Options for 3rd rail conversions to 25KvAC

[steamybrian]

Some of the tunnels on the Hastings line were reduced from double track to single, so might possibly accommodate OLE more easily than most with the track down the centre.
--- old post above --- --- new post below ---


I'm sure someone more knowledgeable on here than me will know

It is true but the tunnels either side of Tunbridge Wells Central station were not modified and remained double track with very, very tight clearances for 3rd rail stock including low speed restrictions. Grove Tunnel was fitted with a concrete slab track base for electrification and is still a tight fit for 3rd rail stock with severe speed restriction. Tunnels in the St. Leonards, Hastings and Ore remain double track also with very tight clearances.
I agree that tunnels that were reduced from double to single track (Somerhill, Strawberry Hill, Wadhurst and Mountfield) should have plenty of room with track laid down the centre giving the best headroom with the highest part of the "horeshoe shape" tunnel profile.

 

[Bald Rick]

Another safe bet is Higham tunnel which finishes just by Strood station. Its enormous. It was built for a waterway to provide a short cut from the river Thames to the river Medway. That was during the napoleonic wars I believe but sailing boats were bigger than the canal boats that came later.

It's not THAT big, particularly since much of it was relined a few years back.

Shakespeare tunnels, however, are cavernous.

 

[yorksrob]

It is true but the tunnels either side of Tunbridge Wells Central station were not modified and remained double track with very, very tight clearances for 3rd rail stock including low speed restrictions. Grove Tunnel was fitted with a concrete slab track base for electrification and is still a tight fit for 3rd rail stock with severe speed restriction. Tunnels in the St. Leonards, Hastings and Ore remain double track also with very tight clearances.
I agree that tunnels that were reduced from double to single track (Somerhill, Strawberry Hill, Wadhurst and Mountfield) should have plenty of room with track laid down the centre giving the best headroom with the highest part of the "horeshoe shape" tunnel profile.

Indeed, although I guessing you're referring to Mt Pleasant rather than Ore tunnel (sorry - it's the pedant in me coming out !).

 

[The Ham]

]



Electrification wouldn't automatically allow longer trains, as they can already run 10 x 23m length trains using 158/159s in multiple. 10 x 23m is generally considered equivalent to 12 x 20m, in terms of overall capacity.

That could already be done by returning all of SWT's DMUs that operate elsewhere to the Salsibury line. So all that needs is more EMUs...

It would allow more seats because rather than 4 trains joined together (2x3 and 2x2 although the normal cofigiration is 3x3) it would be two trains together (2x5), so less spaces taken up for loo's, cabs, etc. It could also mean that there were less first class seats per tain.

Taking capacities from Wikipedia a 3x3 has 516 standard and 72 first class whilst 5x2 has 598 standard and 70 first class.

The other advantage is that while the SWT Diesel fleet can run at 90mph, the electraic fleet can run at 100mph (with some sugesting under OHLE it could be 110mph). This would result in faster journey times even without considering the better acceliration.

Given London to Salisbury is about halfway on the London to Exeter route, with the time savings, it could still be quicker to board an EMU at Waterloo and change to a DMU at Salisbury than currently.

If Salisbury to Basingstoke was electrified then I would assume it was partly to allow frieght diversions from Southampton to Reading, In which case trains from the south coast could also likely be EMU's and make Salisbury a change point for services to the north and west of Salisbury which would be DMU's. This would provide a lot of spare DMU's to be cascaded elsewhere.

 

[Monty]

I'm not sure SWT could run our trains much over 100mph even with OHLE, it may require some if not all parts of the line to be resignalled? Not sure though, if a driver (SWT or otherwise) could confirm or deny this that would be great.

 

[HSTEd]

Speeds greater than 100mph will cause a massive drop in capacity, which is not something that is really a good idea on the Southern Region I think...

One would hope that Southampton to Bournemouth and Weymouth would be higher on the list than starting on the southern central division, as until then pure AC EMUs from XC will be unable to get to Bournemouth which means large numbers of diesels would have to be retained.

