Transcript Building is in the Zone of Protection?

2002
LIGHTNING PROTECTION
for
AIR FORCE FACILITIES
TSgt Gilbert Martinez
Det 1 PACAF-CES
Summary Slide
• INTRODUCTION
• REGULATORY
GUIDANCE
• MATERIAL
REQUIREMENTS
• STRIKE TERMINATION
DEVICES
• CONDUCTORS
• TYPES OF SYSTEMS
• ZONE OF
PROTECTION
• BONDING
• SIDEFLASH
REQUIREMENTS
• SURGE PROTECTION
• GROUND SYSTEMS
• INSPECTION AND
TESTING
• TEST PLANS AND
RECORD KEEPING
INTRODUCTION
The intent of this course is to familiarize and improve the
skills of personnel involved in the installation and
maintenance of lightning protection systems.
We will discuss the design, installation, and maintenance of
lightning protection systems for structures housing explosives
in accordance with applicable standards.
REGULATORY GUIDANCE
AFMAN 91-201 – Implements AF policy and DOD
6055.9 STD
It applies to everyone involved in any explosive
operation in the Air Force, and compliance is
mandatory. Chapter 2, Section D deals with;
Electrical Hazards; Hazardous locations (2.46), Electrical
Service (2.48), Static (2.51 & 2.52), Grounds (2.53), Lightning
Protection (2.54)
DOD 6055.9 STD – Defines minimum explosive
safety criteria for the design, maintenance, testing
and inspection of lightning protection systems.
REGULATORY GUIDANCE
AFI 32-1065 – Implements maintenance
requirements of DOD 6055.9 STD, chapter 7
“Lightning Protection” and assigns maintenance
responsibilities and requirements for grounding,
static, and lightning protection systems on Air Force
installations.
NFPA 780 – (1997 edition) Provides practical
safeguarding for persons and property from hazards
arising from exposure to lightning. Does not cover:
explosive manufacturing buildings and
magazines.
MATERIAL REQUIREMENTS

AFI 32-1065 Requirements

NFPA 780 Requirements

Main Conductor Example
MATERIAL REQUIREMENTS
AFI 32-1065 Requirements
14.1. General. Systems must comply with NFPA 780 and AFM 88-9,
Chapter 3, Electrical Design Lightning and Static Electricity Protection
(except as modified herein). Early streamer emission systems or charge
dissipation systems are not permitted. Parts and materials must carry the
Underwriters Laboratories (UL) label or equivalent. Otherwise, such
components must be approved by the MAJ-COM electrical engineer in
charge of lightning protection. Facilities in foreign countries may use host
nation codes and standards if they offer equivalent protection, as
determined by the MAJCOM electrical engineer with concurrence from HQ
AFCESA/CESE and approval of the DoD Explosive Safety Board (DDESB).
Otherwise, the Status of Forces Agreement (SOFA) must permit their use.
Where the SOFA requires compliance with host nation codes, translate
those required codes into English, make them available to all appropriate
personnel, and perform necessary training. Maintain all installed systems
according to this instruction. If not required, remove the system with
coordination through the using agency.
MATERIAL REQUIREMENTS
NFPA 780 Requirements
Material Requirements, Class I
Table 3.1.1 (a) NFPA 780
Buildings and Structures less than 75 feet in Height
Material Requirements, Class II
Table 3.1.1 (b) NFPA 780
Buildings and Structures greater than 75 feet in Height
MATERIAL REQUIREMENTS
Main Conductor Example
NO. 29R
Copper cable consisting of 29
strands of No. 16 AWG wire.
This cable has a cross-sectional
area of 72,500 cm and a weight
of 215 pounds per 1000 feet.
The outside diameter is
approximately 3/8".
STRIKE TERMINATION DEVICES

NFPA 780 Requirements

Air Terminal Height

Air Terminal Support

Chimneys and Vents
STRIKE TERMINATION DEVICES
NFPA 780 Requirements
3.6 Termination Devices shall meet material and size
requirements in accordance with NFPA 780
Table 3.1.1 (a) & (b)
Table 3.1.1(a) Minimum Class I Material Requirements
Copper
Type of Conductor
Air Terminal, Solid
Air Terminal, Tubular
Diameter
Diameter
Aluminum
Standard
Metric
Standard
3/8 in.
5/8 in.
9.5 mm
15.9 mm
1/2 in.
5/8 in.
Metric
12.7 mm
15.9 mm
Table 3.1.1(b) Minimum Class II Material Requirements
Copper
Type of Conductor
Air Terminal, Solid
Diameter
Standard
Metric
1/2 in.
12.7 mm
Aluminum
Standard
5/8 in.
Metric
15.9 mm
STRIKE TERMINATION DEVICES
3.6.1 Air Terminal Height
 The tip of an air terminal shall be not less than 10 in.
above the object or area it is to protect
• Air terminal exceeding 24 in. in height shall be
supported at a point not less than one-half its height.
 EXCEPTIONS
Strike termination devices shall not be required for
• Metal parts of a structure that are exposed to direct lightning flashes
and that have a metal thickness of 3 /16 in. or greater shall only
require connection to the lightning protection system.
(minimum of two paths to ground)
• Those parts of a structure located within a zone of protection.
STRIKE TERMINATION DEVICES
3.6.2
Air Terminal
Support
 Air terminals shall be
secured against
overturning by
attachment to the
object to be protected
or by means of braces
that shall be
permanently and rigidly
attached to the building.
STRIKE TERMINATION DEVICES
3.8.7 Chimneys and Vents
 Strike termination devices shall be required
on all chimneys and vents that are not located
within a zone of protection
 Chimneys or vents with a metal thickness of
3 /16 in. or more shall require only a
connection to the lightning protection system,
and shall be made using a main size lightning
conductor and a bonding device having a
surface contact area of not less than 3 in.
square, and shall provide two or more paths to
ground.
 Where only one strike termination device is required on a chimney or vent, at
least one main sized conductor shall connect the strike termination device to a
main conductor at the location where the chimney or vent meets the roof surface
and provides two or more paths to ground from that location
CONDUCTORS





