Electrification of Railroads

the conversion of existing railroads to operation by electric traction and the construction of new electric railroads.

In an electric-railroad system, the traction motors of an electric locomotive receive their power from a contact system that is connected to a traction substation. A railroad power-supply system may also provide power to areas adjacent to the railroad and to industrial and agricultural users. In 1975, for example, 26 billion kilowatt-hours (kW-hr) were supplied to users in nontransportation sectors of the economy; the total consumption-by railroad systems was 48.9 billion kW-hr.

Railroad electrification increases hauling capacity and reliability of operation, improves the turnaround cycle, reduces operational expenses, and makes railroad travel more comfortable. On an electric railroad, part of the electric power used can be returned to the contact system when a train is coasting downhill and when it is braking (seeREGENERATIVE BRAKING). Moreover, the electric power provided by district heat and power plants is usually produced with low-grade fuels that cannot be burned in diesel locomotives.

Electric traction found its first commercial application in the USA, where it was introduced on a main-line segment of the Baltimore and Ohio Railroad in 1895. Many countries have devoted a great deal of effort to railroad electrification. Switzerland, for example, has electrified almost 100 percent, or approximately 3,000 km, of its railroad system. Sweden has more than 7,500 km of electrified track, which accounts for more than 60 percent of the country’s system, and Italy has more than 8,000 km, which constitutes approximately 50 percent of the total length of track.

Electrification of Russia’s railroads began after the Great October Socialist Revolution as part of the plan proposed by GOELRO (the State Commission for the Electrification of Russia). The first electric suburban line, the Baku-Sabunchi-Surakhany line, went into operation in 1926. Operation of the Moscow-Mytishchi line of the Northern Railroad began in 1929, and that of the Khashuri-Zestafoni line of the Transcaucasian Railroad began in 1932. By 1941, a total of 1,865 km of track had been converted to electric traction.

Entire routes were electrified between 1946 and 1955. In 1956, the Central Committee of the CPSU and the Council of Ministers of the USSR adopted the General Plan for the Electrification of Railroads, according to which the principal main-line railroad routes were to be converted to electric traction. Between 1958 and 1965, the country’s electrified track grew from a total of 9,500 km to a total of 24,900 km. Major railroad routes—such as the Moscow-Irkutsk line, which is more than 5,000 km long, and the Moscow-Gorky-Sverdlovsk line, which is approximately 2,000 km long—were converted to electric traction, as were suburban lines of large cities and industrial centers.

The contact systems of the electric railroads in the USSR use 3-kilovolt direct current or 25-kilovolt single-phase alternating current at commercial frequencies. Although alternating current requires a more complicated locomotive than does direct current, AC power-supply systems are much simpler than DC systems. The use of higher voltage in an AC contact system makes it possible to increase the distance between traction substations to 50 km, with no additional power loss; the distance between substations in a DC system can be similarly increased to 20–25 km. By using higher voltage the construction costs for a contact system can be decreased by an average of 7 percent; the amount of copper required for a normal contact system is 2.5 times greater than that required when higher voltage is used.

More than 50 percent of all freight traffic is now handled by electric traction, and the percentage of suburban passenger traffic carried by electric trains has risen to 77 percent. The USSR ranks first in the world in total length of electrified railroad track and in the rate of electrification. In early 1978, there were 40,500 km of electrified track, 25,000 km of which used direct current.