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

This part of IEC 61557 specifies the requirements for insulation monitoring devices (IMD) which permanently monitor the insulation resistance to earth of unearthed IT a.c. systems, for IT a.c. systems with galvanically connected d.c. circuits having nominal voltages up to 1 000 V a.c., as well as of unearthed IT d.c. systems with voltages up to 1 500 V d.c. independent from the method of measuring.

Elektrische Sicherheit in Niederspannungsnetzen bis AC 1 000 V und DC 1 500 V - Geräte zum Prüfen, Messen oder Überwachen von Schutzmaßnahmen -- Teil 8: Isolationsüberwachungsgeräte für IT-Systeme

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 8: Contrôleurs d'isolement pour réseaux IT

La présente partie de la CEI 61557 définit les exigences particulières applicables aux contrôleurs d'isolement (IMD) destinés à surveiller en permanence, et quelle que soit la méthode de mesure, la résistance d'isolement par rapport à la terre de réseaux IT c.a. non mis à la terre, ou de réseaux IT c.a. comprenant des circuits à courant continu reliés galvaniquement dont les tensions nominales sont au plus égales à 1 000 V c.a., et de réseaux IT c.c. dont les tensions nominales sont au plus égales à 1 500 V c.c. Cette deuxième édition annule et remplace la première édition publiée en 1997. Cette édition constitue une révision technique. Les principales modifications apportées par cette nouvelle édition sont les suivantes: a) la section sur les 'définitions' a été complétée; b) révision de certaines exigences; c) ajout d'informations relatives aux instructions de fonctionnement; d) les sections 'essais de type' et 'essais individuels de série ' ont été complétées; e) modification du Tableau 1; f) addition des Annexes A et B. Le contenu du corrigendum de mai 2007 a été pris en considération dans cet exemplaire.

Električna varnost v nizkonapetostnih razdelilnih sistemih izmenične napetosti do 1 kV in enosmerne napetosti do 1,5 kV - Oprema za preskušanje, merjenje ali nadzorovanje zaščitnih ukrepov - 8. del: Naprave za nadzor izolacije v napajalnih sistemih IT (EN 61557-8:2007)

General Information

Status
Withdrawn
Publication Date
21-Oct-2007
Withdrawal Date
04-May-2023
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
05-May-2023
Due Date
28-May-2023
Completion Date
05-May-2023

Relations

Buy Standard

Standard
EN 61557-8:2007
English language
27 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day
Draft
prEN 61557-8:2005
English language
18 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61557-8:2007
01-december-2007
1DGRPHãþD
SIST EN 61557-8:2000
(OHNWULþQDYDUQRVWYQL]NRQDSHWRVWQLKUD]GHOLOQLKVLVWHPLKL]PHQLþQHQDSHWRVWLGR
N9LQHQRVPHUQHQDSHWRVWLGRN92SUHPD]DSUHVNXãDQMHPHUMHQMHDOL
QDG]RURYDQMH]DãþLWQLKXNUHSRYGHO1DSUDYH]DQDG]RUL]RODFLMHYQDSDMDOQLK
VLVWHPLK,7 (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 8:
Insulation monitoring devices for IT systems
Elektrische Sicherheit in Niederspannungsnetzen bis AC 1 000 V und DC 1 500 V -
Geräte zum Prüfen, Messen oder Überwachen von Schutzmaßnahmen - Teil 8:
Isolationsüberwachungsgeräte für IT-Systeme
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 8: Contrôleurs d'isolement pour réseaux IT
Ta slovenski standard je istoveten z: EN 61557-8:2007
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
29.080.01 (OHNWULþQDL]RODFLMDQD Electrical insulation in
VSORãQR general
29.240.01 2PUHåMD]DSUHQRVLQ Power transmission and
GLVWULEXFLMRHOHNWULþQHHQHUJLMH distribution networks in
QDVSORãQR general
SIST EN 61557-8:2007 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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

EUROPEAN STANDARD
EN 61557-8

NORME EUROPÉENNE
July 2007
EUROPÄISCHE NORM

ICS 17.220.20; 29.080.01; 29.240.01 Supersedes EN 61557-8:1997


English version


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
(IEC 61557-8:2007 + corrigendum May 2007)


