SIST EN IEC 61557-9:2025

SLOVENSKI STANDARD
01-julij-2025
Električna varnost v nizkonapetostnih razdelilnih sistemih za izmenične napetosti
do 1 000 V in enosmerne napetosti do 1 500 V - Oprema za preskušanje, merjenje
ali nadzorovanje zaščitnih ukrepov - 9. del: Oprema za ugotavljanje mesta
izolacijske okvare v IT-sistemih (IEC 61557-9:2023)
Electrical safety in low voltage distribution systems up to 1 000 V AC and 1 500 V DC -
Equipment for testing, measuring or monitoring of protective measures - Part 9:
Equipment for insulation fault location in IT systems (IEC 61557-9:2023)
Elektrische Sicherheit in Niederspannungsnetzen bis AC 1 000 V und DC 1 500 V –
Geräte zum Prüfen, Messen oder Überwachen von Schutzmaßnahmen – Teil 9:
Einrichtungen zur Isolationsfehlersuche in IT-Systemen (IEC 61557-9:2023)
Sécurité électrique dans les réseaux de distribution basse tension de 1 000 V c.a. et 1
500 V c.c - Dispositifs de contrôle, de mesure ou de surveillance de mesures de
protection - Partie 9: Dispositifs de localisation de défauts d'isolement pour réseaux IT
(IEC 61557-9:2023)
Ta slovenski standard je istoveten z: EN IEC 61557-9:2025
ICS:
17.220.20 Merjenje električnih in Measurement of electrical
magnetnih veličin and magnetic quantities
29.080.01 Električna izolacija na Electrical insulation in
splošno general
29.240.01 Omrežja za prenos in Power transmission and
distribucijo električne energije distribution networks in
na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61557-9

NORME EUROPÉENNE
EUROPÄISCHE NORM April 2025
ICS 25.040.40 Supersedes EN 61557-9:2015; EN 61557-
9:2015/AC:2016-06; EN 61557-9:2015/AC:2017-02
English Version
Electrical safety in low voltage distribution systems up to 1 000 V
AC and 1 500 V DC - Equipment for testing, measuring or
monitoring of protective measures - Part 9: Equipment for
insulation fault location in IT systems
(IEC 61557-9:2023)
Sécurité électrique dans les réseaux de distribution basse Elektrische Sicherheit in Niederspannungsnetzen bis AC
tension au plus égale à 1 000 V en C.A et 1 500 V en C.C - 1 000 V und DC 1 500 V - Geräte zum Prüfen, Messen oder
Dispositifs de contrôle, de mesure ou de surveillance de Überwachen von Schutzmaßnahmen - Teil 9: Einrichtungen
mesures de protection - Partie 9: Dispositifs de localisation zur Isolationsfehlersuche in IT-Systemen
de défauts d'isolement pour réseaux IT (IEC 61557-9:2023)
(IEC 61557-9:2023)
This European Standard was approved by CENELEC on 2024-10-16. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61557-9:2025 E

