Calculation on the composition varying characteristics of decaying SF6 arc in the presence of trace oxygen and moisture

SF6 has been widely used as insulating and arc-extinguishing medium in power equipment. Under discharges, lower fluorides of sulfur generated by the dissociations of SF6 will react with unavoidable moisture and oxygen to form corrosive byproducts (etc., SOF2, SO2F2, SOF4). These byproducts will reduce the insulating and arc-quenching capacity of SF6 power equipment, so it is necessary to study their varying characteristics. In present paper, non-chemical and non-thermodynamic equilibriums were taken into consideration applying chemical kinetic model. The basic reactions of SF6 with H2O and O2 were obtained from literatures. Finally we got the temperature-varying concentrations of the main byproducts SOF2, SO2F2 and SOF4 as well as other important particles. We also analyzed the dominant reactions in different selected temperature ranges. This work can help to understand the varying mechanism of the key species and lay a theoretical basis for life-assessment of SF6 power equipment in further studies.