Answer / dinesh lokhande

Let us first understand type of bushing.
Bushings for 132 kV class transformers are generally OIP
(Oil impregnated paper)bushings. However before charging
transformer air release to be done from tranformer tank and
bushings to release trapped air during oil filling. If in
any part of bushing air is trapped then air gets ionised
and provides a path for voltage beakdown resulting in
brsting of bushing due to high voltage stress in bushing.

Some other reason may be dielectric brakdown due to ageing.

Additional information.
Capacitance Tan delta test for OIP bushings can provide
readings of capacitance and tan delta which are indicative
of bushings deilectric health.

Answer / sathishbabu t

132kv(hi voltage,low current) has less rated current
capacity bushings, if we applied low voltage 6.6kv(low
voltage,hi current) bushing cant withstand hi current.
hence bushing burnt.

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