Power cable monitoring system and method for manufacturing a sensor rope

Abstract

This power cable monitoring system comprises a power cable (100) including a power transmission cable (1) disposed in an inner circumferential portion, an armor wire (2) disposed in an outer circumferential portion, and a sensor rope (3, 4) including an optical fiber (7), for detecting a physical quantity of an object being measured, and a backscattered light measuring device (110) for measuring a distribution of the physical quantity of the object being measured, using backscattered light from the optical fiber (7), wherein a temperature and a strain distribution of the power cable (100) are obtained by means of a frequency shift signal of Rayleigh backscattered light obtained by the backscattered light measuring device (110), and a polarization distribution signal obtained by means of the Rayleigh backscattered light, on the basis of a signal detected by the sensor rope (3, 4).

Description

Technical Field

[0001] This application relates to a power cable monitoring system and a method for manufacturing a sensor rope.

Background Art

[0002] In wind power generation, regarding new needs such as offshore installation, the cases where it is near fisheries, shipping lanes, or where shipping lanes intersect are increasing. Overseas, a total of 90 disconnection accidents have occurred in the seven years from 2009 to 2016 (see, for example, Non-Patent Document 4). Under current laws, the responsibility for these accidents lies with the cable owner. Due to the occurrence of huge insurance premiums, what was previously an optional technical specification has recently become an essential required technical specification.

[0003] On the other hand, the installation of cables between remote islands is also accelerating. As its specification, installation in deep water is required. At that time, high voltage or power is required for the cables used, so huge cables are required to achieve this. Specifically, usually, the cable used is assumed to weigh 32 kg / m. As an example of the requirements for huge cables, the weight specifications are 42 kg / m for a 22 KV specification and 52 Kg / m for a 66 KV specification. Furthermore, the development of cables up to 130 KV and 250 KV specifications is required, and cables of unprecedented size are expected to be put into practical use in the future.

[0004] It is particularly difficult to measure the deformation of a cable by compounding an optical cable with the armor wire of a power cable in the above-mentioned large cables. The reason is that for cables with a diameter exceeding 100 mm, generally, a slip-type configuration is adopted. In the slip type, it is characterized by "slipping" between the conductive core and the outer (outer peripheral part) armor wire, or between the armor wires. Due to this "slipping", when the cable is bent, the strain in the armor wire is significantly (about 1 / 10) reduced, and the so-called "stranded wire" characteristic that can be kept within the allowable range of ordinary steel materials during manufacturing or laying work is utilized. Furthermore, in the case of onshore power cables, the causes of their failures include the increasing anthropogenic activities associated with urbanization, the difficulty of access, and the allowable degree of power outage. The requirements for the operation of cables, the cost and speed of accident response are increasing.

[0005] In the case of large cables as described above, it is difficult to realize a configuration that can easily maintain its own strength, and design, verification, and further monitoring for long-term use are cited as urgent needs.

[0006] At present, even if the cases of installing large cables as described above are few, globally, major companies at home and abroad are in major competitive relationships, and new manufacturing methods for the above large cables have become an issue.

[0007] Also, when installed on a dynamic deep-water platform or when connecting from the ocean to an onshore power grid, a floating cable that floats on the ocean surface is required, and it is necessary to grasp in real time the loads acting on the cable in ocean waves or winds, ships, and fishing operations. In this case, it is known that a speed of 0.1 second is required to follow the wave load. Furthermore, the administrator of the power grid (Grid) needs to predict in advance the failures of the cables related to the above applications, and to grasp the damage situation at the time of an accident, the methods of dealing with the damage, and the confirmation of the effects after the treatment.

[0008] On the other hand, optical fiber distributed measurement technology has been gradually maturing recently. It has been installed alone as a sensor until now, but recently, various studies have been conducted so that it can be integrated into the cable.

[0009] Therefore, at present, the development of cables that can achieve the following content becomes an issue. a) Monitoring of power operation due to heat generation. Realization of so-called Real Time Thermal Rating (RTTR). b) Detection of abnormal current before short circuit and identification of the location where it occurs, and identification of the short circuit location at the time of short circuit, and evaluation of cable structure damage. c) Evaluation of static and dynamic loads generated on the cable by waves or ocean currents. d) Sensing and evaluation of cable shape.

[0010] Conventionally, for high voltage dynamic export cables, a monocore structure and a three-core structure have been proposed, and an optical fiber has also been proposed as a communication line therein (see, for example, Patent Documents 1-3).

[0011] On the other hand, in the Distributed Fiber Optic Sensing (DFOS) technology for optical fibers, many technologies such as separation of temperature and strain, single-ended measurement, acoustic wave measurement, and shape sensing technology have been put into practical use, not limited to temperature measurement of the measurement object, using Brillouin scattering, Rayleigh scattering, and conventional Raman scattering. In addition, in the case of the non-slip type, a technology has been realized in which a large number of optical fibers are mounted on the same dedicated cable, and by acquiring the cable structure information, the three-dimensional displacement information of the cable can be measured. Furthermore, armored cables have been developed, and a cable manufacturing technology in which metal wires such as steel are synchronized with displacement has been established, and a mass-production technology that can simultaneously realize the protection of optical fibers and the measurement of armored rope deformation has been established (see, for example, Non-Patent Documents 1-5).

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

[0013] [Non-Patent Document 1] K. Kishida et al., ”Study of Optical Fibers Strain-Temperature Sensitivities Using Hybrid Brillouin-Rayleigh System”, Photonic Sensors, 2013, DOI: 10.1007 / s13320-013-0136-1. [Non-Patent Document 2] K. Kishida et al., ”Development of Real-Time Gated Digital (TGD) OFDR Method and Its Performance Verification”, Sensors 2021, 21, 4865. https: / / doi.org / 10.3390 / s21144865 [Non-Patent Document 3] Yasutaka Mori, ”Bending / Torsion Deformation Analysis of Electric Wires Considering Double Twisting Structure”, Transactions of the Robotics Society of Japan, Vol. 30, No. 8, 2012, pp. 813-821 [Non-Patent Document 4] B. Matvichuk et al., ”Full length Distributed temperature monitoring of export cables and interconnectors beyond 150km”, Omnisens SA, 2018. [Non-Patent Document 5] Nishimoto et al., ”Development of 66kV CV Submarine Cable with Trauma Detection Wire Using Optical Fiber”, Transactions of the Institute of Electrical Engineers of Japan, Series B, Vol. 112, No. 10, 1992, pp. 921-926 [Summary of the Invention]

Problems to be Solved by the Invention

[0014] However, in the BOTDR (Brillouin Optical Time Domain Reflectometer) using the above-mentioned Brillouin scattering, due to insufficient sensitivity, it may not be possible to detect a short circuit depending on the measurement temperature. Also, due to insufficient spatial resolution, for example, when using a spiral twisted wire, if the pitch of the spiral (about 1.5 m) is not less than 1 / 4, it may not be possible to detect the bending displacement of the measurement target. Also, when the displacement of the measurement target is fast, it has been pointed out that it cannot be detected because the sensitivity to detect the displacement is low (see, for example, Non-Patent Document 4).

