If that was actually the case, I would surmise that the "ground rods"
were not connected to a proper rebar cage (i.e., Ufer ground) that would
normally be able to able to distribute the lightning current over a
sufficiently large surface. Simply putting a couple of ground rods
inside a concrete base is folly, but that is not at all the same as
having a proper Ufer ground inside the base, nor is it the same thing as
running a conductor through the base to a sufficient external ground.
It does not advance the technical competency level of our hobby to make
broad generalizations based upon narrow and poorly defined anecdotal
instances.
Dave AB7E
On 4/25/2018 3:10 PM, Ken G Kopp wrote:
> I should have been more specific in suggesting that grounds that
> might end up carrying a lightening charge not be run through concrete.
>
> The following is from personal "real world" experience.
>
> I know of two specific cases where tower bases were blown apart by
> lightning hits to the towers because ... in the interest of "neatness" ...
> their ground rods were -inside- the concrete bases.
>
> These two events took place in the Tampa Bay (St. Petersburg) area
> of Florida. The Tampa Bay area has the distinction of having the highest
> number of lightening strikes in the western hemisphere, BTW.
>
> I worked aboard a USC&GS (NOAA) ship at the time and we did a lot of
> lightening-related research. Picture flying a balloon-borne wire to
> deliberately
> attract lightening!
>
> Concrete is rarely "dry" even after years of "curing". The dampness becomes
> steam that's instantly created by the current from strike flowing through
> the
> ground that's -inside- the concrete. This steam becomes part of the
> explosion.
>
> 73!
>
> Ken Kopp - K0PP
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