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ArresterWorksArresterFacts 025What is a Deadfront and Separable ArresterUnderstanding Changesin IEEE C62.11-2020The MOV Arrester Test StandardArresterFacts 050Copyright ArresterWorks 2008-2011February 2020Jonathan WoodworthJonathan J. WoodworthPage1
ArresterFacts 050 - Understanding Changes in IEEE C62.11-2020ArresterFacts 050 - Understanding Changes in IEEE C62.11-2020IntroductionThe IEEE arrester test standard C62.11-2020 willbe published in the next few months.Thedocument is the culmination of 8 years of work bythe IEEE Surge Protective Devices Committee WG3.3.11. The working group consists of 20ishmembers that have met 2 times per year for thepast 8 years and several times per year online insmaller groups. This revised standard continuesthe trend set by the 2012 edition to rationalize thetest to contain more realistic requirements while atthe same time harmonize it with the equivalent IECstandard 60099-4. This ArresterFacts is meant tooutline the revisions in a manner that makes themmore understandable and easier to implement byall stakeholders.C62.11-2012 EditionWhen the 2012 edition of this standard waspublished, it too was after numerous years of workto update and improve the standard. The changesin the last edition are covered in ArresterFacts 040.Summary of Fundamental ChangesThe following is a summary of the fundamentalchanges in this standard from the 2012 edition.Each one of these changes are covered in moredetail in this ArresterFacts.1. Arrester AC Voltage Rating:The termArrester Rating has been obsoleted as of thepublication of this standard. This is a longoverdue change to the standard that hascaused confusion in the industry since the termMCOV was introduced in early 1980’s.2. Distribution Arrester Energy HandlingRatings: For the first time, the distributionarrester has an energy handling rating.3. Standard Altitude for normal conditions waslowered from 1800m to 1000m. This is nowharmonized with 60099-4.4. Arrester Housing Withstand Tests: This testwas significantly changed in procedure and isnow harmonized with 60099-4-2014. A fewminor differences still exist, but the tests can beexecuted in a lab using the same procedureand be certified to either standard.5. Switching Impulse Energy Rating Test (Wth):This test was modified slightly in the IEEEversion to harmonize with IEC 60099-4.6. Single-impulse Charge Transfer Rating Test(Qrs): This test previously existed in the IEEEstandard for station class arresters only. It wasmodified only slightly and is now in line with60099-4. It is also now required for distributionarresters in C62.11 as it is in 60099-4.Figure 1 Cover of C62.117. Operating Duty Test for DistributionArresters (Qth): This test was modified morethan any other test in the new C62.11 edition.Since C62.11 also covers gapped MOVarresters, the procedure was split into twoversions, one for gapped and one for nongapped arresters. The non-gapped procedureis now aligned with 60099-4-2014 and thegapped procedure is aligned with 60099-62019.8. Temporary Overvoltage Test: This test wasslightly modified and if carried out correctly, theresults can be used for either IEC or IEEEcertifications.9. Disconnector Test: This test was modifiedsignificantly to accommodate the new testsC62.11 and is also aligned with 60099-4 and60099-6
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Arrester AC Voltage RatingDistribution ClassArresterLightningImpulseClassifyingCurrent Iclass(kA)HighCurrentImpulse(kA)MinimumSingle ImpulseChargeTransfer RatingQrs CoulombsMinimumThermal EnergyWithstandRating QthCoulombsThe term arrester rating hasbeen in use since the middle oflast century. It is the only ACHeavy Duty (HD)101000.41.1(same as IEC DH)voltage rating of the lastNormal Duty (ND)5650.20.7generation of Gapped Silicon(same as IEC DM)Carbide Arresters. In the earlyLight Duty (LD)5400.10.45(same as IEC DL)1980’s when the first edition ofTable 2 Distribution Arrester Classification in IEC and IEEE Standardsthe MOV type arrester standardwas published, the term MCOVcoulombs since they are both related to the currentwas introduced. The rationale for having two ACcarrying capacity of the arrester. The coulomb isratings at that time is not clear, but the confusion itnow the primary unit of energy handling capabilityhas caused in the following years is clear. Sincefor the Distribution Arrester. It is preferred since itthe MCOV rating for the un-gapped MOV typeis not affected by the wave shape of the current orarrester is closely related to the line to groundthe discharge voltage of the arrester, (see Figurevoltage where an arrester is installed, it has1). These classifications are now identical to thebecome the preferred AC rating term by mostIEC classifications other than the name. Note thisstakeholders. The quest to eliminate the termis not kJ/kV MCOV as station arresters areRated voltage that is only related to a voltage levelsometimes classified.used in the Operating Duty Test