Arc suppression coil grounding system single-phase grounding fault line selection method and system

Abstract

The invention relates to an arc suppression coil grounding system single-phase grounding fault line selection method and system. The method comprises the following steps: determining a grounding phase based on three-phase bus voltage; acquiring three-phase current of all lines in the system before and after a single-phase earth fault occurs; respectively calculating a comprehensive index for ground fault line selection of each line; and sorting the lines according to the comprehensive indexes for grounding fault line selection from large to small. The calculation method of the comprehensive index for ground fault line selection comprises the following steps: calculating a ratio method index and a difference method index of each line, carrying out normalization processing, and calculating a ratio method index confidence coefficient and a difference method index confidence coefficient of each line; and according to the normalized ratio method index and difference method index of each line and the corresponding confidence coefficient, calculating a comprehensive index for ground fault line selection of each line. The system comprises a data acquisition module, an information calculation module and a result output module which are connected in sequence. The method is high in line selection accuracy, can improve the fault handling efficiency, is convenient to implement, and is low in cost.

Description

Technical Field

[0001] The present invention relates to the field of single-phase grounding fault line selection in a distribution network, and in particular to a single-phase grounding fault line selection method and system in an arc suppression coil grounding system based on phase current characteristics. Background Art

[0002] Neutral grounding via arc suppression coils is a common neutral grounding method for 10kV and 35kV distribution networks. When a single-phase ground fault occurs within the system, to improve power supply reliability, the system is generally allowed to operate with the fault for 1-2 hours. During this period, the arc suppression coils compensate for the system-wide capacitive current flowing through the ground fault point, minimizing damage to the fault current connection point. However, this also weakens the fault signal characteristics of the faulty line, making fault line selection more difficult.

[0003] The power supply side of a 10kV distribution network typically uses a delta connection, with arc suppression coils connected to the neutral point of a dedicated grounding transformer. Because the operating mode of a 10kV distribution network changes frequently, the arc suppression coil's position is typically automatically adjustable, with two adjustment methods: pre-commissioning and on-demand. Because arc suppression coils present the risk of linear resonance when fully compensated, they are typically operated with moderate overcompensation. Therefore, regardless of the adjustment method used, a certain amount of residual current will remain at the fault point after a single-phase ground fault occurs.

[0004] Currently, methods for single-phase grounding line selection in arc suppression coil grounding systems primarily include transient component methods, steady-state component methods, signal injection methods, and deep learning. However, these methods suffer from numerous drawbacks in practical applications, including increased equipment modification costs, excessively high requirements for transient and zero-sequence data acquisition, and low identification accuracy. Actual fault handling often relies on manual line selection by dispatchers, which not only increases fault analysis time but also has low accuracy, easily leading to the escalation of grounding faults and unnecessary power outages for users. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a single-phase grounding fault line selection method for an arc suppression coil grounding system, which can realize single-phase grounding fault line selection in an arc suppression coil grounding system conveniently, accurately and at low cost.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is: A method for selecting a single-phase grounding fault line in an arc suppression coil grounding system, characterized in that the method comprises the following steps: Step 1: The phase with the lowest bus voltage among the three-phase busbars after the grounding alarm is issued is regarded as the grounding phase, and the other two phases are non-grounding phases; collect the data of all the selected lines in the arc suppression coil grounding system before the single-phase grounding fault occurs. TWithin 1 minute and after a single-phase grounding fault occurs T Three-phase current within 2 minutes; Step 2: Calculate the comprehensive index for ground fault line selection of each line respectively; Step 3: Sort the lines in descending order according to the comprehensive indicators for ground fault line selection to obtain a priority order for single-phase ground fault line selection, thereby completing single-phase ground fault line selection based on the priority order and the grounded phase; The step 2 comprises the following steps: Step 2-1: The lines are defined as Line 1~ N , N is an integer greater than 1, and the line 1~ N Select the lines for which the comprehensive index for ground fault line selection has not been calculated. i ; Step 2-2: According to the line i Before a single-phase ground fault occurs T Within 1 minute and after a single-phase grounding fault occurs T Calculate the three-phase current of the circuit within 2 minutes i Ratio method index Sum-difference method indicator ; Step 2-3: For the circuit i Ratio method index Sum-difference method indicator Perform normalization processing to obtain the line i Normalized value of the ratio method index Normalized value of sum-difference method indicator ; Step 2-4: According to the line i Before a single-phase ground fault occurs T Within 1 minute and after a single-phase grounding fault occurs T Calculate the three-phase current of the circuit within 2 minutes i The average current , and according to the line i The average current Calculate the line i Confidence level of the ratio method index Confidence of Sum Difference Method Index ; Step 2-5: According to the circuit i Normalized value of the ratio method index Normalized value of sum-difference method indicator And the line i Confidence level of the ratio method index Confidence of Sum Difference Method Index , calculate the line i Comprehensive indicators for ground fault line selection ; Step 2-6: If the line 1~ N If the calculation of the ground fault line selection comprehensive index is completed, then continue to step 3, otherwise reselect the line from the lines for which the ground fault line selection comprehensive index has not been calculated. i Then return to step 2-2.

