IEC 61557-12:2018

IEC 61557-12 ®
Edition 2.0 2018-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical safety in low voltage distribution systems up to 1 000 V AC and
1 500 V DC. – Equipment for testing, measuring or monitoring of protective
measures –
Part 12: Power metering and monitoring devices (PMD)

Sécurité électrique dans les réseaux de distribution basse tension jusqu’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 12: Dispositifs de comptage et de surveillance du réseau électrique (PMD)

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IEC 61557-12 ®
Edition 2.0 2018-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical safety in low voltage distribution systems up to 1 000 V AC and

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

measures –
Part 12: Power metering and monitoring devices (PMD)

Sécurité électrique dans les réseaux de distribution basse tension jusqu’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 12: Dispositifs de comptage et de surveillance du réseau électrique (PMD)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.080.01; 29.240.01 ISBN 978-2-8322-6077-7

– 2 – IEC 61557-12:2018 © IEC 2018
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references. 11
3 Terms, definitions and notations. 11
3.1 General definitions . 11
3.2 Definitions related to uncertainty and performance . 13
3.3 Definitions related to electric phenomena . 17
3.4 Definitions related to measurement techniques . 20
3.5 Notations . 21
3.5.1 Functions . 21
3.5.2 Symbols and abbreviations . 21
3.5.3 Indices . 22
4 Requirements . 22
4.1 General requirements . 22
4.2 PMD general architecture . 22
4.3 Classification of PMD . 23
4.4 Structure of PMD. 24
4.4.1 Structure of PMD related to sensors . 24
4.4.2 Requirements for self-powered PMD . 24
4.5 List of applicable performance classes . 25
4.6 Operating and reference conditions for PMD . 25
4.6.1 Reference conditions . 25
4.6.2 Rated operating conditions . 26
4.7 Start-up conditions . 28
4.8 Requirements for PMD functions . 28
4.8.1 General requirements . 28
4.8.2 Active power (P) and active energy (E ) measurements . 29
a
4.8.3 Reactive power (Q , Q ) and reactive energy (E , E ) measurements . 35
A V rA rV
4.8.4 Apparent power (S , S ) and apparent energy (E , E )
A V apA apV
measurements . 38
4.8.5 Frequency (f) measurements . 40
4.8.6 RMS phase current (I) and neutral current (I , I ) measurements . 41
N Nc
4.8.7 RMS voltage (U) measurements . 45
4.8.8 Power factor (PF , PF ) measurements . 47
A V
4.8.9 Short term flicker (P ) and long term flicker (P ) measurements . 47
st lt
4.8.10 Voltage dip (U ) and voltage swell (U ) measurements . 48
dip swl
4.8.11 Voltage interruption (U ) measurements . 53
int
4.8.12 Transient overvoltage (U ) measurements . 54
tr
4.8.13 Voltage unbalance (U , U ) measurements . 54
nb nba
4.8.14 Voltage harmonics (U ) and voltage THD (THD and THD-R )
h u u
measurements . 55
4.8.15 Current unbalance (I , I ) measurements . 56
nb nba
4.8.16 Current harmonics (I ) and current THD (THD and THD-R )
h i i
measurements . 57

4.8.17 Minimum, maximum, peak, three-phases average and demand
measurements . 58
4.9 General mechanical requirements . 58
4.9.1 Vibration requirements . 58
4.9.2 IP requirements . 58
4.10 Safety requirements . 59
4.10.1 Protection against electrical hazards . 59
4.10.2 Protection against mechanical hazards . 60
4.10.3 Protection against other hazards . 60
4.11 EMC requirements . 60
4.11.1 Immunity . 60
4.11.2 Emission . 60
4.12 Inputs and/or outputs . 60
4.12.1 General . 60
4.12.2 Analog outputs . 60
4.12.3 Pulse outputs . 61
4.12.4 Control outputs . 61
4.12.5 Analog inputs . 61
4.12.6 Pulse and control inputs . 61
5 Marking and operating instructions . 61
5.1 General . 61
5.2 Marking . 61
5.3 Operating, installation and maintenance instructions . 62
5.3.1 General . 62
5.3.2 General characteristics . 62
5.3.3 Essential characteristics . 62
6 Tests . 64
6.1 General . 64
6.2 Type tests of PMD . 65
6.2.1 General . 65
6.2.2 Tests of intrinsic uncertainty . 65
6.2.3 Tests of variation of uncertainty with influence quantities . 65
6.2.4 Test of temperature influence . 65
6.2.5 Active power . 66
6.2.6 Apparent power . 68
6.2.7 Power factor . 69
6.2.8 Common mode voltage rejection test . 69
6.2.9 Frequency. 69
6.2.10 Measurement of voltage harmonics and THD . 70
u
6.2.11 Measurement of current harmonics and THD . 70
i
6.2.12 Dips and swells . 71
6.2.13 Voltage interruptions . 71
6.2.14 Outputs tests . 71
6.2.15 Climatic tests . 72
6.2.16 EMC tests . 73
6.2.17 Start-up tests . 73
6.2.18 Gapless measurement test . 73
6.2.19 Safety tests . 73
6.3 Routine tests . 73

