oSIST prEN IEC 61643-332:2023

SLOVENSKI STANDARD
oSIST prEN IEC 61643-332:2023
01-marec-2023
Sestavni deli za nizkonapetostne naprave za zaščito pred prenapetostnimi udari -
332. del: Izbira in načini uporabe za kovinsko-oksidne varistorje (MOV)
Components for low-voltage surge protection - Part 332: Selection and application
principles for metal oxide varistors (MOV)
Composants de protection contre les surtensions basse tension - Partie 332 : Principes
de sélection et d'application pour les varistances à oxyde métallique (MOV)
Ta slovenski standard je istoveten z: prEN IEC 61643-332:2022
ICS:
29.120.50 Varovalke in druga Fuses and other overcurrent
nadtokovna zaščita protection devices
31.040.20 Potenciometri, spremenljivi Potentiometers, variable
upori resistors
oSIST prEN IEC 61643-332:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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37B/230/CDV

COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61643-332 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2022-12-30 2023-03-24
SUPERSEDES DOCUMENTS:
37B/226/CD, 37B/229/CC

IEC SC 37B : COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION
SECRETARIAT: SECRETARY:
United States of America Mr Casey Granata
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:

SC 37A,TC 40,TC 108
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.

TITLE:
Components for low-voltage surge protection – Part 332: Selection and application principles
for metal oxide varistors (MOV)

PROPOSED STABILITY DATE: 2025

NOTE FROM TC/SC OFFICERS:


Copyright © 2022 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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1 CONTENTS
2
3 FOREWORD . 5
4 1 Scope . 7
5 2 Normative references . 7
6 3 Terms, definitions, symbols and abbreviated terms . 8
7 Terms and definitions. 8
8 3.1.1 Ratings . 8
9 3.1.2 Characteristics . 9
10 Symbols and abbreviated terms used in this document . 11
11 3.2.1 Abbreviated terms . 11
12 4 General . 12
13 5 Construction . 12
14 6 Function . 12
15 Theory of operation . 12
16 Thermal protection . 14
17 Failure modes . 14
18 6.3.1 Short-circuit failure mode . 14
19 6.3.2 Degradation failure mode. 15
20 6.3.3 Open-circuit and high clamping voltage failure mode . 15
21 7 Application . 15
22 MOVs basic application . 15
23 7.1.1 Application circuit . 15
24 7.1.2 Operational compatibility . 16
25 7.1.3 Voltage limiting . 16
26 7.1.4 Selection of MOVs . 16
27 7.1.5 Mitigating the consequences of failure . 24
28 7.1.6 Operations to failure . 26
29 7.1.7 Earthing and bonding . 27
30 7.1.8 Location of MOVs . 28
31 7.1.9 Applications for MOVs . 28
32 7.1.10 Parallel connections . 28
33 7.1.11 Series connections . 29
34 Thermally protected metal oxide varistor . 30
35 7.2.1 Introduction . 30
36 7.2.2 Selection of thermally protected MOV . 30
37 7.2.3 Time to open characteristics . 30
38 ESD . 31
39 7.3.1 Background . 31
40 7.3.2 Standards . 31
41 7.3.3 Application example 1 . 31
42 7.3.4 Application example 2 . 31
43 Consideration for TOV . 32
44 7.4.1 Failure of the low-voltage power supply circuit . 32
45 7.4.2 Failure of high voltage or medium voltage power supply circuit . 32
46 8 Safety and hazard information for MOVs . 32
47 General . 32

