PART 1: GENERAL 1. SCOPE This specification covers the design, engineering, manufacture, testing, supply, delivery, offloading and performance requirements of 11/0.433kV distribution transformers for outdoor use in the networks of the WESCO. The transformers shall be double wound, three phase, oil iersed with ONAN cooling. The ratings required are 100kVA, 250kVA and 500kVA. The transformer shall conform in all respects to highest standards of engineering, design, workmanship, this specification and the latest revisions of relevant standards at the time of offer and the Purchaser shall have the power to reject any work or material, which, in his judgement, is not in full accordance therewith. 2. STANDARDS Except where modified by this specification, the transformers shall be designed, manufactured and tested in accordance with the latest editions of the following standards. The Bidder may propose alternative standards, provided it is demonstrated that they give a degree of quality and performance equivalent to or better than the referenced standards. Whether to accept or reject any alternative standard shall be adjudged by the Purchaser. The Bidder shall furnish a copy of the alternative standard proposed along with the bid. If the alternative standard is in a language other than English, an English translation shall be submitted with the standard. In the case of conflict the order of precedence shall be 1) IEC or ISO Standards, 2) Indian Standards, 3) other alternative standards. IEC / ISO Indian Subject Standard IEC 71 Insulation Coordination. IEC 76 IS 2026 Power Transformers. IS 1180-Part 2 Outdoor Three Phase Transformers up to 100kVA 11kV - Sealed Type IEC 137 IS 2099 Bushings for Alternating Voltages above 1000 V. IEC 156 Method of determining Electric Strength of Insulating Oils. IEC 296 IS 335 Specification for Unused Mineral Insulating Oils for Transformers and Switchgear. IS 6792 Method of determination of electric strength of insulating oils. IEC 354 IS 6600 Loading Guide for oil iersed Transformers IEC 437 Radio Influence Voltage Measurement. IEC 551 Determination of Transformer and Reactor Sound Levels. IEC 616 Terminal and Tapping markings for power transformers. IEC 722 Guide to the Lightning and Switching impulse testing of Power Transformers and Reactors. ISO 1460/BS 729 IS 2629 Galvanizing. - 1 -
This list is not to be considered exhaustive and reference to a particular standard or recoendation in this specification does not relieve the Supplier of the necessity of providing the goods complying with other relevant standards or recoendations. 3. SERVICE CONDITIONS The service conditions shall be as follows: maximum altitude above sea level 1,000m maximum ambient air temperature 50 C maximum daily average ambient air temperature 35 C minimum ambient air temperature 5 C maximum temperature attainable by an object exposed to the sun 60 C maximum yearly weighted average ambient temperature 32 C maximum relative humidity 100 average number of thunderstorm days per annum (isokeraunic level) 70 average number of rainy days per annum 120 average annual rainfall 150 cm maximum wind pressure 94.3 /m² 4. SYSTEM CONDITIONS The equipment shall be suitable for installation in supply systems of the following characteristics: Frequency 50Hz Nominal system voltages 33 kv 11 kv 400/230 V Maximum system voltages: 33kV System 36 kv 11kV System LV System 12 kv 476 V - 2 -
Minimum LV voltage 340 V Nominal short circuit levels: 33kV System 25 ka 11kV System 12.5 ka Insulation levels: 1.2/50 µs impulse withstand (positive and negative polarity): 33kV System 170 kv 11kV System 75 kv Power frequency one minute withstand (wet and dry) 33kV System 70 kv 11kV System LV System 28 kv 3 kv Neutral earthing arrangements: 33kV System solidly earthed 11kV System LV System solidly earthed solidly earthed PART 2: TECHNICAL 5. TYPE OF TRANSFORMER The transformers shall be double wound, three phase, oil iersed, 11/0.433kV, 50 Hz with natural oil and air cooling (ONAN). The design of the tank, fittings, bushings, etc. shall be such that it will not be necessary to keep the transformer energised to prevent deterioration as the transformers may be held in reserve, outdoors, for many years. 6. RATINGS The following ratings are covered by this specification: 100kVA; 250kVA; 500kVA - 3 -
All of the above are required with HV and LV bushing terminations. In addition, some 500 kva transformers are required with HV and LV outdoor cable terminations. The transformer shall be capable of supplying a continuous load equal to its kva rating, under the following conditions: the rated secondary voltage held constant by increasing the primary voltage to allow for regulation at all tap positions; constant flux regulation; continuous steady load; design maximum ambient air temperature of 50 C; 55 o C average winding temperature rise and 50 C top oil temperature rise for conventional breathing transformes 55 o C average winding temperature rise and 45 C top oil temperature rise for sealed type transformes The transformer may be overloaded during emergency up to 150 of its continuous rating in accordance with IEC Publication 354 or IS 6600. Bushings, tap changer and other current-carrying parts shall also be designed for this condition. 