A method and system for identifying permanent faults in ultra-high voltage AC transmission lines

Abstract

This invention discloses a method and system for identifying permanent faults in ultra-high voltage (UHV) AC transmission lines, comprising: acquiring fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an UHV transmission line with shunt reactors, and determining the two faulty phases experiencing interphase faults based on the fault waveform data; calculating the interphase differential mode voltage between the two faulty phases based on the fault waveform data; taking the extinction of the arc at the fault point after the circuit breaker trips as the starting time, performing sliding window integration on the interphase differential mode voltage according to a preset time window to obtain the integrated value of the interphase differential mode voltage; within a preset time window, if the integrated value of the interphase differential mode voltage is continuously less than a preset integration threshold, or simultaneously satisfies the condition that the integrated value of the interphase differential mode voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number, then a permanent fault is determined to have occurred. The method of this invention can be applied to fault type analysis of UHV transmission lines and provides scheduling and operation decisions for maintenance personnel.

Description

Technical Field

[0001] This invention relates to the field of fault identification technology for ultra-high voltage AC transmission lines, and more specifically, to a method and system for identifying permanent faults in ultra-high voltage AC transmission lines. Background Technology

[0002] In modern society, electricity is indispensable. Ultra-high voltage (UHV) AC transmission projects continue to advance due to their advantages of large transmission capacity, long transmission distance, and wide coverage. However, influenced by factors such as global warming, extreme disasters are becoming increasingly common, posing a severe challenge to the safe operation of the power grid. Furthermore, UHV transmission lines traverse complex geographical environments, including areas prone to snowstorms and wildfires. How to quickly identify and eliminate safety hazards along transmission lines in such complex environments, and ensure their safe and stable operation, is a significant challenge for transmission line operation and maintenance management.

[0003] Based on power system operation and dispatching experience, line faults can generally be divided into transient faults and permanent faults. Due to the operational strategy of UHV transmission line relay protection devices, the protection device only issues an automatic reclosing command when a single-phase fault occurs. If it is a transient fault, the line resumes operation after the circuit breaker recloses, greatly reducing economic losses caused by power outages. If it is a single-phase permanent fault, the circuit breaker reclosing on the permanent fault causes it to trip again, shutting down the line. If a transient / permanent fault occurs (two-phase-to-phase, two-phase-to-ground, or three-phase-to-ground), the circuit breaker trips permanently, shutting down the line. However, in scenarios involving line faults caused by severe weather conditions such as icing, rain, and snow, weather conditions make it difficult to conduct timely and rapid fault inspections, hindering rapid analysis of fault causes and severely impacting the efficiency of fault diagnosis and power restoration. This has a serious adverse effect on the reliability and resilience of the power grid.

[0004] While reclosing can eliminate line faults and quickly restore power for single-phase transient faults, other types of faults require manual analysis combined with fault inspection to determine the fault type. However, due to limitations in the accuracy of manual analysis and the pace of fault inspection, power restoration is often not rapid, leading to significant economic losses. Therefore, there is an urgent need to develop a method for identifying transient and permanent fault types in UHV transmission lines applicable to different types of faults. Summary of the Invention

[0005] This invention proposes a method and system for identifying permanent faults in ultra-high voltage AC transmission lines, in order to solve the problem of how to efficiently and quickly identify permanent faults in lines.

[0006] To address the aforementioned problems, according to one aspect of the present invention, a method for identifying permanent faults in ultra-high voltage AC transmission lines is provided, the method comprising:

[0007] Obtain fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an ultra-high voltage transmission line with a parallel reactor, and determine the two faulty phases where the interphase fault occurred based on the fault waveform data;

[0008] The phase-to-phase differential voltage between the two faulty phases is calculated based on the fault recording data.

[0009] Taking the moment when the circuit breaker trips and extinguishes the arc at the fault point after the fault as the starting time, the phase-to-phase differential mode voltage is integrated by sliding window according to a preset time window to obtain the phase-to-phase differential mode voltage integral value.

[0010] If, within a preset time window, the integral value of the phase-to-phase differential voltage is continuously less than a preset integration threshold, or if the integral value of the phase-to-phase differential voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number, then a permanent fault is determined to have occurred.

[0011] Preferably, the length of the preset time window is T1 = 2T0, where T0 is the differential mode voltage resonant period.

[0012] Preferably, the preset integration threshold value K = M * T1; where M is a preset coefficient and T1 is the length of a preset time window.

