Electrical engineering for Emosson

The new Nant de Drance power station led to the construction of a new GIS 400kV extra-high voltage substation at the La Bâtiaz site near Martigny. The electricity production of the 2 Emosson generating units, installed in the neighbouring power station, was transferred to this new substation, while the existing 220 kV AIS will be completely dismantled. 

Emosson SA issued a call for tenders to carry out this work, in particular the engineering work for SIA phases 3, 4 and 5. HYDRO Exploitation was chosen for this major project on the strength of its electrical engineering expertise.

A six-year project

Work began with the construction of the transformer pits. After a number of postponements, installation work and primary equipping began on unit 2 in April 2023 and on unit 1 in September 2023. Each stage took around 11 weeks. The challenge was considerable. The key to the success of this complex project was meticulous planning and optimal preparation, close monitoring of the work on site, and close collaboration with the operator.

At the same time as this work was carried out, the secondary part of each unit was renewed and the new 400kV cable links were installed by Swissgrid.

The project in detail

• Procurement and installation of two new 400kV/11kV – 110MVA transformers
• Procurement and installation of two 11kV machine circuit breakers
• Procurement and installation of new 6300A busbars between the equipment
• Construction of two new retention pits for transformers
• Construction of fire walls between the transformers and the power station
• Coordination and integration of this new equipment with the power station and Swissgrid