Restraint device and restraint method

Abstract

The present invention provides a restraint device and restraint method that improve the safety of cable equipment. [Solution] The restraint device 1 includes restraints 11 to 14 and leg members 15 and 16. The restraints 11 to 14 restrain the power cable 2 by applying surface pressure to the power cable 2 from around the power cable 2 in two or more axial directions, and in directions where the central angle of the power cable 2 is equally divided by each axis. The leg member 15 is connected to the restraint 12 and fixed to the mounting base 9. The leg member 16 is connected to the restraint 13 and fixed to the mounting base 9.

Description

[Technical Field]

[0001] The present invention relates to a restraint device and a restraint method. [Background technology]

[0002] In areas where it is difficult to construct new power transmission towers, such as cities and urban areas, electricity is generally transmitted using underground power transmission systems. In underground power transmission systems, power cables for transmitting electricity are buried in the ground. By burying the power cables in the ground, the effects of natural phenomena such as storms and snow are minimized, allowing for safe and reliable electricity transmission.

[0003] In this type of underground power transmission system, there is a method called the conduit system, in which power cables are buried in the ground while protected using pipes made of reinforced plastic or similar materials. In the conduit system, manholes are installed along the conduit to connect the power cables.

[0004] In some cases, there are differences in ground elevation between manholes, causing the conduit to slope. In such cases, changes in the transmission current of the power cable can cause temperature changes in the cable conductor, as well as changes in the ground temperature around the conduit. This can cause the cable conductor to expand and contract longitudinally, leading to the entire power cable moving from a higher position to a lower position. Additionally, in power cables laid in conduits buried under roads with heavy traffic and soft ground, a phenomenon called "cable wave-riding" can occur, causing the power cable to move in the direction of vehicle movement.

[0005] If cable movement progresses excessively, unexpected tension may be generated near connection points where the cable load changes within the manhole, potentially damaging the cable equipment. To counteract this cable movement, restraining devices called cleats are sometimes installed inside manholes. Cleats are used to restrain the longitudinal movement of power cables.

[0006] The structure of a conventional cleat, as defined by unified specifications from power companies and other organizations, is as follows: The cleat is roughly cylindrical with a hollow interior, and is divided into an upper cleat section and a lower cleat section by dividing the cylinder in half at both ends. Rubber spacers are fitted into the inner surfaces of both the upper and lower cleat sections. The upper and lower cleat sections are positioned with their inner surfaces facing each other, sandwiching the power cable. Then, a force such as a spring applies pressure to the upper and lower cleat sections in the direction they are facing each other. This pressure creates surface pressure on the power cable from the upper and lower cleat sections. Based on this surface pressure, the frictional force between the cable corrosion protection layer and the rubber spacers causes the cleat to restrain the longitudinal movement of the power cable.

[0007] Increasing the pressure of the cleat and thereby increasing the surface pressure with the cable corrosion protection layer can increase the restraining force of the cable. However, excessively increasing the surface pressure can deform the cable, potentially damaging the cable metal shielding layer and other components within the cable, which could lead to electrical accidents. To prevent this, based on experimental confirmation of the surface pressure at which the cable is not damaged, the cleat is used at a surface pressure below which the cable is not damaged.

[0008] One proposed cleat technology involves housing the cleat in a frame, fixing the cleat to the frame with the cleat gripping angle matched to the cable's incident angle, and then fixing the frame to the inner wall of the manhole near the cable's conduit opening. Another proposed technology uses a frame similarly, but with a structure that allows the frame to be fixed to the inner wall of the manhole, away from the manhole's inner wall, in a location other than near the power cable's conduit opening. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2014-39402 [Patent Document 2] Japanese Patent Publication No. 2019-68502 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, conventional cleat structures grip the cable in a uniaxial direction perpendicular to the cleat's mounting surface, applying surface pressure. In this structure, the surface pressure applied to the cable corrosion protection layer is maximum in the direction of the axis to which the surface pressure is applied. As the angle with respect to the axis increases, the surface pressure decreases, and at a 90-degree angle, there is almost no surface pressure. Therefore, at positions with a large angle to the uniaxial direction to which the surface pressure is applied, the surface pressure is not reflected in the restraining force, and the restraining force on the power cable decreases. Furthermore, since the surface pressure is not constant depending on the angle direction with respect to the cable corrosion protection layer, if a moving force is applied to the power cable when the restraint is insufficient, the grip by the cleat becomes unstable, which may damage the power cable.

[0011] Furthermore, in all of the aforementioned techniques for housing and fixing cleats within a frame, the method of restraining power cables is the same as that of conventional cleats. Therefore, even using these techniques, sufficient restraining force cannot be obtained, making it difficult to improve the safety of cable equipment.

[0012] The present invention has been made in view of the above, and aims to provide a restraining device and restraining method that improve the safety of cable equipment. [Means for solving the problem]

[0013] In the present invention, the restraint device restrains the power cable by applying surface pressure to the power cable from two or more axial directions around the power cable, and from directions in which the central angle of the power cable is equally divided by each axis. The leg members are connected to the restraint device and fixed to the mounting base. [Effects of the Invention]

[0014] According to the present invention, the safety of cable facilities can be improved.

