KR101692245B1 - System and method for improvement of voltage sag in power system, recording medium for performing the method - Google Patents

Abstract

A system for improving instantaneous undervoltage in a power system includes: a circuit breaker for shutting off a line when a fault occurs in a power system including a power source and a transformer; An overcurrent relay connected to the breaker to sense the fault current of the line; A superconducting fault current limiter installed at the drawing point of the line to limit the fault current; And two or more reclosure circuit breakers connected in series to the load side of the line and selectively operating by performing a period cooperative operation of the cut-off period. As a result, it is possible to secure a sufficient fault current limiting effect of the superconducting fault current limiter and to protect the power system by improving the instantaneous undervoltage phenomenon.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system and method for improving instantaneous undervoltage in a power system, a recording medium for performing the method,

The present invention relates to a system and method for improving instantaneous undervoltage in a power system, and a recording medium for performing the method. More particularly, the present invention relates to a protection cooperative operation in a power system employing a superconducting fault current limiter A system and method for improving the instantaneous undervoltage, and a recording medium for performing the method.

Today, due to the continuous development of Korean industry, electric power demand is increasing in the Seoul metropolitan area, and the increase of electric power demand is a problem that exceeds the short circuit capacity of power system. A fault may occur due to an increase in the short-circuit capacity, exceeding the breaking capacity of a conventional installed breaker.

As a result, it is required to replace existing circuit breakers with devices having a high-level breaking capacity or to install additional devices capable of reducing fault currents. However, in order to reduce the breakdown current, high cost is required for replacing the circuit breaker, which suggests measures such as bus or line separation, sequential opening of circuit breaker, current limiting reactor, high impedance equipment, and application of superconducting fault current limiter.

In the case of separating the bus and the line from the various schemes, the stability of the power system, the reliability of the supply, and the efficiency of the system operation may be deteriorated. In addition, the sequential opening of the circuit breaker can increase the risk of damage to the device. In addition, loss and voltage drop occur in a steady state when a HALF reactor and a high impedance device are used, and the compatibility is deteriorated due to a spatial restriction due to the size of the device. When the superconducting fault current limiter is applied, there is no power loss and voltage drop in a superconducting state in a steady state, and resistance is generated when a fault of a threshold current or more occurs, so that the fault current can be reduced within a few milliseconds.

On the other hand, when a fault occurs in the power distribution system, a short circuit current increases and a momentary undervoltage occurs in the load of the healthy line. Recently, electronic loads such as semiconductors, IT devices, and display devices have a large load, and they are susceptible to instantaneous undervoltage. Voltage compensation devices such as STATCOM and BES are being developed and distributed to solve the effects of instantaneous undervoltage. However, if the compensation devices are not properly controlled for system operation, the fault current of the system may be increased and adversely affected.

Therefore, it is required to develop the application technique of superconducting fault current limiter which can reduce the fault current of the power distribution system and to improve the instantaneous low voltage influence of the load due to the dry wire. In case of a momentary undervoltage, the voltage magnitude changes according to the location of the fault in the event of a fault, and the duration is determined by the operation of the protection device installed in the power system, and a momentary power failure is experienced according to the operation sequence of the protection device. The instantaneous undervoltage phenomenon affects not only fault lines but also neighboring lines, which can have a considerable adverse effect on the customer

Accordingly, it is required to secure a fault current limiting effect and improve the instantaneous undervoltage phenomenon in a power system employing a second limit current limiter.

KR 2001-0013527 A KR 10-2009-0114656 A

Accordingly, it is an object of the present invention to provide a system for stably protecting a power system and improving an instantaneous undervoltage.

It is another object of the present invention to provide a method for improving instantaneous undervoltage in the power system.

It is still another object of the present invention to provide a recording medium for performing a method for improving instantaneous undervoltage in the power system.

According to another aspect of the present invention, there is provided a system for improving instantaneous undervoltage in a power system, including: a circuit breaker for blocking a line when a fault occurs in a power system including a power source and a transformer; An overcurrent relay connected to the breaker to sense a fault current of the line; A superconducting fault current limiter installed at a drawing point of the line to limit the fault current; And two or more reclosing circuit breakers connected in series to the load side of the line and selectively operating by performing a periodic cooperating of the interrupting periods.

