ZnO压敏电阻微观结构参数与宏观电气性能的关联机制OA北大核心CSTPCD

The development of UHV technology has put forward higher requirements for various electrical characteristics of ZnO varistors.As the voltage level of UHV transmission system is too high,the volume,cost and operation reliability of equipment are largely dependent on the insulation level of the system.While the insulation coordination of the system is based on the overvoltage level of the system in various conditions,which is directly determined by the protection capability of the arrester used in the UHV transmission system.Therefore,there are many vital technical problems to be solved in order to develop excellent performance of the arrester for high voltage,such as excellent performance ZnO varistors,uniformity of potential distribution,structural design,and so on.ZnO varistors are the core components of arresters,parameters such as voltage gradient E1mA,nonlinear coefficient α1mA,residual voltage K,leakage current IL,etc.,all play a critical role in the overall performance of arrester.Besides,the preparation process of ZnO varistors is complicated and involves many processes,together with performance testing,which lead to a long preparation cycle and high material cost.At present,the improvement of computing power provides a new means for the study of complex systems.The composition,structure and performance of ZnO varistors can be simulated by computer to control performance,which can significantly improve the research efficiency. Firstly,we studied the correlation mechanism between micro-structure and properties of ZnO varistors through Voronoi network simulation model established by our research group,and optimized the parameters to describe the true conduction mechanism of grain boundary barrier clearly and accurately.Secondly,since choice of the quantity of ZnO grain is the key problem to study the electrical performance parameters of varistor by using simulation model.We analyzed the equivalence effect of different ZnO grain sizes and and found that the simulation results are closer to the real effect as the grain size increases.Finally,the number of 50×50 grain size is used as the equivalent model with good effect and not a long calculation time.The effects of different grain sizes,inhomogeneity of size,grain resistivity,porosity ratio and sample diameter on the macroscopic electrical performance parameters of ZnO varistors are simulated and calculated,then,the influences of these microscopic parameters on various macroscopic electrical performance parameters,such as voltage gradient,nonlinear coefficient,residual voltage ratio,leakage current,etc.,are analyzed successively.Then,the microscopic structure parameters and macroscopic electrical performance parameters are classified according to different effects.The microstructure and electrical properties of ZnO varistors were used as optimization variables.The optimization objectives are classified into two categories according to whether any optimization variable has the same influence on all kinds of optimization objectives,the optimization variables can be divided into three categories according to whether the optimization variables of the same classification have the same effect on the electrical performance parameters. From the simulation analysis,the previous batching-ball milling-spray granulation-water cut-pressing-firing-side insulation treatment and many other processes,plus the performance test and other steps,a long preparation cycle,high material cost of the experimental method has been transformed into a high efficiency and low cost calculation research,which greatly reduces the time and cost.In addition,this paper summarizes and classifies various micro-structure parameters and macro-electrical performance parameters,and simplifies the research process from a complex multi-objective and multi-variable problem to an optimization problem with only two types of objectives and three types of variables,which greatly reduces the difficulty of the problem.Based on the above,a simple optimization strategy is proposed,which has guiding significance for the production of high performance ZnO varistor.