Distribution network feeder line grounding fault line selection and positioning method based on IF-AHP

Abstract

The invention discloses a distribution network feeder line grounding fault line selection and positioning method based on IF-AHP, and belongs to the technical field of grounding fault line selection and positioning, and the method comprises the steps: S1, collecting alarm signals of first terminal equipment, and obtaining target bus information based on the alarm signals of the first terminal equipment; s2, measuring the measurement data of a second terminal device on the feeder line side corresponding to the target bus, and calculating the score of the second terminal device based on the measurement data; s3, establishing a first hierarchical model based on IF-AHP, and calculating a combination weight of factors in the first hierarchical model; and S4, calculating a comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first level model, obtaining a zero-sequence current change coefficient of any two adjacent second terminal devices on the feeder line with the highest comprehensive score before and after the occurrence of the grounding fault, and obtaining a grounding fault range based on the zero-sequence current change coefficient. The problems that the grounding fault range cannot be accurately positioned, so that the troubleshooting and repairing efficiency of the grounding fault of the feeder line of the distribution network is low are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of ground fault line selection and positioning, and in particular to a distribution network feeder ground fault line selection and positioning method based on IF-AHP. Background Art

[0002] As the distribution network system becomes increasingly large, ground faults are inevitable during operation. Ground faults will not only cause damage to power grid equipment and lines, but also cause power grid accidents. Therefore, accurate identification of ground faults is helpful to take timely measures to repair them and avoid the expansion of faults and accidents. For example, a distribution network ground fault identification method and device with patent number CN117741331A includes: obtaining distribution network ground fault identification characteristics, optimizing and training an improved random forest algorithm according to the distribution network ground fault identification characteristics, and obtaining a preset distribution network ground fault identification model; tuning the preset distribution network ground fault identification model to obtain an optimized preset distribution network ground fault identification model; performing fault identification on the collected data to be fault identified based on the optimized preset distribution network ground fault identification model to obtain a distribution network ground fault identification result. This method improves the accuracy of identifying grounding faults in the distribution network, but there is a problem that the line where the grounding fault is located cannot be located. At present, the scope of locating the grounding fault is mainly through the small current line selection device in the substation to confirm the grounding line according to the three-phase current of the feeder, which solves the problem of being unable to locate the line where the grounding fault is located. However, the small current grounding line selection device in the substation can only realize the grounding line selection action, and there is a problem that the scope of the grounding fault cannot be accurately located, resulting in low efficiency in the investigation and repair of distribution network feeder grounding faults. Summary of the invention

[0003] In view of the problem that the existing technology cannot accurately locate the scope of grounding faults, resulting in low efficiency in troubleshooting and repairing distribution network feeder grounding faults, the present invention provides a distribution network feeder grounding fault line selection and positioning method based on IF-AHP, by scoring the equipment on the feeder, and evaluating the equipment reliability by calculating the combined weight, and then combining the equipment score with the equipment reliability, the feeder where the grounding fault is located is located, and by calculating the zero-sequence current variation coefficient of the adjacent equipment on the feeder, the grounding fault is further located to the specific position on the feeder, solving the problem that the distribution network feeder grounding fault is unable to accurately locate the scope of the grounding fault, resulting in low efficiency. The positioning scope of the grounding fault is narrowed, and the accuracy of the grounding fault positioning is improved, thereby accelerating the speed and efficiency of fault repair.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a distribution network feeder grounding fault line selection and location method based on IF-AHP, comprising: S1: after receiving the ground alarm signal, collect the alarm signal of the first terminal device, and obtain the target bus information based on the alarm signal of the first terminal device; S2: calling for measurement data of a second terminal device on the feeder side corresponding to the target bus, and calculating a score of the second terminal device based on the measurement data; S3: Establish the first-level model based on IF-AHP and calculate the combined weights of the factors in the first-level model; S4: Calculate a comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first-level model, obtain the zero-sequence current variation coefficient of any two adjacent second terminal devices on the feeder with the highest comprehensive score before and after the grounding fault occurs, and obtain the grounding fault range based on the zero-sequence current variation coefficient.

