JP2010261506A - Buried pipe shielding structure and buried pipe shielding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problems that a buried pipe shielding structure causes troublesome burying work, and a working space is required therefor. <P>SOLUTION: The buried pipe shielding structure is a buried pipe shielding structure for protecting a buried pipe as an electric conductive pipe with an insulation coating applied thereon, against lightning damage, and a linear electric conductor is disposed along the buried pipe between the buried pipe and the ground surface. Further, the buried pipe shielding method is a buried pipe shielding method for protecting the buried pipe as the electric conductive pipe with an insulation coating applied thereon, against lightning damage, and earth and sand of a predetermined thickness are laid on the buried pipe disposed in a groove. The linear electric conductor is disposed on the earth and sand from above the buried pipe, and the groove is buried by laying earth and sand on the linear electric conductor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a buried pipe shielding structure and a buried pipe shielding method for protecting a buried pipe having an insulating coating on a conductive pipe from lightning damage.

In recent years, the occurrence of localized torrential rain and lightning has tended to increase. Polyethylene is widely used as an outer surface anticorrosive material for buried pipes such as city gas. FIG. 1 is a cross-sectional view of a buried pipe 10 in which an insulating coating 11 is applied to a conductive pipe 12. As the ground potential increases due to lightning strikes, ground faults, etc., there is a concern about the insulation breakdown of the insulation coating (polyethylene). FIG. 2 is a diagram showing the relationship between the dielectric breakdown of the polyethylene insulating coating and the voltage. For example, when the insulation coating thickness of polyethylene is 2.5 × 10 ⁻³ m, dielectric breakdown occurs when a voltage of about 200 kV is applied. Gas leakage accidents may occur due to dielectric breakdown during lightning strikes.

  As a countermeasure against lightning, gas companies have been shielded by sheath tubes and protective iron plates. FIG. 3 is a cross-sectional view showing a buried pipe shielding structure using the sheath pipe 20. FIG. 4 is a cross-sectional view showing a buried pipe shielding structure using the protective iron plate 30. Simulation results showing the effects of these buried pipe shielding structures will be described later.

  Further, Non-Patent Document 1 is known as a conventional technique for protecting a communication cable from a direct lightning strike using a buried ground wire. FIG. 5 is a cross-sectional view (communication cable connection point) when a buried ground wire 41 made of a bare steel strand is buried above a direct communication cable (a communication cable buried directly in the ground) 40. At the communication cable connection point, the metal sheath of the direct communication cable 40 and the buried ground wire 41 are connected by a copper wire or the like.

Kijima Hitoshi, "Grounding and Lightning Protection", The Institute of Electronics, Information and Communication Engineers, April 10, 1997, pp94-100, pp164-166

However, the buried pipe shielding structure by the sheath pipe 20 needs to insert the buried pipe 10 from the opening of the sheath pipe after the sheath pipe 20 is installed in the groove. Therefore, there is a problem that the embedding work becomes complicated.
Further, the buried pipe shielding structure by the protective iron plate 30 or the like has the protective iron plate 30A installed on the side of the groove, and then lays earth and sand, installs the buried pipe 10 and lays earth and sand again, and further on the protective iron plate. There is a problem that it is necessary to install 30B and spread earth and sand, and the burial work becomes complicated.

  Moreover, since the nonpatent literature 1 connects the metal sheath of the direct communication cable 40, and the buried ground wire 41 with the copper wire 42, an operation | work becomes complicated. In Non-Patent Document 1, the direct communication cable 40 is protected from direct lightning strike using the buried ground wire 41, and the ratio of current flowing into the metal sheath of the direct communication cable 40 is reduced to about ½. For the purpose. This is not to prevent insulation breakdown of the insulation coating (polyethylene), but to reduce the risk of electric shock when an operator or the like is performing any work on the direct communication cable. Therefore, in the first place, the technical idea is different from the present invention for preventing the dielectric breakdown of the buried pipe with the insulating coating.

  In order to solve the above-described problems, the buried pipe shielding structure according to the present invention is a buried pipe shielding structure that protects a buried pipe having an insulating coating on a conductive pipe from lightning damage, and includes a linear conductor. Then, it was arranged along the buried pipe between the buried pipe and the ground surface.

