Third Rail Electrification

[HSTEd]

Now as I understand it, third rail electrification is only to be used for "infill" or similar work.
I assume this is where the changeovers would represent operational difficulties such as requiring the use of dual voltage rigged (and not just capable) stock and requiring stops to change over and all the extra signalling work required to ensure everything works properly.

I assume this means that if the Uckfield line were to be electrified it would be electrified at 3rd rail, but there are some other cases that are not so clear cut.

The Marshlink Line for instance runs from Ashford International to Hastings and has third rail at the Hastings end (running as far as Ore) but is dual electrified at the other due to the mess that is Ashford International. Would this be done as third rail, with any HS1 services switching to third rail power at Ashford or would it be done with AC with trains switching to third rail at Ore, or possible even in Hastings itself with Ore being converted?

Another such line is the West of England Main Line, with the improvements in the service, atleast to Salisbury, the case for electrification at least that far is growing stronger, especially iwth the various environmental concerns.
I would assume that if the line was to be done only as far as Salisbury then it woudl be done at DC, but if in the future it was completely electrified, perhasp to eliminate diesel power from the Southwest Trains Franchise entirely, would AC changeover occur as Salisbury with the line being wired or would they just have to hope that either AC electrification never reached Exeter or that the station would be dual signalled at that end?

I know that the last question is probably ridiculous due to the lack of a business case at the present time but it would be interesting to hear your opinions regardless.

 

[Hydro]

The Marshlink line doesn't run into any dual electrified lines at the Ashford end, only onto the third rail lines. Only 3, 4, 5 and 6 are dual electrified. You cannot physically get from the Marshlink to any AC electrification without a fair amount of shunting a long way out of the station.

 

[HSTEd]

Well that settles that question, what about the WEML vis a vis switching at Salisbury or Exeter should it ever be electrified?

 

[swt_passenger]

Well that settles that question, what about the WEML vis a vis switching at Salisbury or Exeter should it ever be electrified?

You have to look at the larger network changes proposed - and as they intend that Reading to Basingstoke would definitely be AC, it seems likely that the Basingstoke station area would then be dual electrified at least as far as Worting Jn. I suggest that then makes it more likely that the WEML would be AC throughout from Basingstoke.

Last time we discussed this (as it comes up every few months) we came to a conclusion that they probably wouldn't want to dual electrify the Eastleigh and Southampton areas if they could get away without it, so a couple of us suggested a changeover at Romsey, a nice simple two track station where all passenger trains will probably stop.

 

[HSTEd]

Will they be pulling up the DC lines into Reading or will they be dual electrifying the signalling there when the time comes, atleast in a couple of the platforms to allow the possibility of electric XC trains running through from Guildford along a completely electrified North Downs Line?

 

[brad465]

They would electrify the West of England line AC at a guess, based on how no lines are electrified out to the west of England right now.

 

[Schnellzug]

You have to look at the larger network changes proposed - and as they intend that Reading to Basingstoke would definitely be AC, it seems likely that the Basingstoke station area would then be dual electrified at least as far as Worting Jn. I suggest that then makes it more likely that the WEML would be AC throughout from Basingstoke..

Need it be? Wouldn't it be convenient to just make the Reading bay overhead? That's all that's needed, surely, since electric XC services or freights are purely in the realms of the hypothetical. Why would anyone want to add all the complexity and expense of making any future extensions AC, when they could just add on third rail beyond Salisbury, nice & simple? It needn't make things too complicated should the wires ever reach Exeter via the GW, as only two platforms & the sidings would need doing with 3rd rail.

 

[HSTEd]

If the WEML were done at third rail you could always cut electric service on the WEML back to Exeter Central and run a diesel shuttle to St Davids in the short term, or even pay up for the very very short AC section between CEntral and St Davids to be done in advance.

But reconstruction of Basingstoke with dual signalling equipment and running AC from Reading to Basingstoke to Salisbury does seem fairly reasonable......

 

[swt_passenger]

Will they be pulling up the DC lines into Reading or will they be dual electrifying the signalling there when the time comes, atleast in a couple of the platforms to allow the possibility of electric XC trains running through from Guildford along a completely electrified North Downs Line?

