雷击树木放电反击配电线路过电压及防护研究

Research on Distribution Line Overvoltage Caused by Tree-Line Gap Breakdown When Lightning Strikes Nearby Trees and Protection Measures

雷电直击线路附近树木时,树木电位被大幅抬高可能会造成树-线间隙击穿放电,引起配电线路产生高幅值雷电过电压而造成严重损害。本研究建立了雷击线路附近树木后对配电线路进行电弧放电的电路仿真模型,将电弧放电采用动静电弧模型相结合的方式模拟树木反击线路的电弧特性。研究了树木高度、树-线路间距、雷电流幅值和波前时间对配电线路过电压的影响,并计算分析了线路型避雷器的雷电防护效果。计算结果表明:雷击附近树木并对线路放电时,线路过电压在感应阶段和电弧放电阶段会出现两次明显峰值;树木高度、树-线路间距、雷电流幅值和波前时间对配电线路过电压均具有不同程度的影响;安装避雷器可降低线路电弧过电压,且隔一级装设一组避雷器的防护效果最好。提出的模型对于雷击附近树木并对线路电弧放电时线路过电压的分析计算具有实用价值,结合地区雷电活动情况可以为线路防雷方案设计提供参考。

When lightning strikes a tree near the line,the potential of tree will be highly improved and may caused the breakdown of tree-line gap. It will cause overvoltage and serious damage to the line. A circuit model simulating that phenomenon is built. To simulate the breakdown process,a combined arc model is built with dynamic and static arc model. Factors that may affect the overvoltage at the distribution line are studied,including tree height,tree-line gap distance,and amplitude and wave-front time of lightning current. And lightning protection effect of line arrester is also studied. Calculation results show that when the lightning strikes the nearby trees with tree-line gap breakdown,there’re two distinct peaks in the induction phase and the arc discharge phase of overvoltage at the distribution line;tree height,tree-line gap distance and amplitude as well as wave-front time of lightning current all have an effect on the overvoltage;the installation of lightning arrester can reduce the arc overvoltage,and to install a group of lightning arresters every other tower can obtain the best protection effect. The proposed model is practically valuable to analyze and evaluate the line lightning overvoltage when lightning strikes a tree and arcing to the near line,and combined with the lightning activity in certain area,it can provide reference for the design of lightning protection scheme.