JP2012033755A - Superconducting device protective operation method and superconducting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconducting device operation method and a superconducting device.SOLUTION: A standard measurement area and a first measurement area are partitioned on the surface of a stabilization layer, and voltages of these areas are measured. Regarding these voltages, the minimum voltage detectable by a voltmeter is set to Vd. An oxide superconductor is cooled to the critical temperature or lower, and power is supplied from a power supply. The temperature and the temperature rise rate of the oxide superconductor at a position in time and space where the minimum voltage Vd is detected are represented by Ta and dTa/dt, respectively. The interruption response time which a switching device may take to interrupt a current from the power supply is represented by Td. The temperature of the oxide superconductor at the point in time of the current interruption is set to Ts. Then, the power supply is disconnected to satisfy a condition of Ts=Ta+dTa/dt×Td≤500K(K: absolute temperature).

Description

  The present invention relates to a protective operation method for a superconducting device and a superconducting device.

Rare earth oxide superconductors (REBa ₂ Cu ₃ O _{7-X, where} RE is a rare earth element including Y) discovered in recent years exhibit superconductivity at liquid nitrogen temperatures and have low current loss. It has been studied as a very promising high-temperature superconductor, and it is desired to process it into a wire and use it as a high-temperature superconducting wire cable for power supply or a high-temperature superconducting coil for generating a magnetic field. Moreover, as a method for processing this type of oxide superconductor into a wire, a metal having high strength, heat resistance, and easy to be processed into a wire is processed into a long tape shape. A method for forming an oxide superconducting layer on an intermediate layer of metal via an intermediate layer has been studied.

High-temperature superconducting cables using the above-mentioned high-temperature superconductors can be operated with low-cost liquid nitrogen compared to low-temperature superconductor cables that require expensive liquid helium, and are promising to reduce energy loss during power transmission. Research and development is ongoing as a technology.
The low temperature superconductor used by cooling with liquid helium has a low critical temperature as low as 10K or less, an operating temperature of about 4K, and is characterized by low specific heat because it is used at a very low temperature. For this reason, in a superconducting coil using a low-temperature superconductor, when a normal conduction transition occurs from the superconducting state for some reason, Joule heat associated with the normal conduction transition occurs in the part where the normal conduction transition occurs. The temperature of the relevant part and the surrounding part rises, the critical current of the superconductor decreases, and as a result, heat is generated in other parts, and the temperature rises repeatedly, and suddenly the normal conduction transition (quenching) Will occur. Therefore, in the case where the low temperature superconductor is energized while being cooled, there is a known method for detecting these quenches by detecting the voltage generated by the normal conduction transition or by detecting the balance voltage. Yes.

However, it is assumed that high temperature superconductors with a critical temperature of about 100K as typified by Bi type and Y type are used at a temperature of about 20K or more, which is known as an operating temperature capable of reducing power consumption of a refrigerator or the like. Has been. Therefore, when comparing the high temperature superconductor with the low temperature superconductor, the specific heat in the operating state is large and the propagation speed at the normal conduction transition is slow. It has been pointed out that body quench may not be detected well.
For example, a low temperature superconductor is supposed to propagate at a speed of several tens of meters to 100 m / second when a normal conduction transition occurs during operation at 4K. According to the inventor's knowledge, when the normal conduction transition is partially generated in the high-temperature superconductor, the normal conduction transition region gradually expands, and the high-temperature superconductor is in the meantime. Is known to increase in temperature.

Conventionally, various technologies for Bi-based high-temperature superconductors have been developed as protection devices for superconducting equipment composed of high-temperature superconductors. As described in Patent Document 1, the ratio of voltage V to current I and the first-order differential value dV A technique for detecting a quench using / dt and a second-order differential value d ² V / dt ² and a technique for protecting a high-temperature superconductor have been proposed.

JP 2006-41274 A

The quench detection technology for the high-temperature superconductor described in the above-mentioned Patent Document 1 is made by reflecting the results of studies on Bi-based oxide superconductors. Regarding the oxide superconductors, the current situation is that no technology has been provided on how to detect quenching by grasping thermal management associated with normal conduction transition.
For example, as shown in FIG. 8, the Bi-based oxide superconducting conductor 100 has a structure manufactured by a roll rolling method or the like so that the Bi-based oxide superconducting layer 101 is covered with an Ag sheath material 102. On the other hand, the rare earth-based oxide superconducting conductor 103 such as Y-based has a completely different structure as shown in FIG.

  The oxide superconducting conductor 103 shown in FIG. 9 is obtained by laminating an oxide superconducting layer 108 on a tape-like metal base material 105 by a film forming method through an intermediate layer 106 and a cap layer 107, and stabilizing layers such as Ag and Cu. Since the multilayer structure is formed by covering 109 and 110, the quench detection technology for the Bi-based oxide superconducting conductor 100 having the structure shown in FIG. 7 is effective for quench detection of the rare earth-based oxide superconducting conductor 103 such as Y-based. There is a background that it has not been verified whether it exists.

  Further, the rare earth-based oxide superconductor such as Y-based material is, for example, a metal substrate 105, an intermediate layer 106, a cap layer 107, an oxide superconducting layer 108, and a stabilizing layer 109, like an oxide superconducting conductor 111 shown in FIG. , 110, and a structure in which the stabilizing layers 112 and 113 are further formed to protect the side and bottom surfaces of the laminated body are being studied. Therefore, the Bi-based structure having the structure shown in FIG. It is not known whether the quench detection technique for the oxide superconducting conductor 100 is effective for quench detection of the rare earth oxide superconducting conductor 111 having the structure shown in FIG.

  The present invention has been made in view of the above-described conventional situation, and an object thereof is to provide a technique effective for quench detection of rare earth-based oxide superconducting conductors such as Y-based.

