Electrification

The single phase alternating-current system possesses an im portant advantage in the use of comparatively little copper in the feeding circuits, through the use of a single contact wire over head. Alternating current at high potentials, such as 16,50o volts, can be collected from this feeding wire, which receives the current from transformers frequently not protected from the weather. A small section of the S.R. in London was electrified on the 6,600 single phase A.C. system in 1909. The three-phase alternating current system has been employed largely for main line use in Europe and is older than the high voltage direct current systems. The Italian State railways have adopted this system widely. Its advantage in part rests upon the three phase induction motor which can be wound for the full potential of 3,00o volts selected. Through the use of alternating current substations containing simple transformers only, requiring no attendance, economies were realized, but the necessity of utilizing double overhead contact wires with the low potentials of 3,000 or 4,000 volts has militated against the extensive adoption of the system, as has also the three phase motor with its characteristic of constant speed, though this latter is often useful in the case of lines with heavy gradients, since it permits the "regeneration" of electric power on falling gradients.

Main Line Electrification.

Amongst the great main line electrification schemes in Europe are those of the Swiss Federal railways ; the Midi and the Paris-Orleans railways, and to a lesser extent the Paris-Lyon-Mediterranee, in France ; and important sections of the German Railway Company. In Spain, Norway, Czecho-Slovakia and Holland, there exist also important sec tions of main lines worked by electric traction. Steep gradients and the lack of coal resources were primarily responsible for the electrification schemes of Switzerland, Italy, Austria, Sweden, Norway, and the Midi Railway of France. The main coalfields of France are far distant from the territories served by the Midi and the Paris-Orleans lines, while the Paris-Lyon-Mediterranee scheme is connected with the operation of the Mont Cenis route to Italy with its long tunnel and steep gradients. Electrified sec tions of the German Railway in Bavaria, Baden, Silesia and Central Germany are largely those with heavy gradients at some considerable distance from the coalfields, while Spanish electrifica tion was due to the same reason.

Apart from the Southern Railway, which, in recent years, has extended the electrification of its main lines as far afield as Hastings and Brighton, Great Britain does not possess any great main line electrification scheme, though the L.M.S.R. possesses

important sections of electrified suburban traffic lines in the Lon don, Liverpool and Manchester areas, while the L.N.E.R. at Newcastle has electrified certain of its suburban lines and a heavy traffic mineral line feeding Middlesborough. The G.W.R. in the London district runs electric trains in conjunction with the Metropolitan, a railway which possesses important electrified lines, parts of which are run in conjunction with the Metropoli tan District Railway, a member of the Underground Group of electric lines to be mentioned later. Unlike the Metropolitan Dis trict, the Metropolitan caters for freight as well as passenger traffic and, consequently, may be classed with the four large British railways, whose electrified mileage in 1927 was as follows :— Electrified suburban sections of main line railways are found also on the German Railway at Berlin and on the State and the Paris Orleans Railways at Paris, and in many other large cities.

In Asia electrified railways are found at Bombay in India, on the Great Indian Peninsula, and the Bombay, Baroda and Central India lines. Primarily of a suburban nature, the former is rapidly also becoming a main line electrification scheme. Japan possesses a large electrified mileage, being rapidly extended to embrace main line and suburban traffic on the 1,5oo volt D.C. system; Java also has a small electrified section of the same type. In Australasia the New Zealand Railways have electrified a 51m. tunnel section using 1,500 volt D.C. ; whilst suburban electrification is being rapidly extended around the centres of Sydney and Melbourne. In Africa, the South African railways electrified a 175m. line section in Natal on the 3,00o volt D.C. system, and suburban electrified lines exist at Capetown. In South America, important electrified sections exist in Brazil (using 3,00o volt D.C.) and Chile, while Argen tina employs 800 volt D.C. ; the two first are of a main line char acter while the last deals with the suburban traffic of Buenos Aires. In North America, Mexico possesses a short electrified mileage on the 3,00o volt D.C. system; Canada employs electric traction mainly for tunnel sections, using 2,400 volt D.C. The United States possesses many noteworthy electrification schemes, notably the 66om. route mile section of the Chicago, Milwaukee, St. Paul and Pacific, and important mileages on the New York, New Haven and Hartford, the Virginian, the Norfolk and Western, the Illinois Central, the Pennsylvania, the Long Island, the Balti more and Ohio, the Detroit, Toledo and Ironton, the Southern Pacific, the Erie, the Boston and Maine and the Great Northern railways.