JP2008061143A - Power line communication system and power line communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the connection of a device which superimposes a signal on a power line in power line communications. <P>SOLUTION: A modem 8 is connected to wiring lines 5 and 7 at a position where line length whose maximum wavelength is 1/100 or more and less than 10 m of a high frequency signal to be used by modems 8 and 13 is isolated from a low voltage side connection terminal 3a of a transformer 3. This line length results in the appearance of the characteristic impedance, and handles the line as a distribution constant circuit. Thus, currents flow through both of them (transformer 3 and the other modem 13) when it is viewed from the signal injection point of the modem 8, and to perform power line communications. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power line communication device and a power line communication method for configuring a network using power lines such as distribution lines.

  Power Line Communication (PLC) is a communication system that superimposes data communication signals on commercial AC voltage (current) using a distribution line drawn into each home or office as a signal transmission line. There is an advantage that it is not necessary to perform indoor wiring for communication. For example, in an apartment house such as a condominium, a transformer is installed in an electric room which is a shared facility, and a distribution line is drawn into each room from there. Therefore, a main unit of a modem for power line communication is installed in the electric room and connected to the low voltage side electric circuit of the transformer. In addition, an optical fiber is connected to the parent device from the outside. On the other hand, a cordless handset is connected to the outlet of each room. Thereby, communication between the parent and child modems becomes possible via the distribution line, and the Internet connection is possible from the child device via the parent device (see, for example, Patent Document 1).

  The transformer has an impedance of approximately 0 ohm with respect to a high-frequency signal for power line communication. Therefore, if the length of the electric circuit from the transformer to the place where the master unit is connected is too short, the impedance on the transformer side viewed from the master unit becomes approximately 0 ohm. As a result, the high-frequency signal emitted from the parent device is sucked into the transformer and does not reach the child device. In order to avoid such a situation, the master unit is connected to a position where a sufficient length (10 m or more) of the electric circuit is secured from the low-voltage side connection terminal of the transformer. By securing a sufficiently long electric circuit, a certain amount of impedance (several ohms or more) is ensured, so that all high-frequency signals can be prevented from being sucked into the transformer.

Japanese Patent Laying-Open No. 2005-150975 (FIG. 4)

However, in the conventional power line communication configuration as described above, since the electric room is usually a narrow space, it may be difficult to ensure a length of 10 m or more in the electric path in the electric room. In such a case, it is possible to secure 10 m or more by installing the master unit in the electric room and performing only the connection outside the electric room, but the construction becomes troublesome.
In view of the conventional problems as described above, an object of the present invention is to facilitate connection of a device that superimposes a signal on a power line in power line communication.

  In the power line communication system of the present invention, the distribution line connected to the low-voltage side connection terminal of the transformer and the line length of 1/100 or more of the maximum wavelength to be used and less than 10 m are separated from the low-voltage side connection terminal. The first power line communication device connected to the distribution line, and the line length from the low-voltage side connection terminal is connected to the distribution line at a position longer than the first power line communication device, and the first power line And a second power line communication device serving as a communication partner of the communication device.

  In the power line communication system configured as described above, by setting the line length to 1/100 or more of the maximum wavelength and less than 10 m, the characteristic impedance of the line appears and the line can be handled as a distributed constant circuit. Accordingly, when viewed from the signal injection point of the first power line communication device, characteristic impedance appears on both the transformer side and the second power line communication device side, and high-frequency current flows in both. Thereby, power line communication becomes possible between two power line communication devices.

In the power line communication system, the first power line communication device may be connected to a connection terminal of a main switch provided in the distribution line.
In this case, since the connection terminal of the main switch is exposed, the connection of the power line communication device is easy.