Sécurité électrique dans les réseaux  Elektrische Sicherheit
de distribution basse tension in Niederspannungsnetzen
de 1 000 V c.a. et 1 500 V c.c. - bis AC 1 000 V und DC 1 500 V -
Dispositifs de contrôle, de mesure Geräte zum Prüfen,
ou de surveillance de mesures Messen oder Überwachen
de protection - von Schutzmaßnahmen -
Partie 8: Contrôleurs d'isolement Teil 8: Isolationsüberwachungsgeräte
pour réseaux IT für IT-Systeme
(CEI 61557-8:2007 (IEC 61557-8:2007
+ corrigendum May 2007) + corrigendum May 2007)


This European Standard was approved by CENELEC on 2007-04-11. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61557-8:2007 E

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

EN 61557-8:2007 - 2 -
Foreword
The text of document 85/296/FDIS, future edition 2 of IEC 61557-8, prepared by IEC TC 85, Measuring
equipment for electrical and electromagnetic quantities, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 61557-8 on 2007-04-11.
This European Standard supersedes EN 61557-8:1997.
The following changes were made with respect to EN 61557-8:1997:
– definitions complemented;
– revision of some requirements;
– addition of information on operating instructions;
– sections “type tests” and “routine tests” complemented;
– modification of Table 1;
– addition of Annexes A and B.
This standard is to be used in conjunction with EN 61557-1.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2008-02-01
– latest date by which the national standards conflicting
(dow) 2010-05-01
with the EN have to be withdrawn
Annexes ZA and ZB have been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61557-8:2007, including the corrigendum May 2007, was
approved by CENELEC as a European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60364-4-41 NOTE  Harmonized as HD 60364-4-41:2007 (modified).
IEC 61140 NOTE  Harmonized as EN 61140:2002 (not modified).
__________

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

- 3 - EN 61557-8:2007
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

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

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60364-7-710 2002 Electrical installations of buildings - - -
(mod) Part 7-710: Requirements for special
installations or locations - Medical locations


1) 2)
IEC 60664-1 - Insulation coordination for equipment within EN 60664-1 2007
low-voltage systems -
Part 1: Principles, requirements and tests


1) 2)
IEC 60664-3 - Insulation coordination for equipment within EN 60664-3 2003
low-voltage systems -
Part 3: Use of coating, potting or moulding for
protection against pollution


IEC 60691 2002 Thermal-links - Requirements and application EN 60691 2003
guide


1) 2)
IEC 60721-3-1 - Classification of environmental conditions - EN 60721-3-1 1997
Part 3: Classification of groups of
environmental parameters and their
severities - Section 1: Storage


1) 2)
IEC 60721-3-2 - Classification of environmental conditions - EN 60721-3-2 1997
Part 3: Classification of groups of
environmental parameters and their
severities - Section 2: Transportation


1) 2)
IEC 60721-3-3 - Classification of environmental conditions - EN 60721-3-3 1995
Part 3: Classification of groups of
environmental parameters and their
severities - Section 3: Stationary use at
weatherprotected locations


1) 2)
IEC 60947-5-1 - Low-voltage switchgear and controlgear - EN 60947-5-1 2004
Part 5-1: Control circuit devices and switching + corr. July 2005
elements - Electromechanical control circuit
devices


1) 2)
IEC 60947-5-4 - Low-voltage switchgear and controlgear - EN 60947-5-4 2003
Part 5-4: Control circuit devices and switching
elements - Method of assessing the
performance of low-energy contacts - Special
tests



1)
Undated reference.
2)
Valid edition at date of issue.

