Optical fiber composite power cable, power line, and abnormal point detection system for power line

Abstract

An optical fiber composite power cable (50) includes: a cable body (60); an armor portion (59) provided on an outer circumference of the cable body (60); a first optical fiber (6) that transmits sensing light; a second optical fiber (7) that transmits backscattered light of the sensing light; and a plurality of auxiliary conductors (8, 9) that transmit electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical fiber composite power cable, a power line, and an abnormal point detection system for a power line. The present application claims the priority based on Japanese Patent Application No. 2023-131137 filed on August 10, 2023. The entire contents of the description in this Japanese patent application are incorporated herein by reference.BACKGROUND ART

[0002] A system that detects an abnormality such as a ground fault accident, external damage or fatigue of a power cable has been conventionally known. For example, a submarine cable in PTL 1 includes a power wire core, a two-layered armor, a line sensor having an optical fiber, and the like. The optical fiber is used to measure a distortion change over the entire length of the submarine cable in accordance with the PPP-BOTDA (Pulse PrePump Brillouin Optical Time Domain Analysis) method.CITATION LISTPATENT LITERATURE

[0003] PTL 1: Japanese Patent Laying-Open No. 2013-36876SUMMARY OF INVENTION

[0004] An optical fiber composite power cable according to the present disclosure includes: a cable body; an armor portion provided on an outer circumference of the cable body; a first optical fiber that transmits sensing light; a second optical fiber that transmits backscattered light of the sensing light; and a plurality of auxiliary conductors that transmit electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light.

[0005] A power line according to the present disclosure includes: two optical fiber composite power cables; and a connection portion that connects the two optical fiber composite power cables, wherein each of the two optical fiber composite power cables includes: a cable body; an armor portion provided on an outer circumference of the cable body; a first optical fiber that transmits sensing light; a second optical fiber that transmits backscattered light of the sensing light; and an auxiliary conductor that transmits electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light, and the connection portion includes: the optical amplification repeater; and the power supply connected to the auxiliary conductor and supplying electric power to the optical amplification repeater.

[0006] An abnormal point detection system for a power line according to the present disclosure includes: a power supply; a laser device that emits sensing light; and a power line, wherein the power line includes: two optical fiber composite power cables; and a connection portion that connects the two optical fiber composite power cables, each of the two optical fiber composite power cables includes: a cable body; an armor portion provided on an outer circumference of the cable body; a first optical fiber that transmits sensing light; a second optical fiber that transmits backscattered light of the sensing light; and an auxiliary conductor that transmits electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light, and the connection portion includes: the optical amplification repeater; and the power supply connected to the auxiliary conductor and supplying electric power to the optical amplification repeater, and the abnormal point detection system for a power line further includes a measurement device that detects an abnormal point of the power line based on a result of detection of the backscattered light.BRIEF DESCRIPTION OF DRAWINGS

[0007] [Fig. 1] Fig. 1 shows a part of a power line 130 according to an embodiment in a longitudinal direction. [Fig. 2] Fig. 2 is a cross-sectional view of an optical fiber composite power cable 50 according to a first embodiment, which is perpendicular to the longitudinal direction. [Fig. 3] Fig. 3 is a cross-sectional view of a detection wire 61 in Fig. 2, which is perpendicular to the longitudinal direction. [Fig. 4] Fig. 4 is a cross-sectional view of a detection wire 71 in Fig. 2, which is perpendicular to the longitudinal direction. [Fig. 5] Fig. 5 is a schematic perspective view of optical fiber composite power cable 50 according to the first embodiment. [Fig. 6] Fig. 6 shows a magnetic field when a fault current flows through the optical fiber composite power cable. [Fig. 7] Fig. 7 shows an induced voltage when a fault current flows through an adjacent optical fiber composite power cable. [Fig. 8] Fig. 8 shows a configuration of a connection portion 80 included in the power line according to the first embodiment. [Fig. 9] Fig. 9 shows a configuration of the interior of a housing 171 in Fig. 8. [Fig. 10] Fig. 10 shows a configuration of an abnormal point detection system 200 for the power line according to the first embodiment. [Fig. 11] Fig. 11 is a flowchart showing an abnormal point detection procedure for power line 130 in the first embodiment. [Fig. 12] Fig. 12 is a cross-sectional view of an optical fiber composite power cable 50A according to a second embodiment, which is perpendicular to the longitudinal direction. [Fig. 13] Fig. 13 is a cross-sectional view of a detection wire 61A in Fig. 12, which is perpendicular to the longitudinal direction. [Fig. 14] Fig. 14 is a cross-sectional view of a detection wire 71A in Fig. 12, which is perpendicular to the longitudinal direction. [Fig. 15] Fig. 15 is a cross-sectional view of an optical fiber composite power cable 50B according to a third embodiment, which is perpendicular to the longitudinal direction. [Fig. 16] Fig. 16 is a cross-sectional view of a detection wire 61B in Fig. 15, which is perpendicular to the longitudinal direction. [Fig. 17] Fig. 17 is a cross-sectional view of an optical fiber composite power cable 50C according to a fourth embodiment, which is perpendicular to the longitudinal direction. [Fig. 18] Fig. 18 is a cross-sectional view of a detection wire 61C in Fig. 17, which is perpendicular to the longitudinal direction. [Fig. 19] Fig. 19 is a cross-sectional view of an optical fiber composite power cable 50D according to a fifth embodiment, which is perpendicular to the longitudinal direction. [Fig. 20] Fig. 20 is a cross-sectional view of a detection wire 61D in Fig. 19, which is perpendicular to the longitudinal direction. [Fig. 21] Fig. 21 is a cross-sectional view of an optical fiber composite power cable 50E according to a sixth embodiment, which is perpendicular to the longitudinal direction. [Fig. 22] Fig. 22 is a cross-sectional view of a detection wire 61E in Fig. 21, which is perpendicular to the longitudinal direction. [Fig. 23] Fig. 23 shows a configuration of a connection portion 80A included in a power line according to a seventh embodiment. [Fig. 24] Fig. 24 shows a configuration of a surge detection processing device 120 included in the power line according to the seventh embodiment. [Fig. 25] Fig. 25 is a flowchart showing an abnormal point detection procedure for power line 130 in the seventh embodiment. [Fig. 26] Fig. 26 shows a configuration of a surge detection processing device 120F included in a power line according to an eighth embodiment. [Fig. 27] Fig. 27 is a cross-sectional view of an optical fiber composite power cable 50F according to the eighth embodiment, which is perpendicular to the longitudinal direction. [Fig. 28] Fig. 28 is a cross-sectional view of a detection wire 71F in Fig. 27, which is perpendicular to the longitudinal direction. [Fig. 29] Fig. 29 shows a configuration of a surge detection processing device 120G included in a power line according to a ninth embodiment. [Fig. 30] Fig. 30 is a cross-sectional view of an optical fiber composite power cable 50G according to a tenth embodiment, which is perpendicular to the longitudinal direction. [Fig. 31] Fig. 31 shows a configuration of a surge detection processing device 120H included in a power line according to the tenth embodiment. [Fig. 32] Fig. 32 shows a configuration of a surge detection processing device 120I included in a power line according to an eleventh embodiment. [Fig. 33] Fig. 33 is a cross-sectional view of an optical fiber composite power cable 50H according to the eleventh embodiment, which is perpendicular to the longitudinal direction. [Fig. 34] Fig. 34 shows a configuration of an abnormal point detection system 200A for a power line according to a twelfth embodiment. DETAILED DESCRIPTION[Problem to be Solved by the Present Disclosure]

[0008] In PTL 1, pulsed light for measurement emitted to one end of an optical fiber and backscattered light are attenuated as the pulsed light and the backscattered light transmit through the optical fiber. This results in a decrease in accuracy with which an optical fiber included in an optical fiber composite power cable detects damage or distortion of a cable body, an armor portion or the like of the power cable. In PTL 1, the length of the power cable over which the optical fiber can measure the above-described damage or distortion is limited to a range that does not cause attenuation of the pulsed light for measurement and the backscattered light.

[0009] Therefore, an object of the present disclosure is to provide a long-distance optical fiber composite power cable and a long-distance power line, and an abnormal point detection system for a long-distance power line, which enable detection of an abnormal point by an optical fiber.[Advantageous Effect of the Present Disclosure]

[0010] According to the present disclosure, an abnormal point of a long-distance power line can be detected.[Description of Embodiments of the Present Disclosure]

