Anglia Electrification Part 2: Overhead Line Neutral Sections (OHNS)

Just to have some further ado, I'll share this diagram first before beginning a chronology of this matter. To have a slightly better quality image, which may then be downloaded and finally become something legible, I have also put it on a flickr account here: https://flic.kr/p/2qx4vK1.

This diagram compares information from three main sources on the locations of overhead line neutral sections (OHNS) in Anglia region both past and present. OHNS locations are given a lable with 2 or 3 colour coded text boxes that refer to those different sources.

If anyone isn't aware, a neutral section is a short section of permenantly earthed overhead line designed to insulate against the voltages on either side (so for a 25kv system, the neutral section insulates 50kv). Neutral sections are nessasary in order to seperate different feeds on an AC system that may not be synchronised with each other. This is because the single phase electrification system has to routinely swap which of the 3 phases it takes from the electricity grid in order not to unduly unbalance the grid supply. DC systems (or AC systems using their own power supply instead of the national utility network) don't need neutral sections and can have multiple feeder stations feeding the same electrically common section. 

On British systems, neutral sections can appear at feeder stations (FS) where that station takes two seperate grid feeds and distributes them in either direction from that feeder station. They also typically appear at track sectioning cabins (TSC) at the mid point between two feeder stations to seperate their incoming feeds (called MPTSC), also at TSCs placed on junctions where multiple different feeds meet and are distributed among adjoining lines. Sometimes an OHNS appears independantly of any track sectioning equipment and simply serves to seperate different electrification schemes that were built at different times. In the context of Anglia region, OHNSs also existed to seperate different OLE voltages either standalone but most often at TSCs and either side of feeder stations. It should be noted that some feeder stations do not use a neutral section if they only use one grid connection and are isolated at either end of their feeding section by MPTSCs or the end of electrification. These, I believe, are called "Tee feeders".

The first source here is a recent sectional appendix (September 2024) to suggest the present day situation. Next is all the information on railcodes.org which often gives indication of installation date, though without any citation. And finally below that is a compilation of the sources from 1960-1975. 

These are:

• British Railways—Eastern Region (Great Eastern Line),  Working Instructions for Electrified Lines, (internal: 1960).
  

• British Railways—Eastern Region (London, Tilbury and Southend Line),  Working Instructions for Electrified Lines, BR 31248 (internal: 1961).

• Ministry of Transport (Railway Accidents), Final report on the Accidents and Failures which occured in Multiple Unit Electric Trains in the Scottish Region and Eastern Region of British Railways, (London: HM Stationery Office, 1962). (In particular, "map 2")
  

• British Railways, Working Instructions for A.C. Electrified Lines, BR29987, (internal: 1975). (In particular, appendix B)
  

By and large all these from 1960 to 1975 agree with other on neutral section locations however there are a few descrpencies that are detailed with extra textboxes on the diagram. On the Chenford scheme, Bethnal Green (WAML) and Bishop's Stortford neutral sections were removed before 1975. On the LTS lines, it seems an OHNS was added at Chalkwell after the orginal opening of the electrification in 1960. It's listed however in 1962 and is said (by railcodes.org) to have been commissioned on 27/04/1963.

Naturally, lines which were not electified by 1962 are only recorded in the 1975 source. In particular, this is the Lea Valley main line route via Tottenham Hale which was commissioned in 1969 (pertaining to Trinity Lane and Clapton (mainline) OHNSs). Also Chelmsford to Colchester was electrified as an extention the 1960 scheme and opened in 1962 and so doesn't feature in the 1960 Working Instructions. This is relevant to Witham and Colchester (Clacton) neutral sections.

As will be discussed later, there is a slight complexity with Colchester (Clacton branch) neutral section (apparently also known as "Hunwick") in that it was originally constructed in 1959 in preperation for the extension towards London but was then resited from the twin track junction onto a single line branch and onto a diveunder on the otherside of the mainline. All this was to do with the remodelling of Colchester to coincide with the electrification down to Chelmsford and to provide a grade seperated junction onto the Clacton line for improved direct services to London. Colchester feeder station was definately intended to supply the route northwards to Ipswich in that future scheme (which came in 1985) so they may have installed a neutral section on the main lines here in preparation for that. It is not known whether this was the case, but not especially important either way.