[0007] According to a specific embodiment of the present invention, in step 2-2, the circuit i Ratio method index The calculation method is: ; The line i Difference method indicator The calculation method is: ; Where, Indicates line i exist t The measured value of the ground phase current at the moment, Indicates line i exist t The sum of the measured values ​​of the non-grounded phase current at the moment, Indicates that after a single-phase ground fault occurs, the line i Ratio method index Sum-difference method indicator exist t The weight value at the moment.

[0008] According to a preferred embodiment of the present invention, after a single-phase grounding fault occurs, the line i Ratio method index Sum-difference method indicator exist t Weight value at the moment The calculation method is: , Where, m is an adjustable parameter used to adjust the weight distribution between moments.

[0009] Preferably, in steps 2-3, the circuit i Normalized value of the ratio method index The calculation method is: ; The normalized value of the difference method indicator The calculation method is: ; Where, is the minimum value of the ratio method index of all the lines, is the maximum value of the ratio method index of all the lines, is the minimum value of the difference method index of all the lines, It is the maximum value of the difference method index of all the lines.

[0010] Furthermore, in the steps 2-4, the circuit i Confidence level of the ratio method index The calculation method is: ; The line i Confidence of difference method index The calculation method is: ; The line i The average current The calculation method is: ; Where, 、 The lines i Confidence level of the ratio method index Confidence of Sum Difference Method Index The corresponding current threshold, and .

[0011] According to a specific embodiment of the present invention, in steps 2-5, the circuit i Comprehensive indicators for ground fault line selection The calculation method is: .

[0012] Preferably, in step 1, T 1= T 2.

[0013] Another aspect of the present invention provides a single-phase grounding fault line selection system for an arc suppression coil grounding system, which is used to implement the above-mentioned single-phase grounding fault line selection method for an arc suppression coil grounding system.

[0014] The arc suppression coil grounding system single-phase grounding fault line selection system includes: The data acquisition module is used to collect the three-phase bus voltage in the arc suppression coil grounding system when a single-phase grounding fault occurs, and to collect the voltage of all selected lines in the arc suppression coil grounding system before a single-phase grounding fault occurs. T Within 1 minute and after a single-phase grounding fault occurs TThree-phase current within 2 minutes; an information calculation module connected to the data acquisition module, the information calculation module being used to identify the grounded phase, calculate a comprehensive index for ground fault line selection for each of the lines, and sort the lines in descending order of the comprehensive index for ground fault line selection to obtain a priority order for single-phase ground fault line selection; A result output module is connected to the information calculation module and is used to output a priority order for line selection for a single-phase grounding fault.

[0015] Furthermore, the arc suppression coil grounding system single-phase grounding fault line selection system also includes: A parameter definition module is connected to the information calculation module and is used to define a plurality of parameters required for calculating the comprehensive index for ground fault line selection.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1. The present invention has a high line selection accuracy, significantly improves fault handling efficiency, and reduces power outage losses for users; 2. The present invention is easy to implement, low-cost, does not require new or upgraded equipment, and is easy to acquire data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Attachment Figure 1 The present invention is a flow chart of the method for selecting a line for a single-phase grounding fault in an arc suppression coil grounding system.

[0018] Attachment Figure 2 This is a three-phase current curve diagram of a certain line before and after grounding provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0020] Example 1: As shown in the attached Figure 1 As shown, a method for selecting a single-phase grounding fault line in an arc suppression coil grounding system includes the following steps: Step 1: Identify the grounded phase based on the three-phase bus voltage, that is, the phase with the lowest bus voltage among the three-phase bus after the grounding alarm is issued is regarded as the grounded phase, and the other two phases are non-grounded phases; collect the data of all selected lines in the same arc suppression coil grounding system before the single-phase grounding fault occurs. T Within 1 minute and after a single-phase grounding fault occurs T Three-phase current within 2 minutes.

