巴基斯坦220kV自耦变压器英文招标书
- 格式:doc
- 大小:563.50 KB
- 文档页数:62
SPECIFICATION P-169 : 83(UDC 621. 314 . 2)AUTO TRANSFRORMERSPAKISTANWATER AND POWER DEVELOPMENT AUTHORITY DESIGN DEPARTMENT (POWER)SPECIFICATION P-169 : 83AUTO TRANSFRORMERSAMENDMENT NO. 2 DATED 30TH SEPTEMBER, 1986Sub Clause 6.1.1 Replace the existing clause with the following:-6.1.1 The 220 & 132 kV Bushings shall be oil filled or of the condenser typeand shall be manufactured and tested in accordance with IEC Publication137 (1973).Add the following new sub clause :-6.1.9 Arcing horns shall not be fitted on the bushings unless specified in thetender.SPECIFICATION P-169 : 83AUTO TRANSFRORMERSAMENDMENT NO. 1 DATED 10TH MARCH, 19861. Table-I, Sr. No. 4, Page - 5Item 4 line 2 may please be amended to read as follows:“Cooling with 55 degC Winding”.2. Table-I, Sr. No. 23, Page - 8(I) Item (i) (a), (ii) (a) and (iii) (a, b) the existing ratios under column 3 and 4 mayplease be replaced with the following :Column-3Column-4i) (a) 2 x 600 / 1-1 2 x 1200 / 1-1ii) (a) 2 x 600 / 1-1 2 x 1200 / 1-1iii) (a) + (b) 2 x 600 / 1-1 2 x 1200 / 1-1 (II) Item (iv) (a), (b) and (c), the existing ratio under column 3 and 4 may please be replaced with the following :iv) (a) 1200 / 1-1 2400 / 1-1(b) 2 2(c) 3 13. Sub-Clause 9.1.2 Page - 29Third line of this clause may please be amended to read as follows :“and a pressure of 0.4 kg / sq. cm. additional to that present”.4. Sub-Clause 11.2 Page - 35The existing sub clause 11.2 may please be replaced with the following :-“11.2In the evaluation of tenders for Auto Transformers, the following rates shall be used for the capitalization of transformer losses and auxiliary power in fans.Capital cost of no-load losses = US$ 1750 per kilowattCapital cost of load losses = US$ 900 per kilowattCapital cost of auxiliary power = US$ 900 per kilowatt5. Sub-Clause 11.3, Page - 35The existing sub clause 11.3 may be replaced with the following :-6. Sub-Clause 13.2, Page – 41Pleas e add “Auxiliary Power of fans “after the word “losses”.7. Sub-Clause 16.4, Sr. No. 43 to 47, Page – 59 & 60The additions / amendments of items under serial No. 43 to 47 may please be incorporated as given in the attached Sheets 1 to 4.42) Tertiary Bushing Current Transformers:a) Number _______________b) Ratio _______________c) Accuracy Class _______________d) Accuracy Limit Factor _______________e) Rated burden _______________VAf) Short time thermal current _______________kAg) Continuous thermal current _______________kAh) Dynamic current _______________kAi) Resistance of secondary winding _______________Ohmsj) No. of Cores _______________k) Limits of temperature rise _______________o C43) Type of on-load tapchanger (catalogue and datato be supplied with tender).a) Manufacturer country of origin _______________b) Type designation _______________c) Rated through current _______________Amperesd) Step voltage _______________Volte) Number of steps _______________VAf) Type of basic connection of tap winding- Linear _______________- Reversing switch _______________- Coarse _______________g) Catalogue No. _______________h) Motor drive :1) Type _______________2) Supply voltage _______________Volts3) H. P. _______________4) Insulation level voltage to earth _______________kV rms5) Catalogue No. _______________i) Insulation levels:1) Voltage to earth _______________kV rms2) Impulse test voltage _______________kV rms3) One minute power frequency testvoltage (50 Hz) _______________kV rmsj) Internal Insulation levels impulse / oneminute power frequency test voltage :1) Between selected and pre-selected tap _______________kV peak2) Across fine tap winding _______________kV rms3) Between phase of fine tap winding _______________kV peak_______________kV rms4) Across coarse and fine tap winding,if applicable. _______________kV peak_______________kV rms5) Across coarse tap winding,if applicable. _______________kV peak_______________kV rms6) Between phase of coarse tap winding _______________kV peak_______________kV rms k) Remote tap position indicator :1) Type designation _______________2) Manufacturer country of origin _______________3) Method of remote indication _______________44) Liquid type oil thermometer (catalogue to beattached with tender).a) Type designation _______________b) Manufacturer country of origin _______________c) Type of liquid _______________d) Contact rating at 110V and 250V DCand 250V AC _______________Amperese) Catalogue No. _______________45) Resistance type oil thermometer (catalogue to beattached with tender).a) Type designation _______________b) Manufacturer country of origin _______________c) Material of sensing device _______________d) Mode of measurement of sensing element _______________e) Contact rating at 110V and 250V DCand 250V AC _______________Amperesf) Catalogue No. _______________46) Oil level indicator (catalogue to beattached with tender).a) Type designation _______________b) Manufacturer country of origin _______________c) Catalogue No. _______________d) Contact rating at 110V and 250V DCand 250V AC _______________Amperes47) Winding temperature indicator (catalogue to beattached with tender).