I have an APC 1500VA UPS in the garage from the days when you actually needed that much for home servers - it runs at about 13% load now on a 2 year old battery
Anyway I (once again - long story) sorted out the UPS alerts so it emails me when there's extended under/overvoltage or mains failure.
Lots of extended overvoltage alerts.
By overvoltage I mean well over 253V, which is the max spec (230V +10%/-6%).
258V is commonplace & we've had 260V in the last day or two. Initially I looked at the overvoltage graph & thought "its at low-demand times", but its not.
The correlation is nearly 100% when the wind speed is over 10mph regardless of time of day - when the wind speed averages 15mph our mains voltage is running at 257.5V and increases to around 260V. The rest of the time then its high (248-250V) but its in spec.
I intend complaining to Western Power Distribution (they deal with mains stuff outside the house here) but I don't really see what they can do about it other than pay daily compensation. Haven't looked into this much but if your mains voltage is out of spec you are entitled to daily compensation rates AFAIK. For anyone wondering "does it make any difference" then yes it does on all your lighting - LED bulbs will blow very early IME.
Was just really surprised that the grid is under that much stress from "renewables".
Edit - we don't have any wind/solar stuff so this is the mains grid voltage varying.