Existing systems - third and fourth rails Railway electrification in Great Britain

1 existing systems - third , fourth rails

1.1 national rail: 650 v - 750 v dc, third rail (top contact)
1.2 630 v dc, third rail (top contact)
1.3 630 v dc, fourth rail (top contact)
1.4 750 v dc, third rail (bottom contact)
1.5 600 v dc, third rail (top contact)
1.6 250 v dc, third rail (top contact)
1.7 110 v dc, third rail (top contact)
1.8 100 v dc, 4 rail

existing systems - third , fourth rails
national rail: 650 v - 750 v dc, third rail (top contact)

lines through clapham junction equipped third rail electrification.



southern electric

the extensive southern third rail electric network covers south london , southern counties of dorset, hampshire, sussex, surrey , kent.

the london , south western railway (l&swr) third-rail system @ 660 v dc began before world war waterloo suburban destinations. southern railway formed in 1923 grouping; adopted l&swr system, , 1929 london, brighton , south coast railway (lb&scr) suburban overhead network replaced third rail. south eastern main line electrified @ 600 v, later upgraded 750 v dc. third rail extended throughout south london lines out of london termini. throughout 1930s, there main line electrification, including brighton main line (including east, west coastways , related routes in 1932-1933), portsmouth direct line (4 july 1937) , maidstone , gillingham (1939).

after world war ii, electrification resumed in newly nationalised british railways southern region. br 1955 modernisation plan included two-stage kent coast electrification . chatham main line completed, followed south eastern main line , related lines. voltage raised 660 v 750 v. since then, electrification has used 750 v; lines electrified before remain @ 660 v. attention switched neglected former l&swr area (then south western division). south western main line (swml) southampton central , bournemouth electrified in 1967 , weymouth in 1988.

during sectorisation in 1980s, network southeast conducted extensive infill electrification. snow hill tunnel reopened, enabling thameslink. hastings line, eastleigh fareham line , oxted line (east grinstead branch) electrified. left few lines unelectrified: west of england main line, wessex main line, north downs line, oxted line (uckfield branch), , marshlink line.

merseyrail

two lines of merseyrail network; northern line , wirral line use 750 v dc third rail (see suburban electrification of london, midland , scottish railway history).

london , north western railway (l&nwr)


euston , broad street watford junction , croxley green (watford dc line)
richmond – north woolwich (north london line)

see suburban electrification of london, midland , scottish railway history. in 1970, north london dc lines , class 501 emus used on these services converted third-rail operation, fourth rail being removed on sections not used lul. fourth rail retained in gunnersbury , queens park areas emergency use lul. closure of broad street, north london line joined stratford north woolwich line; electrified third rail , overhead line far stratford, third rail north woolwich. 2 branches of watford dc line have been closed: rickmansworth in 1952 (to passengers, goods in 1967) , croxley green in 1996.

the watford dc line between queens park , harrow & wealdstone , north london line between richmond , gunnersbury used london overground trains designed 750 v third rail , bakerloo line trains designed 630 v third , fourth rail. compromise, nominal line voltage 650 v, , since 1970 centre rail has been bonded return running rail. there no special provisions required @ queens park, 2 dissimilar systems meet, gap longer 1 coach of bakerloo line train @ entry (and exit from) bakerloo, operates nominal -210 v on fourth rail , +420 v on third rail. there no bridging of incompatible systems trains pass 1 other since, uk electric trains intended run extensively in tunnels, there no continuity of traction power circuits between vehicles of train.

a similar arrangement applies between putney bridge , wimbledon, district line runs on tracks owned network rail, used south west trains, though stock movements.

northern city line

the northern city line connects east coast main line moorgate. isolated abandonment of 1930s new works programme (and development of metropolitan green belt). tube services truncated @ northern end victoria line in 1964 @ drayton park. remainder handed on br in 1975 in conjunction suburban electrification of east coast main line. line uses third-rail dc electrification between moorgate , drayton park, trains switch 25kv ac overhead.

