A study conducted by Portugal’s INESC TEC and Compass Lexecon has identified a systemic voltage control issue, attributed to REE, as the key cause of a recent blackout. This problem was exacerbated by previous maneuvers, especially in Andalusia, leading to an excess of reactive power beyond the technical capacity of the sole combined cycle group active in the area, threatening system stability.
In a statement released today, the association reported that the study highlighted an “increase in overvoltages and inadequacy in voltage control mechanisms,” noting that the “number of hours of overvoltage in the transmission network has been rising alarmingly in recent years.”
The study indicated that there were “prior warnings” following which anomalies remained unaddressed. “Significant voltage fluctuations were detected on April 16, 22, and 24, particularly on April 22, without corrective measures being implemented, and risk conditions reoccurred on April 28,” stated the association.
Additionally, there was “improperly planned distribution of conventional production,” with technical market restrictions incomplete on April 27, water resources not activated, and conventional production in the south not reinforced in time on the day of the blackout.
The study also identified “unrecognized deviations,” asserting that between 10:00 and 12:00 on April 28, there were voltage deviation warnings that REE did not acknowledge despite the available documentation.
Furthermore, “counterproductive maneuvers” were carried out. “Between 12:00 and 12:30, REE reconnected 11 transmission lines in the south, reducing the voltage control margin immediately before the collapse.”
The analysis found “adequate disconnections by power plants,” ensuring that “the report does not identify abnormal behaviors by power plants belonging to Aelec-associated companies,” and the system’s recovery was assured. “Since the reinforcement of conventional production, no further voltage control issues have been recorded,” it noted.
The study also pointed out a lack of access to crucial data held by REE.
In the statement, the association criticized the conclusions of the European Network of Transmission System Operators for Electricity (ENTSO-E) experts.
“The ENTSO-E technical report omits technical data such as the non-replacement of a critical combined cycle unit in Andalusia, previous signs of instability in voltage control, and confusion over applicable voltage limits in Spain—omissions and errors in analysis that weakened system security before the blackout,” it highlighted.
Aelec includes companies like Iberdrola, Endesa, and EDP, among others.
