EU1416-H

■ INSULATION ANDPROTECTION

■ DESIGN TESTS■ BENEFITS■ ARRESTERS REDUCE

OUTAGES■ COMMON QUESTIONS■ DATA SHEET

®®

POWER SYSTEMS, INC.

Protecta*Lite® Systems

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Protecta*Lite® SystemsIn This IssueProtecta*Lite: A Complete Insulation And Protection System

Arrester & Insulator Design Tests

Protecta*Lite Benefits

Hanging Protecta*Lite Arresters Reduce Outages On 115 kV Line

Common Questions About Protecta*Lite

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pages 12-15

page 10

pages 6-9

pages 3-5

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POWER SYSTEMS, INC.

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Protecta*Lite: A Complete InsulationAnd Protection System

In 1988, Ohio Brass introducedProtecta*Lite® Systems.Protecta*Lite is a blending oftwo proven technologies: Hi*Litepolymer insulators and polymer-housed DynaVar metal-oxide arresters.Protecta*Lite eliminates many of thedisadvantages of conventional lineprotection using either porcelain-housed surge arresters or overheadshield wire.

The Protecta*Lite arrester reducesinterruptions caused by lightning andcan be applied as a supplement or as analternative to overhead shield wire.This product is suitable for use ontransmission and distribution systemsranging from 4,160 volts through230,000 volts.

Protecta*Lite consists of polymer-housed surge arresters selectivelyplaced in parallel with insulators ondistribution or transmission lines.These arresters limit the voltageoccurring across the insulator to a levelbelow the flashover voltage.Protecta*Lite units properly applied onvarious T & D structures will achieve aline lightning interruption rate as goodor better than that obtained withproperly designed overhead shieldwires. The Protecta*Lite assembly canbe applied in areas with poor towerfooting resistance and still obtainexcellent lightning performance.

This product is suitable for new lineconstruction or for existing structures.The Protecta*Lite assembly isavailable in a variety of designs andcan be applied horizontally orvertically, on struts, suspension or onpoletop insulators. This line protectionsystem provides many design choices,including single phase or three phaseapplications and can be applied onvirtually any type of structureconfiguration.

Protecta*Lite solves problems regarding lightning related complaints. Unshielded lineperformance can be improved to a level equal to or better than the reliability of aproperly installed line with an OHSW. Protecta*Lite can be used to solve designproblems where it is impractical or too costly to add height to a structure for theaddition of an OHSW. (Photo: 138 kV Proteca*Lite)

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of phase to phase faults on compactedphase spacing.

Line uprating: Increased phaseconductor clearances required forvoltage uprating can be obtainedwithout major structure modificationsby elimination of shield wires and thereplacement of porcelain insulatorswith lightweight polymer insulators.Protecta*Lite can provide primarysystem insulation, as well as improvedreliability, low installed cost and anattractive installation in aestheticallysensitive areas.

Improve outage performance:The Protecta*Lite system will improvethe outage performance of existingshielded and unshielded lines. This isaccomplished by greatly reducing thefrequency of line insulation flashoverdue to shielding failure and backflash.Protecta*Lite assemblies improvecoupling factors and compensate forhigh ground (tower footing) resistance,which is often the cause of backflashon lines protected with overhead shieldwires. Units are providing excellentservice in many locations in the UnitedStates.

Design FeaturesThe Protecta*Lite design possesses

high fault current withstand andresistance to contamination flashover.

In the unlikely event the arresterfails, it is automatically disconnectedfrom the power system in a safe,controlled manner to prevent linelockout. There is clear visual evidenceof arrester failure which allows rapididentification for replacement on anon-emergency basis.

Full system insulation is maintainedunder all normal and abnormal systemoperating conditions. The arrester hasno internal atmosphere therebypreventing moisture ingress which isresponsible for 98 percent of allconventional porcelain arresterfailures.

ApplicationsThe applications for Protecta*Lite

on new and existing constructioninclude:

Line compaction: TheProtecta*Lite allows for maximumreduction in the width and height oftransmission lines by elimination ofoverhead shield wires and prevention

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Unbalanced insulation: Thistechnique is often used in doublecircuit construction to create asacrificial circuit in exposed locations.Lightning induced flashover of thecircuit with less insulation usuallyprotects the parallel circuit, which isnormally the more critical of the twoand the more heavily insulated.Protecta*Lite eliminates the need for asacrificial circuit and can restore suchcircuits to full service.

