Some media outlets have speculated that Spain’s April 28 blackout may have been caused by a disconnected solar plant, but DNV grid analyst Andrea Mansoldo tells pv magazine that it was likely due to a combination of grid weakness and low-frequency oscillations.

Electricity has returned to most of Spain and Portugal but with continued disruptions on the second day after an unknown failure caused a massive blackout across much of western Europe.

The Spanish grid operator has ruled out a cyber attack as the cause of a massive power cut that crippled Spain, Portugal and parts of France on Monday. Red Eléctrica's operations director Eduardo Prieto said preliminary findings suggest "there was no kind of interference in the control systems" to imply an attack,