The apparatus and method disclosed here relate to the field of electrical power transmission and distribution and the need to insulate electrical power systems from short circuits caused by birds and other animals. Long-distance electricity transmission is typically carried with high voltage conductors. Higher voltages reduce resistance power loss, and line voltage for long distance lines is stepped up with generating stations at selected locations. Transmission lines traverse large regions and require numerous support towers. The conductors in high tension powerlines are typically uninsulated because of the cost and additional weight of insulated versus uninsulated conductors.
Electric poles, towers, including substations provide attractive roosts for birds, particularly in treeless regions. If the wings of a bird simultaneously contact a conductor and another object such as an adjacent conductor, support tower or tree, the resulting electrical short-circuit can kill the bird and also damage the power system. The electrical short can further cause electrical system damage resulting in power outages. Because large (and typically protected) birds are more susceptible to such incidental contact, electrocution hazards disproportionately affect large bird species such as raptors.
In particular, substations transform power from transmission voltages to distribution voltages (typically ranging from 2400 volts to 37,500 volts. Distribution voltages allow for reduced system clearences. These reduced clearences between Phase to ground and phase to phase, increase station susceptibility to bird or animal caused outages. During animal or bird caused fault conditions, close in faults often trigger sensitive relay protection schemes resulting in Substation lockouts interupting service to thousands or possibly tens of thousands of customers and at the same time damaging expensive substation equipment.
The variety and number of proposed solutions for repelling birds and other animals from electrocution risks highlights the persistence and magnitude of the problems created by such undesirable intrusion. Many different types of scarecrows and other moving devices have been developed to repel birds. In addition to moving devices, various physical structures have been developed to discourage birds from roosting on structures, particularly involving spikes or other physical barriers. Other bird repelling concepts use electricity or magnetics to discourage bird intrusion. Shield and cage devices have been specifically designed to restrict birds and other animals from short-circuiting electrical leads, such as U.S. Pat. Nos. 5,153,383 and 5,485,307.
The inventor's own prior patent application discloses a method of in situ application of a dielectric coating to live power transmission components, see United States publication no. 20040265497. The variety and number of these efforts indicate significant problems in the exclusion of birds from undesirable areas, and the inherent difficulties in effectively accomplishing such exclusion. Many of these techniques are expensive to employ and are ineffective in preventing birds from landing in a particular spot. While the inventor's own prior patent application supplies a solution for many applications, there remains a need for an improved method and apparatus capable of resisting electrical wire short circuits deleterious to birds and other animals.