Spanish authorities say the massive power outage in April across Spain and Portugal was due to technical and planning errors that led to a cascade of failures in the grid.

MADRID (Reuters) -Spanish grid operator Redeia disputed the findings of a government report that said failure by the operator to calculate the correct mix of energy was one of the factors that led to a massive blackout in Spain and Portugal on April 28.

By Pietro Lombardi and David Latona MADRID (Reuters) -Spanish grid operator REE's failure to calculate the correct mix of energy was one of the factors hindering the grid's ability to cope with a surge in voltage that led to the massive blackout across Spain and Portugal on April 28,