7. VOLTAGE RATIO AND TAPPING RANGE The transformers shall have the following ratio and tapping range: the nominal voltage ratio shall be 11,000/433V; tolerance on the voltage ratio shall be ±0.5; for 100kVA transformers a tap-changer is not required. for transformers rated 250 kva and above, taps shall be provided in the high voltage winding for voltage variation from Tap 1 (+2.5) to Tap 4 (-5.0) in equal steps of 2.5. Tap No.2 shall be the principal tap. The bidder shall state in the technical schedule, the percentage regulation at full load, power factor 1.0 and at full load, power factor 0.85 lagging. The primary voltage variation is based on a winding temperature of 75 C. 8. IMPEDANCE VOLTAGE The guaranteed value of impedance voltage measured at 75 C and on the principal tap (subject to a tolerance of +10 and no negative tolerance, as specified in IEC 76 / IS 2026) shall be 4.0 for all units. 9. SHORT CIRCUIT RATINGS The transformer shall be capable of withstanding the thermal and dynamic effects of short circuits, as specified in IEC 76-5: Ability to withstand short circuits. - 4 -
Each transformer shall be capable of withstanding for 2 seconds a bolted metallic short circuit on the terminals of either winding with rated voltage on the other winding and the tap-changer in any position. If short circuit tests have been carried out on the particular design of transformer offered, the test results shall be supplied with the bid. 10. VECTOR GROUP The transformers shall be connected delta-star, in accordance with vector group reference Dyn11 of IEC 76 / IS 2026. The LV neutral shall be brought out to a terminal bushing, which shall be identical to the phase bushings in all respects. 11. LOSSES No-load loss and load loss values are to be submitted and losses will be capitalized at the rates and added to bid price for the purpose of comparing tenders. Losses shall be measured during routine tests. In the event of either the no-load loss or load loss exceeding their guaranteed values, as stated in the technical data schedules, the relevant rate above shall be applied to the excess and the resulting amount shall be deducted from the Contract Price. Transformers are likely to be rejected if losses exceed the declared values by more than 10. 12. FLUX DENSITY The flux density at any point of the magnetic circuit when the transformer is connected on the center tap and operating at normal voltage and frequency shall be stated and shall not exceed 1.6 Tesla. The transformer must be capable of operating at 10 over voltage at frequency of 48 Hz without saturation occurring or the flux density exceeding 1.9 tesla. 13. INSULATION LEVELS The following insulation levels as defined in IEC 76-3 / IS 2026 Insulation levels and dielectric tests shall apply: Basic Impulse voltage Level (kv) (1.2/50 mic.sec. wave ) Power Frequency voltage withstand level, Wet and Dry (kv) Table 2: Transformer insulation level HV Winding LV Winding 75 Not Applicable 28 3 Bushings and terminals shall be adequate for the winding insulation tests, and shall flash over externally before puncture or internal failure can occur. 14. NOISE LEVEL The average noise level of the transformers shall not exceed the following values: - 5 -
100kVA transformers 51 db 250 kva and 500 kva transformer 57 db The measurements shall be carried out in accordance with IEC 551 at a distance of 300 from the envelope of the transformer. 15. RADIO INFLUENCE VOLTAGE The maximum radio influence voltage shall be 250µV, measured as specified in IEC 437. 16. TAP CHANGING CHARACTERISTICS Tap changing and the tap changing mechanism shall have the following characteristics: tap changing shall be carried out with the transformer off circuit; tap positions shall be numbered as follows: Tap 1 + 2.5 Tap 2 0 (Principal Tap) Tap 3-2.5 Tap 4-5.0 provision shall be made for locking of the tap switch handle by using a padlock with 6 diameter hasp to be furnished by Purchaser; and tap change handles shall be fitted with gasketed covers, so that sealing of the transformer under normal conditions is independent of the switch shaft gland. CORE AND WINDINGS The core shall be constructed from high grade, non-ageing, cold rolled grain oriented silicon steel laminations or superior material. The core and winding shall be capable of withstanding shocks during transport, installation and service. Provision shall be made to prevent movement of the core and windings relative to the tank during these conditions and also during short circuits. The design shall avoid the presence of pockets which would prevent the complete emptying of the tank through the drain valve. 16.1. Windings The winding insulation shall be free from insulating compounds which are liable to soften, ooze out, shrink or collapse. It shall be non catalytic and chemically inert in transformer oil during normal service. The stacks of windings are to receive adequate shrinkage treatment. The windings and connections are to be braced to withstand shocks during transport, switching, short circuit or other transient conditions. The windings shall be uniformly insulated and the LV neutral points shall be insulated for full voltage. The winding conductor shall be of electrolytic copper. As an alternative, however, aluminium winding conductor may be offered for sizes up to 100 kva. The current density shall not exceed 2.5 Amps per sq. for copper, or 1.5 Amps for aluminium at normal full load current. - 6 -
