JP2941833B2 - Superconducting current limiting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a superconducting current limiting device that electromagnetically suppresses an overcurrent in an AC circuit.

(Prior Art) As a conventional apparatus of this kind, for example, Japanese Patent Application Laid-Open No. 60-7493 is disclosed.
There is one disclosed in Japanese Patent Publication No. FIG. 9 is a circuit diagram showing the configuration of this current limiter. In the same figure, a coil 34 and a coil 35 are wound around an iron core 33 so that the magnetomotive force is substantially equal, and the coil 34 is wound so that the direction of the magnetic flux is reversed.
And one end of the coil 35 is connected to the electric circuit 31 on the power supply side, the other end of the coil 34 is connected to the electric circuit 32 on the load side via a switch 38, and the other end of the coil 35 is also connected to the load side. It is connected to the electric circuit 32. A surge absorber 36 is connected to the coil 34 in parallel, and a current limiting resistor 37 is connected to the switch 38 in parallel. On the other hand, current transformer
A switch 39 is provided to trip the switch 38 when an overcurrent is detected.

Here, when a normal level current (hereinafter referred to as a normal current) flows through the electric circuits 31 and 32 with the switch 38 closed, the current is divided into the coils 34 and 35, and the magnetic flux generated in these coils Are canceled out, the current is not affected by the inductances L ₁ and L ₂ . Therefore, power can be supplied to the load with high efficiency except for a small loss due to leakage magnetic flux.

On the other hand, when an excessive current flows in the electric circuits 31 and 32 due to a short circuit of the load or the like, the current transformer 39 detects this and opens the switch 38, and inserts the resistor 37 into the circuit of the coil 34. This allows
At the same time as the current of the coil 34 decreases, the current of the coil 35 increases, and the magnetic flux of the iron core 33 is mainly caused by the coil 35. Therefore, the fault current is limited by the action of the inductance of the coil 35, that is, by the reactor action.

(Problems to be Solved by the Invention) Since a current of several hundreds to several thousand amps flows in the above-described current limiter in a steady state, the cross-sectional area of the coils 34 and 35 must be increased. Since the number of windings must be increased in order to increase the impedance, there is a problem that the device becomes large and a large amount of power loss due to heat cannot be avoided.

In the current limiter described above, a mechanical switch is often used as the switch 38.
Three cycles are required, and during this time, there is a problem that the protection of the track becomes difficult.

As a countermeasure, a semiconductor switch such as a thyristor may be used as the switch 38.However, in this case, power loss occurs due to a voltage drop in the forward direction of the thyristor, and the device becomes larger and more complicated. Its adoption was difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a current limiter which can achieve downsizing of a device and secure line protection, and can suppress power loss due to heat to an extremely low level. Aim.

[Constitution of the Invention] (Means for solving the problem) In order to achieve this object, a first invention has an inductance for suppressing a current of an electric circuit to a limit value or less, and has a critical current not less than the limit value. A superconducting current limiting coil having a value,
A first current connected in parallel, having a critical current value smaller than a current limit value of the electric circuit and larger than a normal current of the electric circuit,
A superconducting trigger coil configured by winding a second superconducting coil in a non-inductive manner; and a return switch connected in series with the superconducting trigger coil for opening and closing a current flowing through the superconducting trigger coil. A superconducting current limiting device, wherein the superconducting current limiting coil and the superconducting trigger coil in which the return switch is connected in series are connected in parallel.

Further, the second invention has a superconducting current limiting coil having an inductance for suppressing a current of an electric circuit to be equal to or less than a limit value and having a critical current value equal to or greater than the limit value, and a non-inductively formed superconducting current limiting coil. A superconducting trigger coil having a critical current value smaller than the current limit value of the electric circuit and larger than the normal current of the electric circuit; and a switch for opening and closing a current flowing in the superconducting trigger coil connected in series with the superconducting trigger coil. A superconducting current limiting device, comprising: a return switch, wherein the superconducting current limiting coil and the superconducting trigger coil in which the return switch is connected in series are connected in parallel.

(Operation) In the first invention, if only a normal current flows through the electric circuit, the first and second superconducting coils connected in parallel have a critical current value larger than the normal current, and have zero resistance. In addition, since the superconducting trigger coil is wound in a non-inductive manner, a large current can be supplied substantially without a voltage drop. When the current in the electric circuit becomes excessive due to a short circuit accident or the like, the trigger coil is quenched, and the resistance value of the superconducting trigger coil rapidly increases. If the resistance value of the superconducting trigger coil at this time is designed to be sufficiently larger than the impedance of the superconducting current limiting coil, the current flowing in the superconducting trigger coil will be diverted to the superconducting current limiting coil, and the short-circuit current will be superconducting. The current is limited to a value determined by the impedance of the current limiting coil. During the current limiting operation, the current according to the resistance value continues to flow in the superconducting trigger coil, but by opening the return switch connected in series with this, the current flowing in the superconducting trigger coil is cut off, The superconducting trigger coil is returned to the superconducting state to prepare for the operation after returning from the accident.

