Half of the cables were laid last year, with the remaining 30 kilometres being installed in the past few weeks, explained RWE's project director, Marcel Sunier.
The development's 48 turbine foundations and the substation foundations were connected together with 33kv cables.
RWE said the substation's topside is due to be completed in July, after which the inter-array cables will be connected to it in August.
Visser and Smit Marine Contracting carried out the cable installation work using the Stemat Spirit and Normand Flower vessels.
The wind project is due to be commissioned in spring 2015 once the 48 Senvion (formally Repower) 6.15MW turbines are installed. Construction of the turbines began in May.