Asynchronous power grid overline fault judgment method and device based on differential current standard deviation

Abstract

The invention discloses an asynchronous power grid overline fault judgment method and device based on differential current standard deviation. The method comprises the steps of obtaining a line differential current sampling value according to the sum of line head and tail end fault currents of collected fault waveforms; calculating a line differential current effective value according to the line differential current sampling value; calculating the standard deviation of the effective value of the differential current of the line; and determining a fault type according to the standard deviation and a pre-constructed overline fault identification criterion.

Description

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

[0002] The present invention relates to the technical field of fault identification in the field of relay protection of AC transmission lines, and more specifically to a method and device for distinguishing cross-line faults in an asynchronous power grid based on differential current standard deviation. Background Art

[0003] In recent years, with the large-scale construction and advancement of asynchronous power grids such as the Northeast and North China Power Grids, the number of transmission lines has continued to increase, and transmission corridors have become increasingly congested. Under these circumstances, the increasing incidence of crossovers between transmission lines has significantly increased the probability of crossover faults in asynchronous power grids. Such faults not only threaten the safe and stable operation of the power grid but can also trigger a chain reaction, further expanding the scope of the fault and posing severe challenges to the reliable power supply and overall operational efficiency of the power system.

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

[0005] In view of the deficiencies in the prior art, the present invention provides a method and device for distinguishing cross-line faults in an asynchronous power grid based on the standard deviation of differential current.

[0006] According to one aspect of the present invention, a method for determining cross-line faults in an asynchronous power grid based on a differential current standard deviation is provided, comprising: The line differential current sampling value is obtained according to the sum of the fault currents at the beginning and end of the line of the collected fault waveform; Calculating the effective value of the line differential current according to the line differential current sampling value; Calculate the standard deviation of the effective value of the line differential current; The fault type is determined based on the standard deviation and pre-established cross-line fault identification criteria.

[0007] According to another aspect of the present invention, there is provided an asynchronous power grid cross-line fault determination device based on differential current standard deviation, comprising: An obtaining module is used to obtain a line differential current sampling value according to the sum of the fault currents at the beginning and end of the line of the collected fault waveform; A first calculation module is used to calculate the effective value of the line differential current according to the line differential current sampling value; The second calculation module is used to calculate the standard deviation of the effective value of the line differential current; The determination module is used to determine the fault type based on the standard deviation and the pre-established cross-line fault identification criteria.

[0008] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and the computer program is used to execute the method according to any one of the above aspects of the present invention.

[0009] According to another aspect of the present invention, an electronic device is provided, comprising: a processor; a memory for storing instructions executable by the processor; and the processor for reading the executable instructions from the memory and executing the instructions to implement the method described in any one of the above aspects of the present invention.

[0010] Therefore, the present invention addresses the problem that existing AC protection is not applicable and even refuses to operate when cross-line faults occur in asynchronous power grids, and proposes a new longitudinal protection method based on the standard deviation of differential current. This method can fully utilize the waveform characteristics of the differential current fault generated when a cross-line fault occurs, and accurately and reliably distinguish between faults inside and outside the zone. In addition, the protection method proposed in the present invention has a natural fault phase selection capability, can accurately identify faults and cut off the faulty part, which is beneficial to ensuring the reliability and safety of the power system. The invention is based on the analysis and calculation of actual engineering model data, and the protection principle is well-founded. It can reliably distinguish faults inside and outside the zone, meet engineering design requirements, and can be promoted and applied in 220kV and 500kV AC asynchronous power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings: Figure 1 1 is a flow chart of a method for determining cross-line faults in an asynchronous power grid based on a differential current standard deviation, provided by an exemplary embodiment of the present invention; Figure 2 1 is another flow chart of a method for determining cross-line faults in an asynchronous power grid based on a differential current standard deviation, provided by an exemplary embodiment of the present invention; Figure 3 This is a schematic diagram of an asynchronous power grid cross-line fault provided by an exemplary embodiment of the present invention; Figure 4 is a composite sequence network diagram of an Aa cross-line fault provided by an exemplary embodiment of the present invention; Figure 5 1 is a schematic diagram of a composite sequence network diagram of an A-bc cross-line fault provided by an exemplary embodiment of the present invention; Figure 61 is a schematic diagram of a composite sequence network diagram of a BC-bc cross-line fault provided by an exemplary embodiment of the present invention; Figure 7 is a schematic diagram of an out-of-zone fault equivalent circuit diagram provided by an exemplary embodiment of the present invention; Figure 8 、 9 They are respectively schematic diagrams of correct protection actions of system I and system II for an asynchronous power grid phase A-phase a cross-line ungrounded fault (voltage phase difference 0°) provided by an exemplary embodiment of the present invention; Figure 10 、 11 They are respectively schematic diagrams of correct protection actions of system I and system II for an asynchronous power grid phase A-phase a cross-line ungrounded fault (voltage phase difference of 30°) provided by an exemplary embodiment of the present invention; Figure 12 、 13 Schematic diagrams of the protection of system I and system II being correct but not operating when an external fault (A phase F2 fault) of an asynchronous power grid system I is provided by an exemplary embodiment of the present invention; Figure 14 1 is a schematic structural diagram of an asynchronous power grid cross-line fault determination device based on differential current standard deviation provided by an exemplary embodiment of the present invention; Figure 15 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0012] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0013] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0014] Those skilled in the art will understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0015] It should also be understood that, in the embodiments of the present invention, “a plurality of” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0016] 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 limited or otherwise indicated in the context.

