It took the HYDRO teams three winters to completely renew the Zmutt high-voltage substation, which supplies the largest pumping station in Grande Dixence, nearly 60 years after it was first commissioned.

Grande Dixence SA hired HYDRO Exploitation to study and realise the complete servicing of the high-voltage (HV) substations of the Grande Dixence facility’s pumping stations. Given that the Zmutt station in the Zermatt valley feeds the biggest pumping station in Grande Dixence, this assignment was of paramount importance. 

Reducing the impact of the work on the plant’s operational availability

Zmutt’s 130kV switching station was commissioned in 1965. The equipment was at the end of its service life. That is why HYDRO Exploitation initially looked at different possibilities for renewing the elements before submitting a work schedule spread over three winters to minimise the impact of the renovations on the plant’s operational availability. 

The switching station has three areas dedicated to the units and internal services, plus three line areas. The facility is powered by two 130 kV overhead lines originating from the Stalden switching station. It powers the Stafel pumping station via a 130 kV overhead line.

Once the contractor had decided to completely renew the station’s elements, HYDRO Exploitation carried the necessary studies and sent out tenders for acquiring, installing, and commissioning the equipment, as well as for the overall management of the project and the local management of the work on site.

Work carried out
  • Replacement of the line breakers and busbars
  • Replacement of the 130 kV switches
  • Replacement of the measuring units, lightning arresters and cables
  • Adaptation of the supports, reinforcement of the base plates and adaptations to comply with the seismic standards of ESTI
  • Control-command lines replaced in full, our workshops in Martigny produced the cabinets
HYDRO Exploitation SA
Rue de l’Industrie 10
CP 315 - CH-1951 Sion
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HYDRO Exploitation SA
Rue de l’Industrie 10 CP 750 - CH-1951 Sion +41 (0)27 328 44 11
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