White Paper Lighting Protection Systems

7/31/2019 White Paper Lighting Protection Systems

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Written By: James Mark Long19 January 2005

Technical White PaperLIGHTNING PROTECTION

REQUIREMENTS AND

SPECIFICATIONS

[For the source of the definitions please see the Bibliography]

1. ELECTRIC UTILITY REQUIREMENTS

The protection of transmission lines naturally divides into two general methods. Thefirst seeks to keep the stroke off the line conductors; and the second allows the lineconductor to be struck but prevents the power follow current from creating aninterruption to service. The first method makes use of overhead ground wires, while thesecond uses such devices as protector tubes, ground-fault neutralizers, or automaticreclosing breakers. (13a) [Authors note, lightning arrestors are now commonly used.The use of lightning arrestors allows the shunting of the lightning energy around theprimary t r a n s f o r m e r s a n d c o n d u c t o r s . Combinations o f both methods are alsocommonly used.]

Counterpoise A conductor buried to a depth of 1 to 3 feet of a material that ismechanically strong and resistant to corrosion. Experience seems to indicate that asize, which is suitable mechanically, will be sufficient from the point of view ofconductivity. (13b) this definition of counterpoise is one of two recommended methodsfor tower grounding, 1) ground rods or 2) buried conductors.

Overhead ground wire The principle of operation of an overhead ground wire is tointercept the stroke and to conduct its current to ground without sufficient potentialdeveloping either at the tower or in the span to cause a flashover between the groundwire or tower, and conductors. Overhead ground wires are placed over the lineconductors in such a manner that lightning makes contact with them rather than with theline conductors. From the point of view of lightning, the ground wires can be made ofany suitable material such as steel, copper, aluminum, or copper-covered steel. Theconductor size will, in general, be determined by mechanical considerations if toosmall it might be burned seriously by the lightning current. The largest conductordefinitely known to have been burned completely through, according to the authorsrecords, is a No. 4 solid copper conductor. It is probable that in most cases the

overhead ground wire should not be smaller than No. 1/0. (13a)

Counterpoise Ground wires which are connected to tower footings to provide anadequate lightning current path to ground. (14a)

Overhead ground wires Wires, which are used in transmission lines to protectthe lines by providing a ground path for lightning. (14b) The ground wire is not part ofany electrical circuit, however, but instead is connected to the earth at frequent intervals,at least every fifth pole, on pole lines. On steel towers it is grounded to each tower,


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by means of the metal clamp with which it is fastened. The ground or earth potential isthereby virtually brought above the transmission line and, hence, the stress on the lineand transformer insulation due to lightning is greatly reduced. A properly installedground wire is highly effective, but its effectiveness depends on low ground resistance.(14c)

Static wires The small wire at the top of the structure are so-called static wires orground wires. They are not insulated and directly connect to the metal hardware on thestructure and the ground. Their purpose is to shield the line conductors from lightning.(14d) [Authors note, the structure referred to is a structure supporting overheadelectrical distribution lines.]

PHOTO OF 15 KV OVERHEAD DISTRIBUTION LINE WITH OVERHEADGUARD WIRE. (AKA OVERHEAD GROUND OR STATIC WIRE)


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FAA-SO-STD-71, PART 3.6 CABLE TRENCH AND DUCT DETAILSDETAIL 4/1 (15)

Use of guard wires Overhead guard wires to protect overhead incoming AC serviceconductors and buried guard wires to protect buried cables runs not enclosed in rigidgalvanized steel conduits have proven effective in protecting against lightning inducedsurges on the conductors. (16a)

Buried guard wire [commonly referred to as counterpoise] .. For other ACconductors to exterior equipment where the use of rigid galvanized steel conduit is notfeasible, the use of a guard wire is required. Bare No. 6 AWG solid copper conductor

has provided effective protection during experimental use. To be effective the guardwire must be embedded in the soil a minimum of 10 inches (25 cm) above and parallelto the protected cable run or duct. The guard wire must be effectively bonded to theground rod at the service transformer and to the earth electrode system of the facilityhousing the service disconnect means. Exothermic welds shall be used to provide thebonding. Lengths of guard wires exceeding 300 feet (90 m) shall have an additionalconnection to earth ground. For each 300 feet (90 m) or portion thereof in excess of300 feet, an earth ground connection shall be made utilizing inch by 10 foot ground


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rods located not less than six (6) feet from the guard wire. These connections to earthshould be located at approximately equal spacings between the ground connections ateach end of the guard wire installation. (16b)

buried guard wire Use of a buried #6 AWG solid copper guard wire (counterpoise)embedded in soil above and parallel to buried cable runs not enclosed in rigidgalvanized steel conduits, including armored cable, has provided effective attenuation oflightning-induced transients. To be effective, the guard wire must be embedded in thesoil a minimum of 10 inches (25 cm) above and parallel to the protected cable run orduct. When the width of the cable run or duct bank does not exceed 3 feet (1 m), oneguard wire, centered over the cable run or duct bank, provides adequate protection.When the cable run or duct bank is more than 3 feet (1 m) wide, two guard wires shallbe installed. The guard wires should be at least 12 inches (30 cm) apart and be notless than 12 inches (30 cm) nor more than 18 inches (45 cm) inside the outermost wiresor the edges of the duct bank. The guard wires must be bonded to the earth electrodesystem at each terminating facility. Exothermic welds or FAA approved pressure

connectors provide effective bonding. Guard wires exceeding 300 feet (90 m) in lengthshall also be connected to a ground rod every 300 feet (90 m) or portion thereof inexcess of 300 feet (90 m). (16c)

EXAMPLE OF FAA-6950.19A, REQUIREMENTS (16)


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Earth Electrode System (EES) 1.1 An earth electrode system shall be installedcapable of dissipating the energy of direct lightning strikes, dissipating DC, AC, and RFcurrents, and conducting power system fault currents to earth. (16d)

Cable guard wires Where indicated on the drawings, the contractor shall install cableguard wires to protect underground conductors from the effects of lightning discharges.Guard wires may be direct earth buried or installed in nonmetallic ducts. Each guardwire shall be a bare solid No. 6 AWG copper conductor installed not less than 10 inchesabove the buried conductors or ducts. (17)

Buried guard wires Buried lines, not completely enclosed in ferrous metal conduit,shall be protected by a bare N0. 6 AWG, solid copper guard wire. The guard wire shallbe embedded in the soil, a minimum of 10 in. directly above and parallel to the lines orcables being protected. The guard wire shall be bonded to the earth electrode systemat each end and to ground rods at intervals not exceeding 300 feet using exothermicwelds or FAA approved pressure connectors. (18)

