EN 60216-1:2001

SLOVENSKI STANDARD
01-oktober-2002
1DGRPHãþD
SIST HD 611.1 S1:1998
SIST HD 611.4.1 S1:1998
(OHNWULþQLL]RODFLMVNLPDWHULDOL/DVWQRVWLWRSORWQHY]GUåOMLYRVWLGHO3RVWRSNL
VWDUDQMDLQYUHGQRWHQMHSUHVNXVQLKUH]XOWDWRY,(&
Electrical insulating materials - Properties of thermal endurance - Part 1: Ageing
procedures and evaluation of test results (IEC 60216-1:2001)
Elektroisolierstoffe - Eigenschaften hinsichtlich des thermischen Langzeitverhaltens - Teil
1: Warmlagerungsverfahren und Auswertung von Prüfergebnissen (IEC 60216-1:2001)
Matériaux isolants électriques - Propriétés d'endurance thermique - Partie 1: Méthodes
de vieillissement et évaluation des résultats d'essai (CEI 60216-1:2001)
Ta slovenski standard je istoveten z: EN 60216-1:2001
ICS:
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 60216-1
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2001
ICS 17.220.99;29.035.01 Supersedes HD 611.1 S1:1992
English version
Electrical insulating materials -
Properties of thermal endurance
Part 1: Ageing procedures and evaluation of test results
(IEC 60216-1:2001)
Matériaux isolants électriques - Elektroisolierstoffe -
Propriétés d'endurance thermique Eigenschaften hinsichtlich des
Partie 1: Méthodes de vieillissement et thermischen Langzeitverhaltens
évaluation des résultats d'essai Teil 1: Warmlagerungsverfahren und
(CEI 60216-1:2001) Auswertung von Prüfergebnissen
(IEC 60216-1:2001)
This European Standard was approved by CENELEC on 2001-10-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60216-1:2001 E
Foreword
The text of document 15E/153/FDIS, future edition 5 of IEC 60216-1, prepared by SC 15E, Methods of
test, of IEC TC 15, Insulating materials, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 60216-1 on 2001-10-01.
This European Standard supersedes HD 611.1 S1:1992.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2002-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-10-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A, B and C are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60216-1:2001 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 60216-1:2001
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60050-212 1990 International Electrotechnical --
Vocabulary (IEV)
Chapter 212: Insulating solids, liquids
and gases
IEC 60212 1971 Standard conditions for use prior to and HD 437 S1 1984
during the testing of solid electrical
insulating materials
IEC 60216-2 1990 Guide for the determination of thermal HD 611.2 S1 1992
endurance properties of electrical
insulating materials
Part 2: Choice of test criteria
1)
IEC 60216-3 Part 3: Instructions for calculating--
thermal endurance characteristics
IEC 60216-4-1 1990 Part 4: Ageing ovens -- Section 1: HD 611.4.1 S1 1992
Single-chamber ovens
IEC 60493-1 1974 Guide for the statistical analysis of--
ageing test data - Part 1: Methods
based on mean values of normally
distributed test results
ISO 291 1997 Plastics - Standard atmospheres for--
conditioning and testing
ISO 2578 1993 Plastics EN ISO 2578 1998
Determination of time-temperature limits
after prolonged exposure to heat
ISO 11346 1997 Rubber, vulcanized or thermoplastic--
Estimation of life-time and maximum
temperature of use from an Arrhenius
plot
1)
To be published.
