A major powercut blacked out all of the Western Isles and the Highlands.
Around 200,000 homes and premises were affected by the outage on Wednesday night.
Power was later restored when island generating stations came on.
Engineers investigating if the fault was caused in the main line near Inverness.
First Minister Alex Salmond was left in the dark when the lights went out during a visit to Stornoway.
Mr Salmond said: “This was a serious power outage affecting communities across the Highlands and Islands, including Stornoway, where I am meeting with members of my Cabinet.
“Earlier (Wednesday) evening I chaired a meeting of the Scottish Government Resilience Committee where it was made clear the network operator was working quickly to restore power to all affected homes.”