Energy Independence Secured: Three Synchronous Compensators in Operation. Construction Work of Synchronisation Project Completed in the Vilnius Region
On Wednesday, the completion of three key synchronisation projects was marked at the Neris transformer substation: the commissioning of the third synchronous compensator, the reconstruction of the Neris substation and the construction of a new Vilnius-Neris power transmission line. Synchronous compensators ensure network inertia and stability when connected to continental European networks. The projects enhance the reliability of the power supply in the Vilnius region and facilitate further network expansion, which is necessary to meet the increasing electricity demand of the city and the region.
Žygimantas Vaičiūnas, Minister of Energy, Marius Vaščega, Head of the European Commission Representation in Lithuania, Robert Duchnevič, Mayor of Vilnius District, members of the Seimas, as well as the CEOs and board members of the energy transmission and exchange group EPSO-G and its subsidiary Litgrid, participated in the commissioning of the last synchronous compensator installed in Lithuania at the Neris transformer substation on Wednesday.
“The completion of these three cornerstone projects marks the end of all essential synchronisation projects. From now on, Vilnius is surrounded by a high-voltage electricity ring. Together with the three synchronous compensators already in operation, new power lines and the renovated Neris substation, we have every opportunity to integrate even more renewable energy sources and thus move closer to our strategic goal of generating more electricity from renewable sources than Lithuania’s annual electricity consumption by 2028,” Energy Minister Žygimantas Vaičiūnas said.
“The reconstruction of the Neris substation, which has been in operation since 1972, involved the installation of two new 300 MVA autotransformers, the replacement of all switchgear and the construction of new equipment necessary for connecting the Vilnius-Neris line and the synchronous compensator. The new line will enable the expansion of the Vilnius transformer substation in the future and further improve conditions for connecting new renewable energy sources (RES) capacities. I would like to thank everyone who contributed to the successful implementation of these complex projects,” Rokas Masiulis, CEO of Litgrid, said.
Neris Synchronous Compensator
A synchronous compensator is a powerful, heavy rotating electric motor connected to the power transmission network that can accumulate rotational energy and, when needed, switch to generator mode. By ensuring inertia, compensating for reactive power, and lowering voltage drops during short circuits it helps stabilise the electrical system’s frequency and improves the network’s dynamic stability.
The device, weighing more than 460 tonnes, was manufactured in Germany and installed in Lithuania by Siemens Energy.
A total of three synchronous compensators are connected to the transmission network in Lithuania – in Telšiai, Alytus and at the Neris transformer substation in Vilnius. Three synchronous compensators are being installed in each of the Baltic countries.
Synchronous compensators are large and powerful electric motors that increase inertia in the grid and thus slow down frequency changes, for example, when a power plant unexpectedly shuts down. These devices are therefore the first line of defence for maintaining frequency until other frequency reserves, such as batteries or power generation capacity, come into play.
Since solar power plants do not create inertia in the grid, the functioning of a synchronous compensator and the inertia it produces are crucial when constructing an electrical system where the majority of the energy is generated by RES. Power plants that rely on wind and solar energy cannot regulate frequency. Older power plants with massive rotating generators, such as nuclear and thermal power plants, are today the source of inertia. As the number of these power plants decreases, the need for equipment that maintains inertia increases.
330 kV Vilnius–Neris Line and Neris Substation
During the construction of Vilnius–Neris, a new 58 km–long line was built from the Neris transformer substation in Nemenčinė to a point in the Marijampolė municipality, where it connected to the former Vilnius–Molodechno line. A 23 km section of the Vilnius–Molodechno overhead line was also reconstructed in the existing engineering corridor from the connection point to the Vilnius transformer substation in Trakų Vokė, Paneriai eldership, Vilnius city. The remaining part of the old line connecting the Lithuanian and Belarusian power systems has been dismantled.
Once the new Vilnius–Neris power transmission line is commissioned, together with the existing 330 kV lines, the Lithuanian power plant–Vilnius and Neris–Lithuanian power plant, it will create a 330 kV power transmission ring around the capital. This will ensure a reliable electricity supply in the Vilnius region.
The reconstruction of the Neris transformer substation was carried out in two stages to ensure uninterrupted operation of the substation. During the first stage, one of the two 330 kV autotransformers was replaced, and half of the 330/110/10 kV switchgear was reconstructed. During the second stage, the second autotransformer was replaced, and the remaining switchgear was reconstructed.
The reconstruction of the Neris substation and the design and construction of the Vilnius-Neris line were carried out by the Žilinskis ir Co company.
Litgrid has already implemented a total of 12 synchronisation projects. These include the reconstruction of the Neris substation, the installation of a frequency stability assessment system, the construction of the 330 kV Darbėnai–Bitėnai power line, the construction of the 330 kV Kruonis hydroelectric plant-Bitėnai power line, the expansion of the 330 kV Bitėnai transformer substation, the construction of the 110 kV Pagėgiai-Bitėnai line, the reconstruction of the 330 kV Lithuanian power plant-Vilnius line, the expansion of the LitPol Link connection, testing of emergency connection to continental European networks via the LitPol Link synchronous connection, optimisation of the North-East Lithuanian transmission network, testing of Lithuania’s isolated operation and installation of an automatic generation control (AGV) system.
The synchronisation projects implemented by the Baltic and Polish electricity transmission system operators are partly financed by the European Union through the Connecting Europe Facility.
Seven more synchronisation projects will be fully completed by the end of 2025. The NordBalt interconnection management system upgrade is scheduled to be finished in 2026, while the Harmony Link interconnection will be put into service in 2030 after switching from an offshore to an onshore solution.
On 8 February this year, the Baltic countries disconnected from the Russian-controlled IPS/UPS electricity system, and, on 9 February, successfully connected their electricity systems to the synchronous area of continental Europe. Synchronisation with the continent enables the Baltic countries to manage their electricity systems in close cooperation with other continental European countries, ensuring stable and reliable frequency regulation, thereby strengthening energy independence and increasing energy security throughout the region. The Baltic countries have joined the continental European network, which serves over 400 million consumers in 26 countries.