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AS/NZS 7000:2016


Overhead line design

This Standard provides Electricity Industry network owners, overhead line maintenance service providers, design consultants, construction contractors, structure designers, and pole manufacturers with an industry standard that replaces all previously used reference guidelines.
Published: 17/05/2016
Pages: 294
Table of contents
Cited references
Content history
Table of contents
About this publication
1 Scope and general
1.1 Scope and general
1.2 Use of alternative materials or methods
1.3 Referenced and related documents
1.4 Definitions
1.5 Notation
2 Design philosophies
2.1 General
2.2 Limit state design
2.2.1 General
2.2.2 Limit states on line components General Structure design limit states Conductors (including earthwires) limit states Insulator limit states Electrical structure clearances limit states
2.3 Design life of overhead lines
2.4 Electrical operational characteristics of an overhead line
2.5 Mechanical operational performance of overhead lines
2.6 Reliability
2.7 Coordination of strength
2.8 Environmental considerations
3 Electrical requirements
3.1 General considerations
3.2 Current considerations
3.3 Insulation system design
3.3.1 General
3.3.2 Coordination with substations
3.4 Lightning performance of overhead lines
3.5 Electrical clearance distances to avoid flashover
3.5.1 Introduction
3.5.2 Inspection and maintenance clearances
3.5.3 Live access clearance
3.5.4 States for calculation of clearances Maximum operating temperature Ice load for determination of electrical clearance Combined wind and snow/ice loads Operating temperature under serviceable wind
3.5.5 Clearances at the structure
3.6 Determination of structure geometry
3.6.1 General
3.6.2 High wind serviceability state
3.6.3 Moderate wind serviceability state
3.6.4 Maintenance clearances
3.7 Spacing of conductors
3.7.1 Conductors of different circuits on different supports (unattached crossing) General Determination of conductor separation Separation in still air Separation under wind
3.7.2 Conductors of different circuits on the same support (attached crossing)
3.7.3 Conductors on the same supports (same or different circuits and shared spans) General At mid span At any point in the span (vertical)
3.7.4 Minimum clearance to inter-span poles
3.8 Insulator and conductor movement at structure
3.8.1 General
3.8.2 Structure clearances
3.8.3 Calculation of swing angles
3.9 Live line maintenance clearances
3.10 Clearances to objects and ground
3.11 Clearances to ground and areas remote from building, railways and navigable waterways
3.11.1 Clearances to ground and roads Lines other than insulated service lines Insulated LV service lines
3.11.2 Clearances to buildings, other lines and recreational areas Structures and buildings Easements
3.12 Power line easements
3.13 Corona effect
3.13.1 General
3.13.2 Radio and television interference
3.13.3 Audible noise
3.13.4 Corona loss
3.14 Electric and magnetic fields
3.14.1 Electric and magnetic fields under a line
3.14.2 Electric and magnetic field induction
3.14.3 Interference with telecommunication circuits
3.14.4 Electrostatic induction
3.15 Single wire earth return (SWER) powerlines
3.15.1 General
3.15.2 Types of SWER distribution systems
4 Conductors and overhead earthwires (ground wires) with or without telecommunication circuits
4.1 Electrical requirements
4.1.1 D.C. resistance
4.1.2 A.C. resistance
4.1.3 Steady state thermal current rating
4.1.4 Short time thermal current rating
4.1.5 Short-circuit thermal current rating
