JP2015233242A - Capacitive coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitive coupler that enables a communication signal to pass between two power lines by a simple workmanship without processing existing power lines.SOLUTION: A capacitive coupler 100 has a metal material 11, a metal material 21, a connection part 3, a maintenance part 12 and a maintenance part 22. Power on which a communication signal is superimposed is made to pass through a power line 1, and power of a system different from the power line 1 is made to pass through a power line 2. The sheet-like metal material 11 is wrapped around the power line 1, whereby the power line 1 and the metal material 11 are capacitively coupled with each other. The sheet-like metal material 21 is wrapped around the power line 2, whereby the power line 2 and the metal material 21 are capacitively coupled with each other. The connection part 3 electrically connects the metal material 11 and the metal material 21, bundles the power line 1 and the power line 2 and makes a communication signal pass between the power lines 1 and 2. The maintenance part 12 maintains the wrap state of the metal material 11, and the maintenance part 22 maintains the wrap state of the metal material 21.

Description

  The present invention generally relates to capacitive couplers, and more particularly to a capacitive coupler for power line communication that allows only communication signals to pass between power lines of different systems.

  Conventionally, in order to superimpose a communication signal on power without processing an existing power line in power line communication, an inductive coupler has been used. However, the inductive coupler has a problem that it is difficult to construct because it is easily broken and increases in size. Therefore, a capacitive coupler that solves these problems and is non-contact and lightweight and has excellent workability has been proposed (see, for example, Patent Document 1).

  This capacitive coupler includes a sheet-like member having flexibility and insulation, a metal film having flexibility provided on one surface of the sheet-like member, and a connection electrically joined to the metal film. It has a terminal. Furthermore, the sheet | seat fixing | fixed part fixed to the state which closely_contact | adhered and wound the surface which provided the metal film on the power line surface is provided, and a power line communication apparatus can be installed, without processing the existing power line.

JP 2007-53704 A

  For example, in a distribution board installed indoors, two different power lines are wired, and there may be a need for a coupler that allows only communication signals to pass between the two power lines. However, the capacitive coupler described in Patent Document 1 assumes that a communication signal is superimposed on one power line wound with a sheet-like member, and has a configuration in which the communication signal is passed between the two power lines. Absent.

  The present invention has been made in view of the above reasons, and provides a capacitive coupler capable of passing a communication signal between two power lines through easy construction without processing an existing power line. Objective.

  The capacitive coupler according to the present invention includes a sheet-like first metal material that is capacitively coupled to the first power line by being wound around the first power line that passes the power on which the communication signal is superimposed, A sheet-like second metal material that is capacitively coupled to the second power line by wrapping around a second power line that passes power of a system different from the power line, and the first power line and the second power line are bundled together, And the connection part which electrically connects a 1st metal material and a 2nd metal material, and lets a communication signal pass between a 1st power line and a 2nd power line, and winding of a 1st metal material It has the 1st maintenance part which maintains a state, and the 2nd maintenance part which maintains the winding state of the 2nd metal material, It is characterized by the above-mentioned.

  According to the present invention, it is possible to pass a communication signal between two power lines by easy construction without processing an existing power line.

1A is a cross-sectional view of the capacitive coupler of Embodiment 1, and FIG. 1B is a top view. FIG. 3 is a perspective view showing a main part of the first embodiment. 3 is an equivalent circuit of the capacitive coupler according to the first embodiment. 4A is a schematic diagram of a modification of the capacitive coupler of Embodiment 1, FIG. 4B is a schematic diagram of another modification, and FIG. 4C is a schematic diagram of still another modification. FIG. 6 is a perspective view illustrating a main part of a capacitive coupler according to a second embodiment. FIG. 6A is a perspective view showing the main part of the capacitive coupler of Embodiment 3, and FIG. 6B is a side view.

(Embodiment 1)
The capacitive coupler according to the present embodiment is a capacitive coupler for power line communication. Power line communication is an information communication technique that uses a power line for AC power as a transmission path for communication signals. In power line communication, since an existing power line is used, it is not necessary to newly lay a communication cable.

  In the field where power line communication is performed, for example, when constructing a LAN (Local Area Network) in indoor wiring using a single-phase three-wire system, there are cases where power lines of different systems are mixed. In this case, a power line communication coupler that couples two different power lines and passes only communication signals is required. A capacitive coupler is useful as a coupler for power line communication that can be easily attached without processing the power line.

