Condition Assessment on Arc Nozzle of High Voltage Circuit Breaker Through SF6 Decomposition Products

The condition of arc nozzle in a gas chamber is significant for the health of a circuit breaker, especially for high frequency interruption circumstance such as AC filter circuit breakers in HVDC system. However, few methods can assess the ablation state of a nozzle without opening the gas chamber. To solve this issue, this research proposes an non-intrusive way to diagnose the nozzle ablation condition. The method is based on tracking the SF₆ decomposed products as the circuit breaker under test is in operation. Additionally, a SF₆ gas chromatography was designed to record and analyse the changing trends of SF₆ decomposed products every 20 minutes in a real-time mode. The results show that CF₄ can be treated as a characteristic component to reflect the nozzle ablation status. The CF₄ content is found to highly correlated with the loss of the nozzle materials and the increment of making and breaking energy.