TenneT is a leading European electricity transmission operator with about 22,000 kilometres of (extra) high-voltage lines and 41 million end-users in the Netherlands and Germany. TenneT is also the developer and operator of offshore grid connections in the Dutch part of the North Sea.
COBRAcable is a 325 kilometres long high voltage direct current (HVDC) cable between Eemshaven in the Netherlands and Endrup in Denmark. The interconnector will be established in collaboration between the Dutch TSO TenneT and the Danish TSO Energinet.dk. The interconnector with a capacity of 700 MW will be commissioned in early 2019. HVDC technology allows for the efficient and economical interconnection of electricity grids over long distance, sub-sea or grids which are not running at the same synchronous frequency. HVDC interconnectors comprise three major systems, being the cable, the converter station and the connection to the on-shore high voltage grid in the case of a sub-sea interconnector.
COBRAcable awarded the design and development of the two converter stations and the HVDC cable to different expert suppliers and the technical integration of the systems is managed in-house. Hence, a simulation model was deemed necessary to facilitate the study of the system integrated design.
DNV GL Energy worked with TenneT to create a computer model for the COBRAcable. A professional simulation tool has been developed to perform mainly steady state, but also transient analysis. The tool simulates the technical characteristics of HVDC connections, converters stations and their control circuits. Additionally, DNV GL provided the expertise to review specifications on converter station equipment, notably power transformers and converter valves.
The COBRAcable will contribute to the security of electricity supply by being a back-up for other connections and to integrate the variable supply of renewable energy in a balanced manner. The COBRAcable makes it also possible to make better use of renewable energy sources, avoiding CO2 emissions in power generation, and it helps to create a stronger and more interconnected European electricity grid.