A method, system, device and medium for single-phase grounding fault location in a distribution network

Abstract

The present invention provides a method, system, device and medium for single-phase grounding fault location in a distribution network. When a single-phase grounding fault occurs in the distribution network, the three-phase input admittances 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 calculated according to the acquired 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. The three-phase asymmetry degree and the mutation rate of the three-phase input admittance of the bus are calculated based on the three-phase input admittances after the fault at the high-voltage side of all distribution transformers and the three-phase input admittances before and after the bus fault after correction. The phase with the maximum asymmetry degree and input admittance mutation rate among the three-phase asymmetry degree and the mutation rate of the three-phase input admittance of the bus is used as the fault phase. The present invention can improve the accuracy and sensitivity of fault location, reduce the calculation and implementation costs of fault location analysis, and effectively avoid the application limitations of grounding modes.

Description

Technical Field

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

[0002] Single-phase grounding faults are the most common faults in a distribution network, accounting for more than 80% of various faults. To ensure the personal safety of users, equipment safety and power supply reliability, medium and low voltage distribution networks usually adopt non-effectively grounded neutral, mainly including ungrounded neutral, resonant grounded neutral and purely resistive 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 close to the line voltage. Long-term fault operation will not only threaten personal and equipment safety, but also may cause more serious phase-to-phase faults due to wire insulation rupture. It is necessary to locate and eliminate the fault within a short time, which has also become a problem that has puzzled the power system so far.

[0003] Existing methods for selecting and locating single-phase grounding faults include the mainstream methods that rely on fault line selection devices and use the dichotomy method to locate the approximate section of single-phase grounding faults, and the non-mainstream methods that combine multiple algorithms. However, in actual engineering applications of the mainstream methods that rely on fault line selection devices and use the dichotomy method to locate the approximate section of single-phase grounding faults, the fault line selection device based on the zero-sequence signal characteristics not only requires additional measurement devices, has a high application cost and is not convenient for maintenance and management, increasing the operation risk of the power grid, but also often shows unsatisfactory states such as incorrect line selection or non-selection. And 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, ignores 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 purpose of the present invention is to provide a method for locating a single-phase grounding fault in a distribution network, which realizes the location of a single-phase grounding fault based on the comprehensive analysis of the three-phase asymmetry degree and the mutation rate of the 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 the grounding mode.

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

[0006] In the first aspect, an embodiment of the present invention provides a method for locating a single-phase grounding fault in a distribution network, and the method includes the following steps:

[0007] When a single - phase grounding fault occurs in the distribution network, according to the occurrence time of the single - phase grounding fault, 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 the distribution transformer are obtained;

[0008] According to the three - phase voltage and current data before and after the bus fault, the three - phase input admittances before and after the bus fault are 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 admittances after the fault on the high - voltage side of the distribution transformer are obtained;

[0009] According to the three - phase input admittances after the fault on the high - voltage side of all distribution transformers, the three - phase input admittances before and after the bus fault are corrected to obtain the corrected three - phase input admittances before and after the bus fault;

[0010] According to the corrected three - phase input admittances 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;

[0011] 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 taken as the fault phase.

[0012] 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:

[0013] Obtain the three - phase current amplitudes and three - phase voltage amplitudes at the corresponding time when the preset time duration is advanced from 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;

[0014] Obtain the three - phase current amplitudes and three - phase voltage amplitudes at the corresponding time when the preset time duration is delayed from 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.

[0015] 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:

[0016] 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, the pre - fault input admittance of the corresponding phase in the three - phase input admittances before and after the bus fault is obtained;

[0017] 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, the post - fault input admittance of the corresponding phase in the three - phase input admittances before and after the bus fault is obtained.

[0018] Further, the step of correcting the three-phase input admittance before and after the bus fault according to the three-phase input admittance of all distribution transformer high-voltage sides after the fault includes:

[0019] Accumulate the phase input admittances in the three-phase input admittances of all distribution transformer high-voltage sides after the fault to obtain the corresponding post-fault three-phase input admittance correction value;

[0020] Correct the post-fault three-phase input admittance in the three-phase input admittance before and after the bus fault according to the post-fault three-phase input admittance correction value to obtain the corresponding corrected post-fault three-phase input admittance;

[0021] Obtain the corrected three-phase input admittance before and after the bus fault according to the corrected post-fault three-phase input admittance and the pre-fault three-phase input admittance in the three-phase input admittance before and after the bus fault.

[0022] 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:

[0023] Obtain the corresponding post-fault phase input admittance change value according to the post-fault phase input admittance and the pre-fault phase input admittance in the corrected three-phase input admittance before and after the bus fault;

[0024] Obtain the three-phase asymmetry degree of the bus according to the ratio of the post-fault phase input admittance change value to the corresponding pre-fault phase input admittance;

[0025] Obtain the mutation rate of the three-phase input admittance of the bus according to the ratio of the post-fault phase input admittance change value to the preset admittance mutation duration.

[0026] Further, the method further includes:

[0027] Calculate the corresponding input admittance before and after the fault of the fault phase and the input admittance of the high-voltage side of each distribution transformer of each fault phase on each feeder after the fault 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 of the high-voltage side of each distribution transformer of each fault phase on each feeder;

[0028] Accumulate the input admittances of the high-voltage sides of all distribution transformers of each fault phase on each feeder after the fault to obtain the corresponding post-fault input admittance correction value of the fault phase;

[0029] Correct the post-fault input admittance of the fault phase in the input admittance before and after the fault of the fault phase according to the post-fault input admittance correction value of the fault phase of each feeder to obtain the corresponding corrected post-fault input admittance of the fault phase;

[0030] Based on the post-fault input admittance of the corrected 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 degree and the mutation rate of the fault-phase input admittance corresponding to each feeder are obtained;

[0031] The fault-phase asymmetry degrees and the mutation rates of the fault-phase input admittances corresponding to each feeder are compared and analyzed, and the feeder with the maximum values of both the fault-phase asymmetry degree and the mutation rate of the fault-phase input admittance is obtained as the faulty feeder.

