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Electrical energy is a traded commodity that is critical component of the daily life of consumers. There is an increasing demand for continuous access to power as consumers are increasingly critical of disturbance free power supply. Electrical disturbances occur at everything from planned to unplanned events on the power and transmission network. In many cases, outages and nuisance recloser operations are the result of animal contacts somewhere on the power system. The writer explains that although animal-caused outages have been a fact of life for electric utilities since the first line was constructed, there is very little general information available on effective methods to eradicate animal interactions and reduce such outages.
The National Rural Electric Cooperative Association (NRECA) and Southern Engineering have prepared field manuals outlining suggested best practices and policies to reduce animal-caused outages on transmission lines, in electrical substations, underground distribution systems and overhead distribution lines. The author observed that it was a common preconception that electrical cooperatives located in rural suffered the most from animal-caused outages, however, more than half the 533 utilities in the study group for the manual reported that they had a significantly higher number of animal caused outages in urban and residential areas. These results suggest that animal-caused outages are more frequent and wide spread than generally believed.
The writer examined various methods to planning programs to reduce animal outages. The writer noted that is important to ensure that there is accuracy in the collection of outage data. Some utilities may evaluate their animal caused outages as a percent of their total system outages from all causes. The writer noted that this method, however, will often understate the seriousness of the problem since animal contacts tend to occur at specific locations. The writer also observed that many utilities reported areas on their system where 80-90% of all outages were caused by animals. The next step is to research and understand information about the animal that is responsible for electrical outages. Knowledge of the animal will assist in explaining why some deterrents are more effective that others and may help utilities to foresee problems and take preventative action before outages occurs. Once commercial and homemade deterrents, design alternatives, and economics have been carefully examined, the utility can develop an efficient and economical plan of action.
The author examines procedures for each category of animal for planning new construction before an outage occurs, and for existing construction after an outage occurs to facilitate the development of efficient policies. To obtain information on animal caused outages and current trends for electrical systems animal control the author developed a four-page survey which sought information from rural electric cooperatives, municipal systems, and public power companies throughout the country. The data from 481 utilities, ranging in size from one-substation municipal systems to 200-substation investor owned power systems, were complete enough to analyse. The data from the surveys was used to build a computer database and a widely used statistical software program (SPSS) was used for the analyses. The author highlighted that animal caused outages were separated into those occurring; on transmission systems, in substations, on distribution overhead systems, and on distribution underground systems. The responses were separated by region to determine if the animals responsible for outages varied in different parts of the country. The regions were defined as follows: Northeast – 36 respondents, Southeast -81 respondents, East North Central – 93 respondents, East South Central – 66 respondents, West North Central – 97 respondents, West South Central -61 respondents, and West – 41 respondents.
The data showed that raptors were the number one cause of transmission outages in the west and the second or third ranked animal in the east. Raccoons were a big contributor to outages in the north central regions. In the southeast and east southcentral regions, no raccoon caused outages were reported. In these regions, cattle were the fifth ranked animal. Birds were the most frequently reported cause of substation outages and ranked high in all regions. Squirrels and raccoons were a prominent cause in the northern regions while snakes were more prominent in the southern regions. Squirrels were the most common cause of overhead distribution outages with birds being a close second. Raccoons caused a high percentage of outages in the north central regions, and cattle contributed to outages in all regions except the northeast. Cats were the fifth ranked animal in the northeast. Snakes caused more outages in the southeast and east south central than raccoons. The regional difference was greatest in underground distribution. Gopher caused outages were almost non-existent in the northeast, southeast and east south-central regions. Squirrel caused outages ranked sixth in the west south central and western regions. Moles caused a significant number of outages in the east north central, east south central, and western regions. Insects were a major cause of outages in the southeast and west south-central regions, and opossums ranked fifth in the northeast.
The study group reported that animals responsible for approximately 95% of all animal-caused outages are 1. Small Digging and Climbing Animals, 2. Common Birds – Starlings, sparrows, doves, blackbirds, woodpeckers, blue herons, and migratory waterfowl. 3. Snakes 4. Medium Climbing Animals – Raccoons, cats, and opossums. 5. Raptors – (Birds of Prey) Eagles, hawks, owls, ospreys, and vu1tures 6. Large Animals – Cattle, horses, bison, and bears. 7. Other Animals – Bats, insects, tree frogs, and beavers. The first section under each category of animal is a discussion of type of behaviour that tends to bring the animal into conflict with electric utilities.
The author noted that squirrels thrive in neighbourhoods and city parks where they are safe from most of their natural enemies and have less competition for food. Squirrels establish elaborate routes through their territory that often include utility poles and substations. In cities where utilities have limited or no right of-way, trees have grown around and over poles and, in some residential areas, yards are small, and the houses close together. Those types of cramped quarters ensure that squirrels will use utility poles as part of their route. Since a squirrel’s instinct is to stay off the ground, they will not hesitate to use artificial structures as trees. Ground squirrels. gophers, and moles, like the tree squirrels, survive very well in urban areas. In the West and Mid-west, gophers cause more outages on underground distribution systems than any other animal. Nation-wide, gophers are the third most frequent cause of outages on underground systems.
