JPH06335160A - Superconducting current-limiter - Google Patents

Abstract

PURPOSE:To provide a current-limiter whose self-inductance is reduced in a superconducting state to reduce a transmission loss in a steady state. CONSTITUTION:In a superconducting coil unit where a coil 2 is applied to the outer circumference of the superconducting cylinder 1 of a superconducting magnetic shielding unit, flange parts 4 which cut off the flux of the coil 2 are provided at least along the circumferences of both ends of the superconducting cylinder 1. With this constitution, the loss of a steady state transmission current in a superconducting state can be reduced substantially.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a superconducting fault current limiter utilizing the magnetic shielding effect of a superconducting magnetic shield.

[0002]

2. Description of the Related Art Conventionally, a current limiting device for limiting a fault current has been devised between a transmission line and a circuit breaker. When the overcurrent flows, the current limiter becomes a resistance and suppresses the overcurrent.
It works to reduce the load on circuit breakers and transformers.
There are various types of current limiting devices, but in recent years, a type of current limiting device using a so-called superconducting magnetic shield has been proposed. This utilizes the magnetic shielding effect and magnetic flux switching effect of the superconducting magnetic shield. First, a conductive wire is wound around the superconducting magnetic shield in a coil shape to form a superconducting fault current limiter. Normally, when a coil is energized, self-inductance causes impedance,
In the above-mentioned superconducting fault current limiter, when the superconducting magnetic shield is in the superconducting state, the magnetic flux is shielded by the magnetic shielding effect, so theoretically the self-inductance disappears. That is,
Since the impedance is extremely small, the loss of normal transmission current is small. However, once an overcurrent is generated due to a short circuit, a lightning strike, or the like, and a magnetic flux of a certain value or more is generated, the critical magnetic field is exceeded, so that the superconducting state is quenched (transitioned) to the normal conducting state, and the magnetic shielding effect of the cylinder disappears. Then, like the ordinary coil, the magnetic flux is linked to the superconducting magnetic shield (flux switching effect), so that self-inductance is generated in the coil and, as a result, the current is limited.

[0003]

Here, when there is a space between the superconducting shield 50 and the coil 52 as shown in FIG. 6, or when the coil 52 is multi-wound, the superconducting magnetic shield 50 and the coil 52 are wound. A magnetic flux B is generated between the coils 52 and between the coils 52 wound on the inner peripheral side. In the steady power transmission state, the smaller the self-inductance of the coil 52, the smaller the current loss, which is preferable. However, at present, the self-inductance is generated by these leakage magnetic fluxes, and the magnetic shielding effect is insufficient. The purpose of the present invention is to
It is an object of the present invention to provide a fault current limiter that reduces self-inductance of a fault current limiter in a superconducting state to reduce transmission loss in a steady state.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventor of the present invention provides the superconducting fault current limiter in which the coil is attached to the outer circumference of the main body of the superconducting magnetic shield in the invention of claim 1. A shield structure for blocking the magnetic flux of the coil is formed around both ends of the main body. In the invention of claim 2, the shield structure has a structure in which flange-shaped projections are formed at both ends of the main body of the superconducting magnetic shield. Further, in the invention of claim 3, the flange-shaped projection has a structure in which a surface of the projection on the coil side is an inclined surface. Further, in the invention of claim 4, the shielding structure is
The superconducting magnetic shield is formed by further disposing the superconducting magnetic shield on the outer circumference of the coil at both ends of the main body of the superconducting magnetic shield.

[0005]

