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 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. IEC 61557-9:2023 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;
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.

Sécurité électrique dans les réseaux de distribution basse tension au plus égale à 1 000 V en C.A et 1 500 V en 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

L'IEC 61557-9:2023 spécifie les exigences applicables aux dispositifs de localisation de défauts d’isolement (DLD) qui, indépendamment du principe de mesure, peuvent localiser les défauts d’isolement des parties de réseaux IT à courant alternatif non mis à la terre et des réseaux IT à courant alternatif non mis à la terre comprenant des circuits à courant continu reliés galvaniquement dont les tensions nominales sont au plus égales à 1 000 V en courant alternatif, et de réseaux IT à courant continu non mis à la terre dont les tensions sont au plus égales à 1 500 V en courant continu. L'IEC 61557-9:2023 annule et remplace la troisième édition parue en 2014. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
a) ajout de nouveaux termes et de nouvelles définitions sur les courants et tensions, alternatifs et continus, de localisation maximaux admissibles;
b) révision des exigences relatives au courant de localisation et à la tension de localisation;
c) ajout d’exigences de performance;
d) révision des exigences d’essai pour le courant de localisation et la tension de localisation;
e) modification de la structure du présent document pour s’adapter à l’IEC 61557-1:2019;
f) modification des valeurs limites de l’Article A.2 pour s’adapter aux méthodes d’essai modifiées en 6.2.3.

General Information

• Status: Published
• Publication Date: 13-Dec-2023
• ICS: 25.040.40 - Industrial process measurement and control
• Technical Committee: TC 85 - Measuring equipment for electrical and electromagnetic quantities
• Drafting Committee: WG 8 - TC 85/WG 8
• Current Stage: PPUB - Publication issued
• Start Date: 14-Dec-2023
• Completion Date: 15-Dec-2023

Relations

• Revises: IEC 61557-9:2014 - Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 9: Equipment for insulation fault location in IT systems
• Effective Date: 05-Sep-2023
• Revises: IEC 61557-9:2014/COR1:2016 - Corrigendum 1 - Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 9: Equipment for insulation fault location in IT systems
• Effective Date: 05-Sep-2023
• Revises: IEC 61557-9:2014/COR2:2017 - Corrigendum 2 - Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 9: Equipment for insulation fault location in IT systems
• Effective Date: 05-Sep-2023

Overview

IEC 61557-9:2023 - part of the IEC 61557 series on electrical safety in low-voltage distribution systems - specifies requirements for Insulation Fault Location Systems (IFLS) used to localize insulation faults in unearthed IT systems. The standard covers IFLS for unearthed IT AC systems (and AC systems with galvanically connected DC circuits) up to 1 000 V AC, and unearthed IT DC systems up to 1 500 V DC, and is independent of the measuring principle used. Edition 4.0 (2023) supersedes the 2014 edition and contains technical revisions to definitions, performance and test requirements, and document structure.

Key topics and technical requirements

• Mandatory and optional functions: Specifies required functions such as location warning, local and remote location warnings (LLW / RLW), and optional features like insulation value indication and self-test.
• Performance requirements: Defines response sensitivity and permissible locating current and locating voltage limits; performance test criteria were newly added in this edition.
• Safety and insulation coordination: Requirements for clearance/creepage distances, protection class, earth connection and permanently admissible voltages.
• Environmental and mechanical requirements: Climatic, mechanical robustness and IP protection class requirements to ensure reliable operation in intended environments.
• Electromagnetic compatibility (EMC): EMC limits and testing applicable to IFLS products, with specific provisions for medical locations (MED‑IFLS).
• Testing and verification: Detailed type and routine tests covering locating current/voltage, response sensitivity, location warning function, loss of sensors, marking and instructions, and record keeping. The structure is aligned with IEC 61557-1:2019.
• Annexes: Normative annexes for medical locations (MED-IFLS) and for portable IFLS, plus an informative annex explaining leakage capacitances and example IFLS layouts.