4.2 Mechanical requirements
4.2.1 Limit states
4.2.2 Conductor tension
4.2.3 Conductor stress and fatigue
4.2.4 Conductor permanent elongation
4.2.5 Conductor annealing and operating temperatures
4.2.6 Conductor final modulus of elasticity
4.2.7 Conductor coefficient of thermal expansion
4.2.8 Conductor cross-sectional area
4.2.9 Conductor diameter
4.2.10 Conductor drag coefficient
4.2.11 Conductor calculated breaking load
4.2.12 Conductor vertical and horizontal sag
4.3 Environmental requirements
4.3.1 Conductor damage risks
4.3.2 Conductor degradation
4.4 Conductor constructions
4.4.1 Bare conductors
4.4.2 Insulated conductors and cable systems
4.4.3 Covered conductors
4.4.4 Optical fibres
4.4.5 Low-voltage aerial bundled cables (LVABC)
4.4.6 Special conductors
4.5 Conductor selection
5 Insulators
5.1 Insulation basics
5.2 Line and substation insulation coordination
5.3 Electrical and mechanical design
5.3.1 General
5.3.2 Design for pollution
5.3.3 Design for power frequency voltages (wet withstand requirement)
5.3.4 Design for switching surge voltages
5.3.5 Insulator mechanical design
5.4 Relevant standards, types and characteristics of insulators
6 Basis of structural design
6.1 General
6.2 Requirements
6.2.1 Basic requirements
6.2.2 Security levels
6.2.3 Wind return periods for design working life and security levels
6.2.4 Security requirements
6.2.5 Safety requirements during construction and maintenance
6.2.6 Additional considerations Dynamic load effects—Seismic loads Environmental considerations
6.2.7 Design working life
6.2.8 Durability
6.3 Limit states
6.3.1 General
6.3.2 Ultimate limit states
6.3.3 Serviceability limit states
6.3.4 Limit state design General Strength reduction factors (ϕ)
6.4 Actions—Principal classifications
6.5 Material properties
6.6 Modelling for structural analysis and soil resistance
6.6.1 General
6.6.2 Interactions between support foundations and soil
7 Action on lines
7.1 Introduction
7.2 Actions, general approach
7.2.1 Permanent loads
7.2.2 Wind loads
7.2.3 Snow and ice loads
7.2.4 Special loads Forces due to short-circuit currents Avalanches and creeping snow loads Earthquakes Other special loads
7.2.5 Construction and maintenance loads General Loads related to line maintenance/construction personnel
7.2.6 Coincident temperatures
7.2.7 Security loads General Failure containment loads Fb General Suspension or intermediate supports Tension supports Distribution systems Residual static load (RSL)
7.3 Load components
7.3.1 Loads from the supported wires
7.3.2 Conductor tensions General Wind condition Ftw Maintenance condition Ftm Everyday condition Fte
7.4 Load combinations
7.4.1 General
7.4.2 Deflections and serviceability limit state
8 Supports
8.1 Initial design considerations
8.2 Materials and design
8.2.1 Lattice steel towers and guyed masts
8.2.2 Steel poles
8.2.3 Concrete poles
8.2.4 Timber poles
8.2.5 Fibre reinforced polymer poles
8.2.6 Other materials
8.2.7 Guyed structures General Second order analysis Design details for guys
8.3 Corrosion protection and finishes
8.3.1 General
8.3.2 Galvanizing
8.3.3 Metal spraying
8.3.4 Paint over galvanizing (duplex system)
8.3.5 Use of weather-resistant steels
8.4 Maintenance facilities
8.4.1 Climbing and working at heights
8.4.2 Maintainability
8.4.3 Safety requirements
8.5 Loading tests
8.5.1 General
8.5.2 Tower structures
8.5.3 Pole type structures Test specimens Test requirements Testing and acceptance
8.5.4 Acceptance criteria
8.5.5 Test reports
9 Foundations
9.1 Design principles
9.2 Soil investigation
9.3 Backfilling of excavated materials
