Abolish Overhead Cabling

[RogerB]

Two days on the trot now overhead cabling faults have seriously disrupted Virgin services. With the advent of much improved battery technology I would like to see third rail pickup systems used in conjunction with batteries and maybe fuel cells. The third rails could be positioned in safe places, e.g. away from stations, level crossings and the like and perhaps on gradients where extra power is needed or regenerative braking is available to put power back into the system. Power could be applied to them on an "as needed" basis, e.g. when a train with depleted batteries is approaching.

Anything to get rid of the eyesore that the overhead catenary system has become!

 

[Bletchleyite]

Battery tech is nowhere near good enough for high speed trains yet.

 

[Aictos]

This has to be a joke because third rail technology is restricted to 100mph so in one stoke you’ve caused countless IC services which used to run at 125mph to be a lot more slower meaning you’ve just overtook Grayling as everyone’s favourite rail minister!

 

[6Gman]

Two days on the trot now overhead cabling faults have seriously disrupted Virgin services. With the advent of much improved battery technology I would like to see third rail pickup systems used in conjunction with batteries and maybe fuel cells. The third rails could be positioned in safe places, e.g. away from stations, level crossings and the like and perhaps on gradients where extra power is needed or regenerative braking is available to put power back into the system. Power could be applied to them on an "as needed" basis, e.g. when a train with depleted batteries is approaching.

Anything to get rid of the eyesore that the overhead catenary system has become!

So, let me understand this.

You want several thousand miles of overhead electrification to be removed, replaced with unproven battery technology and dangerous third rail electrification? The vast majority of the AC rolling stock (presumably) scrapped or expensively rebuilt?

All because of a couple of days of disruption on Virgin services ...

 

[RogerB]

Let's not forget the word "speculative" in the thread title.

Battery tech is nowhere near good enough for high speed trains yet.

With the emphasis on "Yet". Battery tech, along with capacitor development is coming on in leaps and bounds.

So, let me understand this.

You want several thousand miles of overhead electrification to be removed, replaced with unproven battery technology and dangerous third rail electrification? The vast majority of the AC rolling stock (presumably) scrapped or expensively rebuilt?

All because of a couple of days of disruption on Virgin services ...

Obviously existing infrastructure isn't going to be scrapped until it's at the end of its useful life, neither will battery technology be introduced until it is proven; hopefully both will occur simultaneously. Although one way of proving it is to use it. The Aussies have a battery/solar train running as a prototype.

I addressed the safety aspect of third-rail systems in my post, and the current rolling stock will have to be replaced sometime anyway. Are they dismantling the existing 3rd rail system and replacing it with DMUs? If it really was that dangerous in todays safety obsessed world it would have been ripped out already.

Again being speculative, I would suggest future trains will be based on the Bullet Train model, with motors per axle throughout the train most likely with shared bogies, so current trains will be eventually become obsolete anyway.

 

[6Gman]

Obviously existing infrastructure isn't going to be scrapped until it's at the end of its useful life,

But the infrastructure won't all reach the end of its useful life at the same time.

 

[RogerB]

But the infrastructure won't all reach the end of its useful life at the same time.

Just as well. Such a radical change would have to be dealt with bit by bit, it would be too much of an exercise to do the whole lot in one go. Back in the day diesels replaced steam over a period of time whereas technically it could have been done overnight as it was basically just the locos that had to be changed.

 

[6Gman]

Just as well. Such a radical change would have to be dealt with bit by bit, it would be too much of an exercise to do the whole lot in one go. Back in the day diesels replaced steam over a period of time whereas technically it could have been done overnight as it was basically just the locos that had to be changed.

How are you going to run a sensible train service if Euston to Bletchley is overhead wired; Bletchley to Rugby is third rail; Rugby to Nuneaton is overhead etc etc

 

[6Gman]

Just as well. Such a radical change would have to be dealt with bit by bit, it would be too much of an exercise to do the whole lot in one go. Back in the day diesels replaced steam over a period of time whereas technically it could have been done overnight as it was basically just the locos that had to be changed.

I don't think it could. Staff training; reconfiguration of depots etc etc. Not to mention the construction of so many locos for a single changeover.

 

[RogerB]

How are you going to run a sensible train service if Euston to Bletchley is overhead wired; Bletchley to Rugby is third rail; Rugby to Nuneaton is overhead etc etc

I would suggest something along these lines:

http://busandtrain.blogspot.com/2018/05/guest-post-new-stadler-trains-for.html about half way down where it says

"First look at a bi-mode unit diesel power car

These power car units have four impressive V8 engines enabling services that could run from Lowestoft to London to be powered by diesel between Lowestoft and Ipswich switching to electric traction for the journey southward into London. The same principle will work between Norwich and Cambridge - Stansted Airport too."

