In view of the malfunction of the 500 kV circuit breaker failure protection

the analysis is carried out from the aspects of the circuit breaker state at the time of the failure and the direct resistance of the relay contact. It is considered that the poor contact of the backplane contact of the start failure relay is the cause of the failure

and the use of a more reliable backup contact is proposed. The corrective actions of the circuit breaker start failure relay have been verified through the circuit transmission test and the smooth operation of the failure protection device.