Replacing 3rd Rail With OHLE - Benefits

[DynamicSpirit]

1) Whenever there is a trespasser on the track (or worse), or obstruction on the line, in 3rd rail land, the power comes off. This often strands trains far from the incident. This does not happen in OLE areas. Only tonight my train was delayed by a trespasser in an OLE area. We passed through at caution. Had that been in a third rail area, all lines would have been stopped for at least 30 minutes.

Out of interest, would that particular problem be solved if 3rd rail trains were fitted with batteries sufficient to go - say, 20 miles or so in the event of power loss? (I realise it wouldn't solve many other issues associated with 3rd rail and might not be cost-effective, but just wondering on principle).

As a bonus, I guess it would also allow that eastbound 4-car stop at Woolwich Arsenal to be brought back into use, which of course is not at all overkill in terms of millions of pounds to solve a piddling little problem

 

[AM9]

Quite a lot of low bridges between wivelsfield and Brighton, each one would need reconstructing or the UNits would need VERY low pantrogaphs
Wouldn't be viable option to upgrade that part of line

If they are that low then they are probably nearing the end of their lives anyway. That's the case for some of the structures on the SWML where some of them have been replaced for freight clearances. Even tunnels need major surgery near their end of life so in a heavily worked railway, disruption caused by infrastructure work can be integrated witgh that required for overhead electrification. Just look at the number of weekends that the BML has been closed this year for engineering work.

 

[Whistler40145]

Would any electrification on the former Southern Region use the Autotransformer system as has been implemented on the West Coast Mainline?

 

[big all]

Out of interest, would that particular problem be solved if 3rd rail trains were fitted with batteries sufficient to go - say, 20 miles or so in the event of power loss? (I realise it wouldn't solve many other issues associated with 3rd rail and might not be cost-effective, but just wondering on principle).

As a bonus, I guess it would also allow that eastbound 4-car stop at Woolwich Arsenal to be brought back into use, which of course is not at all overkill in terms of millions of pounds to solve a piddling little problem

a 20 mile battery capacity would solve the gatwick to reading problem ------ just
assuming a 90% charge in 15 mins if required with perhaps emergency charge points at blackwater gomshall and deepdene
as an aside a 769 with with one engine and one battery pack would probably perform better than a pure 769
also the same battery capacity would probably cover 20 miles at 70mph 30miles at 50mph 50 miles at 20 mph speed dictates the stored energy required

 

[Taunton]

There was a study a few years ago saying it might be worthwhile to convert the third rail network over a long period, starting with the outer parts of the SW main line where the benefits would be greatest (opportunities for high speed running and electric freight, and some of the existing supply equipment needed replacing anyway). However this was at a time before electrification schemes went way over budget. Converting third rail would be more complicated than just installing OLE .

OHLE schemes have always gone way over budget. The WCML in the early 1960s did when only the north end had been done, and the scheme was paused while the government reassessed the benefits. The follow-on ECML scheme of the era was cancelled.

It would be interesting to compare actual track mile costs for installing the two, including substations; my guess having seen some 3rd rail installed at first hand (and the effort in installing 25Kv that replaced it) is that it probably comes in at about 10% of the cost of overhead. Maybe less.

Typically on a conversion all the track circuits would need to be changed as well. The ones immunised against DC would need changing if AC was installed. In the conversion interim they would need to be immunised against both, which is always a considerable technical expense, as the few places where both systems are present bear witness to.

Did I read that the clever guys who devised the Paisley Canal electrification a few years ago as a bargain basement job were subsequently marginalised for doing this on other schemes by established vested interests.

 

[Belperpete]

Typically on a conversion all the track circuits would need to be changed as well. The ones immunised against DC would need changing if AC was installed. In the conversion interim they would need to be immunised against both, which is always a considerable technical expense, as the few places where both systems are present bear witness to.

