Longest electrified stretch fed from one end?

[GRALISTAIR]

I am trying to get my head around that mathematically and engineering wise. I understand (a little - enough to be dangerous!) 3 phase supply so each phase is 2/3 pi radians -120 degrees different. I partially understand ATF feeding- pi radians - 180 degrees different, but 90 degrees? I shall have to google and study!

Well I have done some research and found this about the 90 degree phase difference.

Scott-T transformer - Wikipedia

en.wikipedia.org

A Scott-T transformer or Scott connection is a type of circuit used to produce two-phase electric power (2 φ, 90 degree phase rotation) from a three-phase (3 φ, 120 degree phase rotation) source, or vice versa. The Scott connection evenly distributes a balanced load between the phases of the source. The Scott three-phase transformer was invented by Westinghouse engineer Charles F. Scott in the late 1890s to bypass Thomas Edison's more expensive rotary converter and thereby permit two-phase generator plants to drive three-phase motors.
At the time of the invention, two-phase motor loads also existed and the Scott connection allowed connecting them to newer three-phase supplies with the currents equal on the three phases. This was valuable for getting equal voltage drop and thus feasible regulation of the voltage from the electric generator (the phases cannot be varied separately in a three-phase machine). Nikola Tesla's original polyphase power system was based on simple-to-build two-phase four-wire components. However, as transmission distances increased, the more transmission-line efficient three-phase system became more common. (Three phase power can be transmitted with only three wires, where the two-phase power systems required four wires, two per phase.) Both 2 φ and 3 φ components coexisted for a number of years and the Scott-T transformer connection allowed them to be interconnected.

This forum never ceases to amaze me - I have learnt so much.

 

[GraphitProjekt]

It's also quite surprising that Scott Transformers have ever been used on a British AC railway. It's one of those techniques for single phase 50Hz electrification that we don't really do but other countries have made a norm (Russia?)
This was an interesting little article about alternative 25kV supply systems most of which I don't think we use. SFCs seemingly are one of a whole family of power electronic solutions.

 

[Tester]

Well I have done some research and found this about the 90 degree phase difference.

Scott-T transformer - Wikipedia

en.wikipedia.org

This forum never ceases to amaze me - I have learnt so much.

The only time I have come across Scott connected transformers was in Hong Kong in 1997, where they were specified for signalling power supplies (650V ac).

They were not a success, and were rewound conventionally before commissioning.

The impression I got was that they were a clever, but impractical, idea.

 

[thecrofter]

Another fact about Biggleswade TSC - it was actually replaced in the late 90s/early 00s as the neutral section was repositioned for whatever reason.

When I used to live in Peterborough, I lived very close to the Delivery Unit depot and saw the old Dunton FS building in there (this was circa 2018). So the Biggleswade replacement must have happened before then...

The original Biggleswade TSC (GEC MKII building) was effectively made redundant by the Corey's Mill scheme (early East Coast PSU if you like). That building was recovered during 2004 by Carillion Rail and sent back to Areva at Stafford in sections to be converted to a replacement Feeder Station for reuse at Dunton on Thameside. It was later commssioned by Carillion Rail in December 2004. The original brick built Dunton Oil Filled (OC36?) Switchgear building was hit by lightning and was catastrophically destroyed. Interesting to see from Google Street View, that the Areva conversion was itself replaced sometime between 2009 (first available date view) and 2012.

Street View of Lower Dunton Rd · Google Maps

www.google.co.uk

 

[RichardAsh1981]

I also think some of the 33kV circuits were handed over to the local electricity board when the lines went to 25kV as there was some mention in 2014 by UKPN about 'finally getting rid of those distribution circuits we have running in railway land'.

I wouldn't read too much into the UKPN quote. It could be correct, but in general lots of public supply DNO cables are routed along railway lines in urban areas because railways offer one of the few opportunities for a long linear wayleave from a single landowner, and a lot less disruptive than digging up streets. These days the restrictions on trackside access mean the are hard to repair if the do fail however.

I wouldn't be surprised if UKPN meant the elimination of 11kV circuits from railway lands, as a slow repair of one of these matters a lot more than at 33kV and above.

