JP2018186037A - Superconducting cable line - Google Patents

Abstract

An object of the present invention is to cause an overcurrent to flow while maintaining a superconducting state without increasing the temperature of a superconducting cable. A superconducting cable having a plurality of superconducting conductor layers formed coaxially with a core by winding a plurality of superconducting wires around the outer periphery of the core, and a short-circuit current provided outside the superconducting cable and flowing in the superconducting cable A superconducting wire, a conductive protective layer including at least one of copper and silver covering the superconducting layer, and a superconducting wire comprising a normal conductor for shunting at least a part of the superconducting wire The film thickness of the protective layer is 40% or less with respect to the film thickness of the superconducting wire. [Selection] Figure 1

Description

  The present invention relates to a superconducting cable line suitable for overcurrent countermeasures.

  Conventionally, a superconducting cable using a superconducting wire that becomes a superconducting state at an extremely low temperature as a conductor is known. The superconducting cable is expected as a power cable capable of transmitting a large current with a low loss, and is being developed for practical use.

  A superconducting cable having a structure in which a single-core or multiple-core cable core is accommodated in a heat insulating tube is known. As a single-core cable core, for example, a former, a superconducting conductor layer, and an electrical insulating layer are sequentially provided from the center, and in addition to this, a cable shield layer, a protective layer, and the like are provided on the outer periphery of the electrical insulating layer. The heat insulation pipe includes an inner pipe (hereinafter referred to as “heat insulation inner pipe”) in which the cable core is accommodated and filled with a refrigerant (for example, liquid nitrogen), and an outer pipe (hereinafter referred to as “heat insulation outer pipe”) covering the outer periphery of the heat insulation inner pipe. Have Between the heat insulating inner tube and the heat insulating outer tube, a vacuum state is set for heat insulation.

  By the way, when a short circuit accident or a ground fault (such as a lightning strike) occurs in a real line such as an AC power transmission line using a superconducting cable, the current is transferred to the former when an overcurrent exceeding the critical current flows. This causes problems such as temperature rise and liquid nitrogen bumping due to Joule heat generation. Therefore, it is desired to take measures against overcurrent in the superconducting cable line.

  For example, in Patent Document 1, a shunt conductor is attached to a 3-core superconducting cable in which three cores of a cable core having a superconducting conductor layer are twisted around the former of a copper twisted wire conductor and collectively stored in a heat insulating tube. A superconducting cable line that is connected in parallel and bypasses a short-circuit current flowing in the cable core is disclosed.

JP 2010-277975 A

  By the way, as the cable core, a coaxial cable core having a plurality of superconducting conductor layers in which superconducting conductor layers and electrical insulating layers are alternately arranged in the same axial center on the outer periphery of the former is known.

  In recent years, as a superconducting cable having such a coaxial cable core, an overcurrent exceeding the critical current flows without increasing the outer diameter of the superconducting cable itself, for example, using a three-homogeneous axis superconducting cable. However, it is desired to construct a superconducting cable line that maintains the superconducting state of the superconducting cable.

  The present invention has been made in view of the above points, and a superconducting cable line capable of receiving an overcurrent while maintaining a superconducting state without causing a problem of temperature rise or liquid nitrogen bumping due to Joule heat generation. The purpose is to provide.

One aspect of the device of the present invention is:
A superconducting cable having a plurality of superconducting conductor layers formed coaxially with the core member by winding a plurality of superconducting wires around the outer periphery of the core member;
A shunt conductor formed of a normal conductor for shunting at least part of an overcurrent flowing in the superconducting cable, provided outside the superconducting cable;
Have
The superconducting wire has a superconducting layer and a conductive protective layer containing at least one of copper and silver covering the superconducting layer, and
The protective layer has a thickness of 40% or less with respect to the thickness of the superconducting wire.

  According to the present invention, an overcurrent can be received and flowed while maintaining a superconducting state without causing problems such as temperature rise and liquid nitrogen bumping due to Joule heat generation.

It is a schematic block diagram which shows typically the principal part structure of the superconducting cable track which concerns on one embodiment of this invention. It is a figure which shows the structure of a superconducting cable. It is sectional drawing which shows the structure of a superconducting wire typically. It is a figure where it uses for description of a state when a short circuit current flows into the superconducting cable track which concerns on one embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  A superconducting cable line 10 shown in FIG. 1 has a superconducting cable 20 and a shunt conductor 30.

