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Animals and electricity supply

Grey-Headed Flying Foxes

Animals are involved in 6-to-7% of outages in the distribution network. The number of outages caused by animals is increasing - and that increase specifically is related to the recent arrival and rapid growth of a Grey-Headed Flying Fox colony.

Of this 6-to-7% of outages caused by animals, Birds are responsible for two-thirds ( ie about 4%, possums 1%, bats 1%) and the balance are caused by rats, termites, snakes and lizards.

Birds can cause outages in a number of ways including individually and collectively. For example, if a bird tries to land on lines and or a Stobie pole and contacts separate lines, they will create a short circuit and most likely be electrocuted. Birds can also get caught on equipment such as Lightning arrestors (which are a device for protecting equipment from lightning strikes or power surges).

Large flocks of birds (such as Corellas) may roost together on lines and when they take off collectively they will cause lines to swing and clash.  In other cases, they get caught in lines -- this has been the issue with recent outages at Mannum where Corellas have got caught between lines near where they connect onto transformers.

We monitor outages to look for patterns and, where we have repeat incidents involving animals, will install targeted solutions aimed at reducing the likelihood of further outages at that location. For example, line spacers are effective in managing impacts of roosting birds. We have a dish-shaped animal guard that, when installed, reduces the risk of possum and bird impacts on insulators; and we will replace older-style equipment such as Rod Air Gaps (lightning arrestors) with modern insulated Lightning arrestors  that are less likely to cause outages when contacted by  birds and bats.

While these solutions reduce incidents and repeat interruptions at targeted locations, we are seeing an increase in the number of bat related outages due to the relatively recent arrival and very rapid expansion of the Flying Fox colony camped in the Parklands between the Adelaide Zoo and Botanic Gardens.

Due to food supply pressure in their normal eastern-state habitats, the bats have grown from a colony of about 3,000 in 2016 to one of about 20,000+ today. In 2016 we had 13 power outages due to bats, in 2017 it was 26 and in 2018 we had 40.

These Flying Foxes are likely to have a growing impact in terms of the number of power outages they cause and because they do not have specific flight paths (they go where the nectar and fruit is) their impact is widespread across our network, making it difficult to undertake targeted defensive action.

The bats, which have a wide wingspan (over one metre), can cause a power outage when they contact between power lines and pole top equipment, including insulators, transformers and switches or when trapped by lightning arrestors.

Our Network Reliability team has been analysing the bat’s behaviour and impact to see what we can do to reduce these kinds of interruptions, but the reality is we have had a number of outages caused by bats at a broad range of locations as they move around as their food sources change. We do install animal guards and cover some overhead equipment in the rare instances where we have repeat interruptions caused by the animals at the same location. However more widespread mitigation across our network to reduce their impact on supply is likely to be cost prohibitive and a long-term undertaking.

We have commissioned a study by the University of Adelaide to help us understand more about what the bats are doing and where we might get best value from outage-mitigation efforts.

Note: the bats do potentially carry a serious disease that is transmissible to humans and should not be handled by members of the public. We have provided funding to Fauna Rescue who will rescue injured animals reported by the public. Their 24/7 bat rescue number is 0475 132 093.

 

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