Zero-sequence current protection method, device, system and storage medium

Abstract

The present application provides a zero-sequence current method, which is applied to a small-resistance grounded system. The method includes: obtaining the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of a bus, and the initial zero-sequence current of any non-faulty feeder; if the initial zero-sequence current is greater than a preset maximum unbalanced current, calculating a correction factor, which is used to correct the zero-sequence current value of the circuit; if the corrected zero-sequence current value of the circuit is greater than a preset zero-sequence current protection setting value, starting a protection action to cut off the faulty line. The above zero-sequence current protection method takes into account the problem of high-resistance grounding faults, and can realize zero-sequence current protection only by using the positive, negative, and zero-sequence voltages and zero-sequence current of the bus. It more comprehensively considers factors such as the line model and line length, constructs a more accurate zero-sequence current correction factor, and compensates for the influence of the transition resistance on the zero-sequence current.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and particularly relates to a zero-sequence current protection method, device, system, and storage medium. Background Art

[0002] The existing distribution network with a neutral point grounded through a small resistor needs to be equipped with zero-sequence over-current protection. Generally, when setting and calculating the action setting value of zero-sequence current protection, the influence of the capacitive current of the protected line and the maximum unbalanced current during normal operation needs to be considered. Therefore, the action current setting value of zero-sequence current protection is relatively high, which may cause the zero-sequence current protection to fail to start in some cases. For example, when a high-resistance grounding fault occurs, the fault current is relatively small, and the zero-sequence current protection often refuses to operate. Although generally a high-resistance grounding fault does not affect the normal power supply of the system to the load, it is extremely likely to cause human electric shock and electrical fire accidents. Therefore, it is particularly important to perform zero-sequence current protection on the high-resistance grounding fault of the distribution network with a neutral point grounded through a small resistor.

[0003] Currently, for the zero-sequence current protection method for high-resistance grounding faults, it is necessary to obtain the current information and voltage information of multiple lines, and has high requirements for the synchronization and accuracy of the measurement equipment, which is difficult to meet in actual applications, so accurate zero-sequence current protection cannot be obtained. Summary of the Invention

[0004] Based on this, the present invention provides a zero-sequence current protection method, device, system, and storage medium. Considering the problem of high-resistance grounding faults, zero-sequence current protection can be achieved only by using the positive, negative, and zero-sequence voltage information of the bus and the zero-sequence current. In addition, factors such as the line model and line length are more comprehensively considered to construct a more accurate zero-sequence current correction coefficient to compensate for the influence of the transition resistance on the zero-sequence current.

[0005] In a first aspect, the present invention provides a zero-sequence current method, which is applied to a small-resistance grounding system. The small-resistance grounding system includes a grounding transformer, a system-side main transformer, a capacitor, a bus, and several feeders; one end of the grounding transformer is connected to the bus, and the other end is grounded; one end of the system-side main transformer is connected to the power grid, and the other end is connected to the bus; one end of the capacitor is connected to the bus, and the other end is grounded; the start end of the feeder is connected to the bus, and the feeder includes a non-faulty feeder and a faulty feeder. The method includes:

[0006] Obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the bus, and the zero-sequence current at the start end of any non-faulty feeder;

[0007] If the zero-sequence current at the start end is greater than the preset maximum unbalanced current, calculate a correction coefficient, and the correction coefficient is used to correct the zero-sequence current value of the circuit;

[0008] If the zero-sequence current value of the corrected circuit is greater than the preset zero-sequence current protection setting value, the protection action is initiated to cut off the faulty line;

[0009] Among them, the correction coefficient is specifically: k is the correction coefficient, is the negative-sequence voltage of the bus, is the positive-sequence voltage of the bus, is the zero-sequence voltage of the bus, b′0 is the zero-sequence voltage proportionality coefficient, and b′2 is the negative-sequence voltage proportionality coefficient.