  Further, the buried pipe shielding method according to the present invention is a buried pipe shielding method for protecting a buried pipe having an insulating coating on a conductive pipe from lightning damage, and is previously placed on the buried pipe disposed in the groove. A predetermined thickness of earth and sand is laid, a linear conductor is placed on the earth and sand along the buried pipe, and the groove is filled by laying earth and sand on the linear conductor.

  The present invention has an effect of providing a lightning protection effect sufficient for preventing dielectric breakdown and facilitating burial work.

The figure which shows the burial example of a burial pipe. The figure which shows the voltage which carries out a dielectric breakdown. The figure which shows the buried pipe shielding structure using a sheath pipe. The figure which shows the buried pipe shielding structure using a protection iron plate. The figure which shows the example of embedding of the nonpatent literature 1. It is an electric field distribution diagram in the case of no shielding. FIG. 7 is an electric field distribution diagram when shielded by a linear conductor 51. (A) is a perspective view showing a configuration example of an embedded pipe shielding structure 100 including a linear conductor 51 and an embedded pipe 10, and (B) is a cross-sectional view perpendicular to the longitudinal direction of the embedded pipe 10. (A) is a space | interval ensuring step, (B) is a linear conductor arrangement | positioning step, (C) is a figure for demonstrating a backfilling step. (A) is a perspective view showing a configuration example of an embedded pipe shielding structure 200 composed of a linear conductor 61 (half cracked pipe) and an embedded pipe 10, and (B) is a sectional view perpendicular to the longitudinal direction of the embedded pipe 10. . The perspective view which shows the structural example of the buried pipe shielding structure 300 which consists of several linear conductors 71 and the buried pipe 10. FIG. The figure which shows the model of a lightning surge. The figure which shows the flow of the electric current when not shielding. The figure which shows the flow of the electric current of Example 1. FIG. (A) is a cross-sectional view when the cross section is a triangle, (B) is a cross-sectional view when the cross section is a quadrangle, (C) is a cross-sectional view when the linear conductor is a stranded wire, and (D) is a linear conductor. Sectional view when the body is plate-shaped, (E) is a sectional view when the linear conductor is a square column half-cracked tube, and (F) is a section when the linear conductor is a hexagonal column half-cracked tube Figure.

[Discussion]
FIG. 6 is an electric field distribution diagram without shielding. FIG. 7 is an electric field distribution diagram when shielded by the linear conductor 51. As can be seen from FIG. 6, the potential of the upper portion of the buried pipe 10 immediately below the lightning strike increases. On the other hand, the buried pipe 10 is provided with an insulating coating on a conductive pipe, and the conductive pipe is grounded at a distance. Therefore, the potential of the conductive tube is 0V (same as ground). Therefore, a strong electric field is generated in the insulating coating. This causes dielectric breakdown. On the other hand, when shielded by the linear conductor 51, since the linear conductor 51 is disposed between the buried pipe 10 and the ground surface in parallel with the buried pipe 10, the linear conductor 51 is equipotential. Thus, a dispersed electric field is generated in the insulating coating of the buried pipe 10 (see FIG. 7). Therefore, unlike the case of FIG. 6, since the electric field does not concentrate on one point, it is considered that dielectric breakdown does not occur. The present invention protects the buried pipe 10 from dielectric breakdown based on the above principle. The simulation results supporting the above principle will be described later. Hereinafter, embodiments of the present invention will be described in detail.

<Built-in pipe shielding structure 100>
The buried pipe shielding structure 100 according to the first embodiment will be described with reference to FIG. FIG. 8A is a perspective view showing a configuration example of the buried pipe shielding structure 100 including the linear conductor 51 and the buried pipe 10, and FIG. 8B is a cross-sectional view perpendicular to the longitudinal direction of the buried pipe 10. The buried pipe shielding structure 100 includes the linear conductor 51 and the buried pipe 10 and can protect the buried pipe 10 from lightning damage.

<Embedded pipe 10>
As shown in FIG. 1, the buried pipe 10 is provided with an insulating coating 11 on a conductive pipe 12. For example, a gas pipe or the like. For example, the distance (for example, 1.5 m) between the upper portion of the buried pipe 10 and the ground surface is ³ to 4 times (for example, about 3.6 times) the outer diameter (for example, 411.4 × 10 ⁻³ m) of the buried pipe 10.