(i) Local:a) Type designation _______________b) Manufacturer country of origin _______________c) Material of sensing device _______________d) Mode of measurement of sensing element _______________e) Catalogue No.f) Contact rating at 110V and 250V DCand 250V AC _______________Amperes (ii) Remote:a) Type designation _______________b) Manufacturer country of origin _______________c) Contact rating at 110V and 250V DCand 250V AC _______________AmperesCONTENTS0. Foreword1. Scope2. Reference specifications3. Service conditions4. Ratings and characteristics5. Accessories6. Bushings and Bushing Type Current Transformers.7. Transformer oil8. On-load tap changer9. Construction requirements10. Rating plates11. Losses12. Tests13. Guaranteed values14. Shipping conditions15. Transportation limitations16. Drawing and descriptive data17. Spare parts18. DrawingPRINTING HISTORYFirst approved on April, 1983.SPECIFICATION P-169 : 83(UDC 621.314.2)AUTO TRANSFRORMERS0. FOREWORD0.1 This specification has been prepared by Design Department of Power Wing, WAPDA. 0.2 This specification is intended for the procurement of materials and does not includes allthe necessary provisions of contract.0.3 The specification for 220 / 132kV Power Transformers was originally written in 1973 as achapter to main volume of the specification for sub station equipment in respect of 220 / 132kV Burhan Grid Station. This practice continued till date for the purpose of tendering.It has now been decided to review and rewrite the chapter in the form of standard specification. The present edition has been written to form a complete specification and is meant for the procurement of equipment either in loose form or for Grid Station works on turnkey basis.0.4 This specification is subject to revision as and when required.1. SCOPE1.1 This specification describes three-phase and single phase auto transformers with tertiarywinding, mineral oil immersed, forced air cooled for ONAF rating and forced oil forced air cooled for OFAF rating, self contained with conservator, breather, radiators, manual and remote electrically controlled on load tapchanger equipped with automatic regulating device, transformer auxiliary panel, outdoor control cabinets and complete with all accessories suitable for outdoor operation under the service conditions mentioned herein.1.2 It covers the transformers of the following ratings:Type Designation MVA Capacity Voltage RatioONAF / OFAF------------------------- --------------------- -----------------------------------------A 125 / 160 MVA 220 / 132kV Three PhaseB 250 / 315 MVA3 3The transformers shall be of either core or shell – form construction. The single phase units shall be connected to form solidly grounded wye, Auto Transformers rated 220 / 132kV, 250 / 315 MVA with delta tertiary. For this purpose the scope also includes the supply of post insulators, brackets and other supporting and connecting materials for making external wye and delta connections.2. REFERENCE SPECIFICATIONS2.1 The transformers shall be supplied and tested in accordance with the followingInternational Electro-technical Commission Specifications.IEC Publication 76 (1976) Power Transformers (Part 1-5)IEC publication 137 (1973) BushingsIEC publication 185 (1966) Current Transformers.IEC publication 214 (1976) On-Load Tap ChangerIEC publication 296 (1969) Transformer Oil2.2 The definitions give in the above IEC publications shall apply herein.2.3 In case the requirements laid down herein differ from those given in the above IECpublications in any particular, the transformers shall comply with the requirements listed herein in regard to that item.3. SERVICE CONDITIONS3.1 The power transformers and all accessories shall be suitable for satisfactory operationunder the following service conditions.3.2 Ambient TemperatureMaximum 50o CMaximum mean over any 24 hours. 