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48 8.1.1 Confirmation of rated performance . 33
49 Fire risks . 33
50 8.2.1 Use between lines . 33
51 8.2.2 Use between line and earth . 33
52 8.2.3 Shatter-proof . 33
53 8.2.4 Prevention of burning . 33
54 8.2.5 Environmental condition . 33
55 Electrical shock risks . 33
56 Typical precaution statement for the use of MOVs . 34
57 8.4.1 Information related to degradation and failures of MOVs . 34
58 8.4.2 Information related to scattering of MOVs . 34
59 8.4.3 Information related to equipment damage or malfunction . 34
60 8.4.4 Information related to accidents caused by unexpected phenomena . 35
61 Annex A (informative)  Terms and explanations . 36
62 A.1 Single-impulse peak current I . 36
TM
63 A.2 Maximum continuous voltage V . 36
M
64 A.3 Standby current I . 36
D
65 A.3.1 AC Standby current . 36
66 A.3.2 DC Standby current I . 37
DC
67 A.4 varistor voltage V . 38
V
68 A.5 Clamping voltage V . 39
C
69 A.6 Capacitance C . 40
V
70 Annex B (informative) MOV durability evaluation under DC bias condition . 41
71 B.1 Introduction . 41
72 B.2 Durability test. 41
73 B.3 Typical performances in MOV durability evaluation . 41
74 B.3.1 Ambient temperature: 85 ℃ . 41
75 B.3.2 Ambient temperature: 105 ℃ . 42
76 B.4 Conclusion . 42
77 Annex C (informative) Typical application circuits of thermally protected MOVs . 43
78 Annex D (informative) MOV application for wind turbine systems . 44
79 Annex E (informative) 5G powering surge protection . 45
80 E.1 AC power protection . 45
81 E.2 DC power protection . 45
82 Annex F (informative) Comparison of MOV terms with other standards . 46
83 Annex G (informative) How to select MOV/thermally protected MOV for equipment . 48
84 Annex H (informative) How to select an MOV/thermally protected MO for an SPD . 50
85 Bibliography . 52
86
87 Figure 1 – V-I characteristic of an MOV . 10
88 Figure 2 – Symbol for an MOV . 11
89 Figure 3 – Symbol for a thermally protected MOV . 11
90 Figure 4 – Schematic depiction of microstructure of MOV . 12
91 Figure 5 – Typical varistor V-I curve plotted log-log scale . 13
92 Figure 6 – MOV equivalent circuit model . 13

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93 Figure 7 – Possible connection of MOVs (simplified) . 16
94 Figure 8 – Overvoltage categories . 18
95 Figure 9 – Test data example of impulse current vs repetitions for 14 mm MOVs . 19
96 Figure 10 – Example of 10 mm, 14 mm and 20 mm MOV voltage current characteristics . 20
97 Figure 11 – K value for various waveforms. 21
98 Figure 12– 5/50 exponential waveform as an example . 22
99 Figure 13– MOV pulse energy versus pulse width for various pulse repetitions . 22
100 Figure 14– Options for MOV fuse connection . 25
101 Figure 15– Time-current characteristic of fast acting and time delay fuse. 26
102 Figure 16– Parallel connection of MOVs . 29
103 Figure 17– Example of V-I characteristics for two parallel MOVs . 29
104 Figure 18– Operating Time . 31
105 Figure 19– Example of MOV application for ESD . 31
106 Figure 20– Example of 4 ports application using MOVs for ESD . 32
107 Figure 21 – Combination an MOV with a GDT . 32
108 Figure A.1 – Short term effect of temperature, frequency, and voltage on standby
109 power of a typical 20 mm MOV . 37
110 Figure A.2 – Typical temperature coefficient of voltage versus current, 14 mm size,
111 −55°C to 125°C . 38
112 Figure A.3 – Typical clamping voltage response to 8/20 test current impulse . 39
113 Figure A.4 – Illustration of static (DC) I–V characteristics on linear scale . 39
114 Figure B.1 – Durability test result at 85 ℃ . 41
115 Figure B.2 – Durability test result at 105 ℃ . 42
116 Figure C.1 – AC Application Circuit . 43
117 Figure C.2 – D-C Photovoltaic Application circuit . 43
118 Figure E.1 – AC power feed protection according to ITU-T K.120 . 45
119 Figure E.2 – DC power feed protection according to ITU-T K.97 and Diode steering . 45
120 Figure G.1 – Flow chart of MOV/thermally protected MOV selection for equipment . 49
121 Figure H.1 – Flow chart of MOV/thermally protected MOV selection for an SPD . 51
122
123 Table D.1 – Example of characteristics of the generator alternator excitation circuit and
124 selected SPD . 44
125 Table F.1 – Comparison of MOV terms/symbols with other standards for MOV voltages . 46
126 Table F.2 – Comparison of MOV terms/symbols with other standards for impulse
127 current ratings . 46
128 Table F.3 – Comparison of MOV terms/symbols with other standards for TOV and
129 abnormal voltage testing . 47
130
131

