Combined Grid Solution inaugurated

20.10.2020

On 20 October, the world’s first hybrid offshore interconnector was ceremoniously put into operation: the Danish-German Combined Grid Solution (CGS). This interconnector in the Baltic Sea links the transmission grids of two countries via national offshore wind farm grid connections. For this purpose, two submarine cables with a length of merely 25 kilometres and a capacity of approx. 200MW each were laid between the offshore transformer platforms of the German wind farm Baltic 2 and the Kriegers Flak wind farm in the Danish part of the Baltic Sea, which is currently under construction. The CGS – a joint project of TSCNET shareholder 50Hertz, one of the four German transmission system operators (TSOs), and TSCNET customer Energinet, the TSO from Denmark – thus not only connects the platforms with each other but also the existing onshore connections of the wind farms. This allows the transmission of offshore wind power to Denmark or Germany and also cross-border electricity trading.

The official opening ceremony, which took place on site in the German capital of Berlin as well as digitally, was attended by Peter Altmaier, German Federal Minister for Economic Affairs and Energy, Dan Jørgensen, the Danish Minister for Climate, Energy and Utilities, as well as Kadri Simson, EU Commissioner for Energy. With their appearance, these high-ranking political representatives acknowledged the CGS as a technical innovation with model character for future offshore power grids. The hybrid nature of CGS is that it is the first electricity interconnector between two countries, that not only provides capacity for electricity trading, but also transports offshore wind energy onshore – in both directions. The costs of the binational EU-funded project amount to around €300m.

A technical obstacle had to be solved in the realisation of CGS: Because the transmission grids in eastern Denmark and Germany do not operate synchronously, it was necessary to install a back-to-back converter at the 50Hertz substation in Bentwisch near the port city of Rostock in the federal state of Mecklenburg-Western Pomerania. The device converts the incoming AC into DC and immediately back. Only in this way is it possible for electricity to flow smoothly from Denmark to Germany and vice versa. But CGS has not only hardware but also software components. The central digital control unit of the system is the Master Controller for Interconnector Operation (MIO), located in the 50Hertz control centre near Berlin. The MIO balances market requirements with offshore electricity production, which depends on wind conditions in the Baltic Sea. Its main function is to ensure optimum use of the CGS while preventing any overload of the line and the operating facilities in the substation.

Stefan Kapferer, CEO of 50Hertz, commented at the inauguration: “With this project, 50Hertz and Energinet are pioneering the efficient integration of offshore wind farms into the cross-border European electricity market. It offers us several effective options to balance the frequency and voltage of our transmission grids at all times, to deal with the integration of renewable energy sources with more flexibility and to increase the stability of the overall system.” Thomas Egebo, CEO of Energinet, added: “The CGS is not only a very important milestone in reaching Denmark’s ambitious goal of a 100 percent green power system in 2030. The groundbreaking project also delivers an important building block for decarbonising the rest of the society.”

The Danish-German Combined Grid Solution has been ceremoniously put into operation (illustration uses photos of 50Hertz, one of which shows Minister Altmeier)

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Improving biodiversity for submarine cabling

15.10.2020

Looking at the big picture – the energy transition and the achievement of the European climate targets – there is no alternative to expanding offshore capacity for the generation and transmission of North Sea wind power. For that reason, both the Dutch and German governments have set ambitious targets for offshore expansion, which the Dutch-German transmission system operator (TSO) TenneT is gradually implementing and has even exceeded for its German North Sea control area. In the individual case, however, each offshore construction and operational measure obviously has an impact on the valuable North Sea and Wadden Sea ecosystems. As TenneT strives to apply and monitor nature-friendly solutions in all of its offshore grid projects, the TSO is now conducting pilot tests with stone coverings of submarine cable intersections.

When the TSCNET shareholder lays submarine cables, e.g. currently for the high-voltage connection of the Hollandse Kust (zuid) wind region, the cables sometimes cross with existing oil and gas pipelines. In such cases, the cables protrude above the seabed and are usually covered with a layer of granite to protect them. To replace granite with alternative solutions that promote biodiversity, TenneT has launched a pilot project in collaboration with the offshore specialist company Van Oord. In this project, different types of stones are deposited at cable crossings to investigate which of these stimulates biodiversity best. In total, the pilot involves twelve locations in the North Sea. In the case of the first six, recently laid submarine cables already cross existing oil and gas pipelines. Another six intersections will follow during the construction of the Hollandse Kust (Zuid) connection in 2021.

