Power transmission line disconnection fault identification method and device based on multi-stage current comparison

Abstract

The invention discloses a transmission line disconnection fault identification method and device based on multi-stage current comparison, and the method comprises the steps: extracting the zero-sequence current data of a fault line and the tripping signal data and reclosing signal data of a protection device from a fault recording file or a protection recording file obtained from the two sides of the fault line, the fault process of the line is divided into a plurality of stages; calculating per unit values of the current fundamental frequency amplitudes of the two sides of the fault line in each stage by taking the maximum value in the current fundamental frequency amplitudes of the stage before the fault as a current amplitude reference value; and judging the disconnection condition of the faulty line based on comparing the per-unit value with the disconnection fault judgment coefficient kdx and the grounding judgment coefficient kjd. According to the invention, the fault process is divided into a plurality of stages, and each time period in which the line may be disconnected or grounded is fully considered; the method can efficiently and accurately judge the line breaking fault of the line and whether the condition of grounding after line breaking exists, and does not cause misjudgment with the grounding fault.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission line protection control, and in particular to a method and device for identifying a transmission line disconnection fault based on multi-stage current comparison. Background Art

[0002] The operating environment of transmission lines is quite complex, and the lines are easily affected by various factors such as insulation aging, environmental erosion, complex weather, and human damage, which may cause failures. Compared with grounding faults, line break faults directly damage the line body. It is a "permanent" fault that cannot be insulated and self-repaired. The damaged wire must be replaced for normal operation. In addition, the wire falls to the ground after the line is broken, which also shows some characteristics of grounding faults. Therefore, it is necessary to accurately identify line break faults from grounding faults, which is of great guiding significance for guiding line forced transmission decisions and subsequent line repair operations.

[0003] Relay protection can trip the disconnected line and ungrounded fault through non-full-phase operation criteria. However, most disconnected line faults are compound disconnected and grounded faults after the conductor falls to the ground, which are difficult to identify with traditional protection methods. At this time, reclosing is unsuccessful, and the nature of the fault is mainly determined by manual inspection, which has the limitations of low efficiency and low accuracy. For example, manual inspection takes a lot of time and manpower, and it is difficult to find the problem at the first time when the fault occurs.

[0004] With the continuous advancement of science and technology, more and more advanced technologies are being applied to line fault judgment. For example, online monitoring devices are used to monitor the operating status of power lines in real time, and data analysis and algorithm models are used to quickly and accurately judge line faults. At the same time, some new monitoring equipment and methods are constantly emerging, such as line fault identification methods based on the collaboration of terminals and cloud master stations, and the use of power Internet of Things technology to identify line faults in distribution networks in real time. The emergence of these methods and technologies provides a new way to improve the accuracy and efficiency of line fault judgment.

[0005] In addition, different types of power systems and equipment have different requirements for line fault judgment. For example, a line fault in a high-voltage transmission line may have a serious impact on the stable operation of the entire power grid, requiring a more accurate and reliable judgment method; while a line fault in a low-voltage distribution network may directly affect the normal power consumption of users, requiring rapid response and processing.

[0006] In summary, researching and developing an efficient and accurate line break fault judgment method to distinguish between ground faults and line break grounding compound faults is of great guiding significance for guiding line forced transmission decisions, subsequent line repair operations, and the stable operation of the entire power grid. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a transmission line disconnection fault identification method based on multi-stage current comparison, which takes the maximum value of the current fundamental frequency amplitude in the pre-fault stage as the reference value of the current fundamental frequency amplitude, and calculates the per-unit value of the current fundamental frequency amplitude in each stage of the fault process on this basis, and by comparing the per-unit value with the pre-set disconnection fault discrimination coefficient and grounding discrimination coefficient, it is possible to efficiently and accurately judge whether a disconnection fault has occurred in the transmission line, and whether there is a situation of grounding after disconnection, without misjudgment of grounding faults.

[0008] To achieve the above purpose, the technical solutions adopted are as follows:

[0009] The first aspect of the present invention discloses a method for identifying a power transmission line disconnection fault based on multi-stage current comparison, comprising the following steps: S1, extracting three-phase current data in the fault line and trip signal data and reclosing signal data of a protection device; S2, calculating and obtaining zero-sequence current data of the fault line based on the extracted three-phase current data, and dividing the fault process of the fault line into a pre-fault stage, a fault stage and a post-reclosing stage based on the obtained zero-sequence current data, as well as the trip signal data and reclosing signal data of the protection device; S3, calculating and obtaining the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data; S4, calculating the obtained three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage The maximum value of the current fundamental frequency amplitude is used as the reference value of the current fundamental frequency amplitude, and based on the reference value of the current fundamental frequency amplitude, the per-unit values ​​of the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage are calculated and obtained; S5, the per-unit value calculated and obtained in step S4 is compared with the preset disconnection fault discrimination coefficient. If there is a per-unit value less than the disconnection fault discrimination coefficient, it is determined that a disconnection fault occurs in the line, otherwise it is determined that no disconnection fault occurs in the line; S6, when a disconnection fault occurs in the line, the per-unit value calculated and obtained in step S4 is compared with the preset grounding discrimination coefficient. If there is a per-unit value greater than the grounding discrimination coefficient, it is determined that the line is grounded after disconnection, otherwise it is determined that the line is not grounded after disconnection.

[0010] In the above disclosed steps, the present invention divides the fault process into multiple stages and judges the line break fault based on the per-unit values ​​in multiple stages, that is, a judgment method combining multiple stages with per-unit values ​​is formed, so that the judgment of the line break fault has real-time and continuity, thereby eliminating the misjudgment caused by the current amplitude judgment only in a single stage; and in the judgment process of the line break fault, the most essential difference between the line break fault and other fault types is utilized, that is, the current amplitude is reduced, and the line break situation of the fault line can be judged efficiently and accurately with the simplest judgment criterion, and no misjudgment will occur between the ground fault.

[0011] In addition, the present invention comprehensively utilizes the zero-sequence current data of the fault line and the tripping signal data and reclosing signal data of the protection device, thereby eliminating the problem that the tripping time and the reclosing time may vary due to various factors, and can more accurately divide the fault process of the fault line into multiple stages, thereby improving the judgment accuracy of the data in each stage.

[0012] In the present invention, the zero-sequence current data provides an early warning of the occurrence of a fault and a preliminary judgment of the fault type, while the protection device signal data clarifies the key action nodes in the fault development process. By combining the zero-sequence current data with the protection device signal data, the various stages of the fault process can be completely divided, forming a complete description of the fault evolution process from the pre-fault stage, fault stage, and post-reclosing stage of the fault process.

