A small current grounding line selection method and device of adaptive double mother operation mode

Abstract

The application discloses a small current grounding line selection method and device in adaptive double bus operation mode, and the method comprises the following steps: when the bus zero sequence voltage exceeds a preset threshold, extracting the bus zero mode voltage characteristic frequency band transient component and all branch zero mode current characteristic frequency band transient component; carrying out threshold discrimination on the fundamental wave amplitude of all branch zero sequence currents, and screening out possible fault branches; calculating the vector sum of all possible fault branch zero sequence current transient components, when the vector sum is 0, if the number of fault buses is 1, then the maximum branch of the transient component cumulative sum is the fault branch; otherwise, according to the fault characteristic correlation characteristics of the branch zero sequence current and the zero sequence voltage after the alignment of the zero sequence voltage singular points, judging whether the current branch is the fault branch; when the vector sum is not 0, if all branch zero sequence current fault characteristics can be classified as no more than the number of fault buses, then the bus is grounded, otherwise, the unique branch of the fault characteristics is the fault branch. The application makes the fault discrimination adaptive to the double bus operation mode.

Description

Technical Field

[0001] This invention relates to the field of single-phase grounding fault detection in a dual-busbar connection mode of a low-current grounding system, specifically to a method and device for selecting a low-current grounding fault in an adaptive dual-busbar operation mode. Background Technology

[0002] When there are large power loads, many important loads, high requirements for power supply reliability, or many feeder circuits, and it is difficult to use a single busbar segmentation method, a double busbar connection method is often used. Due to its advantages of high reliability, uninterrupted power supply during busbar maintenance, uninterrupted power supply during busbar disconnector maintenance, flexible dispatching, and convenient expansion, the double busbar connection method is widely used in the 35-110kV busbar system of the main step-down substation of large industrial enterprises and the 6-10kV busbar system with important high-voltage loads.

[0003] Existing methods and devices for selecting the line in low-current grounding systems require that the zero-sequence current of each branch be strictly associated with its respective busbar; otherwise, it may cause false tripping or failure to trip. Switching operations are more common in double-busbar systems, meaning that the busbar to which a branch belongs is uncertain. This causes the line selection device in the low-current grounding system to fail to update the configuration of the busbar to which each branch belongs in a timely manner, affecting the final line selection result.

[0004] In addition, if a permanent grounding fault occurs in the system and is not handled in time, it may cause a series of hazards: the voltage of non-faulty phases to ground will increase (up to the line voltage value), and weak points in the insulation of the system may break down, causing short circuit faults; the fault current, which is not large, will exist for a long time, which can easily cause electric shock accidents, burn out equipment, and may develop into phase-to-phase short circuit faults; when an intermittent arc is generated at the fault point, a series resonant overvoltage will be generated under certain conditions, which can reach 2.5 to 3 times the phase voltage, which is very harmful to the insulation of the system.

[0005] Therefore, there is an urgent need to propose an adaptive low-current grounding line selection method for dual-bus operation mode to solve the problems of uncertainty in the busbars to which each branch belongs in the dual-bus connection system, which makes it impossible to automatically match, the difficulty in collecting the branch disconnector position in the dual-bus connection mode, and the strong coupling between the branch zero-sequence current and zero-sequence voltage in the existing grounding line selection method. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to propose an adaptive dual-bus operation mode low-current grounding line selection method and device, which solves the problems mentioned in the background art and is applicable to low-current grounding systems with dual-bus connection.

[0007] Technical solution: Firstly, an adaptive dual-bus operation mode low-current grounding fault location method, comprising the following steps:

[0008] The sampled values ​​of the zero-sequence voltage of the two buses are obtained. When the zero-sequence voltage of the bus exceeds the preset voltage threshold, the transient components of the characteristic frequency band of the zero-mode voltage of the bus and the transient components of the characteristic frequency band of the zero-mode current of all branches are extracted by digital filtering method.

[0009] The fundamental amplitude of the zero-sequence current in all branches is determined based on a preset current threshold, and potentially faulty branches are selected.

