DC links
In 2006, TenneT entered into construction of the 700 MW NorNed undersea HVDC submarine power cable with the Norwegian transmission operator Statnett. Commercial operation of the link was delayed by poor weather and a break in the cable, but it eventually entered operation on the night of 6 May 2008.[10] Connecting the Norwegian and Dutch grids at Feda and Eemshaven, the ±450 kV bipolar cable is, at 580 km, the longest undersea power line in the world.[11] During the first two months of test operations, it generated approximately €50 million in revenue, greatly exceeding estimates, and recovering 12% of its cost of construction.[12]
TenneT formed a joint venture with the British transmission operator National Grid to construct the 260 km 1,000 MW BritNed HVDC link between the Isle of Grain, Kent and Maasvlakte, near Rotterdam.[13] Operations began on 1 April 2011,[14][15] and as of January 2012, electricity flow has mostly been from the Netherlands to the UK.[16] The BritNed interconnection is seen as a vital link for the foreseeable European super grid project.
A 700 MW submarine power cable called COBRA (like NorNed, also from Eemshaven) to Denmark is operated with Energinet.dk[17] from 2019, signing contracts with Siemens and Prysmian in 2016.[18] Further 3½ GW offshore DC links are intended to provide a sea grid structure, and 6½ GW AC links are planned between Netherlands and Germany.[19]
Its subsidiary Transpower Stromübertragungs together with Statnett operates the 1400 MW NORD.LINK cable between Norway and Germany from 2020.[20]
TenneT builds the 2 GW SuedLink, an onshore DC link between Hamburg and south Germany (near Frankfurt), but local opposition means that a timeline is unclear.[21] Both SuedLink and NORD.LINK are on the EU "Projects of Common Interest" list, and SuedLink is supported by EU with €40 million.[22][23][24]
TenneT plans onshore AC upgrades in North Germany, connecting new wind power to some of the above DC links.[25]
Dogger Island
In 2016, TenneT suggested a 6 km2 artificial island in the Dutch corner of the Dogger Bank in the middle of the North Sea, connecting several GW of offshore wind farms with alternating current. Converters on the island would then transmit direct current to the countries around the North Sea in a more economic manner than if each wind farm had its own cable to the country building it.[26][27] TenneT called for feasibility studies in 2017,[28] and signed an agreement with Energinet.[29] The challenge of coordinating several DC links is studied by the Technical University of Denmark using the Kriegers Flak connector as an example.[30]
