Power cable termination connection and lifespan determination method

Abstract

The present invention provides a power cable termination connector and a method for determining the lifespan of a power cable termination connector having an insulator made of epoxy resin. [Solution] The power cable termination connection part 1 comprises a power cable 21, a cable head 3 having an insulator tube 311 made of epoxy resin into which the termination part 210 of the power cable 21 is inserted, and an embedded internal conductor 312 embedded in the insulator tube 311 and electrically connected to the power cable 21, and a sacrificial test unit 4 having a unit body 41 having a unit internal conductor 411 electrically connected to the embedded internal conductor 312 and a unit resin part 412 covering the unit internal conductor 411, and a sensor 42 for detecting the occurrence of cracks in the unit resin part 412. The life determination method determines the life of the cable head 3 based on the detection of the occurrence of cracks in the unit resin part 412 by the sensor 42.

Description

Technical Field

[0001] The present invention relates to a power cable terminal connection part and a method for determining its lifespan.

Background Art

[0002] Patent Document 1 discloses a cable terminal connection part connected to the terminal part of a power cable. The cable terminal connection part described in Patent Document 1 has a rubber outer covering that covers the cable terminal part of the power cable. In such a cable terminal connection part having a rubber outer covering, the outer covering may be deteriorated by irradiation such as ultraviolet rays, causing cracks and fissures, and the electrical insulation may deteriorate over time.

[0003] Therefore, in the cable terminal connection part described in Patent Document 1, an elastic ring made of the same material as the outer covering (i.e., rubber) is attached to the outer covering in an extended state. And Patent Document 1 discloses a method for determining that the deterioration of the outer covering is progressing when the elastic ring is broken.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the method described in Patent Document 1 can only be applied to a cable terminal connection part having a rubber outer covering.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a power cable terminal connection part and a method for determining the lifespan thereof, which can determine the lifespan of a power cable terminal connection part having a bushing made of epoxy resin. <000003 {32}>

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides a power cable termination connection unit comprising: a power cable; an insulator made of epoxy resin into which the termination portion of the power cable is inserted; a cable head having an embedded internal conductor embedded in the insulator and electrically connected to the power cable; a unit body having a unit internal conductor electrically connected to the embedded internal conductor and a unit resin part covering the unit internal conductor; and a sensor for detecting the occurrence of cracks in the unit resin part.

[0008] Furthermore, in order to achieve the above objective, the present invention provides a method for determining the lifespan of a cable head comprising an insulator made of epoxy resin into which the termination portion of a power cable is inserted, and an embedded internal conductor embedded in the insulator and electrically connected to the power cable, wherein a unit is attached to the cable head and used, the unit comprising a unit internal conductor electrically connected to the embedded internal conductor, a unit resin part covering the unit internal conductor, and a sensor for detecting the occurrence of cracks in the unit resin part, and the lifespan of the cable head is determined based on the detection of the occurrence of cracks in the unit resin part by the sensor. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a power cable termination connection and a method for determining the lifespan of a power cable termination connection having an insulator made of epoxy resin. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of the power cable termination connection portion in the embodiment. [Figure 2] This is an enlarged view of the area around the sacrificial test unit in Figure 1. [Figure 3] This is a cross-sectional view of the power cable in the embodiment. [Figure 4]This is an objective view of the sacrificial test unit in the embodiment. [Modes for carrying out the invention]

[0011] [Embodiment] Embodiments of the present invention will be described with reference to Figures 1 to 4. The embodiments described below are presented as preferred specific examples for carrying out the present invention, and while some parts specifically illustrate various technically preferable technical matters, the technical scope of the present invention is not limited to these specific embodiments.

[0012] (Power cable termination connection part 1) Figure 1 is a cross-sectional view of the power cable termination connection 1 in this embodiment. Figure 2 is an enlarged view of the area around the sacrificial test unit 4 in Figure 1.

