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Why are electric trains failing?

by ormondotvos Sat Dec 4th, 2010 at 04:53:25 PM EST

http://www.stockholmnews.com/more.aspx?NID=6355

Does anyone know if electric trains and trolleys are susceptible to severe cold and rain or snow due to ice on the lines or insulators, and is this a hitherto unnoticed flaw in electric transport?

I've noticed some pretty heavy knowledge of trains here.


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That is not a problem caused by ice and snow. That is a problem caused by running your network at the ragged edges of its capacity. Catenaries occasionally fall down, for a variety of reasons - that's just life. If your network is properly designed, you have plans and backup capacity to deal with that contingency.

Incidentally, ice on the catenaries does produce some rather spectacular light shows. Quite pretty, actually, though I doubt all those sparks do anything good for the transmission efficiency.

- Jake

Friends come and go. Enemies accumulate.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sat Dec 4th, 2010 at 05:25:39 PM EST
Thank you.

Doesn't the current to run the trains heat the wires?

When trains aren't running enough to keep the wires warm, wouldn't it be cheaper to warm them than to repair them?

I see that the trains are dead with no overhead wirefeed.

Shouldn't there be a small generator onboard for emergencies, to at least keep the toilets running? Perhaps a tank of natgas for heat?

I presume catenaries refers to the shape the feed wires take between supports.

Align culture with our nature. Ot else!

by ormondotvos (ormond.otvosnospamgmialcon) on Sat Dec 4th, 2010 at 06:01:52 PM EST
[ Parent ]
Doesn't the current to run the trains heat the wires?

I hope not. Miles of cabling putting out enough heat to melt ice might be less than entirely efficient.

Separate de-icing systems are available, but I'm not sure how widely they're used.

Shouldn't there be a small generator onboard for emergencies, to at least keep the toilets running? Perhaps a tank of natgas for heat?

Trains have very limited space, and weight is an issue.

In the UK failed electrics are hauled to safety by troubleshooter diesels. But if a long stretch fails, the diesels have to do multiple runs to rescue multiple trains. Which takes a while.

There were plans to create a hybrid diesel/electric next generation Intercity train in the UK, but weight and space requirements made it impractical solution.

I expect when nuclear fusion becomes small enough to fit into an engine car these problems will be solved. But until then catenaries, with all of their faults, remain the best choice.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Sat Dec 4th, 2010 at 06:19:42 PM EST
[ Parent ]
To heat the overhead wires with electricity, you have to short-circuit them, which is both a waste and dangerous. (I know of someone who did it in a cold spell, though...) But serious icing on overhead wires is a rare occurrence and there are some devices against it. However, when overhead wires snap, it usually has to do with some defect. Most often it's some failure of the system to compensate thermal contraction (like a stuck roller), sometimes material failure, and sometimes something falling on or getting stuck in the wires.

Trains have batteries. They don't last forever, though, and in modern times, even a simple passenger car comes with a sophisticated software... which may be ill designed and shut down the system in the 'wrong' kind of emergency. (I could tell stories.)

"Catenary" is American English for "overhead wire"; though recently it is increasingly in use in rail literature this side of the pond, too (I prefer to use it, too).

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Dec 4th, 2010 at 06:41:32 PM EST
[ Parent ]
Trains have batteries. They don't last forever, though, and in modern times, even a simple passenger car comes with a sophisticated software... which may be ill designed and shut down the system in the 'wrong' kind of emergency. (I could tell stories.)

And you may not want to run a train across a section of broken but still possibly live wire. It shouldn't be a problem (trains are pretty good Faraday cages), but with this sort of voltages you prefer safe over sorry.

- Jake

Friends come and go. Enemies accumulate.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sat Dec 4th, 2010 at 06:51:38 PM EST
[ Parent ]
You do not need to 'short' the overhead wire.  You just need to run enough current through it to form a layer of water sufficiently large for the ice to drop off.  Let's do some calculations:

Assume ice at -20C - requires 40kJ/kg to reach 0 plus 334kJ/kg to melt - so let's say 400kJ / kg.

A catenary with a 100g of ice / m would be heavily loaded, and we only want to melt a layer 0.5mm thick on a 1cm dia wire (00 gauge), or about 1.5g of water / m - i.e. 3kg/km or about 600kJ / km

To provide this heat we might heat the wire for 20s every 5 minutes (or perhaps per section ahead of the train?), requiring 30kW of power when heating.  The resistance of 00gauge wire is about 0.25ohm and i^2r = 30kW => 350A which is well within the current rating of the OHW.  To provide this current we do not need to provide 350A*25kV, but rather v^2/r => 86V per km.

