Aimed to clarify the correlation characteristics between the internal partial discharge (PD)\nin negative direct current (DC) gas insulated system (GIS) and gas pressure initiated by two typical\ndefects (i.e., free-metal particles and metal protrusion), this study on PD decomposition of sulfur\nhexafluoride (SF6) was investigated under different pressures on the basis of constructing a SF6\ndecomposition experimental platform with DC PD. Free-metal particles and metal protrusion in a GIS\nwere simulated using a spherical-bowl electrode and a needle-plate electrode, respectively. Trends\nand differences in the performance of SF6 decomposition components SOF2, SO2F2, CO2, and SO2\nat different pressures were compared and analyzed by experiments under different defects. Based\non gas microscopic ionization theory, the relationship between the decomposition component and\ngas pressure was deduced and verified. The concentrations of different decomposition components\nwere found to vary with the change in gas pressure under different defects, whereas the characteristic\nratios of decomposition components versus gas pressure showed a similar trend.
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