One Way Path
Dead Ends
Substitution of Metals
“U” or “V” Pockets
Conductor Bends

Protection and
Securing


Location and Spacing

Connector Fittings
Structural Steel as
Down Conductors
CONDUCTORS
3.9.1 One Way Path
 Strike termination devices on
a lower roof level that are
interconnected by a conductor
run from a higher roof level
shall only require one horizontal
or down-ward path to ground
provided the lower level roof
conductor run does not exceed
40 ft.
CONDUCTORS
3.9.2 Dead Ends
 Strike termination devices shall be
Dead
permitted to be “dead ended” with
only one path to a main conductor
Ends
on roofs below the main protected
level provided the conductor run
from the strike termination device to
A
a main conductor is not more than
16 ft in total length and maintains a
horizontal or downward coursing.
A – Permissible total
conductor length not over
16 ft
CONDUCTORS
3.9.3 Substitution of Metals
 Metal parts of a structure, such as eave troughs, down
spouts, ladders, chutes, or other metal parts, shall not be
substituted for the main lightning conductor. Like-wise, metal
roofing or siding having a thickness of less than 3 /16 in.
(4.8 mm) shall not be substituted for main lightning conductors.
A – Permissible total
conductor length not over
16 ft
CONDUCTORS
3.9.4 “ U” or “ V” Pockets
 Conductors shall maintain a horizontal or downward
coursing free from “U” or “V” (down and up) pockets. Such
pockets, often formed at low-positioned chimneys, dormers,
or other projections.
 A down conductor shall be provided from the base of the
pocket to ground or to an adjacent down-lead run conductors,
and so on.
“U” or “V”
Pockets
Incorrect
Correct
CONDUCTORS
3.9.5 Conductor Bends
 Down conductors must
not have sharp bends or
loops.
Radius of Bend
R
Not less than 8 in.
 All bends must have a
radius of 8 inches or
greater and measure not
less than 90 degrees from
the inside of the bend.
90 Degrees min.
CONDUCTORS
3.9.6 Conductor Supports
3.9.11 Protecting Down Conductors
Conductor Supports
 Support or secure at intervals not to
exceed 3 ft.
Protecting Down Conductors
 Any down conductors subject to
mechanical damage must be protected
with a protective molding or covering
for a minimum of 6 ft above grade.
• If protective covering is metallic
tube/pipe the conductor must be
bonded to both ends of the
tube/pipe.
CONDUCTORS
3.9.7 Roof Conductors
 All main conductors will maintain a downward and
horizontal direction, never rising more than ¼ pitch.
3.9.8 Cross Run Conductors
 Required on flat and gently sloping roofs that exceed 50 ft
in width.
 Shall be connected to main perimeter cable at intervals not
exceeding 150 ft.
CONDUCTORS
3.9.10 Number of Down Conductors
 Pitched Roof Structures Less than 250 feet in Perimeter
• Minimum of two down conductors on opposite corners,
preferably all four corners
 Pitched Roof Structures More than 250 feet in Perimeter
• One down conductor for every 100 feet, or fraction of .
 Irregular- Shaped structures
• May require additional down conductors to provide two
paths to ground for each air terminal
 Flat or Gently Sloping Roofs
• Average distance between down conductors will be no
greater than 100 ft
CONDUCTORS
3.9.13 Down Conductors and Structural Columns
Structural steel shall be permitted to be utilized as the main
conductor of a LPS, IF it is electrically continuous, or it is
made so
 Air terminals
Shall be connected to the structural steel by direct
connection, by use of individual connectors through the
roof or walls to the frame work or by use of an exterior
conductor that interconnects all air terminals, “AND”
• Is connected to the steel frame work at intervals not
greater than 100 feet
 Ground terminals shall be connected approximately
every other steel column at intervals not to exceed 60 feet
CONDUCTORS
3.12 Connector Fittings
Connector fittings shall be used at all “ end-to-end,” “
tee,” or “ Y” splices of lightning conductors.
 They shall be attached so as to withstand a pull test of 200 lb
Conductor connections shall be of the bolted, welded, high compression, or
crimp-type. Crimp-type connections shall not be used with Class II
conductors.
CONDUCTORS
3.12 Connector Fittings
 Fittings used for required connections to metal bodies in or on a structure shall
be secured to the metal body by bolting, brazing, welding, or using highcompression connectors listed for the purpose.
Do not paint Down Conductor connectors unless they are the high compression
or exothermic (or welded) type.
TYPES OF SYSTEMS
• MAST SYSTEM
• CATENARY SYSTEM
• INTEGRAL SYSTEM
TYPES OF SYSTEMS
K.3.1 Mast-Type Systems
Mast-type systems should be designed as
specified in 6.3.3.2
 Each non-metallic pole must have two down
conductors and an air terminal extending at least
2 ft above the top of the pole, securely attached to
the pole, and connected to the grounding system
 Metal masts do not require air terminals and
down conductors, but must have two connections
to the grounding system.
 Separate each mast from any part of the facility
by at least the bonding distance or side flash
distance specified in Chapter 3 & 6 of NFPA 780,
but not less than 6 feet.
TYPES OF SYSTEMS
K.3.2 Overhead Wire (Catenary) Systems
 Each non-metallic pole
must have two down
conductors
 Each wire must be a
continuous run of at least
AWG No. 6 copper, or
equivalent.
 Separate each mast
from any part of the facility
by at least the bonding
distance or side flash
distance specified in
Chapter 3 & 6 of NFPA
780, but not less than 6 ft
Catenary systems
should be designed as specified in 6.3.3.2
TYPES OF SYSTEMS
K.3.2 Overhead Wire (Catenary) Systems
 Shall have an air terminal
extending at least 2 ft above
the top of the pole, securely
attached to the pole, and
connected to the grounding
system.
 Alternate grounding
method
The pole guy wire shall be
permitted to be used as the
down conductor.
TYPES OF SYSTEMS
K.3.3 Integral Systems
An integral lightning protection system is a system that
utilizes air terminals mounted directly on the structure to be
protected. These types of air termination systems are as
described in Chapter 3. Air terminal spacing should be
modified as necessary to provide a zone of protection defined
by a 100-ft (33-m) striking distance. Where an integral
lightning protection system is used to protect the structures
covered by this appendix, it is critical that the bonding
requirements of Chapter 3 be met. It is also
critical that a rigorous maintenance schedule be maintained
for this type of system
TYPES OF SYSTEMS
K.3.3 Integral Systems
 Pitched roofs shall be defined as
 A pitched roof with eaves
roofs having a span of 40 ft or less
and a pitch 1 /8 or greater; and roofs
having a span of more than 40 ft and
a pitch 1 /4 or greater. All other roofs
shall be considered flat or gently
sloping.
height of 50 ft or less above
grade shall require protection for
the ridge only when there is no
horizontal portion of the building
that extends beyond the eaves,
other than a gutter.
TYPES OF SYSTEMS
K.3.3 Integral Systems
 Each air terminal
A - 50 ft maximum spacing between air
terminals
B – 150 ft maximum length of cross run
conductor permitted without a connection to
the main perimeter or down conductor
C – 20-25 ft maximum spacing between air
terminals along edge
must have at least two
paths to ground.
 Air terminals shall be
located within 24 inches
of roof edge
 Each building must
have a minimum of two
down conductors, one
each at opposite
corners (one each on
all corners is preferred).
ZONE OF PROTECTION
NFPA 780 2.1.39 The space adjacent to a lightning
protection system that is substantially immune to
direct lightning flashes.
AFI-32-1065 also states that is necessary to provide
a zone of protection defined by a 100-ft (33-m)
striking distance.
ZONE OF PROTECTION



