A railway electrification system supplies electrical energy to railway locomotives and multiple units so that they can operate without having an on-board prime mover. Their main advantages are high energy efficiency and low operating cost. Building their wires and other infrastructure is expensive, however.
Power supply[change | change source]
Electricity may be sent to the train in different ways. Different countries use different systems. The most widely used systems are:
- Alternating current from overhead lines at 15,000 volts, 16.7 Hz
- Alternating current from overhead lines at 25,000 volts, 50 Hz
- Direct current from overhead lines at 1,500 or 3,000 volts
- Direct current from a third rail at 600 or 750 volts