The 'Southern' lines into Reading, because they are already DC electrified would remain so. They are already effectively isolated from the rest of the station, however it is intended to also provide DC electrification into at least one of the new relief side platforms at Reading, to allow for dual voltage trains to run across Reading onto the 'Southern' via the reopened east end diveunder. The North Downs lines would be DC electrified if it was done, as there are significant stretches already DC, and AC infill would be illogical on that route.

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

Need it be? Wouldn't it be convenient to just make the Reading bay overhead? That's all that's needed, surely, since electric XC services or freights are purely in the realms of the hypothetical. .

No, according to Network Rail the purpose of electrifcation to Basingstoke would be primarily for XC services, not the local stopper, following on after Birmingham to Oxford, and as you know Oxford to Reading is already making progress. They explicitly say it would be AC, primarily because Reading to Newbury would be AC, and because they don't want dual electrification from the west end of Reading to Southcote Junction.

It's probably worth having a read of the Network Rail electrifcation strategy, because nearly all the electrification stages, and voltage type, have been listed, together with the dependencies, and purposes...

http://www.networkrail.co.uk/aspx/4449.aspx

 

[Schnellzug]

No, according to Network Rail the purpose of electrifcation to Basingstoke would be primarily for XC services, not the local stopper, following on after Birmingham to Oxford, and as you know Oxford to Reading is already making progress. They explicitly say it would be AC, primarily because Reading to Newbury would be AC, and because they don't want dual electrification from the west end of Reading to Southcote Junction.

So, are they envisaging dual-mode Voyagers, or, as this seems to be a long-term aspiration, whatever might come after them? Or would they terminate at wherever the wires get to, another victory for operational convenience? Since no one's talking about wires all the way to Bournemouth, they'd have to terminate short of where they do now, whatever.

 

[HSTEd]

Schnellzug, these would be the Bournemouth-Manchester Picadilly services, with Birmingham-Oxford, Oxford-Reading and Reading-Basingstoke the entire route would be electrified and could be handed over to dual voltage electric multiple units.

 

[swt_passenger]

So, are they envisaging dual-mode Voyagers, or, as this seems to be a long-term aspiration, whatever might come after them? Or would they terminate at wherever the wires get to, another victory for operational convenience? Since no one's talking about wires all the way to Bournemouth, they'd have to terminate short of where they do now, whatever.

Officially, no one is even envisaging dual diesel and AC electric Voyagers - this is all long term planning so I wouldn't worry now about possible rolling stock to be used. However, there is nothing technically difficult about providing DC pickup as well as a pan on a suitably converted Voyager.

 

[HSTEd]

Well theres nowhere to fit the shoebeams on Voyager style bogies, but the Voyagers could be withdrawn from Manchester Picc-Bournemouth services if all of these electrifications were completed and replaced with some sort of 125mph capable dual voltage multiple unit, perhaps something based on a 395 with a more intercity style interior.

 

[swt_passenger]

Schnellzug, these would be the Bournemouth-Manchester Picadilly services, with Birmingham-Oxford, Oxford-Reading and Reading-Basingstoke the entire route would be electrified and could be handed over to dual voltage electric multiple units.

Same would apply to the Southampton (Reading) - Newcastle, because York/Leeds and Derby/Birmigham are also down for wires as a XC benefit. (Assuming the MML is already done - and the MML is a proposal for CP5 anyway)...

 

[HSTEd]

You could also probably order the amount of rolling stock actually required and thus restore services to Poole, or perhaps extend them all the way to Weymouth.

 

[A0]

You could also probably order the amount of rolling stock actually required and thus restore services to Poole, or perhaps extend them all the way to Weymouth.

That's assuming there is

a) the demand to extend the services

and

b) the infrastructure and paths available to support the extension

Don't XC stable some units at Bournemouth when they reach the end of their service to allow for cleaning / refuelling?

Running an extension onto Poole or Weymouth may sound nice in theory, but there may be practical reasons against it.

 

[swt_passenger]

Don't XC stable some units at Bournemouth when they reach the end of their service to allow for cleaning / refuelling?

No, but there are 8 units stable at Eastleigh each night. A number of early and late services do not reach Bournemouth at all, some start and finish at Southampton, others run ECS directly to Eastleigh from Reading and Guildford and vice versa in the morning...

 

[heenan73]

While it seems to be against the consensus here, I'd argue that any significant new electrification on the Southern would be AC, not only because of winter, but for the greater efficiency it brings, not to mention the increasing use of cross-regional traffic.

