Great Western Electrification Progress

[HowardGWR]

Strange that I had never before realised the GWML doesn't have the concrete troughs". I can picture it now.

Strange this. As far as I remember, the GW was festooned with concrete troughing, often laid in the 'redundant' 4 ft of the second line when singled, or when two tracked from 4. Perhaps these were telephone wires to replace the pole routes, but I always assumed it was for signalling as well.

Note my use of inverted comma around 'redundant'. It proves that e.g.Filton Bank re-4 tracking was considered never going to happen.

 

[Philip Phlopp]

You can know the condition of buried cables by electrical testing, which does happen. However, you cannot know accurately where the cables are and at what depth. When trenches were dug it was down to the individual Gangers to make those kind of decisions. Most other locations used concrete troughing so the location of the cables is usually pretty easy to find but the former Western Region of BR decided to directly bury theirs. Things change over the years, track alignment can change, buried services can move, there were a number of cable strikes which persuaded those who look at Risk that the danger was so great that every pile would need to find the cables before they started work, hence all the trial holes. I don't know the exact number but figures of 600K have been mentioned, that's a lot of hand digging!

The original plan had been to re-lock and re-control all the signalling, with new lineside cables in troughing before piling started but the signalling works fell further and further behind programme largely due to a severe shortage of capable, competent Signalling Engineers - in particular Data Prep. Engineers for the Electronic Interlockings. If that programme had been adhered to all the trackside cables would have been easily located and piling would have completed much faster.

Did this have anything to do with the endless trouble BRT had when they were originally privatised, or does it pre or post date this period ?

They took four Class 20s with low speed control with them for cable laying operations but if memory serves, they ended up out of service fairly quickly and were eventually sold, with a lot of signalling works being done by hand as they had no plant to efficiently lay cables.

 

[Radedamer]

The association of portal with doorway was actually part of the source of my confusion. :roll:
--- old post above --- --- new post below ---
By the way, I think painting the portals green would probably make quite a difference in terms of visual intrusion and presumably the cost would be relatively minor. Unless too much time is spent choosing the correct shade of green to blend with all vegetation at any season!

 

[Grumpy]

The OLE specification accounts for single digit percentage of the total program cost. The figure that has done the rounds in recent weeks is a cost saving of 0.25% to be achieved in 'downgrading' the OLE and pretty much permanently limiting the GWML to 125mph - the only major saving in the cost is budgeting for a lighter gauge of contact wire and slightly smaller tensioners. Saving is around £7 million, but that's very definitely gossip.

.

Thank you for explaining this. My starting point was Roger Ford's article claiming that, per track mile, GWML electrification was costing 4 times as much as ECML at current prices. Much of the talk on here was about how the OLE design had been improved but as you've explained it that's relatively insignificant.

Ford's article didn't give any reconciliation detailing the causes of the cost increases. There's much muttering about increasing parapets to 1.8m but I cant see that as significant-if you've to deal with the parapets anyway (Leeds NW electrification seemed to affect most bridge parapets) then another couple of rows of bricks (or whatever) aren't going to explain the increase.

So we still don't know (at least the public) why costs have risen so.
--- old post above --- --- new post below ---

By the way, I think painting the portals green would probably make quite a difference in terms of visual intrusion and presumably the cost would be relatively minor. Unless too much time is spent choosing the correct shade of green to blend with all vegetation at any season!

I noticed this summer that the masts along the Rhine Gorge seem to be painted green.

 

[AM9]

I noticed this summer that the masts along the Rhine Gorge seem to be painted green.

Maybe that's just this year's colour.

 

[alxndr]

The Swindon area is still on the old signalling isn't it, so best not piled until replaced later this year?

Might start to find out soon if that's correct, the first stage of the resignalling is a month from now (Uffington - Rushey Platt). Supposed to be completed in three stages by December I believe.

 

[Tio Terry]

Strange this. As far as I remember, the GW was festooned with concrete troughing, often laid in the 'redundant' 4 ft of the second line when singled, or when two tracked from 4. Perhaps these were telephone wires to replace the pole routes, but I always assumed it was for signalling as well.

Note my use of inverted comma around 'redundant'. It proves that e.g.Filton Bank re-4 tracking was considered never going to happen.

