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

IEC 61557-9:2014 specifies the requirements for the insulation fault location system (IFLS) which localizes insulation faults in any part of the system in unearthed IT a.c. systems and unearthed IT a.c. systems with galvanically connected d.c. circuits having nominal voltages up to 1 000 V a.c., as well as in unearthed IT d.c. systems with voltages up to 1 500 V d.c., independent of the measuring principle. 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. This third edition cancels and replaces the second edition published in 2009. This edition constitutes a technical revision which includes the following significant technical changes with respect to the previous edition:
- the scope, normative references, terms and definitions have been complemented;
- abbreviations are listed and explained;
- requirements, marking and operating instructions have been revised;
- mandatory and optional functions have been defined and their terminology has been adapted to IEC 61557-15;
- mechanical requirements have been added;
- Clause 6 "Tests" has been revised; and
- new Tables have been added.
This publication is to be read in conjunction with IEC 61557-1:2007. The contents of the corrigenda of May 2016 and of January 2017 have been included in this copy.

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

L'IEC 61557-9:2014 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. Les réseaux IT sont décrits entre autres dans l'IEC 60364-4-41. Il convient de noter que, pour le choix des appareils, des indications supplémentaires sont données dans d'autres normes. Cette troisième édition annule et remplace la deuxième édition parue en 2009. Elle constitue une révision technique qui inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- le domaine d'application, les références normatives, les termes et définitions ont été complétés;
- énumération et explication des abréviations;
- les exigences de marquage, les instructions de fonctionnement ont été révisées;
- définition des fonctions obligatoires et facultatives et adaptation de leur terminologie à l'IEC 61557-15;
- ajout d'exigences mécaniques;
- l'Article 6 "Essais" a été révisé;
- et des nouveaux Tableaux ont été ajoutés.
Cette publication doit être lue conjointement avec la CEI 61557-1:2007. Le contenu des corrigendas de mai 2016 et de janvier 2017 a été pris en considération dans cet exemplaire.

General Information

• Status: Published
• Publication Date: 10-Dec-2014
• 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: DELPUB - Deleted Publication
• Start Date: 14-Dec-2023
• Completion Date: 30-Jul-2021

Relations

• Corrected By: 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
• Corrected By: 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
• Revised: 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
• Effective Date: 05-Sep-2023
• Revises: IEC 61557-9:2009 - Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 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 61557-9:2014 is an international standard published by the International Electrotechnical Commission (IEC) focusing on electrical safety within low voltage distribution systems. Specifically, it addresses equipment used for testing, measuring, or monitoring protective measures related to insulation fault location in unearthed IT systems. This standard applies to systems with nominal voltages up to 1,000 V alternating current (a.c.) and 1,500 V direct current (d.c.).

The document specifies requirements for insulation fault location systems (IFLS) that identify insulation faults anywhere in unearthed IT a.c. systems, unearthed IT a.c. systems coupled with galvanically connected d.c. circuits, and unearthed IT d.c. systems. The third edition from 2014 replaces earlier versions, introducing enhanced scope, normative references, definitions, mechanical requirements, testing procedures, and revised marking and operating instructions.

Key Topics

• Scope and Normative References
  Defines application range covering insulation fault location in low voltage IT systems and cites related IEC documents such as IEC 61557-1:2007 and IEC 60364-4-41.

• Terms, Definitions, and Abbreviations
  Provides a comprehensive glossary essential for understanding technical terminology related to insulation fault location systems, including definitions for location warnings, locating currents, and insulation values.

• Mandatory and Optional Functions
  Details mandatory features IFLS must provide:

  • Location Warning
  • Local Location Warning (LLW)
  • Remote Location Warning (RLW)

  Optional functions include indications of insulation values and performance under sensor disconnection scenarios.

• Performance Requirements
  Sets criteria for response sensitivity, locating current, locating voltage, electromagnetic compatibility (EMC), safety requirements (including clearance, creepage distances, protection classes), climatic and mechanical robustness.

• Marking and Operating Instructions
  Specifies essential product markings and operation guidance to ensure correct use and maintenance of insulation fault location equipment.

• Testing Procedures
  Outlines mandatory type tests, routine tests, and detailed test methods measuring sensitivity, locating current and voltage, electromagnetic compatibility, and mechanical durability to guarantee reliability and safety.

• Annexes
  Includes specialized requirements and tests for portable equipment and medical locations where IT systems insulation fault location demands additional considerations.