started at least 15years ago. In the 2012 edition we eliminated theterm from the name plate of the arrester, and finallydue to lack of relevance, it is officially obsoleted inLightningSwitchingthis edition.The term MCOV (MaximumImpulseMCOVImpulseClassifyingContinuous Operating Voltage) is exactly what it is,RangeClassifyingCurrentthe maximum voltage across the terminals of the(kV RMS)CurrentIclass(A)arrester that can be applied long term. This is now(kA)the official AC rating of MOV type arrester.Station 448202000Arrester ClassificationsDistribution Arresters: The distribution arresterclassifications are again defined by the tests theyare required to pass however this type of arresternow has two Energy Handling Ratings. Table oneshows the new requirements. Both ratings are inStation246 448152000Station116 245101000Station2.55 11510500Intermediate2.55 1155500Table 2 Station Arrester Classifying CurrentsEnergyClass IEEE SH)(SH)(SH)(SH)(SH)Minimum ThermalEnergy WithstandRating (Wth)kJ/kV-MCOV34.567.591113151821242730Minimum SingleImpulseWithstandRating (Qrs)CoulombsIEC Only 1.0 1.0 1.6 1.6 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4Table 3 Station Arrester Energy RatingsFigure 2 Comparing Charge Vs WaveshapeCopyright ArresterWorks 2020Page 3
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Station Class Arresters: The stationclass arresters require two tables to definetheir classification. Table 2 shows theimpulse characteristics and Table 3defines the energy withstand ratings of thearrester. The IEC ratings are different andare also shown in Table 3. The tests toverify these ratings are nearly identical.Neither one of these tests are new in the2020 edition, however the terms Wth andQrs are new and adopted from the IECstandard.Arrester Housing Insulation WithstandTestsStation Class:Tests to quantify the housing withstandlevel for impulse and power frequencyvoltages can be traced back to the earlieststandards of the last century. Both IECand IEEE standards have sections forstation and distribution class arresters.The objective of both standards is todemonstrate that the housing of theFigure 3 Withstand Test Voltage vs Minimum Strikearrester will always withstand more voltageDistance to Waive Testthan it will ever experience in service.Because arrester housings are protectedby the clamping voltage action of the internal metaloxide disks, the arrester is said to be self-protected.Because of this unique characteristic of the arresterhousing, a special note was included in testrationale of C62.11-2020 edition that states:90%New Note in Standard: It should be noted that theimpulse withstand levels of arrester housings arenot to be compared to BIL or CFO levels ofinsulators. Due to the arrester’s self-protectingnature, the arrester housing can have a lowerwithstand voltage than the rest of the systemwithout any negative impact on the systemwithstand level.GlobalPopulationvs AltitudeAlso, for this reason arresters are used in standardapplications generally do not have standardinsulation withstand ratings.Station Class Housing Insulation WithstandTest Changes:1. For all station class voltage ratings, the standardnormal design elevation was changed from 1800meters to 1000 meters. This aligns more withother IEEE standards as well as IEC 60099-4.The rationale for this change is that most of theworlds population and power systems are locatedat altitudes 1000m and below. See Figure 4Figure 4: World Population vs Altitude2. Added is the option to waive the testing ifsufficient strike distance of the arrester design isused.Formulae are provided for lightningCopyright ArresterWorks 2020Page 4
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Comparison of New and Old IEEE-IEC Housing Withstand Test VoltagesDistributionArrestersStationArrestersPrior Comments1.42 x V@20kA8/20NA1.36 x 10 secTOV WetPower Frequency TestedWet 10 SecRMS test voltage .62 x V@ IClassPeak AC voltage .88 x V@In1 minute Withstand testNew IEEE1.3 x V@ IClassIEC1.3 x V@ In8/20Previous IEEE All1.42 x V@20kA8/20New IEEEMCOV 140kV Uc1.3 x V@ IClassNew IEEEMCOV 140kV 460 kV1.3 x V@ IClassNANANANANew IEEEMCOV 460kVIEC Uc 140kVfor Us 245kVBy AgreementIEC Uc 140kV to 460 kV,for245kV Us 800kVIEC 460kV Uc,for Us 800kV1.3 x V@LIPL1.25 x @VSwitchingImpulseClassifyingCurrentBy Agreement1.3 x V@LIPLNA1.3 x V@LIPL.82 x MaxSwitchingDischargeVoltageRMS test voltage .75 x V@ IClassPower Frequency TestedWet 1 minPower Frequency TestedWet 10 SecPower Frequency TestedWet 1 minSwitching ImpulseTested WetNANAPeak AC 1.06 xV@In 1.25 x MaxV@SIPL1.25 to 1.36 xMax V@SIPLNANAPower Frequency TestedWet 1 minSwitching ImpulseTested WetSwitching ImpulseTested WetTable 4 Comparison of Old and New Withstand Test Voltagesimpulse, switching impulse and power frequencyvoltages to make the necessary calculationsneeded for the waive assessment. This is the firsttime in C62.11 where a test can be waived if thedesign is shown to be designed significantlyabove the standard. Also, C62.11 adopted aslightly less conservative formula than IEC60099-4 for the switching surge calculation.