A method and system for identifying permanent faults in distribution lines with sequential overlap

Abstract

The present invention discloses a method and system for identifying permanent faults of distribution lines with sequential reclosing, which belongs to the technical field of distribution network fault identification. The method comprises: determining the reclosing sequence based on the fault phase selection result after the three-phase tripping of the distribution line; for symmetrical faults, reclosing one phase according to the reclosing sequence, and calculating the symmetrical fault transition resistance value; for asymmetrical faults, obtaining the power frequency voltage and power frequency current on the load side of the phase switch that recloses twice, determining the asymmetrical fault transition resistance value, and performing fault identification according to the symmetrical fault transition resistance value and the asymmetrical fault transition resistance value. The method solves the technical problems that the identification sensitivity of permanent grounding faults is not high and the fault nature identification is difficult.

Description

Background Art

[0002] As a key link in the power system that directly connects with users, the fault handling of the distribution network directly affects the reliability of power supply. On-site statistics show that most faults in the overhead lines of the distribution network are transient faults. Distribution lines generally use three-phase automatic reclosing to improve power supply reliability, but blindly reclosing on permanent faults will cause serious secondary shocks to the system, endanger system safety, and affect the power supply of healthy sections upstream and downstream of the fault point. In addition, it is generally believed that cable lines will not have transient faults, so they are usually not equipped with automatic reclosing. However, with the annual increase in the cableization rate in the distribution network, the reclosing of cable-overhead lines can improve the reliability of power supply by considering the cable laying method and the operating status of the cable line. Actual operation data show that the success rate of 10kV cable reclosing is higher than 65%. The main reason is that most of the cable tripping is caused by non-body faults such as distribution room equipment and cable taps. Giving up reclosing will affect the reliability of power supply. If adaptive reclosing technology is used, cable or cable-overhead hybrid lines can also be reclosed, which can further improve the reliability of power supply.

[0003] The key to adaptive reclosing technology is the identification of permanent faults. At present, domestic and foreign scholars have conducted a lot of research on adaptive reclosing technology for high-voltage transmission lines. Single-phase adaptive reclosing mainly identifies the nature of faults based on residual electrical characteristics after tripping. The research on three-phase adaptive reclosing is mainly aimed at transmission lines with shunt reactors, making full use of the discharge characteristics of line capacitance and shunt reactors after three-phase tripping to identify the nature of faults. Distribution networks usually use three-phase reclosing. After a fault occurs, the single-end circuit breaker trips and the three phases on the load side are connected through a transformer. Due to the low voltage level of the distribution network, small line phase capacitance, weak coupling, and rapid attenuation of electrical quantities after three-phase tripping, it is difficult to identify the nature of the fault, so the permanent fault identification method of the transmission network is not applicable to distribution lines. The detection-type permanent fault identification method using partial phase overlap of phase switches has been widely studied. For example, the patents "Asymmetric fault location and isolation method and system for distribution network based on adaptive reclosing" and "A permanent fault identification method and system for distribution network based on reclosing detection" propose permanent fault identification methods that first reclose one or two phases for different types of faults. However, both are easily affected by transition resistance, and the sensitivity of permanent ground fault identification is not high. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for identifying permanent faults in distribution lines with sequential overlap in view of the deficiencies in the above-mentioned prior art. The method utilizes the difference between the magnitude of the transition resistance calculated from the voltage and current on the load side after one phase of the phase-splitting switch is closed and the set value to distinguish between permanent and transient faults, and is used to solve the technical problems of low sensitivity in identifying permanent grounding faults and difficulty in identifying the nature of the fault.