Applications

IEC 61557-9:2014 is crucial for industries and professionals involved with:

• Electrical safety management in hospitals, data centers, industrial plants, and other facilities with IT power distribution systems.
• Design and manufacturing of insulation fault location equipment intended for low voltage IT systems.
• Installation and maintenance of unearthed electrical distribution networks where timely detection of insulation faults is required to maintain operational continuity and prevent hazards.
• Testing laboratories and certification bodies validating conformity of IFLS devices with international safety and performance standards.
• Facility engineers and electricians responsible for monitoring insulation integrity to enhance system availability and safety.

By adhering to IEC 61557-9, users can assure effective fault localization, minimization of downtime, and compliance with internationally recognized electrical safety protocols.

Related Standards

• IEC 61557-1:2007 - General requirements for testing and measuring equipment for protective measures.
• IEC 60364-4-41 - Low voltage electrical installations - Protection for safety: Protection against electric shock.
• IEC 61557-15 - Additional terms and definitions related to insulation monitoring and fault location.
• Additional parts of IEC 61557 covering insulation monitoring devices, insulation resistance measuring instruments, and other protective devices.

Keywords

Electrical safety, low voltage distribution systems, insulation fault location, IT systems, IEC 61557-9, unearthed systems, insulation fault location system (IFLS), low voltage testing equipment, electrical fault detection, insulation resistance monitoring, protective measure equipment, IEC standards, electrical testing compliance.

Standards Content (Sample)

IEC 61557-9 ®
Edition 3.0 2014-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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

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

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IEC 61557-9 ®
Edition 3.0 2014-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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

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
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 25.040.40 ISBN 978-2-8322-1976-8

– 2 – IEC 61557-9:2014 © IEC 2014
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviations . 8
3.1 Terms, definitions, symbols and units . 8
3.2 Abbreviations . 10
4 Requirements . 10
4.1 General requirements . 10
4.2 Mandatory functions provided by an IFLS . 11
4.2.1 Location warning . 11
4.2.2 Local location warning (LLW) . 11
4.2.3 Remote location warning (RLW). 11
4.3 Optional functions provided by IFLS . 12
4.3.1 Indication of the insulation value . 12
4.3.2 Performance of the IFLS in case of the interruption of the connection to
the locating current sensor (LCS) . 12
4.4 Performance requirements . 12
4.4.1 Response sensitivity . 12
4.4.2 Locating current I . 12
L
4.4.3 Locating voltage U . 12
L
4.5 Electromagnetic compatibility (EMC) . 12
4.6 Safety requirements . 12
4.6.1 General . 12
4.6.2 Clearances and creepage distances . 13
4.6.3 Protection class and earth connection of the IFLS . 13
4.7 Climatic environmental conditions . 13
4.8 Mechanical requirements . 13
4.8.1 General . 13
4.8.2 Product mechanical robustness . 13
4.8.3 IP protection class requirements . 14
5 Marking and operating instructions . 15
5.1 Marking . 15
5.2 Operating instructions . 15
6 Tests . 16
6.1 General . 16
6.2 Type tests . 16
6.2.1 General . 16
6.2.2 Test of response sensitivity of the IFLS . 16
6.2.3 Test of the locating current I . 17
L
6.2.4 Test of the locating voltage U . 17
L
6.2.5 Test of the location warning . 19
6.2.6 Test of the indication of the insulation value . 19
6.2.7 Test of the performance of the LCI . 19
6.2.8 Voltage test . 19
6.2.9 Test of the electromagnetic compatibility (EMC) . 19
6.2.10 Test of the loss of LCS connection . 19

6.2.11 Test of the protection class and the earth connection of the IFLS . 19
6.2.12 Inspection of the marking and operating instructions . 20
6.2.13 Mechanical test . 20
6.2.14 Record of the type test . 20
6.3 Routine tests. 20
6.3.1 General . 20
6.3.2 Test of the response sensitivity. 20
6.3.3 Test of the location warning . 20
6.3.4 Test of the self-test function . 20
6.3.5 Voltage test . 20
6.3.6 Compliance with the tests of Clause 6 . 21
7 Overview of requirements and tests for IFLSs . 21
Annex A (normative) Equipment for insulation fault location in medical locations . 22
A.1 Scope . 22
A.2 Requirements . 22
A.2.1 General . 22
A.2.2 Performance requirements . 22
A.2.3 Electromagnetic compatibility (EMC) . 22
A.3 Marking and operating instructions . 22
A.4 Tests . 23
A.4.1 General . 23
A.4.2 Type tests . 23
Annex B (normative) Portable equipment for insulation fault location . 24
B.1 Scope . 24
B.2 Requirements . 24
B.2.1 General . 24
B.2.2 Performance requirements . 24
B.3 Marking and operating instructions . 24
B.4 Tests . 24
Annex C (informative) Example of an IFLS and explanation of upstream and
downstream system leakage capacitances . 26
C.1 Examples of an IFLS . 26
C.2 Upstream and downstream system leakage capacitance . 28
Bibliography . 29

