JP2012104378A - Ground structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-install ground structure capable of effectively reducing a transient ground resistance.SOLUTION: A ground structure is provided with a mesh body 1 electrically connected to a grounded body, and introducing a surge current from the grounded body while is it embedded in a ground G almost parallely. In the mesh body 1, lattice-like meshes are formed by plural vertical lines 3 parallely aligned at predetermined intervals, and plural horizontal lines 4 orthogonal to the vertical lines 3 and parallely aligned at predetermined interval, so that a steady ground resistance becomes a predetermined value. Using a predetermined intersection of the vertical lines 3 and the horizontal lines 4 except for an outer edge as an introduction portion 5, a wire 9 for a mesh dense part is arranged in a range surrounded by other intersections around the introduction portion 5, and this range is used as a net dense part 7.

Description

  The present invention relates to a grounding structure for electrically connecting a grounded body and the ground.

  A grounding structure is buried in the ground and connected to a grounded object such as a building structure (lightning rod, etc.) or electrical equipment via a grounding wire, and lightning current (surge current) flowing into the building structure or electrical equipment. ) Into the ground. Thereby, the rise in ground potential can be suppressed, the stride voltage can be reduced, and personal injury and dielectric breakdown of electrical equipment can be prevented. In this grounding structure, the lower the transient grounding resistance (surge impedance) against surge current, the quicker the surge current can be discharged into the ground, and the higher the protection effect of the grounded body.

  There are various types of ground structures that reduce the transient ground resistance (Patent Document 1 and Patent Document 2). The grounding structure of Patent Document 1 is a mesh-like mesh body, and this mesh body is embedded in the ground so as to extend in the horizontal direction. The grounding structure of Patent Document 2 is a rod-like body, and this rod-like body is embedded in the ground so as to extend in the horizontal or vertical direction. In substations, when ground faults occur due to reduction of workers' stride voltage, lightning strikes, etc., various electrical equipment installed in the site will not cause dielectric breakdown accidents due to abnormal voltage. In many cases, a net-like body as in Patent Document 1 is used as a grounding structure in order to make the grounding the same potential. Furthermore, as in Patent Document 3, there is known a grounding structure that reduces a potential increase by using a grounding net and a grounding electrode in combination.

JP 2008-66205 A JP 2005-5240 A JP 7-37669 A

  However, when the grounding structure is composed only of a net-like body or a rod-like body, it is difficult to sufficiently reduce the transient grounding resistance in a place where the ground resistivity is extremely high. Moreover, the surge current that flows into the ground flows out radially from the inflow location. For this reason, it is preferable that the grounding structure has a structure that guides the surge current in substantially the same direction as the direction in which the surge current flowing into the ground flows (spreads).

  Therefore, in view of the above circumstances, the present invention provides a grounding structure that can quickly discharge a surge current into the ground and effectively reduce a transient grounding resistance.

  The grounding structure of the present invention is a grounding structure provided with a mesh body that is electrically connected to a grounded body and introduces a surge current from the grounded body in a state of being buried substantially horizontally in the ground. The net-like body has a steady ground resistance between a plurality of vertical lines arranged in parallel at a predetermined interval and a plurality of horizontal lines orthogonal to the vertical line and arranged in parallel at a predetermined interval. A grid-like mesh is formed so as to have a predetermined value, and a meshed portion is formed in a range surrounded by other intersections around the introduction site with the predetermined intersection of the vertical line and the horizontal line excluding the outer edge as the introduction site A wire rod is arranged, and this range is a mesh dense portion.

  According to the grounding structure of the present invention, since the rod-shaped body is provided at the site where the surge current is introduced from the grounded body of the mesh body, the mesh body can guide the surge current in the horizontal direction at the site of introduction. In this case, since the mesh body is provided with a mesh dense portion in a range surrounded by other intersections around the introduction site, the number of flow paths for dividing the surge current is increased in the mesh dense portion so that the surge current can be quickly generated. It can be discharged into the ground.

  The wire for a mesh-dense part can be a diagonal line connecting the introduction part and an intersection point on the diagonal line of the lattice from the introduction part. If the wire rod for the mesh-dense part is a slanted line, the number of added slant lines increases in addition to the plurality of vertical lines and the plurality of horizontal lines orthogonal to the vertical lines in the flow path for dividing the surge current from the introduction site. Become.

