Method for determining fault phase and fault distance during single-phase earth fault

Abstract

The invention discloses a method for determining a fault phase and a fault distance during a single-phase earth fault, and relates to the technical field of power distribution network fault positioning. The method includes: using a power electronic device to inject a common-mode detection signal into a power distribution network; collecting and calculating a current phasor, a voltage phasor, a zero-sequence voltage phasor and a zero-sequence current phasor of the head end of the fault line after the common-mode detection signal is injected; calculating according to the current phasor, the voltage phasor, the zero-sequence voltage phasor and the zero-sequence current phasor to obtain the differential admittance amplitude of each phase; determining a fault phase; obtaining a fundamental frequency line head end zero sequence voltage and a fault phase voltage phasor of a fault phase, calculating a ground fault transition resistance upper limit value, and determining a ground fault transition resistance range; and calculating a fault distance based on the current phasor, the voltage phasor, the zero sequence voltage phasor, the zero sequence current phasor and the grounding fault transition resistance range. According to the invention, the accuracy of single-phase earth fault phase selection and distance measurement of the power distribution network can be improved.

Description

Technical Field

[0001] This application relates to the technical field of distribution network fault location, and particularly to a method for determining a fault phase and a fault distance during a single-phase grounding fault. Background Art

[0002] As an important part of the power system, the distribution network directly supplies power to users. Its safe and stable operation is crucial for ensuring power quality and social and economic activities. The distribution network in China mainly adopts ungrounded neutral and arc suppression coil grounded systems. Due to the wide line coverage and complex operating environment, distribution network faults occur frequently, and single-phase grounding faults account for more than 80%. With the progress of power electronics technology, some scholars have proposed that existing power electronic devices can be used to inject signals into the neutral point of the distribution network, and by analyzing their response characteristics, fault arc suppression and ranging can be achieved. For fault arc suppression, only by accurately identifying the fault phase can the arc suppression device perform targeted arc suppression operations on the fault phase. For fault ranging, once the fault phase is determined, the ranging system can achieve ranging based on the specific electrical characteristics of that phase. Therefore, quickly and accurately identifying the fault phase is an important basis and prerequisite for achieving fault arc suppression and fault ranging. When a single-phase grounding fault occurs in the distribution network, quickly detecting and accurately locating the fault is conducive to timely eliminating the fault, restoring power supply, and improving power supply reliability.

[0003] As an important part of the power system, the distribution network directly supplies power to users. Its safe and stable operation is crucial for ensuring power quality and social and economic activities. The distribution network in China mainly adopts ungrounded neutral and arc suppression coil grounded systems. Due to the wide line coverage and complex operating environment, distribution network faults occur frequently, and single-phase grounding faults account for more than 80%. With the progress of power electronics technology, some scholars have proposed that existing power electronic devices can be used to inject signals into the neutral point of the distribution network, and by analyzing their response characteristics, fault arc suppression and ranging can be achieved. For fault arc suppression, only by accurately identifying the fault phase can the arc suppression device perform targeted arc suppression operations on the fault phase. For fault ranging, once the fault phase is determined, the ranging system can achieve ranging based on the specific electrical characteristics of that phase. Therefore, quickly and accurately identifying the fault phase is an important basis and prerequisite for achieving fault arc suppression and fault ranging. When a single-phase grounding fault occurs in the distribution network, quickly detecting and accurately locating the fault is conducive to timely eliminating the fault, restoring power supply, and improving power supply reliability.

[0004] Therefore, in the prior art, when determining the fault phase and the fault distance, due to external interference, the accuracy of determining the fault phase and the fault distance is poor. Summary of the Invention

[0005] Based on this, it is necessary to provide a method for determining a fault phase and a fault distance during a single-phase grounding fault in view of the above technical problems.