Rats and mice are the world’s most fertile and adaptable animals, quick to exploit any opportunity and able to eat almost anything and their destructive powers are enormous. There is one area where the incidence of rat caused outages may actually be more common than
reported. In older urban areas, distribution poles, conductors, and overhead devices are sometimes crowded very close to buildings where black rats living in the upper floors of old buildings have easy access to utility equipment. Since rats are active at night, their presence on poles and conductors will go unnoticed. It is very probable that some unexplained outages in such areas are caused by rats. In the Southeast, rats are the most common cause of outages on underground distribution system. Nation-wide, rats and mice are responsible for more outages on underground systems than any other animal. The writer noted that native wild mice are carriers of the deadly Hanta virus that first appeared in the southwest. Since the initial outbreak of the Hanta virus in 1993. Wild mice carrying the virus have been found throughout the country.
Raccoons are clever and curious animals, notorious as crop raiders, garbage thieves, and escape artists. Like squirrels, raccoons survive very well in urban areas. In some places, there are as many raccoons in the suburbs as there are in the wild. However, with their highly developed curiosity and clever, nimble paws, raccoons can be extremely annoying neighbours. In the Southeast, raccoons are the major carriers of rabies. Since there are so many raccoons now living in urban areas, the chances of being exposed to a rabid raccoon have increased significantly. Healthy raccoons are active at night and sleep during the day. Any raccoon encountered during the day should be treated with great caution, particularly if it seems dazed or confused or aggressive.
Cats are responsible for a surprising number of power outages, both on overhead distribution lines and in substations. In the Northeast, cats cause more outages than any other animals except squirrels and birds. They climb trees and utility poles when hunting birds’ nests and squirrels and will be attracted by the motion of birds flying in and out of substations. More than any other animal, cats will climb onto utility equipment looking for warm places to nap. The next section in each category describes the types of outages the animal usually causes. The devices most commonly involved in animal Categories 1 and 4 are distribution overhead transformers, cut outs and arresters, reclosers, regulators, capacitors, conductors, poles, underground and padmounted equipment, and substations. The third section describes the types of deterrents most often used by utilities and evaluates their effectiveness.
Barriers, physical, electronic, or chemical, will not stop squirrels from reaching their destination according to one expert. Climbing Guards are not always effective against squirrels since squirrels, as a rule, don’t climb poles. Instead, they will leap from a nearby branch or by run along the service drop. However, climbing guards can be very effective against raccoons and cats. Porcupine Wire is more often used as a deterrent against perching birds but can be used as a climbing guard. Greases and Sticky Gels are often messy, short-lived, and very annoying to maintenance personnel. Poisons, even in the hands of experts, are very dangerous. The requirements of local, environmental, and governmental regulations will usually prohibit or limit the use of poisons and other dangerous chemicals. Repellents have a noxious odour that animals find very unpleasant. Unfortunately, people also find the odour unpleasant and will not tolerate the use of such repellents in residential or commercial areas. Repellents have been successfully used against rats and mice in closed cabinets and underground enclosures. Wildlife Guards, insulating covers on transformer bushings, are one of the oldest and most widely used deterrents. Unfortunately, most utilities are now finding that the guards installed in the early years have severely deteriorated from weathering, ultraviolet light, and chewing by squirrels. It is not uncommon to find that the guards have been pulled off the bushings by the primary drop wire or pushed off by birds and squirrels. Over the years the design and materials used for the guard have improved, but some problems remain. Some guards have hinges that tend to fail in cold weather and some do not have a sufficient number of ports or openings to fit the various approach angles of the primary lead wires. There is still concern that the polyethylene used to manufacture the guards will eventually degrade in ultraviolet light. However, most utilities report a significant reduction in squirrel contacts after these wildlife guards are installed. Heat-shrink Insulation is used on both conductors and bushings. Most utilities find that, while very effective, this method is expensive and labour-intensive since the equipment must be de-energized. Shields can be made from sheets of any insulating material and, with cut outs for bushings, placed on the tops of energized equipment. Since there are no prefabricated products of this type, these sheets must be cut by hand to fit the various devices. Insulating Paint has been tried by a number of utilities without much success. It is very difficult, and time consuming to apply and degrade quickly. Insulating Sprays were developed to protect insulators from tracking and arching in highly contaminated areas. Ultrasonics generate the sounds of loud bird distress calls or the calls of hawks and owls. This type of deterrent may actually attract raccoons and cats, particularly if the sounds are bird calls. However, ultrasonics can be effective against cats provided the units are the types that produce random noise.
Design alternatives can be used when planning new substations to increase clearances between phases and between phases and grounded parts. The height of the bushings on overhead devices can be increased to reduce phase to ground contacts but increased separation between bushings is limited to the size of the fop of the equipment. Increased insulation can be added to poles to increase the distance from the pole top or cross arm to the energized conductor or extension brackets can be used to either raise the insulator and conductor or offset them. Design alternatives can include rerouting distribution lines away from trees, if practical or possible. Economic considerations include factors that are not always easy to quantify. How many angry consumers are too many? What dollar amount can be put on the consumers’ loss of confidence in the utility’s ability to provide reliable service? How much revenue is lost during an outage? What cost is assigned to safety and health hazards? How widespread is the problem? How frequent are the outages? How much will corrective action cost? Some utilities have made an effort to calculate the cost of an outage. These calculations include the cost of repairing or replacing the equipment, labour, loss of revenue based on the duration of the outage, and dispatcher time. Each utility has to decide for itself how much weight to place on consumer complaints and other intangibles. Since a substation outage affects more consumers and the damaged equipment is far more costly, protecting substations may be more economical. Usually it is easier to justify the cost of substation protection since it may be a lower cost per consumer. (RUS (formally REA) cooperatives must have approval before using any nonstandard device or construction)
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