Animal behaviour (Part 1/2)
In the past 20 years, it has become increasingly clear that external effects of wildlife are not under our control and have great effect on electrical equipment functioning well. In addition, the animals often do not survive their encounter with the devices. Environmental bodies (e.g. Four Paws International and WWF) who have the best interests of wildlife at heart, lobby hard for the protection of wildlife not being electrocuted as more than 25% of all power outages are caused by wildlife and vegetation being unintentionally caught into electrical equipment.
The Imperative of Prioritizing Protection
To better protect both the animals and your assets, it is first important to understand the behaviour of wildlife. Broadly speaking the problems created by wildlife (birds and small animals such as possums, rats, snakes and squirrels, or the large predator hunting them) in substations and overhead lines fall into two categories: Bridging and flashover through pollution. Result? a system trip and possible arc flashover. How this is described and what to do to prevent this depends on the products, other applications and the different parts of the equipment.
Bridging – electrocution of animals
Bridging is where a bird or animal makes contact between phases or between phase and ground creating a short circuit. This is most common a large or medium sized bird. The bird has only to land or take off while spreading their majestic wings to cause bridging. In some locations, on occasions, bears, possums or snakes can climb the poles and cause similar problems.
Did you know? 50% of wildlife induced outages are caused by birds.
Imagine you are a stork: A stork on your way picking up babies. You take a short rest on some big construction. You seek shelter from the harsh rain. You are resting your tired wings. Instead of warmth and safety, you get electrocuted. Worst-case scenario? You survive, fall, lay there incapacitated and die a slow and painful death.
Consequences for your equipment? Although the station may be operating normally afterwards, a series of these events can lead to hardware failure, e.g. if at every interaction a single strand of a conductor burns through, the line will eventually burn through entirely. Whether the auto-reclosing system operates successfully after contact with an animal, depends on where they end up falling.
Pollution flashover - bird droppings all around (guano)
Even though less frequent to happen, power outages due to animal natural pollution (bird droppings) is as damaging as bridging induced outages. Unlike bridging, it happens across all voltage ranges right up to transmission levels at HV. In this particular situation, the culprit is guano: the accumulated droppings of bats and different birds originally referred to the large deposits of this material found in the built environment.
Furthermore, those nests birds build while starting a new home, cause outages too when nesting materials are dropped while flying in and out. Birds often attract predators and animals or bring large prey items to the nest, which bridges insulators, bringing us back to bridging.
All countries see some level of disruption caused by wildlife.
The diverse nature of the bird or animal causing the problem plus the different types of equipment found in different countries and the different environmental conditions means often different approaches are required for prevention. Fortunately, once a failure mechanism is recognized modern materials and designs make it preventable to a very high degree, often for the remaining life of the equipment.