[0010] In a second aspect, the present invention provides a zero-sequence current protection device, which is applied to a small-resistance grounding system. The small-resistance grounding system includes a grounding transformer, a system-side main transformer, a capacitor, a bus, and several feeders; one end of the grounding transformer is connected to the bus, and the other end is grounded; one end of the system-side main transformer is connected to the power grid, and the other end is connected to the bus; one end of the capacitor is connected to the bus, and the other end is grounded; the starting end of the feeder is connected to the bus, and the feeder includes a non-faulty feeder and a faulty feeder. The device includes:

[0011] A parameter acquisition module for acquiring the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the bus, and the starting-end zero-sequence current of any non-faulty feeder;

[0012] A first judgment module for calculating a correction coefficient if the starting-end zero-sequence current is greater than the preset maximum unbalanced current. The correction coefficient is used to correct the zero-sequence current value of the circuit;

[0013] A second judgment module for initiating a protection action to cut off the faulty line if the zero-sequence current value of the corrected circuit is greater than the preset zero-sequence current protection setting value;

[0014] Among them, the correction coefficient is specifically: k is the correction coefficient, is the negative-sequence voltage of the bus, is the positive-sequence voltage of the bus, is the zero-sequence voltage of the bus, b′0 is the zero-sequence voltage proportionality coefficient, and b′2 is the negative-sequence voltage proportionality coefficient.

[0015] In a third aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the zero-sequence current protection method in the first aspect are implemented.

[0016] In a fourth aspect, the present invention provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the zero-sequence current protection method in the first aspect is executed.

[0017] The beneficial effects of adopting the above technical solution are as follows: For the low-resistance grounded system in this application, considering the case of high-resistance grounding, only the voltage information of positive, negative, and zero sequence and the zero-sequence current information need to be obtained to achieve zero-sequence current protection. In addition, fully considering factors such as the line model and line length, a more accurate zero-sequence current correction coefficient is constructed to compensate for the influence of the transition resistance on the zero-sequence current, so that the existing setting method of the zero-sequence current protection action value and protection coordination can autonomously adapt to single-phase high-resistance grounding faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0019] Figure 1 It is a schematic diagram of a low-resistance grounded system provided in an embodiment of this application;

[0020] Figure 2 It is a schematic diagram of a zero-sequence current protection method provided in an embodiment of this application;

[0021] Figure 3 It is a schematic diagram of a single-phase grounding composite sequence network of a low-resistance grounded system provided in an embodiment of this application;

[0022] Figure 4 It is a schematic diagram of a single-phase grounding zero-sequence network of a low-resistance grounded system provided in an embodiment of this application;

[0023] Figure 5 It is a schematic diagram of a zero-sequence current protection device provided in an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. In order to describe the present invention in more detail, the zero-sequence current protection method, device, storage medium, and equipment provided by the present invention will be specifically described below with reference to the drawings.

[0025] The set action values of the existing zero-sequence overcurrent protection are all relatively high. When a high-resistance grounding fault occurs, due to the relatively small fault current, the zero-sequence current protection often fails to operate. High-resistance faults are extremely likely to cause electric shock to the human body and electrical fire accidents. Therefore, zero-sequence current protection for high-resistance grounding faults in the distribution network is of great significance.

[0026] The specific application scenarios of the zero-sequence current protection method are provided in the embodiments of the present application. The zero-sequence current protection method is applied to a small-resistance grounding system, such as the one shown in the appendix Figure 1 As shown, the small-resistance grounding system includes a grounding transformer, a main transformer on the system side, a capacitor, a bus, and several feeders; among them, one end of the grounding transformer is connected to the bus, and the other end is grounded; one end of the main transformer on the system side is connected to the power grid, and the other end is connected to the bus; one end of the capacitor is connected to the bus, and the other end is grounded; the starting end of the feeder is connected to the bus, and the feeder includes a non-faulty feeder and a faulty feeder. When the zero-sequence current protection method is applied to the small-resistance grounding system, it also includes a terminal device for data processing, and the terminal device includes but is not limited to a smart phone and a computer device, where the computer device can be at least one of devices such as a desktop computer, a portable computer, a laptop computer, a tablet computer, etc. The user operates the terminal device to issue a start protection instruction for zero-sequence current protection, and the terminal device executes the zero-sequence current protection method of the present invention. For the specific process, please refer to the embodiments of the zero-sequence current protection method.

[0027] Based on this, in the embodiments of the present application, a zero-sequence current protection method is provided. Taking the application of this method to a terminal device as an example, it is described in combination with the schematic diagram of the zero-sequence current protection method shown in the appendix Figure 2 shown.

