IEC/IEEE 62582-2:2011
(Main)Nuclear power plants - Instrumentation and control important to safety - Electrical equipment condition monitoring methods - Part 2: Indenter modulus
Nuclear power plants - Instrumentation and control important to safety - Electrical equipment condition monitoring methods - Part 2: Indenter modulus
IEC/IEEE 62582-2:2011 contains methods for condition monitoring of organic and polymeric materials in instrumentation and control systems using the indenter modulus technique in the detail necessary to produce accurate and reproducible measurements. It includes the requirements for the selection of samples, the measurement system and measurement conditions, and the reporting of the measurement results.
Centrales nucléaires de puissance - Instrumentation et contrôle-commande importants pour la sûreté - Méthodes de surveillance de l'état des matériels électriques - Partie 2: Module indenter
La CEI/IEEE 62582-2:2011 présente des méthodes de surveillance d'état de matériaux organiques et de polymères des systèmes d'instrumentation et de contrôle-commande en utilisant une technique de module indenter, de façon suffisamment détaillée pour obtenir des mesures reproductibles et précises. Elle comprend des exigences concernant la sélection d'échantillons, les systèmes de mesure et les conditions de mesure, ainsi que les rapports des résultats de mesure.
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IEC/IEEE 62582-2
Edition 1.0 2011-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Nuclear power plants – Instrumentation and control important to safety –
Electrical equipment condition monitoring methods –
Part 2: Indenter modulus
Centrales nucléaires de puissance – Instrumentation et contrôle-commande
importants pour la sûreté – Méthodes de surveillance de l’état des matériels
électriques –
Partie 2: Module indenter
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IEC/IEEE 62582-2
Edition 1.0 2011-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Nuclear power plants – Instrumentation and control important to safety –
Electrical equipment condition monitoring methods –
Part 2: Indenter modulus
Centrales nucléaires de puissance – Instrumentation et contrôle-commande
importants pour la sûreté – Méthodes de surveillance de l’état des matériels
électriques –
Partie 2: Module indenter
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
PRICE CODE
R
CODE PRIX
ICS 27.120.20 ISBN 978-2-88912-667-5
– 2 – 62582-2 IEC/IEEE:2011
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope and object . 7
2 Terms and definitions . 7
3 Abbreviations and acronyms . 7
4 General description . 8
5 Applicability, reproducibility, and complexity . 8
5.1 General . 8
5.2 Applicability . 8
5.3 Reproducibility . 8
5.4 Complexity . 9
6 Measurement procedure . 9
6.1 Stabilisation of the polymeric materials. 9
6.2 Sampling and measurement locations . 9
6.3 Conditions for measurement . 9
6.4 Instrumentation . 10
6.5 Calibration and tolerances . 11
6.6 Selection of measurement points . 11
6.7 Selection of probe velocity and maximum force . 11
6.8 Clamping . 11
6.9 Determination of the value of the indenter modulus . 11
6.10 Reporting . 12
Annex A (informative) Examples illustrating factors affecting the variation of the
indenter modulus value . 14
Annex B (informative) Example of a measurement report for indenter measurements in
laboratory . 18
Bibliography . 19
Figure 1 – A schematic representation of the geometry and dimensions of the probe tip
used in the indenter . 10
Figure 2 – Calculation of indenter modulus . 12
Figure A.1 – Example of local variation of indenter modulus due to variation in
equipment dimensions and construction . 14
Figure A.2 – Indenter values measured at different temperatures . 15
Figure A.3 – Normalised indenter mean values . 16
Figure A.4 – Example of change of indenter modulus value in laboratory conditions of
a hygroscopic sample after removal from long-term exposure in a heat chamber . 17
Figure A.5 – Adaptation of a decay curve to the measured indenter modulus values in
Figure A.4 . 17
Figure B.1 – Example of measured force vs displacement . 18
62582-2 IEC/IEEE:2011 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL IMPORTANT TO SAFETY –
ELECTRICAL EQUIPMENT CONDITION MONITORING METHODS –
Part 2: Indenter modulus
FOREWORD
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or IEEE or their directors, employees, servants or agents including individual
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IEC/IEEE Publication or any other IEC or IEEE Publications.
8) Attention is drawn to the normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that implementation of this IEC/IEEE Publication may require use of
material covered by patent rights. By publication of this standard, no position is taken with respect to the
existence or validity of any patent rights in connection therewith. IEC or IEEE shall not be held responsible for
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rights, and the risk of infringement of such rights, is entirely their own responsibility.
– 4 – 62582-2 IEC/IEEE:2011
International Standard IEC/IEEE 62582-2 has been prepared by subcommittee 45A:
Instrumentation and control of nuclear facilities, of IEC technical committee 45: Nuclear
instrumentation, in cooperation with the Nuclear Power Engineering Committee of the Power &
Energy Society of the IEEE , under the IEC/IEEE Dual Logo Agreement between IEC and
IEEE.
This publication is published as an IEC/IEEE Dual Logo standard.
The text of this standard is based on the following IEC documents:
FDIS Report on voting
45A/841/FDIS 45A/850/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.
International standards are drafted in accordance with the rules given in the ISO/IEC
Directives, Part 2.
A list of all parts of IEC/IEEE 62582 series, under the general title Nuclear power plants –
Instrumentation and control important to safety – Electrical equipment condition monitoring
methods, can be found on the IEC website.
The IEC Technical Committee and IEEE Technical Committee have decided that the contents
of this publication will remain unchanged until the stability date indicated on the IEC web site
under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
—————————
A list of IEEE participants can be found at the following URL:http://standards.ieee.org/downloads/62582-2/62582-2-
2011/62582-2-2011_wg-participants.pdf.
62582-2 IEC/IEEE:2011 – 5 –
INTRODUCTION
a) Technical background, main issues and organisation of this standard
This part of this IEC/IEEE standard specifically focuses on indenter modulus methods for
condition monitoring for the management of ageing of electrical equipment installed in nuclear
power plants. The indenter method is commonly used to carry out measurements on cables
(jackets, insulation) and o-rings.
This part of IEC/IEEE 62582 is the second part of the IEC/IEEE 62582. It contains detailed
descriptions of condition monitoring based on indenter modulus measurements.
The IEC/IEEE 62582 series is issued with a joint logo which makes it applicable to the
management of ageing of electrical equipment qualified to IEEE as well as IEC Standards.
Historically, IEEE Std 323-2003 introduced the concept and role that condition based
qualification could be used in equipment qualification as an adjunct to qualified life. In
equipment qualification, the condition of the equipment for which acceptable performance was
demonstrated is the qualified condition. The qualified condition is the condition of equipment,
prior to the start of a design basis event, for which the equipment was demonstrated to meet
the design requirements for the specified service conditions.
