IEC 61557-2:2019

IEC 61557-2 ®
Edition 3.0 2019-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
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 2: Insulation resistance
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IEC 61557-2 ®
Edition 3.0 2019-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
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 2: Insulation resistance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20; 29.080.01; 29.240.01 ISBN 978-2-8322-7232-9

– 2 – IEC 61557-2:2019 RLV © IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Requirements . 6
4.1 General requirements . 6
4.2 Output voltage . 6
4.3 Rated current . 6
4.4 Measuring current . 6
4.5 Influence of external capacitors . 7
4.6 Overvoltage . 7
5 Marking and operating instructions . 7
5.1 Marking . 7
5.2 Operating instructions . 8
6 Tests . 8
6.1 General . 8
6.2 Operating uncertainty . 8
6.3 Open-circuit voltage . 9
6.4 Rated current . 9
6.5 Measuring current . 9
6.6 Overload Overvoltage tests . 9
6.6.1 Overload Overvoltage tests with AC voltage . 9
6.6.2 Overload Overvoltage tests with DC voltage . 10
6.7 Battery life in battery operated instruments . 10
6.8 Stability test . 10

Figure 1 – Example of a pictogram for a 500 V AC system . 7

Table 1 – Calculation of operating uncertainty . 9

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 2: Insulation resistance
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 4 – IEC 61557-2:2019 RLV © IEC 2019

International Standard IEC 61557-2 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 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) addition of requirements as regards measurement category;
b) addition of new requirements for operating instructions;
c) alignment of the structure with that of the whole IEC 61557 series.
The text of this International Standard is based on the following documents:
FDIS Report on voting
85/688/FDIS 85/693/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
This International Standard is to be used in conjunction with IEC 61557-1:2019.
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 "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The “colour inside” logo on the cover page of this publication 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 2: Insulation resistance
1 Scope
This part of IEC 61557 specifies the requirements applicable to equipment for measuring the
insulation resistance of equipment and installations in the de-energized state.
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 61010-1:20012010, Safety requirements for electrical equipment for measurement,
control, and laboratory use – Part 1: General requirements
IEC 61010-1:2010/AMD1:2016
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 61010-2-034:2017, Safety requirements for electrical equipment for measurement, control,
and laboratory use – Part 2-034: Particular requirements for measurement equipment for
insulation resistance and test equipment for electric strength
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61557-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
____________
A consolidated version of this publication exists, comprising IEC 61010-1:2010 and
IEC 61010-1:2010/AMD1:2016.
– 6 – IEC 61557-2:2019 RLV © IEC 2019
3.1
rated output voltage
U
N
voltage output across the measuring equipment terminals when this equipment is loaded with
the rated current
3.1
line-to-line voltage
DEPRECATED: phase-to-phase voltage
voltage between two line conductors at a given point of an electric circuit
[SOURCE: IEC 60050-195:1998, 195-05-01]
4 Requirements
The following requirements as well as those given in IEC 61557-1 shall apply.
4.1 General requirements
The output voltage shall be a d.c. voltage; the indication at the rated output voltage across a
resistor of a value of U × (1 000 Ω/V) shall not differ by more than 10 % relative to the
N
indicated value, as a result of possibly present a.c. voltage components in the output voltage,
when a capacitor of 2 µF is connected in parallel with the insulation resistance to be
measured.
In addition to the requirements of IEC 61557-1:2019, Clause 4, the requirements of Clause 4
of this document shall apply.
Insulation measurement equipment shall fulfil the safety requirements of IEC 61010-2-034.
Test leads and test probes used with insulation measuring equipment shall fulfil the
requirements of IEC 61010-031.
Equipment intended for making measurements on distribution systems shall be rated at least
for measurement category III.
Equipment intended for making measurements on electrical equipment shall be rated at least
for measurement category II.
4.2 Output voltage
The output voltage shall be a DC voltage.
The open-circuit voltage shall not exceed 1,25 times the rated output voltage.
4.3 Rated current
The rated current shall be at least 1 mA.
4.4 Measuring current
The measuring current shall not exceed 15 mA peak. Any AC component present shall not
exceed 1,5 mA peak.
4.5 Influence of external capacitors
The maximum percentage operating uncertainty within the measurement range to be marked
or stated shall not exceed ±30 % with the measured value as fiducial value, as determined in
accordance with Table 1.
The operating uncertainty shall apply under the rated operating conditions in accordance with
IEC 61557-1.
The indication of a measured resistance of 1 (± 1 %) MΩ shall not differ by more than 10 % as
a result of AC voltage components possibly present in the output voltage, when a capacitor of
2 (± 10 %) µF is connected in parallel with the measured resistance. If the manufacturer
specifies a higher capacitance for the object under test, the 2 µF capacitor shall be replaced
to adhere to the manufacturer's specified capacitance value.
4.6 Overvoltage
The user shall not be subjected to danger when extraneous DC or AC voltages up to 120 % of
the highest rated output voltage are accidentally applied for a duration of not less than 10 s to
the measurement terminals of the measuring equipment.
When the measuring equipment bears one of the following markings, the applied extraneous
AC overvoltage can may be reduced to a voltage of 1,1 times the phase to phase line-to-line
voltage:
a) DO NOT USE IN DISTRIBUTION SYSTEMS WITH VOLTAGES HIGHER THAN . V.
The marking shall be written in the corresponding country language.
The value of the voltage shown on the marking shall be 1,1 times the maximum phase to
phase line-to-line voltage.
or
a) Example of pictogram for a 500 V AC system