[0013] Preferably, the method further includes:

[0014] If, within a preset time window, there are consecutive preset number of phase-to-phase differential voltage integral values ​​greater than or equal to a preset integration threshold, then a transient fault is determined to have occurred.

[0015] According to another aspect of the present invention, a permanent fault identification system for ultra-high voltage AC transmission lines is provided, the system comprising:

[0016] The fault phase determination unit is used to acquire fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an ultra-high voltage transmission line with a parallel reactor, and to determine the two fault phases where the inter-phase fault occurred based on the fault waveform data.

[0017] The phase-to-phase differential voltage calculation unit is used to calculate the phase-to-phase differential voltage of the two faulty phases based on the fault recording data.

[0018] The integral value calculation unit is used to perform sliding window integration on the phase-to-phase differential mode voltage according to a preset time window, starting from the moment when the circuit breaker trips and the arc is extinguished at the fault point after the fault, to obtain the phase-to-phase differential mode voltage integral value.

[0019] The fault identification unit is used to determine that a permanent fault has occurred if, within a preset time window, the integral value of the phase-to-phase differential voltage is continuously less than a preset integration threshold, or if the integral value of the phase-to-phase differential voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number.

[0020] Preferably, the length of the preset time window is T1 = 2T0, where T0 is the differential mode voltage resonant period.

[0021] Preferably, the preset integration threshold value K = M * T1; where M is a preset coefficient and T1 is the length of a preset time window.

[0022] Preferably, the fault identification voltage is further used for:

[0023] If, within a preset time window, there are consecutive preset number of phase-to-phase differential voltage integral values ​​greater than or equal to a preset integration threshold, then a transient fault is determined to have occurred.

[0024] According to another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the steps in a method for identifying permanent faults in ultra-high voltage AC transmission lines.

[0025] According to another aspect of the present invention, the present invention provides an electronic device, comprising:

[0026] The aforementioned computer-readable storage medium; and

[0027] One or more processors for executing a program in the computer-readable storage medium.

[0028] This invention provides a method and system for identifying permanent faults in ultra-high voltage (UHV) AC transmission lines, comprising: acquiring fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an UHV transmission line with shunt reactors, and determining the two faulty phases experiencing interphase faults based on the fault waveform data; calculating the interphase differential mode voltage of the two faulty phases based on the fault waveform data; taking the extinction of the arc at the fault point after the circuit breaker trips as the starting time, performing sliding window integration on the interphase differential mode voltage according to a preset time window to obtain the integrated value of the interphase differential mode voltage; within a preset time window, if the integrated value of the interphase differential mode voltage is continuously less than a preset integration threshold, or simultaneously satisfies the condition that the integrated value of the interphase differential mode voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number, then a permanent fault is determined to have occurred. This invention's method, based on the differential mode voltage characteristics of the line after a fault, uses an integral method to identify instantaneous and permanent fault types in UHV transmission lines with shunt reactors. It can be applied to fault type analysis of UHV transmission lines and provides scheduling and operation decisions for maintenance personnel, possessing broad prospects for promotion and application scale. Attached Figure Description

[0029] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0030] Figure 1 A flowchart of a permanent fault identification method 100 for ultra-high voltage AC transmission lines according to an embodiment of the present invention;

[0031] Figure 2 The equivalent circuit diagram of an ultra-high voltage transmission line with parallel reactors at both ends according to an embodiment of the present invention is shown below.

[0032] Figure 3 A simplified equivalent circuit diagram of a transient fault in an ultra-high voltage transmission line according to an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the fault phase difference mode voltage under transient fault according to an embodiment of the present invention;

[0034] Figure 5 A simplified equivalent circuit diagram of a permanent fault in an ultra-high voltage transmission line according to an embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the fault phase differential voltage under a permanent fault according to an embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram of the three-phase differential mode voltage calculated based on actual fault recording data of a permanent two-phase (BC) fault on a certain line according to an embodiment of the present invention.

[0037] Figure 8 This is a schematic diagram of the three-phase differential mode voltage integral value calculated from the actual fault recording data of a line experiencing a permanent two-phase (BC) fault according to an embodiment of the present invention.

