US20150206628A1 - Power cable - Google Patents
Power cable Download PDFInfo
- Publication number
- US20150206628A1 US20150206628A1 US14/307,557 US201414307557A US2015206628A1 US 20150206628 A1 US20150206628 A1 US 20150206628A1 US 201414307557 A US201414307557 A US 201414307557A US 2015206628 A1 US2015206628 A1 US 2015206628A1
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- US
- United States
- Prior art keywords
- cable
- steel pipe
- power cable
- power
- transmission cables
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G9/00—Installations of electric cables or lines in or on the ground or water
- H02G9/06—Installations of electric cables or lines in or on the ground or water in underground tubes or conduits; Tubes or conduits therefor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/06—Gas-pressure cables; Oil-pressure cables; Cables for use in conduits under fluid pressure
- H01B9/0683—Features relating to the conductors of oil-pressure cables
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/06—Gas-pressure cables; Oil-pressure cables; Cables for use in conduits under fluid pressure
- H01B9/0694—Features relating to the enclosing sheath of oil-pressure cables
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G15/00—Cable fittings
- H02G15/08—Cable junctions
- H02G15/10—Cable junctions protected by boxes, e.g. by distribution, connection or junction boxes
- H02G15/103—Cable junctions protected by boxes, e.g. by distribution, connection or junction boxes with devices for relieving electrical stress
- H02G15/105—Cable junctions protected by boxes, e.g. by distribution, connection or junction boxes with devices for relieving electrical stress connected to the cable shield only
- H02G15/1055—Cable junctions protected by boxes, e.g. by distribution, connection or junction boxes with devices for relieving electrical stress connected to the cable shield only with cross-bonding of cable shields
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
- H01B9/029—Screen interconnecting circuits
Definitions
- the present invention relates to a power cable.
- An example of a conventional large-capacity power cable may include three (3) transmission cables that are arranged so that center axes thereof in a cross sectional view substantially correspond to three (3) vertexes of an equilateral triangle, where each transmission cable has a semiconductive layer at an outermost layer portion without providing a metal layer on an outer periphery of an insulator.
- a return path conductor forming a return path for a fault current may be arranged at a center of the equilateral triangle, to be surrounded by the three (3) transmission cables, in order to electrically connect the conductor to the semiconductive layer of the transmission cables.
- An example of such a conventional large-capacity power cable is proposed in Japanese Laid-Open Patent Publication No. 2007-180742.
- the return path conductor forming the return path for the fault current is the only conductor through which the fault current may flow. For this reason, when the fault current is large to a certain extent, a current exceeding a ground-fault capacity of the power cable or the return path conductor may flow and damage the power cable.
- Embodiments of the present invention can provide a power cable that can provide a sufficient path for the fault current.
- a power cable may include a first steel pipe coupled to a reference potential node; three first transmission cables, inserted inside the first steel pipe, and respectively including a first conductor to transmit three-phase alternating current power; and a return cable inserted inside the first steel pipe and coupled to the reference potential node, wherein each of the three first transmission cables includes a first insulating layer covering the first conductor, a metal layer covering the first insulating layer, and a second insulating layer covering the metal layer, wherein the three first transmission cables are twisted around a periphery of the return cable along a longitudinal direction of the return cable, and wherein the metal layer is coupled to the reference potential node.
- FIGS. 1A and 1B are diagrams for explaining an example of a power cable in a first embodiment
- FIGS. 2A and 2B are diagrams for explaining a transmission cable of the power cable in the first embodiment
- FIG. 3 is a diagram for explaining a ground-fault capacity of the power cable in the first embodiment
- FIGS. 4A and 4B are cross sectional views for explaining a transmission cable and an OF (Oil Filled) cable in a comparison example;
- FIG. 5 is a diagram illustrating a state in which a plurality of power cables in the first embodiment are connected via vaults;
- FIG. 6 is a cross sectional view illustrating an example of the power cable in a second embodiment
- FIG. 7 is a diagram for explaining the ground-fault capacity of the power cable in the second embodiment
- FIG. 8 is a diagram illustrating in which a plurality of power cables in the second embodiment are connected via vaults.
- FIGS. 9A and 9B are diagrams for explaining a state in which existing POF (Pipe type Oil Filled) cables are replaced by the power cables in the second embodiment.
- POF Pear type Oil Filled
- FIGS. 1A and 1B are diagrams for explaining an example of a power cable 100 in a first embodiment.
- FIG. 1A illustrates a perspective view of power cable 100
- FIG. 1B illustrates a cross sectional view of the power cable 100 .
- the perspective view illustrated in FIG. 1A illustrates a state of the power cable 100 that is cut along a plane perpendicular to a longitudinal direction of the power cable 100 .
- the power cable 100 includes a steel pipe 110 , transmission cables 120 R, 120 Y and 120 B, and a return cable 130 .
- the steel pipe 110 is be formed by a pipe made of iron, for example.
- the transmission cables 120 R, 120 Y and 120 B, and the return cable 130 are inserted inside the steel pipe 110 .
- the steel pipe 110 is an example of a first steel pipe, and is connected to a reference potential node. In this first embodiment, the steel pipe 110 is grounded and held at a ground potential. The steel pipe 110 is held at the reference potential, in order to use the steel pipe 110 as a return path for a fault current in a case in which the fault current caused by ground fault or the like flows through the transmission cables 120 R, 120 Y and 120 B.
- the steel pipe 110 may be a new, unused steel pipe, or an old, used steel pipe.
- the steel pipe of the existing power cable may be reused as the steel pipe 110 of the power cable 100 .
- the steel pipe of the existing POF (Pipe type Oil Filled) cable, HPFF (High Pressure Fluid Filled) cable, or HPGH (High Pressure Gas Filled) cable may be reused as the steel pipe 110 .
- An inner diameter of the steel pipe 110 may be in a range of 100 mm to 254 mm, for example, and may be 206 mm, for example.
- the inner diameter of the steel pipe 110 may be in a range of 6 inches to 10 inches, for example, and may be 8 inches, for example.
- the transmission cables 120 R, 120 Y and 120 B are arranged so that center axes thereof substantially correspond to three (3) vertexes of an equilateral triangle, and the return cable 130 is arranged at a center of the equilateral triangle, to be surrounded by the transmission cables 120 R, 120 Y and 120 B.
- the transmission cables 120 R, 120 Y and 120 B, and the return cable 130 are inserted into the steel pipe 110 in a state in which the transmission cables 120 R, 120 Y and 120 B are twisted around the return cable 130 along the longitudinal direction of the return cable 130 .
- the transmission cables 120 R, 120 Y and 120 B may be used to transmit power of each phase of three-phase A.C. (Alternating Current) power.
- the transmission cables 120 R, 120 Y and 120 B are examples of three (3) first transmission cables.
- the transmission cables 120 R, 120 Y and 120 B may be categorized as red-phase, yellow-phase and blue-phase cables, respectively, permitting identification of the cables by color.
- the transmission cables 120 R, 120 Y and 120 B have different colors for identification, but have the same configuration. For this reason, when not distinguishing the transmission cables 120 R, 120 Y and 120 B, these transmission cables 120 R, 120 Y and 120 B may also be referred to as “transmission cables 120 ” in the following description.
- the detailed configuration of the transmission cable 120 will be described later in conjunction with FIGS. 2A and 2B .
- the return cable 130 includes a conductor 131 , and a jacket 132 covering the periphery of the conductor 131 .
- the conductor 131 is made of a metal, and for example, copper may be used as the metal.
- the jacket 132 is formed by an insulating layer covering the periphery of the conductor 131 , and made of a material such as an XLPE (Cross Linked Polyethylene), PVC (Poly-Vinyl Chloride), and the like.
- the conductor 131 of the return cable 130 is connected to the reference potential node, similarly to the steel pipe 110 .
- the conductor 131 of the return cable 130 is grounded and held at the ground potential.
- the conductor 131 of the return cable 130 is held at the reference potential, in order to use the return cable 130 as a return path for a fault current in a case in which the fault current caused by ground fault or the like flows through the transmission cables 120 .
- FIGS. 2A and 2B are diagrams for explaining the transmission cable 120 of the power cable 100 in the first embodiment.
- FIG. 2A illustrates a cross sectional view of the transmission cable 120
- FIG. 2B illustrates a perspective view of a triplex formation.
- the transmission cable 120 includes a conductor 121 , a conductor screen 122 , an insulating layer 123 , an insulating screen 124 , a bedding 125 , a metal sheath 126 , and a jacket 127 .
- the conductor screen 122 , the insulator layer 123 , the insulating screen 124 , the bedding 125 , the metal sheath 126 , and the jacket 127 respectively have a hollow cylindrical shape covering, one by one, the conductor 121 having the solid cylindrical shape (that is, formed by a stranded wire).
- the conductor 121 is made of a metal, and for example, copper may be used as the metal.
- the conductor 121 is an example of a first conductor.
- the conductor screen 122 is formed by a semiconductive tape having heat resistance, and a resin layer including carbon powder, and is wound around the periphery of the conductor 121 .
- nylon or polyester may be used as the semiconductive tape having heat resistance
- EEA (Ethylene-Ethylacrylate Copolymer) resin may be used as the resin layer including carbon powder.
- the insulating layer 123 is provided to insulate the conductor 121 .
- the insulating layer 123 may be formed by injection molding using XLPE (Crosslinked Poly-Ethylene), for example.
- XLPE Crosslinked Poly-Ethylene
- the insulating screen 124 is formed by a resin layer including carbon powder, and is wound around the periphery of the insulating layer 123 .
- EEA resin may be used as the resin layer including carbon powder.
- the bedding 125 is the so-called bedding tape, and is wound around the insulating screen 124 .
- the metal sheath 126 is formed by a metal tape that covers the periphery of the bedding 125 along a longitudinal direction of the transmission cable 120 .
- An adhesive layer on this metal tape is bonded to the jacket 127 .
- copper laminated tape may be used as the metal sheath 126 .
- the metal sheath 126 is an example of a metal layer, and is also an example of a metal wrap.
- the metal sheath 126 is provided to achieve electrostatic shielding and electromagnetic induction shielding, and to ensure a path for the fault current to flow.
- the electrostatic shielding covers the periphery of the conductor 121 by a metal member in order to suppress a high voltage from being induced on the ground side due to the electrostatic capacitance between the conductor 121 and the ground, in a case in which a high voltage is applied to the conductor 121 .
- the electromagnetic induction shielding covers the periphery of the conductor 121 by a metal member in order to suppress formation of a magnetic field caused by electromagnetic induction that is generated by a closed loop created by the conductor 121 and the ground, in a case in which the fault current is generated.
- the metal sheath 126 covers the outer periphery of the conductor 121 via the conductor screen 122 , the insulating layer 123 , the insulating screen 124 , and the bedding 125 . Hence, the magnetic field generated due to a current flowing through the conductor 121 is canceled by the current induced by the metal sheath 126 .
- the metal sheath 126 is connected to the reference potential node, similarly to the steel pipe 110 and the return cable 130 as described above in conjunction with FIGS. 1A and 1B .
- the metal sheath 126 is grounded and is held at the ground potential, for example. Because the metal sheath 126 is held at the reference potential, the metal sheath 126 can function as a path for a fault current to flow in a case in which the fault current caused by ground fault or the like flows through the transmission cables 120 .
- the jacket 127 is formed by an insulating layer covering the periphery of the metal sheath 126 , for example, polyethylene may be used for the insulating layer.
- An outer peripheral surface of the jacket 127 can be distinguished amongst the transmission cables 120 R, 120 Y and 120 B by emboss or the like identifying the red-phase, yellow-phase and blue-phase.
- the transmission cables 120 R, 120 Y and 120 B having the configuration described above in conjunction with FIGS. 1A and 1B are twisted around the center, return cable 130 along the longitudinal direction of the power cable 100 , as illustrated in FIG. 2B .
- the twisted configuration of the three (3) transmission cables 120 R, 120 Y and 120 B may be referred to as the “triplex formation”.
