JP2001275249A - Three-phase current limiting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-phase current limiting apparatus at a low cost, which is compact without installing a bypass reactor on the primary side of a transformer of a three-phase AC system. SOLUTION: Each of the three-phase AC reactors L1 to L3 has a secondary winding 16 closely magnetically coupled with a primary winding 15 by air-core structure or air-gap iron core structure. Primary sides of the reactors L1 to L3 are connected with the three-phase system 14. Current limiting elements which are turned into the state of high impedance are connected with secondary sides of the reactors. As a means making the secondary sides open while the current limiting elements maintain current limiting effect on account of system failure, breakers CB1 to CB3 are interposed between the secondary sides of the reactors L1 to L3 and current limiting elements. The current limiting elements are constituted of a three-phase rectifier circuit 11 connected with the secondary sides of the reactors L1 to L3 and a DC reactor L connected between DC terminals of the three-phase rectifier circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase current limiting device, and more particularly to a three-phase current limiting device for suppressing an overcurrent fault current caused by a short-circuit fault in a three-phase AC system such as a transmission and distribution system.

[0002]

2. Description of the Related Art For example, in a three-phase AC system such as a power transmission and distribution system, a current limiting device is installed for the purpose of suppressing an overcurrent fault current caused by a short circuit fault or the like. As an example of such a current limiting device, there is a three-phase rectification type current limiting device including a three-phase rectifier circuit 1 and a DC reactor L as shown in FIG.

[0003] This current limiting device includes a circuit breaker CB in series with a three-phase AC system 4 including a three-phase AC power supply 2 and a power transformer 3.
Transformers T ₁ provided for each of the three phases via ₁ to ₃
Connected to ~ ₃ . That is, the primary side of each of the transformers T ₁ to T ₃ is connected in series with the three-phase AC system 4, and one of the secondary sides of each of the transformers T ₁ to T ₃ is short-circuited, and the other side of the secondary side is connected. A pair of diodes D ₁ connected in parallel to the positive and negative polarities
To ₆ (A phase: D ₁ to ₂ , B phase: D ₃ to ₄ , C phase: D ₅ to ₆ ) corresponding to each phase are provided, respectively, to form a three-phase rectifier circuit 1. Transformer T of three pairs of diodes D ₁ to _6
1-3 the connected opposite divided into the positive side and the negative side and connected,
The DC reactor L is connected between the positive and negative sides.

In the steady state of the three-phase AC system 4, the current limiting device
Generally, a DC current flows through DC reactor L and diode D _1
1-6 becomes the most of the time on and the secondary side of the transformer T ₁ - ₃ is a state of being short-circuited, the impedance seen from the primary side of the transformer T ₁ - ₃ becomes a small value equivalent leakage impedance.

On the other hand, if a short circuit fault or the like occurs in the three-phase AC system 4 and an accident current larger than the DC current flowing in the DC reactor L flows, the diodes D ₁ to D ₆ are turned off and the current of the DC reactor L is reduced. The inductance of the DC reactor L becomes effective in order to increase rapidly, and the transformer T
The fault current of the three-phase AC system 4 can be suppressed by eliminating the secondary-side short circuits ₁ to ₃ .

Since the impedance on the primary side of each of the transformers T ₁ to T ₃ decreases with time, it is necessary to detect the fault current and operate the circuit breakers CB ₁ to CB ₃ to quickly disconnect the system. There is.

[0007]

By the way, in the above-mentioned conventional current limiting device, when a system failure occurs, the DC reactor L instantaneously becomes high impedance due to the current preserving action of the DC reactor L to exhibit the current limiting effect. since the impedance of the primary side of T ₁ ~ ₃ becomes smaller with time, so as to cut off the communication system by Kairetsu quickly line with the fault current detected by operating the circuit breaker CB ₁ ~ ₃ and the ing.

[0008] However, the current limiting device is sometimes applied for the purpose of maintaining the grid connection. When using a three-phase current limiting device in such applications, the bypass reactor B on the primary side of the transformer T ₁ ~ _3, as shown in FIG. 6
The L ₁ ~ ₃ was necessary to parallel connection.

[0009] In this current limiting device, when the system failure, the fault current on that which causes limited by DC reactor L, the impedance of the primary side of the transformer T ₁ ~ ₃ decreases with time, the fault current Although will be detected and to operate the breaker CB ₁ ~ ₃ the bypass reactors BL ₁ ~ ₃
If it the provided after the operation the breaker CB ₁ ~ ₃ also, that the bypass reactors BL ₁ ~ accident current commutating to be able to _3, thereby Kairetsu the interconnection of the three-phase AC system 4 Therefore, the current limiting function for suppressing the fault current can be continued.

