Converting Third Rail To Overhead Wiring

[scrapy]

One wonders if the OHL would be considered visually intrusive, in which case there would also be the cost of planning permission.

I believe there was a plan to electrify the Hope Valley route from Manchester to Sheffield via New Mills in the late seventies when the Woodhead route was being shut. One of the reasons this was scrapped was they would be unlikely to get planning permission as it runs through the Peak District National Park.

 

[142094]

Many are still around, under the name "Tyne & Wear Metro". It's funny to compare the grand North Eastern stations on the Tynemouth loop with the modern shacks on the airport branch (although I think that has a heavy-rail origin as well).

In fact there are a few which were not included, the Riverside branch being one. Plus a lot of stations have either been demolished and not replaced or remodelled, including Manors, Backworth, Heaton.

You are right, trains on the now link to the Airport used to run to Ponteland and there was an ICI factory at Callerton. Even Rowntrees/Nestle at Fawdon had railway sidings.

 

[sprinterguy]

I'm not too sure of the reasoning behind the de-electrification on Tyneside, certainly from what I've read/been told services went downhill with the switchover to diesel. Would be great to have some of the routes still around and still 3rd rail.

The Tyneside electric network was de-electrified to save on maintenance costs. The third rail electrical equipment was becoming life expired, and the majority of the trains were starting to get on a bit as well (Although I think there were some newish ones in operation, and that it was these that went to the Southern?). So it was cheaper to just remove the electrics, and replace them with first gen DMUs that were being built already, instead of having to renew the equipment. Part of the same reason why electric street trams disappeared around the same time in the fifties and sixties.

From pictures I've seen and my Mams' recollections, it seems the mimumum of maintenance was carried out on the Tyneside system through the 60s and 70s; with regards to the track, the trains and the stations, and the first gen DMUs and the stations were extremely run down by the time it shut up shop and the Metro took over.

It is interesting that not only has the Tyneside system gone from third rail electrification to overhead electrification, via a period of diesel operation, but it has also been electrified with a non standard overhead voltage!

 

[Wyvern]

Originally Posted by Wyvern
One wonders if the OHL would be considered visually intrusive, in which case there would also be the cost of planning permission.

I believe there was a plan to electrify the Hope Valley route from Manchester to Sheffield via New Mills in the late seventies when the Woodhead route was being shut. One of the reasons this was scrapped was they would be unlikely to get planning permission as it runs through the Peak District National Park.

That was what I was thinking of. I have to get planning permission if I want to fit a new front door, I imagine there are similar sensitive areas in the south of England.

 

[142094]

The Tyneside electric network was de-electrified to save on maintenance costs. The third rail electrical equipment was becoming life expired, and the majority of the trains were starting to get on a bit as well (Although I think there were some newish ones in operation, and that it was these that went to the Southern?). So it was cheaper to just remove the electrics, and replace them with first gen DMUs that were being built already, instead of having to renew the equipment. Part of the same reason why electric street trams disappeared around the same time in the fifties and sixties.

From pictures I've seen and my Mams' recollections, it seems the mimumum of maintenance was carried out on the Tyneside system through the 60s and 70s; with regards to the track, the trains and the stations, and the first gen DMUs and the stations were extremely run down by the time it shut up shop and the Metro took over.

It is interesting that not only has the Tyneside system gone from third rail electrification to overhead electrification, via a period of diesel operation, but it has also been electrified with a non standard overhead voltage!

That sounds similar to what I had thought - yet it seems silly that they could have kept some of the routes and stations open that they closed with a bit of investment. To bring things upto standard they had to build the Metro atr quite a cost, when they could have had a still decent network of electric trains at a fraction of the cost.

Still I shouldn't complain as I do love the Metro.

 

[sprinterguy]

That sounds similar to what I had thought - yet it seems silly that they could have kept some of the routes and stations open that they closed with a bit of investment. To bring things upto standard they had to build the Metro atr quite a cost, when they could have had a still decent network of electric trains at a fraction of the cost.

Still I shouldn't complain as I do love the Metro.

