Future of Third Rail

[Duncan-231192]

This has probably been covered before, but I am not trawling through tens of thousands of articles.

So, the future of third rail. First, unlike many, I am not going to pretend that the third rail network is ever going to be converted to OHLE. It's not, and that is an end to it. But, it is a extremely inefficient system that needs updating for the 21st century.

So, the question is simple. What are peoples idea for improving the third rails networks for the 21st century?

Personally, I would progressively replace the old Steel Conductor Rail with an Aluminium/Stainless Steel Co-extruded replacement with a larger cross section. Aluminium has far higher conductivity than steel, even high conduction steel, and the hard stainless steel cap provides superior wear resistance than the current rail. This would reduce thermal/resistive losses, and/or increase the power which the conductor rail can carry. I would also replace the grid connections with modern, more efficient alternatives allowing higher efficiency and greater power availability. I wouldn't extend the third rail system westwards, but I would fill in the various gaps in the third rail network such as Marshlink Line, and Uckfield Branch

 

[Tio Terry]

Aluminium/Stainless steel conductor tain works well where the environment is such that the temperature is pretty constant, such as an underground railway tunnel. Where it is subjected to a high level of temperature cycling there have been problems caused by the different rate of expansion of the two metals, they have been known to part company!

The DfT's attitude towards extension of 3rd rail has not been in favour of anything other than short fill ins, Marshlink and Uckfield have been discussed on here before but it doesn't seem to have any chance of being approved.

 

[Lucan]

Maybe convert it to under-contact (like the San Fransisco BART?) with insulated protection on top. Maybe that will overcome the DfT's 3rd rail phobia. 3rd rail is easier and cheaper to install than OHE and in many ways better suited for suburban lines.

 

[RobShipway]

This has probably been covered before, but I am not trawling through tens of thousands of articles.

So, the future of third rail. First, unlike many, I am not going to pretend that the third rail network is ever going to be converted to OHLE. It's not, and that is an end to it. But, it is a extremely inefficient system that needs updating for the 21st century.

So, the question is simple. What are peoples idea for improving the third rails networks for the 21st century?

Personally, I would progressively replace the old Steel Conductor Rail with an Aluminium/Stainless Steel Co-extruded replacement with a larger cross section. Aluminium has far higher conductivity than steel, even high conduction steel, and the hard stainless steel cap provides superior wear resistance than the current rail. This would reduce thermal/resistive losses, and/or increase the power which the conductor rail can carry. I would also replace the grid connections with modern, more efficient alternatives allowing higher efficiency and greater power availability. I wouldn't extend the third rail system westwards, but I would fill in the various gaps in the third rail network such as Marshlink Line, and Uckfield Branch

Why do you think that the third rail lines could not be converted to OHLE?

 

[30907]

Why do you think that the third rail lines could not be converted to OHLE?

Because of the amount of infrastructure work needed, with cost and disruption to consider.

Maybe convert it to under-contact (like the San Fransisco BART?) with insulated protection on top.

Perhaps even more challenging to implement, though no tunnels and bridges to consider.

 

[zwk500]

The DfT's attitude towards extension of 3rd rail has not been in favour of anything other than short fill ins, Marshlink and Uckfield have been discussed on here before but it doesn't seem to have any chance of being approved.

Don't believe the DfT attitude comes into it, It's the RSSB/ORR who put the safety factor very high. I expect the DfT would be quite keen for some cheap electrification.

Why do you think that the third rail lines could not be converted to OHLE?

OP did not say could, only that it would not. And Money is the reason.

 

[Irascible]

Omboard batteries, for demand smoothing. Less draw for accelerating trains & you don't have to dunp power into the conductor rail ( or the air ) for regenerative braking. And you can remove troublesome sections of conductor rail entirely.

 

[Trainbike46]

A way to improve safety might be for someone to create a design for bottom-contact third rail as well as the accompanying shoe, that is fully compatible with top-contact third rail.
That way you could replace top-contact third rail as it is life expired, and use the safer bottom-contact third rail for sensible extensions (such as the third rail diesel islands)

Now of course, making such a design that is both practical to use and safe is likely to be much harder than I made it sound above!

 

[Ken H]

I think having small batteries on each train so some difficult places can be de-electrified, like complicated pointwork, would help. I am thinking enough power for about 400 metres ish, which would get you through most station throats.
It is pointwork where most track workers would be, I think.

