BIRDS ARE A MAJOR PROBLEM FOR UTILITIES. They collide with overhead structures and conductors, contaminate insulators and equipment, and damage facilities leading to customer interruptions. On the flip side, birds don't always get hospitable treatment from utilities either. They are electrocuted, maimed and not so gently encouraged to stay off certain areas of our T&D system.

Utilities need to find better ways to cohabitate with birds so that the impact of their flight, perching and nesting habits leads to minimal power disturbances. Preventative measures also should be taken to safeguard birds, especially the more than 800 species of protected migratory birds in North America.

Birds cause damage and disruptions in many ways. Their size, type and habitat all contribute to the potential negative impact they can have on the power grid. Larger predatory birds like raptors cause some of the more challenging problems.

The Edison Electric Institute identified reasons why raptors are attracted to power lines: Poles increase their range of vision and attack speed when hunting; they provide good hunting and roosting platforms; they are favorable sites for raptors to broadcast territory boundaries; and a good prey base exists along rights of ways.

The contributing factors for raptors becoming electrocuted were identified as:

Large raptors like golden eagles, red-tailed hawks and great-horned owls are more susceptible to electrocution.

Juvenile raptors lack the experience and flight control of adult birds and, as a result, are more frequently electrocuted than adults.

Compared to the wingspan of raptors, the relatively close separation between conductors and conductors-to-ground is one of the leading causes of electrocutions.

Other large, heavy-bodied birds such as herons, cranes, swans and pelicans are also frequently reported casualties because of their large wingspans and lack of agility. Many species of ducks are vulnerable when flying at low altitudes because of their high flight speed. Flying in flocks also restricts maneuverability.

Woodpeckers destroy wood poles, causing structural failures. Parakeets are known to destroy the housings of polymer insulators. In stations, birds cause outages by attracting predators like cats, raccoons and snakes. On distribution lines, birds are responsible for nearly 25% of all outages in the United States. A 1990 IEEE survey reported that 86% of the utilities that responded indicated birds caused major problems in substations, second only to squirrels.

Birds can cause insulator flashovers due to their long streams of stringy, conductive and semi-liquid excrement. Contamination flashover of insulators occurs due to the accumulation of bird droppings. Many times this also might be due to birds building nests in the gaps and on the structures in substations. Nesting causes outages in other ways as well, such as when birds drop nesting materials, contact live conductors while flying in and out of the nest, and attract predators and animals or bring large prey items to the nest, which bridges insulators.

Discussions about these kinds of problems led to the formation of a task force within the IEEE working group on Insulator Contamination and Dielectric Aging. The objective was to provide recommended practices to mitigate bird-related outages.

A common rural, three-phase 7.2-kV/12.5-kV distribution pole is a wooden tangent structure (Fig. 1a). Three-phase distribution tangent structures, without pole-top grounds or pole-mounted equipment, generally provide adequate separation for all but the largest raptors. Additional protection is required in areas with eagles and other large raptors.

The tangent structures can be framed to provide an additional 16 inches (40 cm) of clearance, bringing the total phase-to-phase separation to 60 inches (152 cm). Additional clearance required for eagles can be obtained by lowering the crossarm on new poles. Dropping a crossarm may require shorter spans or taller poles to maintain clearances, adding to the structure cost. Figure 1b shows a common alternative to dropping the arm is using a 10-ft (3-m) crossarm and lowering the arm only an additional 12 inches (30.5 cm). This provides the recommended separation without using taller poles and is the most economical method.

Where collisions are likely to occur, for example at river and wetland crossings, using crossarm construction with horizontal line-post insulators versus vertical conductor construction will reduce the incidence of collisions. If possible, sag multiple crossings to the same elevation and use specular conductors so the lines will be more visible to birds.

On transmission lines where overhead ground wires are often smaller wires than the phase conductors, and so are more likely to cause bird collisions, eliminate static wires and protect energized conductors with surge arresters where feasible. An alternative to removing overhead static wires is to mark the wire with devices like aerial marker spheres, spiral vibration dampers, conductor cover-up, swinging plates, bird-flight diverters and flappers.

