Overhead cable interrogation system and method

Abstract

Systems and methods for interrogating an overhead cable using a coherent light source, such as a laser. The systems and methods may include isolating one or more optical fibers, the optical fibers embedded in or attached to a strength member of the cable, and connecting an interrogation device, such as an OTDR device, to the optical fibers to interrogate the overhead cable to determine a condition of the cable, such as temperature or mechanical strain.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application Serial No. 62 / 814,372, filed on March 6, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of overhead cables including strength members supporting an outer conductive layer, and more particularly to methods and systems for interrogating an electrical conductor cable to determine whether the cable, and particularly the strength members, have been damaged. Background Art

[0004] Overhead cables typically consist of multiple conductive supports wound around and supported by strength members. Traditionally, the strength members have been made from multiple steel strands, a configuration known as aluminum conductor steel reinforced (ACSR). Because fiber-reinforced composite strength members offer numerous advantages over other strength member materials, such as steel, overhead cables incorporating composite strength members are being implemented in many new transmission line projects. Such overhead cables are also being used to reroute existing transmission lines, for example, replacing ACSR conductor cables on existing infrastructure (e.g., existing support towers).

[0005] While steel strength members in an ACSR configuration can be bent sharply and deform plastically without exhibiting significant strength degradation, many fiber-reinforced composites do not deform plastically and merely store kinetic energy when bent. This stored kinetic energy advantageously allows flexible fiber-reinforced composites to return to their original shape when the bending load is released. However, even flexible fiber-reinforced composites can fail in compression or tension failure modes when the bending load is excessive. If some initial damage occurs, this damage can spread over time, leading to further degradation or complete failure of the strength member.

[0006] The utility industry has also recently expressed a need for products and methods to diagnose the health of transmission lines, optimize their operation, reduce maintenance costs, and mitigate the likelihood of catastrophic failures in the transmission grid. However, transmission lines, in addition to being many kilometers long, also comprise geographically diverse and remote infrastructure. This makes it difficult to monitor the entire transmission line, identify problems within the line with a high degree of accuracy regarding their nature and location, and transmit relevant data to a central location, such as for analysis.

[0007] It is also desirable to maximize the utilization of the transmission grid and operate transmission line sections closer to the edge of reliability. However, operating under such conditions creates a higher probability of fault events in the transmission grid, such as failures of overhead cables in the transmission grid. Summary of the Invention

[0008] It would be desirable to be able to interrogate fiber reinforced composite strength members to identify the presence of defects or flaws in the strength members and to measure elongation. It would be particularly desirable to identify such defects or flaws early in the product cycle of manufacture, installation and use of composite strength members in overhead cables.

[0009] One issue identified with interrogating aerial cables using sensing fibers is the extreme difficulty of selectively accessing the sensing fibers from within the composite matrix and establishing a reliable connection between the sensing fibers and the OTDR device. Specifically, sensing fibers have relatively small diameters, making them difficult to position and connect when embedded in the same matrix as the structural fibers. This issue is particularly challenging in the context of aerial cable installations, as the connection must be made on-site by technicians, often under difficult environmental conditions.

[0010] Thus, the products, methods, and systems disclosed herein can enable interrogation of fiber-reinforced composite strength members to detect defects in the composite strength members: (i) after manufacture and prior to installation (e.g., manufacturing defects); (ii) after stranding with the conductive layer to form the electrical conductor and prior to installation (e.g., detecting defects introduced during the stranding process); and / or after installation of the overhead cable but prior to energizing the electrical conductor (e.g., defects resulting from failure to follow installation protocols). By determining whether defects are present in the composite strength member and / or the conductive layer at one or more of these points in the product manufacturing and installation cycle, not only can time and costs be saved due to early detection, but remedial steps can also be taken to correct the manufacturing or installation error that caused the defect.

[0011] It may be advantageous to determine the condition of a composite strength member, such as temperature, strain condition of the strength member, or elongation (e.g., change in length) of the strength member and, therefore, the aerial cable, immediately after energizing an aerial cable installed in a transmission line. Thus, the products, methods, and systems disclosed herein may also enable interrogation of an aerial cable to determine one or more conditions of the aerial cable immediately after energizing the aerial cable. For example, the installation of the aerial cable may result in surface defects on the conductive layer, resulting in "hot spots" where the resistivity of the conductive layer is unacceptably high.

[0012] On the other hand, the condition of the overhead cable can be monitored after installation and during normal transmission operation, such as during use of the overhead cable in a transmission grid. Monitoring the condition of the overhead cable is very ideal, especially due to weather events (such as wind, ice loads) or unexpected events (such as conductor overload, damage to the conductive layer, etc.). For example, the operating temperature of the overhead cable can be measured continuously or periodically. On the other hand, the tensile strain in the overhead cable (i.e., the tensile strain in the strength member) can be measured continuously or periodically. On the other hand, the length of the overhead cable (i.e., the length of the strength member) can be measured continuously or periodically. Such measurements can be used to determine different states of the overhead cable, such as the real-time sag of the overhead cable at any given span in the transmission line, to improve system safety and reliability.

[0013] In one feature, products, systems, and methods incorporate the use of distributed fiber optic sensors. The distributed fiber optic sensors can include sensing fibers positioned along the length of a composite strength member and can be positioned within the strength member, such as within a bonding matrix of the strength member. By using distributed fiber optic sensors, certain conditions of an overhead cable (e.g., temperature or strain) can be determined with high accuracy at substantially any point along the length of the overhead cable, providing both a quantitative measurement of the condition and the location of that condition. In this manner, for example, "hot spots" along the length of the overhead cable can be identified, which can indicate points of increased resistance due to defects in the conductive layer or core.

[0014] Furthermore, by using distributed fiber optic sensors, it is possible to determine the tensile strain in a strength member at various locations along its length, for example, identifying locations where sudden changes in tensile strain occur. Such sudden changes could indicate a problem with the overhead cable, such as a defect in a composite strength member caused by a natural or human-caused event. By detecting these defects early and accurately, corrective action can be taken before the defect leads to a catastrophic failure of the transmission line.

[0015] It may be desirable to operably couple the sensing and monitoring device with a communication module configured to transmit the data to a location where it can be monitored, recorded, and / or analyzed and utilized. Based on this analysis, the transmission grid can be manipulated, such as by increasing or decreasing the amount of power sent through overhead cables. Furthermore, if necessary, the location information of various conditions (e.g., hotspots) can be utilized to effectively and efficiently deploy maintenance teams to the location to further inspect and correct the problem.

[0016] In one embodiment, a system for detecting tensile strain conditions in an aerial cable is disclosed. The system includes at least a first aerial cable forming a section of a power transmission line, and a conductive layer. The aerial cable includes a fiber-reinforced composite strength member comprising a bonding matrix and structural fibers disposed within the bonding matrix. The conductive layer is wound around and supported by the fiber-reinforced strength member. The system also includes a sensor component integrated with the aerial cable and configured to measure, for example, tensile strain in the aerial cable. The sensor component includes at least a first sensing fiber integrally formed within the bonding matrix of the strength member and disposed along the length of a neutral axis of the strength member. The first sensing fiber is configured for distributed sensing of tensile strain, for example, along the length of the aerial cable. The system also includes at least a first laser source configured to transmit coherent light pulses along the length of the first sensing fiber and at least a first signal detector configured to detect at least a first backscattered light component backscattered by the first sensing fiber to a detector and provide data related to at least tensile strain in the aerial cable.

[0017] In one feature, the sensor component includes at least a second sensing fiber offset from the neutral axis along the length of the strength member, wherein the second sensing fiber is configured for distributed temperature sensing along the length of the aerial cable. In another feature, the first sensing fiber is arranged substantially linearly along the length of the neutral axis. In another feature, the first sensing fiber is a single-mode fiber. In another feature, the first sensing fiber is a silica-based fiber. In another feature, the second sensing fiber is a multimode fiber. In another feature, the second sensing fiber is offset from the neutral axis by a distance equal to at least approximately 20% of the diameter of the strength member. In another feature, the second sensing fiber is integrally formed within the bonding matrix of the strength member. In another feature, the second sensing fiber is disposed between the bonding matrix of the strength member and a layer of material surrounding the bonding matrix. In another feature, the structural fibers include carbon fibers. In another feature, the structural fibers include glass fibers. In another feature, the structural fibers include at least a first type of fiber and a second type of fiber different from the first type. In another feature, the structural fibers include a substantially continuous bundle of structural fibers. In another feature, the length of the aerial cable is at least approximately 1000 meters. In another feature, the strength member has a substantially circular cross-section. In another feature, the strength member has a tensile strength of at least about 1400 MPa. In another feature, the first signal detector is configured to detect at least a Brillouin backscattered light component backscattered by the first sensing fiber. In another feature, the first signal detector is configured to detect at least a Raman backscattered light component backscattered by the second sensing fiber. In another feature, the first signal detector is configured to detect at least a length of the overhead cable. In another feature, the strength member comprises a single, unitary fiber reinforced composite member. In another feature, the first signal detector is configured to detect Rayleigh backscattered light by optical time domain reflectometry.

[0018] In another embodiment, a smart power transmission system is disclosed. The system includes at least a first aerial cable strung under tension between a first terminal tower and a second terminal tower and supported by a plurality of suspension towers between the first and second terminal towers to form a section of the power transmission line. The first aerial cable includes a strength member and a conductive layer disposed around and supported by the strength member. At least a first sensing fiber is disposed within the first aerial cable, wherein the first sensing fiber is configured for distributed sensing of at least one of composite material damage, tensile strain, and temperature along the length of the first aerial cable. The system also includes: at least a first pump laser source operably supported by the first terminal tower and configured to direct a coherent optical signal pulse into a first end portion of at least the first sensing fiber; a signal detector operably supported on the first terminal tower and configured to detect at least one of a Brillouin backscattered light component and a Raman backscattered light component of the coherent optical signal pulse backscattered from the first sensing fiber to the signal detector; and a transmission unit operably supported by the first terminal tower and configured to transmit data associated with the backscattered light component to a monitoring facility remote from the first terminal tower.

