North Downs line electrification

[Phil.]

They might not even bother with either AC or DC, they might just use bi-modes. Is there any stretches that have a top speed above 60mph?

Yes, there are bits that are 75.

 

[SpacePhoenix]

Yes, there are bits that are 75.

Are them 75mph stretches currently electrified?

 

[edwin_m]

Facts not fantasy please. The test of the safety,& therefore extension of third rail on the north downs line,is the statistics,the science. There is no evidence that third rail is more of a killer per electrified mile than AC. And since Network Rail cannot deliver new AC work effectively,let the TOC supervise the far simpler third rail extension as per Grayling's new rules.

Eight times more dangerous was quoted, probably back up this thread, with the source being the RSSB risk model. Unfortunately there appears to be nothing in the public domain that gives any details, but I would hope it was normalised by something like the mileage of the respective systems.
--- old post above --- --- new post below ---

The cost of running a train in electricity terms is pence per vehicle-km. (Only about ~2.2kWh/vehicle-km for a Cl357 IIRC). So 30% being lost before it makes the train isn't going to bankrupt the railway given all its other costs. And power can be increased, primitively, by apply more aluminium cable or conductor rail - which aren't that expensive.
30% losses at the current 5-6p/kWh for big electricity users is going to come to about 5p/vehilce-km or something.

Unless you're a climate change denier you would probably have to agree that the UK has a huge challenge in decarbonising the electricity supply and also increasing its capacity to power the road transport network too (the power for batteries and hydrogen has to come from somewhere). Network Rail is already the biggest single consumer of electricity and I suggest the issue here is wider than simply the cost (which if the Hinkley Point agreement is anything to go by will rise hugely during the lifetime of the equipment). So I don't think you can lightly dismiss a 30% saving of consumption.

 

[najaB]

No - I am saying that it is not ludicrously dangerous.

If there was no third-rail electrification and someone proposed it today can you say, in good conscience, that you would see it as a good idea?

 

[Elecman]

Set this to a one year graph. [£10/MWh is 1p/kWh]
Remember the railway pulls the supply direct from the 132kV or even 400kV network. It basically does not pay any significant grid distribution costs. And even with the railways costs they are far lower than typical because it has no enormously expensive 400/230V network that stretches for huge mileages to maintain.

You are missing Triad and Tuos and Duos charges

 

[dviner]

Is it not the case that, because the number of fatalities on the Rail Network that are attributable to electrocution (either AC OLE or DC Third Rail) is so low, they are of little worth when it comes to gauging the overall danger of one system over the other? One extra fatality on either system would skew the results to a considerable extent.

With that in mind, the gauging of how dangerous one system is over the other would need to be done using other methods - e.g. the likelihood of a member of the public coming into contact with a live conductor.

 

[HSTEd]

Unless you're a climate change denier you would probably have to agree that the UK has a huge challenge in decarbonising the electricity supply and also increasing its capacity to power the road transport network too (the power for batteries and hydrogen has to come from somewhere). Network Rail is already the biggest single consumer of electricity and I suggest the issue here is wider than simply the cost (which if the Hinkley Point agreement is anything to go by will rise hugely during the lifetime of the equipment). So I don't think you can lightly dismiss a 30% saving of consumption.

Moorside is projected a breakeven price several pounds per megawatt-hour below Hinkley Point C - and it is expected that future units would have lower costs.
And if NetworK Rail/DfT was concerned about prices it could spend some of its capital budget on buying a CANDU 6 and never have to order outside electricity again.

You are missing Triad and Tuos and Duos charges

The railway won't pay DUOS in any significant way since they will likely draw power directly from 400kV circuits. Or at most from a DNO operated 132kV circuit - and operating 132kV lines is not a major component of DNO's costs. Almost all their costs are incurred in the Low Voltage section, and most of the remainder is incurred at 11kV or below.

TUOS are actually very small.
They will be something less than a penny a unit.

TRIAD is more troublesome - but since the railway tends towards a baseload operation it won't be that significant.

 

[Elecman]

TUOS and TRIAD are not insignificant and do add to the base wholesale price, remember NR do not buy the power from National Grid but through a shipper (EdF) so you gave thier profit to add on as well

 

[HSTEd]

TUOS and TRIAD are not insignificant and do add to the base wholesale price, remember NR do not buy the power from National Grid but through a shipper (EdF) so you gave thier profit to add on as well

They buy electricity from a generator (for 3.2TWh/yr this is EdF). Anyone with a supply is permitted to buy direct from the electricity market. TUOS is at or below a penny a unit and TRIAD is a minor concern for a near baseload demand like the railway.

