Lightning Protection for
Airfield Lighting Systems
6. LIGHTNING PROTECTION
REQUIREMENTS AND
SPECIFICATIONS
[for the source of the definitions please see the Bibliography]
6.1
ELECTRIC UTILITY REQUIREMENTS
“The protection of transmission lines naturally divides into two general methods. The
first seeks to keep the stroke off the line conductors; and the second allows the line
conductor to be struck but prevents the power follow current from creating an
interruption to service. The first method makes use of overhead ground wires, while the
second uses such devices as protector tubes, ground-fault neutralizers, or automatic
reclosing breakers.” (13a) [Author’s note, lightning arrestors are now commonly used.
The use of lightning arrestors allows the shunting of the lightning energy around the
primary transformers and conductors. Combinations of both methods are also
commonly used.]
counterpoise – A conductor buried to a depth of 1 to 3 feet of a material that is
mechanically strong and resistant to corrosion. Experience seems to indicate that a
size, which is suitable mechanically, will be sufficient from the point of view of
conductivity. (13b) This definition of counterpoise is one of two recommended methods
for tower grounding, 1) ground rods or 2) buried conductors.
overhead ground wire – “The principle of operation of an overhead ground wire is to
intercept the stroke and to conduct its current to ground without sufficient potential
developing either at the tower or in the span to cause a flashover between the ground
wire or tower, and conductors.” “Overhead ground wires are placed over the line
conductors in such a manner that lightning makes contact with them rather than with the
line conductors. From the point of view of lightning, the ground wires can be made of
any suitable material such as steel, copper, aluminum, or copper-covered steel. The
conductor size will, in general, be determined by mechanical considerations – if too
small it might be burned seriously by the lightning current. The largest conductor
definitely known to have been burned completely through, according to the author’s
records, 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 an
adequate lightning current path to ground.” (14a)
overhead ground wires – “Wires, which are used in transmission lines to protect the
lines by providing a ground path for lightning.” (14b) “The ground wire is not part of any
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, by
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means of the metal clamp with which it is fastened. The ground or earth potential is
thereby virtually brought above the transmission line and, hence, the stress on the line
and transformer insulation due to lightning is greatly reduced. A properly installed
ground 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 or
ground wires. They are not insulated and directly connect to the metal hardware on the
structure and the ground. Their purpose is to shield the line conductors from lightning.”
(14d) [Author’s note, the structure referred to is a structure supporting overhead
electrical distribution lines.]
PHOTO OF 15 KV OVERHEAD DISTRIBUTION LINE WITH OVERHEAD
GUARD WIRE. (AKA OVERHEAD GROUND OR STATIC WIRE)
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6.2
FAA OWNED FACILITY REQUIREMENTS
counterpoise – “A #6 solid bare soft drawn copper counterpoise wire shall be installed
above cable in accordance with the details shown in Section 3.6.” “The #6 bare soft
drawn copper (BSDC) cable counterpoise shall be installed above direct earth buried
(DEB) cables to provide 450 “cone-of-protection” for all cables installed in the trench.
(15) [Author’s note, Section 3.6 typically shows the counterpoise centered over the
cables/ducts to be protected except when the bare copper would be installed in
concrete backfill. Detail 3/1 shows a concrete encased duct with the encasement filling
the entire duct trench. The #6 BSDC counterpoise is shown off center outside the
concrete encasement.]
FAA-SO-STD-71, PART 3.6 CABLE TRENCH AND DUCT DETAILS
DETAIL 1/1 (15)
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FAA-SO-STD-71, PART 3.6 CABLE TRENCH AND DUCT DETAILS
DETAIL 4/1 (15)
use of guard wires – “Overhead guard wires to protect overhead incoming AC service
conductors and buried guard wires to protect buried cables runs not enclosed in rigid
galvanized steel conduits have proven effective in protecting against lightning induced
surges on the conductors. (16a)
buried guard wire – [commonly referred to as counterpoise] “….. for other AC
conductors to exterior equipment where the use of rigid galvanized steel conduit is not
feasible, 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 guard
wire must be embedded in the soil a minimum of 10 inches (25 cm) above and parallel
to the protected cable run or duct. The guard wire must be effectively bonded to the
ground rod at the service transformer and to the earth electrode system of the facility
housing the service disconnect means. Exothermic welds shall be used to provide the
bonding. Lengths of guard wires exceeding 300 feet (90 m) shall have an additional
connection to earth ground. For each 300 feet (90 m) or portion thereof in excess of
300 feet, an earth ground connection shall be made utilizing ¾ inch by 10 foot ground
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rods located not less than six (6) feet from the guard wire. These connections to earth
should be located at approximately equal spacings between the ground connections at
each 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 rigid
galvanized steel conduits, including armored cable, has provided effective attenuation of
lightning-induced transients. To be effective, the guard wire must be embedded in the
soil a minimum of 10 inches (25 cm) above and parallel to the protected cable run or
duct. When the width of the cable run or duct bank does not exceed 3 feet (1 m), one
guard 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 shall
be installed. The guard wires should be at least 12 inches (30 cm) apart and be not
less than 12 inches (30 cm) nor more than 18 inches (45 cm) inside the outermost wires
or the edges of the duct bank. The guard wires must be bonded to the earth electrode
system at each terminating facility. Exothermic welds or FAA approved pressure
connectors provide effective bonding. Guard wires exceeding 300 feet (90 m) in length
shall also be connected to a ground rod every 300 feet (90 m) or portion thereof in
excess 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 installed
capable of dissipating the energy of direct lightning strikes, dissipating DC, AC, and RF
currents, and conducting power system fault currents to earth.” (16d)
Cable guard wires – “Where indicated on the drawings, the contractor shall install cable
guard wires to protect underground conductors from the effects of lightning discharges.
