UTTAR & DAKSHIN HARYANA BIJLI VITRAN NIGAM

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

TECHNICAL SPECIFICATION OF “8 MVA, 33/11 kV POWER TRANSFORMER”

Issue Month:

Common Specifications Committee UHBVN & DHBVN

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TECHNICAL SPECIFICATION FOR 8 MVA POWER TRANSFORMERS 1.

SCOPE: This specification covers the design, manufacture, assembly, testing at manufacturer’s works before despatch, supply and delivery of 8 MVA ONAN 33/11 KV Dyn 11 Connected Power Transformers with Remote tap change control cubicle (RTCC) with On Load Tap Changer in 2.5% steps range +5% to -15%.

2.

STANDARDS: While drafting this specification, reference has been made to the following Indian & International standard specifications. In case, certain details are not covered in this specification, the mentioned Indian/International standard shall be applicable: IEC-76: Specification for Power Transformers. IS-2026: Specification for Power Transformers. IS-3639: Specification for fittings & accessories for Power Transformers. IS-2099: Specification for bushings. IS-3347: -doIS-6600: Specification for loading of transformers. IS-8468: Specification for on load tap changer. IS-335: Specification for transformer oil.

3. CLIMATIC CONDITIONS: The equipment/material to be supplied against this specification shall be suitable for satisfactory operation under the following climatic Conditions i) Location At various locations in the state of Haryana ii) Max ambient temperature (deg.c) 60 iii) Min ambient air temperature (deg. c) -5 iv) Max average daily ambient 40 temperature (deg. c) v) Max. yearly weighed average ambient 32 temperature (deg. C) vi) Max. altitude above mean sea level 1000 (Meters) vii) Minimum Relative Humidity (%age ) 26 viii) Max. Relative Humidity (%age) 95 ix) Avg. no of Rainy days/ year 120 x) Avg. annual rainfall 900mm xi) Maximum wind pressure 195 Kg./m Sq. The equipment shall be for use in moderately hot and humid tropical climate, conducive to rust and fungus growth. 4.

TYPE & RATING:

4.1 The transformer shall be of two windings step down three phase oil immersed core type ONAN cooling and suitable for outdoor service with On Load Tap Changer.The rating and other electrical characteristics shall be as under: 4.2.1 Max. Continuous Rated Capacity (ONAN) 8 MVA 4.2.2 Number of phases 3 4.2.3 Frequency 50 Hz 4.2.4 Rated Voltage a) HV 33KV b) LV 11KV

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4.2.5 Connections a) HV b) LV c) On Load Tap Changer On high Voltage winding in steps of 2.5% 4.2.6 Vector Group 4.2.7 4.2.8 4.2.9

No load losses at rated voltage and frequency Load Losses at 750c Percentage Impedance voltage on principal

DELTA Star Range +5% to –15% Dyn 11 7.5 KW 43 KW 8.35% + 10%

tapping at 750c 4.2.10. LOSS CAPITALISATION FORMULA: The losses for each transformer shall be stated in the tender. The manufacturer shall state separately no load losses at rated Voltage and frequency. Load losses at full load and Auxiliary losses at 75ºC. For the purpose of arriving at comparable prices. No load, Load and Auxiliary Losses at normal Tap shall be capitalized as per formula given below:Capitalized cost of Transformer =1c + 1,52,847 x Wi + 62362 x Wc + 61139 x Wp Where Ic = Initial cost Wi = Iron (No load) Losses Wc = Copper (Load) Losses Wp = Auxiliary Losses

Rejection of Power Transformer. i) In case during the test, the actual losses are found within guaranteed figures, the transformer shall be accepted without any advantage to the supplier / contractor for lower loss. ii) When actual losses during testing are found in excess of maximum guaranteed figures, the transformer shall be rejected. iii) Impedance value exceeds the guaranteed value by + 10% iv) The difference in impedance value of any two phases during single phase short circuit impedance test exceeds 2% of the average value guaranteed by the vendor. v) Oil or winding temperature rise exceeds the specified value. vi) Transformer fails on impulse test vii) Transformers fails on Power Frequency Voltage withstand test. viii) Transformer is proved to have been manufactured not in accordance with the agreed specifications 4.2.11 Taps: I. Taps shall be provided ranging from +5% to –15% in steps of 2.5% each on HV winding for voltage variation on secondary side. The Tap Changing Mechanism shall be suitable for Remote (Electrical) and Local (Both Manual and Electrical) Operation. II. The circuit arrangement on the RTCCs shall be flexible to provide for addition of transformers for parallel operation such that one of the transformers in the group can be selected to be operated as Master and others as Followers. III. An out of step device shall be provided on each RTCC Panel which shall prevent further tap changing, when any transformer in a group operating in “Parallel” is one tap out of step with other transformers. In addition visual

