technical bulletin - raptor electrocutions and distribution pole types

Raptor Electrocutions – BackgroundAs early as 1971, the electrical utility industry becameaware of the raptor electrocution issue. Due, in largepart, to investigations of poisoning and shooting deathsof bald and golden eagles in Wyoming and Colorado,it was discovered that many birds were also dying bypower line electrocutions. By 1972, the U.S. RuralElectrification Administration (REA) published a firstset of industry guidelines for minimizing raptorelectrocution problems along power lines. In theensuing years a steady stream of studies andpublications, many generated by sources from withinthe industry, fed a rapidly accumulating knowledge basepertaining to the issue (Olendorff, et. al., 1981).Currently, the most complete and up-to-date documentdealing with the raptor protection issue is SuggestedPractices for Raptor Protection on Power Lines: TheState of the Art in 1996, published by the Avian PowerLine Interaction Committee, the Edison ElectricInstitute, and the Raptor Research Foundation.

After 1972 many investor owned utilities (IOU’s) andREA cooperatives adjusted line configurations andgrounding practices, reducing raptor electrocutions.Today Rural Utilities Service (RUS) cooperatives(formerly REA) are required to construct lines withnonconducting wood braces, and to install pole groundsso they are raptor safe. These changes are reflected inthe U.S. Department of Agriculture engineeringpublication entitled, “Specifications and Drawingsfor 7.2/12.5Kv. Line Construction” (RUS Form 804).Additional raptor mitigating measures are up toindividual RUS members, with many choosing toreduce eagle electrocutions by providing increasedconductor separation. The increased separation isoften accomplished by substituting 10-foot woodcrossarms for conventional 8-foot arms, providing60-inches of separation between primary conductors.The Raptor Research Foundation recommends aminimum of 60-inch spacing between phases andphase-to-ground to minimize eagle electrocutions(APLIC 1996). A large female golden eagle can havea 90-inch wingspan, 54 inches between wrists. The60-inch spacing was selected to minimizeelectrocutions of immature eagles when they beginor terminate a flight.

Although utility construction practices have improvedsince 1971, some raptor electrocutions still persist. Theseelectrocutions often cause outages resulting in damagedequipment, safety problems and loss of service toconsumers. A 1993 Institute of Electrical and ElectronicsEngineers, Inc. (IEEE) survey stated the majority of theirrespondents still experience outages caused by squirrels,birds, raccoons and snakes (IEEE Power EngineeringSociety 1993). Nationwide, animals are the third leadingidentifiable cause of all power outages, and birds causemore outages than any other animal (SouthernEngineering Company 1996). The United StatesDepartment of the Interior investigated 4,300 eagledeaths from the early 1960’s to 1995 and reportedelectrocution as the second greatest cause of all detectedgolden eagle mortality and the fourth greatest cause ofbald eagle deaths (LaRoe et al. 1995) (Photo 1).

Electrocutions are not restricted to the United States butoccur worldwide. Cape vulture electrocutions have beena persistent problem in South Africa (Markus 1972, Jarvis1974, Ledger and Annegarn 1981). Haas (1980) reported14 diurnal and 5 nocturnal species of raptor electrocutedby power lines in West Germany; Herren (1969) recordedowl electrocutions in Switzerland. Bevanger (1994)surveyed 175 Norwegian power companies and mostrespondents stated they believed their facilitieselectrocuted raptors.

Photo 1. A juvenile golden eagle electrocuted by a distributionpower line.

2

NAWPC Technical Bulletin

The 2nd International Conference on Raptors (October,1996) organized by the Raptor Research Foundation,included an Energy Development Symposium.Representatives attending the conference from the UnitedStates, South Africa, Tasmania, Russia, Italy and Spainall presented papers on persistent avian electrocutions.

Electrocutions are also a restrictive factor for some raptorpopulations (APLIC 1996). At one point there were only60 California condors left in the North America. Todaycondors are subjected to mock power poles and lowelectrical shocks to deter perching before they arereleased (Graham 2000). The electrocution of Egyptianvultures may be responsible for the overall decline ofthe species near Khartoum, Sudan (Nikolaus 1984).Electrocution is also the primary known cause of deathfor the endangered Spanish eagle in and around DoñanaNational Park, Spain (Ferrer and Fernando 1991, Ferreret al. 1991). They estimate up to the 187 miles of powerlines in and around the park might kill 1200 raptors peryear. Ferrer and Fernando (1991) also concludetechniques for reducing electrocutions in and aroundDoñana National Park, Spain are more effective thanother management techniques employed to increase eagleproductivity.

The electrocution problem will presumably intensify aspower lines are constructed in developing countries withexpanding human populations such as Africa, SouthAmerica, and Asia (Bevanger 1994). Mitigatingmeasures should be encouraged globally because theywill not only minimize electrocutions, but will alsominimize power outages (Negro and Ferrer 1995).Reducing outages may save utilities money in the longterm and will certainly improve system reliability. Forexample, May 9, 2000 the southern half of Portugal,including the capital Lisbon, had a massive poweroutage. The outage lasted almost 2 hours and affectedseveral million people. A bird caused a short circuit ona power line and the automatic protection system at amajor substation did not function.

Raptor Electrocutions – Legal IssuesDespite a wealth of available information, some electricalutilities continue to lag behind standards of raptorprotection along their power lines. In so doing, theseutilities expose themselves to the possibility ofprosecution under statutes that protect the birds that perchon those lines. Disturbed by the continuing large numbersof raptors, particularly eagles, electrocuted along powerlines, the U.S. Fish and Wildlife Service (USFWS) hasbegun to step up enforcement of the Migratory BirdTreaty Act (MBTA), the Bald and Golden EagleProtection Act (BGEPA), and the Endangered SpeciesAct (ESA). The first utility cited for violation of theMigratory Bird Treaty Act was Pacific Gas and Powerof California. In 1993, the utility was fined $1500 forviolations and agreed to retrofit lines to safer standards.In 1998, Sand Point Electric of Alaska was fined $500and was likewise compelled to retrofit dangerousstructures (Suazo 1998).