[0011] First, embodiments of the present disclosure will be listed and described. (1) An optical fiber composite power cable (50) according to one aspect of the present disclosure includes: a cable body (60); an armor portion (59) provided on an outer circumference of the cable body (60); a first optical fiber (6) that transmits sensing light; a second optical fiber (7) that transmits backscattered light of the sensing light; and a plurality of auxiliary conductors (8, 9) that transmit electric power from a power supply (22, 41) to an optical amplification repeater (70) that amplifies the sensing light and the backscattered light. With such a configuration, since the optical amplification repeater (70) can amplify the sensing light and the backscattered light, an abnormal point of a long-distance optical fiber composite power cable (50) or a long-distance power line (130) to which a plurality of optical fiber composite power cables (50) are connected can be detected by the first optical fiber (6) and the second optical fiber (7). Power cable 50 includes the plurality of auxiliary conductors. The plurality of auxiliary conductors are configured to be usable in a state of being electrically insulated from each other. Therefore, (1) a DC power supply can be used, and thus, power cable 50 can be suitably used in a long-distance power line. In addition, (2) at least one auxiliary conductor can be kept as a spare auxiliary conductor, and thus, the spare auxiliary conductor can be used even when a failure occurs, for example, during the work of connecting the auxiliary conductors, which eliminates the need for laying power cable 50 again. (2) In the optical fiber composite power cable (50) according to (1) above, the power supply (22, 41) can supply DC power, and the auxiliary conductors (8, 9) include a first auxiliary conductor (8) connected to a first terminal of the power supply (22), and a second auxiliary conductor (9) connected to a second terminal of the power supply (22). Since the DC power is smaller in power transmission loss than the AC power, such a configuration is suitable when the optical fiber composite power cable constructs a long-distance line laid on the seabed. For example, the first terminal is a positive electrode terminal, and the second terminal is a negative electrode terminal. The first auxiliary conductor connected to the positive electrode terminal and the second auxiliary conductor connected to the negative electrode terminal are used in a state of being electrically insulated from each other. In other words, the first auxiliary conductor and the second auxiliary conductor are electrically insulated from each other. (3) In the optical fiber composite power cable (50) according to (2) above, the armor portion (59) includes a plurality of wires (58a, 61, 71) spirally wound around the outer circumference of the cable body (60), at least one (61) of the plurality of wires (58a, 61, 71) includes at least one metal tube (63) that accommodates the first optical fiber (6) and the second optical fiber (7), and at least one (61, 71) of the plurality of wires (58a, 61, 71) includes the first auxiliary conductor (8) and the second auxiliary conductor (9). With such a configuration, the first optical fiber (6), the second optical fiber (7), the first auxiliary conductor (8), and the second auxiliary conductor (9) can be incorporated into the cable body (60). (4) In the optical fiber composite power cable (50) according to (3) above, the plurality of wires (58a, 61, 71) include a first wire (61) and a second wire (71) disposed adjacent to each other in a circumferential direction of the outer circumference of the cable body (60), the first wire (61) includes: a metal tube (63) that accommodates the first optical fiber (6) and the second optical fiber (7); and the first auxiliary conductor (8), and the second wire (71) includes the second auxiliary conductor (9). Such a configuration can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current, as compared with a case in which the first wire (61) and the second wire (71) are spaced apart from each other in the circumferential direction of the outer circumference of the cable body (60) and a case in which the first wire (61) and the second wire (71) are disposed adjacent to each other in a radial direction of the cable body (60). (5) In the optical fiber composite power cable (50A) according to (3) above, the plurality of wires (58a, 61A, 71A) include a first wire (61A) and a second wire (71A) disposed adjacent to each other in a circumferential direction of the outer circumference of the cable body (60), the first wire (61A) includes: a metal tube (63) that accommodates the first optical fiber (6); and the first auxiliary conductor (8), and the second wire (71A) includes: a metal tube (63) that accommodates the second optical fiber (7); and the second auxiliary conductor (9). Such a configuration can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current, as compared with a case in which the first wire (61A) and the second wire (71A) are spaced apart from each other in the circumferential direction of the outer circumference of the cable body (60) and a case in which the first wire (61A) and the second wire (71A) are disposed adjacent to each other in a radial direction of the cable body (60). (6) In the optical fiber composite power cable (50B) according to (3) above, a first wire (61B) included in the plurality of wires (58a, 61B) includes: a metal tube (63) that accommodates the first optical fiber (6) and the second optical fiber (7); the first auxiliary conductor (8); the second auxiliary conductor (9); and an insulating layer (64A) disposed between the first auxiliary conductor (8) and the second auxiliary conductor (9). The first auxiliary conductor (8) and the second auxiliary conductor (9) are disposed coaxially such that the centers thereof are located on the same axis. In other words, the first wire (61B) has a coaxial structure. Electromotive force is not generated between the first auxiliary conductor (8) and the second auxiliary conductor (9), which can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current. In addition, the first auxiliary conductor (8) and the second auxiliary conductor (9) are included in one wire (61B). In such a configuration, the first wire can be disposed at any position of armor portion (59), and thus, a degree of flexibility in disposing the wire (61B) is higher. (7) In the optical fiber composite power cable (50C) according to (3) above, a first wire (61C) included in the plurality of wires (58a, 61C) includes: a metal tube (63) that accommodates the first optical fiber (6) and the second optical fiber (7); and a plurality of first auxiliary leads (78) and a plurality of second auxiliary leads (79) spirally wound around an outer circumference of the metal tube (63), the plurality of first auxiliary leads (78) constituting the first auxiliary conductor (8), the plurality of second auxiliary leads (79) constituting the second auxiliary conductor (9). Such a configuration can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current, because the first auxiliary leads (78) and the second auxiliary leads (79) are provided such that the first auxiliary leads (78) and the second auxiliary leads (79) are arranged concentrically. In addition, the first auxiliary conductor (8) and the second auxiliary conductor (9) are included in one wire (61C). In such a configuration, the first wire (61C) can be disposed at any position of armor portion (59), and thus, a degree of flexibility in disposing the wire (61C) is higher. In addition, by changing the thickness of the first auxiliary leads (78) and the second auxiliary leads (79), the electrical resistance of the first auxiliary conductor (8) and the second auxiliary conductor (9) can be easily changed, and thus, multiple types of optical fiber composite power cables (50) different in electrical resistance of the first auxiliary conductor (8) and the second auxiliary conductor (9) can be easily manufactured. (8) In the optical fiber composite power cable (50C) according to (7) above, the first auxiliary leads (78) and the second auxiliary leads (79) are disposed alternately in a circumferential direction of the outer circumference of the metal tube (63), and an insulation coating (131) is provided on an outer circumference of at least one of the first auxiliary leads (78) and the second auxiliary leads (79). This can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current, because the first auxiliary conductor (8) and the second auxiliary conductor (9) are arranged concentrically. (9) In the optical fiber composite power cable (50D) according to (7) above, the plurality of first auxiliary leads (78) are disposed continuously in a circumferential direction of the outer circumference of the metal tube (63) in a first region (R1) of the outer circumference of the metal tube (63), the plurality of second auxiliary leads (79) are disposed continuously in a second region (R2) of the outer circumference of the metal tube (63), and an insulating member (132) is disposed in a third region (R3) between the first region (R1) and the second region (R2). This can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current, because the first auxiliary conductor (8) and the second auxiliary conductor (9) are arranged concentrically. (10) In the optical fiber composite power cable (50E) according to (3) above, a first wire (61E) included in the plurality of wires (58a, 61E) includes: a metal tube (63) that accommodates the first optical fiber (6) and the second optical fiber (7); the first auxiliary conductor (8) provided on an outer circumference of the metal tube (63); an insulating layer (133) provided on an outer circumference of the first auxiliary conductor (8); and a plurality of second auxiliary leads (79) spirally wound around an outer circumference of the insulating layer (133), the plurality of second auxiliary leads (79) constituting the second auxiliary conductor (9). The first auxiliary conductor (8) and the second auxiliary conductor (9) are disposed coaxially such that the centers thereof are located on the same axis. In other words, the first wire (61E) has a coaxial structure. Electromotive force is not generated between the first auxiliary conductor (8) and the second auxiliary conductor (9), which can make the first auxiliary conductor (8) and the second auxiliary conductor (9) less likely to be affected by a magnetic field caused by a fault current. (11) In the optical fiber composite power cable (50 to 50E) according to (3) above, a wire (58a) that does not include the metal tube (63), the first auxiliary conductor (8) and the second auxiliary conductor (9), of the plurality of wires, is made of magnetic metal, and the metal tube (63) is made of non-magnetic metal. By combining the magnetic wire (58a) and the non-magnetic metal tube (63), a magnetic flux becomes less likely to flow through these components, and thus, the effect of reducing the influence of a magnetic field caused by a fault current on the first auxiliary conductor (8) and the second auxiliary conductor (9) can be enhanced. (12) A power line (130) according to one aspect of the present disclosure includes: two optical fiber composite power cables (50); and a connection portion (80) that connects the two optical fiber composite power cables (50), wherein each of the two optical fiber composite power cables (50) includes: a cable body (60); an armor portion (59) provided on an outer circumference of the cable body (60); a first optical fiber (6) that transmits sensing light; a second optical fiber (7) that transmits backscattered light of the sensing light; and an auxiliary conductor (8, 9) that transmits electric power from a power supply (22, 41) to an optical amplification repeater (70) that amplifies the sensing light and the backscattered light, and the connection portion (80) includes: the optical amplification repeater (70); and the power supply (41) connected to the auxiliary conductor (8, 9) and supplying electric power to the optical amplification repeater (70). With such a configuration, since the optical amplification repeater (70) can amplify the sensing light and the backscattered light, an abnormal point of a long-distance power line (130) can be detected. (13) In the power line (130) according to (12) above, the power supply (22, 41) includes a DC / DC converter. Since the DC power is smaller in power transmission loss than the AC power, this power line (130) is suitable for a long-distance line laid on the seabed. (14) In the power line (130) according to (12) above, the connection portion (80) further includes: a surge detection unit (220, 220G) that detects a surge wave generated in the cable body (60) of the optical fiber composite power cable (50); and a communication device (123, 123F) that transmits a result of detection of the surge wave, and the surge detection unit (220, 220G) and the communication device (123, 123F) operate with electric power from the power supply (22, 41). With this, the use together of detection of the surge wave generated in the power line (130) when a fault occurs leads to higher accuracy of detection of an abnormal point. (15) In the power line (130) according to (14) above, the armor portion (59) includes a plurality of wires (58a, 125) spirally wound around the outer circumference of the cable body (60), and the surge detection unit (220G) detects a surge wave transmitting through an induction lead (125) included in the plurality of wires (58a, 125). With this, the surge wave can be detected with high accuracy. (16) In the power line (130) according to (14) above, the armor portion (59) includes a plurality of wires (58a, 71F) spirally wound around the outer circumference of the cable body (60), at least one (71F) of the plurality of wires includes a metal tube (63) that accommodates a third optical fiber (124), and the communication device (123F) transmits the result of detection of the surge wave to the outside of the connection portion (80) through the third optical fiber (124). With this, the result of detection of the surge wave can be transmitted to the outside of the connection portion (80) with high accuracy. (17) In the power line (130) according to (14) above, the communication device (123) converts the result of detection of the surge wave into a power line communication signal, and transmits the power line communication signal to the outside of the connection portion (80) by the auxiliary conductor (8, 9). With this, the result of detection of the surge wave can be transmitted to the outside of the connection portion (80), without adding an optical fiber for transmitting a signal indicating the result of detection. (18) In the power line (130) according to (14) above, the connection portion (80) further includes a power storage device (126) configured to be capable of storing electric power transmitting through the auxiliary conductor (8, 9), and the power storage device (126) is configured to be capable of supplying electric power to the communication device (123). The electric power can be intermittently supplied to the communication device (123) by the power storage device (126). In such a configuration, a storage battery can supply required electric power when the communication device (123) performs communication intermittently. (19) In the power line (130) according to (14) above, the power supply (22, 41) can supply DC power, the auxiliary conductor (8, 9) includes a first auxiliary conductor (8) connected to a first terminal of the power supply (22), and a second auxiliary conductor (9) connected to a second terminal of the power supply (22), the armor portion (59) includes a plurality of wires (58a, 61, 71) spirally wound around the outer circumference of the cable body (60), at least one of the plurality of wires (58a, 61, 71) includes the first auxiliary conductor (8), the second auxiliary conductor (9) and an induction lead (125), and the power storage device (126A) stores a ripple current induced between one of the first auxiliary conductor (8) and the second auxiliary conductor (9) and the induction lead (125). With such a configuration, a ripple component in the power cable can be used for storage of electric power. (20) In the power line (130) according to (12) to (19) above, the first optical fiber and the second optical fiber are constituted by one optical fiber (16), and the optical amplification repeater (70A) has a bidirectional optical amplification function. With such a configuration, the number of optical fibers can be reduced. (21) An abnormal point detection system (200) for a power line according to one aspect of the present disclosure includes: a power supply (22, 41); a laser device (21) that emits sensing light; and a power line (130), wherein the power line (130) includes: two optical fiber composite power cables (50); and a connection portion (80) that connects the two optical fiber composite power cables, each of the two optical fiber composite power cables (50) includes: a cable body (60); an armor portion (59) provided on an outer circumference of the cable body (60); a first optical fiber (6) that transmits sensing light; a second optical fiber (7) that transmits backscattered light of the sensing light; and an auxiliary conductor (8, 9) that transmits electric power from a power supply (22, 41) to an optical amplification repeater (70) that amplifies the sensing light and the backscattered light, and the connection portion (80) includes: the optical amplification repeater (70); and the power supply (22) connected to the auxiliary conductor (8, 9) and supplying electric power to the optical amplification repeater (70), and the abnormal point detection system (200) for a power line further includes a measurement device (20) that detects an abnormal point of the power line based on a result of detection of the backscattered light. In such a configuration, the optical amplification repeater (70) can amplify the sensing light and the backscattered light. Therefore, the abnormal point detection system (200) for a power line can detect an abnormal point of a long-distance power line (130) with high accuracy. [Details of Embodiments of the Present Disclosure]

[0012] Embodiments will be described below with reference to the drawings.<First Embodiment>

[0013] A power line 130 according to a first embodiment will be described with reference to Fig. 1.