In an embodiment of the present invention, the superconducting fault current limiter includes a superconducting element in which an electric resistance is zero in a steady state of the power system, and a resistance due to the fault current occurs when a fault occurs; A high speed switch connected in series with the superconducting device and interrupting a current flowing to the superconducting device when the fault current is equal to or greater than a threshold value of the superconducting device; And a current-limiting element connected in parallel to the superconducting element and the high-speed switch, for energizing the fault current when the high-speed switch is turned off.

In the embodiment of the present invention, when the superconducting fault current limiter is installed at the drawing point of the line, the bus line voltage can satisfy the following equation,

Where V _bus is the bus voltage, Z _SOURCE is the power supply impedance, Z _Tr is the transformer impedance, Z _L is the line impedance, Z _SFCL is the impedance of the current-limiting device, and V _SOURCE is the power supply voltage.

In an embodiment of the present invention, the current limiting element may be a resistive component.

In an embodiment of the invention, the power system may be a power distribution system.

In an embodiment of the present invention, each recloser circuit breaker may be equipped with a sequencing coordination unit (SCA).

According to another aspect of the present invention, there is provided a method for improving instantaneous undervoltage in a power system, comprising: sensing a fault current in a power system including a power source and a transformer; Limiting the fault current through a superconducting fault current limiter installed at a drawing point of the line; And selectively operating two or more reclosing breakers connected in series on a load side of the line by performing a periodic cooperation of a blocking period; And blocking the line when the fault current is sensed.

In an embodiment of the present invention, limiting the fault current through the superconducting fault current limiter comprises: zeroing the electric resistance of the superconducting element in the steady state of the power system; Generating an electrical resistance when the fault current is equal to or greater than a threshold value of the superconducting element; And when the superconducting element voltage exceeds the threshold voltage by the generated electric resistance and the fixed current, the high-speed switch is turned off to energize the fault current to the current-operated element.

In the embodiment of the present invention, the current limiting element may be a resistance component, and when the superconducting fault current limiter is installed at the drawing point of the line, the bus line voltage may satisfy the following equation,

Where V _bus is the bus voltage, Z _SOURCE is the power supply impedance, Z _Tr is the transformer impedance, Z _L is the line impedance, Z _SFCL is the impedance of the current-limiting device, and V _SOURCE is the power supply voltage.

According to another aspect of the present invention, there is provided a computer readable storage medium storing a computer program for performing a method for improving an instantaneous undervoltage in a power system described above.

According to the present invention, a superconducting fault current limiter is applied to a line withdrawal point in a power system, and a fault current limiting effect and an instantaneous undervoltage improvement effect of a load can be obtained at the same time through a section cooperative operation of recloser circuit breakers. In addition, the voltage quality of a load that mainly uses electronic products can be improved in consideration of the instantaneous low voltage characteristics appearing on a good line.

1 is a block diagram of a system for improving instantaneous undervoltage in a power system.
2 is a configuration diagram of the superconducting fault current limiter of FIG.
3 is a waveform diagram showing the operating characteristics of the superconducting fault current limiter of FIG.
FIG. 4 is a waveform diagram showing an operation characteristic of the reclosing circuit breaker when the section cooperating is not performed.
5 is a waveform diagram showing the operating characteristics of the reclosing circuit breaker in the case of applying the section cooperating.
6 is a waveform diagram of a case where a superconducting fault current limiter is applied to a line withdrawal point when the circuit breaker of the reclosure circuit breaker is not used.
7 is a waveform diagram of a case where a superconducting fault current limiter is applied to a line withdrawal point when a section cooperative application of a reclosing circuit breaker is applied.
8 is a bus voltage waveform when the impedance of the current-limiting element is a resistance component.
9 is a bus voltage waveform when the impedance of the current-limiting element is a reactance component.
10 is a flowchart of a method for improving instantaneous undervoltage in a power system according to an embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

1 is a block diagram of a system for improving instantaneous undervoltage in a power system. 2 is a configuration diagram of the superconducting fault current limiter of FIG. 3 is a waveform diagram showing the operating characteristics of the superconducting fault current limiter of FIG.

