Animal-Caused Faults on Electrical Systems Have Beleaguered Engineers and Operations Personnel since power facilities were first installed. Today, mammals, birds and snakes cause a significant number of electric outages throughout the world and are increasingly common in both urban and residential areas. The majority of problems occur on distribution overhead lines, but significant problems also occur in substations. Although substation outages are less frequent, they impact a far-greater number of customers.

Squirrels and birds cause many substation problems in North America. These problems increase during the spring due to nesting and during the fall as squirrels prepare for winter and as large numbers of migratory birds flock together.

Snakes and raccoons add to these problems when they enter substations seeking nesting birds and eggs. Older substations are particularly susceptible because they have numerous cavities providing suitable nesting places for birds. Accordingly, an important substation mitigating measure is the regular removal of birds' nests. However, it is important to note that a U.S. Fish and Wildlife Service permit is required to remove any active migratory bird's nest and that in Canada all active migratory birds' nests are protected under the Migratory Birds Convention Act.

Outage problems are concentrated in areas of favorable habitat, making certain substations more prone than others to outages because of their location. Problematic substation equipment includes low-side breakers/reclosers, power transformers and bus bars. Historically, utilities have used a wide variety of measures to mitigate problems with varying results. Success is dependent upon knowing what animals are causing problems and knowing why the animals are using the substation. Potential problems may be anticipated and solutions can be incorporated into new substation design.


There are significant costs that result from wildlife-related power outages. These costs may have financial, social-political or biological implications to the utility and its customers. The financial costs of power outages impact both the utility and its customers. Utility costs result largely from equipment loss and replacement. These costs can be quite variable. One published study, “Factors Affecting Wildlife-Related Power Outages in Electrical Substations” by J.B. James, tracked 203 substation outages in the United States and estimated economic costs ranging from US$500 to more than $140,000 per outage due to equipment replacement and repairs. One U.S. utility even reported a snake causing $2.4 million in damaged equipment (see “Intruders Impact Reliability,” Transmission & Distribution World, April 2001).

Customers, through both momentary and sustained power outages, can incur significant costs. A Lawrence Berkeley National Laboratory study in 2004 estimated that the total cost of power interruptions in the United States is in the area of $80 billion per year and that 98% of these outage costs are borne by commercial and industrial sectors. In a 1996 U.S. survey, 560 utility groups identified wildlife as the third-leading cause of power outages. This implies that a substantial percentage of this estimated $80 billion could be attributed to wildlife.

In addition to economic losses, wildlife-related power outages compromise system reliability, leading to customer dissatisfaction and public awareness, which can lead to negative publicity. Electrocutions of birds also can be a violation of law. For example, the U.S. Migratory Bird Treaty Act protects most species of birds and the contravention of an act such as this can result in significant fines.


AltaLink (Alberta, Canada) is employing an innovative product in its effort to reduce wildlife-related outages. The AltaLink system includes approximately 300 substations and 11,600 km (7208 miles) of transmission line, serving 85% of Alberta's 3.5 million residents.

AltaLink's experience is that up to 20% of all substation power outages can be attributed to wildlife. These outages are primarily caused by ravens and owls, though squirrels and other small animals have been involved, too. Due to the large number of wildlife-caused substation outages, AltaLink was interested in exploring new technologies that could improve system reliability and environmental performance.

In 2003, AltaLink was approached by Cantega Technologies (Edmonton, Alberta, Canada), which had a unique material to insulate exposed electrical equipment and prevent animal-caused outages. A senior power lineman with 25 years of industry experience developed the material, Greenjacket. After piloting the product at an in-service substation, AltaLink decided to collaborate with Cantega to refine the Greenjacket Wildlife Outage Mitigation System.

The early prototype of Greenjacket was applied with a spray gun onto target surfaces inside an in-service substation. During early trials, several limitations were noted with this method of application. The weather had to be warm, there couldn't be wind and a station outage was required for several days. AltaLink found that these requirements could be difficult to accommodate. However, the Greenjacket material showed potential as it has a very high dielectric rating, is resistant to ultraviolet breakdown and is environmentally friendly.

With neither AltaLink nor Cantega wanting to give up on this unique product, a collaborative, multidisciplinary team of individuals from the two companies was formed to readdress the method of application. This collaboration resulted in an array of new cover-up products that have proven to be effective at eliminating wildlife-caused outages in AltaLink substations.


Instead of spraying on the material, the two companies developed a process to apply Greenjacket. Protection requirements for high-risk substations are now determined through a unique CAD system to create protective covers, using the material, to meet AltaLink's design standards. Typical equipment covers include transformer low-side bushings, lightning arresters, breaker bushings, station service transformer bushings, station service fused disconnects, metering potential transformers, gang-operated air breaks mounted on steel supports, support insulators mounted on steel structures and risers.

From a utility perspective, Greenjacket has many features that make it an ideal cover-up. It's an engineered system solution, so the protective covers are designed and manufactured to meet each utility's design standards. It has a high dielectric rating that is resistant to breakdown from ultraviolet radiation, is custom built to fit a vast array of equipment in all shapes and sizes, and can be easily installed and removed in any weather condition. The various types of cover-ups can be stockpiled in a warehouse to be available on demand. Although an outage is still required, the application is no longer weather dependent. The material meets or exceeds several appropriate cover-up tests, including ultraviolet aging; dielectric breakdown (thickness and surface); wet power frequency withstand and flashover; thermal impact; cold weather (field test); and retention (field test).

To date, AltaLink has retrofitted 15 high-risk substations (that is, those that have an unusually high number of wildlife-related power outages) with Greenjacket. Analysis revealed that in certain substations, wildlife-related incidents make up 70% to 100% of recorded outages. Since the first installation in 2005, there has been one outage caused by a raven. After a thorough analysis of the outage, it was concluded that the outage did not occur because of product failure but rather a design flaw on a bushing cover. This analysis was used as a learning experience to improve upon the early bushing cover design. AltaLink estimates that retrofitting the 15 substations has resulted in a reduction of at least 11 outages per year.

AltaLink is encouraged by the early results and is now using Cantega's product almost exclusively. Existing substations will continue to be prioritized and retrofitted. For new substations, Greenjacket is a standard feature installed during construction. This allows AltaLink to be proactive in both protecting wildlife and improving reliability.


Wildlife causes a significant number of outages at electric facilities, which result in enormous costs to utilities and to their customers. These costs are by no means solely economic and can also have social-political and biological implications. As the population grows, energy demands will increase and more electrical facilities will be built. A solution is required for existing and future substations. Substation cover-up products such as Greenjacket offer a long-term solution to wildlife-caused outages in substations. By reducing these outages, service reliability is improved and wildlife is protected.

Nikki Heck has been employed at AltaLink Management Ltd. since 2004. As part of her role as an environmental advisor, she coordinates AltaLink's avian protection program. She has a master's degree in environmental design from the faculty of Environmental Design at the University of Calgary, where her thesis work was conducted on avian collisions with transmission lines.

Rick Harness is a certified wildlife biologist working for the consulting firm EDM International Inc. located in Fort Collins, Colorado, U.S. He has a master's degree in fishery and wildlife biology from Colorado State University, where his thesis work was conducted on raptor electrocutions. His specific areas of strength are in wildlife-utility interactions including power-line electrocutions and bird collisions.