Design tweak could improve high voltage towers

UQ engineers are investigating ways to strengthen high-voltage electricity transmission towers to minimise damage from summer storms.

Downbursts are intense wind fields created when a strong downdraft collides with the ground and diverges.
They are responsible for most of the severe winds during storms in South-East Queensland.

Most high voltage towers, which supply industry and major infrastructure such as mines and airports, were designed to withstand conventional wind gusts but not the loading and unpredictability of downbursts.

UQ Engineering PhD candidate Michael Chay and his advisor Dr Faris Albermani have found that long span structures such as transmission lines could be destabilised by downbursts.

“The type of wind conditions we design for are very different from those that occur during a downburst,” Mr Chay said.

“We need to find a way to incorporate these conditions into our codes of practice to ensure a safe and reliable design and avoid unnecessary expensive repairs.”

Downbursts usually last for a couple of minutes over several square kilometres and often go undetected by weather stations.

Mr Chay and Dr Albermani have spent the last three years researching downbursts and their potential to damage high voltage towers.

They lack accurate data about South-East Queensland downbursts and have been using overseas data instead to test their mathematical model of a downburst.

But Dr Albermani said they hoped to collect local downburst data by installing acceleration and wind meters on three high voltage towers throughout South-East Queensland.

He said it would cost about $70,000 to install the meters and collect the data but it would be worth it as the Queensland’s power supply depended on these towers.

“If they collapse, it’s very expensive. The repair is about $1 million per kilometre of line.

“That’s excluding the insurance and loss of power to industries.

“And usually when they collapse they don’t collapse one at a time, they pull down another three or four.”

Mr Chay said that most people were unaware that downbursts existed and were often wrongly reported as “mini-tornados”.

Engineers can stengthen towers by changing their design to have heavier members, improved connections, extra bracing or wider legs.

Dr Albermani warned that the South East’s changing weather pattern meant more downbursts were expected that could damage the towers.

Media: Dr Albermani (07 3365 4126, f.albermani@uq.edu.au) or Miguel Holland at UQ Communications (07 3365 2619)