Why no longer Third Rail Electrification?

[Camden]

Merseyrails new trains have been designed to make it straightforward to convert them to dual volt. If the Merseyrail network is extended it will be much cheaper to do it with overhead wires than third rail. The loop and link tunnels do not have the height to install overhead wires but I expect the rest of the network will switch to overhead electrification when the current systems become life expired. What is the benefit of extending the third rail network or replacing life expired third rail rather than using dual volt stock?

All new third rail rolling stock is required to be convertible, and this is just for cascade flexibility.

Third rail electrification for Merseyrail expansion would be cheaper than AC overhead.

 

[AM9]

I don't believe this is either true or clear cut. For higher speed lines with infrequent stops (south) AC is more efficient, however for lower speed lines with frequent stops (Merseyrail) DC is more efficient.

Efficient? In what way?

 

[AM9]

All new third rail rolling stock is required to be convertible, and this is just for cascade flexibility.

Third rail electrification for Merseyrail expansion would be cheaper than AC overhead.

Not necessarily. It depends on the number of bridges that will be life expired in the next 3 decades, that increasing cost of safety provisions, the future cost of electricity and its provision, and the required train performance and density away from the built-up area. Even the do-nothing option on the existing urban surface stretches of 3rd rail line may cease to be economically justifiable in the not too distant future.

 

[AM9]

If we're converting a 100mph section of third rail to 100mph OHLE, such as from Basingstoke southwards, I imagine that it won't need to be engineered to the same standard as the Great Western electrification.

There are modern options available to Network Rail. For instance the GEFF (Great Eastern Furrer & Frey) system developed to replaced the old fixed tension system originally erected for the Shenfield 1500VDC electrification in the early '50s has reliability features of the Series 1 design used on the GWML, yet has been installed on some of the original LNER gantries, as well as the motley collection of steelwork added by BR in the '60s and '70s. There's also the Series 2 system being installed in the NW Electrification programme.
The GEFF system is suitable for installation over quad track where there isn't space for single or sometimes even twin-track cantilever designs. The cantilever systems used on open twin track in France take advantage of the increased space available.

 

[GRALISTAIR]

Not necessarily. Even the do-nothing option on the existing urban surface stretches of 3rd rail line may cease to be economically justifiable in the not too distant future.

exactamundo

 

[Domh245]

Efficient? In what way?

I would guess that this is a reference to DC only units being lighter by merit of not having a transformer and pantograph. Of course this is not necessarily the case for units like the 377s which carry around a lump of concrete to keep performance and suspension consistent across DC only and DV fleets, but I can't see any reason why a purely DC fleet (such as the Stadlers) would have to have this provision.

 

[edwin_m]

The proportionate extra cost of carrying a transformer and pantograph would be no more than the proportionate extra weight (and actually less, because aerodynamic losses don't depend on train weight). I don't have a figure for this weight but I would guess two or three tonnes on a unit of over 100 tonnes. By contrast the third rail system loses about 20% of the energy fed into it, mainly to resistance losses heating the rails. So for a typical railway application a high-voltage AC system is likely to be more efficient.

Low voltage may be more efficient on metros where stops are more frequent (so the weight of the train has a more significant effect on power consumption), distances are shorter (so the resistance losses are less) and trains are closer together (so more likely regenerated energy can be re-used). It is probably also more efficient on tramways, but these have to have low voltage anyway for safety reasons.

 

[Camden]

Not necessarily. It depends on the number of bridges that will be life expired in the next 3 decades, that increasing cost of safety provisions, the future cost of electricity and its provision, and the required train performance and density away from the built-up area. Even the do-nothing option on the existing urban surface stretches of 3rd rail line may cease to be economically justifiable in the not too distant future.

Given the escalating costs of AC overhead electrification it would take quite the extraordinary convergence of events for third rail expansion/renewal costs to overtake it.

I don't think you must be too familiar with the area, as the Merseyrail network operates almost entirely within the built-up area, and throughout has stops every minute to two minutes apart. Even if you were to assume that expansions take it further, it would still make no sense to give any marginal AC edge priority for those expansions over the requirements of the general network. If such logic was used it would have been Desiros replacing the A rather than the S (on the Met), not to mention a different product replacing the 507/508.

Even if AC costs were equal to third rail, which they aren't, the additional costs of converting and maintaining dual voltage units would very likely mean that third rail was still preferred anyway.

The only place third rail warrants ripping up is in the 100mph south.

 

[XDM]

We have to face the fact that Network Rail is not fit for purpose. It has been deemed a failed organisation & it clearly can not undertake infrastructure improvements at a sensible price. AC ought to be the electrification standard but since it cannot be built economically in the U.K. third rail should be allowed on 100mph & lower speed Infills. Perhaps even to Salisbury. Third rail is far more reliable than network rail run overhead & just as safe. And you do not have to drag 2 tonne transformers around per 4 coaches or suffer the aerodynamic drag of 3 pantographs per 12 coaches.

 

[najaB]

And you do not have to drag 2 tonne transformers around per 4 coaches or suffer the aerodynamic drag of 3 pantographs per 12 coaches.

