IEC 62568:2015

Overhead lines - Method for fatigue testing of conductors

IEC 62568:2015 provides test procedures to measure the fatigue characteristics of conductor/clamp systems. For the purposes of this standard, clamps shall be of the metallic type only. Key words: Conductors, Fatigue, Fatigue test

Lignes aériennes - Méthode d'essai de fatigue des conducteurs

IEC 62568:2015 fournit des procédures d'essais pour mesurer les caractéristiques de fatigue de systèmes conducteur/pince. Pour les besoins de la présente norme, les pinces doivent être de type métallique uniquement. Mots-clés: conducteurs, fatigue, Essai de fatigue

General Information

• Status: Published
• Publication Date: 08-Jul-2015
• ICS: 29.060.01 - Electrical wires and cables in general
• ICS: 29.240.20 - Power transmission and distribution lines
• Technical Committee: TC 7 - Overhead electrical conductors
• Drafting Committee: PT 62568 - TC 7/PT 62568
• Current Stage: PPUB - Publication issued
• Start Date: 31-Jul-2015
• Completion Date: 09-Jul-2015

IEC 62568:2015 - Overhead Lines: Method for Fatigue Testing of Conductors

Overview

IEC 62568:2015 is an international standard published by the International Electrotechnical Commission (IEC) that defines test procedures for measuring the fatigue characteristics of conductor/clamp systems used in overhead power lines. Specifically, this standard applies to metallic clamps and establishes a method to evaluate conductor fatigue life through resonance fatigue testing, simulating real-world vibration conditions. Understanding fatigue behavior is critical for ensuring the reliability and safety of overhead electrical conductors over their operational lifespan.

Key Topics

• Fatigue Testing Methodology
  The standard specifies a resonance fatigue test setup where conductors undergo cyclic bending motion induced at their natural frequencies. This method replicates the fatigue stress conductors experience due to wind-induced vibrations and other mechanical loads.

• Test Setup and Parameters

  • Use of metallic clamps exclusively for conductor holding during tests
  • Bench length and tension applied to the conductor to simulate field conditions
  • Sinusoidal excitation at resonant frequency to induce fatigue vibrations
  • Measurement of bending amplitude and dynamic stress to assess fatigue

• Failure Criteria
  Fatigue failure is identified when:

  • The first wire breaks, or
  • Three wires or 10% of envelope wires fail in composite conductors, or
  • The entire wire count fails in homogeneous conductors.

• Key Measurements and Definitions

  • Antinode amplitude: Peak vibration amplitude at the mid-loop
  • Bending amplitude: Peak-to-peak vibration amplitude at 89 mm from the last point of contact with the clamp
  • Idealized bending stress/strain: Calculated alternating stress and strain based on measured bending and the Young’s modulus of outer conductor material

• Fatigue Data Interpretation
  Fatigue life is expressed as cycles to failure relative to the vibration intensity, enabling comparison across different conductor types and sizes.

Applications

IEC 62568:2015 serves multiple practical purposes in the power transmission and distribution industry:

• Design and Selection of Conductors and Clamps
  Ensures that conductor/clamp systems withstand mechanical stresses induced by wind and vibrations, enhancing infrastructure durability.

• Quality Assurance and Compliance
  Facilitates standardized fatigue testing for manufacturers seeking international certification and compliance with rigorous safety standards.

• Maintenance Planning
  Helps utilities predict fatigue life and schedule inspections or replacements before conductor failures occur, reducing downtime and outage risks.

• Research and Development
  Provides a reliable test methodology for R&D on new conductor materials, construction types, and clamp designs to improve fatigue resistance.

Related Standards

• IEC 60228 – Conductors of insulated cables: Defines conductors' classifications, relevant for determining conductor properties in fatigue tests.
• IEC 60889 – Overhead lines – Conductors: Covers general conductor specifications which complement fatigue testing standards.
• ISO/IEC Directives Part 2 – Guidelines on drafting international standards, ensuring harmonization in standard development processes.
• IEC 61089 – Overhead lines – Conductors, accessories, and fittings: Offers insights into related hardware used alongside conductors and clamps.

