Swissgrid has begun drilling work on the underground extra-high-voltage cable link between the La Bâtiaz substation and Le Verney in Martigny.
The mini-tunnel boring machine, sporting the colours of Valais and of Switzerland, was christened with a female name, as is the tradition, in the presence of Ms Anne-Laure Couchepin Vouilloz, President of Martigny, at the Verney construction site on Friday 2 October 2020. Answering to the lovely name of Giorgia and weighing some 60 tons, the machine was lowered into the Verney shaft shortly afterwards.
It will take about eight months of work for the machine to drill and secure the 2.5-metre diameter tunnel with concrete pipes between Le Verney and the La Bâtiaz substation, at a depth of 12 to 20 metres. No workers will be present in the tunnel during drilling. The mini-tunnelling machine will be entirely controlled from the control station at the Verney site.
Two-year construction project
Construction of the La Bâtiaz - Le Verney underground cable link, which began in June 2020 with the digging of the Verney shaft, will take two years. The Bâtiaz shaft will be dug during the tunnelling work. The finishing work on the tunnel will then begin in the summer of 2021, followed by construction of the gantry that will connect the cable link to the 380 kV Chamoson - Romanel overhead line in Le Verney. The work will then be completed with the laying of cables in the tunnel. The 1.2-kilometre underground cable link is scheduled to be commissioned in 2022.
Nant de Drance power plant already connected to grid
Swissgrid is responsible for connecting the Nant de Drance power station to the electricity transmission grid. This facility will be one of the most powerful pumped storage power stations in Europe, producing around 2.5 billion kWh per year.
Two of the three sections of the Nant de Drance extra-high-voltage line – the 6.5 kilometres of underground cable link connecting the power station to the Châtelard substation via the station's access tunnel, and the 12.5 kilometres of overhead line connecting the Châtelard and La Bâtiaz substations – have been in service since the end of November 2018. Pending the commissioning of the third and final section, the Nant de Drance power plant has already been connected to the power grid via a temporary solution implemented in 2019 at the time of the voltage increase to 380 kV of one of the two La Bâtiaz - Le Rosel overhead lines.