Foundation laid for DolWin6 converter

28.05.2020

With a dozen operating offshore connection systems for wind farms in the German North Sea totalling a transmission capacity of 7.132GW, the Dutch-German transmission system operator (TSO) TenneT has already in 2019 exceeded the German government’s expansion target for offshore wind energy capacity for 2020 by more than half a million GW. A further 900MW will be provided by DolWin6, like the predecessor projects DolWin3 and BorWin3 a high-voltage direct current (HVDC) connection. The DolWin kappa offshore platform in the Wadden Sea near the island of Norderney will convert the three-phase wind current into DC for transmission via a 45 kilometre submarine cable to the East Frisian mainland and from the landing point via an underground cable, also around 45 kilometres long, to the TenneT site in Emden/East.

Here, the TSCNET shareholder is constructing the DolWin6 onshore converter station and a substation on 23,500m² to reconvert the DC into three-phase current for feeding into the onshore extra-high voltage grid. A significant milestone for DolWin6 was reached on 27 May: The laying of the foundation at the converter construction site was celebrated in Emden/East by embedding a time capsule with coins, a regional daily newspaper, and construction plans into the foundation stone. Due to the Covid-19 pandemic, the event was only celebrated with the most important project managers from TenneT and the plant constructor Siemens.

Concrete preparations for DolWin6 began in the summer of 2017 and 2018 with horizontal drilling on Norderney. In September 2019, the foundation work commenced in Emden/East. Work on the DolWin kappa offshore platform at a dockyard in Cádiz/Andalusia also started in mid-2019 and the DolWin6 cable laying will follow from summer this year. The completion of the HVDC offshore connection is scheduled for 2023.

TenneT celebrated the laying of the foundation stone for the DolWin6 converter in Emden/East (picture: TenneT)

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TenneT develops 525kV HVDC offshore cable system

20.04.2020

In just 10 years, 40% of the Dutch electricity demand will be covered by offshore wind power. Furthermore, the Dutch-German transmission system operator (TSO) TenneT will increase the German offshore grid connection capacity to 17GW by 2030. To meet these high ambitions, the TSCNET shareholder expands its current connection plans and additionally intends to implement a total of five 2GW offshore connections in the Dutch IJmuiden Ver wind energy area and in the German LanWin and BalWin areas. However, since such 2GW offshore grid connections do not yet exist, innovative project development is necessary.

The integration of 2GW offshore grid connections into the onshore grid requires a suitable certified cable system that operates at a voltage level of 525kV DC using extruded insulation types. TenneT has contracted a total of eight cable suppliers to develop these “next-level” submarine cables for the intended high-performance offshore connections. An extruded 525kV high voltage direct current (HVDC) cable system with a 2GW output is currently not implemented in any project worldwide and would thus set a new standard for the connection of offshore wind farms.

The new cable system is expected to reduce manufacturing and installation costs for the entire connection concept, including the HVDC offshore and onshore transformer stations. A reduction in dredging costs is also anticipated, as all cables can be laid in a single trench. Moreover, fewer offshore platforms and shore stations are required, resulting in lower emissions and environmental impact. The adoption of a 525kV 2GW grid concept is a logical step for TenneT after the installation of eight standard AC connections in the Netherlands. The TSO can already draw on extensive experience with DC projects in Germany.

TenneT has contracted eight cable suppliers to develop a 525kV HVDC offshore cable system with a 2GW capacity (exemplary picture of Riffgat cables: TenneT)

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Deep Dig-It trencher at work for TenneT

09.03.2020

The Hollandse Kust (South) offshore wind area in the Dutch North Sea is located 22 kilometres off the coast of the Dutch province of Zuid-Holland. TSCNET shareholder TenneT is responsible for connecting the wind farms under construction there via two corresponding offshore platforms to the onshore high-voltage substation in the industry and port area of Maasvlakte, from where the green electricity is transmitted further to the Randstad 380kV South Ring power line in the Dutch Randstad region, the most densely populated area in Europe, and further.

