Time-domain response model of nonlinear dielectric properties for electrical field grading composites

The electrical field grading materials are expected to well response to arbitrary electrical excitation. In this paper, a modified Voronoi network model is established to simulate the response of electrical field grading materials under arbitrary excitation. The grain-boundary structure of ZnO microvaristors is described by the Voronoi polygons with a distorted hexagonal structure and the nonlinear conductivity is modeled based on the carrier transport mechanism. The network calculations replicate the resistive contacts between fillers and the micro-region breakdown phenomenon of insulating materials during the formation of the conduction path. The accuracy of this model is evaluated using AC and surge measurements for the ZnO/SiR samples. The model can manage the typical nonlinear time-domain responses and well reflect the effect of filler concentrations as well as the relationship between capacitive and resistive components of the responses. This work is helpful to design field grading materials to self-adapt high electrical fields of electronic and electrical devices and increase their stability and durability.