Powerlink incorporated long-term customer benefits with continued power security in engineering a solution to help move one of Australia’s biggest mining machines through the red heart of Central Queensland.
With customers in mind, Powerlink briefly reconfigured its electricity transmission network in two places and moved telecommunications cables underground to allow the safe 77 kilometre transportation of a 3,500 tonne dragline between two mines.
Powerlink Executive General Manager Delivery and Technical Solutions, Stewart Bell, said simply de-energising the powerlines to allow the dragline to pass was not an option.
“Our infrastructure in that area is vital to the supply of electricity to customers, including some large mines and rail networks – customers that can’t afford to be constrained by interruptions to supply,” Dr Bell said.
“This is not the first time we’ve enabled a dragline to cross our transmission lines, however we haven’t previously been challenged with such constraints for outages on this part of the network.”
Using a staged approach that was repeated for both transmission line crossings, the project was months in the planning. Powerlink worked closely with its customer, BHP Mitsui Coal (BMC), to meet their specific business needs and not impact day-to-day operations when they relocated the dragline from the BMA Goonyella Riverside Mine to the BMC South Walker Creek Mine.
Drawing on Powerlink’s depth of experience to deliver an efficient and safe outcome, Dr Bell said the project called for innovative methods to be used that facilitated a number of customer benefits.
“An additional complexity was the need to maintain the extensive fibre optic telecommunications network installed on Powerlink’s transmission towers,” he said.
“The telecommunications fibre optic not only provides us with data on how our network is operating, but provides telecommunication services across Queensland.
“To ensure there was no interruption to the telecommunications network while we allowed the dragline to pass by, we relocated a 375 metre segment of fibre optic underground – providing a long-term solution for our mining customers who may need to move equipment in the future.”
Powerlink built a temporary diversion powerline using wooden poles that was energised to provide an alternative secure route for electricity supply while the normal transmission line was de-energised.
After converting the suspension transmission towers on the normal line to ground-stayed tension towers, the lines were lowered to allow the dragline to safely walk by.
Powerlink Team Leader Projects, Tony Milward, said with processes in place to ensure the work proceeded safely and efficiently, switching supply to and from the temporary diversion powerlines was managed within a tightly restricted window.
“We needed multiple, short-duration outages, so scheduling was meticulously planned and very tightly controlled by Powerlink’s specialist network controllers to avoid impacts to electricity customers and keep our people and those on the ground safe,” Mr Milward said.
“We pre-empted and analysed multiple scenarios and established contingency plans during our preparations to ensure immediate actions could respond to any situation.
“In fact, external factors did arise that caused us to delay and reschedule a number of supply interruptions and we were able to respond quickly with the help of a talented cross-disciplinary team of experts,” he said.
Powerlink Project Manager, Nathan Jackson, said the two 132kV double-circuit transmission lines that stood in its path were dwarfed by the 72 metre tall dragline.
“It was pretty impressive,” Mr Jackson said. “When the dragline passed the de-energised transmission line we reinstated the conductors, tested the line and returned to normal service – the temporary diversion line was then disconnected.
“Enabling each crossing on site took us about one week to complete – without impact on other mining customers in the region or on our wider network,” he said. “That’s a great outcome.”