Note how the wholesale prices listed tend to ghe £40/MWh mark and yet I stated £50-60/MWh. So I have made allowance for these costs

 

[edwin_m]

Moorside is projected a breakeven price several pounds per megawatt-hour below Hinkley Point C - and it is expected that future units would have lower costs.
And if NetworK Rail/DfT was concerned about prices it could spend some of its capital budget on buying a CANDU 6 and never have to order outside electricity again.

That doesn't answer my principal point which was about energy consumption not cost. If they were to buy one power plant they'd still have to buy in when it was out of service. And the point remains that it will be a huge challenge to build sufficient generating capacity, whether reserved for Network Rail or not, so reducing demand has to be part of the solution. This is especially so for something like the railway when the peak demand coincides with the peak of general demand, so it's a question of peak capacity rather than baseload.

 

[DynamicSpirit]

Unless you're a climate change denier you would probably have to agree that the UK has a huge challenge in decarbonising the electricity supply and also increasing its capacity to power the road transport network too (the power for batteries and hydrogen has to come from somewhere). Network Rail is already the biggest single consumer of electricity and I suggest the issue here is wider than simply the cost (which if the Hinkley Point agreement is anything to go by will rise hugely during the lifetime of the equipment). So I don't think you can lightly dismiss a 30% saving of consumption.

I broadly agree with that. But to be picky, I'm guessing that the saving by using OHL isn't 30% - it'd presumably be the 30% loss from 3rd rail minus whatever the % loss using OHL is.

 

[najaB]

...minus whatever the % loss using OHL is.

I seem to remember reading (it might have been in this thread) that AC OHLE losses are around 4%.

 

[XDM]

I seem to remember reading (it might have been in this thread) that AC OHLE losses are around 4%.

Plus the energy cost of each 4 car AC unit having to drag around approx 2 tonnes of transformer. Plus the energy loss in each transformer. I'm told,but haven't checked, 12% of power drawn. This makes the ac loss close to DC's 30% claimed losses. And these DC losses could be reduced if wet ballast was not often piled up against the conductor rail to raise steam!

 

[najaB]

Plus the energy cost of each 4 car AC unit having to drag around approx 2 tonnes of transformer.

Most DC units carry a lump of concrete where the transformer goes in an AC unit. Even so, 2 tonnes only represents something like 1.5% of the mass of a typical EMU. So at worst say 2.25% increase in energy required to accelerate.

Plus the energy loss in each transformer. I'm told,but haven't checked, 12% of power drawn.

Closer to 2% than 12%.

And these DC losses could be reduced if wet ballast was not often piled up against the conductor rail to raise steam!

You keep saying this, but even where it happens the losses won't come anywhere close to the inherent electrical losses involved in high-current power transmission.

 

[AM9]

Most DC units carry a lump of concrete where the transformer goes in an AC unit. Even so, 2 tonnes only represents something like 1.5% of the mass of a typical EMU. So at worst say 2.25% increase in energy required to accelerate.
Closer to 2% than 12%.
You keep saying this, but even where it happens the losses won't come anywhere close to the inherent electrical losses involved in high-current power transmission.

In addition, there is the far greater acceptance of regenerated power from ac traction without the need for resistor banks lineside as for DC (are all DC lines so equipped yet?). With ac traction, the whole of the national grid is there to accept returned current.

 

[najaB]

With ac traction, the whole of the national grid is there to accept returned current.

Which reminds me of the other point I was going to raise about transformer losses: with DC traction there are still transformer losses, as the National Grid supply is AC, and there are more fixed transformers running all the time as compared to AC systems.

 

[edwin_m]

In addition, there is the far greater acceptance of regenerated power from ac traction without the need for resistor banks lineside as for DC (are all DC lines so equipped yet?). With ac traction, the whole of the national grid is there to accept returned current.

Not sure if Network Rail regenerates AC back into the grid, but the lower losses of the AC system mean the train that uses the power can be much further away from the one that is producing. So other things being equal there is a much better chance of finding another train motoring somewhere that can use the energy recovered during braking.

All trains with regenerative braking need to dump the energy as heat if they can't return it to the supply. This is usually done with resistor banks on the train. Resistor banks at substations would also waste the energy - recovering it would need inverters to put it back into the AC supply, which would make the DC substation a lot more complicated compared with a simple diode rectifier.

 

[DynamicSpirit]

Most DC units carry a lump of concrete where the transformer goes in an AC unit.

