SPECIFICATION FOR 11 KV CLASS, 24/15.7, 30/19.7 & 45/29.5 AMPS SPECIAL DESIGN TRANSFORMERS. 1. SCOPE: This specification covers design, manufacture, testing and supply of 6.64/10.12 KV 24/15.7, 30/19.7 & 45/29.5 Amps special design transformers. 2. The supplier shall have to produce an attested copy of the License of manufacturing the special Design Transformer from the patent holder of the concept (GUVNL). 3.1 AMBIENT CONDITIONS : i. Maximum ambient temperature in shade : 45 C ii. Max. weighted average ambient temp. : 40 C iii. Maximum temperature under sun : 55 C iv. Minimum ambient temperature : 0 C v. Maximum relative humidity : 95% vi. Average thunder storm days / annum : 15 vii. Average rainy days per annum : 90 viii. Average annual rail fall : 750/800Ml ix. Number of months of tropical monsoon : 3 x. Maximum wind pressure : 150 Kg/M 2 3.2 INSTALLTION : Outdoor either pole mounted, hung or platform mounted. 3.3 SYSTEM : 11KV CLASS Single Phase, 50 Hz + 3% Voltage Class : 11000 volts Voltage variation : + 5% BIL : 75 KV peak 4. APPLICABLE STANDARDS : Unless otherwise specifically stated in this specification the transformers shall conform to the following standards considering this as single phase transformers. IS 2026 Part I, II, III & IV IS 3639 1966 IS-6600/1972 IS 3347 IS 2099-86 IS 5621-80 IS 7421-88
5. MATERIAL : 5.1 INSULATION : The insulation of wire / strip, inter-layers between two winding and to earth shall be of class A. Wherever wood is used it shall be well-seasoned and dry. Wire/strips shall be DPC. So far as paper, press Boards are used they shall be of reputed makes (Appendix A) and conform to ISI. 5.2 WINDING : Transformers shall have Copper windings except below 30 Amps 11 KV Class which shall have Aluminum winding. 6. STANDARD RATINGS : 6.1 The Standard continuous ratings are 24,30 & 45 Amps. 6.2 No load voltage ratio : 6.64/10.12 KV for 11 KV class. 7. FITTINGS : The following standard fittings shall be provided : i) Phase R should be identified as it is ground phase with symbol 1 ii) iii) iv) The Earthing terminals with symbol 1 with tinned copper lugs. Lifting lugs of adequate size for lifting the transformer and lifting the active parts assembly separately. The lifting lugs shall be made from minimum 8mm thick MS Plate with adequate base. Rating and terminal marking plates. The figures shall be etched and not anodized. The plates shall be riveted on oil level gauge side. v) Thermometer pocket for all ratings. The tube of thermometer pocket shall vi) vii) remain immersed in oil to the extent of at least 100mm. Oil conservator tank (a) filling hole and plug on the top. (b) Oil level gauge and (c) Breather of having aluminum die cast body and silica gel 0.5 Kg. Breather pipe shall be provided. Position of oil level gauge shall be towards rating and terminal marking plate. A drain cum sampling valve of 32 mm dia (1.1/4 Bsp) with plug on top cover of the transformers for drawing sample etc.
8. TECHNICAL PARTICULARS : 8.1 LOSSES AND IMPEDANCE : The no-load loss, load loss and impedance value for transformers shall be as under. The tolerance for percentage impedance shall be + 10% No-load current No load losses at rated voltage & frequency Load losses at 75 C Rating Wind- Impedance ing at 75 C Y-B Short Y-B Short A. a) 24 A/11KV Al. 1% 170 W 1250 W 2.5 % 7.64 % b) 24 A/11KV Cop. 1% 160 W 1140 W 2.5% 7.64 % B. 30 A/11KV Cop. 1% 180 W 1340 W 2.6% 7.75 % C. 45 A/11KV Cop. 1% 230 W 1840 W 2.6% 7.75 % Note : In actual execution if a unit records higher losses i.e. beyond permissible tolerance, the same will be rejected. 8.2 TEMPERATURE RISE LIMIT : a) Temperature rise in top oil by thermometer. : 40 C Max. b) Temperature rise in winding by resistance method : 50 C Max. 9. BUSHING AND METAL PARTS : The HV porcelain bushings and metal parts shall be as per following IS: IS 5621/80 IS 7421/88 IS 2099/86 IS 3347 (Part III/ Sec. I / 1988) IS 3347 (Part -I/ Sec. I / 1979) IS - 3347 (Part III/ Sec. II / 1982) The metal parts shall be made from drawn or rolled quality tinned brass or copper of electro plated. 10. TRANSFORMER OIL : The Transformer oil to be supplied as first filling of transformer shall comply with IS-335/1987 11. TRANSFORMER TANK : 11.1 The tank will be made of prime quality MS sheet of thickness stated below with necessary stiffener to withstand the pressures built in during the expansion of oil due to temperature rise.
