German field report on underground cabling

07.10.2020

The use of underground cables for power transmission in the extra-high voltage three-phase current range is partly still uncharted technical territory for the four German TSCNET shareholders 50Hertz, Amprion, TenneT, and TransnetBW. As most projects are in the planning, approval, or construction phase, no partial earth cabling project is yet in full system operation, let alone a project with exclusive cabling. However, Tennet has commissioned the Wilhelmshaven-Conneforde line as recently as last week: It is the first 380kV line with underground cable sections in three-phase technology connected to the meshed power grid by the Dutch-German transmission system operator (TSO).

To inform politics and public about the current status of underground cabling in the national transmission system, the four German TSOs have, at the request of the German Federal Ministry for Economic Affairs and Energy, jointly prepared a field report on the use of underground cables in the extra high-voltage three-phase current range. The 65-page report examines seven different key issues in respective main chapters, covering technical, administrative, economic, environmental, and social aspects: dialogue and acceptance, approval procedures and the environment, design and construction, operation and operational safety, underground cable technology, systems engineering, and finally economic efficiency. Key findings of 50Hertz, Amprion, TenneT, and TransnetBW can be summarised as follows:

  • Partial underground cabling does not per se lead to a greater acceptance of line construction projects – compared to the construction of overhead power lines, the concern merely shifts from the residents mainly to landowners and farmers.
  • As far as planning, approval, and construction times are concerned, current experience shows that partial underground cabling requires at least one to two years more than overhead lines. More extensive implementation planning, intensive soil investigations, and negotiations with the owners consumed a great deal of time in the pilot projects. The construction itself is also more complex due to the necessary crossing of infrastructures, 40 to 60-metre-wide aisles, and major interventions in the soil ecosystem.
  • Regarding operational and system safety, underground cable installations have a lower availability rate than overhead lines, as repair times are significantly longer in case of damage. Moreover, with an increasing share of partial underground cabling, the complexity of grid operation and thus the risk to system stability also rises.
  • In terms of economic efficiency, the costs of partial underground cabling are significantly higher than those of overhead lines, and this applies to planning, construction, and operation. Depending on the project-related terrain and soil conditions, the investment costs are usually six times higher.

The four German TSOs have published their joint “Field report on the use of underground cables in the extra-high voltage three-phase current range” (picture: TenneT)

Linkup
> See TransnetBW news release, in German (html)
> Open Field Report, in German (pdf, 2.9MB)

See article on single page

TransnetBW modernises Herbertingen-Hoheneck line

01.10.2020

Like any transmission system operator (TSO), TransnetBW, the TSCNET shareholder from the southwest of Germany, regularly evaluates the condition of its facilities and transmission infrastructure to define necessary modernisation measures. This has revealed the need to renew the 380kV overhead line from Herbertingen in the south of the federal state of Baden-Württemberg to the Hoheneck substation in Ludwigsburg, about 20 kilometres north of the Swabian metropolitan city of Stuttgart. As part of the modernisation, several steel parts of 53 existing pylons will be replaced. The basic mast structure, that is height, width, and foundations, is not affected.

For the work on the line in the voltage range of the mast cantilever arms, disconnection of the corresponding electrical circuits is required. This has no effect on the regional power supply. Work on the roughly 120-kilometre-long transmission line began in the last week of September and is expected to be completed by the end of November 2020.

TransnetBW modernises the 380kV overhead line from Herbertingen to Hoheneck (exemplary picture: TransnetBW)

Linkup
> See TransnetBW press release, in German (html)

See article on single page

Network Agency decides on southern routing of SuedLink

25.09.2020

700 kilometres of underground cable to be laid and an investment volume of around €10bn – this makes the 525kV line SuedLink the largest and probably most important individual project of the energy transition in Germany. The exclusive use of underground cables in the project is politically specified to increase the acceptance of the project by the population: For only if one succeeds in effectively connecting the windy regions of northern Germany with the centres of consumption in the industrially highly developed south and west via such “electricity highways” as SuedLink, the German – and European – climate targets can be achieved.

SuedLink is jointly implemented by the two TSCNET shareholders TenneT, the Dutch-German transmission system operator (TSO), and TransnetBW, the TSO from southwest Germany. The project is making step-by-step progress in the regulatory, planning, and implementation areas. This year, for example, regional planning offices have already been set up and the contracts for the cables awarded. Now the competent government authority, the Federal Network Agency (Bundesnetzagentur), has decided on the southern section between the Lower Franconian Arnstein near Schweinfurt and the Großgartach substation in the Stuttgart Metropolitan Region (SuedLink section E). This 137 kilometre long section runs through the control areas of both TSOs involved.