- the transmission cables 120 R, 120 Y and 120 B are twisted around the center, return cable 130 , while maintaining rotational symmetry of order three (3), that is, three-fold symmetry, in the cross sectional view illustrated in FIG. 1B .
- the triplex formation has small expansion and contraction along the longitudinal direction of the transmission cables 120 R, 120 Y and 120 B of the power cable 100 , and enables easy fixing within a vault (or manhole) as will be described later.
- the positional relationship of the transmission cables 120 R, 120 Y and 120 B having the three-fold symmetry in the cross sectional view is not limited to the perfect three-fold symmetry.
- the transmission cables 120 R, 120 Y and 120 B have the three-fold symmetry in the cross sectional view even when a positional error occurs due to inconsistencies in the twisting and the like of the transmission cables 120 R, 120 Y and 120 B around the return cable 130 .
- the transmission cables 120 R, 120 Y and 120 B having the triplex formation are arranged along the outer periphery of the return cable 130 .
- the transmission cables 120 R, 120 Y and 120 B and the return cable 130 are arranged inside the steel pipe 110 as illustrated in FIGS. 1A and 1B .
- the power cable 100 described above in this first embodiment transmits three-phase A.C. power by the transmission cables 120 R, 120 Y and 120 B illustrated in FIGS. 1A and 1B .
- a rated capacity of the power cable 100 is 250 MVA (138 kV, 1045 A).
- this rated capacity is merely an example, and the rated capacity may vary depending on laying conditions, such as the temperature and a burying depth of steel pipe 110 .
- the power cable 100 has a length of 487.68 m (1600 feet), and a plurality of such power cables 100 are connected in series upon use.
- the transmission cables 120 R, 120 Y and 120 B of each power cable 100 are connected to the corresponding transmission cables 120 R, 120 Y and 120 B of another power cable 100 so that the color phases match.
- Connecting the transmission cables 120 R, 120 Y and 120 B of each power cable 100 to the corresponding transmission cables 120 R, 120 Y and 120 B of another power cable 100 so that the color phases match means that the conductors 121 of the transmission cables 120 R are connected, the conductors 121 of the transmission cables 120 Y are connected, and the conductors 121 of the transmission cables 120 B are connected, between two adjacent power cables 100 that are connected in series.
- the metal sheaths 126 of the transmission cables 120 R, 120 Y and 120 B of the two adjacent power cables 100 that are connected in series the metal sheaths 126 of the same color phase may be connected, or the metal sheath 126 may be grounded at each power cable 100 .
- the power cable 100 may be used as a new replacement power cable when replacing a part of a plurality of existing power cables that are connected in series.
- the power cable 100 may be used to replace one of the plurality of existing power cables that are connected in series.
- this steel pipe of the existing power cable to be removed may be used as the steel pipe 110 .
- the conductors 121 of the transmission cables 120 R, 120 Y and 120 B of the power cable 100 may be connected to the conductors of the corresponding transmission cables of the existing power cables at both ends of the power cable 100 so that the color phases match. Further, the metal sheaths 126 of the transmission cables 120 R, 120 Y and 120 B may be grounded in this case.
- the fault current flows from the steel pipe 110 of the power cable 100 in which the insulator breakdown occurs to the steel pipe 110 , the metal sheaths 126 and the return cables 130 of an adjacent power cable 100 that is connected in series to the power cable 100 .
- the steel pipe 110 , the metal sheath 126 , and the return cable 130 of the power cable 100 respectively need to have a ground-fault capacity to a certain extent at least greater than or equal to a fault current dividing ratio.
- the ground-fault capacities are determined by amounts of current that can flow through the steel pipe 110 , the metal sheath 126 , and the return cable 130 that may form the path for the fault current to flow.
- the fault current may still flow through the steel pipe 110 , the metal sheath 126 , and the return cable 130 that may form the path for the fault current to flow.
- the fault current flows through the steel pipe 110 , the metal sheath 126 , and the return cable 130 of an adjacent power cable 100 .
- the ground-fault capacities are evaluated based on amounts of current that can flow through the steel pipe 110 , the metal sheath 126 , and the return cable 130 of the adjacent power cable 100 that is adjacent to the power cable 100 in which the insulator breakdown occurs but the metal sheath 126 or the return cable 130 of the power cable 100 does not melt.
- FIG. 3 is a diagram for explaining the ground-fault capacity of the power cable 100 in the first embodiment.
- a comparison example of the power cable is also considered, in which the return cable 130 is omitted from the power cable 100 in this first embodiment.
- the amount of current flowing through the power cable 100 in this first embodiment and the amount of current flowing through the power cable in the comparison example are compared to the respective ground-fault capacities.
- the current value in FIG. 3 is represented by kA (kilo-Amperes).
- the ground-fault capacities of the steel pipe 110 , the metal sheath 126 , and the return cable 130 that are used are computed under a precondition that the steel pipe 110 , the metal sheath 126 , and the return cable 130 have predetermined cross sectional areas and that the current flows for 0.25 second.
- the ground-fault capacities of the steel pipe 110 , the metal sheath 126 , and the return cable 130 are 60 kA, 15.6 kA, and 15.3 kA, respectively.
- the computed ground-fault capacity of the steel pipe 110 is 60 kA or greater, however, it is assumed for the sake of convenience that the computed ground-fault capacity of the steel pipe 110 is 60 kA.
- the ground-fault capacity of the metal sheath 126 exists for each of the transmission cables 120 R, 120 Y and 120 B, and the metal sheaths 126 of the transmission cables 120 R, 120 Y and 120 B are represented as “metal sheath 126 (R)”, “metal sheath 126 (Y)” and “metal sheath 126 (B)” in FIG. 3 .
- the steel pipe 110 , the metal sheath 126 , and the return cable 130 can allow currents amounting to 60 kA, 15.6 kA and 15.3 kA to flow, respectively.
- a current of 60 kA flows through the transmission cables 120 R, 120 Y and 120 B for 0.25 second, and the fault current is generated in the transmission cable 120 R.
- the phase in which the fault current is generated may also be referred to as a “fault-phase”.
- the current flowing through the steel pipe 110 of the power cable 100 is 17.9 kA
- the current flowing through the fault-phase metal sheath 126 (R) is 15.0 kA
- the current flowing through each of the metal sheaths 126 (Y) and 126 (B) of phases other than the fault-phase is 8.2 kA
- the current flowing through the return cable 130 is 15.3 A.
- the amounts of current flowing through the steel pipe 110 , the metal sheaths 126 (R), 126 (Y) and 126 (B), and the return cable 130 , respectively, are the respective ground-fault capacities or less. Hence, it is confirmed that the power cable 100 in this first embodiment can ensure a sufficient path for the fault current to flow.
- the current flowing through the steel pipe 110 is 23.4 kA
- the current flowing through the fault-phase metal sheath 126 (R) is 18.4 kA.
- the current flowing through each of the metal sheaths 126 (Y) and 126 (B) of phases other than the fault-phase is 11.9 kA.
- the amount of current flowing through the fault-phase metal sheath 126 (R) exceeds its ground-fault capacity, and it is confirmed that a sufficient path for the fault current to flow cannot be ensured by the power cable in the comparison example.
- the power cable 100 that ensures a sufficient path for the fault current to flow, by including the transmission cables 120 R, 120 Y and 120 B having the triplex formation in which the transmission cables 120 R, 120 Y and 120 B are twisted around the periphery of the return cable 130 along the longitudinal direction of the return cable 130 , with the return cable 130 arranged at the center of the transmission cables 120 R, 120 Y and 120 B.
- each of the transmission cables 120 R, 120 Y and 120 B includes the conductor 121 , the conductor screen 122 , the insulating layer 123 , the insulating screen 124 , the bedding 125 , the metal sheath 126 , and the jacket 127 described above.
- the transmission cables of the existing power cable may include a shield.
- a description will be given of the transmission cable in the comparison example, by referring to FIGS. 4A and 4B .
- FIGS. 4A and 4B are cross sectional views for explaining a transmission cable 20 and an OF (Oil Filled) cable 40 in the comparison example.
- FIG. 4A illustrates a cross section of the transmission cable 20 , corresponding to the cross section of the transmission cable 120 illustrated in FIG. 2A .
- the transmission cable 20 includes a conductor 21 , a conductor screen 22 , an insulating layer 23 , an insulating screen 24 , a bedding 25 , a shield 30 , a metal sheath 26 , and a jacket 27 .
- the conductor 21 , the conductor screen 22 , the insulating layer 23 , the insulating screen 24 , the bedding 25 , the metal sheath 26 , and the jacket 27 of the transmission cable 20 in the comparison example correspond to the conductor 121 , the conductor screen 122 , the insulating layer 123 , the insulating screen 124 , the bedding 125 , the metal sheath 126 , and the jacket 127 of the transmission cable 120 in this first embodiment, respectively, and a detailed description thereof will be omitted.
- An outer diameter of the jacket 27 of the transmission cable 20 is equal to an outer diameter of the jacket 127 of the transmission cable 120 . Because the transmission cable 20 includes the shield 30 between the bedding 25 and the metal sheath 26 , the conductor 21 has a size smaller than that of the conductor 121 of the transmission cable 120 .
- the shield 30 is formed by a metal wire member, and is held at the ground potential (reference potential) together with the metal sheath 26 .
- the metal wire member has a configuration in which a large number of conductors having a diameter on the order of approximately 1 mm to 2 mm are wound around the bedding 25 .
- the shield 30 is provided to achieve electrostatic shielding and electromagnetic induction shielding, and to ensure a path for the fault current to flow.
- the OF cable 40 illustrated in FIG. 4B for the POF cable includes a conductor 41 , a conductor screen 42 , an insulating layer 43 , an insulating screen 44 , and a bedding 45 .
- the conductor 41 , the conductor screen 42 , the insulating layer 43 , the insulating screen 44 , and the bedding 45 of the OF cable 40 correspond to the conductor 121 , the conductor screen 122 , the insulating layer 123 , the insulating screen 124 , and the bedding 125 of the transmission cable 120 in this first embodiment, respectively, and a detailed description thereof will be omitted.
- the conductor screen 42 , the insulating layer 43 , the insulating screen 44 , and the bedding 45 are made of paper.
- the OF cable 40 is provided within a steel pipe, and an insulating oil is provided within the steel pipe, so that the steel pipe functions as the metal sheath 126 and the jacket 127 of the transmission cable 120 of this first embodiment.
- the metal sheath 126 provides a sufficient electrostatic shielding property
- the metal sheath 126 and the return cable 130 provide a sufficient electromagnetic induction shielding property.
- the steel pipe 110 can be reused when making repairs, for example.
- the transmission cables 120 R, 120 Y and 120 B, and the return cable 130 may be inserted inside the steel pipe 110 , instead of using a configuration in which a bundle of three (3) transmission cables 20 are included.
- the transmission cable 120 in this case has an outer diameter equal to that of the transmission cable 20 , however, the transmission cable 120 includes no shield 30 . For this reason, the diameter of the conductor 121 in the transmission cable 120 can be made larger than that of the conductor 21 in the transmission cable 20 , to thereby improve the transmission capacity.
- the existing power cable is the POF cable
- the power cable 100 having a high adaptability to the environment without using insulating oil.
- High adaptability to the environment means that it is environmentally-friendly or ecological.
- FIG. 5 is a diagram illustrating the state in which a plurality of power cables 100 A, 100 B and 100 C in the first embodiment are connected via manholes 50 A, 50 B and 50 C.
- FIG. 5 illustrates the plurality of power cables 100 A, 100 B and 100 C which are identical to the power cable 100 described above. For this reason, when not distinguishing the power cables 100 A, 100 B and 100 C, these power cables 100 A, 100 B and 100 C may also be referred to as “power cables 100 ” in the following description.
- FIG. 5 only the steel pipe 110 , the conductor 121 and the metal sheath 126 of the transmission cables 120 R, 120 Y and 120 B, and the return cable 130 of the power cable 100 are illustrated.
- the conductors 121 and the metal sheaths 126 of the transmission cables 120 R, 120 Y and 120 B are respectively represented as conductors 121 R, 121 Y and 121 B and metal sheaths 126 R, 126 Y and 126 B, respectively.
