JPH04210730A - Rated current variable type superconducting limiter - Google Patents

Abstract

PURPOSE:To prevent a cooling efficiency from decreasing and to reduce in size a superconducting limiter by standing longitudinally the limiter, arranging a plurality of the limiters at a predetermined interval, and providing a common electrode for connecting the ends of the plurality of limiters. CONSTITUTION:An electrode 22 is formed of a normal conducting member such as copper of a flat plate. Square recesses are provided at a predetermined interval on one side surface. The ends of superconducting limiters 21 are engaged with the recesses, and electrically connected to the limiters 21 by solders 25, etc. An interval capable of feeding refrigerant 32 without resistance may be obtained between the engaged limiters 21. A current lead wire material 24 is made of a wire material of normal conductor or high temperature superconductor. The electrode 22 and the conductive part of the material 24 have sufficient sectional areas for limiting a current at the time of short-circuiting so as not to generate large heat. Accordingly, since the limiter is longitudinally stood and the limiter itself can support its own weight, an electrically insulating board having a large occupying volume is eliminated.

Description

[Detailed description of the invention]

[00011

[Industrial Field of Application] The present invention relates to a variable rated current type superconducting fault current limiter for suppressing short-circuit currents that occur during ground faults and the like in power transmission and distribution systems. [0002] Conventionally, a superconducting element used in this type of superconducting current limiter has a flat electrically insulating substrate 11 and a comb-shaped structure on one surface of the electrically insulating substrate 11, as shown in FIG. A plurality of superconducting current limiting elements 12 are connected in series or in parallel, and a group of 12 superconducting current limiting elements is placed in a coolant such as liquid nitrogen. Immerse in liquid nitrogen temperature (77K at 1 atm)
The superconducting current limiting device is cooled to an extremely low temperature, and 12 groups of superconducting current limiting elements are connected in series to the power system. [0003] The superconducting element is designed so that the rated current of the power system is less than or equal to the critical current of the superconducting current limiting element 12, and the short circuit current in the event of an accident is less than or equal to the critical current. Therefore, under normal conditions, when a current below the rated current flows through the superconducting current limiter, the superconducting current limiting element 12 is in a superconducting state and has zero electrical resistance, but in the event of an accident, when a short circuit current flows, the superconducting current limiting element 12 transition from the normal conduction state to the normal conduction state, electrical resistance is generated, the impedance of the power system increases, and the short-circuit current is suppressed to a low value. This protects the power system from very large short circuit currents. Furthermore, in recent years, superconducting current limiters have been made smaller and lighter. [0004]

[Problems to be Solved by the Invention] By the way, as shown in FIG. 3, in the superconducting element of the superconducting current limiter, the cross-sectional area of the superconducting current limiting element 12 is small. In this case, it is necessary to connect many superconducting current limiting elements 12 in parallel to increase the overall cross-sectional area. However, if the superconducting current limiter is designed in this way, the space occupied by the superconducting current limiting element 12 becomes large. Furthermore, since the superconducting current limiting element 12 is printed and bonded to or supported by the electrically insulating substrate 11, the space occupied by the electrically insulating substrate 11 also becomes large. For this reason, the ratio of the volume of the electrically insulating substrate and the superconducting current limiting element to the total volume of the superconducting current limiter becomes large, resulting in an increase in the size of the superconducting current limiter, which poses a problem in that miniaturization cannot be achieved sufficiently. [0005] Furthermore, in consideration of the above-mentioned problems, if the cross-sectional area of each superconducting current limiting element is increased and the number of parallel elements is reduced, heat generation due to normal conduction state transition increases, while cooling area decreases. As a result, the cooling efficiency deteriorates, and the temperature rise of the superconducting current limiting element increases significantly, resulting in a problem that it becomes impossible to return to the superconducting state in a short time. In the worst case, there is a risk that the superconducting current limiter will melt due to the heat generated during the transition to a normal conductive state, and the superconducting current limiter, which is supposed to protect the power system, will not be able to function adequately, and it will not be possible to recover from the accident. There was a danger that it could interfere with [00061 The present invention has been made in view of the above-mentioned problems, and provides a variable rated current that can integrate a superconducting current limiting element, prevent a decrease in cooling efficiency, and downsize the superconducting current limiter. The purpose of this invention is to provide a superconducting fault current limiter of the type superconducting current limiter. [0007]