  The block diagram of the capacitive coupler which concerns on this embodiment is shown to FIG. 1A and FIG. 1B. The capacitive coupler 100 includes a first metal material 11, a second metal material 21, a connection part 3, a first maintenance part 12, and a second maintenance part 22. In addition, the metal material 11 and the metal material 21 are comprised using the electroconductive material, and are comprised using copper as an example. The first power line 1 allows power on which a communication signal is superimposed to pass, and the second power line 2 allows power of a system different from the power line 1 to pass. The metal material 11 has a sheet shape, and the power line 1 and the metal material 11 are capacitively coupled by winding the metal material 11 around the power line 1. The metal material 21 has a sheet shape, and the power line 2 and the metal material 21 are capacitively coupled by winding the metal material 21 around the power line 2. The connection part 3 electrically connects the metal material 11 and the metal material 21, and bundles the power line 1 and the power line 2 to pass a communication signal between the power line 1 and the power line 2. The maintenance unit 12 maintains the winding state of the metal material 11, and the maintenance unit 22 maintains the winding state of the metal material 21.

  For the sake of explanation, the longitudinal direction of the power line 1 is the X-axis direction, the direction perpendicular to the X-axis and the power line 1 and the power line 2 are aligned is the Y-axis direction, and the direction perpendicular to the X-axis and the Y-axis is the direction. The Z axis direction.

  Hereinafter, the configuration of the capacitive coupler 100 in the present embodiment will be described in more detail.

  In the present embodiment, both surfaces of the metal material 11 are covered with the first insulating material 13, and the insulating material 13 and the metal material 11 constitute a first laminated body 14. Similarly, both sides of the metal material 21 are covered with the second insulating material 23, and the insulating material 23 and the metal material 21 constitute a second laminated body 24. The insulating material 13 and the insulating material 23 are made of, for example, synthetic resin. The metal material 11 and the metal material 21 are rectangular metal foils, and the insulating material 13 and the insulating material 23 are rectangular insulating sheets. The laminated body 14 and the laminated body 24 are lightweight and flexible, and can be easily wound around each of the power line 1 and the power line 2.

  Here, in FIG. 2, the laminated body 14 and the laminated body 24 are separated from each other at the connection portion 3, and the laminated body 14 in a state in which the laminated body 14 is spread out to be flat is illustrated. On one surface of the laminate 14, a direction parallel to the X axis when wound around the power line 1 is defined as an X1 axis direction, and a direction orthogonal to the X1 axis direction is defined as a Y1 axis direction. Moreover, let the thickness direction of the laminated body 14 be a Z1-axis direction. Since the same applies to the laminate 24, the reference numerals for the laminate 24 are shown in parentheses in FIG. The laminated body 14 and the laminated body 24, the power line 1 and the power line 2, the X1 axis and the X2 axis, the Y1 axis and the Y2 axis, and the Z1 axis and the Z2 axis correspond to each other.

  In the present embodiment, the second surface 142 that is the back surface of the first surface 141 in contact with the power line 1 of the multilayer body 14 does not have the insulating material 13 only in the substantially central portion in the Y1 axis direction, and the metal material 11 is The second surface 142 is exposed. Similarly, the fourth surface 242 which is the back surface of the third surface 241 in contact with the power line 2 of the multilayer body 24 does not have the insulating material 23 only at the substantially central portion in the Y2 axis direction, and the metal material 21 is the fourth material. The surface 242 is exposed. These exposed portions are electrically connected to each other by the connection portion 3. In this embodiment, the exposed portion of the metal material 11 and the exposed portion of the metal material 21 constitute the connection portion 3.

  The maintenance unit 12 of the present embodiment includes a planar fastener 121 that is a first coupling portion and a planar fastener 122 that is a second coupling portion. The maintenance unit 22 includes a planar fastener 221 that is a third coupling portion and a planar fastener 222 that is a fourth coupling portion. The sheet fastener 121 is provided at one end of the laminate 14 in the Y1 axis direction, and the sheet fastener 122 is provided at the end opposite to the sheet fastener 121. Further, the planar fastener 121 is provided on the first surface 141, and the planar fastener 122 is provided on the second surface 142. The planar fastener 121 and the planar fastener 122 can be combined. Similarly, the planar fastener 221 is provided at one end of the laminate 24 in the Y2 axis direction, and an on-surface fastener 222 is provided at the end opposite to the planar fastener 221. Further, the planar fastener 221 is provided on the third surface 241 of the laminate 24, and the planar fastener 222 is provided on the fourth surface 242. The planar fastener 221 and the planar fastener 222 can be combined.