Significant research has been performed on condition monitoring techniques and the use of
these techniques in equipment qualification as noted in NUREG/CR-6704, Vol. 2 (BNL -
NUREG-52610) and JNES-SS-0903, 2009.
It is intended that this IEC/IEEE standard be used by test laboratories, operators of nuclear
power plants, systems evaluators, and licensors.
b) Situation of the current standard in the structure of the IEC SC 45A standard series
Part 2 of IEC/IEEE 62582 is the third level IEC SC 45A document tackling the specific issue of
application and performance of indenter modulus measurements in management of ageing of
electrical instrument and control equipment in nuclear power plants.
Part 2 of IEC/IEEE 62582 is to be read in association with part 1 of IEC/IEEE 62582, which
provides background and guidelines for the application of methods for condition monitoring of
electrical equipment important to safety of nuclear power plants.
For more details on the structure of the IEC SC 45A standard series, see item d) of this
introduction.
c) Recommendations and limitations regarding the application of this standard
It is important to note that this Standard establishes no additional functional requirements for
safety systems.
d) Description of the structure of the IEC SC 45A standard series and relationships
with other IEC documents and other bodies documents (IAEA, ISO)
The top-level document of the IEC SC 45A standard series is IEC 61513. It provides general
requirements for I&C systems and equipment that are used to perform functions important to
safety in NPPs. IEC 61513 structures the IEC SC 45A standard series.
IEC 61513 refers directly to other IEC SC 45A standards for general topics related to
categorisation of functions and classification of systems, qualification, separation of systems,
defence against common cause failure, software aspects of computer-based systems,
– 6 – 62582-2 IEC/IEEE:2011
hardware aspects of computer-based systems, and control room design. The standards
referenced directly at this second level should be considered together with IEC 61513 as a
consistent document set.
At a third level, IEC SC 45A standards not directly referenced by IEC 61513 are standards
related to specific equipment, technical methods, or specific activities. Usually these
documents, which make reference to second-level documents for general topics, can be used
on their own.
A fourth level extending the IEC SC 45A standard series, corresponds to the Technical
Reports which are not normative.
IEC 61513 has adopted a presentation format similar to the basic safety publication
IEC 61508 with an overall safety life-cycle framework and a system life-cycle framework and
provides an interpretation of the general requirements of IEC 61508-1, IEC 61508-2 and
IEC 61508-4, for the nuclear application sector. Compliance with IEC 61513 will facilitate
consistency with the requirements of IEC 61508 as they have been interpreted for the nuclear
industry. In this framework IEC 60880 and IEC 62138 correspond to IEC 61508-3 for the
nuclear application sector.
IEC 61513 refers to ISO as well as to IAEA 50-C-QA (now replaced by IAEA GS-R-3) for
topics related to quality assurance (QA).
The IEC SC 45A standards series consistently implements and details the principles and
basic safety aspects provided in the IAEA code on the safety of NPPs and in the IAEA safety
series, in particular the Requirements NS-R-1, establishing safety requirements related to the
design of Nuclear Power Plants, and the Safety Guide NS-G-1.3 dealing with instrumentation
and control systems important to safety in Nuclear Power Plants. The terminology and
definitions used by SC 45A standards are consistent with those used by the IAEA.
62582-2 IEC/IEEE:2011 – 7 –
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL IMPORTANT TO SAFETY –
ELECTRICAL EQUIPMENT CONDITION MONITORING METHODS –
Part 2: Indenter modulus
1 Scope and object
This part of IEC/IEEE 62582 contains methods for condition monitoring of organic and
polymeric materials in instrumentation and control systems using the indenter modulus
technique in the detail necessary to produce accurate and reproducible measurements. It
includes the requirements for the selection of samples, the measurement system and
measurement conditions, and the reporting of the measurement results.
The different parts of IEC/IEEE 62582 are measurement standards, primarily for use in the
management of ageing in initial qualification and after installation. Part 1 of IEC/IEEE 62582
includes requirements for the application of the other parts of IEC/IEEE 62582 and some
elements which are common to all methods. Information on the role of condition monitoring in
the qualification of equipment important to safety is found in IEEE Std 323.
This standard is intended for application to non-energised equipment.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
2.1
indenter modulus
ratio between the changes in applied force and corresponding displacement of a probe of a
–1
standardised shape, driven into a material. It is expressed in N∙mm .
NOTE The term “modulus” typically refers to the modulus of elasticity of a material which is defined as the ratio of
–2
the applied stress and the corresponding strain and is expressed in N∙m (Pa). However, in the use of the
indenter, it has become common practice to use the term indenter modulus to describe the ratio of the change in
–1
applied force to material deformation and express it in N∙mm .
3 Abbreviations and acronyms
DBE Design Basis Event
IM Indenter Modulus
SiR silicone rubber
CSPE chlorosulphonated polyethylene
EPDM ethylene propylene diene monomer
XLPE crosslinked polyethylene
– 8 – 62582-2 IEC/IEEE:2011
4 General description
A typical indenter uses an instrumented probe, which is driven at a fixed velocity into the
material and includes a load cell or similar force-measuring device, connected to the probe,
which measures the force necessary to maintain the constant velocity. The probe’s
displacement is measured by an appropriate transducer. The travel and force are purposely
limited to protect the material from permanent damage. The indenter modulus is calculated by
dividing the change in force by the corresponding displacement during inward travel.
5 Applicability, reproducibility, and complexity
5.1 General
When organic and polymeric materials age, they often harden which will result in an increase
of indenter modulus. Some materials, such as some formulations of Butyl Rubber, soften
during thermal and/or radiation ageing. The purpose of monitoring changes in indenter
modulus is to estimate degradation rates and levels induced by ageing.
5.2 Applicability
The indenter method is commonly used to carry out measurements on cables (jackets,
insulation) and o-rings. Its use requires special fixtures depending on the geometry of the
samples.
This method should only be applied to materials whose hardness changes monotonically with
ageing.
The indenter method may be carried out on equipment with high integrity in a non-invasive
manner. However, the process of performing indenter measurements on equipment in field
should include controls to ensure that damage – from the probe or from handling in order to
access suitable measurement points – has not been imparted to the equipment. The process
should include correction of any equipment that has been damaged or suspected of incurring
damage.
Measurements in the field require access to the exterior wall of the equipment. For field
measurements on cables, this often limits the measurements to jacket materials. It may be
possible to assess the condition of cable insulation from indenter measurements on its jacket
if there is a known relationship between the ageing degradation of the jacket material and the
degradation of the insulation. This relationship shall be justified to be valid and sufficiently
sensitive to provide the valid monitoring through life.
