Method and system for detecting fault traveling wave head of power distribution network

Abstract

A method and system for detecting a fault traveling wave head of a power distribution network relates to the technical field of traveling wave detection, and the method comprises the steps: constructing a line topological graph for each section of a power distribution line and a connected distributed power supply, and representing electrical equipment comprising a load fluctuation balance unit and a traveling wave detection terminal in the line topological graph; when the distribution line runs, the distribution line distributed power supply switching time and the load fluctuation uniformity degree of each detection point are analyzed, and the type of each section is defined according to an analysis result; the data analysis frequency of the corresponding detection terminal is adjusted according to the type of each paragraph of the distribution line, and the condition that a single parameter in each paragraph exceeds a set value is independently processed; the detection result of the fault traveling wave signal is judged, if the wave head of the fault traveling wave signal is not captured or recognized after the fault occurs, the data analysis frequency of the system is improved, and the traveling wave head signal is analyzed by adopting an auxiliary judgment method. The method has the advantages of being accurate in detection and low in operation and maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of traveling wave detection technology, specifically a method for detecting the traveling wave front of a distribution network fault. Background Technology

[0002] In power systems, when a short circuit or fault occurs, fluctuations in current and voltage propagate through conductors as traveling waves. This wave is a transient fluctuation, often referred to as the fault traveling wave front. By performing phase analysis on the wavefront signals at different locations, the arrival time of the wavefront at each terminal can be determined, thereby calculating the fault location.

[0003] However, when the fault wavefront propagates in the line, it will inevitably be slightly reflected by some equipment. Some of the reflected waves will overlap with the original fault wave, which may lead to an incorrect judgment of the arrival time of the traveling wave, and thus affect the calculation of the fault location.

[0004] With the continuous use of distribution networks (especially the increase in distributed power generation grid connection and off-grid operations on distribution lines), the introduced harmonics will cause more frequent faults. The increasing load fluctuations caused by equipment aging will also lead to more severe interference from detected reflected waves. Therefore, it is necessary to increase the analysis data frequency of the detection terminals to capture more subtle transient waveform characteristics. For different detection terminals, there is a suitable range for the analysis data frequency, and it should not be set too high initially. Existing methods for adjusting the analysis data frequency involve periodically replacing all detection terminals on the distribution network frame, or individually replacing unsuitable terminals. However, the analysis data frequency of the detection terminals does not meet current needs, and the latter has excessively high maintenance costs. Therefore, it is essential to design a method for detecting the traveling wave front of distribution network faults that is both accurate and has low maintenance costs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting the traveling wave front of a fault in a power distribution network, so as to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for detecting the traveling wave front of a distribution network fault includes the following steps:

[0007] S1. Construct a line topology diagram by combining each section of the power distribution line and the connected distributed power sources, and represent the electrical equipment, including the load fluctuation balancing unit and the traveling wave detection terminal, in the line topology diagram.

[0008] S2. During the operation of the power distribution line, analyze the switching time of the distributed power source and the uniformity of load fluctuation at each detection point, and define the type of each segment based on the analysis results;

[0009] S3. Adjust the data analysis frequency of the corresponding detection terminal according to the type of each section of the power distribution line, and handle the case where a single parameter in the section exceeds the set value separately.

[0010] S4. Judge the detection results of the fault traveling wave signal. If the fault traveling wave signal wavehead is not captured or identified after the fault occurs, increase the system analysis data frequency F and use auxiliary judgment methods to analyze the traveling wave wavehead signal.

[0011] As a further optimized technical solution, the specific method for defining the type of each paragraph in S2 is as follows:

[0012] S2-1. Analyze the switching time of distributed power sources on the distribution lines and the uniformity of load fluctuations at each detection point. Record the time of each grid connection and off-grid operation and calculate the switching time Δj of the distributed power sources on the distribution lines. When Δj is greater than the critical value j min When this occurs, the power distribution line in this segment is defined as a potential interference segment. The variance of the load fluctuation amplitude f is collected for calculation. A sequence {f1, f2…f} is obtained by collecting data n times within the collection period. n}, and calculate the average value Δf of the series, if the variance of the load fluctuation range f is If the value is greater than the set value X, then this paragraph is determined to be an affected paragraph, where f i Let be any term in the sequence;

[0013] S2-2, When the switching time Δj of the distributed power source of a power distribution line at a certain detection point is less than the critical value j min If so, this section of the power distribution line is defined as a potentially normal section. If the value is less than the set value X, then this paragraph is considered a normal paragraph.