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

EN 61557-8:2007 - 4 -
Publication Year Title EN/HD Year
IEC 61010-1 2001 Safety requirements for electrical equipment EN 61010-1 2001
for measurement, control, and + corr. June 2002
laboratory use -
Part 1: General requirements


1) 2)
IEC 61326-2-4 - Electrical equipment for measurement, EN 61326-2-4 2006
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


1) 2)
IEC 61557-1 - Electrical safety in low voltage distribution EN 61557-1 2007
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


1) 2)
IEC 61810-2 - Electromechanical elementary relays - EN 61810-2 2005
Part 2: Reliability


1) 2)
CISPR 11 (mod) - Industrial scientific and medical (ISM) radio- EN 55011 2007
frequency equipment - Electromagnetic
disturbance characteristics - Limits and
methods of measurement

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

- 5 - EN 61557-8:2007
Annex ZB
(informative)

A-deviations
A-deviation: National deviation due to regulations, the alteration of which is for the time being outside the
competence of the CENELEC member.
This European Standard falls under Directive 2006/95/EC.
NOTE (from CEN/CENELEC IR Part 2:2006 , 2.17)  Where standards fall under EC Directives, it is the view of the Commission of
the European Communities (OJ No C 59, 1982-03-09) that the effect of the decision of the Court of Justice in case 815/79
Cremonini/Vrankovich (European Court Reports 1980, p. 3583) is that compliance with A-deviations is no longer mandatory and that
the free movement of products complying with such a standard should not be restricted except under the safeguard procedure
provided for in the relevant Directive.
A-deviations in an EFTA-country are valid instead of the relevant provisions of the European Standard in
that country until they have been removed.
Clause Deviation
A.3.5 Spain
(REBT ITC-BT-38)
The device shall include monitoring of the isolation value to verify the alarm and the test
device.
__________

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

NORME CEI
INTERNATIONALE
IEC



61557-8
INTERNATIONAL


Deuxième édition
STANDARD

Second edition

2007-01


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 8: Contrôleurs d'isolement pour réseaux IT

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



© IEC 2007 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
R
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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

61557-8 © IEC:2007 – 3 –
CONTENTS
FOREWORD.5

1 Scope.9
2 Normative references .9
3 Terms and definitions .11
4 Requirements .15
5 Marking and operating instructions .19
5.1 Marking .19
5.2 Operating instructions .21
6 Tests .21
6.1 Type tests .21
6.2 Routine tests .25

Annex A (normative) Medical insulation monitoring devices (IMDs) .29
Annex B (informative) Monitoring of overload and high temperature.37

Bibliography.41

Table 1 – Requirements applicable to insulation monitoring devices .17
Table A.1 – Additional requirements applicable to medical insulation monitoring
devices (IMDs).33
Table A.2 – Emission test for medical insulation monitoring devices (IMDs) .35

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

61557-8 © IEC:2007 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________

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


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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61557-8 has been prepared by IEC technical committee 85:
Measuring equipment for electrical and electromagnetic quantities.
This second edition cancels and replaces the first edition published in 1997. This edition
constitutes a technical revision.
The following changes were made with respect to the previous edition:
a) definitions complemented;
b) revision of some requirements;
c) addition of information on operating instructions;
d) sections “type tests” and “routine tests” complemented;

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

61577-8 © IEC:2007 – 7 –
e) modification of Table 1;
f) addition of Annexes A and B.
The text of this standard is based on the following documents:
FDIS Report on voting
85/296/FDIS 85/306/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 of 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 maintenance result 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 corrigendum of May 2007 have been included in this copy.

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

61557-8 © IEC:2007 – 9 –
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



1 Scope
This part of IEC 61557 specifies the requirements for insulation monitoring devices (IMD)
which permanently monitor the insulation resistance to earth of unearthed IT a.c. systems, for
IT a.c. systems with galvanically connected d.c. circuits having nominal voltages up to
1 000 V a.c., as well as of unearthed IT d.c. systems with voltages up to 1 500 V d.c.
independent from the method of measuring.
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.
NOTE 2 Various standards specify the use of insulation monitoring devices in IT systems. In such cases, the
objective of the equipment is to signal a drop in insulation resistance below a minimum limit.
NOTE 3 Insulation monitoring devices according to this part of IEC 61557 may also be used for de-energized
electrical systems.
2 Normative references
The following referenced documents are indispensable for the application 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 60364-7-710:2002, Electrical installations of buildings – Part 7-710: Requirements for
special installations or locations – Medical locations
IEC 60664-1, Insulation co-ordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 60664-3, Insulation coordination for equipment within low voltage systems – Part 3: Use
of coating, potting or moulding for protection against pollution.
IEC 60691:2002, Thermal-links – Requirements and application guide
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: Classification of groups of
environmental parameters and their severities – Section 3: Stationary use at
weatherprotected locations