[0010] Calculate the vector sum of the transient components of the zero-sequence current in all possible faulty branches. When the vector sum of the transient components is "0", if the number of faulty buses is "1", then the branch with the largest cumulative sum of transient components is determined to be the faulty branch. Otherwise, determine whether the current branch is a faulty branch based on the correlation characteristics between the zero-sequence current and the zero-sequence voltage fault characteristics of each branch after zero-sequence voltage singularity point alignment. When the vector sum of the transient components is not "0", if the fault characteristics of the zero-sequence current in all branches can be classified into categories not greater than the number of faulty buses, then the bus is grounded. Otherwise, the branch with the only fault characteristics is the faulty branch.

[0011] According to certain embodiments of the first aspect, determining whether the bus zero-sequence voltage exceeds a preset voltage threshold includes: according to the formula Calculate the zero-sequence voltage amplitude U of the bus. 0n In the formula u 0nj It is the j-th sampled value of the zero-sequence voltage of bus n, where N is the number of sampling points within half a cycle. The determination is whether U... 0n >U set， U set This is the preset voltage threshold.

[0012] According to certain embodiments of the first aspect, the process of judging the fundamental amplitude of the zero-sequence current of all branches based on a preset current threshold and screening out potentially faulty branches includes: for each branch, obtaining the fundamental amplitude I of the zero-sequence current of the branch. 0Hm1 , if I 0nm1 >I set， If the current branch is a potentially faulty branch, then the current branch is a non-faulty branch. set Using a preset current threshold, select m potentially faulty branches.

[0013] According to certain implementations of the first aspect, the vector sum of the transient components of the zero-sequence current in all possible faulty branches is calculated as follows: In the formula, m is the number of possible faulty branches, and i 0(f) The characteristic frequency band transient component of the zero-sequence current of the branch is given.

[0014] According to certain embodiments of the first aspect, the cumulative sum of transient components is calculated from the transient components of the complete two-cycle characteristic frequency band, as expressed below: E x(f) For the cumulative sum of transient components, i 0(f)is the transient component of the zero-sequence current of the branch in the characteristic frequency band.

[0015] According to some embodiments of the first aspect, the method for selecting a zero-sequence voltage singular point is as follows: determining whether u satisfies i+q >K set u i , if the condition is satisfied, the (i+1)-th point is a singular point, where, u i is the i-th sampling value in the zero-sequence voltage cached data, u i+q is the (i+q)-th sampling value in the zero-sequence voltage cached data, K set is a variation coefficient, and q is the number of consecutive variation points required for determining the (i+1)-th point as a singular point;

[0016] Alignment of zero-sequence voltage singular points comprises: respectively determining an initial fault moment according to the singular points of the zero-sequence voltage transient component in the characteristic frequency band of double busbars, and aligning the zero-sequence voltage and zero-sequence current transient component data in the characteristic frequency band based on the initial fault moment.

[0017] According to some embodiments of the first aspect, determining whether the current branch is a fault branch according to the correlation characteristic of the fault characteristics between the branch zero-sequence current and the zero-sequence voltage comprises: determining a fault characteristic similarity analysis interval according to peak points and valley points of the zero-sequence voltage transient component in the characteristic frequency band of double busbars or the branch zero-sequence current transient component in the characteristic frequency band, determining the similarity between the zero-sequence voltage and the zero-sequence current in the fault characteristic analysis interval, if the characteristics are inversely similar, the current branch is a fault branch; otherwise, the current branch is a non-fault branch, wherein the similarity calculation method is as follows:

[0018]

[0019] wherein, vp is the sequence number of the valley point, pp is the sequence number of the peak point; |vp-pp| is the fault characteristic similarity analysis interval; vp<pp?vp:pp represents taking the smaller value of the two; a and b are respectively the zero-sequence voltage of the busbar and the branch zero-sequence current transient component in the characteristic frequency band; inverse similarity is defined as -1.05≤Coe≤-0.95.

