JP2004336456A - Power line carriage communication system and power line filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of leakage radio wave on a power line in power line carriage communication. <P>SOLUTION: A modem A108 is provided in the wires of a single phase three-wire system on the secondary of a pole transformer 102 and power line carriage communication is performed with a modem B109 in a subscriber's premise 100. Since an earth wire 106 is connected with the neutral line of power lines, i.e. the N phase 104, ground impedance is unbalanced between the N phase power line 104 and the W phase power line 105 and a common current Ic is generated. Ground impedance of the N phase is increased for the communication frequency by loading a clamp coil 107 to the earth wire 106 thus reducing the common current Ic and suppressing generation of a leakage radio wave 113. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power line carrier communication system using a power line as a communication medium.
[0002]
[Prior art]
2. Description of the Related Art In recent years, broadband Internet connection services using DSL and CATV networks have been widely spread. Power line carrier communication uses a power line laid to supply power to equipment as a transmission line, so there is no need to lay a new communication line for communication. It is attracting attention. However, power line carrier communication has a problem that a common mode current is generated due to a difference in the degree of balance on the power line, and a leaked radio wave is easily generated.
[0003]
As a technique for suppressing a leaked radio wave, a common mode is to install a common mode choke coil or the like at an output portion of a power line carrier modem and to suppress a common mode current generated from the modem itself. However, the common mode current flowing through the power line largely depends on the balance of the power line of the transmission line for communication, and is also generated by the difference in the impedance of the paired power line.
[0004]
As a conventional technique for suppressing a common mode current in a power line communication system, for example, there is one disclosed in Patent Document 1. In this power line carrier communication system, a high-pass filter is connected between the branch power line and the ground line on the side where communication is to be cut off, thereby lowering the impedance of the entire branch power line as viewed from the ground line to reduce the induced voltage level. . This makes it possible to reduce the level of leakage from the branch power line to the ground line and cancel the leakage signal on the ground line.
[0005]
[Patent Document 1]
JP-A-7-245576 (Paragraph 0029-0037, FIG. 1)
[0006]
[Problems to be solved by the invention]
The technique of Patent Document 1 described above is effective on the side that wants to interrupt communication. However, in the power line laid via a pole transformer or the like, there is no consideration of a multiple grounding point where one end of the power line is grounded, and there is a problem that imbalance occurs on the power line. .
[0007]
Since the power line is not designed for communication, no consideration is given to the degree of balance. In a phase where one end of the power line is grounded, the impedance is greatly reduced, and imbalance with another phase occurs. In Japan, there are many cases where the power line drawn into the house is located at the location of the pole transformer and is grounded by the ground wire. For this reason, when impedance imbalance occurs in the power line and a common mode current is generated on the power line as a transmission line, a leaked radio wave is generated. If a countermeasure is taken with a common mode choke coil or the like, an operation of removing the existing single-phase three-wire type electric wire and winding it around the coil occurs. For this reason, work involving a power outage of the power supply system is required, and problems such as an increase in the construction scale occur.
[0008]
An object of the present invention is to overcome the above-mentioned problems of the prior art, to reduce a leaked radio wave even in a power line communication system using a power line laid via a pole transformer or the like, and without a power outage. An object of the present invention is to provide an installable power line filter.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a power line carrier communication system in which a power line of a commercial power supply is used as a communication medium and communication is performed by a power line carrier communication device. A plurality of power line carrier communication devices to be connected to the earth line connected to the neutral line of the single-phase three-wire electric wire, a high ground impedance for the frequency of performing the power line communication, and a commercial power supply frequency. A power line filter having a low ground impedance.
[0010]
As a result, the impedance to the ground as viewed from the neutral line connected to the ground line becomes large with respect to the frequency at which the power line communication is performed, and the difference from the impedance of the other phase becomes small. As a result, the unbalance of the power line is reduced, and the generation of the leakage wave can be suppressed by suppressing the generation of the common mode current.
[0011]
Further, the power line communication system of the present invention includes a single-phase three-wire cable between the secondary side of the transformer and the power line communication device, which has a high impedance with respect to a frequency at which the power line communication is performed, a commercial power frequency, , A power line filter having a low impedance is provided.
[0012]
The power line filter provided on the single-phase three-wire cable is provided on both sides of the single-phase three-wire cable fixed to a pole insulator.
[0013]
As a result, it is possible to reduce the common mode current flowing from the single-phase three-wire to the telephone pole, and to suppress the generation of leaked radio waves.
[0014]
Further, the power line carrier communication system of the present invention, the ground line connected to the neutral line of the single-phase three-wire electric wire, high ground impedance for the frequency of the power line carrier communication, for commercial power frequency A first power line filter having a low ground impedance and a high power line communication frequency for a single-phase three-wire cable between the secondary side of the transformer and the power line communication device. A second power line filter having low impedance with respect to impedance and commercial power frequency is provided.