[Means for Solving the Problems] In order to solve the above object, the present invention provides a superconducting element formed by connecting a plurality of superconducting current limiting elements in series or parallel, and cooling the superconducting current limiting element with a refrigerant. A variable rated current type superconducting current limiter which has a cooling means and suppresses the short circuit current according to the electrical resistance value generated in the superconducting current limiting element when a short circuit current flows in the event of an accident, wherein the superconducting current limiting element is Provided is a variable rated current superconducting current limiter, which is provided with a plurality of superconducting current limiting elements standing upright in the longitudinal direction and arranged at predetermined intervals, and having a common electrode connecting the ends of the plurality of superconducting current limiting elements, respectively. do. [0008]

[Operation] A plurality of superconducting current-limiting elements standing upright in the longitudinal direction are packed together at predetermined intervals and connected to a common electrode to be integrated, so that the entire periphery of the superconducting current-limiting element comes into direct contact with liquid nitrogen. Therefore, an electrically insulating substrate becomes unnecessary, the volume occupied by the superconducting current limiting element can be reduced, and a decrease in cooling efficiency can be prevented. [0009]

Embodiment An embodiment of the present invention will be explained based on the drawings of FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram showing an embodiment of a variable rated current type superconducting current limiter according to the present invention. In the figure, a superconducting current limiter main body 30 includes a closed container 31, a refrigerant 32 such as liquid nitrogen filled inside the container, and a superconducting element 20.
It is equipped with A refrigerator 35 as a cooling means is connected to the airtight container 31 via a suction pipe 33 whose tip end is inserted into the refrigerant 32 and a return pipe 34, and the cooled refrigerant 32 is circulated therein. . A temperature control device 36 is connected to the refrigerator 35 to adjust the temperature of the refrigerant 32. [00101 In addition, the airtight container 31 has a feed pipe 37.
A pressurizing pump 38 serving as a pressurizing means filled with pressurizing gas 39 is connected via. The feed pipe 37 is preferably installed at a position 1 above the storage position of the refrigerant 32, such as the ceiling of the closed container 31. As this pressurized gas, a gas having a boiling point lower than that of the refrigerant 32, such as helium gas, can be used. In addition, in the figure, 40 is a pressure relief valve for reducing the pressure inside the closed container 31. [00111 As shown in FIG. 2, the superconducting element 20 includes a plurality of columnar superconducting current limiting elements 21 and a superconducting current limiting element 2.
A superconducting current limiting element 21 is fixedly installed at both ends of the superconducting current limiting element 21 to
A pair of electrodes 22 for flowing the water to the electrode 22 and a port 23 for the
Furthermore, these superconducting current limiting elements 21 are connected in series or in parallel with other superconducting current limiting element groups configured in the same manner as described above. [0012] The superconducting current limiting element 21 is made of bismuth, for example.
The critical temperature for systems such as lead-strontium-calcium-copper-oxygen is liquid nitrogen temperature (77K at 1 aim
) is composed of high-temperature oxide superconductors. The smaller the cross-sectional area of the superconducting current-limiting element 21 is, the better the cooling efficiency is, but the mechanical strength is conversely reduced, so a moderate cross-sectional area is required. In addition, the length of the superconducting current-limiting element 21 is determined in order to increase the resistance value generated during transition to the normal conductive state.
The longer the length, the better, but if it is too long, the mechanical strength will decrease, so it is necessary to keep it within an appropriate range. [0013] Therefore, taking these into consideration, the size of one element 21 is preferably about 5 mm in thickness, 5 mm in width, and 200 to 500 mm in length. In addition, methods for manufacturing the columnar superconducting current limiting element 21 include a method in which superconductor powder is placed in a mold and press-molded, a method in which superconductor powder and an organic binder are mixed and extrusion molded in a paste form, etc. It is possible to use [00141 The electrode 22 is made of a flat plate of normal conductive metal such as copper, and has square recesses provided at predetermined intervals on one surface, and superconducting current limiting elements 2 are placed in the recesses.
1 is fitted, and the superconducting current limiting element 21 and solder 25
etc. are electrically connected. In the embodiment shown in FIG. 2, for example, 15 recesses are provided, and the interval between the recesses is such that the refrigerant 32 between the fitted superconducting current limiting elements 21
It is sufficient to secure an interval that allows the flow of water without resistance, so a distance of about 1 to 3 mm is sufficient. [00151 The current lead wire 24 is made of a normal conductor or a high temperature superconductor wire. The normal conductor portions of the electrode 22 and the current lead wire 24 have a sufficient cross-sectional area for the current limiting current in the event of a short circuit in order to prevent heat generation from increasing. Therefore, in this embodiment, the superconducting current-limiting element is installed vertically in the longitudinal direction, and the superconducting current-limiting element itself can support its own weight, thereby eliminating the need for an electrically insulating substrate that occupies a large volume. In addition, in this embodiment, since the superconducting current limiting elements are closely connected to one set of electrodes, the extra space between the superconducting current limiting elements can also be reduced, thereby reducing the volume occupied by the superconducting current limiting elements. The entire superconducting current limiter can also be downsized. [0016] Also, when the electrically insulating substrate supports the superconducting current limiting element, as in the conventional example shown in FIG. Since at least 14 or more areas around the superconducting current limiting element were in contact with the electrically insulating substrate, the refrigerant did not come into contact with that part, reducing the cooling efficiency. However, in this example, the superconducting current limiting element Since the entire circumference in the longitudinal direction is in direct contact with the refrigerant liquid nitrogen, it also has the effect of improving cooling efficiency. [0017]Furthermore, the superconducting current limiting element according to the present example has sufficient mechanical strength to support its own weight, and the connection part with the @ pole has an end portion of the superconducting current limiting element in the recess provided in the electrode. Since the ends are fitted and connected by soldering or other methods over a large area of the ends, they can have sufficient mechanical strength. [0018]

