Miao Yulong

Influence of gas pressure on SF 6 decomposition characteristic and its mathematical amendment method

SF<inf>6</inf> decomposition method has become an important tool for partial discharge (PD) detection and fault diagnosis, due to its anti-interference against electromagnetic noises and vibration. Actually, the gas density can affect the process of SF<inf>6</inf> decomposition by-products a lot. To study the influence of gas pressure, several experiments of SF<inf>6</inf> gas decomposition at different gas pressures were carried out. Based on the “three zone reaction model” as well as the theory of gas ionization, approximate mathematical expression was derived analytically to demonstrate the correlation between the gas pressure and root-mean-square production rates of SOF<inf>2</inf> and SO<inf>2</inf>. The experimental results indicated that the concentrations of SOF<inf>2</inf>, SO<inf>2</inf>, CO<inf>2</inf>, SO<inf>2</inf>F<inf>2</inf> declined with varying degrees of influence with increasing pressure under the same PD severity (sorted by degrees as SOF<inf>2</inf>>SO<inf>2</inf>>CO<inf>2</inf>>SO<inf>2</inf>F<inf>2</inf>) and the rootmean-square production rates of SOF<inf>2</inf> and SO<inf>2</inf> significantly declined with increasing gas pressure while that of CO<inf>2</inf> and SO<inf>2</inf>F<inf>2</inf> have subtle changes. The fitting results with the proposed mathematical model verifies the correctness of the analytical expression, providing a promising way to fix the effects of gas pressure for the application of characteristic decompositions on GIS fault diagnosis.