Restraint device and restraint method

Abstract

A restraining device and a restraining method are provided that improve the safety of cable installations. [Solution] The restraint device 1 has restraints 11 to 14 and leg members 15 and 16. The restraints 11 to 14 apply surface pressure to the power cable 2 from the periphery of the power cable 2 in two or more axial directions, and in directions in which the central angle of the power cable 2 is equally divided by each axis, to restrain the power cable 2. The leg member 15 is connected to the restraint 12 and fixed to the installation base 9. The leg member 16 is connected to the restraint 13 and fixed to the installation base 9.

Description

[Technical Field]

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

[0002] In areas such as cities and urban areas where it is difficult to erect new transmission towers, electricity is generally transmitted using underground transmission methods. In underground transmission methods, the power cables used to transmit electricity are buried underground. Burying the power cables underground reduces the impact of natural phenomena such as storms and snow, allowing for safe and reliable transmission of electricity.

[0003] One method of burying electric cables in the ground for such underground power transmission systems is called the conduit method, in which the power cables are buried in the ground while protected by pipes made of reinforced plastic or the like. In the conduit method, manholes are installed midway through the conduit to allow the power cables to be connected.

[0004] There may be differences in ground elevation between manholes, causing the conduit to be inclined. In such cases, changes in the temperature of the cable conductor due to changes in the power cable's transmission current or changes in the underground temperature around the conduit may cause the cable conductor to thermally expand and contract in the longitudinal direction, causing the entire power cable to move from a higher position to a lower position. In addition, power cables laid in conduits buried in roads with heavy vehicle traffic and soft ground may move in the direction of vehicle travel due to a phenomenon known as "cable surfing."

[0005] If the cable moves excessively, unexpected tension may occur near the connection point where the cable load changes inside the manhole, which may result in damage to the cable equipment. To prevent this cable movement, restraining devices called cleats are sometimes installed inside the manhole. Cleats are used to restrain the longitudinal movement of the power cable.

[0006] The structure of a typical conventional cleat, as defined by standard specifications set by electric power companies and the like, is as follows: The cleat is roughly cylindrical overall, with a hollow interior, and is divided into an upper cleat portion, one half of the cylinder, and a lower cleat portion, the other half, as if dividing the circle at each end of the cylinder. A rubber spacer is fitted to the inner surface of each of the upper and lower cleat portions. The upper and lower cleat portions are positioned with their inner surfaces facing each other, sandwiching the power cable. Then, a force such as a spring applies pressure in the upper and lower cleat directions toward each other. This pressure exerts a surface pressure on the power cable from the upper and lower cleat portions. The frictional force between the cable corrosion protection layer and the rubber spacer, based on this surface pressure, causes the cleat to restrict longitudinal movement of the power cable.

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

[0008] One proposed cleat technology is to house the cleat in a frame, fix the cleat to the frame with the cleat gripping angle aligned with the cable's entrance angle, and fix the frame to the inner wall of the manhole near the cable's conduit entrance.Other proposed technologies also use a frame, but with a structure that separates the frame from the manhole's inner wall and allows it to be fixed to the manhole's inner wall other than near the power cable's conduit entrance. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-39402 [Patent Document 2] Japanese Patent Application Publication No. 2019-68502 Summary of the Invention [Problem to be solved by the invention]

[0010] However, conventional cleat structures grip the cable in a single axial direction perpendicular to the cleat's installation surface, applying surface pressure. In this structure, the surface pressure applied to the cable corrosion protection layer is greatest in the direction of the axis along which the surface pressure is applied, decreases as the angle relative to the axis increases, and at a 90-degree angle, there is almost no surface pressure. Therefore, at positions where the angle relative to the single axial direction along which the surface pressure is applied is large, the surface pressure is not reflected in the restraining force, and the restraining force on the power cable decreases. Furthermore, because the surface pressure is not constant depending on the angle relative to the cable corrosion protection layer, if a moving force is applied to the power cable when the power cable is not sufficiently restrained, the cleat's grip becomes unstable, which could result in damage to the power cable.

[0011] Furthermore, all of the above-mentioned techniques for fitting cleats into a frame and fixing them use the same method of restraining power cables as conventional general cleat structures, and even if these techniques are used, sufficient restraining force cannot be obtained, making it difficult to improve the safety of cable facilities.

