SIST EN 61000-2-4:2003

SLOVENSKI STANDARD
01-december-2003
1DGRPHãþD
SIST EN 61000-2-4:1997
Electromagnetic compatibility (EMC) - Part 2-4: Environment - Compatibility levels
in industrial plants for low-frequency conducted disturbances (IEC 61000-2-4:2002)
Electromagnetic compatibility (EMC) -- Part 2-4: Environment - Compatibility levels in
industrial plants for low-frequency conducted disturbances
Elektromagnetische Verträglichkeit (EMV) -- Teil 2-4: Umgebungsbedingungen -
Verträglichkeitspegel für niederfrequente leitungsgeführte Störgrößen in Industrieanlagen
Compatibilité électromagnétique (CEM) -- Partie 2-4: Environnement - Niveaux de
compatibilité dans les installations industrielles pour les perturbations conduites à basse
fréquence
Ta slovenski standard je istoveten z: EN 61000-2-4:2002
ICS:
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 61000-2-4
NORME EUROPÉENNE
EUROPÄISCHE NORM September 2002
ICS 33.100.10; 33.100.20 Supersedes EN 61000-2-4:1994
English version
Electromagnetic compatibility (EMC)
Part 2-4: Environment -
Compatibility levels in industrial plants
for low-frequency conducted disturbances
(IEC 61000-2-4:2002)
Compatibilité électromagnétique (CEM) Elektromagnetische Verträglichkeit (EMV)
Partie 2-4: Environnement - Teil 2-4: Umgebungsbedingungen -
Niveaux de compatibilité Verträglichkeitspegel für niederfrequente
dans les installations industrielles leitungsgeführte Störgrößen
pour les perturbations conduites in Industrieanlagen
à basse fréquence (IEC 61000-2-4:2002)
(CEI 61000-2-4:2002)
This European Standard was approved by CENELEC on 2002-09-01. 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
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61000-2-4:2002 E
Foreword
The text of document 77A/378/FDIS, future edition 2 of IEC 61000-2-4, 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 61000-2-4 on 2002-09-01.
This European Standard supersedes EN 61000-2-4:1994.
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) 2003-06-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2005-09-01
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, B and C are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61000-2-4:2002 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 61000-4-7 NOTE Harmonized as EN 61000-4-7:1993 (not modified).
IEC 61000-4-15 NOTE Harmonized as EN 61000-4-15:1998 (not modified).
__________
- 3 - EN 61000-2-4:2002
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
1)
IEC 60050-101 - International Electrotechnical --
Vocabulary (IEV)
Part 101: Mathematics
1)
IEC 60050-161 - Chapter 161: Electromagnetic --
compatibility
1)
IEC 60050-551 - Part 551: Power electronics - -
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
3)
IEC 61000-2-12 - Part 2-12 : Environment - Compatibility--
levels for low-frequency conducted
disturbances and signalling in public
medium-voltage power supply systems

1)
Undated reference.
2)
Valid edition at date of issue.
3)
At draft stage.
NORME CEI
INTERNATIONALE IEC
61000-2-4
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2002-06
PUBLICATION FONDAMENTALE EN CEM
BASIC EMC PUBLICATION
Compatibilité électromagnétique (CEM) –
Partie 2-4:
Environnement – Niveaux de compatibilité
dans les installations industrielles pour les
perturbations conduites à basse fréquence
Electromagnetic compatibility (EMC) –
Part 2-4:
Environment – Compatibility levels in industrial
plants for low-frequency conducted disturbances
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Pour prix, voir catalogue en vigueur
For price, see current catalogue

