What comes after the HST?

[Zoe]

Exeter also has some handy loops and sidings...

So do other stations. I don't think it would be impossible to attach and detach locomotives at Plymouth and you certainly wouldn't need as many locomotives there. Taunton also has a loco siding available that could be used although some extra pointwork would be helpful here to make it easier for a loco off an up train to reach the siding.

As for power supply, you were suggesting that Exeter would be the furthest west on the grid that would be able to cope with the demand so couldn't both Exeter and Plymouth be fed from there rather than Bristol? I don't think there is much of a case for electrifying west of Plymouth though.

 

[HSTEd]

Don't forget that large portions of Salisbury-Exeter line are still single track, courtesy of Dr. Beeching. I'd assume no electrification would happen unless it includes line redoubling. I'd be surprised if someone decided to invest in electrification of that route otherwise.

Well single track means it can be done on the cheap, if you know for a fact that a huge section of the line will only ever be occupied by one EMU with a power draw of 2000hp at peak.

Remember if we were to electrify to Salisbury, and I think there is a case there for it, operational reasons connected to the WEML trains being coupled to the Salisbury-London trains could lead to the rest of the line being electrified fed from Exeter and Salisbury (especially if electrification reaches Exeter from Bristol and thus requires a feeding point in the vicinity anyway).

You could probably support EMU operation on the Cornish Main Line(especially as I doubt an EMU west of Plymouth would ever need anything beyond about notch 2 to match HST timings) from Plymouth or even Exeter with the proper equipment.

 

[Nym]

You could technically feed it all from Reading but it would be ill advised.

Also, since I now know it can be done at Taunton I'll pull my opinion of the limit back to there.

 

[Zoe]

(especially if electrification reaches Exeter from Bristol and thus requires a feeding point in the vicinity anyway).

But it wouldn't do though as if you only electrify as far as Exeter then it can be fed from Bristol.

You could probably support EMU operation on the Cornish Main Line(especially as I doubt an EMU west of Plymouth would ever need anything beyond about notch 2 to match HST timings) from Plymouth or even Exeter with the proper equipment.

But the business case would be quite weak as it's only one train per hour.

 

[HSTEd]

But it wouldn't do though as if you only electrify as far as Exeter then it can be fed from Bristol.

A good point, it would probably require Plymouth atleast before you get a feeding point in the vicinity of Exeter... I am trying to find the longest section of single end-fed track on the network using the 2009 NR electrification RUS.

But the business case would be quite weak as it's only one train per hour.

There would be the 1tp2h to Penzance, the hourly all shacks DMU, the shuttles on the branch lines (since I assume if you are going to do this you would go whole hog and do them too, especially the shorter ones).

 

[Rhydgaled]

But the business case would be quite weak as it's only one train per hour.

Don't some of the Cornish branch lines have half-hourly frequency? This suggests to me that the Plymouth - Penzance service is likely to be an hourly DMU, plus the Intercity services, but I don't know the area so I'm just guessing.

 

[Zoe]

A good point, it would probably require Plymouth atleast before you get a feeding point in the vicinity of Exeter... I am trying to find the longest section of single end-fed track on the network using the 2009 NR electrification RUS.

If Exeter is the furthest west point that would be able to cope with the demand on the grid though, you wouldn't be able to feed Penzance from Plymouth and I'm not sure how well feeding Penzance from Exeter would work.

There would be the 1tp2h to Penzance, the hourly all shacks DMU, the shuttles on the branch lines (since I assume if you are going to do this you would go whole hog and do them too, especially the shorter ones).

Would there be demand for 2 tph between Plymouth and Penzance though?
--- old post above --- --- new post below ---

Don't some of the Cornish branch lines have half-hourly frequency? This suggests to me that the Plymouth - Penzance service is likely to be an hourly DMU, plus the Intercity services, but I don't know the area so I'm just guessing.

For most of the day, the DMU to Penzance only runs when there isn't an intercity service that hour. Also not all the branches are that frequent. St Ives and Falmouth are but the others are not.

 

[HSTEd]

If Exeter is the furthest west point that would be able to cope with the demand on the grid though, you wouldn't be able to feed Penzance from Plymouth and I'm not sure how well feeding Penzance from Exeter would work.

