Official Report Reveals Causes of Blackout That Left Cities in the Iberian Peninsula in the Dark and Caused Disruptions in Three Countries.
A major blackout left millions of people without power in the Iberian Peninsula at the end of April. The incident interrupted the operation of trains, businesses, internet connections, and telephone networks, plunging entire cities into darkness.
Now, an official report points out that the cause was a “voltage surge” in the electrical grid, which triggered a chain reaction.
System Without Sufficient Voltage Control
According to Spain’s Minister of Ecological Transition, Sara Aagesen, the blackout had multiple causes, but the central factor was the system’s inability to control voltage that day.
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Aagesen explained that there were programming failures and deficiencies in the protection structure, which contributed to the loss of control of the electrical grid.
A voltage surge occurs when there is an excess of electricity circulating in the grid, overloading the equipment. This can be caused by atmospheric discharges, failures in protective equipment, or an excess of supply.
When this happens, automatic systems shut down parts of the grid as a form of self-protection, which can result in widespread power cuts.
Inappropriate Disconnections Worsened the Crisis
During the episode, some power plants were shut down “inappropriately” by companies in the electric sector, according to the report.
The minister did not mention the names of the companies but highlighted that the measures were taken to protect their own facilities, without considering the systemic impacts.
This behavior, combined with the failure in voltage regulation, led to a chain collapse. Aagesen stated that the Spanish system, in theory, is robust enough to withstand a voltage surge. However, that day, there was no timely opportunity to take measures to compensate for the excess load.
No Judgment, but Recognized Failures
The minister made it clear that the released document is a technical analysis, not a judgment. The focus is to understand what happened and make recommendations to avoid new collapses. Nevertheless, the report points out “deficiencies” and “vulnerabilities” in the electrical infrastructure.
Since the day of the blackout, which occurred on April 28, the Spanish government has initiated an investigation. The inquiry commission, created by Prime Minister Pedro Sanchez, has already met three times. The government decided to expedite the release of the results after public and opposition pressure, even with investigations still ongoing.
Cyberattack Hypotheses Discarded
Initially, different possibilities for the blackout were raised, such as a cyberattack or an excess of renewable energy generation. Both were dismissed by the minister. The government also rejected the thesis that a lack of nuclear plants caused the failure.
Even so, the right-wing opposition once again criticized the energy policy of the socialist government, which prioritizes renewable sources and has been reducing the presence of nuclear energy in the country’s electricity matrix.
Among the measures proposed in the report are strengthening the supervision of operators, greater rigor in compliance technical requirements, and increasing Spain’s electrical capacity. The necessity to strengthen interconnections with neighboring countries was also highlighted.
Currently, the Spanish electrical grid has low integration with the systems of Portugal, France, and Morocco. On the day of the blackout, support from these countries was crucial to restoring part of the supply.
In response to the incident, the European Investment Bank announced an injection of 1.6 billion euros. The amount will be allocated to the construction of a new interconnection between Spain and France, which is expected to nearly double the energy exchange capacity between the two countries.

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