Spain Says Overvoltage, Grid Missteps Triggered April Blackout

Madrid published its first official investigation into the 28 April blackout that left the Iberian Peninsula without power for hours. Energy Minister Sara Aagesen said the report found “no proof of a cyberattack” and concluded that an overvoltage on the transmission network triggered a chain reaction of automatic shutdowns across Spain and Portugal.

According to the findings, grid instability began shortly after 09:00 and intensified with two unusual oscillations registered at 12:03 and 12:19. At 12:32 a surge overwhelmed the system, and within about 20 seconds successive disconnections plunged the peninsula into darkness. Investigators say the network lacked sufficient dynamic voltage-control capacity because too few thermal plants were online and several generators failed to absorb reactive power as required.

The government apportioned responsibility to grid operator Red Eléctrica for “insufficient” contingency planning and to power producers whose plants either disconnected unjustifiably or did not regulate voltage within technical norms. Aagesen announced a forthcoming decree that will bolster grid-stability rules, authorise the competition watchdog CNMC to conduct inspections and oblige renewable facilities to participate in voltage regulation.

Red Eléctrica rejected the criticism in its own report the following day, contending that power stations—not the operator—were at fault. The utilities’ lobby Aelec, representing Iberdrola, Endesa and others, countered this week with a separate study blaming Red Eléctrica’s planning. With the main parties trading accusations, the CNMC and European network operator ENTSO-E are pressing for additional data as they pursue parallel inquiries.