ABB Transformer Installation manual

August 9, 2017 | Author: jt4fds | Category: Transformer, Safety, Polychlorinated Biphenyl, Petroleum, Valve
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1ZVN460100 – B

Installation manual

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A. TRANSFORMER ASSEMBLY INSTRUCTIONS

CONTENT 1.Scope ............................................................................................................................................ 2 2. Safety Notations............................................................................................................................................. 2 3. General .......................................................................................................................................................... 4 4. Preparation .................................................................................................................................................... 4 5. External Assembly ..........................................................................................................................................4 5.1 Radiators, Coolers and Pumps .................................................................................................................5 5.2 Mounting the COPS Oil Preservation System......................................................................................... .5 5.3 Mounting the Nitrogen Blanket Oil Preservation System ..........................................................................5 5.4 Load Tap-Changers...................................................................................................................................5 6. Internal Assembly .......................................................................................................................................... 7 6.1 General .................................................................................................................................................... 7 6.2 Bushing Installation .................................................................................................................................. 8 6.3 De-energized Tap-Changer...................................................................................................................... 9 6.4 Bushing Current Transformers ................................................................................................................. 9 7. Closing the Transformer and Final Dewpoint Measurements ........................................................................10 8. Electrical Tests................................................................................................................................................11

1. Scope These instructions are intended to help in the installation of transformers to maintain their quality and reliability. The recommendations are not a complete manual for all the operations during the field assembly of a large transformer. It is assumed that competent and responsible supervision and workforce are available for the job - that good order, cleanliness and personal safety precautions are observed - in accordance with common sense and local regulation. The following text highlights a few particular procedures and precautions that are specific for the ABB Transformer make, or are of critical importance for a good result.

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2. Safety Notations Safety notations are intended to alert personnel of possible personal injury, death, or property damage. They have been inserted in the instruction text prior to the step in which the condition is cited. The safety notations are headed by one of three hazard intensity levels, which are defined as follows: 1) Danger - immediate hazard that will result in severe personal injury, death, or property damage. 2) Warning - hazard or unsafe practice that could result in severe personal injury, death, or property damage. 3) Caution - hazard or unsafe practice that could result in minor personal injury, death, or property damage.

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3. General The transformer should not be opened during periods of inclement weather or when condensation is forming on the internal surfaces of the transformer. Never enter a transformer with dirty or wet clothing. Clean cloth overshoes or nitrile rubber overshoes should be worn. All tools, equipment and material entering the transformer shall be listed and checked to verify all material has been removed from the transformer. Tools must have working surfaces hardened so that they will not peel or chip during normal use; also, working surfaces must not be coated in any way such as painting or plating. Tools that are polished metal or have black oxide body finish are preferred. To prevent accidental disassembly during normal use, all tools with movable parts must use double side flush-riveted joints and or all fasteners or moving parts must be retained by staking or deforming the last thread by welding or coating. Tools such as hammers and screwdrivers must have one piece heads. Molded-on plastic or fiberglass handles are preferred; if the handle is wood, it must be retained by a wood or plastic wedge. Nameplates or tags attached to tools should be removed. If a nameplate is necessary for tool identification, the plate must be non-metallic and be secured with non-conducting tape. While the transformer is open, do not permit anyone access to the transformer until they have emptied all pockets, checked for loose objects, and removed watches, rings, and other objects. Dry air must be used to ventilate the inside of the tank when it is opened for internal fitting. The air must have a dew point less than -40°C and sufficient airflow for the number of operators in the tank must be maintained. Do never use nitrogen or other gases than air for ventilation. Nitrile gaskets should be changed during the assembly operations. New gaskets are provided with transformer detail parts. Dumbbell gaskets used for Tap-Changer inspection doors can be reused. They are to be compressed to 5/16” (8mm) when resealing the doors. The mechanical relief devices shall be installed prior to beginning the assembly operations to prevent excessive pressure build-up on the tank. The transformer tank shall be grounded prior to beginning any assembling operations.

4. Preparation The transformer shall be moved into position on the substation pad and the base should be leveled. Install shims under the base for leveling if necessary. The transformer base shall be supported on the foundation pad or piers as noted on the transformer base drawing detailed on the transformer outline drawing. The transformer foundation should be prepared so that the transformer shall have adequate air circulation necessary to cool the transformer.