[0013] At the same time, since the zero-sequence current data and the protection device signal data reflect the fault situation from different angles, it is difficult to determine whether the fault is serious enough to cut off the line only by relying on the zero-sequence current, and relying only on the protection device signal data, the fault may not be discovered in time in the early stage of the fault because the signal has not yet been sent. The present invention avoids the misjudgment caused by a single indicator division by combining the zero-sequence current data with the protection device signal data to divide the fault stage, and greatly improves the accuracy and reliability of the fault stage division.

[0014] In the present invention, the current data in the pre-fault stage is used as a reference value to calculate and obtain the judgment data of each stage of the fault, which is helpful to extract the fault characteristics. Under normal operating conditions, the electrical quantities of the power system have certain stable characteristics. When a fault occurs, by establishing a connection with the data in the pre-fault stage as a reference, the abnormal characteristics caused by the fault can be more clearly identified, thereby improving the accuracy of fault identification.

[0015] Specifically, in step S1, the three-phase current data in the fault line and the tripping signal data and reclosing signal data of the protection device are extracted by opening the fault recording file or the protection recording file through the recording and broadcasting image analysis software, and then the three-phase current data and the tripping signals of each phase of the protection device (or the open and closed signals of each phase circuit breaker) and the reclosing signal and other data are clipped and extracted from the channel corresponding to the fault line and saved as a csv file. The tripping signal data and the reclosing signal data in the csv file are digital signals with values ​​of 0 or 1, and the change of their values ​​represents the change of the state of the tripping signal and the reclosing signal; and the fault recording file and the protection recording file are files with the suffix cfg generated by the fault recording devices and the protection devices on both sides of the fault line. The cfg file contains the discrete sampling values ​​of the voltage and current of the transmission line related to the fault recording device or the protection device, and the tripping signal, reclosing signal and other data of the protection device.

[0016] In the present invention, the two sides of the fault line are respectively the M side and the N side, that is, the two ends of the fault line. By defining the M side and the N side, the position of the fault relative to the two ends of the line can be clearly identified, so as to quickly locate the fault range and improve the search efficiency of the staff. In addition, by defining the M side and the N side, it is also convenient to analyze the fault characteristics and the changing laws of electrical quantities.

[0017] In step S2, the zero-sequence current data of the fault line is calculated based on the extracted three-phase current data. The calculation formula for obtaining the zero-sequence current data of the fault line is as follows:

[0018]

[0019] Where: I A ,I B ,I C A, B, and C phase currents of the faulty line respectively.

[0020] Further, in step S2, the fault process of the fault line is divided into three stages, namely, stages I, II, and III, where stage I is the pre-fault stage, stage II is the fault stage, and stage III is the post-reclosing stage. The steps of obtaining the pre-fault stage, the fault stage, and the post-reclosing stage include:

[0021] The fault recording device and protection device record the recording data of 0.1-0.5s before the fault and several cycles after the fault. The starting time of the recording data is taken as the starting time of the pre-fault stage, and one cycle is taken backward as the pre-fault stage.

[0022] Based on the fact that the time from the occurrence of a fault to the issuance of a trip pulse is greater than one cycle, the change moment of the trip signal data of the protection device is taken as the end moment of the fault stage, and one cycle forward is taken as the fault stage;

[0023] Based on the reclosing signal sent by the protection device, the change time of the reclosing signal data and the sudden change of the zero-sequence current data are combined to determine the starting time of the post-reclosing stage, and one cycle is taken backward as the post-reclosing stage.

[0024] Preferably, in step S2, it is necessary to extract a data window with a length of one cycle in the pre-fault stage, the fault stage and the post-reclosing stage of the line fault process.

[0025] Furthermore, after the length of the data window is determined, the position of the data window can be determined by simply determining its starting point or end point.

[0026] Specifically, in step S3, calculating and obtaining the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data means performing a single-cycle Fourier algorithm on the data window intercepted in step S2, thereby calculating the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage.

[0027] Specifically, in step S4, based on the reference value of the current fundamental frequency amplitude, the step of calculating and obtaining the per unit value of the three-phase current fundamental frequency amplitude at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage includes:

[0028] Based on formula (1), the maximum value of the fundamental frequency amplitude of the three-phase current on both sides of the fault line before the fault is taken as the reference value of the fundamental frequency amplitude of the current:

[0029] I Base =max(I MAΙ ,I MBΙ ,I MCΙ ,I NAΙ ,I NBΙ ,I NCΙ )(1)

[0030] Where: I Base is the reference value of the current fundamental frequency amplitude, I MAΙ ,I MBΙ ,I MCΙ I is the fundamental frequency amplitude of the A, B, and C phase currents on the M side of the fault line before the fault; NAΙ ,I NBΙ ,I NCΙ is the fundamental frequency amplitude of the A, B, and C phase currents on the N side of the fault line before the fault;

[0031] Based on formula (2), based on the reference value of the current fundamental frequency amplitude, the per unit value of the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, fault stage and post-reclosing stage is calculated and obtained:

[0032]

[0033] Where: X∈{A,B,C} represents the three phases A, B, and C; Indicates the pre-fault stage, fault stage and post-reclosing stage; I Base is the reference value of the current fundamental frequency amplitude; and is the per-unit value set of the fundamental frequency amplitude of the three-phase current on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage; and is the set of three-phase current fundamental frequency amplitudes on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage;

[0034] According to the method for identifying a power transmission line disconnection fault based on multi-stage current comparison disclosed in the first aspect of the present invention, in step S5, if there is a per-unit value less than the disconnection fault discrimination coefficient, it is determined that a disconnection fault has occurred in the line, including: when there is a per-unit value less than the disconnection fault discrimination coefficient, determining the corresponding phase difference that is less than the per-unit value of the disconnection fault discrimination coefficient, and judging the occurrence of a disconnection fault of the corresponding phase difference based on the determined corresponding phase difference.