Buried guard wires Buried lines including armored cable, not completely enclosed inferrous conduit, shall be protected by a bare #1/0 AWG copper guard wire. The guardwire shall be embedded in the soil, a minimum of 10 in. (25 cm) directly above andparallel to the lines or cables being protected. When the width of the cable run or ductdoes not exceed 3 ft (90 cm), one guard wire, centered over the cable run or duct,provides adequate protection. When the cable run or duct is more than 3 ft (90 cm) inwidth, 2 guard wires shall be installed. The guard wires should be at least 12 in. (30cm) apart and be not less than 12 in. (30 cm) nor more than 18 in. (45 cm) inside theoutermost wires or the edges of the duct. The guard wire shall be bonded to the EES[earth electrode system] at each end and to ground rods at approximately 90 ft intervals

using exothermic welds. Where cables are run parallel to the edge of a runway anadditional guard wire located between the runway edge and the cable run has beenshown to provide significant reduction in lightning related incidents. The spacingbetween ground rods must vary by 10 20% to prevent resonance. Install the groundrods at approximately 6 feet (2 m) to either side of the trench. (19a)

Lightning Protection System Requirements The intended purpose of the lightningprotection system is to provide preferred paths for lightning discharges to enter or leavethe earth without causing facility damage or injury to personnel or equipment. (19b)

Down Conductor Terminations Down conductors (see paragraph 3.7.3) used to

ground air terminals and roof conductors, shall be exothermically welded to a 4/0 AWGcopper conductor prior to entering the ground. The 4/0 copper conductor shall enter theground and be welded to a ground rod that is exothermically welded to the EES. (19c)


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EXAMPLE OF FAA-STD-019d, REQUIREMENTS (19)


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3. NON-FAA OWNED FACILITY REQUIREMENTS

150/5370-10A L-108-3.9 Bare Counterpoise Wire Installation And Grounding ForLightning Protection. If shown in the plans or specified in job specifications, a strandedbare copper wire, No. 8 AWG minimum size, shall be installed for lightning protection ofthe underground cables. The bare counterpoise wire shall be installed in the sametrench for the entire length of the insulated cables it is designed to protect, and shall beplaced at a distance of approximately 4 inches (100 mm) from the insulated cable. Thecounterpoise wire shall be securely attached to each light fixture base, or mountingstake. The counterpoise wire shall also be securely attached to copper or copper-cladground rods installed not more than 1,000 feet (300 m) apart around the entire circuit.The ground rods shall be of the length and diameter specified in the plans, but in nocase shall they be less than 8-feet (240 cm) long nor less than 5/8 inch (15 mm) indiameter.

The counterpoise system shall terminate at the transformer vault or at the powersource. It shall be securely attached to the vault or equipment grounding system. Theconnections shall be made as shown in the project plans and specifications. (21)

EXAMPLE OF L-108-3.9 REQUIREMENTS


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EXAMPLE OF L-108-3.9 REQUIREMENTS

150/5340-24-7.k Counterpoise. If required, install counterpoise wire for lightningprotection in the same trench 4 inches above the installed cable it is to protect asspecified in paragraph 108-3.9 of AC 150/5370-10. (29)

150/5340-30-12.5 Counterpoise (Lightning Protection) - The counterpoise system is

installed on airfields to provide some degree of protection from lightning strikes tounderground power and control cables. The counterpoise conductor is a bare solidcopper wire, #6 AWG. The conductor is connected to ground rods spaced a maximumof 500 feet apart. Connection to the ground rod is made using exothermic welds.Where cable and/or conduit runs are adjacent to pavement, such as along runway ortaxiway edges, the counterpoise is installed 8 below grade, located half the distancefrom edge of pavement to the cable and/or conduit runs. The counterpoise is notconnected to the light fixture base can or mounting stake. Where cable and/or conduitruns are not adjacent to pavements, the counterpoise is installed 4 minimum above thecable and/or conduit. The height above the cable and/or conduit is calculated to ensurethe cables and/or conduits to be protected are within a 45 zone of protection below the

counterpoise. The counterpoise will be terminated at ground rods located on each sideof a duct crossing. Where conduit or duct runs continue beneath pavement (i.e., apronareas, etc.), install the counterpoise a minimum of 4 inches above conduits or ductsalong the entire run. Counterpoise connections are made to the exterior ground lug onfixture bases of runway touchdown zone lights, runway centerline lights, and taxiwaycenterline lights installed in rigid pavement. The counterpoise is bonded to the rebarcage around the fixture base. Where installed in materials that accelerate the corrosionof the proper conductor, the counterpoise must be type TW insulated. Coat anyexposed copper/brass at connections to the base can with a 6-mil layer of 3MS c o t c h K o t e e l e c t r i c a l c o a t i n g o r a p p r o v e d e q u i v a l e n t . E n s u r e a l l


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counterpoise connections are UL listed for direct earth burial and/or installation inconcrete is applicable. Refer to Figure 108 for counterpoise installation details. (23)

150/5340-30-12.6 Safety (Equipment) Ground - A safety ground must be installed ateach light fixture. The purpose of the safety ground is to protect personnel from

possible contact with an energized light base or mounting stake as the result of ashorted cable or isolation transformer. The safety ground may be a #6 AWG barejumper connected to the ground lug at the fixture base or stake to a 5/8 by 8 footminimum ground rod installed beside the fixture. A safety ground circuit may also beinstalled and connected to the ground bus at the airfield lighting vault. The safetyground circuit may be a #6 AWG insulated wire for 600 volts (XHHW). Insulation shouldbe colored green. Attach the safety ground circuit to the ground lug at each light baseor mounting stake, and secure the entire lighting circuit to the ground bus at the vault.The safety ground circuit must be installed in the same duct or conduit as the lightingpower conductors. (23)

EXAMPLE OF AC 150/5340-30 REQUIREMENTS (23)


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Typical Installation Drawings for Airport Lighting Equipment, dated July 1988 issued bythe FAA Great Lakes Region drawing GL-600-1 matches the requirements of AC150/5340-30. (30)

150/5370-10B 108-3.6 Bare Counterpoise Wire Installation for Lightning Protectionand Grounding. If shown on the plans or included in the job specifications, barecounterpoise copper wire shall be installed for lightning protection of the undergroundcables. Counterpoise wire shall be installed in the same trench for the entire length ofburied cable, conduits and duct banks, which are installed to contain airfield cables.Where the cable or duct/conduit trench runs parallel to the edge of pavement, thecounterpoise shall be installed in a separate trench located half the distance betweenthe pavement edge and the cable or duct/conduit trench. In trenches not parallel topavement edges, counterpoise wire shall be installed continuously a minimum of 4inches above the cable, conduit or duct bank, or as shown on the plans if greater.Additionally, counterpoise wire shall be installed at least 8 inches below the top of sub

grade in paved areas or 10 inches below finished grade in un-paved areas. Thisdimension may be less than 4 inches where conduit is to be embedded in existingpavement. Counterpoise wire shall not be installed in conduit.

The counterpoise wire shall be routed around to each light fixture base, mountingstake, or junction/access structures. The counterpoise wire shall also be exothermicallywelded to ground rods installed as shown on the plans but not more than 500 feet (150m) apart around the entire circuit.

The counterpoise system shall be continuous and terminate at the transformer vault orat the power source. It shall be securely attached to the vault or equipment external

ground ring or other made electrode grounding system. The connections shall be madeas shown on the plans and in the specifications.

If shown on the plans or in the specifications, a separate equipment (safety) groundsystem shall be provided in addition to the counterpoise wire using one of the followingmethods:

1. A ground rod installed at and securely attached to each light fixture base,mounting stake if painted, and to all metal surfaces at junction/access structures.

