JP5166144B2 - Superconducting cable - Google Patents

Description

  The present invention relates to a superconducting cable. In particular, in a superconducting cable including a superconducting shield layer and a normal conducting shield layer, the present invention relates to a superconducting cable that can suppress a current from constantly flowing through the normal conducting shield layer.

  As a superconducting cable, one having a former, a superconducting conductor layer, an insulating layer, a shield layer, and a protective layer in order from the center is known. In particular, as a countermeasure against short-circuit current of an AC superconducting cable, a cable in which a shield layer is composed of an inner superconducting shield layer and an outer normal conducting shield layer is also known (Patent Document 1). Usually, the superconducting conductor layer and the superconducting shield layer are formed in multiple layers by spirally winding a superconducting wire.

  Of these shield layers, a current flows through the superconducting shield layer during normal operation, and the normal conducting shield layer is used as a short-circuit current bypass flow path during a short-circuit accident.

JP 2006-331894 A

  In an AC superconducting cable, the current flowing through the superconducting conductor layer and the superconducting shield layer is adjusted by the winding pitch of the superconducting wire. In such a pitch-adjustable superconducting cable, a large magnetic field is generated in the cable axial direction during operation. Usually, since the resistance of the superconducting wire is very small, the current flows almost through the superconducting wire and does not flow through the normal conducting shield layer. However, it has been found that particularly in a superconducting cable with a large rated current, a current may flow through the normal conducting shield layer due to the magnetic field in the axial direction, resulting in a large loss.

  The present invention has been made in view of the above circumstances, and one of the purposes thereof is a superconducting cable including a superconducting shield layer and a normal conducting shield layer. In a normal state, a current substantially flows through the normal conducting shield layer. It is to provide a superconducting cable that can be prevented.

  When energizing a cable in which the winding direction / pitch of the superconducting wire constituting the superconducting shield layer and the winding direction / pitch of the normal conducting wire constituting the normal conducting shield layer are changed, We examined whether or not a current flows through the conductive shield layer. As a result, it is known that whether or not current flows through the normal conducting wire is largely related to the winding direction and pitch of the outermost superconducting wire in the superconducting shield layer and the winding direction and pitch of the normal conducting wire. As a result, the present invention has been completed.

The superconducting cable of the present invention has a superconducting shield layer in which a superconducting wire is spirally wound, and a normal conducting shield layer in which a normal conducting wire is spirally wound outside the superconducting shield layer. And the normal conducting wire which comprises this normal conducting shield layer is wound on the following conditions, It is characterized by the above-mentioned.
(1) The winding direction of the normal conducting wire is the same as the winding direction of the superconducting wire constituting the outermost layer of the superconducting shield layer.
(2) The pitch of the normal conducting wire is such that the deviation ratio of the pitch of the normal conducting wire to the pitch of the superconducting wire constituting the outermost layer of the superconducting shield layer is -20 to 50%. This deviation ratio is expressed by the following equation.
Deviation ratio (%) = {(pitch of normal conducting wire−pitch of superconducting wire) / pitch of superconducting wire} × 100

  According to this configuration, the current flowing through the normal conducting shield layer in a steady state can be suppressed very slightly, and loss can be reduced.

  In the superconducting cable of the present invention, it is preferable that the normal conductive shield layer is wound with a normal conductive wire at a pitch such that the deviation ratio is -10 to 20%.

  According to this configuration, it is possible to make the current flowing through the normal conducting shield layer substantially in a steady state, and to make a superconducting cable with less loss.

  In the superconducting cable of the present invention, the pitch of the normal conducting wire may be the same as the pitch of the superconducting wire constituting the outermost layer of the superconducting shield layer.

  According to this configuration, it is possible to make the current flowing through the normal conducting shield layer substantially in a steady state, and it is possible to reduce the loss of the superconducting cable.

  According to the superconducting cable of the present invention, it is possible to suppress as much as possible the current flowing through the normal conducting shield layer in a steady state, and to reduce loss.

