The Anonymous Widower

Discontinuous Electrification For Valley Lines?

The title of this post, is the same as that of an article in the May 2018 Edition of Modern Railways.

The Valley Lines in question are the Cardiff Valley Lines, that fan out from Cardiff Central and Cardiff Queen Street stations in various directions.

  • Some of the lines into the valleys are quite steep.
  • The lines in the Cardiff area seem to be typical coastal lines and fairly flat.
  • The lines are a mixture of single and double track.
  • There are various plans to extend some of the branches.

According to the article, it would appear that the current diesel system would be replaced with a system, with these characteristics.

  • Light rail vehicles
  • Discontinuous electrification
  • Use of stored energy.
  • Street running is expected to be in the specification for the vehicles to be used, to allow extension in the Cardiff Bay area and perhaps other places.

The proposal would save costs against full electrification and heavy rail.

My observations follow.

Batteries

Batteries will be an integral part of the design of the new rail vehicles.

Powering The Trains

The article states that battery power will be used to power the trains on sections that are difficult to electrify, like the mile-long Caerphilly Tunnel.

Battery power could also be used on level and downhill sections of track up to a few miles, but I suspect on steep uphill sections, electrification will be needed.

Handling Regenerative Braking

I believe that regenerative braking will be employed on the rail vehicles and the energy generated will be stored in the batteries.

 

The main advantage of this is that it simplifies the power supply to the electrification, as it only has to handle power going to the train.

This less complex electrical system, saves construction costs.

Recovering The Train’s Potential Entry

A train travelling from Cardiff to one of the terminal stations at the heads of the valleys, will need to acquire an amount of potential energy, based on the train’s mass and the height involved. This will be provided by the train’s traction system powered by the electrification and the energy in the batteries.

Coming down the hill, the regenerative braking will control the speed of the train and store any energy generated in the batteries.

This will save on the cost of energy to operate the system.

Charging The Batteries

The batteries will be charged from both the overhead electrification and the regenerative braking.

Extensive simulations of the route on computers would be able to calculate the following, for a wide range of scenarios.

  • The size of the batteries.
  • The power of the traction motors.
  • Where the electrification needs to be installed.
  • The maximum power output of the electrification system.

These calculations could also lead to an energy-saving operating philosophy, that could be programmed into the train’s computer system.

I suspect the worst case scenario, would be a train full of the heaviest Welshmen after an important rugby match at the Millennium Stadium.

 

Electrification

My thoughts on how various sections of track would be electrified follow.

Tracks With A Significant Uphill Gradient

These would need to be electrified, as I doubt battery power on the steepest gradients, would be enough to take a fully-loaded train to the top of the hill.

Electrification would be lighter-weight 750 VDC overhead wires.

The picture shows some of the overhead wires in Birmingham, that are used by the Midland Metro’s Urbos 3 trams.

Tracks With A Downhill Gradient

These would not need to be electrified, as Newton’s friend gravity would do most of the work.

However, as batteries will be fitted, these can have three important functions on downhill stretches of track.

  • Give the tram a nudge if needed.
  • Restart the train after a stop at a station.
  • Store any energy created by regenerative braking.

Note that we could have the unusual situation on a double-track section of line, where the uphill track was electrified and the downhill track was left without electrification.

Tracks With 25 KVAC Electrification

Some of the tracks used by the trains on the Cardiff Valley Lines should be electrified with 25 KVAC, by the end of December 2018.

Class 399 tram-trains, that are used in Sheffield can use either 750 VDC and 25 KVAC overhead electrification.

it would probably be a good idea, if the new vehicles on the Cardiff Valley  Lines could also use both voltages.

Level Tracks

These would not need to be electrified, as battery power would be used to propel the train.

Selected Stations

Some stations could need to be electrified to ensure that the service was reliable. These might include terminal stations or those with tricky gradients on either side.

The pantographs on the vehicles would be raised and lowered automatically to access the electrification.

Tram-Trains?

I very much feel, that tram-trains could be used to advantage.

  • Some of the Valley Lines are also used by freight trains, so couldn’t be converted to trams-only.
  • Tram-trains like the Class 399 tram-train, under test in Sheffield can work on both  750 VDC and 25 KVAC overhead wires.
  • Tram-trains can use conventional railway signalling.
  • Tram-trains could work on the South Wales Main Line to Newport.
  • Modern tram-trains like the Class 399 tram-train have performance, that is about the same as a Class 142 train, which is a Pacer, that works the Cardiff Valley Lines, in large numbers.
  • Tram-trains could run on the streets.

