Influence of Stray Current on Distance Protection in Rail Transit

Nowadays, urban rail transit is developing continuously, which is closely related to the power grid. The stray current generated during the operation of rail transit will invade the power system through the neutral point of the transformer, resulting in a series of effects. Dc magnetic bias caused by stray current will affect the transmission characteristics of current transformer. In this paper, the working principle of current transformer and its transmission characteristics under DC magnetic bias condition are studied. The influence of stray current on the transmission characteristics of current transformer is analyzed, and then the influence of stray current on directional circular impedance relay and power frequency variation distance protection is studied, which provides a basis for the prevention and control of stray current in rail transit.