6 Beautiful Animals That Cause Outages and Dangers in Electrical Facilities

Problems and mitigation techniques

Animals are one of the biggest causes of customer outages for almost every power utility worldwide, after humans and other factors. The problems and mitigation techniques are as diverse as the animals involved. Identifying and addressing physical root causes is often the most cost-effective way to resolve reliability issues.

This whitepaper describes reliability concerns and common safety enhancement strategies for the following classes of animals:

1. Chipmunks,

2. Mice, rats and squirrels,

3. Birds,

4. Snakes,

5. Fire ants and

6. Large animals (cattle, horse, bison and bears).

1. Chipmunks

Squirrels are extremely cute animals. Everyone loves them, but unfortunately they are a reliability concern for all overhead distribution systems near wooded areas. Squirrels don't typically climb power poles, but jump on them from nearby trees and cause faults by bridging grounded equipment with phase conductors.

Of more than 365 species worldwide, reliability concerns primarily concern gray squirrels and red squirrels (see Table 1).

(!) Living in most of the Northern Hemisphere, the gray squirrel is the most common species of tree squirrel. Typical gray squirrels are fifteen inches long, weigh about a pound, and have a bushy tail that is about the length of their head and body. They have a typical diet of nuts, seeds and fruits.

North American red squirrels (also known as pine squirrels and broilers) are smaller than gray (typically eight to ten inches in length), have red to black fur and bushy tails that are the same length as their bodies. Some subspecies may have red or black ear tufts, and most have a white belly.

The red squirrel is found in coniferous forests, where it feeds on the seeds and cones of pine, fir and spruce trees.

Squirrels are extremely agile, persistent and committed to travel routes that may include power poles. Therefore, attempts to keep squirrels away from general use equipment are often futile, and reliability improvement efforts should focus on protecting the equipment.

The most common technique is to place plastic pet guards on the bushings and insulators to prevent squirrels from touching the tank and phase conductors at the same time.

The middle figure shows the bush equipped with a plastic pet guard to prevent the squirrel from causing malfunction. The figure on the right shows the bush equipped with an electrostatic shield that deters an approaching squirrel with a harmless but noticeable electric shock.

2. Mice, Rats and Gophers

Mice, rats and squirrels are rodents that cause malfunctions by gnawing at the insulation of the underground cable. Rats and mice are the most common cause of animal cuts in underground equipment, with squirrels being the third most common (snakes being the second most common).

(!) Mice and rats create reliability problems by attracting snakes as well as chewing on insulation. All equipment cabinets and duct openings must be tightly sealed to prevent these rodents from accessing underground equipment.

Some utilities have successfully used ultrasonic devices to repel mice and rats.

When squirrels burrow, they chew through any obstacle in their path, including electrical wires and plastic pipes. Gophers are most common in the Midwestern United States, where they are often the most common cause of underground equipment failure.

Effective control of squirrels is difficult with methods including traps, bait, poison gas and ultrasonic techniques.

What happens to a mouse that enters the substation?

The electric discharge killed the poor mouse. The transformer crew found the mouse dead with its tail wagging in the wind.

Some of the modern remedies against rodents:

1. Woven glass fiber tapes: It is a dielectric solution that provides very good protection because glass sticks to the mouth of rodents and irritates them. They have shown to be very effective in preventing small rodent attacks.

2. Steel tape: It is a reliable protection, but it may produce electromagnetic interference.

3. Polyamide 12 outer sheath: It is used to protect the fiber optic cable from termites, but rodents can still gnaw the equipment.

4. Polypropylene outer sheath: It is effective in protecting fiber optic cables thanks to its hard surface, it is not as hard as PA 12 Outer sheath and rodents can still gnaw the equipment.

5. Chemical repellents: It is not that effective because rodents do not eat what they bite.

3. Birds

Birds are the most common cause of animal failures in transmission systems, sub-transmission systems, and air-insulated substations. Different types of birds cause different types of problems, but can generally be classified as nesting birds, perching birds, raptors and woodpeckers.

Nesting birds often build their homes in lattice towers, poles, and substations. Nesting materials can cause malfunctions and bird droppings can contaminate insulators.

(!!) It can be difficult to remove nesting sites as the instinctive nature of some birds will cause them to rebuild their nests in the same place. To complicate matters further, nesting birds can attract predators (e.g. raccoons, snakes, cats), which can be a worse reliability issue than the birds themselves.

Perching birds use electrical equipment to rest or seek prey. They cause malfunctions by bridging conductors with their blades and contaminating insulators with their excrement.