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132 INTERNATIONAL ELECTROTECHNICAL COMMISSION
133 ____________
134
135 COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –
136
137 Part 332: Selection and application principles for metal oxide varistors
138 (MOV)
139
140
141
142 FOREWORD
143 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
144 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
145 co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
146 in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
147 Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
148 preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
149 may participate in this preparatory work. International, governmental and non-governmental organizations liaising
150 with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
151 Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
152 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
153 consensus of opinion on the relevant subjects since each technical committee has representation from all
154 interested IEC National Committees.
155 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
156 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
157 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
158 misinterpretation by any end user.
159 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
160 transparently to the maximum extent possible in their national and regional publications. Any divergence between
161 any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
162 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
163 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
164 services carried out by independent certification bodies.
165 6) All users should ensure that they have the latest edition of this publication.
166 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
167 members of its technical committees and IEC National Committees for any personal injury, property damage or
168 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
169 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
170 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
171 indispensable for the correct application of this publication.
172 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
173 rights. IEC shall not be held responsible for identifying any or all such patent rights.
174 International Standard IEC 61643 has been prepared by subcommittee 37B: Components for
175 low voltage surge protection, of IEC technical committee 37: Surge arresters.
176 The text of this International Standard is based on the following documents:
FDIS Report on voting
XX/XX/FDIS XX/XX/RVD
177
178 Full information on the voting for the approval of this International Standard can be found in the
179 report on voting indicated in the above table.
180 This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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181 The committee has decided that the contents of this document will remain unchanged until the
182 stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
183 the specific document. At this date, the document will be
184 • reconfirmed,
185 • withdrawn,
186 • replaced by a revised edition, or
187 • amended.

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188 COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –
189
190 Part 332: Selection and application principles for metal oxide varistors
191 (MOV)
192
193
194
195 1 Scope
196 This part of IEC 61643 presents a description, theory of operation, test characteristics, and
197 application principles for MOVs, which are used for applications up to 1 000 V AC or 1 500 V DC
198 in power line, or telecommunication, or signalling circuits. They are designed to protect
199 apparatus or personnel, or both, from high transient voltages.
200 This specification applies to MOVs having two electrodes and overvoltage protection
201 components with or without disconnectors. This specification also does not apply to mountings
202 and their effect on the MOV’s characteristics. Characteristics given apply solely to the MOV
203 mounted only in the ways described for the tests.
204 This standard specifically discusses the zinc-oxide type of MOVs.
205
206 2 Normative references
207 The following documents are referred to in the text in such a way that some or all of their content
208 constitutes requirements of this document. For dated references, only the edition cited applies.
209 For undated references, the latest edition of the referenced document (including any
210 amendments) applies.
211 IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
212 IEC 60068-2-20:2021, Environmental testing - Part 2-20: Tests - Test Ta and Tb: Test methods
213 for solderability and resistance to soldering heat of devices with leads
214 IEC 60068-2-21:2021, Environmental testing – Part 2-21: Tests – Test U: Robustness of
215 terminations and integral mounting devices
216 IEC 60068-2-78:2012, Environmental testing - Part 2-78: Tests - Test Cab: Damp heat, steady
217 state
218 IEC 60664-1:2020, Insulation coordination for equipment within low-voltage supply systems -
219 Part 1: Principles, requirements and tests
220 IEC 61051-1:2018, Varistors for use in electronic equipment - Part 1: Generic specification
221 IEC 61051-2:1991/AMD1:2009, Ammendment 1- Varistors for use in electronic equipment - Part
222 2: Sectional specification for surge suppression varistors
223 IEC 61643-11:2011, Low-voltage surge protective devices – Part 11: Surge protective devices
224 connected to low-voltage power systems – Requirements and test methods
225 IEC 61643-331:2020, Components for low-voltage surge protection - Part 331: Performance
226 requirements and test methods for metal oxide varistors (MOV)
227 IEC 62368-1:2018, Audio/video, information and communication technology equipment - Part
228 1: Safety requirements

