Kassø-Frøslev: New electricity interconnector to Germany

A new 400 kV overhead line will replace a 220 kV overhead line from the transformer substation Kassø, located west of Aabenraa, to the Danish-German border by Frøslev. From this point on, the interconnection continues through Hadewitt by Flensburg and all the way to the area surrounding Hamburg. The interconnection increases the electricity trading capacity between Denmark and Germany.

Klick on the map to see the detailed routing 


The green transition of the electricity systems has resulted in the construction of a large number of wind turbines in Western Denmark and Northern Germany, as both are areas with favourable wind conditions. Consequently, a large share of the total electricity production is generated far away from major electricity consumers. This in turn creates a need to expand the power highways – the electricity transmission grid – in order to ensure that power generated by wind turbines is able to reach areas with large consumption of electricity and where the value of wind power is thus optimized.


The current infrastructure in the Danish-German electricity market limits trading capacity. The expansion on the Danish side of the border is part of a larger expansion project which enhances the grid that covers the area from South of Hamburg to the Southern part of Denmark.


Interconnection Capacity

The expansion of the interconnection will increase transmission capacity across the Danish-German border up to 2500 MW. Currently, it is possible to transmit 1500 MW in northbound direction, and 1780 MW  in southbound direction.

Important European Project

The expansion of the Danish-German high-voltage interconnection has been included on EU’s list of important infrastructure projects – so-called Projects of Common Interest (PCI) – which are deemed essential to the integration of the European electricity grids. As a result, the project has received EU funding.


Learn more about PCI.


Technical description

The project consists of:

  • Approximately 30 kilometres of a 400 kV double-circuit overhead line, which runs from Kassø substation,  located West of Aabenraa, to Frøslev. The overhead line will be attached to the same Eagle-type towers that are already in use between Kassø and Tjele, by the city of Viborg.

  • Expansion of Kassø transformer station with four new bays West of the current 400 kV facility.

  • Dismantling of the current 220 kV overhead line that runs from Kassø through Kliplev to the border. The current overhead line will be dismantled once the new 400 kV overhead line is commissioned in 2020

  • Dismantling of the current 220/150 kV overhead line between Ensted and Kliplev. Dismantling will commence no later than in 2025.


 Activity      When
 EIA and official approval  2015-2017
 Agreements with landowners and neighbours    2017-2018
 Construction work    2019-2020
 Removal of existing Towers  2021



Project information

Expected in operation