JPH043477A - Ceramic superconducting current limiter - Google Patents

Abstract

PURPOSE:To resist vibrations and a thermal shock, and to obtain a sufficient current- limiting effect by electrically arranging ceramic superconductors integrally in the grooves of a grooved vessel, to which a plurality of the grooves are formed in parallel, and filling or covering the clearances of the ceramic superconductors and the grooves and the top faces of the clearances with a buffer. CONSTITUTION:Ceramic superconductors 3 are disposed to each inside of a plurality of grooves 2 formed in a grooves vessel 1, and each end section of the superconductors 3 is connected integrally in series in succession by connecting media 12. Clearances among the grooves 2 and the ceramic superconductors 3 and the upper sections of the ceramic superconductors 3 are filled or covered with a buffer 4. Current terminals 5 for connection to an external equipment are mounted at both ends of the superconductors 3 integrally connected in series, thus constituting a ceramic superconducting current limiter 6. Since the clearances and the upper sections of the ceramic superconductors 3 are filled or covered with the buffer, the ceramic superconductors are not brought into contact directly with a refrigerant such as fluid nitrogen, thus relaxing cooling by the fluid nitrogen and propagating quenching to not only local parts but also the whole superconductors, then acquiring an excellent current-limiting effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current limiter that uses a ceramic superconductor to limit the large current that occurs during a short-circuit accident in a power transmission circuit.

[Conventional technology]

If a short circuit occurs during power transmission, a large current will flow through the power transmission circuit, damaging the electrical equipment in the circuit. Therefore, a current limiter is used in the power transmission circuit to reduce the high current in case of a short circuit. ing.

The function of the current limiter will be explained below with reference to the drawings.

FIG. 4 is a functional explanatory diagram around the current limiter in the power transmission circuit. The current limiter 16 is constructed by connecting a bypass breaker 7 and a current limiting resistor 8 in parallel.

When a short circuit occurs in the power transmission circuit and a large current flows, the resistor 9 first detects it, and the signal is sent to the bypass circuit breaker 7 of the current limiter 16, and the circuit breaker 7 is turned off. Then, the current flows through the current limiting resistor 8 and is current limited. In this current-limiting state, a predetermined treatment is performed, and then the circuit breaker 10 is opened to stop the current and repair work is performed. However, such a conventional fault current limiter has the disadvantage that the device becomes large because it requires a bypass circuit breaker 7 and a resistor 9 to detect a short circuit accident and commutate current.

For this reason, a current limiter has been proposed in which superconducting conductors are connected in series in a power transmission circuit, and the superconducting conductors have the functions of both short-circuit detection and current limiting.

That is, as shown in Fig. 5, this current limiter uses a ceramic superconductor 3 cooled with liquid nitrogen connected in series to the circuit as a current limiter 6, and a short circuit occurs and a large current flows. Then, quenching occurs in the four superconducting bodies, the superconducting state is broken, resistance is generated, and as a result, current is limited.

FIG. 6 shows a configuration in which a current limiter 6 consisting of four superconducting bodies 3 is connected in parallel with another current limiting resistor 8. This is because the superconductor 4 bodies 3 are quenched due to a short circuit accident, producing resistance, and the current is limited by commutating the fault current to the current limiting resistor 8, and the superconducting 4 bodies 3 are burnt out. This is something I tried to avoid.

By the way, as shown in the plan view of FIG. 7, the current limiter 6 using four superconducting bodies described above is constructed by fixing a plurality of short ceramic superconducting bodies 3 arranged in parallel on a predetermined plate-like body 11. The ends of each superconductor are connected in series with a normal connecting medium 12, and by connecting them in series, the resistance generated when the four superconducting bodies 3 are quenched is increased, and by arranging them in parallel, The magnetic fields generated between the superconducting conductors 3 during energization are mutually canceled out, and the device is made more compact. However, in such a superconducting current limiter, (1) the superconducting conductors themselves and their connections are easily destroyed by vibration or thermal shock, and (2) the four superconducting conductors are in direct contact with liquid nitrogen, so they cannot be quenched. The disadvantage is that the generated heat is immediately cooled down, making it impossible to obtain a sufficient current limiting effect.

