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From: jxyp@lanl.ARPA
Newsgroups: net.dcom
Subject: Re: lightning, PACXs and computers
Message-ID: <29116@lanl.ARPA>
Date: Thu, 1-Aug-85 22:16:28 EDT
Article-I.D.: lanl.29116
Posted: Thu Aug  1 22:16:28 1985
Date-Received: Sat, 3-Aug-85 05:55:27 EDT
References: <1397@islenet.UUCP>
Distribution: net
Organization: University of New Mexico at Los Alamos
Lines: 41

[Apologies if this reaches you twice... problems with an upstream feed.]

> > Briefly, all of the on-campus computer facilities with data communications
> > lines extending beyond their immediate buildings (typically RS232
> > 3-or-4-wire leased phone circuits or similar) suffered burned out
> > ports and burned out terminals ...

> details that weren't mentioned in your note.  In particular I wonder
> if your communications lines are above or below ground?

We are in the midst of our second storm season at our new campus.  It's
a small campus, but we do have several terminals in buildings separate
from the computing center (where the cpu is located).  Except for scale,
we are experiencing (repeatedly!) exactly what happened in Hawaii.

Our remote terminals are connected with rs232 cables, underground, in
conduit.  Our power supply to the VAX is protected.  We have an Emulex
CS11 (DH11 emulator) with 4 distribution panels.  During most electrical
storms we have lost one of the panels and various other peripherals
including terminals and our line printer (which is in the computing
center).  Our first attempt at defense was to install individual surge
protectors at the power connection of each remote terminal.  Next we
added surge protectors to our dialup phone lines.  I assumed that the
data lines to the remote terminals *couldn't* be the culprits, since
they are underground and in conduit.

The latest advice (from one of DEC's field people) is that this is a
typical problem with sites where equipment is in several buildings;
that, during an electrical storm, each building will have a different
potential to ground!  Thus, the ground wire in the rs232 cables suddenly
carries the difference.  I have disconnected (at both ends) all of the
terminals outside the computing center until we can get protection on
the data lines.  We have had several lightning storms since, and (knock
on wood) no more damage.

Please, can someone with experience and *knowledge* join this discussion?
-- 
	Jay Plett
	{cmcl2,ihnp4}!lanl!unm-la!jay
	{gatech,ucbvax}!unmvax!unm-la!jay
	jxyp@lanl.ARPA