‘Perfect storm’ behind 2025 Iberia blackout: experts

Last year’s paralysing blackout in Spain and Portugal was caused by a “perfect storm of multiple factors”, according to a final report by an expert panel published Friday. The April 28 outage raised doubts about Spain’s high dependence on renewables and planned phaseout of nuclear energy, but the leftist government and some experts have rejected claims that they exposed the power grid to a blackout. The report commissioned by the association of electricity grid operators ENTSO-E cited the Iberian electricity system’s inability to control overvoltage events as a “key” factor, but stressed it was not the only one.

“There is no single cause. It was a perfect storm of multiple factors that contributed to the outage,” Damian Cortinas, the president of the association, said during a presentation of the report by 49 European experts. Overvoltage occurs when there is too much electrical voltage in a network, overloading equipment.

It can be caused by surges in networks due to oversupply or lightning strikes, or when protective equipment is insufficient or fails. The massive blackout cut internet and telephone connections, halted trains, shut businesses and plunged cities into darkness across Spain and Portugal for up to 10 hours. It also briefly affected southwestern France.

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It was “the largest and most severe blackout we have ever experienced in the European electricity system in more than 20 years”, Cortinas said. Investigators were unable determine what caused the power surge, citing missing data, and why systems to mitigate it failed. Operators in control rooms took measures to mitigate the issue, such as reducing the exports of power from Spain to France, but could not prevent the system from shutting down.

“The design of voltage control of local generation networks (behind connection point) is not aligned with the system needs,” the report said. The report described a series of voltage fluctuations that led to widespread disconnections of power generation in Spain, particularly among converter-based systems commonly used in renewable energy.

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