IEC TR 61328:2017

Live working - Guidelines for the installation of transmission and distribution line conductors and earth wires - Stringing equipment and accessory items

IEC TR 61328:2017(E) provides recommendations for the selection and testing where necessary of conductor stringing equipment and accessory items used for the installation of bare and insulated overhead distribution conductors, bare overhead transmission conductors and overhead earth wires. This third edition cancels and replaces the second edition published in 2003 and IEC TR 61911:2003. It incorporates some technical changes to update equipment work methods and procedures, bringing them in line with the state of the art.

General Information

• Status: Published
• Publication Date: 09-Apr-2017
• ICS: 13.260 - Protection against electric shock. Live working
• ICS: 29.240.20 - Power transmission and distribution lines
• ICS: 29.260.99 - Other electrical equipment for working in special conditions
• Technical Committee: TC 78 - Live working
• Current Stage: DELPUB - Deleted Publication
• Start Date: 05-Nov-2024
• Completion Date: 28-Apr-2023

Relations

• Replaces: IEC TR 61911:2003 - Live working - Guidelines for installation of distribution line conductors - Stringing equipment and accessory items
• Effective Date: 05-Sep-2023
• Revised: IEC TR 61328:2024 - Live working - Guidelines for the installation of transmission and distribution line conductors and earth wires - Stringing equipment and accessory items
• Effective Date: 05-Sep-2023
• Revises: IEC TR 61328:2003 - Live working - Guidelines for the installation of transmission line conductors and earthwires - Stringing equipment and accessory items
• Effective Date: 05-Sep-2023

Overview

IEC TR 61328:2017 - Live working: Guidelines for the installation of transmission and distribution line conductors and earth wires - stringing equipment and accessory items is a Technical Report from the IEC (3rd edition, 2017). It provides recommendations for selection and, where necessary, testing of conductor stringing equipment and accessories used to install bare and insulated overhead distribution conductors, bare transmission conductors and overhead earth wires. This edition cancels IEC TR 61911:2003 and updates equipment, methods and procedures to reflect the state of the art for live working and conductor stringing.

Key topics and technical requirements

• Hazard fundamentals: electric field induction, magnetic induction, induced voltages and currents, electrostatic charging, re‑energization risks and mechanical hazards associated with live working.
• Stringing methods: guidance on slack stringing and tension stringing techniques and decision factors for method selection.
• Stringing equipment: recommendations for specifying and using tensioners, pullers, bullwheel units, reel winders and reel stands, pilot/pulling ropes, woven wire grips, stringing blocks and rollers, conductor cars and hold‑down blocks.
• Earthing and bonding: special earthing requirements for work sites, running earths, stringing block earths, earth mats and earthing procedures for mid‑span splices, clipping in and dead‑ending.
• Testing: type‑test setup and acceptance criteria for earthing devices and accessory items used during live working and conductor installation.
• Communications and procedures: operational controls and safe work practices for live working stringing operations.

Practical applications and users

IEC TR 61328 is intended for professionals involved in overhead line installation and maintenance who need guidance on safe, modern stringing practice:

• Electric utilities and transmission/distribution line owners
• Live‑working crews and linemen performing conductor stringing near energized circuits
• Design and construction engineers specifying stringing equipment and procedures
• Equipment manufacturers and testers developing or type‑testing tensioners, blocks, running earths and related accessories
• Safety managers, inspectors and consultants assessing compliance and risk mitigation for live working operations

The report is practical for planning conductor installation near energized circuits, selecting appropriate stringing equipment, and establishing earthing and testing protocols to control induced voltages and mechanical risks.

Related standards and access

This Technical Report complements other IEC publications on live working and overhead line safety and replaces IEC TR 61911:2003. For implementation, obtain the latest edition and any corrigenda from the IEC webstore to ensure alignment with current practice and national regulations.

