Power grids are typically only designed to tollerate one or two major faults at once, so if you mess with enough powerplants at the same time you might be able to trigger a failure that cascades through the entire powergrid. In the 2006 European Blackout [1] a single poorly executed line cut led to a cascading failure that left 10 million people over 5 countries without power for two hours.
So better stay a couple countries away from me with experiments. Or maybe don't, better a benevolent chaos monkey than being hit unprepared by your enemy.
I suppose with the state-level hacking of the powergrid is, most can do it, but won't because the enemy can do so, too. So like the nuclear standoff. Nobody uses it, because the enemy can wreck your shit, too.
But the whole grid needs a rework. Also because of renewables and batteries etc. To better react do changing demand and enable a free market, where it is easy to buy and sell power.
A similar thing almost happened recently because of a Romanian power plant. And there was also an incident in Kosovo a few years ago that caused a slight frequency decrease that caused all sorts of problems.
So better stay a couple countries away from me with experiments. Or maybe don't, better a benevolent chaos monkey than being hit unprepared by your enemy.
1: https://en.wikipedia.org/wiki/2006_European_blackout