Resonant grounding power distribution network grounding fault line selection method based on zero sequence current ratio

Abstract

The invention relates to a resonance grounding power distribution network grounding fault line selection method based on a zero sequence current ratio, and belongs to the technical field of power distribution network relay protection. The method comprises the following steps: acquiring neutral point zero-sequence voltage and phase current data of each outgoing line of the power distribution network, and judging whether a fault occurs or not according to whether the zero-sequence voltage exceeds a threshold value or not; if the zero-sequence voltage does not exceed the threshold value, the line selection process is not started, otherwise, the zero-sequence current of each outgoing line is calculated according to the phase current data; calculating the sum of total zero-sequence current of the power distribution network according to the zero-sequence current of each outgoing line, and comparing the zero-sequence current of a single outgoing line with the sum of the total zero-sequence current to obtain a zero-sequence current ratio of each outgoing line; and comparing the waveform of the zero-sequence current ratio, finding a first sharp peak value after the fault occurs, and if the sharp peak value of the outgoing line is opposite to that of other outgoing lines, judging that the outgoing line is a fault outgoing line. According to the method, the fault line with the high-resistance grounding fault in the resonance grounding power distribution network can be accurately identified, and the limitation that the high-resistance fault is difficult to identify in the existing method is overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of distribution networks, and in particular relates to a ground fault line selection method for a resonant grounding distribution network based on a zero-sequence current ratio. Background Art

[0002] Single-phase grounding fault is a common fault type in power systems. Especially in fire-prone areas with high greening rates, single-phase grounding faults can cause transmission line fires, resulting in serious economic losses and casualties. In order to reduce the harm caused by single-phase grounding faults, resonant grounding technology has been widely used in power systems. Resonant grounding technology reduces the fault current to a safe level by compensating for the fault current, thereby preventing the occurrence of transmission line fires.

[0003] However, although the resonant grounding technology reduces the fault current, it also makes the detection of high-resistance faults very difficult. In order to solve the problem that the zero-sequence current is too small to detect and the high-impedance grounding and fault starting angle affect the direction of the fault current, the current mainstream fault identification technology is mainly based on wavelet transform and positive-sequence current. Among them, wavelet changes can provide time and frequency information of the signal, but a high sampling frequency is required to effectively identify high-resistance faults. At low sampling frequencies, wavelet transforms are difficult to distinguish between faulty feeders and normal feeders; the method of using positive-sequence current changes to identify faulty feeders does not require additional measurement equipment, but there is also a problem of high requirements for current sampling frequency. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a ground fault line selection method for a resonant grounded distribution network based on zero-sequence current ratio.

[0005] To achieve the above object, the technical solution of the present invention is: a ground fault line selection method for a resonant grounded distribution network based on zero-sequence current ratio, comprising:

[0006] Step S1, collecting the neutral point zero-sequence voltage and the phase current data of each outgoing line of the distribution network, and judging whether a fault occurs according to whether the zero-sequence voltage exceeds a threshold;

[0007] Step S2: if the zero-sequence voltage does not exceed the threshold, the line selection process is not started; if the zero-sequence voltage exceeds the threshold, the zero-sequence current of each outgoing line is calculated according to the phase current data;

[0008] Step S3, calculating the total zero-sequence current sum of the distribution network according to the zero-sequence current of each outgoing line, and dividing the zero-sequence current of a single outgoing line by the total zero-sequence current sum to obtain the zero-sequence current ratio of each outgoing line;

[0009] Step S4, compare the waveform of the zero-sequence current ratio to find the first sharp peak after the fault occurs. If a sharp peak appears that is opposite to other outgoing lines and has the largest amplitude, the corresponding outgoing line is determined to be a faulty outgoing line.

[0010] In one embodiment of the present invention, in step S1, the formula for determining whether the zero-sequence voltage exceeds the threshold is as follows:

[0011] u 0 >u set

[0012] In the formula, u 0 Indicates the neutral point zero sequence voltage, u set Indicates setting a threshold.