NORME
CEI
INTERNATIONALE IEC
60216-1
INTERNATIONAL
Cinquième édition
STANDARD
Fifth edition
2001-07
Matériaux isolants électriques –
Propriétés d'endurance thermique –
Partie 1:
Méthodes de vieillissement et
évaluation des résultats d'essai
Electrical insulating materials –
Properties of thermal endurance –
Part 1:
Ageing procedures and
evaluation of test results
© IEC 2001 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun procédé, any form or by any means, electronic or mechanical,
électronique ou mécanique, y compris la photocopie et les including photocopying and microfilm, without permission in
microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
W
PRICE CODE
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue

60216-1 © IEC:2001 – 3 –
CONTENTS
FOREWORD . 7
INTRODUCTION . 11
1 Scope . 15
2 Normative references. 15
3 Terms, definitions, symbols and abbreviated terms . 17
3.1 Terms and definitions . 17
3.2 Symbols and abbreviated terms . 21
4 Synopsis of procedures. 23
4.1 Full procedures. 23
4.2 Simplified numerical and graphical evaluation procedures . 23
5 Detailed experimental procedures . 25
5.1 Selection of test procedures. 25
5.1.1 General considerations . 25
5.1.2 Specific instructions for determination of TI. 25
5.1.3 Determination of TI for times other than 20 000 h. 25
5.2 Selection of end-points . 25
5.3 Preparation and number of test specimens . 27
5.3.1 Preparation . 27
5.3.2 Number of specimens . 27
5.4 Establishment of initial property value. 29
5.5 Exposure temperatures and times. 29
5.6 Ageing ovens. 31
5.7 Environmental conditions . 31
5.7.1 Atmospheric conditions during ageing . 31
5.7.2 Conditions for property measurement. 31
5.8 Procedure for ageing . 33
5.8.1 Procedure using a non-destructive test . 33
5.8.2 Procedure using a proof test . 33
5.8.3 Procedure using a destructive test . 35
6 Evaluation. 35
6.1 Numerical analysis of test data . 35
6.2 Thermal endurance characteristics and formats . 35
6.3 Times to end-point, x- and y-values. 37
6.3.1 Non-destructive tests . 37
6.3.2 Proof tests . 39
6.3.3 Destructive tests . 39
6.4 Means and variances . 39
6.4.1 Complete data. 39
6.4.2 Incomplete (censored) data. 41

60216-1 © IEC:2001 – 5 –
6.5 General means and variances and regression analysis . 41
6.6 Statistical tests and data requirements . 41
6.6.1 Data of all types. 41
6.6.2 Proof tests . 43
6.6.3 Destructive tests . 43
6.7 Thermal endurance graph and thermal endurance characteristics . 45
6.8 Test report. 45
7 Simplified procedures . 47
7.1 Outline description of procedures. 47
7.2 Experimental procedures . 47
7.2.1 Choice of diagnostic test . 47
7.2.2 Choice of end-point. 47
7.2.3 Test specimens. 47
7.3 Exposure temperatures. 49
7.4 Ageing ovens. 49
7.5 Procedure. 49
7.5.1 Initial property values. 49
7.5.2 Ageing procedure. 51
7.6 Simplified calculation procedures. 51
7.6.1 Times to end-point . 51
7.6.2 Calculation of the regression line . 51
7.6.3 Calculation of deviation from linearity. 53
7.6.4 Temperature index and halving interval. 55
7.6.5 Validity of simplified calculations. 55
7.6.6 Test report . 55
Annex A (informative) Dispersion and non-linearity. 67
Annex B (informative) Exposure temperatures and times. 71
Annex C (informative) Concepts in earlier editions . 77
Figure 1 – Property variation – Determination of time to end-point at each temperature
(destructive and non-destructive tests) . 59
Figure 2 – Estimation of times to end-point – Property value (ordinate, arbitrary units)
versus time (abscissa, log scale, arbitrary units) . 61
Figure 3 – Destructive tests – Estimation of time to end-point . 63
Figure 4 – Thermal endurance graph. 65
Figure C.1 – Relative temperature index . 79
Table 1 – Suggested exposure temperatures and times. 57
Table B.1 – Groups .75

60216-1 © IEC:2001 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATING MATERIALS –
PROPERTIES OF THERMAL ENDURANCE –
Part 1: Ageing procedures and evaluation of test results
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60216-1 has been prepared by subcommittee 15E: Methods of
test, of IEC technical committee 15: Insulating materials.
This fifth edition cancels and replaces the fourth edition published in 1990 and constitutes a
technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
15E/153/FDIS 15E/155/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 3.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next revision.

