[time-nuts] Simple AC mains zero-cross detector
Charles Steinmetz
csteinmetz at yandex.com
Sat Dec 20 16:56:55 EST 2014
Magnus wrote:
>So, I do not completely agree that a through-zero measurement with a
>TIC has all the information
No, a series of time-stamped zero crossings doesn't have all of the
information in the original signal, and a small glitch that occurs
during the middle of a cycle (far away from a zero cross) could hide
and show nothing more than a slight displacement of one or two zero
crosses. Grid-nuts can ignore such short glitches. Utilities can't,
particularly in today's cybersecurity environment. Horses for courses.
From my observations of the AC mains while I was testing the simple
ZCD, I would expect such hidden glitches [that are real grid-related
phenomena, not just someone starting a motor downstairs] to be very
rare. The grid phenomena I saw typically last more than one grid
cycle and thus affect more than one zero cross, and/or are large in
magnitude and cause serious displacement of at least one zero
crossing, or several extra zero crossings.
Best regards,
Charles
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