(See Figure 3)3. The IEEE adopted the IEC method of testingarrester housings with MCOV ratings above 140kV. This new test method uses a switchingimpulse voltage instead of AC voltage to verifythe low frequency wet withstand level of thearrester. These higher rated arresters are nowtested with a lightning and a switching surgeimpulse to certify housing withstand and nottested with AC.4. For arresters with an MCOV rating less than 140kV, switching surge withstand tests are not usedand instead the familiar AC withstand test isapplied. For harmonization, the IEEE standardhad to accept a 1 min wet withstand test insteadof the 10 second wet withstand test of the past.Since arresters are over designed in this area,this was not a difficult change (see Figure 4 formore details). The specified test voltages weresimilar between the two standards, but there werea few compromises where in some cases a lessconservative value was accepted by the IEEEgroup, however in other cases the values aremore conservative. In all cases, the test voltagesrequirements are lower than the actual designlevels presently in use. Also, in all cases thespecified test voltages have safety margins builtin for a 1000 m altitude (13%) and variations inimpulse current of 10-15%.Copyright ArresterWorks 2020Page 5
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Insulation Withstand Test Changes forDistribution Class ArresterOpen Air Polymer Housed Arresters:For the distribution class arresters, the housingwithstand tests are tested the same as they werein the past, with lightning impulse discharges andpower frequency withstand tests.Even though the test methods are similar, toharmonize the standards, details in the test weremodified.1. The power frequency withstand test became a1-minute test instead of a 10 second test. Thislowered the test voltage slightly.2. The lightning impulse withstand test remainedthe same with a slight reduction in level due tothe change in normal design altitude from 1800meters down to 1000 meters.3. For the first time in IEEE arrester standards, ifthe strike distance of the arrester is longenough, the testing can be waived. The samecalculations used to predict the station classwithstand voltage based on length are used fordistribution arresters. If the calculated voltageexceeds the specified minimum withstandvoltage, then the test can be waived. In C62.11,the withstand voltage of the insulating hangeris evaluated for its power frequency withstandlevel. It must withstand a 1.5pu MCOV voltagefor 10 seconds wet, between hanger mountingpoint and the ground end of the arrester. IEC60099-4 has no equivalent test requirement.Deadfront Arresters:One area not harmonized with IEC for distributionarresters is the deadfront arrester design. The testrequirements were significantly changed in C62.11based on changes in IEEE 386.The testrequirements in 60099-4 will need to be updated tomeet these new requirements since this is basicallyan IEEE only design.Tests That Did Not ChangeDischarge-voltage Characteristics TestThis test was harmonized with IEC in the 2012edition of C62.11 and is 100% the same as IEC60099-4 with one exception. In the IEEE std, themaximum current level to test is 40 kA and is 20 kAin the IEC.Accelerated Aging Test of Metal-oxide DisksThe test procedures for this test are nearly identicalbetween C62.11 and 60099-4 however the pass-failcriteria are not exactly the same. In both cases,this test must be satisfied for disks of the samedesign to be used in the rest of the certificationprocess. If disks do not pass this test, there is norecourse other than to use disks of a differentdesign.This test was not changed in C62.11-2020.Accelerated Aging Test of Polymer-housedDistribution Arresters with Exposure to Lightand Electrical StressThis section is unique to C62.11 and has noequivalent in 60099-4. This test partially overlapswith the salt fog test, but the salt fog test does notevaluate the insulating hanger. For this reason, itneeds to be evaluated again in the next C62.11edition. Work in both standards is needed here toharmonize.Accelerated Aging Test of Polymer-housedArresters with Exposure to Salt FogThis test is harmonized with IEC 60099-4 Section10.8.17.2.There is some discussion in bothworking groups and this section may change in thenext edition of each standard.Contamination TestThis test is similar to Annex C.7.1 in IEC 60099-4.However, these two sections are not harmonized.Much work will be needed to harmonize this test.Distribution Arrester Seal Integrity Design TestThere is no equivalent test in IEC 60099-4 or60099-6. IEC needs to adopt this test in its entirety.Radio-influence Voltage (RIV) TestThis test applies to arresters with an MCOV 70 kV.The procedure and results are harmonized withIEC.Power-frequency Sparkover TestThis test applies only to gapped MOV arresters andis harmonized with IEC 60099-6.Impulse Protective Level Voltage-timeCharacteristic TestThis test applies only to Gapped MOV arrestersand is harmonized with IEC 60099-6.Copyright ArresterWorks 2020Page 6
