PLC Communication Analysis In Nigerian Distribution Network
Transcript of PLC Communication Analysis In Nigerian Distribution Network
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
1/22
PERFORMANCE ANALYSIS OF PLC FOR NARROW AND BROAD
BAND APPLICATIONS IN NIGERIAN DISTRIBUTION NETWORKS
FACILITY
Awalu, S. O. & Aliyu, U. O.
Abubakar Tafawa Balewa University,
Bauchi-Nigeria.
ABSTRACT
Communication over electric power distribution lines (PLC) has wide area of
applications. Areas of application of power line communication include distribution
automation, internet communication, local area networking and industrial control. Designing
and planning an efficient power line communication system over any distribution network
require information on signal transmission characteristics of the network. This paper presents
signal transmission characterization and performance analysis of power line communication
system over some selected distribution networks in Nigeria with respect to frequency bands
of 50-500 kHz and 1-10 MHz for low and high bit rate applications respectively. The
simulation results and field measurements are discussed extensively from the stand points of
signal attenuation in the Nigerian distribution network infrastructure.
I INTRODUCTION
In addition to transmitting power at 50 Hz/60Hz, electric power lines are also used as
communication media for transmitting communication signals. This technology of sending
communication signals through existing electric power networks is known as power line
communication (PLC). The areas of applications of power line communication includes
1
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
2/22
distribution automation, industrial control, local area networking, home automation and
internet communications (Selandar,1999; Newbury,1996; Patrick et al,1995). While the
utility companies that operate power systems have a natural interest in the development of
such techniques for control and communication for purposes of distribution automation, the
driving force for others is the benefits of the technology in the context of home automation,
internet communication and industrial control.
Unlike other communication channels, power lines are not designed specifically for
communication purposes as such they present unique technical problems as communication
medium. Generally, the characteristics of power lines which are channels for power line
communication system are time and location dependent. The impedance, noise and
attenuation of power line vary with frequency, time, distance and location (Abraham and
Roy, 1992; Tang et al., 2003). Many electrical devices which are connected to the lines inject
significant noise back into the network. In addition, the variation of electrical loads connected
to the networks creates a timevarying environment altering characteristic impedance of the
line as well as the noise (Cavdar, 2004). These represent the most critical obstacle to a
universal design for power line communication system. Therefore, it is necessary to
investigate into characteristics of power line communication systems from different parts of
the world for the design of standard power line communication system. The aim of this paper
is to investigate the performance of power line communication system in Nigerian
distribution system facilities for narrowband and broadband applications.
The rest of the paper is divided as follows. In Section II, power line communication
signal attenuation of low voltage distribution network based on theoretical models is
described. Section III presents field measurements of signal attenuation of out-door and in-
door low voltage distribution networks., In Section IV, signal attenuation obtained from
theoretical and measurement results have been applied to differential phase shift keying
2
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
3/22
(DPSK) channel to determine the performance of power line communication system over the
distribution networks. Section V presents the results and section VI presents results analysis.
II DERIVATION OF SIGNAL ATTENUATION FROM THEORETICAL MODELS
Transmitters in power line communication systems are connected either between two
line conductors or between a conductor and ground. Their signals must pass through
distribution transformers, electric power cables, electrical loads and PLC modems before
reaching the receiver. These elements are responsible for signal attenuation due to their
characteristics combined with power line communication modems. Therefore, to determine
the power line communication signal attenuation, all the network elements mentioned above
and other PLC communication equipments must be considered. The overall PLC signal
attenuation model is obtained by combining the individual component models of distribution
transformer, distribution line, electrical load and PLC modem.
In secondary distribution networks, PLC modems are connected at the secondary port
of the transformer, therefore for circuit analysis, transformer model is referred to the
secondary (Cavdar, 2004). For secondary distribution circuits, lumped series parameter
model have been found to be satisfactory for evaluation of power line communication
(Wasley and Momoh, 1978). Generally transformer-capacitor coupling circuits are used in
power line communication modem mainly because the transformer provides galvanic
isolation from the power line network and acts as a limiter when saturated by high voltage
transients. In such coupling circuits, the capacitor and self-inductance of the transformer form
a series resonance circuit, a high pass filter which remove power frequency signal, its
harmonics and all other spectral components with low frequencies. Figure 1 shows the parsio
3
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
4/22
nosious power line communication signal attenuation model developed for a typical 415/240
V distribution network.