To get this 90V per km we might treat up and down wires as separate lines, running the current up one side and back down the other.  We would connect the overheat wires together at one and, and insert a 350A, 90V*km*2 transformer between them at the other end, normally shorted together, but turned on to deice.  Such a transformer might consist of four turns of catenary wire on the secondary, and for a 25kV supply, 1000/(km*2) turns on the primary.

If an electric train normally uses 1MW, on a 25kV line, it should in fact produce enough heating to melt the ice (apparently not quickly enough to prevent damage), but this approach would only need 30kW*20s/300s = 2kW average to maintain the ice free wire.

Numbers are all made up; substitute better ones if you know them.

by njh on Sat Dec 4th, 2010 at 08:54:57 PM EST
[ Parent ]
First a nitpick: the 350 A heating system you describe is shorting the catenary, just not by earthing the normal 'working' voltage. Your system is certainly practical, especially if it is DC; I suspect some Nordic countries use something like that.

For the electric part of your calculation, I can only give slightly different numbers which don't result in changes of magnitude. For a European catenary type, let's take Re200, with a maximum 0.15 Ω/km (and as low as 0.04 Ω/km if there are parallel lines). For ormondotvos's Swedish example, the voltage is 15 kV; and we can easily assume 3 MW, giving us 200 A. That's 6 kW/km. In the extreme case of IORE locos (those double locos on the photo downthread) working at full power (10.8 MW, hence 720 A), we get 77.76 kW/km.

However, I am less sure about the first part of your calculation. I think we should be calculating heat flows rather than amounts of heat. One kilometre of 100 mm² wire has a surface of 35 m² (ignoring the carrying wire here), ice has a minimum thermal conductivity of 2.22 W/mK at 0°C. So even in the IORE case, for steady state, the temperature of the wire needs to rise above that of the air on the other side of the ice only by the numerical value of the width of the ice coat in millimetres (assuming it's uniform). To melt the ice, you really need a burst of power.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Dec 5th, 2010 at 04:50:03 AM EST
[ Parent ]
Why does DC/AC matter?  The heating loop is galvanically isolated from the supply by the use of the transformer.

Don't forget the R1 insulative effect of the still air around the conductor.  I can believe the burst vs continuous argument, even if we move to a very narrow pulse, say 0.5s, that's still only about 1MW which could be provided by the existing infrastructure.

by njh on Sun Dec 5th, 2010 at 11:13:31 PM EST
[ Parent ]
Why does DC/AC matter?

You don't want nice strong impedances, especially with AC train control systems nearby.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Dec 6th, 2010 at 03:58:59 AM EST
[ Parent ]
Isn't there a system that allow for ice melting by making pass a high frequency current through the cable?

As the cable impedance depends on frequency, increasing with frequency, even a low high frequency current results in heating the cable, without having to apply a high voltage.

I remember someone talking about that but I can't recall if it was applied on train catenaries.

by Xavier in Paris on Mon Dec 6th, 2010 at 11:55:55 AM EST
[ Parent ]
I do not understand this statement.
by njh on Mon Dec 6th, 2010 at 06:23:04 PM EST
[ Parent ]
I searched around a little; turns out that the system you propose is already in use on some lines in Europe. One is the Cologne-Frankfurt high-speed line (another one electrified with the 15 kV/16.7 Hz system), where the heating current is applied in bursts in the night hours; unfortunately, I couldn't find details (voltage, frequency if any, length of sections, method of shorting). Another is a rack railway in Switzerland, which runs on DC, but the heating current applied during the night is 50 Hz AC, and applied continuously.

However, neither system was found sufficient.  At the Swiss line, the problem is the time between switching off the heating and the transit of the first train. On the high-speed line, my (German) source doesn't say what's the problem, but says that the more conventional catenary brushing cars are in use, too.

(Other conventional methods I am aware of: spraying a de-icing fluid, sending out a loco in the morning with both pantographs up so that one scraps the ice while the other draws current, and using a 'flamethrower' to de-ice the worst spots.)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Dec 6th, 2010 at 02:01:25 PM EST
[ Parent ]
The scary guy I mentioned who shorted the high voltage did so when, faced with a real bad icing, he judged that freeing the catenary with the flamethrower would take all day. (BTW, I know him well, but I heard this story from others.)

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Mon Dec 6th, 2010 at 02:13:31 PM EST
[ Parent ]
DoDo:
"Catenary" is American English for "overhead wire"; though recently it is increasingly in use in rail literature this side of the pond, too (I prefer to use it, too).

In French: Caténaire. Comes from the same Latin root:

Catenary - Wikipedia, the free encyclopedia

The word catenary is derived from the Latin word catena, which means "chain". Huygens first used the term catenaria in a letter to Leibniz in 1690. However, Thomas Jefferson is usually credited with the English word catenary.
by Bernard on Sun Dec 5th, 2010 at 09:20:13 AM EST
[ Parent ]
Just to add a meta-comment; there is widespread rail transport in snowy and cold places for nearly a hundred years now, so any related problems are hardly hitherto unnoticed, not to mention critical.



