Track updates
iconCreated with Sketch.

AS 1768:2021


Lightning protection

Included in Electrical installation set
Save on multi-year plans. Subscription billed annually.
AS 1768:2021 specifies requirements for the design, installation, maintenance and testing of lightning protection on common structures, and for electrical and electronic systems within those structures for the protection of people and property from the hazards of lightning.
Published: 03/12/2021
Pages: 170
Table of contents
Cited references
Content history
Table of contents
About this publication
1 Scope and general
1.1 Scope and application
1.1.1 Scope
1.1.2 Application
1.2 Normative references
1.3 Terms and definitions
2 Risk assessment
2.1 Scope of section
2.2 General
2.3 Risk management principles
2.4 Tolerable levels of risk
2.5 Assessment of risk due to lightning
2.5.1 Risk components
2.5.2 Risk assessment process
2.5.3 Risk assessment spreadsheet
2.5.4 Multiple structures General Distributed facilities Open air facilities
3 Protection of structures
3.1 General
3.2 Air terminals
3.2.1 General
3.2.2 Air terminal requirements General Use of dedicated air terminals Use of the structure as air terminals (natural components)
3.2.3 Air terminal positioning
3.2.4 Side strike protection
3.3 Downconductors
3.3.1 General
3.3.2 Downconductor requirements
3.3.3 Natural components
3.3.4 Test points
3.4 Strike counters
3.5 Earth termination network
3.5.1 General
3.5.2 Earthing requirements
3.5.3 Earth resistance
3.6 Prevention of side flashing
3.6.1 General
3.6.2 Equipotential bonding
3.6.3 Protection by isolation
3.7 Materials
3.7.1 General
3.7.2 Form and size of conductors
3.7.3 Joints
3.7.4 Fasteners
3.7.5 Galvanic corrosion
4 Protection of equipment
4.1 General
4.2 Surge protection installation
4.2.1 General
4.2.2 Introduction to SPDs
4.3 Transient overvoltages
4.4 Temporary overvoltages
4.5 Lightning protection zones
4.6 Power SPD requirements
4.6.1 General
4.6.2 Overcurrent protection
4.6.3 Primary SPDs (LPZ0/LPZ1)
4.6.4 Secondary SPDs (LPZ1/2…n)
4.7 Signal/data line SPD requirements
5 Testing and maintenance
5.1 General
5.2 Testing
5.3 Records
5.4 Maintenance
5.4.1 General
5.4.2 Maintenance program
5.4.3 Alterations or extensions to the structure
5.4.4 Inspection
5.4.5 Remedial action
6 Personal safety
6.1 General
6.2 Need for personal protection
6.3 Lightning injury mechanisms
6.3.1 General
6.3.2 Electrical injury and death mechanisms
6.3.3 Non-electrical injury mechanisms
6.4 Personal conduct
6.4.1 General
6.4.2 Outdoors
6.4.3 Swimming pools
6.4.4 Indoors
6.5 Lightning detectors and lightning warning systems
Appendix A
A.1 Scope
A.2 Lightning
A.2.1 General
A.2.2 Lightning initiation
A.2.3 Lightning leaders
A.2.3.1 Downward from the cloud
A.2.3.2 Upward from the ground
A.2.4 Return stroke
A.2.5 Successive dart leaders and return strokes
A.2.6 Lightning characteristics and parameters
A.3 Thunderstorm and lightning occurrence
A.4 Effects of lightning
A.4.1 General
A.4.2 Side flash
A.4.3 Potential rise effects
A.4.4 Thermal effects
A.5 Principles of lightning protection
A.5.1 Lightning attachment process
A.5.2 Rolling sphere method (RSM)
A.6 Elements of a lightning protection system
Appendix B
B.1 Scope
B.2 Concept of risk
B.2.1 General
B.2.2 Types of risk due to lightning
B.2.3 Damage due to lightning
B.2.3.1 Sources of damage
B.2.3.2 Types of damage
B.2.3.3 Consequences of damage (types of loss)
B.3 Risks due to lightning
B.3.1 Risk components
B.3.2 Calculation of risk components
B.4 Procedure for risk assessment and management
B.4.1 Description
B.4.2 Protection against direct lightning flashes if Rd > Ra
B.4.3 Protection against indirect lightning flashes if Rd ≤ Ra but Ri > RT
Appendix C
C.1 Scope
C.2 Introduction
C.2.1 General
C.2.2 Multiple structures
C.3 Sample spreadsheet calculations
C.3.1 General
C.3.2 Use of the spreadsheet
C.3.2.1 Structure dimensions
C.3.2.2 Structure attributes