Summary

IEC 62568:2015 is a critical standard for accurately assessing the fatigue behavior of overhead line conductors under dynamic mechanical stress. By defining a method for resonance-type fatigue testing with metallic clamps, it enables power utilities and manufacturers to ensure conductor longevity, optimize design, and enhance safety. Incorporating this standard into testing regimes helps extend service life and reliability of overhead electrical infrastructure in challenging environmental conditions. Key keywords include overhead lines, conductor fatigue, fatigue test, metallic clamps, and resonance fatigue testing.

Standards Content (Sample)

IEC 62568 ®
Edition 1.0 2015-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Overhead lines – Method for fatigue testing of conductors

Lignes aériennes – Méthode d'essai de fatigue des conducteurs

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IEC 62568 ®
Edition 1.0 2015-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Overhead lines – Method for fatigue testing of conductors

Lignes aériennes – Méthode d'essai de fatigue des conducteurs

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.060, 29.240.20 ISBN 978-2-8322-2778-7

– 2 – IEC 62568:2015 © IEC 2015
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Terms and definitions . 6
3 Symbols and abbreviated terms . 7
4 Requirements . 7
5 Test method . 7
5.1 Test set-up . 7
5.1.1 General . 7
5.1.2 Clamp . 7
5.1.3 Length of bench . 7
5.1.4 Conductor tension . 7
5.1.5 Sinusoidal excitation . 8
5.1.6 Excitation frequency . 8
5.2 Test parameters for resonance type benches . 8
5.3 Termination of a test . 8
5.4 Number of tests . 8
6 Test results . 9
Annex A (informative) Fatigue testing of conductors . 10
A.1 Background. 10
A.2 Confirmation . 11
A.3 Present knowledge of fatigue endurance capability of conductors . 11
A.4 Important characteristics related to conductor fatigue . 11
A.5 Test details . 12
A.5.1 Typical test benches for fatigue tests of conductors . 12
A.5.2 Typical configuration recommended . 12
A.6 Failure detection . 12
A.7 Collection of data base results . 13
A.7.1 Simple analytical representation of fatigue phenomenon . 13
A.7.2 Idealized stress . 14
A.8 Use of results. 15
A.9 Type of clamps . 15
A.10 Performance comparison . 15
Bibliography . 16

Figure 1 – Schematic representation of a resonance-type test bench . 8
Figure A.1 – Schematic representation of a typical resonance fatigue test bench . 12
Figure A.2 – Conductor supported in a typical short metallic clamp . 13
Figure A.3 – Bending model of a conductor supported in a metallic clamp, cantilever
beam in a square face block . 13
Figure A.4 – Free loop amplitude y . 14
max
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OVERHEAD LINES – METHOD FOR FATIGUE
TESTING OF CONDUCTORS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62568 has been prepared by IEC technical committee 7: Overhead
electrical conductors.
The text of this standard is based on the following documents:
FDIS Report on voting
7/638/FDIS 7/640/RVD
Full information on the voting for the approval of this standard 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.

– 4 – IEC 62568:2015 © IEC 2015
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
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INTRODUCTION
Fatigue behaviour of conductors cannot simply be calculated from the fatigue characteristics
of the materials used and the stresses that occur. Fatigue characteristics of conductors must
be determined by fatigue tests conducted on specific conductor/clamp systems reproducing
as closely as possible the field loading conditions. In such tests, the fatigue life must be
determined as a function of some measure of vibration intensity rather than of the stress or
stress combination that causes the failure.
Fatigue test data are available for only a small fraction of the conductor sizes and types that
are in use, and such data are expensive to acquire. Since none of the above parameters is
simply related to the fatigue-initiating stresses, results from tests on one conductor size are
not necessarily applicable to others.
This IEC Standard is based on these considerations and others explained in Annex A. The
user of this standard is encouraged to consult this annex in order to understand the origin of
some of the requirements herein.

