oSIST prEN IEC 61643-361:2025

SLOVENSKI STANDARD
01-julij-2025
Nizkonapetostni sestavni deli za zaščito pred prenapetostnimi udari - 361. del:
Prenapetostni izolacijski transformatorji (SIT) za nizkonapetostne napajalne
sisteme - Zahteve in preskusne metode
Low-voltage surge protective components - Part 361: Surge isolation transformers (SITs)
connected to low-voltage distribution system - Requirements and test methods
Composants de protection contre les surtensions dans les réseaux basse tension -
Partie 361: Transformateurs d’isolement contre les surtensions (SIT) connectés aux
réseaux de distribution basse tension - Exigences et méthodes d’essai
Ta slovenski standard je istoveten z: prEN IEC 61643-361:2025
ICS:
29.120.50 Varovalke in druga Fuses and other overcurrent
nadtokovna zaščita protection devices
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

37B/252/CDV
COMMITTEE DRAFT FOR VOTE (CDV)

PROJECT NUMBER:
IEC 61643-361 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2025-06-06 2025-08-29
SUPERSEDES DOCUMENTS:
37B/247/CD, 37B/250/CC
IEC SC 37B : COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION
SECRETARIAT: SECRETARY:
United States of America Mr David Richmond
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

ASPECTS CONCERNED:
Electromagnetic Compatibility
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
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Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some
Countries” clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is
the final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Low-voltage surge protective components - Part 361: Surge isolation transformers (SITs)
connected to low-voltage distribution system – Requirements and test methods

PROPOSED STABILITY DATE: 2030
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2 IEC CDV 61643-361 ED1 © IEC 2025
1 CONTENTS
3 FOREWORD . 3
4 INTRODUCTION . 5
5 1 Scope . 6
6 2 Normative references . 6
7 3 Terms, definitions and symbols . 6
8 3.1 Terms and definition . 6
9 3.2 Symbols . 8
10 3.3 Abbreviations and acronyms . 8
11 4 Service condition . 9
12 4.1 Temperature range . 9
13 4.2 Humidity range. 9
14 4.3 Altitude and air pressure . 9
15 5 SIT surge condition . 9
16 5.2 SITs surge mitigation . 10
17 6 Electrical requirements . 11
18 6.1 General . 11
19 6.2 Insulation resistance . 11
20 6.3 Power frequency withstand voltage . 11
21 6.4 Impulse withstand voltage . 12
22 7 Type tests . 12
23 7.1 General . 12
24 7.2 Test condition . 12
25 7.3 Sample preparation . 12
26 7.4 Insulation resistance . 12
27 7.5 Power frequency withstand voltage . 13
28 7.6 Impulse withstand voltage . 14
29 Annex A (informative) 1,2/50 impulse . 17
30 Bibliography . 18
32 Figure 1– Symbol of SIT for single phase low-voltage power system . 8
33 Figure 2–Symbol of SIT for single phase low-voltage power system . 8
34 Figure 3 – SITs under common mode surge condition . 11
35 Figure 4 – Sample preparation . 12
36 Figure 5 – Test circuit of insulation resistance . 13
37 Figure 6 – Power frequency withstand voltage test circuit . 14
38 Figure 7 – Construction of pass/fail template from the 1,2/50 open-circuit waveform . 15
39 Figure 8 – Pass/fail template and test waveforms . 15
40 Figure 9 – Impulse withstand voltage test circuit . 16
41 Figure A.1 – 1,2/50 time periods and voltage amplitudes . 17
43 Table 1 – List of abbreviations and acronyms used in this standard . 8
44 Table 2 – Conditions used for test . 12
45 Table A.1 – 1,2/50 voltage impulse generator parameters . 17
IEC CDV 61643-361 ED1 © IEC 2025 3
47 INTERNATIONAL ELECTROTECHNICAL COMMISSION
48 IEC SC37B JWG5
50 LOW-VOLTAGE SURGE PROTECTIVE COMPONENTS –
52 Part 361: Surge isolation transformers (SITs) connected to low-voltage
53 distribution system – Requirements and test methods
56 FOREWORD
57 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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84 Publications.
85 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
86 indispensable for the correct application of this publication.
87 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
88 rights. IEC shall not be held responsible for identifying any or all such patent rights.
89 International Standard IEC 61643-361 has been prepared by subcommittee SC37B JWG5, of
90 IEC technical committee TC37
91 This edition includes the following significant technical changes with respect to the previous
92 edition:
93 a) .;
94 b)
95 The text of this International Standard is based on the following documents:
Draft Report on voting
XX/XX/FDIS XX/XX/RVD
97 Full information on the voting for its approval can be found in the report on voting indicated in
98 the above table.
99 The language used for the development of this International Standard is English [change
100 language if necessary].
4 IEC CDV 61643-361 ED1 © IEC 2025
101 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
102 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
103 at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
104 described in greater detail at http://www.iec.ch/standardsdev/publications.
105 The committee has decided that the contents of this document will remain unchanged until the
106 stability date indicated on the IEC website under webstore.iec.ch in the data related to the
107 specific document. At this date, the document will be
108 • reconfirmed,
109 • withdrawn,
110 • replaced by a revised edition, or
111 • amended.
IEC CDV 61643-361 ED1 © IEC 2025 5
113 INTRODUCTION
114 This standard cover SITs (surge isolation transformers) whose rated impulse withstand
115 voltage coordinates with the expected surge environment of the installation location.
116 This type of surge protective component, SPC, isolates and attenuates transient voltage
117 in conjunction with current diverting components (or SPDs).
118 SITs are a product with specific enhanced insulation layers between the primary and
119 secondary windings and an shield (electric screen) inserted between primary and
120 secondary. With these shields and specific enhanced insulation layers, the surge that
121 appears between the primary winding and earth (common-mode) is greatly attenuated
122 and appears between the secondary winding and earth. SITs are product with a
123 particularly improved impulse withstand voltage compared to ordinary isolating
124 transformers.
125 SITs should be protected by SPDs at their primary side to avoid any damage to the SIT
126 itself. SITs are intended to be used in surge protection to establish lightning protection
127 zones.
oSIST prEN IEC 6164
...