[0013] In one embodiment of the present invention, in step S2, the zero-sequence current of each outgoing line is calculated according to the phase current data as follows:

[0014]

[0015] Where ZSC n (t) represents the zero-sequence current of outgoing line n at time t; i a-n (t) represents the phase A current of line n at time t; i b-n (t) represents the B-phase current of output line n at time t; i c-n (t) represents the C-phase current of line n at time t.

[0016] In one embodiment of the present invention, in step S3, the sum of the total zero-sequence current of the distribution network is calculated as follows:

[0017] ZS T (t) = ZSC 1 (t)+ZSC 2 (t)+…+ZSC N (t) (2)

[0018] Where ZSC T (t) represents the sum of the total zero-sequence current of all outgoing lines, ZSC n (t) represents the zero-sequence current appearing in the nth line, and N represents the total number of outgoing lines.

[0019] In one embodiment of the present invention, in step S3, the zero-sequence current ratio of each outgoing line is calculated as follows:

[0020]

[0021] Where ZSC r-n (t) is the zero-sequence current ratio of outgoing line n.

[0022] In one embodiment of the present invention, step S4 is specifically implemented as follows:

[0023] When a single-phase grounding fault occurs in phase A of the i-th outgoing line among N outgoing lines, phases B and C are normal phases;

[0024] The zero-sequence current i of the normal line 0n (t) is calculated as follows:

[0025] i 0n (t) = i cAn (t)+i cBn (t)+i cCn (t) (4)

[0026] In the formula, i cAn (t), i cBn (t) and i cCn (t) represent the capacitance current of phase A, phase B and phase C of normal outgoing line n respectively;

[0027] Zero sequence current i of fault line i 0i (t) is calculated as follows:

[0028]

[0029] In the formula, i cBi (t) and i cCi (t) represents the B-phase and C-phase capacitive currents of the faulty line i. Compared with the normal line, the faulty line has a larger reverse zero-sequence current, so the total zero-sequence current i 0T (t) is:

[0030]

[0031] The zero-sequence current ratio of the fault line to the normal line is ZSC r-i (t) and ZSC r-n (t) are:

[0032]

[0033] As shown in formulas (7) and (8), the zero-sequence current of the fault line has a higher amplitude than that of the normal line, and the direction is opposite; therefore, based on formulas (7) and (8), it can be determined whether the corresponding outgoing line is a faulty outgoing line;

[0034] When the fault phases are B and C, the principle is the same as that of A.

[0035] In one embodiment of the present invention, due to the presence of grounding capacitance, the fault current and zero-sequence current become smaller and the direction of the zero-sequence current is affected; when high-impedance grounding and the fault starting angle are in the third quadrant and the fourth quadrant, i.e., 180° to 360°, the directions of the normal outgoing line and the faulty outgoing line will switch. Obviously, the zero-sequence current ratio of the faulty line to the normal line can avoid the situation where the zero-sequence overcurrent protection cannot detect the zero-sequence current and the directional protection fails.

[0036] The present invention also provides a ground fault line selection system for a resonant grounded distribution network based on zero-sequence current ratio, which executes the method steps as described above, and the system includes:

[0037] The acquisition module collects the neutral point zero-sequence voltage and the phase current data of each outgoing line of the distribution network;

[0038] The discrimination module determines whether the zero-sequence voltage exceeds the threshold. If the zero-sequence voltage does not exceed the threshold, the line selection process will not be started; if the zero-sequence voltage exceeds the threshold, it is judged that a fault has occurred, and the zero-sequence current of each outgoing line is calculated based on the phase current data;

[0039] A calculation module calculates the total zero-sequence current of the distribution network according to the zero-sequence current of each outgoing line, and divides the zero-sequence current of a single outgoing line by the total zero-sequence current to obtain a zero-sequence current ratio of each outgoing line;

[0040] The outgoing line fault identification module compares the waveform of the zero-sequence current ratio and finds the first sharp peak after the fault occurs. If the sharp peak is opposite to that of other outgoing lines and has the largest amplitude, the corresponding outgoing line is judged to be the faulty outgoing line.

