Scottish 25kV substations: grid connections/feeder stations/TSCs

[GraphitProjekt]

I've decided it's finally time to turn my attention on Britain's densest and most complex 25kV network.

As always, my quest is to find out which lines are Normally Fed by which Feeder Stations and I feel I have guessed as much as I reasonably can.

My first task was to chart out all the neutral sections to discover the feeding areas. However, I've found that the online Sectional Appendices and the website railcodes.org.uk are lacking in this regard (it seems the latter is just repeating the former), and I was able to discover more neutral sections from watching cab-ride videos on YouTube. But this makes me think there are likely more neutral sections I've missed.

There are quite a lot of anomalies, the neutral section at Muirhouse South Junction on the Cathcart line (CTC), and at Haughhead Junction on the Hamilton Line (HMN) - they seem to be doing nothing, although it's possible the latter is a work-in-progress with regards to Newton FS. There are also areas that just seem too long, like the lines fed by Greenhill, or the Saltcoats/Ayr area (some 40 route miles off one feeder! Surely not!). I'm also not entirely sure if the Stirling grid connection exists.

So, can anyone shed light on this matter, and I'll update my diagram with corrections. Also any info on intermediate TSCs (those not at neutral sections) is good too as they'll be all missing from here.

In the longer run, this thread might be good for the range of Scottish electrification projects hopefully in the pipeline.
View attachment 1766110856185.png

 

[Tester]

On a quick look over, you have Carstairs as Carlisle.

 

[matchmaker]

I don't think there's a direct connection to the grid at Stirling - there is a feeder station situated between the S&D lines and Perth lines north of the Forth Viaducts. I think it is fed from the grid connection at Greenhill.

 

[GraphitProjekt]

On a quick look over, you have Carstairs as Carlisle.

ah! Embarrassing, thanks though.

I don't think there's a direct connection to the grid at Stirling - there is a feeder station situated between the S&D lines and Perth lines north of the Forth Viaducts. I think it is fed from the grid connection at Greenhill.

From Streetview/Google Earth, there have been some extra transformers at Stirling Grid since some point in the early 2010s, however they don't seem to be 'plugged in', or the bushings are fully underground so I can't see if they're three or one phase - could easily be a red herring.
Considering there's a neutral section at Stirling, I suppose Stirling is fed with a circuit from each transformer at Bonnybridge?
It would be surprising to me if those two supplies are collectively handling Queens Street – Newbridge, the Falkirk loop, Larbert – Dunblane/Alloa, Greenhill – Gartcosh, Gatcosh – Sighthill. That's like, over a hundred route miles in total!

 

[waverley47]

I've replied with some messages from the East Kilbride electrification thread that might be of help.

There is a neutral section between Muirhouse Central junction and Pollokshields West. The only other neutral section is on the Down Inner Cathcart between the Larkfield Curve bridge and Queens Park.

The neutral section on the Down Inner between Queens Park and Pollokshields East is not there to separate overhead line sections but due to a low pipe spanning the line; The pipe is on a slope so there is no need for a neutral section on the Up Outer.

Ah I see,
This does beg the question though, what is the point of the Pollokshields West OHNS? The circuits on either side physically connect to each other around the Cathcart circle so it can never section anything from anything. It's noted as being added in 2023.

Don't think it's been posted yet, ORR Approval letter now published:
https://www.orr.gov.uk/sites/defaul...oject-orr-authorisation-letter-2025-12-03.pdf

I can also give you some pointers on the future feeder stations waiting to go in.

Currie feeder will, from mid next year, serve from Haymarket West Junction to the limit of electrification at the former Dalmeny South Jn. This is not to be confused with Dalmeny North Jn, where the lines from Winchburgh Junction join.

Portobello feeder will be extended to serve the Borders line, as far as a limit alongside Millerhill Road, just before the 275/400kV power lines cross the railway.

Thornton North Jn Feeder, 275kV.
This will serve from the junction, to the following limits of electrification, inclusively:
- the buffers at Leven station
- the A92 overbridge north of Ladybank station on the Perth branch, and the start of the straight to the north of Ladybank station on the Dundee line
- the southern end of the platforms at Kinghorn station,
- the former Lumphinnans Central Jn on the Dunfermline side of the circle

Dundee Feeder, 132kV.
The northern limit will be the Brechin Road overbridge, north of Montrose station.
The southern limit is a little bit complex, depending on whether or not NR think they can run the juice straight through Dock Street tunnel, without requiring a short, 10m permanently earthed section underneath an active sewer. If they can, and they think they can, the limit will be western end of Invergowrie station platforms, with a short stub up the gradient to the Tay Bridge.