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

[0013] In the present invention, The restraint device Around power cables a first restraint device to a fourth restraint device each having a first end and a second end at the divided positions on both sides; and a connecting member connected to at least one of the first restraint device to the fourth restraint device; and a leg member fixed to the installation base. The first to fourth restraint devices are arranged so that the first end of the first restraint device faces the second end of the second restraint device, the first end of the second restraint device faces the second end of the third restraint device, the first end of the third restraint device faces the second end of the fourth restraint device, and the first end of the fourth restraint device faces the second end of the first restraint device, and so as to surround the power cable. By applying a force in the direction in which the first end of the first restraint device and the second end of the second restraint device approach each other and in the direction in which the first end of the third restraint device and the second end of the fourth restraint device approach each other, a force is applied to each of the first to fourth restraint devices in the direction of the first axis, thereby applying a surface pressure in the direction of the first axis of the power cable, and by applying a force in the direction in which the first end of the second restraint device and the second end of the third restraint device approach each other and in the direction in which the first end of the fourth restraint device and the second end of the first restraint device approach each other, a force is applied to each of the first to fourth restraint devices in the direction of a second axis perpendicular to the direction of the first axis, thereby applying a surface pressure in the direction of the second axis of the power cable, On a circumference perpendicular to the central axis of the power cable, The first axis and the second axis From the direction of electric power Apply a surface pressure with the same resultant force to the surface of the cable, electric powerThe surface pressure applied to the surface of the cable toward the center of the cable is electric power A constant value regardless of location on the circumference perpendicular to the central axis of the cable, electric power Cable grip do. [Effects of the Invention]

[0014] According to the present invention, the safety of the cable plant can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing an outline of a cleat according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of a cross section of a cable. [Figure 3] FIG. 3 is a flowchart showing a procedure for restraining a power cable with a cleat. [Figure 4] FIG. 4 is a schematic diagram of the application of surface pressure by cleats. [Figure 5] FIG. 5 is a cross-sectional view showing an outline of a uniaxial restraint cleat. [Figure 6] FIG. 6 shows the conditions used for the comparison. [Figure 7] FIG. 7 is a perspective view of a cleat according to a second embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing an outline of a cleat according to a second embodiment. [Figure 9] FIG. 9 is a transparent perspective view showing the cleat in a state in which the triplex cable is restrained. [Figure 10] FIG. 10 is a cross-sectional view showing an outline of the cleat in a state where the triplex cable is restrained. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the restraint device and restraint method disclosed in the present invention will be described in detail with reference to the drawings. However, the restraint device and restraint method disclosed in the present invention are not limited to the following embodiments. [Example]

[0017] FIG. 1 is a cross-sectional view showing an outline of a cleat according to Example 1. Here, the description will be made using the X-axis, Y-axis, and Z-axis shown in FIG. 1. The X-axis is an axis that is parallel to the mounting base 9 and extends in a direction perpendicular to the longitudinal direction of the cylindrical cleat 1. The Y-axis is an axis that extends perpendicular to the mounting base 9, from the mounting base 9 on which the cleat 1 is mounted, towards the cleat 1 itself. The Z-axis is the longitudinal direction of the cleat 1 and extends in a direction perpendicular to the XY plane.

[0018] Cleat 1 has restraints 11-14 created by dividing a cylindrical member so that the circular cross-sectional shape is divided into four equal parts by arcs with a central angle of 90 degrees, as well as leg members 15 and 16 for installation on installation base 9. Cleat 1 also has tightening bolts 101-104 that connect each of the restraints 11-14 together, and mounting bolts 151 and 161 that secure leg members 15 and 16 to installation base 9.

[0019] The restraining devices 11 to 14 are members made of metal such as aluminum. A rubber spacer 3 having a certain thickness according to the outer diameter of the cable is disposed on the inner wall of the restraining devices 11 to 14. In FIG. 1, a gap is provided between the restraining devices 11 to 14 and the rubber spacer 3 to make it easier to distinguish them. The restraining devices 11 to 14 are disposed so as to surround the power cable 2 and form a cylinder, as shown in FIG. 1.

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

[0021] Restraint device 11 and restraint device 12 are arranged in positions where their ends face each other in the X-axis direction. Restraint device 12 and restraint device 13 are arranged in positions where their ends face each other in the Y-axis direction. Restraint device 13 and restraint device 14 are arranged in positions where their ends face each other in the X-axis direction. Restraint device 11 and restraint device 14 are arranged in positions where their ends face each other in the Y-axis direction.

[0022] Here, the axis along which the surface pressure is applied by the restraining devices 11 and 14 and the axis along which the surface pressure is applied by the restraining devices 12 and 13 extend in the X-axis direction. Furthermore, the axis along which the surface pressure is applied by the restraining devices 11 and 12 and the axis along which the surface pressure is applied by the restraining devices 13 and 14 extend in the Y-axis direction. In other words, the two axes along which the surface pressure is applied by the restraining devices 11 to 14 are perpendicular to each other. In other words, the two axes along which the surface pressure is applied by the restraining devices 11 to 14 are positioned in directions that equally divide the central angle of the power cable 2. Hereinafter, the total pressure of the surface pressures on the two axes by the restraining devices 11 to 14 will be referred to as the "total surface pressure."

