In early January a mysterious drop in frequency in the synchronised European high-voltage power grid occurred. The incident did not cause any breakdowns in connections in Europe, but there was a blackout in the Balkans. The source of the incident seems to have been in Romania, but that is yet to be confirmed. The event shows that the power grid in Europe, which on the one hand is expected to incorporate increasing amounts of green energy and on the other handle the growing demand for energy during frosts and heat waves, is at risk of becoming unstable. In the summer the grid is to be propped up by PV. What about the winter? – writes Bartłomiej Sawicki, editor at BiznesAlert.pl.
On the 8th of January the synchronised European high-voltage power grid split into two areas. The event was caused by a series of consecutive shutdowns of the grid, which occurred within a short period. The synchronization came back to normal after an hour. On the same day the European Network of Transmission System Operators (ENTSO-E) released its first notice about the event.
The grids in continental Europe are interconnected to synchronize their work at a frequency of about 50 Hz. The January 8 event split the synchronized grid into two areas and the south-eastern region is still temporarily separated from continental Europe.
On the 15th of January, ENTSO-E released a more detailed update that included an in-depth description of the occurrence, but still did not reveal the source of the problem as the matter is still being analyzed. I put a lens to the announcements of European operators, the background and history of this kind of events.
What happened on January 8 2021?
According to ENTSO-E’s update from the 15th of January, right after 2:05 p.m. the frequency in the north-western part of the grid dropped for about 15 seconds to 49.74 Hz and then went up to about 49.84 Hz and stayed there. At the same time the frequency in the south-eastern zone increased to 50.6 Hz and then stabilized between 50.2 and 50.3 Hz.
Split into the two zones. Picture by entsoe/PSE
“Due to the underfrequency in the North-West Area, the contracted interruptible services in France and Italy, in total around 1.7 GW, were disconnected in order to reduce the frequency deviation. These services are large customers, who are contracted by the respective Transmission System Operators (TSOs) and get disconnected if frequency drops under a certain threshold,” ENTSO-E explained. “In addition, 420 MW and 60 MW of supportive power were automatically activated from the Nordic and Great Britain Synchronous areas respectively. These countermeasures ensured that, already at 14:09 CET, 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 (see Figure 2),” the organization confirmed.
ENTSO-E also stated that “due to the large overfrequency in the South-East Area, automatic and manual countermeasures were activated (i.e. the reduction of the feed-in of generation units) in order to stabilise the frequency. Thus, at 15.05 CET the frequency deviation in the South-East Area could be limited to +0.1 Hz from the nominal frequency of 50 Hz.”
The association made it clear that “the automatic response and the coordinated actions taken by the TSOs in continental Europe ensured that the situation was quickly restored to normal operations.” ENTSO-E explained the coordinated actions taken by TSOs also allowed to reconnect the two areas. The disconnected contractors were reconnected, in Italy at 2:47 p.m. and in France a minute later. At 3:08 both systems were connected again. ENTSO-E is still investigating the event in detail.
Continental Europe established binding procedures whose goal is to avoid interruptions to the system, especially when it comes to considerable frequency deviations, which may cause some users or power providers to be disconnected. The German TSO Amprion and Switzerland’s Swissgrid are responsible for those procedures and act as synchronous area monitors (SAMs) in continental Europe. The SAMs are responsible for the constant monitoring of the system. They report all significant frequency deviations to all TSOs through the EAS – ENTSO-E Awareness System and launch an extraordinary procedure for frequency deviations in order to quickly and efficiently coordinate all countermeasures undertaken to stabilize the system. A conference call is one of the steps within the procedure. It is organized by Amprion, Swissgrid, RTE (France), TERNA (Italy) and REE (Spain). In this case the call took place at 2:09 p.m. CET on the 8th of January. The parties assessed the situation and the operators reported on the countermeasures that had been already taken. The operators from the north-west and south-east regions also coordinated actions to reconnect the zones to unify continental Europe’s synchronous area. The procedure states that such incidents need to be investigated in detail. According to the 15th January update by ENTSO-E, such an investigation encompasses a thorough analysis of a “large number of real-time recordings from protection devices and other electric power system elements”. ENTSO-E will publish the results of the inquiry once the analysis is finished.
Why is frequency so important? One of the basic quality criteria is the ability to maintain the value and frequency of voltage at a specific level. All elements of the transmission system, such as the transmission lines or transformers work at a specific frequency. If it drops, or goes over that level some of the appliances turn off. In extreme cases this may cause blackouts.
The incident in question, which split the synchronized European grid into south-east and north-west for about an hour is one of the most serious happenings that could have led to the first major blackout in the region since 2006. According to media reports, in some regions sensitive automatic machines stopped working. The reasons behind the incident are unclear, but the defects of grid interconnections in South-Eastern Europe are listed among the possible causes.