  In order to solve the above problems, a method of operating a superconducting device of the present invention is provided on a tape-like base material, an intermediate layer provided on the base material, an oxide superconducting layer, and the oxide superconducting layer. An oxide superconducting conductor having a laminated structure comprising a stabilized layer, a power supply for energizing the oxide superconducting layer of the oxide superconducting conductor, and an oxide of the oxide superconducting conductor from the power supply When operating a superconducting device having a switch device for controlling energization to the superconducting layer, a predetermined length along the length direction of the oxide superconducting conductor is formed on the surface of the stabilizing layer laminated on the oxide superconducting layer. At least a reference measurement area defined with an interval and a first measurement area defined to sandwich the reference measurement area with a first interval longer than the predetermined interval, the reference measurement area Voltage at both ends or front The voltage at both ends of the first measurement area is measured, and the minimum voltage that can be detected by a voltage measuring device is set to Vd for the voltage at both ends of the reference measurement area or the voltage at both ends of the first measurement area, and the oxide superconductor Is cooled to below the critical temperature and energized from the power supply device, the temperature of the oxide superconducting conductor at the time and position at which the minimum voltage Vd is detected is Ta, and the rate of temperature increase at that time and position is dTa / dt. In the case where the switch device is set to Td as the response time for interrupting the current from the power supply device, Ts is the temperature of the oxide superconductor at the time of current interruption, and K is the absolute temperature, Ts = Ta + dTa It is characterized in that energization from the power supply device is cut off so as to satisfy the condition of / dt × Td ≦ 500K.

  The operation method of the superconducting device of the present invention is to measure a temperature-resistance characteristic indicating a relationship between a temperature ranging from room temperature to an operating temperature range below the critical temperature of the oxide superconducting layer and a resistance value for the stabilization layer. The temperature rise rate dTa / dt is calculated by converting the voltage rise state after the minimum voltage measurement into a temperature.

  The superconducting device of the present invention is a laminate comprising a tape-like substrate, an intermediate layer provided on the substrate, an oxide superconducting layer, and a stabilization layer provided on the oxide superconducting layer. An oxide superconducting conductor having a structure, a power supply device for energizing the oxide superconducting layer of the oxide superconducting conductor, and a switch device for controlling energization from the power supply device to the oxide superconducting layer of the oxide superconducting conductor A reference measurement area defined with a predetermined interval along the length direction of the oxide superconducting conductor on the surface of the stabilization layer laminated on the oxide superconducting layer, and more than a predetermined interval above A voltage that measures at least a voltage at both ends of the reference measurement area or a voltage at both ends of the first measurement area by partitioning at least a first measurement area defined to sandwich the reference measurement area with a long first interval Comprising a measuring instrument, For the voltage at both ends of the semi-measurement area or the voltage at both ends of the first measurement area, the lowest voltage that can be detected by the voltage measuring device is set to Vd, the oxide superconductor is cooled to a critical temperature or less, and the power supply device is energized. If the temperature of the oxide superconductor at the time and position at which the minimum voltage Vd is detected is Ta, and the rate of temperature increase at that time and position is dTa / dt, the switch device is connected to the power supply device from the power supply device. When the interruption response time capable of interrupting the current is set to Td, the temperature of the oxide superconductor at the time of the current interruption is set to Ts, and K is set to the absolute temperature, the condition of Ts = Ta + dTa / dt × Td ≦ 500K is satisfied. And a control device that cuts off power from the power supply device by the switch device.

  In the superconducting device of the present invention, the control is performed by measuring a temperature-resistance characteristic indicating a relationship between a temperature ranging from room temperature to an operating temperature range lower than the critical temperature of the oxide superconducting layer and a resistance value of the stabilization layer. The control device is provided with a function of storing in the device and calculating the temperature increase rate dTa / dt by converting the voltage increase state after the minimum voltage measurement into a temperature.

  According to the protection operation method and the superconducting device of the present invention, the surface of the stabilizing layer is used as a reference for the rare earth oxide superconducting conductor having a structure in which an intermediate layer, an oxide superconducting layer, and a stabilizing layer are laminated on a base material. When a normal conduction transition occurs in a part of the oxide superconductor for some reason when the measurement area and the first measurement area surrounding it are divided and the superconducting layer in the superconducting state is energized, the voltage meter measures As the temperature Ta at the time when the lowest possible voltage is detected, the temperature Ta is multiplied by the value obtained by multiplying the temperature rise rate by the shut-off response time from the power supply device so that it does not exceed 500K. Protective operation method and superconducting device capable of preventing temperature rise from damaging oxide superconducting layer when oxide superconducting conductor is quenched by shutting off current from power supply device when disconnected It can be provided.

  Further, according to the present invention, when the temperature-resistance characteristic of the stabilization layer is measured from the critical temperature to the operating temperature range, when the normal conduction transition occurs and a voltage is generated in the normal conduction transition portion, the generated voltage Is converted from the temperature-resistance characteristics into a rate of temperature rise, and the normal measurement transition is performed by dividing the reference measurement region and the first measurement region on the stabilization layer and monitoring the voltage generated in them. Can be detected to cut off the energization from the power supply device, and when the oxide superconducting conductor is quenched, it is possible to prevent a temperature rise from damaging the oxide superconducting layer.

The schematic sectional drawing which shows an example structure of the oxide superconducting conductor with which the superconducting apparatus which concerns on this invention is equipped. The schematic block diagram which shows the voltage measuring device, power supply device, and control apparatus which were connected to the oxide superconducting conductor shown in FIG. The block diagram which shows an example of the superconducting apparatus incorporating the oxide superconducting conductor shown in FIG. 2, a voltage measuring device, a power supply device, and a control apparatus. The block diagram which shows an example of the oxide superconducting conductor built in the superconducting apparatus shown in FIG. 3, and the measurement area divided by it. The diagram which shows an example of the voltage behavior measurement result for every time at the time of quench generation | occurrence | production of the oxide superconducting conductor measured in the Example using the superconducting apparatus shown in FIG. The diagram which shows an example of the result of having calculated | required the relationship between time and temperature in the Example based on the voltage behavior shown in FIG. The diagram which shows the measurement result of the temperature-resistance characteristic of the stabilization layer used in the Example. The fragmentary sectional view which shows an example structure of the conventional Bi type oxide superconducting conductor. The fragmentary sectional view which shows an example structure of the conventional rare earth type oxide superconducting conductor. The fragmentary sectional view which shows the structure of the other example of the conventional rare earth type oxide superconducting conductor.