[0041] The present invention also provides a computer system, including a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, the method steps described above can be implemented.

[0042] The present invention also provides a computer-readable storage medium, on which computer program instructions that can be executed by a processor are stored. When the processor executes the computer program instructions, the method steps described above can be implemented.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1) The present invention can accurately identify the faulty feeder in the case of a high-impedance single-phase grounding fault. The method is not affected by the fault resistance and the fault starting angle, and can accurately identify the faulty feeder in a wider range;

[0045] 2) The present invention does not require high sampling frequency, and can ensure high fault detection accuracy at a low sampling rate of 2kHz, which makes the method compatible with the measurement equipment in the existing power distribution network and convenient for practical application;

[0046] 3) The present invention only needs to measure the phase current of the feeder and calculate its zero-sequence current and zero-sequence current ratio, which has low calculation amount and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention is a flow chart of a ground fault line selection method for a resonant grounded distribution network based on zero-sequence current ratio. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0049] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0051] The present invention provides a method for selecting a ground fault line in a resonant grounded distribution network based on a zero-sequence current ratio, comprising:

[0052] Step S1, collecting the neutral point zero-sequence voltage and the phase current data of each outgoing line of each distribution network, and judging whether a fault occurs according to whether the zero-sequence voltage exceeds a threshold;

[0053] Step S2: if the zero-sequence voltage does not exceed the threshold, the line selection process is not started; if the zero-sequence voltage exceeds the threshold, the zero-sequence current of each outgoing line is calculated according to the phase current data;

[0054] Step S3, calculating the total zero-sequence current sum of the distribution network according to the zero-sequence current of each outgoing line, and dividing the zero-sequence current of a single outgoing line by the total zero-sequence current sum to obtain the zero-sequence current ratio of each outgoing line;

[0055] Step S4, compare the waveform of the zero-sequence current ratio to find the first sharp peak after the fault occurs. If a sharp peak appears that is opposite to other outgoing lines and has the largest amplitude, the corresponding outgoing line is determined to be a faulty outgoing line.

[0056] The following is the specific implementation process of the present invention.

[0057] like Figure 1 As shown, this embodiment provides a ground fault line selection method for a resonant grounded distribution network based on zero-sequence current ratio, and the specific implementation steps are as follows:

[0058] Step (1): Collect the neutral point zero-sequence voltage and the phase current data of each outgoing line of the distribution network, and determine whether a fault occurs based on whether the zero-sequence voltage exceeds a threshold;

[0059] Step (2): If the zero-sequence voltage does not exceed the threshold, the line selection process is not started; if the zero-sequence voltage exceeds the threshold, the zero-sequence current of each outgoing line is calculated based on the phase current data;

[0060] Step (3): Calculate the total zero-sequence current of the distribution network according to the zero-sequence current of each outgoing line, and divide the zero-sequence current of a single outgoing line by the total zero-sequence current sum to obtain the zero-sequence current ratio of each outgoing line.

[0061] Step (4): Compare the waveform of the zero-sequence current ratio and find the first sharp peak after the fault occurs. If the sharp peak is opposite to that of other outgoing lines and has the largest amplitude, it can be determined that the outgoing line is the faulty outgoing line.

[0062] The method for calculating the zero-sequence current of each outgoing line according to the phase current in step (2) of the present invention is:

[0063]

[0064] Where ZSC n (t) represents the zero-sequence current of outgoing line n at time t; i a-n (t) represents the phase A current of line n at time t; i b-n (t) represents the B-phase current of output line n at time t; i c-n (t) represents the C-phase current of line n at time t.

[0065] The sum of the total zero-sequence current in step (2) of the present invention is calculated as follows:

[0066] ZS T (t) = ZSC 1 (t)+ZSC 2 (t)+…+ZSC N (t) (2)

[0067] Where ZSC T (t) represents the sum of the total zero-sequence current of all outgoing lines, ZSC N The N in (t) represents the total number of outgoing lines.