[0005] The present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for identifying permanent faults in a distribution line with sequential overlap, comprising the following steps:

[0007] Determine the reclosing sequence based on the fault phase selection result after the three-phase tripping of the distribution line;

[0008] When the fault phase selection result is a symmetrical fault, one phase is reclosed according to the reclosing sequence, and the symmetrical fault transition resistance value is determined based on the load side voltage and load side current of the switch after reclosing one phase;

[0009] When the fault phase selection result is an asymmetric fault, two phases are reclosed according to the reclosing sequence, and the asymmetric fault transition resistance value is determined based on the power frequency voltage and power frequency current on the load side of the split-phase switch after two reclosings;

[0010] When the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value, the distribution line fault is determined to be a transient fault. When the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value, the distribution line fault is determined to be a permanent fault.

[0011] Preferably, the reclosing sequence is as follows:

[0012] In case of a single-phase grounding fault in an asymmetric fault, a fault phase is sequentially reclosed, the fault phase is tripped, and then a non-fault phase is reclosed;

[0013] In case of a two-phase grounding fault in an asymmetric fault, one of the faulty phases is sequentially reclosed, the faulty phase is tripped, and then a non-faulty phase is reclosed;

[0014] In case of symmetrical fault, close any faulty phase.

[0015] Preferably, the symmetrical fault transition resistance value The calculation is as follows:

[0016]

[0017] in, is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground, They are the three-phase voltages A, B, and C on the load side of the split-phase switch. is the coincident phase current that coincides with phase A.

[0018] Preferably, the asymmetric fault transition resistance value is determined as follows:

[0019] The power frequency voltage and power frequency current on the load side of the phase-splitting switch that overlap twice are obtained, and the sum of the three-phase voltages on the load side of the phase-splitting switch and the sum of the fault phase voltages on the load side of the phase-splitting switch are obtained. The asymmetric fault transition resistance value is determined based on the sum of the three-phase voltages on the load side of the phase-splitting switch and the sum of the fault phase voltages on the load side of the phase-splitting switch.

[0020] Preferably, the asymmetric fault transition resistance value The calculation is as follows:

[0021]

[0022] in, and are the sum of the three-phase voltages on the load side of the first and second coincidences, and are the phase currents on the load side of the first and second coincidences, respectively. is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground.

[0023] Preferably, the sum of the three-phase voltages on the load side of the phase switch is The calculation is as follows:

[0024]

[0025] in, They are the A, B, and C three-phase voltages on the load side of the phase switch.

[0026] Preferably, the sum of the fault phase voltages on the load side of the phase switch is for:

[0027]

[0028] in, They are the A, B, and C three-phase voltages on the load side of the phase switch.

[0029] In a second aspect, an embodiment of the present invention provides a system for identifying permanent faults of distribution lines with sequential overlap, comprising:

[0030] A phase selection module determines the reclosing sequence based on the fault phase selection results after the three-phase tripping of the distribution line;

[0031] The first identification module, when the fault phase selection result is a symmetrical fault, recloses one phase according to the reclosing sequence, and determines the symmetrical fault transition resistance value based on the load side voltage and load side current of the switch after reclosing one phase;

[0032] The second identification module, when the fault phase selection result is an asymmetric fault, recloses two phases according to the reclosing sequence, and determines the asymmetric fault transition resistance value based on the power frequency voltage and power frequency current on the load side of the phase switch that recloses twice;

[0033] The judgment module determines that the distribution line fault is a transient fault when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value; and determines that the distribution line fault is a permanent fault when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value.

[0034] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for identifying permanent faults of distribution lines with sequential overlap when executing the computer program.

[0035] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for identifying permanent faults of distribution lines with sequential overlap.

[0036] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for identifying permanent faults of distribution lines with sequential overlap when executing the computer program.

[0037] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the method for identifying permanent faults of distribution lines with sequential overlap.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] The present invention provides a method for identifying permanent faults of distribution lines with sequential reclosing. According to the phase selection result, the reclosing order of the phase switch is determined. Only one phase is reclosed. The current of the reclosed phase is small and there will be no serious current shock. The transition resistance value is calculated based on the power frequency voltage and power frequency current data on the load side of the phase switch after reclosing. Since the transition resistance value calculated for the transient fault is significantly different from the transition resistance value calculated for the permanent fault, the fault nature characteristics are significantly different. The method of the present invention has high sensitivity and is not affected by load changes. It can greatly improve the problem of reduced sensitivity of identification as the transition resistance of the distribution network grounding fault increases.