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and audible “Tap changing in progress” indication scheme shall be incorporated in the RTCC circuitry. 4.2.12 Insulation level 33KV 11KV Winding Winding a). Rated one minute power 70 KV rms 28 KV rms frequency withstand test voltage. b). Rated 1.2/50 micro sec. 170 KV peak 75 KV peak Lightning impulse withstand voltage. 5 GENERAL DESIGN OF TRANSFORMER: 5.1 The transformer and accessories shall be so designed so as to facilitate inspection, cleaning & repairs. The requirements of Indian Electricity Rules shall be kept in view. 5.2 The design shall ensure satisfactory operation under severe working conditions due to load and voltage variations in the system including those due to short circuits. The transformers shall be designed so as to minimise the risk of accidental short circuit caused by animals, birds and vermin. The design shall incorporate every reasonable precaution and provision for the safety of all those concerned in operation & maintenance of the equipment keeping in view the requirements of Indian Electricity Rules. 5.3 All material used shall be of best quality and of class most suitable for working under the specified conditions and shall withstand the atmospheric conditions and temperature variations without deterioration or distortion or setting up of undue stresses in any part thereof and also without affecting the strength and suitability of the various parts for the work which they have to perform. 5.4 Cast iron shall not be used for any part other than the large valve bodies. 5.5 Corresponding parts liable for replacement shall be inter-changeable. 5.6 All taper pins to be used in the mechanism shall be split type as per latest edition of IS: 2393. 5.7 All mechanism shall be rust and corrosion proof. Means shall be provided for lubrication of moving parts not immersed in oil. 5.8 The construction shall be such as to avoid air or water pockets. Special care shall be exercised to reduce noise due to Magnetostriction and vibration to the minimum level. 5.9 Steel bolts of suitable finish will be used of diameters above 6mm. Brass bolts or studs used for electrical connection shall not be of less than 6mm dia. On out door equipment all bolts, nuts, washers in contact with current carrying non-ferrous parts shall be of phospher bronze. 5.10 All nuts, bolts and pins shall be locked except those, which are external to the transformers. If bolts &nuts are so placed that these are inaccessible by means of ordinary spanners, suitable spanners shall be provided by the supplier free of cost. 5.11 Labels shall be provided for all apparatus like relays, switches, fuses etc. housed in any cubicle or marshalling kiosk. These shall be of in-corrodible material with matt / satin finish and permanent lettering. Labels mounted on black surface shall have white lettering on black surface and danger notice shall have red lettering on a white background. The labels shall be secured by means of brass screws or rust protected steel screws. 5.12 Surface in contact with oil shall not be galvanised or cadmium plated. 5.13 Before painting, all un-galvanised parts shall be cleaned, made free from rust, scale and grease and external rough surface smoothened, filled with metal deposition. The interior of the tank and other oil filled chambers shall be cleaned by shot blasting or any other suitable method.

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5.14

5.15 5.16

5.17

5.18 5.19

All external surfaces shall be given three coats of paint except for nuts, bolts & washers, which may be given one coat after assembly of transformer at works. The final coat shall be glossy, oil and weather proof, non-fading paint of shade 631 of IS: 5. The interior of mechanism chambers and kiosks shall be given 3 coats of paint, the final coat being of a light coloured anti condensation mixture. The outer most radial spacers of the winding shall be locked in position by means of vertical strips so that the same do not fall off/ got displaced during transportation, operation or short circuits through faults. Proper and complete tightening of the nuts of the Coil Clamping Bolts must be ensured. The tightening of the nuts to the desired value and that of the nuts of all the coil clamping bolts are tightened uniformly to same extent should be carried out with torque spanners. The devices used for locking the nuts of coil clamping bolts must be of standard quality and care should be taken first to tighten the nuts & next in locking them in position so that the arrangement does not work loose due to stresses/vibrations caused by short circuit faults, Load fluctuations, Magnetostriction etc. The noise level during operation shall not be more than 5 db above NEMA standard publication TR-1. The transformer shall be designed to have short circuit rating of two seconds as per ISS-2026.

6.

INSULATING OIL The transformer and associated oil filled equipment shall be supplied with first filling of oil. The oil shall comply in all respects with the recommendations of IS: 335 latest editions. Special care shall be taken in the design of transformer to reduce the risk of acidity development in oil. Use of PCB is prohibited.

7. 7.1

TEMPERATURE RISE Each transformer shall be capable of operating continuously at its normal rating without exceeding the following temperature rise limits over maximum ambient air temperature of 50O C. --------------------------------------------------------------------------------------------------Type of Top oil Temperature rise Winding Temperature rise Cooling measured by thermometer measured by resistance method --------------------------------------------------------------------------------------------------ONAN

7.2

7.3

8.

50o C.

55o C.

The temperature of core, metallic parts and adjacent materials, shall in no case reach a value that will damage the core itself, other parts of adjacent materials. In addition to above the transformers shall be so designed that the hot spot temperature of the winding during normal operation shall not exceed 98 O C based on a maximum yearly weighted ambient temperature of 32 O C. The loading of the transformers shall be done as per latest edition of IS: 6600. IMPEDANCE The percentage impedance voltage at 75oC shall be 8.35% at 8 MVA. The impedance values refer to the principal tapping and are subject to a tolerance of + 10% as per IS: 2026.

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9 9.1

FREQUENCY The Transformer shall be suitable for continuous operation with +3% frequency variation from a normal of 50Hz without exceeding the temperature rise as specified in Clause 7 above.

10 10.1

FLUX DENSITY The primary voltage variation which may affect the flux density at every tap shall be kept in view while designing the transformer. The transformer should be so designed that the working flux density does not exceed 1.6 Tesla at normal voltage & frequency for M.4 or high B grade C.R.G.O. Steel core. Tenders with max. flux density higher than specified above shall be summarily rejected. The tenderer shall indicate the maximum continuously allowable flux density as well as allowable over fluxing for time interval of one minute and five seconds and the limit of flux density at which the core material used by them saturates. The name and grade of core material to be used must be mentioned in the tender. The successful tenderer shall be required to furnish magnetization curves of the core material / design calculations and such other data / documents deemed fit by the purchaser for being satisfied that working flux density is within permissible limits.

10.2

NOTE: The above flux density has been specified to meet with the over fluxing of the core due to temporary over voltage of the order of 25% for one minute and 40% for five seconds that may appear in abnormal conditions such as those following sudden loss of large loads. 11. 11.1

SUPPRESSION OF HARMONICS The transformers shall be so designed as to suppress the harmonic voltage especially the 3rd and 5th to eliminate waveform distortion and interference with communication circuits due to high frequency disturbances.

12. 12.1

CORE The cores shall be constructed from high-grade cold rolled non-aging grain oriented silicon steel laminations with oxide silicate coating as insulation.