2. Install an insulated equipment ground conductor internal to the conduit system and

securely attach it to each light fixture base and to all metal surfaces at junction/accessstructures. This equipment ground conductor shall also be exothermically welded toground rods installed not more than 500 feet (150 m) apart around the circuit.

a. Counterpoise Installation Above Multiple Conduits and Duct Banks. Counterpoisewires shall be installed above multiple conduits/duct banks for airfield lighting cables, withthe intent being to provide a complete cone of protection over the airfield lighting cables.When multiple conduits and/or duct banks for airfield cable are installed in the same


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trench, the number and location of counterpoise wires above the conduits shall beadequate to provide a complete cone of protection measured 22 [NFPA 780 states 450]degrees each side of vertical.

Where new duct banks pass under existing pavement, the counterpoise shall be runthrough an uppermost empty conduit and also be bonded exothermically at ground rods,furnished and installed by the Contractor, at each end of the duct bank. Where ductbanks pass under pavement to be constructed in the project, the counterpoise shall beplaced above the duct bank. Reference details on the construction plans.

b. Counterpoise Installation at Existing Duct Banks. When airfield lighting cables areindicated on the plans to be routed through existing duct banks, the new counterpoisewiring shall be terminated at ground rods at each end of the existing duct bank where thecables being protected enter and exit the duct bank. Where approved by the Engineer,the ground rod installation will not be required if the new counterpoise wiring is connectedto the existing duct bank counterpoise wiring system. (22)

150/5370-10B 108-3.7 Exo thermic Bonding. Bonding of counterpoise wire shall be bythe exothermic welding process. Only personnel experienced in and regularly engaged inthis type of work shall make these connections.

Contractor shall demonstrate to the satisfaction of the Engineer, the welding kits,materials and procedures to be used for welded connections prior to any installations inthe field. The installations shall comply with the manufacturer's recommendations andthe following:

All slag shall be removed from welds.

For welds at light fixture base cans, all galvanized coated surface areas and"melt" areas, both inside and outside of base cans, damaged by exothermic bondprocess shall be restored by coating with a liquid cold-galvanizing compoundconforming to U.S. Navy galvanized repair coating meeting Mil. Spec. MIL-P-21035.Surfaces to be coated shall be prepared and compound applied in accordance withmanufacturer's recommendations.

All buried copper and weld material at weld connections shall be thoroughlycoated with heat shrinkable tubing or coated with coal tar bitumastic material to preventsurface exposure to corrosive soil or moisture." (22)

The DRAFT 150/5370-10B description of counterpoise for the individual airfield lightingcircuits complies with the 150/5340-30 Advisory Circular. The DRAFT 150/5370-10Bdescription of counterpoise for the airfield lighting duct banks generally complies withthe existing 150/5370-10A Advisory Circular.


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4. MILITARY FACILITY REQUIREMENTS

TM 5-690 Completely enclose buried lines in ferrous metal, electrically continuous,watertight conduit. Protect against direct lightning strikes to buried cable by installing aguard wire above the cables or cable duct. A 1/0 AWG bare copper cable laid directlyover the protected cables is recommended. At least 25.4 cm (10 inches) should bemaintained between the protected cables and the guard wire. For a relatively narrowspread of cables, 0.9 meters (3 feet) or less, or for a duct less than 0.9 meters (3 feet)wide, only one guard wire cable is necessary. For wider cable spreads or wider ducts,at least two 1/0 AWG cables should be provided. The guard wires should be spaced atleast 30 cm (12 inches) apart and be not less than 30 cm (12 inches) nor more than 45cm (18 inches) inside the outermost wires or the edges of the duct. To be effective, theguard wires must be bonded to the earth electrode subsystem at each terminatingfacility. Exothermic welds provide the most effective bonding. Since the guard wire andprotected cables are embedded in the earth, the applicable zone of protection is notknown. (31)

UFC 3-535-01

12.1.5 Equipment Grounding System. Install #6 copper AWG green-jacketedwires identified as an equipment ground, in ducts with primary circuit and connect alllight bases. Note, if used for approach lights without a light base, connect ground toeach light fixture and to the vault lighting system.

12.1.5.1 Ground Criteria. The ground wire serves as a safety ground, protectingagainst high voltages that could be brought to the light base. As an alternative, eachaviation light base will be grounded with a ground rod. System safety ground wires are

to be bonded only at the vault, manholes, hand holes, light bases and cans. See thefollowing paragraphs for providing a counterpoise system for lightning protection.

12.1.6 Counterpoise Lightning Protection System. Provide a continuouscounterpoise of number 4 (minimum) AWG bare, stranded copper wire over the entirelength of all primary circuits supplying airfield lighting: outside pavements, with aminimum 2.4 meter (8 foot) ground rod installed at least every 300 meters (1,000 feet).Do not connect counterpoise system to the light bases.

12.1.6.1 Counterpoise Criteria. Along runway/taxiway or apron shoulders, installthe counterpoise halfway between the pavement and at approximately half the depth of

the duct (or cable, if direct buried) if at all possible. If this is not practical, installcounterpoise 10-15 centimeters (4-6 inches) above the duct or direct buried cable.Route the counterpoise around each light base or unit, at a distance of about 0.6 meters(2 feet) from the unit; do not connect to the unit. For duct not along a shoulder or forduct bank, lay the counterpoise 10-15 centimeters (4-6 inches) above the uppermostlayer of direct buried ducts, or on the top of the concrete envelope of an encased ductbank. Provide only one counterpoise wire for cables for the same duct bank. Connectall counterpoise wires leading to a duct bank to the single counterpoise wire for the duct


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bank. Lay the counterpoise at least 0.3 meters (12 inches) from any light cans or inrouting counterpoise around manholes or hand holes. Do not connect the counterpoiseto the lighting vault power grounding system. Use brazing or thermoweld for allconnections. The counterpoise resistance to ground must not exceed 25 ohms at anypoint using the drop of potential method. (32)

AFMAN(I) 32-1187/TM 811-5, FINAL DRAFT, Design Standards for Visual AirNavigation Facilities is very similar in its description of counterpoise and grounding toUFC 3-535-01 mentioned above. Details from the AFMAN manual follow. (33)


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AFMAN(I) 32-1187/TM 8111-5 FINAL DRAFT (33)FIGURE 1. DIRECT BURIED DUCT/CONDUIT DETAIL


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AFMAN(I) 32-1187/TM 8111-5 FINAL DRAFT (33)FIGURE 3. COUNTERPOISE & GROUND ROD INSTALLATION DETAIL


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5. INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO) REQUIREMENTS

ICAO Aerodrome Design Manual Part 5 Electrical Systems, First Edition 1983, definesthe requirements for grounding and counterpoise installation. The requirements aresimilar to the FAA requirements except for the bonding of the isolation transformersecondary.