  Hereinafter, the usage method of the capacitive coupler 100 of this embodiment is demonstrated concretely. For example, different power lines 1 and 2 are wired in parallel indoors. A low frequency (50/60 Hz) AC power and a high frequency (10 k to 30 MHz) communication signal pass through the power line 1 or the power line 2. When the laminate 14 is wound around the power line 1, the first capacitor 10 (see FIG. 3) having the metal material 11 and the core wire 15 of the power line 1 as a pair of electrodes is formed. When the laminate 24 is wound around the power line 2, the second capacitor 20 (see FIG. 3) having the metal material 21 and the core wire 25 of the power line 2 as a pair of electrodes is formed. Here, in the capacitor 10, the covering material 16 and the insulating material 13 of the power line 1 are first dielectrics, and in the capacitor 20, the covering material 26 and the insulating material 23 of the power line 2 are second dielectrics. Thus, the metal material 11 and the power line 1 are capacitively coupled, and the metal material 21 and the power line 2 are capacitively coupled.

  Therefore, as shown in FIG. 3, the capacitor 10 and the capacitor 20 are connected in series via the connection portion 3 between the power line 1 and the power line 2. Only the communication signal can pass between the power line 1 and the power line 2 by setting the cutoff frequency of the capacitor higher than the frequency of the AC power and lower than the frequency of the communication signal. From the above, by using the capacitive coupler 100 of the present embodiment, it is possible to pass a communication signal between two power lines by easy construction without processing an existing power line.

Here, the capacitance C [F] of a general parallel plate capacitor uses the electrode plate area S [m ² ], the electrode plate distance d [m], and the dielectric constant ε [F / m] of the dielectric. C = εS / d. When this equation is applied to the capacitive coupler 100, each of the capacitance C1 of the capacitor 10 and the capacitance C2 of the capacitor 20 is expressed by the following equations.

C1 = ε1 × S1 / d1 (1)
C2 = ε2 × S2 / d2 (2)
Here, ε1 is the dielectric constant of the first dielectric composed of the covering material 16 and the insulating material 13, and ε2 is the dielectric constant of the second dielectric composed of the covering material 26 and the insulating material 23. is there. D1 is the thickness of the first dielectric, and d2 is the thickness of the second dielectric. S1 and S2 are respectively an area facing the power line 1 in the metal material 11 (wrapping area of the metal material 11) and an area facing the power line 2 in the metal material 21 (wrapping area of the metal material 21). It is expressed by a formula.

S1 = a1 × b1 (3)
S2 = a2 × b2 (4)
However, the circumferential length 2πr of the power line 1 when the length of the metal material 11 in the X1 axis direction is a1 and the radius of the power line 1 is r is b1. Similarly, the length of the metal material 21 in the X2 axis direction is a2, and the circumferential length of the power line 2 is b2. It is assumed that the thickness of the insulating materials 13 and 23 is negligible.

  From these equations, it can be seen that the capacitance C1 of the capacitor 10 increases in proportion to a1 and b1, and the capacitance C2 of the capacitor 20 increases in proportion to a2 and b2.

  Further, it is desirable that at least one surface of the metal material 11 is covered with the first insulating material 13 as in this embodiment, and at least one surface of the metal material 21 is covered with the second insulating material 23. desirable. The insulating material 13 and the insulating material 23 can prevent deterioration due to oxidation of the metal materials 11 and 21 and signal leakage due to the metal materials 11 and 21 coming into contact with surrounding conductors.