However, the transformer T of the three-phase AC system 4
Must bypass reactors BL _1-3 connected in parallel to the primary side of the _1-3, the overall current-limiting device is disadvantageously lead to cost as well as size.

An object of the present invention is to provide a compact and inexpensive three-phase current limiting device without providing a bypass reactor on the primary side of a transformer of a three-phase AC system.

[0012]

According to a first aspect of the present invention, there is provided a secondary winding in which a primary winding and an air-core structure or a gapped iron-core structure are closely magnetically coupled to each other. Connect the primary side of the three-phase AC reactor having windings to the three-phase AC system, and connect a current-limiting element that increases impedance due to overcurrent to the secondary side,
The secondary side is opened while the current limiting element maintains the current limiting effect due to a system failure.

According to the first aspect of the present invention, when the three-phase AC system is in a steady state, a direct current flows through the current limiting element and the secondary current is apparently short-circuited, so that the three-phase AC reactor is viewed from the primary side. The impedance is the leakage impedance between the primary and secondary windings, and since the primary and secondary windings are tightly magnetically coupled to each other by an air-core structure or a gapped core structure, the three-phase AC reactor Has a very small impedance on the primary side.

On the other hand, in the event of a system failure, if an overcurrent is to flow due to a short circuit accident or the like, the current limiting element instantaneously becomes high impedance, and the magnetic flux between the primary winding and the secondary winding of the three-phase AC reactor is mainly changed by the primary winding. The entire winding is interlinked, and the impedance seen from the primary side of the three-phase AC reactor also increases sharply, thus exhibiting a current limiting effect. If the secondary side of the three-phase AC reactor is opened while the current limiting effect of the current limiting element is maintained, the primary winding of the three-phase AC reactor will exhibit the current limiting effect thereafter. There is no need to provide such a bypass reactor.

According to a second aspect of the present invention, there is provided a three-phase AC reactor as a means for opening the secondary side while the current limiting element maintains the current limiting effect due to the system failure described in the first aspect. Characterized in that a circuit breaker is interposed between the secondary side and the current limiting element. By the operation of the circuit breaker, the secondary side of the three-phase AC reactor can be easily and quickly shut off.

According to a third aspect of the present invention, there is provided a three-phase rectifier circuit in which the current limiting element according to the first or second aspect is connected to a secondary side of a three-phase AC reactor, and a direct current of the three-phase rectifier circuit. And a DC reactor connected between the terminals.

According to the third aspect of the present invention, when an overcurrent is caused to flow due to a system failure or a short circuit accident, a sudden increase in current is suppressed by the inductance of the DC reactor, and the secondary side of the three-phase AC reactor instantaneously has high impedance. The magnetic flux between the primary and secondary windings of the three-phase AC reactor mainly interlinks with the entire primary winding, and the impedance seen from the primary side of the three-phase AC reactor also suddenly increases. Demonstrate the flow effect. If it is opened to shut off the secondary side of the three-phase AC reactor, thereafter, the primary winding of the three-phase AC reactor exhibits a current limiting effect.

According to a fourth aspect of the present invention, the DC reactor according to the third aspect is a superconducting reactor which is quenched by an overcurrent and has a high resistance.

According to the present invention, when a superconducting reactor is quenched due to an overcurrent due to a system failure or a short circuit accident or the like, the secondary side of the three-phase AC reactor instantaneously has a high impedance, and is mainly a three-phase AC reactor. The magnetic flux existing between the primary winding and the secondary winding interlinks with the entire primary winding, and the impedance seen from the primary side of the three-phase AC reactor also sharply increases, thereby exerting a current limiting effect. If the secondary side of the three-phase AC reactor is opened to restore the superconducting reactor, the primary winding of the three-phase AC reactor thereafter exerts a current limiting effect.

According to a fifth aspect of the present invention, of the three pairs of rectifying elements constituting the three-phase rectifying circuit according to the third or fourth aspect, at least two pairs of rectifying elements constituting two phases are rectified switching elements. The secondary side is opened by the rectifying switching element while the DC reactor maintains a current limiting effect due to a system failure.