[0038] Figure 9 This is a schematic diagram of the permanent fault identification system 900 for ultra-high voltage AC transmission lines according to an embodiment of the present invention. Detailed Implementation

[0039] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0040] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0041] To address the challenge of rapidly identifying fault types and making operational scheduling decisions for UHV transmission line faults caused by extreme weather events such as freezing rain and snow, this invention proposes a method for identifying transient and permanent faults in transmission lines based on the integral value of the fault differential voltage. This method eliminates the need for additional data acquisition and analysis modules. By combining line fault waveform data, it can quickly and accurately identify both transient and permanent faults. Furthermore, this invention does not rely on line inspection results. Based on the fault cause identification results obtained by this invention, it provides operational scheduling decisions, effectively supporting line reclosing or trial operation, ensuring rapid and safe restoration of line operation, and reducing economic losses caused by power outages.

[0042] Figure 1 This is a flowchart of a permanent fault identification method 100 for ultra-high voltage AC transmission lines according to an embodiment of the present invention. Figure 1 As shown, the permanent fault identification method for UHV AC transmission lines provided by this invention identifies transient and permanent fault types in UHV transmission lines with shunt reactors based on the differential mode voltage characteristics of the line after a fault, using an integral method. This method can be applied to fault type analysis of UHV transmission lines and provides scheduling and operation decisions for maintenance personnel, showing broad prospects for promotion and application scale. The permanent fault identification method 100 for UHV AC transmission lines provided by this invention starts at step 101. At step 101, fault waveform data of the instantaneous three-phase voltage values ​​after a fault in the UHV transmission line with shunt reactors is acquired, and the two faulty phases where the inter-phase fault occurred are determined based on the fault waveform data.

[0043] In step 102, the phase-to-phase differential voltage of the two faulty phases is calculated based on the fault recording data.

[0044] In step 103, starting from the moment when the circuit breaker trips and extinguishes the arc at the fault point, the phase-to-phase differential voltage is integrated by sliding window according to a preset time window to obtain the phase-to-phase differential voltage integral value.

[0045] In step 104, within a preset time window, if the integral value of the phase-to-phase differential voltage is continuously less than a preset integration threshold, or if the integral value of the phase-to-phase differential voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number, then a permanent fault is determined to have occurred.

[0046] Preferably, the length of the preset time window is T1 = 2T0, where T0 is the differential mode voltage resonant period.

[0047] Preferably, the preset integration threshold value K = M * T1; where M is a preset coefficient and T1 is the length of a preset time window.

[0048] Preferably, the method further includes:

[0049] If, within a preset time window, there are consecutive preset number of phase-to-phase differential voltage integral values ​​greater than or equal to a preset integration threshold, then a transient fault is determined to have occurred.

[0050] Based on the analysis of the differential mode voltage variation characteristics after a fault in an UHV transmission line with a parallel reactor, this invention proposes a method for identifying transient and permanent faults in transmission lines based on the integral value of the differential mode voltage. The following provides a detailed description of the differences in differential mode voltage fault characteristics and the fault identification method.

[0051] (1) Differential mode voltage fault characteristics of UHV transmission lines with parallel reactors

[0052] Ultra-high voltage (UHV) transmission lines have high voltage levels, large transmission capacities, and long transmission distances. However, the capacitive rise effect is significant in long transmission lines, limiting transmission capacity and exacerbating power frequency overvoltage. Therefore, UHV transmission lines typically employ shunt reactors to balance the line-to-ground capacitance and address power frequency overvoltage.

[0053] Taking an ultra-high voltage transmission line with parallel reactors on both sides of the line as an example, the lumped parameter equivalent circuit diagram is as follows: Figure 2 As shown. Where: C0 is the line equivalent capacitance to ground; L is the inductance of the shunt reactor; x is the percentage of the line length from the fault point to the m side of the line; u mx u nx The three-phase voltages on the m and n sides of the line are respectively (x = A, B, C); f is the fault point.

