The Anonymous Widower

Thoughts On The Power System For The New Tube for London

Obviously, very little has been said about the power system of the New Tube for London.

London Underground Electrification

This description of Lundon Underground electrification comes from Electrification in the Wikipedia entry for London Underground Infrastructure.

The lines are electrified with a four-rail DC system: a conductor rail between the rails is energised at −210 V and a rail outside the running rails at +420 V, giving a potential difference of 630 V. On the sections of line shared with main line trains, such as the District line from East Putney to Wimbledon and Gunnersbury to Richmond, and the Bakerloo line north of Queen’s Park, the centre rail is bonded to the running rails, as the electrical return from National Rail trains is via the wheels. This was first used in the early 20th century, the isolated traction current return allowing a train’s position to be detected using DC track circuits, and reduced any earth leakage currents that could affect service pipes and telephone cables.

This picture shows a typical London Underground track on the Central Line at Bank station.

Note the suicide pit under the rails.

This layout is rather unusual and different to the third rail system used by National Rail services in London and the South East and on Merseyrail.

Battery Power

This article on Rail Engineer is entitled London Underground Deep Tube Upgrade.

This is an extract.

More speculatively, there might be a means to independently power a train to the next station, possibly using the auxiliary battery, in the event of traction power loss.

Batteries in the New Tube for London would have other applications.

  • Handling regenerative braking.
  • Moving trains in sidings and depots with no electrification.

It should be born in mind, that battery capacity for a given weight of battery will increase before the first New Tube for London runs on the Piccadilly line around 2023.

Conversion To A Conventional Third-Rail System

Given, that space in the deep tunnels is limited, I wonder if removing the third rail in the middle and going to a third-rail 630 V DC system will give more space under the train, that could be used for equipment and a lower floor.

The following lines could eventually be converted to the New Tube for London.

So could the shared running be eliminated to make conversion easier.

The Bakerloo Line North of Queens Park Station

The New Tube for London must be able to share the track with the Class 710 trains working the Watford DC Line.

There would be no problem with traction, as both types of trains could use conventional third-rail track.

But there would be a problem with platform height.

Between Rayners Lane and Uxbridge Stations

In Can Between Rayners Lane And Uxbridge Stations Be Step-Free?, I investigated the line between these two stations, including these possibilities.

  •  Unattended Train Operation (UTO) on the Piccadilly Line, which may mean platform edge doors.
  • Terminating The Piccadilly Line At Rayners Lane Station
  • Terminating The Metropolitan Line At Rayners Lane Station
  • A Piccadilly Line Service Be Run Between Uxbridge and Ealing Broadway Stations
  • Extending The Central Line To Uxbridge

I came to this conclusion.

There are a lot of possible improvements that can be done to the train service to Uxbridge.

That is probably a bit of a cop-out, but then there are a lot of possibilities, some of which eliminate the Piccadilly and Metropolitan Lines sharing the track to Uxbridge.

Between Acton Town And Ealing Broadway Stations

This map from carto.metro.free.fr shows the lines Between Acton Town and Ealing Broadway stations.

Note how the Piccadilly and District Lines share tracks from Ealing Common station, which then split with District Line trains going to Ealing Broadway station and Piccadilly Line trains going to Rayners Lane and Uxbridge stations.

Transport for London are suggesting the following.

  • Ealing Broadway is served by the Piccadilly Line, rather than the District Line.
  • District Line trains would terminate at Richmond and Wimbledon stations instead of Ealing Broadway.
  • East of Acton Town, Piccadilly Line trains would call at Turnham Green, Ravenscroft Park and Hammersmith
  • District Line trains would call at a relocated Chiswick Park, Turnham Green, Stamford Brook, , Ravenscroft Park and Hammersmith.
  • East of Hammersmith, both District and Piccadilly Line routes would be unchanged.

Passengers needing to travel between Ealing Broadway and stations between Victoria and Whitechapel, would change at Turnham Geen, Ravenscroft Park or Hammersmith, by walking across the platform.

If this change is implemented, there will be no shared running between the Piccadilly and District Lines.

National Rail Shares Tracks With The Metropolitan And District Lines

There is some shared running on the Metropolitan and District Lines but that would be unaffected.

Conclusions On Conversion To A Conventional Third-Rail System

It looks to me, that it would be possible to convert the deep-level Underground Lines to conventional third-rail, by eliminating sharing with other lines.

But would such a radical change to the electrification of London’s deep-level Underground lines be feasible and economic?

Conversion From Four Rails To Three

I suspect that when the New Tube for London is introduced on a line, the track will be renewed or at the least given a good refurbishment.

Some years ago, I obtained a database of all the faults on the London Underground for a year. Very few of the faults were down to track faults and the only problems in tunnels seemed to be water ingress.

So I think we can assume, that the track foundations are probably in good condition. If they aren’t I suspect London Underground know all about the problems.

My project management knowledge leads me to believe that a well-planned series of track closures should be possible  to convert the track.

Safety

At all stations, the rail in the centre of the track would not be there anymore and the only electrified rail could be placed on the far side from the platform in deep-level stations.

This is another picture from Bank station.

Note.

  1. The +420 VDC power rail sitting on insulators close to the wall
  2. The -210 VDC power rail sitting on insulators on posts in the suicide pit.
  3. How the two running rails neatly fit on ledges on either side of the suicide pit.

Imagine how it would look with the negative power rail removed.

The single rail could also be shielded, by perhaps an insulating board on both sides of the rail.

This picture shows an insulated third rail at Oxted station. The yellow insulator is wood, that has been painted.

I would extrude the insulator using recycled plastic. After all polythene’s first major use was as an insulator in radar during World War II.

