BEI interconnector Bornholm-Germany

In order to efficiently bridge the large distance between the two countries, the electricity is transmitted using high-voltage direct current transmission (HVDC). This involves connecting one converter plant on Bornholm and one in Mecklenburg-Western Pomerania directly by cable via so-called point-to-point connections. This direct connection transports the energy with less loss and therefore more efficiently due to the large distance to be bridged. In addition, the converter systems can be used to determine how much electricity flows through the line and in which direction. It is therefore possible to control supply and demand better than with alternating current.

With a direct voltage of 525 kilovolts (kV), the BEI system can transmit electricity with a total capacity of three gigawatts, two gigawatts of which are directed towards Germany. At the grid connection point, the direct current (DC) is converted to 380 kV alternating current (AC) using a converter system and then fed into the overhead line at the substation and thus into the transmission grid.

The approximately 173-kilometer-long interconnector connects the electricity grids of Germany and Denmark.

Progression on land

A new transformer and converter plant is planned at Rappenhagen (Mecklenburg-Western Pomerania). This will be used to connect to an existing overhead line to feed wind power into the German transmission grid. In the other direction, a land cable system will run north from the new transformer station to the port of Vierow on the Greifswald Bodden. The approximately nine-kilometer-long cable will be laid as an underground cable. The installation of the cable conduit system has already begun in connection with the construction work for the Ostwind 3 offshore grid connection system.

Progression at sea

To minimize the impact on the environment, the cables will be laid as short as possible and, where possible, in bundles with existing cables.

From the landing point in the Vierow port area, an approximately 160-kilometre-long submarine cable is planned, which will pass east of Rügen in the coastal sea, then cross areas with existing offshore wind farms in the German Exclusive Economic Zone (EEZ) and finally run through Danish waters to the landing point on Bornholm.

The end point on the island of Bornholm is planned around four kilometers from the landing point at a new converter plant to be built by the Danish electricity grid operator Energinet.

Onshore transformer and converter station

50Hertz is planning a new transformer and converter facility at Rappenhagen (Mecklenburg-Western Pomerania). The direct current of the BEI cable system will be transmitted with a direct voltage of 525 kilovolts (kV) and must be converted to 380 kV alternating current in a converter plant. It will then be fed into the transmission grid via the substation and an overhead line connection to be constructed. A possible expansion perspective for a further direct current system from the sea is also being considered at the site.

50Hertz carries out an extensive and careful examination of numerous criteria before deciding on a location. If possible, the site should be located outside of nature conservation areas and drinking water protection zones. The distance to residential and settlement areas must be observed in order to comply with emission control regulations. It must be possible to connect the transformer and converter plant via suitable roads and railways.

In addition, the existing 50Hertz extra-high voltage grid should be located nearby so that the substation and converter plant can be connected to the electricity grid, taking into account all relevant concerns such as nature conservation, immission control and the landscape.

As a hybrid offshore interconnector between Denmark and Germany, Bornholm Energy Island is a project of common interest (PCI) of the states of the European Union. The project has been taken into account as European project no. 1106 in the ten-year plan for European grid development (TYNDP 2022) by the Association of European Transmission System Operators for Electricity. Based on this, the national grid development plan (NDP) will be developed, presented for public discussion and consolidated. Bornholm Energy Island is included as project P640 in the NDP 2037/2045 (2023), the BEI interconnector Bornholm - Germany as measure M901a. You can find more detailed information at netzentwicklungsplan.de and netzausbau.de.

The construction of the power line is an infrastructure measure that affects many interests along the way, such as development, agriculture and nature conservation. As part of the statutory approval process, these interests are weighed up against each other and balanced as far as possible. To this end, the permits are supplemented by a large number of ancillary provisions, compliance with which minimizes the impact on the marine environment, safety for shipping and air traffic as well as local residents and tourism.

The planned route in the German section can probably run largely within corridors that are already spatially regulated and parallel to other 50Hertz offshore grid connection systems. It is therefore not necessary to carry out a spatial impact assessment. This was confirmed by the higher regional planning authority.

Approval EEZ

The submarine cable of the interconnector runs through the areas of responsibility of various approval authorities. The Stralsund Mining Authority and the Federal Maritime and Hydrographic Agency (BSH) are responsible for approvals in the Baltic Sea EEZ. The approval of the submarine cable route is carried out there in accordance with the Federal Mining Act (BBergG).

Coastal sea permit

A planning approval procedure (PFV) is required for the submarine cable in coastal waters. The responsible authority is the Ministry of Economics, Infrastructure, Tourism and Labor of Mecklenburg-Vorpommern. The legal basis for the planning approval is the Energy Industry Act (EnWG).

Approval of land route

The land route is approved in a planning approval procedure with three components:

1. the cable feed into the already approved and constructed cable conduit system from the landing at Vierow harbor to the Stilow substation,

2. a new cable route from the Stilow substation to the site of the new substation and converter plant,

3. the connection of the new substation and converter plant to the existing 380 kV overhead line.

According to the current status, a planning approval procedure is being carried out for the land cable route and the overhead line connection in the state of Mecklenburg-Vorpommern. The Ministry of Economics, Infrastructure, Tourism and Labor of Mecklenburg-Vorpommern is responsible for approving the land line.

 Approval of transformer and converter system

An application for a permit for the transformer and converter plant will be submitted to the State Office for Agriculture and the Environment of Western Pomerania in accordance with the Federal Immission Control Act.

Formal public participation is partly enshrined in law for the individual approval procedures. Formal participation is prescribed for public interest bodies, such as the State Office for Agriculture and the Environment Vorpommern (StaLU Vorpommern), the specialist authorities of the district concerned, as well as associations and private stakeholders.

50Hertz supports the informal, early public participation prior to the formal public participation. More on this at “Transparenz und Bürgerbeteiligung”. This voluntary form of public participation, which is based on our own experience, ends when the formal public participation of the responsible administration begins.

50Hertz also informs the public transparently about the activities in the affected region in preparation for the construction phase and during the construction work up to commissioning.

Timetable for early public participation:

• April 10, 2025
  Public information market in the project region, information to follow
• April 3, 2025
  Public consultation for public bodies and local politicians), the invitation was sent on 10 March
• April 10, 2024
  Public information market in Brünzow, community center
  The Bornholm Energy Island project was presented to residents and interested parties for the first time (technology, approval steps, etc.).