My proposal to get rid of 3rd rail and convert routes to overhead lines

[mr_jrt]

What do you do with a large concrete block though ?

Install it at the DfT as the most competent minster the place has seen in many years?

 

[HST43257]

What about most of the completely unelectrified lines (north and south) get OHLE then we look at costs and see if 3rd rail is worth it

 

[D365]

What about most of the completely unelectrified lines (north and south) get OHLE then we look at costs and see if 3rd rail is worth it

The two don’t have to be mutually exclusive.

 

[The Ham]

The two don’t have to be mutually exclusive.

Indeed, if it were found that to replace life expired 3rd rail was cheaper to convert to OHLE would it still be better to keep it as 3rd rail just so that is didn't look like the South was getting investment; even if that means less electrification for everywhere else?

 

[HST43257]

The two don’t have to be mutually exclusive.

Of course, but I personally feel a high quality nationwide OHLE system would be more efficient and safer as well.

 

[Gareth]

I'm not convinced Merseyrail, a pretty much standalone metro system, needs to go through the cost and disruption of converting to 25Kv AC OHLE for the sake of national conformity.

The old Southern region is a bit more nuanced, perhaps. But it should be remembered that much of that system is metro and outer suburban services into London. The South West Railway part would probably benefit the most from conversion due to the longer distances and the eventual wiring of the Wessex Mainline at some point. It may also be worth looking at the southern parts of Thameslink or where HS1 services run on classic sections. Even then, probably only when the existing third rail is up for renewal. We certainly shouldn't be just ripping out perfectly fine third rail for the sake of uniformity.

 

[paul1609]

The answer for Ashford - Ore is far more likely to be battery than anything else. The 171s are 17 years old so probably have another 10 years life in them, in which time hybrid / battery will have progressed still further and that saves the whole question of putting down 3rd rail and arranging the power supplies.

Appledore - Lydd is another one for the National Crayon Championships.

In my opinion neither of the Southern 171 routes will be successfully be operated by battery because the electrical power would have to be drawn from the existing third rail either side. The power drawn would still be limited to the maximum of the dc system.
In the case of the Uckfield Line you'd have a 9 car 377 coming back on to the electric at Hurst Green with nearly exhausted batteries and needing to draw maximum current optimised between traction and battery charging all the way to London Bridge and most of the way back to Hurst Green for the next trip. Im pretty much sure that the current electrification won't power a 20 min interval of this without a major upgrade.
Marshlink doesn't have those sort of frequencies but some of the Rye Shuttles diagrams in the peak currently require 80 miles off the juice with only 10 min intervals at Ashford to recharge.
Better to just get on with the electrification ac for marshlink and dc for Uckfield in my opinion.

 

[Bald Rick]

In the case of the Uckfield Line you'd have a 9 car 377 coming back on to the electric at Hurst Green with nearly exhausted batteries and needing to draw maximum current optimised between traction and battery charging all the way to London Bridge and most of the way back to Hurst Green for the next trip. Im pretty much sure that the current electrification won't power a 20 min interval of this without a major upgrade.

It would be a 12 car 377 battery hybrid (or equivalent).

The batteries wouldn’t be exhausted arriving at Hurst Green.

It’s not a 20 minute interval.

The current electrification power supply wouldn’t need a major upgrade. Bear in mind that the line from South Croydon to London Bridge can cope with (approximately) 18 x 12 car and 12 x 10 car trains an hour. One more 12 car drawing power is almost noise in the system, although it does need modelling.

If battery trains are employed to Uckfield (and I hope they are) it’s likely that there would be charging at Uckfield itself from a system that energises only when the train is present, and probably from local energy storage. It’s also possible that the third rail is extended down the branch from Hurst Green a little, as far a the voltage drop allows, to enable acceleration from Hurst Green southbound off the juice and a slightly earlier recharge on the way back.

 

[mr_jrt]

I'm not convinced Merseyrail, a pretty much standalone metro system, needs to go through the cost and disruption of converting to 25Kv AC OHLE for the sake of national conformity.

Merseyrail will always be a bit of a problem, much like the London Underground, due to the core tunnel sections. They're surely never going to be big enough for OHLE, so the big gain of being able to have plain vanilla AC trains won't be a thing - they would always have to remain dual voltage.
Still, might simplify sections where they run alongside AC lines, is much safer for the above ground sections, and makes extensions over the rest of the network a bit easier, if desired.

