Characteristics of the Concentration Ratio of $ \hbox{SO}_{2}\hbox{F}_{2}$ to $\hbox{SOF}_{2}$ as the Decomposition Products of $\hbox{SF}_{6}$ Under Corona Discharge

Partial discharge (PD) is triggered by insulation defects in a gas-insulated switchgear (GIS), leading to the decomposition of SF
₆
gas. The decomposition products of SF
₆
can be used to detect and recognize PD, but feature parameters must first be established. The main stable components of SF
₆
decomposition products are SO
₂
F
₂
and SOF
₂
. Their concentration ratio c(SO
₂
F
₂
)/c(SOF
₂
) is used as a feature parameter in PD recognition. However, the physical significance and characteristics of c(SO
₂
F
₂
)/c(SOF
₂
) have not yet been studied. In this paper, an experimental platform was constructed to simulate SF
₆
decomposition under PD in a GIS. The concentration data of SO
₂
F
₂
and SOF
₂
under different discharge energies, moisture contents, and oxygen contents were obtained. The data show that c(SO
₂
F
₂
)/c(SOF
₂
) increases with increased discharge energy and decreases with increased moisture as well as oxygen contents. These phenomena are explained by the discharge decomposition mechanism of SF
₆
. The results further indicate that c(SO
₂
F
₂
)/c(SOF
₂
) can be used as a feature parameter for determining the discharge energy with which it has a positive relationship. To improve PD recognition, the effects of moisture and oxygen contents must be considered when using c(SO
₂
F
₂
)/c(SOF
₂
) as a feature parameter.