The unprecedentedblackout that brought the Iberian peninsula to a standstill at the end of Aprilwas caused by surging voltages triggering “a chain reaction of disconnections” that shut down the power network, an expert report commissioned by the Spanish government has found.
Speaking to reporters on Tuesday afternoon, the country’s environment minister, Sara Aagesen, ruled out a cyber-attack as the cause of the outage on 28 April, saying it had been down to a “multifactorial” system failure caused by the network’s inability to control grid voltage.
The minister said the system had lacked “sufficient capacity to control the dynamic voltage” because Spain’s national grid operator, Red Eléctrica, did not have enough thermal power stations online to control the surge. She also noted that some of the power-generating companies paid to manage and absorb voltage surges had failed to do so.
The catastrophic power loss,which left people in Spain and Portugal withouttrains, metros, traffic lights, ATMs, phone connections and internet access, led the government to commission the expert report.
Aagesen said the blackout had a “multifactorial origin … In other words, it was caused by the confluence of a combination of factors. The cause of the zero [-power event] was a phenomenon of surging tensions [and] a chain reaction of control disconnections that cause further disconnections.”
The expert investigations focused on what happened at 12.33pm on Monday 28 April when, for five seconds, 15GW of the energy being produced – equivalent to 60% of all the energy being used – suddenly disappeared.
Aagesen said the research had uncovered “voltage instability” on the morning of the blackout and in the days leading up to it, followed by “oscillations” in the system between noon and 12.30 that day.
“A second phase saw power losses, and a third phase led to the peninsular collapse,” she added.
The minister said the report’s key recommendations included strengthening supervision and compliance, and ensuring that Spain was properly protected against future voltage fluctuations.
She defended the socialist-led government’s commitment to increased use of renewable energy, which some had sought to portray as the cause of the blackout.
“We have a solid narrative of events and a verified explanation that allows us to reflect and to act as we surely will,” said Aagesen. “We believe in the energy transition and we know it’s not an ideological question but one of this country’s principal vectors of growth when it comes to re-industrialisation opportunities.”
Aagesen and the prime minister, Pedro Sánchez, have repeatedly rejected any suggestion that the blackout had been caused by the rush to abandon nuclear power in favour of renewables. “Those who link this incident to the lack of nuclear power are frankly lying or demonstrating their ignorance,”Sánchez said the day after the power cut, adding that nuclear power generation “was no more resilient” than other electricity sources.
Aagesen had also previously said that Spain’s electricity on the day in question was generated from a tried-and-testedmix of different sources, with solar power accounting for almost 55% of the total, followed by 10% from wind power, 10% from nuclear power and almost 10% from hydro power.
“The system has worked to perfection with a similar demand situation and with a similar energetic mix [in the past], so pointing the finger at renewables when the system has functioned perfectly in the same context doesn’t seem very appropriate,” she said at the time.
The government and the president of Red Eléctrica have also denied media reports that the failure was caused by a governmentexperiment with renewable energy productionon the day of the blackout. “That’s entirely false,” the operator’s president, Beatriz Corredor,told La Vanguardia last month. “It’s a cathedral-sized piece of fake news.”
The report’s publication comes as Sánchez struggles to contain the fallout from a series of corruption allegations that have engulfed his administration and his Spanish Socialist Workers’ party (PSOE).
Last week, the prime minister apologised to voters but ruled out a snap election after a senior PSOE member resigned hours after a supreme court judge found“firm evidence” of his possible involvement in taking kickbackson public construction contracts.
He has insisted he is doing all he can to tackle corruption and said there would be no return to the polls until the next scheduled general election, in 2027. “This isn’t about me or the socialist party or PSOE MPs; it’s about a political project that’s doing good things for the country,” he said last Thursday.
He has also sought to contrast his approach to corruption with that of the opposition conservative People’s party,which he ousted from governmentwith a no-confidence motion after a major PP graft scandal eight years ago.