Very true, it's a similar case with lots of things: In the long run, it would be cheaper to have maintained the Tyneside electric system to a reasonable standard with periodic renewals as equipment became life expired, but in the short to medium term it is more prudent to just downgrade the system, and then, when demand is seen to be increasing for the services offered, to then invest a massive amount of money in a completely new system (the Metro). Hindsight is a useful thing to have when at the time (late 60s) everything pointed to a rail network in decline around Tyneside.

However, if the cycle of investment-decline-decay-investment-decline-etc didn't occur, then we'd be left with a lot of antiquated operating practices and equipment if older systems were maintained to a reasonable standard from their inception to the present: The process is an essential part of rejuvenation to meet modern demand patterns, and not just within railway circles.

 

[mickey]

That was what I was thinking of. I have to get planning permission if I want to fit a new front door, I imagine there are similar sensitive areas in the south of England.

The cynic in me wonders whether the Chiltern-demolition plan (as locals call HS2) has something to do with this... How much easier would it be to get permission to upgrade Reading-Brum if it were the 'nicer' alternative to a completely new dead-straight line?

 

[TGV]

This is a topic I've looked into - in fact, I wrote to Network Rail when their new electrification plan was released last year under their utilisation plan. They sent me a glossy brochure back with all the facts written in it.

First of all, the most likely Southern candidate for conversion - WERE IT TO EVER HAPPEN (an important point!), is the Basingstoke area - both down to Southampton, across to Salisbury and up to Reading which would then connect with the additionally proposed GWML electrification which would be complete by then (if, of course it happened at all).

This poses a couple of issues though.

1 - stock for Basingstoke, Winchester, So'ton and beyond would need to be dual voltage, transformers, pantographs fitted etc... This would mean slightly less flexibility in rolling stock use and transfer, but not too difficult - SWT could easily, I'd imagine, cope with this given the resources and money to manage it.

2 - The debate of dual voltage lines - it's most likely that if OLE was put up, the 3rd rail would be lifted. Having both DC and AC electrification running alongside each other poses all kinds of earthing and EMC problems for the surrounding environment and the infrastructure. It only works in very short stretches (like between Farringdon and City Thameslink, or the lines out of Euston for a mile or so). SO all the way between Basingstoke and So'ton (a distance of about 30 miles) would pose challanges. You couldn't run wires all the way into waterloo that's for sure. Basingstoke is realistically the furthest towards London that OLE could or would work because of operational restraints, infrastructure restrictions and of course... can anyone here imagine what Clapham Junction - Queenstown Rd would look like if that lot had wires over the top?!

3 - clearances for the overheads on bridges and tunnels not designed for them - an old problem...

In reality the southern network is so deeply aligned to 3rd rail traction, it's unlikely to be changed in any of our lifetimes apart from, at the very most, the above Basingstoke area upgrade (and even that is a stretch) - unless NR has a sudden rush of blood to the wallet and rips the whole lot up and replaces the whole lot with OLE... but as someone else pointed out - WHY?

Let me get this straight - I'm no fan of 3rd rail. I have always seen it as "overgrown underground" traction - not proper main line use, but having experienced it for real, it's got some advantages:

1 - it's robust - strong winds aren't a problem. Even in the snow of last year, trains on the SWML ran very well (with a lot of sparking)
2 - It's cheap(er than 25kV overheads)
3 - The view from the train window isn't ruined by masts every 20m or so. This is also a plus point for all the NIMBY's who live alongside the track.

The negatives are really only two:
1 - It is power restricted, therefore, maximum speeds are limited to around what they are now (and have been for some time), but given the relatively short commuting routes that MOST of the 3rd rail network covers, this isn't a huge issue. The acceleration of a 444 or 450 equals anything anywhere on UK main lines and topping out at 100mph isn't exactly shabby is it?
2 - Safety - 3rd rails are generally considered more dangerous than overheads - not because of the increased current or that it's DC instead of AC (which can be nastier on contact with a person) - it's simply much easier to accidentally come into contact with - particularly at stations or level crossings where the general public have easy access therefore the likelyhood of an accident is higher.

 

[142094]

Anyone know what the difference in cost is for say 1 mile of OHLE to 1 mile of 3rd rail?