Figure 1 – Example of a pictogram for a 500 V AC system
The pictogram and outline in Figure 1 shall contrast with the background. The value of the
voltage shown on the marking shall be 1,1 times the maximum phase to phase line-to-line
voltage.
After applying this reduced AC overvoltage, the equipment shall stay within meet the
specifications of 4.6.
5 Marking and operating instructions
5.1 Marking
In addition to the marking in accordance with IEC 61557-1:2019, 5.1 and 5.2 and
IEC 61010-2-034:2017, Clause 5, the following information shall be provided on the
measuring equipment.
– 8 – IEC 61557-2:2019 RLV © IEC 2019
– rated output voltage,
– rated current,
– measurement range in accordance with 4.5,
– rated voltage to earth and measuring category.
5.2 Operating instructions
The operating instructions shall state the following information in addition to the statements
specified in IEC 61557-1:2019, 5.3 and in IEC 61010-2-034:2017, Clause 5:
– a warning stating that measurements shall be carried out only on parts of an installation or
equipment that is de-energized;
– a statement on the correct operation when power is supplied by a hand-driven generator;
– In accordance with 6.7, the number of possible measurements shall be stated for
measuring equipment with power supplied by batteries/accumulators;
– a statement about the maximum capacitance value of the tested object if higher than 2 µF;
– a statement about intended applications of the equipment;
– a statement about discharge time and relevant capacity of the tested object.
6 Tests
6.1 General
In addition to IEC 61557-1:2019, Clause 6 and IEC 61010-2-034:2017, Clause 6, the following
tests shall be executed performed.
6.2 Operating uncertainty
The maximum percentage operating uncertainty within the measurement range to be marked
or stated shall not exceed ±30 % with the measured value as fiducial value, as determined in
accordance with Table 1.
The operating uncertainty shall be determined in accordance with Table 1. In this process, the
intrinsic uncertainties shall be determined under the following reference conditions:
The operating uncertainty shall apply under the rated operating conditions in accordance with
IEC 61557-1:
– nominal value of the supply voltage;
– nominal r.p.m. r/min when power is supplied by a hand-driven generator;
– reference temperature 23 °C ± 2 °C;
– reference position in accordance with the manufacturer's statement.
The operating uncertainty thus evaluated shall not exceed the limits specified in 4.5.