1, a system 1 for improving instantaneous undervoltage in a power system according to the present invention includes a power source 2, a transformer 3, a circuit breaker 10 connected to each line, an overcurrent relay 30, a superconducting fault current limiter 50 and a recloser (RC). The power system may be a power distribution system.

The overcurrent relay 30 is connected to the circuit breaker 10 to sense a fault current of the circuit and to prevent the circuit breaker 10 ). The circuit breaker 10 can protect the power system by blocking the line when the reclosing circuit breaker RC fails to remove the fault.

The superconducting fault current limiter 50 is installed at a drawing point of each line to limit the fault current. The effect that the superconducting fault current limiter 50 is installed at the draw-out point of each line will be described below with reference to FIG. 6 and FIG.

Referring to FIG. 2, the superconducting fault current limiter 50 may include a superconducting element R _SC , a high speed switch SW, and a current limiting element Z _CLR as a trigger type superconducting fault current limiter. In the steady state of the power system, the electrical resistance of the superconducting element R _SC is zero, and when a fault occurs, a resistance due to the fault current occurs.

If more than the threshold value of the high-speed switch (SW) is the superconducting element (R _SC) and connected in series, the breakdown current of the superconducting element (R _SC) to cut off the current flowing to the superconducting element (R _SC). The current-limiting element Z _CLR is connected in parallel to the superconducting element R _SC and the high-speed switch SW, and when the high-speed switch SW is in the shut-off operation, the fault current is supplied.

For example, the superconducting element R _SC of the superconducting fault current limiter 50 may have an impedance of 2 [?], And the current limiting element Z _CLR may have an impedance of 2 [?] As a resistance component.

3, the current i _SC flowing through the superconducting element R _SC , the current i _CLR flowing through the current flowing element Z _CLR , the fault current i before application of the superconducting fault current limiter 50, ₁₁ ^{w / o} ) waveform. The superconducting element R _SC may be a resistor. The superconducting element R _SC is in a superconducting state in a zero resistance state in a steady state and if the fault current i ₁₁ is greater than a critical current of the superconducting element R _{SC in the} event of a fault at 0.4 [ R _SC is generated and a resistance R _SC is generated.

At this time, when the superconducting element voltage V _SC exceeds the set voltage due to the increased resistance and the fault current, the high-speed switch SW operates and the fault current is supplied to the current-limiting element Z _CLR . That is, the roles which serve to sense the fault current the superconducting element _(SC R), and actually reduce the fault current is to cause the current-limiting device (Z _CLR). Such a configuration can reduce the capacitance of the superconducting element R _SC of the superconducting fault current limiter 50 and reduce the burden of the fault current.

The reclosing circuit breakers (RC) are connected in series to the load side of the line. The recloser circuit breakers (RC) selectively operate by performing a periodic cooperation of the cut-off period. Each of the reclosing breakers (RC) may be equipped with a Sequence Coordination Accessory (SCA).

Specifically, the reclosing circuit breaker (RC), which is used as an important device to eliminate instantaneous faults of about 80 [%] in the power system failure, senses the fault current in the event of the load side fault of the installation point, And automatically performs a reclosing operation to re-pressurize it in a failure section. In an embodiment of the present invention, two recloser circuit breakers (RC) are used in one line, the recloser circuit breaker (RC ₁₂ ) is fixed to 2F2D, the recloser circuit breaker (RC ₁₃ ) is fixed to 2F1D, We have modeled the section coordination through the cooperation device.

The section cooperating device is a device for changing the instantaneous operation time of the RC blocker when the number of the reclosing blocker (RC) installed on the rail is more than 2, the section cooperating device is installed for each of the breakers, Is changed to another curve having a longer operation time or the instantaneous operation time is delayed to enable cooperation.

In order for the section cooperative function to operate normally, the total number of operations of the potential reclosing circuit breaker (RC) must be smaller than or equal to the number of operations of the post-reclosing circuit breaker (RC), and the delay of the potential reclosing circuit breaker (RC) must not be in the same sequence, and the reclosing time of the potential and RC circuit breaker (RC) must be the same.

