Cambridge to King's Lynn Electrification - Gathering Resources

[kp_raileng]

Hello,

I am interested in gathering some resources on the existing Electrified Cambridge to King's Lynn route:

I have noticed that there are significant sections of the route where two-track portals have been used, such as between Newmarket Road / Dimmocks Cote and Holt Fen Level Crossings.

a). Why is this?

b). Is there any documentation explaining the reasoning behind the selection of portals for this section?

c). Is there any corresponding design for two-track portals in a current OLE design range (such as UKMS)?

Many Thanks.

 

[Steve Harris]

Hello,

I am interested in gathering some resources on the existing Electrified Cambridge to King's Lynn route:

I have noticed that there are significant sections of the route where two-track portals have been used, such as between Newmarket Road / Dimmocks Cote and Holt Fen Level Crossings.

a). Why is this?

b). Is there any documentation explaining the reasoning behind the selection of portals for this section?

c). Is there any corresponding design for two-track portals in a current OLE design range (such as UKMS)?

Many Thanks.

I'll take a wild guess it's because of ground conditions. Once your north of Cambridge you are in the "Fens" which many years ago were under water. (The land was drained and is now used for farming).

If you look up info on the building of Ely Southern bypass you will find it went over budget because the foundations for the bridges had to go a lot deeper than originally planned due to the ground conditions.

I've read reports in threads on here that the line north of Ely tends to get closed when there is an extremely dry or wet spell of weather due to the OHLE "moving" and not being in the correct place. In fact, you only need to drive down a Fen road to see subsidence and cracks in the road surface to see how much the ground can move..

 

[edwin_m]

There was actually an accident on this section due to ground conditions affecting OLE: https://www.railwaysarchive.co.uk/docsummary.php?docID=4803

The investigation identified that the pantograph head had lost contact with, and risen above, the overhead line, resulting in the pantograph arm hitting a cantilever overhead line support structure. This impact broke the electrical insulators on which the pantograph assembly was mounted, allowing it to fall from the roof.

The pantograph head lost contact because the overhead line was deflected from its intended position due to a combination of long term movements of the overhead line support mast foundations and the force of the wind at the time of the accident.

The RAIB concluded that maintenance of the overhead line had not been carried out in accordance with Network Rail standards, meaning that the overhead line had not been adjusted to allow for long term foundation movements.

I can't say whether any of the supports were modified after this accident, or whether the portals were there since it was first electrified.

 

[Magdalia]

The Fens are peat that expands and contracts as it absorbs water or dries out. Over the long term the trend is to more drying out and shrinkage which is why large parts of the Fens are now below sea level.

This can cause significant infrastructure issues for both the track and the overhead line. In times of drought, most recently in 2022, there can be long speed restrictions in the Fens, necessitating imposition of emergency timetables.

There was actually an accident on this section due to ground conditions affecting OLE

There can also be displacement of the OLE, and I have been beaten to it on referencing the Littleport dewirement in 2012.

There is a more general discussion on such issues here:

Railways floated across bogs - current engineering issues

I was just watching the new Man at Seat 61 video of the Fort William sleeper. At Rannoch Moor the line was constructed by floating it over the boggy land, as is also the case at Chat Moss on the Liverpool - Manchester line (and possibly other places I am not aware of). This prompted some...

www.railforums.co.uk

 

[Trainbike46]

Peat soil entirely consists of dead, partially decayed plant matter. In natural conditions, the water table in peatlands is so high that decay is limited as there is no oxygen present, and if a peatland is healthy losses through decay will be smaller than the amount of new soil gained from newly produced plant matter at the top.

If a peatland is drained, like the fens are, the peat is exposed to oxygen and the decay processes continue. This means that the soil literally disappears through decay, with significant carbon emissions as a result.

This is entirely on top of the fact that peat contracts if it is drier, and expands if it is wetter. In total you get a soil that has a net downward movement, but not consistently so.

 

[a good off]

All of the above is correct. The ground conditions made things very difficult for the OLE teams, as it did a few years earlier on the ECML in the Holme Fen area. If they ever electrify the Ely to Peterborough line then the same will apply.

