Inter-array cable installation has begun at Gwynt y Môr Offshore Wind Farm, off the coast of North Wales.
The subsea cables will connect 160 turbines to two offshore substations already installed eight miles off North Wales in Liverpool Bay.
The work is being carried out by Surrey-based Reef Subsea Power & Umbilical and uses the Polar Prince vessel.
The £40m contract will see Reef Subsea assist with engineering, project management, remotely operated vehicle and survey operations linked to the subsea installation and burial of all infield array cables.
Toby Edmonds, RWE npower renewables' Gwynt y Môr project director, said: "The start of array cable installation is an important milestone in the construction of Gwynt y Môr.
"148km of 33 kV cable has been manufactured by the Norwegian company Draka, and will be placed in the seabed to connect each turbine to the offshore substations.
"Half of the wind turbine locations already have foundations installed and the array cables will be connected to the transition pieces before the towers, blades and hubs are placed later this year.
"Array cable installation is scheduled to continue throughout 2013 and into 2014."
Electricity generated by the Gwynt y Môr turbines will be carried to the offshore substations and then taken by four subsea export cables to a beach landing point at Pensarn, near Abergele, North Wales.
From there, the energy will be carried underground via an 11km cable route to a new substation near St Asaph and fed into the National Grid.
Wind turbine installation is scheduled to begin from the Port of Mostyn on the Flintshire coast in April, with the first generation expected in the summer 2013.
Tim Sheehan, executive vice president commercial of Reef Subsea, said: "It has been a very complex mobilisation phase, which has demanded a significant amount of pre-engineering work, major vessel enhancements and delivery of a new cable plough."
At 576MW, Gwynt y Môr is one of the largest offshore wind farms currently in construction in Europe. It is a shared investment between partners RWE Innogy, Stadtwerke München GmbH and Siemens.
Once fully operational, energy generation from Gwynt y Môr is expected to be equivalent to the average annual needs of around 400,000 homes.
Gwynt y Môr Offshore Wind Farm has awarded contracts worth more than £80m to companies in Wales.