In modern megacities, stray currents from metro systems intrude into multiple transformers' neutral points becoming a potential threat to the high-capacity transformers. Neutral current anomalies are exacerbated in unprotected substations when we instal guards at single stations. This paper presents a system protection strategy for multiple substations affected by stray currents in modern megacities. The model, taking Shanghai as an example, includes the spatial distribution information of the urban electrical energy transmission structure, the power system, and the metro system. A Particle swarm algorithm is used to calculate the resistance values of the devices for each station. Further stability tests are performed to select the optimal protection solution. The results show that when protection is considered as a system, the protection runs well and the neutral current level remains below the unprotected level when the protection fails at a single station or multiple stations.

中文翻译：

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特大城市电力系统地铁杂散电流系统防护方案

在现代特大城市中，地铁系统的杂散电流侵入多个变压器的中性点，成为对大容量变压器的潜在威胁。当我们在单个变电站安装防护装置时，未受保护的变电站中的中性电流异常会加剧。本文提出了现代大城市受杂散电流影响的多个变电站的系统保护策略。该模型以上海为例，包含了城市电能传输结构、电力系统、地铁系统的空间分布信息。使用粒子群算法来计算每个站的设备的电阻值。进一步进行稳定性测试以选择最佳的保护方案。结果表明，当保护被视为一个系统时，当单站或多站保护失效时，保护运行良好，中性点电流水平保持在未保护水平以下。