Chapter 3.6.2.4, Designing for Integrity and Reliability states ., providing groundwire circuits throughout the system to reduce the effects of lightning and high voltagesurges,. The ground wire circuit is basically a counterpoise conductor as previouslydefined in this document. (34a)

Chapter 5.1.2.6 Ground Wires A ground wire or counterpoise wire should be installedto protect underground power and control cables from high ground current surges inareas where damage from lightning strikes may be expected. The ground wire should

be installed between the earths surface and the underground cables. It is usually anun-insulated, stranded copper conductor. The size of this ground wire should not beless than the largest size conductors, which it protects. Cross-section area of theconductor may range from 8.4 mm2 t o 21 mm2 or larger. [Converting the SI sizes toAWG the Chapter recommends a range from #8 AWG to #4 AWG copper wire.] Itshould be a continuous conductor and connected to each fixture, light base and groundrod or connection along its route. (34b)

Chapter 4.2.3.h of the ICAO Aerodrome Design Manual Part 5, Separation betweenCables states; Ground wire and counterpoises should be approximately 15 cm [ 6]above the uppermost level of cables. (34c)

6. NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) REQUIREMENTS

NFPA 70, National Electrical Code (25a)

Bonding (bonded) - The permanent joining of metallic parts to form an electricallyconductive path that ensures electrical continuity and the capacity to conduct safely anycurrent likely to be imposed. (25a)

Bonding jumper - A reliable conductor to ensure the required electrical conductivity

between metal parts required to be electrically connected. (25a)

Bonding jumper, equipment - The connection between two or more portions of theequipment grounding conductor. (25a)

Bonding jumper, main - The connection between the grounded circuit conductor andthe equipment grounding conductor at the service. (25a)


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Ground - A conducting connection, whether intentional or accidental, between anelectrical circuit or equipment and the earth or to some conducting body that serves inplace of the earth. (25a)

Grounded - Connected to earth or to some conducting body that serves in place of theearth. (25a)

Grounded, effectively - Intentionally connected to earth through a ground connection orconnections of sufficiently low impedance and having sufficient current-carrying capacityto prevent the buildup of voltages that may result in undue hazards to connectedequipment or to persons. (25a)

Grounded conductor - A system or circuit conductor that is intentionallygrounded. (25a)

Grounding conductor - A conductor used to connect equipment or the grounded

circuit of a wiring system to a grounding electrode or electrodes. (25a)

grounding conductor, equipment - The conductor used to connect the noncurrent-carrying metal parts of equipment, raceways, and other enclosures to the systemgrounded conductor, the grounding electrode conductor, or both, at the serviceequipment or at the source of a separately derived system. (25a)

grounding electrode conductor - The conductor used to connect the groundingelectrode(s) to the equipment grounding conductor, to the grounded conductor, or toboth, at the service, at each building or structure where supplied from a commonservice, or at the source of a separately derived system. (25a)

NFPA 780, Standard for the Installation of Lightning Protection Systems (24d)

bonding An electrical connection between an electrically conductive object and acomponent of a lightning protection system that is intended to significantly reducepotential difference created by lightning currents. (24d)

Bonding conductor A conductor used for potential equalization between groundedmetal bodies and a lightning protection system. (24d)

Ground terminal The portion of a lightning protection system, such as a ground rod,

ground plate, or a ground conductor, that is installed for the purpose of providingelectrical contact with the earth. (24d)

Grounded Connected to earth or some conducting body that is connected to earth.(24d)

Lightning protection system A lightning protection system is a complete systemof strike termination devices, conductors, ground terminals, interconnectingconductors, surge suppression devices, and other connectors or fittings required tocomplete the system. (24d)


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Loop conductor A conductor encircling a structure that is used to interconnect groundterminals, main conductors or other grounded bodies. (24d)

side flash An electrical spark, caused by differences of potential, that occurs between

conductive metal bodies or between conductive metal bodies and a component of alightning protection system or ground. (24d)

Strike termination device A component of a lightning protection system that interceptslightning flashes and connects them to a path to ground. Strike termination devicesinclude air terminals, metal masts, permanent metal parts of structures as described inSection 4.9, and overhead ground wires installed in catenary lightning protectionsystems. (24d)

Zone of protection The space adjacent to a lightning protection system that issubstantially immune to direct lightning flashes. (24d)

Common grounding All grounding media in or on a structure shall beinterconnected to provide a common ground potential. This shall include lightningprotection, electric service, telephone and antenna system grounds, as well asunderground metallic piping systems. Underground metallic piping systems shallinclude water service, well casings located within 25 feet (7.6 m) of the structure, gaspiping, underground conduits, underground liquefied petroleum gas piping systems, andso on. Interconnection to a gas line shall be made on the customers side of the gasmeter. Main-size lightning conductors shall be used for interconnecting these groundingsystems to the lightning protection system. (24e)

Ground level potential equalization All grounded media in and on a structure shall beconnected to the lightning protection system within 12 feet (3.6 m) of the base of thestructure in accordance with Section 4.14. (24f)


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LIGHTNING PROTECTIONDISCUSSION

7. WHAT WE HAVE LEARNED SO FAR

1. Lightning strikes originate 15,000 to 20,000 feet above sea level. The strikecomes to earth in 50 yard steps. Within 30 to 50 yards of ground the lightningstrike determines the attachment point.

2. Lightning strikes include current levels approaching 400 kA. The averagestokes current ranges from 25 kA to 40 kA.

3. Stroke currents will divide up among all parallel conductive paths between theattachment point(s) and earth. Division of t he current will be inverselyproportional to the path impedance.

4. Lightning is a current source; output current is independent of load impedance. Ifthe return stroke is 50 kA, then that is the magnitude of the current that will flow,whether it flows through one ohm or 1000 ohms.

5. Voltage transfers from an intended lightning conductor into electrical circuits canoccur due to capacitive coupling, inductive coupling, and/or resistance coupling.

6. Radial horizontal arcing in excess of 65 feet from the base of the lightning flashextends the hazardous environment.

7. Lightning is a capricious, random and unpredictable event.

8. Many lives have been lost due to lightning. Lightning results in about $4 to $5billion in damages each year.

9. Each facility should undergo a lightning risk assessment.

10. Lightning strikes cannot be prevented. Lightning can only be intercepted ordiverted to a path that, if well designed and constructed, will not result indamage.

11. Cone-of-Protection 450 each side of vertical and 150 sphere models.

12. A low impedance connection to earth is key in a properly designed lightningprotection system. The NEC 25 ohm maximum earth resistance requirementmay not be adequate.


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8. AIRFIELD LIGHTING SYSTEM LIGHTNING PROTECTION METHODS

There are currently two widely accepted airfield lighting system lightning protectionmethods.

Method 1 - The first method centers about the interconnection of all metalliccomponents via the counterpoise. The counterpoise system is connected to the earthelectrode system (EES) at the airfield lighting vault. For simplicity of discussion we willrefer to this method as the old method since this method is described in the currenteditions of FAA-STD-019d and AC 150/5370-10A.

Method 2 - The second method recommends not connecting the counterpoise to thebase can or fixture stake and includes the installation of a safety ground. The safetyground consists of a or b below:

a. A bonding conductor installed between the base can or fixture stake andan electrode installed adjacent to the fixture.

b. A conductor within the duct system, bonded to each base can or mountingstake. The safety ground conductor is connected to the EES at the airfieldlighting vault.