– 6 – IEC 62568:2015 © IEC 2015
OVERHEAD LINES – METHOD FOR FATIGUE
TESTING OF CONDUCTORS
1 Scope
This International Standard provides test procedures to measure the fatigue characteristics of
conductor/clamp systems. For the purposes of this standard, clamps shall be of the metallic
type only.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
antinode amplitude
mid-loop single peak vibration amplitude
2.2
bending amplitude
peak-to-peak vibration amplitude of conductor with respect to the clamp, measured 89 mm
from the last point of contact between the conductor and the clamp
2.3
failure criterion
benchmark at which the test is deemed terminated.
Note 1 to entry: Two different failure criteria may be chosen:
a) failure of the first wire, or
b) failure of three wires or of 10% of the total number of envelope wires for composite conductors, or of the total
number of wires for homogeneous conductors
2.4
idealized bending stress
alternating stress amplitude calculated based on the measured bending amplitude
2.5
idealized dynamic stress
alternating stress amplitude calculated based on the measured fy product
max
2.6
idealized strain
computed dynamic bending alternating strain obtained by dividing the idealised stress by the
Young’s modulus of the outer layer material
Note 1 to entry: This calculated idealized strain does not correspond to the strain measured on given wires at the
exit of the clamp
2.7
resonance fatigue test
cyclic motion imposed on a conductor in a vertical plane at a resonant frequency of the
system
3 Symbols and abbreviated terms
f frequency (Hz)
i occurrence of wire failure (first = 1, second = 2, third = 3 …)
N number of cycles of vibration
N number of cycles corresponding to wire failure i
i
Mc million cycle
T conductor mechanical tension
Y bending amplitude
b
y antinode amplitude
max
σ (Y ) idealized bending stress
a b
σ (fy ) idealized dynamic stress
a max
S/N calculated idealised stress S – number of cycles of vibration N
LPC the last point of contact of the conductor with the clamp in the calculation of an
idealized bending stress on an external wire of the conductor in a plane
p-p peak-to-peak (bending amplitude)
RTS rated tensile strength
LVDT linear variable differential transformer
4 Requirements
Fatigue tests on conductor/clamp systems shall be in accordance with the method described
in this standard.
5 Test method
5.1 Test set-up
5.1.1 General
The test set-up shall be conceptually in accordance with Figure 1. The following elements
shall be adhered to:
5.1.2 Clamp
The test bench shall be such as to reproduce the exit angle of the conductor at the clamp.
The clamp shall be fixed in such a way as to prevent any movement.
5.1.3 Length of bench
Behind the clamp where the conductor experiences no motion, there shall be a minimum of
1 m of free conductor between the clamp under test and the dead-end clamp.
There shall be a minimum of 5 m between the clamp under test and the point of excitation.
The active length of the test bench shall be long enough to allow the formation of at least
5 vibrating free loops at the resonant frequency chosen for the test.
5.1.4 Conductor tension
The conductor tension shall be maintained at a constant value with a maximum variation of
± 2,5 %.
– 8 – IEC 62568:2015 © IEC 2015
5.1.5 Sinusoidal excitation
A shaker, or any other appropriate means, shall be placed at the end of the test span opposite
to the clamp under test and shall be capable of maintaining constant (± 5 %) free loop
amplitude and frequency.
nd
2 free loop –
antinode loop velocity
measured here
Suspension clamp
Vibration shaker
which is restricted
from articulation
Constant tension
device
Shaker placed
in first loop
Minimum 5 loops
IEC
Figure 1 – Schematic representation of a resonance-type test bench
5.1.6 Excitation frequency
The frequency of excitation shall be in the range of (10 to 60) Hz.
5.2 Test parameters for resonance type benches
The following parameters shall be monitored:
– bending amplitude Y
b
– antinode amplitude y
max
– frequency f
– conductor mechanical tension T
– number of cycles N
– each occurrence of wire failure and the corresponding number of cycles N
i
5.3 Termination of a test
The test shall be terminated when a predetermined number of wire failures i is recorded or
when the test has reached N = 500 Mc.
At the end of each test, the clamp region of the conductor shall be dissected and the number
of wire failures found shall correspond to the number of failures recorded by the wire failure
detector. If the results cannot be reconciled, the test shall be discarded.
5.4 Number of tests
A minimum of 12 tests shall be performed to determine the endurance limit of a
conductor/clamp system. Three of these tests shall be at an amplitude that shall produce no
wire failure up to 500 Mc. The vibration amplitude of the other nine tests shall be determined
in order to distribute, as evenly as possible, the wire failures between (0,8 and 500) Mc.

