KR20180099431A - Double quench current limiting device for direct current and alternating current - Google Patents

Abstract

Provided is a double quench current limiting device capable of adjusting an impedance limit which comprises: a first current limiting unit for providing a first current flow path and a second current flow path; and a second current limiting unit connected to the first current limiting unit to provide a third current flow path. Each resistance of the first and third flow paths is smaller than a resistance of the second current flow path. The double quench current limiting device operates to allow an input current to flow through the first current flow path when the input current is smaller than or equal to a first threshold value, operates to allow at least a part of the input current to flow through the third current flow path when the input current exceeds the first threshold value, and is smaller than or equal to a second threshold value, as well as allowing the remaining input current to flow through the second current flow path when a part of the input current flows through the third current flow path, and operates to allow the input current to flow through the second current flow path when the input current exceeds the second threshold value.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplex quasi-current limiting device for alternating current and direct current,

The present invention relates to a superconducting current limiting device for alternating current and direct current.

Generally, when an accident such as a short circuit occurs in one of the power systems, the adjacent circuit breaker operates at the point of the accident. This cuts off the power line at the upper end and the line where the short circuit occurs, thereby reducing the power loss due to the overcurrent leakage and protecting the peripheral power equipment. In this way, a current limiter using a superconductor is used so as to prevent the downward phenomenon of the entire system and continuously supply power to the other healthy line.

A power system device or circuit is subjected to continuous rated current in the steady state. However, if a fault occurs on a power system device or circuit, or if a fault current is applied that is beyond the range that the device or circuit can tolerate, the fault current will damage the main components of the power system or circuit.

In order to prevent such a fault current, a current limiting device capable of controlling current by connecting to a power system device or a circuit of a circuit has been developed. Particularly, studies on a superconducting current limiting device using a superconductor having a characteristic in which the electric resistance is substantially close to zero at a cryogenic temperature and the resistance increases sharply as the temperature rises are actively researched.

In this regard, Korean Patent No. 10-1182968 (entitled "Hybrid Superconducting Fault Current Limiter") discloses a superconductor for detecting the occurrence of a fault current while outputting power input to a power input terminal to a power output terminal, A high speed switch for opening the vacuum interrupter when the superconductor senses a fault current and at the same time bypassing the power of the power input while the protective contact is closed and outputting it to the vacuum interrupter; A power semiconductor switching unit provided between the power output stage and being turned off when the superconductor detects a fault current to remove an arc generated when the vacuum interrupter is opened; a capacitor connected between the power input terminal and the power output terminal; , A current-limiting resistor connected in parallel with the capacitor Superconducting Fault groups that are disclosed.

However, the conventional superconducting fault current limiter as described above does not limit the current limitation according to the magnitude of the fault current after switching interruption, but the uniform fault current limit. If the fault current is small, there is a problem that the operation of the main breaker is interrupted because the system breaker can not confirm the failure.

Therefore, there is a need for a method of limiting the fault current by adjusting the number and path of the superconducting elements operating according to the magnitude of the fault current, using the arrangement structure of the superconducting elements and the switching elements.

In some embodiments of the present invention, an auxiliary switch unit including a superconducting device is added to a trigger-type superconducting fault current limiter as a main switch unit to induce a dual value, and the relays are connected to the respective superconducting devices, And to control the limiting impedance by controlling the double limiting current.

In addition, some embodiments of the present invention provide a self-resonance circuit that generates resonance due to a change in current of a superconducting fault current limiting device. And to provide a device for the flow of water.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may exist.

According to an aspect of the present invention, there is provided a dual current type current limiting apparatus for alternating current and direct current, comprising: a first current limiting unit for providing a first current flow path and a second current flow path; And a second current limiter connected to the first current limiter and providing a third current flow path, the resistances of the first and third current flow paths being smaller than the resistances of the second current flow path, respectively Wherein when the input current is less than or equal to the first threshold value, the input current flows into the first current flow path, and when the input current exceeds the first threshold value and less than or equal to the second threshold value, Wherein at least a portion of the input current flows into the third current flow path while the rest of the input current flows into the second current flow path when a portion of the input current flows into the third current flow path, Operates to cause the input current to flow to the second current flow path when the second current flow path exceeds the second threshold value.