As explained above, the present invention includes a superconducting element formed by connecting a plurality of superconducting current limiting elements in series or parallel, and a cooling means for cooling the superconducting current limiting element with a refrigerant. In the variable rated current type superconducting current limiter that suppresses the short circuit current according to the electrical resistance value generated in the superconducting current limiting element when a short circuit current flows during an accident, the superconducting current limiting element is installed vertically in the longitudinal direction. A plurality of superconducting current limiting elements are arranged at predetermined intervals, and a common electrode is provided to connect the ends of the plurality of superconducting current limiting elements. It is possible to downsize the superconducting current limiter without reducing efficiency, and also to integrate a plurality of superconducting current limiting elements, thereby making it possible to downsize the entire superconducting current limiter.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the configuration of a variable rated current type superconducting current limiter according to the present invention.

FIG. 2 is a configuration diagram showing an example of the superconducting element shown in FIG. 1.

FIG. 3 is a configuration diagram showing a conventional superconducting element.

[Explanation of symbols]

11 Electrical insulating substrate 12.21 Superconducting current limiting element 20 Superconducting element 22 Electrode 23 Porto 24 Current lead wire material 32 Refrigerant 35 Refrigerator

[Figure 1]

Claims (1)

[Claims] Claim 1: A superconducting device comprising a plurality of superconducting current limiting devices connected in series or parallel, and cooling means for cooling the superconducting current limiting device with a refrigerant, and when a short circuit current flows in the event of an accident, In a variable rated current superconducting current limiter that suppresses the short-circuit current according to the electrical resistance value generated in the superconducting current limiting element, the superconducting current limiting element is erected in the longitudinal direction, and a plurality of superconducting current limiting elements are arranged at predetermined intervals. A variable rated current type superconducting current limiter, comprising: a common electrode that connects the ends of the plurality of superconducting current limiting elements;