[0032] Further, the method further includes:

[0033] Based on the pre-fault and post-fault voltage and current data of each line section on the fault phase corresponding to the obtained faulty feeder and the post-fault three-phase voltage and current data of the high-voltage side of the distribution transformer in each fault-phase section, the pre-fault and post-fault input admittances corresponding to each line section and the post-fault input admittance of the high-voltage side of the distribution transformer in each fault-phase section are calculated;

[0034] The post-fault input admittances of the high-voltage sides of the distribution transformers in all fault-phase sections on each line section are accumulated to obtain the corrected value of the post-fault input admittance of the corresponding section;

[0035] Based on the corrected value of the post-fault input admittance of each line section, the post-fault input admittance in the pre-fault and post-fault input admittances is corrected to obtain the corresponding corrected post-fault input admittance of the section;

[0036] Based on the corrected post-fault input admittance of each line section and the pre-fault input admittance in the pre-fault and post-fault input admittances, the asymmetry degree of the corresponding line section and the mutation rate of the line-section input admittance are obtained;

[0037] The asymmetry degrees of the line sections and the mutation rates of the line-section input admittances corresponding to each line section are compared and analyzed, and the line section with the maximum values of both the line-section asymmetry degree and the mutation rate of the line-section input admittance is obtained as the ground-fault section.

[0038] In a second aspect, an embodiment of the present invention provides a single-phase ground-fault location system for a distribution network, and the system includes:

[0039] A data acquisition module, configured to obtain the pre-fault and post-fault three-phase voltage and current data of the bus and the post-fault three-phase voltage and current data of the high-voltage side of each distribution transformer according to the occurrence time of the single-phase ground fault when the single-phase ground fault occurs in the distribution network;

[0040] An admittance calculation module, configured to obtain the pre-fault and post-fault three-phase input admittances of the bus according to the pre-fault and post-fault three-phase voltage and current data of the bus, and obtain the post-fault three-phase input admittances of the corresponding high-voltage sides of the distribution transformers according to the post-fault three-phase voltage and current data of the high-voltage sides of each distribution transformer;

[0041] A susceptance correction module, configured to correct the three-phase input susceptance before and after the bus fault according to the three-phase input susceptance after the faults of all distribution transformer high-voltage sides, so as to obtain the corrected three-phase input susceptance before and after the bus fault;

[0042] A susceptance analysis module, configured to calculate the three-phase asymmetry of the bus and the mutation rate of the three-phase input susceptance of the bus according to the corrected three-phase input susceptance before and after the bus fault;

[0043] A fault phase positioning module, configured to use the phase in which the corresponding asymmetry and the mutation rate of the input susceptance in the three-phase asymmetry of the bus and the mutation rate of the three-phase input susceptance of the bus are both the maximum values as the fault phase.

[0044] 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. When the processor executes the computer program, the steps of the above method are implemented.

[0045] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0046] 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 bus fault and three-phase voltage and current data after the faults of all distribution transformer high-voltage sides are obtained according to the occurrence time of the single-phase grounding fault. The three-phase input susceptance 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 susceptance after the faults of each distribution transformer high-voltage side is obtained according to the three-phase voltage and current data after the faults of each distribution transformer high-voltage side. Then, the three-phase input susceptance before and after the bus fault is corrected according to the three-phase input susceptance after the faults of all distribution transformer high-voltage sides. After obtaining the corrected three-phase input susceptance before and after the bus fault, the three-phase asymmetry of the bus and the mutation rate of the three-phase input susceptance of the bus are calculated according to the corrected three-phase input susceptance before and after the bus fault. The phase in which the corresponding asymmetry and the mutation rate of the input susceptance in the three-phase asymmetry of the bus and the mutation rate of the three-phase input susceptance of the bus are both the maximum values 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 and the mutation rate of the input susceptance before and after the grounding fault to realize the analysis of single-phase grounding fault location without adding additional physical measurement devices or complex hardware modifications 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, having a wide range of application scenarios and high practical value. Description of the Drawings

[0047] Figure 1 It is a schematic flow chart of the single-phase grounding fault location method for the distribution network in the embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of the fault model when a phase C grounding fault occurs in the distribution network in the embodiment of the present invention;

[0049] 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 towards the load side;

[0050] Figure 4 It is a schematic diagram of the equivalent model of the distribution network for the normal feeder and the fault feeder in the embodiment of the present invention (the left figure is the normal feeder and the right figure is the fault feeder);

[0051] Figure 5 It is a schematic diagram of the equivalent model of the fault phase of the fault feeder j in the embodiment of the present invention;

[0052] Figure 6 It is a schematic diagram of the distribution network structure deployed with voltage and current monitoring devices in the embodiment of the present invention;

[0053] Figure 7 is Figure 6 When a phase A single-phase grounding fault occurs at the end of L4 in the distribution network structure shown, a schematic diagram of the input admittance of the ABC three phases at the substation;

[0054] Figure 8 is Figure 6 When a phase A single-phase grounding fault occurs at the end of L4 in the distribution network structure shown, a schematic diagram of the input admittance of phase A of each feeder at the substation;

[0055] Figure 9 is Figure 6 When a phase A single-phase grounding fault occurs at the end of L4 in the distribution network structure shown, a schematic diagram of the input admittance of phase A of the fault phase measured by each monitoring device on the fault feeder;

[0056] Figure 10 is Figure 6 When a phase B grounding fault occurs in the middle of L2 in the distribution network structure shown, a schematic diagram of the input admittance of the ABC three phases at the substation;

[0057] Figure 11 is Figure 6 When a phase B grounding fault occurs in the middle of L2 in the distribution network structure shown, a schematic diagram of the input admittance of phase A of each feeder at the substation;

[0058] Figure 12 is Figure 6Schematic diagram of the input admittance of phase A of the fault phase measured by each monitoring device of the faulty feeder when a phase B grounding fault occurs in the middle of L2 in the shown distribution network structure;

