A bus internal fault identification method and system based on a polarization current double-domain criterion

Abstract

The application discloses a bus internal fault identification method and system based on a polarization current double-domain criterion, and belongs to the technical field of power system relay protection. The method comprises the following steps: collecting bus voltage of each phase and branch current of each branch connected to a bus protection area; calculating bus differential current based on the branch current; constructing conductance polarization current, susceptance polarization current, conductance differential current and susceptance differential current based on the bus differential current and the bus voltage; establishing a double-domain criterion based on the polarization current based on the conductance polarization current, the susceptance polarization current, the conductance differential current and the susceptance differential current; outputting a judgment result of bus internal fault according to the double-domain criterion by using OR logic; and the double-domain criterion comprises a susceptance domain amplitude criterion and a conductance domain phase criterion. The application solves the problem of insufficient sensitivity of traditional bus differential protection under the conditions of new energy weak feeding, high transition resistance fault and insufficient fault current amplitude.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and more specifically, to a method and system for identifying internal bus faults based on a dual-domain polarization current criterion. Background Technology

[0002] Busbars are crucial lines in power systems where transmission lines, transformers, and power sources converge. When a busbar fault occurs, if the protection system fails to operate or operates with a delay, multiple lines and main equipment may be affected simultaneously, potentially leading to widespread power outages and system stability issues. Therefore, busbar protection systems must simultaneously possess speed, selectivity, and sensitivity.

[0003] Traditional bus differential protection typically sums the currents of all branches connected to the bus protection zone with uniform polarity to form the bus differential current. When a fault occurs within the bus zone, the currents of each branch supply power to the fault point, increasing the differential current. During normal operation or when a fault occurs outside the zone, the currents of each branch approximately cancel each other out within the protection zone, resulting in a smaller differential current. This method is clear and simple in principle and widely used in engineering.

[0004] However, in new power systems, equipment such as new energy power plants, flexible DC transmission, and power electronic converters are affected by converter current limiting, low voltage ride-through control, and negative sequence current suppression, resulting in a significant reduction in fault current amplitude and alteration of fault characteristics by the control strategy. For high transition resistance grounding faults, the differential current within the busbar area may be lower than the operating threshold of traditional differential protection, leading to insufficient protection sensitivity.

[0005] If existing differential protection relies solely on differential current amplitude and conventional braking quantity, it is difficult to simultaneously ensure sensitive operation for high-resistance, weak-range faults within the protection zone and reliable, non-maloperational operation for faults outside the protection zone. Summary of the Invention

[0006] To address the above problems, this invention proposes a busbar internal fault identification method based on a dual-domain polarization current criterion, comprising: Collect the bus voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; Based on the bus differential current and the bus voltage Construct the conductivity polarization current, susceptance polarization current, conductivity range current, and susceptance range current; Based on the aforementioned conductance polarization current, susceptance polarization current, conductance range difference current, and susceptance range difference current, a dual-domain criterion based on polarization current is established. OR logic is used to output the judgment result of internal bus fault according to the dual-domain criterion. The dual-domain criteria include: amplitude criteria in the susceptance domain and phase criteria in the conductance domain.

[0007] Optionally, the current of each branch of the busbar collected for each phase R=A, B, C The bus differential current is obtained by summing the results according to a unified reference direction. The calculation formula is as follows: in, For the differential current of the 𝜑 phase bus, Let N be the phase current of the nth branch, and N be the number of branches connected to the busbar protection zone.

[0008] Optionally, based on bus voltage The conductivity polarization current and susceptance polarization current are constructed and calculated using the following formulas: in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Set the conductivity value; in, Represented as: in, The rated voltage of the busbar k Gset These are constant coefficients for different voltage levels. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

[0009] Optionally, based on the difference between the bus differential current and the conductance / susceptance polarization current, the conductance polarization current and susceptance polarization current are constructed, and the calculation formulas are as follows: in, The current represents the conductance difference between phases X and Y. The current difference between the susceptance of phases X is denoted as . For the differential current of the 𝜑 phase bus, For phase X conductance polarization current, It is the phase saturation polarization current.