On 14 October, the different stones were loaded onto Van Oord’s special vessel to be placed at the cable intersections in the coming weeks. Among them are small calciferous stones from a marble quarry, which are placed at three of the six cable intersections. Comparison with the other three intersections without calciferous stones will allow to assess the difference in the type of marine life developing at these intersections. “Our expectation is that the calciferous stones will ensure that various benthic species will find it easier to nest here and that a different habitat will emerge at these sites. Over the years, ‛artificial reefs’ can emerge at these sites in the North Sea, where plants and small creatures can settle,” explains Saskia Jaarsma, Head Offshore Developments and Large Projects Offshore at TenneT.

TenneT has launched a pilot project to promote biodiversity at submarine cable intersections (picture: Van Oord)

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Wilhelmshaven-Conneforde line put in operation

05.10.2020

With the Wilhelmshaven-Conneforde line, the Dutch-German transmission system operator (TSO) TenneT has commissioned an important grid expansion project for the German and European energy transition. The 380kV line from the new substation Fedderwarden near Wilhelmshaven on the German North Sea coast to the Conneforde substation in Ammerland, both in the federal state of Lower Saxony, is not only crucial for the transmission of mainly wind power and electricity from regional generators, but also for strengthening security of supply in northern Lower Saxony. Furthermore, it represents a novelty for the TSCNET shareholder in terms of technical implementation: “With this new line, we have put into operation the first pilot project with two underground cable sections in three-phase technology and connected it to the meshed power grid in Germany,” explained Tim Meyerjürgens, COO of TenneT.

The commissioning ceremony on 2 October 2020 in Fedderwarden was attended by representatives from politics, including Andreas Feicht, State Secretary at the German Federal Ministry for Economic Affairs, and Energy and Olaf Lies, Minister for the Environment, Energy, Construction, and Climate Protection of Lower Saxony. The new line is only about 30 kilometres long, but – together with the new construction of the Fedderwarden substation – “of great importance for the entire European electricity trade”, commented Olaf Lies. The Minister was impressed by TenneT’s latest milestone in the energy transition. State Secretary Feicht referred to the newly gained potential for integrating large amounts of wind power into the German electricity market and the technical relevance of the pilot project: “Knowledge obtained in such pilot projects about the construction and operation of the technology will be of great benefit for further power grid expansion in the future.”

The line project was successfully completed after less than two years of construction. Almost 5 kilometres of the line were implemented as underground cables. However, even if TenneT can be satisfied with what has been accomplished so far and is strongly committed to expanding the transmission of green electricity throughout its entire grid area, Meyerjürgens sees a need for further action, especially in view of the increasing offshore wind volumes: “Still, we already see today a further demand for expansion in the Wilhelmshaven and Friesland region.”

TenneT commissioned the new Wilhelmshaven-Conneforde line (picture: TenneT)

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Deep Dig-It starts work for Hollandse Kust (zuid) grid

24.09.2020

Hollandse Kust (zuid), an offshore wind area in the Dutch North Sea, is located a good 20 kilometres off the coast of the Dutch province of Zuid-Holland. The Dutch-German transmission system operator (TSO) TenneT is installing the related offshore grid to connect the new offshore wind farms in the area via two offshore platforms and submarine cables to the onshore high-voltage substation that is being built in the Maasvlakte industrial and port area. The jacket for the first of these two offshore platforms has recently been installed and the offshore connection project is now making further progress with the start of the laying of the submarine cables on 22 September.

Four 220kV AC cables with a total length of 42 kilometres each are to be installed in the seabed, of which the first two to the Alpha platform will be laid this year. The other two to the Beta platform will follow in 2021. First, the two cables were brought ashore to the planned Maasvlakte substation via direct drilling. Thereupon the TSCNET shareholder started the marine installation, with the first ten kilometres of the route from the coast at Maasvlakte being extremely challenging. Over this distance, the cables cross the entrance to the port of Rotterdam – Europe’s busiest cargo port – and thus need to be buried more than 5.5 metres deep. For this purpose, the contracted specialist company Van Oord uses its Deep Dig-It trencher, an enormous remote-controlled trencher.