[0014] Power line 130 includes a plurality of optical fiber composite power cables 50-1, 50-2, ..., and at least one connection portion 80-1, 80-2, .... Optical fiber composite power cable 50-1 is connected to a controller 100. The optical fiber composite power cable here includes a plurality of optical fibers and a power cable having an armor portion. The power cable having the armor portion is typically used as a submarine power cable. A cable body is a main portion of the power cable. The cable body typically includes a conductor, an electrically insulating layer, a semiconducting layer, and a sheath.

[0015] In the following description, optical fiber composite power cables 50-1, 50-2, ... may be collectively denoted as an optical fiber composite power cable 50, and connection portions 80-1, 80-2, ... may be collectively denoted as a connection portion 80. Typically, both ends of power line 130 are disposed on land. When below-described sensing light is emitted from each of both ends of power line 130, controller 100 is provided at each of both ends of power line 130. When the sensing light is emitted from only one end of power line 130, controller 100 is provided at one end of power line 130. Most of power line 130 other than both ends, i.e., an intermediate portion of power line 130 including connection portion 80, is laid on the seabed.

[0016] Optical fiber composite power cable 50 includes a cable body 60, a first optical fiber 6, a second optical fiber 7, a first auxiliary conductor 8, and a second auxiliary conductor 9. For long-distance transmission of light in first optical fiber 6 and second optical fiber 7, an optical amplification repeater and the like are placed in connection portion 80.

[0017] Optical fiber composite power cable 50 according to the first embodiment will be described with reference to Fig. 2.

[0018] Optical fiber composite power cable 50 is formed by incorporating a plurality of optical fibers into a power cable. Optical fiber composite power cable 50 transmits electric power, light, and amplification electric power for optical amplification. Specifically, optical fiber composite power cable 50 includes cable body 60 that transmits the electric power, an armor portion 59, and detection wires 61 and 71 that transmit the light and the amplification electric power. As described below, each of detection wires 61 and 71 includes an optical fiber used for detection of an abnormal point of the power cable or the like, and a structure for transmitting the above-described amplification electric power. The above-described amplification electric power is supplied from a power supply, i.e., here, a main power supply 22 and a secondary power supply 41 described below.

[0019] Cable body 60 is a main portion of the power cable. Cable body 60 is made up of a conductor 51, an inner semiconducting layer 52, an insulating layer 53, an outer semiconducting layer 54, and the like. Conductor 51, inner semiconducting layer 52, insulating layer 53, and outer semiconducting layer 54 are provided in this order from the center of cable body 60. Cable body 60 in the present example further includes a sheath 55 on an outer circumference of outer semiconducting layer 54. Insulating layer 53 is, for example, an electrical insulator made of crosslinked polyethylene. Semiconducting layers 52 and 54 are made of a semiconducting material. Sheath 55 is, for example, a lead sheath. Cable body 60 does not need to include sheath 55. Cable body 60 may also be provided with a shield layer, a water barrier layer, an anti-corrosive layer and the like. The shield layer is made of a conducting material. The water barrier layer is formed, for example, by stacking a metal layer and a resin layer. Armor portion 59 is provided on an outer circumference of cable body 60. Armor portion 59 protects cable body 60 from external damage, or supports a load of optical fiber composite power cable 50.

[0020] Armor portion 59 has a plurality of wires 58a and 58b. Armor portion 59 has a multilayer structure including an inner layer and an outer layer. The plurality of wires 58a constituting the inner layer are disposed along an outer circumferential surface of cable body 60 without any gaps. The plurality of wires 58b constituting the outer layer are disposed along a circumference of an outer circumferential surface formed by the plurality of wires 58a without any gaps. Wires 58a and 58b are made of, for example, metal or fiber-reinforced plastic. Metal is, for example, a magnetic material such as iron. A not-shown resin layer may be provided between the inner layer and the outer layer. Alternatively, a not-shown resin layer formed to cover armor portion 59 may be provided. Each of these resin layers is formed, for example, by winding a string-like member made of resin such as polypropylene. Wires 58a and 58b may be made of a non-magnetic material. When wires 58a and 59b are made of metal, wires 58a and 59b are excellent in strength. When wires 58a and 59b are made of a non-magnetic material such as resin, wires 58a and 59b are light in weight.

[0021] In armor portion 59, at least one of wires 58a constituting the inner layer, of the two layers, is replaced with detection wire 61, 71 to detect an abnormality such as damage or distortion of cable body 60 or armor portion 59. Although detection wire 61, 71 may only be formed in at least one location of armor portion 59, detection wire 61, 71 may be provided in a plurality of locations. In order to make detection wire 61 and detection wire 71 less likely to be affected by a magnetic field caused by a fault current, it is desirable to dispose detection wire 61 and detection wire 71 adjacent to each other in a circumferential direction of cable body 60. Detection wire 61 and detection wire 71 may be spaced apart from each other in the circumferential direction of cable body 60. Alternatively, detection wire 61 and detection wire 71 may be disposed adjacent to each other in a radial direction of cable body 60. Although Fig. 2 illustrates the case in which armor portion 59 has a multilayer structure, armor portion 59 may have a single-layer structure.

[0022] Detection wire 61 will be described with reference to Figs. 2 and 3.

[0023] Detection wire 61 includes a metal tube 63, first auxiliary conductor 8 provided on an outer circumference of metal tube 63, and a sheath 64. Metal constituting metal tube 63 is, for example, non-magnetic stainless steel. First auxiliary conductor 8 is made of metal having a high conductivity, e.g., copper or copper alloy. First auxiliary conductor 8 is a metal layer formed by laminating metal such as copper, a metal layer formed by winding a tape made of the above-described metal, or a metal layer formed by extruding the above-described metal. The metal layer formed by extrusion is seamless and has a uniform thickness over the entire length of metal tube 63. In the manufacturing process, the metal layer can be easily formed by continuously extruding the metal, which is a material of the metal layer, onto the outer circumference of metal tube 63. Therefore, the metal layer formed by extrusion is also more excellent in manufacturability than the other structures. Sheath 64 is made of resin such as polyethylene and constitutes an outermost layer of detection wire 61.

[0024] Metal constituting metal tube 63 may be magnetic stainless steel. Alternatively, metal constituting metal tube 63 may be metal having a high conductivity, such as copper. In this case, even without the above-described metal layer, metal tube 63 can function as first auxiliary conductor 8.

[0025] Metal tube 63 accommodates first optical fiber 6 and second optical fiber 7. Metal tube 63 may further accommodate a not-shown spare optical fiber. A jelly compound 62 is filled into a gap of metal tube 63. Sheath 64 functions as an insulating layer and an anti-corrosive layer.

[0026] A method of wrapping first optical fiber 6 and second optical fiber 7 with metal tube 63 can be used as a method of manufacturing detection wire 61.

[0027] Detection wire 71 will be described with reference to Figs. 2 and 4.

[0028] The basic structure, the constituent material, the size and the like of detection wire 71 can be similar to those of detection wire 61. Detection wire 71 includes metal tube 63, second auxiliary conductor 9 provided on an outer circumference of metal tube 63, and sheath 64. For the constituent material and the like of metal tube 63 and the constituent material and the like of sheath 64, please refer to the above description about metal tube 63 and sheath 64 included in detection wire 61. For the constituent material and the like of second auxiliary conductor 9, please refer to the above description about first auxiliary conductor 8.

[0029] Unlike detection wire 61, metal tube 63 is filled with only jelly compound 62 and does not accommodate an optical fiber. However, as shown in Fig. 28 described below, metal tube 63 may accommodate a spare optical fiber.

[0030] As shown in Fig. 5, wires 58a constituting the inner layer, and detection wires 61 and 71 are spirally wound around the outer circumferential surface of cable body 60 without any gaps. Wires 58b constituting the outer layer are spirally wound around the circumference of the outer circumferential surface formed by wires 58a and detection wires 61 and 71 without any gaps.

[0031] As described above, in the present embodiment, first auxiliary conductor 8 and second auxiliary conductor 9 are incorporated into two detection wires 61 and 71 adjacent to each other in the circumferential direction of cable body 60. Since two detection wires 61 and 71 are disposed adjacent to each other in the above-described circumferential direction, a gap between first auxiliary conductor 8 and second auxiliary conductor 9 arranged concentrically can be made smaller. As shown in Fig. 6, when a ground fault accident occurs in optical fiber composite power cable 50 and a fault current flows through cable body 60, a self-magnetic field centered at cable body 60 is generated. Although first auxiliary conductor 8 and second auxiliary conductor 9 are disposed in the above-described magnetic field (self-magnetic field), a magnetic flux that induces a voltage is less likely to cross a space between first auxiliary conductor 8 and second auxiliary conductor 9, and thus, first auxiliary conductor 8 and second auxiliary conductor 9 are less likely to be affected by the magnetic flux. In addition, since detection wires 61 and 71 are surrounded by wires 58a and 58b made of magnetic metal, the above-described magnetic flux is less likely to flow through detection wires 61 and 71. As a result, first auxiliary conductor 8 and second auxiliary conductor 9 can reliably supply electric power to the optical amplification repeater, and thus, an abnormality of the power cable or the like caused by a ground fault accident or the like is reliably detected.

[0032] Furthermore, detection wires 61 and 71 are spirally wound around the outer circumferential surface of cable body 60 without any gaps. As shown in Fig. 7, when the optical fiber composite power cable transmits DC power, two optical fiber composite power cables X and Y may in some cases be laid as one set. One power cable X is used as a positive electrode cable, and the other power cable Y is used as a negative electrode cable. When a fault occurs in optical fiber composite power cable Y adjacent to optical fiber composite power cable X to which attention is directed, a fault current causes a magnetic field centered at cable body 60 of power cable Y. The magnetic field formed by power cable Y is an external magnetic field as seen from power cable X. Although power cable X is disposed in the above-described external magnetic field, a current based on an induced voltage generated by a magnetic field caused by a fault current of adjacent optical fiber composite power cable Y in a cross section A perpendicular to the longitudinal direction of optical fiber composite power cable X to which attention is directed and a current based on an induced voltage generated by a magnetic field caused by this fault current in another cross section B cancel each other out. Since two detection wires 61 and 71 are disposed adjacent to each other in the circumferential direction of cable body 60 and are spirally wound around the outer circumferential surface of cable body 60, first auxiliary conductor 8 and second auxiliary conductor 9 are less likely to be affected by the magnetic flux based on the self-magnetic field or the external magnetic field, even when the self-magnetic field or the external magnetic field occurs due to the fault as described above.