The original buried cables date from the late 60's and early 70's. Later works did provide troughing but there were still buried cables on the same route.
--- old post above --- --- new post below ---

Did this have anything to do with the endless trouble BRT had when they were originally privatised, or does it pre or post date this period ?

They took four Class 20s with low speed control with them for cable laying operations but if memory serves, they ended up out of service fairly quickly and were eventually sold, with a lot of signalling works being done by hand as they had no plant to efficiently lay cables.

The buried cables pre-date BRT by quite a number of years so I don't think that affected BRT and their decision to scrap their cable laying trains.
--- old post above --- --- new post below ---

The association of portal with doorway was actually part of the source of my confusion. :roll:
--- old post above --- --- new post below ---
By the way, I think painting the portals green would probably make quite a difference in terms of visual intrusion and presumably the cost would be relatively minor. Unless too much time is spent choosing the correct shade of green to blend with all vegetation at any season!

It isn't easy to paint galvanised steel. I got involved in this with respect to GSM-R masts a few years back, it's a specialised process best carried out in a factory before erection. It uses a special epoxy based paint which is best used in warm temperatures. If you use ordinary paint it soon starts to peel off - as we found out!

 

[jimm]

Painting the metalwork was discussed back up the thread and several of us pointed out then that where the catenary is up on an embankment - which seems to be one of the key moans among locals, with much talk of how high up the metalwork goes - that a dark green/brown/whatever post would stand out a lot more against a grey or blue sky than galvanised steel.

They also don't seem to have grasped that the uprights needed for headspan catenary are even taller. But hardly surprising in the light of some of the hyperbole being spouted about environmental damage to an AONB that has the M40 carving its way across another bit of it.
And for some reason no one seems too bothered about the type, size or colour of catenary or signal gantries on the WCML as it crosses the Chilterns AONB between Tring and Berkhamsted, where the dark-coloured signal gantries stick out like a sore thumb.

https://www.flickr.com/photos/locohunter/15301170906

https://c2.staticflickr.com/8/7105/6863148796_a981e1319d.jpg

 

[Philip Phlopp]

Painting the metalwork was discussed back up the thread and several of us pointed out then that where the catenary is up on an embankment - which seems to be one of the key moans among locals, with much talk of how high up the metalwork goes - that a dark green/brown/whatever post would stand out a lot more against a grey or blue sky than galvanised steel.

They also don't seem to have grasped that the uprights needed for headspan catenary are even taller. But hardly surprising in the light of some of the hyperbole being spouted about environmental damage to an AONB that has the M40 carving its way across another bit of it.
And for some reason no one seems too bothered about the type, size or colour of catenary or signal gantries on the WCML as it crosses the Chilterns AONB between Tring and Berkhamsted, where the dark-coloured signal gantries stick out like a sore thumb.

https://www.flickr.com/photos/locohunter/15301170906

https://c2.staticflickr.com/8/7105/6863148796_a981e1319d.jpg

Lovely photos - proper(ish) overheads, being ruined by horrible diesel locomotives. It's worth showing off just what 25kV can do - 5.2MW of locomotives able to climb Shap and Beattock at or just under the train's speed limit.

https://www.flickr.com/photos/neil_harvey_railway_photos/5430952107

 

[GRALISTAIR]

It isn't easy to paint galvanised steel. I got involved in this with respect to GSM-R masts a few years back, it's a specialised process best carried out in a factory before erection. It uses a special epoxy based paint which is best used in warm temperatures. If you use ordinary paint it soon starts to peel off - as we found out!

Correct. Out in the field you have to use etch primers and epoxy definitely cures better in warmer temperatures. Best done at the factory if at all possible.

 

[Class 170101]

However, you cannot know accurately where the cables are and at what depth.

Really? So how comes BT have marked a local street where I live with lots of colourful markings on pavements with numbers then?

 

[Philip Phlopp]

Really? So how comes BT have marked a local street where I live with lots of colourful markings on pavements with numbers then?

That would be because they've put their cables in ducts underground and know where those ducts are.

 

[Class 170101]

That would be because they've put their cables in ducts underground and know where those ducts are.

