Two days after one of Europe’s worst blackouts in decades plunged tens of millions of people across Spain and Portugal into darkness for up to 18 hours, officials from both countries emerged from hourslong meetings and gave little indication publicly that they were any closer to determining the cause.
“We are collecting thousands of data points from the energy system to shed light on what happened,” Sara Aagesen, one of Spain’s vice presidents, said at a news conference on Wednesday after Prime Minister Pedro Sánchez of Spain held two meetings with senior officials in Madrid. She added, “We don’t know the cause, which is why the investigation is essential.”
Neither the Spanish nor Portuguese government has publicly speculated on the cause of the blackout, which began on Monday afternoon, leaving hospitals running on generators, trains halted and supermarkets shut. Electricity was fully restored by Tuesday morning. Parts of France were also briefly affected.
On Wednesday morning, Mr. Sánchez met with National Security Council officials and then with the Council of Ministers at Moncloa Palace, the prime minister’s residence in Madrid, to discuss the outage.
Pilar Alegría, a spokeswoman for the Spanish government, said at the news conference that Mr. Sánchez had set up a new committee to determine the cause and ensure that a blackout would not happen again. Portuguese officials also said the cause was still unknown.
The incident has raised questions about whether Spain and Portugal’s rapid shift to renewable energy left them more vulnerable to outages. Ms. Aagesen, the vice president, who is also the minister overseeing Spain’s ecological transition, on Wednesday denied that the power outage had any connection to Spain’s rapid expansion in renewable energy.
The Spanish government has not ruled out a cyberattack on the transmission grid, even though Red Eléctrica, Spain’s grid operator, said there was no evidence of one.
A judge on Tuesday ordered Red Eléctrica, the intelligence service and the police to produce reports within 10 days about whether a cyberattack was behind the power outage, according to a court document. The National Cryptologic Center, which oversees cyberthreats, was also reviewing Red Eléctrica’s online systems to “ensure no hypothesis is ruled out,” Mr. Sánchez said.
There have been relatively few instances of disruption to electrical systems because of cyberattacks; these issues are more commonly caused by equipment failures, operational errors and effects of storms, according to the International Energy Agency in Paris.
Hannah Christensen, a physics professor at the University of Oxford, said a stable supply of electricity depends on equal amounts of energy flowing in and out of the grid. It can be harder to balance flows in a system that depends on renewable sources, she said.
If there is an imbalance, automatic mechanisms will take companies offline as a precaution. “In the worst case scenario, you get these kind of cascading effects of user after user disconnecting, and then the supply is massively larger than the demand,” she said, adding that this could lead to blackouts.
After power was restored, Spain’s Interior Ministry on Tuesday downgraded many regions from the highest of three alert levels to a medium one. Madrid and the western region of Extremadura remained at the highest level on Wednesday, the ministry said, because of disagreements between local and federal officials.
In Portugal, Prime Minister Luís Montenegro said after an emergency government meeting on Tuesday that the outage was related to an abrupt increase in voltage in the Spanish electricity grid, which activated safety mechanisms that led to the blackout.
“We will calmly assess with the Spanish authorities what happened and try to design better response instruments in the future to avoid a repeat of this occurrence,” he said.
The outage is expected to be a key topic during a debate on Wednesday between Mr. Montenegro and the opposition leader, Pedro Nuno Santos, ahead of a parliamentary election on May 18. The two had originally been scheduled to debate on Monday.
Tiago Carrasco contributed reporting from Lisbon.