“A small number of perching birds is typically not a reliability issue, but the instinctive nature of some birds can cause thousands of birds to perch in one place.

3.1 What is bridging?

Bridging is the contact of a bird or animal between phases or by creating a short circuit between phase and earth. The picture below clearly shows how easily big birds can cause problems with all distribution voltages at substations and overhead lines.

Phase bridging often results in electrocution of the bird or animal and will determine whether the auto-reclosing system is operating successfully based on how the dead bird or animal fell. Often the bird or animal will fall, allowing the auto-recloser to re-energize the circuit as intended.

While this does not normally require an emergency response team investigation, it often leaves undetected damage. Figure 3 on the left shows the typical "narrative" sign of damage caused by wildlife.

While a circuit may be operating normally, this sequence of events can lead to a buildup where the damage gets worse with each trip, eventually causing a hardware failure. For example, each trench has a single conductor of a single wire.

like it burns i and eventually drops the circuit.

If a dead bird or animal falls between the contacts and stays there, it will cause the circuit not to be re-energized and remain that way until an emergency team clears the fault (bird or animal) and re-energizes that circuit.

(!) While such an event can at least be recorded with some certainty as to what happened, it is quite possible that a bird or animal that has fallen on the ground or on a transformer will be picked up by a predator. (The right image of Figure 3 shows a typical formation - before removal).

Most bridging problems occur in Medium Voltage systems (typically <36 kV) designed with “air-gapped” openings where bare conductors, bushings, busbar systems and associated equipment operate smoothly under normal conditions.

3.2 Prevention

Anti-roost devices can be installed on attractive perches to prevent birds from perching (see Figure 4). Places that serve thousands of perching birds may require more extreme deterrent methods such as pyrotechnics and falconry. Some of the larger perching birds tend to empty their bowels (called flounder) when they take off.

In addition to contamination, faults can occur if the flow bridges phase-to-phase or phase-to-ground potentials.

Long blade spans can bridge conductors and cause failure.

Many large birds have a threatened or endangered status, requiring measures to be taken to reduce the number of electrocution regardless of safety concerns from utilities.

This behavior can be prevented by using anti-roost devices, such as the cone shown in the middle figure. Phase-to-phase blade contact can be avoided by protecting the center phase with an insulating sheath similar to the one shown on the right.

Birds of prey are birds of prey such as eagles, hawks, ospreys, owls and vultures.

(!) In addition to the reliability problems associated with perching and nesting birds, raptors have large wings that can bridge phase conductors during takeoff and landing. Besides causing a bug, this can kill a bird of prey. Legal issues can also occur, as most predators are protected by federal law in nearly all countries.

Typical raptor wingspans are shown in Table 2 above.

Woodpeckers dig holes in wood with their beaks when hunting for insects or building nests. This does not harm trees (regenerates bark), but can cause devastating damage to utility poles. Woodpecker reliability problems can be reduced by using steel or concrete posts, placing new posts next to damaged posts, and using a woodpecker repellent.

"Organizations that address woodpecker issues should be aware that certain species are considered threatened or endangered and protected by federal status.

Birds blow up a power transformer

If a large flock of birds sitting at a waterline leaves all at once, they will shake the line (known as a short swing), causing the fuse to blow.

Surprise babies at 115kV substation!

While doing maintenance at an electrical substation in an old factory, I encountered an unusual sight. The mother bird preferred this place surrounded by 115,000 volts to put her babies. An interesting choice.

4. Snakes

If you ask me, I like them a lot, but I don't like them. Snakes are major reliability concerns in both substations and underground systems. They can pass through very small openings, climb almost anything, and are long enough to easily cross phase conductors (see Table 3 for lengths of different snake species).

Snakes cause more transformer outages than any other animal except birds, and more subterranean outages than any other animal except rats.

A snake's length is an important reliability consideration, as many faults occur when snakes bridge phase conductors.

Snakes are cold-blooded animals that focus on regulating their body temperature and obtaining food. In cold weather, snakes may seek warm electrical cabinets. Snakes may search for rats and mice in underground distribution systems, and birds and nests in substations while hunting.

(!) Snake problems can usually be alleviated if the electrical cabinets are well closed and food materials are removed.

Another common solution is to install special snake fences around substations and critical pieces of equipment. Some snake fences use low voltage electric shocks to increase their effectiveness.

Dead anaconda found electrical board

You certainly wouldn't expect to find a fried giant anaconda in a switchgear. It must have been a big shock to this man!