61000-2-4  IEC:2002 – 3 –
4CONTENTS
FOREWORD.7
INTRODUCTION.11
1 Scope.13
2 Normative references.15
3 Definitions .15
3.1 General definitions.15
3.2 Phenomena-related definitions.19
4 Electromagnetic environment classes .23
5 Compatibility levels .25
5.1 General comment .25
5.2 Voltage deviations .25
5.3 Voltage dips and short interruptions .25
5.4 Voltage unbalance (imbalance) .27
5.5 Temporary power-frequency variation .27
5.6 Harmonics .27
5.7 Interharmonics.29
5.8 Voltage components at higher frequencies (above 50th harmonic).31
5.9 Transient overvoltages.31
5.10 DC component.31
6 Compatibility levels .31
Annex A (informative)  Explanations and examples for interharmonics .39
A.1 Resolution of non-sinusoidal voltages and currents.39
A.2 Time varying phenomena .41
A.3 Definition of additional terms .41
Annex B (informative) Examples of expected disturbance levels
in typical industrial networks.45
B.1 Voltage disturbance levels in industrial networks due to large converters .45
B.2 Voltage disturbance levels in industrial networks at high load .51
B.3 Voltages dips and short interruption .55
B.4 Transient overvoltages .57
Annex C (informative) Interharmonic and voltages at higher frequencies.61
C.1 Sources of interharmonics.61
C.2 Mitigation methods.69
C.3 Voltages at higher frequencies .73
Bibliography .75
Figure 1 – Interharmonic compatibility levels (Flickermeter response for P = 1 related
st
to 60-W incandescent lamps) .37
Figure B.1 – Example of power distribution in industry with rolling mills.47

61000-2-4  IEC:2002 – 5 –
Figure B.2 – Example of power distribution in the paper industry.49
Figure B.3 – Example of power distribution in a generic manufacturing industry .53
Figure B.4 – ITI (CEBEMA) – Curve of tolerance envelope of ITE .59
Table 1 – Compatibility levels for voltage tolerance, voltage unbalance and power-
frequency variations .33
Table 2 – Compatibility levels for harmonics – Harmonic voltage components Odd
harmonics non-multiple of three .33
Table 3 – Compatibility levels for harmonics – Harmonic voltage components Odd
harmonics multiple of three .35
Table 4 – Compatibility levels – Harmonic voltage components even order .35
Table 5 – Compatibility levels for total harmonic distortion .35
Table B.1 – Type of network.45
Table B.2 – Voltage disturbance levels in a typical manufacturing industry.51
Table C.1 – Indicative values for interharmonic voltages in low-voltage networks
with respect to the flicker effect .67

61000-2-4  IEC:2002 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 2-4: Environment –
Compatibility levels in industrial plants for
low-frequency conducted disturbances
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 61000-2-4 has been prepared by subcommittee 77A: Low frequency
phenomena, of IEC technical committee 77: Electromagnetic compatibility.
This standard forms part 2-4 of IEC 61000. It has the status of a basic EMC publication in
accordance with IEC Guide 107.
This second edition cancels and replaces the first edition, published in 1994, and constitutes
a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
77A/378/FDIS 77A/383/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 3.
Annexes A, B and C are for information only.

61000-2-4  IEC:2002 – 9 –
The committee has decided that the contents of this publication will remain unchanged until
2010. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61000-2-4  IEC:2002 – 11 –
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,
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: 61000-3-11).
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 and IEC 61000-2-12.