[0013] The power cable termination connector 1 is attached, for example, to the roof of a railway vehicle. The tip of the power cable termination connector 1 (specifically, the fixed terminal 333 described later) is electrically connected to an electrical path (not shown) to which the power cable termination connector 1 is to be connected. The power cable termination connector 1 is used, for example, to electrically connect a power cable 21 to which a high voltage is applied to the wiring of an adjacent railway vehicle, or to electrically connect it to a pantograph.

[0014] The power cable termination connection 1 includes a cable assembly 2, a cable head 3, and a sacrificial test unit 4.

[0015] (Cable Assembly 2) The cable assembly 2 comprises a power cable 21, and a stopper 22, a stress cone 23, a compression device 24, and a cover member 25 fitted onto the power cable 21. Hereafter, the direction in which the central axis C of the power cable 21 extends will be referred to as the axial direction X. The side of the power cable 21 in the axial direction X that is connected to the connection part 33 described later will be referred to as the tip side X1, and the opposite side will be referred to as the base side X2.

[0016] Figure 3 is a cross-sectional view of the power cable 21. The power cable 21 includes, in order from the center, a cable conductor 211, an inner semi-conductive layer 212 of the cable, a cable insulator 213, an outer semi-conductive layer 214 of the cable, a cable shield layer 215, and a cable sheath 216.

[0017] The cable conductor 211 is formed, for example, by twisting a plurality of strands. The inner semi-conductive layer 212 of the cable and the outer semi-conductive layer 214 of the cable are provided to alleviate the concentration of the electric field, and are formed, for example, by extruding a polymer-based material in which conductive powder such as carbon is dispersed to have conductivity. The cable insulator 213 and the cable sheath 216 are formed, for example, by extruding an insulating material. The cable shield layer 215 is composed of, for example, a wire wound around the outer semi-conductive layer 214 of the cable and is grounded during use.

[0018] As shown in FIG. 1, the power cable 21 is stripped step by step so that the cable conductor 211, the cable insulator 213, the outer semi-conductive layer 214 of the cable, and the cable shield layer 215 are exposed in order from the tip side X1.

[0019] The stopper 22 has an annular shape. The stopper 22 is located on the tip side X1 of the stress cone 23 and abuts on the embedded inner conductor 312 described later from the base end side X2. The stopper 22 has a role of receiving a compressive force acting in the axial direction X from the compression device 24 to the stress cone 23.

[0020] The stress cone 23 is fitted to the outer peripheral portions of the cable insulator 213 and the outer semi-conductive layer 214 of the cable. In this embodiment, the stress cone 23 is composed of two members, and includes an insulating portion 231 on the tip side X1 and a semi-conductive portion 232 on the base end side X2. The inner peripheral portion of the semi-conductive portion 232 is in contact with the outer semi-conductive layer 214 of the cable and is connected to the ground potential via the outer semi-conductive layer 214 of the cable or the like. The stress cone 23 is compressed in the axial direction X by the compression device 24 and is in contact with both the power cable 21 and the inner peripheral surface of the bushing 311.

[0021] The compression device 24 is for compressing the stress cone 23 in the axial direction X. The tip side X1 of the compression device 24 abuts against the stress cone 23, and the base end side X2 is locked to the cover member 25. The compression device 24 has, for example, an elastic member such as a coil spring that is elastically deformable in the axial direction X, and compresses the stress cone 23 toward the tip side X1 by the reaction force of this elastic member.

[0022] The cover member 25 is attached to the flange member 32 (to be described later) of the cable head 3 from the base end side X2, and covers a portion exposed on the base end side X2 of the cable assembly 2 excluding the cover member 25, relative to the flange member 32. In the present embodiment, the cover member 25 includes a first cover 251 attached to the flange member 32 using a bolt B1, and a second cover 252 attached to the first cover 251 using a bolt B2. Between the first cover 251 and the cable sheath 216 of the power cable 21, it is sealed by a first sealing portion 26. Between the second cover 252 and the cable sheath 216, it is sealed by a second sealing portion 27.