630 v dc, third rail (top contact)

island line (isle of wight)

the single remaining national rail line on isle of wight electrified in 1967, former london underground rolling stock used, due limited height of ryde tunnel. island line used 630 v dc third rail, cheaper option convert lul stock third rail, , implement third rail on line. rolling stock used br class 483s.

630 v dc, fourth rail (top contact)

the tube s fourth-rail system



london underground track, showing third , fourth rails beside , between running rails



london underground (lu)

the london underground large metro system operating across london , beyond, commonly known tube . 408-kilometre (254 mi) made of 11 lines; electrification began during 1890s. largely unified between 1900 , 1910 , nationalised in 1933, becoming railway component of london transport (lt). major expansion programme (the new works ) launched, in lt took on several urban branches of mainline railways.

the underground in north london; expansion south london limited geology unfavourable tunnelling , extensive main-line network, of being electrified (see southern electric ). underground uses relatively uncommon 4 rail system of electrification. 2 standard gauge rails running rails; outer third rail carries positive current @ +420 v dc , inner fourth rail negative return @ –210 v dc, giving supply voltage of 630 v dc. chief advantage of fourth-rail system that, in tunnels metallic (usually cast-iron) lining, return traction current not leak lining causing electrolytic corrosion there or in neighbouring utility mains. 2 running rails available exclusively track circuits.

the surface sections use fourth rail solely operational consistency; system shares track network rail in several places. track shared 750 v third-rail stock, central rail bonded running rails , outside rail electrified @ 660 v. allows both types of train operate satisfactorily. suburban network of london & north western railway (lnwr) electrified in co-operation underground, during 1970s british rail introduced third-rail emus , sections of lnwr suburban network not used underground had fourth rail removed (see london , north western railway , above).

the underground has carried out studies consider raising voltage above present 630 v nominal. new equipment @ substations allow future increase standard 750 v nominal. in addition, electrical equipment of new trains based on use of 750 v rated equipment. so, whilst new equipment being designed 750 v operation, no decision increase voltage has yet been made public underground.

750 v dc, third rail (bottom contact)

docklands light railway (dlr)

this uses bottom-contact composite third rail, aluminium body , steel contact surface. advantage of low-resistance, high-current-capacity rail durable steel surface current collection. rail may surrounded insulating material on top , sides reduce risk of electrocution railway staff , trespassers. bottom-contact system less prone derangement snow top contact.

600 v dc, third rail (top contact)

glasgow subway, electrified in 1935

250 v dc, third rail (top contact)

hythe pier railway, electrified in 1922

110 v dc, third rail (top contact)

volk s electric railway electrified @ 50 v dc, raised 160 v in 1884 , reduced 110 v dc during 1980s.

100 v dc, 4 rail

the elevated monorail @ national motor museum, beaulieu uses rubber tyres running on 2 metal tracks, 1 on either side of central guide. because rubber-tyred, requires 2 current conductors , 2 collectors (hence four-rail designation).




^ southern electric locomotives . electron . 1989. retrieved 2007-01-19. 
^ merseyrail . nedrailways. archived original on august 27, 2009. retrieved 2010-11-17. 
^ eric peissel & robert schwandl. europe > uk > england > liverpool merseyrail . urbanrail.net. retrieved 2010-11-17. 
^ london , north western railway electrification watford , richmond . easyweb.easynet.co.uk. retrieved 2010-11-17. 
^ horne, mike (2001). bakerloo line: illustrated history. harrow weald: capital transport. p. 71. isbn 1-85414-248-8. 
^ tube facts . london underground. 2007. archived original on 2007-01-01. retrieved 2007-01-03. 
^ carmichael, phil (june 2013). power system planning - optimal solutions . upgrading london underground power supply system (pdf). london underground limited. p. 14. retrieved 26 april 2014.