The dual-current limiting current device according to any one of the above-described objects of the present invention can variably change a current flowing path according to a magnitude of a fault current, thereby providing a fluid limiting impedance according to a fault current magnitude.

In addition, the dual overcurrent limiting device according to any one of the tasks of the present invention can rapidly limit an initial overcurrent for each of different-sized fault currents using a multi-superconducting device, Switches can be individually turned on / off to change the current flow path to effectively protect the internal structure of the current limiting device from the fault current.

The dual-current limiting device according to any one of the means for solving the problems of the present invention is capable of stably operating a direct current without damaging the switch through a self resonant circuit connected in parallel to the switch of the main switch, The operation reliability and the cut-off speed are improved and the maximum internal-current amount is increased.

1 is a configuration diagram of a double-edged current limiting apparatus according to an embodiment of the present invention.
FIGS. 2A to 2C are views for explaining a current path in a double-breakdown current limiting apparatus according to an embodiment of the present invention. FIG.
3 is a configuration diagram of a double-edged current limiting apparatus according to another embodiment of the present invention.
4A to 4C are views for explaining a current path in a double-breakdown current limiting apparatus according to another embodiment of the present invention.
5 is a view showing a current resonance waveform by a self-resonant circuit applied to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

1 is a configuration diagram of a double-edged current limiting apparatus according to an embodiment of the present invention. 2 (a) to 2 (c) are diagrams for explaining a current path in a double-breakdown current limiting apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the dual-current limiting apparatus 10 includes a first current limiting unit 100, a second current limiting unit 200, a self-resonant circuit unit 300, and a switch control unit 400.

The first current limiting unit 100 includes a first superconducting element 110 and a first switch 120 connected in series between an input terminal and an output terminal of the current and a first superconducting element 110 connected in series between an input terminal and an output terminal, And a first current-limiting resistor 130 and a second current-limiting resistor 140 connected in parallel to the first switch 120.

The first and second current limiting resistors 130 and 140 may be a combination of at least one resistor R, a coil L, and a capacitor C, respectively. The impedance value of each of the first and second current limiting resistors 130 and 140 may be preset to a fixed value according to the designer's intention or usage.

One end of the first superconducting element 110 and one end of the first current limiting resistor 130 are respectively connected to an input terminal. The other end of the first superconducting element 110 is connected to one end of the first switch 120, 1 current-limiting resistor 130 is connected to one end of the second current-limiting resistor 140. The other end of the first switch 120 and the second current-limiting resistor 140 are connected to the output terminal, respectively.

The second current limiting unit 200 includes a second superconducting element 210 and a second switch 220 connected in series and the second superconducting element 210 and the second switch 220 include a second current- 140 in parallel.

One end of the second superconducting element 210 is connected between a first current limiting resistor 130 and a second current limiting resistor 140 connected in series and the other end of the second superconducting element 210 is connected to a second switch 220, respectively. The other end of the second switch 220 is connected to the second current-limiting resistor 140 and the output terminal.

At this time, the first current limiter 100 provides a first current flow path and a second current flow path between the input and output ends, and the second current limiter 200 provides a third current flow path.

The switch control unit 400 measures the currents or voltages of the first through third current flow paths and the first and second superconducting elements 110 and 210 and controls the first switch 120 based on the measured current or voltage. And on / off driving of the first switch 220 and the second switch 220. At this time, the switch control unit 400 may include a relay.

The self-resonant circuit unit 300 includes a thyristor 310, a capacitor C 320, and a coil L 330 connected in series to each other. The thyristor 310, the capacitor C 320 and the coil L 330 are connected in parallel to the first switch 120 of the first current limiting unit 100.

