An actual case of 220 kV bus tie breaker during hot standby transfer operation,due to the poor contact of the B-phase energy storage limit switch of the circuit breaker,resulted in the failure of synchronous loop closure,and the circuit breaker control circuit was disconnected before the operation did not issue an alarm.Pointed improvement measures to optimize the circuit breaker control loop disconnection monitoring function.With the continuous scale expansion of Yunnan power grid,this system is having an increasingly higher requirement on the fault limit clearing time for better stability,and the circuit breaker failure is having greater impact on the system stability.Therefore,higher requirements are put forward for the monitoring of circuit breaker control loop disconnection.Combined with a practical case of 220kV bus tie circuit breaker during hot standby operation,the phase B energy storage travel switch of the circuit breaker was in poor contact,resulting in synchronous loop closing failure,and the circuit breaker control loop was disconnected without alarming before operation,this article points out that there is a principle defect in the current commonly used circuit loop monitoring method,which is relay contacts in series at circuit breaker position to start"control loop disconnection"signal loop monitoring method.When the disconnection signal monitoring loop is abnormal,the circuit breaker control loop cannot be self-monitored,resulting in the possible disconnection defect becoming a hidden fault and continuing to exist.An optimization design of circuit breaker control loop self-monitoring loop for disconnection is proposed.By building a monitoring loop on the basis of the original control loop to monitor the whole working condition,the loop of this scheme is simple and reliable,which can realize the dual monitoring effect of both control loop and disconnection signal loop,and provide a comprehensive assessment for the integrity of control loop and disconnection signal loop.It is helpful to discover the hidden defects of control loop in advance and improve the efficiency of disconnection elimination,and further improve the reliability of circuit breaker operation.
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