[0068] The total zero-sequence current ratio of the resonant grounded distribution network system can be calculated by the sum of the outgoing line zero-sequence current and the total zero-sequence current value of the system:

[0069]

[0070] Where ZSC r-n (t) is the zero-sequence current ratio of outgoing line n.

[0071] The principle of comparing the zero-sequence current ratio waveform in step (4) of the present invention and determining the fault line by the peak value and direction of the curve is as follows.

[0072] When a single-phase grounding fault occurs in phase A of the i-th outgoing line among N outgoing lines, phases B and C are normal phases.

[0073] The zero-sequence current i of the normal line 0n (t) is calculated as follows:

[0074] i 0n (t) = i cAn (t)+i cBn (t)+i cCn (t) (4)

[0075] In the formula, i cAn (t), i cBn (t) and i cCn (t) represent the A-phase, B-phase and C-phase capacitor currents of the normal output line n respectively.

[0076] Zero sequence current i of fault line i 0i (t) is calculated as follows:

[0077]

[0078] In the formula, i cBi (t) and i cCi (t) represents the B-phase and C-phase capacitive currents of the fault line i. Compared with the normal line, the fault line has a larger reverse zero-sequence current, so the total zero-sequence current i of the resonant grounding system is 0T (t) is:

[0079]

[0080] Then the zero sequence current ratio of the fault line to the non-fault line is ZSC r-i (t) and ZSC r-n (t) are:

[0081]

[0082] As shown in equations (7) and (8), the zero-sequence current of the fault line has a higher amplitude than that of the normal line and has an opposite direction.

[0083] When the fault phases are B and C, the principle is the same as that of phase A.

[0084] Due to the existence of grounding capacitance, the fault current and zero-sequence current become smaller and the direction of zero-sequence current is affected. When high-impedance grounding occurs and the fault starting angle is in the third and fourth quadrants (i.e., 180° to 360°), the directions of the normal outgoing line and the faulty outgoing line will switch. Obviously, the above electrical characteristics can avoid the situation where the zero-sequence overcurrent protection cannot detect the zero-sequence current and the directional protection fails.

[0085] This note simulates a typical 10kV resonant grounded distribution network single-phase ground fault condition through MATLAB / Simulink. An inductor is connected between the neutral point of the distribution substation and the ground, resonating with the total capacitance of the line. The substation bus is the reference bus, and each feeder uses voltage and current transformers to measure the instantaneous phase current. The three outgoing lines L1, L2 and L3 are 10km, 20km and 30km respectively, and the inductance value of the arc suppression coil is 0.413H. The line parameters in the simulation model are shown in Table 1.

[0086] Table 1 Line parameters

[0087]

[0088] In order to detect faults in the distribution network, the method checks the zero-sequence voltage value. When there is no single-phase ground fault, the zero-sequence voltage value will be less than 1, and when there is a single-phase ground fault, the zero-sequence voltage value will be greater than 1. According to the flow chart, the judgment process continues. The algorithm extracts the phase current of each feeder to determine the zero-sequence current and its ratio of each feeder. The zero-sequence current ratio of the fault feeder will show obvious positive or negative peaks depending on the fault impedance, and the peak direction of the non-fault line is opposite to that of the fault line. In addition, if the fault impedance is greater than 10kΩ, the zero-sequence current ratio of the fault and non-fault lines will produce multiple peaks. At this time, only the first spike after the fault occurs is considered.

[0089] Case 1: Phase A of L1 feeder faulted through a fault impedance of 0.1Ω at very low impedance. The single-phase ground fault occurred at 0.05 seconds and cleared after 0.95 seconds. The zero-sequence current ratio was calculated for all three feeders based on the phase current measurements with a sampling frequency of 2kHz. Since there is a positive sharp peak on the fault feeder L1, while the peaks of the non-fault feeders L2 and L3 are on the negative side after the fault moment, the method based on zero-sequence current ratio effectively detects the faulty feeder for very low impedance fault.

