IEC 61643-352:2018

IEC 61643-352 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Components for low-voltage surge protection –
Part 352: Selection and application principles for telecommunications and
signalling network surge isolation transformers (SITs)

Composants pour protection par parafoudres basse tension –
Partie 352: Principes de choix et d'application pour les transformateurs
d'isolement contre les surtensions (SIT) dans les réseaux de signalisation et de
télécommunications
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IEC 61643-352 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Components for low-voltage surge protection –

Part 352: Selection and application principles for telecommunications and

signalling network surge isolation transformers (SITs)

Composants pour protection par parafoudres basse tension –

Partie 352: Principes de choix et d'application pour les transformateurs

d'isolement contre les surtensions (SIT) dans les réseaux de signalisation et de

télécommunications
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.040.99 ISBN 978-2-8322-5225-3

– 2 – IEC 61643-352:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, symbols and abbreviated terms . 7
3.1 Terms and definitions . 7
3.2 Symbols . 8
3.3 Abbreviated terms . 9
4 Service conditions . 10
4.1 Temperature range . 10
4.2 Humidity . 10
4.3 Altitude . 10
4.4 Microclimate . 10
5 SIT surge conditions . 11
5.1 SIT surge mitigation . 11
5.2 Common-mode surges . 12
5.3 Differential-mode surges . 13
5.3.1 General . 13
5.3.2 Ethernet transformer differential surge action . 13
6 Selection . 13
6.1 General . 13
6.2 Impulse withstand voltage . 13
6.3 Rated values of SIT . 14
7 Applications . 14
7.1 General . 14
7.2 Example of surge protection using SITs with ES for control and terminal
equipment installed in two different buildings respectively . 14
7.3 Example of surge protection using SITs for telecommunication equipment in
substation . 14
7.4 Example of surge protection using SITs for transmission and switching
equipment installed in different floors in a communication building . 16
7.5 Example of surge protection using SITs for computer network equipment in a
data centre . 17
7.6 Example of surge protection using SITs for a Power over Ethernet (PoE)
system . 17
7.7 Example of surge protection using SITs for LAN . 18
Annex A (informative) Lightning overvoltages of telecommunication line . 19
Bibliography . 20

Figure 1 – Symbol for a two-winding SIT . 8
Figure 2 – Symbol for a two-winding SIT with polarity indication . 9
Figure 3 – Symbol for a two-winding SIT with electric screen . 9
Figure 4 – SIT with centre tapped windings . 9
Figure 5 – Common-mode surge conditions for SIT . 11
Figure 6 – Common-mode surge conditions for SIT with an electric screen . 12
Figure 7 – Transformer differential surge truncation . 13

Figure 8 – Example of surge protection using SITs in order to isolate two different
buildings . 14
Figure 9 – Example of surge protection using SITs in substation . 15
Figure 10 – Example of surge protection using SITs in a communication building . 16
Figure 11 – Example of surge protection using SITs in a data centre . 17
Figure 12 – Example of surge protection using SITs for a Power over Ethernet (PoE)
system . 17
Figure 13 – Example of surge protection using SITs for LAN . 18
Figure A.1 – Lightning overvoltages of telecommunication line. 19

Table 1 – List of abbreviated terms used in this document . 10
Table 2 – Classification of microclimate condition . 10

– 4 – IEC 61643-352:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –

Part 352: Selection and application principles for telecommunications and
signalling network surge isolation transformers (SITs)

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 no
...