(1) The selection of circuit breaker type should be based on the usage scenario and protection requirements. Choose plastic shell type as usual; When the short-circuit current is high, select the current limiting type; When the rated current is relatively high or there are selective protection requirements, a frame type should be selected; When controlling and protecting DC circuits containing semiconductor devices, DC fast circuit breakers should be selected.

(2) The rated voltage and current of the circuit breaker should be greater than or equal to the normal operating voltage and current of the line and equipment.

(3) The maximum breaking capacity of the circuit breaker is greater than or equal to the maximum short-circuit current of the circuit.

(4) The rated voltage of the undervoltage release is equal to the rated voltage of the circuit.

(5) The rated current of the overcurrent release is greater than or equal to the maximum load current of the circuit.