[0059] Figure 13 Schematic diagram of the structure of the single-phase grounding fault location system for a distribution network in an embodiment of the present invention;

[0060] Figure 14 Internal structure diagram of a computer device in an embodiment of the present invention. Specific implementation manners

[0061] In order to make the objectives, 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0062] The single-phase grounding fault location method for a distribution network provided by the present invention can be understood as a solution that, based on the fact that the existing single-phase grounding fault location methods for distribution networks need to rely on zero-sequence voltage, zero-sequence current or transient quantities, have limitations in the application of grounding modes, not only increase the implementation cost due to the additional introduction of other physical measurement devices, but also have a relatively complex positioning analysis process, large calculation cost, and insufficient positioning accuracy due to weak signals. It is a solution that can directly utilize the characteristics of the change in line admittance before and after grounding to achieve rapid and accurate positioning at three levels: phase, feeder, and section, without the need for complex hardware transformation or additional introduction of sensing devices. It should be noted that the implementation of the method of the present invention needs to rely on the existing voltage and current measurement devices deployed on the distribution network to achieve. Each voltage and current measurement device can periodically collect and store the current amplitude and voltage amplitude at each grid position 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 at 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 describe the single-phase grounding fault location method for a distribution network of the present invention in detail.

[0063] In one embodiment, as Figure 1As shown, a method for single-phase grounding fault location in a distribution network is provided, including the following steps:

[0064] S11. 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 each distribution transformer; among them, the judgment of the occurrence 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 the zero-sequence voltage of the distribution network obtained by analyzing the data collected by the voltage and current monitoring device at a certain moment reaches the preset threshold, it is considered that a single-phase grounding fault occurs at this moment, and this moment is stored as the occurrence time of the single-phase grounding fault.

[0065] In practical applications, after determining that a single-phase grounding fault occurs in the distribution network, according to the stored occurrence time of the single-phase grounding fault, based on the corresponding voltage and current monitoring device, extract the voltage amplitudes and current amplitudes of each phase before and after the fault of the low-voltage bus of the substation, and based on the distribution transformer acquisition terminal, obtain the voltage amplitudes and current amplitudes of each phase after the fault of the high-voltage side of each distribution transformer; 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 of 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, and the corresponding 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 for 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:

[0066] Obtain the three-phase current amplitudes and three-phase voltage amplitudes at the corresponding moment when the preset duration 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 duration can be determined according to actual application requirements, such as 5 minutes, and no specific limitation is made here.

[0067] Obtain the three-phase current amplitudes and three-phase voltage amplitudes at the corresponding moment when the preset duration 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.

[0068] S12. According to the three-phase voltage and current data before and after the bus fault, obtain the three-phase input admittance before and after the bus fault, and according to the three-phase voltage and current data after the fault of the high-voltage side of each distribution transformer, obtain the corresponding three-phase input admittance after the fault of the high-voltage side of the 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 for 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 include:

[0069] Based on 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, the pre-fault input admittance of the corresponding phase in the three-phase input admittances before and after the bus fault is obtained;

[0070] Based on 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, the post-fault input admittance of the corresponding phase in the three-phase input admittances before and after the bus fault is obtained.

[0071] 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 with a single-phase grounding fault. Assuming that a C-phase grounding fault occurs in the distribution network, the Figure 2 single-phase grounding fault model shown can be obtained, 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 the ground; and from the substation bus looking towards the load side, the Figure 3 equivalent model of the distribution network shown can be obtained, where represents the compensation admittance.

[0072] 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 the ground and the load current, expressed as:

[0073]

[0074] 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 the ground, the voltage of phase B to the ground, and the voltage of phase C to the ground on the substation bus during normal operation respectively; is the angular frequency, and C is the capacitance to the ground. , and respectively represent the equivalent admittances of feeder phase A, feeder phase B, and feeder phase C; 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 the bus, then:

[0075]

[0076] In the formula, , and respectively represent the input admittances of phase A, phase B, and phase C on the substation bus during normal operation.

[0077] As Figure 2 and Figure 3 shown, after a phase C grounding fault occurs in the distribution network, the currents of each phase on the bus can be expressed as:

[0078]

[0079] In the formula, , and respectively represent the currents of phase A, phase B, and phase C on the substation bus during a single-phase grounding fault; , and respectively represent the voltages to the ground of phase A, phase B, and phase C on the substation bus during a single-phase grounding fault; and respectively represent the additional current of one phase and the corresponding additional input admittance of the faulty phase C on the bus due to the presence of the grounding current. It should be noted that if the faulty phase in the actual grounding fault is phase A or phase B, the corresponding or will also increase the corresponding grounding current and .

[0080] Based on the definition of the input admittances of each phase on the distribution network bus, it can be known that after a phase C grounding fault occurs in the corresponding distribution network, the input admittances of each phase on the bus can be expressed as:

[0081]

[0082] In the formula, , and respectively represent the input admittances of phase A, phase B, and phase C of the bus after a phase C grounding fault occurs.

[0083] Considering that the impedance between the phase and the ground changes in the case of a ground fault, and since the inter-phase impedance is not involved in the operation of a single-phase ground fault, the load flowing to the low-voltage side before and after the fault remains unchanged and the capacitance-to-ground parameter is fixed. Therefore, by comparing the input admittances of the bus before and after the C-phase ground fault occurs above, it can be found that only the input admittance of the fault phase C has an additional term (When a single-phase ground fault occurs in phase A, an additional term will appear in the input admittance of phase A ; when a single-phase ground fault occurs in phase B, an additional term will appear in the input admittance of phase B ), that is, it is feasible to determine the fault phase by analyzing the three-phase asymmetry based on the changes in the input admittances of each phase of the bus before and after the fault.

