KR102221729B1 - Control and terminal unit for detecting and processing distribution line fault - Google Patents

Abstract

The present invention relates to control of a protection device for detecting and processing distribution line failures and a terminal device therefor. Provided is a method for distinguishing a quasi-permanent failure and a permanent failure in the event of high current failures to disconnect a power side and a load side of a failure section before re-inserting a circuit breaker or recloser in the event of the quasi-permanent failure and restore a sound section. High resistance ground failures or disconnection failures are very difficult to be detected since a failure current is small or does not flow, and there are no major problems in terms of power supply. However, since the scale of a disaster caused by a human accident or fire can become a national disaster, effective countermeasures are urgently needed. In the present invention, provided is a method for implementing an algorithm capable of detecting the high resistance ground failures and the disconnection failures in the control and terminal device such as substation circuit breakers, line reclosers, circuit breakers, multiple load switchgear, and the like, which are components of distribution lines, and, at the same time, significantly increasing a high current failure handling speed by using a communication system between adjacent protection devices or a central communication system in order to handle the high current failures, the high resistance ground failures, and the disconnection failures in one and the same system.

Description

Control and terminal equipment for detecting and handling failures in distribution lines {CONTROL AND TERMINAL UNIT FOR DETECTING AND PROCESSING DISTRIBUTION LINE FAULT}

The present invention relates to a control and terminal device that detects and processes a failure of a distribution line. In more detail, it relates to a new algorithm control and terminal device that intelligentizes a terminal device that detects and handles a failure of a distribution line, eliminates the fault detection blind spot, and performs a quick recovery.

In the case of a high current failure, the current protection coordination system distinguishes between transient and permanent failures, and after the protection device at the failure point is locked out after a sequence operation, the failure information is transmitted to the center, and the central computer system does this. After reading and sending an open command to the terminal devices at both ends of the fault section, the fault section is separated by opening the switch and the normally open protection device is remotely input to restore the healthy section.

For fault detection, a large current fault mainly reads the magnitude of the fault current, and a directional protection relay method that combines a polarity element and amplitude for a low current fault has been commonly used.

Existing detection and processing methods for large current faults are to check the fault current after a certain period of time when the magnitude of the fault current exceeds the operating current, remove the fault by operating the post-protection device, and then store it as a fault event when it becomes non-voltage. As a method of distinguishing between a transient fault and a permanent fault, if the voltage is not recovered for a time longer than the maximum reclosing time of the post-protection device, it is confirmed as a permanent fault at this time.

However, the problem with this method is that, first, if the post protection device is operated and no voltage is reached, the fault information is destroyed. Second, the fixed time is delayed because the permanent failure is determined by waiting for the maximum reclosing time of the post protection device. The last reclosing time should be corrected for the longest, and whenever the correction of the reclosing time is changed, the terminal device also has the inconvenience of changing the correction value. Third, even though the fault information can be transmitted before the post-protection device is locked out and the fault can be eliminated before reclosing, it cannot be utilized.

In the case of high-resistance ground faults, all the existing technologies allow detection at the power stage of the substation, so the signs of high-resistance ground faults are buried in the total noise resulting from the increase or decrease of load current, making it difficult to detect sensitively. , The detection method based on the high frequency vibration characteristics when re-calling at the point where the arc voltage is high, and the increase of the harmonic current due to the non-linear resistance of the earth according to the magnitude of the arc current, etc. were the main types.

However, when the substation detects a high-resistance ground fault in the entire line section, there is a limit in sensitivity, and even if it is detected with a high probability, opening the entire line is a level of warning because the risk of power supply interruption is enormous. However, since the failure cannot be eliminated directly, it is exposed to the risk of human life and disaster when a failure occurs.

A disconnection fault is a case in which the distribution line is disconnected but not in contact with the ground. As the ground fault current does not flow at all, it is difficult to detect the image current generated in the event of a ground fault, and can be detected only by the reverse phase current generated in the event of a disconnection accident. In addition, when the substation breaker and recloser are to be dealt with, there is a problem in that it is impossible to detect when there is a failure at the end of the line or the sensitivity of the load current is small.

The present invention is intended to solve the problem of detecting and processing important faults that the above-described existing technologies have not overcome, and a new algorithm of an intelligent terminal device will be described based on the design and specific examples.

First, in the case of a large current failure, if the breaker or recloser is opened twice and it is determined that it is a semi-permanent failure, the power side and the load side of the fault section are separated at high speed before the breaker or recloser is reclosed, and at the same time, the normally open switch is inserted to make it sound It provides a method of acquiring high-current fault information that enables the section to be recovered.

Second, in the case of a high-resistance ground fault, the passage of the distribution line increases due to environmental changes such as urbanization and road pavement. It provides a practical means to detect and eliminate a fault in a location close to the fault point by mobilizing a number of attached protective devices.

Third, in case of a disconnection fault, when the line is disconnected and does not contact the ground, it is impossible to detect it with the concept of protection of a normal ground fault, high resistance ground fault, and thus human lives and disasters are caused, so a method to solve this problem is provided.

Fourth, in the case of lines connected with distributed power, distributed power using new and renewable energy is expanding around the world, but the existing protection and cooperation system is disturbed due to the problem of reverse power supply of distributed power, and malfunctions and misinformation are generated. It becomes frequent.

In the standard of the distributed power supply itself, functions such as the inverter are specified, but the problem of grid connection caused by the problem of supplying power until the inverter malfunctions or operates has not been solved. The present invention provides a control means for solving this.

Fifth, it provides a means to detect high-resistance ground faults and disconnection faults in circuit breakers and reclosers constituting the protection coordination system, and to prevent malfunctions in connection with distributed power sources.

The control and terminal device according to an embodiment of the present invention for solving the above-described technical problem, when a large current failure occurs in a distribution line protection coordination system consisting of a substation breaker and a recloser, and a plurality of protection device control and terminal devices. The control and terminal devices classify the type of failure, but the type of the failure is i) one or two of the failure current according to the transient overcurrent in which the post protection device does not operate and the current coefficient of the failure in which the post protection device operates. Transient fault (reset state) when reset after counting times, ii) Semi-permanent fault (cycle state) determined after counting one or two fault currents, or iii) Determined after counting fault current three or four times It is classified as a permanent failure (lockout state), and in case of a semi-permanent failure, the terminal device counts the failure and transmits the failure information through the communication system between adjacent protection devices, separating the failure section before the reclosing of the post-protection device and separating the healthy section. In case of recovery or permanent failure, failure information is transmitted to the center, and a high-current failure processing algorithm and software are operated so that the system can be restored after separating the failure section by a command of the central processing unit.

A control and terminal device according to an embodiment of the present invention for solving the above technical problem updates and stores a reference value of a normal operation state for handling a high resistance ground fault of a distribution line, and an increase in the image current is the reference value. Independently or in parallel processing the first algorithm to determine the fault when exceeding and the current increase in only one phase, and the second algorithm to determine the fault when the increase of the image current and the harmonic component of the current exceed the reference value. However, among the pickup levels of the image current, the first level is greater than or equal to the predetermined maximum load current, and the second level is a directional ground fault processing region using _{image voltage (V 0} ) and image current (I _{0 ), and the maximum load} It is _{operated when V 1} (normal voltage: Positive Sequence Voltage) is normal and exceeds the learned reference value in the normal operation state, and the release time (for a predetermined time even when the pickup is released). Off Time) is a high-resistance ground fault current level corresponding to intermittent Arc, which is 10A, and the fourth level is △I ₀ > the first reference value and _{the harmonic component of △I 0} > the second reference value, and it operates when _{V 1 is normal.} And it is characterized in that the level corresponding to the intermittent Arc through the pickup release time delay.