[0023] Fig. 2 is a diagram showing an example of a cable cross section. The power cable 2 is a single-core cable. As shown in Fig. 2, the power cable 2 has, for example, a conductor 21, an inner semiconductive layer 22, an insulator 23, an outer semiconductive layer 24, a metal shielding layer 25, a holding tape 26, a water-shielding layer 27, and a corrosion-resistant layer 28.

[0024] Returning to Figure 1, the explanation will continue. Figure 1 illustrates the conductor 21 of the power cable 2 as an example of a component of the power cable 2. The restraining devices 11 to 14 apply surface pressure toward the anticorrosion layer 28, which is the outermost layer of the power cable 2. As a result, the rubber spacers 3 of the restraining devices 11 to 14 are brought into close contact with the anticorrosion layer 28 of the power cable 2, thereby gripping the power cable 2. The restraining devices 11 to 14 restrain longitudinal movement of the power cable 2 by the frictional force between the rubber spacers 3 and the anticorrosion layer 28 of the power cable 2. Here, the side of the restraining devices 11 to 14 that comes into contact with the power cable 2 is referred to as the inner side, and the opposite side is referred to as the outer side. In the following, the anticorrosion layer 28 of the power cable 2 may also be referred to as the "cable anticorrosion layer."

[0025] Leg member 15 is connected near the end of restraint device 12 facing restraint device 13. Leg member 15 extends from the connection position to restraint device 12 toward the outside of restraint device 12 and bends at a point a certain distance away from restraint device 12, with an installation plane at the end of the bend. Leg member 15 has a sleeve 112 through which tightening bolt 102 is inserted.

[0026] Leg member 16 is connected near the end of restraint device 13 facing restraint device 12. Leg member 16 extends outward from the connection position to restraint device 13 and bends at a point a certain distance away from restraint device 13, with an installation plane at the end of the bend.

[0027] Restraint device 11 and restraint device 12 are connected to each other at their respective opposing ends by tightening bolt 101. A coil spring 121 is disposed inside a sleeve 111 provided in restraint device 11, with the inserted tightening bolt 101 as its axis. Coil spring 121 is sandwiched between tightening bolt 101 and the bottom surface of sleeve 111. When tightening bolt 101 is tightened, coil spring 121 is compressed, and the resulting stress applies a compressive force toward restraint device 12 as a combined load to restraint device 11. The amount of compression of coil spring 121 is adjusted according to the amount of tightening of tightening bolt 101, and the combined load between restraint device 11 and restraint device 12 is adjusted.

[0028] Leg member 15 is joined near the end of restraint device 12. Leg member 16 is joined near the end of restraint device 13. Leg member 15 and leg member 16 are then joined together with tightening bolt 102, thereby connecting restraint device 12 and restraint device 13 to each other. A coil spring 122 is disposed inside sleeve 112 provided on leg member 15, with its axis center at tightening bolt 102. Coil spring 122 is sandwiched between tightening bolt 102 and the bottom surface of sleeve 112. When tightening bolt 102 is tightened, coil spring 122 is compressed, and the resulting stress applies a compressive force toward leg member 16 to leg member 15 as a connecting load. The amount of compression of coil spring 122 is adjusted according to the amount of tightening of tightening bolt 102, and the connecting load between restraint device 12 and restraint device 13 is adjusted.

[0029] Restraint device 13 and restraint device 14 are connected to each other at their respective opposing ends by tightening bolt 103. A coil spring 123 is disposed inside sleeve 113 provided in restraint device 14, with the inserted tightening bolt 103 as its axis. Coil spring 123 is sandwiched between tightening bolt 103 and the bottom surface of sleeve 113. When tightening bolt 103 is tightened, coil spring 123 is compressed, and the resulting stress applies a compressive force toward restraint device 13 as a coupled load to restraint device 14. The amount of compression of coil spring 123 is adjusted according to the amount of tightening of tightening bolt 103, and the coupled load between restraint device 13 and restraint device 14 is adjusted.

[0030] Restraint device 11 and restraint device 14 are connected to each other at their respective opposing ends by tightening bolt 104. A coil spring 124 is disposed inside sleeve 114 provided in restraint device 11, with the inserted tightening bolt 104 as its axis. Coil spring 124 is sandwiched between tightening bolt 104 and the bottom surface of sleeve 114. When tightening bolt 104 is tightened, coil spring 124 is compressed, and the resulting stress applies a compressive force toward restraint device 14 as a combined load to restraint device 11. The amount of compression of coil spring 124 is adjusted according to the amount of tightening of tightening bolt 104, and the combined load between restraint device 11 and restraint device 14 is adjusted.

[0031] As described above, the restraining devices 11 to 14 grip the power cable 2 by applying surface pressure to the surface of the power cable 2 from the periphery of the power cable 2 in two or more axial directions, each of which equally divides the central angle of the power cable 2. More specifically, the restraining devices 11 to 14 apply surface pressure to the power cable 2 from two orthogonal axial directions. Furthermore, of the two axes along which the restraining devices 11 to 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 installation base 9, and the other extends in the X-axis direction, which is the direction perpendicular to the one axis.

