Case made for £780m Western Isles subsea cable
A document outlining why a subsea cable is needed to carry electricity generated on the Western Isles to the mainland has been sent to Ofgem.
Scottish Hydro-Electric Transmission Ltd, a division of energy giant SSE, said the "needs case" was a key part of the planning process.
Regulator Ofgem will assess whether the interconnector is efficient and economic.
The project has been hit by delays and a rise in costs to an estimated £780m.
Islands local authority, Comhairle nan Eilean Siar, has said major renewable energy projects planned for the isles cannot go ahead without the cable.
The comhairle has welcomed the submission to Ofgem.
Leader Angus Campbell said swift approval of the project could allow a contract for the cable to be awarded this year.
The interconnector would export electricity to the mainland for distribution.
It would stretch to about 50 miles (80km) from Gravir on Lewis to Ullapool on the north-west coast of mainland Scotland.