ISTANBUL 

A preliminary report issued on Friday showed the "unprecedented nature" of the massive blackout in Spain and Portugal in April.

The report issued by the European Network of Transmission System Operators for Electricity (ENTSO-E) revealed that the widespread blackout was of "exceptional" and "unprecedented" nature.

It noted that, for the first time, a cascading series of generation disconnections combined with voltage increases contributed to the blackout.

The report suggested that overvoltage was the immediate cause of the blackout, while the factors behind some of the initial power generation losses remain unclear.

Stressing that several events unfolded within a very short period, the report also noted that determining the exact sequence of events was challenging.

ENTSO-E reaffirmed that a final report will be published in the first quarter of 2026 and presented to the European Commission and member states.

The final report will provide a detailed analysis of the blackout’s root causes, system and generator performance, mitigation measures, and the broader context leading up to the incident.

In June, the Spanish government ruled out the possibility of a cyberattack behind the massive blackout that took place in Spain and Portugal on April 28.

April’s outage plunged large parts of Spain and Portugal, and briefly southwestern France, into darkness for nearly a day, disrupting internet, telephone services, and transportation.