oSIST prEN IEC 61857-33:2023

Electrical insulation systems - Procedures for thermal evaluation - Part 33: Multifactor evaluation with increased ageing factors at elevated temperature

Elektrische Isoliersysteme - Verfahren zur thermischen Bewertung - Teil 33: Multifaktor-Bewertung mit erhöhten Alterungsfaktoren bei erhöhter Temperatur

Sistemi električne izolacije - Postopki za toplotno vrednotenje - 33. del: Ocenjevanje po več faktorjih s povečanimi dejavniki staranja pri povišani temperaturi

General Information

• Status: Not Published
• Public Enquiry End Date: 27-Jul-2023
• ICS: 29.080.30 - Insulation systems
• Technical Committee: IIZS - Insulating materials and systems
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 10-May-2023
• Due Date: 27-Sep-2023
• Completion Date: 19-Jul-2023
• Ref Project: prEN IEC 61857-33:2023 - Electrical insulation systems - Procedures for thermal evaluation - Part 33: Multifactor evaluation with increased ageing factors at elevated temperature

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN IEC 61857-33:2023
01-julij-2023
Sistemi električne izolacije - Postopki za toplotno vrednotenje - 33. del:
Ocenjevanje po več faktorjih s povečanimi dejavniki staranja pri povišani
temperaturi
Electrical insulation systems - Procedures for thermal evaluation - Part 33: Multifactor
evaluation with increased ageing factors at elevated temperature
Ta slovenski standard je istoveten z: prEN IEC 61857-33:2023
ICS:
29.080.30 Izolacijski sistemi Insulation systems
oSIST prEN IEC 61857-33:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN IEC 61857-33:2023

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oSIST prEN IEC 61857-33:2023
112/605/CDV

COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61857-33 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2023-05-05 2023-07-28
SUPERSEDES DOCUMENTS:
112/573/CD, 112/600/CC

IEC TC 112 : EVALUATION AND QUALIFICATION OF ELECTRICAL INSULATING MATERIALS AND SYSTEMS
SECRETARIAT: SECRETARY:
Germany Mr Bernd Komanschek
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:

TC 2,TC 14,TC 15,TC 23,TC 42,TC 55,TC 96
Other TC/SCs are requested to indicate their interest, if any,
in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.

This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of
• any relevant patent rights of which they are aware and to provide supporting documentation,
• any relevant “in some countries” clauses to be included should this proposal proceed. Recipients are reminded that
the enquiry stage is the final stage for submitting "in some countries" clauses. See AC/22/2007.

TITLE:
Electrical insulation systems - Procedures for thermal evaluation - Part 33: Multifactor evaluation with
increased ageing factors at elevated temperature

PROPOSED STABILITY DATE: 2027

NOTE FROM TC/SC OFFICERS:

Copyright © 2023 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

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oSIST prEN IEC 61857-33:2023
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1 CONTENTS
2
3 FOREWORD . 4
4 INTRODUCTION . 6
5 1 Scope . 7
6 2 Normative references . 7
7 3 Terms and definitions . 7
8 4 Procedure . 8
9 5 Test objects . 9
10 6 EIS evaluation . 9
11 6.1 Selection of the appropriate EIS test method . 9
12 6.2 Comparison of the reference and candidate EIS . 10
13 6.3 Evaluation of the additional stresses E, A and/or M in combination with T . 10
14 6.4 Variation . 10
15 7 Illustration of the structure – Thermal evaluation – Step 1 . 10
16 7.1 Establishing the baseline thermal classification. 10
17 7.2 Illustration of the thermal evaluation . 11
18 8 Evaluation of the influence of multifactor stresses – Step 2 . 12
19 8.1 General . 12
20 8.2 Selection of the ageing temperature for the one-temperature comparison . 12
21 8.3 Selection of the ageing temperatures for the two-temperature comparison . 13
22 8.4 Diagnostic tests and end-point criterion applied at elevated temperature . 13
23 8.5 Diagnostics . 13
24 8.6 Using ageing cycles . 13
25 8.7 Diagnostics applied at elevated temperature without ageing cycles. 14
26 8.8 Examples of different ambient/environmental stress during operation . 14
27 8.9 Examples of mechanical stress during operation . 14
28 9 Analysis of data . 15
29 9.1 General . 15
30 9.2 Evaluation of the other stresses of influence . 16
31 9.3 Use of the 5-degree uncertainty criterion . 16
32 The procedure for analysis of the comparison of results between the baseline EIS evaluated
33 with thermal stress as the only dominant stress is compared and the performance
34 when one or more of the other stress factors are simultaneously applied is; . 16
35 9.4 Comparison of the result between the baseline EIS and any of the sets of results for
T
36 other factors of influence . 16
37 10 Report. 16
38 Annex A (informative) Example of a test data sheet report . 18
39 Annex B (informative) Example of a thermal endurance graph – Reference EIS . 19
40 Annex C (informative) Example of a test data sheet for a baseline thermal classification when
41 the reference thermal index value is known . 20
42 Annex D (informative) Establishing the thermal endurance of the baseline using the reference
43 correlation time . 21
44 Annex E (informative) Analysis of data using the 5-degree uncertainty criterion . 23
45 Annex F (informative) . 27

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46 Annex G (informative) . 29
47 Annex H (informative) Calculations for the 5-degree uncertainty criterion . 36
48 Bibliography . 37
49
50 Figure 1 – Overview of the two-step evaluation procedure . 9
51 The thermal classification of the baseline is established when the thermal ageing of both the
52 reference EIS and the candidate EIS have completed as determined in clause 6.1. The
53 analysis of the candidate test results is compared to the reference EIS; refer to . 10
54 Figure 2 – Illustration of the establishment of the thermal classification of the baseline EIS . 11
55 Figure 3 – Comparison of the influence of any of the multifactor exposures with the baseline
56 performance . 12
57 Figure 4 – Comparison of the influence of a different electrical stress applied during thermal
58 exposure with the baseline thermal design . 14
59 Figure 5 – Comparison of the influence of a different ambient/environmental stress applied
60 during thermal exposure with the baseline thermal design . 14
61 Figure 6 – Comparison of the influence of a different mechanical stress applied during thermal
62 exposure with the baseline thermal design . 15
63 Figure B.1 – Time coordinate established at 48 400 h with a known temperature of 185 °C . 19
64 Figure D.1 – Temperature index at 160 °C with a correlation time of 48 400 h . 21
65 Figure E.1 – Plotting the data in Annex C showing confidence ranges . 25
66
67 Table 1 – Example of thermal test results for reference EIS based on data sheets given in
68 Annex A . 11
69 Table A.1 – Example of a test data sheet report . 18
70 Table C.1 – Example of a test data sheet for a baseline thermal classification when the
71 reference thermal index value is known . 20
72 Table E.1 – Example of test results . 24
73 Table E.2 – Limits of the range of ± 5-degrees . 24
74 Table E.3 – Examples of multifactor exposure . 25
75
76
77
78