[0033] Connection portion 80 included in power line 130 according to the first embodiment will be described with reference to Fig. 8.

[0034] A conductor 51A of cable body 60 of optical fiber composite power cable 50-1 and a conductor 51B of cable body 60 of optical fiber composite power cable 50-2 are connected to each other by a sleeve 99. An insulating portion 98 made of an insulating tape or the like is formed around conductors 51A and 51B and sleeve 99. Insulating portion 98 is provided across insulating layers 53A and 53B of above-described cable bodies 60. On an outer perimeter of insulating portion 98, a semiconducting portion 97 is formed across outer semiconducting layers 54A and 54B of above-described cable bodies 60. These are surrounded and protected by a metal tube 94. Metal tube 94 is filled with a not-shown waterproof mixture. Metal tube 94 also functions as a member that electrically connects shield layers 57A and 57B of above-described cable bodies 60. A protective layer 92 made of a protective tape or the like is formed on an outer perimeter surface of metal tube 94.

[0035] Detection wires 61 and 71 are connected to an optical amplification repeater 70 disposed in a housing 171. Detection wires 61 and 71 of optical fiber composite power cables 50-1 and 50-2 are accommodated in housing 171 and connected to each other.

[0036] The interior of housing 171 will be described with reference to Fig. 9.

[0037] Optical amplification repeater 70 and secondary power supply 41 are accommodated in housing 171 of waterproof type. Optical amplification repeater 70 includes a first erbium-doped fiber 1, a second erbium-doped fiber 4, optical directional couplers 3, 5, 44, and 45, a branching optical fiber 39, a first excitation laser device 42, and a second excitation laser device 43.

[0038] Secondary power supply 41 is one type of power supply. The power supply includes main power supply 22 (Fig. 10) and secondary power supply 41. Since main power supply 22 is disposed in controller 100, main power supply 22 is disposed on land. Since secondary power supply 41 is disposed in connection portion 80, secondary power supply 41 is disposed on the seabed. Secondary power supply 41 converts a primary voltage transmitting from main power supply 22 through first auxiliary conductor 8 and second auxiliary conductor 9 into a secondary voltage smaller than the primary voltage. The primary voltage is, for example, approximately several thousand volts. The secondary voltage is approximately several volts and the magnitude that can be used in devices such as laser device 42 is selected. Electric power of the secondary voltage is supplied from secondary power supply 41 to first excitation laser device 42 and second excitation laser device 43. Electric power is directly supplied from secondary power supply 41 to first excitation laser device 42 and second excitation laser device 43, and electric power is indirectly supplied from main power supply 22 to first excitation laser device 42 and second excitation laser device 43.

[0039] When main power supply 22 is a DC power supply, secondary power supply 41 is a DC / DC converter. When main power supply 22 is an AC power supply, secondary power supply 41 is an AC / DC converter.

[0040] First excitation laser device 42 and second excitation laser device 43 operate with the electric power from secondary power supply 41. First excitation laser device 42 emits first excitation light to optical directional coupler 44. Second excitation laser device 43 emits second excitation light to optical directional coupler 45. Each of the first excitation light and the second excitation light has a wavelength of, for example, 1480 nm. First excitation laser device 42 and second excitation laser device 43 constitute an excitation device.

[0041] The excitation device may be configured such that an output of one excitation laser device is bifurcated into two outputs, which are output to optical directional coupler 44 and optical directional coupler 45, instead of using the two excitation laser devices. The number of secondary power supply 41 is not limited to one, and a first secondary power supply that supplies electric power to first excitation laser device 42 and a second secondary power supply that supplies electric power to second excitation laser device 43 may be provided.

[0042] Erbium ions in first erbium-doped fiber 1 are excited by the first excitation light, whereby the sensing light transmitting through first optical fiber 6 is amplified. Erbium ions in second erbium-doped fiber 4 are excited by the second excitation light, whereby the backscattered light transmitting through second optical fiber 7 is amplified.

[0043] Branching optical fiber 39, optical directional coupler 3 and optical directional coupler 5 form a branch structure 38 that guides the backscattered light generated in first optical fiber 6 to second optical fiber 7. Instead of providing branch structure 38, a configuration in which a part of the backscattered light leaks from first optical fiber 6 to second optical fiber 7 may be used. Optical amplification repeater 70 may further include an optical isolator.

[0044] An abnormal point detection system 200 for an optical fiber composite power cable will be described with reference to Fig. 10. Fig. 10 does not show secondary power supply 41 (Fig. 9).

[0045] Abnormal point detection system 200 for an optical fiber composite power cable includes power line 130, optical amplification repeaters 70-1, 70-2, ..., and controller 100.

[0046] Controller 100 includes a pulsed laser device 21 (laser device), a measurement device 20, main power supply 22, an optical isolator 25, and optical directional couplers 30 and 31. Measurement device 20 includes a wavelength filter 28, an optical receiver 23 and an analysis device 12.

[0047] Optical amplification repeaters 70-1, 70-2, ... may be collectively denoted as optical amplification repeater 70. In Fig. 10, of the components of power line 130, first optical fiber 6, second optical fiber 7, first auxiliary conductor 8, second auxiliary conductor 9, and optical amplification repeater 70 are shown.

[0048] Pulsed laser device 21 emits the sensing light having a pulsed wave. Light having a wavelength band called the C band or the L band is, for example, used as the sensing light. The C band is a wavelength band whose wavelength is equal to or more than 1525 nm and equal to or less than 1563 nm. The L band is a wavelength band whose wavelength is equal to or more than 1560 nm and equal to or less than 1610 nm. Pulsed laser device 21 emits the sensing light having a wavelength of, for example, 1560 nm. The light having a wavelength of 1560 nm is known to be small in transmission loss of an optical fiber. Moreover, the light having a long wavelength such as 1560 nm is known to be large in transmission loss with respect to distortion caused by bending or the like, and is suitable for detection of an abnormality of a power cable or the like by an optical fiber.

[0049] First optical fiber 6 and second optical fiber 7 are disposed in proximity to each other. First optical fiber 6 has a first end EA and a second end EB. A direction from first end EA to second end EB may be denoted as a forward direction, and a direction from second end EB to first end EA may be denoted as a reverse direction. Second optical fiber 7 has a first end EC and a second end ED. A direction from first end EC to second end ED may be denoted as a forward direction, and a direction from second end ED to first end EC may be denoted as a reverse direction.

[0050] First optical fiber 6 transmits the sensing light from first end EA to second end EB. Second optical fiber 7 transmits the backscattered light of the sensing light to first end EC.

[0051] It is desirable to use an optical fiber having a low transmission loss and a large effective area as each of first optical fiber 6 and second optical fiber 7 such that the light having great power can be transmitted far away. The optical fiber having a large effective area is, for example, an optical fiber having a core diameter of 110 µm or more. The core diameter of the optical fiber may be 125 µm or more, or may be 135 µm or more.

[0052] Main power supply 22 supplies electric power of the primary voltage to first auxiliary conductor 8 and second auxiliary conductor 9. Although main power supply 22 is a DC power supply or an AC power supply, the DC power supply is preferable in consideration of long-distance transmission. The primary voltage is, for example, approximately several thousand volts. First auxiliary conductor 8 is connected to a first terminal of main power supply 22. Second auxiliary conductor 9 is connected to a second terminal of main power supply 22. When main power supply 22 is a DC power supply, the first terminal is a positive electrode terminal and the second terminal is a negative electrode terminal, and first auxiliary conductor 8 functions as a positive electrode lead and second auxiliary conductor 9 functions as a negative electrode lead.

[0053] In some cases, first auxiliary conductor 8 and second auxiliary conductor 9 are directly connected to the first terminal and the second terminal of main power supply 22, while in other cases, first auxiliary conductor 8 and second auxiliary conductor 9 are indirectly connected to main power supply 22 with an area of connection between first auxiliary conductor 8 and second auxiliary conductor 9 interposed therebetween. The area of connection between first auxiliary conductor 8 and second auxiliary conductor 9 is provided in connection portion 80.

[0054] Optical amplification repeater 70 amplifies the sensing light with the first excitation light and amplifies the backscattered light with the second excitation light.

[0055] Optical isolator 25 is connected to an emission port of pulsed laser device 21. Optical isolator 25 cuts off light transmission to pulsed laser device 21.

[0056] Optical directional coupler 30 is connected to first end EA of first optical fiber 6, optical isolator 25 and optical directional coupler 31. Optical directional coupler 30 transmits the sensing light to first optical fiber 6 in the forward direction. Optical directional coupler 30 sends, to optical directional coupler 31, the backscattered light generated in a location 6a of first optical fiber 6 and transmitting through location 6a in the reverse direction.

[0057] Optical directional coupler 31 is connected to measurement device 20 and optical directional coupler 30. Optical directional coupler 31 sends, to measurement device 20, the backscattered light sent through optical directional coupler 30 and transmitting through location 6a of first optical fiber 6 in the reverse direction. Optical directional coupler 31 sends, to measurement device 20, the backscattered light transmitting through second optical fiber 7 in the reverse direction.

[0058] The configuration and the operation of optical amplification repeater 70 will be described with reference to Figs. 9 and 10.

[0059] Optical amplification repeater 70 includes first erbium-doped fiber 1, optical directional couplers 3, 5, 44, and 45, second erbium-doped fiber 4, and branching optical fiber 39.

[0060] Optical directional coupler 44 sends, to first erbium-doped fiber 1, the sensing light transmitting through first optical fiber 6 in the forward direction. Optical directional coupler 44 sends, to first erbium-doped fiber 1, the first excitation light emitted from first excitation laser device 42.

[0061] First erbium-doped fiber 1 is connected to optical directional coupler 44 and optical directional coupler 3.

[0062] First erbium-doped fiber 1 amplifies the sensing light sent through optical directional coupler 44 with the first excitation light sent through optical directional coupler 44.

[0063] Optical directional coupler 3 is connected to branching optical fiber 39, first erbium-doped fiber 1 and first optical fiber 6. Optical directional coupler 3 sends the amplified sensing light to first optical fiber 6. Optical directional coupler 3 sends, to branching optical fiber 39, the backscattered light generated in a location 6b of first optical fiber 6 and transmitting through location 6b in the reverse direction.

