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

IEC 61000-4-7:2002+A1:2008 applies to instrumentation intended for measuring spectral components in the frequency range up to 9 kHz which are superimposed on the fundamental of the power supply systems at 50 Hz and 60 Hz. For practical considerations, this standard distinguishes between harmonics, interharmonics and other components above the harmonic frequency range, up to 9 kHz. Defines the measurement instrumentation intended for testing individual items of equipment in accordance with emission limits given in certain standards (for example, harmonic current limits as given in IEC 61000-3-2) as well as for the measurement of harmonic currents and voltages in actual supply systems. The contents of the corrigendum of July 2004 have been included in this copy. This consolidated version consists of the second edition (2002) and its amendment 1 (2008). Therefore, no need to order amendment in addition to this publication.

Compatibilité électromagnétique (CEM) - Partie 4-7: Techniques d'essai et de mesure - Guide général relatif aux mesures d'harmoniques et d'interharmoniques, ainsi qu'à l'appareillage de mesure, applicable aux réseaux d'alimentation et aux appareils qui y sont raccordés

La CEI 61000-4-7:2002+A1:2008 s'applique à l'instrumentation destinée à mesurer les composantes spectrales dans la gamme de fréquence allant jusqu'à 9 kHz, qui se superposent au fondamental des réseaux d'alimentation à 50 Hz et 60 Hz. Pour des raisons pratiques, la présente norme établit une distinction entre les harmoniques, les interharmoniques et les composantes au-delà de la plage de fréquence harmonique, jusqu'à 9 kHz. Définit l'instrumentation de mesure destinée aux essais d'appareils individuels conformément aux limites d'émission données dans certaines normes (par exemple, les limites de courant harmonique données dans la CEI 61000-3-2) ainsi qu'à la mesure des courants et tensions harmoniques sur les réseaux d'alimentation eux-mêmes. Le contenu du corrigendum de juillet 2004 a été pris en considération dans cet exemplaire.  Cette version consolidée comprend la deuxième édition (2002) et son amendement 1 (2008). Il n'est donc pas nécessaire de commander l'amendement avec cette publication.

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Publication Date
27-Oct-2009
Current Stage
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IEC 61000-4-7
Edition 2.1 2009-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
BASIC EMC PUBLICATION
PUBLICATION FONDAMENTALE EN CEM
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
Compatibilité électromagnétique (CEM) –
Partie 4-7: Techniques d'essai et de mesure – Guide général relatif aux mesures
d'harmoniques et d'interharmoniques, ainsi qu'à l'appareillage de mesure,
applicable aux réseaux d'alimentation et aux appareils qui y sont raccordés
IEC 61000-4-7:2002+A1:2008
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61000-4-7
Edition 2.1 2009-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
BASIC EMC PUBLICATION
PUBLICATION FONDAMENTALE EN CEM
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
Compatibilité électromagnétique (CEM) –
Partie 4-7: Techniques d'essai et de mesure – Guide général relatif aux mesures
d'harmoniques et d'interharmoniques, ainsi qu'à l'appareillage de mesure,
applicable aux réseaux d'alimentation et aux appareils qui y sont raccordés
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX
ICS 33.100.10; 33.100.20 ISBN 978-2-88910-377-5
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 61000-4-7 © IEC:2002+A1:2008
CONTENTS

FOREWORD...........................................................................................................................4

INTRODUCTION.....................................................................................................................6

1 Scope...............................................................................................................................7

2 Normative references .......................................................................................................7

3 Definitions, symbols and indices.......................................................................................8

3.1 Definitions related to frequency analysis .................................................................8

3.2 Definitions related to harmonics ..............................................................................9

3.3 Definitions related to distortion factors ..................................................................10

3.4 Definitions related to interharmonics .....................................................................11

3.5 Notations...............................................................................................................12

3.5.1 Symbols ....................................................................................................12

3.5.2 Subscripts .................................................................................................13

4 General concepts and common requirements for all types of instrumentation .................14

4.1 Characteristics of the signal to be measured .........................................................14

4.2 Accuracy classes of instrumentation......................................................................14

4.3 Types of measurement ..........................................................................................14

4.4 General structure of the instrument .......................................................................14

4.4.1 Main instrument.........................................................................................14

4.4.2 Post-processing parts................................................................................16

5 Harmonic measurements ................................................................................................16

5.1 Current input circuit...............................................................................................16

5.2 Voltage input circuit...............................................................................................17

