Power Outage Mystery: What Went Wrong in Iberia

A sudden, widespread loss of electricity hit Spain and Portugal on April 28 last year. The event was the biggest blackout in Europe for over twenty years, cutting power to many regions for up to sixteen hours. The European network of electricity operators, ENTSO‑E, investigated the incident. Their final report says no single fault caused the outage; instead, several problems lined up to trigger a voltage spike that threw off power plants and transmission lines. Key factors identified include thermal plants—those running on coal, gas or nuclear—that failed to keep voltage within the limits set by grid rules. Some devices meant to regulate voltage were still controlled manually, which slowed response times. Settings designed to disconnect equipment during a surge did not match the required safety thresholds.The Spanish grid is unusual in that it operates over a broader voltage range than most European systems. This means there was little or no buffer between normal operating levels and the points where protective disconnections would occur. A narrow margin left little room for error when voltage rose unexpectedly. Management of cross‑border links with France may have worsened the situation by influencing how power flowed between the two countries. The report stresses that voltage control failure was the core issue driving the cascade of problems. In some cases, initial plant shutdowns could not be fully explained because owners reported missing data. This lack of information hindered a complete understanding of the early stages of the outage. To reduce future risk, ENTSO‑E recommends stronger system monitoring and better coordination among all parties involved. Sharing data in real time would help operators spot problems before they grow into widespread failures.