Hereinafter, a first embodiment of a superconducting device and an operation method thereof according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example structure of a rare earth oxide superconducting conductor provided in the superconducting device according to the present invention. A plurality of measurement points are defined in the oxide superconducting conductor as shown in FIG. It is incorporated in the superconducting device shown in FIG.
The oxide superconducting conductor 1 of this embodiment shown in FIG. 1 has a diffusion prevention layer 3, a bed layer 4, a first intermediate layer 5, and a second layer on a tape-like long metal base 2. The intermediate layer (cap layer) 6, the oxide superconducting layer 7, the first stabilizing layer 8, and the second stabilizing layer 9 are laminated. In the present invention, the diffusion preventing layer 3 and the bed layer 4 are not essential, and one or both of them may be omitted depending on circumstances.

  The base material 2 can be used as a base material for a normal superconducting wire, has only to be high strength, and is preferably in the form of a tape for making a long cable, and is made of a heat-resistant metal. Is preferred. Examples thereof include various metal materials such as nickel alloys such as stainless steel and hastelloy, or ceramics arranged on these various metal materials. Among various heat resistant metals, nickel alloys are preferable. Especially, if it is a commercial item, Hastelloy (trade name made by US Haynes Co., Ltd.) is suitable, and Hastelloy B, C, G, N, W, which have different amounts of components such as molybdenum, chromium, iron, cobalt, etc. Any type can be used. What is necessary is just to adjust the thickness of the base material 3 suitably according to the objective, Usually, it can be set as the range of 10-500 micrometers.

The diffusion prevention layer 3 is formed for the purpose of preventing the diffusion of the constituent elements of the base material 2, and silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also referred to as “alumina”), or , GZO (Gd ₂ Zr ₂ O ₇ ) and the like, and its thickness is, for example, 10 to 400 nm. When the thickness of the diffusion preventing layer 3 is less than 10 nm, there is a possibility that the diffusion of the constituent elements of the substrate 2 cannot be sufficiently prevented. On the other hand, if the thickness of the diffusion preventing layer 3 exceeds 400 nm, the internal stress of the diffusion preventing layer 3 increases, and this may cause the entire layer including other layers to be easily peeled off from the substrate 2. Further, since the crystallinity of the diffusion preventing layer 3 is not particularly limited, it may be formed by a film forming method such as a normal sputtering method.
The bed layer 4 has high heat resistance and is used for reducing interfacial reactivity, and is used for obtaining the orientation of a film disposed thereon. Such a bed layer 4 is, for example, a rare earth oxide such as yttria (Y ₂ O ₃ ), and is represented by a composition formula (α ₁ O ₂ ) _2x (β ₂ O ₃ ) _(1-x). It can be illustrated. More _{specifically, Er 2 O 3, CeO 2} , Dy 2 O 3, Er 2 O 3, Eu 2 O 3, Ho 2 O 3, can be exemplified _La 2 _{O 3} and the like. The bed layer 4 is formed by a film forming method such as a sputtering method, and has a thickness of 10 to 100 nm, for example. Further, since the crystallinity of the bed layer 4 is not particularly limited, it may be formed by a film forming method such as a normal sputtering method.

The first intermediate layer 5 may be either a single layer structure or a multi-layer structure, and is a biaxially oriented substance for controlling the crystal orientation of the second intermediate layer 6 as a cap layer laminated thereon. Selected from. Specifically, preferred materials for the first intermediate layer 5 include Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O _3. Examples thereof include metal oxides such as Gd ₂ O ₃ , Zr ₂ O ₃ , Ho ₂ O ₃ , and Nd ₂ O ₃ .
If the first intermediate layer 5 is formed with a good crystal orientation (for example, a crystal orientation degree of 16 ° or less) by an IBAD (Ion-Beam-Assisted Deposition) method, the second intermediate layer formed thereon is formed. The crystal orientation of the oxide superconducting layer 7 formed on the second intermediate layer 6 can be improved. As a result, it is possible to obtain the oxide superconducting layer 7 that can exhibit excellent superconducting properties.
For example, the first intermediate layer 5 made of Gd ₂ Zr ₂ O ₇ , MgO or ZrO ₂ —Y ₂ O ₃ (YSZ) has Δψ (FWHM: full width at half maximum) which is an index representing the degree of crystal orientation in the IBAD method. Since the value can be reduced, it is particularly suitable.

  In the case of the first intermediate layer 5 by the IBAD method, a specific crystal of the sputtered film formed by performing ion irradiation at a predetermined incident angle while depositing the constituent particles of the target layer by the sputtering method. The axis is fixed in the ion incident direction, the c-axis of the crystal is oriented in a direction perpendicular to the surface of the metal substrate, and the a-axis and b-axis of the crystal are oriented in a certain direction in the plane. Therefore, the first intermediate layer 5 formed on the bed layer 4 by the IBAD method can obtain a high degree of in-plane orientation, for example, Δφ = 12 to 16 °.

Next, the second intermediate layer 6 as the cap layer is epitaxially grown by being formed on the surface of the first intermediate layer 5 in which the in-plane crystal axes are oriented as described above, and then the grains in the lateral direction. growing, materials crystal grains can self-orientation in the plane direction, a is not particularly limited as long as it, specifically as _{preferred, CeO 2, Y 2 O 3} , Al 2 O 3, Gd 2 O 3 , ZrO ₂ , Ho ₂ O ₃ , Nd ₂ O _{3 and the} like. When the material of the second intermediate layer 6 is CeO ₂ , the second intermediate layer 6 includes a Ce—M—O-based oxide in which part of Ce is substituted with another metal atom or metal ion. May be. For example, since the second intermediate layer 6 made of CeO ₂ is self-oriented as described above, the in-plane orientation degree is higher than that of the first intermediate layer 5, for example, Δφ = about 4 to 6 °. Can be obtained.