The control and terminal device according to an embodiment of the present invention for solving the above-described technical problem calculates the variation value of the reverse phase current that occurs in the event of a failure in order to deal with the breakdown of the distribution line, and increases the increase of _{the reverse phase current I 2 (△} It is characterized as a disconnection fault when I ₂ ) exceeds the learned reference value or △I ₂ /I ₁ exceeds the learned reference value, but V ₁ (normal voltage) is normal and no high current fault is detected.

As an embodiment, a high-resistance ground fault and disconnection fault are detected and processed, but the fault section is separated by using a communication system or a central communication system between adjacent protective devices, or an undervoltage on an individual phase is applied to detect a disconnection state at the load side. When sensing, or when _{the condition of V 0} /V ₁ > 50% persists for longer than the high current fault handling time, the protection device on the load side of the fault point is opened and only the load side protection device closest to the fault point is locked out, and the open and lock Out-related information is transmitted through the communication system between adjacent protection devices or the central communication system so that the power-side protection device at the fault point is separated.

The control and terminal device according to an embodiment of the present invention for solving the above technical problem is the high resistance of the distribution line through the monitoring device of the substation in handling the high resistance ground fault and the negative ground disconnection fault of the distribution line. Instead of detecting ground faults, circuit breakers, reclosers of substations, and multiple protection devices of the distribution line simultaneously detect and handle high resistance ground faults and disconnection faults, thereby detecting high resistance ground faults and negative ground faults, and fault points. The power side and load side of the fault section are separated by the protection device closest to the circuit, and the disconnection fault detection algorithm that detects the disconnection fault is sensitive toward the power stage, and the high resistance ground fault detection algorithm detects the high resistance ground fault. The sensitivity is more sensitive toward the load end, and the disconnection fault detection algorithm and the high resistance ground fault detection algorithm are used in combination with each other.

A control and terminal device according to an embodiment of the present invention for solving the above-described technical problem, in a distributed power connection line, detects reverse power supplied to a circuit breaker, a controller of a recloser, or a plurality of switchgear from the distributed power supply. Or, if I ₀ /I ₁ > 1, the fault pickup information is maintained for more than 2 seconds to enable the fault count by the distributed power protection device, and the distributed power protection device fails to operate for 2 seconds. If the isolated operation state continues after that, it is characterized in that the failure coefficient is performed by detecting an over/under voltage, an over/under frequency, or reverse power.

A distribution line protection coordination system according to an embodiment of the present invention for solving the above technical problem includes a circuit breaker and a recloser, and the circuit breaker and the recloser include the control and terminal devices.

The effect of the present invention has the following effects by the configuration presented in the solution to the problem.

First, by improving the method of acquiring fault information in the event of a large current failure, in the event of a semi-permanent failure, the circuit breaker or recloser is quickly disconnected from the power supply side of the failure point before being locked out after the sequence is closed, and a normally open switch is applied. It enables the power supply of the vehicle and makes it possible to automate the line that does not depend on the operator.

The conventional method takes a long time (approximately 3 minutes) and takes a long time (about 3 minutes) to recover the power supply by remotely separating the fault section by remotely separating the fault section after the breaker or recloser is locked out. Because the system is operated by the system, there are problems such as a problem of waiting for the operator and the expansion of system failures due to operational errors. The present invention can provide semi-permanent fault information capable of separating a fault prior to reclosing of a circuit breaker or recloser through high-speed communication between adjacent protectors, and permanent fault information after lockout of a circuit breaker or recloser as in the conventional method. You can also give it.

Second, if the high-resistance ground fault is in contact with concrete, asphalt, dry ground, etc. when the power line is disconnected, it is difficult to detect the ground fault current. It has been neglected all over the world because it is not there. In the past decades, there have been countless studies and efforts to solve this problem, but it has been limited to the detection method at the substation, and when it is detected at the power stage, the variation of the residual image current is large due to the increase or decrease of the load current of the entire line, so the detection algorithm It has this complex and expensive drawback. Even if it was detected with a considerable probability, the power failure of the entire line by opening the substation breaker could not be implemented due to traffic signal control, paralysis of hospitals, and important commercial buildings. Eventually, it remained at the level of giving an alarm or using it for line maintenance plans. In the meantime, the risk of fire such as personal accidents and wildfires continues, but the situation in the world's power supply network is neglected because of the fact that it is not necessary to quickly eliminate the failure in terms of power supply and there is no economical technology to solve it. .

Based on the self-evident fact that the method of resolving the high-resistance ground fault in the present invention cannot be solved through a monitoring device installed at the location of the power terminal breaker of the substation as in the past, a circuit breaker, a recloser, and a number of protection devices are fully mobilized. This is to suggest a practical plan to detect and eliminate the fault at the nearest point of the fault. When a high-resistance ground fault occurs, the load current is large when viewed from the power end, so the residual image current is large, making it difficult to detect sensitively when a fault occurs at the end of the line, but sensitive detection is possible at the nearest location of the fault point. It is clear what can be opened.

Compared to the monitoring method in the substation, the present invention proposes a simple and more reliable means as a number of protection devices are monitored. This is based on the increase in the image current and the harmonic component of the image current. A detection method is provided in which a reference value determined by learning an increase in the image current in a steady state and an increase in a harmonic current component of the image current is used as a comparison standard.

High-resistance ground faults have a characteristic complementary to the disconnection fault detection method, so high-resistance ground faults become more sensitive toward the load end, and disconnection faults become more sensitive toward the power end. Therefore, the present invention solves the problem by performing these two methods in parallel.

Now, when a fault is detected, the breaker, recloser, and multiple protection devices can directly remove the fault through a time delay, and this information is transmitted to the communication system between adjacent protection devices or the central communication system to control group or central command. The fault can be eliminated by

Third, disconnection failure is an extreme form of high-resistance ground fault, but the ground fault current does not flow in the negative ground state. The more it goes to the power side, the greater the change of the load current when disconnected, and the smaller the change of the load current goes toward the end of the line. Since disconnection failure does not cause image current, it can be detected only with negative sequence current on the power side. Normally, if the load current is in equilibrium, the negative phase current is 0, and if not completely balanced, there is a residual negative phase current. Therefore, when the operation causes the need to analyze the increment (△ I ₂₎ of the opposite-phase currents, and more than a certain multiple of a reference value obtained from the increment (△ I ₂₎ is the normal operating state of the reverse-phase current to the sensitive detection.

When disconnection failure is detected, the breaker, recloser, and multiple protection devices can directly remove the failure through a time delay, and this information is transmitted to the communication system between adjacent protection devices or the central communication system to control group control or central command. The fault can be eliminated.