[0054] Line differential voltage:

[0055]

[0056] When a three-phase or two-phase short circuit occurs on the line, the line protection system issues a trip command, causing both circuit breakers to trip. At this time, due to the coupling between the line-to-ground capacitance and the shunt reactor, a residual voltage with damped oscillations will appear on the line. Depending on the nature of the fault, the differential voltage exhibits different characteristics when the line experiences a transient or permanent fault. Specifically, when a transient fault occurs, after both circuit breakers trip and the arc at the fault point is extinguished, the process is further simplified... Figure 2 It can be obtained as follows Figure 3The equivalent circuit diagram shown illustrates how the residual energy in the line-to-ground capacitance and the parallel reactor oscillates back and forth between the line-to-ground capacitance and the equivalent inductance of the reactor, causing the residual voltage to exhibit the following characteristics: Figure 4 The “beat frequency characteristic” is shown; when a permanent fault occurs in the line, its simplified equivalent circuit diagram is as follows. Figure 5 As shown. At this time, the parallel circuit of the line-to-ground capacitance and the equivalent inductance of the reactor is short-circuited, and the residual voltage of the line decays rapidly, as shown. Figure 6 As shown. Therefore, based on this characteristic, the differential mode voltage integral value can be used to identify transient and permanent line faults.

[0057] (2) Methods for identifying transient and permanent faults in UHV transmission lines with parallel reactors

[0058] As described in (1), the present invention uses the comparison result of the integral value of the fault phase difference mode voltage and the threshold value to identify the transient or permanent fault of the line, as follows:

[0059] B1) First, read the fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an UHV transmission line with a parallel reactor, and confirm the two fault phases.

[0060] B2) Perform Fourier decomposition on the instantaneous voltage value of the fault phase, and calculate the differential mode voltage of the fault phase according to Equation (1).

[0061] B3) Considering that when a transient fault occurs in an UHV transmission line with a parallel reactor, the differential mode voltage exhibits a "beat frequency" resonance characteristic with a relatively long resonance period T0, in order to minimize voltage integral value fluctuations, a time window with a period of T1 is adopted, with the start time being the tripping of the circuit breaker after the fault and the extinction of the arc at the fault point. α U β or U γ Perform sliding window integration and calculate the differential mode voltage integral value dU. α dU β or dU γ Wherein, T1 can be determined according to the differential mode voltage resonant period T0, and is usually taken as T1 = 2T0. To simplify the calculation, the window length can be taken as 10ms.

[0062] B4) Compare the integrated value of the differential-mode voltage of the faulty phase with a preset integration threshold value K. Within a preset time window, if the integrated value of the phase-to-phase differential-mode voltage at N consecutive sampling points is greater than or equal to the preset integration threshold value K, then a transient fault is determined to have occurred. Within a preset time window, if the integrated value of the differential-mode voltage of the faulty phase is continuously less than the preset integration threshold value, or if the integrated value of the phase differential-mode voltage is greater than the preset integration threshold value K but N consecutive sampling points are higher than the threshold value K, then a permanent fault is determined to have occurred. The integration threshold value K is related to the integration time window T1, K = M * T1; where M is a preset coefficient; and T1 is the length of the preset time window. In a 10ms time window, M is 5, so the threshold value K can be 50. When the line length is short, this threshold value can be appropriately reduced. The specific value of N is related to the sampling frequency of the protection device; typically, at a sampling rate of 1000Hz, N = 5.

[0063] According to B1) to B4), based on the actual fault recording data of a permanent two-phase (BC) fault on a certain line, this invention can calculate the following: Figure 7 The three-phase differential mode U shown α U β U γ and such Figure 8 The three-phase differential mode voltage integral value dU shown is... α dU β dU γ .

[0064] according to Figure 8 The calculation results show that the fault phase differential voltage U β integral value dU β If the value remains below the threshold, the fault is identified as a permanent fault, thus verifying the accuracy of the proposed method for identifying transient and permanent fault types in UHV transmission lines with parallel reactors.

[0065] Figure 9 This is a schematic diagram of the structure of a permanent fault identification system 900 for ultra-high voltage AC transmission lines according to an embodiment of the present invention. Figure 9 As shown, the permanent fault identification system 900 for ultra-high voltage AC transmission lines provided in this embodiment of the invention includes: a fault phase determination unit 901, a phase-to-phase differential voltage calculation unit 902, and an integral value calculation unit 903.

[0066] Preferably, the fault phase determination unit 901 is used to acquire fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an ultra-high voltage transmission line with a parallel reactor, and to determine the two fault phases where the inter-phase fault occurred based on the fault waveform data.

[0067] Preferably, the phase-to-phase differential voltage calculation unit 902 is used to calculate the phase-to-phase differential voltage of the two faulty phases based on the fault recording data.

[0068] Preferably, the integral value calculation unit 903 is used to perform sliding window integration on the phase-to-phase differential voltage according to a preset time window, starting from the time when the circuit breaker trips and extinguishes the arc at the fault point after the fault, to obtain the phase-to-phase differential voltage integral value.

