Editing Great Eastern Main Line (section)

=== Electrification ===
The main line is [[Railway electrification in Great Britain|electrified]] at [[25 kV AC railway electrification|25 kV AC 50hz]] using [[Overhead line|overhead wires]] under the control of Romford Electrical Control Room. The branches to {{stnlink|Upminster}}, {{rws|Southend Victoria}}, {{rws|Southminster}}, {{rws|Braintree|England}}, {{rws|Clacton-on-Sea}}, {{rws|Walton-on-the-Naze}} and {{rws|Harwich Town}} are also electrified. The history of electrification on the GEML and adjoining routes is unusually complicated with parts of the line having been electrified with three different systems. Due to this, as well as traffic demands growing throughout the 21st century, the traction supply feeding arrangements are complex and somewhat unintuitive with several seemingly redundant features.

The earliest stretch of electrification was between [[Liverpool Street station|Liverpool Street]] (only platforms 11–18) to [[Shenfield railway station|Shenfield]] along with the branch from Fenchurch Street (platforms 1 and 2) down the [[Bow Curve]] in 1949. This was an overhead line system (OLE) at [[Railway electrification#Overhead lines|1.5kV DC]] and was extended to [[Chelmsford railway station|Chelmsford]] and [[Southend Victoria railway station|Southend Victoria]] in 1956.<ref>{{Cite book |last=Glover |first=John |title=Eastern Electric |publisher=Ian Allen |year=2003 |isbn=0-7110-2934-2 |location=Hersham, Surrey |pages=36}}</ref> Over the weekend of the 5th and 6th of November 1960, the system was converted to [[Railway electrification in Great Britain#6,250 V 50 Hz AC, overhead|6.25kV AC]] at mains frequency (50hz) between Liverpool Street and Southend Victoria,<ref>{{Cite book |last=Glover |first=John |title=Eastern Electric |publisher=Ian Allen |year=2003 |isbn=0-7110-2934-2 |location=Hersham, Surrey |pages=45}}</ref> with the wires from Shenfield to Chelmsford taken out of use to be converted to 25kV AC until re-energisation on the 20th March 1961.<ref name=":1">{{Cite book |last=Keenor |first=Garry |url=https://ocs4rail.com/ |title=Overhead Line Electrification for Railways |year=2021 |edition=6th |pages=Appendix A |type=online e-book |format=PDF}}</ref>(although passenger service with electric trains did not return until the next year). The low voltage AC utilised broadly the same substations, grid connections, OLE components and electrical clearances as the previous DC system.<ref name=":2">{{Cite journal |last=Baker |first=John |date=April 1993 |title=GE Section Overhead Electrification 1935-1969, Part 5 |journal=Great Eastern Journal |volume=74 |pages=18}}</ref> At around the same time, the rest of the platforms and lines out of Liverpool Street (the [[Lea Valley lines]]) and [[London, Tilbury and Southend line|out of Fenchurch Street]] were electrified also at 6.25kV AC in November 1960 and November 1961 respectively.