61000-2-4  IEC:2002 – 13 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 2-4: Environment –
Compatibility levels in industrial plants for
low-frequency conducted disturbances
1 Scope
This part of IEC 61000 is concerned with conducted disturbances in the frequency range
from 0 kHz to 9 kHz. It gives numerical compatibility levels for industrial and non-public
power distribution systems at nominal voltages up to 35 kV and a nominal frequency of
50 Hz or 60 Hz.
Power supply systems on ships, aircraft, offshore platforms and railways are not included.
The compatibility levels specified in this standard apply at the in-plant point of coupling. At the
power input terminals of equipment receiving its supply from the above systems, the severity
levels of the disturbances can, for the most part, be taken to be the same as the levels at the
in-plant point of coupling. In some situations this is not so, particularly in the case of a long
feeder dedicated to the supply of a particular load, or in the case of a disturbance generated or
amplified within the installation of which the equipment forms a part.
Compatibility levels are specified for electromagnetic disturbances of the types which can be
expected at any in-plant point of coupling (IPC) within industrial plants or other non-public
networks, for guidance in
a) limits to be set for disturbance emission into industrial power supply systems (including the
planning levels defined in 3.1.5);
NOTE 1 A very wide range of conditions is possible in the electromagnetic environments of industrial and other
non-public networks. These are approximated in this standard by the three classes described in Clause 4. How-
ever, it is the responsibility of the operator of such a network to take account of the particular electromagnetic
and economic conditions, including equipment characteristics, in setting the above-mentioned limits.
b) the choice of immunity levels for the equipment within these systems.
The disturbance phenomena considered are:
– voltage deviations;
– voltage dips and short interruptions;
– voltage unbalance;
– power-frequency variations;
– harmonics up to order 50;
– interharmonics up to the 50th harmonic;
– voltage components at higher frequencies (above 50th harmonic);
– d.c. component;
– transient overvoltages.
61000-2-4  IEC:2002 – 15 –
The compatibility levels are given for different classes of the electromagnetic environment
determined by the characteristics of the supply network.
NOTE 2 Compatibility levels at the point of common coupling (PCC) on public networks are specified in
IEC 61000-2-2 for low-voltage networks and IEC 61000-2-12 for medium-voltage networks. Technical reports
IEC 61000-3-6 and IEC 61000-3-7 describe the approach of supply authorities to the limitation of emissions from
installations and large loads.
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 60050-101, International Electrotechnical Vocabulary (IEV) – Part 101: Mathematics
IEC 60050-161, International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
IEC 60050-551, International Electrotechnical Vocabulary (IEV) – Part 551: Power electronics
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 61000-2-12, Electromagnetic compatibility (EMC) – Part 2-12: Environment – Compatibility
levels for low-frequency conducted disturbances and signalling in public medium-voltage power
supply systems
3 Definitions
For the purposes of this part of IEC 61000, the definitions given in chapter 161 and parts 101
and 551 of IEC 60050 (IEV) as well as the following 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
amount or magnitude of an electromagnetic disturbance, measured and evaluated in a
specified way
[IEV 161-03-01, modified]
———————
To be published.
61000-2-4  IEC:2002 – 17 –
3.1.3
electromagnetic compatibility
EMC
ability of an equipment or system to function satisfactorily in its electromagnetic environment
without introducing intolerable electromagnetic disturbances to anything in that environment
[IEV 161-01-07]
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.
NOTE 2 Electromagnetic compatibility is achieved only if emission and immunity levels are controlled such that
the immunity level of devices, equipment and systems, at any location, are not exceeded by the disturbance level at
that location, resulting from the cumulative emission 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 or of the
adverse effect 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 effect which devices, equipment and systems undergo from each other or from electromagnetic
phenomena.
3.1.4
(electromagnetic) compatibility level
specified electromagnetic disturbance level used as a reference level in a specified
environment for coordination in the setting of emission and immunity limits
[IEV 161-03-10, modified]
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.
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 emission of large loads and installations, in order to
coordinate 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 explanation, see Annex A of IEC 61000-2-2.)
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]
3.1.7
in-plant point of coupling
IPC
point on a network inside a system or an installation, electrically nearest to a particular load, at
which other loads are, or could be, connected
NOTE The IPC is usually the point for which electromagnetic compatibility is to be considered.

61000-2-4  IEC:2002 – 19 –
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 A.
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 IEV and other standards.
Some of those other definitions, although not used in this standard, are discussed in Annex A.
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 purposes of this standard, the
fundamental frequency is the same as the power supply frequency
[IEV 101-14-50, modified]
NOTE 1 In the case of a periodic function, the fundamental frequency is generally equal to the frequency of the
function itself. (See A.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.
NOTE 3 This definition may be applied to any industrial power supply network, without regard to the load it
supplies (a single load or a combination of loads, rotating machines or other loads), and even if the generator
feeding the network is a semiconductor converter.
3.2.2
fundamental component (or fundamental)
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 named 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 a 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 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 sub-harmonic frequency may also be used.