- these conductors 121 R, 121 Y and 121 B and these metal sheaths 126 R, 126 Y and 126 B may also be referred to as “conductors 121 ” and “metal sheaths 126 ”, respectively, in the following description.
- the vaults 50 A, 50 B and 50 C have the same configuration, and thus, when not distinguishing the vaults 50 A, 50 B and 50 C, these vaults 50 A, 50 B and 50 C may also be referred to as “vaults 50 ” in the following description.
- the vault 50 includes a housing 51 , joints 52 R, 52 Y and 52 B, cables 54 , 54 A, 55 R, 55 Y, 55 B, 56 R, 56 Y and 56 B, and a link box 53 as a connecting location, for example.
- the housing 51 is formed by a concrete, for example, and accommodates connecting parts of the mutually adjacent power cables 100 that are to be connected.
- the connecting parts include the joints 52 R, 52 Y and 52 B, the link box 53 , and the cables 54 , 54 A, 55 R, 55 Y, 55 B, 56 R, 56 Y and 56 B.
- the joint 52 R includes a connecting part 57 A, an insulating part 57 B, and a connecting part 57 C.
- the joints 52 Y and 52 B have configurations similar to that of the joint 52 R.
- the connecting parts 57 A and 57 C are formed by a metal connecting member, respectively, and connect the conductors 121 R of the mutually adjacent power cables 100 A and 100 B, but do not connect the metal sheaths 126 of the mutually adjacent power cables 100 A and 100 B.
- the metal sheaths 126 of the mutually adjacent power cables 100 A and 100 B are insulated by the insulating part 58 B inside the joint 52 R.
- the cable 55 R is connected to the connecting part 57 A of the joint 52 R, and the cable 56 R is connected to the connecting part 57 C of the joint 52 R.
- the cables 55 R and 56 R are connected via a connecting part 53 A of the link box 53 .
- the connecting part 53 A of the link box 53 is grounded, and the metal sheath 126 is held at the ground potential via the connecting part 53 A of the link box 53 .
- the joints 52 Y and 52 B have a configuration similar to that of the joint 52 R. Hence, constituent elements of the joints 52 Y and 52 B are designated by the same reference numerals as the constituent elements of the joint 52 R, except that the subscript “R” is replaced by “Y” and “B”, respectively.
- the link box 53 includes the connecting part 53 A that is held at the ground potential.
- the connecting part 53 A connects the cables 55 R, 55 Y and 55 B to the cables 56 R, 56 Y and 56 B, respectively, and also hold the cables 55 R, 55 Y and 55 B and the cables 56 R, 56 Y and 56 B to the ground potential.
- the cable 54 A that branches from the cable 54 is also connected to the connecting part 53 A, and the connecting part 53 A holds the steel pipe 110 and the return cable 130 to the ground potential.
- the cable 54 connects the steel pipes 110 of the mutually adjacent power cables 100 A and 100 B.
- the return cable 130 is also connected to the cable 54 .
- the cable 54 also connects the return cables 130 of the mutually adjacent power cables 100 A and 100 B.
- the cable 54 A branches from an intermediate part of the cable 54 , and the cable 54 A is connected to the connecting part 53 A of the link box 53 . Because the connecting part 53 A of the link box 53 is held at the ground potential, the steel pipe 110 and the return cable 130 are held at the ground potential via the connecting part 53 A of the link box 53 .
- the cable 55 R connects the connecting part 57 A of the joint 52 R and the connecting part 53 A of the link box 53 .
- the cable 56 R connects the connecting part 57 C of the joint 52 R and the connecting part 53 A of the link box 53 .
- the cables 55 R and 56 R are mutually connected via the connecting part 53 A, and are held at the ground potential.
- the cables 55 Y and 56 Y and the cables 55 B and 56 B have configurations similar to those of the cables 55 R and 56 R.
- constituent elements of the cables 55 Y and 56 Y and the cables 55 B and 56 B are designated by the same reference numerals as the constituent elements of the cables 55 R and 56 R, except that the subscript “R” is replaced by “Y” and “B”, respectively.
- the connecting relationship of the mutually adjacent power cables 100 B and 100 C is similar to that of the mutually adjacent power cables 100 A and 100 B described above, and the mutually adjacent power cables 100 B and 100 C are similarly connected via the vault 50 .
- the fault current generated in the transmission cable 120 R flows to the steel pipe 110 via the metal sheath 126 R or the return cable 130 of the power cable 100 A, and flows through the cable 54 as indicated by an arrow A. Further, a part of the fault current flows to the steel pipe 110 and the return cable 130 of the power cable 100 B via the cable 54 as indicated by an arrow B, and the remaining part of the fault current flows to the connecting part 53 A via the cable 54 A.
- the current flowing to the connecting part 53 A flows to the metal sheaths 126 R, 126 Y and 126 B of the power cable 100 B, via the cables 56 R, 56 Y and 56 B.
- the fault current generated by the insulator breakdown in the transmission cable 120 R of the power cable 100 A flows through the steel pipe 110 of the power cable 100 A, and branches to the steel pipe 110 , the metal sheaths 126 R, 126 Y and 126 B, and the return cable 130 of the power cable 100 B, via the cables 54 , 54 A, 56 R, 56 Y and 56 B.
- the steel pipe 110 , the metal sheaths 126 ( 126 R, 126 Y and 126 B), and the return cable 130 of the power cable 100 provide a path with a sufficient capacity for the fault current to flow.
- FIG. 6 is a cross sectional view illustrating an example of a power cable 200 in a second embodiment.
- the cross section of the power cable 200 illustrated in FIG. 6 corresponds to the cross section of the power cable 100 illustrated in FIG. 1B .
- the power cable 200 illustrated in FIG. 6 includes a steel pipe 110 , transmission cables 120 R, 120 Y and 120 B, a return cable 130 , and three pipes 241 , 242 and 243 .
- the power cable 200 has a configuration in which the pipes 241 , 242 and 243 are additionally provided with respect to the power cable 100 in the first embodiment.
- Parts other than the pipes 241 , 242 and 243 of the power cable 200 are the same as those corresponding parts of the power cable 100 in the first embodiment, and a description thereof will be omitted by designating the same parts by the same reference numerals.
- the pipe 241 is arranged between the transmission cables 120 Y and 120 B
- the pipe 242 is arranged between the transmission cables 120 B and 120 R
- the pipe 243 is arranged between the transmission cables 120 R and 120 Y.
- the pipes 241 , 242 and 243 are twisted along the longitudinal directions of the transmission cables 120 R, 120 Y and 120 B, in a manner similar to the transmission cables 120 R, 120 Y and 120 B.
- the pipe 241 is twisted along the longitudinal directions of the transmission cables 120 Y and 120 B along the outer peripheries of the transmission cables 120 Y and 120 B.
- the pipe 242 is twisted along the longitudinal directions of the transmission cables 120 B and 120 R along the outer peripheries of the transmission cables 120 B and 120 R.
- the pipe 243 is twisted along the longitudinal directions of the transmission cables 120 R and 120 Y along the outer peripheries of the transmission cables 120 R and 120 Y.
- the pipes 241 , 242 and 243 are arranged in a triplex formation around the return cable 130 located at their center, and are twisted around the transmission cables 120 R, 120 Y and 120 B that are also arranged in the triplex formation and twisted.
- the pipes 241 , 242 and 243 maintain the three-fold symmetry in the cross sectional view by the triplex formation around the return cable 130 located at their center, and are twisted around the return table 130 .
- the pipes 241 , 242 and 243 are examples of a second conductor, and are connected to the reference potential node.
- the pipes 241 , 242 and 243 are grounded, for example, and are held at the ground potential.
- the pipes 241 , 242 and 243 are held at the reference potential in order to provide a path for the fault current to flow by the pipes 241 , 242 and 243 in a case in which the fault current is generated in the transmission cable 120 due to ground-fault or the like.
- the pipes 241 , 242 and 243 have the same configuration. Outer peripheries of pipe parts 241 A, 242 A and 243 A of the pipes 241 , 242 and 243 are covered by jackets 241 B, 242 B and 243 B, respectively.
- the pipe parts 241 A, 242 A and 243 A are hollow along the longitudinal directions thereof, and are made of aluminum, for example, in this second embodiment.
- the pipe parts 241 A, 242 A and 243 A may be formed by metal pipes other than aluminum pipes.
- the jackets 241 B, 242 B and 243 B are insulating layers covering the peripheries of the pipe parts 241 A, 242 A and 243 A, respectively, and are made of polyethylene, for example.
- optic fibers 244 , 245 and 246 are inserted into the pipe parts 241 A, 242 A and 243 A, respectively.
- the optic fibers 244 , 245 and 246 may include optic fiber parts 244 A, 245 A and 246 A that are covered by plastic pipes 244 B, 245 B and 246 B, respectively.
- the optic fiber parts 244 A, 245 A and 246 A may be formed by air-blown fibers
- the plastic pipes 244 B, 245 B and 246 B may be formed by pipes designed for the air-blown fibers.
- the pipes 241 , 242 and 243 can be used as a path for the fault current to flow, and also as an information communication network using the optic fibers 244 , 245 and 246 .
- the pipes 241 , 242 and 243 are inserted inside the steel pipe 110 together with the transmission cables 120 R, 120 Y and 120 B, and the return cable 130 , the pipes 241 , 242 and 243 desirably have a diameter that is adjusted so that the pipes 241 , 242 and 243 do not protrude on the outer side of the transmission cables 120 R, 120 Y and 120 B along the radial direction relative to the center where the return cable 130 is located.
- the pipes 241 , 242 and 243 of the adjacent power cables 200 may be connected, or the plastic pipes 244 B, 245 B and 246 B may be inserted through the pipes 241 , 242 and 243 of the adjacent power cables 200 , in order to lay the optic fiber parts 244 A, 245 A and 246 A.
- the fault current flows from the steel pipe 110 of the power cable 200 in which the insulator breakdown occurs to the steel pipe 110 , the metal sheaths 126 , the return cables 130 , and the pipes 241 , 242 and 243 of an adjacent power cable 200 that is connected in series to the power cable 200 .
- the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 of the power cable 200 respectively need to have a ground-fault capacity to a certain extent.
- the ground-fault capacities are determined by amounts of current that can flow through the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 that may form the path for the fault current to flow.
- the fault current may still flow through the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 that may form the path for the fault current to flow.
- the fault current flows through the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 of an adjacent power cable 200 .
- the ground-fault capacities are evaluated based on amounts of current that can flow through the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 of the adjacent power cable 200 that is adjacent to the power cable 200 in which the insulator breakdown occurs but the metal sheath 126 , the return cable 130 , or the pipes 241 , 242 and 243 of the power cable 200 do not melt.
- FIG. 7 is a diagram for explaining the ground-fault capacity of the power cable 200 in the second embodiment.
- the current value in FIG. 7 is represented by kA (kilo-Amperes), and FIG. 7 uses the same designations as those used in FIG. 3 .
- the ground-fault capacities of the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 that are used are computed under a precondition that the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 have predetermined cross sectional areas and that the current flows for 0.25 second.
- the ground-fault capacities of the steel pipe 110 , the metal sheath 126 , and the return cable 130 are 60 kA, 15.6 kA, and 15.3 kA, respectively, which are the same as those illustrated in FIG. 3 for the first embodiment.
- the computed ground-fault capacities of the pipes 241 , 242 and 243 are all 20 kA.
- the steel pipe 110 , the metal sheath 126 , the return cable 130 , and the pipes 241 , 242 and 243 can allow currents amounting to 60 kA, 15.6 kA, 15.3 kA, and 20 kA to flow, respectively.
- a current of 60 kA flows through the transmission cables 120 R, 120 Y and 120 B for 0.25 second, and the fault current is generated in the transmission cable 120 R.
- the phase in which the fault current is generated may also be referred to as a “fault-phase”.
- the current flowing through the steel pipe 110 of the power cable 200 is 8.4 kA
- the current flowing through the fault-phase metal sheath 126 (R) is 10.4 kA
- the current flowing through each of the metal sheaths 126 (Y) and 126 (B) of phases other than the fault-phase is 4.4 kA
- the current flowing through the return cable 130 is 9.0 A.