[0023] (Cable head 3) The cable head 3 includes a bushing structure 31, a flange member 32, and a connection portion 33. The bushing structure 31 includes a bushing 311, and ensures electrical insulation between the power cable 21 and the members arranged around the power cable 21. The flange member 32 is a member for attaching the cable head 3 to the attachment target 10. The connection portion 33 is a part for electrically connecting the power cable 21 to the outside of the power cable terminal connection portion 1.

[0024] The bushing structure 31 includes a bushing 311, an embedded internal conductor 312, and an embedded fixing member 313.

[0025] [[ID=

[0026] The outer circumference of the insulator tube 311 is provided with multiple annular umbrella-shaped portions 311a protruding outwards at predetermined intervals in the axial direction X. By forming multiple umbrella-shaped portions 311a on the insulator tube 311, the creepage distance of the outer surface of the insulator tube 311 can be secured, and the occurrence of creepage discharge along the surface of the insulator tube 311 can be suppressed. The insulator tube 311 is formed by insert molding, in which molten resin is injected into a mold and cured while the embedded internal conductor 312, embedded fixing member 313, etc., which constitute the insulator tube structure 31 are placed inside the mold.

[0027] The buried internal conductor 312 is made of a highly rigid conductor such as copper, brass, or aluminum alloy, and is formed in a cylindrical shape. The buried internal conductor 312 is arranged on the inner circumference of the insulator pipe 311. The terminal portion 210 of the power cable 21 is inserted into the space inside the buried internal conductor 312. The inner diameter of the buried internal conductor 312 is formed to be larger than the outer diameter of the portion of the power cable 21 that is arranged inside the buried internal conductor 312. This makes it easier for the power cable 21 to be inserted inside the buried internal conductor 312. The tip end X1 of the buried internal conductor 312 protrudes from the insulator pipe 311 and is mechanically and electrically connected to the connection portion 33. The buried internal conductor 312 has the role of reinforcing the insulator pipe 311 and, by being electrically connected to the power cable 21 and being at the same potential as the power cable 21, has the role of mitigating electric field concentration around the power cable 21. Although the buried internal conductor 312 is described as a hollow cylindrical shape, it may also be formed in a solid columnar shape, for example, at least a portion of it.

[0028] The embedded fixing member 313 is embedded in the insulator pipe 311, with its base end X2 exposed from the insulator pipe 311. The embedded fixing member 313 is a cap nut with an open female threaded hole formed along the axial direction X, with the base end X2 open. The insulator pipe structure 31 is provided with embedded fixing members 313 at multiple locations in the circumferential direction. The flange member 32 is fixed to the embedded fixing member 313 using bolts B3.

[0029] The flange member 32 is formed in an annular shape, and the cable assembly 2 is inserted through its inner surface. The flange member 32 is fixed to the insulator structure 31 and also to the mounting target 10. The flange member 32 is positioned to face the insulator 311 from the base end side X2. The flange member 32 is fixed to the embedded fixing member 313 using bolts B3. In addition, the flange member 32 is fastened to the mounting target 10 at its outer circumference using bolts B4 and nuts N1. The flange member 32 is made of a conductor such as metal and becomes ground potential via the mounting target 10 when the power cable termination connection part 1 is in use. For example, the flange member 32 is electrically connected to the cable shield layer 215 of the power cable 21 via the cover member 25, and the cable shield layer 215 is grounded.

[0030] As shown in Figures 1 and 2, the connection portion 33 comprises a conductor connecting rod 331, a high-voltage shield 332, a fixed terminal 333, and a fastening nut 334. The conductor connecting rod 331 has a crimping portion 331a with a crimping hole 331b formed on the base end side X2, and a male threaded portion 331c protruding from the crimping portion 331a to the tip side X1. The cable conductor 211 of the power cable 21 is inserted into the crimping hole 331b, and the crimping portion 331a is crimped toward the cable conductor 211. This connects the conductor connecting rod 331 and the power cable 21 mechanically and electrically. The conductor connecting rod 331 also has a male threaded portion 331c protruding from the tip side X1. The male threaded portion 331c is positioned to pass through the high-voltage shield 332 and the fixed terminal 333, respectively.