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

[Superconducting cable]
As shown in FIG. 1, the superconducting cable 1 of the present invention includes a core 10 and a heat insulating tube 50 that houses the core 10. Here, a three-core batch type superconducting cable in which three cores 10 are collectively stored in a heat insulating tube is shown.

{Core configuration}
Each core 10 includes a former 11, a superconducting conductor layer 12, an internal semiconductive layer 13, an insulating layer 14, an external semiconductive layer 15, a superconductive shield layer 16, a normal conductive shield layer 17, and a protective layer 18 in order from the center side. .

  As the former 11, a normal conductive wire made of copper or the like, or a normal conductive pipe made of stainless steel or the like can be suitably used. In an alternating current application, it is preferable that the normal conducting wire is insulated.

  The inner semiconductive layer 13 and the outer semiconductive layer 15 are configured by winding a carbon tape around the outside of the superconducting conductor layer 12 or the outside of the insulating layer 14.

  The insulating layer 14 can be composed of insulating paper such as kraft paper, semi-synthetic paper obtained by laminating insulating paper and plastic tape, and plastic tape alone or in combination. In particular, semi-synthetic paper obtained by laminating polypropylene film and kraft paper is preferable in terms of insulating properties.

  The superconducting conductor layer 12 is formed by winding a superconducting wire in a spiral shape. As the superconducting wire, a tape wire in which a filament made of a Bi-based oxide superconductor is embedded in a stabilizing material such as a silver alloy can be suitably used. In addition, it can be expected to use a thin film superconducting wire in which a YBCO thin film is formed on a substrate. Usually, the superconducting conductor layer 12 is formed in multiple layers. When the superconducting conductor layer 12 is a multilayer, in order to reduce the AC loss by adjusting the current value in each layer or each wire, the winding direction or pitch of the superconducting wire is set for each layer or for some layers. May be adjusted. In the superconducting cable 1 (pitch adjusting type superconducting cable) subjected to such pitch adjustment, a large magnetic field may be generated in the cable axial direction, and a current due to the magnetic field may flow through the normal conducting shield layer 17. In particular, in the superconducting cable 1 having a large rated current, the loss due to the current flowing through the normal conducting shield layer 17 increases.

  In the superconducting shield layer 16, when an alternating current flows through the superconducting conductor layer 12, an induced current flows. As the superconducting shield layer 16, a superconducting wire similar to the superconducting conductor layer 12 can be preferably used. In addition, the superconducting shield layer 16 is also formed by winding a superconducting wire in a spiral like the superconducting conductor layer 12. Usually, the superconducting shield layer 16 is also formed in multiple layers. The superconducting shield layer 16 may also adjust the winding direction and pitch of the superconducting wire for each layer or a part of the layers in order to reduce AC loss.

  The normal conducting shield layer 17 does not substantially flow current during normal operation of the superconducting cable 1, but becomes a shunt path when an accident current such as a short circuit current flows to the superconducting shield layer 16. The normal conductive shield layer 17 is configured by winding a normal conductive wire such as a copper wire in a spiral shape. Usually, the normal conducting shield layer 17 is also formed in multiple layers.

  Here, the winding direction of the normal conducting wire constituting the normal conducting shield layer 17 is set to the same direction as the superconducting wire constituting the outermost layer of the superconducting shield layer 16 (hereinafter referred to as the outer layer wire). Generally, there are S winding and Z winding in the winding direction of the wire. For example, if the winding direction of the outer layer wire is S winding (Z winding), the normal conducting wire constituting the normal conducting shield layer 17 is also S winding (Z winding).

  Further, the deviation ratio of the normal conducting wire pitch to the outer layer wire pitch is set to -20 to 50%. The deviation ratio is represented by {(pitch of normal conducting wire−pitch of superconducting wire) / pitch of superconducting wire} × 100.

  As will be apparent from the calculation example described later, if the normal conducting shield layer 17 is formed so as to satisfy the winding direction and the pitch, even if the pitch-adjustable cable is used, the normal conducting shield layer 17 is formed during steady operation. It is possible to suppress as much as possible that a current hardly flows and a loss occurs.

  The protective layer 18 is formed by winding kraft paper or the like on the normal conductive shield layer 17, and protects the normal conductive shield layer 17.