  In the superconducting cable line 10, the superconducting cable 20 is used as an actual line. When an overcurrent flows through the superconducting cable line 10, the superconducting cable 20 flows a current while maintaining a superconducting state, and the shunt conductor 30 flows the divided overcurrent.

  In the present embodiment, superconducting cable 20 of superconducting cable line 10 has a plurality of superconducting conductor layers 23 (superconducting conductor layers 23U, 23V, 23W) on the same axis. In FIG. 1, the superconducting cable is connected to the superconducting cable line 10 (specifically, a plurality of superconducting conductor layers 23) in a state where a short-circuit current generator 50 capable of supplying overcurrent to the superconducting cable line 10 is connected. The track 10 is shown.

<Configuration of superconducting cable 20>
FIG. 2 is a diagram schematically showing the structure of the superconducting cable.

  A superconducting cable 20 shown in FIG. 2 is a three-homogeneous-axis superconducting cable, and a superconducting conductor layer 23U formed coaxially with the core material 21 by winding a plurality of superconducting wires 40 (see FIG. 3) around the outer periphery of the core material 21. , 23V, 23W.

  The superconducting cable 20 is composed of a core material 21, a superconducting conductor layer 23 (23U, 23V, 23W) capable of three-phase AC power transmission, an insulator layer 25 (25U, 25V, 25W), a ground layer 26, a heat insulating inner tube 27, and a heat insulating outside. It has a tube 28 and an anticorrosion layer 29.

  The core material 21 is a so-called former and has a cylindrical shape. The core material 21 has flexibility, and is a metal corrugated pipe in the present embodiment, specifically, a corrugated pipe made of stainless steel (SUS). Since the core material 21 is a metal corrugated tube, liquid nitrogen or the like can be passed through it. Here, the refrigerant tube that allows liquid nitrogen or the like to pass through and cools the superconducting conductor layer 23 from the inside. Function as.

  Superconducting conductor layers 23 (23U, 23V, 23W) and insulator layers 25 (25U, 25V, 25W) are alternately stacked on the outer periphery of the core material 21.

  Superconducting conductor layer 23 may include a plurality of superconducting conductor layers. Superconducting conductor layer 23 in the present embodiment has a three-phase superconducting conductor layer (23U, 23V, 23W) capable of AC power transmission as a plurality of superconducting conductor layers. Each of the superconducting conductor layers 23 is formed in a cylindrical shape by spirally winding a plurality of superconducting wires 40. Details of the superconducting conductor layer 23 will be described later together with details of the superconducting wire 40.

  An outer periphery of the superconducting conductor layer 23U is provided so as to cover the insulator layer 25U, and a superconducting conductor layer 23V is provided on the outer periphery of the insulator layer 25U. The outer periphery of the superconducting conductor layer 23V is provided so as to cover the insulator layer 25V, and the outer periphery of the insulator layer 25V is provided with the superconducting conductor layer 23W. An insulator layer 25W is provided on the outer periphery of the superconducting conductor layer 23W so as to cover it. A ground layer 26 is disposed on the outer periphery of the insulator layer 25 </ b> W, and a heat insulating inner tube 27 is disposed on the outer periphery of the ground layer 26 so as to cover the ground layer 26. A heat insulating outer tube 28 is disposed around the outer periphery of the heat insulating inner tube 27, and the heat insulating outer tube 28 is covered with an anticorrosion layer 29. In addition, a cable core is comprised by the core material 21, the superconducting conductor layer 23 (23U, 23V, 23W), and the insulator layer 25 (25U, 25V, 25W).

  The insulator layer 25 (25U, 25V, 25W) is provided to ensure insulation between the superconducting conductor layers 23 (23U, 23V, 23W) sandwiching the insulator layer 25.

  In this embodiment, the insulator layer 25 is formed in a cylindrical shape by winding semiconductor paper (not shown) such as carbon paper, metallized paper, kraft paper, metallized paper, and semiconductor paper in layers. Metallized paper reduces dielectric loss, and the surface on the semiconductor paper side is formed as a conductive surface.

