Sofia HVDC offshore converter platform

Located 195 kilometres off the north-east coast of England on the Dogger Bank, the Sofia Offshore Wind Farm is one of the largest in Europe. Under contract to Seatrium, Iv was responsible for the detailed design of the platform, procurement, and integration of all auxiliary systems. The scope also included the design of the transport and installation process, with workshop drawings for the grillages.

The project’s scale and distance from shore placed high demands on the reliability and efficiency of the design. To meet the technical requirements and accommodate the limited space on the platform, Iv implemented a seawater-cooled solution instead of an air-cooled system. This improved heat transfer, created a more compact system layout, and greater operational efficiency, all essential factors for an effective offshore installation. The platform was transported by vessel around the Cape of Good Hope, demonstrating both the scale and logistical complexity of the project.

The HVDC converter platform forms the heart of the Sofia Offshore Wind Farm. It converts the 66 kV alternating current (AC) generated by the wind turbines into 320 kV direct current (DC), enabling transmission to shore with minimal losses via two export cables, each around 220 kilometres long. In doing so, Iv contributes to reliable and efficient long-distance power transmission. With a total capacity of 1.4 gigawatts, the wind farm will supply sustainable electricity to approximately 1.2 million British households.

Dimensions
Topside: 80 x 43 x 45 m (excl. Helideck)

Jacket: 58 x 39 x 44 m 

Weight
Topside: 11,000 mT

Jacket: 4,350 mT

Water depth: 28.5 m (below sea level)

Capacity: 1.4 GW

Number of offshore substations: 1

Number of WTG’s: 100

Client: Sembcorp Marine Offshore Platforms Pte Ltd (SMOP)