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AS/NZS 1768:2007

[Available Superseded]

Lightning protection

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​Provides guidelines for the protection of persons and property from the hazards of lightning. Applies to conventional lightning protection systems consisting of air terminations, downconductors, earthing systems and surge protective devices. Also provides a comprehensive risk management process for the determination of the risk of damage due to lightning for a range of structures.
Published: 10/01/2007
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Table of contents
Cited references
Content history
Table of contents
Header
About this publication
PREFACE
1 SCOPE AND GENERAL
1.1 SCOPE
1.2 APPLICATION
1.3 INTRODUCTION
1.4 REFERENCED DOCUMENTS
1.5 DEFINITIONS
2 ASSESSMENT AND MANAGEMENT OF RISK DUE TO LIGHTNING—ANALYSIS OF NEED FOR PROTECTION
2.1 INTRODUCTION
2.2 SCOPE OF SECTION
2.3 CONCEPT OF RISK
2.3.1 General considerations
2.3.2 Types of risk due to lightning
2.3.3 Tolerable values of risk
2.4 DAMAGE DUE TO LIGHTNING
2.4.1 Sources of damage
2.4.2 Types of damage
2.4.3 Consequences of damage (types of loss)
2.5 RISKS DUE TO LIGHTNING
2.5.1 Risk components
2.5.2 Calculation of risk components
2.6 PROCEDURE FOR RISK ASSESSMENT AND MANAGEMENT
2.6.1 Procedure for risk assessment
2.6.2 Protection against direct lightning strikes if Rd > Ra
2.6.3 Protection against indirect lightning strikes if Rd ≤ Ra but Ri > Ra
2.6.4 Final check if Rd + Ri > Ra
2.7 RISK MANAGEMENT CALCULATION TOOL
2.7.1 General operation
2.7.2 Using the calculation tool in the risk management procedure
3 PRECAUTIONS FOR PERSONAL SAFETY
3.1 SCOPE OF SECTION
3.2 NEED FOR PERSONAL PROTECTION
3.3 PERSONAL CONDUCT
3.3.1 General
3.3.2 Outdoors
3.3.3 Indoor and outdoor swimming pools
3.3.4 Indoors
3.4 EFFECT ON PERSONS AND TREATMENT FOR INJURY BY LIGHTNING
4 PROTECTION OF STRUCTURES
4.1 SCOPE OF SECTION
4.2 PROTECTION LEVEL
4.3 LPS DESIGN RULES
4.3.1 General
4.3.2 Rules for air terminals
4.3.3 Rules for downconductors
4.3.4 Rules for earth terminations
4.4 ZONES OF PROTECTION FOR LIGHTING INTERCEPTION
4.4.1 Basis of recommendations
4.4.2 Rolling sphere method (with a modification for large flat surfaces)
4.5 METHODS OF PROTECTION
4.5.1 Structural steel-framed buildings
4.5.2 Buildings without structural steel frames
4.5.2.1 General
4.5.2.2 Structures with continuous metal
4.5.2.3 Metal-roofed buildings
4.5.2.4 Reinforced concrete buildings
4.5.3 Structures with flammable or explosive atmosphere
4.6 MATTERS TO BE CONSIDERED WHEN PLANNING PROTECTION
4.6.1 Structures to be erected
4.6.2 Design considerations
4.6.2.1 General considerations
4.6.2.2 Route for conductors
4.6.2.3 Trouble-free installation
4.6.2.4 Economy of installation
4.7 MATERIALS
4.7.1 General
4.7.2 Corrosion
4.7.2.1 Basic considerations
4.7.2.2 Air terminals and downconductors
4.7.2.3 The earth termination network
4.8 FORM AND SIZE OF CONDUCTORS
4.8.1 Factors influencing selection
4.8.2 Electrical and thermal considerations
4.8.3 Mechanical strength and corrosion considerations
4.9 JOINTS
4.9.1 Effectiveness of joints
4.9.2 Protective covering
4.10 FASTENERS
4.11 AIR TERMINALS
4.11.1 General requirements
4.11.2 Protection of roofs
4.11.3 Protection of the sides of tall buildings
4.11.3.1 Influence of forms of construction
4.11.3.2 Curtain wall construction
4.12 DOWNCONDUCTORS
4.12.1 Structures—General
4.12.2 Route
4.12.3 Mechanical damage
4.13 TEST LINKS
4.14 EARTH TERMINATIONS
4.14.1 General principles
4.14.2 Earthing resistance
4.14.2.1 Basis for measurements
4.14.2.2 Recommended values
4.14.3 Common earthing electrode and potential equalization
4.14.3.1 Common earthing electrode
4.14.3.2 Communications earths
4.15 EARTHING ELECTRODES
4.15.1 General considerations
4.15.2 Connections to earthing electrodes
4.15.2.1 Mechanical protection
4.15.2.2 Selection of materials
4.15.2.3 Joints