<Linear conductor 51>
The linear conductor 51 is disposed along the buried pipe 10 only between the buried pipe 10 and the ground surface. For example, the linear conductor 51 and the buried pipe 10 may be arranged substantially in parallel, or may be arranged so that the central axis of the buried pipe 10 and the central axis of the linear conductor 51 substantially overlap in the vertical direction. . For example, the linear conductor 51 is a buried ground wire having a circular cross section.

For example, the diameter of the cross section (for example, 20 × 10 ⁻³ m) is 0.025 to 0.1 times (for example, about 0.049 times) the outer diameter (for example, 411.4 × 10 ⁻³ m) of the buried pipe 10. At this time, the distance (for example, 290 × 10 ⁻³ m) between the upper portion of the embedded tube 10 and the center of the linear conductor 51 is 0.5 to 0.5 of the outer diameter (for example, 411.4 × 10 ⁻³ m) of the embedded tube 10. 1.5 times (for example, about 0.70 times).
With such a configuration, it is possible to configure the buried pipe shielding structure 100 that has a sufficient lightning protection effect to prevent dielectric breakdown and that can be easily buried.

<Embedding method>
FIG. 9A is a diagram for explaining an interval securing step, FIG. 9B is a diagram for explaining a linear conductor arranging step, and FIG. 9C is a diagram for explaining a backfilling step. A predetermined thickness of earth and sand is laid on the buried pipe 10 disposed in the groove. Thereby, the space | interval of the buried pipe 10 and the linear conductor 51 is ensured (space | interval ensuring step). The linear conductor 51 is arranged along only the earth and sand from above the buried pipe (linear conductor arrangement step). Further, the trench is filled by laying earth and sand on the linear conductor 51 (backfilling step).

  In the prior art, in order to protect the buried pipe 10, it is considered necessary to enclose the whole with a sheath pipe 20 or cover a portion other than between the buried pipe 10 and the ground surface with a protective iron plate 30 or the like. It was. However, according to the present invention, it has been clarified by simulation that the linear conductor 51 may be disposed only between the buried pipe 10 and the ground surface. Accordingly, the inventors have invented a buried pipe shielding structure and method that have a sufficient lightning protection effect to prevent dielectric breakdown and are easy to bury.

[Modification 1]
Only parts different from the first embodiment will be described. The shape of the linear conductor is different from that of Example 1. FIG. 10A is a perspective view showing a configuration example of a buried pipe shielding structure 200 composed of a linear conductor 61 (half cracked pipe) and the buried pipe 10, and FIG. 10B is a view perpendicular to the longitudinal direction of the buried pipe 10. It is sectional drawing.
<Linear conductor 61>
The linear conductor 61 is a half-cracked tube with the expanded portion on the bottom. For example, the linear conductor 61 and the buried pipe 10 may be arranged substantially in parallel, or may be arranged so that the central axis of the buried pipe 10 and the central axis of the half cracked pipe substantially overlap in the vertical direction. For example, the linear conductor 61 has an arched cross section.

For example, the inner diameter (for example, 589.0 × 10 ⁻³ m) of the half-cracked tube is equal to or larger than the outer diameter (for example, 411.4 × 10 ⁻³ m) of the buried pipe 10, and the distance between the upper portion of the buried pipe 10 and the ground surface ( For example, 1.5 m) is ³ to 4 times (for example, about 3.6 times) the outer diameter of the buried pipe 10 (for example, 411.4 × 10 ⁻³ m), and the distance between the upper part of the buried pipe 10 and the half-cracked pipe ( For example, 300 × 10 ⁻³ m) is 0.5 to 1.5 times (for example, about 0.73 times) the outer diameter of the buried pipe (for example, 411.4 × 10 ⁻³ m).
By adopting such a configuration, unlike the sheath tube 20, the linear conductor 61 can be disposed so as to cover the buried tube 10 from above, and the same effect as in the first embodiment can be obtained.