For example, the CeO ₂ layer can be formed by a PLD method (pulse laser deposition method), a sputtering method, or the like, but it is desirable to use the PLD method in that a high film formation rate can be obtained. The film formation conditions for the CeO ₂ layer by the PLD method can be performed in an oxygen gas atmosphere at a substrate temperature of about 500 to 1000 ° C. and about 0.6 to 100 Pa.
The film thickness of the CeO ₂ layer may be 50 nm or more, but is preferably 100 nm or more in order to obtain sufficient orientation. However, if it is too thick, the crystal orientation deteriorates, so that it can be in the range of 50 to 5000 nm, more preferably in the range of 100 to 5000 nm.

The oxide superconducting layer 7 may be a known high-temperature superconductor, and specifically, a material made of REBa ₂ Cu ₃ O _y (RE represents a rare earth element such as Y, La, Nd, Sm, Er, Gd). Can be illustrated. Examples of the oxide superconducting layer 7 include Y123 (YBa ₂ Cu ₃ O _7-X ) or Gd123 (GdBa ₂ Cu ₃ O _7-X ).
The oxide superconducting layer 7 is laminated by a physical vapor deposition method such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, chemical vapor deposition (CVD), or thermal coating decomposition (MOD). In particular, from the viewpoint of productivity, the PLD (pulse laser deposition) method, the TFA-MOD method (organic metal deposition method using trifluoroacetate, coating pyrolysis method) or the CVD method may be used. it can.

  Here, as described above, when the oxide superconducting layer 7 is formed on the second intermediate layer 6 having good orientation, the oxide superconducting layer 7 laminated on the second intermediate layer is also in the second state. Crystallization is performed so as to match the orientation of the intermediate layer 6. Therefore, the oxide superconducting layer 7 formed on the second intermediate layer 6 is hardly disturbed in crystal orientation, and in each of the crystal grains constituting the oxide superconducting layer 7, a base material is used. The c-axis in which electricity does not easily flow is oriented in the thickness direction 2, and the a-axis or the b-axis is oriented in the length direction of the substrate 2. Therefore, the obtained oxide superconducting layer 7 is excellent in quantum connectivity at the crystal grain boundary, and hardly deteriorates in the superconducting characteristics at the crystal grain boundary. High critical current density can be obtained.

The first stabilization layer 8 laminated on the oxide superconducting layer 7 is formed as a layer made of a metal material having good conductivity, such as Ag or a noble metal, having a low contact resistance with the oxide superconducting layer 7 and a familiarity. Is done. The reason why the first stabilization layer 8 is made of Ag is that it has the property of making it difficult for the doped oxygen to escape from the oxide superconducting layer 7 in the annealing step of doping the oxide superconducting layer 7 with oxygen. be able to. In order to form the Ag first stabilizing layer 8, a film forming method such as a sputtering method can be employed, and the thickness thereof can be formed to about 1 to 30 μm.
The second stabilization layer 9 is preferably made of a highly conductive metal material. When the oxide superconducting layer 7 attempts to transition from the superconducting state to the normal conducting state, the second stabilizing layer 9 together with the first stabilizing layer 8 is superconducting. It functions as a bypass where the current of the layer 7 commutates.

  The metal material constituting the second stabilization layer 9 is not particularly limited as long as it has good conductivity, but is relatively limited to copper alloys such as copper and brass (Cu-Zn alloy), stainless steel, and the like. It is preferable to use an inexpensive material, and copper is more preferable because it has high conductivity and is inexpensive. By using copper, it is possible to increase the thickness of the second stabilization layer 9 while keeping the material cost low, and it is possible to obtain an oxide superconductor that can withstand accident currents at low cost. The thickness of the second stabilization layer 9 is preferably 10 to 300 μm. The second stabilization layer 9 can be formed by a known method, and can be formed by a plating method, a sputtering method, or a method of soldering a metal tape such as copper on the first stabilization layer 8. it can.

  Note that the diffusion preventing layer 3, the bed layer 4, the first intermediate layer 5, the second intermediate layer 6, the oxide superconducting layer 7, the first stabilizing layer 8, and the first layer are formed on the tape-like base material 2. The oxide superconducting conductor 1 having a laminated structure in which two stabilizing layers 9 are formed usually forms a protective layer made of an insulating material formed by wrapping a polyimide tape or the like so as to surround the entire circumference thereof, thereby forming an insulating structure. Used for superconducting equipment such as for superconducting coils.

In the present embodiment, in the long oxide superconducting conductor 1, the surface of the second stabilizing layer 9 at an arbitrary position in the length direction is along the length direction of the oxide superconducting conductor 1 as shown in FIG. A reference measurement area S0 having a predetermined length is partitioned, reference voltage measurement points 10 and 11 are installed at both ends thereof, and a heater 12 is installed at the center of the reference measurement area S0. Further, in the long oxide superconductor 1, the first measurement area S1 is defined so as to extend the same distance in the length direction (left and right direction in FIG. 2) of the oxide superconductor 1 including the reference measurement area S0. The first voltage measurement points 17 and 18 are provided at both end portions.
The heater 12 is installed to forcibly transfer the oxide superconducting conductor from the superconducting state to the normal conducting state, and thus is not installed in a normal operation of the superconducting coil, for example.
The distance between S0 and S1 provided along the oxide superconducting conductor 1 may be arbitrary, but is preferably set so that the connecting portion of the oxide superconducting conductor 1 is not included.

