Single-phase disconnection detection method, device and system

Abstract

The invention provides a single-phase disconnection detection method, device and system. The single-phase disconnection detection method comprises the following steps: collecting three-phase current at a measurement point; obtaining a positive sequence current and a negative sequence current from the collected three-phase current; calculating the change of the positive sequence current and the change of the negative sequence current in the first time interval; and when the amplitude of the positive-sequence current is reduced, the amplitude of the negative-sequence current is increased, the amplitude reduction value of the positive-sequence current is greater than a first preset value, and the ratio of the change amplitude of the negative-sequence current to the change amplitude of the positive-sequence current is greater than a second preset value, a first fault group is determined to occur, and the first fault group comprises single-phase disconnection.

Description

Technical Field

[0001] The present disclosure relates to line break detection, and more particularly to a method, apparatus, and system for detecting a single-phase line break in a power system. Background Art

[0002] Power systems can experience line failures due to various factors, such as aging lines and extreme weather. When a line failure occurs in a power system, the system voltage can significantly change, affecting the system's stable operation and the normal operation of its electrical equipment. Furthermore, in some cases, a line failure can also cause the faulty line to contact the ground, threatening the safety of nearby people and animals and potentially causing wildfires. Therefore, accurate and timely detection of line failures is essential.

[0003] Some traditional single-phase line break detection methods have low accuracy or high cost. Summary of the Invention

[0004] The present disclosure provides a single-phase line break detection method, a single-phase line break detection device, and a single-phase line break detection system with high accuracy and low cost.

[0005] According to one aspect of the present disclosure, a single-phase line break detection method is provided, comprising: collecting three-phase current at a measuring point; obtaining positive-sequence current and negative-sequence current from the collected three-phase current; calculating a change in the positive-sequence current and a change in the negative-sequence current within a first time interval; and determining that a first fault group has occurred when the amplitude of the positive-sequence current decreases, the amplitude of the negative-sequence current increases, the amplitude decrease of the positive-sequence current is greater than a first predetermined value, and the ratio of the amplitude of the change of the negative-sequence current to the amplitude of the change of the positive-sequence current is greater than a second predetermined value, the first fault group comprising a single-phase line break.

[0006] In some embodiments, the ratio of the change amplitude of the negative sequence current to the change amplitude of the positive sequence current is defined as the ratio of the increase in the amplitude of the negative sequence current to the decrease in the amplitude of the positive sequence current, or the ratio of the modulus of the vector change of the negative sequence current to the modulus of the vector change of the positive sequence current.

[0007] In some embodiments, the single-phase line break detection method further includes: collecting the three-phase voltage at the measurement point; obtaining the negative-sequence voltage from the collected three-phase voltage; calculating the change in the negative-sequence voltage within a first time interval; and when the modulus of the vector change of the negative-sequence voltage is less than or equal to a third predetermined value, or the difference between the phase angle of the vector change of the negative-sequence current and the phase angle of the vector change of the negative-sequence voltage is not within a predetermined range, determining that a downstream single-phase line break has occurred in the line where the measurement point is located.

[0008] In some embodiments, the single-phase line break detection method further includes: after determining that a downstream single-phase line break has occurred, calculating the change value of the negative-sequence current amplitude after a preset operation delay from the single-phase line break relative to the negative-sequence current amplitude before the single-phase line break; when the change value is less than a fourth predetermined value, determining that the downstream single-phase line break has been processed.

[0009] In some embodiments, the preset operation delay is set to be longer than the fault clearing time of other faults except the single-phase disconnection.

[0010] In some embodiments, the first predetermined value is greater than or equal to half of the maximum single-phase load current.

[0011] In some embodiments, the second predetermined value is greater than or equal to 0.8.

[0012] In some embodiments, the first time interval is 2 cycles of the three-phase alternating current.

[0013] According to one aspect of the present disclosure, a single-phase line break detection device is provided, comprising: a collection unit configured to collect three-phase currents at a measurement point; a storage unit configured to store the data collected by the collection unit; and a processing unit. The processing unit is configured to: obtain positive-sequence current and negative-sequence current from the collected three-phase currents; calculate a change in the positive-sequence current and a change in the negative-sequence current within a first time interval; and determine that a first fault group has occurred when the amplitude of the positive-sequence current decreases, the amplitude of the negative-sequence current increases, the decrease in the amplitude of the positive-sequence current is greater than a first predetermined value, and the ratio of the change amplitude of the negative-sequence current to the change amplitude of the positive-sequence current is greater than a second predetermined value, the first fault group including a single-phase line break.

