Transpower says the power emergency in the North Island is over and the fault has been fixed.
Earlier it issued two warnings.
The grid emergency notice warned there was a risk of insufficient generation to meet demand in the North Island.
Transpower said there was a fault on the HVDC cable which transfers electricity from the South Island to the North Island.
Some power was still flowing across the cable but a second fault could suddenly stop the flow of electricity, the operator said.
"The System Operator is proactively managing this risk to prevent the risk of cascade grid failure if that second fault were to happen."
It was working with lines companies to to manage controllable load such as hot water systems, and asked on consumers to be mindful of their electricity use on Friday morning.
Transpower general manager operations Dr Stephen Jay said that the System Operator was working with electricity lines companies and large industrial customers connected directly to the grid to reduce demand.
He said that at this stage New Zealanders would not notice any impact as lines companies would largely be turning off controllable load like hot water systems. Hot water systems are switched on and off regularly during winter.
Dr Jay said that if the removal of controllable load was not enough to balance the power system, then Transpower would need to ask for additional demand to be cut until the power grid was secure, which may result in some consumers being disconnected.
"We ask New Zealanders to be mindful of their electricity use this morning to help us get through this situation and avoid power cuts," he said.
The warning covered the period from 7.15am to 9.30am.
Earlier, Transpower issued a warning notice at 5.37am that there was a risk of insufficient generation and reserve offers to meet demand in the North Island. It had asked for more offers of power and moves to decrease demand if necessary.
The emergency notice came after a sudden cold snap moved up the country in recent days.
The cold snap was lingering early on Friday with below-zero temperatures in Rotorua, which was on -3C, and Hamilton (-2C) while in the south Blenheim and Queenstown were on -1C at about 6.30am.
On Tuesday the operator said the Antarctic blast this week could set an October record for electricity demand, and though it expected the lights to stay on it would issue a notice requesting extra generation if needed.
Transpower has said it had made changes since it was held responsible by the electricity watchdog for widespread outages on one of the coldest nights of last year.
RNZ