[0020] According to some embodiments of the first aspect, the judgment that all branch zero-sequence current fault features can be classified into no more than the number of fault busbar classes comprises: determining a fault characteristic similarity analysis interval according to peak points and valley points of the zero-sequence voltage transient component in the characteristic frequency band of double busbars, calculating the similarity between any two branch zero-sequence currents in the analysis interval, and judging whether the value of similarity is no more than the number of fault busbar classes, wherein the similarity calculation method is as follows:

[0021]

[0022] In the formula, vp is the serial number of valley points, and pp is the serial number of peak points; |vp-pp| is the judgment interval of fault feature similarity; vp<pp? vp:pp represents taking the smaller value of the two; c and d are the transient components in the characteristic frequency band of zero-sequence current of two branches.

[0023] In a second aspect, a small current grounding line selection device adaptive to double-bus operation mode includes:

[0024] a transient feature extraction module configured to acquire zero-sequence voltage sampling values of the double bus, and extract the transient components in the characteristic frequency band of bus zero-mode voltage and the transient components in the characteristic frequency band of zero-mode current of all branches by a digital filtering method when the bus zero-sequence voltage exceeds a preset voltage threshold;

[0025] a candidate fault branch screening module configured to discriminate the fundamental amplitude of zero-sequence current of all branches according to a preset current threshold, and screen out candidate fault branches;

[0026] a fault branch identification module configured to calculate the vector sum of zero-sequence current transient components of all candidate fault branches, when the vector sum of transient components is "0", if the number of fault buses is "1", then determine the branch with the largest cumulative sum of transient components as the fault branch; otherwise, judge whether the current branch is a fault branch according to the correlation between the zero-sequence current of each branch and the fault characteristics of zero-sequence voltage after zero-sequence voltage singular point alignment; when the vector sum of transient components is not "0", if the zero-sequence current fault characteristics of all branches can be classified into no more than the number of fault buses, then it is determined as bus grounding, otherwise, the branch with unique fault characteristics is determined as the fault branch.

[0027] In a third aspect, the present invention further provides a computer device, comprising: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and when executed by the processors, the programs implement the steps of the small current grounding line selection method adaptive to double-bus operation mode according to the first aspect of the present invention.

[0028] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the small current grounding line selection method adaptive to double-bus operation mode according to the first aspect of the present invention are implemented.

[0029] Beneficial effects: To address the problem that existing low-current grounding fault location methods are unsuitable due to the strong coupling between branch zero-sequence current and bus zero-sequence voltage, this invention proposes an adaptive low-current grounding fault location method for dual-bus operation. Based on the transient components of zero-sequence voltage and zero-sequence current, and after filtering out the power frequency component, the method performs transient quantity accumulation and similarity judgment to determine the faulty branch. This effectively solves the problem of uncertainty in the busbars to which each branch belongs in a dual-busbar connection system, making automatic matching impossible. The fault identification process no longer depends on the configuration of the busbar to which the line belongs, and has broad practical application value. Attached Figure Description

[0030] Figure 1 This is a typical wiring diagram for a double busbar system;

[0031] Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 This diagram illustrates a typical double busbar wiring configuration. G1 and G2 are the main power supplies for the system. G1 supplies power to bus W1, with L1 and L2 being its outgoing lines. G2 supplies power to bus W2, with L3 and L4 being its outgoing lines. QF is a circuit breaker used for switching operations during maintenance of a busbar to ensure uninterrupted power supply to the load. QS1_1 represents the disconnecting switch when outgoing line L1 is powered by bus W1; QS1_2 represents the disconnecting switch when outgoing line L1 is powered by bus W2; QS2_1 represents the disconnecting switch when outgoing line L2 is powered by bus W1; QS2_2 represents the disconnecting switch when outgoing line L1 is powered by bus W2; QS3_1 represents the disconnecting switch when outgoing line L3 is powered by bus W1; QS3_2 represents the disconnecting switch when outgoing line L3 is powered by bus W2; QS4_1 represents the disconnecting switch when outgoing line L4 is powered by bus W1; QS4_2 represents the disconnecting switch when outgoing line L4 is powered by bus W2. If the W1 busbar needs maintenance, all four outgoing lines L1-L4 will be powered by the W2 busbar. QS1_2 and QS2_2 will be closed, and the power supply for outgoing lines L1 and L2 will change to G2.