[0015]
The power line filter is preferably a clamp type coil. In this case, for the frequency f at which the power line communication is performed, an impedance 2πfL [Ω] is formed by the inductance component L [H] of the coil. On the other hand, since the impedance becomes low with respect to the commercial power supply frequency, the influence on the existing ground resistance can be minimized.
[0016]
The power line filter of the present invention is a single-phase three-wire electric wire serving as a power line, a ground line connected to the neutral line of the commercial power supply, a high ground impedance with respect to the frequency of performing power line communication, and a commercial power supply frequency. In addition, an element having a low ground impedance is provided. The element is a clamp-type coil that can be attached to the single-phase three-wire cable without a power failure.
[0017]
The clamp-type coil has a shape for sandwiching an electric wire, and thus can be easily inserted and installed in the middle without removing an existing electric wire.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a power line communication system according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a power line communication system according to a first embodiment. The power line carrier communication system includes a modem A 108 installed on a single-phase three-wire type electric wire on the secondary side of the transformer 102 and an indoor modem B 109. Specifically, it is connected to the power line W105 and the power line N (neutral line) 104, receives power supply from the power line W105, and serves as a signal transmission path. In the first embodiment, the leakage electric wave 113 is suppressed by providing a power line filter on the ground line 106 connected to the power line N104. This will be specifically described below.
[0019]
When the power line carrier communication signal is transmitted from the modem A 108 to the modem B 109, normal currents 122a and 122b having different directions are generated in the power line W105 and the power line N104. If the ground impedance Zw110 on the power line W105 is equal to the ground impedance Zn111 on the power line N104, both normal currents have the same current level.
[0020]
However, in the configuration of FIG. 1, since the ground line 106 is connected to the power line N104, a part of the normal current component flows as a common mode current. As a result, due to the difference between the normal current 122a and the normal current 122b having different directions, the current flows on the power line as the common mode current Ic112 having a certain directivity.
[0021]
The common mode current Ic112 generates a leaked radio wave 113 by flowing through the power lines N104 and W105. Experimental results show that the leaked radio wave 113 is proportional to the common mode current Ic112 flowing on the power line. By suppressing the generation of the common mode current, it is possible to suppress the leaked radio wave.
[0022]
A major factor that determines the balance of a power line is the ground impedance of a pair of electric wires. In the case of FIG. 1, since one end of the power line N104 of the single-phase three-wire electric wire is grounded by the ground wire 106, the ground impedance Zn111 is significantly lower than that of Zw110, and unbalance occurs.
[0023]
Normally, since the utility pole is grounded by the ground wire 106 connected to the transformer 102 by the class B grounding work, the ground impedance Zn111 has a low value of about 10Ω or less. On the other hand, the ground impedance Zw110 of the W phase is about 150 ± 20Ω according to the actually measured value. As a result, imbalance of the ground impedance occurs, and the common mode current Ic112 is generated.
[0024]
In FIG. 1, the coils 107 are respectively installed as power line filters on the ground lines 106 immediately before the modems A and B. Therefore, the N-phase ground impedance ωL [Ω] is determined by the inductance component L [H] of the coils 107. Increase. The frequency at which power line carrier communication is performed is currently 10 kHz to 450 kHz approved by the Radio Law Enforcement Regulations, and 1.7 MHz to 30 MHz, etc., where deregulation is being studied in the future.
[0025]
Therefore, the coil 107 has a high impedance with respect to the frequency of the power line carrier communication, and has a negligibly low impedance with respect to the commercial power frequency. By appropriately selecting the inductance L, it is possible to balance the ground impedance Zw of the power line W105 and the impedance ωL of the coil 107 with respect to the communication frequency.
[0026]
For example, when the inductance component L is 2 μH, the impedance at 10 MHz becomes a large value of 126Ω and the impedance increases, so that the impedance is balanced with the ground impedance Zw (150 ± 20Ω). The impedance at the commercial power frequency of 60 Hz is 0.001Ω, and the effect on the existing ground resistance can be ignored.
[0027]
This alleviates the unbalanced state of the power line and suppresses the generation of the common mode current 112 flowing into the power lines N104 and W105, thereby making it possible to suppress the leaked radio wave 113.
[0028]
FIG. 2 shows a sectional structure of the clamp type coil. In this example, a clamp-type coil is used as the coil 107 in FIG. 1, and a ferrite core 107b is integrally mounted on a connector 107a. The ferrite core 107b is a C-shaped core having a ring shape and is a magnetic material of a core piece, and is configured to be combined with the ring shape again. The connector 107a has a movable portion 107d such as a hinge, and is fixed by a coupling portion 107c. For the ferrite core 107b, it is preferable to select a material such as a ferrite material or an amorphous alloy material having the most suitable impedance characteristic with respect to the frequency at which power line communication is performed.
