A method and device for detecting cross-line faults in asynchronous power grids based on the standard deviation of differential current.

Abstract

This invention discloses a method and apparatus for identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current. The method includes: obtaining a sampled value of the line differential current based on the sum of the fault currents at the beginning and end of the line from the collected fault waveforms; calculating the effective value of the line differential current based on the sampled value; calculating the standard deviation of the effective value of the line differential current; and determining the fault type based on the standard deviation and a pre-constructed cross-line fault identification criterion.

Description

[0001] A method and device for detecting cross-line faults in asynchronous power grids based on the standard deviation of differential current. Technical Field

[0002] This invention relates to the field of fault identification technology in the field of AC transmission line relay protection, and more specifically, to a method and device for identifying asynchronous power grid cross-line faults based on the standard deviation of differential current. Background Technology

[0003] In recent years, with the large-scale construction and advancement of asynchronous power grids such as the Northeast Power Grid and the North China Power Grid, the number of power transmission lines has been increasing, leading to increasingly strained transmission corridors. Under these circumstances, the phenomenon of transmission lines crossing each other is becoming more frequent, which may significantly increase the probability of cross-crossing faults in asynchronous power grids. Such faults not only threaten the safe and stable operation of the power grid but may also trigger a chain reaction, further expanding the scope of the fault's impact and posing a severe challenge to the reliable power supply and overall operational efficiency of the power system.

[0004] However, unlike conventional transmission line faults, asynchronous power grid cross-line faults are influenced by multiple factors such as system frequency difference and cross-line phase difference, resulting in more complex fault characteristics. Existing current differential protection and distance protection may be inapplicable, or even fail to operate. Therefore, studying the characteristic mechanism of asynchronous power grid cross-line faults and proposing corresponding solutions is of great practical significance for ensuring the safe and stable operation of the power grid. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and apparatus for identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current.

[0006] According to one aspect of the present invention, a method for identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current is provided, comprising:

[0007] The differential current sampling value of the line is obtained by summing the fault currents at the beginning and end of the line based on the collected fault waveforms.

[0008] The effective value of the line differential current is calculated based on the sampled values ​​of the line differential current;

[0009] Calculate the standard deviation of the effective value of the differential current in the line;

[0010] The fault type is determined based on the standard deviation and a pre-built cross-line fault identification criterion.

[0011] According to another aspect of the present invention, an asynchronous power grid cross-line fault detection device based on differential current standard deviation is provided, comprising:

[0012] The module is used to obtain the line differential current sampling value based on the sum of the fault currents at the beginning and end of the line from the collected fault waveform;

[0013] The first calculation module is used to calculate the effective value of the line differential current based on the sampled value of the line differential current;

[0014] The second calculation module is used to calculate the standard deviation of the effective value of the line differential current;

[0015] The determination module is used to determine the fault type based on the standard deviation and pre-built cross-line fault identification criteria.

[0016] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program for performing the methods described in any of the above aspects of the present invention.

[0017] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0018] Therefore, this invention addresses the inapplicability of existing AC protection systems to cross-line faults in asynchronous power grids, and even the occurrence of failure to operate, by proposing a novel longitudinal protection method based on the standard deviation of differential current. This method can fully utilize the differential current fault waveform characteristics generated when a cross-line fault occurs, accurately and reliably distinguishing between internal and external faults. Furthermore, the protection method proposed in this invention possesses inherent fault phase selection capability, accurately identifying and isolating faulty portions, thus contributing to ensuring the reliability and safety of the power system. This invention is based on the analysis and calculation of actual engineering model data, with a sound protection principle, reliably distinguishing between internal and external faults, meeting engineering design requirements, and can be widely applied in 220kV and 500kV AC asynchronous power grids. Attached Figure Description

[0019] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0020] Figure 1 This is a flowchart illustrating an exemplary embodiment of the present invention for a method of identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current.

[0021] Figure 2 This is another flowchart illustrating an exemplary embodiment of the present invention for a method of identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current.

[0022] Figure 3 This is a schematic diagram of an asynchronous power grid cross-line fault provided in an exemplary embodiment of the present invention;

[0023] Figure 4 This is an exemplary embodiment of the present invention, showing the Aa cross-line fault composite sequence network diagram.

