A power cut in Wanaka about 11am yesterday was caused by a fault in protection equipment at the Wanaka substation, Delta systems control manager Graeme Johnson, of Cromwell, said yesterday.
The only areas not affected were Cardrona, Maungawera and Lake Hawea.
Power was restored progressively throughout Wanaka, with some people only having to wait five minutes while others had to wait more than 30 minutes.
Mr Johnson said the fault was frustrating and an investigation was under way.
Technicians would visit the Wanaka substation today to download information from the computer so it could be analysed.
The initial fault occurred in the Cardrona area but it was not related to work being done to upgrade the lines there, Mr Johnson said.
"The fault should have been cleared by our protection gear that feeds the Cardrona area. But unfortunately the protection equipment in the Wanaka substation didn't see it that way and cut the power to everyone," Mr Johnson said.
Cardrona was not affected because its power is being supplied by a generator.
It is the second time this week protection equipment has failed the electricity network. Queenstown and the Wakatipu Basin were left without power for about an hour on Tuesday morning, following a similar type of fault.
Mr Johnson said the network could never be "100% guaranteed" and he could not say a similar fault would not occur again.