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

61557-8 © IEC:2007 – 11 –
IEC 60947-5-1, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
IEC 60947-5-4, 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 61010-1:2001, Safety requirements for electrical equipment for measurement, control,
and laboratory use – Part 1: General requirements
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, 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 61810-2, Electromechanical elementary relays – Part 2: Reliability
CISPR 11, Industrial, scientific and medical (ISM) radio-frequency equipment –
Electromagnetic disturbance characteristics – Limits and methods of measurement
3 Terms and definitions
For the purposes of this document, the definitions given in IEC 61557-1 and the following
definitions apply.
3.1
extraneous d.c. voltage
U
fg
d.c. voltage occurring in a.c. systems between the a.c. conductors and earth (derived from d.c.
parts)
3.2
insulation resistance
R
F
resistance in the system being monitored, including the resistance of all the connected
appliances to earth
3.3
specified response value
R
an
value of the insulation resistance, permanently set or adjustable, on the device and monitored
if the insulation resistance falls below this limit
3.4
response value
R
a
value of the insulation resistance at which the device responds under specified conditions

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

61557-8 © IEC:2007 – 13 –
3.5
relative (percentage) uncertainty
A[ %]
response value minus the specified response value, divided by the specified response value,
multiplied by 100 and stated as a percentage
R − R
a an
A [%] = × 100 %
R
an
3.6
system leakage capacitance
C
e
maximum permissible value of the total capacitance to earth of the system to be monitored,
including any connected appliances, up to which value the insulation monitoring device can
work as specified
3.7
rated contact voltage
voltage for which a relay contact is rated to open and close under specified conditions
3.8
response time
t
an
time required by an insulation monitoring device to respond under the conditions specified in 6.1.2
3.9
measuring voltage
U
m
voltage present at the measuring terminals during the measurement
NOTE Additionally to the definition given in IEC 61557-1, the measuring voltage (U ) is the voltage present in a
m
fault-free and de-energized system between the terminals of the system to be monitored and the terminals of the
protective conductor
3.10
measuring current
I
m
maximum current that can flow between the system and earth, limited by the internal
resistance R from the measuring voltage source of the insulation monitoring device
i
NOTE Measuring current is designated as injected current in IEC 60364-7-710.
3.11
internal impedance
Z
i
total impedance of the insulation monitoring device between the terminals to the system being
monitored and earth, measured at the nominal frequency
3.12
internal d.c. resistance

R
i
resistance of the insulation monitoring device between the terminals to the system being
monitored and earth
3.13
functional earthing
FE
earthing a point or points in a system or in an installation or in equipment for purposes other
than electrical safety
NOTE For insulation monitoring devices this is the measuring connection to earth.

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

61557-8 © IEC:2007 – 15 –
4 Requirements
The following requirements as well as those given in IEC 61557-1 shall apply.
4.1 Insulation monitoring devices shall be capable of monitoring the insulation resistance of
IT systems including symmetrical and asymmetrical components and to give a warning if the
insulation resistance between the system and earth falls below a predetermined level.
NOTE 1 A symmetrical insulation deterioration occurs when the insulation resistance of all conductors in the
system to be monitored decreases (approximately) similarly. An asymmetrical insulation deterioration occurs when
the insulation resistance of, for example, one conductor decreases substantially more than that of the other
conductor(s).
NOTE 2 So-called earth fault relays using a voltage asymmetry (voltage shift) in the presence of an earth fault as
the only measurement criterion, are not insulation monitoring devices in the interpretation of this part of IEC 61557.
NOTE 3 A combination of several measurement methods, including asymmetry monitoring, may become
necessary for fulfilling the task of monitoring under special conditions on the system.
4.2 Insulation monitoring devices shall comprise a test device, or be provided with means for
the connection of a test facility, for detecting whether the insulation monitoring device is
capable of fulfilling its functions. The system to be monitored shall not be directly earthed and
the devices shall not suffer damage. This test is not intended for checking the response value.
4.3 Contrary to IEC 61557-1, the PE connection of insulation monitoring devices is a
measuring connection and may be treated as functional earth connection (FE). If the IMD
additionally has parts which are grounded for protection purposes, this connection shall be
treated as protective connection (PE).
4.4 When the specified response value R of the insulation monitoring device is adjustable,
an
it shall be designed in such a way that it is impossible to modify the settings, except by the
use of a key, a tool or a password.
NOTE Standards for the installation of electrical systems state the lowest value that is permissible as a setting on
insulation monitoring devices with variable response values.
4.5 Insulation monitoring devices shall comprise a visual warning device or be provided with
the facility for connecting such a device which indicates its operation. This device shall not be
provided with means for being switched off. Built-in or externally connectable audible
signalling devices may be fitted with a resetting facility. Sending of an audible signal in the
case of a newly occurring fault, following a fault that has been cleared and after the devices
may have been reset, shall be ensured.
NOTE An indication of the value of the insulation resistance by means of a measuring facility is, in itself, not
sufficient as a facility for visual signalling.
4.6 The maximum operating uncertainty of insulation monitoring devices is expressed by
relative (percentage) uncertainty. The uncertainty and its limits are listed in Table 1.