Often, adequate separation cannot be achieved through spacing, so, alternative measures must be taken. These include bushing covers on apparatus, heat-shrink insulation, insulated wire, cover-up insulation, insulating paint, pole caps, insulated wire and fusing tape on bare conductors.

Some dead-end structures have directional changes and lateral taps. These structures can be especially dangerous to birds due to the bare jumpers used between circuits (Fig. 2). Insulating the jumper wires is the most common retrofit method but cover-up insulation can also be applied. Many of the poles require cover-up on the center phase jumper to allow safe perching. On some structures, jumper wires may need to be re-routed under crossarms to eliminate potential phase-phase contacts.

Transformer structures also can be lethal to birds due to exposed transformer bushings, jumpers, exposed grounds and cutout/arrester contact points. Retrofitting two- and three-phase transformer banks includes installing perch guards on the top crossarm, covers on the transformer bushings, insulated jumper wires, bird spikes between cutouts and arresters, and fusing tape on exposed connectors (Fig. 3).

Perch management attempts to control where birds land or nest on structures. These devices include various designs of perch guards, elevated perching platforms, metal needle wire spikes, nesting platforms, insulated disk barriers and plastic bird spikes.

Several devices are designed to discourage birds from landing at dangerous structure locations. It is important to note that perch guards do not always keep raptors off structures. Placing perch guards on the top of vertical construction can contribute to electrocutions since the birds may choose to roost lower on the pole, near energized conductors. Perch guards can also shift problems onto other line segments.

It is more desirable to allow raptors to safely use the structures rather than shifting them off preferred perches to other structures that may be more lethal. It is also difficult to predict if artificial perches will be successful. Nesting platforms have been used successfully throughout the Western states.

Installing after-market products can lead to new problems. For example, bushing covers are used to cover up exposed bushing termination points on transformers, regulators, capacitors and reclosers. These are generally made of track-resistant polymers that either snap on or slide over a bushing top. No uniform standards exist for bushing covers. Some are more resistant to UV and environmental degradation than others. Some bushing covers also include a matrix of small holes to allow moisture to drain. Small birds have been observed probing these covers for the insects, resulting in additional electrocutions.

Wire-marking devices that physically enlarge the wire act as wind-catching objects, encouraging icing in the winter and increasing the risk of wire and power breaks due to line tension and stress loads. The attachment of devices also may cause physical damage through abrasion to the conductors. However, the effectiveness of some marking methods that target specific species can hardly be questioned, and marking is justified if spans are determined to be dangerous to endangered and vulnerable species. If markers are employed, they should be spaced at 5-m (16-ft) intervals since collision frequency decreases when the space between wire-marking devices is short.

Streamer outages are more common on transmission than on distribution lines. Large birds, such as raptors, herons and cranes, cause streamer outages. Streamer outages have been found to exhibit certain characteristics, such as occurring between the hours of 11 p.m. and 6 a.m., where natural roosts such as trees are scarce, where food is abundant and where the center phase is involved; with a seasonal pattern; with an instantaneous relay operation and successful reclose; with flashed insulators; with burned spots on the upper hardware or structures; and with the presence of dead or injured birds near the structure. These can be used as a guide to attribute unexplained outages to bird streamers. If several of these characteristics are present, bird streamers should be suspected.

Figure 4 shows a typical bird-contaminated insulator in Arizona, having bird droppings — thousands of starlings and pigeons have been sighted in this area — over a period of several months. A series of flashovers occurred on a foggy morning. Apparently, natural washing was ineffective in removing the excrement. Very high values of ESDD was measured, 0.4 mg/cm².

A different utility suffered outages from another scenario: a large flock (thousands) of blackbirds or starlings came to roost in a substation. The overnight accumulation of fecal contamination on the insulators caused an outage. Figure 5 shows the contamination in a substation in Nevada.