变电站地网冲击特性试验研究

Experimental Investigation on Impulse Characteristics of Grounding Grid in Substation

地网冲击特性是变电站防雷设计的重要参考依据,目前的地网冲击特性研究中缺少大尺寸地网在大冲击电流作用下的试验研究。为此,基于某110 k V电压等级的变电站地网,设计并搭建了大冲击电流试验平台,研究了不同注流点（地网中心及地网边缘）、不同冲击电流波形（8/20μs及2.6/50μs）、不同冲击电流幅值（0.2-4 k A）等多种条件下的地网冲击特性。试验结果表明：对大尺寸地网而言,地网冲击接地阻抗远大于工频接地阻抗;地网冲击特性受注流点、冲击电流波形及冲击电流幅值的影响明显;地网高电位区域集中在注流点附近;冲击电流幅值越大,则地网冲击接地阻抗越小,且地网电位分布会越不均匀;冲击电流波前时间越短,则地网冲击接地阻抗越大,且地网电位分布会越不均匀;不同冲击电流波形下的地网散流分布具有一定相似性。测试所得数据可用于校验仿真模型,为完善相关标准提供参考。

The impulse characteristics of grounding grid provide an important reference for the lightning protection design of substation, however, the large impulse current test of grounding grid of substation is lacking. In order to make up for the blank, we built a test platform in a 110 k V substation. Moreover, we measured the characteristic parameters of impulse, including the impulse grounding resistance, potential distribution and current distribution under different current injection points（center or edge）, different impulse current wave-forms（8/20 μs or 2.6/50 μs）, different impulse current amplitudes（0.2~4 k A）. The test result shows that, for the large grounding grid, the impulse grounding resistance is greater than the power frequency ground resistance. The influences of impulse current and injection points on the impulse characteristics are obvious. The high potential area is concentrated near the injection point. The larger current amplitude leads to the smaller impulse grounding resistance and more uneven potential distribution. The shorter front time of waveform leads to the bigger impulse grounding resistance and more uneven potential distribution. The current distribution under different current wave-forms is similar. The test data can be used to verify the simulation model and provide reference for improving the relevant standards.