[time-nuts] Power glitch - Sat morning

[Hal Murray]

A while ago, I clean things up so that my system that monitors the line 
frequency was running off a UPS while watching the non-UPS line.  I looked at 
some graphs.  It seemed to be working.  I moved on to other things.

Last Sat morning, it got tested.  Here is the graph of that area:

http://users.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-2020-Mar-28.png

It's pretty obvious that power was off for 10 seconds, but what are the 2 
points in the middle?

Below is the raw data from around that time.  The second column is 
seconds-this-day.  The samples are 10 seconds apart, grabbing time and count 
from the previous cycle.  The 3rd column is the time and the 4th column is the 
count of cycles since started.  The last column is the number of cycles since 
the previous sample.  The next to the last column is the time since the last 
sample.

58936 60238.841  1585413838.824846 184208171   9.998426  600
58936 60248.843  1585413848.839454 184208772  10.014609  601
58936 60258.845  1585413858.837680 184209372   9.998226  600
58936 60268.846  1585413868.835009 184209968   9.997329  596
58936 60278.857  1585413878.849946 184210296  10.014937  328
58936 60288.867  1585413888.865095 184210897  10.015149  601  <==
58936 60298.876  1585413898.862521 184211146   9.997425  249
58936 60308.877  1585413908.876564 184211747  10.014044  601
58936 60318.888  1585413918.873961 184212347   9.997397  600
58936 60328.893  1585413928.888983 184212948  10.015021  601

The marked line is a typical sample.  The one after is is only 249 cycles in 
10 seconds.  The 2 lines above are both short.

I'm pretty sure what happened is that there were two 5 second dropouts 10-15 
seconds apart.  The first one just barely overlapped the end of a sample 
period: 596 cycles rather than 599, 600, or 601.  Note that the last dot on 
the top line is slightly below the rest of the line.

The second dot of the middle pair is the marked line.


-- 
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