Standards Content (Sample)

IEC TR 61328 ®
Edition 3.0 2017-04
TECHNICAL
REPORT
colour
inside
Live working – Guidelines for the installation of transmission and distribution
line conductors and earth wires – Stringing equipment and accessory items
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IEC TR 61328 ®
Edition 3.0 2017-04
TECHNICAL
REPORT
colour
inside
Live working – Guidelines for the installation of transmission and distribution

line conductors and earth wires – Stringing equipment and accessory items

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.260; 29.240.20; 29.260.99 ISBN 978-2-8322-4130-1

– 2 – IEC TR 61328:2017 © IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Understanding the hazard – Basic theory . 17
4.1 General . 17
4.2 Electric field induction from nearby circuits . 17
4.2.1 Overview . 17
4.2.2 Induced voltage . 18
4.2.3 Induced current . 19
4.2.4 Electrostatic charging . 20
4.3 Magnetic field induction from nearby circuits . 20
4.3.1 Induced current . 20
4.3.2 Induced voltage . 21
4.4 Re-energization . 22
4.5 Mechanical risk . 22
5 Conductor stringing methods and equipment . 23
5.1 General . 23
5.2 Slack stringing method . 23
5.3 Tension stringing method . 25
5.4 Stringing equipment . 34
5.4.1 General. 34
5.4.2 Tensioners . 34
5.4.3 Pullers . 37
5.4.4 Reel winders . 41
5.4.5 Reel stands . 42
5.4.6 Pilot rope puller . 43
5.4.7 Pilot rope, pulling rope . 43
5.4.8 Woven wire grip . 44
5.4.9 Stringing blocks . 44
5.4.10 Stringing rollers . 47
5.4.11 Stringing block earth . 48
5.4.12 Running earth . 49
5.4.13 Hold-down block . 49
5.4.14 Conductor car . 49
5.5 Communications . 53
6 Special earthing requirements . 53
6.1 General . 53
6.2 Work site earthing systems . 54
6.2.1 Overview . 54
6.2.2 Use of earth rods . 55
6.2.3 Equipment earths . 56
6.2.4 Earths for conductor, earth wire, metallic and synthetic rope . 56
6.2.5 Earths for earth mat, conductors or earth wires . 56
6.2.6 Earths for mid-span joining of conductors or earth wires . 56

6.2.7 Earths for clipping in the conductors or earth wires . 57
6.2.8 Earths for installation of jumper loops for the conductor . 57
6.2.9 Stringing block earths . 57
6.2.10 Earth mat . 57
6.3 General procedures and use of earthing systems . 62
6.3.1 Overview . 62
6.3.2 General procedures . 62
6.3.3 Installation of the pilot or pulling rope . 63
6.3.4 Stringing of conductors . 64
6.3.5 Splicing of conductors . 65
6.3.6 Sagging of conductors . 66
6.3.7 Clipping-in conductors . 67
6.3.8 Dead-ending and installation of jumper loops . 67
6.3.9 Spacing . 68
6.3.10 Special work on conductors . 68
6.3.11 Fuelling . 69
7 Testing of earthing devices . 69
7.1 General . 69
7.2 Number of type tests . 70
7.3 Type test set-up . 70
7.4 Type test acceptance criterion . 70
Bibliography . 73

Figure 1 – Electric field induction from nearby circuits – Induced voltage . 18
Figure 2 – Electric field induction from nearby circuits – Induced current . 19
Figure 3 – Magnetic field induction from nearby circuits – Induced current . 21
Figure 4 – Magnetic field induction from nearby circuits – Induced voltage . 22
Figure 5 – Slack stringing method . 25
Figure 6 – Tension stringing method . 33
Figure 7 – Bullwheel tensioners . 37
Figure 8 – Bullwheel pullers . 41
Figure 9 – Stringing blocks . 47
Figure 10 – Stringing rollers . 48
Figure 11 – Conductor cars . 50
Figure 12 – Earthing systems . 62
Figure 13 – Typical test set-up for stringing block earth . 71
Figure 14 – Typical test set-up for running earth . 72

– 4 – IEC TR 61328:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LIVE WORKING – GUIDELINES FOR THE INSTALLATION
OF TRANSMISSION AND DISTRIBUTION LINE CONDUCTORS AND
EARTH WIRES – STRINGING EQUIPMENT AND ACCESSORY ITEMS