[Means to solve the problem]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a ceramic superconducting current limiter that can withstand vibration and thermal shock and provide a sufficient current limiting effect.

That is, in the present invention, a ceramic superconductor is electrically integrally arranged in a groove of a grooved container having a plurality of parallel grooves, and the gap between the ceramic, the ceramic superconductor and the groove, and the ceramic The superconductor is characterized in that the top surface of the superconductor is filled with or covered with a buffer material, and the integrated ceramic superconductor powder is attached thereto.

The present invention will be specifically explained below with reference to the drawings.

Figure 1 shows -I of the grooved container which is a component of the current limiter of the present invention.
FIG. 3 is a plan view showing IiHA. In the figure, 1 is a container with a shoulder, and 2 is a groove provided in the container 1.

A plurality of grooves 2 are provided in parallel in the grooved container 1. FIG. 2A is a plan view and a side sectional view, respectively, showing an embodiment of a ceramic superconducting current limiter 6 in which a ceramic superconducting conductor 3 is disposed within the grooved container 1.

A ceramic superconductor 3 is disposed inside each of the plurality of grooves 2 provided in the grooved container 1, and the ends of the four superconductors 3 are sequentially connected integrally in series by a connecting medium 12. There is. The gap between the groove 2 and the ceramic superconductor 3 and the top of the ceramic superconductor 3 are filled with or covered with a buffer material 4 . Further, current terminals 5 for connecting to external equipment are attached to both ends of the four superconducting bodies 3 connected together in series to form a ceramic superconducting current limiter 6.

In the present invention, the ceraminx superconductor includes, for example, Y-Ba-Cu-0 series, B1-5r-CaCu-0 series,
Tl-Ba-Ca-Cu-0 system, Ln-Ba-Cu-0
It is manufactured by molding any ceramic superconductor powder into a desired shape and then subjecting it to a predetermined heat treatment.

In the present invention, the material of the grooved container in which the four superconductors are placed is preferably FRP, etc., which has excellent electrical insulation properties and is strong in strength and thermal shock at extremely low temperatures such as liquid nitrogen.

In addition, the gap between the groove of the grooved container and the ceramic/custom superconductor placed in the groove, and the cushioning material filled or coated on the top surface of the ceramic superconductor, have elasticity even at extremely low temperatures, and Teflon, etc., which has low conductivity, is used.

The superconducting current limiter of the present invention is manufactured, for example, as follows.

That is, a plurality of parallel grooves are formed in an FRP plate-like body to form a grooved container, and after arranging four superconducting bodies in each groove, the ends of the four superconducting bodies are sequentially connected in series. They are connected to form four integrated long superconducting bodies. Any material such as solder or ceramic conductive powder can be used for the above-mentioned connection medium, but the lower the electrical resistance, the more preferable it is. Current terminals are attached to both ends of the superconducting conductors connected together in this way, and then, for example, room-temperature-curing Teflon is applied to the gap between the superconducting conductor in the groove and the inner surface of the groove and the upper surface of the superconducting conductor. Fill or cover by pouring into
A ceramic superconducting current limiter is manufactured.

If necessary, a plurality of the current limiters may be connected in series by bus bars 13 as shown in FIG. 3.

[Effect]

In the ceramic superconducting current limiter of the present invention, a ceramic superconducting body is arranged in a groove of a grooved container, and a gap between the ceramic superconducting body and the inner surface of the groove and an upper surface of the ceramic superconducting body are filled or coated with a cushioning material. Since the ceramic superconductor is covered with a buffer material and/or a container, the ceramic superconductor does not come into direct contact with a refrigerant such as liquid nitrogen, so cooling by liquid nitrogen is relaxed. As a result, the quench does not remain locally but propagates throughout the superconductor, resulting in an excellent current limiting effect.