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

61557-8 © IEC:2007 – 17 –
Table 1 – Requirements applicable to insulation monitoring devices
a.c. systems with galvanically
Marking Pure a.c. systems connected d.c. circuits and d.c.
systems
a
Response time t
≤10 s at 0,5 × R and C = 1 μF ≤100 s at 0,5 × R and C = 1 μF
an
an e an e
Permanently admissible According to the indications of the manufacturer
≤peak value 1,15 × U not
n,
extraneous d.c. voltage
applicable for d.c. systems
U
fg
Marking For all systems
Peak v
...

SLOVENSKI oSIST prEN 61557-8:2005

PREDSTANDARD
november 2005
Električna varnost v nizkonapetostnih razdelilnih sistemih izmenične
napetosti do 1 kV in enosmerne napetosti do 1,5 kV – Oprema za preskušanje,
merjenje ali nadzorovanje zaščitnih ukrepov – 8. del: Naprave za nadzor
izolacije v sistemih informacijske tehnologije
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
ICS 17.220.20 Referenčna številka
oSIST prEN 61557-8:2005(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------
85/275/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJET DE COMITÉ POUR VOTE (CDV)
Project number IEC 61557-8 Ed. 2.0
Numéro de projet

IEC/TC or SC: Date of circulation Closing date for voting (Voting
TC 85
Date de diffusion mandatory for P-members)
CEI/CE ou SC:

Date de clôture du vote (Vote
2005-07-29
obligatoire pour les membres (P))
2006-01-06
Titre du CE/SC: Equipement de mesure des TC/SC Title: Measuring equipment for electrical
grandeurs électriques et électromagnétiques and electromagnetic quantities
Secretary: Mr. Bo CHEN
Secrétaire:
Also of interest to the following committees Supersedes document
Intéresse également les comités suivants Remplace le document
   85/257/CD and 85/260/CC
Functions concerned
Fonctions concernées
Safety EMC Environment Quality assurance
Sécurité
CEM Environnement Assurance qualité
CE DOCUMENT EST TOUJOURS À L'ÉTUDE ET SUSCEPTIBLE DE THIS DOCUMENT IS STILL UNDER STUDY AND SUBJECT TO CHANGE. IT
MODIFICATION. IL NE PEUT SERVIR DE RÉFÉRENCE. SHOULD NOT BE USED FOR REFERENCE PURPOSES.
LES RÉCIPIENDAIRES DU PRÉSENT DOCUMENT SONT INVITÉS À RECIPIENTS OF THIS DOCUMENT ARE INVITED TO SUBMIT, WITH THEIR
PRÉSENTER, AVEC LEURS OBSERVATIONS, LA NOTIFICATION DES COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF
DROITS DE PROPRIÉTÉ DONT ILS AURAIENT ÉVENTUELLEMENT WHICH THEY ARE AWARE AND TO PROVIDE SUPPORTING
CONNAISSANCE ET À FOURNIR UNE DOCUMENTATION EXPLICATIVE. DOCUMENTATION.