RS
VS
Lt Ct LrCrL R
ZL
Req
Leq
VO
Figure 1: PLC Overall Model for Low Voltage Distribution Network
Where Ct and Cr are modem capacitances at the transmitter and receiver sides
respectively, Req and Leq are equivalent circuit elements of the distribution transformer, Vs is
the transmitted signal, V0 is the received signal, Rs is the source resistance and R and L are
the lumped parameter of a given distribution network
Taking Laplace transforms of the equations describing the model in figure 1 resulted
in the equations:
.(1)
.(2)
.(3)
From equations 1, 2 and 3, the transfer function of the PLC model is obtained to be:
4
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
5/22
.(4)
Where
From the typical values of the system parameters, the poles of the system are in the
left side of the s-plane indicating the stability of the system. Using the transfer function, the
signal attenuation can be obtained as:
.(5)
III FIELD MEASUREMENTS OF SIGNAL TRANSMISSION ATTENUATION
5
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
6/22
Although the distribution network topology and electric wires are known, it is not
adequate to rely on signal attenuation obtained by direct calculation since detail information
on the load is not available. Hence, there is the need for field measurement. In this study,
Signal transmission measurements were carried out in two categories as follows:
- In building signal transmission attenuation measurement
- Out-door signal transmission attenuation measurement
A MEASUREMENT SETUP
The measurements have been carried out with an oscilloscope and function
generators. The oscilloscope is PHYWE 11448.98 2 channels. Two types of function
generators used are 2 MHz and 150 MHz bandwidth types. In order to protect the sensitive
equipments from damaging by the 50Hz main power, passive high pass filters have been
used. Figures 2, 3, and 4 shows the schematic diagram of the measurement setup, photograph
of measurement set-up at the transmitter side and photograph of measurement set-up at the
receiver side respectively
6
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
7/22
FunctionGenerator
CouplingCircuit
CouplingCircuit
OscilloscopeChannel
Figure 2: A schematic diagram of the measurement setup
Figure 3: Photograph of measurement set-up at the transmitter side
7
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
8/22
Figure 4: Photograph of measurement set-up at the receiver side
B IN-BUILDING SIGNAL ATTENUATION MEASUREMENT
In-building signal strength measurement is important for the design of home
automation and internet access in homes and offices via power lines. Two sets of
measurements were carried out for this purpose. Measurement in the frequency range of 50-
500kHz for low data rate applications and measurement in the frequency range of 1-10MHz
for high data rate applications respectively. For this purpose intensive measurements were
carried out in thirty homes in Bauchi metropolitan of north eastern Nigeria over a period of
six months. In these experiments a function generator was used to produce the high frequency
signal which is coupled into the power line through a high pass filter. At a distant location,
the signal was coupled out through a high pass filter and measured with an oscilloscope. The
access points were reached with the help of connection wires whose effects and that of the
8
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
9/22
filters were considered. To obtain the signal attenuation between the two access points, the
received signals were normalized to the transmitted signal level. For each set of
measurement, the means of the signal attenuation and their standard deviations were
determined and plotted as a function of frequency.
C OUT-DOOR SIGNAL ATTENUATION MEASUREMENT
Outdoor signal attenuation measurement is important for the purpose of applications
such as remote meter reading, remote control of home appliances, local area networking and
internet access via power lines. Here also measurements were done in the frequency range of
50-500 kHz and 1-10 MHz for low and high bit rate applications respectively. To determine
the outdoor signal attenuation, extensive measurements of signal strength were carried out in
low voltage distribution networks in Bauchi, north-eastern Nigeria over a period of six
months. The distribution network of the area is over head 415V/240V three phase four wire
low voltage network. High frequency signals were coupled into the power line through a high
pass filter at the transformer and received at various at various remote location in the
network. The means of the signal attenuation and their standard deviations in the frequency
range of 50-500 kHz and 1-10 MHz were determined and plotted as functions of frequency.