 

[GraphitProjekt]

I agree it does sound a bit fantastical but from the quote given in this document, it does seem a rather convenient possibility.

Crowlands/Romford/Gidea Park 33kV Circuits - Replace 33kV solid cable circuits
The three Crowlands Grid/Romford/Gidea Park 33kV cables are situated alongside the Great Eastern main line
railway out of Liverpool Street Station, and for much of the route are suspended on hangers beside the track.
These exposed sections of cable are prone to damage, fires and vandalism as well as accelerated ageing. The
condition and fault rate of these cables is monitored for any further deterioration. It is proposed to replace the
Crowlands – Romford – Gidea Park circuits in a manner to support future demand transfers from Crowlands to a
new grid substation at Gidea Park.

We know that the original grid supply point for the railway's 33kV was Crowlands 132/33 (and a secondary connection at Crosswall later replaced by Bethnal Green), and that there was a DC substation at Gidea Park.

The description of "hangers by the track" does match that of the 1949 system but I admit both are quite vague. There aren't many pictures of the DC system to see what the AC circuits looked like.

 

[D6130]

Not sure if this has been mentioned before, but Bingley to Skipton (12 miles) has a single-ended feed. This always caused problems on the night shunt shift at Skipton when there was an overnight isolation. Additional problems were caused when class 91s replaced HSTs on the morning Skipton-Kings Cross service. Because the voltage dropped to about 17 kV at Skipton, any class 308 units - and particularly 333s - were floundering when the 91 was accelerating away from Skipton or Keighley.

 

[GraphitProjekt]

That suprises me since both Bingley and Kirkstall are 18.75 MVA supplies with distances that aren't super crazy. Is this any different with class 80x units?

 

[D6130]

That suprises me since both Bingley and Kirkstall are 18.75 MVA supplies with distances that aren't super crazy. Is this any different with class 80x units?

Not sure, as I retired in 2012 and moved out of the area. Maybe @InkyScrolls could tell us?

 

[RichardAsh1981]

I agree it does sound a bit fantastical but from the quote given in this document, it does seem a rather convenient possibility.

I think I may have misread the original quote

finally getting rid of those distribution circuits we have running in railway land

as meaning "getting rid of all the remaining cables we own in railway land" when it actually means "this particular group of circuits which are troublesome because of how they are installed in railway land". My scepticism was driven by the conviction that the former would be a monumental undertaking! The latter is quite plausible, and I can well see that cables on trackside hangers would be a liability.

 

[njamescouk]

Isn't the phrase 'volts jolts, mills [milliamps] kills', because it's the current that does the damage, and even 25KV isn't always fatal.

happy memories of the van der graaf generator.

 

[RichardAsh1981]

Weirdly, Facebook just decided to show me some pictures (from a group I'm not in) taken in 1974 at the London end of Gidea Park sidings, showing what are described in the comments as "EEB 33kv cables", with a recollection of patrolling them looking for oil leaks. There are at least three substantial cables supported on hangers either side of concrete posts.
Link to Facebook Post

 

[GraphitProjekt]

how interesting and a great find. This would seem to support the idea that the Railway's 33kV circuits ended up with the local board, although the chronology doesn't fit that well as Gidea Park to Shenfield went to 25kV in 1976 so the whole line would have been 6.25kV in this picture (as you can see from that insulator). So maybe both the railway and the EEB had 33kV cables of a similar design in a similar place?

 

[PeteK]

how interesting and a great find. This would seem to support the idea that the Railway's 33kV circuits ended up with the local board, although the chronology doesn't fit that well as Gidea Park to Shenfield went to 25kV in 1976 so the whole line would have been 6.25kV in this picture (as you can see from that insulator). So maybe both the railway and the EEB had 33kV cables of a similar design in a similar place?

This forum was great to recall my experiences on GE power supplies in early 70s (especially the Scotts and 6.26kV equipment). Some photos attached; have many more.

