The breaker is mainly suited for distribution network of AC 50/60HZ, rated working current up to 6300A, rated voltage up to 690V to distribute power and protect the line and the equipment against the damage due to overload, short circuit, under-voltage and single phase earthing in transformer's neutral point TN distribution system, lt is also used to unfrequently covert the line under normal condition. The breaker can realize selective protection which can improve the reliability of power supply and avoid unnecessary power failure.