Under the deal, the UK consortium will provide the onshore and offshore substations, plus onshore cabling work for the Galloper project, being developed by RWE.
The onshore substation will be located near Sizewell in Suffolk, east England and the onshore cables are due to start being installed early next year.
The 140-turbine project, located 27 kilometres of the UK's east coast, is scheduled for completion in 2017.
Petrofac has previously worked with Siemens on providing the HelWin1, BorWin 2 and BorWin 3 transmission platforms in the North Sea.
Galloper's project director Bart Oberink said the scope of the contract would be widened once a final investment decision (FID) on the development has been made by the government later this year.
Last week, RWE reached an agreement with SSE to allow the utility group to exit the project once a FID had been made. RWE and SSE were equal shareholders in the project.
The German firm is looking to secure a new partner for the project.
