The HVDC Visby–Näs is a bipolar HVDC electric power transmission system between Visby and a wind power centre near Näs on Gotland, Sweden. The project went into service in 1999. The system operates at 80 kV with a maximum power of 50 megawatts. This HVDC system allows for voltage regulation in the connected AC systems.
Because obtaining a right-of-way for an overhead line is a lengthy and expensive procedure, the 70 kilometer line is constructed as an underground cable. Since an alternating current three-phase underground cable would have been more expensive, the HVDC system was selected for this project.
References
HVDC Visby–Näs Wikipedia(Text) CC BY-SA