 

[GraphitProjekt]

This forum was great to recall my experiences on GE power supplies in early 70s (especially the Scotts and 6.26kV equipment). Some photos attached; have many more.View attachment 196915View attachment 196916View attachment 196917View attachment 196918

Thank you these are excellent! Is that Bethnal Green in the first image? My research into this topic suggested that the 33kV traction power system was fed from Bethnal Green from 1960 onwards (replacing a 22/33kV connection at Crosswall) was this actually the case? I have quite a few questions about the power systems in Anglia as there are quite a few curiosities both back then and today

 

[PeteK]

Yes, that is BG showing the three 33/6.25kV single phase transformers. A few more pics.

I was always happy to work in BG and Gas Factory Jnc. Prittlewell as well, as that was another 33kV site.

 

[GraphitProjekt]

Yes, that is BG showing the three 33/6.25kV single phase transformers. A few more pics.

I was always happy to work in BG and Gas Factory Jnc.

Thanks again, that diagram is fascinating. I didn't know BR added Gas Factory Jnc to the 33kV feeder network! Do you have similar info on how the circuits were laid out in the DC era?

Prittlewell as well, as that was another 33kV site.

Ah so was Prittlewell supplied at 33kV from the Grid at Rayleigh? I've seen that Prittlewell, Rayleigh and Ramsden were the 3 locations for feeding 6.25kV for Shenfield to Southend Vic but I had assumed they were all their own grid connections.

 

[PeteK]

As I recall Prittlewell 33kV was fed from Fleet Hall Grid (in those days everything that wasn't railway was "the grid"). This fed two 6.25kV transformers on the opposite side of the track. It also fed via buried cables the two Scott transformers at Southend Central on the C2C (LTS as was). A manual switching facility enables a 33kV feed to a 6.25kV transformer at Shoeburyness. Some more stuff attached. Some of the Visio/PDF diagrams are still a work in progress. Wish I had thought to keep a copy of the major feeding diagram before I left Chadwell Heath.

No info on what was there in the DC days but understand from the BTC Electrification Conference 1960 (another great reference document; I sourced a second hand copy on Amazon and have it in PDF) papers that the 33kV stuff was pretty much what was there in the DC days. The DC substations/switchgear replaced with new buildings for the 6.25kV switchgear. Not sure about Gas Factory as that looked more modern so it may have been added into the ring as you suggest.

 

[GraphitProjekt]

As I recall Prittlewell 33kV was fed from Fleet Hall Grid (in those days everything that wasn't railway was "the grid"). This fed two 6.25kV transformers on the opposite side of the track. It also fed via buried cables the two Scott transformers at Southend Central on the C2C (LTS as was). A manual switching facility enables a 33kV feed to a 6.25kV transformer at Shoeburyness.

That's very interesting because I've often looked on the map these days and though how close those lines are although they are on totally separate supplies now with Southend Central supplying the end of LTS system and all of the Victoria line powered from Rayleigh, could it be useful for them to be able to share power these days? I'm not sure, but the fact it used to work like that is quite interesting.

Some more stuff attached. Some of the Visio/PDF diagrams are still a work in progress.

Thank you again for them they are really informative. I actually got rather curious about this topic about 2 years ago and started a "blog" as it were to house my "research". I'd always heard that "back in the day parts were electrified at 6.25kV for low clearances" but I wanted to know exactly which areas and when. I've not added anything to that old research project in a while focusing instead on mapping present day systems. But it's a rabbit hole I'm glad to be looking back into. I think it's a very interesting topic which is potentially getting forgotten about!

I'll link that blog here if you're interested because, like you, I started drawing rough schematics of the system at select years. (It's very wordy so you I'd just look at the pictures). With the info you're giving me it could do with a significant re-write and some refreshing of the diagrams (my "house-style" has changed a lot since then). I've also learned more in general about electrification so some of my assumptions I made then might not be the case now.

Not sure about Gas Factory as that looked more modern so it may have been added into the ring as you suggest.

