Railway electrification system facts for kids

Electric locomotives under the wires in Sweden

Dual electrification; both overhead wire and third rail for different trains

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

Related pages

• Electric locomotive

Images for kids

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  An unrefurbished Metro-Cammell train on the Kowloon-Canton Railway British Section in Hong Kong in 1993. The Kowloon-Canton Railway British Section is the oldest railway in Hong Kong. It started to operate in 1910 and connects to the Guangzhou-Shenzhen railway.

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  Transition zone of third-rail to overhead-wire supply on Chicago's Yellow Line (the "Skokie Swift"), shown shortly before the conversion to third rail operation in September 2004.

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  An early rail electrification substation at Dartford

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  Nottingham Express Transit in the UK uses a 750 V DC overhead, in common with most modern tram systems.

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  A bottom-contact third rail on the Amsterdam Metro, Netherlands

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  With top-contact third (and fourth) rail a heavy shoe attached to the underside of a wooden beam which in turn is attached to the bogie, collects power by sliding over the top surface of the conductor rail.

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  London Underground track at Ealing Common on the District line, showing the third and fourth rails beside and between the running rails

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  A train on Milan Metro's Line 1 showing the fourth-rail contact shoe.

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  The bogie of an MP 05, showing the flanged steel wheel inside the rubber-tyred one, as well as the vertical contact shoe on top of the steel rail

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  Bogie from an MP 89 Paris Métro vehicle. The lateral contact shoe is located between the rubber tyres

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  Image of a sign for high voltage above a railway electrification system

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  15 kV 16.7 Hz AC system used in Switzerland

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  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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  The Royal Border Bridge in England, a protected monument. Adding electric catenary to older structures may be an expensive cost of electrification projects

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  Most overhead electrifications do not allow sufficient clearance for a double-stack car. Each container may be 9 ft 6 in (2.90 m) tall and the bottom of the well is 1 ft 2 in (0.36 m) above rail, making the overall height 20 ft 2 in (6.15 m) including the well car.

See also

In Spanish: Sistema de electrificación ferroviaria para niños