Fourth, the present invention provides a method for detecting and removing a fault at the load side in addition to the second and third methods and processing methods for detecting a fault at the power side. If disconnection occurs and the load side of the fault point is grounded, voltage is applied to the fault line through the △ wiring transformer on the load side at this time, and the fault current is not large, but it may cause personal injury and fire. When disconnection occurs, the unbalanced voltage is detected on the load side, and the undervoltage of each phase can be detected, or a disconnection failure can be recognized by using the phenomenon of _{V 0} /V _{1> 50%.} When the unbalanced voltage is recognized, after a certain period of time delay, all the loads in which the unbalanced voltage is detected are opened to eliminate the reverse pressure phenomenon through the △wiring transformer. At this time, since the unbalanced voltage is detected even after opening of the protection device on the nearest load side of the fault point, it can be locked out, and this information is transmitted to the communication system or central communication system between adjacent protection devices to open the power side of the fault point.

This method is applied to both branch lines or loop lines with protection devices on the load side of the fault point, and can very reliably and clearly solve the high resistance ground fault and disconnection fault problems accompanying the disconnection. Since this method is very certain, it is not necessary to simulate and learn various conditions of the line that may be necessary when trying to grasp a high resistance ground fault or disconnection fault from the power supply side.

If there is no protective device on the load side due to a breakdown of a small branch line or end of a line, the breakdown must still be resolved by a high resistance ground fault algorithm.

In the case of loop lines, the normally open switch can transmit unbalanced voltage information, so high resistance ground faults and disconnection faults can be reliably resolved.In the case of critical branch lines, high resistance ground faults are installed by installing an unbalanced voltage sensor at the end of the line to transmit this information. , It can solve the problem of disconnection and breakdown.

Fifth, when the distributed power supply is connected, the circuit breaker or recloser may malfunction due to reverse power supplied from the distributed power supply, and the switch terminal device may not acquire erroneous information or failure information, thereby disturbing the entire protection coordination system.

In the present invention, the circuit breaker or recloser inhibits the operation when reverse power is detected to prevent malfunction, and the switch terminal device delays the storage time of the fault pickup information by 2 seconds or more to check and store the fault information when the protection device of the distributed power is operated. And, if the isolated operation state continues because the distributed power protection device fails to operate, the fault count is completed when detecting over/under voltage, over/under frequency, and reverse power. In this way, it is possible to solve the problem of disturbance of protection cooperation when connecting distributed power sources.

The implementation effect of the present invention is applied to the entire intelligent terminal device of a circuit breaker, recloser, and switch, and may be applied partially or entirely.

1 is a diagram showing the configuration of a distribution line protection coordination system.
2 to 4 are diagrams for explaining a failure type of a large current in a distribution line.
5 is a diagram showing an ungrounded system diagram of a distribution line.
6 is a diagram showing a multi-ground system diagram of a distribution line.
7 is a diagram showing a vector diagram of an ungrounded system.
8 is a diagram showing a vector diagram of a multi-ground system.

Hereinafter, a look at the invention and a preferred embodiment of the present invention together with the accompanying drawings are as follows.

In describing the present invention, when it is determined that a detailed description of a related known technology or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted, and terms to be described later are terms defined in consideration of functions. This may vary depending on the user's or operator's intention or custom, etc.

The meaning should be made based on the overall description of the control/terminal device for the present invention, the fault detection processing of the distribution line.

Hereinafter, a control and a terminal device for detecting and processing a distribution line failure according to an embodiment of the present invention will be described in detail with reference to the drawings.

Because of the nature of distribution lines, there are a variety of fault factors, so a protection coordination system is built for fault detection and treatment, and substation CB (Circuit Breaker, circuit breaker) and Recloser (recloser, recloser circuit breaker) and a number of switchgear RTU (Remote Terminal) Unit: terminal device) is installed for each line to detect and handle faults.

Failures of distribution lines are largely classified into failures such as high current failure, high impedance ground fault (HIF), and open conductor (OC), and high current failures are easy to detect, but high resistance ground fault or disconnection. In fact, a breakdown in the fault detection blind spot causes a disaster such as a human accident or a fire, and there is a problem of malfunction due to reverse power when a distributed power supply is connected, so a countermeasure is urgently needed.

The present invention improves the method of detecting and handling large current faults while adding a learning function by intelligentizing the switch terminal device in order to compensate for the vulnerability of the current distribution system configuration and protection coordination system and to improve safety and reliability, and a high resistance ground fault fault by a new algorithm. In addition, it provides a new technology that can eliminate detection blind spots in case of disconnection and prevent disturbances in protection cooperation in the event of a failure in a distributed power line.

In addition, the present invention proposes an improvement method of a method for distinguishing between a transient fault and a permanent fault, and a new technique for removing the fault before the post-protection device enters the lockout state.

Since the new control and terminal device according to the present invention can exchange information through a communication system or a central communication system between adjacent protection devices, even in the event of a large current failure, it becomes a semi-permanent failure (Cycle State) before the post circuit breaker or recloser is locked out. If it is determined, both ends of the fault section can be removed at high speed before the post-protection device is re-inserted.

In the present invention, the control and terminal device of a plurality of protection devices installed in the distribution line detects high-resistance ground fault, disconnection fault, and eliminates the fault directly, or transmits fault information through a communication system or a central communication system between adjacent protection devices. It provides the most efficient high-resistance ground fault and disconnection fault treatment method by handling faults.

In the present invention, by detecting and handling high-resistance ground faults and disconnection faults in circuit breakers, reclosers, and a number of intelligent terminal devices, a means for effectively separating the fault point at the nearest point from the fault point is not merely a level of alarming. to provide.

In the present invention, since the fault current is small, the high resistance ground fault or disconnection fault has a longer processing time compared to the high current fault to avoid errors in the case of a power-side fault or a high current fault. However, high-resistance ground fault or disconnection fault may shift to a large current in some cases, so to eliminate the fault directly, it is necessary to operate within the range of the breaking capacity of the switch.

On the other hand, when the distributed power supply is connected to the grid, reverse power is supplied by the distributed power supply, or when the transformer for connecting the distributed power supply is connected to the primary Y ground and the secondary △ connection, power is supplied from the sound phase and the current is supplied to the fault phase. _There is a peculiar phenomenon where 0 = I _a + I _b + I _c.

This problem disturbs the existing protection coordination system, causes malfunction and generates erroneous information, but there is only a functional requirement standard for the inverter as a distributed power control device, but there is no standardized method to solve the contradiction that occurs when linking to the line. However, as the distributed power supply is expanding day by day, a solution is desperately required, so the present invention proposes a solution to solve this problem.

Hereinafter, the contents of the algorithm devised and implemented in order to solve the above-described problems in the present invention will be described in detail according to each failure type.

In the event of a large current failure, the existing failure detection method recognizes as an effective failure when the magnitude of the failure current exceeds the operating current value and continues for a certain period of time, and if the post-protection device removes the failure, it is identified as a failure and information is saved. do. If the potential protection device removes the fault and the fault current disappears, the load current flows, and the transient overcurrent information at this time disappears in several cycles. This means that there is no fault even though the fault current has flowed.Therefore, the transient overcurrent information is stored separately, and if there is a distributed power source, it takes up to 2 seconds for the distributed power to be disconnected. Even if is removed, there is a problem that it cannot be identified as a malfunction. Therefore, the information of the faulty pickup should be maintained for more than 2 seconds. The classification of transient fault and permanent fault is classified as a transient fault when the normal current flows for a certain period of time after the post-protection device is re-inserted, and if the voltage cannot be recovered until the maximum reclose time elapses, the post-protection device terminates the sequence and recognizes that it is locked out. Therefore, it is judged as a permanent failure.