Guard wires may be direct earth buried or installed in nonmetallic ducts. Each guard
wire shall be a bare solid No. 6 AWG copper conductor installed not less than 10 inches
above 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 shall
be embedded in the soil, a minimum of 10 in. directly above and parallel to the lines or
cables being protected. The guard wire shall be bonded to the earth electrode system
at each end and to ground rods at intervals not exceeding 300 feet using exothermic
welds or FAA approved pressure connectors.” (18)
Buried guard wires – “Buried lines including armored cable, not completely enclosed in
ferrous conduit, shall be protected by a bare #1/0 AWG copper guard wire. The guard
wire shall be embedded in the soil, a minimum of 10 in. (25 cm) directly above and
parallel to the lines or cables being protected. When the width of the cable run or duct
does 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) in
width, 2 guard wires shall be installed. The guard wires should be at least 12 in. (30
cm) apart and be not less than 12 in. (30 cm) nor more than 18 in. (45 cm) inside the
outermost 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 an
additional guard wire located between the runway edge and the cable run has been
shown to provide significant reduction in lightning related incidents. The spacing
between ground rods must vary by 10 – 20% to prevent resonance. Install the ground
rods at approximately 6 feet (2 m) to either side of the trench.” (19a)
Lightning Protection System Requirements – “The intended purpose of the lightning
protection system is to provide preferred paths for lightning discharges to enter or leave
the 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 AWG
copper conductor prior to entering the ground. The 4/0 copper conductor shall enter the
ground 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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6.3
NON-FAA OWNED FACILITY REQUIREMENTS
150/5370-10A “L-108-3.9 Bare Counterpoise Wire Installation And Grounding For
Lightning Protection. If shown in the plans or specified in job specifications, a stranded
bare copper wire, No. 8 AWG minimum size, shall be installed for lightning protection of
the underground cables. The bare counterpoise wire shall be installed in the same
trench for the entire length of the insulated cables it is designed to protect, and shall be
placed at a distance of approximately 4 inches (100 mm) from the insulated cable. The
counterpoise wire shall be securely attached to each light fixture base, or mounting
stake. The counterpoise wire shall also be securely attached to copper or copper-clad
ground 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 no
case shall they be less than 8-feet (240 cm) long nor less than 5/8 inch (15 mm) in
diameter.
The counterpoise system shall terminate at the transformer vault or at the power
source. It shall be securely attached to the vault or equipment grounding system. The
connections 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 lightning
protection in the same trench 4 inches above the installed cable it is to protect as
specified 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 to
underground power and control cables. The counterpoise conductor is a bare solid
copper wire, #6 AWG. The conductor is connected to ground rods spaced a maximum
of 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 or
taxiway edges, the counterpoise is installed 8” below grade, located half the distance
from edge of pavement to the cable and/or conduit runs. The counterpoise is not
connected to the light fixture base can or mounting stake. Where cable and/or conduit
runs are not adjacent to pavements, the counterpoise is installed 4” minimum above the
cable and/or conduit. The height above the cable and/or conduit is calculated to ensure
the cables and/or conduits to be protected are within a 45º zone of protection below the
counterpoise. The counterpoise will be terminated at ground rods located on each side
of a duct crossing. Where conduit or duct runs continue beneath pavement (i.e., apron
areas, etc.), install the counterpoise a minimum of 4 inches above conduits or ducts
along the entire run. Counterpoise connections are made to the exterior ground lug on
fixture bases of runway touchdown zone lights, runway centerline lights, and taxiway
centerline lights installed in rigid pavement. The counterpoise is bonded to the rebar
cage around the fixture base. Where installed in materials that accelerate the corrosion
of the proper conductor, the counterpoise must be type TW insulated. Coat any
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exposed copper/brass at connections to the base can with a 6-mil layer of 3M
ScotchKote electrical coating or approved equivalent.