After this point, electrification was extended up the Great Eastern Main Line and on several branches all at 25kV AC. The line from [[Sunshine Coast Line|Colchester to Clacton-on-Sea and Walton-on-the-Naze]] was previously electrified in 1959 at 25kV AC and the gap was filled between Colchester and Chelmsford in 18th June 1962.<ref>{{Cite book |last=Glover |first=John |title=Eastern Electric |publisher=Ian Allen |year=2003 |isbn=0-7110-2934-2 |location=Hersham, Surrey |pages=78}}</ref> From 1975 until 1988, all the sections of 6.25kV AC around London and Southend across all lines in the Anglia region were converted to 25kV AC requiring new substations and significant modifications to the OLE components. In 2022, a small section between Bow Junction and Gidea Park was upgraded to a 2x25kV AC autotransformer system in order to support the [[Elizabeth line|Elizabeth Line]] service. The full timeline for the electrification on the GEML and branches is summarised below. 
{| class="wikitable"
|+Timeline of GEML Electrification<ref name=":1" />
|-
!Date
!Route
!Action
!Voltage
![[Railway electrification in Great Britain#25kV AC heavy rail network|OLE System]]
|-
|26 September 1949
|[[Liverpool Street station|London Liverpool Street]] (plat. 11–18) to [[Shenfield railway station|Shenfield]]
[[Fenchurch Street railway station|London Fenchurch Street]] (plat. 1–2) to Bow Junction{{efn|Over the [[Bow Curve]], line was and is rarely used}}
|new build
|[[Railway electrification#Overhead lines|1.5kV DC]]
|GE/MSW
|-
|11 June 1956
|Shenfield to [[Chelmsford railway station|Chelmsford]]
|new build
|1.5kV DC
|SCS
|-
|31 December 1956
|Shenfield to [[Southend Victoria railway station|Southend Victoria]]
|new build
|1.5kV DC
|SCS
|-
|16 March 1959
|[[Sunshine Coast Line|Colchester to Clacton-on-Sea/Walton-on-the-Naze]]{{efn|Along with the [[Styal line]] in Manchester, this line was a testbed for mains frequency AC electrification that has been standard ever since}}
|new build
|[[25 kV AC railway electrification|25kV AC 50hz]]
|Mark 1
|-
|4 November 1960
|Shenfield to Chelmsford
London Fenchurch Street to Bow Junction{{efn|Line was de-energised due to the impending electrification of all routes out of Fenchurch Street}}
|de-energisation
|(earthed)
| —
|-
|6 November 1960
|London Liverpool Street to Southend Victoria
|conversion
|[[Railway electrification in Great Britain#6,250 V 50 Hz AC, overhead|6.25kV AC 50hz]]
| —
|-
|21 November 1960
|London Liverpool Street (plat. 1–10) to [[Chingford branch line|Chingford]]/[[Enfield Town branch line|Enfield Town]]/[[Southbury Loop|Cheshunt via Seven Sisters]]{{efn|This scheme also electrified the lines from Cheshunt to [[Bishop's Stortford railway station|Bishops Stortford]] and [[Hertford East branch line|Broxbourne to Hertford East]] but at 25kV AC with a voltage changeover at Cheshunt}}
|new build
|6.25kV AC 50hz
|Mark 1
|-
|6 November 1961
|[[London, Tilbury and Southend line|Fenchurch Street (all platforms) to Barking]]/Bow Junction 
[[Forest Gate railway station|Forest Gate]] Junction to Barking{{efn|This scheme also electrified both lines out of Barking but at 25kV AC with the voltage changeover near [[Upney tube station|Upney]] on the main routes and some distance before [[Ripple Lane TMD|Ripple Lane]] on the [[Tilbury loop line|Tilbury Loop]]. Both lines converge at [[Pitsea railway station|Pitsea]] and then change back to 6.25kV AC from [[Leigh-on-Sea railway station|Leigh-on-Sea]] to the terminus at [[Shoeburyness railway station|Shoeburyness]]}}
|new build/
re-energisation
|6.25kV AC 50hz
|Mark 1 (on new parts)
|-
|20 March 1961
|Shenfield to Chelmsford{{efn|Using a new 25kV feeder station at Shenfield which later fed back towards Gidea Park}}
|re-energisation
|25kV AC 50hz
| —
|-
|18 June 1962
|Chelmsford to Colchester
|new build
|25kV AC 50hz
|Mark 1
|-
|1 January 1976
|[[Gidea Park railway station|Gidea Park]] to Shenfield
|conversion
|25kV AC 50hz
| —
|-
|31 October 1977
|[[Braintree branch line|Witham to Braintree]]
|new build
|25kV AC 50hz
|Mark 3a
|-
|2 March 1980
|[[Manor Park railway station|Manor Park]] to Gidea Park{{efn|Using a new 25kV feeder station at Crowlands}}
| rowspan="3" |conversion
| rowspan="3" |25kV AC 50hz
| rowspan="3" | —
|-
|14 September 1980
|Bow Junction to Manor Park{{efn|Using one half of a new 25kV feeder station at Bow Junction}}
|-
|12 October 1980
|London Liverpool Street to Bow Junction
London Liverpool Street to Hackney Downs{{efn|Full commissioning of Bow Junction feeder station, the approach to Liverpool Street from Bow Junction, and the WAML from Bethnal Green to Hackney Downs are electrically common}}

