That's a bit close to the maximum allowable of 253 V. I'd keep an eye on that and report it if you are consistently above 250 V for a say a few hours. If you have any filament lamps their life will be significantly shorter than it should be.
And you drop that far as well. Are those just spikes or is the average over say 5 mins also just as hi/lo?
I've got logging running here recording at 5 minute intervals. The biggest voltage swing is when the E7 timeswitch clunks on in winter and the best part of 12 kW is drawn. But that only makes a 10 V (ish) change. The normal range here is 245 to 235 V with most time being spent just over 240 V.
I can also tell when the local main substation is on the 11 kV backup feed rather than the main 33 kV one as the volts wang about all over the shop and has step changes as the regulator changes taps.
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