[0014] According to one aspect of the present disclosure, a single-phase line break detection system is provided, comprising a first single-phase line break detection device and a second single-phase line break detection device. Each of the first and second single-phase line break detection devices comprises: an acquisition unit configured to acquire three-phase current and three-phase voltage at a measurement point; a storage unit configured to store the data acquired by the acquisition unit; and a processing unit. The processing unit is configured to: obtain positive-sequence current and negative-sequence current from the collected three-phase current; obtain negative-sequence voltage from the collected three-phase voltage; calculate the change of positive-sequence current and the change of negative-sequence current within a first time interval; calculate the change of negative-sequence voltage within the first time interval; determine that a first fault group has occurred when the amplitude of the positive-sequence current decreases, the amplitude of the negative-sequence current increases, the amplitude of the positive-sequence current decreases by more than a first predetermined value, and the ratio of the amplitude of the change of the negative-sequence current to the amplitude of the change of the positive-sequence current is more than a second predetermined value, the first fault group includes a single-phase line break; determine that a downstream single-phase line break has occurred in the line where the measurement point is located when the modulus of the vector change of the negative-sequence voltage is less than or equal to a third predetermined value, or the difference between the phase angle of the vector change of the negative-sequence current and the phase angle of the vector change of the negative-sequence voltage is not within a predetermined range; after determining that the downstream single-phase line break has occurred, calculate the change in the negative-sequence current amplitude after a preset operation delay from the single-phase line break relative to the negative-sequence current amplitude before the single-phase line break; and determine that the downstream single-phase line break has been processed when the change is less than a fourth predetermined value. The second single-phase disconnection detection device is located downstream of the first single-phase disconnection detection device, and the operation delay preset for the second single-phase disconnection detection device is shorter than the operation delay preset for the first single-phase disconnection detection device.

[0015] According to the embodiments of the present disclosure, a single-phase line break in a power system can be detected with higher sensitivity and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and / or other aspects, features and advantages of the present disclosure will become more clear and easily understood through the following description of embodiments in conjunction with the accompanying drawings, in which:

[0017] Figure 1 is a simplified schematic diagram illustrating a portion of a power system according to an embodiment of the present disclosure;

[0018] Figure 2 is a flow chart illustrating a single-phase line break detection method according to an embodiment of the present disclosure;

[0019] Figure 3 is a flow chart illustrating a single-phase disconnection detection method according to another embodiment of the present disclosure;

[0020] Figure 4 is a flow chart illustrating a single-phase disconnection detection method according to another embodiment of the present disclosure;

[0021] Figure 5 is a block diagram illustrating a single-phase line break detection device according to an embodiment of the present disclosure; and

[0022] Figure 6 FIG. 4 is a block diagram illustrating a single-phase line break detection system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] The present disclosure will be described in detail below with reference to exemplary embodiments of the present disclosure. However, the present disclosure is not limited to the embodiments described herein and may be implemented in many different forms. The described embodiments are intended only to make the present disclosure thorough and complete and to fully convey the concepts of the present disclosure to those skilled in the art. The features of the various described embodiments may be combined or replaced with each other unless expressly excluded or should be excluded based on the context.

[0024] A power system typically consists of power sources, substations, transmission lines, and power-consuming equipment. A three-phase power source generates three phases of alternating current (AC) of equal magnitude, frequency, and initial phase difference of 120°. After transformation, the three-phase AC is supplied to various power-consuming equipment via transmission lines. A power system may also include various devices for monitoring parameters such as current, voltage, and power within the system. When a fault or abnormality is detected in the power system, relay protection devices can initiate protective actions, such as issuing an alarm signal or directly isolating or disconnecting the faulty component.

[0025] Figure 1 is a simplified schematic diagram illustrating a portion of a power system according to an embodiment of the present disclosure.

[0026] Figure 1 A portion of a power system is shown, including a busbar B, a feeder F extending from busbar B, multiple loads L1-L4 connected to feeder F, and single-phase line break detection devices R1 and R2. Single-phase line break detection devices R1 and R2 are used to detect whether a single-phase line break has occurred in the power system. Single-phase line break detection devices R1 and R2 can be implemented as relay protection devices, include relay protection devices, be included in relay protection devices, or be connected to relay protection devices. For example, single-phase line break detection devices R1 and R2 can execute a relay protection action or can issue an instruction to execute a relay protection action, causing the relay protection device to execute a relay protection action.