And better security to keep trespassers out. Graffiti suggests its virtually open access. that needs to change in 3rd rail land. That will be difficult.

 

[RobShipway]

A way to improve safety might be for someone to create a design for bottom-contact third rail as well as the accompanying shoe, that is fully compatible with top-contact third rail.
That way you could replace top-contact third rail as it is life expired, and use the safer bottom-contact third rail for sensible extensions (such as the third rail diesel islands)

Now of course, making such a design that is both practical to use and safe is likely to be much harder than I made it sound above!

Surely though that would be as expensive as replacing third rail with OHLE?

 

[Trainbike46]

Surely though that would be as expensive as replacing third rail with OHLE?

It wouldn't be

for starters you wouldn't need to change any bridges or tunnels
and secondly, you could change things as they need replacing, rather than having to do a route at a time or needing to deal with 3rd rail/ohle interfaces

 

[jackot]

Out of interest, just how inefficient is 3rd rail compared to OHLE when considering energy lost? Obviously I get that it has other serious limitations aside from efficiency like how much power can be drawn (considering it is a 750V system) and safety, but is it really as bad as people make out?

 

[AM9]

Out of interest, just how inefficient is 3rd rail compared to OHLE when considering energy lost? Obviously I get that it has other serious limitations aside from efficiency like how much power can be drawn (considering it is a 750V system) and safety, but is it really as bad as people make out?

It has been mentioned many times here that low voltage third rail has an overall electrical efficiency* of around 80-85%, whereas HV OLE is around 95%. The longer the line is, the more the low voltage losses mount. Then there's the difference in the electrical installation, maintenance and replacement costs. Although the first installation may involve civils, they are in the long term mitigated as that needs replacement in it's own right. In terms of infrastructure that forms part of an OLE structure gauging conflict, the majority of overbridges and tunnels built/replaced since the '50s have been OLE compliant so as time goes on, new OLE installations are less likely to require civils.
* i.e. efficiency of actual traction power available at the motors from the railway supply point.

 

[swt_passenger]

Maybe convert it to under-contact (like the San Fransisco BART?) with insulated protection on top. Maybe that will overcome the DfT's 3rd rail phobia. 3rd rail is easier and cheaper to install than OHE and in many ways better suited for suburban lines.

Bottom contact is significantly speed limited. You’d never be able to run at 100 mph on it.

 

[zwk500]

A way to improve safety might be for someone to create a design for bottom-contact third rail as well as the accompanying shoe, that is fully compatible with top-contact third rail.
That way you could replace top-contact third rail as it is life expired, and use the safer bottom-contact third rail for sensible extensions (such as the third rail diesel islands)

Now of course, making such a design that is both practical to use and safe is likely to be much harder than I made it sound above!

The physics of making something that can reliably maintain contact in both and upwards and downwards directions is slightly contradictory, not to mention the clearance issues. You'd need to have completely separate shoes for each system.
Batteries are the better option for the islands.

 

[Snow1964]

With modern power electronics that can switch high power systems might be possible to detect trains and have it automatically cut off after a certain time. Then become live again when next train detected.

Wouldn't be much use in the high train frequency parts, but might save some losses where there is only an infrequent service, or no service at night.

Now that regenerative braking is a thing, might be able to add batteries near stations to charge up from trains stopping at the station and give a boost when it moves off again. Wasn't something with contra-rotating flywheels tried once instead of batteries as an alternative

 

[zwk500]

With modern power electronics that can switch high power systems might be possible to detect trains and have it automatically cut off after a certain time. Then become live again when next train detected.

This just won't be cost-effective because of the need for all the switchable earthing points and so on.

Wouldn't be much use in the high train frequency parts, but might save some losses where there is only an infrequent service, or no service at night.

Would be easier to just get the ECR to shut it off after the last train is off the section.

Now that regenerative braking is a thing, might be able to add batteries near stations to charge up from trains stopping at the station and give a boost when it moves off again. Wasn't something with contra-rotating flywheels tried once instead of batteries as an alternative

This is something that definitely should be (maybe even is being) looked at, trackside large storage batteries (Like Iron-Air or similar) able to help smooth out power supply and demand when trains are running through.

 

[Tio Terry]

Don't believe the DfT attitude comes into it, It's the RSSB/ORR who put the safety factor very high. I expect the DfT would be quite keen for some cheap electrification.

It was the DFT that was responsible for enshrining TSI's into ROGS, in particular the Energy TSI.

