Method and apparatus for assessing the direction of current flow, electronic device and readable medium
The method and device for assessing current flow direction in low-voltage ring networks enhance power supply reliability by accurately determining protection thresholds based on phase angle analysis, addressing detection challenges and reducing computational costs.
Patent Information
- Application Number
- DE112023005643
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-03-21
- Publication Date
- 2025-11-06
AI Technical Summary
In low-voltage ring power networks, detecting current flow direction during faults is difficult, leading to inconsistent selectivity in directed short-time-delayed protection devices, which affects the continuity and reliability of power supply.
A method and device for assessing current flow direction by determining the phase angle of positive sequence current in circuit breakers, distinguishing between biphasic and other short-circuit faults, and setting appropriate protection thresholds.
Enables quick and accurate current flow direction assessment, improving power supply continuity and reliability without additional hardware, reducing computational costs and preventing erroneous circuit breaker triggers.
Smart Images
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Abstract
Description
Technical field
[0001] The embodiments of the present application relate to the technical field of electrical energy, in particular a method and a device for assessing the direction of current flow, an electronic device and a readable medium. State of the art
[0002] Low-voltage power grids are typically hierarchical. However, due to the increasing use of renewable energies, ring or network structures will become predominant in the future. Directional short-time delayed protection devices in low-voltage circuit breakers are already widely used in the electronic trip units of air circuit breakers and cast-case circuit breakers to ensure selectivity in low-voltage power grids with multiple power sources. Selective protection reduces the impact of faults on electrical power systems, thereby improving the continuity and reliability of their power supply. However, in today's ring-shaped low-voltage power grids, it is difficult to determine the direction of current flow when a fault occurs, making it impossible for directional short-time delayed protection devices to consistently maintain their selectivity. Disclosure of the invention
[0003] The embodiments of the present application provide a method and a device for assessing the direction of current flow, an electronic device and a readable medium with which the direction of current flow through a relevant circuit breaker can be assessed quickly and accurately when a short-circuit fault occurs in the ring-shaped low-voltage power network.
[0004] According to a first aspect, a procedure for assessing a current flow direction is provided, which includes: assessing the type of fault when any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault; assessing a current flow direction of a second circuit breaker in the case that the type of fault is a two-phase short-circuit fault, depending on whether the phase angle of an instantaneous value of the positive sequence current of the second circuit breaker among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault exceeds 90°.
[0005] According to a second aspect, a device for assessing the direction of current flow is provided, which includes components for carrying out the individual steps of the procedure provided in the first aspect.
[0006] According to a third aspect, an electronic device is provided which includes: at least a memory configured to store a computer-readable code; at least a processor configured to call the computer-readable code in order to execute the individual steps of the procedure provided in the first aspect.
[0007] According to a fourth aspect, a computer-readable medium is provided on which computer-readable instructions are stored, wherein, when executed by a processor, the computer-readable instructions cause that processor to carry out the individual steps of the procedure provided in the first aspect. Brief description of the characters
[0008] The following accompanying drawings serve only as a schematic description and explanation of the embodiments of the present application, without limiting the scope of the embodiments of the present application. In the figures: Fig. 1 shows a flow diagram of a method for assessing the direction of current flow according to an embodiment of the present application; Fig. Figure 2 shows a schematic view of a device for assessing the direction of current flow according to an embodiment of the present application; and Fig. Figure 3 shows a schematic view of an electronic device according to an embodiment of the present application. Reference symbol list
[0009] 100: Procedure for 101-102: Assessment of a procedure step Current flow direction 20: Setup for 21: first 22: second assessment of an assessment module Assessment module Current flow direction 300: electronic 301: memory 302: processor Device Detailed descriptions
[0010] The subject matter described herein will now be explained with reference to exemplary embodiments. It is understood that the discussion of these embodiments is intended solely to enable the person skilled in the art to better understand and implement the subject matter described herein and is not intended to limit the scope of protection, applicability, or example set forth in the claims. The function and arrangement of the elements discussed may be modified without altering the scope of protection of the content according to the exemplary embodiments of the present application. In various examples, different processes or components may be omitted, replaced, or added as needed. For example, the described method may be carried out in a different sequence than that described herein, and various steps may be added, omitted, or combined.Furthermore, the features described in some examples can also be combined in other examples.
[0011] As used herein, the term "comprise" and its variations are open terms, which are understood to mean "including, but not limited to." The term "based on" means "at least partially based on." The term "an embodiment" means "at least one embodiment." The term "another embodiment" means "at least one further embodiment." The terms "first," "second," and the like may refer to different or the same objects. Other definitions, whether explicit or implicit, may be included below. Unless expressly stated otherwise in the context, the definition of a term is consistent throughout the description.
