Solution for Invasion of Stray Current from Traction Power Supply System on AC Power System

Abstract

The stray current generated by the urban traction power supply system will invade the AC power system through the grounded transformer, and the intuitive impact is the abnormal operation of the transformer, such as the increase of noise and temperature. Based on the field measurement and characteristic analysis of neutral current, this paper presents the principle of stray current from traction power supply system invading AC network. To mitigate the stray current at the neutral point, a capacitor and a converter are connected in series to block the DC and harmonic currents respectively. And the influence of the series connection with the neutral point on the relay protection is discussed, and based on this, a reliable and reasonable bypass protection unit composed of the mechanical switch and the electronic switch is configured to ensure the safe operation of the system. The developed device has been tested and will be applied in the field substation.