NorNed

The NorNed HVDC project is a significant submarine power cable system connecting Norway and the Netherlands. Completed in 2008, it spans 580 kilometers across the North Sea, making it one of the longest undersea high-voltage cables in the world at the time of its construction.

Technical Specifications

The NorNed link is a bipolar HVDC system with a transmission capacity of 700 MW and a voltage rating of ±450 kV DC. The cable utilizes mass-impregnated (MI) technology, which is non-draining and paper-insulated. The project employs two different cable designs: twin-core and single-core, both featuring copper conductors and a layer of semi-conducting carbon paper.

The main circuit configuration is made up of a single 12-pulse converter with a midpoint earth and a DC voltage of +/-450kV. The transmission voltage allows for low cable current and reduced losses. The connection has an efficiency of 95.8%, with losses amounting to 4.2%.

Infrastructure

The two HVDC converter stations are located at Feda in Norway and Eemshaven in the Netherlands. The Feda station connects to a 300 kV AIS substation, while the Eemshaven station links to a 380 kV GIS substation via cables.

The cable route presents various challenges, including trenched land cables in the Netherlands, submarine cables in tidal flats, long stretches of flat sea bottom with boulder fields, the Norwegian trench with depths up to 400 meters, and steep tunnels in Norway.

Project Development and Cost

The NorNed project was a joint venture between TenneT, the Dutch transmission system operator, and Statnett, its Norwegian counterpart. Initially budgeted at €550 million, the final cost reached approximately €600 million. Construction began in 2006, with the first sections installed in early 2006 and the final section laid by the end of 2007.

Economic and Environmental Impact

The NorNed interconnector facilitates power trading between Norway and the Netherlands. It allows Norway, which relies heavily on hydropower, to secure its energy supply by importing thermal power during periods of low water levels. Conversely, during years with high precipitation, Norway can export power to the Netherlands.

This power exchange contributes to a more stable and efficient energy market in both countries. The project reduced carbon dioxide emissions by an estimated 1.7 million tonnes annually, aligning with European Union goals for an integrated and sustainable energy market.

Operational History

Commercial operations commenced on May 5, 2008, with a capacity auction, followed by the first commercial power transfer on May 6, 2008. Within the first two months of operation, the cable generated revenues of about €50 million, surpassing initial annual revenue estimates of €64 million.

The NorNed link has faced some operational challenges. In 2011, a fault caused a seven-week outage. In May 2022, another fault led to a suspension of operations, with resumption in October 2022. More recently, in May 2024, a cable fault caused another outage until October 2024 when service was resumed, albeit at a reduced capacity of 620 MW to minimize stress on the cable.

Market Integration

NorNed was a pioneering connection between the Nordic electrical transmission system (Nordel) and the continental European grid. It operates primarily through day-ahead spot market trading, capitalizing on price differences between the two markets. The net income from this trade is equally shared between TenneT and Statnett.