Originally Fenchurch Street (actually just platform 1 and 2) to Bow Jnc was electrified DC in 1949 with a DC substation at Crosswall which was also the backup 'grid' connection for the 33kV system. When the route was converted to AC in 1960, Bow jnc to FST electrification was out of use for a short period as it was being incorporated into the wider LTS scheme which opened in 1961. So yes Gas Factory Jnc FS would have dated from the early 1960s rather than 1949 like the other sites out of LST. There is another anecdote that because no actual electric service regularly used Fenchurch street between 1949 and 1961, the section was converted to 6.25kV 50Hz in 1955-6 for testing of train bound Germanium rectifiers as an off-shoot of the Lancaster-Morecambe/Heysham test scheme at that time (using the trains too) - so maybe they converted Crosswall DC substation or Gas Factory Jnc actually dates from that brief test scheme.

 

[PeteK]

Thanks for the Blog access. "Wordy" not an issue. One of the diagrams fills in a few gaps in my recollections. Remember having to go in a bonded liquor facility in the arches below Fenchurch St to access the TSC. In my day Crosswall had lost most of its equipment and was just a signalling supply. The CB at Shadwell feeding it was an interesting specimen.

 

[bramling]

Thanks for the Blog access. "Wordy" not an issue. One of the diagrams fills in a few gaps in my recollections. Remember having to go in a bonded liquor facility in the arches below Fenchurch St to access the TSC. In my day Crosswall had lost most of its equipment and was just a signalling supply. The CB at Shadwell feeding it was an interesting specimen.

So what is left on the LTS route today?

I have it as
Fenchurch Street TSL
West Ham FS
Barking FS
Upminster MPTSC
Dunton FS
Pitsea MPTSC
Leigh TSC
Southend FS
Shoeburyness TSL

and

Purfleet TSC
Tilbury Town MPTSC
Mucking Wharf TSC

 

[GraphitProjekt]

I wasn't aware there were still any sectioning substations at Fenchurch St or Shoeburyness, perhaps they're too small to show up on any aerial/cabride imagery.
I find LTS feeding a little bit strange because they're used to be a grid connection at Pitsea which seems to have been replaced by Dunton FS (off Basildon 132kV) some point in the 1990s. Yet there remains a neutral section at Leigh; it's function is unclear to me. I've also heard West Ham feeds the Goblin route. West Ham FS is also a later addition probably from the same era as Dunton because it was originally the mid-point between Gas Factory Jnc and Barking feeders.

I thought I'd quickly sketch up what I think is going on with LTS. Leigh neutral section seems redundant and I'm not sure what's going on with the Woodgrange Park neutral section. It's listed in the sectional appendix but absent in recent cab-ride videos on youtube.


== Doublepost prevention - post automatically merged: 3 Feb 2026 ==

Chanced upon a view of what probably is Fenchurch Street TSL from Goodmans Court on streetview. That particular style of SMOS circuit breaker seems to be what was used in the late 1980s and 1990s. Makes sense as I think 1988 was when the last bits of 6.25kV was removed from LT&S. Still for looking for the one in Shoeburyness though.

 

[PeteK]

So what is left on the LTS route today?

I have it as
Fenchurch Street TSL
West Ham FS
Barking FS
Upminster MPTSC
Dunton FS
Pitsea MPTSC
Leigh TSC
Southend FS
Shoeburyness TSL

and

Purfleet TSC
Tilbury Town MPTSC
Mucking Wharf TSC

Don't get much chance to travel on the LTS but these all look correct from previous research on my part.

== Doublepost prevention - post automatically merged: 4 Feb 2026 ==

I wasn't aware there were still any sectioning substations at Fenchurch St or Shoeburyness, perhaps they're too small to show up on any aerial/cabride imagery.
I find LTS feeding a little bit strange because they're used to be a grid connection at Pitsea which seems to have been replaced by Dunton FS (off Basildon 132kV) some point in the 1990s. Yet there remains a neutral section at Leigh; it's function is unclear to me. I've also heard West Ham feeds the Goblin route. West Ham FS is also a later addition probably from the same era as Dunton because it was originally the mid-point between Gas Factory Jnc and Barking feeders.

