Investigation of signal behaviors when transmitted through different power line characteristics media.
In this part of this work a basic setup circuit has been used and selective parameters of power line characteristics have been studied, certain cable and wires have been chosen; these types of cables and wire are communally used in low voltage power line network and especially used in indoor power line grid.
Experimental works have been established in research laboratory where there were two socket boards as shown in Figures1 and 2. As per realization of normalized environments of power line the socket board No.1 contains four sockets two of these sockets have been used for power supply and for lamp with power of 100watt, while the other sockets have been used for transmitter and receiver connections through interfacing circuits (setup circuits) shown in Figures 6 and 7. Board No.2 consists of four sockets also these four sockets are used for connecting CRO, power supply NO.2, a PC and a printer as shown in Figure 2.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
Board No.1 and board No.2 connected to equipments through different wire length as shown in Figures1 and 2. The main AC power Line used of MCMK low voltage power cable as shown in Figure 3 which shows the structure of this cable.
[FIGURE 3 OMITTED]
Electrical equipments are connected using two wires "line and neutral" while for connecting transmitter and receiver two types of wires have been used with setup circuits" Twisted and Parallel wires" as shown in Figure 4 and 5 respectively.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
Setup circuits are shown in Figures 6 and 7 have been used as isolation circuits from 230Volt 50Hz each circuit consists of two capacitors having a value of .1[micro]F and a transformer having a ratio 1:1. As seen in Figures 6 and 7 these circuits have been used for full connection to power line network and null connection to power line network respectively.
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
The basic instrumentations have been used in this work were: Function Generator provides with Multi-signal (2MHz) has been used for generating the data transmitted and Oscilloscope (20 MHz, 20Volt pick to pick) it has been used to observe the signal response in the receiver.
Aim of this work
To collect enriched data regarding the power wire behavior while using it for communication purposes. Power cables and wires have been used for frequency higher than utility frequency (More than 50 Hz or 60 Hz). Data has been gathered which are related to attenuation behavior of two types of power wire which they are communally used in home wiring installations.
Firstly twisted wire has been used as a communication channel for four different lengths (5 MT, 10MT, 15MT and 20MT) each length has been tested by injection data with frequency from 200Hz-2MHz. For this test two wire topologies have been used, first topology it has been used this wire without been connected to power line network and the second topology by using the same wire but connected to power network.
Secondly Parallel wire has been used and same procedures applied on twisted have been applied to parallel as it has been maintained above.
The signal sent from the receiver has amplitude 5Volt considered as "Vi", the signal recovered in the receiver considered as "Vo" owns different values after subjected to power network environments. By calculating the gain of Vo Vi / and then applying the equation:
Gain (dB) = 20 LogVo / Vi....Eq 1
Optimum case has been considered when wires not connected to power line grid and based on this case the evolutions have been extracted for the cases when wires have been connected to power line.
Comparisons of Amplitude Attenuations have been done between twisted and parallel wires topologies when:
* Connected and not connected to power line for similar wires lengths
* Not connected to power line for similar wires lengths
* Connected to power line for similar wires lengths
* Connected and not connected to power line for different wires lengths
CASE 1: Amplitude Variation and Frequency Response Comparison between Twisted and Parallel Cable 5 Meter Length
Figure 8 and 9 present the amplitude variations due to frequency changes. Frequency response seem similar for the upper curves when a sample of power line cable has been tested away from AC power environment while the lower curves represent the effect of power line environments on the transmitted signal. For this case the length of power line used was five meters for both types of cable chosen "twisted and parallel".
For low frequency the change of amplitude is around 20dB and these variations have been reduced to 10 dB for a frequency above 450 kHz. It has been noted that after 1MHz the amplitude of lower curves (Connected to power line) tend to be similar to upper curves (Not connected to power line) or they approximately parallel but with remarkable dB gap as seen for Figure a around 10 dB and for Figure b dB gap around 5dB. These dB gaps shown in both curves are due to attenuation and multipath effects have been provoked in channel.
[FIGURE 8 OMITTED]
[FIGURE 9 OMITTED]
CASE 2: Amplitude Variation and Frequency Response Comparison between Twisted and Parallel Cable 10 Meter Length
Figure 10 and Figure 11 presents the amplitude attenuation of when sending data through twisted and parallel wires and from each figure an evaluation of the wire status when connected and not connected to power network through setup circuits shown in Figures 6 and 7. It has been noted that the upper curves represent the amplitude variation due to frequency change. It has been noted that for lower frequency the dB gap was high and it's around from 5dB to 25dB for a frequency up to 250 kHz, while for frequencies greater than 1MHz this gap tends to be less for twisted wires and constant for parallel wires. For frequency between 0-1Mhz and from 1 MHz 1.750 MHz amplitude attenuation seem to be instable for twisted wire due to high valuation of power line parameters (C', R', G' and L') lambed due to frequency variation.