{Configuration of insulation pipe}
As the heat insulation pipe 50, a double pipe structure composed of an inner pipe 52 and an outer pipe 54 is used. For both the inner tube 52 and the outer tube 54, a stainless corrugated tube is preferably used. A super insulation 56 for reflecting radiant heat is interposed between the inner tube 52 and the outer tube 54 and is evacuated. Among the heat insulating pipes 50, for example, a refrigerant such as liquid nitrogen is circulated in the inner pipe 52. The outside of the outer tube 54 is covered with an anticorrosion layer 60 such as polyethylene.

[Example of trial calculation]
Next, using the configuration according to the superconducting cable described above as a model, the winding direction / pitch of the superconducting wire constituting the superconducting shield layer and the winding direction / pitch of the normal conducting wire constituting the normal conducting shield layer are changed, The relationship between the value of the current flowing through the normal conducting shield layer was estimated.

<Calculation conditions>
A cable model is shown in FIG. In this model, four superconducting conductor layers C1 to C4 are provided, and two superconducting shield layers S1 and S2 and four normal conducting shield layers D1 to D4 are provided outside thereof. The superconducting wires constituting the superconducting conductor layers C1 to C4 and the superconducting shield layers S1 and S2 are Bi2223 oxide high temperature superconducting tape wires, and the normal conducting wires are copper tape wires. In this model, a trial calculation is performed based on a circuit in which a current flows in parallel in the superconducting conductor layer and an induced current flows in the superconducting shield layer and the normal conducting shield layer. In the trial calculation, the radial inductance depending on the inner diameter of each layer, the axial inductance depending on the pitch, and the resistance of each layer are calculated to obtain the current distribution of each layer. Tables 1 and 2 show the specifications of each layer of the cable model. Among these, the following trial calculation is performed by changing the pitch and winding direction of the normal conducting wires D1 to D4.

<Dependence of current distribution of each layer on winding direction of normal conducting wire>
The pitch of the normal conducting wire constituting the normal conducting shield layers D1 to D4 is all 0.31m, and the winding direction of the normal conducting wire of each layer is SSSS, SZSZ, ZZZZ (winding direction of D1 to D4 from left to right) The current distribution of each layer was estimated. The results are shown in Tables 3 and 4. “I _{D all} ” in Table 4 is the total current value of the normal conducting shield layer. Moreover, the current distribution of each layer of these three models with different winding directions is shown in FIGS.

  As is apparent from Tables 3 and 4, when the winding direction of the normal conducting wire is SSSS, almost no current flows through the normal conducting shield layers D1 to D4. On the other hand, when the winding direction of the normal conducting wire is SZSZ, a large current flows through the normal conducting shield layers D2 and D4 wound with Z, and the winding direction of the normal conducting wire is ZZZZ. It can be seen that a large current flows through all the normal conducting shield layers D1 to D4.

  This can also be seen from FIGS. When the winding direction of the normal conducting wire is SSSS, as shown in FIG. 3, current flows through the superconducting shield layers S1 and S2, but almost no current flows through the normal conducting shield layers D1 to D4. . In this figure, since the currents of the layers D1 to D4 of the normal conducting shield layer are almost zero, the graphs are all overlapped and shown in a horizontal shape. On the other hand, when the winding direction of the normal conducting wire is SZSZ, as shown in Fig. 4, (1) the current graph of the normal conducting shield layers D1 and D3 with S winding shows very small waveforms. (2) Z winding (current graph of normal conducting shield layers D2 and D4 is smaller than current graph of superconducting shield layers S1 and S2, but S winding It can be seen that a relatively large current flows from the current graph of normal conducting shield layers D1 and D3, and that the winding direction of the normal conducting wire is ZZZZ as shown in FIG. In this case, a large current waveform is observed in all the normal conducting shield layers D1 to D4.

  From the above, if the winding direction of the normal conducting wire constituting the normal conducting shield layer is the same direction as the superconducting wire constituting the outermost layer (S winding) in the superconducting shield layer, during normal operation It can be seen that almost no current flows through the normal conducting shield layer.

