The European Network of Transmission System Operators for Electricity (Entso-E) is moving forward with its investigation into the blackout that occurred on April 28 in Spain and Portugal. The focus is on determining the root cause of the initial generation disconnections in southern Spain and why the Spanish and Portuguese System Defense Plans failed to prevent the blackout in both countries. Additionally, the investigation will analyze the management of the interconnection with France before the incident occurred.
Following a second meeting of its expert panel to investigate the blackout on June 3, the organization has outlined the next steps for the ongoing investigation. Currently, European experts are gathering all necessary data to clarify the facts surrounding the incident, including understanding the oscillation phenomena that occurred before the blackout.
Entso-E, despite facing doubts about the transparency and independence of its investigation from major electric companies, has decided to launch a specific website to serve as an informative portal for stakeholders throughout the investigation. This website will provide a preliminary sequence of events since the blackout day, information about the restoration process, the composition of the expert panel, and other relevant aspects. It will be updated as the investigation progresses and new information becomes available.
In terms of the preliminary chronology of events, two periods of oscillations – power and frequency oscillations – were observed in the half-hour leading up to the blackout in the Continental Europe Synchronous Area (AECE). The first period, from 12:03 to 12:07, was localized and mainly affected the electrical systems of Spain and Portugal. The second oscillation, occurring between 12:16 and 12:22, was inter-area and corresponded to the known East-West continental mode. It was effectively mitigated by compensatory exchange measures, which reduced energy flows between France and Spain.
Subsequently, a sequence of events led to the blackout at 12:33. Interruptions in generation in southern Spain caused a significant increase in voltage, triggering a similar increase in Portugal, and a decrease in frequency. Despite activation of the System Defense and automatic load shedding plans in Spain and Portugal, the collapse of the Iberian electrical system could not be prevented.
After the incident, Red Eléctrica de España (REE) and the Portuguese REN immediately activated their respective system restoration plans. The restoration process in some regions of the Iberian Peninsula was aided by the activation of electrical system resources, such as black start processes in some power plants, and existing interconnections with France and Morocco.
The rapid restoration of supply in Spain and Portugal demonstrated the preparedness and efficiency of Red Eléctrica and REN, supported by RTE from France and ONEE from Morocco. The restoration process began with the activation of the black-start mode at the Castelo de Bode hydroelectric plant and the Tapada do Outeiro gas turbine combined cycle plant.
Interconnections between Spain and France, Spain and Morocco, as well as the restoration of various transmission lines, facilitated the successful restoration of the electrical systems in both countries. The expert group established by Entso-E, with representation from system operators, energy regulators, and coordination centers, is working towards completing its final report through a series of meetings. David Alvira from Red Eléctrica and representatives from the CNMC are actively involved in the investigative panel.
The investigation will continue with upcoming meetings scheduled for June 23 and July 15 to further progress towards the final report.
FUENTE