100 Foot Rolling Ball
Theory
Proper Air Terminal
Placement
Proper Air Terminal
Spacing

Structures that do not
exceed 25 ft above earth

Structures that do not
exceed 50 ft above earth

Mast Systems Formula
 Example Question
 Student Exercises
 Catenary Systems Formula
 Student Exercises

Integral Systems Formula
 Student Exercises
ZONE OF PROTECTION
3.7.3 100 Foot Rolling Ball Theory
100 ft
Radius
The zone of protection shall include the space not intruded by a rolling sphere
having a radius of 100 ft. When the sphere is tangent to earth and resting
against a strike termination device, all space in the vertical plane between the
two points of contact and under the sphere are in the zone of protection.
ZONE OF PROTECTION
3.8 Proper Air Terminal Placement
INCORRECT
CORRECT
Improper spacing from
edge of roof
Proper spacing from edge
of roof
Air terminal 4’ from edge
Air terminal no more than 2’
from edge
The zone of protection shall include the space not intruded by a rolling sphere
having a radius of 100 ft. When the sphere is tangent to earth and resting
against a strike termination device, all space in the vertical plane between the
two points of contact and under the sphere are in the zone of protection.
ZONE OF PROTECTION
3.8 Proper Air Terminal Spacing
Proper spacing
between air terminals
Improper spacing
between air terminals
Air terminals 2’
long and
Spaced 20-25’
along edge and
50’ maximum
spacing
A zone of protection is also formed when such a sphere is resting on two
or more strike termination devices and shall include the space in the
vertical plane under the sphere and between those devices.
ZONE OF PROTECTION
3.7.2.1 Structures that do not
exceed 25 ft above earth
 Considered to protect lower portions of a structure located in a
one-to-two zone of protection as shown below.
The zone of protection shall form a cone having an apex at the highest
point of the strike termination device, with walls forming approximately a
22.5 degree angle from the vertical.
2
1
2
1
25 ft
25 ft
ZONE OF PROTECTION
3.7.2.2 Structures that do not
exceed 50 ft above earth
Considered to protect lower portions of a structure located in a
one-to-one zone of protection as shown below
 The zone of protection shall form a cone having an apex at the highest
point of the strike termination device, with walls forming approximately a
45-degree angle from the vertical.
1
1
1
1
50 ft
50 ft
ZONE OF PROTECTION
6.3 Mast Systems Formula
Formula Based on
mast height and
100 ft Ball Theory
Center for_____ height
25
50 75 100
100
100
75
D=
h1 (200-h1) -
100
h2 (200-h2)
D = horizontal distance (ft)
50
75
H1 = height of the pole mast
(ft)
H2 = height of structure (ft)
25
50
25
25
50
75
Horizontal distance (ft)
100
ZONE OF PROTECTION
Mast Systems
Example Question
Mast Height VS Building Size
D=
h1 (200-h1) -
h2 (200-h2)
D = horizontal distance (ft)
H1 = height of the pole mast (ft)
100 ft Radius
H2 = height of structure (ft)
80 Foot Mast
60 ft long and 26 ft high building
ZONE OF PROTECTION
Mast Systems
Example Question Answer
D = horizontal distance (ft)
D=
h1 (200-h1)
-
h2 (200-h2)
80 x (200-80) -
26 x (200-26)
80 x 120
-
26 x 174
9,600
-
4,524
97.97
-
67.26
=
30.71
60 / 2 = 30
H1 = height of the pole mast (ft)
H2 = height of structure (ft)
Mast Height
80 Feet
Building Size
60 Ft Long
26 Ft High
Building is in the Zone of Protection?
ZONE OF PROTECTION
Mast Systems
Student Exercise 1
D=
h1 (200-h1) -
h2 (200-h2)
D = horizontal distance (ft)
H1 = height of the pole mast (ft)
H2 = height of structure (ft)
Mast Height
Building Size
85 feet
60 Ft Long
28 Ft High
Is the building in the Zone of Protection?
ZONE OF PROTECTION
Mast Systems
Student Exercise Answer 1
D = horizontal distance (ft)
D=
h1 (200-h1)
-
h2 (200-h2)
85 x (200-85)
-
28 x (200-28)
85 x 115
-
28 x 172
9,775
-
4,816
98.86
-
69.39
=
29.47 ft
60 / 2 = 30 ft
H1 = height of the pole mast (ft)
H2 = height of structure (ft)
Mast Height
85 Feet
Building Size
60 Ft Long
28 Ft High
Building is not in the Zone of Protection?
ZONE OF PROTECTION
Mast Systems
Student Exercise 2
D=
h1 (200-h1) -
h2 (200-h2)
D = horizontal distance (ft)
H1 = height of the pole mast (ft)
H2 = height of structure (ft)
Mast Height
Building Size
90 feet
40 Ft Long
38 Ft High
Is the building in the Zone of Protection?
ZONE OF PROTECTION
Mast Systems
Student Exercise Answer 2
D = horizontal distance (ft)
D=
h1 (200-h1)
-
h2 (200-h2)
90 x (200-90)
-
38 x (200-38)
90 x 110
-
38 x 162
9,900
-
6,156
99.49
-
78.46
=
21.03 ft
40 / 2 = 20 ft
H1 = height of the pole mast (ft)
H2 = height of structure (ft)
Mast Height
90 Feet
Building Size
40 Ft Long
38 Ft High
Building is in the Zone of Protection?
ZONE OF PROTECTION
6.3 Catenary Systems Formula
D=
h1 (200-h1) h2 (200-h2)
D = horizontal distance (ft)
H1 = height of the mast
H2 = height of the lower
mast (object concerned)
(ft)
ZONE OF PROTECTION
Catenary Systems
Student Exercise 3
D=
h1 (200-h1) -
h2 (200-h2)
D = horizontal distance (ft)
H1 = height of the higher
mast
H2 = height of the lower
mast (object concerned)
(ft)
H1 = 100 ft
15 ft
50 ft
H2 = 50 ft
Is the object in the Zone of Protection?
ZONE OF PROTECTION
Catenary Systems
Student Exercise Answer 3
D=
h1 (200-h1)
D = horizontal distance (ft)
-
h2 (200-h2)
100 x (200-100) -
50 x (200-50)
