Grid connection systems
A grid connection system is the term used to describe all the systems used to transport the electricity produced in the wind farms ashore. Direct current transmission is referred to as the DC grid connection system. Alternating current transmission is referred to as AC grid connection systems.
Grid connection systems in the North Sea
In the North Sea, grid connection systems are operated with direct current and alternating current. The wind turbines produce alternating current, which is collected on the wind farm's own offshore platforms (so-called transformer platforms) and transformed up to a voltage level of 155 kV. The electricity is then transferred from the transformer platform via an AC grid connection system to the converter platform of the transmission grid operator. On the converter platform, the electricity from several wind farms is collected and converted from alternating to direct current in order to be transported to the grid connection point on land. The transmission takes place by means of direct current at a voltage level of 320 kV, because this is considered to be particularly effective for the long distances to the grid connection point due to the comparatively low losses.
Grid connection systems in the Baltic Sea
There are no intermediate converter platforms in the Baltic Sea and consequently no DC transmission systems. Electricity is transported ashore throughout the Baltic Sea by means of AC connections, but at a higher voltage, namely 220 kV. This special feature is due to the smaller number of wind farms and the shorter distance to the grid connection points on land. Since, however, a significantly higher energy potential is also to be exploited in the Baltic Sea in future, it is planned to set up a DC grid connection system there as well in the near future.
The construction of a grid connection system requires official approval. The Federal Maritime and Hydrographic Agency (BSH) is responsible. As a rule, the converter platform, the AC connection system and the DC grid connection system are approved as one project. Due to the high complexity of this project, the legislator has given the BSH the opportunity to permit individual measures for construction or commissioning subject to approval. As a result, part of the official review is shifted to the enforcement procedure.
Since 1 January 2017, the legal basis for the approval regime has been the Wind Energy on Sea Act (WindSeeG). Before the Wind Energy at Sea Act came into force, approval was granted on the basis of the Offshore Installations Ordinance (SeeAnlV).
Both the Wind Energy at Sea Act and the Offshore Installations Ordinance stipulate that a planning approval procedure must be carried out before official approval is granted. Only in exceptional cases can such a procedure be dispensed with and a planning consent be granted. The planning approval decision is issued with a large number of ancillary provisions which ensure that construction and operation do not have any negative effects on the safety of ship and air traffic or on the marine environment.
Once the zoning decision has been issued, the project is subject to supervision by the BSH. If necessary, the BSH may issue orders to ensure proper implementation. In particular, technical approvals according to the standard design, which specifies which specific certified documents are to be submitted to the BSH, are part of the execution.