Shenfield to Southend Victoria{{efn|Not currently known at what point between March and October 1980 that the Southend Line was converted}}
|-
|13 May 1985
|Colchester to Ipswich
| rowspan="6" |new build
| rowspan="6" |25kV AC 50hz
| rowspan="6" |Mark 3b
|-
|22 July 1985
|Ipswich to Stowmarket
|-
| rowspan="3" |12 May 1986
|[[Crouch Valley line|Wickford to Southminster]]
|-
|[[Mayflower line|Manningtree to Harwich]]
|-
|[[Romford–Upminster line|Romford to Upminster]]
|-
|11 May 1987
|Stowmarket to Norwich
|-
|~1988
|London Fenchurch Street to Barking/Bow Junction
Forest Gate Junction to Barking

[[Leigh-on-Sea railway station|Leigh-on-Sea]] to Shoeburyness
|conversion
|25kV AC 50hz
| —
|-
|~2022
|London Liverpool Street to Chelmsford
Shenfield to Southend Victoria
|re-equipping of OLE system{{efn|This scheme replaced all OLE components that originated from 1949 or 1956 and took 15 years to complete beginning in 2007. Voltage and feeding was unaffected. "GEFF" stands for "Great Eastern Furrer+Frey", who were the designer for the bespoke system.<ref>{{Cite web |title=GEFF overhead contact line system for UK’s Great Eastern Route |url=https://www.furrerfrey.ch/en/reference/geff-overhead-contact-line-system-for-uks-great-eastern-route/ |access-date=2025-02-21 |website=Furrer+Frey baut Fahrleitungen - Furrer+Frey }}</ref>}}
| —
|GEFF
|-
|24 June 2022<ref>{{Cite web |date=2022-07-07 |title=Elizabeth line upgrade for the Pudding Mill power supplies |url=https://www.ianvisits.co.uk/articles/elizabeth-line-upgrade-for-the-pudding-mill-power-supplies-55819/ |access-date=2025-02-21 |website=ianVisits }}</ref>
|Bow Junction to Gidea Park
|conversion to AT feeding
|2x 25kV AC
(Autotransformer system)
| —
|}
{{notelist}}

====Historic 6.25kV/25kV voltage changeover====
Since trains would through-run between 6.25kV and 25kV sections in regular operation, all [[Electric multiple unit|EMUs]] built for the Anglia region between 1960 and 1980 were fitted for dual AC voltage with equipment to automatically switch between the two power systems while running.<ref name=":7">{{Cite book |last=Cowley |first=Ian |title=Anglia East |publisher=David & Charles |year=1987 |isbn=0-7153-8978-5 |location=Newton Abbot |pages=70-86}}</ref> The main [[transformer]] on the train had four identical primary windings which could be connected in series for 25 kV working, or in parallel for 6.25kV working, by means of a "supply changeover switch". It was vital that the changeover switch was in the correct position since, if the voltage was too low, the train could not operate, while if the voltage was too high, serious damage could occur. For this reason, the switchover had to be made automatically by way of voltage sensing equipment rather than rely on the driver operating controls.

