Modeling calculation and influence analysis of transformer DC bias current caused by metro stray current

Abstract

The metro stray current leaked during the metro operation causes the nearby surface potential to change, so that the various grounding transformers at different ground potentials, resulting transformer DC bias. First, the leakage path of the metro stray current and the flow path causing the DC bias of the transformer were analyzed. Based on the stray current flow path, the DC-distribution resistance model of the grounding loop coupled with the field path was established. Combined with the grounding potential distribution, the DC current of the neutral point of the transformer and the grounding tower was calculated. Then the DC distribution model of the grounding loop was used to analyze the influencing factors of the transformer DC bias. Last, the DC distribution caused by metro stray current model was verified by the simulation results. The numerical calculation of transformer DC bias current and grounding tower current was realized in this paper, which has certain guiding significance for the evaluation and suppression of transformer DC bias.