H1 = height of the higher mast
100 x 100
-
50 x 150
H2 = height of the lower mast
(object concerned) (ft)
10,000
-
7,500
100
-
86.60
=
13.4 ft
H1 = 100 ft
H2 = 50 ft
Object is not in the
Zone of protection?
15 ft
50 ft
ZONE OF PROTECTION
Catenary Systems
Student Exercise 4
D=
h1 (200-h1) -
h2 (200-h2)
D = horizontal distance (ft)
H1 = height of the higher
mast
H2 = height of the lower
mast (object concerned)
(ft)
H1 = 90 ft
12 ft
30 ft
H2 = 30 ft
Is the object in the Zone of Protection?
ZONE OF PROTECTION
Catenary Systems
Student Exercise Answer 4
D=
D = horizontal distance (ft)
h1 (200-h1)
-
h2 (200-h2)
90 x (200-90)
-
30 x (200-30)
H1 = height of the higher mast
90 x 110
-
30 x 170
H2 = height of the lower mast
(object concerned) (ft)
9,900
-
5,100
99.49
-
71.41
=
28.08 ft
H1 = 90 ft
H2 = 30 ft
Object is in the Zone
of protection?
12 ft
30 ft
ZONE OF PROTECTION
Integral Systems Formula
D=
h1 (200-h1)
-
h2 (200-h2)
D = Horizontal
distance
H1 = height of the
higher roof (ft)
H2 = height of the
lower roof (ft)
100 ft
Radius
ZONE OF PROTECTION
Integral Systems
Student Exercise 5
D=
h1 (200-h1)
-
h2 (200-h2)
D = Horizontal distance
H1 = height of the higher roof
H2 = height of the lower roof (ft)
30 ft
85 ft
30 ft
Is the lower roof of the building in the Zone of Protection?
ZONE OF PROTECTION
Integral Systems
Student Exercise Answer 5
h2 (200-h2)
D = Horizontal distance
-
30 (200-30)
85 x (115)
-
30 x 170
H1 = height of the
higher roof
9,775
-
5,100
98.86
-
71.41
=
27.45
D=
h1 (200-h1)
D=
85 (200-85)
-
30 ft
H2 = height of the lower
roof (ft)
85 ft
30 ft
Building is not in the Zone of Protection?
ZONE OF PROTECTION
Integral Systems
Student Exercise 6
D=
h1 (200-h1)
-
h2 (200-h2)
D = Horizontal distance
H1 = height of the higher roof
H2 = height of the lower roof (ft)
20 ft
60 ft
25 ft
Is the lower roof of the building in the Zone of Protection?
ZONE OF PROTECTION
Integral Systems
Student Exercise Answer 6
h2 (200-h2)
D = Horizontal distance
-
25 (200-25)
60 x (140)
-
25 x 175
H1 = height of the
higher roof
8,400
-
4,375
91.65
-
66.14
=
25.51
D=
h1 (200-h1)
D=
60 (200-60)
-
20 ft
H2 = height of the lower
roof (ft)
60 ft
25 ft
Building is in the Zone of Protection?
BONDING
•
•
•
•
•
•
•
•
•
Bonding Defined
Material Requirements
Bonding Requirements
Determining the Necessity
of Bonding
Bonding Conditions
Condition 1 A
Condition 1 B
Condition 1 C
Condition 2
•
•
•
•
•
•
•
•
The Basic Bonding
Formula (BBF)
Condition 2 A and 2 B (1)
Condition 2 A
Condition 2 B (2)
Condition 3
Condition 3 Example
Bonding of movable
objects
Fences and Railroad
Tracks
BONDING
Bonding Defined
 Bonding is the electrical connection between an electrically
conductive object and a component of a lightning protection
system that is intended to significantly reduce the potential
differences created by lightning currents.
 The rational behind this is to prevent side flash (arcing)
between metal objects that could create a fire hazard.
 Basic requirements for bonding are found in AFI 32-1065
Attachment 3 & NFPA 780, 3.21
BONDING
Material Requirements
 Bonding Conductors shall meet material and size
requirements in accordance with NFPA 780 Table 3.1.1 a & b
Table 3-1.1(a) Minimum Class I Material Requirements
Copper
Type of Conductor
Standard
Bonding Conductor Cable, solid or stranded
Bonding Conductor, solid strip
Min size ea strand
Cross sect. Area
Min. size/Thickness width
17 AWG
26,240 CM
.051 in / ½ in
Table 3-1.1(b) Minimum Class II Material Requirements
Copper
Type of Conductor
Standard
Bonding Conductor Cable, solid or stranded
Bonding Conductor, solid strip
Min size ea strand
Cross sect. Area
Min. size/Thickness width
17 AWG
26,240 CM
.051 in / ½ in
BONDING
Bonding Requirements
 All conductors (piping, phone lines, power cables and etc) buried
underground for a minimum distance of 50 feet prior to entering the
building.
 Earth covered igloos- all metal objects, within side flash distance
bonded to the LPS.
 Grounded metal objects within side flash distance of a down conductor
Bonded to the down conductor.
 Isolated (Ungrounded) metal bodies located close to a lightning
conductor and to a grounded metal body bonded is bonded when within
side flash distance.
BONDING
Bonding Requirements
 Static ground systems located on interior walls opposite a down
conductor. (Recommend moving static system)
 Metal objects located outside the facility, within side flash distance of a
conductor, bonded to the conductor.
 All conductors NOT entering the facility, within side flash distance shall
be bonded to the LPS (fences, railroad tracks, above ground piping)
 All connections must be strong enough to withstand a pull test of 200
pounds.
 Steam, water and air conditioning lines may be run on the ground if
bonded to the facilities LPS before entering the structure.
BONDING
Determining the Necessity of Bonding
Bonding requirements depend on:
 The number of down conductors and their location
 The interconnection of other grounded systems
 Proximity of Grounded metal bodies to the down
conductors
 The flashover medium:
(either AIR or SOLID MATERIALS)
BONDING
Bonding Conditions
Three different conditions or situations dictate the
requirements for bonding within a structure
CONDITION 1 – Long Vertical Metal Bodies
CONDITION 2 – Grounded Metal Bodies