[0010] Optional susceptance domain amplitude criteria are as follows: When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore If the action criteria are not met, and there is an internal fault with a large fault current, such as a metallic fault or a low transition resistance fault within the zone, Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

[0011] Optional phase criteria in the conductance domain are as follows: When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

[0012] Furthermore, this invention also proposes a bus internal fault identification system based on a dual-domain polarization current criterion, comprising: The acquisition unit is used to acquire the bus voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; A calculation unit is used to calculate based on the bus differential current and the bus voltage. Construct the conductivity polarization current, susceptance polarization current, conductivity range current, and susceptance range current; The output unit is used to establish a dual-domain criterion based on the polarization current, susceptance polarization current, conductivity range current and susceptance range current, and to output the judgment result of the internal fault of the bus using OR logic according to the dual-domain criterion. The dual-domain criteria include: amplitude criteria in the susceptance domain and phase criteria in the conductance domain.

[0013] Optionally, the current of each branch of the busbar collected for each phase R=A, B, C The bus differential current is obtained by summing the results according to a unified reference direction. The calculation formula is as follows: in, For the differential current of the 𝜑 phase bus, Let N be the phase current of the nth branch, and N be the number of branches connected to the busbar protection zone.

[0014] Optionally, based on bus voltage The conductivity polarization current and susceptance polarization current are constructed and calculated using the following formulas: in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Set the conductivity value; in, Represented as: in, The rated voltage of the busbar k Gset These are constant coefficients for different voltage levels. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

[0015] Optionally, based on the difference between the bus differential current and the conductance / susceptance polarization current, the conductance polarization current and susceptance polarization current are constructed, and the calculation formulas are as follows: in, The current represents the conductance difference between phases X and Y. The current difference between the susceptance of phases X is denoted as . For the differential current of the 𝜑 phase bus, For phase X conductance polarization current, It is the phase saturation polarization current.

[0016] Optional susceptance domain amplitude criteria are as follows: When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore If the action criteria are not met, and there is an internal fault with a large fault current, such as a metallic fault or a low transition resistance fault within the zone, Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

[0017] Optional phase criteria in the conductance domain are as follows: When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

[0018] In another aspect, the present invention also provides a computing device, comprising: one or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described above is implemented.

[0019] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes a busbar internal fault identification method based on a dual-domain polarization current criterion, comprising: acquiring the busbar voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; based on the bus differential current and the bus voltage... This invention constructs conductance polarization current, susceptance polarization current, conductance range difference current, and susceptance range difference current. Based on these parameters, a dual-domain criterion based on polarization current is established. OR logic is used to output the judgment result of internal bus faults according to the dual-domain criterion. The dual-domain criterion includes: a susceptance domain amplitude criterion and a conductance domain phase criterion. This invention solves the problem of insufficient sensitivity of traditional bus differential protection under conditions of weak new energy feed, high transition resistance faults, and insufficient fault current amplitude. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the polarization current dual-domain criterion protection logic of the method of the present invention; Figure 3 This is a schematic diagram of the single busbar connection method of the present invention; Figure 4 This is a schematic diagram of the double busbar connection method of the present invention; Figure 5 This is a schematic diagram of the 3 / 2 busbar connection method of the present invention; Figure 6 This is a schematic diagram of the polarization current plane in the susceptance domain of the method of the present invention; Figure 7 This is a schematic diagram of the conductivity domain polarization current plane of the method of the present invention; Figure 8 This is a schematic diagram of the fault protection operation timing curve in the high transition resistance region of the method of the present invention. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] Example 1: This invention proposes a busbar internal fault identification method S100 based on a dual-domain polarization current criterion, such as... Figure 1 As shown, it includes: S101, collects the bus voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; S102, based on the bus differential current and the bus voltage Construct the conductivity polarization current, susceptance polarization current, conductivity range current, and susceptance range current; S103. Based on the conductance polarization current, susceptance polarization current, conductance range difference current and susceptance range difference current, establish a dual-domain criterion based on polarization current, and use OR logic to output the judgment result of internal bus fault according to the dual-domain criterion. The dual-domain criteria include: amplitude criteria in the susceptance domain and phase criteria in the conductance domain.

[0025] Among them, the current of each branch of the busbar collected for each phase R=A, B, C The bus differential current is obtained by summing the results according to a unified reference direction. The calculation formula is as follows: in, For the differential current of the 𝜑 phase bus, Let N be the phase current of the nth branch, and N be the number of branches connected to the busbar protection zone.