Brief Description of Drawings

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing an overview of the cleat according to Example 1. [Figure 2] FIG. 2 is a view showing an example of a cable cross-section. [Figure 3] FIG. 3 is a flowchart showing the procedure for restraining a power cable with a cleat. [Figure 4] FIG. 4 is a schematic diagram showing the application of surface pressure by a cleat. [Figure 5] FIG. 5 is a cross-sectional view showing an overview of a uniaxially restrained cleat. [Figure 6] FIG. 6 is a view showing the conditions used for comparison. [Figure 7] FIG. 7 is a perspective view of the cleat according to Example 2. [Figure 8] FIG. 8 is a cross-sectional view showing an overview of the cleat according to Example 2. [Figure 9] FIG. 9 is a perspective view of the cleat restraining a triplex cable. [Figure 10] FIG. 10 is a cross-sectional view showing an overview of the cleat restraining a triplex cable.

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the restraining device and restraining method disclosed by the present invention will be described in detail based on the drawings. Note that the restraining device and restraining method disclosed by the present invention are not limited by the following embodiments.

Examples

[0017] Figure 1 is a schematic cross-sectional view of the cleat according to Embodiment 1. Here, we will explain using the X, Y, and Z axes shown in Figure 1. The X axis is parallel to the mounting base 9 and extends perpendicular to the longitudinal direction of the cylindrical cleat 1. The Y axis is perpendicular to the mounting base 9 and extends from the mounting base 9 to the cleat 1. The Z axis is the longitudinal direction of the cleat 1 and extends perpendicular to the XY plane.

[0018] Cleat 1 has restraints 11-14 made by dividing a cylindrical member so that the annular cross-section is divided into four equal parts by an arc with a central angle of 90 degrees, as well as leg members 15 and 16 for installation on the mounting base 9. Cleat 1 also has tightening bolts 101-104 for connecting each of the restraints 11-14, and mounting bolts 151 and 161 for fixing the leg members 15 and 16 to the mounting base 9.

[0019] The restraints 11-14 are metal components such as aluminum. Rubber spacers 3, having a certain thickness according to the cable's outer diameter, are placed on the inner walls of the restraints 11-14. In Figure 1, a gap has been added between the restraints 11-14 and the rubber spacers 3 to make them easier to distinguish. The restraints 11-14 are arranged to form a cylinder surrounding the power cable 2, as shown in Figure 1.

[0020] The restraint device 11 includes a sleeve 111 through which the tightening bolt 101 is inserted, and a sleeve 114 through which the tightening bolt 104 is inserted. The restraint device 14 also includes a sleeve 113 through which the tightening bolt 103 is inserted.

[0021] Restriction device 11 and restraint device 12 are positioned so that their ends meet in the direction of the X-axis. Restriction device 12 and restraint device 13 are positioned so that their ends meet in the direction of the Y-axis. Restriction device 13 and restraint device 14 are positioned so that their ends meet in the direction of the X-axis. Restriction device 11 and restraint device 14 are positioned so that their ends meet in the direction of the Y-axis.

[0022] Here, the axes through which surface pressure is applied by restraints 11 and 14, and the axes through which surface pressure is applied by restraints 12 and 13, extend in the X-axis direction. Also, the axes through which surface pressure is applied by restraints 11 and 12, and the axes through which surface pressure is applied by restraints 13 and 14, extend in the Y-axis direction. In other words, the two axes through which surface pressure is applied by restraints 11-14 are orthogonal to each other. That is, the two axes through which surface pressure is applied by restraints 11-14 are located in directions that equally divide the central angle of the power cable 2. Hereafter, the total surface pressure of the two axes due to restraints 11-14 will be referred to as the "total surface pressure".

[0023] Figure 2 shows an example of a cable cross-section. The power cable 2 is a single-core cable. The power cable 2 has, for example, a conductor 21, an internal semiconducting layer 22, an insulator 23, an external semiconducting layer 24, a metal shielding layer 25, a fastening tape 26, a water-blocking layer 27, and a corrosion-resistant layer 28, as shown in Figure 2.

[0024] Let's return to Figure 1 and continue the explanation. In Figure 1, the conductor 21 of the power cable 2 is illustrated as an example of a component of the power cable 2. The restraints 11-14 apply surface pressure toward the corrosion-resistant layer 28, which is the outermost layer of the power cable 2. As a result, the rubber spacers 3 of each restraint 11-14 are brought into close contact with the corrosion-resistant layer 28 of the power cable 2, and the power cable 2 is gripped by them. The restraints 11-14 restrain the longitudinal movement of the power cable 2 by the frictional force between the rubber spacers 3 and the corrosion-resistant layer 28 of the power cable 2. Here, for the restraints 11-14, the side that is in contact with the power cable 2 is called the inside, and the opposite side is called the outside. Also, below, the corrosion-resistant layer 28 of the power cable 2 may be referred to as the "cable corrosion-resistant layer".

[0025] The leg member 15 is connected to the end of the restraint 12 facing the restraint 13. The leg member 15 extends outward from the connection point to the restraint 12, bends at a certain distance from the restraint 12, and has a mounting plane at the bent end. The leg member 15 has a sleeve 112 through which the tightening bolt 102 is inserted.

[0026] The leg member 16 is connected to the end of the restraint 13 facing the restraint 12. The leg member 16 extends outward from the connection point to the restraint 13 and bends at a point a certain distance away from the restraint 13, and has a mounting plane at the end of the bend.