[0032] 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 shape obtained by dividing a cylindrical cross section surrounding power cable 2 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 power cable 2. Then, a force is applied in a direction in which the opposing ends of restraining device 11 and restraining device 12 move closer to each other. Also, a force is applied in a direction in which the opposing ends of restraining device 12 and restraining device 13 move closer to each other. A force is applied in a direction in which the opposing ends of restraining device 13 and restraining device 14 move closer to each other. A force is applied in a direction in which the opposing ends of restraining device 14 and restraining device 11 move closer to each other. As a result, restraining devices 11 to 14 apply a surface pressure to 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." Furthermore, 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." Furthermore, 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." Furthermore, 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 member 15 and leg member 16 are placed so that their respective installation surfaces are in contact with installation base 9 and so that the ends of restraint device 12 and restraint device 13 face each other. The installation surface of leg member 15 is fixed to installation base 9 with mounting bolt 151. The installation surface of leg member 16 is fixed to installation base 9 with mounting bolt 161.

[0035] The leg member 15 to which the restraining device 12 is connected is fixed to the installation base 9, thereby fixing the restraining device 12 to the installation base 9. Furthermore, the leg member 16 to which the restraining device 14 is connected is installed and fixed to the installation base 9, thereby fixing the restraining device 14 to the installation base 9. In this way, the restraining device 12 and the restraining device 11 are fixed, and the restraining device 13 and the restraining device 14 are fixed, thereby fixing the entire cleat 1 to the installation base 9.

[0036] In the first embodiment, sleeves 111 and 114 are provided at both ends of restraint device 11, sleeve 112 is provided at the end of leg member 15, and sleeve 113 is provided at the end of restraint device 14, but the positions of sleeves 111 to 114 are not limited to these. Sleeves 111 to 114 may be arranged at other positions as long as opposing pairs of restraint devices 11 to 14 can be fixed by tightening bolts 101 to 104 that pass through them without interfering with each other. For example, sleeve 114 may be provided on the restraint device 14 side.

[0037] (Restraint Procedures) 3 is a flowchart showing the procedure for restraining the power cable with the cleats. Next, the flow of the procedure for restraining the power cable 2 with the cleats 1 will be described with reference to FIG.

[0038] Leg members 15 and 16 are placed so that their respective installation surfaces are in contact with installation base 9 and so that the ends of restraints 12 and 13 face each other, and are temporarily fixed to installation base 9 with mounting bolts 151 and 161 (step S1). Here, in Fig. 1, the bolt hole for mounting bolt 151 provided in leg member 15 and the bolt hole for mounting bolt 161 provided in leg member 16 are not circular but oval in shape extending in the X-axis direction in order to accommodate changes in the distance between restraints 12 and 13.

[0039] Continuing the explanation by returning to Figure 3, power cable 2 is placed inside a semi-cylinder formed by restraint device 12 connected to leg member 15 and restraint device 13 connected to leg member 16 (step S2).

[0040] The restraining devices 11 to 14 are arranged so that the semi-cylinder formed by the restraining devices 11 and 14 covers the power cable 2 and surrounds the periphery of the power cable 2 (step S3).

[0041] The four tightening bolts 101-104 that connect the restraining devices 11-14 are tightened. The tightening of the tightening bolts 101-104 is then adjusted so that the compressive forces of the coil springs 121-124 are uniform, sufficient restraining force is obtained, and the maximum value of the surface pressure falls within the limit of the allowable surface pressure of the power cable 2 (step S4).

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

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

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

[0045] In Figure 4, σ0 is the surface pressure per unit area from 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 angle in the circumferential direction from the vertically upward direction (positive Y-axis direction) from the center of power cable 2. Surface 201 is an infinitesimal surface along the circumference of the cable's outer diameter. Surface 202 is an infinitesimal surface that has the Y-axis as its normal and is at the same position as surface 201 in the Y-axis direction. F1 is the infinitesimal vertically downward surface pressure from cleat 1 that surface 201 receives.

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

[0047]

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[0048] Furthermore, surface 201 is inclined at an angle θ with respect to surface 202, which is perpendicular to the direction in which surface pressure σ0 acts, so if the area of ​​surface 202 is dS2, then the minute surface pressure F1 can be expressed as F1 = σ0 × W × dS2. Therefore, the minute surface pressure F1 in the vertical direction applied to surface 201 by cleat 1 is expressed by the following equation (2). F1 reaches a maximum value σ0Wrdθ when θ = 0, and a minimum value 0 when θ = π / 2, and varies depending on the angle θ.

