Answer Posted / manikandan.c
LBB means local breaker backup protection.This relays are
associated with some important main relays like
distance,differential and busbar relays.If main relays are
fail to open circuit breaker(or any mechanical problem in
breaker) under fault conditions,The LBB relay gives trip
command the same breaker for 100ms.If also not open means
next 200ms,It gives initiation for main busbar protection
and followed by busbar protection operated and direct trip
command send to the remote end.And finally protect the power
system.
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