SIST EN 61643-351:2017

Components for lowvoltage surge protective devices - Part 351: Performance requirements and test methods for telecommunications and signalling network surge isolation transformers (SIT)

Surge isolation transformers (SITs) are used for signal transformer applications with signal
levels up to 400 V peak to peak. SITs are transformers, with or without an internal-winding
screen, with a rated impulse withstand voltage greater than the peak voltage of the expected
common-mode surge environment. SITs are applicable to components for surge protection
against indirect and direct effects of lightning or other transient overvoltage. SITs are used to
mitigate the onward propagation of common-mode voltage surges. This part of IEC 61643
defines test circuits and test methods for determining and verifying the SIT surge parameters.
Preferred performance values for key parameters are given.
This part of IEC 61643 does not cover SIT operation under differential-mode lightning surge
conditions.

Bauelemente für Überspannungsschutzgeräte für Niederspannung - Teil 351: Leistungsanforderungen sowie Prüfschaltungen und -verfahren für Überspannungstrenntransformatoren (SIT) in Telekommunikations- und signalverarbeitenden Netzen

Composants pour parafoudres basse tension - Partie 351: Exigences de performance et méthodes d'essai pour les transformateurs d'isolement contre les surtensions dans les réseaux de signalisation et de télécommunications

L'IEC 61643-351:2016 définit les circuits d'essai et les méthodes d'essai permettant de déterminer et de vérifier les paramètres d'onde de choc des SIT. Les valeurs préférentielles de performances sont indiquées pour les paramètres clés. Les transformateurs d'isolement contre les surtensions (SIT) sont utilisés pour les applications de transformateurs de signaux dont les niveaux de signal atteignent 400 V de crête à crête. Les SIT sont des transformateurs, dotés ou non d'un écran à enroulement interne, dont la tension assignée de tenue aux chocs est supérieure à la tension de crête de l'environnement de tension de choc de mode commun attendu. Ils sont applicables aux appareils de protection contre les effets indirects et directs de la foudre, et les autres types de surtensions transitoires. Ils sont utilisés pour atténuer la propagation de surtensions en mode commun.
Mots clés: Les transformateurs d'isolement contre les surtensions (SIT)

Sestavni deli za nizkonapetostne naprave za zaščito pred prenapetostnimi udari - 351. del: Zahtevane lastnosti in metode preskušanja za izolacijske transformatorje (SIT) v telekomunikacijskih in signalnih omrežjih

Izolacijski transformatorji (SIT) se uporabljajo v signalnih transformatorjih pri ravneh signalov do 400 V od vršne vrednosti do vršne vrednosti. Izolacijski transformatorji so transformatorji z zaslonom notranjega navitja ali brez njega, z nazivno zdržno udarno napetostjo, ki je višja od temenske napetosti pričakovanega običajnega načina okolja prednapetostnega udara. Izolacijski transformatorji se uporabljajo kot komponente za zaščito pred prenapetostnimi udari v primeru posrednih in neposrednih učinkov strele ali drugih prehodnih prenapetosti. Izolacijski transformatorji se uporabljajo za širjenje običajnega načina napetostnih udarov. Ta del standarda IEC 61643 opredeljuje preskusne tokokroge in preskusne metode za ugotavljanje in preverjanje prednapetostnih parametrov izolacijskih transformatorjev. Podane so preferenčne vrednosti lastnosti za ključne parametre. Ta del standarda IEC 61643 ne zajema delovanja izolacijskih transformatorjev v pogojih diferencialnega načina napetostnega udara.

