The massive blackout that plunged Spain and Portugal into darkness on April 28 represents the “first” incident connected to an electrical voltage surge phenomenon in Europe and possibly worldwide, according to an interim report by a panel of 45 European experts conducting technical investigations into the actual events.
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“This is the most serious electrical failure in Europe in the last 20 years, and most importantly, it is connected to successive voltage surge incidents,” stated Damian Cortinas, president of ENTSO-E, presenting the report to journalists. “Such an event has never occurred in Europe before and, as far as we know, not globally either, although we don’t have data from all countries,” he added. The blackout occurred on Monday, April 28 at 12:33 local Spanish time (13:33 Greek time) and affected the entire Iberian Peninsula, causing chaos in Spain and Portugal as residents were left without electricity, internet access, and mobile phone service.
Iberian blackout: “They had not given consent to the Spanish transmission network operator to transmit the data”
This report, which describes the chronological chain that led to the general power outage, does not yet provide the primary causes of the initial events. Following this report, the expert team will announce their final report in the first quarter of 2026, which will include these “primary causes” and make recommendations.
This interim report is based on a massive amount of data, which required “a lot of time” to collect, mainly because certain “third parties” “had not given consent to the Spanish transmission network operator to transmit the data,” emphasized Klaus Kasnitz, second in the hierarchy of the expert panel. Some data continues to be missing.
According to the report, half an hour before the outage, two episodes of “power, voltage and frequency fluctuations” had occurred, mainly affecting the Spanish and Portuguese systems.
An overvoltage phenomenon caused successive production losses followed by sequential disconnections of electricity generation centers – thermal power plants and renewable energy stations – the exact causes of which are not yet known.
Electrical voltage can be compared to the “pressure” that water exerts inside a hose: applied to electricity, it is the “pressure” exerted by electrons in motion.