[Z.sub.L] = [square root of (R'(f) + j2[pi] * L'(f)/G'(f) + j2[pi] * C'(f).... Eq 2  and 
where R' per unit length, the conductance G' per unit length, the inductance L' per unit length and the capacitance C' per unit length, which are generally frequency dependent. Parallel wire topology variation less due to less effect of these parameters on wire impedance [L.sub.Z] as shown in Figure 11.
Now if comparing between Twisted and parallel wires for the two cases: when connected and when it not connected to power line network as shown in Figure 12 and 13
[FIGURE 10 OMITTED]
[FIGURE 11 OMITTED]
CASE 3: Amplitude Variation and Frequency Response Comparison between Twisted and Parallel Cable 15 Meter Length
This case can be considered as extension of power line behaviors on signal transmitted. Due to increasing wire length for both types" twisted and parallel" signal attenuation tends to be more notable. Figure 12 shows clearly the instability of amplitude variations due to connectivity to power line grid for twisted wire while for parallel wire this effects are less as shown in Figure 13.
Frequency changes have an exponential effect on signal transmitted behaviors for the case when both types of power line have not been connected to power line network. When wires connected to power line grid frequency changes have an exact interval of frequency which has different effects on received signal amplitude as shown lower curve on Figure 12.
[FIGURE 12 OMITTED]
[FIGURE 13 OMITTED]
CASE 4: Amplitude Variation and Frequency Response Comparison between Twisted and Parallel Cable 20 Meter Length
[FIGURE 14 OMITTED]
[FIGURE 15 OMITTED]
In this case the wire length has been increases for extra five meters for "twisted and parallel), this change in wire length changes the power line characteristics as these changes have been noted in the previous cases. Attenuation due to connectivity to power line network has less effect when wire type has been change but generally the curves of these four topologies shown in Figures 14 and 15 have been changed exponentially tell appropriate frequency around 1MHz after this frequency attenuation on the transmitted signal seem more remarkable.
[FIGURE 15 OMITTED]
Observations and Results
These curves represent the effect of type and length of wire on signal attenuation for when changing the frequency from 200Hz 2MHz when wires have not been connected to power line grid. From above curves it has been noted that attenuation is frequency and length dependent and curves varies exponentially and this results coincide with the previous research related to this topic . As final result it has been noted that Figure 17 D resumes the effect of length variation on signal attenuation, therefore According to frequency change it is possible to divide the frequency variation to three ranges:
For Twisted wire
First range from 200Hz-500 kHz, second range from 500 kHz-1000 kHz and third range from 1000 kHz 2000 kHz
For parallel wire
First range from 200Hz-750 kHz, second range from 750 kHz-1500 kHz and third range from 1500 kHz 2000 kHz
From curves illustrated in Figure 17, Figure 17 A shows that for wire length 5 meter (twisted and parallel) wire attenuation have less effect on signal propagation while this effect increases when length increases
[FIGURE 17 OMITTED]
It has been observed from above curves that the signal propagation has been subjected to attenuation, impedance fluctuations and multipath effects. This equation is mainly composed of a weighting term, an attenuation term and a delay term :
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.]
[FIGURE 18 OMITTED]
Figure 18 A shows that when wires are not connected to power line network curves are seem similar and have approximately same behaviors except the case of five meters attenuation effect on transmitted signal has less effect for numerous values of frequency changes.
Figure 18 A shows that when wires are connected to power line network curves shapes varying randomly or with more precision power line environments have the major effect on amplitude of signal transmitted and this effect appears as fluctuations of the signal amplitude for certain values of frequency for different lengths. Frequency near to 500 kHz the attenuation values are almost coincide and for a frequencies higher than 500 kHz the curves tracing same shape except the case of 20 meters because the multi-path and delaying effects are more valuable.
In this report a switching circuit have been introduced as shown in Figure 19. Setup system consists of five parts: switching circuit, coupling filter for transmitting, channel, coupling filter for receiving and a circuit for observation purpose. Each part of this system has been designed for power line communication utility. Switching circuit has been designed for injection Ones and Zeros through isolation transformer and capacitors as a low filter. Channel was wires normally used for powerline distribution in power network (twisted or Parallel). A second coupling filter has been used in the receiver it contains the same components that have been used in the transmitter. Finally a receiving circuit has been used to pick up the transmitted signals and as an indication an LED has been used.
[FIGURE 19 OMITTED]
Aim of this Work
To verify and observe the functionality of the switching circuit when using two types of wires "twisted and parallel" for four different lengths (5, 10, 15 and 20 meters).
