Traction power network
Encyclopedia
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
(AC) with a frequency lower than that of the national grid, such as in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
and Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
.
Alternatively, the three-phase alternating current of the power grid can be converted in substations
Traction current converter plant
A traction substation or traction current converter plant is an electrical substation that converts electric power from the form provided by the electrical power industry for public utility service to an appropriate voltage, current type and frequency to supply railways, trams and/or trolleybuses...
by rotary transformers or static inverters into the voltage and type of current required by the trains. For railways which run on direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
(DC), this method is always used, as well as for railways which run on single-phase AC of decreased frequency, as in Mecklenburg-Western Pomerania
Mecklenburg-Western Pomerania
Mecklenburg-Vorpommern is a federal state in northern Germany. The capital city is Schwerin...
, Saxony-Anhalt
Saxony-Anhalt
Saxony-Anhalt is a landlocked state of Germany. Its capital is Magdeburg and it is surrounded by the German states of Lower Saxony, Brandenburg, Saxony, and Thuringia.Saxony-Anhalt covers an area of...
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
. In these areas there are no traction current networks.
History
Separate power for traction apart from industrial power always has historic roots. There is no reason today to apply different frequencies or current types than for transmission and for industrial usage. However, the advantage with DC traction was the easier transmission with single copper wires to the feeder points. The advantage with AC traction is the easier transmission over long distances to the feeder points. Beyond these parameters and securing former investment, no evidence exists to stay with different current schemes in networks.Applications
Dedicated traction current lines are used when railways are supplied with low-frequency alternating current (AC). The traction current supply line is connected to substations along the line of the railway and is usually run separately from the overhead catenary wire from which the locomotives are fed.In countries in which the electric trains run with direct current or with single-phase alternating current with the frequency of the general power grid, the required conversion of the current is performed in the substations, so again no traction current lines are required.
Traction current supply lines are not usually laid parallel to the railway line, in order to allow a shorter line length and to avoid unnecessary influences to the electrical system near the railway line; this also is applied to the current supply of some rapid-transit railways operating with alternating current in Germany.
It is also possible to lay out the traction current supply on special cross beams right on the overhead wire pylons
Lattice tower
A lattice tower or truss tower is a freestanding framework tower. They can be used as electricity pylons especially for voltages above 100 kilovolts, as a radio tower or as an observation tower....
above the catenary wire. Because the overhead line pylons have a smaller cross section than traction current supply masts, the cross beams cannot be too wide, so the standard arrangement of four conductor cables in one level cannot be used. In this case, a two-level arrangement is used, or with two electric circuits for double-railed lines the overhead line pylons for both directions are equipped with cross beams for their own traction current system of two conductor cables each.
In densely populated areas, there are pylons which carry circuits for both traction current and for three-phase alternating current for general power. Such lines are found where right of ways are rare. In particular the parallel route of 110 kV and 220 kV three-phase AC is common. The use of 380 kV power lines on the same pylon requires 220 kV insulators for the traction current line, because in case the 380 kV line fails, voltage spike
Voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage , current , or transferred energy in an electrical circuit....
s can occur along the traction current line, which the 110 kV insulators cannot handle.
As a rule, traction current lines use single conductors, however for the supply of railways with high traffic and in particular for the supply of high speed railway lines, two bundle conductors are used.
Austria
The MariazellerMariazellerbahn
The Mariazell Railway is an electrically operated narrow-gauge railway which connects the Lower Austrian capital Sankt Pölten with the Styrian pilgrimage centre of Mariazell.- Valley Line :...
railway in Lower Austria
Lower Austria
Lower Austria is the northeasternmost state of the nine states in Austria. The capital of Lower Austria since 1986 is Sankt Pölten, the most recently designated capital town in Austria. The capital of Lower Austria had formerly been Vienna, even though Vienna is not officially part of Lower Austria...
operates on single phase AC at a 25 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
utility frequency
Utility frequency
The utility frequency, line frequency or mains frequency is the frequency at which alternating current is transmitted from a power plant to the end-user. In most parts of the world this is 50 Hz, although in the Americas it is typically 60 Hz...
. The railway has its own traction current lines with an operating voltage of 27 kV. These lines are mounted on the pylons of the overhead wire over the catenary wire.
Germany
In GermanyGermany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, single conductors are usually used for traction current lines but, for the ICE
InterCityExpress
The Intercity-Express or ICE is a system of high-speed trains predominantly running in Germany and neighbouring countries. It is the highest service category offered by DB Fernverkehr and is the flagship of Deutsche Bahn...
train, two bundle conductors are used. The traction current supply lines from the nuclear power station Neckarwestheim
Neckarwestheim
Neckarwestheim is a municipality with 3524 inhabitants in the Heilbronn district, Baden-Württemberg, in south-west Germany. It is located on the Neckar river and is well known as the location of a nuclear power station.-Geographical position:...
to the traction current switching station at Neckarwestheim
Neckarwestheim Nuclear Power Plant
Neckarwestheim Nuclear Power Station is a nuclear power plant in Neckarwestheim, Germany. It is sometimes abbreviated GKN . It is operated by EnBW Kernkraft GmbH.-GKN 1:...
and from there to the central substation
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...
in Stuttgart
Stuttgart
Stuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....
