Possible third rail electrifications

[NotATrainspott]

I suspect that if you re-examined the business case for all the current electrifications with an updated forecast of oil prices you likely find that the business case for most of the current schemes were absolute basket cases even before the massive cost overruns were factored in. Someday soon the penny will drop.

The price of crude isn't the sole justification for electrification. As a long term investment when passenger numbers are growing strongly and it will be harder and harder to build emissions-compliant diesel trains in future, electrification is pretty useful.

 

[76020]

change of location................but what's the current thinking on expanding 3rd rail on the LSWR to Exeter?

Basingstoke to Salisbury will come under the Electric Spine, see Tomorrow's Railway on link below, so it will be 25KV.

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

 

[hwl]

The price of crude isn't the sole justification for electrification. As a long term investment when passenger numbers are growing strongly and it will be harder and harder to build emissions-compliant diesel trains in future, electrification is pretty useful.

Electric rolling stock also costs less to build, maintain and operate. The question is more about pay back on the electrification investment and the last of engineers and equipment to everything on the wish-lists.

 

[Gareth]

I'd be very surprised if any future Merseyrail Hunts Cross services run beyond Liverpool South Parkway,let alone any extensions towards Warrington.
The future of the CLC line is with Lime St originating services.

I don't see why necessarily. There is a logic for Merseyrail to take over the stoppers up to around Warrington in that it allows the trains to go straight into the low level platforms of Liverpool South Parkway, avoiding the flat junction at Allerton and reducing conflicts. Also, Hunts Cross was never intended to be a terminus for Merseyrail and the original plans were to run to Gateacre and Warrington Central. Not only is it rather awkward having 4pth turning round at Hunts Cross but the Merseyrail trains terminate in the northern half of the station, maximising conflict with the mainline services. This was because they needed to be on the north side in order to get to Gateacre but this never materialised. A 'do minimum' option of extending 2tph from Hunts Cross to Warrington Central would mean only 2tph turning round at Hunts Cross (although now 2tph turning round at Warrington Central as well). I think there's scope to improve the layout at Hunts Cross so that Merseyrail trains terminate at the south side of the station (Platform 1 rather than 3) and as the line between Hunts Cross and Allerton depot could be made four tracks (as it once was), it would allow a good passing loop for the semifasts & EMT.

The issue is what you do with the West Allerton/Mossley Hill stoppers. The former can go towards Runcorn and the Halton Curve, or even Crewe. I also hope the airport gets a link someday.
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If Wigan - Southport does ever see wires, why would you do a 3rd rail - OHLE changeover in Burscough Bridge where any issue with it would impact all services, rather than at Ormskirk where it could be done without impacting anything else. If they are going to Electrify this area, I could see them doing it all. and running 2 of the 4tph at Ormskirk to Southport and 2 to Preston. Southport - Wigan and Southport - Preston trains wouldn't stop between Southport and Burscough. However this is all a bit irrelevent to 3rd rail

I don't envision Merseyrail services going beyond Burscough Bridge. That station would serve as an interchange staton with the Southport-Wigan line and the Preston line. It also can't be assumed the Southport-Wigan line still be electrified anyway at that point. What tentative plans I've seen suggest Burscough being the most northly extent of Merseyrail on that branch and it's far from certain even that will ever happen.

Whatever does happen if at some point someone decides it is worthwhile spending the money to finish Liverpool's railway system, you are right, the tunnels will be 3rd rail. as well as the clearance issues, you wouldn't want to do your changeover at the busiest station on the network in case you had a problem. This is the only place I could see a sensible 3rd Rail extension as it is the only place I think you could truly argue Gralistair's Point above.

And if you read that quote to the letter of what it says, I could even see some of the none core electrification being turned to OHLE when it comes to renewing life expired equipment. Country side of Green Lane, Birkenhead Park, Brunswick, Walton and Bank Hall.
Boring new tunnels for clearance would class as Grossly Disproportionate, but I'm not sure replacing 3rd rail for OHLE on the rest of the network could be. Not only are the Safety Implications for everyone line-side workers and passengers emergency services / third parties who for whatever reason find themselves track side paramount, the efficiency and maintenance costs of 3rd rail are very poor when compared to the alternative.

