SIST EN 60216-5:2008

Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of relative thermal endurance index (RTE) of an insulating material

This part of IEC 60216 specifies the experimental and calculation procedures to be used for deriving the relative thermal endurance index of a material from experimental data obtained in accordance with the instructions of IEC 60216-1 and IEC 60216-2. The calculation procedures are supplementary to those of IEC 60216-3. Guidance is also given for assessment of thermal ageing after a single fixed time and temperature, without extrapolation. The experimental data may in principle be obtained using destructive, non-destructive or proof tests, although destructive tests have been much more extensively employed. Data obtained from non-destructive or proof tests may be "censored", in that measurement of times taken to reach the endpoint may have been terminated at some point after the median time but before all specimens have reached end-point (see IEC 60216-1). Guidance is given for preliminary assignment of a thermal class for an insulating material, based upon the thermal ageing performance. The calculation procedures of this standard also apply to the determination of the thermal class of an electrical insulation system when the thermal stress is the prevailing ageing factor.

Elektroisolierstoffe - Eigenschaften hinsichtlich des thermischen Langzeitverhaltens - Teil 5: Bestimmung des relativen thermischen Lebensdauer-Indexes (RTE) von Elektroisolierstoffen

Matériaux isolants électriques - Propriétés d'endurance thermique -- Partie 5: Détermination de l’indice d’endurance thermique relatif (RTE) d’un matériau isolant

La CEI 60216-5 spécifie les procédures expérimentales et de calcul à utiliser pour déduire l'indice d'endurance thermique relatif d'un matériau à partir des données expérimentales obtenues conformément aux instructions de la CEI 60216-1 et de la CEI 60216-2. Les procédures de calcul s'ajoutent à celles indiquées dans la CEI 60216-3. Des orientations sont également données pour évaluer le vieillissement thermique après une seule durée déterminée et une seule température, sans extrapolation. Les données expérimentales peuvent en principe être obtenues en utilisant des essais destructifs, non destructifs ou d'épreuve, même si les essais destructifs ont été utilisés de manière beaucoup plus étendue. Les données obtenues à partir des essais non destructifs et d'épreuve peuvent être 'censurées', dans le cas où la mesure du temps effectuée pour atteindre la fin de vie peut avoir été déterminée à un certain point après la durée moyenne, mais avant que toutes les éprouvettes n'aient atteint leur fin de vie (voir la CEI 60216-1). Des orientations sont données pour l'attribution préliminaire d'une classe thermique pour un matériau isolant, fondée sur les performances de vieillissement thermique. Les procédures de calcul de la présente norme sont également applicables à la détermination de la classe thermique d'un système d'isolation électrique lorsque la contrainte thermique est le facteur de vieillissement prédominant. Cette troisième édition clarifie et corrige quelques points et ajoute une Annexe (D) qui fournit des critères pour la sélection de référence ou de la référence MIE. Cette troisième édition fournit des instructions permettant de déduire une estimation temporaire de la température jusqu'à laquelle un matériau peut fournir une performance satisfaisante dans une application (par un essai de vieillissement thermique comparatif par rapport à un matériau de performance connue).

Električni izolacijski materiali - Lastnosti toplotne vzdržljivosti - 5. del: Ugotavljanje indeksa relativne toplotne vzdržljivosti (RTE) izolacijskega materiala (IEC 60216-5:2008)

General Information

• Status: Published
• Publication Date: 20-Jul-2008
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: IIZS - Insulating materials and systems
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 02-Jul-2008
• Due Date: 06-Sep-2008
• Completion Date: 21-Jul-2008
• Ref Project: EN 60216-5:2008 - Electrical insulating materials - Thermal endurance properties - Part 5: Determination of relative thermal endurance index (RTE) of an insulating material