[0049]

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[0050] Here, if the infinitesimal surface pressure F1 is integrated over the upper semicircle, it becomes equal to the surface pressure from the upper half due to cleat 1. Because the upper semicircle is symmetrical in the left and right rotational directions relative to the position where angle θ is 0, twice the value obtained by integrating angle θ 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. Therefore, the surface pressure from the upper half due to cleat 1 can be expressed by the following equation (3).

[0051]

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[0052] Therefore, the surface pressure σ0 per unit area by the 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, 2θ1=φ is set, and the surface pressure σ0 can be expressed as the following equation (5).

[0055]

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[0056] Next, the restraining force of the cleat 1 will be explained using the surface pressure σ0 per unit area calculated above. The cleat 1 exerts a surface pressure on the power cable 2 in the direction of the X-axis in FIG. 1, and also exerts a surface pressure on the power cable 2 in the direction of the Y-axis, which is 90 degrees to the X-axis. In other words, the 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 the same magnitude.

[0057] Let us consider the force that the cleat 1 exerts on the surface 201 shown in FIG. 4 toward the center of the power cable 2. The same symbols as those used in FIG. 4 will be used in the explanation here. The force that acts on the surface 201 toward the center due to the surface pressure in the Y-axis direction of the cleat 1 is expressed as F. 1center Then, F 1center is expressed by the following formula (6): where F1 is the force that the surface 201 receives due to the surface pressure of the cleat 1 in the Y-axis direction.

[0058]

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[0059] In addition, the force acting toward the center of the surface 201 due to the surface pressure in the X-axis direction of the cleat 1 is F 2center Then, F 2center is expressed by the following formula (7): where F2 is the force that the surface 201 receives due to the surface pressure of the 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 is constant, and is not dependent on the angle θ from the X-axis direction extending from the center of the power cable 2, and F center is constant and does not depend on the angle θ.

[0063] Let us consider the force that is used as the basis for determining the limit of the allowable surface pressure applied to the cable corrosion protection layer. The force F applied by cleat 1 toward the center at angle θ iscenter is the same as the maximum value of the minute surface pressure of cleat 1 when pressure is applied from a uniaxial direction at angle θ = 0, which is σ0Wrdθ. In other words, the minute surface pressure of cleat 1 is the same as the maximum value when surface pressure is applied from a uniaxial direction.

[0064] The binding force F of cleat 1 is the force F directed toward the center at angle θ by cleat 1. center is integrated in the circumferential direction of the power cable 2 to calculate the overall pressure, and the calculation result is multiplied by the friction coefficient μ to obtain the following formula (9): where φ is the contact angle of the cleat 1 with respect to the power cable 2.

[0065]

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[0066]

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

[0068]

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[0069] For comparison, we will now explain the restraining force of a cleat that applies pressure from a single axis. Here, a cleat that applies pressure from a single axis is called a uniaxial restraint cleat. Figure 5 is a cross-sectional view showing an outline of a uniaxial restraint cleat. The sleeve and coil spring are omitted from Figure 5.

[0070] As shown in Fig. 5, the single-axis restraint cleat has semi-cylindrical restraints 211 and 212 formed by dividing a cylinder in half in the longitudinal direction. Leg members 213 and 214 are connected to restraint 212. Restraints 211 and 212 are arranged so that their ends face each other, sandwiching power cable 2 between them. Restraints 211 and 212 are joined to each other at their opposing ends by tightening bolts 215 and 216. Although not shown, tightening bolts 215 and 216 are equipped with sleeves and springs, similar to cleat 1, and compressive forces act on restraints 211 and 212 in opposing directions due to stress from the springs. This compressive force causes surface pressure from restraints 211 and 212 to be applied to power cable 2, resulting in a restraining force that limits longitudinal movement of power cable 2.

[0071] Here again, we consider the force acting on the surface 201 shown in Figure 4. The symbols used in the explanation here are the same as those used in Figure 4. The force acting towards the center due to the force acting on the surface 201 from the surface pressure of the uniaxial restraint cleat is expressed as F 1center Then, F 1center is expressed by the following formula (12): where F1 is the force that the surface 201 receives from the surface pressure of the uniaxial restraint cleat in the Y-axis direction.

[0072]

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[0073] Binding force F of uniaxial restraining cleat base 1 is F 1center is calculated by integrating the force in the entire cable direction to find the overall pressure and multiplying it by the friction coefficient μ. In the circumferential direction, θ is symmetrical every π / 2, so it is divided into four and integrated. This gives the restraining force F of the uniaxial restraining cleat. base 1 is expressed by the following equation (13): where θ1 is 90 degrees.

[0074]

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[0075] If θ1 is set to 2θ1=φ to match the contact angle φ of the rubber spacer 3, the restraining force F of the uniaxial restraining cleat base 1 is expressed by the following equation (14).

[0076]

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[0077] Here, by substituting the calculation formula for the surface pressure per unit area σ0 shown in formula (5) into formula (14), the restraint force F of the uniaxial restraint cleat can be calculated. base 1 is expressed by the following equation (15).

