Nant de Drance pumped-storage power station

Autumn 2022 saw the grand opening of the Nant de Drance pumped-storage power station in Canton Valais following the completion of an intense 14-year construction project. The project included the upgrading of the Vieux Emosson dam and the creation of awe-inspiring caverns and tunnels in the mountain to extend the hydropower facility. With its impressive 900 megawatts (MW) output, Nant de Drance plays an important role in ensuring Switzerland’s electricity supply. Located deep underground, the facility is now protected by one of our fire alarm systems.

An underground marvel.

The beating heart of this pumped-storage power station is located 600 metres below the surface in a stately cavern between the Emosson and Vieux Emosson reservoirs in the municipality of Finhaut, Canton Valais. It comprises six pump turbines, each boasting an output of 150 MW. Thanks to their flexibility, these turbines can switch between pumping and power generation at full capacity in less than five minutes. The upper reservoir, Vieux Emosson, holds 25 million cubic metres of water, which equates to a storage capacity of 20 million kWh – enough to charge some 400,000 electric vehicle batteries.

Precise fire protection in the depths of the mountain.

We were tasked with implementing a comprehensive fire protection system for the facility. The key element is the proven SecuriFire Expert fire alarm system, which was specially developed for large-scale installations. Safeguarding the facility are 22 SecuriFire 3000 control panels, all interconnected via a fibre optic network. The complex rooms and the twelve defined extinguishing areas (two per pump turbine) are equipped with 924 SecuriStar MCD 573X multiple sensor detectors for early detection of smoke and fire. In addition, linear smoke detectors in the large cavern also react quickly to signs of smoke or fire. The system includes 165 MCP 545X manual call points for the raising of alarms by personnel. The safety of employees in the long underground tunnels is ensured by a personal tracker system, also designed and implemented by us, which facilitates precise localisation and rapid assistance in the event of an emergency.