[0005] After adopting the above technical solution, the present invention has the following advantages: The second terminal equipment includes intelligent switches, small current grounding devices, fault indicators, distribution transformers, etc., which are used for ground fault alarm reminders. The measurement data reflects whether the second terminal equipment generates a ground fault alarm. The second terminal equipment is scored based on the measurement data, avoiding the collection accuracy, false alarms, and missed alarms of different early warning devices. IF-AHP decomposes the reliability evaluation of the second terminal equipment into multiple levels, each of which focuses on different evaluation indicators. Through multi-level analysis strategies, it promotes the weight allocation and comprehensive consideration between different indicators, making the resulting combined weight more reliable; The score of the second terminal device reflects the degree to which the second terminal device is affected by the ground fault, and the combined weight reflects the reliability of the second terminal device score in assessing the probability of grounding. Therefore, the feeder where the ground fault is located can be accurately located by calculating the comprehensive score based on the two. The zero-sequence current variation coefficient reflects the changes of the two adjacent terminals before and after the ground fault occurs. Therefore, the ground fault range is obtained based on the zero-sequence current variation coefficient. By combining the equipment score, reliability evaluation and zero-sequence current variation coefficient for analysis, the specific location of the line ground fault can be more accurately located, the accuracy of fault range positioning can be improved, and the speed and efficiency of fault repair can be accelerated; The problem of being unable to accurately locate the scope of the grounding fault, resulting in low efficiency in troubleshooting and repairing the distribution network feeder grounding fault, is solved.

[0006] Preferably, S2 includes: S21: establishing an upstream and downstream relationship of the second terminal device according to the feeder power supply path, comparing the measurement data of the second terminal device before and after the ground fault occurs, marking the second terminal device if the set conditions are met, and calculating the score of the device to be scored in the second terminal device based on the number of marked second terminal devices; S22: Classify the devices to be rated and calculate the average score Val of the same type of devices to be rated d .

[0007] If the preset conditions are met, it indicates that the second terminal device is affected by the ground fault, so it is marked. The score of the device to be scored reflects the degree to which the device to be scored is affected by the ground fault. Therefore, the score of the device to be scored in the second terminal device is calculated based on the number of marked second terminal devices. Since the scoring standards of different types of devices to be scored are different, they are classified and the average score of the same type of scoring devices is calculated. Quantitative scoring provides strong data support for subsequent decision-making, while improving the fairness and accuracy of scoring, avoiding scoring differences and biases caused by different types of equipment, and improving the efficiency and accuracy of troubleshooting.

[0008] Preferably, the S21 includes: S211: Obtaining a zero-sequence current change rate of the first monitoring device in the second terminal device before and after the ground fault occurs, and if the zero-sequence current change rate of the first monitoring device in the second terminal device before and after the ground fault occurs is greater than a set zero-sequence current change rate, marking the first monitoring device as an abnormal first monitoring device; S212: Calculate the score of the first device to be scored based on the number of abnormal first monitoring devices that the power supply path from the power source point to the first device to be scored passes through; S213: Obtain the three-phase voltage of the second monitoring device in the second terminal device, calculate the difference between the voltage of any one phase of the three-phase voltage and the rated power supply voltage, and if the difference is greater than a preset difference, mark it as an abnormal second monitoring device, and calculate the score of the second device to be scored in the devices to be scored based on the unidirectional voltage before and after the ground fault occurs; S214: The third monitoring device in the second terminal device identifies the current change of the target bus, and scores the third device to be scored in the devices to be scored based on the change result.

[0009] At the moment of the ground fault, if the second terminal device is affected by the ground fault, the various measurement data of the second terminal device will change accordingly. Therefore, it can be judged whether the second terminal device is affected by the ground fault according to whether the measurement data changes and the degree of change. If affected, the corresponding second terminal device will be marked. In order to obtain the degree of influence of the device to be scored by the ground fault, the score of the device to be scored on the feeder is calculated based on the corresponding data before and after the ground fault. Through the above scheme, the equipment and areas affected by the ground fault can be quickly located, which shortens the troubleshooting time and improves the efficiency of fault handling; through the scoring results, those equipment or areas that are easily affected by the ground fault can be identified, which is helpful to formulate targeted preventive maintenance plans, take measures in advance to prevent the occurrence of faults, and improve the reliability and stability of the system.

[0010] Preferably, in S212, the step of calculating the score of the first device to be scored based on the number of abnormal first monitoring devices through which the power supply path from the power source point to the first device to be scored passes includes: In the formula, Val y is the score of the first device to be scored, M and N are the distance from the power source to the device to be scored, respectively. The number of intelligent switches and the number of fault indicators that the power supply path of the first device to be scored passes through in the device to be scored, m and n are respectively the number of abnormal intelligent switches and the number of abnormal fault indicators that the power supply path from the power point to the first device to be scored passes through in the device to be scored.

