AS/NZS 1768(INT):2003

1 - AS/NZS 1768(Int):2003 LIGHTNING PROTECTION
4 - PREFACE
6 - CONTENTS
8 - SECTION 1 SCOPE AND GENERAL
8 - 1.1 SCOPE
8 - 1.2 APPLICATION
8 - 1.3 INTRODUCTION
9 - 1.4 REFERENCED DOCUMENTS
9 - 1.5 DEFINITIONS
9 - 1.5.1 Air terminal
9 - 1.5.2 Air terminal network
10 - 1.5.3 Base conductors
10 - 1.5.4 Bond (bonding conductor)
10 - 1.5.5 Damage
10 - 1.5.6 Direct lightning flash
10 - 1.5.7 Downconductor
10 - 1.5.8 Earth impedance (Z)
10 - 1.5.9 Earth potential rise (EPR)
10 - 1.5.10 Earthing boss (terminal lug)
10 - 1.5.11 Earthing conductor
10 - 1.5.12 Earthing electrodes (earth rods or ground rods)
10 - 1.5.13 Earthing resistance
10 - 1.5.14 Earth termination (earth termination network)
11 - 1.5.15 Electricity supply service earthing electrode
11 - 1.5.16 Explosive gas atmosphere
11 - 1.5.17 Finial
11 - 1.5.18 Frequency of lightning flashes direct to a service (Nc)
11 - 1.5.19 Frequency of lightning flashes direct to a structure (Nd)
11 - 1.5.20 Frequency of lightning flashes to ground near a service (NI)
11 - 1.5.21 Frequency of lightning flashes to ground near a structure (Nm)
11 - 1.5.22 Hazardous area
11 - 1.5.23 Incoming service
11 - 1.5.24 Indirect lightning flash
11 - 1.5.25 Internal installation
11 - 1.5.26 Joint
11 - 1.5.27 Lightning flash (lightning discharge)
12 - 1.5.28 Lightning flash density (Ng)
12 - 1.5.29 LPS (LPS Type I to IV)
12 - 1.5.30 Lightning protection zone (LPZ)
12 - 1.5.31 Lightning strike
12 - 1.5.32 Lightning strike attachment point
12 - 1.5.33 Lightning stroke
12 - 1.5.34 Loss
12 - 1.5.35 Multiple earthed neutral (MEN) system
12 - 1.5.36 Partial probability of damage (p)
12 - 1.5.37 Probability of damage (P)
12 - 1.5.38 Protection level (I to IV)
12 - 1.5.39 Protection measures
13 - 1.5.40 Resistibility
13 - 1.5.41 Risk (R)
13 - 1.5.42 Risk assessment
13 - 1.5.43 Risk component
13 - 1.5.44 Side flash
13 - 1.5.45 Special damage factors (kn)
13 - 1.5.46 Striking distance (ds)
13 - 1.5.47 Structure or object
13 - 1.5.48 Surge protective device (SPD)
13 - 1.5.49 Test link
13 - 1.5.50 Thunderday
13 - 1.5.51 Tolerable risk (Ra)
13 - 1.5.52 Zone of protection
14 - SECTION 2 ASSESSMENT AND MANAGEMENT OF RISK DUE TO LIGHTNING ANALYSIS OF NEED FOR PROTECTION
14 - 2.1 INTRODUCTION
14 - 2.2 SCOPE OF SECTION
14 - 2.3 CONCEPT OF RISK
14 - 2.3.1 General considerations
15 - 2.3.2 Types of risk due to lightning
15 - 2.3.3 Tolerable values of risk
16 - 2.4 DAMAGE DUE TO LIGHTNING
16 - 2.4.1 Causes of damage
17 - 2.4.2 Types of damage
17 - 2.4.3 Consequences of damage (types of loss)
19 - 2.5 RISKS DUE TO LIGHTNING
19 - 2.5.1 Risk components
20 - 2.5.2 Calculation of risk components
22 - 2.6 PROCEDURE FOR RISK ASSESSMENT AND MANAGEMENT
22 - 2.6.1 Procedure for risk assessment
23 - 2.6.2 Protection against direct lightning strikes if Rd > Ra
23 - 2.6.3 Protection against indirect lightning strikes if Rd <= Ra but Ri > Ra
24 - 2.6.4 Final check if Rd + Ri > Ra
24 - 2.7 RISK MANAGEMENT CALCULATION TOOL
25 - 2.7.1 General operation
25 - 2.7.2 Using the calculation tool in the risk management procedure
30 - SECTION 3 PRECAUTIONS FOR PERSONAL SAFETY
30 - 3.1 SCOPE OF SECTION
30 - 3.2 NEED FOR PERSONAL PROTECTION
30 - 3.3 PERSONAL CONDUCT
30 - 3.3.1 General
30 - 3.3.2 Outdoors
31 - 3.3.3 Indoors
32 - 3.4 EFFECT ON PERSONS AND TREATMENT FOR INJURY BY LIGHTNING
33 - SECTION 4 PROTECTION OF STRUCTURES
33 - 4.1 SCOPE OF SECTION
33 - 4.2 PROTECTION LEVEL
33 - 4.3 LPS DESIGN RULES
