Electricity was cut to thousands of households in Wellington on Sunday afternoon.
Wellington Electricity Lines Limited says 5,558 customers in the suburb of Wadestown lost power because of a fault at the company's Waikowhai substation.
It says the system shut down automatically after detecting a fault, but staff were able to restore the supply in 12 minutes.
The company says crew were able to act quickly because they were already working in the area.
Suspected damage to an underground cable will be investigated on Monday.