[0014] As a further optimized technical solution, the specific method for adjusting the data analysis frequency in S3 is as follows:

[0015] S3-1. Locate the affected segment in the line topology image, increase the data frequency F of the detection terminal for this segment, and increase the magnitude of the increase is positively correlated with both Δj and A. Specifically, F = [1 + kAln(Δj + 1)]F0, where F0 is the initial value of the data frequency and k is the amplitude adjustment coefficient.

[0016] S3-2. Locate the normal segment in the line topology image, and reduce the frequency F of the detection terminal analysis data in this area. The magnitude of the reduction is negatively correlated with both Δj and A. Specifically:

[0017] As a further optimized technical solution, in S2-1 and S2-2, if Δj is detected to be less than the critical value j minIn the case where A > X, at this time F remains unchanged, it is necessary to increase the output power Q of the load fluctuation balancing unit carried by the distributed power source connected to the power distribution line in this paragraph during the low valley of the power consumption load. That is, when Q0 = Q min , Q = Q0 + μA, and reduce the output power Q during the peak of the power consumption load. That is, when Q0 = Q max , Q = Q0 - μA to balance the power consumption load fluctuation. Where Q0 is the output power before adjustment, μ is the output power adjustment coefficient. If it is detected that Δj is greater than the critical value j min and in the case where A < X, it is determined that the abnormal increase of the distributed power source grid connection and off-grid operation occurs, then disconnect the distributed power source connected to the power distribution line in this paragraph, and all use the power supply of the power grid itself until it is detected that A > X and then connect the distributed power source.

[0018] As a further optimized technical solution, in S4, if the fault traveling wave signal wavefront still cannot be accurately identified after improvement, the following processing method is adopted:

[0019] S4-1. For the equipment configured with the reclosing function, utilize the specific traveling wave after the reclosing delay of the equipment to coincide with the fault wave, capture the fault wave and the specific traveling wave signal after the reclosing, and judge the starting position of the fault wave;

[0020] S4-2. For the equipment without the reclosing function, manually remotely cut off the small load at the end of the line to cause the line load fluctuation, and use the fluctuation signal caused by the cut-off point as the specific traveling wave signal to determine the fault position.

[0021] As a further optimized technical solution, in S4-1 and S4-2, the reclosing is delayed and opened and closed multiple times, and the small load at the end of the line is cut off, and the high-frequency traveling wave current data is sampled. At the reclosing equipment and the small load, the specific traveling wave that exactly overlaps with the fault wavefront is captured. After filtering, denoising and decomposition of the sampled data, the original fault wave without the reflected wave is obtained, and the local entropy H of the S transform of the time-frequency matrix is calculated local To judge the real wavefront, the formula is: where M h is the upper limit of the frequency range, M l is the lower limit of the frequency range, S(t, M) is the energy density value of the time-frequency matrix, logS(t, M) represents taking the logarithm of the energy density value of the time-frequency matrix, and at the real wavefront H local < H0, H0 is the high-frequency energy threshold. To judge the position where the real wavefront is located, knowing the position of the real wavefront of the specific traveling wave in the line topology diagram and the reclosing opening and closing time, calculate the propagation speed of the fault wave and the position of the fault wavefront, and deduce the starting position of the fault wave.

[0022] The present invention also provides a detection system for the traveling wave front of a power distribution network fault, including an information acquisition module, a detection and adjustment module, and an auxiliary judgment module;

[0023] The information acquisition module is used to collect data on load fluctuations and distributed power generation switching times of power distribution lines, and to construct a line topology diagram of each section of the power distribution line and the connected distributed power generation. The electrical equipment, including the load fluctuation balancing unit and the traveling wave detection terminal, is represented in the line topology diagram.

[0024] The detection and adjustment module is used to analyze the switching time of distributed power sources and the uniformity of load fluctuations at each detection point of the power distribution line during operation based on the collected data. It defines the type of each segment based on the analysis results, adjusts the data analysis frequency of the corresponding detection terminal according to the type of each segment of the power distribution line, and handles the case where a single parameter in a segment exceeds the set value separately.

[0025] The auxiliary judgment module is used to judge the detection results of the fault traveling wave signal. If the fault traveling wave signal wavehead is not captured or identified after the fault occurs, the system analysis data frequency F is increased, and auxiliary judgment methods such as manual processing methods are used to analyze the traveling wave wavehead signal.