[0069] Preferably, the fault identification unit 904 is configured to determine that a permanent fault has occurred if, within a preset time window, the integral value of the phase-to-phase differential voltage is continuously less than a preset integration threshold, or if, at the same time, the integral value of the phase-to-phase differential voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number.

[0070] Preferably, the length of the preset time window is T1 = 2T0, where T0 is the differential mode voltage resonant period.

[0071] Preferably, the preset integration threshold value K = M * T1; where M is a preset coefficient and T1 is the length of a preset time window.

[0072] Preferably, the fault identification voltage 904 is further used for:

[0073] If, within a preset time window, there are consecutive preset number of phase-to-phase differential voltage integral values ​​greater than or equal to a preset integration threshold, then a transient fault is determined to have occurred.

[0074] The permanent fault identification system 900 for UHV AC transmission lines in one embodiment of the present invention corresponds to the permanent fault identification method 100 for UHV AC transmission lines in another embodiment of the present invention, and will not be described again here.

[0075] According to another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the steps in a method for identifying permanent faults in ultra-high voltage AC transmission lines.

[0076] According to another aspect of the present invention, the present invention provides an electronic device, comprising:

[0077] The aforementioned computer-readable storage medium; and

[0078] One or more processors for executing a program in the computer-readable storage medium.

[0079] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0080] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0081] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0082] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0083] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0084] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for identifying permanent faults in ultra-high voltage AC transmission lines, characterized in that, The method includes: Obtain fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an ultra-high voltage transmission line with a parallel reactor, and determine the two faulty phases where the interphase fault occurred based on the fault waveform data; The phase-to-phase differential voltage between the two faulty phases is calculated based on the fault recording data. Taking the moment when the circuit breaker trips and extinguishes the arc at the fault point after the fault as the starting time, the phase-to-phase differential mode voltage is integrated by sliding window according to a preset time window to obtain the phase-to-phase differential mode voltage integral value. If, within a preset time window, the integral value of the phase-to-phase differential voltage is continuously less than a preset integration threshold, or if the integral value of the phase-to-phase differential voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number, then a permanent fault is determined to have occurred. The method further includes: If, within a preset time window, there are consecutive preset number of phase-to-phase differential voltage integral values ​​greater than or equal to a preset integration threshold, then a transient fault is determined to have occurred.

2. The method according to claim 1, characterized in that, The length of the preset time window is T1 = 2T0, where T0 is the differential mode voltage resonance period.

3. The method according to claim 1, characterized in that, The preset integration threshold value K = M * T1; where M is a preset coefficient; and T1 is the length of the preset time window.

4. A permanent fault identification system for ultra-high voltage AC transmission lines, characterized in that, The system includes: The fault phase determination unit is used to acquire fault waveform data of the instantaneous three-phase voltage values ​​after a fault in an ultra-high voltage transmission line with a parallel reactor, and to determine the two fault phases where the inter-phase fault occurred based on the fault waveform data. The phase-to-phase differential voltage calculation unit is used to calculate the phase-to-phase differential voltage of the two faulty phases based on the fault recording data. The integral value calculation unit is used to perform sliding window integration on the phase-to-phase differential mode voltage according to a preset time window, starting from the moment when the circuit breaker trips and the arc is extinguished at the fault point after the fault, to obtain the phase-to-phase differential mode voltage integral value. The fault identification unit is used to determine that a permanent fault has occurred if, within a preset time window, the integral value of the phase-to-phase differential voltage is continuously less than a preset integration threshold, or if the integral value of the phase-to-phase differential voltage is greater than the preset integration threshold but the number of sampling points is continuously less than a preset number. The fault identification voltage is also used for: If, within a preset time window, there are consecutive preset number of phase-to-phase differential voltage integral values ​​greater than or equal to a preset integration threshold, then a transient fault is determined to have occurred.

5. The system according to claim 4, characterized in that, The length of the preset time window is T1 = 2T0, where T0 is the differential mode voltage resonance period.

6. The system according to claim 4, characterized in that, The preset integration threshold value K = M * T1; where M is a preset coefficient; and T1 is the length of the preset time window.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-3.

8. An electronic device, characterized in that, include: The computer-readable storage medium as described in claim 7; as well as One or more processors for executing a program in the computer-readable storage medium.

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