Most recently, however, a plea agreement between theUnited States Department of Justice and the USFWS withMoon Lake Electrical Association, Inc. (MLEA) of Utahushered in an entirely new era of enforcement (Williams2000). Under the agreement, MLEA was given threeyears of probation, ordered to pay $100,000 in fines andrestitution, and required to retrofit structures dangerousto migratory birds. MLEA was also required to enterinto a Memorandum of Understanding (MOU) with theUSFWS and to hire a qualified consultant to develop anAvian Protection Plan.

Altogether, MLEA was charged with six counts ofviolating the Migratory Bird Treaty Act and the Baldand Golden Eagle Protection Act. Although MLEA wascharged with killing 17 large raptors (including, but notlimited to, golden eagles), at least another 21 raptors inexcess of the 17 enumerated in the charges had beenelectrocuted over a period of several years under theAssociation’s power lines. Complicating matters for theutility was the fact that MLEA had been repeatedlynotified of dangerous structures along their lines, butopted to retrofit only structures already known to havekilled birds (Melcher and Suazo 1999). Multiple killswere also recorded under some structures.

3

Raptor Electrocutions

Table 1. Penalty Provisions in USFWS Statutes

In a pre-trial motion, MLEA argued that it had notdeliberately killed any of the raptors and was thereforenot liable to charges under either the MBTA or theBGEPA. Moon Lake argued, in part, that the MBTA andBGEPA were intended to apply only “intentionallyharmful” activities such as those entailed in hunting,poaching, and trapping. District Court Judge LewisBabcock denied this motion. In the case of the MBTA,Judge Babcock found that the language of the MBTA,“it shall be unlawful at any time, by any means, or inany manner, to pursue, hunt, take, capture, kill, attemptto take, capture, or kill … any migratory bird …,” doesnot restrict application to deliberate types of killingnormally associated with poaching or hunting. WhileJudge Babcock allowed that innocent technical violationsmight be taken care of by a small fine, a case such asthat of MLEA raises more serious issues. Specificallynoted by the judge was the fact that MLEA failed to installinexpensive retrofits on 2,450 of 3,096 poles in the areain question. Additionally, Judge Babcock also rejectedMLEA’s claim that they were subject to selectiveenforcement of the law, noting that “conscious exerciseof some selectivity in enforcement is not in itself a federalconstitutional violation so long as the selection was notdeliberately based upon an unjustifiable standard suchas race, religion, or other arbitrary classification (45F.Supp.2d 1070).”

Violations of the MBTA are examples of strict liabilitycrimes, meaning that a party can be convicted under thestatute without demonstration of specific intent or guiltyknowledge. In contrast to the MBTA, the BGEPAproscribes behavior by which an entity “knowingly orwith wanton disregard for the consequences of his act”takes a Bald or golden eagle. Citing numerousprecedents, Judge Babcock ruled that “take” includes anyact of killing without respect to method.

Further, the judge found that a determination of whetheror not MLEA had acted “knowingly or with wantondisregard” in the killing of the eagles was a matter forthe jury’s determination and therefore not subject tochallenge by a pre-trial motion (45 F. Supp. 2d 1070).

All said, if MLEA had not entered into a plea agreement,the Association would have stood trial on all six countsof the violations of both the MBTA and the BGEPA. Thisis the first significant case law of a utility being criminallyprosecuted under the MBTA and BGEPA.

Although not applicable to the MLEA case, theEndangered Species Act may also apply in certain casesof avian electrocutions. Once again, the definition of“take” comes into play. Although a party must knowinglytake a threatened or endangered species to be criminallyliable under the ESA, civil penalties may apply in casesof strict liability as well.

All three of the Acts in question have provisions forsubstantial financial penalties (see Table 1). Under theMBTA, misdemeanor convictions can bring fines of upto $15,000 per individual and $30,000 per organization.Also, the law allows for up to six months of imprisonmentfor individuals involved in the illegal activity. Underthe BGEPA, misdemeanor fines run much higher, up to$100,000 per individual and $200,000 per organization.A second conviction under the act allows for the fines toreach $250,000 and $500,000, respectively. In addition,prison terms of up to one year may be imposed. Finally,violations of the ESA carry similarly severe penalties.Convictions under the ESA carry fines of up to $100,000per individual and $200,000 per organization, with theadded possibility of a one-year prison term.

4

NAWPC

Act

MBTA

BGEPA

ESA

PenaltyProvisions16 USC

70716 USC

66816 USC

1540

FelonyClass

E

E

Felony Jail2 Yrs.

2 Yrs.

Felony Fines250,000/500,000250,000/500,000

Misdem.Class

B

A

A

Misdem.Jail

6 Mo

1 Yr

1 Yr

Misdem.Fines

15,000/30,000

100,000/200,000100,000/200,000

Technical Bulletin

Wind direction relative to utility crossarm orientationalso affects the probability of electrocution (Boeker 1972;Nelson and Nelson 1976; Nelson 1977; Benson 1981).Crossarms mounted perpendicular to the wind allowraptors to easily soar away from the structure and attachedwires. Raptors taking off from crossarmsmounted parallelto prevailing winds can more easily be blown intoenergized conductors.Wind orientation presumablyplaces inexperienced fledgling birds at greatest risk.

Photo 2. Electrocutions can occur if an animal spans phase-to-phase,phase-to-neutral, or phase-to-ground.

Numerous factors in addition to raptor size (Table 2) andconductor separation contribute to electrocutions.Inclement weather, particularly wet snows are a majorcontributing factor to many eagle electrocutions (Benson1981). Feathers are good insulators unless they becomewet. Raptors with wet feathers are ten times as vulnerableto electrocution above 5,000 volts (Nelson 1979a;Olendorff et al. 1981). Dry birds contacting live wireswith their beak and foot however can still be killed atvoltages below 5,000 (Olendorff et al. 1981). Wet birdsmay also have greater difficulty navigating aroundenergized conductors when flying to and from poles.

Table 2. Average Size and Weight of Six Raptor Species.

It is important to note the MBTA protects all migratorybirds, not just raptors. There are over 800 species ofmigratory birds in North America and the only ones notgiven protection are non-native species including thehouse sparrow, European starling, feral pigeon, and monkparakeet.

