The reason a helicopter was circling over Rotorua

Rotorua residents were curious about a helicopter flying overhead. Photo / Getty Images

A helicopter circling over Rotorua on Thursday attracted the curiosity of some residents who took to social media to question its presence.

However, in the end, there was a simple answer.

Unison relationship manager Danny Gough told the Rotorua Daily Post line inspections were often done by air.

"That doesn't kick off in full until later this year but what they were doing yesterday was a single flight to ensure the helicopter and equipment could meet our specifications in terms of the project," he said.

"It was a one-off but it certainly was related to Unison asset inspections."

Gough said the inspections later in the year would use thermal imaging cameras to scan for potential issues on the region's power lines with the ultimate goal of preventing power cuts.

"We're looking for heat at the end of the day. Where we can see an area on the line, or the network itself, where we have a build-up of heat, it tells us there might be a potential problem.

"We can then carry out a further physical inspection where we can dispatch crews to go up and have a look at what's going on. We can then do prevention of maintenance by repairing or replacing that piece of equipment.

"We're going to do that across the whole network using multiple choppers so it will be really comprehensive and unique. It will give us a full picture of the state of the network which is a really important tool in avoiding power outages, ultimately."

He said the full inspections later in the year would be "comprehensively publicised".