Cascading blackout: report reveals critical failures, but no culprits

The major blackout that left millions of people across the Iberian Peninsula without electricity on 28 April 2025 was not caused by a cyberattack. That is what the report presented by the committee of experts tasked with investigating the incident states; it was made public this Tuesday after the Council of Ministers meeting. According to the document, the cause was a combination of technical failures, questionable operational decisions and electrical phenomena that were not damped in time.

The Minister for Ecological Transition, Sara Aagesen, explained that ten thermal power plants had been scheduled to maintain the system’s voltage balance, but one of them reported that it would be unavailable the night before. Despite the warning, the decision was made to continue with lower capacity than planned for the following day. At the express request of the entities involved, the report does not reveal the identity of the plant or the operators concerned.

During 28 April, a series of oscillations in the power grid, a natural phenomenon though unusual in its scale, complicated control of the system. The first signs of instability arrived before midday and, although the planned protocols were applied, the measures taken unintentionally increased overall voltage, triggering automatic protective disconnections at several electrical installations. The document also states that there was sufficient generation capacity to avert the collapse, but the systems responsible for absorbing reactive energy, key to stabilising voltage, did not respond as expected despite being paid to do so. Some disconnections, according to the report, occurred outside the expected limits and helped extend the blackout’s reach.

Aagesen stressed that the report does not seek culprits, but rather to understand what happened in order to prevent future crises, and acknowledged that vulnerabilities requiring urgent attention have been detected in the electricity grid. The Government says it is already working on corrective measures and a review of the operational framework, although the names of the companies involved have not been made public. The event of 28 April has once again put the fragility of critical systems on the table, even in countries with advanced infrastructure, and has ignited debate about transparency in managing the electricity grid. For now, the causes are clear, but the solutions still have to be built.