Some Kaitaia folk experienced a momentary loss of electricity on Sunday afternoon, but the essential maintenance (replacing a structure on the main 110kV line) was completed during the planned nine-hour outage, with three generators keeping the power on for thousands of Top Energy customers.

The job was finished on schedule despite the vandalising of an excavator and a vehicle at the lines company's Fairburn site, which chief executive Russell Shaw said made for a frustrating start to the day for the crews, who had some tough deadlines to meet.

"We know the inconvenience outages cause. It is extremely frustrating to have our work impeded by such a senseless act, which ripples out to the whole community," he said.

He was "cautiously optimistic" that this may be the last time that an outage of Sunday's duration would be required for annual maintenance on the single 110kV line, however.

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"This year, with the use of back-up generation in Taipa and Kaitaia, we were able to limit the scale of the outage to 4850 customers. Without the diesel generators, 10,000 customers would have been affected," he said.

The company was currently progressing its resource consent application for a Kaitaia-based "generation farm" that would provide total back-up generation of 16MW, which could supply 10,000 customers. The two diesel generators at Taipa together provide 4MW.

"This means we can maintain power during planned and unplanned outages," Mr Shaw said.

"It also means that we have more flexibility in how we manage out network, and can move the generators to the source of the outage rather than having to invest in costly upgrades.

"This is certainly pertinent in the current environment, as we can no longer undertake live line work. There have also been delays to the building of a second 110kV line due to further legal challenges from land owners.

"Diesel generation is becoming, through necessity, a key network management strategy to keep the power on."

Meanwhile Top Energy had embarked on a $170 million investment strategy that, in addition to diesel generation, explored the viability of micro-distribution networks such as solar panels, batteries and other localised generation.

That approach would help provide service to areas that were connected to the network but were either uneconomic or challenging to access due to their remote location and restricted customer numbers.

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Some of those who did the work on Sunday needed no explanation of the difficulties presented by remote locations and rugged terrain. Four teams completed insulator and crossarm maintenance work at sites in the Takahue Saddle where there was no vehicle access, one crew facing a 50-minute walk from the end of the ATV track to their site.

The other three teams had things a little easier in terms of access, but had a lot of work to do within the deadline. They completed the installation and commissioning of three new automated switching devices that would enable better remote control and isolation of the network on the remote South Road feeder, while also removing redundant equipment and updating other switching devices.

Top Energy technical safety adviser Andy Rogerson was on deck throughout, monitoring the three generators keeping the town supplied.

Power consumption was well within the generators' capacity to provide, and he was grateful to customers who heard the company's request to keep consumption to a minimum during the outage, by not using power-hungry devices such as washing machines and air conditioning.