  On the other hand, in the power line communication method of the present invention, the power line communication device is connected to the distribution line at a position where the line length is 1/100 or more of the maximum wavelength of the high-frequency signal to be used and less than 10 m from the low-voltage side connection terminal of the transformer. It is connected to perform high-frequency signal injection and extraction. In particular, the power line communication device is connected to the existing distribution line at a position that is 1/100 or more of the maximum wavelength of the high-frequency signal to be used and less than 10 m away from the low-voltage side connection terminal of the transformer. This is highly useful in the case of injection and extraction.

  In the above power line communication method, by separating the line length of 1/100 or more of the maximum wavelength and less than 10 m from the low-voltage side connection terminal of the transformer, the characteristic impedance of the line appears and the line is treated as a distributed constant circuit. be able to. Therefore, the characteristic impedance appears on both the transformer side and the other when viewed from the signal injection point, and the high frequency current flows in both. Thereby, power line communication is possible with another power line communication device provided on the other side.

  According to the power line communication system or the power line communication method of the present invention, by setting the line length to 1/100 or more of the maximum wavelength and less than 10 m, characteristic impedance appears and power line communication becomes possible. A power line communication device can be arranged and connection is easy. A track length of less than 10 m can be secured even in a narrow electric room. The present invention is particularly useful when a power line communication device is connected to an existing distribution line to inject and extract a high frequency signal.

  FIG. 1 is a connection diagram illustrating an example in which a power line communication system is configured in an apartment house such as a condominium. In the figure, a condominium 1 is provided with a shared electric room 2, and a transformer 3 is installed in the electric room 2. The transformer 3 transforms the high voltage supplied from the high voltage cable 4 into a low voltage (100 / 200V). A main switch (breaker such as MCCB serving as a main trunk) 6 is connected to the distribution line 5 on the low voltage side of the transformer, and the distribution line 7 on the secondary side is drawn into each door 1A, 1B, 1C.

  On the other hand, the secondary side of the main switch 6 is connected to a modem 8 serving as a master unit of the power line communication device. The modem 8 constitutes a communication line connected to the Internet 10 through the optical fiber 9. The distribution line 7 drawn into each house is connected to a distribution line 12 in the house via a circuit breaker (MCCB) 11. A slave modem 13 is connected to the distribution line 12 in the house, and a personal computer 14 is connected to the modem 13. In addition, other home appliances 15, 16, and 17 are connected to the distribution line 12.

  FIG. 2 is a connection diagram showing the main part in FIG. 1 in a form closer to the actual wiring. In the figure, a distribution line 5 (copper bar or cable) is connected to the low-voltage side connection terminal 3a of the transformer 3, and a main switch 6 is connected to the end thereof. The distribution line 7 is connected to the secondary side connection terminal 6a of the main switch 6, and the circuit breaker 11 is connected to the tip. An outlet 18 is provided on the distribution line 12 on the secondary side of the circuit breaker 11. A plug 13 a of the modem 13 is inserted into the outlet 18, thereby enabling power line communication between the modem 8 and the modem 13.

  In FIG. 2, the line length L from the low voltage side connection terminal 3a of the transformer 3 to the secondary side connection terminal 6a of the main switch 6 to which the modem 8 is connected is secured to 1 m or more. In general, a line length of 1 m or longer is naturally secured from the necessity of physical arrangement of the transformer 3 and the main switch 6. However, the modem 8 may be connected to the primary side connection terminal 6b of the main switch 6 as long as 1 m or more can be secured.

  The connection terminals 6a and 6b of the main switch 6 are used in a state in which a silver-plated copper bar is exposed, and the distribution lines 5 and 7 can be connected thereto by bolting. Therefore, it is very easy to connect the power cord 8a of the modem 8 together.

  If the distribution line 5 is a copper bar and the line length of 1 m or more can be secured in the middle, the modem 8 may be connected in the middle. In addition, when the distribution line 5 is a cable, in order to connect the modem 8 on the way, it is necessary to peel off insulation coating, and it is not preferable in reality. Therefore, in that case, it is preferable to connect to the secondary side connection terminal 6a (or the primary side connection terminal 6b) of the main switch 6 as described above.