[0034] Reference Figure 2 This invention provides a method for selecting a low-current grounding line in an adaptive dual-bus operation mode, comprising the following steps:

[0035] Step S1: Real-time centralized monitoring of zero-sequence voltage U of the two bus sections 0n That is, the zero-sequence voltage of busbars W1 and W2; and the zero-sequence current i0 of the branch is collected.

[0036] Step S2: When the collected bus zero-sequence voltage amplitude U 0n Exceeding the preset threshold U0set If this occurs, it is determined that a single-phase ground fault has occurred in the system;

[0037] U is usually set 0set =15V, bus zero-sequence voltage amplitude U 0n The calculation method is as follows:

[0038]

[0039] In the formula u 0nj It is the j-th sampled value of the zero-sequence voltage of bus n, and N is the number of sampling points within half a cycle.

[0040] Step S3: Extract the transient component u of the characteristic frequency band of the zero-sequence voltage of the bus. 0n(f) and the transient components of the zero-sequence current characteristic frequency band of all branches i 0(f) ;

[0041] Based on the bus zero-sequence voltage amplitude and the sampled values ​​of zero-sequence current in all branches, digital filtering technology is used to filter out its power frequency component, obtaining the transient component u of the characteristic frequency band of the filtered zero-sequence voltage. 0n(f) and the transient components of the zero-sequence current characteristic frequency band of all branches i 0(f) The filtering expression is as follows:

[0042]

[0043]

[0044] In the formula, i0 is the sampled value of the zero-sequence current of the branch. filter() represents the filtering function, which can be a bandpass filter or a wavelet transform.

[0045] Step S4: Based on the fundamental amplitude I of the branch zero-sequence current 0Hm1 With preset threshold I set Make a judgment and filter out the branches that may be faulty;

[0046] If the fundamental amplitude of the zero-sequence current in a certain branch is I 0Hm1 >I set If the current branch is a potentially faulty branch, then it is a potentially faulty branch; otherwise, it is a non-faulty branch. This process filters out m potentially faulty branches. 0Hm1 It is the fundamental value calculated based on the zero-sequence current sampling value i0 of the branch.

[0047] Step S5: Determine the vector sum of the transient components of the zero-sequence current in the potentially faulty branch. 0sum(f) If the value is "0", proceed to step S6; otherwise, proceed to step S10.

[0048] Vector sum of transient components of zero-sequence current in potentially faulty branches The calculation expression is as follows:

[0049]

[0050] In the formula, m is the number of possible faulty branches.

[0051] Step S6: Determine if the number of faulty buses "n" is "1". If so, the transient sum E is calculated. x(f) If the largest branch is a faulty branch, proceed to step S11; otherwise, proceed to step S7.

[0052] The transient quantity accumulation and E x(f) It is calculated from the transient components of the complete two-cycle characteristic frequency band, and the expression is as follows:

[0053]

[0054] Step S7: Determine the initial time of the fault based on the singular points of the transient components of the zero-sequence voltage characteristic frequency band of the two bus sections, and align the transient component data of the zero-sequence voltage and zero-sequence current characteristic frequency bands based on this.

[0055] The alignment refers to finding the initial time of the zero-sequence voltage and zero-sequence current faults respectively, and re-numbering them from the initial time. For example, if the zero-sequence voltage and current data numbers are 1 to 256 and the initial time is 128, then the subsequent data are reordered starting from 128, that is, the numbers 128 to 256 are reassigned to 1 to 127.

[0056] The method for selecting singular points based on the transient component of the zero-sequence voltage characteristic frequency band is as follows:

[0057] u i+q >K set U i

[0058] If the above formula is satisfied, then the (i+1)th point is determined to be a singular point. In the formula, u i u is the sampled value at point i within the zero-sequence voltage buffer data. i+q K represents the sampled value at point (i+q) within the zero-sequence voltage buffer data. set q is the coefficient of change, and q is the number of consecutive change points required to determine that the (i+1)th point is a singular point, which is usually set to 4.