 

[Magdalia]

The ground conditions made things very difficult for the OLE teams, as it did a few years earlier on the ECML in the Holme Fen area.

Which is why Holme Fen is still 2 tracks and 100 mph.

If they ever electrify the Ely to Peterborough line then the same will apply.

I am old enough to remember travelling by train in the 1976 drought. March-Whittlesea was restricted to 20 mph and it took more than 40 minutes to do March-Peterborough.

 

[Trainbike46]

I wonder if rewetting the peatland (so moving the water table upwards to within 10 cm of the surface) would improve or worsen things for track stability. It should reduce subsidence (and carbon emissions!), but if I understand it correctly, saturated soils bring their own challenges to stability

 

[twpsaesneg]

Hello,

I am interested in gathering some resources on the existing Electrified Cambridge to King's Lynn route:

I have noticed that there are significant sections of the route where two-track portals have been used, such as between Newmarket Road / Dimmocks Cote and Holt Fen Level Crossings.

a). Why is this?

b). Is there any documentation explaining the reasoning behind the selection of portals for this section?

c). Is there any corresponding design for two-track portals in a current OLE design range (such as UKMS)?

Many Thanks.

a) Ground conditions, as stated above
b) Pinned base portals have a large reduction in cross-track forces, which enable a foundation less effected by soil movement to be used. There are also even older designs that allow the foundation to move without affecting the mast position (they have a cradle holding one mast, very clever)
c) Yes, pinned portals exist in UKMS, however some more recent structure designs on this route have been installed with very deep CHS foundations to drive right down though the fen into the underlying soil.

There was actually an accident on this section due to ground conditions affecting OLE: https://www.railwaysarchive.co.uk/docsummary.php?docID=4803

I can't say whether any of the supports were modified after this accident, or whether the portals were there since it was first electrified.

Some portals have been replaced in the twin track section, however the incident actually happened in the single line section and I don't believe any portals have been installed there (although it's a long time since I have looked!).

Ignore this - I was thinking of another dewirement!

 

[eastdyke]

I wonder if rewetting the peatland (so moving the water table upwards to within 10 cm of the surface) would improve or worsen things for track stability. It should reduce subsidence (and carbon emissions!), but if I understand it correctly, saturated soils bring their own challenges to stability

Which of course would defeat the reasons why 'The Fens' were drained in the first place [long before 'The Railway].
Viz. to manage 'Levels' for agriculture and to prevent flooding.

 

[Trainbike46]

Which of course would defeat the reasons why 'The Fens' were drained in the first place [long before 'The Railway].
Viz. to manage 'Levels' for agriculture and to prevent flooding.

There have been trials on the viability of doing agriculture on the fens with those kind of watertables!

But yes, that is obviously not a railway decision, but it is interesting how a potential rewetting decision would impact the railway

 

[Magdalia]

Some portals have been replaced in the twin track section, however the incident actually happened in the single line section and I don't believe any portals have been installed there (although it's a long time since I have looked!).

The 5 January 2012 dewirement was in the two track section between Littleport and Ely North Junction, see the accident report.

14 The accident occurred at 74 miles 02 chains, on the up line of the route between Kings Lynn and Cambridge, 2 miles (3.2 km) south of Littleport. This line is used by trains heading towards Cambridge and London. 15 The line at the accident location is double track, consisting of an up line and a down line. This is a stretch of straight track, with no points or level crossings in the immediate vicinity. The maximum permitted speed for electric multiple units is 80 mph (129 km/h). 16 Overhead line equipment, of a design known as Mk3b, is installed along the line to supply electricity, at 25 kV AC, to trains. The overhead line is supported by cantilever structures, mounted on separate masts. The electrification on the route is controlled from the electrical control room at Romford.

 

[twpsaesneg]

The 5 January 2012 dewirement was in the two track section between Littleport and Ely North Junction, see the accident report.

Apologies, I must be thinking of a different one!

 

[Spekejunction]

One of the best things Kings Lynn council did was pay towards the cost of electrification of the line from Ely.

 

[GRALISTAIR]

One of the best things Kings Lynn council did was pay towards the cost of electrification of the line from Ely.

