There is no record of the Victorian transmission network being the cause of a bushfire. Design standards, operation and maintenance of transmission assets mitigate risk and enable assets to withstand bushfire conditions.
The transmission network has different infrastructure to the distribution network. Each network has specific management plans that set out processes and procedures for fire prevention and vegetation management.
Transmission lines and easements
Wherever there are transmission lines, there are transmission line easements. We own and manage easements across the transmission network. Transmission line easements protect public safety and give us safe, clear access to our infrastructure so we can maintain a reliable transmission network. We have the right to access transmission line easements at any time to ensure safe operation and to inspect and maintain the towers and lines. This right also extends to our trusted delivery partners. For more information on our inspection and maintenance program, see Transmission line inspections.
Regulation
The Victorian Government regulates the maintenance and operation of the transmission network. We must implement processes and procedures outlined by Energy Safe Victoria (ESV), who are responsible for electricity, gas and pipeline safety. In compliance with ESV regulations, we have prepared a:
- Vegetation Management Plan that outlines the vegetation easement inspection and maintenance program in our transmission network
- Bushfire Mitigation Plan that outlines how the transmission network mitigates bushfire risk.
These Plans are audited every year by ESV. To read the plans, see Regulatory publications.
Transmission Vegetation and Easements Program
Our Transmission Vegetation and Easements Program focuses on maintaining safe clearances between vegetation and transmission lines to reduce bushfire risk. As part of the regular inspection and maintenance program, we inspect our lines from the air using high-resolution cameras to enable light detection and ranging (LiDAR) data and aerial imagery. LiDAR data provides important detail of the height and type of vegetation across the transmission line easements and identifies areas where we need to manage vegetation. Within transmission line easements, mature tree and shrub growth of up to three metres in height is permitted. For vegetation above three metres in height, a safety assessment is required to ensure that minimum clearances and fuel load densities are maintained. Maximum height cannot exceed eight metres. For more information, see Vegetation management.
Total Fire Ban (TFB) days
On TFB days, we carry out a risk assessment of all our planned construction works and put measures in place to ensure the work is done safely.
What happens to the transmission network during a bushfire?
We have a commitment to provide our customers with a reliable and safe electricity supply. During a bushfire, we work closely with Emergency Management Victoria (EMV), Fire Rescue Victoria (FRV), Country Fire Authority (CFA) and Forest Fire Management Victoria (FFMV) and follow all agreed and mandatory directions. If required, this can include turning off the power across parts of the transmission network.
Using easements to support firefighting efforts
As transmission easements are largely free of vegetation, they have a low fuel load and can act as a line of defence against bushfires. We also work with FFMV on backburning operations. A backburn is a fire lit close to the edge of an active bushfire, which burns out the fuel between the bushfire and an established control line. Backburning helps reduce the intensity of a bushfire by reducing fuel load. FFMV is responsible for planned control burns and preparedness activities, like slashing, mowing and creating fuel breaks on public land.
Use of aerial firefighting
We work with EMV and CFA to ensure aerial firefighting can operate in the vicinity of high-voltage transmission lines. The transmission towers and lines are well defined on aeronautical maps. The safe flying distance from the transmission towers is determined by the individual pilot based on their experience and regulations set by the Civil Aviation Safety Authority (CASA). We regularly inspect our transmission network as part of our aerial inspection program and adhere to CASA regulations.
Planned burning
Planned burning helps manage and reduce fuel load. This can help reduce the intensity of a bushfire, by slowing it down and increasing the likelihood of suppression during the early stages of the fire. FFMV and the CFA notify AusNet Services in advance of planned burns. Planned burns are organised on days when weather conditions are suitable, and the wind is heading away from transmission infrastructure. In general, smoke from a planned burn is not a risk to electricity infrastructure.
Fire prevention control
Terminal stations and transmission lines are remotely operated so that they can be shut down when required. If a fault were to occur on the transmission network, the protection systems will detect and switch off the power in a very short period of time to prevent an electrical fire. For a fault on a 220kV transmission network, power is turned off within 120 milliseconds (0.12 of a second). Similarly, for a fault on a 500kV transmission network, power is turned off within 80 milliseconds (0.08 of a second). Once the power has been turned off, there is no longer any risk of electricity sparks starting a fire. Fire is unable to travel along transmission lines because the lines are not flammable.
Lightning strikes
Transmission lines have ground/earth wires installed above the lines at the top of the transmission tower. The ground wire is designed to shield the transmission lines from lightning strikes. If lightning strikes the ground wire on top of the tower, the power in the strike is directed safely into the ground through the ground wire and towers without putting the transmission lines at risk of strike. Redirecting lightning strikes safely to ground allows the electricity supply to be maintained without interruptions, avoids damage to network infrastructure, and reduces the risk of a bushfire being ignited from dry lightning strikes in the immediate area. Ground wires form an essential part of a safe and reliable transmission network.
2009 Victorian Bushfire Royal Commission
The 2009 Victorian Bushfires Royal Commission made, among others, eight key recommendations focused on reducing the risk of fires related to electricity distribution infrastructure. This included more inspections, better hazard management plans, improved training and infrastructure upgrades. The commission did not place any recommendation on the operation or maintenance regime of the Victorian electricity transmission network. Read the 2009 Victorian Bushfires Royal Commission final report.