TEN Thüringer Energienetze GmbH & Co. KG is the largest distribution system operator (DSO) in the German state of Thuringia. The company is responsible for operating approximately 40,000 km of electricity and gas networks, supplying more than one million people as well as industrial and commercial customers across Thuringia and neighboring regions.

Driven by the energy transition, the continuous expansion of renewable energy generation, and increasing requirements for decentralization, electrification, and grid stability, ongoing investments in grid modernization and expansion are essential to ensure a future-ready network infrastructure. At the Frössen substation, an existing 8DB10 SF₆-insulated switchgear installation had to be expanded with additional switchgear panels while remaining in operation. Since a complete shutdown of the installation was not feasible, the integration of modern F-gas-free technology into the existing system had to be implemented within a tight project schedule while maintaining the highest level of supply reliability.

Extension of the existing medium-voltage switchgear with new 8DAB24 Clean Air insulated, F-gas-free switchgear panels, integrated step by step in two construction phases across both busbars.

Project scope

• Engineering, design, manufacturing, delivery, and installation of three F-gas-free 8DAB24 switchgear panels.
• Busbar modification work on both switchgear sections, including gas handling and testing activities.
• Creating of gas-tight transitions between the existing SF₆ technology and the new Clean Air technology.
• High-voltage and partial-discharge testing, commissioning, and final inspection.