The Bundesnetzagentur’s decision largely follows the proposal by TenneT and TransnetBW, according to which the Würzburg metropolitan area is largely bypassed in the west. The proposal of the two TSOs had already incorporated the results of the application conferences and requirements of the Bundesnetzagentur. The last 16 kilometres to the Großgartach substation are a special construction feature. Here an existing salt mine is to be used for an underground course of the cable project. This increases construction costs, but these are outweighed by other benefits, in particular the reduced impact on the environment and residential areas. After the completion of the federal sectoral planning for the SuedLink section E, planning approval procedures are to follow which will determine the exact route of the line within the corridor and the technical implementation.

The German Federal Network Agency has decided on the southern section of the SuedLink power line, a joint project of TenneT and TransnetBW (picture: TenneT)

Linkup
> See press release by Bundesnetzagentur, in German (html)

See article on single page

Foundation stone laid for ULTRANET substation

17.09.2020

On the site of the former Philippsburg nuclear power plant, which was shut down completely on 31 December 2019, a new DC substation for the German supra-regional “power highway” ULTRANET is being constructed. The Philippsburg substation in the German state of Baden-Württemberg represents the southern end point of ULTRANET, where the high-voltage direct current (HVDC) line will be connected to the regional 380kV AC grid. The new substation is thus to become one of the most important energy hubs in Germany’s future energy landscape. It is being built on behalf of TSCNET shareholder TransnetBW, the transmission system operator (TSO) from Baden-Württemberg. In its entirety, ULTRANET is a joint project of TransnetBW and further German TSCNET shareholder Amprion. It will transmit wind energy generated in the northwest of Germany to the industrially highly developed southwest. On the other hand, the Philippsburg substation will enable the conversion of AC to DC, e.g. to transport excess photovoltaic electricity from the south to the north.

In March 2020, the construction of the ULTRANET substation was approved by the competent authority and in May, the demolition of the two cooling towers of the former power plant created the necessary construction space of around 100,000m². Now, the ceremonial laying of the foundation stone took place in Phillipsburg in the presence of high-ranking representatives from politics, business, and society – and in strict compliance with the Corona regulations. Dr. Werner Götz, Chairman of the TransnetBW Executive Board, commented: “It was nevertheless very important to us not to let this important day pass without expressing our thanks to politicians, partners, and the project team.”

Andreas Feicht, State Secretary at the German Federal Ministry for Economic Affairs and Energy, recognised the progress of the European Project of Common Interest (PCI): “The converter in Philippsburg illustrates that the grid expansion is progressing in large steps.” Franz Untersteller, Minister of the Environment, Climate Protection, and the Energy Sector of Baden-Württemberg, emphasised the specific nature of the location and its symbolic value: “There are few places where the energy transition can be visualised in such a condensed form as here in Philippsburg. After the two cooling towers were detonated in May of this year, the old world made way for the new.”

TransnetBW has celebrated the laying of the foundation stone for the ULTRANET substation in Philippsburg (picture: TransnetBW)

Linkup
> See TransnetBW press release, in German (html)

See article on single page

Worldwide unique equipment for TransnetBW substation

18.07.2020

European transmission system operators (TSOs) respond to the increasing need for grid regulation – resulting from the growing share of volatile renewable energies and the proceeding shutdown of conventional power plants – with reactive power compensation measures, such as the installation of shunt reactors. Shunt reactors are absorbers of reactive power and support security of supply and system management by keeping the grid voltage within the specified range, especially during low load periods. They thus stabilise the power grids and increase the energy efficiency of the transmission system.

In the Stuttgart-Mühlhausen substation, TransnetBW, one of the four German TSOs, has commissioned a variable shunt reactor for reactive power compensation developed especially for the TSCNET shareholder. Up to now in the TransnetBW control area, shunt reactors have only been used in the 110kV grid. Compared to customary reactors, the new system provides a much more precise control of the grid voltage. The 360-tonne reactor has a control bandwidth of 50-250MVAr in 33 stages and a permanently permissible system voltage of 440kV. With these specifications, the Mühlhausen shunt reactor is not only a novelty for TransnetBW, but for the entire energy sector.