[0059] Step S8: Based on the peak point u of the transient component of the zero-sequence voltage characteristic frequency band of the two bus segments... 0n(f)_pp Valley point u 0n(f)_vp Select fault feature similarity assessment intervals respectively;

[0060] Step S9: Determine the similarity between the zero-sequence voltage and zero-sequence current within the fault characteristic judgment interval. If they are inversely similar, the current branch is a faulty branch; otherwise, it is a non-faulty branch. Proceed to step S11.

[0061] Step S10: if the similarity between zero-sequence currents within the fault feature research and judgment interval can be classified into no more than n categories, where n is the number of fault busbars, it is determined that the busbar has a ground fault; otherwise, the branch with unique fault features is the grounded branch;

[0062] In step S9 and step S10, the calculation method for the similarity between zero-sequence voltage and zero-sequence current and between different zero-sequence currents within the fault feature research and judgment interval is as follows:

[0063]

[0064] wherein, vp is the sequence number of the valley point, pp is the sequence number of the peak point; |vp-pp| is the fault feature similarity research and judgment interval; vp<pp?vp:pp means judging the size of vp and pp to take the smaller value, that is, if vp is smaller than pp, take vp, otherwise take pp; a and b are transient components in the characteristic frequency band of busbar zero-sequence voltage or branch zero-sequence current. In the present invention, there are two types of similarity: the similarity between busbar zero-sequence voltage and branch zero-sequence current, and the similarity between zero-sequence currents of different branches. That is, when a is the transient component in the characteristic frequency band of busbar zero-sequence voltage, b is the transient component in the characteristic frequency band of branch zero-sequence current; or when a is the transient component in the characteristic frequency band of branch zero-sequence current, b is the transient component in the characteristic frequency band of busbar zero-sequence voltage; or both a and b are transient components in the characteristic frequency band of branch zero-sequence current. Since the sampling of voltage and current is synchronized, the corresponding current is extracted according to the sampling sequence numbers corresponding to the peak and valley of voltage. For example, if the peak and valley of voltage correspond to sampling points 32 and 64 respectively, the data of current from point 32 to point 64 is extracted accordingly.

[0065] With line numbers marked sequentially, similarity calculation is performed for each line in sequence.

[0066] The similarity between zero-sequence voltage and zero-sequence current and between different zero-sequence currents needs to satisfy positive similarity or negative similarity, and the specific classification principles are as follows:

[0067] 1) If more than one branch of a certain branch satisfies positive similarity, similarity classification with other branches will no longer be performed;

[0068] 2) If a certain branch satisfies negative similarity or is classified into other categories with all other branches, it indicates that the fault feature of this branch is unique.

[0069] wherein,

[0070] Definition of positive similarity: 0.95≤Coe≤1.05;

[0071] Definition of negative similarity: -1.05≤Coe≤-0.95;

[0072] Definition of other categories: Coe<-1.05||-0.95<coe<0.95||Coe>1.05.

[0073] In step S10, the similarity between zero-sequence currents within the fault characteristic analysis interval is used to determine whether the fault can be classified into a category no greater than the number of faulty busbars (n), thus determining whether the busbar is grounded. For example, n = 2 represents 2 busbars. Performing zero-sequence current similarity calculations, the similarity between the outgoing lines from busbars W1 and W2 is close to 1. However, after cross-calculation of similarity, the result may be a random number. If any cross-calculation yields this random number, then it is classified into category 2, indicating busbar grounding. For example, if there is only one busbar segment, there is only one similarity. If there are two busbar segments operating separately and both are grounded, the fault characteristic similarity is 1 (comparison between lines on this busbar segment) and 1 unknown (comparison between lines on different busbars, between -1 and 1), still no greater than the number of busbars (2), so it is still busbar grounding. Otherwise, the branch with the only fault characteristic is the grounding branch, meaning only this line is a grounding fault branch.

[0074] Step S11: End.

[0075] Based on the same technical concept as the method embodiments, the present invention also provides a low-current grounding fault location device for adaptive dual-bus operation, comprising:

[0076] The transient feature extraction module is configured to acquire the sampled values ​​of the zero-sequence voltage of the two buses. When the zero-sequence voltage of the bus exceeds the preset voltage threshold, the transient components of the zero-mode voltage characteristic frequency band of the bus and the transient components of the zero-mode current characteristic frequency band of all branches are extracted by digital filtering method.