5.3 Reproducibility
Indenter modulus values can be influenced by variability in specimen dimensions and
construction, temperature and moisture content of the specimen, stabilisation of the
specimen, and contamination of the specimen. If measurements are made under excessive
vibration, this can influence the measured value. The influence by variability in the specimen
dimensions and construction is typically the case for measurements on cables, where the
measurement point may be situated above a cavity beneath the jacket surface. The cross-
section of typical cable core insulation may differ substantially from that of an ideal tube and
can result in variability in the measured values of indenter modulus depending on where the
measurement is made. These variations tend to be localised. Measurements shall be taken at
several points on the equipment to compensate for these local variations (see 6.6).
An illustration of variations due to variability in specimen dimensions and construction is given
in Annex A.
62582-2 IEC/IEEE:2011 – 9 –
NOTE A good knowledge of the construction of the equipment is important before the selection of measurement
positions is made. In the case of loosely constructed cables, the variability is expected to be high and it is
important that the measurements on the jacket are made over a conductor rather than free space.
5.4 Complexity
The degree of complexity experienced during indenter modulus measurements in the field will
often depend on cable accessibility. Existing instruments may be used in the field on cables
that are accessible. In this case, data generation is rapid and measurements at a large
number of points can be carried out over short time periods. Instruments can be configured
such that data are generated and stored directly. Measurements on equipment with more
complex geometries and limited accessibility may require the development of special fixtures.
The same fixture shall be used for repeated indenter modulus measurements.
6 Measurement procedure
6.1 Stabilisation of the polymeric materials
An appropriate time period shall be allowed for the polymeric materials in recently
manufactured equipments to stabilise before any condition monitoring or accelerated ageing
programmes are carried out. The time period over which the polymeric materials stabilise is
normally dependent on the processing additives and polymer composition. If manufacturers’
stabilisation time data are not available, a period of 6 months should be allowed.
6.2 Sampling and measurement locations
Laboratory measurements of indenter modulus on samples selected from the field and
indenter modulus measurements in the field only provide information on the status of the
equipment at a specific location. Knowledge of the environmental conditions in representative
areas during plant operation is a prerequisite for selecting locations. Since equipment heating
and radiation effects could be most apparent closest to the sources of heat and radiation, the
choice of locations should consider capturing the potential for significant ageing effects near
sources of heating and radiation. The position of the locations and available information about
the environmental time history of the locations selected shall be documented.
Sampling and measurement procedures shall comply with local instructions, taking into
account the safety of personnel and equipment. Handling of equipment during measurement
or removal of samples from the plant should be minimised e.g. cables should not be bent
more than necessary for the measurement or for the removal of the sample.
6.3 Conditions for measurement
The surface on which the measurements are made shall be cleaned of surface debris. In the
field, it may be necessary to apply a dry wipe to remove accumulated dirt from the surface
and prevent contamination of the indenter instrument. Under no circumstances shall solvents
be used for surface cleaning.
The indenter modulus varies with the temperature and moisture content of the sample as
shown in Annex A.
When measurements are carried out in the laboratory, e.g. after accelerated thermal ageing,
they shall be made in a surrounding air temperature of 20 ± 5 °C and a relative humidity of
45 % to 75 %. Samples shall be allowed time to reach equilibrium with their surroundings
before measurements are started.
NOTE 1 Where the materials are hygroscopic, it should be noted that the sample can be extremely dry after
artificial accelerated ageing as a consequence of long-term exposure to high temperatures in an oven. For these
materials, the values of indenter modulus measured can be significantly higher than for a sample in equilibrium
with the laboratory atmosphere. This is particularly important for condition monitoring of hygroscopic insulation
material when the final value of indenter modulus, on which qualified condition is based, is measured on
– 10 – 62582-2 IEC/IEEE:2011
completion of accelerated thermal ageing before the sample is subjected to a DBE test. Clause A.3 provides
guidance on dealing with this specific concern.
It may not be possible to make field measurements in standard atmospheric conditions. In
such cases the surrounding air temperature and the temperature at the surface at which the
measurements are made shall be recorded.
NOTE 2 Annex A shows a method for transformation of a measured indenter modulus to a corresponding modulus
at a different temperature. In addition to reporting the temperature at which the value has been measured, it is
recommended that the corresponding value at 20 ºC be calculated and reported.
6.4 Instrumentation
The indenter functions by driving an instrumented probe at a fixed velocity into the material
whilst a load cell or similar force-measuring device, connected to the probe, measures the
applied force. The probe shall have the shape of a truncated steel cone with the geometry
and dimensions shown in Figure 1. The probe’s displacement is measured by an appropriate
transducer. The point at which the tip of the probe is brought into contact with the material is
sensed by a change in force. The probe’s total displacement is normally limited to a fraction
of a mm to prevent permanent deformation and to keep within the range of approximate linear
proportionality between force and displacement. The indenter modulus (IM) is then calculated
by dividing the change in force by the corresponding displacement during inward travel. The
small displacements and loads that occur during this process prevent permanent effects on
the material.
NOTE Although the total displacement is limited, for some materials the relationship between force and
displacement is still significantly non-linear.
35°
Truncated cone ∅ 0,79 mm
IEC 1961/11
Figure 1 – A schematic representation of the geometry and dimensions
of the probe tip used in the indenter
A typical indenter is a hand held cylindrical instrument. At the head of the instrument, an
appropriate clamping device holds a cable or wire securely in position so that the probe can
be driven uniformly into the jacket or insulation of the cable or wire respectively. The probe is
situated within the instrument and is attached to a sensitive load cell. A servo-controlled
electric motor with appropriate gearing provides the capability to drive the probe towards the
sample and the probe’s position is measured by a transducer. A temperature sensor is
located close to the clamping device. The power and servo-control to the electric motor, and
outputs from the load cell, transducer and temperature sensor are fed by cable into a
separate controller which may be directly connected to a computer or capable of data storage
in-situ which may be downloaded into a remote computer. Parameters such as probe
velocity, and maximum load, and displacement are preloaded into the controller before the
start of measurement. The instrument is also designed such that the cable clamp can be
modified to allow calibration of the load cell using an appropriate weight and the probe travel
using a dial gauge.
62582-2 IEC/IEEE:2011 – 11 –
6.5 Calibration and tolerances
The indenter and the measurement system shall be calibrated before each series of
measurements in accordance with the manufacturer’s instructions. The calibration shall be
carried out on both the force sensor and probe velocity. The total error of force measurement
shall be less than 3 % of the upper limit of the force range, including instrumentation
tolerances as well as reading precision. The probe velocity shall be constant. The total
measurement error of the required velocity shall be less than 2 %.