Not just the track circuits. You also need to make sure the point machines and their control and detection circuits are properly immunised.
In ac traction areas, the circuits that feed the signal heads are limited to 200m, and all other circuits running in trackside cables are limited to a maximum of 2km. This is to limit the amount of voltage that can be induced into the circuits running parallel with the OLE. These limits do not apply in DC traction areas. So, when converting DC to AC traction, in an area with relay signalling, realistically you are probably going to have to renew most of the line side signalling cupboards and cabling.

 

[edwin_m]

Typically on a conversion all the track circuits would need to be changed as well. The ones immunised against DC would need changing if AC was installed. In the conversion interim they would need to be immunised against both, which is always a considerable technical expense, as the few places where both systems are present bear witness to.

Not just the track circuits. You also need to make sure the point machines and their control and detection circuits are properly immunised.
In ac traction areas, the circuits that feed the signal heads are limited to 200m, and all other circuits running in trackside cables are limited to a maximum of 2km. This is to limit the amount of voltage that can be induced into the circuits running parallel with the OLE. These limits do not apply in DC traction areas. So, when converting DC to AC traction, in an area with relay signalling, realistically you are probably going to have to renew most of the line side signalling cupboards and cabling.

More modern signalling uses axle counters or dual-immune types of track circuit as standard, and techniques such as digital coding to increase immunity to traction interference. Any large areas of relay-based signalling are likely to be at least 25 years old and therefore approaching life-expiry in any case.

The study I referred to earlier proposed that any conversion to 25kV would start with the outer part of the SW main line, where the signalling equipment is relatively recent. The last big relay-based scheme was probably Waterloo, so any hypothetical conversion would have left this area until much later when that equipment along with the DC-only 455s had been replaced. However as I suggested above it's now highly unlikely to happen in any case.

 

[Bald Rick]

More modern signalling uses axle counters or dual-immune types of track circuit as standard, and techniques such as digital coding to increase immunity to traction interference. Any large areas of relay-based signalling are likely to be at least 25 years old and therefore approaching life-expiry in any case.

The study I referred to earlier proposed that any conversion to 25kV would start with the outer part of the SW main line, where the signalling equipment is relatively recent. The last big relay-based scheme was probably Waterloo, so any hypothetical conversion would have left this area until much later when that equipment along with the DC-only 455s had been replaced. However as I suggested above it's now highly unlikely to happen in any case.

There’s often relays in the track circuits, regardless of the type of interlocking. It’s the former that needs the immunisation, not the latter.

 

[Meerkat]

Not possible unless you lose all the freight. There’s been many previous discussions about this..

Pedantically..... the chap said Woking-Basingstoke and on to Eastleigh/Salisbury via the non-electrified....not the two track bit to Southampton.
Woking to Basingstoke has fast lines along the middle and is pretty straight....
Tri-modes on WEML would speed it up and get stinking noisy diesels out of our stations

Electrify to Reading too and extend some GWR Reading terminators (will there be any post Crossrail?) would open up some good Thames Valley commuting opportunities.

 

[swt_passenger]

Pedantically..... the chap said Woking-Basingstoke and on to Eastleigh/Salisbury via the non-electrified....not the two track bit to Southampton.
Woking to Basingstoke has fast lines along the middle and is pretty straight....
Tri-modes on WEML would speed it up and get stinking noisy diesels out of our stations
.

Oh yeah. But going on from Basingstoke to Eastleigh/Salisbury? Salisbury as part of an Exeter route maybe valid, but going on to Eastleigh via Salisbury at 125 mph would give no advantage over the present electrified 100 mph route, given the extra distance. There are also proposals to use Southampton to Basingstoke via Laverstock for additional freight capacity. The major traffic objective is Southampton direct. Alternatively, heading via Salisbury (Laverstock )to Southampton via Romsey doesn’t give any advantages to passengers over the status quo either.

 

[Meerkat]

Yeah, I wasn’t sure if the proposal was for speed increase Salisbury southward, or just to electrify it (fleet of dual voltage at Salisbury for Salisbury terminators and Romsey 6 services)

Would the freight companies be amenable to going the long way round if it meant not getting looped and avoiding Southampton? The electrification to Reading would then be ready for the electric spine....who is that laughing at the back?!