[0027] Restabilizers 11 and 12 are joined to each other at their opposing ends by a tightening bolt 101. A coil spring 121 is positioned inside a sleeve 111 provided in restabilizer 11, with the inserted tightening bolt 101 as its axis. The coil spring 121 is sandwiched between the tightening bolt 101 and the bottom surface of the sleeve 111. When the tightening bolt 101 is tightened, the coil spring 121 is compressed, and this stress applies a compressive force to restabilizer 11, directed toward restabilizer 12, as a coupling load. The amount of compression of the coil spring 121 is adjusted according to the amount of tightening of the tightening bolt 101, and the coupling load between restabilizer 11 and restabilizer 12 is adjusted.

[0028] A leg member 15 is joined to the vicinity of the end of the restraint 12. Similarly, a leg member 16 is joined to the vicinity of the end of the restraint 13. The leg members 15 and 16 are then joined together by a tightening bolt 102, thereby connecting the restraint 12 and 13 to each other. A coil spring 122 is positioned inside a sleeve 112 provided on the leg member 15, with the inserted tightening bolt 102 as its axis. The coil spring 122 is sandwiched between the tightening bolt 102 and the bottom surface of the sleeve 112. When the tightening bolt 102 is tightened, the coil spring 122 is compressed, and this stress applies a compressive force to the leg member 15, directed towards the leg member 16, as a connecting load. The amount of compression of the coil spring 122 is adjusted according to the amount of tightening of the tightening bolt 102, and the connecting load between the restraint 12 and the restraint 13 is adjusted.

[0029] Restabilizers 13 and 14 are joined to each other at their opposing ends by a tightening bolt 103. A coil spring 123 is positioned inside a sleeve 113 provided in restabilizer 14, with the inserted tightening bolt 103 as its axis. The coil spring 123 is sandwiched between the tightening bolt 103 and the bottom surface of the sleeve 113. When the tightening bolt 103 is tightened, the coil spring 123 is compressed, and this stress applies a compressive force to restabilizer 14, directed toward restabilizer 13, as a coupling load. The amount of compression of the coil spring 123 is adjusted according to the amount of tightening of the tightening bolt 103, and the coupling load between restabilizer 13 and restabilizer 14 is adjusted.

[0030] Restabilizers 11 and 14 are joined to each other at their opposing ends by tightening bolts 104. A coil spring 124 is positioned inside a sleeve 114 provided in restabilizer 11, with the inserted tightening bolt 104 as its axis. The coil spring 124 is sandwiched between the tightening bolt 104 and the bottom surface of the sleeve 114. When the tightening bolt 104 is tightened, the coil spring 124 is compressed, and this stress applies a compressive force to restabilizer 11, directed toward restabilizer 14, as a coupling load. The amount of compression of the coil spring 124 is adjusted according to the amount of tightening of the tightening bolt 104, and the coupling load between restabilizer 11 and restabilizer 14 is adjusted.

[0031] As described above, the restraints 11-14 grip the power cable 2 by applying surface pressure to its surface from around the power cable 2 in two or more axial directions, and from directions in which the central angle of the power cable 2 is equally divided by each axis. More specifically, the restraints 11-14 apply surface pressure to the power cable 2 from two orthogonal axial directions. Furthermore, of the two axes from which the restraints 11-14 apply surface pressure to the power cable 2, one extends in the Y-axis direction, which is the direction from the center of the power cable 2 toward the mounting base 9, and the other extends in the X-axis direction, which is perpendicular to the other axis.

[0032] Furthermore, restraint 11 is an example of a "first restraint," restraint 12 is an example of a "second restraint," restraint 13 is an example of a "third restraint," and restraint 14 is an example of a "fourth restraint." Restraints 11 to 14 have a cylindrical shape in which the circular cross-section surrounding the power cable 2 is divided into four equal parts. One divided end of restraint 11 faces one divided end of restraint 12. The other divided end of restraint 12 faces one divided end of restraint 13. The other divided end of restraint 13 faces one divided end of restraint 14. The other divided end of restraint 14 faces the other divided end of restraint 11. In this way, restraints 11 to 14 are arranged to surround the power cable 2. Then, a force is applied in a direction that brings the opposing ends of restraint 11 and restraint 12 closer together. Also, a force is applied in a direction that brings the opposing ends of restraint 12 and restraint 13 closer together. A force is applied in a direction that brings the opposing ends of restraint 13 and restraint 14 closer together. A force is applied in a direction that brings the opposing ends of restraint 14 and restraint 11 closer together. As a result, restraints 11 to 14 exert surface pressure on the power cable 2.

[0033] Furthermore, coil spring 121 is an example of a "first spring that applies force in a direction that brings the opposing ends of the first and second restraints closer together." Coil spring 122 is an example of a "second spring that applies force in a direction that brings the opposing ends of the second and third restraints closer together." Coil spring 123 is an example of a "third spring that applies force in a direction that brings the opposing ends of the third and fourth restraints closer together." Coil spring 124 is an example of a "fourth spring that applies force in a direction that brings the opposing ends of the fourth and first restraints closer together."

[0034] Leg members 15 and 16 are placed so that their respective mounting surfaces are in contact with the mounting base 9, and the ends of the restraints 12 and 13 face each other. The mounting surface of leg member 15 is fixed to the mounting base 9 by mounting bolts 151. The mounting surface of leg member 16 is also fixed to the mounting base 9 by mounting bolts 161.