60216-1 © IEC:2001 – 9 –
Annexes A, B and C are for information only.
The committee has decided that the contents of this publication will remain unchanged
until 2006. At this date, the publication will be
 reconfirmed;
 withdrawn;
 replaced by a revised edition, or
 amended.
60216-1 © IEC:2001 – 11 –
INTRODUCTION
The listing of the thermal capabilities of electrical insulating materials, based on service
experience, was found to be impractical, owing to the rapid development of polymer and
insulation technologies and the long time necessary to acquire appropriate service
experience. Accelerated ageing and test procedures were therefore required to obtain the
necessary information. The IEC 60216 series has been developed to formalize these
procedures and the interpretation of their results.
Physico-chemical models postulated for the ageing processes led to the almost universal
assumption of the Arrhenius equations to describe the rate of ageing. Out of this arose
the concept of the temperature index (TI) as a single-point characteristic based upon
accelerated ageing data. This is the numerical value of the temperature in °C at which the
time taken for deterioration of a selected property to reach an accepted end-point is that
specified (usually 20 000 h).
NOTE The term Arrhenius is widely used (and understood) to indicate a linear relationship between the logarithm
of a time and the reciprocal of the thermodynamic (absolute or kelvin) temperature. The correct usage is restricted
to such a relationship between a reaction rate constant and the thermodynamic temperature. The common usage is
employed throughout this standard.
The large statistical scatter of test data which was found, together with the frequent
occurrence of substantial deviations from the ideal behaviour, demonstrated the need for tests
to assess the validity of the basic physico-chemical model. The application of conventional
statistical tests, as set out in IEC 60493, fulfilled this requirement, resulting in the "confidence
limit", (TC) of TI, but the simple, single-point TI was found inadequate to describe the
capabilities of materials. This led to the concept of the "Thermal Endurance Profile" (TEP)
given in the second edition of this part of IEC 60216, incorporating the temperature index, its
variation with specified ageing time, and a confidence limit.
A complicating factor is that the properties of a material subjected to thermal ageing may not
all deteriorate at the same rate, and different end-points may be relevant for different
applications. Consequently, a material may be assigned more than one temperature index,
derived, for example, from the measurement of different properties and the use of different
end-point times.
A useful addition to the standard was the relative temperature index (RTI) obtained by simul-
taneous ageing of a known reference material with the test material, eliminating some of the
uncertainties associated with, for example, oven temperature control.
It was subsequently found that the statistical confidence index included in the TEP was not
widely understood or used. However, the statistical tests were considered essential,
particularly after minor modifications to make them relate better to practical circumstances:
the concept of the halving interval (HIC) was introduced to indicate the rate of change of
ageing time with temperature. TEP was then abandoned, with the TI and HIC being reported
in a way which indicated whether or not the statistical tests had been fully satisfied. At the
same time, the calculation procedures were made more comprehensive, enabling full
statistical testing of data obtained using a diagnostic property of any type, including the
particular case of partially incomplete data. The calculation procedures (by now quite
complex) were made more acceptable by the provision of computer programmes suitable for
low-price personal computers.
60216-1 © IEC:2001 – 13 –
At the time of preparation of the present edition, it was decided that RTI should be made the
subject of a separate standard.
Simultaneously with the development of the IEC 60216 series, other standards were being
developed in ISO, intended to satisfy a similar requirement for plastics and rubber materials.
These are ISO 2578 and ISO 11346 respectively, which use less rigorous statistical
procedures and more restricted experimental techniques. It is hoped that the wide availability
of the computer facilities mentioned above and the inclusion of a section of simplified
procedures will remove the need for these separate standards.
IEC 60216, which deals with the determination of thermal endurance properties of electrical
insulating materials is composed of several parts:
Part 1: Ageing procedures and evaluation of test results;
Part 2: Choice of test criteria;
Part 3: Instruction for calculating thermal endurance characteristics;
Part 4-1: Ageing ovens – Section 1: Single-chamber ovens;
Part 4-2: Ageing ovens – Precision ovens for use up to 300 °C;
Part 4-3: Ageing ovens – Multi-chamber ovens;
Part 5: Guidelines for the application of thermal endurance characteristics.