In terms of the information provided, the 1960/1961 Working Instructions both include diagrammatic maps of lines and stations that are electrified with TSCs, neutral sections, feeder stations and control stations marked out. However they only give general positions of those locations with details like "located near milepost 12" for TSCs and FSs only, so the exact location of the neutral section connected to the FS/TSC can only be guessed at. The 1975 source lists all neutral sections in the country at that time with a miles and feet measurement. The milages that appear in the green lables are conversions to mile and chain made out of this information and so milage is vauge where the 1975 source doesn't mention said OHNS (Bethnal Green WAML and Bishop's Stortford). Meanwhile the 1962 MoT report gives positions of neutral sections of a geographical map without any specific milage information. That map also indicates which lines were under construction at that time (Chelmsford to Colchester and LTS which technically would have opened before this document was published) and what lines were proposed to be electrified later.

In reference to railcodes.org and the sectional appendix, railcodes.org is of course unofficial, lists no sources and is occaisionly incorrect enough for my research to challenge their claims. The sectional appendix (table A is the useful part) is also innaccurate on some matters and only updates table A pages as and when meaning some parts can be quite old even if the document is re-issued every quarter. It also could be possible that information is withheld from the public releases.

Of course, lines electrified after 1975 only have the later two sources given. Lines are colour coded as to which set of schemes first electrified them:

• 1.5kv DC system of 1949-1956
  

• Liverpool Street/Fenchurch Street to Shenfield (1949, using GE/MSW OLE)

• Shenfield to Chelmsford/Southend Victoria (1956, using SCS OLE)
  

• 1959-1963 mixed voltage AC lines using BR mark 1 OLE

• Colchester to Clacton/Walton (1959, 25kv AC)

• Chenford (1960, 6.25kv AC/25kv AC)
  

• LTS lines including Forest Gate junction to Barking (1961, 6.25kv AC/25kv AC)

• Chelmsford to Colchester (1962, 25kv AC)
  

• Ockenden branch (1963, 25Kv AC)

• The previously DC lines were converted to 6.25kv AC in 1960 (Except for Shenfield to Chelmsford which was earthed from 1960 until re-energised at 25kv AC in 1962).
  

• 1969 in-fill from Clapton junction to Cheshunt via Tottenham Hale (otherwise known as the Lea Valley mainline) using mark 3 OLE at 25kv AC as with all schemes from this point onwards.
  

• Anglia East and West schemes from 1977-1988 all using mark 3 OLE

• Braintree Branch (1977), 

• Colchester to Ipswich (1985), 

• In 1986
  

• Manningtree to Harwich, 

• Southminster branch, 

• Romford to Upminster, 

• The Graham Road curve (wiring being Reading Lane Junction to Dalston Kingsland station)

• Ipswich to Stowmarket

• In 1987 

• Stowmarket to Norwich

• Bishop's Stortford to Cambridge

• Royston to Shepreth Branch Junction (1988)
  

• Then a few infill schemes in London

• Camden Road to Stratford (previously electrified with third rail) in 1988

• The map does not show this line beyond Navarino Road junction
  

• Stratford to Coppermill Junction via Lea Bridge (1989) 

• Tottenham South Junction to Seven Sisters (1989)

• Extensions to Anglia West in the 1990s

• Stansted Airport branch (1991)

• Cambridge to King's Lynn (1992)

• The small addition of Stratford platforms 1 and 2 for the new London Overground service in 2009

• Further London Overground extensions using Series 2 OLE (all schmes since 1969 had been using various subtypes of BR mark 3)

• Gospel Oak to Barking (specifically, Woodgrange Park junction to Gospel Oak although this map stops just before Harringay Green Lanes) in 2018

• Barking Riverside branch in 2022.

At a glance this does show a certain slowing down of electrification progress since privatisation. Indeed all lines in London except for Gospel Oak - Barking were wired by the 1990s so the number of obvious choices in Anglia region has been somewhat low. But it should be mentioned that the 1962 MoT report states that Felixstowe branch was definately proposed for wiring back then. In my speculation, Felixstowe to Ipswich, Stowmarket to Ely/Cambridge and Ely to Peterborough are the most likely candidates to get proposed (or reproposed) simply because of the container freight eminating from Felixstowe. Indeed, the North London Line and other inner suburban lines around Stratford were electrified in the late 1980s in order for freight flows to be accomodated from the WCML to GEML and LTS lines. I can say with some certainty that the Sudbury branch, East Suffolk line, Wherry lines and Bittern line will never be electrified - the Breckland line could believably go either way. This is also the recommendation of the oft forgotten Traction Decarbonisation Network Stratergy (interim) of 2020.

This map serves as a useful baseline reference for placing in time and space the more detailed machinations I will be investigating later. This is especially true because no other diagram I have made will show positions of stations. The yellow labled text are the Engineer's Line Reference (ELR) for each stretch of railway.

