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[TowerTalk] More Musings on Lightning Protection

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Subject: [TowerTalk] More Musings on Lightning Protection
From: (Bob Wanderer)
Date: Sun, 7 Jun 1998 17:00:26 -0700
Through most of the postings on this subject runs the common thread
of direct strikes. In actuality, it is the indirect (or nearby) strike which
causes most of the problems. A strike can occur quite some distance
away, even as much as several miles, and cause damage. This usually
takes one or more of several routes: directly through the power lines;
induced through the power lines; induced through other cabling such as
RF, cable television and telephone; or in its after-effects. When I was with
TCI in the early 90's we conducted a survey which discovered that most of
the damage and problems to our plant relative to a power outage (for 
whatever the reason) was due to the surge which occurred when power was
restored. These surges or spikes caused fuses to blow (what we termed 
"nuisance blowing." Employing surge suppressors designed with the
specific purpose of attenuation of these power spikes solved many of these

It is the indirect damage from a relatively far away storm which makes me
shudder at the concept of "well, I'll just disconnect everything when the storm
comes by." Even if every I/O to and from the ham shack is left disconnected
when not in use (rather unwieldy I would suggest), one can still lose home
appliances etc. to a surge entering through the power lines (unless you are
self powered - which is rather unlikely). Even if you have a ground mounted
vertical and your neighbor has a 100' tower and he gets struck every time and
you don't, you are still at risk from induced surge energy on your various I/Os.
Just think about it for a while.

One of the laws of physics which saves our bacon and the bacon of the 
manufacturers of these surge suppressors too is inductance. Unless one takes
a direct hit at the weatherhead or the RF cable where it enters the house, the
inductance of these wires and cables will spread the energy over time and allow
the damage (if unprotected) to be reduced or eliminated and for those who are
protected, for the protective device to do its function without being fried. The
*amount* of energy (area under the curve) remains the same, however. It is this
factor which allows manufacturers such as APC and PANAMAX to offer $25,000
insurance policies if the device plugs in to the suppressor is damaged. Of
course, as Amos once remarked, "The big print giveth and the little print taketh
away." As an example, APC says if you plug their UPS/suppressor into another
suppressor, or an extension cord, or otherwise fail to follow directions, the 
is null and void. While the suppressors on these devices are relatively adequate
for the usual ac-related problems (spikes), they are relatively useless against 
close-in lightning-induced spike. However, if you plug your APC into a 
you void the insurance policy. I assume it's up to you to prove to APC that you 
not do anything proscribed by them. If that room in which your computer was in 
heavily damaged by fire, how can you prove anything? I personally would be very
leery of any surge suppressor in a plastic container (which is true of many, if
not most, on the market). Poly uses a metal container. It is interesting to 
note that
UL refused to certify Poly products because of this. They demanded the container
be plastic (why, I don't know; from what I can see the most important aspect of 
is to make the $20k for their little sticker). Fortunately, Congress decided 
that UL
shouldn't be the only game in town for certification and created the NRTL 
Nationally Recognized Testing Laboratory) program. A NRTL seal of approval is
just as valid as one from UL itself. A NRTL (MET) decided that Poly's metal 
case was
acceptable and the company got the UL1449 rating for its AC outlet surge 

There was a posting to the effect that suppressors cannot survive 
and handle a direct surge. This is untrue. PolyPhasers for a fact 
can, do, and have survived direct hits and protected the equipment. 
Yes, quite often they "died" in the act of protection and on those 
occasions there may have been damage to the equipment from 
subsequent strikes. I cannot speak for other brands, but I would 
think it true for some of them as well depending on the specifics
of the strike.

To synopsize, get protection.

(former Senior Applications Engineer for PolyPhaser
and still a believer in the superiority of their product
[if not the people who own and run the company]).

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