Lightning protection
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The document provides an introduction to lightning protection, including its purpose, history, facts about lightning, definitions of key terms, considerations for designing a lightning protection system, and standards for lightning protection. It details the components of a lightning protection system, such as air terminals, conductors, ground terminals, and surge arresters. It also discusses how to protect different types of structures and roofs based on their geometry, materials, and other factors.
Lightning protection
- 1. Purpose of Lightning Protection • The practical safe guarding of persons and property from hazard arising from exposure to lightning. Introduction to Lightning ProtectionIntroduction to Lightning Protection
- 2. Who invented lightning Protection?Who invented lightning Protection? • Benjamin Franklin invented lightningBenjamin Franklin invented lightning rods in 1752rods in 1752 Introduction to Lightning ProtectionIntroduction to Lightning Protection
- 3. Introduction to Lightning ProtectionIntroduction to Lightning Protection Lightning FactsLightning Facts • Globally some 2000 on going thunderstormsGlobally some 2000 on going thunderstorms cause about 100 lightning strikes to earth eachcause about 100 lightning strikes to earth each second.second. • Insurance Company information shows onInsurance Company information shows on home owner’s damage claim for every 57home owner’s damage claim for every 57 lightning strikes.lightning strikes. • Annually in the USA lightning causes moreAnnually in the USA lightning causes more than 26,000 fires with damage to property inthan 26,000 fires with damage to property in excess of 5 billion dollars.excess of 5 billion dollars. • Lightning usually travels at 1/3 the speed ofLightning usually travels at 1/3 the speed of light.light.
- 4. Introduction to Lightning ProtectionIntroduction to Lightning Protection Lightning DefinitionsLightning Definitions • Air Terminal – A strike termination device that is aAir Terminal – A strike termination device that is a receptor for attachment of flashes to the lightningreceptor for attachment of flashes to the lightning protection system and is listed for the purpose.protection system and is listed for the purpose. • Class I Materials – Lightning conductors, air terminals,Class I Materials – Lightning conductors, air terminals, ground terminals and associated fittings required by thisground terminals and associated fittings required by this standard for protection of structures not exceeding 75ft.standard for protection of structures not exceeding 75ft. in height.in height. • Class II Materials - Class I Materials – LightningClass II Materials - Class I Materials – Lightning conductors, air terminals, ground terminals andconductors, air terminals, ground terminals and associated fittings required by this standard forassociated fittings required by this standard for protection of structures exceeding 75ft. in height.protection of structures exceeding 75ft. in height.
- 5. Introduction to Lightning ProtectionIntroduction to Lightning Protection Lightning DefinitionsLightning Definitions • Bonding Conductor – A conductor used forBonding Conductor – A conductor used for potential equalization between grounded metalpotential equalization between grounded metal bodies and a lightning protection system.bodies and a lightning protection system. • Ground Terminal – The portion of a lightningGround Terminal – The portion of a lightning protection system such as a ground rod,protection system such as a ground rod, ground plate or ground conductor that isground plate or ground conductor that is installed for the purpose of providing electricalinstalled for the purpose of providing electrical contact to earth.contact to earth. • Side Flash – An electrical spark caused bySide Flash – An electrical spark caused by difference in potential that occurs betweendifference in potential that occurs between conductive metal bodies and a component of aconductive metal bodies and a component of a lightning protection system or ground.lightning protection system or ground.
- 6. Introduction to Lightning ProtectionIntroduction to Lightning Protection Lightning DefinitionsLightning Definitions • Surge Arrester – A protective device used forSurge Arrester – A protective device used for limiting surge voltages by discharging or bylimiting surge voltages by discharging or by passing surge current that can also preventpassing surge current that can also prevent continued flow of follow current whilecontinued flow of follow current while remaining capable of discharging or by passingremaining capable of discharging or by passing surge current.surge current. • Zone of Protection – The space adjacent to aZone of Protection – The space adjacent to a lightning protection system, that islightning protection system, that is substantially immune to direct lightningsubstantially immune to direct lightning flashes.flashes.
- 7. Introduction to Lightning ProtectionIntroduction to Lightning Protection Considerations before designing aConsiderations before designing a lightning protection systemlightning protection system 1.1. Roof types and pitchRoof types and pitch a)a) GableGable b)b) HipHip c)c) Broken GableBroken Gable d)d) FlatFlat e)e) MansardMansard f)f) GambrelGambrel
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- 9. Introduction to Lightning ProtectionIntroduction to Lightning Protection 2.2. PitchPitch The roof span, rise and run is takenThe roof span, rise and run is taken into account.into account.
