Need and legal background
For the Ostwind 3 grid connection project, 50Hertz is planning to build a new substation between Stilow and Klein Ernsthof (both part of the municipality of Brünzow), where the current will be transformed from 220 kilovolts (kV) to 380 kV. As there is not enough space, the existing substation in the neighbouring municipality of Lubmin no longer offers the possibility to connect additional submarine cables. Furthermore, technical grid aspects play an important role here: the connection of an additional system to this site, which already has two offshore grid connections, would pose a larger risk of disturbances and system outages.
For the substation, the survey area in the municipalities Lubmin/Brünzow/Wusterhusen and Kemnitz was specified in Grid Development Plan 2030 (2019). Within this area, an extensive and careful examination of many different criteria will be performed to decide on the final location. The site should, for instance, be located outside of nature conservation areas and drinking water protection zones insofar as possible. Sufficient distance to residential and settlement areas shall also be taken into account. The traffic connection of the substation shall also be possible via suitable streets and rails. Moreover, the existing 50Hertz extra high-voltage grid, in this case a 380-kV overhead line, shall also be nearby, so that the substation can be connected to the 50Hertz grid.
For the construction of the new substation in Stilow and the onshore cable route, 50Hertz is following a planning approval procedure (Planfeststellungsverfahren, PFV). The competent permitting authority is the Ministry of Economics, Infrastructure, Tourism and Labour of the state of Mecklenburg-Western Pomerania (WM M-V). A PFV is a detailed permitting check that does not concern the “whether” but the “how”, i.e. the specification of the site, the construction method and the technical execution of the substation.
Part of the PFV is the formal public participation that is laid down by law. The public agencies are involved in this process, such as the State Agency for Agriculture and Environment of Vorpommern (Staatliches Amt für Landwirtschaft und Umwelt, StaLU Vorpommern) As a rule, the PFV takes 12 to 24 months. The permitting process follows § 43 of the German energy industry act (Energiewirtschaftsgesetz, EnWG).
In the scope of the planning approval, the so-called tap point is also applied for. The tap point is the connection of the substation to the existing transmission grid of 50Hertz. This completes the integration of the wind farm into the German transmission grid.
In support of the formal public participation that is laid down by law, 50Hertz organises an informal public participation in the form of public dialogue. Citizen dialogue builds on 50Hertz's own experiences, not on legal stipulations. This difference is important, as the citizen dialogue ends where the formal public participation laid down by law begins (see also Transparency and public participation).
Construction method and technology
The purpose of a substation is to connect different voltage levels. In this case, the substation transforms the electricity from 220 kV to 380 kV and feeds it into the 50Hertz transmission grid.
The substation in Stilow will be built as an air-insulated switchgear. This means that normal air is used as the insulating medium between the live and de-energised parts within the installation. Such air-insulated switchgear require enough space to create sufficient distance and thus enough insulation between the technical equipment.
Accordingly, the larger part of the area on the premises of the substation in Stilow will accommodate the high-voltage equipment or the equipment that is an active part of the power line, the so-called primary technology.
Furthermore, there is a building in each substation in which the so-called secondary technology is situated. This technology functions as the brain of the primary technology. In other words, it protects and controls the grid connection system. The secondary technology acts as protection in the event of a fault and as a control system during normal operation, and is controlled from the 50Hertz Control Center.