Circuit breaker operates in O-CO-CO (Open-Close, Open-Close, Open) and recloser in O-CO-CO-CO sequence. Locked out after opening times.

However, if the distribution line is re-entered once, about 85% of the transient fault is eliminated, and if it is opened twice, the possibility of a permanent fault is 95% or more, so there is no need to wait for three to four operations to confirm a permanent fault. .

In the present invention, in order to solve the above problem, the transient overcurrent in which the post protection device does not operate and the fault in which the post protection device operates, and the failure in which the post protection device operates is classified into transient failure, semi-permanent failure, and permanent failure. A method of counting fault current is proposed and is as follows.

Level 1 is the transient overcurrent in which the post protection device does not operate.

Level 2 is a transient failure when the coefficient is reset because the normal current state continues after the fault current counts.

Level 3 is a semi-permanent failure after counting the fault current once or twice

Level 4 is classified into permanent faults that are checked when the post-protection device is locked out after counting the fault current three to four times.

Existing methods are only Level 2 and Level 4, and this also takes a long time since you have to wait for the maximum reclosing time, not at the time of counting.

Since there is no Level 1, if the potential protection device is in operation, the fault indication device in the post protection device section indicates that it is not a fault, so it cannot accurately display the fault situation and there is no Level 3, so post protection through high-speed communication at the point of a semi-permanent fault. Although the fault section can be removed before re-inserting the device, it cannot be utilized.

In addition, in order to solve the problem of malfunction in which failure information cannot be obtained when the distributed power supply is connected, this information is extended to more than 2 seconds after failure pickup, and in case the distributed power cannot be separated after 2 seconds, the over/under voltage, over/under frequency, When reverse power is detected, it is counted as a failure.

A high-resistance ground fault is a case where the wire contacts a place with high resistance, such as asphalt, concrete, dry land, etc., and is much smaller than the normal ground fault current. In the 3-phase 4-wire system, residual image current exists due to the unbalanced relative ground load. Sensitive detection is difficult because the residual image current also varies as the current increases or decreases.

Above all, if the substation tries to detect the high-resistance ground fault of the entire line, the signs of the high-resistance ground current are buried due to the noise and residual image current included in the normal load current, so it is difficult to accurately detect and even if it is detected, the entire line is opened. Because the fault cannot be eliminated due to the resulting risk, it is virtually in the blind spot for fault detection, and the risk of human life and disasters persists, so the countermeasure is desperately needed.

The essence of the present invention is to provide a more sensitive high-resistance ground fault detection by detecting a fault through a plurality of distributed protection devices, and to provide an effective means of directly removing a fault section.

The high-resistance ground fault in the 3-phase 3-wire system is classified as a Sensitive Earth Fault (SEF: small current ground fault) because the _{image current (I 0) is almost zero.} If this is extremely small, you can increase the sensitivity by calculating the ground fault impedance or conductance, but in the 3-phase 4-wire system, there is always a constant residual image current due to the unbalance of the load between the relative ground, and the amount of the image current according to the increase or decrease of the load current. Because of fluctuations, the signs of high-resistance ground faults are buried in residual image currents, and various means have been studied to distinguish them.

Typical methods are the method of seeing the increase of the harmonic component and measuring the magnitude, frequency, and duration of the instantaneous increase and decrease of the image current by dividing the data before 1 cycle through the Harmonic Notching Filter, etc. Techniques such as a method of learning the reference level and picking up a certain multiple of it (determining exceeding the detection reference value), and Wavelet transformation (extraction of specific harmonic waveforms) to capture the harmonic vibration that occurs when the arc intermittent and sudden arc current occurs were used. .

However, in the present invention, since a plurality of intelligent terminal devices are installed on a line and close to a fault point to detect a fault, the fault can be detected more simply and reliably. Since the high-resistance ground fault eventually appears in the form of an increase in the image current, in the present invention, an increase in the image current of more than a value (for example, 10A) that cannot be increased alone in any one phase in the normal normal operation state is achieved by using the increase in the image current. When detected, the image current value in the past normal state is fixed, and this value is continuously calculated to analyze the increase in image current.

Since this fault current may be continuous or intermittent, if a fault is detected again within a certain period of time, it is regarded as the continuation of the fault.

Since the operating reference value may fluctuate according to the normal system state and the magnitude of the load current, it detects an increase in the image current in the normal state and learns the reference value, and if the image current exceeds a certain multiple of this reference value, it is regarded as a failure and usually fails with a large current. Set the operation time longer than this duration.

A high-resistance ground fault lower than the above value inevitably has an intermittent arc characteristic or a high harmonic component due to the nonlinear resistance characteristic of the ground resistance. If the reference value based on the harmonic component ratio of the image current is exceeded, it is regarded as a failure.

Ground faults can be classified into low-resistance ground faults and high-resistance ground faults.

Level 1 does not require a directional ground fault protection relay due to a ground fault above the maximum load current, and level 2 is a fault above the maximum load current and the load unbalanced current between the maximum relative ground, resulting in a fault between the image voltage, the size of the image current, the image voltage, and the image current. It requires a directional ground fault to compare the phases.

This is because the increase in the image current due to a power voltage drop in case of a failure of another line or the increase in the image current when the single-phase protection device (fuse) on the load side is operated cannot exceed the maximum load current. In the case of lowering the ground fault current operation level to less than the maximum load current, the limit value will be more than the normal maximum image current and more than the image current that increases during operation of the potential side single-phase protection device, but if the fault current is small, the image voltage is extremely small and the general forward direction. The directional ground fault relay, which is judged as a forward fault or reverse fault, does not recognize a forward fault. Therefore, in this case, it is necessary to operate when it is not a reverse fault, and the lower limit of the operating current will vary depending on the line, but it will be about 50A.

Level 3 is a ground fault of less than about 50A. If this is to be detected, it is impossible to use the usual method at this time, and a special method must be considered because of the residual image current due to the fluctuation of the load imbalance between the relative ground.

First, it is necessary to extract and analyze the image current due to ground fault by removing the residual image current, and second, to distinguish the image current due to the increase or decrease of the load current and the image current due to a ground fault in one phase, and the third is a failure. At the moment of determination, the image current waveform in the past normal state should be fixed and the increase in the image current should be calculated even in the process of opening and re-entry. Fourth, according to the characteristics of the line, it learns how the image current changes according to the increase or decrease of the load current in normal times to create a reference value and operate when the reference value exceeds a certain multiple.

Normally, if any one phase increases more than 10A, it is almost a ground fault, so this can be a criterion, and since the arc in such a low current region has intermittent characteristics, it is necessary not to reset it immediately when the arc is temporarily stopped. There is. Of course, in this case as well, it should be operated in case of Non Reverse Fault.

Level 4 is an area that is determined by analyzing the harmonic component of the increase in image current based on the nonlinearity of the ground resistance and the intermittentness of the arc in case of a high resistance ground fault. Sensitivity may be higher than level 3, and a reference value is made by learning the change of the harmonic component of the image current in the past steady state, and it is operated when the reference value is exceeded by a certain multiple.