NOTE This series may be extended. For revisions and new parts, see the current catalogue of IEC publications
for an up-to-date list.
60216-1 © IEC:2001 – 15 –
ELECTRICAL INSULATING MATERIALS –
PROPERTIES OF THERMAL ENDURANCE –
Part 1: Ageing procedures and evaluation of test results
1 Scope
This part of IEC 60216 specifies the general ageing conditions and procedures to be used for
deriving thermal endurance characteristics and gives guidance in using the detailed
instructions and guidelines in the other parts of the standard.
Simplified procedures are also given, with the conditions under which these procedures may
be used.
Although originally developed for use with electrical insulating materials and simple
combinations of such materials, the procedures are considered to be of more general
applicability and are widely used in the assessment of materials not intended for use as
electrical insulation.
In the application of this standard, it is assumed that a practically linear relationship exists
between the logarithm of the time required to cause the predetermined property change and
the reciprocal of the corresponding absolute temperature (Arrhenius relationship).
For the valid application of the standard, no transition, in particular no first-order transition,
should occur in the temperature range under study.
Throughout the rest of this standard the term "insulating materials" is always taken to mean
"insulating materials and simple combinations of such materials".
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 60216. For dated references, subsequent amend-
ments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this part of IEC 60216 are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of IEC
and ISO maintain registers of currently valid International Standards.
IEC 60050(212):1990, International Electrotechnical Vocabulary (IEV) – Chapter 212:
Insulating solids, liquids and gases
IEC 60212:1971, Standard conditions for use prior to and during the testing of solid electrical
insulating materials
IEC 60216-2:1990, Guide for the determination of thermal endurance properties of electrical
insulating materials – Part 2: Choice of test criteria

60216-1 © IEC:2001 – 17 –
IEC 60216-3, Guide for the determination of thermal endurance properties of electrical
insulating materials – Part 3: Instructions for calculating thermal endurance characteristics
IEC 60216-4-1:1990, Guide for the determination of thermal endurance properties of electrical
insulating materials – Part 4: Ageing ovens – Section 1: Single-chamber ovens
IEC 60493-1:1974, Guide for the statistical analysis of ageing test data – Part 1: Methods
based on mean values of normally distributed test results
ISO 291:1997, Plastics – Standard atmospheres for conditioning and testing
ISO 2578:1993, Plastics – Determination of time-temperature limits after prolonged exposure
to heat
ISO 11346:1997, Rubber, vulcanized or thermoplastic – Estimation of life-time and maximum
temperature of use from an Arrhenius plot
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this part of IEC 60216, the following definitions apply:
3.1.1
temperature index
TI
numerical value of the temperature in degrees Celsius derived from the thermal endurance
relationship at a time of 20 000 h (or other specified time)
[IEV 212-02-08, modified]
3.1.2
halving interval
HIC
numerical value of the temperature interval in kelvins which expresses the halving of the time
to end-point taken at the temperature equal to TI
[IEV 212-02-10, modified]
3.1.3
thermal endurance graph
graph in which the logarithm of the time to reach a specified end-point in a thermal endurance
test is plotted against the reciprocal thermodynamic (absolute) test temperature
[IEV 212-02-07]
3.1.4
thermal endurance graph paper
graph paper having a logarithmic time scale as the ordinate, graduated in powers of ten
(from 10 h to 100 000 h is often a convenient range). Values of the abscissa are proportional
to the reciprocal of the thermodynamic (absolute) temperature. The abscissa is usually
graduated in a non-linear (Celsius) temperature scale oriented with temperature increasing
from left to right.
3.1.5
ordered data
set of data arranged in sequence so that, in the appropriate direction through the sequence,
each member is greater than, or equal to, its predecessor.