I believe that a three-rail track could be designed, that would surely be much safer than the current track, should anybody fall or be pushed off the platform.

There is also the possibility of using battery power in some or even all stations. Power would only be supplied to the trains between stations, where batteries would be charged.

The third rail would stop perhaps forty metres at either side of a station and the gaps would be bridged by battery power.

It might be possible to make stations, with no electrified rails visible or accessible.

Eliminating The Gap

I would imagine that the design of the New Tube for London will make sure that the doors are aligned with the platform, as these doors on a Class 378 train are with the platform on the London Overground.

I would imagine, that  by making certain that the running rails are correctly adjusted, then step-free access between train and platform can be achieved.

I’ve certainly seen passengers in wheel-chairs push themselves in and out of trains at Dalston Junction station.

Electrolytic Corrosion

Mark said this in a comment.

There is a very important reason why the tube uses two power rails. It was quickly discovered that using a ground return on a DC circuit lead to the return current actually coming back via te cast iron tunnel lining rings and electrolysis and electrolytic corrosion of the lining.

Transport for London’s engineers would be very aware of any problems, and I suspect that they have a viable solution.

This article on Rail Engineer is entitled New London Underground Slab Track Cast In-Situ.

It describes how they are using slab track cast in the tunnel to fit problems in short tunnels. They also expect the solution to last a hundred years.

Such a solution would surely work in the cast-iron deep-level tunnels to allow new track to be installed in whatever format was desired.

There Is One Major Problem

The New Tube for London won’t be able to run on the existing track and the current 1973 Stock won’t be able to run on the future track.

So London Underground sensible policy of phasing in the new trains alongside the old ones, as was done on the Victoria Line would not be possible.

The first line to be equipped with New Tube for London trains will be the Piccadilly Line, which has the following characteristics.

  • There are two depots; Cockfosters and Northfields, which are conveniently at each end of the line.
  • There are sidings at Arnos Grove, South Harrow and Uxbridge.
  • Trains can be turned back to the West at Acton Town, Arnos Grove and Wood Green
  • Trains can be turned back to the North at Acton Town, Barons Court, Green Park and Rayner’s Lane.
  • There are crossovers at Hatton Cross, Hounslow Central and Kings Cross St. Pancras.

There are many more sidings, turnbacks and crossovers than most other lines.

These may enable a phased conversion of the line to the new track design, signalling and trains.

Conclusion

I believe it is feasible to convert London’s deep-level Underground lines to a conventional third-rail system, as used in the rest of London, the South East and Merseyrail.

This would give these advantages.

Running On Coventional Third-Rail Tracks

New Tube for London trains could run on the following lines and share with trains like Aventras, Desiro Cities, Electrostars and Networkers equipped for third-rail operation.

Routes where this might be useful include.

  1. Extending the Bakerloo Line along the Watford DC Line, to the North of Queens Park station.
  2. Extending  the Bakerloo Line Extension to the South of Lewisham station to Beckenham Junction, Bromley North and Hayes stations.

Route 2 would release paths into an overcrowded London Bridge station.

Look at this map from carto.metro.free.fr, which shows the new terminus of the Northern Line at Battersea Power Station station.

The under-construction Northern Line Extension is shown dotted.

Could Northern Line services come to the surface, join the surface lines and run to Clapham Junction station and possibly beyond?

Creating More Space And A Level Floor In The New Trains

Removing the centre rail will give more space in the limited tunnels of the deep-level Underground lines and must make it easier to squeeze in all the equipment that has been specified for the new trains.

Increasing Safety

It is my view, that the suicide pit under the train will be wider and will not be guarded by an electric rail.

The main power supply will be right out of the way in stations and could even be eliminated from stations by the use of batteries.

 

 

 

 

October 6, 2018 - Posted by | Travel | , ,

7 Comments »

  1. […] In Thoughts On The Power System For The New Tube for London, I proposed that the New Tube for London could run on a conventional third-rail system. […]

    Pingback by Will The Extended Bakerloo Line Be Twenty-Seven Trains Per Hour All The Way? « The Anonymous Widower | October 7, 2018 | Reply

  2. There is a very important reason why the tube uses two power rails. It was quickly discovered that using a ground return on a DC circuit lead to the return current actually coming back via te cast iron tunnel lining rings and electrolysis and electrolytic corrosion of the lining.

    Comment by Mark Clayton | October 7, 2018 | Reply

    • I think they’ve solved that problem, as Merseyrail and the Northern City Line use conventional three rail track. If you look at tracks like the Piccadilly, there are lots of what could be earth leads to all the running rails.

      Comment by AnonW | October 7, 2018 | Reply

      • I’ll check when I get home, but I think Merseyrail fitted slab track in the Wirral Line tunnel under Liverpool. That wouls isolate everything and stop any electrolytic action.

        Comment by AnonW | October 7, 2018

      • No problem AFAICS on the sub surface lines either – their tunnels are brick.

        Comment by Mark Clayton | October 7, 2018

  3. […] The Piccadilly Line will be self-contained, after the sorting of the shared sections West Rayners Lane and between Ealing Broadway and Acton Town, that I discussed in Thoughts On The Power System For The New Tube for London. […]

    Pingback by What Will Be The Operating Speed Of The New Tube for London? « The Anonymous Widower | October 7, 2018 | Reply

  4. […] Thoughts On The Power System For The New Tube for London, I felt that changing to a conventional three-rail electrification could be possible on the […]

    Pingback by Connecting The Bakerloo Line Extension At Lewisham To The Hayes Line « The Anonymous Widower | October 7, 2018 | Reply


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