Analysis and Mitigation of Stray Current in Modern Metro Systems With OVPD and PSD

Recently, excessive stray current resulting from frequent activation of the overvoltage protection device (OVPD) have seriously intensified corrosion of buried metal and transformer dc bias. Consequently, analyzing and mitigating these stray current has become urgent. Platform screen doors (PSDs) are widely used in modern metro systems and play a role similar to OVPD in protecting passengers in some cases. Therefore, it is necessary to consider the operation of PSD and re-examine the triggering strategy of OVPD for mitigating stray current, but it has not been discussed yet. This article first synchronously measures and analyzes the level of rail potential in different PSD states. Measured data shows that rail potential at the station is lower during PSD opening periods than closing periods. Moreover, a stray current evaluation model is proposed and verified to comprehensively investigate this phenomenon. Simulation results under different train densities confirm the universality of this phenomenon. Therefore, a stray current mitigation method based on the coordination of OVPD and PSD functions is proposed. Additionally, the effectiveness and safety risk of this method are analyzed. Results show that this method completely prevents stray current leaked from OVPD and not pose any additional safety risks.