ECN Forum
Posted By: C-H Trains! - 11/12/02 09:47 AM
When I sat on the early morning train today I looked at the reflections on the snow from the arcing between the "tap" and the overhead line. This made me wonder about the power to trains: There must be terrible disturbances in the power judging from the intensity of the arcing.

Anyone who knows this field?

(Most trains here run on 15 kV, 16 2/3 Hz)
Posted By: Trainwire Re: Trains! - 11/12/02 11:11 AM
C-H
I can't speak from hands on experience, but my grandfather was a powermaster for the Pennsylvania Railroad for many years, and electric locomotives are a favorite of mine. I work around steam locomotives every day.
The electric trains around here don't arc much. I think the answer to your question is, brute force is a wonderful thing. By the time you get the power transformered down to something that the rest of the equipment can use, most of the "junk" is filtered out. This is assuming that the trains "over ther" work the same way as the electric trains do over here.

The latest electrics actually convert incoming "juice" into dc, then run it back through converters, to control both the frequency, and the voltage to the motors. This is the same controls that the new deseasels use too. By the time the electric is run through all of that curcuitry, it is cleaned up quite a bit.

I'll root around a bit, I might be able to find a better answer from the museum across the street.

Trainwire
Posted By: C-H Re: Trains! - 11/12/02 01:12 PM
I should perhaps add that the arcs only occurs when the line is covered in ice. But as this is the case a good many mornings during the winter and the trains doesn't seem to have a problem with it I became curious.

Several other things fail because of the ice and snow: The switches freeze (despite the electrical heating) and moving parts in the undercarriage of the train jam. (Only last night was my train delayed 20 minutes due to a switch problem) Last winter the trains looked like balls of ice when they rolled into the station. If they maintenance crew managed to get them rolling at all, that is.

(New trains were ordered early this year: the spec calls for operating temperatures down to -35°C (about the same in °F))

Trainwire: I've got another question. When the trains here derail, they have on at least two occasions in last three years torn down the wire too. I can't see how the "tap" (what is it called?) can tear the wire down. Can you explain how this happens?
Posted By: Trainwire Re: Trains! - 11/12/02 01:48 PM
C-H,
Not being very familiar with railroading in your country, I can only relate what I know about it in this country.
the "american" term for the funny thingy on top, is a pantograph. Some of them have ice breakers on them for just the situation that you are describing. The arcs you see are the result of the pantograph being pushed off of the wire by the ice, electrically it probably isn't all that much of a big deal. It is of such short duration, the voltage and current being what it is, it just puts on a cool light show.

If a derailment brings the wire down it means that the pantograph is hooking over the wire. The contact shoe on US loco's are fairly wide, so to hook over the top of the wire the loco needs to rock pretty hard as it's coming to its unplanned stop. If my memory serves, European loco's shoes are much narrower, meaning that if the loco rocks to the side and then straigtens up it can hook over the top of the wire then catch on a support wire, and bring the whole thing down on your head.
A derailment is usually pretty catastrophic, especially at speed, it's a wonder that any of the equipment even stays upright. Now imagine trying to put 1.5 million pounds back on the rail. That's how much the biggest steam engines weigh.

TW
Posted By: SvenNYC Re: Trains! - 11/12/02 05:37 PM
Trainwire:

I always thought the current-gathering part of the pantographs just rode on the bottom side of the overhead wire instead of hooking into it? At least that is what it always seemed like from the ground. [Linked Image]

When I was in San Francisco in 1998, I would occasionally see a trolley-bus ride off it's overhead wire. The driver would have to get out and use a long pole with a hook to get that springloaded arm back into contact with the power line. Granted the trolley arms are long enough and swiveled so it doesn't happen often...

At the end of the arm (don't know the correct term) there is a grooved roller that pushes up against and rides on the underside of the wire (and occasionally throws out a few sparks).

Does San Francisco still have trolley-buses? I know they're expanding their railed street-car network, but dunno about the trolley bus system. Most of those were pretty dilapidated (just like their gasoline powered brethren). [Linked Image]
Posted By: Trainwire Re: Trains! - 11/12/02 06:04 PM
Schven, your right, the shoe of the pantograph only pushes up on the bottom of the catenary. What C-H was asking is why a derailment brings the "cat" down. The cat comes down when the shoe, that is supposed to be under the wire, hooks over the top of the wire due to the locomotive wandering around places it's not supposed to be, eg, the tie's (or sleepers if your in England) instead of the rail.

TW
Posted By: Hutch Re: Trains! - 11/12/02 08:32 PM
Ice on the conductor can bring the service to a complete halt. On the 3rd rail system in southern England (750 V DC) they run so-called 'ghost trains' all night when ice build up is a risk. This is empty stock whose only purpose is to scrape the ice off the conductor rail before it builds up too much. Fantastic night-time fireworks seeing them go by.
Posted By: harold endean Re: Trains! - 11/12/02 10:19 PM
Trainwire,

My grandfather use to work on the Lackawanna railroad in the '20s, then it became the Eire-Lackawanna while my dad worked there. My grandfather was a electrician back then and the E-L would run 13,000 volts DC for their electric lines. Just in the '70-'80s did the E-L upgrade to AC power to mach the Penn-Central. At least that is what I was told. The Penn-Central ran 33,000 volt AC. Any more info on that?
Posted By: SvenNYC Re: Trains! - 11/12/02 10:25 PM
The New York City Subway (or metro, underground railway, choose your favorite name [Linked Image] ) third rails are covered on top by a wooden plank that is held several inches above the rail by iron brackets.

The whole assembly (rail and plank) is held about 4 inches above the ties by ceramic insulators.

