IEC TR 61328:2024

IEC TR 61328 ®
Edition 4.0 2024-11
TECHNICAL
REPORT
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 4.0 2024-11
TECHNICAL
REPORT
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 978-2-8322-9554-0

– 2 – IEC TR 61328:2024 © IEC 2024
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and acronyms . 7
3.1 Terms and definitions . 7
3.2 Acronyms . 15
4 Understanding the hazards – Basic theory . 15
4.1 General . 15
4.2 Electric field induction from nearby circuits . 16
4.2.1 Overview . 16
4.2.2 Induced voltage . 16
4.2.3 Induced current . 17
4.2.4 Electrostatic charging . 18
4.3 Magnetic field induction from nearby circuits . 18
4.3.1 Induced current . 18
4.3.2 Induced voltage . 20
4.4 Re-energization . 20
4.5 Mechanical risk . 21
5 Conductor stringing methods and equipment . 21
5.1 General . 21
5.2 Slack stringing method . 22
5.3 Tension stringing method . 24
5.4 Stringing equipment . 32
5.4.1 General . 32
5.4.2 Tensioners . 32
5.4.3 Pullers . 34
5.4.4 Reel winders . 38
5.4.5 Reel stands . 39
5.4.6 Pilot rope puller . 41
5.4.7 Pilot rope and pulling rope . 41
5.4.8 Woven wire grip . 42
5.4.9 Stringing blocks . 42
5.4.10 Stringing rollers . 45
5.4.11 Stringing block earth . 46
5.4.12 Running earth . 47
5.4.13 Hold-down block . 47
6 Special earthing applications . 48
6.1 General . 48
6.2 Earthing systems . 49
6.2.1 Overview . 49
6.2.2 Use of earth rods . 49
6.2.3 Equipment earths . 50
6.2.4 Earths for conductor, earth wire, metallic and synthetic rope . 50
6.2.5 Earths for earth mat, conductors or earth wires. 50
6.2.6 Earths for mid-span joining of conductors or earth wires . 51

6.2.7 Earths for clipping in the conductors or earth wires . 51
6.2.8 Earths for installation of jumper loops for the conductor . 51
6.2.9 Stringing block earths . 51
6.2.10 Earth mat . 51
6.3 Procedures and application of earthing systems . 56
6.3.1 Overview . 56
6.3.2 Installation of the pilot or pulling rope . 56
6.3.3 Stringing of conductors . 57
6.3.4 Splicing of conductors . 57
6.3.5 Sagging of conductors . 57
6.3.6 Clipping-in conductors . 57
6.3.7 Dead-ending and installation of jumper loops . 58
6.3.8 Spacing . 58
6.3.9 Special work on conductors . 58
6.3.10 Fuelling . 58
Bibliography . 59

Figure 1 – Electric field induction from nearby circuits – Induced voltage . 17
Figure 2 – Electric field induction from nearby circuits – Induced current . 18
Figure 3 – Magnetic field induction from nearby circuits – Induced current . 19
Figure 4 – Magnetic field induction from nearby circuits – Induced voltage . 20
Figure 5 – Slack stringing method . 24
Figure 6 – Tension stringing method . 31
Figure 7 – Bullwheel tensioners . 34
Figure 8 – Bullwheel pullers . 37
Figure 9 – Reel winder . 39
Figure 10 – Reel stand and carrier . 40
Figure 11 – Stringing blocks. 45
Figure 12 – Stringing rollers . 46
Figure 13 – Hold-down block diagram of use . 48
Figure 14 – Earthing systems . 56

– 4 – IEC TR 61328:2024 © IEC 2024
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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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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IEC TR 61328 has been prepared by IEC technical committee 78: Live working. It is a Technical
Report.
This fourth edition cancels and replaces the third edition published in 2017. It incorporates
some technical changes to update equipment work methods and procedures, bringing them in
line with the state of the art. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Keeping the content of the previous edition but without mandatory terms as required by IEC
ISO Directives 2 for a Technical Report.

The text of this Technical Report is based on the following documents:
Draft Report on voting
78/1455/DTR 78/1475/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
In this document, the following print types are used:
• Terms defined in Clause 3 are given in italic font.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC TR 61328:2024 © IEC 2024
INTRODUCTION
This document discusses general tensions, stringing methods of transmission and distribution
line conductors. Special attention is given to the equipment involved, such as tensioners,
pullers, grips, blocks and rollers. Due to the hazards involved in stringing near energized lines,
the general concepts of electric and magnetic induction are presented along with safe
application methods of earthing equipment.
The overall intent of this document is to provide state of the art methods in an informative
manner, recognizing that there are several procedural variations within the industry. There are
also multiple standards and regulatory jurisdictions which prescribe methods and requirements
beyond the scope of this document.