A smaller than standard car which will generate and/or collect power from whatever source is available and distribute to the drive electronics and thence to the motors. I understand there are existing units than can work on overhead and 3rd rail supplies. As the infrastructure evolves the trains can brought up to date by replacing this power car. I'm sure I read somewhere that something like this is being introduced into the UK already, possibly by Alstom???

I don't think it could. Staff training; reconfiguration of depots etc etc. Not to mention the construction of so many locos for a single changeover.

Exactly, which is why I said

...Such a radical change would have to be dealt with bit by bit, it would be too much of an exercise to do the whole lot in one go. ....

 

[Bald Rick]

As it happens, neither of the ‘faults’ affection Virgin were anything to do with a fault with the OLE, and everything to do with a fault with adjacent vegetation landing on the wires. And had it not been for the wires, it would have landed on the tracks (and any conductor rails) and messed up the train service anyway.

Therefore rather than spending billions on a less safe and less efficient infrastructure solution, that doesn’t actually solve the problem, let’s just spend a few quid on chopping down some trees.

And that’s before we get to all the other problems third rail causes - much higher maintenance costs, worse overall system reliability, more complicated signalling, doesn’t like cold rain, etc etc.

 

[RogerB]

^^ Interesting. I would have thought 3rd rail would be less vulnerable due to the fact that it is stronger than wires? If the 3rd rail was damaged I reckon it would be easier to fix, no need for working at height for a start.

The system I proposed is a hybrid with 3rd rail, battery and on-board generation. If the 3rd rail is damaged just use the other two power sources to get on your way. With the present system you're stuck.

I addressed safety in my original post.

And that’s before we get to all the other problems third rail causes - much higher maintenance costs, worse overall system reliability, more complicated signalling, doesn’t like cold rain, etc etc.

I'd like to know more about all this, especially why signalling should be more complicated.

...
Therefore rather than spending billions on a less safe and less efficient infrastructure solution, that doesn’t actually solve the problem,

..
Obviously existing infrastructure isn't going to be scrapped until it's at the end of its useful life....

so there's going to be expenditure anyway. Surely a 3rd rail down the centre of the four foot would be much cheaper than all the gantries, their foundations and insulated cable supports?

 

[RogerB]

...third rail technology is restricted to 100mph ...

What's the reason for that then?

 

[Bald Rick]

Electrification is a system, which itself is part of a railway system; there is so much more to it than the contact element (OLE or third rail). I have managed and operated both systems, and there is no question that OLE is better. We have had previous threads on this, but in summary:

Safety: the OLE is up in the air and largely out of the way. Conductor rail is on the ground and very much in the way. I know several people who through work (or in 2 cases, trespassing) have come into contact with the con rail; I don’t know anyone who has come into contact with the OLE. This safety issue then comes into maintenance...

Maintenance: because of the safety issue, almost any work to the track needs the con rail isolated. This adds time to the maintenance process, and time = money. For a given no trains period, track maintenance in con rail areas is about 20% less efficient as a result. Signalling is more complicated due to the high currents associated with con rail electrification, this requires much more robust kit and extra bonding. This also means extra maintenance, costs more to install and is more to fail. Maintenance of the conrail itself is relatively straightforward, it’s only a rail, but all the cabling, bonding, and distribution system is more chunky and clunky, and all of it is necessarily at ground level.

Reliability: the con rail itself is relatively reliable, although it does fail as Southern passengers found out earlier this week, and London Overground passengers into Euston will tell you this morning. However all the distribution kit behind it is vulnerable, particularly the power connections and bonding, and they regularly fail, sometimes spectacularly. This is very rare with OLE. Much more of an issue though is consequent effects of other incidents. With con rail in the event of trespass, a suicide, flooding, deep lying snow, obstruction on the line, and more, the power has to go off. We have seen all these (except the snow) this week in third rail areas, and we do most weeks (flooding excepted). With OLE it’s not an issue. With the power off not only can’t trains move, but trains in the affected section but unaffected by the incident itself are stranded, and this can lead to passengers self-detraining, as we see regularly. And then the power has to stay off longer. The con rail is also very vulnerable to ice, even heavy frost, whilst OLE isnt except in extreme conditions. Aside from a major failure of a feeder station (which can happen with either system), the only reliability problem with the OLE is something falling on it, a failure of the contact or catenary wire, some of which is caused by a pantograph problem on the train. There is no doubt in my mined that a OLE railway is significantly more reliable than a con rail railway.

