Improvement of Withstand Voltage at Particle Contamination in DC-GIS Due to Dielectric Coating on Conductor

±500kV DC transmission between Honshu island and Shikoku island in Japan will be operated at the beginning of the next century. High voltage DC-Gas Insulated Switchgear (DC-GIS) equipped in the DC-AC converter station has been developed. One of considerable items for designing the DC-GIS is the effect of the particle contamination to electrical properties more crucial than conventional GIS. the particles floating around the high voltage conductor with negative DC voltage give the most detrimental effect to the insulation properties at application of positive lightning impulse. Therefore it is essential to study and elucidate the phenomena for the realization of compact and highly reliable DC-GIS.