Spain’s government has concluded that a widespread power outage in April was caused by a combination of voltage instability, system oscillations, and premature disconnection of power plants, according to a report presented to the Council of Ministers on Tuesday.
The findings, delivered by Ecological Transition Minister Sara Aagesen, rule out earlier speculation of a cyberattack and identify the 28 April blackout as having a “multifactorial origin.”
“Within just 49 days, the committee has delivered a rigorous diagnosis that will allow us to strengthen the system,” Aagesen said.
The investigation, led by Spain’s national electricity crisis committee, detailed a cascading failure that began with abnormal frequency oscillations at 12:03, lasting over four minutes. System operator interventions—including reduced power exports to France and changes in grid configuration—were found to have inadvertently increased overall voltage.
The second phase, beginning at 12:32:57, saw rapid and sustained voltage spikes triggering widespread generator shutdowns across provinces including Granada, Badajoz, Huelva, and Seville. The final phase resulted in a loss of frequency synchronisation with the rest of Europe between 12:33:18 and 12:33:30.
While power restoration was swift—reaching 50% of demand by 22:00 and 99.95% by 07:00 the next day—the report cited multiple failings in system operation and plant response.
“The system had sufficient generation capacity to manage the event,” the report noted. “What was lacking was control—either because the resources were not properly scheduled, or those that were scheduled did not respond as required.”
Key issues included inadequate performance by synchronous plants tasked with voltage control, some of which produced reactive power rather than reducing it. The report also found the number of such plants in operation that day to be the lowest recorded in 2024.
Additionally, some generators disconnected before voltage exceeded regulatory thresholds of 380kV to 435kV, while protective systems meant to prevent damage in high-stress scenarios worsened the situation by further destabilising voltage levels.
To prevent similar incidents, the committee issued several recommendations, including improved supervision of generator compliance, stronger voltage and oscillation controls, accelerated implementation of PO 7.4 regulation to enable voltage control from asynchronous sources, and increased demand-side flexibility and interconnection capacity.
Although no evidence of cyber intrusion was found, the report recommends fast-tracking EU-aligned cybersecurity protocols, segmenting networks, and deploying real-time threat detection.
The committee also cited challenges in obtaining timely data from several system agents, noting that specific cases would be referred to the National Commission on Markets and Competition (CNMC) for potential administrative review.
“Transparency and confidentiality have guided this process,” the report stated. “But where necessary, further action will be taken.
