Smart Grid and Renewable Energy, 2012, 3, 152-157 Published Online May 2012 ( 1
A Novel Device for Real-Time Monitoring of High
Frequency Phenomena in CENELEC PLC Band
Bashir Ahmed Siddiqui, Pertti Pakonen, Pekka Verho
Department of Electrical Energy Engineering, Tampere University of Technology, Tampere, Finland.
Received January 19th, 2012; revised February 27th, 2012; accepted March 7th, 2012
This paper proposes the design and development of a novel, portable and low-cost intelligent electronic device (IED)
for real-time monitoring of high frequency phenomena in CENELEC PLC band. A high speed floating-point digital
signal processor (DSP) along with 4 MSPS analog-to-digital converter (ADC) is used to develop the intelligent elec-
tronic device. An optimized algorithm to process the analog signal in real-time and to extract the meaningful result us -
ing signal processing techniques has been implemented on the device. A laboratory environment has setup with all the
necessary equipment including the development of the load model to evaluate the performance of the IED. Smart meter
and concentrator is also connected to the low voltage (LV) network to monitor the PLC communication using the IED.
The device has been tested in the laboratory and it has produced very promising results for time domain as well as fre-
quency domain analysis. Those results imply that the IED is fully cap able of monitoring high frequ ency disturbances in
Keywords: Power Line Communication (PLC); Digital Signal Process or (DSP); Analog-to-Digital Converter (ADC);
Fast Fourier Transform (FFT); High Frequency (HF) Interference
1. Introduction
Recent technological developments have enabled the
evolution of devices that uses power line communication
(PLC) to send and receive control signals with some de-
gree of reliability. The primary purpose of power line is
to carry power not data which means reliable communi-
cation over power lines are difficult due to noise created
by loads and devices connected to the PLC network. All
power electronic devices generate and emit unwanted
electrical signals (EMI noise) that can lead to a perform-
ance degradation of PLC network. They generate high
frequency conducted and radiated EMI noise and draw
distorted line currents due to the sharp edges of the switch-
ing waveform with high du/dt. The most common high
frequency noise sources are compact fluorescent lamps
(CFL), switched power supplies, frequency converters
and AC motors that can cause significant amount of re-
duction in signal-to-noise ratio (SNR) in PLC network
[1]. For Western Europe, the regulation concerning com-
munications over low voltage network are described in
CENELEC standard EN 50065-1 entitled “Signalling on
low-voltage electrical installation in the frequency range
3 kHz to 148.5 kHz”. Th e allowed frequency rang e i.e. 3
to 148.5 kHz is further divided into five sub-bands. The
use of frequency band 3 kHz up to 95 kHz is restricted to
electricity suppliers and their licensees [2]. The object of
the standard is to limit interference caused by signal
transmission equipment to sensitive electronic equip-
The frequency range in the “traditional” harmonic range
up to 2 to 3 kHz has been under investigation for several
years and large amount of knowledge has been gathered
through the years on this issue. However, little or no at-
tention has been paid to the frequency range above the
low-frequency harmonic range, or at least between 2 to
150 kHz. This is probably due to the apparent absence of
well documented cases of interference found within this
frequency range [3]. Another more fundamental reason is
the lack of appropriate measuring equipment to record
and analyze high frequency phenomenon in PLC network.
Conventional monitoring equipment such as, oscilloscope,
network analyzer and spectrum analyzer are not opti-
mized for PLC application because they cannot do any
post-processing on the measured data which is necessary
to monitor the behavior of PLC network. Some previous
work carried out on this topic have been presented in [4,5]
but they are currently unavailable and work presented in
[6] has a limited functionality fo r a specific platfor m. One
main reason for concern is the possible interference of
high frequency distortion with power line communication
Copyright © 2012 SciRes. SGRE
A Novel Device for Real-Time Monitoring of High Frequency Phenomena in CENELEC PLC Band 153
e.g., automatic meter reading (AMR). The frequency
range used for PLC i.e. 3 to 95 kHz is the same range that
is often used for switching in switched mode power sup-
plies, high frequency (HF) ballasts, etc. It is a consider-
able issue for the successful and efficient operation of an
AMR. Therefore, long term measurements and real-time
analysis of high frequency interference to monitor the
power quality of the PLC network has become more es-
sential than ever before. This paper discusses the devel-
opment of a novel and low-cost intelligent electronic de-
vice (IED) for continuous monitoring of power quality
and high frequ ency phenomena in PLC network.