[0064] Optical directional coupler 5 is connected to branching optical fiber 39, second optical fiber 7 and optical directional coupler 45. Optical directional coupler 5 sends, to optical directional coupler 45, the backscattered light transmitting through branching optical fiber 39 (i.e., the backscattered light generated in location 6b of first optical fiber 6 and transmitting through location 6b in the reverse direction) and the backscattered light transmitting through second optical fiber 7 in the reverse direction (i.e., the backscattered light generated in a not-shown location (on a side close to second end EB) of first optical fiber 6 and sent to second optical fiber 7 through not-shown optical amplification repeater 70).

[0065] Optical directional coupler 45 is connected to optical directional coupler 5 and second erbium-doped fiber 4. Optical directional coupler 45 sends, to second erbium-doped fiber 4, the backscattered light sent from optical directional coupler 5. Optical directional coupler 45 sends, to second erbium-doped fiber 4, the second excitation light emitted from second excitation laser device 43.

[0066] Second erbium-doped fiber 4 is connected to optical directional coupler 45 and second optical fiber 7. Second erbium-doped fiber 4 amplifies the backscattered light sent through optical directional coupler 45 with the second excitation light sent through optical directional coupler 45, and outputs the amplified backscattered light to second optical fiber 7.

[0067] Optical directional coupler 45 may be connected to second optical fiber 7 and second erbium-doped fiber 4, and second erbium-doped fiber 4 may be connected to optical directional coupler 5.

[0068] Wavelength filter 28 is connected to optical directional coupler 31. Wavelength filter 28 allows the backscattered light, of the light sent through optical directional coupler 31, to pass therethrough. A wavelength of the backscattered light passing through wavelength filter 28 is, for example, the same as the wavelength of the sensing light. An output of wavelength filter 28 is sent to optical receiver 23.

[0069] Optical receiver 23 has a semiconductor light receiving element. Optical receiver 23 converts the light sent through wavelength filter 28 into an electrical signal. Although not shown here, the detection sensitivity can be enhanced by applying the coherence of an optical signal to detection.

[0070] Analysis device 12 detects whether an abnormality has occurred in power line 130, using a plurality of signals sent through optical receiver 23, and when the abnormality has occurred, analysis device 12 detects an abnormal point. Basically, analysis device 12 can detect a position of the abnormal point of power line 130 based on a time lag between the time when the sensing signal is transmitted and the time when the backscattered light is received. For example, a C-OTDR (Coherent-Optical Time-Domain Reflectometer) that measures an increase in loss caused by damage of an optical fiber, a DAS (Distributed Acoustic Sensor) that detects distortion or vibration of optical fiber composite power cable 50, or the like can be used as a detection method. When an abnormality occurs in cable body 60, armor portion 59 or the like, damage, distortion, vibration or the like caused by the above-described abnormality is applied to the optical fiber. Using the damage or the like in the optical fiber, the abnormal point of power line 130 can be detected.

[0071] An abnormal point detection procedure for power line 130 in the first embodiment will be described with reference to Fig. 11.

[0072] Before the below-described steps, main power supply 22 and secondary power supply 41 are made ready for supplying electric power.

[0073] In step S102, pulsed laser device 21 emits the sensing light (pulsed light). The sensing light transmits through first optical fiber 6.

[0074] In step S103, optical amplification repeater 70 that operates with the electric power from secondary power supply 41 amplifies the sensing light with the first excitation light. The backscattered light transmits through first optical fiber 6 in the reverse direction and enters optical amplification repeater 70.

[0075] In step S104, optical amplification repeater 70 that operates with the electric power from secondary power supply 41 amplifies the backscattered light with the second excitation light and sends the amplified backscattered light to second optical fiber 7. The backscattered light transmits through second optical fiber 7 in the reverse direction, is amplified with the second excitation light in optical amplification repeater 70 provided midway, and enters measurement device 20. When an abnormality occurs in optical fiber composite power cable 50, physical quantities (such as an intensity and a phase) of the backscattered light vary (attenuated in the case of an intensity). Therefore, by configuring measurement device 20 to grasp the presence or absence of the above-described variation in physical quantities, the occurrence of the abnormality and the location of occurrence of the abnormality can be grasped.

[0076] In step S105, measurement device 20 performs backscattered light reception processing. In other words, wavelength filter 28 sends the backscattered light, of the light sent through optical directional coupler 31, to optical receiver 23. Optical receiver 23 converts the light sent through wavelength filter 28 into an electrical signal and sends the electrical signal to analysis device 12.

[0077] In step S106, when one measurement period T has elapsed from the previous emission of the sensing light (pulsed light), the process proceeds to step S107. One measurement period T may be set to be equal to or longer than a time lag between the time when the sensing light is emitted from pulsed laser device 21 and the time when optical receiver 23 receives the backscattered light generated at second end EB of first optical fiber 6. When one measurement period T is the time lag between the above-described times, the accuracy of abnormality sensing is enhanced. The above-described times depend on the length of an optical fiber and the light transmission speed in an optical fiber. Therefore, when the length of each of first optical fiber 6 and second optical fiber 7 is, for example, 500 km, one measurement period T is about 5 msec. Measurement device 20 continues to receive the backscattered light during one measurement period T.

[0078] In step S107, analysis device 12 determines physical quantities from the backscattered light sent through optical receiver 23. Using the determined physical quantities (hereinafter, called latest physical quantities), analysis device 12 detects the presence or absence of an abnormality.

[0079] Detection of the presence or absence of an abnormality may be performed, for example, by comparing the latest physical quantities with one or more threshold values. The one or more threshold values are values corresponding to respective positions of optical fiber composite power cable 50, and are set based on physical quantities of the backscattered light calculated in accordance with a transmission distance when there is no abnormality in optical fiber composite power cable 50, for example. Physical quantities determined for each one measurement period T may be accumulated and this accumulated information may be used. The accumulated information indicates trends in the past and the use of the accumulated information tends to lead to smaller influence of noise. For example, analysis device 12 may compare a difference between the latest physical quantities and immediately preceding physical quantities with a preset threshold value. Instead of the above-described immediately preceding physical quantities, an average value of physical quantities for a certain time period in the past may be used. Instead of the above-described average value, a variance value of physical quantities for a certain time period may be used as a comparison target or a threshold value. In this analysis processing, the presence or absence of an abnormality that may occur in a short time period is detected.

[0080] In step S108, analysis device 12 adds physical quantities (such as an intensity, a phase difference and a phase change of the backscattered light) of the signals sent through optical receiver 23.

[0081] In step S109, every time the addition processing for the predetermined number of times ends, the process proceeds to step S110. Otherwise, the process returns to step S102. The added values are stored and saved whenever needed.

[0082] In step S110, analysis device 12 again detects the presence or absence of an abnormality, using the added values including the latest physical quantities (hereinafter, called latest added values) and added values in the past. For example, analysis device 12 compares a difference between an average value of the added values in the past and an average value of the latest added values with a preset threshold value. The average value of the added values is, for example, calculated by dividing the added values by the predetermined number of times. Instead of the above-described average value, a variance value of the above-described added values may be used as a comparison target or a threshold value. The variance value indicates variations in signals caused by noise. The use of the accumulated information such as the average value of the added values in the past tends to lead to even smaller influence of noise. In this analysis processing, the presence or absence of an abnormality that may occur over a long time period (such as minute distortion or a phase change kept over a long time period) is detected. In other words, the occurrence of permanent damage such as external damage or fatigue of optical fiber composite power cable 50 can also be sensed. Thereafter, the added values are reset, and the process returns to step S102.

[0083] As described above, according to the present embodiment, since optical fibers 6 and 7 and optical amplification repeater 70 that amplifies the light transmitting through optical fibers 6 and 7 are used, an abnormal point such as a ground fault accident, external damage or fatigue of long-distance power line 130 of 300 km or longer and even 500 km or longer can be detected with high accuracy and in a short time.

[0084] According to the present embodiment, since the sensing light is emitted from each of both ends of power line 130, an abnormal point such as a ground fault accident, external damage or fatigue of long-distance power line 130 of 1000 km or longer can be expected to be detected with high accuracy and in a short time. Particularly when optical fiber composite power cable 50 is laid on the seabed, the time and effort required to pull up optical fiber composite power cable 50 onto a ship and perform inspection can be saved.

[0085] According to the present embodiment, a fault point of power line 130 can be detected immediately after a ground fault accident occurs. Furthermore, according to the present embodiment, the electric power for driving first excitation laser device 42 and second excitation laser device 43 of optical amplification repeater 70 can be transmitted to connection portion 80 by first auxiliary conductor 8 and second auxiliary conductor 9. Secondary power supply 41 in connection portion 80 can convert the electric power of the primary voltage from main power supply 22 into the electric power of the secondary voltage suitable for optical amplification repeater 70. Optical amplification repeater 70 operate with the electric power of the secondary voltage and can amplify the sensing light and the backscattered light.<Second Embodiment>

[0086] In a second embodiment and subsequent embodiments, differences from the first embodiment will be mainly described and description about the common matters will not be repeated.

[0087] An optical fiber composite power cable 50A according to the second embodiment will be described with reference to Fig. 12.

[0088] Optical fiber composite power cable 50A is different from optical fiber composite power cable 50 according to the first embodiment in that optical fiber composite power cable 50A includes detection wires 61A and 71A instead of detection wires 61 and 71.

[0089] Detection wire 61A will be described with reference to Fig. 13.

[0090] Detection wire 61A is different from detection wire 61 described in the first embodiment in that metal tube 63 accommodates first optical fiber 6 and does not accommodate second optical fiber 7 in detection wire 61A.

[0091] Detection wire 71A will be described with reference to Fig. 14.

[0092] Detection wire 71A is different from detection wire 71 described in the first embodiment in that metal tube 63 accommodates second optical fiber 7 in detection wire 71A.

[0093] Similarly to the first embodiment, the present embodiment can also make first auxiliary conductor 8 and second auxiliary conductor 9 less likely to be affected by a magnetic field caused by a fault current.<Third Embodiment>

[0094] An optical fiber composite power cable 50B according to a third embodiment will be described with reference to Fig. 15.

[0095] Optical fiber composite power cable 50B is different from optical fiber composite power cable 50 according to the first embodiment in that optical fiber composite power cable 50B includes a detection wire 61B instead of detection wires 61 and 71.

[0096] Detection wire 61B will be described with reference to Fig. 16.

[0097] Detection wire 61B includes metal tube 63, first auxiliary conductor 8 provided on an outer circumference of metal tube 63, an insulating layer 64A provided on an outer circumference of first auxiliary conductor 8, second auxiliary conductor 9 provided on an outer circumference of insulating layer 64A, and sheath 64 provided on an outer circumference of second auxiliary conductor 9. Sheath 64 is made of resin such as polyethylene and constitutes an outermost layer of detection wire 61B. Insulating layer 64A is made of an electrically insulating material, e.g., resin such as polyethylene. First auxiliary conductor 8 and second auxiliary conductor 9 are spaced apart from each other in a radial direction of detection wire 61B. Insulating layer 64A is provided between first auxiliary conductor 8 and second auxiliary conductor 9, whereby second auxiliary conductor 9 also functions as a magnetic shield layer. The positions of first auxiliary conductor 8 and second auxiliary conductor 9 may be interchanged.