[0026] As a further optimized technical solution, the information acquisition module includes a grid-connected and off-grid recording module, a load fluctuation acquisition module, a distributed power source, a line topology module, a traveling wave detection terminal, and a load fluctuation balancing unit. The grid-connected and off-grid recording module is electrically connected to the distributed power source, and the line topology module is electrically connected to the traveling wave detection terminal. The grid-connected and off-grid recording module is used to record the grid-connected and off-grid operations of the distributed power source corresponding to each power distribution line segment. The load fluctuation acquisition module is used to acquire the load fluctuations of the load connected to the power distribution line segment. The distributed power source is used to provide power to the power distribution line using distributed power supply. The line topology module is used to generate topology images of each power distribution line segment. The traveling wave detection terminal is used to detect the traveling wave signal of the fault wave to locate the fault location. The load fluctuation balancing unit is used to adjust the power of the distributed power source of the power distribution line to cope with load fluctuations and reduce the interference of reflected waves.

[0027] The detection and adjustment module includes an analysis data frequency adjustment module, a load fluctuation analysis module, a judgment result input module, an output power adjustment module, and a parameter judgment module. The analysis data frequency adjustment module and the parameter judgment module are electrically connected, and the output power adjustment module is electrically connected to the load fluctuation balancing unit. The load fluctuation analysis module is used to analyze the amplitude of load fluctuations. The judgment result input module is used to input the judgment result of the fault wave location after on-site detection. The output power adjustment module is used to adjust the output power of the load fluctuation balancing unit. The parameter judgment module is used to determine whether the switching time of the distributed power source and the load fluctuation amplitude exceed the set value.

[0028] The auxiliary judgment module includes a reclosing control module, a low-load triggering module, and a fault location module. The reclosing control module and the low-load triggering module are electrically connected to the judgment result input module and the fault location module. The fault location module is used to locate the fault wave using auxiliary means. The reclosing control module is used to control the reclosing operation of equipment configured with reclosing function. The low-load triggering module is used to use low load to assist in judging the traveling wave initiation point of equipment without reclosing function.

[0029] As a further optimized technical solution, the specific method for defining the type of each paragraph is as follows:

[0030] S2-1. Analyze the switching time of distributed power sources on the distribution lines and the uniformity of load fluctuations at each detection point. Record the time of each grid connection and off-grid operation and calculate the switching time Δj of the distributed power sources on the distribution lines. When Δj is greater than the critical value j min When this occurs, the power distribution line in this segment is defined as a potential interference segment. The variance of the load fluctuation amplitude f is collected for calculation. A sequence {f1, f2…f} is obtained by collecting data n times within the collection period. n}, and calculate the average value Δf of the series, if the variance of the load fluctuation range f is If the value is greater than the set value X, then this paragraph is determined to be an affected paragraph, where f i Let be any term in the sequence;

[0031] S2-2, When the switching time Δj of the distributed power source of a power distribution line at a certain detection point is less than the critical value j min If so, this section of the power distribution line is defined as a potentially normal section. If the value is less than the set value X, then this paragraph is considered a normal paragraph.

[0032] The specific method for adjusting the data analysis frequency is as follows:

[0033] S3-1. Locate the disturbed section position in the line topology image, increase the analysis data frequency F of the detection terminal for this section. The increased amplitude is positively correlated with both Δj and A. Specifically, F = [1 + kAln(Δj + 1)]F0, where F0 is the initial value of the data frequency and k is the amplitude adjustment coefficient;

[0034] S3-2. Locate the normal section position in the line topology image, decrease the analysis data frequency F of the detection terminal for this area. The decreased amplitude is negatively correlated with both Δj and A. Specifically,

[0035] As a further optimized technical solution, if increasing the system analysis data frequency F still fails to accurately identify the wave head of the fault traveling wave signal, the following processing methods are adopted:

[0036] S4-1. For the equipment configured with the reclosing function, utilize the specific traveling wave after the delayed reclosing of the equipment to coincide with the fault wave, capture the fault wave and the specific traveling wave signal after the coincidence, and judge the starting position of the fault wave;

[0037] S4-2. For the equipment not configured with the reclosing function, manually remotely cut off the small load at the end of the line to cause line load fluctuations, and use the fluctuation signal caused by the cut-off point as the specific traveling wave signal to determine the fault position;

[0038] Among them, the reclosing is delayed and opened and closed multiple times, and the small load at the end of the line is cut off. The high-frequency traveling wave current data is sampled, and the specific traveling wave that happens to be aliased with the fault wave head is captured at the reclosing equipment and the small load. After filtering, denoising and decomposition of the sampled data, the original fault wave without the reflected wave is obtained, and the local entropy H of the S transform of the time-frequency matrix is calculated local Judge the real wave head. The formula is: Where M h is the upper limit of the frequency range, M l is the lower limit of the frequency range, S(t, M) is the energy density value of the time-frequency matrix, logS(t, M) represents taking the logarithm of the energy density value of the time-frequency matrix, and at the real wave head, H local < H0, H0 is the high-frequency energy threshold. Judge the position of the real wave head. Given the position of the real wave head of the specific traveling wave in the line topology diagram and the reclosing time, calculate the propagation speed of the fault wave and the position of the fault wave head, and deduce the starting position of the fault wave.