[0024] Figure 5 This is a schematic diagram of a composite sequence network diagram of A-bc cross-line faults provided in an exemplary embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of a BC-bc cross-line fault composite sequence network provided in an exemplary embodiment of the present invention;

[0026] Figure 7 This is a schematic diagram of an equivalent circuit for an external fault provided in an exemplary embodiment of the present invention;

[0027] Figure 8 , 9 These are schematic diagrams illustrating the correct operation of System I and System II protection for an asynchronous power grid A-phase-a phase cross-line ungrounded fault (voltage phase difference 0°) provided by an exemplary embodiment of the present invention.

[0028] Figure 10 , 11 These are schematic diagrams illustrating the correct operation of System I and System II protections for an asynchronous power grid A-phase-a phase cross-line ungrounded fault (voltage phase difference 30°) provided by an exemplary embodiment of the present invention.

[0029] Figure 12 , 13 These are schematic diagrams showing that the protection of System I and System II of the asynchronous power grid system I is correctly not operating under an external fault (A-phase F2 fault) provided by an exemplary embodiment of the present invention.

[0030] Figure 14 This is a schematic diagram of the structure of an asynchronous power grid cross-line fault detection device based on differential current standard deviation provided in an exemplary embodiment of the present invention;

[0031] Figure 15 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0032] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0033] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0034] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0035] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0036] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0037] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0038] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0039] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0040] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0041] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0042] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0043] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0044] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0045] Exemplary methods

[0046] Figure 1 This is a flowchart illustrating an exemplary embodiment of the present invention regarding a method for identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current. This embodiment can be applied to electronic devices, such as… Figure 1 As shown, the asynchronous power grid cross-line fault identification method 100 based on differential current standard deviation includes the following steps:

[0047] Step 101: Obtain the line differential current sampling value based on the sum of the fault currents at the beginning and end of the line from the collected fault waveforms.

[0048] Step 102: Calculate the effective value of the line differential current based on the sampled values ​​of the line differential current;

[0049] Step 103: Calculate the standard deviation of the effective value of the line differential current;

[0050] Step 104: Determine the fault type based on the standard deviation and the pre-built cross-line fault identification criteria.

[0051] Specifically, this invention addresses the inapplicability of existing current differential protection and distance protection methods to cross-line faults in asynchronous power grids, and even the occurrence of failure to operate. It proposes a novel longitudinal protection method for cross-line faults in asynchronous power grids based on the standard deviation of the differential current. For cross-line faults in asynchronous power grids, an improved composite sequence network diagram method is proposed to analyze the characteristic mechanism of cross-line faults, taking into account the response characteristics of two system voltage sources with frequency differences. An analytical expression for the differential current of the cross-line fault line is derived, and the standard deviation of the differential current is used to characterize the beat frequency characteristics of the fault current, quantifying the dispersion of the effective value of the differential current. A cross-line fault identification criterion is constructed to reliably identify cross-line faults of different phases under different fault phase angles. The protection method proposed in this invention has a natural fault phase selection capability; the operating phase of the protection is the fault phase, which can accurately identify the fault and isolate the faulty part, thus helping to ensure the reliability and safety of the power system.

[0052] like Figure 2 The diagram shown is a flowchart of the method of the present invention. The present invention proposes a longitudinal protection method for cross-line faults in asynchronous power grids based on the standard deviation of differential current. The method includes the following steps:

[0053] Step 1: Obtain the fault current at the beginning and end of the line based on the fault waveform data, and calculate the effective value of the line differential current. Effective value of line differential current. i dR As shown in the following formula: ,in i d This is the sampled value of the differential current of the line (i.e., the sum of the fault currents at the beginning and end of the line). J This represents the number of sampling points within the data window.

[0054] Step 2: Based on the waveform characteristics of the differential current fault during a cross-line fault in an asynchronous power grid, construct the cross-line fault identification criterion. Specifically, calculate the standard deviation of the effective value of the differential current based on equation (1), use the standard deviation to characterize the beat frequency characteristics of the fault current, quantify the dispersion of the effective value of the differential current, and construct the cross-line fault identification criterion shown in equation (2).

[0055] (1)

[0056] In the formula, σ idR Let be the standard deviation of the differential current RMS value, and let be the RMS value of the differential current. i dR The mean, N This represents the number of sampling points within the data window.