12.2

The design shall be such as to avoid static discharges, short circuit paths within itself or to earthed clamping devices and production of flux component at right angles to the plane of the lamination, which may cause local heating. Adequate oil ducts shall be provided in the core for cooling. Tinned copper strip bridging pieces shall be used for maintaining electrical continuity whereever the magnetic circuit is provided into pockets by such ducts or insulating material thicker than 0.25 mm. There should be no movement of the core assembly relative to the tank during transportation or while in service due to sudden jerks caused by short circuits, fluctuating load and Magnetostriction etc. Adequate lifting lugs shall be provided to enable core and winding to be lifted. The insulation structure for core to bolts and /or core to clamping plates shall be such as to with- stand power frequency voltage of 2KV (rms) for one minute.

12.3

12.4

12.5 12.6

13

WINDINGS

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13.1

13.2

13.3 13.4

13.5

13.6 13.7

13.8

13.9

14. 14.1 14.2

14.3

14.4

14.5

The 33 KV Windings and 11KV Windings shall be made of Electrolytic High Conductivity Copper & shall be fully insulated. 11 KV neutral point shall be insulated as per IS: 2026. The transformer shall be capable of giving rated output without injury on all Taps within + 10% of the rated voltage corresponding to the relevant Tap. The windings and connections, insulation material shall not soften, loose out, shrink or collapse during service. No strip conductor wound on edge shall have a width exceeding six times its thickness. The conductor shall be transposed at sufficient intervals to minimize eddy currents and equalize the current and temperature distribution along the length of the winding. Adequate pre shrinkage of the coils assembly using pre-compressed press board, material having low moisture content for radial spacer blocks shall be ensured by the manufacturers so that there is no displacement of the radial spacer blocks due to frequent faults through short circuit on the transformers. In addition to this the drying process be sufficiently extended for proper stabilization of the coil assembly. More than one cycle of soaking in oil followed by re-tightening of the coil assembly should be adopted. The windings and connections shall be properly brazed to withstand shocks during transportation or under transient conditions during service. The coil-clamping ring where ever used, shall preferably be of flat insulated steel laminations. Axially laminated material except bakelised paper shall not be used. The clamping arrangement shall exert equal pressure on all columns of spacers of the transformer windings built of sections or disc coil separated by spacers. The joints shall be brazed/ crimped to take care of vibration due to short circuits and load fluctuations. INTERNAL EARTHING ARRANGEMENTS All metal parts of the transformer except individual core laminations, core bolt and individual-clamping plates shall be maintained at a fixed potential. The Earthing connectors shall have a minimum area of cross section of 0.8 Sq. cm. Except connections inserted between the laminations and in close terminal connections with them, which may have area of cross section of 0.2 Sq. cm. The top main core clamping structure shall be connected to tank body by copper strip. The bottom clamping structure shall also be earthed by following methods. The magnetic circuit shall be earthed to clamping structure by a link connection from the top yoke near the bridging pieces referred to in Clause 12.3. on the side of main earth. An inspection hatch shall be provided over the link in the tank cover. For individual insulated sections of the magnetic circuits, separate links shall be provided. The bridged construction as per Clause 12.3 shall not be taken as being of sectional construction.

15.1 TANK CONSTRUCTION 15.1.1 The tank shall be fabricated of suitable grade low Carban steel and strong enough to allow the lifting of complete transformer with oil by means of crane or jacks and transported to site without over straining the joints etc. 15.1.2 The main tank body shall be capable of withstanding a vacuum of 68.0KN/m2 (500mm of Hg).

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15.1.3 The base shall be so designed as to allow the transformer to be moved by skidding without any injury. 15.1.4 The tank construction shall be free of air pockets. Where such pockets can not be avoided vent pipe of 15 mm internal dia shall be provided to vent gases into the main expansion pipe. In case of short branch pipes, however, minimum diameter may be taken as 6 mm. 15.1.5 All channeled constructions and stiffeners shall be designed to avoid retention of water 15.1.6 All joints other than those, which may have to be broken, shall be welded. 15.1.7 Suitable lifting lugs for lifting the transformer filled with oil shall be provided on the tank. 15.1.8 Four jacking lugs shall be provided to enable the transformer complete with oil, to be lifted to or lowered by means of Jacks. The lugs should be fitted at a minimum height (excluding under base if detachable) of 300 mm for transformers upto 10 tonnes weight and 500 mm for transformers above 10 tonnes weight. 15.1.9 The transformers shall be provided with flanged wheels of suitable dia for use on a 1435 mm gauge track. These wheels shall be bi-directional and mounted on swivels which can be turned through 900 when the tank is jacked up and capable of being locked in position parallel to as well as at right angles to longitudinal axis. 15.1.10 Tank shall be engraved as under: a) Specification No. b) Capacity (MVA) c) Manufacturer’s Name & S. No. d) Year of manufacture e) Iron Losses f) Copper Losses g) Property of UHBVN h) PO No. of UHBVN / date 15.2 TANK COVER 15.2.1 The tank cover shall be bolted type and of adequate strength so as not to distort when lifted. Suitable inspection cover shall be provided with lifting arrangements to give access to portion of bushings under cover, winding connections or inspecting the earth connections. The weight of each inspection cover shall not exceed 25 Kg. 15.2.2 Pockets shall be provided in the position of maximum oil temperature at CMR for fitting a Thermometer and for both of oil & winding temperature indicators. The tank cover shall be fitted with two pockets for Stem Type Thermo-meters. Each thermometer pocket shall be fitted with a captive screwed cap to prevent ingress of water. 15.3 CONSERVATOR TANK OIL LEVEL GAUGE AND BREATHER: 15.3.1 A conservator tank complete with sump and drain valves shall be provided in such a position as not to obstruct electrical connections to the transformer. 15.3.2 If the sump is formed by extending the feed pipe inside the conservator tank, this extension shall be of at least 25 mm. 15.3.3 One side of the conservator tank shall be bolted type to facilitate cleaning. 15.3.4 The conservator for main tank shall be provided with magnetic oil level gauge with oil level at 300 C clearly marked on its dial. 15.3.5 The oil connections from the transformer tank to the conservator tank shall be at a rising angle of 3 to 5 degrees to the horizontal upto Buchholz”s relay. The inside dia of the pipe shall be 50 mm. Two No valves shall be provided one on each side of Buchholzs relay to cut off oil supply to the

