Isolaters in Substation

Why isolaters in substation ?

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.