Core Points - A rare nationwide blackout occurred in Spain and Portugal on April 28, affecting transportation, communication, and healthcare systems, with millions impacted and economic losses estimated in billions of euros [2][3][4] Group 1: Event Overview - The blackout began at approximately 12:33 PM local time, with around 15 gigawatts of power generation capacity lost in just 5 seconds, equating to 60% of the national power demand at that time [3] - The blackout led to the shutdown of airports, railways, and subways, stranding thousands of passengers and disrupting daily life for approximately 60 million people [3][4] - Recovery of power supply took several hours, with the system only returning to normal by April 29 [3] Group 2: Causes and Theories - The blackout was attributed to an electrical frequency imbalance in the Iberian Peninsula's power grid, triggering a "self-protective blackout" [4] - Various theories regarding the cause of the power imbalance include a fire damaging a high-voltage line in France, which was later denied by French authorities [5] - Cyberattack suspicions were raised, but initial investigations found no evidence, although the Spanish government has not ruled out this possibility [6] - Another theory suggested extreme temperature fluctuations causing unusual oscillations in high-voltage lines, but this was also dismissed by meteorological authorities [6] - The reliance on renewable energy sources, particularly wind and solar, was highlighted as a potential factor, as wind generation was low prior to the blackout [7] - Some analysts argue that the nature and scale of the blackout are unlikely to be solely due to renewable energy issues, suggesting a combination of factors may have contributed [7][8]