[0040] Furthermore, the method only recloses a single phase according to a preset reclosing sequence, and the reclosing phase current is less than the maximum load current, so there will be no serious fault current impact.

[0041] Furthermore, after analysis, it was found that an asymmetric fault requires the sequential reclosing of two phases, and the transition resistance value is calculated based on the voltage and current data on the load side of the phase switch after the two reclosings; a symmetrical fault only requires the reclosing of one phase to calculate the transition resistance value, which makes the operation steps simple and convenient for practical application.

[0042] Furthermore, when the transition resistance value is greater than the set value, it is a transient fault, and when the transition resistance value is less than or equal to the set value, it is a permanent fault. The nature of the fault can be obtained by simply comparing the calculated transition resistance value with the set value, which is convenient for practical application.

[0043] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0044] In summary, the permanent fault identification method of the distribution network of the present invention only needs to overlap one phase, the current of the overlapped phase is small, there will be no serious fault current impact, and it can solve the problem that the algorithm discrimination sensitivity decreases as the transition resistance of the permanent grounding fault in the distribution network increases.

[0045] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 This is a flow chart of a method for determining the nature of a fault based on parameter identification according to the present invention;

[0048] Figure 2 This is a schematic diagram of a 10kV AC distribution network model;

[0049] Figure 3 This is a schematic diagram of grounding fault in an ungrounded system;

[0050] Figure 4 This is a schematic diagram of grounding fault in the arc suppression coil grounding system;

[0051] Figure 5 A schematic diagram of a computer device provided for an embodiment of the present invention;

[0052] Figure 6 A block diagram of an electronic device provided by an embodiment of the present invention.

[0053] Among them, 60. computer equipment; 61. processor; 62. memory; 63. computer program; 600. electronic device; 610. processing unit; 620. storage unit; 6201. random access storage unit; 6202. cache storage unit; 6203. read-only storage unit; 6204. program / utility; 6205. program module; 630. bus; 640. display unit; 650. input / output interface; 660. network adapter; 700. external device. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0056] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0057] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0058] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0059] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0060] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0061] The present invention provides a method for identifying permanent faults in a distribution line with sequential overlap. On the premise that a phase-splitting switch is used in the distribution line and the phase selection result is known, the three-phase voltage and current information on the load side of the phase-splitting switch is used to identify permanent faults.

[0062] Example 1

[0063] See also Figure 1 The present invention provides a method for identifying permanent faults of distribution lines with sequential overlap, comprising the following steps:

[0064] S1, determine the reclosing sequence based on the fault phase selection result after the three-phase tripping of the distribution line;

[0065] Based on the phase selection result, before the three-phase split switch is closed, one or two phases are closed sequentially according to the preset closing sequence; the specific steps are as follows:

[0066] In case of a single-phase grounding fault, the fault phase is reclosed in sequence, the phase is tripped, and then one of the non-fault phases is reclosed. That is, in case of an AG fault, phases A and B are reclosed in sequence, in case of a BG fault, phases B and C are reclosed in sequence, and in case of a CG fault, phases C and A are reclosed in sequence.

[0067] In case of two-phase grounding fault, one of the faulty phases is reclosed in sequence, the phase is tripped, and then a non-faulty phase is reclosed. That is, in case of ABG fault, phases A and C are reclosed in sequence, in case of BCG fault, phases B and A are reclosed in sequence, and in case of CAG fault, phases C and B are reclosed in sequence.

[0068] In case of a three-phase grounding fault, only one phase needs to be reclosed, and phase A can be reclosed.

[0069] Among them, AG fault means the fault between phase A and ground, that is, single-phase grounding fault. Phase A is reclosed first, phase A is tripped, and then phase B is reclosed;

[0070] BG fault indicates a fault between phase B and ground, i.e. a single-phase grounding fault. First, phase B is reclosed, then phase B is disconnected, and then phase C is reclosed.