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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The main task of IEC technical committees is to prepare International Standards. However, a
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data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 61328, which is a Technical Report, has been prepared by IEC technical committee
78: Live working.
This third edition cancels and replaces the second edition published in 2003 and
IEC TR 61911:2003. It incorporates some technical changes to update equipment work
methods and procedures, bringing them in line with the state of the art.
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
78/1145/DTR 78/1174/RVDTR
Full information on the voting for the approval of this Technical Report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
Terms defined in Clause 3 are given in italic print throughout this standard.
The committee has decided that the contents of this publication will remain unchanged until
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related to the specific publication. At this date, the publication will be
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– 6 – IEC TR 61328:2017 © IEC 2017
INTRODUCTION
With the increased difficulty of de-energizing existing overhead lines, installing conductors or
earth wire in circuits nearby, or crossing these existing circuits, creates hazards requiring
special considerations particularly with regard to earthing and bonding. It is also important to
provide protections against induced static charge due to atmospheric conditions, lightning
strikes, or accidental energization.
These potential electrical hazards demand that certain requirements be observed when
choosing equipment and work methods for the protection of personnel or equipment.

LIVE WORKING – GUIDELINES FOR THE INSTALLATION
OF TRANSMISSION AND DISTRIBUTION LINE CONDUCTORS AND
EARTH WIRES – STRINGING EQUIPMENT AND ACCESSORY ITEMS

1 Scope
This document, which is a Technical Report, provides recommendations for the selection and
testing where necessary of conductor stringing equipment and accessory items used for the
installation of bare and insulated overhead distribution conductors, bare overhead
transmission conductors and overhead earth wires.
Procedures are recommended for proper earthing in order to protect equipment, components
and personnel from currents which can result from accidental contact with nearby energized
conductors or from the induced or fault currents which can result in some circumstances.
The items of equipment under consideration in this document are used for transmission and
distribution systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60050-466, International Electrotechnical Vocabulary – Chapter 466: Overhead lines
(available at www.electropedia.org)
IEC 60050-651, International Electrotechnical Vocabulary – Part 651: Live working
(available at www.electropedia.org)
IEC 60743, Live working – Terminology for tools, devices and equipment
3 Terms and definitions
NOTE Terminology for equipment and procedures associated with the installation of overhead conductors and
earth wires varies widely throughout the utility industry.
For the purposes of this document, the terms and definitions given in IEC 60050-466,
IEC 60050-651, IEC 60743 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

– 8 – IEC TR 61328:2017 © IEC 2017
3.1
anchor
anchor log
deadman
sledge
snub
device that serves as a reliable support to hold an object firmly in place
3.2
basket
bucket
device designed to be attached to the boom tip of a line truck, crane or aerial lift to support
workmen in an elevated working position
3.3
birdcaging
opening up of the outer layers of a conductor to form a bulge in the conductor
3.4
block
tackle
pulley
device designed with one or more sheaves, a synthetic plastic or metal shell, and an
attachment hook or shackle
3.5
bond
equipotential connection
connection
electrical connection used to bring all personnel and objects in the work area to the same
potential
3.6
bullwheel
wheel or wheels incorporated as an integral part of a puller or tensioner with multiple offset
grooves allowing the continuous winding of a conductor or a rope to generate pulling or
braking tension, through friction
3.7
circuit
conductor or system of conductors through which an electric current is
intended to flow
Note 1 to entry: In transmission and distribution lines, a circuit usually consists of three phases for AC lines, and
two poles for DC lines.
[SOURCE: IEC 60050-466:1990, 466-01-07]
3.8
clearance
minimum separation between two conductors operating at different voltages, between
conductors and supports or other objects, or between conductors and the earth
3.9
clipping-in
clamping-in
clipping
transferring of sagged conductors from the stringing blocks to their permanent suspension
positions and the installing of the permanent suspension clamps

