The massive electricity supply cut of April 28, 2025 originated from “multiple factors that interacted with each other” starting from a “very local problem” in southern Spain that “escalated very quickly,” according to the conclusions of the final report prepared by the panel of experts of the European Network of Transmission System Operators for Electricity (Entso-E) about this event.
In line with the factual document released in October, the European investigation avoids pinpointing a single party responsible for the blackout and confirms that the power outage was contributed to by “a combination of many factors and was not due to a single root cause,” as explained by the director of the investigation, Klaus Kaschnitz, during an informative appearance before the media.
“There is no single culprit. And, in fact, that was not our task. Our task consisted of looking for the reasons. We discovered that there were several factors that contributed to it, and the combination of these was what caused this incident in the end,” he/she pointed out.
The document details that the historic 'blackout' of the peninsular electrical system occurred after a chain of events that combined voltage variations and oscillatory phenomena. That sequence led to massive generation disconnections in Spain, especially in inverter-based installations, which were followed by a cascade of overvoltage disconnections that ultimately resulted in the loss of synchronism of the Iberian system with the rest of the European network.
The president of the Entso-E Committee, Damian Cortinas, wanted to highlight the exceptional nature of the episode, describing it as a blackout of unprecedented dimensions. “This type of 'blackout' did not exist, but now we know it can happen and there are several lessons we can take from what has happened to prevent it in the future,” he stated.
“A perfect storm” and a failure that spread from the south
Cortinas reiterated that it is not possible to attribute the origin of the blackout to a single element, since "it was a perfect storm of multiple factors that contributed to the 'blackout'."
The head of Entso-E stressed that the incident started out as “very local”, with its focus in southern Spain, and that “escalating very quickly” ended up also affecting Portugal. “It only stopped in the Pyrenees before spreading to the rest of Europe. But at first, it was a very local problem. When all the factors that contributed to the event are observed, the only one that was not local were the interregional oscillations,” he added, alluding to the two oscillations detected in the half hour prior to the blackout, which ended up triggering the general failure at 12:32 on that day.
The report equally underlines that, even when the system's defense plans were activated adequately, “the nature and magnitude of the cascading events caused the total collapse of the Spanish and Portuguese systems in a matter of seconds”.
Regarding the system's recovery after the electrical zero, the panel values that the restoration work started immediately and concluded in 12 hours in Portugal and in 16 hours in Spain, supported by restoration procedures “exhaustive, contingency strategies and the full commitment of all agents -operators, generators and others-.