[0031] The high-voltage shield 332 is made of a conductor and has a closed-bottom cylindrical shape that is open at the base end X2. The high-voltage shield 332 covers the portion of the buried internal conductor 312 that protrudes from the insulator 311 to the tip end X1.

[0032] The fixed terminal 333 is plate-shaped and is positioned to overlap the front end X1 surface of the high-voltage shield 332. The fixed terminal 333 is formed as a long plate, with a male threaded portion 331c passing through one end in the longitudinal direction, and a connection hole 333a for connecting an external object at the other end. The fixed terminal 333 and the high-voltage shield 332 are fastened together between the crimping portion 331a and the fastening nut 334, thereby electrically connecting the fixed terminal 333, the high-voltage shield 332, and the conductor connecting rod 331 to each other. The sacrificial test unit 4 is then fixed to the front end X1 of the fastening nut 334 using a nut N2 that is screwed onto the male threaded portion 331c.

[0033] (Sacrificial Test Unit 4) Sacrificial test unit 4 is used to determine the lifespan of the cable head 3. Sacrificial test unit 4 is a so-called sacrificial test piece that is attached to the cable head 3 and configured to cause a crack in the unit resin part 412 (described later) before the insulator 311.

[0034] First, let's explain the lifespan of the cable head 3. The cable head 3 experiences fatigue due to repeated thermal stress on the insulator 311 caused by changes in ambient temperature and temperature changes due to energization. Specifically, repeated thermal stress is generated in the insulator 311 due to the difference in the coefficient of linear expansion between the epoxy resin insulator 311 and the metal embedded within the insulator 311 (in this embodiment, the embedded internal conductor 312 and the embedded fixing member 313). Furthermore, since the multiple embedded fixing members 313 of the insulator 311 are fixed to the flange member 32, repeated thermal stress can also be generated in the insulator 311 if the thermal expansion or contraction of the insulator 311 is hindered by the multiple embedded fixing members 313 fixed to the flange member 32. If repeated stress is generated in the insulator 311 and cracks occur in the insulator 311, the electrical insulation performance of the insulator 311 may be severely reduced.

[0035] Therefore, in this embodiment, the fatigue life of the insulator 311 of the cable head 3 can be determined using the sacrificial test unit 4, and the use of the cable head 3 can be stopped before cracks occur in the insulator 311. The configuration of the sacrificial test unit 4 will be described below.

[0036] Figure 4 is a perspective view of the sacrificial test unit 4. As shown in Figures 2 and 4, the sacrificial test unit 4 comprises a unit body 41 having a unit internal conductor 411 electrically connected to the buried internal conductor 312 and a unit resin part 412 covering the unit internal conductor 411, and a sensor 42 for detecting the occurrence of cracks in the unit resin part 412.

[0037] The internal conductor 411 of the unit is formed in a disc shape with thickness in the axial direction X. The internal conductor 411 of the unit has a through hole 411a through which the male threaded portion 331c of the connection portion 33 is inserted. The sacrificial test unit 4 is fixed to the connection portion 33 by inserting the male threaded portion 331c through the through hole 411a and tightening it with a nut N2 from its tip side X1. In this way, the internal conductor 411 of the unit is electrically connected to the buried internal conductor 312 and the power cable 21 via the connection portion 33. Because the internal conductor 411 of the unit is electrically connected to the buried internal conductor 312, the internal conductor 411 undergoes repeated changes in current temperature, similar to the buried internal conductor 312 of the cable head 3, and undergoes repeated thermal expansion and contraction. In other words, the crack generation mode of the insulator 311 in the cable head 3 is simulated in the sacrificial test unit 4. The method of fixing the sacrificial test unit 4 to the cable head 3 is not particularly limited, as long as the unit's internal conductor 411 is electrically connected to the buried internal conductor 312. For example, the sacrificial test unit 4 may be fixed to the cable head 3 by welding or the like so that the unit's internal conductor 411 and the connection part 33 are electrically connected.

