Power distribution network single-phase earth fault positioning method, system, device and medium

Abstract

The invention provides a power distribution network single-phase earth fault positioning method, a power distribution network single-phase earth fault positioning system, power distribution network single-phase earth fault positioning equipment and a medium. Calculating the three-phase input admittance before and after the bus fault and the three-phase input admittance after the distribution transformer high-voltage side fault according to the obtained three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the distribution transformer high-voltage side fault; based on all the three-phase input admittances after the distribution transformer high-voltage side fault, correcting the three-phase input admittances before and after the bus fault to obtain the three-phase input admittances before and after the bus fault, and calculating the three-phase asymmetry degree of the bus and the abrupt change rate of the three-phase input admittances of the bus; and taking the phase with the maximum asymmetry degree and the maximum input admittance abrupt change rate in the three-phase asymmetry degree of the bus and the three-phase input admittance abrupt change rate of the bus as a fault phase. According to the invention, the accuracy and sensitivity of fault positioning can be improved, the calculation and implementation cost of fault positioning analysis can be reduced, and the application limitation of a grounding mode can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of single-phase grounding fault detection in distribution networks, and particularly to a method, system, device and medium for locating single-phase grounding faults in distribution networks. Background Art

[0002] Single-phase grounding faults are the most common faults in distribution networks, accounting for more than 80% of various faults. To ensure the personal and equipment safety of users and the power supply reliability, medium- and low-voltage distribution networks usually adopt non-effectively grounded neutral, mainly including ungrounded neutral, resonant grounded neutral and pure-resistance grounded neutral. The above-mentioned distribution networks with neutral modes have the advantages of small fault current and symmetrical line voltage when a single-phase grounding fault occurs. However, when a fault occurs, the normal phase voltage will rise to approach the line voltage. Long-term fault operation will not only threaten personal and equipment safety, but also may cause more serious inter-phase faults due to wire insulation rupture. Therefore, it is necessary to locate and eliminate the fault within a short time, which has also become a difficult problem puzzling the power system so far.

[0003] Existing methods for selecting and locating single-phase grounding faults include the mainstream methods relying on fault line selection devices and the dichotomy method to locate the general section of single-phase grounding faults, as well as the non-mainstream methods based on the combined use of multiple algorithms. However, in practical engineering applications of the mainstream methods relying on fault line selection devices and the dichotomy method to locate the general section of single-phase grounding faults, the fault line selection device based on the zero-sequence signal characteristics not only requires additional measurement devices, with high application costs and inconvenient maintenance and management, increasing the operation risk of the power grid, but also often shows unsatisfactory states such as wrong line selection or non-selection. Moreover, even if the line selection is successful, the fault area judgment based on the dichotomy method still requires manual operation to narrow the fault area, resulting in problems such as long time, low efficiency and potential safety hazards. At the same time, the method based on the combination of multiple algorithms focuses on signal transformation and processing, ignoring the essence of the single-phase grounding fault problem, and its calculation is too complex, which also limits its practicability. Therefore, there is an urgent need to provide a simple, efficient and accurate low-cost method for locating single-phase grounding faults. Summary of the Invention

[0004] The object of the present invention is to provide a method for locating single-phase grounding faults in distribution networks, which realizes the location of single-phase grounding faults based on the comprehensive analysis of the three-phase asymmetry degree and the mutation rate of input admittance, can not only improve the accuracy and sensitivity of fault location, but also reduce the calculation and implementation costs of fault location analysis, and can effectively avoid the application limitations of grounding modes.

[0005] To achieve the above object, a method, system, device and medium for locating single-phase grounding faults in distribution networks are provided.

[0006] In the first aspect, an embodiment of the present invention provides a method for locating single-phase grounding faults in distribution networks, and the method includes the following steps: When a single-phase grounding fault occurs in the distribution network, according to the occurrence time of the single-phase grounding fault, obtain the three-phase voltage and current data before and after the fault of the bus and the three-phase voltage and current data after the fault of the high-voltage side of the distribution transformer; According to the three-phase voltage and current data before and after the bus fault, obtain the three-phase input admittances before and after the bus fault, and according to the three-phase voltage and current data after the fault of each distribution transformer high-voltage side, obtain the corresponding three-phase input admittances after the fault of the distribution transformer high-voltage side; According to all the three-phase input admittances after the fault of the distribution transformer high-voltage side, correct the three-phase input admittances before and after the bus fault to obtain the corrected three-phase input admittances before and after the bus fault; According to the corrected three-phase input admittances before and after the bus fault, calculate the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus; Take the phase with the maximum corresponding asymmetry degree and input admittance mutation rate among the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus as the fault phase.

[0007] Further, the occurrence time of the single-phase grounding is the time when the zero-sequence voltage of the distribution network reaches a preset threshold; the step of obtaining the three-phase voltage and current data before and after the fault according to the occurrence time of the single-phase grounding fault includes: Obtain the three-phase current amplitudes and three-phase voltage amplitudes at the time corresponding to a preset time period before the occurrence time of the single-phase grounding as the corresponding three-phase pre-fault current amplitudes and three-phase pre-fault voltage amplitudes respectively; Obtain the three-phase current amplitudes and three-phase voltage amplitudes at the time corresponding to a preset time period after the occurrence time of the single-phase grounding fault as the corresponding three-phase post-fault current amplitudes and three-phase post-fault voltage amplitudes respectively.

[0008] Further, the step of obtaining the three-phase input admittances before and after the bus fault according to the three-phase voltage and current data before and after the bus fault includes: According to the ratio of the pre-fault current data to the pre-fault voltage data of each phase in the three-phase voltage and current data before and after the bus fault, obtain the pre-fault input admittance of the corresponding phase in the three-phase input admittances before and after the bus fault; According to the ratio of the post-fault current data to the post-fault voltage data of each phase in the three-phase voltage and current data before and after the bus fault, obtain the post-fault input admittance of the corresponding phase in the three-phase input admittances before and after the bus fault.

[0009] Further, the step of correcting the three-phase input admittances before and after the bus fault according to all the three-phase input admittances after the fault of the distribution transformer high-voltage side to obtain the corrected three-phase input admittances before and after the bus fault includes: Accumulate the input admittances of each phase in all the three-phase input admittances after the fault of the distribution transformer high-voltage side to obtain the corresponding post-fault three-phase input admittance correction value; The post-fault three-phase input admittance among the three-phase input admittances before and after the bus fault is corrected according to the corrected value of the post-fault three-phase input admittance of the bus to obtain the corresponding corrected post-fault three-phase input admittance; The corrected three-phase input admittance before and after the bus fault is obtained according to the corrected post-fault three-phase input admittance and the pre-fault three-phase input admittance among the three-phase input admittances before and after the bus fault.

[0010] Further, the step of calculating the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus according to the corrected three-phase input admittance before and after the bus fault includes: The change value of each phase input admittance after the fault is obtained according to the input admittance of each phase after the fault and the input admittance of each phase before the fault among the corrected three-phase input admittances before and after the bus fault; The three-phase asymmetry degree of the bus is obtained according to the ratio of the change value of each phase input admittance after the fault to the input admittance of each corresponding phase before the fault; The mutation rate of the three-phase input admittance of the bus is obtained according to the ratio of the change value of each phase input admittance after the fault to the preset admittance mutation duration.

[0011] Further, the method further includes: According to the voltage and current data before and after the fault of the fault phase of each feeder and the three-phase voltage and current data after the fault of the high-voltage side of the transformer on each fault phase of each feeder, the input admittance before and after the fault of the corresponding fault phase and the input admittance after the fault of the high-voltage side of the transformer on each fault phase of each feeder are calculated; The input admittances after the fault of the high-voltage sides of all transformers on the fault phases of each feeder are accumulated to obtain the corrected value of the input admittance after the fault of the corresponding fault phase; The input admittance after the fault of the fault phase among the input admittances before and after the fault of the fault phase is corrected according to the corrected value of the input admittance after the fault of the fault phase of each feeder to obtain the corresponding corrected input admittance after the fault of the fault phase; According to the corrected input admittance after the fault of the fault phase of each feeder and the input admittance before the fault of the fault phase among the input admittances before and after the fault of the fault phase, the asymmetry degree of the fault phase and the mutation rate of the input admittance of the fault phase corresponding to each feeder are obtained; The asymmetry degree of the fault phase and the mutation rate of the input admittance of the fault phase corresponding to each feeder are compared and analyzed, and the feeder with the maximum values of both the asymmetry degree of the fault phase and the mutation rate of the input admittance of the fault phase is used as the fault feeder.

