Direct current system ground fault positioning method and device

Abstract

The invention provides a DC system grounding fault positioning method and device, and relates to the technical field of DC power transmission system power transmission line protection, and the method comprises the steps: S1, collecting the bus voltage in a DC system circuit and the leakage current in each circuit loop in real time; s2, judging whether the collected leakage current exceeds a preset current threshold value or not, and if yes, executing the step S3; otherwise, not processing; s3, judging whether the change value of the bus voltage collected within a preset duration from the current moment exceeds a preset voltage change quantity threshold value or not, and if yes, judging the loop with the leakage current exceeding the preset threshold value as the loop with the grounding fault in the direct current system circuit, and if not, judging the loop with the leakage current exceeding the preset threshold value as the loop with the grounding fault in the direct current system circuit; otherwise, no processing is carried out. On the basis of judging whether the leakage current in each circuit loop is abnormal or not, the loop with the grounding fault is comprehensively confirmed according to the change value of the bus voltage within the preset duration, and the accuracy and efficiency of grounding fault detection are improved.

Description

Technical Field

[0001] This invention relates to the field of power line protection technology for DC power transmission systems, specifically to a method and apparatus for locating ground faults in DC systems. Background Technology

[0002] In power systems, DC systems serve as crucial auxiliary power sources, widely applied in high-voltage direct current (HVDC) transmission, subway traction, marine systems, and communication systems. The stable operation of DC systems directly impacts the safety and reliability of these applications. DC system grounding faults are common power failures. Once they occur, they can damage equipment and trigger malfunctions or failures to operate protection devices, severely impacting the safe operation of the power system. Therefore, quickly and accurately locating DC system grounding faults is of paramount importance for the stable operation of the power system.

[0003] Existing methods for detecting grounding faults in DC systems primarily rely on DC sensors to determine potential grounding locations based on on-site operating conditions, operational status, and weather conditions. Following a principle of gradually narrowing down the search area from outdoor to indoor locations, from main power supply to branch power supply, this method involves sequentially disconnecting each branch power supply in the DC system and observing whether the grounding phenomenon disappears. This method is time-consuming, especially in large and complex DC systems, resulting in low detection efficiency. Furthermore, due to the complexity and diversity of DC systems, relying solely on on-site operating conditions, operational status, and weather conditions to determine the grounding point may not be accurate enough, easily leading to misjudgments or missed detections. This is a shortcoming of existing technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method and apparatus for locating ground faults in a DC system. It simultaneously collects the bus voltage and leakage current in each circuit of the DC system. Based on determining whether there are abnormalities in the leakage current in each circuit, it comprehensively identifies the circuit experiencing a ground fault based on the change in the bus voltage over a preset time period, thereby improving the accuracy and efficiency of ground fault detection.

[0005] In a first aspect, the present invention provides a method for locating ground faults in a DC system, the method comprising: S1. Real-time acquisition of bus voltage and leakage current in each circuit loop of the DC system circuit; S2. Determine whether the leakage current in each circuit loop exceeds the preset current threshold. If the leakage current in each circuit loop exceeds the preset current threshold, proceed to step S3; otherwise, do not process it. S3. Determine whether the change value of the bus voltage collected within the preset time period from the current moment exceeds the preset voltage change threshold. If the change value of the bus voltage collected within the preset time period exceeds the preset voltage change threshold, then the circuit loop with leakage current exceeding the preset threshold is identified as a circuit loop with a ground fault in the DC system circuit and displayed; otherwise, no action is taken.

[0006] Further, step S3 includes: When the leakage current of only one circuit loop exceeds the preset threshold, that circuit loop will be identified as having a ground fault and displayed. When the leakage current of multiple circuit loops exceeds a preset threshold, based on the leakage current of each circuit loop collected within the preset time period, a leakage current curve for each circuit loop within the preset time period is generated. The slope of the leakage current curve of each circuit loop at the current time point is calculated. Based on the bus voltage collected within the preset time period, a bus voltage curve for the preset time period is generated. The correlation coefficient between the generated leakage current curve of each circuit loop and the generated bus voltage curve is calculated. The current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop. Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults and displayed.