[0038] The unit resin portion 412 is formed in an annular shape (specifically, a circular shape) so as to surround the unit internal conductor 411 around its entire circumference. The unit resin portion 412 is molded by insert molding, in which molten resin is injected into a mold and cured while the unit internal conductor 411 is placed inside the mold.

[0039] The unit resin part 412 is designed to be more susceptible to thermal stress than the insulator tube 311 when repeated temperature changes occur at the power cable termination connection part 1, and to crack before the insulator tube 311. As will be described in detail later, in the method for determining the lifespan of the cable head 3 in this embodiment, the lifespan of the cable head 3 is determined based on the timing of crack occurrence in the unit resin part 412. Therefore, the unit resin part 412 is designed to crack earlier than the timing of crack occurrence in the insulator tube 311 of the cable head 3. Examples of measures taken in this embodiment to accelerate the occurrence of cracks in the unit resin part 412 are given below.

[0040] The first innovation is to make the difference in the coefficient of linear expansion between the unit's internal conductor 411 and the unit's resin part 412 greater than the difference in the coefficient of linear expansion between the buried internal conductor 312 and the insulator 311. This relatively increases the stress generated in the unit's resin part 412, making it more susceptible to cracking. As a specific example, if the buried internal conductor 312 of the cable head 3 is made of copper and the insulator 311 is made of epoxy resin, the unit's internal conductor 411 of the sacrificial test unit 4 may be made of Invar, SuperInvar, Kovar, etc., which have a lower coefficient of linear expansion than copper, and the unit's resin part 412 may be made of the same epoxy resin as the insulator 311. However, this is not limited to this, and the unit's resin part 412 and the insulator 311 may be made of different epoxy resins, etc.

[0041] The second innovation is to make the electrical resistivity of the unit's internal conductor 411 greater than that of the buried internal conductor 312. As a result, the unit's internal conductor 411 generates more heat when energized, and consequently, the thermal expansion and contraction of the unit's internal conductor 411 tend to be greater than that of the buried internal conductor 312 of the cable head 3. As mentioned in the first innovation, for example, if the buried internal conductor 312 is made of copper and the unit's internal conductor 411 is made of Invar, Super Invar, Kovar, etc., the electrical resistivity of the unit's internal conductor 411 will be greater than that of the buried internal conductor 312.

[0042] The third improvement is to make the thickness of the unit resin part 412 smaller than the thickness of the insulator pipe 311 in the area where the embedded internal conductor 312 is installed. As a result, the rigidity of the unit resin part 412 becomes less than that of the insulator pipe 311, making the unit resin part 412 more prone to cracking.

[0043] The fourth innovation is to configure the unit body 41 so that its overall size is sufficiently smaller than that of the cable head 3. For example, in this embodiment, the combined volume of the unit's internal conductor 411 and the unit's resin part 412 is less than 1 / 100th the volume of the insulator 311. As a result, the heat capacity of the unit's internal conductor 411 and the unit's resin part 412 is relatively small, and even when the cable head 3 and the sacrificial test unit 4 are placed in the same temperature environment, each part of the sacrificial test unit 4 is more susceptible to temperature changes (i.e., thermal expansion and contraction) than each part of the cable head 3. Therefore, cracks are more likely to occur in the unit's resin part 412.

[0044] By appropriately combining the aforementioned measures, the timing of crack occurrence in the unit resin part 412 will be earlier than the timing of crack occurrence in the insulator tube 311. In addition, other measures may be appropriately combined. For example, the shape of the unit resin part 412 may be modified so that stress tends to concentrate particularly in only a part of the unit resin part 412. As an example, by providing a recess in a part of the circumferential direction of the outer surface of the unit resin part 412, stress may be concentrated near the recess of the unit resin part 412.

