be made to prevent, the gases forming in the tank from rising into the safety valve pipe and thereby by-passing the buchholz relay.

x)

One double float English Electric or equivalent make type OBG M-3 E gas detector relay (buchholz relay) with alarm and tripping contacts to detect accumulation of gas and sudden change of pressure, complete with shut off valves on both the ends and flange couplings to permit easy removal without lowering oil level in the main tank or conservator, a bleed valve for gas venting, and a test valve.

xi)

Heat exchangers or radiators with shut off valves at top and bottom. These will have lifting lugs and oil filling and drain plugs.

xii) xiii) xiv) xv) xvi)

An oil conservator for main tank as well as OLTC Cooling fans supported on the main tank or the radiators Eye bolts and lugs on all parts for ease of handling Oil surge relay for the OLTC diverter switch compartment. Two grounding pads suitable for 75x10 mm G.I. flat with four studs.

3.25.1.1

Diagram and rating plate (for ease of identification at site and stores). It is desired that in addition to diagram and rating plate all equipments shall carry a metallic plate giving following information got marked by the manufacturers itself. i) Name of equipment with specification No. ii) S.No. as per the bill of material iii) Year of order iv) Sl. No. of transformer Guaranteed as well as measured values of percentage impedances and No load / Load losses / and Auxiliary losses without any plus tolerance at 75°C shall also be inscribed on the diagram and rating plate.

3.25.1.2

TERMINAL CLAMPS Bimetallic terminal connectors for HV & LV: shall be suitable for ACSR PANTHER for 132 KV bushing and for 33 KV bushings the connectors shall be suitable for twin Zebra ACSR conductor. All connectors should be suitable for horizontal as well vertical take off. Information shall be furnished by the tenderers for following items: i) Material of clamps ii) Name of manufacturer iii) Drawings of clamp iv) Weight of clamp 279

v) vi) vii) viii)

Metal of clamp Testing facility for terminal connectors available at manufacturer’s work as per relevant I.S. Make of bolts, nuts and check nuts Make of washers.

3.25.1.3

The tenderers are required to note that :i) 132 KV clamps should have at least 2 pairs of bolts on conductor, as well as terminal end. ii) The clamp should be designed with large factor of safety and should comply in all respects of temperature rise, resistance and short circuit current with stand capacity and other conditions specified in I.S. 5561-1970 iii) A check nut should be provided on each bolt to avoid loosening of nuts due to vibration etc and these should be hot dip galvanized. iv) Bolts and nuts should be manufactured by a highly reputed concern. v) The prices of clamps should be quoted separately.

3.25.2

The transformers shall be complete with marshalling box or kiosk in which all the leads from Buchholz relays, oil / winding temp., indicators and magnetic oil level gauges shall be brought out to suitable terminals. This kiosk shall be weather proof and vermin proof and shall be provided with a front door as well as a back door and mounted on the transformer on its side so that it will be possible to open both the doors during service. Engraved single line diagram on non rusting steel plate will be provided on RTCC/Marshalling Box on back of front door. The font side shall be used to mount all the fittings, fuses, switchgears and contactors etc., and the back side for the wiring. All the fixtures will be provided with a level plate in the front as well as in the back side for identification. The terminal blocks shall be provided in the side.

3.25.2.1

Necessary cable glands shall also be provided at the base of this kiosk. It shall be complete with hinges and padlock arrangement, space heater, cubicle light, fuses etc. The necessary cables between transformer and the marshalling box shall also be provided by the tenderer.

3.25.3

The transformer shall also have a separate motor drive unit to accommodate the motor drive for the OLTC along with the contractor’s relays and auxiliary transformer etc., required for the operation of the OLTC. This will also be weather proof and vermin proof and shall be mounted on the transformer. Necessary cable glands, pad lock, space heater, light and protection devices shall be provided into it.

3.25.4

The equipment and accessories required with the transformer shall be suitably mounted on the transformer for ease of operation, inspection and maintenance, and the mounting details shall be subject to the approval of the purchaser. All valves shall be provided either with blind companion flanges or with pipe lugs for protection.

3.25.5

Indication, alarm and relay equipment shall have contacts suitable for operation with 110 Volts D.C. supply.

