Offshore substation

The 155kV offshore substation is the heart of the wind farm. The energy of all 54 wind turbines is transferred via the 33kV subsea cables to the offshore substation. There the voltage is transformed from 33kV up to 155kV via two grid transformers. The energy is transmitted further via two 155kV subsea cables, provided by the transmission system operator, to the Dolwin Beta AC/DC converter station.

The Offshore substation comprises of the upper part - the topside - with a weight of circa 2,200 tons, and the lower part, the jacket foundation, with a weight of circa 1,400 tons. The jacket is held in place by a grouted connection to four piles driven into the seabed.

The topside is a steel building with four levels, and houses the grid transformers, switchgear and auxiliary power supply for lights, safety systems and data and control system. The grid transformers provide a total power transmission capacity of 332MW from the wind turbines to the German electricity grid. The offshore substation is standing approximately 40m above sea level. A helicopter landing platform on the top deck of the offshore substation allows for weather independent access to the platform for operation and maintenance works.

Technical Data:

Voltage Levels: 155 kV/33 kV (AC)
Power from the wind turbines: 332 MW
Grid Transformers: 2 x 200 MVA, 155/33 kV air cooled
Auxiliary Transformers: 2 x 1,6 MVA, 33/0,4 kV, hermetic sealed
Emergengy Diesel Generator: 1 x 220 kVA
Park Diesel Generators (for Turbines):    2 x 4,1 MVA, 400 V (AC)


Topside (L x W x H):    32 x 16 x 18 Meter
Jacket (H): 51 Meter
Water Depths: 28 Meter
Topside Weight: 2,293 tons full operational
Jacket Weight: 1,683 tons excl. piles
Topside Decks: 4 incl. Roof Deck with helicopter landing deck

substation Nordsee One