[0012] Further, the method further includes: According to the voltage and current data before and after the fault of each line section on the faulty phase corresponding to the faulty feeder obtained, and the three-phase voltage and current data after the fault on the high-voltage side of the distribution transformer in each faulty phase section, calculate the input admittance before and after the fault corresponding to each line section and the input admittance after the fault on the high-voltage side of the distribution transformer in each faulty phase section; Accumulate the input admittance after the fault on the high-voltage side of the distribution transformer in all faulty phase sections on each line section to obtain the corresponding corrected value of the input admittance after the section fault; According to the corrected value of the input admittance after the section fault of each line section, correct the input admittance after the fault in the input admittance before and after the fault to obtain the corresponding corrected input admittance after the section fault; According to the corrected input admittance after the section fault of each line section and the input admittance before the fault in the input admittance before and after the fault, obtain the corresponding line section asymmetry degree and the line section input admittance mutation rate; Compare and analyze the line section asymmetry degree and the line section input admittance mutation rate corresponding to each line section, and take the line section with the maximum line section asymmetry degree and the line section input admittance mutation rate as the grounding fault section.

[0013] In a second aspect, an embodiment of the present invention provides a single-phase grounding fault location system for a distribution network, and the system includes: A data acquisition module, configured to obtain three-phase voltage and current data before and after the bus fault and three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer according to the occurrence time of the single-phase grounding fault when a single-phase grounding fault occurs in the distribution network; An admittance calculation module, configured to obtain the three-phase input admittance before and after the bus fault according to the three-phase voltage and current data before and after the bus fault, and obtain the corresponding three-phase input admittance after the fault on the high-voltage side of the distribution transformer according to the three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer; An admittance correction module, configured to correct the three-phase input admittance before and after the bus fault according to the three-phase input admittance after the fault on the high-voltage side of all distribution transformers to obtain the corrected three-phase input admittance before and after the bus fault; An admittance analysis module, configured to calculate the bus three-phase asymmetry degree and the bus three-phase input admittance mutation rate according to the corrected three-phase input admittance before and after the bus fault; A faulty phase location module, configured to take the phase with the maximum corresponding asymmetry degree and input admittance mutation rate in the bus three-phase asymmetry degree and the bus three-phase input admittance mutation rate as the faulty phase.

[0014] In a third aspect, an embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the computer program, the steps of the above method are implemented.

[0015] Fourthly, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0016] The present invention provides a method, a system, a computer device and a storage medium for locating single-phase grounding faults in a distribution network. By the method, when a single-phase grounding fault occurs in the distribution network, three-phase voltage and current data before and after the fault of the bus and three-phase voltage and current data after the fault of the high-voltage side of the distribution transformer are obtained according to the occurrence time of the single-phase grounding fault. The three-phase input admittance before and after the bus fault is obtained according to the three-phase voltage and current data before and after the bus fault. The three-phase input admittance after the fault of each distribution transformer high-voltage side is obtained according to the three-phase voltage and current data after the fault of each distribution transformer high-voltage side, and the three-phase input admittance before and after the bus fault is corrected according to the three-phase input admittance after the fault of all distribution transformer high-voltage sides. After obtaining the corrected three-phase input admittance before and after the bus fault, the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus are calculated. The phase with the maximum asymmetry degree and input admittance mutation rate corresponding to the three-phase asymmetry degree of the bus and the three-phase input admittance mutation rate of the bus is used as the fault phase. Compared with the prior art, this method for locating single-phase grounding faults in a distribution network can directly use the three-phase asymmetry degree and input admittance mutation rate before and after the grounding fault to realize the analysis of single-phase grounding fault location without additional physical measurement equipment or complex hardware transformation based only on the existing voltage transformers and current transformers on the distribution network. It can not only improve the accuracy and sensitivity of fault location, but also reduce the calculation and implementation costs of fault location analysis, and effectively avoid the application limitations of grounding modes, with a wide range of application scenarios and high practical value. Description of the Drawings

[0017] Figure 1 is a schematic flow chart of the method for locating single-phase grounding faults in a distribution network according to an embodiment of the present invention; Figure 2 is a schematic diagram of a fault model of a C-phase grounding fault occurring in a distribution network according to an embodiment of the present invention; Figure 3 is Figure 2 a schematic diagram of the equivalent model of the distribution network corresponding to the fault model looking from the substation bus to the load side; Figure 4 is a schematic diagram of the equivalent models of the distribution network of a normal feeder and a fault feeder in an embodiment of the present invention (the left figure is the normal feeder, and the right figure is the fault feeder); Figure 5 is a schematic diagram of the equivalent model of the fault phase of the distribution network of the fault feeder j in an embodiment of the present invention; Figure 6 is a schematic diagram of the structure of a distribution network deployed with voltage and current monitoring devices in an embodiment of the present invention; Figure 7 is Figure 6 the schematic diagram of the input admittances of the three phases ABC of the substation when a single-phase ground fault of phase A occurs at the end of L in the shown distribution network structure; 4 the schematic diagram of the input admittances of the three phases ABC of the substation when a single-phase ground fault of phase A occurs at the end of L in the shown distribution network structure; Figure 8 is Figure 6 the schematic diagram of the input admittance of phase A of each feeder of the substation when a single-phase ground fault of phase A occurs at the end of L in the shown distribution network structure; 4 the schematic diagram of the input admittance of phase A of each feeder of the substation when a single-phase ground fault of phase A occurs at the end of L in the shown distribution network structure; Figure 9 is Figure 6 the schematic diagram of the input admittance of the fault phase A measured by each monitoring device of the fault feeder when a single-phase ground fault of phase A occurs at the end of L in the shown distribution network structure; 4 the schematic diagram of the input admittance of the fault phase A measured by each monitoring device of the fault feeder when a single-phase ground fault of phase A occurs at the end of L in the shown distribution network structure; Figure 10 is Figure 6 the schematic diagram of the input admittances of the three phases ABC of the substation when a single-phase ground fault of phase B occurs in the middle of L in the shown distribution network structure; 2 the schematic diagram of the input admittances of the three phases ABC of the substation when a single-phase ground fault of phase B occurs in the middle of L in the shown distribution network structure; Figure 11 is Figure 6 the schematic diagram of the input admittance of phase A of each feeder of the substation when a single-phase ground fault of phase B occurs in the middle of L in the shown distribution network structure; 2 the schematic diagram of the input admittance of phase A of each feeder of the substation when a single-phase ground fault of phase B occurs in the middle of L in the shown distribution network structure; Figure 12 is Figure 6 the schematic diagram of the input admittance of the fault phase A measured by each monitoring device of the fault feeder when a single-phase ground fault of phase B occurs in the middle of L in the shown distribution network structure; 2 the schematic diagram of the input admittance of the fault phase A measured by each monitoring device of the fault feeder when a single-phase ground fault of phase B occurs in the middle of L in the shown distribution network structure; Figure 13 is the schematic diagram of the structure of the single-phase ground fault location system for the distribution network in the embodiment of the present invention; Figure 14 is the internal structure diagram of the computer device in the embodiment of the present invention. Detailed implementation manners