[0098] Metal tube 63 accommodates first optical fiber 6 and second optical fiber 7. Jelly compound 62 is filled into a gap of metal tube 63.

[0099] In the present embodiment, first auxiliary conductor 8 and second auxiliary conductor 9 are disposed coaxially. In other words, detection wire 61B has a coaxial structure. Electromotive force is not generated between first auxiliary conductor 8 and second auxiliary conductor 9 that are arranged coaxially. Therefore, even when a magnetic field caused by a fault current occurs, generation of an induced voltage in first auxiliary conductor 8 and second auxiliary conductor 9 due to the magnetic field can be prevented.

[0100] An optical fiber composite power cable 50C according to a fourth embodiment will be described with reference to Fig. 17.

[0101] Optical fiber composite power cable 50C is different from optical fiber composite power cable 50 according to the first embodiment in that optical fiber composite power cable 50C includes a detection wire 61C instead of detection wires 61 and 71.

[0102] Detection wire 61C will be described with reference to Fig. 18.

[0103] Detection wire 61C includes metal tube 63, a plurality of positive electrode leads (first auxiliary leads) 78 and a plurality of negative electrode leads (second auxiliary leads) 79 spirally wound around a circumferential surface of metal tube 63 without any gaps, and sheath 64. Sheath 64 is made of resin such as polyethylene and constitutes an outermost layer of detection wire 61C. The plurality of positive electrode leads 78 constitute first auxiliary conductor 8. The plurality of negative electrode leads 79 constitute second auxiliary conductor 9. Each of the plurality of positive electrode leads 78 and the plurality of negative electrode leads 79 is a copper wire. Positive electrode leads 78 and negative electrode leads 79 are disposed alternately. Negative electrode leads 79 are disposed on the right side of and on the left side of positive electrode lead 78, and positive electrode leads 78 are disposed on the right side of and on the left side of negative electrode lead 79. An insulation coating 131 is provided on an outer circumference of negative electrode lead 79. Insulation coating 131 may be provided on an outer circumference of positive electrode lead 78.

[0104] Metal tube 63 accommodates first optical fiber 6 and second optical fiber 7. Jelly compound 62 is filled into a gap of metal tube 63. Sheath 64 functions as an anti-corrosive layer and an insulating layer.

[0105] In the present embodiment, positive electrode leads (first auxiliary leads) 78 and negative electrode leads (second auxiliary leads) 79 are disposed alternately in the circumferential direction of metal tube 63, and thus, positive electrode leads 78 and negative electrode leads 79 are disposed concentrically. Therefore, generation of an induced voltage due to a magnetic field caused by a fault current can be prevented.

[0106] It is also conceivable to dispose positive electrode leads (first auxiliary leads) 78 and not dispose negative electrode leads (second auxiliary leads) 79 in detection wire 61C, and dispose negative electrode leads (second auxiliary leads) 79 and not dispose positive electrode leads (first auxiliary leads) 78 in a detection wire adjacent to detection wire 61C. In this case, all of leads 78 and 79 do not need to include insulation coating 131.<Fifth Embodiment>

[0107] An optical fiber composite power cable 50D according to a fifth embodiment will be described with reference to Fig. 19.

[0108] Optical fiber composite power cable 50D is different from optical fiber composite power cable 50 according to the first embodiment in that optical fiber composite power cable 50D includes a detection wire 61D instead of detection wires 61 and 71.

[0109] Detection wire 61D will be described with reference to Fig. 20.

[0110] Detection wire 61D includes metal tube 63, a plurality of positive electrode leads 78 and a plurality of negative electrode leads 79 spirally wound around an outer circumferential surface of metal tube 63 without any gaps, and sheath 64. Sheath 64 is made of resin such as polyethylene and constitutes an outermost layer of detection wire 61D.

[0111] The plurality of positive electrode leads 78 constitute first auxiliary conductor 8. The plurality of negative electrode leads 79 constitute second auxiliary conductor 9. The plurality of positive electrode leads 78 are disposed continuously in a first region R1, and the plurality of negative electrode leads 79 are disposed continuously in a second region R2. An insulating member 132 is disposed in a third region R3 between first region R1 and second region R2. Each of first region R1 and second region R2 is a roughly half region of the outer circumferential surface of metal tube 63.

[0112] Metal tube 63 accommodates first optical fiber 6 and second optical fiber 7. Jelly compound 62 is filled into a gap of metal tube 63. Sheath 64 functions as an anti-corrosive layer and an insulating layer.

[0113] Similarly to the fourth embodiment, in the present embodiment as well, positive electrode leads 78 and negative electrode leads 79 are disposed concentrically. Therefore, generation of an induced voltage due to a magnetic field caused by a fault current can be prevented. In the present embodiment, all of leads 78 and 79 do not need to include insulation coating 131.<Sixth Embodiment>

[0114] An optical fiber composite power cable 50E according to a sixth embodiment will be described with reference to Fig. 21.

[0115] Optical fiber composite power cable 50E is different from optical fiber composite power cable 50 according to the first embodiment in that optical fiber composite power cable 50E includes a detection wire 61E instead of detection wires 61 and 71.

[0116] Detection wire 61E will be described with reference to Fig. 22.

[0117] Detection wire 61E includes metal tube 63, first auxiliary conductor 8 provided on an outer circumference of metal tube 63, an insulating layer 133 provided on an outer circumference of the first auxiliary lead, a plurality of negative electrode leads 79 spirally wound around an outer circumferential surface of insulating layer 133 without any gaps, and sheath 64. Sheath 64 is made of resin such as polyethylene and constitutes an outermost layer of detection wire 61E. Metal tube 63 accommodates first optical fiber 6 and second optical fiber 7. Jelly compound 62 is filled into a gap of metal tube 63. Sheath 64 functions as an anti-corrosive layer and an insulating layer. First auxiliary conductor 8 functions as a positive electrode lead. The plurality of negative electrode leads 79 constitute second auxiliary conductor 9.

[0118] The positions of first auxiliary conductor 8 and second auxiliary conductor 9 may be interchanged. In other words, second auxiliary conductor 9 may be provided on the outer circumference of metal tube 63, and a plurality of positive electrode leads spirally wound around the outer circumferential surface of insulating layer 133 without any gaps may be provided.

[0119] Similarly to the third embodiment, in the present embodiment as well, first auxiliary conductor 8 and second auxiliary conductor 9 are disposed coaxially. Therefore, even when a magnetic field caused by a fault current occurs, generation of an induced voltage in first auxiliary conductor 8 and second auxiliary conductor 9 due to the magnetic field can be prevented.<Seventh Embodiment>

[0120] A connection portion 80A included in power line 130 according to a seventh embodiment will be described with reference to Fig. 23.

[0121] Connection portion 80A is different from connection portion 80 described in the first embodiment in that connection portion 80 includes a surge detection processing device 120.

[0122] Surge detection processing device 120 will be described with reference to Fig. 24.

[0123] Surge detection processing device 120 includes a surge detection unit 220 and a communication device 123. Surge detection unit 220 includes a surge detection sensor 121 and a surge detector 122. Surge detector 122 and communication device 123 may be accommodated in housing 171. Surge detector 122 and communication device 123 operate with electric power from secondary power supply 41.

[0124] Surge detection unit 220 detects a surge wave generated in cable body 60 of optical fiber composite power cable 50. For example, surge detection sensor 121 is placed on a surface of metal tube 94 that electrically connects shield layer 57A of cable body 60 of optical fiber composite power cable 50-1 and shield layer 57B of cable body 60 of optical fiber composite power cable 50-2. Surge detection sensor 121 detects a surge voltage induced in metal tube 94 or a surge current flowing through metal tube 94. Surge detection sensor 121 is a voltage sensor, a current sensor, a partial discharge sensing sensor, or the like. The inclusion of surge detection sensor 121 also enables the application to detection of partial discharge. By directly attaching surge detection unit 220 to cable body 60, the surge wave can be detected without adding an induction lead.

[0125] Surge detector 122 creates information indicating a surge detection result, based on a detection signal from surge detection sensor 121.

[0126] Communication device 123 converts the surge detection result into a power line communication signal, and transmits the power line communication signal to analysis device 12 in controller 100 through one or both of first auxiliary conductor 8 and second auxiliary conductor 9.

[0127] An abnormal point detection procedure for power line 130 in the seventh embodiment will be described with reference to Fig. 25. A flowchart in Fig. 25 is different from the flowchart in the first embodiment shown in Fig. 11 in that the flowchart in Fig. 25 includes step S210 instead of step S110.

[0128] In parallel with the processing in steps S102 to S109, surge detection is performed. In other words, surge detection unit 220 detects the surge wave transmitting through cable body 60 of optical fiber composite power cable 50. Communication device 123 transmits the information indicating the surge detection result to analysis device 12 in controller 100 through one or both of first auxiliary conductor 8 and second auxiliary conductor 9 in accordance with a power line communication scheme.

[0129] In step S210, analysis device 12 performs determination of an abnormality (one optical fiber composite power cable identified as having an abnormality) based on the surge detection results from surge detection processing devices 120 of the plurality of connection portions 80-1, 80-2, ..., in addition to determination of an abnormal point (an abnormal location of one optical fiber composite power cable identified as having an abnormality) using the backscattered light. In other words, analysis device 12 performs double-checking.

[0130] Specifically, analysis device 12 identifies an abnormal optical fiber composite power cable, of the plurality of optical fiber composite power cables 50-1, 50-2, ..., using the backscattered light, and further, identifies a position where the abnormality has occurred in the identified optical fiber composite power cable.

[0131] Furthermore, analysis device 12 identifies an abnormal optical fiber composite power cable, of the plurality of optical fiber composite power cables 50-1, 50-2, ..., using the surge detection results from surge detection processing devices 102 of connection portions 80-1, 80-2, .... For example, when optical fiber composite power cable 50-2 has an abnormality, the surge wave is detected in connection portion 80-1 and connection portion 80-2.

[0132] Analysis device 12 determines whether the abnormal optical fiber composite power cable identified based on the result of determination of the abnormal point using the backscattered light matches the abnormal optical fiber composite power cable identified by determination based on the surge detection results. When they match, the reliability of the result of determination of the abnormal point using the backscattered light is enhanced. When they do not match, a higher priority may be given to the result of determination of the abnormal point using the backscattered light. This is because detection of an abnormal point using an optical fiber is usually higher in accuracy than detection of an abnormal point using a surge.<Eighth Embodiment>

[0133] A surge detection processing device 120F included in a power line according to an eighth embodiment will be described with reference to Fig. 26.

[0134] Surge detection processing device 120F is different from surge detection processing device 120 described in the seventh embodiment in that surge detection processing device 120F includes a communication device 123F instead of communication device 123.

