Frank Gronwald

Ralf Conrads

Reinhard Janssen

Thomas Weber

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 C I R E D 22nd International Conference on Electricity Distribution Stockholm, 10-13 June 2013 
 
Paper 1120 
 
 
CIRED2013 Session 2 Paper No  1120     
Efficient immunity testing of smart meter devices  
in the frequency range 2-150 kHz 
 
 
 Frank Gronwald  Ralf Conrads and Reinhard Janssen  Thomas Weber 
Hamburg University of Technology EWE AG Oldenburg TÜV NORD CERT GmbH 
 Germany Germany Germany 
            gronwald@tuhh.de ralf.conrads@ewe.de; reinhard.janssen@ewe.de tweber@tuev-nord.de 
 
 
ABSTRACT 
Energy networks are subject to considerable disturbing 
currents in the frequency range of 2-150 kHz, due to 
insufficient Electromagnetic Compatibility standards, and it 
is important that smart meter devices exhibit in this 
frequency range sufficient immunity. It is shown that 
corresponding immunity tests in frequency domain must 
utilize small enough frequency spacing since smart meter 
susceptibilities can be rather narrowband, as is shown by 
example. It is also pointed out that for efficient testing the 
use of broadband test pulses provides advantages if 
compared to single frequency sweeps.        
 
INTRODUCTION 
It is known that smart meter devices can be subject to 
conducted disturbances that seriously affect operational 
states. The related EMC-problems are of particular concern 
in the frequency range 2-150 kHz [1]. This frequency range, 
at present, is not satisfactorily regulated by obligatory EMC 
standards, as can be seen from the EMC standards that are 
currently in effect and concern immunity testing of smart 
meter devices. These comprise the following basic 
standards, as listed in the relevant product standard IEC 
62052-11 [2]: 
 
 Standard IEC 61000-4-2 which is related to 
immunity testing with respect to electrostatic 
discharge [3].  
 Standard IEC 61000-4-3 which is related to 
immunity testing with respect to external radiated 
electromagnetic fields in the frequency range 80 
MHz to 2 GHz [4]. 
 Standard IEC 61000-4-4 which is related to 
immunity testing with respect to fast transients and 
bursts, as can be produced by fast switching 
processes [5].  
 Standard IEC 61000-4-5 which is related to 
immunity testing with respect to transients of a 
double exponential form, as can be produced by 
lightning or slow switching processes [6]. 
 Standard IEC 61000-4-6 which is related to 
immunity testing with respect to conducted 
disturbances in the frequency range 150 kHz to 80 
MHz [7]. 
 Standard IEC 61000-4-12 which is related to 
immunity testing with respect to non-repetitive 
damped sinusoidal transients that also are called 
“ring waves”. The test frequencies of these 
sinusoidal transients are given by 100 kHz and 1 
MHz [8]. 
 
Concerning immunity testing with respect to conducted 
disturbances, it is seen that the relevant basic standard IEC 
61000-4-6 only covers the frequency range 150 kHz to 80 
MHz. A closer inspection of this standard additionally 
reveals that only common mode signals are applied to the 
test objects, while in typical energy distribution networks it 
is the differential mode which is mostly relevant [9,10]. 
To also take into account conducted differential mode 
disturbances in the frequency range below 150 kHz, a new 
basic standard IEC 61000-4-19 with draft title “Testing and 
measurement techniques - Test for immunity to conducted, 
differential mode disturbances in the frequency range from 
2 kHz to 150 kHz, at a.c. ports” is currently under 
discussion. It is not yet known when this standard will be 
finalized and whether it will be made obligatory for smart 
meter devices. Also, it still needs to turn out in practice 
whether the test procedures described in this standard will 
be sufficient enough to assure proper functioning of smart 
meter devices under all circumstances that are usually 
encountered in power distribution networks.  
To summarize, it can be stated that at present there is no 
international and standardized test procedure in effect which 
guarantees a proper immunity of smart meter devices with 
respect to conducted disturbances in the frequency range 2-
150 kHz. Clearly, this situation is not satisfying for the 
manufacturers and users of smart meter devices since it is 
left to their own responsibility, at least to a considerable 
extent, to assure sufficient EMC immunity of their smart 
meter devices within actual energy networks.  
While the draft standard IEC 61000-4-19 already provides 
guidance with respect to comprehensive immunity testing in 
frequency domain, the following points are noted: 
 