[0035] Specifically, if there is a per-unit value less than the line-break fault discrimination coefficient, and the smallest per-unit value belongs to the per-unit value of the fundamental frequency amplitude of the A-phase current on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that the line has an A-phase line-break fault;

[0036] If there is a per-unit value smaller than the line-break fault discrimination coefficient, and the smallest per-unit value belongs to the per-unit value of the fundamental frequency amplitude of the B-phase current on both sides of the faulty line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that a B-phase line-break fault occurs in the line;

[0037] If there is a per-unit value smaller than the line break fault discrimination coefficient, and the smallest per-unit value belongs to the per-unit value of the fundamental frequency amplitude of the C-phase current on both sides of the faulty line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is determined that a C-phase line break fault has occurred in the line.

[0038] According to the method for identifying power line disconnection faults based on multi-stage current comparison disclosed in the first aspect of the present invention, in step S6, for the disconnected phase determined in step S5, if there is a per-unit value greater than the grounding discrimination coefficient, it is determined that the line is disconnected and then grounded, including: for the disconnected phase determined in step S5, when there is a per-unit value greater than the grounding discrimination coefficient, the side where the per-unit value greater than the grounding discrimination coefficient is located is determined, and based on the determined side, it is determined that a disconnection and then grounding fault has occurred on that side.

[0039] Specifically, when a phase A line disconnection fault occurs in the line, for phase A, if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase A is disconnected, and grounding is performed after the M side is disconnected; if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase A is disconnected, and grounding is performed after the N side is disconnected; if among all per-unit values ​​greater than the grounding discrimination coefficient, there are both per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase A is disconnected, and grounding is performed after both the M side and the N side are disconnected;

[0040] When a B-phase line break fault occurs in the line, for phase B, if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase B is broken, and grounding is performed after the M side is broken; if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase B is broken, and grounding is performed after the N side is broken; if among all per-unit values ​​greater than the grounding discrimination coefficient, there are both per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase B is broken, and grounding is performed after both the M side and the N side are broken;

[0041] When a C-phase line break fault occurs in the line, for phase C, if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase C is broken, and grounding is performed after the M side is broken; if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase C is broken, and grounding is performed after the N side is broken; if among all per-unit values ​​greater than the grounding discrimination coefficient, there are both per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase C is broken, and grounding is performed after both the M side and the N side are broken.

[0042] The second aspect of the present invention discloses a transmission line disconnection fault identification device based on multi-stage current comparison, comprising:

[0043] A fault line data extraction unit is configured to extract three-phase current data in the fault line and trip signal data and reclosing signal data of the protection device;

[0044] A fault process stage division unit is configured to calculate and obtain zero-sequence current data of the fault line based on the extracted three-phase current data, and divide the fault process of the fault line into a pre-fault stage, a fault stage, and a post-reclosing stage based on the obtained zero-sequence current data and the trip signal data and reclosing signal data of the protection device;

[0045] A current fundamental frequency amplitude acquisition unit is configured to calculate and acquire the three-phase current fundamental frequency amplitudes at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data;

[0046] A current fundamental frequency amplitude per unit value acquisition unit is configured to use the maximum value of the acquired three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage as a reference value of the current fundamental frequency amplitude, and based on the reference value of the current fundamental frequency amplitude, calculate and acquire the per unit values ​​of the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage;

[0047] The line break fault judgment unit is configured to compare the per-unit value calculated and obtained in the current fundamental frequency amplitude per-unit value obtaining unit with a preset line break fault judgment coefficient, and if there is a per-unit value smaller than the line break fault judgment coefficient, it is judged that a line break fault occurs in the line, otherwise it is judged that no line break fault occurs in the line;

[0048] The grounding judgment unit after a line break fault is constructed to compare the per-unit value calculated and obtained in the current fundamental frequency amplitude per-unit value acquisition unit with a preset grounding judgment coefficient when a line break fault occurs. If there is a per-unit value greater than the grounding judgment coefficient, it is judged that the line is grounded after the line break, otherwise it is judged that the line is not grounded after the line break.

[0049] The third aspect of the present invention discloses an electronic device, including a memory and a processor, the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the transmission line disconnection fault identification method based on multi-stage current comparison disclosed in the first aspect of the present invention.

[0050] The fourth aspect of the present invention discloses a computer-readable storage medium, which stores a computer program. The computer program is suitable for being loaded by a processor and executing the transmission line disconnection fault identification method based on multi-stage current comparison disclosed in the first aspect of the present invention.

[0051] The beneficial effects of the present invention are as follows:

[0052] The present invention divides the fault process into multiple stages and judges the line break fault based on the per-unit values ​​in multiple stages, that is, a judgment method combining multiple stages with per-unit values ​​is formed, so that the judgment of the line break fault has real-time and continuity, thereby eliminating the misjudgment caused by judging the current amplitude only in a single stage; and in the judgment of the line break fault, the most essential difference between the line break fault and other fault types is utilized, that is, the current amplitude is reduced, and the line break situation of the fault line can be judged efficiently and accurately with the simplest judgment criterion, and no misjudgment will occur between the ground fault; and the present invention comprehensively utilizes the zero-sequence current data of the fault line and the tripping signal data and the reclosing signal data of the protection device, eliminates the problem that the tripping time and the reclosing time are affected by multiple factors and have different effects, and can more accurately divide the fault process of the fault line into multiple stages, thereby improving the judgment accuracy of the data in each stage; at the same time, by combining the zero-sequence current data with the protection device signal data to divide the fault stage, the misjudgment caused by the single indicator division is effectively avoided, and the accuracy and reliability of the fault stage division are greatly improved.

[0053] The following discloses in detail the power transmission line disconnection fault identification method and device based on multi-stage current comparison of the present invention in conjunction with the embodiments shown in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a flow chart of the steps of the method for identifying a power transmission line disconnection fault based on multi-stage current comparison of the present invention;

[0055] Figure 2 The voltage and current waveform diagram of the transmission line M side in the first embodiment of the present invention;

[0056] Figure 3 This is the pre-fault stage of the M-side fault process in the first embodiment of the present invention;

[0057] Figure 4 This is the fault stage of the M-side fault process in the first embodiment of the present invention;

[0058] Figure 5 This is the post-reclosing stage of the M-side fault process in the first embodiment of the present invention;

[0059] Figure 6 The voltage and current waveform diagram of the N side of the power transmission line in the first embodiment of the present invention;

[0060] Figure 7 This is the pre-fault stage of the N-side fault process in the first embodiment of the present invention;

[0061] Figure 8This is the fault stage of the N-side fault process in the first embodiment of the present invention;

[0062] Fig. 9 This is the post-reclosing stage of the N-side fault process in the first embodiment of the present invention;

[0063] Fig.10 The voltage and current waveform diagram of the transmission line M side in the second embodiment of the present invention;

[0064] Fig.11 1 is a voltage and current waveform diagram of the N side of the transmission line in the second embodiment of the present invention. DETAILED DESCRIPTION

[0065] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other without conflict.