Efficiency: distributing 750v D.C. means, (because of the laws of physics), that more power is lost before it reaches the train. I can’t rememeber the precise number, but I think it’s about 20%, ie you need 20% more power from the grid to achieve the same result on the train. Also, and this is important, it is more difficult to deliver the high power necessary for intensive / long / quick service patterns with con rail. This is why all dual voltage trains are reduced in power when they get to the con rail - it’s not that the train isn’t capable, out there isn’t enough power in the con rail. To rectify this (pardon the pun), means, effectively doubling the number of substations and all the distribution kit. That’s billions.

 

[hexagon789]

What's the reason for that then?

I don't think sufficient contact between third rail and collector shoes can be assured at higher speeds. That and the wear is likely quite significant on the third rail as well.

 

[RogerB]

Electrification is a system, which itself is part of a railway system; there is so much more to it than the contact element (OLE or third rail). I have managed and operated both systems, and there is no question that OLE is better. We have had previous threads on this, but in summary:

Safety: the OLE is up in the air and largely out of the way. Conductor rail is on the ground and very much in the way. I know several people who through work (or in 2 cases, trespassing) have come into contact with the con rail; I don’t know anyone who has come into contact with the OLE. This safety issue then comes into maintenance...

Maintenance: because of the safety issue, almost any work to the track needs the con rail isolated. This adds time to the maintenance process, and time = money. For a given no trains period, track maintenance in con rail areas is about 20% less efficient as a result. Signalling is more complicated due to the high currents associated with con rail electrification, this requires much more robust kit and extra bonding. This also means extra maintenance, costs more to install and is more to fail. Maintenance of the conrail itself is relatively straightforward, it’s only a rail, but all the cabling, bonding, and distribution system is more chunky and clunky, and all of it is necessarily at ground level.

Reliability: the con rail itself is relatively reliable, although it does fail as Southern passengers found out earlier this week, and London Overground passengers into Euston will tell you this morning. However all the distribution kit behind it is vulnerable, particularly the power connections and bonding, and they regularly fail, sometimes spectacularly. This is very rare with OLE. Much more of an issue though is consequent effects of other incidents. With con rail in the event of trespass, a suicide, flooding, deep lying snow, obstruction on the line, and more, the power has to go off. We have seen all these (except the snow) this week in third rail areas, and we do most weeks (flooding excepted). With OLE it’s not an issue. With the power off not only can’t trains move, but trains in the affected section but unaffected by the incident itself are stranded, and this can lead to passengers self-detraining, as we see regularly. And then the power has to stay off longer. The con rail is also very vulnerable to ice, even heavy frost, whilst OLE isnt except in extreme conditions. Aside from a major failure of a feeder station (which can happen with either system), the only reliability problem with the OLE is something falling on it, a failure of the contact or catenary wire, some of which is caused by a pantograph problem on the train. There is no doubt in my mined that a OLE railway is significantly more reliable than a con rail railway.

Efficiency: distributing 750v D.C. means, (because of the laws of physics), that more power is lost before it reaches the train. I can’t rememeber the precise number, but I think it’s about 20%, ie you need 20% more power from the grid to achieve the same result on the train. Also, and this is important, it is more difficult to deliver the high power necessary for intensive / long / quick service patterns with con rail. This is why all dual voltage trains are reduced in power when they get to the con rail - it’s not that the train isn’t capable, out there isn’t enough power in the con rail. To rectify this (pardon the pun), means, effectively doubling the number of substations and all the distribution kit. That’s billions.

Many thanks for that, it's nice to have a constructive and informed reply.

Safety: I see your point 100%, which is why I suggested a "connect on demand" arrangement and keeping the 3rd rail out of dangerous locations. As sections of potentially live rail would be relative short a train would be able to pass a dead section using the other on-board power systems I suggested. Where the Orange Army is working the contactors would be locked-out and shorting clamps in place. As the 3rd rail wouldn't necessarily be supplying traction power, reduced voltages could be available at certain locations for safety.

Signalling: You're spot on with that, I'd forgotten signalling currents pass through the rails, and I'm well aware of the havoc caused by stray currents on signal voltages from over 30 years computer engineering experience! As this is a speculative thread and we are looking to the future I would see signals &c served by fibre-optics, on a network similar to the familiar PC networks so there would be no need to have signal currents in the track. Sensing equipment which currently (you want puns, I've got puns ) relies on the train's contact with the track would be replaced with equipment that doesn't. Also in-cab signalling will be in common usage by this time.