Next, the basis of the “1m” will be described. The frequency of the high frequency signal used for power line communication between the modems 8 and 13 is 2 to 30 MHz. The transmission speed of the high-frequency signal on the power line (distribution line and connection device) is approximately 2 × 10 ⁸ m / sec. In this case, the wavelength λ _{2M of 2} MHz and the wavelength λ _30M of 30 MHz are respectively
λ _2M = (2 × 10 ⁸ ) / (2 × 10 ⁶ ) = 100 [m]
λ _30M = (2 × 10 ⁸ ) / (30 × 10 ⁶ ) = 6.7 [m]
It becomes. Therefore, the wavelength of power line communication on the power line is in the range of 6.7 to 100 [m].

  Here, in the electric circuit through which a high frequency signal of 2 to 30 MHz propagates, the characteristic impedance of the line appears when the line length is approximately 1/100 or more of the wavelength, and can be handled as a distributed constant circuit. Therefore, by securing a line length of 1 m which is 1/100 of 100 m of the maximum wavelength, the line of 1 m or more has a characteristic impedance with respect to the high frequency signal and can be handled as a distributed constant circuit.

FIG. 3 is a circuit diagram in which the line portion in the connection diagram of FIG. 2 is viewed as a distributed constant circuit. In the figure, a distributed constant circuit d1 having an inductance L, a resistance R, a capacitance C, and a conductance G as basic components exists on the left side from the connection location of the modem 8. Further, a similar distributed constant circuit d2 exists on the right side from the connection location of the modem 8. The characteristic impedance Z ₀ of these distributed constant circuits is expressed by Z ₀ ≈ (L / C) ^1/2 , and the high frequency current flows in both d 1 and d 2. That is, it is possible to prevent a situation in which a high frequency signal is sucked into the transformer 3 and does not reach the modem 13. Therefore, power line communication between the modem 8 and the modem 13 is possible.

In addition, as an upper limit of the distance L, 5-6 m is suitable, but if it is less than 10 m in length, it can be secured even in a narrow electric room. If it is 10 m or longer, it may not be secured in the electrical room.
Also, for example, unlike the above embodiment, when connecting a pole transformer and a modem attached to the same utility pole, the connection can be made within a range of 1 m or more and less than 10 m. If it is 10m or more, it is too long and difficult to install.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined not by the above-mentioned meaning but by the scope of claims for patent, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims for patent.

It is a connection diagram which shows an example which comprised the power line communication system in apartment houses, such as an apartment. FIG. 2 is a connection diagram showing the main part in FIG. 1 in a form closer to the actual wiring. It is the circuit diagram which looked at the track | line part in the connection diagram of FIG. 2 as a distributed constant circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Transformer 3a Low voltage side connection terminal 5 Distribution line 6 Main switch 6a Secondary side connection terminal 6b Primary side connection terminal 7 Distribution line 8 Modem (1st power line communication apparatus)
13 Modem (second power line communication device)

Claims (3)

A distribution line connected to the low-voltage side connection terminal of the transformer;
A first power line communication device connected to the distribution line at a position that is 1/100 or more of the maximum wavelength of the high-frequency signal to be used and less than 10 m away from the low-voltage side connection terminal;
A second power line communication device connected to the distribution line at a position where a line length from the low-voltage side connection terminal is longer than that of the first power line communication device, and serving as a communication partner of the first power line communication device. A power line communication system characterized by the above.   The power line communication system according to claim 1, wherein the first power line communication device is connected to a connection terminal of a main switch provided in the distribution line.   Inject and extract high-frequency signals by connecting a power line communication device to the distribution line at a position where the line length is 1/100 or more of the maximum wavelength of the high-frequency signal used and less than 10 m away from the low-voltage side connection terminal of the transformer. A power line communication method characterized by performing.

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