17. BUSHINGS AND TERMINATIONS 17.1. Bushings Bushings shall be of the outdoor type and easily replaceable. Cemented in types will not be acceptable. They shall be sufficiently robust to withstand normal transport and erection hazards and shall conform to IEC 137 / IS 3347 and 2099. All bushings shall have a minimum creepage distance of 25 /kv and shall have a continuous rating of 200 of the transformer rating. The protected creepage distance shall not be less than 50 of the total. The following minimum 11kV clearances shall be provided : Enclosed External Phase to phase 127 255 Phase to earth 76 140 The 11 kv bushings of transformers shall be provided with a bi-metallic terminal connector or suitable device to receive 25-100 sq.. AAAC or ACSR conductor directly without any bi-metallic action. The secondary bushings of 100kVA shall be fitted with non ferrous threaded terminals. With the exception of brass the terminals shall be protected from atmospheric deterioration by suitable tinning or by some other approved coating. For transformers of rating 250kVA and higher the LV bushings shall be fitted with terminal plates. The number of 17 diameter holes to be drilled in these plates depends on the size of transformer and shall be : kva Rating No. of Holes 250 2 500 3 The terminals are to be supplied with one 16 bolt, one conic spring washer, one matching flat washer, one nut and one lock nut for each hole in the terminal plate. 17.2. Bushing Labels The HV bushings shall be labelled U, V and W and the LV bushings u, v, w and n. Marking letters shall be at least 12 high. The means of marking shall be either: engraved metal plate; or etched anodized aluminum. Phase identification by adhesive stickers shall not be acceptable. If labeling is to be carried out on the tank, it is preferred that one plate be used rather than individual markings for each phase, in order to prevent incorrect phase markings. Labels shall conform to the requirements of the section on Labels in this specification. 17.3. Cable Terminations Some 500kVA transformers will be required with HV and LV cable terminations. These transformers are to be fitted with weatherproof cable entry boxes suitable for connection of the following sizes of cables : - 7 -
High Voltage Side Low Voltage Side Transformer Size ( kva ) Cable Size Range ( sq. ) No. of Cables per phase Cable Size ( sq. ) No. of Cables per phase No. of Cables neutral 500 25-70 Al XLPE 1 300s Al PVC 3 3 Type of cable Three core cable with steel armour Single core cable with out armour The design of the cable boxes shall be such that all tests can be carried out on the transformer in the factory and dielectric tests can be carried out on the cable on site, simply and without the need for complicated procedures. The 11kV cable box must be suitable for bolted heat shrink terminations in air. 17.4. Earthing Terminals All transformers shall be provided with two earthing terminals comprising an M12 ISO metric bolt and nut which shall be non ferrous. It shall include a spring washer and a lock washer. 18. TANK FABRICATION Transformers shall have bolted tank covers and may be either of the sealed type, or non-sealed type. Nonsealed transformers may be designed with or without conservators. Transformer tanks of all types shall be designed so that the completed transformer can be lifted and transported without permanent deformation or oil leakage. Stiffeners provided for rigidity should be so designed that there is no accumulation of water. The tank shall be fabricated of mild steel with minimum thickness of 3. Top and bottom covers of the tank shall have a minimum thickness of 5. Thickness below this value will be considered only in exceptional cases, such as where superior material or special protective finishes are offered. The bidder shall provide full information about any such special material or finish, including any field experience. The transformer tank and the top cover shall be designed in such a manner as to leave no external pockets in which water can lodge, or any internal pocket where air/gas can accumulate. All sealing washers/gaskets shall be made of oil and heat resistant nitrile rubber or neoprene bonded cork seals suitable for temperature as stipulated in this specification. Surfaces at gasketed joints shall be such that an even face is presented to the gasket, thereby eliminating the necessity for the gasket to take up surface irregularities. All pipes, radiators, stiffeners or corrugations which are welded to the tank wall shall be welded externally and shall be double welded wherever possible. All welds shall be stress relieved. 18.1. Pressure Relief Device Transformers of 250 kva and above shall be fitted with a pressure relief device in the form of explosion vent or pressure relief valve. The tenderer shall state the pressure at which it is designed to operate. - 8 -
