Volume 9, Number 1 
Is there any relationship between the two? Clearly!
Birds represent a major threat to the reliability of power delivery and the insulator (and sometimes also the bird itself) is typically the victim. For many utilities, birds represent a major cause of insulator-related outages - almost on par with the single leading source of insulator problems, namely lightning surges. And these are only the utilities who have recognized the seriousness of the problem. There are cases of utilities experiencing unexplained flashover problems from time to time, but who still may not have identified these as being somehow related to birds.
Currently, there are people in various organizations and encompassing various disciplines who are working zealously to minimize bird-related power interruptions. The result is that, while the problem is not yet completely solved, we are in a better position today to achieve a win-win situation (both for the birds and the insulators). For example, a range of products are now available to mitigate bird-related outages.
In hindsight, this problem should have been anticipated since the construction of the first transmission lines. Since these lines usually traverse large uninhabited and often desolate areas, transmission towers provide birds with a convenient perch for roosting or hunting.
Birds on transmission structures can cause problems in several ways. First, during take-off or landing from the tower, they could establish contact with energized conductors, a situation which is usually fatal to the bird and which can cause at least a temporary power interruption. A second source of power interruption that many-a-time goes unnoticed is caused by bird excrement - today euphemistically referred to as bird streamers. These are extremely conductive, long filamentary channels capable of causing a short circuit across the least distance between the conductor and the ground structure, which invariably is in the immediate vicinity of the insulator.
Yet a third mode of failure results from the insulator being covered with bird guano in the form of a classical contamination flashover. In this case, there is usually sufficient evidence in the form of residue on the insulator surface, confirming that this was the cause of failure. The fourth cause, and this one limited to composite polymer insulators, is birds pecking away at the housing material and exposing the core rod to the elements. This can ultimately lead to both electrical and mechanical failure. A failure of this type would necessitate replacement of the insulator and could well result in a long-term power outage.
With such possible failure modes, it should not be surprising that birds pose such a threat to the reliability of power delivery. What can be done to minimize the problem?
Counter-measures range from mounting strips of wire on the structure right above the insulator to installing alternate sites for perching, or even devices to discourage birds from sitting on the structure for any significant duration. One thing however is clear so far – there is no “bird-proofing” solution yet.
A panel session devoted to this topic was held during the recently-concluded IEEE Winter Power Meeting. In fact, this topic generated enough interest to warrant setting up a new Task Force in the IEEE Working Group on Insulator Contamination. Hopefully, an interim report summarizing the seriousness of the problem and the effectiveness of alternate methods to combat the problem will be issued within a year.
So far, most of the counter-measures seem to provide only temporary relief. It appears that birds like the heights provided by overhead line structures, so not much can be done to discourage them from perching on these. The goal then is to ensure that the birds do not perch directly above the insulator, in case of a suspension string assembly, nor on top of the V formed by the V-string insulator assembly. Birds seem to adapt to the presence to these added devices on structures, and after a while, may even take a liking to them. What is needed is a long-term solution, one that is bird-friendly, environmentally friendly and, of course, which is inexpensive enough for utilities to consider implementing it. This is indeed a challenge although there are certainly cost savings benefits which may make it worthwhile to pursue.
It is ironic that birds perched on energized conductors are perfectly safe, yet when they move to the grounded structure they cause a lot of problems to themselves and to the power delivery system. This reminds me of the announcement in airplanes that it is perfectly safe to walk inside when the aircraft is cruising at speeds of over 800 km/h, yet passengers need to wear seatbelts whenever the aircraft is almost crawling on the runway.
Dr. Ravi S. Gorur