6.6 Selection of measurement points
In each of the selected locations for field measurements, measurements shall be carried out
at several points and the mean value and standard deviation shall be reported. If the number
of points is more than 7, the highest and lowest value shall be deleted before calculation of
the mean value and the standard deviation. For measurements on cables, a minimum of three
points around the circumference at each of three longitudinal positions shall be used. Where
space is limited, it may not be possible to rotate around the cable circumference. In this case,
a minimum of nine points shall be selected with a separation of 60 mm to 100 mm along the
cable length.
In the case of laboratory measurements on samples of cables, a minimum of three points
around the circumference at each of three longitudinal positions shall be used. None of the
measurement points shall be less than 100 mm from the ends of the sample.
For measurements on o-rings, a similar number of points shall be measured if the size of the
o-ring allows.
6.7 Selection of probe velocity and maximum force
Before the start of the measurement, the test parameters shall be loaded into the
measurement system. In particular, the required maximum load and maximum displacement
should be set as limits to prevent damage to the equipment measured.
The probe velocity can have a significant influence on the measured value of indenter
–1 –1
modulus. The probe velocity shall be 5 mm∙min to 5,2 mm∙min . The probe velocity that is
selected shall be reported.
The maximum force that is selected needs to be a compromise between a value which is high
enough to achieve reasonable resolution in the displacement axis and a value that is low
enough to ensure that the probe does not damage the cable. For many polymeric insulation
materials, a maximum force of 10 N is recommended. This will normally result in a probe
penetration depth which is significantly less than 1 mm. For certain insulation materials, such
as SiR, a maximum value lower than 10 N may be required to avoid excessive penetration.
6.8 Clamping
When carrying out measurements on cables, the measured value of indenter modulus may be
strongly affected by variations in the force used to keep the cables securely in position within
the clamp. In order to minimise these effects, the cable shall be clamped using the minimum
force required to keep it in place. Problems in clamping shall be included in the measurement
report.
6.9 Determination of the value of the indenter modulus
The indenter modulus is determined by the slope of the force-displacement curve and is
–1
expressed in N∙mm .
IM = (F – F )/(d – d ) (1)
2 1 2 1
– 12 – 62582-2 IEC/IEEE:2011
Where
IM is the indenter modulus;
F is the corresponding force value at displacement d
i i.
IM shall be determined by using the values F = 1 N and F = 4 N, see Figure 2.
1 2
d – d
2 1
F – F
2 1
0 0,1 0,2 0,3 0,4 0,5 0,6
Displacement (mm)
IEC 1962/11
Figure 2 – Calculation of indenter modulus
6.10 Reporting
The measurement report shall as a minimum include the following items
a) Identification of the equipment measured, including the material formulation. For selection
of samples from the field or measurements in the field this shall include plant and location
relative to heat and radiation sources (6.2).
b) Pre-history of the equipment. This may include
• indenter measurements on samples of new (un-aged) equipment: storage and time
interval between production of the equipment sampled and start of the measurement
(6.1);
• indenter measurements on artificially aged samples: ageing conditions of the samples
(6.2);
• indenter measurements on naturally aged samples (e.g. field measurements): history
of environmental conditions to which the sample has been subjected (6.2).
c) Place and date of the measurement (laboratory, on-site).
d) For laboratory measurement of samples subjected to artificial thermal ageing: time interval
between removing the sample from the heat chamber until start of measurement (6.3).
e) Ambient and surface temperature at the time of measurement (6.3).
f) Other local conditions and situations encountered during measurement that may influence
the results.
g) Measurement instrumentation, including software version (6.4).
h) Calibration procedure (6.5).
i) Measurement points (6.6).
j) Probe velocity (6.7).
k) Maximum force (6.7).
Load (N)
62582-2 IEC/IEEE:2011 – 13 –
l) Mounting of the sample and problems in clamping (6.8).
m) For measurements in the field: observations on the condition of the equipment before and
after indenter measurements (6.2).
n) Mean value and standard deviation of indenter modulus ( after deleting the highest and
–1
lowest value), in N∙mm together with information on the force interval for which it has
been determined (normally 1 N to 4 N) (6.6 and 6.9).
NOTE If the indenter measurements are made at a temperature above 25 °C, it is recommended that the value
referenced to 20 °C is also reported, calculated according to Annex A.
o) Diagram showing a typical force versus displacement curve.
p) Any other information of importance in interpretation of the measurement results in
relation to the purposes of the measurements.
An example of a measurement report is given in Annex B.
– 14 – 62582-2 IEC/IEEE:2011
Annex A
(informative)
Examples illustrating factors affecting the variation
of the indenter modulus value
A.1 Example of influence of variability in equipment dimensions and
construction
Figure A.1 illustrates the variations due to variability in equipment dimensions and
construction, showing sets of data from indenter measurements at eight points on the jacket
of a 7 core cable with jacket material CSPE and insulator material EPDM. The mean values
–1
and
and standard deviations of the indenter modulus measured were 15,57 N∙mm
–1 –1 –1
0,58 N∙mm for the unaged cable jacket, 23,21 N∙mm and 1,06 N∙mm for the thermally
aged cable jacket.
Thermally aged
Unaged
1 008 h at 120 °C
6 66
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
Displacement (mm) Displacement (mm)
IEC 1963/11 IEC 1964/11
Figure A.1 – Example of local variation of indenter modulus due to variation
in equipment dimensions and construction
A.2 Examples of temperature dependence
These examples come from a study of the temperature dependence of the indenter values of
three types of thermally aged cables:
– jacket and lead insulation materials CSPE,
– jacket material CSPE, lead insulation material XLPE,
– jacket and lead insulation materials EPDM.
The measurements were made at 9 (3×3) points on the jacket and the indenter modulus
values were obtained from the slope of the force-distance curve between 1 N and 4 N. All
cables had been thermally aged at 120 °C for 48 days. The measurements were made after
temperature stabilisation at 21 °C, 35 °C and 50 °C.
Figure A.2 shows the results in terms of mean values and standard deviation of the indenter
modulus.
Load (N)
Load (N)
62582-2 IEC/IEEE:2011 – 15 –
CSPE/CSPE CSPE/XLPE EPDM/EPDM
EPDM/EPDM
CSPE/XLPE
CSPE/CSPE
18 1122 3322
15 1100
1122 8 1188
10 20 30 40 50 60 10 20 30 40 50 60 10 20 30 40 50 60
10 20 30 40 50 60 10 20 30 40 50 60 10 20 30 40 50 60
o
Temperature (°C) o Temperature (°Co) Temperature (°C)
Temperature, C Temperature, C Temperature, C
IEC 1965/11 IEC 1966/11 IEC 1967/11
Figure A.2 – Indenter values measured at different temperatures
The results illustrate the temperature dependence of indenter modulus measurements.