61000-2-4  IEC:2002 – 21 –
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 (for 50 Hz systems) or 12 fundamental periods (for 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
hH=
Q 
h
THD =  
∑
 Q 
h=2 1
where:
Q represents either current or voltage;
Q is the r.m.s. value of the fundamental component;
h is the harmonic order;
Q is the r.m.s. value of the harmonic component of order h;
h
H is 50 for the purpose of the compatibility levels in this standard.
NOTE THD takes account of harmonics only. For the case where interharmonics are to be included, see A.3.1.
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 angle 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 Generally voltage unbalance, in relation to three-phase systems, is considered through its negative phase
sequence only. However, in some circumstances, the zero sequence component should also be considered.
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
U + U + U
12 23 31
e.g.  voltage unbalance  = 6 × − 2
()U + U + U
12 23 31
where U , U , U are the three fundamental line-to-line voltages.
12 23 31
3.2.9
voltage deviation
increase or decrease of the r.m.s. supply voltage normally due to the variation of the load on
the supply network or a part of it, or a rapid voltage change repeated, or not, due to a rapid
change of load (see the first paragraph of 4.2 of IEC 61000-2-2); the part of transients with no
remaining effects is excluded
NOTE Some voltage deviations may be fast changes due to adaptation of the voltage network to the load
conditions (example: voltage taps changes of transformers, permanent effect of capacitor bank switching). Voltage
fluctuation, which may cause flicker is a different phenomenon (series of voltage changes or cyclical voltage
changes). Voltage variations and voltage fluctuations are the major types of voltage changes.

61000-2-4  IEC:2002 – 23 –
3.2.10
voltage dip (voltage sag)
sudden reduction of the voltage at a particular point on an electricity supply system below a dip
threshold voltage, followed by its recovery after a brief interval
NOTE 1 Typically a dip is associated with the occurrence and termination of a short circuit or other extreme
current increase on the system or installations connected to it.
NOTE 2 Generally the threshold corresponds to the minimum value of the tolerance band.
3.2.11
transient overvoltage
oscillatory or non-oscillatory overvoltage, highly damped and up to a few ms in duration.
Compatibility level is related to the peak value line to earth
NOTE The origin of transient overvoltages is generally atmospheric or in operations in the network (switching,
fuses). Its rise time may be from less than 1 μs to a few ms.
4 Electromagnetic environment classes
Several classes of electromagnetic environment can be defined, but for simplicity only three
are considered and defined in this standard, as follows.
Class 1 This class applies to protected supplies and has compatibility levels lower than
those on public networks. It relates to the use of equipment very sensitive to
disturbances in the power supply, for instance electrical instrumentation in
laboratories, some automation and protection equipment, some computers, etc.
Class 2 This class applies generally to PCCs and to IPCs in the environments of industrial
and other non-public power supplies. The compatibility levels of this class are
generally identical to those of public networks. Therefore, components designed for
supply from public networks may be used in this class of industrial environment.
Class 3 This class applies only to IPCs in industrial environments. It has higher com-
patibility levels than those of class 2 for some disturbance phenomena. For
instance, this class should be considered when any of the following conditions
are met:
– a major part of the load is fed through converters;
– welding machines are present;
– large motors are frequently started;
– loads vary rapidly.
The class applicable for new plants and extensions of existing plants cannot be determined a
priori and should relate to the type of equipment and process under consideration.
NOTE 1 Class 1 environments normally contain equipment which requires protection by such apparatus as
uninterruptible power systems (UPS), filters or surge suppressers.
NOTE 2 In some cases, highly sensitive equipment may require compatibility levels lower than the ones relevant
to class 1 environments. The compatibility levels are then to be agreed upon case by case (controlled environment).
NOTE 3 The supply to highly disturbing loads, such as arc-furnaces and large converters which are generally
supplied from a segregated busbar, frequently has disturbance levels in excess of class 3 (harsh environment). In
such special situations, the compatibility levels should be agreed upon.
NOTE 4 Taking account of diversity of industrial environments, different classes can be relevant for different
phenomena in any given network.