I've read some weak justifications for 3rd rail over OHLE but come on, aerodynamic drag from pantographs?! Have you seen the frontal area of the average EMU? The drag caused by the pantograph wouldn't even be distinguishable in comparison.

 

[Elecman]

Perhaps a little rethink of your sweeping statement that Network Rail is not fit for purpose, if various government departments/ organisations stopped altering thier requirements mid scheme / at every political soundbite we might have electrification at a known rate. Scotland seemed to manage quite adequately till someone in a government department altered the ground rules on clearances mid schemes without allowing the derogations that were available for schemes in advance stages, ditto GWR and Northwest.

 

[AM9]

I don't think you must be too familiar with the area, as the Merseyrail network operates almost entirely within the built-up area, and throughout has stops every minute to two minutes apart. Even if you were to assume that expansions take it further, it would still make no sense to give any marginal AC edge priority for those expansions over the requirements of the general network. If such logic was used it would have been Desiros replacing the A rather than the S (on the Met), not to mention a different product replacing the 507/508.

I have, relatively recently travelled on the whole length of the Northern line from Southport to Central. To refresh my memory, on checking Google Earth I see that there are only 11 road overbridges plus one rail overbridge from Southport to the tunnel portal between Sandhills and Moorfields, a distance of over 18 miles.
By comparison, one of the few lines within the London suburban area undergoing electrification is the GOBlin. It is just 12 miles long but has 34 road and two rail overbridges. Yet no suggestion was ever made about anything other than OLE.

Even if AC costs were equal to third rail, which they aren't, the additional costs of converting and maintaining dual voltage units would very likely mean that third rail was still preferred anyway.

If the rolling stock is being replaced anyway, the difference in cost between the mandated ac/DC stock and a stripped-out DC only version would be wiped-out by the additional energy costs of inefficient low voltage supply in the first couple of years. A single ac feed to OLE can supply over 10,000 hp of traction energy. Moreover, that feed can support a line 20+ miles long.

 

[apk55]

One logical extension of the Merseyrail network would be Hunts cross to Warrington local trains. They would not want to electrify this with anything other than 25KV as other trains would be running to to lime street. Another extension would be Ormskirk to Preston where to problems of dual electrifying a section in Preston would make this unattractive. Possibly also in future Merseyrail might want to take over some other services such as Runcorn and Wigan.

Therefor the possibility of converting to dual voltage operation is worth including. If the parts are not fitted but provision is made it probably only adds about 1% to the cost (few extra control cables, modified roof section and some brackets for the transformer, 4 quad converter and changeover relays)

 

[edwin_m]

We have to face the fact that Network Rail is not fit for purpose. It has been deemed a failed organisation & it clearly can not undertake infrastructure improvements at a sensible price. AC ought to be the electrification standard but since it cannot be built economically in the U.K. third rail should be allowed on 100mph & lower speed Infills. Perhaps even to Salisbury.

If NR is indeed "not fit for purpose" then isn't it likely it would overspend even more on a new third rail scheme? The last significant third rail electrification was even longer ago than the last significant OLE electrification before the current batch.

 

[yorksrob]

For decades and decades we had the perfectly sensible suggestion that OLE should be the preferred electrification method, with shortish infills and extensions allowed of the existing third rail networks where practical.

Surely it's time that this sensible approach was restored by the ORR, rather than the hysterical presumption that the third rail is somehow inherently dangerous.

 

[SpacePhoenix]

For decades and decades we had the perfectly sensible suggestion that OLE should be the preferred electrification method, with shortish infills and extensions allowed of the existing third rail networks where practical.

Surely it's time that this sensible approach was restored by the ORR, rather than the hysterical presumption that the third rail is somehow inherently dangerous.

If that were to happen would infill of the NDL and extension from the SWML to Salisbury (is Salisbury the western limit of the bulk of the London commuter traffic on the Exter-Waterloo route) be allowed?

 

[NSEFAN]

If that were to happen would infill of the NDL and extension from the SWML to Salisbury (is Salisbury the western limit of the bulk of the London commuter traffic on the Exeter-Waterloo route) be allowed?

I'd argue that Oxted - Uckfield, Ore - Ashford and Reading - Redhill are all infill projects (they're surrounded by 3rd rail systems), whereas Basingstoke/Southampton - Salisbury is an extension.

Given the 159s will be up for replacement in a few years, there may be a good opportunity to time electrification with new dual-voltage stock for the Waterloo - Exeter route, using 25kV overhead. Indeed timing electrification and rolling stock deliveries together is how it should be done, but the railway isn't quite organised enough to get the timings right.

 

[Deepgreen]

I must point out that all these arguments have been very well rehearsed elsewhere, most recently in the North Downs Line Electrification thread.

 

[Deepgreen]

I'd argue that Oxted - Uckfield, Ore - Ashford and Reading - Redhill are all infill projects (they're surrounded by 3rd rail systems), whereas Basingstoke/Southampton - Salisbury is an extension.

Given the 159s will be up for replacement in a few years, there may be a good opportunity to time electrification with new dual-voltage stock for the Waterloo - Exeter route, using 25kV overhead. Indeed timing electrification and rolling stock deliveries together is how it should be done, but the railway isn't quite organised enough to get the timings right.

