SiC/Epoxy Coating with Graded Conductivity for Surface Charge Inhibition Based on Electric Field-Induced Assistant Technology

Applying a SiC/Epoxy composite coating on the surface of DC insulators is an effective method to restrain surface charge accumulation and to homogenize the electric field distribution along the surface. However, the limited and constant nonlinear conductivity coefficient of a uniform coating makes it difficult to match the regional differences in surface charge distribution and spatial electric field variations. Therefore, in this paper, a nonlinear conductivity gradient coating is constructed by using electric field-induced assistant technology (EFIA) to arrange SiC in a gradient within the SiC/Epoxy coating. Optical microscopy was used to determine the gradient configuration of SiC in the EFIA-coating, and the surface charge accumulation characteristics of both the ordinary coating and the EFIA-coating were tested and analyzed. The results indicate that the conductivity of the EFIA-coating in regions with originally strong electric fields is obviously improved, effectively homogenizing the surface resistive electric field distribution of the insulator. Additionally, the high-density charge accumulation area near the high-voltage electrode is suppressed under high applied voltage. At 15kV, the EFIA-coating reduced maximum surface charge density by 30.43% and increased the uniformity of the electric field by 45.58%.