In the case where indenter measurements are made at a temperatures which differ
substantially from the standard temperature for testing t (20 °C), e.g. on site, normalisation
ref
to a value IM at 20 °C can be made. The calculated value of IM is given by the following
ref ref
empirical formula
IM = [1 + A × (t – t ) / (t – t )] × IM (A.1)
ref ref 1 2 t
A = (IM – IM ) / [(IM + IM )/2]
2 1 2 1
where
t is the temperature at which the measurement in the field is made;
IM is the measured value of indenter modulus at temperature t;
t
IM and IM are the values of indenter modulus at two different temperatures t and t
1 2 1 2
respectively from laboratory measurements made on the same material.
t should be selected in the region of the highest temperature at which measurements in the
field may be made, and t should be in the region of 20 °C. Figure A.3 shows the mean values
in Figure A.2 normalised according to Equation (A.1).
–1
-1
IndeIndentntere mr modulodulus us (N, ×N mm∙mm)
–1
-1
Indenter modulus (N × mm )
Indenter modulus, N∙mm
–1
-1
Indenter modulus, N∙mm
Indenter modulus (N × mm )
– 16 – 62582-2 IEC/IEEE:2011
CSPE/CSPE CSPE/XLPE EPDM/EPDM
EPDM/EPDM
CSPE/CSPE CSPE/XLPE
18 12 32
18 12 32
1515 10
12 8
12 8 1818
10 20 30 40 50 60 10 20 30 40 50 60 10 20 30 40 50 60
10 20 30 40 50 60 10 20 30 40 50 60
10 20 30 40 50 60
o o o
Temperature (°C)
Temperature (°C) Temperature (°C)
Temperature, C Temperature, C Temperature, C
IEC 1968/11 IEC 1969/11
IEC 1970/11
NOTE The diamond represents the measured value and the circle represents the normalised value.
Figure A.3 – Normalised indenter mean values
The normalisation works well over the meas
...
IEC/IEEE 62582-2 ®
Edition 1.1 2016-02
CONSOLIDATED VERSION
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Centrales nucléaires de puissance – Instrumentation et contrôle-commande
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Partie 2: Module indenter
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IEC/IEEE 62582-2 ®
Edition 1.1 2016-02
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation and control important to safety –
Electrical equipment condition monitoring methods –
Part 2: Indenter modulus
Centrales nucléaires de puissance – Instrumentation et contrôle-commande
importants pour la sûreté – Méthodes de surveillance de l’état des matériels
électriques –
Partie 2: Module indenter
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.120.20 ISBN 978-2-8322-3201-9
IEC/IEEE 62582-2 ®
Edition 1.1 2016-02
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Nuclear power plants – Instrumentation and control important to safety –
Electrical equipment condition monitoring methods –
Part 2: Indenter modulus
Centrales nucléaires de puissance – Instrumentation et contrôle-commande
importants pour la sûreté – Méthodes de surveillance de l’état des matériels
électriques –
Partie 2: Module indenter
– 2 – IEC/IEEE 62582-2:2011+AMD1:2016 CSV
IEC/IEEE 2016
CONTENTS
FOREWORD. 3
INTRODUCTION . 5
1 Scope and object . 7
2 Terms and definitions . 7
3 Abbreviations and acronyms . 7
4 General description . 8
5 Applicability, reproducibility, and complexity . 8
5.1 General . 8
5.2 Applicability . 8
5.3 Reproducibility . 8
5.4 Complexity . 9
6 Measurement procedure . 9
6.1 Stabilisation of the polymeric materials . 9
6.2 Sampling and measurement locations . 9
6.3 Conditions for measurement . 9
6.4 Instrumentation. 10
6.5 Calibration and tolerances . 11
6.6 Selection of measurement points . 12
6.7 Selection of probe velocity and maximum force . 12
6.8 Clamping . 12
6.9 Determination of the value of the indenter modulus . 12
6.10 Reporting . 13
Annex A (informative) Examples illustrating factors affecting the variation of the
indenter modulus value . 15
Annex B (informative) Example of a measurement report for indenter measurements in
laboratory . 19
Bibliography . 21
Figure 1 – A schematic representation of the Geometry and dimensions of the profile
of the probe tip (truncated cone) used in the indenter . 11
Figure 2 – Calculation of indenter modulus . 13
Figure A.1 – Example of local variation of indenter modulus due to variation in
equipment dimensions and construction . 15
Figure A.2 – Indenter values measured at different temperatures . 16
Figure A.3 – Normalised indenter mean values . 17
Figure A.4 – Example of change of indenter modulus value in laboratory conditions of
a hygroscopic sample after removal from long-term exposure in a heat chamber . 18
Figure A.5 – Adaptation of a decay curve to the measured indenter modulus values in
Figure A.4 . 18
Figure B.1 – Example of measured force versus deplacement time . 20
IEC/IEEE 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL IMPORTANT TO SAFETY –
ELECTRICAL EQUIPMENT CONDITION MONITORING METHODS –
Part 2: Indenter modulus
FOREWORD
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7) No liability shall attach to IEC or IEEE or their directors, employees, servants or agents including individual
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rights, and the risk of infringement of such rights, is entirely their own responsibility.
– 4 – IEC/IEEE 62582-2:2011+AMD1:2016 CSV
© IEC/IEEE 2016
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC/IEEE 62582-2 edition 1.1 contains the first edition (2011-08) [documents 45A/841/
FDIS and 45A/850/RVD] and its amendment 1 (2016-02) [documents 45A/1054/FDIS and
45A/1067/RVD].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red
text. A separate Final version with all changes accepted is available in this publication.
International Standard IEC/IEEE 62582-2 has been prepared by subcommittee 45A:
Instrumentation and control of nuclear facilities, of IEC technical committee 45: Nuclear
instrumentation, in cooperation with the Nuclear Power Engineering Committee of the Power &
Energy Society of the IEEE , under the IEC/IEEE Dual Logo Agreement between IEC and
IEEE.
This publication is published as an IEC/IEEE Dual Logo standard.
International standards are drafted in accordance with the rules given in the ISO/IEC
Directives, Part 2.
A list of all parts of IEC/IEEE 62582 series, under the general title Nuclear power plants
– Instrumentation and control important to safety – Electrical equipment condition
monitoring methods, can be found on the IEC website.
The IEC Technical Committee and IEEE Technical Committee have decided that the contents
of this publication and its amendment 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,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.
—————————
The lists of IEEE participants can be found at the following URLs: http://standards.ieee.org/downloads/62582-2/62582-2-
2011/62582-2-2011_wg-participants.pdf and http://standards.ieee.org/downloads/62582-2/62582-2-amd1-2016/62582-2-
amd1-2016_wg-participants.pdf.