Technically, Oxted to Uckfield is an extension as there is no southern end connection to which to link, but for completeness of service it could be regarded as infill.

 

[swt_passenger]

If that were to happen would infill of the NDL and extension from the SWML to Salisbury (is Salisbury the western limit of the bulk of the London commuter traffic on the Exter-Waterloo route) be allowed?

The 2009 electrification RUS treated them differently, NDL was apparently going to be third rail, but Salisbury was being seen as AC:

Gap A3.1 Wokingham to Ash and Shalford to Reigate
Option A3.1 Electrify Wokingham to Ash and Shalford to Reigate with DC electrification. Convert Reading to
Gatwick Airport and Reading to Redhill local services to electric traction.

and...

Gap A4.1 Basingstoke to Salisbury
Option A4.1a Electrify Basingstoke to Salisbury*. Convert Waterloo to Salisbury service to electric traction.
*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

I don't think you can define Salisbury as the notional commuting limit, it is more that it is the limit of the 2 tph all day service. But there are plenty of peak extra (commuter time) services that run beyond Salisbury already. It isn't as clear cut as might be thought.

 

[yorksrob]

If that were to happen would infill of the NDL and extension from the SWML to Salisbury (is Salisbury the western limit of the bulk of the London commuter traffic on the Exter-Waterloo route) be allowed?

Salisbury is inevitably a bit of a grey area as there's always the potential for OLE from the Exeter direction. However, I'd have thought the gaps in the NDL would be a top priority.

To the Southern infills, I'd also add Ormskirk - Preston.

 

[Deepgreen]

Salisbury is inevitably a bit of a grey area as there's always the potential for OLE from the Exeter direction. However, I'd have thought the gaps in the NDL would be a top priority.

To the Southern infills, I'd also add Ormskirk - Preston.

Not really - as there is almost no scope for extending the service at either end, it remains self-contained. This, combined with the significant route mileage infill required, and the difficult in increasing either the frequency or the length of trains, the business case is poor. I suspect the existing arrangements will prevail for a long time.

 

[GRALISTAIR]

- I'd also add Ormskirk - Preston.

I think as does Northern Sparks that this is lower down the priority list for electrification. I also think AC in conjunction with Wigan Southport etc is more likely - yes I know that means dual voltage units for Merseyrail etc. Reinstate the curves while we are at it.

 

[yorksrob]

Not really - as there is almost no scope for extending the service at either end, it remains self-contained. This, combined with the significant route mileage infill required, and the difficult in increasing either the frequency or the length of trains, the business case is poor. I suspect the existing arrangements will prevail for a long time.

The lack of scope for extending the service northward is the primary reason why it would suit third rail rather than OLE. For a rural railway, it already has a reasonably intensive service of a sort that lends itself to electric traction, and doubtless there would be efficiencies in staffing and stock diagrmming were it integrated with it's neighbouring third rail franchises, rather than a long branch line from Great Western land.

In terms of length, the only longish section is Reigate - Guildford, and even that's not particularly long compared to the other diesel islands.

 

[yorksrob]

I think as does Northern Sparks that this is lower down the priority list for electrification. I also think AC in conjunction with Wigan Southport etc is more likely - yes I know that means dual voltage units for Merseyrail etc. Reinstate the curves while we are at it.

Those other lines tend to operate into the rest of the northern network, so OLE may be justified at some stage. Preston-Ormskirk isn't likely to be linked up to anything else any time soon, so extending from the Liverpool end would make more sense.

 

[DerekC]

In discussing the costs of OLE vs 3rd rail, one point to be considered is that the 3rd rail standards would be likely to get a good going-over in the (unlikely) event that ORR gave in on extending the system. Therefore it might not be as cheap as you think. Also to be remembered is that you need a lot more substations for 750VDC than for 25kV AC, and they are more expensive per MW. Set against this is that the AC trains are a bit more expensive - and of course the much-discussed costs of raising bridges etc.

 

[NSEFAN]

Technically, Oxted to Uckfield is an extension as there is no southern end connection to which to link, but for completeness of service it could be regarded as infill.

I was assuming that infill meant to take the entire region of 3rd rail as a geographical area, and fill in any unelectrified sections within it with 3rd rail, in order to remove "diesel islands".

 

[SpacePhoenix]

How many new substations would be needed for infilling the gaps in the 3rd rail on the NDL?

 

[Sean Emmett]

Worting Jn - Laverstock Jn:
When the various overbridges were raised for the (diverted) container traffic IIRC they were raised sufficiently to be 25kV compliant, can anyone confirm?
Quite a few were demolished and not replaced.

 

[HarleyDavidson]

How many new substations would be needed for infilling the gaps in the 3rd rail on the NDL?

Approximately 8 + DC Containers (TPHs).

Crowthorne - Blackwater - Shalford - Albury - Gomshall - Westcott - Betchworth - Reigate

Approx 3 miles apart.

They might be able to do one at Farnborough North as there's a substation there which feeds the mainline (conveniently), so just increase it in size or power. So the above locations between Wokingham & Ash might need rejigging a bit.