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 information for the selection of conductor
stringing, earthing and bonding equipment used for the installation of bare and insulated
overhead distribution conductors, as well as overhead transmission conductors and overhead
earth wires.
Procedures are given for installation and maintenance of distribution and transmission
conductors. A discussion of electric hazards is provided as well as relevant earthing and
bonding techniques.
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 60050-466:1990, International Electrotechnical Vocabulary (IEV) – Part 466: Overhead
lines (available at www.electropedia.org)
IEC 60050-651:2014, International Electrotechnical Vocabulary (IEV) – Part 651: Live working
(available at www.electropedia.org)
IEC 60743:2013, Live working – Terminology for tools, devices and equipment
3 Terms, definitions and acronyms
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 terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Terms and definitions
3.1.1
anchor
anchor log
deadman
sledge
snub
device that serves as a reliable support to hold an object firmly in place

– 8 – IEC TR 61328:2024 © IEC 2024
3.1.2
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
3.1.3
block
tackle
pulley
device designed with one or more sheaves, a synthetic plastic or metal shell, and an attachment
hook or shackle
3.1.4
bond
equipotential connection
connection
electrical connection used to bring all personnel and objects in the work area to the same
potential
3.1.5
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
3.1.6
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]
3.1.7
clearance
minimum separation between two conductors operating at different voltages, between
conductors and supports or other objects, or between conductors and the earth
3.1.8
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
3.1.9
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

3.1.10
conductor
cable
wire
bare or insulated wire or combination of wires, suitable for carrying an electric current
3.1.11
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]
3.1.12
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
3.1.13
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.
3.1.14
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
3.1.15
dead-ending
procedure which results in the termination of conductors at an anchor structure
3.1.16
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
3.1.17
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]

– 10 – IEC TR 61328:2024 © IEC 2024
3.1.18
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
3.1.19
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.
3.1.20
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]
3.1.21
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]
3.1.22
earthing system
system consisting of all interconnected earthing connections in a specific area, such as a pull
section
3.1.23
electromagnetic induction
electromagnetic coupling
phenomenon that produces both an induced voltage and current either through electric or
magnetic field induction
3.1.24
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

3.1.25
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]
3.1.26
equipotential
set of points all of which have the same potential
3.1.27
fault
physical condition that causes a device, a component, or an element to fail to perform in a
required manner
3.1.28
fault current
earth fault current
current flowing at a given point of a network resulting from a fault at another point of this network
3.1.29
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
3.1.30
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.
3.1.31
jumper
dead end loop
conductor that connects the conductors on opposite sides of a dead-end structure
3.1.32
magnetic field induction
inductive coupling
process of generating voltages and/or currents in an electrical circuit by means of time-varying
magnetic fields
3.1.33
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

– 12 – IEC TR 61328:2024 © IEC 2024
3.1.34
pilot rope puller
device designed to payout and rewind pilot ropes during stringing operations
3.1.35
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
3.1.36
pull section
pull setting
stringing section
section of line where the conductor is being pulled into place by the puller and tensioner
3.1.37
pull site
puller set-up
location in a pull section where the puller, reel winder and anchors (snubs) are located
3.1.38
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]
3.1.39
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]
3.1.40
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
3.1.41
pulling vehicle
pulling tractor
towing vehicle
piece of mobile ground or air borne equipment capable of pulling pilot ropes, pulling ropes or
conductors
3.1.42
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
3.1.43
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
3.1.44
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]
3.1.45
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]
3.1.46
sagging
process of pulling conductors up to their final tension or sag
3.1.47
slack stringing
method of stringing conductor(s) slack without the use of a tensioner, with some minimal braking
applied to the conductor reel
3.1.48
spacing
spacering
process of installing the spacers between the bundle subconductors in each phase
3.1.49
splicing
jointing
process of joining the ends of conductor lengths to form a continuous mechanical and electrical
connection
– 14 – IEC TR 61328:2024 © IEC 2024
3.1.50
stringing
process of pulling pilot ropes, pulling ropes and conductors over stringing blocks supported on
structures of overhead lines
3.1.51
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]
3.1.52
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
3.1.53
structure
pole
tower
tower or pole which supports the conductors on insulators, usually steel lattice or tubular type
for transmission and distribution line and wood, metal, synthetic, or concrete for distribution line
3.1.54
subconductor
each conductor in a conductor bundle arranged in a vertical, horizontal, square, round, or other
suitable configuration
3.1.55
swivel
bullet, swivel joint
device joining one pulling rope to a conductor or conductors to a running board relieving
torsional forces on conductors
3.1.56
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
3.1.57
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
3.1.58
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]
3.1.59
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
3.1.60
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
3.2 Acronyms
AC alternating current
DC direct current
HTLS high temperature low sag
HVDC high voltage direct current
OPGW optical ground wire
TV television
TW trapezoidal wire
4 Understanding the hazards – Basic theory
4.1 General
The process of installing conductors on transmission and distribution lines exposes personnel
to both electrical and mechanical risk.
Electrical worksite hazards include induced voltages and currents from energized adjacent lines
as well as accidental energization of the conductors being installed. Personnel protection can
be achieved through correct work methods, specialized training and properly applying adequate
protective earthing and bonding systems.