European foreword
The text of document 85/896/FDIS, future edition 4 of IEC 61557-9, prepared by TC 85 "Measuring
equipment for electrical and electromagnetic quantities" was submitted to the IEC-CENELEC parallel
vote and approved by CENELEC as EN IEC 61557-9:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-04-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-04-30
document have to be withdrawn
This document supersedes EN 61557-9:2015 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61557-9:2023 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 standard indicated:
IEC 60364-4-41:2005 NOTE Approved as HD 60364-4-41:2017 +A11:2017
IEC 60664 series NOTE Approved as EN 60664 series
IEC 60664-1 NOTE Approved as EN IEC 60664-1
IEC 60664-3 NOTE Approved as EN 60664-3
IEC 61557-15 NOTE Approved as EN 61557-15
IEC 61810-2:2017 NOTE Approved as EN 61810-2:2017 (not modified)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where 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.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60068-2-1 2007 Environmental testing - Part 2-1: Tests - EN 60068-2-1 2007
Test A: Cold
IEC 60068-2-2 2007 Environmental testing - Part 2-2: Tests - EN 60068-2-2 2007
Test B: Dry heat
IEC 60068-2-6 - Environmental testing - Part 2-6: Tests - EN 60068-2-6 -
Test Fc: Vibration (sinusoidal)
IEC 60068-2-27 2008 Environmental testing - Part 2-27: Tests - EN 60068-2-27 2009
Test Ea and guidance: Shock
IEC 60364-7-710 2021 Low-voltage electrical installations - Part 7- HD 60364-7-710 2024
710: Requirements for special installations
or locations - Medical locations
IEC 60529 - Degrees of protection provided by EN 60529 -
enclosures (IP Code)
IEC 60721-3-1 2018 Classification of environmental conditions - EN IEC 60721-3-1 2018
Part 3-1: Classification of groups of
environmental parameters and their
severities - Storage
IEC 60721-3-2 2018 Classification of environmental conditions - EN IEC 60721-3-2 2018
Part 3-2: Classification of groups of
environmental parameters and their
severities - Transportation and Handling
IEC 60721-3-3 2019 Classification of environmental conditions - EN IEC 60721-3-3 2019
Part 3-3: Classification of groups of
environmental parameters and their
severities - Stationary use at
weatherprotected locations
IEC 60947-5-1 2016 Low-voltage switchgear and controlgear - EN 60947-5-1 2017
Part 5-1: Control circuit devices and
switching elements - Electromechanical
control circuit devices
Publication Year Title EN/HD Year
IEC 60947-5-4 2002 Low-voltage switchgear and controlgear - EN 60947-5-4 2003
Part 5-4: Control circuit devices and
switching elements - Method of assessing
the performance of low-energy contacts -
Special tests
+ A1 2019 + A1 2019
IEC 61010-1 2010 Safety requirements for electrical EN 61010-1 2010
equipment for measurement, control, and
laboratory use - Part 1: General
requirements
+ A1 (mod) 2016 + A1 2019
IEC 61010-2-030 - Safety requirements for electrical EN IEC 61010-2- -
equipment for measurement, control, and 030
laboratory use - Part 2-030: Particular
requirements for equipment having testing
or measuring circuits
IEC 61010-031 - Safety requirements for electrical EN IEC 61010-031 -
equipment for measurement, control, and
laboratory use - Part 031: Safety
requirements for hand-held and hand-
manipulated probe assemblies for
electrical test and measurement
IEC 61010-2-032 - Safety requirements for electrical EN IEC 61010-2- -
equipment for measurement, control, and 032
laboratory use - Part 2-032: Particular
requirements for hand-held and hand-
manipulated current sensors for electrical
test and measurement
IEC 61140 - Protection against electric shock - EN 61140 -
Common aspects for installation and
equipment
IEC 61326-1 2020 Electrical equipment for measurement, EN IEC 61326-1 2021
control and laboratory use - EMC
requirements - Part 1: General
requirements
IEC 61326-2-2 - Electrical equipment for measurement, EN IEC 61326-2-2 -
control and laboratory use - EMC
requirements - Part 2-2: Particular
requirements - Test configurations,
operational conditions and performance
criteria for portable testing, measuring and
monitoring equipment used in low-voltage
distribution systems
IEC 61326-2-4 - Electrical equipment for measurement, EN IEC 61326-2-4 -
control and laboratory use - EMC
requirements - Part 2-4: Particular
requirements - Test configurations,
operational conditions and performance
criteria for insulation monitoring devices
according to IEC 61557-8 and for
equipment for insulation fault location
according to IEC 61557-9
Publication Year Title EN/HD Year
IEC 61557-1 2019 Electrical safety in low voltage distribution EN IEC 61557-1 2021
systems up to 1 000 V AC and 1 500 V DC
- Equipment for testing, measuring or
monitoring of protective measures - Part 1:
General requirements
IEC 61557-8 2014 Electrical safety in low voltage distribution EN 61557-8 2015
systems up to 1 000 V a.c. and 1 500 V
d.c. - Equipment for testing, measuring or
monitoring of protective measures - Part 8:
Insulation monitoring devices for IT
systems
IEC 61810-2 2017 Electromechanical elementary relays - Part EN 61810-2 2017
2: Reliability
IEC 61557-9 ®
Edition 4.0 2023-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical safety in low voltage distribution systems up to 1 000 V AC and