IEC/IEEE 2016
INTRODUCTION
a) Technical background, main issues and organisation of this standard
This part of this IEC/IEEE standard specifically focuses on indenter modulus methods for
condition monitoring for the management of ageing of electrical equipment installed in nuclear
power plants. The indenter method is commonly used to carry out measurements on cables
(jackets, insulation) and o-rings.
This part of IEC/IEEE 62582 is the second part of the IEC/IEEE 62582. It contains detailed
descriptions of condition monitoring based on indenter modulus measurements.
The IEC/IEEE 62582 series is issued with a joint logo which makes it applicable to the
management of ageing of electrical equipment qualified to IEEE as well as IEC Standards.
Historically, IEEE Std 323-2003 introduced the concept and role that condition based
qualification could be used in equipment qualification as an adjunct to qualified life. In
equipment qualification, the condition of the equipment for which acceptable performance was
demonstrated is the qualified condition. The qualified condition is the condition of equipment,
prior to the start of a design basis event, for which the equipment was demonstrated to meet
the design requirements for the specified service conditions.
Significant research has been performed on condition monitoring techniques and the use of
these techniques in equipment qualification as noted in NUREG/CR-6704, Vol. 2 (BNL -
NUREG-52610) and JNES-SS-0903, 2009.
It is intended that this IEC/IEEE standard be used by test laboratories, operators of nuclear
power plants, systems evaluators, and licensors.
b) Situation of the current standard in the structure of the IEC SC 45A standard series
Part 2 of IEC/IEEE 62582 is the third level IEC SC 45A document tackling the specific issue of
application and performance of indenter modulus measurements in management of ageing of
electrical instrument and control equipment in nuclear power plants.
Part 2 of IEC/IEEE 62582 is to be read in association with part 1 of IEC/IEEE 62582, which
provides background and guidelines for the application of methods for condition monitoring of
electrical equipment important to safety of nuclear power plants.
For more details on the structure of the IEC SC 45A standard series, see item d) of this
introduction.
c) Recommendations and limitations regarding the application of this standard
It is important to note that this Standard establishes no additional functional requirements for
safety systems.
d) Description of the structure of the IEC SC 45A standard series and relationships
with other IEC documents and other bodies documents (IAEA, ISO)
The top-level document of the IEC SC 45A standard series is IEC 61513. It provides general
requirements for I&C systems and equipment that are used to perform functions important to
safety in NPPs. IEC 61513 structures the IEC SC 45A standard series.
IEC 61513 refers directly to other IEC SC 45A standards for general topics related to
categorisation of functions and classification of systems, qualification, separation of systems,
defence against common cause failure, software aspects of computer-based systems,
– 6 – IEC/IEEE 62582-2:2011+AMD1:2016 CSV
IEC/IEEE 2016
hardware aspects of computer-based systems, and control room design. The standards
referenced directly at this second level should be considered together with IEC 61513 as a
consistent document set.
At a third level, IEC SC 45A standards not directly referenced by IEC 61513 are standards
related to specific equipment, technical methods, or specific activities. Usually these
documents, which make reference to second-level documents for general topics, can be used
on their own.
A fourth level extending the IEC SC 45A standard series, corresponds to the Technical
Reports which are not normative.
IEC 61513 has adopted a presentation format similar to the basic safety publication
IEC 61508 with an overall safety life-cycle framework and a system life-cycle framework and
provides an interpretation of the general requirements of IEC 61508-1, IEC 61508-2 and
IEC 61508-4, for the nuclear application sector. Compliance with IEC 61513 will facilitate
consistency with the requirements of IEC 61508 as they have been interpreted for the nuclear
industry. In this framework IEC 60880 and IEC 62138 correspond to IEC 61508-3 for the
nuclear application sector.
IEC 61513 refers to ISO as well as to IAEA 50-C-QA (now replaced by IAEA GS-R-3) for
topics related to quality assurance (QA).
The IEC SC 45A standards series consistently implements and details the principles and
basic safety aspects provided in the IAEA code on the safety of NPPs and in the IAEA safety
series, in particular the Requirements NS-R-1, establishing safety requirements related to the
design of Nuclear Power Plants, and the Safety Guide NS-G-1.3 dealing with instrumentation
and control systems important to safety in Nuclear Power Plants. The terminology and
definitions used by SC 45A standards are consistent with those used by the IAEA.
IEC/IEEE 2016
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL IMPORTANT TO SAFETY –
ELECTRICAL EQUIPMENT CONDITION MONITORING METHODS –
Part 2: Indenter modulus
1 Scope and object
This part of IEC/IEEE 62582 contains methods for condition monitoring of organic and
polymeric materials in instrumentation and control systems using the indenter modulus
technique in the detail necessary to produce accurate and reproducible measurements. It
includes the requirements for the selection of samples, the measurement system and
measurement conditions, and the reporting of the measurement results.
The different parts of IEC/IEEE 62582 are measurement standards, primarily for use in the
management of ageing in initial qualification and after installation. Part 1 of IEC/IEEE 62582
includes requirements for the application of the other parts of IEC/IEEE 62582 and some
elements which are common to all methods. Information on the role of condition monitoring in
the qualification of equipment important to safety is found in IEEE Std 323.
This standard is intended for application to non-energised equipment.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
2.1
indenter modulus
ratio between the changes in applied force and corresponding displacement of a probe of a
–1
standardised shape, driven into a material. It is expressed in N∙mm .
NOTE The term “modulus” typically refers to the modulus of elasticity of a material which is defined as the ratio of
–2
the applied stress and the corresponding strain and is expressed in N∙m (Pa). However, in the use of the
indenter, it has become common practice to use the term indenter modulus to describe the ratio of the change in
–1
applied force to material deformation and express it in N∙mm .
3 Abbreviations and acronyms
DBE Design Basis Event
IM Indenter Modulus
SiR silicone rubber
CSPE chlorosulphonated polyethylene
EPDM ethylene propylene diene monomer
XLPE crosslinked polyethylene
– 8 – IEC/IEEE 62582-2:2011+AMD1:2016 CSV
IEC/IEEE 2016
4 General description
A typical indenter uses an instrumented probe, which is driven at a fixed velocity into the
material and includes a load cell or similar force-measuring device, connected to the probe,
which measures the force necessary to maintain the constant velocity. The probe’s
displacement is measured by an appropriate transducer. The travel and force are purposely
limited to protect the material from permanent damage. The indenter modulus is calculated by
dividing the change in force by the corresponding displacement during inward travel.
5 Applicability, reproducibility, and complexity
5.1 General
When organic and polymeric materials age, they often harden which will result in an increase
of indenter modulus. Some materials, such as some formulations of Butyl Rubber, soften
during thermal and/or radiation ageing. The purpose of monitoring changes in indenter
modulus is to estimate degradation rates and levels induced by ageing.