[0015] Also, slip-type cable bending sensing has not yet been realized. For example, in the bending detection method by loss detection in the OTDR (Optical Time Domain Reflectometer) method, since the sensitivity is low, the cable diameter is gradually decreased from a large value, and loss can be detected only when bending a 15-mm cable. However, the reality is that the cable itself has already been damaged. Conversely, if the cable diameter is made small to facilitate cable bending, the safety will be impaired (see, for example, Non-Patent Document 5).

[0016] When organizing the above-mentioned problems related to practical application, they can be roughly classified into the following three. The first is the requirement for the implementation method of the optical fiber. In the case of FIMT fiber, temperature measurement is possible if it is well made, but for strain, since it has a free structure, measurement is theoretically impossible. That is, conventionally, there was a precedent of implementing an optical fiber in a high-voltage-resistant cable with a large weight. In this case, the optical fiber was implemented in a loose tube, and the deformation of the optical fiber did not match the deformation of the cable that is the measurement target. Therefore, with an optical fiber having such a normal structure, it is impossible to detect the strain of the measurement target, and it is also impossible to detect it as a structure. In addition, the manufacturing method of a high-voltage-resistant cable with a large weight does not conform to existing equipment, and a manufacturing method and a cable structure that conform to existing manufacturing equipment are desired.

[0017] The second is the requirement for having a function to monitor the measurement target. Regarding this, there are the following problems. The first problem is that it is possible to distributively measure the strain and temperature below the twist pitch of the armor wire (about 20 cm) with respect to the measurement target. The second problem is that it is possible to measure bending. The third problem is that it is possible to measure sound waves with respect to the measurement target. The fourth problem is that it is possible to measure the location of temperature abnormality for the measurement target. The fifth problem is that it is possible to detect flooding with respect to the measurement target. In other words, a technology that can detect and monitor in real time against a dynamically changing load such as waves has not been realized. Also, there is no monitoring measurement system that can satisfy a service life of several decades.

[0018] The third is the issue regarding the selection of what to use for the measurement technology. First, regarding Brillouin-based measurement, there is other company's technology, and a measurement range of 100 km for a fragment can be realized, but there is a problem that the measurement accuracy is insufficient. On the other hand, regarding Rayleigh-based and DAS-based measurement, ultra-long-distance measurement exceeding 100 km required for submarine cables cannot be sufficiently measured at present. In practical use, a technology applicable to the 10 km class and an optimal technology that can satisfy each required specification at least at a distance of 50 km or more are required.

[0019] This application discloses a technology for solving the above problems, and aims to accurately measure the distribution of strain and temperature, bending, and sound waves generated in a power cable including a floating cable installed on the ocean and a submarine cable installed on the seabed. It also aims to be able to detect temperature abnormal locations and water intrusion locations generated in the power cable.

Means for Solving the Problems

[0020] The power cable monitoring system disclosed in this application includes a power transmission cable arranged in the inner peripheral part, an armor wire arranged in the outer peripheral part, and an armored optical module having the same diameter as the armor wire and an optical fiber for detecting the physical quantity of the object to be measured. A backscattered light measuring device that measures the distribution of the physical quantity of the object to be measured by using the backscattered light from the optical fiber. and is provided with Based on the signal detected by the armored optical module, the temperature and strain distributions of the power cable are obtained from the frequency shift signal of the Rayleigh backscattered light and the polarization distribution signal obtained from the Rayleigh backscattered light obtained by the backscattered light measuring device. It is characterized by the above.

Effects of the Invention

[0021] According to the power cable monitoring system disclosed in this application, the distribution of strain and temperature, bending, and sound waves generated in a power cable including a floating cable installed on the ocean and a submarine cable installed on the seabed can be accurately measured. In addition, temperature abnormal locations and water intrusion locations generated in the power cable can be detected.

Brief Description of the Drawings

[0022]

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[0023] The intelligent power cable and the power cable monitoring system of the present application will be described below with reference to the drawings. The intelligent power cable of the present application is configured as an armored cable in which an SK steel wire (hereinafter also simply referred to as an SK wire), which faithfully detects a strain distribution and has a strength and flexibility equal to or higher than that of FIMT, is arranged and mounted at an intervening portion of individual steel wire wires, instead of a power cable that has conventionally used only FIMT (Fiber In Metallic Tube). Here, an armored cable is usually a component inherent to a power cable and is used for the purpose of protecting against tensile strength during cable laying, anchors, or injuries caused by fishing gear. The details will be described below with reference to the drawings.

[0024] Embodiment 1. First, a power cable monitoring system using the intelligent power cable according to Embodiment 1 will be described with reference to FIG. 1.

[0025] FIG. 1 is a diagram showing an example of the power cable monitoring system 200 according to Embodiment 1. As shown in FIG. 1, for the purpose of monitoring a submarine cable 101 laid on the seabed, a floating cable 102 connected from the seabed to the ocean surface, and a buried cable 103 buried underground on land (hereinafter collectively referred to as the intelligent power cable 100), a monitoring center 120 is provided with a hybrid type backscattered light measuring device 110 that can utilize both Brillouin scattering and Rayleigh scattering to process signals from the measurement fiber sensors built in the intelligent power cable 100. Here, the backscattered light measuring device 110 is provided with a beam splitter for measuring the polarization distribution from Rayleigh backscattered light, which will be described in detail below, and a processing device for processing backscattered light signals and the like (see Non-Patent Document 2). Note that the symbol "Q" in the figure indicates the position of the sea surface (ocean surface).

[0026] Here, as shown in FIG. 1, the submarine cable 101 is arranged along the seabed over a long distance to the seabed position to be installed from the monitoring center 120. The floating cable 102 is installed along the sea surface (see "Q" in the figure) using a floating body 102a or the like to the ocean surface position to be installed from the monitoring center 120. Further, the buried cable 103 is installed with most of it buried underground from the monitoring center 120 to the building position to be monitored.