The rest of the paper is organized as follows. Section 2
briefly explains the hardware architecture of the IED.
Section 3 discusses about the prototype development of
the IED. Section 4 describes the design flow and efficient
signal processing algorithm implementation on a low-
cost digital signal processor (DSP) to meet the real-time
challenges. Section 5 talks about the detailed laboratory
setup to test the PLC and other high frequency signals
with the IED. The experimental results obtained by IED
are discussed in Section 6. Finally, the paper is summa-
rized in Section 7.
2. Hardware Architecture
The hardware architecture of this novel and low-cost IED
is based on the development idea proposed in [7]. Figure
1 shows the modified block diagram of the architecture.
The hardware architecture includes signal conditioning,
data acquisition and DSP block. Analog signal coming
from the LV network needs signal cond itioning before an
acquisition unit can reliably and accurately acquire the
signal. The signal conditioning block includes steps like
signal decoupling from the LV network, attenuation, fil-
tering and amplification. Data acquisition block is equipped
with ADS7881, a 12-bit analog-to-digital converter to sam-
ple the analog signal. Afterwards, a high speed floating-
point DSP C6713 with an operating frequency of 225
MHz is used to apply signal processing algorithms to
mathematically manipulate the digital data.
A high pass filter and voltage divider circuit as shown
in Figure 2 has been developed as a front-end module to
couple with LV network to attenu ate the voltag e sig nal to
±2.5 volt. It is the common input voltage range for data
acquisition unit.
Figure 1. Development approach of the IED.
Figure 2. Front-end module for LV network.
3. Prototype of Intelligent Electronic Device
The prototype of intelligent electronic device following
the hardware architecture discussed in Section 2 has been
developed which is shown in Figure 3. The data acquisi-
tion block has been interfaced with DSP using 5 - 6K
Interface board developed by Texas Instrument. The 5 -
6K board is intended to maintain a compatible interface
with the TMS320 series of DSP according to the guide-
lines set forth in the TMS320 Cross-Platform Daughter
Card Specification (SPRA711) [8]. Additional power of
±12 V and +5 V are required to power up the interface
board which is necessary for the analog front end and
analog power rail of the ADS7881, respectively.
4. Software Interface
Main novelty of the device comes in the software part
where the objective is to capture and process the signal in
real-time continuously for a longer period of time (days
or weeks). The software interface has been developed to
collect and process the samples as quickly as possible.
Figure 4 depicts the DSP design implementation flow
diagram of the IED. It starts with initializing the neces-
sary functions for bo ard support libraries, DSP and ADC
interfaces, resetting interrupt and timer. The most effi-
cient way of accomplishing real-time processing is by
using a timer, hardware interrupt and a software interrupt.
Figure 3. Prototype of the intelligent electronic device.
Copyright © 2012 SciRes. SGRE
A Novel Device for Real-Time Monitoring of High Frequency Phenomena in CENELEC PLC Band
Figure 4. DSP design implementation flow of the IED.
The algorithm is written to collect 1024 continuous sam-
ples of analog signal then computing FFT then perform-
ing additional post-processing on the FFT data. As soon
as 1024 samples are stored into the Buffer, ADC inter-
rupts the DSP which trigger software interrupt (SWI) and
go back to fill another set of data to the Buffer. During
the time another set of 1024 samples are stored into the
Buffer, the SWI executes the inter service routine (ISR)
which includes the scaling and computation of signal
processing algorithm of the sampled data. The only time
constraint is that all the d ata inside software interrupt ser-
vice routine must be processed before the active Buffer
fills up. It is much easier to meet the real-time constrain ts
with this implementation.