- the currents flowing through the pipes 241 , 242 and 243 are 4.6 kA, 12.6 kA and 11.6 kA, respectively. It may be regarded that a distribution is generated in the amounts of current flowing through the pipes 241 , 242 and 243 due to the positional relationship of the pipes 241 , 242 and 243 with respect to the fault-phase.
- the currents flowing through the pipes 241 , 242 and 243 are considerably lower than the corresponding ground-fault capacities which are 20 kA.
- the amounts of current flowing through the steel pipe 110 , the metal sheaths 126 (R), 126 (Y) and 126 (B), the return cable 130 , and the pipes 241 , 242 and 243 , respectively, are the respective ground-fault capacities or less.
- the power cable 200 in this second embodiment can ensure a sufficient path for the fault current to flow.
- the power cable 200 that ensures a sufficient path for the fault current to flow, by including the transmission cables 120 R, 120 Y and 120 B having the triplex formation, and the pipes 241 , 242 and 243 having the triplex formation.
- the transmission cables 120 R, 120 Y and 120 B, and the pipes 241 , 242 and 243 are respectively twisted around the periphery of the return cable 130 along the longitudinal direction of the return cable 130 by the triplex formations thereof, with the return cable 130 arranged at the center of the transmission cables 120 R, 120 Y and 120 B and the pipes 241 , 242 and 243 .
- the pipes 241 , 242 and 243 can be used as the information communication network through the optic fibers 244 , 245 and 246 .
- the insides of the pipes 241 , 242 and 243 may be maintained in the hollow state, without arranging the optic fibers 244 , 245 and 246 (including the optic fiber parts 244 A, 245 A and 246 A, and the plastic pipes 244 B, 245 B and 246 B) inside the pipes 241 , 242 and 243 , respectively.
- the optic fibers 244 , 245 and 246 may be utilized to form a fiber-optic DTS (Distributed Temperature Sensing) system, such as OPTHERMO (registered trademark).
- the fiber-optic DTS system can measure the temperature distribution along the optic fibers for several tens of kilometers in real-time, for example, using the optic fibers 244 , 245 and 246 themselves as temperature sensors.
- the flow passage for the insulating oil of the adjacent POF cable can be formed by flowing the insulating oil inside the pipe parts 241 A, 242 A and 243 A, as will be described later in conjunction with FIGS. 9A and 9B .
- the transmission cable 120 can be cooled by flowing a cooling liquid (for example, water) inside the pipes 241 , 242 and 243 .
- a cooling liquid for example, water
- each of the pipes 241 , 242 and 243 may function to provide a path or passage for the composite optic fiber, cooling, and oil.
- FIG. 8 is a diagram illustrating the state in which a plurality of power cables 200 A, 200 B and 200 C in the second embodiment are connected via vaults 250 A, 250 B and 250 C.
- FIG. 8 illustrates the plurality of power cables 200 A, 200 B and 200 C which are identical to the power cable 200 described above. For this reason, when not distinguishing the power cables 200 A, 200 B and 200 C, these power cables 200 A, 200 B and 200 C may also be referred to as “power cables 200 ” in the following description.
- FIG. 8 only the steel pipe 110 , the conductor 121 and the metal sheath 126 of the transmission cables 120 R, 120 Y and 120 B, the return cable 130 , and the pipes 241 , 242 and 243 of the power cable 200 are illustrated.
- the conductors 121 and the metal sheaths 126 of the transmission cables 120 R, 120 Y and 120 B are respectively represented as conductors 121 R, 121 Y and 121 B and metal sheaths 126 R, 126 Y and 126 B, respectively.
- the vaults 250 A, 250 B and 250 C have the same configuration, and thus, when not distinguishing the vaults 250 A, 250 B and 250 C, these vaults 250 A, 250 B and 250 C may also be referred to as “vaults 250 ” in the following description.
- the vault 250 has the same configuration as the vault 50 in the first embodiment illustrated in FIG. 5 , except that the joints 52 R, 52 Y and 52 B are replaced by joints 252 R, 252 Y and 252 B, respectively. Since other parts of the vault 250 are the same as the corresponding parts of the vault 50 , those parts in FIG. 8 that are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.
- the joints 252 R, 252 Y and 252 B have the same configuration, and thus, a description will be given only with respect to the configuration of the joint 252 R.
- the joint 252 R includes a connecting part 57 A, an insulating part 57 B, a connecting part 57 C, and projecting parts 58 A and 58 B.
- the connecting parts 57 A and 57 C, and the insulating part 57 B have the same configurations as those of the joint 52 R.
- the projecting parts 58 A and 58 B are provided on the connecting parts 57 A and 57 C, respectively.
- the projecting parts 58 A and 58 B project to the outer side of the connecting parts 57 A and 57 C, respectively, and are made of a metal, similarly to the connecting parts 57 A and 57 C.
- the pipe 241 of the power cable 200 A is connected to the connecting part 57 A, and the pipe 241 of the power cable 200 B is connected to the connecting part 57 C. Hence, the pipe 241 is held at the ground potential.
- the connections at the joints 252 Y and 252 B are similar to that at the joint 252 R.
- the joint 252 Y connects the pipe 241 of the power cable 200 A and the pipe 241 of the power cable 200 B.
- the joint 252 B connects the pipe 241 of the power cable 200 A and the pipe 241 of the power cable 200 B.
- the connecting relationship of the mutually adjacent power cables 200 B and 200 C is similar to that of the mutually adjacent power cables 200 A and 200 B described above, and the mutually adjacent power cables 200 B and 200 C are similarly connected via the vault 250 .
- the fault current generated in the transmission cable 120 R flows to the steel pipe 110 via the metal sheath 126 R, the return cable 130 , or the pipes 241 , 242 and 243 of the power cable 200 A, and flows through the cable 54 as indicated by an arrow A. Further, a part of the fault current flows to the steel pipe 110 and the return cable 130 of the power cable 200 B via the cable 54 as indicated by an arrow B, and the remaining part of the fault current flows to the connecting part 53 A via the cable 54 A.
- the current flowing to the connecting part 53 A flows to the metal sheaths 126 R, 126 Y and 126 B and the pipes 241 , 242 and 243 of the power cable 200 B, via the cables 56 R, 56 Y and 56 B.
- the fault current generated by the insulator breakdown in the transmission cable 120 R of the power cable 200 A flows through the steel pipe 110 of the power cable 200 A, and branches to the steel pipe 110 , the metal sheaths 126 R, 126 Y and 126 B, the return cable 130 , and the pipes 241 , 242 and 243 of the power cable 200 B, via the cables 54 , 54 A, 55 R, 55 Y, 55 B, 56 R, 56 Y and 56 B.
- the steel pipe 110 , the metal sheaths 126 ( 126 R, 126 Y and 126 B), the return cable 130 , and the pipes 241 , 242 and 243 of the power cable 200 provide a path with a sufficient capacity for the fault current to flow.
- the capacity of the path for the fault current to flow in the power cable 200 in this second embodiment can be increased by approximately 50%.
- pipes 241 , 242 and 243 are used in this second embodiment, it is possible to use conductors or wires in place of the pipes 241 , 242 and 243 . In addition, only one or two of the pipes 241 , 242 and 243 may be provided.
- FIGS. 9A and 9B are diagrams for explaining a state in which the existing POF cables are replaced by the power cables 200 A and 200 B in the second embodiment.
- FIGS. 9A and 9B illustrate only one transmission cable 120 and one pipe 241 and the steel pipe 110 with respect to the power cables 200 A and 200 B.
- each of POF cables 70 A, 70 B, 70 C and 70 D include three (3) OF cables 40 inserted into the steel pipe 110 thereof, and that the insulating oil is provided inside this steel pipe 110 .
- the OF cable 40 is the OF cable 40 in the comparison example illustrated in FIG. 4B .
- FIGS. 9A and 9B illustrate only the steel pipe 110 and one OF cable 40 with respect to each of the POF cables 70 A, 70 B, 70 C and 70 D.
- the POF cable may function as an oil line
- the steel pipe 110 thereof may be treated as an oil line.
- the transmission cables 120 of the power cables 200 A and 200 B are connected between the OF cable 40 of the POF cable 70 A and the OF cable 40 of the POF cable 70 B, via joints 80 A and 80 B.
- the OF cables 40 of the POF cables 70 C and 70 D are connected on the right side of the OF cable 40 of the POF cable 70 B, via joints 80 D and 80 E.
- the transmission cables 120 of the power cables 200 A and 200 B are connected via a joint 80 B.
- the steel pipe 110 of the POF cable 70 A, the pipes 241 of the power cables 200 A and 200 B, and the steel pipes 110 of the POF cables 70 B, 70 C and 70 D are connected via joints 72 .
- the pipe parts 241 A of the pipe 241 is connected to the steel pipe 110 .
- there are three (3) pipes 241 , 242 and 243 and thus, there are three (3) pipe parts 241 A, 242 A and 243 A.
- the three (3) pipe parts 241 A, 242 A and 243 A are actually merged at the joint 72 and connected to the steel pipe 110 .
- a part of the joint 80 A may be formed by one joint 72
- a part of the joint 80 C may be formed by another joint 72 .
- a terminating part 90 A is connected on the left side of the POF cable 70 A, and a terminating part 90 B is connected on the right side of the POF cable 70 D.
- An oil supply device 90 E is connected to the steel pipe 110 of the POF cable 70 A, and an oil supply device 90 F is connected to the steel pipe 110 of the POF cable 70 D.
- the joint 80 B is a connecting part similar to the vaults 250 A through 250 C illustrated in FIG. 8 .
- the terminating parts 90 A and 90 B are connected to a supply source or a supply destination of the power.
- the terminating parts 90 A and 90 B are also connected to the oil supply device, in order to manage and adjust the pressure of the insulating oil and the like inside the POF cables 70 A through 70 D.
- the replacement by the power cables 200 A and 200 B, and the provision of the flow passage for the insulating oil between the POF cables 70 A and 70 B can be achieved simultaneously, by connecting the pipes 241 of the power cables 200 A and 200 B to the steel pipes 110 of the POF cables 70 A and 70 B.
- the POF cable 70 A, the joint 80 A, the power cable 200 A, the joint 80 B, the power cable 200 B, the joint 80 C, and a power cable 270 E are connected to the terminating part 90 A.
- the power cable 270 E is a dry type power cable that does not use insulating oil.
- the power cable 270 E is an example of a line or path that is set up at a location where no steel pipe 110 is provided, or at a location where the line or path is not provided inside the steel pipe 110 .
- An oil line 90 C branches from the joint 80 C, and connects to an existing oil supply device 90 D, for example.
- FIG. 8B illustrates a case in which the connection of the plurality of POF cables, the oil supply device 90 D, and the power cable 270 E that are connected on the right side of the POF cable 70 A in a power transmission system before the replacement is modified, by replacing the POF cables other than the POF cable 70 A by the power cables 200 A and 200 B, and reconnecting the modified power transmission system to the existing oil supply device 90 D.
- the power is transmitted between the terminating part 90 A and the power cable 270 E.
- the oil supply device 90 D manages and adjusts the pressure and the like of the insulating oil in the steel pipe 110 of the POF cable 70 A, via the pipes 241 of the power cables 200 A and 200 B and the oil line 90 C.
- the pipes 241 , 242 and 243 can be utilized as the flow path for the insulating oil, and can be used to replace a part of the existing POF cable.
- the power cable can provide a sufficient path for the fault current.
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Abstract
A power cable includes a steel pipe coupled to a reference potential node, three transmission cables within the steel pipe and respectively including a conductor to transmit three-phase alternating current power, and a return cable within the steel pipe and coupled to the reference potential node. Each of the three transmission cables includes a first insulating layer covering the conductor, a metal layer covering the first insulating layer, and a second insulating layer covering the metal layer. The three transmission cables are twisted around a periphery of the return cable along a longitudinal direction of the return cable, and the metal layer is coupled to the reference potential node.
Description
- This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2014-008452 filed on Jan. 21, 2014, the entire contents of which are incorporated herein by reference.
