Answer / k.prakashchandra

Which relay ? SEFR or back -up EFR ? Are the gens connected
to grid ? Whether all the gens trip simultaneously ?
Whenever there is a momentary heavy earth fault in the
outgoing feeder,all the gens trip on back-up EFR with
instantaneous trip indication,though the line does not
trip.So ,it is advised to disable instantaneous fault trip
i.e. high-set of the back-up EFR.

Answer / k.prakashchandra

Another probability. If there is any earth fault before the
GT primary bushings ,the gen may trip on SEFR if voltage
based( open delta) relay is used.Then you have to check
cable,termination glands and the stator winding for earth
fault either by meggering or better by applying rated voltage.

Answer / biplab

check the stator insulation with megger of each gen........

Answer / ronnie

this might be the result accumulation of moisture near the
earthing bit during evening time.which causes the generator
to trip showing earth fault....

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