USFWS Director Jamie Rappaport Clark addressed theEdison Electric Institute - Natural Resources Workshopon April 26, 1999. This speech was a month after theMLEA settlement. In that speech the Director stated theUSFWS would rather partnership with utilities to solveraptor problems than to step up enforcement of lawsprotecting migratory birds. Director Clark also statedtheir goal is voluntary compliance on the part of theindustry and the USFWS will work with any and allutilities to make this happen.

The Mechanics of an ElectrocutionAnimals are not hurt or injured by voltagealone. Squirrels running on or birds perchingon an energized wire without incident arean everyday reminder of this fact. Injuryoccurs when an animal becomes a path forcurrent flow. As current flows from a higherpotential (or voltage) to a lower potential(often ground), the animal must complete a connectionbetween the two potentials to have current flow throughit. In the case of a distribution power line, high potentialsexist on the three phase conductors, and low potentialexists on any conducting part of the structure connectedto an earth ground. The other case of potential differencesoccurs between phase conductors, where one phase ofvoltage can “appear” as a lower potential to another phaseof voltage. In summary, anywhere an animal can createa path between high voltage and ground (or another phaseof high voltage), electrocution can occur (Photo 2).

Species Length (In.)

Wingspan (In.)

Weight (Lbs.)

Golden Eagle 30 79 10 Bald Eagle 31 80 9.5 Ferruginous Hawk 23 56 3.5 Red-tailed Hawk 19 49 2.4 Rough-legged Hawk 21 53 2.2 Swainson’s Hawk 19 51 1.9

5

PHASETOPHASE

PHASETO

NEUTRAL PHASETO

GROUND


This factor is particularly important for rural distributionsystems, where buildings, structures, trees, etc. aretypically fewer in number near the line, and thus provideless protection from direct lightning strikes to the line.

When lightning strikes a distribution line, a current andvoltage surge is placed on the line. It travels down theline looking for a path to ground, which is the path ofleast resistance, or lowest insulation level. At this point,the surge may cause a flashover between phases or aphase and ground, which is to be avoided. The air spacebetween conductors yields large amounts of resistanceto flashover, so the path of least resistance is normallyfound somewhere on a structure. Proper structure designkeeps the insulation between phases high enough to avoidmost flashovers, and channels the energy to groundthrough the use of shield wires or lightning arresters.

The ability to withstand flashovers caused by lightningsurges is the Basic Impulse Insulation Level or CriticalImpulse Flashover rating. After field-testing and debate,300 kV BIL has become the accepted standard for 7.2kV and 14.4 kV (line-to-ground) on RUS distributionsystems. RUS has stated this as a design standard forwood pole construction, and is releasing a draft standardstating the same for distribution construction using steelpoles (RUS 2000).

BIL and Steel/Concrete Pole ConstructionThe current structure design standards for using woodand fiberglass poles need no modifications to provide aminimum of 300kV BIL. However, this does not applyfor standards using steel and concrete poles. Since woodhas insular value, part of the BIL in the structure designcomes from the BIL of the wood poles and crossarms.However, steel poles and crossarms have no insular value,thus providing no measure of BIL to the structure. Spunconcrete poles also have an internal metal rebar supportstructure and are considered to have no insular value.Appropriate BIL can be achieved in steel and concretepole structure design through the use of either fiberglassor wood crossarms (instead of steel crossarms), longerinsulators, and fiberglass pole-top pin extensions.

Raptor electrocutions often fluctuate seasonally. In thewinter, power line poles are valuable sit-and-wait huntingsites, allowing raptors to seek prey without expendingenergy on active flight hunting (Benson 1981). Duringthe spring, raptors may increase their exposure toelectrocution by utilizing pole structures as nesting sites.Seasonal fluctuations of prey abundance may alsoinfluence the number of raptors electrocuted in aparticular area (Olendorff 1972; Benson 1981).

Age is a significant factor in golden eagle electrocutions.Parents feed the immature eagles the first few monthsafter fledging. During this period the young eagles gainflight experience by short perch-to-perch flights. As thesebirds begin to hunt for themselves they generally stillrely on stationary perches. The young eagles areinexperienced in takeoffs and landings and less adept atmaneuvering than adults (Nelson and Nelson 1976;Nelson 1979a, 1979b). Short flights from perch-to-perch,hunting from the perch and takeoff and landinginexperience all place young eagles at a high risk forelectrocution (Olendorff 1993). Dawson and Mannan(1995) indicated that fledgling Harris’ hawks in and nearTucson, Arizona are also especially susceptible toelectrocution during the first 2 weeks after fledging.

Wood, Fiberglass, Concrete, and Steel PolesFrom the beginning, North American distribution utilitiesselected wood as the material of choice for poles andcrossarms. Accordingly, most raptor-proofing techniquesare designed for use on wood pole structures. Recentlyother materials such as fiberglass, concrete and steel polesare being used in distribution line construction. As thesematerials are used as an alternative to wood, constructiontechniques must adhere to established engineering criteriasuch as Basic Impulse Insulation Level (BIL) and state-of-the-art raptor protection.

BIL and Line ConstructionThe ability of a distribution line to withstand, isolate,and quench the effects of lightning strikes must beconsidered when designing an overhead distributionsystem.

6


Photo by Cynthia Melcher

Photo 3. Concrete pole associated with raptorelectrocutions in San Pedro, Mexico.

Raptors and Steel/Concrete Pole ConstructionNon-wood poles are commonly used in distribution lineconstruction in Europe and other parts of the world andJanss and Ferrer (1999) report differences in electrocutionrates of birds on wooden versus metal power poles.Whereas typical electrocution problems in NorthAmerica are often wire-to-wire, European problems areoften wire-to-pole. Accordingly, European mitigationmethods differ because measures effective on woodenpower poles have not solved electrocution problems onmetal poles (Negro and Ferrer 1995). For example,artificial perches attached at “safe” locations (far fromconductors) on poles, and perch guards designed toprevent raptors from contacting conductors, are lesseffective in preventing electrocutions than modificationsthat insulate conductors from birds. The use of pin-typeinsulators on steel is even illegal in parts of Spain due tolethality to raptors (Janss and Ferrer 1999). A Europeanraptor-safe steel pole-top assembly that may be of use inNorth America was presented at EPRI’s “AvianInteractions With Utility Structures” workshop held inCharleston, South Carolina on December 2-3, 1999. RUSis in the process of evaluating the unit for use on theirsystems.

