Electromagnetic compatibility (EMC) -- Part 2-12 : Environment - Compatibility levels for low-frequency conducted disturbances and signalling in public medium-voltage power supply systems

This part of EN 61000 is concerned with conducted disturbances in the frequency range from 0 kHz to 9 kHz, with an extension up to 148,5 kHz specifically for mains signalling systems. Compatibility levels are specified for electromagnetic disturbances of the types which can be expected in public medium voltage power supply systems, for guidance in: a) the limits to be set for disturbance emission into public power supply systems (including the planning levels defined in 3.1.5); b) the immunity limits to be set by product committees and others for the equipment exposed to the conducted disturbances present in public power supply systems. The disturbance phenomena considered are: voltage fluctuations and flicker, harmonics up to and including order 50, inter-harmonics up to the 50th harmonic, voltage distortions at higher frequencies (above 50th harmonic), voltage dips and short supply interruptions, voltage unbalance, transient overvoltages, power frequency variation, d.c. components, mains signalling. The medium-voltage systems covered by this standard are public distribution systems supplying either: a) private installations in which equipment is connected directly or through transformers, or b) substations feeding public low-voltage distribution systems.

Elektromagnetische Verträglichkeit -- Teil 2-12: Umgebungsbedingungen - Verträglichkeitspegel für niederfrequente leitungsgeführte Störgrößen und Signalübertragung in öffentlichen Mittelspannungsnetzen

Compatibilité électromagnétique (CEM) -- Partie 2-12: Environnement - Niveaux de compatibilité pour les perturbations conduites à basse fréquence et la transmission des signaux sur les réseaux publics d'alimentation moyenne tension

La présente partie de la EN 61000 s'applique aux perturbations conduites dans le domaine de fréquence de 0 kHz à 9 kHz, avec une extension jusqu'à 148,5 kHz pour les systèmes de transmission de signaux sur le réseau. Les niveaux de compatibilité sont donnés pour les types de perturbations électromagnétiques auxquelles on peut s'attendre sur les réseaux de distribution publics moyenne tension, dans le but d'aider à définir: a) les limites devant être établies pour les émissions perturbatrices sur les réseaux publics de distribution d'énergie (comprenant également les niveaux de planification tels que définis en 3.1.5); b) les limites d'immunité devant être établies par les comités de produit ou autres concernant les équipements soumis aux perturbations conduites par les réseaux publics de distribution d'énergie. Les phénomènes perturbateurs considérés sont: les fluctuations de tension et le flicker, les harmoniques jusque et y compris le rang 50, les interharmoniques jusqu'au rang 50, les distorsions de tension aux fréquences supérieures (au-dessus du rang 50), les creux de tension et les coupures brèves, le déséquilibre de tension, les surtensions transitoires, les variations de fréquence, les composantes continues, les systèmes de transmission de signaux sur le réseau. Les réseaux moyenne tension couverts par cette norme sont des réseaux de distribution publics alimentant: a) soit des installations privées dans lesquelles le matériel est raccordé directement ou à travers de transformateurs, b) soit des postes de transformation alimentant des réseaux de distribution publics basse tension.

Electromagnetic compatibility (EMC) -- Part 2-12: Environment - Compatibility levels for low-frequency conducted disturbances and signalling in public medium-voltage power supply systems (IEC 61000-2-12:2003)

General Information

Status
Published
Publication Date
30-Nov-2003
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Dec-2003
Due Date
01-Dec-2003
Completion Date
01-Dec-2003

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SLOVENSKI STANDARD
SIST EN 61000-2-12:2003
01-december-2003
Electromagnetic compatibility (EMC) -- Part 2-12: Environment - Compatibility
levels for low-frequency conducted disturbances and signalling in public medium-
voltage power supply systems (IEC 61000-2-12:2003)

Electromagnetic compatibility (EMC) -- Part 2-12 : Environment - Compatibility levels for

low-frequency conducted disturbances and signalling in public medium-voltage power

supply systems
Elektromagnetische Verträglichkeit -- Teil 2-12: Umgebungsbedingungen -
Verträglichkeitspegel für niederfrequente leitungsgeführte Störgrößen und
Signalübertragung in öffentlichen Mittelspannungsnetzen
Compatibilité électromagnétique (CEM) -- Partie 2-12: Environnement - Niveaux de

compatibilité pour les perturbations conduites à basse fréquence et la transmission des