[0019] In one feature, the system includes a second aerial cable strung under tension between a first terminal tower and a second terminal tower and supported by a plurality of suspension towers, the second aerial cable including a strength member, a conductive layer disposed about and supported by the strength member, and at least a first sensing fiber disposed within the second aerial cable, wherein the first sensing fiber is configured for distributed sensing of at least one of tensile strain and temperature along a length of the second aerial cable. A first pump laser source is configured to direct coherent optical signal pulses into a first end of the first sensing fiber and a first end of the second sensing fiber.

[0020] In another feature, a terminal fitting attaches the aerial cable to a terminal tower, and wherein the first laser source is operably integrated with the terminal fitting. In another feature, at least a second laser source is configured to direct counter-propagating probe light signal pulses through at least the first sensing fiber. In another feature, the distance between the first and second terminal towers is at least approximately 1,500 meters. In another feature, the distance between the first and second terminal towers is no greater than approximately 6,000 meters.

[0021] In another embodiment, an aerial cable configured for use in a transmission line segment is disclosed. A fiber-reinforced composite strength member includes a resin matrix and structural fibers disposed within the resin matrix, a conductive layer wound around and supported by the strength member, and at least a first sensing fiber integrally formed within the resin matrix of the strength member and disposed along a length of a neutral axis of the strength member, wherein the first sensing fiber is configured for distributed sensing of tensile strain along the length of the aerial cable.

[0022] In one feature, the cable includes at least a second sensing fiber offset from the neutral axis along the length of the strength member, wherein the second sensing fiber is configured for distributed temperature sensing along the length of the aerial cable. In another feature, the first sensing fiber is arranged substantially linearly along the length of the neutral axis. In another feature, the first sensing fiber is a single-mode fiber. In another feature, the first sensing fiber is a silica-based fiber. In another feature, the second sensing fiber is a multimode fiber. In another feature, the second sensing fiber is offset from the neutral axis by a distance equal to at least approximately 20% of the diameter of the strength member. In another feature, the second sensing fiber is integrally formed within the resin matrix of the strength member. In another feature, the second sensing fiber is disposed between the resin matrix of the strength member and a material layer surrounding the resin matrix. In another feature, the structural fibers include carbon fibers. In another feature, the structural fibers include glass fibers. In another feature, the structural fibers include a substantially continuous strand of structural fibers. In another feature, the aerial cable has a length of at least approximately 1000 meters. In another feature, the fiber-reinforced composite member has a tensile strength of at least approximately 1400 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A perspective view of an overhead cable is shown.

[0024] Figure 2 A-2F shows a cross-sectional view of a fiber-reinforced composite member.

[0025] Figures 3A-3B Shown is a perspective cross-sectional view of a fiber reinforced composite component having a sensing optical fiber disposed along its length.

[0026] Figure 4 Shown is a perspective cross-sectional view of an electrical conductor including a fiber reinforced composite strength member having two sensing optical fibers disposed along its length.

[0027] Figure 5 A perspective view of an overhead transmission line is shown.

[0028] Figure 6 Components of the backscattered light signal that can be analyzed using a distributed sensor system are shown.

[0029] Figure 7 A connection system for coupling an optical fiber from a composite strength member to an interrogation device is schematically shown.

[0030] Figure 8 An arrangement for protecting the optical fiber and facilitating coupling of the optical fiber to an interrogation device is shown schematically.

[0031] Figure 9 The attachment of an optical fiber to a fiber alignment device is schematically shown.

[0032] Figure 10 A method and apparatus for chemically removing a bonding matrix to expose an optical fiber is schematically illustrated.

[0033] Figure 11 A method and apparatus for thermally removing a bonding matrix to expose an optical fiber is schematically illustrated. DETAILED DESCRIPTION

[0034] In summary, disclosed herein are products, methods, and systems capable of continuously and / or periodically interrogating fiber-reinforced composite strength members in overhead cables to determine one or more conditions (e.g., mechanical or thermal conditions) of the fiber-reinforced composite strength members. The determined conditions can be used individually or in combination (e.g., via an algorithm) to accurately determine the state of the fiber-reinforced composite member and / or the environment surrounding the fiber-reinforced composite member at one or more locations along its length. The products, methods, and systems are particularly useful for interrogating and monitoring overhead cables that include composite strength members that form transmission and distribution lines for transmission grids used to transmit electrical power, particularly over long distances.

[0035] An example of such an overhead cable is shown schematically in Figure 1 The overhead cable 120 includes a first conductive layer 122a comprising a plurality of conductive strands 124a helically wound around a composite strength member 126. The conductive strands 124a may be made of a conductive metal such as copper or aluminum, and are typically made of aluminum, such as hardened aluminum, annealed aluminum, and / or an aluminum alloy. Figure 1 As shown, the conductive strands 124a have a substantially trapezoidal cross-section, although other configurations, such as a circular cross-section, may also be employed. For the same effective cable diameter, for example, using a polygonal cross-section such as a trapezoidal cross-section advantageously increases the cross-sectional area of the conductive metal compared to strands having a circular cross-section. Figure 1 As shown, the aerial cable 120 also includes a second conductive layer 122b comprising a plurality of conductive strands 124b helically wound around the first conductive layer 122a. It should be understood that such an aerial cable may include a single conductive layer, or more than two conductive layers, depending on the desired use of the aerial cable.

[0036] As mentioned above, the conductive layers 124a / 124b made of, for example, aluminum do not have sufficient mechanical properties (e.g., sufficient tensile strength) to be self-supporting when strung between support towers to form an aerial conductor. Therefore, the aerial cable 120 includes strength members 126 to support the conductive layers 124a / 124b when the aerial cable 120 is strung between support towers under high mechanical tension. Traditional strength members are made of steel, particularly multiple steel elements (e.g., rods) wound together to form a strength member. Recently, steel strength members have been replaced by strength members made of composite materials, such as fiber reinforced composite materials, which provide many significant benefits. As Figure 1 As shown, such composite strength members can be composed of a single element (e.g., a single rod). An example of such a configuration is shown in U.S. Patent No. 7,368,162 to Hiel et al., the entire contents of which are incorporated herein by reference. Alternatively, the composite strength member can be composed of a plurality of separate composite elements (e.g., separate rods) that are operably combined (e.g., spirally twisted together) to form a strength member. Examples of such multi-component composite strength members include, but are not limited to, the multi-element aluminum matrix composite strength member shown in U.S. Patent No. 6,245,425 to McCullough et al.; the multi-element carbon fiber strength member shown in U.S. Patent No. 6,015,953 to Tosaka et al.; and the multi-element strength member shown in U.S. Patent No. 9,685,257 to Daniel et al. Each of these U.S. patents is incorporated herein by reference in its entirety.

[0037] Generally speaking, a fiber reinforced composite strength member may include a bonding matrix and a plurality of structural fibers operatively disposed (eg, embedded) within the bonding matrix, ie, the matrix binds the structural fibers together to form the composite member.

[0038] The bonding matrix in which the structural fibers are embedded can include any type of inorganic or organic material that can operatively embed and bind the structural fibers into the fiber-reinforced composite strength member. Thus, the bonding matrix can primarily include, for example, an inorganic material, such as a ceramic or a metal. In another aspect, the bonding matrix can primarily include an organic material, such as a polymer, for example, a synthetic polymer.

[0039] For example, the bonding matrix can include thermoplastic polymers, including semi-crystalline thermoplastics. Specific examples of useful thermoplastics include, but are not limited to, polyetheretherketone (PEEK), polypropylene (PP), polypropylene sulfide (PPS), polyetherimide (PEI), liquid crystal polymers (LCP), polyoxymethylene (POM or acetal), polyamide (PA or nylon), polyethylene (PE), fluoropolymers, and thermoplastic polyesters. Other examples of polymeric materials that can be used for the bonding matrix can include addition-cured phenolic resins (e.g., bismaleimide), polyetheramides, various anhydrides, or imides.

[0040] In one aspect, the bonding matrix includes a thermosetting polymer, such as an epoxy resin (e.g., epoxy resin). Examples of useful epoxy resins include, but are not limited to, benzoxazines, thermosetting polyimides (PI), polyetheramide resins (PEAR), phenolic resins, epoxy vinyl ester resins, polycyanate resins, and cyanate ester resins. In one exemplary embodiment, a vinyl ester resin is used in the bonding matrix. Another embodiment includes using an epoxy resin that is a reaction product of epichlorohydrin and bisphenol A. Another embodiment includes using diglycidyl ether of bisphenol A (DGEBA).

[0041] The curing agent (eg, hardener) of the epoxy resin can be selected based on the desired properties and processing methods of the fiber reinforced composite strength member. For example, the curing agent can be selected from aliphatic polyamines, polyamides, and modified versions of these compounds.

[0042] The epoxy resin may also be selected to provide resistance to a broad spectrum of aggressive chemicals and may be selected to have stable dielectric and insulation properties. It may be advantageous for the resin to meet ASTM E595 exhaust standards and UL94 flammability standards and to be capable of at least intermittent operation in a temperature range between about 100° C. and 200° C. without significant degradation (e.g., thermal or mechanical degradation) of the fiber reinforced composite strength member.

[0043] Epoxy resin can also comprise the component that helps to make and / or improves the performance of binding matrix.For example, can be combined with catalyst for realizing the desired performance of fiber reinforced composite material strength member and the thermosetting epoxy resin system that is easy to make.Can select catalyst (for example " accelerator ") to promote epoxy resin component to solidify and / or reduce the side reaction that may cause the cracking of solidified resin matrix.Also may wish catalyst to be relatively inactive at low temperatures, to extend resin life (for example " pot life "), and very active at higher temperatures, to improve the manufacturing speed in the composite material strength member manufacturing process.Epoxy resin can also be further modified with additional processing aid (for example releasing agent) and performance enhancing filler, for example, with toughening or hardening matrix such as elastomer, thermoplastics.

