- Ground-level power supply
300px|thumb|right|A section of APS track showing the neutral sections at the end of the powered segments plus one of the insulating joint boxes whichmechanically and electrically join the APS rail segments
Ground-level power supply, also known as surface current collection and Alimentation par Sol (APS) is a modern method of third-rail electrical pick-up for street
trams. It was invented for the Bordeaux tramway, which was constructed from 2000 and opened in 2003. Currently this is the only place it is used, but there were and are proposals to install it elsewhere:
*Nice (abandoned in favour of nickel metal hydride batteries)
*Florence (Firenze), Italy
Gold Coast, Queensland, Australia
Washington, D.C, United States
*Al Sufouh Tram in
Dubai, United Arab Emiratescite news | title=Al Safouh tram project consortium selected |publisher=" Railway Gazette International" |date=2008-4-29 |url=http://www.railwaygazette.com/news_view/article/2008/04/8374/al_safouh_tram_project_consortium_selected.html | accessdate=2008-05-02 ]
It is used, primarily for aesthetic reasons, as an alternative to
overhead lines. It is different from the conduit current collectionsystem which was used in historic tram systems in Washington, Manhattan and parts of London, which buried a third and fourth rail in an underground conduit (‘vault’) between the running rails.
Unlike the track-side
third railused by most metro trains and some main-line railways, APS does not pose a danger to people or animals, and so can be used in pedestrian areas and city streets.
APS uses a third rail placed between the running rails, divided electrically into eight-metre segments with three metre neutral sections between. Each tram has two power collection skates, next to which are antennas that send radio signals to energise the power rail segments as the tram passes over them. At any one time no more than two consecutive segments under the tram should actually be live.
Use in Bordeaux
Modern ground-level current collection was pioneered by the recent Bordeaux tramway in
France. The public had assumed that the new system would use a traditional conduit system, like that of the Bordeaux trams which ran prior to 1958, and objected when they learned that it was not considered safe, and that overhead wires were to be used instead. Facing complaints both from the public and the French Ministry of Culture, planners developed APS as a modern way of replicating the conduit system.
APS was developed by Innorail, a subsidiary of Spie Enertrans, but was sold to
Alstomwhen Spie was acquired by Amec. [cite news | title=Third-rail trams across the Garonne |publisher=" Railway Gazette International" |date=2004-02-01 |url=http://www.railwaygazette.com/news_view/article/2004/02/961/third_rail_trams_across_the_garonne.html | accessdate=2008-05-02 ]
There are 12 km of APS tramway in the three-line network of 21.3 km total length, expected to be 40 km by 2007. Sources suggest that APS adds about €100,000 to the cost of the trams, whilst the infrastructure is about 300% more expensive than overhead wires.Fact|date=September 2008 Bordeaux
Citadis trams use pantographs and electric overhead linesin outlying areas.
Before use in Bordeaux, APS was tested and proved viable on a short section of reserved-track tramway in the French city of
Marseilles. Nevertheless, Bordeaux has experienced problems, with APS being so temperamental that at one stage the Mayor issued an ultimatum that if reliability could not be guaranteed, it would have to be replaced with overhead wires. Although things have improved, in October 2005 it was announced that 1 km of APS tramway is to be converted to overhead wires.
Problems have included water-logging, when the water does not disperse or flow away quickly enough after heavy rain.
APS in other cities
In summer 2006 it was announced that two new French tram systems would be using APS over part of their networks. These will be
Angersand Reims, with both systems expected to open around 2009/2010. A couple of months later another French city was added to the list, this being Orléans, which will use APS on a section of their second tram line. The planned Al Sufouh Tram in Dubai will use APS.
Stud contact system
The predecessors of APS (known as
Stud contact systems) were developed around 1900, and used on several tramway companies in Paris and in England. Associated with these systems were the inventors Dolter and Diatto.
There were two main differences from APS:
* Power was supplied not from rails but from studs, set in the road at intervals
* Switching in of the contacts was done by strong electromagnets beneath each car. Each contact contained a fuse, which would be blown by an earthed safety shoe on the rear of the tram should the contact not have switched out. This proved to be unsatisfactory, because the strong currents melted down the switch contacts, resulting in contacts frequently remaining 'live'.
Another system of ground-level power supply was used by Budapest trams from 1887. Catenary was considered an eyesore, so builder
Siemensdeveloped the following system: on the inner side of one rail, a powered third rail is hidden underground in a half-covered ditch, with a narrow slit opening upwards, through which a trolley pole reaches downward from the trams. The Budapest system was generally safe, and water-protected. However, there was no defense against snow and ice, dirt filled up the ditches, and trolley poles suffered strong wear. Catenaries replaced the "Budapest system" everywhere by the 1920s.
Stud contact system
* [http://web.archive.org/web/20041017010645/http://www.lrta.org/dd011.html Tram Power - A New Method] (LRTA)
* [http://web.archive.org/web/20041017010553/http://lrta.org/art0212.html Bordeaux: Fronting the French tramway revolution] (LRTA)
* [http://citytransport.info/Bod.htm More information, images and some sound clips from Bordeaux.]
Wikimedia Foundation. 2010.
Look at other dictionaries:
Power supply — For the Budgie album, see Power Supply (album). A vacuum tube rackmount adjustable power supply, capable of +/ 1500 volts DC, 0 to 100mA output, with amperage limiting capability. A power supply is a device that supplies electrical energy … Wikipedia
Uninterruptible power supply — A small free standing UPS … Wikipedia
Power optimization (EDA) — Power optimization refers to the use of electronic design automation tools to optimize (reduce) the power consumption of a digital design, while preserving the functionality.Introduction and historyThe increasing speed and complexity of today’s… … Wikipedia
Level sensor — Level sensors are used to detect liquid level. The liquid to be measured can be inside a container or can be in its natural form (e.g. a river or a lake). The level measurement can be either continuous or point values. Continuous level sensors… … Wikipedia
Power strip — Power bar redirects here. For the manufacturer of energy food products, see PowerBar. French/Belgian power strip A power strip (also known as an extension block, power board and by many other variations) is a block of electrical sockets that… … Wikipedia
Power Mac G4 — The Graphite Power Mac G4 Developer Apple Inc. Release date August 31, 1999 Discontinued June 9, 2004 … Wikipedia
Ground (electricity) — In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth. A typical earthing… … Wikipedia
Power distribution unit — TCP/IP controlled 19 PDU with USB webcam, environmental IP monitoring … Wikipedia
Ground-attack aircraft — An A 10 Thunderbolt II firing an AGM 65 Ground attack aircraft are military aircraft with primary role of attacking targets on the ground with greater precision than bombers and prepared to face stronger low level air defense … Wikipedia
Ground support equipment — (GSE) is found at an airport, usually on the ramp, the servicing area by the terminal. This equipment is used to service the aircraft between flights. As its name implies, GSE is there to support the operations of aircraft on the ground. The… … Wikipedia