In the following, the effect of reducing the fault current and improving the instantaneous undervoltage phenomenon will be examined when two recloser circuit breakers (RC) are installed on one line to provide protection cooperations of the recloser circuit breakers (RC). The sequence of the reclosing breakers RC is modeled so that the reclosing circuit breaker RC ₁₂ performs the sequence operation of 2F2D and the reclosing breaker circuit RC ₁₃ performs the sequential operation of 2F1D, and two or more recloser breakers (RC) When installed, a section cooperative apparatus was constructed to minimize the static section.

Referring to FIG. 4, it is a waveform of a fault current when a fault coordinator is not simulated with respect to the recloser breaker RC ₁₂ and the recloser breaker RC ₁₃ when a fault location (see FIG. 1) fails. If a failure occurs, the reclosers (RC ₁₃₎ is an instantaneous operation time of the reclosers first operation (1F), because less than the instantaneous operating time of the (RC _12), and wherein the reclosers (RC ₁₂₎ is out of order is It detects but does not operate and maintains the input state. Since the reclosing interrupter RC ₁₃ is charged after the first reclosing time and the failure has not been removed, the reclosing interrupter RC ₁₃ performs an instantaneous operation (2F) and the reclosing interrupter (RC ₁₂ ) Detects but maintains the state of input.

The material after the second reclosing time of the closed circuit breaker (RC ₁₃₎ is turned again, the reclosers (RC ₁₂₎ is has not the operation once the first instant (1F), the order to operate and the reclosers (RC ₁₃₎ is the instantaneous operating time of the first delay operation procedure, but the reclosers (RC ₁₂₎ to (1D) hayeoteumeuro twice the instantaneous operation is shorter than the delay action time of the reclosers (RC ₁₃₎ , The recloser circuit breaker (RC ₁₂ ) operates and the recloser circuit breaker (RC ₁₃ ) remains in the charged state.

The reclosing interrupter RC ₁₂ is charged after the first reclosing time and the reclosing interrupter RC ₁₂ performs the second instantaneous operation 2F and the reclosing interrupter RC ₁₃ is in the continuously charged state . The reclosing interrupter (RC ₁₂ ) is put into operation after the second reclosing time, and the instantaneous operation is performed twice, so that the first delay operation (1D) is performed. In this case, because the more the same delay operation time delay operating time of the reclosers (RC ₁₃₎ short the reclosers delay operation (1D) is generated, the reclosers (RC ₁₃₎ after the (RC ₁₃₎ is Since the magnetic sequence (2F1D) is completed, the fault section is completely disconnected by being locked-out.

As a result, the recloser circuit breaker (RC ₁₃ ) has separated the fault section, but during this period, the interval between the recloser circuit breaker (RC ₁₂ ) and the recloser circuit breaker (RC ₁₃ ) Experience.

Referring to FIG. 5, a waveform of a fault current is shown when a fault coordination device is simulated with respect to the recloser circuit breaker (RC ₁₂ ) and the recloser circuit breaker (RC ₁₃ ) at the time of a fault position failure. If a failure occurs, the instantaneous operating time is, the reclosers (RC ₁₃₎ (1F) The first operation, since less than the instantaneous operating time of the reclosers (RC ₁₂₎ of the reclosers (RC ₁₃₎ and the material The closed circuit breaker (RC ₁₂ ) detects the fault but does not operate and remains in the charged state.

At this time, the pick protection apparatus attached to the reclosers (RC ₁₂₎ is considered to be the operation sequence of the reclosers (RC ₁₂₎ and transfers to the next. The reclosers (RC _13), the first reclose time being added after the reclosers (RC _13), the second instantaneous operation (2F), and the reclosers (RC ₁₂₎ is the sequence in committed state Only. The reclosing interrupter (RC ₁₃ ) is charged after the second reclosing time and the reclosing interrupter (RC ₁₃ ) is in the order of performing the first delay operation and the reclosing interrupter (RC ₁₂ ) So it is the order of the first delay operation.

The material is a delay operating time of the closed circuit breaker (RC _13), so shorter than the delay action time of the reclosers (RC _12), the reclosers (RC ₁₃₎ is running and the reclosers (RC ₁₂₎ first is Maintain the input state. At this time, since the recloser circuit breaker (RC ₁₃ ) completes the self sequence, it disconnects the fault section while being locked-out, and the recloser circuit breaker (RC ₁₂ ) returns after returning to the charged state. Compared with FIG. 4, it is possible to compare that the number of times of blackout is reduced due to the area cooperative operation.

