A Spanish government report released on Tuesday attributed a major power outage that paralysed the Iberian Peninsula in April to “overvoltage” on the electricity grid, which triggered a “chain reaction.”
Ecological Transition Minister Sara Aagesen stated that the April 28 blackout had “multiple” causes and that the system “lacked sufficient voltage control capacity” on that day.
Overvoltage, which occurs when excessive electrical voltage overloads equipment, can be caused by surges due to oversupply, lightning strikes, or insufficient protective equipment.
When overvoltage occurs, protective systems shut down parts of the grid, potentially leading to widespread blackouts.
Aagesen specifically pointed to the role of Spanish grid operator REE and unnamed energy companies that “inappropriately” disconnected their plants to protect their installations.
She also cited a programming flaw contributing to the “insufficient voltage control capacity,” despite Spain’s grid theoretically being robust enough for such situations. These misjudgments, she explained, led to an “uncontrollable chain reaction” that could only have been prevented by prior measures to absorb overvoltage.
Aagesen clarified that the report aimed to determine causes and make recommendations, not to assign blame to the head of the grid operator.
Authorities had urgently sought answers after the blackout disrupted internet and telephone services, halted trains, closed businesses, and plunged cities into darkness across Spain and Portugal, also briefly affecting southwestern France.
Prime Minister Pedro Sanchez had formed an inquiry commission led by the ecological transition ministry following the blackout, urging patience for the complex investigation’s findings.
The report dismissed earlier theories of a cyberattack or excess renewable energy production as causes, though Aagesen acknowledged “vulnerabilities” and “deficiencies” in Spain’s power grid security systems.
The right-wing opposition has criticised the government’s phase-out of nuclear energy and reliance on renewables, but the government maintains there is no evidence linking these to the crisis.
Sarah Brown of energy think tank Ember argued that renewables were crucial in restoring stability and power quickly, countering “unhelpful and inaccurate speculation.” She emphasised the need for “enhanced grid optimisation and flexibility” for system resilience.
Recommendations from the government report include stricter supervision and compliance requirements for operators, increasing Spain’s overall electrical capacity, and boosting electricity connections with neighbouring countries.
The blackout exposed the Iberian Peninsula’s limited interconnections, with support from France and Morocco playing a significant role in restoring power.
The European Investment Bank also announced €1.6 billion ($1.8 billion) in funding for a major electricity interconnection between France and Spain, which would nearly double power exchange capacity.