The old Southern region is a bit more nuanced, perhaps. But it should be remembered that much of that system is metro and outer suburban services into London. The South West Railway part would probably benefit the most from conversion due to the longer distances and the eventual wiring of the Wessex Mainline at some point. It may also be worth looking at the southern parts of Thameslink or where HS1 services run on classic sections. Even then, probably only when the existing third rail is up for renewal. We certainly shouldn't be just ripping out perfectly fine third rail for the sake of uniformity.

Problem of course being that you don't want to be purely limiting yourself to just where the renewals are due otherwise the trains will be hopping back and forth between DC and AC - you'll wear out the motors in the pans. So there would have to be an element of asset recovery and reuse from the extremities for renewals of the middle routes. You wouldn't want to use half-worn stuff in the bits that would be converted last - you'd just be doubling the eventual renewals work required...but the mid sections of the routes, the bits that are likely to be able to hold on until they are candidates for conversion themselves, those are where you could use the stuff safely.

Uniformity isn't in itself the end goal, but it is the means to an end.

 

[paul1609]

It would be a 12 car 377 battery hybrid (or equivalent).

The batteries wouldn’t be exhausted arriving at Hurst Green.

It’s not a 20 minute interval.

The current electrification power supply wouldn’t need a major upgrade. Bear in mind that the line from South Croydon to London Bridge can cope with (approximately) 18 x 12 car and 12 x 10 car trains an hour. One more 12 car drawing power is almost noise in the system, although it does need modelling.

If battery trains are employed to Uckfield (and I hope they are) it’s likely that there would be charging at Uckfield itself from a system that energises only when the train is present, and probably from local energy storage. It’s also possible that the third rail is extended down the branch from Hurst Green a little, as far a the voltage drop allows, to enable acceleration from Hurst Green southbound off the juice and a slightly earlier recharge on the way back.

Sighs,
Currently the 171s run on the Uckfield Line on a 3 hour cycle.Departing at XX.07 from London Bridge, leaving the dc network at Hurst Green at XX39 and arriving at Uckfield at XX+1 22, they then have an 11 min turnaround before heading back to London at XX+1 33 passing back on to the dc network at XX+2 16 and arriving at London Bridge at XX+53 before enjoying a t 20 min turnaround and restarting the cycle.
So with the current rolling stock they spend 54% of running time away from the dc network.
London Bridge to Uckfield is 45m 78ch, Hurst Green Junction is at 21 m 23 chains so currently 46.5 % of the route by mileage is electrified.
Hurst Green to Hurst Green is 49.5 miles in a relatively heavy 1990s EMU operating a 70 mph frequently stopping service.

The 11 min turnaround at Uckfield cant be extended without infrastructure improvements because of the need to pass the following service. Indeed for a reliable service the 11 min turnaround at Uckfield has to be sacrificed in the event of a delayed down service. So a fast charge at Uckfield is pie in the sky.
In the winter the high auxiliary load and reduced battery performance will ensure that the battery 377 indeed arrives back at Hurst Green with almost flat batteries.

A battery 377 on the dc on this cycle will not just be another 12 coach train, it will need to be a 12 coach train drawing more or less maximum current continuously all the way from Hurst Green to London Bridge and part of the way back if its is to achieve enough charge to get to Uckfield and back a second time.

Im no expert at dc mapping but considering the fiasco encountered at the introduction of the Electrostars I wouldn't mind betting that at least the South Croydon to Hurst Green section is going to need serious upgrading to accommodate the Batteryostars.

Hopefully somebody will see some sense and the whole thing will be filed under "Potty Ideas"

 

[Bald Rick]

Sighs,
Currently the 171s run on the Uckfield Line on a 3 hour cycle.Departing at XX.07 from London Bridge, leaving the dc network at Hurst Green at XX39 and arriving at Uckfield at XX+1 22, they then have an 11 min turnaround before heading back to London at XX+1 33 passing back on to the dc network at XX+2 16 and arriving at London Bridge at XX+53 before enjoying a t 20 min turnaround and restarting the cycle.
So with the current rolling stock they spend 54% of running time away from the dc network.
London Bridge to Uckfield is 45m 78ch, Hurst Green Junction is at 21 m 23 chains so currently 46.5 % of the route by mileage is electrified.
Hurst Green to Hurst Green is 49.5 miles in a relatively heavy 1990s EMU operating a 70 mph frequently stopping service.

The 11 min turnaround at Uckfield cant be extended without infrastructure improvements because of the need to pass the following service. Indeed for a reliable service the 11 min turnaround at Uckfield has to be sacrificed in the event of a delayed down service. So a fast charge at Uckfield is pie in the sky.
In the winter the high auxiliary load and reduced battery performance will ensure that the battery 377 indeed arrives back at Hurst Green with almost flat batteries.