[0027] When monitoring the intelligent power cable using the above power cable monitoring system, by connecting the backscattered light measurement device 110 and the intelligent power cable 100, the backscattered light measurement device 110 can measure the frequency shift of the scattered light corresponding to the installation position of the intelligent power cable. Then, based on the measured value, it can be used as a power cable monitoring system 200 to detect abnormalities such as mutations that have occurred in the intelligent power cable. In this way, the power cable monitoring system 200 mainly includes an intelligent power cable 100 and a backscattered light measurement device 110 as its main components.

[0028] As described above, by deploying the power cable monitoring system 200, based on the position near the monitoring center, it is possible to monitor the occurrence of abnormalities in the intelligent power cable 100 to be monitored for a long period of more than several decades at all positions where the intelligent power cable is installed. Here, as a measurement technique applicable to the power cable monitoring system 200, there is a RIP (Rayleigh Intensity Pattern) technique that can be applied to a measurement distance of 50 km or more, but 100 km is almost the limit. In the case of a long distance of about 200 km or more, the measurable distance ranges from both ends are monitored, but if it is necessary to measure the entire length for longer distances, it is necessary to extend the distance using a relay device. In COTDR, which is the basic technology of the RIP technique, there is a record of 9000 km when there is a relay device. Therefore, next, an example of the power cable monitoring system 200 of Embodiment 1 will be described below from the perspective of the measurement method.

[0029] FIG. 2 is a diagram for explaining the outline of the measurement method of the present application. It shows, in comparison with the "DTS" method (DTS: Distributed Temperature Sensing), which is a conventional method mainly using Raman scattering with MM fiber, the "separation by cable" method that simultaneously uses two types of SM fibers, and the "R&B hybrid" method that uses the same SM fiber to simultaneously measure the frequency shifts of both Rayleigh scattered light and Brillouin scattered light. That is, in the present application, the "separation by cable" method shown in the central column of this figure and the "R&B hybrid" method shown in the column to its right are used.

[0030] By using the above-described methods, measurements can be performed with high precision (spatial resolution less than 100 cm) over a long distance (10 km or more). In contrast, in the conventional "DTS" method, due to drift, the accuracy of the measurement data is inferior to that of the method of the present application, and the distance resolution is usually 100 cm or more, which is not as good as 10 cm or less of the present application. In the "R&B hybrid" method, due to the constraint in mainly using Brillouin measurement, the accuracy of the measured temperature is 0.3°C, 「Separation by Cable」 which is slightly inferior compared to 0.1°C or less of the method. Therefore, next, with reference to FIG. 3 described below, the details of the measurement method that enables the above-described high-precision measurement will be explained in correspondence with the configuration of the intelligent power cable used in the present application.

[0031] FIG. 3 is a block diagram for explaining the measurement method used in the power cable monitoring system of Embodiment 1 and the measurement FO (Fiber Optic) module used in the above measurement method, which is composed of this intelligent power cable (the upper part within the square frame surrounded by the dotted line in FIG. 3 shows the above measurement method, and the lower part within the square frame surrounded by the dotted line in FIG. 3 shows the above measurement FO module).

[0032] As described above, the part within the square frame surrounded by the dotted line in Fig. 3 indicates the features of the power cable monitoring system of Embodiment 1. In Embodiment 1, by combining the measurement FO module shown in the lower part within the square frame and the measurement method shown in the upper part of Fig. 3, high-precision measurement with a spatial resolution of less than 100 cm can be realized in a section with a measurement distance of 10 km or more.

[0033] Here, as shown in the measurement method in the upper part of Fig. 3, a method that utilizes the polarization distribution obtained from Rayleigh scattering, that is, a measurement method that measures the twist angle of a cable or rope to be measured from the Rayleigh scattering optical signal, and hybridizes the measured data with the RIP obtained from the Rayleigh scattering optical signal, can obtain high-precision data with a resolution (resolution with respect to the measurable distance) of 10 cm or less compared to the conventional measurement method. In particular, in the measurement of temperature and strain, it is possible to obtain an accuracy with a spatial resolution of less than 10 cm within a distance range of less than 10 km by a method that hybridizes Rayleigh scattering and Brillouin scattering. Also, in the measurement of temperature, strain, and deformation of a slip-type cable, it is possible to obtain an accuracy with a spatial resolution of less than 10 cm within a distance range greater than 50 km by a method that hybridizes RIP or high-speed RIP and the polarization distribution. Furthermore, in the measurement of the acoustic wave distribution, it is possible to obtain an accuracy with a spatial resolution of less than 100 cm within a distance range greater than 50 km by a method that hybridizes high-speed RIP and the polarization distribution.

[0034] Also, as shown in the measurement FO module in the lower part of FIG. 3, first, using one or several armored optical modules (refer to modules 3, 4, and 5 in the figure) in which one or several armor wires of a power cable (indicated by reference numeral 2 in FIG. 5 described below) have the same diameter, by distributively measuring the strain or torsion, which is a physical quantity of the armor wire, the conductor of the power cable surrounded by the armor wire or the shape of the cable can be measured. The following descriptions regarding the power cable monitoring system according to Embodiment 1 all explain the optical module having this feature. Note that the armored optical module used in the power cable monitoring system according to Embodiment 1 of the present invention has an elastic modulus of about 80% of that of the armor wires of the same diameter and can be manufactured by ordinary manufacturing equipment. For module 1 composed only of a conventional FIMT or module 2 composed of an FIMT and an SK wire, in the power cable monitoring system according to Embodiment 1 of the present invention, an armored optical module having the same diameter as the armor wire is used. Specifically, using module 3 composed of an FIMT with fixed points at regular intervals and an SK wire, the temperature and strain of the object to be measured, or the temperature and strain of the object to be measured and the deformation of the slip-type cable are measured respectively. Also, using module 4 composed of a Kira wire with excess length (romanized notation of "Kira" wire) (described later) and an SK wire, the temperature and strain of the object to be measured and the deformation of the slip-type cable are measured. In this case, as described above with reference to FIG. 2, two different single-mode (SM) optical fibers mounted on the same cable are used as a temperature measurement fiber and a strain measurement fiber respectively. Further, using module 5 composed of three or more SK wires, the temperature and strain of the object to be measured and the deformation of the slip-type cable are measured. In this case, both Rayleigh scattered light and Brillouin scattered light from at least three SM optical fibers are utilized. Note that when simultaneously measuring RIP and polarization distribution (measuring based on the simultaneously measured Rayleigh scattered light), even if there is one SK wire, it is possible to measure the deformation of the object to be measured.

[0035] For comparison with Modules 3 to 5 (collectively also referred to as armored optical modules), Modules 1 and 2, which are conventional FO modules, are shown in accordance with FIG. 3. Module 1 measures only temperature, and Module 2 is a module for measuring temperature and strain, or temperature, strain, and deformation of a slip-type cable.