  A rod-shaped body that is provided perpendicularly to the mesh body at the site where the surge current is introduced from the grounded body of the mesh body and guides the surge current introduced by the mesh body into the ground is provided. Can do. In this way, the rod-shaped body can guide the surge current in the vertical direction. That is, the net-like body and the rod-like body have a three-dimensional structure that guides the surge current in a direction substantially the same as the direction in which the surge current flows (spreads) from the introduction site.

  The rod-shaped body is a solid or hollow column body, and includes a first electrode for introducing a surge current from the grounded body into the ground, and a plurality of flat plates projecting radially from the outer periphery of the first electrode. And a second electrode for guiding a surge current from the first electrode to the outer peripheral side, and the flat plate body of the second electrode extends substantially along the entire length in the axial direction of the first electrode and extends along the circumferential direction. It can arrange | position so that it may arrange | position at equal intervals and the protrusion length of the radial direction may become the same. As a result, the first electrode and the second electrode can form a three-dimensional shape, and the second electrode extends in substantially the same direction as the direction in which the surge current flowing into the ground spreads. In addition, since the second electrode extends over substantially the entire length in the axial direction of the first electrode and is composed of a plurality of flat plates arranged so that the protruding length in the radial direction is the same, the first electrode It is possible to guide the surge current introduced in step (b) to the outer peripheral side in the entire axial length. That is, since the flat plate guides the surge current to the outer peripheral side over the entire length of the first electrode in the axial direction, the transient grounding resistance can be reduced.

  In this case, it is preferable that the rod-shaped body has a cross shape having four flat plates. When the distance between adjacent flat plates is close, the underground portion that serves as a flow path for surge current flowing out from each adjacent flat plate is shared, and the surge current is less likely to flow into the ground. . Therefore, the surge current can be effectively discharged into the ground by arranging the four flat bodies in a cross shape.

  In the grounding structure of the present invention, since there are many flow paths for shunting the surge current in the mesh dense part of the mesh body, the surge current flowing from the introduction site is shunted and quickly discharged into the ground, and the transient grounding resistance is reduced. Can be small.

  When the mesh dense portion wire is diagonal, the surge current can be divided into eight directions and discharged into the ground by the vertical and horizontal lines and the mesh dense wire, so that the transient ground resistance can be reduced. . In addition, if a wire for a mesh-tight portion is added to an existing mesh body, the mesh-tight portion can be easily formed, and measures for reducing transient ground resistance can be implemented at low cost.

  When the three-dimensional structure is made up of a net-like body and a rod-like body, a surge current can be discharged into the ground more quickly, and the transient ground resistance can be reduced.

  When the rod-shaped body is composed of the first electrode and the second electrode as described above, the second electrode extends in substantially the same direction as the direction in which the surge current flowing into the ground spreads, and the axial direction of the first electrode Since the entire length is guided to the outer peripheral side, the transient grounding resistance can be reduced with a simple configuration. Even when the transient grounding resistance is reduced in this way, the weight can be relatively reduced. Thereby, a rod-shaped body becomes what is easy to carry and can make installation work easy. Moreover, a 2nd electrode can be attached to the existing 1st electrode, a material cost and a processing cost can be reduced, and cost reduction can be aimed at.

  By arranging the four flat bodies in a cross shape, a surge current can be effectively discharged into the ground. Further, it is sufficient to arrange the flat plates at a pitch of 90 °, which makes it easy to manufacture and process.

It is a simplified perspective view of the grounding structure which shows 1st Embodiment of this invention. It is a top view of the mesh body which comprises the grounding structure which shows 1st Embodiment of this invention. It is a perspective view of the rod-shaped body which comprises the earthing | grounding structure which shows 1st Embodiment of this invention. It is a top view of the rod-shaped body which comprises the earthing | grounding structure which shows 1st Embodiment of this invention. It is a circuit diagram for measuring the transient grounding resistance of the grounding structure of an Example and a comparative example. FIG. 3 is a plan view of a mesh body having a ground structure according to the first embodiment. It is a graph which shows the electric potential in the point a-e of the mesh body of the said FIG. It is a top view of the grounding structure of Example 2, (1)-(3) is a comparative example, (4)-(6) is an Example. It is a graph which shows the frequency characteristic of the grounding resistance of the grounding structure of Example 2, (a) is a comparative example, (b) is an Example. It is a perspective view which shows each grounding body of the comparative example used in Example 3. FIG. It is a graph which shows the frequency characteristic of the grounding resistance of the grounding body of Example 3 and a comparative example. The grounding body (1) of the comparative example used in Example 4 is shown, (a) is a side view, (b) is a perspective view.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a simplified perspective view of a grounding structure according to a first embodiment of the present invention. As shown in FIG. 1, this grounding structure is embedded in the underground G and electrically connects a grounded body (not shown) of an electrical facility or a building structure (such as a lightning rod) and the underground G. It is. In the present embodiment, the grounded body is a lightning arrester of a substation.