– 4 – IEC 61557-12:2018 © IEC 2018
6.3.1 Protective bonding test . 73
6.3.2 Dielectric strength test . 74
6.3.3 Uncertainty test . 74
Annex A (informative) Metering, measuring and monitoring applications . 75
A.1 Applications on demand side and supply side . 75
A.2 Link between applications, devices and standards . 75
Annex B (informative) Definitions of electrical parameters . 77
B.1 General . 77
B.2 Definitions in the presence of a neutral . 77
B.3 Power measurement in three-phase three-wire systems using the two-
wattmeter method . 81
B.3.1 General . 81
B.3.2 Total active power . 82
B.3.3 Total vector reactive power using quadrature phase shift definition . 82
B.3.4 Total vector reactive power using Budeanu’s definition . 83
B.4 Additional relationships in case of sinusoidal voltage . 83
Annex C (informative) Convention about the sign of the power factor . 84
C.1 General . 84
C.2 Convention for power factor (consumer perspective) . 84
C.3 Convention for power factor (producer reference frame) . 85
Annex D (normative) Definitions of minimum, maximum, peak and demand values . 87
D.1 Demand quantities . 87
D.1.1 General . 87
D.1.2 Power demand . 87
D.1.3 Current demand . 87
D.1.4 Thermal current demand (or bi-metal current demand) . 87
D.1.5 Specified intervals for demand calculation . 87
D.2 Peak demand quantities . 88
D.3 Three-phase average quantities . 88
D.4 Maximum and minimum quantities . 88
Annex E (informative) Intrinsic uncertainty and operating uncertainty . 89
E.1 General . 89
E.2 Operating uncertainty calculation . 89
Annex F (informative) Recommended sensor classes for the different kinds of PMD . 91
F.1 General considerations . 91
F.2 Specific case of an active power and energy measurement, achieved by a
PMD associated with an external current sensor or/and a voltage sensor . 91
F.3 List of functions affected by uncertainty of external sensors . 91
Annex G (informative) Notion of measurement uncertainty . 93
G.1 General considerations . 93
G.2 Computing the expanded uncertainty . 93
G.2.1 General . 93
G.2.2 Estimated standard deviation . 93
G.2.3 Expanded uncertainty . 94
G.3 Determining the measurement uncertainty . 95
G.3.1 Systematic error . 95
G.3.2 Measurement uncertainty . 95
G.4 Using the measurement uncertainty as a pass/fail criterion . 96

G.4.1 Intrinsic uncertainty tests . 96
G.4.2 Tests with influence quantities . 96
G.4.3 Overall pass/fail criterion . 96
Bibliography . 98

Figure 1 – PMD generic measurement chain . 23
Figure 2 – Description of different types of PMD . 24
Figure 3 – Relationship between ambient air temperature and relative humidity . 28
Figure 4 – Waveform for odd harmonics influence test on active power measurement . 66
Figure 5 – Spectral content for odd harmonics influence test on active power
measurement . 67
Figure 6 – Waveform for sub-harmonics influence test on active power measurement . 68
Figure 7 – Spectral content for sub-harmonics influence test on active power

measurement . 68
Figure 8 – Common mode voltage influence testing . 69
Figure 9 – Waveform for harmonics influence test on frequency measurement . 70
Figure A.1 – Simplified overview of measurement applications on supply side and
demand side . 75
Figure B.1 – Arithmetic and vector apparent powers in sinusoidal situation . 81
Figure B.2 – Three-phase circuit without neutral . 82
Figure C.1 – Formatting of power factor with a consumer perspective . 84
Figure C.2 – Convention for power factor with a producer perspective . 85
Figure D.1 – Thermal current demand . 87
Figure D.2 – Fixed block interval . 88
Figure D.3 – Sliding block interval . 88
Figure E.1 – Different kinds of uncertainties . 89
Figure E.2 – Flowchart for the determination of the operating uncertainty . 90
Figure G.1 – Illustration of the notion of measurement uncertainty . 95
Figure G.2 – Overview of the uncertainty test procedure . 97