signaux sur les réseaux publics d'alimentation moyenne tension
Ta slovenski standard je istoveten z: EN 61000-2-12:2003
ICS:
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
SIST EN 61000-2-12:2003 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 61000-2-12:2003
---------------------- Page: 2 ----------------------
SIST EN 61000-2-12:2003
EUROPEAN STANDARD EN 61000-2-12
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2003
ICS 33.100.01
English version
Electromagnetic compatibility (EMC)
Part 2-12 : Environment –
Compatibility levels for low-frequency conducted disturbances and
signalling in public medium-voltage power supply systems
(IEC 61000-2-12:2003)
Compatibilité électromagnétique (CEM) Elektromagnetische Verträglichkeit
Partie 2-12: Environnement – Teil 2-12: Umgebungsbedingungen -
Niveaux de compatibilité pour Verträglichkeitspegel für niederfrequente
les perturbations conduites à basse leitungsgeführte Störgrößen und
fréquence et la transmission des signaux Signalübertragung in öffentlichen
sur les réseaux publics d'alimentation Mittelspannungsnetzen
moyenne tension (IEC 61000-2-12:2003)
(CEI 61000-2-12:2003)

This European Standard was approved by CENELEC on 2003-06-01. 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, Czech Republic,

Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,

Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and 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

© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61000-2-12:2003 E
---------------------- Page: 3 ----------------------
SIST EN 61000-2-12:2003
EN 61000-2-12:2003 - 2 -
Foreword

The text of document 77A/404/FDIS, future edition 1 of IEC 61000-2-12, prepared by SC 77A, Low

frequency phenomena, of IEC TC 77, Electromagnetic compatibility, was submitted to the

IEC-CENELEC parallel vote and was approved by CENELEC as EN 61000-2-12 on 2003-06-01.

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) 2004-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2006-06-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A and B are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 61000-2-12:2003 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 60038 NOTE Harmonized as HD 472 S1:1989 (modified).
IEC 60868 NOTE Harmonized as HD 498 S1:1987 (not modified).
IEC 60868-0 NOTE Harmonized as EN 60868-0:1993 (not modified).
IEC 61000-3-2 NOTE Harmonized as EN 61000-3-2:2000 (modified).
IEC 61000-3-3 NOTE Harmonized as EN 61000-3-3:1995 (not modified).
__________
---------------------- Page: 4 ----------------------
SIST EN 61000-2-12:2003
- 3 - EN 61000-2-12:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

This European Standard incorporates by dated or undated reference, provisions from other

publications. These normative references are cited at the appropriate places in the text and the

publications are listed hereafter. For dated references, subsequent amendments to or revisions of any

of these publications apply to this European Standard only when incorporated in it by amendment or

revision. For undated references the latest edition of the publication referred to applies (including

amendments).

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 60071 Series Insulation co-ordination EN 60071 Series
1) 2)
IEC 60071-1 - Insulation co-ordination EN 60071-1 1995
Part 1: Definitions, principles and rules
1) 2)
IEC 61000-2-2 - Electromagnetic compatibility (EMC) EN 61000-2-2 2002
Part 2-2: Environment - Compatibility
levels for low-frequency conducted
disturbances and signalling in public
low-voltage power supply systems
1) 2)
IEC 61000-2-4 - Part 2-4: Environment - Compatibility EN 61000-2-4 2002
levels in industrial plants for low-
frequency conducted disturbances
1) 2)
IEC 61000-4-7 - Part 4-7: Testing and measurement EN 61000-4-7 2002
techniques - General guide on
harmonics and interharmonics
measurements and instrumentation, for
power supply systems and equipment
connected thereto
Undated reference.
Valid edition at date of issue.
---------------------- Page: 5 ----------------------
SIST EN 61000-2-12:2003
---------------------- Page: 6 ----------------------
SIST EN 61000-2-12:2003
NORME CEI
INTERNATIONALE IEC
61000-2-12
INTERNATIONAL
Première édition
STANDARD
First edition
2003-04
Compatibilité électromagnétique (CEM) –
Partie 2-12:
Environnement – Niveaux de compatibilité
pour les perturbations conduites à basse
fréquence et la transmission des signaux
sur les réseaux publics d'alimentation
moyenne tension
Electromagnetic compatibility (EMC) –
Part 2-12:
Environment – Compatibility levels for
low-frequency conducted disturbances and
signalling in public medium-voltage power
supply systems
 IEC 2003 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
Commission Electrotechnique Internationale PRICE CODE
International Electrotechnical Commission
Международная Электротехническая Комиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 7 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 3 –
CONTENTS