  The insulating layer 25U in the superconducting cable 20 insulates the U-phase superconducting conductor layer 23U from the V-phase superconducting conductor layer 23V, and the insulating layer 25V includes the V-phase superconducting conductor layer 23V and the W-phase superconducting conductor layer. Insulate from 23W. The insulator layer 25W insulates the W-phase superconducting conductor layer 23W from the ground layer 26.

  The ground layer 26 has conductivity, and is formed in a cylindrical shape that is disposed so as to cover the cable core. The ground layer 26 holds the outer surface of the cable core at the ground potential by being grounded (see FIG. 1).

  The ground layer 26 may be formed by, for example, winding a conductive tape such as a copper tape around the outer periphery of the insulator layer 25W, or formed by a copper pipe or a braided wire copper wire wound in a cylindrical shape. May be. The ground layer 26 may be formed by applying a conductive paint to the outer surface of the insulator layer 25W.

  The heat insulating inner tube 27 constitutes a double tube structure together with the heat insulating outer tube 28, and prevents heat from entering the heat insulating inner tube 27 from the inside of the heat insulating inner tube 27 and the outside of the heat insulating outer tube 28. The heat insulating inner tube 27 preferably has a corrugated shape together with the heat insulating outer tube 28. For the heat insulating inner tube 27 and the heat insulating outer tube 28, for example, a corrugated tube (corrugated tube) made of stainless steel (SUS) is applied.

  The heat insulating inner tube 27 accommodates the cable core and is filled with a refrigerant (for example, liquid nitrogen) during operation. Thereby, the superconducting conductor layers 23U, 23V, and 23W in the cable core are maintained in a superconducting state. Further, between the heat insulating inner tube 27 and the heat insulating outer tube 28 is kept in a vacuum state during operation for heat insulation.

  The anticorrosion layer 29 not only prevents corrosion of the heat insulating outer tube but also has desired withstand voltage characteristics, and is used in a room temperature environment. The anticorrosion layer 29 may be made of a material having a proven track record in normal conducting cables and having excellent electrical insulation strength, such as polyethylene (PE) and polyvinyl chloride (PVC). With such an insulating resin, the anticorrosion layer 29 can be easily formed simply by extruding the insulating resin on the outer periphery of the heat insulating outer tube 28.

<Configuration of superconducting wire>
FIG. 3 is a cross-sectional view schematically showing the configuration of the superconducting wire 40 constituting the superconducting conductor layer 23 (23U, 23V, 23W).

Superconducting conductor layer 23 (23U, 23V, 23W) is formed in a cylindrical shape by superconducting wire 40. Here, the superconducting wire 40 is a REBa _y Cu ₃ O _z system (RE represents one or more elements selected from Y, Nd, Sm, Eu, Gd, and Ho, and y ≦ 2 and z = 6. 2 to 7)). The thickness is not particularly limited, but is preferably 0.3 μm or more.

  The superconducting wire 40 is formed by sequentially laminating a superconducting layer 43, which is a tape-shaped oxide superconducting thin film, and a protective layer 44 on an intermediate layer 42 formed on a tape-shaped metal substrate 41. Have been made.

  The substrate 41 has a tape shape, and is, for example, nickel (Ni), a nickel alloy, or stainless steel. Here, the metal substrate 41 is a crystal grain non-oriented, heat-resistant, high-strength metal substrate, such as a Ni-W-based, Ni-Cr-based (specifically, a Ni-Cr-Fe-Mo-based Hastelloy). (Registered trademark) B, C, X, etc.), W—Mo, Fe—Cr (for example, austenitic stainless), Fe—Ni (for example, non-magnetic composition), and the like. Cubic Vickers hardness (Hv) = 150 or more nonmagnetic alloy. The thickness of the substrate 41 is preferably 0.1 mm or less, for example.

  The intermediate layer 42 is, for example, a first intermediate layer (diffusion prevention layer) for preventing diffusion of elements from the substrate 41 from reaching the superconducting layer 43, and orienting the crystals of the YBCO superconducting layer 43 in a certain direction. A plurality of intermediate layers, such as a second intermediate layer (alignment layer).