Relations

• Replaces: SIST EN 60216-5:2004 - Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of relative thermal endurance index (RTE) of an insulating material
• Effective Date: 01-Sep-2008
• Replaced By: SIST EN IEC 60216-5:2023 - Electrical insulating materials - Thermal endurance properties - Part 5: Determination of relative temperature index (RTI) of an insulating material (IEC 60216-5:2022)
• Effective Date: 27-Dec-2022
• Replaces: SIST EN 60216-5:2004 - Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of relative thermal endurance index (RTE) of an insulating material
• Effective Date: 28-Jan-2023
• Revised: SIST EN IEC 60216-5:2023 - Electrical insulating materials - Thermal endurance properties - Part 5: Determination of relative temperature index (RTI) of an insulating material (IEC 60216-5:2022)
• Effective Date: 29-Oct-2019
• Replaces: SIST EN 60216-5:2004 - Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of relative thermal endurance index (RTE) of an insulating material
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60216-5:2008
01-september-2008
1DGRPHãþD
SIST EN 60216-5:2004
(OHNWULþQLL]RODFLMVNLPDWHULDOL/DVWQRVWLWRSORWQHY]GUåOMLYRVWLGHO
8JRWDYOMDQMHLQGHNVDUHODWLYQHWRSORWQHY]GUåOMLYRVWL57(L]RODFLMVNHJDPDWHULDOD
,(&
Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of
relative thermal endurance index (RTE) of an insulating material
Elektroisolierstoffe - Eigenschaften hinsichtlich des thermischen Langzeitverhaltens - Teil
5: Bestimmung des relativen thermischen Lebensdauer-Indexes (RTE) von
Elektroisolierstoffen
Matériaux isolants électriques - Propriétés d'endurance thermique -- Partie 5:
Détermination de l’indice d’endurance thermique relatif (RTE) d’un matériau isolant
Ta slovenski standard je istoveten z: EN 60216-5:2008
ICS:
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
SIST EN 60216-5:2008 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60216-5:2008

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SIST EN 60216-5:2008

EUROPEAN STANDARD
EN 60216-5

NORME EUROPÉENNE
May 2008
EUROPÄISCHE NORM

ICS 19.020; 29.020; 29.035.01 Supersedes EN 60216-5:2003


English version


Electrical insulating materials -
Thermal endurance properties -
Part 5: Determination of relative thermal endurance index (RTE)
of an insulating material
(IEC 60216-5:2008)


Matériaux isolants électriques -  Elektroisolierstoffe -
Propriétés d'endurance thermique - Eigenschaften hinsichtlich des
Partie 5: Détermination de l’indice thermischen Langzeitverhaltens -
d’endurance thermique relatif (RTE) Teil 5: Bestimmung des relativen
d’un matériau isolant thermischen Lebensdauer-Indexes (RTE)
(CEI 60216-5:2008) von Elektroisolierstoffen
(IEC 60216-5:2008)




This European Standard was approved by CENELEC on 2008-05-01. 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, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the 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


© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60216-5:2008 E

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SIST EN 60216-5:2008
EN 60216-5:2008 - 2 -
Foreword
The text of document 112/89/FDIS, future edition 3 of IEC 60216-5, prepared by IEC TC 112, Evaluation
and qualification of electrical insulating materials and systems, was submitted to the IEC-CENELEC
parallel vote and was approved by CENELEC as EN 60216-5 on 2008-05-01.
This European Standard supersedes EN 60216-5:2003.
EN 60216-5:2008 clarifies and corrects a few items and adds an Annex D which provides criteria for the
selection of the reference (or reference EIM). EN 60216-5:2008 provides instructions for deriving a
provisional estimate of the temperature up to which a material may give satisfactory performance in an
application (by comparative thermal ageing with a material of known performance).
This standard is to be used in conjunction with EN 60216-1, EN 60216-2 and EN 60216-3.
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) 2009-02-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2011-05-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60216-5:2008 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60085 NOTE  Harmonized as EN 60085:2008 (not modified).
__________

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SIST EN 60216-5:2008
- 3 - EN 60216-5:2008
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

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 60216-1 2001 Electrical insulating materials - Properties of EN 60216-1 2001
thermal endurance -
Part 1: Ageing procedures and evaluation of
test results


1) 2)
IEC 60216-2 - Electrical insulating materials - Thermal EN 60216-2 2005
endurance properties -
Part 2: Determination of thermal endurance
properties of electrical insulating materials -
Choice of test criteria


IEC 60216-3 2006 Electrical insulating materials - Thermal EN 60216-3 2006
endurance properties -
Part 3: Instructions for calculating thermal
endurance characteristics




1)
Undated reference.
2)
Valid edition at date of issue.

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SIST EN 60216-5:2008

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SIST EN 60216-5:2008
IEC 60216-5
Edition 3.0 2008-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Electrical insulating materials – Thermal endurance properties –
Part 5: Determination of relative thermal endurance index (RTE) of an insulating
material

Matériaux isolants électriques – Propriétés d'endurance thermique –
Partie 5: Détermination de l’indice d’endurance thermique relatif (RTE) d’un
matériau isolant

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
T
CODE PRIX
ICS 19.020; 29.020; 29.035.01 ISBN 2-8318-9655-X