45o CMean in any year 30o CMinimum-10o C3.3 Relative HumidityThe relative humidity may range upto 100%. The maximum values of the ambient temperature and humidity however do not occur simultaneously. During the monsoons high humidity may persist for many days at a time, with temperature ranging 30o C to 40oC.3.4 AltitudeInstallations will be upto 1000 mm above sea level.3.5 Atmospheric Conditions3.5.1 It may be assumed that the air is not normally heavily polluted by dust, smoke,aggressive gases, vapours or salt spray. However at certain times of the year severe dust storms may be experienced.3.5.2 Certain areas are subjected of heavily polluted atmosphere and insulation or bushingsfor installation in such areas shall have an extended creepage distance from live to earthed parts.3.6 Provision shall be made in the design of the transformer accessories and control panelsto ensure that proper operation is not impaired by vermin, insects, small animals and birds.3.7 Auxiliary services3.7.1 The AC supply for control and auxiliary circuits shall be as under:3.7.2 The DC supply for auxiliary circuits shall be 220 V nominal. The limits of variations areplus 10 percent and minus 15 percent.4. RATING AND CHARCTERISTICS4.1 GeneralThe power transformers shall be of core type mineral oil immersed, forced air cooled for ONAF rating, self contained, with conservators, radiators, on-load tap changer with automatic regulating facility, breather, transformer auxiliary panel, outdoor control cabinets and complete with all accessories.4.2 Rating4.2.1 The specified ratings and design data of the power transformers shall be in accordancewith Table-I given herein.TABLE – I : STANDARD RATINGS OF AUTO TRANSFORMERSTABLE – IITAPPING VOLTAGES FOR HIGH VOLTAGE WINDINGS4.3 Tolerances for the Guaranteed Values4.3.1 Voltage Ratios (no-load)Tapping voltages for the tapped HV windings have been specified in Table-II givenherein. The voltage ratios at different tapes, including the principal tap, shall notvary by more than 0.5 percent of the specified values.4.3.2 Impedance Voltage and Short – Circuit Impedance4.3.2.1 The impedance voltage at principal tap between HV and LV windings of thetransformers shall not differ by more than plus minus 10 percent of the specifiedvalues. The short-circuit impedance at the extreme taps shall not differ by morethan plus, minus 10 percent of the guaranteed values.4.3.2.2 The impedance voltage between HV –tertiary winding at principal tap and LV –tertiary winding shall not Iffer by more than plus, minus fifteen percent of theguaranteed value.4.3.2.3 In case any of the impedance voltages between HV – LV winding as principal tapdiffers by more than five percent of the specific field / guarantee value, a penalty atthe rate of Rs. 50,000/- (Rupees Fifty Thousands) per one percent of difference inimpedance from specified impedance shall be payable by the Contractor.4.3.3 RegulationVoltage regulation, computed from the impedance volts and watts, may exceed theguaranteed regulations at unity and 0.8 lagging power factor by no more than tenpercent.4.3.4 Losses4.3.4.1 The tolerance for total losses shall not exceed 10 percent of the guaranteedfigures. The component losses may exceed the respective guaranteed figures byupto 15 percent provided the tolerance for total losses is not exceeded.4.3.4.2 A penalty at twice the rate of the capital costs of “No-load and load losses”indicated in clause 11 shall be payable by the contractor for the losses in excess ofthe guaranteed figures.4.3.5 No-load currentThe tolerance for the no-load current shall be plus 30 percent of the guaranteedvalue.4.4 4.4.1 Rated PowerThe series and common windings shall be assigned two power ratings as specified in TABLE-I. These ratings shall be such that the transformer can deliver respective rated current under steady loading conditions without exceeding the limits of temperature rise specified in TABLE-I and clause 4.10. This requirement must also be met with the tertiary winding supplying rated KVA power.4.4.2 The ONAN rating of the power transformer shall also be indicated.4.4.3 The power transformers may alternatively be offered with ONAN / ONAF ratingsagainst the specified values mentioned in TABLE-I4.5 The impedances specified in TABLE-I are positive sequence based on lowerpower and with taps set on rated voltage position. The HV to tertiary and LV totertiary impedance are tentative and Bidder is required to give the exact values. 