The mechanism of SF6 decomposition characteristics under partial discharge at different gas pressures and voltage

摘要

SF is applied in high-voltage equipment due to its excellent insulating and arcing performance. However, a partial discharge is often caused by some insulation defects. Under partial discharge, The decomposition products including SOF, SOF, SO, CF, CS, will be formed. The types, content, and change trend of products will encounter serious disagreements due to the difference of discharge type. The partial discharge can be detected by the analysis of the decomposition products of SF. In recent years, the method to detect the partial discharge has seen a reduction in interferences and an increase in sensitivity. Due to these changes, researchers pay more attention to the decomposition characteristics of SF. In this paper, the decomposition characteristics of SF under partial discharge at different gas pressures and voltage levels were studied. In the experiments, gas chromatography was adopted to quantitatively determine the characteristic components of decomposition. The results show that SF decomposition products include SOF, SOF, SO under the needle-plate defects. The concentrations of SOF+SO and SOF increase over time and the former rate of reaction is faster than that of SOF. The concentrations of SOF+SO and SOF increase with increased voltage and decrease with increased pressure. Then, characteristic parameters of SF dissociation rate examed to explain the SF gas decomposition mechanism under different pressures and voltage levels. Under partial discharge, SF will first decompose into SF, SF, SF2, etc, by electron impact-induced dissociation. The low fluorine sulfides will then react chemically with insulating material, and oxygen in SF to form the decomposition products. Dissociation rate affected by gas pressures and voltage controls the stability of the decomposition product rate. Finally, by calculating dissociation rate, it is found that dissociation rate at different gas pressures and voltage levels influenced the decomposition product concentration were drawn.