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Answer Posted / a s nath
Local Breaker Backup (LBB) or Breaker Failure Pretection is
associated with Busbar Protection. If breaker fails to
operate due to its inoperable condition in spite of
operation of protective relays, there will be damage to the
system.This condition is being monitored by LBB relay or
BFR relay (Breaker Failure Relay)and will initiate the
Busbar protection and thus clears the bus.
The LBB protection will operate under the following
conditions:
(i) Lockout relay should operate
(ii)Current shall be more than 20% of normal current rating
(iii) The above currents shall persist after a time,
generally 200ms
When all the three conditions satisfy,it is considered that
the breaker is stuck and LBB protection will operate to
clear the bus.
By A S Nath
| Is This Answer Correct ? | 117 Yes | 8 No |
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