[0039] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention, by statistically analyzing the switching time of distributed power sources in the distribution line and the detected load fluctuation amplitude, can estimate the interference level of reflected waves, and adaptively adjust the analysis data frequency of the detection terminals of different distribution lines on the distribution network frame, so that the analysis data frequency can better match the current needs, and reduce false alarms of traveling waves caused by load fluctuations and distributed power source grid connection and disconnection.

[0040] Based on the cases where the load fluctuation amplitude and distributed power supply switching time of each segment exceed the set value individually, targeted processing is carried out to keep the frequency of data analysis as unchanged as possible, thus avoiding the risk of diminishing marginal effects caused by simply increasing the frequency of data analysis. Attached Figure Description

[0041] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0042] Figure 1 This is a schematic diagram of the overall modular structure of the present invention.

[0043] Figure 2 This is a flowchart of the method for detecting the traveling wave front of a power distribution network fault according to the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Please see Figure 1 This invention provides a method for detecting the traveling wave front of a distribution network fault, which employs a distribution network fault traveling wave front detection system. The system includes an information acquisition module, a detection and adjustment module, and an auxiliary judgment module.

[0046] The information acquisition module collects data on load fluctuations and distributed power source switching times of power distribution lines, and constructs a line topology map of each section of the power distribution line and the connected distributed power sources. Electrical equipment, including the load fluctuation balancing unit and the traveling wave detection terminal, is represented in the line topology map. The information acquisition module includes a grid-connected / off-grid recording module, a load fluctuation acquisition module, distributed power sources, a line topology module, a traveling wave detection terminal, and a load fluctuation balancing unit. The grid-connected / off-grid recording module is electrically connected to the distributed power sources, and the line topology module is electrically connected to the traveling wave detection terminal. The grid-connected / off-grid recording module records the grid-connected and off-grid operations of the distributed power sources corresponding to each power distribution line section. The load fluctuation acquisition module collects load fluctuations of the loads connected to the power distribution line sections. The distributed power sources provide power to the power distribution lines using distributed power supply. The line topology module generates topology images of each section of the power distribution line. The traveling wave detection terminal detects traveling wave signals of fault waves to locate the fault location. The load fluctuation balancing unit regulates the power of the distributed power sources in the power distribution line to cope with load fluctuations and reduce interference from reflected waves.

[0047] The detection and adjustment module is used to analyze the switching time of distributed power sources and the uniformity of load fluctuations at various detection points of the power distribution line during operation, based on the collected data. It defines the type of each segment based on the analysis results and adjusts the data analysis frequency of the corresponding detection terminal according to the type of each segment. It also handles cases where a single parameter in a segment exceeds a set value individually. The detection and adjustment module includes an analysis data frequency adjustment module, a load fluctuation analysis module, a judgment result input module, an output power adjustment module, and a parameter judgment module. The analysis data frequency adjustment module and the parameter judgment module are electrically connected, and the output power adjustment module is electrically connected to the load fluctuation balancing unit. The load fluctuation analysis module analyzes the amplitude of load fluctuations. The judgment result input module inputs the judgment results of the fault wave location after on-site detection. The output power adjustment module adjusts the output power of the load fluctuation balancing unit, and the parameter judgment module determines whether the switching time of distributed power sources and the amplitude of load fluctuations exceed set values.

[0048] The auxiliary judgment module is used to judge the detection results of the fault traveling wave signal. If the fault traveling wave signal wavehead cannot be captured or identified after the fault occurs, the system analysis data frequency F is increased, and auxiliary judgment methods, such as manual processing, are used to analyze the traveling wave wavehead signal. The auxiliary judgment module includes a reclosing control module, a low-load triggering module, and a fault location module. The reclosing control module and the low-load triggering module are electrically connected to the judgment result input module and the fault location module. The fault location module is used to locate the fault wave using auxiliary means. The reclosing control module is used to control the reclosing operation of equipment configured with reclosing function. The low-load triggering module is used to use a low load to assist in judging the traveling wave initiation point for equipment without reclosing function.