[0028] Step S101: Obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the bus, and the starting-end zero-sequence current of any non-faulty feeder.

[0029] Step S102: If the starting-end zero-sequence current is greater than the preset maximum unbalanced current, calculate a correction factor, and the correction factor is used to correct the zero-sequence current value of the circuit.

[0030] Among them, the correction factor is specifically: k is the correction factor, is the negative-sequence voltage of the bus, is the positive-sequence voltage of the bus, is the zero-sequence voltage of the bus, b′0 is the zero-sequence voltage proportionality coefficient, and b′2 is the negative-sequence voltage proportionality coefficient.

[0031]

[0032] Among them, b′0 is the zero-sequence voltage proportionality coefficient, b′2 is the negative-sequence voltage proportionality coefficient, c2 is the negative-sequence capacitance to ground per unit length of the faulty feeder, z2 is the negative-sequence impedance per unit length of the faulty feeder, Y up(2) is the negative-sequence equivalent admittance of the faulty feeder, c0 is the zero-sequence capacitance to ground per unit length of the faulty feeder, z0 is the zero-sequence impedance per unit length of the faulty feeder, Y up(0) is the zero-sequence effective admittance of the faulty feeder, l nis the total length of the faulty feeder.

[0033] After calculating the specific correction factor, correct the zero-sequence current value in the entire circuit.

[0034] Specifically, in combination with the Figure 3 schematic diagram of the composite sequence network for single-phase grounding in a small-resistance grounding system and the Figure 4 schematic diagram of the zero-sequence network for single-phase grounding in a small-resistance grounding system, the derivation process of the correction factor is as follows:

[0035] The specific expression of the zero-sequence current at the beginning of the faulty feeder in step S1011 is:

[0036]

[0037] The specific expression of the zero-sequence current at the beginning of any non-faulty feeder is:

[0038]

[0039] Among them, is the equivalent power supply electromotive force, Z 1∑ is the positive-sequence network equivalent impedance transition resistance, Z 2∑ is the negative-sequence network equivalent impedance transition resistance, Z 0∑ is the zero-sequence network equivalent impedance transition resistance, R f is the transition resistance, c0 is the zero-sequence capacitance to ground per unit length of the faulty feeder, z0 is the zero-sequence impedance per unit length of the faulty feeder, l nu is the length from the fault point to the beginning of the faulty feeder, Y up(0) is the zero-sequence effective admittance of the faulty feeder.

[0040] Step S1012: Construct the specific expression of the correction factor as:

[0041] Step S1013: Using this correction factor to correct the zero-sequence current of the faulty feeder and non-faulty feeder, we can get:

[0042] The specific expression of the corrected zero-sequence current at the beginning of the faulty feeder is:

[0043]

[0044] The specific expression of the corrected zero-sequence current at the beginning of the non-faulty feeder is:

[0045]

[0046] Step S1014: The expression of the corrected zero-sequence current at the beginning of the faulty feeder is exactly the same as the expression when the faulty feeder has a solid grounding fault. From this, we can get:

[0047] The specific expression of the zero-sequence voltage at the busbar outlet is as follows:

[0048]

[0049] The specific expression of the zero-sequence voltage at the fault point is as follows:

[0050]

[0051] Then the zero-sequence voltage at the busbar outlet can also be expressed as:

[0052]

[0053] Among them, b0 is the first zero-sequence voltage proportionality coefficient.

[0054] Similarly, the specific expression of the negative-sequence voltage at the busbar outlet is as follows:

[0055]

[0056] The specific expression of the negative-sequence voltage at the fault point is as follows:

[0057]

[0058] Then the negative-sequence voltage at the busbar outlet can also be expressed as:

[0059]

[0060] Among them, b2 is the first negative-sequence voltage proportionality coefficient.

[0061] Step S1015: According to the fact that the formula structures of the negative-sequence voltage and the zero-sequence voltage at the fault point are the same, the two can be divided to obtain the ratio of the negative-sequence equivalent impedance to the zero-sequence equivalent impedance:

[0062]

[0063] The formula can be transformed and expressed as:

[0064]

[0065] Furthermore, set the positive and negative sequence impedances of the load to be equal, and the equivalent positive and negative impedances to be equal to the line positive and negative impedances, then there is: Z 1∑ = Z 2∑ .