Photo 4. Electrocuted red-tailed hawkunder a steel distribution underbuildmounted on a steel transmission pole.

Concrete poles with their internal support structure ofmetal rebar, pose similar risks to electrocution as steelpoles. A 102 mile long concrete pole line constructedwith steel crossarms near Janos, Mexico was recentlyinspected and 49 dead birds were discovered, suspectedto be electrocutions (pers. comm. Gail Garber 2000)(Photo 3). Of these 10 were ferruginous hawks, 9 weregolden eagles including 5 adults; the rest were acombination of red-tailed hawks, prairie falcons, and oneAmerican kestrel.

Sometimes non-wood poles are used because they arenot susceptible to woodpecker damage. In some regionsof the United States, woodpecker damage to wood polesis the most significant cause of pole deterioration (Abbeyet al. 1997). However, steel or concrete distributionpower lines constructed utilizing standard utilityconfigurations, can significantly reduce phase-to-groundclearances needed by birds of prey. These reducedclearances can result in electrocuted birds of prey (Photo4). Because fiberglass poles are insulated, they can beframed in a similar fashion to wood poles.

7


Raptor Electrocution Mitigation MeasuresThe following discussion covers typical methods usedto frame different pole types (e.g. wood, fiberglass,concrete, steel) to raptor-safe standards. This sectionaddresses the application of mitigation measures to newconstruction only. Retrofitting mitigation measures aresimilar to new construction but generally entail higherlabor costs. The increased labor is due to working aroundenergized conductors. Poles requiring retrofitting arealso often located in remote locations, requiring greatertravel time. Some utilities may also not allow hot gloving.This requires a utility to take an outage to retrofitstructures, impacting both the utility and their consumers.Because of more labor associated with retrofitting,mitigating measures using more expensive materials thatcan be installed hot are often more attractive in retrofittingthan in new construction.

RUS standards were selected because RUS requiresspecific BIL levels and their construction is standardizedacross the Nation. Investor Owned Utilities andMunicipal Utilities also serve into rural areas andexperience problems with raptor electrocutions but theirconstruction standards are variable from utility to utility.For simplification, only the 12.5/7.2 kV design standardsare used.

The figures on the following pages depict some typicalRUS structure designs. The first structure shown in eachfigure depicts an unaltered design, with potentialelectrocution hazards highlighted. Subsequent structuresin each figure depict various mitigation options reducingelectrocution hazards. Wood, steel, concrete andfiberglass pole structures are designed to achieve 300kV BIL required by the RUS.

A list of figures is as follows:

• Figure 1 – Single phase tangent, wood/fiberglass poleconstruction

• Figure 2 – Single phase tangent, steel/concrete poleconstruction

• Figure 3 – Three phase tangent, wood/fiberglass poleconstruction

• Figure 4 – Three phase tangent, steel/concrete poleconstruction

Each section discusses the cost differential betweenmitigating methods on a per structure basis. Tablescontain a list of additional materials needed for thesemitigation options (beyond the normal materials for theconstruction unit), plus estimated material costs basedon manufacturers’ suggested retail pricing. Labor costswere also included but may vary greatly between utilities,contractors, and methods of installation.

Differences between pole costs can also be disparate. Ingeneral, fiberglass and concrete distribution poles aremuch more costly than wood poles. Cost comparisonsin this paper are limited to steel and wood because theyare much closer in cost.

The price of wood and thin walled steel poles varysignificantly depending upon a variety of factorsincluding wood species, geographic location, framingrequirements, coatings and class size. For purposes ofthis analysis for distribution line construction we havelooked at data for an average of 40-foot class 4 southernpine pole prices compared to 40-foot class 4 thin-walledsteel. Southern yellow pine was selected because itcomprises approximately 80% of the wood pole market.Using this analysis we assume the average wood pole,including freight will cost $210 and the average steelpole, including freight will cost $280 or a difference of$70.

It is important for the user to remember comparisons areon a per structure basis and the price analysis considersthe thin walled steel poles sizes and thus costcomparisons, as being based upon wood equivalents.This is true only in Grade B design, when distribution ismore likely to be designed to Grade C standards wheresignificantly more or larger steel poles would be requiredto meet code in a manner equivalent to wood.

For raptor protection purposes, wood and fiberglass polesare treated as nonconductive although under certainweather conditions poles can become grounded due largeamounts of moisture. Although electrocutions can occuron phase to wet wood, they are relatively rare (Harness1997). Steel and concrete are treated as conductive forBIL and raptor protection.

8


Fiberglass crossarms are sometimes employed on steeland concrete poles but cost more than conventional woodcrossarms. For purposes of cost comparison, allstructures were evaluated using wooden arms framedwith wooden braces.

Different grounding methods are also used for steel poles.On all poles requiring ground rods (i.e. transformer,reclosers, etc.) the labor and material is the same at thepole base, but wood poles also require running a grounddown the pole. For purposes of cost comparison, allwood structures were evaluated including the additionallabor and material required to run a ground wire to thepole base.

Single Phase Tangent StructuresThe most common distribution unit types located in ruralareas are tangent structures. Figure 1 illustrates a typicalsingle-phase tangent structure constructed on a wood orfiberglass pole.

Single-phase lines are usually constructed withoutcrossarms and support a single energized phase conductoron a pole-top insulator. Distribution tangent structures,without pole-top grounds or pole-mounted equipment,generally provide adequate separation for all raptors.

If steel or concrete is substituted for wood or fiberglass(Figure 2), the critical clearance for birds of prey is thephase-to-pole top (i.e. ground) clearance. A goldeneagle’s tail can extend 10 inches below its perch.Although dry feathers can withstand voltages up to 70kV, wet feathers burn at 5 kV (Nelson 1979b). Therefore,a large bird of prey can be electrocuted while perchingon a center phase pin under wet conditions if its tailfeathers contact a grounded surface, such as a steel orconcrete pole. The proximity of the wire to the steelpole also does not meet RUS BIL requirements.

Figure 1. Typical rural distributionsingle-phase pole configuration,7.2kV.

Figure 2. Inadequate BIL andraptor clearance with steel andreinforced concrete poles.