[0017] In addition, the term "and / or" in this invention merely describes an association relationship between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this invention generally indicates that the related objects are in an "or" relationship.

[0018] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced with each other. For the sake of brevity, they will not be described one by one.

[0019] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0020] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0021] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0022] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0023] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate in conjunction with numerous other general-purpose or specialized computing system environments or configurations. Examples of well-known terminal devices, computing systems, environments, and / or configurations suitable for use with terminal devices, computer systems, servers, and other electronic devices 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 personal computers, minicomputer systems, mainframe computer systems, and distributed cloud computing technology environments including any of the above.

[0024] 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. Generally, 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 a distributed cloud computing environment, where tasks are performed by remote processing devices linked via a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media, including storage devices.

[0025] Exemplary Methods Figure 1 This is a flow chart of a method for determining cross-line faults in an asynchronous power grid based on the standard deviation of differential current provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as Figure 1 As shown, the asynchronous power grid cross-line fault determination method 100 based on the differential current standard deviation includes the following steps: Step 101, obtaining a line differential current sampling value according to the sum of the fault currents at the beginning and end of the line of the collected fault waveform; Step 102, calculating the effective value of the line differential current according to the line differential current sampling value; Step 103, calculating the standard deviation of the effective value of the line differential current; Step 104 : Determine the fault type based on the standard deviation and pre-established cross-line fault identification criteria.

[0026] Specifically, the present invention addresses the problem that existing current differential protection and distance protection are not applicable and even refuse to operate when cross-line faults occur in asynchronous power grids, and proposes a new method of longitudinal protection for cross-line faults in asynchronous power grids based on the standard deviation of 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, and the response characteristics of the two system voltage sources with frequency difference are taken into account. The analytical expression of 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. The discrete degree of the effective value of the differential current is quantified, and 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 the present invention has a natural fault phase selection capability. The action phase of the protection is the fault phase, which can accurately identify the fault and cut off the fault part, which is beneficial to ensuring the reliability and safety of the power system.

[0027] like Figure 2 The figure shows a flow chart of the method of the present invention. The present invention proposes a method for cross-line fault longitudinal protection of an asynchronous power grid based on the standard deviation of differential current. The method comprises the following steps: 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. i dR As shown in the following formula: ,in i d is the line differential current sampling value (i.e. the sum of the fault currents at the beginning and end of the line), J is the number of sampling points in the data window.

[0028] Step 2: Based on the waveform characteristics of the differential current fault during a cross-line fault in an asynchronous power grid, a cross-line fault identification criterion is constructed. Specifically, the standard deviation of the differential current RMS value is calculated based on Equation (1). The standard deviation is used to characterize the fault current beat frequency characteristics and quantify the degree of dispersion of the differential current RMS value. The cross-line fault identification criterion shown in Equation (2) is constructed.

[0029] (1) Where, σ idR is the standard deviation of the differential current effective value, is the differential current effective value i dR The mean of N is the number of sampling points in the data window.