There have been a number of updates and changes since then and TSI's have become NTSN's due to Brexit, but the requirements are still the same. The RSSB/ORR are following DFT guidance.

 

[MarkyT]

Maybe convert it to under-contact (like the San Fransisco BART?) with insulated protection on top. Maybe that will overcome the DfT's 3rd rail phobia. 3rd rail is easier and cheaper to install than OHE and in many ways better suited for suburban lines.

Bottom contact is significantly speed limited. You’d never be able to run at 100 mph on it.

UK top-contact 3rd rail is installed much closer to the nearest running rail than typical bottom-contact systems, which wouldn't fit in the gap between the track and many platform faces and bridge girders here.

 

[RobShipway]

The physics of making something that can reliably maintain contact in both and upwards and downwards directions is slightly contradictory, not to mention the clearance issues. You'd need to have completely separate shoes for each system.
Batteries are the better option for the islands.

It wouldn't be

for starters you wouldn't need to change any bridges or tunnels
and secondly, you could change things as they need replacing, rather than having to do a route at a time or needing to deal with 3rd rail/ohle interfaces

You are still going to need a process to charge up the batteries, whether it is installing OHLE at destination sites or having some sort of connection configure through the ground that can be connected by the driver when they reach the destination to charge the batteries, given the distances many services within Third rail routes take.

Now that regenerative braking is a thing, might be able to add batteries near stations to charge up from trains stopping at the station and give a boost when it moves off again. Wasn't something with contra-rotating flywheels tried once instead of batteries as an alternative

The above goes with what I was saying above to be able to charge up the batteries of a train, whether on route or at end to end.

Now as many have said due to cost, you cannot replace third rail in one full swing to be OHLE. But you can do it planned phases over say a 40 or 60 year period, when finances at the DFT allow.

The first stage, would be to install OHLE recharging points at Eastbourne, Seaford, Ashford International, Uckfield and London Bridge. With Uckfield being the first point to have OHLE charging point installed.

Now, some may say that other than Seaford, the other sites are places where the class 171 units work to/from which is correct. The reason why I included Seaford though is to have third rail removed between Seaford and Newhaven Harbour, due to the foot crossing at Tide Mills. The trains that would be used on both the Seaford - Brighton route and the class 171 routes, would be trains that can operate on both battery and third rail, with the ability to be adapted in the future to use OHLE as most EMU units have been for the last 20 years.

With the right trains, the batteries for the trains could be charged up through the use of Third rail to the units initially, both from standstill at station and with the use of regenerative braking as Snow1964 states. Doing this will probably take up the first 10 - 20 years of the process. The rest of the 40 years of the 60 year process would be taken up with batteries getting more efficient and more lighter with being able to do more miles, such that batteries either replace third rail or is used as part of the process to replace third rail with OHLE though the 60 year process.

Battery technology say since the 1960's/1970's with the milk float have come quite far to what we have with the likes of Tesla cars today. But you still have the issue of distance and the ability to recharge said batteries within a timetable that leaves units little or no time to recharge in the time required. Hence, why I suspect that it comes to replacing the class 171 units with Southern, that it will be done with units that have similar abilities to the class 93 with being able to work from electricity, diesel and battery power given the details of current known power technologies.

 

[MarkyT]

This is something that definitely should be (maybe even is being) looked at, trackside large storage batteries (Like Iron-Air or similar) able to help smooth out power supply and demand when trains are running through.

LUL did a trial of flywheel storage at stations many years ago but I don't think anything ever came of it. Having some battery storage on board would seem a better solution as that could harvest braking energy and assist acceleration and hill climbing anywhere en route rather than just around stations that are equipped. A trial site for this might be the Isle of Wight with its new D-Trains that could plausibly have a moderately sized traction battery added.

 

[zwk500]

You are still going to need a process to charge up the batteries, whether it is installing OHLE at destination sites or having some sort of connection configure through the ground that can be connected by the driver when they reach the destination to charge the batteries, given the distances many services within Third rail routes take.

Uckfield, Marshlink and North Downs/Blackwater (the only signficant third rail gaps) are all within the range of battery EMUs running today in other countries

Other 3rd rail isn't likely to go anywhere.

LUL did a trial of flywheel storage at stations many years ago but I don't think anything ever came of it. Having some battery storage on board would seem a better solution as that could harvest braking energy and assist acceleration and hill climbing anywhere en route rather than just around stations that are equipped. A trial site for this might be the Isle of Wight with its new D-Trains that could plausibly have a moderately sized traction battery added.

