Due to unplanned high flows of electricity from the southeast to the west of Europe, on 8 January 2021, at 14:04 CET, the high voltage switch in the Ernestinovo substation was switched off due to the correct operation of the overload protection. In this chain reaction, a series of transmission line outages occurred in Serbia, Romania and Croatia, which ultimately led to the division of the European electricity system into two parts.
Croatian electricity transmission system operator HOPS denies the information published in some media that a malfunction occurred in the Ernestinovo substation near Osijek three weeks ago, which could have cause blackouts throughout Europe.
HOPS operations staff reconnected the two separated European synchronous areas by switching off the switch in the Ernestinovo substation one hour after the moment of separation.
The European electricity system is prepared for such and similar disruptions, and is capable of rapid operation of regulatory and protection systems to limit the operation of disruptions and thus prevent interruptions in electricity supply. HOPS noted that the European electricity system has never been threatened by a complete or limited breakdown that would cut off electricity supply in Europe.
The causes, chronology and consequences of the incident are being investigated at European level, and a final report is expected within the envisaged period of 6 months. HOPS actively participates in the analysis of events with colleagues from other European transmission system operators, and is a member of a special expert group that prepared a press release published on the website of the Association of European Transmission System Operators (ENTSO-E).