Spain’s massive blackout was caused by overvoltage on the transmission system and the failure of the country’s generators to compensate by absorbing more reactive power, according to the official government investigation.
Investigators found no evidence a cyber-attack contributed to the nationwide blackout and did not directly blame the high share of renewable generation for causing a cascading failure across the network.
But investigators did note there was not enough synchronised generation connected to the network to maintain voltage within acceptable limits and those generators failed to behave as expected.
Efforts to connect an extra thermal generator came too late to prevent worsening instability and repeated overvoltage from causing the system to collapse.
Investigators recommended stricter enforcement of existing voltage control obligations for synchronised generators as well as the deployment of synchronised compensators across the network to improve stability.
The report also concluded that non-synchronous generators (including wind and solar generators) should be incentivised to contribute to voltage control in future.
The instability seems to have originated within Spain itself rather than being imported from the Europe-wide transmission network that stretches from Iberia all the way to Ukraine and Turkey.
Nonetheless, investigators noted Spain’s relative isolation from the continent-spanning transmission system may have made the instability worse.
Spain’s interconnections via France account for only 3% of capacity on the country’s network, well below the 15% recommended by EU regulations.
More interconnections with the rest of the European grid would probably not have averted the blackout but they have been a long-sought objective, one that investigators repeated.