Phase Conductor

Neutral Wire

Wood orFiberglass

Inadequate BILand Insuffi-cientRaptor Clear-ance

Phase Conductor

9"

Neutral Wire

Steel or Con-crete

9


The caps also minimize noise from air blowing acrossthe pole top and keep out moisture. In preliminary testsutilizing captive raptors at the Rocky Mountain RaptorCenter, a pole-top cap discouraged birds from perchingbecause of the caps’ slick surface (Photo 5). It is uncertainhowever how these caps will perform in the field(Harness 1998).

Cost: Providing 300kV BIL and raptor protectionrequires steel and concrete poles to include a pultrudedfiberglass pole-top pin and a pole cap designed todiscourage perching (see Table 3). Because steel polesdo not require ground wires and staples, there is somesavings over wood and fiberglass. However the BIL andraptor protection pushes the overall material price of thesingle-phase steel construction to approximately $96.95more than wood. The overall steel labor cost is $14.31less than wood. The total labor and material cost is$82.64 more for steel.

A solution to this problem is to place the phase wire on amore expensive pultruded fiberglass pin to rise up thephase conductor (Figure 2 – Option 1). Although thismodification effectively restores the steel pole structureBIL to 300 kV, the fiberglass pole-top pin extensioncreates a new hazard to raptors. The increased distanceeliminates the possibility of electrocutions to birdsperching on the pin insulator, however the modificationmakes it possible for a raptor to perch directly below thephase wire on the grounded pole top. This new conditioncan be lethal to birds such as the red-tailed hawk that aresufficiently large to bridge the gap between the steel poletop and center phase wire. Therefore, steel structuresusing extended pole-top pins need additionalmodification to keep large birds off the pole top or awayfrom the center phase.

One solution to keep birds off the pole top is the use ofplastic pole caps (Figure 2 – Option 2). Steel poles aretypically fitted with pole caps toprevent small birds and insects fromnesting inside the structures.

Figure 2 - Option 2. Adequate BILdue to pultruded fiberglass pole-top pin and raptor protection dueto pole cap.

Figure 2 - Option 1. Adequate BIL dueto pultruded fiberglass pole-top pinbut insufficient raptor clearance.

Photo 5. Distribution steel pole fitted witha pole-top cap to exclude perching.

Adequate BILbut Insuffi-cientRaptorClearance

Phase Conductor

Neutral Wire

Steel orConcrete

19"

30"

Pole Cap toExclude Perching

Phase Conductor

Neutral Wire

Steel orConcrete

30"

10

NAWPC

FIBERGLASSPOLE-TOP PIN

POLE TOP CAP

Technical Bulletin

Table 3. Differential Costs - Single Phase Tangent Unit, Wood and Steel.

The steel pole sizes used for these examples assume a strength equivalency to wood that is based on 1997 NESC Grade Bdesign requirements. For distribution pole lines that are designed using 1997 NESC Grade C requirements, in order forsteel to be equivalent to wood, the steel poles would likely need to be 1 to 3 classes larger or would require shorter spanswith more poles. For example, if a Class 4 wood pole were required for a typical tangent pole in Grade C design, the GradeB equivalent steel pole would likely have to be between a Class 3 and a Class 1 design, depending upon the overload factorused for design. This would increase the price differentials between steel and wood in these examples.

a 20-degree angle between the outer and center phasewire. This separation is appropriate in areas where largeraptors are less likely to occur. Additional protection isrequired in areas with eagles and other large raptors.

In rural areas, three-phase tangent structures should beframed to provide an additional 16 inches of clearance,bringing the total phase-to-phase separation to 60 inchesas recommended in “Suggested Practices for Raptor Pro-tection on PowerLines: The State of theArt in 1996”. The ad-ditional clearance re-quired for eagles canbe obtained by lower-ing the crossarm 27inches on new poles(Figure 3 – OptionW1).

Figure 3. Typical rural distribution three-phase pole configuration, 7.2/12.47kV.

Three Phase Tangent StructuresA common three-phase distribution unit located in ruralareas is a tangent structure. Figure 3 illustrates a typicalthree-phase tangent structure constructed on a wood orfiberglass pole. Three-phase power lines are usuallyconstructed with an8-foot crossarmsupporting two con-ductors. A singleenergized phase con-ductor typically sits ona pole-top insulator.Distribution three-phase tangent struc-tures, without pole-topgrounds or pole-mounted equipment,generally provideadequate separationfor all but the largestraptors since 44-inchesof phase separation isprovided. There is also

PhaseConductor

Wood orF i b e r -glass

NeutralWire

8' WoodCrossarm

InsufficientEagleClearance

90"

60"

Wing tips

Wrist Wood orFiberglass

Neutral

8' WoodCrossarm

Addi-tionalVerticalSpacing

Option W1

EAGLEMEASUREMENTS

40"8"

18"

26"

44"

8" 40"

18" 60"

26"

27"

Figure 3 - Option W1. Eagle safethree-phase pole configuration usinga dropped crossarm, 7.2/12.47kV.

11

StructureType

Wood,RaptorSafe

Steel,RaptorSafe

Description

Wood Pole, 40-4Pole-top PinGround Wire and Staples

Steel Pole, 40-4Fiberglass Pole-top PinPole-top Cap

Qty

11

30

111

Unit Cost

210.004.550.17

280.0030.006.60

Mat.Total

210.004.555.10

280.0030.00

6.60

LaborCost

296.917.15

21.46

296.917.157.15

StructureTotal

$545.17

$627.81


Dropping a crossarm an additional 27 inches may requireshorter spans or taller poles to maintain clearances,adding to the structure cost (see Table 4). A commonalternative to dropping the arm is to use a 10-footcrossarm and lowering the arm only an additional 12inches (Figure 3 – Option W2). This provides therecommended 60-inches of separation without usingtaller poles and is the most economical method to raptor-proof (see Table 4).

When steel or concrete is substituted for wood orfiberglass, the critical clearances for birds of preybecomes both the phase-to-pole (i.e. phase-to-ground)and phase-to-phase separation (Figure 4).

As in the single-phase unit, additional clearances mustbe met for the center pole-top phase conductor by placingthe phase wire on a pultruded pole-top fiberglass pin witha pole-top cap to discourage perching.

Figure 4. Three-phase steel/concrete pole configuration withinadequate raptor separation, 7.2/12.47kV.