[0036] Furthermore, below FIG. 3, characteristics regarding ease of cable manufacturing and strength / lifetime are shown corresponding to the modules with the above-described configuration. In Modules 1 and 2, both of these characteristics are at a low level, whereas in Module 3, both of these characteristics are at a medium (ordinary) level, and in Modules 4 and 5, both of these characteristics exhibit a high-level (high) effect. Therefore, below, the characteristics of each element constituting Modules 3 to 5 will be described with reference to the drawings.

[0037] FIG. 4 is a diagram showing the configuration and characteristics of three measurement FO modules, Module 3, Module 4, and Module 5, each having an optical fiber, which are used in the power cable monitoring system according to Embodiment 1.

[0038] As shown in this figure, each of Module 3 is composed of an FIMT with equally spaced fixed points (for temperature measurement; detailed structure will be described later) having an optical fiber for measurement and SK lines (three or more; mainly for strain measurement), and can provide high-quality temperature information and strain information of 0.1 °C or less for the measurement target. Also, each of Module 4 is composed of a Kira line with extra length (for temperature measurement; detailed content will be described later) having an optical fiber for measurement and SK lines (three or more; mainly for strain measurement), and can provide high-quality temperature information and strain information of 0.1 °C or less for the measurement target. Further, each of Module 5 is composed only of three or more SK lines having an optical fiber for measurement (for temperature measurement and strain measurement), simultaneously senses (detects) signals for obtaining strain and temperature, and separates and obtains the values of strain and temperature using the above-described backscattered light measuring device 110. Here, the outer diameter of the armored optical module used for Module 5 may be different from that of the above-mentioned armored cable (for example, a cable with an armored tension member structure covering the outer periphery), or may be the same. The reason for using three or more SK lines as described above will be explained in detail later.

[0039] Next, the intelligent power cable with the above measurement FO module will be described with reference to the figure. The intelligent power cable 100 (hereinafter also simply referred to as the power cable 100) used in the power cable monitoring system 200 of Embodiment 1 will be described with reference to FIG. 5.

[0040] FIG. 5 is a schematic cross-sectional view showing an example of the power cable 100 using a three-core power transmission cable 1, typically a CV cable (abbreviation for cross-linked polyethylene insulated vinyl sheath cable).

[0041] As shown in FIG. 5, the power cable 100 is this power cable 100Three power transmission cables 1 are arranged in the inner peripheral part (central part) thereof and have the conductor 11 in their axial parts, a plurality of armor wires 2 (hereinafter also referred to as first twisted wire wires 2) arranged in the outer peripheral part of the power cable, a plurality (three or more) of sensor ropes 3 (mainly for strain measurement) corresponding to the SK wires of each module, a sensor rope 4 (mainly for temperature measurement) corresponding to an FIMT with fixed points at regular intervals or a Kira wire with extra length, and an insulating layer 5 filled with resin or the like in the gap parts of the elements described above, and a shield part 6 in the outermost peripheral part, and are provided with these as main components. Here, the armor wire 2 has a stranded form in which a large number of twisted wires are assembled. Note that the reason for arranging the sensor rope 3 or the like in the outer peripheral part of the power cable is that the deformation of the cable is more remarkable in the outer peripheral part than in the inner peripheral part, and there is an advantage in giving priority to the evaluation there.

[0042] Next, an example of the above-mentioned sensor rope 3 or sensor rope 4 will be described in more detail with reference to FIGS. 6A and 6B.

[0043] FIG. 6A is a cross-sectional view (corresponding to a plane orthogonal to the rope axis) showing an example of the structure of a sensor rope 3a which is an example of the sensor rope 3, and FIG. 6B is a cross-sectional view (corresponding to a plane orthogonal to the rope axis) showing the structure of a sensor rope 4a which is one of the sensor ropes 4 and is an example of a Kira wire with extra length.

[0044] In any of the sensor ropes, the optical fiber 7 is disposed in the axial center portion, and five second twisted wire 20s spirally disposed outside thereof (appearing as an annular shape in this cross-sectional view) are adhesively fixed via resins 8a and 8b coaxially arranged with the optical fiber 7, respectively. Here, as will be described later, the resin 8a is filled as an adhesive over the entire length of the sensor rope 3a, and the resin 8b is not filled as an adhesive over the entire length of the sensor rope 4a, but is intermittently filled as an adhesive in the axial direction (at regular intervals). That is, it is characterized in that there is an extra length of the optical fiber between the filling portions (the same as the fixing portions). And the outer diameter D1 of the circumscribed circle of the sensor rope 3a (hereinafter simply referred to as the outer peripheral diameter D1. The same applies to the names of the outer diameters of the circumscribed circles of other sensor ropes. Refer to Fig. 6A), and the outer peripheral diameter D2 of the sensor rope 4a (refer to Fig. 6B) are both approximately 1.2 to 8 mm. Note that in any of Figs. 6A and 6B, as described above, the number of the second twisted wire 20s is five, and the cable's resistance to side pressure can be increased compared to the case where the number of the twisted wires is six. Also, in any of Figs. 6A and 6B, the sensing optical fiber 7 is disposed at the central axis positions of the sensor rope 3a and the sensor rope 4a, respectively.

[0045] Therefore, next, the manufacturing method of the sensor rope 4a (an example of the Kira wire with extra length) of the intelligent power cable according to Embodiment 1 will be described in detail below with reference to Fig. 7.

[0046] As shown in Fig. 7, the optical fiber 7 is fed out horizontally to the right from the outlet (not shown) of the optical fiber feeding device 60 at a constant speed (linear speed V2). This optical fiber feeding device 60 includes a bobbin 61 around which the optical fiber 7 is wound, and four pulleys 62a, 62b, 62c, and 62d for feeding out the optical fiber 7 wound around the bobbin 61 at a constant speed (linear speed V2) without slack. Here, the portion by which the length of the optical fiber becomes longer than the cable length is called the surplus length. The surplus length is set to be larger than the thermal expansion of the steel wire and the optical fiber with respect to the use temperature range. For example, if the use temperature range is 100 °C, the thermal expansion difference between the steel wire and the optical fiber is 6 με / °C, and the surplus length is set to 0.06% (600 με) or more.

[0047] When the bobbin 61 starts to rotate (the rotation direction is clockwise), the optical fiber 7 wound around the bobbin 61 sequentially passes through the outer peripheral portions of the pulleys 62b and 62d, which are configured to rotate in pairs with the pulleys 62a and 62c, and is fed out horizontally to the right at a linear speed V2 from the outlet of the optical fiber feeding device 60.