IV PERFORMANCE OF POWER LINE COMMUNICATION WITH DPSK
MODULATION
9
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
10/22
By PLC performance, we mean whether receivers in the power line communication
system will be able to correctly interpret the messages sent to them. The crucial factors are
the signal and noise levels at the receivers. Several indices may be constructed to measure the
performance of a communication system among which is the bit error probability, Pe. The
modulation schemes often used for power line communication are PSK, OFSK and Spread
Spectrum among which PSK has the best bandwidth efficiency (Proakis, 1995 and Cavdar,
2004). In modern communication bandwidth is limited and precious resource which makes
bandwidth efficiency essential. The bit error probability Pe for coherent DPSK as derived by
Shanmungam (1979) is:
)exp(2/12
2
br
A
eP =
(6)
Where A = amplitude of the received signal and rb = bit rate
Selandar (1999) showed that for DPSK, the bandwidth is given as;
bMLog
rW2
3= ... (7)
Where M = number of signal alternatives
For binary PSK, M = 2
W = 3rb ... (8)
V PRESENTATION OF FIELD MEASUREMENTS AND SIMULATION RESULTS
In order to determine the actual signal attenuation of the low voltage distribution
networks, field measurements were carried out over indoor and outdoor distribution
networks. Average indoor and outdoor signal attenuations in the frequency bands of 50-500
kHz and 1-10 MHz are presented in figures 5 and 6. The corresponding standard deviation of
signal attenuation for indoor and outdoor distribution networks in the frequency bands 50-
500 kHz and 1-10 MHz are presented in figures 7 and 8. From the results, the attenuation is
10
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
11/22
frequency selective. To obtain the signal attenuation from theoretical models, the model in
Figure 1 was simulated for some distribution networks in north eastern Nigeria in the Matlab
environment in the frequency range of 10 z-500 kHz and 1-10 MHz with Rs = 1 , Ct = Cr =
1 F and Lt = Lr = 10-5 H. The distribution network is an over head 415V/240V three phase
four wire low voltage network. The model parameters for the distribution network are:
equivalent secondary impedance of the distribution transformer is 0.01 - 0.2 and the line
inductance and resistance are 0.001 mH/m and 0.001 /m respectively. These parameters
were calculated from the data collected from the electric power utility distribution company.
The variation of signal attenuation with frequency, load and distance are shown in figures 9-
14.
To determine performance of power line communication system over electric power
distribution networks in Nigeria, attenuation obtained from field measurements and
simulation of theoretical models were applied to equation (6). Abraham and Roy (1992) and
Selandar (1999) measured noise power spectral density of distribution networks in the
frequency range of 0-500kHz. They reported noise power spectral density to be between
-110dB and -158dB. Dostert (1998) and Selandar (1999) measured noise power spectral
density of distribution networks to be between -120dB and -160dB in the frequency range of
1-16MHz. To represent the worst case, the maximum value of the noise power and the signal
attenuation obtained from both the theoretical models and field measurements were used.
Figures 15-20 showed the variation of bit error probability with frequency, load impedance
and line length.
