Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/32—Insulated conductors or cables characterised by their form with arrangements for indicating defects, e.g. breaks or leaks
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B9/00—Power cables
  • H01B9/005—Power cables including optical transmission elements

Definitions

• the present invention relates generally to a power cable capable of detecting failure and, more particularly, to a power cable, which is constructed to allow a location at which external or internal failure of various kinds of power cables for transmitting or distributing power occurs to be easily found.
• the power cable When such a power cable is used as a ground distribution line or a ground transmission line, the power cable is apt to be damaged by natural disasters or external impacts. Further, when a transmission line or a distribution line forms an underground line, it may be easily damaged by accidents or corrosion upon deterioration with age.
• a conventional power cable is designed to satisfy only electrical requirements, without considering the method of easily determining a failure location when there is a problem with the power cable.
• a submarine cable is a power cable which couples the land to an island or couples islands to each other.
• An insulated cable filled with insulating oil has been mainly used as the submarine cable.
• the cable may fail due to an external impact, such as an anchor of a ship or a trawl of a trawl boat, or a defect in the cable.
• the conventional submarine cable is designed to satisfy only the electrical requirements required for the submarine cable. However, a method of easily finding a failure location in the submarine cable has not been realized yet.
• an object of the present invention is to provide a power cable or a submarine cable capable of helping the detection of failure, which is constructed to enable rapid and easy determination of a failure location.
• the present invention provides a power cable including a conductor, and an auxiliary line inserted into an inner layer provided between the conductor and an outermost layer, and installed to extend in a longitudinal direction in a spiral arrangement.
• the power cable is a transmission line or a distribution line which carries power underground.
• the power cable is a submarine power cable which carries power in the sea.
• the inner layer corresponds to an anti-corrosive layer formed to protect against external impact or corrosion, or a polyethylene sheath which covers an insulator covering the conductor.
• the auxiliary line is inserted between several layers forming the inner layer of the power cable.
• the auxiliary line is made of an optical fiber, and preferable a plastic optical fiber.
• the thickness of the auxiliary line is determined so that the auxiliary line is cut or deformed by a force sufficient to cause damage to insulator covering the conductor, and it is preferable that the thickness of the auxiliary line is 2mm or less.
• laser light is applied to the auxiliary line continuously, or at regular intervals, or intermittently, so as to detect failure of the power cable, and a failure location of the power cable is detected based on time it takes for reflection waves, reflected from the failure location where the auxiliary line is ' broken, to reach a location where the laser light is applied.
• FIG. 1 is a cross-sectional view showing a power cable capable of detecting failure, according to the first embodiment of the present invention
• FIG. 2 is a view showing the state where an auxiliary line for detecting failure is installed in the power cable according to the present invention
• FIG. 3 is a view representing experimental stress test results of the auxiliary line for detecting failure, according to the present invention
• FIG. 4 is a view illustrating the state where the auxiliary line for detecting failure according to the first embodiment of this invention is cut due to damage to the power cable;
• FIG. 5 is a view showing the connected state of the auxiliary line for enabling detection of the failure or determining a failure location of the power cable, according to the first embodiment of the present invention.
• FIG. 6 is a cross-sectional view showing a submarine power cable capable of detecting failure, according to the second embodiment of the present invention.
• Features, elements, and aspects of the invention that are referenced by the same numerals in different figures represent the same, equivalent, or similar features, elements, or aspects in accordance with one or more embodiments. 5. Modes for Carrying out the Invention
• FIG. 1 is a cross-sectional view showing a power cable capable of enabling detection of failure, according to the first embodiment of the present invention.
• the power cable according to the first embodiment of this invention includes a conductor 10 which has a predetermined thickness and carries power to the central portion of the power cable.
• the conductor 10 is covered with an insulator
• a sheath 30 is provided on the outer portion of the insulator
• an auxiliary line 50 for detecting failure is inserted into the anti-corrosive layer 40 in such a way as to extend in the same direction as the conductor 10. As shown in FIG. 2, the auxiliary line 50 is installed to extend in a regular spiral shape along the longitudinal direction of the corresponding power cable, thus detecting the failure along the entire power cable.
• the auxiliary line for detecting failure is installed parallel to the longitudinal direction of the power cable, the auxiliary line may not be damaged or cut when a portion having no auxiliary line, as seen in a cross section of the power cable, is damaged.
• the auxiliary line is installed to extend in the longitudinal direction of the power cable in a regular spiral arrangement.
• the auxiliary line is a wire, such as an enameled wire
• the spiral arrangement increases reactance, thus hindering the flow of electric current in the auxiliary line. That is, if the wire is installed in a spiral arrangement, transmission loss is increased. Thereby, closed-circuit detectors for detecting the location of defects must be installed at much smaller intervals .
• the auxiliary line is made of an optical fiber which has very low transmission loss.
• the optical fiber serves to transmit light, for example laser light, output from a light source. When the optical fiber is deformed or damaged, the intensity, phase, polarization, and wavelength of light passing through the optical fiber are changed. Such variation is detected by a photo-detector.
• the location where the optical fiber breaks can be detected using the time it takes for laser light to be reflected from the broken fiber portion.
• the spiral pitch of the auxiliary line when the spiral pitch of the auxiliary line is long, the auxiliary line may not be damaged. In this case, damage to the cable may not be detected. Conversely, when the spiral pitch of the auxiliary line is short, the length of the auxiliary line to be used in the power cable is increased. Thus, it is desirable that 154kV OF cable or XLPE cable having a diameter of 10cm to 12cm have a spiral pitch of 3cm or less.