NOTE Ascending order in this standard implies that the data is ordered in this way, the first order-statistic being
the smallest.
60216-1 © IEC:2001 – 19 –
3.1.6
order-statistics
each individual value in a set of ordered data is referred to as an order-statistics identified by
its numerical position in the sequence
3.1.7
incomplete data
ordered data, where the values above and/or below defined points are not known
3.1.8
censored data
incomplete data, where the number of unknown values is known.
NOTE If the censoring is begun above/below a specified numerical value, the censoring is of type 1. If above/
below a specified order-statistic, it is of type 2. This standard is concerned only with type 2.
3.1.9
degrees of freedom
number of data values minus the number of parameter values
3.1.10
variance of a data set
sum of the squares of the deviations of the data from a reference level defined by one or more
parameters, divided by the number of degrees of freedom
NOTE The reference level may for example, be a mean value (one parameter) or a line (two parameters, slope
and intercept.
3.1.11
covariance of data sets
for two sets of data with equal numbers of elements where each element in one set
corresponds to one in the other, the sum of the products of the deviations of the corres-
ponding members from their set means, divided by the number of degrees of freedom
3.1.12
regression analysis
process of deducing the best-fit line expressing the relation of corresponding members of two
data groups by minimizing the sum of squares of deviations of members of one of the groups
from the line.
NOTE The parameters are referred to as the regression coefficients.
3.1.13
correlation coefficient
number expressing the completeness of the relation between members of two data sets, equal
to the covariance divided by the square root of the product of the variances of the sets
NOTE The value of its square is between 0 (no correlation) and 1 (complete correlation).
3.1.14
confidence limit
TC
statistical parameter, calculated from the test data, which with 95 % confidence constitutes a
lower limit for the true value of the temperature index estimated by TI
NOTE 1 95 % confidence implies that there is only 5 % probability that the true value of the temperature index is
actually smaller than TC.
NOTE 2 In other connections, confidence values other than 95 % may sometimes be used; for example, in the
linearity test for destructive test data.

60216-1 © IEC:2001 – 21 –
3.1.15
destructive test
diagnostic property test, where the test specimen is irreversibly changed by the property
measurement, in a way which precludes a repeated measurement on the same specimen
3.1.16
non-destructive test
diagnostic property test, where the properties of the test specimen are not permanently
changed by the measurement, so that a further measurement on the same specimen may be
made after appropriate treatment
3.1.17
proof test
diagnostic property test, where each test specimen is, at the end of each ageing cycle,
subjected to a specified stress, further ageing cycles being conducted until the specimen fails
on testing
3.1.18
temperature group (of specimens)
number of specimens being exposed together to the same temperature ageing in the same
oven
NOTE Where there is no risk of ambiguity, either temperature groups or test groups may be referred to simply as
groups.
3.1.19
test group (of specimens)
number of specimens removed together from a temperature group (as above) for destructive
testing
3.2 Symbols and abbreviated terms
Clause
a,b Regression coefficients
a,b,c,d Numbers of specimens for destructive tests . 5.3.2.3, 7.2.3
Number of -values .
n y 6.4.1
N
Total number of test specimens . 5.3.2.3, 7.2.3
Number of specimens in temperature group i (censored data).
m 6.3.2
i
r Correlation coefficient . 7.6.3
F Fisher distributed stochastic variable . 6.6.1
s Square root of mean square deviation of points from regression line
y
x
Reciprocal thermodynamic temperature (1/Θ)
y Logarithm of time to end-point
ϑ Temperature, °C
Temperature, thermodynamic (kelvins)
Θ
Value in kelvins of 0 °C (273,15 K)
Θ
τ Time (to end-point)
2 2
χ χ -distributed stochastic variable
µ Central second moment of group of values
TI Temperature Index
TC Lower 95 % confidence limit of TI
HIC Halving interval at temperature equal to TI
TEP Thermal endurance profile
RTI Relative temperature index

60216-1 © IEC:2001 – 23 –
4 Synopsis of procedures
4.1 Full procedures
The standardized procedure for the evaluation of the thermal properties of a material consists
of a sequence of steps, as follows.