Ensure all counterpoise
connections are UL listed for direct earth burial and/or installation in concrete 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 at
each 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 a
shorted cable or isolation transformer. The safety ground may be a #6 AWG bare
jumper connected to the ground lug at the fixture base or stake to a 5/8” by 8 foot
minimum ground rod installed beside the fixture. A safety ground circuit may also be
installed and connected to the ground bus at the airfield lighting vault. The safety
ground circuit may be a #6 AWG insulated wire for 600 volts (XHHW). Insulation should
be colored green. Attach the safety ground circuit to the ground lug at each light base
or 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 lighting
power conductors”. (23)
EXAMPLE OF AC 150/5340-30 REQUIREMENTS (23)
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EXAMPLE OF AC 150/5340-30 REQUIREMENTS (23)
EXAMPLE OF AC 150/5340-30 REQUIREMENTS (23)
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Typical Installation Drawings for Airport Lighting Equipment, dated July 1988 issued by
the FAA Great Lakes Region drawing GL-600-1 matches the requirements of AC
150/5340-30. (30)
150/5370-10B “108-3.6 Bare Counterpoise Wire Installation for Lightning Protection
and Grounding. If shown on the plans or included in the job specifications, bare
counterpoise copper wire shall be installed for lightning protection of the underground
cables. Counterpoise wire shall be installed in the same trench for the entire length of
buried 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, the
counterpoise shall be installed in a separate trench located half the distance between
the pavement edge and the cable or duct/conduit trench. In trenches not parallel to
pavement edges, counterpoise wire shall be installed continuously a minimum of 4
inches 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
subgrade in paved areas or 10 inches below finished grade in un-paved areas. This
dimension may be less than 4 inches where conduit is to be embedded in existing
pavement. Counterpoise wire shall not be installed in conduit”.
“The counterpoise wire shall be routed around to each light fixture base, mounting
stake, or junction/access structures. The counterpoise wire shall also be exothermically
welded to ground rods installed as shown on the plans but not more than 500 feet (150
m) apart around the entire circuit”.
“The counterpoise system shall be continuous and terminate at the transformer vault or
at 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 made
as shown on the plans and in the specifications”.
“If shown on the plans or in the specifications, a separate equipment (safety) ground
system shall be provided in addition to the counterpoise wire using one of the following
methods:”
“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/access
structures. This equipment ground conductor shall also be exothermically welded to
ground rods installed not more than 500 feet (150 m) apart around the circuit”.
“a. Counterpoise Installation Above Multiple Conduits and Duct Banks. Counterpoise
wires shall be installed above multiple conduits/duct banks for airfield lighting cables, with
the 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 be
adequate to provide a complete cone of protection measured 22 ½ [NFPA 780 states 450]
degrees each side of vertical”.
“Where new duct banks pass under existing pavement, the counterpoise shall be run
through 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 duct
banks pass under pavement to be constructed in the project, the counterpoise shall be
placed above the duct bank. Reference details on the construction plans”.
“b. Counterpoise Installation at Existing Duct Banks. When airfield lighting cables are
indicated on the plans to be routed through existing duct banks, the new counterpoise
wiring shall be terminated at ground rods at each end of the existing duct bank where the
cables 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 connected
to the existing duct bank counterpoise wiring system”. (22)
150/5370-10B “108-3.7 Exothermic Bonding. Bonding of counterpoise wire shall be by
the exothermic welding process. Only personnel experienced in and regularly engaged in
this 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 in
the field. The installations shall comply with the manufacturer's recommendations and
the 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 bond
process shall be restored by coating with a liquid cold-galvanizing compound
conforming 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 with
manufacturer's recommendations”.
“All buried copper and weld material at weld connections shall be thoroughly
coated with heat shrinkable tubing or coated with coal tar bitumastic material to prevent
surface exposure to corrosive soil or moisture." (22)
The DRAFT 150/5370-10B description of counterpoise for the individual airfield lighting
circuits complies with the 150/5340-30 Advisory Circular. The DRAFT 150/5370-10B
description of counterpoise for the airfield lighting duct banks generally complies with
the existing 150/5370-10A Advisory Circular.
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6.4
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 a
guard wire above the cables or cable duct. A 1/0 AWG bare copper cable laid directly
over the protected cables is recommended. At least 25.4 cm (10 inches) should be
maintained between the protected cables and the guard wire. For a relatively narrow
spread 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 at
least 30 cm (12 inches) apart and be not less than 30 cm (12 inches) nor more than 45
cm (18 inches) inside the outermost wires or the edges of the duct. To be effective, the
guard wires must be bonded to the earth electrode subsystem at each terminating
facility. Exothermic welds provide the most effective bonding. Since the guard wire and
protected cables are embedded in the earth, the applicable zone of protection is not
known”. (31)
UFC 3-535-01
12.1.5
Equipment Grounding System. Install #6 copper AWG green-jacketed
wires identified as an equipment ground, in ducts with primary circuit and connect all
light bases. Note, if used for approach lights without a light base, connect ground to
each light fixture and to the vault lighting system.
12.1.5.1
Ground Criteria. The ground wire serves as a safety ground, protecting
against high voltages that could be brought to the light base. As an alternative, each
aviation 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 the
following paragraphs for providing a counterpoise system for lightning protection.
