Research on the Influence of Urban Subway on Neutral Current of High-Voltage Substations Along the Line Under Complex Environment

Abstract

During the operation of the urban subway, there will be stray current leaking into the ground, which may invade the neutral point of the transformer along the line, causing the working magnetization curve of the transformer core to shift, thereby causing the direct-current (DC) bias effect of the transformer. Since there are unknown parameters in the equivalent circuit model of the stray current of the subway, in order to simplify the process of the influence of the subway operation on the neutral current, based on the analysis of the formation mechanism of stray current, a real subway line has been selected and a monitoring platform in the nearby high-voltage (HV) substation has been built to record the neutral current. Meanwhile, through the on-site recording of the entry and exit time of subway trains at four consecutive stations, the running trajectories of the subway trains can be reversed. According to the trajectory of the subway train, the recorded neutral current was re-divided into time periods, and the synergistic analysis of the neutral current and the train trajectory in the corresponding time period was carried out. The neutral current measurement results for 4 consecutive days indicate that the influence of the subway train on the neutral current of the substation is mainly the influence of the unbalanced load, and the degree of the unbalance mainly comes from the distance and the acceleration and braking of the subway train. The trajectory of the subway train is related to the amplitude of the neutral current. The closer the subway train is to the substation, the greater the impact on the neutral current.