A battery 377 on the dc on this cycle will not just be another 12 coach train, it will need to be a 12 coach train drawing more or less maximum current continuously all the way from Hurst Green to London Bridge and part of the way back if its is to achieve enough charge to get to Uckfield and back a second time.

Im no expert at dc mapping but considering the fiasco encountered at the introduction of the Electrostars I wouldn't mind betting that at least the South Croydon to Hurst Green section is going to need serious upgrading to accommodate the Batteryostars.

Hopefully somebody will see some sense and the whole thing will be filed under "Potty Ideas"

A few things.

Firstly, such a battery train would not be at full power the whole journey off the juice. Far from it. Which means that when recharging, it doesn’t need to do so at full power the whole time either (far from it).

Secondly being electric, it will be a little quicker to and from Uckfield, perhaps only a minute or two given the single line constraints, but that would be enough to extend the turnaround a little. And that would be very worthwhile, noting that as you say sometimes for quicker turnarounds the opportunity may be less. Even more so if the charging section at Uckfield can be used to get the train up to speed away from the station (on a ‘live when train in section’ principle). 15 mins recharging would almost fully charge the battery given the energy expended getting there.

Thirdly, a short (say 1km) extension of the third rail from Hurst Green would, I’m sure, be permitted, and very cheap as you wouldn’t need another substation. This would be enough to get the train up to speed away from Hurst Green without using the battery, and also shortens the off juice section. It’s the acceleration that drains the battery the most.

All told, this would reduce the off juice times to less than 50% of the cycle. And if battery capacity is an issue, insert a bigger battery! As mentioned elsewhere, trains with a bigger range than needed here are on the market, with still larger ranges on the way.

 

[paul1609]

A few things.

Firstly, such a battery train would not be at full power the whole journey off the juice. Far from it. Which means that when recharging, it doesn’t need to do so at full power the whole time either (far from it).

Secondly being electric, it will be a little quicker to and from Uckfield, perhaps only a minute or two given the single line constraints, but that would be enough to extend the turnaround a little. And that would be very worthwhile, noting that as you say sometimes for quicker turnarounds the opportunity may be less. Even more so if the charging section at Uckfield can be used to get the train up to speed away from the station (on a ‘live when train in section’ principle). 15 mins recharging would almost fully charge the battery given the energy expended getting there.

Thirdly, a short (say 1km) extension of the third rail from Hurst Green would, I’m sure, be permitted, and very cheap as you wouldn’t need another substation. This would be enough to get the train up to speed away from Hurst Green without using the battery, and also shortens the off juice section. It’s the acceleration that drains the battery the most.

All told, this would reduce the off juice times to less than 50% of the cycle. And if battery capacity is an issue, insert a bigger battery! As mentioned elsewhere, trains with a bigger range than needed here are on the market, with still larger ranges on the way.

Firstly, stating the obvious
Secondly, on the peak service you are looking at a time reduction between the end of the double track section north of Buxted and Uckfield at the most its a few seconds. On the hourly interval service you are looking at the time saving from acceleration from Hever to Uckfield at the most 30 secs.
Thirdly, an extension of 1 km at Hurst Green and a 1Km section at Uckfield would increase the electrified by route mileage to a tadge under 49%. I cant see within the normal Southern region capacities how you could possibly accelerate a 12 car train from rest and fast charge the batteries at the same time.
Where are the trains proven (even in prototype) to be able to charge in such a cycle from a 750 v dc system on the market? Id suggest there are exactly none.
I'd further suggest that introducing such theoretical trains to a route that interacts with the Thameslink system for 10 miles or 21 miles (East Croydon or Hurst Green) to such an extent is a folly that is exponential to even such recent Network Rail Project triumphs such as Great Western Electrification .

 

[Bald Rick]

Secondly, on the peak service you are looking at a time reduction between the end of the double track section north of Buxted and Uckfield at the most its a few seconds. On the hourly interval service you are looking at the time saving from acceleration from Hever to Uckfield at the most 30 secs.

It could conceivably be 30 seconds a stop.

I cant see within the normal Southern region capacities how you could possibly accelerate a 12 car train from rest and fast charge the batteries at the same time.

You couldn’t. That’s not the point. The point is that by accelerating off the juice you are not calling on the battery.

Where are the trains proven (even in prototype) to be able to charge in such a cycle from a 750 v dc system on the market? Id suggest there are exactly none.

There aren’t any. But they have been looked into, at least twice, and Vivarail have developed the concept. But if we waited before having proven technology in service before adopting it, we’d still be walking everywhere barefoot.