3.10
compression joint
conductor splice
sleeve
splice
tubular compression (or implosive) sleeves designed and fabricated from aluminium, copper
or steel compressed to join or terminate conductors or overhead earth wires
3.11
conductor
cable
wire
bare or insulated wire or combination of wires, suitable for carrying an electric current
3.12
conductor bundle
set of individual conductors connected in parallel and disposed in a uniform geometrical
configuration, that constitutes one phase or pole of a line
[SOURCE: IEC 60050-466:1990, 466-10-20]
3.13
conductor car
cable buggy
cable car
conductor trolley
line car
spacer buggy
spacing bicycle
spacer cart
device designed to carry workmen riding on sagged single or bundle conductors, enabling
them to inspect the conductors for damage or install spacers, dampers or other attachments
3.14
conductor cover
line hose
line guard
flexible or rigid protective cover used to shroud the conductor providing electrical protection
3.15
conductor clamp
chicago grip
conductor grip
come-along
come-along clamp
preformed, bolted or wedge-type device designed to permit the pulling or temporary holding of
the conductor or of the rope without splicing on fittings, eyes, etc.
3.16
connector link
pulling rope connector
link
peanut
fixed joint
rigid link designed to connect pulling ropes and usually designed to pass through the grooves
of bullwheels on the puller when under load

– 10 – IEC TR 61328:2017 © IEC 2017
3.17
cradle blocks system
system of cradle stringing blocks, spacer rope, pulling rope, a brake unit, and a radio
controlled motorized tug, which use the existing conductor as support when installing the new
conductor, to create a supporting protection in case of critical crossings
3.18
crossing structure
guard structure
H-frame
rider pole structure
scaffolding
temporary structure
structure built of poles, tubes, or other specialized equipment, sometimes using rope nets,
used whenever conductors are strung over roads, power lines, communications circuits,
highways or railroads to prevent the conductor from contacting any of these facilities in the
event of equipment failure, broken pulling ropes, loss of tension, etc.
3.19
dead
de-energized
at an electric potential equal to or not significantly different from that of the earth at the work
site
[SOURCE: IEC 60050-651:2014, 651-21-09]
3.20
dead-ending
procedure which results in the termination of conductors at an anchor structure
3.21
(local) earth
(local) ground (US)
part of the Earth which is in electric contact with an earth electrode and the electric potential
of which is not necessarily equal to zero
[SOURCE: IEC 60050-195:1998, 195-01-03]
3.22
earthing cable
flexible conductor usually of stranded copper with a transparent cable protective sheath, and
attached at both ends to clamps, designed to connect conductors or equipment to earth or to
an earth mat
3.23
earth clamp
clamp forming part of an earthing and short-circuiting device connecting an earthing cable, or
a connecting cluster to an earthing conductor, or an earth electrode or a reference potential
[SOURCE: IEC 60050-651:2014, 651-25-03]
3.24
earth mat
counterpoise
earth grid
system of interconnected bare conductors arranged in a pattern over a specified area on, or
buried below, the surface of the Earth

3.25
earth rod
earth electrode
rod driven into the Earth to serve as an earthing terminal
EXAMPLE Copper-clad steel rod, solid copper rod, or galvanized steel rod.
3.26
earth wire
shield wire
skywire
static wire
conductor connected to earth at some or all supports, which is suspended usually but not
necessarily above the line conductors to provide a degree of protection against lightning
strikes
[SOURCE: IEC 60050-466:1990, 466-10-25]
3.27
earthing stick
earthing pole
insulating component equipped with a permanent or detachable end fitting for installing
clamps, short-circuiting bars or conductive extension components onto electrical installation
[SOURCE: IEC 60050-651:2014, 651-25-05]
3.28
earthing system
system consisting of all interconnected earthing connections in a specific area, such as a pull
section
3.29
electromagnetic induction
electromagnetic coupling
phenomenon that produces both an induced voltage and current either through electric or
magnetic field induction
3.30
electric field induction
capacitive coupling
process of generating voltages and/or currents in a conductive object or electrical circuit by
means of time-varying electric fields
3.31
energized
alive
current-carrying
hot
live
at a potential significantly different from that of the earth at the work site and which presents
an electrical hazard
Note 1 to entry: A part is energized when it is electrically connected to a source of electric energy. It can also be
energized when it is electrically charged under the influence of an electric or magnetic field.
[SOURCE: IEC 60050-651:2014, 651-21-08]

