3rd rail for some electrification projects

[Bucephalus]

I visited Barcelona earlier in the year and was slightly surprised to see their Metro is OHLE. I'd assumed 3rd rail would be the natural method for a metro, but they seem to have gone for overhead, often rigid bar. Some of their lines date back to the 19th century, presumably they were lucky enough to have the space for that?

Though if they go for that in a metro application, third rail in wide open country seems hard to justify.

From what I have read, it used to be 3rd rail. I don't know the reason why but it must have been a good one.

Referring to the original post about "more costly and difficult electrification projects, such as MML, North TPE and Hope Valley?"

For TPE and hope Valley at least I think of a few drawbacks regarding 3rd rail:

1 too many substations required due to long distances.
2. 100mph speed limit reducing benefit on a long distance railway.
3. Inclement weather freezing the conductor rail.

After some sort of feasibility study it might work out cheaper to re-bore tunnels for OLE or continue with diesel.

 

[Bletchleyite]

From what I have read, it used to be 3rd rail. I don't know the reason why but it must have been a good one

Off the shelf vehicles? If I was building a new U-Bahn now I'd build it to modern tram spec, which would mean OHLE.

 

[Bigman]

If you were to electrify a 3m 64 yard tunnel (eg Standedge). purely in terms of installation cost, would it be cheaper to 3rd rail a tunnel than to OHLE it? This would avoid clearances/dropping the track bed etc.

 

[TSG]

If you were to electrify a 3m 64 yard tunnel (eg Standedge). purely in terms of installation cost, would it be cheaper to 3rd rail a tunnel than to OHLE it? This would avoid clearances/dropping the track bed etc.

Pure installation cost, quite possibly, but you only lower the track once. The ongoing costs would be much higher, so any saving is likely to pale into insignificance quite quickly.

 

[Dr Hoo]

Depending on local circumstances you might well end up missing out on the opportunity to enhance the gauge for full-size containers on common wagons. You would also probably need extra feeder stations at either end and complex bespoke power supply control arrangements assuming that other parts of the route were electrified on 25kV.

 

[Bigman]

Thanks for the replies. I just wondered. I guess that is where bi-modes would come into their own...no electrification costs at all in the tunnels.

 

[zwk500]

Thanks for the replies. I just wondered. I guess that is where bi-modes would come into their own...no electrification costs at all in the tunnels.

If the entire rest of the route was electrified, then spending a large amount of money on building and maintaining bi-modes purely for tunnels would also probably show a worse return on investment than just wiring the tunnel. Also, having a gap in the electrification network is not usually desirable.
If the Bi-Modes are being ordered anyway for non-electrified routes to operate as part of the intended service, AND not wiring the Tunnel tipped the scales on the BCR, then it might be feasible. But you'd be making wiring the tunnel itself in future (which would be almost inevitable) a lot more difficult as all the engineering access would have to be repeated, hacking off passengers (who would ask why it wasn't done first time), and duplicating costs all over the place. You'd also be restricting the route from fully-electric traction in the event of amended working for the sake of 3 miles.

E.g. the Severn tunnel. Was always planned to be wired, but the problems (and therefore costs were getting astronomical). Bi-Modes were already being used so interim solution was to switch over to diesel for the jaunt through the tunnel. Once they'd found a solution to the problems with the wires the Bi-Modes stayed on electric power the whole way. Given it was worth finding a solution to the problems with the wires even though all the other OLE was live and the Bi-Modes were going to run anyway, I'd say wiring the tunnel is still the most cost-effective decision.

 

[Bald Rick]

Wiring tunnels is often cheaper (much) than open track. No structures or foundations to worry about, no buried cables in the way, etc. Just bolt the SPS to the wall.

It’s only an issue if there isn’t clearance (there often is). Then it’s track lowering, and most track lowering is relatively straightforward.

 

[Bigman]

The other consideration I guess is that bi-modes create less issues where you have to divert via the Calder Valley due to engineering/disruptions. If the WCML is shut North of Preston, what happens with TPE 397's heading North?

 

[zwk500]

The other consideration I guess is that bi-modes create less issues where you have to divert via the Calder Valley due to engineering/disruptions. If the WCML is shut North of Preston, what happens with TPE 397's heading North?