Practical applications

• Locating insulation faults in unearthed IT systems to support electrical safety and continuity of service in:
  • Industrial plants and process installations
  • Power distribution within buildings and complexes
  • Renewable energy and DC microgrids using unearthed architectures
  • Medical locations (special MED‑IFLS requirements)
• Enhances maintenance, reduces downtime and helps comply with electrical safety regimes by providing clear requirements for equipment performance, testing and documentation.

Who should use this standard

• Manufacturers and designers of IFLS equipment
• Test laboratories and certification bodies performing type and routine tests
• Electrical safety engineers, installers and maintenance teams working with unearthed IT AC/DC systems
• Facility managers and medical-planning engineers specifying equipment for critical installations

Related standards

• IEC 61557 series (general requirements for equipment for testing, measuring or monitoring protective measures)
• IEC 61557-1:2019 (general requirements and structure alignment)

Keywords: IEC 61557-9, insulation fault location, IFLS, IT systems, unearthed IT, locating current, locating voltage, electrical safety, low voltage distribution.

Standards Content (Sample)

IEC 61557-9 ®
Edition 4.0 2023-12
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
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
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.
IEC Secretariat Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.
IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 19 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary
(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC 61557-9 ®
Edition 4.0 2023-12
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
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
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40 ISBN 978-2-8322-8055-3
– 2 – IEC 61557-9:2023 CMV © 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 Mandatory 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 . 15
4.3.1 Indication of the insulation value . 15
Performance of the IFLS Alarm in case of the interruption of the loss of
the connection to the locating current sensor (LCS) . 15
4.3.3 Self-test . 15
4.4 Performance requirements . 15
4.4.1 Response sensitivity . 15
Locating current I
L .
Locating voltage U
L .
4.4.2 Locating current I and locating voltage U . 16
L L
4.4.3 Permanently admissible nominal voltage U . 16
pa
4.4.4 Supply voltage U . 16
s
4.5 Safety requirements . 17
General .
4.5.1 Clearance and creepage distances . 17
4.5.2 Protection class and earth connection of the IFLS . 17
4.6 Electromagnetic compatibility . 17
4.7 Mechanical requirements . 18
General .
4.7.1 Product mechanical robustness. 18
IP protection class requirements . 19
4.8 Climatic environmental conditions . 19
5 Marking and operating instructions . 19
5.1 Marking . 19
5.2 Operating instructions . 19
6 Tests . 20
6.1 General . 20
6.2 Type tests . 21
General .
6.2.1 Climatic tests . 21
Test of response sensitivity of the IFLS . 21
Test of the locating current I and locating voltage U . 22
L L
Test of the locating voltage U
L .

Test of the location warning . 28
Test of the indication of the insulation value . 28
6.2.6 Verification of insulation coordination . 28
Test of the performance of the LCI .
Voltage test .
Test of the electromagnetic compatibility (EMC) . 28
Test of the loss of LCS connection . 28
Test of the protection class and of the earth connection of the IFLS . 28
Inspection of the marking and operating instructions . 28
Mechanical test . 29
6.2.12 Record of the type test . 29
6.3 Routine tests . 29
General . 29
Test of the response sensitivity .
Test of the location warning .
Test of the self-test function .
Voltage test . 30
Compliance with the tests of Clause 6 .
6.3.3 Recording of routine tests . 30
7 Overview of requirements and tests for IFLS . 30
Annex A (normative) Equipment for Insulation fault location system in medical
locations (MED-IFLS) . 32
A.1 Scope General . 32
A.2 Requirements . 32
A.2.1 General . 32
A.2.2 Performance requirements . 32
A.2.3 Electromagnetic compatibility . 33
A.3 Marking and operating instructions .
A.4 Tests .
A.3 Additional tests . 34
A.3.1 General . 34
A.3.2 Test of the performance requirements . 34
A.3.3 Test of the response time . 34
A.3.4 Test of the electromagnetic compatibility (EMC) . 34
Annex B (normative) Portable equipment for insulation fault location . 36
B.1 Scope General . 36
B.2 Additional requirements . 36
B.2.1 General . 36
B.2.2 Performance requirements . 36
B.3 Marking and operating instructions . 36
B.4 Additional tests . 36
Annex C (informative) Example of an IFLS and explanation of upstream and
downstream system leakage capacitances . 38
C.1 Examples for the functions of an IFLS . 38
C.2 Upstream and downstream system leakage capacitance . 40
Bibliography . 41
List of comments . 42