The counterpoise, when installed for conductors adjacent to pavement (edge lightcircuits), is installed midway between the edge of pavement and the cable/duct run.The counterpoise is connected to the base can when installed with centerline ortouchdown zone lights.

We will refer to this method as the new method since this method is described in AC150/5340-30 and DRAFT AC 150/5370-10B.

9. BASIS OF LIGHTNING STRIKE SCENARIOS DESCRIBED BELOW

The following scenarios will address the advantages and disadvantages of the old andnew methods. The behavior of lightning cannot be predicted with absolute accuracy.Earth impedance and the variation in lightning frequencies (kHz to MHz range) make itdifficult to characterize lightnings behavior on the ground. (35) Site unique conditionswill also impact the lightnings behavior.

We are also assuming that the counterpoise conductors installed for either method havelow impedance and will divert the lightning energy from the components to be protected.

All base cans and mounting stakes considered in this discussion are galvanized steel.A non-metallic base can or painted mounting stake would present a very highimpedance to a lightning strike. The base cans or mounting stakes are grounded byvirtue of their being installed in the earth. However the base cans or mounting stakeswithout supplemental ground connections would present a higher than desiredimpedance to a lightning strike.


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In each scenario we will be assuming an average lightning strike between 25 kA and 40kA; we can expect radial arcing up to 65 feet from the strike attachment point. It isestimated that less than 15% of a lightning strikes current penetrates the earth. (6)

The following three figures may be used to follow each of the lightning strike scenarios.


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10.SCENARIO # 1 LIGHTNING STRIKES ADJACENT TO EDGE LIGHTCIRCUIT EDGE LIGHT IS OUTSIDE AREA OF RADIAL ARCING

Old method The counterpoise wire and grounded base can should divert the strikecurrent that penetrates the earth away from the airfield lighting system. Thecounterpoise conductor being buried in the earth will bleed off the strike currentthroughout its length. The average current decay rate is approximately 1% per meter.(36a) The base can should act as a Faraday Cage and should normally protect theisolation transformer and airfield lighting system cables. Minimal damage to the onefixture could occur.

New method, with safety ground rod - The counterpoise wire and grounded base can(including safety ground rod) should divert the strike current that penetrates the earthaway from the airfield lighting system. The base can should act as a Faraday Cage andshould normally protect the isolation transformer and airfield lighting system cables.Minimal damage to the one fixture could occur.

However, a base can in concrete (40 ohms) and a single ground rod (50 ohms) inFlorida will have an earth resistance of approximately 26 ohms (parallel resistanceformula X multiplier 1.16). An average lightning strike of 25 kA (15% penetrates theearth) and a 60/40 strike current split between counterpoise and base can, respectively,could result in a 39 kV drop over the base can earth connection for severalmicroseconds. This could couple a high voltage on the airfield lighting circuitconductors resulting in a strain on the airfield lighting conductor insulation.

New method, with safety ground conductor - The counterpoise wire should divertsome of the strike current that penetrates the earth away from the airfield lighting

system. Some of the strike current that penetrates the earth will see the base can.There will be a potential difference developed between the counterpoise and the basecan. This potential difference could result in arcing and the boiling away of the moisturein the soil. The impedance of the lightning circuit will determine the current splitbetween the counterpoise and the base can. We will assume an average strike currentof 25 kA, 15% (3.75 kA) of which penetrates the earth. For discussion purposes letsassume the counterpoise carries 90% of the current and the base can carries thebalance. The #6 AWG copper safety ground conductor will be asked to carry 375 A forthe duration of the strike. The #6 copper conductor should be able to safely carry the375 A for the short duration of the strike. However, a voltage will be coupled into theairfield lighting circuit, which could strain the airfield lighting circuit conductor insulation.

Damage to the one fixture could occur. A 60/40 counterpoise/base can current split asused in the previous scenario would result in a 1500 A current in the safety ground.


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11.SCENARIO # 2 LIGHTNING STRIKES ADJACENT TO EDGE LIGHTCIRCUIT EDGE LIGHT IS WITHIN AREA OF RADIAL ARCING

Old method The surface arcing will travel across the earth in all directions from thepoint of strike attachment. The impedance of the strike attachment will determine theamount of current that each branch carries. Assume one of the radial arcs finds theedge light base plate. The counterpoise wire and grounded base can should divert thestrike current away from the airfield lighting system. The base can should act as aFaraday Cage and should normally protect the isolation transformer and airfield lightingsystem cables. The counterpoise conductor could be asked to carry the strike currentfor a short time. The counterpoise conductor being buried in the earth will bleed off thestrike current throughout its length. Minimal damage to the one fixture could occur.

New method, with safety ground rod - The surface arcing will travel across the earthin all directions from the point of strike attachment. The impedance of the strikeattachment will determine the amount of current that each branch carries. Assume one

of the radial arcs finds the edge light base plate. The earth electrode and groundedbase can should divert the strike current away from the airfield lighting system. Thebase can should act as a Faraday Cage and should normally protect the isolationtransformer and airfield lighting system cables. However, because of the 26 ohm earthresistance there could be a significant voltage drop across the base can to earthinterface. This could induce a strain on the airfield lighting circuit conductor insulation.Minimal damage to the one fixture and system cabling could occur.

New method, with safety ground conductor - The surface arcing will travel acrossthe earth in all directions from the point of strike attachment. The impedance of thestrike attachment will determine the amount of current that each branch carries.

Assume one of the radial arcs finds the edge light base plate. The counterpoise wireshould divert some of the strike current that penetrates the earth away from the airfieldlighting system. The base can is grounded by virtue of being buried in the earth andtherefore will divert some of the strike current away from the airfield lighting systemconductors. The surface arcing that has connected to the edge light base plate will beconducted to the safety ground conductor, via the base can. The safety groundconductor is routed with the airfield lighting circuit conductors. The safety groundconductor has no way to bleed off the strike current until it reaches the next base can orthe EES at the airfield lighting vault. Since the safety ground does not have a lowimpedance path to divert the strike current, the safety ground could be destroyed. Thedestruction of the safety ground could damage the airfield lighting circuit conductors.

The current in the safety ground could also induce significant voltage into the airfieldlighting circuit resulting in constant current regulator (CCR) damage. Damage to theone or more fixtures could be expected.


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12.SCENARIO # 3 LIGHTNING DIRECTLY STRIKES TOP OF ELEVATEDEDGE LIGHT

Old method Strike current divides among all conductive paths. The impedance of thestrike attachment will determine the amount of current that each branch carries. Thecounterpoise wire and grounded base can should divert the majority of the strike currentaway from the airfield lighting system. The counterpoise conductor could be asked tocarry the strike current for a short time. The counterpoise conductor being buried in theearth will bleed off the strike current throughout its length. The average current decayrate is approximately 1% per meter. (36a) A portion of the strike current will probablyenter the fixture and couple to the secondary L-830 wiring. This would in turn couple avoltage to the L-830 primary and airfield lighting circuit conductors. This scenario wouldprobably result in the destruction of the fixture, L-830 transformer and require cablereplacement to the next fixture.