[0007] Furthermore, the correlation coefficient between the leakage current curve of each generated circuit loop and the generated bus voltage curve is calculated, including: The Pearson correlation coefficient between the leakage current curve and the generated bus voltage curve of each generated circuit loop is calculated according to the Pearson correlation coefficient calculation formula and is used as the correlation coefficient between the leakage current curve and the generated bus voltage curve of each generated circuit loop. The Pearson correlation coefficient The calculation formula is: ; in, This represents the number of sample points selected on the leakage current curve of the circuit loop, and also the number of sample points selected on the bus voltage curve. The first selected on the bus voltage curve The value of each sample point The first one selected on the leakage current curve of the circuit loop The value of each sample point , This is the average value of the sample points on the bus voltage curve. It is the average value of the sample points on the leakage current curve of the circuit loop.

[0008] Furthermore, the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop, including: The leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve are obtained in advance. According to the formula Based on the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve corresponding to each circuit loop and the generated bus voltage curve, the comprehensive weight of each circuit loop is calculated. in, Indicates the overall weight. The weighting of leakage current in a circuit loop. The weights representing the slopes of the leakage current curve corresponding to the leakage current in the circuit loop. The weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. This indicates the current leakage current in the circuit loop. The slope of the leakage current curve corresponding to the current leakage current in the circuit loop. This represents the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve.

[0009] Furthermore, the methods for obtaining the weights of the leakage current in the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve include: A hierarchical model is constructed, comprising a target layer, a criterion layer, and a scheme layer. The target layer represents the operating state of the circuit loop. The criterion layer comprises evaluation indicators, including the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. The scheme layer includes each circuit loop. The evaluation indicators at the same level within the hierarchical structure model are compared with each other, and the comparison results are quantified using the nine-level scaling method to construct a discriminant matrix. : ; Based on the discriminant matrix Calculate the discriminant matrix Maximum eigenvalue and discriminant matrix The eigenvectors are calculated, and the discrimination matrix is ​​adjusted based on the calculated largest eigenvalue. Perform a consistency check; The calculated feature vector is normalized to obtain three elements. Each element in the processed feature vector is the weight of the evaluation index. The positions of the three elements are matched one-to-one with the order of the evaluation index in the criterion layer to obtain the weight of each evaluation index, that is, the weight of the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. in, Represents the discriminant matrix The Middle The evaluation indicator is relative to the first The importance score of each evaluation indicator , .

[0010] Furthermore, circuit loops exceeding a preset weight threshold are identified as circuit loops with grounding faults and displayed accordingly, including: Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults, and are sorted in descending order of their comprehensive weight. The sorted circuit loops are then displayed.

[0011] Furthermore, the method also includes: An alarm will be triggered each time the change in the collected bus voltage exceeds the preset voltage change threshold within a preset time period.

[0012] Secondly, the present invention provides a DC system grounding fault location device, the device comprising: a display unit, a power supply module, an analog acquisition unit, and a control unit; The analog acquisition unit is connected to the control unit and is used to acquire the bus voltage and leakage current of each circuit loop in the DC system circuit in real time. The power module is connected to the display unit, analog acquisition unit and control unit respectively, and is used to provide power. The display unit is connected to the control module and is used to display the circuit loop where a grounding fault has occurred. The control unit is used to determine whether the leakage current collected by the analog acquisition unit exceeds a preset current threshold; it is also used to determine whether the change value of the bus voltage collected within a preset time period from the current moment exceeds a preset voltage change threshold when it is determined that the collected leakage current exceeds the preset current threshold. If the change value of the collected bus voltage within the preset time period exceeds the preset voltage change threshold, a current fault occurs in the DC system circuit. The circuit loop with leakage current exceeding the preset threshold is identified as the circuit loop with ground fault, and the display unit is controlled to display the circuit loop with ground fault. If the change value of the collected bus voltage within the preset time period exceeds the preset voltage change threshold, no action is taken; if the collected leakage current does not exceed the preset threshold, no action is taken.

