380-kV high-voltage power line in Central Switzerland: Upgraded Rigi section goes ‘live’

On 28 November 2008 Atel Transmission Ltd. put into operation an upgraded section of the 380-kV high-voltage Lavorgo-Mettlen power line on the north flank of the Rigi. 28 pylons along the 8.5-kilometer long section were completely replaced between May and November.

Electricity has been flowing through the upgraded section of the key North-South axis of the Swiss transmission grid since 28 November 2008. Complete replacement of the pylons between Arth and Küssnacht am Rigi took seven months and cost CHF 15 million. Delivery problems experienced by the steelwork fabrication contractors caused a postponement of the go-live date from late October to late November. 35 or so riggers assembled the 28 pylons piece by piece. That involved inserting roughly a ton of bolts into each of the steel supports, which have an average height of 64 metres and together weigh 800 tons. With the supports in place, the riggers went on to sling 100 kilometres of conducting cable along their route. The aluminium alloy cable is 30 millimetres in diameter.

The overall upgrade became necessary due to heavy corrosion of the supports after 60 years in continuous service, and because the old pylons no longer met the stricter requirements imposed on high-voltage lines. The line axis remains unchanged. The new supports are somewhat taller than the old pylons, for two reasons: increased distance between the conducting cables and the ground/buildings affords greater protection against non-ionising radiation. And the higher pylons improve operational reliability of the 380-kV line.

Replacement of 28 pylons between Arth and Küssnacht am Rigi is part of the overall upgrade of the 380-kV power line between Amsteg and Mettlen. Plans for the renovation work were officially published in the spring of 2002. A construction permit was granted in March 2008. In the next few years it is planned to replace the pylons on a section of the line between Ingenbohl and Arth in the canton of Schwyz, as well as the section between Küssnacht am Rigi and Udligenswil in the canton of Lucerne. Atel launched the first phase in 1989, and in 2006 the company replaced a total of 17 supports between Sisikon and Ingenbohl.

Atel Transmission Ltd.