The satisfactory operation and reliability of power depends upon the reliable operation of switchgear. A circuit breaker must be capable of carrying, making and breaking currents under normal and abnormal conditions. In a system, a circuit breaker has to withstand power frequency over voltage and transient over voltage due to switching and lighting. Also circuit breakers should be capable of performing various switching duties such as interruption of low inductive currents, capacitive currents, interruption of terminal as well as short line faults, phase opposition switching in addition to satisfying the rated breaking and making capacities.
The performance of a circuit breaker under normal and abnormal conditions can be verified by performing different type of tests on circuit breakers. The purpose of testing of circuit breakers is to evaluate their constructional and operational characteristics and to check their performance in making and breaking high currents.