6 Test results
The following information shall be provided in the report for each test:
– the failure criterion used
– number of cycles corresponding to wire failure(s) N
i
– number of cycles N completed if there was no failure
– mapping of the wire failure locations in the transverse and the longitudinal planes with
respect to the support clamp
– frequency f, antinode amplitude y and, the resulting fatigue indicator fy
max max
– bending amplitude Y
b
– conductor mechanical tension T
– S/N diagram of the idealized bending stress σ (Y ) using the Poffenberger-Swart
a b
relationship. (see A.7.2)
– S/N diagram of the idealized dynamic stress σ (fy ) (see A.7.2)
a max
– The endurance limits σ (Y ) and σ (fy )which correspond to the maximum vibration
a b a max
amplitude under which the conductor has experienced no fatigue damage up to 500 Mc.

– 10 – IEC 62568:2015 © IEC 2015
Annex A
(informative)
Fatigue testing of conductors
A.1 Background
It has long been recognized that conductor fatigue and its resulting consequence, the
breaking of conductor strands, was due to a phenomenon known as fretting fatigue, in
locations on the conductor where its motion is restrained, e.g. suspension clamps, spacer
clamps or damper clamps.
Relating the measurable vibration of an overhead span of conductor to the likelihood of
fatigue of its strand is a complicated matter. The stresses that cause the failures are not
related in a simple way to the gross motions of the conductor. The failures originate at
locations where there is surface contact and fretting between components (wire/wire or
wire/support contacts). A valid analysis relating the fretting fatigue mechanism to the vibration
of the conductor has yet to be published.
Fatigue behaviour of conductors cannot simply be calculated from the fatigue characteristics
of the materials used and the stresses that occur. Fatigue characteristics of conductors must
be determined by fatigue tests conducted on specific conductor/clamp systems reproducing
as closely as possible the field loading conditions. In such tests, the fatigue life must be
determined as a function of some measure of vibration intensity rather than of the stress or
stress combination that causes the failure.
Several parameters of vibration intensities have been employed. None came out as
outstanding to relate results from tests on laboratory spans to actual in situ measurements of
conductor vibration with different conductor/clamp systems. For practical reasons, the
bending amplitude Y and the product of the free loop amplitude y and the frequency f
b max
(fy ) have gradually been accepted with their inherent limitations.
max
Fatigue test data are available for only a small fraction of the conductor sizes and types that
are in use, and such data is expensive to acquire. Since none of the above parameters is
simply related to the fatigue-initiating stresses, results from tests on one conductor size are
not necessarily applicable to others. To deal with that situation, an idealized stress (or strain)
that can be calculated from vibration amplitude and that correlates well enough with conductor
fatigue life to permit its use in establishing a single endurance limit for a range of conductor
sizes and type of support was assumed.
Use of such an idealized stress lacks a fundamental analytical basis. However, ranges of
conductor size and support arrangement have been found where its use gives results that are
reliable enough to be usefully applied. It is important and useful to propose an IEC Standard
based on the previous considerations to characterize the fatigue behaviour of
conductor/clamp systems.
The scope of the new standard is to provide test procedures based on the experience gained
in the recent years. The following three references are particularly relevant:
– CIGRE SC 22 WG 04 Guide for Endurance Tests of Conductors Inside Clamps, ELECTRA
No 100, 1985, May pp.77-86
– CIGRE SC B2 WG11 TF7 Fatigue Endurance capability of Conductor/Clamp Systems –
Update of Present Knowledge, CIGRE TB # 332, 2007, Paris
– EPRI Chapter 3, Fatigue of Overhead Conductors, EPRI Transmission Line Reference
nd
Ed., EPRI, Palo Alto, CA 2006
Book: Wind-Induced Conductor Motion, 2

