No major damage to the power system but some customers were disconnected

Avoiding tripping of generation connected to distribution systems is essential to maintaining system security

The Expert Panel composed of ENTSO-E and the relevant Transmission System Operators (TSOs) as well as ACER and relevant National Regulatory Authority (NRA) representatives publish their Final Report on an incident which separated on 24 July 2021 for about an hour the Iberian Peninsula from the rest of the Continental Europe power system.

In view of the customer disconnections, the incident was ranked level two according to the ICS Methodology and an expert panel was set up on 22 October 2021 to carry out an investigation.

Today, after several months of intensive and close collaboration of all parties involved, the expert panel issues its final report. It provides a comprehensive analytical overview of the incident – the causes and the consequences - and proposes recommendations to prevent and mitigate the consequences of similar events in the future.

The Expert Panel’s analysis concludes that this incident was atypical in that it resulted from the failure of an efficient and suitable communication channel between the emergency services and the TSO. It did not originate from any faults in system operation or planning. The system defence plans functioned properly and coordinated measures were activated quickly.

Avoiding tripping of generation connected to distribution systems is essential to maintaining system security

The incident revealed that the limits of stable system operation can be reached, even if all security evaluations are executed correctly and timely. With the increase in distributed generation connected to the grid to achieve the de-carbonisation of the energy system, non-compliance with the technical requirements of the binding EU network codes may generate uncontrollable and unmanageable breaches of the security of the electricity system.

Key Recommendations

The expert panel makes several recommendations and in particular,

  • One Key Recommendation is that NRAs, TSOs, Distribution System Operators (DSOs) and Owners of Distributed Generation Units work together to ensure that the mandatory system security requirements are implemented and monitored for their compliance. The Expert Panel recommends that this issue is addressed at the European level;
  • A second Key Recommendation is for TSOs to continuously develop and improve their environmental risk identification and mitigation processes to be prepared for a potential increase in their occurrence due to the effects of climate change.

The Expert Panel calls for ENTSO-E/TSOs and ACER/national regulators to follow up on the implementation of these recommendations to prevent and mitigate the consequences of similar incidents in the future.