[0044] The fiber reinforced composite strength member also includes a plurality of structural fibers operably arranged in (e.g., dispersed in) a binding matrix. The structural fibers can include substantially continuous fibers (e.g., fiber bundles) and / or can include discontinuous fibers (e.g., fiber whiskers). The structural fibers can be aligned in a binding matrix (e.g., an isotropic composite material), or can be randomly arranged in a binding matrix (e.g., an anisotropic composite material). In one feature, the structural fibers include continuous fibers, e.g., in the form of one or more elongated fiber bundles distributed throughout a binding matrix. A fiber bundle is an untwisted bundle of substantially continuous single filaments, typically comprising thousands of individual fibers in a single fiber bundle.

[0045] The structural fibers used in the fiber reinforced composite strength member can be selected from synthetic fibers or natural fibers. In another feature, the structural fibers can be selected from organic fibers or inorganic fibers. For example, the structural fibers can include carbon fibers (such as graphite fibers or carbon nanofibers), aramid fibers (such as KEVLAR TM ), glass fibers (including basalt fibers), ceramic fibers, boron fibers, liquid crystal fibers, high performance polyethylene fibers (e.g., SPECTRA fibers), steel fibers (e.g., steel hard wire), including high carbon steel fibers or fibers based on carbon nanotubes. The fibers may optionally be coated to enhance processing and / or mechanical properties, for example by using an adhesive reinforcement coating.

[0046] In one aspect, the structural fibers include carbon fibers, such as carbon fibers selected from the group consisting of high-strength (HS) carbon fibers, intermediate-modulus (IM) carbon fibers, high-modulus (HM) carbon fibers, and ultra-high-modulus (UHM) carbon fibers. The carbon fibers can be made from precursors such as rayon, polyacrylonitrile (PAN), or petroleum pitch. Non-limiting examples of useful carbon fibers include ZOLTEK PANEX TM ,ZOLTEKPYRON TM ,HEXCEL TM ,TORAY TM ,GRAFIL or THORNEL TM Series of carbon fiber products. Other examples of carbon fibers may include TORAY M46J, TORAY T700 SC-24K, TORAY T700SC-12K, GRAFIL TRH50-18M, TORAY T800H-12K, TORAY T1000G, PyroFil TR-50S, or rayon byproducts. Those skilled in the art will recognize the various types of carbon fibers that can be used in fiber-reinforced composite strength components.

[0047] Different types of glass fibers can also be used alone or in combination with other fiber types such as carbon for fiber-reinforced composite strength components. For example, A-glass, B-glass, C-glass, D-glass, E-glass, H-glass, S-glass, AR-glass, R-glass, or basalt (e.g., volcanic glass) fibers can be used for composite strength components. Glass fibers and secondary glasses can also be used. For example, S-2 glass 758-AB-225, S-2 glass 758-AB-675; E-glass 366-AC-250; E-glass 366-AB-450, E-glass 366-AB-675, and basalt containing E-glass can all be used as structural fibers. In one example, boron-free glass such as E-Glass is used as the glass fiber.

[0048] Ceramic fibers can also be used as structural fibers in composite strength members. Such ceramic fibers can include, for example, carbide fibers such as silicon carbide fibers (SiC), nitride fibers such as silicon nitride fibers (Si3N4), metal oxide fibers such as zirconium oxide-based fibers (ZrO2), aluminum oxide fibers (Al2O3), aluminosilicate fibers, and aluminoborosilicate fibers. Examples of reinforcing ceramic fibers are fibers available under the brand NEXTEL from 3M Company (St.Paul, MN, USA), such as NEXTEL continuous filament ceramic oxide fibers 312, 440, 550, 610, and 720. Although described herein as ceramic fibers, it should be understood that such fibers can include crystalline and glassy (e.g., amorphous) material phases.

[0049] In one feature, the composite strength member may include at least two fiber types, i.e., fibers of at least two different material compositions and / or different fiber types. The two or more fiber types may be mixed or may be arranged in discrete portions of the fiber-reinforced composite strength member, such as concentric portions. The two fiber types may belong to one fiber material category. For example, the composite strength member may include E-glass and S-glass fibers, which are two different fiber types in the glass fiber category. In another example, the fiber-reinforced composite strength member may include two different fiber types in the carbon fiber category, such as HS carbon fiber and HM carbon fiber. Combinations of different fibers may be used, such as combining cheaper fiber types with more expensive fiber types, to achieve desired results at reduced costs.

[0050] As described above, the structural fibers may also include discontinuous fibers (eg, whiskers), alone or in combination with continuous fibers. The discontinuous fibers may be optionally aligned within the bonding matrix to form an isotropic fiber reinforced composite component, or may be randomly oriented within the bonding matrix.

[0051] In a specific embodiment, the fiber reinforced composite strength member includes structural fibers that extend substantially continuously through the length of the strength member. For example, the fiber reinforced composite strength member may include one or more elongated structural fiber bundles dispersed in a resin matrix. A fiber bundle is a bundle (e.g., untwisted) of continuous fibers (filaments), wherein the number of individual fibers in the bundle is expressed as its yield (yards per pound), or as its K value. For example, a 12K fiber bundle includes approximately 12,000 individual fibers. For example, a fiber reinforced composite strength member may be manufactured by selecting a carbon fiber bundle in the range of about 4K to about 60K or more. Glass fiber bundles can typically be selected in the range of about 100 yields to about 1600 yields, for example, from about 5000 tex to about 250 tex (g / km).

[0052] Typically, for glass fibers, the diameter of individual structural fibers in the fiber bundle can be selected to be at least about 8 μm and not more than about 25 μm, for example, glass fibers having a diameter of at least about 8 μm and not more than about 18 μm. Carbon fibers having a diameter of at least about 4 μm and not more than about 10 μm can be selected, for example, carbon fibers having a diameter of at least about 5 μm and not more than about 8 μm. For example, ceramic fibers can have a diameter of at least about 7 μm and not more than about 13 μm. For other types of structural fibers, a suitable size range can be determined based on the desired physical properties of the composite strength member, or based on the desired wetting characteristics, or other manufacturing considerations. For example, structural fibers having a diameter of no more than about 5 μm may pose certain health risks to people handling the fibers. Structural fibers having a diameter exceeding about 25 μm generally do not have the desired tensile properties and / or processing properties.

[0053] Fiber reinforced composite strength members can have different cross-sectional shapes, such as polygonal cross-sectional shapes, elliptical cross-sectional shapes, and virtually any other cross-sectional shape, including symmetrical and asymmetrical shapes. In addition, the placement of structural fibers within the bonding matrix can include layers or sections of various cross-sectional configurations. For example, Figure 2 A-2F illustrate a variety of different cross-sectional configurations of a fiber-reinforced composite strength member having a circular cross-sectional shape, such as taken perpendicular to the longitudinal axis of the composite strength member.

[0054] Figure 2 A shows a fiber-reinforced composite strength member 216A, which includes a composite portion 218A including substantially uniformly distributed structural fibers 224A, which are uniformly dispersed within a bonding matrix 226A. The structural fibers 224A throughout the composite portion 218A can be a single fiber type (e.g., carbon, glass, or ceramic), or can be a mixture of two or more fiber types (e.g., carbon and glass, carbon and ceramic, glass and ceramic, etc.).

[0055] Fiber reinforced composite strength members may also comprise two or more distinct parts. Figure 2 B shows a fiber-reinforced composite strength member 216B, which includes two different fiber-reinforced composite parts, wherein a first fiber-reinforced composite part 218Bb surrounds a second fiber-reinforced composite part 218Ba. The second composite part 218Ba may include first structural fibers 224Ba dispersed in a first bonding matrix 226Ba, and the second fiber-reinforced composite part 218Ba may include second structural fibers 224Ba dispersed in a second bonding matrix 226Ba. In this example, the first structural fibers 224Ba may be the same as or different from the second structural fibers 224Bb. For example, the second structural fibers 224Bb may be low-modulus fibers having a relatively low elastic modulus and / or electrical insulation, such as glass fibers, while the first structural fibers 224Ba may be structural fibers having a higher elastic modulus and / or tensile strength than the first structural fibers 224Ba, such as carbon fibers. Furthermore, the first bonding matrix 226Ba may be the same as or different from the second bonding matrix 226Bb. In one embodiment, the first bonding matrix 226Ba and the second bonding matrix 226Bb comprise the same material (e.g., the same epoxy resin), while the first structural fibers 224Ba differ from the second structural fibers 224Bb, e.g., the first and second structural fibers have at least one different material property. The different material properties can be any material property, such as elastic modulus, electrical conductivity, tensile strength, elongation, and / or coefficient of thermal expansion. As a result, the first and second composite material portions 218Ba and 218Bb can have one or more different material properties, such as different elastic modulus, electrical conductivity, tensile strength, elongation, and / or coefficient of thermal expansion. In one feature, the second composite material portion 218Bb has a higher elastic modulus and lower electrical conductivity than the second composite material portion 218Bb. In another feature, the first composite material portion 218Ba has a higher tensile strength than the first composite material portion 218Bb. The fiber-to-matrix ratio in the first fiber-reinforced composite material portion 218Ba can also differ from the fiber-to-matrix ratio in the second fiber-reinforced composite material portion 218Bb. The fiber to resin ratio may vary, regardless of whether the structural fiber and bonding matrix materials of the various parts are the same or different.

[0056] exist Figure 2 In the embodiment shown in C, the fiber reinforced composite strength member 216C includes a first fiber reinforced portion 218Ca surrounded by a second fiber reinforced composite portion 218Cb. The strength member 216C also includes a third fiber reinforced composite portion 218Cc surrounded by the first portion 218Ca. Figure 2As shown in FIG. 3 , third portion 218Cc includes third structural fibers 224Cc dispersed in a third bonding matrix 226Cc. Third structural fibers 224Cc may be the same as or different from the structural fibers of the first and / or second fiber-reinforced composite portion, and third bonding matrix 226Cc may be the same as or different from the bonding matrix of the first and / or second fiber-reinforced composite portion.