• auxiliary line 50 comprising an optical fiber, continuously, or at regular intervals, or intermittently. Further, the thickness of the auxiliary line 50 is determined so that the auxiliary line 50 is easily cut or deformed as a result of impact when cable is damaged by external impacts or internal factors.
• the auxiliary line 50 made of an optical fiber, is inserted into the anti-corrosive layer 40 of the power cable. Displacement deforming the sheath 30 by a pressure of 50 bar acts on the anti-corrosive layer 40 as loading conditions thereof. In such a state, the results obtained from changing the diameter of the auxiliary line 50 inserted into the anti-corrosive layer 40 are represented in FIG. 3.
• the thickness of the optical fiber when the thickness of the optical fiber is 2mm or less, the stress applied to the optical fiber after the sheath is damaged is larger than the tensile strength of the optical fiber, that is, 6.7kgf/mm2. This means that the auxiliary- line made of the optical fiber is damaged when the power cable is damaged. Thus, it is preferable that the thickness of the optical fiber be 2mm or less.
• FIG. 3 shows the fracture characteristics according to the thickness of the optical fiber used as a material of the auxiliary- line 50. Using the fracture characteristics, it is possible to appropriately adjust the thickness and pitch of the optical fiber according to the characteristics of the installation position of the power cable or the surrounding environment.
• the auxiliary line 50 for detecting failure may be inserted into the anti -corrosive layer 40.
• the auxiliary line 50 may be inserted between layers forming the power cable, such as between the insulator 20 and the sheath 30 or between the sheath 30 and the anti-corrosive layer 40.
• the optical fiber used as the auxiliary line 50 for detecting failure may be made of glass or plastic.
• the auxiliary line comprises an optical fiber made of plastic, which has higher ductility.
• the auxiliary line 50 is installed in the anti-corrosive layer 40 of the power cable in such a way as to extend spirally along in the longitudinal direction of the corresponding power cable.
• laser light is applied from a light source in the light detectors 70, installed at regular intervals of the power cable, to the auxiliary line 50.
• each of the light detectors 70 includes a light source which generates laser light or the like that is transmitted through the auxiliary line 50, a photo-detector which detects reflection waves reflected from the broken auxiliary line, and a calculation unit which calculates the failure location using the time difference between application of the laser light and arrival of the reflected waves.
• each light detector 70 may also include a communication module which informs a server, which is provided at a remote position and controls the condition of the power cable, of the detected failure location.
• the light source of each light detector 70 generates light, for example, laser light, having an intensity that can be transmitted to and reflected from a subsequent light detector, and applies the generated light to the auxiliary line 50.
• the auxiliary line 50 of a failure location 60 is broken due to impact.
• the auxiliary line 50 breaks at the failure location 60 of the power cable, an associated portion of the auxiliary line 50 is opened. Using the reflection waves reflected at the open portion, the open state and the open location caused by the breakage of the auxiliary line 50 may be detected at the light detectors 70, installed at regular intervals of the power cable, as shown in FIG. 5.
• the second embodiment of the present invention will be described in detail with reference to the accompanying drawings.
• FIG. 6 is a cross-sectional view showing a submarine power cable capable of detecting failure, according to the second
• the submarine power cable according to the second embodiment of this invention includes a conductor 80 which has a predetermined thickness and carries power to the central portion of the power cable.
• the conductor 80 is covered
• a polyethylene sheath 84 is provided on the outer portion of the insulator 82 to cover the insulator 82.
• Armor 86 is installed outside the polyethylene sheath 84 to protect the cable against external impact. Further, an outer sheath 88 having a predetermined thickness is provided outside
• an auxiliary line 90 for detecting failure is inserted into the polyethylene sheath 84 and extends in the same direction as the conductor 80.
• the auxiliary line 90 for detecting failure is inserted into the polyethylene sheath 84 and extends in the same direction as the conductor 80.
• the auxiliary line 90 is installed in such a way as to extend in a regular spiral shape along the longitudinal direction of the corresponding submarine cable, thus detecting failure along the 25 entire length of submarine power cable.
• auxiliary line 90 In order to monitor failure due to damage to the submarine power cable, laser light is applied from a light source to the auxiliary line 90 continuously, or at regular intervals, or intermittently. Further, it is preferable that the auxiliary line 30 90 is made of an optical fiber, for example a plastic optical fiber having a thickness of 2mm or less so that the auxiliary line 90 is easily cut due to impact when the polyethylene sheath 84 of the cable is damaged by external impacts or internal factors.
• the auxiliary line 90 is installed in the polyethylene sheath 84 of the submarine cable in such a way as to extend spirally in the longitudinal direction of the corresponding submarine cable. In such a state, laser light is applied to the auxiliary line 90.
• the auxiliary line 90 of a failure location is broken due to impact .
• the auxiliary line 90 breaks at the failure location of the submarine cable, an associated portion of the auxiliary line 90 is opened. Using the reflection waves reflected at the open portion, the open state and the open location caused by the breakage of the auxiliary line 90 may be detected at light detectors, installed at regular intervals of the submarine cable.
• the present invention has the effect of enabling rapid detection of a failure location in a power cable or a submarine cable .

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• Communication Cables (AREA)
• Insulated Conductors (AREA)
• Laying Of Electric Cables Or Lines Outside (AREA)

Applications Claiming Priority (1)

Publications (2)

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ID=38541301

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Citations (6)

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• 2006
  • 2006-03-24 JP JP2009502648A patent/JP2009531826A/ja active Pending
  • 2006-03-24 EP EP06716522A patent/EP1999761A4/de not_active Withdrawn
  • 2006-03-24 WO PCT/KR2006/001094 patent/WO2007111389A1/en active Application Filing

Patent Citations (6)

Non-Patent Citations (1)

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