Tweedbank Feeder, 132kV
The southern limit will be the buffers at Tweedbank station.
The northern limit will be the southern portal of Bowshank tunnel.


I can also confirm that there is no feeder station at Stirling North. There is a 25kV substation, fed by an extension cable from Greenhill, as well as a track sectioning cabin, however the full distance is indeed supplied from Greenhill FS, itself served by the Bonnybridge 275kV substation. However, in the early drafts of EGIP, we did run into issues regarding theoretical maximum capacity at Greenhill, so late in the day it was proposed that Springburn to Gartcosh would be served by Parkhead FS, via Springburn. I do not remember if this happened, and I do not think it did, but it was definitely proposed and got quite far, so I will see if i can dig out what happened. Electrification is a very different discipline from my usual wheelhouse, and I leave that to the electrical engineers, but I might have the full planning document lying around somewhere...

 

[GraphitProjekt]

I've replied with some messages from the East Kilbride electrification thread that might be of help.

Yeah, I've still not found a satisfying conclusion for what's going on with Muirhouse South Jnc OHNS on the Cathcart line. Elsewhere in the thread there was lots of discussion about an extension cable from a new building at Eglinton Street FS to Muirhouse South for Barrhead/East Kilbride which is clear enough.
There is some mention of a Newton FS (probably Clyde's Mill 275kV) in the works once or twice on this website, which I assume is what Haughead OHNS is about.
Loads of press releases about the "six new Feeder Stations" announcement: and I assume those are Fergulsie, Curriehill, Thornton North Jnc, Dundee, Tweedbank and finally Newton.

I can also give you some pointers on the future feeder stations waiting to go in.

Thanks for these, very detailed!

I can also confirm that there is no feeder station at Stirling North. There is a 25kV substation, fed by an extension cable from Greenhill, as well as a track sectioning cabin, however the full distance is indeed supplied from Greenhill FS, itself served by the Bonnybridge 275kV substation. However, in the early drafts of EGIP, we did run into issues regarding theoretical maximum capacity at Greenhill, so late in the day it was proposed that Springburn to Gartcosh would be served by Parkhead FS, via Springburn.

Floating around the internet is a GRIP 1 document from 2007 which says about as much - that Springburn - Gartcosh will be from Parkhead FS.
But I didn't go with that in my diagram because the arrangement of neutral sections that was actually built looks a bit different around the Cowlairs/Springburn and Greenhill
They have it as this:

Unless I've missed something (very possible), there aren't neutral sections on the Cowlairs chord or between Springburn West and Cowlairs West as depicted in the 2007 document. Instead they are actually on the Cumbernauld line as it goes over the Springburn line. It also says the neutral section on the mainline at Greenhill is west of the Greenhill curve, but in the end it is east of it: so whatever goes to Queens Street also goes to Larbert. The document also says the eastern extent of Greenhill's area was to be Winchburgh, but it looks like that became Newbridge instead.

Of course, it's possible Gartcosh-Springburn is supplied by Parkhead via Coatbridge TSC

I do not remember if this happened, and I do not think it did, but it was definitely proposed and got quite far, so I will see if i can dig out what happened. Electrification is a very different discipline from my usual wheelhouse, and I leave that to the electrical engineers, but I might have the full planning document lying around somewhere...

Someone on the forum did once mention a cable from Parkhead to Bellgrove coming about when Cumbernauld was electrified.
(#4,047 on this old thread)

 

[TrainViation]

- the southern end of the platforms at Kinghorn station

As stated in a letter from a Kirkcaldy local, it was said the OLE was to be brough down to Seafield, just about half way between Kinghorn and Kirkcaldy.
If you know, is this still the case, or is it now all the way down to Kinghorn station?

And thank you for that information about the other feeder station limits, it's good to know exactly where the OLE terminates, especially nowadays when lines aren't being fully electrified.

 

[Nicholas Lewis]

I've replied with some messages from the East Kilbride electrification thread that might be of help.