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transformer from conservator stank when Buchholz’s relay is being repaired. 15.3.6 The conservator tank shall be provided with a Silicagel Breather. The breather shall be mounted at approximately 1400 mm above ground level. 15.3.7 The oil level gauge of OLTC Tank portion of conservator tank shall be plain sight glass marked with oil Level for -50c, 300c and 980c.

15.4 VALVES 15.4.1 The transformer tank shall be provided with a flitter valve of 50 mm size mounted at top of the main tank for oil circulation and one drain valve of 50 mm size with bolted blanking plates. The conservator tank shall also have a drain valve of 15 mm size. 15.4.2 Sampling device shall be provided at the bottom and top of main tank in addition to filter valves to take out transformer oil samples for testing from bottom as well as top of transformer tank. 15.4.3 One air release plug of 19 mm shall be provided on top of the main tank. 15.4.4 Plugs shall be supplied for all valves opening to atmosphere. 15.4.5 All valves shall comply with the latest edition of IS: 3639. 15.5

PRESSURE RELIEF DEVICE. A suitable pressure relief device shall be provided on the main tank for rapid release of any excessive pressure generated in the transformer tank due to internal faults, which may endanger the equipment. The device shall operate at static pressure less than hydraulic test pressure for transformer main tank. If the device is mounted on main tank cover, it shall be fitted with a skirt projecting 25 mm inside the tank and be of such construction as to avoid gas accumulation. 15.6 EARTHING TERMINALS: 15.6.1 Two earthing terminals capable of carrying full short circuit current of the transformer for 4 seconds shall be provided at the bottom on opposite corners of the main tank. 15.7 JOINTS AND GASKETS: All gaskets used for making oil tight joints shall be of neoprene granulated cork bonded with synthetic rubber. Metal stops shall be provided for preventing over-compression wherever compressible gaskets are provided. 15.8 RATING AND DIAGRAM PLATES: 15.8.1 Each transformer shall be provided with a rating plate bearing data & Diagram as specified in IS 2026. In addition to this contract/PO no. with Date & ‘Property of UHBVN' should be marked on the rating plate. 15.8.2 Each transformer shall carry a diagram plate showing internal connection, voltage vector relationship of different windings, plan view of the transformer showing physical relationship of the terminals and no load voltage for each tap. 15.8.3 Insulation resistance values of various windings to earth and between each pair of windings, along with temperature at the time of testing in the factory, shall be indicated on rating plate or on a separate plate to be provided on the transformer. 16 COOLING PLANT: 16.1 Detachable radiators shall be fitted on the main tank with machined flanged outlet and inlet. Each radiator shall be provided with 19 mm drain plug at bottom and 19 mm air release plug at the top. The plugs shall have neoprene rubber gaskets only. Valves shall be provided on the tank at

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16.2 16.3 16.4

each point of connection to radiator. These valves shall have neoprene rubber gaskets 6 mm thick on either side. The radiator fins shall be manufactured from a steel sheet with a thickness not less than 1.25mm. All radiators groups shall be provided with by buffing of 50x50x6 mm MS Angle. The oil-circuits of Oil coolers shall be provided with the following: a) A valve at each point of connection to the transformer tank. b) Removable blanking plates to permit the blanking-off the main oil connection of each cooler. c) A drain valve of 25 mm at the lowest point of each bank of cooler. d) Air release plug 15 mm.

17 17.1

ON LOAD VOLTAGE CONTROL: The transformer shall be provided with O.L.T.C. equipment for varying its effective transformation ratio, without phase displacement. The tap range shall be (+) 5% to (-) 15% with step of 2.5% on H V winding for adjustment of output voltage of L V side with variable H V input. 17.2 Each O.L T.C. shall have local manual, local electrical and remote electrical controls in such a way that only one may be engaged at a time. 17.3 The equipment shall be suitable for supervisory control and indication. A multiway switch (make before break after) having one fixed contact for each tap position, shall be provided in addition to any switch required for remote tap position indicator. Supervisory indication for “TAP CHANGE INCOMPLETE” shall also be provided. 17.4 Only one tap change shall be completed at a time and control switch must return to the off position for the next operation. 17.5 The equipment shall be such as to ensure that once a tap change has been initiated it shall be completed independently of the operation of control relays and switches 17.6 Adequate safeguard shall be provided for the transformers and auxiliary equipment in case of auxiliary supply failure, leaving the tap change incomplete. 17.7 Provision shall be made for buzzer and light indication at the remote control panel to show the tap change in progress. The mechanical and electrical indication of the number of tap in use shall be provided at the transformer and remote control panel. 17.8 The main tap changing equipment shall be transition resistance type oil immersed. These oil compartments which contain current making or breaking contacts, shall be kept under the conservator head by means of a pipe connection from the highest point of compartment to conservator tank and controlled by suitable valve. Any gas generated in it, shall pass through single float gas and oil surge actuated relay to trip the transformer controlling circuit breaker, in the event of a fault in the O.L.T.C. tank mechanism. 17.9 The oil in the current interrupting or making chamber, shall not come in contact with oil in the main transformer tank or other than non current interrupting chamber. 17.10 Each compartment which is not maintained under the conservator head shall be provided with prismatic oil gauge 17.11 All control and indicating gear shall be designed for 415 V, 3 phase, 4 wires and 50 Hz supply subject to a variation of +10 % to –20%. 17.12 Limit switches shall be provided in the circuit of motor, to prevent over running of mechanism beyond minimum and maximum tap position in addition to a mechanical stop.