New method, with safety ground rod - Strike current divides among all conductive

paths. The impedance of the strike attachment will determine the amount of current thateach branch carries. The earth electrode and grounded base can should divert most ofthe strike current away from the airfield lighting system. However, because of the 26ohm earth resistance there could be a significant increase in the amount of voltagecoupled into the L-830 transformer and primary circuit, versus the old method, resultingin additional damage to the airfield lighting system.

New method, with safety ground conductor - Strike current divides among allconductive paths. The impedance of the strike attachment will determine the amount ofcurrent that each branch carries. The counterpoise wire should divert some of the strikecurrent that penetrates the earth away from the airfield lighting system. The base can is

grounded by virtue of being buried in the earth and therefore will divert some of thestrike current away from the airfield lighting system conductors. The strike current thathas connected to the edge light will be conducted to the safety ground conductor, viathe base can. The safety ground conductor is routed with the airfield lighting circuitconductors. The safety ground conductor has no way to bleed off the strike current untilit reaches the next base can or the EES at the airfield lighting vault. Since the safetyground does not have a low impedance path to divert the strike current, the safetyground could be destroyed. The destruction of the safety ground could damage theairfield lighting circuit conductors. The current in the safety ground could also inducesignificant voltage into the airfield lighting circuit resulting in constant current regulator(CCR) damage. A portion of the strike current will probably enter the fixture and couple

to the secondary L-830 wiring. This would in turn couple a voltage to the L-830 primaryand airfield lighting circuit conductors. This scenario would probably result in thedestruction of the fixture, all L-830 transformers and cables within the limits of the safetyground wires ability to bleed off the strike current.


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13.SCENARIO # 4 LIGHTNING DIRECTLY STRIKES TOP OF SEMIFLUSHCENTERLINE FIXTURE, COUNTERPOISE IS CONNECTED TO BASE CANSAS REQUIRED BY OLD AND NEW METHODS

Old method Strike current divides among all conductive paths. The impedance of thestrike attachment will determine the amount of current that each branch carries. Thecounterpoise wire and grounded base can should divert the majority of the strike currentaway from the airfield lighting system. The counterpoise conductor could be asked tocarry the strike current for a short time. The counterpoise conductor being buried in theearth will bleed off the strike current throughout its length. The average current decayrate is approximately 1% per meter. (36a) A portion of the strike current will probablyenter the fixture and couple to the secondary L-830 wiring. This would in turn couple avoltage to the L-830 primary and airfield lighting circuit conductors. This scenario wouldprobably result in the destruction of the fixture, L-830 transformer and require cablereplacement to the next fixture.

New method, with safety ground rod - The new method for the centerline fixtures alsohas the counterpoise connected to each base can. The outcome should be similar tothe old method discussed above.

New method, with safety ground conductor The new method for the centerlinefixtures also has the counterpoise connected to each base can. However the safetyground will also carry some of the strike current. A portion of the strike current that hasconnected to the base can will be conducted to the safety ground conductor, via thebase can. The safety ground conductor is routed with the airfield lighting circuitconductors. The safety ground conductor has no way to bleed off the strike current untilit reaches the next base can or the EES at the airfield lighting vault. Since the safety

ground does not have a low impedance path to divert the strike current, the safetyground could be damaged. The damage to the safety ground could damage the airfieldlighting circuit conductors. The current in the safety ground could also induce significantvoltage into the airfield lighting circuit resulting in cable insulation stresses and possibleCCR damage.


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SAFETY GROUNDS

The safety ground implemented in AC 150/5340-30 has its roots in NFPA 70, TheNational Electrical Code (NEC). While the principle is sound, there are several flaws

with the method of implementation.

The NEC requires the grounding conductor to be installed in the same raceway or cablewith the ungrounded conductors. An explanatory note in the NEC Handbook states;One of the functions of an equipment grounding conductor is to provide a low-impedance ground-fault path between a ground fault and the electrical source. Thispath allows the over-current protective device to actuate, interrupting the current.To keep the impedance at a minimum, it is necessary to run the equipment groundingconductor within the same raceway or cable as the circuit conductor(s). This practiceallows the magnetic field developed by the circuit conductor and the equipmentgrounding conductor to cancel, reducing their impedance. Magnetic flux strength is

inversely proportional to the square of the distance between two conductors. By placingan equipment grounding conductor away from the conductor delivering the fault current,the magnetic flux cancellation decreases. This increases the impedance of the faultpath and delays operation of the protective device.

AC 150/5345-10E, Specification for Constant Current Regulators and RegulatorMonitors, October 16, 1984, requires CCRs 10 kW and larger to have over-currentprotection. The over-current protective device is required to open the primaryswitch within 5 seconds for a 5% over-current and within 1 second of a 25% over-current. This over-current protection is not dependant upon a grounding conductorenclosed in the same conduit as the airfield lighting circuit conductors.

The NEC is based upon a voltage source system. Airfield lighting circuits powered by aCCR are a current source system. The requirement for the grounding conductor to berouted in the same raceway with the ungrounded conductors is not applicable. Asshown in the previous scenarios the inclusion of the safety ground with the series circuitconductors can actually increase damage to the system.

The counterpoise routed over the duct and bonded to each base can provides the sameelectrical grounding function as the safety ground without increasing the possibility ofdamage from lightning.

The term safety ground as described in 150/5340-30 may also be a placebo. Thespecified GE RTV-118 self-leveling sealant used to seal between components is aninsulator.

On a newly installed L-868 base can at Orlando International airport the resistancebetween base can components was measured and recorded. The base can sectionsare installed in accordance with the applicable FAA Advisory Circulars.


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a. Resistance between L-868B bottom base can section and top base cansection. Zero ohms. This connection is bolted.

b. Resistance between top can section and top of the third spacer ring.Greater than 1000 ohms! This connection is bolted only when the fixtureis installed. It is expected that the resistance between the bolted fixtureand top can section would be zero ohms.

A 1000 k ohm resistance with a 6.6 A current results in a 6,600 volt drop!

Many of us have heard the statement You should have seen the sparks fly when Iremoved the last bolt.

PHOTO OF NEWLY INSTALLED TAXIWAY CENTERLINE LIGHTON TAXIWAY F AT ORLANDO INTERNATIONAL AIRPORT


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CASE STUDY

Pinecastle Army Airfield was founded in 1942. The site was transferred to the City of

Orlando in 1947. In 1951, the United States Government reacquired Pinecastle ArmyAirfield. In April 1952, Pinecastle Air Force Base was reactivated.

In 1957, an aircraft accident took the life of Colonel Michael N. McCoy and three others.Colonel McCoy is credited with saving the lives of many on the ground during theaccident. The base was renamed McCoy Air Force Base on May 7, 1958 in ColonelMcCoys honor.

In 1970 McCoy Air Force Base started scheduled commercial air carrier service. Theinitial air carriers were Delta Airlines, Eastern Airlines, National Airlines and SouthernAirlines.

