Overvoltages in DC Urban Light Railway Systems: Statistical Analysis and Possible Causes

In DC light railway systems the equipment in the power substations and certain devices along the lines are protected against lightning overvoltages thanks to surge arresters. This paper analyses the overvoltages occurring on the tram network of Torino, Italy to discover the causes that brought to the explosion of several surge arresters in the past years. The cause is found to be the regenerative breaking of a particular type of vehicles, in conditions of low load in the system. The benefits of regenerative breaking are discussed in the light of the possible problems introduced. Finally, possible solutions are proposed.