[0021] Typically, you can choose T 1= T 2= T , the three-phase current collected in this step is the current of all selected lines in the same arc suppression coil grounding system before and after the single-phase grounding fault occurs. T Three-phase current within minutes. In this embodiment, T Take it as 15. For a set of arc suppression coil grounding system, the arc suppression coil grounding system has a total of 10 outgoing lines, then these 10 outgoing lines are all lines to be selected, and one of the outgoing line switches is T The three-phase current curve within minutes is shown in the attached figure. Figure 2 When a single-phase grounding fault occurs in this system, the voltage of phase A is the lowest. In this arc suppression coil grounding system, the grounded phase is phase A, and the ungrounded phases are phases B and C.

[0022] Step 2: Calculate the comprehensive index for ground fault line selection for each line.

[0023] This step includes calculating the ratio method index and the difference method index of each line, normalizing the ratio method index and the difference method index of each line respectively, calculating the confidence level of the ratio method index and the difference method index of each line respectively based on the average current of each line, and calculating the comprehensive index for ground fault line selection of each line based on the normalized ratio method index and difference method index of each line and the corresponding confidence level. The details are as follows: Step 2 includes the following steps: Step 2-1: All the routes to be selected are defined as route 1~ N ( N is an integer greater than 1), by line 1~ N Select the lines for which the comprehensive indicators for ground fault line selection have not yet been calculated i .

[0024] Step 2-2: For the currently selected line i , according to the line i Before a single-phase ground fault occurs T Within 1 minute and after a single-phase grounding fault occurs T Three-phase current within 2 minutes, calculate the circuit i Ratio method index Sum-difference method indicator .

[0025] line i Ratio method index The calculation method is: (1) line i Difference method indicator The calculation method is: (2) Since in this embodiment T 1= T 2= T , then the line i Ratio method index The calculation method is: (3) line i Difference method indicator The calculation method is: (4) In formulas (1)-(4), T Indicates the time section number of data collection before and after the single-phase grounding fault occurs. Indicates line i exist t The measured value of the ground phase current at the moment, Indicates line i exist t The sum of the measured values ​​of the non-grounded phase current at the moment, Indicates that after a single-phase ground fault occurs, the line i Ratio method index Sum-difference method indicator exist t The weight value at the moment.

[0026] Among them, after a single-phase grounding fault occurs, the line i Ratio method index Sum-difference method indicator exist t Weight value at the moment The calculation method is: (5) Right now (6) In formula (5) and (6), m is an adjustable parameter used to adjust the weight distribution between each moment. In this embodiment, the adjustable parameter m Set to 10.

[0027] Step 2-3: Line alignment i Ratio method index Sum-difference method indicator Perform normalization and get the line i Normalized value of the ratio method index Normalized value of sum-difference method indicator .

[0028] line i Normalized value of the ratio method index The calculation method is: (7) Normalized value of difference method indicator The calculation method is: (8) In formula (7) and (8), is the minimum value of the ratio method index of all lines, is the maximum value of the ratio method index of all lines, is the minimum value of the difference method index of all lines, It is the maximum value of the difference method index of all lines.

[0029] For the 10 outgoing lines in the arc suppression coil grounding system of this embodiment, the ratio method index and difference method index before and after grounding and their normalized data are shown in Table 1.

[0030]

[0031] Step 2-4: According to the line i Before a single-phase ground fault occurs T Within 1 minute and after a single-phase grounding fault occurs T Three-phase current calculation circuit within 2 minutes i The average current , and according to the line i The average current Calculation route i Confidence level of the ratio method index Confidence of Sum Difference Method Index .

[0032] line i Confidence level of the ratio method index The calculation method is: (9) line i Confidence of difference method index The calculation method is: (10) line i The average current The calculation method is: (11) Right now (12) In formula (9) and (10), 、 Separate lines i Confidence level of the ratio method index Confidence of Sum Difference Method Index The corresponding current threshold, and In this embodiment 1, and They are set at 20A and 300A respectively.

[0033] Table 2 shows the average currents of the 10 outgoing lines in the arc suppression coil grounding system of this embodiment, as well as the confidence levels of the ratio method indicators and the difference method indicators.

[0034]

[0035] Step 2-5: According to the line i Normalized value of the ratio method index Normalized value of sum-difference method indicator and lines i Confidence level of the ratio method index Confidence of Sum Difference Method Index , calculate the circuit i Comprehensive indicators for ground fault line selection .

