Discontinuous electrification schemes should be replaced by continuous electrification

[TT-ONR-NRN]

Moderator note: split from

South Wales 'Metro' updates

I thought it would be worthwhile to start a discussion on the South Wales 'Metro'. Basically, this is the scheme to enhance transport links across south east Wales. One of the key issues that needs to be addressed is what form of transport will be used on the Cardiff Valley lines network -...

www.railforums.co.uk

Amazing how other countries seem to be able to produce lightweight elegant gantries for high speed main line railways, but here we have heavy ugly things for relatively low speed trams.

All things considered, the way they've decided to electrify it is silly.

They've chosen equipment far more expensive than will ever be needed for a route to be served solely by tram-trains.

And what with the many gaps in between the wires, requiring said tram-trains to switch to battery mode temporarily, with those batteries then recharged by the wires when the tram-train returns under them, regular heavy rail electric trains wouldn't be able to run the line even if TfW wanted them to.

 

[K.o.R]

All things considered, the way they've decided to electrify it is silly. They've chosen equipment far more expensive than will ever be needed for a route to be served solely by tram-trains. And what with the many gaps in between the wires, requiring said tram-trains to switch to battery mode temporarily, with those batteries then recharged by the wires when the tram-train returns under them, regular heavy rail electric trains wouldn't be able to run the line even if TfW wanted them to.

The entire thing is ridiculous in its complexity. I wonder how much more expensive it will turn out to be in the long run vs doing it properly the first time?

 

[John R]

All things considered, the way they've decided to electrify it is silly. They've chosen equipment far more expensive than will ever be needed for a route to be served solely by tram-trains. And what with the many gaps in between the wires, requiring said tram-trains to switch to battery mode temporarily, with those batteries then recharged by the wires when the tram-train returns under them, regular heavy rail electric trains wouldn't be able to run the line even if TfW wanted them to.

How many routes converted wholly to light rail in the UK can you name that have subsequently converted back to heavy rail?

I know it's not perfect, but it's still going to be a hell of a lot better than if responsibility and funding for the railway had remained with the DfT. Given 40 years ago the tops of the valleys were down to a train every two hours, and the Aberdare line not even reopened, redoubling of substantial sections of the lines and a 4 tph frequency of electric trains is going to be an astonishing turnaround.

 

[Peter Sarf]

How many routes converted wholly to light rail in the UK can you name that have subsequently converted back to heavy rail?

I know it's not perfect, but it's still going to be a hell of a lot better than if responsibility and funding for the railway had remained with the DfT. Given 40 years ago the tops of the valleys were down to a train every two hours, and the Aberdare line not even reopened, redoubling of substantial sections of the lines and a 4 tph frequency of electric trains is going to be an astonishing turnaround.

Indeed. Then I will suffer any growing pains gladly if the present investment decisions are overtaken by growth.

Even in London the under-specified DLR has exceeded those original justifications. Hindsight is a wonderful thing but would anything have been built if a more optimistic original network had been proposed ?.

 

[stuu]

How many routes converted wholly to light rail in the UK can you name that have subsequently converted back to heavy rail?

I know it's not perfect, but it's still going to be a hell of a lot better than if responsibility and funding for the railway had remained with the DfT. Given 40 years ago the tops of the valleys were down to a train every two hours, and the Aberdare line not even reopened, redoubling of substantial sections of the lines and a 4 tph frequency of electric trains is going to be an astonishing turnaround.

His point is that they haven't been converted completely to light rail though, they have gone with a hybrid system. It would be interesting to know if they did a BCA of installing 750v DC tram electrification and tram standards instead of putting in footbridges with lifts, and possibly having dual voltage trams for running onto NR lines

 

[TT-ONR-NRN]

How many routes converted wholly to light rail in the UK can you name that have subsequently converted back to heavy rail?

Agreed, so why are they using OHLE types meant for heavy rail routes?

 

[tomuk]

Agreed, so why are they using OHLE types meant for heavy rail routes?

Because it is heavy rail they aren't converting it to light rail.

 

[TT-ONR-NRN]

Because it is heavy rail they aren't converting it to light rail.

Oh god the pedantry continues.
Alright, light rail VEHICLES then.
@DanNCL you can explain it better than me, you mentioned this even before I did!

 

[tomuk]

Oh god the pedantry continues.
Alright, light rail VEHICLES then.
@DanNCL you can explain it better than me, you mentioned this even before I did!

