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Railway electrification in Great Britain
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Railway electrification in Great Britain describes the past and present electrification systems used to supply traction current to railways and tramways in Great Britain with a chronological record of development, a list of lines using each system, and a history and a technical description of each system.
way electrification emerged at the end of the nineteenth century. Advantages over the then predominant steam traction, particularly in respect of its quick acceleration (ideal for urban (metro) and suburban (commuter) services) and power (ideal for heavy freight trains through mountainous/hilly sections).
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Encyclopedia
Railway electrification in Great Britain describes the past and present electrification systems used to supply traction current to railways and tramways in Great Britain with a chronological record of development, a list of lines using each system, and a history and a technical description of each system.
History
Railway electrification emerged at the end of the nineteenth century. Advantages over the then predominant steam traction, particularly in respect of its quick acceleration (ideal for urban (metro) and suburban (commuter) services) and power (ideal for heavy freight trains through mountainous/hilly sections). Many systems emerged in the first twenty years of the twentieth century (as listed below). In 1928 a government committee chose 1500 V DC overhead to be the national standard, but little implementation followed, and many different systems co-existed.
After World War II, with nationalisation (1948), British Railways expanded electrification (the 1500 V DC overhead and Southern Region third rail systems) but soon (mid 1950s) adopted 25 kV AC overhead for its proposed mainline electrification.
Despite the following years of minimal capital investment, the 25 kV AC network has continued to expand, slowly, although large areas of the country outside London are still non-electrified, despite their urban, suburban, hilly or intercity nature.
Facts and figures
, 40% (3,062 miles / 4,928 km) of the British rail network is electrified and 60% of all rail journeys are by electric traction (both by locomotives and multiple units)
According to Network Rail, 66% of the electrified network uses the 25 kV a.c. overhead system and 36% uses the 660/750 V d.c. third rail system .
emissions
If electricity is generated by renewables or by nuclear power then railway electrification is one way of reducing greenhouse gas emissions.
The British government's preferred option is to use diesel trains and run them on biodiesel. In the White Paper Delivering a Sustainable Railway the government rules out large-scale railway electrification for the foreseeable future.
Systems no longer used
Great Britain has used a number of different electrification systems in the past. Many of these date from the early part of the 20th century when electricity was being experimented with for traction purposes. This section describes each system, in order of increasing voltage.
500 V DC, Overhead Line
525 V DC, Third Rail
- The Liverpool Overhead Railway was one of the earliest electric railways in Great Britain. The first section between Alexandra Dock and Herculaneum Dock was opened in 1893. The line connected with Lancashire and Yorkshire Railway's North Mersey Branch. It was never nationalised and it closed on 30 December 1956 due to extensive corrosion throughout its iron infrastructure, which was deemed uneconomical to replace.
600 V DC, Third Rail
- This was originally electrified in 1904, in response to extensive competition from new electric trams. The concept was a success for the North Eastern Railway (NER) a noted early pioneer in electrification, as passenger numbers returned to pre Tram levels. As the stock reached life expectancy in 1937, the network was remodelled by London and North Eastern Railway (LNER) to reflect the changing industrial and residential makeup of the area. Electrified at the same time was the dockside branch, where a pair of Class ES1 (formerly NER No.1 and 2) locomotives were introduced from 1905. These British Thomson-Houston locomotives operated from both the third rail and from overhead catenary. British Rail brought in third-rail stock (12 2EPBs) from the Southern Region in 1955. The system was de-electrified by British Rail in between 1963 and 1967, citing the changing industrial and population makeup of the area, reducing the need for electric traction. In an "interesting" reversal of policy much of the Tyneside network was re-electrified using a 1500 V d.c., overhead line system (see below) as the Tyne and Wear Metro.