[0035] The restraint 12 is fixed to the mounting base 9 by fixing the leg member 15 to which the restraint 12 is attached. Also, the restraint 14 is fixed to the mounting base 9 by installing and fixing the leg member 16 to which the restraint 14 is attached. As a result, the restraint 12 and restraint 11 are fixed together, and the restraint 13 and restraint 14 are fixed together, thereby fixing the entire cleat 1 to the mounting base 9.

[0036] In Embodiment 1, sleeves 111 and 114 were provided at both ends of the restraint 11, sleeve 112 at the end of the leg member 15, and sleeve 113 at the end of the restraint 14. However, the positions of sleeves 111 to 114 are not limited to these. Sleeves 111 to 114 may be placed in other positions as long as the opposing sets of restraints 11 to 14 can be fixed by tightening bolts 101 to 104 that pass through each of them without interfering with each other. For example, sleeve 114 may be provided on the side of restraint 14.

[0037] (Restraint procedure) Figure 3 is a flowchart showing the procedure for securing a power cable with a cleat. Next, referring to Figure 3, the procedure for securing power cable 2 with cleat 1 will be explained.

[0038] The leg members 15 and 16 are placed so that their respective mounting planes are in contact with the mounting base 9 and the ends of the restraints 12 and 13 face each other, and are temporarily fixed to the mounting base 9 with mounting bolts 151 and 161 (step S1). Here, in Figure 1, the bolt holes for the mounting bolts 151 in the leg member 15 and the bolt holes for the mounting bolts 161 in the leg member 16 are not circular but elongated ovals extending in the X-axis direction to accommodate changes in the distance between the restraints 12 and 13.

[0039] Returning to Figure 3, the explanation continues. The power cable 2 is placed inside the semi-cylindrical space formed by the restraint 12 to which leg member 15 is connected and the restraint 13 to which leg member 16 is connected (step S2).

[0040] The semi-cylindrical shapes formed by the restraints 11 and 14 are placed over the power cable 2, and the restraints 11 to 14 are positioned to surround the power cable 2 (step S3).

[0041] The four fastening bolts 101-104 connecting the restraints 11-14 are tightened. The tightening of the fastening bolts 101-104 is adjusted so that the compressive force from the coil springs 121-124 is evenly distributed, sufficient restraining force is obtained, and the maximum surface pressure is within the allowable surface pressure limit of the power cable 2 (step S4).

[0042] The mounting bolts 151 and 161 permanently fix the leg members 15 and 16 so that the mounting base 9 does not move in the X direction (step S5).

[0043] (The restraining force of Cleat 1) Next, we will explain the restraining force exerted by cleat 1 on the power cable 2. Before calculating the restraining force of cleat 1, we will derive the formula for calculating the surface pressure per unit area applied to the power cable 2 by cleat 1.

[0044] Figure 4 is a schematic diagram of the application of surface pressure by the cleat. Here, with respect to the power cable 2, the positive Y-axis direction, where the Y-axis arrow in Figure 4 points, is called the upward direction, and the negative Y-axis direction is called the downward direction. In Figure 4, the surface pressure applied to the power cable 2 by the cleat 1, as indicated by arrow p, is explained as an example. For example, in the state shown in Figure 1, when a coupling load is applied from restraint 11 to restraint 12 and from restraint 14 to restraint 13 due to tightening by fastening bolts 101 and 103, the force indicated by arrow p in Figure 4 acts.

[0045] In Figure 4, σ0 is the surface pressure per unit area due to cleat 1. W is the cleat width. r is the cable radius of power cable 2, and D is the cable diameter. θ is the circumferential angle from the vertically upward direction (positive Y-axis direction) from the center of power cable 2. Surface 201 is a small surface along the circumference of the cable's outer diameter. Surface 202 is a small surface at the same position as surface 201 in the Y-axis direction, with the Y-axis as the normal. F1 is the small vertical downward surface pressure exerted on surface 201 by cleat 1.

[0046] Here, we will explain the minute surface pressure acting on the surface of the power cable 2 at a position offset by an angle θ in the circumferential direction from the positive Y-axis direction extending upward from the center of the power cable 2. The minute area dS1 of surface 201 at a small angle dθ from the circumferential angle θ of the power cable 2 is expressed by the following equation (1).

[0047]

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[0048] Furthermore, since surface 201 is inclined at an angle θ with respect to surface 202, which is perpendicular to the direction of action of the surface pressure σ0, if the area of ​​surface 202 is dS2, then the infinitesimal surface pressure F1 can be expressed as F1 = σ0 × W × dS2. Thus, the infinitesimal vertical surface pressure F1 acting on surface 201 due to the cleat 1 is expressed by the following equation (2). F1 reaches a maximum value of σ0Wrdθ at θ=0 and a minimum value of 0 at θ=π / 2, and changes depending on the angle θ.

[0049]

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[0050] Here, integrating the small surface pressure F1 over the upper semicircle yields the same surface pressure from the upper half due to cleat 1. Since the upper semicircle is symmetrical in the left-right rotational direction with respect to the position where angle θ is 0, twice the value obtained by integrating as angle θ changes from 0 to π / 2 is equal to the surface pressure from the upper half due to cleat 1. Furthermore, the surface pressure from the upper half due to cleat 1 can be expressed as NP, where N is the number of springs and P is the force of one spring. Thus, the surface pressure from the upper half due to cleat 1 is expressed by the following equation (3).