Titre :    Title : IEC 61557-8 Ed. 2.0: 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 8: Insulation monitoring devices for IT
systems



Note d'introduction Introductory note



ATTENTION ATTENTION

CDV soumis en parallèle au vote (CEI) Parallel IEC CDV/CENELEC Enquiry
et à l’enquête (CENELEC)

Copyright © 2005 International Electrotechnical Commission, IEC. All rights reserved. It is
permitted to download this electronic file, to make a copy and to print out the content for the sole
purpose of preparing National Committee positions. You may not copy or "mirror" the file or
printed version of the document, or any part of it, for any other purpose without permission in
writing from IEC.
FORM CDV (IEC) 2002-08-09

---------------------- Page: 2 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 2 – 85/285/CDV
CONTENTS
 Page
FOREWORD. 3
Clause
1 Scope. 4
2 Normative references. 4
3 Definitions. 5
4 Requirements. 6
5 Marking and operating instructions. 7
6 Tests. 8

Table 1 – Requirements applicable to insulation monitoring devices. 10
Annex A …….…………………………………………………………………………………………….   13
Annex B ……………………………………………………………………………………………………    18

2

---------------------- Page: 3 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 3 – 85/285/CDV
INTERNATIONAL ELECTROTECHNICAL COMMISSION
–––––––
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 8: Insulation monitoring devices for IT systems
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61557-8 has been prepared by IEC technical committee 85:
Measuring equipment for electrical and electromagnetic quantities.
The text of this standard is based on the following documents:
FDIS Report on voting
85/xx/FDIS 85/xxx/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 part of IEC 61557 shall be used in conjunction with part 1.
The committee has decided that the contents of this publication will remain unchanged until
2010.  At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
•  amended.
3

---------------------- Page: 4 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 4 – 85/285/CDV
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 8: Insulation monitoring devices for IT systems

1 Scope
This part of IEC 61557 specifies the requirements for insulation monitoring devices which
permanently monitor the insulation resistance to earth of unearthed IT a.c. systems, for IT a.c.
systems with galvanically connected d.c. circuits having nominal voltages up to 1000 V a.c.,
as well as of unearthed IT d.c. systems with voltages up to 1500 V d.c. independent from the
method of measuring.
NOTE 1 IT systems are described in IEC 60364-4-41 amongst other literature. Additional data for a
selection of devices in other standards is to be noted.
NOTE 2 Various standards specify the use of insulation monitoring devices on in IT systems. In such
cases, the objective of the equipment is to signal a drop in insulation resistance below a minimum limit.
NOTE 3 Insulation monitoring devices according to this part of IEC 61557 may also be used for de-
energized electrical systems.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61557. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and parties to
agreements based on this part of IEC 61557 are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 60255-23:1994, Electrical relays – Part 23: Contact performance
IEC 60364-4-41: 2001, Electrical installations of buildings – Part 4: Protection for safety –
Chapter 41: Protection against electric shock
IEC 60664-1: 2002, Insulation co-ordination for equipment within low-voltage systems – Part
1: Principles, requirements and tests
IEC 60664-3: 2003, Insulation coordination for equipment within low voltage systems – Part 3:
Use of coating, potting or moulding for protection against pollution.
IEC 60721-3-1: 1997, Classification of environmental conditions – Part 3: Classification of
groups of environmental parameters and their severities – Section 1: Storage
IEC 60721-3-2: 1997, Classification of environmental conditions – Part 3: Classification of
groups of environmental parameters and their severities – Section 2: Transportation
IEC 60721-3-3: 1997, Classification of environmental conditions – Part 3: Classification of
groups of environmental parameters and their severities – Section 3: Stationary use at
weatherprotected locations
IEC 60947-5-1:2003, 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 61010-1: 2001, Safety requirements for electrical equipment for measurement, control,
and laboratory use – Part 1: General requirements
4