CONDITION 3 – Isolated Metal Bodies
BONDING
Condition 1 A
3.21.1 Long Vertical Metal Bodies
GREATER than 60 feet in height
A. Steel Framed Structures
 Grounded and ungrounded metal bodies shall be
bonded to structural steel members as near to their
extremities as possible unless inherently bonded
through construction “at these locations”
 To conductors “when” within side flash distance
BONDING
Condition 1 B
3.21.1 Long Vertical Metal Bodies
GREATER than 60 feet in height
B. Reinforced Concrete Structures:
where the rebar is interconnected, and grounded IAW
NFPA 780, Section 3.15.3
 Grounded and ungrounded metal bodies shall be
bonded to the LPS as near as practical to their
extremities, unless inherently bonded through
construction at these locations
BONDING
Condition 1 C
3.21.1 Long Vertical Metal Bodies
GREATER than 60 feet in height
C. Other Structures: (Composite)
 Bonding of grounded and ungrounded long vertical
metal bodies shall be determined by NFPA 780,
Sections 3.21.2 and 3.21.3
BONDING
Condition 2
3.21.2 Grounded Metal Bodies
Grounded metal bodies shall be bonded to the LPS when the
body is located within the distance “D” as determined by the
Basic Bonding Formula (BBF)
The “BBF” for grounded metal bodies will be used when:
 Grounded metal bodies are connected to the LPS at
“only one” extremity and:
 Branches of grounded metal bodies connected to
the LPS at their extremities if they change vertical
direction more than 12 feet
BONDING
The Basic Bonding Formula (BBF)
D = h/6n x Km
D = Minimum side flash distance between a grounded body
and a conductor at which a bond becomes necessary
h = Height of the building, or the vertical distance from the
bond being considered, to the nearest LPS bond
n = number of down conductors
Km = 1 if the flashover is through air, or 0.50 if through
dense material (concrete, brick, wood)
BONDING
The Basic Bonding Formula (BBF)
D = h/6n x Km
Grounded
object
(water pipe,
panel, etc…)
BONDING
Condition 2 A and 2 B (1)
Condition 2A – Structures 40 feet and less in height
Condition 2B (1) – Structures over 40 feet – bonding required within 60 ft
of the top of the structure
D = h/6n x Km
h = Height of the building, or the greatest vertical distance between the
bond being considered and the nearest other lightning Protection system
bond, (or to ground if no other bond is present)
n = number of down conductors spaced more than 25 feet apart and
located within 100 feet of the bond in question:
n = 1 (if only 1 down conductor); n = 1.5 (if only 2 down conductors); n =
2.25 (if 3 or more down conductors)
Km = 1 if the flashover is through air, or 0.50 if through dense material
(concrete, brick, wood)
BONDING
h = Height of the building, or the
Condition 2 A
Structures 40 feet and less in height
D = h/6n x Km
greatest vertical distance between
40/6 x 1.5(N) x 1(Km)
the bond being considered and the
= 9.99 ft
nearest other lightning Protection
system bond, (or to ground if no
Down conductors
30 ‘
other bond is present)
currently 3’ away
n = number of down conductors from grounded
spaced more than 25 feet apart
metal body
and located within 100 feet of the
bond in question:
n = 1 (if only 1 down conductor); n
40 ‘
= 1.5 (if only 2 down conductors); n
= 2.25 (if 3 or more down
conductors)
Km = 1 if the flashover is through
air, or 0.50 if through dense
material (concrete, brick, wood)
Must down conductors be bonded?
BONDING
Condition 2 B (2)
Structures over 40 feet – bonding required below 60 ft from
the top of the structure
D = h/6n x Km
h = The vertical distance between the bond being considered and the
nearest LPS bond, (or ground if no other bond is present)
n = The TOTAL number of down conductors in the LPS
Km = 1 if the flashover is through air, or 0.50 if through dense material
(concrete, brick, wood)
BONDING
Condition 2B (1) and 2B (2) Example
Condition 2B (1) – Structures over 40 feet – bonding required within 60 ft
of the top of the structure
Condition 2B (2) – Structures over 40 feet – bonding required below 60
ft from the top of the structure
D = h/6n x Km
Condition 2B (1)
D = 100/6 (1.5) x 1
60 ft
= 25 ft
100 ft
40 ft
30 ft
Condition 2B (2)
D = 30/6 (3) x 1
= 15 ft
BONDING
Condition 3 Example
3.21.3 Isolated (non-grounded) Metallic Bodies
Down Conductor
If a + b < Calculated bonding
distance, then bond A to B directly
A
D = h/6n x Km
40/6 x 1.5(N) x 1
= 9.99 ft
If a + b > Calculated bonding
distance, bonds not required
a
2 ft
Window Frame
b
4 ft
Grounded object
B
BONDING
Bonding of movable objects
 Bond Connections MUST BE of the flexible conductor or strap type
 When conductors are mechanically protected or concealed
conductors may be
No. 10 AWG copper
Otherwise
NO. 6 AWG copper wire or larger
 At least two separate flexible bonding straps will be provided
 Bonding Resistance – Maximum – 1 Ohm
 Replace Braided bonding wires excessively frayed – 1/2
BONDING
Fences and Railroad Tracks
Fences:
 Bond across gates and other discontinuities
 Shall be bonded to the Lightning Protection System (LPS) ground loop
conductor if they cross or come within 6 feet of the structure’s LPS
Railroad Tracks:
 All tracks within 6 feet of the LPS or sideflash distance
 Tracks that enter a facility shall be bonded to the frame of the structure
or equivalent
SIDEFLASH REQUIREMENTS