[0030] Step 3: Based on the fault identification criterion shown in formula (2), the fault identification is performed as follows. When the fault occurs in the zone, the differential current i dR is a time-varying quantity; for out-of-zone faults, i dR It is approximately a constant value and does not change with time. Therefore, the effective value of the fault time difference flow in the area i dR The standard deviation of the fault is greater than that of the fault outside the area.

[0031] (2) Where, σ set is the protection threshold, which 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. σ set is 0.01. If σ idR If equation (2) is satisfied, it is judged as an internal fault; otherwise, it is judged as an external fault.

[0032] Step 4: The protection proposed in this invention has a natural fault phase selection capability. The action phase of the protection is the fault phase, which can accurately identify the fault and remove the faulty part, which is beneficial to ensure the reliability and safety of the power system. The standard deviation of the differential current effective value is calculated using formula (1): σidR ,if σ idR If equation (2) is satisfied, it is determined to be an internal fault; otherwise, it is determined to be an external fault. If it is determined to be an internal fault, the operating phase is the faulty phase. If only one of the three-phase currents satisfies equation (2), it is determined to be a single-phase fault, and the faulty phase circuit breaker is tripped. If two or three of the three-phase currents satisfy equation (2), it is determined to be an interphase fault, and the three-phase circuit breaker is tripped.

[0033] Specifically, the present invention proposes a new pilot protection method based on the standard deviation of differential current for asynchronous power grid cross-line faults. The specific implementation method is as follows: 1. Extracting cross-line fault characteristics of asynchronous power grid The schematic diagram of the asynchronous power grid transmission line short circuit fault is shown in the attached figure. Figure 3 As shown in the figure, “System I” and “System II” represent two asynchronous power grid systems (voltage frequency is 50 Hz and 50.1 Hz respectively). F0~F4 represent different fault point locations. is the fault voltage, is the fault current. K Represents the phase to short-circuit point switch, and its different closing or opening combinations represent different types of cross-line faults. It is the fault point voltage, K g Indicates a grounding switch.

[0034] For cross-line ungrounded faults, K g disconnect, Not 0. Take Aa (A phase cross a phase fault) as an example for detailed theoretical derivation. Figure 3 middle K A 、 K a Close.

[0035] First, write the boundary relationship at the fault point of system I as follows: (3) Convert the phase component into sequence component to satisfy the following formula: (4) According to the previous formula, the attached Figure 4 The left part of the sequence network diagram shown is point m and n. Z I1 、 Z I2 and Z I0 are the three-sequence impedances of system I merged to the short-circuit point, Z II1 、Z II2 and Z II0 are the three-sequence impedances of system II merged to the short-circuit point, are the pre-fault voltages of the fault points of system I and system II respectively.

[0036] Write down the boundary relationship of the fault position of System II as follows: (5) Convert the phase component into sequence component to satisfy the following formula: (6) Similarly, based on formula (6), the following Figure 4 The right part of points m and n in the sequence network diagram shown.

[0037] Fault voltage in the sequence diagram of system I and II Therefore, the composite sequence network diagrams of system I and II are combined into an improved sequence network diagram, as shown in the attached figure. Figure 4 .

[0038] According to the attached Figure 4 , using the superposition theorem, we can get the positive sequence current It can be expressed as the following formula: (7) Where, (8) In addition, it can be seen from the figure that (9) For system I, the differential current of the fault line can be expressed as follows: (10) Similarly, by the Figure 4 It can be seen that the positive sequence current can be expressed as follows: (11) In addition, it can be seen from the figure that (12) For system II, the differential current of the fault line can be expressed as follows: (13) Equations (10) and (13) show that after a cross-line ungrounded fault occurs, the differential current of the faulted line for both System I and System II contains the responses of two voltage sources with frequencies of 50 Hz and 50.1 Hz. Due to the frequency difference, the superposition of two sinusoidal signals with slightly different frequencies produces a periodically varying amplitude phenomenon, resulting in a beat frequency phenomenon. In other words, at this point, the differential current after the fault exhibits a beat frequency characteristic, with the amplitude varying periodically.

[0039] Take A-bc (A phase across bc two-phase ungrounded short circuit) as an example to illustrate the characteristics of single-phase across two-phase ungrounded fault. Figure 3 middle K A 、 K b 、 K c closure.

