Converting 3rd Rail infrastructure to 25kv AC OHL infrastructure

[j.crocker355]

Just been musing, if the government woke up one day and decided to "upgrade" the SWR routes out of Waterloo to 25kv AC OHL from the existing DC 3rd rail, how much work would this be compared to say existing OHL projects on the GWML?

It got me wondering that's all if one of the reason First/MTR want new stock is that it could be AC as well as DC capable?



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[DarloRich]

Just been musing, if the government woke up one day and decided to "upgrade" the SWR routes out of Waterloo to 25kv AC OHL from the existing DC 3rd rail, how much work would this be compared to say existing OHL projects on the GWML?

It got me wondering that's all if one of the reason First/MTR want new stock is that it could be AC as well as DC capable?



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It would be like building a OHLE line form new. I suspect it wouldn't be any easier or cheaper because there is already a rd rail system.

I am fairly certain the is DfT asking for convertible stock to allow it to be moved away form third rail land if required.

 

[edwin_m]

There was a study about five years ago that claimed it was no more expensive to convert to 25kV than to renew a lot of the SWML 750V infrastructure that was approaching end of life (probably the substations and feeders rather than the third rail itself.

However since then the costs of "standard" 25kV electrification has gone through the roof and the Government won't even fund new electrification it has already committed to. So it's highly unlikely there will be any money for a conversion that will be more complicated and risky than a totally new electrification. It would also have less benefit than a totally new electrification because all it would do is allow a few diesel trains to be replaced by electric and the existing electric trains to have better performance with lower power consumption.

This probably means that the ageing 750V equipment will be replaced with equivalent modern equipment and the "window of opportunity" for economical conversion, if it ever existed, will be closed for several decades.

The rolling stock wasn't too much of an issue, as Basingstoke to Southampton would have been done first and virtually all the existing electric services are run by 444s and 450s that are designed for easy conversion to dual voltage. This would have created opportunities for freight and Cross Country to use electric traction. Inward from Basingstoke was proposed as a later phase, when the 455 and 456 units had been withdrawn and also the older signalling replaced by modern equipment compatible with either electrification system.

 

[AM9]

I suppose that the 25kV clearance requirements may come under some review if the hardline EU leavers get their way. A more likely scenario could be that increasing feright traffic through Southampton might call for further gauge enhancement, particularly southwest of Basingstoke. If tunnels and bridges are being replaced for reasons of W12 (or any future enhanced gauge), clearance and/or age and deterioration through use, the additional cost of ensuring OLE clearance would be much easier to swallow. That relatively short section of the SWML (31 miles) would be key to several other electrification opportunities where the long-term benefits may outweigh the costs of infrastructure modifications, e.g. Basingstoke to Andover/Salisbury, Reading to Basingstoke, Southampton to Romsey and Eastleigh, - maybe even a start of the Portsmouth Direct via Botley, Cosham Havant all the way to Guildford or Woking.
I'm not saying that any of this would be sometime soon, but once through (25kV) electrification starts in a region, it tends to follow through primary routes where the CBR case gets better.

 

[mr_jrt]

...the follow up projects to the electric spine were to be to enable the Javelin services to operate purely on OHLE, so Gravesend to Ashford via Margate and Ashford to Dover. Beyond that, Ashford to Hastings was proposed, along with Uckfield and East Grinstead to South Croydon or thereabouts. Finally, the southern end of the Brighton mainline was proposed, and designs even drawn up.

 

[coppercapped]

Just been musing, if the government woke up one day and decided to "upgrade" the SWR routes out of Waterloo to 25kv AC OHL from the existing DC 3rd rail, how much work would this be compared to say existing OHL projects on the GWML?

It got me wondering that's all if one of the reason First/MTR want new stock is that it could be AC as well as DC capable?



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If the dc stock is fitted with variable frequency ac motors - which for a range of reasons practically all dc stock is now - then by definition the stock can run on an ac supply.

The reason is that the inverter which supplies the variable frequency, variable voltage 3phase ac to the motors has a dc input. The dc can be supplied from the 3rd rail or be a rectified output from a high voltage transformer, the primary of which picks up its power from the overhead.

So to convert a modern dc train to ac requires the addition of a pantograph, transformer, rectifier and the necessary control gear. All the recent Siemens stock on the South Western already have the pantograph well built in, and the first two 707 also have been fitted with pantographs and transformers. The only stock which might be problematic to modify are the 455 and 458 trains as the physical changes might be more complex - the 455s because they never had a pantograph well in the roof and the 458s because they have been cobbled together and there are differences between some of the units. Both, however, already use 3 phase drives. The 442s, which are to be rebuilt under the solebar to use 3 phase drives, would also need a pantograph well.