According to the above structure, in any of the inventions, the superconducting fault current limiter in which the coil is mounted on the outer circumference of the main body of the superconducting magnetic shield has a shielding structure formed around both ends of the main body.
In the superconducting state, the magnetic flux between the coils and between the coil and the superconducting magnetic shield is cut off. Therefore, the self-inductance of the coil is extremely small.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a current limiting device using the superconducting magnetic shield of the present invention will be described in detail below with reference to FIGS. However, the following embodiments are not experimentally applied to actual routes but experimentally manufactured. (1) Example 1 As shown in FIGS. 1 and 2, a superconducting fault current limiter 6 is composed of a cylindrical superconducting cylinder 1 which is a superconducting magnetic shield, a coil 2 and an insulator 3. The superconducting cylinder 1 is made of hollow ceramic (specific components and properties will be described later) and has a length of 50 m.
m, and the outer diameter is 50 mmφ. Flange portions 4 as a shielding structure are formed at both ends of the superconducting cylinder 1.
The flange portion 4 is located outside the outer peripheral surface of the superconducting cylinder 9.
It is formed around the entire circumference at a height of 25 mm. The coil 2 is made of a copper-based alloy having an outer diameter of 1 mmφ and is wound around the outer circumference of the superconducting cylinder 1 in five steps of 200 turns. As shown in FIG. 1, in this embodiment, the flange portion 4 has substantially the same height as the inner diameter of the coil wire on the outermost peripheral side of the coil 2. The insulator 3 is arranged between the superconducting cylinder 1 and the coil 2, and is made of, for example, a vinyl chloride pipe, FRP, silicone rubber or the like.

Conventionally, when the superconducting cylinder 50 is in the superconducting state, the magnetic flux B generated by the coil 52 is generated.
Is the coil 52 and the superconducting cylinder 50 as shown by the broken line in FIG.
It occurs between the insulator 51 and each coil wire in between. However, in the present embodiment, when the flange portion 4 is formed at the end of the superconducting cylinder 1, the magnetic flux B is blocked as shown in FIG. As a result, the magnetic flux generated in the coil is suppressed, and the self-inductance generated in the coil becomes extremely small. In this embodiment, the outer diameter of the flange portion 4 is 68.5 mmφ while the outer diameter of the superconducting cylinder 1 is 50 mmφ.
The impedance value is 0.
It is a decrease of 5Ω.

In a fault current limiter having such a superconducting fault current limiter 6, once an overcurrent flows due to a ground fault, a lightning strike, etc. and exceeds the critical magnetic field of the superconducting magnetic shield (superconducting cylinder 1), the superconducting magnetic shield The shielding effect of is lost. That is, the superconducting magnetic shield is quenched from the superconducting state to the normal conducting state. Then, the blocking effect of the superconducting cylinder 1 on the magnetic flux B disappears, and the self-inductance that has been controlled up to now is generated in the entire coil 2 to limit the current.

With the above construction, the following effects are produced. That is, the magnetic flux B between the coil and the superconducting magnetic shield (superconducting cylinder 1) is blocked by the flange portion 4, its self-inductance becomes extremely small, and the loss of steady transmission current is almost eliminated. Since the magnetic flux B is cut off, energy loss (iron loss) does not occur. In addition, since both side ends of the superconducting cylinder 1 are regulated by the flange portion 4, lateral displacement of the coil 2 is also prevented.

Next, experimental data in the present invention will be described. The superconducting magnetic shield of the superconducting cylinder 1 is a ceramic mainly composed of usual bismuth, strontium, calcium, copper, and oxides, and the critical conditions are a critical temperature of 115K, a critical magnetic field of 50 gauss, and a critical current of 300.
It is 0A. 50 mmφ (flange height 0 mm), 62 as experimental data obtained by changing the outer diameter of the flange portion 4
mmφ (flange portion height 6 mm), 63.5 mmφ (flange portion height 6.75 mm), 66 mmφ (flange portion height 8 mm), 68.5 φmm (flange portion height 9.2)
5 mm), and each self-inductance was measured. These measured values are plotted on the graph shown in FIG. In this graph, the vertical axis indicates the flange portion 9
Shows the magnitude of the self-inductance (B ') when the self-inductance (Bb) at a diameter of 68.5 mm (flange height 9.25 mm) is 1, and the horizontal axis shows the outer diameter φ of the flange 4. did.

