Lightning Protection Slide
Transcript of Lightning Protection Slide
Harger Lightning & Grounding © 2005
Lightning Protection System DesignLightning Protection System DesignHarger Lightning & Grounding
2005
Harger Lightning & Grounding © 2005
Lightning Protection System Lightning Protection System DesignDesign
I. What is Lightning/Lightning Protection?II. Basic Principles of Lightning ProtectionIII. Applicable Codes/Standards IV. Lightning Protection Design BasicsV. “Zone of Protection”VI. Basic ComponentsVII. “ Typical ” Roof Top Detail VIII. Inspections
Harger Lightning & Grounding © 2005
I. What is Lightning?
Consider Lightning a Gigantic Electrical Spark traveling betweenConsider Lightning a Gigantic Electrical Spark traveling betweenCloud to Cloud or Cloud to Earth containing an average Charge ofCloud to Cloud or Cloud to Earth containing an average Charge of30 to 50 Million Volts and a Current of 18,000 Amps.30 to 50 Million Volts and a Current of 18,000 Amps.
Harger Lightning & Grounding © 2003
Harger Lightning & Grounding © 2005
Lightning Damage Can Be Traced ToLightning Damage Can Be Traced To
Inadequate (or no) direct strike protection
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Risks Posed from a Direct Strike
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Risks Posed from an Indirect StrikeRisks Posed from an Indirect Strike
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What is Lightning Protection?What is Lightning Protection?
NFPA 780 NFPA 780 --
A Complete System of Air Terminals, Conductors, Ground Terminals, Interconnecting Conductors, Surge Suppression Devices, and other Connectors or Fittings required to complete the System.
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What is What is notnot Lightning Protection?Lightning Protection?
Early Streamer Emission – ESERadioactivePulsed VoltageSparking – Controlled Leader Trigger (CLT)
Lightning EliminationDissipation Array Systems (DAS)Charge Transfer Systems (CTS)
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Non Conventional Lightning Protection SystemsNon Conventional Lightning Protection Systems
These systems are not allowed by:
US National Fire Protection Association (NFPA)IEEEIECUS MilitaryUnderwriters Laboratory (UL)
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II. Basic Principles of Lightning ProtectionII. Basic Principles of Lightning Protection
Intercept the Lightning DischargeSafely Conduct the Lightning CurrentsDissipate the Lightning Currents in the EarthMinimize the Effects of Lightning Currents
Proper Bonding & routing of down-conductorsSurge Suppression
Protect incoming power circuitsProtect incoming telephone/data circuits
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III. Applicable Codes/StandardsIII. Applicable Codes/Standards
NFPA 780NFPA 780UL 96AUL 96AUL 96UL 96
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NFPA 780NFPA 780
Standard for the Installation of Lightning Protection Systems (2004)Most Active Standard AvailableNot a Code, (not enforced)
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UL 96 & 96AUL 96 & 96A
UL96A - Installation Standard“Master Label”Independent Third Party Testing
UL96 - Manufacturing Standard for Listed LP Components
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UL Master Label ProgramUL Master Label Program
Must be UL Listed to be Eligible
Materials must be UL Listed
System will be subjected to Inspection by UL
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UL Master Label ProgramUL Master Label Program
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IV. Lightning Protection Design Basics
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
2004 Edition2004 Edition
Chapter 3 Protection for Ordinary Structures
3-6 Strike Termination Devices. Strike termination devices shall be provided for all parts of a structure that are likely to be damaged by direct lightning flashes. Metal parts of a structure that are exposed to direct lightning flashes and that have a metal thickness of 3/16 in. (4.8 mm) or greater shall only require connection to the lightning protection system. Such connections shall provide a minimum of two paths to ground. Strike termination devices shall not be required for those parts of a structure located within a zone of protection.
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-6.1 Air Terminal Height. The tip of an air terminal shall be not less than 10 in. (254mm) above the object or area it is to protect. (See figure 3-6.1.)
Figure 3-6.1 Air terminal height.A: 10 in. (254 mm). See 3-6.1.
24 in. (600 mm). See 3-6.2.
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-6.2 Air Terminal Support. Air terminals shall be secured against overturning by attachment to the object to be protected or by means of braces that shall be permanently and rigidly attached to the building. An air terminal exceeding 24 in. (600 mm) in height shall be supported at a point not less than one-half its height.
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-8.1 Strike termination devices shall be placed at or within 2 ft (0.6m) of ridge ends on pitched roofs or at edges and outside corners of flat or gently sloping roofs.
Strike termination devices shall be placed on ridges of pitched roofs and around the perimeter of flat or gently sloping roofs at intervals not exceeding 20 ft (6m).
