In ground return mode of high-voltage direct current (HVDC) transmission, direct current is injected into the soil through a ground electrode, causing ground potential rise in different areas and direct current at the neutral point of transformers. Earth surface potential (ESP) and neutral current are closely related to the 3-D structure of soil, but few studies treat the soil three dimensionally when calculating these two parameters. In this article, a 3-D resistor network (RN) is developed to construct the soil model, and a soil–grid unified circuit model is proposed to simplify the calculation of neutral current. The RN method is verified by calculating ESP of a horizontal multilayer soil model and contrasting the result with that of CDEGS software. The feasibility and accuracy of the soil–grid unified circuit model is demonstrated through comparing neutral currents of two substations with the results calculated by finite-element method (FEM). The influence of resistivity changes in a water-bearing fault on ESP and neutral current is specifically analyzed using RN method and FEM to prove the necessity of considering the 3-D complex soil structure. The results of this article contribute to the simulation of DC distribution of wide-area HVDC transmission in complex soil structures.

中文翻译：

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考虑三维复杂土壤结构的高压直流输电引起的地表电位和中性电流计算

在高压直流（HVDC）输电的接地回路模式中，直流电通过接地电极注入土壤，导致不同区域的地电位升高，并在变压器中性点产生直流电。地表电位（ESP）和中性电流与土壤的三维结构密切相关，但很少有研究在计算这两个参数时对土壤进行三维处理。在本文中，开发了 3-D 电阻网络 (RN) 来构建土壤模型，并提出了土壤-电网统一电路模型以简化中性线电流的计算。通过计算水平多层土壤模型的 ESP 并将结果与​​ CDEGS 软件的结果进行对比，验证了 RN 方法。通过比较两个变电站的中性线电流与有限元法 (FEM) 计算的结果，证明了土壤-电网统一电路模型的可行性和准确性。使用RN方法和有限元法具体分析了含水断层电阻率变化对ESP和中性电流的影响，以证明考虑3-D复杂土壤结构的必要性。本文的结果有助于模拟复杂土壤结构中广域高压直流输电的直流配电。