Railway electrification system
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
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
Railway Electrification System Media
The LGV Sud-Est in France is electrified using 25 kV 50 Hz overhead lines.
The Angers tramway in Angers, France uses 750 V DC overhead lines, in common with many other modern tram systems.
A bottom-contact third rail electrification system on the Bucharest Metro, Romania
The London Underground uses third and fourth rails beside and between the running rails for electrification.
Bogie from an MP 89 Paris Métro vehicle. The lateral contact shoe is located between the rubber tyres.
An ÖBB train using 15 kV 16.7 Hz AC overhead lines in Austria
Schema of 2×25 kV power supply:1. Supply transformer (center-tapped output)2. Power supply3. Overhead line4. Running rail5. Feeder line6. Pantograph7. Locomotive transformer8. Overhead line9. Autotransformer10. Running rail
The Jungfrau Railway, the highest in Europe, uses three-phase electric power between two overhead lines and the rails.
Lots Road Power Station in a poster from 1910. This private power station, used by London Underground, gave London trains and trams a power supply independent from the main power network.
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