Table 1 – Calculation of operating uncertainty
Requirements
Intrinsic
Reference conditions or Designation or tests in accordance Type of
uncertainty or
specified operating range code with relevant parts of test
influence quantity
IEC 61557
Intrinsic uncertainty Reference conditions A Part 2, subclause 6.1 R
Position Reference position ±90° E Part 1, subclause 4.2 R
approximately
IEC 61557-1:2019, 4.2
Supply voltage At the limits stated by the E Part 1, subclauses 4.2, 4.3 R
manufacturer IEC 61557-1:2019, 4.2, 4.3
Temperature 0 °C and 35 °C E Part 1, subclause 4.2 T
(± 2 °C)
IEC 61557-1:2019, 4.2
Operating Part 2, subclause 4.5 R

uncertainty
Key
B
B % =±× 100 %


A = intrinsic uncertainty
F
E E = variations
n
i
R = routine test
T = type test
F = fiducial value
6.3 Open-circuit voltage
The open-circuit voltage shall be checked with a test circuit with a loading resistance of a
minimum of U × 100 kΩ/V for compliance with the specification in 4.2 (routine test).
N
6.4 Rated current
The rated current shall be tested through a test resistor of a value of U × 1 000 Ω/V.
N
Compliance with the requirements in 4.3 shall be checked (routine test).
6.5 Measuring current
The measuring current shall be tested and compliance with the requirements in 4.4 shall be
checked (routine test).
NOTE When an AC voltage is superimposed on the DC voltage, the measuring equipment for
measuring the peak value of the current must shall be used applied.
6.5 Tests shall establish that the indication is stable and does not change by more than
10 % when a capacitor of 2 µF ± 10% is connected in parallel. In this condition, the measuring
equipment is loaded by a resistor free from capacitance and inductance in such a manner that
the rated output voltage and rated current will occur (type test).
6.6 Overload Overvoltage tests
6.6.1 Overload Overvoltage tests with AC voltage
The permissible overload overvoltage in accordance with 4.6 or 4.6.1 shall be tested. For this
purpose an AC voltage according to 4.6. or 4.6.1 shall be applied for a duration of not less
than 10 s whilst the equipment is switched on and off (type test).

– 10 – IEC 61557-2:2019 RLV © IEC 2019
The AC test source shall have the capability to activate protective devices and to indicate
weak points of circuitry. If protective devices are activated or parts are damaged, the test
shall be repeated with a test source having a capability according to IEC 61010-1:20012010,
16.2.
After the test with AC overvoltage according to 4.6, defects, if any, shall be clearly indicated;
indications and displayed values shall not lead to unsafe interpretations.
After tests with AC overvoltages according to 4.6.1., the equipment shall stay within the
specification.
This includes reactivation of protective devices by the user without any repair.
NOTE The replacement of fuses accessible to the user should be considered as reactivation
of a protective device.
6.6.2 Overload Overvoltage tests with DC voltage
In addition to the overvoltage tests with AC, a DC voltage of 1,2 times the magnitude of the
highest rated output voltage stored on a capacitor of 2 µF shall be applied in both polarities
whilst the equipment is switched on and off. After this, the measuring equipment shall stay
within the specification, but without activation of the protective devices (type test).
6.7 Battery life in battery operated instruments
The number of possible measurements shall be determined until the limit of the voltage range
determined by the battery check facility is reached (type test).
In this process, the measuring equipment shall be loaded with a test resistance of
U × 1 000 Ω/V alternating between 5 s for a loading period not less than 5 s, and with
N
intervals of about not less than 25 s prior to each new loading (type test).
6.8 Compliance with the tests in this clause shall be recorded.
6.8 Stability test
Tests shall verify that the indication of measured resistance of 1 (±1 %) MΩ is stable and
does not change by more than 10 % when a capacitor of 2 (±10 %) µF (or a higher
capacitance value, if specified) is connected in parallel. Resistance and inductance of the test
capacitor shall be negligible (type test).

___________
IEC 61557-2 ®
Edition 3.0 2019-07
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 2: Insulation resistance
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 2: Résistance d'isolement

– 2 – IEC 61557-2:2019 © IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Requirements . 6
4.1 General requirements . 6
4.2 Output voltage . 6
4.3 Rated current . 6
4.4 Measuring current . 6
4.5 Influence of external capacitors . 6
4.6 Overvoltage . 6
5 Marking and operating instructions . 7
5.1 Marking . 7
5.2 Operating instructions . 7
6 Tests . 8
6.1 General . 8
6.2 Operating uncertainty . 8
6.3 Open-circuit voltage . 8
6.4 Rated current . 8
6.5 Measuring current . 9
6.6 Overvoltage tests . 9
6.6.1 Overvoltage tests with AC voltage . 9
6.6.2 Overvoltage tests with DC voltage . 9
6.7 Battery life in battery operated instruments . 9
6.8 Stability test . 9

