Method for measuring surface pressure of cable connection part

Abstract

To provide a method for measuring the surface pressure of a cable connection part that makes it possible to easily and appropriately evaluate the soundness of the cable connection part.SOLUTION: There is provided a method for measuring the surface pressure of a cable connection part in which a cable terminal part is connected to an insulation unit. The method includes: disposing a sheet-like surface pressure sensor with a thickness of 0.3 mm or less capable of measuring the surface pressure distribution in a predetermined region, on the outer peripheral surface of a component of the cable terminal part that forms an interface serving as a measurement target of surface pressure; inserting the cable terminal part on which the surface pressure sensor is disposed into the insulation unit; fixing the cable terminal part in a pressed state; and measuring the surface pressure on the basis of the output result of the surface pressure sensor at that time.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for measuring surface pressure at a cable connection. [Background technology]

[0002] Conventionally, known cable connections include terminal connections such as in-gas terminal connections, in-oil terminal connections, and in-air terminal connections, as well as intermediate connections such as straight connections and branch connections. Generally, a cable connection is formed by connecting a cable terminal to an insulating unit having an internal electrode and an insulator arranged on the outer periphery of the internal electrode.

[0003] In the above-mentioned cable connection, the cable terminal is inserted into the insulation unit and fixed in a pressed state so that a predetermined surface pressure is generated at the interface between the two. Patent Document 1 discloses that in a prefabricated cable connection, a surface pressure sensor is placed on the outermost diameter portion made of semiconductive rubber of a premolded insulator (also called a stress cone), which is the connecting material of the cable terminal, and this surface pressure sensor measures the surface pressure generated at the interface between the insulation unit and the cable terminal to evaluate the soundness of the cable connection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-111124 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 cannot directly measure and evaluate the surface pressure that occurs at the interface between the insulating rubber part of the pre-molded insulator and the insulating unit, or at the interface between the pre-molded insulator and the cable insulator, which affect the insulating performance of the cable connection.In addition, Patent Document 1 discloses that the appropriateness of the surface pressure distribution in the circumferential direction can be evaluated by placing surface pressure sensors at 90° intervals in the circumferential direction, but it is not possible to continuously grasp the surface pressure distribution over a wide range.

[0006] Conventionally, direct measurement of the surface pressure occurring at the interface between a premolded insulator and a cable insulator has been performed by cutting out a groove in the outer surface of the cable insulator and embedding a pressure sensor such as a strain sensor in the groove. This method poses a problem in terms of workability, as it requires the work of forming the groove in the outer surface of the cable insulator and, after placing the pressure sensor in the groove, filling the groove with an insulating material such as silicone rubber. In particular, when evaluating the surface pressure distribution, the workability is further impaired because pressure sensors must be placed in multiple locations.

[0007] An object of the present disclosure is to provide a method for measuring the surface pressure of a cable connection portion that can easily and appropriately evaluate the soundness of the cable connection portion. [Means for solving the problem]

[0008] A method for measuring surface pressure at a cable connection portion according to the present disclosure includes: A method for measuring surface pressure at a cable connection portion in which a cable terminal portion is connected to an insulation unit, comprising: a sheet-like surface pressure sensor having a thickness of 0.3 mm or less and capable of measuring the surface pressure distribution in a predetermined area is disposed on the outer peripheral surface of a component of the cable terminal portion that forms the interface that is the object of surface pressure measurement; The cable terminal portion on which the surface pressure sensor is disposed is inserted into the insulation unit and fixed in a pressed state; The surface pressure is measured based on the output result of the surface pressure sensor at this time. [Effects of the Invention]

[0009] According to the present disclosure, the soundness of a cable connection can be easily and appropriately evaluated. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a cable connection portion to which a surface pressure measuring method according to a first embodiment can be applied. [Figure 2] FIG. 2 is a diagram showing an example of a surface pressure measurement system including a surface pressure sensor. [Figure 3] FIG. 3 is a diagram showing an example of the measurement results of the surface pressure sensor. [Figure 4] 4A to 4C are diagrams illustrating a surface pressure measuring method according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an example of a method for fixing the surface pressure sensor. [Figure 6] FIG. 6 is a diagram showing a cable connection portion to which the surface pressure measuring method according to the second embodiment can be applied. [Figure 7] 7A and 7B are diagrams showing a surface pressure measuring method according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] [First embodiment] Fig. 1 is a cross-sectional view showing the overall configuration of a cable connection 1 to which the surface pressure measurement method according to the first embodiment can be applied. The cable connection 1 shown in Fig. 1 is an example of an intermediate connection that connects cable terminals together. The overall structure of the cable connection 1 is similar to that of a conventional cable connection, so it will only be briefly described.