 

[TGV]

Anyone know what the difference in cost is for say 1 mile of OHLE to 1 mile of 3rd rail?

Someone might have a more official figure, but I'd say (whatever the actual cost) that the relative cost is abouut 3:1 - i.e. OLE is about 3x the cost of 3rd rail per unit of length electrified.

I reckon it costs nearly as much to electrify at 25kV overheads as it did to lay the track in the first place if you include all the bridge and tunnel work and national grid supply.

 

[swt_passenger]

2 - It's cheap(er than 25kV overheads)

1 - It is power restricted, therefore, maximum speeds are limited to around what they are now (and have been for some time), but given the relatively short commuting routes that MOST of the 3rd rail network covers, this isn't a huge issue. The acceleration of a 444 or 450 equals anything anywhere on UK main lines and topping out at 100mph isn't exactly shabby is it?

It isn't cheaper - as a couple of us have already pointed out, and as implied in NR's literature. This has also been the line taken by traction supply engineers in other foruims over the last few years. It could well be cheaper to put the actual third rail down than an overhead catenary and mast system up, but not once you include the bulk supplies and conversion in substations.

The third rail itself isn't power restricted as such, it's the substations. If you connect more grid inputs and an increased number of substations to the system, the power allowed to be drawn by the trains could be increased. Exactly the same sort of limitations would apply to an AC OHLE system - it is designed for a finite traction load, ie a particular number of a given train type, and ultimately there'd be a limit applied to the number of AC trains running around. You can see this already on various parts of the ECML and particular some of the branches around Leeds, or beyond Cambridge.

But as you say for most of the SR area existing speeds and acceleration are fine anyway.

Regarding dual voltage units, don't forget that in the Southampton area Southern would also have to use them, as would SWT's Portsmouth to Southampton and Waterloo via Basingstoke services. Numbers involved soon add up to more than just the main line services...

I reckon the Basingstoke area would become an AC/DC changeover point in the event of GWML and XC electrification, but the changeover would be just outside the station on the Reading line. I can't see dual electrification over long distances as you rightly point out - so I suggest a DC/AC changeover for the West of England trains beyond Worting junction, after the routes have separated. If you start looking at Southampton - Romsey - Salisbury, well there's another minefield straightaway...

 

[TGV]

I have a gadget that logs GPS data (speed, altitude and position) and it displays it in it's own software which includes google maps. I logged a journey tonight from waterloo to Basingstoke and the speed vs time graph is shown on the bottom right of this image (the dip in the middle was stopping at Woking), and the point of maximum speed (100.4mph) is shown on the map with the red flag.

Edit: I've just posted this as a main topic if anyone is interested.

 

[TGV]

It isn't cheaper - as a couple of us have already pointed out, and as implied in NR's literature. This has also been the line taken by traction supply engineers in other foruims over the last few years. It could well be cheaper to put the actual third rail down than an overhead catenary and mast system up, but not once you include the bulk supplies and conversion in substations.

The third rail itself isn't power restricted as such, it's the substations. If you connect more grid inputs and an increased number of substations to the system, the power allowed to be drawn by the trains could be increased. Exactly the same sort of limitations would apply to an AC OHLE system - it is designed for a finite traction load, ie a particular number of a given train type, and ultimately there'd be a limit applied to the number of AC trains running around. You can see this already on various parts of the ECML and particular some of the branches around Leeds, or beyond Cambridge.

I think you're being picky on the power limitation point! I meant as a whole system not just the rail itself! And yes you can throw as much as you want in terms of substations, but the reality is the AC systems can and do in the real world support much more power supply (and much more efficiently) than a DC system. Witness Eurostar being limited to 1/3 max power on 3rd rail *even AFTER the 3rd rail network there had a supply upgrade* compared it it's 25kV operation.

The power - like for like - will always be less on 3rd Rail DC because of the inherent inefficencies with transmitting larger currents at lower voltages. The ECML is a bad example ot cite - it has very high power traction using it over MUCH longer sections (up to 10 times the length) than any Southern region 3rd rail section. By your own argument, you can just chuck another substation in there and have almost unlimited power!