A.2 Confirmation
A standard to measure a mechanical characteristic of a component should:
• correctly represent conditions of loading to which the component is subjected to;
• specify acceptable conditions of loading and range of loads representative of in situ
conditions of use;
• propose set up for testing enabling duplication of results by independent laboratories;
• permit collection of data leading to the use of simple and current methods of interpretation;
• lend itself to interpretation of results without ambiguous application to the cases being
evaluated.
A.3 Present knowledge of fatigue endurance capability of conductors
Present knowledge of fatigue endurance capability of conductors includes the following:
• Conductor fatigue, resulting in the breaking of conductor strands, is due to fretting fatigue
(contact stresses and micro-slip at wire/wire or wire/clamp contacts).
• Conductor fatigue happens where conductor motion is restrained (e.g. at suspension
clamps, spacer clamps, damper clamps, etc).
• The stresses (contact stresses and micro-slip) that cause the strand failures are not
related in a simple way to the gross motion of the conductor.
• A valid analysis relating the fretting fatigue mechanism to the vibration motion of
conductors has yet to be developed.
• The characterization in fatigue of conductor wires alone is not yet possible; fatigue
characteristics of conductors are determined by fatigue tests conducted on specific
conductor/clamp systems.
• The bending amplitude model presently in use represents a conductor supported as a
cantilever beam in a square face block.
• The bending amplitude model proposes, as a fatigue index, the calculation of an idealized
bending stress on an external wire of the conductor in a plane encompassing the last point
of contact (LPC) of the conductor with the clamp.
• For practical reasons, the bending amplitude Y (measured at 89 mm from the LPC) and
b
the product of the frequency f and the free loop amplitude y (fy ) have gradually
max max
been accepted as parameters for the calculation of the amplitude of the idealized bending
stress.
A.4 Important characteristics related to conductor fatigue
Some important characteristics related to conductor fatigue include:
• Aeolian vibration, with a frequency range of (3 to 150) Hz and antinode amplitudes (p-p)
up to 1 conductor diameter, is the main cause of conductor fatigue.
• Free loop amplitudes of aeolian vibration are variable and result in spectrum loading at the
support.
• The frequency is related to the wind velocity by a law proposed by Strouhal (f = 0,185 V/d).
• Large amplitude vibrations at conductor support, related to conductor galloping, are also
reckoned as possible source of fretting fatigue of conductors.

– 12 – IEC 62568:2015 © IEC 2015
A.5 Test details
A.5.1 Typical test benches for fatigue tests of conductors
Typical test benches for fatigue tests of conductors include:
• Resonance type: a cyclic motion is imposed on a conductor in a vertical plane at a
resonant frequency of the system. It is the most common and the most accepted way for
testing conductor fatigue.
• Alternating tension: a cyclic tension force is applied to a piece of conductor in a tension
machine.
• Inverted bending: a cyclic motion is imposed to a conductor by imposing a forced cyclic
motion to the supporting clamp.
• Fretting fatigue of wires: fatigue tests are performed directly on conductor wires.
A.5.2 Typical configuration recommended
The resonance type test bench is the configuration retained for the IEC standard as illustrated
in Figure 1. A typical resonance fatigue test bench is also shown in Figure A.1.
Pneumatic tensioning system
Suspension clamp
Dynamometer
Amplitude measuring system
End clamp
Rubber dampers
Turnbuckle
Wire break detection
5,5°
Vibrator
Slider
2 m Active length: 7 m 2 m
IEC
Figure A.1 – Schematic representation of a typical resonance fatigue test bench
Its main characteristics can be summarized as follows:
• Asymmetrical model: only one side of the supported conductor forms the test bench to
evaluate a given conductor/clamp system.
• Clamp angle: The test bench permits to reproduce the exit angle of the conductor at the
clamp (e.g. suspension clamp, spacer clamp, etc).
• Fixation of clamp: although the suspension clamp is normally articulated, fatigue tests are
conducted in a configuration restricted from articulation (rotation). It thus ensures more
repeatable and meaningful results. If the clamp is allowed to rotate, the amount of rotation
will affect the fatigue results.
• Conductor mechanical tension: the tension for the test is held constant (± 2,5 %) at a
value typical of the H/w normally encountered (or typical % RTS).
• Length of the test bench: The active “free length” of the test bench is dictated by its ability
to produce a minimum of 5 loop resonant frequency in the range of the frequencies
encountered by a given conductor.
A.6 Failure detection
Comparable results may be obtained based on the means available to determine conductor
wire damage. Due to complicated stress distribution and fretting conditions inside the
conductor, failures are also observed in the inner layers. Detection of failures by periodic