[0078]

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

[0080]

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[0081] Here, the restraining force F of the uniaxial restraining cleat before considering the reduction rate α due to heat cycle and the safety factor β is base Consider 1. The restraining force F of the axial restraining cleat base As shown in formula (13), the surface pressure F 1 toward the center of the power cable 2 at the angle θ shown in formula (12) is 1center is calculated by integrating in the circumferential direction of the uniaxial restraint cleat. 1center is dependent 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, so that it does not contribute 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 is 0, which is the maximum value. 1center This can be judged based on the criteria.

[0082] (Comparison of binding force) Based on the above, the difference in restraining force between the cleat 1 according to Example 1 and a uniaxial restraint cleat will be explained. Here, a CV80mm2 cable with copper wire shielding was used as the power cable 2 used to compare restraining force. Figure 6 shows the conditions used in 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 the cleat 1 according to Example 1, the contact angle and tightening force are the same as those in Table 302, and two springs are arranged on each of two axes offset by 90 degrees, so that compressive force is applied in the two axial directions.

[0083] The surface pressure σ0 per unit area in one axis direction at a normal temperature of 20°C is calculated using equation (5). According to Table 302, the cable tightening force P of one spring is 921 N, 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 the following equation (17).

[0084]

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[0085] As a limit of the surface pressure applied to the cable corrosion protection layer, when the surface pressure toward the center of the power cable 2 is used as a reference, F center and F in a uniaxial restraint cleat 1center The maximum value of is the same.

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

[0087]

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

[0089]

number

[0090] For these, the allowable surface pressure conditions are the same as the maximum value of the minute surface pressure at θ = 0° when calculating the surface pressure per unit area σ0. Therefore, the minute surface pressure of cleat 1 can be kept within the allowable range of the allowable surface pressure, just like the maximum value of the minute surface pressure of a uniaxial restraint cleat, and the restraint force can be improved from 852 N to 1372 N compared to a uniaxial restraint cleat.

[0091] As described above, the cleat 1 according to the first embodiment applies surface pressure to the power cable 2 from two axial directions that are 90 degrees apart in the circumferential direction. This allows the minute surface pressure applied to the cable corrosion protection layer to be kept the same as the maximum minute surface pressure of a uniaxial restraint cleat, while improving the restraining force compared to that of a uniaxial restraint cleat. In other words, the cable restraining force can be increased without changing the maximum surface pressure applied to the cable corrosion protection layer. This makes it possible to improve the safety of cable installations. [Example]

[0092] Fig. 7 is a see-through perspective view of a cleat according to Example 2. Fig. 7 shows a see-through view of the interior to make the configuration easier to understand, but also includes parts that are not actually visible from the outside, such as the coil spring 121. Fig. 7 also shows, by way of example, the conductor 21, inner semiconductive layer 22, metal shielding layer 25, and anticorrosion layer 28, which are the main components of the power cable 2.

[0093] The cleat 1 according to Example 2 has two axes for applying surface pressure that are shifted by 45 degrees from the two axes for applying surface pressure in Example 1. The configuration of the cleat 1 according to Example 2 will be described below.

[0094] Fig. 8 is a cross-sectional view showing an outline of a cleat according to Example 2. In Fig. 8, the sleeve and coil spring are omitted.

[0095] Cleat 1 has restraints 11-14 made by dividing a cylindrical member so that the circular cross-sectional shape is divided into four equal parts by arcs with a central angle of 90 degrees, as well as leg members 15 and 16 for installation on installation base 9. Cleat 1 also has tightening bolts 101-104 that connect each of the restraints 11-14 together, and mounting bolts 151 and 161 that secure leg members 15 and 16 to installation base 9.

[0096] The restraining devices 11 to 14 are members made of metal such as aluminum. A rubber spacer 3 having a certain thickness according to the outer diameter of the cable is arranged on the inner wall of the restraining devices 11 to 14. The restraining devices 11 to 14 are arranged so as to surround the power cable 2 and form a cylinder, as shown in FIG.

[0097] Restraints 11 and 12 are positioned so that their ends face in the direction obtained by rotating 45 degrees clockwise around the X-axis as viewed from the paper. Similarly, restraints 13 and 14 are positioned so that their ends face in the direction obtained by rotating 45 degrees clockwise around the X-axis as viewed from the paper. Furthermore, restraints 12 and 13 are positioned so that their ends face in the direction obtained by rotating 45 degrees counterclockwise around the X-axis. Similarly, restraints 11 and 14 are positioned so that their ends face in the direction obtained by rotating 45 degrees counterclockwise around the X-axis.

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

[0099] In this way, of the two axes along which restraint devices 11 to 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 installation base 9. Also, of the two axes along which restraint devices 11 to 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 installation base 9.

