Answer Posted / vijay krishna rao
Yes both are tripping devices. But for breakers to trip,
relays send respective (frequency,voltage,current) signals
and accordingly trip based on the settings. Contactors trip
with no intentional time lag as soon as the voltage falls
below (may be 0.6-0.7 p.u), no signalling devices are used.
That's why one may have come across a situation, when there
is a grid fault and generator trips on auxillary motors
failure. As there (aux motors) are contactors present and
for a fault voltage drops, so contactors trip.
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