 

[markymark2000]

The issue is that in many cases, you are looking at an all or nothing type thing and you would have huge blockades while whole areas got switched over. You can't do many sections in smaller segments because the services interwork or has a very busy section which is served by trains on other routes.
For this, i'll use Merseyrail as an example and putting infrastructure issues aside. IF you change the Ellesmere Port line, you have to change the Chester line. You then need to do the Liverpool loop. West Kirkby and New Brighton then at the same time as the lines all link up. There's a similar situation on the 'Northern' line but both Northern and Wirral lines need doing together because stock changes via the Stock Exchange Line as stock moves each night between the two.


The compromise for this is smaller changeovers like branch lines with standalone services or services which are already served by OHLE/3rd rail trains. This is doable but it presents an issue where you would need a huge amount of Bimodes as trains would need to get onto the main lines for storage or some through services.
Southern Electrics networks for example you also have quite a few lines which could be changed to OHLE as they are or could be ran with bi modes but then you have an issue where non bimodes are restricted on where they can go at times of disruption and you will have situations where trains then frequently switch between modes which can't be good for the train changing to OHLE/3rd rail every 10-15 minutes. An example of this could be Catford. Thameslink have Bimodes so that is all fine. The issue comes with 3rd rail from Orpington to Shortlands, OHLE to Nunhead and then 3rd rail to City Thameslink. Sheerness branch could be made OHLE but you then need Bimodes to get the units to the depot and for the commuter trips to London. Bromley North similarly.

Theres only a few sections which does make sense/would be possible to do overhead lines without causing operational issues so the only possible issues would be infrastructure wise.
1. Extending overhead lines from Willesden Junction to Clapham Junction since it would have zero effect on normal operations (Overground services to Clapham would have no need for 3rd rail capabilities and Southern WCML service it would just reduce the amount of 3rd rail it uses.
2. Extending Thameslink overhead lines from City Thameslink to certainly Blackfriars but maybe to Herne Hill (3rd rail kept into Blackfriars though for trains from London Bridge)
3. Watford DC lines from Harrow and Wealdstone to Watford Junction. Possibly Euston to Queens Road as well. This would need some bimode units though for this to happen. Potential engineering benefit as then you aren't dealing with 2 systems around Watford but operational inconvenience short term while bimodes are found.

 

[Bald Rick]

1. Extending overhead lines from Willesden Junction to Clapham Junction since it would have zero effect on normal operations (Overground services to Clapham would have no need for 3rd rail capabilities and Southern WCML service it would just reduce the amount of 3rd rail it uses.

Apart from the Clapham to Sheperds Bush shuttles, which are D.C. only.

2. Extending Thameslink overhead lines from City Thameslink to certainly Blackfriars but maybe to Herne Hill (3rd rail kept into Blackfriars though for trains from London Bridge)

That brings the rather significant problem of signalling immunisation and earthing arrangements for all the lines to Charing Cross and possibly Victoria. A colleague was only half joking when he once said the AC could go no further south than City Thameslink lest we “end up earthing the whole of the Southern Region”

3. Watford DC lines from Harrow and Wealdstone to Watford Junction. Possibly Euston to Queens Road as well. This would need some bimode units though for this to happen. Potential engineering benefit as then you aren't dealing with 2 systems around Watford but operational inconvenience short term while bimodes are found.

Assuming you mean dual voltage (rather than bi mode), the D.C. lines already run with dual voltage units and have done for about 35 years. The engineering benefit you suggest is essentially negligible.

 

[markymark2000]

Apart from the Clapham to Sheperds Bush shuttles, which are D.C. only.

Ahh, I didn't know that. There aren't many of them trips are there in the normal (like Dec 2019 or May 2021 when things were/are more normal). Does Southern have enough dual voltage trains to cover that shuttle if it was changed?

That brings the rather significant problem of signalling immunisation and earthing arrangements for all the lines to Charing Cross and possibly Victoria. A colleague was only half joking when he once said the AC could go no further south than City Thameslink lest we “end up earthing the whole of the Southern Region”

Can you expand further on that in simpler terms? Is it possible to do but it would be extremely complex? Is this one example where operationally it may be of benefit but from an engineering side, it would be a non starter for some of the reasons you mention?

Assuming you mean dual voltage (rather than bi mode), the D.C. lines already run with dual voltage units and have done for about 35 years. The engineering benefit you suggest is essentially negligible.

