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On 10 January, Elering commissioned an essential component for maintaining the frequency of the electricity grid from the constructor – Estonia’s second synchronous condenser plant at Kiisa. Püssi synchronous condenser plant has already been completed in addition to the aforementioned plant. The third plant at Viru substation is expected to be completed this summer.

Siemens Energy, the subcontractor for Elering, began construction work on the synchronous condenser plant in May 2022. The first major pieces of equipment – the generator and the transformer – were installed in May 2023. Installation of various smaller pieces of equipment and general construction work related to buildings and installations took place throughout this period. Testing and final configuration of the equipment began in August, while acceptance testing was finished in November. A short-circuit test, comprising a part of the conformity assessment of the plant, was successfully conducted in December 2023.

The synchronous condensers represent an important addition to the electricity system, as they will allow the operator to maintain stability of frequency – the key parameter of any such system – even in critical circumstances. A synchronous condenser is a device that decelerates rapid changes in frequency upon a steep change in generation or consumption. The plants are not in continuous operation and are switched on when necessary as a precaution. The biggest and most important components of the synchronous condenser – the generator and the flywheel – weigh a total of nearly 350 tons.

Synchronous condensers are a part of critical importance in desynchronising from the Russian network and joining the frequency area of continental Europe. The completion of the synchronous condenser plants will be a major step forward in Estonia’s ability to maintain the stability of its electricity system after disconnecting from the Russian network.

The Latvian and Lithuanian system operators are also building three synchronous compensator plants, similarly to Estonia. The plant at Püssi was the first synchronous condenser plant to be completed in the Baltics in spring 2023. The total cost of this major project amounts to ca. 90 million euros in Estonia.

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