More specifically, one end of the thyristor 310 is connected to one end of the first switch 120, and the other end of the thyristor 310 is connected to one end of the capacitor 320. The other end of the capacitor 320 is connected to one end of the coil 330 and the other end of the coil 330 is connected to the other end and the output end of the first switch 120. The operation of the self-resonant circuit unit 300 will be described in detail with reference to FIG. 5 below.

 Hereinafter, the current limiting method in the dual-current type current limiting apparatus 10 according to the embodiment of the present invention will be described in detail with reference to FIGS. 2A to 2C. 2A to 2C, the self-resonant circuit unit 300 is schematically shown in a block form for convenience, but includes the thyristor 310, the capacitor 320, and the coil 330 connected in series as described above with reference to FIG.

The dual current type current limiting apparatus 10 controls the operation of the first and second switches 120 and 220 differently according to the magnitude of the fault current.

More specifically, the first superconducting element 110 of the first current limiting unit 100 limits the initial transient current, and the switch control unit 400 controls the on / off operation of the first switch 120 2 commutating current limiter 200. In this way, For reference, the transient current at this time is a current exceeding a first threshold value which causes the resistance of the first superconducting element 110 to rise to block the current, and is hereinafter referred to as a 'primary transient current'.

When the transient current is input after the commutating operation, the second superconducting element 210 of the second current limiter 200 limits the transient current and controls the on / off operation of the second switch 220 in succession 1 and the second current-limiting resistors 130, 140, respectively. This limits the fault current to a large limiting impedance. At this time, the transient current limited by the second superconducting element 210 exceeds the second threshold value, which causes the resistance of the second superconducting element 210 to rise to block the current, Quot; The first and second threshold values may be changed according to the designer's intention or usage, respectively. In an embodiment of the present invention, the second threshold value may be set to a value higher than the first threshold value.

2A shows the flow of current through the first current flow path.

At an ordinary time when the input current is equal to or lower than the first threshold value, the switch control unit 400 turns on both the first switch 120 and the second switch 220. At this time, the initial impedance values of the first superconducting element 110 and the second superconducting element 210 are smaller than the impedance values of the first and second current limiting resistors 130 and 140, respectively. Accordingly, the input current flows through the first superconducting element 110 and the first switch 120. [ That is, the first current flow path can be expressed by the path (i _SFCL? I _SC1? I _SW1 ) in Fig.

FIG. 2B shows the flow of current through the third current flow path.

When the input current exceeds the first threshold value and is equal to or less than the second threshold value, that is, when the first transient current is input, the switch control unit 400 turns off the first switch 120 and turns on the second switch 220 . At this time, the initial transient current of the first transient current is instantaneously limited by the first superconducting element 110, and the input current flows to the third current flow path by the turn-off operation of the first switch 120 commutating. Thus, the input current flows through the first current-limiting resistor 130, the second superconducting element 210, and the second switch 220. That is, the third current flow path can be represented by the path (i _SFCL? I _CLR1? I _SC2? I _SW2 ) in Fig. 2B.

2C shows the flow of current through the second current flow path.

When the input current exceeds the second threshold value, that is, when the secondary transient current is input, the switch control unit 400 turns off both the first switch 120 and the second switch 220. At this time, the secondary transient current is instantaneously limited by the second superconducting element 210, and the input current is commutated to the second current flow path in accordance with the turn-off operation of the subsequent second switch 220. Thereby, the input current flows through the first NW resistance 130 and the second NW resistance 140. That is, the second current flow path can be expressed by a path (i _SFCL? I _CLR1? I _CLR2 ) in Fig. 2C.

On the other hand, the case where the input current is AC is described above. However, the dual-current type current limiting apparatus 10 according to an embodiment of the present invention processes the same current limiting operation even if the input current is direct current.

Generally, the DC current does not have a time point when the magnitude becomes zero unlike AC, so an arc is generated when the DC current is interrupted. Therefore, in the past, damage to the circuit breaker had to be taken each time. However, even if a direct current is inputted, the double-breakdown current limiting apparatus 10 according to an embodiment of the present invention is configured such that the current i _SW1 flowing through the first switch 120 through current resonance by the self- The resonance can be induced to reach the point where the magnitude becomes zero.

