Residual Current circuit breaker is in conformity with standards of VDE 0664, CEE27 and BS4293. It apply to the circuit of AC 50/60Hz, 240V single phase, 415V three phases and below it for industrial and mining enterprise, building, commerce and family. To mainly prevent electric fire and personal casualty accident caused by personal electric shock or leakage of electrified wire netting, this RCCB is a current-operated, fast leakage protector of pure electromagnetic type, which can break off fault circuit rapidly in order to avoid occurrence of accident. The item is precise in structure, less elements, without auxiliary power and high working reliability. The function of the switch won't be influenced by ambient temperature and lightning.