[0018] In order to make the purpose, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the following described embodiments are part of the embodiments of the present invention, and are only used to illustrate the present invention, but not to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0019] The single-phase grounding fault location method for a distribution network provided by the present invention can be understood as follows: Based on the existing single-phase grounding fault location methods for distribution networks that rely on zero-sequence voltage, zero-sequence current, or transient quantities, there are limitations in the application of grounding modes. At the same time, not only will the implementation cost increase due to the additional introduction of other physical measurement devices, but the location analysis process is relatively complex, the calculation cost is large, and the location accuracy is insufficient due to weak signals. Therefore, a solution is proposed that can directly utilize the characteristics of the line admittance change before and after grounding to achieve fast and accurate location at three levels, namely phase, feeder, and section, without the need for complex hardware modification or additional introduction of sensing devices. It should be noted that the implementation of the method of the present invention relies on the existing voltage and current measurement devices deployed on the distribution network. Each voltage and current measurement device can periodically collect and store the current amplitude and voltage amplitude at each grid location according to a preset data acquisition frequency (1 minute) for analysis. For example, the three-phase voltage and current data before and after the bus fault required in the method of the present invention can be monitored based on the voltage transformer and current transformer on the bus side. The three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer are obtained based on the deployed distribution transformer acquisition terminal. The voltage and current data of the fault phase before and after the fault of each feeder can be obtained based on the voltage transformer on the bus side and the current transformer deployed at the outlet of each feeder. The voltage and current data before and after the fault of each line section can be monitored based on the voltage transformer and current transformer deployed at the input end of each line section. The following embodiments will detail the single-phase grounding fault location method for the distribution network of the present invention.

[0020] In one embodiment, as Figure 1 shown, a single-phase grounding fault location method for a distribution network is provided, including the following steps: S11. When a single-phase grounding fault occurs in the distribution network, according to the moment when the single-phase grounding fault occurs, obtain the three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer. Among them, the judgment of a single-phase grounding fault in the distribution network can be understood as using whether the zero-sequence voltage of the distribution network reaches a preset threshold and lasts for a preset duration (for example, 5 minutes) as the criterion to determine that a single-phase grounding fault occurs in the distribution network. That is, when it is analyzed based on the data collected by the voltage and current monitoring devices at a certain moment that the zero-sequence voltage of the distribution network reaches the preset threshold, it is considered that a single-phase grounding fault occurs at that moment, and that moment is stored as the moment when the single-phase grounding fault occurs.

[0021] In practical applications, after determining that a single-phase grounding fault has occurred in the distribution network, based on the stored occurrence time of the single-phase grounding fault, the voltage amplitudes and current amplitudes of each phase before and after the fault on the low-voltage bus of the substation can be extracted based on the corresponding voltage and current monitoring devices, and the voltage amplitudes and current amplitudes of each phase after the fault on the high-voltage side of each distribution transformer can be obtained based on the distribution transformer acquisition terminal; it should be noted that the three-phase voltage and current data in the three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the fault on the high-voltage side of the distribution transformer can be understood as including the voltage data and current data of phases A, B, and C at the same time. Correspondingly, the three-phase input admittance, three-phase asymmetry, and three-phase input admittance mutation rate in the following text can be understood as including the corresponding data of phases A, B, and C at the same time. Specifically, the steps of obtaining the three-phase voltage and current data before and after the fault according to the occurrence time of the single-phase grounding fault include: Obtain the three-phase current amplitudes and three-phase voltage amplitudes at the corresponding time when the preset time period is advanced before the occurrence time of the single-phase grounding as the corresponding three-phase pre-fault current amplitudes and three-phase pre-fault voltage amplitudes respectively; among them, the preset time period can be determined according to actual application requirements, such as 5 minutes, and no specific limitation is made here.

[0022] Obtain the three-phase current amplitudes and three-phase voltage amplitudes at the corresponding time when the preset time period is postponed after the occurrence time of the single-phase grounding fault as the corresponding three-phase post-fault current amplitudes and three-phase post-fault voltage amplitudes respectively.

[0023] S12. Obtain the three-phase input admittances before and after the bus fault according to the three-phase voltage and current data before and after the bus fault, and obtain the three-phase input admittances after the fault on the high-voltage side of the corresponding distribution transformer according to the three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer; among them, the calculation of the input admittance of each phase can be understood as being obtained based on the ratio of the current and voltage of each phase; specifically, the steps of obtaining the three-phase input admittances before and after the bus fault according to the three-phase voltage and current data before and after the bus fault include: Obtain the pre-fault input admittance of the corresponding phase in the three-phase input admittances before and after the bus fault according to the ratio of the pre-fault current data and pre-fault voltage data of each phase in the three-phase voltage and current data before and after the bus fault; Obtain the post-fault input admittance of the corresponding phase in the three-phase input admittances before and after the bus fault according to the ratio of the post-fault current data and post-fault voltage data of each phase in the three-phase voltage and current data before and after the bus fault.

[0024] To verify the rationality of using the input admittance before and after the fault as the basis for fault location analysis in the embodiments of the present invention, a principle analysis is performed on the input admittance of each phase of the bus where a single-phase grounding fault occurs. Assuming that a C-phase grounding fault occurs in the distribution network, then the following can be obtained Figure 2 The single-phase grounding fault model shown, where 、 、 , , , , , , , , , , and represent the compensation impedance, the electromotive force of phase A, the electromotive force of phase B, the electromotive force of phase C, the current of phase A of branch line i, the current of phase B of branch line i, the current of phase C of branch line i, the current of phase A of branch line j, the current of phase B of branch line j, the current of phase C of branch line j, the line impedance of feeder i, the line impedance before the fault point of feeder j, and the line impedance after the fault point of feeder j respectively; C represents the capacitance to ground; and the equivalent model of the distribution network shown in Figure 3 can be obtained when looking from the substation bus towards the load side, where represents the compensation admittance.

[0025] When Figure 2 the distribution network shown is operating normally, the currents of each phase on the low-voltage bus of the substation are the sum of the capacitance current to ground and the load current, and are expressed as: In the formula, , and represent the current of phase A, the current of phase B, and the current of phase C on the substation bus during normal operation respectively; , and represent the voltage of phase A to ground, the voltage of phase B to ground, and the voltage of phase C to ground on the substation bus during normal operation respectively; is the angular frequency, C is the capacitance to ground, , and represent the equivalent admittance of phase A of the feeder, the equivalent admittance of phase B of the feeder, and the equivalent admittance of phase C of the feeder respectively; the ratio of the current of each phase on the substation bus to the voltage of that phase is defined as the input admittance of that bus, then: In the formula, , and represent the input admittance of phase A, the input admittance of phase B, and the input admittance of phase C on the substation bus during normal operation respectively.

[0026] As Figure 2 and Figure 3 shown, after a phase C ground fault occurs in the distribution network, the currents of each phase on the bus can be expressed as: In the formula, , and respectively represent the phase A current, phase B current, and phase C current on the substation bus during a single-phase ground fault; , and respectively represent the phase A-to-ground voltage, phase B-to-ground voltage, and phase C-to-ground voltage on the substation bus during a single-phase ground fault; and respectively represent the current of one phase increased due to the existence of the grounding current in the faulty phase C on the bus and the corresponding increased input admittance. It should be noted that if the faulty phase in the actual ground fault is phase A or phase B, the corresponding or will also increase the corresponding grounding current and .

[0027] Based on the definition of the input admittance of each phase on the distribution network bus, after a phase C ground fault occurs in the corresponding distribution network, the input admittance of each phase on the bus can be expressed as: In the formula, , and respectively represent the phase A input admittance, phase B input admittance, and phase C input admittance of the bus after a phase C ground fault occurs.

[0028] Considering that the ground fault changes the impedance between the phase and the ground, and since the inter-phase impedance does not participate in the operation of the single-phase ground fault, the load flowing to the low-voltage side before and after the fault does not change and the ground capacitance parameter is fixed; then, by comparing the input admittance of the bus before and after the above-mentioned phase C ground fault occurs, it can be found that only the input admittance of the faulty phase C has an additional term (when a single-phase ground fault occurs in phase A, the phase A input admittance will have an additional term ; when a single-phase ground fault occurs in phase B, the phase B input admittance will have an additional term ). That is, it is feasible to determine the faulty phase by analyzing the three-phase asymmetry based on the change in the input admittance of each phase of the bus before and after the fault.

