Checkpoint for
interval of 6 months
1) Check transformer oil
for acidity (<=0.03 mg KOH/g), sludge content (non detectable), flash point
(>=140 degree), Dielectric dissipation factor (tan delta) (<=0.010) , Interfacial tension
(>=35 mN/m) and specific resistance (resistivity) (>=6x10^12 om cm at 90 degree).
OIL ACIDITY TEST
OIL SLUDGE TEST
OIL FLASH POONT TEST
OIL TAN DELTA TEST
OIL INTERFACIAL TEST
Yearly checkpoint of Transformer
1) Check mechanical function of Buchholz
relay.
2) Marshalling box to be cleaned from
inside. All illumination, space heaters, to be checked whether they are
functioning properly or not. Check all the terminal connections of control and
relay wiring and tighten.
3) Clean all the relays,
alarms and control switches along with their circuit, in R&C panel (Relay
and Control Panel) and RTCC (Remote Tap Changer Control Panel) by appropriate
cleaning agent.
4) Check pockets for OTI & WTI (Oil Temperature Indicator & Winding
Temperature Indicator) on the transformer top cover and replace oil if
required.
5) Check proper function of Pressure Release Device.
6) Check insulation resistance and polarization index of transformer with battery
operated megger of 5 KV range.
7) Check resistive value of earth connection
and rizer with clamp on earth resistance meter.
8) Check DGA (Dissolve Gas Analysis) of transformer Oil annually for
higher KV rating transformer and once in 2 years for lower KV rating
transformer.
9) Check for proper sealing of marshalling box for cable holes.
10) Check all protections and alarm circuits by actual external
initiation with relay operation.
11) Check IR value of cooling motor winding, noise and vibration of
fan.
12) Check painting and surface finish.
13) Check tightness of bolts in gasket joints.
Checkpoint for
interval of 2 years
1) Check calibration of OTI and WTI.
2) Check tan-delta measurement of bushings of transformer.
3) Check operation of gauge and healthiness of air cell.
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