A partially high conductive coating adjusting surface charge distribution for mitigating surface flashover

High voltage direct current (HVDC) energy transmission has solved the problems of deliverying electric power of large capacity over long distances. During the operation of DC excitation, large amounts of charges inevitabley accumulate on insualtion surface, posing a hazardous effect on surface insulation performance. How to effectively control surface charge accumulation still remains as a chanllenge that we must face. In this study, a partially high conductive coating method for regulating surface charge distribution on spacers is proposed. The surface charge behavior after DC excitation is obtained on four kinds of partial coating, namely HV coating, GND coating, MID coating and $\mathbf{HV}+\mathbf{GND}$ coating. The DC flashover performance on this four kinds of coated spacers is also measured. The corresponding charge transport and flashover mechanism are revealed. It is hoped this research could provide valueable referances for designing insulation structure of DC power equipment.