The risks of power supply in power systems attributed to stray currents caused by denser metro lines are increasing in modern megacities. Factors such as multi-layered soil and multiple metro operating lines (MOLs) make it more difficult to analyze dc coupling between the metro and power system. This article proposes a model for dc coupling of the metro and power system considering the two systems’ spatial information, the actual multi-layered soil, and the non-linear ionization of soil caused by stray currents. This article presents a dc coupling model suitable for studying multiple metro lines and large-scale power systems in modern megacities, which has an average relative error of 6.3% compared with experimental results. The neutral current of the transformer in a substation is up to 43 A (normal operation requires it to be less than 6 A in amplitude) under the influence of multiple MOL. The non-linear ionization of the soil near the power substations’ grounding network will decrease the soil resistance, this also results in greater dc currents intruding into power substations.

中文翻译：

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考虑现代特大城市复杂地质条件的地铁杂散电流侵入电力系统建模

在现代特大城市中，由更密集的地铁线路引起的杂散电流导致的电力系统供电风险正在增加。多层土壤和多条地铁运营线 (MOL) 等因素使得分析地铁和电力系统之间的直流耦合变得更加困难。本文提出了地铁和电力系统的直流耦合模型，考虑了两个系统的空间信息、实际的多层土壤以及杂散电流引起的土壤非线性电离。本文提出了一种适用于研究现代特大城市多条地铁线路和大型电力系统的直流耦合模型，与实验结果相比，其平均相对误差为 6.3%。变电站变压器中性点电流在多级MOL影响下高达43A（正常运行要求幅值小于6A）。变电站接地网附近土壤的非线性电离会降低土壤电阻，这也导致更大的直流电流侵入变电站。