Rail Potential Calculation Model for DC Railway Power Supply Equipped with Voltage Limiting Device

In DC electric railways, voltage is generated between rail and earth, i.e., rail potential. To keep the voltage below the permissible voltage limit specified by the international standard IEC 62128, a voltage limiting device (VLD) is added to railway power supply equipment. A VLD is a switch that connects the rail and the earth. The switch is closed when the rail potential rises above a permissible voltage. This lowers the voltage of the rail potential because the rail and the earth are shorted by the closed switch. We added a VLD model to a rail potential calculation model to evaluate the VLD's affection. The VLD was modeled as variable resistance that changed the resistance value depending on the open/closed status of the switch. Once the voltage between the rail and the earth exceeds the predefined limit, the status changes to close and stays closed for a predefined time before it is reopened. The results of the case study show that rail potential is reduced to almost zero by closing multiple VLDs installed in the line. However, stray current increases because it flows through the closed VLDs. The results obtained from the actual route will be compared with the simulation results in future work.