The metro stray current leaked during the subway operation causes the nearby earth surface potential to change, so that the various neutral‐grounded transformers to be at different earth surface potentials, resulting transformer DC bias. In order to analyze the influence of metro stray current on transformer DC bias, the polarization potential monitoring data in metro traction power supply system and neutral point current of nearby transformer were compared, and the positive correlation characteristics between the two were pointed out. By studying the stray current leakage reason in the metro traction power supply system and the circulation path causing transformer DC bias, the mechanism of the transformer DC bias under the subway operating environment was revealed. Based on the discrete model of the stray current distribution, considering the mechanism of stray current on DC bias, the equivalent resistance model of the transformer DC bias caused by metro stray current was built with double‐end power supply environment. Then the calculation formula of transformer neutral point current changing with subway operating conditions was derived, the numerical calculation of DC bias current of transformer caused by metro stray current was realized. The validity of the proposed model was verified by current distribution, electromagnetic field, grounding and soil structure analysis, the simulation results showed that the proposed model can calculate the stray current distribution and the nearby transformer DC bias current with high accuracy, which provided a quantitative analysis method for studying the correlation between metro stray current and transformer DC bias phenomenon. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

中文翻译：

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地铁杂散电流引起的变压器直流偏置电流建模与分析

在地铁运行期间泄漏的地铁杂散电流会导致附近的地表电位发生变化，从而使各种中性线接地的变压器处于不同的地表电位，从而导致变压器直流偏置。为了分析地铁杂散电流对变压器直流偏置的影响，比较了地铁牵引供电系统极化电位监测数据和附近变压器的中性点电流，指出了两者之间的正相关特性。通过研究地铁牵引供电系统中杂散电流泄漏的原因以及引起变压器直流偏置的循环路径，揭示了地铁运行环境下变压器直流偏置的机理。根据杂散电流分布的离散模型，考虑杂散电流对直流偏置的作用机理，在双端供电环境下，建立了地铁杂散电流引起的变压器直流偏置的等效电阻模型。然后推导了变压器中性点电流随地铁工况变化的计算公式，实现了由地铁杂散电流引起的变压器直流偏置电流的数值计算。通过电流分布，电磁场，接地和土壤结构分析验证了该模型的有效性，仿真结果表明，该模型可以高精度计算杂散电流分布和附近的变压器直流偏置电流，从而提供了定量的方法。分析方法来研究地铁杂散电流与变压器直流偏置现象之间的关系。©2020日本电气工程师学会。由Wiley Periodicals LLC发布。