3rd Rail Infill suggestions

[Tio Terry]

How difficult would it be to arrange for a section of third rail to only become live as a train approached and passed over it?

Technically, yes possibly. Financially, very expensive!

 

[Bald Rick]

How difficult would it be to arrange for a section of third rail to only become live as a train approached and passed over it?

It needs a lot of automatic switching, and section gaps. Clearly, more of both the shorter the sections are. Definitely possible, but it builds in unreliability.

 

[swt_passenger]

How difficult would it be to arrange for a section of third rail to only become live as a train approached and passed over it?

You’d need extra parallel cabling able to carry the whole third rail current, with similar resistance to the third rail, because it effectively acts as it’s own distribution system, it’s all connected together. Then a set of high current switchgear every few hundred metres, or more frequently if your trains were short. Incredibly costly, high maintenance equipment and a heck of a lot of it.

 

[MarkyT]

How difficult would it be to arrange for a section of third rail to only become live as a train approached and passed over it?

Not difficult conceptually, but a lot of remote trackside switchgear interfaced to the signalling system would be required. Combined with moderate on-board battery provision, extra-long gaps through platforms and level crossings could mitigate trespass risk and reduce the complexity of conductor provision around junctions. Most if not all smaller footpath and private access crossings could be closed to minimise risk. Obstacle detection techniques, as used at crossings today, might be applied at potential access points around stations and remaining crossings. Unexpected incursions could thus be sensed, triggering alarms and automated isolations. At some stations, particularly terminals and other places where trains layover, sections of conductor rail could be switched on only when there's a stationary train present above it, to enable charging.

== Doublepost prevention - post automatically merged: 29 May 2021 ==

It needs a lot of automatic switching, and section gaps. Clearly, more of both the shorter the sections are. Definitely possible, but it builds in unreliability.

You’d need extra parallel cabling able to carry the whole third rail current, with similar resistance to the third rail, because it effectively acts as it’s own distribution system, it’s all connected together. Then a set of high current switchgear every few hundred metres, or more frequently if your trains were short. Incredibly costly, high maintenance equipment and a heck of a lot of it.

On the lines being discussed, the signal sections are fairly long. Assuming the whole section is switched as one, the complexity wouldn't be that great. Many of the substations would likely be just switched on or off as a whole, so the parallel conductor wouldn't be necessary in those cases.

 

[JonathanH]

You’d need extra parallel cabling able to carry the whole third rail current, with similar resistance to the third rail, because it effectively acts as it’s own distribution system, it’s all connected together. Then a set of high current switchgear every few hundred metres, or more frequently if your trains were short. Incredibly costly, high maintenance equipment and a heck of a lot of it.

I'm guessing that the system in Bordeaux used for the tramway has a technical limitation to the possible speed which wouldn't work on the UK third rail network?

https://en.wikipedia.org/wiki/Alstom_APS

Alstom APS, also known as Alimentation par Sol or Alimentation Par le Sol (which literally means "feeding via the ground"), is a form of ground-level power supply for street trams and, potentially, other vehicles. APS was developed by Innorail, a subsidiary of Spie Enertrans but was sold to Alstom when Spie was acquired by Amec. It was originally created for the Bordeaux tramway, which was constructed from 2000 and opened in 2003. From 2011, the technology has been used in a number of other cities around the world.

APS is used, primarily for aesthetic reasons, as an alternative to overhead lines. As such it competes with other ground-level power supply systems, but also with energy storage systems such as batteries. In 2015, Alstom developed a derivative of APS, Alstom SRS (Système de Recharge statique par le sol or static-based ground charging system), which can be used to recharge battery powered trams and buses whilst they are stationary at stops.

 

[swt_passenger]

I'm guessing that the system in Bordeaux used for the tramway has a technical limitation to the possible speed which wouldn't work on the UK third rail network?

https://en.wikipedia.org/wiki/Alstom_APS

Yes, and it’s been discussed in this context before quite a few times. Eg just how does it “scale up” to 240m trains drawing thousands of amps each, running a few signals apart in the Waterloo 8 track approach, or through Bermondsey with its 11 tracks. The sheer amount of high current switchgear to make sure only the section under the train is ever live would be impressive. IIRC someone worked out that for typical 4 car EMU equivalent to the tramway you’d need to divide the third rail into 40m sections. But then you’d have to place shoe gear only in the centre of the unit to prevent the shoes livening up track outside the bodywork. It all gets incredibly complex trackside.

