Great Western Electrification Progress

Linda smith · 26 Jun 2019

Just a quick point of interest, over the weekend a lot of the sps equipment was being installed west of somerton bridge in Newport. And on Tuesday evening, I noticed that a run of earth wire has gone up from the tunnel west of Newport station and past caerleon bridge.

RailUK Forums

ATW158Xpress · 28 Jun 2019

https://www.bbc.co.uk/news/uk-wales Severn Tunnel could be another Steventon gap in wires if this doesn’t get sorted out soon!

Dai Corner · 28 Jun 2019

ATW158Xpress said:
https://www.bbc.co.uk/news/uk-wales Severn Tunnel could be another Steventon gap in wires if this doesn’t get sorted out soon!

From a technical and commercial point of view it would probably have been better to end the wires at Filton once it was decided not to electrify to Temple Meads and Swansea. That probably wouldn't have been politically acceptable though.

Phil G · 28 Jun 2019

Bet they are glad they made the bimode decision! Rather going to scupper the open access class 91 proposal!

Brissle Girl · 28 Jun 2019

And the Class 387 extras for major events in Cardiff.

Mag_seven · 28 Jun 2019

ATW158Xpress said:
https://www.bbc.co.uk/news/uk-wales Severn Tunnel could be another Steventon gap in wires if this doesn’t get sorted out soon!

Here is a quote from the article to comply with the forum rules:

Full electrification of the main south Wales to London railway is in doubt as engineers on the £2.8bn project have an "issue" electrifying the Severn Tunnel.

The kit holding electric wires above the track in the four-mile (6km) tunnel is failing because of the salty conditions under the Bristol Channel.

The article goes on to say:

They have drafted in electric rail specialists to help solve the issue.

The UK Department for Transport has said they are "aware of an issue within the Severn Tunnel works" and insist Network Rail is currently "carrying out investigations to resolve this as quickly as possible".

So it looks like its not all doom and gloom as they are working on a solution.

kevin_roche · 28 Jun 2019

The idea of a sacrificial anode comes to mind like they have on boats. https://en.wikipedia.org/wiki/Galvanic_anode

A galvanic anode is the main component of a galvanic cathodic protection (CP) system used to protect buried or submerged metal structures from corrosion.

Grumbler · 28 Jun 2019

Mag_seven said:
Here is a quote from the article to comply with the forum rules:

The article goes on to say:

So it looks like its not all doom and gloom as they are working on a solution.

Seems to me that they have found the solution - i.e. use diesel over this stretch. This could be the solution for awkward parts of other routes - e.g. Leicester. This could save quite a bit in electrification costs.

HSTEd · 28 Jun 2019

And just another reason the tunnel should be replaced with a modern crossing..... but you can't tell people that.

Linda smith · 28 Jun 2019

Going for diesel thru stj is indeed the easy option. But one has to wonder if a layer of shotcrete before they installed the contact rail would have helped? Thou it may be a tad too late now like.

Mag_seven · 28 Jun 2019

Grumbler said:
Seems to me that they have found the solution - i.e. use diesel over this stretch. This could be the solution for awkward parts of other routes - e.g. Leicester. This could save quite a bit in electrification costs.

But not all electric trains are bi-modes!

oglord · 28 Jun 2019

As has already been pointed out, running on diesel is not a solution. We are supposed to be getting away from Diesel, and this would restrict IC services to being bi-mode forever, not to mention scuppering any chances of running pure local EMUs anywhere. F+F should be able to find a solution.

Linda smith · 28 Jun 2019

Grumbler said:
Seems to me that they have found the solution - i.e. use diesel over this stretch. This could be the solution for awkward parts of other routes - e.g. Leicester. This could save quite a bit in electrification costs.

HSTEd said:
And just another reason the tunnel should be replaced with a modern crossing..... but you can't tell people that.

the problem is - the existing tunnel is 4 miles in length. To bore a new tunnel or build a dedicated bridge would have cost several billion in it's own right.

Dai Corner · 28 Jun 2019

Phil G said:
Bet they are glad they made the bimode decision! Rather going to scupper the open access class 91 proposal!

Brissle Girl said:
And the Class 387 extras for major events in Cardiff.

Nah. Just have a diesel loco follow them into the tunnel and give them a shove if they can't coast all the way to the juice :lol:

HSTEd · 28 Jun 2019

Linda smith said:
the problem is - the existing tunnel is 4 miles in length. To bore a new tunnel or build a dedicated bridge would have cost several billion in it's own right.

Probably not several billion, after all the New Severn Bridge only cost a few hundred million pounds, albeit in the 90s.

A cable stayed rail bridge could be built along the lines of those being built in China, and would allow the rather troublesome tunnel alignment to be abandoned - it would also obviously cut journey times by allowing a faster run and cutting the maintenance issues that plague the bridge.

They've spend £20m to absolutely no effect so far and it now appears they are just going to give up, after a suitable interval to let the furore die down.

MarkyT · 28 Jun 2019

Through a long tunnel is possibly the worst place to selectively use diesel capability from an air quality point of view. Soot will deposit on surfaces and be blown around as trains pass. There may be some chemical effects from this pollution long term. On board traction batteries would be much better for this sort of thing where the off wire section is fairly short compared to the total trip. Cardiff metro style discontinuous electrification.

Dai Corner · 28 Jun 2019

MarkyT said:
Through a long tunnel is possibly the worst place to selectively use diesel capability from an air quality point of view. Soot will deposit on surfaces and be blown around as trains pass. There may be some chemical effects from this pollution long term. On board traction batteries would be much better for this sort of thing where the off wire section is fairly short compared to the total trip. Cardiff metro style discontinuous electrification.

Though remember there will be more diesel trains through the tunnel than electric even if/once the problem is fixed.

