Surface Resistivity Measurement for Ageing Test of GIS Spacer

Gas Insulated Switchgear (GIS) has shown a high reliability due to the application of excellent SF6 insulating gas and epoxy-filled spacers. In the GIS insulation breakdown accident, most breakdown accidents occurred along the insulator’s surface. In addition to the factors that long working time causes the ageing of the material, the change of surface resistivity is one of the important influencing factors on surface breakdown strength. In this paper, the measurement method of the surface resistivity of the GIS spacer is proposed, and it can solve the measurement requirement of the surface resistivity of the insulator’s curvature surface. The surface resistivity measurement setup uses two annular electrodes, named as a guarded electrode and the unguarded electrode, which are in ring-shape and are close to each other with a gap of 2 mm. The central conductor of the spacer can be as the guard electrode, and they formed an electrode arrangement with three electrodes. The arc length s between the guarded electrode and the unguarded electrode can be calculated according to the design size of the GIS spacer. Several groups of fixed diameters of electrodes can be designed. When used in combination, the measurement of the surface resistivity at a different location of the spacer can be achieved.