Provide a continuous
12.1.6
Counterpoise Lightning Protection System.
counterpoise of number 4 (minimum) AWG bare, stranded copper wire over the entire
length of all primary circuits supplying airfield lighting: outside pavements, with a
minimum 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, install
the 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, install
counterpoise 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 for
duct bank, lay the counterpoise 10-15 centimeters (4-6 inches) above the uppermost
layer of direct buried ducts, or on the top of the concrete envelope of an encased duct
bank. Provide only one counterpoise wire for cables for the same duct bank. Connect
all 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 in
routing counterpoise around manholes or hand holes. Do not connect the counterpoise
to the lighting vault power grounding system. Use brazing or thermoweld for all
connections. The counterpoise resistance to ground must not exceed 25 ohms at any
point using the drop of potential method. (32)
AFMAN(I) 32-1187/TM 811-5, FINAL DRAFT, Design Standards for Visual Air
Navigation Facilities is very similar in its description of counterpoise and grounding to
UFC 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 2. DIRECT BURIED CABLE TRENCH DETAILS
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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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6.5
INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO) REQUIREMENTS
ICAO Aerodrome Design Manual Part 5 Electrical Systems, First Edition – 1983, defines
the requirements for grounding and counterpoise installation. The requirements are
similar to the FAA requirements except for the bonding of the isolation transformer
secondary.
Chapter 3.6.2.4, “Designing for Integrity and Reliability” states …., providing ground
wire circuits throughout the system to reduce the effects of lightning and high voltage
surges,….” The ground wire circuit is basically a counterpoise conductor as previously
defined in this document. (34a)
Chapter 5.1.2.6 Ground Wires “A ground wire or counterpoise wire should be installed
to protect underground power and control cables from high ground current surges in
areas where damage from lightning strikes may be expected. The ground wire should
be installed between the earth’s surface and the underground cables. It is usually an
uninsulated, stranded copper conductor. The size of this ground wire should not be less
than the largest size conductors, which it protects. Cross-section area of the conductor
may range from 8.4 mm2 to 21 mm2 or larger. [Converting the SI sizes to AWG the
Chapter recommends a range from #8 AWG to #4 AWG copper wire.] It should be a
continuous conductor and connected to each fixture, light base and ground rod or
connection along its route.” (34b)
Chapter 4.2.3.h of the ICAO Aerodrome Design Manual Part 5, “Separation between
Cables” states; “Ground wire and counterpoises should be approximately 15 cm [ 6”]
above the uppermost level of cables.” (34c)
6.6
NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) REQUIREMENTS
NFPA 70, National Electrical Code (25a)
“bonding (bonded) - The permanent joining of metallic parts to form an electrically
conductive path that ensures electrical continuity and the capacity to conduct safely any
current 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 the
equipment grounding conductor.” (25a)
“bonding jumper, main - The connection between the grounded circuit conductor and
the equipment grounding conductor at the service.” (25a)
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“ground - A conducting connection, whether intentional or accidental, between an
electrical circuit or equipment and the earth or to some conducting body that serves in
place of the earth.” (25a)
“grounded - Connected to earth or to some conducting body that serves in place of the
earth.” (25a)
“grounded, effectively - Intentionally connected to earth through a ground connection or
connections of sufficiently low impedance and having sufficient current-carrying capacity
to prevent the buildup of voltages that may result in undue hazards to connected
equipment or to persons.” (25a)
“grounded conductor - A system or circuit conductor that is intentionally grounded.”
(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 non–currentcarrying metal parts of equipment, raceways, and other enclosures to the system
grounded conductor, the grounding electrode conductor, or both, at the service
equipment or at the source of a separately derived system.” (25a)
“grounding electrode conductor - The conductor used to connect the grounding
electrode(s) to the equipment grounding conductor, to the grounded conductor, or to
both, at the service, at each building or structure where supplied from a common
service, 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 a
component of a lightning protection system that is intended to significantly reduce
potential difference created by lightning currents.” (24d)
“bonding conductor – A conductor used for potential equalization between grounded
metal 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 providing
electrical 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 system of
strike termination devices, conductors, ground terminals, interconnecting conductors,
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surge suppression devices, and other connectors or fittings required to complete the
system.” (24d)
“loop conductor – A conductor encircling a structure that is used to interconnect ground
terminals, main conductors or other grounded bodies.” (24d)
“sideflash – An electrical spark, caused by differences of potential, that occurs between
conductive metal bodies or between conductive metal bodies and a component of a
lightning protection system or ground.” (24d)
“strike termination device – A component of a lightning protection system that intercepts
lightning flashes and connects them to a path to ground. Strike termination devices
include air terminals, metal masts, permanent metal parts of structures as described in
Section 4.9, and overhead ground wires installed in catenary lightning protection
systems.” (24d)
“zone of protection – The space adjacent to a lightning protection system that is
substantially immune to direct lightning flashes.” (24d)
“common grounding – All grounding media in or on a structure shall be interconnected
to provide a common ground potential. This shall include lightning protection, electric
service, telephone and antenna system grounds, as well as underground metallic piping
systems. Underground metallic piping systems shall include water service, well casings
located within 25 feet (7.6 m) of the structure, gas piping, underground conduits,
underground liquefied petroleum gas piping systems, and so on. Interconnection to a
gas line shall be made on the customer’s side of the gas meter. Main-size lightning
conductors shall be used for interconnecting these grounding systems to the lightning
protection system.” (24e)
“ground level potential equalization – All grounded media in and on a structure shall be
connected to the lightning protection system within 12 feet (3.6 m) of the base of the
structure in accordance with Section 4.14.” (24f)
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7. LIGHTNING PROTECTION
DISCUSSION
7.1
WHAT WE HAVE LEARNED SO FAR
1.