[0057] Figure 2 Figure D shows another embodiment of a composite strength member 216D, which includes a first material portion 218Da surrounding a second material portion 218Db. In this embodiment, the first material portion 218Da comprises a first material 226Da (e.g., a polymer) that is substantially free of structural fibers. In other words, the first portion 218Da is substantially comprised of a "matrix" 226Da, e.g., a matrix material. The first material portion 218Da surrounds a fiber-reinforced second portion 218Db, which comprises structural fibers 224Db dispersed within a second bonding matrix 226Db. The first matrix 226Da can be the same as or different from the second bonding matrix 226Db. In one feature, the structural fibers 224Db of the fiber-reinforced second portion 218Db comprise carbon fibers, while the first material portion 218Da comprises insulating (e.g., electrically insulating) carbon fibers. Furthermore, the first material portion 218Da, which is substantially free of structural fibers, can have a lower elastic modulus than the fiber-reinforced second portion 218Db, thereby providing a degree of flexibility to the composite strength member 216D.

[0058] exist Figure 2 In the embodiment shown in FIG. 2 , a composite strength member 216E includes a fiber-reinforced first material portion 218Ea that substantially surrounds a second portion 218Eb. In this embodiment, the first portion 218Ea includes structural fibers 224Ea dispersed in a first bonding matrix 226Ea. The second portion 218Eb is substantially free of structural fibers and may include a second bonding matrix 226Eb (e.g., may be substantially comprised of the bonding matrix 226Eb), which may be the same or different from the epoxy resin of the first bonding matrix 226Ea. Alternatively, the second portion 218Eb may be substantially free of any material, i.e., may be hollow throughout the length of the fiber-reinforced composite strength member 216E. In another feature, the second portion 218Eb may include a lightweight filler material, such as a polymer foam, to reduce the overall weight (e.g., weight per unit length) of the fiber-reinforced composite strength member 218Ea.

[0059] In addition to the binding matrix and the structural fibers dispersed in the binding matrix, that is, in addition to the above-mentioned fiber reinforced composite materials, the fiber reinforced composite strength member may also include other features. For example, the fiber reinforced composite strength member may also include a material layer, such as a coating, arranged around the outer surface of the binding resin matrix. The additional material layer may be selected to provide additional protection for the composite material (such as resin and / or structural fibers), or may be selected to provide additional functions to the composite strength member. The additional material layer may be a metal layer, a metal oxide layer, a glass layer or a polymer layer. In one configuration, the additional material layer is a polymer layer, which is selected to provide protection for the fiber reinforced composite material, for example as a moisture barrier layer and / or as a dielectric layer. Such a polymer layer can be provided on the fiber reinforced composite material by methods such as dipping, spraying, etc., and can be applied during the manufacture of the fiber reinforced composite material or after the manufacture of the composite material.

[0060] exist Figure 2 In the embodiment shown in F, a fiber reinforced composite strength member 216F includes a fiber reinforced composite portion 218F including structural fibers 224F dispersed in a bonding matrix 226F. The composite portion 218F is surrounded by a material layer 222F. The material layer 222F may include a coating disposed around and substantially surrounding the composite portion 218F. In one feature, the composite portion 218F may include carbon structural fibers disposed in an epoxy resin matrix, and the material layer 222F may include a coating selected to protect the carbon fibers and the resin from degradation, such as a polymer coating or a metallic coating. Examples of fiber reinforced composite members including outer material layers are shown in U.S. Patent Publication No. 2007 / 0193767 to Guery et al. and U.S. Patent Publication No. 2012 / 0090892 to Meyer et al., the entire contents of each of which are incorporated herein by reference. Furthermore, such outer material layers may be used in conjunction with any strength member configuration, such as Figure 2 Any configuration shown in A-2F.

[0061] The fiber-reinforced composite portion can have a relatively high fiber-to-resin ratio to provide sufficient properties (e.g., tensile strength) for a composite strength member. In one feature, the fiber-reinforced composite portion includes at least about 50% by volume fiber, such as at least about 60% by volume fiber.

[0062] According to the products, methods, and systems disclosed herein, a fiber reinforced composite strength member can incorporate at least a first sensing optical fiber that is integrally disposed (e.g., completely disposed) within the structure of the fiber reinforced composite strength member. For example, the sensing optical fiber can be disposed between the fiber reinforced composite portion and an outer material layer surrounding the fiber reinforced composite portion (e.g., see FIG. Figure 2F).

[0063] In a particular feature, the sensing fiber is disposed within the binding matrix along the length of the binding matrix, for example substantially along the entire length of the fiber reinforced composite strength member. It is particularly advantageous that the sensing fiber can be disposed below the outer material layer, or can be disposed entirely within the binding matrix, i.e., the sensing fiber is not directly exposed to the external environment along its length. For example, by disposing the sensing fiber entirely within the fiber reinforced composite strength member, the sensing fiber is completely protected (e.g., shielded) from the external environment by the outer material layer and / or the binding matrix, thereby ensuring that natural or man-made environmental factors (e.g., heat, impact stress, etc.) do not significantly impair the performance of the sensing fiber. In addition, in particular, by disposing the sensing fiber within the binding matrix, the sensing fiber is physically and tightly bonded to the matrix within the fiber reinforced composite portion, and forces (e.g., tensile strain) acting on the fiber reinforced composite strength member will be fully and consistently transmitted to the sensing fiber along the entire length of the fiber reinforced composite strength member, ensuring highly accurate measurement of, for example, stress and strain.

[0064] In order to be able to interrogate the fiber reinforced composite strength member and detect conditions of the fiber reinforced composite strength member along its length, one or more sensing fibers may be positioned along the length of the composite strength member. Figure 3A A partial cross-sectional view of a fiber reinforced composite strength member is shown, the cross-sectional configuration of which is similar to Figure 2 B. Fiber-reinforced composite strength member 316A includes an inner portion 318Aa and an outer portion 318Ab surrounding inner portion 318Aa. In one feature, inner portion 318Aa includes a plurality of substantially continuous reinforcing carbon fibers in a bonding matrix, while outer portion 318Ab is a fiber-reinforced composite portion that includes a plurality of substantially continuous reinforcing glass fibers in a bonding resin matrix, which may be the same as or different from the bonding matrix of inner portion 318Aa. For illustrative purposes, outer portion 318Ab is shown partially peeled away from inner portion 318Aa.

[0065] At least the first sensing fiber 328Aa is disposed within the fiber reinforced composite strength member 316A. Figure 3AAs shown, first sensing fiber 328Aa is completely disposed within the bonding matrix of inner portion 318Aa along the length of fiber-reinforced composite strength member 316A. "Completely disposed" means that sensing fiber 328Aa is completely surrounded by the bonding matrix of fiber-reinforced composite strength member 316A along the length of sensing fiber 328Aa in contact with fiber-reinforced composite strength member 316A. Thus, end portion 330Aa of sensing fiber 328Aa can extend beyond end portion 332A of fiber-reinforced composite strength member 316A, for example, to allow sensing fiber 328Aa to be operatively coupled to an optical signal source (e.g., a laser) and / or a signal detector, as described below.

[0066] Additionally, first sensing fiber 328Aa can be integrally formed within the bonding matrix of strength member 316 A. That is, first sensing fiber 328Aa can be in direct contact (eg, without intervening layers of material) to facilitate mechanical coupling of fiber 328Aa to the bonding matrix.

[0067] The sensing fiber disclosed herein (e.g., the first sensing fiber 328Aa) is defined as a cylindrical glass fiber that transmits light along its longitudinal axis by total internal reflection. The sensing fiber comprises a core and a cladding surrounding the core, wherein the refractive index of the core is greater than the refractive index of the cladding. Both the core and the cladding typically comprise silica-based glass that is carefully doped with other elements (e.g., Ge, Al, F, B) to control the refractive index of the core and the cladding. Such sensing fibers may also be provided with a polymer surrounding the fiber, such as a UV-curable coating.

[0068] The sensing optical fiber 328Aa can be a single-mode optical fiber. A single-mode optical fiber is configured to transmit a single light ray (e.g., a single mode) and typically includes a relatively small diameter core (e.g., 8 μm to 10.5 μm in diameter) surrounded by a relatively thick cladding (e.g., a cladding diameter of approximately 125 μm). Alternatively, the sensing optical fiber 328Aa can be a multimode optical fiber. A multimode optical fiber is configured to transmit multiple light rays (e.g., multiple modes) and has a larger core diameter (e.g., 50 μm to 100 μm) than a single-mode optical fiber. In either case, the optical fiber can be provided in lengths of several kilometers or longer, for example, for incorporation into fiber-reinforced composite components that are several kilometers or longer.

[0069] like Figure 3AAs shown, the first sensing fiber 328Aa is positioned substantially along a neutral axis 334A (e.g., a neutral bending axis) that passes through the length of the fiber-reinforced composite strength member 316A. The neutral axis 334A is an axis passing through the cross-section of the fiber-reinforced composite strength member 316A along which there is substantially no longitudinal bending stress or strain. For a symmetrical composite strength member (e.g., a symmetrical cross-sectional shape), the neutral axis will be the geometric centroid of the cross-section. As discussed in more detail below, positioning at least the first sensing fiber 328Aa along the neutral axis 334A can advantageously reduce or eliminate the effects of bending modes on the sensing fiber 328Aa. As a result, the first sensing fiber 328Aa may be subjected only to tensile stresses, which can more accurately measure those tensile stresses in the sensing fiber 328Aa and, therefore, in the fiber-reinforced composite strength member 316A, particularly when the first sensing fiber 328Aa is integrally formed with the bonding matrix.

[0070] like Figure 3A As shown, the fiber reinforced composite strength member 316A further includes at least a second sensing fiber 328Ab that is completely disposed within the composite strength member 316A, for example, completely disposed within the binding matrix along the length of the fiber reinforced composite strength member 316A. The above-described characteristics of the first sensing fiber 328Aa may also apply to the second sensing fiber 328Ab. Figure 3A As shown, second sensing fiber 328Ab is offset from neutral axis 334A along the length of fiber-reinforced composite strength member 316A, for example, from first sensing fiber 328Aa. For example, second sensing fiber 328Ab can be offset from neutral axis 334A by at least about 1.5 mm, such as at least about 2.0 mm. In other words, second sensing fiber 328Ab can be positioned proximate to an outer surface of fiber-reinforced composite strength member 316A, for example, within 0.5 mm of the outer surface of fiber-reinforced composite strength member 316A.