[0013] As shown in Fig. 1, the cable connection part 1 is constructed by attaching a cable terminal part 10 to an insulating unit 20. In this embodiment, the cable connection part 1 is an intermediate connection part, and is called a rubber block joint (RBJ).

[0014] The cable terminal 10 includes power cables 10A and 10B and a conductor connection tube 14.

[0015] The power cables 10A and 10B have, in order from the center, a cable conductor 11, a cable insulator 12, a cable outer semiconductive layer 13, a cable shielding layer (not shown), and a cable sheath (not shown). At the cable terminal 10, each layer is exposed by step-stripping a predetermined length from the tip of the power cables 10A and 10B.

[0016] The conductor connection pipe 14 electrically and mechanically connects the cable conductors 11, 11 of the power cables 10A, 10B. The conductor connection pipe 14 is made of a conductive metal material suitable for conducting electricity, such as copper, aluminum, a copper alloy, or an aluminum alloy.

[0017] The insulating unit 20 is arranged to surround the outside of the cable terminal 10. The insulating unit 20 is a one-piece rubber block insulator in which a rubber insulating portion 21, an internal electrode 22, a stress cone portion 23, and an external shielding layer 24 are integrally molded.

[0018] The insulating unit 20 shown in Fig. 1 has an unbroken structure in which the external shielding layer 24 is connected to both stress cone portions 23. Note that the insulating unit 20 is not limited to an unbroken structure, and may have a one-end unbroken structure in which the external shielding layer 24 is connected to either one of the stress cone portions 23, 23, or a double-end unbroken structure in which the external shielding layer 24 is not connected to either of the stress cone portions 23, 23.

[0019] Suitable rubber materials for forming the insulating unit 20 include, for example, silicone rubber or ethylene propylene rubber (EP rubber). When the insulating unit 20 is formed by molding, the internal electrode 22, stress cone portion 23, and external shielding layer 24 are preferably formed from the same material, such as semiconductive silicone rubber or semiconductive ethylene propylene rubber (semiconductive EP rubber). The rubber insulating portion 21 is also preferably formed from the same type of non-conductive insulating material.

[0020] Although both the internal electrode 22 and the stress cone portion 23 are conductive, they do not have to be made entirely of semiconductive rubber as long as at least the surface is conductive. For example, they may be made of insulating rubber and only the surface may be coated with a conductive paint such as semiconductive paint. Furthermore, although the external shielding layer 24 is conductive, it may be formed by coating a conductive paint such as semiconductive paint instead of semiconductive rubber.

[0021] The cable connection portion 1 is assembled, for example, by a diameter expansion method. In the diameter expansion method assembly process, the cable insertion hole 25 (see FIG. 4) of the insulation unit 20 is previously held in an expanded state by a diameter expansion member such as a spiral core (not shown). The insulation unit 20 is inserted into one power cable 10A, and in this state, the cable conductors 11, 11 of the power cables 10A, 10B are connected to the conductor connection tube 14. Thereafter, the insulation unit 20 is moved to a position where the conductor connection tube 14 and the internal electrode 22 are electrically connected, and the diameter of the insulation unit 20 is reduced. In this way, the cable terminal portion 10 is attached to the insulation unit 20.

[0022] A protective case 51 is disposed on the outside of the cable terminal portion 10 and the insulating unit 20. The protective case 51 is fixed to the cable sheaths of the power cables 10A and 10B, for example, by forming an anticorrosion layer 52 by wrapping tape around the end portion. Furthermore, a waterproof mixture (for example, a waterproof compound such as urethane) is filled between the insulating unit 20 and the protective case 51. The cable connection portion 1 is waterproofed by the protective case 51 and the waterproof mixture.

[0023] The conductor connection tube 14 is electrically connected to the internal electrode 22. Furthermore, the cable insulators 12 of the power cables 10A and 10B are connected to the rubber insulating portion 21 and the stress cone portion 23 of the insulation unit 20 in a state where a predetermined surface pressure is applied.

[0024] The conductor connecting tube 14 and the internal electrode 22 may be electrically connected by wrapping a semiconductive tape (not shown) around the outer periphery of the conductor connecting tube 14 and bringing the semiconductive tape into contact with the internal electrode 22, or by configuring the internal electrode 22 and the conductor connecting tube 14 to be in direct contact with each other.