397s aren't cleared for the S&C, so I'd guess TPE just terminate at Preston & Carlisle. A better example is GWR/LNER, as discussed on the Battery Tri-Mode thread. GWR have 4 separate routes between Reading and Exeter (via Newbury, Badminton, Bath and Yeovil) so being Bi-Mode allows diversion to take place immediately (subject to Driver Knowledge), rather than having to wait for diesel locos to be in position. LNER regularly divert from Doncaster via Lincoln to Peterbrough (and have gone Doncaster-Lincoln-Newark/Grantham before), and the bi-modes mean they no longer have to stop to attach/detach the 67.

 

[Philip Phlopp]

Wiring tunnels is often cheaper (much) than open track. No structures or foundations to worry about, no Burke£ cables in the way, etc. Just bolt the SPS to the wall.

It’s only an issue if there isn’t clearance (there often is). Then it’s track lowering, and most track lowering is relatively straightforward.

Truth.

The track lowering that we often have to undertake in tunnels for electrification often takes the railhead level back to where it was when the tunnels were built, people tend to forget that most tunnels were built with quite a decent level of clearance to enable draughting in steam locomotives and to ensure the smoke was lifted as clear as possible from around the locomotive for the benefit of driver signal sighting/visibility.

Track geometry has been allowed to drift; particularly during the war and then under BR, there was a tendency, thanks to very tight budgets and inability to close routes for lengthy periods, of "just chuck some more ballast down, that'll fix those drainage issues or those rough riding issues or those subsidence issues, or all of the above". The successive reballasting without longer closures and proper excavations to remove all of the old ballast are what have seen the track level increase often fairly significantly from the original level during construction.

 

[Wolfie]

... but apparently perfectly acceptable for London Underground, which as we know is actually mostly above ground.

London Underground is, as l understand it, technically four rail. The latest new tube line (the Jubilee, large parts of which were taken from existing lines) opened over 20 years ago.

== Doublepost prevention - post automatically merged: 19 Dec 2020 ==

Clearly extended from Whitechapel to Highbury and Islington.

Not a tube line

 

[Railwaysceptic]

Truth.

The track lowering that we often have to undertake in tunnels for electrification often takes the railhead level back to where it was when the tunnels were built, people tend to forget that most tunnels were built with quite a decent level of clearance to enable draughting in steam locomotives and to ensure the smoke was lifted as clear as possible from around the locomotive for the benefit of driver signal sighting/visibility.

Track geometry has been allowed to drift; particularly during the war and then under BR, there was a tendency, thanks to very tight budgets and inability to close routes for lengthy periods, of "just chuck some more ballast down, that'll fix those drainage issues or those rough riding issues or those subsidence issues, or all of the above". The successive reballasting without longer closures and proper excavations to remove all of the old ballast are what have seen the track level increase often fairly significantly from the original level during construction.

Thank you for that. I didn't know that so I've just learned something!

 

[Class 170101]

Not a tube line

But a 'BR' extension then so why not Uckfield, Ore to Asford or parts of Reading to Gatwick as appropriate. Surprised in a way tht the line from Highbury to Shoreditch wasn't electrified on 25kv overhead to be honest.

 

[Wolfie]

Surely anyone working at the ORR enjoys sovereign immunity?

Legal terminology: In UK government can, in some circumstances (increasingly decreasing), have Crown immunity albeit that the Courts often overrule. Sovereign immunity in UK law relates to actions of UK government overseas and/or other governments.

I visited Barcelona earlier in the year and was slightly surprised to see their Metro is OHLE. I'd assumed 3rd rail would be the natural method for a metro, but they seem to have gone for overhead, often rigid bar. Some of their lines date back to the 19th century, presumably they were lucky enough to have the space for that?

Though if they go for that in a metro application, third rail in wide open country seems hard to justify.

I could be wrong but l thought that in Barcelona (which l haven't been to for a while), like Madrid (which l've been to more recently), only some lines were overhead. I suspect that it depends on who originally built them.

== Doublepost prevention - post automatically merged: 19 Dec 2020 ==

But a 'BR' extension then so why not Uckfield, Ore to Asford or parts of Reading to Gatwick as appropriate. Surprised in a way tht the line from Highbury to Shoreditch wasn't electrified on 25kv overhead to be honest.

Interestingly, when those works were done the OHLE was significantly extended on the North London line. An area l know damn well as l live 2 minutes from Canonbury station.

I agree with you with respect to infills/gap filling.