[0135] Communication device 123F transmits information indicating a surge detection result to analysis device 12 in controller 100 through a third optical fiber 124.

[0136] An optical fiber composite power cable 50F according to the eighth embodiment will be described with reference to Fig. 27.

[0137] Optical fiber composite power cable 50F is different from optical fiber composite power cable 50 according to the first embodiment in that optical fiber composite power cable 50F includes a detection wire 71F instead of detection wire 71.

[0138] Detection wire 71F will be described with reference to Fig. 28.

[0139] Detection wire 71F is different from detection wire 71 described in the first embodiment in that metal tube 63 accommodates third optical fiber 124 in detection wire 71F. Third optical fiber 124 is not used for transmission of the light used for abnormality sensing, such as the sensing light and the backscattered light, but used for transmission of a communication signal such as an analysis result as described above.<Ninth Embodiment>

[0140] A surge detection processing device 120G included in a power line according to a ninth embodiment will be described with reference to Fig. 29.

[0141] Surge detection processing device 120G is different from surge detection processing device 120 described in the seventh embodiment in that surge detection processing device 120G includes a surge detection sensor 121G instead of surge detection sensor 121. Surge detection sensor 121G, surge detector 122 and communication device 123 may be accommodated in housing 171.

[0142] As described above, first auxiliary conductor 8 and second auxiliary conductor 9 are disposed such that an induced current is less likely to flow. In the present embodiment, an induction lead 125 that is susceptible to induction caused by a surge in the event of a fault is disposed. Induction lead 125 is made of metal having a high conductivity, e.g., copper.

[0143] Surge detection sensor 121G detects an induced voltage between induction lead 125 and second auxiliary conductor 9.

[0144] An optical fiber composite power cable 50G according to the ninth embodiment will be described with reference to Fig. 30.

[0145] Optical fiber composite power cable 50G is different from optical fiber composite power cable 50 according to the first embodiment in that at least one of wires 58a constituting the inner layer, of the two layers, is replaced with induction lead 125 in armor portion 59. Induction lead 125 does not need to be disposed adjacent to detection wire 61 or detection wire 71.<Tenth Embodiment>

[0146] Power line 130 according to a tenth embodiment will be described with reference to Fig. 31.

[0147] Power line 130 according to the tenth embodiment is different from power line 130 according to the seventh embodiment in that power line 130 includes a power storage device 126. Surge detection sensor 121, surge detector 122, communication device 123, and power storage device 126 may be accommodated in housing 171. Power storage device 126 may be included in secondary power supply 41.

[0148] When a DC power supply is used, electric power can be stored in power storage device 126. Power storage device 126 has a power storage element such as, for example, a supercapacitor, and a charging device.

[0149] The components (first excitation laser device 42 and second excitation laser device 43) in optical amplification repeater 70 are configured to be capable of operating with electric power from main power supply 22 and secondary power supply 41 in a normal mode, and operating with electric power stored in power storage device 126 in an emergency mode in which electric power supply from main power supply 22 is interrupted. Because of this configuration, electric power is constantly supplied to optical amplification repeater 70. Therefore, detection of an abnormality of power line 130 can be constantly performed.

[0150] Communication device 123 may be operated constantly, or may be operated intermittently. Thus, communication device 123 is configured to be capable of operating with electric power stored in power storage device 126 in a normal mode. Communication device 123 may be configured to be capable of operating with electric power from secondary power supply 41 when an amount of electric power stored in power storage device 126 is small. Surge detection unit 220G may also be supplied with electric power intermittently by power storage device 126.

[0151] The timing of electric power supply from power storage device 126 may be controlled by a timer in power storage device 126, or by a start signal transmitted from controller 100 in accordance with the power line communication scheme.<Eleventh Embodiment>

[0152] Power line 130 according to an eleventh embodiment will be described with reference to Fig. 32.

[0153] When cable body 60 transmits DC power, a ripple component is included in conductor 51 of cable body 60, in addition to a DC current. This ripple component can be used for storage of electric power.

[0154] In the present embodiment, a power storage device 126A stores a ripple current induced between one of first auxiliary conductor 8 and second auxiliary conductor 9 and induction lead 125 based on the ripple component generated in conductor 51 of cable body 60. Power storage device 126A has a power storage element such as, for example, a supercapacitor, and a charging device. In the example of Fig. 32, power storage device 126A stores a ripple current induced between second auxiliary conductor 9 and induction lead 125. Power storage device 126A supplies DC power to the electronic devices such as communication device 123 and surge detector 122 accommodated in connection portion 80. By adjusting a spacing between one of first auxiliary conductor 8 and second auxiliary conductor 9 and induction lead 125, an induced voltage can be adjusted.

[0155] As shown in Fig. 30, the size of induction lead 125 may be the same as the size of detection wires 61 and 71. Induction lead 125 may be disposed adjacent to at least one of detection wires 61 and 71 in the circumferential direction of cable body 60. Induction lead 125 may be disposed such that the center of induction lead 125 is located on the same circle as a circle A passing through the center of detection wire 61, 71.

[0156] Alternatively, the size of induction lead 125 may be different from the size of detection wires 61 and 71. Induction lead 125 may be disposed not adjacent to at least one of detection wires 61 and 71 in the circumferential direction of cable body 60. In other words, induction lead 125 may be spaced apart from at least one of detection wires 61 and 71 in the circumferential direction of cable body 60.

[0157] Induction lead 125 may be disposed such that the center of induction lead 125 is not located on the same circle as above-described circle A and is displaced from circle A. Induction lead 125 disposed in this way is preferable because a voltage is more likely to be induced.

[0158] For example, when the size of induction lead 125 is the same as the size of detection wires 61 and 71, detection wires 61 and 71 may be disposed at a position of an inner circumferential layer of armor portion 59 (may be replaced with wires 58a) and induction lead 125 may be disposed at a position of an outer circumferential layer of armor portion 59 (may be replaced with wire 58b), although not shown. In this case, detection wires 61 and 71 and induction lead 125 may be disposed adjacent to each other in the radial direction of cable body 60, or may be disposed not adjacent to each other in the above-described radial direction and disposed to be displaced in the circumferential direction of cable body 60.

[0159] Alternatively, as in an optical fiber composite power cable 50H shown in Fig. 33, induction lead 125 may be a wire having a wire diameter smaller than a diameter of detection wires 61 and 71. This induction lead 125 having a small wire diameter may be disposed in a gap between detection wires 61 and 71 and cable body 60. In this case, induction lead 125 is disposed adjacent to detection wires 61 and 71.

[0160] Although not shown, induction lead 125 may be disposed adjacent to only detection wire 61 or only detection wire 71. Induction lead 125 may be disposed not adjacent to both of detection wires 61 and 71 and spaced apart from detection wires 61 and 71. In this case, induction lead 125 is disposed in a gap formed by adjacent wires 58a. Induction lead 125 may be disposed at a position of the outer circumferential layer of armor portion 59. In this case, induction lead 125 is disposed in a gap formed by adjacent wires 58b. Induction lead 125 does not need to be disposed in the above-described gap. In this case, the size of induction lead 125 may be larger than the size that allows induction lead 125 to be disposed in the above-described gap. An armor wire or the like whose size is adjusted to eliminate a height difference caused by a difference in wire diameter between wires 61, 71, 58a, and 58b and induction lead 125 may be disposed in armor portion 59.<Twelfth Embodiment>

[0161] An abnormal point detection system 200A for an optical fiber composite power cable will be described with reference to Fig. 34. Fig. 34 does not show secondary power supply 41 (Fig. 9).

[0162] Abnormal point detection system 200A for an optical fiber composite power cable includes power line 130, a shared-use optical fiber 16, optical amplification repeaters 70A-1, 70A-2, ... each having a bidirectional amplification function, and a controller 100A. In Fig. 34, of the components of power line 130, shared-use optical fiber 16, first auxiliary conductor 8, second auxiliary conductor 9, and optical amplification repeater 70A are shown. Shared-use optical fiber 16 constitutes first optical fiber 6 and second optical fiber 7 in the first embodiment.

[0163] Shared-use optical fiber 16 has first end EA and second end EB. A direction from first end EA to second end EB may be denoted as a forward direction, and a direction from second end EB to first end EA may be denoted as a reverse direction. Shared-use optical fiber 16 transmits the sensing light from first end EA to second end EB. Shared-use optical fiber 16 transmits the backscattered light of the sensing light to first end EA.

[0164] Controller 100A includes a circulator 17 instead of optical directional couplers 30 and 31 in the first embodiment. A commercially available three-port-type circulator or a commercially available four-port-type circulator can, for example, be used as circulator 17. In Fig. 34, circulator 17 of three-port type is shown.

[0165] Circulator 17 has a first port P1, a second port P2 and a third port P3. A signal input to first port P1 is output from second port P2. A signal input to second port P2 is output from third port P3. First port P1 is connected to optical isolator 25. Second port P2 is connected to first end EA of shared-use optical fiber 16. Third port P3 is connected to measurement device 20.

[0166] Circulator 17 transmits the sensing light sent from pulsed laser device 21 through optical isolator 25 in the forward direction of shared-use optical fiber 16. Circulator 17 sends, to measurement device 20, the backscattered light transmitting through shared-use optical fiber 16 in the reverse direction.

[0167] Similarly to the first embodiment, optical amplification repeater 70A amplifies the sensing light with the first excitation light and amplifies the backscattered light with the second excitation light. Optical amplification repeater 70A includes a circulator 18 and a circulator 19 instead of optical directional couplers 3 and 5 in the first embodiment.

[0168] A commercially available four-port-type circulator can, for example, be used as each of circulators 18 and 19.

[0169] Circulator 18 has first port P1, second port P2, third port P3, and a fourth port P4. A signal input to first port P1 is output from second port P2. A signal input to fourth port P4 is output from first port P1. In Fig. 34, third port P3 is a free port and is not shown. First port P1 is connected to shared-use optical fiber 16. Second port P2 is connected to optical directional coupler 44. Fourth port P4 is connected to second erbium-doped fiber 4.

[0170] Circulator 18 sends, to optical directional coupler 44, the sensing light transmitting through shared-use optical fiber 16 in the forward direction. Circulator 18 sends, to shared-use optical fiber 16, the backscattered light of the sensing light from second erbium-doped fiber 4, and causes the backscattered light to transmit through shared-use optical fiber 16 in the reverse direction.

[0171] Circulator 19 has first port P1, second port P2, third port P3, and fourth port P4. A signal input to first port P1 is output from second port P2. A signal input to second port P2 is output from third port P3. In Fig. 34, fourth port P4 is a free port and is not shown. First port P1 is connected to first erbium-doped fiber 1. Second port P2 is connected to shared-use optical fiber 16. Third port P3 is connected to optical directional coupler 45.