[0006] The present specification adopts the following technical solutions: The present specification provides a method for determining a fault phase and a fault distance during a single-phase grounding fault, including: Injecting a common-mode detection signal into the distribution network using a power electronic device; Collecting and calculating the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor at the head end of the fault line after injecting the common-mode detection signal; Calculating the magnitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor; Taking the phase corresponding to the minimum differential admittance magnitude among the differential admittance magnitudes of each phase as the first phase, and determining whether the ratio of the second differential admittance magnitude of the second phase and the third differential admittance magnitude of the third phase satisfies a preset ratio range. If so, determining the first phase as the fault phase; Obtaining the zero-sequence voltage at the head end of the line at the fundamental frequency and the fault-phase voltage phasor of the fault phase, calculating the upper limit value of the grounding fault transition resistance, and determining the grounding fault transition resistance range; Calculating the fault distance based on the current phasor, voltage phasor, zero-sequence voltage phasor, zero-sequence current phasor, and the grounding fault transition resistance range.

[0007] Optionally, injecting a common-mode detection signal into the distribution network using a power electronic device specifically includes: Injecting a common-mode detection signal into the distribution network according to an injection strategy using a power electronic device; Among them, the injection strategy includes a constant voltage strategy and a constant current injection strategy; The frequency of the common-mode detection signal is less than the carrier frequency of the power electronic device, the upper limit of the frequency band of the measurement device, and the upper limit of the applicable frequency band of the line π model. The injection duration of the common-mode detection signal is not less than the stabilization time of the common-mode detection signal and is greater than the data window duration of the ranging algorithm; The injection voltage magnitude of the constant voltage strategy is less than 10% of the rated voltage, and the injection current of the constant current injection strategy is less than 10% of the rated current.

[0008] Optionally, calculating the magnitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor, and the formula used is: ; Among them, DIFA, DIFB, and DIFC respectively represent the magnitude of the A-phase differential admittance, the magnitude of the B-phase differential admittance, and the magnitude of the C-phase differential admittance, , and represent the current phasor, , and represent the voltage phasor, represents the zero-sequence voltage phasor.

[0009] Optionally, the preset ratio range is: ; where is the magnitude of the second differential admittance, is the magnitude of the third differential admittance, and are respectively the upper and lower limits of the ratio of the magnitudes of the differential admittances.

[0010] Optionally, the formula for calculating the upper limit of the grounding fault transition resistance is: ; where , respectively represent the total line-to-ground admittances of phases A, B, and C, , , , represents the total distributed line-to-ground capacitance of phases A, B, and C, represents the neutral-to-ground admittance. For an ungrounded system = 0, represents the fundamental frequency steady-state voltage of the neutral point, represents the fundamental frequency steady-state voltage of the faulty phase, represents the upper limit value of the grounding fault transition resistance, represents the imaginary unit, represents the angular frequency; The range of the grounding fault transition resistance is: ; where is the grounding fault transition resistance.

[0011] Optionally, the formula for calculating the fault distance is: ; where and are respectively the voltage and current of the faulty phase at the head of the line, and are respectively the zero-sequence voltage and current at the head of the line, , and are respectively the positive-sequence resistance, inductance, and capacitance per unit length of the line, , , are the zero-sequence resistance, inductance, and capacitance per unit length of the line, is the distance from the head of the line to the fault point, is the transition resistance at the fault point, and the zero-sequence current compensation coefficient , , zero-sequence voltage compensation coefficient , represents a function containing the fault distance, represents the zero-sequence voltage at the fault point, represents the zero-sequence voltage at the end of the line, represents the current value flowing through the series branch of the A-phase line upstream of the fault point, represents the zero-sequence current upstream of the fault point, represents the imaginary unit, represents the angular frequency, represents the total length of the line.

[0012] This specification provides a device for determining the fault phase and fault distance during single-phase grounding faults, including: A signal injection module, specifically used to inject a common-mode detection signal into the distribution network using a power electronic device; A data calculation module, specifically used to collect and calculate the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor at the head of the fault line after injecting the common-mode detection signal; calculate the magnitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor; A fault phase determination module, specifically used to take the phase corresponding to the minimum differential admittance magnitude among the differential admittance magnitudes of each phase as the first phase, and determine whether the ratio of the second differential admittance magnitude of the second phase and the third differential admittance magnitude of the third phase satisfies a preset ratio range. If so, determine the first phase as the fault phase; A fault distance determination module, specifically used to obtain the zero-sequence voltage at the head of the line at the fundamental frequency and the fault phase voltage phasor of the fault phase, calculate the upper limit value of the grounding fault transition resistance, and determine the range of the grounding fault transition resistance; calculate the fault distance based on the current phasor, voltage phasor, zero-sequence voltage phasor, zero-sequence current phasor, and the range of the grounding fault transition resistance.