[0027] Although Figure 1 Only one busbar B, one feeder F derived from this busbar B, and four loads L1-L4 are shown in the figure, but it should be understood that the number of lines and loads in the power system is not limited to this. There can be multiple busbars, and multiple feeders can be derived from each busbar. Each feeder can be connected to any number of loads. Each feeder can generally include an A-phase line, a B-phase line, a C-phase line, and a neutral line. Although Figure 1 The feeder is shown as a single line with an arrow, but it should be understood that the feeder does not consist of just one conductor. Figure 1 FIG. 4 shows that the feeder is disconnected downstream of the relay protection device R2 , but the disconnected portion represents a single-phase break in the feeder, not that all conductors of the feeder are disconnected.

[0028] When the power system operates normally, the voltages on phases A, B, and C are symmetrical, the three-phase loads on the line are essentially balanced, and the negative-sequence current in the system is zero or essentially zero. During operation, various faults may occur in the power system, such as short circuits and line breaks, disrupting the system's three-phase symmetry. When a single-phase line break occurs in a line, the first condition is satisfied: the amplitude of the positive-sequence current in that line decreases, and the decrease is greater than a predetermined value. However, when other system faults, such as a short circuit, occur in the line, the amplitude of the positive-sequence current in that line increases. Therefore, the first condition can be used to distinguish single-phase line breaks from other system faults in the same line.

[0029] In addition, when a single-phase line break occurs in the line, the negative-sequence current increases. Generally speaking, when a single-phase line break occurs, the amplitude of change of the negative-sequence current and the amplitude of change of the positive-sequence current are roughly the same. Ideally, the amplitude of change of the negative-sequence current can be equal to the amplitude of change of the positive-sequence current. However, in some cases, such as when the load includes an electric motor, due to the inertia of the electric motor, after a single-phase line break occurs, the amplitude of change of the negative-sequence current will be greater than the amplitude of change of the positive-sequence current. Through the second condition, that is, the ratio of the amplitude of change of the negative-sequence current to the amplitude of change of the positive-sequence current is greater than the predetermined value, it can be further determined that a single-phase line break is likely to have occurred in the line. For different power systems, different predetermined values ​​can be set according to system parameters.

[0030] Faults detected based on the first and second conditions are not limited to single-phase line breaks downstream of the measurement point. They may also involve unbalanced faults upstream of the measurement point or in adjacent lines, such as single-phase line breaks upstream of the measurement point, or interphase short circuits or single-phase ground faults in adjacent lines. The third condition can be further used to more accurately determine that the detected fault is a single-phase line break downstream of the measurement point, ensuring that the relay performs protective relaying only in the event of a single-phase line break downstream.

[0031] If the third condition is met (i.e., the ratio of the magnitude of the vector variation of the negative-sequence voltage to the rated voltage is greater than a predetermined value and the difference between the phase angle of the vector variation of the negative-sequence current and the phase angle of the vector variation of the negative-sequence voltage is within a predetermined range), then the fault detected according to the first and second conditions can be determined to be an unbalanced fault in the line upstream of the measurement point or in an adjacent line to the measurement point, rather than a single-phase line break downstream of the measurement point. In this case, the relay protection device corresponding to the measurement point is not allowed to perform relay protection. If the third condition is not met (i.e., the magnitude of the vector variation of the negative-sequence voltage is less than or equal to a predetermined value (the third predetermined value), or the difference between the phase angle of the vector variation of the negative-sequence current and the phase angle of the vector variation of the negative-sequence voltage is not within a predetermined range), then a single-phase line break downstream of the measurement point is determined to have occurred. In this case, relay protection can be performed.

[0032] Furthermore, in power systems, when a single-phase line break occurs, it is desirable to execute relay protection within the shortest possible line length to minimize the impact on the entire line. To this end, multiple single-phase line break detection devices can be installed at different locations along the line. When a line break occurs, the single-phase line break detection device upstream and closest to the fault location is the first to execute relay protection or issue a relay protection command based on the detection results.

