Earlier quoted context omitted.
I wouldn't be so quick to dismiss timerol's point as nonsense. I live in Belgium. I was doing some electrical work in my home recently. On the 29th of May, I noticed two out of three phases were close to 250V instead of the intended 230V. This is the limit where inverters of solar installations switch themselves of; it indicates more solar power was being produced than could be absorbed by the grid. It turns out the…
Oh, and as for the 'intended 230 V' -> grid voltage can be between 228 and 252 inclusive without violating the standard. Nominally it is 240 V, not 230 V. The way inverters inject power into the grid is by syncing to it and then leading the phases a bit to cause current to flow. The RMS voltage will rise as a consequence of that.
This is specified by the EN 50160 standard: https://www.se.com/ww/library/SCHNEIDER_ELECTRIC/SE_LOCAL/AP...
The range you specified sounds like the US tolerances.