650 V DC, Overhead
1200 V DC, Third Rail (Side-Contact)
- Manchester Victoria - Bury
- In 1917 the line between Manchester Victoria and Bury was electrified using a 1200 V d.c. third rail (side contact) system. The line between Bury and Holcombe Brook that had been electrified using 3500 V d.c. overhead system in 1913 was converted to this system in 1918. This system was abandoned in 1991 when the line was converted to a 750 V d.c. overhead system and became part of the Manchester Metrolink
1500 V DC, Overhead
In the wake of World War I, the British Government set up a committee to investigate the various systems of railway electrification and in 1928 it reported that 1500 V DC overhead should be the future national standard. Several schemes (see below) were implemented in its wake, although the Great Depression and World War II meant very little work was done. Technological advances post-war saw a government U-turn and the 25 kV AC system was adopted instead, for the West Coast Main line and Glasgow suburban electrification, as set out in the BR 1955 Modernisation Plan - at the same time the large amounts of money had/were still being spent converting several lines to 1500 V DC.
- A joint LMS and LNER effort, opened on 11 May 1931. The success of this scheme propelled LNER's later electrification efforts. The line was converted to 25 kV AC in 1971 but the stretch between Altrincham and Trafford Bar plus the stretch between Trafford Bar and the Cornbrook viaduct were later incorporated into Manchester Metrolink and converted again, to 750 V DC.
- Known as the Woodhead Route. The LNER chose this hilly and busy mainline for its first mainline electrification, with work starting in 1936. Due to the depression and World War II it wasn't completed until the 1950s. However upon completion the government chose to standardise on 25 kV AC instead, leaving the Woodhead Route and the few other 1500 V DC. lines isolated and non-standard. Subsequent rationalisation by BR saw much of this route closed east of Hadfield in 1981 (in favour of the more southerly Hope Valley Line, which serves more local communities). The remaining stub in Manchester was converted to 25 kV AC in December 1984.
- LNER decided to electrify the Liverpool Street to Shenfield section of the Great Eastern Main Line (GEML), known as the Shenfield Metro. Civil engineering works began in the 1930s but World War II intervened. Work was completed in 1949 and extended to Chelmsford and Southend (Victoria) in 1956 using Class 306 (AM6) EMUs. It was converted to the new standard of 25 kV AC, initially with some sections at 6.25 kV AC, on 4—6 November 1960, in the wake of the BR 1955 Modernisation Plan that called for 25 kV AC to be the new standard. The rest of the GEML was subsequently electrified.
- This line ran from Shildon (County Durham) to Newport (near Middlesbrough). In the wake of the electrification of Tyneside by the NER, this coal carrying line was electrified between 1 July 1915 and 1 January 1916, as a planned precursor to electrifying NER's busy York to Newcastle mainline (part of the ECML). It was dismantled by LNER, as due to the the decline in the coal market it was uneconomic to undertake the significant renewals required to continue electric operation, it was thus dismantled from 7 January 1935 to 8 July 1935. The locos were stored for other electrified routes .
3500 V DC, Overhead
- This was electrified by the Lancashire and Yorkshire Railway in 1913 as part of a trial system for export. The system was converted to third rail in 1918 (see above) .
6250 V (6.25kV), 50 Hz AC, Overhead Line
During the initial electrification of parts of the network to 25 kV, 50 Hz a.c. overhead the initial solution to the limited clearance problems in suburban areas (due to numerous tunnels and bridges) – notably London and Glasgow – was to use the lower voltage of 6.25 kV, 50 Hz a.c. overhead. Latter technological improvements in insulation allowed these area to be converted to 25 kV, 50 Hz a.c. overhead. The last sections of 6.25 kV, 50 Hz a.c. overhead were converted to 25 kV, 50 Hz a.c. overhead in the 1980s and this system of electrification is now obsolete in the UK.
- London, Tilbury and Southend (LTS)
- The majority of the line was electrified at 6.25 kV a.c. overhead in the early 1960s. Some sections were able to be electrified using 25 kV a.c. overhead from the outset. The sections electrified at 6.25 kV a.c. overhead were converted to 25 kV a.c. overhead in the early 1980s.