[0077] The potential fault branch screening module is configured to identify potential fault branches by judging the fundamental amplitude of the zero-sequence current of all branches based on a preset current threshold.

[0078] The fault branch identification module is configured to calculate the vector sum of the transient components of the zero-sequence current of all possible faulty branches. When the vector sum of the transient components is "0", if the number of faulty buses is "1", then the branch with the largest cumulative sum of transient components is determined to be a faulty branch; otherwise, the correlation characteristics between the zero-sequence current and the zero-sequence voltage fault characteristics of each branch after zero-sequence voltage singularity point alignment are used to determine whether the current branch is a faulty branch; when the vector sum of the transient components is not "0", if the fault characteristics of the zero-sequence current of all branches can be classified into categories not greater than the number of faulty buses, then the bus is grounded; otherwise, the branch with the only fault characteristics is a faulty branch.

[0079] The low-current grounding fault location device can be installed in a substation and can integrate bus zero-sequence voltage and current monitoring functions. It should be understood that the low-current grounding fault location device can achieve all the functions described in the above method embodiments, and its functional modules can implement one or more corresponding steps in the method embodiments. For example, the transient feature extraction module can implement the functions of steps S1-S3, the possible fault branch screening module can implement the function of step S4, and the fault branch identification module can implement the functions of steps S5-S11.

[0080] The present invention also provides a computer device comprising: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, wherein when the programs are executed by the processors, they implement the steps of the low-current grounding line selection method as described in the present invention for adaptive dual-bus operation.

[0081] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the low-current grounding line selection method as described in the present invention for adaptive dual-bus operation mode.

[0082] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0083] This invention is described with reference to flowchart illustrations of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each step in the flowchart, and combinations of steps in the flowchart, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the steps in the flowchart. Figure 1 A device for a function specified in one or more processes.

[0084] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 The function specified in one or more processes.

[0085] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 Steps of a specified function in one or more processes.

Claims

1. A method for selecting a low-current grounding line in an adaptive dual-bus operation mode, characterized in that, Includes the following steps: The sampled values ​​of the zero-sequence voltage of the two buses are obtained. When the zero-sequence voltage of the bus exceeds the preset voltage threshold, the transient components of the characteristic frequency band of the zero-mode voltage of the bus and the transient components of the characteristic frequency band of the zero-mode current of all branches are extracted by digital filtering method. The fundamental amplitude of the zero-sequence current in all branches is determined based on a preset current threshold, and potentially faulty branches are selected. Calculate the vector sum of the transient components of the zero-sequence current in all possible faulty branches. When the vector sum of the transient components is "0", if the number of faulty buses is "1", then the branch with the largest cumulative sum of transient components is determined to be the faulty branch; otherwise, determine whether the current branch is a faulty branch based on the correlation characteristics between the zero-sequence current and the zero-sequence voltage fault characteristics of each branch after zero-sequence voltage singularity point alignment; when the vector sum of the transient components is not "0", if the zero-sequence current fault characteristics of all branches are classified as not greater than the number of faulty buses, then the bus is grounded; otherwise, the branch with the only fault characteristics is the faulty branch. Among them, determining whether the current branch is a faulty branch based on the correlation characteristics of the zero-sequence current and zero-sequence voltage fault characteristics includes: determining the fault characteristic similarity judgment interval based on the peak point and valley point of the transient component of the zero-sequence voltage characteristic frequency band of the double busbar, judging the similarity of the zero-sequence voltage and zero-sequence current within the judgment interval, if they are similar, then the current branch is a faulty branch, otherwise it is a non-faulty branch; The judgment that all branch zero-sequence current fault characteristics are classified into categories not greater than the number of fault busbars includes: determining the fault characteristic similarity judgment interval based on the peak and valley points of the transient components of the characteristic frequency band of the double busbar zero-sequence voltage, calculating the similarity between any two branch zero-sequence currents within the judgment interval, and judging whether the similarity value is not greater than the number of fault busbar categories.