- 10. Introduction to Lightning ProtectionIntroduction to Lightning Protection 3.3. Materials used shall be resistant to corrosionMaterials used shall be resistant to corrosion a)a) CopperCopper b)b) Copper AlloysCopper Alloys c)c) AluminumAluminum i.i. Notes:Notes: Copper lightning protection materials shall not beCopper lightning protection materials shall not be installed on aluminum roofing, siding or otherinstalled on aluminum roofing, siding or other aluminum surfaces.aluminum surfaces. Aluminum lightning protection materials shall notAluminum lightning protection materials shall not be installed on copper surfaces.be installed on copper surfaces.
- 11. Introduction to Lightning ProtectionIntroduction to Lightning Protection i.i. Notes continued:Notes continued: Aluminum materials shall not be used whereAluminum materials shall not be used where they come in to direct contact with earth. Athey come in to direct contact with earth. A bimetallic connector shall be installed notbimetallic connector shall be installed not less than 10” above earth level.less than 10” above earth level. Aluminum conductors shall not be attachedAluminum conductors shall not be attached to a surface coated with alkaline base paint,to a surface coated with alkaline base paint, embedded in concrete or masonry, orembedded in concrete or masonry, or installed in a location subject to excessiveinstalled in a location subject to excessive moisture.moisture.
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- 13. Introduction to Lightning ProtectionIntroduction to Lightning Protection 4.4. Air Terminal heightAir Terminal height The tip of an air terminal shall not be lessThe tip of an air terminal shall not be less then 10 inches above the object or area itthen 10 inches above the object or area it is to protect.is to protect. 4.4. Zone of protectionZone of protection To determine the zone of protection, theTo determine the zone of protection, the geometry of the structure shall begeometry of the structure shall be considered.considered.
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- 16. Introduction to Lightning ProtectionIntroduction to Lightning Protection 6.6. Location of devicesLocation of devices • There are set distances that an airThere are set distances that an air terminal can be installed apart from eachterminal can be installed apart from each other on a roof peak or at the edge of theother on a roof peak or at the edge of the roof that is pitched or flat.roof that is pitched or flat. a)a) Within 2’ of the edge of the roofWithin 2’ of the edge of the roof b)b) 20-25 ft. maximum spacing along the ridge.20-25 ft. maximum spacing along the ridge.
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- 18. Introduction to Lightning ProtectionIntroduction to Lightning Protection 7.7. Area on roofs that require specialArea on roofs that require special attentionattention a)a) DormersDormers b)b) ExhaustExhaust c)c) FluesFlues d)d) ChimneysChimneys e)e) StacksStacks f)f) HandrailsHandrails g)g) Anything that is higher than the roof tipAnything that is higher than the roof tip
- 19. Introduction to Lightning ProtectionIntroduction to Lightning Protection 8.8. Cross-run conductorsCross-run conductors • Cross-run conductors (main conductors) shall beCross-run conductors (main conductors) shall be required to interconnect the strike termination devicesrequired to interconnect the strike termination devices on flat or greatly sloping roofs that exceed 50ft. In widthon flat or greatly sloping roofs that exceed 50ft. In width 8.8. Down ConductorsDown Conductors • Down conductors shall be widely separated as practical.Down conductors shall be widely separated as practical. Their location shall depend on the followingTheir location shall depend on the following considerations:considerations: a)a) Placement of strike termination devicesPlacement of strike termination devices b)b) Most direct course of conductorsMost direct course of conductors c)c) Earth conditionsEarth conditions d)d) Security against displacementSecurity against displacement e)e) Location of large metallic bodiesLocation of large metallic bodies f)f) Location of underground metallic piping systemsLocation of underground metallic piping systems
- 20. Introduction to Lightning ProtectionIntroduction to Lightning Protection 10.10. Number of down conductorsNumber of down conductors a)a) At least two down conductors shall be provide on anyAt least two down conductors shall be provide on any kind of structure.kind of structure. b)b) Structures exceeding 250ft. In perimeter shall have aStructures exceeding 250ft. In perimeter shall have a down conductor for every 100ft. of perimeter.down conductor for every 100ft. of perimeter. 10.10. Protecting down conductorsProtecting down conductors • The down conductor shall be protected for a minimumThe down conductor shall be protected for a minimum distance of 6ft. Above ground level. Usually in a PVCdistance of 6ft. Above ground level. Usually in a PVC raceway.raceway. 10.10. Ground terminalsGround terminals • Each down conductor shall terminate at a groundEach down conductor shall terminate at a ground terminal dedicated to the lightning protection system.terminal dedicated to the lightning protection system.