 

[D365]

How difficult would it be to arrange for a section of third rail to only become live as a train approached and passed over it?

My feeling is (from what I’ve learned about their stance on third rail and their view on third rail-based ”fast charging”) is that this still wouldn’t be enough to satisfy the ORR.

 

[mmh]

Yes, and it’s been discussed in this context before quite a few times. Eg just how does it “scale up” to 240m trains drawing thousands of amps each, running a few signals apart in the Waterloo 8 track approach, or through Bermondsey with its 11 tracks. The sheer amount of high current switchgear to make sure only the section under the train is ever live would be impressive. IIRC someone worked out that for typical 4 car EMU equivalent to the tramway you’d need to divide the third rail into 40m sections. But then you’d have to place shoe gear only in the centre of the unit to prevent the shoes livening up track outside the bodywork. It all gets incredibly complex trackside.

Why would it ever be used in those situations? Both of the places you mention have been fully and permanently electrified for decades, are highly segregated - on viaducts - from the public and are the very opposite of places where "infill" electrification might be considered.

 

[swt_passenger]

Why would it ever be used in those situations? Both of the places you mention have been fully and permanently electrified for decades, are highly segregated - on viaducts - from the public and are the very opposite of places where "infill" electrification might be considered.

I doubt it would ever be used anywhere on a mainline network. Just explaining how the technology doesn’t scale up to mainlines at all, especially busy ones.

 

[mmh]

I doubt it would ever be used anywhere on a mainline network. Just explaining how the technology doesn’t scale up to mainlines at all, especially busy ones.

I doubt it would too. A whacking great fence seems more likely, as HS1 has and presumably HS2 will have.

 

[Tio Terry]

I doubt it would too. A whacking great fence seems more likely, as HS1 has and presumably HS2 will have.

HS1 has a double fence each side. Not sure what HS2 is doing but I guess it will be the same.

 

[AM9]

Not difficult conceptually, but a lot of remote trackside switchgear interfaced to the signalling system would be required. Combined with moderate on-board battery provision, extra-long gaps through platforms and level crossings could mitigate trespass risk and reduce the complexity of conductor provision around junctions. Most if not all smaller footpath and private access crossings could be closed to minimise risk. Obstacle detection techniques, as used at crossings today, might be applied at potential access points around stations and remaining crossings. Unexpected incursions could thus be sensed, triggering alarms and automated isolations. At some stations, particularly terminals and other places where trains layover, sections of conductor rail could be switched on only when there's a stationary train present above it, to enable charging.

== Doublepost prevention - post automatically merged: 29 May 2021 ==



On the lines being discussed, the signal sections are fairly long. Assuming the whole section is switched as one, the complexity wouldn't be that great. Many of the substations would likely be just switched on or off as a whole, so the parallel conductor wouldn't be necessary in those cases.

Add to that the additional risk of a 'part time' live rail. Once a few tresspassers get to know that the track is only live when a train is on it (supposedly), there is a tendency to normalise the risk to zero. That is dangerous because any failure of the system becomes highly lethal, and unless every 3rd rail over a large area must also be protected in the same way. Just like when OLE is turned on, to have a stretch where it was turned off for a reason, there would be some who assume that it is safe.

 

[BrianW]

Add to that the additional risk of a 'part time' live rail. Once a few tresspassers get to know that the track is only live when a train is on it (supposedly), there is a tendency to normalise the risk to zero. That is dangerous because any failure of the system becomes highly lethal, and unless every 3rd rail over a large area must also be protected in the same way. Just like when OLE is turned on, to have a stretch where it was turned off for a reason, there would be some who assume that it is safe.

That's a good observation- rather like 'I wonder if this paint's dry?'; ot if this knife's sharp.
And owners have responsibilities to trespassers as the courts have determined with burglars and with kids and guard-dogs on the loose on construction sites ...

 

[A0]

There’s a good reason at the Basingstoke end, and that is a desire to avoid earthing half the SW ‘division’ D.C. Network. It would be much cheaper to have a short stretch of third rail up the branch from Basingstoke, and OLE from there. Operationally difficult of course. I expect the engineers will have to be inventive to find a way to get the OLE into Basingstoke.

But isn't there a plan for OHL beyond Worting Junc to Salisbury and Romsey as well as part of the Electric Spine? Or is that just RF speculation?

If it is, then Basingstoke's going to become a problem that will need fixing sooner or later.

 

[RobShipway]

But isn't there a plan for OHL beyond Worting Junc to Salisbury and Romsey as well as part of the Electric Spine? Or is that just RF speculation?