[0066] like Figure 1 As shown, the present invention discloses a method for identifying a power transmission line disconnection fault based on multi-stage current comparison, which is characterized by comprising the following steps: S1, extracting three-phase current data in the fault line and trip signal data and reclosing signal data of a protection device; S2, calculating and obtaining zero-sequence current data of the fault line based on the extracted three-phase current data, and dividing the fault process of the fault line into a pre-fault stage, a fault stage and a post-reclosing stage based on the obtained zero-sequence current data, as well as the trip signal data and reclosing signal data of the protection device; S3, calculating and obtaining the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data; S4, calculating the obtained three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage The maximum value of the three-phase current fundamental frequency amplitude is used as the reference value of the current fundamental frequency amplitude, and based on the reference value of the current fundamental frequency amplitude, the per-unit value of the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage is calculated and obtained; S5, the per-unit value calculated and obtained in step S4 is compared with the preset disconnection fault discrimination coefficient. If there is a per-unit value less than the disconnection fault discrimination coefficient, it is determined that a disconnection fault occurs in the line, otherwise it is determined that no disconnection fault occurs in the line; S6, when a disconnection fault occurs in the line, the per-unit value calculated and obtained in step S4 is compared with the preset grounding discrimination coefficient. If there is a per-unit value greater than the grounding discrimination coefficient, it is determined that the line is grounded after disconnection, otherwise it is determined that the line is not grounded after disconnection.

[0067] The present invention divides the fault process into multiple stages and judges the line break fault based on the per-unit values ​​in multiple stages, that is, a judgment method combining multiple stages with per-unit values ​​is formed, so that the judgment of the line break fault has real-time and continuity, thereby eliminating the misjudgment caused by judging the current amplitude only in a single stage; and in the judgment of the line break fault, the most essential difference between the line break fault and other fault types is used, that is, the current amplitude is reduced, so the line break situation of the fault line can be judged efficiently and accurately with the simplest judgment criterion, and no misjudgment will occur between the fault and the ground fault.

[0068] Specifically, in step S1, the three-phase current data in the fault line and the tripping signal data and reclosing signal data of the protection device are extracted by opening the fault recording file or the protection recording file through the recording and broadcasting image analysis software, and then the three-phase current data and the tripping signals of each phase of the protection device (or the open and closed signals of each phase circuit breaker) and the reclosing signal data are clipped and extracted from the channel corresponding to the fault line and saved as a csv file. The tripping signal data and the reclosing signal data in the csv file are both digital signals with values ​​of 0 or 1, and the change of their values ​​represents the change of the state of the tripping signal and the reclosing signal.

[0069] In a preferred embodiment, the protection recording files on both sides of the fault line are downloaded through the security system. The protection recording files refer to files with the suffix cfg generated by the fault recording devices and protection devices on both sides of the line, which contain discrete sampling values ​​of voltage and current of the transmission lines related to the fault recording device or the protection device, as well as tripping signals, reclosing signals and other data of the protection device.

[0070] In the present invention, the two sides of the fault line are defined as the M side and the N side, that is, the two ends of the fault line. By defining the M side and the N side, the position of the fault relative to the two ends of the line can be clearly identified, thereby quickly locating the fault range, improving the search efficiency of the staff, and facilitating the analysis of fault characteristics and the changing laws of electrical quantities.

[0071] In this embodiment, the interfaces of the cfg files on the M and N sides after being opened by the recording and broadcasting image analysis software are as follows: Figure 2 and Figure 6 shown. Figure 2 There are 8 channels in total, from top to bottom: C phase trip signal, reclosing signal, A phase voltage, B phase voltage, C phase voltage, zero-sequence voltage, A phase current, B phase current, C phase current and zero-sequence current. Figure 6 There are 8 channels in total, from top to bottom: reclosing signal, C phase trip signal, A phase voltage, B phase voltage, C phase voltage, zero-sequence voltage, A phase current, B phase current, C phase current and zero-sequence current.

[0072] In step S2, the zero-sequence current data of the fault line is calculated based on the extracted three-phase current data. The calculation formula for obtaining the zero-sequence current data of the fault line is as follows:

[0073]

[0074] Where: I A ,I B ,I C A, B, and C phase currents of the faulty line respectively.

[0075] Further, in step S2, the fault process of the fault line is divided into three stages, namely, stages I, II, and III, where stage I is the pre-fault stage, stage II is the fault stage, and stage III is the post-reclosing stage. The steps of obtaining the pre-fault stage, the fault stage, and the post-reclosing stage include:

[0076] 1) Based on the fault recording device and the protection device, the recording data of 0.1-0.5s before the fault and several cycles after the fault are recorded, the starting time of the recording data is taken as the starting time of the pre-fault stage, and one cycle is taken backward as the pre-fault stage;

[0077] 2) Based on the fact that the time from the occurrence of a fault to the issuance of a trip pulse is generally greater than one cycle, the change time of the trip signal data of the protection device is taken as the end time of the fault stage, and one cycle forward is taken as the fault stage;

[0078] 3) If the protection device sends a reclosing signal (i.e., the reclosing signal data changes), it means that there is a reclosing process in the fault, and the change time of the reclosing signal data is used as the initial value of the starting time of the post-reclosing stage. Since the reclosing time is affected by many factors and varies, it is necessary to combine the sudden change of the zero-sequence current data to determine the starting time after reclosing, and then take one cycle backward as the post-reclosing stage.

[0079] Preferably, in step S2, a data window with a length of one cycle is intercepted in the pre-fault stage, the fault stage and the post-reclosing stage of the line fault process.

[0080] Furthermore, after the length of the data window is determined, the position of the data window can be determined by simply determining its starting point or end point.

[0081] Figures 3 to 5 1 shows the various stages of the fault process on the M side of the transmission line in this embodiment, Figures 7 to 9 The various stages of the fault process on the N side of the transmission line in this embodiment are shown. The vertical dotted line on the left side of the figure represents the starting time of each stage, and the vertical dotted line on the right side represents the ending time of each stage.

[0082] Specifically, in step S3, calculating and obtaining the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data means performing a single-cycle Fourier algorithm on the data window intercepted in step S2, thereby calculating the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage.