33 - 4.3.1 General
34 - 4.3.2 Rules for air terminals
34 - 4.3.3 Rules for downconductors
35 - 4.3.4 Rules for earth terminations
35 - 4.4 ZONES OF PROTECTION FOR LIGHTING INTERCEPTION
35 - 4.4.1 Basis of recommendations
35 - 4.4.2 Rolling sphere method (with a modification for large flat surfaces)
43 - 4.5 METHODS OF PROTECTION
43 - 4.5.1 Structural steel-framed buildings
43 - 4.5.2 Buildings without structural steel frames
45 - 4.5.3 Structures with flammable or explosive atmosphere
45 - 4.6 MATTERS TO BE CONSIDERED WHEN PLANNING PROTECTION
45 - 4.6.1 Structures to be erected
45 - 4.6.2 Design considerations
49 - 4.7 MATERIALS
49 - 4.7.1 General
49 - 4.7.2 Corrosion
53 - 4.8 FORM AND SIZE OF CONDUCTORS
53 - 4.8.1 Factors influencing selection
53 - 4.8.2 Electrical and thermal considerations
54 - 4.8.3 Mechanical strength and corrosion considerations
54 - 4.9 JOINTS
54 - 4.9.1 Effectiveness of joints
54 - 4.9.2 Protective covering
54 - 4.10 FASTENERS
55 - 4.11 AIR TERMINALS
55 - 4.11.1 General requirements
56 - 4.11.2 Protection of roofs
56 - 4.11.3 Protection of the sides of tall buildings
57 - 4.12 DOWNCONDUCTORS
57 - 4.12.1 Structures-General
57 - 4.12.2 Route
58 - 4.12.3 Mechanical damage
58 - 4.13 TEST LINKS
59 - 4.14 EARTH TERMINATIONS
59 - 4.14.1 General principles
59 - 4.14.2 Earthing resistance
61 - 4.14.3 Common earthing electrode and potential equalization
62 - 4.15 EARTHING ELECTRODES
62 - 4.15.1 General considerations
62 - 4.15.2 Connections to earthing electrodes
63 - 4.15.3 Inspection and testing of earthing electrodes
63 - 4.16 METAL IN AND ON A STRUCTURE
63 - 4.16.1 Use of metal in or on a structure as a part of the lightning protection system
64 - 4.16.2 Prevention of side flashing
68 - SECTION 5 PROTECTION OF PERSONS AND EQUIPMENT WITHIN BUILDINGS
68 - 5.1 SCOPE OF SECTION
68 - 5.2 NEED FOR PROTECTION
68 - 5.3 MODES OF ENTRY OF LIGHTNING IMPULSES
71 - 5.4 GENERAL CONSIDERATIONS FOR PROTECTION
72 - 5.5 PROTECTION OF PERSONS WITHIN BUILDINGS
72 - 5.5.1 Objectives of protection
73 - 5.5.2 Installation of equipotential bonding
75 - 5.6 PROTECTION OF EQUIPMENT
75 - 5.6.1 General
75 - 5.6.2 Primary protection
75 - 5.6.3 Secondary protection
82 - SECTION 6 PROTECTION OF MISCELLANEOUS STRUCTURES AND PROPERTY
82 - 6.1 SCOPE OF SECTION
82 - 6.2 STRUCTURES WITH RADIO AND TELEVISION AERIALS
82 - 6.2.1 Indoor aerial system
82 - 6.2.2 Outdoor aerials on protected structures
82 - 6.2.3 Aerials on unprotected structures
82 - 6.2.4 Earthing of radio systems
82 - 6.3 STRUCTURES NEAR TREES
83 - 6.4 PROTECTION OF TREES
83 - 6.5 CHIMNEYS, METAL GUY°WIRES OR WIRE ROPES
83 - 6.5.1 General
83 - 6.5.2 Metal ladders and metal linings
84 - 6.5.3 Chimneys
84 - 6.6 PROTECTION OF MINES
84 - 6.6.1 Factors influencing need for protection
84 - 6.6.2 Object of recommendations
84 - 6.6.3 Underground workings
86 - 6.6.4 Surface workings
86 - 6.6.5 Lightning detector
86 - 6.7 PROTECTION OF BOATS
86 - 6.7.1 General
86 - 6.7.2 Elements of the protection system
87 - 6.7.3 Installation recommendations
88 - 6.7.4 Precautions for persons and maintenance suggestions
88 - 6.7.5 Bonding the lightning protection system to the vessel's electrical wiring system earth
89 - 6.8 FENCES
90 - 6.9 MISCELLANEOUS STRUCTURES
90 - 6.9.1 Rotundas and other shelter and shade structures in the public domain
90 - 6.9.2 Large tents and marquees
90 - 6.9.3 Small tents
91 - 6.9.4 Metal scaffolding and similar structures, including overbridges