Yes indeed. If there were more cooperation of this sort, a lot more rail improvements could get done.

 

[BanburyBlue]

Sorry - what do we mean by 'two track portals'?

 

[twpsaesneg]

One of these. This is at Waterbeach, a little further down the line.

 

[GRALISTAIR]

Sorry - what do we mean by 'two track portals'?

Exactly as @twpsaesneg says and a picture does indeed paint a thousand words. Portals are mainly used when there is 3 or 4 or more tracks and you don't want headspans because of resiliency. So a portal over two tracks is afaik much less common.

 

[BanburyBlue]

Exactly as @twpsaesneg says and a picture does indeed paint a thousand words. Portals are mainly used when there is 3 or 4 or more tracks and you don't want headspans because of resiliency. So a portal over two tracks is afaik much less common.

Great thanks - so portals as opposed to individual power masts on each side of the track.

 

[GRALISTAIR]

Great thanks - so portals as opposed to individual power masts on each side of the track.

They are usually called single track cantilevers STCs.

 

[BanburyBlue]

They are usually called single track cantilevers STCs.

thanks

 

[plugwash]

Sorry - what do we mean by 'two track portals'?

In general there are three main types of electrification support structure.

Cantilivers, an upright next to the line with a rigid peice over the track cantilievered off it. Cantilevers can be either single track (usually fairly lightweight) or two track (much more substantial structure).

Portals, supports on either side of the tracks, with a rigid beam between them, forming a "portal" through which the train passes. Portals are usually used to cross four or more tracks, but there are some lines with portals crossing only two. The approaches to and/or outdoor parts of large stations can often include some very large portals. There is one at picadilly that is about 50 meters long!

Headspans, supports on both sides of the track with wires strung between them to support the electrification. Used in the past as a cheaper alternative to portals, but have fallen out of favour due to maintinance and reliability issues. Headspan wires can also be hung from the ceiling structure of large stations.

 

[GraphitProjekt]

Exactly as @twpsaesneg says and a picture does indeed paint a thousand words. Portals are mainly used when there is 3 or 4 or more tracks and you don't want headspans because of resiliency. So a portal over two tracks is afaik much less common.

I believe also the other reason to use portals is for poor ground conditions because the bulker structure can take more of the rotational forces that the ground might not. I think this is why you almost always see portals on viaducts even in the mark 3 era of using head-spans everywhere (and for 2 tracks ofc). However many portals in mark 3 installations are not actually built with mechanically independent registration and use a lower span-wire for the registration of contact lines even in a portal: Wakefield viaduct is an example of that. (see a screenshot from the LNER youtube uploaded cabride)

Similarly, single track cantilevers opposite each other have sometimes been braced with a beam connecting the two effectively turning them into a portal (See screenshot from Garry Keenor's book)

Hello,

I am interested in gathering some resources on the existing Electrified Cambridge to King's Lynn route:

This may or may not be of interest to you but Cambridge to King's Lynn is also notable for its lengthy backup OLE feed as was discussed on this thread https://www.railforums.co.uk/threads/fen-line-ole-whats-the-extra-wire.199320/

 

[GRALISTAIR]

I believe also the other reason to use portals is for poor ground conditions because the bulker structure can take more of the rotational forces that the ground might not. I think this is why you almost always see portals on viaducts even in the mark 3 era of using head-spans everywhere (and for 2 tracks ofc).

Oh, absolutely. The Fens being one such place.

 

[Cambridgejcn]

Hello,

I am interested in gathering some resources on the existing Electrified Cambridge to King's Lynn route:

I have noticed that there are significant sections of the route where two-track portals have been used, such as between Newmarket Road / Dimmocks Cote and Holt Fen Level Crossings.

a). Why is this?

b). Is there any documentation explaining the reasoning behind the selection of portals for this section?

c). Is there any corresponding design for two-track portals in a current OLE design range (such as UKMS)?

Many Thanks.

Have you thought of contacting the author of the book 'The Cambridge to King's Lynn Line', published in 2023 via the publisher, Amberley Press, as maybe they could help you? There's a fair bit of background about that electrification scheme in it.