Now, that still doesn't adress the problem of current collection at high speeds and power - a pantograph will always win that battle in terms of high speed current collection vs. shoegear.

As for cost - I struggle to accept that 3rd rail - even as a whole system including substations - is cheaper than 25kV overheads. I have read that RUS report and as a professional, I still can't agree with some of the statements therein.

 

[swt_passenger]

Anyone know what the difference in cost is for say 1 mile of OHLE to 1 mile of 3rd rail?

As I posted earlier, quoting from the NR Electrification RUS, where either option is possible, AC will be chosen for cost reasons, eg Basingstoke - Salisbury - Exeter has this footnote:

In view of the route length and service density, AC electrification is considered likely to be the more cost effective option for this route.
This would be further examined in the detailed development of a scheme

Suggesting otherwise is going against the evidence, I'm afraid...

 

[tbtc]

I believe there was a plan to electrify the Hope Valley route from Manchester to Sheffield via New Mills in the late seventies when the Woodhead route was being shut. One of the reasons this was scrapped was they would be unlikely to get planning permission as it runs through the Peak District National Park.

That may be the case, but it didn't stop wiring through the Lake District

In answer to the other points, I think 100 mph is sufficient for most lines, to be frank - many lines don't get anywhere near that anyway...

 

[swt_passenger]

I think you're being picky on the power limitation point! I meant as a whole system not just the rail itself! And yes you can throw as much as you want in terms of substations, but the reality is the AC systems can and do in the real world support much more power supply (and much more efficiently) than a DC system. Witness Eurostar being limited to 1/3 max power on 3rd rail *even AFTER the 3rd rail network there had a supply upgrade* compared it it's 25kV operation.

The power - like for like - will always be less on 3rd Rail DC because of the inherent inefficencies with transmitting larger currents at lower voltages. The ECML is a bad example ot cite - it has very high power traction using it over MUCH longer sections (up to 10 times the length) than any Southern region 3rd rail section. By your own argument, you can just chuck another substation in there and have almost unlimited power!

Now, that still doesn't adress the problem of current collection at high speeds and power - a pantograph will always win that battle in terms of high speed current collection vs. shoegear.

As for cost - I struggle to accept that 3rd rail - even as a whole system including substations - is cheaper than 25kV overheads. I have read that RUS report and as a professional, I still can't agree with some of the statements therein.

Well your perfectly valid comments above help to explain why the costs differ so markedly, and all those transmission losses have a cost which has to be budgeted for. I cannot link to a set of current figures, but I know from previous online discussions with specialists in the field, that modern AC systems have grid supplies approx 50 km apart, and DC typically about every 4 to 5 km, and the transformers, rectifiers, DC switchgear, protection systems and AC bulk supply distribution to all those places increases the costs hugely over the relatively straightforward transformers in an AC substation.

Another debate that has raged for a few years has been Wrexham to Bidston to extend the Merseyrail system. There are a number of online sources that explain that DC has been chucked out for cost reasons but AC is still being looked at.

I also have a book (somewhere in the loft unfortunately) that reckoned at the time of the original Bed-Pan electrification, (in the early 70s?), mile for mile the AC cost was 75% of the DC cost.

 

[TGV]

Well your perfectly valid comments above help to explain why the costs differ so markedly, and all those transmission losses have a cost which has to be budgeted for. I cannot link to a set of current figures, but I know from previous online discussions with specialists in the field, that modern AC systems have grid supplies approx 50 km apart, and DC typically about every 4 to 5 km, and the transformers, rectifiers, DC switchgear, protection systems and AC bulk supply distribution to all those places increases the costs hugely over the relatively straightforward transformers in an AC substation.

Another debate that has raged for a few years has been Wrexham to Bidston to extend the Merseyrail system. There are a number of online sources that explain that DC has been chucked out for cost reasons but AC is still being looked at.

I also have a book (somewhere in the loft unfortunately) that reckoned at the time of the original Bed-Pan electrification, (in the early 70s?), mile for mile the AC cost was 75% of the DC cost.