[0013] Furthermore, if the change in the collected bus voltage within a preset time period exceeds a preset voltage change threshold, a current fault occurs in the DC system circuit. The circuit loop with leakage current exceeding the preset threshold is identified as the circuit loop experiencing a ground fault, and the display unit is controlled to display the circuit loop experiencing the ground fault, including: When the control unit determines that the leakage current of only one circuit loop exceeds the preset threshold, it will identify that circuit loop as having a ground fault and control the display unit to display that circuit loop. When the control unit determines that the leakage current of multiple circuit loops exceeds a preset threshold, it generates a leakage current curve for each circuit loop within the preset time period based on the leakage current of each circuit loop collected within the preset time period, calculates the slope of the leakage current curve of each circuit loop at the current time point, generates a bus voltage curve within the preset time period based on the bus voltage collected within the preset time period, calculates the correlation coefficient between the generated leakage current curve of each circuit loop and the generated bus voltage curve, and performs a weighted summation of the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve to obtain the comprehensive weight of each circuit loop. The circuit loops that exceed the preset weight threshold are identified as circuit loops with grounding faults, and the display unit is controlled to display the circuit loops with grounding faults.

[0014] Furthermore, the device also includes a voice alarm unit; The voice alarm unit is connected to the control module and is used to issue an alarm prompt each time the control unit determines that the change value of the collected bus voltage within a preset time period exceeds the preset voltage change threshold.

[0015] As can be seen from the above technical solutions, the present invention has the following advantages: This invention achieves real-time monitoring of the system status by acquiring the bus voltage and leakage current in each circuit of a DC system. Compared with the traditional circuit-finding method, this method eliminates the need to sequentially disconnect the power supply of each branch circuit, significantly shortening the detection time. This is particularly beneficial in large and complex DC systems, where detection efficiency is significantly improved. Furthermore, this invention considers changes in leakage current and combines this with changes in the bus voltage over a preset time period for comprehensive judgment. This dual judgment mechanism effectively reduces the possibility of misjudgment or missed detection that might arise from relying solely on a single parameter, thus improving the accuracy of fault detection.

[0016] Secondly, this invention is not limited by the scale and complexity of DC systems, and can be widely applied to DC systems in various fields such as high-voltage DC transmission, subway traction, ship systems, and communication systems, and has strong adaptability and promotional value.

[0017] Furthermore, the design principle of this invention is reliable, the structure is simple, and it has a very wide range of application prospects. Attached Figure Description

[0018] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of an embodiment of the DC system grounding fault location method of the present invention; Figure 2 This is a schematic block diagram of one embodiment of the DC system ground fault location device of the present invention; Figure 3 This is a schematic block diagram of another embodiment of the DC system grounding fault location device described in this invention. Detailed Implementation

[0020] 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.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] like Figure 1 As shown, the present invention provides a method for locating ground faults in a DC system, the method comprising: S1. Real-time acquisition of bus voltage and leakage current in each circuit loop of the DC system circuit; S2. Determine whether the leakage current in each circuit loop exceeds the preset current threshold. If the leakage current in each circuit loop exceeds the preset current threshold, proceed to step S3; otherwise, do not process it. S3. Determine whether the change value of the bus voltage collected within the preset time period from the current moment exceeds the preset voltage change threshold. If the change value of the bus voltage collected within the preset time period exceeds the preset voltage change threshold, then the circuit loop with leakage current exceeding the preset threshold is identified as a circuit loop with a ground fault in the DC system circuit and displayed; otherwise, no action is taken.

[0023] To facilitate understanding of the present invention, the following description further illustrates the DC system ground fault location method provided by the present invention, based on the principle of the DC system ground fault location method and the process of the DC system ground fault location method in the embodiments.

[0024] Specifically, the DC system ground fault location method includes: Step 110: Real-time acquisition of bus voltage and leakage current in each circuit loop of the DC system circuit.