 

[kp_raileng]

Hi all, thanks for the information and thoughts provided - I've found the insights on OLE very helpful. I am now doing some research into the Electrical feeding used for this section by looking into the substations at Milton (north Cambridge) and King's Lynn South to assess it's suitability for providing sufficient Power to an increased demand in rail traffic in the future. I'm currently trying to get hold of MVA ratings for both these substations: currently I've been looking into data on the UK Power Networks Website [the DNO for both these substations], however I am finding no information on Power Ratings for the 132 kV side of the substations at these sites (and no mention of any 132:25 kV transformers that should be present for the Feeder stations). Does anyone have any suggestions of where I can find this information? Am I looking in the wrong place, or could this be restricted information for public access (i.e. security concerns due to links with railway infrastructure)?

Many Thanks

 

[GraphitProjekt]

UKPN published a series of regional development plans (rdp) but they are all probably 10 years old this is the link for all of them. One can hope that things haven't changed since then. RDP5 for Burwell Grid Supply Point is the region that includes Melton so I found this information, I'm not sure if this is really what you were looking for though.
Unfortunately, the RDP for the Kings Lynn area (#01 Walpole) does not mention the 132kV network at all. I don't why this is but it's exactly the same on the GEML side where Stowmarket FS is discussed but the smaller single feed at Norwich goes completely unmentioned; kinda interesting that the late '80s extensions of GEML and WAML/fen line wiring have very similar power design. A single supply FS nearby to the original extents of wiring (Ugley on WAML and Manningtree on GEML) followed by a full-size double supply FS at Stowmarket and Milton and then a (likely) low power single supply at each terminus.

For a general discussion, it's worth knowing about Network Rail's internal strategy for power supply going forward. Of course, it's not publicly available in any way other than being mentioned in this PWI video (

) for which they uploaded the slides. A few blurry images seem to suggest they might want new FSs on the branches at March, Whittlesea or Thetford.

 

[Transilien]

I thought it was to do with the fact that this line was originally electrified at 1.5KV DC.

 

[m0ffy]

UKPN published a series of regional development plans (rdp) but they are all probably 10 years old this is the link for all of them. One can hope that things haven't changed since then. RDP5 for Burwell Grid Supply Point is the region that includes Melton so I found this information, I'm not sure if this is really what you were looking for though.
View attachment 174251View attachment 174248Unfortunately, the RDP for the Kings Lynn area (#01 Walpole) does not mention the 132kV network at all. I don't why this is but it's exactly the same on the GEML side where Stowmarket FS is discussed but the smaller single feed at Norwich goes completely unmentioned; kinda interesting that the late '80s extensions of GEML and WAML/fen line wiring have very similar power design. A single supply FS nearby to the original extents of wiring (Ugley on WAML and Manningtree on GEML) followed by a full-size double supply FS at Stowmarket and Milton and then a (likely) low power single supply at each terminus.

For a general discussion, it's worth knowing about Network Rail's internal strategy for power supply going forward. Of course, it's not publicly available in any way other than being mentioned in this PWI video (

) for which they uploaded the slides. A few blurry images seem to suggest they might want new FSs on the branches at March, Whittlesea or Thetford.

The trend in recent years has been away from 132kV connections, towards 275 or 400kV supplies. This would almost certainly be the case for Walpole.

 

[GraphitProjekt]

The trend in recent years has been away from 132kV connections, towards 275 or 400kV supplies. This would almost certainly be the case for Walpole, which is a Grid Supply Point.

I'd expect Kings Lynn FS and Norwich FS to be 132kV connections though, considering their age (1992 and 1987 respectively) and relatively low power consumption: Kings Lynn supplies about two train movements in an hour.
In any case, it's called Walpole because the document covers the area of Cambridgeshire/West Norfolk that is dependant on Walpole 400kV (six 132kV grid substations which supply 33 primary substations), not because it has anything to do with the railway.

I thought it was to do with the fact that this line was originally electrified at 1.5KV DC.

well... the caption to the picture on the book says it's for poor ground conditions rather than OLE component weight. I have seen it said that Shenfield to Chelmsford originally used register span wires which were altered to become cantilevers on portals when it was converted to 25kV, presumably because of the insulator weights?