  As shown in FIG. 1, the grounding structure of the present invention is a mesh body 1 that is electrically connected to a grounded body and introduces a surge current from the grounded body in a state of being embedded in the ground in a substantially horizontal direction. And a rod-like body 2 for guiding a surge current introduced by the mesh-like body 1 to the underground G below the mesh-like body 1.

  As shown in FIG. 2, the mesh body 1 includes a plurality of (five in the illustrated example) vertical lines 3 arranged in parallel with a predetermined interval (for example, 5 m), and a predetermined interval orthogonal to the vertical line 3. A grid-like mesh is formed by a plurality of (for example, 5 in the illustrated example) horizontal lines 4 arranged in parallel across (for example, 5 m). This predetermined interval is set such that the steady grounding resistance in a steady state has a predetermined value (for example, 10Ω). In the present embodiment, the reticulated body 1 is composed of a hard copper strand 100 sq.

  As shown in FIG. 1, a rising ground wire 6 (conductive wire) is connected to one of the intersection points excluding the outer edges of the vertical line 3 and the horizontal line 4 of the mesh body 1. It is connected to a lightning arrester as a grounded body. As a result, the intersection where the rising ground wire 6 is connected becomes the surge current introduction site 5, and when surge current flows into the grounded body, the surge current is passed to the underground introduction site 5 via the startup ground wire 6. Can be introduced.

  As shown in FIG. 2, a mesh dense portion 7 is provided in a range surrounded by other intersections 8 around the introduction site 5 (four lattices surrounding the introduction site 5). The mesh dense portion 7 is formed by arranging the mesh dense portion wire 9 on each lattice. That is, the oblique line connecting the introduction part 5 and the intersection 8 on the diagonal line of the lattice from the introduction part 5 is used as a mesh dense portion wire 9, and the mesh of these four lattices is made denser than the meshes of the other lattices. . In this case, since there are four intersections 8 on the diagonal line of the grid surrounding the introduction site 5, four mesh-dense portion wire rods (oblique lines) 9 are provided. As a result, there are eight paths extending outward from the introduction site 5. For this reason, the surge current introduced from the introduction part 5 flows in the mesh dense portion 7 by diverting the mesh 1 through the vertical lines 3 and the horizontal wires 4 and the wire for the mesh dense portion, so that the surge current can be quickly brought into the ground. It is possible to reduce the transient grounding resistance by discharging to the ground.

  As shown in FIGS. 3 and 4, the rod-shaped body 2 includes a first electrode 11 that introduces a surge current from the grounded body into the ground G, and a second electrode that guides the surge current from the first electrode 11 to the outer peripheral side. And the electrode 12. The rod-like body 2 is provided directly below the mesh-like body 1 and is connected to the mesh-like body 1 so as to extend in the vertical direction by a conducting wire (not shown). In the present embodiment, the rod-like body 2 is provided at five locations immediately below the introduction site 5 and immediately below the four corners of the mesh-like body 1 as shown in FIG.

  The 1st electrode 11 consists of metal cylinders. The material of the first electrode 11 is preferably copper, which has a low resistivity and allows a surge current to flow easily, but may be composed of other metals such as iron and stainless steel. The first electrode 11 is buried in the ground such that its longitudinal direction is along the vertical direction of the ground G.

  As shown in FIG. 3, the second electrode 12 is composed of a plurality of (four in the present embodiment) metal flat plate 13. Each flat plate 13 has a length substantially equal to that of the first electrode 11, and the flat plate 13 protrudes in the radial direction from the outer periphery of the first electrode 11 over the entire length in the axial direction of the first electrode 11. . Thereby, the flat plate 13 extends over substantially the entire length of the first electrode 11 in the axial direction. The flat plates 13 are arranged at equal intervals along the circumferential direction, that is, at a pitch of 90 °, and are arranged so that the protruding lengths in the radial direction of the flat plates 13 are the same. The rod-like body has a cross shape in plan view as shown in FIG. The second electrode 12 is also made of the same material as the first electrode 11.