[0013] This specification provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, it implements the above method for determining the fault phase and fault distance during single-phase grounding faults.

[0014] This specification 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 program, it implements the above method for determining the fault phase and fault distance during single-phase grounding faults.

[0015] The above at least one technical solution adopted by this specification can achieve the following beneficial effects: In the method for determining the fault phase and fault distance during single-phase ground fault provided in this specification, a common-mode detection signal is injected into the neutral point of the distribution network by using a power electronic device, and the injected detection signal is used for fault phase selection and distance measurement.

[0016] Combined with the high controllability of existing power electronic equipment, the present invention injects a common-mode detection signal into the distribution network, enhances the fault characteristics, overcomes the influence of the transition resistance, and improves the accuracy of fault phase selection and distance measurement for single-phase ground faults in the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments and descriptions thereof are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0018] Figure 1 It is a schematic flow chart of a method for determining the fault phase and fault distance during single-phase ground fault provided in this specification; Figure 2 It is a schematic diagram of a simulation experiment for verifying the method of the present invention; Figure 3 It is a schematic diagram of a device for determining the fault phase and fault distance during single-phase ground fault provided in this specification; Figure 4 It is a schematic diagram of a computer device for implementing the method for determining the fault phase and fault distance during single-phase ground fault provided in this specification. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To make the purpose, technical solutions and advantages of this specification clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the specific embodiments of this specification and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of them. Based on the embodiments in the specification, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present application.

[0020] In the distribution network system, the system zero-sequence voltage increases after a single-phase ground fault in the distribution network, significantly deviating from the normal value. The corresponding starting criterion is shown in the formula: ; In the formula: Generally, 10% of the system rated voltage is taken; is the absolute value of the nth sampling point of the power frequency steady-state zero-sequence voltage at the neutral point of the distribution network, and is the absolute value of the mth sampling point of the power frequency steady-state zero-sequence voltage at the neutral point of the distribution network.

[0021] For example, under normal circumstances, the zero-sequence voltage is like calm water with very little fluctuation (such as 0.05 kV). When a leakage occurs, the voltage suddenly soars to 1.2 kV, 1.3 kV, 1.4 kV (three consecutive points exceeding 1 kV), and the system immediately alarms and cuts off the faulty line. Among them, there will be interference situations. For example, the voltage occasionally jumps to 1.1 kV, but the next point returns to 0.2 kV. The system will ignore this fluctuation and not report an error. Therefore, only when the voltage anomaly exceeds the standard three times in a row is it confirmed that there is a real leakage, and then the power is quickly cut off to protect the equipment. This can avoid misjudgment and quickly respond to real faults.

[0022] The following will, in conjunction with the accompanying drawings, elaborate in detail on the technical solutions provided by each embodiment of the present application.

[0023] Figure 1 It is a schematic flowchart of a method for determining a faulty phase and a fault distance during a single-phase grounding fault in this specification, which specifically includes the following steps: S101: Inject a common-mode detection signal into the distribution network using a power electronic device.

[0024] In this embodiment, injecting a common-mode detection signal into the distribution network using a power electronic device specifically includes: Injecting a common-mode detection signal into the distribution network according to an injection strategy using a power electronic device; wherein, the injection strategy includes a constant voltage strategy and a constant current injection strategy; the frequency of the common-mode detection signal is less than the carrier frequency of the power electronic device, the upper limit of the frequency band of the measurement device, and the upper limit of the applicable frequency band of the line π model. The injection duration of the common-mode detection signal is not less than the stabilization time of the common-mode detection signal and is greater than the data window duration of the ranging algorithm; the injection voltage amplitude of the constant voltage strategy is less than 10% of the rated voltage, and the injection current of the constant current injection strategy is less than 10% of the rated current.

[0025] Based on this, in one or more embodiments of this specification, the execution entity can be a hardware device or system with multi-modal data acquisition, processing, and analysis capabilities, including servers, edge computing devices, etc.

