Electrical safety of DC urban rail traction systems

In this paper the electrical safety of DC urban traction systems is analysed, with particular focus on fault current detection and on dangerous voltages which could arise in case of fault. For the discussion the tram network of Turin, Italy, is used as a case study. Firstly the structure of the DC traction power supply is described; then the safety of the system is analysed, examining possible types of fault. In particular, ground faults inside the substation and along the line are analysed in detail. Fault currents and dangerous voltages are calculated thanks to a simplified circuital model of the traction system. Finally, the consequent risks for the people are examined and some conclusions are presented.