FOREWORD .......................................................................................................................... 5

INTRODUCTION ....................................................................................................................9

1 Scope and object ............................................................................................................11

2 Normative references......................................................................................................13

3 Terms and definitions......................................................................................................13

3.1 General definitions.................................................................................................13

3.2 Phenomena related definitions ...............................................................................15

4 Compatibility levels .........................................................................................................19

4.1 General comment ..................................................................................................19

4.2 Voltage fluctuations and flicker...............................................................................21

4.3 Harmonics .............................................................................................................21

4.4 Interharmonics and voltage components at frequencies above that of the

50 harmonic........................................................................................................23

4.5 Voltage dips and short supply interruptions.............................................................23

4.6 Voltage unbalance .................................................................................................25

4.7 Transient overvoltages...........................................................................................25

4.8 Temporary power frequency variation.....................................................................25

4.9 DC component.......................................................................................................25

4.10 Mains signalling .....................................................................................................27

Annex A (informative) The function of compatibility levels and planning levels in EMC...........31

A.1 The need for compatibility levels ............................................................................31

A.2 Relation between compatibility level and immunity levels ........................................31

A.3 Relation between compatibility level and emission limits .........................................33

A.4 Planning levels.......................................................................................................37

A.5 Illustration of compatibility, emission, immunity and planning levels ........................37

Annex B (informative) Discussion of some disturbance phenomena ......................................41

B.1 Resolution of non-sinusoidal voltages and currents ................................................41

B.2 Interharmonics and voltage components at frequencies above that of the 50

harmonic................................................................................................................45

B.3 Voltage dips and short supply interruptions.............................................................51

B.4 Transient overvoltages...........................................................................................53

B.5 DC component.......................................................................................................53

Bibliography ..........................................................................................................................55

---------------------- Page: 8 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 2-12: Environment –
Compatibility levels for low-frequency conducted disturbances and
signalling in public medium-voltage power supply 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 specifications, 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 61000-2-12 has been prepared by subcommittee 77A: Low

frequency phenomena, of IEC technical committee 77: Electromagnetic compatibility.

It has the status of a basic EMC publication in accordance with IEC Guide 107.
The text of this standard is based on the following documents:
FDIS Report on voting
77A/404/FDIS 77A/413/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.

---------------------- Page: 9 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 7 –

The committee has decided that the contents of this publication will remain unchanged until

2005. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
---------------------- Page: 10 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 9 –
INTRODUCTION
IEC 61000 is published in separate parts according to the following structure:
Part 1: General
General considerations (introduction, fundamental principles)
Definitions, terminology
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits

Immunity limits (in so far as they do not fall under the responsibility of the product

committees)
Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Part 9: Miscellaneous

Each part is further subdivided into several parts, published either as International Standards

or as technical specifications or technical reports, some of which have already been published

as sections. Others will be published with the part number followed by a dash and a second

number identifying the subdivision (example: 61000-6-1).

Detailed information on the various types of disturbances that can be expected on public power

supply systems can be found in IEC 61000-2-1.
---------------------- Page: 11 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 11 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 2-12: Environment –
Compatibility levels for low-frequency conducted disturbances and
signalling in public medium-voltage power supply systems
1 Scope and object

This part of IEC 61000 is concerned with conducted disturbances in the frequency range from

0 kHz to 9 kHz, with an extension up to 148,5 kHz specifically for mains signalling systems. It

gives compatibility levels for public medium voltage a.c. distribution systems having a nominal

voltage between 1 kV and 35 kV and a nominal frequency of 50 Hz or 60 Hz (see IEC 60038).

Compatibility levels are specified for electromagnetic disturbances of the types which can be

expected in public medium voltage power supply systems, for guidance in:

a) the limits to be set for disturbance emission into public power supply systems (including the

planning levels defined in 3.1.5);

b) the immunity limits to be set by product committees and others for the equipment exposed

to the conducted disturbances present in public power supply systems.
The disturbance phenomena considered are:
• voltage fluctuations and flicker;
• harmonics up to and including order 50;
• inter-harmonics up to the 50 harmonic;
• voltage distortions at higher frequencies (above 50 harmonic);
• voltage dips and short supply interruptions;
• voltage unbalance;
• transient overvoltages;
• power frequency variation;
• d.c. components;
• mains signalling.

Most of these phenomena are described in IEC 61000-2-1. In cases where it is not yet possible

to establish compatibility levels, some information is provided.