In summary, the pickup level of the image current is the first level above the maximum load current, the second level is the _{directional ground fault processing region using the image voltage (V 0} ) and image current (I ₀ ), from less than the maximum load current to about 50A. , The third level is about 10A, and it operates when the normal voltage (Positive Sequence Voltage) is normal and exceeds the learned reference value in the normal operation state. Even when the pickup is released, the Off Time (release time) is delayed for a certain period of time to intermittently. High resistance ground current level corresponding to Arc, 4th level is △I ₀ > △I _0Ref , △I _0H (Harmonic component of △I ₀ )> △I _0HRef and _{operates when V 1} is normal, Pickup Off Time Delay It refers to the algorithm and firmware that responds to the intermittent Arc through.

Levels 3 and 4 have longer operating times than levels 1 and 2 to prevent malfunction and secure the necessary reading time.

When the above method is used, the change in residual image current is small as it goes to the load terminal, so sensitive protection is possible.When it is detected at several levels at the same time, the priority of the operation is set from level 1 to level 4 to make the best choice. Let's do it.

When a fault is picked up, the terminal device transmits fault information to the center and separates the fault section by a central command or transmits it to the terminal device of the adjacent protection device, so that the rear terminal device picks up the fault and the preceding terminal device does not pick up the fault. When you can open it.

The next breakdown is when the distribution line is disconnected but is simply suspended without being grounded. At this time, the ground fault current does not flow.

Disconnection failure causes unbalance of load current between phases, which can be detected by negative sequence _{current (I 2 ).} In the case of a large load current, such as a substation or recloser, it is not an effective means because the change in reverse phase current is small in case of a disconnection failure at the end of the line. It is possible to detect the change of the reverse phase current.

Increasing the negative-phase current can be detected as _{△I 2 , and in the case of △I 2} /I ₁ , it is linked with the size of the load current, so a more sensitive detection is possible.

The disconnection fault, similar to the high resistance ground fault, needs to be operated longer than the high-current fault operation time, thereby avoiding malfunction in the case of a fault in the power stage or a high current fault. In the case of the main line with a large load current, the disconnection fault handling algorithm is more sensitive and more reliable than all types of high-resistance ground fault algorithms, so it is desirable to have the same operation delay time as in the case of high-resistance ground fault.

_{However, if △I 2} is very small due to a branch line with a small load current or a breakdown at the end of a line, it must be basically protected by a high-resistance ground-fault handling algorithm because it is not protected by the breakdown breakdown algorithm.

If there is an unbalanced voltage sensor at the end of the line, it _{can detect the condition of V 0} /V ₁ > 50% and transmit it to the post-protection device or the central system at the point of failure, and all forms of disconnection and breakdown can be prevented.

The method of detecting the disconnection condition on the load side can detect the phase loss by detecting the undervoltage of each phase, or it can be detected through a condition such as _{V 0} /V _{1> 50%.}

If the end of the line is not the end of the line, the high-resistance ground fault accompanying the disconnection, or in the case of a negative ground disconnection, the terminal device on the load side at the fault point detects the disconnection state, and if this state is maintained longer than the high current fault operation time, it is opened collectively and the fault point After locking out, the protection device on the power side of the fault can be opened and locked out by transmitting a signal to the center.

The phase-loss information itself may appear in the event of a power-side failure, a large current failure, or even in a disconnection state, so it was not utilized and neglected due to lack of discrimination power. In the present invention, the disconnection fault determination time is long and the phase loss condition is detected under the condition that the fault current does not flow, thereby solving errors in the case of power-side faults and large current faults, and collectively opening lockout of the load-side opening of the fault point to prevent personal accidents. It solves the problem of overvoltage caused by resonance, and by transmitting this information to the center, it is possible to separate even the power side of the fault point.

This method detects high resistance ground fault or disconnection fault at the load side and resolves it through communication.It is different from the above-described method of detecting high resistance ground fault or disconnection fault at the power side, but high resistance ground fault and disconnection fault are the last. It is a useful method in trunk lines or large-scale branch lines when it occurs after a protective device or does not occur in a small branch line. As described above, when the function of detecting high-resistance ground faults and disconnection faults is given to the substation breaker, recloser, and multiple switchgear, several methods of constituting the protection coordination system of the entire line are presented.

First, in the case of a large current fault or a level 1, level 2 ground fault, the breaker or recloser removes the fault through the operation according to the sequence as in the past. In case of a semi-permanent failure, the switch terminal device transfers information to the adjacent protection device through a communication system between adjacent protection devices before the breaker or recloser is reclosed, thereby separating the power side and the load side of the fault section at high speed. In the case of a high-resistance ground fault or disconnection, the breaker, recloser, and switchgear terminal devices do not operate directly, but the fault information is transmitted to the center to separate the fault from the central computer.

Secondly, in case of high resistance ground fault of level 3 and level 4 and disconnection of negative ground, a number of breakers or reclosers operate first from the load side through delay in operation time and reclose if necessary, giving an opportunity to eliminate excessive faults. The load side of the fault point is opened by command from the central computer.

Thirdly, in the case of a disconnection of a negative ground or a high-resistance ground fault, when the disconnection continues, the protection devices on the load side of the fault point are collectively opened, and only the protection devices adjacent to the fault point are locked out, and then the lockout information is transmitted to the center. This is a method for the computer to open and lockout the power-side protection device adjacent to the fault point.

Next, if the distributed power supply is connected to the grid, it may cause a malfunction with a normal directional ground fault algorithm. When the distributed power supply itself supplies reverse power, it is difficult to discriminate as a directional ground fault element because the fault current is generally not large. To solve this problem, reverse power is sensed and failure detection is suppressed if it is above a certain value.

If the transformer for distributed power connection fails in the line during primary Y ground, secondary △ wiring, the connected transformer receives power from the healthy phase regardless of the distributed power itself, supplies reverse power to the faulty phase, and flows from the healthy phase. The current transitions by ±60° and flows to the power stage of the substation. In the faulty phase, the fault current is supplied to the faulty point, and the current in each phase is the same in magnitude and direction.

Therefore, the image current becomes I ₀ = I _a + I _b + I _c , so that the size of the image current becomes larger than the normal current. This is a response to a fault on the power side, which is a malfunction and must be prevented.

In the case of using current-only information, I ₀ /I _{1 is always less than 1 when there is no distributed power supply, and I 0} /I ₁ has a value greater than 1 when there is a distributed power supply.

When voltage and current information are used at the same time, the active power of each phase becomes negative (reverse power) and the operation is suppressed when it exceeds a certain reference value.

Protection devices that directly eliminate faults such as circuit breakers and reclosers prevent malfunction by the above method, and in the case of switchgear terminal devices, in addition to the above conditions, the fault information should be memorized for more than 2 seconds after fault pickup. If voltage, over/under frequency, or reverse power are detected, check and count as a fault.

Hereinafter, main embodiments of the present invention will be further described with reference to the drawings.

1 is a diagram showing the configuration of a distribution line protection coordination system.

As shown in FIG. 1, the components of the protection coordination system 1000 interworking with a control and terminal device for detecting and processing a distribution line failure according to the present invention will be described as follows.