I can also give you some pointers on the future feeder stations waiting to go in.

Currie feeder will, from mid next year, serve from Haymarket West Junction to the limit of electrification at the former Dalmeny South Jn. This is not to be confused with Dalmeny North Jn, where the lines from Winchburgh Junction join.

Portobello feeder will be extended to serve the Borders line, as far as a limit alongside Millerhill Road, just before the 275/400kV power lines cross the railway.

Thornton North Jn Feeder, 275kV.
This will serve from the junction, to the following limits of electrification, inclusively:
- the buffers at Leven station
- the A92 overbridge north of Ladybank station on the Perth branch, and the start of the straight to the north of Ladybank station on the Dundee line
- the southern end of the platforms at Kinghorn station,
- the former Lumphinnans Central Jn on the Dunfermline side of the circle

Dundee Feeder, 132kV.
The northern limit will be the Brechin Road overbridge, north of Montrose station.
The southern limit is a little bit complex, depending on whether or not NR think they can run the juice straight through Dock Street tunnel, without requiring a short, 10m permanently earthed section underneath an active sewer. If they can, and they think they can, the limit will be western end of Invergowrie station platforms, with a short stub up the gradient to the Tay Bridge.

Tweedbank Feeder, 132kV
The southern limit will be the buffers at Tweedbank station.
The northern limit will be the southern portal of Bowshank tunnel.


I can also confirm that there is no feeder station at Stirling North. There is a 25kV substation, fed by an extension cable from Greenhill, as well as a track sectioning cabin, however the full distance is indeed supplied from Greenhill FS, itself served by the Bonnybridge 275kV substation. However, in the early drafts of EGIP, we did run into issues regarding theoretical maximum capacity at Greenhill, so late in the day it was proposed that Springburn to Gartcosh would be served by Parkhead FS, via Springburn. I do not remember if this happened, and I do not think it did, but it was definitely proposed and got quite far, so I will see if i can dig out what happened. Electrification is a very different discipline from my usual wheelhouse, and I leave that to the electrical engineers, but I might have the full planning document lying around somewhere...

Do you know what the Firm Service Capacity is at each of these new feeder stations?

 

[zwk500]

Tweedbank Feeder, 132kV
The southern limit will be the buffers at Tweedbank station.
The northern limit will be the southern portal of Bowshank tunnel.

Will this section be completely isolated on the 'railway' side of the grid connection?
How is redundancy being provided for?

 

[waverley47]

Will this section be completely isolated on the 'railway' side of the grid connection?
How is redundancy being provided for?

Yes, and batteries inside the units.

Do you know what the Firm Service Capacity is at each of these new feeder stations?

I am unfortunately not an electrical engineer, and therefore I have no idea.

As stated in a letter from a Kirkcaldy local, it was said the OLE was to be brough down to Seafield, just about half way between Kinghorn and Kirkcaldy.
If you know, is this still the case, or is it now all the way down to Kinghorn station?

And thank you for that information about the other feeder station limits, it's good to know exactly where the OLE terminates, especially nowadays when lines aren't being fully electrified.

The formal planning limit is Kinghorn station, that might have changed, but I don't think it has. I'll see what I can find out, but it might have been trimmed back at a little bit for ease of access

 

[InOban]

The Saltcoats FS must be significantly South of Saltcoats because they regularly have to switch off the supply to that whole branch when the waves break over the sea wall before the town

 

[GraphitProjekt]

Do you know what the Firm Service Capacity is at each of these new feeder stations?

I've seen that the FSC for Dundee is 16.2MW off of 25MVA transformers. From the overview document on SHEN's page on the new Stannergate 132kV substation to be built.
The Tweedbank transformers are said to be 10 MVA, so one can only guess that the FSC would be maybe half that? I've no idea what goes into the difference between physical capacity and FSC - I imagine it ranges a lot with local conditions. Ardsley FS in Leeds has two transformers, 1 at 18.75 and the other at 10 MVA (only one of which in use at a time), and its FSC is 6 MVA

The Saltcoats FS must be significantly South of Saltcoats because they regularly have to switch off the supply to that whole branch when the waves break over the sea wall before the town

Interesting! My assumption was that it's the substation at the junction with the Ardrossan branch. I feel there must be another grid connection for the Ayr line somewhere. Even with Fergulsie that came online a couple of years ago, Saltcoats is still feeding ~40 route miles