[0071] CG fault, indicating a fault between phase C and ground, i.e., a single-phase grounding fault, first reclose phase C, then open phase C, and then reclose phase A;

[0072] ABG fault, indicating a fault between phase A, phase B and ground, i.e. a two-phase grounding fault, first reclose phase A, then disconnect phase A, and then reclose phase C;

[0073] BCG fault indicates a fault between phase B, phase C and ground, i.e. a two-phase grounding fault. First, phase B is reclosed, then phase B is tripped, and then phase A is reclosed;

[0074] CAG fault indicates a fault between phase C, phase A and ground, i.e. a two-phase grounding fault. Phase C is reclosed first, then phase C is tripped, and then phase B is reclosed.

[0075] An ABCG fault indicates a fault between phases A, B, C and the ground, that is, a three-phase grounding fault, with phase A being overlapped.

[0076] S2. For single-phase grounding fault and two-phase grounding fault, i.e. asymmetric fault, the power frequency voltage and power frequency current on the load side of the phase switch that overlap twice are selected to obtain the sum of the three-phase voltage on the load side of the phase switch and the sum of the fault phase voltage on the load side of the phase switch. The asymmetric fault transition resistance value is finally calculated based on the power frequency voltage and power frequency current on the load side of the phase switch that overlap twice. When the asymmetric fault transition resistance value is When it is greater than the set value, it is a transient fault. When the transition resistance value of an asymmetric fault is When it is less than or equal to the set value, it is a permanent fault;

[0077] The sum of the three-phase voltages on the load side of the phase switch is calculated as follows:

[0078] (1)

[0079] in, is the sum of the three-phase voltages on the load side of the phase switch, is the phase voltage on the load side of the switch.

[0080] The sum of the fault phase voltages and the coincident phase current on the load side of the split-phase switches of different fault phases is:

[0081] (2)

[0082] in, is the sum of the voltages of the fault phases on the load side of the phase splitting switch, is the coincident phase current.

[0083] Asymmetric fault transition resistance The calculation is as follows:

[0084] (3)

[0085] in, and are the sum of the three-phase voltages on the load side of the first and second coincidences, and are the phase currents on the load side of the first and second coincidences, respectively. is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground.

[0086] S3. For a three-phase grounding fault, that is, a symmetrical fault, only one phase needs to be overlapped. The symmetrical fault transition resistance value is calculated based on the obtained switch load side voltage and load side current. When the symmetrical fault transition resistance value is greater than the set value, the distribution line fault is determined to be a transient fault. When the symmetrical fault transition resistance value is less than or equal to the set value, the distribution line fault is determined to be a permanent fault.

[0087] Symmetrical fault transition resistance The calculation is as follows:

[0088] (4)

[0089] in, is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground, They are the three-phase voltages A, B, and C on the load side of the split-phase switch. is the coincident phase current that coincides with phase A.

[0090] When the calculated symmetrical fault transition resistance value When it is greater than the set value, it is a transient fault, as shown in formula (5).

[0091] (5)

[0092] in, is the setting value of the transition resistance, which is 4000Ω.

[0093] When the calculated symmetrical fault transition resistance value is less than or equal to the set value, it is a permanent fault.

[0094] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0095] Example 2

[0096] The present invention provides a permanent fault identification system for a distribution line with sequential overlap, which can be used to implement the above-mentioned permanent fault identification method for a distribution line with sequential overlap. Specifically, the permanent fault identification system for a distribution line with sequential overlap includes a phase selection module, a first identification module, a second identification module and a judgment module.

[0097] Among them, the phase selection module determines the reclosing sequence based on the fault phase selection result after the three-phase tripping of the distribution line;

[0098] In case of single-phase grounding fault, the fault phase is reclosed in sequence, the phase is tripped, and then one of the non-fault phases is reclosed;

[0099] In case of two-phase grounding fault, one of the faulty phases is reclosed in sequence, the phase is tripped, and then a non-faulty phase is reclosed;

[0100] In the event of a three-phase ground fault, only one phase is reclosed.