The protection cooperation system 1000 includes a substation 10, a circuit breaker (CB, 100) installed in the substation, a distribution line 20 drawn out from the breaker 100, and a recloser ( REC, 200), the controller 210 that controls the recloser 200, the high-current fault detection algorithm 211 of the controller 210, the high resistance ground fault and disconnection fault detection algorithm 212 of the controller 210 , And a plurality of switchgear that is drawn out from the circuit breaker 100 and detects a failure and opens and closes the line in a non-voltage state in case of a large current failure, and directly opens the line in the case of a high resistance ground fault or disconnection failure, or opens and closes the line in a non-voltage state. (300, 400, 500, 600, 700, 800). At this time, each of the switchgear (300, 400, 500, 600, 700, 800) includes a control and terminal device (310, 410, 510, 610, 710, 810), and each of the control and terminal devices (310, 410). , 510, 610, 710, 810) include high current fault detection algorithms (311, 411, 511, 611, 711, 811) and high resistance ground fault and disconnection fault detection algorithms (312, 412, 512, 612, 712, 812). Included.

Further, the protection coordination system 1000 is a central computer system 900 connected to all protection devices of the distribution line and in charge of protection coordination, and a central communication system 30 connecting each component of the protection coordination system 1000. It includes, and further includes a communication means 31 between the control and terminal devices for communicatively connecting each of the components (10, 100, 200, 300, 400, 500, 600, 700, 800).

At this time, the central computer system 900 may include measurement and monitoring information software 910 and failure determination and processing software 920, and there may be a failure point F at any one point of the distribution line. .

The breaker 100 and the recloser 200 can directly block the failure in case of a large current failure, and the switch (or load switch, 300, 400, 500, 600, 700, 800) can only block the load current. Serial coordination of a plurality of circuit breakers increases the damage of the line as the operation delay time increases toward the power side, so in the event of a large current failure, only the circuit breaker 100 and the recloser 200 operate to provide protection between Daegu and the circuit breaker 100, If the closure 200 operates once or twice and it is confirmed as a semi-permanent failure, the breaker 100 and the recloser 200 are reclosed through the communication system 31 between adjacent protection devices. Automatically restores the power of the healthy section. The load-side healthy section at the fault point restores power by disconnecting the fault section and turning on a normally open switch.

In the existing technology, when the breaker 100 and the recloser 200 cooperate to eliminate the fault at point F and lock out after a series of closing and opening sequence operations, the fourth switch 400, the fourth switch 400, The fault information is acquired through the high-current fault detection algorithms (411, 511, 611) of the 5 switch 500 and the sixth switch 600, and the central computer system 900 determines the fault section through the central communication system 30. The 6th switch 600 and the 7th switch 700 are determined as the section, and the sixth switch 600 and the seventh switch 700 are remotely opened to separate the faulty section. At this time, the circuit breaker 100 is opened three times (O-CO-CO) and the recloser 200 is opened four times (O-CO-CO-CO) and then locked out.

In the present invention, if the breaker 100 and the recloser 200 are opened twice, it is determined as a semi-permanent failure, and before the breaker 100 and the recloser 200 are re-inserted, the communication system 31 between adjacent protection devices is used. The fault section is automatically separated at high speed, and at the same time, the normally open switch (800) is inserted to restore the load side healthy section of the fault point, and the breaker (100) and recloser (200) are reclosed to restore the power section healthy section of the fault point. do.

In the case of high-resistance ground fault and disconnection fault, there is a difference from the operation method in the case of a high current fault.

The first method is that the circuit breaker 100, recloser 200, the third switch 300, the fourth switch 400, the fifth switch 500, and the sixth switch 600 are high-resistance ground fault, disconnection fault. When fault information is acquired through detection algorithms 212, 312, 412, 512, 612, 712, 812, the information is transmitted to the central computer system 900 through the central communication system 30, and the central computer system 900 The fault section is determined as the 6th switch 600 and the 7th switch 700 through the failure determination and processing software 920, and a command is issued from the remote to open the 6th switch 600 and the 7th switch 700. Separating at both ends of the fault section and inserting the normally open switch 800 completes the process of separating the fault section. At this time, the high-resistance ground fault _{analyzes the increase in the image current (△I 0} ), and the disconnection failure analyzes the increase in the negative sequence current (△I ₂ ). At this time, make sure that the power side of the fault section is in a normal voltage state, not reverse power state, and a condition that is not a large current fault, and the load side of the fault section is a condition where V ₀ /V ₁ > 50% or more. The fault detection time is maintained longer than the high current fault handling time to avoid errors in case of a fault on the power side or a fault on the high current.

The second method is that the circuit breaker 100, recloser 200, and switch (300, 400, 500, 600, 700) have high resistance ground fault, disconnection fault detection algorithm (212, 312, 412, 512, 612, 712, If fault information is obtained through 812), the load-side switchgear 700 is operated quickly and the circuit breaker 100 is cooperated through an operation time delay to operate the latest. When the power-side protection device in the fault section operates, this information is transmitted to the central computer system 900 through the central communication system 30 to open the load-side protection device in the fault section or through the communication system 31 between adjacent protection devices. Separate the load side of the fault section.

The third method is that when the load-side protective device switch 700 detects V ₀ /V ₁ > 50% of the fault section and continues until after the high current fault handling time, the load-side protective device switch 700 is opened directly and this information is stored. It is transmitted to the central communication system 30 or the communication system 31 between adjacent protection devices to separate the power side of the fault section.

2 to 4 are diagrams for explaining a failure type of a large current in a distribution line.

FIG. 2 shows a case where the transient overcurrent disappears without the operation of the circuit breaker 100 and the recloser 200 due to the transient overcurrent, or the potential-side protection device operates in advance, and does not have a failure coefficient, but obtains information about the transient overcurrent. This solves the problem of the conventional method of checking fault information only when the after-protection device is opened after fault detection.

3 shows a case of transient fault information that occurs when the breaker 100 or the recloser 200 is operated when a fault occurs, and the fault current is extinguished upon reclosing and is reset from the normal current state.

4 shows that when the breaker 100 or the recloser 200 cuts off the fault current twice and a permanent failure is confirmed, it is confirmed as a semi-permanent failure, and the breaker 100 or the recloser 200 is at high speed before reclosing. Shows the case of semi-permanent fault information for separating faults. To use this information, a communication system 31 between adjacent protection devices is required.

In addition, FIG. 4 shows a case of permanent failure lockout information when the breaker 100 is blocked 3 times and the recloser 200 is blocked 4 times. When only the central communication system 30 is used without the communication system 31 between adjacent protective devices, the breaker or recloser is locked out, the breaker is separated, and the breaker or recloser is remotely closed. The time is getting longer.

5 is a diagram showing a non-grounded system diagram of a distribution line, and FIG. 6 is a diagram showing a multi-grounded system diagram of a distribution line.

5 is a non-grounding system, the neutral point of the power transformer (A) is not grounded, the load is only a load between phases, and in the event of a ground fault, the ground fault current flows only through the capacitance between the counterparts, so the current is small. In the case of a faulty line, the image current flows through the power-side capacitance, and the line that does not fail, the image current flows through the load-side capacitance.At this time, in case of a forward fault (failed line) or reverse fault (non-faulty line) based on the image voltage. The direction of the image current of is reversed.

There are various methods of detecting ground faults in non-ground faults, but among them, a method of comparing the magnitude of the image voltage, the magnitude of the image current, and the phase angle between the image voltage and the image current is common. This method is well established in the existing technology. However, in the present invention, the image current increment (△I ₀ ) is extracted and analyzed for more sensitive earth fault current detection. fault (if not a reverse fault) utilizes △ △ I ₀ and I _0H (harmonic component ratio of △ I ₀₎ from the condition.