[0040] At this time, the sequence components in system I still satisfy equation (4), and the composite sequence network diagram is the same as the attached Figure 4 The left ends of the midpoints m and n are the same.

[0041] Write down the boundary relationship of the fault position of System II as follows: (14) Convert the phase component into sequence component to satisfy the following formula: (15) According to the previous formula, the attached Figure 4 The right part of points m and n in the sequence network diagram shown.

[0042] The fault voltages in the sequence network diagrams of systems I and II are the same, so the composite sequence network diagrams of systems I and II are combined into an improved sequence network diagram, as shown in the attached figure. Figure 5 .

[0043] By the attached Figure 5 It can be seen that the positive sequence current can be expressed as follows: (16) Where, (17) (18) It can be obtained that for system I, the differential current of the fault line can be expressed as follows: (19) It can be seen from formula (19) that after a cross-line ungrounded fault occurs, for system I, the differential current of the fault line is composed of two sinusoidal signals with slightly different frequencies superimposed on each other. The differential current presents a beat frequency characteristic and the amplitude changes periodically.

[0044] Similarly, for System II, it can be deduced that the differential current of the fault line exhibits a beat frequency characteristic in response to two voltage sources with frequencies of 50 Hz and 50.1 Hz, and the amplitude varies periodically. Due to limited space, the specific derivation process is not described in detail.

[0045] Take BC-bc (BC phase cross bc ungrounded fault) as an example to analyze the characteristics of two-phase cross two-phase ungrounded fault. Figure 3 middle K B 、 K C 、 K b 、 K c closure.

[0046] Write down the boundary relationship of the fault position of system I as follows: (20) Convert the phase component into sequence component to satisfy the following formula: (twenty one) According to the previous formula, the attached Figure 6 The left part of points m and n in the sequence network diagram shown.

[0047] Similar to System I, the boundary conditions of the sequence components at the fault point of System II are listed as follows: (twenty two) Similarly, based on the boundary conditions shown in formula (22), draw the attached Figure 6 Point m and the right end of n.

[0048] The fault voltages in the sequence network diagrams of systems I and II are the same, so the composite sequence network diagrams of systems I and II are combined into an improved sequence network diagram, as shown in the attached figure. Figure 6 .

[0049] Similar to the theoretical derivation for the A-bc cross-line fault, it can be inferred that for Systems I and II, the differential current in the faulted line exhibits a beat frequency characteristic in response to two voltage sources at 50 Hz and 50.1 Hz, with the amplitude varying periodically. Due to limited space, a detailed derivation is not provided here. Similar derivations can be used for other types of cross-line ungrounded faults, so these will not be detailed here.

[0050] In summary, based on the improved composite sequence network diagram, we can derive expressions for fault currents under different fault types. This shows 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 currents of each system are affected by another system parameter, and ungrounded faults also contain a zero-sequence component in the fault current.

[0051] For the fault outside the asynchronous power grid, take the fault outside the F2 zone of system I as an example to deduce the detailed fault characteristics. The equivalent fault analysis circuit is shown in the attached figure. Figure 7 As shown in the figure, i M and i N Respectively represent the fault current on both sides of the line, i MC and i NC Represent the distributed capacitance current on the M side and the N side respectively, u M and u N Respectively represent the fault voltages on both sides of the line.

[0052] When an out-of-zone 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: (twenty three) Due to the distributed characteristics of the capacitance and the uniform distribution of the voltage along the entire line, the distributed capacitance current of the line satisfies the following equation: (twenty four) Therefore, when an out-of-zone fault occurs, the line differential current can be expressed as shown below: (25) From formula (25), we can see that since the voltage source is a power frequency sinusoidal quantity, the line differential current obtained after differentiation is a power frequency waveform, that is, when an out-of-zone fault occurs, the differential current presents a sine (or cosine) waveform, and the amplitude of the differential current effective value remains unchanged.

[0053] When a fault outside the F1 zone occurs in system I or a fault outside the F3 or F4 zone occurs in system II, the fault characteristics are similar to the above inferences and will not be repeated here.

