TT:
----- Original Message -----
From: "jimlux" <jimlux@earthlink.net>
To: "K1TTT" <K1TTT@ARRL.NET>
Cc: "'towertalk reflector'" <towertalk@contesting.com>
Sent: Friday, September 04, 2009 10:23 AM
Subject: Re: [TowerTalk] Static Discharge Wicks
>
> What radius? you'd have to look at the fields.. but let's say the field
> is 10kV/meter under the thunderstorm. You have a 20 meter high tower,
> so the potential of "the air" at 20 meters, if the tower weren't there,
> would be about 200kV. If the tower didn't perturb the field (which it
> does, but that just helps, here).. the grounded antenna would be at that
> potential relative to the surroundings. The radius of curvature needed
> to prevent breakdown at 200kV is on the order of 3" (6" diameter) which
> is pretty big.
>
It is for this same reason (high field intensity surrounding a small
energized conductor) that power transmission lines operating at 500 kV and
up use two conductors per phase. You can see the paralleled wires suspended
from twin sets of insulators at each end of a span and jumpered together
along the span with shorting bars. To operate the lines as single
conductors would only cause arcing and concommitant energy loss along the
entire line. The dual conductors spread out the E-field that surrounds the
phase, keeping the field from getting too high and arcing over in air. (The
two conductors are NOT needed to carry the current.)
Just thought you'd want to know.
73 de
Gene Smar AD3F
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