[0025] Specifically, the bus voltage in the DC system circuit is collected in real time by a DC voltage sensor; and the leakage current in each circuit loop of the DC system circuit is collected in real time by a Hall sensor.

[0026] Step 120: Determine whether the leakage current in each circuit loop exceeds the preset current threshold. If the leakage current in each circuit loop exceeds the preset current threshold, proceed to step 130; otherwise, no action is taken.

[0027] Specifically, the preset current threshold can be set according to the actual needs of those skilled in the art.

[0028] Step 130: Determine whether the change value of the bus voltage collected within the preset time period from the current moment exceeds the preset voltage change threshold. If the change value of the bus voltage collected within the preset time period exceeds the preset voltage change threshold, then the circuit loop with leakage current exceeding the preset threshold is identified as a circuit loop with grounding fault in the DC system circuit and displayed; otherwise, no processing is performed.

[0029] Specifically, the preset voltage change threshold can be set according to the actual needs of those skilled in the art.

[0030] At the beginning of the current preset time period, the bus voltage is recorded as the initial value of the bus voltage for the current preset time period. At the end of the current preset time period, the bus voltage is recorded as the ending value of the bus voltage for the current preset time period. The difference between the initial value and the ending value of the bus voltage for the current preset time period is calculated as the change value of the bus voltage over the preset time period from the current moment. If the bus voltage change value collected within the preset time period exceeds the preset voltage change threshold, it is determined that a current fault has occurred in the DC system circuit. Circuit loops with leakage current exceeding the preset threshold are identified as circuit loops with ground faults in the DC system circuit and displayed. Otherwise, no action is taken.

[0031] Calculate the change: Subtract the initial voltage from the final voltage, and use this difference as the change in bus voltage. This change can be an absolute value or a percentage relative to the rated voltage.

[0032] Specifically, when the leakage current of only one circuit loop exceeds a preset threshold, that circuit loop will be displayed as a circuit loop with a grounding fault.

[0033] When the leakage current of multiple circuit loops exceeds a preset threshold, based on the leakage current of each circuit loop collected within the preset time period, a leakage current curve for each circuit loop within the preset time period is generated. The slope of the leakage current curve of each circuit loop at the current time point is calculated. Based on the bus voltage collected within the preset time period, a bus voltage curve for the preset time period is generated. The correlation coefficient between the generated leakage current curve of each circuit loop and the generated bus voltage curve is calculated. The current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop. Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults and displayed.

[0034] As an embodiment of the present invention, the correlation coefficient between the leakage current curve of each generated circuit loop and the generated bus voltage curve is calculated, including: The Pearson correlation coefficient between the leakage current curve and the generated bus voltage curve of each generated circuit loop is calculated according to the Pearson correlation coefficient calculation formula and is used as the correlation coefficient between the leakage current curve and the generated bus voltage curve of each generated circuit loop. The Pearson correlation coefficient The calculation formula is: ; in, This represents the number of sample points selected on the leakage current curve of the circuit loop, and also the number of sample points selected on the bus voltage curve. The first selected on the bus voltage curve The value of each sample point The first one selected on the leakage current curve of the circuit loop The value of each sample point , This is the average value of the sample points on the bus voltage curve. It is the average value of the sample points on the leakage current curve of the circuit loop.

[0035] As an embodiment of the present invention, the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve corresponding to each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop, including: The leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve are obtained in advance. According to the formula Based on the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve corresponding to each circuit loop and the generated bus voltage curve, the comprehensive weight of each circuit loop is calculated.

[0036] in, Indicates the overall weight. The weighting of leakage current in a circuit loop. The weights representing the slopes of the leakage current curve corresponding to the leakage current in the circuit loop. The weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. This indicates the current leakage current in the circuit loop. The slope of the leakage current curve corresponding to the current leakage current in the circuit loop. This represents the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve.