That's the phrase I have been looking for. Thank you.
I did think the engineering benefit would be small but a benefit nevertheless. Not worth the investment on it's own but it's one of the few areas where modes could be changed (stock dependant)

 

[mr_jrt]

The central areas you've listed would certainly be the last areas you would convert - the extremities make more sense as starting points. If anything whatsoever ends up getting converted at all, it's most likely to be Basingstoke to Southampton. Southampton to Weymouth as a follow-on maybe makes sense as a follow-up to reduce the number of changeovers. I'm not sure when that section is next up for renewal, but IIRC it was a reasonably modern installation so it could provide a good stock of reasonably modern components to be reused elsewhere (i.e. the North Downs, and/or Uckfield).

I doubt it'd be done in a continual sequence, but I'd imagine an eventual programme would look a bit like working along the coastway line towards Brighton, minimising changeovers, i.e. Southampton to Havant & the Portsmouth branch, with changeovers at Havant. Then from Havant to Barnham & the Bognor branch. Then things get complicated as there are non-stop services between Barnham and Horsham, so unless you plan for changeovers on the move, you'll have to either introduce stops somewhere in the Arun Valley or wire up all the way to Horsham when you do the Littlehampton area of Barnham to Worthing. Worthing to Hove is simple enough, then that's the West Coastway essentially done until you're ready to deal with the Brighton mainline itself, and at all times you have at most one changeover point in play for a given service. A similar sequence can be concocted for the East Coastway working along from Ashford to Brighton.

 

[markymark2000]

The central areas you've listed would certainly be the last areas you would convert - the extremities make more sense as starting points. If anything whatsoever ends up getting converted at all, it's most likely to be Basingstoke to Southampton. Southampton to Weymouth as a follow-on maybe makes sense as a follow-up to reduce the number of changeovers. I'm not sure when that section is next up for renewal, but IIRC it was a reasonably modern installation so it could provide a good stock of reasonably modern components to be reused elsewhere (i.e. the North Downs, and/or Uckfield).

I doubt it'd be done in a continual sequence, but I'd imagine an eventual programme would look a bit like working along the coastway line towards Brighton, minimising changeovers, i.e. Southampton to Havant & the Portsmouth branch, with changeovers at Havant. Then from Havant to Barnham & the Bognor branch. Then things get complicated as there are non-stop services between Barnham and Horsham, so unless you plan for changeovers on the move, you'll have to either introduce stops somewhere in the Arun Valley or wire up all the way to Horsham when you do the Littlehampton area of Barnham to Worthing. Worthing to Hove is simple enough, then that's the West Coastway essentially done until you're ready to deal with the Brighton mainline itself, and at all times you have at most one changeover point in play for a given service. A similar sequence can be concocted for the East Coastway working along from Ashford to Brighton.

Basingstoke to Southampton doesn't make much sense without Didcot - Birmingham electrification as you would have no use for freight and it would mean a lot of new dual voltage trains needed because of the amount of trains on different services which travel through that section. Weymouth to Southampton would make more sense from the perspective that less services would need to be forced into dual voltage.

If you wanted to start in isolated random areas, you would be looking Alton to Ascot and Guildford (covering a whole service and only Alton to Waterloo needs bimodes), Bromley North/Grove Park shuttle (perhaps battery and AC traction so the battery can take the train to the depot), Sheerness to Sittingbourne branch (difficulties surrounding the commuter runs though and getting back to the depot). Ideally, when you set up overhead lines to replace 3rd rail, it will be where dual voltage trains already run or have the services AC only to try and minimise the amount of new dual voltage trains needed.

 

[Bald Rick]

Can you expand further on that in simpler terms? Is it possible to do but it would be extremely complex? Is this one example where operationally it may be of benefit but from an engineering side, it would be a non starter for some of the reasons you mention?

It’s a complex subject and I am by no means an expert. But in simple terms all electrical circuits have to be complete, and for trains that means the return current must flow from the train back to the substation. In both AC and D.C. systems this is done via the rails, which for AC systems is usually ‘helped’ up to a return conductor that runs outside the masts. In AC systems the return current path is earthed and is effectively at 0V. In D.C. systems the return current is larger (because of the lower voltage) and must be kept isolated from Earth to prevent issues with surrounding equipment etc. This is done by having the return current path (rails and return cables) completely insulated from early. The return current is therefore slightly above 0V.

Where you mix systems, a D.C. return current will look for the easiest path, and if there is an earthed AC return current path it will head that way which has the potential to damage the AC equipment and plenty of other things around it. This isn’t an issue where the D.C. system is relatively lightly used (Euston for example), but would be a massive problem if there was an AC path connected to a piece of D.C. railway that has a high intensity of operation.