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SIST EN 60216-5:2008
– 2 – 60216-5 © IEC:2008
CONTENTS
FOREWORD.03
1 Scope.1H1H5
2 Normative references .2H2H5
3 Terms, definitions, symbols, units and abbreviations .3H3H5
3.1 Terms, abbreviations, and definitions .4H4H6
3.2 Symbols and units .5H5H7
3.3 Objectives of RTE determination .6H6H8
4 Experimental procedures .7H7H8
4.1 Selection of reference EIM .8H8H8
4.2 Selection of diagnostic test for extent of ageing.9H9H9
4.3 Ageing procedures .10H10H9
5 Calculation procedures.11H11H10
5.1 Thermal endurance data – Calculation of intermediate parameters.12H12H10
5.2 Calculation of RTE .13H13H11
5.3 Statistical and numerical tests .14H14H11
5.3.1 Tests of IEC 60216-3.15H15H11
5.3.2 Precision of correlation time .16H16H12
5.3.3 Lower confidence interval of RTE .17H17H12
5.3.4 Extrapolation .18H18H13
6 Report .19H19H13
6.1 Results of statistical and numerical tests .20H20H13
6.2 Results.21H21H13
6.3 Report .22H22H13
7 Material testing by short-term thermal ageing .23H23H13
8 Insulation classification .24H24H14
Annex A (informative) Repeatability of correlation time .25H25H15
Annex B (informative) Thermal class assignment .26H26H18
Annex C (informative) Computer program .27H27H20
Annex D (informative) Selection of the reference EIM .28H28H21
Bibliography.29H29H23

Figure 1 – Thermal endurance graphs.30H30H9
Figure 2 – Unacceptable thermal endurance graphs .31H31H10

Table 1 – Input parameters for the calculations concerning RTE.32H32H11
Table B.1 – Thermal class equivalents for insulating material .33H33H18
Table B.2 – F– function; p = 0,05 .34H34H19
Table B.3 – t–function.35H35H19

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SIST EN 60216-5:2008
60216-5 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ELECTRICAL INSULATING MATERIALS –
THERMAL ENDURANCE PROPERTIES –

Part 5: Determination of relative thermal endurance
index (RTE) of an insulating material


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. 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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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 some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60216-5 has been prepared by IEC technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This third edition cancels and replaces the second edition, published in 2003, and constitutes
a technical revision.
This third edition clarifies and corrects a few items and adds an Annex D which provides
criteria for the selection of the reference (or reference EIM). The third edition provides
instructions for deriving a provisional estimate of the temperature up to which a material may
give satisfactory performance in an application (by comparative thermal ageing with a material
of known performance).
This standard is to be read in conjunction with IEC 60216-1, IEC 60216-2 and IEC 60216-3.

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SIST EN 60216-5:2008
– 4 – 60216-5 © IEC:2008
The text of this standard is based on the following documents:
FDIS Report on voting
112/89/FDIS 112/94/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The list of all the parts of the IEC 60216 series, under the general title Electrical insulating
materials – Thermal endurance properties, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date0 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.

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SIST EN 60216-5:2008
60216-5 © IEC:2008 – 5 –
ELECTRICAL INSULATING MATERIALS –
THERMAL ENDURANCE PROPERTIES –

Part 5: Determination of relative thermal endurance
index (RTE) of an insulating material



1 Scope
This part of IEC 60216 specifies the experimental and calculation procedures to be used for
deriving the relative thermal endurance index of a material from experimental data obtained in
accordance with the instructions of IEC 60216-1 and IEC 60216-2. The calculation procedures
are supplementary to those of IEC 60216-3.
Guidance is also given for assessment of thermal ageing after a single fixed time and
temperature, without extrapolation.
The experimental data may in principle be obtained using destructive, non-destructive or proof
tests, although destructive tests have been much more extensively employed. Data obtained
from non-destructive or proof tests may be “censored”, in that measurement of times taken to
reach the endpoint may have been terminated at some point after the median time but before
all specimens have reached end-point (see IEC 60216-1).
Guidance is given for preliminary assignment of a thermal class for an insulating material,
based upon the thermal ageing performance.
The calculation procedures of this standard also apply to the determination of the thermal
class of an electrical insulation system when the thermal stress is the prevailing ageing factor.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60216-1:2001, Electrical insulating materials – Properties of thermal endurance – Part 1:
Ageing procedures and evaluation of test results
IEC 60216-2, Electrical insulating materials – Thermal endurance properties – Part 2:
Determination of thermal endurance properties of electrical insulating materials – Choice of
test criteria
IEC 60216-3:2006, Electrical insulating materials – Thermal endurance properties – Part 3:
Instructions for calculating thermal endurance characteristics
3 Terms, definitions, symbols, units and abbreviations
For the purposes of this document, the following terms, definitions, symbols, units and
abbreviated terms apply.