On the other hand, when the superconducting fault current limiter 50 is installed on the secondary side of the transformer 3, the fault current of the fault location device is reduced, but the bus line voltage is expressed by the following equation (1) (Z _SFCL ) is added. Therefore, the bus voltage is further reduced and the instantaneous undervoltage can not be improved.

[Equation 1]

Where V _bus is the bus voltage, Z _SOURCE is the power supply impedance, Z _Tr is the transformer impedance, Z _L is the line impedance, Z _SFCL is the impedance of the current-limiting device, and V _SOURCE is the power supply voltage.

On the other hand, when the superconducting fault current limiter 50 is applied to the line draw-out point, the impedance (Z _SFCL ) of the current-limiting device is added to the numerator and denominator of the bus voltage as shown in Equation 2 below, . At this time, the improvement effect of instantaneous undervoltage depends on the component and magnitude of the impedance.

&Quot; (2) "

Specifically, when the superconducting fault current limiter 50 is applied to a line drawing point, the waveform of the instantaneous undervoltage is analyzed.

FIG. 6 shows the resultant waveform according to the application of the superconducting fault current limiter 50 to the line withdrawal point in a situation where the section coordination of the reclosing circuit breakers (RCs) is not simulated in the fault position failure. 6 (a) shows the breakdown current and the recloser breaker integrated value, and Fig. 6 (b) shows the bus line voltage and the resistance of the superconducting element.

In a situation where the phase coordination between the recloser circuit breakers (RC) is not simulated, the same fault current reduction effect is obtained as when the superconducting fault current limiter is applied to the secondary side of the transformer. It can be seen that the improvement effect is shown when the superconducting fault current limiter is compared with the application of the superconducting fault current limiter to the secondary side of the transformer because the added superconducting fault current limiter affects the bus voltage depending on the application position. However, as in the case where the superconducting fault current limiter is applied to the secondary side of the transformer, the delay time of the protection device due to the reduction of the fault current increases the low voltage experience time and the unnecessary power failure interval and frequency.

FIG. 7 is a waveform diagram of the superconducting fault current limiter 50 applied to the line withdrawal point in a situation where the coordination between the reclosing circuit breakers (RCs) is simulated at the fault position failure. 7 (a) shows the breakdown current and the recloser breaker integrated value, and Fig. 7 (b) shows the bus voltage and the resistance of the superconducting element.

In the situation where the coordination between sections is simulated between the recloser circuit breakers (RC), only the recloser circuit breaker (RC ₁₃ ), which is a potential protection device, operates without unnecessary power failure intervals and the number of times is not generated. It appears to be shorter than when it is not.

As such, application of the superconducting fault current limiter 50 to the line withdrawal point in the power distribution system results in a significant instantaneous undervoltage effect improvement. Since the improvement effect of the instantaneous undervoltage is different according to the component and size of the impedance as shown in Equation (2), the application of the superconducting fault current limiter (50) to the line drawing point will analyze the improvement of the instantaneous undervoltage effect according to the impedance change. Table 1 below is a case table constructed to analyze the effect of instantaneous undervoltage improvement according to impedance.

Superconducting element
(R _SC ) 2 [Ω] Korean Wave Device
(Z _CLR ) Resistance [Ω] Reactance [Ω] One j1 2 j2 3 j3

Referring to FIG. 8, when a fault occurs at a fault position, the impedance of the current-limiting element (Z _CLR ) of the superconducting fault current limiter 50 is changed from 1 to 3 [?]. As the resistance increases, the instantaneous undervoltage improvement effect increases, but the operating time of the recloser circuit breaker (RC) is delayed due to the decrease in the fault current due to the increased resistance.

Referring to FIG. 9, when a fault occurs at a fault position, the impedance Z _CLR of the superconducting fault current limiter 50 is constituted by a reactance component and is a bus voltage waveform when the impedance is varied from j1 to j3 [OMEGA]. As shown in FIG. 7, as the reactance increases, the effect of improving the instantaneous undervoltage increases, and the operation delay of the recloser circuit breaker (RC) is displayed, thereby increasing the instantaneous power failure time.