[0029] Meanwhile, considering that in the actual operation of the distribution network, the three-phase asymmetry may also change due to the change of single-phase load. To ensure the accuracy of determining the fault phase based on the three-phase asymmetry, in this embodiment, while calculating the three-phase input admittance of the bus before and after the fault, the three-phase input admittance of the high-voltage side of the distribution transformer after the fault is also analyzed to correct the three-phase input admittance of the bus after the fault, so as to ensure the reliability of the three-phase asymmetry analysis after the fault. In addition, to verify the rationality of using the three-phase input admittance of the high-voltage side of the distribution transformer to correct the three-phase input admittance of the bus after the fault, this embodiment also takes the Yn / D distribution transformer used in the distribution network as an example for the following relevant principle analysis: When the single-phase load on the low-voltage side of the k-th distribution transformer increases, the change of the input admittance of the high-voltage side of the k-th distribution transformer is as follows: In the formula, 、 and respectively represent the phase-A voltage, phase-B voltage and phase-C voltage of the low-voltage side of the k-th distribution transformer; 、 and respectively represent the phase-A current, phase-B current and phase-C current of the low-voltage side of the k-th distribution transformer; represents the short-circuit impedance of the k-th distribution transformer; 、 and respectively represent the phase-A current, phase-B current and phase-C current of the high-voltage side of the k-th distribution transformer; 、 and respectively represent the change value of the phase-A input admittance, the change value of the phase-B input admittance and the change value of the phase-C input admittance of the high-voltage side of the k-th distribution transformer.

[0030] When the phase-A load on the low-voltage side of the k-th distribution transformer increases, opposite-direction and equal-magnitude currents will be induced in the phase-A and phase-C of the high-voltage side of the distribution transformer. And based on the parameters of the low-voltage side of the distribution transformer to represent the change of the admittance of the high-voltage side of the distribution transformer, we can get: In the formula, 、 and respectively represent the change value of the phase-A input admittance, the change value of the phase-B input admittance and the change value of the phase-C input admittance of the high-voltage side of the k-th distribution transformer when the phase-A load on the low-voltage side of the k-th distribution transformer increases; represents the phase-A current of the low-voltage side when the phase-A load on the low-voltage side of the k-th distribution transformer increases; When the phase-B load on the low-voltage side of the k-th distribution transformer increases, opposite-direction and equal-magnitude currents will be induced in the phase-A and phase-B of the high-voltage side of the distribution transformer. The corresponding change of the admittance of the high-voltage side of the distribution transformer can be expressed as: In the formula, , and respectively represent the variation values of the A-phase input admittance, B-phase input admittance, and C-phase input admittance on the high-voltage side of the kth distribution transformer when the load on the B-phase of the low-voltage side of the kth distribution transformer increases; represents the current of the B-phase on the low-voltage side of the distribution transformer when the load on the B-phase of the low-voltage side of the kth distribution transformer increases.

[0031] When the load on the C-phase of the low-voltage side of the kth distribution transformer increases, currents with opposite directions and the same magnitude will be induced in the B-phase and C-phase on the high-voltage side of the distribution transformer. The corresponding changes in the admittance on the high-voltage side of the distribution transformer can be expressed as: In the formula, , and respectively represent the variation values of the A-phase input admittance, B-phase input admittance, and C-phase input admittance on the high-voltage side of the distribution transformer when the load on the C-phase of the low-voltage side of the kth distribution transformer increases; represents the current of the C-phase on the low-voltage side when the load on the C-phase of the low-voltage side of the kth distribution transformer increases.

[0032] Based on the above analysis, it can be seen that when the load of a phase increases, the current of the corresponding phase increases. When the load on the A-phase of the low-voltage side of the distribution transformer increases, the admittances of both the A-phase and C-phase on the high-voltage side increase. When the load on the B-phase of the low-voltage side of the distribution transformer increases, the admittances of both the A-phase and B-phase on the high-voltage side increase. When the load on the C-phase of the low-voltage side of the distribution transformer increases, the admittances of both the B-phase and C-phase on the high-voltage side increase. Therefore, in order to avoid misjudgment of single-phase grounding caused by the increase of single-phase load and ensure the accuracy of the calculation of the three-phase input admittance after the busbar fault, it is necessary to correct the three-phase input admittance of the busbar after the fault by using the three-phase input admittance of the high-voltage side of the distribution transformer after the fault.

[0033] S13. Correct the three-phase input admittance of the busbar before and after the fault according to the three-phase input admittance of all high-voltage sides of the distribution transformers after the fault to obtain the corrected three-phase input admittance of the busbar before and after the fault; among them, the three-phase input admittance of the busbar before the fault in the corrected three-phase input admittance of the busbar before and after the fault is consistent with the three-phase input admittance of the busbar before the fault in the three-phase input admittance of the busbar before and after the fault, and the corresponding three-phase input admittance of the busbar after the fault is the corrected three-phase input admittance obtained by correcting based on the three-phase input admittance of the high-voltage side of the distribution transformer after the fault. Specifically, the step of correcting the three-phase input admittance of the busbar before and after the fault according to the three-phase input admittance of all high-voltage sides of the distribution transformers after the fault to obtain the corrected three-phase input admittance of the busbar before and after the fault includes: Accumulate the input admittances of each phase in the three-phase input admittances of all high-voltage sides of the distribution transformers after the fault to obtain the corresponding corrected value of the three-phase input admittance after the fault, which is expressed as: In the formula, , and respectively represent the variation values of the admittance of phase A, phase B, and phase C on the high-voltage side when the load increases, which are the corrected values of the three-phase input admittance after the fault required above; K represents the total number of distribution transformers.

[0034] According to the corrected values of the three-phase input admittance after the fault, correct the three-phase input admittance after the fault in the three-phase input admittance before and after the bus fault to obtain the corresponding corrected three-phase input admittance after the fault; among them, the corrected three-phase input admittance after the fault is expressed as: In the formula, and respectively represent the input admittance after the fault of phase A of the bus and the corresponding corrected input admittance after the fault; and respectively represent the input admittance after the fault of phase B of the bus and the corresponding corrected input admittance after the fault; and respectively represent the input admittance after the fault of phase C of the bus and the corresponding corrected input admittance after the fault; , and respectively represent the variation values of the admittance of phase A, phase B, and phase C on the high-voltage side when the load increases.

[0035] According to the corrected three-phase input admittance after the fault and the three-phase input admittance before the fault in the three-phase input admittance before and after the bus fault, obtain the corrected three-phase input admittance before and after the bus fault.

[0036] Based on the analysis formula of the variation of the three-phase input admittance before and after the bus fault above, it can be seen that the theoretical value of each phase input admittance is composed of the grounding admittance and the line distribution parameters, and does not include the admittance of the neutral point through a small resistor or an arc suppression coil, nor does it involve the zero-sequence component. It can not only overcome the deficiency of misjudgment caused by weak signals when relying on zero-sequence voltage, zero-sequence current, or transient quantity analysis in the traditional method, but also avoid the dependence on specific grounding modes in the traditional method. It is applicable to different types of small-current grounding systems (such as ungrounded neutral or arc-suppression coil grounded systems). Whether it is high-resistance grounding (grounding resistance 1000Ω) or low-resistance grounding, regardless of the grounding distance, the above input admittance analysis method can be applied, and it has high robustness.

[0037] S14. Calculate the three-phase asymmetry of the busbar and the mutation rate of the three-phase input admittance of the busbar based on the corrected three-phase input admittances before and after the busbar fault. Among them, the three-phase asymmetry of the busbar can be understood as the three-phase unbalance degree of the busbar calculated based on the change of the input admittance before and after the three-phase fault of the busbar, and the mutation rate of the three-phase input admittance of the busbar can be understood as the change rate of the input admittance calculated based on the change of the input admittance before and after the three-phase fault of the busbar.

