grid leak

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spuffock

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It is well known that it is possible to light a fluorescent tube in the field produced by the national grid. This will be effectively a tapping on a very high impedance capacitive divider between the line and ground, and will be a horrible mismatch to the load, namely the tube. Has anyone thought of ways of improving the match in order to extract a useful few watts?
 

If you did it's called 'theft', and you could expect to be prosecuted for it.
 
Well, setting aside any potential legal (or moral) issues that this raises (and which I feel unprepared to comment on myself), this seems an interesting problem of how to capture energy from an electric field.

I immediately thought "long wire--antenna", but then it occurred to me that since you're not dealing with RF waves here, but instead by a surrounding EMF field, it seems that you need some kind of plate to collect current. In other words, some kind of flat conductive surface. To make this practical, how about an umbrella with a metallized top surface? you could connect a wire to it and use that to feed your load. Not sure if you'd need a ground connection, but it probably would help.

I wonder what kind of shock one would get if one actually ventured under a HV power line with such a rig ...
 
Some years back a person here in Oz designed a device he had in his back yard that produced power for the radiation off the HV power lines that ran just outside his property.

All was fine till he went public and tried to sell the idea and was promptly sued for theft that costed him $1000's as they used him for an example to deter others from such activities.

So yes Nigel is correct that it is a prosecutable offence.
 
Grid Leak Image Attached.

A long time ago I actually did some research on this subject. Looking at for example high voltage (250 KV and 500 KV) power lines and distances. The general take was that it was impractical and there was no was sans miles of coil that you could get much of anything to speak of. The field off a transmission line drops off real quick and if I recall correctly in log fashion. It was long ago but again, the consensus was not worth the effort.

Ron
 

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carbonzit said:
Heh. That's what I was thinking when I read the subject line. But then I'm one of those old farts ...
Click to expand...

Years ago when I worked with tubes and amateur radio QST magazine always had humorous cartoons about grid leak so I tried to imitate one. Yeah, at 61 I ain't getting any younger.

Ron
 
Hmm you need some sort of way to capture and pipe the magnetic field through a coil, sort of like in a generator. Either that or just one BIG coil of wire.

Could it be possible to get some static from the very high voltage lines, like 500kV ones? They are just bare wire hanging from big insulators.

I also wonder about the frequency of the electricity you would generate, cause there is three-phase power! It would be three times the powerline frequency right?

carbonzit said:
Heh. That's what I was thinking when I read the subject line. But then I'm one of those old farts ...
Click to expand...
lol I thought the same, although I am not as old..

Who here lives by some big power lines?

-Ben
 
Why a capacitive divider? Does the line have to be AC for it to work?

The electric field is in units of volts/meter, so if the line is 15 meters away, has 15kV on it and my tube is 1m long (I might be over compensating), the tube could have up to 1kV along it (except it will conduct & therefore have less).
 
This is all based I believe on inductive coupling. Works well for my electric toothbrush charger. As to getting a fluorescent tube or neon tube to have the gas in it ionize that is a different principal I think. When I was a kid and into amateur radio a fun thing was to place small gas filled tubes in close proximity to a diapole antenna and key up the transmitter.

Anyway, as to power lines this is a good video on the subject.

Now for a more realistic approach and back to reality this is a nice video to watch.

Ron
 

Hmm I have a massager that gets charged up by magnetic coupling, the base has some sort of coil inside and the device itself does too, dunno exactly how it works, as It hasn't broken yet so I have not looked inside. There are no wire connections to the device from the charger, only a magnetic connection.

-Ben
 
carbonzit said:
Heh. That's what I was thinking when I read the subject line. But then I'm one of those old farts ...
Click to expand...
yup, same here..... i had an antique one-tube radio with a goniometer (two coils wrapped in a sphere shape, the inner coil mounted on a shaft and the inside and outside wired in series. with the shaft one way the coils cancelled, with the shaft the other way they were in phase) type coil and a large variable cap. one of the components was a resistor with pointed ends and mounted on clips (much like an automobile dome-light bulb). printed on the side of the paper cylinder was "grid leak resistor element. 1,000,000 ohms"
 
I dont care about the legality, since the possible solutions would be bulky, fixed, and much more expensive than a small battery. I just wondered if it were possible to get a better match to the load, given the circumstances.
In response to the question about DC, no, it wouldnt work on DC, there would be no current.
I had half expected someone to suggest winding a 10 kilohenry inductor...........
 
carbonzit said:
Heh. That's what I was thinking when I read the subject line. But then I'm one of those old farts ...
Click to expand...

I build valve amps and that's exactly what got me to click on this thread as well!

That being said, yes you need an alternating magnetic field in order to induce a constant electric current into an electrical conductor that resides within said magnetic field. This can only be accomplished via an alternating physical magnetic field (i.e. a physical magnetic field which transitions from north to south pole) or simply an alternating magnetic field produced by an alternating current, be it from a pure sine wave or DC which is constantly being switched on/off such as what you'd find in an automotive ignition system and/or a switch mode power supply.
 
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first, you have to contend with the inverse square law, and most of the large transmission lines have a right-of-way easement that you would not be able to put anything on (if you did, you could get ticketed for trespassing), so there is a limitation on how close you could get your device.

second, the actual radiated field around transmission lines is limited by the fact that the AC field cancels itself. the field around a single wire is canceled by the net field radiated by the other two wires (3 phases, remember).

you might be able to pick up a little useful energy from ground stakes placed a mile or more apart. this wouldn't be from induction, but more likely from leakage paths, and the amount of energy would vary with the weather and with the loading of the system. even an inductive "pickup" would suffer from variations in the loading of the system, since the strength of the field is proportional to the current.
 
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