More specifically, the capacitor 320 of the self-resonant circuit 300 and the thyristor 310 connected in series with the coil 330 are unidirectional switches that receive external signals and conduct the line. Therefore, no current flows to the self-resonant circuit unit 300 during a normal time (before the generation of the transient current). When a signal is detected by the thyristor 310 due to the occurrence of a fault current, the thyristor 310 is turned on, So that a current flows through the circuit portion 300. That is, the self-resonant circuit unit 300 is connected in parallel to the first switch 120 to start resonance of the current. As shown in FIG. 5, a time point at which the DC current resonates and the current magnitude becomes zero is generated.

5 is a view showing a current resonance waveform by a self-resonant circuit applied to the present invention.

Referring to FIG. 5, since the arc is not generated even when the first switch 120 operates, the operation reliability and the cut-off speed are improved in the moment of interruption in which the magnitude of the current becomes 0, Can be increased.

When a DC current is input to the dual current type current-limiting device 10, the current of the first switch 120 is resonated by the resonance induced by the self-resonance circuit unit 300 in the occurrence of an overcurrent. At this time, the current value flowing through the first switch 120 can be expressed by Equation (1) below.

&Quot; (1) "

In Equation 1, i _t denotes an initial current value, p and q are circuit constants, and t denotes time.

As a result, when the DC current is input to the dual-breaker current limiting device 10, the first switch 120 operates immediately after the initial transient current is cut off by the first superconducting element 110 when the first transient current is generated An arc is not generated in the switch due to the operation of the first switch 120 in a state where resonance is generated with respect to the direct current by the self resonant circuit unit 300. [ That is, the dual-current limiting device 10 according to the embodiment of the present invention effectively handles the current limiting operation irrespective of the alternating current and the direct current.

The operation and effects of the self-resonant circuit unit 300 described above with reference to FIG. 5 are equally applied to a double-breakdown current limiting apparatus according to another embodiment of the present invention to be described below.

3 is a configuration diagram of a double-edged current limiting apparatus according to another embodiment of the present invention. 4A to 4C are views for explaining a current path in a double-breakdown current limiting apparatus according to another embodiment of the present invention.

Referring to FIG. 3, the dual-current limiting apparatus 20 includes a first current limiting unit 500, a second current limiting unit 600, a self-resonant circuit unit 700, and a switch control unit 800.

The first current limiting unit 500 includes a first superconducting element 510 and a first switch 520 connected in series between an input terminal and an output terminal of the current and a second switch 500 connected to the first superconducting element 510 and the first switch 520 And a first current-limiting resistor 530 and a second current-limiting resistor 540 connected in parallel.

The second current limiting unit 600 includes a second superconducting element 610 and a second switch 620 connected in series between the second current limiting resistor 540 and the output terminal. The second current limiting unit 540 and the second current limiting unit 600 are connected in parallel to the first current limiting resistor 530.

The first and second current limiting resistors 530 and 540 may be formed of a combination of at least one resistor R, a coil L, and a capacitor C, respectively. The impedance value of each of the first and second current limiting resistors 530 and 540 may be preset to a fixed value according to the designer's intention or usage.

 One end of the first superconducting element 510, the first current limiting resistance 530 and the second current limiting resistance 540 are respectively connected to the input terminal and the other end of the first superconducting element 510 is connected to the first switch 520 And the other end of the first current-sourcing resistor 530 and the first switch 520 are connected to the output terminal, respectively. The other end of the second current limiting resistor 540 is connected to one end of the second switch 620. The other end of the second switch 620 is connected to one end of the second superconducting element 610, And the other end of the first current mirror resistor 610 is connected to the other end and the output end of the first current mirror resistor 530 and the first switch 520, respectively.

At this time, the first current limiter 500 provides a first current flow path and a second current flow path between the input and output ends, and the second current limiter 600 provides a third current flow path.