[0057] Step 3: Based on the fault identification criterion shown in equation (2), identify faults inside and outside the zone, as follows. When the fault is inside the zone, the differential current... i dR It is a quantity that changes over time; while for faults outside the zone,i dR It approximates a constant value and does not change with time. Therefore, the effective value of the fault time difference current within the area... i dR The standard deviation is greater than the standard deviation when there is an out-of-area fault.

[0058] (2)

[0059] In the formula, σ set To protect the threshold, this value should be greater than the maximum value of the standard deviation of the differential current effective value that may occur when there is a fault outside the zone. Here, it is set... σ set It is 0.01. If σ idR If equation (2) is satisfied, it is judged as an intra-zone fault; otherwise, it is judged as an extra-zone fault.

[0060] Step 4: The protection proposed in this invention has a natural fault phase selection capability. The operating phase of the protection is the fault phase, which can accurately identify the fault and disconnect the faulty part, thus helping to ensure the reliability and safety of the power system. The standard deviation of the differential current RMS value is calculated using equation (1). σ idR ,if σ idR If equation (2) is satisfied, it is judged as an intra-zone fault; otherwise, it is judged as an extra-zone fault. If it is judged as an intra-zone fault, the operating phase is the faulty phase. If only one phase of the three-phase current satisfies equation (2), it is judged as a single-phase fault, and the faulty phase circuit breaker is tripped; if two phases of the three-phase current or all three phases of the current satisfy equation (2), it is judged as a phase-to-phase fault, and the three-phase circuit breaker is tripped.

[0061] Specifically, this invention proposes a novel longitudinal protection method based on the standard deviation of differential current for cross-line faults in asynchronous power grids. The specific implementation method is as follows:

[0062] 1. Extracting cross-line fault characteristics of asynchronous power grids

[0063] A schematic diagram of a cross-line short-circuit fault in an asynchronous power grid transmission line is attached. Figure 3 As shown in the figure. "System I" and "System II" represent two asynchronous power grid systems (voltage frequencies of 50 Hz and 50.1 Hz, respectively). F0~F4 represent different fault locations. This is the fault voltage. This is the fault current. K This represents a phase-to-short-circuit switch. Different combinations of its closed or open states represent different types of cross-line faults, and the fault point voltage is also represented. K g This indicates a grounding switch.

[0064] For cross-line ungrounded faults K g disconnect, Not zero. A detailed theoretical derivation is given using Aa (A-phase to a-phase fault) as an example. At this point, [the following is attached]. Figure 3 middle K A , K a Close it.

[0065] First, the boundary relation equations at the fault point of system I are listed as follows:

[0066] (3)

[0067] The phase components are transformed into order components, satisfying the following equation:

[0068] (4)

[0069] Based on the previous formula, we can deduce the appendix. Figure 4 The diagram shows the left portion of points m and n in the sequence network. Z I1 , Z I2 and Z I0 These are the three-sequence impedances of system I, which are then incorporated into the short-circuit point. Z II1 , Z II2 and Z II0 These are the three-sequence impedances of System II, which are then incorporated into the short-circuit point. These are the pre-fault voltages at the fault points of System I and System II, respectively.

[0070] The boundary relation equations at the fault location in System II are listed below:

[0071] (5)

[0072] The phase components are transformed into order components, satisfying the following equation:

[0073] (6)

[0074] Similarly, based on equation (6), the appendix is ​​derived. Figure 4 The part to the right of points m and n in the sequence network diagram shown.

[0075] Fault voltage in system I and II sequence network diagrams Therefore, the composite sequence network diagrams of systems I and II are combined into an improved sequence network diagram, as shown in the appendix. Figure 4 .

[0076] According to the appendix Figure 4Using the superposition theorem, the positive sequence current is obtained. It can be expressed as the following formula:

[0077] (7)

[0078] In the formula,

[0079] (8)

[0080] Furthermore, as can be seen from the figure,

[0081] (9)

[0082] For system I, the differential current of the faulty line can be expressed as follows:

[0083] (10)

[0084] Similarly, by appendix Figure 4 It can be seen that the positive sequence current can be expressed as the following formula:

[0085] (11)

[0086] Furthermore, as can be seen from the figure,

[0087] (12)

[0088] For system II, the differential current of the faulty line can be expressed as follows:

[0089] (13)

[0090] As shown in equations (10) and (13), after a cross-line ungrounded fault occurs, for both System I and System II, the differential current of the faulted line contains the responses of two voltage sources with frequencies of 50Hz and 50.1Hz. Due to the frequency difference, the two slightly different sinusoidal signals superimpose each other, resulting in a periodically changing amplitude phenomenon, known as beat frequency phenomenon. That is, at this time, the differential current after the fault exhibits beat frequency characteristics, and its amplitude changes periodically.