- 21. Introduction to Lightning ProtectionIntroduction to Lightning Protection 13.13. Ground Electrodes (Ground rods)Ground Electrodes (Ground rods) a)a) Shall be installed below the frost line whereShall be installed below the frost line where possible.possible. 13.13. Concrete encased electrode (Ufer ground)Concrete encased electrode (Ufer ground) • These shall only be used in new construction.These shall only be used in new construction. The electrode shall be located near the bottomThe electrode shall be located near the bottom of the concrete foundation or footing encased byof the concrete foundation or footing encased by not less than 2” of concrete. The encasednot less than 2” of concrete. The encased electrode shall consist of the following:electrode shall consist of the following: a)a) Not less that 20ft. of bare copperNot less that 20ft. of bare copper b)b) An electrode consisting of at least 20ft. of one orAn electrode consisting of at least 20ft. of one or more steel reinforcing bars that have beenmore steel reinforcing bars that have been bundled together by welding or secure wire tying.bundled together by welding or secure wire tying.
- 22. Introduction to Lightning ProtectionIntroduction to Lightning Protection 15.15. Ground plates are an option when soil is shallowGround plates are an option when soil is shallow and rods can’t be driven deep enough.and rods can’t be driven deep enough. • Ground plates are a minimum 2ft. Square, buried noGround plates are a minimum 2ft. Square, buried no less than 18” deep and are at least .032in thick.less than 18” deep and are at least .032in thick. 15.15. Lightning protection for miscellaneous structuresLightning protection for miscellaneous structures • Metal towers and tanks constructed so as to receive aMetal towers and tanks constructed so as to receive a stroke of lightning without damage shall require onlystroke of lightning without damage shall require only bonding to ground terminals.bonding to ground terminals. 15.15. Concrete tanks and silosConcrete tanks and silos • Lightning protection systems for concrete tanksLightning protection systems for concrete tanks containing flammable vapors, flammable gases, andcontaining flammable vapors, flammable gases, and liquids that can produce flammable vapors andliquids that can produce flammable vapors and concrete silos containing materials susceptible to dustconcrete silos containing materials susceptible to dust explosions shall be provided with either externalexplosions shall be provided with either external conductors or with conductors embedded in theconductors or with conductors embedded in the concrete.concrete.
- 23. Introduction to Lightning ProtectionIntroduction to Lightning Protection 18.18. Protection for heavy duty stacksProtection for heavy duty stacks a)a) Smoke or vent stack shall be classified as heavySmoke or vent stack shall be classified as heavy duty if cross sectional area of flue is greater thatduty if cross sectional area of flue is greater that 500 in squared and a height greater than 75ft.500 in squared and a height greater than 75ft. b)b) Air terminals shall be placed at 8’ spacing max.Air terminals shall be placed at 8’ spacing max. c)c) All equipment on upper 25ft. Of stack to be leadAll equipment on upper 25ft. Of stack to be lead covered copper, stainless steel or approvedcovered copper, stainless steel or approved corrosion resistant material.corrosion resistant material. d)d) If the stack has platform and ladders each ofIf the stack has platform and ladders each of these will be bonded to the lightning protectionthese will be bonded to the lightning protection system on the way down the stack.system on the way down the stack.
- 24. Introduction to Lightning ProtectionIntroduction to Lightning Protection 19.19. Surge SuppressionSurge Suppression a)a) Surge suppression should also be considered for yourSurge suppression should also be considered for your main electrical devices in the plant.main electrical devices in the plant. In all instances use high quality, high speed, self-In all instances use high quality, high speed, self- diagnosing protective components. Transientdiagnosing protective components. Transient limiting devices may use a combination of arc gaplimiting devices may use a combination of arc gap diverters-metal oxide varistor-silicon avlanchediverters-metal oxide varistor-silicon avlanche diode technologies. Hybrid devices using adiode technologies. Hybrid devices using a combination of these technologies are preferred.combination of these technologies are preferred. Know your clamping voltage requirements. ConfirmKnow your clamping voltage requirements. Confirm that your vendors products have been tested tothat your vendors products have been tested to rigid ANSI/IEEE/ISO 9000 testing standards.rigid ANSI/IEEE/ISO 9000 testing standards.
- 25. Introduction to Lightning ProtectionIntroduction to Lightning Protection 20.20. Standards for Lightning protectionStandards for Lightning protection Standard NFPA 780Standard NFPA 780 2008 NEC Article 2502008 NEC Article 250 Article 280 Surge Arrester over 1 KvArticle 280 Surge Arrester over 1 Kv Article 285 Surge Protective Devices 1Article 285 Surge Protective Devices 1 Kv or lessKv or less
- 26. Introduction to Lightning ProtectionIntroduction to Lightning Protection Any Questions?Any Questions?