考虑土壤频变特性的接地系统有限元模型

The FEM Model of Grounding System Considering Soil Frequency-Dependence

基于电磁场理论的有限元法(FEM)和傅里叶变换相结合,通过引入Visacro-Alipio土壤频变公式,建立了可以考虑土壤电参数频变性的接地系统有限元模型。按照文献所给典型Heidler首次回击、后续回击雷电流冲击10 m水平接地极的试验条件,用Comsol Multiphysics软件的AC/DC模块建模仿真,将结果与文献试验数据对比,验证了模型的准确性。并进一步对3m垂直接地极分别埋于电导率0.01 S/m、0.002 S/m、0.001 S/m、0.0005 S/m土壤中时土壤频变性情况进行仿真分析,仿真发现,土壤频变性与土壤工频电阻率关系密切,土壤工频电阻率越高,频变作用越明显。在高电阻率(≥500Ω·m)土壤接地冲击计算中,有必要将土壤电参数的频变性考虑进来。

Based on the combination of the electromagnetic field theory FEM and Fourier transform, through introducing the Visacro-Alipio soil frequency-dependence expressions, a grounding FEM model which considered the soil frequency-dependence is established. According to the test condition in literature, the typical Heidler first and subsequent return stroke lightning current of a 10 m horizontal grounding electrode, based on the AC/DC module in Comsol Multiphysics software, the model is built, simulated, and the its accuracy is verified. Further simulation analysis of a 3 m vertical grounding electrode buried in 0.01 S/m, 0.002 S/m, 0.001 S/m, 0.0005 S/m soils is done to evaluate the frequency- dependence effect of soil electrical parameters, the results show that there is a close relationship between the soil frequency-dependence and soil power frequency resistivity： with the increase of soil power frequency resistivity, the frequency-dependence effect is more obvious. In the practical impulse calculation of high resistivity （≥ 500μm） soil, it is necessary to take the frequency-dependence of soil electrical parameters into account.