The Deep Dig-It is one of the largest and most powerful devices in its class. The trencher weighs 125 tonnes, is more than 17 metres long, well over 8 metres high, and 11 metres wide. With its enormous power it can bury cables deeply even in very hard ground. The trencher is controlled from an offshore installation vessel equipped with a crane to lower and lift out the high-performance machine. The Deep Dig-It moves unmanned over the seabed and creates a deep trench for the cables by liquefying the seabed. Simultaneously, the Deep Dig-It inserts the cables into the trench and seals the seabed afterwards. With work progressing well, Tennet expects the 1,400MW Hollandse Kust (zuid) grid connection to be completed in 2022.

TenneT has started the laying of submarine cables for the Hollandse Kust (zuid) grid connection (picture: Van Oord)

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Cooperation to link offshore wind farms

22.09.2020

Realising the full potential of offshore wind energy in the North Sea will be crucial for the decarbonisation of the European economy and society. The transmission system operators (TSOs), whose control areas border the North Sea, are aware of this, including the Dutch-German TSO TenneT and National Grid from the UK. Both the Netherlands and the UK have set ambitious targets for their respective development of wind capacity in the North Sea. However, to achieve large-scale growth in offshore wind energy, significant amounts of new infrastructure and close cooperation between the countries around the North Sea will be essential.

On 22 September, TenneT and National Grid announced a cooperation agreement to examine the feasibility of interconnecting Dutch and British wind farms to the energy systems of both countries via submarine cables. The announcement is following a recent decision by the Dutch government to secure the first 2GW offshore transmission grids for high-voltage direct current (HVDC) in the Netherlands for the IJmuiden Ver wind farm zone, located some 80km off the Dutch north-west coast. Under the cooperation agreement, TenneT and National Grid will explore the development of a multi-purpose interconnector (MPI) to simultaneously connect up to 4GW of Dutch and British offshore wind energy between the two national electricity systems, thereby creating an additional 2GW of interconnection capacity.

By connecting to both systems, the MPI will allow the use of free transmission capacity for electricity trade between the two countries, thus improving the utilisation of offshore infrastructure – and possibly decreasing the need for additional infrastructure. This will also reduce the environmental impact on coastal communities compared to the current approach of separately developing and connecting interconnectors and wind farms. The two TSOs intend to have defined a “pathfinder project” by the end of 2021 with the aim of creating an operational system by 2029.

Manon van Beek, CEO of TenneT, comments on the agreement: “TenneT has been at the forefront of developing multi-purpose interconnection to enable the large-scale growth of offshore wind in the North Sea. This agreement allows us to work with National Grid in the North Sea to develop innovative infrastructure that uses every spare electron of offshore wind generation to reach our decarbonisation targets.”

TenneT has concluded an agreement with National Grid to investigate the interconnection of UK and Dutch offshore wind farms (exemplary picture: TenneT)

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Jacket for Hollandse Kust (zuid) Alpha platform installed

08.09.2020

The offshore wind area Hollandse Kust (zuid) is located 22 kilometres off the coast of the Dutch province of Zuid-Holland. The Dutch-German transmission system operator (TSO) TenneT will connect the wind farms in this area to the onshore substation in the industrial and port area of Maasvlakte via two offshore platforms – Alpha and Beta – and submarine cables. The jacket for the Hollandse Kust (zuid) Alpha platform was transported to the operation site by a heavy-duty vessel on 5 September and successfully installed on the seabed. The Alpha jacket is 29 meters long, 20 meters wide, 46 meters high and weighs 3200 tonnes. It will be further installed in the coming days.

The two 220kv submarine cables will be connected to the jacket over the next few months. In 2021, the platform top side will be placed on the jacket. The Hollandse Kust (zuid) Alpha platform is expected to be operational by the end of 2021. The projects in this new wind area are part of the large-scale offshore expansion programme of TenneT. By the end of 2023, the TSCNET shareholder will have installed 3.5GW of offshore grid connections in the Netherlands, of which the first 1.4GW have already been achieved with Borssele Alpha and Beta. The connection to follow Hollandse Kust (south) will be Hollandse Kust (nord). For all the wind farms in these two areas, TenneT will deploy five identical 700MW transformer platforms and identical 220kV cable connections. “Such standardisation enables TenneT to complete these projects more efficiently, more quickly, and more economically,” explains TenneT COO Tim Meyerjürgens.