- 1. Field of the Invention
- The present invention relates to a power cable.
- 2. Description of the Related Art
- An example of a conventional large-capacity power cable may include three (3) transmission cables that are arranged so that center axes thereof in a cross sectional view substantially correspond to three (3) vertexes of an equilateral triangle, where each transmission cable has a semiconductive layer at an outermost layer portion without providing a metal layer on an outer periphery of an insulator. A return path conductor forming a return path for a fault current may be arranged at a center of the equilateral triangle, to be surrounded by the three (3) transmission cables, in order to electrically connect the conductor to the semiconductive layer of the transmission cables. An example of such a conventional large-capacity power cable is proposed in Japanese Laid-Open Patent Publication No. 2007-180742.
- In the conventional power cable, the return path conductor forming the return path for the fault current is the only conductor through which the fault current may flow. For this reason, when the fault current is large to a certain extent, a current exceeding a ground-fault capacity of the power cable or the return path conductor may flow and damage the power cable.
- Embodiments of the present invention can provide a power cable that can provide a sufficient path for the fault current.
- According to one aspect of the present invention, a power cable may include a first steel pipe coupled to a reference potential node; three first transmission cables, inserted inside the first steel pipe, and respectively including a first conductor to transmit three-phase alternating current power; and a return cable inserted inside the first steel pipe and coupled to the reference potential node, wherein each of the three first transmission cables includes a first insulating layer covering the first conductor, a metal layer covering the first insulating layer, and a second insulating layer covering the metal layer, wherein the three first transmission cables are twisted around a periphery of the return cable along a longitudinal direction of the return cable, and wherein the metal layer is coupled to the reference potential node.
- Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
-
FIGS. 1A and 1B are diagrams for explaining an example of a power cable in a first embodiment; -
FIGS. 2A and 2B are diagrams for explaining a transmission cable of the power cable in the first embodiment; -
FIG. 3 is a diagram for explaining a ground-fault capacity of the power cable in the first embodiment; -
FIGS. 4A and 4B are cross sectional views for explaining a transmission cable and an OF (Oil Filled) cable in a comparison example; -
FIG. 5 is a diagram illustrating a state in which a plurality of power cables in the first embodiment are connected via vaults; -
FIG. 6 is a cross sectional view illustrating an example of the power cable in a second embodiment; -
FIG. 7 is a diagram for explaining the ground-fault capacity of the power cable in the second embodiment; -
FIG. 8 is a diagram illustrating in which a plurality of power cables in the second embodiment are connected via vaults; and -
FIGS. 9A and 9B are diagrams for explaining a state in which existing POF (Pipe type Oil Filled) cables are replaced by the power cables in the second embodiment. - A description will be given of the power cable in embodiments of the present invention, by referring to the drawings.
-
FIGS. 1A and 1B are diagrams for explaining an example of apower cable 100 in a first embodiment.FIG. 1A illustrates a perspective view ofpower cable 100, andFIG. 1B illustrates a cross sectional view of thepower cable 100. The perspective view illustrated inFIG. 1A illustrates a state of thepower cable 100 that is cut along a plane perpendicular to a longitudinal direction of thepower cable 100. - The
power cable 100 includes asteel pipe 110,transmission cables return cable 130. - The
steel pipe 110 is be formed by a pipe made of iron, for example. Thetransmission cables return cable 130 are inserted inside thesteel pipe 110. Thesteel pipe 110 is an example of a first steel pipe, and is connected to a reference potential node. In this first embodiment, thesteel pipe 110 is grounded and held at a ground potential. Thesteel pipe 110 is held at the reference potential, in order to use thesteel pipe 110 as a return path for a fault current in a case in which the fault current caused by ground fault or the like flows through thetransmission cables - The
steel pipe 110 may be a new, unused steel pipe, or an old, used steel pipe. For example, when replacing an existing power cable by thepower cable 100 in this first embodiment, the steel pipe of the existing power cable may be reused as thesteel pipe 110 of thepower cable 100. - More particularly, the steel pipe of the existing POF (Pipe type Oil Filled) cable, HPFF (High Pressure Fluid Filled) cable, or HPGH (High Pressure Gas Filled) cable, for example, after removing the transmission cables and an insulating oil therefrom and cleaning, may be reused as the
steel pipe 110. In this first embodiment, it is assumed for the sake of convenience that the steel pipe of the existing POF cable is reused as thesteel pipe 110. An inner diameter of thesteel pipe 110 may be in a range of 100 mm to 254 mm, for example, and may be 206 mm, for example. Alternatively, the inner diameter of thesteel pipe 110 may be in a range of 6 inches to 10 inches, for example, and may be 8 inches, for example. - In the cross sectional view illustrated in
FIG. 1B , thetransmission cables return cable 130 is arranged at a center of the equilateral triangle, to be surrounded by thetransmission cables transmission cables return cable 130 are inserted into thesteel pipe 110 in a state in which thetransmission cables return cable 130 along the longitudinal direction of thereturn cable 130. Thetransmission cables transmission cables - For example, the
transmission cables transmission cables transmission cables transmission cables transmission cables 120” in the following description. The detailed configuration of thetransmission cable 120 will be described later in conjunction withFIGS. 2A and 2B . - The
return cable 130 includes aconductor 131, and ajacket 132 covering the periphery of theconductor 131. Theconductor 131 is made of a metal, and for example, copper may be used as the metal. Thejacket 132 is formed by an insulating layer covering the periphery of theconductor 131, and made of a material such as an XLPE (Cross Linked Polyethylene), PVC (Poly-Vinyl Chloride), and the like. - The
conductor 131 of thereturn cable 130 is connected to the reference potential node, similarly to thesteel pipe 110. In this first embodiment, theconductor 131 of thereturn cable 130 is grounded and held at the ground potential. Theconductor 131 of thereturn cable 130 is held at the reference potential, in order to use thereturn cable 130 as a return path for a fault current in a case in which the fault current caused by ground fault or the like flows through thetransmission cables 120. - Next, a description will be given of the detailed configuration of the
transmission cable 120, by referring toFIGS. 2A and 2B . -
FIGS. 2A and 2B are diagrams for explaining thetransmission cable 120 of thepower cable 100 in the first embodiment.FIG. 2A illustrates a cross sectional view of thetransmission cable 120, andFIG. 2B illustrates a perspective view of a triplex formation. - As illustrated in
FIG. 2A , thetransmission cable 120 includes aconductor 121, aconductor screen 122, an insulatinglayer 123, an insulatingscreen 124, abedding 125, ametal sheath 126, and ajacket 127. In this example, theconductor screen 122, theinsulator layer 123, the insulatingscreen 124, thebedding 125, themetal sheath 126, and thejacket 127 respectively have a hollow cylindrical shape covering, one by one, theconductor 121 having the solid cylindrical shape (that is, formed by a stranded wire). - The
conductor 121 is made of a metal, and for example, copper may be used as the metal. Theconductor 121 is an example of a first conductor. - The
conductor screen 122 is formed by a semiconductive tape having heat resistance, and a resin layer including carbon powder, and is wound around the periphery of theconductor 121. For example, nylon or polyester may be used as the semiconductive tape having heat resistance, and for example, EEA (Ethylene-Ethylacrylate Copolymer) resin may be used as the resin layer including carbon powder. - The insulating
layer 123 is provided to insulate theconductor 121. The insulatinglayer 123 may be formed by injection molding using XLPE (Crosslinked Poly-Ethylene), for example. In this example, it is assumed that XLPE is used for the insulatinglayer 123, however, a material other than XLPE may be used for the insulatinglayer 123 as long as the material is insulative and heat resistant. - The insulating
screen 124 is formed by a resin layer including carbon powder, and is wound around the periphery of the insulatinglayer 123. For example, EEA resin may be used as the resin layer including carbon powder. - The
bedding 125 is the so-called bedding tape, and is wound around the insulatingscreen 124. - The
metal sheath 126 is formed by a metal tape that covers the periphery of thebedding 125 along a longitudinal direction of thetransmission cable 120. An adhesive layer on this metal tape is bonded to thejacket 127. For example, copper laminated tape may be used as themetal sheath 126. Themetal sheath 126 is an example of a metal layer, and is also an example of a metal wrap. - The
metal sheath 126 is provided to achieve electrostatic shielding and electromagnetic induction shielding, and to ensure a path for the fault current to flow. - The electrostatic shielding covers the periphery of the
conductor 121 by a metal member in order to suppress a high voltage from being induced on the ground side due to the electrostatic capacitance between theconductor 121 and the ground, in a case in which a high voltage is applied to theconductor 121. - The electromagnetic induction shielding covers the periphery of the
conductor 121 by a metal member in order to suppress formation of a magnetic field caused by electromagnetic induction that is generated by a closed loop created by theconductor 121 and the ground, in a case in which the fault current is generated. - The
metal sheath 126 covers the outer periphery of theconductor 121 via theconductor screen 122, the insulatinglayer 123, the insulatingscreen 124, and thebedding 125. Hence, the magnetic field generated due to a current flowing through theconductor 121 is canceled by the current induced by themetal sheath 126. - In addition, the
metal sheath 126 is connected to the reference potential node, similarly to thesteel pipe 110 and thereturn cable 130 as described above in conjunction withFIGS. 1A and 1B . In this first embodiment, themetal sheath 126 is grounded and is held at the ground potential, for example. Because themetal sheath 126 is held at the reference potential, themetal sheath 126 can function as a path for a fault current to flow in a case in which the fault current caused by ground fault or the like flows through thetransmission cables 120. - The
jacket 127 is formed by an insulating layer covering the periphery of themetal sheath 126, for example, polyethylene may be used for the insulating layer. An outer peripheral surface of thejacket 127 can be distinguished amongst thetransmission cables - The
transmission cables FIGS. 1A and 1B are twisted around the center, returncable 130 along the longitudinal direction of thepower cable 100, as illustrated inFIG. 2B . The twisted configuration of the three (3)transmission cables - According to the triplex formation of the
transmission cables transmission cables cable 130, while maintaining rotational symmetry of order three (3), that is, three-fold symmetry, in the cross sectional view illustrated inFIG. 1B . The triplex formation has small expansion and contraction along the longitudinal direction of thetransmission cables power cable 100, and enables easy fixing within a vault (or manhole) as will be described later. The positional relationship of thetransmission cables transmission cables transmission cables return cable 130. - In this first embodiment, in a state in which the
transmission cables return cable 130, thetransmission cables return cable 130 are arranged inside thesteel pipe 110 as illustrated inFIGS. 1A and 1B . - The
power cable 100 described above in this first embodiment transmits three-phase A.C. power by thetransmission cables FIGS. 1A and 1B . For example, a rated capacity of thepower cable 100 is 250 MVA (138 kV, 1045 A). However, this rated capacity is merely an example, and the rated capacity may vary depending on laying conditions, such as the temperature and a burying depth ofsteel pipe 110. - For example, the
power cable 100 has a length of 487.68 m (1600 feet), and a plurality ofsuch power cables 100 are connected in series upon use. In this case, thetransmission cables power cable 100 are connected to the correspondingtransmission cables power cable 100 so that the color phases match. Connecting thetransmission cables power cable 100 to the correspondingtransmission cables power cable 100 so that the color phases match means that theconductors 121 of thetransmission cables 120R are connected, theconductors 121 of thetransmission cables 120Y are connected, and theconductors 121 of thetransmission cables 120B are connected, between twoadjacent power cables 100 that are connected in series. In this case, with regard to themetal sheaths 126 of thetransmission cables adjacent power cables 100 that are connected in series, themetal sheaths 126 of the same color phase may be connected, or themetal sheath 126 may be grounded at eachpower cable 100. - In addition, the
power cable 100 may be used as a new replacement power cable when replacing a part of a plurality of existing power cables that are connected in series. For example, thepower cable 100 may be used to replace one of the plurality of existing power cables that are connected in series. In this case, when the existing power cable to be removed has a steel pipe similar to thesteel pipe 110 and thetransmission cables return cable 130 can be inserted into this steel pipe, this steel pipe of the existing power cable to be removed may be used as thesteel pipe 110. - In the above described case, the
conductors 121 of thetransmission cables power cable 100 may be connected to the conductors of the corresponding transmission cables of the existing power cables at both ends of thepower cable 100 so that the color phases match. Further, themetal sheaths 126 of thetransmission cables - Next, consideration will be given of ground-fault capacities of the