Table 1 – Functional classification of PMD with minimal required functions . 23
Table 2 – Structure of PMD . 24
Table 3 – List of applicable performance classes . 25
Table 4 – Reference conditions for testing . 26
Table 5 – Rated operating temperatures for portable equipment . 26
Table 6 – Rated operating temperatures for fixed installed equipment . 27
Table 7 – Humidity and altitude operating conditions . 27
Table 8 – Intrinsic uncertainty table for active power and active energy measurement . 30
Table 9 – Influence quantities for active power and active energy measurement (1 of 3) . 31
Table 10 – Minimum test period . 34
Table 11 – Starting current for active power and active energy measurement . 35
Table 12 – Intrinsic uncertainty table for reactive power and reactive energy
measurement . 35
Table 13 – Influence quantities for reactive power and reactive energy measurement . 36
Table 14 – Minimum test period . 37

– 6 – IEC 61557-12:2018 © IEC 2018
Table 15 – Starting current for reactive energy measurement . 38
Table 16 – Intrinsic uncertainty table for apparent power and apparent energy
measurement . 38
Table 17 – Influence quantities for apparent power and apparent energy measurement . 39
Table 18 – Intrinsic uncertainty table for frequency measurement . 40
Table 19 – Influence quantities for frequency measurement . 41
Table 20 – Rated range of operation for phase current measurement . 41
Table 21 – Rated range of operation for neutral current (calculated or measured) . 42
Table 22 – Intrinsic uncertainty table for phase current . 42
Table 23 – Intrinsic uncertainty table for neutral current measurement . 42
Table 24 – Intrinsic uncertainty table for neutral current calculation . 43
Table 25 – Influence quantities for phase current and neutral current measurement . 44
Table 26 – Rated range of operation for RMS voltage measurement . 45
Table 27 – Intrinsic uncertainty table for RMS voltage measurement . 45
Table 28 – Influence quantities for RMS voltage measurement . 46
Table 29 – Intrinsic uncertainty table for power factor measurement . 47
Table 30 – Intrinsic uncertainty table for flicker measurement . 48
Table 31 – Rated range of operation for voltage dips and swells measurement . 50
Table 32 – Intrinsic uncertainty table for voltage dips and swells measurement . 51
Table 33 – Influence quantities for dips and swells measurement . 52
Table 34 – Intrinsic uncertainty table for voltage interruption measurement . 54
Table 35 – Intrinsic uncertainty table for transient overvoltage measurement . 54
Table 36 – Intrinsic uncertainty table for voltage unbalance measurement . 55
Table 37 – Rated range of operation for voltage harmonics measurement . 55
Table 38 – Intrinsic uncertainty table for voltage harmonics measurement . 55
Table 39 – Intrinsic uncertainty table for voltage THD or THD-R measurement . 56
u u
Table 40 – Intrinsic uncertainty table for current unbalance measurement . 56
Table 41 – Rated range of operation for current harmonics measurement . 57
Table 42 – Intrinsic uncertainty table for current harmonics measurement . 57
Table 43 – Intrinsic uncertainty table for current THD and THD-R measurement . 57
i i
Table 44 – Minimum IP requirements for PMD . 58
Table 45 – PMD specification form . 63
Table 46 – Characteristics specification template . 64
Table A.1 – Main measurement applications . 76
Table B.1 – Definition of symbols . 77
Table B.2 – Calculation definitions for electrical parameters . 78
Table C.1 – Conventions for the sign of Power factor with a Consumer perspective . 85
Table C.2 – Conventions for the sign of power factor with a producer perspective . 86
Table F.1 – PMD SD associated with current sensor or PMD DS associated with
voltage sensor or PMD SS associated with voltage and current sensors . 91
Table F.2 – List of functions affected by uncertainty of external sensors . 92
Table G.1 – Correction factor C(N) for sample size N . 94

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 12: Power metering and monitoring devices (PMD)

