IEC 61000-4-7:2002/AMD1:2008

IEC 61000-4-7
Edition 2.0 2008-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 1
AMENDEMENT 1
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 A1:2008
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IEC 61000-4-7
Edition 2.0 2008-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 1
AMENDEMENT 1
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
T
CODE PRIX
ICS 33.100.10; 33.100.20 ISBN 2-8318-9848-X

– 2 – 61000-4-7 Amend. 1 © IEC:2008
FOREWORD
This amendment has been prepared by subcommittee 77A: Low frequency phenomena, of
IEC technical committee 77: Electromagnetic compatibility.
The text of this amendment is based on the following documents:
FDIS Report on voting
77A/645/FDIS 77A/651/RVD
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication 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• withdrawn,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.
_____________
Page 13
2 Normative references
Insert, in the existing list, the following standards:
IEC 60038, IEC standard voltages
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 61000-3-12, 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
Delete from the existing list the following standard:
IEC 61967-1, Integrated circuits – Measurement of electromagnetic emissions, 150 kHz to
1 GHz – Part 1: Measurement conditions and definitions

Pages 15 and 17
3.1 Definitions related to frequency analysis
Replace the entire subclause, including the NOTES, by the following new text:
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:
61000-4-7 Amend. 1 © IEC:2008 – 3 –
∞
k
⎛ ⎞
()
f t = c + c sin⎜ ω t + ϕ ⎟ (1)
0 ∑ k 1 k
N
⎝ ⎠
k =1
⎧
2 2
c = b + ja = a + b
k k k
⎪ k k
⎪
c
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
⎩
T
⎧
N
2 ⎛ k ⎞
⎪
b = f()t × sin ω t dt
⎜ ⎟
k 1
∫
⎪
T N
⎝ ⎠
N
⎪ 0
⎪
T
N
⎪
2 k
⎛ ⎞
a = f()t × cos ω t dt
⎜ ⎟
⎨
and: k 1 (3)
∫
T N
⎝ ⎠
N
⎪
⎪
T
N
⎪
⎪
c = f()t dt
∫
⎪ T
N
⎩
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
N
function over which the Fourier transform is performed;
c is the d.c. component;
k
c is the amplitude of the component with frequency f = f ;
k C,k H,1
N
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
T
N
⎝ ⎠
N is the number of fundamental periods within the window width;
ϕ is the phase angle of spectral line k.
k
– 4 – 61000-4-7 Amend. 1 © IEC:2008
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
N
period T of the system voltage: T = N × T . The sampling rate is in this case f = M/(NT ) (where M = number of
1 s
1 N
samples within T ).
N
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 a and b of the corresponding spectral-component
k k
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
i
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.
Page 17
3.2 Definitions related to harmonics
Replace the existing terms and definitions 3.2.1 to 3.2.5, including NOTES, if any, by the
following:
3.2.1
harmonic frequency
f
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
h
(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 )
N
3.2.3
r.m.s. value of a harmonic component
Y
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”
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
61000-4-7 Amend. 1 © IEC:2008 – 5 –
Page 19
3.2.4
r.m.s. value of a harmonic group
Y
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
Y
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.
Page 19
3.3 Definitions related to distortion factors
Replace the existing terms and definitions 3.3.1 to 3.3.4, including NOTES, if any, by the
following:
3.3.1
total harmonic distortion
THD
THD (symbol)
Y
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
h
max
⎛ ⎞
Y
H,h
⎜ ⎟
THD = (4)
Y ∑
⎜ ⎟
Y
⎝ ⎠
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 in a standard concerned with limits (IEC 61000-3
max
series).
3.3.2
group total harmonic distortion
THDG
THDG (symbol)
Y
ratio of the r.m.s. value of the harmonic groups (Y ) to the r.m.s. value of the group
g,h
associated with the fundamental (Y ):
g,1
h
max
⎛ ⎞
Y
g,h
⎜ ⎟
THDG =      where  h ≥ 2 (5)
Y ∑ min
⎟
⎜
Y
⎝ g,1⎠
h=h
min
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 2 and that of h is 40 if no other values are defined in a standard concerned with limits (for example
min max
IEC 61000-3 series).
– 6 – 61000-4-7 Amend. 1 © IEC:2008
Page 21
3.3.3
THDS
subgroup total harmonic distortion
THDS (symbol)
Y
ratio of the r.m.s. value of the harmonic sub-groups (Y ) to the r.m.s. value of the sub-group
sg,h
associated with the fundamental (Y ):
sg,1
h
max
⎛ ⎞
Y
sg,h
⎜ ⎟
THDS =     where  h ≥ 2 (6)
Y ∑
min
⎜ ⎟
Y
⎝ sg,1⎠
h=h
min
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 2 and that of h is 40 if no other values are defined in a standard concerned with
min max
limits (for example IEC 61000-3 series).