Mast Systems

Mast Systems Student Exercise

Catenary Wire to Structure

Catenary Wire to Structure
Student Exercise
SIDEFLASH REQUIREMENTS
6.3.3.3 Mast Systems
Sideflash distances – Mast to Structure
D = h/6
h = height of structure or the object under consideration
SIDEFLASH REQUIREMENTS
6.3.3.3 Mast Systems
Student Exercise 7
Sideflash distances – Mast to Structure
D = h/6
h = height of structure or the object under consideration
30 ft
SIDEFLASH REQUIREMENTS
6.3.3.3 Catenary Wire to Structure
D = L/6n
L = length of lightning protection conductor between its grounded point
and the point under consideration (closest to roof)
n = 1 where there is a single overhead conductor that exceeds 200 ft in
horizontal length
n = 1.5 where there is a single overhead wire or more than one wire
interconnected above the structure to be protected, such that only two
down conductors are located greater than 20 ft and less then 100 ft apart
n = 2.25 where there are more than two down conductors spaced more
than 25 ft apart within a 100-ft wide area that are interconnected above
the structure being protected
SIDEFLASH REQUIREMENTS
6.3.3.3 Catenary wire to Structure
Student Exercise 8
D = L/6n
95 ft
L = length of lightning protection
conductor between its grounded point
and the point under consideration
(closest to roof)
n = 1 where there is a single overhead
conductor that exceeds 200 ft in
horizontal length
185 ft
6 ft
n = 1.5 where there is a single overhead
wire or more than one wire
interconnected above the structure to be
protected, such that only two down
conductors are located greater than 20 ft
and less then 100 ft apart
n = 2.25 where there are more than two
down conductors spaced more than 25 ft
apart within a 100-ft wide area that are
interconnected above the structure being
protected
Does building meet sideflash requirements?
SIDEFLASH REQUIREMENTS
6.3.3.3 Catenary wire to Structure
Student Exercise Answer 8
D = L/6n
185/ 6x1.5
185/ 90 = 2.05 ft
L = length of lightning protection
conductor between its grounded point
and the point under consideration
(closest to roof)
95 ft
n = 1 where there is a single overhead
conductor that exceeds 200 ft in
horizontal length
185 ft
6 ft
n = 1.5 where there is a single overhead
wire or more than one wire
interconnected above the structure to be
protected, such that only two down
conductors are located greater than 20 ft
and less then 100 ft apart
n = 2.25 where there are more than two
down conductors spaced more than 25 ft
apart within a 100-ft wide area that are
interconnected above the structure being
protected
Building meets sideflash requirements?
SURGE PROTECTION
Lightning protection systems that protects structures that
HOUSE EXPLOSIVES shall include surge protection for all
incoming and exiting lines to include:
 Overhead or underground power lines
 Communication systems (instrumentation & intrusion detection)
 Television or radio antennas not necessarily restricted to associated
wiring systems and appliances
Therefore, such systems should be equipped with appropriate protective
devices, bonded to ensure a common potential, and must enter the facility
in shielded cables, or metallic conduits buried underground for a minimum
of 50 feet prior to entering the structure.
GROUND SYSTEMS
• Ground Terminals
• Ground Rods
• Ground Rod
Terminations
• Ground Rod Depth
• Concrete Encased
Electrodes
• Concrete Encased
Electrode Terminations
• Ground Ring Electrode
• Ground Ring Electrode
Terminations
• Shallow Topsoil
• Sandy Soil Conditions
• Combinations
• Common Grounding
GROUND SYSTEMS
3.13 Ground Terminals
Each down conductor shall terminate at a ground terminal
dedicated to the lightning protection system. The design,
size, depth, and number of ground terminals used shall
comply with 3.13.1 through 3.13.4 and AFI 32-1065.
 Electrical system and telecommunication grounding
electrodes shall not be used in lieu of lightning ground
electrodes.
 The down conductor(s) shall be attached permanently to
the grounding electrode system by bolting, brazing, welding,
or high-compression connectors listed for the purpose, and
clamps shall be suitable for direct burial.
GROUND SYSTEMS
3.13 Ground Terminals
 Ground terminals shall be copper-clad steel, solid copper,
hot-dipped galvanized steel, or stainless steel. Stainless
steel ground rods are prohibited by AFI 32-1065 A2.2.1
 Ground electrodes shall be installed below the frost line
where possible (excluding shallow topsoil conditions).
 Ground rods must be at least 10 feet long, made of not less
than 0.75 inch diameter pipe or equivalent solid rod made of
copper or copper clad steel.
GROUND SYSTEMS
Ground Rod Terminations
Attached to the ground rod by:
 Bolting (Clamps shall be suitable for direct soil burial)
 Exothermic Welding
 High-compression connectors listed for the purpose
GROUND SYSTEMS
3.13.1 Ground Rods
Ground rods shall be not less than 1 /2 in. (12.7 mm) in
diameter and 8 ft (2.4 m) long. Rods shall be free of paint or
other nonconductive coatings.
AFI 32-1065 Ground rods must be at least 10 feet long,
made of not less than 0.75 inch diameter pipe or equivalent
solid rod made of copper or copper clad steel.
GROUND SYSTEMS
3.13.1.1 Ground Rod Depth
 1 foot below grade
1 ft
 Not less than 10 feet deep
3 ft
 3 ft from building walls
 Spaced no closer than 10 feet
 Maximum of 25 ohms of earth resistance
10 ft
GROUND SYSTEMS
3.13.2 Concrete-Encased Electrodes

Shall only be used in new construction.

