About 11,000 customers in the Wakatipu basin were left without power for just over an hour yesterday morning after a fault in a Transpower line.
The power went out from Gibbston to Glenorchy just after 8.30am when the 110,000 volt overhead power line between Cromwell and Frankton sent a faulty signal.
Transpower communications manager Rebecca Wilson, of Wellington, said the piece of equipment at Cromwell was part of Transpower's communication network.
"Throughout the network, certain pieces of equipment `talk' to others.
"The piece of equipment talked to one at the Frankton substation, but it sent a wrong or faulty signal," Ms Wilson said.
Ms Wilson said that signal caused the line to trip, due to Transpower's protection mechanism.
Contractors travelled to the Cromwell substation yesterday morning to investigate the cause of the fault, she said.
The piece of equipment was removed and would be fully tested before it was reinstalled.
Power was back reinstated to all affected areas at 9.50am.