[0048] In response to the movement of this optical fiber, five second twisted wire wires 20 (two of the total five second twisted wire wires 20 are shown in Fig. 7 for simplicity), which are respectively fed out so as to sandwich the optical fiber 7 at a predetermined angle θ, change their moving directions to the horizontal direction in the vicinity of the horizontal position P 50 and are joined while moving horizontally at a constant speed (linear speed V1) in a spiral shape while being twisted integrally with the above-mentioned optical fiber 7 by the resin intermittently (intermittently) injected at a predetermined time interval for a certain period of time from the resin injection device 50 installed at the position P 50 . Hereinafter, the portion intermittently joined by this resin is called the joint portion (also called the fixing portion) 22.

[0049] At that time, the optical fiber 7 and the second twisted wire 20 joined to each other at the position P 50 are at the position P 50With the above as a boundary, while moving rightward at a wire speed V1 smaller than the above wire speed V2, they are joined to form a joint 22. As a result, the sensor rope 4a is configured to have a structure in which non-joined portions 21 (not covered with resin) and joined portions 22 joined with resin are alternately formed.

[0050] As described above, the optical fiber 7 is disposed in a non-linear manner (with an extra length) in the inner portion of the sensor rope 4a as shown by the dotted line in Fig. 7. Note that the outer diameter of the manufactured sensor rope 4a is a constant value D defined by the wire speed V1 and the wire speed V2. 21 That is, the sensor rope 4a is, as a result of the magnitude relationship between the wire speed V1 and the wire speed V2 (V1 < V2), manufactured as a Kira wire with an extra length whose outer peripheral diameter is D. 21 By adopting the manufacturing method as described above and fixing the optical fiber, the manufacturing of the sensor rope 4a becomes easy, and also the strength and lifespan of the entire sensor rope are improved.

[0051] In the description of the manufacturing method of the sensor rope 4a as described above, the two second twisted wire wires 20 were described on the premise that they are steel wires. However, it is not limited to steel wires, and aluminum wires (Al wires) or copper wires plastically deformed using an extrusion method or the like may also be used. In this case, the Al wires or copper wires have the same strength as the steel wires.

[0052] In the above, the case where the sensor rope 4 is a Kira wire with an extra length has been described. Next, the structure of the case where the sensor rope 4 is a FIMT4b with fixed points at regular intervals (also referred to as the sensor rope 4b) will be described with reference to the drawings.

[0053] Fig. 8 is an axial cross-sectional view for explaining the structure of the FIMT4b with fixed points at regular intervals. As shown in this figure, the optical fiber 7 used for measurement is intermittently joined at joint portions 22 at regular intervals in the axial direction by resin or the like within an insulator 8c filled inside a metal tube FIMT23 provided on the outer peripheral portion.​

[0054] The FIMT4b with fixed points at regular intervals configured as described above, similar to the case of the Kira wire with excess length, is superior in terms of ease of manufacture and strength or lifespan compared to Module 1 or Module 2, which are measurement FO modules using the conventional structure of FIMT. As a result, it becomes possible to configure Module 3, which is a measurement module with better performance compared to the conventional one.

[0055] In addition to the above, FIGS. 9A and 9B show other examples of the sensor rope 3 used. These figures are all schematic cross-sectional views when cut along a plane orthogonal to their axes. Also, for comparison with these, a schematic cross-sectional view of the sensor rope 4b is shown in FIG. 9C.

[0056] First, the sensor rope 3b shown in FIG. 9A is composed of 6 steel wires, which is one more than the sensor rope 3a, and the other configurations are the same as those of the sensor rope 3a. Also, its outer diameter D3 is slightly larger than that of the sensor rope 3a, but is approximately the same at 1.2 to 8 mm. Next, the sensor rope 3c (also called the Jacket Type sensor rope) shown in FIG. 9B is configured in the same way as the sensor rope 3b, except that its outside is covered with an insulator 8d such as rubber. Also, its outer diameter D4 is slightly larger than that of the sensor rope 3b, but is approximately the same at 1.2 to 8 mm. Note that the outer diameter D5 of the sensor rope 4b is also 1.2 to 8 mm, the same as these.

[0057] Next, specific embodiments of using the various sensor ropes 3 or sensor ropes 4 described above as a combined structure with a stranded cable added in terms of configuration for a measurement module for power cable monitoring (hereinafter, simply referred to as a power monitoring module) will be described in detail below with reference to FIGS. 10A, 10B, 11A, and 11B. In addition, each of the above-described various sensor ropes 3 or sensor ropes 4 can be used alone or in combination of the sensor rope 3 and the sensor rope 4 as a measurement module for power cable monitoring without further adding a stranded cable.

[0058] [Example 1] FIG. 10A shows a schematic cross-sectional view of the power monitoring module 30a of Example 1. In the power monitoring module 30a of this Example 1, a steel wire 30 is arranged at the central portion. The outer peripheral portion is composed of five ropes wound in a spiral, three of which are ropes composed of a third stranded wire 40, and the other two are ropes for measurement fiber sensors. Here, the ropes for measurement fiber sensors, that is, the sensor ropes 3a and the sensor rope 4a are arranged separately from each other. Note that the outer diameter D6 of the power monitoring module 30a of this Example 1 is 6 to 8 mm. Also, the sensor rope 4a can be replaced with the sensor rope 4b.

[0059] [Example 2] FIG. 10B shows a schematic cross-sectional view of the power monitoring module 30b of Example 2. Since most of the power monitoring module 30b of this Example 2 is the same as that of the power monitoring module 30a of Example 1, here, the parts different from Example 1 will be described, and the description of the parts similar to Example 1 will be simplified. In Example 2, it is different from Embodiment 1 in that the sensor ropes 3a and the sensor rope 4a, which are two of the five ropes wound in a spiral that constitute the outer peripheral portion and are ropes for measurement fiber sensors, are arranged adjacent to each other. Note that the outer diameter D7 of the power monitoring module 30b of this Example 2 is 6 to 8 mm, the same as that of Example 1. Also, the sensor rope 4a can be replaced with the sensor rope 4b.

[0060] [Example 3] FIG. 11A shows a schematic cross-sectional view of the above-described power monitoring module 30c of Example 3. In the power monitoring module 30c of this Example 3, it is composed of six ropes with the outer peripheral portion spirally wound, four of which are ropes composed of the third stranded wire 40, and the remaining two are sensor ropes for measurement fiber sensors, sensor rope 3b and sensor rope 4b. As shown in FIG. 11A, these sensor ropes 3b and 4b are characterized by being arranged separately from each other at axially symmetric positions of this power monitoring module 30c. Note that the outer diameter D8 of the power monitoring module 30c of this Example 3 is 6 to 8 mm, similar to Example 1 and Example 2.