A voltage measuring device 19 for individually measuring the voltage V0 generated between the reference voltage measuring points 10 and 11 and the voltage V1 generated between the first voltage measuring points 17 and 18 with respect to the oxide superconductor 1 is provided. It is connected. Each of the measurement points 10, 11, 17, 18 is connected to a voltage measuring device 19 through wirings 10a, 11a, 17a, 18a connected to them, and is configured to measure a voltage generated at each measurement point. Yes.
The voltage measuring device 19 can measure the above-described V0 and V1. Also, what is indicated by reference numeral 24 in FIG. 2 is a thermocouple that is installed near the reference voltage measurement point 10 on the surface of the second stabilization layer 9 and measures the temperature of the oxide superconductor 1.

  Next, the switch device 22 and the power supply device 23 are connected to both ends of the long oxide superconducting conductor 1 via connection wires 20 and 21, and the oxide of the oxide superconducting conductor 1 is connected from the power supply device 23. The superconducting layer 7 can be energized, and the switch device 22 can switch between starting and stopping energization from the power supply device 23 to the oxide superconducting conductor 1 as necessary. Further, a control device 25 is electrically connected to the switch device 22 and the power supply device 23 via connection lines 26 and 27, and the control device 25 switches the on / off operation of the switch device 22 to switch the oxide superconductivity. The conductor 1 is configured so as to be able to control on / off of energization to the oxide superconducting layer 7.

Next, the oxide superconducting conductor 1, the switch device 22, the power supply device 23, and the control device 25 shown in FIG. 2 are more specifically incorporated in the superconducting device 30 having the structure shown in FIG.
The superconducting device 30 according to the present embodiment includes a superconducting coil 32 inside a storage container 31 such as a vacuum container, and includes a refrigerator 33 for cooling the superconducting coil 32 inside the storage container 31 to a critical temperature or lower. Has been. The storage container 31 of this embodiment is connected to a vacuum pump 34 and configured to be able to depressurize the interior to a desired degree of vacuum.

  The superconducting coil 32 is configured by winding the oxide superconducting conductor 1 described above in a coil shape around a bobbin composed of a winding drum 36 and a flange plate 37, and the flange plates 37 formed on both ends of the winding drum 36. Is installed on the bottom side of the container 31 with the winding cylinder 36 in the vertical direction. The winding body 36 is wound around the oxide superconducting conductor 1 having the above laminated structure covered with a coating layer, and insulated, but to the measurement point described above with reference to FIG. The wiring of the heater, the wiring of the heater, etc. are extended so as to be appropriately drawn out from the coating layer.

Next, the container 31 is connected to a DC power supply 23 for energizing the oxide superconducting conductor 1 of the superconducting coil 32, and the power supply 23 and the oxide superconducting conductor 1 inside the container 31 are connected. The connection is made by connecting wires 20 and 21, and the oxide superconducting conductor 1 can be energized from the power supply device 23. Note that a sweeper 23a is attached to the power supply device 23 of this embodiment so that an energization test can be performed while adjusting the value of the current applied to the oxide superconductor 1 stepwise.
In addition, the heater 11 installed in the reference measurement area S0 of the oxide superconductor 1 in the superconducting coil 32 is connected to a heater power source 37 separately provided outside the container 31 via a connection line 38. The reference measurement area S0 of the oxide superconducting conductor 1 can be heated with a target calorific value according to the voltage value supplied from the heater power source 37.
Inside the storage container 31, there are provided a heater 40 for temperature control of the whole oxide superconducting conductor 1 constituting the superconducting coil 32 and a temperature sensor 41 for temperature control. 31 is electrically connected to a temperature controller 42 provided outside 31 by a connection line 42 a, and is configured to be able to control the entire temperature of the oxide superconductor 1 by the control of the temperature controller 42. .

A recording device 43 and a measuring instrument (data logger) 44 are installed outside the storage container 31, and these are connected to each of the measurement areas S 0 to S 1 of the oxide superconducting conductor 1 inside the storage container 31 via a connection line 45. Connected to measurement points 10 to 18 and configured to be able to individually measure and record the voltages of the measurement areas S0 to S1, and these measurement results are connected to a data processing device 46 connected to a measuring instrument 44. Yes.
The data processing device 46 and the control device 25 are electrically connected by a connection line 47, and when data processing is performed in the control device 25, voltage measurement of each measurement area S0 to S3 stored in the data processing device 46 is performed. The connection line 47 is also connected to the temperature controller 42 while being configured so that the result can be referred to.
With the above configuration, the control device 25 is configured to be able to perform operation control of the DC power source 23, operation control of the heater power source 37, and operation control of the temperature regulator 42.

Next, a method of evaluating and operating the temperature behavior and voltage behavior during quenching of the oxide superconducting conductor 1 using the superconducting device 30 having the configuration shown in FIG. 3 will be described below.
As a preparation before operating the superconducting device 30 for evaluation, a copper tape having the same width and the same thickness as the second stabilization layer 9 applied to the oxide superconducting conductor 1 having the above structure, A copper tape with Sn solder plating, which is the same as the Sn solder plating used to fix the second stabilization layer 9 on the first stabilization layer, is prepared, while cooling the copper tape with Sn solder plating. A test for energization is performed separately, and the temperature-resistance characteristics for the copper tape up to the operating temperature range in actual use lower than the critical temperature of the corresponding oxide superconducting layer 7 are measured.
This is because when the oxide superconducting conductor 1 is subjected to an energization test using the superconducting device 30, the resistance becomes 0 when the oxide superconducting layer 7 is in a superconducting state, and the resistance of the second stabilizing layer 9 cannot be measured. Because. For example, if the temperature at which the oxide superconductor 1 is to be operated is 77K, the temperature-resistance characteristics of the rare earth oxide superconductor constituting the oxide superconductor layer 7 from the critical temperature to 77K are measured. If the temperature at which the superconductor 1 is to be operated is 50K, the temperature-resistance characteristics of the rare earth oxide superconductor constituting the oxide superconductor layer 7 from the critical temperature to 55K shall be measured. If the temperature at which the conductor 1 is to be operated is 20K, the temperature-resistance characteristics of the rare earth oxide superconductor constituting the oxide superconducting layer 7 from the critical temperature to 20K are measured. These temperature-resistance characteristics are measured and the results are stored in the memory of the control device 25.