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SIST EN 60216-5:2008
– 6 – 60216-5 © IEC:2008
3.1 Terms, abbreviations, and definitions
3.1.1
electrical insulating material
EIM
solid or fluid with negligibly low electric conductivity, or a simple combination of such
materials, used to separate conducting parts at different electrical potential in electrotechnical
devices
3.1.2
assessed thermal endurance index
ATE
numerical value of the temperature in degrees Celsius, up to which the reference EIM
possesses known, satisfactory service performance in the specified application
NOTE 1 The value of the ATE may vary between applications for the same material.
NOTE 2 Sometimes referred to as “absolute” thermal endurance index.
3.1.3
candidate EIM
material for which an estimate of the thermal endurance is required to be determined
NOTE The determination is made by simultaneous thermal ageing of the material and a reference EIM.
3.1.4
reference EIM
material with known thermal endurance, preferably derived from service experience, used as
a reference for comparative tests with the candidate EIM
3.1.5
central second moment of a data group
sum of the squares of the differences between the data values and the value of the group
mean divided by the number of data in the group
3.1.6
correlation time
estimated time to endpoint of the reference EIM at a temperature equal to its assessed
thermal endurance (ATE) in degrees Celsius
3.1.7
degrees of freedom
number of data values minus the number of parameter values
3.1.8
standard error
standard error of an estimate of the true value of a data group property is the value of the
standard deviation of the hypothetical sampling population of which the group property may
be considered to be a member
NOTE 1 For the group mean it is equal to the group standard deviation divided by the square root of the number
of data in the group, and indicates the uncertainty in the true value of the mean.
NOTE 2 This standard is concerned only with means and the difference between two means (see Clause 36H36HA.2).
3.1.9
standard deviation
square root of the variance of a data group or sub-group

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SIST EN 60216-5:2008
60216-5 © IEC:2008 – 7 –
3.1.10
relative thermal endurance index
RTE
numerical value of the temperature in degrees Celsius at which the estimated time to endpoint
of the candidate EIM is the same as the estimated time to endpoint of the reference EIM at a
temperature equal to its assessed thermal endurance (ATE)
3.1.11
variance of a data group
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 (1 parameter) or a line (2 parameters, in this
standard, the slope and the intercept with the y axis).
3.2 Symbols and units
Regression coefficient (y-intercept) of thermal endurance equation for reference
a
A
EIM
Regression coefficient (y-intercept) of thermal endurance equation for candidate
a
B
EIM
b Regression coefficient (slope) of thermal endurance equation for reference EIM
A
b Regression coefficient (slope) of thermal endurance equation for candidate EIM
B
X
Variable for statistical analysis equal to 1/(ϑ +Θ )
0
Y
Variable for statistical analysis equal to ln (τ )
ϑ Ageing temperature in determination of RTE
Θ
Temperature on Kelvin scale equal to 0 °C
0
τ
Time to endpoint
τ Estimated time to endpoint of reference EIM at a temperature equal to ATE
c
(“correlation time”)
μ
2(A) Central second moment of x values for reference EIM
μ
Central second moment of x values for candidate EIM
2(B)
n Number of y values for reference EIM data
A
n Number of y values for candidate EIM data
B
T Student’s t distributed stochastic variable
S
Standard error of the difference of two means
2
s Variance of y values for reference EIM data
A
2
s Variance of y values for candidate EIM data
B
x
General mean of x-values for reference EIM data
A
x
General mean of x-values for candidate EIM data
B
y General mean of y-values for reference EIM data
A
y General mean of y-values for candidate EIM data
B
θ Temperature in degrees Celsius equal to ATE
A
θ
Temperature in degrees Celsius equal to RTE
B

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SIST EN 60216-5:2008
– 8 – 60216-5 © IEC:2008
ˆ
x value corresponding to θ
X B
B
ˆ x value corresponding to θ
X
A
A
θ
Lower confidence limit of θ
c(B)
B
θ Lower confidence limit of θ
c(A)
A
X x value corresponding to lower confidence limit of θ
B
L(B)
X x value corresponding to lower confidence limit of θ
L(A) A
Δ
B Lower confidence interval of θ
B
Δ
A θ
Lower confidence interval of
A

