Official Report: Spanish grid operator error led to historic blackout
The study confirms that renewable energies played no role in causing the blackout and were, in fact, instrumental in helping restore supply.
A Spanish government investigation into the massive April blackout across Spain and Portugal has concluded that errors by its national power grid operator, Red Eléctrica (REE), were central to the collapse.
The report, released by Energy Minister Sara Aagesen Muñoz, cites a failure by REE to properly manage voltage control, underuse of thermal plants, and cascading disconnections as the primary causes of the April 28 outage, which left millions without power.
Notably, the study confirms that wind and solar played no role in causing the blackout and were, in fact, instrumental in helping restore supply.
Multiple Failures Triggered Collapse
According to the Ministry for the Ecological Transition (MITECO), the blackout was caused by three core issues:
Inadequate grid control capabilities;
Unusual and unmitigated voltage and frequency oscillations;
Premature disconnection of conventional power plants.
Some of these plants, including nuclear and gas-fired stations, shut down before hitting the voltage thresholds required for disconnection.
“Voltage control protections failed or even exacerbated the instability,” Aagesen Muñoz said, noting that some protections triggered further surges.
One key misstep: REE had asked 10 thermal plants to be on standby for voltage control, but failed to replace a plant that declared itself unavailable.
Additionally, a power plant in southern Spain was asked to activate just hours before the blackout, far too late to respond effectively.
Oscillations Before Blackout Felt as Far as Germany
In the lead-up to the April 28 Iberian blackout, significant voltage and frequency oscillations originating in Spain were not only detected across Portugal but also reached substations in France and as far as Freiburg, Germany.
According to the Spanish government report, the first major oscillation occurred at 11:03 AM and lasted nearly five minutes, with sharp and repetitive voltage swings especially affecting southern and western Iberia.
Red Eléctrica responded by attempting to reduce electricity exports to Portugal and France and activate backup thermal power plants, actions that ultimately proved too late.
A solar plant in Badajoz, identified by media as Iberdrola’s Núñez de Balboa, experienced a disconnection that triggered a cascade of failures, cutting Spain’s exports to France and, in turn, plunging the entire Iberian Peninsula into darkness.
The power mix at the time was 82% renewables, 10% nuclear, and the remainder gas and coal, but critical nuclear and gas capacity was offline.
The report found that over 500 MW of generation was lost in the final moments, including widespread automatic disconnection of small solar installations.
Portugal, which was still importing electricity from Spain at the time, was unable to prevent the blackout.
Though Portuguese operator REN received requests from Spain to reduce interconnection flows, it was not clearly warned of an impending crisis.
Spain’s utilities, through lobby group Aelec, have denied fault, saying their plants complied with voltage control rules and accused REE of poor planning and failing to dispatch enough synchronous generation.
In response, Spain’s energy regulator CNMC has updated technical rules for voltage control, and the European network ENTSO-E continues its independent investigation.
By 11:33 a.m. local time, the Iberian grid shut down entirely.
No Cyberattack, No Renewable Blame
The government dismissed theories of a cyberattack, confirming instead that the blackout stemmed from internal planning and grid stability issues.
Critically, the report highlights that conventional energy sources, long considered reliable, failed to stabilize the system.
Of nine plants expected to deliver voltage support, several did not comply, despite being compensated for it.
Juliet Phillips of Beyond Fossil Fuels said the findings “undermine the fossil fuel lobby’s attempts to blame renewables,” and called for urgent investment in a flexible, clean grid.
Solar and wind, the report notes, actually aided in system recovery.
Industry groups, including SolarPower Europe and UNEF, called for accelerated investment in grid resilience technologies such as grid-forming inverters and battery storage.