 

[swt_passenger]

But a 'BR' extension then so why not Uckfield, Ore to Asford or parts of Reading to Gatwick as appropriate. Surprised in a way tht the line from Highbury to Shoreditch wasn't electrified on 25kv overhead to be honest.

It’s probably because the ELL extension had been designed and built well before ORR decided to move their goalposts. I suspect dual voltage wouldn’t have been considered, as through running to the wider NLL was never initially planned (and still isn’t possible).

 

[Wolfie]

It’s probably because the ELL extension had been designed and built well before ORR decided to move their goalposts. I suspect dual voltage wouldn’t have been considered, as through running to the wider NLL was never initially planned (and still isn’t possible).

Also the Brunel tunnel is listed which constrained what could be done to it.

Thames Tunnel project, East London Line

CIVIL ENGINEERING CATEGORY

www.architectsjournal.co.uk

 

[Bald Rick]

Track geometry has been allowed to drift; particularly during the war and then under BR, there was a tendency, thanks to very tight budgets and inability to close routes for lengthy periods, of "just chuck some more ballast down, that'll fix those drainage issues or those rough riding issues or those subsidence issues, or all of the above". The successive reballasting without longer closures and proper excavations to remove all of the old ballast are what have seen the track level increase often fairly significantly from the original level during construction.

Indeed so. Shakespeare tunnel being a fine example - the rail level there’s must be getting on for half a metre or more above its original level.

 

[Taunton]

Also the Brunel tunnel is listed which constrained what could be done to it.

There are a very large number of listed rail structures which have had OHLE installed. If it's desired to keep it in Brunel's condition the rails would have to be removed.

I do increasingly get the impression that ORR would be accepting of a reasoned case for 3rd rail infill, and it's the overhead zealot engineers at NR etc, salivating at a project whose OHLE installation costs are 10 times what it costs to put in 3rd rail (having physically witnessed the 3rd rail being put in over one weekend on Custom House to North Woolwich I feel that's no exaggeration and maybe even an understatement), who are behind the story of it being banned.

 

[swt_passenger]

Indeed so. Shakespeare tunnel being a fine example - the rail level there’s must be getting on for half a metre or more above its original level.

At that sort of height, presumably fixing it (if ever decided) would extend a fairly long distance either side of the tunnel too?

 

[Bald Rick]

At that sort of height, presumably fixing it (if ever decided) would extend a fairly long distance either side of the tunnel too?

Yep!

 

[Philip Phlopp]

There are a very large number of listed rail structures which have had OHLE installed. If it's desired to keep it in Brunel's condition the rails would have to be removed.

I do increasingly get the impression that ORR would be accepting of a reasoned case for 3rd rail infill, and it's the overhead zealot engineers at NR etc, salivating at a project whose OHLE installation costs are 10 times what it costs to put in 3rd rail (having physically witnessed the 3rd rail being put in over one weekend on Custom House to North Woolwich I feel that's no exaggeration and maybe even an understatement), who are behind the story of it being banned.

You don't half talk some utter nonsense.

There's no conspiracy to deploy OLE where it's not appropriate.

There's also not a 10x difference between OLE and third rail if you include the minor inconvenience of getting electricity into the OLE or third rail - you're forgetting that third rail needs a complex and expensive 'secondary' grid that sits in between the National Grid or DNO and the actual juice rail itself, as part of that grid, it's substations every few miles and tonnes of additional cabling. It's also not terribly good at meeting the supply demands placed upon it by modern rolling stock.

 

[Taunton]

it's substations every few miles

Sounds more efficient than substations under each 4-car unit, sat in the sidings for most of the day.

 

[Metal_gee_man]

Wiring tunnels is often cheaper (much) than open track. No structures or foundations to worry about, no buried cables in the way, etc. Just bolt the SPS to the wall.

It’s only an issue if there isn’t clearance (there often is). Then it’s track lowering, and most track lowering is relatively straightforward.

