An 11kv system consisting of an underground cable to a sub
station about 300 meters away was shut down for about 10
hrs. On energising, it tripped off on earth fault about
10---20 mins later 6 times but since than it is not
tripping.its already 3 weeks now. The SPAJ was found to be
fine. what could be the cause.No test had been done to
determine the cause of the trippings till now because of
demand.

Answer Posted / pillay

thanks but I had managed to ON the system and remained
energized with some load for a few minutes (10 -20 mins)
before it tripped again on earth fault , it happened 6 times
on (4/6/2011) and till today (13/07/2011) no problem. we
are using ABB spaj oc/ef relay.

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