[0051]

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[0052] Therefore, the surface pressure σ0 per unit area due to cleat 1 can be calculated from the force and number of springs, and is expressed by the following formula (4).

[0053]

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[0054] Here, the contact angle φ of the rubber spacer 3 is set with respect to the semicircle of the cleat 1, so to match this, we set 2θ1 = φ, and the surface pressure σ0 can be expressed by the following equation (5).

[0055]

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[0056] Next, we will explain the restraining force provided by cleat 1 using the surface pressure σ0 per unit area calculated above. With cleat 1, surface pressure acts on the power cable 2 in the direction of the X axis in Figure 1, and surface pressure also acts on the power cable 2 in the direction of the Y axis, which is 90 degrees from the X axis. In other words, cleat 1 restrains the power cable 2 from two axial directions. Here, the tightening bolts 101 to 104 are adjusted so that the compressive force in the X axis direction and the compressive force in the Y axis direction are of the same magnitude.

[0057] Let's consider the force exerted by the surface 201 shown in Figure 4 on the cleat 1 toward the center of the power cable 2. The symbols used in this explanation are the same as those used in Figure 4. The force F is the force that acts on surface 201 toward the center due to the surface pressure in the Y-axis direction of the cleat 1. 1center Therefore, F 1center This is shown by the following equation (6). Here, F1 is the force exerted on surface 201 by the surface pressure of cleat 1 in the Y-axis direction.

[0058]

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[0059] Furthermore, surface 201 exerts a force F in the direction toward the center due to the surface pressure in the X-axis direction of the cleat 1. 2center Therefore, F 2center This is shown by the following equation (7). Here, F2 is the force exerted on surface 201 by the surface pressure of cleat 1 in the X-axis direction.

[0060]

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[0061]

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[0062] Here, dθ is a small angle and constant, and does not depend on the angle θ from the X-axis direction extending from the center of the power cable 2, F center This value remains constant regardless of the angle θ.

[0063] Let's consider the force used as the criterion for determining the limit of the allowable surface pressure applied to the cable corrosion protection layer. F is the force directed towards the center at angle θ due to cleat 1.center is the same as the maximum value at the angle θ = 0 among the micro - surface pressures of the concrete 1 when pressure is applied from the direction of one axis, and is σ0Wrdθ. That is, the micro - surface pressure of the concrete 1 becomes the same as the maximum value when surface pressure is applied from the direction of one axis.

[0064] And the restraining force F of the concrete 1 is the force F directed towards the central direction at the angle θ by the concrete 1 center is integrated in the circumferential direction of the power cable 2 to calculate the total surface pressure, and by multiplying the calculation result by the friction coefficient μ, it is calculated as the following formula (9). Here, φ represents the contact angle of the concrete 1 with respect to the power cable 2.

[0065]

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[0066]

Equation

[0067] Furthermore, considering the reduction rate α and safety factor β due to the heat cycle, the restraining force F of the concrete 1 used in actual operation is expressed by the following formula (11).

[0068]

Equation

[0069] Here, as a comparison object, the restraining force of the concrete when pressure is applied from the direction of one axis will be described. Here, the concrete to which pressure is applied from one axial direction is called a one - axis restrained concrete. Fig. 5 is a cross - sectional view showing the schematic of the one - axis restrained concrete. In Fig. 5, the sleeve and coil spring are omitted.

[0070] As shown in Figure 5, the uniaxial restraint cleat has semi-cylindrical restraints 211 and 212, which are formed by dividing a cylinder in half along its longitudinal direction. Leg members 213 and 214 are connected to restraint 212. Restraints 211 and 212 are positioned so that their ends face each other with the power cable 2 in between. Restraints 211 and 212 are joined to each other at their opposing ends by tightening bolts 215 and 216. Although not shown, sleeves and springs are arranged on the tightening bolts 215 and 216, similar to cleat 1, and a compressive force acts on restraints 211 and 212 in the direction opposite to each other due to stress from the springs. This compressive force applies surface pressure from restraints 211 and 212 to the power cable 2, creating a restraining force that restricts the longitudinal movement of the power cable 2.

[0071] Here again, we consider the force acting on surface 201 shown in Figure 4. The symbols used in this explanation are the same as those used in Figure 4. The force acting on surface 201 from the surface pressure of the uniaxially constrained cleat, directed towards the center, is F. 1center Therefore, F 1center This is shown by the following equation (12). Here, F1 is the force that surface 201 receives from the surface pressure of the uniaxially constrained cleat in the Y-axis direction.

[0072]

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[0073] Constraint force F of a uniaxial constrained cleat base 1 is F 1center The pressure across the entire circumference of the cable is obtained by integrating the coefficient of friction μ, and then multiplying by the coefficient of friction μ. In the circumferential direction, since θ is symmetrical every π / 2, the integration is performed in four divisions. This gives the restraint force F of the uniaxial restraint cleat. base 1 is shown by the following equation (13), where θ1 is 90 degrees.

[0074]

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[0075] If we set 2θ1 = φ to match the contact angle φ of the rubber spacer 3, then the constraint force F of the uniaxial constrained cleat is... base 1 is represented by the following formula (14).

[0076]

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[0077] Here, by substituting the formula for calculating the surface pressure σ0 per unit area shown in formula (5) into formula (14), we can obtain the constraint force F of the uniaxial constrained cleat. base The value of 1 is represented by the following formula (15).