[0091] Taking A-bc (a short circuit between phases A and bc without grounding) as an example, the characteristics of a single-phase fault spanning two phases without grounding are explained, with appendix. Figure 3 middle K A , K b , K c closure.

[0092] At this point, the ordered components in system I still satisfy equation (4), and the composite ordered network diagram and appendix... Figure 4 The left ends of the midpoints m and n are the same.

[0093] The boundary relation equations at the fault location in System II are listed below:

[0094] (14)

[0095] The phase components are transformed into order components, satisfying the following equation:

[0096] (15)

[0097] Based on the previous formula, we can deduce the appendix. Figure 4 The part to the right of points m and n in the sequence network diagram shown.

[0098] Since the fault voltages are the same in system I and II sequence network diagrams, the composite sequence network diagrams of system I and II are combined into an improved sequence network diagram, as shown in the appendix. Figure 5 .

[0099] From the appendix Figure 5 It can be seen that the positive sequence current can be expressed as the following formula:

[0100] (16)

[0101] In the formula,

[0102] (17)

[0103] (18)

[0104] Therefore, for system I, the differential current of the faulty line can be expressed as follows:

[0105] (19)

[0106] As can be seen from equation (19), after a cross-line ungrounded fault occurs, for system I, the differential current of the faulted line is formed by the superposition of two sinusoidal signals with slightly different frequencies. The differential current exhibits beat frequency characteristics and its amplitude changes periodically.

[0107] Similarly, for System II, it can be deduced that the differential current of the faulty line exhibits beat frequency characteristics under the response of two voltage sources with frequencies of 50Hz and 50.1Hz, and the amplitude changes periodically. Due to space limitations, the specific derivation process will not be elaborated here.

[0108] Taking BC-bc (BC phase ungrounded fault across bc) as an example, this paper analyzes and explains the characteristics of two-phase ungrounded faults across two phases. (See attached diagram) Figure 3 middle K B , K C , K b ,K c closure.

[0109] The boundary relation equations for the fault location in system I are listed below:

[0110] (20)

[0111] The phase components are transformed into order components, satisfying the following equation:

[0112] (twenty one)

[0113] Based on the previous formula, we can deduce the appendix. Figure 6 The left side of points m and n in the sequence network diagram shown.

[0114] Similar to System I, the order component boundary conditions at the fault point in System II are listed below:

[0115] (twenty two)

[0116] Similarly, based on the boundary conditions shown in equation (22), draw the attached... Figure 6 The right-hand side of points m and n.

[0117] Since the fault voltages are the same in system I and II sequence network diagrams, the composite sequence network diagrams of system I and II are combined into an improved sequence network diagram, as shown in the appendix. Figure 6 .

[0118] Similar to the theoretical derivation of the A-bc cross-line fault, it can be deduced that for System I and System II, the differential current of the faulty line exhibits beat frequency characteristics under the responses of two voltage sources at frequencies of 50Hz and 50.1Hz, with the amplitude changing periodically. Due to space limitations, the detailed derivation will not be elaborated here. Other types of ungrounded cross-line faults can be derived using a similar method, which will not be detailed further.

[0119] In summary, based on the improved composite sequence network diagram described above, expressions for fault currents under different fault types can be obtained. It is evident that the characteristics of ungrounded cross-line faults in asynchronous power grids differ significantly from those of traditional single-point faults. In this case, the short-circuit current of each system is influenced by another system parameter, and the fault current also contains a zero-sequence component during ungrounded faults.

[0120] For asynchronous grid faults outside the designated area, taking the F2 fault in system I as an example, a detailed fault characteristic derivation is performed. The equivalent fault analysis circuit is shown in the appendix. Figure 7 As shown in the figure, i M and i N These represent the fault currents on both sides of the line. i MC andi NC These represent the distributed capacitor currents on the M and N sides, respectively. u M and u N These represent the fault voltages on both sides of the line.

