Blackout. Independent investigation finds "omissions and inaccuracies"
The main electricity companies operating in Spain warn of "inaccuracies and omissions" in the analysis that independent experts are conducting into the causes of the Iberian blackout.
In an update to the study presented in early July by the association comprising Endesa, Iberdrola, and EDP, AELEC states that the most recent technical report released by the committee appointed by ENTSO-E (a network of European operators) omits technical data it considers relevant. It calls for the sharing of observations on critical technical aspects that were not "properly addressed and that affect the diagnosis of the causes that led to the electricity outage that affected the Iberian system on April 28th."
Among the omissions, they mention the failure to replace a combined cycle power plant considered critical to meeting demand and which was unavailable, and the previous signs of instability in the voltage control of the Spanish electricity grid, observed in previous days.
It was these omissions and analysis errors (now on the part of REE — Red Eléctrica de España) “that weakened the security of the electrical system” before the blackout, the association says.
In the climate of cross-accusations between the main actors in the Spanish energy sector (and politicians) that followed the blackout, AELEC requested an independent report from two consultants — one of which, INESC TEC, linked to the University of Porto, is Portuguese.
The initial findings of this parallel investigation already pointed to a systemic failure in voltage control on the power grid, a responsibility that "is the sole responsibility of the grid operator," REE. In its initial disclosure, AELEC focused on what it considered flaws in the already known reports on the causes of the blackout prepared by Spanish entities, focusing in particular on the internal investigation conducted by REE, but also on the investigation conducted by the group appointed by the Spanish government.
It was excess voltage that caused the blackout, but power companies blame the Spanish grid.
Now, the association's consultants are extending their focus to the latest investigation status report , released on July 16th by the panel of independent experts appointed by the electricity system operators, a group of experts at ENTSO-E. The final report of these experts is not yet available. Although REE is not represented on the panel—which includes a Portuguese representative—the Spanish operator is part of ENTSO-E and provided the data for the investigation. The Spanish electricity grid manager is simultaneously an "involved actor and part of the analysis," under conditions that, according to AELEC, do not guarantee the necessary independence and objectivity.
What is being omitted or undervalued, according to the electrical companies.
- The study commissioned by AELEC questions the adequacy of the generation mix that would have supplied consumption that day. In particular, it questions why REE did not activate another gas-fired power plant (these units contribute to grid stability, unlike much renewable generation). At the time of the blackout, only one gas-fired power plant was connected to the grid, in Arcos de la Frontera, which reduced voltage control capacity in southern Spain.
- Previous warnings and episodes of overvoltage that revealed grid instability between April 22 and 24 were ignored , as were technical indicators that signaled a growing risk in the days leading up to April 28.
- There was a lack of coordination with the distribution companies (owned by the power companies). Despite exceeding the voltage limits, REE did not activate the required coordination measures or notify the distributors as required by the protocols.
- Confusion regarding voltage limits in Spain and Portugal, with ENTSO-E assuming that the upper limit is different in the two countries and that in Spain it is 435 kV (kilovolt), when the normal range varies between 390-420 kV.
The work conducted by INESC TEC and the consulting firm Compass Lexecon identifies the main technical and operational factors that contributed to the massive system disconnection, as well as the protection mechanisms, coordination, and response provided during the event. Among the findings are:
The main cause of the blackout was a systemic voltage control problem, aggravated by prior maneuvers by the grid operator, particularly in Andalusia, a region in which excess reactive power was generated compared to the absorption capacity of the only natural gas group connected to the grid.
The advance warnings regarding localized faults that occurred on the previous days — April 16, 22 and 24 — and which resulted from significant fluctuations in the voltage level that were not considered or corrected by REE.
The planning for the production and distribution of conventional generation—gas, nuclear, coal, and hydroelectric plants—was poorly executed and insufficient. On the eve of the blackout, the system's service offerings in the technical constraints market were not completed, available hydropower resources were not activated, and thermal generation was not reinforced in a timely manner.
The maneuvers carried out by REE between 12:00 and 12:30 on April 28, which involved the reconnection of 11 transmission lines in southern Spain, had the counterproductive effect of reducing the voltage control margin instead of strengthening it.
The report (prepared for the electricity companies association) did not identify any anomalous behavior on the part of the generating plants which, in the REE report, are identified as having disconnected from the grid inappropriately.
Access to key data held by REE is still lacking .
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