5.3 Accuracy requirements..........................................................................................17

5.4 Measurement set-up and supply voltage................................................................19

5.4.1 Measurement set-up for emission assessment...........................................19

5.4.2 Supply voltage for emission assessment ...................................................19

5.4.3 Equipment power.......................................................................................21

5.5 Assessment of harmonic emissions .......................................................................21

5.5.1 Grouping and smoothing............................................................................21

5.5.2 Compliance with emission limits ................................................................23

5.6 Assessment of voltage harmonic subgroups ..........................................................23

6 Other analysis principles ................................................................................................23

7 Transitional period..........................................................................................................24

8 General ..........................................................................................................................24

Annex A (informative) Measurement of interharmonics ........................................................25

Annex B (informative) Measurements above the harmonic frequency range up to 9 kHz............27

Annex C (informative) Technical considerations for grouping method...................................32

Bibliography..........................................................................................................................41

---------------------- Page: 4 ----------------------
61000-4-7 © IEC:2002+A1:2008 – 3 –

Figure 1 – General structure of the measuring instrument .....................................................15

Figure 2 – Measurement set-up for single-phase emission measurement..............................19

Figure 3 – Measurement set-up for three-phase emission measurements .............................19

Figure 4 – Illustration of harmonic and interharmonic groups

(here shown for a 50-Hz supply) ...........................................................................................21

Figure 5 – Realization of a digital low-pass filter: z designates a window width delay,

α and β are the filter coefficients (see Table 2 for values) .....................................................22

Figure 6 – Illustration of a harmonic subgroup and an interharmonic centred subgroup

(here shown for a 50 Hz supply) ...........................................................................................23

Figure B.1 – Illustration of frequency bands for measurement in the range

harmonic order for 50 Hz power system up to 9 kHz ......................................28

above the 40

Figure B.2 – General measurement setup .............................................................................29

Figure B.3 – Artificial mains network for 16-A current and below...........................................30

Figure B.4 – Artificial mains network impedance viewed by the EUT .....................................31

Figure C.1 – Large 5th harmonic current fluctuation..............................................................35

Figure C.2 – Large 5th harmonic voltage fluctuation .............................................................35

Figure C.3 – Fluctuating 3rd harmonic current of a micro-wave appliance .............................36

Figure C.4 – Communication signal of 178 Hz together with 3rd and 5th harmonics ..............37

Figure C.5 – Interharmonic at 287 Hz, 5th and 6th harmonic.................................................37

Figure C.6 – Modulated 5th harmonic and interharmonic at 287 Hz.......................................39

Figure C.7 – Component vectors at frequencies of 245 Hz and 255Hz ..................................40

Table 1 – Accuracy requirements for current, voltage and power measurements...................18

Table 2 – Smoothing filter coefficients according to the window width...................................22

---------------------- Page: 5 ----------------------
– 4 – 61000-4-7 © IEC:2002+A1:2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
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
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

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in the subject dealt with may participate in this preparatory work. International, governmental and non-

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with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61000-4-7 has been prepared by subcommittee 77A: Low

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

This consolidated version of IEC 61000-4-7 consists of the second edition (2002) [documents

77A/382/FDIS and 77A/387/RVD], its amendment 1 (2008) [documents 77A/645/FDIS and

77A/651/RVD] and its corrigendum of July 2004.

The technical content is therefore identical to the base edition and its amendment and has

been prepared for user convenience.
It bears the edition number 2.1.
---------------------- Page: 6 ----------------------
61000-4-7 © IEC:2002+A1:2008 – 5 –

A vertical line in the margin shows where the base publication has been modified by

amendment 1.

This standard forms part 4-7 of IEC 61000. It has the status of a basic EMC publication in

accordance with IEC Guide 107.
Annexes A, B and C are for information only.

The committee has decided that the contents of the base publication and its amendments will

remain unchanged until the maintenance result date indicated on the IEC web site under

"http://webstore.iec.ch" in the data related to the specific publication. At this date,

the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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 publication using a colour printer.

---------------------- Page: 7 ----------------------
– 6 – 61000-4-7 © IEC:2002+A1:2008
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. Other will be published with the part number followed by a dash and a second

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

These publications will be published in chronological order and numbered accordingly.

This part is an International Standard for the measurement of harmonic currents and voltages

in power supply systems and harmonic currents emitted by equipment. It also specifies the

performance of a standard measuring instrument.
---------------------- Page: 8 ----------------------
61000-4-7 © IEC:2002+A1:2008 – 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
1 Scope

This part of IEC 61000 is applicable to instrumentation intended for measuring spectral

components in the frequency range up to 9 kHz which are superimposed on the fundamental

of the power supply systems at 50 Hz and 60 Hz. For practical considerations, this standard

distinguishes between harmonics, interharmonics and other components above the harmonic

frequency range, up to 9 kHz.

