Challenges of the green transition in Denmark

05.11.2020

In Denmark, as in Europe in general, the energy transition presents new and challenging tasks for the players in the energy sector. To improve the information basis and to prepare adequately for these challenges, TSCNET customer Energinet, the Danish transmission system operator (TSO), has created two reports on long-term development needs in the Danish energy system. There are two reports, as Energinet is not only the national TSO for electricity, but also for gas.

The forecasts in “Long-term Development Needs in the Power Grid” are similar to those of other European TSOs and allow similar conclusions. Not surprisingly, Denmark, as a world leader in renewable energy, needs to make even greater efforts to integrate these amounts of energy from renewable sources. In concrete terms, the TSO expects that by 2040 the maximum generation of wind turbines and solar cells could increase from 7.4GW today to perhaps 26GW. Such a tripling or quadrupling will cause problems for the current high-voltage grid, which is not designed to transmit such large amounts of energy.

Some challenges may not be due for 10-20 years, but others are already on the doorstep. In some places in Denmark, large-scale local production from wind and solar energy is already putting a considerable strain on the power grid. Hanne Storm Edlefsen, Head of the Strategic Planning division in Energinet Elsystemansvar, the TSO’s electricity system operator branch, emphasises the need for cooperation at all economic, political, and social levels to make the green transition a success and, for example, to ensure that “a doubling of electricity demand does not mean twice as many power pylons and overhead lines”.

The analyses show, among other things, the locations in Denmark where high-voltage grid extensions are required, either as underground cables or overhead lines. However, Edlefsen also points to other solution approaches beyond mere expansion: The proper placement of wind farms or large photovoltaic systems can reduce the need for grid reinforcement. And electrolysis plants of the future, which convert green electricity into hydrogen and other green fuels, could be located close to major green generation units so that electricity need not be transported across the country.

Energinet has presented two reports on the Danish long-term development needs in the power grid and in the gas system (picture: Energinet)

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Transmission capacity and renewable generation do not match

03.11.2020

The Austrian transmission system operator (TSO) APG has been monitoring the development of the electricity market since the beginning of the corona crisis and regularly publishes charts on topics such as energy exchange, electricity consumption in Austria and Europe, or electricity imports and exports. A look at the September charts of the TSCNET shareholder reveals, on the one hand, the strong role that renewable energies are already playing in Austria and have also continued to play during the pandemic. On the other hand, this particularly good generation from hydropower, wind, and photovoltaic plants could not be fully exploited due to the lack of transmission capacity.

“The streamflow of the Danube accounts for the majority of the run-of-river hydroelectricity generation, which this year has ranged 40 percent above the longtime average on several days. This is the reason why Austria is currently still able to export electricity,” explains Thomas Karall, CFO of APG. However, the insufficient use of renewable energies is also evident from the statistics of APG, especially regarding redispatch. Until the end of September, redispatch measures had to be carried out almost daily. This resulted in costs amounting to around €103m. „This figure shows the importance of the timely realisation of grid expansion and renovation measures – in particular of the Salzburg Line”, concludes Karall. The Salzburg Line (“Salzburgleitung“) is currently APG’s most important infrastructure project and crucial for the integration of renewables.

The September energy charts of APG show solid renewable generation and insufficient transmission capacity (picture showing the Austrian hydroelectric power station Gössendorf in the south of Graz: Eduard Aldrian)

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Middle Axis increases capacity sevenfold

27.10.2020

Since the 60s of the 20th century, a 220kV overhead line has been in operation between Hamburg and Denmark, thus crossing Schleswig-Holstein, the northernmost of the German federal states, in its entirety. Schleswig-Holstein is a true “wind power state” in terms of generation, but consumes very little energy in comparison to the southern and western German states. The green electricity produced here therefore has to be transmitted to the centres of consumption. As a result of the energy transition with increasing shares of wind energy, the capacity of the old line has long since been insufficient, resulting in grid bottlenecks. The Dutch-German transmission system operator (TSO) TenneT, whose control area includes the state between the North and the Baltic Sea, thus has replaced the old line with a new 380kV line capable of transmitting seven times as much green electricity.

The new overhead line is called Middle Axis (“Mittelachse”), as it is flanked by two other line projects of the TSCNET shareholder, the East-Coast-Line and the West-Coast-Line. On the Danish side of the border, the Danish TSCNET customer Energinet continues the Middle Axis from Frøslev to the Kassø substation, thereby increasing the electricity trading capacity between Denmark and Germany. On 21 October, TenneT put officially into operation the two northern sections of the Middle Axis between the Audorf substation near Rendsburg and the border with Denmark. With a symbolic push of a button at the substation Handewitt near Flensburg, Thomas Bareiß, Parliamentary State Secretary at the German Federal Ministry for Economic Affairs and Energy, Jan Philipp Albrecht, Minister of Energy, Agriculture, the Environment, Nature and Digitalisation of Schleswig-Holstein, Henrik Riis, CEO of Energinet-Eltransmission, and TenneT COO Tim Meyerjürgens connected the new 82 kilometres long power line to the grid.

