Study of the Spread of Potential Rise Between Two Grounding Electrodes

The groundings of the power distribution, signaling, and power systems of a railway system are individually performed to realize fail safe, and the groundings are often installed in close proximity. Thus, when a grounding electrode is invaded by a lightning current, its ground potential rises together with the potential of the adjacent grounding electrodes; hence, there is a possibility of a large overvoltage being applied to the connected devices. In this paper, we have investigated the potential spread between two rod-shaped electrodes widely used in the grounding of the power, signal, and distribution systems of a railway system using the finite-difference time-domain method. The results of this paper are organized in such a way that the extent of the potential spread to the neighboring grounding electrodes can be understood from information such as the grounding resistivity at the installation location of the ground electrode and the wavefront duration of the lightning current, and these findings will be useful for grounding design. We also investigate the effect of the insulator between two neighboring electrodes to prevent the potential spread.