[0011] If it is an abnormal intelligent switch or an abnormal fault indicator, it means that the intelligent switch or fault indicator is affected by the ground fault. The score of the first device to be scored is calculated by the number of abnormal intelligent switches and the number of abnormal fault indicators passed, and the degree to which the first device to be scored is affected by the ground fault is obtained. When a ground fault occurs, the scope and degree of the fault can be quickly assessed, providing strong support for emergency response, helping to shorten the fault handling time and reduce the impact of the fault on the system; through the scoring results, those devices or areas that are easily affected by ground faults can be identified, which helps to formulate targeted preventive maintenance plans, take measures in advance to prevent faults, and improve the reliability and stability of the system.

[0012] Preferably, in S213, the step of calculating the score of the second device to be scored in the devices to be scored based on the unidirectional voltage before and after the ground fault occurs includes: In the formula, Val tirepresents the score of the i-th second device to be scored, and v and v are the unidirectional voltages of the second device to be scored before and after the ground fault occurs, respectively.

[0013] The score of the second device to be scored reflects the degree to which the second device to be scored is affected by the ground fault. By calculating the score of the second device to be scored, when a ground fault occurs, the scope and degree of the fault can be quickly evaluated, providing strong support for emergency response, helping to shorten the fault handling time, and reducing the impact of the fault on the system; through the scoring results, those devices or areas that are easily affected by the ground fault can be identified, which is helpful to formulate targeted preventive maintenance plans, take measures in advance to prevent the occurrence of faults, and improve the reliability and stability of the system.

[0014] Preferably, S3 includes: S31: Establish the first level model based on the opinions of the operation administrator and experts; S32: Construct an intuitive judgment matrix based on the qualitative evaluation terms and the intuitive fuzzy correspondence table, and calculate the weight vector W between the first-level indicators in the first-level model based on the intuitive judgment matrix A , based on the intuitive judgment matrix, calculate the weight vector W between the secondary indicators corresponding to the primary indicators in the first-level model B ; S33: Based on W A With W B Calculate the combined weights of the first-level indicators in the first-level model.

[0015] When evaluating equipment reliability, it is necessary not only to rely on objective data, but also to fully express personal subjective judgment and uncertainty. Therefore, the first-level model and the intuitive judgment matrix are established. Since the first-level model decomposes the equipment reliability evaluation into multiple levels, each level focuses on different evaluation indicators, and different indicators contribute differently to the probability of feeder grounding faults, and the secondary indicators under different primary indicators have different effects on the primary indicators, based on W A With W B Calculate the combined weights of the first-level indicators in the first-level model. This multi-level analysis strategy not only enhances the depth and breadth of the evaluation, but also promotes the weight allocation and comprehensive consideration between different indicators, making the final equipment reliability evaluation more fair and reasonable; combining qualitative expert judgment with quantitative data analysis makes the evaluation process more scientific and rigorous, avoiding the limitations of relying solely on objective data or subjective judgment, and improving the credibility of the evaluation; the above scheme helps to quickly and accurately locate the subsequent grounding fault location, shortens the time for fault detection, and improves the efficiency of fault handling.

[0016] Preferably, the S32 includes: S321: In the formula, u ij Indicates the degree to which the decision maker is biased towards i when evaluating the importance of i and j, v ij It indicates the degree to which decision makers tend to favor j when evaluating the importance of i and j. n1 is the number of primary indicators in the first-level model, and n2 is the number of secondary indicators corresponding to the primary indicators in the first-level model. Combining qualitative expert judgment with quantitative data analysis makes the evaluation process more scientific and rigorous, avoids the limitations of relying solely on objective data or subjective judgment, and improves the credibility of the evaluation.

[0017] Preferably, the S33 includes: In the formula, Q j is the combined weight of the jth first-level indicator, is the weight of the i-th secondary indicator corresponding to the j-th primary indicator in the first-level model, is the weight of the jth first-level indicator in the first-level model.

[0018] Preferably, in S4, the calculation of the comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first-level model includes: In the formula, Val l For the comprehensive rating.

[0019] The score of the second terminal device reflects the degree to which the second terminal device is affected by the ground fault, and the combined weight reflects the reliability of the second terminal device score in assessing the probability of grounding. Therefore, the feeder where the ground fault is located can be located based on the comprehensive score calculated based on the two. Through equipment scoring and reliability evaluation, the specific location of the line grounding fault can be more accurately located, improving the accuracy of fault range positioning, thereby accelerating the speed and efficiency of fault repair.