[0045] The sacrificial test unit 4 is attached to the tip side X1 of the insulator tube 311. That is, the sacrificial test unit 4 is not present in the outer peripheral region of the insulator tube 311. This suppresses its influence on the electric field distribution around the insulator tube 311. From this viewpoint, it is preferable that the size of the unit body 41 is small. For example, it is preferable that the outer diameter of the unit body 41 is smaller than the outer diameter of the umbrella portion 311a located at the very tip side X1 of the insulator tube 311.

[0046] Furthermore, in this embodiment, since the sacrificial test unit 4 is attached to the tip of the cable head 3, it is not necessary to form a special shape on the insulator tube 311 itself for attaching the sacrificial test unit 4, for example, making attachment to the cable head 3 easy.

[0047] The sensor 42 is attached to the surface of the unit resin part 412. Figures 2 and 4 show an example in which the sensor 42 is attached to the outer circumferential surface of the unit resin part 412, but the sensor 42 may also be attached to, for example, the axial end face X of the unit resin part 412. The sensor 42 may be provided at one location on the surface of the unit resin part 412, or at multiple locations.

[0048] As shown in Figure 2, the sensor 42 comprises an element section 421, a power supply section 422, and a wireless transmission section 423. The element section 421 only needs to be able to detect the occurrence of cracks in the unit resin section 412, and can be an element such as a strain sensor, vibration sensor, or AE (Acoustic Emission) sensor.

[0049] The power supply unit 422 supplies power to the element unit 421 of the sensor 42 by energy harvesting. This eliminates the need to replace the power supply of the sensor 42. The power supply unit 422 can use known energy harvesting techniques, such as generating power from vibration or temperature differences.

[0050] The wireless transmitter 423 is a communication module capable of communication according to a predetermined wireless communication method, for example, and outputs the detection results of the sensor 42 to the outside. For example, when the power cable termination connection 1 is used for a railway vehicle as in this embodiment, the wireless transmitter 423 outputs a signal to the driver's cab of the railway vehicle or to a control center that monitors the operating status of the railway vehicle. In this embodiment, the sensor 42 is configured wirelessly by supplying power to the sensor 42 by energy harvesting and communicating wirelessly. This prevents the electric field distribution around the insulator 311 from being obstructed by the wire. In this embodiment, the power supply unit 422 and the wireless transmitter 423 are shown as being integrated into the sensor 42, but they may be provided separately from the sensor 42.

[0051] (Lifespan determination method) Next, the method for determining the lifespan of the cable head 3 according to this embodiment will be explained. The lifespan of the cable head 3 is the time when the cable head 3 should be replaced, and it is not necessarily the time when a crack occurs in the insulator tube 311 of the cable head 3. For example, the lifespan of the cable head 3 may be the time when it is expected that a crack will not occur in the insulator tube 311, and this time may be suitable for replacing the cable head 3.

[0052] The lifespan determination method can be performed, for example, by a lifespan determination unit 5, which includes a computer installed in the driver's cab, control room, etc. The lifespan determination unit 5 includes a control area that includes a processor and RAM, which is the calculation area when the processor is operating, and a storage unit that has ROM, a hard disk, etc., and stores programs executed by the CPU. The storage unit also stores the signal-to-noise ratio diagrams of the sacrificial test unit 4 and the cable head 3 obtained from prior tests.

[0053] The life determination unit 5 continuously receives the detection results from the sensor 42 from the time the power cable termination connection unit 1 is put into use and stores the history thereof. The detection results from the sensor 42 are stored as a change in stress over time. This history is stored at least until a crack is detected in the unit resin part 412 of the sacrificial test unit 4. Crack detection can be performed, for example, based on the change in stress over time exceeding a predetermined threshold.