The Dutch national roadmap for offshore development provides for an additional 6.1GW of offshore wind farms in the wind energy areas Hollandse Kust (West), Ten Noorden van de Waddeneilanden, and IJmuiden Ver from 2024 to the end of 2030. For the first two areas, TenneT will again use standardised 700MW offshore platforms. The efficient connection of IJmuiden Ver, which is located further out in the North Sea, partly requires other technologies based on DC instead of AC. IJmuiden Ver will have two offshore transformer platforms with a capacity of 2GW each, which is unique in the offshore wind industry.

TenneT has installed the jacket for the Hollandse Kust (zuid) Alpha platform (picture: TenneT)

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TenneT commisions “green” substation

04.09.2020

In recent years, the seaport of Eemshaven in the province of Groningen in the north of the Netherlands has become more and more important for the Dutch energy transition. Eemshaven has taken on the role of an energy port: with power plants, sustainable generation, connections to offshore wind farms, and submarine cable interconnectors to Norway and Denmark. The Dutch-German transmission system operator (TSO) TenneT – together with regional distribution system operator (DSO) Enexis Netbeheer – now has commissioned the new high-voltage substation Eemshaven as the first substation entirely built for the suply of wind and solar energy.

The station was built as part of the grid reinforcement for the growing amount of sustainably generated energy in the north of the Netherlands which requires an increase in transmission capacity. Other measures of the TSCNET shareholder include a 380kV connection between the Eemshaven (Oudeschip) high-voltage substation and Vierverlaten near Groningen as well as the extension of the Vierverlaten substation. This new 380kV “power highway” will replace the existing 220kV line. Until it is put into operation – scheduled for 2023 – TenneT will commission a provisional 380kV substation in Eemshaven (Oostpolder) in October 2020.

TenneT has put into operation the new substation Eemshaven for the supply of green electricity (picture: TenneT)

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TenneT continues offshore cost reduction with BorWin5

12.08.2020

BorWin5 is to become the 15th offshore grid connection system implemented by the Dutch-German transmission system operator (TSO) TenneT in the German North Sea, the twelfth DC connection, and the fourth offshore grid connection off the coast of the island of Borkum using HVDC transmission technology. With a total length of 230 kilometres, BorWin5 will also be the longest offshore connection of the TSCNET shareholder. The realisation of BorWin5, expected to be commissioned in 2025, is progressing well, as TenneT has now placed orders for the construction of the onshore and offshore converter stations as well as for the production and installation of the DC underground and submarine cables. The contract for the converter stations has been awarded to a consortium of Siemens and Dragados Offshore and for the cables to NKT HV Cables.

The key technical data of BorWin5 reflect TenneT’s extensive experience and expertise in the offshore sector on the one hand, and the TSO’s commitment to constantly improving established technology on the other. For example, BorWin5 is the second project, after DolWin5, in which the wind turbines are connected directly to the corresponding offshore platform via 66-kv three-phase power cables. This dispenses with, among other things, the transformer stations otherwise required in wind farms. With this direct connection, BorWin5 represents the new generation of cost-efficient offshore connections. Moreover, with BorWin5’s smart platform concept, the TSO is advancing standardisation further by installing only such technology on offshore platforms as is absolutely necessary on the offshore side.

Tim Meyerjürgens, COO of TenneT, emphasises the company’s continuous cost reduction in the construction of offshore grid connection systems – a highly significant aspect for the success of the energy transition – and the specific cost efficiency of BorWin5: “Compared to the predecessor project DolWin5, we were again able to achieve a significant cost reduction for the converter stations. One reason is that for BorWin5 the smart platform concept is being used for the first time. This not only keeps the costs for the platform construction manageable, but also allows us to extend the intervals for maintenance and servicing to once a year.”

TenneT awarded contracts for the on- and offshore converter stations as well as the underground and submarine cables for BorWin5 (picture shows the preparatory horizontal drilling for BorWin5 on Norderney in 2019)

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TenneT to invest up to €5bn p.a. for the energy transition

31.07.2020

The Dutch-German transmission system operator (TSO) TenneT has just published its first-half 2020 report. Needless to say, the second quarter of 2020 was characterised by the corona pandemic and the extensive measures taken to ensure a safe and healthy working environment, but despite this, the TSO has made significant progress in developing the transmission grid onshore and offshore and in integrating growing amounts of renewable electricity. At the same time, TenneT has maintained a high level of supply security of 99.99% for 42m end consumers in Germany and the Netherlands.