, Zazenhausen are implemented as a four-bundle conductor circuit.
Scandinavia
In SwedenSweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and some areas of the former German Democratic Republic
German Democratic Republic
The German Democratic Republic , informally called East Germany by West Germany and other countries, was a socialist state established in 1949 in the Soviet zone of occupied Germany, including East Berlin of the Allied-occupied capital city...
, three phase AC-current
Three-phase electric power
Three-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by grids worldwide to transfer power. It is also used to power large motors and other heavy loads...
is converted into single phase AC current with a frequency of 16.7 cycles per second at the substations. Unlike in Germany, there are no dedicated power plants for railway electricity. All power comes from general electricity suppliers. Although in this regions there is, in principle, no requirement for traction power lines, there is a 132 kV-single AC power grid for railway power supply in Central Sweden ( see Electric power supply system of railways in Sweden
Electric power supply system of railways in Sweden
Electric railways in Sweden are powered from a single-phase AC supply of 16 2/3 Hz, as used in Germany, Austria and Switzerland. Unlike these countries, the 132 kV traction current grid covers only part of the country, approximately north of Stockholm...
). In Norway, there is a small 55 kV single phase AC network for power supply of trains in the South, fed by Hakavik Power Station
Hakavik Power Station
Hakavik Power Station is a hydroelectric power plant in Øvre Eiker, Norway with a power of 7 MW inaugurated in 1922.It generates only single phase AC for railway purpose and is the startpoint of a 55 kV- single phase AC powerline for traction current to Sande and an other to Sundhaugen Switching...
. A further power station, at Kjofossen feeds single phase AC directly in the overhead wire. In Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
and Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, 50 Hz is used for the main lines (if electrified) and the electricity comes from general suppliers. As such, much simpler equipment than in Sweden and Norway is needed for conversion.
South Africa
In the Republic of South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
there are extensive AC and DC traction schemes, including 50 kV and 25 kV AC single phase systems. Electrification in Natal was stimulated by the takeover of the South African Railways' system by the Electricity Supply Commission (now Eskom
Eskom
Eskom is a South African electricity public utility, established in 1923 as the Electricity Supply Commission by the government of South Africa in terms of the Electricity Act . It was also known by its Afrikaans name Elektrisiteitsvoorsieningskommissie . The two acronyms were combined in 1986 and...
) based on the Colenso
Colenso, KwaZulu-Natal
Colenso is a town in KwaZulu-Natal, South Africa. It is located on the southern bank of the Tugela River. The original settlement was contained within a loop on the river, but it subsequently expanded southwards and eastwards...
power station.
United Kingdom
In the United KingdomUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, the Network Rail
Network Rail
Network Rail is the government-created owner and operator of most of the rail infrastructure in Great Britain .; it is not responsible for railway infrastructure in Northern Ireland...
750 V DC electrification system
Railway electrification system
A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...
in the southeast of England is supplied with power from an extensive 33 kV power distribution network.
Areas with traction power networks
- United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
- GermanyGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
(except Mecklenburg-Western Pomerania and Saxony-Anhalt), total length 7959 km - SwitzerlandSwitzerlandSwitzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
- AustriaAustriaAustria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
(separate traction power network for the Mariazeller Bahn) - Central SwedenElectric power supply system of railways in SwedenElectric railways in Sweden are powered from a single-phase AC supply of 16 2/3 Hz, as used in Germany, Austria and Switzerland. Unlike these countries, the 132 kV traction current grid covers only part of the country, approximately north of Stockholm...
- Southern Norway east of OsloElectric power supply system of railways in NorwayNorway, like Germany, Austria and Switzerland uses single phase 15 kV AC railway electrification at 16 2/3 Hz for electric train systems. However there are differences in the supply of power....
- USA (in New York and Washington DC area for railway lines running with single phase 25 Hz AC, see also 25Hz Power Transmission System25Hz Power Transmission SystemAmtrak's 25 Hz Traction Power System is a traction power grid operated by Amtrak along the southern portion of its Northeast Corridor : the 363 route miles between Washington, D.C. and New York City and the 104 route miles between Philadelphia and Harrisburg, Pennsylvania. The Pennsylvania...
) - South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
- MelbourneMelbourneMelbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
(dedicated high voltage transmission wires between former Newport A Power Station and traction substations. However these lines are operated with three phase AC)
See also
- Third railThird railA third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...
- Traction current converter plantTraction current converter plantA traction substation or traction current converter plant is an electrical substation that converts electric power from the form provided by the electrical power industry for public utility service to an appropriate voltage, current type and frequency to supply railways, trams and/or trolleybuses...
- Traction powerstationTraction powerstationA traction power station is a power station that produces only traction current, that is, electric current used for railways, trams, trolleybuses or other conveyances. Pure traction power stations are rare and there are many more power stations that generate current for other purposes, such as...