 Due to the finite frequency spacing of the 
narrowband test pulses it is possible that 
narrowband susceptibilities of smart meter devices 
are missed. 
 Testing in the frequency domain is considered as 
time-consuming since, depending on the frequency 
spacing, hundreds of test frequencies have to be 
considered to cover the whole frequency range 2-
150 kHz. This issue becomes a serious problem if 
a smart meter devices is tested which for the test 
engineer requires many seconds to evaluate the 
operational state of the device under test. 
 C I R E D 22nd International Conference on Electricity Distribution Stockholm, 10-13 June 2013 
 
Paper 1120 
 
 
CIRED2013 Session 2 Paper No  1120     
 
In this contribution we reconsider the physical basis of 
immunity testing in frequency domain. It will be seen that 
the susceptibility of smart meter devices can be 
considerably narrowband such that broadband test pulses 
that are defined in time should also be considered to obtain 
more reliable test results. 
 
IMMUNITY TESTING AND QUALITY 
FACTORS OF COMPLEX SYSTEMS  
From the point of view of EMC modelling, a smart meter 
device is not a canonical structure, such as a simple 
transmission line or antenna, but rather a complex system. 
Usually, linearity and time-invariance is assumed and then 
the immunity of a complex system often is characterized by 
a transfer function )(sH which relates an output quantity, 
such as the observable )(sO of an operational state, to an 
input quantity, such as a disturbing current )(sI . These 
transfer functions can be discussed in the framework of the 
so-called singularity expansion method (SEM) and then are 
written in the general form 
 












M
m m
m
m
m
ss
R
ss
R
sI
sO
sH
1
*
*
)(
)(
)(  (1) 
 
where the approximation sign indicates that in general the 
relation is not a mathematically exact equality but of 
sufficient accuracy if M dominant poles ms of the system 
are taken into account. These poles represent the 
frequencies where the complex system considered is 
potentially susceptible to the input quantity )(sI . The 
variable s  denotes the Laplace variable in the complex 
plane and for the mth pole the variable mR denotes the 
residue associated to each resonance pole,  
 
mmm js        (2) 
 
The real part m , for passive systems, is negative and 
represents losses of the system, the imaginary part m is  
the resonance frequency associated to the pole ms . If the 
representation (1) is compared to the transfer function of a 
damped harmonic oscillator, such as an RLC resonant 
circuit, it is seen after some analysis that the variables m  
and m can also be expressed in terms of an 
Eigenfrequency m,0 and a quality factor Qm . The 
corresponding relations are given by [5] 
 
m
m
mmm Qs 


2
,0
,0    (3) 
 
These notions and concepts are important in order to 
correctly interpret immunity testing in frequency domain 
[13]. As an example, in Fig. 1 the frequency dependency of 
the received power of a small dipole antenna is displayed in 
the vicinity of resonance, serving as an elementary model of 
an EMC victim. At resonance, the received power attains a 
maximum and the susceptibility of this system becomes, in 
this frequency range, largest as well. For reliable immunity 
testing it is decisive to hit the maxima of susceptibility and 
this, in turn, requires choosing the frequency steps 
accordingly. If testing with a margin of 1dB with respect to 
maximum susceptibility is desired this requires, in the 
example of Fig. 1, to choose frequency steps nf according 
to a 2.3% rule, that is,     
 
023,11  nn ff      (4) 
 
as can be seen from Fig. 1 where the 2,3% bandwidth is 
indicated. This measure is closely connected to the quality 
factor Q = 23 of the system, the reciprocal of which 
indicates the 3dB-bandwidth. 
In the draft standard IEC 61000-4-19, frequency steps are 
prescribed according to a 2% rule. This allows reliable 
testing of systems up to a quality factor of 26 if a 1 dB 
margin is desired. For higher quality factors it is then 
possible to miss frequencies where susceptibility is at a 
maximum and, as a consequence, immunity at a minimum. 
For smart meter devices it is not immediate to determine a 
quality factor on the basis of physical models. The reason is 
that smart metering involves a considerable amount of 
digital signal processing which is not directly accessible to 
electromagnetic theory. That is, within a smart metering 
device analog signals are readily converted to digital signals 
Figure 1. The diagram shows the received power of a 
matched, small dipole antenna of quality factor Q = 23. 
It can be noted that the quality factor is given by the 
reciprocal of the percentage of the 3db-bandwidth 
relative to the resonance frequency, i.e., Q = 23 ~ 
1/(0.045). 
 