visual inspection of the conductor’s outer surface is not sufficient and this problem can be
solved using a strand failure detector.
Every available non-destructive method may be used during the fatigue test, such as
radiography, shock detection, torsional effects, etc. A simple method based on torsional
effects has been developed at Alcoa Laboratories and has been extensively used at
GREMCA’s Laboratories (EPRI Chapter 3). It consists of a small arm attached to the
conductor in order to amplify its relaxation in torsion when a strand failure occurs. The
rotational motion of the arm is detected by any suitable sensor (LVDT, proximity sensor,
optical sensor), that sends a step signal that may be associated with N, the number of cycles
applied.
A.7 Collection of data base results
A.7.1 Simple analytical representation of fatigue phenomenon
The conductor/clamp system may be simply represented as a cantilever beam supported in a
square face block. Although this model is not exact, because the conductor fatigue is caused
by inter wire fretting and not by bending of the wire only, it gives the engineer some useful
tools to correctly monitor different aspects of the fatigue endurance capability of conductor
clamp/systems. Figures A.2 and A.3 illustrate clearly why the bending amplitude method may
be valid for conductors fitted with solid metallic clamps, but invalid for conductors in
cushioned clamps. In the latter case, it is not possible to locate a precise position for an
equivalent plane for the last point of contact (LPC).
Plane of
last point of contact
IEC
Figure A.2 – Conductor supported in a typical short metallic clamp
X = 89 mm
b
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Figure A.3 – Bending model of a conductor supported in a metallic clamp,
cantilever beam in a square face block
Y
b
– 14 – IEC 62568:2015 © IEC 2015
A.7.2 Idealized stress
A.7.2.1 Idealized bending stress σ (Y )
a b
From the model shown in Figure A.3, Poffenberger and Swart proposed the calculation of an
idealized bending stress σ (Y ) in the top-most outer-layer strand of the conductor, in the
a b
plane of the last point of contact:
E d p
a
σ (Y ) = Y
a b b
px
(A.1)
4(e 1+ px)
where:
Y : bending amplitude (m peak-to-peak)
b
E : Young’s modulus of elasticity of outer-layer wire material (N/m )
a
d: diameter of outer layer wire (m)
½
p = (H/EI)
H: conductor tension at average temperature during test period (N)
EI: sum of flexural rigidities of individual wires in the cable (N m )
x: distance from the point of measurement to the last point of contact between the clamp
and the conductor (m).
In Equation (A.1) the idealized bending stress is expressed as a function of the bending
amplitude Y .
b
A.7.2.2 Idealized dynamic stress σ (fy )
a max
However in certain circumstances, the product of the free loop amplitude of vibrations y by
max
the frequency f (the parameter fy ), could be a more practical parameter. Figure A.4 shows
max
the case of a standing wave vibration with a rigidly fixed supporting clamp at the left end of
section (a).
y
β
a
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Figure A.4 – Free loop amplitude y
max
In that case, the idealized dynamic stress σ (fy )can be expressed as a function of fy :
a max max
m
σ ( fy ) = π d E fy
a max a max (A.2)
EI
where:
E : Young’s modulus of elasticity of outer-layer wire material (N/m )
a
d: diameter of outer layer wire (m)
y
max
f: frequency of the motion (Hz)
y : free loop amplitude (m peak)
max
m: conductor mass per unit length (kg/m)
EI: sum of flexural rigidities of individual wires in the cable (N m )
The most common format for presenting conductor fatigue test results is the semi logarithmic
fatigue endurance curve, representing the S/N curve. The abscissa is the number of cycles N
and the ordinate the calculated idealised stress. Calculations results differ based on whether
Y or fy is used (EPRI Chap. 3).
b max
st nd rd th
It is possible to superimpose on the same graph points indicating the 1 , 2 , 3 , and k
strand failures for a series of tests. The dispersion of the results is then shown as well as
certain particular anomalies when, for instance, an early first failure occurs but is not followed
by a second one within the first 500 Mc duration of the test.
The correlation of calculated values and measured values of σ may appear to be somewhat
a
academic, since the stresses that initiate fatigue failures are located at metal-to-metal
contacts and σ is a free-surface stress. The comparisons do, however, provide some
a
measure of the sensitivity of the analysis to the degree of idealization involved in the
assumptions employed. There is a strong temptation to attribute to σ a meaning different
a
from that of a useful index for a rational interpretation of the bending amplitude of conductors
measured at the mouth of a rigid metallic clamp. The reader is urged not to succumb to this
temptation! It is common practice to report fatigue performance of conductors relative to either
Y or fy (EPRI Chap. 3).
b max
A.8 Use of results
The results can be used as follows:
– The S/N curves enable one to establish the fatigue endurance limit of a conductor /clamp
system when it includes tests up to N = 500 Mc .
– In certain cases special techniques are used to take into account cumulative damage due
to spectrum loading. To assist in the interpretation of available data on the fatigue
endurance of certain conductor/clamp systems, statistical analysis allows the
determination of various S/N curves on a probabilistic basis.
– Tests are useful for a comparison of clamps and other accessories on the basis of their
influence on the endurance of the conductors.
A.9 Type of clamps
Although this standard is solely intended to test metal-to-metal clamps, its use may be
extended to other type of clamps. However, in those cases, the stress derived from the
bending amplitude Y measured at the clamp end can no longer be compared with the
b
bending amplitude obtained with other clamps since the conductor curvature is no longer
comparable due to the local influence of the elastomer stiffness. The comparison may only be
done through the fatigue indicator fY .
max
A.10 Performance comparison
Tests to compare the performance of a conductor/clamp system with another one are
sometimes requested. In that case, a minimum of 6 tests shall be performed. The vibration
amplitude of the six tests shall be determined in order to distribute, as evenly as possible, the
wire failures between (0,8 and 100) Mc.