9.4 Construction and installation
10 Earthing systems
10.1 General purpose
10.2 Earthing measures against lightning effects
10.3 Dimensioning with respect to corrosion and mechanical strength
10.3.1 Earth electrodes
10.3.2 Earthing and bonding conductors
10.4 Dimensioning with respect to thermal strength
10.4.1 General
10.4.2 Current rating calculation
10.5 Design for earth potential rise (EG-0 approach)
10.5.1 Introduction
10.5.2 Standard curves
10.5.3 Societal risk assessment General Assumptions Application notes
10.5.4 Standard curve earthing design process
10.6 Design for earth potential rise (EEA approach)
10.6.1 Introduction
10.6.2 Risk management flowchart
10.6.3 Risk assessment
10.6.4 Individual risk
10.6.5 Societal risk
10.6.6 Acceptance criteria
10.6.7 Cost evaluation of mitigation
10.6.8 Appendix T General Deterministic approach for design for earth potential rise Special location Normal location
10.7 Electrical aspects of staywire design
10.7.1 General
10.7.2 Corrosion and leakage currents
10.7.3 Stay earthing for control of touch potentials Distribution and sub transmission lines Transmission lines
10.8 Choice of earthing materials
11 Line equipment—Overhead line fittings
11.1 General
11.2 Electrical requirements
11.2.1 Requirements applicable to all fittings
11.2.2 Requirements applicable to current carrying fittings
11.3 RIV requirements and corona extinction voltage
11.4 Short-circuit current and power arc requirements
11.5 Mechanical requirements
11.6 Durability requirements
11.7 Material selection and specification
11.8 Characteristics and dimensions of fittings
11.8.1 General
11.8.2 Termination fittings
11.8.3 Suspension and support fittings
11.8.4 Repair fittings
11.8.5 Spacers and spacer dampers
11.8.6 Vibration dampers
11.8.7 Conductor fittings for use at elevated temperatures
11.8.8 Conductor fittings used at near freezing temperatures
11.9 Test requirements
12 Life extension (refurbishment, upgrading, uprating) of existing overhead lines
12.1 General
12.2 Assessment of structures
12.2.1 General
12.2.2 Line importance
12.2.3 Inspection
12.2.4 Material properties
12.3 Component capacity
12.4 Proof loading
12.5 Upgrading of overhead line structures
13 Provisions for climbing and working at heights
14 Co-use of overhead line supports (signage, banners, communications carrier cables, telecommunications repeaters)
14.1 Signs and banners and traffic mirrors
14.1.1 General
14.1.2 Location
14.1.3 Attachments
14.1.4 Size of banners
14.1.5 Duration of attachment
14.1.6 Wind loads on signs and banners Strength limit state Serviceability limit state General Top attached banners Top and bottom attached banners
14.2 Communications carrier cables
14.3 Telecommunications repeaters equipment and traffic mirrors
14.3.1 General
14.3.2 Safety considerations
14.4 Flags
Appendix A
A1 Referenced documents
A2 Related documents
A3 Additional reading material
Appendix B
B1 Australia
B2 New Zealand
B3 Synoptic wind regions (Australia Zone I and Zone III and all Zealand regions)
B4 Downdraft wind regions (Australia Zone II and Zone III and New Zealand regions A7)
B4.1 General
B4.2 Downdraft winds
B4.3 Tornadoes (applies to all high security/high reliability overhead lines only such as regional transmission interconnectors)
B4.3.1 General
B4.3.2 High security and high reliability overhead lines
B5 Wind pressures
B5.1 General
B5.2 Wind pressures on lattice steel towers
B5.3 Wind pressure on poles
B5.4 Wind forces on conductors
B5.4.1 Span reduction factor (SRF and TSRF) for synoptic wind regions
B5.4.2 Span reduction factor (SRF and TSRF) for downdraft wind regions