[0026] The server mentioned in this specification can be a server set up on a service platform or a device such as a desktop computer or a laptop computer that can execute the solution of this specification. For the convenience of description, only the server is used as the execution entity for description below.

[0027] Exemplarily, a common-mode detection signal can be injected into the distribution network using a power electronic device, which can be injected into the neutral point of the distribution network. The neutral point in the distribution network refers to the common point of the star connection in a three-phase AC power system, and usually achieves voltage balance and fault control through different electrical connection methods (grounded or ungrounded) with the ground. It is a core parameter for the safe operation of the power grid and directly affects the system insulation level, overvoltage suppression, relay protection logic, and power supply reliability.

[0028] Optionally, for the frequency of the injected non-power frequency signal, the upper limit does not exceed the smaller value among the carrier frequency of the power electronic device, the upper limit of the frequency band of the measuring device, and the upper limit of the applicable frequency band of the line π model; avoid the power frequency harmonic frequency band; when injecting a fixed voltage, the injected voltage amplitude does not exceed 10% of the rated voltage, and when injecting a fixed current, it does not exceed 10% of the rated current; the duration of the injected signal should ensure that the injected signal reaches stability and is greater than the data window duration required by the ranging algorithm.

[0029] Among them, the data window duration of the ranging algorithm represents the data window duration for determining the fault distance.

[0030] S102: Collect and calculate the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor at the head end of the fault line after injecting the common-mode detection signal.

[0031] Exemplarily, the head end of the fault line is a section of the fault line in the distribution network after injecting the common-mode detection signal, and the collected and calculated ones are the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor of the common-mode signal.

[0032] The common-mode detection signal is an artificially injected common-mode voltage or current signal with controllable frequency and amplitude into the distribution network using a power electronic device. The common-mode signal refers to the voltage / current component with the same phase for all phase lines to the ground that naturally exists in the distribution network or is triggered by the detection signal. Fault detection is achieved by analyzing the disturbance response in the common-mode signal.

[0033] Among them, the current phasor can be expressed as 、 and ,the voltage phasor can be expressed as 、 and ,the zero-sequence voltage phasor and zero-sequence current phasor can be expressed as and 。

[0034] S103: Calculate the amplitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor.

[0035] In this embodiment, the magnitudes of differential admittances of each phase are calculated based on current phasors, voltage phasors, zero-sequence voltage phasors, and zero-sequence current phasors. The formula used is: ; where DIFA, DIFB, and DIFC represent the magnitudes of differential admittances of phase A, phase B, and phase C, respectively. , and represent current phasors. , and represent voltage phasors. represents the zero-sequence voltage phasor.

[0036] S104: Take the phase corresponding to the minimum differential admittance magnitude among the differential admittance magnitudes of each phase as the first phase, and determine whether the ratio of the second differential admittance magnitude of the second phase and the third differential admittance magnitude of the third phase satisfies a preset ratio interval. If so, determine the first phase as the fault phase.

[0037] In this embodiment, the preset ratio interval is: ; where is the second differential admittance magnitude, is the third differential admittance magnitude, and are the upper and lower limits of the ratio of differential admittance magnitudes, respectively.

[0038] Exemplarily, during the determination of the fault phase, a zero-sequence signal is injected, so the voltage and current of the non-fault phases are equal. And after injection, the voltage and current at the leading ends of the two non-fault phases should be equal, so the differential admittance magnitude of the fault phase is equal to 0. And in the stored historical data, there is a corresponding proportional relationship for the ratio of the differential admittance magnitudes of the fault phase. Therefore, the preset ratio interval can be determined according to the ratio of the differential admittance magnitudes of the two non-fault phases in the historical data to judge the relationship of the differential admittance magnitude ratio satisfied by the non-fault phases.

[0039] Optionally, during the determination of the fault phase, the first differential admittance magnitude of the first phase satisfies the following formula: ; where DIFA, DIFB, and DIFC represent the magnitudes of differential admittances of phase A, phase B, and phase C, respectively. is the first differential admittance magnitude; S105: Obtain the zero-sequence voltage at the leading end of the line at the fundamental frequency and the fault-phase voltage phasor of the fault phase, calculate the upper limit value of the grounding fault transition resistance, and determine the range of the grounding fault transition resistance.

