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Author Topic: Electrification - even of thin long lines  (Read 2136 times)
stuving
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« Reply #15 on: February 13, 2020, 05:32:38 pm »

With Atlantic gales and storms of the Ciara ilk, light-weight electrification on the Newquay branch might prove a bit flimsy. Although the line skirts the Cornish Alps, I'm not sure they provide quite the same shelter as the Swiss & Austrian ones.

Speak to Blackpool if you want advice on how to make it strong enough for gales on a coastline.

I suspect that's an imaginary problem. Direct wind damage to overhead wires and supports of any design, whether for railways or power distribution, should not happen if they are in good nick. It needs something extra, such as trees and other wind-blown stuff, or else rot and rust. For OLE, the main impact of wind isn't damage, it's the wires being pulled off too far sideways or bouncing about and preventing continuous contact. Series 1 is of course specified to cope, but so should earlier designs as this isn't anything new.

The big danger is icing, which can add huge extra loads, both weight and windage. However, icing is rare in Britain, and even rarer in Cornwall. Oh course it does occasionally happen - there was one famous big (very tall) example of icing damage, and the Queensferry Crossing was closed this week due to a form of icing (though for some reason it wasn't called that). In that latest case the bridge wasn't damaged, it was just dropping chunks of ice on cars.

While you'd expect better resilience where icing is common, such as the Alps, enyone can be caught out. A few months ago, around Lyon, a lot of small electricity poles were felled by very heavy icing on the wires - 7 kg/m where the design loading was 2 kg/m was mentioned. And the Chinese have had problems with their new electrified lines through mountains, though in their case icing of the pantographs and roof-mounted busbars is also a big issue.

Power lines also suffer from galloping, induced by the wrong kind of wind and growing to large amplitudes because of the large droop in the cables. Railway OLE has enough tension to keep that to very low levels, but again there can be adverse conditions. Asymmetry in the wire shape is one of those, and icing features again as it can add an aerofoil shaped tail to a wire. Again, it's the Chinese who have found out this can cause significant damage (because it can happen to a long stretch of line in one event). Series 1 does (of course) have a design requirement for icing, which is 9.5 mm thickness except on the GWML where it is 3.5 mm.
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CyclingSid
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« Reply #16 on: February 14, 2020, 06:54:38 am »

In the 1987 storm one of the main cause of the National Grid lines dropping out were plastic bags. Acting like a sail when they blew onto the lines.
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TonyK
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« Reply #17 on: February 14, 2020, 10:36:29 pm »

In the 1987 storm one of the main cause of the National Grid lines dropping out were plastic bags. Acting like a sail when they blew onto the lines.

Since then, the privately owned trampoline has become more common, usually bounced on a few times, then forgotten about until it's not there the morning after the storm.
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stuving
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« Reply #18 on: February 14, 2020, 11:04:56 pm »

In the 1987 storm one of the main cause of the National Grid lines dropping out were plastic bags. Acting like a sail when they blew onto the lines.

Do you mean National Grid? Or even national grid (still run by the CEGB in 1987)? I think that would relate to local distribution, via 33 kV lines on wooden poles. I've known one of those to be broken by a lad throwing a stick for his dog.

But in a big storm, there's much bigger stuff than carrier bags goes flying: not only industrial communal trampolines and bouncy castles (which were rare in 1987), but haystack tarpaulins, trees, and roofs. I vaguely recall metal roofing sheets landing inside grid substations makes quite a mess of the switchgear, and loudly.
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Noggin
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« Reply #19 on: February 19, 2020, 10:12:10 pm »

Would have thought that stringing up wires was the easy bit, don't forget:

1) Signalling immunisation
2) Structure clearances (quite a lot being done to improve matters, but Chippenham shows what a headache listed footbridges can be)
3) Traction feeds
4) Traction depots
5) Control centres and staff training

On that basis, simple infill like Blackpool South and perhaps even some longer schemes of 'simple' double or single track 'could' be quite cheap if it built on existing infrastructure (though don't forget the Nimby factor).

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TonyK
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« Reply #20 on: February 21, 2020, 01:30:11 pm »

On that basis, simple infill like Blackpool South and perhaps even some longer schemes of 'simple' double or single track 'could' be quite cheap if it built on existing infrastructure (though don't forget the Nimby factor).

Blackpool South wouldn't be too tricky, but unless the track was improved, either by doubling or a couple of passing loops, it would still be a little used (1 tph) 20 mile route to Preston taking almost an hour. There is debate there currently on options, which include conversion to join the tram network at Kirkham and Wesham, conversion to tram to Lytham St Annes with heavy rail from there, or building a tram line next to the  existing line to Lytham, and running both. Currently, though, the emphasis is on Poulton le Fylde to Fleetwood, and of course finishing the tram extension to Blackpool North. Work on the latter is set to continue from April with the closure of the Wilko store blocking the way, with trams to a temporary terminus next year and the full station opening in 2022.
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« Reply #21 on: February 21, 2020, 08:08:50 pm »

Would have thought that stringing up wires was the easy bit, don't forget:

1) Signalling immunisation
2) Structure clearances (quite a lot being done to improve matters, but Chippenham shows what a headache listed footbridges can be)
3) Traction feeds
4) Traction depots
5) Control centres and staff training

On that basis, simple infill like Blackpool South and perhaps even some longer schemes of 'simple' double or single track 'could' be quite cheap if it built on existing infrastructure (though don't forget the Nimby factor).


These have been the traditional additional items that add to the cost, however some are less of an issue.

1) All re-signalling schemes traction immunisation is built in to the equipment, track circuits / train detection even on lines where there are no immediate electrification planned; the only thing may be left out is the screening conductor.

2) Structure clearances are perhaps the biggest issue, although new bridges and replacement bridges, signal structures etc are built for 25kV clearance, even in the depths of the third rail area.

3) Traction feeds are long lead items, typically National Grid need a 5 years to plan their outages; they are expensive but given the whole life cost based on 50 to 60+ years for a transformer and 30+ years for the switchgear.  Whole life costs is something we are not good are utilising in the UK in part due to the short political life of a Government.

4) Traction depots are more electrification is rolled out this become less of an issue, also as most of the train maintenance is built into the supply contract again based over the whole lie cost of a train 30+ years this is less significant.

5) Control centres (Electrical) NR are rationalising these, also a common control system software is currently being rolled out.  I doubt there will be the need for any new additional electrical control rooms.
Training of staff is an ongoing issue anyway.  The thing that may cause some issues is the UK leaving the EU, the construction companies involved in electrification work in the UK move there teams around the EU and bolstering up the teams at short notice or short durations utilising the freedom of movement this process has kept the costs down and enabled program recovery in the past.
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onthecushions
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« Reply #22 on: February 21, 2020, 10:13:19 pm »

Another hidden cost that one could argue about, arises from the superior performance of electric trains. They go faster, have low marginal costs, attract more custom, merit increased frequencies and so need costly improved track maintenance both for speed and capacity. The early SR electrifications also did not show savings in running costs (vide G T Moody's book), rather a vast increase in patronage, train miles and farebox income.

How one compares analytically and validly, a mediocre diesel service with a good quality electric timetable, I'm not really sure, even with BCR's. We just know which one's better.

OTC
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