I wonder if that “power event” was actually a
daily scheduled one, for your UPS “Testing Itself”. It would be very brief,
possibly just dipping its backup battery to make sure it can revive
an outage.
My TRIPP-LITE back-up does that, since I
programmed a daily check in its PowerAlert Agent, test schedule.
Maybe yours does something
similar, every day at precisely the same time.