3.3.4
partial weighted harmonic distortion
PWHD
PWHD (symbol)
H,Y
ratio of the r.m.s. value, weighted with the harmonic order h, of a selected group of higher
order harmonics (from the order h to h ) to the r.m.s. value of the fundamental:
min max
h
max
⎛ ⎞
Y
H,h
⎜ ⎟
PWHD = h (7)
Y
H, ∑
⎜ ⎟
Y
H,1
⎝ ⎠
h=h
min
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 concept of partial weighted harmonic distortion is introduced to allow for the possibility of specifying
a single limit for the aggregation of higher order harmonic components. The partial weighted group harmonic
distortion PWHD can be evaluated by replacing the quantity Y by the quantity Y . The partial weighted sub-
g Y H,h g,h
,
group harmonic distortion PWHD can be evaluated by replacing the quantity Y by the quantity Y . The type of
sg,Y H,h sg,h
PWHD (PWHD , PWHD or PWHD ) is defined in each standard which uses the PWHD, for example in standards concerned
H,Y g,Y sg,Y
with limits (IEC 61000-3 series).
NOTE 3 The values of h and h are defined in each standard which uses the PWHD , for example in a standard
min max
Y
concerned with limits (IEC 61000-3 series).
Page 21
3.4 Definitions related to interharmonics
Replace the existing terms and definitions 3.4.1 to 3.4.5, including NOTES, if any, by the
following:
3.4.1
r.m.s. value of a spectral component
Y
C,k
in the analysis of a waveform, the r.m.s. value of a component whose frequency is a multiple
of the inverse of the duration of the time window
NOTE 1 If the duration of the time window is multiple of the fundamental period, only some of the spectral
components have frequencies which are integer multiples of the fundamental frequency.
NOTE 2 The frequency interval between two consecutive spectral components is the inverse of the width of the
time window, approximately 5 Hz for the purposes of this standard.
NOTE 3 The symbol Y is replaced, as required, by the symbol I for currents or by the symbol U for voltages.

61000-4-7 Amend. 1 © IEC:2008 – 7 –
3.4.2
r.m.s. value of an interharmonic component
Y
C,i
r.m.s. value of a spectral component, Y , with a frequency between two consecutive
C,k ≠ h × N
harmonic frequencies (see Figure 4). For brevity, such a component may be referred to simply
as an “interharmonic”.
NOTE 1 The frequency of the interharmonic component is given by the frequency of the spectral line. This
frequency is not an integer multiple of the fundamental frequency.
NOTE 2 A difference is made between an “interharmonic component” produced as a physical component by an
equipment, for example at 183,333 Hz, and a “spectral component” calculated by the instrument as the result of the
waveform analysis e.g. for a 50 Hz system at 185 Hz (the frequency of the FFT bin). The “spectral component” is
also the “harmonic component” for h × N where h is an integer.
Page 23
3.4.3
r.m.s. value of an interharmonic group
Y
ig,h
r.m.s. value of all spectral components in the interval between two consecutive harmonic
frequencies (see Figure 4).
NOTE 1 For the purpose of this standard, the r.m.s. value of the interharmonic group between the harmonic
orders h and h + 1 is designated as Y , for example the group between h = 5 and h = 6 is designated as Y .
ig,h ig,5
NOTE 2 The symbol Y is replaced, as required, by the symbol I for currents or by the symbol U for voltages.
3.4.4
r.m.s. value of an interharmonic centred subgroup
Y
isg,h
r.m.s. value of all spectral components in the interval between two consecutive harmonic
frequencies, excluding spectral components directly adjacent to the harmonic frequencies
(see Figure 6)
NOTE 1 For the purpose of this standard, the r.m.s. value of the centred subgroup between the harmonic orders h
and h + 1 is designated as Y , for example the centred subgroup between h = 5 and h = 6 is designated as Y .
isg,h isg,5
NOTE 2 The symbol Y is replaced, as required, by the symbol I for currents or by the symbol U for voltages.
3.4.5
interharmonic group frequency
f
ig,h
mean of the two harmonic frequencies between which the group is situated, i.e. f = (f +
ig,h H,h
f )/2.
H,h+1
Add the following new term and definition:
3.4.6
interharmonic centred subgroup frequency
f
isg,h
mean of the two harmonic frequencies between which the subgroup is situated, i.e. f =
isg,h
(f + f )/2.
H,h H,h+1
Pages 23 and 25
3.5 Notations
Replace the entire subclause by the following new subclause:
3.5.1 Symbols
In this standard, voltage and current values are r.m.s. unless otherwise stated.
a amplitude coefficient of a cosine component in a Fourier series
b amplitude coefficient of a sine component in a Fourier series

