Much of the current transmission grid in Norway is too weak to meet future needs for secure electricity supply.
An important step towards the next-generation main grid is to increase the grid voltage from 300 to 420 kV, referred to as a voltage upgrade. This will be done by converting existing 300 kV power lines and substations, or by replacing old low-capacity lines with new ones. In this way, the capacity of each line can be increased, with very limited reservation of new land.
In this project, Statnett will make minor changes to the pylons by extending the insulator chains in the pylons in addition to making changes in the substations in Nedre Røssåga and in Tunnsjødal. Statnett is also planning to make minor changes in the substation in Trofors. Statnett views the upgrade as a technically sound and environmentally friendly solution that will renew the grid, increase capacity and reduce losses with little impact on the landscape.
After it was granted a licence, Statnett upgraded most of the pylons between Nedre Røssåga and Tunnsjødal in 2011. Fifteen pylons remain on the section. The remaining 23 pylons with suspension strings between Namsskogan and Tunnsjødal are scheduled to be upgraded to 420 kV. On a 13-km section between Sandådalen and Nerfjellet in Namsskogan Municipality there are plans to build a new 420 kV power line in parallel with the existing 300 kV power line, which will then be demolished. This is being done to establish 420 kV voltage between Nedre Røssåga and Namsos without rebuilding switching facilities in Kolsvik and Namsskogan. The line between Kolsvik and Namsskogan (101 pylons) is scheduled for a voltage upgrade. The same applies to 168 pylons on the section between Tunnsjødal and Namsos.
There are plans to expand the substations in Nedre Røssåga and Tunnsjødal with several additional fields and be upgraded to 420 kV voltage, and minor upgrades/adjustments are planned for the Trofors substation.
The overall objectives of this power upgrade project are:
- Facilitate renewable production in Central Norway and Nordland, as well as help meet Norway's international climate commitments.
- Part of Statnett's long-term plan to upgrade the 300 kV power lines to 420 kV.
- Provide flexibility for future development of the consumption and production of electricity, and safeguard the security of supply in the region in the long term.