Lightning strikes originate 15,000 to 20,000 feet above sea level. The strike
comes to earth in 50 yard steps. Within 30 to 50 yards of ground the lightning
strike determines the attachment point.
2.
Lightning strikes include current levels approaching 400 kA. The average stoke
current ranges from 25 kA to 40 kA.
3.
Stroke currents will divide up among all parallel conductive paths between the
attachment point(s) and earth. Division of the current will be inversely
proportional to the path impedance.
4.
Lightning is a current source; output current is independent of load impedance. If
the 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 can
occur 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 flash
extends 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 $5
billion in damages each year.
9.
Each facility should undergo a lightning risk assessment.
10.
Lightning strikes cannot be prevented. Lightning can only be intercepted or
diverted to a path that, if well designed and constructed, will not result in
damage.
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 lightning
protection system. The NEC 25 ohm maximum earth resistance requirement
may not be adequate.
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7.2
AIRFIELD LIGHTING SYSTEM LIGHTNING PROTECTION METHODS
There are currently two widely accepted airfield lighting system lightning protection
methods.
Method 1 - The first method centers about the interconnection of all metallic
components via the counterpoise. The counterpoise system is connected to the earth
electrode system (EES) at the airfield lighting vault. For simplicity of discussion we will
refer to this method as the “old method” since this method is described in the current
editions of FAA-STD-019d and AC 150/5370-10A.
Method 2 - The second method recommends not connecting the counterpoise to the
base can or fixture stake and includes the installation of a “safety ground”. The safety
ground consists of “a” or “b” below:
a.
b.
A bonding conductor installed between the base can or fixture stake and
an electrode installed adjacent to the fixture.
A conductor within the duct system, bonded to each base can or mounting
stake. The safety ground conductor is connected to the EES at the airfield
lighting vault.
The counterpoise, when installed for conductors adjacent to pavement (edge light
circuits), 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 or
touchdown zone lights.
We will refer to this method as the “new method” since this method is described in AC
150/5340-30 and DRAFT AC 150/5370-10B.
7.3
BASIS OF LIGHTNING STRIKE SCENARIOS DESCRIBED BELOW
The following scenarios will address the advantages and disadvantages of the old and
new methods. The behavior of lightning cannot be predicted with absolute accuracy.
Earth impedance and the variation in lightning frequencies (kHZ to mHZ range) make it
difficult to characterize lightning’s behavior on the ground. (35) Site unique conditions
will also impact the lightning’s behavior.
We are also assuming that the counterpoise conductors installed for either method have
a low 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 high
impedance to a lightning strike. The base cans or mounting stakes are grounded by
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virtue of their being installed in the earth. However the base cans or mounting stakes
without supplemental ground connections would present a higher than desired
impedance to a lightning strike.
In each scenario we will be assuming an average lightning strike between 25 kA and 40
kA, we can expect radial arcing up to 65 feet from the strike attachment point. It is
estimated that less than 15% of a lightning strike’s current penetrates the earth. (6)
The following three figures may be used to follow each of the lightning strike scenarios.
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7.4
SCENARIO # 1 – LIGHTNING STRIKES ADJACENT TO EDGE LIGHT
CIRCUIT – EDGE LIGHT IS OUTSIDE AREA OF RADIAL ARCING
Old method – The counterpoise wire and grounded base can should divert the strike
current that penetrates the earth away from the airfield lighting system. The
counterpoise conductor being buried in the earth will bleed off the strike current
throughout 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 the
isolation transformer and airfield lighting system cables. Minimal damage to the one
fixture 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 earth
away from the airfield lighting system. The base can should act as a Faraday Cage and
should 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) in
Florida will have an earth resistance of approximately 26 ohms (parallel resistance
formula X multiplier 1.16). An average lightning strike of 25 kA (15% penetrates the
earth) 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 several
microseconds. This could couple a high voltage on the airfield lighting circuit
conductors resulting in a strain on the airfield lighting conductor insulation.
New method, with safety ground conductor - The counterpoise wire should divert
some 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 base
can. This potential difference could result in arcing and the boiling away of the moisture
in the soil. The impedance of the lightning circuit will determine the current split
between the counterpoise and the base can. We will assume an average strike current
of 25 kA, 15% (3.75 kA) of which penetrates the earth. For discussion purposes lets
assume the counterpoise carries 90% of the current and the base can carries the
balance. The #6 AWG copper safety ground conductor will be asked to carry 375 A for
the duration of the strike. The #6 copper conductor should be able to safely carry the
375 A for the short duration of the strike. However, a voltage will be coupled into the
airfield 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 as
used in the previous scenario would result in a 1500 A current in the safety ground.