[0100] Restraint device 11 and restraint device 12 are connected to each other at their respective opposing ends by tightening bolt 101. Restraint device 12 and restraint device 13 are connected to each other at their respective opposing ends by tightening bolt 102. Restraint device 13 and restraint device 14 are connected to each other at their respective opposing ends by tightening bolt 103. Restraint device 11 and restraint device 14 are connected to each other at their respective opposing ends by tightening bolt 104.

[0101] The restraining devices 11 to 14 apply surface pressure toward the anticorrosion layer 28, which is the outermost layer of the power cable 2, and the rubber spacer 3 that each has comes into close contact with the anticorrosion layer 28 of the power cable 2. The restraining devices 11 to 14 restrain the movement of the power cable 2 in the longitudinal direction by the frictional force between the rubber spacer 3 and the anticorrosion layer 28 of the power cable 2.

[0102] Leg member 15 is connected to the outer wall of restraint 13 near a position halfway along the arc. Leg member 15 extends from the connection position to restraint 13 toward the outside of restraint 12, then bends at a point a certain distance away from restraint 13, and has an installation plane at the end of the bend.

[0103] Leg member 16 is connected to the outer wall of restraint 13 at a position opposite to leg member 15 with respect to the halfway position of the arc. Leg member 16 extends from the connection position to restraint 13 toward the outside of restraint 13 and bends at a point a certain distance away from restraint 13, with an installation plane at the end of the bend.

[0104] The leg members 15 and 16 are placed so that their respective installation surfaces are in contact with the installation base 9. The installation surface of the leg member 15 is fixed to the installation base 9 with a mounting bolt 151. The installation surface of the leg member 16 is fixed to the installation base 9 with a mounting bolt 161.

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

[0106] As described above, in the cleat 1 according to Example 2, the two axes for applying surface pressure are positioned at 45 degrees clockwise or counterclockwise from the X-axis. In other words, the joining positions of the restraining devices 12 and 13 and the joining positions of the restraining devices 13 and 14 are shifted from positions directly below the center. This eliminates the need to position the tightening bolts that sandwich the leg members 15 and 16. In other words, as shown in FIG. 8, the joining positions of the restraining devices 12 and 13 and the joining positions of the restraining devices 13 and 14 can be positioned at positions 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 installation base 9 do not need to be movable relative to the installation base 9. Furthermore, the tightening bolt 103 does not need to penetrate the installation plane of the leg members 15 and 16, and can have the same configuration as the other tightening bolts 101, 102, and 104. This simplifies the structure of the cleat 1 and makes it easier to manufacture. Furthermore, in this case, the binding force is the same as in Example 1, so the binding force can be improved, and the safety of the cable installation can be improved.

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

[0109] In the above, the cleat 1 has been described as restraining the power cable 2, which is a single-core cable, but the same applies to a triplex cable. Fig. 9 is a perspective view showing the cleat in a state where it is restraining a triplex cable.

[0110] The triplex cable 4 is a single power cable made up of three power cables 2. As shown in Fig. 9, the cleat 1 surrounds the triplex cable 4 with restraints 11 to 14 via a rubber spacer 3. The cleat 1 grips the triplex cable 4 by applying surface pressure in two orthogonal axial directions.

[0111] 10 is a cross-sectional view showing an outline of the cleat with the triplex cable restrained. As shown in FIG. 10, a leg member 17 is connected to the restraining device 13. The leg member 17 has one leg extending from the restraining device 13, and has a flat surface at the end of the extended leg. The leg member 17 is fixed to the installation base 9 with mounting bolts 151 and 161.

[0112] Here, 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 the cleat 1 is fixed to the installation base 9 using two leg members 15 and 16 may be used. Also, in the case of a single-core cable 2 as shown in FIG. 8, a configuration in which the cleat 1 is fixed to the installation base 9 using a leg member 17 having one leg may be used.

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

[0114] In this case as well, restraint device 11 and restraint device 12 are connected to each other at their respective opposing ends by tightening bolt 101. Restraint device 12 and restraint device 13 are connected to each other at their respective opposing ends by tightening bolt 102. Restraint device 13 and restraint device 14 are connected to each other at their respective opposing ends by tightening bolt 103. Restraint device 11 and restraint device 14 are connected to each other at their respective opposing ends by tightening bolt 104.

[0115] The restraining devices 11 to 14 apply surface pressure toward the anticorrosion layers 28, which are the outermost layers of the three power cables 2 included in the triplex cable 4, so that the rubber spacers 3 come into close contact with the anticorrosion layers 28 of the triplex cable 4. The restraining devices 11 to 14 restrain the movement of the triplex cable 4 in the longitudinal direction by the frictional force between the rubber spacers 3 and the anticorrosion layers 28 of the power cables 2.