– 8 – 61000-4-7 Amend. 1 © IEC:2008
c amplitude coefficient in a Fourier series
f frequency; function
f
C,k spectral component frequency of order k
f the frequency of the spectral component of order 1. The frequency resolution is equal to this
C,1
frequency
f
g,h harmonic-group frequency of order h
f
sg,h harmonic-subgroup frequency of order h
f
ig,h interharmonic-group frequency of order h
f
isg,h interharmonic centred subgroup frequency of order h
f
H,h harmonic component frequency of order h
f
H,1 fundamental frequency of the power system
f sampling rate
s
h the order of the highest harmonic that is taken into account
max
h the order of the lowest harmonic that is taken into account

min
j −1
t running time
B bandwidth
I current (r.m.s. value)
M integer number; number of samples within the window width
N number of power supply periods within the window width
P power
T time interval
T fundamental period of the power supply system
T window width comprising N fundamental periods
N
U voltage (r.m.s. value)
Y Variable replaceable by I, U
Y r.m.s. value of the spectral component of order k
C,k
Y r.m.s. value of harmonic group
g,h
Y r.m.s. value of the harmonic component of order h

H,h
Y r.m.s. value of interharmonic group
ig,h
Y r.m.s. value of interharmonic centred subgroup
isg,h
Y r.m.s. value of harmonic subgroup
sg,h
ω angular frequency
ω angular frequency of the power supply
ϕ phase angle
Page 25
Replace the entire subclause by the following new subclause:
3.5.2 Subscripts
b centre-band frequency
h running-integer number for harmonic orders
k running-integer number for spectral components
m measured value
61000-4-7 Amend. 1 © IEC:2008 – 9 –
max maximum value
min minimum value
o smoothed value
g grouped value
sg sub-grouped value
i interharmonic value
g,h harmonic group associated with harmonic order h
sg,h harmonic subgroup associated with harmonic order h
ig,h interharmonic group above harmonic order h
isg,h interharmonic centred sub-group above harmonic order h
og,h smoothed harmonic group of order h
nom nominal value
s sampled
C value related to spectral component
H harmonic
f frequency
0 d.c. related
Page 25
4.1 Characteristics of the signal to be measured
Replace the existing text of this subclause by the following new text:
Instruments for the following types of measurement are considered:
a) harmonic emission measurement,
b) interharmonic emission measurement,
c) measurements above harmonic frequency range up to 9 kHz.
Strictly speaking the (Fast) Fourier Transform produces accurate results for steady state
signals only. Signals whose amplitudes vary with time cannot be described correctly by their
harmonic components only. In order to obtain reproducible harmonic emission analysis results
when measuring products with fluctuating power, and thus fluctuating fundamental current
and possibly fluctuating harmonic current levels, a combination of averaging techniques and
sufficiently long measurement cycles can be used. This standard therefore provides a
simplified method employing specific averaging methods (see 5.5.1). Furthermore, a test
observation period, long enough to obtain successive measurement results that are within
acceptable tolerance levels is specified in the harmonic emission standards referring to this
standard.
Page 27
4.4.1 Main instrument
Replace, in the fourth dashed item of the first paragraph:
"a " by "a " and "b " by "b "
m k m k
Replace, the entire third paragraph (paragraph below Note 2) by the following new text:
The window width shall be 10 (50 Hz systems) or 12 (60 Hz systems) fundamental periods (T
N
= [10 or 12] × T ≈ 200ms) with rectangular weighting, synchronized to the fundamental
frequency of the power system. Hanning weighting is allowed only in the case of loss of
synchronisation. The loss of synchronization shall be indicated on the instrument display and

– 10 – 61000-4-7 Amend. 1 © IEC:2008
the data so acquired shall be flagged and shall not be used for the purpose of determining
compliance, but may be used for other purposes.