Big rat snake entered 13kV substation

This is video of the explosion that resulted in a large rat snake entering the 13,000 volt North Athens substation. Video provided by the Athens Utilities Board, Athens, Tennessee.

5. Fire Ants

Maybe they don't deserve the adjective "Beautiful" as the title above states, but what and how they live and work is absolutely beautiful!

Originally from South America, fire ants are small but have a severe sting. They have proliferated throughout much of the southern US, and it is in these areas that it is common for fire ants to nest on litter-mounted equipment.

Nesting materials can cause short circuits, ants can eat the conductive insulation, and their presence can complicate equipment maintenance.

There are actually two types of fire ants: black and red. The black fire ant, accidentally imported from South America to Mobile, Alabama, was first reported in 1918. Its distribution is still limited to parts of Mississippi and Alabama. The red fire ant was imported in the 1930s and has spread to most states in the Southeast.

This species has become very abundant, replacing many native ant species. Fire ants have the potential to spread widely throughout the South, Southeast, and Pacific Coast.

“Fire ants were accidentally brought to the United States from South America in the early 1900s. Since then, they have spread widely in the southern U.S., replacing native ant species and building nests in electrical equipment, causing reliability problems.

Moving all colonies to electrical boxes

Fire ants can be found in electrical homes at any time of the year. Air conditioners, traffic signal boxes and other devices may be damaged. Ants that nest in these units are highly defensive to their colonies and can be a medical threat to caregivers.

Electrical enclosures (for example, outside power outages, junction boxes, screed-mounted transformers, etc.) provide warmth during the winter, a dry nesting area during heavy rains, and an undisturbed nesting site year-round.

When a colony enters the electrical box, worker ants import soil for nesting. This material can cause corrosion and hinder maintenance operations.

(!!) In electrical transformer boxes, oil regulates the temperature in half of the box. When moisture from the mound causes corrosion, oil will seep in, hindering temperature regulation and causing transformer failure. In addition to corrosion, once ants get in, they trample on insulation and can cause short circuits or interfere with switching mechanisms.

Mechanisms and replacement mechanisms of foraging worker ants. Imported fire ant colonies (mounds) are usually located at or near the base (floor) of electrical units. Worker ants leave these nests in search of food to bring back to the rest of the colony members (larvae, other workers, and indirectly the queen and breeding ants).

However, when worker ants enter the switching mechanisms of electrical equipment, ants can become a problem.

Fire ants are causing electrical problems in the Rowlett neighborhood.

6. Big Animals

Large animals typically cause reliability issues through contact with the guy wires and posts. Because they are large and powerful, they can inflict physical damage and cause a sudden outage or make the system more prone to future outages.

Most major animal problems are caused by cattle, horses, bison and bears.

The cattle rub against the tension wires, causing reliability issues. Because they are habit-forming animals, the same males will continue to rub against the wires, eventually causing the poles to bow. This behavior is difficult to deter and mitigation strategies should focus on barricading or removing the guy wires.

(!) Horses can also rub against the tension wires, causing reliability problems, but more commonly they collide with horses that they cannot see. Even if these collisions do not cause reliability problems, 

can kill or injure the horse and create liability concerns. Collisions can be avoided by barricades or by making the guy wires more visible.

Bison are large and strong and like to rub their heads against objects. If this object is a lamppost, it could be pushed all the way up and cause a major blackout. There is usually no viable way to deter this behavior and mitigation efforts must resort to barricades or the removal of poles.

As the U.S. population expands into previously unpopulated areas, bears are becoming more of a distribution reliability concern. Most reliability issues are associated with wooden power poles, as both brown and black bears can destroy wooden posts by using them as scratching posts.

" Also, grizzly bears can climb wooden power poles and come into contact with live conductors, causing malfunctions. Bear-related problems can be mitigated by placing fencing around wooden poles or replacing wooden poles with steel or concrete.

Some more great videos about animals

Snakes Chasing Birds on Power Line

I was in the backyard of my house and I heard birds chirping and saw this snake balancing on a power cord trying to catch the birds. The birds seem to be playing catch me if you can, and the snake did a good job balancing it by moving along the cable, trying the birds but failing and returning to the hungry, palm tree.

Primate swings from live power lines, falls off utility pole

According to city officials, the chimpanzee escaped from the Yagiyama Zoological Park in the city of Sendai, Miyagi Province, in the early afternoon. A male chimpanzee has been caught by city officials after falling from a power pole in northern Japan.

The chimpanzee was free for more than an hour before climbing a lamppost where authorities shot the monkey with tranquilizers.