[Server-devel] School networks and electrical equipment damage

Daniel Drake dsd at laptop.org
Thu Jun 6 15:58:58 EDT 2013


Those of us familiar with setting up school networks (server + switch
+ APs) in some of our deployments will be familiar with  the
occasional loss of hardware, due to surges in the low quality
electrical supply or whatever, even when the system is protected by a
cheap UPS which supposedly offers some protection.

This has often been the case in Nicaragua, so the group is now buying
more expensive UPSes, PoE switches, and PoE access points for new
schools. This means that the server and switch are connected to mains
power via a UPS which hopefully protects them, and none of the APs are
connected directly to the mains (instead they get Power over Ethernet)
which hopefully offers some isolation from bad electrical conditions.

This equipment is expensive, especially in places like Nicaragua where
lots of import taxes are applied. But the hope is that the investment
pays off in that the equipment doesn't get zapped.

However, one week after deploying this equipment in the first school,
we are left with a server that doesn't boot, 3 out of 4 access points
broken with a nice burning electronics smell, and a broken switch with
a lot of visible damage to the electronics.

And the most surprising thing - we had not even turned on the network
yet, pending some electrical work. Everything was connected up except
one crucial link - the UPS was not plugged into mains power. So all of
this damage happened without any of the devices having a connection to
the mains.

Connectivity-wise, the setup was:
WAN: Phone line - ADSL modem - XS
LAN: XS - Switch - 4 APs

And power connections: the XS, ADSL modem and switch were connected to
the UPS. The APs were connected to the switch over ethernet for both
power and data. Again, since the battery was not connected to mains
power, none of the devices had a power source.

The connectivity engineer's best bet is that a lightening bolt landed
at the school or nearby, and that this caused a power surge on the
phone line. This surge passed through the ADSL modem, server, switch,
and 4 APs, destroying everything in its path (except 1 AP that was
connected over a longer cable than the rest).

I figured this is a story worth sharing, for any other projects
considering splashing out on more expensive equipment...

Also, I'm wondering if anyone has any advice/experience here. Would
others expect this more expensive setup to be more resilient to bad
electrical conditions than a cheaper setup - will the investment pay

I figure that the case of a lightening bolt might be a bit extreme,
but electrical storms are a nightly occurance here almost daily during
the 6 month rainy season.

I have seen that some UPSs (unfortunately not these ones) allow a
phone line to be passed through them, supposedly offering some
protection. Would such a system protect against a lightening bolt,
assuming thats what happened here?


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