[TowerTalk] Fwd: Earthing a tower

[Randy]

FWIW I *do* recall a gent, on this list, a few years back, that said 
that lightning had, in fact,
caused his concrete *guy anchor* to fail, resulting in the loss of the 
tower, at some point
some years prior. This was in one of these similar threads.

That's not to say that it's safe to assume anything about the anchor 
prior to the strike.

I'm merely pointing out that, in the "real world", there appears to be 
at least one case
of this happening.

I locate underground water leaks here in Florida, and lots of them are 
caused by lightning,
and I've seen *plenty* of spalling associated with those same strikes. 
And, yes, lightning
does do just whatever it wants to do. Enough of it can make it into a 
home and down a
buried 3/4" copper pipe to leak anywhere in the home it wants to. I feel 
like "most" of
the strikes I deal with come down the electrical mains, and yet do not 
necessarily cause
the leak at some point near the electrical service entrance. Whatever 
the mode may be,
however it "gets in", it feels no obligation to cause the leak very near 
to the outer perimeter
of the home, as one might expect...if you "expect" lightning to behave 
predictably.

73 and HNY
Randy
KZ4RV

On 12/30/2012 9:45 PM, Jim Lux wrote:
> On 12/30/12 3:06 PM, Hans Hammarquist wrote:
>>
>> Anecdote or not. If you push enough current though any conductor it
>> will "explode". (This is actually use in one type of detonators.)
>
> Oddly, I have personal experience with exploding wires (not EBW 
> detonators, but in other applications)...
>
> THere's nowhere near enough *energy dissipated* in a lightning strike 
> through a Ufer ground to do this.  The actual stroke is about 100 
> kJ/meter & the dissipation in the stroke in air is substantially 
> higher than in a grounding system.  To put 100kJ in context, TNT is 
> about 4 MJ/kg. about 110kJ/ounce.  So, put an ounce of TNT in a 
> properly designed hole in some concrete, and you can split it or spall 
> it.
>
>
> I
>> don't know how much current required to crack concrete and if a
>> direct lightning strike can be enough, but I don't think we have to
>> worry so much about that as such a "super" strike will cause more
>> harm in other places around the tower hit.
>
> Yes..
>
>>
>> I have my present house designed to take a "super" strike. I am using
>> 3/4" copper pipes in all four corners of the house. According to the
>> engineer, helping with this design, my house is ready for one of
>> these "super" strikes, observed on occasions. I believe it is a
>> lightning with a peak current of 300 kA, maybe it was even more.
>> Anyhow, after three confirmed, direct hits in the house, I feel
>> relatively sure I did something right.
>
> yes..
>
> The key thing on destruction is the I^2*t (called the action).. 
> Because that's related to the energy deposited
>
>
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