BasicGroundingSafetygrounding

LightningprotectionGroundloops

ReasonsforthisPresentation• Safety• ProtectionoftheequipmentfoundinatypicalHAMshack.• DuringthisresearchIhavefoundthat:

– Grounding/lightningprotectionisarelativelycomplexsubject.– Thereisasignificantlevelofmiss-informationand/ormultiplicityof

opinion.– Theaveragehamcannotusuallyimplementanidealgroundsystem.– Practicalsystemswillbesomethingofacompromisebasedonhome

layoutandavailableresources(cost,time,etc).– Therearesomekeythingsthatcanbedonetohelpoptimizea

practicalsystem.

Motivation(continued)• Thispresentationstrivesto:– Provideinformationonlightningandappreciationforthedifficultyoflightningprotection.

– Summarizethekeyfeaturesandprinciplesofaneffectivelightningprotectiongroundsystem.

– Helpothersachieveandeffectivesystemfortheirparticularlayoutandresource.

– Themainreasonforthispresentationistoincreaseawareness!

• Disclaimer – Youareresponsible fordeterminingwhatyouinstalloruseforgrounding!NotinformationyougetfromawellintentionedpresentationJ

Code• Followyourlocal/statecodes.• Whichcodetofollow:– NEC (NationalElectricalCode)– NFPA(NationalFireProtectionAssociation)– NEMA(NationalElectricalManufacturesAssoc.)– NEIS(NationalElectricalInstallationStandards)– NESC(NationalElectricSafetyCode)…

• Therearemanystandardsorganizationsacrossthecountrybutyoushouldalwaysfollowthecodethatyourareahasadopted.

Section1SafetyGrounding

Groundwires

GroundRodBasics(Servicepanel)• Secondgroundrod. Asinglegroundrodthathasaresistancetogroundof25ohmsorlessmustbeaugmentedbyasecondgroundrod.Oncethesecondgroundrodisinstalled,it'snotnecessaryforthetwotomeettheresistancerequirement.Asapracticalmatter,fewelectriciansdotheresistancemeasurement.

• Youcannotuseasimpleohmmetertotestthisbecausethatwouldrequireaknownperfectground.Specialequipmentandproceduresareneeded.– It'scommonpracticetosimplydriveasecondgroundrod.– Youmustlocatethematleast8ormorefeetapart.Greaterdistanceisevenbetter.

• Groundresistancewillbefurtherdiminishedifbothrodsandthebaregroundelectrodeconductoraredirectlyunderthedriplineoftheroof(bad).

Groundrodbasics(continued)• Duringcurrentsurgetheeartharoundthegroundrodbecomes“saturated”loweringit’sresistivity(duetolocalizedundergroundarcing).

• Optimalrodplacement/spacingisaboutequalto2rodlengths,thusavoidingoverlapofactiveearthvolumes.

CommonGroundRods

Whydoyouneedgroundrods?

Section2– LightningProtection

SourceofLightning• OriginatesfromchargedCumulonimbusclouds.• Typicallyinvolveselectronmovementfromcloudtoearth

(althoughpositivelightningcanoccuroccasionally).• Cloudtocloudlightningisthemostfrequent.• Intenseelectricfieldcreatesionizationchannels(plasma)in

randomsequentialsteps.• Largecurrentdischargesoccursinseveralrepetitivestrokes.

Lightningstatistics• AverageUSyearlylightningstrikes– 22million.• NumberofyearlyUSinsuranceclaimsfiledforlightningdamage– 307,000.• EstimatedyearlyUSlightningdamagecosts- $330milliondollars.• Lightningionizationchanneltemperature– 15,000to30,000deg.C(about3timesthesurfacetemperatureofthesun).• Averagepeakcurrent– 25,000Amps.• Averagestrokesperflash– 4.• Averagechannelblastwaveenergy– Equivalentto200poundsofTNT.

MechanismsofLightningInvasionNumberedbyCommonality

• Directstrikesondwellingisrare.• Conductionthroughutilitiessystemstrikesarecommon.• Localstrikesgenerateelectromagneticfieldsthatcoupleto

electrical/signallines.• Themainphysicalcouplingmechanismsare:

• Conduction• CapacitiveCoupling• MagneticCoupling

Whyshouldweprotectagainstlightning?DamageCausedbyLightning

MoreLightningDamage

MoreLightningDamage

Evenbreakersarenotsafefromlightning

BasicHAMShack

• Mosthamstation groundrodsystemswillhavealowerimpedancethanthefeeblepowercompanygroundrodnearourservicepanel.

• Lightningtransientonpowerlinewillseekoutthebestgroundpath

• Panel/strap/rodsystemwithnobondingallowsthepathtogothroughourhamequipment– thisisverydangerous

SimplisticGroundingFacts

Towergrounding• Thegreenareaiswhere

mostlightningcurrentpasses.

• Thebondingshouldbewideflashingusingeitherhightemperaturesilversolderorcadweldingtothegroundrods.

• Groundingdoesnotpreventlightningstrikes.Itreducesthechanceofthecableshieldsandcontrolwiresfrombeingthesolepathfromalightningstrike.

Basictowerground

• Inthisdiagramthereisonegroundrodpertowerleg.

• Eachlegistiedtoitsownrod.

• Allrodsarebondedtogether.

Tower– ShackGround

Thisslideshowsmanypointswhereyoushouldground atower,antenna,andyourshack.Weoften forgettobond allconnectionstogether. Seethereddotswhereground rodsarespacedevery8orsofeetalong theground wireused.FollowtheNECguidelines.

BallGapLightningProtectionInsulated towersrequireruggedlightningdischargepoints

GroundConnections

Grounding- WaterPipes

Goodandbad

What'swrongwiththis?

BondingGroundRods

• Bonding (connecting)ground rods.

• Whenbonding ground rods,followyour localelectricalcode.NEC810.21(J)

• TheNECcodestatethatallground rodsneedtobebonded toequalizeimpedance.

• Somepeopleprefertouse4AWGasthebondingjumper.

MakingconnectionsExothermic(cad)Welding

Video ofCadWelding- 2:38https://youtu.be/T5DoB26TFtI

HighTempSilverSoldering

ShackEntrance

• Shackgroundrod– steelcladcopper.

• Stainlesssteelfasteners.• Attachedlightningarrestors.• Braidedgroundcablefeedingtoshack.

• Incorrectlyusedpipeclampatthebottomwithattachedsolidcopperwire.

• Thegroundrodhasapipeoverittoincreasetherodssize.L

Notforeveryone

Practicalsystemswillbesomethingofacompromisebasedonhomelayoutandavailableresources(cost,time,etc)

Section3GroundLoops

Whataregroundloops?• Unwantedelectriccurrentpathinacircuitresultinginstraysignalsorinterferenceoccurring,e.g.,whentwoearthedpointsinthesamecircuithavedifferentpotentials.

• Video 3:11

– Groundloopscan=Noiseinyourradio– https://youtu.be/WIfcNKkkuvE

GroundLoops• Whatisagroundloop(noise)• Pictureofcommongroundloop

Manyloops

Somesimplefixestogroundloops

Warning– Donoteliminateyoursafetyground!!!

Transformers/Isolator Prepackagedsolutions

Eliminateredundant grounding

Whatelsemightbeneeded

Wholehousesurgeprotection

Therearemanypossibleproblemsandsolutions

• Groundingissues.• Antennaandcablingissues.• Radios,Antennaturners,coaxswitches,powersupplies…

• NowisthetimetobringinyourfriendsandElmer's!

ThemostimportantthingtoknowishaveFun withyourhobby!