In 1974 McCoy Air Force Base (MCO) was closed and the deed was transferred to theCity of Orlando. In 1975 The Greater Orlando Aviation Authority (GOAA) is created bya special legislative act. In 1976 the airport is renamed Orlando International Airport.

GOAA inherited a 1950s vintage airfield lighting system. Lightning damage at MCOwas a significant maintenance problem. Orlando is located in the lightning capital of theUnited States. In 1987, the design of the New Third Runway (R/W 17-35), GOAApersonnel and the design team researched FAA design standards and utility designstandards to implement the best lightning protection system available.

The design included a #6 AWG copper counterpoise routed over the center of eachunderground duct/conduit. The counterpoise was bonded to each base can and groundrods were installed at 500 foot maximum intervals. The counterpoise was also bondedto the base can rebar cages, manholes and all metallic elements within the airfieldlighting system. Each ground rod was designed to have an earth resistance not toexceed 5 ohms. In addition a 4/0 AWG copper ground grid was installed under thepavement. The 4/0 grid consisted of roughly 500 foot interconnected squares with aground rod at each corner. The counterpoise was bonded to the 4/0 grid at everycrossing. The counterpoise and ground grid were both connected to the airfield lightingvault EES. The airfield lighting vaults lightning protection was designed in accordancewith NFPA 780. Each CCR was specified with input and output lightning protection.

Transient voltage surge suppression (TVSS) was provided for all sensitive or criticalloads. The goal was to achieve minimum earth impedance to a lightning strike and toprovide maximum reliability for the airfield lighting system. The Runway 17-35 wasopened in 1989.

While exact quantities of items damaged by lightning were not kept, GOAAMaintenance soon noticed the Third Runway was not suffering the severity of lightningdamage of either of the other two runways.


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In the 1990s the two existing military runways were rehabilitated. Experience dictatedthat the rehabilitation of the two runways include the same lightning protectionmeasures incorporated for the Third Runway. Again GOAA Maintenance noticed asignificant drop in the amount of damage caused by lightning.

In 2000 design of the Fourth Runway was started. Again the design included theproven lightning protection measures.

In 2001 the local electric utility company referenced a study, which is quoted as statingthat a #4 AWG copper wire is the smallest copper conductor that typically will notvaporize when struck by a direct high intensity lightning stroke. The #6 coppercounterpoise does not vaporize in all strikes but is dependent on voltage level,impedance, etc. The study determined that #4 AWG copper wire is the minimum sizethat will survive the intense heat generated by the high voltage and current in a lightingstrike.

Although attempts have been made to obtain a copy of the study, we have not beenable to locate the paper. Independently we have been able to verify therecommendation for using a #4 AWG copper counterpoise. The Standard HandbookFor Electrical Engineers, Tenth Edition, states in part 26-14 Physical Requirements:The largest conductor definitely known to have been burned completely through,according to the authors records, is a No. 4 solid copper conductor. This reference isfor an overhead ground wire (used for lightning protection) on overhead electricaldistribution/transmission lines.

The counterpoise size for the 4th Runway was changed from a #6 AWG copper to a #4

AWG copper based upon the utilitys information.

The 4th Runway was opened to air carrier traffic on December 25, 2003. The followingphotos are an overview of the 4th Runway lightning protection.


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4th RUNWAY SITE WITH AIRFIELD LIGHTINGVAULT LIGHTNING PROTECTION


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4th RUNWAY SITE WITH 4/0 AWGCOPPER GROUND GRID


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4th RUNWAY SITE WITH #4 AWG COPPER COUNTERPOISEAND 4/0 COPPER GROUND GRID


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RECOMMENDATIONS

1. Perform a Lightning Risk Assessment for each airfield lighting system.

2. Implement lightning protection measures in according with the results of thelightning risk assessment.

3. Delete r e q u i r e m e n t f o r safety g r o u n d w i t h i n c o n d u i t w i t hs e r i e s c i r c u i t conductors.

4. Require counter poi se (safety ground) to be rou ted above duct/conduitand bonded to each base can, rebar and all metallic items making up the airfieldlighting system.

5. Route counterpoise to airfield lighting vault and bond to vault EES.

6. Install ground rods at 500 maximum intervals along series circuits. Bond groundrod to counterpoise.

7. Minimum size of copper counterpoise - #4 AWG.

8. Recommend maximum earth resistance of 10 ohms. NEC maximum earthresistance of 25 ohms is too high.

9. Install lightning protection on airfield lighting vault in accordance with NFPA 780.

Incorporate input and output lightning protection on CCRs and TVSS for criticalloads.

10. Explore addition of bonding jumper between fixture and bolted base can section.

11. Explore requirement for all frangible couplings to be conductive or requirebonding jumper.

SUMMARY

The design and installation of a quality lightning protection system is critical to todays

airport lighting systems. The lightning protection system is as important to the airfieldlighting system as the actual lighting circuit wiring.

Without proper lightning protection the airfield lighting systems can incur frequent andsubstantial outages. The cost of a well designed and installed lightning protectionsystem is minimal when compared with component repair and replacement, runway ortaxiway closures or aircraft being rerouted to another airport.


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BIBLIOGRAPHY

1 Frequently Asked Questions About Lightning, National Oceanic and

Atmospheric Administration's (NOAA) National Severe Storms Laboratory, Website,http://www.nssl.noaa.gov/researchitems/lightning.shtml

2 A lightning Primer, National Aeronautics and Space Administration's (NASA)Global Hydrology and Climate Center (GHCC), Web site,http://thunder.msfc.nasa.gov/

3 Contemporary Lightning Safety for Environments Containing SensitiveElectronics, Explosives and Volatile Substances, By Richard Kithil, President& CEO, National Lightning Safety Institute.

4 IEEE Recommended Practice for Grounding of Industrial and CommercialPower Systems, IEEE Std 142-1991, IEEE Green Book. (4a) Page 110 Par3.3.1.1; (4b) Page 112 Par 3.3.1.2; (4c) Page 116, Par 3.3.3.1; (4d) Page 117Par 3.3.3.1 last two paragraphs; (4e) Page 126, Par 4; (4f) Page 127, Figure 61& Table 9; (4g) Page 132, Table 14; (4h) Page 132, Par 4.1.5; (4i) Page 133, Par4.1.6; (4J) Page 129, Par 4.1.3; (4k) Page 118, Par 3.3.3.2; (4l) Page 128, Par4.1.2;

5 An Examination of Lightning-Strike-Grounding Physics, C. B. Moore, G.D.Aulich and William Rison Langmuir Laboratory for Atmospheric Research, New

Mexico Tech, Socorro, NM 87801 with photo from December 1943 NationalGeographic Magazine, Page 662.

6 21st Century Lightning Safety for Explosives Facilities, By Richard Kithil,President & CEO, National Lightning Safety Institute.

7 Lightning Fatalities, Injuries and Damage Reports in the United States,National Lightning Safety Institute, web sitehttp://www.lightningsafety.com/nlsi_lls/fatalities_us.html

8 Metal Objects Do Not Attract Lightning, White paper by Jack McKay, Ph.D.

Physics, M.S.E.E.