At the points where the two systems met – such as on the main line just east of Shenfield – there was a short length of overhead line which was electrically neutral. Neutral sections were installed either at breaks between supply areas or where the two voltages met. Whether or not the voltage was different on the other side of the neutral section, the on-train equipment operated in exactly the same way. At each end of the neutral section there were track-mounted permeant magnets referred to as Automatic Power Control (APC) magnets.<ref name=":8">{{Cite book |last=Keenor |first=Garry |title=Overhead Line Electrification for Railways |year=2021 |edition=6th |pages=93}}</ref>

On board the train, the operation of the dual-voltage mechanism depended on the action of the main air-blast [[circuit breaker]] and voltage-sensing relays. When passing the first APC magnet, detection equipment fitted to the bogies would activate the circuit breaker cutting all power to the train. Once the train had passed the neutral section, the second set of APC magnets are detected by the bogie-mounted inducers which causes a lock to be released on the circuit breaker meaning its reclosing would be under the control of the voltage-detection equipment. This consisted of four voltage relays that would allow for a line voltage between 4.1 and 6.9kV for the low-voltage mode, and 16.5 to 27.5kV for the high-voltage mode. If the first relay was tripped, the changeover switch at the transformer was set to the low-voltage mode and the circuit breaker closed. All four relays were activated if the voltage was above 16.5kV. In that case, the current was sent to a magnetic switch that would set the changeover switch at the transformer to the 25kV position.

The other relays were installed to stop the changeover switch from being activated to low-voltage mode if the line voltage fell under 16.5kV but greater than 6.9kV. The changeover system was interlocked with the circuit breaker and the action of the APC magnets since any movement of the changeover switch while the circuit breaker was closed and connecting the system to any live current would cause destructive arcing for the internal components. Following testing and some in service incidents, modifications were made to the changeover equipment such that a switch to the low-voltage mode could only be made when the line voltage had dropped to below 3kV and then risen to 4.1kV, and that the re-closing of the circuit breaker is only made after a two-second wait following the detection of the second APC magnet to ensure a correct reading of the voltage.<ref>{{cite book |title=British Rail Locomotives and other motive power: Combined volume |year=1968 |publisher=[[Ian Allan Publishing|Ian Allan]] |location=London |isbn=0-7110-0008-5 |page=11 }}</ref><ref name=":9">{{cite report |url=https://www.railwaysarchive.co.uk/docsummary.php?docID=732 |title=Failures of Multiple-unit Electric Trains on British Railways: Final Report |last=Langley |first=C.A. |date=17 March 1962 |via=The Railways Archive |access-date=23 February 2025 |at=paragraphs 24, 44, 65, 68, 142–144; figures 1 & 2; map 2 }}</ref>

As well as new EMUs introduced after 1960, the previous [[British Rail Class 306|class 306]] and [[British Rail Class 307|307]] units originally built for the 1.5kV DC system underwent conversion to become 6.25/25kV dual-mode EMUs. The conversion of both these classes of train involved significant interventions particularly the relocating of the pantograph to a different carriage and the associated internal layout changes this caused.<ref name=":7" /> The full 92-unit fleet of class 306s and the 32 units of class 307 fleet underwent alterations at [[Stratford Works]] with new equipment provided by Associated Electrical Industries at Manchester.<ref name=":9" />

Neutral sections are, or course, still required on the modern 25kV system and APC magnets are still used to automatically trigger the opening of the train's circuit breaker so that an arc is not caused at OLE when the pantograph travels between live and earthed wire.<ref name=":8" />

