From: Greg Pierce
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Subject: Re: Info on protecting UTP network / phone / AC mains so lightning
on cable doesn't destroy everything (again)?
Date: Tue, 05 Nov 2002 15:41:08 GMT
NNTP-Posting-Date: Tue, 05 Nov 2002 10:41:08 EST
Organization: Cox Communications
Tony (remove \"_\" from email address) wrote:
> Hi all,
> I'm just getting back on air after lightning somehow got into my cable and blew
> out my cable modem, NIC, printer, CDRW, related ports etc (PC still goes except
> for the lost ports, but who knows for how long). It seems dozens of neighbours
> suffered the same or worse fate, too.
> I therefore want to define a substantial ground plane, say at a network hub,
> which all network lines, AC mains, phone and other I/O pass over and get clamped
> to (electrically).
> AC mains are easy - MOVs and some X/Y filter caps (maybe I'll add some common
> mode and series mode chokes too, and maybe even a brownout relay to drop it all
> out if the AC volts sag too much. And of course I'll make it safe for humans
> Phone protection I assume is gas arrestors in parallel with TVSs; but what
> ratings are reasonable? and do I need resistors, fuses or PTCs between them?
> Network is harder - at 100Mb/s I don't feel I can put anything much across
> without affecting the signal. Maybe shottky diodes clamping to a grunty +/-
> Cable is harder still - I can't imagine any way to protect it, but I am content
> to lose the cable modem if another strike occurs, as long as I can reduce the
> probability of losing other equipment - and of course I know there's nothing I
> can do about a direct hit (c'est la vie).
> All suggestions would be welcome.
Well, to be quite honest, the best suggestion I can offer is to get some
decent homeowners insurance. All of the surge protectors on the market
are designed for surges, not lightning strikes. Surges can come from a
vast number of sources, and while they are not terribly powerful they
can still damage your equipment. Those are what the surge protectors are
designed for. The only protection from a lightning strike would be to
power your system from a generator, disconnect all outside lines, and
build a Faraday cage around it. Even then I am not so sure... :-)
"I have seen things you losers wouldn't believe.
I've seen lights glitter in the dark near the Mail Gate.
I've seen monitors on fire off the side of the multimedia lab.
All of these moments will be lost in time, like the root partition last
Time to die."