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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 61557-12 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 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) PMD-A has been withdrawn due the fact these devices are now mainly covered by the IEC
62586 series of standards.
b) Three categories of PMD have been created with a list of minimum required functions for
each category.
– 8 – IEC 61557-12:2018 © IEC 2018
c) Added a new Annex A explaining the different applications linked to the relevant standards
and devices, and another new Annex C about the power factor conventions.
The text of this International Standard is based on the following documents:
FDIS Report on voting
85/644/FDIS 85/649/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.
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.
INTRODUCTION
Energy distribution systems need to guarantee energy efficiency, availability and network
performances in order to address the following challenges:
– sustainable development requirements where energy measurement, for instance, is
recognised as an essential element of energy management, part of the overall drive to
reduce carbon emissions and to improve the commercial efficiency of manufacturing,
commercial organizations and public services;
– technological evolutions (electronic loads, electronic measuring methods, etc.);
– end-users needs (cost saving, compliance with aspects of building regulations, etc.)
regarding electrical energy management as well as other energies, or fluids. Other
functionalities involving several non electrical parameters are often needed in parallel;
– safety and continuity of service;
– evolution of installation standards, for instance over-current detection is now a new
requirement for the neutral conductor due to harmonic content.
Monitoring electrical quantities in internal networks allows to address these challenges.
The devices on the current market have different characteristics, which need a common
system of references. Therefore there is a need for this document in order to facilitate the
choices of the end-users in terms of performance, safety, interpretation of the indications, etc.
This document provides a basis by which such devices can be specified and described, and
their performance evaluated.
In order to fulfil the requirements of the energy efficiency project, many PMD measuring
electrical parameters can also collect data (water, air, gas, temperature…) coming from other
sensors or meters inside building or plant areas. In order to be able to transmit all these data
to a supervision software it will be relevant to equip the PMD with a communication bus. The
supervision software will then manage all the collected data in order to monitor them and
produce useful reports for energy usage and consumption analysis.

– 10 – IEC 61557-12:2018 © IEC 2018
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 12: Power metering and monitoring devices (PMD)

1 Scope
This part of IEC 61557 specifies requirements for power metering and monitoring devices
(PMD) that measure and monitor the electrical quantities within electrical distribution systems,
and optionally other external signals. These requirements also define the performance in
single- and three-phase AC or DC systems having rated voltages up to 1 000 V AC or up to
1 500 V DC.
These devices are fixed or portable. They are intended to be used indoors and/or outdoors.
Power metering and monitoring devices (PMD), as defined in this document, give additional
safety information, which aids the verification of the installation and enhances the
performance of the distribution systems.
The power metering and monitoring devices (PMD) for electrical parameters described in this
document are used for general industrial and commercial applications.
This document does not address functional safety and cyber security aspects.
This document is not applicable for:
– electricity metering equipment that complies with IEC 62053-21, IEC 62053-22,
IEC 62053-23 and IEC 62053-24. Nevertheless, uncertainties defined in this document for
active and reactive energy measurement are derived from those defined in IEC 62053 (all
parts);
– the measurement and monitoring of electrical parameters defined in IEC 61557-2 to
IEC 61557-9 and IEC 61557-13 or in IEC 62020;
– power quality instrument (PQI) according IEC 62586 (all parts);
– devices covered by IEC 60051 (all parts) (direct acting analogue electrical measuring
instrument).
NOTE 1 Generally such types of devices are used in the following applications or for the following general needs:
– energy management inside the installation, such as facilitating the implementation of documents such as
ISO 50001 and IEC 60364-8-1;
– monitoring and/or measurement of electrical parameters;
– measurement and/or monitoring of the quality of energy inside commercial/industrial installations.
NOTE 2 A measuring and monitoring device of electrical parameters usually consists of several functional
modules. All or some of the functional modules are combined in one device. Examples of functional modules are:
– measurement and monitoring of several electrical parameters simultaneously;
– energy measurement and/or monitoring, as well as sometimes compliance with aspects of building regulations;
– alarms functions;
– demand side quality (current and voltage harmonics, over/under voltages, voltage dips and swells, etc.).
NOTE 3 PMD are historically called power meter, power monitor, power monitor device, power energy monitoring
device, power analyser, multifunction meter, measuring multifunction equipment, energy meters.

NOTE 4 Metering, measuring and monitoring applications are explained in Annex A.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2: Tests – Tests B: Dry heat
IEC 60068-2-30, Environmental testing – Part 2-30 – Tests – Test Db: Damp heat, cyclic
(12 h + 12 h cycle)
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61000-4-30:2015, Electromagnetic compatibility (EMC) – Part 4-30: Testing and
measurement techniques – Power quality measurem
...