[0026] Among them, based on bus voltage The conductivity polarization current and susceptance polarization current are constructed and calculated using the following formulas: in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Set the conductivity value; in, Represented as: in, The rated voltage of the busbar k Gset These are constant coefficients for different voltage levels. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

[0027] The conductance difference current and susceptance difference current are constructed based on the difference between the bus differential current and the conductance / susceptance polarization current, and the calculation formulas are as follows: in, The current represents the conductance difference between phases X and Y. The current difference between the susceptance of phases X is denoted as . For the differential current of the 𝜑 phase bus, For phase X conductance polarization current, It is the phase saturation polarization current.

[0028] The susceptance domain amplitude criterion is as follows: When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore If the action criteria are not met, and there is an internal fault with a large fault current, such as a metallic fault or a low transition resistance fault within the zone, Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

[0029] The phase criterion in the conductance domain is as follows: When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

[0030] The present invention will be further described below with reference to specific examples: The implementation process of a specific case is as follows: For each phase 𝜑, collect the bus voltage. and the current of each branch connected to the busbar protection zone First, calculate the bus differential current, then construct the conductance polarization current, susceptance polarization current, conductance range difference current, and susceptance range difference current. Finally, establish amplitude criteria in the susceptance domain and phase criteria in the conductance domain, and use OR logic to output the fault judgment result in the output region, such as... Figure 2 As shown, this allows us to determine whether the protection system has activated.

[0031] Among them, the bus differential current calculation is as follows: For each phase R=A, B, C, collect the current of each branch. And summed according to a unified reference direction, the bus differential current is obtained: (1) in, For the differential current of the 𝜑 phase bus, For the first n The phase current of the branch, N This refers to the number of branches connected to the busbar protection zone. During normal operation or during external faults, The main components are stray capacitance currents on the busbars with relatively small amplitudes; during faults within the zone, It is mainly determined by the fault current within the zone.

[0032] Bus polarization current calculation: Based on bus voltage The two types of polarization currents, conductance and susceptance, are constructed as follows: (2) in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Here, is the conductance setpoint, and is the reciprocal of the maximum transition resistance to be considered in a single-phase ground fault. Since the maximum transition resistance is related to the voltage level, Represented as , This is the rated voltage of the busbar. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

[0033] Busbar range current calculation: The polarity current is constructed based on the difference between the bus differential current and the polarization current. The conductance and susceptance of the polarity current are respectively: (3) in, The current represents the conductance difference between phases X and Y. This is the phase susceptance difference current. The difference current reflects the degree of deviation of the actual bus differential current from the polarization reference current.

[0034] Susceptance domain amplitude criterion: Constructing the susceptance domain amplitude criterion: (4) When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore The action criteria are not met. This applies to internal faults with large fault currents, such as metallic faults or low transition resistance faults within the zone. Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

[0035] Phase criterion in the conductance domain: Constructing the phase criterion for the conductance domain: (5) When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

[0036] Comprehensive action logic: For any phase R, if the amplitude criterion in the susceptance domain or the phase criterion in the conductance domain is satisfied, then phase R is determined to have fault characteristics within the zone. When any phase satisfies the fault criterion within the zone, a bus protection action signal is output. The action logic is as follows: (6) Selection and calculation of data acquisition parameters for different busbar wiring configurations: For different busbar connection methods, corresponding busbar voltage and current acquisition and calculation methods are proposed, so that the polarization current dual-domain criterion can be applied to different busbar connection forms.

[0037] Single busbar connection, such as Figure 3 As shown: In a single busbar configuration, all outgoing lines, main transformers, tie lines, and other branches are connected to the same busbar protection zone; therefore, the busbar voltage is taken from that busbar voltage. Current in each branch Since the boundaries of the protected area are clearly defined, the calculation process for differential current, polarization current, extreme difference current, and dual-domain criteria can be directly applied under the single busbar method.

[0038] Double busbar connection, such as Figure 4 As shown; For a double busbar connection, both the large differential protection for the busbars and the small differential protection for each busbar section should be considered simultaneously. Taking the diagram as an example, the bus tie current is... The large differential current in the protected area is the sum of the currents of all branches connected to busbar I and busbar II. The bus voltage is For busbar I, branch 1 and branch 3 are connected to busbar I, and the small differential current is... The bus voltage is For busbar II, branch 2 to branch... N Connected to bus II, the small differential current is The bus voltage is .

[0039] 3 / 2 busbar connection, such as Figure 5 As shown; For the 3 / 2 circuit breaker configuration, busbar I and busbar II are treated as independent protection objects. For any busbar, the busbar differential current calculation selects the currents of all branches connected to that busbar, and the busbar voltage is taken as the corresponding busbar voltage. .

