A few days ago, I stopped beside the highway to talk with the foreman of a line
crew that was
stringing a new, 240-KVolt transmission line on 80-foot concrete towers. I
noticed that the three
transmission cables (not yet energized) were tied togetherand grounded with what
humongous clip leads. I thought this was a routine safety measure to avoid
injury if a new cable
might accidently fall onto the pre-existing, 130-KVolt lines.
The foreman explained that, with 3-5 miles of continuous cable swaying in the
wind (the supports
were about 600 feet, or more apart) there was significant danger from voltages
generated by the
cables' motion within the earth's magnetic field. In fact, he said, men have
been killed when these
new cables are not grounded.
I can understand that a few miles of high-line is a really serious antenna but
didn't think that a
one-turn (or half a turn) coil could generate any real energy. It seems to me
that the wind motion
would cause a polarity reversal with each reversal of cable direction thus
cancelling any serious
generation. Also, there's a good probability that different catenary spans would
out-of-phase ways, with further cancelling effects.
Then there's the possibility of inductive coupling with existing high-voltage
cabling parrallel to
the new lines. Now that, I think, could pick up some significant energy! And
what about lightning
in the area?. I would guess there could be some serious voltage pulses
generated, especially here in
"lightning alley, USA." (South Florida.)
Funny how my brain works. . . (funny peculiar, not funny ha ha.) I wonder if it
is possible, within
reason, to build a pickup coil big enough to string in your back yard and (if
you lived beside one
of those easements containing a dozen or so transmission lines at about 250,000
Volts) pick up
enough energy to provide power for lighting, etc.
I live in a condo quite a long distance from any high lines so my experimental
urges must remain
frustrated. But I think it's a kinda fun idea! I'm many decades removed from
my courses in
electromagnetic induction so the local utility is safe from my poaching.
Has anyone any practical experience with this matter? Or was that old guy
running that crew just
having a little fun with me? What do you think?
Pixmaker in FLL
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