5.2 Applicability
The indenter method is commonly used to carry out measurements on cables (jackets,
insulation) and o-rings. Its use requires special fixtures depending on the geometry of the
samples.
This method should only be applied to materials whose hardness changes monotonically with
ageing.
The indenter method may be carried out on equipment with high integrity in a non-invasive
manner. However, the process of performing indenter measurements on equipment in field
should include controls to ensure that damage – from the probe or from handling in order to
access suitable measurement points – has not been imparted to the equipment. The process
should include correction of any equipment that has been damaged or suspected of incurring
damage.
Measurements in the field require access to the exterior wall of the equipment. For field
measurements on cables, this often limits the measurements to jacket materials. It may be
possible to assess the condition of cable insulation from indenter measurements on its jacket
if there is a known relationship between the ageing degradation of the jacket material and the
degradation of the insulation. This relationship shall be justified to be valid and sufficiently
sensitive to provide the valid monitoring through life.
5.3 Reproducibility
Indenter modulus values can be influenced by variability in specimen dimensions and
construction, temperature and moisture content of the specimen, stabilisation of the
specimen, and contamination of the specimen. If measurements are made under excessive
vibration, this can influence the measured value. The influence by variability in the specimen
dimensions and construction is typically the case for measurements on cables, where the
measurement point may be situated above a cavity beneath the jacket surface. The cross-
section of typical cable core insulation may differ substantially from that of an ideal tube and
can result in variability in the measured values of indenter modulus depending on where the
measurement is made. These variations tend to be localised. Measurements shall be taken at
several points on the equipment to compensate for these local variations (see 6.6).
An illustration of variations due to variability in specimen dimensions and construction is given
in Annex A.
IEC/IEEE 2016
NOTE A good knowledge of the construction of the equipment is important before the selection of measurement
positions is made. In the case of loosely constructed cables, the variability is expected to be high and it is
important that the measurements on the jacket are made over a conductor rather than free space.
5.4 Complexity
The degree of complexity experienced during indenter modulus measurements in the field will
often depend on cable accessibility. Existing instruments may be used in the field on cables
that are accessible. In this case, data generation is rapid and measurements at a large
number of points can be carried out over short time periods. Instruments can be configured
such that data are generated and stored directly. Measurements on equipment with more
complex geometries and limited accessibility may require the development of special fixtures.
The same fixture shall be used for repeated indenter modulus measurements.
6 Measurement procedure
6.1 Stabilisation of the polymeric materials
An appropriate time period shall be allowed for the polymeric materials in recently
manufactured equipments to stabilise before any condition monitoring or accelerated ageing
programmes are carried out. The time period over which the polymeric materials stabilise is
normally dependent on the processing additives and polymer composition. If manufacturers’
stabilisation time data are not available, a period of 6 months should be allowed.
6.2 Sampling and measurement locations
Laboratory measurements of indenter modulus on samples selected from the field and
indenter modulus measurements in the field only provide information on the status of the
equipment at a specific location. Knowledge of the environmental conditions in representative
areas during plant operation is a prerequisite for selecting locations. Since equipment heating
and radiation effects could be most apparent closest to the sources of heat and radiation, the
choice of locations should consider capturing the potential for significant ageing effects near
sources of heating and radiation. The position of the locations and available information about
the environmental time history of the locations selected shall be documented.
Sampling and measurement procedures shall comply with local instructions, taking into
account the safety of personnel and equipment. Handling of equipment during measurement
or removal of samples from the plant should be minimised e.g. cables should not be bent
more than necessary for the measurement or for the removal of the sample.
6.3 Conditions for measurement
The surface on which the measurements are made shall be cleaned of surface debris. In the
field, it may be necessary to apply a dry wipe to remove accumulated dirt from the surface
and prevent contamination of the indenter instrument. Under no circumstances shall solvents
be used for surface cleaning.
The indenter modulus varies with the temperature and moisture content of the sample as
shown in Annex A.
When measurements are carried out in the laboratory, e.g. after accelerated thermal ageing,
they shall be made in a surrounding air temperature of 20 ± 5 °C and a relative humidity of
45 % to 75 %. Samples shall be allowed time to reach equilibrium with their surroundings
before measurements are started.
NOTE 1 Where the materials are hygroscopic, it should be noted that the sample can be extremely dry after
artificial accelerated ageing as a consequence of long-term exposure to high temperatures in an oven. For these
materials, the values of indenter modulus measured can be significantly higher than for a sample in equilibrium
with the laboratory atmosphere. This is particularly important for condition monitoring of hygroscopic insulation
material when the final value of indenter modulus, on which qualified condition is based, is measured on
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IEC/IEEE 2016
completion of accelerated thermal ageing before the sample is subjected to a DBE test. Clause A.3 provides
guidance on dealing with this specific concern.
It may not be possible to make field measurements in standard atmospheric conditions. In
such cases the surrounding air temperature and the temperature at the surface at which the
measurements are made shall be recorded.
NOTE 2 Annex A shows a method for transformation of a measured indenter modulus to a corresponding modulus
at a different temperature. In addition to reporting the temperature at which the value has been measured, it is
recommended that the corresponding value at 20 ºC be calculated and reported.
6.4 Instrumentation
The indenter functions by driving an instrumented probe at a fixed velocity into the material
whilst a load cell or similar force-measuring device, connected to the probe, measures the
applied force. The probe shall have the shape of a truncated steel cone with the geometry
and dimensions shown in Figure 1. The probe’s displacement is measured by an appropriate
transducer. The point at which the tip of the probe is brought into contact with the material is
sensed by a change in force. The probe’s total displacement is normally limited to a fraction
of a mm to prevent permanent deformation and to keep within the range of approximate linear
proportionality between force and displacement. The indenter modulus (IM) is then calculated
by dividing the change in force by the corresponding displacement during inward travel. The
small displacements and loads that occur during this process prevent permanent effects on
the material.
NOTE Although the total displacement is limited, for some materials the relationship between force and
displacement is still significantly non-linear.
IEC/IEEE 2016
35°
Truncated cone ∅ 0,79 mm
IEC 1961/11
Dimensions in millimetres
17,5°
≈ R0,1
IEC
Figure 1 – A schematic representation of the Geometry and dimensions
of the profile of the probe tip (truncated cone) used in the indenter
A typical indenter is a hand held cylindrical instrument. At the head of the instrument, an
appropriate clamping device holds a cable or wire securely in position so that the probe can
be driven uniformly into the jacket or insulation of the cable or wire respectively. The probe is
situated within the instrument and is attached to a sensitive load cell. A servo-controlled
electric motor with appropriate gearing provides the capability to drive the probe towards the
sample and the probe’s position is measured by a transducer. A temperature sensor is
located close to the clamping device. The power and servo-control to the electric motor, and
outputs from the load cell, transducer and temperature sensor are fed by cable into a
separate controller which may be directly connected to a computer or capable of data storage
in-situ which may be downloaded into a remote computer. Parameters such as probe
velocity, and maximum load, and displacement are preloaded into the controller before the
start of measurement. The instrument is also designed such that the cable clamp can be
modified to allow calibration of the load cell using an appropriate weight and the probe travel
using a dial gauge.