The question that needs to be answered is 'Would such a change be economic?' That is would any reduced operating costs of infrastructure and trains, and possible increased income, outweigh the costs of the changeover?

 

[Bald Rick]

...the follow up projects to the electric spine were to be to enable the Javelin services to operate purely on OHLE, so Gravesend to Ashford via Margate and Ashford to Dover. Beyond that, Ashford to Hastings was proposed, along with Uckfield and East Grinstead to South Croydon or thereabouts. Finally, the southern end of the Brighton mainline was proposed, and designs even drawn up.

I can confirm that there were no such 'follow up projects', and certainly no designs drawn up.

 

[JohnElliott]

It would be like building a OHLE line form new. I suspect it wouldn't be any easier or cheaper because there is already a rd rail system.

I'd think it would be a lot harder than building an OHLE line from new, because of the need to work around an operating railway. With a live rail at ankle height.

 

[Jake.Norman17]

I can't see the line out of waterloo been electrified with OHL for a good long time yet. Especially when there are still main lines without any sort of electrification. Plus most OHL electric schemes at the moment are usually been reduced or abandoned such as MML north of Kettering.

Also isn't most of SWR inherited stock capable of been modified to run on OHL. I believe the 444, 450 and 458 already have a gap where a pantograph can go so they could possibly be converted in the future.

 

[Joseph_Locke]

I'd think it would be a lot harder than building an OHLE line from new, because of the need to work around an operating railway.

And working round all the DC feeding and switching kit, having a stage where the signalling system has to be AC and DC immune (or renewed) and potentially a complex earthing and bonding nightmare.

 

[edwin_m]

I suppose that the 25kV clearance requirements may come under some review if the hardline EU leavers get their way. A more likely scenario could be that increasing feright traffic through Southampton might call for further gauge enhancement, particularly southwest of Basingstoke. If tunnels and bridges are being replaced for reasons of W12 (or any future enhanced gauge), clearance and/or age and deterioration through use, the additional cost of ensuring OLE clearance would be much easier to swallow.

I'd like to think the clearance issue could be solved by someone banging the heads of the various UK safety bodies together (in the safest possible way of course). It was never a problem before and as far as I can tell it relates solely to the failure of the UK to request continuation of an exemption which the EU would have been happy to grant.

Basingstoke to Southampton was gauge-enhanced some years ago and I've seen photos of some of the re-built bridges where the space above a train is enough for 25kV wires and associated clearances - this is pretty much standard when re-building a bridge. There may of course be others that didn't need to be re-built for gauging purposes but would need work for electrification.

 

[mr_jrt]

I can confirm that there were no such 'follow up projects', and certainly no designs drawn up.

I saw the designs for the BML in the presentation!

Just for you I went and managed to track down a copy still online. Page 15! https://www.imeche.org/docs/default...to_AC_Conversion_by_Steve_Yianni.pdf?sfvrsn=0

 

[GRALISTAIR]

I saw the designs for the BML in the presentation!

Just for you I went and managed to track down a copy still online. Page 15! https://www.imeche.org/docs/default...to_AC_Conversion_by_Steve_Yianni.pdf?sfvrsn=0

Struggling - there must be so many hits on this at the moment that it is consuming so much bandwith - I am not getting an error message but it is taking forever just to get there. Looking forward to reading this and putting it in the sticky.

 

[mr_jrt]

It was still in my browser cache from earlier, so I've saved a copy should it vanish due to the load. I've nowhere to make it available from for the time being, however.

 

[GRALISTAIR]

It was still in my browser cache from earlier, so I've saved a copy should it vanish due to the load. I've nowhere to make it available from for the time being, however.

I got it eventually and got a PDF (only 2.136 MBytes so not that bad) - I have referenced in the sticky now also. I think it is a great read - and hoping that even if not happening in my lifetime - it may happen eventually. I am the eternal optimist !!

If anyone struggles - pm me and I will good old fashioned email them the PDF .

 

[AM9]

I'd like to think the clearance issue could be solved by someone banging the heads of the various UK safety bodies together (in the safest possible way of course). It was never a problem before and as far as I can tell it relates solely to the failure of the UK to request continuation of an exemption which the EU would have been happy to grant.

Such a move would be preferable, but it may need to wait until those who failed to prevent the lapse of the exemption 'take the next step in their careers'.

Basingstoke to Southampton was gauge-enhanced some years ago and I've seen photos of some of the re-built bridges where the space above a train is enough for 25kV wires and associated clearances - this is pretty much standard when re-building a bridge. There may of course be others that didn't need to be re-built for gauging purposes but would need work for electrification.

