JP5243323B2 - Power cable shielding layer grounding device and grounding method - Google Patents

Description

  The present invention relates to a grounding device and a grounding method for a shielding layer of a power cable used at high voltage or extra high voltage.

  In a power cable used at a high voltage or extra high voltage, a high voltage is generated in the shielding layer by electrostatic induction. In order to protect nearby equipment and prevent electric shock from such high voltage, the shielding layer of the power cable is usually grounded.

FIG. 5 is a perspective view showing a cross-sectional structure of a general power cable.
First, the structure of a general power cable will be described with reference to FIG. The power cable is formed by arranging a circular core wire in the center of a tubular shielding layer, insulating between the shielding layer and the core wire with an insulating layer, and further insulating the shielding layer with a sheath.

FIG. 6 is a diagram illustrating a conventional method for grounding a shielding layer of a power cable.
In the example shown in FIG. 6, both ends of the electrically insulated shielding layer of the power cable are grounded. As described above, when both ends of each shielding layer are grounded, a part of the current flowing from the shielding layer to the ground line is expected to return to the power source through the adjacent shielding layer, but the remaining It is inevitable that the current flows out to the ground.

FIG. 7 is a diagram showing another grounding method for the shielding layer of the conventional power cable.
In the example shown in FIG. 7, one end on the power source side of the electrically insulated shielding layer of the power cable is grounded. In this way, when one end of each shielding layer on the power supply side is grounded, all of the current that flows to the ground line drawn from the shielding layer flows to the ground. Similarly, when one end on the load side of the electrically insulated shielding layer of the power cable is grounded, all of the current flowing out to the ground line drawn from the shielding layer flows out to the ground.

Kenkyusha, issued on November 1, 2008 Railway Research Institute Vol. 22, No. 11 “Fundamental study of zero-phase high-frequency resonance in feeding circuits of levitated railways” Figure 3

  However, in the conventional method for grounding the power cable shielding layer as described above, the alternating current leaking from the core wire to the shielding layer via the electrostatic capacitance between the cable core wire and the shielding layer is transferred from the ground wire to the ground. There is a problem that it leaks and becomes a cause of noise for underground communication lines.

  The present invention was made in view of such circumstances, and by returning the current flowing from the shielding layer of the power cable toward the ground to the shielding layer closer to the power source than the shielding layer, An object of the present invention is to provide a grounding device and a grounding method for a power cable shielding layer capable of suppressing the current from flowing to the ground.

  In order to solve the above problems, a grounding device for a power cable shielding layer according to the present invention includes a magnetically coupled primary conductor and a secondary conductor formed as a two-terminal pair circuit, and an output of the primary conductor. The terminal and the input terminal of the secondary conductor are commonly grounded, and the current input to the input terminal of the primary conductor is transformed to be output from the output terminal of the secondary conductor.

  For example, the primary conductor and the secondary conductor are respectively wound around the same annular iron core, and the primary conductor and the secondary conductor are magnetically coupled, or the secondary conductor is wound around the annular iron core, A conductor is passed through the hollow of the annular iron core, and the primary conductor and the secondary conductor are magnetically coupled.

 Preferably, when a surge protection device is connected in parallel with at least one or both of the primary conductor and the secondary conductor, and an abnormal high voltage is generated between the shielding layer and the ground, the grounding is performed. Protect equipment.

 Further, preferably, when a predetermined current or more flows through the primary conductor due to magnetic coupling between the primary conductor and the secondary conductor, the current does not induce a certain current or more in the secondary conductor. Let

  Preferably, an impedance is connected to the output terminal of the secondary conductor to suppress a stray current that flows directly from the ground point to the secondary conductor side.

  In order to solve the above problems, a grounding method for a power cable shielding layer according to the present invention uses a grounding device for a power cable having a magnetically coupled primary conductor and secondary conductor formed as a two-terminal pair circuit. A power cable grounding method comprising: connecting an input terminal of the primary conductor to a first shielding layer of the power cable; and isolating an output terminal of the secondary conductor from the first shielding layer of the power cable. Connected to a second shielding layer, the output terminal of the primary conductor and the input terminal of the secondary conductor are grounded together, and the current input from the first shielding layer to the input terminal of the primary conductor is transformed. And output from the output terminal of the secondary conductor and fed back to the second shielding layer.