TransnetBW has commissioned a state-of-the-art shunt reactor in the Stuttgart-Mühlhausen substation (symbolic picture: Siemens)

Linkup
> See TransnetBW press information, in German (html)

See article on single page

Successful start of FCR auctions

01.07.2020

The cooperation on regional procurement and exchange of frequency containment reserve (FCR) is a voluntary initiative of eight transmission system operators (TSOs): the six TSCNET shareholders 50Hertz, Amprion, and TransnetBW from Germany, APG from Austria, Swissgrid from Switzerland, and the Dutch-German TSO TenneT, as well as Elia from Belgium and the French TSO RTE. The FCR project is the first regional cooperation for a common market based on the methodology for the exchange of control reserves set out in the EU Guideline on Electricity Balancing. Within the scope of a cooperation model with Amprion, the Luxembourg TSCNET customer Creos is also involved.

The next milestone in the development of the largest European market for primary balancing power reserve has now been reached, as the first D-1 auction for FCR with 4-hour products was successfully conducted on 30 June 2020. This means, the FCR cooperation reduces the product length from one day to four hours and thus the market for primary balancing power is brought closer to real time.

Due to stronger competition between service providers and technologies, the joint auction allows TSOs to procure FCRs at minimum cost to end-users while offering a large common market for all providers of balancing services. It also increases the market attractiveness for short-term flexibility, limits price volatility and improves the security of grid operation by executing cross zonal procurement of FCR. The FCR market, already the largest in Europe, will be extended to western Denmark and Slovenia in the first quarter of 2021, so that with Energinet and ELES two further TSCNET shareholders will broaden the project.

The FCR cooperation successfully conducted the first D-1 auction for FCR with 4-hour products 

Linkup
> See Swissgrid news release (html)

See article on single page

Contracts for 525kV SuedLink cables

29.06.2020

SuedLink is evolving in major steps this year. The DC line – realised jointly by the two TSCNET shareholders TenneT, the Dutch-German transmission system operator (TSO), and TransnetBW, the TSO from southwest Germany – is the largest and probably most important single project of the energy transition in Germany. With around 700 kilometres of underground cable to be laid and an investment of around €10bn, SuedLink will connect the windy regions of northern Germany with the centres of consumption in the industrially highly developed south and west. In February 2020, the Federal Network Agency (Bundesnetzagentur) initiated the plan approval procedure for the first SuedLink sections, in May the orders for the regional planning offices were placed and now TenneT and TransnetBW have awarded the contracts for the plastic-insulated 525kV underground cables – in parallel with the ongoing approval procedures.

NKT and Prysmian PowerLink have eventually been selected as providers for the SuedLink cables, with a total order value of approximately €2bn. The contract comprises design, manufacture, supply, laying of the underground cables, further installation work, and the final high-voltage testing of the cable system. Both companies have demonstrated their expertise in numerous international connection projects on and offshore, and both have proven the quality of their cables in extensive prequalification tests with several cable manufacturers in a multi-year test phase. They were also commissioned for the German affiliate project, SuedostLink, by the two TSOs 50Hertz and TenneT.

TenneT and TransnetBW chose plastic-insulated underground DC cables with a voltage level of 525kV because they transmit more power compared to a 320kV solution and only require half as many cables. Less transmission loss and less civil engineering work translate into both, financial benefits for the TSOs and minimal environmental impact. TenneT Managing Director Tim Meyerjürgens comments: “In the future, SuedLink will form the backbone of the energy transition in Germany. With the commissioning of the DC ground cables, we are now moving from the planning stage to the realisation of this important power link.” Dr. Werner Götz, Chairman of the TransnetBW Executive Board, adds: “We are very happy to be able to apply this innovative and environmentally benign technology for SuedLink.”

TenneT and TransnetBW awarded the contracts for the 525kV DC underground cables for the SuedLink power highway (picture: TenneT)

Linkup
> See TenneT press release (html)
> See TenneT press release, in German (html)
> See TransnetBW press release (html)
> See TransnetBW press release, in German (html)

See article on single page

Redispatch harmonisation in Germany

26.06.2020

Up until now, redispatch measures between the four German transmission system operators (TSOs) – 50Hertz, Amprion, TenneT, and TransnetBW – and the operators of power plants and storage facilities with a capacity of more than 10MW have been carried out on the basis of IT tools specific to the particular TSO control area. In order to align the individual procedures nationwide, the four TSCNET shareholders on 26 June successfully put the first component of their joint redispatch platform into operation, the “Redispatch Settlement Server” (“Redispatch-Abwicklungsserver” – RAS).

The German electricity market is increasingly characterised by volatile generation and RAS is an instrument to initiate redispatch measures both faster and more flexibly. With harmonised data formats and processes, the redispatch platform, of which the RAS is the first part, provides the basis for the integration of renewable energies into the existing redispatch processes, that is, for future-proof congestion management. In concrete terms, RAS allows TSO control centres to monitor and process all relevant power plant interventions. As a result, TSOs can coordinate their redispatch decisions and activities more efficiently. Moreover, the central management introduces frictionless settlement and transparency processes.