 C I R E D 22nd International Conference on Electricity Distribution Stockholm, 10-13 June 2013 
 
Paper 1120 
 
 
CIRED2013 Session 2 Paper No  1120     
and then further processed. Disturbances in the frequency 
range 2-150 kHz may affect this process but there is no 
general rule for this since it strongly depends on the actual 
AD converter.  
In order to obtain more information on typical quality 
factors of smart meter devices, if considered as an EMC 
victim, an actual smart meter has been investigated by 
means of an EMC test setup which is sketched in Fig. 2. A 
rather small frequency step width of 0.37% was chosen, 
yielding the result curve of Fig.3.      
 
 
The test result exhibits narrowband susceptibilities that lead 
to abnormal operational states where acceptable accuracy 
limits are clearly exceeded. To exhibit these narrowband 
susceptibilities, a frequency step width of 0.37% proved to 
be useful.  
The visible peaks can be approximated by resonance peaks 
of the mathematical form displayed in Fig. 1, even though 
this analogy is physically somewhat vague since it can be 
assumed that the observed narrowband failure of the smart 
meter device is due to poor filtering or poor signal 
processing of high-frequency disturbances rather than due  
to a physical resonance. Then the associated quality factors 
of the observed peaks clearly exceed the value of 26 which 
is identified as the maximum value that can be analyzed by 
means of a standard frequency step width of 2%. Therefore 
it turns out by this example that the susceptibility of actual 
smart meter devices can be narrowband to an extent which 
makes it necessary to use a much finer frequency stepping 
than the standard one. 
 
NARROWBAND VERSUS BROADBAND TEST 
SIGNALS 
As already mentioned in the introduction, the use of small 
frequency steps is not always practical since it can be 
connected to a considerable increase of test time. Therefore 
it is recommended to also use broadband test signals which 
reduce the risk of missing susceptibilities due to 
insufficiently large frequency steps. In the context of the 
EMC of complex systems this idea is not new and leads to 
the question whether certain test pulses are equivalent but 
more time efficient if compared to single frequency 
continuous wave signals. Discussions of this point can be 
found, in particular, in the context of “Intentional 
Electromagnetic Interference (IEMI)”. In relation to energy 
networks a corresponding investigation with useful 
literature is given in [14].    
Here we limit ourselves to mention the double exponential 
pulse  
 
  ttItI   exp)exp()( exp,0exp   (5) 
 
and the damped sinusoidal pulse 
 
 ttItI 0sin,0sin sin)exp()(     (6) 
 
It is interesting to note that these waveforms, with certain 
specified parameters, already are utilized in the standards 
 
Power Source 
 
Coupling/ 
Decoupling 
Network 
 
Interference 
Signal 
Generator 
 
Smart Meter 
 
Load 
 
Readout Unit 
Figure 2. EMC test setup which is suitable to investigate 
the immunity of smart meter devices. It follows the 
generic setup for conducted immunity tests [10]. Special 
care must be taken, however, that the 
coupling/decoupling network is adapted to the required 
frequency range 2-150 kHz.   
Figure 3. Result of immunity testing of an actual smart 
meter device. Two pronounced susceptibilities which 
indicate an abnormal operational state can clearly be 
recognized. 
 C I R E D 22nd International Conference on Electricity Distribution Stockholm, 10-13 June 2013 
 
Paper 1120 
 
 
CIRED2013 Session 2 Paper No  1120     
IEC 61000-4-4 [5] and IEC 61000-4-12 [8] which are 
prescribed for smart meter devices. However, they are not 
yet used to close the standardization gap in the frequency 
range 2-150 kHz. 
The waveforms (5) and (6) have the advantage that their 
Fourier transforms can easily be obtained as 
 