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79 INTERNATIONAL ELECTROTECHNICAL COMMISSION
80 ____________
81
82 ELECTRICAL INSULATION SYSTEMS –
83 PROCEDURES FOR THERMAL EVALUATION –
84
85 Part 33: Multifactor evaluation with increased ageing factors
86 at elevated temperature
87
88 FOREWORD
89 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national
90 electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all
91 questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities,
92 IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS)
93 and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC
94 National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental
95 and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with
96 the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between
97 the two organizations.
98 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus
99 of opinion on the relevant subjects since each technical committee has representation from all interested IEC National
100 Committees.
101 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in
102 that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC
103 cannot be held responsible for the way in which they are used or for any misinterpretation by any end user.
104 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to
105 the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and
106 the corresponding national or regional publication shall be clearly indicated in the latter.
107 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment
108 services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by
109 independent certification bodies.
110 6) All users should ensure that they have the latest edition of this publication.
111 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of
112 its technical committees and IEC National Committees for any personal injury, property damage or other damage of any
113 nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication,
114 use of, or reliance upon, this IEC Publication or any other IEC Publications.
115 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable
116 for the correct application of this publication.
117 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights.
118 IEC shall not be held responsible for identifying any or all such patent rights.
119 International Standard IEC 61857-33 has been prepared by IEC technical committee 112: Evaluation
120 and qualification of electrical insulating materials and systems.
121 The text of this International Standard is based on the following documents:
FDIS Report on voting
112/XXX/FDIS 112/XXX/RVD
122
123 Full information on the voting for the approval of this International Standard can be found in the report
124 on voting indicated in the above table.
125 This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
126 A list of all parts in the IEC 61857 series, published under the general title Electrical insulation systems
127 – Procedures for thermal evaluation, can be found on the IEC website.

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128 The committee has decided that the contents of this document will remain unchanged until the stability
129 date indicated on the IEC website under "http://webstore.iec.ch" in the data related to the specific
130 document. At this date, the document will be
131 • reconfirmed,
132 • withdrawn,
133 • replaced by a revised edition, or
134 • amended.
135
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.
136
137
138
139

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140 INTRODUCTION
141 Accelerated thermal ageing of an electrical insulation system (EIS) is intended to evaluate the thermal
142 classification of the EIS. Many applications need to include the evaluation of other ageing stresses in
143 addition to the thermal stress.
144 IEC 60505 provides four categories of ageing stresses which influence the performance of products in
145 use under a wide range of operating conditions. In IEC 60505 the stresses are presented as thermal (T),
146 electrical (E), environmental (E) and mechanical (M). In this part of IEC 61857, environmental (E) is
147 replaced with ambient (A) to avoid the confusion of having two stresses represented by the same letter.
148 In this part of IEC 61857-33 the stresses are therefore presented as thermal (T), electrical (E),
149 ambient/environmental (A) and mechanical (M).
150 This document follows the structure presented in the Scope of IEC 60505, the evaluation of either
151 thermal, electrical, ambient/environmental, mechanical or combination of these as multifactor stresses.
152 In order to determine the thermal endurance of an EIS, ageing tests are carried out in accordance with
153 the selected test method of IEC TR 61857-2. To obtain the results within reasonable time these tests
154 are performed at several temperatures considerably higher than the normal service temperature. This
155 document deals with testing where the test objects are exposed to other possible ageing stresses, such
156 as E, A, and/or M in combination with T.
157 Both the reference EIS and the candidate EIS undergo thermal ageing at three or more elevated
158 temperatures. In this document the examples use three ageing temperatures of high, middle, and low.
159 A total of three sets of test objects for the reference EIS plus a total of three sets of test objects for the
160 candidate EIS are used in comparisons. The preferred number of test objects per set is provided in the
161 selected EIS test method from IEC TR 61857-2.
162 This document provides the structure for the evaluation of one or more of the three additional stresses
163 E, A and M in combination with T by direct comparison to the baseline established by T. Without the
164 baseline, analysis of the influence of the additional factors is limited.
165 A test is performed with thermal stress as the only ageing factor. Similar tests are then performed with
166 one or more of the other ageing factors E, A and/or M simultaneously added. Analyses of the results
167 are made to reveal the influence of the E, A and/or M factors.
168 While similar in their conception, IEC 61857-32 (Multifactor evaluation by diagnostic procedures) and
169 IEC 61857-33 (Multifactor evaluation with increased factors at elevated temperature) have different
170 structure and evaluation conditions. IEC 61857-32 uses thermal exposure as the only intended ageing
171 stress and applies additional stress(es) only during the diagnostic part of each test cycle. IEC 61857-
172 33 combines two or more ageing stresses and the combination of the stresses are applied continuously
173 throughout the ageing process. In other words, IEC 61857-32 uses additional diagnostic procedure(s)
174 and IEC 61857-33 uses additional ageing or stress exposure procedure(s).
175