I'm pretty sure renewal of life-expired third rail with new third rail doesn't count as an extension and I'm fairly certain this has happened on Merseyrail over the years. If you accept that the tunnels will always be 3rd rail then I don't see why you'd still want to do piecemeal replacements of portions of the surface sections with OHLE. What benefits are there forcing trains to change over at Birkenhead Park or Bank Hall? It's needless faff that I don't believe is outweighted by any significant benefits. I'm not even certain what the benefits are. Electocution just doesn't happen that often (virtually zero X 16), and the benefits of 25kv AC in terms of less loss, less substations etc are far more marginal in metropolitan systems, which is why 3rd rail is still chosen for some new systems around the world (albeit, usually with side or bottom contact shoes).

And it is a faff changing power. It's just yet another thing that can go wrong. The train has to wait longer at the station than it would otherwise. The driver has to remember to lower the pantograph when leaving the OHLE area. The mechanism which raises and lowers the pantograph can fail. These are things the likes of Thameslink have to contend with. The big difference is that Thameslink was essentially a joining together of two different networks which developed separately and so had different power to begin with. The faff of changing power is far outweighed by the benefits of through running through Central London brings and how it makes direct journeys like Bedford to Brighton possible. Now, what benefit is there in making a Merseyrail train change power at Birkenhead Park on its way to New Brighton?

Really, flexibility and common sense are needed when it comes to this sort of thing. An uncompromising view that all the National Rail network should be on one type of power and any areas non-complying must be converted regardless of any particular local situation seems to be an OCD crave for uniformity. If Merseyrail was hived off from the National Rail network, would we be still having this discussion? The East London Line is another interesting one: presumably as part of the National Rail network it must also be converted what come may; however, if it was still part of the London Underground, still powered with the very similar 4th rail system, I presume that it wouldn't be seen as an issue (as it isn't in the extant Underground network), despite being pretty much the exact same metro line not withstanding the extra rail. Also, it's interesting that they didn't convert the ELL to OHLE during the Underground-to-Overground changeover works, choosing 3rd rail instead. Clearly, any crave for uniformity with lines as diverse as the East Coast Mainline just because they're all part of the National Rail lost out to more pragmatic decisions in terms of cost and the local nature & practicalities of the line prevailed.

 

[mcnw35282]

I'll never understand the fascination with converting merseyrail to AC when it's functioned quite well for over 100 years on DC.

 

[Camden]

Yep, odd indeed.

 

[WatcherZero]

Its a relevant argument from a south eastern persons perspective but Merseyrail doesn't suffer most of the same problems facing 750v DC third rail in the South East, long rural stretches requiring extra secure fencing due to greater risk of electrocution, or that of power hungry 12 carriage trains, hitting a maximum practical speed of ~110mph. Merseyrail operates 3-6 carriages at an average speed of only around 30mph, its not practical to lengthen platforms in tunnels so they will operate more frequent rather than longer in future, trains are also getting more power hungry because of gadgets and luxuries at the same time they have become more energy efficient to propel which is mostly balancing out but Merseyrail only really needs a little more juice at the extremities of the Network where there is a voltage drop issue to operate the planned future services whose needs can be supplied by a couple more transformers.

 

[notlob.divad]

I don't envision Merseyrail services going beyond Burscough Bridge.

I do, as Southport <-> Ormskirk is the only flow of people I see significant enough to justify re-opening the Southern Curve and extending beyond what is currently there.

It also can't be assumed the Southport-Wigan line still won't be electrified anyway at that point.

I was assuming it was, hence changing over at Ormskirk.

I'm pretty sure renewal of life-expired third rail with new third rail doesn't count as an extension and I'm fairly certain this has happened on Merseyrail over the years.

Like for like replacement as ongoing maintenance is one thing, but when it comes to justifying the next full upgrade project. It would as was stated above have to prove to be grossly disproportionate.