[0066] In addition, when the positive and negative sequence impedances of the load are equal, the positive-sequence voltage at the busbar outlet is specifically expressed as:

[0067]

[0068] Among them, c1 is the positive-sequence capacitance to ground per unit length of the faulty feeder, z1 is the positive-sequence impedance per unit length of the faulty feeder, and Y down(1) is the positive-sequence effective admittance of the faulty feeder.

[0069] The negative-sequence voltage at the bus outlet is specifically expressed as:

[0070]

[0071] Since the third term in the brackets of the positive-sequence voltage and negative-sequence voltage expressions is much smaller than 1, it can be ignored. Therefore, the factors in the brackets of the positive-sequence voltage and negative-sequence voltage expressions are equal, and the division of the two gives:

[0072]

[0073] Step S1016: The specific expression of the correction coefficient k can be constructed as:

[0074]

[0075] Among them, This ratio is affected by the fault location.

[0076] Since the embodiments of the present invention need to consider the situation where the fault characteristics are not obvious as much as possible, the situation where the fault occurs at the end of the line is taken as the priority correction consideration, and we get:

[0077]

[0078] Step S103: If the zero-sequence current value of the corrected circuit is greater than the preset zero-sequence current protection setting value, the protection action is started to cut off the faulty line.

[0079] Compare the zero-sequence current of the entire corrected circuit with the preset zero-sequence current protection setting value. When the zero-sequence current of the entire corrected circuit is greater than the preset zero-sequence current protection setting value, start the protection action to cut off the faulty line to prevent the faulty line from causing electric shock or electrical fire accidents.

[0080] This application is for a small-resistance grounded system. Considering the case of high-resistance grounding, only the voltage information of positive, negative, and zero sequences and the zero-sequence current information need to be obtained to achieve zero-sequence current protection; in addition, factors such as the line model and line length are fully considered to construct a more accurate zero-sequence current correction coefficient to compensate for the influence of the transition resistance on the zero-sequence current, so that the existing zero-sequence current protection action value setting method and protection coordination can autonomously adapt to single-phase high-resistance grounding faults.

[0081] In addition, the zero-sequence current protection method according to the embodiment of the present application further includes step S201: if the zero-sequence current at the starting end is less than or equal to the preset maximum unbalanced current, return to step S101 to re-obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the bus, and the zero-sequence current at the starting end of any non-faulty feeder, and determine whether the zero-sequence current at the starting end is greater than the preset maximum unbalanced current; until the zero-sequence current at the starting end is greater than the preset maximum unbalanced current. In addition, the zero-sequence current protection method according to the embodiment of the present application further includes step S202: if the zero-sequence current value of the corrected circuit is less than or equal to the preset zero-sequence current protection setting value, return to step S101 to re-obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the bus, and the zero-sequence current at the starting end of any non-faulty feeder, and determine whether the zero-sequence current at the starting end is greater than the preset maximum unbalanced current; until the zero-sequence current value of the corrected circuit is greater than the preset zero-sequence current protection setting value.

[0082] It should be understood that although the steps in the attached Figure 2 flowchart are shown in sequence according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the attached Figure 2 flowchart may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least a part of other steps or sub-stages or stages of other steps.

[0083] In the above embodiments disclosed by the present invention, the zero-sequence current protection method is described in detail. The above method disclosed by the present invention can be implemented by devices in various forms. Therefore, the present invention also discloses a zero-sequence current protection device corresponding to the above method, and specific embodiments are given below for detailed description.

[0084] As shown in the attached Figure 5 figure, the embodiment of the present invention discloses a zero-sequence current protection device. The device is applied to a small-resistance grounding system. The small-resistance grounding system includes a grounding transformer, a system-side main transformer, a capacitor, a bus, and several feeders; one end of the grounding transformer is connected to the bus, and the other end is grounded; one end of the system-side main transformer is connected to the power grid, and the other end is connected to the bus; one end of the capacitor is connected to the bus, and the other end is grounded; the starting end of the feeder is connected to the bus. The feeder includes a non-faulty feeder and a faulty feeder. The device includes:

[0085] a parameter acquisition module 301, configured to acquire the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the bus, and the zero-sequence current at the starting end of any non-faulty feeder;

[0086] The first judgment module 302 is configured to calculate a correction coefficient if the initial zero-sequence current is greater than a preset maximum unbalanced current, and the correction coefficient is used to correct the zero-sequence current value of the circuit;

[0087] The second judgment module 303 is configured to initiate a protection action to cut off the faulty line if the zero-sequence current value of the corrected circuit is greater than a preset zero-sequence current protection setting value;

[0088] Wherein, the correction coefficient is specifically: k is the correction coefficient, is the negative-sequence voltage of the bus, is the positive-sequence voltage of the bus, is the zero-sequence voltage of the bus, b′0 is the zero-sequence voltage proportionality coefficient, and b′2 is the negative-sequence voltage proportionality coefficient.