6.5 Calibration and tolerances
The indenter and the measurement system shall be calibrated before each series of
measurements in accordance with the manufacturer’s instructions. The calibration shall be
carried out on both the force sensor and probe velocity. The total error of force measurement
shall be less than 3 % of the upper limit of the force range, including instrumentation
0,56
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IEC/IEEE 2016
tolerances as well as reading precision. The probe velocity shall be constant. The total
measurement error of the required velocity shall be less than 2 %.
6.6 Selection of measurement points
In each of the selected locations for field measurements, measurements shall be carried out
at several points and the mean value and standard deviation shall be reported. If the number
of points is more than 7, the highest and lowest value shall be deleted before calculation of
the mean value and the standard deviation. For measurements on cables, a minimum of three
points around the circumference at each of three longitudinal positions shall be used. Where
space is limited, it may not be possible to rotate around the cable circumference. In this case,
a minimum of nine points shall be selected with a separation of 60 mm to 100 mm along the
cable length.
In the case of laboratory measurements on samples of cables, a minimum of three points
around the circumference at each of three longitudinal positions shall be used. None of the
measurement points shall be less than 100 mm from the ends of the sample.
For measurements on o-rings, a similar number of points shall be measured if the size of the
o-ring allows.
6.7 Selection of probe velocity and maximum force
Before the start of the measurement, the test parameters shall be loaded into the
measurement system. In particular, the required maximum load and maximum displacement
should be set as limits to prevent damage to the equipment measured.
The probe velocity can have a significant influence on the measured value of indenter
–1 –1
modulus. The probe velocity shall be 5 mm∙min to 5,2 mm∙min . The probe velocity that is
selected shall be reported.
The maximum force that is selected needs to be a compromise between a value which is high
enough to achieve reasonable resolution in the displacement axis and a value that is low
enough to ensure that the probe does not damage the cable. For many polymeric insulation
materials, a maximum force of 10 N is recommended. This will normally result in a probe
penetration depth which is significantly less than 1 mm. For certain insulation materials, such
as SiR, a maximum value lower than 10 N may be required to avoid excessive penetration.
6.8 Clamping
When carrying out measurements on cables, the measured value of indenter modulus may be
strongly affected by variations in the force used to keep the cables securely in position within
the clamp. In order to minimise these effects, the cable shall be clamped using the minimum
force required to keep it in place. Problems in clamping shall be included in the measurement
report.
6.9 Determination of the value of the indenter modulus
The indenter modulus is determined by the slope of the force-displacement curve and is
–1
expressed in N∙mm .
IM = (F – F )/(d – d ) (1)
2 1 2 1
where
IM is the indenter modulus;
F is the corresponding force value at displacement d
i i.
IM shall be determined by using the values F = 1 N and F = 4 N, see Figure 2.
1 2
IEC/IEEE 2016
d – d
2 1
F – F
2 1
0 0,1 0,2 0,3 0,4 0,5 0,6
Displacement (mm)
IEC 1962/11
d – d
2 1
0 0,1 0,2 0,3 0,4 0,5 0,6
Displacement (mm)
IEC
Figure 2 – Calculation of indenter modulus
–1
NOTE Some instruments used for indenter measurements show the result in load versus time (in N∙s ). The
–1 –1
value of the indenter modulus in N∙mm is then calculated as the value in N∙s divided by the probe velocity in
–1
mm∙s .
6.10 Reporting
The measurement report shall as a minimum include the following items
a) Identification of the equipment measured, including the material formulation. For selection
of samples from the field or measurements in the field this shall include plant and location
relative to heat and radiation sources (6.2).
b) Pre-history of the equipment. This may include
• indenter measurements on samples of new (un-aged) equipment: storage and time
interval between production of the equipment sampled and start of the measurement
(6.1);
• indenter measurements on artificially aged samples: ageing conditions of the samples
(6.2);
• indenter measurements on naturally aged samples (e.g. field measurements): history
of environmental conditions to which the sample has been subjected (6.2).
Load (N)
Load (N)
F – F
2 1
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IEC/IEEE 2016
c) Place and date of the measurement (laboratory, on-site).
d) For laboratory measurement of samples subjected to artificial thermal ageing: time interval
between removing the sample from the heat chamber until start of measurement (6.3).
e) Ambient and surface temperature at the time of measurement (6.3).
f) Other local conditions and situations encountered during measurement that may influence
the results.
g) Measurement instrumentation, including software version (6.4).
h) Calibration procedure (6.5).
i) Measurement points (6.6).
j) Probe velocity (6.7).
k) Maximum force (6.7).
l) Mounting of the sample and problems in clamping (6.8).
m) For measurements in the field: observations on the condition of the equipment before and
after indenter measurements (6.2).
n) Mean value and standard deviation of indenter modulus ( after deleting the highest and
–1
lowest value), in N∙mm together with information on the force interval for which it has
been determined (normally 1 N to 4 N) (6.6 and 6.9).
NOTE If the indenter measurements are made at a temperature above 25 °C, it is recommended that the value
referenced to 20 °C is also reported, calculated according to Annex A.
o) Diagram showing a typical force versus displacement curve.
p) Any other information of importance in interpretation of the measurement results in
relation to the purposes of the measurements.
An example of a measurement report is given in Annex B.
IEC/IEEE 2016
Annex A
(informative)
Examples illustrating factors affecting the variation
of the indenter modulus value
A.1 Example of influence of variability in equipment dimensions and
construction
Figure A.1 illustrates the variations due to variability in equipment dimensions and
construction, showing sets of data from indenter measurements at eight points on the jacket
of a 7 core cable with jacket material CSPE and insulator material EPDM. The mean values
–1
and standard deviations of the indenter modulus measured were 15,57 N∙mm and
–1 –1 –1
0,58 N∙mm for the unaged cable jacket, 23,21 N∙mm and 1,06 N∙mm for the thermally
aged cable jacket.
Thermally aged
Unaged
1 008 h at 120 °C
6 66
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
Displacement (mm) Displacement (mm)
IEC 1963/11 IEC 1964/11
Thermally aged
o
1008 h at 120 C
Unaged
...
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