Continuous monitoring of the PLC network is another
major aspect of this novel device. It is not possible to
meet such goal due to the limited amount of memory
available on the DSP. To overcome this issue, a laptop
has been attached to the IED which works as a data stor-
age unit. A C code is written to transfer the processed
data to the laptop through JTAG emulation.
Frequency Domain Analysis
Time domain waveform does not provide sufficient in-
formation about the signals. Therefore, frequency domain
analysis is necessary to draw the meaningful result. The
waveform assessment is indeed a challenging and time
consuming task. It requires an appropriate method and
tool especially if real-time processing is a big concern.
There are quite a few methods of waveform parameters
estimation but, arguably, one of the most popular tools is
discrete Fourier transform (DFT), especially its fast algo-
rithm version called fast Fourier transform (FFT). An ef-
ficient FFT algorithm is implemented on the IED to meet
the real-time challenges. Typical FFT algorithms assume
complex input and output data. Most of the time domain
data ar e real valued. A s imple solu tion to th is probl em i s to
pad N-length zero-valued sequence as imaginary compo-
nent with real-valued signal to make it a complex input to
compute the FFT. However, this method is obviously in-
efficient. The algorithm used in this application assumes
N-point real sequence as N/2-point complex valued se-
quence then it computes N/2-point complex FFT on the
complex valued sequence. In the first step, only N/2
points of the N-point sequence are computed. Since the
FFT of a real-sequence has symmetric properties, the re-
maining N/2 points FFT are easy to compute with equa-
tions. Complete description of the algorithm along with
equations can be found i n [9].
5. Experimental Setup
The prototype IED has been tested in the laboratory. A
setup using smart energy meter and data concentrator
which acts as a central unit has been used. These meters
are fully electronic and smart which record the consump-
tion of electric energy and send that information to the
utility for billing purposes. They communicate over low
voltage network using power line communication. Fig-
ure 5 shows the necessary connection setup to power the
signal conditioning, data acquisition and DSP block of
the IED. Figure 6 shows the smart meter and concentra-
tor setup used to test the PLC communication using the
prototype IED. Modern energy saving lighting can emit
high frequency interference in the frequency range cho-
sen for PLC communication. A low-power load model
based on CFL and LED lamps as shown in Figure 7 is
developed to test the capab ility of IED to detect the high
frequency phenomena in PLC network. A block diagram
showing the experimental setup among LV network,
smart meter, concentrator and load model is shown in
Figure 8. Prototype IED is used to monitor the adverse
interaction between PLC communication signals and
noise generated by the load.
6. Results
This section explains about the results computed by the
prototype IED. Matlab has been used to plot all the fig-
ures for better presentation. Before making any meas-
urements with the load setup, a reliability test of the IED
Copyright © 2012 SciRes. SGRE
A Novel Device for Real-Time Monitoring of High Frequency Phenomena in CENELEC PLC Band 155
Figure 5. Connection se tup in the laboratory.
Figure 6. Smart meter and concentrator setup.
Figure 7. Load model based on CFL and LED lamps.
Figure 8. Block diagram showing the experimental setup.
along with the software algorithm implemented on the
IED has been made by comparing the FFT spectrum of
the known signal computed by the IED and measured by
Rhode & Schwarz spectrum analyzer ESPI-3. Figure 9
shows the spectrum of 80 kHz signal captured by IED
and spectrum analyzer. The spectrum analyzer is typi-
cally a more expensive piece of test equipment when
compared with this low-cost IED. Despite the low sam-
pling frequency and dynamic range, IED has detected the
80 kHz signal quite accurately comparing to the spec-
trum analyzer which is evident from the graph.
