[AustinDev]

12:03 – 12:07 CEST – first period of oscillations in the grid detected and mitigated. 12:19 – 12:21 CEST – second period of oscillations in the grid detected and mitigated. Since then the grid appeared stable, with no oscillations detected. 12:32:57 – 12:33:17 CEST – a series of generation trips in southern Spain, the first near Granada, the second near Badajoz and the third near Seville causes a loss of 2200 MW in generation capacity. Frequency decreased and voltage increased. 12:33:18 – 12:33:21 CEST – grid frequency of the Iberian Peninsula drops below 48.0Hz. Automatic load shedding is activated.

https://en.wikipedia.org/wiki/2025_Iberian_Peninsula_blackou...

Looks like the first few oscillations were successfully mitigated. I'm not sure what type of generation got cutoff that led to the cascade. Not sure how reliable this infrastructure map is but that area seems to have a pretty good mix of Natural Gas, Hydro Storage and Solar. https://openinframap.org/#9.14/37.4625/-5.8656

[codingbot3000]

Exactly, and as a consequence of the automatic load shedding, the fission reactors shut down for safety reasons, and had to be cooled using their Diesel generators, which wasn't nice to watch: https://www.lavanguardia.com/vida/20250428/10625069/nucleare...

Which unfortunately meant they were unable to support the "reboot" of the network. That was started in the evening to avoid working hours (we were lucky and hat our electricity back at 18:30, while some people had to wait quite a bit longer). The reboot used mostly hydro, gas, and as much electricity as possible from France and Marocco. (well summed up in https://en.wikipedia.org/wiki/2025_Iberian_Peninsula_blackou...)

I wonder whether there could be a safe mode during load shedding that would not require a complete reactor shutdown. If that were the case, nuclear could have a stabilizing effect same as gas or hydro.

I am quite eager to learn about what really went wrong. We enjoy really cheap consumer prices for electricity (we use it to heat and cool, like in the US), thanks to solar and wind. I hope investing in batteries and network reliability will be enough to mitigate the problems.

[AustinDev]

>Exactly, and as a consequence of the automatic load shedding, the fission reactors shut down for safety reasons, and had to be cooled using their Diesel generators, which wasn't nice to watch

The shutdown is due to an abundance of caution and is regulatory (in the US). When the grid falls below a certain threshold of stability the reactors are programmatically shutdown. (At least that's how it worked 20 years ago.) They have significant inertia but that only goes so far, as you mentioned until we see the final report we won't know for sure if the shutdown was manual or programmatic.

Depending on how long the Reactors were shutdown down Xeon poisoning could have also been why they took longer to start back up. Xeon poisoning is one of the attributes of our current fission technology that makes Nuclear less able to cope with instability compared to combustion generation.

>I am quite eager to learn about what really went wrong. We enjoy really cheap consumer prices for electricity (we use it to heat and cool, like in the US)

Air conditioning is a great application of Solar especially in the sunbelt. It just makes so much sense. When it is daylight and the Sun is unobstructed A/C draws a lot of power likewise Solar is at peak efficiency. I've never been to Spain but, if you all believe in A/C I may have to stop by next time I'm sailing the Med.