[Modification 2]
Only parts different from the first embodiment will be described. The shape of the linear conductor is different from that of Example 1. FIG. 11 is a perspective view illustrating a configuration example of an embedded pipe shielding structure 300 including a plurality of linear conductors 71 and the embedded pipe 10.
<Linear conductor 71>
There are a plurality of linear conductors 71, and the plurality of conductors 71 are arranged in tandem along the buried pipe 10 between the buried pipe 10 and the ground surface. Furthermore, the linear conductors 71 are not connected to each other. For example, the linear conductor 71 and the buried pipe 10 may be arranged substantially in parallel, or the central axis of the buried pipe 10 and the central axis of the linear conductor 71 may be arranged substantially in the vertical direction. . For example, the linear conductor 71 has a circular cross section. The plurality of conductors 71 may be disposed only between the buried pipe 10 and the ground surface as in the first embodiment.

For example, the distance between the linear conductors 71 (for example, 100 × 10 ⁻³ m) is 0.25 times or less (for example, 0.24 times) the outer diameter (for example, 411.4 × 10 ⁻³ m) of the buried pipe 10. It is. Further, for example, the length (for example, 1.0 m) of each linear conductor 71 is at least twice (for example, 2.4 times) the outer diameter (for example, 411.4 × 10 ⁻³ m) of the buried pipe 10.

<Embedding method>
The embedding method of the modification 2 is demonstrated using FIG. A predetermined thickness of earth and sand is laid on the buried pipe 10 disposed in the groove. Thereby, the space | interval of the buried pipe 10 and the linear conductor 71 is ensured (space | interval ensuring step). A plurality of linear conductors 71 are arranged in tandem along the buried pipe in a state where they are not connected to each other on the earth and sand (linear conductor arrangement step). Further, the trench is filled by laying earth and sand on the linear conductor 71 (backfilling step).

Note that “not connected” means not electrically connected by welding or screwing. In the prior art, it has been considered that the sheath tube and the protective iron plate need to be electrically connected. However, according to the present invention, it has been clarified by simulation that the linear conductors may be arranged in a line at a predetermined interval or less even if they are not electrically connected. Accordingly, the inventors have invented a buried pipe shielding structure and method that have a sufficient lightning protection effect to prevent dielectric breakdown and are easy to bury. By adopting such a configuration, the same effect as in the first embodiment can be obtained. Furthermore, the length of each linear conductor can be made easy to handle, and the arrangement becomes easy. Each linear conductor does not need to be electrically connected by welding or the like. Even when the linear conductors are in contact with each other at the time of arrangement, the same effects as those of the first embodiment can be obtained. The worker can install the device without worrying about the distance between the linear conductors 71 and can perform the work quickly and easily.
It should be noted that the same effect can be obtained even when the semi-cracked tube-shaped conductor of Modification 1 is used as a plurality of conductors.

[simulation result]
Using the finite element method, lightning damage countermeasure simulation is performed using JMAG, a magnetic field analysis software made by the Japan Research Institute. The finite element method is described in detail by Takayoshi Nakata and Norio Takahashi, “Fine Element Method of Electrical Engineering”, Morikita Publishing, July 15, 1982.

<Simulation conditions>
As shown in FIG. 1, the burial depth of the burial pipe 10 is set to a general depth of 1.5 m. The conductive tube 12 is made of steel and has an inner diameter of 387.4 × 10 ⁻³ m, an outer diameter of 406.4 × 10 ⁻³ m, a steel pipe thickness of 9.5 × 10 ⁻³ m, a tube length of 20.0 m, and a volume resistivity of 1.5 × 10 ⁻⁷ Ω · m and relative permeability 280. The insulating coating 12 is made of polyethylene, and has an insulating coating thickness of 2.5 × 10 ⁻³ m, an insulating coating length of 20.0 m, a volume resistivity of 1.0 × 10 ¹⁴ Ω · m, and a relative dielectric constant of 2.3. The outer diameter of the buried pipe 10 including the insulating coating 12 is 411.4 × 10 ⁻³ m.
FIG. 2 shows that the insulation breakdown voltage of polyethylene is 200 kV (= 2.0E + 5V) when the insulation coating thickness is 2.5 × 10 ⁻³ m. This value is compared with the value calculated by simulation to examine how much the shielding effect is.