As for Southampton, the second largest container port, I'd have thought AC would be central to any plans.

As for converting existing lines, there's only one prime candidate, London to Brighton, but until the economy perks up, that ain't gonna happen!

 

[lewisf]

As for converting existing lines, there's only one prime candidate, London to Brighton, but until the economy perks up, that ain't gonna happen!

I've always imagined that this would be achieved by having DC/AC changeovers at Hove for the Cliftonville curve, Wivelsfield for the Plumpton line, Three Bridges for the Arun Valley and the slow lines changing back to DC at Purley. Then just the fast lines at AC to Victoria and Farringdon via London Bridge.

 

[ushawk]

Re-electrification wouldnt happen as it would prove too expensive as the money could be better used electrifying other lines.

And if the BML was AC, you will then have 3 sections of the line blocked up at times for a couple of minutes for the current to be changed, seeing as the BML is congested already, this probably couldnt happen. Dont see how or why it should ever be changed to AC anyway when there isnt really any problem with DC.

With infilling, Uckfield and Marshlink lines should be 3rd railed (if High Speed services are extended towards Hastings eventually then that could be sorted when it comes to it), as should the North Downs as sections are already electrified. The "Salisbury 6" should be 3rd rail and Reading to Exeter via Basingstoke should be AC. Whilst were on it GOBLIN should be electrified with AC as parts of the line already have that.

 

[HSTEd]

While it seems to be against the consensus here, I'd argue that any significant new electrification on the Southern would be AC, not only because of winter, but for the greater efficiency it brings, not to mention the increasing use of cross-regional traffic.

As for Southampton, the second largest container port, I'd have thought AC would be central to any plans.

As for converting existing lines, there's only one prime candidate, London to Brighton, but until the economy perks up, that ain't gonna happen!

Winterisation benefits are massively overstated, especially with all this equipment that has now apparently been procured, especially third rail/shoe heating gear and all that.

Converting container freight to AC would not really increase the flows, as if I remember correctly there are Class 92s that are not in traffic due to lack of demand and they have no problem with being dual voltage. Even if they are not it would seem reasonable that any additional electric locomotives would be built as dual voltage units, there are not even that many other stored electric locomotives with the majority of the Class 90s already in traffic and all of the 8xs long gone.

The minor operational benefits dont justify the expenditure neccesary to reclear every single line in the Southern region and fit AC, as well as converting any and all AC track circuits to DC track circuits and everything like that.

Oh and you would have to do the entire Southern Region otherwise you just make the flexibility issues worse, and what happens to all the non dual voltage capable rolling stock still in service, you can't send it all to Merseyrail and Britain already uses more third rail main line trains than the rest of the world combined so there isnt anywhere to sell them.

 

[apk55]

Third rail is normally more expensive than 25KV AC overhead and also less able to supply high power. To supply via a third rail 4MW (or 7200A per train) such as Eurostar requires substations every 2Km. And even then the voltage drop to the train between substations can be of the order of 10% as the conductor rail and return rail has a resistance in the order of 20mili ohms per Km. If lower powered trains are acceptable and higher voltage drops can be tolerated then the substation distance can be increased, but this is at the expense of operational flexibility and also electrical efficiency. If the train power is reduced to 2MW then for a 6 car train the performance will be little difference from a good modern DMU. And if a larger substation distance is chosen, then in a few years time upgrading is considered it would be very expensive as the substation number would need to be doubled.

Substations require power supplies from a bulk power source as the power requirements is normally above what the local network can supply, so new cables are required to feed the substations. Not a problem in a dense urban area where there are plenty of bulk supply points available, but in sparsely populated areas they are far apart so much extra supply cabling would be required so costs would be much grater.

While there are some cases for new electrification with third rail (such as the Uckfield branch) these are quite limited.

While a dual voltage electrification involves more expensive stock the cost overall could be less. On a section of line with an hourly service of fast trains ( such as Salisbury Exeter) the DC system would not be very efficient. Supplying the many substations would be expensive as it is a sparsely populated area with few bulk supply points so much supply cabling would be required. It would not be very efficient electrically as the substations would have a poor duty factor (Average load/ peak load) of probably less than 10%. With high voltage AC only a small number of substations would be required, and train loads of over 4MW could easily be be accommodated.