Predicting molded-case circuit breaker let-through characteristics in an electrical system under short-circuit conditions

The authors discuss the MCCB (molded-cased circuit breaker) as a circuit element and describe one method of calculating system behavior with the MCCB as an element. Circuit breaker behavior in a system is determined using six parameters of the circuit breaker´s measured behavior. The proposed method satisfies any condition for power factor and closing angle of fault current level within the instantaneous operating range of the circuit breaker. As verified by tests, the method outputs conservative estimates of key circuit parameters relative to recommended values for safe applications.<>