18.2. Oil Level Gauge A suitable oil level gauge shall be fitted on all types of transformer and so located that it can be easily read from ground level. The gauge shall be graduated for temperatures of 0 C, +45 C and +90 C. Where a conservator tank is fitted the gauge shall be on the conservator. 19. CONSERVATORS AND BREATHERS. The conservator tank shall be so designed and located as to eliminate any trapping of air in the transformer or pipe work. It shall be inclined at an angle of about 5 degrees to the horizontal towards the drain plug and the pipe connecting the main tank to the conservator should project about 20 above the bottom of the conservator so as to create a sump for the collection of impurities. Minimum oil level corresponding to 0 C shall be well above the sump level. All transformers shall be fitted with a silica gel breather of weatherproof design at a convenient height with oil seal at the bottom to isolate the silica gel from the atmosphere. The breather shall be connected to the conservator tank. 20. FITTINGS The following standard fittings shall be provided : rating, diagram and terminal marking plate. two earthing terminals lifting lugs pressure relief device / explosion vent as required silica gel breather (for all non-sealed transformers) filling and drain / sampling plugs (note that for transformer sizes up to 100kVA, a single drain / filling plug shall consist of a 20 pipe inside the transformer tank, starting from the bottom and projecting to the top cover with a hermetically sealed / welded plug). a magnetic or prismatic oil level gauge for all transformers. The fittings and accessories listed are indicative only and any other fittings and accessories which are generally required for satisfactory operation of the transformer are to be provided without any extra cost. 21. SURGE ARRESTER ATTACHMENTS Transformers shall be fitted with means of attaching a surge arrester support bracket, consisting of brackets or extensions to the cover plate. These shall be located opposite each HV bushing and shall be drilled with holes of 13 diameter for fixing the arrester brackets. The final arrester position must provide a nominal 100 clearance between bushing and arrester. 22. TRANSFORMER OIL The transformers shall be supplied filled with class 1 mineral oil conforming to IEC 296 or IS 335 whichever is more stringent. The complete first filling shall be of new oil free from inhibitors and additives. The dielectric strength of the oil shall not be less than 60kV when tested in accordance with IS 6792, 1972. If an anti-oxidant inhibitor is recoended, its use shall be subject to the purchaser s approval. - 9 -
23. RATING AND CONNECTION PLATE Each transformer shall be provided with a rating plate of weatherproof material showing the following items indelibly marked: type of transformer; standard to which it is manufactured (preferably IEC 76); manufacturer's name; transformer serial number; year of manufacture; rated frequency in Hz (50); rated voltages in kv (11/0.433); Number of phases (3); rated power in kva; type of cooling (ONAN); rated currents in A; vector group symbol (Dyn11); 1.2/50µs wave impulse voltage withstand level in kv; power frequency withstand voltage in kv; impedance voltage at rated current and frequency in percentage; load loss in kw at rated current; no-load loss in kw at rated voltage and frequency; continuous ambient temperature at which ratings apply in C (45); top oil and winding temperature rise at rated load in C; winding connection diagram; total weight in ; volume of oil in litres; weight of core and windings in ; and name of the purchaser (Grid Corporation of Orissa Ltd.). The rating plate shall conform to the requirements of the section on Labels in this specification. 24. MOUNTING ARRANGEMENT The underbase of all transformers shall be provided with two 75 x 40 channels, 460 long with holes of 14 diameter at a centre to centre distance of 415 to make them suitable for fixing on a platform or plinth. - 10 -
25. SURFACE TREATMENT The transformer tank and accessories shall be adequately protected against corrosion. The inside of the tank shall be painted with an approved oil resisting varnish. External surfaces shall be painted as specified in the section on Surface Treatment in this specification, or to a superior standard. Any alternative surface treatment shall be subject to approval of the Purchaser. An alternative quotation shall be made for the external surfaces of the transformer tank and its steel attachments to be hot dip galvanised as specified in the section on Surface Treatment of this specification. In the case of transformers rated 100kVA and higher, the galvanising shall be followed by one coat of weatherproof enamel paint to a minimum thickness of 30µm. The colour shall be grey, colour No. 631 of IS 5. Sufficient pretreatment of the zinc surface should be carried out as necessary in order to guarantee long life adhesion. 