A power surge that caused a paralysing blackout across all of Spain and Portugal in April was an unprecedented event in Europe and possibly the world, but the root cause remains unknown, an expert panel said Friday.
"This was the most severe blackout incident in Europe in the last 20 years," Damian Cortinas, president of the association of electricity grid operators ENTSO-E, said during a presentation of the panel's preliminary report into the incident.