1 500 V DC – Equipment for testing, measuring or monitoring of protective

measures –
Part 9: Equipment for insulation fault location in IT systems

Sécurité électrique dans les réseaux de distribution basse tension au plus égale

à 1 000 V C.A et 1 500 V C.C – Dispositifs de contrôle, de mesure ou de

surveillance de mesures de protection –

Partie 9: Dispositifs de localisation de défauts d'isolement pour réseaux IT

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40  ISBN 978-2-8322-7836-9

– 2 – IEC 61557-9:2023 © IEC 2023
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 9
3.1 Terms, definitions, symbols and units . 9
3.2 Abbreviated terms and symbols . 12
4 Requirements . 13
4.1 General requirements . 13
4.2 Functions provided by an IFLS . 14
4.2.1 Location warning . 14
4.2.2 Local location warning (LLW) . 14
4.2.3 Remote location warning (RLW). 14
4.3 Optional functions provided by IFLS . 14
4.3.1 Indication of the insulation value . 14
4.3.2 Alarm in case of the interruption of the loss of the connection to the
locating current sensor (LCS) . 14
4.3.3 Self-test . 14
4.4 Performance requirements . 15
4.4.1 Response sensitivity . 15
4.4.2 Locating current I and locating voltage U . 15
L L
4.4.3 Permanently admissible nominal voltage U . 15
pa
4.4.4 Supply voltage U . 16
s
4.5 Safety requirements . 16
4.5.1 Clearance and creepage distances . 16
4.5.2 Protection class and earth connection of the IFLS . 16
4.6 Electromagnetic compatibility . 16
4.7 Mechanical requirements . 16
4.7.1 Product mechanical robustness . 16
4.7.2 IP protection class requirements . 16
4.8 Climatic environmental conditions . 17
5 Marking and operating instructions . 17
5.1 Marking . 17
5.2 Operating instructions . 17
6 Tests . 18
6.1 General . 18
6.2 Type tests . 18
6.2.1 Climatic tests . 18
6.2.2 Test of response sensitivity of the IFLS . 19
6.2.3 Test of the locating current I and locating voltage U . 20
L L
6.2.4 Test of the location warning . 23
6.2.5 Test of the indication of the insulation value . 23
6.2.6 Verification of insulation coordination . 23
6.2.7 Test of the electromagnetic compatibility (EMC) . 23
6.2.8 Test of the loss of LCS connection . 23
6.2.9 Test of the protection class and of the earth connection of the IFLS . 23
6.2.10 Inspection of the marking and operating instructions . 23

IEC 61557-9:2023 © IEC 2023 – 3 –
6.2.11 Mechanical test . 23
6.2.12 Record of the type test . 24
6.3 Routine tests. 24
6.3.1 General . 24
6.3.2 Voltage test . 24
6.3.3 Recording of routine tests . 24
7 Overview of requirements and tests for IFLS . 25
Annex A (normative) Insulation fault location system in medical locations (MED-IFLS) . 26
A.1 General . 26
A.2 Requirements . 26
A.2.1 General . 26
A.2.2 Performance requirements . 26
A.2.3 Electromagnetic compatibility . 26
A.3 Additional tests . 27
A.3.1 General . 27
A.3.2 Test of the performance requirements . 27
A.3.3 Test of the response time . 27
A.3.4 Test of the electromagnetic compatibility (EMC) . 27
Annex B (normative) Portable equipment for insulation fault location . 29
B.1 General . 29
B.2 Additional requirements . 29
B.2.1 General . 29
B.2.2 Performance requirements . 29
B.3 Marking and operating instructions . 29
B.4 Additional tests . 29
Annex C (informative) Example of an IFLS and explanation of upstream and
downstream system leakage capacitances . 30
C.1 Examples for the functions of an IFLS . 30
C.2 Upstream and downstream system leakage capacitance . 32
Bibliography . 33

Figure 1 – Test configuration: I driven directly from the system to be monitored . 21
L
Figure 2 – Test configuration: Active locating source . 22
Figure 3 – Test configuration for current testing: Active locating source is used with a
locating voltage above 50 V AC RMS and 70 V peak or 120 V DC . 22
Figure C.1 – Example of an IFLS . 31
Figure C.2 – Explanation of upstream and downstream system leakage capacitance . 32

Table 1 – Abbreviated terms and symbols . 12
Table 2 – Minimum IP requirements for IFLS . 17
Table 3 – Reference conditions for testing . 18
Table 4 – Climatic tests in operation . 19
Table 5 – Climatic tests for storage . 19
Table 6 – List of test conditions (TC) . 19
Table 7 – Product mechanical test . 24
Table 8 – Requirements and tests on IFLSs . 25

