[BC] lightning protection

[Mike McCarthy]

While I  agree with BOTH sides of the argument, I have to agree with 
Alan and his real experiences. What I point out to owners is the 
devices can circumvent (note I do not say "DO") smaller strikes from 
developing in the immediate area of the tower by the bleeding effect 
discussed. I also tell owners that there is nothing out there which 
will prevent major strikes from occurring IF the charge intensity is 
there. It is what it is and even the heaviest of devices have 
saturation limits. Plus there are the laws of phyiscs.  That's the 
randomness of nature at work.

I install the ERI system for a couple reasons I won't go into here as 
a matter of simple precaution when ever we're doing structural work 
on our towers which don't have them. Not from any empirical evidence 
mind you. The argument is one strike diverted (versus prevented) is 
one potential damage event averted.  Which with insurance deductibles 
$5K and more per event, the $1500 for an A-3 installed is really 
cheap on-site insurance.

As for the validity of whether they work on objects other than 
towers, I'm not an expert by any stretch of the imagination.  But the 
bottom line is the concept is SO misunderstood in it's scope as well 
as implementation that the skepticism from that misunderstanding will 
never allow it into mainstream use except by specific incorporation 
by architects and engineers specifying such AND high efficiency 
ground systems to support them.  Which will be rare indeed except for 
towers and tall buildings.

Not helping matters is the reality that strikes can hit at lower 
points on the structure. So that tends to negate the effect UNLESS 
they're installed below the top as well.  Which can become costly as 
well as wasted windload depending on the location and ice loading.

MM


At 03:12 AM 5/27/2008 -0400, Alan Alsobrook wrote
>Hate to say this, but I have had the opportunity to see a few CD 
>systems installed, and according to the CE's of the sites, their 
>annual lightning damage went from about 200K a year, down to less 
>than 1K per year. The facilities in question were TV.