Replace the fifth paragraph (last paragraph before Figure 1) by the following new text:
The output OUT 1 (see Figure 1) shall provide the individual coefficients a and b of the DFT
k k
as well as Y , for the current or voltage, i.e. the value of each frequency component
C,k
calculated.
Page 29
Figure 1 – General structure of the measuring instrument
Replace the existing figure by the following new figure:
Sampling
frequency
generation
Input
Preprocessing
voltage
Sampling &
Main instrument
DFT OUT 1 (a , b , Y )
k k C,k
Conversion
Input
Preprocessing
current
Grouping
Input for Active Power
see notes 3 and 4
OUT 2a (Y )
g,h
Smoothing
OUT 2b (Y )
og,h
Check for
Compliance
OUT 3 (pass or fail)
IEC  858/08
Page 33
5.3 Accuracy requirements
Table 1 – Accuracy requirements for current, voltage and power measurements
Replace, in the last column, in the third row of Class I:
"P " by "P ".
nom m
Replace in the existing third explanatory note by the following:
U and I : Measured values by U , I and P : Measured values.
m m m m m
61000-4-7 Amend. 1 © IEC:2008 – 11 –
Replace the existing NOTE 2 by the following new NOTE:
NOTE 2 Class I instruments are recommended for emission measurements, Class II is recommended for general
surveys, but can also be used for emission measurements if the values are such that, even allowing for the
increased uncertainty, it is clear that the limits are not exceeded. In practice, this means that the measured values
of harmonics should be <90 % of the allowed limits.
Replace the existing NOTE 3 by the following new NOTE:
NOTE 3 Additionally, for Class I instruments, the phase shift between individual channels should be smaller than
h × 1º.
Pages 35 and 37
5.4 Measurement set-up for emission assessment
Replace the title and the entire text and figures of this subclause by the following new titles,
figures and text:
5.4 Measurement set-up and supply voltage
5.4.1 Measurement set-up for emission assessment
The measurement set-up is given in Figures 2 and 3.
Key
Δ
U L
U Source voltage line-neutral
S
L
S
U EUT terminal voltage
O
Z
L
Z Impedance of wiring and current sensing part

U E
L,N
US U
R U EUT Equipment under test
Z
N
C T
ΔU Voltage drop across Z and Z (ΔU = ΔU + ΔU )
L N L N
E
N
L Line connection
Δ U
N
IEC  859/08 N Neutral connection

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

Δ U
L Key
L U Source voltage line-neutral
S
Z
L
U EUT terminal voltage
S
Z Impedance of wiring and current sensing part

L L,N
O E
Z EUT Equipment under test
L
U U
ΔU Voltage drop across Z and Z (ΔU=ΔU +ΔU );
R T L N L N
L
C
For interphase connection, ΔU=2 × ΔU
Z
L L
E
L Line connections
1-3
U U
S
N Neutral connection
Z
N
N
Δ U
N
IEC  860/08
Figure 3 – Measurement set-up for three-phase emission measurements
5.4.2 Supply voltage for emission assessment
5.4.2.1 General
While measurements for assessing harmonics up to the 40th harmonic of the mains frequency
are being made, the test voltage U at the terminals of the EUT shall meet the following
requirements:
5.4.2.2 Requirements for equipment with input current less than or equal to 16 A per
phase
The following requirements for equipment with input current ≤16 A per phase shall be met:

– 12 – 61000-4-7 Amend. 1 © IEC:2008
a) The stability of the test voltage shall be maintained within ±2 % of the selected value and
the frequency shall be maintained within ±0,5 % of the selected value during the test. If
the EUT has a specified supply voltage range, the test voltage shall correspond to the
nominal voltage of the power system expected to supply the equipment (for example,
230 V line-neutral, corresponding to 400 V line-line). In order to facilitate ease of
measurements, for three-wire, three-phase delta connections, an artificial neutral point
realized with three resistors matched within 1 % may be used if the neutral conductor is
not available from the source. The purpose of the artificial neutral point is to permit
voltage and power-per-phase measurements to be made in a line-to-neutral configuration
as well as line-to-line. The errors introduced into measurements of EUT currents, during
emission tests by the loading effect of the voltmeter part of the instrument and any
installed artificial neutral network shall not exceed 0,05 %.
NOTE In many cases the artificial neutral is not required, but if it is, several approaches can be used. It may
be provided by the three input impedances of the voltmeters in the measuring instrument. Alternatively, the
artificial neutral may effectively consist of the combined effect of an explicit network plus the input impedances
of the voltmeters in the measuring instrument. It is also possible that the artificial neutral network, if it is
present, and the input impedances of the voltmeters may be so connected as not to introduce any errors in
current measurements (because the loading occurs on the source side of the current transducer). In still other
cases, errors introduced by the loading effect of the artificial neutral network and the input impedances of the
voltmeters in the instrument may be adequately compensated by regulating feedback loops in the source such
that errors that otherwise might be introduced do not, in fact, occur. Many other configurations may be
satisfactory, provided the required uncertainty is not exceeded.
b) For a three–phase supply, the three line voltages shall have a phase relationship of 0°,
120° ± 1,5°, 240° ± 1,5°.
c) The voltage harmonic distortion of the EUT test voltage U shall not exceed the following
values with the EUT connected and operating under the specified test conditions:
0,9 % for harmonic of order 3;
0,4 % for harmonic of order 5;
0,3 % for harmonic of order 7;
0,2 % for harmonic of order 9;
0,2 % for even harmonics of order from 2 to 10;
0,1 % for harmonics of order from 11 to 40.
d) The peak value of the test voltage shall be within a range of 1,404 to 1,424 times its r.m.s.
value and shall be reached between 87° and 93° after the zero crossing.
e) The voltage drop ΔU across the impedance of the current sensing part and the wiring shall
not exceed a peak voltage of 0,5 V.
5.4.2.3 Requirements for equipment with input current above 16 A and less than or
equal to 75 A per phase
The following requirements for equipment with input current >16 A and ≤75 A per phase shall
be met:
a) The output voltage U shall be the rated voltage of the equipment. In the case of a voltage
range, the output voltage shall be a nominal system voltage according to IEC 60038 (for
example: 120 V or 230 V for single-phase or 400 V line-line for three-phase). In order to
facilitate ease of measurements, for three-wire, three-phase delta connections, an
artificial neutral point realized with three resistors matched within 1 % may be used if the
neutral conductor is not available from the source. The purpose of the artificial neutral
point is to permit voltage and power-per-phase measurements to be made in a line-to-
neutral configuration as well as line-to-line. The errors introduced into measurements of
EUT currents, during emission tests by the loading effect of the voltmeter part of the
instrument and any installed artificial neutral network shall not exceed 0,05 %.
b) The output voltage shall be maintained within ±2,0 % and the frequency within ±0,5 % of
the nominal value.
c) In the case of a three-phase supply, the voltage unbalance shall be less than 50 % of the
voltage unbalance compatibility level given in IEC 61000-2-2.
d) The harmonic ratios of the output voltage U in no-load condition shall not exceed:

61000-4-7 Amend. 1 © IEC:2008 – 13 –
– 1,5 % for harmonic of order 5;
– 1,25 % for harmonics of order 3 and 7;
– 0,7 % for harmonic of order 11;
– 0,6 % for harmonics of order 9 and 13;
– 0,4 % for even harmonics of order 2 to 10;
– 0,3 % for harmonics of order 12 and 14 to 40.
e) For the application of Tables 2 and 3 in IEC 61000-3-12, the impedance of the supply
source is such that the short-circuit ratio R (as defined in IEC 61000-3-12) is equal to or
sce
higher than the minimum R value (R ) allowing the compliance of the equipment,
sce sce min
with possible insertion of reactors. For the application of Table 4 in IEC 61000-3-12, the
impedance of the supply source is such that the R is equal to or higher than 1,6 times
sce
the minimum R value allowing the compliance of the equipment, with possible insertion
sce
of reactors.
NOTE 1 The factor 1,6 is intended to take into account the fact that if an equipment is connected to a supply
that gives a higher R value than R , the harmonic emission currents increase. An allowance for this is
sce sce min
already included in Tables 2 and 3 in IEC 61000-3-12, so that no further allowance in terms of the value of
R to be used for testing is considered necessary.
sce
f) The impedance of the current-sensing part and the wiring is included in the impedance of
the supply source.
NOTE 2 The values of impedance and distortion given above have been chosen as a compromise,
considering that high quality supplies of very high current capacity are extremely rare. The repeatability of
results, using different supplies, can be very poor with the above-mentioned values of distortion and
impedance. The repeatability using the same supply is not so poor. If at all possible, a supply with lower
distortion and impedance should be used.
5.4.3 Equipment power
Equipment power, if required, shall be measured using the EUT terminal voltage U in Figure 2
or Figure 3 and the current into the EUT. For sources that include the current sensing part,
equipment power shall be measured using the voltage at the source output terminals and the
current into the EUT. In this case, the voltage shall be measured on the EUT side of the
current sensing part on the presumption that the source is regulated at its output terminals.