– 4 – IEC 61557-9:2023 CMV © IEC 2023
Figure 1 – Test configuration: I driven directly from the system to be monitored . 25
L
Figure 2 – Test configuration: Independent locating voltage source with a locating
voltage equal or below 50 V a.c. or 120 V d.c. .
Figure 2 – Test configuration: Active locating source . 26
Figure 3 – Test configuration: Independent voltage source is used with a locating
voltage above 50 V a.c. or 120 V d.c.
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 . 27
Figure C.1 – Example of an IFLS . 39
Figure C.2 – Explanation of upstream and downstream system leakage capacitance . 40

Table 1 – Abbreviated terms and symbols . 12
Table 2 – Product mechanical requirements .
Table 2 – Minimum IP requirements for IFLS . 19
Table 3 – Reference conditions for testing . 21
Table 4 – Reference conditions for tests in operation Climatic tests in operation . 21
Table 5 – Reference conditions for storage tests Climatic tests for storage . 21
Table 6 – List of test conditions (TC) . 22
Table 7 – Product mechanical test . 29
Table 8 – Requirements and tests on IFLSs . 31
Table A.1 – Additional requirements applicable to equipment for insulation fault
location in medical locations .
Table A.2 – Emission test for equipment for insulation fault location in medical
locations .
Table A.1 – Additional requirements applicable to MED-IFLS . 35
Table A.2 – Emission test for MED-IFLS . 35

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.
This commented version (CMV) of the official standard IEC 61557-9:2023 edition 4.0
allows the user to identify the changes made to the previous IEC 61557-9:2014
edition 3.0. Furthermore, comments from IEC TC 85 experts are provided to explain the
reasons of the most relevant changes, or to clarify any part of the content.
A vertical bar appears in the margin wherever a change has been made. Additions are in
green text, deletions are in strikethrough red text. Experts' comments are identified by a
blue-background number. Mouse over a number to display a pop-up note with the
comment.
This publication contains the CMV and the official standard. The full list of comments is
available at the end of the CMV.

– 6 – IEC 61557-9:2023 CMV © IEC 2023
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;
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.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

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 amongst other literature. Additional data for a selection of
devices in other standards should be noted. 1 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 60364-5-53:20012019/AMD1:2020, 2 531.3.
NOTE 2 This document covers both passive IFLS and active IFLS. Active IFLS can be used in de-energised
systems. 3
NOTE 3 This document does not cover IMD complying with IEC 61557-8. 4
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 60364-7-710:20022021, Low-voltage electrical installations of buildings – Part 7-710:
Requirements for special installations or locations – Medical locations
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664 (all parts): Insulation coordination for equipment within low-voltage systems
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

– 8 – IEC 61557-9:2023 CMV © IEC 2023
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
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 andor
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 and test
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 61557-1:20072019, 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
ncy disturbance
CISPR 11, Industrial, scientific and medical equipment - Radio-freque
characteristics - Limits and methods of measurement

