Answer / monty

LBB called as a line breaker back up protection and it is used for the saftey of our equipment whenever fault occurs on line than the breaker of uper stream will be open if lower stream breaker will not operated.

Answer / tpfasil200

Local breaker backup or breaker fail relay(LBB)..It is used when the trip command is given and the breaker fails to open due to some mechanical problem. The protection is time delayed and initiated by all trip conditions.On LBB operation, busbar protection is initiated, as all the breakers connected to that particular bus to which the circuit is connected have to be tripped.I t also trips the tie breaker and sends a direct trip command to the other end breaker.

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