Another day-long outage on way

HANGING IN THERE: The slip that has critically damaged a Top Energy pylon on the Mangamuka Gorge.

DAMAGED PYLON PUTTING POWER SUPPLY AT RISK

Top Energy is planning another nine-hour power outage north of the Hokianga Harbour and Mangamuka Gorge on Sunday March 15, the second in six weeks, this time to repair a damaged pylon that has the potential to cut the supply for days.

Chief executive Russell Shaw said powers beyond the company's control were responsible, and that the alternative did not bear thinking about.

Heavy rain shortly before Christmas had resulted in a 100-metre slip on the southern side of the Maungataniwha Ranges, directly beneath one of the legs of a lattice tower carrying the only high-voltage line supplying electricity to Kaitaia. The slip had not moved since it was discovered, and plastic sheeting had been laid to prevent further rain from making it worse, but the situation was not safe.

The worst case scenario was that the tower would fall, bringing live lines down across SH1.

"I'm keeping a very close eye on the weather forecast," Mr Shaw said, adding that the pylon had been doing its job for perhaps 60 years and had never caused concern before.

The day-long outage was very much the lesser of two evils, he added. If the tower collapsed it would cut all power to Kaitaia for as long as a week. Top Energy would use generators to supply power to the town in that event, but there would still be rolling blackouts.

"We have been evaluating a number of repair options for some time, hoping that we might be able to come up with a solution that would avoid us having to cut power to Kaitaia for a second time," he said.

"It's now clear, unfortunately, that the only way forward is to build a new tower nearby and to swing the high voltage lines from the damaged structure to the new one.

" That will be a complex engineering operation, made all the more difficult by the remote, rugged location. We looked at trying to do this job at the same time as the other work on February 1, but the sheer scale of the project meant that even if we'd abandoned our plans for that day and focused entirely on this single repair job, one day would not have been enough for us to complete the job safely."

Work on replacing the damaged tower did begin during the first outage though, along with other planned network expansion and repair work, involving 34 staff from other lines networks, including some from the South Island.

It was now working on Phase 2 of the $550,000 repair job, building a foundation for the new structure, erecting it and transferring the lines that could be moved safely without disrupting power to Kaitaia.

The final phase would involve swinging a single remaining 110 kilovolt (kV) line from the damaged tower to the new one, and the power had to be turned off to do that.

Mr Shaw said he was painfully aware of how unpopular the second outage would be but it was "absolutely necessary," and he could only apologise for the inconvenience it would undoubtedly cause.

"I can promise that, when complete, the second high-voltage line that we're building up the east coast to Kaitaia will eliminate the town's dependence on the single supply that currently exists from Kaikohe. And that the improvement in the reliability of Kaitaia's electricity supply will be significant," he added.

The Department of Conservation had been very helpful (a resource consent would not be needed given that this was an emergency situation), the company had kept the local marae informed and had briefed Mayor John Carter.