<Dependence of current distribution of each layer on pitch of normal conducting wire>
Next, SSSS was used as the winding direction of the normal conducting wire constituting the normal conducting shield layers D1 to D4, and the current distribution of each layer D1 to D4 was estimated by changing the pitch of these normal conducting wires. Here, the calculation was performed using a model in which the pitch of the superconducting wire constituting the outermost layer of the superconducting shield layers S1 and S2 is 0.31 m as a reference and the pitch of the normal conducting wire is shifted with respect to this reference. The pitch deviation ratio was {(pitch of normal conducting wire-pitch of superconducting wire) / pitch of superconducting wire} × 100. The results are shown in Table 5. The trial calculation results are shown in FIG.

As is apparent from Table 5 and FIG. 6, it can be seen that the total amount of current I _{D all} flowing through the normal conducting shield layers D1 to D4 is minimized when the pitch of the normal conducting wire is 320 mm. In addition, it can be seen from the graph of FIG. 6 that if the heat generation in the normal conducting shield layers D1 to D4 is set to 1 W / m or less, the deviation ratio may be set to -20 to 50%. In particular, when the deviation ratio is set to -10 to 20%, it can be seen that the loss can be reduced to an almost negligible level.

  In addition, this invention is not necessarily limited to said Example, A various change can be made.

  The superconducting cable of the present invention can be suitably used for large-capacity power transmission.

It is an edge part perspective view of the superconducting cable which concerns on embodiment of this invention. It is explanatory drawing which shows the model of the superconducting cable used in the example of calculation. In a calculation example, it is a graph which shows the electric current waveform of each cable layer when the winding direction of a normal conducting wire is set to SSSS. In a calculation example, it is a graph which shows the electric current waveform of each cable layer when the winding direction of a normal conducting wire is set to SZSZ. In a calculation example, it is a graph which shows the electric current waveform of each cable layer when the winding direction of a normal conducting wire is set to ZZZZ. In a calculation example, it is a graph which shows the electric current and the emitted-heat amount of a normal conducting shield layer at the time of changing the pitch of a normal conducting material.

Explanation of symbols

1 Superconducting cable
10 core
11 Former 12 Superconducting conductor layer 13 Internal semiconductive layer 14 Insulating layer
15 External semiconductive layer 16 Superconducting shield layer 17 Normal conducting shield layer
18 Protective layer
50 Insulated pipe
52 Inner pipe 54 Outer pipe 56 Super insulation
60 Anticorrosive layer

Claims (5)

A superconducting conductor layer in which a superconducting wire is spirally wound;
An insulating layer formed outside the superconducting conductor layer;
A superconducting shield layer in which a superconducting wire is spirally wound outside the insulating layer;
A superconducting cable having a normal conducting shield layer in which a normal conducting wire is spirally wound outside the superconducting shield layer,
The normal conducting shield layer is
In the normal operation of the superconducting cable, substantially no current flows, but in the event of an accident it is a shunt path for the accident current,
The winding direction of the normal conducting wire is the same as the winding direction of the superconducting wire constituting the outermost layer of the superconducting shield layer,
Superconductivity characterized in that the pitch of the normal conducting wire is configured such that the deviation ratio of the pitch of the normal conducting wire to the pitch of the superconducting wire constituting the outermost layer of the superconducting shield layer is -20 to 50% cable.
Deviation ratio (%) = {(pitch of normal conducting wire−pitch of superconducting wire) / pitch of superconducting wire} × 100   The superconducting cable according to claim 1, wherein the normal conducting shield layer is formed by winding a normal conducting wire at a pitch such that the deviation ratio is −10 to 20%.   The superconducting cable according to claim 1 or 2, wherein the pitch of the normal conducting wire is the same as the pitch of the superconducting wire constituting the outermost layer of the superconducting shield layer. 4. The superconducting conductor layer is provided in a plurality of layers, and the winding direction and pitch of the superconducting wire are adjusted so as to reduce AC loss for each layer or a part of the layers. The superconducting cable according to any one of the above.   The superconducting cable according to any one of claims 1 to 4, wherein a case where the deviation ratio is 0% or less is excluded.

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