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17.13 The motor and control circuit shall be provided with thermal protection. All relays fuses and switches shall be mounted in marshalling box or driver gear housing and clearly labeled. 17.14 A five-digit counter shall be fitted to indicate the number of operations completed by the tap changer. 17.15 A permanently legible lubricating charge shall be put in the driving mechanism chamber. 17.16 All wiring and cabling shall comply with Clause 23. 17.17 All remote control and indicating equipments shall be mounted on remote control cubicle of suitable size, complete with fitting for mounting inside the control room. It shall be painted as per Clause 5.14. It shall also be provided with 80W, 230 V AC, 50 Hz metal heater, controlled by a switch toward off moisture condensation. 17.18 The following type and routine Tests shall be carried out on the On load tap changer and motor driver mechanism in accordance with IS: 84681977 or its latest version. The type tests should not be more than 5 years old. ON LOAD TAP CHANGER I. Type Tests Type tests shall be performed on the samples of the relevant tap changer or components after their final development. The following shall constitute the type tests. a) Mechanical Test b) Auxiliary Circuit insulation tests. c) Tests for temperature rise of contacts d) Switching tests e) Short circuit tests f) Transition impedance test. g) Mechanical life test h) Dielectric test II. ROUNTINE TESTS: The following shall constitute the routine tests: a) Mechanical test b) Auxiliary Circuit insulation tests c) Dielectric Tests. 17.19 MOTOR DRIVEN MECHANISM I)

18. 18.1

Type Tests. The following shall constitute the type tests. a) Mechanical tests b) Auxiliary Circuit insulation tests. c) Mechanical load test d) Over run test e) Protection of Motor Driver Cubicle. II) ROUTINE TESTS The following shall constitute the routine tests a) Mechanical Tests b) Auxiliary Circuit insulation tests. PARALLEL OPERATION In addition to individual control of tap changer, provision shall be made for simultaneous tap change of all the transformers, when a number of units are running in parallel.

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18.2

Suitable selector switch shall be provided so that any transformer of the group can at a time be selected as “ Master” “follower” ‘OR “independent”. Arrangement shall be made that only one of the transformers can be selected as “Master” at a time.

18.3

19. 19.1

19.2

19.3 19.4

19.5

20 20.1

An out of step device shall be provided for each transformer indicating out of step condition by visual indication and buzzer. It shall be arranged to prevent further tap changing, when any one transformer in a group, operating in parallel is on one tap out of step. BUSHING INSULATORS AND TERMINALS The Characteristics of the bushings shall be in accordance with IS:20991986 and IS 3347as amended from time to time. All type and routine tests shall be carried out in accordance with IS: 2099-1986 as reproduced below: Nominal Rated Visible One minute lightning System Voltage discharge wet & dry impulse Voltage of bushing test withstand withstand Test test(impulse Voltage) KV KV KV KV KV 11 12 9 35 75 33 36 27 75 170 The dimensions of the 12 KV Bushings ( 11 KV side ) shall conform to IS : 3347 ( Part-III) and those of 36 KV bushing ( 33 KV side) shall conform to IS : 3347( Part V). All porcelain shall be free from defects and thoroughly vitrified with a smooth hard and uniform brown glaze. It should be capable of satisfactory use, under the climatic conditions as specified in Clause 3. In case of paper insulation care shall be taken to prevent ingress of moisture and final coat of non-hygroscopic varnish shall be given to them. All clamps and fittings made of malleable iron or steel shall be galvanized as per IS: 2633. The bushing flanges shall not be of re-entrant shape, which may trap air. Bimetallic terminal connectors shall be provided on HV and LV side suitable for 0.2 Sq. Inch ACSR Conductor, code word “Panther” & LV side suitable for 11 kV, 3-core 400 mm² XPLE cable. The connectors shall have six number bolts provided with check-nuts & washers. The connectors shall have rating corresponding to those of equipment or higher and shall be designed most liberally with a higher factor of safety to comply in all respects, with temperature rise, resistance, tensile strength, short circuit withstand capacity tests as specified in IS: 5561-1970 or amendment thereof (latest edition). Aluminium Alloy used in the manufacture of bimetallic connectors shall conform to designation Grade 4600 of IS 617-1975. The steel bolts, nuts, washers and check nuts shall be hot dip galvanised, marked with ISI certification mark or of GKW make. TEMPERATURE INDICATING DEVICES: The transformers shall be provided with two Nos. Dial type thermometers. One for indicating top oil temperature with one electrical contact for alarm and another of dial type thermometer for indicating winding temperature

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on load with three pairs of electrical contacts for alarm, trip and for ‘ON’ & ‘OFF’ Motor Blowers (Cooling fans). 20.2

One No. CT of appropriate CT ratio shall be provided in one HV Line/Phase to produce actual temperature differential between Top oil and winding temperature on load.

20.3 20.4

21 21.1 21.2 21.3 21.4

21.5

The temperature indicators shall be housed in a marshalling box except where out-door type indicators are provided. All contacts should be accessible on removal of the cover and adjustable to scale. It shall also be possible to move the pointers by hand for checking the operation of contacts and associated equipment. GAS AND OIL ACTUATED RELAYS: Each transformer shall be provided with gas and oil actuated relay fitted with alarm and trip contacts as per IS: 3637. Each relay shall be provided with a test cock to take flexible connections for checking relay operation. A machined surface shall be provided on the top of relay for checking mounting angle in the pipe and cross level of relay and it’s setting. The pipe work shall be such as to allow any gas formed in the tank to pass through the relay. The oil circuit through the relay shall not form a parallel delivery path with any circulating oil pipe, nor shall it be tied into or connected through the pressure relief vent. Adequate clearance between oil pipe work and live metal parts shall be provided.