 

[Jonny]

Hi there,
Yes, the inner London system is complex. That's why I think that if the 3rd rail to OHLE conversion is done, it will be from the outside in.

By that I mean that the branches and lesser used routes would be done first. These would all have changeovers in stations or just off the main lines, probably in a similar way to the WLL rather than the complexity of City Thameslink.

With these branches done and tested, it could be easier to have a complete conversion over a short time period as resources would have to be focused only on the main lines.
(Amusingly this logical extension of this thought is that Uckfield could see OHLE before Brighton!)

Of course, if some clever electrical engineers figure out a way to permit dual 3rd rail and OHLE operation at low cost or even equipment that could be moved from section to section once a block is converted then it'll be very different.
Jason

Two points - one it shouldn't be too difficult to arrange dual voltage if someone was really determined (pie in the sky bit), it would involve using quite a lot of off-track conductors for the return currents, effectively limiting the rails' use to pickups and probably a lot of feed-in points over smaller sections as well. Perhaps one track as pickup for each system?

Second point - I thought a short add-on scheme for 3rd rail electrification, like the Uckfield branch, would be OK as it is an extension to an existing 3rd rail system.

 

[TheJRB]

Second point - I thought a short add-on scheme for 3rd rail electrification, like the Uckfield branch, would be OK as it is an extension to an existing 3rd rail system.

This was my question in another thread. Does this announcement of converting Reading to Southampton from third rail to overhead now rule out any further extension of third rail to Uckfield, the Marshlink and the North Downs line? I'm guessing the answer will probably be yes in order to save unnecessary hassle in the future but who knows?

 

[jopsuk]

I'm not sure SWT could run our trains much over 100mph even with OHLE, it may require some if not all parts of the line to be resignalled? Not sure though, if a driver (SWT or otherwise) could confirm or deny this that would be great.

I'd suspect that some level of resignalling will be required anyway with the change in electrification?

 

[The Ham]

Speeds greater than 100mph will cause a massive drop in capacity, which is not something that is really a good idea on the Southern Region I think...

One would hope that Southampton to Bournemouth and Weymouth would be higher on the list than starting on the southern central division, as until then pure AC EMUs from XC will be unable to get to Bournemouth which means large numbers of diesels would have to be retained.

From Woking to Basingstoke and then onto Salisbury the lines do not have a lot of traffic, 6 tph (i think) Woking to Basingstoke fast lines & 2 tph Basingstoke to Salisbury, so not really a lot of problems with lossing some capacity.

I agree that there are other parts of the network which are likely to be higher prority, however if when the 3rd rail is up for renewal it becomes standard practice to OHLE then on to Weymouth will be done anyway (due to cost savings).

 

[yorksrob]

This was my question in another thread. Does this announcement of converting Reading to Southampton from third rail to overhead now rule out any further extension of third rail to Uckfield, the Marshlink and the North Downs line? I'm guessing the answer will probably be yes in order to save unnecessary hassle in the future but who knows?

I'm not sure it's banned as such, but I doubt anyone would invest in third rail there if there were a plan to convert the whole system.

 

[The Ham]

This was my question in another thread. Does this announcement of converting Reading to Southampton from third rail to overhead now rule out any further extension of third rail to Uckfield, the Marshlink and the North Downs line? I'm guessing the answer will probably be yes in order to save unnecessary hassle in the future but who knows?

FGW (or whoever is running the trains at the time) would push hard for OHLE on the North Downs Line once part of the network that they run over have them as it would mean not having to stable diesels at Reading. Especially if by then some of the southern network is able to run solely OHLE routes and can cascade their duel voltage trains.

 

[swt_passenger]

I'm not sure it's banned as such, but I doubt anyone would invest in third rail there if there were a plan to convert the whole system.

I don't think it will necesarily be the end of DC installations. The total DC track mileage, rather than 'route' mileage (given the amount of four tracking) is pretty high.

Although much of the Bournemouth line is old equipment, there were a few new substations and feeders installed within the last 10 years for the Desiro rollout, (as there were elsewhere in the SE for the various new Bombardier EMUs).