Moreover, the grounding method of the power cable shielding layer according to the present invention for solving the above-mentioned problem is a grounding device for a power cable having a magnetically coupled primary conductor and secondary conductor formed as a two-terminal pair circuit. a grounding method of the power cable shielding layer using the input terminals of the primary conductor is connected to the wall layer shielding of the power cable, to connect the output terminal of the secondary conductor to the outside of the metal conductor, said primary conductor and a shared ground the output terminal and the input terminal of said secondary conductors, current input from front Kisaegi soldiers layer to an input terminal of the primary conductor is flowed variable, output from the output terminal of the secondary conductor, Returning to the external metal conductor.

  According to the present invention, the current flowing from the shielding layer of the power cable toward the ground is returned to the shielding layer closer to the power source than the shielding layer, thereby suppressing the current from flowing out to the ground. Can do.

1 is a perspective view of a power cable grounding device 10 according to a first embodiment. It is a perspective view of the grounding device 20 for electric power cables which concerns on 2nd Embodiment. It is a figure which shows the 1st usage example of the grounding apparatus for electric power cables which concerns on this embodiment. It is a figure which shows the 2nd usage example of the grounding apparatus 10 for electric power cables which concerns on this embodiment. It is a perspective view which shows the cross-section of a general power cable. It is a figure which shows the grounding method of the shielding layer of the conventional power cable. It is a figure which shows another grounding method of the shielding layer of the conventional power cable.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

FIG. 1 is a perspective view of a power cable grounding device 10 according to the first embodiment.
First, with reference to FIG. 1, the structure of the grounding device 10 for electric power cables which concerns on 1st Embodiment is demonstrated. The power cable grounding device 10 has a magnetically coupled primary conductor 11 and secondary conductor 12 formed as a two-terminal pair circuit. The primary conductor 11 and the secondary conductor 12 are respectively wound around the same annular core 13 and both are magnetically coupled. The output terminal of the primary conductor 11 and the input terminal of the secondary conductor 12 are shared ground.

  With such a configuration, in the power cable grounding device 10, when a current is input to the input terminal of the primary conductor 11, the two terminals formed by the secondary conductor 12 magnetically coupled to the primary conductor 11. The current is transformed by a pair circuit and output from the output terminal of the secondary conductor 12. In this case, the primary wound around the annular core 13 so that the current value of the current input to the input terminal of the primary conductor 11 and the current value of the current output from the output terminal of the secondary conductor 12 are about the same. The number of turns of the conductor 11 and the secondary conductor 12 is adjusted.

FIG. 2 is a perspective view of the power cable grounding device 20 according to the second embodiment.
Next, the structure of the power cable grounding device 20 according to the second embodiment will be described with reference to FIG. The power cable grounding device 20 has a magnetically coupled primary conductor 21 and secondary conductor 22 formed as a two-terminal pair circuit. The primary conductor 21 passes through the hollow of the annular core 23, and the secondary conductor 22 is wound around the annular core 23, and both the primary conductor 21 and the secondary conductor 22 are magnetically coupled. The output terminal of the primary conductor 21 and the input terminal of the secondary conductor 22 are shared ground.

  With such a configuration, in the power cable grounding device 20, when a current is input to the input terminal of the primary conductor 21, the two terminals formed by the secondary conductor 22 magnetically coupled to the primary conductor 21. The current is transformed by a pair circuit and output from the output terminal of the secondary conductor 22. In this case, the current value of the current input to the input terminal of the primary conductor 21 and the current value of the current output from the output terminal of the secondary conductor 22 are approximately equal to each other. The number of turns of the secondary conductor 12 is adjusted.

FIG. 3 shows a first usage example of the grounding device 10 according to the present embodiment.
Next, an embodiment in which the shielding layer of the power cable is grounded using the grounding device 10 will be described with reference to FIG. Since each grounding device 10 is the same as the grounding device 10 shown in FIG. 1, detailed description thereof is omitted. Moreover, since the Example which earth | grounds the shielding layer of an electric power cable using the grounding apparatus 20 is the same as that of the case where the grounding apparatus 10 is used, the detailed description is abbreviate | omitted. In the present embodiment, the electrically insulated shielding layers 61 to 63 of the power cable 60 connected to the AC power supply 50 are grounded.

