ABB will supply onshore and offshore substations, plus "related power infrastructure", such as switchgears, to the project. Rampion located 13 kilometres off the Sussex coast in the English Channel.
The firm said it will also make an increase the existing National Grid substation at Bolney in Sussex to help it accommodate the 400MW development's output.
Onshore construction of the project is expected to begin this month, with offshore activities due to commence in "early 2016", according to E.on.
In May, E.on made a final investment decision on the £1.3 billion (€1.79 billion) project after the Green Investment Bank acquired a 19% stake.
MHI-Vestas was also contracted to supply 116 V112-3.45MW turbines.
Rampion will the UK's first Round Three project to begin construction. It is expected online in 2018.