[0036] line i Comprehensive indicators for ground fault line selection The calculation method is: (13) Table 3 shows the comprehensive indicators for ground fault line selection for the 10 outgoing lines in the arc suppression coil grounding system of this embodiment.

[0037]

[0038] Step 2-6: If line 1~ N If all comprehensive indicators for ground fault line selection are calculated, proceed to step 3. Otherwise, reselect the line from the lines for which comprehensive indicators for ground fault line selection have not been calculated. i Then return to step 2-2.

[0039] Step 3: Line 1~ NAfter all the comprehensive indicators for ground fault line selection are calculated, the lines are sorted in descending order according to the comprehensive indicators for ground fault line selection to obtain the priority order for single-phase ground fault line selection, and then the single-phase ground fault line selection is completed based on the priority order and the grounded phase. That is, the higher the priority order, the greater the possibility of a single-phase ground fault occurring in the line.

[0040] Based on the results described in Table 3, in the arc suppression coil grounding system of this embodiment, the first three line numbers of the single-phase grounding line selection are line 7, line 9 and line 3, respectively, and the line where grounding actually occurs is line 7, which verifies the effectiveness of this line selection method.

[0041] In the above scheme, the adjustable parameters m , confidence level of ratio method index Corresponding current threshold , confidence level of difference method index Corresponding current threshold The setting is determined based on the substation operating conditions, historical ground fault current characteristics and accident handling experience.

[0042] The above arc suppression coil grounding system single-phase grounding fault line selection method is implemented by the following arc suppression coil grounding system single-phase grounding fault line selection system.

[0043] The arc suppression coil grounding system single-phase grounding fault line selection system mainly includes a data acquisition module, an information calculation module and a result output module. The information calculation module is connected to the data acquisition module, and the result output module is connected to the information calculation module. The data acquisition module is used to collect the three-phase bus voltage in the arc suppression coil grounding system when a single-phase grounding fault occurs, and to collect the voltage of all lines to be selected in the arc suppression coil grounding system before the single-phase grounding fault occurs. T Within 1 minute and after a single-phase grounding fault occurs T The three-phase current within 2 minutes. The information calculation module is used to identify the grounded phase, calculate the comprehensive index for ground fault line selection for each line, and sort the lines from highest to lowest comprehensive index to determine the priority order for single-phase ground fault line selection. The result output module is used to output the priority order for single-phase ground fault line selection.

[0044] Preferably, the arc suppression coil grounding system single-phase ground fault line selection system also includes a parameter definition module connected to the information calculation module. The parameter definition module is used to define multiple parameters required for calculating the comprehensive index for ground fault line selection, specifically including defining adjustable parameters m , difference method and ratio method indicator current threshold and , data collection time span T .

[0045] The beneficial effects of the present invention are: compared with the existing technology, the implementation cost of the present invention is low, and it is only necessary to write relevant programs in the dispatching automation system to perform calculations to obtain the analysis results, without paying additional equipment installation and upgrade costs; data acquisition is convenient, the present invention only needs to collect the three-phase currents of each line before and after the single-phase grounding fault, and the data accuracy can reach the minute level. There is no need to collect transient quantities and zero-sequence quantities, and no need to perform phase calculations; the line selection accuracy is high. For single-phase metallic grounding faults in conventional arc suppression coil grounding systems, the line selection accuracy can be close to 100%, which significantly improves the fault handling efficiency and reduces power outage losses to users.

