According to the expert panel of the European association of transmission system operators Entso-E, the power outage that struck Spain and Portugal on 28 April 2025 was the most serious event in the European power grid for over two decades. The panel has now presented its final report, in which it identifies the causes and issues recommendations to prevent similar incidents in future. The panel was chaired by experts from two unaffected TSOs.
Multiple factors led to the collapse
According to the report, the blackout was the result of several interacting factors. The incident developed through a series of voltage fluctuations and oscillatory phenomena, which triggered widespread shutdowns of generation facilities in Spain – particularly inverter-based installations such as photovoltaic and wind power plants. This was followed by cascading overvoltage shutdowns. Ultimately, the Iberian system lost synchronisation with the Continental Europe Synchronous Area (CESA).
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Despite the correct activation of system protection plans, the nature and scale of the cascading events led to the complete collapse of the Spanish and Portuguese power grids within seconds. Restoration of supply began immediately after the blackout. In Portugal, the process was completed after 12 hours; in Spain, after 16 hours. The expert panel attributes this to comprehensive restoration procedures, fallback strategies and the full commitment of all parties involved – including transmission system operators (TSOs), distribution system operators (DSOs) and generators.
Recommendations in two categories
The panel divides its recommendations into two categories: those directly related to the causes of the incident and those that are indirectly relevant. In addition, the report includes further suggestions for improvement which, while not directly linked to the event, are considered beneficial for the ongoing development of the system.
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The recommendations aim to strengthen operational resilience, improve information exchange between stakeholders and maintain a high level of supply security in the European power grid. Based on these findings, the experts formulate guidance for the future, including improved monitoring of system behaviour, closer coordination and more intensive data exchange among actors in the power system.
Adapting regulatory frameworks
The findings also highlight the need to adapt regulatory frameworks to the changing nature of the power system. The panel emphasises that enhanced coordination between TSOs, DSOs, generators and other stakeholders is essential for managing complex system events such as this. According to the panel, implementation of the recommendations is the sole responsibility of the respective recipients. The report is available for download here. (nhp)
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