An example of lightning-protection measures in railway signaling systems

Railway signaling systems have various types of signal and control cable lines connected to them from long distances. Usually, surge protective devices (SPDs) are used on the lines as a lightning-protection measure. However, certain types of cable lines cannot have an SPD installed on them from a fail-safe perspective, which may result in system failure caused by overvoltage when struck by lightning. In this study, using the finite deference time domain method, we examined inhibitory effects to mitigate overvoltage on cable lines that cannot have an SPD installed (hereafter called “conditional lines”) when an SPD is installed on other unoccupied lines, as a way to make effective use of spare lines. The results showed that overvoltage is expected to be mitigated if spare lines are utilized, in comparison with cases where no spare line is used.