==== Feeding arrangements ====
The majority of the GEML network is electrified using the [[Railway electrification in Great Britain#Feeding Arrangements (Classic)|'classic' feeding arrangement]] connected to the 132kV distribution grid all controlled by [[UK Power Networks]]. In accordance with the [[Crossrail]] project, [[Railway electrification in Great Britain#Feeding Arrangements (Autotransformer)|autotransformer feeding]] was fitted between the new autotransformer feeder station (ATFS) at Pudding Mill Lane and Gidea Park. Pudding Mill Lane ATFS also feeds the Crossrail core from that point to the Westbourne Park tunnel portal and towards Abbey Wood.<ref>{{Cite web |title=East meets west |url=https://www.railtechnologymagazine.com/Comment/east-meets-west |access-date=2025-02-21 |website=www.railtechnologymagazine.com}}</ref> This entirely replaced Crowlands classic feeder station (located between [[Chadwell Heath]] and [[Romford railway station|Romford]]) and significantly reduced the load of the Bow Junction classic feeder station. The feeder station is connected to the [[National Grid (Great Britain)|National Grid]] 400kV transmission substation also named Pudding Mill Lane.

The line between Gidea Park and Shenfield is fitted out to be converted to autotransformer feeding in the near future with a sectioning autotransformer station (SATS) already completed at Shenfield in 2018.<ref>{{Cite web |title=Shenfield SATS sub-station |url=https://vgcgroup.co.uk/case-studies/shenfield-sats-sub-stations/ |access-date=2025-02-22 |website=VGC Group }}</ref> Autotransformer feeding is also due to be extended as far as [[Beaulieu Park railway station|Beulieu Park]] as a new ATFS is being constructed just north of the station at the same site as the Springfield classic feeder station.<ref>{{Cite web |title=Great Eastern Main Line Power Supply Upgrade Beaulieu Feeder Station (GRIP 2 to 8) |url=https://www.amey.co.uk/media/news/2020/february/great-eastern-main-line-power-supply-upgrade-beaulieu-feeder-station-grip-2-to-8/ |access-date=2025-02-22 |website=Amey }}</ref>

The original 1.5kV DC system of 1949 used traction substations at Bethnal Green, Stratford, Chadwell Heath, Gidea Park, and Shenfield all supplied by 33kV 3 phase AC distribution ring owned and operated by the railway. The 33kV ring was itself supplied by the utility grid at Chadwell Heath and Crosswall (near Fenchurch Street).<ref name=":4">{{Cite book |last=British Railways—Eastern Region (Great Eastern Line) |title=Liverpool Street and Fenchurch Street to Chelmsford and Southend (Victoria) Electrified Lines Working Instructions |publisher=(internal) |year=1956 |ref=BR29818}}</ref> Beyond Shenfield, the DC system installed in 1956 to Chelmsford and Southend Victoria did not use the railway distribution lines but were connected directly to the public utility grid at 33kV.<ref name=":5">{{Cite journal |last=Baker |first=John |date=Oct 1992 |title=GE Section Overhead Electrification 1935-1969, Part 3 |journal=Great Eastern Journal |volume=72 |pages=27}}</ref> Between Liverpool Street and Shenfield, the DC substations were significantly altered but retained for the conversion to 6.25kV in 1960 but were unsuitable for the further upgrades to 25kV. So too were the 33kV distribution lines which were reinforced by replacing the Crosswall grid connection with a stronger one at Bethnal Green. However after 1960, the distribution lines no longer powered Shenfield substation as a new feeder station was built that could supply both 6.25kV southwards and on the Southend line and 25kV for the line north to Chelmsford and for the future upgrade.<ref name=":2" />