IEC 61557-12 ®
Edition 2.1 2021-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical safety in low voltage distribution systems up to 1 000 V AC and
1 500 V DC – Equipment for testing, measuring or monitoring of protective
measures –
Part 12: Power metering and monitoring devices (PMD)

Sécurité électrique dans les réseaux de distribution basse tension jusqu’à
1 000 V en courant alternatif et 1 500 V en courant continu – Dispositifs de
contrôle, de mesure ou de surveillance de mesures de protection –
Partie 12: Dispositifs de comptage et de surveillance du réseau électrique (PMD)
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IEC 61557-12 ®
Edition 2.1 2021-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electrical safety in low voltage distribution systems up to 1 000 V AC and

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

measures –
Part 12: Power metering and monitoring devices (PMD)

Sécurité électrique dans les réseaux de distribution basse tension jusqu’à

1 000 V en courant alternatif et 1 500 V en courant continu – Dispositifs de

contrôle, de mesure ou de surveillance de mesures de protection –

Partie 12: Dispositifs de comptage et de surveillance du réseau électrique (PMD)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.080.01; 29.240.01 ISBN 978-2-8322-9845-9

IEC 61557-12 ®
Edition 2.1 2021-05
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Electrical safety in low voltage distribution systems up to 1 000 V AC and
1 500 V DC – Equipment for testing, measuring or monitoring of protective
measures –
Part 12: Power metering and monitoring devices (PMD)

Sécurité électrique dans les réseaux de distribution basse tension jusqu’à
1 000 V en courant alternatif et 1 500 V en courant continu – Dispositifs de
contrôle, de mesure ou de surveillance de mesures de protection –
Partie 12: Dispositifs de comptage et de surveillance du réseau électrique (PMD)

– 2 – IEC 61557-12:2018+AMD1:2021 CSV
© IEC 2021
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 13
3 Terms, definitions and notations . 13
3.1 General definitions . 14
3.2 Definitions related to uncertainty and performance . 16
3.3 Definitions related to electric phenomena . 19
3.4 Definitions related to measurement techniques . 22
3.5 Notations . 23
3.5.1 Functions . 23
3.5.2 Symbols and abbreviations . 23
3.5.3 Indices . 24
4 Requirements . 24
4.1 General requirements . 24
4.2 PMD general architecture . 24
4.3 Classification of PMD . 25
4.4 Structure of PMD . 26
4.4.1 Structure of PMD related to sensors . 26
4.4.2 Requirements for self-powered PMD . 26
4.5 List of applicable performance classes . 27
4.6 Operating and reference conditions for PMD . 27
4.6.1 Reference conditions . 27
4.6.2 Rated operating conditions . 28
4.7 Start-up conditions . 30
4.8 Requirements for PMD functions . 30
4.8.1 General requirements . 30
4.8.2 Active power (P) and active energy (E ) measurements . 31
a
4.8.3 Reactive power (Q , Q ) and reactive energy (E , E ) measurements . 37
A V rA rV
4.8.4 Apparent power (S , S ) and apparent energy (E , E )
A V apA apV
measurements . 40
4.8.5 Frequency (f) measurements . 42
4.8.6 RMS phase current (I) and neutral current (I , I ) measurements . 43
N Nc
4.8.7 RMS voltage (U) measurements . 47
4.8.8 Power factor (PF , PF ) measurements . 49
A V
4.8.9 Short term flicker (P ) and long term flicker (P ) measurements . 49
st lt
4.8.10 Voltage dip (U ) and voltage swell (U ) measurements . 50
dip swl
4.8.11 Voltage interruption (U ) measurements . 55
int
4.8.12 Transient overvoltage (U ) measurements . 56
tr
4.8.13 Voltage unbalance (U , U ) measurements . 56
nb nba
4.8.14 Voltage harmonics (U ) and voltage THD (THD and THD-R )
h u u
measurements . 57
4.8.15 Current unbalance (I , I ) measurements . 58
nb nba
4.8.16 Current harmonics (I ) and current THD (THD and THD-R )
h i i
measurements . 59