 

[mr_jrt]

Basingstoke to Southampton doesn't make much sense without Didcot - Birmingham electrification as you would have no use for freight and it would mean a lot of new dual voltage trains needed because of the amount of trains on different services which travel through that section. Weymouth to Southampton would make more sense from the perspective that less services would need to be forced into dual voltage.

IIRC AC can deliver more power than DC, so it makes more sense on busier routes like Basingstoke to Southampton, quite aside from the freight aspect. That's the reason EMUs are limited on the DC network to reduce current draw, so you can't get their full performace out of them, not to mention having to have less units in use. As for the freight aspect, you have to start somewhere - a big bang all at once isn't going to happen, so you have to nibble off bits where you can. Hopefully sense will prevail and EWR gets wires from the outset and then the Oxford wiring that is progressing will give a AC route from Southampton all the way to the WCML and MML sooner rather than later.

If you wanted to start in isolated random areas, you would be looking Alton to Ascot and Guildford (covering a whole service and only Alton to Waterloo needs bimodes), Bromley North/Grove Park shuttle (perhaps battery and AC traction so the battery can take the train to the depot), Sheerness to Sittingbourne branch (difficulties surrounding the commuter runs though and getting back to the depot). Ideally, when you set up overhead lines to replace 3rd rail, it will be where dual voltage trains already run or have the services AC only to try and minimise the amount of new dual voltage trains needed.

The last thing you want is to start doing random bits here and there. For one thing, where is the power supply going to come from? In a large network those branches would likely be fed from the mainline, but if those aren't being done then where does the AC power come from?

 

[paul1609]

It could conceivably be 30 seconds a stop.

No it couldn't lets be realistic. The acceleration to stopping service line speeds Class 171 v Batterystar would be negligible. That even assumes that full power is available on battery. On the coastway between Hastings and Eastbourne Southern/ Network Rail time a 377 exactly the same as a 171 on a similar stopping service.

You couldn’t. That’s not the point. The point is that by accelerating off the juice you are not calling on the battery.

I understand that but at Hurst Green a 12 car 377 will have accelerated to a maximum of 40 mph ish before the front unit runs out of conductor rail because the driver has to wait for the back coach to clear the junction speed limit before opening up.
The benefit of the conductor rail extension would be pretty marginal. Its probably more useful to stop a battery star fouling the junction when its run out of charge.

There aren’t any. But they have been looked into, at least twice, and Vivarail have developed the concept. But if we waited before having proven technology in service before adopting it, we’d still be walking everywhere barefoot.

Where exactly are these studies? The 379 battery pr stunt that was just a development on ac and would have been a total failure in public service?
Or are you suggesting that we are going to have ex London Underground Units running down the fast lines of the Brighton Main Line between 8tph of Thameslink?

You really need to do a credibility check on the projects you are advocating.

 

[Thebaz]

I wonder about the comparative costs of converting some 377s to battery (let's say we'd need 10 minimum, 12-15 to provide some redundancy) versus purchasing or leasing the same number of new units (with more battery range) versus DC electrification the rest of the Hurst Green-Uckfield/Ore-Ashford branches? That isn't a trick or sarcastic question, I'm genuinely interested to know.

And on that, while it might potentially be permissible to extend the juice rail a few hundred meters beyond Hurst Green towards Uckfield, and then having juice rail at Uckfield for charging purposes, you surely might as well just fill in the rest. Despite the current assumption against installing more 3rd rail, there is plenty of precedent for it still happening in much larger chunks than those just mentioned. The oft-quoted main reason for not doing any more 3rd rail - Health & Safety - is surely just the same for 1 metre of juice rail as it is for 21 miles, and just as negligible as a percentage of coverage over the entire DC network?

Anyway I would not be surprised if the southern DC network is never converted to AC such is the extent and such would be the cost of conversion. It seems very much like a luxury to me and I am sure that there will always be other more worthy infrastructure projects on which to embark.

 

[markymark2000]

It’s a complex subject and I am by no means an expert. But in simple terms all electrical circuits have to be complete, and for trains that means the return current must flow from the train back to the substation. In both AC and D.C. systems this is done via the rails, which for AC systems is usually ‘helped’ up to a return conductor that runs outside the masts. In AC systems the return current path is earthed and is effectively at 0V. In D.C. systems the return current is larger (because of the lower voltage) and must be kept isolated from Earth to prevent issues with surrounding equipment etc. This is done by having the return current path (rails and return cables) completely insulated from early. The return current is therefore slightly above 0V.