According to the fifth aspect of the present invention, the secondary side of the three-phase AC reactor can be opened in the event of a system failure by the cutoff function of the rectifying switching element. This is equivalent to opening the secondary side of the AC reactor.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a three-phase current limiting device according to the present invention will be described in detail below.

The three-phase current limiting device of the embodiment shown in FIG. 1 has a three-phase alternating current having a primary winding 15 and a secondary winding 16 which is magnetically tightly coupled to each other by an air core structure or a gapped iron core structure (described later). the primary side of the reactor L ₁ ~ ₃ connected to a three-phase AC system 14, the three-phase AC reactors L ₁ ~ ₃ of the secondary to the primary side via the circuit breaker CB ₁ ~ ₃ which correspond to each phase three-phase rectifier circuit 11 is connected, and a DC reactor L is connected between the DC terminals of the three-phase rectifier circuit 11.

The primary windings 15 arranged on the primary side of the three-phase AC reactors L ₁ to L ₃ are connected in series to the three-phase AC system 14 corresponding to the respective phases. In addition, one end of the secondary winding 16 arranged on the secondary side of the three-phase AC reactors L ₁ to L ₃ is short-circuited, and the other end of the secondary winding 16 is connected to circuit breakers CB ₁ to CB ₃ corresponding to each phase. Is connected to the three-phase rectifier circuit 11 via the.

In this embodiment, the three-phase AC reactor L
A three-phase rectifier circuit 11 is connected to the other ends of the _first to _third secondary windings 16 in which a pair of rectifiers D ₁ to D ₆ connected in parallel with opposite polarities are connected to correspond to respective phases, respectively. connect separately connected to the three-phase AC reactors L ₁ ~ ₃ of the rectifying elements D ₁ ~ ₆ of the three pairs constituting opposite to the positive side and the negative side, connect the DC reactor L between its positive and negative.

The three-phase AC reactors L ₁ to L ₃ are shown in FIG.
As shown in FIG. 3, a gap-filled core structure X wound tightly and magnetically coupled between the primary winding 15 and the secondary winding 16 so as to minimize the leakage impedance is provided. In the coil winding structure shown in the figure, the magnetic field strength H is only in the positive axial direction. On the other hand, as shown in FIG. 2B, if the air-core structure Y in which the primary windings 15a and 15b and the secondary winding 16 are divided and alternately wound is used, the strength H of the magnetic field is positive or negative in the axial direction. Since it is in both directions, the leakage impedance can be further reduced. The structure shown in the figure shows a structure in which the primary windings 15a and 15b are divided into two parts. If the number of divisions is increased, the leakage impedance can be further reduced. In addition, the alternate arrangement of the primary windings 15a and 15b and the secondary winding 16 may be opposite to that shown in the figure. Although FIG. 2A shows the core structure X with a gap, the core structure may be an air core structure. FIG. 2B shows the core structure with an air core Y, but the core structure with a gap may be used.

When the three-phase AC system 14 is in a steady state, a DC current flows through the DC reactor L, and the diodes D ₁ to D ₆ are turned on for most of one cycle, so that an apparently secondary short circuit occurs. , The impedance as viewed from the primary side of the three-phase AC reactors L ₁ to L ₃ is the primary winding 15 and the secondary winding 16.
Since the primary winding 15 and the secondary winding 16 are tightly magnetically coupled to each other by an air core structure or a gapped iron core structure, the primary winding 1
The primary side of the three-phase AC reactors L ₁ to L ₃ has a very small impedance due to the mutual induction between the secondary winding 5 and the secondary winding 16.

On the other hand, in the event of a system failure, if an overcurrent is to flow due to a short circuit accident or the like, a sudden increase in current is suppressed by the inductance of the DC reactor L, and the secondary sides of the three-phase AC reactors L ₁ to L ₃ instantaneously become high impedance. mainly of the three-phase AC reactors L ₁ ~ ₃ of the primary winding 15 and secondary winding 16 in time magnetic flux is the primary winding across interlinked so, viewed from the primary side of the three-phase AC reactors L ₁ ~ ₃ The current limiting effect is also increased due to the sudden increase in impedance.