steel pipe 110 of thepower cable 100, themetal sheaths 126 of thetransmission cables return cable 130. When an insulator breakdown occurs in thetransmission cables power cable 100, themetal sheath 126 or thereturn cable 130 included in thetransmission cable 120 in which the insulator breakdown occurs may melt, and a fault current may flow through thesteel pipe 110. - In such a case, the fault current flows from the
steel pipe 110 of thepower cable 100 in which the insulator breakdown occurs to thesteel pipe 110, themetal sheaths 126 and thereturn cables 130 of anadjacent power cable 100 that is connected in series to thepower cable 100. - Accordingly, the
steel pipe 110, themetal sheath 126, and thereturn cable 130 of thepower cable 100 respectively need to have a ground-fault capacity to a certain extent at least greater than or equal to a fault current dividing ratio. The ground-fault capacities are determined by amounts of current that can flow through thesteel pipe 110, themetal sheath 126, and thereturn cable 130 that may form the path for the fault current to flow. - In the case of a
power cable 100 in which the insulator breakdown occurs but themetal sheath 126 or thereturn cable 130 of thepower cable 100 does not melt, the fault current may still flow through thesteel pipe 110, themetal sheath 126, and thereturn cable 130 that may form the path for the fault current to flow. - However, even in such a case, the fault current flows through the
steel pipe 110, themetal sheath 126, and thereturn cable 130 of anadjacent power cable 100. Hence, the ground-fault capacities are evaluated based on amounts of current that can flow through thesteel pipe 110, themetal sheath 126, and thereturn cable 130 of theadjacent power cable 100 that is adjacent to thepower cable 100 in which the insulator breakdown occurs but themetal sheath 126 or thereturn cable 130 of thepower cable 100 does not melt. -
FIG. 3 is a diagram for explaining the ground-fault capacity of thepower cable 100 in the first embodiment. InFIG. 3 , a comparison example of the power cable is also considered, in which thereturn cable 130 is omitted from thepower cable 100 in this first embodiment. In the following, the amount of current flowing through thepower cable 100 in this first embodiment and the amount of current flowing through the power cable in the comparison example are compared to the respective ground-fault capacities. The current value inFIG. 3 is represented by kA (kilo-Amperes). - For example, the ground-fault capacities of the
steel pipe 110, themetal sheath 126, and thereturn cable 130 that are used are computed under a precondition that thesteel pipe 110, themetal sheath 126, and thereturn cable 130 have predetermined cross sectional areas and that the current flows for 0.25 second. - The ground-fault capacities of the
steel pipe 110, themetal sheath 126, and thereturn cable 130 are 60 kA, 15.6 kA, and 15.3 kA, respectively. The computed ground-fault capacity of thesteel pipe 110 is 60 kA or greater, however, it is assumed for the sake of convenience that the computed ground-fault capacity of thesteel pipe 110 is 60 kA. In addition, the ground-fault capacity of themetal sheath 126 exists for each of thetransmission cables metal sheaths 126 of thetransmission cables FIG. 3 . - Therefore, for up to a time of 0.25 second, the
steel pipe 110, themetal sheath 126, and thereturn cable 130 can allow currents amounting to 60 kA, 15.6 kA and 15.3 kA to flow, respectively. - In the following description, it is assumed that, in the case in which the
steel pipe 110, themetal sheath 126, and thereturn cable 130 have the ground-fault capacities described above, a current of 60 kA flows through thetransmission cables transmission cable 120R. Further, in the following description, the phase in which the fault current is generated may also be referred to as a “fault-phase”. - In this first embodiment, the current flowing through the
steel pipe 110 of thepower cable 100 is 17.9 kA, and the current flowing through the fault-phase metal sheath 126 (R) is 15.0 kA. The current flowing through each of the metal sheaths 126 (Y) and 126 (B) of phases other than the fault-phase is 8.2 kA, and the current flowing through thereturn cable 130 is 15.3 A. - Accordingly, the amounts of current flowing through the
steel pipe 110, the metal sheaths 126 (R), 126 (Y) and 126 (B), and thereturn cable 130, respectively, are the respective ground-fault capacities or less. Hence, it is confirmed that thepower cable 100 in this first embodiment can ensure a sufficient path for the fault current to flow. - On the other hand, in a case in which a current of 60 kA flows through the
transmission cables return cable 130 for 0.25 second, and the fault current is generated in thetransmission cable 120R, the current flowing through thesteel pipe 110 is 23.4 kA, and the current flowing through the fault-phase metal sheath 126 (R) is 18.4 kA. The current flowing through each of the metal sheaths 126 (Y) and 126 (B) of phases other than the fault-phase is 11.9 kA. - Accordingly, in the case of the power cable in the comparison example, the amount of current flowing through the fault-phase metal sheath 126 (R) exceeds its ground-fault capacity, and it is confirmed that a sufficient path for the fault current to flow cannot be ensured by the power cable in the comparison example.
- According to this first embodiment, it is possible to provide the
power cable 100 that ensures a sufficient path for the fault current to flow, by including thetransmission cables transmission cables return cable 130 along the longitudinal direction of thereturn cable 130, with thereturn cable 130 arranged at the center of thetransmission cables - In addition, each of the
transmission cables conductor 121, theconductor screen 122, the insulatinglayer 123, the insulatingscreen 124, thebedding 125, themetal sheath 126, and thejacket 127 described above. - For example, when replacing the existing power cable by the
power cable 100 in this first embodiment, the the transmission cables of the existing power cable may include a shield. Hence, a description will be given of the transmission cable in the comparison example, by referring toFIGS. 4A and 4B . -
FIGS. 4A and 4B are cross sectional views for explaining atransmission cable 20 and an OF (Oil Filled)cable 40 in the comparison example.FIG. 4A illustrates a cross section of thetransmission cable 20, corresponding to the cross section of thetransmission cable 120 illustrated inFIG. 2A . - The
transmission cable 20 includes aconductor 21, aconductor screen 22, an insulatinglayer 23, an insulatingscreen 24, abedding 25, ashield 30, ametal sheath 26, and ajacket 27. Theconductor 21, theconductor screen 22, the insulatinglayer 23, the insulatingscreen 24, thebedding 25, themetal sheath 26, and thejacket 27 of thetransmission cable 20 in the comparison example correspond to theconductor 121, theconductor screen 122, the insulatinglayer 123, the insulatingscreen 124, thebedding 125, themetal sheath 126, and thejacket 127 of thetransmission cable 120 in this first embodiment, respectively, and a detailed description thereof will be omitted. - An outer diameter of the
jacket 27 of thetransmission cable 20 is equal to an outer diameter of thejacket 127 of thetransmission cable 120. Because thetransmission cable 20 includes theshield 30 between thebedding 25 and themetal sheath 26, theconductor 21 has a size smaller than that of theconductor 121 of thetransmission cable 120. - The
shield 30 is formed by a metal wire member, and is held at the ground potential (reference potential) together with themetal sheath 26. For example, the metal wire member has a configuration in which a large number of conductors having a diameter on the order of approximately 1 mm to 2 mm are wound around thebedding 25. Theshield 30 is provided to achieve electrostatic shielding and electromagnetic induction shielding, and to ensure a path for the fault current to flow. - On the other hand, the
OF cable 40 illustrated inFIG. 4B for the POF cable includes aconductor 41, aconductor screen 42, an insulatinglayer 43, an insulatingscreen 44, and abedding 45. - The
conductor 41, theconductor screen 42, the insulatinglayer 43, the insulatingscreen 44, and thebedding 45 of theOF cable 40 correspond to theconductor 121, theconductor screen 122, the insulatinglayer 123, the insulatingscreen 124, and thebedding 125 of thetransmission cable 120 in this first embodiment, respectively, and a detailed description thereof will be omitted. In theOF cable 40, theconductor screen 42, the insulatinglayer 43, the insulatingscreen 44, and thebedding 45 are made of paper. In the existing POF cable, theOF cable 40 is provided within a steel pipe, and an insulating oil is provided within the steel pipe, so that the steel pipe functions as themetal sheath 126 and thejacket 127 of thetransmission cable 120 of this first embodiment. - According to the
transmission cable 120 in this first embodiment, themetal sheath 126 provides a sufficient electrostatic shielding property, and themetal sheath 126 and thereturn cable 130 provide a sufficient electromagnetic induction shielding property. For this reason, in a case in which the existing POF cable has a configuration in which the OFcable 40 is included inside thesteel pipe 110, for example, thesteel pipe 110 can be reused when making repairs, for example. In this case, when laying thepower cable 100, thetransmission cables return cable 130 may be inserted inside thesteel pipe 110, instead of using a configuration in which a bundle of three (3)transmission cables 20 are included. - The
transmission cable 120 in this case has an outer diameter equal to that of thetransmission cable 20, however, thetransmission cable 120 includes noshield 30. For this reason, the diameter of theconductor 121 in thetransmission cable 120 can be made larger than that of theconductor 21 in thetransmission cable 20, to thereby improve the transmission capacity. - In addition, in a case in which the existing power cable is the POF cable, it is possible to replace the power cable by the
power cable 100 having a high adaptability to the environment without using insulating oil. As a result, it is possible to simultaneously improve the transmission capacity and ensure high adaptability to the environment. High adaptability to the environment means that it is environmentally-friendly or ecological. - Next, a description will be given of a state in which a plurality of
power cables 100 are connected via vaults, by referring toFIG. 5 . -
FIG. 5 is a diagram illustrating the state in which a plurality ofpower cables manholes FIG. 5 illustrates the plurality ofpower cables power cable 100 described above. For this reason, when not distinguishing thepower cables power cables power cables 100” in the following description. - In
FIG. 5 , only thesteel pipe 110, theconductor 121 and themetal sheath 126 of thetransmission cables return cable 130 of thepower cable 100 are illustrated. Theconductors 121 and themetal sheaths 126 of thetransmission cables conductors metal sheaths - When not distinguishing the
conductors metal sheaths transmission cables conductors metal sheaths conductors 121” and “metal sheaths 126”, respectively, in the following description. - The
vaults vaults vaults - The vault 50 includes a
housing 51,joints cables link box 53 as a connecting location, for example. - The
housing 51 is formed by a concrete, for example, and accommodates connecting parts of the mutuallyadjacent power cables 100 that are to be connected. The connecting parts include thejoints link box 53, and thecables - The joint 52R includes a connecting
part 57A, an insulatingpart 57B, and a connectingpart 57C. Thejoints parts conductors 121R of the mutuallyadjacent power cables metal sheaths 126 of the mutuallyadjacent power cables metal sheaths 126 of the mutuallyadjacent power cables part 58B inside the joint 52R. - The
cable 55R is connected to the connectingpart 57A of the joint 52R, and thecable 56R is connected to the connectingpart 57C of the joint 52R. Thecables part 53A of thelink box 53. The connectingpart 53A of thelink box 53 is grounded, and themetal sheath 126 is held at the ground potential via the connectingpart 53A of thelink box 53. - The
joints joints - As described above, the
link box 53 includes the connectingpart 53A that is held at the ground potential. The connectingpart 53A connects thecables cables cables cables cable 54A that branches from thecable 54 is also connected to the connectingpart 53A, and the connectingpart 53A holds thesteel pipe 110 and thereturn cable 130 to the ground potential. - The
cable 54 connects thesteel pipes 110 of the mutuallyadjacent power cables return cable 130 is also connected to thecable 54. For this reason, thecable 54 also connects thereturn cables 130 of the mutuallyadjacent power cables - The
cable 54A branches from an intermediate part of thecable 54, and thecable 54A is connected to the connectingpart 53A of thelink box 53. Because the connectingpart 53A of thelink box 53 is held at the ground potential, thesteel pipe 110 and thereturn cable 130 are held at the ground potential via the connectingpart 53A of thelink box 53. - The
cable 55R connects the connectingpart 57A of the joint 52R and the connectingpart 53A of thelink box 53. Thecable 56R connects the connectingpart 57C of the joint 52R and the connectingpart 53A of thelink box 53. Thecables part 53A, and are held at the ground potential. - The
cables cables cables cables cables cables - The connecting relationship of the mutually
adjacent power cables adjacent power cables adjacent power cables - A case will be considered in which the insulator breakdown occurs in the
transmission cable 120R illustrated inFIG. 1B of thepower cable 100A including theconductor 121R, when thepower cables - In this case, the fault current generated in the
transmission cable 120R flows to thesteel pipe 110 via themetal sheath 126R or thereturn cable 130 of thepower cable 100A, and flows through thecable 54 as indicated by an arrow A. Further, a part of the fault current flows to thesteel pipe 110 and thereturn cable 130 of thepower cable 100B via thecable 54 as indicated by an arrow B, and the remaining part of the fault current flows to the connectingpart 53A via thecable 54A. The current flowing to the connectingpart 53A flows to themetal sheaths power cable 100B, via thecables - Accordingly, the fault current generated by the insulator breakdown in the
transmission cable 120R of thepower cable 100A flows through thesteel pipe 110 of thepower cable 100A, and branches to thesteel pipe 110, themetal sheaths return cable 130 of thepower cable 100B, via thecables - As described above in conjunction with
FIG. 3 , thesteel pipe 110, the metal sheaths 126 (126R, 126Y and 126B), and thereturn cable 130 of thepower cable 100 provide a path with a sufficient capacity for the fault current to flow. - For this reason, even when the fault current is generated due to the insulator breakdown in the
