Under the contract, Nexans will supply, install and commission six 380kV XLPE-insulated underground cables, each approximately 5km in length, which will be laid in parallel in the project’s underground access tunnel. The cables, which will connect the new plant to the EHV power transmission grid, comprise copper core conductors with a cross-section of 1600mm².

The Limmern power station is being built as part of Linthal 2015 upgrade project – currently the largest hydro power and infrastructure project in the Swiss energy industry – in the canton of Glarus. The project provides for a comprehensive expansion of the KLL plants.

The main component of the project is the construction of the underground pumped storage plant between Limmern and Muttsee, above Linthal, thus increasing the performance of the KLL plants by 1000MW to 1460MW. The pumped storage plant is located at an altitude of about 1700m a.s.l. and is built around 600m inside the mountain. Four turbine-generator-sets with a capacity of 250MW each – supplied by alstom Hydro – will be installed in the power house cavern.

The project features an adjustable pump and turbine with a maximum output of 1000MW. It will pump water from the existing reservoir Limmernboden at 1860m asl. into the 600m higher Muttsee and in reverse will generate electricity during turbine operation mode. To accomplish the required output it is necessary to increase the Muttsee water level by 30m.

Starting at Tierfehd near the valley’s bottom a new access tunnel will be created for access to the powerhouse cavern. The tunnel will be equipped with a funicular railway.

Major works of the new hydro power plant started in January 2010, following extensive preparatory works which were completed in early summer 2008.

Other companies involved in the scheme include DSD Noell of Germany, who will design, supply and erect two penstocks, and ABB, who will provide the power station’s electrical equipment, including transformers, medium-voltage switchgears, and instrumentation and automation systems.