Report of the Spain Blackout
On 28 April 2025, at 12:33 CEST, the power systems of Spain and Portugal experienced a blackout. A small area in France, close to the border with Spain, was also affected for a limited duration.
This page provides consolidated information on the incident, including the affected areas, a preliminary sequence of events, the restoration process, and details about the Expert Panel established to investigate the causes. Further updates will be provided as the investigation progresses.
01. Affected Area
The blackout impacted the entire Iberian Peninsula, encompassing both Spain and Portugal. Additionally, in France, a small area near the Spanish border experienced disruptions for a limited duration, and several industrial consumers and generators were affected, more notably a nuclear power unit that tripped around the same time as the incident in the Iberian Peninsula. The remainder of the power system of Continental Europe did not experience any significant disturbance.
02. Preliminary Chronology of Events
A preliminary chronology based on the information known so far has been identified regarding the complex sequence of events which have occurred prior to the blackout. The final description of the sequence of events will be established by the Expert Panel in a factual report, followed by the in-depth analysis and recommendations in the final report which will be published.
System conditions on the morning of 28 April (09:00 – 12:00 CEST)
During the night of 27 to 28 April, the Iberian power system operated normally, without notable variations in the voltage profile. From approximately 09:00 CEST, the variability of the voltage in Spain started increasing but without significant variations until 10:30 CEST. From 10:30 CEST, more significant voltage variations started to occur as illustrated in Figures 2a and 2b.
Figure 4 provides a visual representation of the voltage distribution at 12:00 CEST in the 400 kV network of Spain and Portugal (400kV corresponds to 1 p.u.). At that moment, the voltage was again close to 400 kV, after the voltage variations described above :
System conditions prior to the incident (12:00 – 12:30 CEST)
During the half hour preceding the blackout, two main periods of oscillations (power and frequency swings) were observed in the Continental Europe Synchronous Area (CE SA).
The first one took place from 12:03 to 12:07 CEST. Preliminary analysis of the available information indicates that this was a local, forced oscillation (i.e. induced by an external source), with a dominant frequency of 0.64 Hz, primarily affecting the Spanish and Portuguese power systems. As visible in the Figure 5, the forced oscillation excites also the interarea mode East-Centre-West (0.21 Hz) with a small amplitude.
After these first oscillations, the operation mode of the HVDC link between Spain and France was changed to fixed power, set up from 12:11 CEST, as a mitigation measure to stabilise the system. Additional measures (shunt reactors manoeuvres, topological changes to minimize system impedance) were also applied to further improve the system damping.
The second oscillation occurred between 12:19 and 12:22 CEST. This was an inter-area oscillation, with a dominant frequency of 0.21 Hz, corresponding to the well-known East-Centre-West Continental mode.
This second oscillation was effectively mitigated through countertrading measures, which reduced power flows between France and Spain, also with the coupling of the internal power lines in the South of Spain.
Following the second oscillation, the voltage was within the range of 390–420 kV, before increasing again, but still within the operational voltage range in the transmission network. At that moment, Spain’s international scheduled exchanges – all in the export direction – were 1,000 MW to France, 2,000 MW to Portugal and 800 MW to Morocco.
For more information,please check:28 April 2025 Blackout.
