Series compensation is an innovative technology that significantly increases voltage stability in transmission systems. The Dutch-German transmission system operator (TSO) TenneT is constructing Germany’s first series compensation system in the Stadorf substation in the Lüneburger Heath. From 2023, this will prevent grid bottlenecks in the German state of Lower Saxony. On 15 July 2020, the future heart of the upgraded substation reached Stadorf after an intricate transport by ship, rail and road and was placed on its foundation: a direct-coupling transformer with a transport weight of 528 tonnes.
The TSCNET shareholder supplies large areas of the eastern part of Lower Saxony with electricity via the Stadorf substation. Due to the energy transition and the corresponding transmission of wind power from the north of Germany to the consumption centres in the south, the substation will assume a supra-regional and important function in the future. For this purpose, Stadorf is being comprehensively modernised and extended by a so-called Thyristor Controlled Series Capacitor (TCSC) facility, the first of its kind in Germany.
TCSC allows a fast-dynamic modulation of the inserted reactance and in this case specifically to relieve persistently overloaded lines and redirect load flows. The new direct coupling transformer with a transmission capacity of 300MVA connects the 380kV lines of TenneT with the 110kV lines of the regional distribution system operator (DSO). It provides load flow in both directions, so that locally generated surplus green electricity can be transferred if required. As a result of the substation upgrade with TCSC equipment, the disconnection of wind turbines, regulatory intervention in the grid, and the associated costs will be reduced – and overall system security increased. TenneT anticipates annual savings in the double-digit million euro range.