 

[Ginaro]

The formal planning limit is Kinghorn station, that might have changed, but I don't think it has. I'll see what I can find out, but it might have been trimmed back at a little bit for ease of access

There was a planning application in 2022 which was decided as EIA not required, the plans show the southern limit being the bridge over the A921 at Seafield https://planning.fife.gov.uk/online/caseDetails.do?caseType=Application&keyVal=REA8VMHF1AL00 - dunno if that's before or after your information. Would be nice for the people of Kinghorn if it was the southern end of the platforms as that would probably require the footbridge to be replaced and step-free access could be done at the same time.

 

[waverley47]

There was a planning application in 2022 which was decided as EIA not required, the plans show the southern limit being the bridge over the A921 at Seafield https://planning.fife.gov.uk/online/caseDetails.do?caseType=Application&keyVal=REA8VMHF1AL00 - dunno if that's before or after your information. Would be nice for the people of Kinghorn if it was the southern end of the platforms as that would probably require the footbridge to be replaced and step-free access could be done at the same time.

That probably has changed then. Our original modelling for it basically decided that we would extend it south as far as the next overbridge, which was the Kinghorn station footbridge, which would mean stoppers could pan up in the station, however lack of space for lifts at Kinghorn was a bit of a long running issue.

 

[GraphitProjekt]

Found an old document with regards to the previous contract renewal of Avanti West Coast.

We are also experiencing issues in the area supplied from Gowkthrapple feeder station (in Scotland), which the new Currie feeder station will help alleviate...planned to take place in spring 2023

So when Haymarket-Carstairs was wired back in the 1990s - Currie(hill?) was the midpoint between Portobello and Gowkthrapple. But this means Gowkthrapple also fed the Shotts line from 2019 to 2023 so that would have been quite a lot of mileage and services on that feeder!

 

[385102]

I've decided it's finally time to turn my attention on Britain's densest and most complex 25kV network.

As always, my quest is to find out which lines are Normally Fed by which Feeder Stations and I feel I have guessed as much as I reasonably can.

My first task was to chart out all the neutral sections to discover the feeding areas. However, I've found that the online Sectional Appendices and the website railcodes.org.uk are lacking in this regard (it seems the latter is just repeating the former), and I was able to discover more neutral sections from watching cab-ride videos on YouTube. But this makes me think there are likely more neutral sections I've missed.

There are quite a lot of anomalies, the neutral section at Muirhouse South Junction on the Cathcart line (CTC), and at Haughhead Junction on the Hamilton Line (HMN) - they seem to be doing nothing, although it's possible the latter is a work-in-progress with regards to Newton FS. There are also areas that just seem too long, like the lines fed by Greenhill, or the Saltcoats/Ayr area (some 40 route miles off one feeder! Surely not!). I'm also not entirely sure if the Stirling grid connection exists.

So, can anyone shed light on this matter, and I'll update my diagram with corrections. Also any info on intermediate TSCs (those not at neutral sections) is good too as they'll be all missing from here.

In the longer run, this thread might be good for the range of Scottish electrification projects hopefully in the pipeline.
View attachment 194152
View attachment 194153

There are some additional neutral sections and TSC's in Ayrshire as follows:

1. Neutral section between Ayr and Newton-On-Ayr where the railway passes under the A79 at Tams Brig. This OHNS is solely due to restricted headroom under the bridge and does not perform any role in separating phases/feeds.
2. Neutral section between Byrehill Junction and Dubbs Junction in Kilwinning on the route between Ayr and Largs that avoids Kilwinning station.
3. Neutral section north of Ardrossan South Beach on the Largs branch where the railway passes under the A78 in Ardrossan.
4. TSC adjacent to Ayr Townhead depot.
5. TSC between Troon and Barassie.
6. TSC at Kilwinning station at the junction between the Ayr and Largs branches.

On the WCML there are additional TSC's at Lamington between Carstairs and Elvanfoot (at least it was still there the last time I passed), at Nethercleugh between Beattock and Lockerbie and also at Cranberry between Ecclefechan and Gretna Junction. One minor point to note is that the OHNS you have labelled at Wamphrey is actually called Murthat OHNS.

On the ECML there are additional neutral sections to the east of Portobello Junction on the main line towards Musselburgh and also on the line from Millerhill Yard towards Monktonhall Junction.