If you accept that the tunnels will always be 3rd rail then I don't see why you'd still want to do piecemeal replacements of portions of the surface sections with OHLE.....

Given by the time this question comes around, duel voltage stock would already be available, the experience that will have been gained by changing the Southern networks over, and the ever diminishing amounts of third rail technology that will make the equipment unique and more expensive. It will end up being not only safer but cheaper, particularly when the long term maintenance costs are taken into account. Ideally the whole lot would be changed over, but the costs of the clearance work in the tunnels are likely to prevent that. You are quite right in that there will always be a market for some 3rd rail equipment, but it will eventually become so marginalized and expensive that you will want to reduce it down to the minimum amounts possible. And with technological advances and automating the changeover we could speed it up remove the 'faf' and reduce the unreliability.

It isn't a fascination. More an eventual inevitability. If the service does ever expand along OHLE powered lines, the extent of those wires would work their way back towards the centre as far as they could. Take it the CLC gets wired in x number of years and Merseyrail does run the envisaged 2tph to Warrington Central as proposed above. Well there is no point turning trains at Hunts Cross anymore you would turn the 2 extras back at Parkway or in a perfect world run them and some more to the airport using OHLE. So you remove the 3rd rail to Hunts Cross and replace with OHLE. (It has already caused complications with Allerton Depot so you could solve that problem and be able to re-establish the Eastern Link in) So where does it become grossly disproportionate to continue? From the other end, Electrifying to Southport, and possibly building a Skelmersdale delta junction. Well those will both be OHLE from the East, so it may as well go to Kirkby. Repeat the above argument. Southport and or Preston to Ormskirk. Again repeat the argument. Everywhere you look the argument gets repeated, to expand the system you will need to have 3rd rail to OHLE changeover. It may as well be as close to the middle to reduce the amount of 3rd rail, for safety, efficiency and overall reduced cost.

 

[snowball]

You are quite right in that there will always be a market for some 3rd rail equipment, but it will eventually become so marginalized and expensive that you will want to reduce it down to the minimum amounts possible.

Most of LU is unlikely to move away from 3rd and 4th rail. There must be a good deal of commonality of equipment between 3rd rail 750V and 3rd and 4th rail 630V.

 

[hwl]

Most of LU is unlikely to move away from 3rd and 4th rail. There must be a good deal of commonality of equipment between 3rd rail 750V and 3rd and 4th rail 630V.

Possibility even more commonality as LU want to move to 750V when they can.

 

[Gareth]

We're simply not going to agree on this, notlob. Insisting that any upgrade to the Merseyrail surface network must be OHLE what come may is what I consider grossly disproportionate. Third rail is not disappearing from the world any time soon and it would have to somehow become insanely expensive to maintain in order for a change over to OHLE and the cost that would cause in terms of disruption, altering bridges etc, to be justified.

Where on the National Rail network does AC/DC changeover occur currently? I don't have in depth knowledge of the the network throughout the length and breadth of the land but so far as I'm aware it only occurs in the South East: Thameslink, London Overground, Southeastern HS1 etc. What all these services seem to have in common is that they make through journeys that weren't possible previously. Breaking up fully DC services so they have to switch power but with no prospect of new journey possibilities is looney tunes. There's no pre-existing AC powered system you can go onto from West Kirby or New Brighton. Forcing New Brighton/West Kirby Merseyrail trains to power change at Birkenhead Park is a waste of time unless it's a stopgap to converting the entire network but as you accept the underground sections won't ever be changed, then even that one scenario is out. And I'm more than confident it'll never happen. Common sense will prevail over an overly literal interpretation of a directive. The only part I agree with you on, with regards to the existing network, is between Liverpool South Parkway and Hunts Cross. Even then, only if the line was extended eastwards to make the faff of changeover at Parkway worthwhile.

