[RFI] ISOBAR

[David Robbins]

Sep 19, 2012 11:55:43 AM, svetanoff at 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.