– 4 – IEC 61557-9:2023 © IEC 2023
Table A.1 – Additional requirements applicable to MED-IFLS . 27
Table A.2 – Emission test for MED-IFLS . 28

IEC 61557-9:2023 © IEC 2023 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION SYSTEMS UP
TO 1 000 V AC AND 1 500 V DC – EQUIPMENT FOR TESTING, MEASURING
OR MONITORING OF PROTECTIVE MEASURES –

Part 9: Equipment for insulation fault location in IT systems

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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 61557-9 has been prepared by IEC technical committee 85: Measuring equipment for
electrical and electromagnetic quantities. It is an International Standard.
This fourth edition cancels and replaces the third edition published in 2014. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) new terms and definitions on maximum admissible locating AC and DC currents and
voltages;
b) the requirements on locating current and locating voltage have been revised;

– 6 – IEC 61557-9:2023 © IEC 2023
c) performance requirements have been added;
d) the test requirements for locating current and locating voltage have been revised;
e) the structure of this document has been adapted to that of IEC 61557-1:2019;
f) the limit values under Clause A.2 were adapted to fit the changed test methods in 6.2.3.
The text of this International Standard is based on the following documents:
Draft Report on voting
85/896/FDIS 85/901/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 61557 series, published under the general title Electrical safety in
low voltage distribution systems up to 1 000 V AC and 1 500 V DC – Equipment for testing,
measuring or monitoring of protective measures, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IEC 61557-9:2023 © IEC 2023 – 7 –
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION SYSTEMS UP
TO 1 000 V AC AND 1 500 V DC – EQUIPMENT FOR TESTING, MEASURING
OR MONITORING OF PROTECTIVE MEASURES –

Part 9: Equipment for insulation fault location in IT systems

1 Scope
This part of IEC 61557 specifies the requirements for the insulation fault location system (IFLS)
that localizes insulation faults in any part of the system in unearthed IT AC systems and
unearthed IT AC systems with galvanically connected DC circuits having nominal voltages up
to 1 000 V AC, as well as in unearthed IT DC systems with voltages up to 1 500 V DC,
independent of the measuring principle.
NOTE 1 IT systems are described in IEC 60364-4-41. Further information on insulation fault location can be found
in the following International Standards: IEC 60364-4-41:2005, 411.6 and IEC 60364-4-41:2005/AMD1:2017, 411.6,
and IEC 60364-5-53:2019/AMD1:2020, 531.3.
NOTE 2 This document covers both passive IFLS and active IFLS. Active IFLS can be used in de-energised
systems.
NOTE 3 This document does not cover IMD complying with IEC 61557-8.
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 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-27:2008, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60364-7-710:2021, Low-voltage electrical installations – Part 7-710: Requirements for
special installations or locations – Medical locations
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60721-3-1:2018, Classification of environmental conditions – Part 3-1: Classification of
groups of environmental parameters and their severities – Storage
IEC 60721-3-2:2018, Classification of environmental conditions – Part 3-2: Classification of
groups of environmental parameters and their severities – Transportation and handling
IEC 60721-3-3:2019, Classification of environmental conditions – Part 3-3: Classification of
groups of environmental parameters and their severities – Stationary use at weatherprotected
locations
– 8 – IEC 61557-9:2023 © IEC 2023
IEC 60947-5-1:2016, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
IEC 60947-5-4:2002, Low-voltage switchgear and controlgear – Part 5-4: Control circuit devices
and switching elements – Method of assessing the performance of low-energy contacts –
Special tests
IEC 60947-5-4:2002/AMD1:2019
IEC 61010-1:2010, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 1: General requirements
IEC 61010-1:2010/AMD1:2016
IEC 61010-2-030, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 2-030: Particular requirements for equipment having testing or measuring
circuits
IEC 61010-031, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 031: Safety requirements for hand-held and hand-manipulated probe
assemblies for electrical test and measurement
IEC 61010-2-032, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 2-032: Particular requirements for hand-held and hand-manipulated
current sensors for electrical test and measurement
IEC 61140, Protection against electric shock – Common aspects for installation and equipment
IEC 61326-1:2020, Electrical equipment for measurement, control and laboratory use – EMC
requirements – Part 1: General requirements
IEC 61326-2-2, Electrical equipment for measurement, control and laboratory use – EMC
requirements – Part 2-2: Particular requirements – Test configurations, operational conditions
and performance criteria for portable testing, measuring and monitoring equipment used in
low-voltage distribution systems
IEC 61326-2-4, Electrical equipment for measurement, control and laboratory use – EMC
requirements – Part 2-4: Particular requirements – Test configurations, operational conditions
and performance criteria for insulation monitoring devices according to IEC 61557-8 and for
equipment for insulation fault location according to IEC 61557-9
IEC 61557-1:2019, Electrical safety in low voltage distribution systems up to 1 000 V AC and
1 500 V DC – Equipment for testing, measuring or monitoring of protective measures – Part 1:
General requirements
IEC 61557-8:2014, Electrical safety in low voltage distribution systems up to 1 000 V AC and
1 500 V DC – Equipment for testing, measuring or monitoring of protective measures – Part 8:
Insulation monitoring devices for IT systems
IEC 61810-2:2017, Electromechanical elementary relays – Part 2: Reliability