11
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
12/22
12
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
13/22
13
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
14/22
14
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10 110 210 310 410
Attenuation(dB)
f (kHz)
Figure 9: Variation of signal attenuation with frequency for different values of load impedance and line lenght of1000m
ZL=0.1 ohm ZL=1 ohm ZL=10 ohm ZL=20 ohm
-100
-80
-60
-40
-20
0 2 4 6 8 10 12 14 16 18 20
Attenuation(dB)
load impedance (ohm)
Fig ure 10 : Variation o f signal attenuation with load impedance for various frequencies and line lenght of1000m
f=200 kHz f=250kHz f=300kHz f="350kHz"
f=400kHz f=450kHz f=500kHz
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
15/22
15
-140
-120
-100
-80
-60
-40
-20
0
100 200 300 400 500 600 700 800 900 1000
Attenuation(dB)
Distance (m)
Figure 8 : Variation of signal attenuation with d istance for various combination of frequenccies and loadimpedance
f=2.5MHz,ZL=O.1ohm f=2.5MHz,ZL=1ohm f=5MHz,ZL=0.1ohm
f=5MHz,ZL=1ohm f=7.5MHz,ZL=0.1ohm f=7.5MHz,ZL=1ohm
f=10MHz,ZL=0.1ohm f=10MHz,ZL=1ohm
-140
-120
-100
-80
-60
-40
-20
0
1 2 3 4 5 6 7 8 9 10
Attenuatio
n(dB)
f (MHz)
Fig ure 12 : Variation o f signal attenuation with with frequency for various load impedance and a linelenght of 1000m
ZL=0.1 ohm ZL=1ohm ZL=10ohm
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
16/22
16
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
0 2 4 6 8 10
Attenuation(dB)
Load im pedance (ohm)
Figure 13 : Variation of signal attenuation wi th load impedance for various frequencies and li nelengh t of 1000m
f=2MHz f=4MHz f=6MHz f=8MHz f=10MHz
-140
-120
-100
-80
-60
-40
-20
0
100 200 300 400 500 600 700 800 900 1000
Attenuation(dB)
Distance (m)
Fig ure 14: Variation of signal attenuation with distance for various combination offrequenccies and load impedance
f=2.5MHz,ZL=O.1ohm f=2.5MHz,ZL=1ohm
f=5MHz,ZL=0.1ohm f=5MHz,ZL=1ohm
f=7.5MHz,ZL=0.1ohm f=7.5MHz,ZL=1ohm
f=10MHz,ZL=0.1ohm f=10MHz,ZL=1ohm
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
17/22
17
0
0.1
0.2
0.3
0.4
0.5
0.6
10 90 170 250 330 410 490
Biterrorprobability
f(kHz)
Figure 15: Effect of frequency on bit error probability for various loads and line
lenght of 1000 m
ZL=0.1 ohm ZL=1 ohm
ZL=10 ohm ZL=20 ohm
0
0.05
0. 1
0.15
0. 2
0.25
0. 3
0.35
0. 4
0.45
0. 5
0 2 4 6 8 10 12 14 16 18 20
Biterrorprobabity
L o a d i m p e d a n c e (o h
Figure 16: Effect of load im pedance on error probability f frequencies and line lenght of 1000 m
f =200 k H z f=250 k H z f =300 k H z
f =350 k H z f=400 k H z f = 450 k H z
f=500 kHz
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
18/22
18
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
19/22
19
0.47
0.475
0.48
0.485
0.49
0.495
0.5
0.505
0 1 2 3 4 5 6 7 8 9 10
Biterrorprobability
Load imp edance (ohm
Fig ure 19: Effect of load imped ance on bit error probability for various frequency and line lenght
f=2 MHz f=4 MHz f=6 MHz
f=8 MHz f=10 MHz
0.4
0.41
0.42
0.43
0.44
0.45
0.46
0.47
0.48
0.49
0.5
100 400 700 1000
Biterrorprobability
Distance (m)
Figure 2 0:Ef fect of distance on bit error probability for various combination frequency and load for line lengh t of 10
f= 2.5 MHz,ZL=0.1 ohm f=2. 5 M Hz, ZL=1 ohm
f=5 MHz,ZL=0.1 ohm f=5 MHz,ZL=1 ohm
f= 7.5 MHz,ZL=0.1 ohm f=7. 5 M Hz, ZL=1 ohm
f=10 MHz,ZL=0.1 ohm f=10 MHz,ZL=1 ohm
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
20/22
VI DISCUSSION OF RESULTS
Figures 5-8 shows the mean and standard deviation of signal attenuation obtained in
the field measurements in the frequency bands of 50-500 kHz and 1-10 MHz for indoor and
outdoor distribution networks. As shown in figures 5 and 6 the signal attenuation is
frequency selective. In the frequency band of 50-500 kHz, the attenuation generally decreases
with frequency while in the frequency band of 1-10 MHz, the attenuation increases with
frequency. Similar behavior was reported by Dostert (1998), Tang et al (2003) and Selandar
(1999). The in-door signal attenuation varies between -29.12 to -6.02 dB and -28.79 to -7.23
dB in the frequency range of 50-500 kHz and 1- 10 MHz respectively. For the out-door case,
the signal attenuation was found to vary between -32.04 to -9.12 dB and -36.1 to -9.51 dB in
the frequency range of 50-500 kHz and 1-10 MHz respectively.