[0061] [Example 4] FIG. 11B shows a schematic cross-sectional view of the above-described power monitoring module 30d of Example 4. In the power monitoring module 30d (also referred to as the Jacket Type module 30d. The same applies hereinafter) of this Example 4, it is composed of six ropes with the outer peripheral portion spirally wound, two of which are sensor ropes for measurement fiber sensors, and these are arranged separately from each other at axially symmetric positions of the power monitoring module 30d, which is the same as in Example 3. However, it is different from Example 3 in that sensor rope 3c is used instead of sensor rope 3b. Note that the outer diameter D9 of the power monitoring module 30d of this Example 4 is 6 to 8 mm, similar to Example 1 to Example 3.

[0062] Therefore, next, as a representative example of the power cable, regarding the power monitoring module 30b of Example 2 in which the sensor rope 4a (Kira wire with extra length) and the sensor rope 3a are simultaneously mounted among the above-described power monitoring modules, the fact that the temperature and strain at a predetermined position can be obtained simultaneously will be described in detail below.

[0063] As described above, two measurement fiber sensor ropes are installed adjacent to the outer peripheral portion of this power monitoring module 30b. One of them is the sensor rope 3a of the type without extra length, and the other is the sensor rope 4a of the type with extra length. By using the signals detected by these two types of fiber sensors for measurement, among the three-dimensional components of the strain of the cable to be measured detected by the power monitoring module 30b to be measured, the strain in one direction (one dimension) does not need to be considered. Therefore, in order to measure the strain caused by deformation or the like generated in the above power cable, only the evaluation formulas of the frequency shifts of the following three Rayleigh frequencies, namely, formulas (1) to (3), need to be used.

[0064]

Number

Number

Number

[0065] When the above three formulas (1), (2), and (3) are solved simultaneously, the temperature and strain at the measurement position to be obtained can be obtained at the same time. Here, the temperature T obtained by the temperature sensor installed on the seabed sea is set as the reference temperature T ref then the following formula (4) holds. Therefore, the temperature T to be obtained can be obtained by the following formula (5) from the relational expression of the Rayleigh frequency shift shown in the above formula (2) using the above reference temperature T ref as follows.

[0066]

Number

Number

[0067] Embodiment 2. In Embodiment 1, in the intelligent power cable used in the power cable monitoring system, the case where the measurement fiber sensor (sensor rope) is mounted only on the outer peripheral portion of the intelligent power cable was described. In the intelligent power cable 100a of Embodiment 2 (hereinafter, also simply referred to as the power cable 100a), the measurement fiber sensor used for the power cable to be measured is mounted not only on the outer peripheral portion but also on the central axis portion sandwiched between the power transmission cables 1 typified by a plurality of CV cables (hereinafter, also simply referred to as CV cables), which is a significant difference.

[0068] The intelligent power cable 100a of this Embodiment 2 will be described below with reference to FIG. 12. Even when implemented in this way, it is possible to obtain the same effects as in the case of Embodiment 1, and furthermore, it is possible to improve the measurement accuracy of strain or temperature with respect to the measurement object.

[0069] FIG. 12 is a schematic cross-sectional view showing an example of the intelligent power cable of Embodiment 2. As shown in FIG. 12, in the intelligent power cable of Embodiment 2, the three-core power transmission cable 1 is arranged at its central axis portion, and the sensor rope 3 is arranged so as to be sandwiched between the three-core power transmission cables 1, which is the most different point from the intelligent power cable of Embodiment 1. Also, as shown in FIG. 12, although the sensor rope 4 is arranged on the outer peripheral portion, different from Embodiment 1, it is mounted on a different outer peripheral layer from the plurality of armor wires 2 arranged, that is, a layer slightly inside the layer of the plurality of armor wires 2 arranged. As a result, the intelligent power cable of Embodiment 2 has higher accuracy in measuring the temperature of the insulating layer than the intelligent power cable of Embodiment 1 described above, and has an advantage when evaluating the maximum operating power.

[0070] In the intelligent power cable according to Embodiment 2, since the sensor rope is arranged in the central axis portion, it is possible to more accurately measure the temperature characteristics and the like of the CV cable. Therefore, since the change over time of the CV cable can be grasped with higher accuracy, it is effective as a monitoring cable for the CV cable. In this case, if the sensor rope 4a is used, the temperature characteristics of the CV cable can be measured at a position closer to the CV cable because of the smaller outer diameter thereof, and more accurate measurement of the intelligent power cable becomes possible.

[0071] As described above, in the intelligent power cable 100a according to Embodiment 2, it is possible to more accurately measure the strain and temperature (particularly temperature measurement) of the power cable to be measured, and a more reliable monitoring power cable can be realized.

[0072] When the power transmission cable 1 is energized using the intelligent power cable according to Embodiment 1 or Embodiment 2 described above, the function of the power cable can be monitored by monitoring the temperature change during energization. Further, since the above-described strain measurement module can detect humidity, it is also possible to monitor the ingress of water into the power cable. Regarding this, based on the graph of the temperature change during energization, it will be described below.

[0073] First, FIG. 13 shows data comparing the temperature change during energization in air and in water. As shown in this figure, energization starts at about 4 minutes after the start of the test, and energization ends at about 10 minutes. From FIG. 13, during the above-described elapsed time, the difference in temperature change between air and water is clearly detected, and it can be seen that the temperature change is larger in air than in water. The measurement of the temperature change of the cable during energization is for the purpose of monitoring the cable function, such as checking for damage to the laid cable (for example, determining the presence or absence of insulation breakdown of the cable using the temperature rise characteristic), or checking for the presence or absence of water ingress into the cable using the characteristics of the temperature change in air and in water during energization.

[0074] Next, the results of measuring the temperature distribution over a distance of several kilometers using an intelligent power cable will be described. The reason such long-distance measurement is necessary is usually that when laying an intelligent power cable, since the cable wound around a winder with an outer diameter of several meters or more is unwound from the outermost winding position of the winder at the laying site and laid at a predetermined laying position, it is necessary to inspect for damage to the cable inside the winder.

[0075] That is, to determine whether there is insulation breakdown in the power cable, or if insulation breakdown has occurred, to identify the location of the breakdown, the above temperature distribution measurement is performed. The reason is that in the vicinity of the position where insulation breakdown has occurred, the power wire and the steel wire for cable construction are in contact, and in such a place, since the electrical resistance is small, a large current is generated. When a large current is generated, the power cable is heated at the location where the large current is generated, resulting in a temperature rise at that location. Thus, the presence or absence of insulation breakdown can be determined. Note that the temperature change is observed not only at the location where the temperature change directly occurs but also at adjacent layer positions.