[0101] The first identification module, when the fault phase selection result is a symmetrical fault, recloses one phase according to the reclosing sequence, and determines the symmetrical fault transition resistance value based on the obtained load side voltage and load side current of the switch;

[0102] For symmetrical faults, only one phase is overlapped, and the symmetrical fault transition resistance value is calculated. The fault is identified based on the symmetrical fault transition resistance value. When the symmetrical fault transition resistance value is greater than the setting value, it is a transient fault. When the symmetrical fault transition resistance value is less than or equal to the setting value, it is a permanent fault.

[0103] The symmetrical fault transition resistance value is calculated as follows:

[0104]

[0105] in, is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground, They are the three-phase voltages A, B, and C on the load side of the split-phase switch. is the coincident phase current that coincides with phase A.

[0106] The second identification module, when the fault phase selection result is an asymmetric fault, recloses two phases according to the reclosing sequence, and determines the asymmetric fault transition resistance value based on the power frequency voltage and power frequency current on the load side of the phase switch that recloses twice;

[0107] For asymmetric faults, the power frequency voltage and power frequency current on the load side of the phase switch that overlap twice are selected to obtain the sum of the three-phase voltages on the load side of the phase switch and the sum of the fault phase voltages on the load side of the phase switch. Finally, the asymmetric fault transition resistance is calculated, and the fault is identified based on the asymmetric fault transition resistance value. When the asymmetric fault transition resistance value is greater than the set value, it is a transient fault. When the asymmetric fault transition resistance value is less than or equal to the set value, it is a permanent fault.

[0108] Asymmetric fault transition resistance The calculation is as follows:

[0109]

[0110] in, and are the sum of the three-phase voltages on the load side of the first and second coincidences, and are the phase currents on the load side of the first and second coincidences, respectively. is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground.

[0111] The judgment module determines that the distribution line fault is a transient fault when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value; and determines that the distribution line fault is a permanent fault when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value.

[0112] Example 3

[0113] The present invention provides a terminal device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the method for identifying permanent faults of distribution lines with sequential overlap, including:

[0114] The reclosing sequence is determined based on the fault phase selection result after the three-phase tripping of the distribution line; when the fault phase selection result is a symmetrical fault, one phase is reclosed according to the reclosing sequence, and the symmetrical fault transition resistance value is determined based on the obtained load-side voltage and load-side current of the switch; when the fault phase selection result is an asymmetrical fault, two of the phases are reclosed according to the reclosing sequence, and the asymmetrical fault transition resistance value is determined based on the power frequency voltage and power frequency current on the load side of the phase switch that are reclosed twice; when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value, the distribution line fault is determined to be a transient fault, and when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value, the distribution line fault is determined to be a permanent fault.

[0115] See also Figure 5, the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the method for identifying permanent faults of distribution lines with overlapping sequences in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the system for identifying permanent faults of distribution lines with overlapping sequences in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0116] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 5 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0117] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0118] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0119] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0120] See also Figure 6 The terminal device is an electronic device 600, which is in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0121] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0122] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access storage unit 6201 and / or a cache storage unit 6202 , and may further include a read-only storage unit 6203 .

[0123] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0124] Bus 630 may represent one or more of several types of bus structures, including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0125] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., local area networks, wide area networks, and / or public networks, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms, etc.

[0126] Example 4

[0127] The present invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It is understandable that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device, and can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that more specific examples (non-exhaustive list) of the computer-readable storage medium here include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory, a read-only memory, an erasable programmable read-only memory, an optical fiber, a portable compact disk read-only memory, an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0128] Computer readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program code. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate or transmit a program for use by or in conjunction with an instruction execution system, device or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, radio frequency, etc., or any suitable combination of the above.