I'm fairly sure the OHLE of the Severn Tunnel was one of the most challenging engineering challenges on the UK network, the tunnels leak like sieves so the walls/brickwork are not only fairly soft and rotten, but unable to support some of the weight of the structure, specialist OHLE equipment which wasn't going to rust out in a few years in the salty saline water/environment.
Unsurprisingly 3rd rail would have been much cheaper, easier to install and maintain (yes it was never going to happen because the rest of the route was OHLE) just remember OHLE isn't always the answer but they'll put their hands in their pockets to make it work

 

[Philip Phlopp]

I'm fairly sure the OHLE of the Severn Tunnel was one of the most challenging challenges on the UK network, the tunnels leak like sieves so the walls/brickwork are not only fairly soft and rotten, but unable to support some of the weight of the structure, specialist OHLE equipment which wasn't going to rust out in a few years in the salty saline water/environment.
Unsurprisingly 3rd rail would have been much cheaper, easier to install and maintain (yes it was never going to happen because the rest of the route was OHLE) just remember OHLE isn't always the answer but they'll put their hands in their pockets to make it work

Third rail would have been even more problematic in the tunnel - I'd be surprised if you could make it through a week without it tripping, given how wet the tunnel is at track level.

 

[Elecman]

Third rail would have been even more problematic in the tunnel - I'd be surprised if you could make it through a week without it tripping, given how wet the tunnel is at track level.

Absolutely, wet salty water all over the insulators

 

[Bald Rick]

I'm fairly sure the OHLE of the Severn Tunnel was one of the most challenging engineering challenges on the UK network, the tunnels leak like sieves so the walls/brickwork are not only fairly soft and rotten, but unable to support some of the weight of the structure, specialist OHLE equipment which wasn't going to rust out in a few years in the salty saline water/environment.
Unsurprisingly 3rd rail would have been much cheaper, easier to install and maintain (yes it was never going to happen because the rest of the route was OHLE) just remember OHLE isn't always the answer but they'll put their hands in their pockets to make it work

I can think of several engineering challenges that were tougher than electrification of the Severn tunnel. Signalling on the class 345s for example. Return currents in the Thameslink core. The Medway viaduct. Etc.

3rd Rail wouldn’t have been cheaper. It would have needed a substation the size of 2 portakabins (other relocatable building brands are available) in the middle of the tunnel somewhere. I’ll leave you to work out how you would have put them there, and what it would have cost.

Fortunately, now that there is electrification through the longest, wettest and most chemically challenging Tunnel in the country, the rest will be easy.

 

[Wolfie]

I'm fairly sure the OHLE of the Severn Tunnel was one of the most challenging engineering challenges on the UK network, the tunnels leak like sieves so the walls/brickwork are not only fairly soft and rotten, but unable to support some of the weight of the structure, specialist OHLE equipment which wasn't going to rust out in a few years in the salty saline water/environment.
Unsurprisingly 3rd rail would have been much cheaper, easier to install and maintain (yes it was never going to happen because the rest of the route was OHLE) just remember OHLE isn't always the answer but they'll put their hands in their pockets to make it work

If it's that wet wouldn't the third rail have been in standing water?

 

[D365]

Quite possibly, but the engineers at NR and their contractors most certainly do not, and the buck will likely stop with them

You don't half talk some utter nonsense.

There's no conspiracy to deploy OLE where it's not appropriate.

There's also not a 10x difference between OLE and third rail if you include the minor inconvenience of getting electricity into the OLE or third rail - you're forgetting that third rail needs a complex and expensive 'secondary' grid that sits in between the National Grid or DNO and the actual juice rail itself, as part of that grid, it's substations every few miles and tonnes of additional cabling. It's also not terribly good at meeting the supply demands placed upon it by modern rolling stock.

Amen to both.

If third rail truly was a solution to our electrification woes, why are we the only country with swathes of third rail electrified mainlines?

 

[MarkyT]

I can think of several engineering challenges that were tougher than electrification of the Severn tunnel. Signalling on the class 345s for example. Return currents in the Thameslink core. The Medway viaduct. Etc.

3rd Rail wouldn’t have been cheaper. It would have needed a substation the size of 2 portakabins (other relocatable building brands are available) in the middle of the tunnel somewhere. I’ll leave you to work out how you would have put them there, and what it would have cost.

Fortunately, now that there is electrification through the longest, wettest and most chemically challenging Tunnel in the country, the rest will be easy.

I read OHLE engineers had to change materials used in elements of the system, for which they needed to undertake some research and pursue a standards challenge, but that has now solved the problem effectively, along with repair/replacement of a preexisting 'drip tray' system that was supposed to direct water away in certain problem areas but had been allowed to degrade over decades. The knowledge gained and new materials approved will no doubt be useful for future wet tunnel electrification schemes.