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176 ELECTRICAL INSULATION SYSTEMS –
177 PROCEDURES FOR THERMAL EVALUATION –
178
179 Part 33: Multifactor evaluation with increased ageing factors
180 at elevated temperature
181
182
183 1 Scope
184 This part of IEC 61857 series is applicable to the evaluation of an EIS for applications where the
185 stresses of the application are a combination of the multifactor ageing stresses identified in IEC 60505.
186 The increased stress factors are expected to occur during operation at elevated temperatures.
187 This document establishes the procedure to evaluate the influence of stresses on the performance
188 established following the thermal classification of the EIS. The thermal classification is established in
189 Step 1 where the only ageing stress is thermal. The candidate EIS is first evaluated based on thermal
190 stress only. This evaluation is defined as the baseline of the candidate EIS. In Step 2, the evaluation of
191 the additional stresses applied at elevated temperatures provides the measurement needed to establish
192 the influence of the additional stress factors on the thermal performance of the baseline EIS established
193 in Step 1.
194 This document is about thermal endurance testing with one or more stresses added during the thermal
195 ageing process. It provides guidance regarding interpretation of the test results.
196 For performance requirements of any product designed and constructed using the EIS established in
197 accordance with this document refer to the appropriate IEC Technical Committee applicable to the
198 application.
199 This document is applicable to a range of established EIS test standards. IEC TR 61857-2 provides a list of
200 many established EIS test standards which cover low-voltage [up to 1kV a.c.] and high-voltage [above 1kV a.c.].
201 The use of 1kV as the transition voltage point between low-voltage and high-voltage can be found in standards
202 such as IEC TC 17 High-voltage switchgear and control gear.
203 2 Normative references
204 The following documents are referred to in the text in such a way that some or all of their content
205 constitutes requirements of this document. For dated references, only the edition cited applies. For
206 undated references, the latest edition of the referenced document (including any amendments) applies.
207 IEC 60505, Evaluation and qualification of electrical insulation systems
208 IEC TR 61857-2, Electrical insulation systems – Procedures for thermal evaluation – Part 2: Selection
209 of the appropriate test method for evaluation and classification of electrical insulation systems
210 IEC 61858-1, Electrical insulation systems – Thermal evaluation of modifications to an established
211 electrical insulation system (EIS) – Part 1: Wire-wound winding EIS
212
213 3 Terms and definitions
214 For the purposes of this document, the terms and definitions given in IEC 60505 and the following apply.
215 ISO and IEC maintain terminological databases for use in standardization at the following addresses:
216 • IEC Electropedia: available at http://www.electropedia.org
217 • ISO Online browsing platform: available at http://www.iso.org/obp

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218 3.1
219 reference EIS
220 an established EIS evaluated on the base of either a known service experience record or a known
221 comparative functional evaluation
222 Note to entry: Refer to IEC 60505
223 3.2
224 thermal classification of the reference EIS
RT
225 established thermal classification of the reference EIS where the thermal index value of the reference
226 EIS is used to establish the correlation time needed to calculate the thermal index value of the candidate
227 EIS
228 3.3
229 thermal candidate EIS
CT
230 EIS under evaluation to determine its service capability with regard to thermal stress
231 3.4
232 thermal classification of the candidate EIS
CT
233 assigned thermal classification of the candidate EIS based on the comparison to the reference EIS
234 represented as the temperature coordinate of the time/temperature graph when the time coordinate of
235 the intercept is the value of the correlation time
236 3.5
237 Baseline EIS
T
238 the designated candidate EIS after completion of the thermal classification and used to evaluate the
239 influence of additional stresses
240 3.6
241 Multifactor candidate EIS
TX
242 EIS under evaluation to determine its service capability with regard to thermal stress in combination
243 with electrical, ambient/environmental, or mechanical stress(es), where “X” is replaced with E for
244 electrical, A for environmental/ambient or M for mechanical)
245 3.7
246 5-degree uncertainty criterion
247 When two sets of ageing test results are within ±5 K of each other the analysis of the test results
248 cannot distinguish a significant difference in long-term endurance of the EIS.
249
250 3.8
251 EIS assessed thermal endurance index EIS ATE
252 numerical value of temperature in degrees Celsius for the reference EIS as derived from known
253 service experience or a known comparative functional evaluation
254
255
256 3.9
257 EIS relative thermal endurance index EIS RTE
258 numerical value of the temperature in degrees Celsius for the candidate EIS which is relative to
259 the known EIS ATE of a reference EIS, when both EIS are subjected to the same ageing and
260 diagnostic procedures in a comparative test
261 4 Procedure
262 Figure 1 shows an overview of the two steps of the evaluation procedure starting with the established
263 thermal classification of the reference system EIS and including the additional ageing influences (E,
RT
264 A, M) at elevated temperature of the candidate system EIS .
CT