[0129] Program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network or a wide area network, or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0130] One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the method for identifying permanent faults of distribution lines with sequential overlap in the above embodiment; one or more instructions in the computer-readable storage medium may be loaded and executed by a processor as follows:

[0131] The reclosing sequence is determined based on the fault phase selection result after the three-phase tripping of the distribution line; when the fault phase selection result is a symmetrical fault, one phase is reclosed according to the reclosing sequence, and the symmetrical fault transition resistance value is determined based on the obtained load-side voltage and load-side current of the switch; when the fault phase selection result is an asymmetrical fault, two of the phases are reclosed according to the reclosing sequence, and the asymmetrical fault transition resistance value is determined based on the power frequency voltage and power frequency current on the load side of the phase switch that are reclosed twice; when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value, the distribution line fault is determined to be a transient fault, and when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value, the distribution line fault is determined to be a permanent fault.

[0132] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0133] Simulation Verification

[0134] In order to verify the correctness of the proposed permanent fault identification method, a 10 kV distribution network is taken as an example to establish the following in the electromagnetic transient simulation software (Power Systems Computer Aided Design, PSCAD): Figure 2 In the 10kV distribution network model shown in the figure, the grid-side power supply is connected to 5 lines through the busbar. The grid-side power supply includes the grid-side power supply G 1 and grid-side power supply G 2. The busbar connection has a neutral point to ground impedance Z N .

[0135] Among them, line 1 includes three branches and is divided into L 1 section, L 6 sections, L 7 sections, L 8 sections, L Section 9, the loads of the three branches are S 1. S 2 and S 3;

[0136] Line 2 consists of three branches and is divided into L 2 sections, L 10 Section, L 11 Section, L 12 Section, L 13 The loads of the three branches are S 4. S 5 and S 6;

[0137] Line 3 consists of three branches and is divided into L 3 sections,L 14 Section, L 15 Section, L 16 Section, L 17 The loads of the three branches are S 7. S 8 and S 9;

[0138] Line 4 consists of three branches and is divided into L 4 sections, L 18 Section, L 19 Section, L 20 Section, L 21 The loads of the three branches are S 10 , S 11 and S 12 ;

[0139] Line 5 division L Section 5, the load of line 5 is S 13 .

[0140] exist L A phase-splitting switch is installed at the head end of section 1. L Section 1 gives faults of different fault types and transition resistances;

[0141] For different faults, the reclosing sequence is set in advance, and the transition resistance value is calculated based on the voltage and current data on the load side of the switch obtained during reclosing. The calculated transition resistance value is compared with the set value (the set value is 4000Ω during simulation) to verify the accuracy of the theoretical analysis and permanent fault identification criteria. Neutral point to ground impedance Z N Different values ​​represent different grounding methods. The line parameters are as follows:

[0142] 1) Positive sequence parameters:

[0143]

[0144] 2) Zero sequence parameters:

[0145]

[0146] in, is the positive sequence resistance, is the positive sequence reactance, is the positive sequence conductance, is the zero-sequence resistance, is the zero-sequence reactance, is the zero-sequence conductance.

[0147] When this method is used to identify permanent faults, the criteria used depend on the results of the previous fault phase selection. L Faults of different types and transition resistances are set in section 1 to verify the accuracy of the permanent fault identification criteria under different neutral point grounding methods.

[0148] (1) Ungrounded system

[0149] For ungrounded neutral point systems ( Z N tends to infinity), the length of each segment is:

[0150] L 1= L 10 =0.1km

[0151] L 2= L 15 = L 19 =0.2km

[0152] L 3= L 4= L 6= L 9= L 13 = L 16 = L 20 =0.3km

[0153] L 5= L 7= L 11 = L 14 = L 17 = L 18 = L 21 =0.5km

[0154] L 8= L 12 =0.8km.

[0155] The load capacity is:

[0156] S 1=S 8= S 12 = S 13 =1MV·A

[0157] S 2= S 3= S 9=2MV·A

[0158] S 4= S 10 =0.5MV·A

[0159] S 5=0.7MV·A

[0160] S 6=0.8MV·A

[0161] S 7= S 11 =0.1MV·A

[0162] The power factor is 0.85.