General Information

• Status: Published
• Publication Date: 16-Mar-2017
• ICS: 29.240.10 - Substations. Surge arresters
• ICS: 33.040.99 - Other equipment for telecommunication systems
• Technical Committee: POD - Surge aresters
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 03-Mar-2017
• Due Date: 08-May-2017
• Completion Date: 17-Mar-2017
• Ref Project: EN 61643-351:2017 - Components for low-voltage surge protective devices - Part 351: Performance requirements and test methods for telecommunications and signalling network surge isolation transformers (SIT)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61643-351:2017
01-april-2017
6HVWDYQLGHOL]DQL]NRQDSHWRVWQHQDSUDYH]D]DãþLWRSUHGSUHQDSHWRVWQLPLXGDUL
GHO=DKWHYDQHODVWQRVWLLQPHWRGHSUHVNXãDQMD]DL]RODFLMVNHWUDQVIRUPDWRUMH
6,7YWHOHNRPXQLNDFLMVNLKLQVLJQDOQLKRPUHåMLK
Components for lowvoltage surge protective devices - Part 351: Performance
requirements and test methods for telecommunications and signalling network surge
isolation transformers (SIT)
Composants pour parafoudres basse tension - Partie 351: Exigences de performance et
méthodes d'essai pour les transformateurs d'isolement contre les surtensions dans les
réseaux de signalisation et de télécommunications
Ta slovenski standard je istoveten z: EN 61643-351:2017
ICS:
29.240.10 Transformatorske postaje. Substations. Surge arresters
Prenapetostni odvodniki
33.040.99 Druga oprema za Other equipment for
telekomunikacijske sisteme telecommunication systems
SIST EN 61643-351:2017 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN 61643-351:2017

---------------------- Page: 2 ----------------------

SIST EN 61643-351:2017


EUROPEAN STANDARD EN 61643-351

NORME EUROPÉENNE

EUROPÄISCHE NORM
February 2017
ICS 33.040.99

English Version
Components for low-voltage surge protective devices -
Part 351: Performance requirements and test methods for
telecommunications and signalling network surge isolation
transformers (SIT)
(IEC 61643-351:2016)
Composants pour parafoudres basse tension -  Bauelemente für Überspannungsschutzgeräte für
Partie 351: Exigences de performance et méthodes d'essai Niederspannung - Teil 351: Leistungsanforderungen sowie
pour les transformateurs d'isolement contre les surtensions Prüfschaltungen und -verfahren für
dans les réseaux de signalisation et de télécommunications Blitzisoliertransformatoren in Telekommunikations- und
(IEC 61643-351:2016) signalverarbeitenden Netzen
(IEC 61643-351:2016)
This European Standard was approved by CENELEC on 2016-12-02. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.


European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN 61643-351:2017 E

---------------------- Page: 3 ----------------------

SIST EN 61643-351:2017
EN 61643-351:2017
European foreword
The text of document 37B/155/FDIS, future edition 1 of IEC 61643-351, prepared by SC 37B “Specific
components for surge arresters and surge protective devices” of IEC/TC 37 “Surge arresters" was
submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 61643-351:2017.

The following dates are fixed:
(dop) 2017-09-02
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2019-12-02
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.

Endorsement notice
The text of the International Standard IEC 61643-351:2016 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 60060-1:2010 NOTE Harmonized as EN 60060-1:2010 (not modified).
IEC 60068-2-1:2007 NOTE Harmonized as EN 60068-2-1:2007 (not modified).
IEC 60068-2-2:2007 NOTE Harmonized as EN 60068-2-2:2007 (not modified).
IEC 60076-1 NOTE Harmonized as EN 60076-1.
IEC 60721-3-9:1993 NOTE Harmonized as EN 60721-3-9:1993 (not modified).
IEC 61340-4-8 NOTE Harmonized as EN 61340-4-8.
IEC 61558-1 NOTE Harmonized as EN 61558-1.
IEC 61558-2-4 NOTE Harmonized as EN 61558-2-4.
IEC 61558-2-6 NOTE Harmonized as EN 61558-2-6.
2

---------------------- Page: 4 ----------------------

SIST EN 61643-351:2017
EN 61643-351:2017
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When 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 60721-3-3 -  Classification of environmental conditions - EN 60721-3-3 -
- Part 3: Classification of groups of
environmental parameters and their
severities -
Section 3: Stationary use at
weatherprotected locations
IEC/TR 60664-2-1 2011 Insulation coordination for equipment - -
within low-voltage systems -
Part 2-1: Application guide - Explanation of
the application of the IEC 60664 series,
dimensioning examples and dielectric
testing

3

---------------------- Page: 5 ----------------------

SIST EN 61643-351:2017

---------------------- Page: 6 ----------------------

SIST EN 61643-351:2017



IEC 61643-351

®


Edition 1.0 2016-10




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE











Components for low-voltage surge protective devices –

Part 351: Performance requirements and test methods for telecommunications

and signalling network surge isolation transformers (SIT)




Composants pour parafoudres basse tension –

Partie 351: Exigences de performance et méthodes d'essai pour les


transformateurs d'isolement contre les surtensions dans les réseaux de

signalisation et de télécommunications












INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 33.040.99 ISBN 978-2-8322-3717-5