IEC 61557-9:2023 © IEC 2023 – 9 –
3 Terms, definitions and abbreviated terms
3.1 Terms, definitions, symbols and units
For the purposes of this document, the terms and definitions given in IEC 61557-1, IEC 61557-8
and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
insulation fault location system
IFLS
device, equipment or combination of devices used for insulation fault location in IT systems
Note 1 to entry: IFLS functionality can be used in addition to insulation monitoring functionality. It injects a locating
current between the electrical system and earth and locates the insulation fault.
3.1.2
locating current
I
L
current that is injected by the locating current injector during the location process
Note 1 to entry: The locating current can be generated by:
– an active locating source with a sufficiently large internal impedance using an independent voltage source
different from the system to be monitored, or
– a passive locating current source driven directly from the system to be monitored.
3.1.3
locating voltage
U
L
voltage present at the measuring terminals of the locating current injector during the
measurement when the device has an active locating source
Note 1 to entry: In a fault-free, de-energized system, this represents the voltage present between the terminals of
the locating device to the system to be monitored and the terminals for the connection to the PE conductor.
3.1.4
response sensitivity
value of the locating current or insulation resistance at which the insulation fault locator
responds under specified conditions
Note 1 to entry: Response sensitivity may either be a fixed threshold or a response curve.
3.1.5
insulation fault locator
IFL
device or part of a device, that has the function to locate the insulation fault
3.1.6
locating current sensor
LCS
sensor for the detection of the locating current used for the location of the insulation fault

– 10 – IEC 61557-9:2023 © IEC 2023
3.1.7
locating current injector
LCI
device or part of a device, that has the function to inject the locating current into the IT system
in order to locate the insulation fault
3.1.8
passive locating current injector
PLCI
locating current injector that generates the locating current directly from the system to be
monitored
3.1.9
active locating current injector
ALCI
locating current injector that generates the locating current from a locating voltage source which
is different from the system to be monitored
3.1.10
insulation fault location system in medical location
MED-IFLS
specific insulation fault location equipment dedicated to locating insulation faults in IT systems
of group 2 medical locations
Note 1 to entry: The MED-IFLS is described in IEC 61557-9:2023, Annex A.
Note 2 to entry: Medical locations are defined in IEC 60364-7-710.
3.1.11
response time
t
al
time required by insulation fault location equipment to respond under specified performance
conditions
Note 1 to entry: The requirements for the condition can be found in IEC 61557-9:2023, A.2.2.4.
3.1.12
group 2 medical location
medical location where ME equipment or ME systems are intended to be used intrusively,
externally or invasively to any part of the patient and where discontinuity of the electrical supply,
such as protection against electric shock, represents a risk to the safety of the patient
[SOURCE: IEC 60364-7-710:2021, 710.3.9, modified – "medical location" added to the source
term "group 2".]
3.1.13
portable equipment for insulation fault location
PIFL
equipment used for temporary insulation fault location in IT systems instead of, or in addition
to, fixed installed equipment for insulation fault location
Note 1 to entry: The requirements for PIFL are defined in Annex B of this document.