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265
266 Figure 1 – Overview of the two-step evaluation procedure
267 The thermal classification of the baseline EIS is established in Step 1. It is derived from the reference
268 EIS for which test data and experience exist.
269 Step 2 evaluates only the influence of one or more other stresses (E, A, and/or M) in combination with
270 T but cannot alter or change the thermal classification of the baseline candidate EIS ; this procedure
CT
271 only evaluates the influence of the multifactor stress combination.
272 Further detail is provided in IEC TR 61857-2 with examples provided in 6.1 of the standard and Annex
273 E of this document.
274 5 Test objects
275 Both the reference EIS and the candidate EIS undergo thermal ageing at three or more elevated
276 temperatures. The examples in this document use three ageing temperatures of high, middle, and low.
277 A total of three sets of test objects for the reference EIS plus a total of three sets of test objects for the
278 candidate EIS are used in the examples. Test objects shall be in accordance with the test method
279 selected from IEC TR 61857-2.
280 The design of the sets of test objects shall be in accordance with the test method selected. When part
281 of the evaluation is to compare processing or alternate designs of the same functioning product, the
282 modifications of the design or processing shall be part of the multifactor test object construction with all
283 modifications documented in the report.
284 The preferred number of test objects is contained in individual test methods in IEC TR 61857-2.
285 6 EIS evaluation
286 6.1 Selection of the appropriate EIS test method
287 The EIS being evaluated is referred to as the candidate EIS until completion of the thermal classification.
288 Once the thermal classification has been established the candidate is described as the baseline EIS.
289 IEC TR 61857-2 provides a list of EIS test methods covering a range of applications. Selection of the
290 EIS test method should be based on the most appropriate match to the application.
291 EXAMPLE 1 The application is for form-wound motors with an operating voltage of 4,2 kV. An appropriate EIS test method to
292 establish the thermal classification is IEC 60034-18-31.
293 EXAMPLE 2 The application is for an encapsulated low-voltage motor. An appropriate EIS test method to establish the thermal
294 classification is IEC 61857-22.
295 EXAMPLE 3 The application is for oil immersed transformers. An appropriate EIS test method is either IEC TS 62332-1 or
296 IEC TS 62332-2 depending on the selection of time and test object.
297 EXAMPLE 4 The application is for form-wound generators when the influence of mechanical (M) stress in the endurance of the
298 EIS is of interest. An appropriate EIS test method is IEC 60034-18-34, a thermomechanical test.

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299 6.2 Comparison of the reference and candidate EIS
300 The reference EIS and candidate EIS shall be evaluated using the same test method, ageing cycle,
301 conditioning, and diagnostic testing. The end-point criterion of the reference and candidate shall be the
302 same. This direct comparison is essential for analysis of the results. All sets of test objects of the
303 reference and candidate EIS shall be of the same design and construction unless the purpose of the
304 project is to evaluate design changes.
305 There is no requirement for the reference and candidate EIS to be expected to have the same thermal
306 classification since the thermal classification of the candidate EIS cannot be known until completio
...