The primary purpose is to give some semblance of protection to track workers (so they don't step on the live rail while one foot is on the ground). However certain track work calls for covering the entire section of third rail with a thick rubber mat.

On elevated sections, the wooden cover helps prevent snow buildup somewhat.

There are 600 volts across the third rail and ground. I believe it is DC for traction and until recently was generated by rotary AC/DC converters in substations running both at 25 hertz and 60 hertz AC.

The 25 hertz ones have since been taken off line and substituted with solid-state equipment. The train cars each have their own traction motors (modern cars are permanently lashed together in consists of 6), batteries and other things to power the 110-volt lights and fans and heaters inside the cars.

This is what one of those old rotary converters looked like:

[Linked Image from nycsubway.org]


and you can read more about them at ]http://www.nycsubway.org/tech/power/sub21-01.jpg [/URL]

Impressive beasts!!! [Linked Image] [Linked Image]

[This message has been edited by SvenNYC (edited 11-12-2002).]
Posted By: pauluk Re: Trains! - 11/12/02 11:22 PM
The shoe on top of most pantographs also curves downward slightly at its ends, so the train has to move a considerable distance off the straight-and-narrow before the panto will spring up enough to hook over the line. The overhead line isn't usually rigged to run exactly parallel to the tracks however. If it did so, there would be excessive wear at the central portion of the collector. Instead, the line weaves left and right along its length to even out the wear on the collector shoe. If the train happened to lurch off the rails in the wrong direction when the line was over to one side, it might be easier to hook over it then.

The London Undergound also gives quite an impressive fireworks display at night from the third and fourth conductor rails (630V DC). In this case, there are multiple pick-up points along the train, so if a shoe does lose contact with the rail at some point the spark is just the result of a break in one or several parallel paths.

I don't know if they still do it, but years ago on the above-ground sections of the Underground ice was cleared before the first trains of the morning by shorting the rails together at the end of a section and passing low-voltage high-current through the tracks to warm them sufficiently to melt the ice.

In recent years, our regular train service has become a national joke as to what lame excuse they'll come up with next. One winter we were treated to "It was the wrong sort of snow."
Posted By: andylea Re: Trains! - 11/13/02 02:29 AM
interesting. ever wondered what happens to a pantograph when the train goes threw a tunnel.this is what is sposed to happen, a transponder detects at a point on the track, the pantograph is lowered and the shoe takes over for the duration of the tunnel. my one regret was not being around when they tested this in kent one time. it didnt work.pretty spectacular by all accounts.
Posted By: andylea Re: Trains! - 11/13/02 02:30 AM
hahaha,,,,,i remember the wrong type of snow comment. and then they hit us again with the 'wrong type of leaves'.
Posted By: Hutch Re: Trains! - 11/13/02 02:52 AM
Andy,

Not too sure what you're referring to here. The only area in Kent that I know that involves switching between a third rail supply and the overhead is at the entrance to the Channel Tunnel where a France/Belgium bound train raises its pantograph and lifts its shoes prior to *entering* the tunnel.

There are maximum and minimum heights for the overhead wire above the train and sometimes through tunnels the wire is pretty near its minimum. A classic example is the Manchester Metrolink tram (trolley) system whose panographs reach up for the wire in town (a maximum for safety) but then squeeze through Heaton Park Tunnel (ex-railway) with the wire and tram in closest proximity.

Where space is at a premium, a double track railway can be singled and slewed to the centre of the tunnel to take maximum advantage of the arch.

[This message has been edited by Hutch (edited 11-12-2002).]
Posted By: C-H Re: Trains! - 11/13/02 06:37 AM
Wow, now I know quite a few things I didn't yesterday! And cool new words too, "pantograph" and "catenary"!

It's indeed rare for trains to derail here too, but it does happen when they hit cars or when they try to "force" switches. (A switch frozen in wrong position can be forced right by running the train into it at a suitable speed. I don't know how this works, but I've seen that some switches have warning signs saying that you should not do this. The problem is if the switch still refuses to move when the train runs over it [Linked Image] )

[This message has been edited by C-H (edited 11-13-2002).]
Posted By: Scott35 Re: Trains! - 11/14/02 05:14 AM
Did someone say the "T" word??? As in "T"rains???

[Linked Image] [Linked Image] [Linked Image]

Scott s.e.t.
Posted By: ThinkGood Re: Trains! - 11/14/02 06:22 AM
Here are some good photos from Penn Central RR's "Electrical Operating Instructions" http://www.rr-fallenflags.org/pc/pc-eoi.html

Here's a link for many more RR links: http://www.railroad.net/

Specifically, the thread in the URL below ties in with this thread: http://www.railroad.net/

Enjoy,
TG
Posted By: andylea Re: Trains! - 11/14/02 04:23 PM
it wasnt the channel tunnel train. it was one of the 365's. i was told about the incident on an adtranz training course.im trying to remember the name of the town it happened near, but for the life of me it alludes me.
Posted By: pauluk Re: Trains! - 11/14/02 09:36 PM
Derailment sure can happen! New Year's Eve 1995 I was riding Amtrak from Chicago to Omaha. Thanks to a derailed freight train somewhere in Iowa we got detoured on slow tracks down through Missouri and back up again. We finally pulled into Omaha about 6 hours late. Still, there was a good "Happy New Year" with everyone on board -- Somewhere on the edges of Kansas City, if I recall correctly. [Linked Image]

By the way, the NYC to Chicago run was within 5 minutes of the scheduled time, despite 950 miles of ice and snow across the Mid-West. British Railways, please take note!
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