Existing network

There is currently no transmission infrastructure on the Orkney Islands. The existing network is a distribution network operating at 33kV or below, and the Islands are connected to the mainland by two 33kV subsea cables installed in 1982 and 1998 respectively between Rackwick Bay on Hoy, and Murkle Bay near Thurso.

These cables have a total capacity of 40MW and the currently connected generation in Orkney uses all of the available export capacity in the existing 33kV cables. Demand on the islands varies between 7MW and 46MW and is secured in the event of a network fault with the assistance of a standby diesel generator installed at Kirkwall.

There is no additional capacity in the existing network, and consequently, any increase in the connected generation on Orkney will require a reinforcement of the existing network on the islands and to the connection to the mainland.

Project need

At present, there are five contracted connection agreements between National Grid and developers in the Orkney Islands. We are therefore looking at options for a new transmission subsea cable link between the Orkney Islands and Caithness, new inter-island cable links between Mainland Orkney, Hoy and South Ronaldsay, and associated new onshore transmission infrastructure.