[133040] in North American Network Operators' Group
Re: Want to move to all 208V for server racks
daemon@ATHENA.MIT.EDU (Ingo Flaschberger)
Fri Dec 3 13:25:46 2010
Date: Fri, 3 Dec 2010 19:23:44 +0100 (CET)
From: Ingo Flaschberger <if@xip.at>
To: Leo Bicknell <bicknell@ufp.org>
In-Reply-To: <20101203174210.GB82989@ussenterprise.ufp.org>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Dear Leo,
> I worked in a data center with something I thought was very, very cool.
>
> http://www.hilkar.com/highresistance.htm
>
> The concept, at a high level, is rather than tie the (service, not
> signal) ground back to grounding rods directly you run it through a
> large resistor. Now when a phase is "grounded" it runs through the
> resistor, allowing a small but safe current to flow.
currents above 1mA and 50V are dangerous.
also the net-frequency of 50hz/60hz cause troubles for the heart
(Ventricular fibrillation).
If a really fail-tolerant system is needed, that the only solution if to
have a ground-free system. the incomming power is transformed (1:1 for
example) and not earthed.
a special device monitors the voltage between earth and power and do an
alarm if one of the power-lines connects to earth - but do no shutdown.
the fault can then be repaired without shutdowns.
only when 2 faults occur the breakers trip.
usually hospitals use such a configuration.
probably hilkar system is similar to this one.
Kind regards,
Ingo Flaschberger
