Abstract: In ord to ensure that reliable and stable operation of the pow system, the circuit breakers of 220kV and above transmission lines mostly adopt split phase.The three phases of the circuit breaker may open one or two phases,resulting in incomplete phase operation.In ord to prevent misoperation or refuse operation of that circuit breaker due to inconsistent three-phase position of the circuit breaker, the circuit breaker of this kind shall be equipped with three-phase inconsistent protection which can reflect the non-full-phase operation state of the circuit breaker.The circuit breaker in abnormal state can be tripped timely to ensure the normal operation of the system.