Effect of Field-dependent Conductivity on Surface Charge Decay in ZnO/Silicone Rubber Composites

Abstract

Insulators in the HV power equipment are threatened by the surface charge accumulation, which can distort the local electric field, make an early insulation aging and even lead to a surface flashover accident in the worst case. This study tries to modify the dynamic behaviors of the surface charge accumulation and decay by introducing a nonlinear conductivity into the insulating material. The relationship between the field- dependent conductivity and the surface charge dynamics in zinc oxide (ZnO)/silicone rubber composites (SiRCs) was investigated in this paper. The results showed that with the increase of ZnO content from 7.9 vol% to 12.8 vol%, the nonlinear conductivity of ZnO/SiR composites was enhanced, resulting in an acceleration of charge transport and decay through percolating paths within polymer bulk, as the surface-charge-induced field exceeded its nonlinear threshold field. The theoretical model and experimental results both indicated that the differential coefficients of the surface potential in logarithmic coordinates were proportional to the field-dependent conductivity, at each instant of time during the course of surface charge decay. Owning to the ability of the charge self-releasing, the ZnO/SiR composites with nonlinear conductivity have potential applications for suppressing the surface charge accumulation.