  Assume that a lightning surge strikes the ground directly. Create a model in which currents flow in parallel. The lightning surge model requires a current to flow to an infinite point on the earth, but the analysis is complicated. Therefore, the model shown in FIG. 12 is analyzed at 100 kA, 1 Hz, which is not affected by eddy currents. In order to examine the shielding effect due to the difference in soil resistance, the soil resistivity ρs was set to 30, 100, and 1000 Ω · m. The low soil efficiency ρs = 30Ω · m corresponds to Tabata, ρs = 100Ω · m corresponds to the Kanto Loam layer, and ρs = 1000Ω · m corresponds to the mountainous area.

<No shielding>
FIG. 13 shows the flow of current when shielding is not performed. From FIG. 13, it can be seen that currents flow in parallel. It was also found that a very large current flows through the buried pipe 10. Table 1 shows the electric field strength at the position of the buried pipe 10 when shielding is not performed.

In the future, for comparison, the electric field strength without shielding is assumed to be 100%. Next, dielectric breakdown of the insulation coating (soil resistance ρs = 100Ω · m) is considered. Since the voltage is the integration of the electric field strength up to 1.5m,
2.64E + 7V >> 2.0E + 5V
It became. From this result, it was found that a voltage exceeding the dielectric breakdown voltage value of polyethylene was applied, and if no countermeasures were taken, the insulation coating would cause dielectric breakdown and had holes.

<Sheath tube 20>
Table 2 shows the electric field strength at the position of the buried pipe 10 when the sheath pipe 20 is shielded as shown in FIG. The burial depth of the sheath tube 20 is 1.4 m underground, the sheath tube 20 is made of steel, the inner diameter is 589.0 × 10 ⁻³ m, the outer diameter of the sheath tube is 609.6 × 10 ⁻³ m, and the sheath tube thickness is 10.3 × 10. ^-3 m, sheath tube length 20.0 m, volume resistivity 1.5 × 10 ⁻⁷ Ω · m, relative permeability 280.

When the sheath tube 20 is used, the electric field strength is significantly lower than that without shielding, and it is clear that shielding is possible. Current flows more evenly than without shielding. It is estimated that the current from all directions could be shielded by surrounding the entire surface of the buried pipe 10 with the sheath pipe 20. Considering the dielectric breakdown of the insulation coating (soil resistance ρs = 100 Ω · m)
1.90E + 3V << 2.0E + 5V
It became. From this result, it was found that the dielectric breakdown voltage value of polyethylene was lower. This is considered to be a very effective protective measure when the sheath tube 20 is used. However, as described above, there is a problem that the embedding operation becomes complicated and requires a work space more than double that of the sheath tube.

<Protective iron plate 30>
Table 3 shows the electric field strength at the position of the buried pipe 10 when shielded using the protective iron plates 30A and 30B as shown in FIG. The depth of the protective iron plate 30B is 1.2m underground, the protective iron plate is 1.0m wide, the protective iron plate thickness is 6.0 × 10 ^-3 m, the protective iron plate length is 20.0 m, and the volume resistivity is 1.5 × 10 ^-7 Ω. m, relative permeability 280, and the distance between the protective iron plate 30A and the buried pipe 10 is 0.3 m.

From Table 3, it can be seen that the electric field strength is lower than that without shielding. Although the current is cut off by the upper and left protective iron plates, the current does not surround the entire surface of the buried pipe 10 like the sheath pipe 20, so that the current from the right side and the lower side without the protective wall is shielded. It is speculated that this was not possible. Considering the dielectric breakdown of the insulation coating (soil resistance ρs = 100 Ω · m)
4.01E + 4V << 2.0E + 5V
It became. From this result, it was found that the dielectric breakdown voltage value of polyethylene was lower. Even when a protective iron plate is used, it can be said that it can be an effective protective measure. However, as described above, there is a problem that the embedding work becomes complicated.

<Linear conductor 51 (one)>
FIG. 14 shows a current flow of the first embodiment. The buried depth of the linear conductor 51 is 1.2 m underground, the radius of the linear conductor 51 is 1.0 × 10 ⁻² m, the length of the linear conductor is 20.0 m, the volume resistivity is 1.5 × 10 ⁻⁷ Ω · m, The relative permeability is 280. Table 4 shows the electric field strength at the position of the buried pipe 10 when the linear conductor 51 is used as shown in FIG.