NOTE It is strongly recommended that the full evaluation procedure, as described below and in 5.1 to 5.8, be
used. Because the calculations as specified in IEC 60216-3 are complex and tedious if carried out using a hand
calculator, IEC 60216-3 also contains a computer programme which greatly simplifies the task, and, in addition,
displays the thermal endurance graph on the computer screen.
a) Preparing suitable specimens appropriate for the intended property measurements
(see 5.3).
b) Subjecting groups of specimens to ageing at several fixed levels of elevated temperature,
either continuously, or cyclically for a number of periods between which the specimens are
normally returned to room temperature or another standard temperature (see 5.5).
c) Subjecting specimens to a diagnostic procedure in order to reveal the degree of ageing.
Diagnostic procedures may be non-destructive or destructive determinations of a property
or potentially destructive proof tests (see 5.1 and 5.2).
d) Extending the continuous heat exposure or the thermal cycling until the specified
end-point, i.e. failure of specimens or a specified degree of change in the measured
property, is reached (see 5.1, 5.2 and 5.5).
e) Reporting the test results in a way depending on the kind of ageing procedure (continuous
or cyclic) and diagnostic procedure (see under item c)): ageing curves, or time or number
of cycles to reach the end-point, for each specimen.
f) Evaluating these data numerically and presenting them graphically, as explained in 6.1
and 6.8.
g) Expressing the complete information in abbreviated numerical form, as described in 6.2 by
means of the temperature index and halving interval.
The full experimental and evaluation procedures are given in clause 5 to subclause 6.8.
4.2 Simplified numerical and graphical evaluation procedures
Simplified procedures, which do not test the data dispersion but only deviations from linear
behaviour, are also available. These are described in 7.1 to 7.6.
It is also possible, with some limitations, to evaluate the thermal endurance data graphically.
In this case, statistical assessment of data dispersion is not possible, but it is considered
important to evaluate any deviation of the data from the linear relationship. Instructions for the
graphical procedures are also given in 7.1 to 7.6.

60216-1 © IEC:2001 – 25 –
5 Detailed experimental procedures
5.1 Selection of test procedures
5.1.1 General considerations
Each test procedure should specify the shape, dimensions and number of the test specimens,
the temperatures and times of exposure, the property to which TI is related, the methods of its
determination, the end-point, and the derivation of the thermal endurance characteristics from
the experimental data.
The chosen property should reflect, in a significant fashion if possible, a function of the
material in practical use. A choice of properties is given in IEC 60216-2.
To provide uniform conditions, the conditioning of specimens after removal from the oven and
before measurement may need to be specified.
5.1.2 Specific instructions for determination of TI
If IEC material specifications are available, property requirements in terms of acceptable
lower limits of TI values are usually given. If such material specifications are not available, a
selection of properties and methods for the evaluation of thermal endurance is given in
IEC 60216-2. (If such a method cannot be found, an international, national or institution
standard or a specially devised method should be used, and in that order of preference.)
5.1.3 Determination of TI for times other than 20 000 h.
In the majority of cases, the required thermal endurance characteristics are for a projected
duration of 20 000 h. However, there is often a need for such information related to other
longer or shorter times. In cases of longer times, the times given as requirements or
recommendations in the text of this standard (for example, 5 000 h for the minimum value
of the longest time to end-point) shall be increased in the ratio of the actual specification time
to 20 000 h. In the same way, the ageing cycle durations should be changed in approximately
the same ratio. The temperature extrapolation again shall not exceed 25 K. In cases of
shorter specification times, the related times may be decreased in the same ratio if
necessary.
Particular care will be needed for very short specification times, since the higher ageing
temperatures may lead into temperature regions which include transition points, for example,
glass transition temperature or partial melting, with consequent non-linearity. Very long
specification times may also lead to non-linearity (see also annex A).