So returning to your original post are you suggesting that the lines to Treherbet, Merthyr and Aberdare on which the 398 are due to run should be electrified at 750v dc and operated as light rail?

 

[Lawner]

It's not really pedantry from tomuk as light rail and heavy rail are built to different standards and the core valley lines are built to heavy rail standards. The choice to use AC would likely be because this is a standard heavy rail railway where 25V AC is the standard system. The CVL is fully segregated, it doesn't feature any on street running so there isn't any need to use 750V DC equipment. DC equipment doesn't perform as well as AC and comes with its own problems like the requirement for smaller electrical sections needing more substations and more complex earthing and bonding arrangements. If you were to use DC equipment then 1500 or 3000V DC would be more suitable but doesn't provide any advantage over 25kV AC. I'm not familiar with the line speeds within the CVL but the class 398's are specified to achieve speeds over 60mph and lighter OLE equipment is in my experience limited to 50mph.

 

[edwin_m]

The CVL is fully segregated, it doesn't feature any on street running so there isn't any need to use 750V DC equipment.

The plan is to have a short section of street running in the Bay with the possibility of more in the longer term. The tram-trains will use battery power on these sections. If in the future there is a very long extension then they may have to install some 25kV to top up the batteries, with measures to keep people off that part of the track. I believe the tram-trains have no 750Vdc capability, although it might be possible to upgrade them as the traction package probably runs on 750V internally.

 

[Lawner]

The plan is to have a short section of street running in the Bay with the possibility of more in the longer term. The tram-trains will use battery power on these sections. If in the future there is a very long extension then they may have to install some 25kV to top up the batteries, with measures to keep people off that part of the track. I believe the tram-trains have no 750Vdc capability, although it might be possible to upgrade them as the traction package probably runs on 750V internally.

That isn't part of the CVL. What I've heard about the Bay project though is that they're considering installing chargers at the stations. Still there's not much point in using 750DC for the whole route because another project in the future might consider using DC for a small section of street running.
Another thought is that the project covers a lot of track which remains in NR ownership and it's a easier to use equipment which is already approved and use it across the whole project than to use 2 different systems adding unnecessary complexity for little if any benefit.

 

[tomuk]

Still there's not much point in using 750DC for the whole route because another project in the future might consider using DC for a small section of street running.

You could say the same for the use of Tram Trains.

 

[Tomos y Tanc]

You could say the same for the use of Tram Trains.

Well, you could but why would you limit future flexibility?

 

[tomuk]

Well, you could but why would you limit future flexibility?

Because you waste money now for flexibility in the future you may not need plus by buying the stock now you are already reducing your future flexibility locking you into a decided path.

 

[Peter Sarf]

Because you waste money now for flexibility in the future you may not need plus by buying the stock now you are already reducing your future flexibility locking you into a decided path.

Investing in these tram-trains is however not as much of a tie in as having non-heavy rail electrification etc.

 

[John R]

Investing in these tram-trains is however not as much of a tie in as having non-heavy rail electrification etc.

Out of interest, what exactly precludes heavy rail vehicles from using the routes in the future? Scotland is going for discontinuous electrification with heavy rail stock, so I don’t see the difference.

 

[Lawner]

Out of interest, what exactly precludes heavy rail vehicles from using the routes in the future? Scotland is going for discontinuous electrification with heavy rail stock, so I don’t see the difference.

At the moment nothing prevents heavy rail rolling stock from the route. Scotland the discussion around discontinous electrification has been around using it only as an interim solution in their rolling electrification programme. I wouldn't be surprised if they do change their mind given the problems Core Valley Lines has been having. My speculation is that discontinous won't last long term in the valleys and will be replaced with controlled voltage technology like Great Western used on the bridge between Cardiff Central and Queen street.

 

[John R]

At the moment nothing prevents heavy rail rolling stock from the route. Scotland the discussion around discontinous electrification has been around using it only as an interim solution in their rolling electrification programme. I wouldn't be surprised if they do change their mind given the problems Core Valley Lines has been having. My speculation is that discontinous won't last long term in the valleys and will be replaced with controlled voltage technology like Great Western used on the bridge between Cardiff Central and Queen street.

How many of the problems you cite have been down to the discontinuous electrification? They mainly seem to be around other things which would have happened even with full electrification. Eg utilities needing moving.