– 12 – IEC TR 61328:2017 © IEC 2017
3.32
equipotential
set of points all of which have the same potential
3.33
factor of safety
ratio of ultimate strength or yield strength to the maximum allowable applied force or load
3.34
fault
physical condition that causes a device, a component, or an element to fail to perform in a
required manner
3.35
fault current
earth fault current
current flowing at a given point of a network resulting from a fault at another point of this
network
3.36
hold-down block
block designed to prevent uplift and to maintain the pilot rope or conductor(s) inside the
sheaves of the stringing block installed on the tower
3.37
isolated
disconnected completely from other devices or circuits, and thus separated
physically, electrically and mechanically from all sources of electrical energy
Note 1 to entry: Such separation may not eliminate all effects of electromagnetic induction.
3.38
joint protector
joint stiffener
sleeve protector
splice protector
cover joint
split sleeve which fits over a compression joint or splice, and is used to protect the
compression joint from bending or damage if the joint passes through stringing blocks
3.39
jumper
dead end loop
conductor that connects the conductors on opposite sides of a dead-end structure
3.40
magnetic field induction
inductive coupling
process of generating voltages and/or currents in an electrical circuit by means of time-
varying magnetic fields
3.41
pilot rope
lead line/rope
leader
P-line/rope
straw line/rope
pre-pilot rope
lightweight rope, either wire rope or synthetic fibre rope, used to pull heavier pulling ropes
which in turn are used to pull the conductor
3.42
pilot rope puller
device designed to payout and rewind pilot ropes during stringing operations
3.43
portable earth interrupter tool
portable switching device designed to break high circulating currents, and which prevents an
unmanageable large arc from occurring in the removal of the last earth in an earthing system
3.44
pull section
pull setting
stringing section
section of line where the conductor is being pulled into place by the puller and tensioner
3.45
pull site
puller set-up
location in a pull section where the puller, reel winder and anchors (snubs) are located
3.46
puller
drum
hoist
tugger
equipment designed to pull pulling ropes during stringing operations
[SOURCE: IEC 60743:2013, 14.1.3, modified — Admitted terms have been changed,
"conductor(s)" has been deleted from the definition, and Notes to entry have been deleted.]
3.47
puller-tensioner
equipment designed to pull pulling ropes or conductor(s) or to hold mechanical tension
against a pulling rope or conductor(s) during stringing operations
[SOURCE: IEC 60743:2013, 14.1.5, modified — Notes to entry have been deleted.]
3.48
pulling rope
bull line/rope
hard line/rope
sock line/rope
anti-twisting braided rope
high strength rope, normally steel wire rope or less frequently synthetic fibre rope, used to
pull the conductor, with formation and construction that ensure non-twisting capability under
pull operation
– 14 – IEC TR 61328:2017 © IEC 2017
3.49
pulling vehicle
pulling tractor
towing vehicle
piece of mobile ground or air borne equipment capable of pulling pilot ropes, pulling ropes or
conductors
3.50
reel stand
reel elevator
reel trailer
reel truck
drum stand
drum elevator
device designed to support one or more reels and having the possibility of being skid, trailer
or truck mounted
3.51
reel winder
takeup reel winder
takeup stand
takeup winder
machine designed to work in conjunction with a bullwheel puller or puller-tensioner, and to
serve as a recovery unit for the pulling rope
3.52
running board
headboard
pulling device designed to permit stringing several conductors simultaneously with a single
pulling rope
[SOURCE: IEC 60743:2013, 14.2.3, modified — Notes to entry have been deleted.]
3.53
running earth
earthing roller
moving earth
rolling earth
travelling earth
portable device designed to connect a moving conductor or a pulling/pilot rope to an electrical
earth
[SOURCE: IEC 60743:2013, 14.2.1, modified — In the definition, "used" has been replaced by
"designed", and Note 1 to entry has been deleted.]
3.54
sagging
process of pulling conductors up to their final tension or sag
3.55
slack stringing
method of stringing conductor(s) slack without the use of a tensioner, with some minimal
braking applied to the conductor reel
3.56
spacing
spacering
process of installing the spacers between the bundle subconductors in each phase