OK, that's encouraging. Then there is the issue of the tunnels at Micheldever and the tunnel near Kings Worthy. Also, I know that the clearance in the Southampton tunnel was recently increased for freight by lowering the floor but I don't know whether it could now accommodate OLE, - nor the overbridges just east of it.

 

[59CosG95]

Also isn't most of SWR inherited stock capable of been modified to run on OHL. I believe the 444, 450 and 458 already have a gap where a pantograph can go so they could possibly be converted in the future.

The 444s, 450s and the original 30 458s (not the ex-460 converts, 458531-536) are indeed equipped with pantograph wells; however, since the 458s are due to leave SWR at FirstMTR's request, they may have difficulty in finding a new home. Besides, SWR's 442 plan rather implies we won't be seeing wires in Waterloo for a good while!

 

[The Ham]

The 444s, 450s and the original 30 458s (not the ex-460 converts, 458531-536) are indeed equipped with pantograph wells; however, since the 458s are due to leave SWR at FirstMTR's request, they may have difficulty in finding a new home. Besides, SWR's 442 plan rather implies we won't be seeing wires in Waterloo for a good while!

At best my guess for wires into Waterloo would be post 2035 so that Crossrail 2 can help spread the loading of passengers.

 

[Mikey C]

I'd think it would be a lot harder than building an OHLE line from new, because of the need to work around an operating railway. With a live rail at ankle height.

On such busy railways that would be a nightmare

From memory, the only relatively recent conversion of 3rd rail to OHLE would have been on the North London line. Was the line closed to do this - it has been closed on many occasions for upgrade work?

 

[HSTEd]

On such busy railways that would be a nightmare

From memory, the only relatively recent conversion of 3rd rail to OHLE would have been on the North London line. Was the line closed to do this - it has been closed on many occasions for upgrade work?

The line was already electrified and operated with both systems for a period of time, it was only electrified at 25kV for the benefit of freight operations.
The third rail was disabled later once the services in question were taken over by Class 313s.
Although by many accounts many fun corrosion issues had surfaced - which was why the conversion was undertaken.

Now that the 25kV estimates that claimed reelectrification woudl be cheaper than renewal have been shown to be junk - this idea is well and truly dead.
Indeed even the Gibb report pointed out that electrification with third rail was likely cheaper than at 25kV and only regulatory problems stand in the way of the former.

 

[mike57]

I think conversion of 3rd rail to OHL in the current climate not going to happen:

1. The various parties have been unable to deliver the current electrification plans hence the cut backs
2. The political fallout of converting an existing electrified 3rd rail line to OHL would be unacceptable given the cutbacks to electrification in other areas.
3. Common sense says it will be probably be more complex to OH electrify an existing 750v DC line whilst keeping the DC active than wiring up from nothing with no DC complication.

So I wont say Never, as never is a long time, but Not in the foreseeable future, So new stock being dual voltage (or easily converted) allows it move around the system, nothing more

 

[Bald Rick]

I saw the designs for the BML in the presentation!

Just for you I went and managed to track down a copy still online. Page 15! https://www.imeche.org/docs/default...to_AC_Conversion_by_Steve_Yianni.pdf?sfvrsn=0

Ha ha! I haven't laughed so much in ages! That's not a design, or anything remotely close to it. It's a conceptual electrical feeding diagram. It is the sort of thing that gets done on the back of an envelope to demonstrate that it might be worth considering starting up a project. The guy who did it (not the presentation author) lives in Brighton, and would have drawn that on his train home one evening to show that it could be done.

None of the oval areas on the map were ever taken forward.

 

[AM9]

I think conversion of 3rd rail to OHL in the current climate not going to happen:

1. The various parties have been unable to deliver the current electrification plans hence the cut backs
2. The political fallout of converting an existing electrified 3rd rail line to OHL would be unacceptable given the cutbacks to electrification in other areas.
3. Common sense says it will be probably be more complex to OH electrify an existing 750v DC line whilst keeping the DC active than wiring up from nothing with no DC complication.

So I wont say Never, as never is a long time, but Not in the foreseeable future, So new stock being dual voltage (or easily converted) allows it move around the system, nothing more

But 750VDC is a constraint on heavy freight between Basingstoke and Southampton making it difficult to accomodate heavy trains in amongst the passenger service, so if (or maybe when) the Reading to Basingstoke link electrification is back on the agenda, the pressure will be on to complete the full-power capable route through to Southampton Docks.