[0025] At the cable connection portion 1, the inner diameter dimensions of the insulation unit 20 when contracted are designed so that a predetermined surface pressure is generated at the interface between the cable insulator 12 and the insulation unit 20 (specifically, the rubber insulation portion 21).

[0026] In this embodiment, the surface pressure generated at the interface between the cable insulator 12 and the insulating unit 20 is measured using a surface pressure sensor 101. Fig. 2 is a diagram showing an example of a surface pressure measurement system 100 including the surface pressure sensor 101. For example, "I-SCAN" manufactured by Nitta Corporation can be applied to the surface pressure measurement system 100.

[0027] The surface pressure sensor 101 is a sheet-like sensor capable of measuring the surface pressure distribution in a predetermined area. The surface pressure sensor 101 shown in Fig. 2 is a resistive film type (pressure-sensitive type) sensor. Note that the surface pressure sensor 101 may also be a capacitance type or strain gauge type sensor.

[0028] The surface pressure sensor 101 has a pressure-sensitive portion 102 and a lead portion 103. In the case of a resistive film type, the pressure-sensitive portion 102 is formed, for example, by bonding two sheets on which electrodes 104 are formed in parallel at regular intervals so that the electrodes 104 are arranged in a grid pattern. In the pressure-sensitive portion 102, each grid point of the electrodes 104 becomes a measurement point.

[0029] An electrical signal indicating the electrical resistance value at each measurement point is output to, for example, a processing device 105 (for example, a personal computer) connected to the lead portion 103. The processing device 105 displays the measurement results from the surface pressure sensor 101, i.e., the surface pressure distribution measured by the pressure sensitive portion 102, in a visually recognizable manner (see FIG. 3).

[0030] The surface pressure sensor 101 can be easily attached to the outer circumferential surface of the measurement target portion by, for example, gluing. There is no need for the conventional complicated work of forming a groove in the cable insulator 12 and embedding the surface pressure sensor therein.

[0031] The surface pressure sensor 101 preferably has a thickness of 0.3 mm or less. This means that even if the surface pressure sensor 101 is placed at the interface of the measurement target area, the effect on the surface pressure generated at the interface is extremely small, allowing the surface pressure distribution to be measured with high accuracy. For example, it is preferable to use a general-purpose surface pressure sensor 101 with a thickness of 0.2 mm. A thin surface pressure sensor 101 with a thickness of 0.1 mm may also be used. The size of the pressure-sensitive part 102 of the surface pressure sensor 101 is set appropriately depending on the size of the measurement target area.

[0032] It is preferable that the surface pressure sensor 101 is heat resistant. The usable temperature range of the surface pressure sensor 101 is, for example, −40 to 120° C. This makes it possible to measure the surface pressure distribution in a state that simulates the temperature environment during actual use of the cable connection part 1.

[0033] 4A to 4C are diagrams showing a surface pressure measurement method according to the first embodiment. Note that the surface pressure measurement may use cable pieces corresponding to the power cables 10A and 10B (the ends of the power cables from which the cable conductor 11, the cable insulator 12, and the cable outer semiconductive layer 13 are exposed, cut into short lengths).

[0034] First, prepare the insulation unit 20 and power cables 10A and 10B to be measured (see FIG. 4A). The insulation unit 20 holds the cable insertion hole 25 in an expanded state using a diameter expanding member such as a spiral core. The power cables 10A and 10B are also stripped at their ends so that at least the cable insulation 12 and the cable outer semiconductive layer 13 are exposed. If connection to a conductor connection tube 14 is required, the cable conductor 11 is also exposed.

[0035] Next, a surface pressure sensor 101 is arranged on the outer circumferential surface of the power cables 10A and 10B (see FIG. 4B). The surface pressure sensor 101 is arranged, for example, so that the pressure-sensitive part 102 straddles the cable insulation 12 and the cable outer semiconductive layer 13. The surface pressure sensor 101 may also be arranged so that the pressure-sensitive part 102 is located only on the cable insulation 12.

[0036] A plurality of surface pressure sensors 101 may be arranged in the circumferential direction of the cable insulator 12. By using a plurality of surface pressure sensors 101, the surface pressure distribution occurring at the interface between the cable insulator 12 and the insulation unit 20 can be obtained continuously over a wider range.