5. External Assembly The items removed and shipped separately are listed on the outline drawing, the outside assembly drawing, or packing list. The items generally removed and shipped separately are the bushings, cooling equipment, forced oil pumps (if the transformer has an FOA rating), arresters and arrester mounting brackets and the sudden pressure relay. The number of accessory items removed will vary depending on the physical size of the transformer.

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All air or gas fittings and all oil fitting joints that are preassembled at the factory must be checked for leaks and resealed.

5.1. Radiators, Coolers and Pumps Radiators, coolers, the associated oil pumps and piping shipped as detail items that are assembled at the final location must be thoroughly inspected prior to installation to be certain that no water or foreign material is in the oil space. Avoid opening the equipment when it is at a temperature lower than the ambient air in order to prevent condensation. The radiators or coolers should be installed on the transformer the same day they are opened. Do not permit thecooling apparatus to stand exposed after opening for inspection. The detailed illustrations for mounting and pipingarrangements will be shown on the outside assembly or the outline drawings. Use new gasket material when installing the radiators, coolers, or pumps. 5.2. Mounting the COPS Oil Preservation System If the transformer is equipped with a constant oil pressure (COPS) oil preservation system, mount the support structure for the COPS tank, mount the tank and install the valves on the main tank and the COPS tank. The valve to the COPS piping on the transformer cover should remain closed. The detailed illustrations for mounting and piping the COPS system will be shown on the outside assembly or the outline drawings. Do not install the connected piping between the main tank and the COPS system until the vacuum filling process of the main tank has been completed. 5.3. Mounting the Nitrogen Blanket Oil Preservation System If the transformer is equipped with a nitrogen blanket oil preservation system, the nitrogen system control cabinet generally remains on the transformer for shipment. If it was removed, install the cabinet and the nitrogen bottle. If the cabinet is already mounted, install the nitrogen bottle and connect the piping to the control. If the transformerwas shipped in oil, the tubing connection from the cabinet to the gas space is not connected. This prevents oil from entering the line during shipment. Check the line to be certain it is clear of oil and connect the tubing at the cabinet. The nitrogen supply valve should remain closed in either case. 5.4. Load Tap-Changers General The UVT, UTT and RMT-1 Tap-Changers are usually shipped mounted on the transformer. The UZE and UZF TapChangers are also shipped mounted on the transformer.

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The compartment for Tap-Changers such as the Reinhausen M, T, and G and the ABB type UCG, UCL will be removed for shipment unless shipping dimensions allow the compartment to remain attached to the transformer or the Tap-Changers are mounted within the main tank. Temporary shipping braces are sometimes used in the Tap-Changer compartment if it remains on the transformer. These braces will be shown on the internal assembly drawing. The braces must be removed before the Tap-Changer is placed in service.

WARNING

DO NOT OPEN ANY COVERS OR FITTINGS UNLESS THE INTERNAL PRESSURE IS AT ZERO GAUGE. FAILURE TO RELIEVE THE PRESSURE COULD CAUSE THE PART BEING REMOVED TO BE A HAZARDOUS FLYING OBJECT. ALWAYS RELIEVE INTERNAL PRESSURE SLOWLY THROUGH VALVES. Before placing Tap-Changers in service, read the appropriate Tap-Changer instruction leaflet. The leaflets are included in the transformer instruction book. Always follow the inspection and filling instructions given in the Tap- Changer instruction leaflet.

Tap-Changers Mounted for Shipment No internal assembly operations or taping are requied

Tap-Changers Removed for Shipment - optional The leads will need to be connected to the terminal board and taping will be required. Work in the Tap-Changer compartment should be completed as quickly as possible. The leads are identified by a number stamped in the end of the lug; the leads and corresponding terminal lugs are match marked. Start connecting leads to the terminal board in the center and work towards the outside. This allows a little more room for taping. The correct thickness must be applied; too little tape can result in an electrical failure and too much tape can cause overheating of the joint. Follow the taping drawings included in the instruction book for the transformer. This drawing shows where the capacitor tissue is applied and how to apply the crepe tape over the capacitor tissue and lead. Remove all items used during taping the leads before you close the Tap-Changer compartment. Before final oil filling and placing the Tap-Changer in service, check the operation of the Tap-Changer as noted in the instruction book. Fill the Tap-Changer compartment as instructed in the Tap-Changer instruction leaflet.