OK - that's interesting. I'm a rolling stock engineer, so my infrastructure knowledge is based on discussions with my colleagues on the "static" side of the operation! But yes, I can see the issue with DC sub-stations every 2 miles vs. AC substations every 20-30 miles. However, I still maintain that the modification of raising bridges, or lowering the trackbed under tunnels to incorporate OLE would still offset that - but I may be wrong.

 

[jopsuk]

I've wondered to myself if the Thameslink Brighton route, or possibly Kent lines running on from HS1, might be candidates for conversion to OHL at some point. These would then be extensions to existing OHL routes, rather than replacement of entirely 3rd rail. They also run a lot of dual voltage (or DV capable) stock already

 

[atomicdanny]

I've wondered to myself if the Thameslink Brighton route, or possibly Kent lines running on from HS1, might be candidates for conversion to OHL at some point. These would then be extensions to existing OHL routes, rather than replacement of entirely 3rd rail. They also run a lot of dual voltage (or DV capable) stock already

I think the only problem with that would be all of the bridges, tunnels, footbridges and similar would have to be rebuilt or changed in some way to even consider Overhead wires since these at the moment would be too low for them!

 

[Peter Mugridge]

With restricted clearances, on parts of the RER in Paris they got round the problem by installing, believe it or not, an overhead live rail under an insulated panel on sections where they could not get the wires to fit although admittedly the sections in question are at 1500v DC rather than 25kV AC.

And yes, it operates with a pantograph.

Now, I wonder, if they could make a much wider insulated panel would it be theortetically possible to run a short section of overhead live rail at 25kV AC, or would, as I suspect, the size of the cross section of the rail itself generate too much resistance for the current to flow efficiently?

 

[LE Greys]

As I posted earlier, quoting from the NR Electrification RUS, where either option is possible, AC will be chosen for cost reasons, eg Basingstoke - Salisbury - Exeter has this footnote:

Suggesting otherwise is going against the evidence, I'm afraid...

That's curious. I had always expected that Salisbury would be 3rd rail, so that some SWT suburban services could extend out there from Basingstoke. I also rather expected that Salisbury-Exeter would never happen, simply because an hourly service is simply not enough to warrant electrification. Maybe if they dualled the whole line and introduced a half-hourly service, one of which ran fast, but not at current service levels.

I've wondered to myself if the Thameslink Brighton route, or possibly Kent lines running on from HS1, might be candidates for conversion to OHL at some point. These would then be extensions to existing OHL routes, rather than replacement of entirely 3rd rail. They also run a lot of dual voltage (or DV capable) stock already

East Kent from Ashford and Ebbsfleet would be a possibility. Ashford already has changeover platforms and Northfleet could act as a second changeover point for the Chatham line. That might also provide an excuse to modernise the signalling on the Canterbury East Line among other things. Not good for appearances, but perhaps good for passengers in providing a decent, fast service.

With restricted clearances, on parts of the RER in Paris they got round the problem by installing, believe it or not, an overhead live rail under an insulated panel on sections where they could not get the wires to fit although admittedly the sections in question are at 1500v DC rather than 25kV AC.

And yes, it operates with a pantograph.

Now, I wonder, if they could make a much wider insulated panel would it be theortetically possible to run a short section of overhead live rail at 25kV AC, or would, as I suspect, the size of the cross section of the rail itself generate too much resistance for the current to flow efficiently?

Apparently, the Trowse Swing Bridge has an overhead live rail, which self-isolates whenever the bridge opens. I don't know much about the insulation (it's a steel bridge) but it evidently works. Anyone have any further details?

 

[atomicdanny]

That might also provide an excuse to modernise the signalling on the Canterbury East Line among other things. Not good for appearances, but perhaps good for passengers in providing a decent, fast service.

I think that you are a bit late on that one since they are already in the process of doing that one if not finished it (well last time I was I used my local station (aylesham) there was a brand new LED Signal

 

[Peter Mugridge]

That's interesting; I had thought that Trowse was just a neutral section.

However, it's relatively short isn't it? The real question is whether a 25kV AC OHLR would be technically viable in those restricted tunnels - so as a supplementary question I'd wonder if anyone can calculate that?