B5.4.3 Conductor tensions
B5.5 Wind forces on insulators and fittings
Appendix C
C1 General
C2 Forces due to short-circuit currents
C3 Creeping snow
C4 Earthquakes
C4.1 General
C4.2 General principles relating to overhead lines
C4.3 Seismic mass
C4.4 Fundamental period of structure (T1)
C4.5 Ductility factor
C4.6 Modelling of cables and conductors
C4.7 Methods of analysis
C4.7.1 Equivalent static force method
C4.7.2 Modal response spectrum analysis
C4.7.3 Time history analysis
C4.8 Combination of effects
C4.9 Second order effect analysis (Pδ)
C4.10 P-Δ Effects
C4.11 Vertical seismic response
C4.12 Seismic displacements
C4.13 Liquefaction
C4.14 Holding-down bolts
C5 Mining subsidence
C5.1 General
C5.2 General design provisions
Appendix D
D1 General
D2 Suggested nominal service life
D3 Additional considerations
D3.1 Soil type
D3.2 High water tables
D3.3 Accumulation of condensation
D3.4 Regions of low humidity
D3.5 Accidental damage
D3.6 Fire
D3.7 Concrete poles
D3.8 Timber poles
D3.9 Steel poles and lattice steel towers
D3.9.1 General
D3.9.2 Environmental
D3.10 Composite fibre poles (fibre reinforced resin composite material)
Appendix E
E1 General
E2 Estimation of line outages due to lightning
E3 Measures to improve lightning performance
E4 Reference
Appendix F
F1 General
F2 Notation
F3 Characteristic strengths and elastic moduli
F4 Design factors—Material
F4.1 Capacity factor (strength reduction factor)
F4.2 Duration of load effects (strength)
F4.3 Duration of load effects (stiffness)
F4.4 Pole degradation factors
F4.5 Factor for immaturity
F4.6 Shaving factor
F4.7 Processing factor
F4.8 Stability factor for compression
F5 Design capacity
F5.1 Bending strength
F5.2 Shear strength
F5.3 Compressive strength
F5.4 Combined bending and compression strength
F5.5 Torsional strength
F5.6 Pole top deflection
Appendix G
G1 Calculation of internal forces and moments
G1.1 Method of analysis of lattice steel towers
G1.2 Guyed structures
G2 Embedment of steel members into concrete by means of anchoring elements
G3 Cranked K bracing
G4 Portal frames
G5 Secondary (redundant) members
G6 Security of fasteners
G6.1 General application
G6.2 Bolts in tension
G6.3 Deterrent to vandalism
G7 Anti climbing devices
G8 Plan bracing
G9 Strength factors (ϕ)
Appendix H
H1 Corona
H1.1 General
H1.2 Design
H1.3 Radio interference voltage
H1.4 Audible noise
H1.4.1 General
H1.4.2 Design influences
H1.5 Corona loss
H2 Electrostatic induction
H3 Electromagnetic induction
Appendix I
I1 General
I2 Strength
I2.1 Characteristic or specified compressive strength
I2.2 Tensile strength
I2.3 Combined bending and compression strength
I3 Strength capacity factor
I4 Serviceability
I4.1 General
I4.2 Deflection and rotation
I4.3 Crack width
I5 Concrete cover
I5.1 Exposure classifications
I5.2 Exposure classifications other than C, or U more severe than C
I5.3 Exposure classification C, or U more severe than C
I6 Reinforcement and tendons
I6.1 General
I6.2 Poles designed by load testing
I6.3 Poles designed by calculation
I7 Electrical earthing
Appendix J
J1 General
J2 Strength
J3 Serviceability limits
Appendix K
K1 General
K2 Strength factors (ϕ)
K3 Minimum thickness
K4 Requirements for plate thickness less than 3 mm
K5 Low temperature requirements
K6 Welding procedure for thick base plates
K7 Hydrogen embrittlement issues with hot dip galvanizing after incremental bending
K8 Internal treatment of steel poles
K9 Slip jointing
K10 Anchor bolts
K11 Electrical earthing
Appendix L
L1 General principles
L2 Geotechnical parameters of soils and rocks
L2.1 General
L2.2 Typical soil properties
