A study on the analysis and recommendations for ground current in the signal machine room of high-speed rail

Through the construction of high-speed railways and the electrification projects, the railway ground was switched to the common grounding method with the individual(or independent) grounding method. The common grounding method can eliminate the potential difference between the equipment connected to the common grounding line, but the line is used for the path which the return current of a train flows. As a result, it has been confirmed that the impulse surge current invades the signal machine room through the ground wires of the track circuit cable that connects the track circuit devices in the field and the transmitter and receiver in the signal machine room. It was also confirmed that the grounding current that entered the signal machine room affects the grounding current of other equipment in the room. The grounding system inside the signal machine room consisted of the common grounding line buried along the track and a steel frame of the building structure, but the steel frame grounding of the building structure was used as a path for another impulse surge current to enter the room. The ground current that entered the signal machine room continued to adversely affect certain equipment in the machine room, causing the equipment to malfunction or eventually burn out. Therefore, in this paper, we analyze the state of the ground current in the signal machine room and present measures to prevent the impulse surge current from entering the room and suppress the generation of ground circulating current in the room. Copyright © The Korean Institute of Electrical Engineers.