In the second invention, if only a normal current flows in the electric circuit, the superconducting current limiting coil and the superconducting trigger coil are kept in a superconducting state, and are wound in a non-inductive manner with each other. The impedance is almost zero, and a large current can flow in the electric circuit with substantially no voltage drop. Since the two coils are connected in parallel, this current shunts approximately equally to each. When the current in the electric circuit becomes excessive due to a short circuit accident or the like, the superconducting trigger coil having a small critical current value quenches, and the resistance value of the superconducting trigger coil rapidly increases. For this reason, the non-inductive state is lost, and the inductance of the superconducting current limiting coil instantaneously appears on the electric circuit, and the fault current is limited to a value equal to or less than the limit value. The resistance value of the superconducting trigger coil at the time of quench can be set to a required value because the length of the winding of the superconducting trigger coil can be arbitrarily determined. During the current-limiting operation, the current corresponding to the resistance continues to flow through the superconducting trigger coil, but by opening the reset switch connected in series with this, the current flowing through the superconducting trigger coil is cut off, Return the trigger coil to superconductivity and prepare for the operation after returning from the accident.

(Embodiment) FIG. 1 is a circuit diagram showing a configuration of an embodiment corresponding to the first invention of this application together with an application object. In FIG. 1, a circuit breaker 2 and a current limiter 3 are inserted into one of the lines as an electric circuit connecting the AC power supply 1 and the load 5. Note that reference numeral 4
Indicates a line impedance. Here, the current limiter 3
A superconducting current limiting coil 3a that is wound so as to have an inductance that keeps the current of the line below the limit value and that has a critical current value larger than the current limit value, and that is larger than the normal current of the circuit and smaller than the current limit value has a critical current value, and connected in parallel first superconducting coil 3b ₁ and second superconducting coil 3b ₂ and the inductance was is constituted by unguided (AP) wound so as to be substantially zero super A conduction trigger coil 3b and a return switch 3c connected in series with the superconducting current limiting coil 3a, and a superconducting trigger coil 3b in which the return switch 3c is connected in series are connected in parallel. .

FIG. 2 is a diagram showing a specific configuration of the superconducting current limiting coil 3a, the superconducting trigger coil 3b, and the switch 3c. The superconducting current limiting coil 3a is wound around a bobbin 3g, and the superconducting trigger coil 3b is wound around a bobbin 3d. Moreover, the superconducting trigger coil 3b is arranged concentrically inside the superconducting coil 3a,
The coil end is commonly connected to 3f via terminal 3e and switch 3c.

The operation of the present embodiment configured as described above will be described below.

First, the superconducting current limiting coil 3a and the superconducting trigger coil
When both 3b are in the superconducting state, the superconducting coil 3a exhibits a relatively large impedance to the current flowing through the line, but the impedance becomes substantially zero because the superconducting trigger coil 3b is non-inductive. Figure 3 is a diagram for explaining that this, when the current i ₀ of the direction of the arrow flows through the superconducting current limiting coil 3a and the superconducting trigger coil 3b, inductance flux phi ₀ is generated by the superconducting current limiting coil 3a However, the magnetic fluxes φ ₁ and φ ₂ of the superconducting trigger coil 3b wound by the AP are canceled out, and the impedance becomes substantially zero.

When there is no accident on the load 5 side and a normal current i ₀ flows through the load 5, the current flowing in the superconducting current limiting coil 3a is i ₁₁ , and the current flowing in the superconducting trigger coil 3b is i _L2. Is established.

i ₀ = i _L1 + i _L2 (1) i _L1 ≪i _L2 (2) Therefore, most of the current i ₀ of the line flows through the superconducting trigger coil 3b, and the voltage drop associated therewith is substantially reduced. It is zero.

Next, an overcurrent flows in the line due to a short circuit accident of the load 5 and the like, and when the value exceeds the critical current _Jc1 of the superconducting trigger coil 3b, the superconducting trigger coil 3b instantaneously quenches and becomes an extremely large resistor. . As a result, most of the current flowing through the superconducting trigger coil 3b is diverted to the superconducting current limiting coil 3a, and the two currents have a relationship represented by the following equation.

i _L1 ≫i _L2 (3) Accordingly, the line current is limited to the limit value by the inductance of the superconducting current limiting coil 3a. In this case, since the current i _L2 flowing through the superconducting trigger coil 3b is extremely small, the power loss consumed as heat is extremely slightly suppressed.