- Shenfield Metro
- The line was originally electrified at 1500 V d.c. overhead in the 1950s. In the early 1960s the line was converted to 6.25 kV a.c. overhead. In the early 1980s the line was converted for a second time to 25 kV a.c. overhead.
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- Glasgow Suburban network
- The majority of the network was originally electrified at 6.25 kV a.c. overhead in the early 1960s. Some sections were able to electrified using 25 kV a.c. overhead from the outset. The sections electrified at 6.25 kV a.c. overhead were converted to 25 kV a.c. overhead in the early 1980s.
- North Clyde Line - the central area, Springburn, Bridgeton and Milngavie branches and the Yoker loop)
- Cathcart Circle Line
- See SPT and Transport in Glasgow
6600 V (6.6 kV), 25 Hz AC, Overhead
Existing Systems - Conductor Rail Type (Third and Fourth Rails)
600 V DC, Third Rail
- This was electrified in 1935.
630 V DC, Fourth Rail
The London Underground is a large metro system operating across London, and beyond, commonly known as "the Tube". The 408 km (253 miles) network is made up of 12 lines and has been electrified for some time, starting in the 1890s. The network was largely unified between 1900-1910 and nationalised in 1933 becoming the railway component of London Transport (LT). A major expansion programme, the "New Works", was immediately launched, which saw LT take over several urban branches of mainline railways.
The London Underground network has historically been located in north London. In south London, expansion was limited by the poor geology (for building tunnels) and the extensive above-ground railway network already in that area, this being soon electrified (see "Southern Electric").
Due to the early pioneering work by the City & South London Railway (now part of the Northern line), the Underground uses a relatively obscure four rail system of electrification. Two rails, at standard gauge spacing, are the running rails for the trains; the outer - "third" - rail carries a positive current at +420 V DC, while the inner, middle - "fourth" - rail is a negative return of –210 V DC, giving an equivalent supply voltage of +630 V DC.
The advantage of the fourth rail system is that the two running rails are available exclusively for track circuits, of which there are many, though this was not the primary reason for adopting a fourth-rail scheme. Most of the deep-level tube lines run in cast iron tunnels (only some of the more recent constructions use concrete tunnel lining). Using a third-rail scheme necessitates that the return current is conducted through one (earthed) running rail. Such current is just as easily able to travel through the cast iron tunnel lining. Unless the joints between the sections are electrically sound, the current will arc across the sections causing considerable damage, or corrode the tunnel segments via electrolysis.
Further, there are many cast iron gas and water mains in the vicinity of the tube tunnels, and the return current would travel along these just as easily. Some of these mains date back to the 19th century and the joints between separate sections would certainly not have been designed to be electrically sound, as deep-level electric tube trains were unthought of.
The surface sections of the lines are constructed using fourth-rail purely to permit through running of the same trains, there being no other technical reason to do so.
The system shares track with Network Rail in several places. Some of these are non-electrified sections of the national rail network (e.g. Chiltern Railways out of Marylebone station), and diesel trains are used (by Network Rail). The suburban network of London North Western Railway (LNWR) was electrified in co-operation with London Underground, however in the 1970s British Rail introduced common, third-rail EMUs and the sections of the LNWR suburban network not used by the Underground had the fourth rail removed (see London and North Western Railway section below).
650 V-850 V DC, Third rail "Southern Electric"
The LSWR third rail system (at 660 V DC) was initially constructed prior to World War One out of Waterloo, to various suburban destinations. With grouping in the wake of World War One to form Southern Railway, the LSWR method of electrification was adopted. The 1920s saw LBSCR's 6600 V AC overhead suburban network replaced with third rail (1928/29). The Third rail extended throughout most South London lines under Southern control quickly (LBSCR and SECR), out all its London termini. The 1930s saw a wave of mainline electrification with the Brighton mainline (1932/33, including East and West Coastways and other related routes), followed by Portsmouth Direct (4 July 1937), and mid-Kent (Maidstone and Gillingham 1939).
