Jun 10, 2025
Spain's investigation into the blackout will concentrate on the causes of the overvoltage.
The external investigation into the April Iberian blackout will examine the disconnection of first-generation units and the failure of system defense plans to prevent complete power loss, according to European TSO group Entso-e on June 6.
Preliminary report findings reveal that two oscillation periods were detected in the Continental Europe Synchronous Area (CE SA) during the half hour before the April 28 blackout. The first, a local oscillation, occurred about 30 minutes prior and affected the Spanish and Portuguese systems for four minutes. The second oscillation, lasting six minutes and related to the East-West Continental mode, began roughly 15 minutes before the incident; it was mitigated by countertrading measures that reduced power flows between France and Spain and involved switching the HVDC link operation mode.
The voltage returned to 390–420 kV before rising again, remaining within the operational range. Spain was set to export 1,000 MW to France, 2,000 MW to Portugal, and 800 MW to Morocco at that time. Full data for April 28 and 29 is pending from grid operator REE, which experienced equipment failures due to the power loss.
The main incident occurred at 12:33 CEST, with three Spanish generation trips totaling 2,200 MW in southwest Spain happening in quick succession. This resulted in voltage increases in Spain, which also affected Portugal, triggering generation losses and a frequency drop in the Iberian system, disconnecting it from the European System.
Despite the activation of automatic load shedding and system defense plans in Spain and Portugal, the collapse of the Iberian power system could not be prevented. Consequently, protective devices disconnected the AC lines between France and Spain, halting HVDC power transmission.
An external expert panel will reconvene on June 23 and July 15, intending to publish a final report for the European Commission and Member States. The Spanish and Portuguese governments are conducting their own investigations but have not released further information. They are urging France to establish clear timelines and agreements for new interconnectors.
Currently, cross-border capacity between France and Spain stands at 2.8 GW, while a planned 2-GW Bay of Biscay link has been postponed to 2028, initially aimed for May 2025. Portugal continues to limit power imports from Spain during peak solar hours, resulting in a price decoupling between the two markets.
Following the blackout, Spain's grid has faced scrutiny, with reports linking it to a prior incident on April 22 that affected the national rail operator and Cartagena refinery. Since the blackout on April 28, grid operator Red Electrica has been carefully balancing renewable energy supplies in the daily market.
Preliminary report findings reveal that two oscillation periods were detected in the Continental Europe Synchronous Area (CE SA) during the half hour before the April 28 blackout. The first, a local oscillation, occurred about 30 minutes prior and affected the Spanish and Portuguese systems for four minutes. The second oscillation, lasting six minutes and related to the East-West Continental mode, began roughly 15 minutes before the incident; it was mitigated by countertrading measures that reduced power flows between France and Spain and involved switching the HVDC link operation mode.
The voltage returned to 390–420 kV before rising again, remaining within the operational range. Spain was set to export 1,000 MW to France, 2,000 MW to Portugal, and 800 MW to Morocco at that time. Full data for April 28 and 29 is pending from grid operator REE, which experienced equipment failures due to the power loss.
The main incident occurred at 12:33 CEST, with three Spanish generation trips totaling 2,200 MW in southwest Spain happening in quick succession. This resulted in voltage increases in Spain, which also affected Portugal, triggering generation losses and a frequency drop in the Iberian system, disconnecting it from the European System.
Despite the activation of automatic load shedding and system defense plans in Spain and Portugal, the collapse of the Iberian power system could not be prevented. Consequently, protective devices disconnected the AC lines between France and Spain, halting HVDC power transmission.
An external expert panel will reconvene on June 23 and July 15, intending to publish a final report for the European Commission and Member States. The Spanish and Portuguese governments are conducting their own investigations but have not released further information. They are urging France to establish clear timelines and agreements for new interconnectors.
Currently, cross-border capacity between France and Spain stands at 2.8 GW, while a planned 2-GW Bay of Biscay link has been postponed to 2028, initially aimed for May 2025. Portugal continues to limit power imports from Spain during peak solar hours, resulting in a price decoupling between the two markets.
Following the blackout, Spain's grid has faced scrutiny, with reports linking it to a prior incident on April 22 that affected the national rail operator and Cartagena refinery. Since the blackout on April 28, grid operator Red Electrica has been carefully balancing renewable energy supplies in the daily market.