Contribution of nano-SiC/epoxy coating with nonlinear conduction characteristics to surface charge accumulation under DC voltage

In order to suppress surface charge accumulation, a nano-SiC/epoxy composite with nonlinear conduction characteristic was employed to coat a pure epoxy substrate in this paper. Surface potential distributions on the insulator were measured after being charged by a pair of finger-shaped electrodes (one was powered at -10 kV, and the other was grounded). For the insulators with and without coating, there were mainly positive potentials on the whole surface, and the area with higher potential located near the high voltage electrode. As the charging time increased, the high potential area began to shrink, indicating a possible charge migration. When the charging time exceeded 60 min, the potential distribution was almost kept unchanged. Compared with the pure epoxy substrate, the amount of surface charges had a slight increment after being coated with 3 wt% nano-particles. The accumulated surface charges were progressively reduced when the content of fillers became higher. Especially for the samples with 7 wt% and 10 wt% ingredients, there was a sharp decrease of accumulated surface charges in the distributed area and magnitude from 40 to 60 min. In terms of surface trapping characteristics and nonlinear conduction of the composite, the effect of coating on the surface charge accumulation was discussed.