IEC 61557-9:2023 © IEC 2023 – 11 –
3.1.14
system leakage capacitance for IFLS
C
el
maximum value of the total capacitance to earth of the system to be monitored including any
connected appliances up to which the IFLS can work as specified
Note 1 to entry: The system leakage capacitance is the sum of the leakage capacitances of all phase conductors
including the neutral conductor to earth.
3.1.15
maximum admissible locating AC current
I
limit AC
maximum peak value of the locating current above a pre-set level of frequency
Note 1 to entry: The frequency and current levels are derived from IEC 61140.
3.1.16
maximum admissible locating DC current
I
limit DC
maximum peak value of the locating current below a pre-set level of frequency
Note 1 to entry: The frequency and current levels are derived from IEC 61140.
3.1.17
maximum admissible locating AC voltage
U
limit AC
maximum peak value of the locating voltage above a pre-set level of frequency
Note 1 to entry: The frequency and voltage levels are derived from IEC 61140.
3.1.18
maximum admissible locating DC voltage
U
limit DC
maximum peak value of the locating voltage below a pre-set level of frequency
Note 1 to entry: The frequency and voltage levels are derived from IEC 61140.
3.1.19
injection resistance
R
i
resistance of the locating current injector between the injection terminal and the earth terminal
3.1.20
injection impedance
Z
i
total impedance of the locating current injector between the injection terminal and the earth
terminal, measured at the nominal frequency
3.1.21
symmetrical insulation fault
defect in the insulation of an electric installation or equipment creating a resistive path to earth
having approximately the same resistance from all phase conductors to earth
3.1.22
asymmetrical insulation fault
defect in the insulation of an electric installation or equipment creating a resistive path to earth
having different resistances from all phase conductors to earth

– 12 – IEC 61557-9:2023 © IEC 2023
3.2 Abbreviated terms and symbols
The abbreviated terms and symbols listed in Table 1 apply to this document.
Table 1 – Abbreviated terms and symbols
Abbreviated term or Explanation
symbol
C System leakage capacitance downstream of the locating current sensor
Ld
C System leakage capacitance upstream of the locating current sensor
Lu
C
System leakage capacitance for IFLS
el
EMC Electromagnetic compatibility
FE Functional earth terminal
g Standard acceleration of free fall
n
IFL Insulation fault locator
IFLS Insulation fault location system
I Locating current
L
IMD Insulation monitoring device
IP Degree of protection of enclosure
LCI Locating current injector
LCS Locating current sensor
LLW Local location warning
PE Protective earth conductor
PIFL Portable equipment for insulation fault location
PLCI Passive locating current injector
ALCI Active locating current injector
PLCS Portable locating current sensor
Q Quality factor
R Insulation resistance
F
RLW Remote location warning
RMS Root-mean-square value, effective value
T Transformer in an IT system
I Maximum admissible locating AC current
limit AC
I Maximum admissible locating DC current
limit DC
U
Maximum admissible locating AC voltage
limit AC
U Maximum admissible locating DC voltage
limit DC
MED-IFLS Insulation fault location system in medical locations
t Response time
al
RLW Remote location warning
µF Microfarad
The farad (symbol: F) is the SI derived unit of electrical capacitance.
1 μF (microfarad, one millionth (10−6) of a farad)
U Formula symbol for a voltage in the SI unit volt
U
Calculated voltage for the locating voltage assessment
U Measured voltage for the locating current assessment
B
IEC 61557-9:2023 © IEC 2023 – 13 –
Abbreviated term or Explanation
symbol
U
Locating voltage
L
U Permanently admissible nominal voltage
pa
U Nominal system voltage
n
U Supply voltage
s
MΩ megaohm
The ohm (symbol: Ω) is the SI derived unit of electrical resistance. 1 MΩ (megohm)
corresponds to one million ohms
Z Injection impedance
i
Total impedance of IFLS between the terminals to the system and earth, measured at
the rated frequency f
N
R Injection resistance
i
R First resistance of the voltage divider
H
R Second resistance of the voltage divider
T
R
First resistance of the voltage divider representing resistance of human skin
S
R Second resistance of the voltage divider representing resistance of a human body
B
C Capacitance of anti-aliasing filter
f
µs Microsecond
The second (symbol: s) is the base unit of time in the International System of Units
(SI).
Fc Test Fc: Vibration (sinusoidal)
Ea Test Ea and guidance: Shock
nF nanofarad
The farad (symbol: F) is the SI derived unit of electrical capacitance.

4 Requirements
4.1 General requirements
Equipment for insulation fault location shall be capable of localizing symmetrical insulation
faults as well as asymmetrical insulation faults in an IT system and to give a location warnin
...