[0071] By including at least two sensing fibers, one along the neutral axis 334A and one offset from the neutral axis 334A, various conditions of the fiber-reinforced composite strength member 316A can be accurately determined, for example, by comparative analysis of data obtained from the two sensing fibers 328Aa and 328Ab. It may be advantageous for the second sensing fiber 328Ab to be positioned substantially linearly with respect to the neutral axis (e.g., linearly with respect to the first sensing fiber 328Aa).

[0072] The second sensing fiber 328Ab can be the same or similar to the first sensing fiber 328Aa (e.g., two single-mode fibers or two multimode fibers). Alternatively, the sensing fibers can be of different types. In a particular embodiment, the first sensing fiber 328Aa is a single-mode fiber (e.g., configured for distributed sensing of tensile strain) and the second sensing fiber 328Ab is a multimode fiber (e.g., configured for distributed sensing of temperature). Alternatively, the first sensing fiber 328Aa can be a multimode fiber and the second sensing fiber 328Ab can be a single-mode fiber.

[0073] In addition to the first sensing fiber 328Aa and the second sensing fiber 328Ab, additional sensing fibers can be incorporated into the fiber-reinforced composite strength member, e.g., disposed within a bonding matrix. Such additional sensing fibers can be placed, for example, at varying distances (e.g., along a cross-section) from the neutral axis 334A of the fiber-reinforced composite strength member 334A, including near an outer surface of the fiber-reinforced composite member 334A. Such additional sensing fibers can enable detection of additional conditions of the fiber-reinforced composite strength member 334A and / or can provide redundancy, e.g., in the event that one or more other sensing fibers fail to function as intended.

[0074] Figure 3B Another configuration of a fiber reinforced composite strength member is shown that incorporates sensing optical fibers along the length of the strength member. The fiber reinforced composite strength member 316B includes a fiber reinforced composite portion 318B comprised of structural fibers (e.g., carbon fibers) and a bonding matrix (e.g., a resin matrix). Figure 3B In the illustrated embodiment, the fiber-reinforced composite strength member 316B further includes a material layer 322B (e.g., a coating) disposed around the composite portion 318B. (For illustrative purposes, the material layer 322B is shown partially removed from the composite portion 318B.) For example, the material layer 322B may be an insulating and durable polymer, such as polyetheretherketone (PEEK). Other polymers that may be used for the material layer 322B may include polytetrafluoroethylene (PTFE), fluorinated ethylene polymer (FEP), and polyoxymethylene (POM). The material layer 322B may also be a metal, such as aluminum. Furthermore, more than one material layer may be disposed around the composite portion 318B.

[0075] The fiber reinforced composite strength member 316B includes a sensing fiber 328B disposed between the fiber reinforced composite portion 318B and the material layer 322B. In this manner, the material layer 322B can advantageously protect the sensing fiber 328B and the composite portion 318B from damage by the surrounding environment (e.g., moisture) and / or impact. Placing the sensing fiber 328B near (e.g., adjacent to) the outer circumference of the fiber reinforced composite strength member 316B in this manner can enhance the ability of the sensing fiber 328B to more accurately detect environmental conditions (e.g., temperature) external to the fiber reinforced composite strength member 316B. As Figure 3A In the configuration shown, fiber-reinforced composite strength member 316B may include additional sensing fibers along its length, such as disposed within the bonding matrix or between composite portion 318B and material layer 322B. For example, the additional sensing fibers may be disposed along the neutral axis of composite strength member 316B, as described above.

[0076] As described above, the fiber reinforced composite strength member includes at least one sensing optical fiber disposed within the fiber reinforced composite strength member, for example, disposed within a binding resin matrix and / or disposed between the fiber reinforced composite portion and an outer material layer. The sensing optical fiber can be a long, continuous optical fiber that substantially extends through the entire length of the fiber reinforced composite strength member. In addition, as described above, the fiber reinforced composite strength member can include substantially continuous structural fibers, such as substantially continuous structural fiber bundles. Such a structure can be manufactured using various methods, such as manual stacking, tape placement, or other methods. In one feature, the fiber reinforced composite strength member (e.g., a fiber reinforced composite portion) is manufactured at least in part by a pultrusion process.

[0077] The fiber-reinforced composite strength member is particularly configured for use in an overhead cable, particularly a high-voltage overhead transmission line, such as a high-voltage, extra-high-voltage (EHV), or ultra-high-voltage (UHV) overhead transmission line. In this regard, a conductive layer can be disposed around an outer surface (e.g., an outer circumference) of the fiber-reinforced composite strength member, such as by twisting the strength member with a single strand of conductive material. Figure 4 Shows something like Figure 1 A cross-sectional perspective view of an aerial cable 410 is shown. The aerial cable 410 includes an elongated fiber reinforced composite strength member 416 that extends substantially the entire length of the aerial cable 410. The strength member 416 is a fiber reinforced composite strength member that may include one or more fiber types disposed in a resin matrix, as discussed in detail above (see Figure 2 A-2F). Figure 4As shown, the strength member 416 has a generally circular cross-sectional shape. For use in an overhead cable, a single-element (e.g., single-rod) strength member 416 can have an effective outer diameter of, for example, at least about 3 mm and no greater than about 15 mm, although the present disclosure is not limited to use with strength members of any particular diameter.

[0078] A first sensing fiber 428a is disposed within the composite strength member 416 along its neutral axis (e.g., at the geometric center of its circular cross-section), and a second sensing fiber 428b is disposed within the strength member 416 along an axis offset from (e.g., spaced apart from) the neutral axis. Figure 2 (a). Sensing fibers 428a, 428b can be single-mode fibers or multimode fibers. In one configuration, a first sensing fiber 428a (e.g., disposed along the neutral axis) is configured to measure strain (e.g., tensile strain) along the length of strength member 416 and is a single-mode fiber. In this configuration, a second sensing fiber 428b is configured to measure temperature and can be a multimode fiber. This configuration will be discussed in more detail below.

[0079] The overhead cable 410 also includes a first conductive layer 412a disposed around a strength member 416. The conductive layer 412a includes multiple strands of conductive material (eg, conductive strands 414a) helically wound (eg, twisted) around the strength member 416. Figure 4 As shown, the aerial cable 410 also includes a second conductive layer 412b, which also includes multiple strands of conductive material (e.g., strands 414b). It should be understood that additional conductive layers may also be provided, which may be desirable to provide a higher cross-sectional area to increase conductivity (e.g., reduced resistivity) across the aerial cable 410.

[0080] The conductive layers 412a / 412b can be made of any conductive material desired for a particular application, including copper, aluminum, and alloys thereof. In one feature, the conductive layers 412a / 412b include aluminum strands, particularly aluminum strands configured (e.g., sized) to carry high voltages (e.g., in excess of 100 kV). Various types of aluminum (including aluminum alloys) can be used for the conductive layers 412a / 412b. In one feature, the conductive strands are made of fully annealed aluminum, such as fully annealed 1350-O aluminum. Fully annealed aluminum advantageously has a relatively high conductivity, approximately 63% IACS (International Annealed Copper Standard), and excellent heat resistance for use in overhead cables.

[0081] In addition, the strands 414a / 414b are non-circular strands (e.g., polygonal in cross-section) and, in one feature, are trapezoidal strands, i.e., have a trapezoidal cross-section. The use of trapezoidal strands advantageously enables more conductive materials (e.g., conductors of higher cross-sectional area) to be provided in an equivalent diameter configuration (e.g., the diameter of an overhead cable) compared to round strands. Strands with other cross-sections may be used, such as those available from Nexans (Paris, FR) known as Z-WIRE strands.

[0082] An overhead cable including a fiber reinforced composite strength member having a sensing optical fiber operably disposed therein may be used in transmission lines forming the backbone of an electric power transmission grid. Figure 5 A perspective view of a portion of a transmission line 500, such as one that forms part of a power transmission grid by interconnecting with other transmission lines, is shown. Transmission line 500 includes a plurality of suspension towers 502 spaced apart at predetermined distances. Each suspension tower 502 includes a vertical support portion 504 that vertically elevates and supports a plurality of cross arms 506a, 506b, and 506c in a vertically spaced relationship. Each cross arm, in turn, supports at least one pair of overhead cables (e.g., overhead cables 508a and 510a) on opposite sides of suspension tower 502, which are isolated from the suspension tower by electrical insulators (not shown). In suspension tower 502, the insulators are typically in a vertical position or arranged in a V-shape. Those skilled in the art will recognize that other configurations of suspension towers can be used, such as those that support overhead cables in a horizontally spaced relationship.

[0083] When constructing transmission line 500, overhead cables are strung on suspension towers 502 and pulled at very high mechanical tension to ensure that the overhead cables are elevated a sufficient vertical distance above the ground or above any objects below the overhead cables, such as man-made objects such as buildings, roads, train tracks, or natural objects such as trees. The suspension towers are positioned between at least two terminal towers (e.g., anchor towers), to which the ends of the overhead cables can be anchored after being pulled under high tension. As known to those skilled in the art, terminal towers are constructed to be more robust than suspension towers and may have wider bases and / or stronger attachment points for the overhead cables. Terminal towers are used where transmission lines end, where they make sharp turns, or on either side of major intersections (e.g., rivers or valleys). Terminal towers are also used to divide transmission lines into segments at predetermined intervals (e.g., up to approximately 6 km). For example, a transmission line segment may include two terminal towers and approximately 6 to 15 suspension towers between the two terminal towers (e.g., at least approximately 1500 meters). Segmenting a transmission line can prevent catastrophic failures from propagating beyond each segment.

[0084] To be able to apply such high tensions in the electrical conductors, the fiber reinforced composite strength members in the overhead cables may be characterized by very high tensile strengths, such as at least about 1400 MPa, or even at least about 2000 MPa.

[0085] Fiber-reinforced composite strength members in overhead cables can also have sufficient flexibility (e.g., elastic modulus) to be wound onto storage reels for storage and / or transportation of the strength members to stranding facilities (e.g., where the strength members are wrapped with a conductive layer to form an electrical conductor), and for transportation of the electrical conductor to a transmission line construction site.