[0033] To this end, when the first and second conditions are met but the third condition is not met, the single-phase line break detection device does not immediately execute a relay protection action or issue a relay protection instruction, but waits for a preset operation delay. After determining that a downstream single-phase line break has occurred, the change in the negative sequence current amplitude after the preset operation delay from the single-phase line break relative to the negative sequence current amplitude before the single-phase line break is calculated. When the change value is less than a predetermined value, it indicates that the negative sequence current amplitude has fallen after the preset operation delay, indicating that the downstream single-phase line break has been processed, and therefore the single-phase line break detection device does not execute a relay protection action or issue a relay protection instruction. If, after the preset operation delay, the change in the negative sequence current amplitude relative to the negative sequence current amplitude before the single-phase line break is still greater than the predetermined value, it indicates that the single-phase line break still exists, and therefore the single-phase line break detection device needs to execute a relay protection action or issue a relay protection instruction.

[0034] Figure 2 FIG. 4 is a flow chart illustrating a single-phase line break detection method according to an embodiment of the present disclosure.

[0035] like Figure 2As shown, the method includes: at step 210, collecting the three-phase current at the measurement point; at step 220, obtaining the positive-sequence current and the negative-sequence current from the collected three-phase current; at step 230, calculating the change of the positive-sequence current and the change of the negative-sequence current within a first time interval; and at step 240, when the amplitude of the positive-sequence current decreases, the amplitude of the negative-sequence current increases, the decrease in the amplitude of the positive-sequence current is greater than a first predetermined value, and the ratio of the change amplitude of the negative-sequence current to the change amplitude of the positive-sequence current is greater than a second predetermined value, determining that a first fault group has occurred, and the first fault group includes a single-phase line break.

[0036] According to one embodiment, at step 210, a single sequential line detection device (eg Figure 1 The single-phase current detection device can be installed at a substation or recloser, for example, but is not limited to these locations. It can be installed anywhere on the line.

[0037] According to one embodiment, at step 220, the positive sequence current and the negative sequence current may be obtained from the collected three-phase current according to the symmetrical component method. The symmetrical component method is a commonly used method in power system analysis and is not described in detail here for the sake of brevity.

[0038] According to an embodiment, at step 230 , the change in the positive sequence current may include a vector change and / or a magnitude change of the positive sequence current, and the change in the negative sequence current may include a vector change and / or a magnitude change of the negative sequence current.

[0039] The vector change of the positive sequence current can be expressed by the following equation 1:

[0040]

[0041] in, represents the vector change of the positive sequence current in the first time interval ΔT1, represents the positive sequence current vector at time t, Represents the positive sequence current vector at time t-ΔT1.

[0042] The amplitude change of the positive sequence current can be expressed by the following equation 2:

[0043]

[0044] Wherein, ΔI1 represents the amplitude change of the positive sequence current in the first time interval ΔT1, represents the amplitude of the positive sequence current at time t, Represents the amplitude of the positive sequence current at time t-ΔT1.

[0045] The vector change of negative sequence current can be expressed by the following equation 3:

[0046]

[0047] in, represents the vector change of negative sequence current in the first time interval ΔT1, represents the negative sequence current vector at time t, Represents the negative sequence current vector at time t-ΔT1.

[0048] The magnitude change of the negative sequence current can be expressed by the following equation 4:

[0049]

[0050] Wherein, ΔI2 represents the amplitude change of the negative sequence current within the first time interval ΔT1, represents the amplitude of the negative sequence current at time t, Represents the amplitude of the negative sequence current at time t-ΔT1.

[0051] According to one embodiment, the first time interval ΔT1 may be 2 cycles of the three-phase alternating current.

[0052] According to one embodiment, at step 240, the ratio of the change amplitude of the negative sequence current to the change amplitude of the positive sequence current can be defined as the ratio of the increase value of the negative sequence current amplitude to the decrease value of the positive sequence current amplitude |ΔI2 / ΔI1|, or can be defined as the ratio of the vector change modulus of the negative sequence current to the vector change modulus of the positive sequence current.

[0053] According to one embodiment, at step 240, the first predetermined value may be half of the maximum single-phase load current. According to one embodiment, the second predetermined value may be greater than or equal to 0.8. In particular, the second predetermined value may be set to 0.9.

[0054] Because the amplitude of change in the negative-sequence current is roughly the same as or greater than that of the positive-sequence current when a single-phase power outage occurs, this method offers high accuracy in detecting single-phase power outages. Furthermore, since single-phase power outages can be detected solely through data collected at the measurement point, without requiring other methods such as communication between detection devices, this method offers low cost.