  The maintenance unit 12 includes a first coupling unit 121 and a second coupling unit 122 as in the present embodiment, and the maintenance unit 22 includes a third coupling unit 221 and a fourth coupling unit 222. Is preferred. The coupling portion 121 is provided on the first surface that is one surface in the thickness direction of the stacked body 14, and the coupling portion 122 is provided on the second surface that is the back surface of the first surface. 121 and the coupling part 122 are preferably connectable. Further, the coupling portion 221 is provided on the third surface that is one surface of the laminate 24 in the thickness direction, and the coupling portion 222 is provided on the fourth surface that is the back surface of the third surface. It is preferable that the coupling part 222 can be coupled. By these coupling portions, it is possible to easily maintain the state in which each of the stacked body 14 and the stacked body 24 is wound around each of the power line 1 and the power line 2.

  The laminated body 14 has the insulating material 13 between the power line 1 and the metal material 11 as in this embodiment, and the laminated body 24 has the insulating material 23 between the power line 2 and the metal material 21. Is desirable. Further, it is desirable that the dielectric constant of the insulating material 13 is higher than the dielectric constant of the covering material 16, and the dielectric constant of the insulating material 23 is higher than the dielectric constant of the covering material 26. As a result, the capacitance of the capacitor 10 and the capacitance of the capacitor 20 can be increased, and the capacitors 10 and 20 can pass communication signals closer to lower frequencies.

  In this embodiment, both surfaces of the metal material 11 are covered with the insulating material 13, and both surfaces of the metal material 21 are covered with the insulating material 23, but even if only one surface of the metal material 11 is covered with the insulating material 13, The metal material 21 may be covered with the insulating material 23 only on one surface. Further, the metal material 11 may not be covered with the insulating material 13, and the metal material 21 may not be covered with the insulating material 23.

  In the present embodiment, the maintenance unit 12 includes the coupling unit 121 and the coupling unit 122, and the maintenance unit 22 includes the coupling unit 221 and the coupling unit 222. However, the metal material 11 and the metal material 21 are, for example, shape memory alloys. And may serve as both the maintenance unit 12 and the maintenance unit 22. That is, the metal materials 11 and 21 may have a function of maintaining the state where the metal materials 11 and 21 are wound around the power lines 1 and 2, and the maintenance units 12 and 22 may not be provided separately. Further, the connecting portions 121, 122, 221, and 222 do not need to be planar fasteners as in this embodiment, and may be adhesive tapes such as double-sided tapes.

  In the present embodiment, the connection portion 3 connects the central portion of the stacked body 14 in the Y1 axis direction and the central portion of the stacked body 24 in the Y2 axis direction. However, the connecting portion 3 may connect the end portion of the stacked body 14 in the Y1 axis direction and the end portion of the stacked body 24 in the Y2 axis direction. An example in which the connection portion 3 connects the end portions of the stacked body 14 and the stacked body 24 in this manner is shown in FIGS. 4A, 4B, and 4C. 4A, 4B, and 4C are cross-sectional views of the capacitive coupler, each of which has a different shape in which the laminate 14 and the laminate 24 are wound around the power lines 1 and 2, respectively.

  In FIG. 4A, the stacked body 14 and the stacked body 24 are connected so that the first surface 141 of the stacked body 14 and the fourth surface 242 of the stacked body 24 are on the same side. Therefore, in a state where the laminate 14 is wound around the power line 1 and the laminate 14 is wound around the power line 2, the laminate 14 and the laminate 24 are formed in an S shape as a whole. In FIG. 4B, the stacked body 14 and the stacked body 24 are connected so that the first surface 141 of the stacked body 14 and the third surface 241 of the stacked body 24 are on the same side. Therefore, in a state where the laminate 14 is wound around the power line 1 and the laminate 14 is wound around the power line 2, the laminate 14 and the laminate 24 are formed in a W shape as a whole. FIG. 4C is a modification of FIG. 4B. In FIG. 4B, the laminates 14 and 24 are wound around the power lines 1 and 2, respectively, whereas in FIG. 4C, the laminates 14 and 24 are wound around the pair of power lines 1 and 2 together. And the laminated body 24 is O-shaped as a whole.

(Embodiment 2)
The capacitive coupler 100 of this embodiment is shown in FIG. The capacitive coupler 100 has a scale 17 in which the laminate 14 is arranged on at least one surface along a direction orthogonal to the longitudinal direction of the power line 1, and the laminate 24 is at least on one surface in a direction orthogonal to the longitudinal direction of the power line 2. The second embodiment is different from the first embodiment in that the scale 27 is arranged along the line.

