In order to improve the complicated soil structure reasonable grounding location and avoid HVDC system monopole ground operation into the adverse effects of the current to the power grid, a composite soil geological model is set up for the typical fracture structure near the UHVDC grounding electrode. The calculation formula of surface potential is derived by combining the traveling wave method with the mirror image method. Based on the Matlab simulation platform, the surface potential distribution of two soil models under horizontal and composite conditions is compared, and the surface potential distribution under the influence of fracture and parameters is studied. The results show that the surface potential is closer to the measured value under the composite soil geological model. The distance from the fault to the ground electrode has great influence on the surface potential in the large area. The influence of the electrical resistivity at the fracture site is mainly considered in the near area of the grounding electrode. The conclusion is of great significance to locate the site of the ground pole and prevent the DC magnetic bias.%为了提高复杂地质条件下接地极选址的合理性,避免直流系统单极大地运行时入地电流对交流电网产生不利影响,针对特高压直流接地极周边典型断裂结构建立复合土壤地质模型,将行波法与镜像法相结合推导地表电位计算公式.运用 Matlab 仿真平台比较了水平和复合两种土壤地质模型下的地表电位分布情况,研究断裂及其参数影响下的地表电位分布规律.结果表明:复合土壤地质模型下地表电位更接近实测值;大区域内断裂到接地极距离对地表电位影响较大;接地极近区应主要考虑断裂处电阻率的影响.该结论对接地极选址及预防直流偏磁都有重要意义.
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