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,
where the insulation fault location system is used in addition to an insulation monitoring device
and is used to locate insulation faults 5
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. 5
3.1.2
locating current
I
L
r.m.s. value of the 6 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 independent locating voltage source, or
– an independent locating current source, or
– it can be driven directly from the system to be monitored
– 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. 7
3.1.3
locating voltage
U
L
r.m.s. value of the 8 voltage present at the measuring terminals of the locating current injector
during the measurement when the device has an independent active 9 locating voltage or
current 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 evaluating locating current or insulation resistance at which the evaluator insulation
fault locator responds under specified conditions 10
Note 1 to entry: Response sensitivity can may either be a fixed threshold or a response curve.
3.1.5
insulation fault locator
IFL
device or part of a device for the location of, that has the function to locate 11 the insulation
fault
– 10 – IEC 61557-9:2023 CMV © IEC 2023
3.1.6
locating current sensor
LCS
sensor for the detection of the locating current used for the location of the insulation fault
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 independent different 12 from the system to be monitored
3.1.10
equipment for 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 complying with Annex A
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. 13
3.1.11
response time
t
al
time required by insulation fault location equipment to respond under the conditions of A.2.2.4
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 locations, where applied parts are intended to be used in applications such as
intracardiac procedures, operating theatres and vital treatment, where discontinuity (failure) of
the supply can cause danger to life
Note 1 to entry: An intracardiac procedure is a procedure, whereby an electrical conductor is placed within the
cardiac zone of a patient or is likely to come into contact with the heart, such conductor being accessible outside the
patient's body. In this context, an electrical conductor includes insulated wires, such as cardiac pacing electrodes or
intracardiac ECG-electrodes, or insulated tubes filled with conducting fluids.
[SOURCE: IEC 60364-7-710:2002, 710.3.7]
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".] 14 15
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 insulation fault location equipment equipment for insulation fault location
Note 1 to entry: The requirements for PIFL are defined in Annex B of this document.
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. 16
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. 17
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. 17
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. 18
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. 18
3.1.19
injection resistance
R
i
resistance of the locating current injector between the injection terminal and the earth terminal 19
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 19

– 12 – IEC 61557-9:2023 CMV © IEC 2023
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 20
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 20
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 Term Explanation Clause Other referenced
or symbol (in this part 9) standard
C System leakage capacitance downstream Figure C.2
Ld
of the evaluating locating current sensor
C System leakage capacitance upstream of Figure C.2
Lu
the evaluating locating current sensor
C System leakage capacitance for IFLS
el
EMC Electromagnetic compatibility 4.5 IEC 60050-
161:1990,
161-01-07
FE Functional earth terminal 4.6.3 IEC 61010-1
g Standard acceleration of free fall
n
IFL Insulation fault locator 3.1.5, C.1
IFLS Insulation fault location system 3.1.1, Annex C
I Locating current 4.4.2, C.1
L
IMD Insulation monitoring device Annex C IEC 61557-8,
3.1.14
IP Degree of protection of enclosure 4.8.3 IEC 60050-
246:2008,
426-04-02
LCI Locating current injector 3.1.7, C.2
LCS Locating current sensor 3.1.6, C.1
LLW Local location warning 4.2.2
PE Protective earth conductor 4.6.3 IEC 60050-
195:1998,
195-02-09
PIFL Portable equipment for insulation fault Annex C
location
PLCI Passive locating current injector
ALCI Active locating current injector
PLCS Portable locating current sensor B.2.2.1
Q Quality factor
R Insulation resistance 6.2.2, C.2 IEC 61557-8, 3.1.2
F
RLW Remote location warning 4.2.3
RMS Root-mean-square value, effective value
T Transformer in an IT system Annex C