[0090] Case 2: For high impedance fault, a different fault instant (i.e., 0.355 seconds at fault onset) is considered while maintaining the 2kHz sampling frequency, and the fault impedance is 30kΩ. The fault is applied to phase A of feeder L1 and cleared at 1.3 seconds, with a fault onset angle of 90°. The zero-sequence current ratio calculation is repeated for all feeders, and the fault feeder L1 has a sharp positive peak, while the peaks of L2 and L3 are in the negative direction. Therefore, the proposed scheme is effective for this high impedance fault.

[0091] The present invention also provides a ground fault line selection system for a resonant grounded distribution network based on zero-sequence current ratio, which executes the method steps as described above, and the system includes:

[0092] The acquisition module collects the neutral point zero-sequence voltage and the phase current data of each outgoing line of each distribution network;

[0093] The discrimination module determines whether the zero-sequence voltage exceeds the threshold. If the zero-sequence voltage does not exceed the threshold, the line selection process will not be started; if the zero-sequence voltage exceeds the threshold, it is judged that a fault has occurred, and the zero-sequence current of each outgoing line is calculated based on the phase current data;

[0094] A calculation module calculates the total zero-sequence current of the distribution network according to the zero-sequence current of each outgoing line, and divides the zero-sequence current of a single outgoing line by the total zero-sequence current to obtain a zero-sequence current ratio of each outgoing line;

[0095] The outgoing line fault identification module compares the waveform of the zero-sequence current ratio and finds the first sharp peak after the fault occurs. If the sharp peak is opposite to that of other outgoing lines and has the largest amplitude, the corresponding outgoing line is judged to be the faulty outgoing line.

[0096] The present invention also provides a computer system, including a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, the method steps described above can be implemented.

[0097] The present invention also provides a computer-readable storage medium, on which computer program instructions that can be executed by a processor are stored. When the processor executes the computer program instructions, the method steps described above can be implemented.

[0098] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0099] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0100] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0102] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for selecting ground fault line in a resonant grounded distribution network based on zero-sequence current ratio, characterized in that: include: Step S1, collecting the neutral point zero-sequence voltage and the phase current data of each outgoing line of the distribution network, and judging whether a fault occurs according to whether the zero-sequence voltage exceeds a threshold; Step S2: if the zero-sequence voltage does not exceed the threshold, the line selection process is not started; if the zero-sequence voltage exceeds the threshold, the zero-sequence current of each outgoing line is calculated according to the phase current data; Step S3, calculating the total zero-sequence current sum of the distribution network according to the zero-sequence current of each outgoing line, and dividing the zero-sequence current of a single outgoing line by the total zero-sequence current sum to obtain the zero-sequence current ratio of each outgoing line; Step S4, compare the waveform of the zero-sequence current ratio to find the first sharp peak after the fault occurs. If a sharp peak appears that is opposite to other outgoing lines and has the largest amplitude, the corresponding outgoing line is determined to be a faulty outgoing line.

2. The method for selecting ground fault line in a resonant grounded distribution network based on zero-sequence current ratio according to claim 1, characterized in that: In step S1, the formula for determining whether the zero-sequence voltage exceeds the threshold is as follows: u0>u set Where, u0 represents the neutral point zero sequence voltage, u set Indicates setting a threshold.

3. The method for selecting ground fault line in a resonant grounded distribution network based on zero-sequence current ratio according to claim 1, characterized in that: In step S2, the zero-sequence current of each outgoing line is calculated according to the phase current data as follows: Where ZSC n (t) represents the zero-sequence current of outgoing line n at time t; i a-n (t) represents the phase A current of line n at time t; i b-n (t) represents the B-phase current of the outgoing line n at time t; i c-n (t) represents the C-phase current of line n at time t.