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Switching Impulse Energy Rating Test(Wth)This test was first introduced into the IEEE withC62.11-2012. It is similar to the previously titledOperating Duty Cycle Test for Station Classarresters.This test is fully harmonized with 60099-4. Theprimary difference between C62.11-2012 and the2020 edition is the elimination of the 18preconditioning impulses. It has been agreedbased on research that the only effectivepreconditioning of metal-oxide disks comes fromhigh current impulses and not from lower currentsurges. The test is now referred to as the Wth ratingtest however the resulting energy ratings are stillthe same in the 2020 edition as they were in the2012 edition but now defined as Wth as it is in60099-4.See Figure below to compare theprocedures of past and present tests.Switching Surge Energy Rating Test (Wth)This was a newtest in 2012Renamed toHarmonize withIECSimulates aging overlife of arresterRemoved because proven not toage arresterSimulates warmestpossible environment itModified toaccommodate no RatedVoltageDemonstrates Arrestersability to recover fromsurge while energized2020 - Switching Surge Energy Rating Test WthAdded to calculate testrecovery voltagesNote this is an ArresterEnergy Withstand testthat demonstratesthermal recoverySimulates energy dissipated by arresterduring switching surgeCopyright ArresterWorks 2020Page 7
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Single-impulse Charge TransferRating Test (Qrs)This test was previously called the Single ImpulseWithstand Rating Test, for the sake ofharmonization it is now referred to as a ChargeTransfer Rating Test with the actual parameter ofimportance being Qrs.The most significant difference in this test is notthe test itself, but the fact that it is now applied toall arresters, not just station class arresters as ithad in the past. This change along with a finalhigher current impulse at the end of the testharmonized this test with IEC 60099-4 and IEC60099-6. See figure below to compare the detailsof past and future test procedures.The one difference between IEC and IEEE withthe Qrs rating, is that in the IEEE, there is nominimum for station arresters.In the IECminimum ratings are given. This may change ineither of the standards in the next cycle as moreQrs data evolves.Single Impulse Charge Transfer Rating Test (Qrs)This was a newtest in 20122012Renamed toHarmonize withIECNote this is an MOVDisk CurrentWithstand test withno demonstration ofthermal recoverySimulates the maximum singleswitching or lightning dischargecurrent the disks can withstandmultiple times without damageAdded to doublecheck disk is notdamaged2020Added to distributionarrester test sequenceCopyright ArresterWorks 2020Page 8
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Operating Duty Test for Un-GappedDistribution Arresters (Qth)The Operating Duty Test was a big change for theIEEE team if it was to harmonize with 60099-4.However, after months of discussion and theseparation of the test into gapped and nongapped procedures it happened. As of the nextedition of C62.11, we will have an improved dutycycle test that verifies the thermal charge transferrating (Qth) of distribution arresters. See below tocompare the details of the past and future testprocedures.The fundamental difference is that 20 low current(10 kA) preconditioning impulses are replacedwith a single high current impulse. This changewas accepted because it was clarified in theactivity of CIGRE WG A3.17 that the importantcondition for the verification of thermal stabilitywas the total charge and amplitude of thepreconditioning impulses rather than the numberof impulses. This work was published in CIGRETB 544-2013. Because the gapped metal-oxidearrester is not included in this test, the IEEEaccepted the removal of the preconditioningimpulses at 10 kA with rated voltage applied.Operating Duty Test for Non-Gapped Distribution Arresters Qth)2012VersionAdded to replace20 impulsesSimulates agingover life of arresterRemoved because proven not to ageMOV type arresterNote this is aDistributionArrester EnergyWithstand testthatdemonstratesthermalrecoverySimulates warmestpossible environment itRenamed toHarmonize withIECModified toaccommodate noRated Voltage2020 editionSimulates energy dissipated by arresterduring lightning surgeCopyright ArresterWorks 2020Demonstrates Arresters ability torecover from surge while energizedPage 9