4.6 TapingsThe tapings shall be provided in the high voltage windings. The tapping powershall be equal to the rated power for connections on all tappings. The category ofregulation shall be constant flux regulation. The voltage range for which thetappings are to be designed is specified in TABLE-I.4.7 Operation at higher than rated voltage4.7.1 The transformer shall be capable of continuous operation at an applied voltageequal to 110% of rated voltage or tapping voltage if operating at a tap other thanthe principal tap and at maximum frequency. At such higher applied voltage it shallbe capable of delivering continuously the rated current or tapping current ifoperating at a tap other than the principal tap, except that for applied voltagesgreater than the System Highest Voltage the continuous current capability may belower than the rated values.4.7.2 A slightly increased temperature rise such that it dose not materially affect the lifeof the transformer is permissible. This temperature rise shall be stated by themanufacture.4.7.3 The manufacture shall determine the operating conditions under which themaximum flux density will be attained in the core and shall state the maximum fluxdensity.4.8 Short-circuit withstand capability4.8.1 The transformers shall be designed and constructed to withstand without damagethe thermal and dynamic effects of any external short circuit at any terminal whenconnected to a high capacity 220 KV or 132 KV systems. The maximumsymmetrical short-circuit current in any winding is specified in TABLE-I as amultiple of rated current based on lower rated power for the winding.4.8.2 The transformers shall be capable of withstanding the electromagnetic forces,arising under short-circuit conditions with the peak value of the asymmetricalcurrent equal to 2.5 times the rms value of the specified short-circuit current.4.8.3 The transformers shall be capable of withstanding the thermal effects of the short-circuit specified for three seconds. The maximum temperature of the windingscalculated in accordance with clause 2.1.5 of IEC publication 76-5 (1976) shall notexceed 250 degC.4.8.4 The neutral terminal of windings shall be designed for highest over-current thatcan flow through this terminal.4.9 Tertiary Winding4.9.1 A delta-connected tertiary winding shall be provided in the transformers, whichshall have voltage rating, characteristics and power rating as specified in TABLE-I.This rated power shall be obtained with the other two windings also operating atrated power under either cooling conditions. The tertiary windings shall be capableof withstanding the over-currents resulting from different forms of system faultsthat can arise in service associated with system ear thing conditions.4.10 Temperature Rise4.10.1 The maximum ambient temperature is 50 degC and as such the temperature riseof windings, core and oil when tested shall not exceed the following:1) Winding (measured by resistance) 55 degC2) Top oil (measured by thermometer) 50 degC3) For core and other parts, the temperature rise shall be such that in oncase the temperature should reach a value that will injure the core itself or adjacent parts, or materially affect the life of the transformer.4.11 InsulationThe 220 kV or 132 kV windings may be graded. The grading of the insulation shallbe such that the winding can meet the test voltage requirements laid down inTABLE-I. Motors and other apparatus for auxiliary equipment shall fulfill insulationrequirements according to relevant IEC standard.5. ACCESSORIES5.1 The transformers shall be provided with the following accessories moundedgenerally in accordance with drawing No. EW / TS-193.1) Oil level indicators magnetic type2) Oil temperature indicators3) Winding temperature indicators4) Thermometer pockets5) Buchholz relay6) Fans, oil pump and controls7) Auxiliary panel8) Terminal boxes / cabinets9) Lifting eyes for cover10) Facilities for lifting the core and coil assembly.11) Lugs for lifting complete transformer.12) Moving facilities / flanged roller wheels.13) Jacking facilities.14) Oil Conservator with breather.15) Drain and filter valves comprising of :(i) One drain valve 80 to 100 mm dia(ii) Two filter valves of about 75 mm dia.(iii) Two sampling valves of about 20 mm dia.(iv) Air release plug.(v) Oil filling plug.16) Pressure relief device.17) Earthing terminals for tank.18) Inspection facilities.19) Rating plate.20) Terminal marking plate.21) On-load tapchanger and controls.5.1.1 Accessories not indicated in Drawing No. EW/TS-193 shall be located at suitable placesby the manufacturer, who shall obtain specific approval of WAPDA prior to manufacture.5.1.2 Accessories with markings or dials shall be mounted at a height of approximately 1.5meters from the base of transformer in such positions as to be easily readable by a person standing on the ground. If necessary, dial faces shall be mounted at an inclined angle for easy visibility.5.2 Ground conditionsA 25 kV insulated ground connection from the neutral bushing through the neutral CT tothe ground pad at the base of autotransformers, shall be provided. Also a ground connection from tertiary winding bushing to the pad at the base of the autotransformers shall be provided.5.3 Temperature Rise of AccessoriesFor transformer accessories and their parts, the temperature rise, when tested at the most severe operating ratings, shall not exceed the values given below. The values