Figures 9-14 showed the variation of simulated signal attenuation with frequency,
load impedance and line for a typical distribution network in the frequency bands of 10-500
kHz and 1-10 MHz. The results showed that the signal strength depends on frequency, load
impedance and line length. At high frequency, low load impedance and long distance, the
received signal level is low which put restrictions on frequency and line length for power line
communication. Variation of bit error probability with frequency, load impedance, and line
length are shown in figures 15-20. From the results, there will be communication problems
with 116 dB V signal amplitude for low load impedance distribution networks. However,
field measurements results showed that distribution networks in Nigeria are characterized
20
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
21/22
with high load impedance. This resulted in bit error probability nearly equal to zero for the
worst case for signal amplitude of 116 dB V.
VII CONCLUSION
To design an efficient power line communication system over distribution networks,
signal transmission characterization is essential. In this work signal transmission
characterization of in-door and out-door power line distribution networks is presented for low
and high bit rate power line communication system. It was observed that the signal
attenuation varies with frequency for both in-door and out-door distribution networks hence
they are frequency selective. The results obtained in this study indicated that power line
communication system can be applied in Nigeria distribution networks with signal amplitude
of 116 dB V.
REFERENCES
Abraham, K.C. and Roy, S. (1992). A Novel High Speed PLC Communication Modem.
IEEE
Transaction on Power Delivery, Vol. 7, No. 4
Cavdar, I.H. (2004). Performance Analysis of FSK Power Line Communication System
over the Time-Varying Channels. Presented at IEEE Power Engineering Society
General Meeting, Toronto, Canada.
Dostert, K (1998). RF-Models of the Electrical Power Distribution Grid. International
Symposium on Power Line Commnication and its Applications, Tokyo, Japan.
Newbury, J (1996). Communications Field Trials for Total Utility Metering. IEEE
21
-
8/8/2019 PLC Communication Analysis In Nigerian Distribution Network
22/22
IEEE Transactions on Power Delivery, Vol.11, No. 2.Vol. PAS-99, No.6.
Patrick, A., Newbury, J. and Gargan, N (1998). Two Way Communication Systems in
Electricity Supply Industry. IEEE Transactions on Power Delivery, Vol.13, No.1.
Proakis, J. G (1995). Digital Communications.McGraw-Hill.
Selandar, L. (1999). Channel Properties and Communication Strategies Online.
Available:http://www.energyse/knowledgebase/publications/thesis/power-line.htw.
Shanmungam, K.S (1979). Digital and Analog Communication Systems. John Wiley, New
York.
Tang, L.T, So, P.L, Gunawan, E, Guan, Y.L, Chen, S and Lie, T.T (2003). Characterization
And Modeling of In-Building Power Lines for High-Speed Data Transmission. IEEE
Transactions on Power Delivery, Vol. 18, No. 1.
Wasley, R.G and Momoh, J. (1978a). Method for Comparing Distributed and Lumped
Parameter Multiconductor Power Line Simulation Models. IEEE Transactions on
Power Apparatus and Systems, Vol. PAS-97, No. 6.
22
http://www.energyse/knowledgebase/publications/thesis/power-line.htwhttp://www.energyse/knowledgebase/publications/thesis/power-line.htw