Utility Transformer DC Bias Caused by Metro Stray Current—A Review

Adisu Makeyaw, Xiaofeng Yang (), Xiangxuan Sun, Ke Liu, Tianyi Wu and Lu Chen
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Adisu Makeyaw: School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China
Xiaofeng Yang: School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China
Xiangxuan Sun: School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China
Ke Liu: School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China
Tianyi Wu: State Grid Shanghai Electric Power Research Institute, Shanghai 201199, China
Lu Chen: State Grid Shanghai Electric Power Research Institute, Shanghai 201199, China

Energies, 2025, vol. 18, issue 14, 1-33

Abstract: The rapid expansion of the urban rail network has increased concerns regarding stray current generated by the DC traction power supply system. This stray current, which arises from inadequate insulation between the rail and the ground, can cause electrochemical corrosion and operational challenges to nearby buried metallic infrastructures. A portion of stray current entering utility transformers may induce DC bias risk, thereby affecting the stability and reliability of distribution networks. This review studies the trends in utility transformer-related DC bias caused by metro stray current. Various modeling approaches and suppression measures are discussed, with an emphasis on comprehensively understanding stray current distribution behavior, the DC bias coupling loop, and its impacts. This review underscores the need for a thorough evaluation of existing DC bias suppression measures, and more effective and efficient measures must be developed to enhance the resilience of distribution networks. The gaps in current research are highlighted, and further studies are advocated, particularly those focusing on dynamic metro conditions, supported by advanced modeling, field applications, and interdisciplinary collaboration, to address the challenges of DC bias in urban rail environments.

Keywords: urban rail; stray current; DC bias; utility transformer; suppression measures (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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