 

[GraphitProjekt]

There are some additional neutral sections and TSC's in Ayrshire as follows:

1. Neutral section between Ayr and Newton-On-Ayr where the railway passes under the A79 at Tams Brig. This OHNS is solely due to restricted headroom under the bridge and does not perform any role in separating phases/feeds.
2. Neutral section between Byrehill Junction and Dubbs Junction in Kilwinning on the route between Ayr and Largs that avoids Kilwinning station.
3. Neutral section north of Ardrossan South Beach on the Largs branch where the railway passes under the A78 in Ardrossan.
4. TSC adjacent to Ayr Townhead depot.
5. TSC between Troon and Barassie.
6. TSC at Kilwinning station at the junction between the Ayr and Largs branches.

On the WCML there are additional TSC's at Lamington between Carstairs and Elvanfoot (at least it was still there the last time I passed), at Nethercleugh between Beattock and Lockerbie and also at Cranberry between Ecclefechan and Gretna Junction. One minor point to note is that the OHNS you have labelled at Wamphrey is actually called Murthat OHNS.

On the ECML there are additional neutral sections to the east of Portobello Junction on the main line towards Musselburgh and also on the line from Millerhill Yard towards Monktonhall Junction.

Thanks for that, very helpful - what is the point of #2 there, the OHNS on the Byrehill chord? Also, does Port Glasgow FS have a neutral section?

 

[385102]

Thanks for that, very helpful - what is the point of #2 there, the OHNS on the Byrehill chord? Also, does Port Glasgow FS have a neutral section?

Sorry, I don't know the reason for Byrehill OHNS.

Port Glasgow FS does not have a neutral section.

 

[GraphitProjekt]

Looking over Greenhill again, looks like Bonnybridge 275kV has 3x 25kV transformers, maybe Greenhill receives from all 3 at once - this would make sense given the impressive geographic scope apparently resting on Greenhill but is an arrangement I've not seen before. 25kV supply transformers look really quite distinctive given they only have two bushings/bus bars.

 

[GRALISTAIR]

3 transformers so I assume one per phase or is it not quite that simple?

 

[Elecman]

3 transformers so I assume one per phase or is it not quite that simple?

Probably but without being able to trace the incoming feed cables on that image impossible to confirm

 

[QueensCurve]

I've decided it's finally time to turn my attention on Britain's densest and most complex 25kV network.

As always, my quest is to find out which lines are Normally Fed by which Feeder Stations and I feel I have guessed as much as I reasonably can.

My first task was to chart out all the neutral sections to discover the feeding areas. However, I've found that the online Sectional Appendices and the website railcodes.org.uk are lacking in this regard (it seems the latter is just repeating the former), and I was able to discover more neutral sections from watching cab-ride videos on YouTube. But this makes me think there are likely more neutral sections I've missed.

There are quite a lot of anomalies, the neutral section at Muirhouse South Junction on the Cathcart line (CTC), and at Haughhead Junction on the Hamilton Line (HMN) - they seem to be doing nothing, although it's possible the latter is a work-in-progress with regards to Newton FS. There are also areas that just seem too long, like the lines fed by Greenhill, or the Saltcoats/Ayr area (some 40 route miles off one feeder! Surely not!). I'm also not entirely sure if the Stirling grid connection exists.

So, can anyone shed light on this matter, and I'll update my diagram with corrections. Also any info on intermediate TSCs (those not at neutral sections) is good too as they'll be all missing from here.

In the longer run, this thread might be good for the range of Scottish electrification projects hopefully in the pipeline.
View attachment 194152
View attachment 194153

was there always a neutral section at the Braidhurst loops or is this a new thing with more recent electrifications North of Mossend Yard?

 

[GraphitProjekt]

According to the RailCodes website, they were put in Christmas 2002 which honestly is more confusing

 

[WAO]

3 transformers so I assume one per phase or is it not quite that simple?

There are several electrified lines here - the Greenhill curve and the Falkirk line, so perhaps there are three feeds. The FS looks to be in the triangle where Reilly Rd meets Greenhill Rd.

WAO

 

[GraphitProjekt]

Also, update to the diagram with all the new info [again on 11/01 with new info in Dalreoch, Port Glasgow and Innerwick]