[0020] Preferably, in S4, the step of obtaining the zero-sequence current variation coefficients of all two adjacent second terminal devices on the feeder with the highest comprehensive score before and after the ground fault occurs, and obtaining the ground fault range based on the zero-sequence current variation coefficient includes: when the zero-sequence current variation coefficients of all two adjacent second terminal devices before and after the ground fault occurs are greater than a preset threshold, the fault point is located between the substation outlet and the first second terminal device passing through the substation outlet; when there are two adjacent second terminal devices whose zero-sequence current variation coefficients before and after the ground fault occurs are less than the set threshold, the fault point is located between the two adjacent second terminal devices with the largest zero-sequence current variation coefficients; When the zero-sequence current variation coefficients of all two adjacent second terminal devices before and after the ground fault occurs are less than the set threshold, the fault point is located after the second terminal device at the end, starting from the substation outgoing line.

[0021] The zero-sequence current variation coefficient reflects the change of two adjacent second terminal devices before and after the grounding fault occurs. The larger the coefficient, the greater the difference between the two adjacent second terminal devices before and after the fault, that is, the higher the possibility that the fault point is located between the two adjacent second terminal devices. When the fault occurs before the first second terminal device, the zero-sequence current variation coefficients of all the two adjacent second terminal devices on the line side are relatively large. When the fault occurs after the terminal second terminal device, the zero-sequence current variation coefficients of all the two adjacent second terminal devices on the line side are relatively small. Therefore, when the zero-sequence current variation coefficients of all the two adjacent second terminal devices are greater than the preset threshold, the fault point is located between the substation outgoing line and the first second terminal device. When some zero-sequence current variation coefficients are greater than the preset threshold, the fault point is located between the two second terminal devices with the largest zero-sequence current variation coefficients. When the zero-sequence current variation coefficients of all the two adjacent terminals are less than the preset threshold, the fault point is located after the terminal second terminal device. Rapidly narrowing the fault range can more accurately locate the specific location of the line grounding fault, improve the accuracy of fault range positioning, and thus accelerate the speed and efficiency of fault repair.

[0022] After adopting the above technical solution, the present invention has the following advantages: Whether the second terminal device is affected by the ground fault is determined based on whether the measured data changes and the degree of change. The score reflects the degree of impact of the ground fault on the device to be scored. Through the scoring results, those devices or areas that are easily affected by the ground fault can be identified, which helps to formulate targeted preventive maintenance plans, take measures in advance to prevent the occurrence of faults, and improve the reliability and stability of the system; at the same time, by calculating multiple scoring results, the collection accuracy, false alarms, and missed alarms of different early warning devices are avoided, and the accuracy of the alarm is improved; When evaluating equipment reliability, the first-level model decomposes the equipment reliability evaluation into multiple levels. Each level focuses on different evaluation indicators, and different indicators contribute differently to the probability of feeder grounding fault. Therefore, based on W A With W B Calculate the combined weights of the first-level indicators in the first-level model. Combining qualitative expert judgment with quantitative data analysis makes the evaluation process more scientific and rigorous, avoids the limitations of relying solely on objective data or subjective judgment, and improves the credibility of reliability evaluation; The score of the second terminal device reflects the degree to which the second terminal device is affected by the grounding fault. The combined weight reflects the reliability of the second terminal device score in evaluating the grounding probability. The feeder where the grounding fault is located is determined through equipment scoring and reliability evaluation. By comparing the zero-sequence current variation coefficient with the preset threshold, the position of the grounding fault on the feeder is determined, and the fault range is quickly narrowed. The specific location of the line grounding fault can be located more accurately, which improves the accuracy of fault range positioning, thereby accelerating the speed and efficiency of fault repair.

[0023] The above solution solves the problem that the scope of the grounding fault cannot be accurately located, resulting in low efficiency in troubleshooting and repairing the distribution network feeder grounding fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the drawings to represent the same parts.

[0025] Figure 1 The present invention is a flow chart of a method for selecting and locating a distribution network feeder grounding fault based on IF-AHP. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the operations (or steps) as sequential processes, many of the operations (or steps) therein can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the drawings; the process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0028] Example: Figure 1 As shown, a method for selecting and locating a distribution network feeder grounding fault based on IF-AHP includes: S1: After receiving the ground alarm signal, collect the alarm signal of the first terminal device, and obtain the target bus information based on the alarm signal of the first terminal device.