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Operating Duty Test for Gapped DistributionArresters (Qth)60099-6. It is essentially the same as the Nongapped metal-oxide arrester test except it still hasthe 20 preconditioning impulses with AC voltageapplied. These preconditioning impulses verifythe durability and long term dependability of thegaps of the arrester.The Operating Duty Test for gapped metal-oxidearresters is as follows and is harmonized with IECOperating Duty Test for Gapped Distribution Arresters (Qth)2012VersionAdded to age disksinstead of the 20shotsRetained because it ages and checksgap reseal capability at max stressModified toaccommodate noRated VoltageSimulates aging over lifeof the MOV disksSimulates warmest possibleenvironment it will seeModified toaccommodate noRated VoltageRenamed toHarmonize withIEC2020 Operating duty test for gapped distribution arresters thermal charge transfer rating QthNote this is a Distribution Arrester EnergyWithstand test that demonstrates thermalrecoverySimulates energy dissipated by arresterduring lightning surgeCopyright ArresterWorks 2020Demonstrates Arrestersability to recover fromsurge while energizedPage 10
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Temporary Overvoltage (TOV) TestThe TOV test was the last of the major tests to beharmonized to IEC 60099-4. Since the testprocedures were already very similar, onlySimulates warmestpossible environment itwill seemodification to the overvoltage durations wasneeded. In the end, even though they are notidentical, the two tests can be executed so thatthey will meet both standards if that is desired.The figure below shows the details of the TOVtest procedure.Temporary Overvoltage Test2012 and 2020 Temporary Overvoltage Test (TOV)Modified toaccommodate noRated Voltage2020 Modified toharmonize withIECNote this is an ArresterOvervoltage Withstandtest that demonstratesthermal recoverySimulates energy dissipated byarrester during a switching for priorduty test on the arrester before TOVDemonstrates Arrestersability to recover fromsurge while energizedTests Removed from the 2020 EditionHigh-current Short-duration TestThis test has been in the arrester standard fordecades. It was eliminated as a separate test inthis edition and rolled into the Operating DutyTest as an means of aging the MOV material.This means of aging the MOV material wasproven in the CIGRE work that was published inTB 544-2013.Low-current Long-duration TestThis test was eliminated as a stand-alone test inthe 2020 edition. It had been in the standardsince the 1950’s but was never really justifiedsince long duration surges are not typicallypresent on distribution systems. A similar typesurge has been introduced in the Single ImpulseCharge Transfer Test for distribution arresters.Copyright ArresterWorks 2020Page 11
ArresterFacts 050Understanding Changes in IEEE C62.11-2020Arrester Disconnector Test ChangesThe test objective did not change, however sincethe High-current Short-duration test and the Lowcurrent Long-duration test were eliminated fromthe standard, the disconnector test could notinclude them. Instead the disconnector will nowbe part of the Single Impulse Charge TransferTest and the Operating Duty Test. In both ofthese tests, they must endure the test withoutoperation.The disconnectors will continue to be tested forproper operation during fault current tests of 20800 amps.Closing ThoughtsC62.11-2020 will publish this year, and the nextrevision of the standard will also start this year.Working Group 3.3.11 is titled continuous revisionof C62.11 and that is how we operate. There areseveral minor tests that still need updating andharmonizing, they are on our hit list.ArresterFacts are a compilation of facts aboutarresters to assist all stakeholders in theapplication and understanding of arresters. AllArresterFacts assume a base knowledge of surgeprotection of power systems; however, we alwayswelcome the opportunity to assist a student inobtaining their goal, so please call if you have anyquestions. Visit our library of ArresterFacts formore reading on topics of interest to thoseinvolved in the protection of power system atwww.arresterworks.com.About the author:Jonathan started his career afterreceiving his Bachelor's degreein Electronic Engineering fromTheOhioInstituteofTechnology, at Fermi NationalAcceleratorLaboratoryinBatavia, IL. As an EngineeringPhysicist at Fermi Lab, he wasan integral member of the high energy particlephysics team in search of the elusive quark.Wishing to return to his home state, he joined thedesign engineering team at McGraw Edison (laterCooper Power Systems) in Olean, New York.During his tenure at Cooper, he was involved inthe design, development, and manufacturing ofarresters. He served as Engineering Manager aswell as Arrester Marketing Manager during thattime. Jonathan has been active for the last 30years in the IEEE and IEC standard associations.Jonathan is inventor/co-inventor on five USpatents. Jonathan received his MBA from St.Bonaventure @arresterworks.com 1.716.307.2431Copyright ArresterWorks 2020Page 12
ArresterFacts 050 Understanding Changes in IEEE C62.11- -2020 ArresterFacts 050 - Understanding Changes in IEEE C62.11-2020 Introduction The IEEE arrester test standard C62.11-2020 will be published in the next few months. The document is the culmination of 8 years of work by the IE
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