[0083] The single-cycle Fourier algorithm refers to an improved single-cycle Fourier algorithm that can eliminate the influence of non-periodic components on the calculation accuracy. When the input signal is a periodic signal, the fast Fourier transform can accurately find the fundamental frequency component in the signal. In other words, the calculation accuracy of the fast Fourier transform is not affected by the constant DC component and the whole harmonic component. However, in actual fault conditions, the fault signal does not change periodically. For example, the non-periodic component is not a constant pure DC component, but decays according to the exponential law. For transmission line protection, the high-frequency component in the fault transient signal is related to the distance between the fault point and the protection installation, and is not necessarily a whole harmonic component. Moreover, these high-frequency components also decay over time. Therefore, when using the fast Fourier transform to calculate the fundamental frequency amplitude, a certain error will still occur. Considering that the fast Fourier transform has a very strong filtering ability for high-frequency components, even if no other measures are taken, good filtering accuracy can generally be guaranteed. For low-frequency components, the filtering effect of the fast Fourier transform is relatively poor. Therefore, preferably, in step S3, an improved fast Fourier transform that can filter out non-periodic components is used to calculate the amplitude of the fundamental frequency of the three-phase current at each stage of the fault process.

[0084] For the ordinary single-cycle Fourier algorithm, the error caused by the non-periodic component is shown in the following formula.

[0085]

[0086] Where: and are the real and imaginary parts of the error due to the non-periodic component, respectively; N represents the length of the data window; i(n) represents the nth data in the data window, and n∈[0,N-1].

[0087] Finally, we only need to subtract the error from the real and imaginary parts of each wave calculated by the ordinary single-cycle Fourier algorithm to obtain the real and imaginary parts of each wave calculated by the improved Fourier algorithm, as shown in the following formula.

[0088]

[0089] Where: and They are the real and imaginary parts of each wave calculated by the ordinary single-cycle Fourier algorithm; and They are the real and imaginary parts of each wave calculated by the improved single-cycle Fourier algorithm.

[0090] Table 1 and Table 2 respectively show the fundamental frequency amplitudes of the three-phase currents on the M side and the N side of the transmission line in the pre-fault stage, the fault stage and the post-reclosing stage in this embodiment.

[0091] Table 1 (Unit: A)

[0092]

[0093] Table 2 (Unit: A)

[0094]

[0095]

[0096] Specifically, in step S4, based on the reference value of the current fundamental frequency amplitude, the step of calculating and obtaining the per unit value of the three-phase current fundamental frequency amplitude on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage includes:

[0097] Based on formula (1), the maximum value of the three-phase current fundamental frequency amplitude on the M side and the N side of the fault line before the fault is taken as the reference value of the current fundamental frequency amplitude:

[0098] I Base =max(I MAΙ ,I MBΙ ,I MCΙ ,I NAΙ ,I NBΙ ,I NCΙ )(1)

[0099] Where: I Base is the reference value of the current fundamental frequency amplitude, I MAΙ ,I MBΙ ,I MCΙ I is the fundamental frequency amplitude of the A, B, and C phase currents on the M side of the fault line before the fault; NAΙ ,I NBΙ ,I NCΙ is the fundamental frequency amplitude of the A, B, and C phase currents on the N side of the fault line before the fault;

[0100] Substituting the values ​​in Table 1 and Table 2, we get:

[0101] I Base =2.1104A

[0102] Further, based on formula (2), based on the reference value of the current fundamental frequency amplitude, the per unit value of the three-phase current fundamental frequency amplitude on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage is calculated and obtained:

[0103]

[0104] Where: X∈{A,B,C} represents the three phases A, B, and C; Indicates the pre-fault stage, fault stage and post-reclosing stage; I Base is the reference value of the current fundamental frequency amplitude; and is the per-unit value set of the fundamental frequency amplitude of the three-phase current on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage; and is the set of three-phase current fundamental frequency amplitudes on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage;

[0105] Table 3 and Table 4 respectively show the per unit values ​​of the fundamental frequency amplitudes of the three-phase currents on the M side and the N side of the transmission line in the pre-fault stage, the fault stage and the post-reclosing stage in this embodiment.

[0106] Table 3

[0107]

[0108]

[0109] Table 4

[0110]

[0111] In step S5, the per-unit value calculated in step S4 is compared with the preset disconnection fault discrimination coefficient k. dx For comparison, if there is a value less than the disconnection fault discrimination coefficient k dx If the per-unit value is greater than , it is determined that a line disconnection fault occurs, otherwise it is determined that no line disconnection fault occurs. As shown below:

[0112]

[0113] Where: φ represents the disconnection status of the line, a value of 1 indicates disconnection, and a value of 0 indicates non-disconnection; It represents the minimum value of the per-unit values ​​of the fundamental frequency amplitude of the three-phase current on the M side and the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage; k dx ∈(0,1), is the preset disconnection fault discrimination coefficient.

[0114] This embodiment k dx The value of will affect the accuracy of the judgment of the complete disconnection fault: if it is too large, it will be affected by the unbalanced current of the line and easily misjudged; if it is too small, it will reduce the sensitivity of the model and easily miss the judgment. dx Take 0.3.

[0115] Substituting the values ​​in Table 3 and Table 4, we get:

[0116] I min =0.0027

[0117] Because I min =0.0027<k dx =0.3, so φ=1, which means that a line break occurs.

[0118] In a preferred embodiment, in step S5, when there is a fault less than the line break fault discrimination coefficient k dx When the per unit value is less than the disconnection fault discrimination coefficient k dx The corresponding phase of the standard value is determined, and based on the determined corresponding phase, it is determined that a line break fault of the corresponding phase occurs.

[0119] In a specific embodiment, if it is less than the disconnection fault discrimination coefficient k dx When the per-unit value of is equal to the per-unit value of the fundamental frequency amplitude of the A-phase current on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is judged that the line has an A-phase disconnection fault; if it is less than the disconnection fault discrimination coefficient k dx When the per-unit value of is equal to the per-unit value of the fundamental frequency amplitude of the B-phase current on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is judged that the line has a B-phase disconnection fault; if it is less than the disconnection fault discrimination coefficient k dx When the per-unit value of is equal to the per-unit value of the fundamental frequency amplitude of the C-phase current on both sides of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that a C-phase disconnection fault occurs in the line. As shown in the following formula:

[0120]

[0121] Where: D represents the disconnected phase of the fault line; are the per-unit values ​​of the fundamental frequency amplitudes of the A, B, and C phase currents on the M side of the fault line in the pre-fault stage, the fault stage, and the post-reclosing stage respectively; They are the per-unit values ​​of the fundamental frequency amplitudes of the A, B, and C phase currents on the N side of the fault line in the pre-fault stage, fault stage, and post-reclosing stage, respectively.

