A new overhead transmission line is needed in order to secure the quality of supply in Denmark. Denmark puts a great effort into reducing CO2 emissions by expanding the production capacity based on renewable energy. Consequently, a more flexible electricity grid is needed to be able to transport the power from the offshore wind parks to the consumers as well as increasing the transmission capacity between international markets.
The overhead transmission line from Kassø in the southern part of Jutland to Tjele in the Northern part (172 km) is the backbone of the 400kV grid and plays an important role as a backbone transmission line. The capacity is increased in the new line to 3.6 GW.
In order to get the permission to build the new line, a new design with a smaller impact on the landscape has been developed. The design is more slender than the traditional lattice towers – with an increase in the steel amount per tower as a consequence.
Design of towers
Traditionally, overhead transmission line towers have been produced from steel. However, the layout of lattice towers is not popular in the public. Since towers with a cylindrical shaft give a more calm impression, these towers are more acceptable. This implies an increase in the required amount of steel to approximately 2½ times the amount used for traditional lattice towers.
Furthermore monopiles of steel are the optimal solution for the suspension towers of the Eagle type since the width of the tower is limited in the bottom.
Design of foundations
Two different foundations have been designed for the towers:
- Concrete plate foundation
- Monopile foundation
For the suspension towers the monopiles have proven to be superior to the concrete plate foundation for several reasons:
- Fast installation
- No groundwater problems
- Have a smaller impact on the environment than plate foundations
- More economical