  The grounding device 10 is connected so as to straddle adjacent shielding layers among the shielding layers 61 to 63. Specifically, the input terminal of the primary conductor 11 of the grounding device 10 is connected to the shielding layer on the side far from the AC power supply 50, and the shielding layer on the side where the output terminal of the secondary conductor 12 of the grounding device 10 is close to the AC power supply 50. Connected to. That is, in the grounding device 10 that connects the shielding layer 62 and the shielding layer 63, the input terminal of the primary conductor 11 of the grounding device 10 is connected to the shielding layer 63 far from the AC power supply 50, and the output of the secondary conductor 12 of the grounding device 10. The terminal is connected to the shielding layer 62 on the side close to the AC power supply 50.

  Similarly, between the shielding layer 61 and the shielding layer 62, the input terminal of the primary conductor 11 of the grounding device 10 is connected to the shielding layer 62 far from the AC power supply 50, and the output terminal of the secondary conductor 12 of the grounding device 10 is connected to the AC power supply. It is connected to the shielding layer 61 on the side close to 50. However, since the grounding device 10 connected to the end of the shielding layer 61 near the AC power supply 50 does not have a shielding layer of the power cable 60 to which the output terminal of the secondary conductor 12 is connected, the output terminal is connected to the AC power supply. Connected to 50 ground points.

  With such a configuration, each grounding device 10 is connected to a plurality of electrically insulated shielding layers 61 to 63 of the power cable 60. When the grounding device 10 is connected in this way, a primary current flows into the input terminal of the primary conductor 11 of each grounding device 10. Each grounding device 10 forms a magnetic circuit with the primary conductor 11 and the secondary conductor 12. When a primary current flows into the input terminal of the primary conductor 11, the output of the secondary conductor 12 is generated by the action of the magnetic circuit. A secondary current in the reverse direction is induced at the terminal. As a result, the current flowing from each shielding layer toward the ground can be forcibly guided to the adjacent shielding layer, and the current flowing out to the ground can be suppressed.

  In the present embodiment, the surge protection device 14 is connected in parallel to the secondary conductor 12 of each grounding device 10. The surge protection device 14 protects the grounding device 10 when an abnormal high voltage is generated between the shielding layer and the ground due to lightning or the like. The surge protection device 14 may be connected in parallel to the primary conductor 11 of the grounding device 10, or connected in parallel to both the primary conductor 11 and the secondary conductor 12 of the grounding device 10. You may make it do.

  In the present embodiment, the connection between the metal wire on the secondary conductor 12 side of each grounding device 10 and the shielding layer close to the AC power supply 50 is made via an impedance 15 such as a capacitor. The impedance 15 suppresses the stray current that flows directly from the ground point to the secondary conductor 12 side.

FIG. 4 shows a second usage example of the grounding device 10 according to the present embodiment.
Next, with reference to FIG. 4, another embodiment in which the shielding layer of the power cable is grounded using the grounding device 10 will be described. Since each grounding device 10 is the same as the grounding device 10 shown in FIG. 1, detailed description thereof is omitted. Moreover, since the Example which earth | grounds the shielding layer of an electric power cable using the grounding apparatus 20 is the same as that of the case where the grounding apparatus 10 is used, the detailed description is abbreviate | omitted. In the present embodiment, the electrically insulated shielding layers 81 to 83 of the power cable 80 connected to the AC power source 70 are grounded. In the present embodiment, the metal conductor 90 connected to the ground point of the AC power supply 70 is installed along the power cable 80.

  The grounding device 10 is connected so as to straddle the shielding layers 81 to 83 and the metal conductor 90. Specifically, the input terminal of the primary conductor 11 of the grounding device 10 is connected to the shielding layer, and the output terminal of the secondary conductor 12 of the grounding device 10 is connected to the metal conductor 90. That is, in the grounding device 10 connected to the shielding layer 83, the input terminal of the primary conductor 11 of the grounding device 10 is connected to the shielding layer 83, and the output terminal of the secondary conductor 12 of the grounding device 10 is connected to the metal conductor 90. .

  Similarly, in the shielding layer 82, the metal wire on the primary conductor 11 side of the grounding device 10 is connected to the shielding layer 82, and the metal wire on the secondary conductor 12 side of the grounding device 10 is connected to the metal conductor 90. Similarly, in the shielding layer 81, the metal wire on the primary conductor 11 side of the grounding device 10 is connected to the shielding layer 81, and the metal wire on the secondary conductor 12 side of the grounding device 10 is connected to the metal conductor 90.

