A massive power outage which brought much of Spain and Portugal to a standstill earlier this year is the first known blackout caused by excessive voltage, a report has found.
The blackout on 28 April stranded thousands of train passengers and left millions of people without phone and internet coverage and access to cash from ATMs across the Iberian Peninsula.
Huge swathes of Spain and Portugal, including major cities like Barcelona, Lisbon, Madrid, Porto and Seville, were affected by the power outage – Europe’s most significant blackout in more than two decades.
Like previous probes, the report by the European network of electricity transmission system operators pointed to a surge in voltage as the immediate cause of the outage.
A final report, due in the first quarter of 2026, will investigate the root causes and steps taken to control voltage in the system.
Damian Cortinas, chair of ENTSO-E’s board, said there was no indication that a cyber attack had occurred.
Mr Cortinas also said that Spain’s increasing dependence on renewable energy and its limited power interconnections with other countries had not contributed to the outage.
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“If there had been double the interconnection capacity, this would not have stopped the blackout, and this would not have accelerated the recovery,” Mr Cortinas said.
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After the blackout, the Spanish and Portuguese governments have urged the EU to help them develop new power links with other countries, which they say would help their power grids respond to disruptions.
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Its report follows several others by the Spanish government and power and grid companies. The national energy watchdog and Spanish politicians are also conducting separate probes.
Redeia, owner of grid operator REE, has blamed the blackout on some power plants’ failure to help maintain appropriate voltage while Spanish utilities blamed the Spanish grid operator’s poor planning.
