‘Islands’ of third-rail electric power are being assessed for the West of England line between Basingstoke and Exeter. Network Rail and South Western Railway have been working for two years on plans to remove diesel trains on the long-distance route.
They have involved train manufacturers and rolling stock leasing companies in studies to fit battery power to either Class 450 Desiros or new Class 701 Arterio trains, able to recharge on sections of discontinuous third-rail track…
Should be read in conjunction with: https://www.newcivilengineer.com/in-depth/why-is-rail-electrification-so-slow-in-the-uk-16-10-2024/
Slightly off-topic, there is a much more immediate problem with electrification.
Namely, removing the isolated “islands” of diesel traction & units in an otherwise fully-electrified area. Removing this by running the 3rd rail, in some form between wokingham – Ash / Guildford – Reigate / Hurst Green – Uckfield / Ashford- Ore would give very considerable service benfits & a definite decrease in running costs.
Unfortunately, as repeatedly noted by Alan Williams, Ian Walmsley, other journalists & professional interested parties, there is a serious obstacle to this: The ORR.
This body seems to have set its face against 3rd-rail anywahere, under any circumstances { See also: “Headbolt Lane” } & at any price. The principle of “ALARP” as regards safety, appears to have been abandoned in favour of dogma.
It is possible, in view of the headline article in this section, that ORR are modifying their views, of course.
We will have to wait & see, I suppose.
I struggle with the concept of discontinuous electrification for several reasons:
1) The electrical supply needs to be sufficient for the whole route irrespective of the areas of discontinuity, so for the West of England line this might imply fewer but much bigger sub-stations. Also the conductor rail would need to be able to handle higher current and the shoe pick up sysem would need to be beefier to cater for simultaneous battery charging and powering the train.
2) I can see the value of discontinuous AC electrification where there are serious issues with obtaining the right electrical clearances, for example around historic bridges perhaps linked to really complex junctions. But absense of OLE either means that there needs to be an insulated cable joining the discontinuous ends or more sub stations than would normally be required. That said, the Cardiff Valley line electrification made a good case for discontinuous electrification even following Network Rail’s work to reduce clearances to an absolute minimum
3) For 3rd rail DC, the issues with electrical clearances don’t really exist. The only argument I can see for discontinuous electrification on DC lines is if extraordinary measures are required to overcome the ORR’s ‘ban’ (I know ORR doesn’t use that word!) on further 3rd rail electrification.
4) If it were me, I’d fit 3rd rail throughout except around points and crossings, and would put effort into ensuring good quality lineside fencing. Trains would have a small battery to extract trains from areas where they may become gapped. This battery would be able to move a train just a few hundred metres. This battery would be a simple one without all the hearing and cooling stuff necessary to keep long range batteries in their performance zone. Conductor rails around points and crossings with all the gaps and ramps are an added cost with little performance benefit, and the battery would make all sorts of areas easier to manage as train gapping risk would be eliminated.
Given how easy it is for, for example, Thameslink and HS1 Javelin trains to switch power between third rail and OLE, I can see the the ORR has a point.
I guess the question of locking in an area operated by a particular toc (Southeastern, Southern and SWR) into using third rail because… 1930s…. rather than lock in the advantages of OLE (faster trains, less losses etc) which will require a few new trains (from the “fat” leasing companies) to be able to operate with both system.
In the longer run having the ability to bring the benefits of overhead power to railways being dragged from diesel to electric seems to justify new trains to bring flexibility to the network as a whole.
Discontinuous electrification is better than no electrification, I suppose
@100andthirty
Every mile of conductor rail will have a price tag, plus putting the “islands” at major stations could mitigate the “charging while running” load problem. But I agree it feels like penny pinching at its most desperate.
From the article –
Brian Butterworth,
Given how easy it is for, for example, Thameslink and HS1 Javelin trains to switch power between third rail and OLE, I can see the the ORR has a point.
It might appear easy to the train operator and the passengers but I suspect an electrical engineer will tell you it is anything but easy.
@PoP
I only have A-Level physics to go by, which is as far as my electrical engineering went.
