Final report on the grid incident in Spain and Portugal on 28 april 2025

This report presents the final findings of the Expert Panel investigating the major blackout that affected Spain and Portugal on 28 April 2025, the most severe power system failure in Europe in two decades. The analysis provides a detailed technical account of the incident, examining pre-event system conditions, cascading failures, and the restoration process, with the aim of strengthening the resilience of interconnected electricity systems.

This report of the Expert Panel’s investigation highlights that the blackout is the result of multiple interacting factors. The incident evolved through a sequence involving a combination of voltage fluctuations and oscillatory phenomena, leading to widespread generation disconnections in Spain, particularly inverter-based resources, followed by a cascade of overvoltage disconnections and culminating in the loss of synchronism of the Iberian system with the Continental Europe Synchronous Area.