C.3.2.3 Environment
C.3.2.4 Service lines
C. Powerline
C. Other overhead services
C. Other underground services
C.3.2.5 Loss categories
C. Category 1 — Loss of human life
C. Category 2 — Loss of essential services
C. Category 3 — Loss of cultural heritage
C. Category 4 — Economic loss
C.3.3 Case studies
C.3.4 Case study 1 — 40 m high office block in Brisbane
C.3.4.1 General
C.3.4.2 Providing protection for the building
C.3.4.3 Outcome
C.3.5 Case study 2 — Hotel in Darwin
C.3.6 Case study 3 — Historic church
C.3.7 Case study 4 — Remote pump station
C.3.8 Case study 5 — Two storey house
C.3.9 Case study 6 — Mountaintop broadcasting site
Appendix D
D.1 Scope
D.2 Determination of required protection level (LPL)
D.3 Rolling sphere method (RSM)
D.3.1 General
D.3.2 Practical application
D.3.3 Equations
Appendix E
E.1 Scope
E.2 Function
E.2.1 General
E.2.2 Side flashes and sparking
E.2.3 Safety of personnel
E.3 Design
E.3.1 General
E.3.2 Critical length
E.3.3 LPS design factors
E.3.4 Factors influencing earth impedance
E.3.5 Soil resistivity
E.3.6 Calculation of earth resistance
E.3.7 Measures for reducing earth impedance
E.3.7.1 General
E.3.7.2 Electrode arrangement
E.3.7.3 Low-resistivity backfills
E.3.8 Service separation
E.3.9 Methods of equipotential bonding
E.3.9.1 General
E.3.9.2 Using a bonding bar
E.3.9.3 Common bonding network
E.3.9.4 Use of a ring earth
E.4 Construction
E.4.1 General
E.4.2 Driven or drilled earth electrodes
E.4.2.1 General
E.4.2.2 Safety
E.4.2.3 Installation
E.4.2.4 Sleeving of upper part of vertical earth electrode
E.4.3 Buried strip earth electrodes
E.4.4 Reinforced concrete footings as earth electrodes
E.5 Measurement
E.5.1 General
E.5.2 Soil resistivity
E.5.2.1 General
E.5.2.2 Instrumentation
E.5.3 Electrical continuity
E.5.4 Earth resistance
E.5.5 Fall-of-potential (FOP) method
E.5.5.1 General
E.5.5.2 Test lead considerations
E.5.5.3 Instrumentation
E.5.6 Other test methods
E.5.6.1 General
E.5.6.2 Selective method
E.5.6.3 Stakeless (clamp-on) method
E.5.6.4 Surge impedance testing
Appendix F
F.1 Scope
F.1.1 General
F.1.2 TN networks
F.2 Primary protection — One-port SPD for MEN systems
F.3 Secondary protection — One-port SPD for distribution boards
F.4 Primary protection — One-port SPD for TT systems
F.5 Primary protection — One-port SPD for IT system
F.6 Primary protection — Two-port SPD for MEN and TT systems
F.7 Secondary protection — Two-port SPD — Power and signal
Appendix G
G.1 General
G.2 SPD components
G.3 Application of SPDs
G.4 Installed performance
G.5 Application examples
G.5.1 Determine protection needs
G.5.2 Protection procedure
G.5.3 Protection examples
Appendix H
H.1 General
H.2 IEC impulse withstand
H.3 IEC impulse immunity
Appendix I
I.1 General
I.2 Structures with antennas
I.2.1 Antennas on protected structures
I.2.2 Antennas on unprotected structures
I.2.3 Earthing of radio systems
I.3 Structures near trees
I.4 Protection of trees
I.5 Chimneys, metal guy wires or wire ropes
I.5.1 General
I.5.2 Metal ladders and metal linings
I.5.3 Chimneys
I.6 Protection of boats
I.6.1 General
I.6.2 Elements of the protection system
I.6.2.1 Air terminal
I.6.2.2 Downconductors
I.6.2.3 Earthing
I.6.2.4 Metallic objects
I.6.2.5 Radio transceivers
I.6.2.6 Corrosion
I.6.3 Installation recommendations
I.6.3.1 Protection of boats with masts
I.6.3.2 Protection of boats without masts
I.6.3.3 Precautions for crew and equipment
I.6.3.4 Electrical wiring of the vessel
I.7 Fences
I.8 Miscellaneous structures
I.8.1 Shelters, shade structures and rotundas in the public domain
I.8.2 Large tents and marquees
I.8.3 Small tents
I.8.4 Metal scaffolding and similar structures, including overbridges
I.8.5 Tall metal masts, towers, cranes, revolving and travelling structures
I.9 Protection of metallic pipelines
I.10 Protection of houses and small buildings
I.10.1 General considerations
I.10.2 Air terminals
I.10.3 Downconductors
I.10.4 Earthing