– 16 – IEC 62568:2015 © IEC 2015
Bibliography
CIGRE SC 22 WG 04 Guide for Endurance Tests of Conductors Inside Clamps, ELECTRA
No 100, 1985, May pp.77-86
CIGRE SC B2 WG11 TF7 Fatigue Endurance capability of Conductor/Clamp Systems –
Update of Present Knowledge, CIGRE TB # 332, 2007, Paris
EPRI Chapter 3, Fatigue of Overhead Conductors, EPRI Transmission Line Reference Book:
nd
Wind-Induced Conductor Motion, 2 Ed., EPRI, Palo Alto, CA 2006

_____________
– 18 – IEC 62568:2015 © IEC 2015
SOMMAIRE
AVANT-PROPOS . 19
INTRODUCTION . 21
1 Domaine d’application . 22
2 Termes et définitions . 22
3 Symboles et abréviations . 23
4 Exigences . 23
5 Méthode d’essai . 23
5.1 Montage d’essai . 23
5.1.1 Généralités . 23
5.1.2 Pince . 23
5.1.3 Longueur du banc . 23
5.1.4 Tension du conducteur . 23
5.1.5 Excitation sinusoïdale . 24
5.1.6 Fréquence d'excitation . 24
5.2 Paramètres d'essai pour des bancs de type à la résonance . 24
5.3 Fin d'un essai . 24
5.4 Nombre d'essais . 24
6 Résultats d’essais . 25
Annexe A (informative) Essai de fatigue des conducteurs . 26
A.1 Contexte . 26
A.2 Confirmation . 27
A.3 Connaissances actuelles de la capacité d'endurance en fatigue de
conducteurs . 27
A.4 Caractéristiques importantes liées à la fatigue des conducteurs . 27
A.5 Détails des essais . 28
A.5.1 Bancs d'essais typiques pour les essais de fatigue de conducteurs . 28
A.5.2 Configuration typique recommandée . 28
A.6 Détection de défaillances . 29
A.7 Collecte des résultats de la base de données . 29
A.7.1 Représentation analytique simple du phénomène de fatigue . 29
A.7.2 Contrainte idéale . 30
A.8 Exploitation des résultats . 31
A.9 Types de pinces . 32
A.10 Comparaison des performances . 32
Bibliographie . 33

Figure 1 – Représentation schématique d'un banc d'essai de type à la résonance . 24
Figure A.1 – Représentation schématique d'un banc d'essai de fatigue à la résonance
typique . 28
Figure A.2 – Conducteur attaché par une petite pince métallique typique . 29
Figure A.3 – Modèle de flexion d'un conducteur attaché par une pince métallique,
console dans un bloc à faces carrées . 30
Figure A.4 – Amplitude de boucle libre y . 31
max
...