Where you mix systems, a D.C. return current will look for the easiest path, and if there is an earthed AC return current path it will head that way which has the potential to damage the AC equipment and plenty of other things around it. This isn’t an issue where the D.C. system is relatively lightly used (Euston for example), but would be a massive problem if there was an AC path connected to a piece of D.C. railway that has a high intensity of operation.

Shouldn't this all be an issue then at Acton as the Overground is quite a high intensity service similarly at Farringdon/City Thameslink as Thameslink is certainly a high intensity? The only alternative would be switching on the move wouldn't it and make the power change on the curve down to London Bridge (The curve is only used then by trains which have to switch) as Blackfriars to Herne Hill shouldn't have an issue really (based on the day AC goes live, DC shuts off).

IIRC AC can deliver more power than DC, so it makes more sense on busier routes like Basingstoke to Southampton, quite aside from the freight aspect. That's the reason EMUs are limited on the DC network to reduce current draw, so you can't get their full performace out of them, not to mention having to have less units in use. As for the freight aspect, you have to start somewhere - a big bang all at once isn't going to happen, so you have to nibble off bits where you can. Hopefully sense will prevail and EWR gets wires from the outset and then the Oxford wiring that is progressing will give a AC route from Southampton all the way to the WCML and MML sooner rather than later.

Makes sense from that perspective but doesn't from the other side that you would need a lot of dual voltage units due to the amount of trains which go through the section so in addition to the cost of changing DC to AC, you need a lot of dual voltage units which is costly. Starting further away or in random areas, you have the advantage of needing less dual voltage and as the network then expands, you expand the network, some dual voltage services to AC only and the dual voltage trains them move up the track onto the next section which helps reduce the overall costs. Thats why I think if anything, I would push for it to be an area which is already ran with bimodes (so the cost is only changing 3rd rail to overhead lines) or it should be done in an area where as few trains as possible need switching to dual voltage simply on a cost basis.

 

[swt_passenger]

Shouldn't this all be an issue then at Acton as the Overground is quite a high intensity service similarly at Farringdon/City Thameslink as Thameslink is certainly a high intensity? The only alternative would be switching on the move wouldn't it and make the power change on the curve down to London Bridge (The curve is only used then by trains which have to switch) as Blackfriars to Herne Hill shouldn't have an issue really (based on the day AC goes live, DC shuts off).

Farringdon to City Thameslink already has a very complicated, very expensive dual electrification corridor that is designed specifically for both changing mode at either of the two stations, and for changing mode on the move if necessary. The switching systems effectively alter the track connections and traction return paths to suit DC or AC modes on the fly as a train progresses through, under control of the signalling system.

As has been covered before however, it is apparently far too complex a system to scale it up to much wider areas, it‘s complex enough on what is basically about a mile of two track railway.

 

[mr_jrt]

Makes sense from that perspective but doesn't from the other side that you would need a lot of dual voltage units due to the amount of trains which go through the section so in addition to the cost of changing DC to AC, you need a lot of dual voltage units which is costly. Starting further away or in random areas, you have the advantage of needing less dual voltage and as the network then expands, you expand the network, some dual voltage services to AC only and the dual voltage trains them move up the track onto the next section which helps reduce the overall costs. Thats why I think if anything, I would push for it to be an area which is already ran with bimodes (so the cost is only changing 3rd rail to overhead lines) or it should be done in an area where as few trains as possible need switching to dual voltage simply on a cost basis.

Aren't pretty much all units in use already dual voltage, abet with a block of concrete pretending to be the transformer and no pans. So yes, there's a cost of fitting those missing bits, but can't be too much damage, relatively speaking. There are still a few old DC-only units about on these routes though (i.e. the refurbished 442s), but presumably they'll be long gone by the time anything like this would actually be in a position to switch over.

 

[Bald Rick]

I’ll preface this by saying I’m being deliberately slightly provocative, as through every study into battery trains there are a whole host of people lined up saying “it can’t be done”, but when really pushed they struggle to justify that position. In particular rolling stock engineers. One actually said to me “we don’t want a sub fleet of battery trains, as it means different maintenance regimes and allocation”. I asked what different regime it would mean. He didn’t know. I then asked what the different regime was for the 171s. He knew that alright, and liked the units as they “were something different, and means we get to play with engines”.

Where exactly are these studies?

Ahh. Well I can’t say. Not in the public domain. One some years ago which set out the principles, another much more recently for a rolling stock owner which dealt with the detail. But they were VERY interesting reading.

