A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by over load or short circuit.
Its basic function is to isolate the circuit in case of a fault. By interrupting continuity, flow of electricity through the faulty circuit is stopped
Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
There are different types of circuit breakers. From LV Miniature CBs to 800KV SF6 CBs, we can see wide range of breakers
The circuit breaker serves two basic purposes
Switching during normal operating conditions for the purpose of operation and maintenance.
Switching during abnormal conditions such as short circuit or any other faults... thereby isolating the circuit.