Out of interest, why?

 

[najaB]

Out of interest, why?

It allows DC and AC versions of a design to share a common suspension setup.

 

[59CosG95]

It allows DC and AC versions of a design to share a common suspension setup.

By that dint also, it allows conversion with relative ease. Just whack a pantograph on top, replace the concrete lump with a transformer and you're good to go! (though obviously it's a little more complex than all that)

 

[HSTEd]

This is especially so for something like the railway when the peak demand coincides with the peak of general demand, so it's a question of peak capacity rather than baseload.

Does it?
I can't imagine the railway has a heavily peaked demand profile anyway - and with modern timetabling practice of near clockface operation I think the demand probably stays mostly constant throughout the bulk of the day.

The capacity factor is probably intermediate rather than peaking as such.

Additionally with CCGTs being ~£800/kW and 60% efficient, and most reasonable nuclear being around ~£3000/kW with zero carbon, the enormous capital cost of the new EU-approved 25kV specification looks awful risky economically.

It is also worth noting that if you were to disable DC regeneration on a section of track you could significantly cut losses by upping the substation voltage up to ~890V and still remain within the at-train specification.
Which might be useful out in the middle no nowhere on a lightly used line like the North Downs where there is unlikely to be anything to regenerate to anyway.

 

[glbotu]

Does it?
I can't imagine the railway has a heavily peaked demand profile anyway - and with modern timetabling practice of near clockface operation I think the demand probably stays mostly constant throughout the bulk of the day.

The capacity factor is probably intermediate rather than peaking as such.

Additionally with CCGTs being ~£800/kW and 60% efficient, and most reasonable nuclear being around ~£3000/kW with zero carbon, the enormous capital cost of the new EU-approved 25kV specification looks awful risky economically.

It is also worth noting that if you were to disable DC regeneration on a section of track you could significantly cut losses by upping the substation voltage up to ~890V and still remain within the at-train specification.
Which might be useful out in the middle no nowhere on a lightly used line like the North Downs where there is unlikely to be anything to regenerate to anyway.

I wouldn't be so sure about the railway being non-peaked. I mean, just thinking about London, I'd suggest the morning and evening peaks would give a decent spike, just because the trains tend to end up as 12 car, rather than 8 or 4, not to mention PIXC busters. While it's not as peaked as the total nation-wide demand, the shear power requirement of trains is pretty impressive, so I'd suggest it's a solid increase. Addtionally, the night is basically empty, with most freight running round on diesel, so it certainly "troughs".

 

[hwl]

By that dint also, it allows conversion with relative ease. Just whack a pantograph on top, replace the concrete lump with a transformer and you're good to go! (though obviously it's a little more complex than all that)

Not much more, just plenty of electrical safety testing and update the train management software settings so it knows it is now dual volatage.

The HV cabling is all there just needs VCB and and some other control gear the existing traction converter will sort out the output of the transformer as 3rd Rail DC is pretty rough and and unsmoothed so not too much difference in some ways.

 

[SpacePhoenix]

Not much more, just plenty of electrical safety testing and update the train management software settings so it knows it is now dual volatage.

The HV cabling is all there just needs VCB and and some other control gear the existing traction converter will sort out the output of the transformer as 3rd Rail DC is pretty rough and and unsmoothed so not too much difference in some ways.

Would "input select" and pan up/down switches be the only new switches that would be needed in the cab?

 

[Elecman]

They buy electricity from a generator (for 3.2TWh/yr this is EdF). Anyone with a supply is permitted to buy direct from the electricity market. TUOS is at or below a penny a unit and TRIAD is a minor concern for a near baseload demand like the railway.

Note how the wholesale prices listed tend to ghe £40/MWh mark and yet I stated £50-60/MWh. So I have made allowance for these costs

I have checked today and the average cost Network Rail pay over the country for Traction electricity is 8.5p/unit inclusive of DUOS/ TUOS and TRIAD.

 

[HSTEd]

I have checked today and the average cost Network Rail pay over the country for Traction electricity is 8.5p/unit inclusive of DUOS/ TUOS and TRIAD.

Excellent - it is always good to have real data instead of estimates!
That means an EMU uses ~18p/vehicle-km in electricity. Even 30% losses is only ~7p/vehicle-km. And in low demand areas losses will often be below this figure

 

[DerekC]

Does it?
I can't imagine the railway has a heavily peaked demand profile anyway - and with modern timetabling practice of near clockface operation I think the demand probably stays mostly constant throughout the bulk of the day.