2. The method according to claim 1, characterized in that, Determining whether the bus zero-sequence voltage exceeds a preset voltage threshold includes: according to the formula Calculate the zero-sequence voltage amplitude of the bus. In the formula It is the j-th sampled value of the zero-sequence voltage of bus n, where N is the number of sampling points within half a cycle. The determination is made as follows: , This is the preset voltage threshold.

3. The method according to claim 1, characterized in that, Based on a preset current threshold, the fundamental amplitude of the zero-sequence current in all branches is determined, and potentially faulty branches are screened out. For each branch, the fundamental amplitude of the zero-sequence current is obtained. ,like If the current branch is a possible faulty branch, then the current branch is a fault-free branch; otherwise, the current branch is a non-faulty branch. Using a preset current threshold, select m potentially faulty branches.

4. The method according to claim 1, characterized in that, The expression for calculating the vector sum of the transient components of the zero-sequence current in all possible faulty branches is as follows: In the formula, m is the number of potentially faulty branches. The transient component of the zero-sequence current characteristic frequency band of the branch is given. The cumulative sum of the transient components is calculated from the transient components of the complete two-cycle characteristic frequency band, as shown in the following expression: , The sum of transient components is N, and N is the number of sampling points within half a period.

5. The method according to claim 1, characterized in that, The method for selecting singularities of zero-sequence voltage is as follows: Determine whether the following conditions are met. If the condition is met, then the (i+1)th point is a singular point, where... This is the sampled value at point i within the zero-sequence voltage buffer data. This is the sampled value at point i+q within the zero-sequence voltage buffer data. Here, q is the coefficient of change, and q is the number of consecutive change points required to determine that the (i+1)th point is a singular point. Zero-sequence voltage singularity alignment includes: determining the fault initial time based on the singularities of the transient components of the zero-sequence voltage characteristic frequency band of the two buses, and aligning the zero-sequence voltage and zero-sequence current characteristic frequency band transient component data based on the fault initial time.

6. The method according to claim 1, characterized in that, The similarity calculation method for zero-sequence voltage and zero-sequence current within the evaluation interval is as follows: In the formula, vp is the valley point number and pp is the peak point number; It is the interval for judging the similarity of fault characteristics; This indicates taking the smaller of the two values; a and b are the characteristic frequency band transient components of the bus zero-sequence voltage and the branch zero-sequence current, respectively. Anti-similarity is defined as .

7. The method according to claim 1, characterized in that, The method for calculating the similarity between the zero-sequence currents of any two branches within the interval is as follows: In the formula, vp is the valley point number and pp is the peak point number; It is the interval for judging the similarity of fault characteristics; This indicates taking the smaller of the two values; c and d are the transient components of the zero-sequence current characteristic frequency band of the two branches.

8. A low-current grounding fault location device for adaptive dual-bus operation mode, used to implement the method described in claim 1, characterized in that, include: The transient feature extraction module is configured to acquire the sampled values ​​of the zero-sequence voltage of the two buses. When the zero-sequence voltage of the bus exceeds the preset voltage threshold, the transient components of the zero-mode voltage characteristic frequency band of the bus and the transient components of the zero-mode current characteristic frequency band of all branches are extracted by digital filtering method. The potential fault branch screening module is configured to identify potential fault branches by judging the fundamental amplitude of the zero-sequence current of all branches based on a preset current threshold. The fault branch identification module is configured to calculate the vector sum of the transient components of the zero-sequence current of all possible faulty branches. When the vector sum of the transient components is "0", if the number of faulty buses is "1", then the branch with the largest cumulative sum of transient components is determined to be a faulty branch; otherwise, the correlation characteristics between the zero-sequence current and the zero-sequence voltage fault characteristics of each branch after zero-sequence voltage singularity point alignment are used to determine whether the current branch is a faulty branch; when the vector sum of the transient components is not "0", if the zero-sequence current fault characteristics of all branches are classified as not greater than the number of faulty buses, then the bus is grounded; otherwise, the branch with the only fault characteristics is a faulty branch.

9. A computer device, characterized in that, include: One or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, wherein when the programs are executed by the processors, they implement the steps of the low-current grounding line selection method for adaptive dual-bus operation as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the low-current grounding line selection method in the adaptive dual-bus operation mode as described in any one of claims 1-7.

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