Hornsea Project Two, being developed by Ørsted, will have a total capacity of 1.4GW and supply renewable electricity to more than 1.3 million homes when operational in 2022.
The new substation will transform the power produced by the wind farm before connecting to the national grid.
Balfour Beatty also built the onshore substation for the Hornsea Project One offshore wind farm on the adjacent site.
Duncan Clark, Programme Director for Hornsea Projects One and Two, said: “Their team is already on site having nearly finished Hornsea Project One’s substation and having this continuity of the team will ensure optimum efficiencies.
“We’re committed to investing in the UK and we’re very pleased to be working with a UK firm that we have confidence will deliver a good quality build, on time and most importantly, with a continued high focus on safety.”