Tbh a mix of both on-train and at-track storage is the most efficient option. A good power control system would be able to optimise the balance between all sources.

 

[MarkyT]

Tbh a mix of both on-train and at-track storage is the most efficient option. A good power control system would be able to optimise the balance between all sources.

Makes sense. That's my vision for the general purpose grid too, i.e. storage everywhere, at every level, in homes, in vehicle batteries, in domestic substations, and at grid level.

 

[D365]

For an application such as third rail 'peak smoothing', I have to agree that lineside storage would potentially be the more viable concept. Especially in conjunction with lineside solar arrays.

 

[tomuk]

1) Substation upgrades - Apply modern power electronics i.e. SMPS to reduce power losses increase safety.
2) Lineside storage - based on the timetable and route suitable subtations easily identfied.
3) Composite third rail - Al\Steel but what about actual composites
4) Insulator maintenance\replacement - can reduce losses by replacing insulators with better materials or just by cleaning around third rail.

 

[Ken H]

1) Substation upgrades - Apply modern power electronics i.e. SMPS to reduce power losses increase safety.
2) Lineside storage - based on the timetable and route suitable subtations easily identfied.
3) Composite third rail - Al\Steel but what about actual composites
4) Insulator maintenance\replacement - can reduce losses by replacing insulators with better materials or just by cleaning around third rail.

wonder if washing the pots would help. how much leccy leaks down the crud on the sides.

 

[Peter Sarf]

What about side contact third rail ?. Would that work at high speeds. Would it be much safer - at least the top could be protected. I assume ice formation would be reduced and snow could not build up.

 

[Ken H]

What about side contact third rail ?. Would that work at high speeds. Would it be much safer - at least the top could be protected. I assume ice formation would be reduced and snow could not build up.

dig out the old Cl 504's

 

[RobShipway]

What about side contact third rail ?. Would that work at high speeds. Would it be much safer - at least the top could be protected. I assume ice formation would be reduced and snow could not build up.

I am not sure that it would help, as you would have to be paying out a lot of money to be redesigning and building third rail shoes for existing stock. The money you would be paying out I think would be better with being paid to be adding batteries to existing EMU units and doing as Tomuk's comment which is below:

1) Substation upgrades - Apply modern power electronics i.e. SMPS to reduce power losses increase safety.
2) Lineside storage - based on the timetable and route suitable subtations easily identfied.
3) Composite third rail - Al\Steel but what about actual composites
4) Insulator maintenance\replacement - can reduce losses by replacing insulators with better materials or just by cleaning around third rail.

For point 3, you would want the rail such that when touch by humans or animals that they do not get electrocuted, but still provide the power for the units operating on the rails. It should also be something that could be used with existing third rail shoes on existing EMU's, otherwise you will have just a higher cost than you would have if you had changed any third rail routes into OHLE routes potentially.

On any of the routes where third rail exists, I doubt that you will ever need any speed above 100mph, which is why I doubt that there is a need to be changing the third rail for higher speeds, other than to be changing the makeup of the third rail itself to be safer as per my comment above.

You have to remember for the most part, the third network covers the commuter areas of the South, South East and Merseyside. But you also have to think about what can be used to cover the gaps in the third rail systems to enable people to travel as well. Like for instance the battery power that can be used on the class 777 units, which enable the class 777 units to travel behind the power of the Merseyside third rail power.

Uckfield, Marshlink and North Downs/Blackwater (the only signficant third rail gaps) are all within the range of battery EMUs running today in other countries

Other 3rd rail isn't likely to go anywhere.

True. But I think it will take longer to get past the good old British resistance. That having been said, the class 777 being given battery units, the Class 168 Hydroflex test and the Class 93 having available added power if only for 10 minutes from a battery while the diesel engine is being used is a step in the right direction.

 

[43066]

So, the question is simple. What are peoples idea for improving the third rails networks for the 21st century?

I’d authorise the remaining diesel islands in the former southern electric region to be filled in with new third rail installation. It’s absolutely ludicrous that this isn’t allowed when the the “safety” impact is minimal (and IIRC statistically only really benefits trespassers, so tail wagging dog).

Elimination of the islands would allow an improvement of services on the east coastway line, and would remove the need for a diesel micro fleet with the associated long diesel ECS moves from Selhurst to the coast and back.