26. SUPPRESSION OF HARMONICS. The transformer shall be designed with attention to the suppression of harmonic voltages, especially the third and fifth. 27. TESTS 27.1. Routine Tests Routine tests shall be carried out on all transformers and the tests shall be conducted in accordance with IEC 76 / IS 2026 where this is applicable. In addition tank tests in accordance with IS:1180 Part 2 shall be carried out. The following routine measurements and tests shall be carried out: a) measurement of winding resistance at principal tap and two extreme taps; b) voltage ratio measurement and check of polarity and vector group at all tap positions. Bushing positions shall have permanent markings at this stage of production; c) measurement of impedance voltages /short circuit impedance at rated current and frequency at principal tap; d) measurement of load loss at full load and 75 C; e) measurement of no-load loss and no-load currents at full, 90 and 110 voltages; f) induced overvoltage withstand test: 22kV for 60 sec on the HV windings; g) separate source voltage withstand tests on HV and LV windings: h) air pressure test for sealed transformers. ( IS:1180 Part 2) i) Magnetic balance test. j) Polarization Index test. Index shall be not less than 1.5. k) oil leakage test: The criterion of leakage shall be discoloration by oil of whitewash applied externally to suspected parts at an oil temperature of 90 C or other method approved by the purchaser; l) galvanising tests, where applicable. Bushings and oil shall be subject to the following routine tests. m) Bushing routine tests: in accordance with IEC 137/IS 3347; - 11 -
n) oil dielectric and moisture content test: conforming to IEC 156 or IS 335. Routine test certificates shall include in addition to the test results, the purchaser's order number, the transformer serial number, outline drawing number and transformer kva rating. 27.2. Type Tests The measurements and tests shall be carried out in accordance with the standard specified in each case in table 6 below: Table 6: Transformer type tests Type Test Standard Temperature Rise Test IEC 76/IS 2026 Impulse Voltage Withstand Test, Including Full Waves and Chopped Waves as listed below IEC 76/IS 2026 Noise Level Measurement IEC 551 Short Circuit Test. IEC 76 / IS 2026 Air Pressure Test ( Sealed type transformers only) IS:1180 Part 2. In accordance with IEC 76-3 the following sequence of impulses shall be applied: one full wave at 50 BIL; one full wave at 100 BIL; one chopped wave at 50 BIL; two chopped waves at 100 BIL; and two full waves at 100 BIL. PART 3 GENERAL PARTICULARS AND GUARANTEES 28. COMPLIANCE WITH SPECIFICATION The transformers shall comply in all respects with the requirements of this specification. However, any minor departure from the provisions of the specification shall be disclosed at the time of tendering in the Non Compliance Schedule in Part 3 of this document. The mass and dimensions of any item of equipment shall not exceed the figures stated in the Schedules. 29. COMPLIANCE WITH REGULATIONS All the equipment shall comply in all respects with the Indian Regulations and acts in force. The equipment and connections shall be designed and arranged to minimise the risk of fire and any damage which might be caused in the event of fire. - 12 -
29.1. Inspection and Testing The Purchaser shall have free entry at all times, while work on the contract is being performed, to all parts of the manufacturer's works which concern the processing of the equipment ordered. The manufacturer shall afford the Purchaser without charge, all reasonable facilities to assure that the equipment being furnished is in accordance with this specification. The equipment shall successfully pass all the type tests and routine tests referred to in Clause 42, Part 2 and those listed in the most recent edition of the standards given in Clause 2, Part 1 of this specification. The Purchaser reserves the right to reject an item of equipment if the test results do not comply with the values specified or with the data given in the technical data schedule. Type tests shall be carried out at an independent testing laboratory or be witnessed by a representative of such laboratory or some other representative acceptable to the Purchaser. Routine tests shall be carried out by the Supplier at no extra charge at the manufacturer's works. Type tests may be dispensed with at the Purchaser's discretion if the Supplier furnishes evidence to the Purchaser's satisfaction that the relevant tests have already been performed on identical equipment. In this case test certificates shall be submitted with the bid for evaluation. The Purchaser may witness routine and type tests. In order to facilitate this, the Supplier shall give the Purchaser a minimum of four weeks notice that the material is ready for testing. If the Purchaser does not indicate his intention to participate in the testing, the manufacturer may proceed with the tests and shall furnish the results thereof to the Purchaser. Full details of the proposed methods of testing, including connection diagrams, shall be submitted to the Purchaser by the Supplier for approval, at least one month