As shown in Figure 19 the channel has been connected to power line network and the points of connection has a certain properties that related to type of appliances connected to power network when the system has been tested. As has been mentioned in part A different type of appliances have been connected to the boards of sockets. There were four cases have been established and observations have been noted as following:
For the case when communication channel consists of five meter long and using twisted wire it has been observed that:
* The frequency range used for transmission was from 5-20 kHz for the switching circuit.
* Using 12.5 Volt as a supply for a switching circuit the voltage required for the receiver end was only 3.5 Volt.
* When the PC's monitor switched ON the receiver affected and fluctuations occur.
* Current needed for the receiver when sending OFF signal was 0.22 Amp.
* Current needed for the receiver when sending ON signal was 0.1 Amp.
For 10 meter wire length the same observations have been noted for the first case "5 meter".
For 15 meter wire length a delay occurs for about 2 seconds then relay of the receiver circuit reacts while for 20 meter wire length the same observations of the third case "15 meter" have been noted.
The same test has been realized using parallel wire and same wire lengths (5, 10, 15, and 20) observations were the following:
* For 5 and 10 meter wire length same observations have been obtained for twisted wire for the same length.
* For 15 and 10 meter wire length same observations have been obtained for twisted wire for the same length but voltage required for the receiver circuit to operate the relay was 2.6 Volt and current 0.1 Amp.
Results have been obtained from part A and B can be resumed as following:
* Power line channel of any type of wire has unpredictable behavior due to the frequency dependant of the channel.
* Due to instability of the impedance of power line time delay occurs.
* Each portion of power line has its own characteristics because of frequency variations and length.
* Results obtained by this report coincide with results obtained in references  and  "Data Transmitted with High Frequency" but for lower frequencies regarding amplitude behavior .
* Multipath effects occur because of impedance mismatching of the numerous branches.
* Power cables exhibit signal attenuation which has been increased with length and frequency as mentioned in reference .
 G. T. Andreou, E. K. Manitsas, D. P. Labridis, P. L. katsis, F. N. Pavilidou, P. S. Dokopoulos, Finite element characterization of LV power distribution lines for high frequency communications signals, Proceedings of the 7th International Symposium on Power-Line Communications and its Applications (ISPLC), Kyoto, Japan, 109-119 March 26-28, 2003.
 M. Zimmermann, K. Dostert, The low voltage distribution network as last mile access network--signal propagation and noise scenario in the HF- range, AE 'U International Journal of Electronics and Communications, (1), 13-22 2000.
 Manfred Zimmermann, Klaus Dostert "A Multi-Path Signal Propagation Model for the power line Channel in the High Frequency Range" 1998.
 Alexandre Matov, "Measurements and Modeling of Power Line channel at High Frequencies", 2002.
 Tooraj Esmailian, Frank R. Kschischang and P. Glenn Gulak. "In-building power lines as high-speed communication channels: channel characterization and a test channel ensemble". International Journal of Communication Systems, Int.J. of Commun. Syst. 2003; 16:381-400(DOI:10.1002/dac.596).
Adnan S. Obeed got a diploma on Electrical engineering from Nancy II, France 1988; in 1999 he received his B.E in electrical engineering from University of technology, Department of Electrical engineering, Baghdad, Iraq. He worked as an aircraft electrical engineer for 15 years. He received M.Sc. in Electronic Science from Department of Electronic Science University of technology Al-Rashid College, Baghdad, Iraq. He was a lecturer from 2004-2005 in technical College, Musiab, Ministry of higher Education and Scientific Research Baghdad, Iraq. Now he is doing a Ph.D. research work under Indian scholarship (ICCR) since 2006 in Power Line Communication technology in University of Pune Department of Electronic Science.
Dr. Nitin M. Kulkarni received M.Sc. and Ph.D. degree from Department of Electronic Science, University of Pune. Since 1986, he has been with Department of Electronic Science, Fergusson College Pune. Presently, he is a Reader in Electronic Science. His research interests are intelligent instrumentation and sensor network. He is a member of SERNET and Instrumentation society of India.
Dr. Arvind D. Shaligram, presently Head of the Department of Electronic Science at University of Pune, has a research experience of more than 25 years. After completing Ph.D. degree from University of Pune, he joined the University department as faculty member and continues to works till date. He has guided 18 Ph.D students and 12 M.Phil students so far. His major research interests are in the fields of intelligent systems, Optoelectronic sensors and systems, biomedical instrumentation and sensor networks and their applications.
Adnan S. Obeed (1), Nitin M. Kulkarni (2) And Arvind D. Shaligram (3)
(1,2,3) Department of Electronic science, Fergusson College, Pune FC Road, Pune, Maharashtra, 411004, India
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|Author:||Obeed, Adnan S.; Kulkarni, Nitin M.; Shaligram, Arvind D.|
|Publication:||International Journal of Applied Engineering Research|
|Date:||Jun 1, 2009|
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