91 - 6.9.5 Tall metal masts, towers, cranes and revolving and travelling structures
91 - 6.10 PROTECTION OF HOUSES AND SMALL BUILDINGS
91 - 6.10.1 General considerations
92 - 6.10.2 Air terminal network for the building
92 - 6.10.3 Provision of downconductors for the building
92 - 6.10.4 Provision of earthing electrodes
92 - 6.11 PROTECTION OF METALLIC PIPELINES
93 - SECTION 7 PROTECTION OF STRUCTURES WITH EXPLOSIVE OR HIGHLY°FLAMMABLE CONTENTS
93 - 7.1 SCOPE OF SECTION
93 - 7.2 GENERAL CONSIDERATIONS
93 - 7.2.1 Risk assessment
93 - 7.2.2 Protection required
93 - 7.2.3 Electrostatic shielding
93 - 7.3 AREAS OF APPLICATION
94 - 7.4 EQUIPMENT APPLICATION
94 - 7.4.1 Earth bosses
94 - 7.4.2 Bonding conductors
95 - 7.4.3 Sizes of copper strips
95 - 7.4.4 Downconductors (see Clause 4.12)
95 - 7.4.5 Air terminals (see Clause 4.11)
95 - 7.5 SPECIFIC OCCUPANCIES
95 - 7.5.1 Protection of steel tanks
97 - 7.5.2 Installations handling crude oil and products
98 - 7.5.3 Aircraft fuelling and de-fuelling
98 - 7.5.4 Structures with explosive or highly flammable contents
101 - SECTION 8 INSTALLATION AND MAINTENANCE PRACTICE
101 - 8.1 WORK ON SITE
101 - 8.2 INSPECTION
101 - 8.3 TESTING
102 - 8.4 RECORDS
102 - 8.5 MAINTENANCE
103 - APPENDIX A - EXAMPLES OF LIGHTNING RISK CALCULATIONS
103 - A1 INTRODUCTION
104 - A2 SAMPLE SPREADSHEET CALCULATIONS
104 - A2.1 Example 1-40 metre high office block
105 - A2.2 Example 2-Darwin hotel
106 - A2.3 Example 3-Historic church
107 - A2.4 Example 4-Remote pump station
108 - A2.5 Example 5-Two storey house
109 - A3 SAMPLE BY-HAND CALCULATION-40 METRE HIGH OFFICE BLOCK
125 - APPENDIX B - THE NATURE OF LIGHTNING AND THE PRINCIPLES OF LIGHTNING PROTECTION
125 - B1 SCOPE OF APPENDIX
125 - B2 THE NATURE OF LIGHTNING
125 - B2.1 Nature of lightning
125 - B2.2 The lightning attachment process
126 - B2.3 Thunderstorm and lightning occurrence
126 - B3 EFFECTS OF LIGHTNING
128 - B4 POTENTIAL DIFFERENCES CAUSED BY LIGHTNING
128 - B4.1 General
129 - B4.2 Earth currents
129 - B4.3 Side°flash
129 - B4.4 Potential (voltage) differences
129 - B5 PRINCIPLES OF LIGHTNING PROTECTION
129 - B5.1 Purpose of protection
129 - B5.2 Interception of lightning
130 - B5.3 Determination of lightning strike attachment points to buildings
131 - B5.4 Protection of the sides of tall buildings
134 - B5.5 Safe discharge to earth
134 - B5.6 Potential equalization
135 - B6 ELEMENTS OF A PROTECTION SYSTEM
136 - APPENDIX C - NOTES ON EARTHING ELECTRODES AND MEASUREMENT OF EARTH IMPEDANCE
136 - C1 GENERAL
136 - C1.1 Function of an earthing electrode
136 - C1.2 Factors influencing earth impedance
136 - C1.3 Measures for reducing earth impedance
137 - C2 RESISTIVITY OF SOIL
137 - C2.1 General
139 - C2.2 Artificial reduction of soil resistivity
139 - C2.3 Determining soil resistivity by test
140 - C3 CALCULATION OF EARTH RESISTANCE OF AN EARTHING ELECTRODE
142 - C4 USE OF EARTHING ELECTRODES IN PARALLEL
143 - C5 DRIVEN OR DRILLED EARTHING ELECTRODES
143 - C5.1 General
143 - C5.2 Safety
143 - C5.3 Installation
143 - C5.4 Materials for earthing electrodes
143 - C5.5 Earthing electrode diameter
143 - C5.6 Depth of installation
144 - C5.7 Sleeving of exposed part of vertical earthing electrode
145 - C5.8 Comparison with other earthing electrode types
145 - C6 BURIED STRIP EARTHING ELECTRODES
145 - C7 BURIED PLATE EARTHING ELECTRODES
145 - C8 CONCRETE FOOTING EARTHING ELECTRODES
146 - C9 INSPECTION AND MAINTENANCE OF EARTHING ELECTRODES
