Single-phase earth fault line selection method and system for arc suppression coil earthed systems

Abstract

The present invention relates to a method and system for selecting a single-phase grounding fault line in an arc suppression coil grounding system. The method comprises the following steps: determining the grounded phase based on the three-phase bus voltage; collecting the three-phase currents of all lines in the system before and after a single-phase grounding fault occurs; calculating a comprehensive index for grounding fault line selection for each line; and sorting the lines in descending order according to the comprehensive index for grounding fault line selection. The method for calculating the comprehensive index for grounding fault line selection comprises the following steps: calculating the ratio method index and the difference method index for each line and normalizing them, calculating the confidence level of the ratio method index and the confidence level of the difference method index for each line, and calculating the comprehensive index for grounding fault line selection for each line based on the normalized ratio method index and the difference method index and the corresponding confidence level. The system comprises a data acquisition module, an information calculation module, and a result output module connected in sequence. The present invention has a high line selection accuracy, can improve fault handling efficiency, is easy to implement, and has low cost.

Description

TECHNICAL FIELD

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

[0002] The neutral point grounding through arc suppression coil is a common neutral point grounding mode for 10kV and 35kV power distribution network system. When a single-phase grounding fault occurs in the system, in order to improve the reliability of power supply, the system is generally allowed to operate with fault for 1-2 hours during which the arc suppression coil can compensate the capacitive current flowing through the grounding fault point of the whole system, reducing the damage of fault current to the grounding point, but it also weakens the fault characteristics of the fault line and increases the difficulty of fault line selection.

[0003] The power supply side of 10kV power distribution network is usually connected in delta, and the arc suppression coil is led out through the neutral point of the special grounding transformer. Due to the frequent change of the operation mode of 10kV power distribution network, the gear of the arc suppression coil can usually be automatically adjusted, and the gear adjustment mode is divided into pre-adjustment and follow-up adjustment. Since there is a risk of linear resonance in the full compensation state of the arc suppression coil, the arc suppression coil usually operates with moderate over-compensation, so whether the pre-adjustment or follow-up adjustment is adopted, there will be a certain residual current at the grounding fault point after a single-phase grounding fault occurs.

[0004] At present, there are mainly transient component method, steady component method, signal injection method and deep learning method for single-phase grounding line selection of arc suppression coil grounding system, but the above methods have many shortcomings in actual application, such as increasing the cost of equipment modification, requiring too high for transient quantity and zero sequence quantity collection, and low recognition result accuracy. In actual fault handling, it is still necessary to rely on the experience of dispatchers for manual line selection, which not only increases the time of fault analysis and judgment, but also has low accuracy, which is easy to cause the expansion of grounding fault and unnecessary power outage of users. SUMMARY

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

[0006] To solve the above problems, the technical scheme adopted by the present application is:

[0007] A single-phase grounding fault line selection method for arc suppression coil grounding system, characterized in that the single-phase grounding fault line selection method for arc suppression coil grounding system comprises the following steps:

[0008] 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;

[0009] Step 2: Calculate the comprehensive index for ground fault line selection of each line respectively;

[0010] 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;

[0011] The step 2 comprises the following steps:

[0012] 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 ;

[0013] 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 ;

[0014] 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 ;

[0015] 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 ;

[0016] 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 ;

[0017] 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.

[0018] According to a specific embodiment of the present invention, in step 2-2, the circuit i Ratio method index The calculation method is:

[0019] ;

[0020] The line i Difference method indicator The calculation method is:

[0021] ;

[0022] 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.

[0023] 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:

[0024] ,

[0025] Where, m is an adjustable parameter used to adjust the weight distribution between moments.

[0026] Preferably, in steps 2-3, the circuit i Normalized value of the ratio method index The calculation method is:

[0027] ;

[0028] The normalized value of the difference method indicator The calculation method is:

[0029] ;

[0030] 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.

[0031] Furthermore, in the steps 2-4, the circuit i Confidence level of the ratio method index The calculation method is:

[0032] ;

[0033] The line i Confidence of difference method index The calculation method is:

[0034] ;

[0035] The line i The average current The calculation method is:

[0036] ;

[0037] Where, 、 The lines i Confidence level of the ratio method index Confidence of Sum Difference Method Index The corresponding current threshold, and .

[0038] 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:

[0039] .

[0040] Preferably, in step 1, T 1= T 2.

[0041] 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.

[0042] The arc suppression coil grounding system single-phase grounding fault line selection system includes:

[0043] 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;

[0044] 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;

[0045] 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.

[0046] Furthermore, the arc suppression coil grounding system single-phase grounding fault line selection system also includes:

[0047] 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.

[0048] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0049] 1. The present invention has a high line selection accuracy, significantly improves fault handling efficiency, and reduces power outage losses for users;

[0050] 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

[0051] 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.

[0052] 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

[0053] 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.

[0054] 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:

[0055] 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.

[0056] 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.

[0057] Step 2: Calculate the comprehensive index for ground fault line selection for each line.

[0058] 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:

[0059] Step 2 includes the following steps:

[0060] 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 .

[0061] 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 .

