JPH099499A - Current limiter - Google Patents

Abstract

PURPOSE: To limit short-circuit current by forming a three-winding reactor and the secondary windings of transformers in respective phases connected in series with the threewinding reactor using a superconductor, and short- circuiting the secondary windings. CONSTITUTION: Coils 2, 3, 4, 5, 6, 7 are formed using an iron core 1 as a magnetic path, and coils 11, 12, 13, 14, 15, 16 are formed using iron cores 8, 9, 10 as magnetic paths. The coils 2, 7, 11 are connected in series with one another. The coil 12 is obtained by winding a superconductor and the start and end of winding are short-circuited with each other. Similarly, the coils 3, 6, 13 are connected in series with one another. The coil 14 is obtained by winding a superconductor and the start and end of winding are short-circuited with each other. Similarly, the coils 4, 5, 15 are connected in series with one another. The coil 16 is obtained by winding a superconductor and the start and end of winding are short-circuited with each other. In case of a system fault other than one-line ground fault, the coils 12, 14, 16 as the superconductive short- circuited coils are quenched to produce a current limiting effect. In case of one-line ground fault, an current limiting effect is also produced because of a large zero-phase-sequence reactance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault current limiter for limiting a short circuit current when a short circuit accident occurs in a three-phase transmission line or distribution line.

[0002]

2. Description of the Related Art As a fault current limiter, a superconducting fault current limiter such as a three-winding reactor type superconducting fault current limiter, a non-induction winding type superconducting fault current limiter, and a superconducting transformer type fault current limiter is known.

Since the three-winding reactor type superconducting fault current limiter has a large zero-phase reactance, it has the characteristic of being able to limit the current without a superconducting transition in a one-line ground fault, but in the other faults, a current higher than the critical current is generated. The current is limited by the generation of resistance due to the normal conduction transition due to the flow.

The non-induction winding type superconducting fault current limiter carries out current limiting due to the generation of resistance due to the transition of normal conduction due to the flow of a current higher than the critical current at the time of system failure.

In the superconducting transformer type fault current limiter, a short circuit coil of the superconducting wire is placed on the secondary side and a small impedance due to a small leakage reactance appears only in a steady state.
The current is limited by a large impedance appearing in the primary winding due to the transition of the normal conduction due to the current exceeding the critical current flowing in the secondary winding during a system failure.

In the superconducting winding, there has been a demand for a fault current limiter capable of suppressing a fault current in a power system and increasing a short circuit capacity by utilizing a large difference in electric resistance between the superconducting state and the normal conducting state.

[0007]

In the three-winding reactor type superconducting fault current limiter and the non-induction winding type superconducting fault current limiter, a coil in series with the transmission line is required. Therefore, the current lead connecting the cryogenic portion and the room temperature portion is required. is necessary. At the current lead portion, there is evaporation of the refrigerant, for example liquid helium, due to heat intrusion. Also,
Helium gas near room temperature has a smaller withstand voltage than air and others.

The non-inductive winding type superconducting fault current limiter and the superconducting transformer type fault current limiter have a problem that even when a one-line ground fault occurs, the current can be limited only by the transition to the normal conduction state.

About 90% of short circuit failures in power transmission lines are 1
It is a line-to-ground fault, and it is required that normal conduction transition does not occur when a one-line ground fault occurs.

An object of the present invention is to provide a current limiting device which limits a short circuit current when a short circuit accident occurs in a three-phase transmission line or distribution line.

[0011]

SUMMARY OF THE INVENTION The above-mentioned object is, in a fault current limiter attached to a three-phase power transmission line, a secondary of a three-winding reactor and a transformer of each phase attached in series to the three-winding reactor. This is accomplished by forming the winding with a superconducting wire and shorting its secondary winding.

More specifically, in a fault current limiter attached to a three-phase transmission line, a magnetic path of a three-winding reactor is divided into three equal parts in a cross section, and a main iron core having a magnetic gap, and Each of the equally divided main iron cores is composed of legs and yokes forming a magnetic circuit, and the 3-winding reactor is wound around the main iron cores and the legs, and the coils wound on the respective yokes are 3 turns. Connected in series to the line reactor so as to form a primary winding of any one of three-phase transformers, the secondary winding of the transformer is made of a superconducting wire, and the secondary winding is short-circuited Is.