[0076] The actual measurement example of the temperature change due to insulation leakage at one location at a distance of several kilometers described above is shown in Fig. 14. From this figure, it can be seen that the temperature measurement results by the armored optical module at different winding positions in the radial direction of the cable show the maximum temperature change near the distance (position) of 2459 m where insulation leakage occurred. Here, the reference temperature of the cable was 25°C. By comparing the measurement results of multiple different measurement layers and the winding pitch (length) of the cable at the same distance (position), more reliable measurement results can be obtained, and this comparison was also performed by actual measurement.

[0077] In addition, by using the above intelligent power cable, it is possible to monitor the shape of the cable. In the following, it is shown that if the twist and elongation of the cable are monitored simultaneously, the bending of the cable can be monitored, and based on this, the deformed shape of the cable can be monitored. That is, if the axial strain and twist of the SK wire can be measured distributively, the direction vector of the deformation of the entire cable can be obtained, and by integrating this, the deformed shape such as the bending of the cable can be understood. Based on this information, the strain at the time of cable deformation can be obtained, thereby enabling the monitoring of the cable shape and, using the law of Baskin or the like, enabling the prediction of the cable life (see Non-Patent Document 3).

[0078] As characteristics of the power cable as described above, it can be mentioned that it is not only (axially) long, but usually has a large cable radius and a large weight. Therefore, when monitoring the shape of such a cable, it is necessary to evaluate the deformation as at least a three-dimensional cylindrical body rather than as a "line", and without such evaluation, it is impossible to accurately grasp the deformation. In actuality, as shown in Fig. 15A, since the cable is configured in a stranded shape (a plurality of cables), first, the explanation will start from approximating a plurality of cables as a (single) cylindrical body.

[0079] Therefore, next, with reference to Figs. 15A and 15B, the three-dimensional evaluation method of such a cable will be described below (see Non-Patent Document 3). Fig. 15A shows a method for creating an evaluation model of the cable shape change. In this evaluation model, the wire strand (corresponding to the above plurality of cables) of the electric wire is assumed to be a single dense elastic body. In an actual cable, a plurality (six) of SK steel wires are spirally wound around each other to form a strand.

[0080] Therefore, first, it is considered that the central axis of each wire strand is spirally wound around a cylindrical surface having a certain radius, and modeling is performed. That is, as shown in Fig. 15A, a virtual cylinder connecting the central axes of the six strands is considered, and the evaluation starts from evaluating the deformation of this virtual cylinder. Then, for this virtual cylinder, first, set up the coordinate system shown in FIG. 15B. This coordinate system considers a set of three orthogonal unit vectors along the central axis curve of the linear object, that is, the (t, n, b) coordinates (Frenet frame) and the (ζ, η, ξ) coordinates. Note that the three vector components of each coordinate represent the tangent vector, the principal normal vector, and the binormal vector, respectively.

[0081] Next, evaluation models in the case of torsion and bending occurring on the above virtual cylinder are shown in FIGS. 16A, 16B, and 16C. First, regarding the shape of the bundle of generatrices with the central axis on the virtual cylinder, it can be determined by α and β shown in FIG. 16A. α is the angle (pitch angle) between the central axis of the virtual cylinder and the central axis of the bundle of generatrices, and β is the torsion angle of the bundle of generatrices with respect to the normal of the virtual cylinder. By determining these α and β, the shape of the cable is determined.

[0082] Next, consider the virtual cylindrical surface based on FIG. 16B. Therefore, using the local coordinates (u, v), express the coordinates x(u, v) on the virtual cylindrical surface. Then, consider the perpendicular cross-section of the electric wire passing through the point r1(u) on the virtual cylinder axis (FIG. 16C). Here, R1 and R2 represent the virtual cylinder radius and the radius of the bundle of generatrices, respectively. Also, u and v are parameters representing the virtual cylindrical surface (the coordinate axis u indicates the neutral axis of deformation. The axis orthogonal to this (axis on the curvilinear coordinates) is the coordinate axis v).

[0083] From FIGS. 15A, 15B, and FIGS. 16A, 16B, and 16C, if the axial strain and torsion of the SK line are measured distributively, the deformation direction vector regarding the deformation of the entire cable can be obtained. Therefore, by integrating it, the bending shape can be derived. As described above, in this monitoring system, the reason why three or more SK lines are required in principle is that it is necessary to measure the axial strain and torsion of the SK line distributively, that is, to measure the deformation of the SK line distributively in three dimensions (using three independent parameters).

[0084] Therefore, by considering the above modeling method, it can be seen that the intelligent monitoring system can appropriately measure the deformation of the cable. Next, using the above method, the deformation of the cable will be examined as an example where the cable is pulled by an anchor by the intelligent monitoring system. As an example of this examination, an example of measuring the strain generated by bending the cable will be described below with reference to FIGS. 17A, 17B, and 17C.

[0085] FIG. 17A is an image diagram showing a schematic diagram of the deformation of the cable that occurs when the anchor catches the cable. FIG. 17B shown below it is a graph showing the deformed state of the cable shown in FIG. 17A, with the distance of the cable set in the horizontal direction and the deflection or strain of the cable set in the vertical direction. Further, FIG. 17C shows the strain generated in three measurement fibers (each measurement fiber is installed on the outer layer of the cable) corresponding to the deformation of the three-core power transmission cable in this case, corresponding to the distance. In FIG. 17C, it shows the strain waveform for the bending deformation that occurs when a displacement of 1 mm is given in the vertical direction to a cable having three optical fibers wound at a pitch of 40 cm.

[0086] As shown in FIG. 17C, it can be seen that deformation (strain) occurs in the smallest winding pitch unit of the armor wire. Also, from this figure, it becomes possible to obtain detailed information such as the starting point of the deformation or the displacement between each wire. Further, from this figure, it can be seen that the influence of the deformation becomes considerably small when the distance is close to 53 m.

[0087] Therefore, in order to confirm the accuracy of the above bending measurement, bending measurement was performed using the polarization signal of the Rayleigh scattering signal. Specifically, the twist angle due to the helical deformation generated in the cable was measured from the difference between the Rayleigh scattering signals generated in the SK wire after deformation (spirally wound and subjected to planar bending processing) and the SK wire before deformation (not subjected to deformation processing). The measurement results are shown in FIGS. 18A and 18B.