L3 Foundation design for poles
L3.1 Foundation types
L3.2 Bored piers
L3.3 Analytical procedure for determination of failure load/moment
L3.3.1 Brinch Hansen method
L3.3.2 Shear design for bored piers
L3.3.3 Design of shear reinforcement
L4 Foundation design for lattice steel towers
L4.1 General
L4.2 Foundation types
L4.3 Common symbols
L4.4 Footing design
L4.4.1 Bored piers
L4.4.2 Uplift analysis for piers in soil
L4.4.2.1 General
L4.4.2.2 Undercut pier uplift capacity by shear failure model
L4.4.2.3 Undercut pier uplift capacity by equivalent cylinder failure model
L4.4.2.4 Undercut pier uplift capacity by the earth cone pullout model
L4.4.2.5 Straight-sided pier uplift capacity by shear failure model
L4.4.2.6 Straight-sided pier uplift capacity by the earth cone pullout model
L4.4.3 Pier compression analysis
L4.4.4 Bored piers socketed into rock
L4.4.4.1 General
L4.4.4.2 Pier uplift capacity by mobilization of rock mass
L4.4.4.3 Pier uplift capacity by shear failure model
L4.4.4.4 Pier compression analysis
L4.5 Spread footings
L4.5.1 General
L4.5.2 The earth cone pullout model with no undercut
L4.5.3 The earth cone pullout model with undercut
L4.5.4 The pier pullout by cylinder failure model
L4.6 Rock or soil anchored footings
L4.6.1 General
L4.6.2 Deep piled footings
L4.6.3 Raft footings
L4.6.4 Load transfer from tower leg to footings
L4.6.4.1 General
L4.6.4.2 Design of base plates
L4.6.4.3 Design of stubs
L5 Guyed anchors
L5.1 Cast in situ anchor blocks
L5.2 Bored pier anchors
L5.3 Rock anchors
L6 Foundation testing
L7 Cathodic protection
L8 References
Appendix M
M1 General overview
M2 Reference Standards for climbing and working at heights
Appendix N
N1 Scope
N2 General requirements
N3 Purpose of upgrade
N4 Structural assesment
N5 Working on loaded structures
N6 Load test on structures
N7 Structure upgrade
N7.1 Lattice steel structure upgrade
N7.1.1 General
N7.1.2 Tension member upgrade
N7.1.3 Compression members upgrade
N7.1.4 Connection upgrade and consideration in connection design
N7.1.5 Force distribution in newly formed composite section
N7.1.6 Guying of structures
N7.2 Pole upgrade
N7.2.1 Timber pole structure upgrade
N7.2.2 Steel pole structure upgrade
N7.2.2.1 Direct embedded poles and socketed base type poles
N7.2.2.2 Base plate mounted poles
N7.2.2.3 Slip joints and internal surface protection
N7.2.3 Concrete pole structure upgrade
N7.2.4 Composite pole structure upgrade
N8 Foundation upgrade
N9 Modification of lattice steel structure
N10 Modification of pole structure
N11 Safety
N11.1 Construction and maintenance work procedures
N11.2 Personnel access
Appendix O
O1 Scope
O2 Principle
O3 Apparatus
O4 Condition of sample poles
O5 Preparation of test specimen
O6 Test procedures
O6.1 General
O6.2 Procedures
O6.2.1 Determination of dry mass (m1)
O6.2.2 Immersion procedure
O6.2.3 Determination of saturated surface-dry mass (m2)
O7 Calculations
O8 Records and reports
O8.1 Records
O8.2 Reports
Appendix P
P1 Insulation coordination basics
P2 Design for pollution
P3 Design for switching surge design and lightning performance considerations
P4 Selection of insulators
P4.1 General
P4.2 Standard and fog profile disc insulators
P4.3 Ceramic pin, shackle and posts
P4.4 Composite long rod and line post insulators
Appendix Q
Q1 Meteorological assumptions
Q2 Suspension insulator swing
Q3 Conductor blowout
Q4 Combined suspension insulator swing and conductor blowout
Appendix R
R1 General
R2 Terminology
R3 Variables
R4 Models
R5 Equivalent span
R6 Loading conditions
R7 Tension constraints
R8 Tension changes
R9 Sagging tensions