transmission cable 120, it is possible to suppress the currents flowing through thesteel pipe 110, the metal sheaths 126 (126R, 126Y and 126B), and thereturn cable 130 from exceeding the respective ground-fault capacities thereof, and provide thepower cable 100 in which a sufficient path is ensured for the fault current to flow. -
FIG. 6 is a cross sectional view illustrating an example of apower cable 200 in a second embodiment. The cross section of thepower cable 200 illustrated inFIG. 6 corresponds to the cross section of thepower cable 100 illustrated inFIG. 1B . - The
power cable 200 illustrated inFIG. 6 includes asteel pipe 110,transmission cables return cable 130, and threepipes power cable 200 has a configuration in which thepipes power cable 100 in the first embodiment. Parts other than thepipes power cable 200 are the same as those corresponding parts of thepower cable 100 in the first embodiment, and a description thereof will be omitted by designating the same parts by the same reference numerals. - In the cross sectional view of
FIG. 6 , thepipe 241 is arranged between thetransmission cables pipe 242 is arranged between thetransmission cables pipe 243 is arranged between thetransmission cables pipes transmission cables transmission cables - More particularly, in a state arranged between the
transmission cables pipe 241 is twisted along the longitudinal directions of thetransmission cables transmission cables - Similarly, in a state arranged between the
transmission cables pipe 242 is twisted along the longitudinal directions of thetransmission cables transmission cables transmission cables pipe 243 is twisted along the longitudinal directions of thetransmission cables transmission cables - The
pipes return cable 130 located at their center, and are twisted around thetransmission cables - The
pipes return cable 130 located at their center, and are twisted around the return table 130. - The
pipes pipes pipes pipes transmission cable 120 due to ground-fault or the like. - The
pipes pipe parts pipes jackets - The
pipe parts pipe parts - The
jackets pipe parts - In addition,
optic fibers pipe parts optic fibers optic fiber parts plastic pipes optic fiber parts plastic pipes - By arranging the
optic fibers pipe parts pipes optic fibers - Because the
pipes steel pipe 110 together with thetransmission cables return cable 130, thepipes pipes transmission cables return cable 130 is located. - In addition, when connecting a plurality of
power cables 200, thepipes adjacent power cables 200 may be connected, or theplastic pipes pipes adjacent power cables 200, in order to lay theoptic fiber parts - Next, consideration will be given of ground-fault capacities of the
steel pipe 110 of thepower cable 200, themetal sheaths 126 of thetransmission cables return cable 130, and thepipes transmission cables power cable 200, themetal sheath 126, thereturn cable 130, or thepipes power cable 200 in which the insulator breakdown occurs may melt, and a fault current may flow through thesteel pipe 110. - In such a case, the fault current flows from the
steel pipe 110 of thepower cable 200 in which the insulator breakdown occurs to thesteel pipe 110, themetal sheaths 126, thereturn cables 130, and thepipes adjacent power cable 200 that is connected in series to thepower cable 200. - Accordingly, the
steel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes power cable 200 respectively need to have a ground-fault capacity to a certain extent. The ground-fault capacities are determined by amounts of current that can flow through thesteel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes - In the case of a
power cable 200 in which the insulator breakdown occurs but themetal sheath 126, thereturn cable 130, or thepipes power cable 200 do not melt, the fault current may still flow through thesteel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes - However, even in such a case, the fault current flows through the
steel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes adjacent power cable 200. Hence, the ground-fault capacities are evaluated based on amounts of current that can flow through thesteel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes adjacent power cable 200 that is adjacent to thepower cable 200 in which the insulator breakdown occurs but themetal sheath 126, thereturn cable 130, or thepipes power cable 200 do not melt. -
FIG. 7 is a diagram for explaining the ground-fault capacity of thepower cable 200 in the second embodiment. In the following, the amounts of current flowing through thepower cable 200 in this second embodiment are compared to the respective ground-fault capacities. The current value inFIG. 7 is represented by kA (kilo-Amperes), andFIG. 7 uses the same designations as those used inFIG. 3 . - For example, the ground-fault capacities of the
steel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes steel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes - The ground-fault capacities of the
steel pipe 110, themetal sheath 126, and thereturn cable 130 are 60 kA, 15.6 kA, and 15.3 kA, respectively, which are the same as those illustrated inFIG. 3 for the first embodiment. The computed ground-fault capacities of thepipes - Therefore, for up to a time of 0.25 second, the
steel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes - In the following description, it is assumed that, in the case in which the
steel pipe 110, themetal sheath 126, thereturn cable 130, and thepipes transmission cables transmission cable 120R. Further, in the following description, the phase in which the fault current is generated may also be referred to as a “fault-phase”. - In this second embodiment, the current flowing through the
steel pipe 110 of thepower cable 200 is 8.4 kA, and the current flowing through the fault-phase metal sheath 126 (R) is 10.4 kA. The current flowing through each of the metal sheaths 126 (Y) and 126 (B) of phases other than the fault-phase is 4.4 kA, and the current flowing through thereturn cable 130 is 9.0 A. These amounts of current are reduced compared to the corresponding amounts of current flowing in thepower cable 100 described above in the first embodiment. It may be regarded that the amounts of current are reduced in this second embodiment due to the additional provision of thepipes - The currents flowing through the
pipes pipes pipes pipes - Accordingly, the amounts of current flowing through the
steel pipe 110, the metal sheaths 126 (R), 126 (Y) and 126 (B), thereturn cable 130, and thepipes power cable 200 in this second embodiment can ensure a sufficient path for the fault current to flow. - According to this second embodiment, it is possible to provide the
power cable 200 that ensures a sufficient path for the fault current to flow, by including thetransmission cables pipes transmission cables pipes return cable 130 along the longitudinal direction of thereturn cable 130 by the triplex formations thereof, with thereturn cable 130 arranged at the center of thetransmission cables pipes - In addition to being used as the path for the fault current to flow, the
pipes optic fibers pipes optic fibers optic fiber parts plastic pipes pipes - The
optic fibers optic fibers - In addition, in a case in which a POF cable is connected to one end or both ends of one or a plurality of
power cables 200 in order to replace an existing POF cable by thepower cable 200, it is possible to utilize the internal spaces within thepipe parts optic fibers optic fiber parts plastic pipes pipes pipe parts FIGS. 9A and 9B . Further, thetransmission cable 120 can be cooled by flowing a cooling liquid (for example, water) inside thepipes pipes - Next, a description will be given of a state in which a plurality of
power cables 200 are connected via a vault, by referring toFIG. 8 . -
FIG. 8 is a diagram illustrating the state in which a plurality ofpower cables vaults FIG. 8 illustrates the plurality ofpower cables power cable 200 described above. For this reason, when not distinguishing thepower cables power cables power cables 200” in the following description. - In
FIG. 8 , only thesteel pipe 110, theconductor 121 and themetal sheath 126 of thetransmission cables return cable 130, and thepipes power cable 200 are illustrated. Theconductors 121 and themetal sheaths 126 of thetransmission cables conductors metal sheaths vaults vaults vaults - The vault 250 has the same configuration as the vault 50 in the first embodiment illustrated in
FIG. 5 , except that thejoints joints FIG. 8 that are the same as those corresponding parts inFIG. 5 are designated by the same reference numerals, and a description thereof will be omitted. - The
joints - The joint 252R includes a connecting
part 57A, an insulatingpart 57B, a connectingpart 57C, and projectingparts parts part 57B have the same configurations as those of the joint 52R. - The projecting
parts parts parts parts parts - The
pipe 241 of thepower cable 200A is connected to the connectingpart 57A, and thepipe 241 of thepower cable 200B is connected to the connectingpart 57C. Hence, thepipe 241 is held at the ground potential. - The connections at the
joints pipe 241 of thepower cable 200A and thepipe 241 of thepower cable 200B. The joint 252B connects thepipe 241 of thepower cable 200A and thepipe 241 of thepower cable 200B. - The connecting relationship of the mutually
adjacent power cables adjacent power cables adjacent power cables - A case will be considered in which the insulator breakdown occurs in the
transmission cable 120R illustrated inFIG. 6B of thepower cable 200A including theconductor 121R, when thepower cables - In this case, the fault current generated in the
transmission cable 120R flows to thesteel pipe 110 via themetal sheath 126R, thereturn cable 130, or thepipes power cable 200A, and flows through thecable 54 as indicated by an arrow A. Further, a part of the fault current flows to thesteel pipe 110 and thereturn cable 130 of thepower cable 200B via thecable 54 as indicated by an arrow B, and the remaining part of the fault current flows to the connectingpart 53A via thecable 54A. The current flowing to the connectingpart 53A flows to themetal sheaths pipes power cable 200B, via thecables - Accordingly, the fault current generated by the insulator breakdown in the
transmission cable 120R of thepower cable 200A flows through thesteel pipe 110 of thepower cable 200A, and branches to thesteel pipe 110, themetal sheaths return cable 130, and thepipes power cable 200B, via thecables - As described above in conjunction with
FIG. 7 , thesteel pipe 110, the metal sheaths 126 (126R, 126Y and 126B), thereturn cable 130, and thepipes power cable 200 provide a path with a sufficient capacity for the fault current to flow. Compared to thepower cable 100 in the first embodiment, the capacity of the path for the fault current to flow in thepower cable 200 in this second embodiment can be increased by approximately 50%. - For this reason, even when the fault current is generated due to the insulator breakdown in the
transmission cable 120, it is possible to suppress the currents flowing through thesteel pipe 110, the metal sheaths 126 (126R, 126Y and 126B), thereturn cable 130, and thepipes power cable 200 in which a sufficient path is ensured for the fault current to flow. - Although the
pipes pipes pipes - Next, a description will be given of a case in which an existing POF cable is replaced by the
power cable 200, in order to provide a flow passage for the insulating oil, by flowing the insulating oil of the POF cables at both ends of thepower cable 200 inside thepipes power cable 200. -
FIGS. 9A and 9B are diagrams for explaining a state in which the existing POF cables are replaced by thepower cables FIGS. 9A and 9B illustrate only onetransmission cable 120 and onepipe 241 and thesteel pipe 110 with respect to thepower cables - In addition, it is assumed in
FIGS. 9A and 9B that each ofPOF cables cables 40 inserted into thesteel pipe 110 thereof, and that the insulating oil is provided inside thissteel pipe 110. The OFcable 40 is theOF cable 40 in the comparison example illustrated inFIG. 4B . For the sake of convenience,FIGS. 9A and 9B illustrate only thesteel pipe 110 and one OFcable 40 with respect to each of thePOF cables steel pipe 110 thereof may be treated as an oil line. - In
FIG. 9A , thetransmission cables 120 of thepower cables OF cable 40 of thePOF cable 70A and theOF cable 40 of thePOF cable 70B, viajoints cables 40 of thePOF cables OF cable 40 of thePOF cable 70B, viajoints transmission cables 120 of thepower cables - The
steel pipe 110 of thePOF cable 70A, thepipes 241 of thepower cables steel pipes 110 of thePOF cables pipe 241, thepipe parts 241A of thepipe 241 is connected to thesteel pipe 110. Actually, there are three (3)pipes pipe parts pipe parts steel pipe 110. A part of the joint 80A may be formed by one joint 72, and a part of the joint 80C may be formed by another joint 72. - In addition, a terminating
part 90A is connected on the left side of thePOF cable 70A, and a terminatingpart 90B is connected on the right side of thePOF cable 70D. Anoil supply device 90E is connected to thesteel pipe 110 of thePOF cable 70A, and anoil supply device 90F is connected to thesteel pipe 110 of thePOF cable 70D. - The joint 80B is a connecting part similar to the
vaults 250A through 250C illustrated inFIG. 8 . The terminatingparts parts POF cables 70A through 70D. - When laying the
power cables POF cables power cables FIG. 9A . - In this case, the replacement by the
power cables POF cables pipes 241 of thepower cables steel pipes 110 of thePOF cables - Further, in
FIG. 9B , thePOF cable 70A, the joint 80A, thepower cable 200A, the joint 80B, thepower cable 200B, the joint 80C, and apower cable 270E are connected to the terminatingpart 90A. Thepower cable 270E is a dry type power cable that does not use insulating oil. Thepower cable 270E is an example of a line or path that is set up at a location where nosteel pipe 110 is provided, or at a location where the line or path is not provided inside thesteel pipe 110. - An oil line 90C branches from the joint 80C, and connects to an existing
oil supply device 90D, for example. -
FIG. 8B illustrates a case in which the connection of the plurality of POF cables, theoil supply device 90D, and thepower cable 270E that are connected on the right side of thePOF cable 70A in a power transmission system before the replacement is modified, by replacing the POF cables other than thePOF cable 70A by thepower cables oil supply device 90D. - In the power transmission system illustrated in
FIG. 9B , the power is transmitted between the terminatingpart 90A and thepower cable 270E. In addition, theoil supply device 90D manages and adjusts the pressure and the like of the insulating oil in thesteel pipe 110 of thePOF cable 70A, via thepipes 241 of thepower cables - According to the
power cable 200 in this second embodiment, thepipes - According to the embodiments described above, the power cable can provide a sufficient path for the fault current.
- Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.
Claims (20)
1. A power cable comprising:
a first steel pipe coupled to a reference potential node;
three first transmission cables, inserted inside the first steel pipe, and respectively including a first conductor to transmit three-phase alternating current power; and
a return cable inserted inside the first steel pipe and coupled to the reference potential node,
wherein each of the three first transmission cables includes a first insulating layer covering the first conductor, a metal layer covering the first insulating layer, and a second insulating layer covering the metal layer, without a shield wire,
wherein the three first transmission cables are twisted around a periphery of the return cable along a longitudinal direction of the return cable, and
wherein the metal layer is coupled to the reference potential node.
2. The power cable as claimed in claim 1 , wherein the three first transmission cables, in a cross sectional view of the power cable, have a positional relationship maintaining a three-fold symmetry with respect to the return cable that is located at a center of the three first transmission cables in the cross sectional view.
3. The power cable as claimed in claim 1 , wherein the metal layer includes a metal wrap that wraps the first insulating layer.
4. The power cable as claimed in claim 1 , further comprising:
a second conductor, coupled to the reference potential node, and twisted around the periphery of the return cable along the longitudinal direction of the return cable, together with the three first transmission cables.
5. The power cable as claimed in claim 1 , further comprising:
three second conductors twisted around the periphery of the return cable along the longitudinal direction of the return cable, together with the three first transmission cables.
6. The power cable as claimed in claim 5 , wherein the three second conductors, in a cross sectional view of the power cable, have a positional relationship maintaining a three-fold symmetry with respect to the return cable that is located at a center of the three second conductors in the cross sectional view.
7. The power cable as claimed in claim 5 , wherein each of the three second conductors includes a metal pipe.
8. The power cable as claimed in claim 7 , further comprising:
an optic fiber arranged inside the metal pipe.
9. A power transmission system comprising:
the power cable as claimed in claim 8 ,
wherein the power cable is coupled to a pipe type oil filled cable that includes a second steel pipe, a second transmission cable arranged inside the second steel pipe and coupled to one of the three first transmission cables, and an insulating oil covering the second transmission cable inside the second steel pipe, and
wherein the metal pipe supplies the insulating oil of the pipe type oil filled cable via the second steel pipe, or receives the insulating oil of the pipe type oil filled cable via the second steel pipe.
10. A power cable comprising:
a first steel pipe coupled to a reference potential node;
three first transmission cables, inserted inside the first steel pipe, and respectively including a first conductor to transmit three-phase alternating current power; and
a return cable inserted inside the first steel pipe and coupled to the reference potential node,
wherein each of the three first transmission cables includes a first insulating layer covering the first conductor, a metal layer covering the first insulating layer, and a second insulating layer covering the metal layer,
wherein the three first transmission cables are twisted around a periphery of the return cable along a longitudinal direction of the return cable,
wherein the metal layer is coupled to the reference potential node, and
wherein the three first transmission cables include no shield wire between the first insulating layer and the second insulating layer.
11. The power cable as claimed in claim 10 , wherein the three first transmission cables, in a cross sectional view of the power cable, have a positional relationship maintaining a three-fold symmetry with respect to the return cable that is located at a center of the three first transmission cables in the cross sectional view.
12. The power cable as claimed in claim 10 , wherein the metal layer includes a metal wrap that wraps the first insulating layer.
13. The power cable as claimed in claim 10 , further comprising:
a second conductor, coupled to the reference potential node, and twisted around the periphery of the return cable along the longitudinal direction of the return cable, together with the three first transmission cables.
14. The power cable as claimed in claim 10 , further comprising:
three second conductors twisted around the periphery of the return cable along the longitudinal direction of the return cable, together with the three first transmission cables.
15. The power cable as claimed in claim 14 , wherein the three second conductors, in a cross sectional view of the power cable, have a positional relationship maintaining a three-fold symmetry with respect to the return cable that is located at a center of the three second conductors in the cross sectional view.
16. The power cable as claimed in claim 14 , wherein each of the three second conductors includes a metal pipe.
17. The power cable as claimed in claim 16 , further comprising:
an optic fiber arranged inside the metal pipe.
18. A power transmission system comprising:
the power cable as claimed in claim 17 ,
wherein the power cable is coupled to a pipe type oil filled cable that includes a second steel pipe, a second transmission cable arranged inside the second steel pipe and coupled to one of the three first transmission cables, and an insulating oil covering the second transmission cable inside the second steel pipe, and
wherein the metal pipe supplies the insulating oil of the pipe type oil filled cable via the second steel pipe, or receives the insulating oil of the pipe type oil filled cable via the second steel pipe.
19. A power cable comprising:
a first steel pipe coupled to a reference potential node;
three first transmission cables, inserted inside the first steel pipe, and respectively including a first conductor to transmit three-phase alternating current power; and
a return cable inserted inside the first steel pipe and coupled to the reference potential node,
wherein each of the three first transmission cables includes a first insulating layer covering the first conductor, a metal layer covering the first insulating layer, and a second insulating layer covering the metal layer,
wherein the three first transmission cables are twisted around a periphery of the return cable along a longitudinal direction of the return cable, and
wherein the metal layer is coupled to the reference potential node.
20. The power cable as claimed in claim 19 , wherein the metal layer is formed by a sheathed metal having a hollow cylindrical shape.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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CA2875411A CA2875411C (en) | 2014-01-21 | 2014-12-19 | Power cable |
US14/661,076 US9129722B2 (en) | 2014-01-21 | 2015-03-18 | Power cable |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2014-008452 | 2014-01-21 | ||
JP2014008452A JP5871339B2 (en) | 2014-01-21 | 2014-01-21 | Power cable |
Related Child Applications (1)
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US14/661,076 Continuation US9129722B2 (en) | 2014-01-21 | 2015-03-18 | Power cable |
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US20150206628A1 true US20150206628A1 (en) | 2015-07-23 |
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US14/307,557 Abandoned US20150206628A1 (en) | 2014-01-21 | 2014-06-18 | Power cable |
US14/661,076 Active US9129722B2 (en) | 2014-01-21 | 2015-03-18 | Power cable |
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Application Number | Title | Priority Date | Filing Date |
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US14/661,076 Active US9129722B2 (en) | 2014-01-21 | 2015-03-18 | Power cable |
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US (2) | US20150206628A1 (en) |
JP (1) | JP5871339B2 (en) |
CA (1) | CA2875411C (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105702371A (en) * | 2016-04-23 | 2016-06-22 | 许玉蕊 | Three-phase alternating current power cable |
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JP2019046561A (en) * | 2017-08-30 | 2019-03-22 | 住友電気工業株式会社 | Power cable |
US20190244726A1 (en) * | 2018-02-02 | 2019-08-08 | Averatek Corporation | Maximizing surfaces and minimizing proximity effects for electric wires and cables |
US10276280B1 (en) | 2018-03-23 | 2019-04-30 | Superior Essex International LP | Power over ethernet twisted pair communications cables with a shield used as a return conductor |
IT201800007853A1 (en) * | 2018-08-03 | 2020-02-03 | Prysmian Spa | HIGH VOLTAGE THREE-PHASE CABLE. |
US10991479B2 (en) * | 2019-01-22 | 2021-04-27 | Electric Power Research Institute, Inc. | Electric power cable |
JP7243433B2 (en) * | 2019-05-20 | 2023-03-22 | 住友電気工業株式会社 | CABLE CONNECTION STRUCTURE, CABLE CONNECTION STRUCTURE MEMBER, AND CABLE CONNECTION STRUCTURE MANUFACTURING METHOD |
CN111585060A (en) * | 2020-04-29 | 2020-08-25 | 昆明理工大学 | Novel single-core power cable metal sheath grounding mode |
CN117790067A (en) * | 2023-12-19 | 2024-03-29 | 京缆电缆有限公司 | 35kV cable for power generation of wind energy |
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- 2014-01-21 JP JP2014008452A patent/JP5871339B2/en active Active
- 2014-06-18 US US14/307,557 patent/US20150206628A1/en not_active Abandoned
- 2014-12-19 CA CA2875411A patent/CA2875411C/en active Active
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2015
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CN105702371A (en) * | 2016-04-23 | 2016-06-22 | 许玉蕊 | Three-phase alternating current power cable |
Also Published As
Publication number | Publication date |
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CA2875411C (en) | 2021-03-23 |
US20150206629A1 (en) | 2015-07-23 |
CA2875411A1 (en) | 2015-07-21 |
JP2015139241A (en) | 2015-07-30 |
JP5871339B2 (en) | 2016-03-01 |
US9129722B2 (en) | 2015-09-08 |
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Legal Events
Date | Code | Title | Description |
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AS | Assignment |
Owner name: J-POWER SYSTEMS CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ONA, SATOSHI;MASHIO, SHOJI;KUMAGAWA, KINYA;AND OTHERS;SIGNING DATES FROM 20140411 TO 20140514;REEL/FRAME:033125/0170 |
|
AS | Assignment |
Owner name: J-POWER SYSTEMS CORPORATION, JAPAN Free format text: ASSIGNEE CHANGE OF ADDRESS;ASSIGNORS:ONA, SATOSHI;MASHIO, SHOJI;KUMAGAWA, KINYA;AND OTHERS;SIGNING DATES FROM 20140411 TO 20140514;REEL/FRAME:035349/0105 |
|
STCB | Information on status: application discontinuation |
Free format text: EXPRESSLY ABANDONED -- DURING EXAMINATION |