On Monday, 28 April, a massive blackout hit Spain, Portugal and part of southern France, causing serious disruption to civil life and infrastructure. With the causes of the outage still unclear – ranging from technical failure to suspected cyber attacks – two professors from the Department of Energy at Politecnico di Milano were called in as experts to help the public understand the complexity of the event.

Professor Alberto Berizzi, full professor of Electrical Energy Systems, provided some technical insights to help frame the complexity of the event. He explained that the electricity grid is an interconnected system in dynamic equilibrium, in which a single failure can trigger a chain reaction if the protection and containment mechanisms fail to act promptly. Although detailed information was not available, Berizzi pointed out that similar incidents can result from combinations of local events, system errors or sub-optimal operating conditions. He also highlighted how the progressive increase in energy produced from renewable sources – which are often unpredictable – is changing the management of grid stability, making advanced monitoring and coordination tools between European electricity system operators essential. His speech helped to clarify the systemic scope of the blackout, emphasising the importance of strengthening the resilience of networks in an increasingly complex and interconnected energy context.

Professor Maurizio Delfanti, also a full professor of Electrical Energy Systems at Politecnico di Milano, contributed to the analysis of the event in the mainstream media, highlighting various structural and risk factors in the Iberian electricity system. In particular, he pointed out that Spain and Portugal share a network that is heavily oriented towards renewable sources, with approximately 60% of installed capacity coming from wind, solar and hydroelectric power, supplemented by nuclear and natural gas plants. This advanced mix, although positive in terms of decarbonisation, entails greater complexity for grid stability. Delfanti also highlighted the limited degree of interconnection between the Iberian and Central European systems – due to orographic barriers and political choices – which may have affected the extent of the blackout. Finally, he commented on the hypothesis, put forward by some media outlets and now under official investigation, of a possible cyber cause for the event. While reiterating the lack of concrete evidence, Delfanti stressed that the high level of digitisation and interconnection of electrical infrastructures exposes them to potential cyber attacks, making it increasingly urgent to strengthen the defence systems of critical networks.

The Department of Energy at Politecnico di Milano would like to thank Professors Berizzi and Delfanti for their timely and authoritative contribution to the public understanding of an event that highlights both the fragility and resilience of modern energy systems.