[0088] In Fig. 18A, with the parameter being the number of measurement times, for the measurement data of the angle difference (the angle difference of the phase signal included in the polarization signal) corresponding to the spiral portion (refer to the arrow portion in the figure), for four types of multiple times (2 5 times, 2 10 times, 2 12 times, 2 14 times), the measurement results are stable respectively, and the figure shows the values averaged for each time. Also, Fig. 18B shows the measurement data of the average (angle) difference of 30° of bending corresponding to the bending portion (refer to the arrow portion in the figure). From Fig. 18A and Fig. 18B, it was found that the actual twist angle and the measurement of bending in the spirally wound cable can be performed.

[0089] Note that the sampling interval during measurement is 5 cm, but this value is sufficiently small compared to the pitch of 1.5 m of the armor of the armored wire 2, and it can be seen that it is sufficiently applicable to the deformation measurement of the armored wire 2.

[0090] Regarding the application example of the present technology related to the above technology, its outline will be described below. Fig. 19 is a diagram showing an outline of a method for specifying the navigation location of a ship that may damage a cable. Here, the navigation position of the target ship is specified by measuring the distribution of sound waves (for example, sound waves caused by the engine sound of the ship to be measured) using a DAS suitable for high-speed RIP measurement. At that time, as shown in Fig. 19, the ship is detected and specified by multi-point simultaneous measurement. Specifically, when position 1 (for example, based on the sound wave signal, a position 10.33 km west and 1.22 km north from the reference position) is the ship A under navigation and position 2 (for example, based on the sound wave signal, a position 15.56 km west and 4.27 km north from the reference position) is the ship B under navigation, the ship A at position 1, which is closer to the reference position, is specified. Thereby, it becomes possible to notify the measurement information to the specified ship A and call for attention.

[0091] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more of the embodiments are not limited to the application of a particular embodiment, but are applicable to the embodiments alone or in various combinations. Accordingly, countless variations not illustrated are envisioned within the scope of the technology disclosed in this application specification. For example, it shall include cases where at least one component is deformed, added, or omitted, and further, cases where at least one component is extracted and combined with components of other embodiments.

Description of Reference Numerals

[0092] 1 Power transmission cable, 2 Armor wire (first stranded wire), 3, 3a, 3b, 3c, 4 Sensor rope, 4a Sensor rope (Kira wire with extra length), 4b Sensor rope (FIMT with fixed points at regular intervals), 5 Insulation layer, 6 Shield part, 7 Optical fiber, 8a, 8b Resin, 8c, 8d Insulator, 11 Conductor, 20 Second stranded wire, 21 Non-joint part, 22 Joint part, 23 FIMT, 30 Steel wire, 30a, 30b, 30c, 30d Power monitoring module, 40 Third stranded wire, 50 Resin injection device, 60 Optical fiber delivery device, 61 Bobbin, 62a, 62b, 62c, 62d Pulley 100, 100a Intelligent power cable (power cable), 101 Submarine cable, 102 Floating cable, 103 Buried cable, 110 Backscattered light measurement device, 200 Power cable monitoring system

Claims

1. A power cable having a power transmission cable disposed in the inner peripheral portion, an armor wire disposed in the outer peripheral portion, and an armored optical module having an optical fiber for detecting a physical quantity of an object to be measured and having the same diameter as the armor wire. A backscattered light measuring device that measures the distribution of the physical quantity of the object to be measured by using the backscattered light from the optical fiber. Comprising: Based on the signal detected by the armored optical module, the frequency shift signal of the Rayleigh backscattered light obtained by the backscattered light measuring device and the polarization distribution signal obtained from the Rayleigh backscattered light are used to obtain the temperature and strain distributions of the power cable. A power cable monitoring system characterized by the above.

2. The armor wire is composed of a first stranded wire. The armored optical module includes a first sensor rope having a second stranded wire that spirally covers the optical fiber and is joined to the optical fiber over the entire axial length via a resin, and a second sensor rope having a second stranded wire that spirally covers the optical fiber and is intermittently joined to the optical fiber in the axial direction via a resin, or a FIMT with fixed intervals having the optical fiber intermittently joined in the axial direction by a resin. Comprising: The power cable monitoring system according to claim 1, characterized by the above.

3. A power cable having a power transmission cable disposed in the inner peripheral portion, an armor wire composed of a first stranded wire and disposed in the outer peripheral portion, and an armored optical module having an optical fiber for detecting a physical quantity of an object to be measured and having a second stranded wire that spirally covers the optical fiber and is joined to the optical fiber over the entire axial length via a resin, and having a first sensor rope. A backscattered light measuring device that measures the distribution of the physical quantity of the object to be measured by using the backscattered light from the optical fiber. Comprising: Based on the signal detected by the armored optical module. The temperature and strain distributions of the power cable are obtained by the frequency shift signals of the Rayleigh backscattered light and the Brillouin backscattered light obtained by the backscattered light measuring device. A power cable monitoring system characterized by the above.

4. The power cable further includes a plurality of the power transmission cables and the second sensor rope disposed so as to be sandwiched between the plurality of power transmission cables. The power cable monitoring system according to claim 2, characterized in that...

5. The first sensor rope has five or six of the second stranded wires. The power cable monitoring system according to claim 2 or claim 3, characterized in that...

6. The outer side of the first sensor rope is covered with an insulator. The power cable monitoring system according to any one of claims 2 to 5, characterized in that...

7. The first sensor rope and the second sensor rope are arranged separately, characterized in that... The power cable monitoring system according to claim 2 or claim 4.

8. The first sensor rope and the second sensor rope are arranged adjacent to each other, characterized in that... The power cable monitoring system according to claim 2 or claim 4.

9. The Rayleigh backscattered light obtained by the backscattered light measuring device is high-speed Rayleigh scattered light with a detection frequency of 2000 times / s or more. The power cable monitoring system according to any one of claims 1, 2, and 4, characterized in that...

10. A power cable monitoring system according to any one of claims 1, 2, and 4, wherein a signal of the twist angle distribution of the power cable is obtained from the polarization distribution signal. The power cable monitoring system, characterized in that...

11. A manufacturing method of a second sensor rope of a power cable provided in the power cable monitoring system according to claim 2 or claim 4, having a bobbin around which the optical fiber is wound, and a pulley that rotates in conjunction with the rotation of the bobbin and moves while bringing the optical fiber into contact with the outer periphery, and an optical fiber feeding device that feeds the optical fiber to the outside, and a resin injection device that injects a resin for joining the optical fiber and the second stranded wire at a position where the optical fiber and the second stranded wire start to wind around each other, comprising: setting the speed in the feeding direction for feeding the optical fiber to be greater than the axial moving speed when the optical fiber and the second stranded wire are wound around each other, and intermittently injecting the resin from the resin injection device at the position. The manufacturing method of the sensor rope, characterized in that...

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