 

[DynamicSpirit]

I imagine one problem with electrifying Basingstoke-Salisbury as OHLE is that, unless you electrified all the way to Exeter, you'd end up needing to build a small micro-fleet of tri-mode trains to run Waterloo-Exeter. I would presume the costs of designing and building such a small fleet would be somewhat disproportionate per train.

Also, unless you also electrified Basingstoke-Reading, you'd have an isolated island of OHLE, not connected to the rest of the OHLE network (I'm not sure whether that is or is not a problem?). Having said that, if you did electrify Reading-Basingstoke, you could perhaps get some economies of scale on the trains by supplying X-Country with tri-modes as well, to run their Bournemouth-the North services.

 

[Meerkat]

With my ‘engineering is simple’ hat on....
Is a tri-mode that hard? Desiros come in 750v, 25kv, both, and Diesel varieties. Just mash it all together
769s are going to do it and that’s going just swell.....

 

[Taunton]

Interesting thought is whether, for the huge eventual cost of the GW 25Kv electrification, we could have electrified ALL the trunk lines in Britain by 3rd rail.

So 3rd rail is not suitable for 125mph. But how much of this is required now. The old days of Paddington to Bath nonstop in an hour are gone. The train service is now essentially an outer suburban one, operating at near-Metro frequency and stopping every 20-25 miles or less. The opportunities to accelerate to over 100mph now are pretty limited before the brakes go on for the next stop. All those transformer substations that are being heaved around under the floor of the new trains, now not even used for half the trip or more would be saved. It's surely more efficient and reliable to put them trackside rather than under trains.

 

[JamesRowden]

OHLE schemes have always gone way over budget. The WCML in the early 1960s did when only the north end had been done, and the scheme was paused while the government reassessed the benefits. The follow-on ECML scheme of the era was cancelled.

It would be interesting to compare actual track mile costs for installing the two, including substations; my guess having seen some 3rd rail installed at first hand (and the effort in installing 25Kv that replaced it) is that it probably comes in at about 10% of the cost of overhead. Maybe less.

Typically on a conversion all the track circuits would need to be changed as well. The ones immunised against DC would need changing if AC was installed. In the conversion interim they would need to be immunised against both, which is always a considerable technical expense, as the few places where both systems are present bear witness to.

Did I read that the clever guys who devised the Paisley Canal electrification a few years ago as a bargain basement job were subsequently marginalised for doing this on other schemes by established vested interests.

The Kent Route Study Technical Appendix gave the following estimates for electrifying Ore-Ashford (Marshlink):

• Third Rail: 100M-250M
• Overhead Line: 250M-500M

The Wessex Route Study (when considering options for Reading-Redhill (North Downs)) showed that Third Rail gives significantly higher acceleration compared to diesel, and that Overhead is significantly better for acceleration than Third Rail.

A hypothetical all stations service between Reading and Gatwick would take:

• Diesel (165): 100.5m
• Third Rail (450) 93.5m
• Overhead (350): 89m

The existing semi-fast services:

• Diesel (165): 72.5m
• Third Rail (450): 70m
• Overhead (350): 67.5m

So converting lines from third rail to overhead may allow higher top speeds on 2 track railways since time lost by a local service stopping will be less.

 

[swt_passenger]

Yeah, I wasn’t sure if the proposal was for speed increase Salisbury southward, or just to electrify it (fleet of dual voltage at Salisbury for Salisbury terminators and Romsey 6 services)

Would the freight companies be amenable to going the long way round if it meant not getting looped and avoiding Southampton? The electrification to Reading would then be ready for the electric spine....who is that laughing at the back?!

I think in the Wessex route study freight on the usual route is almost maxed out, so new freight paths would have to go via Andover, ie it wouldn’t be an either/or decision. I suspect freight would eventually limit speeds on both routes.