On 28 April 2025 at 12:33 CEST, Spain and Portugal suffered a system-wide blackout; a small border area in France was briefly affected. The rest of Continental Europe did not experience significant disturbance. Following the blackout incident, on 12 May 2025, ENTSO-E set up a joint Expert Panel with the task to produce a report about the causes of the blackout. An ENTSO-E’s page consolidates what is known so far—affected areas, a preliminary chronology, restoration milestones, and the remit and timeline of the Expert Panel investigating root causes.
System conditions and pre-incident dynamics. Operations were normal overnight. From around 09:00–10:30, voltage variability in Spain increased modestly; after 10:30, more pronounced variations occurred, although 400 kV and 220 kV transmission voltages remained within national operational limits. In the 30 minutes before the collapse, two oscillation periods were observed across the Continental Europe synchronous area: 12:03–12:07 (a local, forced oscillation—plant-induced—with a dominant 0.64 Hz component that also excited a low-amplitude 0.21 Hz inter-area mode) and 12:19–12:21. Mode-shape analysis suggests a local mode between generation clusters in north-east Spain and south-west Spain/Portugal.
Immediate sequence and collapse. Just before and during 12:33:18–12:33:21, sharp over-voltage in southern Spain (propagating into Portugal) coincided with a cascade of generation losses and falling frequency. At 12:33:19, Spain and Portugal began to lose synchronism with the rest of Europe; automatic load shedding and System Defense Plans activated between 12:33:19–12:33:22 but could not prevent collapse. At 12:33:21, AC interconnectors between France and Spain tripped on out-of-step protection, and at 12:33:24 all system parameters in Spain and Portugal collapsed; France–Spain HVDC links ceased power transfer. ENTSO-E notes no generator trips in Portugal or France within this timeframe.
Restoration milestones. Restoration leveraged black-start resources and interconnections with France and Morocco, with coordinated actions by Red Electrica (Spain), REN (Portugal), RTE (France) and support from Morocco’s ONEE. Key steps include: 12:35/12:43—Portugal requests black-start at Castelo do Bode and Tapada do Outeiro; 12:44—first 400 kV France–Spain AC line re-energized (west); 13:04—Spain–Morocco interconnection re-energized; 13:35—eastern France–Spain AC interconnection re-energized; 16:11 and 17:26—two Portuguese restoration “islands” established; 18:36—first 220 kV Spain–Portugal tie-line re-energized; 21:35—southern 400 kV Spain–Portugal tie-line re-energized; 00:22 CEST (29 April)—Portugal’s transmission grid restoration completed; ~04:00 CEST—Spain’s transmission grid restoration completed.
Investigation and governance. ENTSO-E formed a joint Expert Panel on 12 May 2025 under the SO GL and ICS Methodology (incident classified as Scale 3 – blackout). The Panel—comprising TSO/RCC experts plus ACER and NRA representatives—will deliver a factual chronology and a final analytical report with recommendations. Meetings were scheduled on 12 May, 3 June, 23 June, 15 July, 18 August, 2 September, 19 September, and 14 October 2025; an ACER-chaired stakeholder workshop took place 18 July. ENTSO-E cautions that findings remain preliminary and subject to update.
Overall, the page depicts a complex, multi-stage disturbance: pre-event oscillations, rapid loss of synchronism, defense-plan activation, full collapse, and a swift, coordinated restoration—with the root-cause analysis ongoing.
For detailed information visit :
https://www.entsoe.eu/publications/blackout/28-april-2025-iberian-blackout