[0013]

In the steady state, the three-winding reactor cancels each other except for the leakage reactance of each of the three phases, so that only a very small impedance appears. On the other hand, when there is a one-line ground fault, since there is a large zero-phase reactance, a large current limiting effect appears. This is for the following reason.

[0014]

## EQU1 ## Va = jωLIa + jωM (Ib + Ic) (Equation 1) This equation can be rewritten as follows.

[0015]

## EQU00002 ## Va = j.omega. (LM) Ia + j.omega.M (Ia + Ib + Ic) (Equation 2) where Io = Ia + Ib + Ic

[0016]

## EQU00003 ## Va = j.omega. (LM) Ia + j.omega.MIo (Equation 3) where Va: a-phase voltage Ia, Ib, Ic: a, b, c-phase current appearing at the terminals of the three-winding reactor j: Indicates an imaginary number ω: Angular frequency of current L: Self-inductance of 3-winding reactor a-phase winding M: 3-winding reactor Mutual inductance (LM) between a-phase winding and b-phase or c-phase winding is This is small because it exhibits leakage reactance. There is no Io in the steady state. Therefore, the reactance in the steady state is small. From the last equation, the zero-phase impedance is ω
(3M), which is a large value. Therefore,
The short-circuit current at the time of one-line ground fault, which is mainly the zero-phase current, cannot be made large due to this large zero-phase impedance, and the current limiting effect appears.

As described above, in the case of a one-wire ground fault, the current is limited by a large zero-phase reactance, so that an overcurrent does not appear. In other faults, the short-circuited secondary winding of the transformer is quenched and the primary winding is quenched. A large impedance appears in the winding and the current is limited.

[0018]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

An embodiment of the present invention is shown in FIG. In FIG. 1, coils 2, 3, 4, 5, 6, 7 with the iron core 1 as a magnetic path.
Is wound. The coils 11, 12, 13, 14, 15, 16 are wound with the iron cores 8, 9, 10 as magnetic paths.

The coils 2, 7 and 11 are connected in series. The coil 12 is wound by a superconducting conductor, and the winding start and winding end are short-circuited. Similarly, the coils 3, 6 and 13 are connected in series, the coil 14 is wound with a superconducting conductor, and the winding start and winding end are short-circuited. Similarly, the coils 4, 5 and 15 are connected in series, the coil 16 is wound with a superconducting conductor, and the winding start and winding end are short-circuited.

For example, the coils 2, 7, 11 are supplied with the a-phase current, the coils 3, 6, 13 are supplied with the b-phase current, and the coils 4, 4,
5 and 14 are connected to a power transmission line so that a c-phase current flows. Of course, other combinations may be used.

When a system fault other than the one-line ground fault occurs, a large positive-phase and negative-phase current flows, and thus it is not possible to limit the current with only a large zero-phase impedance, but it is induced in the coils 12, 14, 16 which are superconducting short-circuit coils. The large current quenches the coils 12, 14, 16 and causes the coil 1 to
A large leakage reactance is generated in 1, 13, 15 and a current limiting effect is generated.

Coil 2,3,4,5,6,7,11,1
3, 15 may be superconducting coils or ordinary copper coils.
However, when the superconducting coil is used, the coils 2, 3,
The quench resistance of 4,5,6,7,11,13,15 is made larger than that of the coils 12,14,16.

However, the coils 2, 3, 4, 5, 6, 7,
In view of their functions, 11, 13, 15 do not need to be superconducting coils, but may be ordinary copper coils. A normal copper coil has the advantages of a cryostat structure, which is necessary when it is used as a superconducting coil, the problem that the withstand voltage becomes small by using a refrigerant such as helium, and the heat loss due to the consumption of the refrigerant due to intrusion heat is eliminated. .