before testing. All costs in connection with the testing, including any necessary re-testing, shall be borne by the Supplier who shall provide the Purchaser with all the test facilities which the latter may require, free of charge. The Purchaser shall have the right to select the samples for test and shall also have the right to assure that the testing apparatus is correct. Measuring apparatus for routine tests shall be calibrated at the expense of the Supplier at an approved laboratory and shall be approved by the Purchaser. The Supplier shall be responsible for the proper testing of the plant or materials supplied by subsuppliers to the same extent as if the work, plant or materials were completed or supplied by the Supplier. Any cost incurred by the Purchaser in connection with inspection and re-testing as a result of failure of the equipment under test or damage during transport or offloading shall be to the account of the Supplier. The Supplier shall submit to the Purchaser five signed copies of the test certificates, giving the results of the tests as required. No materials shall be dispatched until the test certificates have been received by the Purchaser and the Supplier has been informed that they are acceptable. The test certificates must show the actual values obtained from the tests, in the units used in this specification, and not merely confirm that the requirements have been met. In the case of components for which specific type tests or routine tests are not given in Part 2, or in the quoted standards in Clause 2, of this specification, the Supplier shall include a list of the tests normally required for these components. All materials used in the Contract shall withstand and shall be certified to have satisfactorily passed such tests. No inspection or lack of inspection or passing by the Purchaser s Representative of equipment or materials whether supplied by the Supplier or sub-supplier, shall relieve the Supplier from his liability to complete the contract works in accordance with the contract or exonerate him from any of his guarantees. - 13 -
29.2. Guarantee The Supplier shall guarantee the following : Quality and strength of materials used; Satisfactory operation during the guarantee period of five year from the date of coissioning, or 72 months from the date of acceptance of the equipment by the Purchaser following delivery, whichever is the earlier; Performance figures as supplied by the tenderer in the schedule of guaranteed particulars; The offered surface treatment shall protect the treated metal from corrosion for a period of not less than five years from the date of delivery. 30. SUBMITTALS The following shall be required with each copy of the bid : completed technical data schedule; descriptive literature giving full technical details of equipment offered; outline dimension drawing for each major component, general arrangement drawing showing component layout and general schematic diagrams; type test certificates, where available, and sample routine test reports; detailed reference list of customers already using equipment offered during the last 5 years with particular emphasis on units of similar design and rating; details of manufacturer's quality assurance standards and prograe and ISO 9000 series or equivalent national certification; deviations from this specification. Only deviations approved in writing before award of contract shall be accepted; list of recoended spare parts and consumable items for five years of operation with prices and spare parts catalogue with price list for future requirements. 30.1. Technical Data Schedule for 100kVA Three Phase Transformer 1 GENERAL Name and address of manufacturer International or national standards with which the transformer and accessories comply Nominal frequency Hz 50 IEC -76 IS-2026 IS-1180 nominal power rating kva 100-14 -
Maximum continuous power rating kva 100 Nominal primary voltage kv 11 Nominal secondary voltage V 433 Type of cooling Vector Group Winding polarity 2 IMPEDANCE VOLTAGE Impedance at rated current and frequency 4 Resistance component of impedance Reactance component of impedance 3 SHORT CIRCUIT PERFORMANCE Short circuit current withstand capability ka ONAN Dyn11 Duration sec 2 sec X/R ratio 4 INSULATION LEVELS a) Separate source power frequency withstand voltage HV winding kv rms 28 LV winding kv rms 3 b) Induced overvoltage withstand level HV winding kv rms LV winding kv rms c) Full wave 1.2/50 µs lightning impulse withstand level HV winding kv peak 75 5 OVERLOAD / TEMPERATURE RISE Duration of overload: 25 Duration of overload: 50 Design maximum ambient temperature Design average ambient temperature Maximum winding temperature rise min min o C 50 0 o C 35 0 o C 55 0 Top oil temperature rise Maximum hot spot temperature at ambient temperature of 45 o C o C o C 45 0 sealed. - 15 -
