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)

This part of IEC 60216 specifies the experimental and calculation procedures to be used for
deriving the relative temperature 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 can 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 can be “censored”, in that measurement of times taken to
reach the endpoint 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 electrical insulating
material (EIM), based upon the thermal ageing performance.
While the thermal classification of an EIM is not directly related to the thermal classification of
an electrical insulation system (EIS), the thermal classification of an EIS follows the same
concepts as presented in this part of the 60216 series. The calculation procedures of this
standard apply to the determination of the thermal class of an EIS when the thermal stress is
the prevailing ageing factor.

Elektroisolierstoffe - Eigenschaften hinsichtlich des thermischen Langzeitverhaltens - Teil 5: Bestimmung des relativen Temperaturindexes (RTI) von Elektroisolierstoffen (IEC 60216-5:2022)

Matériaux isolants électriques - Propriétés d'endurance thermique - Partie 5: Détermination de l’indice de température relatif (ITR) d’un matériau isolant (IEC 60216-5:2022)

L’IEC 60216-5:2022 spécifie les procédures expérimentales et de calcul à utiliser pour déduire l’indice de température relatif d’un matériau à partir des données expérimentales obtenues conformément aux instructions de l’IEC 60216-1 et de l’IEC 60216-2. Les procédures de calcul s’ajoutent à celles indiquées dans l’IEC 60216-3. Des recommandations sont également données pour évaluer le vieillissement thermique après une seule durée déterminée et une seule température, sans extrapolation. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:

   
1. l’Annexe C "Programme informatique" a été complètement remaniée;

   
2. en 3.1, les termes "ATE" et "RTE" ont été remplacés par "ATI" et "ITR" pour souligner leur référence à un matériau isolant électrique (MIE).

Cette norme doit être lue conjointement avec l’IEC 60216-1:2013, l’IEC 60216-2:2005 et l’IEC 60216-3:2021.

Električni izolacijski materiali - Lastnosti toplotne vzdržljivosti - 5. del: Ugotavljanje indeksa relativne toplotne vzdržljivosti (RTI) izolacijskega materiala (IEC 60216-5:2022)

Ta del standarda IEC 60216 določa eksperimentalne in računske postopke, ki naj se uporabijo za izpeljavo relativnega temperaturnega indeksa materiala iz eksperimentalnih podatkov, pridobljenih v skladu z navodili iz standardov IEC 60216-1 in IEC 60216-2. Računski postopki dopolnjujejo postopke iz standarda IEC 60216-3. Podane so tudi smernice za oceno toplotnega staranja po enkratnem določenem času in temperaturi, brez ekstrapolacije. Eksperimentalne podatke je načeloma mogoče pridobiti z uporabo porušitvenih, neporušitvenih ali dokaznih preskusov, čeprav so porušitveni preskusi najbolj razširjeni. Podatke, pridobljene z neporušitvenimi ali dokaznimi preskusi, je mogoče »cenzurirati«, tako da se meritve časov, potrebnih za dosego končne točke, končajo na neki točki po mediani časa, vendar preden vsi vzorci dosežejo končno točko (glej standard IEC 60216-1). Podane so smernice za predhodno dodelitev električnega izolacijskega materiala (EIM) v toplotni razred, ki temelji na zmogljivosti toplotnega staranja. Medtem ko toplotna klasifikacija električnega izolacijskega materiala ni neposredno povezana s toplotno klasifikacijo električnega izolacijskega sistema (EIS), toplotna klasifikacija EIS sledi istim konceptom, kot so predstavljeni v tem delu skupine standardov 60216. Računski postopki tega standarda se uporabljajo za določanje toplotnega razreda električnega izolacijskega sistema, kadar je toplotna obremenitev prevladujoči dejavnik staranja.

