The Iberian Blackout 28/04/2025 – What lessons for the future

The blackout that affected the Iberian Peninsula on 28 April 2025 was one of the most severe disturbances experienced by the European power system in more than two decades. This keynote analyses the sequence of events that led to the system collapse.

Prior to the blackout, the Spanish transmission system experienced significant voltage fluctuations and poorly frequency damped intra-area and inter-area oscillations. At the same time, conventional synchronous generation was relatively limited and geographically concentrated, while large volumes of renewable generation, especially solar PV, were connected mainly in the South of Spain under operational requirements that restricted their active participation in voltage regulation. The analysis to the available data indicated, that low system inertia was not the primary cause of the blackout, with the estimated Iberian system inertia remaining above 2.5 s. Instead, increasing overvoltage’s triggered successive losses of renewable and conventional generation, transforming a voltage stability problem into a severe frequency disturbance with loss of synchronism with the Central European system.

Using frequency and voltage measurements from the event together with physics-based dynamic modelling, it was possible to understand how the disturbance developed and identify lessons for operating future power systems dominated by converter-interfaced renewable generation. Attention is given to exploiting the voltage and frequency control capabilities of renewable power converters, strengthening and rigorously verifying grid-code requirements, and improving system-wide observability and coordinated voltage control.

The presentation concludes that the energy transition requires not only additional renewable capacity, but also a fundamental evolution of operational practices and dynamic security management solutions to be adopted by system operators. Wide-area monitoring and control, advanced operational decision-support tools, enhanced reactive-power capabilities and strategically deployed grid-forming converters will be essential to ensure that highly renewable power systems remain secure, resilient and capable of recovering from major disturbances.