[0049] The method for detecting the traveling wave front of a distribution network fault includes the following steps:

[0050] S1. Construct a line topology diagram by combining each section of the power distribution line and the connected distributed power sources, and represent the electrical equipment, including the load fluctuation balancing unit and the traveling wave detection terminal, in the line topology diagram.

[0051] S2. During the operation of the power distribution line, analyze the switching time of the distributed power source and the uniformity of load fluctuation at each detection point, and define the type of each segment based on the analysis results;

[0052] S3. Adjust the data analysis frequency of the corresponding detection terminal according to the type of each section of the power distribution line, and handle the case where a single parameter in the section exceeds the set value separately.

[0053] S4. Judge the detection results of the fault traveling wave signal. If the fault traveling wave signal wavehead is not captured or identified after the fault occurs, increase the system analysis data frequency F and use auxiliary judgment methods to analyze the traveling wave wavehead signal.

[0054] In S2, the specific way to define the type of each paragraph is as follows:

[0055] S2-1. Analyze the switching time of distributed power sources on the distribution lines and the uniformity of load fluctuations at each detection point. Record the time of each grid connection and off-grid operation and calculate the switching time Δj of the distributed power sources on the distribution lines. When Δj is greater than the critical value j min When this occurs, the power distribution line in this segment is defined as a potential interference segment. The variance of the load fluctuation amplitude f is collected for calculation. A sequence {f1, f2…f} is obtained by collecting data n times within the collection period. n}, and calculate the average value Δf of the series, if the variance of the load fluctuation range f is If the value is greater than the set value X, then this paragraph is determined to be an affected paragraph, where f i Let be any term in the sequence;

[0056] S2-2. When the switching time Δj of the distributed power source of the power distribution line at a certain detection point is less than the critical value j min then define the power distribution line of this paragraph as a potentially normal paragraph. If it is less than the set value X, then determine that this paragraph is a normal paragraph; by screening two parameters of the paragraph, increase the analysis frequency in the dangerous paragraph and decrease the analysis frequency in the safe paragraph, which can save computing resources and will not cause the analysis frequency to be set too high at the beginning.

[0057] In S3, the specific method for adjusting the data analysis frequency is as follows:

[0058] S3-1. Find the position of the disturbed paragraph in the line topology image, increase the data analysis frequency F of the detection terminal of this paragraph. The increased amplitude is positively correlated with both Δj and A. Specifically, F = [1 + kAln(Δj + 1)]F0, where F0 is the initial value of the data frequency and k is the amplitude adjustment coefficient;

[0059] S3-2. Find the position of the normal paragraph in the line topology image, decrease the data analysis frequency F of the detection terminal of this area. The decreased amplitude is negatively correlated with both Δj and A. Specifically,

[0060] In S2-1 and S2-2, if it is detected that Δj is less than the critical value j min and A > X, in this case, F remains unchanged. It is necessary to increase the output power Q of the load fluctuation balance unit carried by the distributed power source connected to the power distribution line of this paragraph at the low valley of the power consumption load, that is, when Q0 = Q min then Q = Q0 + μA, and decrease the output power Q at the peak of the power consumption load, that is, when Q0 = Q max then Q = Q0 - μA, to balance the power consumption load fluctuation. Here, Q0 is the output power before adjustment, μ is the output power adjustment coefficient. If it is detected that Δj is greater than the critical value j min and A < X, then it is judged that the abnormal increase of the grid connection and off-grid operation of the distributed power source occurs, and disconnect the distributed power source connected to the power distribution line of this paragraph, and all use the power supply of the power grid itself until it is detected that A > X and then connect the distributed power source; only when both exceed the set value will F be changed. In other cases, adopt a targeted optimization strategy to make Δj and A increase asynchronously as much as possible, and avoid changing F due to a single factor.

[0061] In S4, if the fault traveling wave signal wavefront still cannot be accurately identified after improvement, adopt the following processing method:

[0062] S4-1. For the equipment configured with the reclosing function, utilize the specific traveling wave after the delayed reclosing of the equipment to coincide with the fault wave, capture the fault wave and the specific traveling wave signal after reclosing, and judge the starting position of the fault wave.

[0063] S4-2. For the equipment without the reclosing function, manually remotely cut off the small load at the end of the line to cause load fluctuations on the line, and use the fluctuation signal caused by the cut-off point as the specific traveling wave signal to determine the fault location.