The electrode shall be located near the bottom of a concrete
foundation or footing that is in direct contact with the earth and shall
be encased by not less than 2 in. of concrete.
Encased electrode shall consist of;
A. Not less than 20 ft of bare copper main size conductor
OR
B. An electrode consisting of at least 20 ft of one or more steel
reinforcing bars or rods not less than 1 /2 in. diameter that have
been effectively bonded together by either welding or overlapping 20
diameters and securely wire-tying.
GROUND SYSTEMS
Concrete Encased Electrode Terminations
Shall be permanently attached to the encased system by;
 Bolting connectors listed for the purpose
 Exothermic Welding
 High-compression connectors listed for the purpose
GROUND SYSTEMS
3.13.3 Ground Ring Electrode
A ground ring electrode encircling
a structure shall be
NFPA 780 and
as shown in Figure 3.13.3, in AFI
direct
contact with earth
32-1065
at a depth of not less than 18 in. (457 mm) or
Attachment 2.2.1.4 and 4
encased in a concrete footing in accordance with
3.13.2. The encased electrode shall consist of not
less than 20 continuous ft (6.1 m) of bare copper
main-size conductor. The ground ring electrode shall
be not smaller than the equivalent of a main-size
lightning conductor.
AFI 32-1065 specifies AWG 1/0 copper
GROUND SYSTEMS
Ground Ring Electrode Terminations
Down conductors shall be permanently attached to the
ground ring by;
 Exothermic Welding
 High-Compression fittings
Connections shall be
Suitable for direct burial
 Bolting
 Brazing
GROUND SYSTEMS
3.13.7.1 Shallow Topsoil
Where bedrock is near the surface, the conductor shall be
laid in trenches extending away from the building at each
down conductor not less than 12 ft in length.
 Clay Soil – Buried 1- 2 ft in depth
 Sandy or Gravelly Soil – Buried 2 ft in depth.
If these methods prove impractical or impossible, bury
directly on bedrock a minimum distance of 2 ft from the
foundation or exterior footing. The cable shall terminate by
attachment to a buried copper ground plate at least 0.032 in.
thick and having a minimum surface area of 2 ft square
GROUND SYSTEMS
3.13.7.2 Sandy Soil Conditions
 Two or more ground rods, at not less
than 10-ft spacings
 1 foot below grade
 Not less than 10 feet deep
3 ft
12 inches
10 ft
 3 ft from building walls
 Maximum of 25 ohms of earth resistance
10 ft
GROUND SYSTEMS
3.13.7.2 Sandy Soil Conditions
Alternate Configurations
3 ft
3 ft
10 ft
GROUND SYSTEMS
3.13.6 Combinations
Combinations of the grounding terminals in Section
3.13 shall be permitted.
Common Grounding
All grounding media in, or on, a structure shall be
interconnected to provide a common ground
potential and bonding as per NFPA 780 and
AFI 32-1065
INSPECTION AND TESTING
 SCHEDULED MAINTENANCE
 VISUAL INSPECTIONS
 TESTING REQUIREMENTS
 TESTS PERFORMED
 GROUND RESISTANCE TEST
 CONTINUITY TEST
INSPECTION AND TESTING
Scheduled Maintenance
Scheduled Maintenance for Grounding Systems must be
done in accordance with AFI 32-1065 Table 1 Reference AFMAN 91-201
Lightning Protection (Base Civil Engineer Responsibilities)
Visual Inspections
12 months
Ground Resistance Check
24 months
Continuity Checks
24 months
INSPECTION AND TESTING
Visual Inspections
Must be accomplished in accordance with AFI 32-1065
Visual/physical inspection must determine if:
 The system is in good repair. No loose connections that might cause
high resistance joints.
 Corrosion or vibration has weakened any part of the system.
 Braided bonding wires are excessively frayed
(cross sectional area reduced by half).
 Ground wires on lightning protection masts are damaged by lawn
mowers or other equipment.
 Conductors and system components are securely fastened. Down
conductors, roof conductors, and ground terminals are intact.
 Additions or alterations to the protected structure require additional
protection.
INSPECTION AND TESTING
