Path: utzoo!attcan!uunet!tektronix!tekgen!steves
From: steves@tekgen.BV.TEK.COM (Steve Shellans)
Newsgroups: sci.electronics
Subject: Free power from 'whispering wires' ??
Keywords: power transmission
Message-ID: <3170@tekgen.BV.TEK.COM>
Date: 1 Jul 88 20:09:51 GMT
Organization: Tektronix Inc., Beaverton, Or.
Lines: 36

All this talk about "whispering wires" has started a train of thought.
Would it be possible to tap part of the energy from those high voltage
power transmission lines?

Here is my line of reasoning.  I'm a CS type, not an EE, so please excuse
any blunders.  If you have an AC transmission line, each wire has a
60Hz magnetic field around it (in USA).  If you place an inductor (at ground
level) such that it is closer to one wire than the others, it seems to me
you could draw power out of it.  Or perhaps you could shield it in such
a way that it "saw" only one of the wires.

If it's a DC transmission line, you would have to rotate the inductor
thru the field.  Couldn't this be accomplished by a motor that ran
off (some) of the power that you were extracting?  Of course, it
would have to be started by hand.

Questions:

  1. Are the transmission wires far enough apart that you could get the
     magnetic field from one of them without being cancelled out by
     the other(s)?  Alternatively, how could the device be shielded
     so that it 'saw' only one wire?

  2. Does anyone know how to do the calculations to see how much power
     you could get as a function of voltage and current thru the
     transmission line, distance from the line(s), and size of the
     inductor?

  3. Can anyone suggest some equipment for a field experiment?

  4. What percentage of the high-voltage lines that one sees in the
     countryside are AC and what percentage are DC?

Steve Shellans
Tektronix, Beaverton, OR
tektronix!tekgen!steves