Page 39
5.5.1 Grouping and smoothing
Replace the existing text, including equations, Figures, Tables and NOTES, by the following
new subclause:
For assessment of harmonics, the output OUT 1 (see figure 1) of the DFT is first grouped to
be the sum of squared intermediate components between two adjacent harmonics according
to equation 8, visualized in figure 4. Only intermediate components above the second order
harmonic shall be used. The resulting harmonic group of order h (corresponding to the centre
component in the hatched area) has the magnitude Y (for 50 Hz this magnitude equals the
g,h
square root of the sum of the integer harmonic bin value squared plus the squared values of
the adjacent bins from n − 4 through n + 4 plus half of the squared values of the n − 5 bin and
n + 5 bin).
()N 2 −1
1 1
2 2 2 2
Y = ⋅ Y + Y + ⋅ Y (8)
g,h
∑
C,()N ×h − N 2 C,()N ×h +k C,()N ×h + N 2
2 2
()
k = − N 2 +1
NOTE In this equation, only intermediate components above the second order harmonic are taken into account.
In this equation, Y is the r.m.s. value of the spectral component corresponding to an
C,(N×h)+k
output bin (spectral component) of the DFT, (N × h) + k is the order of the spectral
components, and Y is the resulting r.m.s. value of the harmonic group.
g,h
– 14 – 61000-4-7 Amend. 1 © IEC:2008
Interharmonic group
Harmonic
group
h + 4
h + 2
Y
c
DFT output
Harmonic
h h + 1 h + 2 h + 3 h + 4 h + 5 h + 6
order
IEC  861/08
Figure 4 – Illustration of harmonic and interharmonic groups
(here shown for a 50-Hz supply)
NOTE The grouping of interharmonics is illustrated in Figure 4 only to clarify the definitions (see Annex A for
interharmonic current assessment).
A smoothing of the signal shall be performed over the r.m.s. value Y of each harmonic
g,h
order, according to equation 8 (OUT 2a of Figure 1), using a digital equivalent of a first order
low-pass filter with a time constant of 1,5 s, as shown in Figure 5.
SUM
α
Y or P Y or P
g,h og,h o
-1
β z
IEC  862/08
–1
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)

Table 2 – Smoothing filter coefficients according to the window width
Sampling Rate
(of the digital
Cycles N in
Frequency α β
low-pass filter)
Window
ms
50 10 8,012 7,012
≈ 1/200
60 12 8,012 7,012
≈ 1/200
50 16 5,206 4,206
≈ 1/320
60 16 6,14 5,14
≈ 1/267
For the fundamental component Y (if required, as, for example, for Class C in
H,1
Y
IEC 61000-3-2 and possibly for distortion factors), the same smoothing of the r.m.s value
H,1
from OUT 1 shall be performed.
If emission limits include the distortion factors THD or PWHD derived from the harmonic
Y H,Y
components Y according to 3.3, they shall be calculated using the values of OUT 1.
H,h
If emission limits include the distortion factors THDG , THDS , PWHD or PWHD derived
Y Y g,Y sg,Y
from the grouped values Y or Y according to 3.3, they shall be calculated using the
g,h sg,h
values of OUT 2a.
61000-4-7 Amend. 1 © IEC:2008 – 15 –
If a smoothing is required for the above distortion factors in the relevant standards, a digital
equivalent of a first-order low-pass filter with a time constant of 1,5 s, as shown in Figure 5
with the coefficients in Table 2, shall be used.
For the active power P and the power factor (if required as, for example, for Classes C and D
in IEC 61000-3-2), a similar smoothing of the modulus of the active power value and the power
factor value shall be performed.
NOTE An external power meter may be used provided that the power P is measured with a time resolution of
≈200 ms. Therefore, an input for an external power meter may be foreseen at the smoothing block, see Figure 1.
To co-ordinate with surveys of harmonic voltages (see IEC 61000-4-30), it is highly
recommended to provide a further type of smoothing, where the output is derived from the
components according to equation 8 as an r.m.s. value over 15 contiguous time windows,
updated either every time window (about each 200 ms) or every 15 time windows (about each
3 s).
Page 41
5.5.2 Compliance with emission limits
Replace the entire existing text by the following new text:
Assessment of compliance with emission limits shall be performed by statistical handling of
the data according to the conditions given in the relevant standards, such as IEC 61000-3-2,
IEC 61000-3-6, IEC 61000-3-12 and IEC 61000-4-30.
5.6 Assessment of voltage harmonic subgroups
Replace the existing text, including equations, Figures and NOTES, by the following new
subclause:
The Fourier transform analysis assumes that the signal is stationary. However, the voltage
magnitude of the power system may fluctuate, spreading out the energy of harmonic
components to adjacent spectral-component frequencies. To improve the assessment
accuracy of the voltage, the output components U for each 5 Hz of the DFT shall be
C,k
grouped according to Figure 6 and equation 9:
2 2
Y = Y
(9)
sg,h ∑
()
C, N × h + k
k = −1
Harmonic Interharmonic centred
subgroup subgroup
h + 2 h + 4
Y
c
DFT output
Harmonic
h h + 1 h + 2 h + 3 h + 4 h + 5 h + 6
order
IEC  863/08
Figure 6 – Illustration of a harmonic subgroup and an interharmonic
centred subgroup (here shown for a 50 Hz supply)
NOTE Further smoothing procedures to assess voltage subgroups are specified in IEC 61000-4-30.

