[142456] in North American Network Operators' Group
Re: Wacky Weekend: NERC to relax power grid frequency strictures [OT]
daemon@ATHENA.MIT.EDU (Pete Carah)
Sun Jun 26 18:55:11 2011
Date: Sun, 26 Jun 2011 18:54:24 -0400
From: Pete Carah <pete@altadena.net>
To: nanog@nanog.org
In-Reply-To: <20110626215505.GH25848@pokute.pelzi.net>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 06/26/2011 05:55 PM, Jussi Peltola wrote:
> On Sun, Jun 26, 2011 at 11:36:24PM +0200, Ingo Flaschberger wrote:
>> but transforming is not easy.
>> ac/ac transformers are easy tu build and very immune against lightning
>> strikes - inverter systems are not.
> Switching DC is also problematic since there is no zero crossing to
> extinguish the arc.
Sometime look at break ratings for AC and DC breakers and compare the
relative sizes. Shows this effect.
Easy answer is: don't use mechanical switches for routine switching...
(easy if there is an inverter present, like in a VF drive or switching
power supply). Big enough AC breakers maintain the arc over more than
one cycle so have this problem too. (plasma quench time at atmospheric
pressure can be a while...)
Given the technology of the time, AC won rightfully. Still better for
most distribution.
-- Pete
