Surface charge accumulation on HVDC-GIS-spacer

The paper deals with the surface charge accumulation on spacers of gas-insulated substations (GIS) applied to HVDC. The surface charge accumulation on solid insulators is a major problem of HVDC systems because it distorts the field distribution and reduces the breakdown voltage. The paper presents the mechanism and effects of surface charge accumulation on standard spacers used in GIS. A tool based on numerical field calculation has been developed to simulate and analyse the transient surface charging process and to gain the final steady state of a fully charged spacer. The numerical results are confirmed by measurements in a real GIS setup. Possible solutions to prevent surface charging are presented and discussed.