A worker stands among several electric cables.

Sydvästlänken- The world’s longest and most powerful underground cable link

Assigned by ABB and Svenska Kraftnät NCC has built a 190 km long DC power cable between Hurva in Skåne and Barkeryd in Småland.

This is part of SydVästlänken, an extension to the main power grid, which is being built to increase the distribution of electricity to southern Sweden and improve the Swedish power grid's reliability. SydVästlänken has a total length of 430 km, consisting of both overhead and underground power lines. The DC power cable between the Hurva and Barkeryd is the world's longest and most powerful underground cable link.

The assignment included the transport, pulling out and installation of 4 parallel DC power cables that would be able to transmit 2 x 720 MW at a voltage of 300 kV. The power lines had to be ready in less than two years. Land availability, road building, excavation and cable installation were all handled simultaneously, in order to keep to the time schedule.

NCC developed several unique solutions to ensure production effectiveness and an improved logistics chain. Among other things, this included a specially-built trailer that could both load and unload itself. The dimensions of the trailer were optimised to fit the roads' width and height limits. As such, the cable drums, at 3m wide and 4.5m high, could be transported without an escort.

In order to avoid the time-consuming procedures of placing the cable drums using traditional reeling and placing equipment, we also developed special under-rollers which made it possible to loosen the cables and prepare to unreel them quickly. We also developed our own methodology for cable control. In all, these lead to significant time savings and a safer working environment where things like heavy lifts can be avoided.