[0163] In a system with an ungrounded neutral point, L When different transition resistances and different types of ground faults occur in the 1st section, the transition resistance values ​​of permanent faults and transient faults are calculated by sequential coincidence. Figure 3 shown.

[0164] Depend on Figure 3 It can be seen that the transition resistance value can be accurately calculated using the parameter identification algorithm in the ungrounded system, and the transition resistance value during the transient fault is much larger than the transition resistance value during the permanent fault. This feature is obvious, and the parameter identification algorithm can be used to distinguish permanent grounding faults.

[0165] (2) Arc suppression coil grounding system

[0166] For the arc suppression coil grounding system (compensation degree is 8%), the length of each section is:

[0167] L 1= L 8= L 15 = L 19 =2km

[0168] L 2=L 16 = L 20 =1km

[0169] L 3=L 4= L 6=0.5km

[0170] L 5=4km

[0171] L 7= L 12 = L 17 = L 21 =3km

[0172] L 8= L 15 = L 19 =2km

[0173] L 9= L 13 = L 14 = L 18 =2.5km

[0174] L 10 =1.5km

[0175] L 11 =5km.

[0176] In the load and neutral point ungrounded system, arc suppression coil grounded system, section L When different transition resistances and different types of ground faults occur in 1, the transition resistance values ​​of permanent faults and transient faults are calculated by sequential coincidence. Figure 4 shown.

[0177] Depend on Figure 4 It can be seen that the transition resistance value can also be accurately calculated in the arc suppression coil grounding system, and the transition resistance value during instantaneous faults is much larger than the transition resistance value during permanent faults. This feature is obvious, and the parameter identification algorithm can be used to distinguish permanent grounding faults, which is sensitive and reliable.

[0178] In summary, the present invention provides a method and system for identifying permanent faults in distribution lines with sequential overlap, which only requires the overlap of one or two phases. The overlapped phase current is small and there will be no serious fault current shock. By comparing the calculated transition resistance value with the set value, the nature of the fault can be accurately identified, solving the problem that the discrimination sensitivity decreases as the transition resistance of the permanent grounding fault in the distribution network increases.

[0179] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for identifying permanent faults in a distribution line with sequential overlap, characterized in that: The following steps are involved: The reclosing sequence is determined based on the fault phase selection results after the three-phase tripping of the distribution line. The specific reclosing sequence is: In case of a single-phase grounding fault in an asymmetric fault, a fault phase is sequentially reclosed, the fault phase is tripped, and then a non-fault phase is reclosed; In case of a two-phase grounding fault in an asymmetric fault, one of the faulty phases is sequentially reclosed, the faulty phase is tripped, and then a non-faulty phase is reclosed; In case of symmetrical fault, close any faulty phase; When the fault phase selection result is a symmetrical fault, one phase is reclosed according to the reclosing sequence, and the symmetrical fault transition resistance value is determined based on the load side voltage and load side current of the switch after reclosing one phase; When the fault phase selection result is an asymmetric fault, two phases are reclosed according to the reclosing sequence, and the asymmetric fault transition resistance value is determined based on the power frequency voltage and power frequency current on the load side of the split-phase switch after two reclosings, specifically: Obtain the power frequency voltage and power frequency current on the load side of the split-phase switch that overlaps twice, obtain the sum of the three-phase voltages on the load side of the split-phase switch, and the sum of the fault phase voltages on the load side of the split-phase switch, and determine the asymmetric fault transition resistance value according to the sum of the three-phase voltages on the load side of the split-phase switch and the sum of the fault phase voltages on the load side of the split-phase switch; When the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value, the distribution line fault is determined to be a transient fault. When the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value, the distribution line fault is determined to be a permanent fault.