[0122] From the data in Table 3 and Table 4, we can see that I min The per unit value of the fundamental frequency amplitude of the C phase current on the M side of the transmission line before the fault Right now Therefore, D=C, that is, the disconnected phase is C.

[0123] In step S6, when a line break fault occurs, the per-unit value calculated in step S4 is compared with the pre-set grounding discrimination coefficient. For the broken phase determined in step S5, if there is a per-unit value greater than the grounding discrimination coefficient, it is determined that the line is broken and then grounded; otherwise, it is determined that the line is not grounded after being broken.

[0124] In a preferred embodiment, in step S6, for the disconnected phase determined in step S5, when there is a phase with a value greater than the grounding discrimination coefficient k jd When the per unit value is greater than the grounding discrimination coefficient k jd The side where the per-unit value is located is determined, and based on the determined side, it is determined that a grounding fault occurs after the line is broken on the side.

[0125] In a specific embodiment, when a phase A disconnection fault occurs in the line, for phase A, if it is greater than the grounding discrimination coefficient k jd When all per-unit values ​​of belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that the A phase is broken and then grounded after the M side is broken; if it is greater than the grounding discrimination coefficient k jd When all per-unit values ​​of belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that the A phase is broken and then grounded after the N side is broken; if it is greater than the grounding discrimination coefficient k jd When there are per-unit values ​​of the three-phase current fundamental frequency amplitudes on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and there are per-unit values ​​of the three-phase current fundamental frequency amplitudes on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that the A phase is disconnected, and is grounded after both the M side and the N side are disconnected;

[0126] When a phase B disconnection fault occurs in the line, for phase B, if it is greater than the grounding discrimination coefficient k jd If all per-unit values ​​of belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that the B phase is broken and then grounded after the M side is broken; if it is greater than the grounding discrimination coefficient k jd When all per-unit values ​​of belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that the B phase is broken and then grounded after the N side is broken; if it is greater than the grounding discrimination coefficient k jd When there are per-unit values ​​of the three-phase current fundamental frequency amplitudes on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and there are per-unit values ​​of the three-phase current fundamental frequency amplitudes on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that the B phase is disconnected, and is grounded after both the M side and the N side are disconnected;

[0127] When a phase C disconnection fault occurs in the line, for phase C, if it is greater than the grounding discrimination coefficient k jd If all per-unit values ​​of belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that the C phase is broken and then grounded after the M side is broken; if it is greater than the grounding discrimination coefficient k jd If all per-unit values ​​of belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of the fault line in the pre-fault stage, fault stage and post-reclosing stage, it is judged that the C phase is broken and then grounded after the N side is broken; if it is greater than the grounding discrimination coefficient k jd Among all the per-unit values, if there are both per-unit values ​​of the three-phase current fundamental frequency amplitudes on the M side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and per-unit values ​​of the three-phase current fundamental frequency amplitudes on the N side of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is judged that phase C is broken, and is grounded after both the M side and the N side are broken.

[0128] Determine whether it is greater than the grounding discrimination coefficient k jd The side where the per-unit value is located is determined, and based on the determined side, it is determined that a grounding fault has occurred after the line is broken on the side. As shown in the following formula:

[0129]

[0130] Where: γ M ,γ N They are the grounding after line breaking on the M side and the N side of the fault line, respectively. A value of 1 indicates grounding after line breaking, and a value of 0 indicates no grounding after line breaking. It represents the maximum value among the per-unit values ​​of the fundamental frequency amplitude of the disconnected phase current on the M side of the fault line in the pre-fault stage, fault stage and post-reclosing stage; It represents the maximum value among the per-unit values ​​of the fundamental frequency amplitude of the broken phase current on the N side of the fault line in the pre-fault stage, fault stage and post-reclosing stage.

[0131] In this embodiment, preferably, k jd Take 10.

[0132] Substituting the values ​​in Table 3 and Table 4, we get:

[0133]

[0134] Therefore

[0135]

[0136] That is, the transmission line is not grounded after the line is broken on the M side, and is grounded again after the line is broken on the N side.

[0137] Table 5 shows the disconnection situation judgment table of the present invention.

[0138] Table 5

[0139] φ D <![CDATA[γ M ]]> <![CDATA[γ N ]]> Disconnection 0 \ \ \ Non-disconnection fault 1 A 0 0 Phase A is disconnected and is not grounded after disconnection 1 A 0 1 Phase A is disconnected, and the N side is disconnected and then grounded 1 A 1 0 Phase A is disconnected, and the M side is disconnected and then grounded 1 A 1 1 Phase A is disconnected, and both sides are disconnected before grounding 1 B 0 0 Phase B is disconnected and is not grounded after disconnection 1 B 0 1 Phase B is disconnected, and the N side is disconnected and then grounded 1 B 1 0 Phase B is disconnected, and the M side is disconnected and then grounded 1 B 1 1 Phase B is disconnected, and both sides are disconnected before grounding 1 C 0 0 Phase C is disconnected and is not grounded after disconnection 1 C 0 1 Phase C is disconnected, and the N side is disconnected and then grounded 1 C 1 0 Phase C is disconnected, and the M side is disconnected and then grounded 1 C 1 1 Phase C is disconnected, and both sides are disconnected before grounding

[0140] Table 6 shows various variables related to the line break fault situation in this embodiment.

[0141] Table 6

[0142] φ D <![CDATA[γ M ]]> <![CDATA[γ N ]]> 1 C 0 1

[0143] By comparing Table 5, it can be seen that the disconnection situation of this embodiment is that the C phase is disconnected, and the N side is disconnected and then grounded.

[0144] This embodiment is based on a real case. It can be seen from the fault description and line inspection report that the C phase is disconnected and one side of the transmission line is grounded due to a broken conductor, which is consistent with the judgment result of the transmission line disconnection fault identification method based on multi-stage current comparison of the present invention.