Figure 1 – Test configuration: I driven directly from the system to be monitored . 18
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. . 18
Figure 3 – Test configuration: Independent voltage source is used with a locating
voltage above 50 V a.c. or 120 V d.c. 19
Figure C.1 – Example of an IFLS . 27
Figure C.2 – Explanation of upstream and downstream system leakage capacitance . 28

Table 1 – Abbreviations . 10
Table 2 – Product mechanical requirements . 14
Table 3 – Minimum IP requirements for IFLS . 15
Table 4 – Reference conditions for tests in operation . 16
Table 5 – Reference conditions for storage tests . 16

– 4 – IEC 61557-9:2014 © IEC 2014
Table 6 – Requirements and tests on IFLSs . 21
Table A.1 – Additional requirements applicable to equipment for insulation fault
location in medical locations . 23
Table A.2 – Emission test for equipment for insulation fault location in medical
locations . 23

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
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indispensable for the correct application of this publication.
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61557-9 has been prepared by IEC technical committee 85:
Measuring equipment for electrical and electromagnetic quantities.
This third edition cancels and replaces the second edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the scope, normative references, terms and definitions have been complemented;
b) abbreviations are listed and explained;
c) requirements, marking and operating instructions have been revised;
d) mandatory and optional functions have been defined and their terminology has been
adapted to IEC 61557-15;
– 6 – IEC 61557-9:2014 © IEC 2014
e) mechanical requirements have been added;
f) Clause 6 “Tests” has been revised;
g) new Tables have been added.
The text of this standard is based on the following documents:
FDIS Report on voting
85/486/FDIS 85/503/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This part of IEC 61557 shall be used in conjunction with Part 1.
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 a.c. and 1 500 V d.c. – 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 publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigenda 1 (May 2016) and 2 (January 2017) have been included in
this copy.
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) which localizes insulation faults in any part of the system in unearthed IT a.c. systems
and unearthed IT a.c. systems with galvanically connected d.c. circuits having nominal
voltages up to 1 000 V a.c., as well as in unearthed IT d.c. systems with voltages up to
1 500 V d.c., independent of the measuring principle.
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.
NOTE Further information on insulation fault location can be found in the following standards:
IEC 60364-4-41:2005, 411.6, and IEC 60364-5-53:2001, 531.3.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, 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, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60364-7-710:2002, Electrical installations of buildings – Part 7-710: Requirements for
special installations or locations – Medical locations
IEC 60529, Degree of protection provided by enclosures (IP Code)
IEC 60664 (all parts): Insulation coordination for equipment within low-voltage systems
IEC 60721-3-1, Classification of environmental conditions – Part 3: Classification of groups of
environmental parameters and their severities – Section 1: Storage
IEC 60721-3-2, Classification of environmental conditions – Part 3: Classification of groups of
environmental parameters and their severities – Section 2: Transportation
IEC 60721-3-3, Classification of environmental conditions – Part 3-3: Classification of groups
of environmental parameters and their severities – Stationary use at weatherprotected
locations
– 8 – IEC 61557-9:2014 © IEC 2014
IEC 61010-1:2010, Safety requirements for electrical equipment for measurement, control,
and laboratory use – Part 1: General requirements
IEC 61010-2-030, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 2-030: Particular requirements for testing and measuring circuits
IEC 61010-031, Safety requirements for electrical equipment for measurement, control and
laboratory use – Part 031: Safety requirements for hand-held probe assemblies for
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 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 test, 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 61557-1:2007, 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 1:
General requirements
IEC 61557-8, 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 8:
Insulation monitoring devices for IT systems
CISPR 11, Industrial, scientific and medical equipment - Radio-frequency disturbance
characteristics - Limits and methods of measurement
3 Terms, definitions and abbreviations
3.1 Terms, definitions, symbols and units
For the purposes of this document, the terms and definitions given in IEC 61557-1 and
IEC 61557-8 and the following apply.
3.1.1
insulation fault location system
IFLS
device 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
Note 1 to entry: An IFLS injects a locating current between the electrical system and earth.
3.1.2
locating current
I
L
r.m.s. value of the current that is injected by the locating current injector during the location
process. 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
3.1.3
locating voltage
U
L
r.m.s. value of the voltage present at the measuring terminals of the locating current injector
during the measurement when the device has an independent 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 current or insulation resistance at which the evaluator responds under
specified conditions
Note 1 to entry: Response sensitivity can either be a fixed threshold or a response curve.
3.1.5
insulation fault locator
device or part of a device for the location of the insulation fault
3.1.6
locating current sensor
sensor for the detection of the locating current used for the location of the insulation fault
3.1.7
locating current injector
device or part of a device, which function it is to inject the locating current in the IT system in
order to locate the insulation fault
3.1.8
passive locating current injector
locating current injector that generates the locating current directly from the system to be
monitored
3.1.9
active locating current injector
locating current injector that generates the locating current from a locating voltage source
which is independent from the system to be monitored
3.1.10
equipment for insulation fault location in medical locations
specific insulation fault location equipment dedicated to locating insulations faults in IT
systems of group 2 medical locations complying with Annex A
3.1.11
response time
t
al
time required by insulation fault location equipment to respond under the conditions of A.2.2.4
3.1.12
group 2 medical locations
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

