I have had one lightning strike at my home QTH in over 45 years of hamming.
Lighting hit an electrical fence next to our main barn (curiously, not the
barn nor the tree close nearby, which were both significantly higher) and
evaporated all 5 strands before digging a small crater in the ground. The
barn power is fed from the meter center at the house, some 300+ feet away,
and per the NEC has its own ground rod at the barn distribution center. All
the damage we had, which was all over the place, was due to the difference
in ground potential between the barn ground and back at the house ground at
the meter center. Even circuits which were switched off sustained damage,
since the ground wire remains connected. Curiously, although the computer in
the ham shack was affected, none of the radio gear was at all bothered, and
it is all tied together to its own ground rods (4) just 10-20 feet away.
Everything was plugged in at the time, too. I remember when we installed the
barn power thinking that this could be a problem in this type of situation,
but understood the more likely danger would be an elevated ground in the
barn if the circuits there were not provided their own ground, so it went in
per the NEC.
=Vic=
WA4THR
----------------------------------------------------------------------------
----------------------
From: Jim Brown <k9yc@audiosystemsgroup.com>
Reply-to: k9yc@arrl.net, Discussion of Ten-Tec Equipment
<tentec@contesting.com>
Date: Wed, 14 Sep 2011 00:28:32 -0700
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Hi Joe,
Yes, the AC power line is a common entry point. I agree that a good
whole house protector at the main feed is a good thing. I've bought one,
but haven't installed it yet. It is critical that the leads between the
protector, the power line, and the green wire be VERY short. It is also
critical that everything in your premises be bonded properly.
Earth connections are not SOURCES of trouble (unless they are not
properly bonded together), so they do not require protection. The lines
that need protection are all signal and control lines that enter your
premises, like CATV, telephone, and antennas. Again, it is critical that
protectors be properly bonded to the ground system.
You should absolutely avoid shunt mode (MOV) surge protection on branch
circuits (the sort of things built into outlet strips, and most
dedicated surge protectors). MOVs on branch circuits are more likely to
CAUSE damage than to prevent it. MOVs are entirely appropriate at the
service entrance if they are properly bonded. The ONLY safe protection
for branch circuits are SERIES MODE protection devices. I use and
recommend SurgeX products. Yes, I have done consulting for them --
teaching, technical writing, and some of their more difficult tech
support troubleshooting -- but I was specifying them for ten years
before they hired me for anything. :)
73, Jim Brown K9YC
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