shall be determined by the resistance method.Insulation Class Maximum temperature rise, Deg CY 40A 55E 70B 80F 105H 130G No LimitThe classification of insulating materials is according to IEC Publication 85.5.4 Oil Level Indicators5.4.1 Two oil level indicators shall be fitted, one on each end of the conservator. Theindicators shall be of the magnetic type. Both the indicators shall be provided with alarm contacts for low oil level.5.4.2 The indicators shall have a dark face dial with light markings and a light colouredindicating hand. The diameter of the dial shall be about 150 mm. The dial marking shall show the -10, 5, 15, 25, 35, 45 and 55o C as well as the high and the low oil level.5.4.3 The words “Oil Level” shall be marked on the dial or on a suitable nameplate.5.4.4 The alarm contacts shall be suitable for making or breaking 2 Amps. between the limitsof 24 Volts to 250 Volts AC or DC.5.5 Oil Temperature Indicators.5.5.1 Three oil temperature indicators, one mercury type and two of resistance type shall beprovided to indicate the top oil temperature.5.5.2 The indicators shall have a dark face dial with light markings, a light coloured indicatinghand and an orange maximum indicating hand with provisions for resetting. The diameter of the dial (inside bezel) shall be about 125 mm. The dial markings shall covera range of 0 to 120 deg C. The words “Oil Temperature” shall be marked on the dial oron a suitable name – plate.5.5.3 The mercury type oil temperature indicators shall be direct stem-mounted in a close well.5.5.4 The measuring element of the resistance type oil temperature indicator shall be mountedinside a stainless steel tube. The indicating dial shall be mounted in the outdoor control cabinet. Two separate sets of contacts one to operate an alarm and the other to trip circuit breaker shall be provided. Contacts shall also be provided for control of fans and oil pumps. The contacts shall be wired and connected to terminal blocks in the outdoor control cabinet. The contacts for forced cooling and for alarm and trip shall be wired for use as described in Clause 5.6. Necessary wiring diagrams shall be provided showing the scheme and the changes required for the change-over.5.5.5 The alarm and tripping contacts shall be adjustable to close between 60 – 120 deg C.Both shall reopen when the temperature has fallen by not more than 10 deg C below the preset value. The forces cooling control contacts shall be adjustable to close at any temperature between 50 deg C and 100 Deg C and to reopen when the temperature has dropped by 15 deg C to 30 deg C. All contacts shall be conveniently adjustable and a setting scale shall be fitted. They shall be accessible on removal of the cover. Alarm and trip contacts shall be suitable for making or breaking 5 Amps. between the limits of 24 Volts to 250 Volts AC or DC.5.5.6 It shall be possible to move the pointers of the temperature indicators by hand in order totest the tripping, alarm and cooling apparatus circuits. The working parts of the instruments shall be visible through glass-fronted covers.5.6 Winding Temperature Indicators5.6.1 The transformers shall be provided with two numbers resistance type devices forindicating the hottest spot winding temperature.5.6.2 Each device shall have a dial type indicator and a pointer to register the highesttemperature reached. Two separate sets of contacts, one to operate an alarm and the other to trip the breaker shall be provided for each device. Contacts shall also be provided for control of fans, oil pumps and for remote indication. The contacts of both the temperature indicating devices be connected in parallel. The dial marking shall cover a range of 0-130 degC. The words “Winding Temperature” shall be marked on the dial or on a suitable nameplate.5.6.3 The temperature indicator(s) shall mounted in the outdoor control cabinet. There shallbe provided a remote electrically operated repeat indicator for mounting on the transformer auxiliary panel in the control room.5.6.4 The alarm and tripping contacts shall be adjustable to close between 70 –130 degC.Both shall reopen when the temperature has fallen by not more than 10 degC below the present value. The fans and oil pumps control contacts shall be adjustable to close at any temperature between 50 degC and 100 degC and to reopen when the temperature has dropped by 15 degC to 30 degC. All contacts shall be conveniently adjustable and a setting scale shall be fitted. They shall be accessible on removal of the cover. Alarm and trip contacts shall be suitable for marking or breaking 5 Amps. Between the limits of 24 volts to 250 volts AC or DC.5.6.5 The power supply of the winding temperature indicator shall be 220 V