Half a century on from the world’s first installation of HVDC technology and another landmark is on the horizon. This time a more flexible European energy network will be established by the installation of the world’s longest subsea HVDC connection.

Robin Rowshangohar, Assistant Editor

cottish economist and philosopher Adam Smith once wrote: “Whether the advantages which one country has over another be natural or acquired is in this respect of no consequence. As long as the one country has those advantages and the other wants them, it will always be more advantageous for the latter to buy of the former than to make.”

This passage featured in Smith’s The Wealth of Nations, which was first published in 1776 and went on to become one of the works that acted as a foundation for the liberal trade era that marked the 19th Century.

Two hundred and thirty years later and his words still ring true as Europe continues with its plan to develop a far-reaching, stable and multi-purpose electricity transmission network.

In December 2004, plans were approved for the creation of a submarine High Voltage Direct Current (HVDC) link that would connect the power markets of Norway and the Netherlands. When completed in December 2007, those involved with the 580 km project will be able to proudly boast that they were involved in the creation of the longest underwater high voltage electricity link in the world. The so-called NorNed project will set new benchmarks for the 50 year-old HVDC industry by more than doubling in size the existing length leader.

Project purpose

Few will disagree that while European countries have relatively strong national grids, they are in many places weakly interconnected. This is affecting the ease of trading and the ability to deliver a reliable energy supply, two issues that are becoming increasingly important in the modern European climate as nations strive to lower emissions, enhance fuel supplies and draw from a more varied generation mix.

According to the project’s director, Jan Erik Skog, state owned utilities, TenneT of the Netherlands and Statnett of Norway, have developed NorNed because of these very fundamentals and he points out where the concept started: “The project is motivated by the large variation of Norwegian power supply.”

Figure 1. The HVDC link will span 580 km from Freda in Norway to Eemshaven in the Netherlands
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Norway is almost entirely dependent on hydropower for its energy needs whereas the Netherlands has an abundance of thermal capacity. While hydropower is low cost to produce, it is vulnerable to rainfall fluctuations. And while thermal power is reliable it is, for a variety of reasons, becoming increasingly more expensive to produce. The idea was therefore a simple one. For Norway and the Netherlands to share the benefits and burdens of each other’s market and to develop a more flexible grid for the rest of Europe.

Technical leap

Once the concept had been decided upon, the solution had to be selected. That solution was provided by ABB which assured the project developers that its HVDC technology would mean transmission losses of just 3.7 per cent, half that of alternative solutions. Under a contract worth $270 million, ABB will provide a link between a substation in Freda, Norway and a substation in Eemshaven in the Netherlands. It will have a 600 MW rating, but yet will be able to continuously deliver 700 MW of power between the two grids.

“Why HVDC? There is no other option”, says Statnett’s Skog, “AC cannot take power over that distance. AC’s technical limit is 100 km, before losses begin to grow to unacceptable levels. HVDC provides a robust and rational, safe and reliable solution.”

The length of the NorNed link would not only provide AC technology with problems, but it would be a challenge to any HVDC producer, given that the longest subsea HVDC connection in the world at the moment is the SwePol link, spanning 245 km. This is a challenge ABB takes on with a look over its shoulder. Bo Nomark, director of marketing ABB’s HVDC technology globally, surmises: “The biggest challenge is the sheer size of the project. A total of 3000 km of this cable has been installed world-wide in the 50 years since it emerged as a product. ABB is to install 20 per cent of that amount in a single project.”

Figure 2. Equipment for the project is currently being manufactured
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Nexans is also involved with the link and will provide deep sea and shallow water cables after it was awarded a €50 million ($61 million) contract. Two 156 km deep water NOVA-L cables will be supplied, each with a rating of 450 kV and measurements of 1 x 700 mm2 Cu. The NOVA-L is an HVDC cable with mass impregnated paper insulation, lead alloy sheath, inner polythene sheath, reinforcement of galvanized steel tapes and armoury of two layers of galvanized steel wires applied in opposite direction and outer casing of polypropylene yarn with bitumen. The cable it will supply to bring the link ashore is the NODE-L 450 kV, which has a similar make-up to the deep-sea cable; only its dimensions are slightly larger at 1 x 760 mm2 Cu. Over 200 km of the cable has already been produced. When completed, the total cable for the project is expected to weigh 40 000 t.

The 580 km long NorNed will be made up of two separate cables bound together in the factory and it will use only one converter, combining low cost and low losses with elimination of electrodes. According to Nomark, the converters will be a “traditional design, similar to many others.” However, instead of using 0 to 450 kV they will use a midpoint grounded 12 pulse converter for +450 kV to -450 kV, and that will act like a 900 kV converter with request to losses for the transmission.

Construction began on the project in January 2005 and it is only really the cable being produced that will stop it being installed tomorrow. A company named Tideway B.V from the Netherlands has the main contract for the marine works and it has formed a joint venture with Submarine Cable & Pipe GmbH & Co KG from Germany for the laying works. Nomark expects the laying to be straightforward, and is confident that after it is laid in one go, it will be operational in time to welcome in 2008.

Benefits beyond

Norway and the Netherlands will not only have a physical power connection in 2008, but they will also have a trading connection after both countries agreed to couple their power exchanges and use the NorNed link as an open interconnection. New trading possibilities will create the potential for lower, more stable prices and an increase in security of supply due to the increase in market size, a decrease in concentration and a more diverse energy generation mix.

Although contract details are still being negotiated between the Dutch (APX) and Nordic (Nordpool) power exchanges, the deal has been agreed in principle, and Statnett’s chairman of the board cannot wait to enjoy the benefits: “Norwegian and Dutch power markets complement each other extremely well, and in terms of security of supply, it is particularly fortunate that Statnett and TenneT have now been authorized to exchange electric power between Norway and the Netherlands.”

The link’s developers have stated that it will always operate simply so that power is delivered from a lower cost area to a higher cost area. This will mean trading possibilities not only from seasonal shifts, but from daily patterns too, as Norway is most likely to export power during the day and import it at night.

Figure 3. NorNed will be commissioned in 2008
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A study commissioned by TenneT concluded that the economic value of investing in an interconnection with Norway far outweighed the benefits that expanding the countries’ existing interconnections and building additional varied capacity would bring. The project is estimated to cost €600 million, split equally between the two utilities, and if this cost were equated to the current cost of CO2 emissions under the EU’s Emissions Trading Scheme, it would be a maximum of 12 years before the project had paid for itself. The project is expected to bring a reduction of 1.7 million t of CO2 per year, saving around €50 million in today’s market.

It has been just over 50 years since the first installation of HVDC technology connected a Swedish island to the mainland. Another landmark in the lifespan of this technology again has associations with Scandinavia and importantly it will again prove that it can offer a new dimension to a contemporary energy market.

Originally planned to enter operation in 2001, NorNed was delayed due to the restructuring and liberalizing of the Dutch power industry, which meant that agreements that were in place had to be renegotiated. “It is difficult to work with changing framework,” Skog says when asked what caused the problems. This sums up exactly what the project is trying to achieve. It is aiming to simplify. ‘I need some more power? I’ll buy some from you.’ ‘Mine is more expensive? I’ll buy some that is cheaper from you.’ The result? A functioning liberal market that 230 years ago, not even Adam Smith could have predicted.