The Iberian Blackout: A Black Swan or a Gray Rhino? A Thorough Power System Analysis

Abstract

On April 28, 2025, the Iberian power system suffered a full blackout. It was the first documented overvoltage-driven cascade in Europe. The event sparked debate about root causes, including high renewables output, low inertia, and operator actions. This paper presents a thorough power system analysis of the incident to sort signal from noise and explain, step by step, how the blackout unfolded. Specifically, we (i) reconstruct the timeline and causal chain of the incident, (ii) present and summarize contributing factors using factual findings from incident reports, (iii) reproduce the blackout on an IEEE test system, (iv) analyze the incident from a system-theoretic, voltage-control perspective, and (v) translate our analysis into practical, technical measures that aim to mitigate and prevent similar incidents.