[0038] Specifically, the steps of calculating the three-phase asymmetry of the busbar and the mutation rate of the three-phase input admittance of the busbar based on the corrected three-phase input admittances before and after the busbar fault include: Obtain the corresponding change values of the input admittances of each phase after the fault according to the input admittances of each phase after the fault and the input admittances of each phase before the fault in the corrected three-phase input admittances before and after the busbar fault. Obtain the three-phase asymmetry of the busbar according to the ratio of the change value of the input admittance of each phase after the fault to the input admittance of each phase before the corresponding fault. That is, the three-phase asymmetry of the busbar is expressed as: In the formula, and respectively represent the input admittance before the fault and the corrected input admittance after the fault of phase A of the busbar; and respectively represent the input admittance before the fault and the corrected input admittance after the fault of phase B of the busbar; and respectively represent the input admittance after the fault and the corresponding corrected input admittance after the fault of phase C of the busbar; 、 and respectively represent the asymmetry of phase A, phase B, and phase C of the busbar; Obtain the mutation rate of the three-phase input admittance of the busbar according to the ratio of the change value of the input admittance of each phase after the fault to the preset admittance mutation duration. Among them, the preset admittance mutation duration can be understood as the difference between the time when the voltage and current data after the single-phase ground fault are obtained and the time when the voltage and current data before the single-phase ground fault are obtained, which will not be elaborated here. The corresponding mutation rate of the three-phase input admittance of the busbar is expressed as: In the formula, represents the preset admittance mutation duration; 、 and respectively represent the mutation rate of the input admittance of phase A, phase B, and phase C of the busbar.

[0039] In this embodiment, the mutation rate of the busbar three-phase input admittance can be understood as a further criterion for excluding the possibility of other factors in the power grid affecting the input admittance value. Considering the characteristics that during a single-phase grounding fault, the input admittance changes rapidly before and after the fault due to the sudden and drastic changes in current and voltage, another criterion for assisting in judging whether it is a single-phase grounding fault is introduced based on the busbar three-phase asymmetry.

[0040] S15. Take the phase with the maximum corresponding asymmetry and input admittance mutation rate among the busbar three-phase asymmetry and the busbar three-phase input admittance mutation rate as the fault phase; that is, the determination condition of the fault phase is as follows: When , and , it is determined that a single-phase grounding fault occurs in phase A; When , and , it is determined that a single-phase grounding fault occurs in phase B; When , and , it is determined that a single-phase grounding fault occurs in phase C.

[0041] From the expression of the post-fault input admittance of the fault phase mentioned above, it is easy to know that the fault phase increases the grounding admittance , and only the asymmetry of the fault phase is greater than 0, while the input admittance of the normal phase does not increase additional admittance before and after the fault, and the corresponding asymmetry is basically zero. At the same time, the input admittance mutation rate is introduced to assist in judging the fault phase, which can effectively avoid misjudgment caused by load fluctuations and improve the scientificity and accuracy of fault phase determination.

[0042] In the embodiment of the present invention, without the need to additionally increase physical measurement equipment or perform complex hardware transformation based only on the existing voltage transformers and current transformers on the distribution network, the single-phase grounding fault location analysis can be directly realized by using the three-phase asymmetry and the input admittance mutation rate before and after the grounding fault. This can not only improve the accuracy and sensitivity of fault location, but also reduce the calculation and implementation costs of fault location analysis, and effectively avoid the application limitations of grounding modes.

[0043] At the same time, to further improve the analysis depth of fault location, this embodiment can also select the fault feeder based on the two indicators of three-phase asymmetry and input admittance mutation rate on the basis of determining the fault phase; specifically, the method further includes: According to the voltage and current data of the faulty phase before and after the fault of each feeder obtained, and the three-phase voltage and current data of the high-voltage side of the transformer corresponding to each faulty phase on each feeder after the fault, calculate the input admittance of the faulty phase before and after the fault and the input admittance of the high-voltage side of the transformer corresponding to each faulty phase on each feeder after the fault; Accumulate the input admittances of the high-voltage sides of all transformers corresponding to the faulty phases on each feeder after the fault to obtain the corrected value of the input admittance of the corresponding faulty phase after the fault; According to the corrected value of the input admittance of the faulty phase of each feeder, correct the input admittance of the faulty phase after the fault in the input admittance of the faulty phase before and after the fault to obtain the corrected input admittance of the corresponding faulty phase after the fault; According to the corrected input admittance of the faulty phase of each feeder and the input admittance of the faulty phase before the fault in the input admittance of the faulty phase before and after the fault, obtain the asymmetry degree of the faulty phase and the mutation rate of the input admittance of the faulty phase corresponding to each feeder; Compare and analyze the asymmetry degree of the faulty phase and the mutation rate of the input admittance of the faulty phase corresponding to each feeder, and take the feeder with the maximum values of both the asymmetry degree of the faulty phase and the mutation rate of the input admittance of the faulty phase as the faulty feeder.

[0044] In practical applications, the faulty phase is determined through the above method steps After that, in combination with Figure 2 and Figure 4 (The left figure is the normal feeder i, and the right figure is the faulty feeder j, and represent the input admittances of feeders i and j respectively), the method for selecting the faulty feeder in this embodiment can be explained theoretically: Assume that there are N feeders in the substation, and when the distribution network is operating normally, the current of the faulty phase of each feeder (not having a fault, but for the convenience of comparison, it is called the faulty phase during normal operation) is expressed as: In the formula, is the current of the faulty phase of the i-th feeder on the substation bus under normal conditions, is the voltage of the faulty phase of the i-th feeder on the substation bus under normal conditions; is the angular frequency, is the capacitance to ground of the i-th feeder on the substation bus; is the load admittance of the faulty phase of the i-th feeder on the power station bus; Define the input admittance of the feeder as looking from the substation side of the feeder to the load side, then the calculation formula for the input admittance of the feeder is: In the formula, is the input admittance of the i-th feeder on the substation bus under normal conditions, that is, when the distribution network is operating normally (before the fault), the input admittance of each feeder is composed of the capacitance to ground parameter of the feeder and the load admittance of each feeder.

[0045] When a single-phase grounding fault occurs in the distribution network, the faulty phase of each feeder has a current of: In the formula, and respectively represent the faulty-phase current and faulty-phase voltage of the i-th feeder on the substation bus when a single-phase grounding fault occurs.

[0046] Similarly, according to the definition of the faulty-phase input admittance of the feeder before the fault, the faulty-phase input admittance after the fault can be obtained as: In the formula, represents the faulty-phase input admittance of the i-th feeder on the substation bus when a single-phase grounding fault occurs; that is, after the fault occurs, the input admittance of the faulty feeder increases by the grounding admittance , and for the non-faulty phases, the input admittances before and after the fault are the same, that is .

[0047] Similarly, based on the three-phase voltage and current data after the fault at the high-voltage side of the distribution transformer for each faulty phase on each feeder, the input admittance after the fault at the high-voltage side of the distribution transformer for each faulty phase can be calculated, and then the sum of the input admittances after the fault at the high-voltage side of the distribution transformer for each faulty phase is used to obtain the correction value of the input admittance after the fault for the faulty phase of each feeder, which is expressed as: In the formula, represents the correction value of the input admittance after the fault for the faulty phase of the i-th feeder; represents the input admittance after the fault at the high-voltage side of the v-th distribution transformer for the faulty phase of the i-th feeder; V represents the total number of distribution transformers on the i-th feeder.

[0048] Then, the correction value of the input admittance after the fault for the faulty phase is used to correct the input admittance after the fault for the faulty phase of the feeder, and the corresponding corrected input admittance after the fault for the faulty phase is obtained, which is expressed as: In the formula, and respectively represent the corrected input admittance after the fault for the faulty phase of the i-th feeder and the input admittance after the fault for the faulty phase.

[0049] Based on the input admittances before and after the fault for the faulty phases of each feeder obtained above, the asymmetry degree and input admittance mutation rate of the faulty phase of each feeder can be calculated accordingly: In the formula, and respectively represent the faulty phase of the i-th feeder on the substation bus corresponding faulty phase asymmetry and input admittance mutation rate.

