Study on the Effect of SF6 Decomposition Solid Products on DC Surface Flash-over Voltage

According to statistics, SF6 decomposed solid products produced at the butt joint of Ultra-high Voltage Direct Current (UHVDC) wall bushing are likely to adhere to the surface of insulating materials. Thus, studying the effect of SF6 decomposed solid products on DC surface flash-over voltage is of great significance for evaluating the internal insulation of UHVDC wall bushing. The electrical parameters of SF6 decomposed solid products were measured and compared with those of composite insulating materials of epoxy impregnated paper. The comparison result shows that there is a significant difference between them, which demonstrate that the solid products decomposed by SF6 may have an impact on the DC flash-over voltage of composite insulating materials of epoxy impregnated paper. Furthermore, by means of the DC surface flash-over platform, the characteristic of the surface flash-over voltage of the composite insulating materials of epoxy impregnated paper with the SF6 decomposed solid products attached directly is analyzed. It's found that the decrease of the surface flash-over voltage is closely related to the type of solid product, gas pressure, distance between electrodes, way of attachment, etc.