General Information

• Status: Published
• Publication Date: 09-Jan-2023
• ICS: 19.020 - Test conditions and procedures in general
• ICS: 29.020 - Electrical engineering in general
• 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: 04-Jan-2023
• Due Date: 11-Mar-2023
• Completion Date: 10-Jan-2023
• Ref Project: EN IEC 60216-5:2022 - Electrical insulating materials - Thermal endurance properties - Part 5: Determination of relative temperature index (RTI) of an insulating material

Relations

• Revised: SIST EN 60216-5:2008 - Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of relative thermal endurance index (RTE) of an insulating material
• Effective Date: 29-Oct-2019
• Replaces: SIST EN 60216-5:2008 - Electrical insulating materials - Thermal endurance properties -- Part 5: Determination of relative thermal endurance index (RTE) of an insulating material
• Effective Date: 27-Dec-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN IEC 60216-5:2023
01-februar-2023
Nadomešča:
SIST EN 60216-5:2008
Električni izolacijski materiali - Lastnosti toplotne vzdržljivosti - 5. del:
Ugotavljanje indeksa relativne toplotne vzdržljivosti (RTI) izolacijskega materiala
(IEC 60216-5:2022)
Electrical insulating materials - Thermal endurance properties - Part 5: Determination of
relative temperature index (RTI) of an insulating material (IEC 60216-5:2022)
Elektroisolierstoffe - Eigenschaften hinsichtlich des thermischen Langzeitverhaltens - Teil
5: Bestimmung des relativen Temperaturindexes (RTI) von Elektroisolierstoffen (IEC
60216-5:2022)
Matériaux isolants électriques - Propriétés d'endurance thermique - Partie 5:
Détermination de l’indice de température relatif (ITR) d’un matériau isolant (IEC 60216-
5:2022)
Ta slovenski standard je istoveten z: EN IEC 60216-5:2022
ICS:
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
SIST EN IEC 60216-5:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 60216-5:2023

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SIST EN IEC 60216-5:2023


EUROPEAN STANDARD EN IEC 60216-5

NORME EUROPÉENNE

EUROPÄISCHE NORM December 2022
ICS 19.020; 29.020; 29.035.01 Supersedes EN 60216-5:2008
English Version
Electrical insulating materials - Thermal endurance properties -
Part 5: Determination of relative temperature index (RTI) of an
insulating material
(IEC 60216-5:2022)
Matériaux isolants électriques - Propriétés d'endurance Elektroisolierstoffe - Eigenschaften hinsichtlich des
thermique - Partie 5: Détermination de l'indice de thermischen Langzeitverhaltens - Teil 5: Bestimmung des
température relatif (ITR) d'un matériau isolant relativen Temperaturindexes (RTI) von Elektroisolierstoffen
(IEC 60216-5:2022) (IEC 60216-5:2022)
This European Standard was approved by CENELEC on 2022-12-22. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.


European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN IEC 60216-5:2022 E

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SIST EN IEC 60216-5:2023
EN IEC 60216-5:2022 (E)
European foreword
The text of document 112/582/FDIS, future edition 4 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 approved by CENELEC as EN IEC 60216-5:2022.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2023-09-22
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2025-12-22
document have to be withdrawn
This document supersedes EN 60216-5:2008 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document is read in conjunction with EN 60216-1:2013, EN 60216-2:2005 and
EN IEC 60216-3:2021.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60216-5:2022 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
2

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SIST EN IEC 60216-5:2023
EN IEC 60216-5:2022 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60216-1 2013 Electrical insulating materials - Thermal EN 60216-1 2013
endurance properties - Part 1: Ageing
procedures and evaluation of test results
IEC 60216-2 2005 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 2021 Electrical insulating materials - Thermal EN IEC 60216-3 2021
endurance properties - Part 3: Instructions for
calculating thermal endurance characteristics
3

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SIST EN IEC 60216-5:2023

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SIST EN IEC 60216-5:2023




IEC 60216-5

®


Edition 4.0 2022-11




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Electrical insulating materials – Thermal endurance properties –

Part 5: Determination of relative temperature index (RTI) of an insulating material



Matériaux isolants électriques – Propriétés d'endurance thermique –

Partie 5: Détermination de l’indice de température relatif (ITR) d’un matériau

isolant















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 19.020; 29.020; 29.035.01 ISBN 978-2-8322-6014-2




Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN IEC 60216-5:2023
– 2 – IEC 60216-5:2022 © IEC 2022
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, symbols and units . 7
3.1 Terms and definitions. 7
3.2 Symbols and units . 8
4 Objectives of RTI determination . 10
5 Experimental procedures . 10
5.1 Selection of reference EIM . 10
5.2 Selection of diagnostic test for extent of ageing . 10
5.3 Ageing procedures . 10
6 Calculation procedures . 11
6.1 Thermal endurance data – Calculation of intermediate parameters . 11
6.2 Calculation of RTI . 12
6.3 Statistical and numerical tests . 13
6.3.1 Tests of IEC 60216-3 . 13
6.3.2 Precision of correlation time . 13
6.3.3 Lower confidence interval of RTI. 13
6.3.4 Extrapolation . 14
7 Results and report . 14
7.1 Results of statistical and numerical tests . 14
7.2 Results . 14
7.3 Report . 15
8 Material testing by short-term thermal ageing . 15
9 Insulation classification. 16
Annex A (informative) Repeatability of correlation time . 17
A.1 Overview . 17
A.2 F-test for linearity . 17
A.3 Standard error of the difference of two means . 17
A.4 Student’s t-test for difference of two means . 18
A.5 Combination of data . 19
Annex B (informative) Thermal class assignment . 20
Annex C (informative) Computer program . 23
C.1 General . 23
C.1.1 Overview . 23
C.1.2 Convenience program execution . 24
C.2 Structure of data files used by the program . 25
C.3 Executing the calculation of RTI . 26
C.4 Output files and graph. 26
Annex D (informative) Selection of the reference EIM . 28
D.1 Overview . 28
D.2 Designation of reference EIM . 28
D.3 Reporting items for reference EIM. 28
Bibliography . 29

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SIST EN IEC 60216-5:2023
IEC 60216-5:2022 © IEC 2022 – 3 –
Figure 1 – Thermal endurance graphs. 11
Figure 2 – Unacceptable thermal endurance graphs . 11
Figure C.1 – Shortcut property dialog for program launch . 25
Figure C.2 – Thermal endurance graphs . 26
Figure C.3 – Example thermal endurance graphs . 27

Table 1 – Input parameters for the calculations concerning RTI . 12
Table B.1 – Thermal class equivalents for insulating material . 20
Table B.2 – F– function; p = 0,05 . 21
Table B.3 – t–function . 22

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SIST EN IEC 60216-5:2023
– 4 – IEC 60216-5:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ELECTRICAL INSULATING MATERIALS –
THERMAL ENDURANCE PROPERTIES –

Part 5: Determination of relative
temperature index (RTI) 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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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.
IEC 60216-5 has been prepared by IEC technical committee 112: Evaluation and qualification
of electrical insulating materials and systems. It is an International Standard.
This fourth edition cancels and replaces the third edition published in 2008. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Annex C “Computer program” has been completely reworked;
b) in 3.1, the terms “ATE” and “RTE” were replaced by “ATI” and “RTI” to emphasize their
reference to an electrical insulating material (EIM).
This standard is to be read in conjunction with IEC 60216-1:2013, IEC 60216-2:2005 and
IEC 60216-3:2021.

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SIST EN IEC 60216-5:2023
IEC 60216-5:2022 © IEC 2022 – 5 –
The text of this International Standard is based on the following documents:
Draft Report on voting
112/582/FDIS 112/588/RVD

Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 60216 series, published 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 document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

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SIST EN IEC 60216-5:2023
– 6 – IEC 60216-5:2022 © IEC 2022
ELECTRICAL INSULATING MATERIALS –
THERMAL ENDURANCE PROPERTIES –

Part 5: Determination of relative
temperature index (RTI) of an insulating material