[0050] As can be seen from the foregoing analysis, the faulty phase of the faulty feeder will increase the grounding admittance and the input admittance mutation rate is the largest. Then, based on the following criterion, the grounding fault feeder can be determined: That is, the feeder j that simultaneously satisfies the conditions of the maximum asymmetry and the maximum input admittance mutation rate is determined as the faulty feeder, realizing simple and accurate positioning of the faulty feeder.

[0051] In addition, to further improve the refinement of fault location, based on determining the faulty phase and the faulty feeder, this embodiment can also achieve fault section location based on two indicators of three-phase asymmetry and input admittance mutation rate; specifically, the method further includes: According to the voltage and current data before and after the fault of each line section on the faulty phase corresponding to the faulty feeder obtained, and the three-phase voltage and current data after the fault on the high-voltage side of the distribution transformer in each faulty phase section, calculate the input admittance before and after the fault corresponding to each line section and the input admittance after the fault on the high-voltage side of the distribution transformer in each faulty phase section; Accumulate the input admittances after the fault on the high-voltage side of the distribution transformer in all faulty phase sections on each line section to obtain the corresponding corrected value of the input admittance after the section fault; According to the corrected value of the input admittance after the section fault of each line section, correct the input admittance after the fault in the input admittance before and after the fault to obtain the corresponding corrected input admittance after the section fault; According to the corrected input admittance after the section fault of each line section and the input admittance before the fault in the input admittance before and after the fault, obtain the corresponding line section asymmetry and line section input admittance mutation rate; Compare and analyze the line section asymmetry and line section input admittance mutation rate corresponding to each line section, and take the line section with the maximum line section asymmetry and line section input admittance mutation rate as the grounding fault section.

[0052] In practical applications, the faulty phase is determined through the foregoing method steps and the faulty feeder j, and then combined with Figure 2 and Figure 5 ( and respectively represent the l-th and m-th monitoring devices on the feeder j; and respectively represent the faulty phase currents measured by the l-th and m-th monitoring devices on the feeder j; and respectively represent the fault phase voltages measured by the l-th and m-th monitoring devices on feeder j; (After the fault, the change value of the input admittance measured by the monitoring device in the fault section on the fault feeder j) can be used to explain the principle of the fault feeder selection method in this embodiment: Before the fault occurs, feeder j includes m voltage and current monitoring devices (the positions of each device are deployed according to requirements), and the input admittance measured by each device is defined as looking from this device to the load side, expressed as: In the formula, and respectively represent the fault phase current and fault phase voltage measured by the l-th monitoring device on the fault feeder j during normal operation; represents the input admittance measured by the l-th monitoring device on the fault feeder j during normal operation; is the angular frequency, and respectively represent the capacitance to ground and load admittance corresponding to the l-th monitoring device on the fault feeder j during normal operation.

[0053] The input admittance measured by the monitoring devices on each line section of the fault feeder after the fault can be expressed as: In the formula, and respectively represent the fault phase current and fault phase voltage measured by the l-th monitoring device on the fault feeder j after the fault; represents the input admittance measured by the l-th monitoring device on the fault feeder j after the fault; represents the change value of the input admittance measured by the l-th monitoring device on the fault feeder j after the fault, and the corresponding value of the monitoring device at the back end of the fault is 0.

[0054] Similarly, based on the three-phase voltage and current data after the fault on the high-voltage side of the distribution transformer in each fault phase section of each line section, the input admittance after the fault on the high-voltage side of the distribution transformer in each fault phase section can be calculated, and then the input admittance correction value after the fault of each line section can be obtained by adding the input admittances after the fault on the high-voltage side of the distribution transformer in each fault phase section of each line section, expressed as: In the formula, represents the input admittance correction value after the fault of the l-th line section on the fault feeder j; represents the input admittance after the fault on the high-voltage side of the w-th fault phase section of the l-th line section on the fault feeder j; W represents the total number of distribution transformers in the l-th line section of the fault feeder j.

[0055] Then, use the post-fault input admittance correction value of the section to correct the post-fault input admittance of the line section, and obtain the corresponding corrected post-fault input admittance of the section, which is expressed as: In the formula, and respectively represent the corrected post-fault input admittance and the post-fault input admittance of the l-th line section on the fault feeder j.

[0056] Based on the pre-fault and post-fault input admittances of the fault phases in each segmented area of each feeder obtained above, the line section asymmetry and the line section input admittance mutation rate of each segmented area can be calculated accordingly: In the formula, and respectively represent the line section asymmetry and the line section input admittance mutation rate corresponding to the fault phase of the l-th monitoring device on the fault feeder j.

[0057] Since each monitoring device before the grounding point includes a grounding admittance, but the load admittance and the capacitance to the ground are different at each location, only the device closest to the grounding has the largest asymmetry, and the fault downstream does not include a grounding admittance, the three-phase asymmetry is 0, and the asymmetry upstream of the fault is greater than 0. That is, it can be judged that the fault is located in the area with the largest difference in asymmetry; based on this, the grounding admittance of the fault phase of the fault line section increases and the input admittance mutation rate is the largest, then the grounding fault feeder can be determined based on the following criterion: Based on the above criterion, it can be known that the line section that simultaneously satisfies the conditions of the largest asymmetry and the largest input admittance mutation rate is

[0058] In the embodiments of the present invention, without the need to additionally introduce physical devices, based only on the data information collected by the existing voltage transformers, current transformers or distribution transformer terminals in the distribution network, the significant change characteristics of the admittance in the system before and after single-phase grounding are compared and analyzed. The changes in the three-phase asymmetry and the sudden change of the input admittance are respectively analyzed at the three levels of phase, feeder and section. And based on the maximum values of the three-phase asymmetry and the input admittance mutation rate, a method for discriminating and locating the single-phase grounding fault phase, fault feeder and fault section of the distribution network is realized. It can quickly and accurately locate high-resistance grounding faults or asymmetric faults in complex network environments. It can not only improve the accuracy and sensitivity of fault location, but also reduce the calculation and implementation costs of fault location analysis, and effectively avoid the application limitations of grounding modes, with wide application scenarios and high practical value.

[0059] To verify the effectiveness of the proposed single-phase grounding fault location method for the distribution network, this embodiment also takes Figure 6 the shown distribution network structure (M, M 1 , M 2 , M 21 , M 22 , M 3 , M 31 , M 4 and M 41 represent voltage and current monitoring devices; L 1 , L 2 , L 3 and L 4 represent feeders, L 21 and L 22 represent the two branch lines of feeder L 2 ) as an example to conduct the following single-phase fault location simulation: 1) At 0.3 s, simulate a single-phase grounding fault of phase A at the end of line L 4 ; Based on Figure 7 the ABC three-phase input admittances on the low-voltage bus of the shown substation, it can be seen that the input admittance of phase A has a significant increase. The input admittance before the fault is 0.000295, and the input admittance after the fault is 0.078. The corresponding asymmetry is 263.41%, and the input admittance mutation rate is 0.11. While there is no obvious fluctuation in phase B and phase C, and the corresponding asymmetry and input admittance mutation rate are both 0. Then it can be judged that the fault phase is phase A; After judging that a single-phase grounding fault has occurred in phase A, the Figure 8 A-phase input admittances of each feeder shown are obtained. The input admittance of line L 4 is the largest at 0.0485, the asymmetry is 709.78%, and the admittance mutation rate is 4.949. While the input admittance of line L 2After the fault occurs, the input admittance is 0.0099, the asymmetry is 59.08%, and the admittance mutation rate is 4.87; therefore, it can be judged that the fault is on line L 4 ; Based on Figure 9 the input admittances measured by each monitoring device on the fault feeder L 4 it can be seen that the input admittance measured by monitoring device M 41 is 0.07954, and the input admittance mutation rate is 4.950. The input admittance measured by device M 4 is 0.0485, and the input admittance mutation rate is 4.949. Therefore, it can be judged that the fault occurs in the line section after monitoring device M 41 .

