Estimation of lightning overvoltages according to lightning conditions and effect on decreasing lightning hazards due to SPD for railway signalling systems

Effective and economical lightning protection measures are necessary for railway signalling systems because suspended operation or train delays due to lightning damage may cause social disruption. The authors have measured lightning overvoltages on railway signalling cables laid at ground surface, overhead power lines and rails in the field to enable quantitative analysis of the frequency of lightning overvoltage occurrence from 2010 to 2013. We investigated the correlation of lightning overvoltages on signalling cables, power lines and rails with lightning conditions, such as the stroke current and the strike position, and derived the equations for estimation of the lightning overvoltages according to the lightning conditions. Moreover, we examined the effect on decreasing lightning overvoltages due to SPD attached on railway signalling cables and evaluated the effect on decreasing lightning hazards for railway signalling systems.