 

[edwin_m]

Another issue to consider is that of feeder stations. A 25kV feeder station is a large and expensive bit of kit and needs a good feed from the National Grid, but once you've spent the money on one it can power trains several tens of kilometres away. A 750V feeder is more modest but still needs a fairly hefty power supply, which may be difficult to find particularly in rural areas. This is incidentally one of the reasons DC makes less and less sense the further away you are from a big city. So DC electrified railways often have a higher-voltage AC feed in trackside cables inter-linking the substations, and I guess the electrical equipment to power this isn't too different from what would be feeding the OLE on an AC railway.

This means that were it proposed to, say, extend Merseyrail to Skelmersdale and do nothing else, using 25kV would need a whole AC feeder to be built (or preferably two for a reliable supply) just for that short section. On the other hand if Wigan to Skelmersdale was being electrified at AC at the same time (or had been done already) then it is probable that the feed from the Wigan end would power all the way to Kirkby. And even if a new feeder was needed for that extension, it could strengthen the network elsewhere by providing an alternative source of power for Wigan and beyond.

So in short, DC to AC conversion is more likely to happen in areas adjoining other AC electrification rather than just in isolated islands. This also helps avoid the earthing problems that occur in dual-electrified areas.

 

[hwl]

A 750V feeder is more modest but still needs a fairly hefty power supply, which may be difficult to find particularly in rural areas. This is incidentally one of the reasons DC makes less and less sense the further away you are from a big city. So DC electrified railways often have a higher-voltage AC feed in trackside cables inter-linking the substations, and I guess the electrical equipment to power this isn't too different from what would be feeding the OLE on an AC railway. ...

So in short, DC to AC conversion is more likely to happen in areas adjoining other AC electrification rather than just in isolated islands. This also helps avoid the earthing problems that occur in dual-electrified areas.

DC substations usually fed form 3 phase 33kv supply but occasionally an 11kv.

 

[mcnw35282]

Merseyrail doesn't need AC...if it ain't broke, don't fix it! Besides...OLE is an eyesore!

 

[mr_jrt]

Given the desire to simplify infrastructure LU has removed connections between various lines (i.e. with the Jubilee around Finchley Road, etc), which means that although the tube lines will never have OHLE, there's a remote possibility that the the SSL lines could eventually end up with it throughout, and a reasonable possibility in the long-term that the above ground stretches away from the core could get it even if the core never does. You only have to witness Thameslink through Farringdon to see it's quite doable. It certainly won't happen until there's a critical mass of life-expired DC infrastructure though, so we're talking another 30-40 years at least in all likelihood, barring some massive upheaval.

By the same reasoning the above ground sections of Merseyrail will get OHLE. Modern rolling stock can changeover on the move, and DC islands will be minimised as infrastructure is renewed.

 

[Camden]

Modern rolling stock can changeover on the move

Have you got some working examples of metro systems that do this? And working examples of metro systems which are being converted piecemeal from DC third rail to AC OHLE?

 

[edwin_m]

Have you got some working examples of metro systems that do this? And working examples of metro systems which are being converted piecemeal from DC third rail to AC OHLE?

Thameslink has been mentioned. The Paris RER and various tram-train routes also switch between two overhead voltages, which is actually more complicated because of the risk of feeding the wrong voltage into the pantograph.

 

[Gareth]

The big difference being that Thameslink didn't start out initially as DC both sides of Farringdon. A standalone system like Merseyrail will never change from being completely DC to mixed power. London Underground lines are yet even less likely.

 

[Flying_Turtle]

Are there any possible places where third rail could be installed, rather than OHLE?
(...)

You can't do it on national rail I believe. Only with extensions of existing installations (Besides, I don t think that many people know how many substations you need in DC when compared to 25 kv
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Possibility even more commonality as LU want to move to 750V when they can.

Have they solved the electrolysis problem?

 

[mr_jrt]

A standalone system like Merseyrail will never change from being completely DC to mixed power.

Bold statement.

We'll see how things stack up when the infrastructure needs replacing, let alone when the lines from Wigan and Preston get wired up as cheap infill.

