A drop in frequency on the synchronously interconnected Continental Europe system was registered on 10 January 2019 at around 21.00.
The causes of this drop are still under investigation by the transmission system operators (TSOs) of ENTSO-E Regional Group Continental Europe.
A mismeasurement on lines between Germany and Austria was identified and corrected by TenneT Germany. However, this mismeasurement cannot explain the entire frequency drop on 10 January. The investigation, which is still on-going, is reviewing the significant variation in European production around 21.00 which coincided with changes in trade between different countries.
The frequency drop was sufficient to alert the TSOs but did not at any moment endanger security of supply.
TSOs of ENTSO-E Continental Europe Regional Group are taking collective actions to restore frequency as foreseen in such cases and continue their technical analysis of the incident.