22

MARSHALLING BOX:

22.1

A steel sheet min. of 2.5 mm thick vermin proof well ventilated and weather proof Marshalling box of suitable construction shall be provided for the transformer auxiliary apparatus. The box shall have sloping roof. Ventilation cover shall also be provided. It shall be painted as per Clause 5.15.

22.2

The marshalling box shall accommodate temperature indicators, terminal boards and gland plates entry and exit of Control Cable. The equipment shall be mounted on panels and panel wiring shall be done at the back for inter connections. The temperature indicators shall be mounted at about 1600 mm from ground level. An 80 Watt, 230V, AC 50 Hz metal clad heater shall be provided in the Marshalling Box and will be controlled by a water proof rotary switch on the outside of the Marshalling box. The incoming and out going control cables shall enter from the bottom with gland plate not less than 450 mm from the base of the box. Care shall be taken to avoid ingress of water from the cable trench.

22.3 22.4

22.5

23

CONTROL CONNECTIONS, BOARD & FUSES:

INSTRUMENT

23.1

All cable and wiring shall be suitable for use under the conditions as specified at CI. 3. Any wiring liable to come in contact with oil shall be with oil resisting insulation. The bare ends of stranded wire shall be sweated together to prevent oil from creeping along the wire.

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WIRING,

TERMINAL

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23.2 23.3

23.4

23.5

23.6

23.7

24

The instrument and panel wiring shall be run in flexible PVC pipe or non rusting metal cleats of limited compression type. The box wiring shall be as per relevant IS. All wirings shall be stranded copper of 660V grade and size not less than 4 sq. mm for CT leads and not less than 2.5 sq mm for other connections. The panel wires and multicore control cable shall bear ferrules of white insulating material with indelible marking in black and as per relevant ISS. Same ferrule number shall not be used on wires in different circuits. Double ferrule may be provided where a change in number is required. Stranded wires shall be terminated with tinned ross Courtney terminals, clow washer or crimped tubular lugs. Separate washers shall be used for each wire. Wires shall not have joints between terminal points. Where apparatus is mounted on panel, all metal cases shall be separately earthed by copper wires or strip of not less than 2 sq. mm. The screen of screened pair of multicore cables shall be earthed at one end of the cable only. All terminal boards shall be of stud type & mounted obliquely towards the rear door and these boards shall be spaced not less than 100 mm apart. Suitable insulation barriers shall be provided between adjacent connections. No live metal shall be exposed at the back of terminal boards. All fuses shall be of HRC cartridge type fuses and links shall be properly labeled. MARKING: All transformers shall have the marking as per requirements of relevant IS.

25

PACKING: The packing may be in accordance with the tenderer’s standard practice but he should give full particulars of packing for approval of the purchaser. Special arrangements should be made to facilitate handling and to protect the projecting connections from damage in transit. The transformer shall be transported filled with oil. All parts shall be adequately marked to facilitate field erection. Boxes & crates shall be marked with the contract number and shall have packing list enclosed showing the parts contained therein.

26

26.1

FACTORY ASSEMBLY TESTS AND INSPECTION: The transformer shall be completely assembled and tested at factory. If the purchaser desires to depute his representative, all the tests performed by Firm’s Engineer shall be witnessed by him. Tests shall be performed in accordance with IS: 2026-1977,IS-8468-1977 & relevant IEC latest versions. All the reasonable facilities shall be provided by the supplier to the representative of the purchaser to witness the above tests. The supplier shall give sufficient advance intimation (at least 15 days notice) to the purchaser to enable him to depute his representative for witnessing the test. The supplier shall give works test certificates along with the inspection call. ROUTINE TESTS: All the transformers shall be subjected to the following routine tests at the manufacturer’s works. The tests are to be carried out in accordance with the details specified in IS: 2026-1977 /relevant IEC (latest versions). a)

Measurement of winding resistance.

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26.2

26.3 I.

II

b) Measurement of voltage ratio and check of polarity and phase relationship. c) Measurement of impedence voltage/ short circuit impedence (Principal tapping) and load loss. d) Measurement of no load loss and magnetizing current e) Measurement of insulation resistance. f) Separate source voltage withstand test. g) Induced over voltage withstand test. h) Tests on ‘on load tap changer’ as specified in Clause 17 & 18. i) Oil leakage, gas collection, oil surge and voltage test on gas and oil actuated relays. TYPE TESTS: Type Test certificates for the tests carried out on power transformer of similar specification from recognized Test House as per relevant IS/IEC shall be submitted alongwith the tender. The purchaser, however reserves the right to have the following tests conducted on one or more than one unit at the cost of supplier. The tenderers who don’t agree for free testing should indicate their charges for each test separately. a) Temperature Rise Test. b) Lightning Impulse Test. c) Short Circuit Test. d) Tan Delta Measurement & Capacitance of each winding to earth & between all windings together to earth. e) Measurement of Zero Sequence test. f) Dielectric test. g) Measurement of Voltage Ratio & voltage vector relationship. h) Measurement of Acoustic Noise Level i) Measurement of Insulation Resistance & winding resistance TANKS ROUTINE TEST: OIL LEAKAGE TEST: One of the completed Transformer completely filled with oil shall be tested for oil tightness by being completely filled with air / oil of viscosity not greater than that of insulating oil to IS: 335 at the ambient temperature and subjected to a pressure equal to the normal pressure plus 35 KN per m2 ( 5 Lb. Per sq. Inch.) measured at the base of the tank. This pressure shall be maintained for a period of not less than 12 hours for oil and one hour for air during which time no leakage shall occur. TYPE TEST: a) VACUUM TEST: One transformer tank of each size shall be subjected to the specified vacuum as in CI. 15.1.2. The tanks designed for full vacuum shall be tested at an internal pressure of 3.33 KN per m2 ( 25 mm of Hg.) for one hour. The permanent deflection of flat plates, after the vacuum has been released shall not exceed the value specified below without affecting the performance of the transformer: Horizontal length of flat plate Permanent Deflection in mm in mm Up to & including 750 5 751 to 1250 6.5 1251 to 1750 8 1751 to 2000 9.5 2001 to 2250 11 2251 To 2500 12.5 2501 To 3000 16 Above 3000 19