The medium-voltage systems covered by this standard are public distribution systems

supplying either:

a) private installations in which equipment is connected directly or through transformers, or

b) substations feeding public low-voltage distribution systems.
---------------------- Page: 12 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 13 –

The compatibility levels specified in this standard apply at the point of common coupling in the

case of (a) and at the medium-voltage terminals of the substation in the case of (b). See

Clause 4.
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 60071(all parts), Insulation co-ordination

IEC 60071-1, Insulation co-ordination – Part 1: Definitions, principles and rules

IEC 61000-2-2, Electromagnetic compatibility (EMC) – Part 2-2: Environment – Compatibility

levels for low-frequency conducted disturbances and signalling in public low-voltage power

supply systems

IEC 61000-2-4, Electromagnetic compatibility (EMC) – Part 2-4: Environment – Compatibility

levels in industrial plants for low-frequency conducted disturbances

IEC 61000-4-7, Electromagnetic compatibility (EMC) – Part 4-7: Testing and measurement

techniques – General guide on harmonics and interharmonics measurements and
instrumentation, for power supply systems and equipment connected thereto
3 Terms and definitions
For the purpose of this present document, the following definitions apply.
3.1 General definitions
3.1.1
(electromagnetic) disturbance

any electromagnetic phenomenon which, by being present in the electromagnetic environment,

can cause electrical equipment to depart from its intended performance
[IEV 161-01-05 modified]
3.1.2
disturbance level

the amount or magnitude of an electromagnetic disturbance, measured and evaluated in a

specified way
[IEV 161-03-01 modified]
3.1.3
electromagnetic compatibility
EMC (abbreviation)

ability of an equipment or system to function satisfactorily in its electromagnetic environment

without introducing intolerable electromagnetic disturbances to anything in that environment

NOTE 1 Electromagnetic compatibility is a condition of the electromagnetic environment such that, for every

phenomenon, the disturbance emission level is sufficiently low and immunity levels are sufficiently high so that all

devices, equipment and systems operate as intended.
---------------------- Page: 13 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 15 –

NOTE 2 Electromagnetic compatibility is achieved only if emission and immunity levels are controlled such that

the immunity levels of the devices, equipment and systems at any location are not exceeded by the disturbance

level at that location resulting from the cumulative emissions of all sources and other factors such as circuit

impedances. Conventionally, compatibility is said to exist if the probability of the departure from intended

performance is sufficiently low. See Clause 4 of IEC 61000-2-1.

NOTE 3 Where the context requires it, compatibility may be understood to refer to a single disturbance or class of

disturbances.

NOTE 4 Electromagnetic compatibility is a term used also to describe the field of study of the adverse

electromagnetic effects which devices, equipment and systems undergo from each other or from electromagnetic

phenomena.
[IEV 161-01-07 modified]
3.1.4
(electromagnetic) compatibility level

specified electromagnetic disturbance level used as a reference level in a specified

environment for co-ordination in the setting of emission and immunity limits

NOTE By convention, the compatibility level is chosen so that there is only a small probability that it will be

exceeded by the actual disturbance level.
[IEV 161-03-10 modified]
3.1.5
planning level

level of a particular disturbance in a particular environment, adopted as a reference value for

the limits to be set for the emissions from large loads and installations, in order to co-ordinate

those limits with all the limits adopted for equipment intended to be connected to the power

supply system

NOTE The planning level is locally specific, and is adopted by those responsible for planning and operating the

power supply network in the relevant area. (For further information, see Annex A.)

3.1.6
point of common coupling
PCC

point on a public power supply network, electrically nearest to a particular load, at which other

loads are, or could be, connected
[IEV 161-07-15 modified]
3.2 Phenomena related definitions

The definitions below that relate to harmonics are based on the analysis of system voltages or

currents by the Discrete Fourier Transform method (DFT). This is the practical application of

the Fourier transform as defined in IEV 101-13-09. See Annex B.

NOTE The Fourier Transform of a function of time, whether periodic or non-periodic, is a function in the frequency

domain and is referred to as the frequency spectrum of the time function, or simply spectrum. If the time function is

periodic the spectrum is constituted of discrete lines (or components). If the time function is not periodic, the

spectrum is a continuous function, indicating components at all frequencies.

Other definitions related to harmonics or interharmonics are given in the IEV and other

standards. Some of those other definitions, although not used in this standard, are discussed in

Annex B.
---------------------- Page: 14 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 17 –
3.2.1
fundamental frequency

frequency in the spectrum obtained from a Fourier transform of a time function, to which all the

frequencies of the spectrum are referred. For the purpose of this standard, the fundamental

frequency is the same as the power supply frequency

NOTE 1 In the case of a periodic function, the fundamental frequency is generally equal to the frequency of the

function itself. (See Annex B.1).