Figure 1 – Example of a pictogram for a 500 V AC system . 7

Table 1 – Calculation of operating uncertainty . 8

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 2: Insulation resistance
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61557-2 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 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) addition of requirements as regards measurement category;
b) addition of new requirements for operating instructions;
c) alignment of the structure with that of the whole IEC 61557 series.

– 4 – IEC 61557-2:2019 © IEC 2019
The text of this International Standard is based on the following documents:
FDIS Report on voting
85/688/FDIS 85/693/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
This International Standard is to be used in conjunction with IEC 61557-1:2019.
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 "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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 2: Insulation resistance
1 Scope
This part of IEC 61557 specifies the requirements applicable to equipment for measuring the
insulation resistance of equipment and installations in the de-energized state.
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 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 61010-031, 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 61010-2-034:2017, Safety requirements for electrical equipment for measurement, control,
and laboratory use – Part 2-034: Particular requirements for measurement equipment for
insulation resistance and test equipment for electric strength
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61557-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
____________
A consolidated version of this publication exists, comprising IEC 61010-1:2010 and
IEC 61010-1:2010/AMD1:2016.
– 6 – IEC 61557-2:2019 © IEC 2019
3.1
line-to-line voltage
DEPRECATED: phase-to-phase voltage
voltage between two line conductors at a given point of an electric circuit
[SOURCE: IEC 60050-195:1998, 195-05-01]
4 Requirements
4.1 General requirements
In addition to the requirements of IEC 61557-1:2019, Clause 4, the requirements of Clause 4
of this document shall apply.
Insulation measurement equipment shall fulfil the safety requirements of IEC 61010-2-034.
Test leads and test probes used with insulation measuring equipment shall fulfil the
requirements of IEC 61010-031.
Equipment intended for making measurements on distribution systems shall be rated at least
for measurement category III.
Equipment intended for making measurements on electrical equipment shall be rated at least
for measurement category II.
4.2 Output voltage
The output voltage shall be a DC voltage.
The open-circuit voltage shall not exceed 1,25 times the rated output voltage.
4.3 Rated current
The rated current shall be at least 1 mA.
4.4 Measuring current
The measuring current shall not exceed 15 mA peak. Any AC component present shall not
exceed 1,5 mA peak.
4.5 Influence of external capacitors
The indication of a measured resistance of 1 (± 1 %) MΩ shall not differ by more than 10 % as
a result of AC voltage components possibly present in the output voltage, when a capacitor of
2 (± 10 %) µF is connected in parallel with the measured resistance. If the manufacturer
specifies a higher capacitance for the object under test, the 2 µF capacitor shall be replaced
to adhere to the manufacturer's specified capacitance value.
4.6 Overvoltage
The user shall not be subjected to danger when extraneous DC or AC voltages up to 120 % of
the highest rated output voltage are accidentally applied for a duration of not less than 10 s to
the measurement terminals of the measuring equipment.
When the measuring equipment bears one of the following markings, the applied extraneous
AC overvoltage may be reduced to a voltage of 1,1 times the line-to-line voltage:

a) DO NOT USE IN DISTRIBUTION SYSTEMS WITH VOLTAGES HIGHER THAN . V.
The marking shall be written in the corresponding country language.
The value of the voltage shown on the marking shall be 1,1 times the maximum line-to-line
voltage.
or
b) Example of pictogram for a 500 V AC system

