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<DIV>This and the other posts in this thread have great data points and
anecdotal evidence. It would be nice to have it synthesized into a wiki
page.</DIV>
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<DIV style="font-color: black"><B>From:</B> <A title=kgordon420@gmail.com
href="mailto:kgordon420@gmail.com">Kevin Gordon</A> </DIV>
<DIV><B>Sent:</B> Friday, June 07, 2013 8:39 AM</DIV>
<DIV><B>To:</B> <A title=wad@laptop.org href="mailto:wad@laptop.org">John
Watlington</A> </DIV>
<DIV><B>Cc:</B> <A title=server-devel@lists.laptop.org
href="mailto:server-devel@lists.laptop.org">XS Devel</A> ; <A
title=devel@lists.laptop.org href="mailto:devel@lists.laptop.org">OLPC Devel</A>
</DIV>
<DIV><B>Subject:</B> Re: [Server-devel] School networks and electrical equipment
damage</DIV></DIV></DIV>
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<DIV>More data:</DIV>
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<DIV>In general, we have placed the UPS for the phone line protection directly
between the biccs block (or phone company termination point) and the first jack
on the line, which is usually the split jack for voice/dsl. From the split jack,
the DSL line goes into a second UPS which powers the DSL modem and the
first AP.</DIV>
<DIV> </DIV>
<DIV>Certainly the UPS should be grounded. However, to be trite, I have seen
cases in the wild where power is being saved, and sometimes the UPS is turned
off, and/or unplugged. So, it might be important to evaluate whether the surge
suppression still works when the UPS are unplugged from mains, and/or if they
have fried first. Also, we have found that the surge suppression has a
fixed number of faults before it is no longer effective. seems to depend
on the make/model/quality and the alignment of the planets. In the case of
the APC RS 1500 series, a stress test showed that spiking to just double
voltage, which did not fry the UPS machine, there was no protection left after 5
such jolts. Therefore, it is also important to monitor the UPS logs
regularly to see what is going on.</DIV>
<DIV> </DIV>
<DIV>As of yet and as far as I know, <knocking on head> we have
never been hit by lightning,but we have lost UPS do to surging, usually on
unplanned power outages. Again, so far, we have never lost an AP or a
modem.</DIV>
<DIV> </DIV>
<DIV>Last night I ran 100 <A href="http://speedtest.net">speedtest.net</A>
scripts 50 with the phone line plugged into the UPS and alternated every-other
with 50 not plugged in, on a 5Mb synchronous DSL. There was no significant
difference, and in fact the average score was a teeny tiny tad higher on the
protected tests, for all of Ping, Download, and Upload. </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>So, as usual, your mileage may vary, but this has been our
experience.</DIV>
<DIV> </DIV>
<DIV>Cheers,</DIV>
<DIV>KG</DIV>
<DIV> </DIV>
<DIV>PS: in raw cost, a good UPS is more expensive to replace than an AP or
switch. However, you don't lose your configuration, and sometimes it takes
days to get a DSL modem replaced from the telco. Sometimes it makes sense
to put the more expensive UPS in the way of even cheap
infrastructure.</DIV></DIV>
<DIV class=gmail_extra><BR><BR>
<DIV class=gmail_quote>On Fri, Jun 7, 2013 at 12:44 AM, John Watlington <SPAN
dir=ltr><<A href="mailto:wad@laptop.org"
target=_blank>wad@laptop.org</A>></SPAN> wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><BR>I
considered sources such as James' theory, as well as someone<BR>connecting one
of the ethernet cables to line voltage, and neither<BR>accounted for the level
of damage you described.<BR><BR>But I can't agree more with James' point about
building from the ground<BR>up. The first thing we used to wire up
in a computer room was the<BR>frame grounds --- with modern SOHO gear that all
comes through<BR>the grounded power plug. But it has to be plugged
in to be grounded<BR>(i.e. protected).<BR><BR>Coincidentally, today I checked
out the earth ground in the new hardware office<BR>and wired up the workbench