HIC
Halving interval of candidate EIM at a time equal to τ
B(c) c
2
Variance associated with the difference between the mean y-values for the two
s
D
materials
2
n Degrees of freedom of s
D D
υ , υ
Logarithms of the longest mean times to endpoint for materials A and B
A B
b Intermediate variable: adjusted value of b for calculation of temperature confidence
r
interval
s Intermediate variable: adjusted value of s for calculation of temperature confidence
r
interval
3.3 Objectives of RTE determination
The objectives of the determination are as follows.
a) To exploit an assumed relationship between thermal endurance (with an appropriate test
criterion for ageing) and service performance, and to use this to predict a value for a
preliminary assessment of service temperature of a material for which there is relatively
little service experience (by comparison with a known reference EIM, see Clauses 37H37H4
and 5).
NOTE In the majority of cases, this will involve extrapolation to a longer time and/or lower temperature than
in the experimental data. This extrapolation should be kept to a minimum by appropriate choice of ageing
temperatures and times, since the uncertainty in the result increases rapidly as the extrapolation is increased.
However, even when there is no extrapolation, the uncertainty is still finite, on account of the variances of the
experimental data and experimental errors.
b) To improve the precision of a thermal endurance determination by reduction of systematic
errors in the ageing process. If, after ageing, the results for the reference EIM are found
to be significantly different from earlier experience, this may indicate changes in material
or equipment. This may be investigated and possibly corrected. In any case, the
simultaneous ageing of reference and candidate will at least partially compensate for
systematic changes. Statistical procedures for use in assessing the significance of
changes are given in 38H38HAnnex A.
c) To provide instructions for assigning a thermal class to an EIM.
4 Experimental procedures
4.1 Selection of reference EIM
The primary requirement for the reference EIM is that it has a known thermal endurance index
(ATE) for the application under consideration. The thermal endurance index, if determined by
an RTE procedure, is preferably supported by actual service experience (see Annex D).

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SIST EN 60216-5:2008
60216-5 © IEC:2008 – 9 –
The expected ageing mechanisms and rates of both materials shall be similar, and relevant to
the application.
4.2 Selection of diagnostic test for extent of ageing
The diagnostic test shall be one considered relevant to the application for which the RTE is
required. The same test shall be applied to both reference and candidate EIM.
4.3 Ageing procedures
The number and type of test specimens of each material and the ageing temperatures and
times shall be in accordance with the requirements of IEC 60216-1 (5.3.2, 5.4 and the first
paragraph of 5.5). At each ageing temperature, the oven load shall comprise appropriate
numbers of test specimens of both materials in the same oven. The specimens shall be
evenly distributed in the oven so that there is likely to be no systematic difference between
the ageing conditions applied to the specimens of the two materials. It is important that test
specimens of both materials are aged simultaneously at a minimum of three temperatures to
be included in the calculations.
NOTE As an example, while the data represented in Figure 1 would be acceptable for analysis, of the data
represented by Figure 2, the lowest temperature group of the candidate EIM and the highest temperature group of
the reference cannot be included, since in each case, the specimen group is made up of only one material or one
of the two materials did not reach the chosen end point within the test time.
If, when ageing at the selected temperatures is completed, the results from either material do
not satisfy the requirements of 39H39H6.1 b) of this standard, a further specimen group shall be
aged, within the same oven, at an appropriate temperature. This group shall again be
composed of the required number and type of specimens of each material.

θ θ
B A
τ
C
B
A
RTE ATE
Temperature
IEC  353/08

Key
A = reference EIM
B = candidate EIM
Figure 1 – Thermal endurance graphs
Log time

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SIST EN 60216-5:2008
– 10 – 60216-5 © IEC:2008
θ
B θ
A
τ
C
B
A
RTE ATE
Temperature
IEC  354/08

Key
A = reference EIM
B = candidate EIM
NOTE The test specimens of both materials are not aged simultaneously at a minimum of three temperatures.
Figure 2 – Unacceptable thermal endurance graphs

5 Calculation procedures
5.1 Thermal endurance data – Calculation of intermediate parameters
Calculation of the thermal endurance equations shall be made in accordance with the
instructions of IEC 60216-3.
The following input parameters as set out in Table 1 are needed for the calculations relevant
to RTE, and should be recorded (each of the symbols may have either subscript A for
reference EIM or B for candidate EIM).
Log time

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SIST EN 60216-5:2008
60216-5 © IEC:2008 – 11 –
Table 1 – Input parameters for the calculations concerning RTE
Symbol in Equation in Symbol in
Parameter
IEC 60216-3 IEC 60216-3 IEC 60216-5
b b
Slope of regression line b (33)
A B
a a
Intercept of regression line a (34)
A B
Weighted mean of x values (26) x x
x
A B
nd
μ μ
Central 2 moment of x values μ (x) (31)
2(A)
...