[0040] In this embodiment, the upper limit calculation formula of the grounding fault transition resistance is as follows: ; Wherein, 、 respectively represent the total admittances to the ground of the three-phase lines A, B, and C, 、 、 , represents the total distributed capacitance to the ground of the three-phase lines A, B, and C, represents the admittance of the neutral point to the ground. For an ungrounded system =0, represents the fundamental frequency steady-state voltage of the neutral point, represents the fundamental frequency steady-state voltage of the faulty phase, represents the upper limit value of the grounding fault transition resistance, represents the imaginary unit, represents the angular frequency; The range of the grounding fault transition resistance is: ; Wherein, is the grounding fault transition resistance.

[0041] S106: Calculate the fault distance based on the current phasor, voltage phasor, zero-sequence voltage phasor, zero-sequence current phasor, and the range of the grounding fault transition resistance.

[0042] In this embodiment, the fault distance calculation formula is: ; Wherein, and are respectively the voltage and current of the faulty phase at the head of the line, and are respectively the zero-sequence voltage and current at the head of the line, 、 and are respectively the positive-sequence resistance, inductance, and capacitance per unit length of the line, 、 、 are the zero-sequence resistance, inductance, and capacitance per unit length of the line, is the distance from the head of the line to the fault point, is the transition resistance at the fault point, the zero-sequence current compensation coefficient , , the zero-sequence voltage compensation coefficient , represents a function containing the fault distance, represents the zero-sequence voltage at the fault point, represents the zero-sequence voltage at the end of the line, It represents the current value flowing through the series branch of phase A line upstream of the fault point. It represents the zero-sequence current upstream of the fault point. It represents the imaginary unit. It represents the angular frequency. It represents the total length of the line.

[0043] In this embodiment, when solving the fault distance calculation formula, starting from decrease to 0 Ω, substitute each value and the electrical quantity of the characteristic frequency at the line head. When the imaginary part of is closest to 0, the real part of ; where, represents the total length of the line, represents the nth solution that satisfies , represents the set of all solutions of represents the i th solution's imaginary part, represents p the real part of

[0044] Optionally, in this embodiment, the single-phase grounding fault model of a 10 kV neutral ungrounded distribution network based on the electromagnetic transient simulation software PSCAD / EMTDC can also be used as an example for simulation analysis to verify the correctness and accuracy of the present invention.

[0045] As Figure 2 shown, Figure 2 is a schematic diagram of the simulation experiment for verifying the method of the present invention. In Figure 2 , the distribution network simulation model consists of multiple feeders, the load of each feeder is set to 1 MV·A, and a phase A grounding fault occurs 4 km away from the bus on feeder L 2. Point M in the figure is the measuring point of the electrical quantity at the line head. As shown in Table 1, Table 1 is the cable parameters in the simulation schematic diagram.

[0046] Table 1 Cable Parameters

[0047] In Figure 2 the schematic diagram of the simulation experiment shown, control the power electronic device to inject a current signal with a frequency of 575 Hz at the neutral point, the injection current amplitude is 20 A, and execute the method of the present invention. By changing the transition resistance and the fault feeder LSimulate at a 2-load condition to obtain the voltage and current data at the M end of the line at 575 Hz after the fault. The phase selection and distance measurement results are shown in Tables 2 and 3. Table 2 is the summary table of phase selection results under different fault conditions, and Table 3 is the summary table of distance measurement results under different fault conditions.

[0048] Table 2 Summary Table of Phase Selection Results under Different Fault Conditions

[0049] According to Table 2, it can be obtained that for the method for determining the fault phase and fault distance during single-phase grounding faults proposed by the present invention, the grounding fault phase selection method is accurate and effective.

[0050] Table 3 Summary Table of Distance Measurement Results under Different Fault Conditions

[0051] From the distance measurement results in Table 3, it can be seen that the relative error is defined as = │distance measurement result - actual fault distance│ / total line length. The maximum relative error is 0.21%, and the maximum absolute error is 24.8 m. The distance measurement accuracy is high and is not affected by the transition resistance and load.