61000-2-4  IEC:2002 – 25 –
5 Compatibility levels
5.1 General comment
The compatibility levels are set down 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 Clause A.2 of IEC 61000-2-2.
Levels are provided in Table 1 to Table 5. See also guidance for interharmonics in Annex C.
IPCs should be categorized according to their compatibility levels. To enable the selection of
specific equipment or devices such as rotating machines, power-capacitor banks, filters, it may
be necessary to obtain a specific description of the voltage deviations that may be present at
the equipment terminals. The technical committees responsible for the relevant product
standards will specify the information to facilitate the proper selection of components. They
should also take into account the compatibility levels in this standard when specifying the
supply operating conditions of the equipment.
Compatibility levels are given at the IPCs, but this does not imply that disturbances at these
levels will satisfy the emission requirements at the PCC. This fact is to be carefully considered
when selecting the equipment.
NOTE 1 Equipment operating within class 1 is generally low-voltage equipment.
NOTE 2 To illustrate disturbance levels caused by power converters in various industrial environments, a few
examples of calculated results are given in Annex B.
NOTE 3 The compatibility levels of class 3 cover the possible disturbances in industrial environments. For a
specific installation it is expected that only some types of disturbances occur with the level pertaining to class 3.
Since equipment or devices have different sensitivities to the various types of disturbances, a specific equipment or
device may be used conditionally with a class 3 supply depending on the actual disturbance levels.
NOTE 4  Disturbance levels, which have both time and location variations, cannot be controlled at all locations and
at all times. Therefore, evaluation should be made for the entire industrial system being considered, rather than at a
specific location within that system.
5.2 Voltage deviations
See Table 1. For class 3, voltage deviations resulting in supply voltages in the range 0,85 U to
C
0,9 U are expected for a duration not longer than 60 s. For longer durations the range 0,9 U
C C
to 1,1 U applies.
C
NOTE 1 Voltage fluctuation leading to flicker is generally of concern only to lighting equipment. This should be
connected to a class 2 supply. The compatibility levels of IEC 61000-2-2 apply.
NOTE 2 In certain circumstances, some equipment might be sensitive to rapid voltage changes.
5.3 Voltage dips and short interruptions
For class 1 IPCs, a protection provided by UPSs is considered and dips are not expected.
For a discussion of the other aspects of these phenomena see Clause B.3.

61000-2-4  IEC:2002 – 27 –
5.4 Voltage unbalance (imbalance)
In this standard, voltage unbalance is considered only in relation to the negative phase
sequence component, this being the component relevant to possible interference with
equipment connected to the power supply systems covered by this standard. In this standard,
voltage unbalance is considered in relation to long-term effect, i.e. for durations equal to or
higher than 10 min.
NOTE 1 Some protection equipment may be sensitive to the zero sequence voltage component. Care should be
taken of this aspect at the installation level.
NOTE 2 Zero sequence voltages are of concern mainly for harmonics multiples of 3.
NOTE 3 Electronic converters produce characteristic harmonic orders due to their topology when used under their
rated operating conditions. Different operating conditions such as unbalance, non-ideal commutation instants, etc.
may cause other harmonic orders to be produced.
The voltage unbalance caused by a single-phase load connected line-to-line is in practice
equal to the ratio of the load power to the network three-phase short circuit power. If no
substantial single-phase load is present, the compatibility levels of class 2 may be applied.
5.5 Temporary power-frequency variation
The compatibility levels of power-frequency deviations of the public network apply to industrial
plants fed from the public power supply.
For the most part, the range is within 1 Hz of the nominal frequency as stated in 4.8 of
IEC 61000-2-2. Where synchronous interconnection is implemented on a continental scale, the
variation is usually very much less.
The compatibility level for the temporary variation of frequency from the nominal frequency
is ±1 Hz. The steady-state deviation of frequency from the nominal frequency is much less.
NOTE 1 For some equipment the rate of change of frequency is significant.
NOTE 2 In the case of supply systems isolated from the public network, frequency variations up to ±4 % are
expected. The actual compatibility levels in this instance are to be agreed upon.
5.6 Harmonics
The compatibility levels for individual harmonic components of the voltage shall be understood
to relate to quasi-stationary or steady-state harmonics and are given as reference values for
both long-term effects and very short-term effects.
The long-term effects relate mainly to thermal effects on cables, transformers, motors,
capacitors, etc. They arise from harmonic levels which are sustained for periods equal to or
higher than 10 min.
With reference to long-term effects, compatibility levels for individual harmonic components of
the voltage are given in Tables 2 to 4. The corresponding compatibility levels for the total
harmonic distortion are given in Table 5.
Very short-term effects relate mainly to disturbing effects on electronic devices that may be
susceptible to harmonic levels sustained for 3 s or less. Transients are not included.
With reference to very short-term effects in class 1 and class 3, compatibility levels for
individual harmonic components of the voltage, and for total harmonic distortion, are 1,5 times
the values given in Tables 2 to 5.