DC.5.6.6 It shall be possible to move the pointers of the temperature indicators by hand in order totest the tripping, alarm and cooling apparatus circuits. The working parts of the instrument shall be excisable through glass-fronted covers.5.6.7 Terminals, links and an ammeter shall be provided in the outdoor control cabinet foreach winding temperature indicator for:a) Checking the output of the C.T.b) Disconnecting the heating coil from the C.T. secondary to enable the instrumentto be used as an oil temperature indicator.5.6.8 A diagram and instruction plate for the above shall be fixed in outdoor control cabinet. Itshall be durable and non-corrosive. The maintenance instructions shall include graphs or table showing the relationship between current injected into the heating coil and the corresponding indicated readings between no-load and full-load of the transformer.5.7 Buchholz Relay5.7.1 A buchholz relay shall be provided. It shall be designed to operate rapidly for internaltransformer faults and shall be equipped with two contacts, one for alarm and the other for tripping circuit breaker. The alarm contact shall be set to operate from a low rate of gas evolution. The tripping contact shall be operated from a high rate of gas revolution or oil movement such as experienced from internal transformer faults or internal flashover.5.7.2 A gas-sampling device shall be provided.5.7.3 Alarm and trip contacts shall be suitable for making or breaking 5.Amps between thelimits of 24 volts to 250 volts AC or DC.5.8 Fans and Control5.8.1 The transformers shall be fitted with fans meet the ONEF and OFAF ratings. Thenumber of fans shall be such that full rating of the transformer can be obtained with 25 percent of the fans not working. When the number of fans is four or less, the transformers shall be capable of full output with at least one fan shut down.5.8.2 The fans shall be powerful, rugged motor driven and of design suitable for continuousoperation in the service conditions specified with minimum noise. All necessary ducting shall be supplied and shall consist of galvanized steel sheet suitable stiffened by angles.The fan blades shall be made of galvanized steel unless otherwise approved.Galvanised wire mesh guards with mesh not greater than 20mm shall be provided over the blowers and all moving shafts and coupling shall be guarded. It shall be possible to remove a fan unit without dismantling of radiators or the supporting structures.5.8.3 The motors for forced cooling equipment shall be rated 415 volts three phase AC. Theoutput rating of the motors shall be sufficient for the duty required. The temperature rise of fan motors shall be such that the maximum permissible temperature for the motors insulation is not exceeded under the reduction in the allowable temperature rise of 10 degC and corresponding derating of motor output. The oil pump motors shall be liberally rated.5.8.4 Each fan or a group of fan shall be provided with a miniature circuit breaker forprotection and with an electrically operated contactor starter and with controls for starting and stopping the motors by hand or automatically. It shall be possible to select automatic or manual control. Selection for hand / automatic operation shall be made at the transformer auxiliary panel.5.8.5 The automatic starting of the fan motors shall be controlled from the contacts on thewinding temperature indicator described in clause 5.6. Contacts shall be provided for remote indication of fan operation of failure.5.8.6 The control equipment shall be mouted in the outdoor control cabinet and all wiring,conduit and cable boxes between the outdoor control cabinet and the transformer shall be provided.5.8.7 An AC under voltage relay with contact closure after the voltage failure adjustablebetween 0.2 and 4.0 second shall be provided on each transformer to actuate alarm of service power failure. The contacts shall be suitable for operation on ungrounded 220 volts DC service. This relay shall be located in the outdoor control cabinet.5.9 Transformer Auxiliary Panel5.9.1 Each power transformer shall be supplied with a transformer auxiliary panel for remotecontrol, and following equipment shall be mounted on the front of the panel:i) Tap position indicator.ii) Winding temperature remote indicator.iii) Switches / push buttons for manual raise / lower of tap changer taps.iv) Indicating lights for “tap changer in progress”, “raise” and “lower” of tap changer taps.v) Selector switch for individual / parallel operation of transformer tap changers.vi) Switches / push buttons for manual operation of cooling fan and oil pumps from remote.vii) Indicating lamps for indicating operation of each group of fans and oil pumps.。