11 KV Rating Minimum thickness of plate in mm For sides For Top & Bottom 24 Amps 3.15 5 30 Amps 4.50 5 45 Amps 4.50 5 11.1 The exterior of the transformer tank and other ferrous fittings shall be thoroughly cleaned, scraped/ sand blasted and given a priming coat and two finishing coats of durable oil and weather resistant paint of light admiralty Gray conforming to colour code No. 697 of IS-5/1978. 11.1.2 Inside of the tank shall be thoroughly cleaned/scrapped/sand blasted and coated with oil resistant paint or epoxy coat or phonemic / melamine varnish coat. These protective coats shall not contaminate the oil due to due to peeling or decomposition during the life of the transformers. 11.1.3 All the screws, bolts and nuts exposed to atmosphere shall be hot dip galvanized if diameter is 12 mm or more. They shall be either electro galvanized or hot dip galvanized if diameter is less than 12 mm. The screws and clamps for fixing HV bushing shall also be electro-galvanized. The inside dimension of the tank and shape to clearly indicated in the drawings. Only positive 5% tolerance will be allowed in actual fabrication of tank, no negative tolerance will be allowed. 12. CORE : 12.1 CORE MATERIALS : Non edging, oxide film coated CRGO laminations of prime quality shall be used as core material. 12.2 CONSTRUCTION : 12.2.1 Core shall be so constructed that there are adequate vertical cooling ducts to cool the core. The core when vertically standing shall be rigid. Insulated core / type bolts shall be provided wherever necessary. 12.2.2 The core shall be so constructed that the air-gaps in all the limbs are identical. 12.2.3 FLUX DENSITY : The flux density shall be so selected that over fluxing is limited to 5% over voltage (Max. 1.9 Tesla)
12.2.4 NO LOAD CURRENT : The percentage no load current shall be as under : Minimum percentage no load current at Normal voltage 5% over voltage 24 Amps 1 2 30 Amps 1 2 45 Amps 1 2 13 WINDING : This is generally of round wire and coils are in form of packets and number of coils are connected in series to achieve the necessary voltage ratio. The coils assembly should be sand with type The number of coils per limb shall depend upon the necessary cooling surface and the mechanical strength. 13.1 CONNECTION : The coil series connections shall be crimped / brazed or screw connected after thoroughly cleaning the ends. The joint in the coil shall be buttwelded. However the brazing of copper wire shall be acceptable. All connections shall be insulated by paper wrapping, leads shall be properly supported and secured in place avoiding accidental short circuit. Coils supports shall be of rigid non-compressible insulating material. 14. ASSEMBLY : The core and coil assembly shall be supported by press channels and the coils fully pressed by the tie rods. Guides on all the four sides shall be provided to prevent shifting of the active parts and thereby accidental touching the tank. 15. DRAWING : The Tenderer shall submit the following drawings along with offer. 15.1 GENERAL ARRANGEMENT : G.A. drawing showing fittings shall be furnished. The details of cooling system, viz. Number of cooling tubes radiators, their size and position on tank must be very clearly indicated. The details on drawing shall be in line with G.T.P.