– 10 – IEC 61557-9:2014 © IEC 2014
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]
3.1.13
portable equipment for insulation fault location
equipment used for temporary insulation fault location in IT systems instead of, or additionally,
to fixed installed insulation fault location equipment
3.2 Abbreviations
For the purposes of this document, the terms and abbreviations given in Table 1 apply.
Table 1 – Abbreviations
Abbreviation Term Clause Other referenced standard
(in this part 9)
C System leakage capacitance Figure C.2
Ld
downstream of the evaluating current
sensor
C System leakage capacitance upstream Figure C.2
Lu
of the evaluating current sensor
EMC Electromagnetic Compatibility 4.5 IEC 60050-161:1990, 161-01-
FE Functional Earth 4.6.3 IEC 61010-1
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-
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 4.6.3 IEC 60050-195:1998,
195-02-09
PIFL Portable Insulation Fault Locator Annex C
PLCS Portable Locating Current Sensor B.2.2.1
R Insulation resistance 6.2.2, C.2 IEC 61557-8, 3.1.2
F
RLW Remote Location Warning 4.2.3
T Transformer in an IT system Annex C

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.
Equipment for insulation fault location shall be capable of localizing symmetrical 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.
NOTE 3 Warning indication can be done by a lamp, a buzzer or by any other kind of indication.
NOTE 4 An IFLS can have a self-test function. Checking the response sensitivity is not necessary.
NOTE 5 An IFLS with an active locating current source can also be used for insulation fault location in de-
energized systems.
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 allow connection to such a device for the indication of a fault. If externally connectable
audible signalling devices are provided, they may be fitted with a resetting facility. In this case,
after clearing a fault or resetting the device, the audible signal shall sound if a new 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 functions aims at issuing a warning signal when 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 local
warning.
A local warning should be made by visual indicators or 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 functions 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 be used in some applications for switching.