[0062] line i Ratio method index The calculation method is:

[0063] (1)

[0064] line i Difference method indicator The calculation method is:

[0065] (2)

[0066] Since in this embodiment T 1= T 2= T , then the line i Ratio method index The calculation method is:

[0067] (3)

[0068] line i Difference method indicator The calculation method is:

[0069] (4)

[0070] In formula (1)-(4), T represents the number of time sections for data collection before and after the single-phase ground fault occurs, represents the line i In t the ground phase current measured value at the moment, represents the line i In t the sum of the non-ground phase current measured value at the moment, represents the ratio method index of the line i after the single-phase ground fault occurs and the difference method index In t the weight value at the moment.

[0071] wherein the ratio method index of the line i after the single-phase ground fault occurs and the difference method index In t the weight value at the moment The calculation method of

[0072] (5)

[0073] That is

[0074] (6)

[0075] In formula (5) (6), m is an adjustable parameter for adjusting the weight distribution between each moment. In the embodiment, the adjustable parameter m is defined as 10.

[0076] Step 2-3: The ratio method index i and the difference method index of the line are normalized to obtain the normalized value of the ratio method index i and the normalized value of the difference method index of the line .

[0077] The calculation method of the normalized value of the ratio method index i of the line is:

[0078] (7)

[0079] The calculation method of the normalized value of the difference method index is:

[0080] (8)

[0081] In formula (7) (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, is the maximum value of the difference method index of all lines.

[0082] For 10 outgoing lines in the arc suppression coil grounding system of the present embodiment, the ratio method index and the difference method index before and after grounding and the normalized data thereof are shown in Table 1.

[0083]

[0084] Step 2-4: According to the average current of line i before the occurrence of single-phase grounding fault T within 1 minute and after the occurrence of single-phase grounding fault T within 2 minutes, the average current of line i is calculated , and the ratio method index confidence of line i and the difference method index confidence of line are calculated according to the average current of line i . .

[0085] The calculation method of the ratio method index confidence of line i is as follows:

[0086] (9)

[0087] The calculation method of the difference method index confidence of line i is as follows:

[0088] (10)

[0089] The calculation method of the average current of line i is as follows:

[0090] (11)

[0091] That is,

[0092] (12)

[0093] In formula (9) (10), , line 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.

[0094] 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.

[0095]

[0096] 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 .

[0097] line i Comprehensive indicators for ground fault line selection The calculation method is:

[0098] (13)

[0099] 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.

[0100]

[0101] 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.

[0102] Step 3: Line 1~ N After 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.

[0103] Based on the results described in Table 3, in the arc suppression coil grounding system of the embodiment, the top three line numbers of single-phase grounding line selection are line 7, line 9 and line 3, and the actual grounding line is line 7, which verifies the effectiveness of the line selection method.

[0104] In the above scheme, the adjustable parameters m , the ratio method index confidence , the corresponding current threshold , the difference method index confidence , the corresponding current threshold are set according to the operation state of the substation, the historical grounding fault current characteristics and the accident disposal experience.

[0105] The single-phase grounding fault line selection method of the arc suppression coil grounding system described above is implemented through the following single-phase grounding fault line selection system of the arc suppression coil grounding system.

[0106] The single-phase grounding fault line selection system of the arc suppression coil grounding system mainly includes a data acquisition module, an information calculation module and a result output module. The information calculation module is connected with the data acquisition module, and the result output module is connected with the information calculation module. The data acquisition module is used to acquire the three-phase bus voltage in the arc suppression coil grounding system when a single-phase grounding fault occurs, and to acquire the three-phase current of all lines to be selected in the arc suppression coil grounding system within T 1 minute before and T 2 minutes after the single-phase grounding fault occurs. The information calculation module is used to determine the grounding phase, to calculate the grounding fault line selection comprehensive index of each line respectively, and to sort the lines according to the grounding fault line selection comprehensive index from large to small to obtain the priority order of single-phase grounding fault line selection. The result output module is used to output the priority order of single-phase grounding fault line selection.

[0107] Preferably, the single-phase grounding fault line selection system of the arc suppression coil grounding system further includes a parameter definition module connected with the information calculation module. The parameter definition module is used to define a plurality of parameters required when calculating the grounding fault line selection comprehensive index, specifically including defining adjustable parameters m , difference method and ratio method index current threshold , and , data acquisition time span T .

[0108] The application has the advantages that, compared with the prior art, the application has low implementation cost, the judgment result can be obtained by writing a relevant program in the dispatching automation system for calculation, no additional equipment installation and upgrading cost needs to be paid, data acquisition is convenient, the application only needs to collect three-phase currents of each line before and after single-phase grounding fault, the data precision reaches minute level, no transient quantity and zero sequence quantity needs to be collected, no phase quantity calculation needs to be performed, the line selection accuracy is high, for a single-phase metallic grounding fault of a conventional arc-extinguishing coil grounding system, the line selection accuracy can be close to 100%, the fault disposal efficiency is significantly improved, and the power loss of users is reduced.

[0109] The above examples are only for illustrating the technical concept and characteristics of the application, and the purpose is to enable those skilled in the art to understand the content of the application and implement it, and cannot limit the protection scope of the application. Any equivalent changes or modifications made according to the spirit and principle of the application should be covered within the protection scope of the application.

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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