电力电缆介质击穿特性和状态监测方法

Dielectric Breakdown Characteristic and State Monitoring Method of Power Cable

在对绝缘介质击穿特性分析的基础上提出了一种电力电缆状态监测方法．建立了含有缺陷点的绝缘介质击穿模型,指出电缆绝缘层内部及表面存在空洞、夹杂物和隆凸不平是缺陷产生的内在因素,缺陷点处的击穿概率较大．推断电缆的水树具有分形结构,属于有限扩散凝聚生长模型．借助于含有缺陷的绝缘击穿模型,利用电力系统固有的干扰作为信号源,直接测量电缆屏蔽层的损耗电流,监测电力电缆绝缘运行状态．仿真结果表明,当绝缘介质树化时,损耗电流的分形维数大于1,分形维数可作为判定电缆绝缘状态的依据．

A state monitoring method of power cable based on the analysis of dielectric breakdown characteristic was presented. A breakdown model of dielectrics, which exists some blemish inside or on the surface, such as hole, impurity and heave at which breakdown probability is larger than that at other points, was established. Water tree of power cable is a fractal structure, which is attribute to diffusion-limited aggregation model. Based on the breakdown model of blemish dielectrics, the dielectrics state of power cable can be monitored using measures of the loss current from the shield of power cable that is sparked by the disturbing source in power network. Simulation results show that the fractal dimension of loss current is more than one when water tree occurs inside the dielectrics of power cable, and the operation state of power cable can be estimated from the fractal dimension of loss current.