[0089] For the specific limitations of the zero-sequence current protection device, reference can be made to the limitations on the method in the above text, which will not be elaborated here. Each module in the above device can be implemented in whole or in part by software, hardware, and their combination. Each of the above modules can be embedded in the processor of the terminal device in hardware form or independent of it, or stored in the memory of the terminal device in software form, so that the processor can call and execute the operations corresponding to each of the above modules.

[0090] In one embodiment, the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above zero-sequence current protection method are implemented.

[0091] The computer-readable storage medium may be an electronic memory such as a flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), a hard disk, or a ROM. Optionally, the computer-readable storage medium includes a non-transitory computer-readable storage medium. The computer-readable storage medium has a storage space for program codes for executing any method steps in the above method. These program codes can be read from or written into one or more computer program products, and the program codes can be compressed in an appropriate form.

[0092] In one embodiment, the present invention provides a computer device, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps of the above zero-sequence current protection method are executed.

[0093] The computer device includes a memory, a processor, and one or more computer programs. One or more computer programs can be stored in the memory and configured to be executed by one or more processors. One or more application programs are configured to execute the above zero-sequence current protection method.

[0094] The processor may include one or more processing cores. The processor connects various parts within the entire computer device using various interfaces and lines. By running or executing instructions, programs, code sets, or instruction sets stored in the memory, and by invoking data stored in the memory, it performs various functions of the computer device and processes data. Optionally, the processor can be implemented in at least one hardware form of Digital Signal Processing (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor can integrate one or a combination of several of the Central Processing Unit (CPU), the reporting verifier for buried point data (Graphics Processing Unit, GPU), and a modem, etc. Among them, the CPU mainly processes the operating system, user interface, application programs, etc.; the GPU is responsible for rendering and drawing the displayed content; the modem is used to process wireless communication. It can be understood that the above modem may not be integrated into the processor and can be implemented separately through a communication chip.

[0095] The memory may include Random Access Memory (RAM) and may also include Read-Only Memory. The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory can include a program storage area and a data storage area. Among them, the program storage area can store instructions for implementing the operating system, instructions for implementing at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above various method embodiments, etc. The data storage area can also store data created during the use of the terminal device.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A zero-sequence current protection method, which is applied to a small-resistance grounded system. The small-resistance grounded system includes a grounding transformer, a system-side main transformer, a capacitor, a bus, and a number of feeders; one end of the grounding transformer is connected to the bus, and the other end is grounded; one end of the system-side main transformer is connected to the power grid, and the other end is connected to the bus; one end of the capacitor is connected to the bus, and the other end is grounded; the starting end of the feeder is connected to the bus, and the feeder includes a non-faulty feeder and a faulty feeder, and is characterized in that, The method includes: Obtaining the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the busbar, and the zero-sequence current at the beginning of any non-faulty feeder; If the zero-sequence current at the beginning is greater than a preset maximum unbalanced current, calculate a correction factor, which is used to correct the zero-sequence current value of the circuit; If the corrected zero-sequence current value of the circuit is greater than a preset zero-sequence current protection setting value, initiate a protection action to cut off the faulty line; Among them, the correction coefficient is specifically: k is the correction coefficient, is the negative-sequence voltage of the busbar, is the positive-sequence voltage of the busbar, is the zero-sequence voltage of the busbar, b0 ′ is the zero-sequence voltage proportionality coefficient, b2 ′ is the negative-sequence voltage proportionality coefficient; Among them, b0 ′ is the zero-sequence voltage proportionality coefficient, b2 ′ is the negative-sequence voltage proportionality coefficient, c2 is the negative-sequence capacitance to ground per unit length of the faulty feeder, z2 is the negative-sequence impedance per unit length of the faulty feeder, Y up(2) is the negative-sequence equivalent admittance of the faulty feeder, c0 is the zero-sequence capacitance to ground per unit length of the faulty feeder, z0 is the zero-sequence impedance per unit length of the faulty feeder, Y up(0) is the zero-sequence effective admittance of the faulty feeder, l n is the total length of the faulty feeder.