---------------------- Page: 5 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 5 – 85/285/CDV
IEC 61140: 2001, Protection against electric shock – Common aspects for installation and
equipment
Draft of IEC 61326-2 Ed.1 [IEC 65A/405/CD], Electrical equipment for measurement, control
and laboratory use - EMC requirements
IEC 61557-1: 1997, 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 1:
General requirements
3 Definitions
For the purposes of this part of IEC 61557, the definitions given in IEC 61557-1 and the
following definitions apply.
3.1 extraneous d.c. voltage (U ): A d.c. voltage occurring in a.c. systems between the
fg
a.c. conductors and earth (derived from d.c. parts)
3.2 insulation resistance (R ): Resistance in the system being monitored, including the
F
resistance of all the connected appliances to earth
3.3 specified response value (R ): Value of the insulation resistance, permanently set or
an
adjustable, on the device and monitored if the insulation resistance falls below this limit
3.4 response value (R ): Value of the insulation resistance at which the device responds
a
under specified conditions
3.5 relative (percentage) erroruncertainty (A[%]): Response value minus the specified
response value, divided by the specified response value, multiplied by 100 and stated as a
percentage
R −R
a an
A[%] = ×100 %
R
an
system leakage capacitance (C ): Maximum permissible value of the total capacitance
3.6
e
to earth of the system to be monitored, including any connected appliances, up to which value
the insulation monitoring device can work as specified
3.7 rated contact voltage: Voltage for which a relay contact is rated to open and close
under specified conditions
3.8 response time (t ): Time required by an insulation monitoring device to respond under
an
the conditions specified in 6.1.2
3.9 measuring voltage (U ): Voltage present at the measuring terminals during the
m
measurement.
NOTE 1 In a fault-free and de-energized system, this represents the voltage present between the terminals of
the system to be monitored and the terminals of the protective conductor.
NOTE 2 Additionally to the definition in IEC 61557-1, the measuring voltage (U ) is the voltage present in a
m
fault-free and de-energized system between the terminals of the system to be monitored and the terminals of
the protective conductor.
3.10 measuring current (I ): Maximum current that can flow between the system and earth,
m
limited by the internal resistance R from the measuring voltage source of the insulation
i
monitoring device
3.11 internal impedance (Z ): Total impedance of the insulation monitoring device between
i
the terminals to the system being monitored and earth, measured at the nominal frequency
5

---------------------- Page: 6 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 6 – 85/285/CDV
3.12 internal d.c. resistance (R ): Resistance of the insulation monitoring device between
i
the terminals to the system being monitored and earth
3.13 functional earthing (FE): Earthing a point or points in a system or in an installation or
in equipment for purposes other than electrical safety
  NOTE For insulation monitoring devices this is the measuring connection to earth
4 Requirements
The following requirements as well as those given in IEC 61557-1 shall apply.
4.1 Insulation monitoring devices shall be capable of monitoring the insulation resistance of
IT systems including symmetrical and asymmetrical components and to give a warning, if the
insulation resistance between the system and earth falls below a predetermined level.
NOTE 1 A symmetrical insulation deterioration occurs when the insulation resistance of all conductors in
the system to be monitored decreases (approximately) similarly. An asymmetrical insulation deterioration
occurs when the insulation resistance of, for example, one conductor decreases substantially more than that of
the other conductor(s).
NOTE 2 So-called earth fault relays using a voltage asymmetry (voltage shift) in the presence of an earth
fault as the only measurement criterion, are not insulation monitoring devices in the interpretation of this part of
IEC 61557.
NOTE 3 A combination of several measurement methods, including asymmetry monitoring, may become
necessary for fulfilling the task of monitoring under special conditions on the system.
4.2 Insulation monitoring devices shall comprise a test device, or be provided with means
for the connection of a test facility, for detecting whether the insulation monitoring device is
capable of fulfilling its functions. The system to be monitored shall not be directly earthed and
the devices shall not suffer damage. This test is not intended for checking the response value.
4.3 Contrary to IEC 61557-1 the PE connection of iInsulation monitoring devices is a measuring
connection and may be treated as functional earth connection (FE). If the IMD additionally has parts,
which are grounded for protection purposes, this connection shall be treated as protective connection
(PE).
4.4 When the specified response value R of the insulation monitoring device is adjustable,
an
unintentional changes of the setting shall be prevented by suitable means.
NOTE  Standards for the installation of electrical systems state the lowest value that is permissible as a setting
on insulation monitoring devices with variable response values.
4.5 Insulation monitoring devices shall comprise a visual warning device or be provided
with the facility for connecting such a device which indicates its operation. This device shall
not be provided with means for being switched off. Built-in or externally connectable audible
signalling devices may be fitted with a resetting facility. Sending of an audible signal in the
case of a newly occurring fault, following a fault that has been cleared and after the devices
may have been reset, shall be ensured.
NOTE  An indication of the value of the insulation resistance by means of a measuring facility is, in itself, not
sufficient as a facility for visual signalling.
4.6 The maximum operating erroruncertainty of insulation monitoring devices is expressed
by relative (percentage) erroruncertainty. The erroruncertainty and its limits are listed in table
1.
4.7 When insulation monitoring devices include facilities for indicating the insulation
resistance, the erroruncertainty of these facilities under nominal operating conditions should
shall be stated by the manufacturer.
4.8  Insulation monitoring devices shall have minimum clearances and creepage distances in
accordance with IEC 60664-1 and IEC 60664-3.
Clearances and creepage distances shall be selected in accordance with
6

