Sep 19, 2012 11:55:43 AM, svetanoff@earthlink.net wrote:
"
I have 2 aluminum entrance panels: a small one on the south end of
the house and a large one on the north end, 54 feet apart. They are both
bonded to the perimeter ground. The perimeter ground is bonded to the
electric power ground right adjacent to the power entrance, on the south
side of the house. My shack is in the NE corner of the basement and is
bonded to the north entrance panel. ALL cable I/Os pass thru protectors in
one of the two entrance boxes.
"
And this is a perfect example of how people who understand impedance, but not
lightning transients, think they are protected, but they aren't really. That
54' gives enough time for a lightning surge coming from the shack end of the
ground ring to raise the voltage on the shack equipment cases before the
lightning protection at the power entrance sees the surge and equalizes the
power conductors with it to protect the equipment. remember, the power
conductors coming from their entrance panel are at their normal 120v level
until the surge current travels all the way to the panel, 54', through the
surge arrester there, and back another 54' to the radio room. that is
something more than .33usec which can give even a moderate lightning stroke
time to get the ground voltage up to 10's if not 100's of kv above the power
ground. that gives more than enough time for a flashover from the ground to
the power line through the radio to do damage.
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