考虑微观特性的ZnO压敏电阻计算模拟模型

电力设备的绝缘水平建立在避雷器的过电压保护水平基础之上。ZnO压敏电阻具有优良的非线性电压-电流特性和浪涌能量吸收能力,被广泛用作电力系统避雷器的核心元件。ZnO压敏电阻的电气特性由其复杂的微结构和晶界特性决定。该文以Voronoi网络模型为基础,建立ZnO压敏电阻的微观结构模型。采用考虑晶间旁路效应的晶界分区模型,建立求解氧化锌压敏电阻宏观电气性能的大规模非线性电阻网络方程。针对难以采用常规牛顿迭代方法求解的问题,提出基于分段线性化和差分重构的快速求解优化算法,计算结果误差指标在10-3数量级以下。采用模型计算得到了尖晶石含量、晶粒尺寸不均匀度以及气孔率等微观结构参数对ZnO压敏电阻宏观电气性能的影响规律。

The Calculation Model for ZnO Varistor Considering Micro-characteristics

The insulation level of power system is based on the overvoltage protection level of arresters. ZnO varistor is widely used as the core element in power arrester and surge suppressor because of its excellent nonlinear voltage-current characteristics and high surge energy absorption capability. ZnO varistor’s electrical characteristics are determined by its complex micro-structure and grain boundary characteristics. In this study, the microstructure model of ZnO varistor was established based on Voronoi model. And a large-scale nonlinear resistance network equation for solving the macroscopic electrical properties of ZnO varistors was established by using a grain boundary zoning model considering intergranular bypass effect. For it is difficult to solve the large-scale nonlinear resistance network equation by using the conventional Newton iterative method, a fast optimization algorithm based on piecewise linearization and differential reconstruction was proposed. The error index of the calculation result is less than 10-3 orders of magnitude. Besides, the effects of microstructure parameters, such as spinel content, non-uniformity of grain size and porosity, on the electrical properties of ZnO varistors were obtained by calculation.