As a last note: railcodes.org and the 1975 source offer specific names for neutral sections while the sectional appendix and 1960-1962 sources do not.

Anglia Electrification Part 1: Introduction and Sources

Introduction

Aims & Objectives

In any mention of the electrification of the lines into East London, it is often stated that the first section of GEML was at 1.5kv DC and then this was replaced by a ‘mixed system’ of 25kv and 6.25kv AC where clearances were considered not permitting. Little elaboration is given beyond this. So I intend here to ascertain exactly which lines in the Anglia region were at 6.25kv and at what times they were upgraded to 25kv. I also intend to piece together an impression of the traction power feeding arrangements at various points in time. For both these, I will construct explanatory maps and diagrams to display this information visually, perhaps for the first time.

This is also part of a wider study in establishing basic information about electrical control rooms on the British rail network both past and present; so some mention is given to that topic where revelations are made. I declare my intents here so as to remind any concerned that many of the sources I have consulted also give good detail on many other aspects of past electrification projects (financing, civils, remodelling, signalling, OLE systems, rolling stock, timetabling, etc) however I have not generally made note of these other topics.

Context & Overview

                In 1949 the GEML between Liverpool Street and Shenfield was electrified at 1.5kv DC. This was followed in 1956 by an extension of the system to Chelmsford and Southend Victoria. In 1959 Colchester to Clacton was electrified at 25kv AC as one of two early pilot schemes into high voltage AC systems using industrial frequencies. In 1960, Liverpool Street to Southend was converted to 6.25kv AC (a compromise voltage to accommodate the tighter clearances that 1.5kv DC could achieve) with Shenfield to Chelmsford converted straight to 25kv two years later. 

Also in 1960 the lines from Liverpool Street to Hertford East and Bishops Stortford via the Southbury Loop, and to Enfield, and to Cheshunt were electrified with the mixed system of both voltages (known as the 'Chenford' scheme). Then in 1961 all lines out of Fenchurch Street were electrified with the mixed system as well; this was the introduction of new 6.25kv electrification. Seemingly all EMUs built in the 1950s, 60s and 70s for this region were capable of dual voltage operation until the introduction of class 315s in the early 1980s.

In 1969 the Lea Valley mainline route was added at 25kv AC and from 1975 it is said that conversion to 25kv started to take place on all lines. From 1985 new schemes brought further extensions to the 25kv in the region. By 1987 electrification had reached the end of the GEML at Norwich (along with the branches to Braintree, Southminster and Harwich) and as far as Cambridge on the WAML with the last stretch to Kings Lynn opening in 1992. By the time of the introduction of class 357s on the LTS network in 2000, it would not have been possible for any 6.25kv lines to still exist.

From the late 2000s work began to re-equip the OLE system between Liverpool Street, Chelmsford and Southend because the 1940s/50s designed registration, support and tensioning systems had become unacceptably unreliable. In conjunction with this, autotransformer feeding was installed in the Shenfield in connection with the Crossrail project.

Sources

Present day Network

For AC overhead systems, voltages and feeds have to be separated by neutral sections. Because neutral sections are important to train drivers and their regular duties, they tend to be the best attested components of feeding arrangements. Neutral sections are listed in modern sectional appendices and on the archive website railwaycodes.org.uk which together give a generally accurate account of neutral section locations for present day installations. 

The website openinframap.com claims to have recorded all grid transmission and top level distribution lines currently active, and since GB 25kv AC systems connect to the grid at ≥132kv substations, a combination of OpenInfraMap and the sectional appendices that Network Rail have started publishing online can give an indication of feeder station and MPTSC/MPATS sites on the present day network, in lieu of better information. Recent cab ride videos and satellite imagery can somewhat allude to track sectioning locations. Furthermore, work related to new installations are sometimes mentioned in corporate media bulletins (though occasionally with un-corroborative factuality).

One of the most instrumental sources I have continually reffered to in this project is a set of blurry images taken of Romford ECR's mimick panel in August 2010. Although a lot of detail is missing and a lot of subtleties are likely lost on me, they still give a good general sense of the feeding arrangements immediately prior to alterations made for the autotransformer system. The pictures are publically available of the always insightful photos.signalling.org. In addition to this, there is one very blurry picture of Romford ECR's new TPCMS (Traction Power Centralised Management System) VDU board taken (presumably during testing) in November 2017. This I found from an unlikely source called Highways Today, one of a fair number little known corperate periodicals that has reported on Network Rail's modernisation of electrical control (princapally the renewal and standardisation of SCADA technologies into a new system known as TPCMS). It is the banner image of an article they published on the 12th of March 2018 when the new system was commisioned at Romford titled "Traction Power Centralised Management System goes live for Network Rail upgrade" that can be read here. I take some measures to communicate in this text what these sources actually are rather than just "click this link" as I know all too well how links can very easily go missing over time.