[0084] At the same time, considering that in the actual operation of the distribution network, there will also be a situation where the three-phase asymmetry changes due to the change of single-phase load. In order to ensure the accuracy of determining the fault phase based on the three-phase asymmetry subsequently, in this embodiment, while calculating the three-phase input admittances of the bus before and after the fault, the three-phase input admittances of the high-voltage side of the distribution transformer after the fault are also analyzed to correct the three-phase input admittances of the bus after the fault, so as to ensure the reliability of the three-phase asymmetry analysis after the fault. In addition, in order to verify the rationality of using the three-phase input admittances of the high-voltage side of the distribution transformer after the fault to correct the three-phase input admittances of the bus after the fault, this embodiment also takes the distribution network using Yn / D distribution transformers as an example for the following relevant principle analysis:

[0085] When the single-phase load on the low-voltage side of the kth distribution transformer increases, the change in the input admittance of the high-voltage side of the kth distribution transformer is as follows:

[0086]

[0087] In the formula, , and respectively represent the phase-A voltage, phase-B voltage, and phase-C voltage of the low-voltage side of the kth distribution transformer; , and respectively represent the phase-A current, phase-B current, and phase-C current of the low-voltage side of the kth distribution transformer; represents the short-circuit impedance of the kth distribution transformer; , and respectively represent the phase-A current, phase-B current, and phase-C current of the high-voltage side of the kth 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 kth distribution transformer.

[0088] When the load on the A phase of the low-voltage side of the k-th distribution transformer increases, currents with opposite directions and the same magnitude will be induced in the A and C phases of the high-voltage side of the distribution transformer. Based on the parameters of the low-voltage side of the distribution transformer to represent the change in admittance of the high-voltage side of the distribution transformer, we can obtain:

[0089]

[0090] In the formula, 、 and respectively represent the change values of the input admittance of the A phase, B phase, and C phase on the high-voltage side of the k-th distribution transformer when the load on the A phase of the low-voltage side of the k-th distribution transformer increases; represents the current of the A phase on the low-voltage side when the load on the A phase of the low-voltage side of the k-th distribution transformer increases;

[0091] When the load on the B phase of the low-voltage side of the k-th distribution transformer increases, currents with opposite directions and the same magnitude will be induced in the A and B phases of the high-voltage side of the distribution transformer. The corresponding change in admittance of the high-voltage side of the distribution transformer can be expressed as:

[0092]

[0093] In the formula, 、 and respectively represent the change values of the input admittance of the A phase, B phase, and C phase on the high-voltage side of the k-th distribution transformer when the load on the B phase of the low-voltage side of the k-th distribution transformer increases; represents the current of the B phase on the low-voltage side when the load on the B phase of the low-voltage side of the k-th distribution transformer increases.

[0094] When the load on the C phase of the low-voltage side of the k-th distribution transformer increases, currents with opposite directions and the same magnitude will be induced in the B and C phases of the high-voltage side of the distribution transformer. The corresponding change in admittance of the high-voltage side of the distribution transformer can be expressed as:

[0095]

[0096] In the formula, 、 and respectively represent the change values of the input admittance of the A phase, B phase, and C phase on the high-voltage side of the distribution transformer when the load on the C phase of the low-voltage side of the k-th 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 k-th distribution transformer increases.

[0097] Based on the above analysis, when the load of a phase increases, the current of the corresponding phase increases. When the load of phase A on the low-voltage side of the distribution transformer increases, the admittances of both phase A and phase C on the high-voltage side will increase. When the load of phase B on the low-voltage side of the distribution transformer increases, the admittances of both phase A and phase B on the high-voltage side will increase. When the load of phase C on the low-voltage side of the distribution transformer increases, the admittances of both phase B and phase C on the high-voltage side will 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 after the busbar fault by using the three-phase input admittance after the fault of the high-voltage side of the distribution transformer.

[0098] S13. Correct the three-phase input admittances before and after the busbar fault according to the three-phase input admittances after the fault of all high-voltage sides of the distribution transformers to obtain the corrected three-phase input admittances before and after the busbar fault; among them, the three-phase input admittance before the busbar fault in the corrected three-phase input admittances before and after the busbar fault is the same as the three-phase input admittance before the busbar fault in the three-phase input admittances before and after the busbar fault, and the corresponding three-phase input admittance after the busbar fault is the corrected three-phase input admittance obtained by correcting based on the three-phase input admittance after the fault of the high-voltage side of the distribution transformer. Specifically, the step of correcting the three-phase input admittances before and after the busbar fault according to the three-phase input admittances after the fault of all high-voltage sides of the distribution transformers to obtain the corrected three-phase input admittances before and after the busbar fault includes:

[0099] Accumulate the input admittances of each phase in the three-phase input admittances after the fault of all high-voltage sides of the distribution transformers to obtain the corresponding correction value of the three-phase input admittance after the fault, which is expressed as:

[0100]

[0101] In the formula, 、 and respectively represent the change values of the admittances of phase A, phase B, and phase C on the high-voltage side when the load increases, that is, the correction value of the three-phase input admittance after the fault required above; K represents the total number of distribution transformers.

[0102] Correct the three-phase input admittance after the busbar fault in the three-phase input admittances before and after the busbar fault according to the correction value of the three-phase input admittance after the 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:

[0103]

[0104] In the formula, and respectively represent the input admittance after the busbar fault of phase A of the busbar and the corresponding corrected input admittance after the fault; and respectively represent the post-fault input admittance of phase B of the busbar and the corresponding corrected post-fault input admittance; and respectively represent the post-fault input admittance of phase C of the busbar and the corresponding corrected post-fault input admittance; , 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.

[0105] Based on the pre-fault three-phase input admittance among the corrected post-fault three-phase input admittances of the busbar and the three-phase input admittances of the busbar before and after the busbar fault, the corrected three-phase input admittances of the busbar before and after the busbar fault are obtained.

[0106] Based on the analysis formula of the variation of the three-phase input admittances of the busbar before and after the busbar fault above, 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 through an arc suppression coil, nor does it involve sequence components. 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.