  Thereafter, the refrigerator 33 of the superconducting device 30 is operated, and the temperature of the oxide superconducting conductor 1 is gradually lowered from room temperature to 90K under the control of the temperature controller 42. At this time, the stabilization layer 9 of the oxide superconductor 1 is energized from the power supply device 23, and the temperature-resistance characteristics from room temperature to 90K are measured. Since the oxide superconductor 1 has the oxide superconductor layer 7 made of a rare earth oxide superconductor, the oxide superconductor 1 is an insulator up to its critical temperature of 90K, and when cooled to below the critical temperature, its resistance becomes 0 and the superconducting current flows. It begins to flow. Accordingly, in the temperature range from room temperature to 90K, almost all of the current flowing through the oxide superconductor 1 flows through the stabilization layer 9, and the stabilization layer 9 is made of copper, so that there is resistance, and this resistance value is the temperature. Since it changes according to the descent, it is measured as a relationship between temperature and resistance.

Next, the oxide superconductor 1 of the superconducting device 30 is subjected to a steady operation in which it is energized while maintaining the target operating temperature below the critical temperature, for example, a constant temperature of 77K, 50K, or 20K. Confirm that the desired superconducting current flows.
Thereafter, the heater power source 37 is activated by the control device 25 to activate the heater 12, and the stabilization layer 9 of the oxide superconducting conductor 1 is heated to change the oxide superconducting layer 7 below to the normal conducting state. Let When the oxide superconducting layer 7 is partially subjected to normal conduction transition, the normal conduction transition portion of the oxide superconducting layer 7 gradually propagates and spreads along the oxide superconducting layer 7, and the reference measurement is performed according to the propagation state. Resistance is generated in the area S0 and the first measurement area S1.

The graph shown in FIG. 5 shows a heating heater in the example described later from a state in which the oxide superconducting conductor 1 having a copper stabilization layer having a specific thickness is cooled to 77 K and 100 A is energized to the oxide superconducting layer 7. When the oxide superconducting layer 7 in the reference measurement area S0 is forcibly transferred (quenched) to the normal conducting state by energizing the current, the voltage V1 in the first measuring area increases with time. .
From the graph shown in FIG. 5, it can be seen that the voltage value gradually increases in each of the measurement areas V0 and V1 after the elapse of time. As described above, when the normal conduction transition occurs once in part of the oxide superconducting layer 7, the normal conduction transition is surely propagated in the length direction of the oxide superconducting conductor 1 without stopping. Here, even when the energization to the heater is stopped, the normal conduction transition is surely propagated in the length direction of the oxide superconducting conductor 1 without stopping.
Thereafter, the control device 25 measures the temperature-resistance characteristics from the room temperature to 90K, which have been measured and stored in the memory, and measures the temperature-resistance characteristics from 90K to the operating temperature, for example, 50K and 20K. With reference to the result, the voltage on the vertical axis in FIG. 5 is converted into temperature as shown in FIG. 6 and, for example, the voltage V1 in the first measurement area S1 is displayed as a graph shown in FIG. FIG. 7 shows an example of measurement results of temperature-resistance characteristics from room temperature to 90 K that have been measured and stored in the memory.

  Here, when the oxide superconducting conductor 1 is energized to cause quenching, and in this case, when designing a device that stops energizing the oxide superconducting conductor 1, the resistance starts from the case where the resistance is 0 in the superconducting state. In general, in a voltage measuring device for detecting that a normal conducting state is generated, the minimum voltage detection sensitivity can be set to 0.01 mV. Therefore, the time point at which a voltage of 0.01 mV is generated from the state where the resistance is 0 in the superconducting state is regarded as the time point when the normal conducting transition is made, and in FIG.

Next, when the oxide superconductor 1 is quenched, it is detected as a voltage. Since the voltage detector 19 can recognize that the flow of electricity has surely occurred from the superconducting state, the potential difference is about 0.1 V with a margin. In the graph of FIG. 5, the time for 0.1V is 4.1 seconds, and in FIG. 6 the temperature converted value is 135K at 4.1 seconds.
The temperature rise around 100 msec at this time is 3K, for example, as will be described later. However, the time required for the power supply device 23 to be stopped after the control device 25 is stopped and the power supply is stopped is about 300 msec in the current technology. Therefore, after a time of about 300 msec, the temperature of the portion that has undergone the normal conduction transition rises to 144 K from the relational expression of 135 K + 3 K × 3.
Here, in the oxide superconducting layer 7 made of the rare earth-based oxide superconductor having the above-described laminated structure, when the oxide superconductor 1 is placed in a constant temperature bath at 250 ° C. or higher and installed in a high temperature environment. In addition, since it is easy to escape oxygen from the crystal of the oxide superconducting layer 7, or the constituent elements on the base material side diffuse to the oxide superconducting layer 7 side and the superconducting characteristics are deteriorated, the above-mentioned knowledge is obtained. Thus, even if the temperature rises to 144 K, the oxide superconducting layer 7 does not deteriorate.
Therefore, it is evaluated that the oxide superconducting conductor 1 including the copper stabilization layer having the specific thickness is less likely to deteriorate the oxide superconducting layer 7 even if the normal conducting transition is caused by some factor. it can.

