试验回路布置对变电站地网冲击特性测试的影响

Influence of Test Circuit Arrangement on the Impulse Characteristics of Substation Grounding Grid

开展地网冲击特性测试需搭建冲击放电回路,试验回路布置的差异会对地网冲击特性测试产生较大影响。在分析现有接地装置冲击试验系统构成的基础上,搭建试验回路对110 kV变电站地网进行了现场试验,研究了注流点对地网冲击特性的影响,并通过仿真计算研究了回流点对地网冲击特性的影响。试验结果表明,试验回路中注流点、回流点的选择会明显影响地网电位分布和电流的大小。在雷电冲击下地网高电位区域会集中在注流点附近,远离注流点的区域地网电位分布较均匀,注流点附近区域的地网散流变化大,远离注流点区域的地网散流较平均。仿真结果表明,由于回流极的影响,地网电位分布均匀度会低于无回流极情况,地网散流比例会略高于无回流极情况,增大回流极距离有助于减小地网冲击特性测量误差。

It is necessary to build an impulse current circuit for the impulse characteristics measurement of grounding grid.The differences in the arrangement of the test circuit will have greateffect on the test result.In this paper,based on the analysis of the existing impulse test system for grounding device,an impulse test circuit is built to perform field tests on 110 kV substation.The influence of the injection point on the impulse characteristics of grounding grid is researched by the test,and the influence of the reflow electrode on the impulse characteristics is studied by simulation calculation.The results show that the choice of injection point and reflow electrode will greatly affect the potential distribution and current distribution of grounding grid.The high potential area is concentrated near the injection point under the lightning impulse.The potential distribution in the area far from the injection point is relatively uniform.The current flowed through the grounding grid in the area near the injection point changes greatly.Far from the injection point area,the current distribution is more uniform.Due to the influence of the reflow electrode,the uniformity of the potential distribution is lower than that without the reflow electrode and the current distribution ratio is slightly higher than that without the reflow electrode.Increasing the distance of reflow electrode helps to reduce the difference from the actual lightning impulse condition.