Seaway Heavy Lifting's Stanisalv Yudin vessel completed the work at the 210MW project, which will be made up of 35 Siemens 6MW turbines.
The substation was manufactured at STX France's St Nazaire shipyard in western France. With the installation of the topside mass on the jacket, the substation is now positioned within the 35-square-kilometre site and will be linked to the turbines via a series of inter-array cables.
Developer Dong Energy said is set to start turbine installation at the project in "late summer" after the foundations were completed in May. The wind farm is expected to be commissioned in 2015.
Westermost Rough is jointly owned by Dong, Japanese corporation Marubeni and the UK's Green Investment Bank. The project represents the first time Siemens' new 6MW turbine will be used on a commercial project.