The switch control unit 800 measures the currents or voltages of the first to third current flow paths and the first and second superconducting elements 530 and 540 and controls the first switch 520 based on the measured current or voltage. And on / off driving of the second switch 620 are controlled. At this time, the switch control unit 800 may include a relay.

The self-resonant circuit portion 700 includes a thyristor 710, a capacitor 720, and a coil 730 connected in series to each other. The thyristor 710, the capacitor 720 and the coil 730 are connected in parallel to the first switch 520 of the first current limiting unit 500.

Specifically, one end of the thyristor 710 is connected to one end of the first switch 520, and the other end of the thyristor 710 is connected to one end of the capacitor 720. The other end of the capacitor 720 is connected to one end of the coil 730 and the other end of the coil 730 is connected to the other end and the output end of the first switch 520. The operation of the self-resonant circuit unit 700 will be omitted because it is described in detail in the description of the double-breakdown current limiting apparatus 10 according to the embodiment of the present invention.

 Hereinafter, the current limiting method in the double-breakdown current limiting apparatus 20 according to another embodiment of the present invention will be described in detail with reference to FIGS. 4A to 4C. 4A to 4C, the self resonant circuit portion 700 is schematically shown in a block form for convenience, but includes the thyristor 710, the capacitor 720, and the coil 730 connected in series as described above with reference to FIG.

The double-wave current limiting device 20 controls the operation of the first and second switches 530 and 540 according to the magnitude of the fault current.

More specifically, the first superconducting element 510 of the first current limiting unit 500 limits the initial transient current, and the switch control unit 800 controls the on / off operation of the first switch 520 1 current limiting resistor 530 and the current to the second current limiting resistor 540 and the second current limiting portion 600 simultaneously. For reference, the transient current at this time is a current exceeding a first threshold value which causes the resistance of the first superconducting element 310 to rise to block the current, and is hereinafter referred to as a 'primary transient current'.

The second superconducting element 610 of the second current limiter 600 limits the transient current when the transient current is input after the commutating operation and the switch controller 800 controls the on / Off operation to induce current (commutating) to the first current-limiting resistor 530. [ This limits the fault current to a large limiting impedance. Here, the transient current limited by the second superconducting element 610 is a current exceeding the second threshold value, which causes the resistance of the second superconducting element 610 to rise to block the current, Quot; The first and second threshold values may be changed according to the designer's intention or usage purpose, respectively. In another embodiment of the present invention, the second threshold value may be set to a value higher than the first threshold value.

4A shows the flow of current through the first current flow path.

When the input current is equal to or lower than the first threshold value, the switch control unit 800 turns both the first switch 520 and the second switch 620 on. At this time, the initial impedance values of the first superconducting element 510 and the second superconducting element 610 are smaller than the impedance values of the first and second current-blocking resistors 530 and 540, respectively. Therefore, the input current flows through the first superconducting element 510 and the first switch 520. [ That is, the first current flow path can be expressed by the path (i _SFCL? I _SC1? I _SW1 ) in Fig. 4A.

FIG. 4B shows the flow of current through the second and third current flow paths.

When the input current exceeds the first threshold value and is equal to or less than the second threshold value, that is, when the first transient current is input, the switch control unit 800 turns off the first switch 520 and turns on the second switch 620 . At this time, the initial transient current of the first transient current is instantaneously limited by the first superconducting element 510, and the input current is supplied to the second and third current flow paths < RTI ID = 0.0 > And is commutated. A portion of the input current flows through the first current limiting resistor 530 and the remainder of the input current flows through the second current limiting resistor 540, the second switch 620 and the second superconducting element 610 Flow. That is, the second current flow path can be expressed by the path (i _SFCL? I _CLR1 ) in FIG. 4B, and the third current flow path can be represented by the path (i _{SFCL ?} I _CLR2? I _SW2? I _SC2 ).

4C shows the flow of current through the second current flow path.

