The Theiß thermal power plant, EVN AG’s largest and most powerful facility, has completed a major upgrade aimed at enhancing efficiency, sustainability, and reliability. Located in the Lower Austrian community of Theiß, the plant now operates with a cutting-edge generator circuit-breaker provided by Siemens, replacing a decades-old system that had reached the end of its service life.
Originally built in the early 1970s, the 800-megawatt power station has undergone numerous upgrades to keep pace with evolving energy demands. Primarily powered by natural gas, it plays a critical role in grid stabilization, especially when renewable sources like hydro and wind power fall short. In addition, it supplies district heating to the city of Krems and the municipality of Gebersdorf through Europe’s largest thermal storage tower. The plant also contributes reserve capacity to Germany’s electricity grid in the wake of the country’s nuclear phase-out.
Shift to Environmentally Friendly Technology
The latest modernization effort began in 2020 with the installation of a refurbished 240 MW gas turbine sourced from Norway. In 2024, EVN decided to replace the aging generator circuit-breaker originally installed in 1977. According to Gerhard Lemp, Head of Measurement and Control Technology at EVN-Wärmekraftwerke, the old switchgear had become increasingly difficult and costly to maintain. “Rising maintenance costs, declining availability, and limited spare part supplies made continued operation uneconomical,” said Lemp.
Following a public tender process, Siemens was awarded the contract to deliver, install, and commission the new system. The solution: the Siemens HB3 generator circuit-breaker, which does not use sulfur hexafluoride (SF₆), a greenhouse gas with a high global warming potential. Instead, the HB3 utilizes vacuum switching technology, which is both environmentally sustainable and nearly maintenance-free over its 20,000-cycle lifespan.
Designed for Retrofit, Built for Performance
“Vacuum circuit-breakers eliminate the contact erosion typical of SF₆-based systems, resulting in less wear and tear,” said Thomas Idinger, Sales Specialist for Electrification & Automation at Siemens. “This not only reduces maintenance requirements but also contributes to long-term operational efficiency.”
The HB3’s compact design was a decisive factor in its selection. Retrofitting aging power infrastructure often comes with two significant challenges: adapting to existing structural conditions and fitting within constrained spaces. “Thanks to its dimensions, the HB3 is an ideal retrofit solution,” Idinger noted.
To accommodate the unique layout of the Theiß plant, Siemens customized the HB3 unit. Modifications included direct mounting onto I-beams without the standard pedestal and the relocation of the control panel, which is typically attached directly to the breaker. Installation involved precision lifting with a telescopic crane to navigate the plant’s complex piping and structural components.
Turnkey Installation and Seamless Commissioning
The single-phase encapsulated breaker, weighing 1.44 metric tons per switching pole, was installed without significant structural changes to the facility. Idinger and Lemp confirmed that commissioning was completed smoothly, marking the end of a successful project.
“The new switchgear not only meets the highest standards for interrupting capability and operating speed, but also enhances protection for downstream systems,” said Lemp. “This ensures a high level of operational security.”
A Commitment to Sustainability
Beyond technical performance, EVN’s latest upgrade reflects a strong commitment to environmental responsibility. “Our decision to avoid SF₆-based systems is a clear signal of our dedication to climate protection,” Lemp stated. “The HB3 unit is a net-zero product, manufactured with CO₂-neutral processes. It demonstrates that high availability, efficiency, and sustainability can go hand in hand.”
As Austria and Europe continue transitioning toward greener energy systems, the Theiß power plant stands as a model of how legacy infrastructure can be modernized with forward-looking, climate-conscious technologies.
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