The 33,000-volt overhead line snapped above State Highway 6, near Queenstown’s Shotover Bridge, before 7.30pm on Thursday.
Power was cut to hundreds of customers between Lake Hayes Estate and Arrowtown — some for more than three hours — and motorists travelling west out of the resort were forced to take a detour through Arthurs Point.
A 33,000-volt line came down on State Highway 6 at Arrow Junction last July.
Delta general manager operations and risk John Campbell said the wire came down after breaking "mid-span".
"The fault was detected by our control room alarm at 7.32pm and NZ Fire Service advised us at 7.42pm that they were in attendance."
The cause of the failure would be investigated.
Protection equipment automatically tripped the line when it hit the ground, and no other lines or equipment were damaged, Mr Campbell said.
The fault was detected by Delta staff about 7.30pm, and repairs completed at 11.20pm.
Former Delta worker Richard Healey said the line almost certainly failed because it was "old and fatigued".
Mr Healey, who resigned from the company last October to blow the whistle on the state of Aurora Energy’s network, said a lack of maintenance on ageing lines in the area was the most likely explanation for the failure. If the protection equipment had failed, the ground beneath the line would have been electrified.
