A major failure of the 20-mile subsea power cable between the isles of Skye and Harris could take months to repair – and it may even need to be replaced at huge cost.
The fault is in deep water and was responsible for a significant power cut on Friday, affecting all of Harris and Lewis.
Scottish and Southern Electricity Networks (SSEN) said almost 18,000 properties on the two islands are now being powered by the diesel-fired turbines at Battery Point power station at Stornoway – and that this will continue for the foreseeable future.
The undersea cable break means the only power link between the whole mainland transmission network and the northern half of the Western Isles has been severed, although power continues to flow to the southern isles through a separate spur of undersea cable from Skye.
Negotiations are under way with mainland power station teams to bring manpower to the islands and keep the Stornoway power station running through the winter and possibly for months thereafter and with Scottish Fuels to arrange for extra diesel deliveries.
These will keep both Battery Point and back-up turbines at Arnish powering the islands.
Angus MacNeil, MP for the Western Isles, said the failure of the line gives rise to concern for the power supply to the islands heading into the winter months.
“We are now on long term backup, which should be a short-term solution,” he said.
“What happens if something goes wrong with the backup? We are not very resilient with energy in the islands.”
A spokesman for SSEN said: “Initial location testing indicates a fault on the cable, which runs from Ardmore, Skye, to Beacravik, Harris, around 9.3 miles from shore and in an area of deep water,” and that the organisation is committed to restoring the network to full operation as soon as possible.
Investigations will determine whether a repair or “end-to-end cable replacement” is required. SSEN said the fault should have no impact on supply to homes and businesses on Lewis and Harris.
Battery Point Power Station will remain in full operation for the duration of the fault, alongside on-island renewable generation.
A subsea survey of the Skye to Harris cable was undertaken this summer which did not identify any problems.