At 11:14 AM 6/7/2024, Scott Newell wrote: >At 07:51 AM 6/7/2024, John Vendely via time-nuts wrote: >>As I recall, the western power grid system (WECC) discontinued line >>frequency regulation for timekeeping purposes some time ago. The >>eastern grid (EI) still maintains time and, here in Florida, >>line-operated clocks typically stay within about +/- 15 seconds of >>my UTC clocks. > >That fits with my Memorial Day data collected here in Arkansas >(eastern grid)--maybe 3.5 seconds vs. Hal's graph showing 15 >seconds. Graph attached. Spoke too soon. I'm seeing nearly 15 seconds in about 16 hours on June 15th (two locations in Arkansas). I've offset the data from my grid monitor at work by 10 cycles to make the graph clear (and show that the two sites track pretty well). Another interesting event--we evidently had an open neutral in our underground AC service last week. I'm using a r-pi pico to monitor the grid at home, and it also logs the approximate line voltage. (There's no data from June 19th and I don't feel like fighting gnuplot to correct the chart.) -- newell N5TNL