Correct option is A
· Circuit breaker usually operates when there is a fault in the line. Circuit breaker is a mechanical device which has the ability to close and open the circuit under normal and abnormal conditions.
· When the circuit breaker is closed it acts as a short switch, thus, the impedance of an ideal circuit breaker should be zero before interruption.
· When the circuit breaker is open it acts as an open switch thus the impedance of the ideal circuit breaker after the interruption should be infinite.
· Rating of circuit breaker is in MVA.