The intermediate layer 42 may be composed of any number of layers including one or more layers. For example, the intermediate layer 42 is a first layer made of an aluminum oxide (Al ₂ O ₃ ) layer, a gallium-doped zinc oxide layer (Gd ₂ Zr ₂ O ₇ : GZO), a yttrium-stabilized zirconia (YSZ), or the like on the substrate 41. A _second layer that is a layer such as Y ₂ O ₃ or LaMnO _{3, a third} layer that is composed of magnesium oxide (MgO), a fourth layer that is a layer such as lanthanum manganese oxide (LaMnO ₃ ), cerium oxide (CeO) ₂ ) The fifth layer, which is a layer, is formed by laminating in order. The first layer and the second layer are formed by a sputtering method. In addition, as for the thickness of each layer (1-4 layers) which comprises the intermediate | middle layer 42, 1000 nm or less is preferable. A superconducting layer 43 is formed on the intermediate layer 42.

  The superconducting layer 43 is formed on an intermediate layer by an MOD method (Metal Organic Deposition Processes) using an organic metal salt or an organic metal compound as a raw material without using a vacuum process. In the MOD method, a metal organic acid salt on a composite substrate provided with an intermediate layer on a metal substrate is heated and thermally decomposed to form a thin film as a superconducting layer on the composite substrate.

Here, the superconducting layer 43 of the present embodiment is constituted by an yttrium oxide superconductor (RE123). This superconducting layer is a REBa _y Cu ₃ O _z system (RE represents one or more elements selected from Y, Nd, Sm, Gd, Eu, Yb, Pr and Ho, and y ≦ 2 and z = 6 2 to 7)) of the high-temperature superconducting thin film. In the superconducting layer, oxide particles of 50 nm or less containing at least one additive element of Zr, Sn, Ce, Ti, Hf, and Nb may be dispersed as a magnetic flux pinning point. More preferably, the flux pinning point is 5-30 nm oxide particles.

  The protective layer 44 has conductivity and is formed on the superconducting layer 43. The protective layer 44 is made of a noble metal such as silver, gold, platinum, or an alloy thereof and a low resistance metal. The protective layer 44 is formed directly on the superconducting layer 43 by sputtering or the like. The protective layer 44 prevents the performance degradation caused by the reaction of the superconducting layer 43 by direct contact with a precious metal such as gold or silver or a material other than an alloy thereof. In addition to this, the protective layer 44 disperses heat generated by an accident current or alternating current to prevent destruction and performance degradation due to heat generation.

  The protective layer 44 in the superconducting wire 40 of the present embodiment has an Ag layer 441 formed of silver on the superconducting layer 43 and a Cu layer 442 formed on the Ag layer 441. For example, the film thickness of the Ag 441 layer is preferably 7 μm or less, and the film thickness of the Cu layer 442 is preferably 70 μm or less.

  The Cu layer 442 may be disposed so as to cover the entire base material from the substrate 41 to the Ag layer 441. In the present embodiment, the protective layer 44 includes the Ag layer 441 and the Cu layer 442. However, the protective layer 44 may be formed only of the Cu layer 442 or may be formed of only the Ag layer 441.

  The superconducting wire 40 is covered with a protective layer 44 having conductivity, in this embodiment, an Ag layer 441 and a Cu layer 442, and the film thickness of the protective layer 44 is 40% or less with respect to the film thickness of the superconducting wire. Preferably, it is 30% or less. When the above range is exceeded, when an overcurrent flows through the superconducting cable line 10, the current is transferred to the former, so that the temperature rises and liquid nitrogen bumps due to Joule heat generation. Accordingly, it takes a considerable time to return to the predetermined temperature. On the other hand, when it is below the above range, overcurrent is shunted to the shunt conductor 30 while the superconducting cable line 10 maintains the superconducting state.

The superconducting wire 40 is spirally wound on the core material 21, the insulator layer 25U, the insulator layer 25V, and the insulator layer 25W with the substrate 41 facing the inner periphery and the protective layer 44 facing the outer periphery. By rotating, the respective superconducting conductor layers 23U, 23V, and 23W are formed.
Each of the superconducting conductor layers 23U, 23V, and 23W is connected to the shunt conductor 30 (30U, 30V, and 30W) in parallel.