  With such a configuration, each grounding device 10 is connected to a plurality of electrically insulated shielding layers 81 to 83 of the power cable 80. When the grounding device 10 is connected in this way, a primary current flows into the metal wire on the primary conductor 11 side of each grounding device 10. Each grounding device 10 forms a magnetic circuit with the primary conductor 11 and the secondary conductor 12, and when the primary current flows into the metal wire on the primary conductor 11 side, the secondary conductor 12 side is caused by the action of the magnetic circuit. A secondary current in the reverse direction is induced in the metal wire. As a result, it is possible to forcibly induce a current flowing from each shielding layer toward the ground to the metal conductor 90 and suppress a current flowing out to the ground.

  Also in this embodiment, the surge protection device 14 is connected in parallel to the secondary conductor 12 of each grounding device 10. The surge protection device 14 protects the grounding device 10 when an abnormal high voltage is generated between the shielding layer and the ground due to lightning or the like. Further, the surge protection device 14 may be connected in parallel to the primary conductor 11 of the grounding device 10, or may be connected in parallel to both the primary conductor 11 and the secondary conductor 12 of the grounding device 10. . Further, in the present embodiment, when the metal wire on the secondary conductor 12 side of each grounding device 10 and the metal conductor 90 are connected, they are connected via an impedance 15 such as a capacitor. The impedance 15 functions to suppress a stray current flowing from the ground.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Grounding device 11 Primary conductor 12 Secondary conductor 13 Annular iron core 14 Surge protection device 15 Impedance 20 Grounding device 21 Primary conductor 22 Secondary conductor 23 Annular iron core 30 Grounding 40 Grounding 60 Power cable 61 1st shielding layer 62 2nd shielding Layer 63 Third shielding layer 70 AC power supply 80 Power cable 81 First shielding layer 82 Second shielding layer 83 Third shielding layer 90 Metal conductor

Claims (8)

A magnetically coupled primary and secondary conductor formed as a two-terminal pair circuit;
The output terminal of the primary conductor and the input terminal of the secondary conductor are shared ground,
A grounding device for a power cable shielding layer, wherein a current input to an input terminal of the primary conductor is transformed and output from an output terminal of the secondary conductor.   The power cable shielding layer according to claim 1, wherein the primary conductor and the secondary conductor are respectively wound around the same annular iron core to magnetically couple the primary conductor and the secondary conductor. Grounding device.   The primary conductor and the secondary conductor are magnetically coupled to each other by winding the secondary conductor around an annular iron core and passing the primary conductor through the hollow of the annular core. Power cable shielding layer grounding device.  A surge protection device is connected in parallel with at least one or both of the primary conductor and the secondary conductor to protect the grounding device when an abnormally high voltage is generated between the shielding layer and the ground. The grounding device for a power cable shielding layer according to claim 1.  When the primary conductor and the secondary conductor are magnetically coupled, when a current of a predetermined level or more flows through the primary conductor, the secondary conductor is caused to act so as not to induce a current of a certain level or more. The power cable shielding layer grounding device according to claim 1.  2. The power cable shielding layer grounding device according to claim 1, wherein an impedance is connected to an output terminal of the secondary conductor to suppress a stray current that flows directly from the ground point to the secondary conductor side. A method for grounding a power cable shielding layer using a grounding device for a power cable having a magnetically coupled primary conductor and a secondary conductor formed as a two-terminal pair circuit,
Connecting the input terminal of the primary conductor to a first shielding layer of a power cable;
Connecting the output terminal of the secondary conductor to a second shielding layer insulated from the first shielding layer of the power cable;
Shared grounding of the output terminal of the primary conductor and the input terminal of the secondary conductor,
A current input from the first shielding layer to the input terminal of the primary conductor is transformed, output from the output terminal of the secondary conductor, and fed back to the second shielding layer. The method of grounding the power cable shielding layer. A method for grounding a power cable shielding layer using a grounding device for a power cable having a magnetically coupled primary conductor and a secondary conductor formed as a two-terminal pair circuit,
The input terminals of the primary conductor is connected to the wall layer shielding of the power cable,
Connecting the output terminal of the secondary conductor to an external metal conductor;
Shared grounding of the output terminal of the primary conductor and the input terminal of the secondary conductor,
Current input from front Kisaegi soldiers layer to an input terminal of the primary conductor is flowed variable, output from the output terminal of said secondary conductors, characterized in that so as to be fed back to the external metallic conductor Grounding method for power cable shielding layer.

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