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7.5
SCENARIO # 2 – LIGHTNING STRIKES ADJACENT TO EDGE LIGHT
CIRCUIT – EDGE LIGHT IS WITHIN AREA OF RADIAL ARCING
Old method – The surface arcing will travel across the earth in all directions from the
point of strike attachment. The impedance of the strike 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 wire and grounded base can should divert the
strike current away from the airfield lighting system. The base can should act as a
Faraday Cage and should normally protect the isolation transformer and airfield lighting
system cables. The counterpoise conductor could be asked to carry the strike current
for a short time. The counterpoise conductor being buried in the earth will bleed off the
strike 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 earth
in all directions from the point of strike attachment. The impedance of the strike
attachment 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 grounded
base can should divert the strike current away from the airfield lighting system. The
base can should act as a Faraday Cage and should normally protect the isolation
transformer and airfield lighting system cables. However, because of the 26 ohm earth
resistance there could be a significant voltage drop across the base can to earth
interface. 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 across
the earth in all directions from the point of strike attachment. The impedance of the
strike 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 wire
should divert some of the strike current 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 the strike current away from the airfield lighting system
conductors. The surface arcing that has connected to the edge light base plate will be
conducted to the safety ground conductor, via the base can. The safety ground
conductor is routed with the airfield lighting circuit conductors. The safety ground
conductor has no way to bleed off the strike current until it 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 safety ground could be destroyed. The
destruction of the safety ground could damage the airfield lighting circuit conductors.
The current in the safety ground could also induce significant voltage into the airfield
lighting circuit resulting in constant current regulator (CCR) damage. Damage to the
one or more fixtures could be expected.
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7.6
SCENARIO # 3 – LIGHTNING DIRECTLY STRIKES TOP OF ELEVATED
EDGE LIGHT
Old method – Strike current divides among all conductive paths. The impedance of the
strike attachment will determine the amount of current that each branch carries. The
counterpoise wire and grounded base can should divert the majority of the strike current
away from the airfield lighting system. The counterpoise conductor could be asked to
carry the strike current for a short time. The counterpoise conductor being buried in the
earth will bleed off the strike current throughout its length. The average current decay
rate is approximately 1% per meter. (36a) 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 primary and airfield lighting circuit conductors. This scenario would
probably result in the destruction of the fixture, L-830 transformer and require cable
replacement 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 that
each branch carries. The earth electrode and grounded base can should divert most of
the strike current away from the airfield lighting system. However, because of the 26
ohm earth resistance there could be a significant increase in the amount of voltage
coupled into the L-830 transformer and primary circuit, versus the old method, resulting
in additional damage to the airfield lighting system.
New method, with safety ground conductor - Strike current divides among all
conductive paths. The impedance of the strike attachment will determine the amount of
current that each branch carries. The counterpoise wire should divert some of the strike
current 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 the
strike current away from the airfield lighting system conductors. The strike current that
has connected to the edge light will be conducted to the safety ground conductor, via
the base can. The safety ground conductor is routed with the airfield lighting circuit
conductors. The safety ground conductor has no way to bleed off the strike current until
it 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 safety
ground could be destroyed. The destruction of the safety ground could damage the
airfield lighting circuit conductors. The current in the safety ground could also induce
significant 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 primary
and airfield lighting circuit conductors. This scenario would probably result in the
destruction of the fixture, all L-830 transformers and cables within the limits of the safety
ground wires ability to bleed off the strike current.
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7.7
SCENARIO # 4 – LIGHTNING DIRECTLY STRIKES TOP OF SEMIFLUSH
CENTERLINE FIXTURE, COUNTERPOISE IS CONNECTED TO BASE CANS
AS REQUIRED BY OLD AND NEW METHODS
Old method – Strike current divides among all conductive paths. The impedance of the
strike attachment will determine the amount of current that each branch carries. The
counterpoise wire and grounded base can should divert the majority of the strike current
away from the airfield lighting system. The counterpoise conductor could be asked to
carry the strike current for a short time. The counterpoise conductor being buried in the
earth will bleed off the strike current throughout its length. The average current decay
rate is approximately 1% per meter. (36a) 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 primary and airfield lighting circuit conductors. This scenario would
probably result in the destruction of the fixture, L-830 transformer and require cable
replacement to the next fixture.
New method, with safety ground rod - The new method for the centerline fixtures also
has the counterpoise connected to each base can. The outcome should be similar to
the old method discussed above.
New method, with safety ground conductor – The new method for the centerline
fixtures also has the counterpoise connected to each base can. However the safety
ground will also carry some of the strike current. A portion of the strike current that has
connected to the base can will be conducted to the safety ground conductor, via the
base can. The safety ground conductor is routed with the airfield lighting circuit
conductors. The safety ground conductor has no way to bleed off the strike current until
it 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 safety
ground could be damaged. The damage to the safety ground could damage the airfield
lighting circuit conductors. The current in the safety ground could also induce significant
voltage into the airfield lighting circuit resulting in cable insulation stresses and possible
CCR damage.