[0029]
FIG. 3 is an external view of the clamp-type coil, showing a state where the coil is inserted into the ground wire 106. The clamp-type coil shown in FIG. 2 is inserted into the ground wire 106, closed in the state shown in FIG. 3, and fixed by the joint 107c. If such a clamp-type coil is used, the earth wire 106 is not detached when the coil 107 is attached, and there is no need for a power failure, so that the construction can be simplified.
[0030]
FIG. 4 is an external view showing a method of attaching another coil to the ground wire. As illustrated, the impedance can be changed by looping the ground wire 106 around the clamp coil 107. A desired impedance can be obtained by adjusting the number of loops.
[0031]
FIG. 9 is a characteristic diagram showing the effect of the first embodiment. As shown in the figure, the common current flowing through the ground wire 106 is suppressed by 15 dBμA at the maximum when the coil 107 is provided, as compared with the case where no coil is provided.
[0032]
In the first embodiment, the case where the present invention is applied to a power line outside the house is described. However, the present invention can be widely applied to a ground line such as a washing machine or a microwave oven grounded inside the house, and the same effect can be obtained. To play.
[0033]
FIG. 5 is a configuration diagram illustrating Embodiment 2 of the power line communication system. The arrangement of the power line and the modem is the same as in FIG. 1, and power line carrier communication is performed from the modem A 108 installed on the secondary side of the transformer 102 to the modem B 109 of the subscriber home 100. In this case, the experimental results show that the common current Ic112 flowing through the single-phase three-wire electric wire 118 (all three wires) propagates in the air due to the high frequency, and also flows through the electric pole 101 through the arm 119 wound around the power pole 101. ing.
[0034]
Therefore, a coil 114 is provided for the single-phase three-wire type electric wire 118 between the secondary side of the transformer 102 and the modem A 108 or on both sides of the power pole 101 in a lump. Thereby, the common mode current Ic112 can be suppressed, and the common mode currents Ic-A116 and Ic-B117 flowing into the utility pole 101 can be suppressed.
[0035]
6 and 7 are explanatory diagrams showing a mechanism of magnetic flux generation in a normal current and a common mode current flowing through the clamp type coil. In FIG. 6, the magnetic flux 123a induced by the normal current 122a of the W-phase power line W105 and the magnetic flux 123b induced by the normal current 122b of the N-phase power line N104 are in opposite directions. Therefore, the mutual magnetic fluxes are canceled out and no impedance is generated, and the influence on the normal current component can be minimized.
[0036]
On the other hand, as shown in FIG. 7, the magnetic flux 124 induced by the common mode current 112 has the same direction in both the W phase and the N phase. For this reason, the magnetic fluxes 124 are added together, function as an inductance that generates a large impedance, and can attenuate the common mode current.
[0037]
As described above, when the clamp type coil 114 is attached to the single-phase three-wire type electric wire 118, it is possible to suppress only the common mode current without attenuating the normal current serving as the communication signal. In the above description, the coil 114 is collectively provided on the single-phase three-wire type electric wire 118. However, when only two power lines are actually used for power line communication, the coil 114 is provided for the two lines. It may be.
[0038]
FIG. 8 is an explanatory diagram showing installation of a clamp coil as one specific example of the second embodiment. Clamp-type coils 114 are provided on both sides of a single-phase three-wire electric wire 118 fixed to a low-voltage insulator 120 on a power pole 101. As shown in FIGS. 6 and 7, the single-phase three-wire type electric wire 118 is wrapped around the single-phase three-wire type electric wire 118 in a lump, so that it is not necessary to remove the single-phase three-wire type electric wire 118 during construction.
[0039]
Since the leaked radio wave 113 has a proportional relationship with the common mode current Ic112 flowing through the single-phase three-wire 118, the generation of the common mode current 112 flowing through the power pole 101 through the arm 119 is suppressed, and the leaked radio wave 113 can be suppressed.
[0040]
FIG. 10 is a characteristic diagram showing the effect of the second embodiment. Compared to the case without the clamp type coil, the common current flowing through the single-phase three-wire type electric wire 118 is suppressed at the maximum by 20 dBμA with the clamp type coil.
[0041]
As described above, according to the first embodiment, the coil is attached to the ground wire in order to suppress the common current flowing from the single-phase three-wire electric wire through the ground wire. Further, according to the second embodiment, in order to suppress a common current flowing from a single-phase three-wire type electric wire to a utility pole or the like, a coil is attached to each of the single-phase three-wire type electric wires. Therefore, in the third embodiment, the first embodiment and the second embodiment are combined, and the first clamp coil is attached to the ground wire from the single-phase three-wire electric wire, and all the single-phase three-wire electric wires are combined, or A second clamp-type coil is attached to two wires used for communication. According to this, the advantages of both are compensated for, and a more effective countermeasure for the leaked radio wave becomes possible.
