Under the contract, Alstom and Petrofac will provide the onshore and offshore substations as well as onshore cabling for the wind farm, which is expected to generate enough energy for about 330,000 homes in the UK.
RWE will be responsible for ongoing decisions and funding of the project.
The consortium will provide the detailed design of the electrical system which includes ordering of several major electrical parts like transformers, static VAR compensators and offshore switchgear.
Galloper Wind Farm project director Bart Oberink said: "The announcement of preferred supplier status and the awarding of this major contract is a key milestone for the delivery of the project and the rest of the supplier negotiations are advancing to timetable.
"We expect to extend the scope of Alstom and Petrofac’s contract once the Financial Investment Decision for Galloper is announced later this year."
The wind farm is a joint venture between RWE and SSE.
However, SSE recently signed an agreement to sell its stake after a review of offshore wind development portfolio.
The wind farm’s onshore cable installation work is scheduled to start in early 2015.
RWE is expected to make announcements on the selection of preferred suppliers for other key contracts in the near future.