---------------------- Page: 7 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 7 – 85/285/CDV
    - overvoltage category III
    - pollution degree 3 for all external connections and user accessible parts
    - pollution degree 2 for printed circuit boards inside the IMD
- pollution degree 1 for printed circuits inside the IMD which are coated according to IEC
60664-3
4.9 Where different voltages are used by an insulation monitoring device (e.g. U , U ),
v n
clearances and creepages shall be designed for the highest voltage.
4.10 A division into circuits with different nominal insulation voltages is permissible in device
combinations (e.g. for IT systems with nominal voltages higher than 1000 V a.c. and 1500 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 (safety impedance) in the voltage
divider.
4.11 Insulation monitoring devices shall comply with the requirements for electromagnetic
compatibility (EMC) in accordance with the draft of IEC 61326-2 [IEC 65A/405/CD], Annex G.
4.12 Additional requirements for insulation monitoring devices are listed in table 1.

5 Marking and operating instructions
5.1 Marking
In addition to the marking in accordance with IEC 61557-1, the following information shall be
provided on the insulation monitoring device.
5.1.1 Type of device as well as mark of origin or name of the manufacturer.
5.1.2 IT system to be monitored (if the IMD is designed for a specific type of IT system).
5.1.3 Wiring diagram or number of the wiring diagram or number of the operating
instructions.
5.1.4 Nominal system voltage U or range of the nominal voltage.
n
5.1.5 Nominal value of the supply voltage U U or working range of supply voltage.
v s
5.1.6 Nominal frequency of the supply voltage U or working range of frequencies for the
v
supply voltage .
5.1.7 Specified response value R or minimum and maximum response value R and, if
an an
applicable, the range of specified response values where the relative (percentage)
erroruncertainty is higher than that listed in table 1.
5.1.8 Mandatory on the outside and, if necessary, inside the device: serial number, year of
manufacture or type designation.
The data given in 5.1.1 shall be indelibly marked on the insulation monitoring device in such a
manner that they remain legible after installation of the device.
5.2 Operating instructions
The operating instructions shall state the following in addition to the statements given in
IEC 61557-1.
7

---------------------- Page: 8 ----------------------
61557-8 © IEC: 2006 Ed.2.0 – 8 – 85/285/CDV
5.2.1 Internal impedance Z of the measuring circuit as a function of the nominal frequency.
i
5.2.2 Peak value of the measuring voltage U in accordance with table 1 when fed with the
m
nominal value of the supply voltage U U .
v s
5.2.3 Maximum value of the measuring current I in accordance with table 1 when the
m
terminals are short-circuited.
5.2.4 Technical data of the interface for the connection of an external warning device
including rated voltage and current, rated insulation voltage and explanation of the interface
function. For contact circuits, data shall reference to IEC 60255-23 or IEC 60947-5-1 and IEC
60947-5-4.
5.2.5 Information that insulation monitoring devices shall not be connected in parallel (e.g.
when systems are coupled).
5.2.6 Wiring diagram when this is not marked on the devices in accordance with subsection 5.1.3.
5.2.7 Information relating to the effect of the system leakage capacitances C , and their
e
permissible maximum value.
5.2.8 Extraneous d.c. voltage (U ) of any polarit
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.