© IEC 2021
4.8.17 Minimum, maximum, peak, three-phases average and demand
measurements . 60
4.9 General mechanical requirements . 60
4.9.1 Vibration requirements . 60
4.9.2 IP requirements . 60
4.10 Safety requirements . 61
4.10.1 Protection against electrical hazards . 61
4.10.2 Protection against mechanical hazards . 62
4.10.3 Protection against other hazards . 62
4.11 EMC requirements . 62
4.11.1 Immunity . 62
4.11.2 Emission . 62
4.12 Inputs and/or outputs . 62
4.12.1 General . 62
4.12.2 Analog outputs . 62
4.12.3 Pulse outputs . 63
4.12.4 Control outputs . 63
4.12.5 Analog inputs . 63
4.12.6 Pulse and control inputs . 63
5 Marking and operating instructions . 63
5.1 General . 63
5.2 Marking . 63
5.3 Operating, installation and maintenance instructions . 64
5.3.1 General . 64
5.3.2 General characteristics . 64
5.3.3 Essential characteristics . 64
6 Tests . 66
6.1 General . 66
6.2 Type tests of PMD . 67
6.2.1 General . 67
6.2.2 Tests of intrinsic uncertainty . 67
6.2.3 Tests of variation of uncertainty with influence quantities . 67
6.2.4 Test of temperature influence . 67
6.2.5 Active power . 68
6.2.6 Apparent power . 70
6.2.7 Power factor . 71
6.2.8 Common mode voltage rejection test . 71
6.2.9 Frequency . 71
6.2.10 Measurement of voltage harmonics and THD . 72
u
6.2.11 Measurement of current harmonics and THD . 72
i
6.2.12 Dips and swells . 73
6.2.13 Voltage interruptions . 73
6.2.14 Outputs tests . 73
6.2.15 Climatic tests . 74
6.2.16 EMC tests . 75
6.2.17 Start-up tests . 75
6.2.18 Gapless measurement test . 75
6.2.19 Safety tests . 75
6.3 Routine tests. 75

– 4 – IEC 61557-12:2018+AMD1:2021 CSV
© IEC 2021
6.3.1 Protective bonding test . 75
6.3.2 Dielectric strength test . 76
6.3.3 Uncertainty test . 76
Annex A (informative) Metering, measuring and monitoring applications . 77
A.1 Applications on demand side and supply side . 77
A.2 Link between applications, devices and standards . 77
Annex B (informative) Definitions of electrical parameters . 79
B.1 General . 79
B.2 Definitions in the presence of a neutral . 79
B.3 Power measurement in three-phase three-wire systems using the two-
wattmeter method . 83
B.3.1 General . 83
B.3.2 Total active power . 84
B.3.3 Total vector reactive power using quadrature phase shift definition . 84
B.3.4 Total vector reactive power using Budeanu’s definition . 85
B.4 Additional relationships in case of sinusoidal voltage . 85
Annex C (informative) Convention about the sign of the power factor . 86
C.1 General . 86
C.2 Convention for power factor (consumer perspective) . 86
C.3 Convention for power factor (producer reference frame) . 87
Annex D (normative) Definitions of minimum, maximum, peak and demand values . 89
D.1 Demand quantities . 89
D.1.1 General . 89
D.1.2 Power demand. 89
D.1.3 Current demand . 89
D.1.4 Thermal current demand (or bi-metal current demand). 89
D.1.5 Specified intervals for demand calculation . 89
D.2 Peak demand quantities . 90
D.3 Three-phase average quantities . 90
D.4 Maximum and minimum quantities . 90
Annex E (informative) Intrinsic uncertainty and operating uncertainty . 91
E.1 General . 91
E.2 Operating uncertainty calculation . 91
Annex F (informative) Recommended sensor classes for the different kinds of PMD . 93
F.1 General considerations . 93
F.2 Specific case of an active power and energy measurement, achieved by a
PMD associated with an external current sensor or/and a voltage sensor . 93
F.3 List of functions affected by uncertainty of external sensors . 93
Annex G (informative) Notion of measurement uncertainty . 95
G.1 General considerations . 95
G.2 Computing the expanded uncertainty . 95
G.2.1 General . 95
G.2.2 Estimated standard deviation . 95
G.2.3 Expanded uncertainty . 96
G.3 Determining the measurement uncertainty . 97
G.3.1 Systematic error . 97
G.3.2 Measurement uncertainty. 97
G.4 Using the measurement uncertainty as a pass/fail criterion . 98