*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Dec 4th, 2010 at 06:59:13 PM EST
Most of the problems are related to snow on the tracks, not the electricity supply. You could use steam instead of electricity, but the snow would still be there...

by asdf on Sat Dec 4th, 2010 at 11:46:07 PM EST
[ Parent ]
Yeah, but sending out a snowplow and switching on an electric switch heater can be less fuss than repairing catenary in a snowstorm. Assuming the electric heating installation programme wasn't held up by "cost-saving" and the number of snowplows wasn't reduced by the same...

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 05:02:23 AM EST
[ Parent ]
IT's probably a factor too that when a train gets stopped by a frozen switch, it's still easy to evacuate passengers to a station building nearby, as opposed to a train broken down on the open line; hence the more numerious switch failures earn less news space.

Winter chaos in train traffic - Stockholm News

One train stopped for several hours in Östegötland yesterday while the 700-800 passengers where without food or electricity. The toilet tanks onboard are also reported to have been full. The stop was due to an electric wire that had been torn down. The passengers were later evacuated to another train which later was affected by a failure in a security system and the passengers had to evacuate once again. Shortly after, another train hit an ice bloc (!) on the rail and broke. At other places trains stopped due to frozen switches.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 05:13:46 AM EST
[ Parent ]
Like this:

by asdf on Sun Dec 5th, 2010 at 10:00:53 AM EST
[ Parent ]
there is widespread rail transport

electric rail transport.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Dec 5th, 2010 at 04:59:50 AM EST
[ Parent ]
Yay, Malmbanan on the first pic! The busiest piece of railroad in Sweden, far north of the arctic circle, with the most powerful locomotives in the world. Sometimes people joke that it works so well because it's not run by the state railroad, but by the mining company LKAB...

For the last 15 years Swedish infrastrucuture has been under attack from neoliberalism, and the accumulated lack of maintenance is becoming clearer for every passing year: last winter the rail system was in shambles, and this year it's close to collapse. There have been considerable issues with the power grid as well this year. Granted that this winter and the last were the snowiest and coldest for decades.

Peak oil is not an energy crisis. It is a liquid fuel crisis.

by Starvid on Sun Dec 5th, 2010 at 09:19:53 AM EST
[ Parent ]
For the last 15 years Swedish infrastrucuture has been under attack from neoliberalism, and the accumulated lack of maintenance is becoming clearer for every passing year: last winter the rail system was in shambles, and this year it's close to collapse

Allow me to snigger: you have no idea what's close to collapse :-) Here, cost-saving on maintenance is much more 'advanced', and we get the cold weather catenary ruptures (not one, but a couple in a row) already in autumn. So you still have a lot of neolib destruction ahead of you :-)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Dec 5th, 2010 at 02:02:41 PM EST
[ Parent ]
Ah, just wait until you get to USA (#1) style maintenance and operating practices! Even though things have improved markedly from the dark days of the 1970's-80's when even cars parked in yards would derail, we still have a long, long way to go to approach European levels of service quality.
by Jace on Mon Dec 6th, 2010 at 03:26:26 PM EST
[ Parent ]
One of my favorite railways; the Malmbanan was so comfortable with catenary and snow that they used one of the very few overhead powered rotary snowplows.
by Jace on Mon Dec 6th, 2010 at 04:33:56 PM EST
[ Parent ]
Well, damn, youse guys is very helpful. How come yer not running the world instead of these here dipshitlomats?

Thanks for the elaborate technical explanation. A few missed descriptors, but about the way I'd run the problem if I knew the voltages and conductor sizes.

I can't believe a train with Mw engine would mind the equivalent of one or two passengers for heat and light. And it's always easier to use diesel or gasoline for stored energy. Viz electric cars.

But, as you say, public utilities or profit utilities each have their reasons for pushing the envelope of safety.

I like the failure of the contraction compensators. That's subtle.

Align culture with our nature. Ot else!

by ormondotvos (ormond.otvosnospamgmialcon) on Sun Dec 5th, 2010 at 01:10:09 AM EST
I should add, one catenary failure in all of Sweden during one cold spell is not an indication of massive maintenance problems. Travel disruption can be serious if it happens at an important line section with no avoiding line -- it's shit happens category.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 05:05:07 AM EST
[ Parent ]
The South entrance to Stockholm is a frequent failing point. The basic problem here is that Stockholm rail was originally planned for about ten trains a day. So instead of running the rails north and south around Stockholm and leading the rail to Stockholm into a cul-de-sac Central, all rail runs through Stockholm making in expensive and politically trying to expand capacity enough. And local rail runs on the same tracks. This is not only shit happens, it is a 19th century built in weakness that it takes to much political will to overcome.