– 16 – IEC TR 61328:2024 © IEC 2024
Electrical charges or voltage can appear on a conductor being installed, or on other equipment
and components such as conducting (metallic) pulling rope, pilot rope or earth wires due to one
or more of the following factors:
a) electromagnetic induction from adjacent energized lines/circuits, 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.
Mechanical worksite hazards include unexpected breaking of the pulling line elements,
movement of the equipment under load, handling of material, lifting of material and tools on the
tower and working activity at height.
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.
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
systems 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 can 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.

a) Pictorial view
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 capacitor, and a charging current flows across the air gap between them (see
Figure 2).
The two following aspects are 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 can 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, since the induced voltage can be high enough to cause arc-
over. Also, the steady-state capacitive current occurring after the contact can reach a
dangerous level.
– 18 – IEC TR 61328:2024 © IEC 2024

a) Pictorial view
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
4.2.4 Electrostatic charging
A potential hazard exists where a line to be worked on is still insulated but has been isolated,
as it can have a voltage due to electrostatic charging resulting from atmospheric conditions, or
trapped charges from switching. This hazard is mitigated by earthing the line at only 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 can be
looked upon as the primary and secondary windings of an air-core transformer.

If the new conductor is earthed at two places, it acts like the secondary coil of an air-core
transformer, short-circuited through the earth. A circulating current will flow along the
new conductor, through one earth connection, back through the earth and up the other earth to
complete the loop (see Figure 3a).
This electromagnetic current is proportional to the current in the energized line and is
dependent on the geometry and impedance of the system.
If a series of earths is applied, a series of loops is formed, each carrying current (see Figure 3b).
It would appear that the currents would cancel in the intermediate earths.
If there is a great difference in impedance of the earths in adjacent loops, for example a lake in
the earth return of one, and rock in the other, the intermediate earth can carry almost the full
circulating current.
If there are transpositions in the energized circuit, the phase angle of the induced current will
be different along the line and can also create large circulating currents in the earthing system.
When work is being done in the vicinity of a heavily loaded energized line, or a fault occurs on
the adjacent energized line, the current induced in the new conductor being installed can be
very large and can affect the choice of earthing assemblies.

a) Two earths on new conductor allow circulating current to flow

b) Circulating currents with multiple earths

NOTE These figures are simplified. The three phases of the existing energized line are involved in the induction.
Figure 3 – Magnetic field induction from nearby circuits – Induced current

– 20 – IEC TR 61328:2024 © IEC 2024
4.3.2 Induced voltage
Continuing the analogy of an air-core transformer, if the new conductor being installed becomes
earthed at one point only, for example by the removal of the last but one temporary earth, an
open circuit secondary voltage to earth appears on the line. This voltage is essentially zero at
the location of the remaining earth and increases in proportion to the length of the parallel
(Figure 4a)).
At the moment of removing the last but one earth, the circulating electromagnetic current is
broken and a voltage appears across the gap. This voltage can become dangerously high, in
the case of a long parallel between the energized line and the new conductor being installed. It
might have to be limited by a technique of sequential earthing, in which the new conductor is
subdivided by intermediate earths. The sections are then short enough to limit the open circuit
voltage because the earths are sequentially removed (Figure 4b)).

a) Open circuit voltage with one earth only

NOTE In area of high induction, removal of the last earth can be done with a portable earth interrupter tool.
b) Temporary earths to be applied and removed sequentially

Figure 4 – Magnetic field induction from nearby circuits – Induced voltage
4.4 Re-energization
Accidental contact with an energized conductor, or a switching error, can occur. Equipotential
earth systems applied on each site are an effective means of providing a safe work zone in
these situations.
4.5 Mechanical risk
The maximum pulling tension applied is usually different from that applied at the tensioner This
depends on the design of the line and the orography of the line path. In the case of mountainous
areas, the maximum value of the pull force applied could be much greater than sag tension.
Moreover, tension values are close to the sagging tension values when crossing existing lines
where limited clearance must be respected.
It is possible that the weight of the stringing equipment is not able to provide the necessary
stability and can need additional anchoring. Equipment manufactures usually specify the proper
set up methods to avoid u
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