[0054] Then, when the lifespan determination unit 5 detects a crack in the unit resin part 412, it calculates the lifespan of the cable head 3. The lifespan of the cable head 3 is calculated based on Minor's rule. An example of how the lifespan of the cable head 3 is calculated is described below.

[0055] When the life determination unit 5 detects a crack in the unit resin part 412, it obtains the number of stress cycles applied to the sacrificial test unit 4 up to the time of crack occurrence, based on the history of stress changes up to the time of crack occurrence. Then, the life determination unit 5 obtains an estimated stress amplitude based on the obtained number of cycles and the S / N diagram of the sacrificial test unit 4 stored in the life determination unit 5.

[0056] The life determination unit 5 then determines the lifespan of the cable head 3 based on the obtained number of repetitions and estimated stress amplitude, as well as the S / N diagram of the cable head 3 stored in the memory unit. As described above, the lifespan of the cable head 3 is determined using the sacrificial test unit 4.

[0057] Alternatively, artificial intelligence (AI) may be used to estimate the lifespan of the cable head 3 from the detection results of the sensor 42.

[0058] Furthermore, it is not always necessary to calculate the lifespan as described above. For example, if the sacrificial test unit 4 is configured such that the difference between the crack occurrence timing of the sacrificial test unit 4 and the crack occurrence timing of the insulator tube 311 of the cable head 3 is small, the crack occurrence timing of the sacrificial test unit 4 may be determined as the lifespan of the insulator tube 311 of the cable head 3.

[0059] (Operation and Effects of the Embodiment) The power cable termination connection unit 1 in this embodiment includes a unit body 41 having a unit internal conductor 411 electrically connected to an embedded internal conductor 312 and a unit resin part 412 covering the unit internal conductor 411, and a sacrificial test unit 4 having a sensor 42 for detecting the occurrence of cracks in the unit resin part 412. Therefore, the embedded internal conductor 312 of the sacrificial test unit 4 is energized in the same way as the embedded internal conductor 312 of the cable head 3, and the crack occurrence mode of the insulator 311 is reproduced in the sacrificial test unit 4. This makes it possible to determine the lifespan of the cable head 3 based on the occurrence of cracks in the unit resin part 412.

[0060] Furthermore, the difference in the coefficient of linear expansion between the internal conductor 411 and the resin part 412 of the sacrificial test unit 4 is greater than the difference in the coefficient of linear expansion between the buried internal conductor 312 and the insulator 311 of the cable head 3. As a result, the thermal stress generated in the sacrificial test unit 4 is greater than the thermal stress generated in the cable head 3, making it more likely for cracks to occur in the sacrificial test unit 4 before the cable head 3.

[0061] Furthermore, the sacrificial test unit 4 is located at the tip side X1 of the insulator tube 311. Therefore, the placement of the sacrificial test unit 4 on the cable head 3 suppresses the influence on the electric field distribution around the insulator tube 311.

[0062] Furthermore, the sacrificial test unit 4 includes a power supply unit 422 that supplies power to the sensor 42 by energy harvesting. Therefore, frequent replacement of the power supply unit 422 is unnecessary. Also, long wiring for supplying power to the sensor 42 is unnecessary. In particular, the area around the insulator 311 is designed to have a desired electric field distribution, and this electric field distribution is prevented from being obstructed by the aforementioned long wiring.

[0063] Furthermore, the sensor 42 outputs detection results wirelessly and is configured wirelessly. This also suppresses the influence of the electric field distribution around the insulator 311 on the wiring used to output the results from the sensor 42.

[0064] As described above, this embodiment provides a power cable termination connector and a lifespan determination method that can determine the lifespan of a power cable termination connector having an insulator made of epoxy resin.