[0037] The surface pressure sensor 101 is fixed to the power cables 10A, 10B in a manner that allows it to be easily attached and detached. The surface pressure sensor 101 is fixed to the power cables 10A, 10B, for example, by wrapping a tape 106 around it (see FIG. 5). The tape 106 is preferably 0.15 mm or less in thickness and highly elastic. The tape 106 is preferably made of a fluororesin such as polytetrafluoroethylene (PTFE), and a suitable example is a 0.13 mm thick Teflon (registered trademark) tape. A thin 0.08 mm thick Teflon (registered trademark) tape may also be used for the tape 106.

[0038] By using tape 106 that is thinner than surface pressure sensor 101 and covering the entire surface pressure sensor 101 with tape 106, it is possible to prevent the tip of surface pressure sensor 101 from coming into contact with insulation unit 20 and becoming curled up when power cables 10A, 10B are attached to insulation unit 20. Furthermore, by applying a lubricant such as silicone grease to the outside of tape 106, it is possible to more effectively prevent surface pressure sensor 101 from becoming curled up.

[0039] It is preferable to spirally wind the tape 106 while butting it together so as not to overlap. This makes the thickness of the tape on the surface pressure sensor 101 uniform, preventing measurement errors in the surface pressure distribution due to uneven tape thickness.

[0040] Next, the power cables 10A and 10B with the surface pressure sensor 101 attached are inserted to a predetermined position in the insulating unit 20, and the insulating unit 20 is fixed by reducing its diameter (see FIG. 4C). Based on the output result of the surface pressure sensor 101 at this time, the surface pressure occurring at the interface between the cable insulator 12 and the insulating unit 20 is measured.

[0041] 4A to 4C, a surface pressure measurement method is described in which the power cables 10A, 10B are inserted from the right side of the insulation unit 20. In this case, the left side of the insulation unit 20 may be left without one of the power cables 10A, 10B inserted, or a jig having approximately the same diameter as the cable insulators 12 of the power cables 10A, 10B may be inserted to mount the power cables 10A, 10B in a balanced manner to the insulation unit 20. Also, the cable conductors 11 of the power cables 10A, 10B may be compression-connected to each other with conductor connection tubes 14, as in a normal assembly process, before they are mounted in the insulation unit 20.

[0042] In this embodiment, by measuring the surface pressure using the surface pressure sensor 101, the surface pressure distribution occurring at the interface between the cable insulator 12 and the insulation unit 20 (particularly the rubber insulation part 21) can be continuously obtained over a wide range.

[0043] Furthermore, by positioning the surface pressure sensor 101 (specifically, the pressure-sensitive portion 102) so as to straddle the cable insulator 12 and the cable outer semiconductive layer 13, it is possible to measure not only the surface pressure distribution occurring at the interface with the insulating portion (in this embodiment, the rubber insulating portion 21) located on the outer periphery of the cable insulator 12, but also the surface pressure occurring at the interface with the rising portion P1 of the stress cone portion 23 (hereinafter referred to as the ``stress cone rising portion P1'') (i.e., the interface between the cable insulator 12 and the stress cone rising portion P1), and the surface pressure at the interface with the semiconductive portion (in this embodiment, the stress cone portion 23) located on the outer periphery of the cable outer semiconductive layer 13.

[0044] The stress cone rising portion P1 is positioned closer to the tip of the cable's outer semiconductive layer 13 in the cable insertion direction, and is therefore located at the interface between the cable insulation 12 and the stress cone portion 23. If the surface pressure at the interface between the cable's outer semiconductive layer 13 and the stress cone portion 23 is inappropriate, sufficient surface pressure may not be applied to the stress cone rising portion P1, where the electric field is high. If the contact surface pressure between the cable's outer semiconductive layer 13 and the stress cone portion 23 is insufficient, the tip of the cable's outer semiconductive layer 13 may become an electrical protrusion, which may cause partial discharge. By positioning the surface pressure sensor 101 so that it straddles the cable insulation 12 and the cable's outer semiconductive layer 13, it is possible to check for abnormalities in these before completing the assembly of the cable connection portion 1.

[0045] When measuring surface pressure by embedding a surface pressure sensor in the cable insulator 12 as in the past, it is difficult to reproduce the measurement state of the surface pressure sensor, but with the surface pressure measurement method of this embodiment, the measurement state of the surface pressure sensor 101 can be easily reproduced, making it possible to calibrate the surface pressure sensor 101 with high accuracy, and even to perform calibration in a high-temperature environment. Furthermore, the surface pressure sensor 101 is detachably fixed to the outer peripheral surface of the cable insulator 12 and can be easily disassembled, allowing it to be reused and reducing the cost of measuring surface pressure.