61000-2-4  IEC:2002 – 29 –
In class 2, they are the values given in Tables 2 to 4 multiplied by a factor k, where k is as
follows:
0,7
()
k = 1,3 + × h − 5
The corresponding compatibility level for the total harmonic distortion in class 2 is 8 %
(THD = 8 %) with reference to very short term.
NOTE 1 Commutation notches are included here as regards their contribution to the harmonic content of the
voltage. Other aspects (for example, the influence on the commutation of other converters, or any influence on
other equipment which involves the higher harmonic components of the spectrum) require a time-domain
description (see the relevant product standard).
NOTE 2 Everywhere they are used in industrial networks, power factor correction capacitors should be connected
through series reactors, particularly those which are intended to be connected to IPCs of class 3. Where
interharmonics may be present, there is a risk of resonance effects, and this should be carefully investigated.
Where the absence of resonance effects is clearly proved and the higher harmonics values are far less than those
given for class 3, series reactors may not be necessary, but this has to be checked carefully.
NOTE 3 The values specified for total harmonic distortion are not related to specific equipment or devices, but
have regard to the possible simultaneous presence of several harmonic components at significant amplitude.
5.7 Interharmonics
Annex C provides information on sources, effects and mitigation methods related to inter-
harmonics. It also provides levels for guidance, until more experience makes publication of
compatibility levels possible.
In this standard, compatibility levels are given only for the case of an interharmonic voltage
occurring at a frequency close to the fundamental frequency (50 Hz or 60 Hz), resulting in
amplitude modulation of the supply voltage.
In these conditions certain loads that are sensitive to the square of the voltage, especially
lighting devices, exhibit a beat effect, resulting in flicker. (See note 1 in 5.2.) The beat
frequency is the difference between the frequencies of the two coincident voltages – i.e.
between the interharmonic and fundamental frequencies.
NOTE 1 Below interharmonic order 0,2 compatibility levels are determined by flicker requirements, with P = 1.
st
For this purpose the flicker severity should be calculated in accordance with Annex A of IEC 61000-3-7 using the
shape factor given for periodic and sinusoidal voltage fluctuations. The conservative value of the shape factor is 0,8
for 0,04 < m ≤ 0,2, and 0,4 for m ≤ 0,04.
NOTE 2 A similar situation is possible when there is an appreciable level of voltage at a harmonic frequency
(particularly of order 3 or 5) coincident with an interharmonic voltage at a nearby frequency. The effect should be
assessed by means of Figure 1, with amplitude given by the product of the relative amplitudes of the harmonic and
interharmonic at the origin of the beat frequency. The result is unlikely to be significant.
The compatibility level for the interharmonic voltage in the above case, expressed as the ratio
of its amplitude to that of the fundamental, is shown in Figure 1 as a function of the beat
frequency. It is based on a flicker level of P = 1 for lamps operated at 120 V and 230 V and is
st
applicable only to circuits which include lighting devices.

61000-2-4  IEC:2002 – 31 –
5.8 Voltage components at higher frequencies (above 50th harmonic)
Distortion of the voltage wave form can be such as to be equivalent to the superposition of
voltages
...