© IEC 2021
G.4.1 Intrinsic uncertainty tests . 98
G.4.2 Tests with influence quantities . 98
G.4.3 Overall pass/fail criterion . 98
Annex H (normative) Requirements for power metering and monitoring function (PMF)
and additional requirements for equipment embedding power metering and monitoring
function (EPMF) . 100
H.1 Scope . 100
H.2 Normative references . 100
H.3 Terms, definitions and notations . 101
H.4 Requirements for PMF and additional requirements for EPMF . 101
H.4.1 General requirements . 101
H.4.2 EPMF general architecture . 102
H.4.3 Classification of PMF . 102
H.4.4 Structure of EPMF . 103
H.4.5 List of applicable performance classes for PMF . 103
H.4.6 Operating and reference conditions . 103
H.4.7 Start-up conditions for EPMF . 104
H.4.8 Requirements for PMF . 104
H.4.9 General mechanical requirements . 104
H.4.10 Safety requirements. 104
H.4.11 EMC requirements . 104
H.4.12 Inputs and/or outputs . 104
H.5 Marking and operating instructions . 105
H.5.1 General . 105
H.5.2 Marking . 105
H.5.3 Operating, installation and maintenance instructions . 105
H.6 Tests . 106
H.6.1 General . 106
H.6.2 Type tests of EPMF . 106
H.6.3 Routine tests of EPMF . 108
Annex I (informative) Potential new requirements derived from IEC 62053-2x series of
standards . 109
I.1 Scope . 109
I.2 Future requirements for active power (P) and active energy (E )
a
measurements . 110
I.2.1 Future intrinsic uncertainty tables . 110
I.2.2 Future limits of variations due to influence quantities . 111
I.3 Future requirements for reactive power (Q) and reactive energy (E )
r
measurements . 116
I.3.1 Future intrinsic uncertainty tables . 116
I.3.2 Limits of variation in percentage error due to influence quantities . 116
Bibliography . 119

Figure 1 – PMD generic measurement chain . 25
Figure 2 – Description of different types of PMD . 26
Figure 3 – Relationship between ambient air temperature and relative humidity . 30
Figure 4 – Waveform for odd harmonics influence test on active power measurement . 68
Figure 5 – Spectral content for odd harmonics influence test on active power
measurement . 69

– 6 – IEC 61557-12:2018+AMD1:2021 CSV
© IEC 2021
Figure 6 – Waveform for sub-harmonics influence test on active power measurement. 70
Figure 7 – Spectral content for sub-harmonics influence test on active power
measurement . 70
Figure 8 – Common mode voltage influence testing . 71
Figure 9 – Waveform for harmonics influence test on frequency measurement . 72
Figure A.1 – Simplified overview of measurement applications on supply side and
demand side . 77
Figure B.1 – Arithmetic and vector apparent powers in sinusoidal situation . 83
Figure B.2 – Three-phase circuit without neutral . 84
Figure C.1 – Formatting of power factor with a consumer perspective . 86
Figure C.2 – Convention for power factor with a producer perspective . 87
Figure D.1 – Thermal current demand . 89
Figure D.2 – Fixed block interval . 90
Figure D.3 – Sliding block interval . 90
Figure E.1 – Different kinds of uncertainties . 91
Figure E.2 – Flowchart for the determination of the operating uncertainty . 92
Figure G.1 – Illustration of the notion of measurement uncertainty . 97
Figure G.2 – Overview of the uncertainty test procedure . 99
Figure H.1 – Example of architecture of EPMF . 102

Table 1 – Functional classification of PMD with minimal required functions . 25
Table 2 – Structure of PMD . 26
Table 3 – List of applicable performance classes . 27
Table 4 – Reference conditions for testing . 28
Table 5 – Rated operating temperatures for portable equipment . 28
Table 6 – Rated operating temperatures for fixed installed equipment . 29
Table 7 – Humidity and altitude operating conditions . 29
Table 8 – Intrinsic uncertainty table for active power and active energy measurement . 32
Table 9 – Influence quantities for active power and active energy measurement (1 of 3) . 33
Table 10 – Minimum test period . 36
Table 11 – Starting current for active power and active energy measurement . 37
Table 12 – Intrinsic uncertainty table for reactive power and reactive energy
measurement . 37
Table 13 – Influence quantities for reactive power and reactive energy measurement . 38
Table 14 – Minimum test period . 39
Table 15 – Starting current for reactive energy measurement . 40
Table 16 – Intrinsic uncertainty table for apparent power and apparent energy
measurement . 40
Table 17 – Influence quantities for apparent power and apparent energy measurement . 41
Table 18 – Intrinsic uncertainty table for frequency measurement . 42
Table 19 – Influence quantities for frequency measurement . 43
Table 20 – Rated range of operation for phase current measurement . 43
Table 21 – Rated range of operation for neutral current (calculated or measured) . 44
Table 22 – Intrinsic uncertainty table for phase current . 44

