Railway electrification in Great Britain

Railway electrification in Great Britain began during the late 19th century. A range of voltages has been used, employing both overhead lines and conductor rails; the two most common systems are 25 kV AC using overhead lines and the 750 V DC third rail system used in southeast England and on Merseyrail. In 2006, 40%—3,062 miles (4,928 km) of the British rail network was electrified, and 60% of all rail journeys were by electric traction (both by locomotives and multiple units). According to Network Rail, 64% of the electrified network uses the 25 kV AC overhead system, and 36% uses the 660/750 V DC third-rail system.

The electrified network is set to expand over coming years, as 25 kV electrification is extended to currently unelectrified lines, such as the Great Western Main Line, the Midland Main Line and lines in the North of England as part of the Northern Hub.

The first electric railway in Great Britain was Volk's Electric Railway in Brighton which opened in 1883, and still functions to this day. The London Underground began operating electric services using a fourth rail system in 1890 on the City and South London Railway, now part of the Northern line. Main line electrification of some suburban lines began in the early years of the 20th century, using a variety of different systems. In 1921 a government committee chose 1,500 V DC overhead to be the national standard, but little implementation followed and many different systems co-existed. During the interwar period, the Southern Railway adopted the 660 V DC third rail system as its standard and greatly expanded this system across its network of lines south of London.

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