[0046] The surface pressure measurement method in this embodiment is intended to evaluate the soundness of the cable connection part 1, specifically to determine the suitability of the cable connection part 1 (particularly the insulation unit 20) before actual use, and there is no need to take into account the insulation performance during actual use (when electricity is applied), etc.

[0047] As described above, the surface pressure measuring method according to the first embodiment has the following features either alone or in appropriate combination.

[0048] That is, the surface pressure measurement method according to the first embodiment is a method for measuring the surface pressure of a cable connection portion 1 in which a cable terminal portion 10 is connected to an insulating unit 20, and includes arranging a sheet-like surface pressure sensor 101, which is 0.3 mm or less in thickness and is capable of measuring the surface pressure distribution in a predetermined area, on the outer peripheral surface of a component of the cable terminal portion 10 that forms the interface that is the object of surface pressure measurement, inserting the cable terminal portion 10 with the surface pressure sensor 101 arranged thereon into the insulating unit 20 and fixing it in a pressed state, and measuring the surface pressure based on the output result of the surface pressure sensor 101 at this time.

[0049] Specifically, the insulation unit 20 is a rubber block insulator having a rubber insulating portion 21 formed from insulating rubber, a conductive internal electrode 22, and a conductive stress cone portion 23, and a surface pressure sensor 101 is disposed on the outer peripheral surface of the cable insulator 12 of the cable terminal portion 10, and the surface pressure sensor 101 measures the surface pressure at the interface between the rubber insulating portion 21 and the cable insulator 12. Alternatively, the surface pressure sensor 101 may be disposed so as to straddle the outer peripheral surface of the cable insulator 12 of the cable terminal portion 10 and the outer peripheral surface of the cable outer semiconductive layer 13.

[0050] According to the surface pressure measurement method of this embodiment, the surface pressure sensor 101 can be easily attached to the measurement target portion, improving workability. Furthermore, the surface pressure distribution occurring at the interface between the cable insulator 12 and the insulation unit 20 (particularly the rubber insulation portion 21) can be continuously obtained over a wide range by the surface pressure sensor 101. Therefore, the soundness of the cable connection 1 can be easily and appropriately evaluated, and the quality of the cable connection 1 can be improved.

[0051] Additionally, a tape having a thickness of 0.15 mm or less is spirally wound around the entire surface of the surface pressure sensor 101 without overlapping, to fix the surface pressure sensor 101 to the cable insulator 12 (component). Furthermore, a lubricant is applied to the outer surface of the tape 106. This prevents the tip of the surface pressure sensor 101 from coming into contact with the insulation unit 20 and being turned up when inserting the cable terminal portion 10 into the insulation unit 20, further improving workability.

[0052] [Second embodiment] Fig. 6 is a cross-sectional view showing the overall configuration of a cable connection section 2 to which the surface pressure measurement method according to the second embodiment can be applied. The cable connection section 2 shown in Fig. 6 is another example of an intermediate connection section that connects cable terminal sections together. Elements that are the same as or correspond to those in the first embodiment are given the same reference numerals, and duplicate explanations will be omitted.

[0053] As shown in Fig. 6, the cable connection part 2 is constructed by attaching a cable terminal part 30 to an insulating unit 40. In this embodiment, the cable connection part 2 is an intermediate connection part, and is also called a prefabricated intermediate connection part, a premolded intermediate connection part, or a prefabricated joint. Unlike the outer cone type of the first embodiment, the second embodiment is also called an inner cone type.

[0054] As in the first embodiment, the cable terminal portion 30 has power cables 10A, 10B and a conductor connection tube 14. In the cable connection portion 2, connection parts such as a stress cone 31 (also called a pre-molded insulator) and a compression device 32 are attached to the cable terminal portion 30. The compression device 32 is a member that applies surface pressure to the interface between the insulating rubber portion 31a of the stress cone 31 and the main insulating portion 41 of the insulation unit 40 by pressing the stress cone 31 from the rear end side, and a known configuration including, for example, a coil spring can be applied.

[0055] The stress cone 31 is composed of an insulating rubber portion 31a and a semiconductive rubber portion 31b connected to the rear end side of the insulating rubber portion 31a. The rubber material forming the stress cone 31 is preferably ethylene propylene rubber (EP rubber) or silicone rubber.

