Decomposition characteristics of SF6 under overheating conditions.

Overheating is one of the severe defects in gas-insulated switchgear (GIS). However, researches on decomposition characteristics of SF6 under overheating conditions are relatively limited. In this paper, SF6 decomposition products are studied under three overheating conditions which are overheating of solid insulation, overheating of metal, and overheating of metal adjacent to insulating material. Influence of overheating temperature, gas pressure, initial moisture content and adsorbent on the decomposition characteristics of SF6 is discussed. The results show that typical decomposition products of SF6 under overheating of solid insulation are H2, CO, CO2, CH4, SOF2, SO2, H2S, COS and CF4, and typical decomposition products of SF6 under overheating of metal are SOF2, SO2, CO and CO2. Besides, typical decomposition products of SF6 under overheating of metal adjacent to insulating material are CO, CO2, SOF2, SO2, CF4, CS2 and COS. Types of overheating can be recognized by characteristic ratio of (SOF2+SO2)/(CO+CO2): for overheating of solid insulation, the ratio is 0 to 0.25, and for overheating involving metal, it is greater than 1. Two types of overheating involving metal can be distinguished by their characteristic products such as CS2, COS and CF4. [ABSTRACT FROM AUTHOR]