Raptors, Poles, and Conductors...


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(To repeat our introduction, in case you've read the section on raptors and overhead devices first)... Utilities face two problems when it's suspected raptors are interacting (usually fatally) with utility equipment. First, raptor electrocutions don't always cause outages; often the event is a temporary fault and cleared by the up-line recloser. These types of events are usually not investigated and it may be some time (if ever) that the carcass is found. Even if an outage occurs, more than likely it's in a fairly remote rural area since this where raptors normally live. By the time the crew arrives, other predators may have already removed the carcass.

Second, because of the raptor's protected status, utilities are obligated to place their focus on reducing or preventing electrocutions. Reducing or preventing outages, recloser operations ("blinks"), or equipment damage are secondary priorities.

Research programs to reduce raptor electrocutions on poles and conductors have been in place for more than twenty years. The first report issued on this topic was REA Bulletin 61-10 "Powerline Contacts by Large Birds" in 1972 by the Rural Electrification Administration (REA), now known as the Rural Utility Services (RUS). Electrocutions are the result of an unfortunate combination of utility design and construction and raptor size and behavior.

Almost all raptor electrocutions occur on poles and conductors at distribution voltage, the majority at 25 kV or less. The determining factor is the distance between phases and between conductors (or jumpers) and ground. At transmission voltages, the clearances required by the National Electric Safety Code (NESC) are sufficient to prevent wingtip contacts by even the largest raptors.

One of the most lethal utility constructions consists of an energized conductor mounted on a pole top grounded insulator. Despite efforts by rural electric cooperatives, RUS, and the Raptor Research Foundation to identify and modify these poles, many are still in place. RUS banned the use of this design in the early 1960s, but some non-RUS utilities are still using it. Another particularly lethal construction used by non-RUS utilities is a three phase line with one phase mounted on one side of the crossarm and the other two phases mounted on the other side of the crossarm. In this design, the two phases are close enough for even a small raptor to cause a wingtip contact. This type of construction was also banned by RUS in the early 1960s, but is still used by other utilities.

On multi-phase distribution poles, "Suggested Practices for Raptor Protection on Powerlines - The State of the Art in 1996", published by the Avian Powerline Interaction Committee (APLIC), recommends a minimum clearance of 5 feet between conductors (or conductors and ground). However, this requires 10 foot crossarms and the usual utility practice is to use poles with 8 foot crossarms. It is certainly feasible for utilities to adopt a policy of using 10 foot crossarms on new construction and, indeed, many have done so. But the prospect (and expense) of retro-fitting existing poles can be overwhelming.

Obviously, not every pole on the system would require 10 foot crossarms, only those in areas of known or probable raptor populations. But it is sometimes difficult for utilities to identify what poles may be at risk until an electrocution occurs. This is particularly true in areas of relatively flat terrain. Here, no one pole offers any advantage over any other pole. Raptors may move from pole to pole and show no preference for any particular one.

In a recent study, wildlife biologist Richard E. Harness states some utility operations and maintenance crews question the effectiveness of 10 foot crossarms. Based on their field experience, they feel far more raptors are electrocuted on riser poles, tap and angle structures, and transformer poles than tangent poles with 8 foot crossarms. We think this is probably true in many instances. As we said before, the determining factor is the distance between phases and between conductors (or jumpers) and ground. Obviously, riser poles, tap and angle structures, and transformer (or voltage regulator, capacitor, by-pass switch) poles offer too many opportunities for contacts.

The mitigating efforts made by most utilities are perching guards to prevent raptors from using risky poles (Case Studies describe how this was not a good idea for one utility), mounting perches above the crossarms, and installing bushing and stinger covers on devices. At least one manufacturer is developing an insulating cover that can be placed on conductors and over pole tops.

To repeat ourselves again...It can be difficult for utilities to identify what poles are at risk until after an event occurs. Mr. Harness, in his study, states that many utility personnel are unaware that hawks, owls, and vultures are raptors and electrocutions are often not reported. It is likely that no efforts are made to mitigate these types of electrocution unless outages are involved.

Utilities may be unaware that there are raptors in their service territory and, therefore, take no preventative measures. We don't understand why, but the United States Fish and Wildlife Service (USFWS) does not notify electric utilities of existing or new populations of raptors in the utility's service territory. Considering the fines, penalties, and liabilities that can be imposed on utilities involved in raptor electrocutions, and the lack of notification by the USFWS, it is in the utility's best interest to identify any protected species within its' territory. And, needless to say, take appropriate preventative measures.

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