[0056] The insulating unit 40 is disposed so as to surround the outside of the cable terminal portion 30. The insulating unit 40 includes a main insulating portion 41, an internal electrode 42, and a shielding layer 43. The main insulating portion 41 is formed of a hard plastic resin material with high mechanical strength (e.g., epoxy resin or fiber reinforced plastics (FRP)). The internal electrode 42 is formed of a conductive metal material suitable for conducting electricity, such as copper, aluminum, a copper alloy, or an aluminum alloy. The main insulating portion 41 and the internal electrode 42 are integrally formed, for example, by molding, so that a portion of the internal electrode 42 is exposed from the inner circumferential surface. The shielding layer 43 is formed, for example, by applying a conductive paint to the outer circumferential surface of the main insulating portion 41.

[0057] In the assembly process of the cable connection portion 2, first, the protective fittings 33, compression devices 32, and stress cones 31 are inserted into each of the power cables 10A and 10B. An insulation unit 40 is then inserted into one of the power cables, the power cable 10A. In this state, the cable conductors 11, 11 of the power cables 10A and 10B are connected to the conductor connection tube 14. The insulation unit 40 is then moved to a position where the conductor connection tube 14 and the inner conductor 42 are electrically connected. Then, for each of the power cables 10A and 10B, the compression devices 32 are pressed toward the stress cones 31, and the protective fittings 33 are bolted, thereby attaching the cable terminal portion 30 to the insulation unit 40. Copper mesh tape, semiconducting tape, copper pipes, and heat-shrink tubing (all not shown) are arranged on the outside of the insulation unit 40, thereby waterproofing the cable connection portion 2.

[0058] The conductor connection tube 14 is electrically connected to the inner conductor 42. The inner peripheral surface of the stress cone 31 is connected to the cable insulator 12 of the power cables 10A and 10B with a predetermined surface pressure applied, and the outer peripheral surface of the stress cone 31 is connected to the main insulating portion 41 of the insulation unit 40 with a predetermined surface pressure applied.

[0059] At the cable connection portion 2, the pressing force, etc., applied by the compression device 32 is set so that a predetermined surface pressure is generated at each of the interfaces between the cable insulator 12 and the stress cone 31 (specifically, the insulating rubber portion 31a), and between the insulating unit 40 (specifically, the main insulating portion 41) and the stress cone 31 (specifically, the insulating rubber portion 31a).

[0060] The same surface pressure measurement method as in the first embodiment can be applied to the second embodiment. In the case of a prefabricated cable connection 2, by placing a surface pressure sensor 101 at the interface between the cable insulator 12 and the stress cone 31, it is possible to measure the surface pressure distribution occurring at the interface between the cable insulator 12 and the stress cone 31 (see FIG. 7A).

[0061] Furthermore, by arranging the surface pressure sensor 101 (specifically, the pressure-sensitive part 102) so as to straddle the cable insulator 12 and the cable outer semiconductive layer 13, as shown in Figure 7A, it is possible to measure not only the surface pressure distribution occurring at the interface with the insulating part located on the outer periphery of the cable insulator 12 (in this embodiment, the insulating rubber part 31a), but also the surface pressure occurring at the interface with the rising part P2 of the semiconductive rubber part 31b of the stress cone 31 (hereinafter referred to as the "stress cone rising part P2") (i.e., the interface between the cable insulator 12 and the stress cone rising part P2), and the surface pressure at the interface with the semiconductive part located on the outer periphery of the cable outer semiconductive layer 13 (in this embodiment, the semiconductive rubber part 31b).

[0062] The stress cone rising portion P2 is positioned closer to the leading end of the cable outer semiconductive layer 13 in the cable insertion direction, and is therefore located at the interface between the cable insulator 12 and the semiconductive rubber portion 31b. If the surface pressure at the interface between the cable outer semiconductive layer 13 and the semiconductive rubber portion 31b is inappropriate, sufficient surface pressure may not be applied to the stress cone rising portion P2, where the electric field is high. If the contact between the cable outer semiconductive layer 13 and the semiconductive rubber portion 31b is insufficient, the leading end of the cable outer semiconductive layer 13 may become an electrical protrusion, which may cause partial discharge. By positioning the surface pressure sensor 101 so that it straddles the cable insulator 12 and the cable outer semiconductive layer 13, it is possible to check for abnormalities in these before completing the assembly of the cable connection portion 2.

[0063] In addition, in the case of a prefabricated cable connection part 2, by placing a surface pressure sensor 101 at the interface between the insulation unit 40 and the stress cone 31, it is possible to measure the surface pressure distribution occurring at the interface between the insulation unit 40 and the stress cone 31 (see Figure 7B).

[0064] As described above, the surface pressure measuring method according to the second embodiment has the following features either alone or in appropriate combination.