5.2 Selection of end-points
The thermal endurance of materials may need to be characterized by different endurance data
(derived using different properties and/or end-points), in order to facilitate the adequate
selection of the material in respect of its particular application in an insulation system. See
IEC 60216-2.
There are two alternative ways in which the end-point may be defined.
a) As a percentage increase or decrease in the measured value of the property from the
original level. This approach will provide comparisons among materials but bears a poorer
relationship than item b) to the property values required in normal service. For the
determination of the initial value, see 5.4.

60216-1 © IEC:2001 – 27 –
b) As a fixed value of the property. This value might be selected with respect to usual service
requirements. End-points of proof tests are predominantly given in the form of fixed values
of the property.
The end-point should be selected to indicate a degree of deterioration of the insulating
material which has reduced its ability to withstand a stress encountered in actual service in an
insulation system. The degree of degradation indicated as the end-point of the test should be
related to the allowable safe value for the material property which is desired in practice.
5.3 Preparation and number of test specimens
5.3.1 Preparation
The specimens used for the ageing test should constitute a random sample from the
population investigated and are to be treated uniformly.
The material specifications or the test standards will contain all necessary instructions for the
preparation of specimens.
The thickness of specimens is in some cases specified in the list of property measurements
for the determination of thermal endurance. See IEC 60216-2. If not, the thickness shall be
reported. Some physical properties are sensitive even to minor variations of specimen
thickness. In such cases, the thickness after each ageing period may need to be determined
and reported if required in the relevant specification.
The thickness is also important because the rate of ageing may vary with thickness. Ageing
data of materials with different thicknesses are not always comparable. Consequently, a
material may be assigned more than one thermal endurance characteristic derived from the
measurement of properties at different thicknesses.
The tolerances of specimen dimensions should be the same as those normally used for
general testing; where specimen dimensions need smaller tolerances than those normally
used, these special tolerances should be given. Screening measurements ensure that
specimens are of uniform quality and typical of the material to be tested.
Since processing conditions may significantly affect the ageing characteristics of some
materials, it shall be ensured that, for example, sampling, cutting sheet from the supply roll,
cutting of anisotropic material in a given direction, moulding, curing, pre-conditioning, are
performed in the same manner for all specimens.
5.3.2 Number of specimens
The accuracy of endurance test results depends largely on the number of specimens aged
at each temperature. Instructions for an adequate number of specimens are given in
IEC 60216-3. Generally, the following instructions (5.3.2.1 to 5.3.2.3), which influence the
testing procedure given in 5.8, apply.
It is good practice to prepare additional specimens, or at least to provide a reserve of the
original material batch from which such specimens may subsequently be prepared. In this
way, any required ageing of additional specimens in case of unforeseen complications will
introduce a minimum risk of producing systematic differences between groups of specimens.
Such complications may arise, for example, if the thermal endurance relationship turns out to
be non-linear, or if specimens are lost due to thermal runaway of an oven.

60216-1 © IEC:2001 – 29 –
Where the test criterion for non-destructive or proof tests is based upon the initial value of the
property, this should be determined from a group of specimens of at least twice the number of
specimens in each temperature group. For destructive tests, see 5.3.2.3.
5.3.2.1 Number of specimens for non-destructive tests
For each exposure temperature, in most cases a group of five specimens will be adequate.
However, further guidance will be found in IEC 60216-3.
5.3.2.2 Number of specimens for proof tests
In most cases a group of at least 11 specimens for each exposure temperature will be
required. For graphical derivation and in some other cases the treatment of data may be
simpler if the number of specimens in each group is odd. Further guidance will be found in
IEC 60216-3.
5.3.2.3 Number of specimens for destructive tests
This number (N) is derived as follows: N = a × b × c + d
where
a is the number of specimens in a test group undergoing identical treatment at one
temperature and discarded after determination of the property (usually five);
b is the number of treatments, i.e. total number of exposure times, at one temperature;
c is the number of ageing temperature levels;
d is the number of specimens in the group used to establish the initial value of the property.
Normal practice is to select d = 2a when the diagnostic criterion is a percentage change of
the p
...