[0060] 2) At 0.4 s, a single-phase ground fault of phase B occurs in the middle of line simulation L 2 , and when the fault occurs, the load on line L 21 is increased by 10,000 W; Based on Figure 10 the input admittances of three phases ABC on the low-voltage bus of the substation shown, it can be seen that the input admittance of phase B has a significant increase. The input admittance before the fault is 0.000022, and the input admittance after the fault is 0.126. The corresponding asymmetry is 5726.27% and the input admittance mutation rate is 7.58. The corrected admittance of phase B is 0.063, and the corrected asymmetry is 2862.64%. The other two phases have no obvious fluctuations, and the corresponding asymmetry and input admittance rate mutation rate are both 0. It can be judged that the fault phase is phase B; after judging that a single-phase ground fault occurs in phase B, the B-phase input admittances of each feeder shown in Figure 11 are obtained. The maximum input admittance of line L 2 is 0.108, the asymmetry is 4908.09%, the admittance mutation rate is 7.56, and the corrected input admittance is 0.045, the asymmetry is 22044.45%, and the admittance mutation rate is 7.43. Therefore, it can be judged that the fault occurs on line L 2 ; Based on Figure 12 the input admittances measured by each monitoring device on the fault feeder L 2 it can be seen that the input admittance after the fault measured by monitoring device M 11 is 0.01034, the asymmetry is 469.10%, the input admittance mutation rate is 1.03, the corrected input admittance after the fault is 0.01034, the asymmetry is 469.10%, the input admittance mutation rate is 1.03, and because the load increase has no effect on this branch, the corrected admittance remains unchanged; monitoring device M 12The measured post-fault input admittance is 0.07546, the asymmetry is 3429%, the input admittance mutation rate is 7.56, the corrected post-fault input admittance is 0.01246, the asymmetry is 5565.36%, and the input admittance mutation rate is 7.55; monitoring device M 2 The measured post-fault input admittance is 0.108, the asymmetry is 4908.09%, the input admittance mutation rate is 7.56, the corresponding corrected post-fault admittance is 0.045, the asymmetry is 2044.45%, and the input admittance mutation rate is 7.43; therefore, it can be judged that the fault occurs in monitoring device M 2 -M 21 between.

[0061] It should be noted that, as Figure 6 shown, the monitoring device for the faulty phase can be deployed between the low-voltage side of the distribution transformer and the bus, because the current here is the sum of the currents of all feeders, and the voltage collects the bus voltage; the monitoring device for the faulty feeder needs to be deployed at the outlet of each feeder to measure the current, and the voltage still uses the bus voltage; if there are long lines in the substation, monitoring devices need to be deployed in the middle of each feeder to help narrow the scope of the fault area. It should be noted that generally when the substation is put into operation, current transformers have been put into operation at the low-voltage side of the distribution transformer and each feeder, and voltage transformers have also been put into operation at the low-voltage bus of the distribution transformer. Therefore, the monitoring devices for the faulty phase and the faulty feeder can directly use the existing voltage and current transformers without additional investment and construction, while the monitoring devices for the line sections on the faulty feeder can be monitored by means of the integrated primary and secondary equipment switch without additional investment, which has high economic efficiency and popularization value.

[0062] It should be noted that although the steps in the above flow chart are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders.

[0063] In one embodiment, as Figure 13 shown, a single-phase grounding fault location system for a distribution network is provided, and the system includes: Data acquisition module 1, which is used to obtain the three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the fault of each distribution transformer high-voltage side according to the moment when a single-phase grounding fault occurs in the distribution network; Admittance calculation module 2, which is used to obtain the three-phase input admittances before and after the bus fault according to the three-phase voltage and current data before and after the bus fault, and obtain the corresponding three-phase input admittances after the fault of each distribution transformer high-voltage side according to the three-phase voltage and current data after the fault of each distribution transformer high-voltage side; A admittance correction module 3, configured to correct the three-phase input admittances of the bus before and after the fault according to the three-phase input admittances after the faults at the high-voltage sides of all distribution transformers, so as to obtain the corrected three-phase input admittances of the bus before and after the fault; An admittance analysis module 4, configured to calculate the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus according to the corrected three-phase input admittances of the bus before and after the fault; A fault phase positioning module, configured to use the phase with the maximum asymmetry degree and the maximum mutation rate of the input admittance corresponding to the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus as the fault phase.

[0064] In one embodiment, a single-phase grounding fault location system for a distribution network is provided, and the system further includes: A fault feeder location module, configured to calculate the input admittances before and after the fault of the corresponding fault phase according to the voltage and current data before and after the fault of the fault phase of each feeder obtained, and obtain the asymmetry degree of the fault phase and the mutation rate of the input admittance of the fault phase corresponding to each feeder according to the input admittances before and after the fault of the fault phase, and perform a comparison and analysis on the asymmetry degree of the fault phase and the mutation rate of the input admittance of the fault phase corresponding to each feeder, and use the feeder with the maximum asymmetry degree of the fault phase and the maximum mutation rate of the input admittance of the fault phase as the fault feeder.

[0065] In one embodiment, a single-phase grounding fault location system for a distribution network is provided, and the system further includes: A fault section location module, configured to obtain the voltage and current data before and after the fault of each line section on the fault phase corresponding to the fault feeder, obtain the input admittances before and after the fault corresponding to each line section according to the voltage and current data before and after the fault, and obtain the asymmetry degree of the corresponding line section and the mutation rate of the input admittance of the line section according to the input admittances before and after the fault corresponding to each line section, and perform a comparison and analysis on the asymmetry degree of the line section and the mutation rate of the input admittance of the line section corresponding to each line section, and use the line section with the maximum asymmetry degree of the line section and the maximum mutation rate of the input admittance of the line section as the grounding fault section.

[0066] For the specific limitations of the single-phase grounding fault location system for a distribution network, reference may be made to the limitations on the single-phase grounding fault location method for a distribution network in the foregoing text, and the corresponding technical effects can also be equivalently obtained, which will not be elaborated herein. Each module in the above single-phase grounding fault location system for a distribution network can be implemented in whole or in part by software, hardware, and their combination. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or stored in the memory in the computer device in the form of software, so as to facilitate the processor to call and execute the operations corresponding to the above modules.

[0067] Figure 14The internal structure diagram of a computer device in an embodiment is shown. The computer device may specifically be a terminal or a server. As Figure 14 shown, the computer device includes a processor, a memory, a network interface, a display, a camera, and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it implements the method for single-phase grounding fault location in a distribution network. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device may be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the housing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0068] Those of ordinary skill in the art can understand that Figure 14 the structure shown in

[0069] is only a block diagram of some structures related to the solution of the present invention, and does not constitute a limitation on the computer device to which the solution of the present invention is applied. A specific computing device may include more or fewer components than those shown in the figure, or combine certain components, or have a different component layout.

[0070] In an embodiment, a computer device is provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the above method are implemented.

[0071] In summary, the single-phase grounding fault location method and system provided by the embodiments of the present invention can, when a single-phase grounding fault occurs in a distribution network, obtain the three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the fault at the high-voltage side of each distribution transformer according to the moment when the single-phase grounding fault occurs. The three-phase input admittances before and after the bus fault are obtained based on the three-phase voltage and current data before and after the bus fault, and the three-phase input admittances after the fault at the high-voltage side of each distribution transformer are obtained based on the three-phase voltage and current data after the fault at the high-voltage side of each distribution transformer. Then, the three-phase input admittances before and after the bus fault are corrected according to the three-phase input admittances after the fault at all distribution transformer high-voltage sides. After obtaining the corrected three-phase input admittances before and after the bus fault, the three-phase asymmetry degree and the mutation rate of the three-phase input admittance of the bus are calculated according to the corrected three-phase input admittances before and after the bus fault. The phase with the corresponding asymmetry degree and input admittance mutation rate both being the maximum value among the three-phase asymmetry degree of the bus and the mutation rate of the three-phase input admittance of the bus is used as the fault phase. Without the need to additionally increase physical measurement devices or perform complex hardware modifications, directly using the three-phase asymmetry degree and the mutation rate of the input admittance before and after the grounding fault can achieve single-phase grounding fault location analysis. This method can not only improve the accuracy and sensitivity of fault location, but also reduce the calculation and implementation costs of fault location analysis, and effectively avoid the application limitations of grounding modes, having a wide range of application scenarios and high practical value.

