MADRID (Reuters)

Spanish grid operator Redeia blamed power plants for the massive blackout that affected the Iberian Peninsula in April, as it disputed a government report that said its failure to calculate the correct energy mix was a key factor.

While agreeing that a surge in voltage was the immediate cause of the outage, REE-owner Redeia blamed it on some conventional power plants – thermal power plants using coal, gas and nuclear – for failing to help maintain an appropriate voltage.

“Based on our calculation, there was enough voltage control capabilities planned” by Redeia, operations chief Concha Sanchez told a news briefing on Wednesday (June 18).

“Had conventional power plants done their job in controlling the voltage there would have been no blackout,” she said.

Redeia, which is partly state-owned, also discovered anomalies in the disconnection of power plants in the run up to the April 28 outage, even though voltage in the system was within legal limits, Sanchez said.

A combined-cycle plant that was supposed to provide stability to the system disconnected in the first seconds of the blackout when it should not have, while there was also an anomalous growth in demand from the transport network, she said.

Aelec, which represents Spain’s main electricity companies including Iberdrola and Endesa, said in a statement on Tuesday it agreed that voltage control was the main cause of the outage, but said that, as system operator, Redeia was ultimately responsible for controlling voltage.

Redeia on Wednesday released its own full report on the causes of the outage, a day after the Spanish government published its findings.

The government’s report released on Tuesday said Redeia’s miscalculation was one of the factors hindering the grid’s ability to cope with a surge in voltage that led to the outage that caused gridlock in cities across the Iberian peninsula and left tens of thousands stranded on trains overnight or stuck in lifts.

But Sanchez said the system was in “absolutely normal conditions” at noon just before the blackout and that adding another gas plant to the system to absorb additional voltage would have made no difference.

Redeia chair, Beatriz Corredor, told the same news briefing she had absolute faith in the company’s calculations and that the operator had complied with all procedures and rules.

“Red Electrica didn’t breach any procedure and has acted diligently,” chief executive Roberto Garcia Merino said at the briefing, adding that as a result he did not expect the company to face any claims.