[0037] Furthermore, the methods for obtaining the weights of the leakage current in the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve include: A hierarchical model is constructed, comprising a target layer, a criterion layer, and a scheme layer. The target layer represents the operating state of the circuit loop. The criterion layer comprises evaluation indicators, including the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. The scheme layer includes each circuit loop. The system collects historical leakage current during circuit loop faults, the slope of the historical leakage current curve during circuit loop faults at the time of historical leakage current collection, and the correlation coefficient between the historical leakage current curve during circuit loop faults and the generated historical bus voltage curve. The collected data is then standardized, including using the maximum-minimum standardization method to convert the historical leakage current values ​​into values ​​between 0 and 1. Clearly define the comparison criteria between evaluation indicators, invite experts or professionals in relevant fields to participate in the comparison process, compare evaluation indicators at the same level within the hierarchical structure model, assess their relative importance, quantify the comparison results using a nine-level scaling method, and construct a discriminant matrix based on the comparison results. : ; Based on the discriminant matrix The discriminant matrix is ​​calculated using the sum-product method. Maximum eigenvalue Through formula Calculate the discriminant matrix Consistency index Then, the random consistency index is looked up in the table. According to the formula Calculate the discriminant matrix Consistency ratio ,like Then the judgment matrix It has satisfactory consistency, if Then it is necessary to perform pairwise comparisons again and construct a new discrimination matrix. Calculate the newly constructed discriminant matrix Maximum eigenvalue Perform consistency checks until the discriminant matrix is ​​reached. It exhibits satisfactory consistency; When the discrimination matrix When satisfactory consistency is achieved, the discriminant matrix is ​​calculated. The eigenvectors will be used to calculate the discrimination matrix. The feature vector is normalized to obtain three elements. Each element in the processed feature vector is the weight of the evaluation index. The positions of the three elements are mapped one-to-one with the order of the evaluation index in the criterion layer to obtain the weight of each evaluation index. That is, the weights of the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve are obtained.

[0038] in, Represents the discriminant matrix Consistency indicators Represents the discriminant matrix Consistency ratio , The random consistency index represents the discriminant matrix. Represents the discriminant matrix The order, that is, the number of evaluation indicators. Represents the discriminant matrix The Middle The evaluation indicator is relative to the first The importance score of each evaluation indicator , .

[0039] As an embodiment of the present invention, circuit loops exceeding a preset weight threshold are identified as circuit loops with grounding faults and displayed accordingly, including: Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults, and are sorted in descending order of their comprehensive weight. The sorted circuit loops are then displayed.

[0040] As an embodiment of the present invention, the method further includes: An alarm will be triggered each time the change in the collected bus voltage exceeds the preset voltage change threshold within a preset time period.

[0041] As one embodiment of the present invention, such as Figure 2 As shown, the present invention also provides a DC system grounding fault location device, the device 200 including: a display unit 210, a power module 220, an analog acquisition unit 230 and a control unit 240; The analog acquisition unit 230 is connected to the control unit 240 and is used to acquire the bus voltage and leakage current of each circuit loop in the DC system circuit in real time. The power module 220 is connected to the display unit 210, the analog acquisition unit 230 and the control unit 240 respectively, and is used to provide power. The display unit 210 is connected to the control module 240 and is used to display the circuit where a grounding fault has occurred. The control unit 240 is used to determine whether the leakage current collected by the analog acquisition unit 230 exceeds a preset current threshold; it is also used to determine whether the change value of the bus voltage collected within a preset time period from the current moment exceeds a preset voltage change threshold when it is determined that the collected leakage current exceeds the preset current threshold. If the change value of the collected bus voltage within the preset time period exceeds the preset voltage change threshold, a current fault occurs in the DC system circuit. The circuit loop with leakage current exceeding the preset threshold is identified as the circuit loop with ground fault, and the display unit 210 is controlled to display the circuit loop with ground fault. If the change value of the collected bus voltage within the preset time period does not exceed the preset voltage change threshold, no action is taken. If the collected leakage current does not exceed the preset threshold, no action is taken.

