Principal Research Results

Elucidation of Transmission Characteristics ofPower Line Communication (PLC) Signal− Development of Calculation Method of Coupling Efficiency inOut-phase Lines−Background
Power line communication (PLC), which uses existing power lines as communication circuits, is very promising forconstructing LAN. However, there are in-phase lines and out-phase lines in indoor main power lines of single-phase three-wiresystems. PLC modems are connected to in-phase and out-phase lines arbitrarily as shown in Fig.1. Transmission speed is not enoughsometimes when a pair of outlets which connect to out-phase lines are used. Although we have already developed a simulator ＊ 1 toestimate transmission characteristics in in-phase connection, the transmission characteristics in out-phase connection have not beenstudied sufficiently.

Objectives
To clear up transmission characteristics of out-phase lines, a dominant part of signal transition is experimentally investigatedby using samples of indoor main power lines, and a calculation method of signal transmission characteristics of out-phase using
distributed constant circuit is proposed.

Principal Results
1. Specifying a dominant part of signal transitions in out-phase lines
It was clarified that significant signal transitions in out-phase lines occur in indoor main power lines such as CVT cables ＊ 2
because in-phase and out-phase lines are aligned closely. CVT cables and multidrop lines used in interior wirings were simplified asshown in Fig. 2. Signals were inputted into between black and white lines and then the outputted signals between red and white lines
were measured as out-phase signal transitions. In-phase signal transitions were also measured as reference. Termination conditions
shown as “A” were changed open, short or resistance (75 Ω). Measured results of coupling efficiency are shown in Fig. 3. From thisresult, it became clear that PLC signals significantly transferred to out-phase lines in indoor main power lines, though the lines were
not connected directly.
2. Development of a calculation method for signal transmission characteristics of out-phase lines
A calculation method of signal transmission characteristics of out-phase lines using distributed constant circuit was developed. Indoor main power lines should be explained using distributed constant circuit because wavelengths of PLC signals are 10m (at30MHz) to 150m (at 2MHz). An equivalent circuit model of divisive indoor main power lines which used capacitance, self-inductanceand a mutual-inductance was developed as shown in Fig. 4. The values of each element were calculated from geometric layout ofcopper lines. The equivalent circuit model of divisive indoor main power lines was connected in series and coupling efficiencies ofeach termination conditions were calculated. The calculated results and measured results are shown in Fig. 5. The peak levels of calculated results and measured results were well in agreement. Signal transmission characteristics of out-phase lines could be calculated bythis proposed method.
This research was requested by the Tokyo Electric Power Co., Inc.

Future Developments
Transmission characteristics of out-phase connection including distribution board and interior wiring with indoor main
power lines will be clarified.
Main Researcher:Kensuke Ikeda, Ph. D., Research Scientist, Communication Systems Sector, System Engineering Research Laboratory
Kazuma Takeshita, Research Scientist, Communication Systems Sector, System Engineering Research Laboratory
Reference
K. Ikeda, et al., 2008, “An estimation method of PLC signal transition level in indoor main power line,” The paper of technicalmeeting on communication, IEE Japan, CMN-08-2, pp. 7-12. (in Japanese)＊1：R. Ishino, K. Takeshita and T. Suzuki, 2001, “Power line communication Simulator on low voltage distribution lines with OFDM
modulator”, CRIEPI Report R00009 (in Japanese)＊ 2：CVT cable: Triplex type cross-linked polyethylene insulated vinyl sheath cable116

8. Information and Communication

Fig.1 Connection configuration of PLC modems

Fig.2 Measured setup of coupling efficiency

Fig.3 Measured results of coupling efficiency

Fig.4 Equivalent circuit of CVT cable

8Fig.5 Calculated and measured results of coupling efficiency

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