Right, I have found what I think is the longest single end fed section on the network, I make it 28 route kilometres between Saltcoats feeding station and Ayr on the Ayrshire Coast line (although it is isn't technically single end feeding in the normal sense, it does not seem to be able to draw on another feeding point as far as I can tell with second place going to Skipton being fed from Bingley feeding point at roughly 20 route kilometres.

I shall resume plotting and report back soon.

EDIT:

If we use the gap between Marshall Meadows and Ulgham Crossing on the ECML as an example of pushing the gap between substations to the limit (as we all know the ECML was bargain-basement, although I still defend the quality of the workmanship). That gives us a figure in the vicinity of 78-80km of route between two substations.

This means that if we assume there is a substation in the vicinity of Bristol TM (which would make sense as it can support both of the routes to Bristol and the SWML from that position) we would need a feeding point somewhere just west of Taunton.

Taunton to Exeter is too far for single-end feeding in near main line conditions (or atleast Ayr Line conditions) so it would appear that a new feeding point is required anyway, which could be positioned adjacent to Exeter St David's station.

Unfortunately I don't think single end feeding Plymouth from Exeter is practical (due to it being 70+km) requiring another point at Plymouth, additionally electrifying the WEML using this settup would require only one new feeding point, one somewhere just east of Salisbury (and would be needed for electrification to salisbury anyway assuming 25kV with switchover at Overton). The light traffic on the line and its low power nature (even a six coach EMU would probably draw only 2000hp peak) means it could be fed from Salisbury-East and Exeter.

Feeding Paignton is a challenge but the branch is sufficiently short that it could be single end fed via the branch by Plymouth and Exeter feeding points.

It would appear that there are major effects that mean once you commit to electrify beyond Bristol you have to go quite a ways......
Placing a point at Plymouth (if we assume its the furthest west we can go without seriously unbalancing the local grid) would give us the various secondary lines around there, but the branch lines radiating from around Exeter would require relocating the Newton Abbot point into Exeter.

EDIT #2: I note that the 2009 NR Electrification RUS includes the line to Plymouth and Paignton in its "Cross Country" scheme.... the one with the BCR of 5.1/3.4 (the latter includes the Colton Junction-Leeds section which I believe has already been commited as part of the North Transpennine project?)
Isn't BCR of 3.4 above the one normally given as the cutoff value? (2.0?)
WEML comes out with a BCR of 3.1 too.

 

[Zoe]

Unfortunately I don't think single end feeding Plymouth from Exeter is practical (due to it being 70+km) requiring another point at Plymouth

It was stated that the grid wouldn't be able to cope with any feeding points west of Exeter so there couldn't be one at Plymouth.
--- old post above --- --- new post below ---

Placing a point at Plymouth (if we assume its the furthest west we can go without seriously unbalancing the local grid) would give us the various secondary lines around there, but the branch lines radiating from around Exeter would require relocating the Newton Abbot point into Exeter.

I don't see anywhere suggesting a feeding point at Newton Abbot and it's still west of Exeter so the grid may not be be able to cope with it.

 

[Nym]

You could technically feed it from wherever you wanted and create a psudo-grid as part of the electrification scheme, but all pointers are now heading toward a likely outcome of Taunton being the outer limit of electrification at the moment.

And heres somthing you won't see often, an admission that my knowledge of the National Grid isn't that up to date, the 400kV grid has now moved into Cornwall, the current loads it can take I don't know but it's likely able to take a hit from the current draw, but it's still an unknown if it can take the phase imbalance in this part of the grid, unusually, 3rd Rail would be better from a grid point of view.

If one can understand single line diagrams, this is what we have available to play with...
http://www.nationalgrid.com/uk/library/documents/sys05/chapA/images/figA-4-1.pdf

400kV Sub Stations are available at:
Seabank, Hinkley Point, Axminster, Indian Queens, and Exeter.

400kV Interconnectors are available at: Alverdisscott, Taunton and Abham Copse.

