What caused it?
The Portuguese prime minister, Luís Montenegro, said that the issue originated in Spain. Portugal’s REN said a “rare atmospheric phenomenon” had caused a severe imbalance in temperatures that led to the widespread shutdowns.
REN said: “Due to extreme temperature variations in the interior or 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.”
Georg Zachmann, a senior fellow at Bruegel, a Brussels thinktank, said it was unclear what caused the initial problem, but after that the system suffered “cascading disconnections of power plants” – including at one in France – when the frequency of the grid dropped below the European standard of 50 hertz.
No Cyber Bunnies involved I'm afraid.........