Evaluation of rail potential control devices performance for control of rail potential of DC electrified railway systems

Electrified railway systems are widely used for urban transportation around the world. In most DC electrified transit systems the running rails are used as the return conductor for traction current. Due to the resistances of running rails and rail-to-ground in totally floating earth systems, there will be a potential rise between the running rails and the ground known as the touch voltage which is caused by traction currents returning to the substations. This voltage can be dangerously high and may affect human safety. In order to reduce the voltages on rails, several rail potential control devices exist. Most of these devices allow a direct connection to earth when a certain voltage threshold is exceeded. In this paper, the working principles of these devices are given and the effect of certain parameters related with these devices on the minimum achievable touch potentials is investigated. In this paper, the model DC electrified railway system is built using SimPower Systems toolbox provided by Matlab/Simulink, and the simulation results are given out. Based on analysis, several factors that have obvious influence on rail potential are pointed out.