[0107] S14. Calculate the three-phase asymmetry degree of the busbar and the mutation rate of the three-phase input admittance of the busbar according to the corrected three-phase input admittances of the busbar before and after the busbar fault; among them, the three-phase asymmetry degree of the busbar can be understood as the three-phase unbalance degree calculated based on the variation of the input admittances of the three phases of the busbar 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 variation rate of the input admittance calculated based on the variation of the input admittances of the three phases of the busbar before and after the three-phase fault of the busbar.

[0108] Specifically, the steps of calculating the three-phase asymmetry degree of the busbar and the mutation rate of the three-phase input admittance of the busbar according to the corrected three-phase input admittances of the busbar before and after the busbar fault include:

[0109] Based on the post-fault input admittances of each phase and the pre-fault input admittances of each phase among the corrected three-phase input admittances of the busbar before and after the busbar fault, obtain the corresponding variation values of the post-fault input admittances of each phase;

[0110] Based on the ratio of the variation values of the post-fault input admittances of each phase to the corresponding pre-fault input admittances of each phase, obtain the three-phase asymmetry degree of the busbar; that is, the three-phase asymmetry degree of the busbar is expressed as:

[0111]

[0112] In the formula, and respectively represent the pre-fault input admittance and the corrected post-fault input admittance of phase A of the busbar; and respectively represent the pre-fault input admittance and the corrected post-fault input admittance of phase B of the busbar; and respectively represent the post-fault input admittance of phase C of the busbar and the corresponding corrected post-fault input admittance; 、 and respectively represent the asymmetry of phase A, phase B, and phase C of the busbar;

[0113] According to the ratio of the change value of the post-fault input admittance of each phase to the preset admittance mutation duration, the three-phase input admittance mutation rate of the busbar is obtained; where the preset admittance mutation duration can be understood as the difference between the time of obtaining the post-single-phase ground fault voltage and current data and the time of obtaining the pre-single-phase ground fault voltage and current data, which will not be elaborated here; the corresponding three-phase input admittance mutation rate of the busbar is expressed as:

[0114]

[0115] In the formula, represents the preset admittance mutation duration; 、 and respectively represent the input admittance mutation rate of phase A, phase B, and phase C of the busbar.

[0116] The three-phase input admittance mutation rate of the busbar in this embodiment can be understood as another criterion for assisting in judging whether there is a single-phase ground fault, which is to further exclude the possibility of other factors in the power grid affecting the input admittance value, and considering the characteristic that the input admittance changes rapidly before and after the single-phase ground fault due to the sudden and intense current and voltage.

[0117] S15. Take the phase with the maximum corresponding asymmetry and input admittance mutation rate among the three-phase asymmetry of the busbar and the three-phase input admittance mutation rate of the busbar as the fault phase; that is, the determination condition of the fault phase is as follows:

[0118] When , and ,it is determined that a single-phase ground fault occurs in phase A;

[0119] When , and ,it is determined that a single-phase ground fault occurs in phase B;

[0120] When the conditions , and are met, it is determined that a single-phase grounding fault has occurred in phase C.

[0121] It can be easily known from the post-fault input admittance expression of the aforementioned faulty phase that the faulty phase increases the grounding admittance , and only the asymmetry of the faulty 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 faulty phase, which can effectively avoid misjudgment caused by load fluctuations and improve the scientificity and accuracy of faulty phase determination.

[0122] 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.

[0123] At the same time, to further improve the analysis depth of fault location, on the basis of determining the faulty phase, this embodiment can also realize fault feeder selection based on two indicators of three-phase asymmetry and input admittance mutation rate; specifically, the method further includes:

[0124] According to the voltage and current data before and after the fault of the faulty phase of each feeder and the three-phase voltage and current data after the fault on the high-voltage side of the transformer of each faulty phase on each feeder, calculate the input admittance before and after the fault of the corresponding faulty phase and the input admittance after the fault on the high-voltage side of the transformer of each faulty phase on each feeder;

[0125] Accumulate the input admittances after the fault on the high-voltage side of the transformers of all faulty phases on each feeder to obtain the corrected value of the input admittance after the fault of the corresponding faulty phase;

[0126] According to the corrected value of the input admittance after the fault of the faulty phase of each feeder, correct the input admittance after the fault of the faulty phase in the input admittance before and after the fault of the faulty phase to obtain the corrected input admittance after the fault of the corresponding faulty phase;

[0127] According to the corrected input admittance after the fault of the faulty phase of each feeder and the input admittance before the fault of the faulty phase in the input admittance before and after the fault of the faulty phase, obtain the asymmetry of the faulty phase and the input admittance mutation rate of the faulty phase corresponding to each feeder;

[0128] 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 obtain the feeder with the maximum asymmetry degree of the faulty phase and the mutation rate of the input admittance of the faulty phase as the faulty feeder.

[0129] In the implementation and application, the faulty phase is determined through the foregoing method steps After that, combined with Figure 2 and Figure 4 (The left figure is the normal feeder i, and the right figure is the faulty feeder j, and respectively represent the input admittances of feeders i and j), 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 (not faulty, but called the faulty phase during normal operation for the convenience of comparison) of each feeder is expressed as:

[0130]

[0131] 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; The input admittance of the feeder is defined 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:

[0132]

[0133] 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.

[0134] When a single-phase grounding fault occurs in the distribution network, the current of the faulty phase of each feeder is:

[0135]

[0136] In the formula, and respectively represent the current of the faulty phase and the voltage of the faulty phase of the i-th feeder on the substation bus when a single-phase grounding fault occurs.

[0137] Similarly, according to the definition of the input admittance of the faulty phase of the feeder before the fault, the input admittance of the faulty phase after the fault can be obtained as:

[0138]

[0139] In the formula, represents the input admittance of the fault phase of the i-th feeder on the substation bus when a single-phase ground fault occurs; that is, after the fault occurs, the input admittance of the fault feeder increases by the grounding admittance , and for the non-fault phases, the input admittances before and after the fault are the same, that is .

