[TowerTalk] lightning

[David Robbins]

that is the direction we are going with hv transmission line designs also.  the
low frequency safety ground is not always very effective for the high frequency
transients.  a series of short(50-100') buried radials seems to be better then
long wires or long rods.  though to satisfy electrical safety codes you may also
have to add deep rods to get a satisfactory 60hz safety ground.


aa7e@juno.com wrote:
> 
> I have just moved from Oregon to central Florida.  As such, I have a
> renewed interest in lightning protection.
> 
> Coming from the TV broadcast industry, maybe I can inject another issue
> on the subject.
> 
> As we all know, a square wave contains energy at all frequencies.
> Similarly, lightning contains energy all the way up to 50 MHz or so.  So
> often, grounding systems are designed as if all the energy was at or near
> DC.  As a case in point, a translator station had a problem with
> lightning so they installed a new and "improved" grounding system.  As a
> result, the lightning problem was made even worse.
> 
> The problem was traced to long lengths of wire between the tower and the
> grounding rods.  Although these might have been effective at DC, they
> appeared as open circuits at the higher frequencies.
> 
> Since the watertable in my local area is 30 feet down, I have been told
> that grounding rods need to be drilled down to that level.  I would have
> thought that such a system might have the same problem.  I am thinking
> that the solution might be to parallel the rods with a copper sheet mat
> just below the surface.  This mat would provide some sort of grounding at
> the higher frequency content of the lightning energy.  Any comments would
> be gratefully received.
> 
> 73, AA7E
> 
> aa7e@juno.com
> 
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-- 
David Robbins K1TTT
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