Testing Requirements
AFI-32-1065 Attachment 6 for resistance and continuity test
requirements for typical systems.
 Instruments must be able to measure 10 ohms +/- 10 percent for ground
resistance tests, and 1 ohm +/- 10 percent for continuity testing.
 Only instruments designed specifically for earth-ground systems are
acceptable for ground resistance testing.
 MAJCOM electrical engineer may modify the test procedures due to
local conditions, as long as the intent of the test is still achieved.
INSPECTION AND TESTING
Tests Performed
Grounding System Resistance Test (Earth Ohms Test)
 Use the procedure described in AFI 32-1065 or the procedure
recommended by the test instrument manufacturer except as modified by
AFI 32-1065.
 Periodic tests should be made at approximately the same time each
year to minimize confusion resulting from seasonal changes.
Continuity Tests
 If the resistance measured during continuity tests is greater than 1 ohm,
check for deficiencies and repair, then retest.
 When per-forming a continuity test over very long lengths of
conductors (more than 20m with no parallel paths), readings above one
ohm but less than 3 ohms may occur. This is acceptable.
INSPECTION AND TESTING
Ground Resistance Test
Fall of Potential Method
Potential
Distances X and Y Must Be
Greater Than D/2 But Not
Less Than 25 ft
Y
Probe
Current
X
Probe
Ground Rod
Service
Entrance
D
Ground Loop
Conductor
INSPECTION AND TESTING
Ground Resistance Test
Fall of Potential Method
Distances X and Y Must Be
Greater Than D/2 But Not
Less Than 25 ft
Ground Rod
Potential
Current
Probe
Probe
Y
X
Service
Entrance
D
X
1
Ground Loop
Conductor
2
INSPECTION AND TESTING
Ground Resistance Test
Fall of Potential Method
Distances X and Y Must Be
Greater Than D/2 But Not
Less Than 25 ft
Ground Rod
Potential
Current
Probe
Probe
Y
X
Service
Entrance
D
C1
P1 P2 C2
Ground Loop
Conductor
INSPECTION AND TESTING
Continuity Test
Ground Rod
OHM
Meter
1
4
Service
Entrance
2
Top of building
3
Ground Loop
Conductor
INSPECTION AND TESTING
Continuity Test
Ground Rod
1
OHM
Meter
4
Service
Entrance
2
Top of building
3
Ground Loop
Conductor
INSPECTION AND TESTING
Continuity Test
Static Buss Bars
Ground Rod
X
Service
X
X
Inside Building
Connect one lead to the
Ground rod and the
Other lead to the Static
Buss bars at all free ends
OHM
Meter
X
Entrance
Ground Loop
Conductor
TEST PLANS AND
RECORD KEEPING
• Test Plan Requirements
• Test Plan Sample Sketch
• Record Keeping Requirements
• Common Deficiencies
TEST PLANS
Requirements
 Developed by Organization performing inspections & tests
 Must include sketch of grounding and LPS test points
 Date action performed
 Name of person(s) performing tests
 General condition of components
TEST PLANS
Requirements Continued
 Condition of corrosion protection measures
 Resistance measurements at various Parts of ground
terminal system
 Discrepancies noted and corrective Actions taken with
dates of repairs
 Review Process
TEST PLANS
Sample Sketch
Include a facility drawing containing
 Building & area configuration
 Location of LPS components
 Test Point identification
TEST PLANS
Sample Sketch
BLDG. 10655
A
4
3
5
Current as of: 27 Mar 01
7
6
8
16
9
15
17
18
19
2
10
Service
1
B
14
13
12
11
OUTSIDE INSPECTION POINTS
Entrance
RECORD KEEPING
Requirements
 Use of locally generated form recommended
 Keep record for 6 inspection cycles for explosive facilities
 Records kept by organization performing tests and
inspections
 Copy of test results given to user
RECORD KEEPING
Common Deficiencies
 Several paths to ground exceed allowed rate of rise
 Air terminals with loose connections
 Air terminals over 24 inches from edge of roof
 Air terminals taller than 24 inches without required supports
 Down conductor not attached to cross run conductors
 Dissimilar metals to join system components
 Improper conductor radius of bend
 User did not have copies of test results