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

---------------------- Page: 7 ----------------------

SIST EN 61643-351:2017
– 2 – IEC 61643-351:2016 © IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, symbols, abbreviations and acronyms . 7
3.1 Terms and definitions . 7
3.2 Symbols . 10
3.3 Abbreviations and acronyms . 12
4 Service conditions . 12
4.1 Temperature range . 12
4.2 Humidity . 12
4.3 Altitude . 12
4.4 Microclimate . 12
5 SIT surge conditions . 13
5.1 SIT surge mitigation . 13
5.2 Common-mode surges . 14
5.3 Differential-mode surges . 14
6 Characteristics . 15
6.1 Characteristic measurement . 15
6.2 Input winding to output winding capacitance . 15
6.3 Insulation resistance (IR) . 16
6.4 Signal SIT voltage-time product . 18
7 Ratings . 19
7.1 Rated impulse withstand voltage . 19
7.2 Signal SIT rated winding direct current . 22
8 Identification . 24
8.1 General . 24
8.2 Datasheet . 24
8.3 Marking . 24
Annex A (informative)  1,2/50 impulse . 25
Bibliography . 26

Figure 1 – Symbol for two-winding SIT . 10
Figure 2 – Symbol for a two-winding SIT with polarity indication . 11
Figure 3 – Symbol for a two-winding SIT with electric screen . 11
Figure 4 – SIT with centre tapped windings . 11
Figure 5 – Common-mode surge conditions for SIT . 13
Figure 6 – Common-mode surge conditions for SIT with an electric screen . 14
Figure 7 – Test circuit to measure SIT internal-winding capacitance . 15
Figure 8 – Test circuit to measure the internal-winding capacitance of SIT with an
electric screen . 16
Figure 9 – Test circuit to measure the insulation resistance of SIT . 17
Figure 10 – Test circuit to measure the insulation resistance of SIT with an electric
screen . 17
Figure 11 – Test circuit to measure SIT voltage-time product . 18

---------------------- Page: 8 ----------------------

SIST EN 61643-351:2017
IEC 61643-351:2016 © IEC 2016 – 3 –
Figure 12 – Generator and SIT secondary voltage waveforms . 18
Figure 13 – SIT rated impulse voltage test circuit . 19
Figure 14 – Rated impulse voltage test circuit for SIT with an electric screen . 20
Figure 15 – Construction of pass/fail template from the 1,2/50 open-circuit waveform . 20
Figure 16 – Pass/fail template and test waveforms . 21
Figure 17 – Winding conductor temperature rise test circuit . 23
Figure A.1 – 1,2/50 time periods and voltage amplitudes . 25

Table 1 – Classification of microclimate condition . 12
Table 2 – Impulse withstand test voltage for rated impulse voltage . 22
Table A.1 – 1,2/50 voltage impulse generator parameters . 25

---------------------- Page: 9 ----------------------

SIST EN 61643-351:2017
– 4 – IEC 61643-351:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

Part 351: Performance requirements and test methods
for telecommunications and signalling network surge
isolation transformers (SIT)

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.
International Standard IEC 61643-351 has been prepared by subcommittee 37B: Specific
components for surge arresters and surge protective devices, of IEC technical committee 37:
Surge arresters.
The text of this standard is based on the following documents:
FDIS Report on voting
37B/155/FDIS 37B/156/RVD

Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 10 ----------------------

SIST EN 61643-351:2017
IEC 61643-351:2016 © IEC 2016 – 5 –
A list of all parts in the IEC 61643 series, published under the general title Components for
low-voltage surge protective devices, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.

---------------------- Page: 11 ----------------------

SIST EN 61643-351:2017
– 6 – IEC 61643-351:2016 © IEC 2016
INTRODUCTION
This part of IEC 61643 covers surge isolation transformers whose rated impulse withstand
voltage coordinates with the expected surge environment of the installation. This type of
surge protective component, SPC, isolates and attenuates transient voltages in conjunction
with current diverting components (e.g. GDT, MOV, etc.) or surge protective devices (SPDs).
It can be used in SPDs.