[0042] As an embodiment of the present invention, if the change value of the collected bus voltage within a preset time period exceeds a preset voltage change threshold, a current fault occurs in the DC system circuit. The circuit with leakage current exceeding the preset threshold is identified as the circuit with a ground fault, and the display unit 210 is controlled to display the circuit with the ground fault, including: When the control unit 240 determines that there is only one circuit loop whose leakage current exceeds the preset threshold, it will identify the circuit loop as the circuit with a ground fault and control the display unit 210 to display the circuit loop. When the control unit 240 determines that the leakage current of multiple circuit loops exceeds a preset threshold, it generates a leakage current curve for each circuit loop within the preset time period based on the leakage current of each circuit loop collected within the preset time period, calculates the slope of the leakage current curve of each circuit loop at the current time point, generates a bus voltage curve within the preset time period based on the bus voltage collected within the preset time period, calculates the correlation coefficient between the generated leakage current curve of each circuit loop and the generated bus voltage curve, and performs a weighted summation of the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve to obtain the comprehensive weight of each circuit loop. The circuit loops that exceed the preset weight threshold are identified as circuit loops with grounding faults, and the display unit 210 is controlled to display the circuit loops with grounding faults.

[0043] Specifically, the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop. Circuit loops exceeding the preset weight threshold are identified as circuit loops with ground faults, and the display unit 210 is controlled to display the circuit loops with ground faults, including: The weights of the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve are obtained. According to the formula Based on the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve corresponding to each circuit loop and the generated bus voltage curve, the comprehensive weight of each circuit loop is calculated. Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults, and are sorted in descending order of their comprehensive weight. The display unit 210 is then controlled to display the sorted circuit loops with grounding faults.

[0044] in, Indicates the overall weight. The weighting of leakage current in a circuit loop. The weights representing the slopes of the leakage current curve corresponding to the leakage current in the circuit loop. The weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. This indicates the current leakage current in the circuit loop. The slope of the leakage current curve corresponding to the current leakage current in the circuit loop. This represents the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve.

[0045] Furthermore, the method for obtaining the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve includes: A hierarchical model is constructed, comprising a target layer, a criterion layer, and a scheme layer. The target layer represents the operating state of the circuit loop. The criterion layer comprises evaluation indicators, including the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. The scheme layer includes each circuit loop. The evaluation indicators at the same level within the hierarchical structure model are compared with each other, and the comparison results are quantified using the nine-level scaling method to construct a discriminant matrix. : ; Based on the discriminant matrix Calculate the discriminant matrix Maximum eigenvalue and discriminant matrix The eigenvectors are calculated, and the discrimination matrix is ​​adjusted based on the calculated largest eigenvalue. Perform a consistency check; The calculated feature vector is normalized to obtain three elements. Each element in the processed feature vector is the weight of the evaluation index. The positions of the three elements are matched one-to-one with the order of the evaluation index in the criterion layer to obtain the weight of each evaluation index, that is, the weight of the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. in, Represents the discriminant matrix The Middle The evaluation indicator is relative to the first The importance score of each evaluation indicator , .

[0046] As one embodiment of the present invention, such as Figure 3 As shown, the device 200 also includes a voice alarm unit 250; The voice alarm unit 250 is connected to the control module 240 and is used to issue an alarm prompt each time the control unit 250 determines that the change value of the collected bus voltage within a preset time exceeds the preset voltage change threshold.

[0047] This invention achieves real-time monitoring of the system status by acquiring the bus voltage and leakage current in each circuit of a DC system. Compared with the traditional circuit-finding method, this method eliminates the need to sequentially disconnect the power supply of each branch circuit, significantly shortening the detection time. This is particularly beneficial in large and complex DC systems, where detection efficiency is significantly improved. Furthermore, this invention considers changes in leakage current and combines this with changes in the bus voltage over a preset time period for comprehensive judgment. This dual judgment mechanism effectively reduces the possibility of misjudgment or missed detection that might arise from relying solely on a single parameter, thus improving the accuracy of fault detection.