[0065] That is, the surface pressure measurement method according to the second embodiment is a method for measuring the surface pressure of a cable connection portion 2 in which a cable terminal portion 30 is connected to an insulating unit 40, in which a sheet-like surface pressure sensor 101, which is 0.3 mm or less in thickness and can measure the surface pressure distribution in a predetermined area, is placed on the outer surface of a component of the cable terminal portion 30 that forms the interface that is the object of surface pressure measurement, the cable terminal portion 30 on which the surface pressure sensor 101 is placed is inserted into the insulating unit 20 and fixed in a pressed state, and the surface pressure is measured based on the output result of the surface pressure sensor 101 at this time.

[0066] Specifically, the insulation unit 40 has at least a main insulation portion 41 formed from a hard plastic resin material and an internal electrode 42 formed from a conductive metal material, and the cable terminal portion 30 has power cables 10A and 10B, stress cones 31 attached to the power cables 10A and 10B, and a compression device 32 that presses the stress cones 31 against the insulation unit 40, and a surface pressure sensor 101 is arranged on the outer surface of the cable insulator 12 of the power cables 10A and 10B, and the surface pressure sensor 101 measures the surface pressure at the interface between the stress cone 31 and the cable insulator 12.

[0067] In addition, the insulation unit 40 has at least a main insulation portion 41 formed from a hard plastic resin material and an internal electrode 42 formed from a conductive metal material, and the cable terminal portion 30 has power cables 10A, 10B, a stress cone 31 attached to the power cables 10A, 10B, and a compression device 32 that presses the stress cone 31 against the insulation unit 40, and a surface pressure sensor 101 is arranged on the outer peripheral surface of the stress cone 31, and the surface pressure sensor 101 measures the surface pressure at the interface between the stress cone 31 and the insulation unit 40.

[0068] According to the surface pressure measurement method of this embodiment, the surface pressure sensor 101 can be easily attached to the measurement target area, improving workability. Furthermore, the surface pressure sensor 101 can continuously acquire the surface pressure distribution occurring at the interface between the cable insulator 12 and the stress cone 31 and the interface between the stress cone 31 and the insulation unit 40 over a wide range. Therefore, the soundness of the cable connection 2 can be easily and appropriately evaluated, and the quality of the cable connection 2 can be improved.

[0069] Additionally, a tape having a thickness of 0.15 mm or less is spirally wound around the entire surface of the surface pressure sensor 101 without overlapping, to fix the surface pressure sensor 101 to the cable insulator 12 or stress cone 31 (component). Furthermore, a lubricant is applied to the outer surface of the tape 106. This prevents the front end of the surface pressure sensor 101 from coming into contact with the insulation unit 40 or the rear end of the surface pressure sensor 101 from coming into contact with the stress cone 31 and becoming rolled up when the cable terminal portion 10 is inserted into the insulation unit 40, further improving workability.

[0070] The invention made by the inventor has been specifically described above based on an embodiment, but the present invention is not limited to the above embodiment and can be modified within the scope of the gist thereof.

[0071] In the above embodiment, the surface pressure measurement method according to the present invention has been described as being applied to an intermediate joint connecting two power cables 10A and 10B, but the present invention is not limited to this and may also be applied to a terminal joint. The terminal joint to which the present invention can be applied may be any of a gas terminal joint, an oil terminal joint, and an air terminal joint.

[0072] For example, when the rubber block insulator (insulating unit 20) of the first embodiment is used as a cable termination, a main body material is attached to one side of the rubber block insulator (the left side in FIG. 1) instead of the power cable 10B on the left side of FIG. 1. That is, at the cable termination, the cable terminal 10 is connected to the main body material of the cable termination via the insulating unit 20. The main body material is made of a hard plastic resin material with high mechanical strength (e.g., epoxy resin or fiber-reinforced plastics (FRP)). The structure when using a rubber block insulator as a cable termination is described, for example, in JP 2005-354880 A.

[0073] On the outer peripheral surface of the connection point of the main body material with the rubber block insulator, a conductive paint is applied at a position corresponding to the cable outer semiconductive layer 13 of the power cable 10B, and the paint is electrically connected to the stress cone portion 23 of the rubber block insulator. In this embodiment, a surface pressure sensor 101 is disposed on the outer peripheral surface of the connection point of the main body material with the rubber block insulator, and the surface pressure sensor 101 can measure the surface pressure at the interface between the rubber insulating portion 21 and the main body material.