When the outer diameter of the flange portion 9 was 50 mmφ, it was 135 (B '/ Bb) (A). Also 62 mm
In φ, it was 60 (B ′ / Bb), and the impedance value was 0.22Ω as described above for 50 mmφ (B). Also, at 63.5 mmφ, 24 (B
′ / Bb), the impedance value was 0.13Ω for 50 mmφ (C). Similarly, at 66 mmφ, 13 (B '/ Bb) 0.048 Ω (D) and 68.5 m
Similarly, for mφ, it was 1 (B ′ / Bb) 4 × 10 ⁻³ Ω (E). Based on these plots, a certain correlation indicated by a curve in the graph was observed between the outer diameter φ of the flange portion 4 and H / h. (2) Example 2 As shown in FIG. 4, the cylindrical superconducting cylinder 10 is formed thicker toward both ends of the outer circumference, and has a concealing structure that gradually rises toward the ends. Other configurations are similar to those of the first embodiment. Even with such a configuration, leakage of magnetic flux is prevented as in the first embodiment. (3) Third Embodiment As shown in FIG. 5, ring-shaped superconductors 19 are arranged at both outer peripheral ends of a coil 18 wound around the outer periphery of a superconducting cylinder 17. Other configurations are similar to those of the first embodiment. The superconductors 19 at both ends of the outer circumference can prevent the magnetic flux leaking to the outside of the coil 18 as shown by the broken line in the figure.
Further, the superconducting magnetic shield is not necessarily provided on the outer peripheral side of the coil 18.
It is also possible to cover not only both ends of the coil 18 but the entire coil 18. That is, the coil 18 may have a double structure in which it is sandwiched between two superconducting cylinders on the inner side and the outer side.

The embodiment of the present invention has been described above.
The present invention can be implemented by being modified into other aspects. For example, although the coil 2 is wound five times in the first embodiment, it is of course possible to wind the coil 2 more than five times.
On the contrary, it may be a single layer. In this case, the height of the flange portion 4 is changed according to the height of the coil 2 wound. Further, the height of the flange portion 4 was 9.25 mm in the above-mentioned embodiment, but as can be seen from the experimental data, the flange portion 4 does not necessarily have to be formed at a height equal to or higher than the coiled height of the coil 2. Since the effect of blocking the magnetic flux B of the coil 2 is exerted, it is free to form the flange portion 4 at a desired height. Further, the flange portion 4 may be necessarily formed at a place other than both side ends of the superconducting cylinder 1. Besides, the present invention can be freely modified and implemented within the scope of the invention.

[0013]

As described above, according to the present invention, since the shielding structure for shielding the magnetic flux of the coil is formed around at least both ends of the superconducting cylinder made of the superconducting magnetic shield, the power transmission current in the steady state in the superconducting state is formed. The loss of is extremely small.

[Brief description of drawings]

FIG. 1 is a side sectional view illustrating a main part of a superconducting fault current limiter that is Embodiment 1 of the present invention.

FIG. 2 is a side sectional view of the superconducting fault current limiter in the same Example 1.

FIG. 3 is a graph showing the relationship between the self-inductance and the outer diameter of the shield in the same Example 1.

FIG. 4 is a side sectional view of a superconducting fault current limiter according to another embodiment 2.

FIG. 5 is a side sectional view of a superconducting fault current limiter according to a third embodiment.

FIG. 6 is a side sectional view illustrating a main part of a conventional current limiting device.

[Explanation of symbols]

1, 17 ... Superconducting cylinder as superconducting magnetic shield, 2, 18
... Coil, 4 ... Shielding structure and flange-like flange, 6 ... Superconducting fault current limiter, 12, 15, 19 ... Superconducting magnetic shield, superconductor.

Claims (4)

[Claims] 1. A superconducting fault current limiter in which a coil is mounted on the outer periphery of a main body of a superconducting magnetic shield, wherein a shielding structure for cutting off the magnetic flux of the coil is formed at least around both ends of the main body. Sink. 2. The superconducting fault current limiter according to claim 1, wherein the shielding structure is a superconducting magnetic shield having flange-shaped protrusions formed at both ends of the main body. 3. The superconducting fault current limiter according to claim 2, wherein the flange-shaped projection has a coil-side surface of the projection as an inclined surface. 4. The superconducting fault current limiter according to claim 1, wherein the shielding structure is formed by further disposing superconducting magnetic shields on the outer circumference of the coil at both ends of the main body of the superconducting magnetic shield.