The first level of high-resistance ground fault protects using an increase in image current under non-reverse fault conditions, and the second level is a constant multiple of the reference value learned in normal operation when the harmonic component ratio of _{△I 0 under non-reverse fault conditions} It works when it exceeds.

In handling high-resistance ground faults, fundamental wave voltage and current elements are used, and if the current decreases below the reference level after fault detection in consideration of intermittent arc, it is not reset immediately, and if fault is detected again within the reset time, it is recognized as a valid fault. do. A ground fault in a non-grounded system is itself a high impedance fault, but in the case of a high-resistance ground fault, the image voltage may not be detected, so a Non Reverse Fault condition is required, and at this time, the intermittentness of the arc increases.

An important feature of the present invention is to combine a high-resistance ground fault detection and a disconnection fault algorithm. A high-resistance ground fault accompanying a disconnection can be detected and resolved more reliably through the disconnection fault algorithm.

6 is a multi-ground system, the neutral line of the power transformer (B) is grounded, and the load can connect the phase-to-phase load and the relative-ground load. Phase-to-phase load does not generate image current, but the imbalance of the relative ground load generates residual image current, so the image current changes from time to time according to the increase or decrease of the load current. The range of fluctuations increased due to the operating current of the protective device, and so far, it has been recognized that handling of high resistance ground faults is not possible through fundamental wave analysis of the image current. However, this phenomenon is a case of detecting a high-resistance ground fault of the entire line at the exit end of a substation, and when a large number of protective devices attempt to detect a high-resistance ground fault, very sensitive protection becomes possible.

The first reason is that when a large number of protection devices try to detect a high resistance ground fault, the protection devices adjacent to the fault point can provide more sensitive protection because the residual image current due to the unbalanced relative ground load is usually small.

The second reason is that if a disconnection occurs, the disconnection fault at the load end cannot be confirmed at the power terminal, but when a number of protection devices are mobilized, whether it is a high resistance ground fault or a negative ground disconnection fault, the unbalanced current between the phases (reverse phase current I ₂ ) is easy and reliable. It is because it is detected.

Conventional methods do not use the magnitude of the fundamental wave image current when detecting a high-resistance ground fault, but analyze the sub-harmonics current such as 3 harmonics and 5 harmonics to analyze the arc energy and the intermittent arc of the high-resistance ground fault current. A technique such as transformation was used.

In the present invention, an increase in the image current (ΔI ₀ ) and an increase in the harmonic component of the image current ( _{ΔI 0H} ) are calculated for a high resistance ground fault.

I ₀ is calculated, and the fundamental one chasan the past, I ₀ 'in the current I ₀ value △ I ₀ = I ₀ - I ₀ 'and a, △ I ₀ value is when the predetermined multiple of the reference value △ I _0Ref Pickup learning in a steady state wherein the past and I _0' are fixed values. This value is memorized even if the power is lost and is released when it is in a normal state. _{△I 0Ref} is not updated for a certain period of time when a large current fault flows, power is lost, or is _turned on, and △I 0Ref uses a fixed time constant averager in the form of IIR (Infinite Impulse Response). At this time, △I _0Ref(K) = (1-α)×△I ₀ + α×△I _0Ref(K-1) format, and △I _0HRef(K) = (1-α)×△I _0H + α× It becomes △I _0HRef(K-1) .

Here, the definition of each variable used is as follows.

△I ₀ : Image current (I ₀ ) increase

△I _0Ref(K) : Current △I ₀ operation reference value

△I _0HRef(K) : Reference value of the current △I _{0 harmonic component}

△I _0Ref(K-1) : Past △I ₀ operation reference value

△I _0HRef(K-1) : Reference value of the previous △I _{0 harmonic component}

α: weight

_{The operating reference value △I 0Ref(K)} for detecting a high-resistance ground fault is an average value calculated by distributing α (weight) to △I ₀ (increased image current) and previously calculated △I _0Ref(K-1). As a result, this operation reference value fluctuates in conjunction with the unbalanced video current at normal times, but depending on α, the current unbalanced video current factor can be reflected quickly or slowly.

7 is a diagram showing a vector diagram of an ungrounded system, and FIG. 8 is a diagram showing a vector diagram of a multi-grounded system.

In the direct grounding three-phase three-wire system shown in FIG. 7, I ₂ = 0 when the load is balanced, but when the A phase is disconnected, I _BN and I _CN are 180° in the opposite direction, and I ₂ = -I _A appears.

In the multi-ground three-phase four-wire system shown in FIG. 8, since the reverse phase current I ₂ is represented by the combined value of the unbalanced interphase load and the relative _{ground unbalanced current I 0 , △I 2} is substantially △(I ₂ -I ₀ ). Calculation is more sensitive to detecting disconnection faults. If the disconnection fault is to be detected only at the power supply of the substation, the disconnection fault at the load end cannot be used as the current change is insignificant or the residual phase-to-phase unbalanced current is normally used. It is a reliable detection means in the event of a concomitant or negative ground disconnection failure.

In case of disconnection failure, △I ₂ = I ₂ -I ₂ , and △I _2Ref(K) = (1-α)×△I ₂ + α×△I _2Ref(K-1) .

Here, the definition of each variable used is as follows.

△I ₂ : Increasing the reverse phase current (I ₂ )

△I _2Ref(K) : Current △I ₂ operation reference value

△I _2HRef(K) : Reference value of the current △I _{2 harmonic component}

△I _2Ref(K-1) : Past △I ₂ operation reference value

△I _2HRef(K-1) : Reference value for operation of △I _{2 harmonic components in the past}

α: weight

_{The operating reference value △I 2Ref(K)} for detecting a high-resistance ground fault is an average value calculated by distributing α (weight) to △I ₂ (increase in reverse phase current) and previously calculated △I _{2Ref (K-1).} As a result, this operation reference value fluctuates in conjunction with the unbalanced reverse phase current at normal times, but depending on α, the current component of the unbalanced reverse phase current can be reflected quickly or slowly.

_{In the above, a method based on an increase in image current ΔI 0} and an increase in reverse phase current ΔI ₂ has been described in order to detect a high resistance ground fault and disconnection fault in the power supply side, but the present invention also proposes a means for detecting a failure in the load side.

The load-side control and terminal device in the disconnection section detects the unbalanced voltage due to disconnection, which can be detected under the condition that _{part of the phase voltage becomes undervoltage or V 0} /V _{1> 50%.} If a fault is detected and maintained for longer than the high current fault handling time, the load-side protection devices at all fault points are collectively opened, only the adjacent load-side protection devices are locked out, and this information is transmitted through the communication system between adjacent protection devices or the central communication system. Open the protection device on the power supply side adjacent to the fault point.

In the case of distributed power connection lines, when detecting reverse power supplied from the distributed power supply to the circuit breaker, recloser control, multiple switchgear and terminal equipment, or when I ₀ /I ₁ > 1, operation is suppressed and direct fault is not eliminated. Switchgear control and terminal devices that do not maintain failure pickup information for more than 2 seconds to enable failure counting during operation of the distributed power protection device, and if the isolated operation status continues after 2 seconds due to the inability of the distributed power protection device to operate, over or under voltage, The fault count is completed by detecting the over/under frequency and reverse power.

