Commissioning Of Transformer

• Sample of oil taken from the transformer and subjected to electric test (break down value) of 50KV (RMS) as specified in IS: 335.
• Release trapped air through air release plugs and valve fitted for the purpose on various fittings like radiators, bushing caps, tank cover, Bushing turrets etc.
• The float lever of the magnetic oil level indicator (if provided) should be moved up and down between the end position to check that the mechanism does not stick at any point. If the indicator has signaling contact they should be checked at the same time for correct operation. Checking the gauge by draining oil is a more positive test.
• Check whether gas operated (if provided) is mounted at angle by placing a spirit level on the top of the relay. Check whether the conservator is filled upto the filling oil level marked on plain oil gauge side and corresponding to the pointer reading in MOG side. Check the operation of the alarm and trip contacts of the relay independently by injecting air through the top cocks using a dry air bottle. The air should be released after the tests. Make sure that transformer oil runs through pert cock of buchholz relay.
• Check alarm and trip contacts of WTIs, dial type thermometer, magnetic oil gauge etc. (if provided).
• Ensure that off circuit switch handle is locked at the desired tap position with padlock.
• Make sure that all valves except drain, filter and sampling valves are opened (Such as radiator valves, valves on the buchholz relay pipe line if provided).
• Check the condition of silicagel in the breather to ensure that it is active and colour is blue. Also check that the transformer oil is filled in the silicagel breather upto the level indicated.
• Check tightness of external electrical connections to bushings.
• Give a physical check on all bushing for any crack or any breakage of porcelain. Bushing with cracks or any other defects should be immediately replaced.
• Check the neutral earthing if specified. Make sure that neutrals of HV I LV are effectively earthed.
• Tank should be effectively earthed at two points.
• Check that the thermometer pockets on tank cover are filled with oil.
• If the oil temperature indicator is not working satisfactorily, loosen and remove the thermometer bulb from the pocket on the cover and place it with a standard.