But there is a major challenge to be met by the Dutch-German transmission system operator (TSO): On the first ten kilometres of the offshore route, the four submarine cables to be laid are crossing the entrance to Europe’s busiest cargo port, the port of Rotterdam. To pass through the busy Rotterdam-Maasmond shipping lane, the cables here must be buried more than 5 metres deep into the seabed. For this specific job, the Dutch maritime contracting company Van Oord designed and built the Deep Dig-It trencher, a gigantic remote-controlled trencher.

Last Friday, final tests were carried out in the Aleksiahaven of Maasvlakte in preparation for the actual laying of the submarine cables in July. The innovative device is a so-called Tracked Remotely Operated Vehicle, which drives unmanned over the seabed, creates a deep trench for the cables, inserts the cables and closes the trench again. The Deep Dig-It is the largest and most powerful machine in its class. The trencher weighs 125 tonnes, is more than 17 metres long, well over 8 metres high and 11 metres wide. This makes it possible to bury cables in very hard ground, while the burial depth that can be achieved with the Deep Dig-It is well over 5 metres.

TenneT employs the powerful Deep Dig-It trencher to connect the Hollandse Kust (South) wind farms to the onshore grid (picture: Van Oord nv)

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COBRAcable proves to be a great success

06.03.2020

It is now half a year since TSCNET customer Energinet, the transmission system operator (TSO) from Denmark, and TSCNET shareholder TenneT, the Dutch-German TSO, made COBRAcable available to the market. The high-voltage DC cable with a length of about 325km and a capacity of 700MW is the first direct connection between the electricity markets of Denmark and the Netherlands. The basic idea behind COBRAcable is to compensate for the volatility of wind power. Consequently, the Netherlands imports electricity via the cable on days with large Danish wind power generation, while on days with little wind in Denmark the electricity is transported in the opposite direction.

This works perfectly, as the interconnector’s transmission data from the first six-month period prove: In total, Denmark has imported almost 700GWh via the COBRAcable and the Netherlands almost 1,400GWh. On average, COBRAcable was operated at full capacity 79% of the time during the last half year. The impressive traffic on this binational connection proves its adequacy through its operation. The new interconnector therefore substantially contributes to the energy transition by exchanging volatile renewable energy across borders and additionally creates a trading profit on the spot market for electricity – a multiple benefit for nature, society and the companies involved.

The transmission data from the COBRAcable of Energinet and TenneT confirm a high level of traffic on the line (picture: screenshot taken from Energinet-video “Constructing the green COBRAcable”, Vimeo)

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Ostwind 1 in regular operation

14.02.2020

In April 2019, the Arkona wind farm in the “Westlich Adlergrund” cluster in the Baltic Sea near the German island of Rügen was commisioned, giving the go-ahead for full operation of the Ostwind 1 grid connection of TSCNET shareholder 50Hertz, the transmission system operator (TSO) from northeast Germany. Ostwind 1 is the first grid connection in the Baltic Sea with 220kV three-phase current technology, which enables a higher transmission capacity.

Now Ostwind 1 has gone into regular operation and the two connected wind farms, besides Arkona also the Viking wind farm, have been successfully connected to the onshore grid on schedule. But 50Hertz considers this success no cause to rest on its laurels, for the expansion of offshore wind energy must continue if the energy transition is to succeed. This is why the TSO has already made good progress with the follow-up project Ostwind 2.

For instance, 50Hertz has long since begun preparations for the construction of three submarine cable systems for the Ostwind 2 project. For the land section, the 12 nautical mile zone of Mecklenburg-Western Pomerania and an approximately 5km-long section in the exclusive economic zone, the building permits have already been issued. 50Hertz has set up a new website for the Ostwind 2 project, where further information can be found.