I thought I'd quickly sketch up what I think is going on with LTS. Leigh neutral section seems redundant and I'm not sure what's going on with the Woodgrange Park neutral section. It's listed in the sectional appendix but absent in recent cab-ride videos on youtube.
View attachment 197312

== Doublepost prevention - post automatically merged: 3 Feb 2026 ==

Chanced upon a view of what probably is Fenchurch Street TSL from Goodmans Court on streetview. That particular style of SMOS circuit breaker seems to be what was used in the late 1980s and 1990s. Makes sense as I think 1988 was when the last bits of 6.25kV was removed from LT&S. Still for looking for the one in Shoeburyness though.
View attachment 197316

The feeder station at Pitsea was fed from the 132kV grid site at Basildon (Dunton) via underground cables. The FS is, of course, now adjacent to the 132kV site.
According to the pictures of the Romford ECR "dumb" mimic diagram from 2010 there is no NS shown at Leigh.
Cannot imagine West Ham FS feeding to Barking for Goblin. Would assume that it would be fed from existing OHL from Barking FS, particularly with the extension to Riverside.

 

[GraphitProjekt]

The feeder station at Pitsea was fed from the 132kV grid site at Basildon (Dunton) via underground cables. The FS is, of course, now adjacent to the 132kV site.

Ah I see, perhaps they wanted more power than the cables could provide? Also, do you know anything about an ECR at Pitsea? It was mentioned in documents I've seen from 1961 and 1962 but never again.

According to the pictures of the Romford ECR "dumb" mimic diagram from 2010 there is no NS shown at Leigh.

Ah yes, I've spent a long time starring at that blurry album! Indeed it doesn't show an neutral section at Leigh, however it's visible in cab rides on Youtube from 2021 and 2011 (timestamped links btw). And it's been in all the last recent sectional appendices. Back in the day, I take it this substation and NS at Leigh was the 25/6.25kV changeover.

Cannot imagine West Ham FS feeding to Barking for Goblin. Would assume that it would be fed from existing OHL from Barking FS, particularly with the extension to Riverside.

Feeding of Gospel Oak to Barking from West Ham (and Acton Lane) I got from this Network Rail news statement. There is some oddness to it and it seems just as likely that Barking does it particularly as the arrangement of neutral sections fully segregates the line from the circuits running Barking to West Ham.

 

[PeteK]

Ah I see, perhaps they wanted more power than the cables could provide? Also, do you know anything about an ECR at Pitsea? It was mentioned in documents I've seen from 1961 and 1962 but never again.

Ah yes, I've spent a long time starring at that blurry album! Indeed it doesn't show an neutral section at Leigh, however it's visible in cab rides on Youtube from 2021 and 2011 (timestamped links btw). And it's been in all the last recent sectional appendices. Back in the day, I take it this substation and NS at Leigh was the 25/6.25kV changeover.

Feeding of Gospel Oak to Barking from West Ham (and Acton Lane) I got from this Network Rail news statement. There is some oddness to it and it seems just as likely that Barking does it particularly as the arrangement of neutral sections fully segregates the line from the circuits running Barking to West Ham.

Yes, right at the beginning of that cab ride you can see the 25/6.25kV transformer briefly.

Yes, there was an ECR at Pitsea. Similar to Romford it was part of the OHL depot. It had a smaller flat (as opposed to curved mimic) but all the STC supervisory (SCADA as is now) equipment was the same as Romford. Worked there on many occassions.

 

[GraphitProjekt]

Yes, right at the beginning of that cab ride you can see the 25/6.25kV transformer briefly.

Well it'd be long gone by either of those dates, the TSC building at Leigh looks like the modern style of 2010s era electrification so it's possible it was rebuilt recently with a neutral section put back in for some reason. There is one last cab ride video I know of from some point in the 1980s and there you can definitely see the 25/6.25kV transformer even through the blur. You can't really see that there's a neutral section up there but the APC magnets are legible. Commentary from the crew throughout the video is interesting as well.

Yes, there was an ECR at Pitsea. Similar to Romford it was part of the OHL depot. It had a smaller flat (as opposed to curved mimic) but all the STC supervisory (SCADA as is now) equipment was the same as Romford. Worked there on many occassions.

That's so fascinating. As opposed to signalling, there's very little enthusiast interest in the other form of control rooms and there's very little even basic information about them.