The second part of the redispatch platform is the “Redispatch Determination Server” (“Redispatch-Ermittlungsserver” – RES). RES will complement or replace existing forecasting tools for expectable grid situations such as imminent bottlenecks. It will identify those options for action that are compliant with the regulations and most cost-efficient. Based on RES calculations, TSOs can resolve both predicted and existing grid congestions more efficiently than today. RES is scheduled to go into operation in 2021.

The four German TSOs have succesfully launched RAS, a joint server for redispatch settlement

Linkup
> See 50Hertz press release (html)
> See Amprion press release, in German (html)
> See TenneT press release, in German (html)
> See TransnetBW press release, in German (html)

See article on single page

SuedLink: Regional planning offices take up work

10.06.2020

With around 700 kilometres of underground cables to be laid and around €10b to be invested, the SuedLink 525kV line is the largest and probably the most important individual project of the energy transition in Germany. By connecting the windy regions of northern Germany with the consumption centres in the industrially highly developed south and west, “power highways” such as SuedLink are indispensable for achieving Germany’s and Europe’s climate goals. SuedLink is realised jointly by the two TSCNET shareholders TenneT, the Dutch-German transmission system operator (TSO), and TransnetBW, the TSO from southwest Germany.

SuedLink has just taken the next big step: After the Federal Network Agency (Bundesnetzagentur) initiated the plan approval procedure for the first sections in February 2020, the two TSOs have now awarded the contracts for the regional planning offices, which are responsible for the detailed planning of the underground DC connection. These offices, some of which have already been involved in the previous SuedLink planning, take care of all operational tasks – initially in the context of the approval procedure, and later also in the supervision of construction. This includes, among other things, route mapping, construction logistics, environmental planning, and awarding of contracts for civil engineering work. On special topics such as soil investigations, they cooperate with local companies.

The overall project was divided into nine planning sections for the award of contracts. After an extensive bidding competition, a total of four companies were awarded the contract for the three northern sections under the responsibility of TenneT and the six southern sections under the responsibility of TransnetBW. TenneT Managing Director Tim Meyerjürgens explains: “The offices are now preparing the detailed planning for the routing and are taking a very close look at the conditions on site.” This will help the TSOs to accurately develop appropriate routing proposals. Dr. Werner Götz, Chairman of the TransnetBW Executive Board, adds that, due to their local presence, the offices can optimally consider the regional conditions for the detailed planning. “They are intended to discuss the proposals together with the project developers in a close dialogue with the owners and land managers concerned and to review their advice when preparing the approval documents.”

TenneT and TransnetBW awarded the contracts for regional planning offices for the SuedLink power highway (picture: TenneT)

Linkup
> See TenneT press release, in German (html)
> See TransnetBW press release, in German (html)

See article on single page

Luxembourg integrated into FCR cooperation

01.06.2020

Eight central European transmission system operators (TSOs) cooperate in the regional procurement and exchange of Frequency Containment Reserve (FCR). Their joint FCR project is the first regional cooperation in Europe to implement market harmonisation in accordance with the EU Guideline on Electricity Balancing. The participating TSOs are APG, 50Hertz, Amprion, TransnetBW, and Swissgrid – the Austrian, German and Swiss TSCNET shareholders –, the Dutch-German shareholder TenneT as well as the Belgian TSO Elia and the French TSO RTE. It is intended to extend the joint FCR procurement towards western Denmark, so that the central European TSOs are supplemented by Energinet from Denmark as a non-active member.

Luxembourg was missing in the cooperation so far, but cross-border primary control reserve (PCR) between Germany and Luxembourg is now also possible: Since 1 June 2020, balancing service providers (BSPs) from Luxembourg are participating in the joint tender for FCR cooperation. For this purpose, the TSO Amprion, whose German control area is bordering the Grand-Duchy, and the Luxembourgian TSCNET customer Creos have developed a cooperation model. Under this model, Amprion assumes the role of the connecting TSO, carries out the prequalification of the BSPs, concludes the framework agreement for PCR, and takes over the settlement with the BSPs from the Creos control area.

Since Amprion and Creos operate a joint load-frequency-control area, a pooling of technical units within this common area is permissible. Thus, a pool can include Luxembourgian as well as German units that provide balancing services. This means that a BSP may combine generation units or controllable consumer loads from both countries and offer them collectively on the PCR market.

The central European FCR cooperation was extended to Luxembourg (picture: Cedric Letsch)

Linkup
> See Amprion press release, in German (html)

See article on single page