Study on the effect of solid products on DC surface flash-over voltage.

According to statistics, solid product formed by the reaction between SF6 gas and metal electrodes at the connecting joint of ultra-high-voltage direct current (UHVDC) wall bushing is likely to adhere to the surface of insulating materials, which may seriously threaten the insulation of the bushing. Thus, studying the effect of the 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 the solid products were measured and compared with those of epoxy-impregnated composite insulating materials. The comparison result shows that there is a significant difference between them, which demonstrate that the solid products may have an impact on the DC flash-over voltage of epoxy-impregnated composite insulating materials. Furthermore, by means of the DC surface flash-over platform, the characteristic of the surface flash-over voltage of the epoxy-impregnated composite insulating materials with the solid products attached directly is analyzed. It is found that the decrease in the surface flash-over voltage is closely related to the type of solid product, gas pressure, distance between electrodes, way of attachment, etc. [ABSTRACT FROM AUTHOR]