Polishing Orientation Affecting Surface Charging and Flashover Characteristics of GIL/GIS Epoxy Spacer

In this article, the influence of polishing orientation on surface charge accumulation and flashover characteristics of the basin spacer in a downsized dc-gas insulated transmission line (GIL) are explored by experiments. Results show that the surface charge distribution of the polished spacers is different from the untreated one. Heteropolar charges can be observed in the polished area and outward expansion area under prestressing condition. The flashover voltages of all polished spacers are decreased. The radial polishing (RP) has the greatest impact on the flashover voltage, and the flashover voltage of the radially polished spacer is decreased by 11% under positive prestressing condition. The metal dust adsorptions of the spacers are also measured, which shows that the radially polished spacer is easier to absorb metal dust and the metal dust diffuses in the radial direction. SEM and energy spectrum scanning of different spacers show that there are more exposed alumina particles on the surface of the polished area. The microdischarge induced by alumina particles is the source of heteropolar charges. When the polished area of the spacers is repaired with epoxy paint, heteropolar charges disappear on the surface of the repaired spacer. It is confirmed that charge accumulation and flashover along the spacer surface are mainly affected by the change of surface morphology on the polished area.

I. Introduction

The large-scale application of ac gas insulated switchgear and gas insulated transmission line (GIS/GIL) in power system has promoted the miniaturization and high reliability of power equipment [1], [2]. However, dc GIS/GIL has not made a substantive breakthrough for a long time, which is subjected to the surface flashover of epoxy spacer caused by random charge accumulation [3]–[5]. The traceability of the random surface charging, especially the heteropolar charges, and its influences on triggering surface flashover are still unsolved, which need further investigation to give impetus to the industrial application of dc GIS/GIL [6], [7].