 

[LE Greys]

That's interesting; I had thought that Trowse was just a neutral section.

However, it's relatively short isn't it? The real question is whether a 25kV AC OHLR would be technically viable in those restricted tunnels - so as a supplementary question I'd wonder if anyone can calculate that?

I said "apparently", because I'm not entirely certain (the rail might just be to prevent the pan from rising too far). I can't seem to find confirmation one way or the other, does anyone else know?

 

[paul1609]

The cost of buying and fitting pans and transformers to the existing fleet of units is vanishingly small against the cost of re-electrifying thousands and thousands of miles of railway. If it works well enough (even if it is not the most efficient or effective system of electrification) leave it alone.

However, CRE (3rd rail to you) does need to be limited because of it's inefficiencies. I was appalled when I realised that the ELL extension would done using CRE rather than installing OLE on the new extended section and introducing dual-voltage units. This was a completely new railway operating a self-contained service that did not need to continue with such an outdated system of electrification. OK so it's better than diesel, but why couldn't it have been done to the modern standard (itself established over 50 years ago)?

O L Leigh

In theory a modern dc EMU will be more efficient than its ac counterpart for low speed services with frequent stops as it doesnt have to cart around the heavy weight of the ac transformer. Most of the disadvantages of DC emus for this sort of service have disappeared with the advent of modern power electronics (IGBTs etc).

Given the East London Line Extension only really comprises about 2 miles of new railway and the rest is conversion of a existing dc railway. I guess it was very much a no-brainer.

 

[jopsuk]

There's plenty of AC through tunnels- doesn't the electrification through the Mound tunnels in Edinburgh use overhead rails?
As for the East London, whilst it was previously a DC system, with the change to Overground the entire line was fully relaid wasn't it? Apart from anything, they were changing from a four rail system to a three rail system- with all the alterations to the return path that entails. I'm pretty sure the conductor rail was laid afresh. If it had been wired up, changeover could have been made at New Cross Gate, and Surrey Canal Road would have been a potential changeover location for Phase 2 (I appreciate this station is pretty much not going to happen).
Changeovers would, of course, have been required- it is not, as O L Leigh mistakenly says, a self-contained system- part of the whole point of the conversion of the system was to integrate it with the South London operation.

 

[paul1609]

I doubt that the East London Line Tunnels had the necessary clearances for 25Kv:
http://photo.clifford.ac/2006/June/dscn0101.jpg

 

[MrC]

In answer to the other points, I think 100 mph is sufficient for most lines, to be frank - many lines don't get anywhere near that anyway...

A maximum speed of 100 mph is likely all that's needed in the areas being talked about. However one thing that could be improved is acceleration - it can take a long time to get to that 100 mph and sometimes you never get there (eg Winchester up to Steventon).

Another negative point against 3rd rail is the limited capability for regenerative braking as, with the current designs of DC substation, regenerated power is only available to units in the area covered by the same substation. Changing the substations to allow a feed back into the distribution network would probably be prohibitively expensive.

 

[mickey]

it is designed for a finite traction load, ie a particular number of a given train type, and ultimately there'd be a limit applied to the number of AC trains running around. You can see this already on various parts of the ECML and particular some of the branches around Leeds, or beyond Cambridge.

Isn't that the excuse they gave for sending an HST for the Skipton direct service? Is it really so bad that just one extra train (albeit quite a long one!) will kill the power supply?

Another debate that has raged for a few years has been Wrexham to Bidston to extend the Merseyrail system. There are a number of online sources that explain that DC has been chucked out for cost reasons but AC is still being looked at.

For anyone who knows the area, apparently there is enough juice in the current system to take them up to Woodchurch; beyond that the cost and uncertainty becomes prohibitive.

 

[Lampshade]

Isn't that the excuse they gave for sending an HST for the Skipton direct service? Is it really so bad that just one extra train (albeit quite a long one!) will kill the power supply?

It's not an excuse, it's fact. The OHLE was done on the cheap and when they tried using a 225 on the Skipton line it caused a voltage drop significant enough to stop every EMU in the area.