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6. Internal Assembly 6.1. General When opening the transformer, take necessary precautions to prevent moisture or dirt from entering the transformer or moisture condensation in the transformer. Necessary confined entry procedures should be followed in compliance with company policy or local regulations.

WARNING

When transformer has been shipped with nitrogen, the gas should be replaced with dry air prior to making any entrance into the tank. The oxygen content must be at least 19.5% prior to entering the tank. To remove the nitrogen, it is advisable to pull vacuum to fully remove all nitrogen and break the vacuum with dry air.

CAUTION

Be certain the internal pressure in the transformer is a zero gauge before opening the manhole cover.

Open the transformer at the manhole cover. It is preferred to have only one manhole open at a time. It is also recommended that the tank opening be covered with clear plastic or a tarp. Purge the air hoses with dry air from the supply to remove any moisture and dirt in the hoses prior to use. Make the connections for the dry air supply in the tank space below the working level in the tank.

WARNING

DO NOT ENTER THE TRANSFORMER OR BREATHE THE INTERNAL ATMOSPHERE UNLESS THE OXYGEN CONTENT OF THE GAS INSIDE THE TRANSFORMER IS AT LEAST 19.5%. OXYGEN CONTENTS LESS THAN THIS CAN CAUSE DROWSINESS, INJURY OR DEATH. TRANSFORMERS SHIPPED IN GAS ARE NOT SAFE TO ENTER. ALWAYS CHECK THE OXYGEN CONTENT.

CAUTION To prevent contamination of the transformer, only the manhole and the opening for the item being installed should be opened. Cover all other openings with dry pressboard or a clean plastic sheet. This

will also minimize the flow of dry air from the unit. Start the air flow into the transformer. The volume must be sufficient to maintain continuous air flow outward through the tank openings.

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6.2. Bushing Installation On large transformers, the bushings will be removed for shipment to meet shipping clearances and to avoid shipping damage to the bushings. The bushing leads may be supported by temporary shipping braces which are an integralpart of the blind flange. The flange will be stenciled with a warning note if this method is used. The bushing leads must be disconnected from these temporary braces before the blind flange covers or shipping covers are removed. An alternate method of supporting the bushing leads is to tie the coiled lead to the highest point on the transformersuperstructure.

CAUTION

Failure to disconnect the leads from the temporary shipping braces before the blind flanges or shipping covers are lifted can cause damage to the leads, bridge structure and associated coils, and may necessitate

return of the transformer to the factory for repair and retesting. The bushings removed for shipment should remain in the shipping crates until they are required for the transformer assembly provided that the shipping crates maintains a 7 Degree angle of inclination. Note the requirements in the bushing instruction leaflet for temporary storage. Clean the bushing thoroughly before installing it in the transformer. It is recommended to perform a power factor and capacitance test of the bushings as noted in the bushing instruction leaflet prior to installation in the transformer. Install the bushings in the transformer. When a draw-through-lead or draw-rod design is used, this will be noted on the outline drawing. The procedure for installing the bushing and connecting the leads is described in the bushing instruction leaflet. For bottom connected bushing designs, the connection details will be shown on the outline drawing or the internal assembly drawing. Ground the external bushing terminals after they are installed and connected. The inside assembly drawings or taping sketch furnished with the instruction book contain taping requirements and lead clearances. The internal assembly drawings identify all internal items requiring field taping. Non-metallic bolts, nuts and studs are sometimes used on insulation structures. Nuts of this type should be tightened to a snug fit only since breakage or thread stripping may occur. Bolts and studs installed at the factory will either have the nuts cemented on or use a second nut as a jamb nut so that retightening should not be necessary.

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6.3. De-energized Tap-Changer Check the de-energized Tap-Changer to confirm that the contacts are on the correct positions. Check the external operators to confirm they are on the correct positions. Operate all de-energized Tap-Changers in both directions to each limit to verify the correct alignment of the Tap- Changer contacts. Perform a winding ratio check at each tap position and record the results. Refer to the Tap-Changer instruction leaflet for procedures to correct the contact alignment if the ratio checks are not satisfactory. 6.4. Bushing Current Transformers Check the current transformer ratios, lead continuity, and polarity at the terminal points in the control cabinet.

