[TowerTalk] The Need for Grounding

[Patrick Greenlee]

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