As a result, when the impedance of the current limiting element (Z _CLR ) of the superconducting fault current limiter 50 is divided by the resistance and the reactance component, the instantaneous undervoltage suppression effect of the bus line voltage is confirmed . This result is because the impedance component ratio of the power distribution system in Equation (2) is larger than the reactance component.

According to the present invention, a superconducting fault current limiter is applied to a line withdrawal point in a power system, and a fault current limiting effect and an instantaneous undervoltage improvement effect of a load can be obtained at the same time through a section cooperative operation of recloser circuit breakers.

10 is a flowchart of a method for improving instantaneous undervoltage in a power system according to an embodiment of the present invention.

The method for improving the instantaneous undervoltage in the power system according to the present embodiment can be carried out in substantially the same configuration as the system 1 for improving the instantaneous undervoltage in Fig. Therefore, the same components as those of the system 1 for improving the instantaneous undervoltage of FIG. 1 are denoted by the same reference numerals, and repeated descriptions are omitted.

Referring to FIG. 10, a method for improving instantaneous undervoltage in a power system including a power source and a transformer according to the present embodiment detects a fault current of a line in a power system (step S10).

When the fault current is detected in step S10, the fault current is limited through the superconducting fault current limiter installed at the drawing point of the line (step S30).

The step of limiting the fault current through the superconducting fault current limiter (step S30) includes the steps of: when the electric resistance of the superconducting element is zero in a steady state of the power system; when the fault current is not less than a threshold value of the superconducting element And when the superconducting element voltage exceeds the threshold voltage by the generated electric resistance and the generated fixed current, the high-speed switch is turned off to energize the fault current to the current-operated element.

When the superconducting fault current limiter is installed at the draw-out point of the line, the impedance Z _SFCL of the current-limiting device is added to the numerator and denominator of the bus voltage as shown in Equation (2) Further, since the impedance component ratio of the power distribution system is larger than that of the resistive component, the effect of improving the instantaneous undervoltage is greater when the impedance (Z _SFCL ) of the current limiting element is a resistance component.

In addition, two or more recloser interrupters (RC) connected in series to the load side of the line can be selectively operated by performing the period coordination of the cut-off period (step S50), thereby preventing an unnecessary power interruption period.

If the operation of the reclosing breaker (RC) is not performed, the line is shut off to protect the power system (S70).

In the power system according to the present invention, the method of coordinating the operation of the distance relay may be implemented in the form of program instructions that can be executed through various computer components and recorded in a computer-readable recording medium. The computer-readable recording medium may include program commands, data files, data structures, and the like, alone or in combination.

The program instructions recorded on the computer-readable recording medium may be ones that are specially designed and configured for the present invention and are known and available to those skilled in the art of computer software.

Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like.

Examples of program instructions include machine language code such as those generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules for performing the processing according to the present invention, and vice versa.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. You will understand.

A method and system for improving instantaneous undervoltage in a power system according to the present invention is characterized in that a fault current is limited by using a superconducting fault current limiter unlike a conventional voltage compensating device, The voltage quality of the load to be used can be improved. In addition, by applying the line drawing point of the superconducting fault current limiter, it is possible to simultaneously obtain the effect of limiting the fault current and improving the instantaneous undervoltage of the load. Therefore, it can contribute to the economic effect of stably protecting the power system, reducing the cost and labor for facilities management and restoration.

1: System for instantaneous low-voltage improvement 2: Power supply
3: transformer 10: breaker
30: overcurrent relay 50: superconducting fault current limiter
RC: recloser breaker

Claims (10)