16. TERNIMAL ARRANGEMENT : 17. The HV bushings shall be of approved makes. (please refer Appendix A for approved suppliers) 17.1 TERNIMAL ARRANGEMENT : (a) Phase to phase (b) Phase to earth H.V. 11 KV 255mm 205mm 18. ROUTINE TESTS : All routine tests as per Appendix C attached. 19. DEVIATION FROM SPECIFICATION : There shall be no deviatio0n from these specifications, norms and procedures. However, if tenderer to do so, the same shall be indicated only of the guaranteed technical particulars. 20. PACKING : The packing shall be robust enough for the rough handling which is normal during rail / road transport. The details of the packing are however, left kto the discretion of the manufacturer. 21. GUARANTEED TECHNICAL PARTICULARS (GTP) : Tenderer should submit the details in Appendix B attached. 22. ESTING INSTRUMENTS : The class of accuracy of instruments shall be as under : (a) Watt meters - 0.2 class or better (b) Voltmeter & Ammeter - 1.0 class or better 23. GUARANTEE & WARANTEE : The guarantee period shall be 12 months from the date of supply for the manufacturing defect. If the transformer fails during guarantee period the supplier should arrange to repair the failed transformer with in one month on receipt of GP failed transformer at their works. To and fro arrangement shall be made by the Company. 24. TESTING OF TRANSFORMER OIL : The sample of transformer oil to be drained from one of the transformer selected randomly from the lot offered for inspection and the test results must match as per IS 335 / 1987.
A P E N D I X A APPROVED SUPPLIERS FOR VARIO9US MATERIALS ARE AS UNDER: (1) Bushings : H.V. 1. BEPCO 2. JAYASHREE 3. W.S.I. 4. ASSOCIATED PORCELAIN (Only 11KV) 5. SESHASAYEE 6. JAIPUR GLASS (Only 11KV) 7. LUSTER CERAMICS NOTE : Embossing showing the manufacturer s name should be clearly visible, even after fixing the same on transformer. (2) Insulation Paper : (1) Triveni Tissus or any other reputed make (2) Any other reputed imported make (3) Insulating Materials : (1) Senapati Whitely (2) Raman Boards (3) Shalimar (4) Permali-Wallace (5) Wipro
A P P E N D I X B Manufacturers name and address : G.T.P. Sr.No. Particulars Confirmation 1 It shall be conventional 2. Voltage H.V. 11000 3. Impulse withstand voltage of 75 KV Peak for 11 KV Class. 4. Transformers shall Copper windings except below 30 Amps 11 KV Class which shall have Aluminum winding. 5. Insulation Class A 6. a) Top oil temperature rise limit of 40 C by thermometer with feeding of guaranteed load loss plus tolerance converted to 75 C and guaranteed no load loss plus tolerance. b) Temperature rise limit of 50 C of winding by resistance method. 7. LOSSES & IMPEDANCE : 7.1 Maximum no load current & losses at 50 HZ and rated voltage Rating Winding No-load current No load losses at rated voltage & frequency A. a) 24 A/11KV b) 24 A/11KV Al. Cop. 1% 1% 171 W 160 W B. 30 A/11KV Cop. 1% 180 W C. 45 A/11KV Cop. 1% 230 W
7.2 Maximum load losses at full load in watts & maximum percentage impedance at 75ºC Rating Winding Load losses at 75 C Impedance at 75 C Y-B Short Y-B Short A. a) 24 A/11KV b) 24 A/11KV Al. Cop. 1250 W 1140 W 2.5 % 2.5% 7.64 % 7.64 % B. 30 A/11KV Cop. 1340 W 2.6% 7.75 % C. 45 A/11KV Cop. 1840 W 2.6% 7.75 % 7.3 Operating flux density at 50 Hz : 1.69 Tesla Max 7.4 Percentage no/load current (Max) at normal voltage and frequency a) 24 Amps 1 b) 30 Amps 1 c) 45 Amps 1 7.5 ----- do ------- but at 105% normal voltage a) 24 Amps 2 b) 30 Amps 2 c) 45 Amps 2 8. Pressure test of tank as per IS-1180 Part - I 9. Outside paint Light admiralty Grey as per IS 5 colour code 697. 10. Transformer oil shall conform with IS 335/1987 11. Only GUVNL approved make of HV Bushing shall be used. 12. Minimum external clearance as under shall be maintained. 11 KV (a) HV Phase to phase 255mm (b) HV Phase to earth 205mm 13. Thickness of sheet metal in mm for tank shall be following minimum Ratings Sides Top & Bottom a) 24 Amps 3.15 5 b) 30 Amps 4.50 5 c) 45 Amps 4.50 5