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One of the most critical near-blackout since 2006: system separation in Continental Europe

On 8 January 2021, the European electricity grid just missed a large-scale collapse, with a drop in frequency that could have paralysed Europe.

A near power grid outbreak cut Europe’s power grid into a South-Eastern and a North-Western part for about an hour due to outages of several transmission network elements in a very short time. It was described as one of the most critical near-blackout situations since the region’s last major blackout in 2006.

Map of Continental Europe showing the two separated areas during the system event on 8 January 2021.
Source: ENTSO-E.

“The frequency in the North-West Area of Continental Europe initially decreased to a value of 49.74 Hz within a period of around 15 seconds,” reported the European Network of Transmission System Operators for Electricity (ENTSO-E). “Afterwards, the frequency reached a steady-state value of approximately 49.84 Hz. At the same time, the frequency in the South-East Area initially increased to a value of up to 50.6 Hz before settling at a steady-state frequency between 50.2 Hz and 50.3 Hz.”

Thanks to the fast cooperation of interruptible services in France and Italy and Transmission System Operators (TSOs), after a few minutes the frequency deviation was limited to a deviation of around 0.1 Hz in the North-West Area from the nominal frequency of 50 Hz.

“Sensitive machines have already felt the frequency drop,” said Stefan Zach, spokesman of Austrian-based producer and transporter of electricity Energieversorgung Niederösterreich (EVN). “If the fluctuations are too high, machines switch themselves off to protect themselves.”

According to him, this can also happen with power plants, which would cause a critical situation.

Due to the large over frequency in the South-East area, automatic and manual countermeasures were activated in order to stabilise the frequency. The disruption also affected Serbia, Croatia, Romania and the south of Hungary. However, the automatic response and the coordinated actions taken by the TSOs ensured that the situation was quickly restored to normal operations.

The ENTSO-E recalled that a separation of the synchronous area with a much larger disturbance and impacts on customers took place in Continental Europe on 4 November 2006. This event was extensively analysed and led to a number of substantial developments, like the European Awareness System (EAS) which is a platform allowing TSOs to exchange operational information in real-time, enabling them to react immediately in case of unusual system condition.

“The TSOs are therefore well prepared in order to coordinate and manage such events and limit the consequences,” continued the report prepared by ENTSO-E. “This preparedness and a permanent observation of the system frequency allowed to resynchronize the two separated areas in a very short period of time.”

Also, the German TSO Amprion and the Swiss one Swissgrid (responsible for these procedures in their role as synchronous area monitor) continuously observed the system frequency and informed all TSOs via the EAS and launched an extraordinary procedure for the occurred frequency deviation to coordinate countermeasures in a fast and effective manner in order to stabilise the system. It had already happened within 4 minutes after the detection.

It is still not clear what caused the separation, but a detailed investigation is ongoing on the event and ENTSO-E will publish the results as soon as the analysis is finalised.

As pointed out by Michael Strebl, managing director of Austria’s Wien Energie such fire-fighting operations are not a viable long-term business model.

According to theories, the reason can be the strong expansion of volatile renewable electricity generation and the elimination of large backup power plants in Europe. Also, the number of emergency operations has increased from around 15 to up to 240 per year in recent years.

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