Appendix J
J.1 Scope
J.2 General
J.2.1 Use of the risk assessment spreadsheet
J.2.2 Equipotential bonding
J.2.3 Earth bonding points
J.2.4 Suspended air terminal network
J.2.5 Surge protection
J.3 Hazardous areas
J.3.1 Structures with Zones 2 and 22
J.3.2 Structures with Zones 1 and 21
J.3.3 Structures with Zones 0 and 20
J.4 Tests of system
J.4.1 Particular structures
J.4.1.1 Steel tanks
J. General
J. Steel tanks with non-metallic roofs
J.4.1.2 Jetties for tankers and barges
J.5 Explosive substances or explosive articles
J.5.1 General
J.5.2 Surge protection
J.5.3 Below ground structures
J.5.4 Soil-covered structures
J.5.5 Explosives stored in the open
J.5.6 Interconnection of earth terminations
J.5.6.1 General
J.5.6.2 Bonding of internal metal
J.5.6.3 Bonding of external services
J.5.6.4 Conductive services entering structure
J.5.6.5 Electrical conductors connected to overhead services
J.5.6.6 Fences and retaining walls
J.5.6.7 Avoidance of tall components
J.5.6.8 Electrostatic shielding
Appendix K
K.1 Introduction
K.2 Turbine protection
K.2.1 General
K.2.2 Wind turbine blades
K.2.3 Wind turbine structure
K.2.4 Blade-to-hub connection
K.2.5 Wiring inside the blades
K.2.6 Protection of bearings and gearbox
K.2.7 Protection of electrical and control system
K.3 Earthing
K.4 Personal safety
Appendix L
L.1 Scope
L.2 General
L.3 Protection levels for high voltage power systems
L.3.1 General
L.3.2 Lightning hazards in power systems
L.3.3 Determining the level of protection
L.4 Protection of primary plant
L.4.1 General
L.4.2 Direct lightning strike protection of primary plant
L.4.2.1 General
L.4.2.2 Determination of a suitable substation lightning protection solution
L.4.2.3 Calculation of an effective substation lightning protection solution
L.4.3 Primary plant BIL
L.4.4 Surge protection of primary plant
L.5 Protection of secondary systems
L.6 Protection of substation buildings
L.7 Protection of transmission and distribution powerlines
L.7.1 General
L.7.2 Overhead line reliability
L.7.3 Direct lightning strike protection for overhead powerlines
L.7.3.1 General
L.7.3.2 Installation of overhead earth wires
L.7.3.3 Use of wood or fibreglass composites
L.7.3.4 Increasing flashover voltage
L.7.3.5 Reducing structure footing resistance
L.7.3.6 Modelling and improving powerline lightning performance
L.7.4 Impulse clearances of overhead powerlines
L.7.5 Underground power cables
L.7.6 Covered conductor thick
L.8 Insulation coordination between substations and powerlines
L.9 Power stations
Appendix M
M.1 General
M.2 Need for protection
M.3 Surface mines
M.3.1 Blasting on-site precautions
M.3.2 Electrical cables and overhead lines
M.3.3 Mobile plant
M.3.4 Tyre explosions
M.4 Surface structures
M.5 Underground mines
M.5.1 General
M.5.2 Identification of potential connections
M.5.3 Separation
M.5.4 Earthing
M.5.5 Boreholes
M.5.6 Redundant boreholes
M.5.7 Underground protection measures
M.5.7.1 Conductive roof and rib mesh
M.5.7.2 Sealed areas and abandoned workings
M.5.7.3 Boreholes
M.5.7.4 Blasting operations
M.5.7.5 Electric detonators
M.5.7.6 Further precautions
M.6 Lightning detectors and lightning warning systems
Appendix N
Cited references in this standard
Electrical installations (known as the Australian/New Zealand Wiring Rules)
Content history
[Available Superseded]
DR AS 1768:2021
Inclusive of GST
Additional files available
When you purchase this publication, additional resources will be available to you in your content library.
Available formats
iconCreated with Sketch.
Available formats
icon_export/16/closeCreated with Sketch.
Web Reader
Instantly view standards in your browser. Search, bookmark, highlight, and comment for anytime access - online and offline.
Web Reader (PDF)
View standards in PDF format in your browser. Search, bookmark, highlight, and comment for anytime access - online and offline.
Web Reader
1 user
Add to cart
visa logo
mastercard logo
amex logo