NOTE 2 In case of any remaining risk of ambiguity, the power supply frequency should be referred to the polarity

and speed of rotation of the synchronous generator(s) feeding the system.
[IEV 101-14-50, modified]
3.2.2
fundamental component
component whose frequency is the fundamental frequency
3.2.3
harmonic frequency

frequency which is an integer multiple of the fundamental frequency. The ratio of the harmonic

frequency to the fundamental frequency is the harmonic order (recommended notation: “h”)

3.2.4
harmonic component

any of the components having a harmonic frequency. Its value is normally expressed as an

r.m.s. value
For brevity, such a component may be referred to simply as an harmonic
3.2.5
interharmonic frequency
any frequency which is not an integer multiple of the fundamental frequency

NOTE 1 By extension from harmonic order, the interharmonic order is the ratio of an interharmonic frequency to

the fundamental frequency. This ratio is not an integer. (Recommended notation “m”).

NOTE 2 In the case where m< 1 the term subharmonic frequency may be used.
3.2.6
interharmonic component

component having an interharmonic frequency. Its value is normally expressed as an r.m.s.

value
For brevity, such a component may be referred to simply as an “interharmonic”

NOTE For the purpose of this standard and as stated in IEC 61000-4-7, the time window has a width of 10

fundamental periods (50 Hz systems) or 12 fundamental periods (60 Hz systems), i.e. approximately 200 ms. The

difference in frequency between two consecutive interharmonic components is, therefore, approximately 5 Hz.

3.2.7
total harmonic distortion
THD

ratio of the r.m.s. value of the sum of all the harmonic components up to a specified order

(recommended notation “H”) to the r.m.s. value of the fundamental component
h=H
Q 
 
THD =
 
h=2 1
 
---------------------- Page: 15 ----------------------
SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 19 –
where
Q represents either current or voltage
Q = r.m.s. value of the fundamental component
h = harmonic order
Q = r.m.s. value of the harmonic component of order h
H = 50 generally, but 25 when the risk of resonance at higher orders is low.

NOTE THD takes account of harmonics only. For the case where interharmonics are to be included, see B.1.2.1,

Annex B.
3.2.8
voltage unbalance (imbalance)

condition in a polyphase system in which the r.m.s. values of the line-to-line voltages

(fundamental component), or the phase angles between consecutive line-to-line voltages, are

not all equal. The degree of the inequality is usually expressed as the ratios of the negative and

zero sequence components to the positive sequence component
[IEV 161-08-09 modified]

NOTE 1 In this standard, voltage unbalance is considered in relation to three-phase systems and negative phase

sequence only.

NOTE 2 Several approximations give reasonably accurate results for the levels of unbalance normally encountered

(ratio of negative to positive sequence components):
2 2 2
6()U + U + U
12 23 31
Voltage unbalance = − 2
U + U + U
12 23 31
where U , U and U are the three line-to-line voltages.
12 23 31
4 Compatibility levels
4.1 General comment

The following subclauses set down compatibility levels for the various disturbances on an

individual basis only. However, the electromagnetic environment usually contains several

disturbances simultaneously, and the performance of some equipment can be degraded by

particular combinations of disturbances. See Annex A.

At the power input terminals of equipment receiving its supply from the medium-voltage

distribution systems covered by this standard, the severity levels of the disturbances can, for

the most part, be taken to be the same as the levels at the point of common coupling. In some

situations this is not so, particularly in the following cases:
• a long line dedicated to the supply of a particular installation;
• equipment being part of an extensive installation;

• a disturbance generated or amplified within the installation of which the equipment forms a

part.

In the case of medium voltage networks associated with downstream low voltage networks, the

actual disturbance levels are usually lower on the medium voltage networks than on the low

voltage networks. This is especially the case for harmonics and interharmonics. Exceptions can

arise from causes such as resonance and the aggregation of disturbances from other parts of

the network. Given the co-ordination function of compatibility levels, it is important that they

reflect the disturbance levels that have a significant probability of being encountered in

practice, although that probability is quite low.
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SIST EN 61000-2-12:2003
61000-2-12  IEC:2003 – 21 –

The MV compatibility level is not intended to be representative of average conditions, but must

take account of exceptional conditions that have a significant risk of
...

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