[0054] In summary, when an ungrounded cross-line fault occurs within a zone, the line differential current is composed of two sinusoidal signals with slightly different frequencies superimposed on each other, exhibiting a beat-frequency characteristic and periodic amplitude variations. During an out-of-zone fault, the line differential current exhibits a single sine (or cosine) waveform, with the effective value of the differential current remaining unchanged. Therefore, the present invention constructs a cross-line fault protection criterion for asynchronous power grids based on these differences in fault characteristics.

[0055] 2. Construct cross-line fault identification criteria In mathematical statistics, the standard deviation can well reflect the sign variability of the data population. Therefore, the present invention uses the standard deviation to characterize the degree of dispersion of the differential current effective value, as shown in the following formula (26): (26) Where, σ idR is the standard deviation of the differential current effective value, is the differential current effective value i dR The mean of N is the number of sampling points in the data window.

[0056] When a fault occurs in the area, i dR is a time-varying quantity, and for out-of-zone faults, i dR It is approximately a constant value and does not change with time. Therefore, the effective value of the fault time difference flow in the area i dR The standard deviation of is greater than the standard deviation of the fault outside the zone. Therefore, the fault identification criterion shown in formula (27) is constructed: (27) Where, σ set is the protection threshold, which should be greater than the standard deviation of the maximum differential current effective value that may occur when there is a fault outside the zone. σ set is 0.01. If σ idR If equation (27) is satisfied, it is judged as an internal fault; otherwise, it is judged as an external fault.

[0057] 3. Fault phase selection and protection logic The protection proposed in this paper has a natural fault phase selection capability. The action phase of this protection is the fault phase. It can accurately identify the fault and cut off the faulty part, which is beneficial to ensure the reliability and safety of the power system.

[0058] Calculate the standard deviation of the differential current effective value using formula (26) σ idR ,if σ idR If equation (27) is satisfied, it is determined to be an internal fault; otherwise, it is determined to be an external fault. If it is determined to be an internal fault, the operating phase is the faulty phase. If it is determined to be a single-phase fault, the faulty phase circuit breaker is tripped; if it is determined to be an interphase fault, the three-phase circuit breaker is tripped.

[0059] 4. Simulation Verification The results of fault identification according to the method of the present invention are shown in the attached figure. Figure 8 、 9 , 10, 11, 12 and 13, it can be seen that the proposed protection criterion can reliably identify faults inside and outside the zone.

[0060] Therefore, the present invention addresses the problem that existing AC protection is not applicable and even refuses to operate when cross-line faults occur in asynchronous power grids, and proposes a new longitudinal protection method based on the standard deviation of differential current. This method can fully utilize the waveform characteristics of the differential current fault generated when a cross-line fault occurs, and accurately and reliably distinguish between faults inside and outside the zone. In addition, the protection method proposed in the present invention has a natural fault phase selection capability, can accurately identify faults and cut off the faulty part, which is beneficial to ensuring the reliability and safety of the power system. The invention is based on the analysis and calculation of actual engineering model data, and the protection principle is well-founded. It can reliably distinguish faults inside and outside the zone, meet engineering design requirements, and can be promoted and applied in 220kV and 500kV AC asynchronous power grids.

[0061] Exemplary devices Figure 14 FIG. 1 is a schematic diagram of a device for determining cross-line faults in an asynchronous power grid based on the standard deviation of differential currents according to an exemplary embodiment of the present invention. Figure 14 As shown, the apparatus 1400 includes: An obtaining module 1410 is configured to obtain a line differential current sampling value based on the sum of the fault currents at the beginning and end of the line of the acquired fault waveform; A first calculation module 1420 is configured to calculate an effective value of a line differential current according to a line differential current sampling value; The second calculation module 1430 is used to calculate the standard deviation of the effective value of the line differential current; The determination module 14140 is used to determine the fault type according to the standard deviation and the pre-established cross-line fault identification criteria.

[0062] Exemplary electronic devices Figure 15 This is the structure of an electronic device provided by an exemplary embodiment of the present invention. Figure 15 As shown, the electronic device 150 includes one or more processors 151 and a memory 152 .

[0063] The processor 151 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0064] The 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), a hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 151 may execute the program instructions to implement the software program methods and / or other desired functions of the various embodiments of the present invention described above. In one example, the electronic device may further include an input device 153 and an output device 154, which are interconnected via a bus system and / or other form of connection mechanism (not shown).

[0065] In addition, the input device 153 may also include, for example, a keyboard, a mouse, and the like.

