Top Energy chief executive Russell Shaw said it was "extremely unfortunate" that Kaitaia's power would have to be turned off again, just six weeks after the February 1 shutdown.
"We hope the people of Kaitaia understand just how important this is," he said.
Mr Shaw said it appeared the wires were the only thing now holding the pylon up.
To stop it collapsing when the wires were removed the pylon had been tethered to a series of five-tonne concrete weights. Gauges on the strops would provide warning of any changes in tension. The weights had been flown in by helicopter, one tonne at a time.
The company had already built a replacement tower, a 17m-high double-pole structure, to carry the high-voltage lines. It had also reinforced the towers on either side of the damaged pylon.
Replacement wires have already been strung to the new tower with only the switch over and removal of the old wires to be done on Sunday. The power had to be off to do that.
The trickiest part of the operation would be releasing the wires from the damaged pylon, Mr Shaw said. It would have to be done without putting any extra strain on the pylon.
The pylon could then be gradually cut up and removed as scrap, probably by helicopter to minimise impact on the scenic reserve.
The company was working with the Department of Conservation and had consulted iwi.
"We recognise how important the area is. We don't want to damage the flora or fauna but we do have to put the line through."
Eighty-five workers, 50 of them from Top Energy, would be involved in Sunday's operation led by Whangarei-based Northpower. The project is expected to cost $550,000.
The company would make the most of the power shutdown by carrying out other maintenance such as installing new lightning arresters.
If bad weather hit, the work would be postponed to March 22. The forecast so far was promising.
Mr Shaw had looked at hiring large generators to keep the power on in Kaitaia but all were hired out as backup supplies for Cricket World Cup venues.
Top Energy is currently building a second high-voltage line to Kaitaia. Once complete there will be no more need for day-long outages.
The Northland District Health Board has a generator which will keep the power on at Kaitaia Hospital during the outage. It was tested last week to make sure it's ready.
The power will go out from 8am-5pm on March 15 in Kaitaia, the Aupouri Peninsula and much of North Hokianga. Doubtless Bay has a backup generator at Taipa so will only lose power from 5-6pm, though residents are asked to minimise power use from 8am-5pm to avoid overloading the generator and triggering rolling blackouts.
