The Cook Strait power cable is back in service after an onshore part of the link near Wellington overheated.
The Pole 2 cable was taken down at 3am on Tuesday, meaning no power was flowing from electricity generators in the South Island to meet North Island demand.
Transpower says the fault related to high voltage overhead lines, not the undersea cable or converter stations. It says the fault was fixed just after 4pm.
It is the second time this year the cable has been down. Last month, a fault took four days to fix.
The outage helped to cause a big difference in wholesale prices between the islands, but Transpower says both had ample electricty to meet public needs.
Household electricity bills would not have been affected.
