中文摘要：

针对如何构造合理的土壤导电模型来准确计算流过变压器中性点直流量的难题，基于特定土壤导电模型，分析了不同土壤配置下模型简化对地表电位的影响，结果表明在一定条件下简化模型仅改变地表电位绝对值，对各变电站间电位差影响可以忽略，提出了合理选取土壤导电模型的判据及其阈值。研究结果有助于准确评估流过变压器中性点直流量，为实际工程中直流接地板附近变电站的选址提供了理论参考。

英文摘要：

In order to calculate DC current flowing through transformer＇s neutral point accurately, the key challenge that hasn＇t been solved effectively is how to establish the proper conducting soil model. Based on the specified conducting soil model, the influence of model simplification on the earth surface potential （ESP） was analyzed for different soil structure configurations. It is found that simplifications only change the absolute value of ESP, but the influence of ESP difference between the transformer substations can be ignored under certain conditions. Therefore, the criteria and threshold value for selection of conducting soil model reasonably are introduced. The results show that the proposed simplication method can properly evaluate the DC values flowing through transformer＇s neutral point and therefore provide theoretical references for selection of substations near the HVDC ~round electrode.