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8. SAFETY GROUNDS
The safety ground implemented in AC 150/5340-30 has its roots in NFPA 70, The
National 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 cable
with the ungrounded conductors. An explanatory note in the NEC Handbook states;
“One of the functions of an equipment grounding conductor is to provide a lowimpedance ground-fault path between a ground fault and the electrical source. This
path allows the overcurrent protective device to actuate, interrupting the current. To
keep the impedance at a minimum, it is necessary to run the equipment grounding
conductor within the same raceway or cable as the circuit conductor(s). This practice
allows the magnetic field developed by the circuit conductor and the equipment
grounding conductor to cancel, reducing their impedance. Magnetic flux strength is
inversely proportional to the square of the distance between two conductors. By placing
an equipment grounding conductor away from the conductor delivering the fault current,
the magnetic flux cancellation decreases. This increases the impedance of the fault
path and delays operation of the protective device.”
AC 150/5345-10E, Specification for Constant Current Regulators and Regulator
Monitors, October 16, 1984, requires CCRs 10 kW and larger to have overcurrent
protection. The overcurrent protective device is required to open the primary switch
within 5 seconds for a 5% overcurrent and within 1 second of a 25% overcurrent. This
overcurrent protection is not dependant upon a grounding conductor enclosed in the
same conduit as the airfield lighting circuit conductors.
The NEC is based upon a voltage source system. Airfield lighting circuits powered by a
CCR are a current source system. The requirement for the grounding conductor to be
routed in the same raceway with the ungrounded conductors is not applicable. As
shown in the previous scenarios the inclusion of the safety ground with the series circuit
conductors can actually increase damage to the system.
The counterpoise routed over the duct and bonded to each base can provides the same
electrical grounding function as the safety ground without increasing the possibility of
damage from lightning.
The term “safety ground” as described in 150/5340-30 may also be a placebo. The
specified GE RTV-118 self-leveling sealant used to seal between components is an
insulator.
On a newly installed L-868 base can at Orlando International airport the resistance
between base can components was measured and recorded. The base can sections
are installed in accordance with the applicable FAA Advisory Circulars.
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a.
b.
Resistance between L-868B bottom base can section and top base can
section. Zero ohms. This connection is bolted.
Resistance between top can section and top of the third spacer ring.
Greater than 1000 ohms! This connection is bolted only when the fixture
is installed. It is expected that the resistance between the bolted fixture
and 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 I
removed the last bolt.”
PHOTO OF NEWLY INSTALLED TAXIWAY CENTERLINE
LIGHT ON TAXIWAY F AT ORLANDO INTERNATIONAL AIRPORT
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9. 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 Army
Airfield. 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 the
accident. The base was renamed McCoy Air Force Base on May 7, 1958 in Colonel
McCoy’s honor.
In 1970 McCoy Air Force Base started scheduled commercial air carrier service. The
initial air carriers were Delta Airlines, Eastern Airlines, National Airlines and Southern
Airlines.
In 1974 McCoy Air Force Base (MCO) was closed and the deed was transferred to the
City of Orlando. In 1975 The Greater Orlando Aviation Authority (GOAA) is created by
a special legislative act. In 1976 the airport is renamed Orlando International Airport.
GOAA inherited a 1950’s vintage airfield lighting system. Lightning damage at MCO
was a significant maintenance problem. Orlando is located in the lightning capital of the
United States. In 1987, the design of the New Third Runway (R/W 17-35), GOAA
personnel and the design team researched FAA design standards and utility design
standards to implement the best lightning protection system available.
The design included a #6 AWG copper counterpoise routed over the center of each
underground duct/conduit. The counterpoise was bonded to each base can and ground
rods were installed at 500 foot maximum intervals. The counterpoise was also bonded
to the base can rebar cages, manholes and all metallic elements within the airfield
lighting system. Each ground rod was designed to have an earth resistance not to
exceed 5 ohms. In addition a 4/0 AWG copper ground grid was installed under the
pavement. The 4/0 grid consisted of roughly 500 foot interconnected squares with a
ground rod at each corner. The counterpoise was bonded to the 4/0 grid at every
crossing. The counterpoise and ground grid were both connected to the airfield lighting
vault EES. The airfield lighting vault’s lightning protection was designed in accordance
with NFPA 780. Each CCR was specified with input and output lightning protection.
Transient voltage surge suppression (TVSS) was provided for all sensitive or critical
loads. The goal was to achieve minimum earth impedance to a lightning strike and to
provide maximum reliability for the airfield lighting system. The Runway 17-35 was
opened in 1989.
While exact quantities of items damaged by lightning were not kept, GOAA
Maintenance soon noticed the Third Runway was not suffering the severity of lightning
damage of either of the other two runways.
