Dr Artaud wrote about his recent lightning strike, sorry for your damage
there Dr. I too, took a lightning strike a couple of years ago.
Thankfully, because I took some precautions, my radio gear didn't get
any damage but I can't say the same for the televisions, the cable
modems, phones, etc.
Questions:
1. The router and cable modem were on a different circuit from the power
for the radio and DVD player. The Radio, the DVD player, and the clock
radio were plugged into a spike suppressor strip. My house itself has
whole house spike suppression at the power meter. I took the spike
suppression strip apart to examine for damage, none was visible. If the
surge entered the power system, making it to the lighting panel, why
wasn't it shunted to ground by the power strip and the whole house
suppression which was only about 3 feet from the panel?
It may not have entered that way. Nearby strikes can induce a current
into the power lines running through the house. At a distant point from
the lighting panel the induced voltage could have started. As it courses
its way through the house wiring looking for a ground point it will work
through your appliances, etc. until it finds ground. Meanwhile, it may
never make it back to the panel.
2. Could it have been electromagnetic forces that destroyed the cable
modem and router?
Absolutely. Every cable wire, every phone wire, printer cable, etc acts
just like an antenna...picks up a voltage and carries it to the device.
That nearby strike packs plenty of power to place a huge voltage on a
wire. Most of these devices are low voltage and sucuumb to transients
easily.
3. My equipment was not grounded or bonded. Surprisingly, the items that
were destroyed near my Yaesu were items that had internal power supplies,
so that a direct connection to the neutral was available. The items that
were powered by transformers, including the Yaesu itself, were
unaffected. I have a Uniden metal case scanner atop my Yaesu that was
plugged in, and off with a mechanical switch (part of the volume
control), this radio was unaffected. I also have a speaker system for my
DVD and TV in the bedroom, this was also off by a mechanical switch and
is transformer fed, this was also unaffected. Though the Cable Modem and
Router, as described above, were always on, so is a great deal of other
equipment in the house, including my main TV, DVD Player, AV Receiver,
and so on. Why the preference for some equipment and not the other?
Precisely what I had happen at my strike. The televisions were
unplugged, but I neglected to unplug the cable tv channel boxes and when
the strike entered via the cable it was all that was necessary to
destroy 2 TV's, and 3 cable tv boxes, as well as the cable modem boxes.
Oddly, the computers survived although one modem on a laptop could no
longer be used. I plugged in a modem card and was able to work around
that damage. Sometimes there's no rhyme or reason as to why some pieces
of equipment survive while others don't.
4. Lastly, how can I have an outdoor antenna and survive a strike without
damaging equipment? I know that I should disconnect the wire when before
a storm, which I always do, but this day was not supposed to have storms,
and I couldn't get to the radio in time. Was the wire more likely to be
struck since it had been grounded? Unfortunately, the strike came down my
tree in the backyard, obliterating a limb at the top, (a very tall tree),
and traveling down the outside, casting off bark as it traveled. The line
in the bark comes right to the end of my wire antenna and no lower. Could
a "leader" have been initiated by the antenna grounding system that
actually led to the strike? The antenna itself was several feet from the
tree, tied to the tree trunk with a rubber tube. If the wire had
previously been removed from the radio and simply tossed onto the floor,
what may have happened with the surge?
You need a SINGLE POINT GROUND SYSTEM, I'm not shouting there..just for
emphasis. One and only one common ground system to which all equipment,
and the entrance panel ground share. This way, if a voltage makes it
onto your system, all points rise and fall at the same potential. It is
a potential difference between points that allows current to flow. If
all points rise and fall the same...no current flow, no damage
supposedly. After my strike (which was strong enough to blow ceramic
tiles to dust, and blow a 2 inch deep by 2 inch wide by 6 foot canyon in
my concrete housepad under those tiles!) I contacted PolyPhaser and
several other lightning companies, was invited to a 3 day lightning
damage symposium by Florida Power to learn more and see the various
company displays. I learned a lot. The results of which I have put up on
a web site showing what I did to install more safeguards to my system.
It is at
http://www.knology.net/~res0958z/
I'm a bit to excess on this subject, once you've been hit you realize
the vulnerabilities. And with a 65 foot tower out back, a mere 15 feet
from the house, a bit more sensitive to the possibilities. Good luck
with upgrading your system.
Bill
KC9CS
Thanks for your comments, and be safe when lightning becomes an issue.
Dr. Artaud