Decomposition characteristics of SF6 under thermal fault for temperatures below 400°C

This paper aims to explore the decomposition characteristics of SF
₆
under thermal fault, which can further improve the method of using SF
₆
decomposed components to diagnose inner insulation status of SF
₆
insulated equipment. Hence, the thermal fault simulation system of SF
₆
electrical equipment is designed and serials of experiments are conducted. It initially gets SF
₆
thermal decomposition characteristic for temperature below 400°C. Then it analyzes decomposed component species and their generation regularity, determines the main characteristic component of SF
₆
thermal decomposition and chooses the key component to represent fault severity. The result shows that: SF
₆
begins to decompose obviously at 300°C and the main decomposition components contain CO
₂
, SO
₂
F
₂
, SOF
₂
, SOF
₄
, SO
₂
and H
₂
S; the improvement of fault temperature will promote the decomposition of SF
₆
, but the formation regularity of each decomposed component is different; H
₂
S is the special component only appears when thermal fault proceeds to some degree (above 360°C). Hence, decomposed components and their formation regularity can be used to diagnose the SF
₆
equipment thermal fault. H
₂
S can be used as the key component to represent fault severity.