Influence of Grease on Characteristics of Gas Decomposition Product After Breaking Current of SF6 Circuit Breaker

SF
₆
gas is widely used in circuit breakers and gas insulated switchgear (GIS). In the maintenance of SF
₆
circuit breakers, several cases of overdose grease application were found. Excessive grease would accumulate on the surface of pressure cylinder which had influence on the circuit breakers' insulation and arc extinguishing performance. In this paper, a 40.5 kV SF
₆
circuit breaker was taken as the test object to research the characteristics of SF
₆
gas decomposition products after breaking current in the defect of excessive MoS
₂
grease. Gas chromatography and electrochemistry method were used to detect and analyze the gas decomposition products. The results showed that the gas decomposition products were carbon dioxide (CO
₂
), carbon disulfide (CS
₂
), carbon monoxide (CO), sulfur dioxide (SO
₂
) and thionyl fluoride (SOF
₂
) when the grease applied excessively. The concentration of each gas decomposition product was compared to that applied normal dose of grease. From the experiments results, the effect of excessive grease to SF
₆
gas decomposition products was analyzed, the results can provide guidance for the status assessment and fault diagnosis of SF
₆
electrical equipment.