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-8.1 Strike termination devices 24 in. (600mm) or more above the object or area to be protected shall be permitted to be placed at intervals not exceeding 25 ft (7.6m).
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-8.1.2 Flat or Gently Sloping Roof Area. Flat or gently sloping roofs that exceed 50 ft (15m) in width or length shall have additional strike termination devices located at intervals not to exceed 50 ft (15m) on the flat or gently sloping areas.
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Down Conductor PlacementDown Conductor Placement
Minimum of two per structureOne per every 100’ of perimeterAverage spacing will not exceed 100’
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-9.5 Conductor Bends. No bend of a conductor shall form an included angle of less than 90 degrees, nor shall it have a radius of bend less than 8 in. (203mm).
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
3-13 Ground Terminals.Each down conductor shall terminate at a ground terminal dedicated to the lightning protection system. The design, size, depth, and number of ground terminals used shall comply with 3-13.1 through 3-13.4.
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NFPA 780NFPA 780Standard for the Installation of Lightning Protection SystemsStandard for the Installation of Lightning Protection Systems
ContinuedContinued……
Connections to Building SteelConnections to Building Steel
Clean to base metalBonding plates 8 in2
minimum contact areaWeldedBrazed
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V. Zone of ProtectionV. Zone of Protection
A Zone of Protection is the space adjacent to a lightning protection system that is substantially immune to direct lightning discharges. This can be determined using the Rolling Sphere Method.
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Rolling Sphere MethodRolling Sphere Method
3-7.3 Rolling Sphere Model.3-7.3.1 The zone of protection shall include the space not intruded by a rolling sphere having a radius of 150 ft (46 m). When the sphere is tangent to earth and resting against a strike termination device, all space in the vertical plane between the two points of contact and under the sphere are in the zone of protection.
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Rolling Sphere Method
A zone of protection is also formed when such a sphere is resting on two or more strike termination devices and shall include the space in the vertical plane under the sphere and between those devices, as shown in Figure 3-7.3.1.
All possible placements of the sphere must be considered when determining the zone of protection using the rolling sphere model.
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Rolling Sphere MethodRolling Sphere Method
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Rolling Sphere Formula
d = eh1(300 – h1) - e h2(300 – h2)
where:
d = horizontal distance (ft)h1 = height of the higher roof (ft)h2 = height of the lower roof (top of the object) (ft)
h2
h1
d
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Rolling Sphere Formula
Use of this formula is based on a 150 ft.(46-m) striking distance. For the formula to be valid, the sphere must be tangent to either the lower roof or in contact with the earth, and in contact with the vertical side of the higher portion of the structure. In addition, the difference in height between the upper and lower roof or earth must be 150’ or less.
For Example...For Example...
d
h2
h1
h1= 100’
h2 = 50’
d = 20’
Is the lower roof in the zone of protection?
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For Example...For Example...
d = 100(300 – 100) - 50(300 – 50)
-20000 12500d =
d = 141.42 - 111.80
d = 29.62’
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Rolling Sphere FormulaRolling Sphere Formula
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VII. Basic Components
Air TerminalsLightning ConductorsGround TerminalsConnectors/FittingsSurge Suppression Devices
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Types of Air Terminals
Plain Air TerminalsSafety Air TerminalsFlexible Air Terminals
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Types of Lightning ConductorsTypes of Lightning Conductors
UL Listed Lightning Conductors
Copper Aluminum
Class I Class II
Structural Steel Framework
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Types of Ground TerminalsTypes of Ground Terminals
Ground Rods
Plain/Sectional Copper-Clad Steel, Copper, Galvanized Steel, Stainless Steel
Enhanced Ground Rods
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Types of Ground TerminalsTypes of Ground TerminalsContinued...Continued...
Ground PlatesGround MeshConcrete Encased Electrodes
Reinforcing SteelCopper Conductors
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Connectors/FittingsConnectors/FittingsFunctionsFunctions
Bonds Conductors to Strike Terminals and Ground Terminals Bond Metal Bodies to Provide a Path to GroundAlleviates Potential Differences between System and Metal Bodies Helps Prevent Flashover Potentials
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Surge Suppression DevicesSurge Suppression Devices
Helps Prevent Surge Currentsfrom Entering the Structure via Electrical, Data, Phone, Cable Lines, etc.
Integral Part of TotalProtection Package
UL96A & NFPA SurgeSuppression Requirements vague
Roof Top Detail
VIII.
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Details
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IX. Inspection and MaintenanceIX. Inspection and Maintenance
Inspection after Installation - UL Master Label
Ongoing Inspection -NFPA 780 Appendix B Recommends Periodic (Annual) Inspections
Thank You
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