  Hereinafter, the configuration of the capacitive coupler 100 of the present embodiment will be described in detail. FIG. 5 shows only the configuration of the portion wound around the power line 1 in the capacitive coupler 100 of the present embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals. In addition, since the structure of the part wound around the power line 2 is the same as the structure of the part wound around the power line 1, those reference numerals are shown in parentheses in FIG.

  In the present embodiment, the scale 17 is printed at one end portion in the X1 axis direction on the first surface 141, and the scale 27 is printed at one end portion in the X2 axis direction on the third surface 241. The scale 17 has first scale lines arranged at equal intervals along the Y1 direction, and the scale 27 has second scale lines arranged at equal intervals along the Y2 direction. The first scale line can specify the circumferential length b1 of the power line 1 in a state where the laminate 14 is wound around the power line 1, and the second scale line is a power line in a state where the laminate 24 is wound around the power line 2. A circumferential length b2 of 2 can be specified. Further, the communication signal attenuation A [dB] corresponding to the circumferential length b1 of the specified power line 1 is printed beside the first scale line, and the specified amount beside the second scale line. The attenuation amount B [dB] of the communication signal corresponding to the circumferential length b2 of the power line 2 is printed.

  By the capacitive coupler 100 of the present embodiment, the attenuation A beside the scale line when the laminate 14 is wound around the power line 1, and the attenuation B beside the scale line when the laminate 24 is wrapped around the power line 2; Is easily calculated. This is the amount attenuated by the capacitor 10 and the capacitor 20 when the communication signal passing through the power line 1 or the power line 2 is transmitted to the other power line via the capacitive coupler 100. Therefore, the capacitive coupler 100 of the present embodiment having the scale 17 and the scale 27 can measure the attenuation of the signal when passing through the capacitive coupler 100.

(Embodiment 3)
As shown in FIGS. 6A and 6B, the laminated body 14 has a first connecting portion 181 at one end in the longitudinal direction of the power line 1 and is connected to the opposite end. A second connecting portion 182 that can be coupled to the portion 181 is provided. In addition, the laminate 24 has a third connecting portion 281 at one end in the longitudinal direction of the power line 2 and a fourth connecting portion 282 that can be coupled to the connecting portion 281 at the opposite end. Different from Form 1. Hereinafter, the same configurations as those of the first embodiment are denoted by common reference numerals, and description thereof is omitted as appropriate.

  As described in the first embodiment, the capacitance C1 can be increased by increasing the winding area S1 of the metal material 11, and the capacitance C2 can be increased by increasing the winding area S2 of the metal material 21. Become. Moreover, when the electrostatic capacitance C1 and the electrostatic capacitance C2 become large, the attenuation amount of the communication signal that passes between the power line 1 and the power line 2 can be reduced.

  When the length of the laminated body 14 in the X1 axis direction and the length of the laminated body 24 in the X2 axis direction are determined, in order to increase the winding area S1 of the metal material 11 and the winding area S2 of the metal material 21, It is necessary to connect a plurality of capacitive couplers 100 in the axial direction.

  FIG. 6 shows only the configuration of the portion wound around the power line 1 in the capacitive coupler 100 of the present embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals. In addition, since the structure of the part wound around the power line 2 is the same as the structure of the part wound around the power line 1, those reference numerals are shown in parentheses in FIGS. 6A and 6B.

  6A and 6B, as an example of this embodiment, two capacitive couplers 100 are connected in the X-axis direction. Of the two capacitive couplers 100, one has a connecting portion 181 at one end in the X1 axis direction of the laminate 14 and a connecting portion 182 at the opposite end. The connecting portion 181 is on the first surface 141, and the connecting portion 182 is on the second surface 142. Similarly, the other capacitive coupler 100 has a connecting portion 183 at one end in the X1 axis direction of the laminate 14 and a connecting portion 184 at the opposite end. Further, the connecting portion 183 is on the third surface 241, and the connecting portion 184 is on the fourth surface 242. In addition, the connection parts 181 thru | or 184 in this embodiment are planar fasteners.

  By combining and coupling the coupling portion 182 and the coupling portion 183, the two capacitive couplers 100 are coupled in the X-axis direction, so that the winding area around the power line 1 can be increased. Therefore, the capacitance C1 becomes larger, and the attenuation amount of the communication signal that passes between the power line 1 and the power line 2 can be reduced.