From Table 4, it can be seen that the electric field strength is extremely reduced as compared with the case without shielding. Further, it can be seen from FIG. 14 that the way of current flow is more parallel than when there is no shielding and is concentrated on the linear conductor 51. It is presumed that most of the current gathered in the linear conductor 51 and protected the buried pipe 10 by burying the linear conductor 51 having a high conductivity above the buried pipe 10. Considering the dielectric breakdown of the insulation coating (soil resistance ρs = 100 Ω · m)
3.31E + 3V << 2.0E + 5V
It became. From this result, it was found that the dielectric breakdown voltage value of polyethylene was much lower. An excellent shielding effect can be expected as a shielding measure.

<Linear conductor 61 (half cracked tube)>
Table 5 shows the electric field strength at the position of the buried tube 10 when shielded by using the cracked tube-shaped linear conductor 61 as shown in FIG. The embedded depth of the linear conductor 61 is 1.2 m underground, and the inner diameter, outer diameter, thickness, length, volume resistivity, and relative permeability are the same as those of the sheath tube 20.

Even when the linear conductor 61 is used, the voltage is greatly reduced as compared with the case without shielding, and it can be seen that shielding is possible. Current flows more evenly than without shielding. It is presumed that the current could be shielded by surrounding the upper half of the buried pipe 10 with the linear conductor 61. Considering the dielectric breakdown of the insulation coating (soil resistance ρs = 100 Ω · m)
5.84E + 3V << 2.0E + 5V
It became. From this result, it was found that the dielectric breakdown voltage value of polyethylene was lower. This provides a very effective protective measure when the linear conductor 61 is used.

<Linear conductor 71 (plural)>
Table 6 shows the electric field strength at the position of the buried pipe 10 when shielded by using a plurality of linear conductors 71 as shown in FIG. The embedded depth, radius, volume resistivity, and relative permeability of the linear conductor 71 are the same as those of the linear conductor 51. The length of each linear conductor 71 is 1.0 m, and the distance between the linear conductors is 0.1 m.

Similar to the linear conductor 51, the current flows in parallel and concentrates on the linear conductor 71. Further, even if 1 m linear conductors 71 are installed at an interval of 10 cm, it can be considered that they can be shielded almost in the same manner as one in which one linear conductor 51 is embedded. Considering the dielectric breakdown of the insulation coating (soil resistance ρs = 100 Ω · m)
3.56E + 3V << 2.0E + 5V
It became. From this result, it was found that the dielectric breakdown voltage value of polyethylene was much lower. An excellent shielding effect can be expected as a shielding measure.

<Summary>
Considering the electric field strength, 0.000019% is shielded by the sheath tube 20, 0.0062% is shielded by the protective iron plate, and the linear conductor 51 (1) is compared with the state without the shield (soil resistance ρs = 100Ω · m). Data obtained were 0.000055% by shielding, 0.000021% by shielding by a half-broken tube-shaped linear conductor 61, and 0.099% by shielding by a linear conductor 71 (plural).
Table 7 shows the voltage evaluation of various measures.

From Table 7, the order of the protection methods that can provide the shielding effect is as follows: shielding by the linear conductor 51 (single), shielding by the linear conductors 71 (plural), shielding by the sheath tube 20, and a semi-cracked tubular linear It became clear that the shielding by the conductor 61 and the shielding by the protective iron plate 30 were made.
In consideration of construction cost, construction time, etc., shielding by the linear conductors 71 (multiple) is considered to be the most effective buried pipe shielding structure.
From the above simulation results, it can be seen that the present invention has a lightning protection effect equivalent to or better than that of the prior art, and is easy to bury.

  In addition, Example 1, Modification 1 and Modification 2 do not limit the content of the invention. For example, the linear conductor may be a stranded wire, or may have a polygonal shape such as a triangle or a quadrangle other than a circle. Further, instead of a cylindrical half cracked tube, a prismatic half cracked tube may be used. 15A is a cross-sectional view when the cross section is a triangle, FIG. 15B is a cross-sectional view when the cross section is a quadrangle, FIG. 15C is a cross-sectional view when the linear conductor is a stranded wire, and FIG. (E) is a cross-sectional view when the linear conductor is a square column half-cracked tube, and (F) is a case where the linear conductor is a hexagonal column half-cracked tube. FIG. Even when such a linear conductor is used, the same effect as in the first embodiment can be obtained. Further, the material, thickness, radius, inner diameter, outer shape, and the like of the buried pipe and the linear conductor can be changed as appropriate, such as the distance to the ground surface.