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b)

PRESSURE TEST: One transformer tank of each size shall be subjected to a pressure corresponding to twice the normal head of oil or to the normal pressure plus 35 KN per m2 (5 Lb. Per sq. inch.) which ever is lower measured at the base of the tank and will be maintained for one hour. The permanent deflection of flat plates after the excess pressure has been released shall not exceed the figure specified above.

27

28

29

STAGE INSPECTION: The purchaser reserves the right for stage inspection of one or all the transformers during the course of manufacture to ensure that the internal details are in accordance with the data / information supplied / G.T.P. ‘s as per Contract/P.O. ACCESSORIES AND FITTINGS: Each transformer shall be provided with the following in accordance with details to the extent these are specified in IS 2026-1977/relevant IEC: a) Inspection cover with lifting lugs b) Rating Plate c) Diagram Plate d) Two earthing terminals e) Lifting Lugs f) Jacking Lugs g) Conservator Tank with drain plug and oil filling hole h) Dehydrating Breather i) 1. Thermometer (dial type) with one pair of contacts for top oil over ` temperature alarm. 2. Thermometer (dial Type) with two pairs of contacts for winding over temperature Alarm & Trip & for On & OFF Motor Blower / Cooling fans. j) Thermometer Pockets k) One No. Magnetic oil level gauge mounted on conservator tank for main transformer tank with 3 positions marked as follow:Min -50 C, 300 C and Maximum 980 C for main tank. l) One No. Plain Sight Glass Oil Level Gauge for OLTC Tank with Min.& Max. Oil Level Markings. m) Oil filling hole with cap. n) Air release device. o) Pressure relief device p) i. Gas & oil actuated relay with alarm and trip contacts and shut off valves on conservator as well as main tank side for Main tank. q) ii -do- with one pair of trip contacts for OLTC tank also r) Filter valves (lower valve to be used as a drain valve) s) Terminal marking plate t) Marshalling box u) Necessary oil for the first filling v) Bottom mounting channel w) Flanged bi-directional rollers (four Nos.) x) Studs & pulling eyes in both directions. SPECIAL TOOLS: Any special tools required for erection and for maintenance work shall be provided alongwith each transformer.

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30.

Direct real time measurement of winding temperature through fiber optic technology30.1 Fibre optic based Temp. Measuring system:- In order to measure the hot adopt directly fiber optic based sensors are inserted in all the three winding at the hottest zones of the winding which are line and discs. 30.2 Gas based fiber optic sensor scheme shall consist of the following: a. Fiber optic sensor. b. Internal extension cable with TC connector. c. Optical Feedthrough. d. Transfer tank wall plate unit’s protective cover. e. External tuber optic extension cable with ST connectors. f. Single conditioner. 30.3 The sensor should have the following key features. i. Upto 8 measurement channels. ii. High linearly & Precise. iii. RS 232 & RS 485 serial O/P unit SCP/ & Modbus Protocol. iv. PLC optional contract for data acquisition & extended control capabilities. v. Relays & analog output available option. vi. Wall mount version with LCD screen display. The bidder shall have to confirm that this offer is inclusive of all the above features and shall indicate the ‘Make’ of this instrument in his offer clearly. 31. GUARANTEE / WARRANTEE The supplier shall be responsible to replace, free of cost, with no transportation or insurance cost to the Purchaser, up to destination, the whole or any part of the material which in normal and proper use proves the defective in quality or workmanship, subject to the condition that the defect is noticed within 78 months from the date of receipt of material in stores or 72 months from the date of commissioning whichever period may expire earlier. The consignee or any other officer of Nigam actually using the material will give prompt notice of each such defect to the supplier. The replacement shall be effected by the supplier within a reasonable time, but not, in any case, exceeding 45 days. The supplier shall, also, arrange to remove the defective within a reasonable period, but not exceeding 45 days from the date of issue of notice in respect thereof, failing which, the purchaser reserve the right to dispose of defective material in any manner considered fit by him (Purchaser), at the sole risk and cost of the supplier. Any sale proceeds of the defective material after meeting the expenses incurred on its custody, disposal handling etc., shall however be credited to the supplier’s account and set off against any outstanding dues of the purchaser against the supplier. The warranty for 72/78 months shall be one time. 32. DRAWINGS: 32.1 The manufacturer shall submit drawings in quadruplicate describing the details of equipment for approval and subsequently five complete sets of final drawings per transformer one of which shall be suitable for reproduction. 32.2` The following drawings shall be supplied as part of the tender: 1) General arrangement of Transformer

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2) 3)

Outline dimensional drawings of transformer & accessories. Drawings showing core, HV & LV windings with arrangements of insulation and terminal connections arrangement. 4) HV & LV Bushing and terminal connector drawings showing dimensions material and weights. 5) Schematic Control and wiring diagram for auxiliary equipment like O.L.T.C. Control gear, Marshalling Kiosk. Detailed write up for Schematic shall also be supplied. 6) Outline dimensional drawings of remote control cubical for O.L.T.C. showing various instruments/ fittings and terminal blocks. 7) General arrangement of Marshalling Box 8) Tap-changer phase diagram 9) Name Plate 10) Six copies of Instruction Books, erection and maintenance manuals per Transformer 33. SPARES: a. The Tenderer shall quote separately for the following spares. b. Complete set of coils for one limb of winding c. HV Bushings d. LV Bushings e. LV Neutral Bushings f. Plain oil gauge g. Oil and winding temperature indicator h. Set of Gaskets i. Pressure Relief valve 34. Schedule of Guaranteed and other Technical particulars be supplied as per Annexure “A” alongwith tender. 35. Deviation from specification should be clearly listed and brought out separately. 36.