2. The method for identifying permanent faults in distribution lines with sequential overlap according to claim 1, characterized in that: Symmetrical fault transition resistance The calculation is as follows: in, is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground, They are the three-phase voltages A, B, and C on the load side of the split-phase switch. is the coincident phase current that coincides with phase A.

3. The method for identifying permanent faults in distribution lines with sequential overlap according to claim 1, characterized in that: Asymmetric fault transition resistance The calculation is as follows: in, and are the sum of the three-phase voltages on the load side of the first and second coincidences, and are the phase currents on the load side of the first and second coincidences, respectively. is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground.

4. The method for identifying permanent faults in distribution lines with sequential overlap according to claim 1, characterized in that: The sum of the three-phase voltages on the load side of the phase switch The calculation is as follows: in, They are the A, B, and C three-phase voltages on the load side of the phase switch.

5. The method for identifying permanent faults in distribution lines with sequential overlap according to claim 1, characterized in that: The sum of the fault phase voltages on the load side of the split-phase switch for: in, They are the A, B, and C three-phase voltages on the load side of the phase switch.

6. A permanent fault identification system for distribution lines with sequential overlap, characterized in that: include: The phase selection module determines the reclosing sequence based on the fault phase selection results after the three-phase tripping of the distribution line. The specific reclosing sequence is: In case of a single-phase grounding fault in an asymmetric fault, a fault phase is sequentially reclosed, the fault phase is tripped, and then a non-fault phase is reclosed; In case of a two-phase grounding fault in an asymmetric fault, one of the faulty phases is sequentially reclosed, the faulty phase is tripped, and then a non-faulty phase is reclosed; In case of symmetrical fault, close any faulty phase; The first identification module, when the fault phase selection result is a symmetrical fault, recloses one phase according to the reclosing sequence, and determines the symmetrical fault transition resistance value based on the load side voltage and load side current of the switch after reclosing one phase; The second identification module, when the fault phase selection result is an asymmetric fault, recloses two phases according to the reclosing sequence, and determines the asymmetric fault transition resistance value based on the power frequency voltage and power frequency current on the load side of the phase switch that recloses twice, specifically: Obtain the power frequency voltage and power frequency current on the load side of the split-phase switch that overlaps twice, obtain the sum of the three-phase voltages on the load side of the split-phase switch, and the sum of the fault phase voltages on the load side of the split-phase switch, and determine the asymmetric fault transition resistance value according to the sum of the three-phase voltages on the load side of the split-phase switch and the sum of the fault phase voltages on the load side of the split-phase switch; The judgment module determines that the distribution line fault is a transient fault when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is greater than the set value; and determines that the distribution line fault is a permanent fault when the symmetrical fault transition resistance value or the asymmetrical fault transition resistance value is less than or equal to the set value.

7. The system for identifying permanent faults of power distribution lines with sequential overlap according to claim 6, characterized in that: In the second identification module, the asymmetric fault transition resistance value The calculation is as follows: in, and are the sum of the three-phase voltages on the load side of the first and second coincidences, and are the phase currents on the load side of the first and second coincidences, respectively. is the system susceptance downstream of the split-phase switch, is the ratio of the system capacitance to ground downstream of the switch to the system capacitance to ground, is the imaginary unit, is the angular frequency of the power frequency, is the system capacitance to ground.

8. The distribution line permanent fault identification system with sequential overlap according to claim 7, characterized in that: The sum of the three-phase voltages on the load side of the phase switch The calculation is as follows: in, They are the three-phase voltages A, B and C on the load side of the split-phase switch; The sum of the fault phase voltages on the load side of the split-phase switch for: in, They are the A, B, and C three-phase voltages on the load side of the phase switch.

9. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions, which, when executed by a computing device, cause the computing device to execute the method for identifying permanent faults in distribution lines with sequential coincidence as claimed in any one of claims 1 to 5.

10. A computing device, characterized in that include: One or more processors, a memory and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include a method for identifying permanent faults in distribution lines with sequential overlap as described in any one of claims 1 to 5.

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