[0145] In another preferred embodiment, the interfaces of the cfg files on the M and N sides after being opened by the recording and broadcasting image analysis software are as follows: Fig.10 and Fig.11 shown. Fig.10 There are 8 channels in total, from top to bottom: reclosing signal, phase A trip signal, phase A voltage, phase B voltage, phase C voltage, zero-sequence voltage, phase A current, phase B current, phase C current and zero-sequence current. Fig.11 There are 8 channels in total, from top to bottom: phase A trip signal, reclosing signal, phase A voltage, phase B voltage, phase C voltage, zero-sequence voltage, phase A current, phase B current, phase C current and zero-sequence current.

[0146] Table 7 and Table 8 respectively show the fundamental frequency amplitudes of the three-phase currents on the M side and the N side of the transmission line in the pre-fault stage, the fault stage and the post-reclosing stage in this embodiment.

[0147] Table 7 (Unit: A)

[0148]

[0149] Table 8 (Unit: A)

[0150]

[0151] Table 9 and Table 10 respectively show the per unit values ​​of the fundamental frequency amplitudes of the three-phase currents on the M side and the N side of the transmission line in the pre-fault stage, the fault stage and the post-reclosing stage in this embodiment.

[0152] Table 9

[0153]

[0154] Table 10

[0155]

[0156]

[0157] Table 11 shows various variables related to the line break fault condition in this embodiment.

[0158] Table 11

[0159] φ D <![CDATA[γ M ]]> <![CDATA[γ N ]]> 0 \ \ \

[0160] By comparing Table 5, it can be seen that the disconnection condition of this embodiment is a non-disconnection fault.

[0161] This embodiment is derived from a real lightning fault case, and is consistent with the judgment result of the power transmission line disconnection fault identification method based on multi-stage current comparison of the present invention.

[0162] The present invention also discloses a transmission line disconnection fault identification device based on multi-stage current comparison, comprising:

[0163] A fault line data extraction unit is configured to extract three-phase current data in the fault line and trip signal data and reclosing signal data of the protection device;

[0164] A fault process stage division unit is configured to calculate and obtain zero-sequence current data of the fault line based on the extracted three-phase current data, and divide the fault process of the fault line into a pre-fault stage, a fault stage, and a post-reclosing stage based on the obtained zero-sequence current data and the trip signal data and reclosing signal data of the protection device;

[0165] A current fundamental frequency amplitude acquisition unit is configured to calculate and acquire the three-phase current fundamental frequency amplitudes at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data;

[0166] A current fundamental frequency amplitude per unit value acquisition unit is configured to use the maximum value of the acquired three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage as a reference value of the current fundamental frequency amplitude, and based on the reference value of the current fundamental frequency amplitude, calculate and acquire the per unit values ​​of the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage;

[0167] The line break fault judgment unit is configured to compare the per-unit value calculated and obtained in the current fundamental frequency amplitude per-unit value obtaining unit with a preset line break fault judgment coefficient, and if there is a per-unit value smaller than the line break fault judgment coefficient, it is judged that a line break fault occurs in the line, otherwise it is judged that no line break fault occurs in the line;

[0168] The grounding judgment unit after a line break fault is constructed to compare the per-unit value calculated and obtained in the current fundamental frequency amplitude per-unit value acquisition unit with a preset grounding judgment coefficient when a line break fault occurs. If there is a per-unit value greater than the grounding judgment coefficient, it is judged that the line is grounded after the line break, otherwise it is judged that the line is not grounded after the line break.

[0169] The present invention also discloses an electronic device, including a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the transmission line disconnection fault identification method based on multi-stage current comparison disclosed in the first aspect of the present invention.

[0170] The present invention also discloses a computer-readable storage medium storing a computer program, wherein the computer program is suitable for being loaded by a processor and executing the transmission line disconnection fault identification method based on multi-stage current comparison disclosed in the first aspect of the present invention.

[0171] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0172] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0173] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0174] The above description is only an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0175] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0176] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0177] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for identifying a power transmission line disconnection fault based on multi-stage current comparison, characterized in that: The following steps are involved: S1, extracting three-phase current data in the fault line and tripping signal data and reclosing signal data of the protection device; S2, calculating and obtaining zero-sequence current data of the fault line based on the extracted three-phase current data, and dividing the fault process of the fault line into a pre-fault stage, a fault stage, and a post-reclosing stage based on the obtained zero-sequence current data, as well as the tripping signal data and the reclosing signal data of the protection device; S3, calculating and obtaining the three-phase current fundamental frequency amplitudes at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data; S4, taking the maximum value of the fundamental frequency amplitude of the three-phase current on both sides of the fault line in the pre-fault stage as the reference value of the fundamental frequency amplitude of the current, and based on the reference value of the fundamental frequency amplitude of the current, calculating and obtaining the per unit value of the fundamental frequency amplitude of the three-phase current on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage; S5, comparing the per-unit value calculated in step S4 with a preset line break fault discrimination coefficient, if there is a per-unit value smaller than the line break fault discrimination coefficient, it is determined that a line break fault occurs in the line, otherwise it is determined that no line break fault occurs in the line; S6, when a line disconnection fault occurs, the per-unit value calculated in step S4 is compared with a preset grounding discrimination coefficient. If there is a per-unit value greater than the grounding discrimination coefficient, it is determined that the line is grounded after the line disconnection, otherwise it is determined that the line is not grounded after the line disconnection.

2. The method for identifying a power transmission line disconnection fault based on multi-stage current comparison according to claim 1, characterized in that: In step S5, if there is a per-unit value less than the line break fault discrimination coefficient, it is determined that a line break fault has occurred, including: when there is a per-unit value less than the line break fault discrimination coefficient, determining the corresponding phase difference that is less than the per-unit value of the line break fault discrimination coefficient, and judging the occurrence of a line break fault of the corresponding phase difference based on the determined corresponding phase difference.

3. The method for identifying power line disconnection fault based on multi-stage current comparison according to claim 2, characterized in that: If there is a per-unit value smaller than the line-break fault discrimination coefficient, and the smallest per-unit value belongs to the per-unit value of the fundamental frequency amplitude of the A-phase current at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that the line has an A-phase line-break fault; If there is a per-unit value smaller than the line-break fault discrimination coefficient, and the smallest per-unit value belongs to the per-unit value of the fundamental frequency amplitude of the B-phase current at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that a B-phase line-break fault occurs in the line; If there is a per-unit value smaller than the line break fault discrimination coefficient, and the smallest per-unit value belongs to the per-unit value of the C-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, it is determined that a C-phase line break fault has occurred in the line.