While the current limiting effect of the DC reactor L is maintained, that is, the generated high impedance becomes smaller with the passage of time, the overcurrent or the DC reactor L is generated while the predetermined high impedance is exhibited. Is detected by a detection circuit (not shown), and based on the detection signal, a control circuit (not shown)
By operating B ₁ to B ₃ , the three-phase AC reactor L ₁
If opening of the secondary side of the _1-3, thereafter, the three-phase AC reactors L ₁ to ₃ of the primary winding 15 exhibits a current limiting effect,
Conventional bypass reactors BL ₁ to BL ₃ (see FIG. 6)
There is no need to provide

[0030] will be described below with reference to the equivalent circuit shown in FIG. 3 the operation of the three-phase AC reactors L ₁ ~ _3. Although FIG. 3 shows a single-phase equivalent circuit for simplification, the same principle applies to a three-phase circuit. FIG. 4A shows an iron core 2.
1 is a transformer 2 in which a primary winding 22 and a secondary winding 23 are wound.
4 (b) shows an iron core reactor 27 in which a primary winding 22 and a secondary winding 23 are wound around an iron core 26 having an air gap 25, and the reactor having a secondary winding has an iron core. What is represented by an equivalent circuit very similar to the transformer 24 is that an iron core reactor 27 having an air gap 25 is provided.
Can be easily understood from the fact that the air gap 25 corresponds to the exciting impedance of the transformer 24.

As shown in FIG. 3, when the system is in a steady state, the secondary side is apparently short-circuited as described above. Therefore, the impedance viewed from the primary side of the AC reactors L ₁ to L ₃ is the parallel of the leakage impedance 17 and the main inductance 18. It becomes a circuit and has a small value of about 17 leakage impedance. In contrast, when the secondary side of the AC reactor L ₁ ~ ₃ as it overcurrent to flow through system fault such as short circuit is high impedance, also it increases the impedance seen from the primary side of the AC reactor L ₁ ~ _3, The current shunts to the main inductance 18 side. If opened breaker CB ₁ ~ _3, which is provided in the current limiting operation on the secondary side of the AC reactor L ₁ ~ _3, a current flows only in the main inductance 18, the current limiting reactor (the conventional case shown in FIG. 6 Bypass reactor BL ₁ to ₃
Function).

In the above embodiment, the three-phase rectifier circuit 1
Although the case where the diodes D ₁ to D ₆ are applied as the three pairs of rectifying elements constituting 1 has been described, the present invention is not limited to this. May be rectifying switching elements, for example, thyristors.

By using a thyristor as the rectifying element constituting the two phases in this manner, the secondary side of the three-phase AC reactors L ₁ to L ₃ can be opened at the time of a system failure due to the shut-off function of the thyristor. becomes equivalent to the case of opening the secondary side of the circuit breaker CB ₁ ~ ₃ by a three-phase AC reactors L ₁ ~ ₃ described in the above embodiment, as a result, AC reactors L
_1-3 necessary to provide a circuit breaker CB _1-3 between three-phase rectifier circuit 11 is eliminated.

Here, the thyristor can be turned off by using a diode as the one-phase rectifying element among the three pairs of rectifying elements constituting the three phases. That is,
Since the short-circuit circuit of the DC reactor L can be configured by using a diode as the one-phase rectifier element, the energy accumulated by the charging current flowing into the DC reactor L due to the occurrence of the system failure is regenerated by the diode. By refluxing, the two-phase thyristor can be quickly turned off.

The rectifying switching element is
At least a two-phase rectifying element is sufficient.
It is also possible to use thyristors for all three-phase rectifiers. However, for the two-phase thyristor turned off when a system failure occurs, the remaining one-phase thyristor needs to be turned on to operate the diode. As the rectifying switching element, a GTO or the like can be used other than the thyristor.

It is also possible to use a superconducting reactor as the DC reactor L connected between the DC terminals of the three-phase rectifier circuit 11. Using this superconducting reactor, overcurrent quenched instantaneously flows in the superconducting reactor high resistance, thereby a high impedance is generated in the primary side of the three-phase AC reactors L ₁ ~ _3, the overcurrent current limiting It is possible to do. Since the current constantly flowing in the superconducting reactor is direct current, there is no AC loss, and it is possible to simplify the refrigerator of the superconducting reactor, use an inexpensive DC superconducting wire, and use one expensive superconducting reactor. And so on. Since the temperature of the superconducting reactor rises when it is quenched, it is necessary to disconnect the superconducting reactor from the circuit once and cool it down in order to restore the superconducting reactor, and is usually used in combination with the above-described circuit breaker.