– 12 – IEC 61557-9:2014 © IEC 2014
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 Performance of the IFLS in case of the interruption 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.
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 the evaluating 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 The system leakage capacitance is the sum of the leakage capacitances of all phase conductors, including
the neutral conductor to PE.
4.4.2 Locating current I
L
The maximum locating current I shall be limited to 500 mA r.m.s., to ensure that the locating
L
current does not produce touch voltages above the conventional voltage limit (50 V a.c.,
120 V d.c.) under the first fault in the distribution system. The locating current shall not
increase above 500 mA r.m.s., 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 voltage U above 50 V a.c. or 120 V d.c. is used the locating current shall
L
not exceed 3,5 mA a.c. (r.m.s.) or 10 mA d.c. through a pure resistance of 2 kΩ.
If an active locating voltage U equal or below 50 V a.c. or 120 V d.c. is used, the locating
L
current shall not exceed 500 mA r.m.s. through a shunt.
4.4.3 Locating voltage U
L
If an active locating voltage or locating current is used, the locating voltage U shall be equal
L
or below 50 V a.c. or 120 V d.c. (see IEC 60364-4-41) under no load conditions.
4.5 Electromagnetic compatibility (EMC)
An IFLS shall comply with the EMC requirements in accordance with IEC 61326-2-4.
4.6 Safety requirements
4.6.1 General
In addition to the safety requirements of IEC 61010-1 and IEC 61010-2-030 the following
safety requirements apply.
4.6.2 Clearances and creepage distances
An IFLS shall have minimum clearances and creepage distances in accordance with
IEC 61010-1 and IEC 61010-2-030.
Clearances and creepage distances for fixed installed equipment according to Table 3 can be
dimensioned in accordance with IEC 60664 series.
Clearances and creepage distances shall be selected for:
– overvoltage or measuring category III or II, depending on the overvoltage or measuring
category in the system to be monitored;
– pollution degree 2.
NOTE Pollution degree 3 can be used for accessible parts on the outside of the housing.
A division into circuits with different nominal insulation voltages is permissible in device
combinations for example for IT systems with nominal voltages U higher than 1 000 V a.c.
n
and 1 500 V d.c., when the electrical connection is made via resistive, capacitive or inductive
voltage dividers and if, in the case of a fault, the occurrence of inadmissibly high touch
voltages or inadmissibly high currents to earth are prevented by circuit design features. Such
circuit design features (see IEC 61140) can be, for example, additionally provided in the form
of reliable voltage dividers or a duplication of the resistors (protective impedance) in the
voltage divider.
4.6.3 Protection class and earth connection of the IFLS
Contrary to IEC 61557-1, the PE connection of an IFLS (LCI) is a measuring connection and
shall be treated as functional earth connection (FE). If the IFLS has accessible parts which
are earthed for protective purposes, these connections shall be treated as protective earth
connections (PE).
4.7 Climatic environmental conditions
The IFLS shall operate at least under the following climatic conditions:
– operation: class 3K5 according to IEC 60721-3-3, -5 °C to +45 °C, except condensation
and formation of ice,
– transport: class 2K3 according to IEC 60721-3-2, -25 °C to +70 °C,
– storage: class 1K4 according to IEC 60721-3-1, -25 °C to +55 °C.
4.8 Mechanical requirements
4.8.1 General
Instead of the requirements of 4.10 of IEC 61557-1:2007 the requirements of 4.8.2 and 4.8.3
apply.
4.8.2 Product mechanical robustness
Requirements of Table 2 shall be tested as type-tests.

– 14 – IEC 61557-9:2014 © IEC 2014
Table 2 – Product mechanical requirements
Mechanical robustness, in Standard and level Test parameters Other information
operation test
Behaviour to vibrations IEC 60068-2-6 2 Hz to 13,2 Hz- amplitude Duration in case of no
resonance condition 9 min
± 1 mm
Test Fc
at 30 Hz.
13,2 Hz to 100 Hz –
Duration at each resonance
acceleration ± 0,7 g.
frequency at which Q ≥ 2 is
For severe vibration
recorded – 90 min.
conditions such as e.g.
diesel engines, air During the vibration test,
compressors etc.: functional tests are to be
carried out.
2,0 Hz to 25,0 Hz –
Tests to be carried out in
amplitude ± 1.6 mm
three mutually
25,0 Hz to 100 Hz –
perpendicular planes.
acceleration ± 4 g
As a guide, it is
NOTE More severe
recommended that Q does
conditions may exist for
not exceed 5.
example on exhaust
Where a sweep test is to be
manifolds of diesel engines
carried out instead of the
especially for medium and
discrete frequency test and
high speed engines Values
a number of resonant
may be required to be in
frequencies are detected
these cases 40 Hz to
close to each other,
2 000 Hz – acceleration
duration of the test is to be
± 10,0g at 600 °C, duration
120 min. Sweep over a
90 min.
restricted frequency range
between 0,8 times and
1.2 times the critical
frequencies can be used
where appropriate.
NOTE Critical frequency is
a frequency at which the
equipment being tested can
exhibit:
– Malfunction and/or
performance
deterioration
– Mechanical resonances
and/or other response
effects occur, e.g.
chatter
Behaviour to shocks IEC 60068-2-27 10 gn / 11 ms, 3 pulses
Test Ea
4.8.3 IP protection class requirements
The manufacturer shall document equipment IP protection class according to IEC 60529. The
minimum requirements are given in Table 3, which specifies minimum IP requirements for the
different kinds of IFLS housings.

Table 3 – Minimum IP requirements for IFLS
Front Housing, except
Kind of IFLS
panel front panel
Fixed installed IFLS IP 40 IP 2X
panel mounted devices.
Fixed installed IFLS IP 40 IP 2X
modular devices snapped on DIN rails within distribution panel.
Fixed installed IFLS IP 2X IP 2X
housing devices snapped on DIN rails within distribution panel.
Portable IFLS IP 40 IP 40
5 Marking and operating instructions
5.1 Marking
In addition to the marking in accordance with Clause 5 of IEC 61557-1:2007, the following
information shall be provided on the IFLS, if applicable.
– type of device as well as mark of origin or name of the manufacturer,
– type of IT system to be monitored (if the IFLS is designed for a specific type of IT system),
– nominal system voltage U or range of the nominal voltage,
...