A power surge that caused a widespread blackout in Spain and Portugal was the most severe in Europe in the last 20 years, and the first of its kind, a report has found.
Damian Cortinas, president of the association of electricity grid operators Entso-e, said the incident was the first known blackout to be caused by overvoltage, which occurs when there is too much electrical voltage in a network.
This is new territory, Cortinas said, adding the role of Entso-e was not to apportion blame to any party over the cause.
April's outage caused significant disruption for nearly a day when it plunged areas into darkness, cutting internet and telephone connections and halting transport links.
The blackout affected large parts of Spain and Portugal, and briefly impacted southwestern France. A report released on Friday focused on the condition of the power systems on the day of the outage and the sequence of events leading up to it.
A series of cascading overvoltages—an increase in the electrical supply voltage above the established norm—was behind the outage, the report concluded. Overvoltage can be caused by surges in networks due to oversupply or lightning strikes, or due to insufficient protective equipment.
According to the report, automatic defence plans were activated but could not prevent the power system from shutting down. The Entso-e report follows several investigations by the Spanish government, as well as power and grid companies, with the national energy watchdog and Spanish lawmakers also conducting probes.
The Spanish government believes the Entso-e report supports its own findings. Sara Aagesen, minister for ecological transition, stated that it was completely in line with the results of an investigation it commissioned in June, concluding that both the national grid provider Red Eléctrica and private electricity companies were at fault.
However, both Red Eléctrica and private firms have insisted they are not to blame. Redeia, owner of Red Eléctrica, accused certain coal, gas, and nuclear power plants of failing to help maintain appropriate voltage levels.
The Entso-e report noted that some important data was missing, stating, collecting complete, high-quality data proved very challenging for this investigation. A final report is expected to be released in the first quarter of next year to investigate the root causes of the overvoltage and the actions employed to manage voltage levels in the system.
The outage triggered a broad political debate about Spain's energy model. The opposition suggested an increased reliance on renewable energy, supported by the left-wing government of Pedro Sánchez, could have contributed to the blackout, particularly as the country faced a decreasing supply of nuclear energy that could have served as a reliable backup.
The government refuted these theories, and the new report was cautious not to take sides regarding the causes of the unprecedented blackout in April. The loss of power forced the organizers of the Madrid Open Tennis to halt a match halfway through.
All nuclear power plants in Spain stopped automatically during the blackout, and the Spanish oil company Moeve halted operations at its oil refineries.
Buildings were plunged into darkness, affecting mobile phone service and traffic lights. Long queues formed as cash payments became necessary.
Emergency services responded to 286 incidents where individuals were trapped in elevators in the Madrid area, while hospitals enacted emergency plans, suspending routine procedures.