[0086] The fiber-reinforced composite strength members configured for use in an overhead cable can also be characterized as having a length sufficient to construct the transmission line 500, e.g., without requiring an undesirably large number of joints to connect discrete lengths of electrical conductors. In one aspect, the fiber-reinforced composite strength members (and the overhead cable) have a continuous length of at least about 500 meters, e.g., at least about 1 km, at least about 2 km, at least about 3 km, or even at least about 5 km. In practice, the fiber-reinforced composite strength members and the overhead cable typically have a length not exceeding about 10 km.

[0087] Examples of overhead cables that include fiber-reinforced composite strength members are described in US Pat. No. 7,211,319 to Hiel et al. and US Pat. No. 7,368,162 to Hiel et al., both of which are incorporated herein by reference in their entirety.

[0088] As described above, the fiber reinforced composite strength member of the overhead cable disclosed herein includes at least a first sensing optical fiber disposed therein, and may include two or more sensing optical fibers disposed therein. These sensing optical fibers may be components of a sensor system configured to interrogate the fiber reinforced composite strength member to detect a condition of the fiber reinforced composite strength member. Examples of fiber reinforced composite strength member conditions that may be determined using the disclosed sensor system include strain (e.g., tensile strain), temperature, and length of the fiber reinforced composite strength member. Based on one or more of these conditions, the state of the fiber reinforced composite strength member and the electrical conductor, such as line sag, the presence of defects, current flow, and the like, may be determined.

[0089] An advantage of the configuration disclosed herein is that the sensing fiber is disposed within (e.g., integral with) the fiber reinforced composite strength member. In this way, the temperature, strain, and other conditions of the sensing fiber will be closely related to the conditions actually experienced by the fiber reinforced composite strength member and the overhead cable. For example, the tensile strain experienced by the fiber reinforced composite strength member will be substantially the same as the tensile strain experienced by the sensing fiber because, when forces act on the composite strength member, the sensing fiber will be strained to the same extent as the composite material (e.g., as a bonding matrix). In other words, the sensing fiber is directly and tightly bonded to the fiber reinforced composite member (e.g., the bonding matrix) such that the sensing fiber is subjected to the same conditions as the fiber reinforced composite member. Furthermore, the bonding matrix will protect the sensing fiber from environmental influences that might otherwise damage the sensing fiber, including during the manufacture (e.g., stranding) of the overhead cable and during the installation of the overhead cable.

[0090] In one feature, the sensor system is configured as a distributed fiber optic sensor system. The distributed sensor system utilizes a sensing fiber as a linear sensor that can determine a condition of a fiber-reinforced composite strength member at any location along the length of the fiber-reinforced composite strength member. That is, the distributed sensor can determine a condition and the location of the condition along the length of the fiber-reinforced composite strength member with considerable accuracy. The distributed sensor system provides the unique advantage of being able to determine the condition along the entire length of the sensing fiber, even when the length of the sensing fiber is several kilometers or longer, and without requiring any specialized sensor structures (e.g., Bragg gratings) placed along the length of the composite strength member.

[0091] A distributed fiber optic sensor system may include a coherent light source (e.g., a pump laser source) operably coupled to a sensing fiber to enable light to pass (e.g., pulse) into the fiber in a controlled manner. The light source is configured to transmit a signal (e.g., a pulse) along the sensing fiber and to detect (e.g., measure) a condition in the fiber by analyzing light backscattered by the fiber optic sensor. In this regard, the sensor system may further include a signal detector, such as an interferometer, configured to detect the backscattered light signal.

[0092] refer to Figure 6 , the components of backscattered light can be divided into Rayleigh, Brillouin, and Raman components. The Rayleigh component of backscatter has the same frequency (i.e., the same wavelength) as the primary light source and has a relatively high intensity. By using an optical time domain reflectometer (OTDR), the Rayleigh component of the backscattered light signal can be analyzed to determine the length of the sensing fiber. Therefore, the Rayleigh component can be used to detect breaks in the optical fiber, indicating possible damage to the conductor cable. However, the Rayleigh component does not provide any further important information about the condition of the sensing fiber.

[0093] In one feature, a distributed fiber optic sensor system is based on (e.g., implements) analysis of at least one of a Raman backscattered light component (e.g., a Raman distributed sensor) and a Brillouin backscattered light component (e.g., a Brillouin distributed sensor). Both Raman and Brillouin distributed sensor systems utilize nonlinear interactions between a primary optical signal and the sensing fiber material. When a primary optical signal of known wavelength (l0) is input into the optical fiber, a very small amount of the optical signal is scattered back (e.g., a backscattered light signal) at each point along the sensing fiber. The backscattered light contains a component with a wavelength that is offset from the primary optical signal. The light component that is offset to a longer wavelength (i.e., lower energy) is called a Stokes component, while the light component that is offset to a shorter wavelength (i.e., higher energy) is called an anti-Stokes component. See Figure 6 These shifted backscattered light components can be detected and analyzed to determine information about the local conditions of the sensing fiber, such as strain and temperature at different points along the length of the sensing fiber.

[0094] In one configuration, at least one sensing fiber is a component of a Raman distributed temperature sensor. In a Raman distributed temperature sensor, the interaction between a primary optical signal (e.g., a pump laser signal) and optical phonons in the sensing fiber material (e.g., silica) generates two backscattered light components in the backscattered light spectrum, namely Raman Stokes and Raman Anti-Stokes. Figure 6 As shown, the Raman Anti-Stokes component is temperature-dependent, meaning that its intensity increases with increasing temperature of the sensing fiber. Consequently, the relative intensities of the Raman Stokes and Raman Anti-Stokes backscattered light components can be measured and used to determine the temperature of the sensing fiber. The Raman Stokes and Raman Anti-Stokes backscattered light components can be detected by a signal detector, such as an interferometer or a dispersive spectrometer.

[0095] The location of the temperature reading along the length of the sensing fiber can also be determined from the Raman backscattered light components. When a pulsed light signal (e.g., a few nanoseconds in duration) is used to interrogate the sensing fiber, the backscattered intensities of the Raman Stokes and Raman anti-Stokes backscattered light components can be recorded as a function of time (e.g., the "round trip" time), making it possible to obtain the temperature distribution along the length of the sensing fiber, i.e., along the length of the fiber-reinforced composite strength member.

[0096] In one feature, a sensor system incorporated into a fiber-reinforced composite strength member includes a Raman distributed temperature sensor having a multimode sensing fiber. The multimode sensing fiber having a high numerical aperture can increase the intensity of backscattered light, which can be important because the amplitude of the Raman backscattered light signal is relatively low.

[0097] Examples of Raman distributed temperature sensors include sensors from Sensa (Southampton, UK), the DiTemp system from Smartec (Switzerland), and Sensortran (Austin, Texas, USA).

[0098] In one configuration, at least one sensing fiber is a component of a Brillouin distributed sensor system. Brillouin distributed sensors utilize Brillouin backscattering, which results from the interaction between a primary optical signal and time-varying optical density variations (i.e., acoustic phonons) within the optical fiber. Acoustic phonons produce a periodic modulation of the refractive index (i.e., optical density) of the sensing fiber material. Brillouin scattering occurs when the propagating primary optical signal is diffracted back by the moving "grating," resulting in a frequency (and wavelength)-shifted component in the backscattered optical signal (i.e., spontaneous Brillouin scattering).

[0099] like Figure 6 As shown in Figure 2, as the temperature of the sensing fiber increases, the wavelength of the Brillouin backscattered component shifts further away from the main wavelength λ o This wavelength shift can be used to determine the temperature of the sensing fiber. As with Raman distributed temperature sensors, the temperature position along the length of the sensing fiber can also be determined using the time-of-flight information of the backscattered light signal.

[0100] Unlike Raman distributed sensors, Brillouin distributed sensors can also be used to detect strain (e.g., tensile strain) in a sensing fiber. Specifically, changes in strain within the sensing fiber cause a wavelength shift in the Brillouin backscattered light component due to changes in the optical density of the sensing fiber. Consequently, the strain experienced by the sensing fiber, and therefore the composite strength member, at any point along its length can be determined.

[0101] Brillouin distributed sensors can be configured to implement either a spontaneous Brillouin-based technique, known as Brillouin optical time-domain reflectometry (BOTDR), or a stimulated Brillouin-based technique, known as Brillouin optical time-domain analysis (BOTDA). An advantage of the BOTDR configuration is that a single coherent pump light source can be utilized (i.e., at one end of the sensing fiber). BOTDR is also capable of simultaneously measuring the temperature and strain of the sensing fiber. However, the detected backscattered light signal is typically very weak, requiring signal processing and long integration times.

[0102] In another configuration, the Brillouin distributed sensor system implements BOTDA technology. In BOTDA, a counter-propagating input optical signal (sometimes called a "probe" signal or "reverse wave" signal) is used with a wavelength difference equal to the Brillouin frequency shift. This probe signal enhances the number of phonons in the sensing fiber, resulting in a higher signal-to-noise ratio. When the main (pump) optical signal is a short pulse and its reflection intensity is analyzed based on the flight time and wavelength shift, the distribution of the Brillouin frequency shift along the length of the sensing fiber can be obtained. The BOTDA technology generally requires that the wavelengths of the two counter-propagating optical signals are very stable (for example, synchronized laser sources). Advantageously, a temperature resolution of less than 10°C or even less than 0.5°C can be achieved. In addition, very small strain offsets experienced by the sensing fiber can be detected.

[0103] Brillouin distributed sensors are therefore used for temperature monitoring and are particularly well-suited for strain measurement. In this context, it is often necessary to know the wavelength shift in the sensing fiber at a reference temperature in order to calculate the absolute temperature at any point along the sensing fiber. It is also often necessary to know the wavelength shift of the unstrained fiber in order to be able to make absolute strain measurements.

[0104] Examples of Brillouin distributed sensors for strain and / or temperature measurement are disclosed in U.S. Patent Nos. 7,499,151 and 7,599,047, each of which is incorporated herein by reference in its entirety. Examples of Brillouin distributed sensors are available from Oz Optics (Ottawa, ON, Canada) and Omnisens (Morges, Switzerland).