From 1976 to 1980 the 6.25kV lines between Liverpool Street and Southend Victoria were upgraded to 25kV which required entirely new grid connections and substations. New feeder stations were installed at Crowlands and at Bow Junction. The substation at Gidea Park became the MPTSC between Shenfield and Crowlands, and a brand new MPTSC was installed at Manor Park to separate Crowlands and Bow Junction feeder stations. Bow Junction feeder station also supplied the WAML up to a new MPTSC at Hackney Downs by way of a new Spitalfields TSC around Bethnal Green junction.<ref name=":6">{{Cite web |title=Anglia / Romford ECR {{!}} Signalling Photos |url=https://photos.signalling.org/index?/category/235-romford_ecr |access-date=2025-02-22 |website=photos.signalling.org}}</ref>
{| class="wikitable"
|+List of traction substations on the Great Eastern Main Line<ref name=":4" /><ref name=":5" /><ref name=":6" /><ref>{{Cite book |last=British Railways—Eastern Region (Great Eastern Line) |title=Working Instructions for Electrified Lines |publisher=(internal) |year=1960}}</ref><ref>{{Cite book |last=British Railways—Eastern Region (London, Tilbury and Southend Line) |title=Working Instructions for Electrified Lines |publisher=(internal) |publication-date=1961 |ref=BR31248}}</ref><ref>{{Cite book |last=British Railways |title=Working Instructions for A.C. Electrified Lines |publisher=(internal) |year=1975 |ref=BR29987}}</ref><ref>{{Cite journal |last=Ministry of Transport (Railway Accidents) |year=1962 |title=Final report on the Accidents and Failures which occurred in Multiple Unit Electric Trains in the Scottish Region and Eastern Region of British Railways |journal=London: HM Stationery Office}}</ref>
!Mileage{{Efn|1=Measured in miles and chains (80 chains = 1 mile)}}
!Substation
![[Railway electrification in Great Britain#Feeding Arrangements (Classic)|Type]]
!In use
!Neutral Section
!Grid Connection
!Notes
|-
|0m 0c
| colspan="6" |[London Liverpool Street station: datum point for the line]
|-
|0m 30c
|''Liverpool Street''
|''TSC{{Efn|Technically speaking, a TSC on a DC railway should be referred to as a Track Paralleling Hut (TPH), they are functionally similar. However, this table will call them TSC for simplicity with terminology for AC systems. In addition, the original documentation for the DC system used the term TSC.}}''
|''1949–1980''
|''no''
|''n/a''
|Converted in 1960 from 1.5kV DC to 6.25kV AC
|-
|01m 14c
|Spitalfields
|TSC
|since 1980
|no
|n/a
|Allows Bow Junction "A" to feed the WAML that splits at Bethnal Green. Replaced Liverpool Street TSC
|-
|01m 22c
|''Bethnal Green''
|''FS''
|''1949–1980''
|''yes (from 1960)''
|''Railway owned 33kV ring''
|Converted in 1960 from 1.5kV DC to 6.25kV AC. Substation also fed WAML from 1960.
|-
|02m 68c
|''Bow Junction''
|''TSC''
|1949–1980
|''no''
|''n/a''
|Converted in 1960 from 1.5kV DC to 6.25kV AC
|-
|03m 15c
|Bow Junction
|FS
|since 1980
|yes{{Efn|Neutral sections at Bow FS were moved to 2m 70c in 1995, and to 2m 68c in 2015.
03m 15c represents where the substation is approximately located}} 
|[[UK Power Networks|UKPN]] 132kV underground power line
(Hackney Supergrid 132 to Bow 132)<ref>{{Cite web |last=UK Power Networks |year=2014 |title=LPN Regional Development Plan (North London) |url=https://library.ukpowernetworks.co.uk/Library/GetPdf?pdfUrl=Asset_Management_Documents%2FRegional_Development_Plans%2FLPN%2FLPN_RDP_North_London_Islington_Hackney.pdf |format=pdf}}</ref>