Reliability: I thought the OLE was switched off if there was an incident on the track? I can see why you would get bonding and connection problems with DC (electrolytic corrosion), but a 3rd rail doesn't have to be DC. Corrosion would be reduced with AC. Take your points regarding ice and show, there are shrouded con rail systems.

Efficiency: I realised this from the outset. Power = volts x amps, power loss in the conductors = amps x amps x voltage drop. This means to get the power with low currents you need high voltages, halving the current reduces the loss by a factor of 4. But again with a mix of power generating technologies on board current consumption could be evened out, use the batteries/fuel cell when power is needed and take reduced power from the rails, when coasting (which I believe trains do quite a bit) still take (reduced) power from con rail to charge the batteries. I understand the AC on OLE systems is low frequency, using mains frequency would reduce the cost of the infrastructure.

Slightly OT, where do the substations you see alongside the track get their power from?

 

[RogerB]

I don't think sufficient contact between third rail and collector shoes can be assured at higher speeds. That and the wear is likely quite significant on the third rail as well.

Yeah, and heat build-up too. Maybe modern materials would help, Graphene seems to the electrical elixir at the moment.

One (rather ugly) solution would be to have a rotating pickup and slip rings. The ratio of the wheel diameter to the slip ring diameter would give a suitable linear speed at the brushes, and reduce wear on the rail.

 

[hexagon789]

Yeah, and heat build-up too. Maybe modern materials would help, Graphene seems to the electrical elixir at the moment.

One (rather ugly) solution would be to have a rotating pickup and slip rings. The ratio of the wheel diameter to the slip ring diameter would give a suitable linear speed at the brushes, and reduce wear on the rail.

Improvements could likely be made, but higher voltage overhead systems are I think always going to be superior especially for higher-speeds.

 

[Belperpete]

I think your solution might be slightly more practical if you had suggested sections of OLE, rather than third rail, for recharging the batteries, use on steep gradients, etc. However, the big problem would be the size and weight of the batteries that the trains would need to carry. Accelerating an 8 coach train up to 125mph requires a significant amount of power. Accelerating a freight train up to full speed requires a phenomenal amount of power. I don't think there is any way a loco or individual power car could carry sufficient batteries.

 

[Bald Rick]

I think your solution might be slightly more practical if you had suggested sections of OLE, rather than third rail, for recharging the batteries, use on steep gradients, etc. However, the big problem would be the size and weight of the batteries that the trains would need to carry. Accelerating an 8 coach train up to 125mph requires a significant amount of power. Accelerating a freight train up to full speed requires a phenomenal amount of power. I don't think there is any way a loco or individual power car could carry sufficient batteries.

Don’t bet on it! The railway managed the first 140 years of existence with locomotives carrying around a separate vehicle with all their energy stored on it; we may well see a return to that (just with Lithium rather than carbon).

 

[Belperpete]

Don’t bet on it! The railway managed the first 140 years of existence with locomotives carrying around a separate vehicle with all their energy stored on it; we may well see a return to that (just with Lithium rather than carbon).

So an electric loco hauling a couple of "battery tenders", similar to the brake tenders that diesel locos used to need with unfitted freights. Would increase complexity at run-rounds, unless the battery tenders also had driving cabs.

 

[MarkyT]

So an electric loco hauling a couple of "battery tenders", similar to the brake tenders that diesel locos used to need with unfitted freights. Would increase complexity at run-rounds, unless the battery tenders also had driving cabs.

Electric locos are often ballasted to increase adhesive weight and thus tractive effort. Modern power equipment and motors aren't usually heavy enough on their own. That's why electro-diesels, or bi-modes as they're known today, are a good idea if you can squeeze a big enough lump in within the limited UK loading gauge. Batteries as ballasting is a good alternative and the shape of a battery bank is more flexible, so distributed groups of cells might be tucked into various corners all over a vehicle if desired.

 

[MarkyT]

Very high return currents flowing in the running rails can cause spectacular explosive faults even without the additional complication of signalling track circuits for train detection. In low voltage DC networks, the running rails are insulated and never earthed, to encourage the vast majority of the current to stay in the rails. This is counter to the paradigm in 25kV OHLE where everything metalic in the vicinity of the railway has to be earthed for safety reasons. Dual electrified areas are particularly complex because the safety concerns of high voltage must take precedence. The high DC currents thus have many complex paths to return through via every bonded object and structure, which are thus subject to stray current corrosion. The only remedy is to dramatically improve the desired path, making it as low resistance as possible with heavy expensive parallel strengthening conductors, so as much current as possible is encouraged to go the correct way. Stray currents can never be eliminated entirely by this method though and dual electrification is kept to the absolute minimum for these reasons. That would make a staged migration from AC OHLE to DC third rail more difficult as the superficially simple idea of having both systems energised for a period during the changeover is undesirable over wide areas. The main difficulty with signalling and any kind of electrification using the running rails for traction return has been in train detection with the traditional track circuit, which by necessity has to share some electrical commonality with the power system, and that's where many faults manifested with the complexity and expense of impedance bonds that filter one system from the other. When things go wrong however, track circuit relays and entire signalling equipment cabinets have been known to go up in flames when thousands of amps of traction return are misrouted into a low voltage relay. Track circuits have mostly been superseded in new schemes by axle counters which have inductive sensors bolted to the rails. They still have to be able to cope with the electro-magnetically noisy environment but at least share no direct electrical commonality. Once track circuits are removed from the equation, traction return bonding can be much simpler and more resilient and requires no impedance bonds.