General: There are many otherlocal or general applications whereProtecta*Lite will be of benefit. Theseinclude very high structures with longspans (river crossings, for example)and other terrain which make shieldwires impractical or impossible.

Many circuits were built withoutshield wires because the expense wasnot justified or perhaps the circuitswere not considered to be critical at thetime of construction. In such cases itmay be impractical to retrofit shieldwires but Protecta*Lite can easily beinstalled to provide lightningprotection.

Another consideration in retrofit isthat overhead shield wires mustgenerally be installed over the entireline to be effective. This requires alengthy line outage. The same benefitscan be obtained immediately withProtecta*Lite through selective, stagedapplications without a lengthy outage.

DefinitionsIt is important to be familiar with

some terms necessary in the discussionof lightning performance and lineprotection.

Backflash — occurs when lightningstrikes a grounded tower or overheadshield wire. The lightning discharge

current, flowing through the towerimpedance and tower footingresistance, produces a dischargevoltage which appears across the lineinsulation. Backflash is most prevalentwhen tower footing resistance is high.

Shielding failure — occurs whenlightning strikes a phase conductor of aline protected by overhead shield wiresor by natural shielding.

Shield angle — is the includedangle between a shield wire and phaseconductor (or one protected phaseconductor to an unprotected phaseconductor).

Shadow angle — is the protectiveshadow of a transmission line cast onthe surface of the earth below.Normally any lightning stroke withinthis shadow terminates on thetransmission line. This angle isassumed to be 631⁄2 degrees on eitherside of the line and results in a shadowwidth that is four times the elevation ofthe highest conductor.

Isokeraunic level — is the numberof annual thunderstorm days for agiven region. The value is obtainedfrom a contour isokeraunic map whichis published periodically by the U.S.Weather Bureau. Isokeraunic levelsrange from five along the Pacific coastto 100 in Florida. It does not define theactual thunderstorm activity nor aprecise number of annual thunderstorms.More accurate data on lightningdensity, and other lightning flashcharacteristics, are available fromgeographical lightning detectionnetworks.1

Traveling wave — occurs whenlightning strikes a transmission linespan and a high current surge isinjected onto the struck conductor. Theimpulse voltage and current wavesdivide and propagate in both directions

from the stroke terminal withmagnitudes determined by the strokecurrent and line surge impedance at avelocity of 984 feet per microsecond.

Coupling factor — is the ratio ofinduced surge voltage on a parallelconductor to that on a struckconductor. This factor is determinedfrom the geometric relationshipsbetween phase and ground (orprotected phase) conductors. A valueoften used for estimation purposes is0.25. The coupling factor, with coronaconsidered, is calculated by theequation:

C = log b/alog 2h/r

Where: C = coupling factorb = distance from phase

conductor to image ofground

a = distance from phaseconductor to groundwire

h = height of ground wirer = radius of ground wire

Tower footing resistance —includes total resistance of the towerand the tower to ground. This value isdependent upon soil resistivity and canbe improved by driven ground rods orcounterpoise.

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Choices to be MadeOhio Brass will help you study your

line protection problems and willrecommend one or more possiblesolutions for your consideration. Somedecisions will need to be made, such asdetermining the desired level oflightning performance and the bestmethods of achieving that objective.

Lightning PerformanceEvaluation

It is important to remember thatlightning strokes to power lines arestatistical events.

Procedures for estimating thelightning performance of lines and forselection and application of lineprotection are discussed in manypapers, handbooks and otherpublications on the subject. Theseprocedures all involve the followingsteps:1. Determine the number of lightning

strokes to the earth in the vicinityof the line (isokeraunic level ormeasured cloud to ground flashdensity).

2. Calculate the percentage of thesestrokes that are intercepted by theline (shadow angle).

3. Determine the proportionatenumbers that strike at midspan,quarterspan and support structures.

4. Compute the number of strokesthat are likely to cause insulatorflashover.

5. If the line is currently in service,examine the historical operatingperformance.

6. Select a protection scheme thatwill most economically achievethe desired level of performance.

REFERENCE1. “Lightning Flash Characteristics:1986” EPRI EL-5667, Research Project2431-1, Interim Report, February, 1988.