The basic idea of the present invention may be limited to a large current fault current part, may be used for high resistance ground fault, disconnection fault, and may also be applied as a new protection coordination method for distributed power connection lines, but partial application is the purpose of the present invention. It is obvious that it does not go beyond the range of and. Therefore, it should be understood that the above-described design and embodiments are illustrative and non-limiting, and the scope of the present invention should be interpreted by the claims.

In the above, even if all the constituent elements constituting the embodiments of the present disclosure have been described as being combined into one or operating in combination, the technical idea of the present disclosure is not necessarily limited to these embodiments. That is, as long as it is within the scope of the object of the present disclosure, one or more of the components may be selectively combined and operated.

Although the operations are illustrated in a specific order in the drawings, it should not be understood that the operations must be executed in the specific order shown or in a sequential order, or all illustrated operations must be executed to obtain a desired result. In certain situations, multitasking and parallel processing may be advantageous. Moreover, the separation of the various components in the above-described embodiments should not be understood as necessarily requiring such separation, and the described program components and systems may generally be integrated together into a single software product or packaged into multiple software products. It should be understood that there is.

10: S/S [Substation: Substation]
20: D/L [Distribution line]
30: central communication system 31: communication system between adjacent protection devices
40: F [Fault: breakdown] 100: CB [Circuit Breaker: breaker]
110: Control [control device] 111: high current fault detection algorithm
112: High resistance ground fault, disconnection fault detection algorithm
200: REC [Recloser: Recloser breaker]
210: C-RTU [Recloser control and terminal equipment]
211, 311, 411, 511, 611, 711, 811: high current fault detection algorithm
212, 312, 412, 512, 612, 712, 812: high resistance ground fault, disconnection fault detection algorithm
300, 400, 500, 600, 700: Switch [switch]
800: Switch [switch, normally open]
310, 410, 510, 610, 710, 810: C-RTU [Control-Remote Terminal Unit: control and terminal device]
900: TOC [Total Operation Center: Central Computer System]
910: Measurement and monitoring information 920: Fault determination and processing software

Claims (7)

In a distribution line protection coordination system comprising a substation breaker, a plurality of protection devices including a recloser and a terminal device for controlling the plurality of protection devices,
When a large current failure occurs, the terminal device distinguishes the type of the large current failure, but distinguishes between the transient overcurrent state in which the post protection device does not operate from the plurality of protection devices and the high current failure in which the post protection device operates, and the post protection Depending on the current coefficient of the fault in which the device is operating, the type of the large current fault is counted once or twice, and then the transient fault is reset (reset state), and the quasi-permanent fault is determined after counting the fault current once or twice. It is classified as one of (cycle status), permanent failure (lockout status) judged after counting the fault current 3 or 4 times,
In the case of a high-resistance ground fault that does not involve disconnection when a small-current fault occurs, the low-current fault is generated according to the current coefficient of the fault in which the post-protection device operates through a sequence of opening, re-closing, and opening of the post protection device. The type is classified as either a semi-permanent fault determined after counting the fault current once or twice, or a permanent fault determined after counting the fault current three or four times,
In the case of a high-resistance ground fault or an unearthed disconnection fault accompanied by a disconnection fault in the event of a small current fault, it is classified as a permanent fault when the above protection device is opened once,
When the communication means between the plurality of protection devices is provided, in the semi-permanent failure state of the large current failure or the semi-permanent failure state of the small current failure, the distribution line protection coordination system through the communication means between the plurality of protection devices. Before the reclosing operation, both ends of the faulty section are separated and the healthy section is restored.
In the case where the communication means between the plurality of protection devices is not provided, both ends of the fault section are separated from each other in the permanent fault state of the high current fault or the permanent fault state of the small current fault, and the healthy section is restored,
Terminal device for controlling protection devices. The method of claim 1,
A high-resistance ground fault detection algorithm with sensitive sensitivity toward the power end and a high-resistance ground fault detection algorithm with sensitive sensitivity toward the load end are combined to detect high-resistance ground faults and negative ground faults. It characterized in that the power side and the load side of the fault section are separated through an adjacent protection device,
Terminal device for controlling protection devices. The method of claim 1,
In order to deal with a high resistance ground fault of a distribution line, the terminal device that controls the plurality of protection devices updates and stores the reference value of the normal operation state by learning,
The first algorithm for determining a fault when the increase of the image current exceeds the reference value and an increase in current of only one phase occurs, and the second algorithm for determining the fault when the increase of the image current and the harmonic component of the current exceed the reference value. Including algorithms that process independently or in parallel,
The pickup level of the image current is
The first level is greater than or equal to a predetermined maximum load current,
The second level is _{a directional ground fault processing level using image voltage (V 0} ) and image current (I ₀ ), and is equal to or higher than the third level below the maximum load current,
The third level is applied when △I ₀ is 10A and the positive sequence voltage V ₁ is within a predetermined normal range and exceeds the reference value in the normal operation state, and the pickup is canceled at the third level. Even if it is, it is a predetermined high resistance ground fault current level corresponding to intermittent arc by delaying the off time for a certain period of time.
A fourth level corresponding to the intermittent Arc through the △ I _0> reference value and △ harmonic component of the I _0> reference value, and V ₁ is turned off time delay may be applied when within the normal range, the pickup is turned off in the fourth level Characterized in that it is a predetermined level to,
Terminal device for controlling protection devices. The method of claim 1,
To deal with the breakdown of the distribution line, calculate the fluctuation value of the reverse-phase current that occurs in the event of a failure, and the increment of _{the reverse-phase current I 2 (△I 2} ) exceeds the learned reference value or △I ₂ (the increase of the reverse-phase current)/I ₁ ( A normal current) exceeds the learned reference value, but V ₁ (normal voltage) is within a predetermined normal range and a high current failure is not detected, characterized in that it comprises an algorithm for determining as a disconnection failure,
Terminal device for controlling protection devices. The method of claim 1,
In detecting and handling high-resistance ground faults and disconnection faults, the fault section is separated using a communication means between the plurality of protection devices or a central communication system that communicates with the distribution line protection cooperation system, or a disconnection state is detected at the load side. In order to do so, when the undervoltage of an individual phase is detected, or when a condition of V ₀ (video voltage)/V ₁ (normal voltage)> 50% or more persists for longer than the high current fault handling time, the load-side protection device of the fault section among the plurality of protection devices Open and lockout only the load-side protection device closest to the fault section,
And a high-resistance ground fault and disconnection fault detection algorithm that transmits the open and lockout information through a communication means between the plurality of protection devices or the central communication system to separate the power-side protection device in the fault section. Made by,
Terminal device for controlling protection devices. The method of claim 1,
In the distributed power connection line,
As a terminal device for controlling a protection device that does not directly perform separation of the fault section when detecting reverse power supplied from the distributed power source or when I ₀ (video current)/I _{1 (normal current)> 1,} Failure pick-up information is maintained for 2 seconds or more so that the protection device of the distributed power supply can calculate a failure count when the protection device of the distributed power supply is in operation, and if the isolated operation state continues after 2 seconds because the protection device of the distributed power supply fails to operate, over-under voltage , Characterized in that to perform a failure coefficient by detecting the over-shortage frequency and reverse power
Terminal device for controlling protection devices. delete

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