[0042]
【The invention's effect】
According to the present invention, since a power line filter is provided for a ground line connected to a single-phase three-wire type electric wire used for power line carrier communication, the impedance at the communication frequency is increased, and the balance of the power line is improved. This has the effect of suppressing the leaked radio waves.
[0043]
Further, according to the present invention, since the power line filter is provided collectively on the single-phase three-wire type electric wire, there is an effect of increasing the impedance with respect to the common current flowing through the pole and suppressing the leaked radio wave.
[0044]
In addition, since a clamp-type coil is used as a power line filter, there is an effect that attachment to an electric wire can be easily performed without a power failure.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a power line carrier communication system according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a clamp-type coil showing an example of the power line filter of the present invention.
FIG. 3 is an external view showing a method of using a clamp-type coil.
FIG. 4 is an external view showing another method of using the clamp-type coil.
FIG. 5 is a configuration diagram illustrating a power line carrier communication system according to a second embodiment of the present invention.
FIG. 6 is an explanatory diagram showing a method of using a clamp-type coil and a behavior of a magnetic flux in a normal mode according to a second embodiment.
FIG. 7 is an explanatory diagram showing a behavior of a magnetic flux in a common mode of the clamp-type coil in the second embodiment.
FIG. 8 is a diagram showing a clamp type coil according to a specific example of the second embodiment;
FIG. 9 is a characteristic diagram showing the effect of the first embodiment.
FIG. 10 is a characteristic diagram showing the effect of the second embodiment.
[Explanation of symbols]
100: Customer A, 101: Power pole, 102: Transformer, 103: Power line V (phase), 104: Power line N (phase), 105: Power line W (phase), 106: Ground wire, 107: Clamp coil 108 Power line carrier communication modem A, 109 Power line carrier communication modem B, 110 Ground impedance Zw, 111 Ground impedance Zn, 112 Common current Ic, 113 Leakage radio wave, 114 Clamp coil, 115 Load, 116 ... common current Ic-A, 117 ... common current Ic-B, 118 ... single-phase three-wire, 119 ... arm, 120 ... low-voltage insulator.

Claims (8)

In a power line carrier communication system in which a power line of a commercial power supply is used as a communication medium and communication is performed by a power line carrier communication device,
The power line is connected to a plurality of power line carrier communication devices for transmitting / receiving to a single-phase three-wire cable serving as a transmission path, and a power line carrier communication is performed with respect to a ground wire connected to a neutral wire of the single-phase three-wire cable. A power line filter having a high ground impedance for the frequency at which the power supply is performed and a low ground impedance for the commercial power frequency. In a power line carrier communication system in which a power line of a commercial power supply is used as a communication medium and communication is performed by a power line carrier communication device,
A single-phase three-wire electric wire between the secondary side of the transformer and the power line communication device is provided with a power line filter having a high impedance for a frequency performing the power line communication and a low impedance for a commercial power frequency. A power line carrier communication system, comprising: In claim 2,
The power line carrier communication system, wherein the power line filter is provided on both sides of the single-phase three-wire electric wire fixed to a pole insulator. In a power line carrier communication system in which a power line of a commercial power supply is used as a communication medium and communication is performed by a power line carrier communication device,
The power line is connected to a power line carrier communication device and a power line carrier communication device to be transmitted to a single-phase three-wire electric wire to be a transmission path, and to a ground wire connected to a neutral wire of the single-phase three-wire electric wire, A first power line filter having a high ground impedance for a frequency at which power line communication is performed and a low ground impedance for a commercial power frequency is provided, and a first power line filter is provided between a secondary side of a transformer and the power line communication device. A single-phase three-wire electric wire provided with a second power line filter having a high impedance at a frequency for performing power line communication and a low impedance at a commercial power frequency. In any one of claims 1-4,
The power line carrier communication system according to claim 1, wherein the power line filter is a coil that can be attached to the single-phase three-wire without a power failure. In a power line filter for suppressing leaked radio waves of a power line carrier communication system using a power line of a commercial power supply as a communication medium,
An element that has a high ground impedance for the frequency of power line carrier communication and a low ground impedance for the commercial power frequency on the ground wire connected to the neutral line of the commercial power supply of a single-phase three-wire electric wire that becomes the power line. And a power line filter. In claim 6,
A power line filter, wherein the element is a clamp-type coil that can be attached to the single-phase three-wire electric wire without a power failure. In claim 7,
The clamp type coil is a power line filter made of an oxide ferrite material or an amorphous alloy material.

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