Just a thought about interpreting data: The mains frequency changes as the loads on the system change. Dispatchers bring more generators on line or drop them. Some of this is predictable, depending on business hours, weekends, holidays and the seasons.
Just as one can take the crystal aging out of the frequency vs. time display, it should be possible to subtract an average of the variations caused by predictable load changes. This leaves a display that makes unusual deviations much more visible. The line frequency is not like a disciplined crystal oscillator. There is no phase locked loop adjusting the line frequency, just dispatchers trying to produce the same number of cycles per day. The length of a day is precisely known from national time standards. Short term plots (e.g. daily and weekly) of line frequency should be referenced to time of day, not elapsed time. It would be interesting to see how the daily load averages vary from region to region. Bill Hawkins _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.