  At this time, the flat plate 13 is provided with four pieces from the first electrode 11 to the outer peripheral side, and has a cross shape arranged at a pitch of 90 °. When the distance between adjacent flat plates is close, the underground portion that serves as a flow path for surge current flowing out from each adjacent flat plate is shared, and the surge current is less likely to flow into the ground. . Therefore, if the interval between the adjacent flat plates 3 is widely arranged at a pitch of 90 °, the surge current can be quickly discharged into the ground and the transient grounding resistance can be prevented from increasing.

  In the transient state, as shown in FIG. 2, the surge current flows through the mesh body 1 and the rod-shaped body 2. That is, the surge current that has flowed into the introduction site 5 spreads throughout the net 1 while following eight paths extending outward. At the same time, the surge current that has flowed into the introduction site 5 is also guided to the first electrode 11 disposed below the introduction site 5, and the flat body 13 of the second electrode 12 has a total axial length of the first electrode 11. Guided to the outer periphery. Furthermore, the surge current guided to the mesh body 1 is also guided to the underground G in the rod-shaped body 2 arranged at the corner of the mesh body 1. Thus, since the net-like body 1 and the rod-like body 2 extend in substantially the same direction as the direction in which the surge current flowing into the underground G spreads from the introduction site 5, the transient grounding resistance can be reduced.

  In the grounding structure of the present invention, the net-like body 1 and the rod-like body 2 have a three-dimensional structure that guides the surge current in a direction substantially the same as the direction in which the surge current flows (spreads) from the introduction site 5. Moreover, since the number of paths extending outward from the introduction site 5 in the mesh dense portion 7 of the mesh body 1 increases, the flow path of surge current can be increased. As a result, the surge current can be shunted in the mesh-tight part 7, and the surge current can be quickly discharged into the ground, and the transient grounding resistance can be reduced.

  When the mesh dense portion wire 9 is slanted, the surge current can be divided into eight directions by the vertical line 3 and the horizontal wire 4 and the mesh dense portion wire 9 to be discharged into the ground, thereby reducing the transient grounding resistance. Can do. In addition, if the wire 9 for the mesh portion is added to the existing mesh body 1, the mesh portion 7 can be easily formed, and measures for reducing the transient ground resistance can be implemented at low cost.

  When the rod-shaped body 2 is composed of the first electrode 11 and the second electrode 12, the second electrode 12 extends in substantially the same direction as the direction in which the surge current flowing into the underground G spreads. Since the guide is guided to the outer peripheral side in the entire axial length, the transient grounding resistance can be reduced with a simple configuration. In addition, the simple configuration makes it light and easy to carry, saving labor for installation, and can reduce the material cost and the processing cost in the manufacture of the electrode, thereby making it possible to manufacture the electrode at low cost.

  Since it has a cross shape with four flat plates 13, it is possible to effectively discharge a surge current into the ground, and it is easy to manufacture and process.

  While the embodiments and examples of the present invention have been described above, the present invention is not limited to these and various modifications can be made. For example, the material and cross-sectional area of the net-like body 1 can be various, and may be a single wire. Various intervals and the number of the vertical lines 3 and the horizontal lines 4 of the net 1 can be set. The number of vertical lines 3 and horizontal lines 4 may be different. Since the rod-shaped body 2 only needs to be at least below the introduction site 5, the rod-shaped body 2 arranged at the corner of the mesh-shaped body 1 may be omitted. The material of the first electrode 11 and the second electrode 12 can be various. The total length of the first electrode 11 and the second electrode 12 can be set to various lengths, and the total length of the first electrode 11 and the total length of the second electrode 12 may be different.

  An experiment for verifying the effectiveness of the grounding structure according to the present invention will be described. In this experiment, the grounding structure as shown in FIG. 6 is embedded in the ground using the experimental circuit shown in FIG. 5, and the potential at the site where the surge current is introduced (point a in FIG. 6) in the grounding structure is grounded. Potentials at a plurality of locations in the structure (points b to e in FIG. 6) were measured. The grounding structure is composed only of a net-like body, and has a lattice shape in which vertical lines and horizontal lines are arranged at 5 m × 5 m. The reticulated body was a 100 sq hard copper strand (HDCC), and the embedding depth from the ground was 1 m. The earth resistivity is 42 Ωm.

