Characteristics of the Concentration Ratio of $\hbox {SO}_{2}\hbox {F}_{2}$ to $\hbox {SOF}_{2}$

Partial discharge (PD) is triggered by insulation defects in a gas-insulated switchgear (GIS), leading to the decomposition of SF₆ gas. The decomposition products of SF₆ can be used to detect and recognize PD, but feature parameters must first be established. The main stable components of SF₆ decomposition products are SO₂F₂ and SOF₂. Their concentration ratio c(SO₂F₂)/c(SOF₂) is used as a feature parameter in PD recognition. However, the physical significance and characteristics of c(SO₂F₂)/c(SOF₂) have not yet been studied. In this paper, an experimental platform was constructed to simulate SF₆ decomposition under PD in a GIS. The concentration data of SO₂F₂ and SOF₂ under different discharge energies, moisture contents, and oxygen contents were obtained. The data show that c(SO₂F₂)/c(SOF₂) 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 SF₆. The results further indicate that c(SO₂F₂)/c(SOF₂) 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(SO₂F₂)/c(SOF₂) as a feature parameter.