in our 6.6kv motor feeder[it is having two sources from Bus A&B] earth fa

in our 6.6kv motor feeder[it is having two sources from
Bus A&B] earth fault relay is acting, we checked CBCT
connection and cable meggerd values found very good still
earth fault acting during first two are three start after
that it will hold. please clarify what was the reason. if
same motor is starting from other Bus-A it will start.

Question Posted / p.raghavendrarao

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in our 6.6kv motor feeder[it is having two sources from Bus A&B] earth fault relay is acting,..

Answer / a.p.nanjappa

WHAT IS THE TYPE OF 6.6KV SW.GR. hOW OLD IS THIS?
tHE EARTH FAULT RELAYS ARE VERY SENSITIVE. INSULATION
RESISTANCE OR MEGGER CAN NOT MEASURE.
CARRY OUT HV CAPACITANCE MEASUREMENT OF MOTOR,CABLE FEEDER.
AND hIGH POT TEST.
MEASURE THE TANGENT DELTA FROM DC HIGH POT.

IF MIN OIL CIRCUIT BREAKER,TEST THE OIL AND REPLACE.

WE ALSO EXPERIENCED THIS DUE TO BURNED CEREMIC/BAKELITE
PARTITION PLATES OF 6.6KV SW.GR

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