[0066] The output device 154 can output various information to the outside, and can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto.

[0067] Of course, to simplify, Figure 15 Only some of the components related to the present invention in the electronic device are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, the electronic device may further include any other appropriate components according to specific application conditions.

[0068] Exemplary computer program products and computer-readable storage media In addition to the above-mentioned methods and devices, an embodiment of the present invention may also be a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to perform the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

[0069] The computer program product may be written in any combination of one or more programming languages ​​to implement the operations of embodiments of the present invention, including object-oriented programming languages ​​such as Java, C++, and conventional procedural programming languages ​​such as C or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's computing device, as a stand-alone 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.

[0070] In addition, an embodiment of the present invention may also be a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

[0071] The computer-readable storage medium may be any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium may include, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, system, or device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0072] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in the present invention are merely illustrative and non-limiting, and should not be construed as necessarily possessed by each embodiment of the present invention. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, and are not intended to be limiting. These details do not necessarily limit the present invention to being implemented using these specific details.

[0073] Each embodiment in this specification is described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. Reference can be made to the descriptions of the identical or similar parts between the various embodiments. For system embodiments, since they are essentially identical to the method embodiments, their description is relatively simple. For relevant parts, refer to the descriptions of the method embodiments.

[0074] The block diagrams of the devices, systems, equipment, and systems involved in the present 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 will be appreciated by those skilled in the art, these devices, systems, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0075] The method and system of the present invention may be implemented in many ways. For example, the method and system of the present invention may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above, unless otherwise specified. In addition, in some embodiments, the present invention may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present invention. Thus, the present invention also covers recording media that store programs for executing the method according to the present invention.

[0076] It should also be noted that, in the system, device and method of the present invention, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent schemes of the present invention. The above description of the disclosed aspects is provided to enable any technician in this field to make or use the present invention. Various modifications to these aspects will be very obvious to those skilled in the art, and the general principles defined here can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown here, but according to the widest scope consistent with the principles disclosed here and novel features.

[0077] The above description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example 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 differential current standard deviation, characterized in that: include: The line differential current sampling value is obtained according to the sum of the fault currents at the beginning and end of the line of the collected fault waveform; Calculating the effective value of the line differential current according to the line differential current sampling value; Calculating the standard deviation of the effective value of the line differential current; The fault type is determined based on the standard deviation and a pre-established cross-line fault identification criterion.

2. The method according to claim 1, characterized in that The calculation expression of the effective value of the line differential current is: Where, i d is the line differential current sampling value, J is the number of sampling points in the data window.

3. The method according to claim 1, characterized in that The calculation expression of the standard deviation of the effective value of the line differential current is: Where, σ idR is the standard deviation of the effective value of the line differential current, is the effective value of differential current i dR The mean of N is the number of sampling points in the data window.

4. The method according to claim 1, wherein The expression of the pre-built cross-line fault identification criterion is: Where, σ idR is the standard deviation of the effective value of the line differential current, σ set is the protection threshold.

5. The method according to claim 1, wherein Also includes: According to the improved composite sequence network diagram of the asynchronous power grid, the fault current expressions under different fault types are obtained; According to the fault current expressions under different fault types, the asynchronous power grid cross-line fault characteristics are extracted, wherein the asynchronous power grid cross-line fault characteristics are the effective values ​​of the line differential currents.

6. A device for identifying cross-line faults in an asynchronous power grid based on the standard deviation of differential current, characterized in that: include: An obtaining module is used to obtain a line differential current sampling value according to the sum of the fault currents at the beginning and end of the line of the collected fault waveform; A first calculation module is used to calculate the effective value of the line differential current according to the line differential current sampling value; A second calculation module is used to calculate the standard deviation of the effective value of the line differential current; The determination module is used to determine the fault type according to the standard deviation and a pre-established cross-line fault identification criterion.

7. The device according to claim 6, characterized in that Also includes: A construction module is used to obtain fault current expressions under different fault types according to the improved composite sequence network diagram of the constructed asynchronous power grid; The extraction module is used to extract the asynchronous power grid cross-line fault characteristics according to the fault current expressions under different fault types, wherein the asynchronous power grid cross-line fault characteristics are the effective values ​​of the line differential currents.

8. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 5.

9. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1 to 5.

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