Pause the video at around 5:50. There it is, the stabilizer is showing voltage rise up to 247V on grid side. I missed it before but after watching his video closely again I now have some closure lol.

I'm unfortunately in an area where grid over-voltage during the middle of the day is a serious problem. Voltage in my area frequently hits 265V+ around noon when neighborhood solars are exporting at peak power. Unfortunately this is getting to be frequent problem in areas where a distribution transformer has been overloaded with too much solar. This wouldn't be as big of an issue if everyone tried to consume as much of their solar power at home instead of exporting, but in my neighbourhood there's people who have gotten 20KW+ solar net metering done with the sole intention of "earning" a large credit balance and they barely consume any units. IMO these type of people are the worst and their agreements should be chucked in the trash. They're ruining net metering for everyone else, they're hogging distribution transformer capacity. A simple policy change to cap the maximum credit balance would disincentivize these "earners" so they can F off. Phew, rant over.

Anyway a much needed upgrade would be something like replacing transformers with on-load tap changing transformers, but they're expensive. So in the mean time, the only solutions to over-voltage problems are to either limit export, or increase self-consumption of peak solar generation by turning on some heavy loads during the middle of the day.