[0065] (Summary of the embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0066] [1] A power cable termination connection unit 1 comprising a power cable 21, a cable head 3 having an insulator tube 311 made of epoxy resin into which the termination portion 210 of the power cable 21 is inserted, and an embedded internal conductor 312 embedded in the insulator tube 311 and electrically connected to the power cable 21, and a sacrificial test unit 4 having a unit internal conductor 411 electrically connected to the embedded internal conductor 312 and a unit resin part 412 covering the unit internal conductor 411, and a sensor 42 for detecting the occurrence of cracks in the unit resin part 412.

[0067] [2] The difference in coefficient of linear expansion between the internal conductor 411 of the unit and the resin part 412 of the unit in the sacrificial test unit 4 is greater than the difference in coefficient of linear expansion between the buried internal conductor 312 and the insulator 311 in the cable head 3, as described in [1].

[0068] [3] The sacrificial test unit 4 is located on the tip side X1 of the insulator tube 311, and is the power cable termination connection part 1 as described in [1] or [2].

[0069] [4] The power cable termination connection unit 1 according to any one of [1] to [3], comprising a power supply unit 422 that supplies power to the sensor 42 by energy harvesting, the sacrificial test unit 4.

[0070] [5] The power cable termination connection unit 1 according to any one of [1] to [4], wherein the sensor 42 outputs detection results wirelessly and is configured wirelessly.

[0071] [6] A method for determining the lifespan of a cable head 3, which includes an insulator 311 made of epoxy resin into which the terminal portion 210 of a power cable 21 is inserted, and an embedded internal conductor 312 embedded in the insulator 311 and electrically connected to the power cable 21, wherein a unit is attached to the cable head 3 and used, the unit includes an internal unit conductor 411 electrically connected to the embedded internal conductor 312, a resin unit part 412 covering the internal unit conductor 411, and a sensor 42 for detecting the occurrence of cracks in the resin unit part 412, and the lifespan of the cable head 3 is determined based on the detection of the occurrence of cracks in the resin unit part 412 by the sensor 42.

[0072] (Note) Although embodiments of the present invention have been described above, the embodiments described herein do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. Moreover, the present invention can be implemented with appropriate modifications without departing from its spirit. [Explanation of symbols]

[0073] 1…Power cable termination connection 21…Power cables 210...Terminal section 3… Cable head 311...Insulator tube 312... Buried internal conductor 4… Sacrifice Test Unit 41...Unit body 411...Internal conductor of the unit 412...Unit resin part 42...Sensor 422... Power supply unit X1...Tip side

Claims

1. Power cables and The cable head includes an insulator made of epoxy resin into which the terminal end of the power cable is inserted, and an embedded internal conductor embedded in the insulator and electrically connected to the power cable. The sacrificial test unit comprises a unit body having an internal unit conductor electrically connected to the buried internal conductor and a unit resin part covering the internal unit conductor, and a sensor for detecting the occurrence of cracks in the unit resin part. Power cable termination connection.

2. The difference in linear expansion coefficients between the internal conductor of the unit and the resin part of the unit in the sacrificial test unit is greater than the difference in linear expansion coefficients between the buried internal conductor and the insulator in the cable head. The power cable termination connection part according to claim 1.

3. The sacrificial test unit is located on the tip side of the insulator tube. The power cable termination connection part according to claim 1 or 2.

4. The sacrificial test unit includes a power supply unit that supplies power to the sensor by energy harvesting. The power cable termination connection part according to claim 1 or 2.

5. The aforementioned sensor outputs detection results wirelessly and is configured wirelessly. The power cable termination connection part according to claim 1 or 2.

6. A method for determining the lifespan of a cable head comprising an insulator made of epoxy resin into which the termination portion of a power cable is inserted, and an embedded internal conductor embedded in the insulator and electrically connected to the power cable, The cable head, A unit internal conductor electrically connected to the aforementioned buried internal conductor, The unit resin part that covers the internal conductor of the unit, A unit is used with a sensor that detects the occurrence of cracks in the resin part of the unit, Based on the detection by the sensor of a crack occurring in the resin part of the unit, the lifespan of the cable head is determined. Lifespan determination method.

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