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A Protecta*Lite assemblyconsists of the polymer-housed MOV surge arresterin parallel with any of the Ohio Brassinsulators — Hi*Lite line posts, stationposts or suspensions. With the appro-priate hardware for mechanical andelectrical connection, the Protecta*Liteis used for new construction, linecompaction and other applications.

Protecta*Lite surge arresters areinstalled electrically in parallel withcoordinated transmission and distribu-tion insulators at the line supportstructures. In many retrofit applicationsthe arresters can be used with theexisting porcelain or polymer insula-tors.

ANSI C29.11 (“American NationalStandard For Tests To CompositeSuspension Insulators For OverheadTransmission Lines”) defines the teststo be performed and the acceptancecriteria for tests to composite suspen-sion insulators.

The Hi*Lite suspension insulatorsused in Protecta*Lite assemblies meetall requirements of ANSI C29.11 aswell as the corresponding IEC 1109.

In the absence of ANSI standardsfor composite post insulators, Hi*Litepost insulators meet the applicableelectrical, mechanical and dimensionalrequirements of ANSI C29.1 (“TestMethods for Electrical Power Insula-tors”), ANSI C29.7 (Line Posts) andANSI C29.9 (Station Posts).

The structural member in bothsuspension and post insulators is afiberglass rod of extremely highmechanical and dielectric strength. Theweathersheds are injection-moldedfrom proprietary ESP rubber alloyed toresist the oxidation, aging and degrada-tion typically associated with anenergized environment.

Arrester And Insulator Design TestsProtecta*Lite® Insulation Designs

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The hardware end fittings of allHi*Lite insulators are directly swagedto the rod with a proprietary process. Aresilient silicone dielectric compoundinterface between the fiberglass rodand protective weathersheds is an

integral part of the Hi*Lite andProtecta*Lite designs for transmissionvoltages.

In addition to the design, conform-ance, and routine tests required orrecognized by industry and utility

standards, Hi*Lite insulators and theircomponents have been subjected to avariety of special electrical, mechani-cal, thermal, contamination andweathering tests.

Test reports are available.

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Evolution and Test of Protecta*Lite Arresters

Electric utilities have appliedsurge arresters on trans-mission systems for manydecades. From the early 1930s to thelate 50s, expulsion or protector tubeswere used in new line constructioninstead of overhead shield wire.Experience with these early vintagearresters resulted in good line perfor-mance; however, excessive mainte-nance costs and limited life of thesearresters eventually led to theirobsolescence.

After the discontinuance of theseearly arrester designs, some utilitiesresorted to placing porcelain-housedintermediate or station class surgearresters on critical transmissionstructures. One of the primary designrequirements in this application wasthe ability to vent excessive pressuresgenerated during an arrester failure.The successful venting of thesepressures eliminates or decreases thepossibility of having an arresterexplode in close proximity to aninsulator or other equipment.

With the advent of the polymerarrester first introduced by Ohio Brassin 1986, pressure relief was achievedin an arrester at a fraction of the costtypically associated with an intermedi-ate or station class arrester. The abilityto obtain this pressure relief feature ata low cost, along with the excellentprotective characteristics associatedwith MOV arresters, and adisconnector to prevent lockout, hasallowed the polymer design to beinstalled economically on transmissionsystems.

The ESP rubber-housed arresterwith epoxy/fiberglass-wrapped MOVdisc modules eliminates the majorhazard of an arrester failure by not

having a porcelain housing to explodeif a power arc is established within thearrester. Moisture ingress is the majorcause of conventional porcelainarrester failures. The ESP polymer-housed arrester has virtually nointernal atmosphere and thus theproblem of moisture ingress is elimi-nated. This technology has beenexpanded from distribution voltagelevels to transmission voltages. Thepolymer arrester design is proven withits years of success.

Full Scale Fault Current TestsA series of full voltage tests was

conducted in accordance with Section8.10 of ANSI/IEEE C62.11-1987 todetermine the failure modes of thepolymer arresters. The 8.4 kV MCOVProtecta*Lite specimens were as-sembled with fine fuse wire shuntingthe blocks before assembly within themodule. As described by the standard,this technique simulates the result ofarrester failure by internal dielectricbreakdown.