MarkyT · 28 Jun 2019

Dai Corner said:
Though remember there will be more diesel trains through the tunnel than electric even if/once the problem is fixed.

True but many of those might be 'hybridised' on future fleet renewals.

MatthewRead · 28 Jun 2019

They said on the report that there would be no trains to Bristol would that mean no GWR DMU's at Cardiff Central?

59CosG95 · 28 Jun 2019

What are the current clearances like in the tunnel? If it's large enough to accommodate a new shotcrete lining sprayed over the existing brickwork, then I'm all for such a solution.

Grumbler · 28 Jun 2019

Mag_seven said:
But not all electric trains are bi-modes!

Install diesel engines in them then!

themiller · 28 Jun 2019

ATW158Xpress said:
https://www.bbc.co.uk/news/uk-wales Severn Tunnel could be another Steventon gap in wires if this doesn’t get sorted out soon!

The

ATW158Xpress said:
https://www.bbc.co.uk/news/uk-wales Severn Tunnel could be another Steventon gap in wires if this doesn’t get sorted out soon!

Thats one of the problems in depending upon Victorian infrastructure instead of accepting that, at some point, you’re going to have to invest in replacing it. The original investment in the current tunnel has probably paid off. A new tunnel would improve the service for another hundred years.

edwin_m · 28 Jun 2019

Abandoning the electrification through the tunnel would leave the South Wales section with a single feed, and possibly inadequate feeder arrangements in the Parkway-Filton area. Another extension lead might be needed to address this - or live with diesel operation over a much wider area if one of the feeders is under maintenance or supply is lost.

deltic08 · 28 Jun 2019

Dai Corner said:
Nah. Just have a diesel loco follow them into the tunnel and give them a shove if they can't coast all the way to the juice

Coasting not possible. It is two miles uphill at 1 in 70 each way from the midpoint.

MarkyT said:
Through a long tunnel is possibly the worst place to selectively use diesel capability from an air quality point of view. Soot will deposit on surfaces and be blown around as trains pass. There may be some chemical effects from this pollution long term. On board traction batteries would be much better for this sort of thing where the off wire section is fairly short compared to the total trip. Cardiff metro style discontinuous electrification.

They have just removed 150 years worth of soot from the roof of the tunnel before installing overhead contact bars to reduce acid attack. They should have left it as it would have neutralised salt attack!

Dai Corner · 28 Jun 2019

deltic08 said:
Coasting not possible. It is two miles uphill at 1 in 70 each way from the midpoint.

I was only joking, but it's also two miles downhill at 1 in 70 to the midpoint so my schoolboy physics tells me that if a train is going fast enough on entering the tunnel it should be able to coast all the way through.

But better have a loco on standby just in case. :lol:

Dai Corner · 28 Jun 2019

Getting back in topic, BBC Wales TV News have just reported that the corrosion is to a 'safety feature' which is causing the power to trip.

Does this mean anything to our technical friends here?

MarkyT · 28 Jun 2019

Dai Corner said:
Getting back in topic, BBC Wales TV News have just reported that the corrosion is to a 'safety feature' which is causing the power to trip.
Does this mean anything to our technical friends here?

The report says:

Earth straps - a safety feature on the overhead connectors holding up the power line - were corroding in the salt water environment within months when they are supposed to have a 25-year lifespan, meaning the line through the tunnel could not be electrified safely. It means the electrification system within the brickwork tunnel - the longest underwater tunnel in the world for more than 100 years after it opened in 1886 - struggles to maintain voltage and regularly trips.

So it could be that systems are monitoring the integrity of these deteriorating earthing conductors and tripping the supply? With 25kV supplies remember everything metallic anywhere in the vicinity of the railway must be earthed adequately to reduce touch potential risk.

absolutelymilk · 28 Jun 2019

Dai Corner said:
I was only joking, but it's also two miles downhill at 1 in 70 to the midpoint so my schoolboy physics tells me that if a train is going fast enough on entering the tunnel it should be able to coast all the way through. But better have a loco on standby just in case.

Through some slightly more detailed calculations, the train should lose roughly 70mph of speed on the uphill section due to the gradient. So when you account for air resistance and rolling resistance, it would have to be going pretty quickly to be able to make it down the other side at a reasonable speed. What's the speed limit through the tunnel?

height change= 2 * 1600 * 1/70=51m
Change in kinetic energy = change in gravitational potential energy
0.5 m (change in v)^2= m g (change in height)
delta v^2 =2 g delta h
delta v = sqrt(2 g delta h)
= sqrt(2*51*9.81)
= 31.6 m/s
=70mph

Brissle Girl · 28 Jun 2019

absolutelymilk said:
Through some slightly more detailed calculations, the train should lose roughly 70mph of speed on the uphill section due to the gradient. So when you account for air resistance and rolling resistance, it would have to be going pretty quickly to be able to make it down the other side at a reasonable speed. What's the speed limit through the tunnel?

height change= 2 * 1600 * 1/70=51m
Change in kinetic energy = change in gravitational potential energy
0.5 m (change in v)^2= m g (change in height)
delta v^2 =2 g delta h
delta v = sqrt(2 g delta h)
= sqrt(2*51*9.81)
= 31.6 m/s
=70mph

75mph! And of course even if the train did manage to just crawl back up, it would have lost much of the time gain electrification and the new trains bring.

Remembering that the the suggestion was tongue in cheek, how about pedals in front of all the seats, so that passengers can give the train a helping hand (and keep fit too).

kevin_roche · 28 Jun 2019

Brissle Girl said:
Remembering that the the suggestion was tongue in cheek, how about pedals in front of all the seats, so that passengers can give the train a helping hand (and keep fit too).

I like the idea of a gym for first class passengers with the treadmill driving the wheels. They could charge extra for that!

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