中文摘要：

首次利用物理意义明确的模拟镜像法推导出三维复合分层土壤模型格林函数,基于特定土壤模型,分析了不同土壤配置下土壤模型对地表电位的影响.结果表明,在一定条件下土壤模型变化仅改变地表电位绝对值,基本不改变地表电位差,从理论上阐明了土壤参数变化对地表电位影响的物理机理.针对如何选取合适土壤模型来准确计算流过变压器中性点的直流量难题,提出了合理选取土壤模型的判据及其阈值,避免了土壤模型选取的随意性和盲目性,为准确评估流过变压器中性点直流量和直流接地极附近变电站选址提供理论依据.

英文摘要：

The Green’s function of three-dimensional combined-layer soil model is firstly derived using simulated image method. Based on the specified soil model, the influence of soil model on the earth surface potential （ESP） is analyzed for different soil structure configurations. It is found that difference in soil model only changes the absolute value of ESP, but the influence of ESP difference can be ignored under certain conditions. And the physical mechanism for the effect of soil parameter change on ESP is explained theoretically. One of the challenges that have not been solved effectively is how to establish the proper soil model to calculate DC current flowing through the neutral point of transformer accurately. For this challenge, the criteria and threshold value for selecting the soil model reasonably are introduced. Therefore, the arbitrariness and blindness of selecting the soil model can be avoided. The results are useful for calculating accurate results, which can further provide theoretical references for selecting substations near the HVDC ground electrode.