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3.25.6

Any fittings accessories of apparatus which might not have been mentioned in the specifications but which are usual and necessary in the equipment of similar design and are recommended by the manufacturer for satisfactory operation are to be provided by the contractor without extra cost. All apparatus must be complete in all details whether mentioned in the specification or not.

3.26 3.26.1

PAINTING Before dispatch, all steel surfaces, not under oil, shall be painted with a primary coat of anti-corrosive paint of durable nature and final two coats of light grey shade corresponding to IS: 631 paint of best quality. The interior surface shall be painted according to the contractor’s standard practice/ provision in ISS.

3.27 3.27.1

PACKING The packing may be in accordance with the tenderers standard practice so as to ensure safe transit by goods train or road. Special arrangements should be made to facilitate handling and to protect the projecting parts against damage in transit. The transformer shall be dispatched filled with oil or if necessary with insert gas with a pressure gauge and a spare gas cylinder to replenish the gas pressure in transit or during its storage at the destination until it is filled up with oil. All parts shall be adequately marked to facilitate identification and erection. Boxes and crates shall be marked with the tender specns. No. and shall have a packing list enclosed showing the parts contained therein. Bill of Material: The supplier shall make available a consolidated bill of material for one transformer unit complete in all respects required as per cl.2.6.3 of General Requirements of Specifications. The bill shall be made out on drg. of A-3 size giving a serial no. for each item of fitting and accessories required for one transformer, and this no. shall be mentioned in the packing list and the challan to facilitate the cross checking of all the items by the consignees and to ensure that all the components of the transformer unit have been received.

3.27.2

3.27.3

3.27.4

3.28 3.28.1

FACTORY ASSEMBLY AND TEST (a)Stage inspection: Purchaser shall have the option to depute their representative to check the progress during any stage of manufacturing of each transformer. However, following will be hold points where the bidder will have to offer advance inspection call notice. i) CORE: Thickness of laminations, overall height, width, window height & width ,cross section area & flux density ii) COIL : ID,OD of HV, LV & Regulating windings, cross sectional area of copper conductor used, number of turns, their parallel conductors &calculation of copper used in manufacture of transformer. iii) TANK : Physical dimensions, thickness of bottom, sides, radiators and conservator tank sheet. Weight of tank. Vacuum and pressure test . (b)

Final inspection:

281

The transformers shall be

completely assembled and tested at the factory.

If the purchaser selects to send a representative, all tests shall be witnessed by him. Tests shall be performed in compliance with I S 2026-1977 or latest amendment thereof 3.28.2

The following tests shall be made on transformers :i) All double welds shall be tested for leaks with dry nitrogen at a pressure not less than 7 kg/sq. cms. (atmosphere) ii) All tanks, single welds, cooling coils, radiators, valves and other parts necessary for complete transformer shall be tested for leak and strength by applying to the completed tank filled with oil an air pressure not less than 0.7 atmosphere for a period of 24 hours or not less than 1.0. Atmospheres for a period of six hrs. If leaks occur, the tests shall be conducted again till all leaks have been stopped. iii) Routine tests as per IS-2026-1977 or its latest amendment iv) Temperature rise test on one unit as per IS:2026-1977. v) Impulse test on all limbs of HV & LV windings of one unit as per CI.13 of IS-2026-1977. vi) Zero phase sequence impedance measurement on each Transformer. vii) Regulation at rated load at 1.0, 0.9, 0.8 lagging power factor (calculated) viii) Exciting current at 90%, 100%, 110% and 120% of rated voltage ix) Excitation losses at 90, 100, 110 and 120% percent of rated voltage measured by the average voltmeter method. x) Magnetic balance test on HV/LV winding on all the transformer xi) Exciting current measurement on both the HV/LV winding of all the transformer at 440 Volts. X) Tan –Delta of complete Transformer

3.29 3.29.1

TEST AT SITE After erection at site, the purchaser shall carry out the following tests on transformers:i) Insulation resistance test ii) Ratio and polarity test iii) Di-electric test on oil.

