Answer / vishwa theja c

Commissioning Of Transformer
After finalization of the erection work the following tests
should be conducted:

Pre Test Inspection

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.

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