Hi Jonathan,
The answer to your question about how much ground is required to
dissipate a strike safely is: "It varies". The problem is that
this requirement is profoundly affected by so many variables that
nobody can give you a good answer to that question. Some of the
variables can even be highly time variant at the chosen site.
In short, you are asking the wrong question. You should be
asking: "How do I configure my installation to prevent damage
from this source?".
You can have any proximity you desire so long as the system is
bonded together with a fast enough path. If the bonding is
adequate, voltage differentials between adjacent conductors are
not permitted to rise to the level that will cause a plasma
channel to take a shortcut across the gap. If the conductors are
bonded together adequately, they will all rise and fall in
potential at approximately the same rate. In this case, if the
earth terminal system is not adequate to dissipate all the strike
energy without saturating the volume of dirt affected by the
ground rod(s) and generating a plasma spark into the earth, the
spark will form at the bottom tip of the ground rod(s) where it
will do no damage. Please consult the Lightning Protection Code
(NFPA-78 and later versions) for information about how to
properly bond the system together and tie it into earth.
73, Eric N7CL
To: <towertalk@contesting.com>
>Date: Fri, 22 Jan 1999 23:52:13 -0800
>From: Jonathan Kaplan <jonk@jskent.com>
>
>I had to step in and say STOP! Everyone is off on some tangent
>which has nothing to do with what I originally asked.
>
>What I originally wanted to know was how close to the Tower's
>base and grounding rods I could have the electrical and gas
>mains to the house without a lightning strike jumping from the
>rods through the ground to the wiring and piping.
>
>In other words, how much ground is necessary around a ground rod
>to safely dissapate a lightning strike? If someone knows the
>answer, I'd appreciate hearing from you.
>
>Thanks
>Jonathan KO6XS
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