3.30

FURTHER TESTS

3.30.1

SHORT CIRCUIT TEST: If it is so desired that short circuit test at CPRI, Banglore/Bhopal may be carried out on any unit randomly selected for short circuit test. Firm will make all necessary arrangements for above test, expenditure on above will be reimbursed by department on actual basis.

3.30.2

The purchaser reserves the right of having other reasonable tests carried out at his own expense either before dispatch or at site to ensure that the transformer complies with the requirements of these specifications. The transformers shall be dispatch only after issue of dispatch authorization. In case the transformer dispatched without proper dispatch authorization, penalty will be deducted on the basis the date of issue of dispatch 282

authorization and will be entertained.

transit period. In this context no correspondence

3.31

After all tests have been completed, six certified copies of each test report shall be furnished. Each report shall have following information:i) Complete identification data including serial no. of the transformer ii) Method of application, where applied, duration, and interpretation of results for each test. iii) Losses / Impedance corrected to 75°C

3.32

Drawings and instructions book for erection, commissioning, operation and maintenance manual to be furnished by the supplier On placement of the order, the manufacturer shall supply three copies of all the drgs., which will describe the equipments in detail as per the provisions of cl.2.6. of the General Requirements of Specifications for approval.

3.32.1

Drawings All the drawings are required to be furnished in A-3 size only, for proper filing and making folders having card paper covers of the same size. In case some of the drgs., cannot be prepared directly in A-3 size, these could be prepared on larger sheets and submitted for approval. These large size drgs., after approval (made in ink) shall be photographically reduced and printed in A-3 size on a plastic film only to be used as a master copy. Additional prints on ammonia paper or photo copies on white sheets of A-3 size shall be made out from the master copy.

3.32.2

The size of letters and the numerical figures on the reduced drg., shall be of 2 mm, size or more.

3.32.3

The wiring drawings and the general arrangement drawing, if necessary, could be splitted into more than one A-3 sheet, so that these could be understood and read correctly.

3.32.4

After approval the contractor shall submit to the engineer and consignee(s), within a reasonable time but before commencement of any dispatches of equipment, the following:;(a) i) Six sets of prints of each approved drawing for each consignee ii) Total six sets of prints per contract to the engineer of the contract (b) i) Six set of bound copies of approved manuals for each consignee and six sets for the engineer of the contract (c) Six set of detailed bill of material for each consignee & six set for E.O.C. (d) One good quality direct reading reproducible of each approved drawing and also of bill of material to Engineer of Contract (E.O.C).

3.32.5

In the event of non-supply of aforesaid drawing & manuals in the quantity and in the manner as required above, the contractor shall deduct from his bill(s) an amount equal to two (2%) of ex-works price of the equipments. This amount can, however, be claimed by the contractor only after supplying the above.

3.32.6

The following drawing shall be required to be supplied by the successful tenderer, on placement of the order:General Arrangement Drawings 1. Outline general arrangement drg. of transfomer

3.32.6.1

283

2.

2.1

3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

3.32.6.2

Details of winding and core as per schedule of technical particulars with specific mention of size of conductor in L.V & H.V. OD/ID of H.V. LV and tap windings, and their relative placement and position. Outline dimentions of the core and winding along with the weight of the active parts to be lifted for over-hauling of the transformer, showing the minimum lift required to takeout the core & windings out of the transformer tank. General arrangement of OLTC panel, frontview as well as rear view development General arrangement of marshalling kiosk cum cooler control panel General arrangement of driving mechanism. General arrangement of H.V. bushing with their electrical and mechanical characteristics General arrangement of LV, LV(N) and HV (N) bushings with their electrical and mechanical characteristics L.V. bushing without current carrying parts with make and type (porcelain part) Foundation plan of transformer, with required cable trench position Bi-metallic terminal connectors drawings for H.V as well as L.V.bushings Braded copper strip drawing with clamping arrangement for neutral bushing Winding temp. indicator, oil temp. indicator, buchholz relay, silicagel breather, M.O.L.G. and pressure release device drawings. Transportation sketch or transformer super imposed on the loading diagram of the railway wagon (in two views)