When the input current exceeds the second threshold value, that is, when the second transient current is input, both the first switch 520 and the second switch 620 are turned off. At this time, the secondary transient current is instantaneously limited by the second superconducting element 610, and the input current is commutated to the second current flow path in accordance with the turn-off operation of the subsequent second switch 620. Thereby, the input current flows through the first current-limiting resistor 530. That is, the second current flow path can be expressed as a path (i _{SFCL ?} I _CLR1 ) in FIG. 4C, which is shown in (2) of FIG.

As described above, according to various embodiments of the present invention, the dual current type current limiting device can variably change the current flowing path according to the magnitude of the fault current, thereby effectively protecting the internal configuration of the current limiting device from the fault current. It is also possible to effectively protect the objects to be protected (eg power system).

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention.

10, 20: double-winding current limiting device 100, 500: first current limiting section
200, 600: second current limiter 110, 510: first superconducting element
120, 520: first switch 130, 530: first current resistance
140, 540: second current resistance 210, 610: second superconducting element
220, 620: second switch 300, 700: self-resonant circuit
310, 710: Thyristor 320, 720: Capacitor
330, 730: coil 400, 800: switch control section

Claims (8)

In a double-eddy current apparatus for alternating current and direct current,
A first current limiting unit providing a first current flow path and a second current flow path; And
And a second current limiter connected to the first current limiter and providing a third current flow path,
The resistances of the first and third current flow paths are each less than the resistance of the second current flow path,
And to cause the input current to flow to the first current flow path when the input current is below a first threshold value,
Wherein at least a portion of the input current flows into the third current flow path when the input current exceeds the first threshold and is below a second threshold, The remaining current of the input current flows to the second current flow path,
And the input current flows to the second current flow path when the input current exceeds the second threshold value.
The method according to claim 1,
Wherein the first current limiting unit includes:
A first superconducting element and a first switch connected in series between an input terminal and an output terminal, and a first current limiting resistance and a second current limiting resistance connected in series between the input terminal and the output terminal,
Wherein the first current-limiting resistor and the second current-limiting resistor are connected in parallel with the first superconducting element and the first switch,
Wherein the second current limiter comprises:
A second superconducting element connected in series and a second switch,
And the second current limiting portion is connected in parallel to the second current limiting resistor.
3. The method of claim 2,
When the input current is equal to or less than the first threshold value, turning on the first switch and the second switch to operate the current through the first superconducting element and the first switch,
When the input current exceeds the first threshold value and is lower than the second threshold value, the first current-limiting resistor, the second superconducting element, and the second switch are turned on by turning off the first switch and turning on the second switch And the current flows through the resistor
And to turn off the first switch and the second switch, respectively, when the input current exceeds the second threshold value, to operate the current through the first current-limiting resistor and the second current- Wave current device.
The method according to claim 1,
Wherein the first current limiting unit includes:
A first superconducting element and a first switch connected in series between an input terminal and an output terminal, and a first current limiting resistance and a second current limiting resistance connected in parallel to the first superconducting element and the first switch,
Wherein the second current limiter comprises:
And a second switch and a second superconducting element connected in series between one end of the second current limiting resistor and the output end.
5. The method of claim 4,
When the input current is equal to or less than the first threshold value, turning on the first switch and the second switch to operate the current through the first superconducting element and the first switch,
And when the input current exceeds the first threshold and is less than the second threshold, turning off the first switch and turning on the second switch causes a portion of the input current to flow through the first current- And the rest of the input current is caused to flow through the second current-limiting resistor, the second switch and the second superconducting element,
And to turn off the first switch and the second switch, respectively, when the input current exceeds the second threshold, to operate to flow current via the first current-limiting resistor.
The method according to claim 2 or 4,
And a self-resonant circuit part connected in parallel to the first switch,
The self-
A double-eddy current-limiting device comprising a series-connected thyristor, a capacitor and a coil.
The method according to claim 6,
Wherein when the input current is a direct current and exceeds the first threshold and is less than the second threshold, the thyristor conducts and a current flows through the self-resonant circuit.
The method according to claim 2 or 4,
Further comprising a switch control section for controlling operations of said first and second switches based on said first to third current flow paths, the current or voltage of said first superconducting element and said second superconducting element, Device.

Images