Fault currents of 500 to 20,000amperes RMS symmetrical fordurations of 10 to 120 cycles wereused in the Protecta*Lite arresterstudies. Successful performance wasdemonstrated when the epoxy/fiberglass-wrapped modules eitherruptured or burned through to relieveinternal pressure. The polymerhousings then split open to relievepressure. At high fault currents, thehousing may become detached fromthe MOV module. Since Protecta*Litearresters are assembled by usingmodular construction, the test resultsare valid for all arrester voltage ratings.

The test sequence was recorded byultra high-speed movies and still

A three-unit Protecta*Lite surgearrester with its polymer-housedepoxy/fiberglass wrapped metal-oxide disc modules ruptured torelieve internal pressure generatedby a fault current arc of 10,000 ampsfor 10 cycles. Note the polymerhousing has been split open, but thehousing remains attached.

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photographs of the before and aftercondition of the arresters. Additionaltests were performed on 42 kV MOVarresters in accordance with theprocedures outlined in Section 3.9 ofANSI/IEEE CC2.11.

Note: If you would like a complete design test report on the Protecta*Litearrester, please contact your Ohio Brass representative.

Test

High CurrentShort Duration

Low CurrentLong Duration

Duty Cycle

Protecta*Lite

2 -100 kADischarges

20 - 250A x 2000μsec Discharges

20 - 10 kAplus

2 - 40 kADischarges

The above is merely a summary of a portion of the design tests performed onProtecta*Lite arresters. Contact your Ohio Brass representative for completetest reports on these two arresters.

Protecta*Lite ArresterDesign Test Report Summary

Protecta*Lite arresters have been tested in accordance with ANSI StandardC62.11-1987 for metal-oxide surge arresters.

The table below summarizes the capabilities of these designs.

Protecta*Lite ArresterFault Current Withstand Ratings

Current Magnitude(Amps-Sym rms)

5002,5005,00010,00020,000

Test Duration(Cycles)

12060301010

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Protecta*Lite® Benefits

Note: When installed on top phase only,“shielding failures” are still possible. Thechance of this occurring are the same aswhat could be expected from an OHSW.Also, “backflash” is still possible in thisconfiguration if grounding is notadequate. Neither of these shortcomingsis a consideration if Protecta*Lite isinstalled on all three phases.

Protecta*Lite Benefits:■ Eliminates or substantially reduces

breaker operations resulting in lessmaintenance and improved servicereliability.

■ Equivalent performance to anoverhead shield wire can beobtained by using an arrester onthe top phase only. Like shieldwire, success is dependent on agood ground.

■ Performance superior to anOHSW can be obtained by usingarresters on all three phases.Unlike shield wire, success is notlimited by the requirement for agood ground.

■ When Protecta*Lite is installed onall three phases, shielding failuresand backflash problems arevirtually eliminated.

■ Easy to install on either new orexisting structures.

■ Installation can be accomplishedon an “as needed” basis. It maynot be necessary to include theseas a “budget item”.

■ May be installed in “troublezones” only.

■ Can be installed on lines with anOHSW to eliminate backflashproblems caused by poor ground-ing. In many cases this is lessexpensive than improving groundswhich may average $1,500 to$2,000 per structure.

■ Electrical losses are minimal.■ Polymer material has a life

expectancy in excess of 50 years.■ Hi*Lite insulators, commercially

available since 1976, have provenpolymer durability.

■ Metal-oxide varistor technologyhas existed since 1976. The lifeexpectancy of MOV blocks farexceeds the expected life of anytransmission line.

■ The concept of placing arresterson transmission lines is not new.Expulsion tubes have successfullyprotected transmission lines fordecades. The design shortcomingsassociated with expulsion tubeshave been overcome.

■ The Protecta*Lite arrester has anunlimited discharge life.

■ The polymer arrester has beenavailable since 1986 with anelectrical failure rate less than .002percent in environments with themost severe lightning duty.

■ The Protecta*Lite arrester canpass 100,000 amp discharges andremain in service.

■ The Protecta*Lite arrester has a“no lockout” feature.

■ Upgrading transmission lines isfacilitated with Protecta*Lite bythe ability to use existing struc-tures, right-of-way, and in someinstances the same insulators.

■ Protecta*Lite arresters offer aclean appearance and are moreaesthetically appealing than ataller structure with an OHSW.

■ Protecta*Lite arrester is availablein combination with an insulatorfor new construction or without aninsulator for retrofit applications.

