How it works (or doesn't)

 The blackouts in Texas had me wondering why, during increased demand, it was necessary to shut off functional power plants. Indeed, the claim was that if this wasn't done, the generators would be damaged. Turns out, my favorite blogger Kevin Drum wondered the same thing, but neither he nor I have the electrical engineering chops to suss it out. Fortunately, a reader posted an explanation on Kevin's blog:

"The fundamental reason why grid operators have to resort to induced blackouts to protect their generation stations (and why it's sometimes done automatically) is that AC frequency management is everything in grid safety. Every generation hooked to the grid that uses physical motion (typically a turbine) has huge, expensive, precise turbines turning at some local multiple of 60Hz, and all of them are putting out AC whose waves are synchronized with one another. A small gas plant in El Paso phase peaks within a few milliseconds of when the steam turbines at the Comanche Peak nuclear plants do.

Under normal conditions that's just how AC power works — if it wasn't in sync no one would get power anywhere. Under strain, such as when demand surpasses capacity, frequency starts to drop — turbines start getting more magnetic resistance from their coils, solar inverters start heating up, wind turbines get more rotational resistance from their generators, etc. Most of that equipment can't tolerate going out of phase or frequency target more than slightly before it's damaged in big expensive ways. Hence they'll trip off the grid to protect themselves if needed, and grid operators have to drop loads rather than letting the frequency drop when they're out of generation capacity. They wouldn't "blow up" if they just stayed connected, but the damage would be real. There's nothing special about Texas' grid in that respect — all AC grids work that way.

There's a whole side market in energy just around frequency management — batteries and generators that can add or take away energy just to maintain stable frequency in the phase of short-term load shifts." https://jabberwocking.com/heres-why-texas-power-stations-had-to-be-shut-down/