BarcelonaThe great total power blackout (blackout) recorded in Spain and Portugal on April 28 was a unique event in the world and was due to a "surge cascade" that began in the south of the state and spread throughout Spain and Portugal within minutes, according to the technical report published today by the European Network of Transmission System Operators. However, the report does not point to blame and makes it clear that "the problem here is not that there were renewables, but that we need generation that has voltage control."
"The good news is that it can be done just like with traditional generation," explained the president of Entso-E, Damián Cortinas, when asked about the responsibility of green generation sources. This blackout has been described as "the most serious in Europe in the last twenty years" and the first under a kind of "cascading surge," although he avoided pointing fingers.
Voltage is the level of energy and must be maintained within certain limits. A classic cause of a blackout is a voltage drop due to an imbalance between supply and demand. "A voltage problem must be resolved locally, close to where it occurred. This means you need the capacity to regulate it within the system. It's a very old technology; it's nothing new. We have to see if the control voltage level required by most countries is sufficient today," Cortinas added.
The massive blackout was caused by factors such as the sudden disconnection of several renewable energy facilities, a sharp increase in voltage, previous local fluctuations, cuts in interconnections with Morocco and France and an increase in voltage, as well as limitations of automatic defense mechanisms.
This Friday, after five months of collecting data from governments and actors involved after the blackout, the European Network of Transmission System Operators for Electricity (Entso-E) has presented its "factual" report, with which the organization seeks to offer "a technical and objective explanation of what happened" by compiling the facts. However, this report will not be definitive, as the organization is working on a final report, expected to be published in the first quarter of 2026. This report will provide a detailed analysis of the root causes and recommendations for preventing future similar incidents in the European electricity system.
"Something like this has never happened in Europe, and we know it for sure," Damian Cortinas told the press regarding this cascading surge effect that caused the collapse of the peninsular electrical system. "This is new. That's why we also need time to analyze what happened and what could happen. But it is something new. This cascading surge effect that causes a total blackout has never been seen in Europe. And, of course, a total blackout in two countries has significant repercussions for citizens and society," he said.
No blame pointed.
In any case, Cortinas makes it clear that the objective of this report, carried out by a panel of 45 experts from transmission system operators—including the Spanish operator Red Eléctrica de España (REE)—and regulatory authorities from across Europe, and based on extensive data collection from generating units, is not to point fingers, a "technical and objective" explanation of what happened.
"Entso-E's role is not to attribute liability to any of the parties. This is not our mandate. We are not a police agency. We are not a judicial body. We know that liability issues are very serious, especially in Spain. This is not the objective of this report. It is something that the Spanish authorities will assign when it arrives."
Lack of information
Regarding the information collected, the agency regrets not having been able to obtain all the necessary information, since, although Red Eléctrica obtained the consent of 33 generation companies and energy distribution operators to share all the relevant data at its disposal with the panel of experts, there were "eight that did not give their consent."
The Spanish transmission grid operator, Red Eléctrica, believes that the report presented this Friday by the Entso-E panel of experts confirms the sequence of events it included in its analysis of the June 18 blackout of the peninsular electricity system. In a statement, the system operator states that the tensions in the transmission grid managed by Red Eléctrica "were within the operational limit." Furthermore, following the sequence of events in the report, it notes that the first generation disconnections occurred in the distribution networks, "which are not managed by Red Eléctrica," and at a time when tensions in the transmission grid "were within the operational limit."
Chronology of the collapse
In less than 20 seconds, 2.5 gigawatts were lost.
The morning of April 28th was marked by a progressive increase in renewable generation, a drop in prices on the daily market, and an increase in Spanish electricity exports (5 GW in total). From 9:00 a.m. onward, voltage variability in Spain began to increase, although no significant fluctuations were detected until 12:03 p.m., when "the system was placed under stress." During the half hour prior to the blackout, two main periods of fluctuations were observed in the European electricity system. To mitigate these, operators reduced Spain-France exports, assembled internal lines in the south, and changed the operating mode of the Franco-Spanish link. "They reduced the fluctuations but increased the voltage in the Iberian system," notes Entso-E.
Starting at 12:32:00 a.m., several significant events occurred, with the loss of 208 megawatts (MW) of wind and solar generators distributed across northern and southern Spain, plus 317 MW of net load increase on distribution networks, likely due to the disconnection of small photovoltaic generators. The impact of solar roofs is "very difficult to investigate," but experts will attempt to delve deeper into them. In addition, a transformer supplying photovoltaic, solar thermal, and wind generation infrastructure tripped in Granada at 12:32:57 a.m. to protect the grid from overvoltage, and a few seconds later, another 725 MW of photovoltaic and solar thermal power were lost in Badajoz, the causes of which remain unclear. Another 950 MW of wind power generation subsequently disappeared in Segovia, Huelva, Seville, and Cáceres, in some cases due to "overvoltage" and in others "without an identified cause," the experts add. In total, 2.5 gigawatts (GW) of renewable generation were lost in Spain in less than 20 seconds.
Many of the disconnected units consumed reactive power, which helped maintain voltage. As voltage was lost without compensation, voltage rose rapidly across the Iberian grid. It lost synchronization, and defense and load-shedding plans were automatically activated, but they failed to prevent the collapse. Connections with Morocco were cut, and lines with France were opened for protection. Five seconds later, the Iberian system collapsed, and links with France ceased to function. Portugal completed the restoration of the transmission grid at 00:22 on April 29, and Spain at around 4:00.
![Third Vice President and Minister for Ecological Transition, Sara Aagesen, at a press conference this Tuesday.](data:image/svg+xml,%3Csvg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 9"%3E%3C/svg%3E)
