| Focus on Australia Bushfire risk: get it covered
With the increasing risk of wildfires from bare electrical lines, Australia’s DNOs are turning to covered conductors to protect communities. This is proving to be a cost-effective way to manage bushfire risk and enhance reliability
Steve Rutland MD, Amokabel Australia
Photos (above and on next page) show Australian overhead lines employing Amokabel covered conductors
Australia’s distribution network operators (DNOs) are taking action to reduce the risk of bushfire, with fire seasons becoming longer and more intense – a trend attributable to climate change. The 2019/20 bushfire season caused immediate damage worth around AU$2 billion (US$1.6 billion). But when account is taken of less tangible impacts, eg, on healthcare and loss of future production, costs may rise to AU$100 billion (US$80 billion).
The chances of arcing or sparking on any single span are slim. However, the impact can be significant.
A bushfire can start when a tree branch drops onto a live overhead cable, if a pole falls or lines clash. Alternatively, high winds can cause a power line to fall into dry vegetation.
Applying the lessons from Black Saturday
That is what happened in the state of Victoria in February 2009, igniting the Kilmore East fire. This was the most serious of a series of fires that became known as the Black Saturday bushfires. Together, these resulted in the loss of 173 lives, more than 7500 people being displaced and huge losses of livestock, agricultural and business assets.
The Victorian government took swift action in the wake of Black Saturday, establishing a Royal Commission to investigate. It reviewed policies,
procedures and standards for everything from building codes and tree cutting to electrical system design and operation.
One of the outcomes of the Royal Commission is that DNOs now have a mandate to reduce the bushfire risk from electrical lines by controlling fault currents and protecting lines from the elements with a physical barrier. However, a challenge is that Australia has one of the lowest population densities in the world and as a result, its utilities need long lines stretching over large distances to serve customers. They use three-phase grids for more densely populated areas and single wire earth return (SWER) networks for cost-effective distribution to remote communities.
Three technology solutions With power continuity being vital for many customers, DNOs are following the Royal Commission’s recommendations to minimise faults that might lead to arcing. For example, they have a rigorous approach to clearing trees and vegetation and inspecting customer connections. In addition, they switch off automatic reclosing on lines during the peak fire season. They have two additional technologies to choose from to further de-risk their networks. The first option is undergrounding. This significantly reduces bushfire risk as the lines are buried underground with little interface with dry
vegetation. The challenge is that undergrounding is capital-intensive and is therefore best suited to high-risk bushfire areas.
The other option is to use covered conductor for overhead lines in place of conventional bare wire. The insulated jacket acts as a protective barrier that encapsulates the conductor. Not only does this prevent the release of sparks and reduce fire risk, but it also improves reliability as it prevents faults arising in the first place. It also dramatically reduces the risk of members of the public or wildlife coming into contact with the conductors.
Covered conductor is well established as a solution in Australia but DNOs have used it sparingly. That is because previous standards relied on heavy-duty materials as insulation. This made lines heavy, utilities had to upgrade poles and add extra poles, as well as creating a challenge for installers when handling and stringing lines in the field.
New-generation covered conductor
A new generation of covered conductor has been developed with lightweight insulation and has huge potential for both three-phase and SWER lines.
It is suitable for restringing on existing poles and can be delivered for 25% of the cost of undergrounding or less, depending on the
www.modernpowersystems.com | July/August 2021 | 11
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