By Kate Abnett and Pietro Lombardi
BRUSSELS/MADRID (Reuters) -The massive blackout that hit the Iberian peninsula in April is the first known blackout caused by excessive voltage, the European network of electricity transmission system operators said in a report on Friday.
The report, released ahead of an October 28 legal deadline, focused on the power systems’ condition on the day of the outage and the sequence of events, and did not look into what acted as its trigger.
The report, like previous probes, pointed to a surge in voltage as the immediate cause of the April 28 outage, Europe’s most significant blackout in more than two decades, which paralysed cities and kept people stranded on trains and in elevators across Portugal and Spain.
A final report, due in the first quarter of 2026, will investigate key issues, such as root causes, steps taken to control voltage in the system and the performance of power generators in helping control voltage.
MISSING DATA AND UNEXPLAINED POWER GENERATION LOSSES
The report said that the reasons for some initial power generation losses were still unknown and that, according to power plant owners, they lacked important data that could shed light on what happened before the blackout.
“Collecting complete, high-quality data proved very challenging for this investigation,” in particular from power operators in Spain, according to the report.
The European group’s report follows several separate probes and reports by the Spanish government and power and grid companies. The national energy watchdog and Spanish lawmakers are also conducting separate probes.
Redeia, owner of grid operator REE, has blamed the blackout on some coal, gas and nuclear power plants’ failure to help maintain appropriate voltage while Spanish utilities blamed the Spanish grid operator’s poor planning.
The European systems operator’s group behind the latest report includes representatives from Spanish and Portuguese grid operators.
Redeia said in a statement on Friday that the report confirms the sequence of events described in its own findings.
Spanish power utility lobby Aelec declined to comment.
(Reporting by Kate Abnett and Pietro Lombardi, editing by Inti Landauro and Tomasz Janowski)
