Wacky Weekend: NERC to relax power grid frequency strictures [OT]

Pete Carah pete at altadena.net
Sun Jun 26 17:54:24 CDT 2011


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





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