FIG. 2 is a front view of the present invention, FIG. 3 is an elevational view of the present invention, and FIGS. 2 and 3 show the structure of the iron core. The main iron core 17 is divided into three equal sections and magnetically has a gap. A main iron core 17 divided into three equal parts, legs 18, 19, 20 and yokes 21, 22, 23 constitute a magnetic circuit. The 3-winding reactor is wound around the main iron core 17. Each phase of this 3-winding reactor is connected in series to the transformer in the leg 18, 19, 20 part.

As for the transformer portion, as shown in FIG. 4 (one phase is shown in the figure), one third of the leg 18 and the main iron core 17 is provided.
Form a magnetic path, and in a steady state, the short-circuit coil 12 is the coil 11
Since a magnetic field is emitted so as to cancel the magnetic field created by, only a small impedance appears. The large zero-phase impedance of the three-winding reactor exerts a current limiting effect when there is a one-wire ground fault, and the coils 12, 1
When coils 4 and 16 are quenched, coils 11, 13 and 15
The fact that a large leak reactance appears in and shows the current limiting effect is the same as in the case of the embodiment shown in FIG. However, in the embodiment shown in FIG. 4, since the member forming the magnetic path of the three-winding reactor is also used as the magnetic path of the transformer, a compact current limiting device can be realized.

2 and 3, the main iron core 17 and the leg 1 are shown.
When a 3-winding reactor is formed on the 8, 19, and 20 parts and three-phase transformer parts are formed on the yoke parts 21, 22, and 23, the configuration shown in FIG. 5 (one phase is shown in the figure) is obtained. A compact current limiting device can be realized for the same reason as above.

That is, since the 3-winding reactor has a large zero-phase reactance at the time of 1-line ground fault, a large current limiting effect appears.

When a system fault other than the one-wire ground fault occurs, the coils 12, 14, 16 which are superconducting short-circuit coils are quenched, and large leakage reactances are generated in the coils 11, 13, 15 and a current limiting effect is produced.

[0030]

According to the present invention, a superconducting fault current limiter which is compact and has a small heat loss can be obtained without quenching of the superconducting coil during a one-wire ground fault.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a plan view of an embodiment of the present invention.

FIG. 3 is an elevational view of an embodiment of the present invention.

FIG. 4 is a schematic diagram showing another embodiment of the present invention.

FIG. 5 is a schematic view showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Iron core, 2, 3, 4, 5, 6, 7, 11, 13, 15
... coil, 8, 9, 10 ... iron core, 12, 14, 16 ... superconducting short-circuit coil, 17 ... main iron core, 18, 19, 20 ...
Legs 21, 22, 23 ... Yoke part.

Claims (5)

[Claims] 1. A current limiter connected to a three-phase transmission line, comprising:
A current limiting circuit characterized by comprising a three-winding reactor and a transformer connected in series to the reactor, at least a part of a secondary winding of the transformer being formed of a superconducting wire, and the secondary winding being short-circuited. vessel. 2. A current limiting device connected to a three-phase transmission line,
The magnetic path of the three-winding reactor is divided into three equal parts in a cross section, and a main iron core having a magnetic gap, and legs and yokes forming a magnetic circuit with each of the three equal divided main iron cores are provided. A 3-winding reactor is wound around the main iron core, and coils wound around the legs are connected in series with the 3-winding reactor in series.
A transformer characterized in that it is connected to form a primary winding of one of the transformers, at least a part of the secondary winding of the transformer is formed of a superconducting wire, and the secondary winding is short-circuited. Sink. 3. A current limiting device connected to a three-phase transmission line, comprising:
The magnetic path of the three-winding reactor is divided into three equal parts in a cross section, and a main iron core having a magnetic gap, and legs and yokes forming a magnetic circuit with each of the three equal divided main iron cores are provided. A three-winding reactor is wound around the main iron core and this leg, and coils wound around respective yokes are connected in series to the three-winding reactor to form the primary winding of any one of the three phases. A current limiting device, characterized in that at least a part of the secondary winding of the transformer is formed of a superconducting wire, and the secondary winding is short-circuited. 4. A fault current limiter characterized in that the three-winding reactor according to any one of claims 1, 2 and 3 comprises a normal conducting coil. 5. A current limiting device, characterized in that the primary winding of the transformer according to claim 1, 2 or 3 is composed of a normal conducting coil.