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229 3 Terms, definitions, symbols and abbreviated terms
230 ISO and IEC maintain terminological databases for use in standardization at the following
231 addresses:
232 • IEC Electropedia: available at http://www.electropedia.org/
233 • ISO Online browsing platform: available at http://www.iso.org/obp
234
235 Terms and definitions
236 3.1.1 Ratings
237 3.1.1.1
238 rating
239 either a limiting capability or a limiting condition beyond which damage to the MOV may occur
240 Note 1 to entry: A limiting condition may be either a maximum or a minimum.
241 3.1.1.2
242 nominal discharge current
243 I
n
244 crest value of the current through the MOV having a current waveshape of 8/20
245 [SOURCE: IEC 61643-331:2020, 3.1.1.3]
246 3.1.1.3
247 maximum continuous voltage
248 VM
249 voltage that may be applied continuously at a specified temperature
250 Note 1 to entry: May also be called U or MCOV (Maximum continuous operating voltage).
C
251 Note 2 to entry: See Figure 1.
252 [SOURCE: IEC 61643-331:2020, 3.1.1.7, modified (addition of "Maximum continuous operating
253 voltage" to Note 1 to entry)]
254 3.1.1.4
255 maximum continuous AC voltage
256 VM(AC)
257 value of r.m.s. power frequency voltage (less than 5 % total harmonic distortion) that may be
258 applied continuously at a specified temperature
259 [SOURCE: IEC 61643-331:2020, 3.1.1.8]
260 3.1.1.5
261 maximum continuous DC voltage
262 VM(DC)
263 DC voltage that may be applied continuously at a specified temperature
264 [SOURCE: IEC 61643-331:2020, 3.1.1.9]
265 3.1.1.6
266 maximum discharge current
267 I
max
268 crest value of a current through the SPD having an 8/20 waveshape and magnitude according
269 to the manufacturers specification.
270 Note 1 to entry: I is equal to or greater than I
max n
271 [SOURCE: IEC 61643-11:2011, 3.1.48]
272 3.1.1.7
273 impulse discharge current for class I test
274 Iimp

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275 crest value of a discharge current through the SPD with specified charge transfer Q and
276 specified energy W/R in the specified time
277 [SOURCE: definition 3.1.10 of IEC 61643-11:2011]
278 3.1.1.8
279 rated average dissipation power
280 PM
281 maximum average dissipation power of repetitive pulses allowed to be applied to the varistors
282 at ambient temperature of 25 °C
283
284 [SOURCE: definition of IEC 61051-1:2018, 3.23]
285 3.1.2 Characteristics
286 3.1.2.1
287 characteristics
288 inherent and measurable properties of an MOV
289 [SOURCE: IEC 61643-331:2020, 3.1.2.1]
290 3.1.2.2
291 standby current
292 ID
293 current passing through MOV at maximum continuous voltage V
M
294 Note 1 to entry: The current passing through the MOV at less than V is called leakage current
M
295 [SOURCE: IEC 61643-331:2020, 3.1.2.2]
296 3.1.2.3
297 varistor voltage
298 V
V
299 voltage across the MOV measured at a specified current (typically 1 mA) for a specific duration
300 Note 1 to entry: The MOV manufacturer specifies the current. Otherwise, 1 mA DC for a duration of 20 to 100 ms
301 is normally used.
302 Note 2 to entry: See Figure 1
303 [SOURCE: IEC 61643-331:2020, 3.1.2.3]

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304
305 Figure 1 – V-I characteristic of an MOV
306 3.1.2.4
307 Clamping voltage
308 V
C
309 peak voltage across the MOV measured under conditions of a specified peak pulse current (Ip)
310 and specified waveform
311 [SOURCE: IEC 61643-331:2020, 3.1.2.5]
312 3.1.2.5
313 Capacitance
314 C
V
315 capacitance across the MOV measured at a specified frequency, voltage and time
316 [SOURCE: IEC 61643-331:2020, 3.1.2.6]
317 3.1.2.6
318 metal oxide varistor (MOV)
319 non-linear resistor made of a sintered mixture of metal oxides whose conductance, at a g
...