European Railroad Discussion > The “Other” Paddington Station

Across the street from the mainline (former-GWR) Paddington Station is the Metropolitan Railway's station.  Now part of the London Underground system, it was built as a conventional steam railway running largely in cut-and-cover tunnels through central London and has a much larger loading gauge than the "tube" lines.  I'll stop there and let our British colleagues build on this story, but I was there yesterday and for the first  time really noticed this station.

Gordon



Edited 1 time(s). Last edit at 12/01/21 09:06 by gbmott.

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Makes the "underground" look quite important. Is both the outside third rail and the center rail for power? Thanks for sharing.

For reasons I hope someone else can explain, the LU uses a center rail for the current return rather than the running rails as in most other electrification systems.
  -- Gordon

gbmott Wrote:
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> For reasons I hope someone else can explain, the
> LU uses a center rail for the current return
> rather than the running rails as in most other
> electrification systems.
>   -- Gordon

So they have a current "roller" on the trucks like my old 3 rail Lionel trains did?

gbmott Wrote:
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> For reasons I hope someone else can explain, the
> LU uses a center rail for the current return
> rather than the running rails as in most other
> electrification systems.

My understanding of the bizarre tube power system (+420 on the outside rail, -210 on the inside, and isolated from the running rails) was that they had problems with stray return currents in the early years causing galvanic corrosion in the iron tunnel linings.  Since insulators wouldn't stand up to the weight of being on the running rails, they went to a four rail system where no power travels through an uninsulated rail.  Baffled me the first time I saw it, too.

"Regent Dry Cleaners"
British Empire Royalty only? May commoners use the River Thames?

Lurch_in_ABQ Wrote:
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> "Regent Dry Cleaners"
> British Empire Royalty only? May commoners use the River Thames?


Neat picture.

And now I want a bagel.

Brian

NDHolmes Wrote:
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> gbmott Wrote:
> --------------------------------------------------
> -----
> > For reasons I hope someone else can explain,
> the
> > LU uses a center rail for the current return
> > rather than the running rails as in most other
> > electrification systems.
>
> My understanding of the bizarre tube power system
> (+420 on the outside rail, -210 on the inside, and
> isolated from the running rails) was that they had
> problems with stray return currents in the early
> years causing galvanic corrosion in the iron
> tunnel linings.  Since insulators wouldn't stand
> up to the weight of being on the running rails,
> they went to a four rail system where no power
> travels through an uninsulated rail.  Baffled me
> the first time I saw it, too.

Current leakage was part of it certainly, but it also allowed the use of DC track circuits for train detection.

Nowadays it's not as simple to call it 630V third rail - there are actually 3 systems in use presently.

Firstly the traditional, -210V centre rail/+420V outer rail, nominal 630V system, this remains the default on the deep level lines.

There is then bonded fourth rail, the 'fourth' centre rail is electrically bonded to the running rails and the outer rail operates at +750V, this is comments where London Underground shares tracks with Network Rail infrastructure and the legacy ex-Southern 750V 3rd rail system prevalent in the South/Southeast of England.

The bonded 4th rail system can be found on sections such as:
- Between Queen's Park and Harrow & Wealdstone on the Watford DC line, served by Bakerloo line and London Overground trains
- Between Richmond and Gunnersbury on the District line which is shared with the London Overground
- Between East Putney and Wimbledon on a section of the District line that was transferred from British Rail

Finally there is the upgraded 4th rail, where the nominal voltage is upgraded to 750V to improve performance. The centre rail is -250V and the outer is +500V. This is used on the entire sub-surface network with the exception of Uxbridge to Finchley Road where older Picadilly Line 1973 stock shares the tracks.

These all refer to the 'supplied' traction voltages but there is also what is referred to as the 'permissible' traction voltage. This refers to the maximum voltage that may be used by S-stock trains when they are feeding electricity back into the traction rails during regenerative braking. Originally this was set at 650V back when the supplied voltage was still the non-upgraded nominal 630V, but it has since been increased twice - first to 790V and finally to 890V as part of the upgrading of the traction supply on S-stock routes to 750V. This allows for some useful headroom with the increased levels of regenerative braking being permitted.

Posted from Android

Thanks for all the responses on the power pick-up. I had no idea it was this elaborate.

Any photos of the station interior?

King_Coal Wrote:
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> Any photos of the station interior?

The photo with the trains is in the station, but I didn't take any in the ticketing area, sorry.
   -- Gordon

King_Coal Wrote:
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> Thanks for all the responses on the power pick-up.
> I had no idea it was this elaborate.
>
> Any photos of the station interior?

A considerable number of passengers, probably the majority, would enter and exit through a tunnel that connects the Underground station with Paddington mainline station across the street, and would have little sense of a station "interior" as such.
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