[0064] In S4-1 and S4-2, repeatedly delay the opening and closing of the reclosing and cut off the small load at the end of the line, sample the high-frequency traveling wave current data, capture the specific traveling wave that exactly overlaps with the fault wave head at the reclosing equipment and the small load, and after filtering, denoising and decomposing the sampled data, obtain the original fault wave without reflected waves, and calculate the local entropy H of the S transform of the time-frequency matrix. local Judge the true wave head, and the formula is: where M h is the upper limit of the frequency range, M l is the lower limit of the frequency range, S(t,M) is the energy density value of the time-frequency matrix, logS(t,M) represents taking the logarithm of the energy density value of the time-frequency matrix, and at the true wave head, H local < H0, H0 is the high-frequency energy threshold, judge the position of the true wave head, knowing the position of the true wave head of the specific traveling wave in the line topology diagram and the reclosing time of opening and closing, calculate the propagation speed of the fault wave and the position of the fault wave head, and deduce the starting position of the fault wave. The interference caused by the overlap of the reflected wave and the original fault wave can be offset by the artificially created traveling wave overlap phenomenon, and the reflected wave in the current line is eliminated to make the data analysis of the detection terminal more accurate, and the service life of the detection terminal is improved on the premise of尽可能 reducing the data analysis frequency.

[0065] By substituting the known parameters to obtain the corrected operation relationship and then obtain the unknown parameters, this method can correct the errors of the detection terminal. Since the correction will only be carried out under the above premise, it will not cause excessive reclosing and small load cut-off operations, and keep the load stable in the distribution line.

[0066] By counting the switching time of the distributed power source on the distribution line and the detected load fluctuation amplitude, estimate the interference degree of the reflected wave, and adaptively adjust the analysis data frequency of the detection terminals on different distribution lines of the distribution network framework, so that the analysis data frequency can better match the current requirements and reduce the traveling wave false alarms caused by load fluctuations and the grid connection and disconnection of distributed power sources.

[0067] Based on the cases where the load fluctuation amplitude and distributed power supply switching time of each segment exceed the set value individually, targeted processing is carried out to keep the frequency of data analysis as unchanged as possible, thus avoiding the risk of diminishing marginal effects caused by simply increasing the frequency of data analysis.

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting the traveling wave front of a distribution network fault, characterized in that: Includes the following steps: S1. Construct a line topology diagram by combining each section of the power distribution line with the connected distributed power sources, and represent the electrical equipment, including the load fluctuation balancing unit and the traveling wave detection terminal, in the line topology diagram. S2. During the operation of the power distribution line, analyze the switching time of the distributed power source and the uniformity of load fluctuation at each detection point, and define the type of each segment based on the analysis results; S3. Adjust the data analysis frequency of the corresponding detection terminal according to the type of each section of the power distribution line, and handle the case where a single parameter in the section exceeds the set value separately. S4. Judge the detection results of the fault traveling wave signal. If the fault traveling wave signal wavehead is not captured or identified after the fault occurs, increase the system analysis data frequency F and use auxiliary judgment methods to analyze the traveling wave wavehead signal.

2. The method for detecting the traveling wave front of a distribution network fault according to claim 1, characterized in that: In S2, the specific method for defining the type of each paragraph is as follows: S2-1. Analyze the switching time of distributed power sources on the distribution lines and the uniformity of load fluctuations at each detection point. Record the time of each grid connection and off-grid operation and calculate the switching time Δj of the distributed power sources on the distribution lines. When Δj is greater than the critical value j min When this occurs, the power distribution line in this segment is defined as a potential interference segment. The variance of the load fluctuation amplitude f is collected for calculation. A sequence {f1, f2…f} is obtained by collecting data n times within the collection period. n }, and calculate the average value Δf of the series, if the variance of the load fluctuation range f is If the value is greater than the set value X, then this paragraph is determined to be an affected paragraph, where f i Let be any term in the sequence; S2-2, When the switching time Δj of the distributed power source of a power distribution line at a certain detection point is less than the critical value j min If so, this section of the power distribution line is defined as a potentially normal section. If the value is less than the set value X, then this paragraph is considered a normal paragraph.