And 275kV Interconnectors at: Bridgewater

So a feeder station at Hinkley Point and Exeter would likely be able to reach Plymouth and if you wanted to reach all of Cornwall you'd proberbly need another one down at Landulph

(Please note: The location of these sub stations does not indicate the location of feeder stations, merely 'strong points' in the grid where an additional HV AC connection will be available.)

 

[Zoe]

So a feeder station at Hinkley Point and Exeter would likely be able to reach Plymouth and if you wanted to reach all of Cornwall you'd proberbly need another one down at Landulph

What is at Landulph?

You could technically feed it from wherever you wanted and create a psudo-grid as part of the electrification scheme, but all pointers are now heading toward a likely outcome of Taunton being the outer limit of electrification at the moment.

If the grid will allow the wires to reach Plymouth then why not continue the electrification all the way? The current intercity frequency on the GWML is 2 tph from Taunton to Plymouth most of the day.

 

[Nym]

Didn't say the grid would be able to allow it, remember it's still a pretty heavy single phase current draw, just that the 400kV Network reaches that far.

Landulph has a secondary dual set 400kV Sub and Switching Station.

 

[Zoe]

Didn't say the grid would be able to allow it, remember it's still a pretty heavy single phase current draw, just that the 400kV Network reaches that far.

You were saying though that Plymouth could likely be fed from Hinkley and Exeter.

 

[Nym]

It could also be fed from sodding Didcot, it doesn't mean that the grid will allow such a large single phase draw in that part of the network.

It's not just getting it there to worry about, it's the fact that we run a three phase grid and trains only need one of these phases to work. Drawing an imbalance of phases will not be appreciated by National Grid and they could refuse the connection.

 

[Zoe]

So, what would make this part of the grid less able to cope with a heavy single phase draw than other parts?

 

[Nym]

less trains

 

[Zoe]

less trains

So the more trains you run the better the grid can cope with a single phase draw?

 

[Nym]

No, you distribute them across the phases.

 

[Zoe]

So it wouldn't be possible to do this in Devon based on a 2 tph GWML service between Taunton and Plymouth and some branches electrified?

 

[Kneedown]

Ely and Norwich can easily take HSTs, I should know as I travelled on a East Midlands Trains one last year from St Pancras International to Peterborough via the Mid Norfolk Railway and Norwich

I'll second that as i was one of the Drivers on it!

What a lovely thought to have HST's on the Liv-Nor's.
I can't ever see it happening though, even with a reduced formation. The station dwell times are not generally sufficient to permit regular slam door working, and a bit of work would have to be done on a fair bit of track to make it worthwhile.
The HST's will only become available after MML electrification, and it seems to be still up in the air as to whether that will happen!

 

[Nym]

1) Zoe, its possible but potentially expensive.
2) The HSTs demoted to reigonal work would be fitted with power doors a la chiltern so slam door isnt a problem.

 

[AndyLandy]

Well single track means it can be done on the cheap, if you know for a fact that a huge section of the line will only ever be occupied by one EMU with a power draw of 2000hp at peak.

Remember if we were to electrify to Salisbury, and I think there is a case there for it, operational reasons connected to the WEML trains being coupled to the Salisbury-London trains could lead to the rest of the line being electrified fed from Exeter and Salisbury (especially if electrification reaches Exeter from Bristol and thus requires a feeding point in the vicinity anyway).

But which 'flavour' of electrification? Operationally, it would make sense to extend the 3rd rail, but I don't believe there's any appetite for investing in 3rd rail electric. Indeed I even heard a suggestion that it may all be in line for replacement with 25kV AC in the non-too-distant future.

Oh, and there's always the possibility of electrifying to Salisbury and doing splits/joins with an EMU and a DMU, but we're getting dangerously close to bi-modal trains again at that point...

 

[HSTEd]

We do also have some other options with regards to phase imbalances now.

The advances in power electronics stacks have caused the cost of back to back phase converters to fall through the floor. Relatively soon it may be possible to build a system that could synthesise a single phase circuit from a near balanced three phase circuit.

Or you could just use a Scott-T transformer to convert the three phase to two phase which cuts down on the number of phase breks you need to supply.

 

[Telcontar]

No, you distribute them across the phases.