A circuit breaker to shut off the line in the event of a fault in a power system including a power source and a transformer;
An overcurrent relay connected to the breaker to sense a fault current of the line;
The impedance of the power source, the impedance of the power source, and the impedance of the line, and the numerator and denominator of the variable denoted by the fraction, and the impedance value of the current limiting element The superconducting fault current limiter is provided to simultaneously calculate the bus voltage with improved instantaneous undervoltage; And
And two or more reclosing breakers connected in series to the load side of the line and operated in accordance with a sequence of a predetermined instantaneous operation or a delay operation when a failure occurs,
In the section cooperation,
A condition in which the total number of operations of the potential reclosing circuit breakers among the two or more reclosing circuit breakers is less than or equal to the number of operations of the rear circuit reclosing circuit breakers among the two or more circuit breakers, The condition that the instantaneous operation of the reclosing circuit breaker is not in the same sequence and the reclosing time of the potential reclosing circuit breaker and the post-
The two or more reclosing circuit breakers are selectively operated by performing the section cooperation,
When a failure occurs and the potential reclosing circuit breaker first operates, the circuit breaker detects a failure but does not operate, but passes the sequence of the reclosing reclosing circuit breaker to the next, Wherein the delay operation is performed immediately after the instantaneous operation by the non-operation of the circuit breaker and is locked-out to shut off the line.
The superconducting fault current limiter according to claim 1,
A superconducting element in which electric resistance is zero in a steady state of the power system and resistance is generated by a fault current when a fault occurs;
A high speed switch connected in series with the superconducting device and interrupting a current flowing to the superconducting device when the fault current is equal to or greater than a threshold value of the superconducting device; And
And a current-limiting element connected in parallel to the superconducting element and the high-speed switch, the current-limiting element conducting the fault current when the high-speed switch performs a shutdown operation.
3. The method of claim 2,
When the superconducting fault current limiter is installed at the drawing point of the line, the bus line voltage satisfies the following equation,

Where V _bus is the bus voltage, Z _SOURCE is the power supply impedance, Z _Tr is the transformer impedance, Z _L is the line impedance, Z _SFCL is the impedance of the current-limiting device, and V _SOURCE is the power supply voltage. .
3. The method of claim 2,
Wherein the current limiting element is a resistive component, for improving instantaneous undervoltage in a power system.
The method according to claim 1,
Wherein the power system is a power distribution system, the system for improving instantaneous low voltage in a power system.
The method according to claim 1,
Wherein each recloser circuit breaker is equipped with a Sequence Coordination Accessory (SCA), the system for improving instantaneous undervoltage in a power system.
Detecting a fault current in the line in a power system including a power source and a transformer;
Limiting the fault current through a superconducting fault current limiter installed at a drawing point of the line;
And selectively operating two or more reclosing circuit breakers connected in series to the load side of the line by performing a periodic cooperation of the blocking period; And
And blocking the line when the fault current is detected,
In the section cooperation,
A condition that the total number of operations of the potential reclosing circuit breakers among the two or more reclosing circuit breakers is smaller than or equal to the number of operations of the rear circuit reclosing circuit breakers among the two or more circuit breakers, The condition that the instantaneous operation of the reclosing circuit breaker is not in the same sequence and the reclosing time of the potential reclosing circuit breaker and the post-
Wherein the step of selectively operating the two or more reclosing breakers connected in series to the load side of the line by performing the interval co-
When a failure occurs and the potential reclosing circuit breaker among the two or more reclosing circuit breakers performs instantaneous operation according to a predetermined instantaneous operation sequence, the remaining reclosing circuit breaker excluding the dislocation reclosing circuit breaker, among the two or more reclosing circuit breakers, Wherein the in-line recloser circuit breaker senses a fault but does not operate but passes the sequence of the recloser recloser circuit to the next;
The potential reclosing circuit breaker performs a delay operation according to a predetermined delay operation sequence of the recloser circuit breaker and is locked-out to shut off the line; And
And returning after the reset recloser circuit breaker has gone through a return time.
8. The method of claim 7, wherein limiting the fault current through the superconducting fault current limiter comprises:
The electrical resistance of the superconducting element being zero in a steady state of the power system;
Generating an electrical resistance when the fault current is equal to or greater than a threshold value of the superconducting element; And
And when the superconducting element voltage exceeds the threshold voltage by the generated electric resistance and the fault current, the high-speed switch is turned off to energize the fault current to the current-limiting element.
9. The method of claim 8,
Wherein the current limiting element is a resistance component,
When the superconducting fault current limiter is installed at the drawing point of the line, the bus line voltage satisfies the following equation,

Here, V _bus is the bus voltage, Z _SOURCE is the power supply impedance, Z _Tr is the transformer impedance, Z _L is the line impedance, Z _SFCL is the impedance of the current-limiting device, and V _SOURCE is the power supply voltage. .
A computer-readable recording medium for performing a method for instantaneous undervoltage improvement in a power system according to any one of claims 7 to 9.

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