  The experimental results are described below. In FIG. 7, the horizontal axis represents time [μs], and the vertical axis represents potential [V]. As shown in FIG. 7A, the maximum potential at point a (surge current introduction site) is 150V. 7B, the maximum potential at the point b is 4.4V, the maximum potential at the point c from FIG. 7C is 11V, the potential at the point d from FIG. 7D is 30V, and FIG. 7E. To e potential was 9.5V. That is, the potential 150V appearing in FIG. 7A, which is the introduction site, is attenuated 97% at point b to 4.4V, similarly 93% attenuated at point c 11V, and attenuated 80% at point d. 30V and at point e, it is 94% attenuated to 9.5V. As a result, measures to reduce the transient grounding resistance are focused on in the vicinity of the introduction part of the mesh body (four grids surrounding the introduction part) that is electrically connected to the grounded object such as a surge arrester into which surge current flows. By doing so, it was found that a large effect can be obtained at a low cost without widely implementing the mesh.

  Next, the frequency characteristics of the grounding resistance of various grounding structures were measured using the experimental circuit shown in FIG. Each ground structure shown in (1), (2), (3), (4), (5), and (6) of FIG. 8 is buried in the ground, and a lightning arrester as a grounded body is connected. A surge current was applied to the introduction site P, and the frequency characteristics of the ground resistance were measured. (1), (2), (3) are comparative examples, and (4), (5), (6) are examples. The size of one mesh of the mesh is 5 m × 5 m. The earth resistivity was 109 Ωm.

  Hereinafter, the experimental results of the comparative example will be described. FIG. 9A shows the frequency characteristics of the ground resistance in (1), (2), and (3) with one graph. The horizontal axis is frequency [Hz], and the vertical axis is ground resistance [Ω]. The frequency region of the surge current is as high as several MHz, and the effectiveness was verified by a ground resistance value at 2 MHz (indicated by an arrow in FIG. 9) (in this embodiment, this value is referred to as a transient ground resistance). The one-dot chain line in the figure indicates (1), the broken line indicates (2), and the solid line indicates (3). It was 88Ω in the ground structure of (1), and 55Ω in (2) and (3). As the frequency increases, the ground resistance increases as the frequency rises as a whole. However, the increase tendency is suppressed by using the rod electrode together.

  Hereinafter, experimental results of the examples will be described. FIG. 9B shows the frequency characteristics of the ground resistance in (4), (5), and (6) with one graph. The horizontal axis is frequency [Hz], and the vertical axis is ground resistance [Ω]. The evaluation of effectiveness is the same as the experimental result of the comparative example. The dashed line in the figure indicates (4), the broken line indicates (5), and the solid line indicates (6). In the ground structure of (4), 50Ω, (5) was 35Ω, and (3) was 23Ω. Although the overall trend is upward, the increasing trend is smaller than that of the comparative example.

Next, the rod-shaped body was buried in the ground, and the frequency characteristics of the ground resistance were measured. In this experiment, three different rods were embedded in the same soil using the experimental circuit shown in FIG. Except for the rod-shaped body, the experimental conditions were the same. As shown in FIG. 10 (a), the rod-shaped body has (1) a spiral electrode formed by twisting a plate steel plate having a width of 150 mm, and (2) 1 shown in FIG. 10 (b). A steel L-shaped electrode having a side of 75 mm and an L-shaped cross section, as shown in FIG. 10 (c), (3) a steel tube first electrode having a diameter of 50 mm, and 90 mm on the outer periphery of the first electrode. A cross-shaped electrode composed of four flat plates each having a width of 100 mm at a pitch was used. (1) and (2) are comparative examples, and (3) is an example. Each grounding body is a steel material having a length of 1 m and a thickness of 4 mm. The surface area of the ground body, (1) and (2) is 0.3 m ^2, (3) is 0.96 m ^2. The earth resistivity is 109 Ωm.

  The experimental results are described below. FIG. 11 shows the frequency characteristics of the ground resistance, where the horizontal axis represents the frequency [Hz] and the vertical axis represents the ground resistance [Ω]. The frequency region of the surge current is as high as several MHz, and the effectiveness was verified by a ground resistance value at 2 MHz (indicated by an arrow in FIG. 11) (in this embodiment, this value is referred to as a transient ground resistance). Moreover, the peak value of the grounding resistance of each grounding body is also seen around 2 MHz. In the figure, the alternate long and short dash line indicates (1) spiral electrode, the broken line indicates (2) L-shaped electrode, and the solid line indicates (3) cross-shaped electrode. From this experimental result, the cross-shaped electrode of (3) shows the lowest resistance value, and the transient ground resistance is (280) for (1), 230Ω for (2), 80Ω for (3) and (3) for the most. It showed a low value. When the steady ground resistance was measured, (1) was 135Ω, (2) was 112Ω, and (3) was 45Ω. The cross-shaped resistance of (3) has a large contact area with soil in the ground compared to other electrodes, so that in addition to being able to reduce the transient ground resistance, the steady ground resistance was also reduced.