[0078]

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[0079] Furthermore, taking into account the rate of decrease α due to heat cycling and the safety factor β, the restraining force F of a uniaxial restraining cleat used in actual operation can be expressed by the following equation (16).

[0080]

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[0081] Here, the restraint force F of the uniaxial restraint cleat before considering the reduction rate α due to heat cycling and the safety factor β. base Let's consider point 1. The constraint force F of a uniaxially constrained cleat. base 1 is the surface pressure F directed toward the center of the power cable 2 at the angle θ shown in equation (12), as shown in equation (13). 1center The surface pressure F is obtained by integrating it around the entire circumference of the uniaxially constrained cleat. 1center This depends on the angle θ, reaching a maximum value σ0Wrdθ when the angle θ is 0, decreasing as the angle θ approaches π / 2, and becoming zero when the angle θ is 90 degrees, thus not contributing to the restraining force. In this case, the limit on the surface pressure applied to the cable corrosion protection layer is the surface pressure F when the angle θ, which is at its maximum value, is 0. 1center It can be judged based on that criterion.

[0082] (Comparison of binding forces) Based on the above, the difference in restraint force between Cleat 1 according to Example 1 and the uniaxial restraint cleat will be explained. Here, a CV80mm2 cable with copper wire shielding was used as the power cable 2 used for comparing restraint forces. Figure 6 is a diagram showing the conditions used for the comparison. Table 301 in Figure 6 shows the specifications of the power cable 2 used here. Table 302 shows the specifications of the uniaxial restraint cleat used for comparison. Furthermore, for Cleat 1 according to Example 1, the contact angle and clamping force are the same as in Table 302, and two springs are placed on each of the two axes offset by 90 degrees, applying compressive force from two axial directions.

[0083] The surface pressure σ0 per unit area in the uniaxial direction at a constant temperature of 20°C is calculated using formula (5). According to Table 302, the cable clamping force P of one spring is 921N, and the contact angle φ of cleat 1 is 143.0 degrees. In this case, the surface pressure σ0 per unit area is calculated to be 0.444 MPa, as shown in formula (17).

[0084]

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[0085] As a limit on the surface pressure applied to the cable corrosion protection layer, if the surface pressure directed toward the center of the power cable 2 is used as the reference, then F in the cleat 1 according to Example 1 center And, F in a uniaxially constrained cleat 1center It is the same as the maximum value.

[0086] The restraining force of a uniaxial restrained cleat at a constant temperature of 20°C is calculated using equation (16). In this case, the restraining force of the uniaxial restrained cleat is calculated to be 852N, as shown in the following equation (18).

[0087]

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[0088] Furthermore, the restraining force of cleat 1 in Example 1, when the constant temperature is 20°C, is calculated using formula (11). In this case, the restraining force of cleat 1 is calculated to be 1372N, as shown in formula (19).

[0089]

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[0090] For these, the conditions for the allowable surface pressure are the same as the maximum value of the minute surface pressure at θ=0° for calculating the surface pressure σ0 per unit area. Therefore, the minute surface pressure of cleat 1 can be kept within the allowable range of the allowable surface pressure, similar to the maximum value of the minute surface pressure of the uniaxially constrained cleat, and the restraining force can be increased from 852N to 1372N compared to the uniaxially constrained cleat.

[0091] As described above, the cleat 1 according to Example 1 applies surface pressure to the power cable 2 from two axial directions offset by 90 degrees in the circumferential direction. This makes it possible to suppress the minute surface pressure applied to the cable corrosion protection layer to the same level as the maximum value of the minute surface pressure of a uniaxial restraint cleat, while improving the restraining force compared to a uniaxial restraint cleat. In other words, it is possible to increase the restraining force of the cable without changing the maximum surface pressure applied to the cable corrosion protection layer. Therefore, it is possible to improve the safety of the cable equipment. [Examples]

[0092] Figure 7 is a perspective view of the cleat according to Example 2. In Figure 7, the internal structure is shown in order to make it easier to understand the configuration, but parts that are not actually visible from the outside, such as the coil spring 121, are also included in the illustration. Also, in Figure 7, the main components of the power cable 2, namely the conductor 21, the internal semiconducting layer 22, the metal shielding layer 25, and the corrosion protection layer 28, are illustrated as an example.

[0093] The cleat 1 according to Example 2 has two axes that apply surface pressure at positions offset by 45 degrees from each of the two axes that apply surface pressure in Example 1. The configuration of the cleat 1 according to Example 2 will be described below.

[0094] Figure 8 is a schematic cross-sectional view of the cleat according to Example 2. In Figure 8, the sleeve and coil spring have been omitted.

[0095] Cleat 1 has restraints 11-14 made by dividing a cylindrical member into four equal parts such that the annular cross-section is divided into arcs with a central angle of 90 degrees, and leg members 15 and 16 for installation on the mounting base 9. Cleat 1 also has tightening bolts 101-104 for connecting each of the restraints 11-14, and mounting bolts 151 and 161 for fixing the leg members 15 and 16 to the mounting base 9.

[0096] The restraints 11-14 are metal components such as aluminum. The restraints 11-14 have rubber spacers 3 on their inner walls, each having a certain thickness corresponding to the cable's outer diameter. As shown in Figure 8, the restraints 11-14 are arranged to surround the power cable 2, forming a cylindrical structure.