World War Two saw extensive damage to the region, but electrification was soon resumed under the newly nationalised British Rail's southern region. The BR 1955 Modernisation Plan, with the two stage "Kent Coast Electrification". The Chatham mainline was completed first, followed by SER mainline and related lines. At this time voltage used was changed from 660 V DC to 750 V DC. Since then all further electrification has used 750 V DC, but the lines electrified before this time remain at 660 V DC. Attention then switched to the neglected LSWR region (now titled the South Western Division). The South Western Main Line (SWML) to Southampton and Bournemouth was electrified in 1967, as was the Island Line.
Under sectorisation in the 1980s, Network SouthEast conducted extensive infill electrification. The SWML was completed to Weymouth 1988. The Snow Hill tunnel was reopened, enabling Thameslink. The Hastings Line, Eastleigh to Fareham Line, Oxted Line - East Grinstead branch were also electrified. This left only a few generally isolated, rural lines and freight branches unelectrified (West of England Main Line, North Downs Line, Marshlink Line, and Oxted Line - Uckfield branch).
650 V - 850 V DC, Third rail ('Other')
Third-rail lines that were not formerly part of the Southern Region of British Railways:
- This uses a 750 V system . A history can be found here
- A short history can be found here . In 1970 the North London dc lines and the Class 501 EMUs used on these services were converted for 3rd rail only operation, with (as general theme) the fourth rail being removed on sections of lines not used by LUL stock. Some 4th rail was retained in the Gunnersbury and Queens Park areas for emergency use by LUL trains. With the closure of Broad Street, the NLL was joined with former Broad Street to North Woolwich via Stratford line, to extend the NLL - this section was electrified for the first time with third rail and OLE as far as Stratford and just third rail to North Woolwich. Two branches off the Watford DC Line have been closed; the branch to Rickmansworth was closed in 1952 (to passengers, goods 1967) and the branch to Croxley Green closed in 1996.
- The Watford DC Line between Queens Park and Harrow & Wealdstone features track sharing with London Overground trains, designed for 750 V third rail, and Bakerloo Line trains designed for 630 V third and fourth rail. As a compromise the nominal line voltage is set at 650 V, and the centre rail is bonded to the running rails, whereas in normal London Underground usage the traction supply floats with the centre rail at nominally -210 V and the outer rail at nominally +420 V giving 630 V overall.
- The North London Line between Richmond and Gunnersbury features track sharing with London Overground trains, designed for 750 V third rail, and District Line trains designed for 630 V third and fourth rail. As a compromise the nominal line voltage is set at 660 V, and the centre rail is bonded to the running rails. A similar arrangement also applies on the District Line between Putney Bridge and Wimbledon stations, where District Line trains operate on tracks also used by South West Trains, although the latter are not normally in passenger service.
The Northern City Line connects the East Coast Main Line to Moorgate - It was a former main line taken over by the Underground and turned into a tube line. It was however isolated by the abandonment of the 1930s "New Works" programme (and the development of the greenbelt). Tube services were further truncated by the new Victoria Line in 1964 (which truncated the northern end of the line to Drayton Park). The remainder was handed over to BR in 1975 in conjunction with the suburban electrification of the East Coast Main Line. The line uses 25kV AC overhead and Third Rail DC electrification, (with the switchover occurring with trains in the platform at Drayton Park).
750 V DC, Third rail (Bottom Contact)
- This system uses a bottom-contact third rail. The third rail uses a composite conductor rail made of an aluminium body with a steel contact surface. The benefit of this is a low-resistance, high current capacity rail that has a durable steel surface for the current collection shoegear of the train.
Existing Systems - Overhead Line (OHL) Type
1500 V DC, Overhead
- When the former "Tyneside Electrics" routes (which had been electrified using third rail until the 1960s when BR discontinued the "non-standard" equipment in favour of diesels) were rebuilt as the "Tyne and Wear Metro" in the 1970s, this system was used. Styled as "Light Rail" it is in practice normal heavy rail, and even shares the Durham Coast Line with the national rail network (unlike the other tram systems in the UK which operate alongside but on separate rights of way).