4. The method for selecting ground fault line in a resonant grounded distribution network based on zero-sequence current ratio according to claim 1, characterized in that: In step S3, the total zero-sequence current of the distribution network is calculated as follows: ZSC T (t)=ZSC1(t)+ZSC2(t)+…+ZSC N (t) (2) Where ZSC T (t) represents the sum of the total zero-sequence current of all outgoing lines, ZSC n (t) represents the zero-sequence current appearing in the nth line, and N represents the total number of outgoing lines.

5. The method for selecting ground fault line in a resonant grounded distribution network based on zero-sequence current ratio according to claim 4, characterized in that: In step S3, the zero-sequence current ratio of each outgoing line is calculated as follows: Where ZSC r-n (t) is the zero-sequence current ratio of outgoing line n.

6. The method for selecting ground fault line in a resonant grounded distribution network based on zero-sequence current ratio according to claim 1, characterized in that: Step S4 is specifically implemented as follows: When a single-phase grounding fault occurs in phase A of the i-th outgoing line among N outgoing lines, phases B and C are normal phases; The zero-sequence current i of the normal line 0n (t) is calculated as follows: i 0n (t)=i cAn (t)+i cBn (t)+i cCn (t) (4) In the formula, i cAn (t), i cBn (t) and i cCn (t) represent the capacitance current of phase A, phase B and phase C of normal outgoing line n respectively; Zero sequence current i of fault line i 0i (t) is calculated as follows: In the formula, i cBi (t) and i cCi (t) represents the B-phase and C-phase capacitance currents of the faulty outgoing line i; Compared with the normal line, the fault line has a larger magnitude of reverse zero-sequence current, so the total zero-sequence current i 0T (t) is: The zero-sequence current ratio of the fault line to the normal line is ZSC r-i (t) and ZSC r-n (t) are: As shown in formulas (7) and (8), the zero-sequence current of the fault line has a higher amplitude than that of the normal line, and the direction is opposite; therefore, based on formulas (7) and (8), it can be determined whether the corresponding outgoing line is a faulty outgoing line; When the fault phases are B and C, the principle is the same as that of A.

7. A method for selecting ground fault lines in a resonant grounded distribution network based on zero-sequence current ratio according to claim 6, characterized in that: Due to the existence of grounding capacitance, the fault current and zero-sequence current become smaller and the direction of zero-sequence current is affected. When high-impedance grounding and the fault starting angle are in the third and fourth quadrants, i.e., 180° to 360°, the directions of the normal outgoing line and the faulty outgoing line will switch. Obviously, the zero-sequence current ratio of the faulty line to the normal line can avoid the situation where the zero-sequence overcurrent protection cannot detect the zero-sequence current and the directional protection fails.

8. A ground fault line selection system for a resonant grounded distribution network based on zero-sequence current ratio, characterized in that: Executing the method steps as described in any one of claims 1 to 7, the system comprises: The acquisition module collects the neutral point zero-sequence voltage and the phase current data of each outgoing line of the distribution network; The discrimination module determines whether the zero-sequence voltage exceeds the threshold. If the zero-sequence voltage does not exceed the threshold, the line selection process will not be started; if the zero-sequence voltage exceeds the threshold, it is judged that a fault has occurred, and the zero-sequence current of each outgoing line is calculated based on the phase current data; A calculation module calculates the total zero-sequence current of the distribution network according to the zero-sequence current of each outgoing line, and divides the zero-sequence current of a single outgoing line by the total zero-sequence current to obtain a zero-sequence current ratio of each outgoing line; The outgoing line fault identification module compares the waveform of the zero-sequence current ratio and finds the first sharp peak after the fault occurs. If the sharp peak is opposite to that of other outgoing lines and has the largest amplitude, the corresponding outgoing line is judged to be the faulty outgoing line.

9. A computer system, characterized in that: The method comprises a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, the method steps described in any one of claims 1 to 7 can be implemented.

10. A computer-readable storage medium storing computer program instructions that can be executed by a processor, wherein when the processor executes the computer program instructions, the method steps according to any one of claims 1 to 7 can be implemented.

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