In addition to the factors that long working time causes the aging of the material

the surface resistivity isan important parameter to characteristic ageing condition. In this paper

the measurement method of surface resistivi-ty of GIS spacer is proposed

and a surface resistivity measurement is developed for the surface resistivity measure-ment of the insulator’s curvature surface. The surface resistivity measurement setup uses two annular electrodes

named as guarded electrode and unguarded electrode

which are in ring-shape and are close to each other with a gapin 2 mm. The central conductor of spacer can be as the guard electrode

and they formed an electrode arrangementwith three electrodes. The arc length between guarded electrode and unguarded electrode can be calculated accord-ing to the design size of GIS spacer. Considering to the applied voltage and steady state current

the surface resistivityof the spacer can be calculated. According to the experimental results of new and used 126 k V GIS spacers

this meth-od can be used to evaluate its insulation ageing condition.