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Re: [TowerTalk] The Need for Grounding

To: towertalk@contesting.com
Subject: Re: [TowerTalk] The Need for Grounding
From: Patrick Greenlee <patrick_g@windstream.net>
Date: Thu, 14 Jan 2016 08:19:41 -0600
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Why must we, supposedly technical types, anthropomorphize lightning and its "behaviors?" Lightning has no mind of its own, no desires, no ability to choose a path. It is just a manifestation of physical law. Attributes of the phenomenon, lightning, are governed by the immutable laws of physics. Our inability to predict, in detail, what lightning will do is a reflection of our paucity of understanding of physical law compounded by chaos where small changes in initial conditions can produce large and often unpredictable outcomes. The laws of electronics are a subset of the laws of physics dealing with voltage, current, charge, etc. Lightning "obeys" these laws completely with no deviation irrespective of our ability to understand the fine detail sufficiently to explain outcomes.

Lightning follows "the rules" as surely as a simple flashlight does. The challenge is to divine how "the rules" are applied in what becomes an exceedingly complex time varying electrical network problem. We apply simplifying assumptions in order to deal with what would otherwise be overwhelming complexity. The simpler we make the problem the easier it is for us to understand but the less accurate our model parallels or describes reality. This leads to unexpected results where our expectations are not met by that nasty ole lightning seemingly having a mind of its own.

The more we simplify our model the greater the potential for deviation of reality vs our flawed expectation. Along the way, over time, folks dealing with lightning have worked out some basic guidelines that, when applied, reduce the probability of lightning caused damage. I am not aware of any exposed but fully lightning protected installations of any useful complexity. The statistical likelihood of lightning damage may be reduced but I would think it impossible to be fully eliminated in practical applications. The cost vs protection ratio rapidly escalates as higher degrees of protection are attempted. At some point it is easier to accept some amount of risk as it might be more economical than trying to further reduce the likelihood of damage.

Excellent insurance is available from an ARRL approved source that in many instances would make replacing equipment damaged by lightning less expensive than paying to get greater lightning protection which is still no guarantee against damage just a reduction in probability.

I wish everyone a lightning safe new year and the good luck to avoid being smacked by Thor.

Patrick        NJ5G

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