10 buried pipes 51, 61, 71 linear conductors 100, 200, 300 buried pipe shielding structure

Claims (10)

A buried pipe shielding structure for protecting a buried pipe with an insulating coating on a conductive pipe from lightning damage,
A buried pipe shielding structure characterized in that a linear conductor is disposed along the buried pipe only between the buried pipe and the ground surface. A buried pipe shielding structure for protecting a buried pipe with an insulating coating on a conductive pipe from lightning damage,
A buried pipe shielding structure in which a plurality of linear conductors are arranged in a column along the buried pipe between the buried pipe and the ground surface, and the linear conductors are not connected to each other. . The buried pipe shielding structure according to claim 2,
The buried pipe shielding structure, wherein an interval between the linear conductors is 0.25 times or less of an outer diameter of the buried pipe. The buried pipe shielding structure according to any one of claims 1 to 3,
The linear conductor is a buried ground wire having a circular cross section,
The diameter of the cross section of the buried ground wire is 0.025 to 0.1 times the outer diameter of the buried pipe,
The distance between the upper part of the buried pipe and the ground surface is 3 to 4 times the outer diameter of the buried pipe,
The buried tube shielding structure, wherein the distance between the upper portion of the buried pipe and the center of the linear conductor is 0.5 to 1.5 times the outer diameter of the buried pipe. The buried pipe shielding structure according to any one of claims 1 to 3,
The linear conductor is a half-cracked tube with the expanded portion underneath,
The inner diameter of the half cracked tube is equal to or greater than the outer diameter of the buried tube,
The distance between the upper part of the buried pipe and the ground surface is 3 to 4 times the outer diameter of the buried pipe,
The buried pipe shielding structure, wherein a distance between the upper part of the buried pipe and the upper part of the half cracked pipe is 0.5 to 1.5 times the outer diameter of the buried pipe. A buried pipe shielding method for protecting a buried pipe with an insulating coating on a conductive pipe from lightning damage,
An interval securing step for spreading earth and sand having a predetermined thickness on the buried pipe disposed in the groove;
A linear conductor arranging step for arranging a linear conductor only on the earth and sand along the buried pipe from above,
A backfilling step of filling the groove by laying earth and sand on the linear conductor;
A buried pipe shielding method characterized by comprising: A buried pipe shielding method for protecting a buried pipe with an insulating coating on a conductive pipe from lightning damage,
An interval securing step for spreading earth and sand having a predetermined thickness on the buried pipe disposed in the groove;
A plurality of linear conductors on the earth and sand, arranged in a column along the buried pipe in a state where they are not connected to each other;
A backfilling step of filling the groove by laying earth and sand on the linear conductor;
A buried pipe shielding method characterized by comprising: The buried pipe shielding method according to claim 7,
The space | interval of the said linear conductors is 0.25 times or less of the outer diameter of the said buried pipe. The buried pipe shielding method characterized by the above-mentioned. The buried pipe shielding method according to any one of claims 6 to 8,
The linear conductor is a buried ground wire having a circular cross section,
The diameter of the cross section of the buried ground wire is 0.025 to 0.1 times the outer diameter of the buried pipe,
The distance between the upper part of the buried pipe and the ground surface is 3 to 4 times the outer diameter of the buried pipe,
The buried pipe shielding method, wherein the distance between the upper part of the buried pipe and the center of the linear conductor is 0.5 to 1.5 times the outer diameter of the buried pipe. The buried pipe shielding method according to any one of claims 6 to 8,
The linear conductor is a half-cracked tube with the expanded portion underneath,
The inner diameter of the half cracked tube is equal to or greater than the outer diameter of the buried tube,
The distance between the upper part of the buried pipe and the ground surface is 3 to 4 times the outer diameter of the buried pipe,
The distance between the upper part of the buried pipe and the upper part of the half cracked pipe is 0.5 to 1.5 times the outer diameter of the buried pipe.

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