<Diversion conductor 30>
The shunt conductor 30 (30U, 30V, 30W) is provided outside the superconducting cable 20 and is used as an electric path for shunting at least part of the overcurrent (short-circuit current) flowing through the superconducting cable 20. The shunt conductor 30 (30U, 30V, 30W) is made of a normal conductor, and may be formed of, for example, a copper twisted conductor. In the present embodiment, a CV cable (cross-linked polyethylene insulated vinyl sheath cable) is used for the shunt conductor 30. The split fluid 30 has a higher resistance than the superconducting cable 20.

  A CV cable is a cable in which a conductor is covered with crosslinked polyethylene and the outer periphery thereof is covered with a vinyl sheath. In the present embodiment, the CV cable includes a cable shielding layer and a vinyl chloride sheath, which are formed of a cable inner semiconductive layer (not shown), a cable insulator, a cable outer semiconductive layer, an aluminum corrugated sheath, and the like on the cable conductor. A cable sheath is provided. In addition, the cable inner semiconductive layer, the cable insulator, and the cable outer semiconductive layer are usually formed by extrusion coating three layers simultaneously.

  By stripping both ends of the CV cable, the cable shielding layer, the cable outer semiconductive layer, the cable insulator, and the cable conductor are sequentially exposed. The exposed portions of both ends of these CV cables are electrically connected in parallel to the respective superconducting conductor layers 23U, 23V, and 23W on both ends (the portions stripped at both ends) of the superconducting conductor layers 23U, 23V, and 23W of the respective phases. Connected.

  The CV cable that is the shunt conductor 30 (30U, 30V, 30W) has a cross-sectional area that is designed for shunting the short-circuit current that passes through the superconducting conductor layer.

  The shunt conductor 30U is connected in parallel to the U-phase superconducting conductor layer 23U of the superconducting cable 20, and an overcurrent such as a short-circuit current flowing in the superconducting conductor layer 23U is shunted to the shunt conductor 30U. The shunt conductor 30V is connected in parallel to the V-phase superconducting conductor layer 23V of the superconducting cable 20, and an overcurrent such as a short-circuit current flowing in the superconducting conductor layer 23V is shunted to the shunt conductor 30V. The shunt conductor 30W is connected in parallel to the W-phase superconducting conductor layer 23W of the superconducting cable 20, and an overcurrent such as a short-circuit current flowing in the superconducting conductor layer 23W is shunted to the shunt conductor 30W.

<Effect>
<During steady operation>
In the normal operation state of the superconducting cable line 10, the superconducting state without resistance is maintained in each of the superconducting conductor layers 23U, 23V, and 23W of the superconducting cable 20. Therefore, the superconducting cable line 10 efficiently transmits an alternating current using the superconducting cable 20.

<During overcurrent transmission>
In the superconducting cable line 10, as shown in FIG. 1, a short-circuit current generator 50 is connected to one end of the superconducting cable 20, the other end is grounded, and an overcurrent is applied to the superconducting cable 20 from one end, that is, the primary side. As a short circuit current. For example, the superconducting cable 20 is energized with a rated voltage of 22 kV and a rated current of 3 kA from the primary side.

  FIG. 4 is a diagram for explaining a state when a short-circuit current flows through the superconducting cable line according to the embodiment. In FIG. 4, since the plurality of superconducting conductor layers 23U, 23V, and 23W through which a short-circuit current flows have the same function, the U-phase superconducting conductor layer 23U among these superconducting conductor layers 23U, 23V, and 23W Indicates the magnitude of the current, and the description of the V phase and the W phase is omitted.

  FIG. 4A shows a current generated by the short-circuit current generator 50 and flowing in the superconducting conductor layer 23U of the superconducting cable 20, that is, a current on the primary side of the superconducting cable 20. 4B shows the current flowing through the superconducting cable 20 (specifically, the superconducting conductor layer 23U), and FIG. 4C shows the current flowing through the shunting conductor 30 (specifically, the shunting conductor 30U), which is a CV cable. It is a figure which shows the electric current which flows through a normal conductor. For example, a three-phase short-circuit current of 25 kA is passed through a parallel line of the superconducting cable 20 and the shunt conductor 30 as the superconducting cable line 10 for 2 seconds, and measurement is performed by the DC four-terminal method (in liquid nitrogen temperature of 77.3 K).