Maximum temperature gradient o C/ 6 CURRENT AND FLUX DENSITY Maximum current density at full load current. HV winding A/ 2 2.5(Cu)/1.5(Al) LV winding A/ 2 2.5(Cu)/1.5(Al) Maximum Flux density at rated voltage and frequency. Maximum flux density at 12kV and 48 Hz Tesla 1.6 Tesla 7 GUARANTEED LOSSES Core losses at rated voltage and frequency. Winding losses at rated current at 75 C W W No load current (at 11kV) as percentage of full load current. Regulation at 75 C :full load at PF =1 full load, PF=0.85 8 CORE AND WINDINGS Silicone steel of core: Conductor for HV winding: conductor material Conductor for LV winding: conductor material Cross section area of HV winding 2 CRGO Cross section area of LV winding 2 9 CLEARANCES Minimum HV Phase to Phase clearance: in oil 127 outside oil. 255 Minimum HV clearance Phase to earth in oil 76 outside oil 140 Insulation material HV winding: : - 16 -
Insulation material LV winding: : 10 BUSHINGS AND TERMINALS HV bushings: LV bushings: Type of HV terminal Metal used for terminal studs Tightening bolt diameter Type of atmospheric protection Minimum phase to phase clearance 255 Minimum phase to earth clearance 140 Type of LV terminal Metal used for terminal Tightening bolt diameter Type of atmospheric protection Minimum phase to phase clearance Minimum phase to earth clearance Type of earth terminal material Are spring and lock washers included? Yes/No Yes Non ferrous Bolt and Nut 11 TRANSFORMER OIL IEC:296/IS:335 Oil: Quantity of oil litres Breakdown Voltage at the time of filling. kv 60 Moisture content at the time of filling 12 TRANSFORMER TANK ppm Sealed Type Yes/No Yes Type of steel Grade of steel class-1 mineral oil Mild steel High Grade - 17 -
Minimum thickness of : tank steel 3 top cover 5 bottom cover 5 cooling surfaces Top oil temperature corresponding to 100 kn/sq.m pressure Steady load to give top oil temp (50 o C ambient) Steady load to give top oil temp (50 o C ambient and solar radiation of 1,200 W/m 2 ) o C kva kva Pressure for actuating relief device fitted Corrosion protection supplier Paint/ Galvanising Thickness of coating microns 200/64 13 DIMENSIONS AND WEIGHTS Overall width Overall height Overall depth Weight of core Weight of tank Weight of windings Weight of oil at 20 0 C Total weight of transformer, ready for service Shipping weight of transformer 14 EFFICIENCY Efficiencies at 75 o C at unity power factor a) at full load b) at 3/4 full load c) at 1/2 full load d) at 120 full load e) Load at which maximum efficiency occurs f)maximum efficiency 15 INSULATION RESISTANCE Values at 30 o C kva - 18 -
HV to Earth LV to Earth HV to LV Megaohms Megaohms Megaohms - 19 -
30.2. Technical Data Schedule for 250kVA Three Phase Transformer 1 GENERAL Name and address of manufacturer International or national standards with which the transformer and accessories comply Nominal frequency Hz 50 nominal power rating kva 250 Maximum continuous power rating kva 250 Nominal primary voltage kv 11 Nominal secondary voltage V 433 Type of cooling Vector Group Winding polarity 2 IMPEDANCE VOLTAGE Impedance at rated current and frequency 4 Resistance component of impedance Reactance component of impedance 3 SHORT CIRCUIT PERFORMANCE Short circuit current withstand capability IEC -76 IS-2026 IS-1180 ONAN Dyn11 Duration sec 2 sec X/R ratio 4 INSULATION LEVELS a) Separate source power frequency withstand voltage HV winding kv rms 28 ka LV winding kv rms 3 b) Induced overvoltage withstand level HV winding kv rms LV winding kv rms c) Full wave 1.2/50 µs lightning impulse withstand level HV winding kv peak 75-20 -
5 OVERLOAD / TEMPERATURE RISE Duration of overload: 25 Duration of overload: 50 Design maximum ambient temperature Design average ambient temperature Maximum winding temperature rise min min o C 50 0 o C 35 0 o C 55 0 Top oil temperature rise Maximum hot spot temperature at ambient temperature of 45 o C Maximum temperature gradient 6 CURRENT AND FLUX DENSITY Maximum current density at full load current. o C o C o C/ 45 0 sealed. 50 0 unsealed HV winding A/ 2 2.5(Cu)/1.5(Al) LV winding A/ 2 2.5(Cu)/1.5(Al) Maximum Flux density at rated voltage and frequency. Maximum flux density at 12kV and 48 Hz Tesla 1.6 Tesla 7 GUARANTEED LOSSES Core losses at rated voltage and frequency. Winding losses at rated current at 75 C W W No load current (at 11kV) as percentage of full load current. Regulation at 75 C : full load at PF =1 full load, at PF=0.85 8 CORE AND WINDINGS Silicone steel of core: Conductor for HV winding: conductor material Conductor for LV winding: conductor material CRGO Copper Copper Cross section area of HV winding 2-21 -
Cross section area of LV winding 2 9 CLEARANCES Minimum HV Phase to Phase clearance: in oil 127 outside oil. 255 Minimum HV clearance Phase to earth in oil 76 outside oil 140 Insulation material HV winding: : Insulation material LV winding: : 10 BUSHINGS AND TERMINALS HV bushings: LV bushings: Type of HV terminal Metal used for terminal studs Tightening bolt diameter Type of atmospheric protection Minimum phase to phase clearance 255 Minimum phase to earth clearance 140 Type of LV terminal Metal used for terminal Tightening bolt diameter Type of atmospheric protection Minimum phase to phase clearance Minimum phase to earth clearance Type of earth terminal material Are spring and lock washers included? Yes/No Yes Non ferrous Bolt and Nut - 22 -