Ostwind 1 grid connection of 50Hertz in the Baltic Sea has gone into regular operation (picture of Arkona wind farm: Ein Dahmer / CC BY-SA 4.0)

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Borssele Alpha ready to operate

05.09.2019

Just one month ago, TSCNET shareholder TenneT fully implemented BorWin3 in the German Bight, the twelfth offshore grid connection project of the Dutch-German transmission system operator (TSO). Now there is once again good news for the energy transition, this time from the Dutch North Sea: Borssele Alpha, TenneT’s first and largest connection system for wind farms in Dutch territorial waters, is ready for operation – right on schedule and within budget. From 2020 on, Borssele Alpha will supply the green electricity from the offshore wind farms Borssele I and II ashore.

The two Borssele wind farms will have a capacity of around 700MW. The Borssele Alpha grid connection will transmit the electricity to the substation near the town of Borssele in the Dutch province of Zeeland, where TenneT has built a new transformer station next to the existing station. The Borssele grid connection is TenneT’s first Dutch major project under the National Energy Agreement for offshore wind farms and fully complies with the conditions set out in the Dutch government’s Offshore Wind Energy Development Framework.

According to the Energy Agreement, TenneT will have installed 3,500MW of grid connections for offshore wind farms by the end of 2023. The next project is Borssele Beta, followed by Hollandse Kust (zuid) Alpha and Beta and Hollandse Kust (noord). TenneT’s standardised procedure for offshore connections will make it possible to complete these projects more efficiently, quickly and economically. In line with the Dutch Follow-up Roadmap for Offshore Wind Energy, a further 6,100MW of offshore wind energy will be realised between 2024 and 2030.

The Borssele Alpha offshore grid connection of TenneT is operational (picture: Screenshot taken from the Borssele video)

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COBRAcable market launch on 7 September

02.09.2019

After three years of construction, including the laying of the submarine cables as well as the construction of two onshore converter stations, and a successful test phase earlier this year, COBRAcable will be available for the electricity market as of the delivery day of 7 September, which is exactly on schedule. The first direct connection between the electricity markets of Denmark and the Netherlands was jointly realised and is operated by the two TSCNET shareholders Energinet, the Danish transmission system operator (TSO), and TenneT, the Dutch-German TSO.

The high-voltage DC cable with a length of about 325km has a capacity of 700MW. The Netherlands can import more sustainable electricity from Denmark through COBRAcable, mainly wind energy. In addition, the cable provides Dutch capacity on a structural basis for the Danish electricity grid, thus ensuring security of supply in Denmark, which of course also works the other way round. Moreover, the cable connection is designed in such a way that an offshore wind farm can be connected at a later date, so that COBRAcable contributes to a sustainable European energy landscape.

The COBRAcable interconnector of Energinet and Tennet is available to the market from 7 September (picture: screenshot taken from TenneT-video “First pile COBRAcable”, YouTube)

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TenneT on track for the energy transition

31.07.2019

Highly satisfactory business results and maintenance of the high level of 99.99% security of supply, are hallmarks of the half year report of the Dutch-German TSCNET shareholder Tennet. The latter is a growing challenge for the transmission system operator (TSO) because of the increased feed-in of volatile renewable energy. But above all, the report illustrates the commitment of the TSO to the European energy transition.

To take further steps in shaping the energy system of the future, TenneT has launched a series of strategic initiatives and partnerships to join forces across sectors. TenneT is participating in a German power-to-gas pilot project and is working together with regional grid operators and market partners on smart solutions to optimise the use of existing electricity infrastructure. The TSO is also involved in blockchain pilots to create flexibility for balancing the power system from decentralised sources.

TenneT has further strengthened its position as a leading offshore TSO. In Germany, TenneT has awarded DolWin 5, the 14th offshore grid connection. TenneT will increase its current offshore transmission capacity from 6,232MW in the German North Sea to almost 9GW by 2024. In the Netherlands, too, the development of the offshore grid with the Borssele Alpha and Beta projects is on schedule. TenneT intends to provide a total of 10.6GW of connection capacity for Dutch offshore wind farms by 2030. The TSO is also carrying out several onshore projects to ensure the transport of the growing amount of green electricity and thus security of supply in its control areas. Important interconnecting projects are the NordLink cable connection, which is currently being built to directly link the German and Norwegian markets for the first time. The COBRAcable between the Netherlands and Denmark has “landed” at the Dutch shore and will go into operation this year.

