[cesarb]

> The cause is the frequency drop that was not compensated by the inertia of rotating turbines due to increasing use of photovoltaics.

But what caused the frequency drop? Large-scale grids are designed and operated in such a manner that any single fault, even one which causes a frequency drop (like a generator or a power line getting disconnected), will not cause a blackout. Which means: if there isn't enough inertia to compensate the frequency drop caused by a single fault anywhere in the grid, the system operator will either order photovoltaics and wind turbines to reduce their generation to a safer level, or order traditional rotating generators to operate as synchronous condensers (which adds inertia without adding generation).

Which means that either there was a double fault (two faults close enough in time that there wasn't enough time to reconfigure the system to a safer state before the second fault), or that the modeling of how the photovoltaics and wind turbines would react to a single fault was incorrect (for instance, expecting them to stay connected for longer on that level of frequency drop). My personal guess is that we're going to see a repeat of what happened here in Brazil in 2023, as I explained in another comment on an earlier thread (https://news.ycombinator.com/item?id=43821801), where a single fault was enough to destabilize the system because the inverters in wind and solar power plants disconnected earlier than expected.

[cft]

According to my friend, the freq drop was caused by a sudden large supply surplus over the instantaneous demand. Nuclear plants were offline and there was nothing to absorb the freq drop at that moment.

[cesarb]

> According to my friend, the freq drop was caused by a sudden large supply surplus over the instantaneous demand.

Wouldn't a supply surplus cause a frequency increase, not a frequency drop?

[cft]

In the case of the rotating generators, yes. In the case of the solar panels, I do not know: I guess it depends on the inverters characterists? Spanish is not my native language, so I may have mixed it up when talking to him.