[0121] When an external fault occurs, the fault current exhibits a through-current characteristic, and the line differential current is a distributed capacitance current, as shown in the following formula:

[0122] (twenty three)

[0123] Due to the distributed characteristics of capacitance, and given that the voltage across the entire line is uniformly distributed, the distributed capacitance current of the line satisfies the following equation:

[0124] (twenty four)

[0125] Therefore, in the event of an external fault, the line differential current can be expressed as follows:

[0126] (25)

[0127] As can be seen from equation (25), since the voltage source is a sinusoidal quantity of power frequency, the differential current of the line after differentiation is a power frequency waveform. That is, when there is a fault outside the zone, the differential current is a sinusoidal (or cosine) waveform, and the effective value amplitude of the differential current remains unchanged.

[0128] When System I experiences a fault outside the F1 zone, or System II experiences a fault outside the F3 or F4 zone, the fault characteristics are similar to the above inferences, and will not be repeated here.

[0129] In summary, when an ungrounded cross-line fault occurs within the fault zone, the line differential current is formed by the superposition of two slightly different sinusoidal signals, exhibiting beat frequency characteristics and periodic amplitude variations. Conversely, when an external fault occurs, the line differential current exhibits a single sinusoidal (or cosine) waveform, and the effective value of the differential current remains constant. Therefore, this invention constructs a cross-line fault protection criterion for asynchronous power grids based on these differences in fault characteristics.

[0130] 2. Constructing cross-line fault identification criteria

[0131] In mathematical statistics, standard deviation can effectively reflect the degree of variation of a population. Therefore, this invention uses standard deviation to characterize the dispersion of the effective value of differential current, as shown in equation (26):

[0132] (26)

[0133] In the formula, σ idR The standard deviation of the differential current RMS value is given by [value]. idR The mean, N This represents the number of sampling points within the data window.

[0134] When a fault occurs within the zone i dR It is a quantity that changes over time, and for faults outside the zone, i dR It approximates a constant value and does not change with time. Therefore, the effective value of the fault time difference current within the area... i dR The standard deviation of the fault is greater than the standard deviation of the fault outside the fault zone. Therefore, the fault identification criterion shown in formula (27) is constructed as follows:

[0135] (27)

[0136] In the formula, σ set To protect the threshold, this value should be greater than the standard deviation of the maximum effective value of the differential current that may occur during an external fault. Let... σ set It is 0.01. If σ idR If equation (27) is satisfied, it is judged as an intra-zone fault; otherwise, it is judged as an extra-zone fault.

[0137] 3. Fault phase selection and protection logic

[0138] The protection proposed in this paper has a natural fault phase selection capability. The operating phase of the protection is the fault phase, which can accurately identify the fault and disconnect the faulty part, thus helping to ensure the reliability and safety of the power system.

[0139] The standard deviation of the effective value of the differential current is calculated using equation (26). σ idR ,if σ idR If equation (27) is satisfied, the fault is determined to be within the zone; otherwise, it is determined to be outside the zone. If the fault is determined to be within the zone, the operating phase is the faulty phase. If the fault is determined to be a single-phase fault, the circuit breaker of the faulty phase is tripped; if the fault is determined to be between phases, the three-phase circuit breaker is tripped.

[0140] 4. Simulation verification

[0141] The results of fault identification according to the method of the present invention are as follows: Figure 8 , 9 As shown in Figures 10, 11, 12, and 13, the proposed protection criteria can reliably identify faults inside and outside the protection zone.

[0142] Therefore, this invention addresses the inapplicability of existing AC protection systems to cross-line faults in asynchronous power grids, and even the occurrence of failure to operate, by proposing a novel longitudinal protection method based on the standard deviation of differential current. This method can fully utilize the differential current fault waveform characteristics generated when a cross-line fault occurs, accurately and reliably distinguishing between internal and external faults. Furthermore, the protection method proposed in this invention possesses inherent fault phase selection capability, accurately identifying and isolating faulty portions, thus contributing to ensuring the reliability and safety of the power system. This invention is based on the analysis and calculation of actual engineering model data, with a sound protection principle, reliably distinguishing between internal and external faults, meeting engineering design requirements, and can be widely applied in 220kV and 500kV AC asynchronous power grids.