 

[HSTEd]

But 750VDC is a constraint on heavy freight between Basingstoke and Southampton making it difficult to accomodate heavy trains in amongst the passenger service, so if (or maybe when) the Reading to Basingstoke link electrification is back on the agenda, the pressure will be on to complete the full-power capable route through to Southampton Docks.

Assuming the freight operators actually want to convert to electric operation - which we have little evidence that they do judging by the cold reception to the whole 'Electric Spine' concept.

This has to be weighed against the extra maintenance of all the extra pantographs and transformers on all the passenger units that would run over the converted section.

Additionally a Class 92 can still develop over five thousand horsepower on third rail. [4000kW, coincidentally the same peak demand as a pair of Class 444s]

More likely further power supply upgrades to support regular electric freights would be far more economic than conversion to 25kV.

 

[Bald Rick]

The third rail was disabled later once the services in question were taken over by Class 313s.
Although by many accounts many fun corrosion issues had surfaced - which was why the conversion was undertaken.

.

The first part - not so. Both systems were live on the two track section between Channelsea Jn and Cannonbury for about 25 years until the line was closed for a few months for upgrading in 2010/11. The 313s usually ran on AC, changing at Hackney Wick and Dalston. However if there was ever a problem with the AC, they would stay on DC. The track circuits down there were a particular design and frequency to cope, however it was very much preferred for trains to be in AC to limit return current problems. Even so, with 3-4 X 3 car trains an hour, the return current issue was nothing as significant as on Thameslink.

The corrosion issues were worst at Acton, where the AC DC changeover was in the same area as the voltage gradient (where NR DC went from 660 - 750v), lots of other stray currents from the GWML, WCML, LUL, etc etc. This bit had al the masts replaced in 2004 - I poured the concrete on some of the new foundations!

The reason for conversion of Cannonbury - Channelsea was mostly because the anticipated increase in service for London Overground: double the frequency, each 378 roughly double the power of the 313s, meant that the DC system did not have sufficient capacity. So it was taken out, and eliminated three voltage changeovers at the same time (Hackney Wick, Dalston, Camden)

 

[GRALISTAIR]

I think conversion of 3rd rail to OHL in the current climate not going to happen:

So I wont say Never, as never is a long time, but Not in the foreseeable future,

I think most/all on here would agree.

 

[NotATrainspott]

Assuming the freight operators actually want to convert to electric operation - which we have little evidence that they do judging by the cold reception to the whole 'Electric Spine' concept.

This has to be weighed against the extra maintenance of all the extra pantographs and transformers on all the passenger units that would run over the converted section.

Additionally a Class 92 can still develop over five thousand horsepower on third rail. [4000kW, coincidentally the same peak demand as a pair of Class 444s]

More likely further power supply upgrades to support regular electric freights would be far more economic than conversion to 25kV.

A 92 can only deliver 4MW if that power is available in the third rail. The consequence of using 750V DC is that it's much harder to provide that sort of power efficiently. Megawatt-level loads really do take 750V DC third rail well beyond its comfort zone, while 25kV wouldn't be breaking a sweat. Of course, you can mitigate this by providing lots of feeder stations, but the train interface is still never going to work well.

As you say though, if major increases in electric freight are unlikely then DC power supply issues aren't as important.

 

[InOban]

Perhaps someone needs some more 88s with third-rail shoes...

 

[GRALISTAIR]

Perhaps someone needs some more 88s with third-rail shoes...

Trimodes Not to get too far OT but I don't mind as long as they (politicians) use bi/tri modes as a means to buy time. But I really do think it better to concentrate precious resources on AC OHL electrifying lines with no electrification rather than converting DC lines which are already electrified.

 

[JohnElliott]

Indeed even the Gibb report pointed out that electrification with third rail was likely cheaper than at 25kV and only regulatory problems stand in the way of the former.

In the case of the Uckfield branch, he said the exact opposite (p61 of the report):

Popular opinion is that it should be cheap, safe and easy to extend third rail electrification. However I have found this not to be the case in respect of the Uckfield line. The largest single item cost is the connection to the National Grid, and this is necessary for both third rail and overhead systems. A third rail system would require feeder stations every 2-3 miles, whereas overhead may only require one feeder station for the 25 miles between Hurst Green and Uckfield.
Given the availability of dual voltage trains on the GTR network for the foreseeable future, I believe the preferred option for electrification should be 25kV AC overhead electrification. I have been told by several experts that it should be cheaper than an extension of the third rail. I believe there will be performance benefits from an overhead system, particularly in winter, and a minor reduction in journey times from faster acceleration and DOO operation.

(In a Modern Railways interview, he expanded on the substations point: Substations would also require land to be purchased to put them on).