Calculation model by Voronoi network and verification of zinc oxide varistor considering conduction mechanism

This paper investigates the impact of the microstructure of zinc oxide varistor ceramics on their electrical properties. The microstructure of varistor was characterized by Voronoi network, and the relationship between microstructure and electrical properties was studied by experiments. The results of the calculations indicate that the reduction of grain size leads to a linear increase in voltage gradient but also reduces the energy handling capacity and current-carrying capacity. An increase in grain nonuniformity causes a decrease in voltage gradient and leakage current, while the nonlinear coefficient and residual voltage ratio increase. The variation of grain resistivity significantly affects the residual voltage ratio, and the two are almost proportional. When the grain resistivity reaches 50 Ω·m, the residual voltage ratio is as high as 2.37. The influence of grain resistivity on flow capacity has an obvious inflection point and reaches the maximum value at about 1 Ω·m, about 5000 A. The increase in sample diameter size leads to a decrease in the varistor voltage gradient and nonlinear coefficient. The results can better characterize the effect of the changes of the structure of the varistor on the electrical properties.