[0072] Each embodiment in this specification is described in a progressive manner. For parts that are the same or similar in each embodiment, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0073] The above-described embodiments only represent several preferred implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the protection scope of the claims.

Claims

1. A method for locating a single-phase grounding fault in a distribution network, characterized in that: The method comprises the following steps: When a single-phase grounding fault occurs in the distribution network, the three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer are obtained according to the time when the single-phase grounding fault occurs; According to the three-phase voltage and current data before and after the bus fault, the three-phase input admittance before and after the bus fault is obtained, and according to the three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer, the corresponding three-phase input admittance after the fault on the high-voltage side of the distribution transformer is obtained; The three-phase input admittance before and after the bus fault is corrected according to the three-phase input admittance after the high-voltage side fault of all distribution transformers to obtain the corrected three-phase input admittance before and after the bus fault; Calculating the bus three-phase asymmetry and the bus three-phase input admittance mutation rate according to the corrected bus three-phase input admittance before and after the fault; The phase whose corresponding asymmetry degree and input admittance mutation rate in the three-phase asymmetry degree of the bus and the three-phase input admittance mutation rate of the bus are both maximum is taken as the fault phase.

2. The method for locating a single-phase grounding fault in a distribution network according to claim 1, characterized in that: The single-phase ground fault occurrence time is the time when the zero-sequence voltage of the distribution network reaches a preset threshold value; according to the single-phase ground fault occurrence time, the step of obtaining the three-phase voltage and current data before and after the fault includes: Obtain the three-phase current amplitude and the three-phase voltage amplitude at the time corresponding to the preset time length shifted forward of the single-phase grounding occurrence moment as the corresponding three-phase pre-fault current amplitude and three-phase pre-fault voltage amplitude respectively; The three-phase current amplitude and the three-phase voltage amplitude at the time corresponding to the preset time length after the occurrence of the single-phase grounding fault are obtained as the corresponding three-phase post-fault current amplitude and three-phase post-fault voltage amplitude respectively.

3. The method for locating a single-phase grounding fault in a distribution network according to claim 1, characterized in that: The step of obtaining the three-phase input admittance before and after the bus fault according to the three-phase voltage and current data before and after the bus fault comprises: According to the ratio of the pre-fault current data of each phase in the three-phase voltage and current data before and after the bus fault to the pre-fault voltage data, the pre-fault input admittance of the corresponding phase in the three-phase input admittance before and after the bus fault is obtained; According to the ratio of the post-fault current data of each phase in the three-phase voltage and current data before and after the bus fault to the post-fault voltage data, the post-fault input admittance of the corresponding phase in the three-phase input admittance before and after the bus fault is obtained.

4. The method for locating a single-phase grounding fault in a distribution network according to claim 1, characterized in that: The step of correcting the three-phase input admittance before and after the bus fault according to the three-phase input admittance after the high-voltage side fault of all distribution transformers to obtain the corrected three-phase input admittance before and after the bus fault comprises: The input admittance of each phase in the three-phase input admittance after the fault on the high-voltage side of all distribution transformers is accumulated to obtain the corresponding three-phase input admittance correction value after the fault; Correcting the post-fault three-phase input admittance of the three-phase input admittance before and after the bus fault according to the post-fault three-phase input admittance correction value to obtain a corresponding corrected post-fault three-phase input admittance; The modified three-phase input admittance before and after the bus fault is obtained according to the modified three-phase input admittance after the fault and the three-phase input admittance before and after the bus fault.

5. The method for locating a single-phase grounding fault in a distribution network according to claim 1, characterized in that: The step of calculating the bus three-phase asymmetry and the bus three-phase input admittance mutation rate according to the corrected bus three-phase input admittance before and after the bus fault comprises: According to the input admittance of each phase after the fault and the input admittance of each phase before the fault in the three-phase input admittance before and after the bus fault, a corresponding change value of the input admittance of each phase after the fault is obtained; Obtaining the three-phase asymmetry of the busbar according to the ratio of the input admittance change value of each phase after the fault to the corresponding input admittance of each phase before the fault; The bus three-phase input admittance mutation rate is obtained according to the ratio of the input admittance change value of each phase after the fault to the preset admittance mutation time length.

6. The method for locating a single-phase grounding fault in a distribution network according to claim 1, characterized in that: The method further comprises: According to the acquired voltage and current data of the fault phase of each feeder before and after the fault and the three-phase voltage and current data of the high-voltage side of each fault phase matching transformer on each feeder after the fault, the input admittance of the corresponding fault phase before and after the fault and the input admittance of the high-voltage side of each fault phase matching transformer after the fault are calculated; The post-fault input admittances of the high-voltage side of all fault phase transformers on each feeder are accumulated to obtain the post-fault input admittance correction value of the corresponding fault phase; According to the fault phase post-fault input admittance correction value of each feeder, the fault phase post-fault input admittance in the fault phase pre-fault and post-fault input admittance is corrected to obtain the corresponding corrected fault phase post-fault input admittance; According to the corrected post-fault input admittance of the fault phase of each feeder and the pre-fault input admittance of the fault phase among the pre-fault and post-fault input admittances of the fault phase, the fault phase asymmetry and the fault phase input admittance mutation rate corresponding to each feeder are obtained; The fault phase asymmetry and fault phase input admittance mutation rate corresponding to each feeder are compared and analyzed, and the feeder with the maximum fault phase asymmetry and fault phase input admittance mutation rate is taken as the fault feeder.

7. The method for locating a single-phase grounding fault in a distribution network according to claim 6, characterized in that: The method further comprises: Calculate the input admittance before and after the fault corresponding to each line section and the input admittance after the fault on the high-voltage side of each fault phase section according to the obtained voltage and current data before and after the fault of each line section on the fault phase corresponding to the fault feeder and the three-phase voltage and current data after the fault on the high-voltage side of each fault phase section; The post-fault input admittances of the high-voltage side of all fault phase sections of each line section are accumulated to obtain the corresponding section post-fault input admittance correction value; Correcting the post-fault input admittance in the pre- and post-fault input admittances according to the post-fault input admittance correction value of each line section to obtain a corresponding corrected section post-fault input admittance; According to the corrected section post-fault input admittance of each line section and the pre-fault input admittance of the pre-fault and post-fault input admittances, the corresponding line section asymmetry and the line section input admittance mutation rate are obtained; The line section asymmetry and line section input admittance mutation rate corresponding to each line section are compared and analyzed, and the line section with the maximum line section asymmetry and line section input admittance mutation rate is obtained as the grounding fault section.

8. A single-phase grounding fault location system for a distribution network, characterized in that: The system comprises: The data acquisition module is used to obtain the three-phase voltage and current data before and after the bus fault and the three-phase voltage and current data after the fault on the high-voltage side of each distribution transformer according to the time when the single-phase grounding fault occurs in the distribution network; The admittance calculation module is used to obtain the three-phase input admittance before and after the bus fault according to the three-phase voltage and current data before and after the bus fault, and obtain the corresponding three-phase input admittance after the high-voltage side fault of the distribution transformer according to the three-phase voltage and current data after the high-voltage side fault of each distribution transformer; An admittance correction module is used to correct the three-phase input admittance before and after the bus fault according to the three-phase input admittance after the high-voltage side fault of all distribution transformers, so as to obtain the corrected three-phase input admittance before and after the bus fault; An admittance analysis module, used for calculating the bus three-phase asymmetry and the bus three-phase input admittance mutation rate according to the corrected bus three-phase input admittance before and after the bus fault; The fault phase locating module is used to take the phase with the maximum asymmetry and input admittance mutation rate in the three-phase asymmetry of the bus and the three-phase input admittance mutation rate of the bus as the fault phase.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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