4.15.2.4 Test links
4.15.3 Inspection and testing of earthing electrodes
4.16 METAL IN AND ON A STRUCTURE
4.16.1 Use of metal in or on a structure as a part of the lightning protection system
4.16.2 Prevention of side-flashing
4.16.2.1 Methods of prevention
4.16.2.2 Bonding
4.16.2.3 Isolation
4.16.2.4 Effects of bonding on cathodically-protected metal
4.16.2.5 Bonding of underground services
5 PROTECTION OF PERSONS AND EQUIPMENT WITHIN BUILDINGS
5.1 SCOPE OF SECTION
5.2 NEED FOR PROTECTION
5.3 MODES OF ENTRY OF LIGHTNING IMPULSES
5.4 GENERAL CONSIDERATIONS FOR PROTECTION
5.5 PROTECTION OF PERSONS WITHIN BUILDINGS
5.5.1 Objectives of protection
5.5.2 Installation of equipotential bonding
5.6 PROTECTION OF EQUIPMENT
5.6.1 General
5.6.2 Equipotential bonding for equipment protection
5.6.3 Surge protective devices (SPDs)
5.6.3.1 Introduction to SPDs
5.6.3.2 Components
5.6.3.3 SPD configuration
5.6.3.4 Multi-service surge protection device (MSPD)
5.6.3.5 Parameters of an SPD
5.6.3.6 Temporary overvoltage (TOV)
5.6.3.7 Application of SPDs
5.6.4 Magnetic shielding and line routing
5.6.5 Practical installation examples
5.6.5.1 Determine protection needs
5.6.5.2 Protection procedure
5.6.5.3 Protection examples
6 PROTECTION OF MISCELLANEOUS STRUCTURES AND PROPERTY
6.1 SCOPE OF SECTION
6.2 STRUCTURES WITH ANTENNAS
6.2.1 Indoor antenna system
6.2.2 Outdoor antennas on protected structures
6.2.3 Antennas on unprotected structures
6.2.4 Earthing of radio systems
6.3 STRUCTURES NEAR TREES
6.4 PROTECTION OF TREES
6.5 CHIMNEYS, METAL GUY-WIRES OR WIRE ROPES
6.5.1 General
6.5.2 Metal ladders and metal linings
6.5.3 Chimneys
6.6 PROTECTION OF MINES
6.6.1 Factors influencing need for protection
6.6.2 Object of recommendations
6.6.3 Underground workings
6.6.3.1 General
6.6.3.2 Electric detonators
6.6.3.3 Shot firing circuit
6.6.3.4 Overhead electricity supply service lines
6.6.3.5 Surface structures
6.6.3.6 Bonding of surface metalwork
6.6.3.7 Bonding of underground metalwork
6.6.3.8 Further precautions
6.6.4 Surface workings
6.6.4.1 General
6.6.4.2 Equipment
6.6.4.3 On-site precautions
6.6.5 Lightning detector
6.7 PROTECTION OF BOATS
6.7.1 General
6.7.2 Elements of the protection system
6.7.2.1 Air terminal
6.7.2.2 Downconductors
6.7.2.3 Earthing
6.7.2.4 Metallic objects
6.7.2.5 Radio transceivers
6.7.2.6 Corrosion
6.7.3 Installation recommendations
6.7.3.1 Protection of boats with masts
6.7.3.2 Protection of boats without masts
6.7.4 Precautions for persons and maintenance suggestions
6.7.5 Bonding the lightning protection system to the vessel’s electrical wiring system earth
6.8 FENCES
6.9 MISCELLANEOUS STRUCTURES
6.9.1 Shelters, shade structures and rotundas in the public domain
6.9.2 Large tents and marquees
6.9.3 Small tents
6.9.4 Metal scaffolding and similar structures, including overbridges
6.9.5 Tall metal masts, towers, cranes and revolving and travelling structures
6.10 PROTECTION OF HOUSES AND SMALL BUILDINGS
6.10.1 General considerations
6.10.2 Air terminal network for the building
6.10.3 Provision of downconductors for the building
6.10.4 Provision of earthing electrodes
6.11 PROTECTION OF METALLIC PIPELINES
7 PROTECTION OF STRUCTURES WITH EXPLOSIVE OR HIGHLY - FLAMMABLE CONTENTS
7.1 SCOPE OF SECTION
7.2 GENERAL CONSIDERATIONS
7.2.1 Risk assessment
7.2.2 Protection required
7.2.3 Electrostatic shielding
7.3 AREAS OF APPLICATION
7.4 EQUIPMENT APPLICATION
7.4.1 Earth bonding points
7.4.2 Bonding conductors
7.4.3 Sizes of copper strips
7.4.4 Downconductors (see Clause 4.12)
7.4.5 Air terminals (see Clause 4.11)
7.5 SPECIFIC OCCUPANCIES
7.5.1 Protection of steel tanks
7.5.1.1 General precautions
7.5.1.2 Above-ground steel tanks containing flammable liquids at atmospheric pressure
7.5.1.3 Steel tanks with non-metallic roofs
7.5.2 Installations handling crude oil and products—Jetties for marine tankers and barges
7.5.3 Aircraft fuelling and de-fuelling
7.5.4 Structures with explosive or highly-flammable contents