[0029] The grounding alarm signal includes bus grounding alarm signal, low current line selection device signal, distribution network line side terminal grounding, overcurrent signal and other signals. Receiving one of the above alarm signals is receiving the alarm signal. The first terminal device includes a low current grounding line selection device, an intelligent switch, a DTU, a fault indicator, a distribution transformer and other equipment. When the first terminal device detects a grounding fault, a corresponding alarm signal is generated. The alarm signal includes the first terminal device number, the fault type, etc. The power system usually has a detailed topology database that records the connection relationship and detailed location between the various devices in the system. By processing and comparing the alarm signal with the topology database, the target bus can be determined. By determining the target bus, the scope of grounding fault investigation is narrowed, so that the operation and maintenance personnel can find the fault point and repair it more quickly. Quickly locating and repairing the fault can reduce the economic losses caused by equipment downtime, while reducing maintenance costs and time costs.

[0030] S2: Calling for measurement data of a second terminal device on the feeder side corresponding to the target bus, and calculating a score of the second terminal device based on the measurement data.

[0031] The S2 includes: S21: establishing an upstream and downstream relationship of the second terminal device according to the feeder power supply path, comparing the measurement data of the second terminal device before and after the ground fault occurs, marking the second terminal device if the set conditions are met, and calculating the score of the device to be scored in the second terminal device based on the number of marked second terminal devices; S22: Classify the devices to be rated and calculate the average score Val of the same type of devices to be rated d .

[0032] The S21 includes: S211: Obtaining a zero-sequence current change rate of the first monitoring device in the second terminal device before and after the ground fault occurs, and if the zero-sequence current change rate of the first monitoring device in the second terminal device before and after the ground fault occurs is greater than a set zero-sequence current change rate, marking the first monitoring device as an abnormal first monitoring device; S212: Calculate the score of the first device to be scored based on the number of abnormal first monitoring devices that the power supply path from the power source point to the first device to be scored passes through; S213: Obtain the three-phase voltage of the second monitoring device in the second terminal device, calculate the difference between the voltage of any one phase of the three-phase voltage and the rated power supply voltage, and if the difference is greater than a preset difference, mark it as an abnormal second monitoring device, and calculate the score of the second device to be scored in the devices to be scored based on the unidirectional voltage before and after the ground fault occurs; S214: The third monitoring device in the second terminal device identifies the current change of the target bus, and scores the third device to be scored in the devices to be scored based on the change result.

[0033] In S212, the step of calculating the score of the first device to be scored based on the number of abnormal first monitoring devices passed through by the power supply path from the power source point to the first device to be scored among the devices to be scored includes: In the formula, Val y is the score of the first device to be scored, M and N are respectively the number of intelligent switches and the number of fault indicators that the power supply path from the power point to the first device to be scored passes through, and m and n are respectively the number of abnormal intelligent switches and the number of abnormal fault indicators that the power supply path from the power point to the first device to be scored passes through.

[0034] In S213, the step of calculating the score of the second device to be scored in the devices to be scored based on the unidirectional voltages before and after the ground fault occurs includes: In the formula, Val ti represents the score of the i-th second device to be scored, V and v are the unidirectional voltages of the second device to be scored before and after the ground fault occurs, respectively.

[0035] The second terminal equipment includes a small current grounding device, a fault indicator, an intelligent switch, and a distribution transformer. The measured data includes the three-phase current data and zero-sequence current data of the second terminal equipment. The asymmetric component method is used to calculate the zero-sequence current data of the equipment that cannot successfully measure the zero-sequence current data. The calculation formula is: In the formula, They are the three-phase currents of the corresponding equipment respectively.