CAUTION AN ENERGIZED CURRENT TRANSFORMER IS DANGEROUS IF THE SECONDARY IS AN OPEN CIRCUIT. DEATH OR SERIOUS INJURY CAN RESULT FROM CONTACT WITH THE TERMINALS. THE SHORT CIRCUITING DEVICES MUST BE CONNECTED TO THE APPROPRIATE TERMINALS IN THE CONTROL CABINET IF THERE IS NO LOAD CONNECTED TO THE TRANSFORMER.

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7. Closing the Transformer and Final Dewpoint Measurements After the assembly has been completed, remove all the tools and working material from the transformer, seal the transformer and pressurize with dry air or nitrogen to 20 kPa; 3 PSI (.2 bar). If the exposure time has been excessive or there are others factors that suggest the transformer may have been exposed to excessive moisture contamination, then it is advised that transformer be evacuated to 2 Torr (.266 Pascal) or less and held for 4 hours. The vacuum shall then be broken with dry air or nitrogen until the pressure reaches 20 kPa 3 PSI (.2 bar) The transformer shall remain under pressure for at least 12 hours until equilibrium is reached, and then measure the dewpoint. If the surface moisture is less than 0.8%, based upon the dewpoint of the gas and the insulation temperature, proceed with the final vacuum filling procedures. If the dewpoint is unacceptable, the transformer insulation must be dried. When taking dewpoint measurements, it is advisable to take the measurement in the early morning hours prior to sunrise. When this is done, the insulation temperature can be taken to closely match the gas temperature. When taking the dewpoint during periods of extreme ambient temperature variation or during the afternoon hours, the insulation temperature should be measured directly after the dewpoint is taken

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8. Electrical Tests If the following electrical tests have not been made as part of the receiving inspection, make the following tests before beginning any oil filling procedures. Please refer to the “Site test and commissioning” (Paragraph 11)

CAUTION

If the transformer tank is not filled with oil, the test voltage on the windings must be limited to 1,000 volts or less. 1. Measure the power factor and capacitance of the bushings before installing the bushings in the transformers. Refer to the appropriate bushing instruction leaflet for the proper procedures. (Optional Test) 2. Measure the core resistance to ground. The minimum acceptable value is 500 kOhm when measured at 1000 volts. 3. Measure the core clamp resistance to ground. The minimum acceptable value is 500 kOhm when measured at 1000 volts. 4. Measure the ratio of all bushing current transformers and verify proper polarity.. 5. Check the turns ratio of the transformer (TTR) at all tap positions. The measured turns ratio should be + 0.5 % of the nameplate voltage ratio.

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B. TRANSFORMER OIL ON SITE - QUALITY CONTROL

CONTENT 1.General.............................................................................................................................................. 12 2. Different types of oil, characterised by origin and chemical composition.....................................................….. 12 2.1 Inhibited oils.............................................................................................................................................. 12 3. Supplier certificate ............................................................................................................................................. 13 4. Sampling on site. .............................................................................................................................................. 13 5. Testing of samples. Oil characteristics. ............................................................................................................ 14 6. Treatment of the oil before filling the transformer.............................................................................................. 15

1. General This Instruction lists the main quality requirements that are to be fulfilled when transformer oil is delivered to an installation site for filling into the transformer. The oil shall fulfil the requirements in material specification. The user of the transformer may have issued an oil specification of his own, or may have specified oil of a particular trade mark from an internationally recognised supplier. This may add to, but does not relieve any of the requirements specified in this Instruction. They are necessary for long-time reliable operation of the transformer. 2. Different types of oil, characterised by origin and chemical composition Transformer oils are specially refined products made from crude oils of different types from different wells. Terms as "naphtenic” ,parafinic”, “aromatic”, “aliphatic" refer to different types of hydrocarbons in the oil, which are balanced by the manufacturer to give a combination of high insulation withstand strength, low viscosity, low volatility/high flammability temperature, low sulphur content, and low ageing(oxidation) tendency. At the present time there is no essential, documented difference in overall quality between materials from different crude origins, as long as the final products are manufactured by competent refineries and fulfil the requirements of the ABB material specification. When transformers are shipped from the ABB Transformers factory filled with oil, or when oil for the first filling is part of the delivery from ABB, it is supplied against ABB own Material Specification 1ZBA 117001-1, 2, 3 or 4. Provision of samples for testing may be required in addition to examination of the suppliers quality specification. 2.1. Inhibited oils An inhibitor is a particular substance, added to the oil in small quantities in order to disarm certain intermediate "radicals" - agents in the process of oxidation of the oil. The result is a retardation of the ageing, until the quantity of inhibitor has been consumed. From that time onwards, the ageing will proceed and accelerate freely. The efficiency of the inhibitor depends on the degree of refining of the oil. Due to that, the best result is obtained if the oil was refined with the objective to be inhibited. An inhibited oil of good quality in normal operation will sometimes need addition of inhibitor after more than 20 years. Some users hold the view that inhibitors should not be used, because they may mask, for a while, the inherent ageing properties of the oil and lull the operating staff into false security. After the inhibitor has been consumed, it may escape attention that the oil deteriorates more rapidly. ABB Transformers does not share this view, and recommends inhibited transformer oil. However, if a customer