4 (a), it illustrates how to change (b) in a time of the impedance Z _SC normal operation of the current i and the current limiting device and the current limiting operation, so how. That is, during a steady operation, the impedance Z _SC of the current limiting device 3 is extremely small, and the line current i ₀ is mainly the impedance of the load.
It is maintained properly by Z _l. On the other hand, when a load short circuit occurs, the estimated short circuit current _if tends to flow in the line. However, the moment the line current exceeds the critical current value J _c1 of the superconducting trigger coil 3b, in heating dance current limiting device as described above is increased in Z _SC ', the short-circuit current is limited to flow below the limit value.

In this case, the critical current value _Jc2 of the superconducting current limiting coil 3a is set to be larger than the current limit value of the line. Further, the superconducting trigger coil 3b is cooled by shutting off i _L1 by the return switch 3c, and easily returns to the steady state.

In the above-described embodiment, the superconducting coils are concentrically arranged, so that the superconducting coils are remarkably downsized and easily maintained in the superconducting state. Can be done.

According to this embodiment, the employment of the superconducting coils and the concentric arrangement of these superconducting coils realize the simplification of the configuration and the miniaturization of the device, and at the same time, the responsiveness is high and the reliability is high. Track protection becomes possible,
Further, by providing the return switch, it is possible to easily return from the current limiting state to the steady state.

FIG. 5 is a circuit diagram showing a configuration of an embodiment corresponding to the second invention of this application together with an application object. In FIG. 1, a circuit breaker 2 and a current limiting device including a superconducting reactor 6 and a return switch 7 are inserted into one of the lines connecting the AC power supply 1 and the load 5. Reference numeral 4 denotes a line impedance. Here, the superconducting reactor 6 has an inductance that suppresses the current of the line to a value equal to or less than the limit value. The superconducting current limiting coil 6a has a critical current value larger than the current control value and the superconducting current limiting coil. It consists of a superconducting trigger coil 6b that is wound on the same bobbin and has the same magnetomotive force when inserted in parallel to the line and cancels out the magnetic flux.When currents i _L1 and i _L2 flow in, respectively, the impedance is substantially Becomes zero. On the other hand, the return switch 7 is connected in series to the superconducting trigger coil 6b.

FIG. 6 is a diagram showing a specific configuration of the superconducting reactor 6. The superconducting current limiting coil 6a is wound around the bobbin 6c, the superconducting trigger coil 6b is wound around the bobbin 6d, and the superconducting trigger coil 6b is The two ends of both coils are commonly connected to a terminal 6e, the other end of the superconducting current limiting coil 6a is connected to a terminal 6f, and the other end of the superconducting trigger coil 6b is connected to a terminal 6g. It is connected. Here, h is a spacer for maintaining insulation between the terminals 6f and 6g of these superconducting coils.

FIG. 7 is a diagram showing the state of the internal connection and the magnetic flux of the superconducting reactor 6, and shows the magnetic flux φ generated in the superconducting current limiting coil 6a when the superconducting coils 6a and 6b are connected in parallel to the line.
₁ and a magnetic flux phi ₂ that occurs in the superconducting trigger coil 6b is turned configured to be canceled.

The superconducting current-limiting coil that constitutes the superconducting reactor
The critical current value of 6a is manufactured to be larger than the current limit value of the line, and the superconducting trigger coil 6b is manufactured to quench when the current of the superconducting trigger coil 6b increases in response to the overcurrent of the line. I have.

The operation of the present embodiment configured as described above will be described below.

First, path is normal current i ₀ which flows in line, coils 6a constituting the superconducting reactor 6, 6b is held both in the superconducting state. As a result, the resistance of the superconducting current limiting coil 6a and the superconducting trigger coil 6b constituting the superconducting reactor 6 is zero, and is a non-inductive element. Therefore, the current i ₀ is reduced by the superconducting current limiting coil 6a,
The magnetic flux is offset by the currents i _L1 and i _{L2 shunted} to the coil b and these coils are in a non-inductive state.

Then, by accident a load short circuit occurs, when tends to flow estimated short-circuit current i _f determined by the impedance Z ₁ of the power supply voltage E and the line, also the current of the superconducting reactor 6 in accordance with the increase in current increases I do. This superconducting reactor 6
The superconducting trigger coil 6b has a critical current value _Jc2 corresponding to the current value in the middle of the increase, and the current i _L2 flowing through the superconducting trigger coil 6b exceeds the current value _Jc2 and quenches at the same time, and the superconducting trigger coil Current i _L2 flowing through 6b is commutated to superconducting current limiting coil 6a. As a result,
Most of the current flowing through the line flows through the superconducting current limiting coil 6a. Therefore, the superconducting reactor 6 includes the superconducting current limiting coil 6a.
There will have a large inductance by the magnetic flux phi ₁ that occurs. The superconducting trigger coil 6b changes to an element having an extremely large resistance value R, and i _L2 becomes an extremely small value. The line current i ₀ is limited by the self-inductance L ₁ of the superconducting current limiting coil 6a.

