2 Apr
2024
2 Apr
'24
3:13 p.m.
On Apr 2, 2024, at 11:01 AM, Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
On 4/2/24 00:03, Just Kant via cctalk wrote:
Some years ago we had a lightning strike on the driveway next to the house. It took out
every single device directly or indirectly connected to the cable TV (also Internet)
connection. The reason was something I knew about but which I did not sufficiently
understand: the cable TV connection came into the house at the opposite end from power and
telephone, and was grounded there.
A lightning strike will set up a voltage gradient in the soil near the strike, so the
"ground" seen by power and phone was at a very different voltage than the
"ground" seen by the ground rod "protecting" the cable TV entry. The
resulting current actually evaporated the cable TV surge protector innards, and took out
TV, printer, cable modem, Ethernet switch, PC, and a bunch of other things.
Lesson learned: I rerouted the cable TV to go first to the power entry point, and attached
its protector to the same copper ground sheet that the other two protectors sit on.
A great reference for all this is the handbook "The grounds for lightning
protection" by Polyphase Co., a maker of professional lightning protection devices.
I haven't done everything they call for -- for example, our house doesn't have a
perimeter ground. But it does now have single point grounding, and as a result we've
had no trouble even though there have been plenty of lightning strikes in the
neighborhood.
paul
Accordimg to certain individuals on this list,
going back a few years, electronics/computers can be damaged due to an electrical storm,
presumably very intense activity, even while off. Go look through the archives.
I have had two incidents where nearby lightning strikes blew out components on
gear I had. Many years ago, I had two computers connected by a parallel port cable, and
chips on both ends were popped by a strike that might have hit power lines about two
blocks away.
About a decade ago, we had a lightning strike that hit trees half a block away. It took
out an ethernet port on one computer, and blew out a bunch of stuff on a burglar alarm I
had built. Both involved long wire runs.