For Pitsea ECR, I presume its territory met Romford's at Bow Curve neutral section and Forest Gate Jcn neutral section (which in the 25kV era had Manor Park MPTSC). But the operations must have been more intertwined than since Prittlewell was exporting 2x 33kV circuits to Southend Central s/s and Gas Factory Jnc s/s was connected to Stratford and Bethnal Green.

Also, at what point did Pitsea ECR shut down? I heard that Romford was upgraded with a more computerised SCADA system in 1986 so I've been assuming around that time.

 

[PeteK]

Had a better look at the three cab rides. The 305 one shows the old SFS at Leigh with the 25/6.25kV Tx so I don't know that ride took place. Of the other two the up direction one shows the replacement grey TSC. Cannot see the requirement for a MPTSC (and NS) here as the midpoint is at Pitsea. In the down direction one the TSC (whether new or old) is not visible. In the 305 ride I can see Chalkwell TSC and East Ham TSC. I also spotted the Shadwell 33kV CB "kiosk" (as we used to call it) that feeds down to Crosswall. It is a grey "cube" with a yellow gantry crane on the right (down side) a little bit beyond Limehouse.

As far as Pitsea is concerned I cannot tell when it closed. Like you I imagine it was after conversion and transfer of control to the new Romford system. Both ECRs were part of the same ETE Ilford organisation. I recall some joint operations at the interfaces; Gas Factory 33kV (and presumably the Shadwell CB and Crosswall) was controlled by Romford. There might have been some sort of control over the Southend feeder OCBs from Romford seeing as they were fed from Prittlewell.

By the latter part of 1975 I had moved on from the GE on the GNSE but still have fond memories and interest in the GE area.

 

[MadMac]

According to this old map:

View attachment 195723

It should be this building. I may be wrong though, it doesn't really look like a 1960s 25kV substation
View attachment 195724


I've heard this as well. It seems clear to me that the point of the cable was to allow for a double outage at Parkhead, Dalreoch would feed from the west and Motherwell would from the east via the cable and a substation at Coatbridge. But even though Motherwell-Gartsherrie was wired, it doesn't seem like the capability to feed onto the North Clyde line is actually directly possible anymore and there is, as far as I can tell, no TSC at Coatbridge. Instead, if both Parkhead circuits go out, the line east of Parkhead is fed from Bathgate. (And for completeness, the section west of is would be fed by Eglinton Street via the Argyle line and Rutherglen + Finnieston TSCs.)

Coming back to this, the Final report into EMU transformer failures states in Section 32 that Motherwell fed the “sub feeder station“ at Coatbridge.

 

[GraphitProjekt]

Coming back to this, the Final report into EMU transformer failures states in Section 32 that Motherwell fed the “sub feeder station“ at Coatbridge.

Indeed it does, but since there is no neutral section east of Parkhead FS, I'm inclined to believe that Parkhead normally fed the line all the way to Airdrie and Motherwell was not normally feeding the Coatbridge substation. The term "sub feeder station" is one I find slightly confusing because on the Anglia lines the term seems to only have been used where a substation steps down 25kV on one side to go to 6.25kV on the other. One of this type seems to exist at Westerton Junction, but the fact the sub-feeder symbol is also applied at Finnieston and Coatbridge is a bit odd (and for that matter, not applied at Cheshunt and Leigh on the map adjacent).

This website has some maps for Cathcart Circle/Neilston/Kirkhill lines which suggests that Motherwell also supplied 25kV through Kirkhill to a "sub-feeder station" (named as such) at Cathcart which also cabled the 25kV to a neutral section at the start of the Neilston Line. There is also listed a feeder station at Eglinton Street supplying 6.25kV directly and since the only neutral sections are at Cathcart (one on the Neilston line and one on the Kirkhill line), it seems Motherwell only supplied a 25/6.25kV transformer at Cathcart when Eglinton Street was fully out of order.

Another question is when Gowkthrapple replaced Motherwell? Could it be another situation where the power always actually came from Wishaw substation and moving the FS to Gowkthrapple removed the use of a feeder cable?