3. The method for detecting the traveling wave front of a distribution network fault according to claim 2, characterized in that: In S3, the specific method for adjusting the data analysis frequency is as follows: S3-1. Locate the affected segment in the line topology image, increase the data frequency F of the detection terminal for this segment, and increase the magnitude of the increase is positively correlated with both Δj and A. Specifically, F = [1 + kAln(Δj + 1)]F0, where F0 is the initial value of the data frequency and k is the amplitude adjustment coefficient. S3-2. Locate the normal segment in the line topology image, and reduce the frequency F of the detection terminal analysis data in this area. The magnitude of the reduction is negatively correlated with both Δj and A. Specifically:

4. The method for detecting the traveling wave front of a distribution network fault according to claim 3, characterized in that: In S2-1 and S2-2, if it is detected that Δj is less than the critical value j min and A > X, at this time, F remains unchanged, and it is necessary to increase the output power Q of the load fluctuation balancing unit carried by the distributed power source connected to the distribution line of this paragraph during the low valley of the power consumption load, that is, when Q0 = Q min Q = Q0 + μA, and reduce the output power Q during the peak of the power consumption load, that is, when Q0 = Q max Q = Q0 - μA to balance the power consumption load fluctuation, where Q0 is the output power before adjustment, and μ is the output power adjustment coefficient. If it is detected that Δj is greater than the critical value j min and A < X, it is determined that the abnormal increase of the grid connection and off-grid operation of the distributed power source occurs, then the distributed power source connected to the distribution line of this paragraph is disconnected, and the power grid itself is used for power supply until it is detected that A > X and then the distributed power source is connected again.

5. The method for detecting the traveling wave front of a distribution network fault according to claim 4, characterized in that: In step S4, if the fault traveling wave signal front still cannot be accurately identified after the improvement, the following processing method is adopted: S4-1. For equipment configured with reclosing function, the specific traveling wave after the equipment delays reclosing overlaps with the fault wave, and the fault wave and the specific traveling wave signal after reclosing are captured to determine the starting position of the fault wave. S4-2. For equipment without reclosing function, a small load at the end of the line is manually disconnected by remote control, causing line load fluctuation. The fluctuation signal caused by the disconnection point is used as a specific traveling wave signal to determine the fault location.

6. The method for detecting the traveling wave front of a distribution network fault according to claim 5, characterized in that: In S4-1 and S4-2, the reclosing with multiple time delays and the disconnection of small loads at the end of the line are performed. High-frequency traveling wave current data are sampled, and specific traveling waves that happen to be aliased with the fault wavefront are captured at the reclosing device and the small load. After filtering, denoising, and decomposing the sampled data, the original fault wave without reflected waves is obtained, and the local entropy H of the S transform of the time-frequency matrix is calculated. local Judge the true wavefront. The formula is: Where M h is the upper limit of the frequency range, M l is the lower limit of the frequency range, S(t,M) is the energy density value of the time-frequency matrix, logS(t,M) represents taking the logarithm of the energy density value of the time-frequency matrix, and at the true wavefront, H local < H0, where H0 is the high-frequency energy threshold. Judge the position of the true wavefront. Given the position of the true wavefront of the specific traveling wave in the line topology diagram and the reclosing time, calculate the propagation speed and the position of the fault wavefront of the fault wave, and deduce the starting position of the fault wave.

7. A system for detecting the traveling wave front of a distribution network fault, characterized in that: It includes an information collection module, a detection and adjustment module, and an auxiliary judgment module; The information acquisition module is used to collect data on load fluctuations and distributed power generation switching times of power distribution lines, and to construct a line topology diagram of each section of the power distribution line and the connected distributed power generation. The electrical equipment, including the load fluctuation balancing unit and the traveling wave detection terminal, is represented in the line topology diagram. The detection and adjustment module is used to analyze the switching time of distributed power sources and the uniformity of load fluctuations at each detection point of the power distribution line during operation based on the collected data. It defines the type of each segment based on the analysis results, adjusts the data analysis frequency of the corresponding detection terminal according to the type of each segment of the power distribution line, and handles the case where a single parameter in a segment exceeds the set value separately. The auxiliary judgment module is used to judge the detection results of the fault traveling wave signal. If the fault traveling wave signal wavehead is not captured or identified after the fault occurs, the system analysis data frequency F is increased, and auxiliary judgment methods such as manual processing methods are used to analyze the traveling wave wavehead signal.

