Independent seismic wave technology has been used to locate more degraded power poles at The Sisters despite Powercor claims it has a rigorous maintenance program.
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Dairy farmers Jill Porter and Jack Kenna engaged an independent company, Groundline Engineering, to test poles in the St Patrick’s Day The Sisters/Garvoc fire area, using a high-tech testing device known as Thor.
Groundline had previously found two poles in poor condition on the Sparrow Spur line, near the rotten pole No. 4 which sparked The Sisters/Garvoc fire after it snapped off in high winds.
On Monday it was revealed that pole No. 2 on the line has a crack through the middle and a significant cavity in the middle of the structure.
More checks this week have revealed that Poles No. 9 and 11 were also degraded.
A stunned Mrs Porter was left speechless that poles checked in November last year and again since the March fire were in such poor condition.
"It is simply beyond belief," she said, adding most of the poles on the Sparrow Spur line had been destroyed in the fires and been replaced.
On Monday she said that having two degraded power poles within sight of her home was like having a burning match in her backyard.
Groundline Engineering director Ian Flatley said on Wednesday that the Thor testing revealed pole No. 2 was less than half the strength of a new pole.
He said the Thor system - developed in coordination with Swinburne University and named after the hammer-wielding god associated with thunder, lightning and the protection of mankind - runs a seismic wave up and down the whole pole.
Traditional pole testing system - known as dig and drill - involves digging down about 300mm, using a hammer to sound against the pole and then drilling into the pole to try and identify irregularities.
The Thor system has been used to test about 45,000 poles globally and a couple of thousand poles in Victoria.
"Thor testing flags the pole for further investigation through maintenance processes. We're working with a UK-based company using artificial intelligence to determine specific defects,” Mr Flatley said.
"The dig and drill method is very old school, prehistoric. It does not provide accurate technology-based information.
“Poles of inferior standard are simply not being detected.”.
Mr Flatley said any pole testing aimed to detect evidence of termites, decay or soft rot.
He said the Thor system was quick, repeatable and no other comparative technology came close.
"The Thor system uses a seismic wave, it applies high-end digital analogue hardware to the pole. We are effectively competing with a guy with a spade and drill bit," he said.
"This is a solution tool which can be used to test 80 to 100 poles a day. It takes seconds."
A Powercor spokeswoman said the company had inspected poles and wires in the regions impacted by the St Patrick's Day fires and replaced a number of assets.
"We have also inspected 13,500 poles in 2018 on power lines extending from Camperdown, Koroit, Terang and Warrnambool as part of our cyclical inspection program," she said.
"In addition, we have specifically checked poles similar to the one that fell in March using a technology called Woodscan and we are confident we have mitigated the chance of this happening again.
"Woodscan is state-of-the-art wood pole inspection technology that uses ultrasonic signals to assess the integrity of poles.
"We are continually investigating and evaluating new technologies that could improve network safety,” she said.
Experts said Thor scanned a whole pole using a seismic wave, providing a sound or suspect result, while Woodscan was used as a secondary horizontal cross-section check to determine specific problems.
The Powercor spokeswoman said that this year the company had invested in its largest ever capital works program as it implemented the Victorian Bushfire Royal Commission recommendations and continued to strengthen the network.
"We take very seriously our responsibility to ensure we do everything we can to make our network safe and reliable," she said.
"We will be discussing the poles on Mrs Porter’s property directly with her.”
Mr Flatley said covered conductor technology would also have prevented all four St Patrick's Day fires in the south-west.
"If covered conductor had been in place you would not have had fires here on St Patrick's Day," he said.
"Covered conductor involves wire covered with four layers of polyethylene and meets all standard in relation to abrasives, UV, electrical and mechanical. It's been used in a south-east Melbourne trial to help the reliability of power lines.”
An Energy Safe Victoria spokesman said audits for south-west Victoria, including the review of the four St Patrick's Day fires, were yet to be completed.
He said those investigations were ongoing but were expected to be completed and the results released early next year.