This standard defines the measurement instrumentation intended for testing individual items

of equipment in accordance with emission limits given in certain standards (for example,

harmonic current limits as given in IEC 61000-3-2) as well as for the measurement of

harmonic currents and voltages in actual supply systems. Instrumentation for measurements

above the harmonic frequency range, up to 9 kHz is tentatively defined (see Annex B).

NOTE 1 This document deals in detail with instruments based on the discrete Fourier transform.

NOTE 2 The description of the functions and structure of the measuring instruments in this standard is very

explicit and meant to be taken literally. This is due to the necessity of having reference instruments with

reproducible results irrespective of the characteristics of the input signals.

NOTE 3 The instrument is defined to accommodate measurements of harmonics up to the 50th order.

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 60038, IEC standard voltages

IEC 60050-161, International Electrotechnical Vocabulary – Chapter 161: Electromagnetic

compatibility

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 61000-3-2, Electromagnetic compatibility (EMC) – Part 3-2: Limits – Limits for harmonic

current emissions (equipment input current ≤16 A per phase)

IEC 61000-3-12, Electromagnetic compatibility (EMC) – Part 3-12: Limits – Limits for

harmonic currents produced by equipment connected to public low-voltage systems with input

current >16 A and ≤75 A per phase
---------------------- Page: 9 ----------------------
– 8 – 61000-4-7 © IEC:2002+A1:2008
3 Definitions, symbols and indices

For the purposes of this part of IEC 61000, the definitions given in IEC 60050-161 (IEV) and

the following, apply.
3.1 Definitions related to frequency analysis

Notations: The following notations are used in the present guide for the Fourier series

development because it is easier to measure phase angles by observations of the zero

crossings:
⎛ k ⎞
f()t = c + c sin ω t + ϕ (1)
⎜ ⎟
0 ∑ k 1 k
⎝ ⎠
k =1
2 2
c = b + ja = a + b
k k k
k k
Y =
C,k
⎛ ⎞ ⎛ ⎞
a a
k k
⎜ ⎟ ⎜ ⎟
ϕ =π + arctan if b < 0 ϕ = arctan if b > 0
k k k k
⎪ ⎜ ⎟ ⎜ ⎟
b b
k k
⎝ ⎠ ⎝ ⎠
with: (2)
π π

ϕ = if b = 0 and a > 0 ϕ = − if b = 0 and a < 0

k k k k k k
⎪ 2 2
ϕ = 0 if b ≤ ε and a ≤ ε,
k k k
with ε = 0,05 % U and ε = 0,15 % I
nom nom
or ε = 0,15 % U and ε = 0,5 % I
nom nom
respectively, see table 1 in IEC 61000-4-7
2 k
⎛ ⎞
b = f()t × sin ω t dt
⎜ ⎟
k 1
T N
⎝ ⎠
⎪ 0
2 k
⎛ ⎞
a = f()t × cos ⎜ ω t⎟ dt
⎨ k 1
and: (3)
T N
⎝ ⎠
c = f t dt

NOTE 1 The above definition setting φ to zero for the cases where b and a have very small values provides

k k k

guidance to instrument manufacturers, as phase measurements of very small amplitudes may result in very large

deviations, hence there is no requirement to measure phase for such small signals.

ω is the angular frequency of the fundamental (ω = 2πf );
1 1 H,1

T is the width (or duration) of the time window; the time window is that time span of a time

function over which the Fourier transform is performed;
c is the d.c. component;
---------------------- Page: 10 ----------------------
61000-4-7 © IEC:2002+A1:2008 – 9 –
c is the amplitude of the component with frequency f = f ;
k C,k H,1
Y is the r.m.s. value of component c ;
C,k k
f is the fundamental frequency of the power system;
H,1

k is the ordinal number (order of the spectral component) related to the frequency resolution

⎛ ⎞
f = ;
⎜ ⎟
C,1
⎝ ⎠
N is the number of fundamental periods within the window width;
ϕ is the phase angle of spectral line k.

NOTE 2 Strictly speaking these definitions apply to steady-state signals only. The Fourier series is actually in

most cases performed digitally, i.e. as a Discrete Fourier Transform DFT, or a variant thereof, being the FFT.