[0048] Secondly, this invention is not limited by the scale and complexity of DC systems, and can be widely applied to DC systems in various fields such as high-voltage DC transmission, subway traction, ship systems, and communication systems, and has strong adaptability and promotional value.

[0049] Furthermore, the design principle of this invention is reliable, the structure is simple, and it has a very wide range of application prospects.

[0050] The technical effects achievable in this embodiment can be found in the description above, and will not be repeated here.

[0051] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the invention should also be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be determined by the scope of the claims.

Claims

1. A method for locating ground faults in a DC system, characterized in that, The method includes: S1. Real-time acquisition of bus voltage and leakage current in each circuit loop of the DC system circuit; S2. Determine whether the leakage current in each circuit loop exceeds the preset current threshold. If the leakage current in each circuit loop exceeds the preset current threshold, proceed to step S3; otherwise, do not process it. S3. Determine whether the change value of the bus voltage collected within the preset time period from the current moment exceeds the preset voltage change threshold. If the change value of the bus voltage collected within the preset time period exceeds the preset voltage change threshold, the circuit loop with leakage current exceeding the preset threshold is identified as a circuit loop with a ground fault in the DC system circuit and displayed; otherwise, no action is taken.

2. The DC system grounding fault location method according to claim 1, characterized in that, Step S3 includes: When the leakage current of only one circuit loop exceeds the preset threshold, that circuit loop will be identified as having a ground fault and displayed. When the leakage current of multiple circuit loops exceeds a preset threshold, based on the leakage current of each circuit loop collected within the preset time period, a leakage current curve for each circuit loop within the preset time period is generated. The slope of the leakage current curve of each circuit loop at the current time point is calculated. Based on the bus voltage collected within the preset time period, a bus voltage curve for the preset time period is generated. The correlation coefficient between the generated leakage current curve of each circuit loop and the generated bus voltage curve is calculated. The current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop. Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults and displayed.

3. The DC system grounding fault location method according to claim 2, characterized in that, The correlation coefficient between the leakage current curve of each generated circuit loop and the generated bus voltage curve is calculated, including: The Pearson correlation coefficient between the leakage current curve and the generated bus voltage curve of each generated circuit loop is calculated according to the Pearson correlation coefficient calculation formula and is used as the correlation coefficient between the leakage current curve and the generated bus voltage curve of each generated circuit loop. The Pearson correlation coefficient The calculation formula is: ； in, This represents the number of sample points selected on the leakage current curve of the circuit loop, and also the number of sample points selected on the bus voltage curve. The first selected on the bus voltage curve The value of each sample point The first one selected on the leakage current curve of the circuit loop The value of each sample point , This is the average value of the sample points on the bus voltage curve. It is the average value of the sample points on the leakage current curve of the circuit loop.

4. The DC system grounding fault location method according to claim 2, characterized in that, The current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve are weighted and summed to obtain the comprehensive weight of each circuit loop, including: The leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve are obtained in advance. According to the formula Based on the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve corresponding to each circuit loop and the generated bus voltage curve, the comprehensive weight of each circuit loop is calculated. in, Indicates the overall weight. The weighting of leakage current in a circuit loop. The weights representing the slopes of the leakage current curve corresponding to the leakage current in the circuit loop. The weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. This indicates the current leakage current in the circuit loop. The slope of the leakage current curve corresponding to the current leakage current in the circuit loop. This represents the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve.

