Loy Yang Power drives long-term success

Victoria’s largest energy producer, Loy Yang Power, recently embarked on an upgrade of its four-level open-cut coal mine facility, Loy Yang Mine. The ‘in progress’ upgrade includes the redesign and progressive changeover of the mine’s existing coal transfer conveyor drive systems. With a combined length in excess of 25 km, the mine’s conveying system transfers the freshly mined coal from the mine floor to the surface.

According to Loy Yang Mine senior electrical engineer, Steve Cleaver, providing a steady flow of coal feedstock to the coal bunker is essential to keeping the power generation process online and producing cost-effective electricity. “The coal bunker only has enough capacity to fuel 20 hours of power generation. Therefore, the pressure on the conveying system to perform is relentless,” he says.

The legacy transfer conveyor drive systems at Loy Yang Mine were based on water-cooled eddy-current coupling (ECC) technology. When first installed many years ago, the ECCs were the ideal drive solution for providing high torque over a wide speed range — perfect for hauling enormous quantities of coal from the bottom of the mine to the surface.
However, in recent years it had become clear to the Loy Yang Power mine engineering team that the legacy drive systems were struggling to move the coal as efficiently as they believed was now possible. Furthermore, the existing drive cooling systems were not coping with the production demand and were frequently overheating. “We can’t afford to have a conveyor go offline, especially given the ever-increasing demand for electricity during peak-load periods,” Cleaver says. “When we’re offline we’re not selling electricity, so downtime is catastrophic. It was time to make a change.”

To obtain a drive solution capable of withstanding the rugged mine environment while delivering premium around-the-clock performance, Loy Yang Power enlisted the engineering experience of automation specialist, Rockwell Automation.

As part of the mine upgrade, Loy Yang Power implemented a drive solution incorporating the latest technology. “With so many conveyors on-site, it was important that the new drive technology could be brought online gradually and was able to integrate with our existing drive systems and control architecture,” says Cleaver.

In a collaborative effort, Rockwell Automation and the Loy Yang Power engineering team developed a new drive solution, founded on the Allen-Bradley PowerFlex 7000 medium voltage (MV) AC drive. These drives feature ‘direct-to-drive’ technology that helps eliminate the need for isolation transformers on applications with either new or existing motors. This provides a space-efficient and portable solution suitable for the needs of Loy Yang Power.

The mine engineering team came up with an idea to equip each conveyor with a fully self-contained, cooled and removable drive package that could be easily installed or uninstalled on any of the mine’s conveyors.

According to Rockwell Automation technical consultant, Gary Spotswood, the compact nature of the PowerFlex 7000 drive simplified the development of the portable drive packages. “The transformerless configuration of the PowerFlex 7000 meant we were able to help minimise the footprint of the drive package,” he says. “We developed a partitioned stainless steel IP67-rated enclosure, equipped with an air-conditioned cooling system, to house each of the 6.6 kV PowerFlex drives. Not only was it a more elegant drive set-up, it also eliminated the mixture of water and electricity used with the ECC cooling systems.”

Cleaver was especially impressed with Rockwell Automation’s willingness to fully explain the inner workings of its drive solution. “We didn’t want any proprietary ‘black box’ technology,” says Cleaver. “In a process such as ours, we can’t afford to wait around for specialised service teams. We need to be familiar with the product and its inner workings so we can set it up, monitor it and troubleshoot it if necessary. Rockwell Automation was excellent in this respect; they were able to ‘explain and train’.”

With the mine upgrade at Loy Yang Mine only partially complete, there is much work ahead. Cleaver and his team are planning to progressively replace many other ECC drives across the mine with PowerFlex 7000 drives. “We have been impressed with the Rockwell Automation drive solution,” says Cleaver. “It provides us with the combination of reliability and performance we are looking for.”

Rockwell Automation Australia
www.rockwellautomation.com.au