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Electricity from Railway Tracks 4

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McDermott1711

Mechanical
Nov 17, 2010
318
A couple of days ago, I saw this video ( and thought of the source of energy. Is it from nearby high-voltage power line induction or traction of the train itself causes this differential potential energy.
I've heard from one of my colleagues that some years ago a poor electrician died when touching two cables which were cut from main line, due to voltage which was inducted from nearby high voltage power line.
 
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Maybe you don't know, but most railroads put a voltage on the rails as a method to detect if the track is occupied by a train or rail car.

How do you think the crossing lights know there is a train?
 
Well, it's not exactly a lethal voltage that is being used for ATC and similar purposes. And the other story sounds more like a copper thief than a poor electrician. It could, of cause, have been a really poor electrician. But I guess that is another story.

Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
 
Thanks cranky108 for your reply.
But as you see from the youtube link, the voltage is very changing (when the loudspeaker is connected) and does not correspond to a predetermined applied one.
 
If it was induced from a powerline, then the line is not very close, or it does not parallel the tracks for very long.

Honestly, I've seen more induced voltage from a car parked in a substation.
 
Did you notice the pulsing?
_ .. _ .. _ .. _ ..
Most likely part of the signalling system.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
cranky108 and waross hit the nail. It is traditional railway signalling system before the digital world. There are many zones to sectionalize the tracks, and low voltage DC is applied to the tracks. A small leakage current is measured when When no train is passing the zone or section, a large short circuit current will be measured when a training is passing. I am not sure with today's GPS technology has changed that.
 
GPS technology hasn't changed it (because you want to know that the whole train is clear of the track section, not just the bit with the GPS receiver in it) - but there are some initiatives to replace track circuit interlocking with axle counting - a system that checks that as many wheelsets come out the far end of the section as went in.

Incidental effect of this new strategy is that you lose the ability (admittedly a bit hit and miss with track circuits anyway) to detect obstructions that just arrive in the middle of the section, rather than rolling in from the end.

A.
 
It is definitely a code and from the sound from the speaker, an AC code. This will allow it to be discriminated from possible overlapping signals from adjacent sections.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
Needless to say, the DC is part of the detection, and the AC is part of the interblock communications. And likely the AC is not shorted out by a passing train.

I believe the interblock communications is like the power line carrier used in the power industry. And with that some of the signal will migrate from one rail to the other.
 
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