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In the 1990’s the two existing military runways were rehabilitated. Experience dictated
that the rehabilitation of the two runways include the same lightning protection
measures incorporated for the Third Runway. Again GOAA Maintenance noticed a
significant drop in the amount of damage caused by lightning.
In 2000 design of the Fourth Runway was started.
proven lightning protection measures.
Again the design included the
In 2001 the local electric utility company referenced a study, which is quoted as stating
that a #4 AWG copper wire is the smallest copper conductor that typically will not
vaporize when struck by a direct high intensity lightning stroke. The #6 copper
counterpoise 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 size
that will survive the intense heat generated by the high voltage and current in a lighting
strike.
Although attempts have been made to obtain a copy of the study, we have not been
able to locate the paper.
Independently we have been able to verify the
recommendation for using a #4 AWG copper counterpoise. The Standard Handbook
For 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 author’s records, is a No. 4 solid copper conductor.” This reference is
for an overhead ground wire (used for lightning protection) on overhead electrical
distribution/transmission lines.
The counterpoise size for the 4th Runway was changed from a #6 AWG copper to a #4
AWG copper based upon the utility’s information.
The 4th Runway was opened to air carrier traffic on December 25, 2003. The following
photos are an overview of the 4th Runway lightning protection.
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4th RUNWAY SITE WITH AIRFIELD LIGHTING
VAULT LIGHTNING PROTECTION
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4th RUNWAY SITE WITH 4/0 AWG
COPPER GROUND GRID
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4th RUNWAY SITE WITH #4 AWG COPPER COUNTERPOISE
AND 4/0 COPPER GROUND GRID
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10.
RECOMMENDATIONS
1.
Perform a Lightning Risk Assessment for each airfield lighting system.
2.
Implement lightning protection measures in according with the results of the
lightning risk assessment.
3.
Delete requirement for “safety ground” within conduit with series circuit
conductors.
4.
Require counterpoise (safety ground) to be routed above duct/conduit and
bonded to each base can, rebar and all metallic items making up the airfield
lighting 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 ground
rod to counterpoise.
7.
Minimum size of copper counterpoise - #4 AWG.
8.
Recommend maximum earth resistance of 10 ohms.
resistance 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 critical
loads.
10.
Explore addition of bonding jumper between fixture and bolted base can section.
11.
Explore requirement for all frangible couplings to be conductive or require
bonding jumper.
11.
NEC maximum earth
SUMMARY
The design and installation of a quality lightning protection system is critical to today’s
airport lighting systems. The lightning protection system is as important to the airfield
lighting system as the actual lighting circuit wiring.
Without proper lightning protection the airfield lighting systems can incur frequent and
substantial outages. The cost of a well designed and installed lightning protection
system is minimal when compared with component repair and replacement, runway or
taxiway 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, Web
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http://www.nssl.noaa.gov/researchitems/lightning.shtml
2 A lightning Primer, National Aeronautics and Space Administration's (NASA)
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http://thunder.msfc.nasa.gov/
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Ph.D. Professor of the Department of Electrical and Computer Engineering,
University of Florida, Gainesville.
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11 Electrical Protection Fundamentals, United States Department of Agriculture,
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(16b) Page 137; (16c) Page 159; (16d) Appendix 3 Page 12;
17 FAA-C-1391b, Installation and Splicing Of Underground Cables, January 1,
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18 FAA-STD-19b, Lightning and Surge Protection, Grounding, Bonding and
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19 FAA-STD-19d, Lightning and Surge Protection, Grounding, Bonding and
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(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;
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21 AC 150/5370-10A, Standards for specifying the Construction of Airports, Item L108, Installation of Underground Cable for Airports, 2/17/89
22 AC 150/5370-10B, Standards for specifying the Construction of Airports, Item L108, 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, 2004
Edition, 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, Figure
4.7.3.1(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 and
2002 National Fire Protection Association, Inc. (25a) Article 100; (25b) Article
250;
26 “Getting Down to Earth… A Manual on Earth Resistance Testing for the
Practical Man, Fifth Edition, February 1998, Copyright 1998, Distributor:
MeterCenter
(800)
230-6008,
http://www.biddlemegger.com/biddleug/GettingDownToEarth.pdf (26a) Page 12, Figure 4; (26b) Page 24, “How To
Improve Earth Resistance”; (26c) Page 12, “Nature of an Earth Electrode”;
27 Lightning Fatalities from 1990 through 2003, by Holle Meteorology and
Photography, 22 May 2004.
28 The Lightning Attachment Process and Risk Management of the Hazard, By
Richard Kithil, President & CEO, National Lightning Safety Institute.
29 AC 150/5340-24 Change 1, Runway and Taxiway Edge Lighting System, March
14, 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 Air
Navagation 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, Par
3.6.2.4; (34b) Page 5-80, Par 5.1.2.6; (34c) Page 5-64, Par 4.2.3;
Page 69 of 70
Lightning Protection for
Airfield Lighting Systems
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, Mirela
Bejleri, 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 Regulator
Monitors, October 16, 1984, (37a) Page 4, Par 3.3.9.2;
Page 70 of 70