KontiSkan

Project Overview

The Konti-Skan HVDC link is a HVDC system that connects the Swedish and Danish power grids, specifically linking the SE3 region in Sweden with the DK1 region in Denmark. It was the first interconnection between Sweden and western Denmark, designed to facilitate electricity exchange, enhance grid stability, and enable the export of surplus hydroelectric energy from the Nordic system to Denmark and Germany.

System Structure and Ownership

The Konti-Skan system is a bipolar HVDC link, consisting of two poles known as Konti-Skan 1 and Konti-Skan 2. It is owned and operated by Svenska Kraftnät in Sweden and Energinet in Denmark. The main converter stations are located at Vester Hassing in Denmark and Lindome in Sweden, with the original Swedish station for Pole 1 being Stenkullen. The system was engineered to span the Kattegatt sea, using a combination of overhead lines, submarine cables, and underground cables, with complex arrangements for electrode lines and grounding.

Konti-Skan 1: Technical Details

Konti-Skan 1, the first pole, was commissioned in 1965. It originally used mercury arc valves but was upgraded in 2006 with thyristor-based technology provided by GE/Alstom. The original rated power was 250 MW, which was later increased to 380 MW. The DC voltage was initially 250 kV and was later upgraded 285 kV. The transmission route for this pole includes 87 kilometers of submarine cable and 61 kilometers of overhead line. Notable technical milestones include the installation of a second-generation thyristor test valve in 1973, a light-triggered thyristor test valve in 1988, and the world’s first air-insulated outdoor thyristor valve in 1992 at Stenkullen.

Konti-Skan 2: Technical Details

Konti-Skan 2, the second pole, was commissioned in 1988 and was equipped with thyristor valves from the outset. It has a rated power of 300 MW and operates at a DC voltage of 285 to 300 kV, with an AC voltage of 400 kV at both ends. This pole also uses 87 kilometers of submarine cable and 61 kilometers of overhead line. Technical milestones associated with Konti-Skan 2 include the introduction of the first active DC filter in 1991 and the first electronically controlled AC filter, known as ConTune, in 1993, both at the Lindome station.

Converter Stations and Control Systems

Both converter stations have undergone significant upgrades, replacing mercury arc systems with modern thyristor valve technology. Key components of these stations include valve halls with H400 series valves from GE/Alstom, three-phase transformers, AC and DC harmonic filters, DC smoothing reactors, and cooling systems for both valves and transformers. The stations are equipped with fully digital control and protection systems, including SCADA integration, Series V digital control from GE, and later ABB/Hitachi MACH control systems for enhanced reliability and remote diagnostics.

The control and protection systems feature a redundant, fully digital architecture with automatic failover and remote monitoring capabilities. The latest upgrades introduced ABB Ability MACH and Hitachi Energy MACH Modular Advanced Control for HVDC, which provide advanced fault registration, remote control, and full system integration.

Reactive Power and Filtering

The system’s reactive power exchange is ±40 Mvar at the busbar, and the maximum filter rating is 65 Mvar. Automatic AC voltage control and operator-controlled reactive power exchange are standard features. The Konti-Skan link was the first in the world to use an active DC filter and an electronically controlled AC filter.

Key Technical Achievements

Throughout its history, Konti-Skan has achieved several technical firsts in HVDC technology. These include the first active DC filter and the first electronically controlled AC filter, both at Lindome, as well as the first air-insulated outdoor thyristor valve at Stenkullen. The project also pioneered the use of light-triggered thyristors and modular, air-insulated valve designs that incorporate composite insulators for fiber optics, cooling, and ventilation. Early adoption of fully digital, microprocessor-based control systems with remote diagnostics and upgradeability further set the project apart.

Future Developments

Looking ahead, both Konti-Skan 1 and 2 are scheduled for replacement by a new, modern HVDC link by 2036. The planned new link will have a transmission capacity of 1,000 MW. The project will involve new cables and converter stations between Lindome and Vester Hassing.