Additionally, nonconducting wood or fiberglasscrossarms should always be used. Steel crossarms onsteel poles should always be avoided. Because steel polesdo not require ground wires and staples, there is somematerial and labor savings over wood, concrete, andfiberglass. The phase-to-pole clearances can be satisfiedin several ways.

The reduced phase-to-ground clearances on steel polescan be mitigated by insulating the pole top (Figure 4 -Option S1). This can be achieved by wrapping the poletop with a band of 40-mil thermoplastic polymermembrane wrap backed with a pressure sensitiveadhesive above the crossarm or spraying on a protectivecoating that has sufficient dielectric strength. RUSrequires an insulating coating of at least 15kV (RUS2000). This is the most economical steel pole option(see Table 4).

Figure 3 - Option W2. Eagle-safethree-phase pole configurationusing a 10-foot crossarm, 7.2/12.47kV.

Figure 4 – Option S1. Three-phase steel/concrete poleconfiguration with thermoplasticwrap, 7.2/12.47kV.

Wood orF i b e r -glass

10' WoodCrossarm

AdditionalVerticalSpacing

90"Wing tips

Wrist

EAGLEMEASUREMENTS

NeutralWire

60"

InsufficientClearance forRaptor Protection

8' Wood orFiberglassCrossarm

NeutralWire

Steel orConcrete

InsufficientClearance forRaptor Protection


NeutralWire

Steel orConcrete

ThermoplasticCoating

Pole Cap

Option W2

Option S1

8"

26"

18"

52"

60"

12"48"19"

18"

26"

8" 40"

37"

60"

36"

8" 40"26"

12


Perch guards can also be mounted on crossarms to keepraptors away from the pole instead of an insulating polewrap (Figure 4 - Option S2). Although this method canbe used to discourage perching, it will not always besuccessful. Lines fitted with triangular perch guards areeffective in reducing mortality but will not alwayseliminate mortality (Harness and Garrett 1999). Perchguards may also simply shift raptors to other nearby polestructures.

Another suitable method to raptor proof is to cover upthe outer 2 phase conductors with a Kaddas Bird Guard™insulator cover to prevent phase-to-pole contacts (Figure4 - Option S3). Although the Kaddas Bird Guard™ iseasily installed, this is the most costly option due to theprice of the Guards (see Table 4).

An alternative to constructing lines in a traditionalmanner is to frame them in a form that allows safeperching (Figure 4 – Option S4). Safe perching can beaccomplished by suspending two of the energizedconductors under the crossarm, instead of supportingthem on the arm. Option S4 requires suspensioninsulators and clamps. Each suspension insulatorassembly (insulator, eyebolt, and shoe) costs $5.41 more(see Table 4) than a standard pin insulator assembly(insulator, crossarm pin, and tie).

Suspending the conductors allows birds to perch on thecrossarm without coming in close proximity to energizedconductors. A pole-top cap must still be employed todiscourage perching. Suspending the insulators andconductors will also allow utilities to achieve the RaptorResearch Foundation’s recommended 60-inches withshorter crossarms.

Figure 4 – Option S2. Three-phasesteel/concrete pole configurationwith perch guards, 7.2/12.47kV. Figure 4 – Option S3. Three-phase

steel/concrete pole configurationwith Kaddas Bird Guards™, 7.2/

12.47kV.

Figure 4 – Option S4. Three-phasesteel/concrete pole configurationframed with adequate raptorseparation, 7.2/12.47kV.


NeutralWire

Steel orConcrete

InsulatorCover SideProfile

Pole Cap

Option S2

Perch Guard

Pole Cap

InsulatorCover


NeutralWire

Steel orConcrete

NeutralWire

Steel orConcrete


Pole Cap

Option S3

Option S4

60"

36"

8" 40"26"

80"

60"

36"

8" 40"26"

4" 32"

61"

20"

27"

13


Cost: The cost analysis (see Table 4) examines sixalternatives (W1, W2, S1, S2, S3, and S4) for making atypical three-phase tangent structure bird-safe.

The steel pole sizes used for these examples assume a strength equivalency to wood that is based on 1997 NESCGrade B design requirements. For distribution pole lines that are designed using 1997 NESC Grade C require-ments, in order for steel to be equivalent to wood, the steel poles would likely need to be 1 to 3 classes larger orwould require shorter spans with more poles. For example, if a Class 4 wood pole were required for a typicaltangent pole in Grade C design, the Grade B equivalent steel pole would likely have to be between a Class 3 anda Class 1 design, depending upon the overload factor used for design. This would increase the price differentialsbetween steel and wood in these examples.

Two wood and four steel approaches were examined onthe basis of new installation. The units in Table 4 arecompared using the differential material and labor costbetween each option.

Table 4. Differential Costs - Three Phase Tangent Unit, Wood and Steel

14

NAWPC

Description

Wood Pole, 45-4Pole-top PinCrossarm, 8-footGround Wire andStaples

Wood Pole, 40-4Pole-top PinCrossarm, 10-footGround Wire andStaples

Steel Pole, 40-4Fiber Pole-top PinPole-top CapCrossarm, 8-footThermoplastic Wrap

Steel Pole, 40-4Fiber Pole-top PinPole-top CapCrossarm, 8-footPerch Guards

Steel Pole, 40-4Fiber Pole-top PinPole-top CapCrossarm, 8-footKaddas BirdGuard™

Steel Pole, 40-4Fiber Pole-top PinPole-top CapCrossarm, 8-footSuspensioninsulator Diff.

StructureType

Wood,Raptor SafeOption W1

Wood,Raptor SafeOption W2

Steel,Raptor SafeOption S1




Qty

11130

11130

11111

11112

11112

11112

UnitCost

240.004.55

31.400.17

210.004.55

38.650.17

280.0030.006.60

31.405.48

280.0030.006.60

31.4032.75

280.0030.006.60

31.40105.00

280.0030.006.60

31.405.41

TotalMat.

240.004.55

31.405.10

210.004.55

38.655.10

280.0030.006.60

31.405.48

280.0030.006.60

31.4065.50

280.0030.006.60

31.40210.00

280.0030.006.60

31.4010.82

TotalLabor

296.917.15

21.4621.46

296.917.15

21.4621.46

296.917.157.15

21.4613.89

296.917.157.15

21.4612.08

296.917.157.15

21.4612.08

296.917.157.15

21.4614.31

StructureTotal

$628.03

$605.28

$700.04

$758.25

$902.75

$705.80

Technical Bulletin

Table 5. Differential Costs - Three Phase Tangent Unit, Wood and Steel.

