Overhead lines

There is an article by an anonymous "Industry Insider" in the current Rail magazine 560 proposing that overhead electrification is more trouble than it is worth. He points out the number of incidents in Britain when high winds have brought it down and thus paralysed the routes. It is possible that winds are already increasing in frequency as a result of climate change, and perhaps also in intensity.

But he admits that during British Rail days some overhead installations were done on the cheap - the East Coast Mainline for example - and therefore they are prone to damage in bad weather.

Of course one possibility is that the contributor is one of the ex-Southern men who think the third rail should have been the standard everywhere.

There is much to be said for the third rail. It certainly isn't affected by wind, though it is disabled by flooding, and can be impaired by snow or frost on the surface. As winters get warmer there is less and less snow and ice.

I live in the third rail area and it is true that it is a long time since I was inconvenienced by bad weather - about 5 years ago there was a problem with snow which resulted in the late train from Waterloo becoming a bus at Basingstoke, and a taxi from Southampton.

What the contributor does not deal with is the need to reduce diesel usage as we face the severe measures we need to take to deal with the climate problem. Electric trains can run on nuclear and hydro power.

He says that the "sparks effect" is no longer valid. Hm. I don't like the smell of diesel, and I don't like the sound of even modern diesel engines under the frame of the carriage - new diesel trains tend to have a diesel in each carriage. I certainly prefer electric, and really hate going under the wires in a diesel - something that was rare in British Rail days.

Instead of doing away with overhead I think it would be better to make it as reliable as it is in other countries, by strengthening it.

Wellington , New Zealand , has some of the highest wind speeds in the world . (occasionally they have to put ropes across pedestrian crossing for pedestreians to hold onto to stop them been blown away ) . Ive never heard of the cantenary wie been blown down there .

David Benton wrote:Wellington , New Zealand , has some of the highest wind speeds in the world . (occasionally they have to put ropes across pedestrian crossing for pedestrians to hold ore being blown down there .

The real problem is that the last major electrification was done cheaply. At the time people praised British Rail for keeping the cost down, but subsequently it appears that the ECML is prone to wind problems, and some of the other recent electrifications too such as Cambridge to Kings Lynn.

There are of course drawbacks to third rail. It isn't suited to high speed - though my local train regularly does 100mph, which isn't bad. It is also very difficult to accommodate Eurostar with its very heavy power load - but after November this year that will not be needed as the CTRL will be open as High Speed One.

Third rail will still expand a bit. For example I think the Uckfield line may well be done eventually and extended to Lewes, after which surely the line to Ashford from Hastings ought to be done at last.

The other third rail system is also expanding a bit. The Wirral lines out of Liverpool expand, and there is even a proposal to do the line to Wrecsam/Wrexham.

the limitation on 3rd rail systems is the voltage cant be too high . too much danger of electrocution , and leakage to ground . So amps must be higher to get a given amount of power . therefore either substations must be closer together , or the 3rd rail , and associated cabling must be heavier .
most 3rd rails are steel i think . you could gain alot of curerent capacity by making it aliminuim , copper would be too expensive nowdays .

David Benton wrote:the limitation on 3rd rail systems is the voltage cant be too high . too much danger of electrocution , and leakage to ground . So amps must be higher to get a given amount of power . therefore either substations must be closer together , or the 3rd rail , and associated cabling must be heavier .
most 3rd rails are steel i think . you could gain alot of curerent capacity by making it aliminium , copper would be too expensive nowdays .

I think the most recent third rail installations use another metal than steel. It may be aluminium.

David Benton wrote:Wellington , New Zealand , has some of the highest wind speeds in the world . (occasionally they have to put ropes across pedestrian crossing for pedestreians to hold onto to stop them been blown away ) . Ive never heard of the cantenary wie been blown down there .

The real problem is: If you don't cut back the trees in spring or summer, they will cut your overhead lines in autumn and winter...

But if you have studied economy and you don't have any idea of railways you can think it will save money and personal not to cut the trees back in summer - if you don't have any idea what will happen in autumn or winter...

Yes all round maintenance is needed .
Most trees in New Zealand are Evergreen , they don't lose thier leaves in winter . I think this tends to make them more supple , so trees blowing down is not so much of a problem here either . Of course this doesnt apply to introduced trees , but they tend to be away form railway lines .
but the lines still need to be cleared of scrub , gorse is one of the worst offenders , ironic because it was spread by railways in the first place . ( seeds in imported coal ).

Down cantenary...

I don't remember that being an issue in Japan either, where a majority (I can't remember the exact percentage, although it has to be in the upper 80 to low 90 percentile) of the railways are electrified.

I can't attest to the durability of the cantenary on the NEC here in the states, you'll have to ask one of the resident experts on the Amtrak forum. But that's a mix of "old school" and "new school" cantenary technology.

Komachi wrote:Down cantenary...

I don't remember that being an issue in Japan either, where a majority (I can't remember the exact percentage, although it has to be in the upper 80 to low 90 percentile) of the railways are electrified.

I can't attest to the durability of the catenary on the NEC here in the states, you'll have to ask one of the resident experts on the Amtrak forum. But that's a mix of "old school" and "new school" catenary technology.

I think a lot of the US overhead line was built and designed in the 1920s. Possibly it was over-designed but I gather it has been very robust. The problem in Britain was that BR was so pressured to cut costs that they cut them too much and built overhead that was too flimsy for the actual conditions. - perfectly all right for most of the year but not when the storms came. That's a short-sighted policy.

Leaves from trees in the autumn is a problem on third rail, but also of course for braking on all kinds of lines.

i remember the delayed trains from autmn leaves form my time working in London .
Speaking of which , the deciduious leaves here are only just starting to drop , about a month or 2 later than usual . late summer .

To the best of my knowledge leaves are a problem on the first and second rails, never heard of them causing loss of electrical contact, only adhesion.
If they got mashed on the third rail, they might even be a good lubricant, save wear. Of course they have no effect on wire either.
LS

Actually the crushed leafs do act as insulator, its very obvious in fall when MNCR's wheels spark like crazy due to bad return thru wheels. Sometimes its so bad that Cab signal goes to restricting while drawing power due to bad wheel shunting.

Leo Sullivan wrote:To the best of my knowledge leaves are a problem on the first and second rails, never heard of them causing loss of electrical contact, only adhesion.
If they got mashed on the third rail, they might even be a good lubricant, save wear. Of course they have no effect on wire either.
LS

I think one sees a lot of flashes at night which suggests current collection is not smooth. Maybe it doesn't cause loss of traction power, butI would guess that the flashes have some kind of consequence, possibly wearing the shoe.
Leaf fall is always a problem on the third rail lines.

Here in Boston, USA, we have the same third rail system as the Southern.
The District, in 1903, copied the dimensions and spacings so, Britain is stuck with our system of 1901, for better or worse. We have more ice and that is the thing that makes me see leaves as electrically negligible. I dont think southern England has more malevolent trees (except in fiction) in fact, they seem to be the same trees. It has not been a noticed problem.
However, you may be right as, English live rail is more rural and less often on embankment or, on protected alignment, allowing leaves a better chance to do mischief. Not to mention that you have thousands of miles to our hundred or so.
LS

Indeed leaves on the track acts like a insulator, as well as traction problems. Lack of traction...

In the Netherlands there was or maybe still is the problem with leaves on the track causing the railroad crossings not to function. especialy with light equipment, and trains with brake discs instead of shoes.

Some disc brake equipment was later equiped with shoes, to clean the wheels.

They do have a special train with cleaner to fight this problem, but I can't think of the name right now.

Erwin