Working of Circuit Breaker

The operation of the circuit breaker is simple it first of all senses the fault occurs in the circuit.
In small circuits or less voltage rating breakers sensing of fault is done by the breaker itself then it breaks the circuit.
Normally heating is produced by the large current of fault used for that detection purpose.
While in large circuits or in grid stations for sensing fault protection relays are used that detect a fault and send a signal to the breaker then it breaks the circuit.
For this large system, there is a need for a separate power source like a battery, but some circuit breakers get supply from current transformers.
After sensing the fault occurring in a circuit the connections of breakers get separated, for these contacts separation mechanical energy provided by the spring or compressed air applies force on these contacts to open.
The magnetic field of current produced by the fault is also used for the tripping of the breaker.
In smaller circuit breakers there is a manually operated lever is installed to remove the load or again join the contacts that separated during a fault.
While in larger circuit breakers motors are installed to provide energy to the spring that was used during tripping.