AC/DC Railway Electrification and Protection

The technical strength of all electrification schemes lies in the fact that the prime mover is removed from the train; but this is also its economic weakness. By taking power from a distribution network there is almost unlimited power available which has been efficiently produced but the cost of providing the fixed installations can only be justified where the traffic is heavy or frequency is high. The 25 kV A.C. 50 Hz electrification system has been developed specifically for railway traction purposes. The main feature that separates this system from the conventional 3 phase and neutral HV distribution network of the public supply authority is that the railway system is a single-phase system with one pole earthed. Even though other railway administration have their own individual electrification schemes the basic design of the systems is the same.