These developments are complemented by solid and impressive figures: Underlying operating result (EBIT) rose from €362m (first half of 2018) to €407m in the first half of 2019. €1,094m (first half of 2018: €904m) were invested in the Dutch and German high-voltage grids (of which €612m in Germany) and a total of €1.75bn green bonds were successfully issued. Manon van Beek, CEO of TenneT, comments on the report: “We have embarked on an irreversible transition to a sustainable society and a new energy system. This requires investments, not only in new electricity connections, but also in innovations and digitalisation. We have to move to holistic energy system thinking and also work on solutions to make better use of the existing high-voltage grids. We are convinced that this is the way forward to limit social costs and at the same time maintain a very high security of supply.”

TenneT presents its half year report 2019 (picture: TenneT)

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Imminent test operation for COBRAcable

24.06.2019

COBRAcable, the first direct interconnection between the electricity markets of Denmark and the Netherlands, is a joint project of the two TSCNET shareholders Energinet, the Danish transmission system operator (TSO), and TenneT, the Dutch-German TSO. Since spring, the partner TSOs have been preparing the commercial operation of COBRAcable. TenneT and Energinet have now launched an Urgent Market Messages (UMM) site for the commissioning of COBRAcable, which is scheduled to take place between 3 July 2019 and 6 September 2019.

A total of around 30 individual tests with different energy charges in the respective transport directions are planned. It is expected that the full capacity of COBRAcable will be available for the day ahead and intraday markets from 7 September. TenneT and Energinet then will offer financial transmission rights on COBRAcable at monthly and annual auctions. The first auction is expected to take place after a full month of stable operation, so probably the auction for November 2019, which will be held in October.

By promoting the exchange of surplus wind energy, COBRAcable will improve the cohesion of the European transmission system and the integration of the electricity market. It will also make a sustainable contribution to the low carbon energy future by allowing future offshore wind farms in the North Sea to be hooked up to the DC interconnector.

Energinet and Tennet will carry out individual tests of COBRAcable as of 3 July (picture: screenshot taken from TenneT video “COBRAcable Cable Pull Fano Denmark Film”, YouTube)

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Laying of NordLink submarine cable near completion

20.06.2019

NordLink, the “green cable”, which for the first time will directly connect the electricity markets of Germany and Norway, has reached another important milestone. With the pull-in of the submarine cable beneath the dyke at Büsum in the northern German state of Schleswig-Holstein on 19 June, the 154-kilometre section from the cable landing point at the dyke through the Wadden Sea and the open sea to the Danish territorial waters is almost complete. TSCNET shareholder TenneT, the Dutch-German transmission system operator (TSO), which is cooperating with the Norwegian TSO Statnet on this European project of common interest (PCI), had started to install the submarine cables for NordLink in the German Bight last year.

“With today’s successful pulling of the subsea cable beneath the land protection dyke, we have practically completed the laying of the NordLink subsea cable,” comments TenneT Managing Director Tim Meyerjürgens. Now the 54-kilometre onshore cable section will be successively laid from the dyke to the converter site in Wilster. Since the laying of the submarine cable in Danish and Norwegian waters is also almost concluded with only a few remaining works, and the construction of the 53km overhead line on the Norwegian mainland is progressing well, NordLink is expected to be commissioned as planned in 2020.

For the submarine cable work, TenneT was in close consultation with nature conservation authorities to ensure that operations in the Wadden Sea National Park were conducted as carefully as possible. Upon completion, the NordLink high-voltage DC interconnector will have a capacity of 1,400MW and a total length of 623km. By coupling different renewable energies and forms of storage – Norwegian hydropower plants with wind farms and solar parks from Germany – NordLink is a “green link” in the truest sense of the word.

TenneT has nearly completed the installation of the NordLink submarine cables (picture: TenneT)

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