The southern section of the Middle Axis from Hamburg/North to Audorf with a length of 70 kilometres was commissioned by TenneT in early 2018. Since 2015, a total of 388 new pylons have been erected along 152 kilometres between Hamburg/North and the border with Denmark, including the required substations Audorf/South, Schuby/West and Handewitt. The extension of the line by Energinet across the border by 30 kilometres into the Danish grid area increases security of supply for both the German and Danish electricity markets and enables the exchange of renewable energy between the two countries.

Tim Meyerjürgens explained: “With the 82 kilometres from Audorf to the Danish border, we are completing the important Middle Axis in the energy transition region of Schleswig-Holstein for the transmission of electricity from renewable sources between the river Elbe and Denmark.” Henrik Riis added: “The Middle Axis is a tremendous success, and it provides a new, continuous electricity highway that runs all the way from Denmark to Hamburg and on to Lower Saxony across the river Elbe. A strong cross-border infrastructure and well-functioning energy markets are essential for all of us – both at national and European level – to shape a future with high security of supply, large amounts of renewable energy and an efficient green energy transition.”

TenneT and Energinet commissioned the northern section of the Middle Axis, a new 380kV line from Denmark to Hamburg (picture showing from right to left Thomas Bareiß, Henrik Riis, Tim Meyerjürgens and Philipp Albrecht at the far left: TenneT)

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Cascade process of C/sells demonstrated successfully

25.10.2020

59 partners cooperate in the southern German smart grid project C/sells, including research institutions, distribution system operators (DSOs), municipal utilities, generators, service providers and consultants in the energy and IT sector – and the two TSCNET shareholders TransnetBW, the south-west German transmission system operator (TSO), and TenneT, the Dutch-German TSO. The aim of C/sells is to make the energy infrastructure renewable, decentralised, flexible, and participatory. The focus here is on the intelligent networking of generation and consumption and the use of innovative grid technologies and operating concepts. The “cell” is the basic unit of C/sells. It can be of a geographical nature, such as a city or district, or it can be a single object, such as an airport or even a single property. These “cells” assume a variety of functions and tasks that serve to stabilise the grid and provide flexibility. C/sells is funded by the German Federal Ministry for Economic Affairs and Energy in the framework of the innovation programme “Smart Energy Showcases” (“Schaufenster intelligente Energie” – SINTEG).

TransnetBW now reports a significant progress for C/sells, because together with the municipal utility of Schwäbisch Hall in the in the German state of Baden-Württemberg and the DSO Netze BW, the partially automated cascade process of C/sells was demonstrated live. A cascade process is usually understood as any process that takes place in a series of steps, and in this case, it is the step-by-step control of plants from downstream networks to remedy critical grid situations in an emergency. In the demonstration of 21 October, a simulated threat to system balancing was resolved by means of the partially automated cascade process and an intelligent measurement system. In the process, facilities were controlled right down to the lowest voltage level. The selected scenario was a realistic situation and required the cooperation of all grid operators.

The demonstration was based on the coordinated power grid cascade developed in C/sells which defines clear rules and processes for the respective grid operators. By means of control centre coupling, information on the state of the grid is continuously exchanged across all voltage levels. Several defined signal phases visualise the grid status in the control centres involved and indicate the measures to be derived from it. Thanks to the communication technology coupling of TransnetBW and Netze BW and the bidirectional exchange of information in real time, emergency situations can now be mastered jointly across voltage levels within just a few minutes. Dr. Rainer Enzenhöfer of TransnetBW and sub-project manager of C/sells comments on the successful demonstration: “With the partial automation of the cascade, it is possible, together with DSOs, to control a large number of decentralised plants in a simple and uncomplicated manner within a very short time in order to eliminate a critical grid situation.”

TransnetBW and its partners successfully demonstrated the cascade process of the C/sells smart grid project (picture: C/sells)

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Final court confirmation for Salzburg Line

21.10.2020

From the first submission of the project to the Salzburg state government in September 2012 until the approval of the construction of the second section of the Salzburg Line (“Salzburgleitung”) by the court of last instance, the beautiful Austrian state of Salzburg has certainly seen many sunsets. The Austrian transmission system operator (TSO) APG is now all the more content with the definite legal groundwork for Austria’s most important infrastructure project. Although the legally valid building permit for the Salzburg Line had already been granted by the Austrian Federal Administrative Court in March 2019, there were still final legal details in connection with the project, which the Supreme Administrative Court has now clarified on 20 October 2020, thus confirming the permit.

The new 380kV overhead line will replace the old 220kV line from the 1960s and will be capable of transporting seven times more electricity than the current line. To improve supply security in the city of Salzburg, the first 46-kilometre section of the Salzburg Line from the St. Peter grid node near the German border to the newly constructed Salzburg substation near Elixhausen was already commissioned in January 2011. The second section of the Salzburg Line, from Elixhausen to the Tauern grid node near Kaprun, will now close the western gap in the Austrian “380kV Ring”. This ring-shaped extra-high voltage grid is the backbone of the national electricity supply and crucial for the integration and transmission of renewable energies.