As Europe’s first cross-border TSO, TenneT promotes the European market integration. The TSCNET shareholder increasingly benefits from its binational integrated approach to grid planning, management, and operation. Manon van Beek, TenneT’s CEO, comments: “Sharing best practices and lessons learned between our German and Dutch operations is paying off more and more in terms of an integrated approach to offshore and onshore grid expansion, better grid utilisation due to European innovations and cross-border energy system planning.”

TenneT currently operates 14 offshore grid connections, twelve in the German and two in the Dutch North Sea. The twelfth offshore grid connection in Germany, BorWin 3, was handed over to TenneT in the first half of 2020. In Dutch waters, the Borssele Alpha grid connection recently transmitted offshore wind power for the first time and the Borssele Beta grid connection has now been commissioned well ahead of schedule. While in the offshore sector experience from the German market is used for the Dutch, the situation is the other way round when it comes to underground cabling. Here, expertise from the Dutch Randstadt project is applied for the DC connections SuedLink and SuedOstLink. These two largest projects of TenneT, which are being entirely installed underground, will be essential for the transmission of wind energy from northern to southern Germany.

Such efforts require huge investments – facilitated by solid financial results: The underlying operating result (EBIT) increased to €414m in the first half of 2020. During the same period, investments in the German and Dutch high and extra-high voltage grids also increased by approximately 30% compared to the first half of 2019, but will do so much more in the future. TenneT expects a further rise in the annual investment volume to €4 to 5bn in the next years. Otto Jager, CFO of TenneT, explains: “We are going to connect growing amounts of renewable electricity to the grid while facilitating the development of a borderless European electricity market. In light of future equity funding needs, the ongoing talks with the German government about a possible equity participation, next to the Dutch State, are welcomed by TenneT.”

TenneT presents Half-year Report 2020 (picture: TenneT)

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Borssele Beta is ready for the grid

31.07.2020

Borssele Beta is the second high-voltage grid connection for offshore wind farms in Dutch territorial waters of the Dutch-German transmission system operator (TSO) TenneT. Like Borssele Alpha, the first Dutch offshore connection, it transmits green electricity generated in the Borssele wind farm area ashore, in this case from the Borssele III, IV and V wind farms. The operators of these three farms can hook up their wind turbines to the high-voltage grid one month earlier than scheduled, as TenneT has just received the “Grid Readiness” certification from the internationally accredited registrar and classification society DNV GL. This means that Borssele Beta fully complies with the criteria of the “Ontwikkelkader windenergie op zee”, the Offshore Wind Energy Development Framework of the Dutch Government.

The Borssele III, IV and V wind farms will have a total capacity of 700MW. The electricity generated here is collected by the offshore transformer platform, which converts the voltage from 66kV to 220kV for transmission via submarine cables to the onshore substation in Borssele. For feeding into the high-voltage grid, the voltage is then converted to 380kV. Marco Kuijpers, Director Offshore Projects at TenneT, comments on the rapid realisation: “We are proud of the fact that the second part of the Borssele high voltage connection is already complete and was realised within budget. Despite all the Covid-19 challenges, we were successful in continuing with the works; a huge achievement from all the contract parties involved.”

By the end of 2023, TenneT will have installed 3.5GW of offshore grid connections in the Netherlands, of which the first 1.4GW have already been achieved with Borssele Alpha and Beta. The next projects are Hollandse Kust (zuid) Alpha and Beta, followed by Hollandse Kust (noord). For these wind farms, TenneT will deploy five identical 700MW transformer platforms and identical 220kV cable connections. This standardisation allows TenneT to realise these projects faster, more efficiently, and more economically. The governmental Dutch follow-up roadmap for offshore development provides for an additional 6.1GW of offshore wind farms from 2024 to the end of 2030, located in the wind energy areas Hollandse Kust (west), Ten Noorden van de Waddeneilanden and IJmuiden Ver. Only for the first two, TenneT will again use standardised 700MW platforms. The efficient connection of IJmuiden Ver, located further out in the North Sea, partly requires other technologies based on DC instead of AC. IJmuiden Ver will have two offshore transformer platforms with a capacity of 2GW each, which is unique in the offshore wind industry.

The Borssele Beta offshore grid connection of TenneT is ready for transmission (picture: TenneT)

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