Historical Network: Primary Sources

                For historical feeding arrangements, British Railways Working Instructions booklets for various installations are usually well detailed for this topic.  I was able to access a 1956 booklet for the Liverpool Street/Fenchurch Street to Chelmsford and Southend Victoria DC system (includes information on the original Liverpool Street to Shenfield extent as well), a 1958 instructional on the Colchester to Clacton pilot scheme, for 1960 LTS AC system and for the 1960 Great Eastern and Lea Valley lines (Liverpool street to Chingford/Enfield Town/Hertford East via Southbury).
                These working instructions include information on the relevant electrical control room, location of substations and track sectioning sites, and a detailed line diagram with signal boxes, wiring extents and neutral sections shown although it is vague on exact mileages. However, it appears that this kind of internal publication about a specific installation stopped being produced at some point and British Railways instead issued general instruction booklets harbouring much of the same information as the earlier ones in regards to staff procedure; but without any specific information on the locations of ECRs, feeder stations or TSCs that were in operation at that time. The only useful information to be gained here is the list of neutral sections with mileages in appendix B. One such publication of this type was available to me dating from May 1975. 
                Interestingly, the high profile failures of certain EMUs introduced to the North East London area in connection with the Chenford scheme caused several highly detailed Ministry of Transport reports to be written and are publicly available on the RailwaysArchive website. The final report includes high quality information on voltage boundaries, feeder stations, TSCs and electrical control arrangements for the LTS, GE AC conversion and Chenford systems as they stood at 1962. Perhaps relevant to a different project, it also include similar information for the Glasgow North of Clyde area, Lancaster/Morecambe/Heysham 50hz install, the first stage of WCML electrification from Manchester to Crew including the Styal line, and - of course - highly specific information on EMU components, circuitry and functionality. This has given some extra insight for Chenford and GEML feeding arrangements at the original AC installation in the early 1960s. From the MoT reports, the 1960/1961/1975 Working Instructions, we can locate the neutral sections of the GEML, LTS and WAML networks to the mile and chain. There are not any discrepancies between the neutral sections listed in 1962 and 1975 (with one exception) implying feeding arrangements stayed largely the same in that period.
                Mention should also be made to an edition of a short lived magazine called Railway Pictorial and Locomotive Review which was apparently one of three mostly unsuccessful periodicals started by a G.H. Lake in the 1940s and 50s. Each time he endeavoured to specialise in high quality photographs and diagrams to be a focal point of each publication. But most of G.H. Lake’s ventures seemed to be either unsuccessful or moved on without him. But where he was able to publish, the quality of information and detail is unexpectedly high including when dealing with (at that time) contemporary developments. From Railway Pictorial and Locomotive Review, a 4 part series (of February, March, May, June 1950) was dedicated to the new DC installation between Liverpool Street and Shenfield was available to me. It includes many elucidating and likely rare photos of the scheme when it had just opened and during construction. Of particular note is around 1000 words written on the operation and functionality of the Chadwell Heath electrical control room. This is the most I have seen reported anywhere on a specific ECR, either historic or modern.

(More information about G.H. Lakes' magazines can eb found on hte page for the Great Eastern Society's purchasble scans of his publications. From the index that I can view, he could have good insights into early Merseyside electrification schemes.)

Historical Network: Secondary Sources

                The main work that touches on this subject is John Glover's Eastern Electric (2003). While the book gives good information on the feeding arrangements of the original DC system and on the AC systems around 1961, less and less detail on that subject is given as the book progresses and very little is given about the timeline of 6.25kv to 25kv conversion. Exceptionally, I was able to access the back catalogue of the Great Eastern Journal (the periodical of the Great Eastern Railway Society) which ran a series of seven articles by John Baker (1992–1994) about the history of Eastern Region electrification. Conspicuously, however, the articles only concern themselves with the period 1949–1969 and so while they added some good details to these systems, on the whole the Great Eastern Journal did little to help with understanding the chronology of 6.25kv electrification.