– 16 – 61000-4-7 Amend. 1 © IEC:2008
Page 43
7 Transitional period
Replace the existing first paragraph, by the following new paragraph and NOTE:
The use of the grouping method, particularly with fluctuating loads, is recommended, but for a
transitional period the use of existing measuring instruments based upon the requirements
given in IEC 61000-4-7 (1991) continues to be permitted. However, measurements
performed with such instruments shall be marked in the test report with "Measuring
instrumentation according to IEC 61000-4-7, 1991”.
NOTE A transitional period is necessary, because changes in IEC 61000-3-2 and IEC 61000-3-12 are necessary
for a number of equipments (for example those using symmetrical multi-cycle controls) before applying the
grouping approach as explained in 5.5.1.

Delete the existing Table 2.
___________
IEC 61000-4-7:1991, Electromagnetic compatibility (EMC) – Part 4: Testing and measurement techniques –
Section 7: General guide on harmonics and interharmonics measurements and instrumentation, for power
supply systems and equipment connected thereto

61000-4-7 Amend. 1 © IEC:2008 – 17 –
Pages 45 and 47
Annex A
(informative)
Measurement of interharmonics
Replace the entire existing text of Annex A by the following:
Spectral components in the interval between two consecutive harmonic frequencies result
from a signal containing interharmonic components. Interharmonic components are caused
primarily by two sources:
– variations of the amplitude and/or phase angle of the fundamental component and/or of
the harmonic components, e.g. inverter drives;
– power electronics circuits with switching frequencies not synchronized to the power
supply frequency, for example, a.c./d.c. supplies and power factor correctors.
Possible effects are, for example:
– noise in audio amplifiers;
– additional torques on motors and generators;
– disturbed zero crossing detectors e.g. in dimmers;
– additional noise in inductive coils (magnetostriction);
– blocking or unintended operation of ripple control receivers.
The measurement set-up is based on the general description given in 5.4.
Spectral components associated with interharmonic components usually vary not only in
magnitude but also in frequency. A grouping of the spectral components in the interval
between two consecutive harmonic components forms an interharmonic group. This grouping
provides an overall value for the spectral components between two discrete harmonics, which
includes the effects of fluctuations of the harmonic components. Equation A.1, depending on
the supply frequency, permits the calculation of the value of the interharmonic group:
N −1
2 2
Y = Y (A.1)
ig,h ∑
C,()N ×h +k
k =1
NOTE In this context, ig,h is the interharmonic group of order h (See Figure 4 and 3.4.3). For the purpose of this
standard, the r.m.s. value of the interharmonic group between the harmonic orders h and h + 1 is designated as
Y , for example the group between h = 5 and h = 6 is designated as Y .
ig,h ig,5
The effects of fluctuations of harmonic amplitudes and phase angles are partially reduced by
excluding from equation A1 the components immediately adjacent to the harmonic
frequencies. Also, to determine the r.m.s. values Y of interharmonic centred sub-groups
isg,h
the components, that is, the
...