[0143] Exemplary device

[0144] Figure 14 This is a schematic diagram of the structure of an asynchronous power grid cross-line fault detection device based on the differential current standard deviation provided in an exemplary embodiment of the present invention. Figure 14 As shown, the device 1400 includes:

[0145] Module 1410 is used to obtain the line differential current sampling value based on the sum of the fault currents at the beginning and end of the line from the collected fault waveform.

[0146] The first calculation module 1420 is used to calculate the effective value of the line differential current based on the sampled value of the line differential current;

[0147] The second calculation module 1430 is used to calculate the standard deviation of the effective value of the line differential current;

[0148] The determination module 14140 is used to determine the fault type based on the standard deviation and a pre-built cross-line fault identification criterion.

[0149] Exemplary electronic devices

[0150] Figure 15 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. For example... Figure 15 As shown, the electronic device 150 includes one or more processors 151 and memory 152.

[0151] The processor 151 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0152] Memory 152 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and processor 151 may execute the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above, and / or other desired functions. In one example, the electronic device may also include an input device 153 and an output device 154, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0153] In addition, the input device 153 may also include, for example, a keyboard, a mouse, etc.

[0154] The output device 154 can output various information to the outside. The output device 154 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0155] Of course, for the sake of simplicity, Figure 15 Only some of the components of this electronic device relevant to the present invention are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0156] Exemplary computer program products and computer-readable storage media

[0157] In addition to the methods and apparatus described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps in the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0158] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0159] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps of the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0160] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, system, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0161] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0162] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0163] The block diagrams of devices, systems, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0164] The methods and systems of the present invention may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0165] It should also be noted that in the systems, apparatus, and methods of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0166] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for identifying cross-line faults in asynchronous power grids based on the standard deviation of differential current, characterized in that, include: The differential current sampling value of the line is obtained by summing the fault currents at the beginning and end of the line based on the collected fault waveforms. The effective value of the line differential current is calculated based on the sampled values ​​of the line differential current. Calculate the standard deviation of the effective value of the differential current of the line; Based on the standard deviation and the pre-constructed cross-line fault identification criteria, the fault type is determined, wherein the fault type includes intra-area faults and inter-area faults; The expression for the pre-constructed cross-line fault identification criterion is: In the formula, σ idR The standard deviation of the effective value of the differential current of the line. σ set To protect the threshold; Based on the improved composite sequence network diagram of the constructed asynchronous power grid, the expressions for fault current under different fault types are obtained; Based on the fault current expressions under different fault types, the characteristics of cross-line faults in asynchronous power grids are extracted, wherein the cross-line fault characteristics of asynchronous power grids are the effective values ​​of line differential currents.

2. The method according to claim 1, characterized in that, The formula for calculating the effective value of the differential current of the line is as follows: In the formula, i d This is the sampled value of the line differential current. J This represents the number of sampling points within the data window.

3. The method according to claim 1, characterized in that, The formula for calculating the standard deviation of the effective value of the differential current of the line is: In the formula, σ idR The standard deviation of the effective value of the differential current of the line. The effective value of differential current i dR The mean, N This represents the number of sampling points within the data window.

4. An asynchronous power grid cross-line fault detection device based on differential current standard deviation, characterized in that, include: The module is used to obtain the line differential current sampling value based on the sum of the fault currents at the beginning and end of the line from the collected fault waveform; The first calculation module is used to calculate the effective value of the line differential current based on the sampled value of the line differential current; The second calculation module is used to calculate the standard deviation of the effective value of the differential current of the line; The determination module is used to determine the fault type based on the standard deviation and the pre-constructed cross-line fault identification criteria, wherein the fault type includes intra-area faults and inter-area faults; The expression for the pre-constructed cross-line fault identification criterion is: In the formula, σ idR The standard deviation of the effective value of the differential current of the line. σ set To protect the threshold; The module is used to obtain the fault current expressions under different fault types based on the improved composite sequence network diagram of the constructed asynchronous power grid. The extraction module is used to extract the cross-line fault characteristics of asynchronous power grids based on the fault current expressions under different fault types, wherein the cross-line fault characteristics of asynchronous power grids are the effective values ​​of line differential currents.

5. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for performing the method described in any one of claims 1-3.

6. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1-3.

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