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North American Network Operators Group

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Re: CAT5 surge/lightning strike protection recommendations?

  • From: Steven M. Bellovin
  • Date: Wed Sep 14 10:00:19 2005

In message <>, "Marshall Eubanks" writes:

>> My direct experience with running long-distance underground cable is 
>> dated -- let's put it like this; we were dealing with RS-232 -- but the 
>> countermeasures to a direct strike on copper cables don't seem to have 
>> improved nearly enough...
>I don't think they will... tens of megavolts is hard to protect against.
>This depends a little on where you are. I have experience with
>cable runs  in Southern Florida (where lightning strikes can occur
>daily), West Virginia and Virginia (with strikes common) and Hawaii
>(where they don't seem to  be as frequent). The cable may be in
>the ground, but it is connected to stuff at either end which isn't,
>and given the potential di fferences that occur in the natural
>environment (~ 150 volts per meter of altitude), this mea ns that
>cable runs can act like lightning rods connected directly to your
>network gear.
>So my jaded perspective is that you WILL get hit if you connect
>buildings with copper, and you WILL NOT like it. Since this can be
>entirely mitigated th rough the use of fiber, use fiber if you
>possibly can.

Right.  When I lived in North Carolina, there was a ground strike close
to my apartment.  It tripped some circuit breakers, burned out some light
bulbs, and fried the cable TV box, the balun, and the RF input on my TV.

And what regularly happened to our computers and terminal gear in the
CS department was scary.

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