Influence of Arcing Contacts Erosion on Decomposition Products under Arc Discharge in SF₆ Circuit Breaker

SF6 is widely used in circuit breakers for rated voltage of 40.5kV and above due to its excellent insulation and arc-quenching performance. Decomposed components analysis (DCA) method is considered one of the most promising methods for the condition monitoring and fault diagnosis of SF6 circuit breaker. The arcing contacts must be eroded by high temperature electric arc when the circuit breaker interrupts current, which has a significant influence on SF6 decomposition products. In this paper, the influence of arcing contacts erosion on SF6 decomposition products was studied. The experiments were carried out on a 40.5kV SF6 circuit breaker. The gas chromatograph and electrochemical sensor were used to analysis the decomposition products. It has been found that the concentration of decomposition products increases with the arc energy. The arcing contacts erosion has a significant effect on the concentration of SO2, SOF2, CO2 and CS2. Comparing with the state before contacts erosion, the concentration of SO2+SOF2 has decreased significantly. The concentration of CS2 has increased, and the concentration of CO2 has increased rapidly. The main reason for the change of decomposition products concentration before and after contacts erosion is discussed. The research results can provide the effective basis for the condition evaluation and fault diagnosis of SF6 circuit breakers.