Electrification never made it beyond Kirkby due to the high cost of 3rd rail, and regardless of what state the existing infrastructure is in, once the OHLE gets to Kirkby & Omskirk, extending Merseyrail services to Wigan & Preston is going to look attractive in terms of simplifying the service patterns, and you could quite easily upgrade back to Kirkdale at that point to have just the one changeover point. When the time comes to renew the Northern Line's infrastructure, that single point can move to Sandhills after the line north of there to Southport is upgraded.

As for the south, any extension from Hunts Cross to Warrington is almost certainly going to need to use the existing lines, and in all likelihood those are going to eventually get OHLE as services from from Manchester will continue to need to run into Lime St. Any extension south to Runcorn would need to be OHLE, so pretty much the only option that doesn't require OHLE would be an extension over the outer loop, IMHO.

 

[Andrew1395]

One day they will electrify the Chiltern lines to Oxford and Birmingham. I wonder if they would take the opportunity to convert the Met line from Baker Street to AC OHLE at the same time. Have a common fleet of innerspring and a fleet of express units? By the time it's done you can see all the outer commuter routes coming under the London Overground, (like say services to Tring from Euston) in addition to the Crossrail routes. So you can see a situation in the medium term where even large DC systems become converted. Rolling stock is not the issue, but infrastructure renewals and enhancements will drive conversion

 

[Philip Phlopp]

A standalone system like Merseyrail will never change from being completely DC to mixed power. London Underground lines are yet even less likely.

Oh dear.

It's actually being looked at as part of the possible North Wales Coast electrification and what to do to avoid DC at Chester. It probably won't come to much, but it's something that is being looked into.

The idea would be a changeover from DC to AC somewhere outside Chester, or possibly even at Hooton, as that creates the option of sending units that are unable to change to AC down to Ellesmere Port and out of the way.

I suppose I'd also best keep quiet about the full design for conversion of the Brighton Main Line, given all this third rail fanaticism on display.

 

[dgl]

Have they solved the electrolysis problem?

It will still be a fourth rail supply with insulated (from the ground) supply rails. This will probably still use a +/- supply (i.e. a potential difference of ~750V but not between 0V and 750V so something like -250 +500) but i can't see that there is any reason if they did change the voltage not to switch to a +750V/0V supply (although there may be reasons that I am not aware of).

It's the fact that the return path is not through the non insulated (from ground) running rails but from separate insulated (from ground) supply rails that prevents electrolytic corrosion.

 

[AM9]

It will still be a fourth rail supply with insulated (from the ground) supply rails. This will probably still use a +/- supply (i.e. a potential difference of ~750V but not between 0V and 750V so something like -250 +500) but i can't see that there is any reason if they did change the voltage not to switch to a +750V/0V supply (although there may be reasons that I am not aware of).

It's the fact that the return path is not through the non insulated (from ground) running rails but from separate insulated (from ground) supply rails that prevents electrolytic corrosion.

The switch from 630VDC on the Underground (and 660VDC on the original Southern Railway electrified routes) has taken a number of years to enact. I think that this is primarily due to the limitations of earlier traction system designs. The simple contactor or cam driven resistor sets meant that the motors were exposed to the full line voltage plus transients, say 1KV. This included motor insulation which was originally designed for 660VDC systems. The ex-SR EMUs were replaced on the mainlines before those on the metro system, the more pressing power demands of the faster services created the opportunities for raising the nominal line voltage to 750VDC.
The isolated DC supplies on the Undeground were created to reduce or prevent electrolytic corrosion of the cast iron tunnel linings. Even with modern concrete tunnels, isolation still gives some reduction of any corrosion of other conductive structures that a common ground system would encourage. I think that the voltage split is just to reduce the voltage of any single rail to ground which slightly reduces the impact of injury to persons if touched. It also spreads the voltage stress on insulators under certain climatic conditions.

 

[Elecman]

It will still be a fourth rail supply with insulated (from the ground) supply rails. This will probably still use a +/- supply (i.e. a potential difference of ~750V but not between 0V and 750V so something like -250 +500) but i can't see that there is any reason if they did change the voltage not to switch to a +750V/0V supply (although there may be reasons that I am not aware of).

