Spain's 2025 Blackout Cascade Stripped Over 2 GW in Twenty Seconds, CIGRE 2026 Panel Finds
A CIGRE 2026 analysis of Spain's April 2025 outage traces three waves of overvoltage disconnections through south-west Spain's 400kV network, despite countermeasures already running.
Voltages on Spain's 400kV network began swinging unusually a couple of hours before the country's April 2025 blackout, and active countermeasures that damped the oscillations still left voltage rising — triggering a cascade of overvoltage disconnections that stripped south-west Spain of 355 MW, then 727 MW, then 928 MW of generation in the space of twenty seconds, according to a panel session at CIGRE 2026 in Paris, reported by wattclarity.com.au on Wednesday (2026-09-09).5
Prior investigations had attributed the outage to different factors. A Reuters report from June 2025 (2025-06-16) found that grid operator REE had failed to calculate the correct energy mix, leaving the network unable to cope with a generation surge. The CIGRE panel's voltage narrative adds a finer-grained sequence: a grid showing warning signs within operational bounds for hours, then protection systems becoming the mechanism of failure as voltage exceeded the thresholds they were designed to defend.2,5
By May 2026, Montel reported that Spain had pushed through emergency measures and was pursuing further grid-stability programmes, drawing on lessons from the April 2025 event. Officials acknowledged the difficulty of maintaining stability as variable generation grows.1
What CIGRE 2026 adds is granularity. The cascade was not a single large failure. Three discrete disconnections arrived sequentially: 355 MW first, then 727 MW, then 928 MW. Each was triggered by the rising overvoltage that countermeasures had failed to suppress. The narrow margin between Spain's operating voltage and its 400kV ceiling, visible in hindsight, left protection relays little room before they tripped generation offline.5
The Australian delegation at CIGRE 2026 drew a related inference. Presentation data cited by wattclarity.com.au showed that AI-driven data centre load can climb 24 MW in half a second, a consequence of training workloads that run in bursts rather than at flat consumption. For grid operators managing high shares of variable renewables, fast and unpredictable demand steps compound exactly the voltage-management problem that Spain's experience exposed.5
Australia has been accumulating that exposure. Utility-scale solar and wind produced a combined 4.6 TWh in May 2026, up 10% from 4.2 TWh in May 2025, Rystad Energy data showed. Battery storage has expanded alongside: 5.4 GWh of capacity was added since December 2025, and on 15 May (2026-05-15) the National Electricity Market saw batteries charge a combined 18,585 MWh in a single day, 26% above the previous record.3,4
But the gap between storage scale and the speed of demand and voltage events is not comfortable arithmetic. In the twelve months to May 2025, batteries across the NEM generated just 860 GWh against 3,274 GWh from open-cycle gas turbines, which remain the fast-response backstop that storage has not yet displaced.4
South Australia spot power stood at A$82.99/MWh on Wednesday morning (2026-09-09), according to NEM data. That reflects a grid not currently under voltage stress. Yet Australian system planners now have a detailed European benchmark: a network that showed hours of anomalous-but-within-limit oscillation, applied countermeasures, and still lost close to 2.1 GW in the time it takes a trader to read a screen.5
What CIGRE 2026 has not yet resolved is the threshold question — at what mix of synchronous and asynchronous generation do conventional voltage-control countermeasures become insufficient? The Spain panel identified the mechanism. The penetration level at which it becomes unavoidable is still unsettled, and Australian operators adding burst-heavy data centre loads to an already fast-moving renewable mix will want that answer before the next voltage event provides one.5