[0040] This invention establishes a bus protection framework that complements amplitude and phase criteria, offering the following advantages compared to traditional bus differential protection: First, it has higher sensitivity to high transition resistance faults and can identify faults within the zone with smaller fault currents. Second, under the condition of weak new energy feed, the fault identification capability is not simply relied on the differential current amplitude, but the phase relationship between polarization current and differential current is used to improve the fault identification capability. Third, rapid action can be taken for metallic faults and low transition resistance faults using the susceptance domain amplitude criterion. Fourth, during normal operation and faults outside the operating zone, neither the susceptance nor the conductance difference current enters the operating zone, thus exhibiting good resistance to maloperation.

[0041] A new energy transmission system was built on the RTDS real-time simulation platform, using a 220kV single busbar model. A single-phase ground fault with a 150Ω transition resistance was applied to the busbar. The simulation results are shown below. Figures 6 to 8 .

[0042] based on Figures 6 to 8It can be seen that the fault current generated after the system failure is only 0.5kA, while the minimum identifiable fault current of existing traditional protection is 0.8kA. Therefore, the traditional differential current protection does not operate. When using the polarization current dual-domain criterion, the amplitude criterion in the susceptance domain is not satisfied under this condition, but the phase criterion in the conductance domain is valid, and the protection operates in 14.17ms. Compared with the traditional protection, the sensitivity of the proposed solution is improved by 0.8 / 0.5 = 1.6 times.

[0043] Example 2: Furthermore, this invention also proposes a bus internal fault identification system 200 based on a dual-domain polarization current criterion, comprising: Acquisition unit 201 is used to acquire the bus voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; Calculation unit 202 is used to calculate based on the bus differential current and the bus voltage. Construct the conductivity polarization current, susceptance polarization current, conductivity range current, and susceptance range current; Output unit 203 is used to establish a dual-domain criterion based on polarization current based on the conductance polarization current, susceptance polarization current, conductance range difference current and susceptance range difference current, and to output the judgment result of internal bus fault using OR logic according to the dual-domain criterion. The dual-domain criteria include: amplitude criteria in the susceptance domain and phase criteria in the conductance domain.

[0044] Among them, the current of each branch of the busbar collected for each phase R=A, B, C The bus differential current is obtained by summing the results according to a unified reference direction. The calculation formula is as follows: in, For the differential current of the 5-phase bus, Let N be the phase current of the nth branch, and N be the number of branches connected to the busbar protection zone.

[0045] Among them, based on bus voltage The conductivity polarization current and susceptance polarization current are constructed and calculated using the following formulas: in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Set the conductivity value; in, Represented as: in, The rated voltage of the busbar k Gset These are constant coefficients for different voltage levels. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

[0046] Specifically, based on the difference between the bus differential current and the conductance / susceptance polarization current, the conductance polarization current and susceptance polarization current are constructed, and the calculation formulas are as follows: in, The current represents the conductance difference between phases X and Y. The current difference between the susceptance of phases X is denoted as . For the differential current of the 5-phase bus, For phase X conductance polarization current, This is the phase saturation polarization current.

[0047] The susceptance domain amplitude criterion is as follows: When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore If the action criteria are not met, and there is an internal fault with a large fault current, such as a metallic fault or a low transition resistance fault within the zone, Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

[0048] The phase criterion in the conductance domain is as follows: When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

[0049] This invention solves the problem of insufficient sensitivity of traditional bus differential protection under conditions of weak new energy feed, high transition resistance faults, and insufficient fault current amplitude.

[0050] Example 3: Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the methods in the above embodiments.

[0051] Example 4: Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiments.

[0052] 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 implemented 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. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0057] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for identifying internal bus faults based on a dual-domain polarization current criterion, characterized in that, include: Collect the bus voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; Based on the bus differential current and the bus voltage Construct the conductivity polarization current, susceptance polarization current, conductivity range current, and susceptance range current; Based on the aforementioned conductance polarization current, susceptance polarization current, conductance range difference current, and susceptance range difference current, a dual-domain criterion based on polarization current is established. OR logic is used to output the judgment result of internal bus fault according to the dual-domain criterion. The dual-domain criteria include: amplitude criteria in the susceptance domain and phase criteria in the conductance domain.