If it is, then Basingstoke's going to become a problem that will need fixing sooner or later.

I am sure that there was a plan at one time, possibly only in draft form to have OHLE from Reading to Southampton port for freight trains?

 

[61653 HTAFC]

Several posters have suggested extending DC to Uckfield. Chris Green's report to Government (22nd June 2017) recommended this be done as AC largely as the major cost either way would be the connection to the National Grid, and DC needed far more substations, and land was not available. See https://www.gov.uk/government/publications/southern-rail-network-gibb-report. Is this suggestion still being actively considered?

I recall reading something to this effect years ago: that 25kvAC overhead was the preferred option for Uckfield as it would only need one grid connection and substation rather than the several that would be required for DC.

The requirement for dual-voltage units is not enough to rule this out IMO. As others have said, Southern already have more DV units than they currently need, and even the 377s that are currently DC only are capable of being converted relatively simply.

 

[Bald Rick]

But isn't there a plan for OHL beyond Worting Junc to Salisbury and Romsey as well as part of the Electric Spine? Or is that just RF speculation?

If it is, then Basingstoke's going to become a problem that will need fixing sooner or later.

No plan currently other that the Traction Decarbonisation study.

 

[RobShipway]

I recall reading something to this effect years ago: that 25kvAC overhead was the preferred option for Uckfield as it would only need one grid connection and substation rather than the several that would be required for DC.

The requirement for dual-voltage units is not enough to rule this out IMO. As others have said, Southern already have more DV units than they currently need, and even the 377s that are currently DC only are capable of being converted relatively simply.

As noted by Paul1609 to my comment about using class 377/3's with pantograph:

377/3s are dc only they don't have the transformers or switchgear fitted for ac operation. The TMS is not compatible with dual voltage. At the time of construction they were designed to be convertible to ac but all of the components have since gone out of production which means that any conversion of 20 year old units would cost more than new trains and is very unlikely.
Assuming precovid traffic levels are catered for a peak Uckfield train would require 4 x 377/3 units whilst they can operate this way on dc I dont think 4 pantographs on 1 train would be accepted without specialist overhead line equipment.

 

[BrianW]

But isn't there a plan for OHL beyond Worting Junc to Salisbury and Romsey as well as part of the Electric Spine? Or is that just RF speculation?

If it is, then Basingstoke's going to become a problem that will need fixing sooner or later.

Ah yes ... the electricless spinellessness that became a nothingness?
Did Williams-Shapps have anything to say relatedly?
Are there electrification and freight strategies coming into alignment?

 

[Bald Rick]

Are there electrification and freight strategies coming into alignment?

It’s the same team writing them, so yes!

 

[61653 HTAFC]

As noted by Paul1609 to my comment about using class 377/3's with pantograph:

377/3s are dc only they don't have the transformers or switchgear fitted for ac operation. The TMS is not compatible with dual voltage. At the time of construction they were designed to be convertible to ac but all of the components have since gone out of production which means that any conversion of 20 year old units would cost more than new trains and is very unlikely.
Assuming precovid traffic levels are catered for a peak Uckfield train would require 4 x 377/3 units whilst they can operate this way on dc I dont think 4 pantographs on 1 train would be accepted without specialist overhead line equipment.

If new-build would be more economical, then clearly that would be the preferred solution. Enthusiasts have this idea that if an EMU doesn't see 40 years of service then it's a waste, but if the numbers don't add up then it makes more sense to build new- that way you can specify a fleet that suits the environment it will operate in. If multiple pans are a problem then simply go for 4-car or 6-car units.

 

[RobShipway]

If new-build would be more economical, then clearly that would be the preferred solution. Enthusiasts have this idea that if an EMU doesn't see 40 years of service then it's a waste, but if the numbers don't add up then it makes more sense to build new- that way you can specify a fleet that suits the environment it will operate in. If multiple pans are a problem then simply go for 4-car or 6-car units.

Personally I would go for an express train version of the Alstom (Was Bombardier) Aventra that can operate on both 3rd rail, AC and is equipped with batteries that can be charged up from either power source. Those batteries should be able to do at least 300 miles away from either 3rd rail or AC OHLE power.

 

[61653 HTAFC]

Personally I would go for an express train version of the Alstom (Was Bombardier) Aventra that can operate on both 3rd rail, AC and is equipped with batteries that can be charged up from either power source. Those batteries should be able to do at least 300 miles away from either 3rd rail or AC OHLE power.