That second hand equipment might support the odd infill - depends how long they see before a change to OHLE in the relevant area - it could be 50 years for all we know, in which case there'll be renewals or repairs anyway, so there's no reason why the odd short new length can't happen...

 

[tbtc]

This was my question in another thread. Does this announcement of converting Reading to Southampton from third rail to overhead now rule out any further extension of third rail to Uckfield, the Marshlink and the North Downs line? I'm guessing the answer will probably be yes in order to save unnecessary hassle in the future but who knows?

I'd be surprised if there were any *new* Third Rail built now. However, I think that the announcement of a gradual move to Overhead for the Southern Region may at least improve the chances of sorting out the "Diesel Islands" like Uckfield. All guesswork, of course, and it'll presumably be decades before the "Farewell To Third Rail" railtours happen

 

[LNW-GW Joint]

I'd be surprised if there were any *new* Third Rail built now.

Can't see the Watford Met-Junction extension being other than 3rd rail.
This might find itself part of TfL anyway one day.

 

[tbtc]

Can't see the Watford Met-Junction extension being other than 3rd rail.
This might find itself part of TfL anyway one day.

Sorry, I should have said "other than London Underground etc" (the ELL extension obviously didn't use overhead wiring either, but I'm struggling to think of the last "other" bit of Third Rail built).

 

[Ivo]

I know it is unlikely, and I am sure we would all hope otherwise, but if this conversion does go ahead is there any current DC stretch that may be left unelectrified after the conversion (the Medway Valley for instance)? Or, on the positive side, would this improve the case for the current diesel routes to be electrified?

I assume though that Merseyrail (certainly the Wirral line anyway) is out of the question owing to tunnel clearances below Liverpool city centre?

 

[HSTEd]

I know it is unlikely, and I am sure we would all hope otherwise, but if this conversion does go ahead is there any current DC stretch that may be left unelectrified after the conversion (the Medway Valley for instance)? Or, on the positive side, would this improve the case for the current diesel routes to be electrified?

I assume though that Merseyrail (certainly the Wirral line anyway) is out of the question owing to tunnel clearances below Liverpool city centre?

Well I doubt that the Watford DC would be converted, that is if the service is not simply eliminated all together.

 

[Ivo]

Well I doubt that the Watford DC would be converted, that is if the service is not simply eliminated all together.

That was proposed for a Bakerloo line extension (again), was it not? Why wouldn't it be converted?

 

[HSTEd]

That was proposed for a Bakerloo line extension (again), was it not? Why wouldn't it be converted?

Because you don't gain anything significant, since a rather large percentage of the route has to be able to share track with Bakerloo line, and there are no freight flows to demand more power all the time.

 

[D6975]

Could be the tunnel, but it was being designed 7 or 8 years ago - or more. Who would realistically have been thinking at that time about SR OHLE conversion?

Network Rail have only publicly mentioned conversion by using the renewals budget in about the last 18 months.

My point is that even before the news of SR overhead projects, it didn't make sense to use 3rd rail. The ELL was always going to be joined to the NLL, so making it 25KV overhead as far as possible was the logical choice.
If you're opening a new line that joins up with DC lines at one end and AC lines at the other, which would you choose for the joining section?

 

[jopsuk]

Because you don't gain anything significant, since a rather large percentage of the route has to be able to share track with Bakerloo line, and there are no freight flows to demand more power all the time.

Aye, to convert thje Watford DC would mean having to terminate the Bakerloo at Queens Park- better (for connectivity, station capacity etc) to extend the 4th rail to Watford and end the Euston service (not enough Bakerloo stock for this)

 

[swt_passenger]

Can't see the Watford Met-Junction extension being other than 3rd rail.
This might find itself part of TfL anyway one day.

The 'Croxley Link'?

It'll have to be 3rd and 4th rail surely, because it is for Metropolitan trains, irrespective of who ultimately owns it.

--- old post above --- --- new post below ---

My point is that even before the news of SR overhead projects, it didn't make sense to use 3rd rail. The ELL was always going to be joined to the NLL, so making it 25KV overhead as far as possible was the logical choice.

