Good news,
the cause was identified by the Portugal Grid Operator and it wasn’t sabotage (see Update in the article)
Due to extreme temperature variations in the interior of Spain, there were anomalous oscillations in the very high voltage lines (400 kV), a phenomenon known as induced atmospheric vibration. These oscillations caused synchronisation failures between the electrical systems, leading to successive disturbances across the interconnected European network.
Apologies for double posting, this is an aside, but extremely interesting, from my limited understanding: https://phys.org/news/2025-04-sun-explosions-echo-earth-skies.html I thought you may find it interesting, as well.
ETA: this says M-class flares, too. https://www.space.com/solar-flares-effects-classification-formation
oooo thanks very much!
Very welcome. I saw an article this morning that said there was another X-class flare either yesterday or day before. It was scant on details and I’ve not looked for a decent article yet, but I’ll post it if I find it.