4. The method for identifying power line disconnection fault based on multi-stage current comparison according to claim 3, characterized in that: In step S6, for the broken phase determined in step S5, if there is a per-unit value greater than the grounding discrimination coefficient, it is determined that the line is broken and then grounded, including: when there is a per-unit value greater than the grounding discrimination coefficient, the side where the per-unit value greater than the grounding discrimination coefficient is located is determined, and based on the determined side, it is determined that a grounding fault occurred after the line is broken on that side.

5. The method for identifying power line disconnection fault based on multi-stage current comparison according to claim 4, characterized in that: When a phase A line disconnection fault occurs in the line, for phase A, if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase A is disconnected, and grounding is performed after the M side is disconnected; if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase A is disconnected, and grounding is performed after the N side is disconnected; if among all per-unit values ​​greater than the grounding discrimination coefficient, there are both per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and there are also per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase A is disconnected, and grounding is performed after both the M side and the N side are disconnected; When a B-phase line break fault occurs in the line, for phase B, if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase B is broken, and grounding is performed after the M side is broken; if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase B is broken, and grounding is performed after the N side is broken; if among all per-unit values ​​greater than the grounding discrimination coefficient, there are both per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and there are also per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side of both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that phase B is broken, and grounding is performed after both the M side and the N side are broken; When a C-phase line break fault occurs in the line, for phase C, if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that the C-phase is broken, and the ground is connected after the M-side is broken; if all per-unit values ​​greater than the grounding discrimination coefficient belong to the per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that the C-phase is broken, and the ground is connected after the N-side is broken; if among all per-unit values ​​greater than the grounding discrimination coefficient, there are both per-unit values ​​of the three-phase current fundamental frequency amplitude on the M side on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, and there are also per-unit values ​​of the three-phase current fundamental frequency amplitude on the N side on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage, then it is judged that the C-phase is broken, and the ground is connected after both the M side and the N side are broken.

6. The method for identifying power transmission line disconnection fault based on multi-stage current comparison according to claim 5, characterized in that: In step S2, the fault process of the fault line is divided into the steps of a pre-fault stage, a fault stage and a post-reclosing stage, including: Based on the recording data of 0.1-0.5s before the fault and several cycles after the fault recorded by the fault recording device and the protection device, the starting time of the recording data is taken as the starting time of the pre-fault stage, and one cycle is taken backward as the pre-fault stage; Based on the fact that the time from the occurrence of the fault to the issuance of the trip pulse is greater than one cycle, the change time of the trip signal data of the protection device is taken as the end time of the fault stage, and one cycle is taken forward as the fault stage; Based on the reclosing signal sent by the protection device, the starting time of the post-reclosing stage is determined by the changing time of the reclosing signal data and the sudden change of the zero-sequence current data, and one cycle is taken backward as the post-reclosing stage.

7. The method for identifying power line disconnection fault based on multi-stage current comparison according to claim 1, characterized in that: In step S4, based on the reference value of the current fundamental frequency amplitude, the step of calculating and obtaining the per unit value of the three-phase current fundamental frequency amplitude at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage includes: Based on formula (1), the maximum value of the fundamental frequency amplitude of the three-phase current on both sides of the fault line in the pre-fault stage is taken as the reference value of the fundamental frequency amplitude of the current: I Base =max(I MAΙ ,I MBΙ ,I MCΙ ,I NAΙ ,I NBΙ ,I NCΙ )(1) Where: I Base is the reference value of the current fundamental frequency amplitude, I MAΙ ,I MBΙ ,I MCΙ I is the fundamental frequency amplitude of the A, B, and C phase currents on the M side of the fault line before the fault; NAΙ ,I NBΙ ,I NCΙ is the fundamental frequency amplitude of the A, B, and C phase currents on the N side of both sides of the faulty line in the pre-fault stage; Based on formula (2), based on the reference value of the current fundamental frequency amplitude, the per unit value of the three-phase current fundamental frequency amplitude on both sides of the fault line in the pre-fault stage, fault stage and post-reclosing stage is calculated and obtained: Where: X∈{A,B,C} represents the three phases A, B, and C; Indicates the pre-fault stage, fault stage and post-reclosing stage; I Base is the reference value of the current fundamental frequency amplitude; and is the per-unit value set of the fundamental frequency amplitude of the three-phase current on the M side and the N side of the fault line at the pre-fault stage, the fault stage and the post-reclosing stage; and It is the set of three-phase current fundamental frequency amplitudes on the M side and the N side of the fault line in the pre-fault stage, fault stage and post-reclosing stage.

8. A transmission line disconnection fault identification device based on multi-stage current comparison, characterized in that: include: A fault line data extraction unit is configured to extract three-phase current data in the fault line and trip signal data and reclosing signal data of the protection device; A fault process stage division unit is configured to calculate and obtain zero-sequence current data of the fault line based on the extracted three-phase current data, and divide the fault process of the fault line into a pre-fault stage, a fault stage, and a post-reclosing stage based on the obtained zero-sequence current data and the trip signal data and reclosing signal data of the protection device; A current fundamental frequency amplitude acquisition unit is configured to calculate and acquire the three-phase current fundamental frequency amplitudes at both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage based on the extracted three-phase current data; A current fundamental frequency amplitude per unit value acquisition unit is configured to use the maximum value of the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage as a reference value of the current fundamental frequency amplitude, and based on the reference value of the current fundamental frequency amplitude, calculate and acquire the per unit values ​​of the three-phase current fundamental frequency amplitudes on both sides of the fault line in the pre-fault stage, the fault stage and the post-reclosing stage; The line break fault judgment unit is configured to compare the per-unit value calculated and obtained in the current fundamental frequency amplitude per-unit value obtaining unit with a preset line break fault judgment coefficient, and if there is a per-unit value smaller than the line break fault judgment coefficient, it is judged that a line break fault occurs in the line, otherwise it is judged that no line break fault occurs in the line; The grounding judgment unit after a line break fault is constructed to compare the per-unit value calculated and obtained in the current fundamental frequency amplitude per-unit value acquisition unit with a preset grounding judgment coefficient when a line break fault occurs. If there is a per-unit value greater than the grounding judgment coefficient, it is judged that the line is grounded after the line break, otherwise it is judged that the line is not grounded after the line break.

9. An electronic device, characterized in that: It comprises a memory and a processor, the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the power transmission line disconnection fault identification method based on multi-stage current comparison as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program is suitable for being loaded by a processor and executing the power transmission line disconnection fault identification method based on multi-stage current comparison according to any one of claims 1 to 7.

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