Green electricity from Norway

NordLink was initiated around eleven years ago. “At that time we had a critical situation here in Norway,” says Stein Håvard Auno, then Project Director for NordLink at Statnett, the state operator of the Norwegian power system. “We had hardly any rain fall in autumn, and the reservoirs were nearly empty in the winter. We needed to import electricity from coal and nuclear power, which caused the energy prices to rise. In that way NordLink is important to Norway's energy security. It helps us keep our electricity prices stable even during dry seasons. And, as NordLink is a “green” cable, our energy mix is becoming more sustainable. In this way, we are making an important contribution to the energy transition in Europe.”

Supply security, stable prices, a faster energy transition – this triad also applies at the other end of the 623-kilometre-long double cable made of positively and negatively poled cables. The counterpart to the substation in Tonstad is in Schleswig-Holstein in the town of Nortorf near Wilster. Converters manufactured by ABB, which convert the alternating current obtained into low-loss direct current for transporting it through the cable and change it back into alternating current at the end, are at the heart of the two substations which count among the most powerful substations in the world. Around three metres above the ground of the converter facility, the silver valves hang on steel cables like precious shrines. They contain the newest generation of a technology that experts call VSCHVDC: high-voltage direct current power transmission in self-commuted power converters.

Read more under the illustration.

On the German side, the power grid is maintained by the Dutch-German electricity grid operator TenneT, says Gunnar Spengel who at the time was the Project Manager for NordLink. “NordLink connects two renewable energy sources that optimally supplement each other,” Spengel says. “Depending on the market situation, a surplus of wind energy can be exported to Norway. Or, if the wind calms in Germany, we can import hydropower from Norway. NordLink thus contributes to reciprocal supply security.” However, Spengel goes on to say, the direction the electricity flows is largely determined by the electricity market. It can be assumed that the exporting party is the one with the cheaper price at the time.

“There is a lot of pressure on the project, to be sure, because this is the first time we are doing some things in these dimensions and there is a lot of attention on us,” says Gerd-Wolf Balk, then Senior Vice President at NKT. “But I feel good about working on a future-oriented project, on a new generation of energy and energy transmission. Also, our cables symbolise that our future will only be a success if we work towards it together.”

850 people work at NKT in Karlskrona, half of them in cable manufacturing. Per shift 25 people were involved in around-the-clock production for the NordLink cable. From the summer of 2016 until February 2019, 208 kilometres of the mass-impregnated 525-kilovolt cable was produced. 54 kilometres of it are in the ground in Northern Germany, 154 kilometres are underwater in Germany's territorial waters; Nexans laid an additional 362 kilometres in the Danish and Norwegian parts of the North Sea.

NKT Management needed to obtain many more approvals for the land route than the sea route. In Schleswig-Holstein, the interests of nearly 100 affected parties needed to be taken into account between the landing in Büsum and the substation in Nortorf, and countless authorities needed to be consulted. Laying the cable in the sea, which was associated with environmental requirements, only required one permit.

On the other hand, the underwater cable was more difficult to lay. Once the Norwegian part in the open sea was completed by the Nexans special ship, Skagerrak, NKT relied on their ship, the NKT Victoria, Offshore Construction Manager Tony Collins and a team of 75 experts. Everything on board of both ships is designed with the only intention to lay submarine cable. The most important aspect: the ships must be able to maintain their positions to minimise straining forces even in rough seas.

The NKT Victoria transported two NordLink sections measuring 60 kilometres each from Karlskrona in its slowly rotating cable carousel, cautiously lowering the cable over the curved stern into the water. The laying takes place at a very low speed of less than half a knot (about 0.9 km/h) - depending on weather and current conditions. The greatest risk to the power connection on the bottom of the North Sea is anchors and otter trawls. So the sea floor of the NordLink corridor, which is made up of sand and clay and has a maximum depth of 410 metres, was flushed out by around one and a half metres. Five crossings with cable running from East to West also needed to be protected.

Published on KfW Stories: 8 September 2020, last updated: 6 June 2022.