The great blackout that paralyzed the Iberian Peninsula on April 28 was “the most serious in Europe in the last 20 years.” This forceful is the main conclusion of the preliminary report presented this Friday by the European Network of Operators of Electricity Transmission Systems (ENTSO-E). The investigation, which avoids pointing directly responsible, identifies as a cause a phenomenon never seen before in the continent: a collapse caused by “cascade overtheions” that the defense systems of Spain and Portugal were unable to contain.
After five months of analysis, the European agency has published a “factual” document that reconstructs the chronology of the incident based on the data provided by the operators and businesses involved. Even so, the definitive analysis, which will include the root causes and recommendations to avoid future collapses, will not be published until the first quarter of 2026.
You may be interested
The Spanish risk premium drills new minimum of 2009 and is 28 points below the French
ERC demands from the government a decree to grant early retirement in the chemical and refining industry
“This has never happened before in Europe, and we know this with certainty,” said Damian Cortinas, president of the Entso-E Committee in charge of the investigation. Curtains highlighted the uniqueness of the event, stressing that they have not found records of a blackout of these characteristics anywhere else in the world. “This waterfall effect that causes a total blackout is never seen. And, of course, a total blackout in two countries has important repercussions for citizens and society,” he added.
The report puts the focus on how an initial loss of just 500 megawatts (MW), a smaller figure for the system as a whole, resulted in less than two minutes in a series of surge that extended throughout Spain and, subsequently, to Portugal. “It was only possible to stop him at the border with France. And to prevent it from extending to the rest of Europe,” Cortinas explained.
However, the Entso-E manager insisted that the objective of the panel of 45 European experts is not to debug responsibilities. “The Entso-E function is not to attribute responsibility to any of the parties. We are not a police or judicial body. It is something that the Spanish authorities will assign when the time comes,” he said, recognizing the severity of the possible legal consequences. In that line, the report regrets not having access to all the necessary information, since eight generation and distribution companies did not give their consent to share all of their data with the panel, despite the efforts of Red Electrica de España (REE) to collect them.
Chronology of a collapse
The document details that the morning of April 28, 2025 was marked by a high generation of renewable energy and a growing variability of tension in the Spanish network. Before the collapse there were two periods of strong power and frequency oscillations, between 12:03 and 12:08, and again between 12:19 and 12:22.
To mitigate these anomalies, operators took measures such as the reduction of electricity export to France. However, the report suggests that these actions, paradoxically, “caused an increase in tension in the Iberian electrical system.”
The incident as such began at 12:32, with several “important” disconnections of wind and lots of generators in the north and south of Spain. In less than a minute, the system lost 208 MW, to which an increase in net load of 317 MW was added, possibly due to the disconnection of small photovoltaic facilities. The causes of these first events are still unknown.
The situation was precipitated between 12:32:57 and 12:33:18, when a series of “important disconnection events” in Andalusia, Extremadura and Castilla y León caused an additional loss of at least 2,000 MW (2 gigawatts). From that moment on, the tension in southern Spain and in Portugal increased abruptly, triggering the waterfall. At 12:33:19, Spanish and Portuguese systems began to lose synchronism with the rest of Europe. Defense plans and automatic cargo displays were activated, but failed to avoid collapse, which was consumed at 12:33:23 with the total separation of the peninsular network.
The restoration of the supply began thanks to the activation of autonomous starting resources in some plants and the interconnections with France and Morocco. Portugal completed the process at 00:22 of April 29, while Spain did it around 04:00 in the morning.