3.57
splicing
jointing
process of joining the ends of conductor lengths to form a continuous mechanical and
electrical connection
3.58
stringing
process of pulling pilot ropes, pulling ropes and conductors over stringing blocks supported on
structures of overhead lines
3.59
stringing block
block
conductor running block
dolly
running out block
sheave
stringing sheave
stringing traveller
traveller
pulley
sheave, or sheaves, complete with a frame used separately or in groups and suspended from
structures to permit the stringing of conductors
[SOURCE: IEC 60743:2013, 14.2.2, modified — Note 1 to entry has been deleted.]
3.60
stringing block earth
conductor running block earth
sheave earth
traveller earth
portable device attached to a stringing block and designed to connect a moving conductor or
pulling/pilot rope to an electrical earth
3.61
structure
pole
tower
tower or pole which supports the conductors on insulators, usually steel lattice or tubular type
for transmission line and wood, metal, synthetic, or concrete for distribution line
3.62
subconductor
each conductor in a conductor bundle arranged in a vertical, horizontal, square, round, or
other suitable configuration
3.63
swivel
bullet, swivel joint
device joining one pulling rope to a conductor or conductors to a running board relieving
torsional forces on conductors

– 16 – IEC TR 61328:2017 © IEC 2017
3.64
tension site
conductor payout station
payout site
reel set-up
tensioner set-up
location on a pull section where the tensioner, reel stands, conductor reels and anchors
(snubs) are located
3.65
tension stringing
process of using pullers and tensioners to give the conductor sufficient tension and positive
control during the stringing operation to keep it clear of the ground surface and other
obstacles which could cause damage to the surface of the conductor
3.66
tensioner
bullwheel tensioner
brake
retarder
equipment designed to hold mechanical tension against a pulling rope or conductor(s) during
the stringing operation
[SOURCE: IEC 60743:2013, 14.1.2, modified — Note 1 to entry has been deleted.]
3.67
tractor
cat
crawler
sag tractor
tracked unit employed to pull pulling/pilot ropes, sag conductors, at clear pull and tension
sites and provide a temporary anchor
3.68
ultimate strength
breaking strength
strength of a member or of part of an assembly at which failure of that member or part of the
assembly occurs, with the result that it can no longer support a load or perform its intended
function
3.69
working load limit
allowable load
maximum load
safe working load
limit of load that can be imposed safely on a member or assembly usually calculated by
dividing the ultimate or breaking strength by the accepted factor of safety
3.70
woven wire grip
kellem
mesh sock
sock
stocking
wire mesh grip
device designed to allow the temporary joining or pulling of conductors without the need of
special eyes, links or grips
3.71
yield strength
strength of a member or of part of an assembly at which permanent deformation of that
member or part of the assembly occurs, with the result that it can no longer perform its
intended function
4 Understanding the hazard – Basic theory
4.1 General
The protection of personnel from injury during the process of installing conductors on
transmission and distribution lines is most important, both for electrical and mechanical risk.
For electrical risk, the personnel at the work site installing these new conductors shall be
protected against induced voltages and currents caused by energized adjacent lines. The
personnel shall also be protected from the hazards which can result from accidental line
energization. Personnel protection can be achieved by properly applying adequate protective
earthing systems at the work area, by the use of correct work methods and specialized
training, and by the use of equipment which incorporates devices to protect against these
types of hazards.
Electrical charges or voltage may appear on a conductor being installed, or on the other
equipment and components such as the ropes involved in the conductor stringing process,
due to one or more of the following factors:
a) electromagnetic induction (i.e. capacitive and/or inductive coupling) from adjacent
energized lines, or when crossing over energized lines;
b) accidental contact of the conductor or ropes being installed, with an existing adjacent
energized line; this is the most likely cause of electrical hazard when working on
distribution lines in crowded urban areas where existing circuits cannot be shut down;
c) electrostatic charging (i.e. conductive coupling) of the conductors or ropes by atmospheric
conditions or by an adjacent high voltage direct current (HVDC) transmission line;
d) switching error in which the conductor being installed is accidentally energized;
e) lightning strikes in the vicinity, or a lightning strike to the conductor being installed or
other equipment and components such as the ropes involved in the stringing process.
The hazards caused by lightning strikes, accidental contact with a live line and switching
errors are generally understood. However, the hazards caused by induced voltages and
currents are probably less understood and are therefore explained in some detail here. It is
important to note that the basic difference between the hazard caused by induction, and the
other sources given above is that the induction is continuous as long as the source line is
energized, rather than instantaneous or transient in the case of lightning or a fault current.
For mechanical risk, the personnel shall be protected against unexpected breaking of the
pulling line elements, movement of the equipment under load, handling of material, lifting of
material and tools on the tower, working activity at height.
NOTE In the following examples, induction is shown as occurring on a conductor; however, the same result and
hazard will occur for other components used in the conductor stringing process, such as conducting (metallic)
pulling or pilot ropes, or earth wires.
4.2 Electric field induction from nearby circuits
4.2.1 Overview
There are two common types of induction problems caused by nearby energized AC lines:
electric field and magnetic field. Each has both voltage and current implications.

