New trial puts lines to the test

A section of power poles on Featherston’s Western Lake Rd is now a test site for a project that’s seeking to “boost power line resilience”.

The new trial is to see how aeolian vibrations that are caused by wind can affect the network.

“Over time, vibrations from certain types of wind can damage power lines, which ultimately causes the conductor to fail at the bonding point and fall to the ground,” Powerco general manager of electricity Karen Frew said.

“It’s hidden damage, with the conductor deteriorating from the inside out; by the time it causes failure of the line, it’s too late, and the line is on the ground.

“Not only does it cut power to customers, it’s also a serious public safety risk as the lines could still be live after they have fallen.”

In the trial, Powerco is using Sentrisense, a piece of solar-powered technology that is attached to the power line and measures the vibrations.

In addition to the solar devices, a weather station is installed at the closed adjacent power pole to capture localised weather data.

Frew believes Powerco is the only electrical distributor in New Zealand doing this research to understand the engineering around how aeolian vibrations affect electricity networks.

“The occurrence known as aeolian vibration is produced when a low-velocity wind flows over a power line conductor at a 90-degree angle; the energy from the wind flow is transferred into the conductor, which starts to vibrate,” she said.

“It usually happens on a cold, frosty morning when the slow winds come over the lines, which starts the vibration.”

Frew said the trial, which will run for 12 months, will see if – and where – aeolian vibrations are happening on the network.

Once that has been established, the company will put vibration dampers on any affected sections of the line to counteract it.

“With around 28,000km of power lines across Powerco’s electricity footprint, it would be inefficient and cost-prohibitive to put damper devices on all its power lines,” she said.

“Modelling of our electricity network enabled Powerco engineers to narrow down to 10 locations.”

In addition to Featherston, there are three of these test sites in Taranaki, two in the Coromandel Peninsula, one in Manawatū-Whanganui, and one in Waikato.