The next most cost effective structure is using an 8-footcrossarm with a 5-foot taller pole (Option W1). The steeloptions increase the cost from $94.76 to $297.47depending upon the material and options selected.

Table 5 provides a list of the cost difference betweeneach option. The most cost effective structure is a woodpole using a 10-foot crossarm (Option W2). Wood poleconstruction using a 10-foot crossarm only minimallyincreases material costs because it requires a standard40-4 wood pole and standard pole-top pin.

15

Alternative

Wood,Raptor SafeOption W1Wood,Raptor SafeOption W2





Description

Wood Pole, 45-4Lowered Crossarm, 8-foot

Wood Pole, 40-4Crossarm, 10-foot

Steel Pole, 40-4Fiberglass Pole-top Pin, Pole-top CapThermoplastic Wrap

Steel Pole, 40-4Fiberglass Pole-top Pin, Pole-top CapPerch Guards

Steel Pole, 40-4Fiberglass Pole-top Pin, Pole-top CapKaddas Bird Guard™

Steel Pole, 40-4Fiberglass Pole-top Pin, Pole-top CapSuspension Insulator Diff.

IntalledCost

Estimate

$628.03

$605.28

$700.04

$758.25

$902.75

$705.80

Differential

$22.75

Base

$94.76

$152.97

$297.47

$100.52

PercentIncrease

4%

Base

16%

25%

49%

17%


Deadend StructuresDeadend structures accommodate directional changesand lateral taps. The 300kV BIL level is especiallyimportant on deadends where voltage doubling can occur.The 300kV BIL can be attained on steel and concretepoles by installing a 24-inch (minimum length) insulatedextension links between the primary deadend suspensioninsulators and the steel pole (Photo 6). The insulatinglinks cost $12.75 each. The insulating links are notrequired to achieve 300kV BIL on wood or fiberglassstructures.

Photo 6. Steel single-phase doubledeadend pole with insulating links toachieve 300kV BIL.

Deadend structures can be lethal toanimals due to bare jumpering betweencircuits (Photo 7). Insulating jumperwires is the most common raptorproofing method. On some structuresjumper wires can simply be reroutedunder crossarms to eliminate potentialphase-to-phase contacts. Thesemitigating measures are typicallysimilar, regardless of pole type.

Photo 7. Deadend structure with inadequate separation betweenjumper wires.

Equipment StructuresDistribution facilities contain an array of pole-mountedequipment such as transformers, capacitors, regulatorsand reclosers. Although equipment poles are relativelywidely spaced on most rural electric systems, they areassociated with a disproportionate number of detectedraptor electrocutions (Harness 1997). Uninsulatedjumper wires connect the primary phase and neutralconductors to the pole-mounted equipment. The spacingof these bare jumper wires can present a hazard to bothsmall and large raptors.

Equipment miti-gating measuresare similar for allpole types. In-stalling raptor-safe equipmentincludes bushingcovers, insulatedjumper wires(600 Volt classinsulation), andbird spikes be-tween cutout/ar-resters (Photo 8).

Photo 8. Retrofitted three-phasetransformer bank.

16

NAWPC

CoveredJumpers

BirdSpikes

BushingCover

InsulatedBracket

InsulatingLinks

Technical Bulletin

ConclusionWhen comparing different pole types, additionalmaterials required to frame poles in a raptor-safe mannershould be included in a cost analysis. The cost to provideestablished engineering criteria such as Basic ImpulseInsulation Level should also be considered. Because steeland reinforced concrete poles are more conductive thanwood or fiberglass, additional costs are required toprovide adequate BIL and raptor protection.

Single-phase and three-phase tangent structures are thecommon structure types in rural areas. Typical single-phase tangent units constructed with wood poles withoutpole-top grounds or pole-mounted equipment are raptorsafe. However, the same single-phase configuration withsteel or reinforced concrete poles requires additionalmeasures to provide raptor protection and 300kV BIL.Additional construction methods typically include theuse of fiberglass pole-top pin extensions and pole-topcaps to exclude perching. These additional measuresadd approximately $12.64 in material and labor costsper pole. The total labor and material increase betweena single-phase raptor-safe wood pole and a raptor-safesteel pole is approximately $82.64 when factoring in theadditional steel pole cost.

Typical three-phase tangent units constructed with woodpoles with wood crossarms also require measures to makethem raptor-safe. The most economical remedy is toconstruct new wood pole units with 10-foot woodcrossarms, providing 60-inches of separation. The samethree-phase configuration on steel or reinforced concretepoles requires additional measures to provide raptorprotection and 300kV BIL. Additional constructionmethods include the use of fiberglass pole-top pinextensions, pole-top caps to exclude perching, and eitherpole-top insulating materials or covers, or perch guards.The most economical way to raptor proof steel andconcrete poles is insulating the pole top with either athermoplastic wrap or spray-on coating. These additionalmeasures add approximately $24.76 in material and laborcosts per pole. The total labor and material increasebetween a three-phase raptor-safe wood pole and a raptor-safe steel pole is approximately $94.76 when factoringin the additional steel pole cost.

The total labor and material increase between a three-phase raptor-safe wood pole (Wood Option-W2) and araptor-safe steel pole will range from approximately$94.76 to $297.47 (Steel Option-S1, Steel Option-S3)depending on the technology chosen.

For convenience this analysis was based on NESC 1997Grade B design, when in fact Grade C construction ismost common for distribution systems and the costdifferentials would be greater as larger or more steelpoles are needed to be equivalent to wood Grade Cdesign.

ReferencesAbbey, M., A. Stewart and J. Morrell. 1997. Existing

strategies for control/remediation of woodpeckerdamage. Proceedings of a workshop on themitigation of woodpecker damage to utility linessponsored by the Electric Power ResearchInstitute.

APLIC (Avian Power Line Interaction Committee). 1996.Suggested Practices for Raptor Protection onPower Lines: The State of the Art in 1996. EdisonElectric Institute/Raptor Research Foundation.Washington, D.C. 125 pp.

