Help extracting summary with derivative or otherwise

From my periodic data (2 cycles shown below) I’d like to run a query or CQ to extract all the points highlighted in red. This will enable me to plot a summary chart of ‘power values just before the device turned off’.
I thought of calculating the derivative as a starting point but that will be one value to further along in time than I want. Can anyone suggest how I may be able to extract this metric please?