ENTSO-EOn 10 January 2019, 21:02 CET, the Continental Europe Power System which stretches across 26 countries registered for nine seconds the largest absolute frequency deviation since 2006. The frequency dropped to 49.8 Hz (compared to 49.0 Hz in 2006).
Today, ENTSO-E issues a detailed and transparent technical analysis into the root causes of the event. It appears the drop was caused by the superposition of two elements. On one hand, a large deterministic frequency deviation. On the other hand, another frequency deviation, registered between 9 and 11 January, caused by a frozen measurement on four interconnection lines between Germany and Austria.
Even if the alert frequency range was reached for nine seconds, security of power supply was never endangered. Activation of reserves across Continental Europe and of interruptible contracts with industrial consumers in France quickly brought the frequency back to normal range.
ENTSO-E technical report points out however the need to find solutions to deterministic deviations in Continental Europe. Even if they have been observed for years, they tend to occur more and more often and are of greater amplitude. This phenomenon is due to the fact that the behaviour of generation units (or large consumption units) follows market rules and not the real time physical conditions of the system. The generation changes stepwise. While the evolution of the demand curve is more linear. This creates imbalance between generation and demand during short period of times around the change of hour.
ENTSO-E will continue investigate possible solutions to deterministic deviations which require change in operation and/or market rules in close dialogue with all concerned parties.
Frequently asked questions
What happened on 10 January around 21.00?
On 10 January 2019, 21:02 CET, the Continental Europe Power System which stretches across 26 countries registered for nine seconds the largest absolute frequency deviation since 2006. The frequency dropped to 49.8 Hz (compared to 49.0 Hz in 2006).
What caused the drop?
After a detailed technical analysis by the TSOs of Continental Europe, it appears the drop was caused by the superposition of a large deterministic frequency deviation on one hand, and another frequency deviation, due to a frozen measurement on four interconnection lines between Germany and Austria that lasted between 9 and 11 January, on the other hand.
Was security of supply endangered?
The alert frequency range was reached during 9 seconds on 10 January at 21:02. Activation of reserves across Continental Europe and of interruptible contracts with industrial consumers in France brought the frequency quickly in normal range. The emergency frequency range was never reached. The security of supply was never endangered.
What is a deterministic frequency deviation?
These frequency deviations are called deterministic because they occur at the same period of time and in the same manner. They are different to other types of frequency deviations caused for example by an unforeseen change in generation or consumption.
The deterministic frequency deviations are observed in all synchronous areas with a power market in function. They occur at the change of hour and coincide with large shifts in power demand. For example, in the morning and evening when the demand significantly increases or decreases (demand peaks). Deterministic frequency deviations tend to be more important in winter time.
This phenomenon is due to the fact that the behaviour of generation units (or large consumption units) follows market rules and not the real time physical conditions of the system. The generation changes stepwise. While the evolution of the demand curve is more linear. This creates imbalance between generation and demand during short period of times around the change of hour.
Why is frequency so important in a power system?
The frequency is the heartbeat of a power system. It permanently reflects the balance between generation and consumption. It needs to stay within certain limits for the power system to properly function. The transmission system operators are ensuring that the frequency stays within these operational security limits. In Continental Europe, 26 countries are synchronously interconnected and therefore need to cooperate to maintain the frequency within security limits across the whole area.
When does electricity security of supply get affected?
In Continental Europe the frequency setpoint is 50 Hz. It shall not go below 47.5 and above 51.5 Hz. At the extreme values of 47.5 Hz (under frequency) and 51.5 Hz (over frequency) all connected generation and devices would automatically disconnect. On 10 January at 21:02, the frequency dropped for 9 seconds at 49.8 Hz.
Why are deterministic frequency deviation an issue?
Deterministic frequency deviations have been observed for a long time in Continental Europe. However, in recent years, they tend to be more frequent and of greater amplitude. One consequence is the need for TSOs to activate the reserves they normally have in place to cover an unforeseen change to generation or demand. This impacts system security. But also end-consumer prices - as activation of reserves is costly.
What are the next steps to best manage deterministic frequency deviations?
After the event on 10 January, ENTSO-E has launched an investigation onto the causes of the incident and possible solutions. The present report is part of this work. It contains a detailed chapter on deterministic frequency deviations. It also underlines solutions at the level of TSOs and/or markets. ENTSO-E will further analyse these solutions in the course of 2019 in dialogue with all concerned parties.
What is a synchronous area?
A synchronous electricity grid is a wide area grid covering different countries or region which operates at a synchronized frequency and is electrically tied together during normal system conditions.
Which countries are part of the Continental Europe synchronous area?
The area is made of 26 countries and covers most of Europe’s continent. Here is a link to the map of the interconnected European Power system:
Where can I see the current frequency in Continental Europe?
The transmission system operators in charge of monitoring the frequency in the Continental Europe area are the Swiss TSO, Swissgrid and the German TSO, Amprion. They act as Coordination Centers for the synchronous, continental European Grid. You can see the actual measurement of frequency at the website: https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html
Was the frequency deviation originating from South Eastern Europe part of the issue on 10 January?
The permanent long-lasting deviation of the Serbia, North Macedonia and Montenegro (SMM) control block - which covers Kosovo* - also affected the frequency. However, the SMM control block did not participate in the large frequency deviation at 21:02 on 10 January as the EMS (Serbian TSO) Control Centre observed the low frequency and took preventive action and did not disconnect, as planned, a 300 MW pump-storage unit that was running in generation mode.
- This designation is without prejudice to positions on status, and is in line with UNSCR 1244/1999 and the ICJ Opinion on the Kosovo declaration of independence.
For media enquiries: please contact the ENTSO-E Communication Team at media@entsoe.eu