  As for the shunt current shunting in the superconducting cable line 10 of the present embodiment, as shown in FIG. 4, when a short-circuit current flows in each of the U phase, the V phase, and the W phase, the superconducting cable 20 and the shunt conductor (CV It can be seen that the effective value of the current flowing in the cable) is equal to the effective value of the current flowing in the primary side of the superconducting cable 20.

  As described above, when a short-circuit current (see FIG. 4A) that is an overcurrent flows through the superconducting cable line 10, the overcurrent is caused by the superconducting cable 20 (specifically, the superconducting conductor layer 23U) and the shunt conductor 30 that is a CV cable. The current is divided into (specifically, the current dividing conductor 30U).

  In the present embodiment, each of the superconducting conductor layers 23U, 23V, 23W of the superconducting cable 20 is formed on the superconducting layer 43 formed on the substrate 41 via the intermediate layer 42, and at least both of Ag and Cu, etc. Since the superconducting wire 40 is formed with the protective layer 44 having a specific film thickness having one, overcurrent is shunted to the shunt conductor while maintaining the superconducting state.

  Thereby, according to the superconducting cable line 10, even if an overcurrent flows through the superconducting cable 20 due to occurrence of a short-circuit accident or the like, the superconducting cable 20 does not increase the temperature without flowing the overcurrent through the superconducting cable 20. Thus, an overcurrent can be shunted through the shunt conductor 30 while a current is passed while maintaining the superconducting state.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The embodiment of the present invention has been described above. The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this. That is, the description of the configuration of the apparatus and the shape of each part is an example, and it is obvious that various modifications and additions to these examples are possible within the scope of the present invention.

  The superconducting cable line according to the present invention is effective as a superconducting cable line using a three-homogeneous-axis superconducting cable, having an effect of receiving an overcurrent while maintaining the superconducting state without increasing the temperature of the superconducting cable. It is.

DESCRIPTION OF SYMBOLS 10 Superconducting cable line 20 Superconducting cable 21 Core 23, 23U, 23V, 23W Superconducting conductor layer 25, 25U, 25V, 25W Insulator layer 26 Grounding layer 27 Heat insulation inner pipe 28 Heat insulation outer pipe 29 Corrosion prevention layer 30, 30U, 30V, 30 W Shunt conductor 40 Superconducting wire 41 Substrate 42 Intermediate layer 43 Superconducting layer 44 Protective layer 50 Short-circuit current generator 441 Ag layer 442 Cu layer

Claims (5)

A superconducting cable having a plurality of superconducting conductor layers that are formed by winding a plurality of superconducting wires around the outer periphery of the core, coaxially with the core; and
A shunt conductor formed of a normal conductor for shunting at least part of an overcurrent flowing in the superconducting cable, provided outside the superconducting cable;
Have
The superconducting wire has a superconducting layer and a conductive protective layer containing at least one of copper and silver covering the superconducting layer, and
The thickness of the protective layer is 40% or less with respect to the thickness of the superconducting wire.
Superconducting cable track. A superconducting cable having a plurality of superconducting conductor layers formed coaxially with the core member by winding a plurality of superconducting wires around the outer periphery of the core member;
A shunt conductor formed of a normal conductor for shunting at least part of an overcurrent flowing in the superconducting cable, provided outside the superconducting cable;
Have
The superconducting conductor layer of the superconducting cable diverts the overcurrent to the shunt conductor while maintaining a superconducting state.
Superconducting cable track. The shunt conductor is a CV cable.
The superconducting cable line according to claim 1 or 2. The core material is a stainless steel core material,
The superconducting cable line according to any one of claims 1 to 3. The superconducting cable is a three homologous axis superconducting cable,
The plurality of layers are a U-phase superconducting conductor layer, a V-phase superconducting conductor layer, and a W-phase superconducting conductor layer, respectively.
A plurality of the shunt conductors;
The plurality of shunt conductors are connected to the U-phase superconducting conductor layer, the V-phase superconducting conductor layer, and the W-phase superconducting conductor layer, respectively.
The superconducting cable line according to any one of claims 1 to 4.

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