[0052] Based on Figure 1 the method for determining the fault phase and fault distance during single-phase grounding faults shown above, combined with the high controllability of existing power electronic equipment, inject a common-mode detection signal into the distribution network to enhance the fault characteristics, overcome the influence of the transition resistance, and improve the accuracy of fault phase selection and distance measurement for single-phase grounding faults in the distribution network.

[0053] When applying the method for determining the fault phase and fault distance during single-phase grounding faults provided in this specification, it is not necessary to execute according to Figure 1 the sequence of each step shown above. The specific execution sequence of each step can be determined as needed, and this specification does not limit this.

[0054] The above is the method for determining the fault phase and fault distance during single-phase grounding faults provided by one or more embodiments of this specification. Based on the same idea, this specification also provides a corresponding device for determining the fault phase and fault distance during single-phase grounding faults, as shown in Figure 3 shown.

[0055] Figure 3 Schematic diagram of a device for determining the fault phase and fault distance during single-phase grounding faults provided by this specification, including: A signal injection module, specifically used to inject a common-mode detection signal into the distribution network using a power electronic device; A data calculation module, specifically used for collecting and calculating the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor at the head end of the faulty line after injecting a common-mode detection signal; calculating the amplitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor. A fault phase determination module, specifically used for taking the phase corresponding to the minimum differential admittance amplitude among the differential admittance amplitudes of each phase as the first phase, and judging whether the ratio of the second differential admittance amplitude of the second phase and the third differential admittance amplitude of the third phase satisfies a preset ratio range. If so, determining the first phase as the fault phase. A fault distance determination module, specifically used for obtaining the zero-sequence voltage at the head end of the line at the fundamental frequency and the fault phase voltage phasor of the fault phase, calculating the upper limit value of the grounding fault transition resistance, and determining the range of the grounding fault transition resistance; calculating the fault distance based on the current phasor, voltage phasor, zero-sequence voltage phasor, zero-sequence current phasor, and the range of the grounding fault transition resistance.

[0056] For the specific limitations of the fault phase and fault distance determination device during single-phase grounding faults, reference can be made to the limitations of the fault phase and fault distance determination method during single-phase grounding faults in the above text, which will not be elaborated here. Each module in the above-mentioned fault phase and fault distance determination device during single-phase grounding faults can be implemented in whole or in part through software, hardware, and their combinations. The above-mentioned 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 as to facilitate the processor to call and execute the operations corresponding to the above-mentioned modules.

[0057] This specification also provides a computer-readable storage medium, which stores a computer program, and the computer program can be used to execute the above Figure 1 provided fault phase and fault distance determination method during single-phase grounding faults.

[0058] This specification also provides Figure 4 the structural schematic diagram of the computer device shown in Figure 4 , at the hardware level, this computer device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory. Of course, it may also include other hardware required for other services. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to implement the above Figure 1 provided fault phase and fault distance determination method during single-phase grounding faults.

[0059] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0060] 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 to be within the scope described in this specification.

Claims

1. A method for determining a fault phase and a fault distance during a single-phase grounding fault, characterized in that Including: Injecting a common-mode detection signal into the distribution network using a power electronic device; Collecting and calculating the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor at the head end of the faulty line after injecting the common-mode detection signal; Calculating the magnitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor; Taking the phase corresponding to the minimum differential admittance magnitude among the differential admittance magnitudes of each phase as the first phase, and determining whether the ratio of the second differential admittance magnitude of the second phase to the third differential admittance magnitude of the third phase satisfies a preset proportional interval. If so, determining the first phase as the faulty phase; Obtaining the zero-sequence voltage at the head end of the line at the fundamental frequency and the faulty-phase voltage phasor of the faulty phase, calculating the upper limit value of the grounding fault transition resistance, and determining the range of the grounding fault transition resistance; Calculating the fault distance based on the current phasor, voltage phasor, zero-sequence voltage phasor, zero-sequence current phasor, and the range of the grounding fault transition resistance.