147 - C10 MEASUREMENT OF SOIL RESISTIVITY, EARTHING ELECTRODE RESISTANCE AND EARTH TERMINATION NETWORK IMPEDANCE
147 - C10.1 Determination of soil resistivity by test
149 - C10.2 Three-pin method
151 - C10.3 Isolation of surge impedance of an earth termination network from other fortuitous earth paths
153 - APPENDIX D - THE CALCULATION OF LIGHTNING DISCHARGE VOLTAGES AND REQUISITE SEPARATION DISTANCES FOR ISOLATION OF A...
153 - D1 GENERAL
155 - D2 TRANSIENT VOLTAGE CALCULATIONS BY TRAVELLING WAVE ANALYSIS
155 - D2.1 Simplified travelling wave characteristics
156 - D2.2 Surge voltage calculation by lattice diagram
158 - D3 SURGE VOLTAGE CALCULATIONS BY LUMPED CIRCUIT APPROXIMATIONS
162 - APPENDIX E - EARTHING AND BONDING
162 - E1 GENERAL
162 - E2 DEFINITIONS
162 - E2.1 Common bonding network (CBN)
162 - E2.2 Common utilities enclosure
162 - E2.3 Main earthing bar (MEB)
162 - E2.4 Main earthing conductor
162 - E2.5 Main switchboard (MSB)
162 - E3 METHODS OF EQUIPOTENTIAL BONDING
162 - E3.1 Using a bonding bar
165 - E3.2 Use of a common bonding network
166 - E3.3 Use of a ring earth
167 - APPENDIX F - WAVESHAPES FOR ASSESSING THE SUSCEPTIBILITY OF EQUIPMENT TO TRANSIENT OVERVOLTAGES DUE TO LIGHTNING
171 - APPENDIX G - REFERENCED DOCUMENTS
171 - G1 REFERENCED STANDARDS AND REGULATORY DOCUMENTS
173 - G2 REFERENCED TECHNICAL PAPERS AND PUBLICATIONS

​Sets out guidelines for the protection of persons and property from the hazards of lightning. Applies to conventional lightning protection systems consisting of air terminations, down conductors, earthing systems and surge protect devices. Provides a comprehensive risk assessment process for the determination of risk due to lightning for a range of structures.

This Standard sets out guidelines for the protection of persons and property from hazards arising from exposure to lightning. The recommendations specifically cover the following applications: (a) The protection of persons, both outdoors, where they may be at risk from the direct effects of a lightning strike, and indoors, where they may be at risk indirectly as a consequence of lightning currents being conducted into the building. (b) The protection of a variety of buildings or structures, including those with explosive or highly-flammable contents, and mines. (c) The protection of sensitive electronic equipment (e.g. facsimile machines, modems, computers) from overvoltages resulting from a lightning strike to the building or its associated services. The nature of lightning and the principles of lightning protection are discussed and guidance is given to assist in a determination of whether protective measures should be taken. This Standard is applicable to conventional lightning protection systems (LPSs) that comprise air terminals, downconductors, earth termination networks and surge protective devices (SPDs). Nothing contained within this Standard neither endorses nor implies the endorsement of non-conventional LPSs that comprise special air terminals or special downconductors that claim enhanced performance or enhanced screening over conventional systems. The performance of such systems is outside the scope of this Standard. Irrespective of claimed performance, air terminals shall be placed in accordance with Section 4 to comply with this Standard.

First published as AS MC1-1969.
Revised and redesignated AS 1768-1975.
Second edition 1983.
Third edition 1991.
Jointly revised and designated as AS/NZS 1768(Int):2003.