Batteries with that kind of range are some way into the future I'd have thought (though I admit I'm not necessarily up to date with where the technology is at present). Certainly fitting them within a fairly tight loading gauge (along with the transformer and all the other electrical gubbins) without sacrificing capacity would be a challenge.

Outside of a few edge-cases, I don't really see batteries as the solution for rail decarbonisation... at least until there's a huge advance in the technology to get past the current "ceiling" of range versus weight.

 

[D365]

Personally I would go for an express train version of the Alstom (Was Bombardier) Aventra that can operate on both 3rd rail, AC and is equipped with batteries that can be charged up from either power source.

The battery charging is a given, since they would be connected to the 750VDC train bus. You’re very ambitious with your projected range though..!

 

[RobShipway]

Batteries with that kind of range are some way into the future I'd have thought (though I admit I'm not necessarily up to date with where the technology is at present). Certainly fitting them within a fairly tight loading gauge (along with the transformer and all the other electrical gubbins) without sacrificing capacity would be a challenge.

Outside of a few edge-cases, I don't really see batteries as the solution for rail decarbonisation... at least until there's a huge advance in the technology to get past the current "ceiling" of range versus weight.

You need to think big and positive. There is technology now for cars to be travelling 300 plus miles on battery power and you do now start to have lorries that can be powered over the same sort of distance by batteries.

Yes, I know the weight and size of a juggernaut lorry is very different to the size and weight of a 3 - 5 coach train. But if you can power a lorry with batteries and they can be going 300 plus miles, I do not see that we should be far off with doing something similar with trains. You have TfW with their diesel-battery class 230 units, where the diesel shuts off and leaves the battery running the train into a station quietly. Vivarail also did a battery-electric version in the form of 230002. So the technology is there, it is just how it is achieved.

The battery charging is a given, since they would be connected to the 750VDC train bus. You’re very ambitious with your projected range though..!

Yep, but for many none electric routes which may never see electrification you have to provide some sort of train service but do it with thought to the environment. I am working on the basis, for routes that may start from a point of a line that has electrification, but goes on for many to the end of the line where there is either electrification of the line again or that there is a end point, but there is no space for recharging the batteries and no time between services.

Given what I have suggested, whether you would still need to infill 3rd rail on lines such as Ore - Ashford or Oxted - Uckfield, who knows. But possibly in the short term until we can get battery power on trains to be covering distances such as 200 - 300 miles, then it is something that needs to be thought about.

 

[Bald Rick]

There is no doubt that trains with battery capacity to operate Hurst Green - Oxted and return, or Ore - Ashford and return could be built, and built easily. Battery trains with a better range than this already exist, and are in use (or about to be) in Germany. A 4 coach Electrostar would ‘only’ need about 5 tonnes of battery pack, and for a D.C. only battery variant that 5 tonnes could take the place of the similar weight of AC transformer that you find in the dual voltage variants.

The issue is charging the battery in the time the unit is on the third rail without overloading the power distribution system, and whether that needs some additional charging ‘opportunity’ on the currently non electrified sections.

 

[D365]

Yep, but for many none electric routes which may never see electrification you have to provide some sort of train service but do it with thought to the environment. I am working on the basis, for routes that may start from a point of a line that has electrification, but goes on for many to the end of the line where there is either electrification of the line again or that there is a end point, but there is no space for recharging the batteries and no time between services.

Until battery technology is capable enough to power railway rolling stock for 200-300 miles between charges (with a suitable safety margin built in), charging points will be an absolute necessity.

 

[Bald Rick]

Until battery technology is capable enough to power railway rolling stock for 200-300 miles between charges (with a suitable safety margin built in), charging points will be an absolute necessity.

Why? If the unelectrified stretch is only a couple of miles long....

 

[D365]

Why? If the unelectrified stretch is only a couple of miles long....

Ah, I got a bit distracted from the point of the thread and was discussing Robbies’ dream of 300 miles range on a battery train..!

 

[RobShipway]

Why? If the unelectrified stretch is only a couple of miles long....

On some routes, the stretch may only be a couple of miles long. Other routes, say like Glasgow to Aberdeen I am guessing that that would be more than a couple of miles? It certainly more than a couple of miles between Oxted to Uckfield and Ore to Ashford. Some of the places, it is very likely that you would not be able to build a recharge point and any train if there was a recharge point may not be able to spend 2 plus hours recharging before having to head back in the direction that it came from in the first place!