HYDRO
AXPO TRUSTS IN THE SOLID POWER UNIT OF THE CURNERA CAVERN HYDROPOWER PLANT For many years, the hydraulic pressure in the works water conduit between the Curnera and Nalps reservoirs in Grisons in Switzerland had to be lowered via a pressure reduction regulator. The installation of a new Curnera hydroelectric unit 250 metres into the mountain now enables this hydroelectric potential to be exploited. To this end, the Vorderrhein KVR power generation group, of which Axpo has a majority holding, integrated a WWS Francis spiral turbine to drive a high-power, high-quality generator manufactured by Hitzinger in Linz. In a regular year this reliable combination of machines guarantees the production of around 10 GWh - enough to supply approximately 3.000 average housholds with green electricity.
Foto: Glanzer
The 2.5 MVA Hitzinger generator has been installed in the old vane chamber.
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photo credits: KVR
T
he works water is transported through a complex 3.7-kilometre system of pipes owned by the Vorderrhein power generation group – from the upper ‘Curnera’ reservoir down to the lower ‘Nalps’ reservoir and navigating a drop of 40 – 75 metres. In 2016, KVR devised a new concept to exploit this previously untapped energy potential. The new small-scale hydropower system was installed in the vane chamber that originally also housed a pressure regulator. The Axpo project team, responsible for operation of the plant cascade, faced several tough challenges, not least those caused by the extremely cramped working conditions and restricted cavern accessibility at around 2,000 metres above sea level – and particularly the logistics of bringing in the components for the power plant infrastructure. Ultimately, a temporary cable car relay had to be set up for the purpose. An electrically- powered towing unit and a carriage wagon were installed to manoeuvre the 6-ton generator into the tunnel via the cavern opening. The extremely limited space available in the vane chamber 250 metres into the mountain made installing the individual parts of the machine very challenging. However, despite all difficulties, work was completed without any hitches.
UPPER AUSTRIAN TECHNOLOGY BEATS AT THE CORE After commencement of installation in the narrow window afforded last summer, the plant went into trial operation in November 2021, and in the same year was put into regular service. The small cavern now houses a Francis spiral turbine manufactured by WWS and built for a nominal power output of 2.5 MW. As well as the turbines, the new generator at the Grisons power plant was also produced in Upper Austria. The rotor of Hitzinger’s synchronous generator is also directly connected to the turbine runner. Set up for 900 V, the generator achieves a power output
of 2.5 MVA and the rotor turns at 750 rpm. In an average year, the new Upper Austrian machine group can be expected to deliver 10 GWh of green electricity to the grid. DESIGNED FOR A LONG LIFE The operating company boasts a wealth of experience across the entire spectrum of hydropower projects, from small to large, and quality was its number one priority when choosing this machinery. After all, KVR invested around 3 million CHF in a small-scale hydropower plant that needs to be as self-sufficient and maintenance-free as possible due to its extreme inaccessibility. The choice of
May 2022
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