On the other hand, when an oxide superconducting conductor having a copper stabilization layer thinner than the oxide superconducting conductor 1 used earlier is used, when a normal conduction transition occurs and current is bypassed to the copper stabilization layer, When the copper thickness is insufficient, the amount of heat generated in the stabilization layer increases, and as a result, the rate of temperature rise of the oxide superconducting layer 7 in contact with the stabilization layer increases, and 0 as in the previous example. Even if the current is cut off after 300 msec from the time when the voltage reaches the 1 V potential difference, if the oxide superconducting layer 7 rises to a temperature exceeding 500 K, the oxide superconducting layer 7 is likely to be thermally deteriorated.
If the oxide superconducting conductor 1 is grasped and evaluated in this way, the temperature rise is predicted assuming the normal conducting transition, and the oxide superconducting conductor does not deteriorate as the thermal history of the oxide superconducting layer 7. The thickness of the stabilization layer can be determined. Even if the normal conduction transition is made, the oxide superconducting layer 7 will not be thermally deteriorated if the power supply 23 is deenergized under the above-mentioned conditions. A conductor can be obtained.

  The voltage behavior is measured as shown in FIG. 5 using the superconducting device 30 described above, the voltage is converted into temperature from the temperature-resistance relationship, the voltage behavior graph is converted into temperature, and the temperature reached at 0.1 V is obtained therefrom. (Ta: K) is obtained, the temperature rise per 100 msec (dTa / dt) is obtained, and the voltage measurement device detects voltage generation and stops energization from the power supply device so that the following relational expression is satisfied. Therefore, the superconducting device 30 is operated.

That is, it comprises a tape-like base material 2, intermediate layers 5 and 6 and oxide superconducting layer 7 provided on the base material, and stabilizing layers 8 and 9 provided on the oxide superconducting layer. The oxide superconducting conductor 1 having a laminated structure, a power supply device 23 for energizing the oxide superconducting layer 7 of the oxide superconducting conductor 1, and the oxide superconducting layer of the oxide superconducting conductor 1 from the power supply device 23 When operating the superconducting device 30 provided with the switch device 22 that controls energization to the
A reference measurement area S0 defined at a predetermined interval along the length direction of the oxide superconducting conductor 1 on the surface of the stabilization layer 9 laminated on the oxide superconducting layer 7, and a predetermined predetermined interval. A first measurement area S1 defined so as to sandwich the reference measurement area S0 with a longer first interval, and measure voltages at both ends of the first measurement area S1,
When the minimum voltage that can be detected by the voltage measuring device 19 is set to Vd with respect to the voltage across the first measurement area, the oxide superconductor 1 is cooled below the critical temperature and energized from the power supply device 23, When the temperature of the oxide superconductor 1 at the time and position at which the minimum voltage Vd is detected is Ta, and the rate of temperature increase at that time and position is dTa / dt, the switch device 22 generates a current from the power supply device 23. When the interruption response time that can be interrupted is set to Td, the temperature of the oxide superconductor at the time of current interruption is set to Ts, and K is set to an absolute temperature,
When the condition of Ts = Ta + dTa / dt × Td ≦ 500 is satisfied, deterioration of the oxide superconducting layer 7 can be prevented.

On a tape-shaped substrate made of Hastelloy C276 (trade name of Haynes, USA) having a width of 10 mm and a thickness of 0.1 mm, a diffusion preventing layer made of Al ₂ O _{3 with} a thickness of 100 nm and Y ₂ O ₃ made of 30 nm A first intermediate layer of MgO having a thickness of 5 to 10 nm obtained by an IBAD method using an ion beam assisted sputtering device, and an alignment layer of MgO using a pulsed laser deposition method (PLD method) A cap layer of CeO _{2 having} a thickness of 500 nm, a GdBa ₂ Cu ₃ O _7-x oxide superconducting layer having a thickness of 1 μm obtained by pulse laser deposition, and a thickness obtained by sputtering. A laminated structure acid comprising a first stabilization layer of 8 μm Ag and a second stabilization layer obtained by bonding a copper tape (0.1 mm thickness) with a single-sided solder (thickness 5 μm). A superconducting conductor was prepared.

The oxide superconducting conductor 1 having the above-described structure is wound around a winding drum 36 to form a superconducting coil, a portion of the coating is removed, and a heater 12 is attached to the surface of the second stabilizing layer 9 as shown in FIG. Measurement points 10, 11, 17, 18 were defined.
In this example, the length of the reference measurement area S0 was 10 mm, and the length of the first measurement area was 300 mm.

In the apparatus shown in FIG. 3, when the inside of the container was depressurized and the refrigerator was operated to lower the temperature from room temperature to 90K, the second stabilization layer was energized and the temperature-resistance characteristics were measured.
The result is shown in FIG. This temperature-resistance characteristic can also be calculated from the resistivity ρ of the material used.

  The operating temperature is set to 77 K in the superconducting device 30 shown in FIG. 3, 100 A is energized as a superconducting state, and it is confirmed that the superconducting current flows, and then the heater installed in the standard measuring area is energized to The oxide superconducting layer was subjected to normal conducting transition, and the voltage behavior of the normal conducting transition was investigated.

Next, since the oxide superconducting layer becomes an insulator when transitioning to the normal state, it is assumed that all the current applied to the oxide superconducting conductor in that region has flowed to the stabilization layer, and the first measurement area The voltage V1 was converted into temperature from the previously measured temperature-resistance characteristic and was defined as temperature.
It was confirmed that the temperature measured by the thermocouple for temperature measurement was almost the same as the value converted from the voltage.
The minimum voltage sensitivity of the measurement system was 0.001 mV, and the time when the voltage was generated (= normal conduction transition) was set to 0 sec. FIG. 5 shows the voltage behavior at each measurement point, and FIG. 6 shows the result of temperature conversion of the voltage on the vertical axis.

  FIG. 5 shows the voltage behavior of V0 and V1. FIG. 6 shows the result of converting the voltage on the vertical axis of FIG. 5 into temperature based on the temperature-resistance characteristics.

  Next, Table 1 below shows the operating temperature of the oxide superconductor, the thickness of the oxide superconductor, the thickness of the first stabilizing layer (μm), the thickness of the second stabilizing layer (μm), and energization. Current (A), temperature reached at 0.1 V (Ta: K), temperature rise per 100 msec (dTa / dt) temperature after 300 msec cut-off response, presence / absence of superconducting property deterioration after cut-off, and detection result.

