Influences of electrode materials on SF6 decomposition characteristics under partial discharge

The chemical activity of metal directly influences the decomposition of SF6 under partial discharge (PD), hence obtaining the regularity of this influence becomes a key issue for establishing fault diagnosis methods based on SF6 decomposition. Therefore, we built common protrusion defect models using needle electrodes of different materials (aluminum, copper and stainless steel) and plate electrodes of stainless steel to comprise a SF6 decomposition test platform, and then performed serial experiments of 96-hour PD decomposition on the plat form. In the experiments, we utilized gas chromatograph to quantitatively analyze the main decomposed components such as CF4, CO2, SO2F2, and SOF2. The results show that the tested electrode materials hardly affect the formation of CO2, but greatly affect the generation of SO2F2 and SOF2, and the reason is that the formation of low-fluorine sulphides and fluorine atoms produced by SF6 decomposition increase with increasing chemical activity of the metals. The electrode materials with higher chemical activity will have more obvious promotion effects, by which more SF2 and SF4 are generated, further reacting to form SOF2 and SO2F2. Hence, the difference of electrode materials at fault locations should be seriously taken into account in GIS insulation status diagnoses using SF6 decomposition characteristics. ©, 2015, Science Press. All right reserved.