On 10 January 2019, the utility frequency of Europe’s power grid dropped to 49.8 hertz. Many factors contributed to the near-blackout that evening, but the incident is not the only one in recent weeks that has shaken the grid.
But, let’s start at the beginning: Thursday , 10 January 2019 at 21:00 CET. Europe was settling in for a relaxing evening on the couch in warmly-lit living rooms at the end of the workday. At that moment, however, things were far from relaxed for employees at European grid stability observation posts. In less than two minutes, the utility frequency plunged toward the critical threshold of 49.8 hertz across Europe and was threatening to sink even further.
Potential production causes of the frequency disruption
|20:00 CET||According to ENTSO-E, 140 MW of available power dropped off the grid at 20:00 from boiler 1 of Spain’s Litoral coal-fired power plant near Almeria. It is not certain, if this had an impact on the utility frequency collapse that occurred about an hour later.|
|20:26 CET||At the French nuclear power plant Penly near Dieppe, ENTSO-E states that reactor 2 went offline at 20:26, taking 850 MW available capacity out of 1,330 MW installed capacity off the grid.|
|21:00 CET||Energy sector news service montelnews.com quoted TenneT press spokesperson Matthias Fischer, who said there was “a short but significant peak of power consumption” when pumps were activated at pumped-storage hydro plants, including the 1.1 GW Goldisthal facility in Thuringia (Germany)|
Additionally, another root cause of the frequency drop can be observed every day at the top of the hour. This is when the ‘hourly handoff ’ takes place, regularly causing a frequency fluctuation of 0.1 hertz in the morning and evening hours. It may not sound like much, but it's half of the 0.2 hertz frequency tolerance of alternating current.
The hourly handoff occurs at the ‘shift change,’ when one set of large power plants hands over power producing duties to another group of plants.
Part of this can be chalked up to power trading that is still, in some cases, conducted in one-hour blocks. At the top of the hour, the first set of power plants shuts down power production as quickly as possible to hit the handoff deadline and to avoid ‘over-producing.’
The incoming power plants try and take over power delivery as late as possible – payment for power produced begins at the agreed upon time, not before. The issue occurs during the ramp times. If turbines and generators are still ‘ramping’ up or down, they are not at full capacity, which causes a dip in the frequency. Controllable renewable energies such as bioenergy, aggregated in virtual power plants, can provide capacity much quicker – just sayin’.
Did a data error cause the frequency failure?
- Failures at large power plants in France and Spain destabilized the integrated European grid.
- A grid controller data error from the TSO TenneT starts up the pumps at the Goldisthal pumped hydro plant – even though the necessary power is not available in the grid.
- The normal hourly handoff between large power plants causes a predictable frequency fluctuation of 0.1 hertz.
- A feed-in shortfall, which can possibly be traced back to the data error.
Why weren’t the power market’s reserves enough?
Fluctuations in the European high-voltage grid are designed by the power market to be regulated by primary control reserve. It kicks in instantly, if the frequency recorded directly at an asset providing control reserve fluctuates up or down within a certain tolerance (dead band). We provide primary control reserve in our Virtual Power Plant and could quickly see that all the available control reserve was used up.
So why wasn’t it enough? After all, in the pan-European pool of primary control reserve providers, we’re a relatively small fish, and there are plenty of large power facilities contributing to the mix. The online portal netzfrequenzmessung.de, which tracks Europe's grid frequency, has come up with a prevailing theoretical analysis that cites two possible reasons:
However, the platform does not provide a reason why these power plants did not fulfill their obligation to provide primary control reserve. In any case, it is reasonable to conclude that providing the necessary primary control reserve to stabilize the grid may have gone against other interests of the plant operators. To put it another way: Providing near-instantaneous control reserve was simply not attractive enough in terms of price.
Why isn't the grid settling back down?
In recent months, stakeholders in the electricity markets are having a tough time shaking the feeling that the usually-stable European grid has fallen into disarray. Three major and several minor incidents have gotten a lot of attention. In addition to the previously described situation on 10 January 2019, there have also been the following incidents:
Rolling blackouts in accordance with Germany’s levy for interruptible loads (AblaV) in December 2018
On 14 December 2018, an incorrect forecast for photovoltaic feed-in led to a grid imbalance. This was corrected by reducing power consumption at certain industrial facilities in accordance with a government levy (AblaV) regarding interruptible loads that can be taken offline to stabilize the grid. Under AblaV, companies are compensated for reducing their power consumption while the measure is in force. We documented the impact of this event in a previous blog article (German only). To summarize: Tempers flared, particularly in the heavy industrial sector, and the FAZ newspaper penned a fiery article.
Dangerous grid frequency increase on 24 January 2019
Attempt at an explanation and hypothetical causes
The approach to grid reserves has changed
The current disruptions, on the other hand, are much more difficult to evaluate and cannot be fully explained by single events such as power plant failures or grid controller errors. It is therefore likely that there are additional reasons for the fluctuations that have nothing to do with the physical grid. One theory is the introduction of mixed-pricing methods on the control reserve market. The resulting consequences – quickly-exhausted reserves, waning commitment from balancing groups – are destabilizing the entire system.