[0105] In a particularly advantageous feature, the effects of temperature variations on fiber strain within a fiber-reinforced composite strength member are addressed by utilizing a multimode sensing fiber (e.g., in a Raman distributed temperature sensor) and a single-mode sensing fiber (e.g., in a Brillouin distributed strain sensor). Strain calculations can then advantageously include using the temperature detected by the Raman distributed temperature sensor system to separate the effects of temperature on strain.

[0106] In another feature, the total length of the fiber reinforced composite component can be determined by measuring the total length of the sensing fiber. The sensing fiber can be used to measure this length information using Rayleigh backscattering, Raman backscattering, and / or Brillouin (OTDR) backscattering.

[0107] Therefore, when using fiber reinforced composite members as strength members, it is highly desirable to ensure that the structural fibers do not break excessively in order to ensure the performance of the aerial cable, as broken structural fibers can reduce the tensile strength and, if there are not enough continuous structural fibers remaining to support the tension load on the aerial cable, the aerial cable may fail (e.g., break). The system disclosed herein can advantageously enable the detection of such breaks before, during, or after the installation of the aerial cable.

[0108] In one feature, the integrity of a fiber-reinforced composite strength member can be interrogated by a distributed sensor system before the strength member is twisted with a conductive layer. For example, a strength member wound on a storage reel can be interrogated using a distributed fiber optic sensor to identify defects in the strength member (e.g., manufacturing defects). In one feature, a Brillouin distributed sensor (e.g., BOTDR or BOTDA) is used to interrogate the strength member to detect strain along its length. Any anomaly in the strain along its length may indicate a defect in the strength member, such as a crack or void in the bonding matrix.

[0109] This method can be advantageously used to quickly determine if a manufacturing defect exists in a strength member before further fabrication (e.g., stranding) of the electrical conductor occurs, thereby avoiding wasted time and cost. The distributed sensor system described herein can also locate defects along the length of a strength member, which may be several kilometers or more in length, thereby determining whether to salvage one or more portions of the strength member that do not include the defect.

[0110] In another feature, the integrity of the fiber-reinforced composite strength members can be interrogated after the strength members are twisted with the conductive layer to form the electrical conductor and before the overhead cable is installed. An improper twisting operation can impose undue stress on the fiber-reinforced composite strength members, resulting in undesirable defects (e.g., cracks) that weaken or compromise the integrity of the strength members.

[0111] In another feature, the integrity of the strength members can be interrogated after the aerial cable is installed but before energizing (e.g., supplying) the aerial cable. In this way, the transmission line operator can be assured that the aerial cable does not contain any substantial defects due to manufacturing, improper twisting, or improper construction of the transmission line.

[0112] The aforementioned interrogation method of the strength member can be performed in discrete steps, i.e. providing information about the core integrity at a particular moment in time. Such information may be useful to manufacturers and installers of overhead cables to provide assurance to transmission line operators that the integrity of the overhead cable has not been compromised.

[0113] In one embodiment, the properties of the fiber reinforced composite strength members and, therefore, the properties of the overhead cables can be interrogated (e.g., monitored) in real time after excitation and during operation of the transmission line, for example, during operation of a power transmission network. Real-time interrogation of the transmission line can provide a number of benefits. For example, a fault in the transmission line, including the location of the fault, can be detected almost immediately so that emergency action (e.g., line repair or diversion of power transmission) can be taken if necessary. In addition, data indicating, for example, temperature and / or strain fluctuations in the overhead cables and the location of these fluctuations can be collected over time to help identify potential fault points before such faults occur. In addition, the data can be used to make real-time adjustments to the operation of the power transmission network including the transmission line, for example, by reducing or increasing the amount of power transmitted by the transmission line and / or other transmission lines within the power transmission network.

[0114] While the primary function of overhead cables is to transmit electrical loads, the electrical conductors must also be strong enough to support their own weight as well as any additional weight (or stress) caused by ice, wind, or other environmental factors. Figure 5 The strength members support the conductive layer and carry substantially all tensile loads imposed on the conductors, in addition to loads caused by other environmental factors. Such loads can cause the conductors to sag, meaning they stretch and drop closer to the ground, potentially creating a dangerous condition or even catastrophic failure of the transmission line.

[0115] For overhead cables, information indicating the sagging of the electrical conductor can be derived (e.g., in real time during transmission line operation) from the Brillouin distributed sensor output (e.g., the combined effects of temperature and tensile strength). This can also facilitate the study and monitoring of ice formation (e.g., through changes in tensile strain) and temperature changes using sensing fibers.

[0116] The sag of an overhead cable can also be determined in whole or in part by directly measuring the length of the sensing fiber. For example, the length can be measured using an OTDR technique that measures Rayleigh backscattered light signals, Raman backscattered light signals, or Brillouin backscattered light signals.

[0117] In overhead cables, it is also necessary to determine the temperature of the electrical conductors and the location of the temperature reading. For example, damage to the outer conductive layer (e.g., from a gunshot wound) may reduce the cross-sectional area and result in a "hot spot" where the operating temperature increases, potentially high enough to cause permanent damage to the overhead cable and lead to a power outage. In one feature described above, the strength member includes a Raman distributed temperature sensor having a multimode optical fiber that is offset from the neutral axis of the strength member, i.e., closer to the outer surface of the strength member. Due to the proximity of the multimode optical fiber to the conductive layer, this configuration can advantageously achieve highly accurate readings of the temperature of the electrical conductor (e.g., the conductive layer).

[0118] In overhead cables, distributed temperature data can also provide valuable information about heating of electrical conductors from electrical loads, including identification of localized "hot spots" for the aforementioned maintenance actions, and for estimating the remaining life of overhead cables by collecting and analyzing data representing their cumulative heat exposure over time. Distributed strain data can also provide valuable information about the condition of electrical conductors, including conductor tension, to ensure safe operation of the electrical conductors and supporting structures. Combined conductor tension and temperature information (e.g., in real time along the entire length of the electrical conductor) can advantageously enable utility operators to determine the current flowing in overhead cables (e.g., in real time) and can alert operators to address emergency situations with sufficient warning time before the emergency causes severe and / or more widespread power outages.

[0119] As mentioned above Figure 5 As described, the transmission line can be divided into segments, such as segments defined by terminal towers to which the aerial cable is anchored at opposite ends of the aerial cable. The aerial cable can be suspended between the two terminal towers via one or more suspension towers. Advantageously, the aerial cable anchored to the first and second terminal towers can be substantially continuous, i.e., not including any electrical connectors along its length. A laser source (e.g., a first pump laser source) can be operably supported by the first terminal tower and can be configured to direct an optical signal (e.g., a laser signal pulse) to a first end portion of at least a first sensing fiber in the first aerial cable. In one feature, a single laser source can be configured (e.g., via a beam splitter) to simultaneously direct laser pulses along multiple sensing fibers disposed in multiple aerial cables. Furthermore, the aerial cable can be anchored to the terminal tower via a terminal fitting, and the laser source can be integrally formed with the one or more terminal fittings. Examples of such terminal fittings are disclosed, for example, in U.S. Patent Nos. 7,019,217 to Bryant et al. and 8,022,301 to Bryant et al., both of which are incorporated herein by reference in their entireties.

[0120] One or more signal detectors (e.g., as described above) may also be operably supported by the first terminal tower. For example, the signal detectors may be integrally formed with the terminal fitting. Alternatively, or in addition to being supported by the first terminal tower, the signal detectors may be supported by a second terminal tower at the end of the aerial cable opposite the laser source.

[0121] In another feature, the sensor system can be controlled and / or data from the sensor system can be collected remotely, such as at a central location that is not near the actual sensor system. Such a centralized location can perform such control and collection for multiple locations along a single transmission line and / or from multiple transmission lines within a transmission grid. For example, the sensor system can be operably coupled to a wireless transmission device (e.g., operably mounted on a terminal tower) so that control signals can be provided to the sensor system and / or data can be collected remotely from the sensor system. The sensor system can also be powered using renewable and / or independent energy sources (e.g., solar panels), and the power source is preferably decoupled from the transmission line to ensure continued operation of the sensor system during power outages.

[0122] In addition to using the fiber reinforced composite components and sensor systems described herein for overhead cables in transmission lines, the fiber reinforced composite components and systems can also be implemented in other components of transmission lines. For example, the fiber reinforced composite components and systems can be used in support towers that vertically support overhead cables (see FIG. Figure 5 ), in particular for the cross arms of the support tower. In this regard, the support arms may be subject to different loads due to different environmental conditions experienced by the transmission line (e.g., icing, wind, etc.). Thus, the condition of the cross arms (e.g., strain in the cross arms) may be detected, and this information may be used to determine the overall condition of the transmission line. Other components of the tower (e.g., Figure 5 The fiber reinforced composite components and systems disclosed herein may also be implemented in a frame of a vertical support tower to provide useful information about the condition of a transmission line.

[0123] By combining one or more of the aforementioned embodiments of strength members for overhead cables and / or other components of transmission lines that include sensor systems (e.g., distributed sensor systems), systems and methods for intelligent operation of transmission lines and / or transmission grids including multiple transmission lines can be provided. Such systems and methods can include continuous or semi-continuous interrogation of overhead cables to detect, for example, temperature conditions, strain conditions, mechanical loads, and / or elongation of the overhead cables, and taking action in response to certain identified conditions. Based on the determination of these conditions, other conditions and / or states can be determined, such as the sag of a particular conductor segment or the current carried by the conductor segment.

[0124] For example, an action may include increasing or decreasing the power supplied to a transmission line. In one feature, a distributed sensor detects an elevated temperature at a location on a transmission line and, in response to the detection, takes an action. For example, the response may include a preventative action, such as reducing the power transmitted through the transmission line, and / or a repair action, such as dispatching a repair crew to investigate and repair the problem. In this regard, the distributed sensor system advantageously enables the location of the problem to be determined with high accuracy (e.g., within a few meters or less), thereby reducing the time required for maintenance personnel to locate the problem.

