The massive power outage that hit Spain and Portugal on April 28 is the “first” linked to an overvoltage phenomenon in Europe, and probably in the world, according to the “factual” interim report by a panel of 45 European experts commissioned to conduct the technical investigations.
“This is the most serious power outage Europe has experienced in the last twenty years, and the most important point is that it is the first of its kind,” meaning related to a phenomenon of “cascading overvoltages,” said Damian Cortinas, chairman of the ENTSO-E board, the European Network of Transmission System Operators for Electricity, during the press presentation of the report.
“This has never happened before in Europe, we are certain. We also believe it has never happened worldwide, even though we do not have all the information from every country. But we have not found any mention of this type of blackout (…) anywhere in the world,” he stated.
This massive outage occurred on Monday, April 28, at 12:33 p.m. Spanish time (10:33 a.m. GMT) and affected the entire Iberian Peninsula. It caused chaos both in Portugal and Spain, where residents were left without power, but also without internet and mobile phone services.
This “factual” report, which outlines the chronological sequence that led to the general outage, does not yet provide the root causes of the initial incidents. Following this report, the group of experts will publish their final report in the first quarter of 2026, which will include these “root causes” and provide recommendations.
The drafting of this interim report relied on a colossal amount of data, which took “a great deal of time” to gather, particularly because some “third parties” “had not given their consent to the Spanish transmission system operator to transmit the data,” emphasized Klaus Kaschnitz, the panel’s second-in-command. Some data is still missing.
According to the report, the half-hour preceding the outage was marked by two episodes of “fluctuations in power, voltage, and frequency” that mainly affected the Spanish and Portuguese electrical systems.
An overvoltage phenomenon triggered a cascade of production losses followed by serial disconnections of power generation centers — both thermal and renewable plants — the exact causes of which are still unknown.
Electrical voltage can be compared to the “pressure” of water in a pipe: applied to electricity, it is the “pressure” that sets electrons in motion.