Benson, P.C. 1981. Large raptor electrocution and powerline utilization: a study in six western states.Ph.D. Dissertation. Brigham Young University,Provo, Utah. 98 pp.

Bevenger, K. 1994. Bird interactions with utilitystructures: collision and electrocution, causesand mitigating measures. Ibis 136:412-425.

Boeker, E.L. 1972. Power lines and bird electrocutions.Unpublished report. U.S. Fish and WildlifeService, Denver Wildlife Research Center.Denver, Colorado. 8 pp.

Dawson, J.W. and R.W. Mannan. 1995. Electrocutionas a mortality factor in an urban population ofHarris’ hawks. Journal of Raptor Research 29.55.

17


Jarvis, M. J. F. 1974. High tension power lines as ahazard to larger birds. Ostrich. 45: 262.

LaRoe, E.T., G.S. Farris, C.E. Puckett, P.D. Doran andM.J. Mac (Eds.). 1995. Our living resources: areport to the nation on the distribution,abundance and health of U.S. plants, animalsand ecosystems. U.S. Department of theInterior, National Biological Service,Washington, D.C. 530 pp.

Ledger, J.A. and H.J. Annegarn. 1981. Electrocutionhazards to the Cape vulture Gyps coprotheres inSouth Africa. Biological Conservation 20: 15-24.

Markus, M.B. 1972. Mortality of vultures causedby electrocution. Nature 238: 228.

Melcher, C. and L. R. Suazo. 1999 . RaptorElectrocutions: The Unnecessary LossesContinue. Journal of the Colorado FieldOrnithologists. 33:221-224.

Negro, J.J. and M. Ferrer. 1995. Mitigating measures toreduce electrocution of birds on power lines: acomment on Bevanger’s review. Ibis:137(3):423-424.

Nelson, M.W. and P. Nelson. 1976. Power lines andbirds of prey. Idaho Wildlife Review. 28(5): 3-7.

Nelson, M.W. 1977. Preventing electrocution deathsand the use of nesting platforms on power poles.Hawk Trust Annual Report. 8: 30-33.

Nelson, M.W. 1979a. Update on eagle protectionpractices. Unpublished report. Boise, Idaho.14 pp.

Nelson, M.W. 1979b. Power lines progress report oneagle protection research. Unpublished report.Boise, Idaho. 13 pp.

Nikolaus, G. 1984. Large numbers of birds killed byelectric power lines. Scopus 8: 42.

Ferrer, M. and H. Fernando. 1991. Evaluation ofmanagement techniques for the Spanish imperialeagle. Wildlife Society Bulletin 19: 436-442.

Ferrer, M., M. De La Riva, and J. Castroviejo. 1991.Electrocution of raptors on power lines insouthwestern Spain. Journal of FieldOrnithology 62(2): 181-190.

Graham Jr., F. 2000. The Day of the Condor. Audubon.January - February 2000. 47-53.

Harness, R.E. and M. Garrett, 1999, Effectiveness ofperch guards to prevent raptor electrocutions,Journal of the Colorado Field Ornithologists Vol.33, No. 4: 215-220.

Harness, R.E. 1998, Steel distribution poles –environmental implications. Pages D1-1 – D1-5 in Proc. of the Rural Electric PowerConference. Institute of Electrical andElectronics Engineers, New York, N.Y.

Harness, R.E. 1997, Raptor electrocutions caused byrural electric distribution power lines. M.S.thesis. Colorado State University, Fort Collins,Colorado. 110 pp.

Hass, D. 1980. Endangerment of our large birds byelectrocution – a documentation. Pages 7-57 inOkolgie der vogel. Vol. 2 Deutscher bund furVogelschutz, Stuttgart.

Herren, H. 1969. Status of the peregrine falcon inSwitzerland. Pages 231–238 in J.J.

Institute of Electrical and Electronics Engineers (IEEE)Power Engineering Society. IEEE guide foranimal deterrents for electric power supplysubstations. Institute of Electrical andElectronics Engineers, Inc., New York. 16 pp.

Janns, G.F.E. and M. Ferrer. 1999. Mitigation of raptorelectrocution on steel power poles. WildlifeSociety Bulletin, 27(2):263-273.

18


Olendorff, R.R. 1972. Eagles, sheep and power lines.Colorado Outdoors. 21: 3-11.

Olendorff, R.R., A. D. Miller, and R. N. Lehman. 1981.Suggested Practices for Raptor Protection onPower Lines: The State of the Art in 1981. Raptorresearch report no. 4, Raptor ResearchFoundation, University of Minnesota, St. Paul,Minnesota. 111 pp.

Olendorff, R.R. 1993. Eagle electrocution. InProceedings: Avian interactions with utilitystructures. International workshop. ElectricPower Research Institute, Palo Alto, California.Section 6 EPRI TR-103268 Project 3041.

Rural Utilities Service (RUS). 2000. Draft - RUSguidelines and approval for use of distributionsteel poles (Version 5). USDA, Washington D.C.6 pp.

Southern Engineering Company. 1996. Animal-causedoutages. National Rural Electric CooperativeAssociation. Arlington, Virginia. 171 pp.

Suazo, L. R. 1998. Power lines and Raptors: UsingRegulatory Influence to Prevent Electrocutions.Paper presented at Fifth World Conference onBirds of Prey and Owls. Midrand, South Africa.

United States of America v. Moon Lake ElectricalAssociation; 45 F.Supp..2d 1070 (1999).

Williams, T. 2000. Zapped! Audubon. January - February2000. 32-44.

19


© 2000 North American Wood Pole Council

DisclaimerThe North American Wood Pole Council and its members believe the information contained herein to be based on up-to-date scientific information. In furnishing this information, the NAWPC and the author make no warranty or representation, either expressed or implied, as to the reliability or accuracy of such information; nor do NAWPC and the author assume any liability resulting from use of or reliance upon the information by any party. This information should not be construed as a recommendation to violate any federal, provincial, state, or municipal law, rule or regulation, and any party using poles should review all such laws, rules, or regulations prior to doing so.

North American Wood Pole Councilwww.woodpoles.org

TB-Raptor-10-00

technical bulletin - raptor electrocutions and distribution pole types

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