8. The distribution network fault traveling wave front detection system according to claim 7, characterized in that: The information acquisition module includes a grid-connected and off-grid recording module, a load fluctuation acquisition module, a distributed power source, a line topology module, a traveling wave detection terminal, and a load fluctuation balancing unit. The grid-connected and off-grid recording module is electrically connected to the distributed power source, and the line topology module is electrically connected to the traveling wave detection terminal. The grid-connected and off-grid recording module is used to record the grid-connected and off-grid operations of the distributed power source corresponding to each power distribution line segment. The load fluctuation acquisition module is used to acquire the load fluctuations of the loads connected to the power distribution line segments. The distributed power source is used to provide power to the power distribution line using distributed power supply. The line topology module is used to generate topology images of each power distribution line segment. The traveling wave detection terminal is used to detect the traveling wave signal of the fault wave to locate the fault location. The load fluctuation balancing unit is used to adjust the power of the distributed power source of the power distribution line to cope with load fluctuations and reduce the interference of reflected waves. The detection and adjustment module includes an analysis data frequency adjustment module, a load fluctuation analysis module, a judgment result input module, an output power adjustment module, and a parameter judgment module. The analysis data frequency adjustment module and the parameter judgment module are electrically connected, and the output power adjustment module is electrically connected to the load fluctuation balancing unit. The load fluctuation analysis module is used to analyze the amplitude of load fluctuations. The judgment result input module is used to input the judgment result of the fault wave location after on-site detection. The output power adjustment module is used to adjust the output power of the load fluctuation balancing unit. The parameter judgment module is used to determine whether the switching time of the distributed power source and the load fluctuation amplitude exceed the set value. The auxiliary judgment module includes a reclosing control module, a low-load triggering module, and a fault location module. The reclosing control module and the low-load triggering module are electrically connected to the judgment result input module and the fault location module. The fault location module is used to locate the fault wave using auxiliary means. The reclosing control module is used to control the reclosing operation of equipment configured with reclosing function. The low-load triggering module is used to use low load to assist in judging the traveling wave initiation point of equipment without reclosing function.

9. The distribution network fault traveling wave front detection system according to claim 7, characterized in that: The specific way to define the type of each paragraph is as follows: S2-1. Analyze the switching time of distributed power sources on the distribution lines and the uniformity of load fluctuations at each detection point. Record the time of each grid connection and off-grid operation and calculate the switching time Δj of the distributed power sources on the distribution lines. When Δj is greater than the critical value j nin When this occurs, the power distribution line in this segment is defined as a potential interference segment. The variance of the load fluctuation amplitude f is collected for calculation. A sequence {f1, f2…f} is obtained by collecting data n times within the collection period. n }, and calculate the average value Δf of the series, if the variance of the load fluctuation range f is If the value is greater than the set value X, then this paragraph is determined to be an affected paragraph, where f i Let be any term in the sequence; S2-2, When the switching time Δj of the distributed power source of a power distribution line at a certain detection point is less than the critical value j min If so, this section of the power distribution line is defined as a potentially normal section. If the value is less than the set value X, then this paragraph is considered a normal paragraph. The specific method for adjusting the data analysis frequency is as follows: S3-1. Locate the affected segment in the line topology image, increase the data frequency F of the detection terminal for this segment, and increase the magnitude of the increase is positively correlated with both Δj and A. Specifically, F = [1 + kAln(Δj + 1)]F0, where F0 is the initial value of the data frequency and k is the amplitude adjustment coefficient. S3-2. Locate the normal segment in the line topology image, and reduce the frequency F of the detection terminal analysis data in this area. The magnitude of the reduction is negatively correlated with both Δj and A. Specifically:

10. The distribution network fault traveling wave front detection system according to claim 9, characterized in that: If increasing the system analysis data frequency F still fails to accurately identify the fault traveling wave signal front, the following processing method should be adopted: S4-1. For equipment configured with reclosing function, the specific traveling wave after the equipment delays reclosing overlaps with the fault wave, and the fault wave and the specific traveling wave signal after reclosing are captured to determine the starting position of the fault wave. S4-2. For equipment without reclosing function, a small load at the end of the line is manually disconnected by remote control, causing line load fluctuation. The fluctuation signal caused by the disconnection point is used as a specific traveling wave signal to determine the fault location. Among them, for multiple delayed closing and reclosing and cutting off small loads at the end of the line, high-frequency traveling wave current data is sampled, and specific traveling waves that happen to be aliased with the fault wavefront are captured at the reclosing device and the small load. After filtering, denoising, and decomposing the sampled data, the original fault wave without reflected waves is obtained, and the local entropy H of the S transform of the time-frequency matrix is calculated local Judge the true wavefront. The formula is: Where M h Is the upper limit of the frequency range, M l Is the lower limit of the frequency range, S(t, M) is the energy density value of the time-frequency matrix, logS(t, M) represents taking the logarithm of the energy density value of the time-frequency matrix, and at the true wavefront, H local < H0, where H0 is the high-frequency energy threshold. Judge the position of the true wavefront. Given the position of the true wavefront of the specific traveling wave in the line topology diagram and the reclosing time, calculate the propagation speed and the position of the fault wavefront of the fault wave, and deduce the starting position of the fault wave.

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