[0036] In this embodiment, the first monitoring device and the first device to be scored both include an intelligent switch and a fault indicator. According to the feeder power supply path, an upstream and downstream relationship is established between the intelligent switch and the fault indicator. The intelligent switch and the fault indicator whose zero-sequence current change rate before and after the fault time is greater than the set zero-sequence current change rate are marked as abnormal intelligent switches and abnormal fault indicators, respectively. If the number of intelligent switches, fault indicators, abnormal intelligent switches and abnormal fault indicators passed through the power supply path from the power point to the first device to be scored are 6, 6, 2 and 3, respectively, the score of the first device to be scored is approximately 41.67. The second monitoring device is a distribution transformer, and the second device to be scored is an abnormal distribution transformer. The three-phase voltage of the distribution transformer is obtained, and the distribution transformer whose difference between any phase voltage and the rated power supply voltage is greater than the preset difference is marked as an abnormal distribution transformer. By formula Calculate the score of the abnormal distribution transformer. The third monitoring device and the third device to be scored are both small current amplifying devices. The small current amplifying device is deployed at the monitoring terminal on the bus side. According to the actual function, the small current score is recorded as 100 points if it occurs, and 0 points if it does not occur. After obtaining the score of the corresponding device to be scored, calculate the average score of the same type of equipment to be scored. If there are 3 smart switches, 3 fault indicators, 2 abnormal distribution transformers, and 1 small current amplifying device on the feeder, the scores of the 3 smart switches and fault indicators are 40, 42, and 44 respectively, the scores of the 2 abnormal distribution transformers are 44 and 46 respectively, and the score of the 1 small current amplifying device is 0. Then the average scores of the smart switches and fault indicators are both 42, the average score of the abnormal distribution transformers is 45, and the average score of the small current amplifying device is 0. The above solution can quickly locate the equipment and areas affected by the ground fault, shorten the troubleshooting time and improve the efficiency of fault handling; through the scoring results, the equipment or areas that are easily affected by the ground fault can be identified, which is helpful to formulate targeted preventive maintenance plans, take measures in advance to prevent the occurrence of faults, and improve the reliability and stability of the system.

[0037] S3: Establish the first-level model based on IF-AHP and calculate the combined weights of the factors in the first-level model.

[0038] The S3 includes: S31: Establish the first level model based on the opinions of the operation administrator and experts; S32: Construct an intuitive judgment matrix based on the correspondence table between qualitative evaluation words and intuitive fuzzy words, calculate the weight vector WA between the first-level indicators in the first-level model based on the intuitive judgment matrix, and calculate the weight vector W between the second-level indicators corresponding to the first-level indicators in the first-level model based on the intuitive judgment matrix. B ; S33: Based on WA and W BCalculate the combined weights of the first-level indicators in the first-level model.

[0039] The S32 includes: S321: In the formula, u ij Indicates the degree to which the decision maker is biased towards i when evaluating the importance of i and j, v ij It indicates the degree to which decision makers tend to favor j when evaluating the importance of i and j. n1 is the number of primary indicators in the first-level model, and n2 is the number of secondary indicators corresponding to the primary indicators in the first-level model.

[0040] The S33 includes: In the formula, Q j is the combined weight of the jth first-level indicator, is the weight of the i-th secondary indicator corresponding to the j-th primary indicator in the first-level model, is the weight of the jth first-level indicator in the first-level model.

[0041] IF-AHP, or improved fuzzy analytic hierarchy process, is a comprehensive evaluation method that combines fuzzy theory and analytic hierarchy process. IF-AHP is an improvement on the traditional AHP and is mainly used to deal with complex decision-making problems with fuzziness and uncertainty. It introduces fuzzy set theory to transform the subjective judgment of experts on evaluation indicators into fuzzy numbers, thereby more accurately reflecting the uncertainty and fuzziness in actual situations.

[0042] Based on the opinions of the on-site operators and experts of the distribution network, the first-level model is established. The probability of feeder grounding fault is set as the overall goal. The four first-level indicators of small current grounding device score, fault indicator score, intelligent switch score, and abnormal distribution transformer score are used as the criterion layer. The indicator layer covers three types of second-level indicators, including equipment parameters (manufacturer, service life, collection accuracy), operation parameters (deployment location, set value range), and historical operation data (number of equipment failures, number of false alarms). The reliability of equipment scores is evaluated from different angles. The factors of the same layer are compared with each other with respect to a criterion in the previous layer. The intuitive judgment matrix R is constructed according to the qualitative evaluation terms and the intuitive fuzzy correspondence table. ij =(r ij ) n*m , where r ij =(u ij , v ij ), i, j∈[1, n], u ij ∈[0, 1], v ij ∈[0, 1], where u ijIndicates the degree to which the decision maker is biased towards i when evaluating the importance of attributes i and j, v ij Indicates the decision maker's bias in evaluating the importance of attributes i and j. There exists u ij =v ij , S ij =1-u ij- v ij Indicates the hesitation and uncertainty of the decision maker. In this embodiment, there are 4 first-level indicators: Each first-level indicator has 7 corresponding second-level indicators. The weight vector matrix of the secondary indicators corresponding to the primary indicators is: Based on W A With W B , using the formula Calculations are performed, and the reliability of the small current grounding device score, fault indicator score, intelligent switch score, and abnormal distribution transformer score is evaluated based on the calculation results. This multi-level analysis strategy not only enhances the depth and breadth of the evaluation, but also promotes the weight allocation and comprehensive consideration between different indicators, making the final equipment reliability evaluation more fair and reasonable; combining qualitative expert judgment with quantitative data analysis makes the evaluation process more scientific and rigorous, avoiding the limitations of relying solely on objective data or subjective judgment, and improving the credibility of the evaluation; the above scheme helps to quickly and accurately locate the subsequent grounding fault location, shortens the time for fault detection, and improves the efficiency of fault handling.