 

[Lawner]

How many of the problems you cite have been down to the discontinuous electrification? They mainly seem to be around other things which would have happened even with full electrification. Eg utilities needing moving.

The main one is that it hasn't saved any money compared to full electrification and loses some of the benefits, the main one being that electric trains are lighter and reduce track wear meaning that money is saved on track maintenance. Battery electrics are not lighter than diesels and so you're not saving any money on track maintenance.
Ian Walmsley wrote about the problems with discontinuous electrification in some detail in Modern Railways February last year.

Electrification deception

Discontinuous electrification is often suggested to reduce the cost of electrification – but only by people who know nothing about electrification

www.modernrailways.com

I think the problems that TfW have given should be treated with some salt, some appear spurious and there are other problems I've heard from people within industry that TfW haven't mentioned at all.

 

[snowball]

The main one is that it hasn't saved any money compared to full electrification

That's a remarkable claim that would require some evidence, given that it's often said that the main cost of electrification is reconstructing bridges.

 

[Lawner]

That's a remarkable claim that would require some evidence, given that it's often said that the main cost of electrification is reconstructing bridges.

I have already given evidence.

 

[John R]

I have already given evidence.

Helpfully to a paywalled article.

 

[Lawner]

Helpfully to a paywalled article.

I didn't have any problems viewing it without a subscription.

 

[snowball]

I will have read it when it was new, as I have a subscription to MR (offline only) and usually read Walmsley's column. Not sure whether I still have the issue.

 

[plugwash]

I didn't have any problems viewing it without a subscription.

A fair number of news sites, let you read the article free if you reach it from google but not if you reach it from elsewhere. I believe this is due to google policies on paywalled content.

Google "modern railways electrification deception", follow the link from there and you can read the article.

 

[Bald Rick]

Out of interest, what exactly precludes heavy rail vehicles from using the routes in the future? Scotland is going for discontinuous electrification with heavy rail stock, so I don’t see the difference.

On the valleys, Heavy rail stock couldn’t access the new depot at Taffs Well. That could be corrected, but at a cost of course.

The main one is that it hasn't saved any money compared to full electrification and loses some of the benefits

Citation needed (and not the Walmsley article)

Battery electrics are not lighter than diesels and so you're not saving any money on track maintenance.
Ian Walmsley wrote about the problems with discontinuous electrification in some detail in Modern Railways February last year.

Yes, myself and Mr W disagreed with that article. As it happens battery electrics are not heavier than DMUs, in general. A Stadler Class 777 with battery is a shade over 100 tonnes for 65 metres of train, a Stadler Class 755/3 is 114t for about the same length of train, a CAF Class 195 is 128t for a slightly longer train.

In any event, the track maintenance saving issue is frankly minimal in the scheme of things.

 

[Envoy]

They needed to go with the battery option in order to cross streets - such as the link from Central to the Bay line via Callaghan Square. Of course, it could be argued that this service could be just provided by buses - as it is at present.

The master plan includes the building of a Metro route from Fairwater on the City Line out north westward to Cregiau & beyond - much of it on former rail routes. Note that where the protected land through the new housing north of M4 J33 (Cardiff West) for this route, no provision has been made for heavy rail should that be desired in future.

 

[Lawner]

On the valleys, Heavy rail stock couldn’t access the new depot at Taffs Well. That could be corrected, but at a cost of course.



Citation needed (and not the Walmsley article)



Yes, myself and Mr W disagreed with that article. As it happens battery electrics are not heavier than DMUs, in general. A Stadler Class 777 with battery is a shade over 100 tonnes for 65 metres of train, a Stadler Class 755/3 is 114t for about the same length of train, a CAF Class 195 is 128t for a slightly longer train.

In any event, the track maintenance saving issue is frankly minimal in the scheme of things.

The Walmsley article is a perfectly valid source and simply saying you disagree isn't a valid criticism.
I never said that battery electrics were heavier than DMUs, I said they were heavier than EMUs. I disagree that the maintenance saving issue is minimal when it has historically been one of the main reasons to electrify.

 

[Dai Corner]

The Walmsley article is a perfectly valid source and simply saying you disagree isn't a valid criticism.
I never said that battery electrics were heavier than DMUs, I said they were heavier than EMUs. I disagree that the maintenance saving issue is minimal when it has historically been one of the main reasons to electrify.

Surely infrastructure maintenance will cost more post-electricification, especially overhead? The savings are in traction maintenance.