Many people may not realize that animals can be a leading cause of electricity outages, which has an adverse impact on overall electric grid reliability. In fact, most electric utilities have experienced the problem of animal intrusions into electric supply substations, which has resulted in equipment damage, interruption or loss of service to customers, and safety problems for operating personnel.
For example, on July 13, 2015 a squirrel worked its way into a transformer and caused an outage that affected more than 6,000 Nashville Electric Service customers in Hendersonville, Tennessee. In early June 2015, Pacific Gas & Electric Company experienced a substation outage in El Cerrito, California impacting 45,000 customers. In this instance, a squirrel caused a flashover on a key circuit breaker linked to multiple transformer sources.
To address these intrusions from the animal kingdom, IEEE has created the standard IEEE 1264™ to guide utilities in deterring animals from causing problems inside substations. This recently revised standard identifies various troublesome animals and the problems caused by their behaviors, while also outlining mitigation methods. What’s more, the standard provides criteria for applying mitigation methods, documentation methods, and recommendations for evaluating effectiveness after the method is applied.
From an earlier survey, North American utilities responded that the top 2 primary sources for animal-related outages are squirrels and birds. Other secondary sources include raccoons, opossums, snakes, cats, mice and rats. Yet there are a number of other rodents, insects, mammals and reptiles that can also cause problems, albeit these are less endemic overall.
The variety of animals and their behavior presents a broad challenge to overcome, and it is further complicated by differing geographies and seasonal weather patterns. Some animals seek the warmth and shelter substations can provide and “homestead” in structures or equipment. As a result, larger predator animals are then attracted to the substation as well. Typical problems that occur include animal contact with energized equipment or conductors, animal waste contamination, gnawing damage to wires or covers, and birds carrying in conductive nesting material.
For utility personnel, animal waste can cause unsanitary conditions, while snakes, bees, wasps, and spiders can also be a serious safety concern. On the other hand, utility personnel can unwittingly contribute to the problem by feeding animals, not properly disposing of food-waste, or leaving boxes, crates or containers outside too long and increasing the likelihood of animal intrusions.
When experiencing an unacceptable level of animal-related problems, a utility should establish a mitigation program. The design of the program can vary, yet is best supported by tracking details such as outage records, frequency of occurrence, animal type, customer impact, damage severity and cost. Monitoring the effectiveness of the program is important, as well as making improvements and adjustments over time. IEEE 1264 advises utilities to consider the impact on adjacent property owners and the community, and to research applicable governmental regulations and laws regarding chemicals or trapping.
Traditional preventive methods include providing cover for energized parts, installing physical climbing barriers and other various deterrents, and increasing electrical insulation levels. Substation layouts and equipment designs vary widely, so a trial-and-error approach employing numerous methods may be necessary to find an effective solution.
Fence designs should prevent animal access from under, over or through the fence by using smaller mesh fabric, smooth barrier sheets, and minimized space gaps. The fence effectiveness can be complicated or compromised by adjacent landscaping and trees, or also by stored material that provides a climbing aid. Line barriers are installed on the energized or guy wires before they cross over protective fences to discourage acrobatic animals from an aerial bypass of the fence. Where a fencing solution isn’t possible, barriers can instead be installed on substation structures to prevent climbing up into the energized equipment.
Some repelling methods involve installing fake predatory animals, such as owls, or deploying disturbing noise generators, chemical repellents, or perching and climbing spikes. More recent deterrents include electric fences and electrostatic shields, snake barriers, insulating coatings, and covers that provide a tighter secure fit on varying connection shapes. There has also been an increased onus on vendors to design more animal-resistant equipment, such as transformers, breakers, switches and structures, and to eliminate or minimize small openings that can attract birds and other nesting animals.
Now that the IEEE 1264 has recently been updated, the IEEE working group is shifting its efforts to craft a tutorial that will be offered at future industry meetings, and sending out an updated utility survey. These and other efforts will further encourage utilities and vendors to participate in the standardization effort to eradicate animal-caused electricity outages and the problems they create for utilities and consumers.