[0055] Figure 3 FIG. 4 is a flow chart illustrating a single-phase line break detection method according to another embodiment of the present disclosure.

[0056] like Figure 3As shown, the method includes: at step 310, collecting three-phase currents at a measurement point; at step 315, collecting three-phase voltages at the measurement point; at step 320, obtaining positive-sequence current and negative-sequence current from the collected three-phase currents; at step 325, obtaining negative-sequence voltage from the collected three-phase voltages; at step 330, calculating changes in positive-sequence current and negative-sequence current within a first time interval; at step 335, calculating changes in negative-sequence voltage within the first time interval; at step 340, determining that a first fault group has occurred when the amplitude of the positive-sequence current decreases, the amplitude of the negative-sequence current increases, the value of the decrease in the amplitude of the positive-sequence current is greater than a first predetermined value, and the ratio of the amplitude of the change of the negative-sequence current to the amplitude of the change of the positive-sequence current is greater than a second predetermined value, the first fault group includes a single-phase line break; and at step 345, determining that a single-phase line break has occurred downstream in the line where the measurement point is located when the modulus of the vector change of the negative-sequence voltage is less than or equal to a third predetermined value or the difference between the phase angle of the vector change of the negative-sequence current and the phase angle of the vector change of the negative-sequence voltage is within a predetermined range.

[0057] Figure 3 Steps 310, 320, 330 and 340 of the single-phase disconnection detection method are respectively Figure 2 Steps 210 , 220 , 230 and 240 of the single-phase disconnection detection method are the same, so repeated descriptions are omitted here.

[0058] According to one embodiment, at step 315, the single-phase line break detection device may measure the three-phase voltage, similarly to measuring the three-phase current. Although measuring the three-phase current and measuring the three-phase voltage are described in two separate steps, the three-phase current and the three-phase voltage may be measured simultaneously.

[0059] According to one embodiment, at step 325, similar to the method for obtaining the positive sequence current and the negative sequence current, the negative sequence voltage can be obtained from the collected three-phase voltage using the symmetrical component method. This calculation method will not be described in detail here.

[0060] According to an embodiment, at step 335 , the change of the negative sequence voltage within the first time interval ΔT1 may include a vector change of the negative sequence voltage.

[0061] The vector change of the negative sequence voltage can be expressed by the following equation 5:

[0062]

[0063] in, represents the vector change of negative voltage in the first time interval ΔT1, represents the negative sequence voltage vector at time t, Represents the negative sequence voltage vector at time t-ΔT1.

[0064] According to an embodiment, at step 345 , it may be determined based on further conditions that a downstream single-phase line break in the line where the measurement point is located occurs.

[0065] If the following condition (third condition) is met, namely, the ratio of the magnitude of the vector change of the negative-sequence voltage to the rated voltage is greater than a predetermined value and the difference between the phase angle of the vector change of the negative-sequence current and the phase angle of the vector change of the negative-sequence voltage is within a predetermined range, it can be determined that the detected fault is not a single-phase line break downstream of the line where the measurement point is located, but rather an unbalanced fault in the line upstream of the measurement point or in an adjacent line to the measurement point, such as a single-phase line break upstream of the measurement point or a phase-to-phase short circuit or single-phase ground fault in an adjacent line to the measurement point. In this case, the single-phase line break detection device can be caused to lock the relay protection operation. According to one embodiment, when the following Inequality 1 and Inequality 2 are simultaneously met, it can be determined that the detected fault is an unbalanced fault in the line upstream of the measurement point or in an adjacent line to the measurement point.

[0066]

[0067]

[0068] in, The magnitude of the vector change of the negative sequence voltage, V n represents the rated voltage of the line, Angle represents the phase angle, and RCA represents the relay protection characteristic angle setting (also known as the sensitivity angle). RCA depends on the line impedance and can be set by the user based on actual conditions. The 2% in Inequality 1 is only an example and can be set to other ratios based on actual conditions.

[0069] If the third condition is not met, the detected fault can be determined to be a single-phase line break downstream of the line where the measurement point is located. Specifically, when the ratio of the magnitude of the vector variation of the negative-sequence voltage to the rated voltage is less than or equal to the predetermined value, or when the difference between the phase angle of the vector variation of the negative-sequence current and the phase angle of the vector variation of the negative-sequence voltage is outside the predetermined range, the detected fault can be determined to be a single-phase line break downstream of the line where the measurement point is located. For example, if Inequality 3 or Inequality 4 below is met, the detected fault can be determined to be a single-phase line break downstream of the line where the measurement point is located.

