Without blaming anyone for the blackout, experts recommend improving monitoring, coordination and regulation

The expert group from the European Network of Transmission System Operators for Electricity (ENTSO-E) published its final report on Friday regarding the blackout that struck the Iberian Peninsula in April last year. The assessment is consistent with that of the preliminary report: “this was the most severe blackout suffered by the European electricity system in over 20 years, and the first of its kind ever” — that is, the first to be caused by overvoltage. Voltage “is the level of energy” and “must be kept within a range”, as Klaus Kaschnitz had already explained in the preliminary report.

The panel identifies three key events leading to the blackout — instances of disconnection due to overvoltage — all in Spain, specifically in Granada, Badajoz and then, simultaneously, in Segovia, Huelva, Badajoz, Seville and Cáceres. The latter occurred at 12:33:17 Madrid time (one hour behind Lisbon). It was at 12:33:18 that the “point of no return, at which the system was lost”, occurred, reports Klaus Kaschnitz, the panel’s coordinator and expert, in a presentation to journalists. It was at this moment that a drop in frequency was detected and that contingency plans were activated on both sides of the border, but they were unable to halt the blackout given its “unprecedented” nature.

In a statement, ENTSO-E summarises that “the investigation concludes that the blackout resulted from a combination of many interacting factors”, and that these factors led to rapid voltage rises and cascading generator tripping, resulting in the blackout across mainland Spain and Portugal. The report constitutes “an expert analysis, not an attribution of liability”, emphasised Damien Cortina, chairman of the ENTSO-E board of directors. This is left to the “competent authorities” of the respective countries.

During the presentation, Kaschnitz mentioned that conventional generators, for example, “are not efficient enough”, and that there is no specific requirement regarding the speed at which they must react. “This blackout highlights how developments at the local level can have system-wide implications and underlines the importance of maintaining strong connections”, the organisation notes in the statement.

The final report sets out 22 recommendations, which the organisation summarises in the statement as follows: “strengthening operational practices, improving monitoring of system behaviour, and closer coordination and data sharing among electricity system stakeholders”. On this last point, the experts describe the interactions between energy producers and transmission and distribution network operators as “complex”, indicating the need to strengthen coordination between them.

More specifically, the expert group suggests harmonising the permitted voltage range – which varies, for example, between Portugal and Spain – and ensuring that fluctuations in the system are better monitored and detected. It also advocates updating contingency plans to include “these new phenomena”, referring to the unprecedented situation of overvoltage.

In response to questions from journalists, the expert group’s spokespersons indicated that “the technology is ready” to address the issue of voltage control, and that it had not been mandatory until now because no incident had ever occurred that was caused by overvoltage. Going forward, they recommend that voltage control be made mandatory in new power generation equipment. As for existing equipment, they state that it is a matter to be assessed as to whether or not it should be upgraded. The costs “are something we need to consider, depending on the scale of production”.

At the same time, the expert suggests “conducting a more in-depth investigation”, in conjunction with Distribution Network Operators and manufacturers, to analyse the behaviour of small generation units, since, taken together, “they can result in a huge amount of production loss”.

Regarding the recovery, Klaus considers that “it was quite rapid”, but suggests additional measures, such as stepping up tests of the blackstart system (which enables the electricity system to be restarted) and also ensuring that telecommunications are guaranteed for at least 24 hours in the event of widespread outages.

The investigation’s findings also highlight the need to adapt regulatory frameworks “to support the constantly evolving nature of the electricity system”.

Lack of cooperation from entities in Spain hinders conclusions

“In Portugal and France, the transmission system operators (TSOs) collected the necessary data and transferred it to the Expert Panel in a timely manner”, reads the summary of the report, made available by ENTSO-E. In Spain, however, “the collection of third-party data proved more challenging”.

In this regard, “some data is still missing, particularly regarding generation tripping events that occurred prior to the blackout, which prevented the Expert Panel from identifying the cause of the generation units’ tripping due to the absence or lack of fault records”. The report’s summary notes that the parties involved, such as the owners of the facilities in question, cited the lack of fault log data as the reason why they were unable to provide this information to the investigation.

On the Portuguese side, data provided by both the low-voltage network operator, E-Redes, and electricity generation companies was aggregated. The report names Akuo, Aquila, Axpo, CwPower, Dos Grados, EDP Produção, EML, Energi Innovation, Engie, EXUS, Galp, Iberdrola, Powersun Solutions, Neoen, Prosolia, Vector Renewables, Voltalia, Welink and WiseEnergy as contributors.

The difficulty in obtaining data was already a complaint raised by ENTSO-E in October last year. Three key points emerged from the preliminary report produced by the organisation and presented that month: it was an unprecedented situation, in that a blackout had never before occurred due to high voltage; the group’s objective is to prevent similar incidents in the future; and the difficulty in gathering the necessary data.