– 18 – IEC TR 61328:2017 © IEC 2017
If the nearby line is an energized DC transmission line, the induced voltage is the result of ion
drift, and can result in even higher voltages than if the nearby line were an AC line. Magnetic
induction would only be related to the ripple effect, and is therefore much less than would be
the case if the nearby line were an AC line.
4.2.2 Induced voltage
The electric field around an energized conductor produces a voltage on an isolated and
unearthed conducting object nearby (see Figure 1).
The voltage produced depends on the source voltage magnitude and the geometry of the
system but not on the length of the parallel between the energized line and the new conductor
being installed.
If the circuit is unearthed, the induced voltage may be as much as 30 % of the energized line
voltage. This induced voltage can be calculated, but it is generally not necessary to do so. If
the new conductor being installed is earthed at any point, the charge is reduced to a much
lower steady state value, depending on the resistance to earth of the earth path.
Existing energized
line
200 Typical voltage
gradient
New conductors
being installed
IEC
a) Pictorial view
Existing energized line
New conductor
being installed
Open line entrance breaker
and switch (isolator)
V
Stringing block earth
Earth
or running earth
Induced voltage
IEC
b) Diagrammatic view
NOTE These figures are simplified. The three phases of the existing energized line are involved in the induction.
Figure 1 – Electric field induction from nearby circuits – Induced voltage

4.2.3 Induced current
With an AC system, the energized lines and the earthed conductor being installed act like the
plates of a condenser or capacitor, and a charging current flows across the air gap between
them (see Figure 2).
The two following aspects should be considered.
a) A current flows through the temporary earth from the conductor to earth. It is proportional
to the length of the parallel between the energized conductor and the new conductor being
installed. This current may amount to several amperes.
b) If the temporary earth becomes defective, is dislodged, or removed, the capacitive voltage
is immediately re-established. Thus, if a worker is in fairly solid contact with the system
and the only earth is dislodged, the worker can be exposed to a dangerous voltage and
current. If the worker attempts to contact the conductor or connected parts, he will receive
a dangerous discharge current, followed by a steady-state current. Thus, the worker
shall avoid coming in close proximity to the conductor or connected parts since the
induced voltage may be high enough to cause arc-over. Also, it should be noted that the
steady-state capacitive current occurring after the contact may reach a dangerous level.
Existing energized
line Current flow
Temporary
earth
New conductors
being installed
IEC
a) Pictorial view
Existing energized line
New conductor
being installed
Open line entrance breaker
and switch (isolator)
A
Temporary
earth
IEC
b) Diagrammatic view
NOTE These figures are simplified. The three phases of the existing energized line are involved in the induction.
Figure 2 – Electric field induction from nearby circuits – Induced current

– 20 – IEC TR 61328:2017 © IEC 2017
4.2.4 Electrostatic charging
It should be noted that a potential hazard exists where a line to be worked on is still insulated
but has been isolated, as it may have a voltage due to electrostatic charging resulting from
atmospheric conditions, or trapped charges from switching. Therefore, before starting any
work operation on the distribution line, it shall be earthed at least at one point to discharge
the electrostatic charge.
4.3 Magnetic field induction from nearby circuits
4.3.1 Induced current
In addition to the electric field caused by the voltage of the adjacent energized line, another
effect is caused by the current flowing in the energized line.
The energized, current-carrying conductor and the nearby conductor being installed may be
looked upon as the p
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