Further, in order to measure the relationship between the shape of the second electrode and the grounding resistance, two different grounding bodies were embedded in the same ground using the experimental circuit shown in FIG. The experimental conditions were the same except for the shape of the grounding body. As shown in FIG. 12, each of the grounding bodies is (1) a disc body additional electrode in which four discs having a diameter of 250 mm are added to a steel pipe having a diameter of 50 mm and a length of 4 m at an equal pitch (1 m interval) along the axial direction. (2) A cross-shaped electrode in which four flat plates having a width of 100 mm and a length of 4 m were added to a steel pipe having a diameter of 50 mm and a length of 4 m at an equal pitch (90 ° interval) along the circumferential direction was used. Each grounding body is a steel material having a thickness of 4 mm. The surface area of the ground body, (1) is 1.02 m ^2, (2) is 3.83 m ^2. (1) is a comparative example, and (2) is an example. (1) The disc body additional electrode and (2) the cruciform electrode both have a flat plate that guides the surge current introduced into the steel tube at the center of the electrode to the outer peripheral side, but (1) is larger in shape than the steel tube. Although it is a circular plate having a diameter, (2) is a rectangular plate having the same length as the steel pipe. These measurement results are shown in Table 1.

  Table 1 shows measured values of the transient grounding resistance and the steady grounding resistance of the (1) disk-shaped additional electrode and (2) the cross-shaped electrode in Example 4.

  From Table 1, (2) the cross-shaped electrode was lower by about 20% in the transient grounding resistance and about 47% in the steady grounding resistance, based on the (1) disk-shaped additional electrode. That is, as in (1), even if it has a portion protruding in the circumferential direction from the steel pipe, the effect of reducing the transient grounding resistance is thin unless it extends continuously along the axial direction of the steel pipe. Therefore, if the grounding body is cross-shaped and the flat body extends over substantially the entire length in the axial direction of the first electrode, it is effective in reducing the transient grounding resistance, and in addition, effective in reducing the steady grounding resistance. It is.

DESCRIPTION OF SYMBOLS 1 Reticulated body 2 Rod-shaped body 3 Vertical line 4 Horizontal line 5 Introduction part 7 Reticulated part 9 Reticulated part wire 11 First electrode 12 Second electrode 13 Flat plate G Underground

Claims (5)

A grounding structure comprising a mesh body that is electrically connected to a grounded body and introduces a surge current from the grounded body in a state of being embedded in a substantially horizontal shape in the ground,
The net-like body has a predetermined steady ground resistance with a plurality of vertical lines arranged in parallel at a predetermined interval and a plurality of horizontal lines orthogonal to the vertical line and arranged in parallel at a predetermined interval. A grid-like mesh is formed so that
With the predetermined intersection of the vertical line and the horizontal line excluding the outer edge as the introduction part, a wire rod for a mesh-dense part is arranged in a range surrounded by other intersections around the introduction part, and this range is a mesh-dense part A grounding structure characterized by   The grounding structure according to claim 1, wherein the wire rod for the mesh-tight portion is a diagonal line connecting the introduction portion and an intersection point on the diagonal line of the lattice from the introduction portion.   A rod-like body that is provided perpendicular to the mesh body at the site where the surge current is introduced from the grounded body of the mesh body and guides the surge current introduced by the mesh body into the ground is provided. The grounding structure according to claim 1 or 2, characterized in that   The rod-shaped body is a solid or hollow column body, and includes a first electrode for introducing a surge current from the grounded body into the ground, and a plurality of flat plates projecting radially from the outer periphery of the first electrode. And a second electrode for guiding a surge current from the first electrode to the outer peripheral side, and the flat plate body of the second electrode extends substantially along the entire length in the axial direction of the first electrode and extends along the circumferential direction. The grounding structure according to claim 3, wherein the grounding structures are arranged at equal intervals so that the protruding lengths in the radial direction are the same.   5. The grounding structure according to claim 4, wherein the rod-shaped body has a cross shape having four flat plates.

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