[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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