The preparatory work for the Chamoson – Chippis VHV overhead line that started last January is nearing completion for the first two sections between Chalais and Sierre and Sion and Vex. The first foundations will be built in these sections by the end of August, and the first metal pylons will be erected in early 2019. The preparatory work for sections 3, 4 and 5 will also begin in the 1st quarter 2019.
As a reminder, the line's route has been divided into five sections in order to complete the work as quickly as possible and optimise the construction plan as much as possible:
- Section 1 - municipalities of Chalais, Chippis and Sierre
- Section 2 - municipalities of Sion and Vex
- Section 3 - municipalities of Sion and Grône
- Section 4 - municipalities of Nendaz and Sion
- Section 5 - municipalities of Chamoson, Ardon, Vétroz, Conthey and Sion.
Controlled construction even in natural hazard areas
The construction of a foundation consists of first digging a shaft in the staked-out position, then concreting it in successive layers and anchoring a metal base in the concrete. In natural hazard areas, special construction and monitoring measures will be implemented in collaboration with the cantonal geologist and geotechnical engineering offices. For example, inclination sensors capable of measuring any ground movement up to 25 metres deep will be installed. The foundations of the pylons will be reinforced and, if necessary, protected against falling rocks with metal mesh. Finally, the feet of certain pylons will be secured and interconnected by reinforced concrete beams.
Swissgrid manages more than 6,700 kilometres of VHV lines and 12,000 pylons throughout Switzerland. Many sections are located at high altitudes in mountainous areas on steep, rocky and difficult to access terrain. Swissgrid has mastered the art of installing and maintaining pylons in unstable zones.
To be commissioned in 2021
Commissioning of the line is scheduled for 2021. It will be followed by the dismantling of 90 km of overhead lines and 322 masts and pylons in the Rhone valley, as required by the specifications in the planning approval dossier. The removal of these various lines will reassure the inhabitants of villages crossed by the current 220 kV overhead line, among others. There will eventually be a reduction of 60 km of electrical overhead lines between Sierre and Martigny.
A necessary project
The completion of the Chamoson – Chippis 380 kV overhead line is essential for the transmission of energy produced by the Valais power plants – in particular the Nant de Drance pumped-storage power plant – to the consumption centres in the Lake Geneva region and on the Swiss plateau. It will eliminate one of the biggest congestion points of the Swiss electricity transmission network. The modernization of the transmission network is a key factor in moving towards the sustainable energy future required by the Confederation and the Swiss people through the Energy Strategy 2050. Other projects to reinforce and extend the Very High Voltage network in Valais are in the pipeline, notably the voltage transformation of the Chippis – Bickigen overhead line from 220 kV to 380 kV, as well as the Chippis – Mörel and Mörel – Ulrichen lines (Gommerleitung).
Initiative of the State Council of the Canton of Valais
The State Council of the Canton of Valais took the initiative to carry out new analyses with a view to moving some pylons in the Grône region, among other things. Swissgrid will bring its technical expertise. The potential future moving of the pylons can only take place after the commissioning of the line authorised by the Federal Court.