Influence of H2O on the decomposition products and discharge mechanism of ac point-plane corona discharge

Abstract

SF 6 has been widely used as an insulating gas, which can decompose into several gaseous byproducts in electric discharges, like arc, spark or corona (partial) discharge, in the presence of the impurities H 2 O and O 2 . Researching on the decomposition products is helpful for improving the personal safety and long-time reliability of SF 6 insulated equipment. The decomposition characteristics of SF 6 under corona discharge is not only related to the insulation fault type but also has close relationship with the concentration of H 2 O in the insulated equipment. The effects of H 2 O on the decomposition products and possible main reactions have been analyzed a lot, however, the influence mechanism remains unaddressed. This work is devoted to obtaining the effects of the concentration of H 2 O on the decomposition products and the main reaction pathways. In this paper, the chemical kinetic model is established for 50Hz ac point-plane corona discharge. The multi-step time is used to obtain the rapid discharge process in the plasma region and the slow reaction process in the gas region simultaneously. The concentrations of SOF 2 , SO 2 F 2 and SO 2 and the main pathways of these three species under different moisture content at 12h are obtained. The moisture content varies from 200ppm to 5000ppm with the oxygen content keeping at 100ppm.