The conclusion is detailed in the summary of the 15th July meeting of the expert group from the European Network of Transmission System Operators for Electricity (ENTSO-E), which is investigating the network collapse that occurred on April 28 in Portugal and Spain. This information was released by the Portuguese Energy Services Regulatory Authority (ERSE), which is part of the panel, alongside operators and regulators from various European countries.
According to ENTSO-E, cascading voltage increases, observed in southern Spain during the final phase of the incident, were followed by sudden production shutdowns, particularly at renewable energy facilities. This led to the electrical separation of the Iberian Peninsula from the continental system, causing a loss of synchronism and the collapse of frequency and voltage.
This type of disturbance had never been identified as the cause of a blackout anywhere in the European grid. If this conclusion is confirmed, an in-depth analysis and investigation by all ENTSO-E electrical systems experts will be necessary, alongside the adoption of new measures to strengthen resilience, as stated in the report.
Among the measures to be implemented, experts emphasize the need to “improve the procedures and management capabilities for voltage control of all active participants in the electrical system” to avoid severe voltage-related incidents in the future.
Another approach is to assess whether the existing defense plans are capable of protecting the European electrical system against “this new type of phenomenon”.
During the incident, automatic response plans were activated in Portugal and Spain as required by European regulations, but they failed to prevent the network collapse.
The report nevertheless highlights the quick and effective restoration, with REN completing the system recovery at 00:22 on April 29 and Red Eléctrica by around 04:00.
Although the legal deadline to produce the factual report on the incident is October 28, 2025, six months after the incident, the expert panel aims to deliver it earlier.
This will be followed by a final report, with recommendations to the European Commission and Member States, expected to be delivered two to three months later.