[0046] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for selecting a single-phase ground fault line in an arc suppression coil grounding system, characterized by: The arc suppression coil grounding system single-phase grounding fault line selection method comprises the following steps: Step 1: The phase with the lowest bus voltage among the three-phase busbars after the grounding alarm is issued is regarded as the grounding phase, and the other two phases are non-grounding phases; collect the data of all the selected lines in the arc suppression coil grounding system before the single-phase grounding fault occurs. T Within 1 minute and after a single-phase grounding fault occurs T Three-phase current within 2 minutes; Step 2: Calculate the comprehensive index for ground fault line selection of each line respectively; Step 3: Sort the lines in descending order according to the comprehensive indicators for ground fault line selection to obtain a priority order for single-phase ground fault line selection, thereby completing single-phase ground fault line selection based on the priority order and the grounded phase; The step 2 comprises the following steps: Step 2-1: The lines are defined as Line 1~ N , N is an integer greater than 1, and the line 1~ N Select the lines for which the comprehensive index for ground fault line selection has not been calculated. i ; Step 2-2: According to the line i Before a single-phase ground fault occurs T Within 1 minute and after a single-phase grounding fault occurs T Calculate the three-phase current of the circuit within 2 minutes i Ratio method index Sum-difference method indicator ; Step 2-3: For the circuit i Ratio method index Sum-difference method indicator Perform normalization processing to obtain the line i Normalized value of the ratio method index Normalized value of sum-difference method indicator ; Step 2-4: According to the line i Before a single-phase ground fault occurs T Within 1 minute and after a single-phase grounding fault occurs T Calculate the three-phase current of the circuit within 2 minutes i The average current , and according to the line i The average current Calculate the line i Confidence level of the ratio method index Confidence of Sum Difference Method Index ; Step 2-5: According to the circuit i Normalized value of the ratio method index Normalized value of sum-difference method indicator And the line i Confidence level of the ratio method index Confidence of Sum Difference Method Index , calculate the line i Comprehensive indicators for ground fault line selection ; Step 2-6: If the line 1~ N If the calculation of the ground fault line selection comprehensive index is completed, then continue to step 3, otherwise reselect the line from the lines for which the ground fault line selection comprehensive index has not been calculated. i Then return to step 2-2.

2. The method for selecting a single-phase ground fault line in an arc suppression coil grounding system according to claim 1, characterized in that: In step 2-2, the circuit i Ratio method index The calculation method is: ； The line i Difference method indicator The calculation method is: ； Where, Indicates line i exist t The measured value of the ground phase current at the moment, Indicates line i exist t The sum of the measured values ​​of the non-grounded phase current at the moment, Indicates that after a single-phase ground fault occurs, the line i Ratio method index Sum-difference method indicator exist t The weight value at the moment.

3. The method for selecting a single-phase ground fault line in an arc suppression coil grounding system according to claim 2, characterized in that: After a single-phase ground fault occurs, the line i Ratio method index Sum-difference method indicator exist t Weight value at the moment The calculation method is: ， Where, m is an adjustable parameter used to adjust the weight distribution between moments.

4. The method for selecting a single-phase ground fault line in an arc suppression coil grounding system according to claim 1, characterized in that: In the steps 2-3, the circuit i Normalized value of the ratio method index The calculation method is: ； The normalized value of the difference method indicator The calculation method is: ； Where, is the minimum value of the ratio method index of all the lines, is the maximum value of the ratio method index of all the lines, is the minimum value of the difference method index of all the lines, It is the maximum value of the difference method index of all the lines.

5. The method for selecting a single-phase ground fault line in an arc suppression coil grounding system according to claim 1, characterized in that: In the steps 2-4, the circuit i Confidence level of the ratio method index The calculation method is: ； The line i Confidence of difference method index The calculation method is: ； The line i The average current The calculation method is: ； Where, 、 The lines i Confidence level of the ratio method index Confidence of Sum Difference Method Index The corresponding current threshold, and .

6. The method for selecting a single-phase ground fault line in an arc suppression coil grounding system according to claim 1, characterized in that: In the steps 2-5, the circuit i Comprehensive indicators for ground fault line selection The calculation method is: 。 7. The method for selecting a single-phase ground fault line in an arc suppression coil grounding system according to claim 1, characterized in that: In the step 1, T 1= T 2.

8. A single-phase grounding fault line selection system for an arc suppression coil grounding system, used to implement the single-phase grounding fault line selection method for an arc suppression coil grounding system according to any one of claims 1 to 7, characterized in that: It includes: The data acquisition module is used to collect the three-phase bus voltage in the arc suppression coil grounding system when a single-phase grounding fault occurs, and to collect the voltage of all selected lines in the arc suppression coil grounding system before a single-phase grounding fault occurs. T Within 1 minute and after a single-phase grounding fault occurs T Three-phase current within 2 minutes; an information calculation module connected to the data acquisition module, the information calculation module being used to identify the grounded phase, calculate a comprehensive index for ground fault line selection for each of the lines, and sort the lines in descending order of the comprehensive index for ground fault line selection to obtain a priority order for single-phase ground fault line selection; A result output module is connected to the information calculation module and is used to output a priority order for line selection for a single-phase grounding fault.

9. The arc suppression coil grounding system single-phase grounding fault line selection system according to claim 8, characterized in that: It also includes: A parameter definition module is connected to the information calculation module and is used to define a plurality of parameters required for calculating the comprehensive index for ground fault line selection.

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