[0070]

[0071]

[0072] In one embodiment, upon detection of a downstream unidirectional disconnection fault, a relay protection action may be executed, for example, the relay protection device corresponding to the measurement point may execute a relay protection action or issue a relay protection instruction. In another embodiment, upon detection of a downstream unidirectional disconnection fault, the relay protection action is not executed immediately, but rather further determination is made after a delay before determining whether to execute the relay protection action.

[0073] Figure 4 FIG. 4 is a flow chart illustrating a single-phase line break detection method according to another embodiment of the present disclosure.

[0074] Figure 4 The single-phase disconnection detection method shown is the same as Figure 3 The single-phase line break detection method shown is basically the same, except that it further includes: at step 450, after determining that a downstream single-phase line break has occurred, calculating the change value of the negative sequence current amplitude after a preset operation delay from the single-phase line break relative to the negative sequence current amplitude before the single-phase line break; and at step 455, when the change value is less than a fourth predetermined value, determining that the downstream single-phase line break has been processed. Figure 4 Steps 410, 415, 420, 425, 430, 435, 440 and 445 of the single-phase disconnection detection method shown can be respectively Figure 3 Steps 310 to 345 of the single-phase disconnection detection method are the same, so repeated descriptions are omitted here.

[0075] According to one embodiment, at step 450, after determining that a single-phase line break has occurred downstream of the line where the measurement point is located according to the previous steps, the single-phase line break detection device does not immediately initiate a relay protection action or issue a relay protection instruction. Instead, the device waits for a preset operation delay. According to one embodiment, during the preset operation delay, changes in the negative-sequence current amplitude can be monitored. For example, during the preset operation delay, the change in the current negative-sequence current amplitude relative to the negative-sequence current amplitude before the single-phase line break can be continuously compared.

[0076] According to one embodiment, the operation delay can be set to be longer than the fault clearing time for faults other than single-phase disconnection, to ensure that the single-phase disconnection detection device does not malfunction before other faults are cleared. Furthermore, according to one embodiment, the operation delay can be set to less than 3 seconds. Typically, fault clearing times in power systems are less than 3 seconds, thus avoiding excessive waiting times before executing relay protection actions, which can lead to increased losses caused by the fault.

[0077] According to one embodiment, at step 455, if the change in the negative-sequence current amplitude is less than the fourth predetermined value, it indicates that the negative-sequence current amplitude has fallen after the preset operation delay, indicating that the downstream single-phase line break has been resolved. Therefore, the single-phase line break detection device does not need to execute a relay protection action or issue a relay protection instruction. Conversely, if the change in the negative-sequence current amplitude relative to the negative-sequence current amplitude before the single-phase line break remains greater than the fourth predetermined value during the preset operation delay, it indicates that the single-phase line break still exists and has not been resolved. Therefore, the single-phase line break detection device needs to execute a relay protection action or issue a relay protection instruction.

[0078] According to steps 450 and 455, since the measuring point waits for the preset operation delay at step 450, the relay protection device downstream of the measuring point has time to process the fault. If the fault is processed by the downstream relay protection device within the preset operation delay for the measuring point, the relay protection device corresponding to the measuring point does not need to execute a relay protection action or issue a relay protection instruction for the fault. This reduces the scope of the line affected by the relay protection action, minimizing the impact of the relay protection action on the entire line.

[0079] Figure 5 FIG. 4 is a block diagram illustrating an apparatus for detecting a single-phase line break in a power system according to an embodiment of the present disclosure.

[0080] According to one embodiment, the single-phase line break detection device 5 may include a collection unit 510, a storage unit 520, and a processing unit 530. The collection unit 510 may be configured to collect three-phase currents and three-phase voltages at a measurement point. The storage unit 520 may be configured to store data collected by the collection unit. The processing unit 530 may be configured to: obtain positive-sequence current and negative-sequence current from the collected three-phase current; calculate the change in positive-sequence current and the change in negative-sequence current within a first time interval; and determine that a first fault group has occurred when the amplitude of the positive-sequence current decreases, the amplitude of the negative-sequence current increases, the decrease in the amplitude of the positive-sequence current is greater than a first predetermined value, and the ratio of the change amplitude of the negative-sequence current to the change amplitude of the positive-sequence current is greater than a second predetermined value, wherein the first fault group includes a single-phase line break.

