Beinahe Blackout


Near-Blackout in Central Europe underlines importance of safety precautions

Jan. 25 2021

On 08.01.2021 at around 2 p.m. Central European Time, a sudden voltage drop in south-eastern Europe caused a disturbance in the grid frequency in the continental European high-voltage transmission grid. This disturbance almost caused a blackout in Central Europe. Thanks to functioning safety precautions, however, such a catastrophe was avoided and hardly anyone noticed the near-blackout.

However, incidents like this underline the enormous importance of appropriate safety precautions and measures.


ENTSO-E is the association through which all transmission system operators are interconnected with their high-voltage grids throughout Europe. This enables interconnected electricity trading – be it the purchase of missing capacities or the sale of surplus electricity.

In a press release ENTSO-E announced that the south-eastern part of the interconnected grid had been separated from the continental part. However, the separation could be resolved again after about an hour.


In Romania, voltage drops and grid fluctuations occurred on 08 January. As a result, the continental grid interconnection was divided into two island grids: Southeast Europe and Central Europe. The disconnection of the sub-grid had a clear impact on the grid frequency: it dropped from the targeted 50 Hz to below 49.8 Hz within 14 seconds.

If the grid frequency had fallen below the value of 49 Hz, automatic load disconnection – i.e. the disconnection of end consumers from the power supply – would have occurred. Only the rapid supply of power reserves by switching on fast-starting gas-fired power plants luckily prevented the blackout.

However, sensitive infrastructures such as servers and automated production plants can suffer considerable damage even from these supposedly minor frequency fluctuations. This can lead to a system failure and thus to the interruption of critical processes.

The following (german) graphic illustrates the effects:

Frequenzgang Europäisches Hochspannungsnetz


Especially in winter, the risk of such near disasters is increased:

  • Low solar power reduces the availability of photovoltaics
  • Wind turbines have to be switched off more often due to strong winds
  • Additional consumption due to electric heating
  • Cold temperatures "stress" power lines and technology

Additional strain due to the Corona pandemic:

  • Pandemic-related operation closures change load behaviour
  • Additional demand due to home office
  • Additional demand due to home schooling

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