|Dual FS with "A" and "B" sides. Installed for 25kV upgrade. Replaced Bethnal Green and Stratford FSs. Since 2022, the "B" side no longer feeds GEML but does supply [[North London line|North London Line]] and [[Lea Valley lines#Route and services|Temple Mills Branch]] via ducting to the Stratford area.
|-
|03m 31c
|Pudding Mill Lane
|ATFS
|since 2022
|yes
|Adjacent [[National Grid (Great Britain)|National Grid]] Pudding Mill Lane 400kV transmission substation
|Dual ATFS. "A" side powers Crossrail Central Operating Section, "B" side powers GEML replacing Bow Junction "B" FS.
|-
|04m 55c
|''Stratford''
|''FS''
|''1949–1980''
|''yes (from 1960)''
|''Railway owned 33kV ring''
|Converted in 1960 from 1.5kV DC to 6.25kV AC
|-
|05m 71c
|Manor Park
|SATS
|since 1980
|yes
|''n/a''
|Installed for 25kV upgrade. Acted as an MPTSC between Bow Junction "B" FS and Crowlands "A" FS until Pudding Mill Lane ATFS replaced both in 2022. Neutral section still in situ so this substation may still be in use in some.
|-
|08m 20c
|Ilford
|SATS
|since 1949
|no
|''n/a''
|Installed originally as a TSC from 1949, converted to 6.25kV in 1960, to 25kV in 1980, and finally converted to a SATS by 2022.
|-
|10m 49c
|''Chadwell Heath''
|''FS''
|''1949–1980''
|''yes (from 1960)''
|''Railway owned 33kV ring''
|Converted in 1960 from 1.5kV DC to 6.25kV AC. Chadwell Heath was the location of the main grid connection for the railway's 33kV ring.
|-
|11m 24c
|Crowlands
|SATS
|since 1980
|yes
|(''1980–2022'') UKPN 132kV underground power line 
(Barking 132kV to Crowlands Grid)<ref name=":3">{{Cite web |last=UK Power Networks |title=EPN Regional Development Plan: Barking, Warley & West Thurrock |url=https://library.ukpowernetworks.co.uk/Library/GetPdf?pdfUrl=Asset_Management_Documents%2FRegional_Development_Plans%2FEPN%2FEPN_RDP_Warley_Barking_West_Thurrock_GSP.pdf |format=pdf}}</ref>
|Originally Dual FS with "A" and "B" sides. Installed for 25kV upgrade. Replaced Chadwell Heath FS and Gidea Park as an FS. The substation may have become a SATS from 2022 since the neutral section is still in situ.
|-
|14m 45c
|Gidea Park
|MPATS/MPTSC
|since 1949
|yes (from 1960)
|(1949–1980) Railway owned 33kV ring
(since 1980) n/a
|Installed originally as an FS from 1949, converted to 6.25kV in 1960. Converted into a MPTSC between Crowlands "B" and Shenfield "A" in 1980 and finally converted to a MPATS by 2022.
|-
|17m 01c
|''Brook Street''
|''MPTSC''
|''1949–1976''
|''yes (from 1960)''
|''n/a''
|Originally as 1.5kV TSC, converted to 6.25kV MPTSC in 1960, substation removed in 1976.
|-
|19m 70c
|''Shenfield [DC]''
|''FS (DC)''
|''1949–1960''
|''no''
|''Railway-owned 33kV ring''
|Only ever a 1.5kV DC feeder station. Replaced by the new Shenfield FS with 132kV grid connection.
|-
|20m 72c
|Shenfield [new]
|FS
|since 1960
|yes
|UKPN 132kV underground power line
(Warley 132kV Grid to Shenfield Grid)<ref name=":3" />
|Dual FS, originally capable of 6.25kV and 25kV operation until 1980 when it fed all lines at 25kV.
Since Springfield FS was introduced, normally only of two supplies is in use for the section Gidea Park to Shenfield. Substation is configured to feed the Southend line if needed.
The site has been added to with a SATS since 2022 that is not yet in use.
|-
|23m 40c
|''Ingatestone''
|''TSC''
