Traction current converter plant
Encyclopedia
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 (streetcars) and/or trolleybuses with traction current.
50Hz or 60Hz alternating current
(AC) for the supply of AC railway electrification system
s at a lower frequency and single phase
, as used by many older systems, or to rectify
AC into direct current
(DC) for those systems (primarily public transit systems) using DC for traction power.
sets containing three-phase synchronous AC motors and single-phase AC generators
, mechanically coupled to a common shaft. Rotary converter
s were also used, especially where the desired output was DC current from an AC source.
rectifier systems are used for conversion from AC power to DC traction power.
or third rail
of the traction system, with no feed into a traction current distribution network) or centralized (for the supply of the traction power network
, usually in addition to the direct supply of the overhead lines or third rail).
Central traction current converter plants are generally found in Germany
(primarily in the cities of Neckarwestheim
, Ulm
, Nuremberg
), Austria
and Switzerland
, while decentralized traction current converter plants are generally found in Norway
, Sweden
and the German states of Mecklenburg-Vorpommern and Brandenburg
as well as parts of Great Britain. A list of current systems for electric rail traction provides further detail.
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...
that converts electric power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
from the form provided by the electrical power industry
Electrical power industry
The electric power industry provides the production and delivery of electric energy, often known as power, or electricity, in sufficient quantities to areas that need electricity through a grid connection. The grid distributes electrical energy to customers...
for public utility
Public utility
A public utility is an organization that maintains the infrastructure for a public service . Public utilities are subject to forms of public control and regulation ranging from local community-based groups to state-wide government monopolies...
service to an appropriate voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
, current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
type and frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
to supply railways, trams (streetcars) and/or trolleybuses with traction current.
Conversions
These systems can be used to convert three-phaseThree-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...
50Hz or 60Hz alternating current
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) for the supply of AC railway 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...
s at a lower frequency and single phase
Single-phase electric power
In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors...
, as used by many older systems, or to rectify
Rectifier
A rectifier is an electrical device that converts alternating current , which periodically reverses direction, to direct current , which flows in only one direction. The process is known as rectification...
AC into 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) for those systems (primarily public transit systems) using DC for traction power.
Rotating
Originally, the conversion equipment usually consisted of one or more motor-generatorMotor-generator
A motor-generator is a device for converting electrical power to another form. Motor-generator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line...
sets containing three-phase synchronous AC motors and single-phase AC generators
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
, mechanically coupled to a common shaft. Rotary converter
Rotary converter
A rotary converter is a type of electrical machine which acts as a mechanical rectifier or inverter. It was used to convert AC to DC or DC to AC power before the advent of chemical or solid state power rectification...
s were also used, especially where the desired output was DC current from an AC source.
Static
In the 1920s, DC was derived using electronic valves (mercury arc rectifiers). In modern systems, high-voltage DC (HVDC) "back-to-back" stations are used instead of mechanical equipment to convert between different frequencies and phases of AC power and solid-state thyristorThyristor
A thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current trigger, and continue to conduct while they are forward biased .Some sources define silicon controlled rectifiers and...
rectifier systems are used for conversion from AC power to DC traction power.
Location
Traction current converter plants are either decentralized (where one plant directly supplies the overhead linesOverhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
or third rail
Third rail
A 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...
of the traction system, with no feed into a traction current distribution network) or centralized (for the supply of the traction power network
Traction power network
A traction network or traction power network is an electricity grid for the supply of electrified rail networks. The installation of a separate traction network generally is only done if the railway in question uses alternating current with a frequency lower than that of the national grid, such as...
, usually in addition to the direct supply of the overhead lines or third rail).
Central traction current converter plants are generally found 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...
(primarily in the cities of 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:...
, Ulm
Ulm
Ulm is a city in the federal German state of Baden-Württemberg, situated on the River Danube. The city, whose population is estimated at 120,000 , forms an urban district of its own and is the administrative seat of the Alb-Donau district. Ulm, founded around 850, is rich in history and...
, Nuremberg
Nuremberg
Nuremberg[p] is a city in the German state of Bavaria, in the administrative region of Middle Franconia. Situated on the Pegnitz river and the Rhine–Main–Danube Canal, it is located about north of Munich and is Franconia's largest city. The population is 505,664...
), 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....
, while decentralized traction current converter plants are generally found in 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...
, 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....
and the German states of Mecklenburg-Vorpommern and Brandenburg
Brandenburg
Brandenburg is one of the sixteen federal-states of Germany. It lies in the east of the country and is one of the new federal states that were re-created in 1990 upon the reunification of the former West Germany and East Germany. The capital is Potsdam...
as well as parts of Great Britain. A list of current systems for electric rail traction provides further detail.
See also
- 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...
- Railway electrification systemRailway electrification systemA 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...