                In short, information on feeding arrangements is not well documented past the early 1960s in the literature I could find. Both Glover and the Great Eastern Journal (itself mentioned as a source to Glover) would surely have used the same “Electrified Lines: Working Instructions” that I could find (Glover explicitly cites a few). I wonder if this kind of technical detail is not sought after for a historical era that could be considered ‘modern’. After all, those early electrification schemes are old enough to intersect with the era of steam traction that has, for many years, driven the scholar-enthusiast interest in railways. Or perhaps that the change in BR policy around electrified line instructional booklets equally affected the secondary sources as well as myself.

                Returning to the website RailCodes.org.uk, they also present an extensive timeline of electrification dates on the mainline network, and on the aforementioned page about neutral sections, occasionally mention a historical neutral section or one added as a modification. From this I gather that significant feeding modifications must have occurred to the GEML in the mid to late 1990s. However, RailCodes.org.uk does not mention its sources, and in terms of its electrification scheme dates, there are a few statements it makes which I believe I have the proof to challenge.

                Furthermore, Garry Keenor’s (2021) high quality and freely available primer on OLE systems also includes a chronology of when all GB OLE installations were opened. It is in this book that the first mention I found of when 6.25kv systems became 25kv in the 1980s was given. Keenor does not, however, say much about feeding arrangements in practice. I also consulted Keenor’s main source The Age of The Electric Train by J.C. Gillham (1988) which added some extra detail about rolling stock moves but is still suitably vague about the Lea Valley lines. Finally, Ian Cowley’s Anglia East (1987) has been consulted as well. This book does not generally discuss feeding arrangements or voltage changes and is mainly focused on the extension of electrification from Colchester to Norwich and Harwich. Though it does have the occasional relevant insight.

Investigate 4/11: First Principles

This blog shall serve as a location to store my investigations into whatever topic is of my intrigue. I claim no subject matter expertise on what I discuss since I am only ever an interested outsider. For the time being, I shall be discussing railway electrification in the UK - in particular - feeding arrangements and electrical control. However, other subjects may seep into this blog if I think I have anything interesting to say about it.

I believe electrical control is a much overlooked topic in the rail-enthusiast space and I have basically never heard of any train nerds discussing it. It feels like a secret sibling to railway signalling and so only mentioned by cold, hardened professionals - likely too busy and too serious to placate the grandiloquent baying of ostentatious rivet counters even if the former had turned their noses towards this niche subject.

When it comes to enthusiast media, the general topic of electrification is too often a brief addendum, relegated to a small paragraph about the 'boring' and 'ugly' things that happened once our belovèd motorised kettles were taken to slaughter. Signalling, though equally modern and now decidedly un-quaint, maintains enthusiasts' interest; perhaps propped up by its connection to the powerful symbology of semaphore arms, block bells and Victorian architecture. Even if those austere LED beacons looming over alien artefacts in the 4 foot evoke a distrustful melancholy, they are at least a direct descendant of the virtuous steam railway: when men were men and blocks were absolute.

Electrification is not often granted the same unconditional respect despite being just as old as the golden age of steam. Is it retroactively understood as an encroachment of modernity? Or maybe too associated with commuter lines and urban living? That being said, I can't deny the deep nostalgia that exists for old electric rolling stock and the dedicated chronicling that this has brought. It's more for the infrastructure side that electrification gets the short end of the stick.

I was completely unaware of the presence of electrical control rooms until I purchased one of the latest editions of the quailmap from Darlington station's WHSmith last year. The very latest editions of quailmap (from 2022 onwards) have started to include ECRs for no apparent reason. I think I must have guessed they existed if someone had asked me the question, maybe as an extra function of signal boxes. What's more telling is that nobody had ever posed that idea in my vicinity or mentioned electrical control even in passing. But it was here I learned electrical control was its own domain with completely different boundaries to signalling and so I was incensed to locate every site of electrical control and the lines that belonged to them. And so I discovered the total lack of commentary online about this subject and so I think it worth me starting this blog to centralise any information I have found.

In addition to conventional sources like books and official documentation, I will also be relaying anything interesting I find mentioned on RailUK Forums. Likely someone on there knows the answer to almost any question I could muster. The general problem with RailUK Forums is that there are a comparatively small number of people who know the information, and quite a lot of people continually asking the same things about a topic. This often leads to the situation where those who know get tired of repeating the same points over and over again and so you get ignored or told to parse 200+pages of random conversation dating back over a decade.

Another sub-function of this blog is to hold information that I'm considering adding to Wikipedia but am not yet satisfied that it reaches their evidencing standards. Even if I put what I've found on a Wikipedia article, I'll be freer here to add more explanation to my judgements and comment on more broader notions.

The first topic I will discuss is the past and present of electrification in the Anglia region.