[0074] Furthermore, when the prefabricated structure of the second embodiment is applied as a cable termination connection, the insulating unit is the main body material of the cable termination connection (sometimes called a "bushing"). In this embodiment, as in the second embodiment, depending on the position of the surface pressure sensor 101, the surface pressure at the interface between the stress cone 31 and the cable insulator 12 and the surface pressure at the interface between the stress cone 31 and the insulating unit can be measured. [Explanation of symbols]

[0075] 1, 2 Cable connection 10, 30 Cable terminal 10A, 10B power cable 11 Cable conductor 12 Cable insulation 13. Cable outer semiconductive layer 14 Conductor connecting tube 20 Isolation Unit 21 Rubber insulation part (insulation part) 22 Internal electrode 23 Stress cone part (semiconductive part) 31 Stress Cone 31a Insulating rubber part (insulating part) 31b Semiconductive rubber part (semiconductive part) 32 Compression device 40 Isolation Unit 41 Main insulation section 42 Internal electrode 100 Surface Pressure Measurement System 101 Surface pressure sensor P1, P2 Stress cone rising part

Claims

1. A method for measuring surface pressure at a cable connection portion in which a cable terminal portion is connected to an insulation unit, comprising: a sheet-like surface pressure sensor having a thickness of 0.3 mm or less and capable of measuring the surface pressure distribution in a predetermined area is disposed on an outer peripheral surface of a component of the cable terminal portion that forms an interface that is an object of surface pressure measurement; The cable terminal portion on which the surface pressure sensor is disposed is inserted into the insulation unit and fixed in a pressed state; The surface pressure is measured based on the output result of the surface pressure sensor at this time. Method for measuring surface pressure at cable connections.

2. the insulating unit is a rubber block insulator having a rubber insulating portion formed of insulating rubber, a conductive internal electrode, and a conductive stress cone portion; The surface pressure sensor is disposed on an outer peripheral surface of a cable insulator of the cable terminal portion, The surface pressure sensor measures the surface pressure at the interface between the rubber insulating portion and the cable insulator. The method for measuring surface pressure at a cable connection according to claim 1.

3. the cable connection portion is a cable termination connection portion formed by connecting the cable terminal portion to a main body material via the insulating unit, the insulating unit is a rubber block insulator having a rubber insulating portion formed of insulating rubber, a conductive internal electrode, a conductive stress cone portion, and a conductive outer shielding layer; The surface pressure sensor is disposed on an outer peripheral surface of a connection portion between the main body material of the cable termination connection portion and the rubber block insulator, The surface pressure sensor measures the surface pressure at the interface between the rubber insulating part and the main body material. The method for measuring surface pressure at a cable connection according to claim 1.

4. the insulating unit has at least a main insulating portion made of a hard plastic resin material and an internal electrode made of a conductive metal material; the cable terminal portion includes a power cable, a stress cone attached to the power cable, and a compression device that presses the stress cone against the insulation unit; The surface pressure sensor is disposed on an outer peripheral surface of a cable insulator of the power cable, The surface pressure sensor measures the surface pressure at the interface between the stress cone and the cable insulator. The method for measuring surface pressure at a cable connection according to claim 1.

5. the insulating unit has at least a main insulating portion made of a hard plastic resin material and an internal electrode made of a conductive metal material; the cable terminal portion includes a power cable, a stress cone attached to the power cable, and a compression device that presses the stress cone against the insulation unit; The surface pressure sensor is disposed on the outer peripheral surface of the stress cone, The surface pressure sensor measures the surface pressure at the interface between the stress cone and the insulation unit. The method for measuring surface pressure at a cable connection according to claim 1.

6. a tape having a thickness of 0.15 mm or less is spirally wound around the entire surface of the surface pressure sensor without overlapping, thereby fixing the surface pressure sensor to the component; The method for measuring surface pressure at a cable connection according to claim 1.

7. Furthermore, a lubricant is applied to the outer peripheral surface of the tape. The method for measuring surface pressure at a cable connection portion according to claim 6.

8. The surface pressure sensor is disposed so as to straddle the outer peripheral surface of the cable insulator and the outer peripheral surface of the cable outer semiconductive layer, The surface pressure sensor measures the surface pressure at the interface with the insulating portion located on the outer periphery of the cable insulator, the surface pressure at the rising portion of the stress cone, and the surface pressure at the interface with the semiconductive portion located on the outer periphery of the cable outer semiconductive layer.

5. The method for measuring surface pressure at a cable connection according to claim 2 or 4.

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