I think you'd have a hard time getting usable power from this scheme. The
precautions about grounding parallel fences etc are more aimed at transients
(lightning and switching).
Consider this:
assume a 500kV AC line 50 feet away
Let's try capacitive coupling:
What's the capacitance between two small wires 50 feet apart? Femto farads?
model it as a pair of 2" wide plates 50 feet (600 inches) apart. C=.224 *
A/D pF, where A is in square inches and D is in inches.. So: .224 * 2 /600
pF/linear inch. Or, .74 fF/inch. A 100 foot long run would be just under a
pF. At 60 Hz, the impedance would be about 400,000 Gigaohms. (X=
1/(377*1E-12).. I don't think you're going to get much current, even at
500kV. (transients are a different matter: the frequency is higher, so the
impedance is lower, etc.) Also, since power lines are usually run in sets,
the fields cancel, particularly at any distance.
If you run the calculations for inductive coupling, you wind up with a
similar finding. Transients are a problem, steady state isn't.
Interestingly, there IS a fairly high field under a power line (although
there's not much power there) which is sufficient to ionize the mercury
vapor in a flourescent tube (although, it takes a time exposure of 1/2
second or more, on a dark night, to see it).
235 kV (a more common voltage)/50 feet -> 5-10 kV/foot 30kV/meter
You could probably get more power from the blowing dust hitting the wire or
from the earth's electric field (a few kV/meter) than from incidental
coupling to a power line.
----- Original Message -----
From: "Jim Miller" <JimMiller@STL-Online.Net>
To: "Gene Smar" <ersmar@comcast.net>; <towertalk@contesting.com>
Sent: Sunday, January 25, 2004 1:32 PM
Subject: Re: [TowerTalk] New power line phenomena problem
> Interesting,
>
> 1. How much power(current through a voltage regulator possibly) and
> 2. what is the minimum power line voltage necessary to induce any "usable"
> amount of power?
> 3. Are we talking dangerous if, say an old electric fence wire now
> disconnected but still mounted and not grounded? Could it do more than
get
> one's attention?
>
> tnx es 73, de Jim KG0KP
>
> ----- Original Message -----
> From: "Gene Smar" <ersmar@comcast.net>
> To: <K7LXC@aol.com>; <towertalk@contesting.com>
> Sent: Saturday, January 24, 2004 11:36 PM
> Subject: Re: [TowerTalk] New power line phenomena problem
>
>
> > TT:
> >
> > This isn't as far-fetched as it might sound. Ignoring the
> > reporter's layman description of the physics involved (power dropping
> > off the line), there are practical applications for such
> > capacitively-coupled energy. (Remember - the power line and long
> > barbed-wire fence wires are two parallel conductors, one of which is
> > energized at considerable voltage. The fence can be energized to
> > considerable voltage, too.)
> >
> > While working for a power company, my colleagues and I were granted
a
> > patent for a thermopile-and-propane-gas uninterruptible power supply
(UPS)
> > for fiber-optic repeaters along power transmission lines:
> >
>
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/net
ahtml/search-bool.html&r=1&f=G&l=50&co1=AND&d=ptxt&s1=smar.INZZ.&OS=IN/smar&
RS=IN/smar .
> > We used this capacitively-coupled energy in a power line's ground wire
> > (connecting the tops of consecutive towers) as the primary heat source
for
> > the UPS's thermopile, and propane would kick in as the backup during
power
> > outages on that line.
> >
> > We got our idea for using the ground wire as a primary source of
> energy
> > from researchers in Hydro Quebec. They used the ground wire of a 735 kV
> > line to power beacon strobes and microwave repeaters. We listed these
> guys
> > under Other References, found near the beginning of our patent
> application.
> >
> > The lesson to be learned here is it IS possible for long wire
fences
> > running in proximity to and parallel with high-voltage power lines to
have
> > electric energy coupled into them. Caveat Amateur!
> >
> > 73 de
> > Gene Smar AD3F
> >
> >
> > ----- Original Message -----
> > From: <K7LXC@aol.com>
> > To: <towertalk@contesting.com>
> > Cc: <k5zg@woh.rr.com>; <dbwalter@globaltaxhelp.com>; <N0AX@arrl.net>;
> > <K7ST@pacificarch.com>; <K7ROK@zipcon.com>; <midnight18@cox.net>;
> > <wwdxc-l@eskimo.com>; <James_L_Campbell@dom.com>
> > Sent: Friday, January 23, 2004 2:53 PM
> > Subject: [TowerTalk] New power line phenomena problem
> >
> >
> > > Greetings, TowerTalkians --
> > >
> > > > He also said that he was shocked once from his own fence.
> Because
> > of the
> > > high voltage, power can drop off the lines, charging metal nearby,
> > Bonneville
> > > Power officials acknowledge. Seattle Times, January 21, 2004.
> > >
> > > Cheers,
> > > Steve K7LXC
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
any
> questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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