Research on DC Bias Magnetic Characteristics of Transformers Along Urban Rail Transit Networks Under Varied Train Densities

With the growing scale of urban rail transit operation, the serious DC transformer bias phenomenon near the subway lines has attracted attention, and the mechanism of the impact of subway operation density on the urban power grid needs to be investigated. In this paper, a simulation calculation method for the distribution of stray current in the power system of rail transit network is proposed. A soil model considering the hydrological structure in the actual urban environment is established. Secondly, the current in the neutral point of the transformer under different train departure intervals is simulated to analyze the influence of train operating density on the bias of the transformer. The simulation results show that there is a strong positive correlation between the operating intensity of the rail transit and the transformer’s bias magnetization effect, and the average value of the neutral current at the substation most seriously affected by the bias magnetization is only 42.73% of the peak current in the low-peak period.