[0125] In another example, the tension (e.g., strain) applied to the overhead conductors is measured, and if the measured strain is deemed to be a risk, remedial measures can be taken. In yet another example, sag (e.g., due to heat loads, ice, or wind) is calculated, for example, by measuring the elongation of the electrical conductors. If the amount of sag is determined to be a risk, remedial measures can be taken to reduce the sag or reduce the power supplied to the transmission line before the overhead cable sags to a dangerous level.

[0126] As mentioned above, one issue that has been identified with interrogating aerial cables using sensing fibers is the extreme difficulty of selectively accessing the sensing fibers from within composite strength members and establishing a reliable connection between the sensing fibers and the OTDR device. Specifically, sensing fibers have relatively small diameters and are difficult to position and connect when embedded in the same matrix as the structural fibers. This issue is particularly challenging in the context of aerial cable installations, as the connection must be made on-site by technicians, often under difficult environmental conditions.

[0127] According to certain embodiments of the present disclosure, systems and methods for connecting an interrogation device (e.g., an OTDR device) to a sensing optical fiber are disclosed. One system and method includes providing loose (e.g., not bound by a bonding matrix) structural fiber and an optical sensing fiber at the end of a composite strength member during a manufacturing process, and mounting a sensing fiber connector to the optical fiber. Another system and method includes cutting a composite strength member (e.g., during installation of an overhead cable) and polishing the end of the strength member, including the optical fiber, to form a smooth surface including the end of the optical fiber, and connecting the optical fiber to the interrogation device via a special alignment device. Another system and method includes cutting a composite strength member (e.g., during installation of an overhead cable) and immersing the end of the strength member in a chemical solution selected to dissolve the bonding matrix, and then connecting the optical fiber to the interrogation device. Another method includes cutting a composite strength member (e.g., during installation of an overhead cable) and burning off the matrix using a specially designed torch, and then connecting the optical fiber to the interrogation device.

[0128] Figure 7 The connection system for coupling an optical fiber from a composite strength member to an interrogation device is schematically shown. Figure 7 As shown, this includes an interrogation device 770, such as an OTDR device. Connector 750 operatively connects interrogation device 770 to optical fiber 728a / 728b. Figure 7 As shown, optical fibers 728a / 728b extend beyond the ends of composite strength member 716. For example, the optical fibers can extend beyond the ends of the strength member by at least about 3 cm, such as at least about 5 cm, or at least about 9 cm. In another feature, the optical fibers extend no more than about 40 cm, such as no more than about 30 cm, beyond the ends of the strength member. The composite strength member itself can have a length of at least about 500 meters, such as at least about 1000 meters, at least about 2000 meters, or even at least about 5000 meters.

[0129] Although illustrated as including two optical fibers, it should be understood that the system can include a single optical fiber or multiple optical fibers, including 3 optical fibers, 4 optical fibers, 5 optical fibers, or more.

[0130] In one embodiment, the manufacturing process is controlled so that at least one end of the composite strength member includes loose fibers, such as structural fibers and optical fibers that are not bound by a bonding matrix. That is, the composite strength member is initially made from loose fibers extending from at least one end of the composite strength member. When the composite strength member is manufactured in this manner, the optical fibers extending from the end may be damaged during handling (e.g., shipping) of the strength member.

[0131] like Figure 8 , an arrangement for protecting optical fibers and facilitating connection of the optical fibers to an interrogation device is shown. Apparatus 880 includes a sleeve 882 having a hole for receiving the end of composite strength member 816 within the sleeve. To protect optical fibers 828a and 828b, the sleeve can be made of a rigid material, such as metal or a hard plastic material. Opposite ends of sleeve 882 are enclosed by a housing that also houses optical fibers 828a / 828b within the housing, which also secures connector 850. The ends of optical fibers 828a / 828b are coupled to connector 850, which is configured to connect optical fibers 828a / 828b to an interrogation device. Both strength member 816 and connector 850 are secured to the ends of apparatus 880, protecting optical fibers 828a / 828b from potential damage during handling and transport of strength member 816.

[0132] In another embodiment, the ends of the composite strength members, including the ends of the optical fibers, can be polished to form a smooth surface. Because OTDRs require very clean fiber connections, it is typically necessary to polish the ends of the strength members with a polishing pad having a grit size of about 1 μm or less. For example, polishing can include multiple polishing steps using progressively smaller polishing grits until the grit size is less than or equal to 0.5 μm or even less than or equal to 0.2 μm. Thereafter, the strength member including the optical fibers can be attached to a fiber alignment device. One embodiment of such a fiber alignment device is Figure 9 As shown. The apparatus 900 includes a 3D platform 986 (e.g., capable of controlled movement in the x-, y-, and z-axes) to move a fiber probe 988 until the fiber probe 988 is aligned with at least one of the optical fibers 928a. The movement of the 3D platform 986 can be manually controlled with the aid of a viewing screen 990, through which an operator can visually identify the optical fibers 928a. An example of a 3D platform that may be useful for this purpose is the XYZ-LSMA-167 platform available from IntelLiDrives, Inc. of Philadelphia, PA, USA.

[0133] After alignment between the fiber probe 988 and the optical fiber 928a is achieved, the interrogation device 970 can be activated. Figure 9 As shown, the apparatus 900 further includes a light guide 987 configured to split light (e.g., a laser beam) into two different light beams. One of the light beams is directed to a viewing screen 990 for aligning a fiber probe 988 with the optical fiber 928a. The other light beam is directed to an OTDR 970 for performing measurements such as temperature, stress, and strain. The light guide 987 may include a fiber splitter, an optical switch, a MEMS (micro-electromechanical system), a collimator with a beam-splitting prism, or a reflective collimator.

[0134] The operation of the apparatus 900 may include the following steps. First, the fiber probe 988 is moved using the 3D precision stage 986 to position the optical fiber 928a in the core. The stage 986 is adjusted to align the probe 988 with the optical fiber 928a and to establish an appropriate distance between the probe 988 and the end of the optical fiber 928a. The movement of the probe 988 can be assisted by visually observing the image of the fiber on the viewing screen 990. If the light guide 987 separates the light, an OTDR measurement can be performed. If the light guide 987 operates by deflecting light, for example, using an optical switch, it is necessary to change the direction of the light toward the OTDR 970 to perform the measurement.

[0135] Another method disclosed herein includes exposing the optical fibers at the ends of the composite strength members by dissolving the bonding matrix with a chemical solvent. Figure 10As shown, the composite strength member 1016 including the sensing optical fiber 1028a can be cut at a desired location based on the requirements of the conductor twisting and / or overhead cable installation. One end of the composite strength member 1016 can be inserted into a container 1092 containing a chemical solvent selected to dissolve the binding matrix without dissolving the optical fiber 1028a. Examples of such chemical solvents include acids. After the matrix is dissolved (e.g., removed), the sensing optical fiber 1028a can be positioned for connection to an interrogation device.

[0136] Figure 11 Another method of removing the matrix to expose the optical fibers is shown. A composite strength member 1116 including optical fibers 1128 can be cut at a desired location based on the requirements of the stranding operation and / or overhead cable installation. One end of the strength member 1116 is inserted into a torch apparatus including a gas supply tube 1196 configured to supply gas to a torch 1198. The bonded matrix can be burned away by the torch 1198 to expose the loose fibers, including the optical fibers 1128.

[0137] In any of the foregoing embodiments for removing the matrix to expose the optical fiber, a coating can be applied to the exposed portion of the optical fiber to protect the optical fiber from damage. For example, the coating can be a polymer coating.

[0138] Furthermore, in any of the foregoing embodiments, the optical fiber can be colored, such as with pigments, dyes, etc., to facilitate positioning of the optical fiber relative to non-optical fibers (eg, reinforcement fibers).

[0139] While various embodiments have been described and characterized in detail, modifications and adaptations of these embodiments will be apparent to those skilled in the art, and it should be clearly understood that these and other such modifications and adaptations are within the spirit and scope of the present disclosure.

Claims

1. A monitoring system configured to monitor the condition of a fiber reinforced composite strength member in an overhead cable, the system comprising: Overhead cables, including: Fiber reinforced composite strength components, including: A fiber reinforced composite part comprising a bonding matrix and a plurality of reinforcing fibers operatively disposed within the bonding matrix, at least a first material layer disposed around the fiber reinforced composite portion, the first material layer comprising a polymer coating, at least a second material layer disposed around the first material layer, the second material layer comprising aluminum, and at least a first sensing optical fiber disposed along a length of the fiber reinforced composite material portion and between the fiber reinforced composite material portion and the first material layer; at least a first plurality of electrically conductive strands wound around the second material layer of the strength member; and an interrogation device operably connected to an end portion of the first sensing optical fiber.

2. The monitoring system according to claim 1, wherein: The overhead cable has a length of at least 500 meters.

3. The monitoring system according to claim 1, wherein: The polymer coating is selected from the group consisting of polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), fluorinated ethylene polymer (FEP) and polyoxymethylene (POM).

4. The monitoring system according to any one of claims 1 to 3, wherein: The interrogation device includes a Brillouin distributed sensor.

5. The monitoring system according to claim 4, wherein: The Brillouin distributed sensor is selected from a BOTDR device and a BOTDA device.

6. The monitoring system according to claim 5, wherein: The interrogation device is configured to monitor strain in the sensing fiber.

7. The monitoring system according to any one of claims 1 to 3, wherein: The monitoring system is configured to monitor the condition of strength members in real time during operation of a transmission line including the overhead cable.

8. The monitoring system according to claim 7, wherein: The monitoring system is operably coupled to a wireless transmission device configured to enable data to be collected remotely from the monitoring system.

9. The monitoring system according to any one of claims 1 to 3, wherein: The reinforcing fibers are selected from carbon fibers and aramid fibers.

10. The monitoring system according to any one of claims 1 to 2, wherein: An end portion of the first sensing optical fiber extends beyond the length of the aerial cable.

11. The monitoring system according to claim 10, wherein: The first sensing fiber end portion extends beyond the aerial cable by a distance of at least 5 cm.

12. The monitoring system according to claim 11, wherein: The end portion of the first sensing optical fiber extends beyond the overhead cable by no more than 40 cm.

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