From the results shown in Table 1, it can be seen that if the condition of Ts = Ta + dTa / dt × Td ≦ 500K is satisfied, deterioration of superconducting characteristics after interruption does not occur.
Further, from the measurement results shown in Table 1, it seems more preferable that the condition of Ts = Ta + dTa / dt × Td ≦ 400K is satisfied.
Further, from the results shown in Table 1, the voltage Vd that can be detected by the voltage measuring device is preferably 0.05 V or more. Further, the value of the temperature increase rate dTa / dt is preferably 100 K or less per 100 msec, more preferably 50 K or less, and most preferably 20 K or less.
From the results shown in Table 1, the temperature rises drastically when the thickness of the second stabilizing layer is 0.1 mm when energized at 400 A as in the sample of Test Example 4, so It can be seen that a favorable condition can be obtained by setting the thickness to 0.3 mm. Therefore, it has been found that if the above-described method is used, it can be used as a method for inspecting the thickness of the stabilization layer necessary for the oxide superconducting conductor in consideration of the normal conduction transition.

  INDUSTRIAL APPLICABILITY The present invention can be used for a protection operation method of a superconducting device to which an oxide superconducting conductor used in various power devices such as a superconducting motor and a current limiter is applied.

DESCRIPTION OF SYMBOLS 1 ... Oxide superconducting conductor, 2 ... Base material, 3 ... Diffusion prevention layer, 4 ... Bed layer, 5 ... 1st intermediate | middle layer, 6 ... 2nd intermediate | middle layer, 7 ... Oxide superconducting layer, 8 ... 1st 9, second stabilization layer, 10, 11, reference voltage measurement point, 12, heater, 13, 14, first voltage measurement point, 15, 16, second voltage measurement point, 17, DESCRIPTION OF SYMBOLS 18 ... 3rd voltage measurement point, 19 ... Voltage measuring device, S0 ... Reference | standard measurement area, S1 ... 1st measurement area, 22 ... Switch apparatus, 23 ... Power supply device, 25 ... Control apparatus.

Claims (4)

An oxide superconducting conductor having a laminated structure comprising a tape-shaped base material, an intermediate layer and an oxide superconducting layer provided on the base material, and a stabilization layer provided on the oxide superconducting layer; And operating a superconducting device including a power supply device for energizing the oxide superconducting layer of the oxide superconducting conductor and a switch device for controlling energization from the power supply device to the oxide superconducting layer of the oxide superconducting conductor. When
A reference measurement area defined at a predetermined interval along the length direction of the oxide superconducting conductor on the surface of the stabilization layer stacked on the oxide superconducting layer, and a reference measurement area longer than the predetermined interval. At least a first measurement area defined so as to sandwich the reference measurement area with an interval of 1, and measure a voltage at both ends of the reference measurement area or a voltage at both ends of the first measurement area;
The lowest voltage that can be detected by a voltage measuring device is set to Vd for the voltage at both ends of the reference measurement area or the voltage at both ends of the first measurement area, and the oxide superconductor is cooled to a critical temperature or less and energized from the power supply device. When the minimum voltage Vd is detected and the temperature of the oxide superconducting conductor at the time and position is Ta, and the temperature rise rate at the time and position is dTa / dt, the switch device is connected to the power supply device. When the interruption response time capable of interrupting the current of Td is set as Td, the temperature of the oxide superconductor at the time of current interruption is set as Ts, and K is set as the absolute temperature
A superconducting device protective operation method, wherein energization from the power supply device is cut off so as to satisfy a condition of Ts = Ta + dTa / dt × Td ≦ 500K.   Measuring and grasping the temperature-resistance characteristic indicating the relationship between the temperature and the resistance value from room temperature to the operating temperature range below the critical temperature of the oxide superconducting layer for the stabilization layer, and measuring the minimum voltage The protective operation method for a superconducting device according to claim 1, wherein the temperature increase rate dTa / dt is obtained by converting into a temperature from a subsequent voltage increase state. An oxide superconducting conductor having a laminated structure comprising a tape-shaped base material, an intermediate layer and an oxide superconducting layer provided on the base material, and a stabilization layer provided on the oxide superconducting layer; A power supply device for energizing the oxide superconducting layer of the oxide superconducting conductor, and a switch device for controlling energization from the power supply device to the oxide superconducting layer of the oxide superconducting conductor,
A reference measurement area defined at a predetermined interval along the length direction of the oxide superconducting conductor on the surface of the stabilization layer stacked on the oxide superconducting layer, and a reference measurement area longer than the predetermined interval. A voltage measuring device that at least divides the first measurement area so as to sandwich the reference measurement area with an interval of 1 and measures the voltage at both ends of the reference measurement area or the voltage at both ends of the first measurement area With
The lowest voltage that can be detected by a voltage measuring device is set to Vd for the voltage at both ends of the reference measurement area or the voltage at both ends of the first measurement area, and the oxide superconductor is cooled to a critical temperature or less and energized from the power supply device. When the minimum voltage Vd is detected and the temperature of the oxide superconducting conductor at the time and position is Ta, and the temperature rise rate at the time and position is dTa / dt, the switch device is connected to the power supply device. When the interruption response time capable of interrupting the current of Td is set as Td, the temperature of the oxide superconductor at the time of current interruption is set as Ts, and K is set as the absolute temperature
A superconducting device comprising a control device that cuts off power from the power supply device by the switch device so as to satisfy a condition of Ts = Ta + dTa / dt × Td ≦ 500K.   A temperature-resistance characteristic indicating a relationship between a temperature ranging from room temperature to an operating temperature range lower than the critical temperature of the oxide superconducting layer and a resistance value is measured and stored in the control device. 4. The superconducting device according to claim 3, wherein the control device has a function of obtaining the temperature increase rate dTa / dt by converting the voltage increase state after the minimum voltage measurement into a temperature. 5.

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