[0081] According to one embodiment, the single-phase disconnection detection device 5 may be a relay protection device, may include a relay protection device, may be included in a relay protection device, or may be connected to a relay protection device. When the single-phase disconnection detection device 5 detects a single-phase disconnection, the single-phase disconnection detection device 5 may execute a relay protection action or issue a relay protection instruction.

[0082] Although the above description of the acquisition unit 510, the storage unit 520 and the processing unit 530 of the single-phase disconnection detection device 5 performs reference Figure 2The single-phase disconnection detection method described in the present disclosure is not limited thereto. According to one embodiment, the acquisition unit 510, the storage unit 520 and the processing unit 530 of the single-phase disconnection detection device 5 can also perform reference Figure 3 The single-phase disconnection detection method described or reference Figure 4 The single-phase disconnection detection method described in the present invention is as follows:

[0083] Figure 6 FIG. 4 is a block diagram illustrating a single-phase line break detection system according to an embodiment of the present disclosure.

[0084] According to an embodiment, the single-phase line break detection system 6 may include a first single-phase line break detection device 610 and a second single-phase line break detection device 620. Each of the first single-phase line break detection device 610 and the second single-phase line break detection device 620 may be a reference Figure 5 A single-phase line break detection device is described.

[0085] The acquisition unit of each of the first single-phase disconnection detection device 610 and the second single-phase disconnection detection device 620 may be configured to perform a reference Figure 4 In the steps 410 and 415 of the single-phase disconnection detection method described above, the processing unit of each of the first single-phase disconnection detection device 610 and the second single-phase disconnection detection device 620 can be configured to perform the reference Figure 4 Steps 420, 425, 430, 435, 440, 445, 450 and 455 in the single-phase line break detection method described above.

[0086] The second single-phase disconnection detection device 620 may be located downstream of the first single-phase disconnection detection device 610. For example, the second single-phase disconnection detection device 620 may be located downstream of the first single-phase disconnection detection device 610. Figure 1 The R2 position in the figure, and the first single-phase line break detection device 610 can be located at Figure 1 The operation delay preset for the second single-phase disconnection detection device 620 can be shorter than the operation delay preset for the first single-phase disconnection detection device 610. Therefore, when executing the reference Figure 4 During steps 450 and 455 of the single-phase disconnection detection method described above, the first single-phase disconnection detection device 610 located upstream can wait for a longer delay than the second single-phase disconnection detection device 620 located downstream. Figure 1When a single-phase line break occurs at the location shown, the second single-phase line break detection device 620, due to its relatively shorter operation delay, can obtain a detection result, allowing relay protection to be executed or a relay protection instruction to be issued more quickly. Because the single-phase line break fault is handled by the second single-phase line break detection device 620, the first single-phase line break detection device 610, still within the operation delay waiting period, does not need to execute a relay protection action or issue a relay protection instruction. Therefore, the impact of the relay protection action on the entire line is minimized.

[0087] The whole or part of each unit (e.g., processing module) described in the present disclosure can be implemented with suitable hardware, software, or hardware combined with software, for example, in a dedicated circuit, firmware, software, or any combination thereof. For example, certain aspects can be implemented in hardware, while other aspects can be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device. For example, the processing module in the present disclosure may include a microprocessing unit (MCU), which can operate in conjunction with software. The storage module of the present disclosure can be any suitable memory or storage area, which can be an independent unit or integrated into other units, such as a processing module.

[0088] The block diagrams of circuits, devices, apparatuses, equipment, and systems described in this disclosure are intended only as illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these circuits, devices, apparatuses, equipment, and systems may be connected, arranged, or configured in any manner as long as the desired purpose is achieved.

[0089] Those skilled in the art should understand that the above-mentioned specific embodiments are merely examples and not limitations, and that various modifications, combinations, partial combinations and replacements may be made to the embodiments of the present disclosure according to design requirements and other factors. As long as they are within the scope of the attached claims or their equivalents, they fall within the scope of rights to be protected by the present disclosure.

