> On Apr 2, 2024, at 11:01 AM, Jon Elson via cctalk <[email protected]>
> wrote:
>
> On 4/2/24 00:03, Just Kant via cctalk wrote:
>> 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.
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