grounding in OLPC Boston's new digs in Davis Sq.<BR><BR>wad<BR>
<DIV class=HOEnZb>
<DIV class=h5><BR>On Jun 6, 2013, at 6:51 PM, James Cameron wrote:<BR><BR>>
On Thu, Jun 06, 2013 at 01:58:58PM -0600, Daniel Drake wrote:<BR>>> And
the most surprising thing - we had not even turned on the network<BR>>>
yet, pending some electrical work. Everything was connected up
except<BR>>> one crucial link - the UPS was not plugged into mains
power. So all of<BR>>> this damage happened without any of the devices
having a connection to<BR>>> the mains.<BR>><BR>> Actually not
plugged in? The whole network was therefore either<BR>> isolated from
building electrical earth ("ground") or had a series of<BR>> surreptitious
connections, the critical one being the telephone line.<BR>><BR>>
Hmm. Lightning wasn't necessary.<BR>><BR>> Here's my
theory:<BR>><BR>> Each long run of ethernet twisted pair becomes one
side of a capacitor,<BR>> the other side being the building wiring, piping,
or structure.<BR>><BR>> The long run of telephone wire picks up static
charge from wind,<BR>> lightning ground currents, test currents from the
telephone exchange<BR>> or line workers, or induced currents from other
subscribers or power<BR>> network switching. Even turning on many
lights.<BR>><BR>> <A href="http://www.pololu.com/docs/0J16/all"
target=_blank>http://www.pololu.com/docs/0J16/all</A> can give you an idea of
what can<BR>> happen. Any of these events will induce a starting
pulse of DC in the<BR>> telephone wire, which is analogous to the length of
DC power cable in<BR>> the Pololu explanation; the inductor. The low
equivalent series<BR>> resistance (ESR) capacitor can be thought of as the
long cabling<BR>> against the building.<BR>><BR>> As a result of the
capacitor and the inductor, the voltage is<BR>> amplified until it reaches
the breakdown voltage of whatever is<BR>> connected.<BR>><BR>> Having
the UPS plugged in might have prevented this voltage from<BR>> finding a
route through something more precious. Instead, it might<BR>> have
found a route through a series of surge protection devices in the<BR>> UPS,
and then the only damaged equipment would be the ADSL modem.<BR>><BR>>
The convention is to build from the ground up. Don't plug the
cables<BR>> in until the ground is available, and then plug them in in
strict<BR>> order. People get away with not doing this because the
damaging pulse<BR>> isn't constant.<BR>><BR>> (Reminds me of the time
that I pulled a UPS input power plug out<BR>> instead of just turning it
off. A bad idea. The last pin to separate<BR>> was
active. The connected equipment lost ground reference, the only<BR>>
ground reference that remained was through a device, so it took a full<BR>>
hit and died. The resulting current passed into the building
ground,<BR>> and triggered the earth leakage breaker on the circuit that
the UPS<BR>> was originally connected to. Other equipment connected
to that<BR>> circuit powered down.)<BR>><BR>> (Reminds me also of
working for a cable contractor in the 1980s,<BR>> looking after their cable
management system on a VAX ... they were<BR>> putting millions of cables
into a power station, and the build was<BR>> done from the ground up; that
is cables were tracked as to whether<BR>> they had been terminated yet, and
the list of unterminated cables was<BR>> a special report from the database
that they always wanted to see.)<BR>><BR>>> I have seen that some
UPSs (unfortunately not these ones) allow a<BR>>> phone line to be
passed through them, supposedly offering some<BR>>> protection. Would
such a system protect against a lightening bolt,<BR>>> assuming thats
what happened here?<BR>><BR>> Yes, but only if the UPS was
earthed. It would also protect the ADSL<BR>> modem. It would
also protect from most other causes of a current<BR>> pulse arriving on the
phone line.<BR>><BR>> --<BR>> James Cameron<BR>> <A
href="http://quozl.linux.org.au/"
target=_blank>http://quozl.linux.org.au/</A><BR>>
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