Several manufacturers make tram-trains, which I believe could be suitablefor the Cardiff Valley Lines.

Stadler’s Class 399 Tram-Trains

Nothing is said about the vehicles, that would be used, but I think they need the following characteristics.

  • Ability to climb the steepest section of the routes using 750 VDC overhead electrification.
  • Ability to store energy.
  • Regenerative braking to charge the batteries coming down the hills into Cardiff.
  • A similar capacity to a Class 150 train, which is around 150 seats.
  • It would be a bonus if they could use 25 KVAC overhead electrification, which will be available on part of some of the routes.
  • Ability to raise and lower the pantograph quickly and automatically.
  • Ability to run on the National Rail network.
  • Ability to run on the street.

This specification is virtually the same as a Class 399 tram-train with the following additions.

  • More seats and possibly an extra car.
  • Batteries.

Class 399 tram-trains are a UK version of the Stadler Citylink tram-train. The German version is used in Karlsruhe to climb into the hills surrounding the city, on routes that are fairly challenging.

So I have no worries about a version of the Class 399 train handling the Cardiff Valley Lines.

I certainly believe after my experience in Karlsruhe, and looking at other Citylink variants, that Stadler can come up with a tram-train for Cardiff based on the Class 399 tram-train.

And Then There’s CAF!

CAF have provided the Urbos 3 trams for Edinburgh Trams and the Midland Metro.

These are modern trams, that will be doing  the following in a few years in the Midlands.

This sounds like a tram-train with stored energy.

Wikipedia also lists a version of the Urbos family, called an Urbos TT, which is described like this.

The Urbos TT series is built with tram-train technology, connecting existing heavy rail infrastructure directly to urban tramway systems.

This document on the CAF web site, gives more details of Urbos variants, including the Urbos TT.

Looking at the modular nature of the design, you could have a custom-built tram-train tailored to the rail network.

But surely, the major factor with CAF, is that they have recently opened a factory at Newport.

If CAF get the order for the Cardiff Valley Lines, they could do a substantial part of the train building in a factory connected directly to the lines.

Converting The Valley Lines

I think that there are advantages and cost savings to be had, by good design in this area.

Could The Rail Vehicles Be Designed To Fit The Existing Platforms?

The first thing to do would be to design, build and fully test the rail vehicles.

Could the tram-trains be built, so that they fitted all the existing platforms?

  • Class 150 trains are 2.82 metres wide.
  • Urbos 3 trams on the Midland Metro are 2.65 wide.

If the tram-trains could run without platform modifications, this would be a big cost saving and still allow diesel units to use the lines, at the same time.

Testing The Trains

If the tram-trains were being given a 25 KVAC  capability, they could even be tested on the quadruple-track the South Wales Main Line after the line is electrified through Newport.

Electrifying The Lines

It could be that the only sections of the valley lines that will need electrification, are the steep lines  into the hills, as all other sections could use stored power or the 25 KVAC, where it exists.

  • It would probably be possible to put up the simpler 750 VDC overhead lines during weekend and perhaps longer possessions.
  • The electrification could be designed so that it doesn’t interfere with existing services.
  • The lines would be converted one at a time.
  • ,Note that  tram-trains  could share track and platform with the current diesel trains working the lines.

If CAF were to get the order surely the Ebbw Valley Line, which could be connected easily to the factory would be the first to be converted.

Conclusion

Obviously, the devil will be in the detail, but it does look like a viable plan will emerge.

I think that if CAF get the order, that they could be big winners.

The Cardiff Valley Lines could demonstrate the following.

  • Running on main lines with 25 KVAC electrification.
  • Running on 750 VDC electrification.
  • Running on batteries.
  • Running on lines with steep hills.
  • Street running.
  • Sharing tracks with freight trains and other passenger services.
  • The tram-trains could also connect to Cardiff Airport.

It is a world-class demonstration and test track for innovative tram-trains, designed to cope with challenging rail networks.

With a factory close by at Newport, the selling of the tram-trains to other operators would be a salesman’s dream.

I think there’s more to CAF coming to Newport, than was apparent, when the deal for the factory was signed.

 

 

 

 

 

May 5, 2018 - Posted by | Travel | , , , , , ,

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