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damage.The arresters chosen were

Protecta*Lite metal-oxide arresters,supplied by Ohio Brass. Thesearresters are of modular, lightweightconstruction and are hung below theinsulators, with the energized endattached to a suspension clampinstalled upside down over the conduc-tor armor rod. The ground end of thearresters is connected to the tower legwith No. 2 AWG copper leads. Thismethod of installation has the addi-tional benefit that failed units are easier

Excessive outages on a 115kV line crossing a moun-tainous terrain in thenortheast corner of Georgia wereapparently caused not by shieldingfailure but by backflash. A helicoptersurvey using gyrostabilized binocularsshowed that the lightning-induceddamage was occurring all along theline and was not limited to themountaintops.

Nick Bledsoe, PE, division trans-mission engineer at Georgia Power Co.explains that, when lightning strikesthe overhead groundwire or a groundedtower, the discharge current flowingthrough the tower impedance and thefooting resistance produces a voltagedrop that appears across the lineinsulator. If this voltage exceeds theinsulator impulse withstand voltage, aflashover from the tower to theconductor results. The 60-Hz follow-through may cause a phase-to-groundfault and service interruption.

Backflash occurs most often whenfooting resistance is high and unfortu-nately, low footing resistance isdifficult to achieve in Georgia’smountainous areas. In 1986, the linesuffered the unacceptable number of16 interruptions.

The solution selected by GeorgiaPower was to place metal-oxidearresters in parallel with selected lineinsulators. Total cost and tower designsmade it impossible to locate arresterson every phase of every structure, sothe devices were spread out, with theproviso that there was at least onearrester on every third structure.

Wherever possible, structures thatallowed arresters on all three phaseswere protected, as well as structuresthat exhibited obvious lightning

to spot.The arresters are rated at 100 kV

with a maximum continuous operatingvoltage of 88 kV and 100,000-ampsurge current capability. With a20,000-amp surge current, the dis-charge voltage generated is 398 kV,well below the impulse flashover of aseven-insulator string.

John Reason, Senior EditorReprinted with permissionElectrical World MagazineApril, 1989

Hanging Protecta*Lite ArrestersReduces Outages On 115 kV Line

Protecta*Lite arresters, which weigh only 35 lbs., are installed below line insulators.

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Common Questions AboutProtecta*Lite® Systems

insulators will flashover. When thisoccurs, a power-arc will be establishedaround the insulator and it is mostprobable that an arc will persist until abreaker or recloser operates.

If the line is protected with a wellgrounded overhead shield wire, thelightning surge will successfully bedischarged to ground without flashing-over the insulators.

If the line is protected with a poorlygrounded shield wire, backflash mayoccur on the phases with the lowestcoupling factors.

What methods are available toimprove lightning performance?

■ Installing a well groundedoverhead shield wire with an adequateshield angle. This option is compara-tively expensive to install and at somevoltages, operating losses are high.Also, some utilities comment thatshield wire needs replacement every 20to 25 years as a result of corrosion.Shield wires are known to fail me-chanically which can result in sus-tained outages on transmission lines.

■ Improving grounds on trans-mission lines protected with anoverhead shield wire. This can beexpensive ($1,500 to $2,000 perstructure) and may need to be donerepeatedly over the life of the line.

■ Adding extra insulation. This isgenerally not cost effective. On anunprotected line, increasing BIL levelsfrom 100 kV to 700 kV (700 percentincrease) will only decrease theprobability of flashover from 98percent to 86 percent.

■ Adding expulsion or protectortubes. While these have been discon-tinued by manufacturers, these oldstyle arresters have provided goodperformance for many utilities from1930 through present day.

Do utilities have anylines which experiencepoor performance?Nearly every utility has some

critical line(s) or customer(s) whichrequire uninterrupted or improvedservice. According to an IEEE paneldiscussion, lightning causes 40 percentof customer outages nationally and isresponsible for 50 percent of allcustomer complaints.

What are the applications forProtecta* Lite?

■ New Lines ■ Rebuild■ Upgrade projects■ Unshielded Lines ■ Backflash

What is the mean lightning strokecurrent?