The analogue signal f(t) which has to be analyzed is sampled, A/D-converted and stored. Each group of M samples

forms a time window on which DFT is performed. According to the principles of Fourier series expansion, the

window width T determines the frequency resolution f = 1/T (i.e. the frequency separation of the spectral

N C,1 N

components) for the analysis. Therefore the window width T must be an integer multiple N of the fundamental

of the system voltage: T = N × T . The sampling rate is in this case f = M/(NT ) (where M = number of

period T 1
1 N 1 s
samples within T ).

Before DFT-processing, the samples in the time window are often weighted by multiplying them with a special

symmetrical function ('windowing function'). However, for periodic signals and synchronous sampling it is

preferable to use a rectangular weighting window which multiplies each sample by unity.

The DFT-processor yields the orthogonal Fourier-coefficients ak and bk of the corresponding spectral-component

frequencies f = k/T , k = 0, 1, 2 ... M-1. However, only k values up to and including half of the maximum value are

C,k N
useful, the other half just duplicates them.

Under synchronized conditions, the component of harmonic order h related to the fundamental frequency f

H,1
appears as the spectral component of order k, where k = hN.

NOTE 3 The Fast Fourier Transform FFT is a special algorithm allowing short computation times. It requires that

the number of samples M be an integer power of 2, M = 2 , with i ≥ 10 for example.

NOTE 4 The symbol Y is replaced, as required by the symbol I for currents, by the symbol U for voltages. Index C

qualifies the variable as spectral component.
3.2 Definitions related to harmonics
3.2.1
harmonic frequency
H,h

frequency which is an integer multiple of the fundamental frequency of the power system

(f = h × f )
H,h H,1

NOTE The harmonic frequency f is identical with the component frequency f with k = h × N.

H,h C,k
3.2.2
harmonic order

(integer) ratio of a harmonic frequency to the fundamental frequency of the power system. In

connection with the analysis using DFT and synchronisation between f and f (sampling

H,1 s

rate), the harmonic order h corresponds to the spectral component k = h × N (k = number of

the spectral component, N = number of periods of the fundamental frequency in time window

T )
3.2.3
r.m.s. value of a harmonic component
H,h

r.m.s. value of one of the components having a harmonic frequency in the analysis of a non-

sinusoidal waveform
For brevity, such a component may be referred to simply as a “harmonic”
---------------------- Page: 11 ----------------------
– 10 – 61000-4-7 © IEC:2002+A1:2008

NOTE 1 The harmonic component Y is identical with the spectral component Y with k = h×N;

H,h C,k

(Y = Y ). The symbol Y is replaced, as required by the symbol I for currents, by the symbol U for voltages.

H,h C,h×N
The index H qualifies the variable I or U as harmonic.

NOTE 2 For the purposes of this standard, the time window has a width of N = 10 (50 Hz systems) or N = 12

(60 Hz system) fundamental periods, i.e. approximately 200 ms (see 4.4.1). This yields Y = Y (50 Hz

H,h C,10×h
systems) and Y = Y (60 Hz systems).
H,h C,12×h
3.2.4
r.m.s. value of a harmonic group
g,h

square root of the sum of the squares of the r.m.s. value of a harmonic and the spectral

components adjacent to it within the time window, thus summing the energy contents of the

neighbouring components with that of the harmonic proper. See also equation 8 and Figure 4.

The harmonic order is given by the harmonic considered.

NOTE The symbol Y is replaced, as required by the symbol I for currents, by the symbol U for voltages.

3.2.5
r.m.s. value of a harmonic subgroup
sg,h

square root of the sum of the squares of the r.m.s. value of a harmonic and the two spectral

components immediately adjacent to it. For the purpose of including the effect of voltage

fluctuation during voltage surveys, a subgroup of output components of the DFT is obtained

by summing the energy contents of the frequency components directly adjacent to a harmonic

with that of the harmonic proper. (See also equation 9 and Figure 6.) The harmonic order is

given by the harmonic considered

NOTE The symbol Y is replaced, as required by the symbol I for currents, by the symbol U for voltages.

3.3 Definitions related to distortion factors
3.3.1
total harmonic distortion
THD
THD (symbol)

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

H,h
order (h ) to the r.m.s. value of the fundamental component (Y ):
max H,1
max
⎛ ⎞
H,h
⎜ ⎟
THD = (4)
⎜ ⎟
⎝ ⎠
H,1
h=2

NOTE 1 The symbol Y is replaced, as required, by the symbol I for currents or by the symbol U for voltages.

NOTE 2 The value of h is 40 if no other value is defined
...

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