I think that I mean “it’s easy to provide and run the equipment”, I didn’t mean it was a trivial engineering matter. I can stick the various figures in a spreadsheet and waying the cost-benefits of providing AC/DC trains compared to DC/battery or diesel/DC trains seems to point to using overhead AC as a long-term solution for a railway.
It’s a bit like saying, if it were a dirt track road, upgrading it to tarmac would be better in the long term than using gravel (because it connects to other gravel paths).
I really worry that the GWR areas are going to get AC overhead power and the poor-side-of-the-tracks will be 1930s “technology”.
100andthirty,
I take the points made and I am not an engineer, let alone an electrical engineer, but surely every line needs to be taken on its own merits.
As a case in point, the one in which I am most familiar take the case of the North Downs line.
Trains generally start at Gatwick. The must be plenty of juice on the Brighton Main Line so no issue as far as Redhill.
Redhill to Reigate takes its juice from the Brighton Main Line and has done since 1933. Electric trains on this section are restricted to four carriages due to the lack of power. Proposals have been made to provide a substation at Reigate in connection with proposed (and consulted on pre-covid) changes to the station. So a decent substation here would kill two birds with one one stone. This should also enable some third rail to be laid in the direction of Betchworth.
At Deepdene where the line is unelectrified, I am fairly sure there is a substation nearby for Dorking (main) station although I can’t locate it. If so, given the lines cross, it would be a fairly simple matter to provide some third rail. Again the present substation must be underpowered because it is only possible to run an hourly service between Dorking and Horsham due to limited power (not that this line needs a more frequent service but it does mean it is not much use as a diversionary route unless one cancels the regular service). Again, an upgrade would have other benefits.
From Guildford to Reading the line is mostly shared with other services that are electrified so there is already discontinuous electrification. Furthermore, there are three electrified lines that cross it so, if necessary, there are opportunities to electrify further but, if I recall correctly, the gaps are relatively short.
To me, it seems discontinuous electrification is a here no-brainer.
We also have the Uckfield line which is only electrified as far as Hurst Green. Yet again there is a great opportunity as the line goes under the Redhill-Tonbridge line in a short tunnel. Redhill-Tonbridge suffers from an inadequate power supply because whenever they need to use it to divert Hastings trains they need to cancel the local service. So, here too, a substation and a section of third rail could be usefully used for the benefit of two lines.
Trains generally spend 11 minutes at the Uckfield terminus so a substation here with as much third rail as can be usefully laid would also assist.
Brian Butterworth,
I am fairly sure that DfT don’t allow 3rd only trains to be built. For years they have had to be ‘AC overhead ready’. That is why even 3rd rail trains have space for the pantograph on one of the carriages. At one point DfT were going to require all new electric trains to have a pantograph fitted but many experts pointed out the stupidity of carrying tons of dead weight on the roof unnecessarily.
Discontinuous electrification might seem attractive at a glance, but I think that each individual case of “hard to electrify” has to be examined both for overhead and third rail electrification.
In particular bridges and tunnels seems extra suitable for third rail electrification if overhead electrification can’t be fitted. There is usually anyway an incentive to fence off the railway good enough to keep people, wildlife and livestock away from the rail anyways.
I doubt that there are many places with switches and whatnot that can’t accommodate overhead wires, if there are any such places at all.
The more I think about this, the more I think that discontinuous electrification has a certain “gadgetbahn” aura over it, but it’s sensible enough that it’s more likely to get a go-ahead.
On the other hand, it’s better if this gets built than nothing at all. Maybe let the battery enthusiasts play with trains if we end up getting rid of some diesel trains?
@100andthirty : Re cooling and heating for the batteries: Even for a battery that can only drive the train a short bit across some switches or whatnot, I doubt that it will even cost more to use battery packs indented for electric cars (that afaik always have liquid cooling/heating) than using some sort of generic batteries without this. In particular if you intend on draining the batteries in under a minute while driving the train 100m then you likely need the best cooling possible. (Sure, you could have batteries able to drive the train for a few km but only able to use 100m at a time due to no cooling, but that’s likely more expensive). Also, batteries like the same temperatures as humans, so heating and cooling might be something that can be shared with heating and cooling of the passenger compartments.