[0140] Similarly, based on the three-phase voltage and current data after the fault on the high-voltage side of the distribution transformer of each fault phase on each feeder, the input admittance after the fault on the high-voltage side of the distribution transformer of each fault phase can be calculated, and then the sum of the input admittances after the fault on the high-voltage side of the distribution transformer of each fault phase is added to obtain the correction value of the input admittance of the fault phase after the fault for each feeder, which is expressed as:

[0141]

[0142] In the formula, represents the correction value of the input admittance of the fault phase after the fault of the i-th feeder; represents the input admittance after the fault on the high-voltage side of the v-th distribution transformer of the fault phase of the i-th feeder; V represents the total number of distribution transformers on the i-th feeder.

[0143] Then, the correction value of the input admittance of the fault phase after the fault is used to correct the input admittance of the fault phase after the fault of the feeder to obtain the corresponding corrected input admittance of the fault phase after the fault, which is expressed as:

[0144]

[0145] In the formula, and represent the corrected input admittance of the fault phase after the fault and the input admittance of the fault phase after the fault of the i-th feeder, respectively.

[0146] Based on the input admittances before and after the fault of the fault phases of each feeder obtained above, the fault phase asymmetry degree and the input admittance mutation rate of each feeder can be calculated accordingly:

[0147]

[0148]

[0149] In the formula, and represent the fault phase corresponding fault phase asymmetry degree and input admittance mutation rate of the i-th feeder on the substation bus, respectively.

[0150] As can be seen from the above analysis, the fault phase of the fault feeder will increase the grounding admittance and the input admittance mutation rate is the largest. Then, the grounding fault feeder can be determined based on the following criterion:

[0151]

[0152] The feeder j that will simultaneously meet the conditions of the maximum asymmetry degree and the maximum input admittance mutation rate is determined as the faulty feeder, realizing simple and accurate positioning of the faulty feeder.

[0153] In addition, to further improve the refinement degree of fault location, based on determining the faulty phase and the faulty feeder, this embodiment can also realize fault section location based on two indicators of the three-phase asymmetry degree and the input admittance mutation rate; specifically, the method further includes:

[0154] 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 of 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 of each faulty phase section;

[0155] Accumulate the input admittance after the fault on the high-voltage side of the distribution transformer of all faulty phase sections on each line section to obtain the corresponding corrected value of the input admittance after the section fault;

[0156] 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;

[0157] 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;

[0158] Compare and analyze the line section asymmetry degree and the line section input admittance mutation rate corresponding to each line section, and obtain the line section where both the line section asymmetry degree and the line section input admittance mutation rate are the maximum values as the grounding fault section.

[0159] In practical applications, determine the faulty phase through the foregoing method steps and the faulty feeder j, and then combine 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 faulty phase voltages measured by the l-th and m-th monitoring devices on the feeder j; After a fault occurs, the change value of the input admittance measured by the monitoring device on the fault section of the fault feeder j can be used to explain the principle of the fault feeder selection method in this embodiment: Before the fault occurs, the 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:

[0160]

[0161] 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.

[0162] The input admittance measured by the monitoring devices on each line section of the fault feeder after the fault can be expressed as:

[0163]

[0164] 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 value corresponding to the monitoring device at the fault rear end is 0.

[0165] Similarly, based on the three-phase voltage and current data after the fault at the high-voltage side of the distribution transformer in each fault phase section of each line section, the input admittance after the fault at 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 at the high-voltage side of the distribution transformer in each fault phase section of each line section, expressed as:

[0166]

[0167] 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 at the high-voltage side of the distribution transformer in 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 on the fault feeder j.

[0168] 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:

[0169]

[0170] 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 faulty feeder j.

[0171] Based on the pre-fault and post-fault input admittances of the faulty phases in each segmented area of each feeder obtained above, the line section asymmetry degree and the line section input admittance mutation rate of each segmented area can be calculated accordingly:

[0172]

[0173]

[0174] In the formula, and respectively represent the line section asymmetry degree and the line section input admittance mutation rate corresponding to the faulty phase of the l-th monitoring device on the faulty feeder j.

[0175] 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 degree, and there is no grounding admittance downstream of the fault, the three-phase asymmetry degree is 0, and the asymmetry degree 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 degree; based on this, the grounding admittance of the faulty phase of the faulty 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:

[0176]

[0177] Based on the above criterion, it can be known that the line section that simultaneously meets the conditions of the largest asymmetry degree and the largest input admittance mutation rate is

[0178] In the embodiment 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 terminal units in the distribution network, the significant change characteristics of the admittance in the system before and after single-phase grounding are analyzed by comparison. The changes in the three-phase asymmetry and the mutation 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, having a wide range of application scenarios and high practical value.

[0179] To verify the effectiveness of the proposed method for locating single-phase grounding faults in the distribution network, this embodiment also takes Figure 6 the distribution network structure shown (M, M1, M2, M 21 , M 22 , M3, M 31 , M4 and M 41 represent voltage and current monitoring devices; L1, L2, L3 and L4 represent feeders, L 21 and L 22 represent two branch lines of feeder L2) as an example to conduct the following single-phase fault location simulation:

[0180] 1) At 0.3 s, simulate an A-phase single-phase grounding fault at the end of line L4; based on Figure 7 the ABC three-phase input admittances on the low-voltage bus of the substation shown, 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 L4 is the largest, which is 0.0485, the asymmetry is 709.78%, and the admittance mutation rate is 4.949. While the input admittance of line L2 after the fault occurs 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 L4; then based on Figure 9 the input admittances measured by each monitoring device on the fault feeder L4 shown, it can be seen that the monitoring device M 41The measured input admittance is 0.07954, the input admittance mutation rate is 4.950, the input admittance measured by device M4 is 0.0485, and the input admittance mutation rate is 4.949. Therefore, it can be determined that the fault occurs in the line section after monitoring device M 41 of the line segment.