---------------------- Page: 12 ----------------------

SIST EN 61643-351:2017
IEC 61643-351:2016 © IEC 2016 – 7 –
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –

Part 351: Performance requirements and test methods
for telecommunications and signalling network surge
isolation transformers (SIT)



1 Scope
Surge isolation transformers (SITs) are used for signal transformer applications with signal
levels up to 400 V peak to peak. SITs are transformers, with or without an internal-winding
screen, with a rated impulse withstand voltage greater than the peak voltage of the expected
common-mode surge environment. SITs are applicable to components for surge protection
against indirect and direct effects of lightning or other transient overvoltage. SITs are used to
mitigate the onward propagation of common-mode voltage surges. This part of IEC 61643
defines test circuits and test methods for determining and verifying the SIT surge parameters.
Preferred performance values for key parameters are given.
This part of IEC 61643 does not cover SIT operation under differential-mode lightning surge
conditions.
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 60721-3-3, Classification of environmental conditions – Part 3: Classification of groups of
environmental parameters and their severities – Section 3: Stationary use at weatherprotected
locations
IEC TR 60664-2-1:2011, Insulation coordination for equipment within low-voltage systems –
Part 2-1: Application guide – Explanation of the application of the IEC 60664 series,
dimensioning examples and dielectric testing
3 Terms, definitions, symbols, abbreviations and acronyms
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 http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
surge isolation transformer
SIT
isolation transformer which has high impulse withstand voltage with/without electric screen
between input and output windings

---------------------- Page: 13 ----------------------

SIST EN 61643-351:2017
– 8 – IEC 61643-351:2016 © IEC 2016
3.1.2
electric screen
ES
screen of conductive material intended to reduce the penetration of an electric field into a
given region
[SOURCE: IEC 60050-151:2001, 151-13-10]
3.1.3
breakdown
failure, at least temporarily, of the insulating properties of an insulating medium under electric
stress
[SOURCE: IEC TR 61340-1:2012, 3.4]
3.1.4
component type
manufacturer’s type of a component, e.g. its product name
3.1.5
clearance
shortest distance in air between two conductive parts
[SOURCE: IEC TR 60664-2-1:2011, 3.4]
3.1.6
creepage distance
shortest distance along the surface of a solid insulating material between two conductive
parts
[SOURCE: IEC TR 60664-2-1:2011, 3.7]
3.1.7
guarded measurement
measurement technique in a three terminal network that allows the direct impedance between
two terminals to be measured correctly by applying a compensating voltage to the third
terminal that removes the shunting effects of any impedances to the third terminal
3.1.8
insulation resistance
resistance under specified conditions between two conductive elements separated by
insulating materials
[SOURCE: IEC TS 61994-4-2:2011, 3.10]
3.1.9
impulse withstand voltage
highest peak value of impulse voltage of prescribed form and polarity which does not cause
breakdown of insulation under specified conditions
[SOURCE: IEC TR 60664-2-1:2011, 3.15]
3.1.10
isolating transformer
transformer with protective separation between the input and output windings
[SOURCE: IEC 60065:2014, 2.7.1]

---------------------- Page: 14 ----------------------

SIST EN 61643-351:2017
IEC 61643-351:2016 © IEC 2016 – 9 –
3.1.11
insulation
that part of an electrotechnical product which separates the conducting parts at different
electrical potentials
[SOURCE: IEC TR 60664-2-1:2011, 3.17]
3.1.12
insulation coordination
mutual correlation of insulation characteristics of electrical equipment taking into account the
expected micro-environment and other influencing stresses
[SOURCE: IEC TR 60664-2-1:2011, 3.18]
3.1.13
overvoltage
any voltage having a peak value exceeding the corresponding peak value of maximum
steady-state voltage at normal operating conditions
[SOURCE: IEC TR 60664-2-1:2011, 3.21]
3.1.14
lightning overvoltage
transient overvoltage at any point of the system due to a specific lightning discharge
[SOURCE: IEC 60664-1:2007, 3.7.4]
3.1.15
thermal equilibrium
variation of less than 1 K between any two out of three consecutive measurements made at
an interval of 5 min
[SOURCE: IEC 61810-1:2014, 3.3.13]
3.1.16
thermal resistance
quotient of the temperature difference between two specified points or regions and the heat
flow between these two points or regions under conditions of thermal equilibrium
Note 1 to entry: For most cases, the heat flow can be assumed to be equal to the power dissipation.
[SOURCE: IEC 62590:2010, 3.9.1]
3.1.17
microclimate
climatic condition at the place where a component is installed in the product
Note 1 to entry: Only the inside product maximum air temperature (classes X1 to X7) and, optionally, the
maximum air humidity class (classes Y1 to Y4) are taken into account.
[SOURCE: IEC 60721-3-9:1993, 3.1, modified – addition of Note 1 to entry]