[0043] S4: Calculate a comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first-level model, obtain the zero-sequence current variation coefficient of any two adjacent second terminal devices on the feeder with the highest comprehensive score before and after the grounding fault occurs, and obtain the grounding fault range based on the zero-sequence current variation coefficient.

[0044] In S4, the calculation of the comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first-level model includes: Where Val1 is the comprehensive score.

[0045] In S4, the zero-sequence current variation coefficients of all two adjacent second terminal devices on the feeder with the highest comprehensive score before and after the ground fault occurs are obtained, and the ground fault range obtained based on the zero-sequence current variation coefficient includes: When the zero-sequence current variation coefficients of all two adjacent second terminal devices before and after the ground fault occurs are greater than the preset threshold, the fault point is located between the substation outgoing line and the first second terminal device passing through the substation outgoing line; when there are two adjacent second terminal devices whose zero-sequence current variation coefficients before and after the ground fault occurs are less than the set threshold, the fault point is located between the two adjacent second terminal devices with the largest zero-sequence current variation coefficients; When the zero-sequence current variation coefficients of all two adjacent second terminal devices before and after the ground fault occurs are less than the set threshold, the fault point is located after the second terminal device at the end, starting from the substation outgoing line.

[0046] Based on the formula Calculate the score, take the feeder with the highest score as the target feeder, obtain the zero-sequence current of all fault indicators and smart switches on the feeder before and after the fault, and determine the zero-sequence current variation coefficient between two adjacent second terminal devices: Where P represents the zero-sequence current variation coefficient of the two second terminal devices before and after the fault occurs, I m1 ,I m2 Respectively represent the zero-sequence current amplitude of the mth second terminal device before and after the fault, I n1 ,I n2 Respectively represent the zero-sequence current amplitude of the nth second terminal device before and after the fault. The zero-sequence current variation coefficient is used to describe the changes of two adjacent second terminal devices before and after the grounding fault occurs. The larger the zero-sequence current variation coefficient, the greater the difference between the two second terminal devices before and after the fault, that is, the higher the possibility that the fault point is located between the two second terminal devices. Considering that when the fault occurs before the first second terminal device on the feeder, the zero-sequence current variation coefficients of all the two adjacent second terminal devices on the line side are relatively large. When the fault occurs after the second terminal device at the end of the feeder, the zero-sequence current variation coefficients of all the two adjacent second terminal devices on the line side are relatively small. Therefore, a preset threshold is set. When the zero-sequence current variation coefficients of all the two adjacent second terminal devices are greater than the threshold, the fault point is located between the substation outgoing line and the first second terminal device; when some zero-sequence current variation coefficients are greater than the threshold, the fault point is located between the two second terminal devices with the largest zero-sequence current variation coefficients; when the zero-sequence current variation coefficients of all the two adjacent second terminal devices are less than the threshold, the fault point is located after the end second terminal device. Through equipment scoring and reliability evaluation, the specific location of the line grounding fault can be located more accurately, improving the accuracy of fault range positioning, thereby accelerating the speed and efficiency of fault repair.

[0047] The specific implementation described above is a preferred implementation of a distribution network feeder grounding fault line selection and positioning method based on IF-AHP of the present invention, and is not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific implementation. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A method for selecting and locating grounding faults in distribution network feeders based on IF-AHP, characterized in that: include: S1: after receiving the ground alarm signal, collect the alarm signal of the first terminal device, and obtain the target bus information based on the alarm signal of the first terminal device; S2: calling for measurement data of a second terminal device on the feeder side corresponding to the target bus, and calculating a score of the second terminal device based on the measurement data; S3: Establish the first-level model based on IF-AHP and calculate the combined weights of the factors in the first-level model; S4: Calculate a comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first-level model, obtain the zero-sequence current variation coefficient of any two adjacent second terminal devices on the feeder with the highest comprehensive score before and after the grounding fault occurs, and obtain the grounding fault range based on the zero-sequence current variation coefficient.

2. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 1, characterized in that: The S2 includes: S21: establishing an upstream and downstream relationship of the second terminal device according to the feeder power supply path, comparing the measurement data of the second terminal device before and after the ground fault occurs, marking the second terminal device if the set conditions are met, and calculating the score of the device to be scored in the second terminal device based on the number of marked second terminal devices; S22: Classify the devices to be rated and calculate the average score Val of the same type of devices to be rated d .

3. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 2, characterized in that: The S21 includes: S211: Obtaining a zero-sequence current change rate of the first monitoring device in the second terminal device before and after the ground fault occurs, and if the zero-sequence current change rate of the first monitoring device in the second terminal device before and after the ground fault occurs is greater than a set zero-sequence current change rate, marking the first monitoring device as an abnormal first monitoring device; S212: Calculate the score of the first device to be scored based on the number of abnormal first monitoring devices that the power supply path from the power source point to the first device to be scored passes through; S213: Obtain the three-phase voltage of the second monitoring device in the second terminal device, calculate the difference between the voltage of any one phase of the three-phase voltage and the rated power supply voltage, and if the difference is greater than a preset difference, mark it as an abnormal second monitoring device, and calculate the score of the second device to be scored in the devices to be scored based on the unidirectional voltage before and after the ground fault occurs; S214: The third monitoring device in the second terminal device identifies the current change of the target bus, and scores the third device to be scored in the devices to be scored based on the change result.

4. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 3, characterized in that: In S212, the step of calculating the score of the first device to be scored based on the number of abnormal first monitoring devices passed through by the power supply path from the power source point to the first device to be scored among the devices to be scored includes: In the formula, Val y is the score of the first device to be scored, M and N are respectively the number of switches and the number of fault indicators that the power supply path from the power point to the first device to be scored passes through, and m and n are respectively the number of abnormal switches and the number of abnormal fault indicators that the power supply path from the power point to the first device to be scored passes through.

5. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 3, characterized in that: In S213, the step of calculating the score of the second device to be scored in the devices to be scored based on the unidirectional voltages before and after the ground fault occurs includes: In the formula, Val ti represents the score of the i-th second device to be scored, V and v are the unidirectional voltages of the second device to be scored before and after the ground fault occurs, respectively.

6. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 2, characterized in that: The S3 includes: S31: Establish the first level model based on the opinions of the operation administrator and experts; S32: Construct an intuitive judgment matrix based on the qualitative evaluation terms and the intuitive fuzzy correspondence table, and calculate the weight vector W between the first-level indicators in the first-level model based on the intuitive judgment matrix A , based on the intuitive judgment matrix, calculate the weight vector W between the secondary indicators corresponding to the primary indicators in the first-level model B ; S33: Based on W A With W B Calculate the combined weights of the first-level indicators in the first-level model.

7. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 6, characterized in that: The S32 includes: S321: In the formula, u ij Indicates the degree to which the decision maker is biased towards i when evaluating the importance of i and j, v ij It indicates the degree to which decision makers tend to favor j when evaluating the importance of i and j. n1 is the number of primary indicators in the first-level model, and n2 is the number of secondary indicators corresponding to the primary indicators in the first-level model.

8. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 7, characterized in that: The S33 includes: In the formula, Q j is the combined weight of the jth first-level indicator, is the weight of the i-th secondary indicator corresponding to the j-th primary indicator in the first-level model, is the weight of the jth first-level indicator in the first-level model.

9. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 8, characterized in that: In S4, the calculation of the comprehensive score based on the score of the second terminal device and the combined weight of the factors in the first-level model includes: In the formula, Val l For the comprehensive rating.

10. The method for selecting and locating a distribution network feeder grounding fault based on IF-AHP according to claim 1, characterized in that: In S4, the zero-sequence current variation coefficients of all two adjacent second terminal devices on the feeder with the highest comprehensive score before and after the ground fault occurs are obtained, and the ground fault range obtained based on the zero-sequence current variation coefficient includes: When the zero-sequence current variation coefficients of all two adjacent second terminal devices before and after the ground fault occurs are greater than the preset threshold, the fault point is located between the substation outgoing line and the first second terminal device that the substation outgoing line passes through; When there are two adjacent second terminal devices whose zero-sequence current variation coefficients before and after the ground fault occurs are less than the set threshold, the fault point is located between the two adjacent second terminal devices with the largest zero-sequence current variation coefficients; When the zero-sequence current variation coefficients of all two adjacent second terminal devices before and after the ground fault occurs are less than the set threshold, the fault point is located after the second terminal device at the end, starting from the substation outgoing line.

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