5. The DC system grounding fault location method according to claim 4, characterized in that, The methods for obtaining the weights of the leakage current in the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve include: A hierarchical model is constructed, comprising a target layer, a criterion layer, and a scheme layer. The target layer represents the operating state of the circuit loop. The criterion layer comprises evaluation indicators, including the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. The scheme layer includes each circuit loop. The evaluation indicators at the same level within the hierarchical structure model are compared with each other, and the comparison results are quantified using the nine-level scaling method to construct a discriminant matrix. : ; Based on the discriminant matrix Calculate the discriminant matrix Maximum eigenvalue and discriminant matrix The eigenvectors are calculated, and the discrimination matrix is ​​adjusted based on the calculated largest eigenvalue. Perform a consistency check; The calculated feature vector is normalized to obtain three elements. Each element in the processed feature vector is the weight of the evaluation index. The positions of the three elements are matched one-to-one with the order of the evaluation index in the criterion layer to obtain the weight of each evaluation index, that is, the weight of the leakage current of the circuit loop, the slope of the leakage current curve corresponding to the leakage current in the circuit loop, and the weight of the correlation coefficient between the leakage current curve corresponding to the circuit loop and the generated bus voltage curve. in, Represents the discriminant matrix The Middle The evaluation indicator is relative to the first The importance score of each evaluation indicator , .

6. The DC system grounding fault location method according to claim 2, characterized in that, Circuit loops exceeding a preset weight threshold are identified as having ground faults and displayed accordingly, including: Circuit loops exceeding the preset weight threshold are identified as circuit loops with grounding faults, and are sorted in descending order of their comprehensive weight. The sorted circuit loops are then displayed.

7. The method for locating ground faults in a DC system according to claim 1, characterized in that, The method also includes: An alarm will be triggered each time the change in the collected bus voltage exceeds the preset voltage change threshold within a preset time period.

8. A ground fault location device for a DC system, characterized in that, The device includes: a display unit, a power module, an analog acquisition unit, and a control unit; The analog acquisition unit is connected to the control unit and is used to acquire the bus voltage and leakage current of each circuit loop in the DC system circuit in real time. The power module is connected to the display unit, analog acquisition unit and control unit respectively, and is used to provide power. The display unit is connected to the control module and is used to display the circuit loop where a grounding fault has occurred. The control unit is used to determine whether the leakage current collected by the analog acquisition unit exceeds a preset current threshold; it is also used to determine whether the change value of the bus voltage collected within a preset time period from the current moment exceeds a preset voltage change threshold when it is determined that the collected leakage current exceeds the preset current threshold. If the change value of the collected bus voltage within the preset time period exceeds the preset voltage change threshold, a current fault occurs in the DC system circuit. The circuit loop with leakage current exceeding the preset threshold is identified as the circuit loop with ground fault, and the display unit is controlled to display the circuit loop with ground fault. If the change value of the collected bus voltage within the preset time period exceeds the preset voltage change threshold, no action is taken; if the collected leakage current does not exceed the preset threshold, no action is taken.

9. The DC system grounding fault location device according to claim 8, characterized in that, If the change in the collected bus voltage exceeds a preset voltage change threshold within a preset time period, a current fault occurs in the DC system circuit. Circuits with leakage current exceeding the preset threshold are identified as circuits with ground faults, and the display unit is controlled to display these circuits, including: When the control unit determines that the leakage current of only one circuit loop exceeds the preset threshold, it will identify that circuit loop as having a ground fault and control the display unit to display that circuit loop. When the control unit determines that the leakage current of multiple circuit loops exceeds a preset threshold, it generates a leakage current curve for each circuit loop within the preset time period based on the leakage current of each circuit loop collected within the preset time period, calculates the slope of the leakage current curve of each circuit loop at the current time point, generates a bus voltage curve within the preset time period based on the bus voltage collected within the preset time period, calculates the correlation coefficient between the generated leakage current curve of each circuit loop and the generated bus voltage curve, and performs a weighted summation of the current leakage current of each circuit loop, the slope of the leakage current curve corresponding to the current leakage current in each circuit loop, and the correlation coefficient between the leakage current curve of each circuit loop and the generated bus voltage curve to obtain the comprehensive weight of each circuit loop. The circuit loops that exceed the preset weight threshold are identified as circuit loops with grounding faults, and the display unit is controlled to display the circuit loops with grounding faults.

10. The DC system grounding fault location device according to claim 8, characterized in that, The device also includes a voice alarm unit; The voice alarm unit is connected to the control module and is used to issue an alarm prompt each time the control unit determines that the change value of the collected bus voltage within a preset time period exceeds the preset voltage change threshold.

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