[0097] Restrictors 11 and 12 are positioned so that their ends face in a direction rotated 45 degrees clockwise around the X-axis toward the plane of the paper. Similarly, restrainors 13 and 14 are positioned so that their ends face in a direction rotated 45 degrees clockwise around the X-axis toward the plane of the paper. Also, restrainors 12 and 13 are positioned so that their ends face in a direction rotated 45 degrees counterclockwise around the X-axis. Similarly, restrainors 11 and 14 are positioned so that their ends face in a direction rotated 45 degrees counterclockwise around the X-axis.

[0098] Thus, the axis through which surface pressure is applied by restraints 11 and 12, and the axis through which surface pressure is applied by restraints 13 and 14, extend in a direction in which the X-axis is tilted 45 degrees clockwise. The axis through which surface pressure is applied by restraints 11 and 14, and the axis through which surface pressure is applied by restraints 12 and 13, extend in a direction in which the X-axis is tilted 45 degrees counterclockwise. The two axes through which surface pressure is applied by restraints 11-14 are orthogonal to each other.

[0099] Thus, of the two axes by which restraint devices 11-14 apply surface pressure to the power cable 2, one extends in a direction shifted 45 degrees clockwise from the Y-axis direction from the center of the power cable 2 toward the mounting base 9. In addition, of the two axes by which restraint devices 11-14 apply surface pressure to the power cable 2, the other extends in a direction shifted 45 degrees counterclockwise from the Y-axis direction from the center of the power cable 2 toward the mounting base 9.

[0100] Restabilizer 11 and restrainizer 12 are joined to each other at their opposing ends by tightening bolts 101. Restabilizer 12 and restrainizer 13 are joined to each other at their opposing ends by tightening bolts 102. Restabilizer 13 and restrainizer 14 are joined to each other at their opposing ends by tightening bolts 103. Restabilizer 11 and restrainizer 14 are joined to each other at their opposing ends by tightening bolts 104.

[0101] The restraints 11-14 apply surface pressure toward the outermost corrosion-resistant layer 28 of the power cable 2, causing their respective rubber spacers 3 to adhere tightly to the corrosion-resistant layer 28 of the power cable 2. The restraints 11-14 restrict the longitudinal movement of the power cable 2 through the frictional force between the rubber spacers 3 and the corrosion-resistant layer 28 of the power cable 2.

[0102] The leg member 15 is connected to the outer wall of the restraint 13 at approximately the halfway point of the arc. The leg member 15 extends outward from the connection point to the restraint 13 towards the outside of the restraint 12, bends at a certain distance from the restraint 13, and has a mounting plane at the end of the bend.

[0103] The leg member 16 is connected to the restraint 13 at a position opposite to that of the leg member 15, relative to the halfway point of the arc of the outer wall of the restraint 13. The leg member 16 extends outward from the connection point to the restraint 13, bends at a point a certain distance from the restraint 13, and has a mounting plane at the end of the bend.

[0104] Leg members 15 and 16 are placed so that their respective mounting surfaces are in contact with the mounting base 9. The mounting surface of leg member 15 is then fixed to the mounting base 9 by mounting bolts 151. Similarly, the mounting surface of leg member 16 is fixed to the mounting base 9 by mounting bolts 161.

[0105] The leg members 15 and 16 to which the restraint 13 is connected are fixed to the mounting base 9, thereby fixing the restraint 13 to the mounting base 9. As a result, the restraint 13 is fixed to the restraints 12 and 14, and the restraint 11 is fixed to the restraints 12 and 14, thereby fixing the entire cleat 1 to the mounting base 9.

[0106] As described above, in the cleat 1 according to Embodiment 2, the two axes on which surface pressure is applied are positioned at an angle of 45 degrees clockwise or counterclockwise from the X-axis. That is, the connection positions of restraint 12 and restraint 13 and restraint 13 and restraint 14 are offset from the position directly below the center. This eliminates the need to place fastening bolts that clamp the leg members 15 and 16. In other words, as shown in Figure 8, the connection positions of restraint 12 and restraint 13 and restraint 13 and restraint 14 can be positioned at locations different from the connection positions of the leg members 15 and 16.

[0107] In this case, the leg members 15 and 16 installed on the mounting base 9 do not need to be movable relative to the mounting base 9. Also, the tightening bolt 103 does not need to penetrate the mounting plane of the leg members 15 and 16, and can have the same configuration as the other tightening bolts 101, 102 and 104. Therefore, the structure of the cleat 1 can be simplified and manufacturing can be made easier. In this case as well, the restraining force is the same as in Embodiment 1, so the restraining force can be improved and the safety of the cable equipment can be improved.

[0108] In this embodiment, the two axes that apply surface pressure are tilted 45 degrees clockwise and counterclockwise from the X-axis. However, the positions of the two axes are not limited to this, as long as the two axes are orthogonal to each other and the leg members 15 and 16 can be connected to any one of the restraints 11 to 14.

[0109] Furthermore, although the above explanation described the case where cleat 1 restrains a single-core power cable 2, the same applies to a triplex cable. Figure 9 is a perspective view showing the cleat restraining a triplex cable.

[0110] The triplex cable 4 is a single power cable composed of three power cables 2 bundled together. As shown in Figure 9, the cleat 1 surrounds the triplex cable 4 with restraints 11-14 via rubber spacers 3. The cleat 1 then grips the triplex cable 4 by applying surface pressure from two orthogonal axial directions.

