[time-nuts] accurate 60 hz reference chips/ckts
Charles Steinmetz
csteinmetz at yandex.com
Fri Dec 15 20:57:28 UTC 2017
Jeremy wrote:
> I'm surprised Vlad is seeing as much as six seconds differential but maybe
> I don't understand the experiment. I've done measurements of the line
> frequency here in California and never seen much variation.
When was the earliest time (year) you started looking seriously at the
offset/frequency of your grid? (California is part of the [North
American] Western Interconnection.)
I have only closely observed the line frequency and offset when I have
been living within the Eastern Interconnection. For years and years
between the 1960s and the 1980s, it was not unusual to observe offsets
of +/- 30 seconds, and +/- 60 seconds was not unheard of. I believe the
policy has always been to provide 5.184e6 cycles per 24-hour day, so the
+ and - offsets had to cancel over a specific 24 hour period.
I then didn't pay any attention to the mains frequency until the late
aughties, and I found that things have changed. Now, I rarely see
offsets greater than +/- 4 to 6 seconds (very rarely, +/- 15 seconds) --
but it does not follow a gaussian distribution, to my (totally
anecdotal) observation. It appears to me (again, completely
anecdotally) that it is more often within the lowest 25% or the highest
25% [combined] than it is the middle 50%, indicating a process that is
being controlled with a marginally stable loop. (Of course, it *is*
being controlled -- with a massively distributed feedback system. So no
surprise there.)
Best regards,
Charles
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