Not sure its just their cables though. water, gas, electric also? Definitely not installed by BT

 

[Domh245]

Not sure its just their cables though. water, gas, electric also? Definitely not installed by BT

No, but there will be drawings of all the services under the pavements held by the relevant people (local authority I am assuming) which they can access and use to make out pavements for works. The GWML doesn't have drawings of where cables are buried

 

[Philip Phlopp]

Not sure its just their cables though. water, gas, electric also? Definitely not installed by BT

The utilities do communicate with each other, it would be completely unworkable if BT adding in fibre broadband dug up a gas and a water pipe - big explosion and fire with no water pressure with which to fight the fire.

British Rail, Railtrack and Network Rail only have themselves to worry about, just put the cables clear of track renewals and tampers, and it's not a problem, indeed reliability hasn't been too bad considering these cables are just sitting in the ballast.

Piling trains have come along, and not digging holes for concrete foundations, tend to disturb signalling cables by putting a pile through them. The lower voltage cables don't really give enough EM interference to pinpoint accurately with the various cable finding devices out there, many are screened anyway to ensure integrity of the signalling, so it's hand digging and moving cables carefully out of the way.

 

[Tio Terry]

Really? So how comes BT have marked a local street where I live with lots of colourful markings on pavements with numbers then?

There is a method of finding cables whereby you apply a signal to a cable pair and then use something like a metal detector and listen for that signal along the cable route so that you can identify where the cable actually is and that's probably what BT have done. It's commonly know as Cat Scanning.

However, the railway has a few problems with this. Firstly, signalling cables are not balanced pair cables like telecoms cables so when you apply a signal to a pair of conductors it's very likely to add that signal to all the wires in the cable because of crosstalk. This can have a serious effect on any other signals - like FDM or TDM circuits used for signalling systems - and can lead to failures. Also, the condition of the insulation on most of the older cables is such that the Route Asset Managers will not allow anybody to work within cable locations unless absolutely necessary because of the frail state of the insulation. So you wouldn't be allowed to apply a signal in the first place.

In addition to this the old interlocking systems that are being replaced by new electronic systems do not have the latest, and safest, designs built in. They are what's known as "single cut" whereby modern relay based systems were always "double cut". This helps prevent faults in the signalling system if insulation problems with lineside cables occur.

As ever, it's not that simple!

 

[Ploughman]

I used to use a CAT and Genny (for creating a signal in cables) on renewal sites when trying to find cable runs.
The survey was a joke but had to be done.
The CAT itself fully approved for use on Network and the Genny also.
Even to people fully trained in its operation you could actually see a cable and were 100% certain that power was being conducted in that cable. (Power lead to a kettle in the office)
Was there any indication from the CAT ? None.

Out on the track detection of cabling was erratic to say the least.
Regular blips on the speaker - were they a pulse signal in a cable, induced current as you pass reinforcing wires in the sleepers or the passage of steel Toe cap boots as you walked along.
Steady tone could be picking up the Track Circuit in the rails. Or from metal filings off the rails.

The moral of the story - Use them properly and try and locate services but never accept that they will indicate all or anything that is down there.
Not forgetting that if you locate a cable run and think you are safe in that knowledge, the CAT will not indicate the 2nd or 3rd run of cables under the one you know about.

 

[edwin_m]

Would ground penetrating radar be any good for locating buried cables?

 

[w1bbl3]

No, but there will be drawings of all the services under the pavements held by the relevant people (local authority I am assuming) which they can access and use to make out pavements for works. The GWML doesn't have drawings of where cables are buried

Statuary authority record drawings are rarely upto date or accurate generally in construction if extensive buried services are expected or if the authority drawings are know to be suspect, or if the site had extensive previous construction and thus foundations you'd commission a detailed survey.

Radiodetection (CAT and Genny) is a quick and relatively cheap way of finding services but will not locate fibre optics, plastic piping, shielded metallic cables or previous foundations. This obviously somewhat or an issue as water and gas mains installed in the last 30 years are generally plastic.

Ground penetrating radar will if used correctly basically find everything but is far slower to get a good scan and the machine needs to held very close to ground so rough terrain is a problem in terms of scanning accuracy.

BSI have published a guidance document on surveying under PAS128 four levels are defined D to A.
A is full invasive survey involving trial excavation.
B requires two methods of non invasive surveying of which ground penetrating radar must be one the other maybe any form of electro-magnetic location.
C is a general walk around and D checking just the record drawings.


