I log the AC mains voltage at my house starting July 2013, you may recall my post where I was concerned about the unusually high voltage readings at home. Now that I have few months of data collected, it is time to do some analysis. I have 405835 measurements in total since then, taken every 10 seconds. I am logging these to emoncms, then exported as CSV and used Tableau Public to generate the below analysis.
Voltage (and frequency) varies with the load of the grid, lower voltage indicates higher consumption in the segment where I am connected and higher voltage means the opposite, i.e. grid is experiencing relatively low load.
I started with analysis of voltage by day of week and then colored by quarter of year, Q4 is when the heating season starts so there is obviously a difference. Wednesdays in Q3 Thursdays in Q4 are the outliers here, I wonder why. Weekends on the other side seem relatively unaffected by the season, probably this has to do with commercial usage.
My next analysis is voltage by month, the hot summer months when air conditioning is used a lot is probably the reason for slightly lower voltages in July and Aug:
..and a more detailed one with trendlines:
Next, analysis by hour of day across month. This is useful to see the variation by time of day, I split the graph by month to see the seasonality:
Finally a histogram analysis:
PS Adding a heat map by day-of-week and hour-of-day:
Interesting stuff, I leave interpreting the data to you.