No it couldn't lets be realistic. The acceleration to stopping service line speeds Class 171 v Batterystar would be negligible. That even assumes that full power is available on battery. On the coastway between Hastings and Eastbourne Southern/ Network Rail time a 377 exactly the same as a 171 on a similar stopping service.

Have a closer look at the working timetable. Plenty of start-stop times are quicker on electric than diesel. Hurst Green - Oxted, Hampden Pk - Pevensey, Collington - Bexhill, St Leonard’s - Hastings. All 30sec quicker on the juice. The same would apply at some locations towards Uckfield. (The study modelling showed that)

I understand that but at Hurst Green a 12 car 377 will have accelerated to a maximum of 40 mph ish before the front unit runs out of conductor rail because the driver has to wait for the back coach to clear the junction speed limit before opening up.

The junction at Hurst Green is 50 mph, almost 200 metres from the station. The front of a 377 can be doing about 35-40 mph through the junction, leaving the next (say) 1000m on the juice to get to 70. Easily doable. The principle of this short extension would be to make it long enough to get it up to speed - it might not need to be 1000m. The key point though is that being a short extension immediately adjacent to an area where con rail exists, the additional safety risk is demonstrably negligible, and you don’t need any extra distribution equipment - it is therefore very cheap. (Unlike con rail the whole way, which will be very expensive).

The key issue in all of this - as you rightly identify - is the power supply capacity to enable the recharging train to draw a higher current from Hurst Green - S Croydon. However, if the Uckfield line was electrified that would be an issue anyway. North of South Croydon it is fine.

== Doublepost prevention - post automatically merged: 19 Oct 2020 ==

Shouldn't this all be an issue then at Acton as the Overground is quite a high intensity service similarly at Farringdon/City Thameslink as Thameslink is certainly a high intensity?

As @swt_passenger correctly says, the arrangements for Thameslink are very complex, were very expensive, and come with a high maintenance cost. It also, occasionally, causes performance issues indirectly.

The issue at Acton Central is slightly different. Firstly the return currents are about 90% less than at City TL / Farringdon, as it’s about a quarter of the service with trains drawing rather less than half the power. Nevertheless it is still an issue - most of the OLE foundations suffered electrolytic corrosion within a decade of their installation. The Masts were all replaced in 2004 - I put some of the foundations in myself - and some clever electrical stuff added to the return bonding to help reduce the effects in future.

 

[markymark2000]

As @swt_passenger correctly says, the arrangements for Thameslink are very complex, were very expensive, and come with a high maintenance cost. It also, occasionally, causes performance issues indirectly.

The issue at Acton Central is slightly different. Firstly the return currents are about 90% less than at City TL / Farringdon, as it’s about a quarter of the service with trains drawing rather less than half the power. Nevertheless it is still an issue - most of the OLE foundations suffered electrolytic corrosion within a decade of their installation. The Masts were all replaced in 2004 - I put some of the foundations in myself - and some clever electrical stuff added to the return bonding to help reduce the effects in future.

Is a way around that to make it so that only Blackfriars has the changeover and it isn't a long section between the stations (So it's the same as most other OHLE installations with just 1 station and everything changes over there) or would that have the same complications?

I'm not disputing what you say by the way, I am just interested into why it can't be done as its just strange that it causes so many issues.

 

[Bald Rick]

Is a way around that to make it so that only Blackfriars has the changeover and it isn't a long section between the stations (So it's the same as most other OHLE installations with just 1 station and everything changes over there) or would that have the same complications?

I'm not disputing what you say by the way, I am just interested into why it can't be done as its just strange that it causes so many issues.

You want the changeover as close to the substation as possible (to reduce DC return current resistance) which is right next to the northbound platform at City TL. You also want to have crossovers that enables a train that fails to changeover to be sent back where it came from without significant disruption. In this case that means a short overlap of systems and changing over as soon as is possible. It has all been very carefully thought through (about 15 years ago).

 

[markymark2000]

You want the changeover as close to the substation as possible (to reduce DC return current resistance) which is right next to the northbound platform at City TL. You also want to have crossovers that enables a train that fails to changeover to be sent back where it came from without significant disruption. In this case that means a short overlap of systems and changing over as soon as is possible. It has all been very carefully thought through (about 15 years ago).

Thank you for your further explanations.

 

[Nicholas Lewis]

Remember that lots of the OHLE is cheap BR electrification, you don't hear the wires on HS1 coming down much.

It wasn't cheap electrification it was designed to be cost efficient with a trade off to be as resilient as funds would afford.

The alternative was a slow progressive decline to eventual closure but what we delivered were routes that were rejuvenated through the sparks effect.