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Railways through Europe |
maps and interoperabilty |
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| Content is mostly outdated and page is not updated anymore. |
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description of DC networks
advantages of 1500V and 3000V DC
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- especially the lack of the large
clearances and extensive insulation needed with high voltage systems
- simple technology in the vehicle: series-connected DC motors (which can
themselves be connected in series, series-parallel and parallel for
operation at different speeds)
- no need to develop robust rectifiers for use on the motive power
- particularly suitable for lines with relatively short trains and
relatively low maximum speeds (eg in the Netherlands)
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disadvantages of 1500V and 3000V DC
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- because the voltage in the catenary cannot exceed 3000V
with this technology, the current drawn by heavy fast trains is relatively high
- the feeder stations must be located relatively close together, the
catenary must be thick and heavy and the pantograph(s) must be pressed hard
against it to minimise the voltage drop between the nearest feeder station and
the motive power
- For example, a line 80km long with a speed limit of 200km/h
needs 6 feeder stations if the power is supplied at 1500V DC. That is why TGV trains
have only one pantograph raised when running at high speed under
catenary at 25kV 50Hz, but need to have both pantographs raised when
running on older lines electrified at 1500V DC like between
Tours and Bordeaux, where double-units of TGV-Atlantique have raised 4 pantographs
at a speed of 220km/h - the limit of this system.
- Furthermore, the power rating of the line's feeder stations sets a limit to the
amount
of electrically powered traffic the line can handle (ie the total number, speed and/or
loading of the trains), which cannot be adjusted quickly whenever the pattern of traffic
changes. Of course, an extra feeder station can be installed wherever the demand for
power is particularly high, but this is expensive and takes time.
- Many of these problems arise because the only simple way to reduce the voltage of
DC power is by inserting a resistance in series with the motor, which is inevitably
wasteful.
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- 750V: South-England, metro networks
- 1500V: Netherlands, Southern part of France
- 3000V: Belgium, Italy, Poland, Czech and Slovakia
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page last updated: 26. March 2018 |
©1998-2013 Thorsten Büker |
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