25000 V (25 kV), 50 Hz AC, Overhead Line
- This covers the lines from London Liverpool Street (Bethnal Green Jn) to Chingford, Enfield Town, Hertford East, and Cambridge. The line was first electrified in the 1960s when the lines to Chingford, Enfield Town and Cheshunt were electrified at electrified at 6.25 kV, 50 Hz a.c., overhead. The line from Cheshunt to Bishop's Stortford and Hertford East was electrified at 25 kV, 50 Hz a.c., overhead. The Lea Valley line between Coppermill Junction and Cheshunt was electrified at 25 kV in 1969. All of the 6.25 kV areas were converted to 25 kV in 1983. In 1987 electrification was extended from Bishop's Stortford to Cambridge using 25 kV. In 1990, the line to Stansted Airport opened, and in 1992, electrification was further extended from Cambridge to King's Lynn along the Fen Line.
- Electrified in two parts, the first between 1975 and 1978 and the second between 1984 and 1991.
- The line between London (Kings Cross) and Royston was electrified between 1976 and 1978 as part of the Great Northern Suburban Electrification Project. This included the Hertford Loop Line.
- In 1984, authority was given to electrify to Edinburgh and Leeds. The section between Hitchin and Peterborough was completed in 1987, and Doncaster and York were reached in 1989. By 1990 electrification had reached Newcastle, and in 1991 the final section to Edinburgh was completed.
- In order to keep the construction teams busy two additional schemes were authorised that extended electrification to Carstairs and to North Berwick (North Berwick Line).
- At the peak of electrification works in the late 1980s it claimed to be the "longest construction site in the world" at over 400 km.
- Electrified between London (St Pancras) and Bedford in 1983. The branch from Dock Junction to Moorgate was also electrified.
- See also Thameslink
- Electrified from the late 1950s to the mid 1960s under the BR 1955 Modernisation Plan as far as Crewe (and branches), it was extended to Scotland in the 1970s.
- Since 1999 the line has been modernised and the overhead line equipment has undergone a programme of refurbishment and renewal as part of works to increase train speeds from 110 mph to 125 mph.
- 1989 saw the electrification of the ECML which goes through Edinburgh, at the time a few local routes were electrified, but the majority of local services are unelectrified.
- – see also: Transport in Edinburgh
Suburban electrification was started in the 1960s in the wake of the BR 1955 Modernisation Plan. Electrification was piecemeal over the preceding year and is still incomplete with several suburban, rural and inter city lines still unelectrified. Rail expansion plans call for reopening of the Airdrie-Bathgate Rail Link, connecting the North Clyde Line and Edinburgh to Bathgate Line. See also: SPT and Transport in Glasgow.
- The Glasgow Suburban railway network can be split into three main areas;
- North Clyde
- South Clyde
- West Coast Main Line
- The main line to Leeds from London (via Wakefield Westgate) was electrified in 1990. In 1994, a project to electrify some of the local lines around Leeds was given authority to proceed. The project was called the "Leeds North West Electrification", and was intended to electrify the lines from Leeds to Bradford (Forster Sqaure), Skipton (Airedale Line) and Ilkley (Wharfedale Line).
- A few lines out of New Street mainly related to the West Coast Main Line.
- Electrified in 1994 between London Paddington and Heathrow Airport. This scheme was a joint venture between the British Railways Board and the British Airports Authority.
- See Heathrow Express and Heathrow Connect
25-0-25 kV, 50 Hz AC, Overhead Line, Autotransformer
- The first time that an auto-transformer system has been used in the UK.
- Currently in use between Ashton (north of Milton Keynes) and Hillmorton (south of Rugby), but planned to be extended along most of the route between London and Glasgow.
See also
External links
Further reading
525 V, d.c., Third Rail
630 V, d.c., Fourth Rail
650 V, d.c., Third Rail
750 V, d.c., Third Rail
1500 V, d.c., Overhead Line
6600 V, 25 Hz a.c., Overhead Line
25kV, 50 Hz a.c., Overhead Line
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