---------------------- Page: 15 ----------------------

SIST EN 61643-351:2017
– 10 – IEC 61643-351:2016 © IEC 2016
3.1.18
virtual front time
T
1
1/0,6 times the interval T between the instants when the impulse is
30 % and 90 % of the peak value
SEE: Figure A.1
[SOURCE: IEC 60060-1:2010, 7.1.18, modified]
3.1.19
virtual origin
O
1
instant at which a straight line drawn through the 30 %
and 90 % amplitude values crosses the time axis
SEE: Figure A.1
[SOURCE: IEC 60060-1:2010, 7.1.19, modified]
3.1.20
virtual time to half-value
T
2
interval of time between the instant of virtual origin O and the instant when the voltage or
1
current has decreased to half the peak value
SEE: Figure A.1
3.1.21
designation of an impulse shape
combination of two numbers, the first representing the virtual front time (T ) and the second
1
the virtual time to half-value on the tail (T )
2
Note 1 to entry: It is written as T /T , both in microseconds, the sign "/" having no mathematical meaning.
1 2
[SOURCE: IEC 60099-4:2014, 3.13]
3.2 Symbols
For the purposes of this document, the following symbols apply.
Figure 1 shows the symbol for a two-winding SIT.
P1 S1
S2
P2
IEC

Key
P1: Primary winding terminal 1 S1: Secondary winding terminal 1
P2: Primary winding terminal 2 S2: Secondary winding terminal 2
Figure 1 – Symbol for two-winding SIT

---------------------- Page: 16 ----------------------

SIST EN 61643-351:2017
IEC 61643-351:2016 © IEC 2016 – 11 –
Figure 2 shows the symbol for a two-winding SIT with instantaneous voltage polarity
indicators, similar to the S00843 symbol of IEC 60617 made with terminal connections.
P1 S1
P2 S2
IEC

Key
P1: Primary winding terminal 1 S1: Secondary winding terminal 1
P2: Primary winding terminal 2 S2: Secondary winding terminal 2
Figure 2 – Symbol for a two-winding SIT with polarity indication
Figure 3 shows the symbol for a two-winding SIT with an electric screen between the windings,
similar to the S00853 symbol of IEC 60617 made with terminal connections.
P1 S1
P2 S2
E
IEC

Key
P1: Primary winding terminal 1 S1: Secondary winding terminal 1
P2: Primary winding terminal 2 S2: Secondary winding terminal 2
E : Earth terminal (electric screen terminal)
Figure 3 – Symbol for a two-winding SIT with electric screen
Figure 4 shows the symbol for a SIT centre tapped windings, similar to the S00855 symbol of
IEC 60617 made with two centre tapped windings and terminal connections. When testing is
done with shorted windings the centre tap is also connected to the short, other testing is done
without any connection to the centre tap terminal.
P1 S1
CT CT
P2 S2
IEC

Key
P1: Primary winding terminal 1 S1: Secondary winding terminal 1
P2: Primary winding terminal 2 S2: Secondary winding terminal 2
CT: Centre tap terminal
Figure 4 – SIT with centre tapped windings

---------------------- Page: 17 ----------------------

SIST EN 61643-351:2017
– 12 – IEC 61643-351:2016 © IEC 2016
3.3 Abbreviations and acronyms
For the purposes of this document, the following abbreviations and acronyms apply.
ES electric screen
ICT information and communications technology
IR insulation resistance
rms root-mean-square
SIT surge isolation transformer
SPD surge protective device

4 Service conditions
4.1 Temperature range
Normal range: −20 °C to 40 °C
Extended range: This range is decided based on agreement between manufacturer and user.
4.2 Humidity
Not exceeding 90 %.
4.3 Altitude
Normal range: Not exceeding 1 000 m.
Extended range: This range is decided based on agreement between manufacturer and user.
4.4 Microclimate
When microclimate conditions apply, use one of the classes given in Table 1.
Table 1 – Classification of microclimate condition
High air temperature Class Typical component Product application
severity temperature range
°C °C
...