11 TRANSFORMER OIL IEC:296/IS:335 Oil: class-1 mineral oil Quantity of oil litres Breakdown Voltage at the time of filling. kv 60 Moisture content at the time of filling ppm 12 TRANSFORMER TANK Sealed Type Yes/No Sealed or unsealed Type of steel Grade of steel Mild steel High Grade Minimum thickness of : tank steel 3 top cover 5 bottom cover 5 cooling surfaces Top oil temperature corresponding to 100 kn/sq.m pressure if sealed type. Steady load to give top oil temp (50 o C ambient) Steady load to give top oil temp (50 o C ambient and solar radiation of 1,200 W/m 2 ) Pressure for actuating relief device fitted o C kva kva Corrosion protection supplier Paint/ Galvanising Thickness of coating microns 200/64 13 DIMENSIONS AND WEIGHTS Overall width Overall height Overall depth Weight of core Weight of tank Weight of windings Weight of oil at 20 0 C Total weight of transformer, ready for service - 23 -
Shipping weight of transformer 14 EFFICIENCY Efficiencies at 75 o C at unity power factor a) at full load b) at 3/4 full load c) at 1/2 full load d) at 120 full load e) Load at which maximum efficiency occurs f)maximum efficiency 15 INSULATION RESISTANCE Values at 30 o C HV to Earth LV to Earth HV to LV kva Megaohms Megaohms Megaohms - 24 -
30.3. Technical Data Schedule for 500kVA Three Phase Transformer 1 GENERAL Name and address of manufacturer International or national standards with which the transformer and accessories comply Nominal frequency Hz 50 nominal power rating kva 500 Maximum continuous power rating kva 500 Nominal primary voltage kv 11 Nominal secondary voltage V 433 Type of cooling Vector Group Winding polarity 2 IMPEDANCE VOLTAGE Impedance at rated current and frequency 4 Resistance component of impedance Reactance component of impedance 3 SHORT CIRCUIT PERFORMANCE Short circuit current withstand capability IEC -76 IS-2026 IS-1180 ONAN Dyn11 Duration sec 2 sec X/R ratio 4 INSULATION LEVELS a) Separate source power frequency withstand voltage HV winding kv rms 28 ka LV winding kv rms 3 b) Induced overvoltage withstand level HV winding kv rms LV winding kv rms c) Full wave 1.2/50 µs lightning impulse withstand level HV winding kv peak 75-25 -
5 OVERLOAD / TEMPERATURE RISE Duration of overload: 25 Duration of overload: 50 Design maximum ambient temperature Design average ambient temperature Maximum winding temperature rise min min o C 50 0 o C 35 0 o C 55 0 Top oil temperature rise Maximum hot spot temperature at ambient temperature of 45 o C Maximum temperature gradient 6 CURRENT AND FLUX DENSITY Maximum current density at full load current. o C o C o C/ 45 0 sealed. 50 0 unsealed HV winding A/ 2 2.5(Cu)/1.5(Al) LV winding A/ 2 2.5(Cu)/1.5(Al) Maximum Flux density at rated voltage and frequency. Maximum flux density at 12kV and 48 Hz Tesla 1.6 Tesla 7 GUARANTEED LOSSES Core losses at rated voltage and frequency. Winding losses at rated current at 75 C W W No load current (at 11kV) as percentage of full load current. Regulation at 75 C : full load PF =1 full load, PF=0.85 8 CORE AND WINDINGS Silicone steel of core: Conductor for HV winding: conductor material Conductor for LV winding: conductor material Cross section area of HV winding 2 CRGO - 26 -
Cross section area of LV winding 2 9 CLEARANCES Minimum HV Phase to Phase clearance: in oil 127 outside oil. 255 Minimum HV clearance Phase to earth in oil 76 outside oil 140 Insulation material HV winding: : Insulation material LV winding: : 10 BUSHINGS AND TERMINALS HV bushings: LV bushings: Type of HV terminal Metal used for terminal studs Tightening bolt diameter Type of atmospheric protection Minimum phase to phase clearance 255 Minimum phase to earth clearance 140 Type of LV terminal Metal used for terminal Tightening bolt diameter Type of atmospheric protection Minimum phase to phase clearance Minimum phase to earth clearance Type of earth terminal material Are spring and lock washers included? Yes/No Yes Non ferrous Bolt and Nut - 27 -
11 TRANSFORMER OIL IEC:296/IS:335 Oil: class-1 mineral oil Quantity of oil litres Breakdown Voltage at the time of filling. kv 60 Moisture content at the time of filling ppm 12 TRANSFORMER TANK Sealed Type Yes/No Sealed or unsealed Type of steel Grade of steel Mild steel High Grade Minimum thickness of : tank steel 3 top cover 5 bottom cover 5 cooling surfaces Top oil temperature corresponding to 100 kn/sq.m pressure if sealed type. Steady load to give top oil temp (50 o C ambient) Steady load to give top oil temp (50 o C ambient and solar radiation of 1,200 W/m 2 ) o C kva kva Pressure for actuating relief device fitted Corrosion protection supplier Paint/ Galvanising Thickness of coating microns 200/64 13 DIMENSIONS AND WEIGHTS Overall width Overall height Overall depth Weight of core Weight of tank Weight of windings Weight of oil at 20 0 C Total weight of transformer, ready for service - 28 -
Shipping weight of transformer 14 EFFICIENCY Efficiencies at 75 o C at unity power factor a) at full load b) at 3/4 full load c) at 1/2 full load d) at 120 full load e) Load at which maximum efficiency occurs f)maximum efficiency 15 INSULATION RESISTANCE Values at 30 o C HV to Earth LV to Earth HV to LV kva Megaohms Megaohms Megaohms 31. - 29 -