The mean lightning stroke currentmagnitude is 35 KA for negativepolarity according to an EPRI study.Negative polarity strokes account for81 percent of all lightning strokes toearth. The remaining strokes (19percent) are positive polarity with amean current magnitude of 55 KA.Positive polarity strokes are mostprevalent in the winter months andtravel a greater distance through airthan the negative strokes. This isbecause positive charges are generallylocated at the top of clouds and agreater potential exists at the time ofthe lightning stroke. Cold (sub-freezing) temperatures tend to result ina greater tendency to form positivestrokes.

What happens when a transmis-sion or distribution line is struckby lightning?

If the line is unprotected, there is an80 to 99 percent chance that the

■ Adding Protecta*Lite arresters.This is an economical, proven methodto increase line performance on allinstallations. These state-of-the-artarresters are capable of successfullydischarging 100 KA lightning strokesand remain operative. They have a lifeexpectancy well in excess of thetypical transmission line and theirdesign has overcome the shortcomingsof the old expulsion tube type arresters.Operating costs are minimal andinstallation is simple and quick.Protecta*Lite installation and materialscost 50 to 75 percent less than the costof installing overhead shield wire on anexisting 69 kV line.

What is backflash?This event is the insulator flashing-

over on phase conductors which have alow coupling factor. Backflash isgenerally the cause of interruptions onshielded lines experiencing a largenumber of tripouts. Backflash is mostprevalent in areas where poor ground-ing exists and thus, lightning inducedvoltages on structures are highest. Thephases with the lowest coupling factorshave the highest voltage stress acrossthe insulators during a lightning

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discharge. Backflash can occur onlines protected with an overhead shieldwire or on lines protected withProtecta*Lite arresters installed on thetop phase only. The success of both ofthese protective schemes is dependenton a good ground. If Protecta*Litearresters are installed on all threephases, backflash problems due topoor grounding can be eliminated.

What is the probability ofbackflash?

The probability of backflash can becalculated from system parameters,line geometry, and statistical lightningdata. Simplifications in the backflashanalysis can be made by calculatingthe individual phase coupling factors,measuring the structure ground,evaluating the probabilities forlightning strokes of various currentmagnitudes, and then applying Ohm’slaw. The voltage stress across thevarious insulators can then be evalu-ated. In general, the better the ground,the lower the probability of backflashoccurring. Protecta*Lite can be used toeffectively improve the couplingfactors, thus reducing the probabilityof backflash.

What is the performance ofProtecta*Lite vs. OHSW?

Protecta*Lite arresters, properlyinstalled and grounded on a top phaseonly protection scheme, will performas well or better than a line protectedwith a properly installed overheadshield wire. Protecta*Lite arrestersinstalled on all three phases willperform better than a line protectedwith an overhead shield wire sincebackflash potential and shieldingfailure are eliminated.

What is the effect of groundresistance?

Ground resistance is a significantcontributing factor to the voltagepotential induced on a structure duringa lightning strokes. This is simply anapplication of Ohm’s law. For a givenstroke current, the higher the resistivepath to ground, the greater the im-pressed voltage.

What is the energy loss ofProtecta*Lite vs OHSW?

Protecta*Lite arresters have a verylow energy loss of 2.5 watts perarrester for 138 kV applications. Shieldwire has an energy loss which maycost a utility thousands of dollars peryear per mile for an equivalentapplication. Shield wire losses aredependent on line current magnitude,

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instead of the overhead shield wire or atop phase protected with a Protecta*Litearrester. The probability of shieldingfailure can be estimated using methodsdescribed in the EPRI, “TransmissionLine Reference Book.” The samecalculations used to calculate theperformance of a line with OHSW canbe used to estimate top phase onlyarrester protection. It should be notedthat when arresters are applied to allthree phases, shielding failures areeliminated since all phases cansuccessfully discharge lightning toground without flashing over theinsulators.

Does structure impedance contrib-ute to the success ofProtecta*Lite?

Yes, wood crossarms, structures,and any other impedance can add tothe insulating characteristics andimpulse strength of the insulatorsapplied on the structure. These sameresistances can also detract from theoverall success of a top phase onlyarrester application or OHSW applica-tion if these members add impedanceto the successful discharge of alightning stroke to ground.

What is the effect of eliminatingthe static wire as a neutral?

If the neutral is used for communi-cation, there are some drawbacks.Most utilities use other methods forcommunicating.