Abbreviated term Term Explanation Clause Other referenced
or symbol (in this part 9) standard
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
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
In addition to the requirements of Clause 4 of IEC 61557-1:2007, the requirements of Clause 4
apply. 21
– 14 – IEC 61557-9:2023 CMV © IEC 2023
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 warning if
the insulation resistance in a part of the installation falls below the response sensitivity.
If equipment for insulation fault location has a self-test function, the self-test shall not produce
an insulation fault to earth.
NOTE 1 See also IEC 61557-8.
NOTE 2 Insulation monitoring devices (IMDs) can be deactivated during the location process. 22
NOTE 3 Warning indication can be done by a lamp, a buzzer or by any other kind of indication. 22
NOTE 4 An IFLS can have a self-test function. Checking the response sensitivity is not necessary. 22
NOTE 5 An IFLS with an active locating current source can also be used for insulation fault location in de-energized
systems.
For the requirements of an insulation fault location system in medical locations, see Annex A.
For the requirements of portable equipment for insulation fault location, see Annex B.
4.2 Mandatory Functions provided by an IFLS
4.2.1 Location warning
An IFLS shall contain a visual warning device, which indicates if an insulation fault is detected
or. Alternatively, an IFLS shall allow for connection to such a visual warning device for the
indication of an insulation fault. If externally connectable audible signalling devices are provided,
they may be fitted with a resetting facility. In this case, after clearing an insulation fault or
resetting the device, the audible signal shall sound if a new insulation fault occurs. The location
warning shall be either a local location warning or a remote location warning or both together.
4.2.2 Local location warning (LLW)
This function aims at issuing a warning signal when the insulation resistance between the
system and earth falls below the set response sensitivity value.
This function will include the localization of an insulation fault in an IT system including
symmetrical and asymmetrical insulation faults, an assessment of this fault and a local warning.
A local warning should be made by visual indicators or by additional audible signals generated
by the product implementing the function.
NOTE Usually this function is provided by the IFLS.
4.2.3 Remote location warning (RLW)
This function aims at issuing a remote warning signal if the insulation resistance between the
system and earth falls below the response sensitivity.
This function will include the localization of an insulation fault in an IT system including
symmetrical and asymmetrical insulation faults, an assessment of this fault and a remote
warning.
A relay contact output or an electronic switching output or a data communication can be used
to report the warning remotely.
NOTE The warning output could also can be used in some applications for switching.

4.3 Optional functions provided by IFLS
4.3.1 Indication of the insulation value
When an IFLS includes means for the indication of the insulation value, the uncertainty of the
indicated value shall be stated by the manufacturer.
Performance of the IFLS Alarm in case of the interruption of the loss of the
connection to the locating current sensor (LCS)
If provided an indication if the connection to one or more LCSs is lost in a manner that the
location function is not ensured shall be issued.
When an IFLS includes a periodic verification of the connection to one or more LCSs, an
indication in case of loss of connection shall be provided.
4.3.3 Self-test
An IFLS can have a self-test function. Checking the response sensitivity by the self-test is not
mandatory.
4.4 Performance requirements
4.4.1 Response sensitivity
An IFLS shall be designed in such a manner that the response sensitivity stated
...

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
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Secretariat Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always have
committee, …). It also gives information on projects, replaced access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 19 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc

If you wish to give us your feedback on this publication or need
further assistance, please contact the Customer Service
Centre: [e-mail].
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC -  IEC Products & Services Portal - products.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications. Avec un
en utilisant différents critères (numéro de référence, texte, abonnement, vous aurez toujours accès à un contenu à jour
comité d’études, …). Elle donne aussi des informations sur les adapté à vos besoins.
projets et les publications remplacées ou retirées.

Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au monde,
Restez informé sur les nouvelles publications IEC. Just
avec plus de 22 300 articles terminologiques en anglais et en
Published détaille les nouvelles publications parues.
français, ainsi que les termes équivalents dans 19 langues
Disponible en ligne et une fois par mois par email.
additionnelles. Egalement appelé Vocabulaire

Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
[e-mail].
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

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

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.
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

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.

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
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 warning if
the insulation resistance in a part of the installation falls below the response sensitivity.
If equipment for insulation fault location has a self-test function, the self-test shall not produce
an insulation fault to earth.
For the requirements of an insulation fault location system in medical locations, see Annex A.
For the requirements of portable equipment for insulation fault location, see Annex B.