After successful reliability test, IED was connected
with the load setup to monitor the behaviour of the PLC
network. Figure 10 depicts the time-domain waveform
(without scaling) of 50 Hz signal captured by the IED. It
is clearly visible that PLC signals are modulated over 50
Hz cycle and communication between meter and concen-
trator is going on in most of the cycle. No communication
is going on between meter and concentrator for a short
duration of tim e whi c h i s al so i ndi cat ed i n the wavef orm.
0 2 4 6 810 12 14 16 18
x 10
Frequenc y (Hz )
Usi ng IED
02 4 6 810 12 14 16 18
x 10
Frequenc y (Hz )
Us i ng Spect rum A n al y zer
Spectrum of 80 k Hz Si gnal
45 dB
Figure 9. Spectrum analysis using IED and spectrum ana-
00.0020.004 0.006 0.0080.010.012
Time-Domain Waveform
Time (s)
Voltage (U)
PLC Communication Signal
No PLC Communication Signal
Figure 10. Time-domain waveform captured by the IED.
Copyright © 2012 SciRes. SGRE
A Novel Device for Real-Time Monitoring of High Frequency Phenomena in CENELEC PLC Band
Frequency-domain analysis gives description about the
distribution of energy in the signal as a function of fre-
quency. It is necessary to determine other high frequency
components present in the signal which act as a noise.
Figures 11 and 12 shows the frequency domain analysis
of the load network computed by the IED. It can be ob-
served from the graphs that the IED is capable of moni-
toring frequencies up to 175.78 kHz with the current
system implementation. High frequency phenomena can
be observed in both the spectrum through the whole PLC
band. The primary source of the noise is the load model
which has CFL and LED lamps connected with it. The
operating frequ ency of a CFL is often just above 40 kH z.
The high frequency components above 40 kHz in both
the spectrum are the emission caused by the switching
element in the CFL. In Figure 11, the fundamental har-
monics can be seen clearly at 43 kHz, followed by a se-
cond harmonic at 86 kHz and a third harmonic at 129
kHz. Harmonics can easily pollute the network which is
a big concern for successful PLC communication. Other
high frequencies present at 12 kHz and 115 kHz as
shown in Figure 12 are probably due to other power
electronic devices connected to the distribution network.
510 15
x 10
Frequency-Domain Spectrum
Fr equency (Hz)
U( dB
86 kHz Signal
43 kHz Signal
129 kHz Signal
Figure 11. Frequency-domain spectrum computed by the
510 15
x 104
Frequency-Domain Spectr um
Frequency (Hz)
12 kHz Signal
115 kHz Signal
41 kHz Signal
Figure 12. Frequency-domain spectrum computed by the
As is known, the noise floor limits the smallest meas-
urement that can be taken with certainty since no meas-
ured amplitude can, on average, be less than the noise
floor. According to the EMC standard EN 55011, con-
ducted emissions from RF equipments should be below
56 dBµV at 150 kHz and decrease to 46 dBµV at 500 kHz.
The IED has been designed to meet the following meas-
urement limits. Noise floor of the IED is around 45 dBµV
which can b e observed from Figure 12.
It can be further analyzed from Figure 9 that spectrum
measured by spectrum analyzer has second harmonic at
160 kHz which is not found in th e spectru m computed by
IED because its amplitude is just below the noise floor of
the IED. The result proves that IED is capable of moni-
toring the lowest possible interference set forth by the
EMC standard.
7. Conclusion
The design and development of a novel intelligent elec-
tronic device for real-time monitoring of high frequency
disturbances in PLC network is presented in this paper.
The prototype IED has been tested in the lab oratory with
adequate equipments. The test results have shown very
efficient performance in the robust distribution network
and computed very accurate results. The IED provides a
versatile environment to study and analyze the behavior
of LV network in general and PLC network in particular.
Moreover, it can be used as a cost-effective platform to
develop tools for electrical utilities to monitor the PLC
network to solve the practical issues related to distur-
bances and PLC communication problems. The future
prospect of the IED is to make index calculation from the
FFT data to extract the valuable information to classify
the quality of the signal. The IED will be installed in real
field for longer durations of time to monitor the time-
variant behavior of the PLC network.
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