[0181] 2) A single-phase ground fault of phase B occurs in the middle of line simulation L2 at 0.4 s, and the load on line L 21 increases by 10,000 W; based on Figure 10 the ABC three-phase input admittances of the low-voltage bus of the substation shown, 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%. There is no obvious fluctuation in the other two phases, 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 Figure 11 input admittances of phase B of each feeder shown are obtained. The input admittance of line L2 is the largest, which 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 determined that the fault occurs on line L2; then based on Figure 12 the input admittances measured by each monitoring device on the fault feeder L2 shown, it can be seen that the input admittance measured by monitoring device M 11 after the fault 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 impact on this branch, the corrected admittance remains unchanged; the input admittance measured by monitoring device M 12 after the fault is 0.07546, the asymmetry is 3429%, the input admittance mutation rate is 7.56, the corrected input admittance after the fault is 0.01246, the asymmetry is 5565.36%, and the input admittance mutation rate is 7.55; the input admittance measured by monitoring device M2 after the fault is 0.108, the asymmetry is 4908.09%, the input admittance mutation rate is 7.56, and 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 determined that the fault occurs between monitoring devices M2-M 21 of the line segment.

[0182] It should be noted that as Figure 6As shown in the figure, the monitoring device for the faulty phase can be deployed between the low-voltage side of the distribution transformer and the busbar, because the current here is the sum of the currents of all feeders, and the voltage collector collects the busbar 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 busbar voltage; if there are long lines in the substation, monitoring devices need to be deployed in the middle of each feeder to help narrow down the scope of the faulty 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 busbar 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. The monitoring device for the line section on the faulty feeder can be monitored by means of a primary-secondary equipment integrated switch without additional investment, which has high economy and promotion value.

[0183] 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.

[0184] In one embodiment, as Figure 13 shown, a single-phase grounding fault location system for a distribution network is provided, and the system includes:

[0185] A data acquisition module 1, configured to obtain three-phase voltage and current data before and after the busbar fault and 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;

[0186] An admittance calculation module 2, configured to obtain the three-phase input admittances before and after the busbar fault according to the three-phase voltage and current data before and after the busbar 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;

[0187] An admittance correction module 3, configured to correct the three-phase input admittances before and after the busbar fault according to the three-phase input admittances after the fault of all distribution transformer high-voltage sides to obtain the corrected three-phase input admittances before and after the busbar fault;

[0188] An admittance analysis module 4, configured to calculate the three-phase asymmetry degree of the busbar and the mutation rate of the three-phase input admittance of the busbar according to the corrected three-phase input admittances before and after the busbar fault;

[0189] A faulty phase location module, configured to use the phase with the maximum asymmetry degree and input admittance mutation rate corresponding to the three-phase asymmetry degree of the busbar and the three-phase input admittance mutation rate of the busbar as the faulty phase.

[0190] In one embodiment, a single-phase grounding fault location system for a distribution network is provided, and the system further includes:

[0191] A fault feeder location module, configured to calculate the input admittance before and after the fault of the corresponding fault phase according to the voltage and current data of the fault phase before and after the fault 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 admittance before and after the fault of the fault phase, and compare and analyze the asymmetry degree of the fault phase and the mutation rate of the input admittance of the fault phase corresponding to each feeder, and take 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 as the fault feeder.

[0192] In one embodiment, a single-phase grounding fault location system for a distribution network is provided, and the system further includes:

[0193] 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 admittance before and after the fault corresponding to each line section according to the voltage and current data before and after the fault, 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 admittance before and after the fault corresponding to each line section, and compare and analyze 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 take the line section with the maximum values of both the asymmetry degree of the line section and the mutation rate of the input admittance of the line section as the grounding fault section.

[0194] For the specific limitations of the single-phase grounding fault location system for a distribution network, reference can be made to the limitations of the single-phase grounding fault location method for a distribution network in the above text, and the corresponding technical effects can also be equivalently obtained, which will not be elaborated here. 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 the processor of the computer device in hardware form or be independent of it, or be stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to the above respective modules.

[0195] Figure 14 The internal structure diagram of a computer device in one embodiment is shown. The computer device can specifically be a terminal or a server. As Figure 14As shown in the figure, the computer device includes a processor, a memory, a network interface, a display, a camera, and an input device connected via 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 computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The network interface of the computer device is used to communicate with external terminals via a network connection. The computer program, when executed by the processor, implements the method for single-phase grounding fault location in a distribution network. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads provided on the outer shell of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0196] Those of ordinary skill in the art can understand that Figure 14 the structure shown in the figure 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. The specific computing device may include more or fewer components than those shown in the figure, or combine some components, or have a different component layout.

[0197] In one 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.

[0198] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by the processor, the steps of the above method are implemented.

[0199] In summary, for the single-phase grounding fault location method and system provided by the embodiments of the present invention, the single-phase grounding fault location method of the distribution network realizes that when a single-phase grounding fault occurs in the distribution network, three-phase voltage and current data before and after the bus fault and three-phase voltage and current data after the fault of each distribution transformer high-voltage side are obtained according to the moment when the single-phase grounding fault occurs. The three-phase input admittances before and after the bus fault are obtained according to the three-phase voltage and current data before and after the bus fault. The three-phase input admittances after the fault of each distribution transformer high-voltage side are obtained according to the three-phase voltage and current data after the fault of each distribution transformer high-voltage side. The three-phase input admittances before and after the bus fault are corrected according to the three-phase input admittances after the fault of 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 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 is used as the fault phase. Without the need to additionally increase physical measurement devices or perform complex hardware transformation, directly using the three-phase asymmetry degree and the mutation rate of the input admittance before and after the grounding fault can realize 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.

[0200] Each embodiment in this specification is described in a progressive manner. For parts that are the same or similar in each embodiment, they can be referred 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 be referred 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 recorded in this specification.