The Papenburg incident that shook Europe
Considering the recent events, it is worth reminding what happened 15 years ago. On the first Saturday of November in 2006 at around 10 p.m. in Germany the demand in E.ON Netz regulatory area was at about 13500 MW. At the same time wind power plants injected 3300 MW of power. Due to the substantial transit of power, the connections to the west were at full. This is a normal situation. At 9:38 p.m. near Papenburg, both 380 kV circuits on the Conneforde-Diele line were switched off to ensure a safe passage of a ship along the Ems river. Beforehand routine calculations and a simulation of the switch-off had been conducted. The tests did not reveal any risks. Once the line was turned off, the load flow changed and the southern power lines took over the load. After a while the E.ON Netz load went up, especially on the Wehrendorf-Landesbergen (eastern Westphalia) line, which connects RWE’s grids. In the following seconds other lines became overloaded, which led to cascading shut-downs. This split the interconnected transmission systems of the Union for the Coordination of the Transmission of Electricity into three systems. In result of a domino effect, the German grid was split into northern and south-eastern parts, and the Austrian network was desynchronized into two parts as well. Island 1 experienced a deficit in power (shortages in generation), because it could not import wind energy from Germany’s offshore wind farms in the north as they were located on island 2. In result, the frequency on island 1 dropped to 49 Hz, which automatically set off the protective device, which shut down the system in line with the UCTE guidelines. Islands 2 and 3 had a surplus load, which meant they had to face a serious increase in frequency.
The three zones in 2006. Picture by entsoe/PSE
In order to restore balance between generation and consumption in the western area, the system was tripped off automatically. The TSOs took actions in accordance with the UCTE safety guidelines, which prevented the event from causing a blackout across Europe. Power was restored within 1-1.5 hours.
The European Commission opened an investigation into the Papengurg incident whose results led to the update of regulations on networks. The package on the EU internal energy market, which was adopted in 2009, became a legal framework for the so-called regional safety coordinators. Today five organizations play this role. They support 44 TSOs across Europe in maintaining power transmission.
After 15 years the problem has returned. The trail leads to Romania
An analysis of information provided by various TSOs leads to a conclusion that the 2021 incident could have had its origins in Southern Europe, probably in one of the countries in the south-east. Experts are especially looking into Romania, as the event caused the biggest damage there. Romania’s TSO Transelectrica was the first one to have informed about the incident. The transmission network in the north-west of the country broke down. A few places in Transylvania remained either entirely or partially without power for almost an hour and a half, while other areas experienced only disturbances in frequency. The problems with blackouts were reported in Cluj, Satu Mare, Maramureș, Bistrița Năsăud, Alba, Brașov, Mureș and Sibiu. The Romanian transmission networks are connected to the rest of Europe via Hungary.
Other European operators recorded issues with frequency as well, but they did not impact their grids. This pertains to Austria’s TSO APG, Germany’s Amprion, Italy’s TERNA and Bulgaria’s ESO. Other states did notice the problem, but did not record any issues with their transmission systems.
The overload of the grid also led to blackouts in some parts of Bulgaria, which were gradually dealt with. Some TSOs suggest the problems may have also affected Greece, Croatia and even Turkey.
The information revealed by Italy’s TERNA points the finger at the Balkan Peninsula. The company stated that a drop in frequency was recorded due to a series of incidents that occurred in the transmission systems in the Balkans, which split the European grid into two parts.
Austria and Germany warn
The disturbance in the synchronised European high-voltage power grid, which split the European network regions forced many to reconsider the safety of Europe’s power system. The German Association of the Power Industry (VIK) warned that the incident was a warning sign against sudden drops in frequency in the European networks, that are at risk of significant disturbances, which may impact the safety of power supply.
The Austrian press directly stated that the increased expansion of renewable energy, which entails the generation of the unstable wind and sun power, has led to increasing fluctuations in power networks. “The number of emergency situations in on the rise. Just a few years ago Wien Energie (Austria’s power and heat company) had to substantially increase its power generation in a short time. In recent yeast this happened about 15 times. Also in recent years the network’s stability had to be restored 240 times,” Austria’s Der Standard daily enumerates.
“Gas-fired power stations are crucial for ensuring power supply. Wien Energie wants to transition to green gas within the medium term. In order to ensure the security of power supply, Austria is increasingly relying on neighboring nuclear and coal-fired power plants,” the article continues. This is why the country’s energy and environmental services company EVN has called for a new legal framework for further exploitation of the existing gas power plants and for introducing incentives to build new, flexible gas turbines that would be easy to bring into use in emergency situations. The company believes this would allow the country to handle any problems without buying power from NPPs or coal-fired power plants from its neighbors. The Austrians have stressed that the wind, the sun and water are not suitable for quickly increasing power generation, even if “the future belongs to green energy”.
Transmission network regulations worked
Europe’s TSOs cooperated well, which is why they were able to restore the target voltage. This means the procedures set out in the so-called winter package from 2018 and the so-called network codes passed the test. Network codes are comprised of the following guidelines: Capacity Allocation & Congestion Management, Forward Capacity Allocation, Electricity Balancing, System Operation. Those documents regulate, among others, the management of transmission systems and issues related to efficient and non-discriminatory access to system interconnections to ensure the exchange of power across borders.
The Commission has the authority to adopt and update the binding guidelines that pertain to the the network codes. To do that, it needs to ask ENTSO-E, the Agency for the Cooperation of Energy Regulators (ACER), TSOs from member states and, depending on the issue, other stakeholders, for an opinion. It is possible that after the analysis of the January incident, the codes will be updated and ENTSO-E and the European Commission will issue guidelines for countries in south-eastern Europe on increasing the flexibility of their power systems. This fits into the wider context of the ongoing changes on those energy markets. In order to increase the security of supply, Romania and Bulgaria want to cooperate with the United States to upgrade their nuclear power capabilities. Whereas Greece, similarly to Poland and Germany, is facing the dilemma of phasing out lignite and replacing it with a more predictable fuel. What happened in Austria proves renewable energy sources are not enough. Europe has to face the problem of an outdated power infrastructure that runs on coal in Serbia and Bosnia and Herzegovina.