@rmann
One more way to visualize the data - as a scatter plot vs. UTC Time of Day (not your local timezone) of the L0 and L1 “deviants”, the “instantaneous” voltages that have deviated the most from the 120V nominal, be the deviation high or low. You’re still the chart on the lower right. The square in the center is where all the points should reside.
Given the new 1 second RMS sampling period input from @JuliaAtSense (thanks !), the detection curve for triggering a Power Quality event would look something like this. Sense wouldn’t necessarily need to see a voltage below the 110V threshold for a full second to log it. A very low dip to near zero would trigger the detection if it lasted about 84msec. The second detection voltage curve for swells/spikes end also runs upward from 130V and is limited on the time side by whatever the max voltage Sense is able to measure.
This article is interesting because it highlights the types of Power Quality issues most often seen on the grid, their symptoms and characteristic time periods, plus their causes.