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Offshore wind farm, North Sea

In 2007, plans were developed for a wind farm in the German North Sea. The wind farm, DanTysk, built by energy companies, Vattenfall and Stadtwerke München München, now has 80 fully operational wind mills.

offshore wind farm


DanTysk needed a solution that would be able to supply reactive power to the generators, which energize the wind mills, in an emergency situation, such as losing connection to shore. In order to maintain warranties on valuable equipment, it was essential that the system be running constantly so that each wind mill can remain dry and controllable at all times. To fulfill the reactive power demand from the grid code, the cables needed to be compensated in case of loss of production by the wind turbine generator. Due to the fact that the topology within the inner array grid can change (in other words, that the cables may be structured in multiple combinations at different times depending on the need), a flexible solution was requested.

Grid voltage during inrush with and without compensation from ADF STATCOM units

Grid voltage during inrush with and without compensation from ADF STATCOM units
The 33kV voltage is in ”per unit” (i.e. 33kV = 1) and the time axis is in seconds. There are five uncompensated measurements (red), and five compensated measurements (blue).


After an initial assessment, four ADF STATCOM units were installed in 2015. The units were installed at the offshore substation, the so-called “heart of the wind farm,” which “forms the gateway for the onward transport of energy to the mainland via submarine cables.”

offshore wind farm
Image © Vattenfall


ADF was seamlessly installed according to expectation and is now an integral part of DanTysk’s efficient operation and function. The value for the wind farm is that they have a reliable reactive power quality solution that compensates the cable capacities during grid outages and is able to optimize the power supply generated from the eighty wind mills, if needed.

ADF also ensures that the wind mills will be supported with power in the event that the connection to shore is lost. Because of this solution, the towers and nacelles are kept in defined climate condition (dry and controllable) constantly, which therefore secures all warranties and maintains efficient service even in the event of a lost connection to shore.

Christopher OSS

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