Figure 1 – Example of a pictogram for a 500 V AC system
The pictogram and outline in Figure 1 shall contrast with the background. The value of the
voltage shown on the marking shall be 1,1 times the maximum line-to-line voltage.
After applying this reduced AC overvoltage, the equipment shall meet the specifications of 4.6.
5 Marking and operating instructions
5.1 Marking
In addition to the marking in accordance with IEC 61557-1:2019, 5.1 and 5.2 and
IEC 61010-2-034:2017, Clause 5, the following information shall be provided on the
measuring equipment.
– rated output voltage,
– rated current,
– measurement range,
– rated voltage to earth and measuring category.
5.2 Operating instructions
The operating instructions shall state the following information in addition to the statements
specified in IEC 61557-1:2019, 5.3 and in IEC 61010-2-034:2017, Clause 5:
– a warning stating that measurements shall be carried out only on parts of an installation or
equipment that is de-energized;
– a statement on the correct operation when power is supplied by a hand-driven generator;
– the number of possible measurements shall be stated for measuring equipment with power
supplied by batteries/accumulators;
– a statement about the maximum capacitance value of the tested object if higher than 2 µF;
– a statement about intended applications of the equipment;
– a statement about discharge time and relevant capacity of the tested object.

– 8 – IEC 61557-2:2019 © IEC 2019
6 Tests
6.1 General
In addition to IEC 61557-1:2019, Clause 6 and IEC 61010-2-034:2017, Clause 6, the following
tests shall be performed.
6.2 Operating uncertainty
The maximum percentage operating uncertainty within the measurement range to be marked
or stated shall not exceed ±30 % with the measured value as fiducial value, as determined in
accordance with Table 1.
The operating uncertainty shall apply under the rated operating conditions in accordance with
IEC 61557-1:
– nominal value of the supply voltage;
– nominal r/min when power is supplied by a hand-driven generator;
– reference temperature 23 °C ± 2 °C;
– reference position in accordance with the manufacturer's statement.
Table 1 – Calculation of operating uncertainty
Requirements
Intrinsic
Reference conditions or Designation or tests in accordance Type of
uncertainty or
specified operating range code with relevant parts of test
influence quantity
IEC 61557
Intrinsic uncertainty Reference conditions A IEC 61557-2:2019, 6.2 R
Position Reference position ±90° E IEC 61557-1:2019, 4.2 R
approximately
Supply voltage At the limits stated by the E IEC 61557-1:2019, 4.2, 4.3 R
manufacturer
Temperature 0 °C and 35 °C E IEC 61557-1:2019, 4.2 T
(± 2 °C)
Operating IEC 61557-2:2019, 6.2 R

uncertainty
Key
B
B % =±× 100 %


A = intrinsic uncertainty
F
E = variations
i
R = routine test
T = type test
F = fiducial value
6.3 Open-circuit voltage
The open-circuit voltage shall be checked with a test circuit with a loading resistance of a
minimum of U × 100 kΩ/V for compliance with the specification in 4.2 (routine test).
N
6.4 Rated current
The rated current shall be tested through a test resistor of a value of U × 1 000 Ω/V.
N
Compliance with the requirements in 4.3 shall be checked (routine test).

6.5 Measuring current
The measuring current shall be tested and compliance with the requirements in 4.4 shall be
checked (routine test).
When an AC voltage is superimposed on the DC voltage, the measuring equipment for
measuring the peak value of the current shall be applied.
6.6 Overvoltage tests
6.6.1 Overvoltage tests with AC voltage
The permissible overvoltage in accordance with 4.6 shall be tested. For this purpose an AC
voltage according to 4.6 shall be applied for a duration of not less than 10 s whilst the
equipment is switched on and off (type test).
The AC test source shall have the capability to activate protective devices and to indicate
weak points of circuitry. If protective devices are activated or parts are damaged, the test
shall be repeated with a test source having a capability according to IEC 61010-1:2010, 16.2.
After the test with AC overvoltage according to 4.6, defects, if any, shall be clearly indicated;
indications and displayed values shall not lead to unsafe interpretations.
After tests with AC overvoltages according to 4.6, the equipment shall stay within the
specification.
This includes reactivation of protective devices by the user without any repair.
The replacement of fuses accessible to the user should be considered as reactivation of a
protective device.
6.6.2 Overvoltage tests with DC voltage
In addition to the overvoltage tests with AC, a DC voltage of 1,2 times the magnitude of the
highest rated output voltage stored on a capacitor of 2 µF shall be applied in both polarities
whilst the equipment is switched on and off. After this, the measuring equipment shall stay
within the specification, but without activation of
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