2. The zero-sequence current protection method according to claim 1, characterized in that, It also includes: If the zero-sequence current at the beginning is less than or equal to the preset maximum unbalanced current, re-obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the busbar, and the zero-sequence current at the beginning of any non-faulty feeder, and determine whether the zero-sequence current at the beginning is greater than the preset maximum unbalanced current; Until the zero-sequence current at the beginning is greater than the preset maximum unbalanced current.

3. The zero-sequence current protection method according to claim 1, characterized in that It also includes: If the corrected zero-sequence current value of the circuit is less than or equal to the preset zero-sequence current protection setting value, re-obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the busbar, and the zero-sequence current at the beginning of any non-faulty feeder, and determine whether the zero-sequence current at the beginning is greater than the preset maximum unbalanced current; Until the corrected zero-sequence current value is greater than the preset zero-sequence current protection setting value.

4. A zero-sequence current protection device, which is applied to a small-resistance grounded system. The small-resistance grounded system includes a grounding transformer, a main transformer on the system side, a capacitor, a busbar, and several feeders; one end of the grounding transformer is connected to the busbar and the other end is grounded; one end of the main transformer on the system side is connected to the power grid and the other end is connected to the busbar; one end of the capacitor is connected to the busbar and the other end is grounded; the starting end of the feeder is connected to the busbar, and the feeder includes a non-faulty feeder and a faulty feeder, and is characterized in that, The device includes: A parameter acquisition module, which is used to obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the busbar, and the zero-sequence current at the beginning of any non-faulty feeder; A first judgment module, which is used to calculate a correction factor if the zero-sequence current at the beginning is greater than a preset maximum unbalanced current, and the correction factor is used to correct the zero-sequence current value of the circuit; A second judgment module, which is used to initiate a protection action to cut off the faulty line if the corrected zero-sequence current value of the circuit is greater than a preset zero-sequence current protection setting value; Among them, the correction coefficient is specifically: k is the correction coefficient, is the negative sequence voltage of the busbar, is the positive sequence voltage of the busbar, is the zero sequence voltage of the busbar, b0 ′ is the zero sequence voltage proportionality coefficient, b2 ′ is the negative sequence voltage proportionality coefficient; where, b0 ′ is the zero-sequence voltage proportionality coefficient, b2 ′ is the negative-sequence voltage proportionality coefficient, c2 is the negative-sequence capacitance to ground per unit length of the faulty feeder, z2 is the negative-sequence impedance per unit length of the faulty feeder, Y up(2) is the negative-sequence equivalent admittance of the faulty feeder, c0 is the zero-sequence capacitance to ground per unit length of the faulty feeder, z0 is the zero-sequence impedance per unit length of the faulty feeder, Y up(0) is the zero-sequence effective admittance of the faulty feeder, l n is the total length of the faulty feeder.

5. The zero-sequence current protection device according to claim 4, characterized in that, It also includes: A first re-judgment module, which is used to re-obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the busbar, and the zero-sequence current at the beginning of any non-faulty feeder if the zero-sequence current at the beginning is less than or equal to the preset maximum unbalanced current, and determine whether the zero-sequence current at the beginning of the line is greater than the preset maximum unbalanced current; Until the zero-sequence current at the beginning is greater than the preset maximum unbalanced current.

6. The zero-sequence current protection device according to claim 4, characterized in that, It also includes: A second re-judgment module, which is used to re-obtain the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage of the busbar, and the zero-sequence current at the beginning of any non-faulty feeder if the corrected zero-sequence current value of the circuit is less than or equal to the preset zero-sequence current protection setting value, and determine whether the zero-sequence current at the beginning is greater than the preset maximum unbalanced current; Until the corrected zero-sequence current value is greater than the preset zero-sequence current protection setting value.

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

8. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it executes the zero-sequence current protection method according to any one of claims 1-3.

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