The total length of the new line, which has 449 pylons, is 128 kilometres. However, as old lines will be dismantled when the Salzburg Line is completed and some of them will run jointly on the new line, there will be 229 fewer masts in Salzburg than before. Commissioning of the Salzburg Line is planned for the year 2025, dismantling will be completed by 2026. “With €890m to be invested, the Salzburg Line is by far the most important investment project in the Austrian electricity infrastructure. Of the approx. €350m that APG is investing in the expansion of the electricity grids this year, the Salzburg Line alone has a share of €125m for the domestic economy,” comments Gerhard Christiner, CTO of the Austrian TSCNET shareholder, who also praised the day of the court ruling as a “good day for the energy transition and for the secure supply of electricity in Salzburg and Austria”.

The Austrian Supreme Administrative Court has definitively confirmed the construction permit for the 380kV Salzburg Line of APG (picture: Martin Lugger / APG)

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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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Successful test run of SINCRO.GRID’s VVC function

07.10.2020

SINCRO.GRID is a smart grid project of the two transmission system operators (TSOs) HOPS from Croatia and ELES from Slovenia. With SINCRO.GRID, the two TSCNET shareholders are responding to the increasing lack of flexibility and reactive power in the transmission system, which in Croatia and Slovenia, as in many parts of Europe, results from the increasing integration of decentralised, volatile renewable energy sources (RES). Two distribution system operators (DSOs) from the respective countries are also involved in the European Project of Common Interest (PCI). The aim of the project partners is to optimise grid efficiency via advanced technologies and innovative data processing, including compensation devices, a dynamic thermal rating system, a battery power storage system, and a virtual cross-border control centre.

As HOPS reports, an important step has been taken towards the establishment of the binational SINCRO.GRID control centre, whose prime task is to integrate reactive power compensation devices in Croatia and Slovenia into a joint operation to fully exploit their synergy potential. The centre will thus enable voltage control and loss optimisation in transmission systems, better control and forecasting of electricity generation from RES, and the participation of RES in the provision of ancillary services.

On 30 September 2020, the SINCRO.GRID Q-U system with Volt Var Control (VVC) function was operated for the first time in fully automatic closed loop for four hours without any human intervention. All calculated VVC data were automatically sent by the Q-U system to seven transformers in three HOPS substations, optimising the transmission network in north-western Croatia. After successful testing in fully automatic mode, the test was continued in semi-automatic mode with transformers and two generators in one power station. The information and experience obtained from the test run will be used for the further analysis of the Q-U system and its application to the whole Croatian transmission system and finally for the implementation of the HOPS-ELES virtual cross-border control centre.

HOPS has carried out a successful test run of the Q-U system with VVC function within the SINCRO.GRID project (picture: HOPS)

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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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TenneT commissions North German grid node

02.10.2020

The town of Wilster is located about 10 kilometres north of the Elbe river in the German federal state of Schleswig-Holstein, which falls within the control area of the Dutch-German transmission system operator (TSO) Tennet. Schleswig-Holstein is of eminent importance for the generation of wind power. In Wilster, after a four-year construction period, the TSCNET shareholder commissioned the renewed Wilster/West substation on 1 October, a significant grid node for the energy transition in the north and beyond. This is because the so-called Westküstenleitung (West-Coast-Line), the NordLink interconnector, which directly links the electricity markets of Germany and Norway, are converging here – and later also the SuedLink “electricity highway” for the transmission of green electricity to the German consumption centres.

For the two high-voltage direct current (HVDC) transmission projects NordLink and SuedLink, the capacity of the former Wilster/West substation was no longer sufficient. An extension of the switchgear was necessary to exclude impermissible load flows and guarantee the short-circuit resistance required in future. Thus, a new 380kV switchgear was built on the ground of the former 380kV substation and the new construction now replaces the old substation on the same site. Furthermore, the connection facilities for the converter stations of SuedLink and NordLink had to be provided. And finally, a 110kV switchgear was installed, which enables the dismantling of the 220kV switchgear in the near substation Itzehoe-West.

“This substation is a central hub for electricity transmission from north to south,” explains TenneT’s COO Tim Meyerjürgens. “Here, electricity from renewable sources is fed into the grid and distributed to regions with high consumption. The Wilster area is of outstanding importance for the energy transition. Because in the grid area between Wilster, Brokdorf, Itzehoe, and Brunsbüttel, three new extra-high voltage lines from TenneT converge: the Westküstenleitung, NordLink, and later also SuedLink.”

TenneT has put into operation the new substation Wilster/West (picture: TenneT)

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> See TenneT press release, in German (html)
> Watch video on the construction and commissioning of Wilster/West, in German (YouTube)

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