A government investigation has determined that a miscalculation by Spain’s national grid operator, Red Eléctrica de España (REE), was responsible for the power outage affecting Spain and Portugal earlier this year. The blackout, which occurred in April, was due to technical and planning errors that left the grid incapable of managing a voltage surge.

According to a Reuters report, Spanish Energy Minister Sara Aagesen confirmed on Tuesday that REE failed to activate a sufficient number of thermal power stations during peak hours, leading to the widespread outage.

“The system did not have sufficient dynamic voltage control capacity,” Aagesen was quoted by the news agency as saying at a news briefing in Madrid.

The incident disconnected both countries from the European electricity grid for several hours, impacting businesses, schools, universities, government buildings, and transport hubs. Traffic lights were also affected, causing significant gridlocks. Thousands were stranded on trains and elevators due to the outage.

The investigation report, released nearly two months after the event, highlighted that certain power plants, legally required to regulate grid voltage, did not perform as expected. These plants failed to absorb the necessary reactive power despite being economically compensated to do so.

The report clarified that there was no evidence of a cyberattack contributing to the incident. The government emphasised that Spain’s renewable energy output was not a factor in the blackout. The Europe electricity grid’s frequency is maintained at 50 Hertz (Hz) for stability, and deviations can lead to equipment and infrastructure damage

In the immediate aftermath, the government had urged patience while the investigation was conducted. The findings now point to a need for improved coordination and planning to prevent future occurrences of similar power disruptions.