This just isn't true on many routes. Look at the profile of train flow on the up main into Waterloo, for example, and you will see a peak of 25 trains per hour, compared with the off-peak flow of about 15 TPH. And on top of that all the peak trains will be full length (10 or 12 car) whereas the off-peaks will be 4, 5 or 8 car. The peak is going to be double the off-peak in terms of power demand.

It is also worth noting that if you were to disable DC regeneration on a section of track you could significantly cut losses by upping the substation voltage up to ~890V and still remain within the at-train specification.
Which might be useful out in the middle no nowhere on a lightly used line like the North Downs where there is unlikely to be anything to regenerate to anyway.

Which is OK (although it wouldn't cut losses) until the train stops taking power, when the voltage at the shoegear promptly goes up to 890V and trips everything on the train instantly (if you are lucky).

PS - and how many times does it have to be repeated that the "new" 25KV spec is UK-self inflicted, not a product of the EU.

Having said all that, DC third rail would be the logical choice for North Downs - but not for anything long distance or faster than 100 mph.

 

[HSTEd]

This just isn't true on many routes. Look at the profile of train flow on the up main into Waterloo, for example, and you will see a peak of 25 trains per hour, compared with the off-peak flow of about 15 TPH. And on top of that all the peak trains will be full length (10 or 12 car) whereas the off-peaks will be 4, 5 or 8 car. The peak is going to be double the off-peak in terms of power demand.

But that is not the issue of this thread is it?
This is talking about electrification of the North DOwns and of remaining diesel routes in the Southern Region traditional operating area. There is hardly anything resembling Waterloo approach left under diesel operation is there?

Which is OK (although it wouldn't cut losses) until the train stops taking power, when the voltage at the shoegear promptly goes up to 890V and trips everything on the train instantly (if you are lucky).

If that happens I am afraid you need to contact your train manufacturer because 890V is a perfectly permissable permanent voltage under the existing third rail specification. It is just not normally achieved unless a train nearby is regenerating lots of power.

Additionally if the at rail voltage is higher the amount of current that must be drawn to achieve the required kilowattage delivered drops significantly, and with reduced current comes drastic reductions in losses.
For example to draw 650kW with a rail voltage of 650V, if the substation voltage 890V instead of ~750V the at-train voltage would be ~800V, which means to draw 650kW you require only, at most, 812A.
Which means your losses will be roughly 66% of the lower-voltage case. And this is conservative as it is assumes a constant voltage drop across the third and running rails, which will actually shrink in the lower current case, reducing losses further.

PS - and how many times does it have to be repeated that the "new" 25KV spec is UK-self inflicted, not a product of the EU.

Yes, but it only exists because the EU regulation gives the larger value and tried to give the UK an opt out, which has now been lost for one reason or another.

Having said all that, DC third rail would be the logical choice for North Downs - but not for anything long distance or faster than 100 mph.

There is only one long distance route left on diesel power in third rail country as it is.

 

[QueensCurve]

Third rail electrification is not "incredibly dangerous" as you would have it. Anything is dangerous if you're not familiar with it which is where H&S jockeys get so much so wrong about so many situations. I'd also question the "grossly inefficient" statement too. It's done southern England very well over the years and for a (relatively) low speed line like the North Downs Line it's perfectly adequate.
After watching the rapidly unpeeling farce that the Great Western electrification is/has become I'd say that third rail supply with it's simplicity of installation (no bridges and tunnel clearances to worry about) and zero visual impact (no locals complaining about ugly masts) has an awful lot going for it.
We used to laugh at other countries getting in a tangle over engineering projects. Remind me again, how long did it take the Chinese to build an 819 mile 186 mph line from Beijing to Shanghai?

Here we go again. 3rd rail doesn't comply with the electricity at wporl regu;work regulations and losses in transmission are proprtional to the square of the curren. Hence it is grossly ineffiicent eeeven though the Southern has coped with it for a Century.

 

[XDM]

Here we go again. 3rd rail doesn't comply with the electricity at wporl regu;work regulations and losses in transmission are proprtional to the square of the curren. Hence it is grossly ineffiicent eeeven though the Southern has coped with it for a Century.

Here we go again. The regulations do not apply. A new third rail up slow came into use into Eastleigh last year. No prosecutions that we have heard of.
The I squared V losses are counteracted by far lower capital costs & the other pro DC factors I & others posted earlier. Third rail,or rather costly battery packs, are the only option for north downs. Network Rail's sickening performance have ruled out new AC,unless essential. But others may do it more cheaply if Grayling's plans are not just puff.