So, with a four-track line, is the load over the three phases evened out over the space of three sections?

I don't know how long each section is, and how many trains are in each one during off-peak times, and how much this affects the balance of the phase loading.

 

[Rhydgaled]

Oh, and there's always the possibility of electrifying to Salisbury and doing splits/joins with an EMU and a DMU, but we're getting dangerously close to bi-modal trains again at that point...

I actually think bi-mode is a good idea, provided the trains already exist as DMUs (DMU to bi-mode is an improvment, EMU to bi-mode is the opposite).

It might even be possible to convice me that a new build of trains almost identical in general to class 158s but with a pantograph on the roof and 3rd rail shoes would be a good idea, depending on what is done with current DMUs and future electrification plans, but new-build Intercity units with built-in diesel engines is a definitive NO. My reasoning there is that we aren't going to have all local lines electrified for a very long time, but I'm 99% sure the remaining unelectrified Intercity routes can all be wired up (excluding things like Pembroke Dock which would be handled using a very small number of diesel locos to shift the EMU/LHCS stock beyond the wires) by 2050 if only the government would agree to it.

 

[tbtc]

I actually think bi-mode is a good idea, provided the trains already exist as DMUs (DMU to bi-mode is an improvment, EMU to bi-mode is the opposite)

We are generally only talking about bi-mode to replace DMUs though, aren't we? Which is an improvement.

 

[Nym]

To be honest, we don't need bi mode, just have a locomotive to haul EMUs beyond the wires, and run Class 180 or 22x units on the B&H Line, then there are no >100mph route without wires anyway.

With autocouplers this is not ever going to be a problem when it takes less than 2mins to attach the locomotive at say Bristol, Taunton or Exeter.

 

[Zoe]

Other than the power supply issues (which don't seem to be preventing electrification anywhere else) is there any reason why you seem so determined that nothing west of Exeter should be electrified? A 2 tph service (up to 4 tph between Newton Exeter and Newton Abbot) should have a reasonable business case. If it's the case that the demand just isn't there for Plymouth then you may as well terminate most intercity services at Exetee and just run a handful of HSTs through to Penzance and so not need any locos at all.

 

[Nym]

The power supply issues can make a large difference to the cost of electrifying the line.

And since building locomotives to haul the SMUs from either end will result in these not only being useful on the Great Western, but also a suitable replacement for LHCS Sleeper Stock, and will also facilitate diversions off wires for when there are issues on the electrified route, or once or twice a day extensions off wires, such as Pembroke Dock, etc, and potentially re-instating more off route ECML services.

And for the cost of electrifying this additional section of route that would need to cover significant amount of additional track to not need a locomotive and accomadate in growth without politically unpopular loss of direct services, would cost significantly more than simply building the locomotive to work with the new EMUs.

Further to this, while electrifying to the end of cornwall, one could carry out a set of much simpler and more popular electrifications such as the Midland Mainline and some infill on commuter routes around the North of England, or the Welsh Valleys that will be very politically popular, and use the same amount of time and effort as throwing knitting up into cornwall and proberbly present a much smaller engineering challenge to do so.

We can come back to it when the other routes with a higher BCR have been completed. (XC Network Core included, so the full benifits can be realised for XC Cornish services to Plymouth and Penzance)

 

[Zoe]

Further to this, while electrifying to the end of cornwall, one could carry out a set of much simpler and more popular electrifications such as the Midland Mainline and some infill on commuter routes around the North of England, or the Welsh Valleys that will be very politically popular, and use the same amount of time and effort as throwing knitting up into cornwall and proberbly present a much smaller engineering challenge to do so.

We can come back to it when the other routes with a higher BCR have been completed. (XC Network Core included, so the full benifits can be realised for XC Cornish services to Plymouth and Penzance)

I wasn't suggesting electrifying any of Cornwall, only Exeter to Plymouth. The majority of XC services don't even enter Cornwall as they terminate at Plymouth. Only three per day continue to Penzance. I don't think there is a business case west of Plymouth but there's a much strongers case for Exeter to Plymouth as then you would only need locos or bi-mode for the limited service between Plymouth and Penzance rather than for almost every train.