[0201] The above 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, 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 single-phase grounding fault location in a distribution network, characterized in that, 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 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 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 at the high-voltage side of each distribution transformer, obtain the corresponding three-phase input admittances after the fault at the high-voltage side of the distribution transformer; Correct the three-phase input admittances before and after the bus fault according to the three-phase input admittances after the fault at the high-voltage side of all distribution transformers, and obtain the corrected three-phase input admittances before and after the bus fault, including: accumulate the phase input admittances in the three-phase input admittances after the fault at the high-voltage side of all distribution transformers to obtain the corresponding corrected value of the three-phase input admittance after the fault; Correct the three-phase input admittance after the fault in the three-phase input admittances before and after the bus fault according to the corrected value of the three-phase input admittance after the fault to obtain the corresponding corrected three-phase input admittance after the fault; Obtain the corrected three-phase input admittances before and after the bus fault 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 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 according to the corrected three-phase input admittances before and after the bus fault; Take the phase with the maximum corresponding asymmetry degree and input admittance mutation rate in 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.

2. The single-phase grounding fault location method for a distribution network according to claim 1, wherein, The occurrence time of the single-phase grounding fault 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 corresponding time when the preset time duration is advanced before the occurrence time of the single-phase grounding fault 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 corresponding time when the preset time duration 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.

3. The single-phase grounding fault location method for a distribution network according to claim 1, characterized in that, 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.

4. The single-phase grounding fault location method for a distribution network according to claim 1, wherein 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 admittances before and after the bus fault includes: According to the post-fault phase input admittances and the pre-fault phase input admittances in the corrected three-phase input admittances before and after the bus fault, obtain the corresponding change values of the post-fault phase input admittances; Obtain the three-phase asymmetry degree of the bus according to the ratio of the post-fault change value of each phase input admittance to the corresponding pre-fault input admittance of each phase. Obtain the three-phase input admittance mutation rate of the bus according to the ratio of the post-fault change value of each phase input admittance to the preset admittance mutation duration.

5. The single-phase grounding fault location method for a distribution network according to claim 1, characterized in that The method further includes: According to the pre-fault and post-fault voltage and current data of the fault phase of each feeder and the post-fault three-phase voltage and current data of the high-voltage side of the transformer corresponding to each fault phase on each feeder, calculate the pre-fault and post-fault input admittances of the corresponding fault phase and the post-fault input admittance of the high-voltage side of the transformer corresponding to each fault phase on each feeder. Accumulate the post-fault input admittances of the high-voltage sides of the transformers corresponding to all fault phases on each feeder to obtain the corrected value of the post-fault input admittance of the corresponding fault phase. Correct the post-fault input admittance of the fault phase in the pre-fault and post-fault input admittances of the fault phase according to the corrected value of the post-fault input admittance of the fault phase of each feeder to obtain the corrected post-fault input admittance of the corresponding fault phase. 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 in the pre-fault and post-fault input admittances of the fault phase, obtain the asymmetry degree of the fault phase and the input admittance mutation rate of the fault phase corresponding to each feeder. Compare and analyze the asymmetry degree of the fault phase and the input admittance mutation rate of the fault phase corresponding to each feeder, and obtain the feeder with the maximum asymmetry degree of the fault phase and the input admittance mutation rate of the fault phase as the faulty feeder.

6. The single-phase grounding fault location method for a distribution network according to claim 5, wherein The method further includes: According to the pre-fault and post-fault voltage and current data of each line section corresponding to the fault phase of the faulty feeder and the post-fault three-phase voltage and current data of the high-voltage side of the transformer corresponding to each fault-phase section on each line section, calculate the pre-fault and post-fault input admittances corresponding to each line section and the post-fault input admittance of the high-voltage side of the transformer corresponding to each fault-phase section on each line section. Accumulate the post-fault input admittances of the high-voltage sides of the transformers corresponding to all fault-phase sections on each line section to obtain the corrected value of the post-fault input admittance of the corresponding section. Correct the post-fault input admittance in the pre-fault and post-fault input admittances according to the corrected value of the post-fault input admittance of each line section to obtain the corrected post-fault input admittance of the corresponding section. According to the corrected post-fault input admittance of each line section and the pre-fault input admittance in the pre-fault and post-fault input admittances, obtain the asymmetry degree of the corresponding line section and the input admittance mutation rate of the line section. Compare and analyze the asymmetry degree of the line section and the input admittance mutation rate of the line section corresponding to each line section, and obtain the line section with the maximum asymmetry degree of the line section and the input admittance mutation rate of the line section as the ground fault section.

7. A single-phase grounding fault location system for a distribution network, characterized in that, The system includes: A data acquisition module, configured 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 the high-voltage side of each transformer according to the occurrence time of the single-phase ground fault when a single-phase ground fault occurs in the distribution network. An admittance calculation module, configured 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 three-phase input admittances after the fault of the corresponding high-voltage side of the transformer according to the three-phase voltage and current data after the fault of the high-voltage side of each transformer. A admittance correction module, which is used to correct the three-phase input admittance before and after the bus fault according to the three-phase input admittances of all distribution transformer high-voltage sides after the fault, so as to obtain the corrected three-phase input admittances before and after the bus fault, including: accumulating the phase input admittances in the three-phase input admittances of all distribution transformer high-voltage sides after the fault to obtain the corresponding corrected value of the three-phase input admittance after the fault; Correcting the three-phase input admittance after the fault in the three-phase input admittances before and after the bus fault according to the corrected value of the three-phase input admittance after the fault to obtain the corresponding corrected three-phase input admittance after the fault; Obtaining the corrected three-phase input admittances before and after the bus fault 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 admittances before and after the bus fault; An admittance analysis module, which is used to calculate the bus three-phase asymmetry degree and the mutation rate of the bus three-phase input admittance according to the corrected three-phase input admittances before and after the bus fault; A fault phase location module, which is used 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 fault phase.

8. A computer device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, the steps of the method described in any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, the steps of the method described in any one of claims 1 to 6 are implemented.

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