 

[Elecman]

Slightly OT, where do the substations you see alongside the track get their power from?

For Traction Power On DC systems from the 11/33 KV distribution cables laid between the substations and the Traction Feeder Intake position. For thier internal domestic power from either a local DNO supply or via an Auxiliary Transformer on the HV distribution system.

 

[Bald Rick]

So an electric loco hauling a couple of "battery tenders", similar to the brake tenders that diesel locos used to need with unfitted freights. Would increase complexity at run-rounds, unless the battery tenders also had driving cabs.

I’m going to go a little dreamy here...

I can see a situation where there are ‘twin’ locos, perhaps half as long again as locos today, with a cab each end. Say Bo-Bo+Bo-Bo, with 5MW. Now a 5MW Vectron weighs around 80 tonnes, so it’s reasonable to assume that something half as long again, with another 4 wheelesets and traction motors but no extra power equipment would weigh about 110t or so. But with 8 axles to play with, that leaves 40 tonnes spare to still meet an RA8 axle load. Battery capacity depends on the type of battery, but if you used the same type as in a Tesla (Lithium Ion), 50 tonnes gets you 10 MWh, enough for two hours at full power. Rarely are freight locos at full power for that long, and they would of course be able to regenerate when braking (or going downhill). In real world cycles, this would give about 4 hours or so of rolling off the wires. Lithium Titanate batteries, which may be better suited to rail applications, would provide about half the juice, but much quicker recharging.

Now 4 hours won’t cover all freight trips, but it would cover many, particularly with some additional electrification to reduce the gaps. Particularly at terminals so that locos can recharge while the ‘goods’ are being loaded / unloaded. For example, if the Felixstowe branch was wired, it would be possible to get to Nuneaton and the WCML via Peterborough. Similarly Southampton to Nuneaton if the wires were extended from Didcot to Oxford.

It would be interesting to know what proportion of freight tonnage involves trips of more than 4hrs off the wires. I suspect it’s less than a third.

Having said all that, given the power / energy demands of freight, it’s more likely that hydrogen will be preferred: higher energy per kg, and therefore better range, albeit volume and storage becomes an issue.

 

[Bald Rick]

For Traction Power On DC systems from the 11/33 KV distribution cables laid between the substations and the Traction Feeder Intake position. For thier internal domestic power from either a local DNO supply or via an Auxiliary Transformer on the HV distribution system.

And the 11/33kV in turn comes from the Grid at feeder stations.

There is a lot more distribution involved for 750v D.C. than 25kVAC.

 

[MarkyT]

I can see a situation where there are ‘twin’ locos, perhaps half as long again as locos today, with a cab each end. Say Bo-Bo+Bo-Bo, with 5MW.

Nice! Sort of like a modern BLS Ae 8/8. Probably room for a moderately sized diesel generator set in that sort of package as well. With eight fully weighted powered axles, it could probably start pretty much anything you could hang on the back. Perhaps time to upgrade to 1000m long intermodals.

 

[Shaw S Hunter]

Nice! Sort of like a modern BLS Ae 8/8. Probably room for a moderately sized diesel generator set in that sort of package as well. With eight fully weighted powered axles, it could probably start pretty much anything you could hang on the back. Perhaps time to upgrade to 1000m long intermodals.

I suspect our resident planning gurus might have something to say about that!

 

[Bald Rick]

I suspect our resident planning gurus might have something to say about that!

As long as there is somewhere long enough to keep them out the way, and they can meet existing planning rules, it’s not a problem.

 

[Shaw S Hunter]

As long as there is somewhere long enough to keep them out the way, and they can meet existing planning rules, it’s not a problem.

My understanding is that even 750m loops are not as common as operators would like so 1000m trains would almost certainly have to be effectively scheduled non-stop from origin to destination while also relying on disruption being infrequent.