© IEC 2021
Table 23 – Intrinsic uncertainty table for neutral current measurement . 44
Table 24 – Intrinsic uncertainty table for neutral current calculation . 45
Table 25 – Influence quantities for phase current and neutral current measurement . 46
Table 26 – Rated range of operation for RMS voltage measurement . 47
Table 27 – Intrinsic uncertainty table for RMS voltage measurement. 47
Table 28 – Influence quantities for RMS voltage measurement . 48
Table 29 – Intrinsic uncertainty table for power factor measurement . 49
Table 30 – Intrinsic uncertainty table for flicker measurement . 50
Table 31 – Rated range of operation for voltage dips and swells measurement . 52
Table 32 – Intrinsic uncertainty table for voltage dips and swells measurement . 53
Table 33 – Influence quantities for dips and swells measurement . 54
Table 34 – Intrinsic uncertainty table for voltage interruption measurement . 56
Table 35 – Intrinsic uncertainty table for transient overvoltage measurement . 56
Table 36 – Intrinsic uncertainty table for voltage unbalance measurement . 57
Table 37 – Rated range of operation for voltage harmonics measurement . 57
Table 38 – Intrinsic uncertainty table for voltage harmonics measurement . 57
Table 39 – Intrinsic uncertainty table for voltage THD or THD-R measurement . 58
u u
Table 40 – Intrinsic uncertainty table for current unbalance measurement . 58
Table 41 – Rated range of operation for current harmonics measurement . 59
Table 42 – Intrinsic uncertainty table for current harmonics measurement . 59
Table 43 – Intrinsic uncertainty table for current THD and THD-R measurement . 59
i i
Table 44 – Minimum IP requirements for PMD . 60
Table 45 – PMD specification form . 65
Table 46 – Characteristics specification template . 66
Table A.1 – Main measurement applications . 78
Table B.1 – Definition of symbols . 79
Table B.2 – Calculation definitions for electrical parameters . 80
Table C.1 – Conventions for the sign of Power factor with a Consumer perspective . 87
Table C.2 – Conventions for the sign of power factor with a producer perspective . 88
Table F.1 – PMD SD associated with current sensor or PMD DS associated with
voltage sensor or PMD SS associated with voltage and current sensors . 93
Table F.2 – List of functions affected by uncertainty of external sensors . 94
Table G.1 – Correction factor C(N) for sample size N . 96
Table H.1 – List of equipment that may embed EPMF . 101
Table H.2 – Functional classification of PMF with minimal required functions . 102
Table H.3 – Structure of EPMF . 103
Table H.4 – Value of current according to the type of EPMF . 104
Table H.5 – EPMF specification form . 105
Table I.1 – Future intrinsic uncertainty table for active power and active energy

measurement for classes > 0,5 . 110
Table I.2 – Future intrinsic uncertainty table for active power and active energy
measurement for classes ≤ 0,5 . 110
Table I.3 – Limits of variation in percentage error due to influence quantities for
classes > 0,5 . 111

– 8 – IEC 61557-12:2018+AMD1:2021 CSV
© IEC 2021
Table I.4 – Limits of variation in percentage error due to influence quantities for
classes ≤ 0,5 . 113
Table I.5 – Future intrinsic uncertainty table for reactive power and reactive energy
measurement . 116
Table I.6 – Limits of variation in percentage error due to influence quantities . 116

© IEC 2021
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 12: Power metering and monitoring devices (PMD)
FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 61557-12 edition 2.1 contains the second edition (2018-10) [documents 85/644/FDIS and
85/649/RVD] and its corrigendum 1 (2022-09), its amendment 1 (2021-05) [documents
85/755/FDIS and 85/764/RVD] and its corrigendum 1 (2022-09). The contents of the
corrigenda only applies to the French versions.
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red
text. A separate Final version with all changes accepted is available in this publication.

– 10 – IEC 61557-12:2018+AMD1:2021 CSV
© IEC 2021
International Standard IEC 61557-12 has been prepared by IEC technical committee 85:
Measuring equipment for electrical and electromagnetic quantities.
This second edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) PMD-A has been withdrawn due the fact these devices are now mainly covered by the IEC
62586 series of standards.
b) Three categories of PMD have been created with a list of minimum required functions for
each category.
c) Added a new Annex A explaining the different applications linked to the relevant standa
...