– 14 – IEC 61557-9:2023 © IEC 2023
4.2 Functions provided by an IFLS
4.2.1 Location warning
An IFLS shall contain a visual warning device, which indicates if an insulation fault is detected.
Alternatively, an IFLS shall allow for connection to such a visual warning device for the
indication of an insulation fault. If externally connectable audible signalling devices are provided,
they may be fitted with a resetting facility. In this case, after clearing an insulation fault or
resetting the device, the audible signal shall sound if a new insulation fault occurs. The location
warning shall be either a local location warning or a remote location warning or both together.
4.2.2 Local location warning (LLW)
This function aims at issuing a warning signal when the insulation resistance between the
system and earth falls below the set response value.
This function will include the localization of an insulation fault in an IT system including
symmetrical and asymmetrical insulation faults, an assessment of this fault and a local warning.
A local warning should be made by visual indicators or by additional audible signals generated
by the product implementing the function.
NOTE Usually this function is provided by the IFLS.
4.2.3 Remote location warning (RLW)
This function aims at issuing a remote warning signal if the insulation resistance between the
system and earth falls below the response sensitivity.
This function will include the localization of an insulation fault in an IT system including
symmetrical and asymmetrical insulation faults, an assessment of this fault and a remote
warning.
A relay contact output or an electronic switching output or a data communication can be used
to report the warning remotely.
NOTE The warning output can be used in some applications for switching.
4.3 Optional functions provided by IFLS
4.3.1 Indication of the insulation value
When an IFLS includes means for the indication of the insulation value, the uncertainty of the
indicated value shall be stated by the manufacturer.
4.3.2 Alarm in case of the interruption of the loss of the connection to the locating
current sensor (LCS)
When an IFLS includes a periodic verification of the connection to one or more LCSs, an
indication in case of loss of connection shall be provided.
4.3.3 Self-test
An IFLS can have a self-test function. Checking the response sensitivity by the self-test is not
mandatory.
4.4 Performance requirements
4.4.1 Response sensitivity
An IFLS shall be designed in such a manner that the response sensitivity stated by the
manufacturer will be met under the specified system conditions, at a total symmetrical system
leakage capacitance of 1 µF upstream of the locating current sensor (C = 1 µF, C = 0 µF
Lu Ld
according to Figure C.2).
Information on the influence of the system leakage capacitances higher than 1 µF on the
response sensitivity as well as possible interference from the distribution system on the
insulation fault location process shall be stated by the manufacturer.
NOTE For additional information about upstream and downstream capacitances, see Annex C.
4.4.2 Locating current I and locating voltage U
L L
If a passive locating current source is used, the locating current I shall be limited to 500 mA
L
RMS. The locating current shall not increase above 500 mA RMS, under foreseeable
component failures in the locating current injector (LCI). When the locating current is adjustable,
unintentional changes of the setting shall be prevented by suitable means.
If an active locating source is used, then there are no additional requirements on the locating
current I when the value of the locating voltage U does not exceed:
L L
– The maximum admissible locating DC voltage U of 120 V peak measured with the
Limit_DC
circuit, which has an equivalent resistance of at least 20 times the injection resistance if the
signal frequency is less than 15 Hz or is DC.
– The maximum admissible locating AC voltage U of 50 V RMS and 70 V peak
Limit_AC
measured with the circuit, which has an equivalent resistance of at least 20 times the
injection resistance, if the signal frequency is greater than or equal to 15 Hz.
For signal frequencies less than 15 Hz or DC, the maximum locating DC current I shall
Limit DC
not exceed 10 mA peak, if the value of the locating voltage U exceeds:
L
– The maximum admissible locating DC voltage U of 120 V peak measured with the
Limit DC
circuit, which has an equivalent resistance of at least 20 times the injection resistance.
For signal frequencies greater than or equal to 15 Hz, the maximum locating AC current I
limit AC
shall not exceed 3,5 mA RMS and 5 mA peak if the value of the locating voltage U exceeds:
L
– The maximum admissible locating AC voltage U of 50 V RMS and 70 V peak
Limit AC
measured with the circuit, which has an equivalent resistance of at least at 20 times the
injection resistance.
Under certain circumstances for the tests in accordance with 6.2.3, injection impedance shall
be considered.
4.4.3 Permanently admissible nominal voltage U
pa
The permanently admissible nominal voltage U shall be at least 105 % of the highest nominal
pa
system voltage U .
n
The permanently admissible nominal voltage U applies between the system connections of
pa
the IFLS and between the system connections and earth.

– 16 – IEC 61557-9:2023 © IEC 2023
If IFLS are applicable in IT systems with frequencies different from the mains nominal frequency,
for example 50 Hz/60 Hz, the manufacturer shall provide information of the permanently
admissible system voltages at the relevant frequency range in the operating instructions.
4.4.4 Supply voltage U
s
For IFLS without separate supply connections w
...