Stuck breaker protection

Stuck breaker protection is a situation in which a circuit breaker fails to operate even after receiving a tripping signal from a relay or a switch.  Stuck breaker can undermine the protection scheme and can cause damage to machinery and is a danger to personnel.  

Common reasons for a circuit breaker not opening are a disconnection in the trip circuit or a mechanical problem with the circuit breaker.  In these conditions, there needs to be a backup protection device which can interrupt the fault and isolate the system.  In some cases, the entire section of the bus to which the breaker is connected is de-energized to interrupt power. 

A simple Stuck breaker protection schemes functions by sensing the position of the circuit breaker through the limit switches in the circuit breaker.  The protection system waits for the open status from the circuit breaker after the open signal has been given.  If the signal is not received within a preset time, the scheme assumes that the breaker is stuck and initiates backup measures. 

However, this system has its limitations.  The system cannot detect a situation where the current continues to flow despite the breaker having tripped.  This can occur due to situations where the arc has not been quenched (failure of the arc extinction system) and the current flows even though the contacts have mechanically separated. 

To ensure proper feedback of the interruption of the current, advanced stuck breaker schemes sense the current as well as the position contacts of the circuit.  This ensures that an accurate feedback of the breaker status.

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