If BT engineers have been a marked a pavement up with all other utilities they'll have done a ground penetrating radar survey.

 

[mewstone]

I was wondering if anyone could tell me, regarding the Series 1 GWR OLE portal gantry structures, why the vertical supports are so much taller than the top section height of the horizontal cross beams. I assume they will stay like this in service, rather than them being cut off level with the top of the horizontal section?

 

[swt_passenger]

I was wondering if anyone could tell me, regarding the Series 1 GWR OLE portal gantry structures, why the vertical supports are so much taller than the top section height of the horizontal cross beams. I assume they will stay like this in service, rather than them being cut off level with the top of the horizontal section?

There'll be other high voltage cables to run between the verticals along the route, as it uses an autotransformer feeder system. As well as the normally positioned 25 kV that the trains are in contact with, there is a separate and 'anti-phase' 25 kV as well, giving an effective 50 kV distribution system along the line.

 

[mewstone]

Many thanks for the response, so effectively there will be a separate distribution system above the horizontal portal as well as the traction pickup wires suspended below it. I just wondered as on the 1950/60's similar structures I have seen on the West Coast routes, the vertical supports do not go above the horizontal cross section.

 

[snowball]

The autotransformer system is relatively recent (though it has been retrofitted to part of the WCML).

 

[swt_passenger]

I just wondered as on the 1950/60's similar structures I have seen on the West Coast routes, the vertical supports do not go above the horizontal cross section.

Possibly a case of needs must when adapting an existing system, so the WCML is not necessarily optimal, but on the GW they'd start with a blank piece of paper.

There's a photo of the way the AT feeders are fitted, top left (1 of 8) of the set at the bottom of this page: http://www.furrerfrey.ch/en/systems/Series-1.html

 

[Philip Phlopp]

Many thanks for the response, so effectively there will be a separate distribution system above the horizontal portal as well as the traction pickup wires suspended below it. I just wondered as on the 1950/60's similar structures I have seen on the West Coast routes, the vertical supports do not go above the horizontal cross section.

The ATF cable runs should be across the top of the portal structures, at or around catenary wire height, which on the classic WCML OLE, run above the portal structure on separate cantilever arms. Slightly stupid design, since they're prone to idiot birds flying into them, but it's lasted reliably for half a century.

If the cable can't be installed in a position of safety, it will be carried at ground level with insulated screened cabling used.

 

[Radedamer]

Getting back to the portals and headspans for a second (though as I've said, I think it's ridiculous to call them 'environmental damage' – I'm just asking out of curiosity) presumably where there are only two tracks there is no need for either, and there will simply be a series of poles at the trackside with a cantilever structure from each pole having one contact wire suspended from it? And no need for any structure linking the poles?

 

[Philip Phlopp]

Getting back to the portals and headspans for a second (though as I've said, I think it's ridiculous to call them 'environmental damage' – I'm just asking out of curiosity) presumably where there are only two tracks there is no need for either, and there will simply be a series of poles at the trackside with a cantilever structure from each pole having one contact wire suspended from it? And no need for any structure linking the poles?

That's generally correct.

There will be some specific locations that demand a twin track cantilever (either Series 1 type, or existing lattice type) because of restricted clearances, signal sighting, for foundation reasons, on stations etc.

 

[Radedamer]

Thanks. I think I've got this all clear in my mind now.

 

[snowball]

Anyone know how the Thames bridge at Maidenhead will be done? It seems to me that the most visually satisfactory method would be T-shaped supports based in the centre of the four-track layout, if the structure allows it, with each side arm of the T holding up the wires for two tracks.

 

[edwin_m]

Anyone know how the Thames bridge at Maidenhead will be done? It seems to me that the most visually satisfactory method would be T-shaped supports based in the centre of the four-track layout, if the structure allows it, with each side arm of the T holding up the wires for two tracks.

It is actually two viaducts very close together so the central column would go down the gap between them. Which might actually be OK, similar to the arrangement often seen where the poles continue downwards to be fixed to the side of the viaduct in a couple of places.

Don't recall seeing any 4-track T-shaped structures anywhere though...