7.5.4.1 Methods of protection
7.5.4.2 Air terminal network
7.5.4.3 Network of horizontal conductors
7.5.4.4 Strikes to the sides of buildings
7.5.4.5 Vertical conductors
7.5.4.6 Below-ground structures
7.5.4.7 Interconnection of earth terminations
7.5.4.8 Bonding of structural metal
7.5.4.9 Bonding of internal metal
7.5.4.10 Electrical conductors entering structure
7.5.4.11 Electrical conductors connected to overhead electricity supply service line
7.5.4.12 Metal not continuously earthed
7.5.4.13 Adit or shaft
7.5.4.14 Fences and retaining walls
7.5.4.15 Avoidance of tall components
7.5.4.16 Tests of system
8 INSTALLATION AND MAINTENANCE PRACTICE
8.1 WORK ON SITE
8.2 INSPECTION
8.3 TESTING
8.4 RECORDS
8.5 MAINTENANCE
APPENDIX A
A1 INTRODUCTION
A2 SAMPLE SPREADSHEET CALCULATIONS
A2.1 Example 1—40 metre high office block
A2.2 Example 2—Darwin hotel
A2.3 Example 3—Historic church
A2.4 Example 4—Remote pump station
A2.5 Example 5—Two storey house
A3 SAMPLE BY-HAND CALCULATION—40 METRE HIGH OFFICE BLOCK
APPENDIX B
B1 SCOPE OF APPENDIX
B2 THE NATURE OF LIGHTNING
B2.1 Nature of lightning
B2.2 The lightning attachment process
B2.3 Thunderstorm and lightning occurrence
B3 EFFECTS OF LIGHTNING
B4 POTENTIAL DIFFERENCES CAUSED BY LIGHTNING
B4.1 General
B4.2 Earth currents
B4.3 Side-flash
B4.4 Potential (voltage) differences
B5 PRINCIPLES OF LIGHTNING PROTECTION
B5.1 Purpose of protection
B5.2 Interception of lightning
B5.3 Determination of lightning strike attachment points to buildings
B5.3.1 The rolling sphere method
B5.3.2 The striking distance
B5.4 Protection of the sides of tall buildings
B5.5 Safe discharge to earth
B5.5.1 General
B5.5.2 Use of reinforcing steel as a downconductor
B5.6 Potential equalization
B6 ELEMENTS OF A PROTECTION SYSTEM
APPENDIX C
C1 GENERAL
C1.1 Function of an earthing electrode
C1.2 Factors influencing earth impedance
C1.3 Measures for reducing earth impedance
C2 RESISTIVITY OF SOIL
C2.1 General
C2.2 Artificial reduction of soil resistivity
C2.3 Determining soil resistivity by test
C3 CALCULATION OF EARTH RESISTANCE OF AN EARTHING ELECTRODE
C4 USE OF EARTHING ELECTRODES IN PARALLEL
C5 DRIVEN OR DRILLED EARTHING ELECTRODES
C5.1 General
C5.2 Safety
C5.3 Installation
C5.4 Materials for earthing electrodes
C5.5 Earthing electrode diameter
C5.6 Depth of installation
C5.7 Sleeving of exposed part of vertical earthing electrode
C5.8 Comparison with other earthing electrode types
C6 BURIED STRIP EARTHING ELECTRODES
C7 BURIED PLATE EARTHING ELECTRODES
C8 CONCRETE FOOTING EARTHING ELECTRODES
C9 INSPECTION AND MAINTENANCE OF EARTHING ELECTRODES
C10 MEASUREMENT OF SOIL RESISTIVITY, EARTHING ELECTRODE RESISTANCE AND EARTH TERMINATION NETWORK IMPEDANCE
C10.1 Determination of soil resistivity by test
C10.1.1 Four-pin method
C10.1.2 Instrumentation for soil resistivity measurement
C10.2 Earth resistance
C10.2.1 General procedure
C10.2.2 Test lead considerations
C10.2.3 Instruments for earth resistance measurement
C10.2.3.1 General
C10.2.3.2 The three and four-pin method
C10.2.3.3 Selective method
C10.2.3.4 Stakeless or clamp-on method
C10.3 Isolation of surge impedance of an earth termination network from other fortuitous earth paths
APPENDIX D
D1 GENERAL
D2 TRANSIENT VOLTAGE CALCULATIONS BY TRAVELLING WAVE ANALYSIS
D2.1 Simplified travelling wave characteristics
D2.2 Surge voltage calculation by lattice diagram
D3 SURGE VOLTAGE CALCULATIONS BY LUMPED CIRCUIT APPROXIMATIONS
APPENDIX E
E1 GENERAL
E2 DEFINITIONS
E3 HAZARDOUS CONDITIONS ASSOCIATED WITH HV POWER EPR
E3.1 General
E3.2 HV sites of particular concern
E4 METHODS OF EQUIPOTENTIAL BONDING
E4.1 General
E4.2 Using a bonding bar
E4.3 Use of a common bonding network
E4.4 Use of a ring earth
APPENDIX F
APPENDIX G
G1 REFERENCED STANDARDS AND REGULATORY DOCUMENTS
G2 REFERENCED TECHNICAL PAPERS AND PUBLICATIONS
Cited references in this standard
Content history
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