Add under-budgeted maintenance and neoliberal ideas about planning and even in the best of years you get delays in winter. And this winter looks like another though one.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se

by A swedish kind of death on Sun Dec 5th, 2010 at 10:46:13 AM EST
[ Parent ]
Well, there is the Citybanan project, though that won't be ready before 2017.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 01:48:49 PM EST
[ Parent ]
Regarding pushing the envelope, the upthread already quoted article brings this context:

Winter chaos in train traffic - Stockholm News

Swedish railways have been poorly maintained for a long time and a political battle has broken out about who is to blame. When the opposition attacks the government for cutting down on the funding for maintaining railroads, the government replies that they still allocate more money for the purpose than the previous Social democratic government did. Both parts are right. The government has now abolished the SEK 600 million extra funding they gave to the maintenance each year during last electoral term, while the ordinary funding is still higher than before 2006.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 05:15:33 AM EST
[ Parent ]
There is the new (?) phenomenon of powder snow making it through the cooling vents, melting, and short-circuiting electronic components as witnessed last winter with Eurostar and ICE trains.

Schengen is toast!
by epochepoque on Sun Dec 5th, 2010 at 04:26:57 AM EST
It's not exactly new; what's new is bad maintenance or even lack of design of proper prevention/mitigation measures (the case with both the Eurostar and DB breakdowns last winter). Even if the operators responsible preferred to blame special weather conditions...

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 04:53:28 AM EST
[ Parent ]
For DB, we had the same in summer, too, with air conditioning not scaled for 40°C outside temperatures... (though that cost-saving idiocy was still not as bad as for the refurbished commuter train coaches around Budapest, which have air conditioning with a power insufficient at any positive temperature difference, as the heat input from direct sunlight was apparently not taken into account...)

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 04:58:17 AM EST
[ Parent ]
This definitely isn't new at least in the states. Some equipment like the M-1's and even the venerable GG-1, all now retired, were particularly sensative to shutting down in fine, powdery snow.

Heavy snow is in general a problem if the equipment is not designed for it. It packs into the suspension, onto cables and blocks vents. The weight can pull cabling apart. Snow/ice jammed suspensions can at least worsen the ride quality. Repeated heating, like on brake gear, will cause the snow to melt and then refreeze to ice potentially causing problems if and when these chunks start falling off. You can also lose braking force due to snow or sometimes lock the brakes on an axle for 240 miles!

This report illustrates both the problems with snow and some of the ways to improve designs to deal with it.

by Jace on Mon Dec 6th, 2010 at 12:44:36 PM EST
[ Parent ]
Thanks for the great links!

Heat the catenary.
It could be necessary to heat the overhead wire at some locations during extra tough weather conditions. Sometimes it is sufficient with the heat generated by the traction current why a frequent traffic is preferable from this aspect. Sometimes an additional reactive current is used to prevent or reduce the build up of rime on the contact wire.

So the Nordic countries indeed do it, too, albeit no details are given.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Dec 6th, 2010 at 02:46:28 PM EST
[ Parent ]
You're welcome. The Swedisn report is quite comprehensive. As for that Canadian accident, nice flat, eh?
by Jace on Mon Dec 6th, 2010 at 03:32:26 PM EST
[ Parent ]
Regarding the toilets, apparently the problem wasn't energy, but storage capaity over the time of wait.

Winter chaos in train traffic - Stockholm News

The toilet tanks onboard are also reported to have been full.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Dec 5th, 2010 at 05:12:09 AM EST
Doesn't the Transsiberian run on electricity, all year round ? How can any railway in the world realistically blame "snow" for circulation problems ?

Un roi sans divertissement est un homme plein de misères
by linca (antonin POINT lucas AROBASE gmail.com) on Sun Dec 5th, 2010 at 12:24:07 PM EST
The main problem in Denmark (aside from the fact that we have no spare capacity to deal with any disruption more serious than a two-minute delay, and on some stretches not even that) is that snow gets into the moveable parts of the track interchanges. I suspect that the Trans-Siberian does not have all that many of those...

- Jake

Friends come and go. Enemies accumulate.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sun Dec 5th, 2010 at 03:06:28 PM EST
[ Parent ]
when I wanted to take the tram to work (I have no trouble handling snow and ice on my bicycle, but I will not presume to speak for every other bugger on the road), it was not running, due to "technical problems".

The Lyon tram system has been implemented over the past ten years, which has featured exceptionally mild winters. I suspect that the current weather is outside spec. The people who specified the tenders should be rounded up and shot.

It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II

by eurogreen on Mon Dec 6th, 2010 at 10:07:21 AM EST


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