specification forbids inhibited oil, the filling will be made with un-inhibited oil fulfilling the ABB material specification.

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Note. The chemical short name for the usual inhibitor substance is DBPC (di-butyl-para-cresol). This must not be confused with the objectionable class of compositions, called PCBs (polychlorinated biphenyls - "askarels" DBPC is not environmentally noxious - as a matter of fact it has an alternative use as a stabiliser agent in foodstuffs.

3. Supplier certificate The supplier of transformer oil shall guarantee, and supply a certificate that the oil, delivered from the refinery, fulfils the list of requirements specified in the actual ABB material specification 1ZBA 117001-1, 2, 3 or 4. The quality of the oil at delivery condition shall be guarantied through certificates of the oil characteristics from the oil in the transportation containers or through sample tests. This certificate or tests shall include Power factor/Dissipation Factor at 100°C or 90°C and the Interfacial Tension against water. These tests are to assure that no contamination of the oil has occurred during transportation and storage. In the purchase contract for the delivery to the site, it may also be agreed to sample the oil on arrival for additional laboratory investigation to verify the quality of the material as delivered. 4. Sampling on site Bulk deliveries of oil in tank trailers are normally scheduled to arrive just in time for the filling procedure, and will be checked right away. Oil in drums will be kept in storage with unbroken seals up to the time when filling procedures are to be commenced. The drums shall be stored in horizontal position, with the openings horizontal (at same height). When the oil is delivered in drums and if it has to be tested the extent of sampling shall be as follows No of drums delivered 2

No of drums sampled -

6 21 51

-

101 201

-

5

2

20

3

50

4

100

7

200

10

400

15

When the oil is delivered in tank trailers: Take two samples from each separate tank compartment. Most of the properties of insulating oil are affected by impurities, particularly water. Care must be taken in order to avoid contamination of the oil-samples. All equipment used in obtaining samples and the sample container shall be clean and dry.

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5. Testing of samples. Oil characteristics The requirement for breakdown strength of the oil at delivery condition is specified according to IEC Standard Publication 296 and ASTM D3487. The test procedure is according to IEC Publication 156 [using hemispherical electrodes (VDE electrodes) with 2.5 mm spacing]. The minimum breakdown strength for oil as delivered is 30 kV/2.5 mm. The test procedure in accordance with ASTM D877 is using cylindrical electrodes with 0.1 inch spacing. The minimum breakdown strength for oil in delivery condition is 30 kV/0.1 “. After heating with particle and vacuum filtration the breakdown strength shall rise to at least: 80 kV/2.5 mm

method IEC 156

64 kV/0.08”

method ASTM D1816

35 kV/0.1”

method ASTM D877 This method is only accepted for transformers with nominal voltage below 230 kV.

Observe that the above values refer to the oil coming out from the vacuum filter equipment and it does not refer to oilsamples from the transformer. For new oil that never has been in contact with the equipment the Power factor/Dissipation Factor

0.005

at 100°C or 90°C and 50 or 60 Hz Interfacial Tension against water

≥ 40 Nm/m at 25 °C

Note. Oil with Power factor at 100°C or 90°C > 0.2 or Interfacial tension against water < 20 Nm/m shall be regenerated or substituted. Oil that is filled into the transformer tank through a valve at the lower part of the transformer tank shall have a maximum gas content of 0.2 % by volume. Oil that is filled into the transformer tank through a valve at the cover of the transformer tank shall have a maximum gas content of 0.5 % by volume. The maximum humidity content of the oil at filling into the transformer shall be < 10 ppm. This is normally verified at periodical control of the degassing filter and than controlled by the temperature and pressure in the degassing chamber