Schematic and wiring diagrams 1. Schematic diagram of O.L.T.C. control scheme also showing coordinated drawing for master follower operation of two transformers based on the standard, C.B.I.P. control scheme. The driving mechanism portion of the scheme to be shown inside a box. 2. Write-up operation of the O.L.T.C. and cooler control scheme giving the sequence of operation of different contactors. The timing diagram for mechanical switches of OLTC for one operation cycle, should be shown in the write-up. 3. Diagram of alarm and annunciation scheme 4. Schematic diagram of marshalling kiosk and cooler control scheme 5. Wiring diagram of RTCC panel 6. Wiring diagram of driving mechanism 7. Wiring diagram of marshalling kiosk cum cooler control panel 8. Terminal block arrangement of R.T.C.C. panel driving mechanism, and cooler controls cubical 9. Interconnection and external cabling details between OLTC, R.T.C.C. marshalling kiosk, transformer and purchaser’s transformer controls panel 10. Cable routing drawing showing the routes of the cables and their clamping arrangement on the transformer tank 11. Consolidated bill of material for the transformer. 12. Erection, commissioning, operation and maintenance manual along with descriptive literature and data on transformer construction, windings, bushings, heat exchangers, tap changer gear etc. 13. Any additional drawing which the supplier may consider necessary.

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3.33

Spare The tenderer shall quote separately for the spares recommended for five years normal operations. The purchaser will decide on the actual spares to be ordered on the basis of the list and the item-wise prices of spare parts.

3.34

Replacement parts In the event of an order being placed, the successful tenderer will be required to supply all damaged, short supplied parts within the period of one month from the date of notifying them the list of all damages / shortages by the consignees. In case the firm is unable to supply the replacement within the above period, then they should agree to refund any payment that might have been paid for the entire equipment which cannot be used as a result of loss, damages or short supplies. If this is not done, the necessary amount would be deducted either from the security or bank guarantee or their other pending bills with the Corporation.

3.35

Deviations from specifications Deviations from these specifications should be clearly listed and brought out separately.

3.36

Schedule of required delivery and prices Nil

3.37

Supervision charges The tenderer shall quote separately in the schedule of prices the rates of supervision charges for erection and commissioning of transformers on daily basis along with their other terms and conditions. It shall be at the option of the purchaser whether or not to avail the service of supplier’s engineer and other staff for supervision of erection and commissioning or to award some other for commissioning only without absolving the supplier of his obligations under cl.30 (Maintenance) of Form ‘B’.

3.38.1

The tenderer has to submit the calculation as per the method stipulated in IS:2026 or amendments thereof, to show the thermal short circuit capability of the transformer, due to external short circuit conditions.

3.38.2

The IEEMA price variation formula applicable for the transformer; is enclosed as per Annexure-II,. The tenderers are required to follow these formula in respect of transformers offered by them.

3.38.3

The postal address of the purchasing authorities for the similar transformers must be attached with ‘tender’ Bid Part-II in the schedule-3 attached.

3.38.4

Tenderers shall quote their rates of material after consideration and absorption of benefits of “MODVAT”.

3.38.5

The supplier shall keep the purchaser informed in advance about various stages of manufacturing program, so that arrangement can be made for stage inspection if so required.

285

3.38.6

The call for final inspection shall be given by the supplier when the goods have actually become ready in all respects in the works of manufacturer and not on the basis of anticipated date of completion. Routine test report of the goods offered for inspection will have to be submitted with inspection call letter. A period of 4 weeks or 6 weeks shall be allowed for UPPTCL for making travel arrangements for their inspecting officer to reach their works. This period of 4 or 6 weeks will be from the date when inspection call is received by UPPTCL. The period of 4 weeks shall be for works situated in U.P. Union Territory of Delhi, Rajasthan, Bihar and West Bengal, and 6 weeks for all the remaining States. In case the goods are not available for inspection at the time of the arrival of the inspecting officer the firm shall pay to UPPTCL towards futile journey charges, a sum decided by Chief Engineer (Transmission) and demanded by the Engineer of Contract. This amount shall be paid within 30 days from the date of demand. Further action for inspection of material shall be taken only after the said amount is deposited.

3.38.7

The unloading of the transformer and its accessories at site shall be the responsibility of the tenderer/supplier. The site of unloading shall be decided by the concerned consignee. Firm may quote the rates for unloading at site in the price schedule-Q separately.

286