Claims

1. A single-phase line break detection method, comprising: Collect three-phase current at the measurement point; Obtaining positive sequence current and negative sequence current from the collected three-phase current; calculating a change in positive sequence current and a change in negative sequence current during a first time interval; as well as When the amplitude of the positive sequence current decreases, the amplitude of the negative sequence current increases, the decrease in the amplitude of the positive sequence current is greater than a first predetermined value, and the ratio of the change amplitude of the negative sequence current to the change amplitude of the positive sequence current is greater than a second predetermined value, it is determined that a first fault group has occurred, and the first fault group includes a single-phase line break.

2. The single-phase line break detection method according to claim 1, wherein the ratio of the change amplitude of the negative sequence current to the change amplitude of the positive sequence current is defined as: The ratio of the increase in the magnitude of the negative sequence current to the decrease in the magnitude of the positive sequence current; or The ratio of the magnitude of the vector change of the negative sequence current to the magnitude of the vector change of the positive sequence current.

3. The single-phase disconnection detection method according to claim 1, further comprising: Collect the three-phase voltage at the measurement point; Obtaining negative sequence voltage from the collected three-phase voltage; calculating a change in negative sequence voltage during a first time interval; as well as When the modulus of the vector change of the negative sequence voltage is less than or equal to a third predetermined value, or the difference between the phase angle of the vector change of the negative sequence current and the phase angle of the vector change of the negative sequence voltage is not within a predetermined range, it is determined that a downstream single-phase line break has occurred in the line where the measurement point is located.

4. The single-phase disconnection detection method according to claim 3, further comprising: After determining that a downstream single-phase line break has occurred, calculating a change in the negative sequence current amplitude after a preset operation delay from the single-phase line break relative to the negative sequence current amplitude before the single-phase line break; When the change value is smaller than a fourth predetermined value, it is determined that the downstream single-phase line break has been processed. 5 . The single-phase disconnection detection method according to claim 4 , wherein the preset operation delay is set to be longer than a fault clearing time of other faults except the single-phase disconnection. 6 . The single-phase line break detection method according to claim 1 , wherein the first predetermined value is greater than or equal to half of the maximum single-phase load current. The single-phase line break detection method according to claim 1 , wherein the second predetermined value is greater than or equal to 0.

8.

8. The single-phase disconnection detection method according to claim 1, wherein The first time interval is 2 cycles of the three-phase alternating current.

9. A single-phase line break detection device, comprising: an acquisition unit configured to acquire three-phase current at a measurement point; a storage unit configured to store data collected by the collection unit; as well as Processing unit, configured as: Obtaining positive sequence current and negative sequence current from the collected three-phase current; calculating a change in positive sequence current and a change in negative sequence current during a first time interval; as well as When the amplitude of the positive sequence current decreases, the amplitude of the negative sequence current increases, the decrease in the amplitude of the positive sequence current is greater than a first predetermined value, and the ratio of the change amplitude of the negative sequence current to the change amplitude of the positive sequence current is greater than a second predetermined value, it is determined that a first fault group has occurred, and the first fault group includes a single-phase line break.

10. A single-phase line break detection system comprising: a first single-phase wire breakage detection device and a second single-phase wire breakage detection device, each of the first single-phase wire breakage detection device and the second single-phase wire breakage detection device being the single-phase wire breakage detection device according to claim 9, The acquisition unit of each of the first single-phase disconnection detection device and the second single-phase disconnection detection device is further configured to acquire the three-phase voltage at the measurement point. The processing unit of each of the first single-phase line break detection device and the second single-phase line break detection device is further configured as follows: Obtaining negative sequence voltage from the collected three-phase voltage; calculating a change in negative sequence voltage during a first time interval; When the modulus of the vector change of the negative sequence voltage is less than or equal to a third predetermined value, or the difference between the phase angle of the vector change of the negative sequence current and the phase angle of the vector change of the negative sequence voltage is not within a predetermined range, it is determined that a downstream single-phase line break has occurred in the line where the measurement point is located; After determining that a downstream single-phase line break has occurred, calculating a change in the negative sequence current amplitude after a preset operation delay from the single-phase line break relative to the negative sequence current amplitude before the single-phase line break; as well as When the change value is less than a fourth predetermined value, it is determined that the downstream single-phase line break has been processed, wherein the second single-phase line break detection device is located downstream of the first single-phase line break detection device, and the operation delay preset for the second single-phase line break detection device is shorter than the operation delay preset for the first single-phase line break detection device.

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