According to several experts, theelimination of the neutral will notaffect most relaying schemes. Thosewhich do rely on the neutral forrelaying can easily be modified to

line configuration, voltage, energyproduction cost, grounding, and otherfactors. As ground resistance islowered (improving the shieldingperformance of OHSW), the lossesalso rise since power loss is equal toI2R. As ground resistance is decreased,a corresponding increase in shield wirecurrent occurs and its contribution toenergy loss is to the second power.

Should we install Protecta*Lite onone phase or all three phases?

This answer depends on individualapplications and design parameters. Inmany cases it is more economical toinstall arresters on all three phases asthe arresters can be spaced further

apart and footing resistance is lesscritical. The increased spacing leads toreduced labor costs. In other cases, it ismore economical to space arrestersevery other or every third structure, onthe top phase only, if good groundsexist at all structures. If backflash is aproblem on shielded lines, it isgenerally most economical andeffective to place Protecta*Litearresters on the lower phases only.

What is the probability of shield-ing failure? Do the same rulesapply for Protecta*Lite as thosewhich apply to OHSW?

Shielding failure occurs whenlightning strikes a phase conductor

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accommodate Protecta*Lite. Modernrelaying schemes typically are capableof sensing ground faults in manydifferent ways.

What is the effect of theProtecta*Lite® System on substa-tion equipment and insulation?

Protecta*Lite will lessen the dutyseen by substation equipment througha reduction in breaker operations,switching surges, and transients thesubstation must withstand. Many oldersubstations have aged equipmentwhich can benefit from reducedoperations caused by events occurringon the transmission line.

What is the effect of Protecta*Liteon current relaying schemes?

Very few lightning strokes have aduration in excess of 1,000 microsec-onds. A “fast” relaying scheme willreact in two cycles, or 33,333 micro-seconds. Thus we see that the actualevent of discharging a long surgethrough an arrester is an insignificantamount of time when consideringrelaying.

How many arresters should weplace per structure?

The function of Protecta*Litedepends on the degree of performanceyou require and the application.Factors which affect these values arelisted in the Data Sheet enclosed. Ageneral rule of thumb, however, is touse 12 to 15 arresters per mile.

What is the experience of utilitiesusing Protecta*Lite?

Every utility which has installedProtecta*Lite arresters has had afavorable experience. Many of thesesame utilities are purchasing hundredor thousands of additional units toinstall on other transmission anddistribution lines. Utility engineers areexcited about how successful thisproduct is and how it is solving manyof their quality power operatingproblems cost effectively.

What is the probability of perfor-mance of Protecta*Lite?

If properly applied, Protecta*Litecan be used to eliminate practically alllightning induced interruptions.Predicting probabilities is somewhatinvolved, yet given the parameters setforth in the Data Sheet, we can preparea recommendation and estimate theprobable performance.

Quality Productsfor over 100 years

Ohio Brass manufactures a complete line of transmission anddistribution arresters and insulators. Over six million PDV arresters protect

distribution lines and over 6,000 miles of transmission line have beenbuilt with Hi*Lite® insulators worldwide.

Polymer-Housed Arresters• PDV-65 for normal duty• PDV-100 for heavy duty• PVR for riser pole• PVI for intermediate class• PVN for station class

Polymer Insulators• Hi*Lite suspension, line posts,

station posts and braced linepost assemblies for transmission

• Veri*Lite™ distributioninsulators

• Protecta*Lite™ arrester andinsulator combination for lineswith lightning interruptionproblems

573-682-5521 Fax 573-682-8714 http://www.hubbellpowersystems.com

NOTE: Because Hubbell has a policy of continuous product improvement, we reserve the right to change design and specifications without notice.

Bulletin EU1416-H

®

POWER SYSTEMS, INC.

UNITED STATES • 210 N. Allen • Centralia, Mo 65240 • Phone: 573-682-5521 • Fax: 573-682-8714 • e-mail: hpsliterature@hps.hubbell.comCANADA • 870 Brock Road South • Pickering, Ontario L1W 1Z8 • Phone: 905-839-1138 • Fax: 905-831-6353 • e-mail: infohps@hubbellonline.comMEXICO • Av. Coyoacan No. 1051 • Col. Del Valle • 03100 Mexico, D.F. • Phone: 52-55-9151-9999 • Fax: 52-55-9151-9988 • e-mail: vtasdf@hubbell.com.mx

573-682-5521 Fax 573-682-8714 http://www.hubbellpowersystems.com

©Copyright 2005 Hubbell Power Systems

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