Improvement of Nonlinear Conductivity and Flashover Characteristics of SiC/LDPE Composite via the DC Electric Field Assist

Nonlinear conductivity characteristic of the nonlinear resistive field grading material is affected by the filler distribution. The dc electric field assist is capable of regulating the filler distribution, but it is rarely used in the development of the nonlinear resistive field grading material. In this article, the influences of the dc electric field assist on the filler distribution and nonlinear conductivity as well as surface flashover characteristics are studied. The SiC/low-density polyethylene (LDPE) composites are prepared under the dc assisted electric field of 0 and 1 kV/mm. The microstructures of the untreated and electric-field assisted composites are characterized using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The dielectric spectra, nonlinear conductivity, surface conductivity, surface potential decay, and surface flashover voltage are also measured, respectively. Experiment results show that the electric-field assisted composite presents a stronger nonlinear conductivity characteristic than the untreated composite. Moreover, the dc electric field assist also contributes to the fast surface potential decay and enhances the surface flashover voltage. These are attributed to the formation of the gradient SiC-filler distribution and the SiC chains under the dc assisted electric field. The dc electric field assist is very useful for the development of the nonlinear resistive field grading material and the dielectric functionally graded material.