Also afaik any reasonable battery needs heating to be charged when it’s below freezing outdoors. Lead-acid batteries can be charged at colder temperatures but afaik the cost-benefit makes those a worse choice after just a few years of usage as compared to more modern batteries.
@PoP: I only have the lowest/simplest level of electronics engineering uni studies, but I would say that switching between two electrification systems isn’t that hard.
If we look at how things were many years ago it was hard. Particularly before semiconductor rectifiers for rail vehicle usage became a thing in the 1950’s-1960’s it was really hard to switch between AC and DC, and even then you would have a transformer with many taps and a multi position switch remotely controlled from the drivers cab, that selected different voltages to the motor, while with DC electrification you would have switches that when starting used resistors in series with the motors, and then switches would connect the motors in series and/or parallel, and it was also possible to connect the rotor and stator windings in series or parallel.
Today afaik almost all trains converts AC electrification to DC at say 1-2kV or similar, and then run an inverter off of that DC that in turn generates multi phase AC for the traction motors.
To add third rail DC capabilities to that type of train, you kind of “only” have to make the inverters able to run at the voltages the third rail can supply. In particular for example the Eurostar trains has a lower power when on third rail power, which leads me to think that the same inverters driving the motors runs off a higher DC voltages when the train uses AC traction.
I would assume that standard constructions for trains use 1.5kV or 3kV as the intermediate voltage, as it’s easy to adapt those trains for running on DC electrification at those voltages (3kV common in many places, 1.5kV in the Netherlands and parts of France (and probably more places)).
There are other things to take into consideration too, like all the auxiliary systems have to be able to run on either electrification system, and the problems with electric noise due to bad contact between the train and the wire/3rd rail is a bit different with AC v.s. DC.
Side track comparison: Not surprisingly it turns out that DC electrification with modern vehicles isn’t always great re noise from bad contact / sparks. In particular both Stockholm and Gothenburg in Sweden run old school electromechanically controlled trams during certain nights to keep frost away from the overhead wires (and also it helps keeping snow away from the tracks), as the newer trams (at least A32 in Stockholm and M32 in Gothenburg, not sure about the even newer trams) struggle when there is too much frost on the wires. Can’t remember if the Stockholm Metro also uses older vehicles to remove ice/snow from the third rail or not.
I think that for some metro sytems there has at least been tests conducted with kind of just short circuiting the 3rd rail in a controlled fashion, causing lots of current to flow through it, in order to melt off ice/frost. Not sure if this is actually used, it seems a bit dangerous as any weak spots would heat up way faster than everything else. I included this as it seems relevant to know for places with lots of 3rd rail mainline electrification.
@PoP It’s not the weight of the pantograph that’s an issue on 3rd rail trains convertible to OLE operation. Not fitting it is a sensible thing to do as it’sll avoid a pantograph detriorating though non use. The weight issue is the transformer that all AC OLE trains have to have. Whilst it’s not fitted to DC only varients, they often have a large concrete block instead as ballast so that the suspension and brakes, sized for the mass of the transformer, operate correctly.
@Brian Butterworth. Last time I was a Farringdon Thameslink, the southbound train was stuck in the platform struggling with the OLE to 3rd rail switchover.
@100andthirty I can check the database but you seem to have witnessed a very unusual event.
How do you know that that was the case?
100andthirty,
Given that technology moves on, I suspect by the time they put a transformer in a converted train, it will be lighter than planned for and occupy less space. So the spare space will be taken up by another, smaller, concrete block so the suspension an brakes can continue to operate correctly!
Re transformer weight:
although technology evolves, in general a transformer has to contain enough copper and an iron core to function, and that more or less sets the weight.
The possible leap that might happen in a not too distant future is if high voltage semiconductors becomes feasible for usage in a switch mode power supply in a train. Compare with the high voltage semiconductors used in HVDC transmission systems.
I wouldn’t count on it happening within the life span of a new train bought today, but on the other hand I would also not be surprised if it happens soon. It’s one of those things that are hard to tell when it becomes feasible.
P.S. would it be possible to circumvent the ORR by buying additional S stock underground trains, or similar, and just decide to run them on mainline?