Furthermore, the buffer material acts to soften the mechanical impact between the inner surface of the groove of the grooved container and the superconducting conductor, so that the superconducting conductor will not be damaged by vibration or the like.

[Example] The present invention will be explained in detail below using examples.

Example 1 FRP with width 70mm, thickness 10m+, length 220ma+
A grooved container was prepared by forming 10 parallel grooves each having a width of 5 m++, a depth of 6 m, and a length of 210 ma+ at intervals of 1 mm on a plate-shaped body.

Next, the calcined powder with the composition of YBa, Cu, and Ox is compacted into bars with a width of 4 m, a thickness of 5 mm, and a length of 100 m++.Next, 20 of these bars are placed in an oxygen atmosphere with a diameter of 95". C5
After heating for 0 hours to form a superconducting conductor, the superconducting conductors were connected two by two to prepare ten superconducting conductors each having a length of 200 m+.

Next, the superconducting conductors each having a length of 200 am are placed in the grooves of the grooved container, and the ends of the superconducting conductors are successively soldered and connected in series, and then the superconducting conductors are placed. Liquid Teflon was injected into the groove and solidified to produce a ceramic superconducting fault current limiter in which the gap between the inner surface of the groove and the upper surface of the superconductor was filled or coated with Teflon. Note that the critical current (Ic') of the superconductor is changed to liquid nitrogen (7
7K) under zero magnetic field, it was 28-34A.

Example 2 Four ceramic superconducting fault limiters manufactured in Example 1 were manufactured, and as shown in FIG. 10m thickness 3
Connected in series with M silver busbars.

Comparative Example 1 A superconducting current limiter was manufactured by connecting and fixing a 200 mm long superconducting conductor on an FRP plate without grooves in the same manner as in Example 1. was manufactured.

Each of the ceramic superconducting current limiters thus obtained was immersed in liquid nitrogen and cooled to form the circuit shown in Figure 5.The circuit was then heated to 100 OA assuming a short-circuit accident. A current was applied to cause quenching in the superconductor of the superconducting fault current limiter, and the current after current limiting was measured. Next, after canceling the energization of 100OA and returning the above-mentioned current limiter to room temperature, the operation of cooling it again to liquid nitrogen temperature and energizing it is repeated.
Durability was examined by repeating the test 0 times.

Table 1 As is clear from Table 1, the product of the present invention (Example 1.2)
The current limit value that satisfies the specifications is obtained, and the above current limit value is
Even after repeating the short-circuit simulation experiment 20 times, there was almost no change, and the product had excellent durability.

On the other hand, since the comparative product (Comparative Example 1) is an exposed type, it is sufficiently cooled by liquid nitrogen and the local quench does not propagate to the entire superconductor, resulting in a high current limit value.
Also, after repeating the short-circuit simulation experiment four times, it became impossible to conduct electricity. When the superconductor was taken out and observed under a microscope, it was found that there were many ranks of fineness. This is because the ceramic superconductor directly receives the thermal shock between liquid nitrogen and room temperature without using a buffer material or the like.

(Effects) As described above, the ceramic superconducting current limiter of the present invention can stably obtain a predetermined current limiting value, has excellent durability, and has remarkable industrial effects.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of a grooved container which is a component of the current limiter of the present invention, FIG. FIG. 3 is a perspective view showing another embodiment of the current limiter of the present invention, FIGS. 4 to 6 are functional explanatory diagrams of the current limiter, and FIG. 7 is a plan view of a conventional superconducting fault limiter. l...Grooved container, 2...Groove, 3...Superconductor, 4...Buffer material, 5...Current terminal, 6...
Ceramic superconducting current limiter, 16...Resistor current limiter.

Claims (1)

[Claims] A ceramic superconductor is electrically and integrally arranged in a groove of a grooved container having a plurality of parallel grooves, and a buffer is provided between the ceramic superconductor and the groove and the upper surface of the ceramic superconductor. 1. A ceramic superconducting current limiter, characterized in that the ceramic superconducting conductor is filled with or coated with a material and current terminals are attached to both ends of the integrated ceramic superconducting conductor.