2. The method for determining the faulty phase and fault distance during single-phase grounding fault according to claim 1, characterized in that, The injecting of the common-mode detection signal into the distribution network using a power electronic device specifically includes: Injecting a common-mode detection signal into the distribution network according to an injection strategy using a power electronic device; Wherein, the injection strategy includes a constant-voltage strategy and a constant-current injection strategy; The frequency of the common-mode detection signal is less than the carrier frequency of the power electronic device, the upper limit of the frequency band of the measuring device, and the upper limit of the applicable frequency band of the line π model. The injection duration of the common-mode detection signal is not less than the stabilization time of the common-mode detection signal and is greater than the data window duration of the ranging algorithm; The injection voltage magnitude of the constant-voltage strategy is less than 10% of the rated voltage, and the injection current of the constant-current injection strategy is less than 10% of the rated current.

3. The method for determining the faulty phase and fault distance during single-phase grounding fault according to claim 1, wherein, The formula used for calculating the magnitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor is: ； Wherein, DIFA, DIFB, and DIFC respectively represent the magnitudes of the differential admittances of phase A, phase B, and phase C, , and represent current phasors, , and represent voltage phasors, represents the zero-sequence voltage phasor.

4. The method for determining the faulty phase and fault distance during single-phase grounding fault according to claim 1, wherein, The preset proportional interval is: ； Among them, is the magnitude of the second differential admittance, is the magnitude of the third differential admittance, and are respectively the upper and lower limits of the ratio of the magnitudes of the differential admittances.

5. The method for determining the faulty phase and fault distance during single-phase grounding fault according to claim 1, characterized in that, The upper limit calculation formula of the grounding fault transition resistance is: ； Among them, and respectively represent the total admittances of the three-phase lines A, B, and C to the ground, and and , represent the total distributed capacitances of the three-phase lines A, B, and C to the ground, represents the admittance of the neutral point to the ground. For an ungrounded system = 0, represents the fundamental frequency steady-state voltage of the neutral point, represents the fundamental frequency steady-state voltage of the faulty phase, represents the upper limit value of the grounding fault transition resistance, represents the imaginary unit, represents the angular frequency; The range of the grounding fault transition resistance is: ； Among them, is the ground fault transition resistance.

6. The method for determining the faulty phase and fault distance during single-phase grounding fault according to claim 1, wherein The fault distance calculation formula is: ； Among them, and are the phase voltage and current of the fault at the line head respectively, and are the zero-sequence voltage and current of the line head respectively, , and are the positive-sequence resistance, inductance and capacitance per unit length of the line respectively, , , are the zero-sequence resistance, inductance and capacitance per unit length of the line, is the distance from the line head to the fault point, is the transition resistance at the fault point, the zero-sequence current compensation coefficient , , the zero-sequence voltage compensation coefficient , represents a function containing the fault distance, represents the zero-sequence voltage at the fault point, represents the zero-sequence voltage at the line end, represents the current value flowing through the series branch of phase A line upstream of the fault point, represents the zero-sequence current upstream of the fault point, represents the imaginary unit, represents the angular frequency, represents the total length of the line.

7. A device for determining the faulty phase and fault distance during a single-phase grounding fault, characterized in that, Including: A signal injection module, specifically used for injecting a common-mode detection signal into the distribution network using a power electronic device; A data calculation module, specifically used for collecting and calculating the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor at the head end of the faulty line after injecting the common-mode detection signal; calculating the magnitude of the differential admittance of each phase based on the current phasor, voltage phasor, zero-sequence voltage phasor, and zero-sequence current phasor; A faulty-phase determination module, specifically used for taking the phase corresponding to the minimum differential admittance magnitude among the differential admittance magnitudes of each phase as the first phase, and determining whether the ratio of the second differential admittance magnitude of the second phase to the third differential admittance magnitude of the third phase satisfies a preset proportional interval. If so, determining the first phase as the faulty phase; The fault distance determination module is specifically configured to obtain the zero-sequence voltage at the head end of the line of the fundamental frequency and the fault-phase voltage phasor of the fault phase, calculate the upper limit value of the grounding fault transition resistance, and determine the grounding fault transition resistance range; and calculate the fault distance based on the current phasor, the voltage phasor, the zero-sequence voltage phasor, the zero-sequence current phasor, and the grounding fault transition resistance range.

8. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, and when the computer program is executed by a processor, the method described in any one of claims 1 to 6 above is implemented.

9. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the method described in any one of claims 1 to 6 above is implemented.

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