The European Network of Transmission System Operators for Electricity (ENTSO-e) has published the final report of the Expert Panel on February 25. regarding the incident that occurred on June 21. 2024. This incident left a significant part of the consumers in Albania, Montenegro, Bosnia and Herzegovina and Croatia without power.
The report identifies seven direct causes whose coincidence on that day led to the power outage:
- Nearly simultaneous fault (with only a 13-minute in between) on two critical transmission lines in the region – the 400kV Ribarevine–Podgorica overhead line and the 400kV Zemblak–Kardia overhead line
- Inability of transmission system operators in the region to detect system inadequacies in the period between the two faults
- Failure to detect voltage instability in the region
- Cascading outage of three additional overhead lines due to overload protection settings
- Automatic response of transformer tap changers to the disturbance
- Insufficient amount of available reactive power across the entire region
- Lack of preventive measures against voltage collapse in the region
Based on the identified causes, the report provides 12 recommendations for improving the operation of all interconnected transmission system operators:
- Review of national policies and processes for vegetation removal in overhead line corridors
- Improving observability areas in monitoring and control systems
- Conducting regular voltage stability assessments
- Identifying key indicators that signal the risk of voltage collapse
- Revising ENTSO-e guidelines for overload protection settings
- Blocking automatic voltage regulation in specific situations
- Assessing the adequacy of resources for voltage control
- Evaluating the feasibility of introducing automatic voltage regulation measures in pre-failure conditions
- Assessing the possibility of installing undervoltage protection for controlled automatic disconnection of certain consumers from the grid
- Verifying the accuracy of data used for security analyses
- Timely updating of information on system element availability
- Checking the accuracy of voltage condition calculations in the region
Along with previously issued recommendations from past incidents within the ENTSO-e area, these measures aim to reduce the likelihood of similar incidents occurring in the European electricity interconnection.
The full report, which involved contributions from over 60 experts across Europe, can be found here: ENTSO-E Report