| Ground-level Power Supply |
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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 Tram s. It was invented for the Bordeaux tramway, which was built in 2000 and entered service in 2003. Currently this is the only place it is used, but there were and are proposals to install it elsewere:
TECHNOLOGY It is used, primarily for aesthetic reasons, as an alternative to Overhead Lines . It is not to be confused with the Conduit Current Collection system which was used in Washington , Manhattan and parts of London , which simply buried a third rail and fourth rail in an underground conduit (‘vault’) between the running rails. Unlike the track-side Third Rail used by most Metro trains and some mainline railways, the power-supply rail used by this system does not pose a danger to people or animals, and so can be used even in pedestrian areas and city streets, although it does actually use the running rails for current return (negative return system). Ground-level power supply uses a third rail placed between the other two rails, which is electrically divided into eight-metre segments with neutral sections between. Each tram is equipped with two power collection skates, next to which are antennae that send radio signals to energise the powered rail segments as the tram passes over them. At any one time no more than two consecutive powered rail segments under the trams should actually be charged. USE IN BORDEAUX Modern ground-level current collection was pioneered by the recent Bordeaux tramway. 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 the new system (known in French as ''alimentation par sol'' or APS) as a modern way to duplicate the appearance of the conduit system. The system's Citadis Tram s still carry Pantograph s, and switch to conventional electric Overhead Lines in outlying areas. In all, there is 12 km of APS powered tramway on a network of three tram lines of 21.3 km total length (but expected to be 40 km by 2007). Sources suggest that the APS system adds about € 100,000 to the cost of the trams, whilst the fixed infrastructure is about 300% more expensive than overhead wires. Before use in Bordeaux, the APS system was tested (and proven viable) on a short section of reserved-track tramway in the French city of Marseilles . Nevertheless, Bordeaux has experienced some problems with the system being so temperamental that at one stage the local Mayor issued an ultimatum that if reliability could not be guaranteed, then the APS would have to be replaced with overhead wires. Although things have improved, in October 2005 it was announced that 1 km of APS equipped tramway is to be converted to overhead wires. Problems have been described as including issues with water-logging when the water does not disperse or flow away quickly enough after heavy rains. EXTERNAL LINKS |
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