Spain’s national electricity grid operator, Red Eléctrica de España (REE), has pointed to a malfunction at a large solar power plant in Badajoz as the trigger for the widespread blackout that hit the country on April 28. This finding challenges the Spanish government’s earlier claim that the crisis stemmed from voltage issues that had been building up beforehand.
In a 21-page technical report released Wednesday, REE said that the incident began at 12:03 p.m. with an unexpected power fluctuation—called a “forced oscillation”—at a solar facility in southern Spain. At the time, the plant, referred to as “Photovoltaic Plant A,” was generating about 250 megawatts of electricity. REE believes the oscillation was caused by an internal fault at the plant and was not part of normal grid behavior. This disturbance set off a series of emergency actions that ultimately led to the collapse of the national power system.
“There was nothing unusual in the grid between midnight and noon,” the report stated, describing the system as stable until the event at 12:03. REE emphasized that the grid had been operating within normal limits and that earlier voltage fluctuations were routine and not cause for concern.
This version of events differs significantly from the government’s 182-page report, which was released earlier this week by the Ministry for the Ecological Transition. That report, compiled by the National Security Council, described the blackout as the result of multiple factors. It suggested that the crisis had been developing for days, with worsening voltage instability culminating in the April 28 outage. The government’s report referred to the 12:03 oscillation as just one incident among many and did not name the solar plant involved.
However, according to Spanish news outlet El Diario, sources familiar with both reports have identified the plant as Núñez de Balboa, a 500-megawatt solar facility owned by utility company Iberdrola.
REE explained that after the initial disturbance, it took steps to stabilize the system, including adjusting transmission line connections and reducing power exports to France and Portugal. While these measures helped contain the oscillation, they also contributed to rising voltage levels across the grid. The blackout fully unfolded at 12:32 p.m. when a 355-megawatt generator in Granada shut down. Within seconds, a cascade of shutdowns followed, affecting both renewable and conventional power plants across southern and central Spain. Altogether, the grid lost about 2,000 megawatts of generation capacity.
REE noted that many power units disconnected even though voltage levels remained within legal limits, indicating possible issues with equipment settings or delayed responses in transformers. Some renewable installations also failed to comply with Spanish grid codes, which require them to stay connected during high-voltage events up to 440 kilovolts for at least an hour.
The report also criticized several plants for not meeting rules on voltage and reactive power management. Under grid guidelines, certain generators are supposed to help stabilize voltage levels, but REE found that some did not. It also revealed that 22% of renewable facilities, especially those producing low amounts of power at the time, failed to meet required power factor standards.
While the government’s report questioned REE’s handling of voltage regulation and its system management decisions, the grid operator defended its performance. It said its protection systems worked properly, emergency procedures were followed, and the high-voltage link with France functioned as intended. Still, REE acknowledged that current regulations may need updates to improve monitoring, enforce technical standards, and modernize voltage protection rules.
Meanwhile, Aelec, Spain’s main electricity industry group representing major power companies, criticized REE’s conclusions. In a statement Thursday, the group accused the operator of failing to activate enough traditional (synchronous) power plants to stabilize the system and of unfairly shifting blame onto energy producers.
“Claiming everything was done correctly while blaming a partial generation issue for a nationwide blackout damages the reputation of Spain’s energy sector,” Aelec said. The group insisted that all its members followed REE’s instructions and operated normally throughout the incident.