9 Frequently Asked Questions About Lightning, VAISALA Group, web sitehttp://www.lightningstorm.com/tux/jsp/faq/index.jsp

10 Email response to questions by Carl Johnson from Dr. Vladimir A. Rakov, M.S.,Ph.D. Professor of the Department of Electrical and Computer Engineering,University of Florida, Gainesville.
http://www.nssl.noaa.gov/researchitems/lightning.shtmlhttp://www.nssl.noaa.gov/researchitems/lightning.shtmlhttp://thunder.msfc.nasa.gov/http://thunder.msfc.nasa.gov/http://www.lightningsafety.com/nlsi_lls/fatalities_us.htmlhttp://www.lightningsafety.com/nlsi_lls/fatalities_us.htmlhttp://www.lightningstorm.com/tux/jsp/faq/index.jsphttp://www.lightningstorm.com/tux/jsp/faq/index.jsphttp://www.lightningstorm.com/tux/jsp/faq/index.jsphttp://www.lightningsafety.com/nlsi_lls/fatalities_us.htmlhttp://thunder.msfc.nasa.gov/http://www.nssl.noaa.gov/researchitems/lightning.shtml


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11 Electrical Protection Fundamentals, United States Department of Agriculture,Rural Utilities Service (RUS); RUS Bulletin 1751F-801. (11a) Page 11, Part3.1.4.4 & 3.1.4.5; (11b) Page 39, Figure 2; (11c) Page 38, Figure 1;

12 Electrical Protection Grounding Fundamentals, United States Department ofAgriculture, Rural Utilities Service (RUS); RUS Bulletin 1751F-802. (12a) Page59, Figure 2;

13 Standard Handbook For Electrical Engineers, Tenth Edition, Donald G. Fink,Editor-in-Chief, John M. Carroll, Associate Editor, McGraw-Hill Book Company,Copyright 1969. (13a) Page 26-12; (13b) Page 26-19

14 The Linemans and Cablemans Handbook, Fifth Edition, Edwin B. Kurtz andThomas M. Shoemaker, McGraw-Hill Book Company, Copyright 1976. (14a)Page 42-3; (14b) Page 42-8; (14c) Page 6-3; (14d) Page 2-7.

15 FAA-SO-STD-71, Specifications For Installation and Splicing Of UndergroundCables, July 2, 1984. (15) Pages 16 through20;

16 FAA Order 6950.19A, Practices and Procedures for Lightning Protection,Grounding, Bonding and Shield Implementation, July 1, 1996. (16a) Page 136;(16b) Page 137; (16c) Page 159; (16d) Appendix 3 Page 12;

17 FAA-C-1391b, Installation and Splicing Of Underground Cables, January 1,1991. (17) Page 12;

18 FAA-STD-19b, Lightning and Surge Protection, Grounding, Bonding andShielding Requirements for Facilities and Electronic Equipment. (18) Paragraph3.2.4;

19 FAA-STD-19d, Lightning and Surge Protection, Grounding, Bonding andShielding Requirements for Facilities and Electronic Equipment, August 9, 2002.(19a) Page 9, Par 3.2.4; (19b) Page 20, Par 3.7.1; (19c) Page 22, Par 3.7.8;(19d) Page 32, Par 3.8.3;

20 Lightning Protection of Structures and Personal Safety, Dr. Vladimir A.Rakov, M.S., Ph.D. Professor of the Department of Electrical and Computer

Engineering, University of Florida, Gainesville. (20a) Page 8,Par 6; (20b) Page 1,Par 2;

21 AC 150/5370-10A, Standards for specifying the Construction of Airports, Item L-108, Installation of Underground Cable for Airports, 2/17/89

22 AC 150/5370-10B, Standards for specifying the Construction of Airports, Item L-108, Installation of Underground Cable for Airports, DRAFT


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23 AC 150/5340-30, Design and Installation Details for Airport Visual Aids, 4/30/04

24 NFPA 780, Standard for the Installation of Lighting Protection Systems, 2004Edition, Copyright 2001 and 2002 National Fire Protection Association, Inc.(24a)Annex L, Page 780-42; (24b) Page 780-9, Par 4.7.3.1; (24c) Page 780-10, Figure4.7.3.1(B); (24d) Page 780-4, Chapter 3; (24e) Page 780-16, Par 4.14; (24f)Page 780-19, Par 4.21, (24g); Page 780-17, Par 4.18 (24h);

25 NFPA 70, National Electrical Code Handbook, 2002 Edition, Copyright 2001 and2002 National Fire Protection Association, Inc. (25a) Article 100; (25b) Article250;

26 Getting Down to Earth A Manual on Earth Resistance Testing for thePractical Man, Fifth Edition, February 1998, Copyright 1998, Distributor:MeterCenter (800) 230-6008, http://www.biddlemegger.com/biddle-

ug/GettingDownToEarth.pdf (26a) Page 12, Figure 4; (26b) Page 24, How ToImprove Earth Resistance; (26c) Page 12, Nature of an Earth Electrode;

27 Lightning Fatalities from 1990 through 2003, by Holle Meteorology andPhotography, 22 May 2004.

28 The Lightning Attachment Process and Risk Management of the Hazard, ByRichard Kithil, President & CEO, National Lightning Safety Institute.

29 AC 150/5340-24 Change 1, Runway and Taxiway Edge Lighting System, March14, 1978, SUPERSEDED BY 150/5340-30, Page 12, Par 7.k;

30 Typical Installation Drawings for Airport Lighting Equipment, July 1988,FAA Great Lakes Region, Drawing GL-600-1.

31 TM 5-690, Grounding and Bonding in Command, Control, Communications,Computer, Intelligence, Surveillance, and Reconnaissance (C41SR)Facilities (Headquarters, Department of the Army, 15 February 2002)

32 UFC 3-535-01, Design Standards for Visual Air Navigation Facilities,November 2002, Part 2 System Information, Chapter 12, Page 128.

33 AFMAN(I) 32-1187/TM 811-5, FINAL DRAFT, Design Standards for Visual AirNavagation Facilities, 27 July 2000. Chapter 12 pages 126 & 127;

34 AERODROME DESIGN MANUAL, Part 5 Electrical Systems, First Edition 1993, International Civil Aviation Organization (ICAO); (34a) Page 5-50, Par3.6.2.4; (34b) Page 5-80, Par 5.1.2.6; (34c) Page 5-64, Par 4.2.3;
http://www.biddlemegger.com/biddle-http://www.biddlemegger.com/biddle-


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35 Email response to questions by Carl Johnson from Richard Kithil, President &CEO, National Lightning Safety Institute.

36 Triggered Lightning Testing of an Airport Runway Lighting System, MirelaBejleri, Vladimir A. Rakov, Fellow, IEEE, Martin A. Uman, Fellow, IEEE, Keith J.Rambo, Carlos T. Mata, Member, IEEE, and Mark I. Fernandez, February 2002.(36a) Par IIIB;

37 AC 150/5345-10E, Specification for Constant Current Regulators and RegulatorMonitors, October 16, 1984, (37a) Page 4, Par 3.3.9.2;

Documents

White Paper Lighting Protection Systems