 
  

jj
II


 exp,0exp )(
~    (7) 
and 
 
 2220
0
sin,0sin )(
~


j
II

    (8) 
 
These analytic formulas allow estimating the energy IE of  
a pulse by means of Parseval’s theorem 
 
 




 IEdIdttI 
2
2 )(
~
2
1
)(   (9) 
 
which also yields an estimate of the energy  2,1 IE in a 
certain frequency interval  21, , given by  
 
  
2
1
21 ,
2
)(
~
2
1 
 

 I
EdI    (10) 
 
For different test pulses to be equivalent, the corresponding 
energies must be comparable in the considered frequency 
interval.  
Modern signal generators that can be taken as interference 
signal generator in a test setup as shown in Fig. 2, usually 
provide a host of predefined test signals, including the 
double exponential pulse and the damped sinusoidal pulse, 
which can repetitively be applied. It has not explicitly been 
shown by the authors, yet, which test signal is an optimal 
choice in terms of efficiency and reliability. However, the 
susceptibilities observed in Fig.3 actually were first 
discovered by experimenting with different pulse shapes 
rather than by applying frequency sweeps. Therefore the use 
of broadband pulses is suggested as a promising means for 
efficient and reliable testing of smart meter devices.  
 
REFERENCES 
 
[1] CENELEC SC 205A, 2010, Study Report on 
Electromagnetic Interference between Electrical 
Equipment/Systems in the Frequency Range below 
150 kHz, SC205A/SEC0260/R. 
 
[2] IEC 62052-11, 2003, Electricity metering equipment 
(AC) - General requirements, tests and test conditions 
- Part 11: Metering equipment. 
 
[3] IEC 61000-4-2, 2008, Electromagnetic compatibility 
(EMC) - Part 4-2: Testing and measurement 
techniques - Electrostatic discharge immunity test.  
 
[4] IEC 61000-4-3, 2010, Electromagnetic compatibility 
(EMC) - Part 4-3: Testing and measurement 
techniques - Radiated, radio-frequency, 
electromagnetic field immunity test. 
 
[5] IEC 61000-4-4, 2012, Electromagnetic compatibility 
(EMC) – Part 4-4: Testing and measurement 
techniques – Electrical fast transient/burst immunity 
test. 
 
[6] IEC 61000-4-5, 2005, Electromagnetic compatibility 
(EMC) - Part 4-5: Testing and measurement 
techniques - Surge immunity test. 
 
[7] IEC 61000-4-6, 2008, Electromagnetic compatibility 
(EMC) - Part 4-6: Testing and measurement 
techniques - Immunity to conducted disturbances, 
induced by radio-frequency fields. 
 
[8] IEC 61000-4-12, 2006, Electromagnetic compatibility 
(EMC) - Part 4-12: Testing and measurement 
techniques - Ring wave immunity test. 
 
[9] R. Strzelecki and G. Benysek (eds.), 2008, Power 
Electronics in Smart Electrical Energy Networks 
(Springer, London, United Kingdom). 
  
[10] C.R. Paul, 2006, Introduction to Electromagnetic 
Compatibility, 2nd ed., (Wiley, New Jersey, USA). 
 
[11] C.E. Baum, 1976, “The Singularity Expansion 
Method”, in Transient Electromagnetic Fields, L.B. 
Felsen (ed.), (Springer, Heidelberg), 129-179. 
 
[12] J. Chauveau, N. de Beaucoudrey, and J. Saillard, 
2007, “Characterization of Perfectly Conducting 
Targets in Resonance Domain with their Quality of 
Resonance”, Progress in Electromagnetic Research, 
vol. 46, 165-188. 
 
[13] F. Gronwald, T. Stadler, R. Kebel, 2012, 
“Compensation of Unavailable Test Frequencies 
during Immunity Measurements”, in   
Proceedings of ESA Workshop on Aerospace EMC, 
(ESA, SP-702). 
 
[14] W. Radasky and E. Savage, 2010, “Intentional 
Electromagnetic Interference (IEMI) and Its Impact on 
the U.S. Power Grid”, (Metatech, Meta-R-32). 


Efficient immunity testing of smart meter devices in the frequency range 2-150 kHz

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Efficient immunity testing of smart meter devices in the frequency range 2-150 kHz

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