2. The busbar internal fault identification method according to claim 1, characterized in that, For each phase R=A, B, C, the current of each branch of the bus is collected. The bus differential current is obtained by summing the results according to a unified reference direction. The calculation formula is as follows: in, For the differential current of the 5-phase bus, Let N be the phase current of the nth branch, and N be the number of branches connected to the busbar protection zone.

3. The busbar internal fault identification method according to claim 1, characterized in that, Based on bus voltage The conductivity polarization current and susceptance polarization current are constructed and calculated using the following formulas: in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Set the conductivity value; in, Represented as: in, The rated voltage of the busbar k Gset These are constant coefficients for different voltage levels. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

4. The busbar internal fault identification method according to claim 1, characterized in that, Based on the difference between the bus differential current and the conductance / susceptance polarization current, the conductance polarization current and susceptance polarization current are constructed, and the calculation formulas are as follows: in, The current represents the conductance difference between phases X and Y. The current difference between the susceptance of phases X is denoted as . For the differential current of the 5-phase bus, For phase X conductance polarization current, This is the phase saturation polarization current.

5. The busbar internal fault identification method according to claim 1, characterized in that, The amplitude criterion in the susceptance domain is as follows: When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore If the action criteria are not met, and there is an internal fault with a large fault current, such as a metallic fault or a low transition resistance fault within the zone, Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

6. The busbar internal fault identification method according to claim 1, characterized in that, The phase criterion in the conductance domain is as follows: When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

7. A busbar internal fault identification system based on polarization current dual-domain criterion, characterized in that, include: The acquisition unit is used to acquire the bus voltage of each phase. and the current of each branch connected to the busbar protection zone Based on the current of each branch Calculate the bus differential current; A calculation unit is used to calculate based on the bus differential current and the bus voltage. Construct the conductivity polarization current, susceptance polarization current, conductivity range current, and susceptance range current; The output unit is used to establish a dual-domain criterion based on the polarization current, susceptance polarization current, conductivity range current and susceptance range current, and to output the judgment result of the internal fault of the bus using OR logic according to the dual-domain criterion. The dual-domain criteria include: amplitude criteria in the susceptance domain and phase criteria in the conductance domain.

8. The busbar internal fault identification system according to claim 7, characterized in that, For each phase R=A, B, C, the current of each branch of the bus is collected. The bus differential current is obtained by summing the results according to a unified reference direction. The calculation formula is as follows: in, For the differential current of the 5-phase bus, Let N be the phase current of the nth branch, and N be the number of branches connected to the busbar protection zone.

9. The busbar internal fault identification system according to claim 7, characterized in that, Based on bus voltage The conductivity polarization current and susceptance polarization current are constructed and calculated using the following formulas: in, For phase X conductance polarization current, The polarization current of phase α is the susceptance. Set the conductivity value; in, Represented as: in, The rated voltage of the busbar k Gset These are constant coefficients for different voltage levels. This is the susceptance setpoint, which is the maximum susceptance value that may occur during normal operation.

10. The busbar internal fault identification system according to claim 7, characterized in that, Based on the difference between the bus differential current and the conductance / susceptance polarization current, the conductance polarization current and susceptance polarization current are constructed, and the calculation formulas are as follows: in, The current represents the conductance difference between phases X and Y. The current difference between the susceptance of phases X is denoted as . For the differential current of the 5-phase bus, For phase X conductance polarization current, This is the phase saturation polarization current.

11. The busbar internal fault identification system according to claim 7, characterized in that, The amplitude criterion in the susceptance domain is as follows: When the system is operating normally or an external fault occurs, the bus differential current is mainly close to the stray capacitance current. Approximately equal to ,therefore If the action criteria are not met, and there is an internal fault with a large fault current, such as a metallic fault or a low transition resistance fault within the zone, Dominated by fault current, The amplitude will increase significantly, and the protection action will be triggered if the susceptance domain amplitude criterion is met.

12. The busbar internal fault identification system according to claim 7, characterized in that, The phase criterion in the conductance domain is as follows: When the system is operating normally or there is an external fault, the bus differential current is mainly a small capacitive current, and the conductance difference current and conductance polarization current do not satisfy the same direction relationship. During internal faults with small bus differential current amplitudes, such as high transition resistance faults or faults in the new energy weak feeder system, the resistive component in the bus differential current that is in phase or approximately in phase with the bus voltage increases, making... and They tend to move in the same direction, thus satisfying the phase criterion.

13. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described in any one of claims 1-5 is implemented.

14. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the method as described in any one of claims 1-5.

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