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• withdrawn,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 c
...