Thus, according to this embodiment, the substantial impedance becomes zero for a normal line current, and instantaneously becomes a reactor for an overcurrent to limit the line current.

FIGS. 8 (a) and 8 (b) show how the current i ₀ and the impedance Z _{SC of the} current limiting device change between the normal operation and the current limiting operation. That is, in a steady state operation, current limiter impedance Z _SC is very small, the current i ₀ of the line is maintained normally primarily by the load impedance Z _l. On the other hand, when a load short circuit occurs, the estimated short circuit current _if tends to flow in the line. However, when the line current is increased to J _g, currents of the superconducting trigger coil 6b exceeds the critical current value J _c2, increases in the moment the impedance of the superconducting reactor 6 Z _SC ', the short-circuit current is limited to the limit value or less Swept away.

Furthermore, the superconducting trigger coil 6b constituting the current limiting device
Is cooled by shutting off i _L2 by the return switch 7 and easily returns to the steady state.

Thus, also in this embodiment, the employment of the superconducting coils and the concentric arrangement of these superconducting coils realize the simplification of the configuration and the miniaturization of the device, and at the same time the quick response and the reliable line. Protection is possible, and a return switch is provided so that the current limit state can be easily returned to the steady state.

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to reduce the size of the device and secure the line protection, to suppress the steady-state power loss due to heat to a remarkably low level, and to reduce any impedance. There is an effect that it can be obtained. Further, the present invention has an excellent effect that it is possible to easily return to the steady state from the current limiting state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment corresponding to the first invention of this application together with an application object, and FIG. 2 is a partial cross-sectional view showing a specific configuration of the embodiment. FIG. 3 is a magnetic flux generation state diagram for explaining the operation of the embodiment, and FIG.
5A and 5B are diagrams showing changes over time in current and impedance for explaining the operation of the embodiment, and FIG. 5 is a configuration of an embodiment corresponding to the second invention of this application. FIG. 6 is a circuit diagram showing the configuration of the main elements of the embodiment, and FIG. 6 is a partial cross-sectional view showing the specific configuration of the main elements of the embodiment. FIG. Fig. 8
FIGS. 9A and 9B are diagrams showing the temporal changes of current and impedance for explaining the operation of the embodiment, and FIG. 9 is a circuit diagram showing the configuration of a conventional current limiting device. 3 ...... FCL, 3a, 6a ...... superconducting current limiting coil, 3b, 6b ...... superconducting trigger coil, 3b ₁ ...... first superconducting coil, 3b ₂ ...... second superconducting coils, 6 ...... superconducting Reactor, 7 ... Return switch

Continuation of the front page (56) References JP-A-1-185127 (JP, A) JP-A-60-74932 (JP, A) JP-A-51-35045 (JP, A) JP-A-63-239876 (JP) JP-A-2-101926 (JP, A) JP-A-51-39734 (JP, U) JP-A-55-94071 (JP, U) JP-B-48-2038 (JP, B1) (58) Surveyed field (Int.Cl. ⁶ , DB name) H02H 9/02 H01F 36/00

Claims (3)

(57) [Claims] 1. A superconducting current limiting coil having an inductance for suppressing a current in a circuit below a limit value and having a critical current value not less than the limit value; The first current having a critical current value greater than the current and connected in parallel
And a second superconducting coil wound in a non-inductive manner with each other, and a return switch connected in series with the superconducting trigger coil for opening and closing a current flowing through the superconducting trigger coil And a superconducting current limiting device, wherein the superconducting current limiting coil is connected in parallel with the superconducting trigger coil in which the return switch is connected in series. 2. A superconducting current limiting coil having an inductance for suppressing a current of a circuit below a limit value and having a critical current value not less than the limit value, and a superconducting current limiting coil formed non-inductively with the superconducting current limiting coil. A superconducting trigger coil having a critical current value smaller than the current limit value and larger than the normal current of the electric circuit; and a return switch connected in series with the superconducting trigger coil for opening and closing the current flowing through the superconducting trigger coil. And a superconducting current limiting device, wherein the superconducting current limiting coil is connected in parallel with the superconducting trigger coil in which the return switch is connected in series. 3. The superconducting current limiting device according to claim 1, wherein the superconducting trigger coil is disposed concentrically inside the superconducting current limiting coil.