|''1956–1960''
|''no''
|''n/a''
|1.5kV DC TSC, removed when line was de-energised in 1960 for conversion to 25kV AC by 1961
|-
|27m 15c
|''Hylands''
|''FS (DC)''
|''1956–1960''
|''no''
|''unknown''
|1.5kV DC FS, removed when line was de-energised in 1960 for conversion to 25kV AC by 1961
|-
|29m 40
|Chelmsford
|TSC
|since 1961
|no
|n/a
|Installed 1961 for the 25kV system
|-
|33m 06c
|Springfield
|FS
|since 1993
|yes
|UKPN 132kV overhead powerline
(Rayleigh Main 132kV to Braintree 132kV)<ref>{{Cite web |last=UK Power Networks |year=2014 |title=Braintree — Rayleigh (EPN) |url=https://library.ukpowernetworks.co.uk/Library/GetPdf?pdfUrl=Asset_Management_Documents%2FRegional_Development_Plans%2FEPN%2FEPN_RDP_Rayleigh_Braintree_Group.pdf |format=pdf}}</ref>
|Dual FS installed ~30 years after this section was originally electrified.
Due to soon become an ATFS
|-
|38m 12c
|Witham
|TSC/MPTSC
|since 1962
|yes
| rowspan="2" |n/a
|Originally installed as an MPTSC between Shenfield and Colchester FSs. Since Springfield FS was introduced, Witham is probably switched through in normal operation.
|-
|43m 50c
|Hill House
|MPTSC (?)
|since 1962
|yes (since 2011)
|Originally installed as a TSC on the Colchester supply in 1962. A neutral section was added in 2011 likely to separate the Springfield "B" and (new) Hythe "A" supplies. Unknown if any switching ability exists at this substation.
|-
|52m 21c
|Colchester
|MPTSC
|since 1959
|yes
|1959–1993: yes (unknown)
1993–present: no
|Originally installed as a dual FS. B side supplying the Clacton line (from 1959) and A side feeding the mainline to Witham in 1962. Colchester likely ceased being an FS in 1993 when Springfield FS on the mainline and Hythe FS (by 1989) on the Clacton line were installed.
Currently it is a three way MPTSC distributing the incoming Hythe FS "A" supply to the mainline south to Hill House as well as terminating the supply from Manningtree FS to the north.
|-
|59m 47c
|Manningtree
|FS 
| rowspan="2" |since 1985
|yes
|UKPN 132kV overhead powerline (Cliff Quay grid to Lawford Grid)<ref>{{Cite web |last=UK Power Networks |date=2014 |title=EPN Regional Development Plan: Bramford – Rayleigh 132kV group network |url=https://library.ukpowernetworks.co.uk/Library/GetPdf?pdfUrl=Asset_Management_Documents%2FRegional_Development_Plans%2FEPN%2FEPN_RDP_Rayleigh_Bramford_Group.pdf |format=pdf}}</ref>
|The first single supply (tee feeding) FS on GEML only feeding southwards to Colchester. The substation also supplies the entirety of the Harwich line.
|-
|69m 42c
|Ipswich
|TSC
|no
|n/a
|
|-
|79m 10c
|Stowmarket
|FS
|since 1986
|yes
|UKPN 132kV overhead powerline
(Bramford Grid to Bury [st Edmunds] Grid)<ref>{{Cite web |last=UK Power Networks |date=2014 |title=EPN Regional Development Plan: Bramford Grid - West Suffolk 33kV Network |url=https://library.ukpowernetworks.co.uk/Library/GetPdf?pdfUrl=Asset_Management_Documents%2FRegional_Development_Plans%2FEPN%2FEPN_RDP_Bramford_GSP_West.pdf |format=pdf}}</ref>
|Dual supply FS
|-
|85m 24c
|Cow Green
|TSC
| rowspan="5" |since 1987
|no
| rowspan="4" |n/a
|
|-
|91m 34c
|Mellis
|TSC
|no
|
|-
|98m 76c
|Hales Street
|MPTSC
|yes
|
|-
|106m 63c
|Flordon
|TSC
|no
|
|-
|123m 38c
|Norwich 
|FS
|no
|UKPN 25kV underground powerline to nereby Thorpe 132kV Grid
|Single supply FS
|-
|124m 09c
| colspan="6" |[Norwich Station, end of line]
|}
{{noteslist}}