[0037]

According to the three-phase current limiting device according to the first aspect of the present invention, a three-phase AC reactor having a primary winding and a secondary winding tightly magnetically coupled to each other by an air core structure or a gapped core structure. While the primary side of the current limiting element is connected to a three-phase AC system, and a current limiting element for increasing the impedance due to overcurrent is connected to the secondary side, while the current limiting element maintains the current limiting effect due to a system failure, Since the secondary side is opened, the primary winding of the three-phase AC reactor exhibits a current limiting effect in the event of a system failure, so that there is no need to provide a bypass reactor as in the related art, and the system is compact. An inexpensive three-phase current limiting device can be provided.

As means for opening the secondary side while the current limiting element maintains the current limiting effect due to the system failure described in claim 1 as in the invention according to claim 2, a three-phase device may be used. If a circuit breaker is inserted between the secondary side of the AC reactor and the current limiting element, the secondary side of the three-phase AC reactor can be easily and quickly shut off.

According to a third aspect of the present invention, there is provided a three-phase rectifier circuit in which the current limiting element according to the first or second aspect is connected to a secondary side of a three-phase AC reactor, and the three-phase rectifier circuit. And a DC reactor connected between the DC terminals, the current limiting element can be realized with a simple circuit configuration.

According to a fourth aspect of the present invention, when the DC reactor according to the third aspect is a superconducting reactor that is quenched by an overcurrent and has a high resistance, no AC loss occurs, and the superconducting reactor has Simplification of the refrigerator and use of inexpensive DC superconducting wires are possible, and only one expensive superconducting reactor is required.

According to a fifth aspect of the present invention, of the three pairs of rectifying elements constituting the three-phase rectifying circuit according to the third or fourth aspect, at least two pairs of rectifying elements constituting two phases are rectified. If the rectifying switching element is used to open the secondary side while the DC reactor maintains the current limiting effect due to a system failure due to the rectifying switching element, the secondary side of the three-phase AC reactor and the current limiting element Since there is no need to insert a circuit breaker between the three-phase current limiting device, a more compact and inexpensive three-phase current limiting device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a three-phase current limiting device according to the present invention.

FIG. 2A is a configuration diagram showing a core structure with a gap of an AC reactor, and FIG. 2B is a configuration diagram showing an air core structure of the AC reactor.

FIG. 3 is a single-phase equivalent circuit for explaining the operation of the three-phase AC reactor.

FIG. 4A is a configuration diagram illustrating a configuration example of a single-phase transformer,
(B) is a block diagram showing a structure of an iron core reactor having an air gap.

FIG. 5 is a circuit diagram showing a conventional example of a three-phase current limiting device.

FIG. 6 is a circuit diagram illustrating an example of a three-phase current limiting device provided with a bypass reactor.

[Explanation of symbols]

Three-phase AC reactor having a 11 three-phase rectifier circuit 14 the three-phase AC system 15 primary winding 16 secondary windings D ₁ ~ ₆ rectifying element (diode) L DC reactor L ₁ ~ ₃ secondary windings

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 30/08 H01F 39/00 (72) Inventor Katsuo Matsubara 47 Umezu Takaune-cho, Ukyo-ku, Kyoto-shi, Kyoto Nisshin F term (reference) in Denki Co., Ltd. 5G013 AA01 AA04 BA01 CA02 CA14

Claims (5)

[Claims] 1. A three-phase AC reactor having a primary winding and a secondary winding tightly magnetically coupled to each other by an air core structure or a gapped core structure is connected to a three-phase AC system, and a secondary side thereof is connected to the three-phase AC system. A current limiting element that increases impedance due to overcurrent is connected to the secondary side, and the secondary side is opened while the current limiting element maintains the current limiting effect due to a system failure. Phase limiting device. 2. A means for opening the secondary side while the current limiting element maintains the current limiting effect due to the system failure, includes means between the secondary side of the three-phase AC reactor and the current limiting element. The three-phase current limiting device according to claim 1, wherein a circuit breaker is interposed. 3. A three-phase rectifier circuit comprising: a three-phase rectifier circuit connected to a secondary side of a three-phase AC reactor; and a DC reactor connected between DC terminals of the three-phase rectifier circuit. The three-phase current limiting device according to claim 1 or 2, wherein: 4. The three-phase current limiting device according to claim 3, wherein the DC reactor is a superconducting reactor that is quenched by an overcurrent and has a high resistance. 5. A three-phase rectifier circuit comprising at least two pairs of rectifiers, wherein at least two pairs of rectifiers constitute a rectifier switching element, and the rectifier switching element causes the DC reactor to fail due to a system failure. The three-phase current limiting device according to claim 3 or 4, wherein the secondary side is opened while the current limiting effect is maintained.