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6. Treatment of the oil before filling the transformer The necessary quantity of oil shall be collected and prepared in one or more clean storage tanks. Before being used, the tanks are visually inspected inside for cleanness. Any liquid residue from earlier use will be carefully removed, and the container flushed with a small quantity of new oil which is then discarded. The oil, received in drums, is pumped through the vacuum filter plant into the storage tank. The drums or trailer tanks shall not be emptied to the last drop - a sump of an inch or so is left, to avoid possible solid dirt or water on the bottom. The vacuum filter is then reconnected for circulation of the oil in the tank under continued heating( 50 - 80 °C) and degassing, until samples taken from the oil at the filter outlet shows that the breakdown strength is in accordance with item 5 above. When the dielectric strength of the outgoing oil from the degassing filter is approved the filling of the transformer can start.

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C. FINAL OIL FILLING ON SITE - ATMOSPHERIC PRESSURE

This Assembly Instruction applies to transformers with nominal voltage below 200 kV

shipped with oil nearly up to the cover. Filling up the oil to nominal oil level can in these cases be done with a filter press. The quantities of oil to be filled in are in these cases less than 16 % of the total oil volume in the transformer 1. Supply of the oil. Quality requirements, and cleanliness The necessary quantity of oil for the final oil filling may be part of the supply from ABB, or be procured locally. If the User provides the oil, the Material Specification for the purchase must be in agreement with the corresponding requirements by ABB. Those requirements are specified in 10.2 The cleanliness to be applied during the entire oil handling procedure cannot be enough emphasised. If returned drums are to be used for transformer oil, they should be meticulously cleaned and rinsed. The same of course applies to tanks. If this is neglected or taken easily by a distributor, the result will be that the fine transformer oil gets contaminated by residues of other chemical products. These may even contain additives which work as poison and seriously affect certain properties of the oil. The oil are supplied in drums - or in tanks. Oil in drums or tanks, as delivered, should never be dumped right into the transformer, but always be pumped through a filter unit. It is important that clean and dry filter are used. A small sump quantity should be left unused in the drum or tank. Oil samples should be taken from the delivered quantity on site and checked, before a transformer is filled. The dielectric strength of the filtered oil that is filled into the transformer shall be minimum: 60 kV/2.5 mm method IEC 156 (VDE electrodes). 56 kV/0.08” method ASTM D1816 30 kV/0.1” method ASTM D877 2. Topping up a limited quantity. When a transformer has been shipped more or less complete, and with oil nearly up to the cover, the following procedure is used

to complete the oil volume. A filter press can be used.

Figure 1. The oil, stored in drums or in a storage tank, is pumped through the filter

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2.1 Transformers with conservator For transformers with conservator, the conservator is empty, and its connection to the tank will be shut. The oil is pumped up into the conservator through its draining valve. When the whole quantity has been transferred to the conservator, bleeder valves on the tank are opened and the connection from the conservator to the tank is opened gently to let the oil flow into the transformer slowly to avoid air-bubbles to go deep into the transformer oil volume. As the filling gets completed, the bleeder valves are shut (note particularly the bleeding of turrets and of porcelain bushings communicating with the tank). 2.2 Transformer without conservator. For transformers without conservator the oil is pumped into the transformer through the top filter valve.Transformers designed without conservator are often shipped overfilled with the quantity of oil required to fill the cooling equipment. The data on the oil volume and whether additional oil will be needed at the installation site will be shown on the outline drawing. Obtain a test sample from the main tank and test for dielectric strength. Purge the gas space in the transformer and seal the tank at atmospheric pressure (zero gauge). 3. Filling of coolers and radiators. Fill the cooling equipment by opening the lower valve between the cooler or radiator and the main tank and bleed the air top vent plug from each cooler or radiator. Control that the oil level in the main tank always is above the core top and all insulation material. After finishing all assembling check that the oil level is in accordance with indication correcting for the oil temperature if different from 25 °C. For transformers that shall be pressurised verify that all accessories in contact with the oil or oil preservation system have been assembled before pressurising the transformer. After the oil filling procedure has been completed, the transformer should be left at least four hours before it is energised

©Copyright 2007 ABB, All rights reserved Document Title

Maintenance Manual Document No.

Date & Rev. Ind.

No. of Pages

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