R10 Physical properties
R11 Catenary equations
R12 Parabolic equations
R13 References
Appendix S
S1 Conductor tension measurement
S2 Conductor temperature measurement
S3 Conductor identification
S4 Sight board method
S5 Tangent Method 1
S6 Tangent Method 2
S7 Offset method
S8 Height stick method
S9 Clino method
S10 Wave method
S11 Swing method
S12 Dynamometer method
Appendix T
T1 Risk process
T2 Probability calculation
T3 Faults on towers and cables
T4 Simplified calculation of permissible exposure limits
T5 Advanced calculation of the probability of fatality
T6 Calculation of the probability of fatality for comparable exposure and fault lengths
T7 Tolerable risk limits
T8 Risk treatment measures
T8.1 General
T8.2 Reducing earth grid impedance
T8.3 Overhead shield wires
T8.4 Cable screen
T8.5 Earth electrode enhancement
T8.6 Reduction of earth fault current
T8.7 Reduction of fault clearing times
T8.8 Surface insulating layer
T8.9 Gradient control conductors
T8.10 Separation of HV and LV earth electrodes
T8.11 Isolation
Appendix U
Appendix V
V1 General
V2 Reference
Appendix W
Appendix X
X1 General
X2 Corrosion mechanisms
X2.1 Pit corrosion
X2.2 Crevice corrosion
X2.3 Homogenous Al and Al alloy conductors
X2.4 Homogenous copper conductor corrosion
X2.5 Homogenous galvanized steel wire conductors
X2.6 Non-homogenous Al conductors steel reinforced
X3 Protective greases
X4 Application recommendations
X5 References
Appendix Y
Y1 General
Y2 Static stresses
Y2.1 Static tensile stress
Y2.2 Static bending stress
Y2.3 Static compressive stress
Y3 Dynamic stresses
Y4 Limiting outer layer stresses
Y4.1 Limiting static stresses
Y4.2 Limiting dynamic stresses
Y5 Vibration dampers
Y5.1 General
Y5.2 Damper type
Y5.3 Damper construction
Y5.4 Damping characteristics (mass dampers only)
Y5.4.1 Frequency response and energy dissipation
Y5.4.2 Impedance
Y5.4.3 Endurance
Y5.4.4 Damper stress
Y5.4.5 Number of dampers per span
Y5.4.6 Damper location
Appendix Z
Z1 Fault ratings
Z1.1 General
Z1.2 Annealing
Z1.3 Sag under fault
Z1.4 Movement of conductors under fault
Appendix AA
AA1 General
AA2 Wire fabrication
AA3 Annealing from elevated temperature operation
AA4 Annealing from fault currents
AA5 Maximum operating temperatures
AA6 References
Appendix BB
Appendix CC
Appendix DD
DD1 General
DD2 Australia
DD3 New Zealand
DD3.1 General
DD3.2 Line reliability load multiplier and security requirements
DD3.3 Temperature effects
DD3.4 Conductor tensions (Fts)
DD3.5 Snow and ice regions
DD3.6 Radial snow and ice build-up on conductors
DD3.7 Co-incident wind and ice conditions
DD3.8 Ice densities
DD3.9 Snow densities
DD3.10 Differential ice loading for high security lines (Level III)
DD3.11 Snow loading on pole structures
Appendix EE
EE1 General
Appendix FF
FF1 Scope
FF2 Principle
FF3 Apparatus
FF4 Test loads
FF4.1 General
FF4.2 Strength limit state
FF4.3 Serviceability limit state
FF5 Procedure
FF5.1 Direct embedded poles
FF5.2 Baseplate-mounted poles
FF6 Report
Cited references in this standard
[Pending Revision]
Industrial fall-arrest systems and devices, Part 2: Horizontal lifeline and rail systems
Electric cables — Twisted pair for control and protection circuits
Limits of electromagnetic interference from overhead a.c. powerlines and high voltage equipment installations in the frequency range 0.15 to 1000 MHz
Industrial fall-arrest systems and devices, Part 4: Selection, use and maintenance
Industrial fall-arrest systems and devices, Part 3: Fall-arrest devices
Content history
[Available Superseded]
DR AS/NZS 7000:2015
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