Effect of Nozzle Ablation Amount on the Generation Amount of Decomposition Products for SF₆ Circuit Breaker

Non-uniform arc burning in the nozzle is a common latent fault of SF6 circuit breaker, which will affect its breaking performance. When arcing, PTFE in the nozzle is vaporized and involved in the formation reaction of SF6 decomposition products. Non-uniform arc burning leads to PTFE excessive vaporization and significantly affects the type and concentration of some SF6 decomposition products, which can provide a basis for the latent fault diagnosis. In this paper, 16 times of 31.5kA short-circuit current breaking tests were carried out by two 40.5kV SF6 circuit breakers respectively. The uniform and nonuniform ablation nozzles were obtained. It was found that the concentrations of SOF2, SO2 and SO2F2 were almost not affected by the amount of nozzle ablation. However, when the mass loss of excessive ablation nozzle is 1.8g more than the normal one, CF4, C2F6, CS2 and CO2 of excessive ablation nozzle are 807.5uL/L, 22.5uL/L, 9.0uL/L and 116.9uL/L more than the normal one, respectively. CF4, C2F6, CS2 and CO2 can be used as characteristic decomposition products to diagnose nonuniform arc burning in the nozzle. This study is of great significance for the latent fault diagnosis of SF6 circuit breakers based on decomposition product analysis.