[0111] Figure 10 is a schematic cross-sectional view of the cleat in a state where the triplex cable is restrained. As shown in Figure 10, a leg member 17 is connected to the restraint 13. The leg member 17 has a shape in which one leg extends from the restraint 13 and has a flat surface at the end of the extended leg. The leg member 17 is fixed to the mounting base 9 by mounting bolts 151 and 161.

[0112] In this embodiment, a leg member 17 having one leg is used, but even in the case of restraining a triplex cable 4, a configuration in which two leg members 15 and 16 are used to fix the cleat 1 to the mounting base 9 is also possible. Similarly, in Figure 8 for the case of a single-core cable 2, a configuration in which a leg member 17 having one leg is used to fix the cleat 1 to the mounting base 9 is also possible.

[0113] In this case, the rubber spacer 3 is pressed against the three power cables 2 included in the triplex cable 4, and the frictional force restrains the triplex cable 4.

[0114] In this case as well, restraint 11 and restraint 12 are joined to each other by tightening bolts 101 at their opposing ends. Furthermore, restraint 12 and restraint 13 are joined to each other by tightening bolts 102 at their opposing ends. Also, restraint 13 and restraint 14 are joined to each other by tightening bolts 103 at their opposing ends. Finally, restraint 11 and restraint 14 are joined to each other by tightening bolts 104 at their opposing ends.

[0115] The restraints 11-14 apply surface pressure toward the corrosion-resistant layer 28, which is the outermost layer of the three power cables 2 contained in the triplex cable 4, causing the rubber spacers 3 to adhere tightly to the corrosion-resistant layer 28 of the triplex cable 4. The restraints 11-14 restrict the longitudinal movement of the triplex cable 4 through the frictional force between the rubber spacers 3 and the corrosion-resistant layer 28 of the power cables 2.

[0116] Here, the explanation of how to restrain the triplex cable 4 was given using the example where the two axes onto which surface pressure is applied are tilted 45 degrees clockwise or counterclockwise from the X-axis, but this is not the only example. For example, even if the two axes onto which surface pressure is applied are the X-axis and Y-axis, the cleat 1 can similarly restrain the triplex cable 4.

[0117] As described above, the cleat 1 can grip the triplex cable 4 and restrain its movement in the longitudinal direction.

[0118] Furthermore, the above explanation describes the case where surface pressure is applied from the cleat 1 to the power cable 2 from two axial directions, but the number of axes may be more than two. However, in order to apply surface pressure evenly to the power cable 2, it is preferable that each axis is positioned in a direction that equally divides the central angle of the power cable 2. [Explanation of symbols]

[0119] 1 Cleat 2 Power Cables 3. Rubber spacers 4. Triplex Cable 9. Mounting base 11~14 Restraints 15,16 Leg members 101-103 Tightening bolts 111~114 Sleeves 121-124 Coil springs 151,161 Mounting bolts

Claims

1. A restraint device that grips the power cable by applying surface pressure to the surface of the power cable from around the power cable in two or more axial directions, and in directions where the central angle of the power cable is equally divided by each axis, A leg member connected to the aforementioned restraint device and fixed to the mounting base, A restraint device characterized by being equipped with the following features.

2. The restraint device according to claim 1, characterized in that the restraint device applies surface pressure to the power cable from two orthogonal axis directions.

3. The restraint device according to claim 2, characterized in that of the two axes that apply surface pressure to the power cable, one extends in a direction toward the mounting base from the center of the power cable, and the other extends in a direction perpendicular to the one.

4. The restraint device according to claim 2, characterized in that of the two axes that apply surface pressure to the power cable, one extends in a direction shifted 45 degrees clockwise from the direction toward the mounting base from the center of the power cable, and the other extends in a direction shifted 45 degrees counterclockwise from the direction toward the mounting base from the center of the power cable.

5. The restraint device comprises a first restraint device to a fourth restraint device, each having a cylindrical cross-section that surrounds the power cable and is divided into four equal parts. The first to fourth restraints are, One divided end of the first restraint and one divided end of the second restraint face each other, the other divided end of the second restraint and one divided end of the third restraint face each other, the other divided end of the third restraint and one divided end of the fourth restraint face each other, and the other divided end of the fourth restraint and the other divided end of the first restraint face each other, and are arranged to surround the power cable. When a force is applied in a direction that brings the opposing ends of the first restraint and the second restraint, the opposing ends of the second restraint and the third restraint, the opposing ends of the third restraint and the fourth restraint, and the opposing ends of the fourth restraint and the first restraint, surface pressure is applied to the power cable. The restraint device according to feature 1.

6. A first spring that applies force in a direction that brings the opposing ends of the first restraint and the second restraint closer together, A second spring that applies force in a direction that brings the opposing ends of the second restraint and the third restraint closer together, A third spring that applies force in a direction that brings the opposing ends of the third restraint and the fourth restraint closer together, A fourth spring applies force in a direction that brings the opposing ends of the fourth restraint and the first restraint closer together. The restraint device according to claim 5, characterized by comprising:

7. The power cable is gripped by a restraining device by applying surface pressure to the power cable from two or more axial directions around the power cable, and from directions in which the central angle of the power cable is equally divided by each axis. The restraint device is fixed to the mounting base to restrict the longitudinal movement of the power cable. A restraint method characterized by the following.

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