Operationally it isn't joined to the NLL though, and it isn't ever intended to be. The connection (if it ever becomes available for use) is for stock transfer only...

 

[WatcherZero]

I know it is unlikely, and I am sure we would all hope otherwise, but if this conversion does go ahead is there any current DC stretch that may be left unelectrified after the conversion (the Medway Valley for instance)? Or, on the positive side, would this improve the case for the current diesel routes to be electrified?

I assume though that Merseyrail (certainly the Wirral line anyway) is out of the question owing to tunnel clearances below Liverpool city centre?

The Merseyrail doesnt have the same power supply issues because the trains are half the length and half the max speed.

 

[paul1609]

Thread prompted by mentions of 25KvAC from Reading to Southampton, mentions of the reliability of the (ancient) 3rd rail technology and hints of future conversion to 25KvAC.

Occurs to me that wireing up for 25KvAC most/all of the Southern half of the Thameslink routes would be a good place to start. Then, at least, the new Thameslink trains would not need to be dual voltage (DC capable). The 3rd rail need not be removed straight away as this is needed for other services (e.g. Victoria to Brighton). However there are plenty of existing dual voltage units that could cope if some of it was removed.

If conversion is on the cards then the above would, in my opinion, be a good place to start. I expect its not on the cards but any views ?.

Any other ideas/priorities ?.

I think you may be right! Ive heard rumours than the Southern Region will not be able to accept the proposed Thameslink Service because of power supply limitations South of Croydon




--- old post above --- --- new post below ---

I'd say that the lines that connect with Ashford International would be an ideal candidate, given that platforms 3-6 are already wired, and that it could make for a fully-AC HS1 service. All it just takes is for the remaining platforms that are 3rd rail-only to be wired up, and then for Margate and Dover lines to go full AC, since it would then give the HS1 services a boost in time savings.

At Ashford only platforsm 5 and 6 (domestic) and 3 and 4 have access to HS1 and all have dual electrification.

 

[DXMachina]

re the Watford DC lines, in the 6-track section of the WCML they use different tunnels to the AC WCML services. Smaller ones. And yes, shared in parts with 2 different underground lines in the future....

 

[swt_passenger]

I think you may be right! Ive heard rumours than the Southern Region will not be able to accept the proposed Thameslink Service because of power supply limitations South of Croydon

But all that really means is that it couldn't accept it today. Upgrades are necessary for Thameslink in a number of areas north and south of the Thames.

According to NR's CP4 stuff there have already been power supply upgrades for Key Output 1, and there'll be more for KO2.

 

[Minstral25]

Sorry, I should have said "other than London Underground etc" (the ELL extension obviously didn't use overhead wiring either, but I'm struggling to think of the last "other" bit of Third Rail built).

There is a bit currently being built from Surrey Quays to Queens Road Peckham.

 

[HSTEd]

My point is that even before the news of SR overhead projects, it didn't make sense to use 3rd rail. The ELL was always going to be joined to the NLL, so making it 25KV overhead as far as possible was the logical choice.
If you're opening a new line that joins up with DC lines at one end and AC lines at the other, which would you choose for the joining section?

Over short distances 750V third rail is probably cheaper than 25kV mainline standard electrification (with auto tensioned catenary and the like since we apparently don't believe in specifying to match the required performance any more) as you don't need all those hyper advanced components.

If you have to have a voltage changeover at one end of the line and there is no operational benefit to either kind of operation you can literally just pick one, and as I said 750V was probably cheaper, especially when you consider the clearance issue with OLE.

I am rather skeptical of this idea that the OLE installation will be cheaper than renewing the third rail gear generally, rather than in this rather unique situation. (Heavily loaded third rail and a desire to load it with huge point loads like locomotives).

The clearance issues alone must be enormous.

 

[yorksrob]

Sorry, I should have said "other than London Underground etc" (the ELL extension obviously didn't use overhead wiring either, but I'm struggling to think of the last "other" bit of Third Rail built).

My guess would be either be the West London Line or Tonbridge - Redhill for Eurostar diversions and transfers.