It's the fact that the return path is not through the non insulated (from ground) running rails but from separate insulated (from ground) supply rails that prevents electrolytic corrosion.

I think they may have to replace every insulator pot on the 750 volt rail if they went to 750/0 system, the present newer insulators seem to be half size on the -210 rail compared with the +420 rail

 

[AM9]

I think they may have to replace every insulator pot on the 750 volt rail if they went to 750/0 system, the present newer insulators seem to be half size on the -210 rail compared with the +420 rail

I doubt that clearances for 750V would result in pots any bigger than those for 210V. The sizes are probably determined by the different mechanical stresses encountered by centre and side rails. The centre rail probably gets an easier time given that any roll moments in the suspension have a centre just above that rail whereas the side rail take much larger contact movement, both vertically and laterally.

 

[swt_passenger]

The switch from 630VDC on the Underground (and 660VDC on the original Southern Railway electrified routes) has taken a number of years to enact. I think that this is primarily due to the limitations of earlier traction system designs. .

There are still areas where the LU power supply is common with NR, e.g. in some of the SWML inner routes and the Wimbledon and Richmond branches of the District Line. The latest CP5 enhancement plan reports that the relevant areas will not be increased to 750V nominal until LU can accept it at the end of 2016, when the D stock is assumed to be out of service. This is part of the overall project to support DC re-generation, some work is still planned to be completed during the early part of next year.

Just shows how complex the whole power system is in South London.

 

[Gareth]

Bold statement.

We'll see how things stack up...

Nothing bold about it. And we will see indeed; or more likely, die of old age first.

I've discussed extension to Warrington Central with notlob and others in fair depth in the last few pages. There's generally agreement that such an extension would be OHLE (only Camden disagrees, I think). I can't see Merseyrail extending to Preston; terminating at Burscough Bridge seems more likely and is what seems to be the current frontrunner in any tentative plans. As this plan is just an extension of the existing isolated system with no plans to share traffic, I don't see the problem with this being 3rd rail. Likewise to Skelmersdale (which is more likely than Wigan). I doubt we'll see ever see Runcorn on the Merseyrail network.

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

Oh dear.

It's actually being looked at as part of the possible North Wales Coast electrification and what to do to avoid DC at Chester. It probably won't come to much, but it's something that is being looked into.

The idea would be a changeover from DC to AC somewhere outside Chester, or possibly even at Hooton, as that creates the option of sending units that are unable to change to AC down to Ellesmere Port and out of the way.

I suppose I'd also best keep quiet about the full design for conversion of the Brighton Main Line, given all this third rail fanaticism on display.

Oh dear indeed but not worth responding to considering you're calling people 'third rail fanatics'. You need to read what's actually been said before throwing such barbs.

 

[2392]

I think that the ORR has put it rather beyond doubt' See http://orr.gov.uk/__data/assets/pdf_file/0017/17621/dc-electrification-policy-statement.pdf

In particular: "ii) There is a presumption against the reasonable practicability of new-build or extended DC third rail in view of the safety requirements duty holders must satisfy in order to justify the use of third rail."

"Please do not ask for credit as refusal often offends" springs to mind.

Interesting, in as much as pretty well any time the suggestion that the Bluebell electrify the Horsted Kean Haywood Heath branch with a third rail. Making a first for a heritage line. . As the ORR state provided the rail operator meets the requirements of the relevent regulations, then the powers that be would be happy to say yes, go ahead. And that dates back to the days of the old HMRI and Major Olver, who tended to deal in this instance with the heritage side of railways.

 

[Flying_Turtle]

I doubt that clearances for 750V would result in pots any bigger than those for 210V. The sizes are probably determined by the different mechanical stresses encountered by centre and side rails. The centre rail probably gets an easier time given that any roll moments in the suspension have a centre just above that rail whereas the side rail take much larger contact movement, both vertically and laterally.

As a reference safety distances are 1cm per Kv so no much diffeence there