1 Scope
This part of IEC 60216 specifies the experimental and calculation procedures to be used for
deriving the relative temperature 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 can 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 can be “censored”, in that measurement of times taken to
reach the endpoint 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 electrical insulating
material (EIM), based upon the thermal ageing performance.
While the thermal classification of an EIM is not directly related to the thermal classification of
an electrical insulation system (EIS), the thermal classification of an EIS follows the same
concepts as presented in this part of the 60216 series. The calculation procedures of this
standard apply to the determination of the thermal class of an EIS when the thermal stress is
the prevailing ageing factor.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60216-1:2013, Electrical insulating materials – Thermal endurance properties – Part 1:
Ageing procedures and evaluation of test results
IEC 60216-2:2005, Electrical insulating materials – Thermal endurance properties – Part 2:
Determination of thermal endurance properties of electrical insulating materials – Choice of test
criteria
IEC 60216-3:2021, Electrical insulating materials – Thermal endurance properties – Part 3:
Instructions for calculating thermal endurance characteristics

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SIST EN IEC 60216-5:2023
IEC 60216-5:2022 © IEC 2022 – 7 –
3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
electrical insulating material
EIM
material of low electric conductivity, used to separate conducting parts at different electric
potentials or to isolate such parts from the surroundings
3.1.2
assessed temperature index
ATI
numerical value of the temperature index in degrees Celsius of the reference EIM
Note 1 to entry: The value of the ATI can vary between applications for the same material.
3.1.3
candidate EIM
material for which an estimate of the thermal endurance is required to be determined
Note 1 to entry: 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 (derived from service experience or previous RTI or TI
evaluation), 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 for RTI
estimated time to endpoint of the reference EIM at a temperature equal to its ATI in degrees
Celsius
3.1.7
degrees of freedom
number of data values minus the number of parameter values

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SIST EN IEC 60216-5:2023
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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 can be
considered to be a member
Note 1 to entry: 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 to entry: This standard is concerned only with means and the difference between two means (see
Clause A.3).
3.1.9
standard deviation
square root of the variance of a data group or sub-group
3.1.10
relative temperature index
RTI
determined by test in relation to the thermal performance of a known reference EIM
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 1 to entry: The reference level can, for example, be a mean value (1 parameter) or a line (2 parameters, in
this document, 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
Regression coefficient (slope) of thermal endurance equation for reference EIM
b
A

Regression coefficient (slope) of thermal endurance equation for candidate EIM
b
B

X
1/(ϑ+Θ )
Variable for statistical analysis equal to
0
Y
Variable for statistical analysis equal to ln (τ )
ϑ
Ageing temperature in determination of RTI
Temperature on Kelvin scale equal to 0 °C
Θ
0

Time to endpoint
τ
Estimated time to endpoint of reference EIM at a temperature equal to ATI
τ
c

(“correlation time”)
Central second moment of x values for reference EIM
µ
2(A)
Central second moment of x values for candidate EIM
µ
2(B)
Number of y values for reference EIM data
n
A

Number of y values for candidate EIM data
n
B

T Student’s t distributed stochastic variable

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SIST EN IEC 60216-5:2023
IEC 60216-5:2022 © IEC 2022 – 9 –
S Standard error of the difference of two means
2
Variance of y values for reference EIM data
s
A

2
Variance of y values for candidate EIM data
s
B

General mean of x-values for reference EIM data
x
A

General mean of x-values for candidate EIM data
x
B

General mean of y-values for reference EIM data
y
A

General mean of y-values for candidate EIM data
y
B

Temperature in degrees Celsius equal to ATI
θ
A

Temperature in degrees Celsius equal to RTI
θ
B

ˆ
θ
x value corresponding to
X
B
B

ˆ
θ
x value corresponding to
X
A
A

θ
θ
c(B) Lower confidence limit of
B
θ
θ
c(A) Lower confidence limit of
A

X θ
x value corresponding to lower confidence limit of
L(B)
B

X θ
x value corresponding to lower confidence limit of
L(A)
A
∆
B Lower confidence interval of θ
B
∆
A Lower confidence interval of θ
A

HIC
B(c) τ
Halving interval of candidate EIM at a time equal to
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

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SIST EN IEC 60216-5:2023
– 10 – IEC 60216-5:2022 © IEC 2022
4 Objectives of RTI 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 5 and 6).
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 the systematic
changes. Statistical procedures for use in assessing the significance of changes are given
in Annex A.
c) To provide instructions for assigning a thermal class to an EIM.
5 Experimental procedures
5.1 Selection of reference EIM
The primary requirement for the reference EIM is that it has a
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