  In the present embodiment, the connecting portions 181 to 184 are planar fasteners, but may be an adhesive tape such as a double-sided tape. Further, this embodiment can be combined with the second embodiment.

DESCRIPTION OF SYMBOLS 1 1st power line 2 2nd power line 11 1st metal material 21 2nd metal material 12 1st maintenance part 22 2nd maintenance part 121 1st coupling part 122 2nd coupling part 221 3rd Joint part 222 Fourth joint part 13 First insulating material 23 Second insulating material 14 First laminated body 24 Second laminated body 17 First scale 27 Second scale 181 First connecting part 182 First 2 connection parts 281 3rd connection part 282 4th connection part 3 connection part 100 capacitive coupler

Claims (9)

A sheet-like first metal material that is capacitively coupled to the first power line by wrapping around the first power line that passes the power on which the communication signal is superimposed,
A sheet-like second metal material that is capacitively coupled to the second power line by wrapping around a second power line that passes power of a system different from the first power line;
Bundling the first power line and the second power line, electrically connecting the first metal material and the second metal material, and the first power line and the second power line A connection that allows communication signals to pass between,
A first maintaining unit for maintaining the winding state of the first metal material;
And a second maintaining unit for maintaining the winding state of the second metal material.   2. The capacitor according to claim 1, wherein each of the first metal material and the second metal material has a scale arranged along a direction orthogonal to a longitudinal direction of the power line on at least one surface. Sex coupler. The first metal material has a first connecting portion at a first end which is one end in the longitudinal direction of the first power line, and a second end opposite to the first end. A second connecting portion that can be coupled to the first connecting portion at an end;
The second metal material has a third connecting portion at a third end portion which is one end portion in the longitudinal direction of the second power line, and a fourth connecting portion opposite to the third end portion. 3. The capacitive coupler according to claim 1, further comprising a fourth coupling portion that can be coupled to the third coupling portion at an end portion. 4. The first maintaining portion is provided on a first coupling portion provided on a first surface which is one surface of the first metal material, and on a second surface which is a back surface of the first surface. A second coupling part that can be coupled to the first coupling part,
The second maintaining portion is provided on a third surface provided on a third surface which is one surface of the second metal material and on a fourth surface which is a back surface of the third surface. 4. The capacitive coupler according to claim 1, further comprising a fourth coupling portion that can be coupled to the third coupling portion. 5. The first metal material has at least one surface covered with a first insulating material, and the first insulating material and the first metal material constitute a first laminate,
At least one surface of the second metal material is covered with a second insulating material, and the second insulating material and the second metal material form a second laminate. The capacitive coupler according to claim 1.   6. The capacitor according to claim 5, wherein each of the first stacked body and the second stacked body has a scale arranged along at least one surface along a direction orthogonal to a longitudinal direction of the power line. Sex coupler. The first stacked body has a first connecting portion at a first end which is one end in the longitudinal direction of the first power line, and a second end opposite to the first end. A second connecting portion that can be coupled to the first connecting portion at an end;
The second stacked body has a third connecting portion at a third end portion which is one end portion in the longitudinal direction of the second power line, and a fourth connecting portion opposite to the third end portion. 7. The capacitive coupler according to claim 5, further comprising a fourth coupling portion that can be coupled to the third coupling portion at an end portion. 8. The first maintaining portion is provided on a first coupling portion provided on a first surface which is one surface of the first stacked body, and on a second surface which is a back surface of the first surface. A second coupling part that can be coupled to the first coupling part,
The second maintaining portion is provided on a third coupling portion provided on a third surface which is one surface of the second stacked body, and on a fourth surface which is a back surface of the third surface. The capacitive coupling device according to claim 5, further comprising a fourth coupling portion that can be coupled to the third coupling portion. The first stacked body includes the first insulating material between the first power line and the first metal material, and the second stacked body includes the second power line and the second power line. The second insulating material is provided between the metal material, the dielectric constant of the first insulating material is higher than the dielectric constant of the covering material of the first power line, and the dielectric constant of the second insulating material is 9. The capacitive coupler according to claim 5, wherein the dielectric constant is higher than a dielectric constant of the covering material of the second power line.

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