[0172] Circulator 19 sends, to optical directional coupler 45, the backscattered light of the sensing light transmitting through shared-use optical fiber 16 in the reverse direction. Circulator 19 sends, to shared-use optical fiber 16, the sensing light from first erbium-doped fiber 1, and causes the sensing light to transmit through shared-use optical fiber 16 in the forward direction.

[0173] Instead of circulators 17, 18 and 19, optical directional couplers configured to enable transmission / cutoff of the light similarly to circulators 17, 18 and 19 may be used.

[0174] (Modifications)

[0175] The present disclosure also includes the following modifications. (1) At least one of the optical directional couplers described in the embodiments may be a circulator. (2) In the embodiments, the single-core cable in which optical fiber composite power cable 50 includes one cable body 60 has been described. As another example, optical fiber composite power cable 50 may be a multi-core cable including a plurality of cable bodies 60. Each of the plurality of cable bodies 60 roughly corresponds to a cable core in a known multi-core cable. The plurality of cable bodies 60 are typically a twisted aggregate. A not-shown interposed member is provided on an outer circumference of the aggregate. A not-shown cradle core is provided on an outer circumference of the interposed member. Armor portion 59 is provided on an outer circumference of the cradle core. In the case of a multi-core cable, optical fibers 6 and 7 may be disposed in a gap provided in the above-described aggregate or in an empty space between the above-described aggregate and the cradle core, instead of being disposed in armor portion 59. When optical fiber composite power cable 50 is a multi-core cable, optical fiber composite power cable 50 may be used for transmission of AC power. (Additional Notes)

[0176] The present disclosure includes an embodiment described below.

[0177] A power line comprising: two power cables; and a connection portion that connects the two power cables, wherein each of the two power cables includes: a cable body; and an armor portion provided on an outer circumference of the cable body, the armor portion includes a plurality of wires spirally wound around the outer circumference of the cable body, at least one of the plurality of wires includes a first conductor and a second conductor, the connection portion includes a power storage device that supplies DC power to electronic devices accommodated in the connection portion, and the power storage device stores a ripple current induced between the first conductor and the second conductor based on a ripple component generated in a conductor of the cable body.

[0178] When the power line according to (Additional Notes) above is a DC power transmission line, a ripple component is included in the power cable. By adjusting a spacing between the first conductor and the second conductor, a voltage induced between these conductors can be adjusted. By adjusting the voltage, the above-described ripple component can be stored in the power storage device. The stored electric power can be used in the electronic devices, such as, for example, various sensor devices, accommodated in the connection portion.

[0179] It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the embodiments above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.REFERENCE SIGNS LIST

[0180] 1 first erbium-doped fiber; 3, 5, 30, 31, 44, 45 optical directional coupler; 4 second erbium-doped fiber; 6 first optical fiber; 7 second optical fiber; 8 first auxiliary conductor; 9 second auxiliary conductor; 12 analysis device; 16 shared-use optical fiber; 17, 18, 19 circulator; 20 measurement device; 21 pulsed laser device; 22 main power supply; 23 optical receiver; 25 optical isolator; 28 wavelength filter; 38 branch structure; 39 branching optical fiber; 41 secondary power supply; 42 first excitation laser device; 43 second excitation laser device; 50, 50A, 50B, 50C, 50D, 50E, 50F, 50G, 50H optical fiber composite power cable; 51, 51A, 51B conductor; 52, 54, 54A, 54B semiconducting layer; 53, 53A, 53B, 64A insulating layer; 55, 64 sheath; 57A, 57B shield layer; 58a, 58b wire; 59 armor portion; 60 cable body; 61, 61A, 61B, 61C, 61D, 61E, 71, 71A, 71F detection wire; 62 jelly compound; 63, 94 metal tube; 70, 70A optical amplification repeater; 78 positive electrode lead; 79 negative electrode lead; 80, 80A connection portion; 92 protective layer; 97 semiconducting portion; 98 insulating portion; 99 sleeve; 100, 100A controller; 120, 120F, 120G, 120H, 120I surge detection processing device; 121, 121G surge detection sensor; 122 surge detector; 123, 123F communication device; 124 third optical fiber; 125 induction lead; 126, 126A power storage device; 130 power line; 131 insulation coating; 132, 133 insulating member; 171 housing; 200, 200A abnormal point detection system; 220, 220G surge detection unit; EA, EC first end; EB, ED second end; R1 first region; R2 second region; R3 third region.

Claims

1. An optical fiber composite power cable comprising: a cable body; an armor portion provided on an outer circumference of the cable body; a first optical fiber that transmits sensing light; a second optical fiber that transmits backscattered light of the sensing light; and a plurality of auxiliary conductors that transmit electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light.

2. The optical fiber composite power cable according to claim 1, wherein the power supply can supply DC power, and the auxiliary conductors include a first auxiliary conductor connected to a first terminal of the power supply, and a second auxiliary conductor connected to a second terminal of the power supply.

3. The optical fiber composite power cable according to claim 2, wherein the armor portion includes a plurality of wires spirally wound around the outer circumference of the cable body, at least one of the plurality of wires includes at least one metal tube that accommodates the first optical fiber and the second optical fiber, and at least one of the plurality of wires includes the first auxiliary conductor and the second auxiliary conductor.

4. The optical fiber composite power cable according to claim 3, wherein the plurality of wires include a first wire and a second wire disposed adjacent to each other in a circumferential direction of the outer circumference of the cable body, the first wire includes: a metal tube that accommodates the first optical fiber and the second optical fiber; and the first auxiliary conductor, and the second wire includes the second auxiliary conductor.

5. The optical fiber composite power cable according to claim 3, wherein the plurality of wires include a first wire and a second wire disposed adjacent to each other in a circumferential direction of the outer circumference of the cable body, the first wire includes: a metal tube that accommodates the first optical fiber; and the first auxiliary conductor, and the second wire includes: a metal tube that accommodates the second optical fiber; and the second auxiliary conductor.

6. The optical fiber composite power cable according to claim 3, wherein a first wire included in the plurality of wires includes: a metal tube that accommodates the first optical fiber and the second optical fiber; the first auxiliary conductor; the second auxiliary conductor; and an insulating layer disposed between the first auxiliary conductor and the second auxiliary conductor.

7. The optical fiber composite power cable according to claim 3, wherein a first wire included in the plurality of wires includes: a metal tube that accommodates the first optical fiber and the second optical fiber; and a plurality of first auxiliary leads and a plurality of second auxiliary leads spirally wound around an outer circumference of the metal tube, the plurality of first auxiliary leads constituting the first auxiliary conductor, the plurality of second auxiliary leads constituting the second auxiliary conductor.

8. The optical fiber composite power cable according to claim 7, wherein the first auxiliary leads and the second auxiliary leads are disposed alternately in a circumferential direction of the outer circumference of the metal tube, and an insulation coating is provided on an outer circumference of at least one of the first auxiliary leads and the second auxiliary leads.

9. The optical fiber composite power cable according to claim 7, wherein the plurality of first auxiliary leads are disposed continuously in a circumferential direction of the outer circumference of the metal tube in a first region of the outer circumference of the metal tube, the plurality of second auxiliary leads are disposed continuously in a second region of the outer circumference of the metal tube, and an insulating member is disposed in a third region between the first region and the second region.

10. The optical fiber composite power cable according to claim 3, wherein a first wire included in the plurality of wires includes: a metal tube that accommodates the first optical fiber and the second optical fiber; the first auxiliary conductor provided on an outer circumference of the metal tube; an insulating layer provided on an outer circumference of the first auxiliary conductor; and a plurality of second auxiliary leads spirally wound around an outer circumference of the insulating layer, the plurality of second auxiliary leads constituting the second auxiliary conductor.

11. The optical fiber composite power cable according to claim 3, wherein a wire that does not include the metal tube, the first auxiliary conductor and the second auxiliary conductor, of the plurality of wires, is made of magnetic metal, and the metal tube is made of non-magnetic metal.

12. A power line comprising: two optical fiber composite power cables; and a connection portion that connects the two optical fiber composite power cables, wherein each of the two optical fiber composite power cables includes: a cable body; an armor portion provided on an outer circumference of the cable body; a first optical fiber that transmits sensing light; a second optical fiber that transmits backscattered light of the sensing light; and an auxiliary conductor that transmits electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light, and the connection portion includes: the optical amplification repeater; and the power supply connected to the auxiliary conductor and supplying electric power to the optical amplification repeater.

13. The power line according to claim 12, wherein the power supply includes a DC / DC converter.

14. The power line according to claim 12, wherein the connection portion further includes: a surge detection unit that detects a surge wave generated in the cable body of the optical fiber composite power cable; and a communication device that transmits a result of detection of the surge wave, and the surge detection unit and the communication device operate with electric power from the power supply.

15. The power line according to claim 14, wherein the armor portion includes a plurality of wires spirally wound around the outer circumference of the cable body, and the surge detection unit detects a surge wave transmitting through an induction lead included in the plurality of wires.

16. The power line according to claim 14, wherein the armor portion includes a plurality of wires spirally wound around the outer circumference of the cable body, at least one of the plurality of wires includes a metal tube that accommodates a third optical fiber, and the communication device transmits the result of detection of the surge wave to the outside of the connection portion through the third optical fiber.

17. The power line according to claim 14, wherein the communication device converts the result of detection of the surge wave into a power line communication signal, and transmits the power line communication signal to the outside of the connection portion by the auxiliary conductor.

18. The power line according to claim 14, wherein the connection portion further includes a power storage device configured to be capable of storing electric power transmitting through the auxiliary conductor, and the power storage device is configured to be capable of supplying electric power to the communication device.

19. The power line according to claim 18, wherein the power supply can supply DC power, the auxiliary conductor includes a first auxiliary conductor connected to a first terminal of the power supply, and a second auxiliary conductor connected to a second terminal of the power supply, the armor portion includes a plurality of wires spirally wound around the outer circumference of the cable body, at least one of the plurality of wires includes the first auxiliary conductor, the second auxiliary conductor and an induction lead, and the power storage device stores a ripple current induced between one of the first auxiliary conductor and the second auxiliary conductor and the induction lead.

20. The power line according to any one of claims 12 to 19, wherein the first optical fiber and the second optical fiber are constituted by one optical fiber, and the optical amplification repeater has a bidirectional optical amplification function.

21. An abnormal point detection system for a power line, the abnormal point detection system comprising: a power supply; a laser device that emits sensing light; and a power line, wherein the power line includes: two optical fiber composite power cables; and a connection portion that connects the two optical fiber composite power cables, each of the two optical fiber composite power cables includes: a cable body; an armor portion provided on an outer circumference of the cable body; a first optical fiber that transmits sensing light; a second optical fiber that transmits backscattered light of the sensing light; and an auxiliary conductor that transmits electric power from a power supply to an optical amplification repeater that amplifies the sensing light and the backscattered light, and the connection portion includes: the optical amplification repeater; the power supply connected to the auxiliary conductor and supplying electric power to the optical amplification repeater; and a measurement device that detects an abnormal point of the power line based on a result of detection of the backscattered light.

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