[0116] Here, the case where the two axes along which the surface pressure is applied are inclined 45 degrees clockwise or counterclockwise from the X axis when restraining the triplex cable 4 has been described as an example, but this is not limiting. For example, the cleat 1 can similarly restrain the triplex cable 4 even if the two axes along which the surface pressure is applied are the X-axis and Y-axis directions.

[0117] As described above, the cleat 1 is capable of gripping the triplex cable 4 and restricting movement in the longitudinal direction.

[0118] Furthermore, in the above explanation, the cleat 1 applies surface pressure 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 be 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 Installation base 11~14 Restraints 15,16 Leg members 101~103 Fastening bolts 111~114 Sleeve 121~124 coil spring 151,161 Mounting bolts

Claims

1. first to fourth restraints each having a shape obtained by dividing a cylindrical shape surrounding the power cable so that the circular cross section of the cylindrical shape is divided into four equal parts, and each having a first end and a second end at the divided positions on both sides; a leg member connected to at least one of the first restraint device to the fourth restraint device and fixed to an installation base; a first end of the first restraint and a second end of the second restraint face each other, a first end of the second restraint and a second end of the third restraint face each other, a first end of the third restraint and a second end of the fourth restraint face each other, and a first end of the fourth restraint and a second end of the first restraint face each other, and the restraints are arranged to surround the power cable; By applying a force in a direction in which a first end of the first restraint device and a second end of the second restraint device approach each other and a direction in which a first end of the third restraint device and a second end of the fourth restraint device approach each other, a force is applied to each of the first restraint device to the fourth restraint device in a first axial direction, thereby applying a surface pressure in the first axial direction of the power cable, and by applying a force in a direction in which a first end of the second restraint device and a second end of the third restraint device approach each other and a direction in which a first end of the fourth restraint device and a second end of the first restraint device approach each other, a force is applied to each of the first restraint device to the fourth restraint device in a second axial direction perpendicular to the first axial direction, thereby applying a surface pressure in the second axial direction of the power cable, thereby applying a surface pressure of the same magnitude as a resultant force to a surface of the power cable from the directions of the first axis and the second axis on a circumference perpendicular to the central axis of the power cable, and the surface pressure applied to the surface of the power cable toward the cable center is kept constant regardless of location on the circumference perpendicular to the central axis of the power cable, thereby gripping the power cable. A restraint device characterized by:

2. The restraint device according to claim 1, characterized in that, of the first axis and the second axis that apply surface pressure to the power cable, one of the first axis and the second axis extends in a direction from the center of the power cable toward the installation base, and the other axis extends in a direction perpendicular to the first axis.

3. The restraint device described in claim 1, characterized in that none of the first axis and the second axis that apply surface pressure to the power cable of the first restraint device to the fourth restraint device coincide with the direction from the center of the power cable toward the installation base.

4. a first spring that applies a force in a direction in which a first end of the first restraining device and a second end of the second restraining device approach each other; a second spring that applies a force in a direction in which the first end of the second restraining device and the second end of the third restraining device approach each other; a third spring that applies a force in a direction in which the first end of the third restraining device and the second end of the fourth restraining device approach each other; a fourth spring that applies a force in a direction in which the first end of the fourth restraining device and the second end of the first restraining device approach each other; 2. The restraint device according to claim 1, further comprising:

5. a first restraint to a fourth restraint, each having a shape obtained by dividing a cylindrical cross section surrounding the periphery of a power cable so that the circular cross section is divided into four equal parts, and each having a first end and a second end at the divided positions on both sides, are arranged to surround the periphery of the power cable, with the first end of the first restraint facing the second end of the second restraint, the first end of the second restraint facing the second end of the third restraint, the first end of the third restraint facing the second end of the fourth restraint, and the first end of the fourth restraint facing the second end of the first restraint; a force is applied to each of the first to fourth restraints in a direction in which a first end of the first restraint and a second end of the second restraint approach each other and in a direction in which a first end of the third restraint and a second end of the fourth restraint approach each other, thereby applying a force in a first axial direction to each of the first to fourth restraints, thereby applying a surface pressure in the first axial direction of the power cable; and a force is applied to each of the first to fourth restraints in a direction in which a first end of the second restraint and a second end of the third restraint approach each other and in a direction in which a first end of the fourth restraint and a second end of the first restraint approach each other, thereby applying a force in a second axial direction orthogonal to the first axial direction to each of the first to fourth restraints, thereby applying a surface pressure in the second axial direction of the power cable, thereby applying surface pressure of the same magnitude to the surface of the power cable from the directions of the first axis and the second axis on a circumference orthogonal to the central axis of the power cable, and keeping the surface pressure applied to the surface of the power cable toward the cable center at a constant value regardless of location on the circumference orthogonal to the central axis of the power cable, thereby gripping the power cable; At least one of the first restraint device to the fourth restraint device is fixed to an installation base to restrict movement of the power cable in the longitudinal direction. A restraint method characterized by:

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