Decreasing the Rail Potential of High-Speed Railways Using Ground Wires

Abstract

For high-speed railways, the rail potential, i.e., the electrical potential difference between the rail and the ground, can be considerably higher than that of conventional speed electric railways and become a safety risk to the signaling devices along the line, because of the large train currents and the high rail–ground leakage resistance. Proper countermeasures must be taken to decrease the rail potential to a safe level. This paper first provides a brief theoretical discussion of the principles of how the rail potential arises and how to suppress it. Then, a program, TRANAS, that was developed for traction network analysis is used to calculate the effects of various suppression countermeasures for an AT feeding system, which include cross-bonding of tracks, inserting CPWs, grounding using catenary masts, laying bare buried ground wires and connecting to dedicated grounding grids, which are evaluated based on the calculation results. The use of buried ground wires shows good prospects for solving electric safety problems in an integrated way, which is investigated in detail. The fact that GWs can suppress the rail potential is attributed to the decrease in the leakage resistance of the return circuit, meaning a relatively small cross-section will be enough for them.