CHALLENGE CLAUSE The material offered/received after the inspection by the authorized

inspecting officer may again be subjected to the test for losses or any other parameter from any Testing House/in-house technique of the Nigam & the results if found deviating un-acceptable or not complying to approved GTP's the bidder shall arrange to supply the replacement within thirty (30) days of such detection at his cost including to & fro transportation. In addition to this penalty @10% of cost of the inspected lot of material shall be imposed. This issues with the approval of Common Specifications Committee.

General Manager/P&D Cum-Member Secretary CSC UHBVN Panchkula

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ANNEXURE “A” SCHEDULE OF GUARANTEED AND OTHER TECHNICAL PARTICULARS. NOTE: I For the purpose of this specification the rated load shall be taken as 8 MVA. II. Particulars under guaranteed shall be clearly marked. 1. Name of the Manufacturer: 2. Normal continuous rating with ONAN cooling. 3. Normal ratio of transformer. 4. Phase Connections: a. HV winding. b. LV Winding. c. Vector Group Reference 5. Max. Temperature rise of oil over ambient air temperature of 500C. 6. Max Hot spot Temperature under normal full load conditions with Max. Yearly weighted ambient temperature of 320C. 7. Max. Temperature rise of winding by resistance over a Max. Ambient air temperature of 500C. 8. Temperature Gradient between oil and winding. 9. Calculated time constant of cooling system. 10. No Load loss at normal ratio, rated voltage and rated frequency without any tolerance. 11. Load loss at 8 MVA 12. a) Auxiliary Losses. b) No. of cooling fans 13 Impedance voltage at normal current and voltage at 750C average winding temperature at Tap No. 3. 14. Reactance voltage drop expressed as percent of rated voltage. 15. Efficiency at normal ratio, rated voltage, rated frequency and 750Caverage winding temperature at: a. Rated Load b. ¾ Rated Load c. ½ Rated Load 16 Regulation at rated load and at: a. Unity Power Factor. b. 0.8 Power Factor (Lagging) 17 Max Flux density at normal Voltage and frequency in: a. CORE. b. YOKE 18 Limit for over fluxing 19 Max Current Density at Continuous Maximum Rating in: a. HV Winding. b. LV Winding 20 Magnetising current and its power factor at normal ratio and frequency. 21 CORE: a) Whether core laminations are of cold rolled grain oriented silicon steel b) Insulator material of core laminations c) Detail of oil duct in core (Whether in or at right angles to the plane of core laminations). 22 Type of Winding

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24

25

26 insulated 27 28

29

a. HV Side winding b. LV Side winding Type of Insulation a. HV side winding b. LV side winding c. Between HV & LV Windings Rated short duration power frequency withstand test voltage on: a HV Winding b LV Winding c Neutral and of LV winding Rated lightning impulse with stand test voltage with 1.2/50 micro-second wave on a. HV Winding b. LV Winding Voltage to earth for which the star point shall be Details of special arrangement made to improve stress conditions. Details of Bushings a. HV side b. LV side c. Neutral Side i. Type & standard reference. ii. One minute dry with stand power frequency voltage kV ( rms) iii. One-minute wet withstand Power frequency voltage kV ( rms) iv. Impulse with stand test voltage with 1.2/50 micro sec. Wave kV ( Peak) v. Creepage distance in air vi. Maximum current rating of the Bushing both HV & LV vii. Recommended gap setting viii. Assembled weight of bushing(Kg) Detail of OLTC gear a) Make & type designation b) Rated Voltage c) Rated Current d) Step Voltage e) No. of Steps f) Whether provided with local manuals, local electrical and removed electrical control? g) Whether provisions of parallel operation exists? h) Detail of protective device provided on OLTC i) Auxiliary supply details j) Approx. over all dimensions k) Approx. over all weight l) Approx. quantity of oil

30 31

Type & Details of winding Temperature indicator. Type & Details of Transformer oil Temperature

32

i) Type & Details of main Buchholz relay

indicator

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33

ii) Type & Details of OLTC Buchholz relay. Weight of copper to be used in the complete

transformer 34 35 36 37 38

39 40 41

a) Weight of core (Kg) b) Weight of Winding (Kg) Weight of Oil in Transformer (Kg) Weight of Transformer complete with oil and accessories (Kg) Weight of complete Transformer arranged for transport or the heaviest packet if broken down (Kg) Dimensions of transformer a) Over all length b) Over all breadth c) Max. height to top of conservator. Volume of conservator tank between the highest & lowest indicated levels. Free space required at top for removal of bushings. List of reference of similar transformer already in

service 42 43 44 45

NOTE:

Deviation from this technical Specification No. of years for which the design offered has been in commercial use. Noise level when energised at normal voltage and normal frequency at no load. Shipping details: i) Parts detached for transport ii) Weight of heaviest package (Kg) iii) Weight of other heavy packages (Kg) iv) Dimensions of largest package a. Length in mm. b. Breadth in mm. c. Height in mm.

The transformer oil shall comply in all respects with the requirement of IS:335.

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