[0012] The embodiments of the present application are described in detail below in connection with the figures.
[0013] Fig. Figure 1 shows a flowchart of a method for assessing the direction of current flow according to an embodiment of the present application. As in Fig. As shown in 1, the procedure for assessing a current flow direction 100 comprises the following steps: Step 101: Assess the nature of a fault when any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault.
[0014] Optionally, it is provided that, before assessing the type of fault, the instantaneous value of a positive sequence current and the instantaneous value of a negative sequence current of each circuit breaker are calculated among all circuit breakers in the ring circuit.
[0015] Optionally, the instantaneous value I can be positiveThe positive sequence current can be calculated using the following formula: Ipositive=13(IA+αIB+α2IC), where α=ej120°=12+j32
[0016] This stands for I A I represents the instantaneous value of the phase current of phase A, which is detected by the relevant circuit breaker after removal of the harmonic current. B for the instantaneous value of the phase current of phase B, which is detected by the relevant circuit breaker after removal of the harmonic current, and stands for I C for the instantaneous value of the phase current of phase C, which is detected by the relevant circuit breaker after removal of the harmonic current.
[0017] The instantaneous value I negative The negative sequence current can be calculated using the following formula: Inegative=13(IA+α2IB+αIC), where α=ej120°=12+j32
[0018] This stands for I AI represents the instantaneous value of the phase current of phase A, which is detected by the relevant circuit breaker after removal of the harmonic current. B for the instantaneous value of the phase current of phase B, which is detected by the relevant circuit breaker after removal of the harmonic current, and stands for I C for the instantaneous value of the phase current of phase C, which is detected by the relevant circuit breaker after removal of the harmonic current.
[0019] Step 102: Assess the current flow direction of a second circuit breaker in the event that the fault type is a two-phase short-circuit fault, depending on whether the phase angle of an instantaneous value of the positive sequence current of the second circuit breaker exceeds 90° among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault.
[0020] Optionally, the second circuit breaker can be either any circuit breaker among all the circuit breakers or any circuit breaker.
[0021] Optionally, the fault type is assessed based on the instantaneous values of a positive sequence current and a negative sequence current of a first circuit breaker through which the fault is detected. Optionally, the fault type is assessed as a two-phase short-circuit fault if the instantaneous value of the positive sequence current of the first circuit breaker exceeds 50% of the rated current and the instantaneous value of its negative sequence current also exceeds 50% of the rated current.
[0022] Optionally, the current flow direction of the second circuit breaker is considered negative if the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker is greater than 90° among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault. If the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker is less than or equal to 90° among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault, the current flow direction of the second circuit breaker is considered positive.
[0023] If the current flow direction of the first circuit breaker is assessed as positive / negative, the corresponding information is optionally reported to the directional short-time delayed protective device within the first circuit breaker in order to determine the appropriate protection thresholds. These protection thresholds can include, in particular, a positive short-time delayed setting for the tripping current and a negative setting for the short-time tripping current, as well as a positive setting for the tripping time and a negative setting for the tripping time.
[0024] When a circuit fault is detected by any circuit breaker in the ring circuit, the embodiments of the present application first assess whether the fault is a two-phase short-circuit fault. This is because the relevant simulation results show that, in the case of a two-phase short-circuit fault, the circuit breaker control detects both a positive and a negative current flow simultaneously, whereas this problem does not occur with a single-phase or three-phase short-circuit fault. Optionally, the relevant simulation results can be obtained by creating a circuit model based on actual parameters in a simulation tool and then assuming the test scenarios and conditions.If the fault is a two-phase short-circuit fault, the current flow direction of the second circuit breaker is assessed depending on whether the phase angle of an instantaneous value of the positive sequence current of the second circuit breaker exceeds 90° among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault.
[0025] Using the embodiments of the present application, the direction of current flow through a relevant circuit breaker can be quickly and accurately assessed in order to determine the corresponding protection thresholds for the directed short-time delayed protection device and thus improve the continuity and reliability of the power supply in the entire ring-shaped low-voltage power grid system. Since the embodiments of the present application also do not require any additional hardware, computational costs are reduced. Furthermore, they can be easily processed by a standard single-chip microcomputer.
[0026] In one embodiment, the type of fault is assessed as a single-phase or three-phase short-circuit fault if the following conditions are not met: namely, that the instantaneous value of the positive sequence current of the first circuit breaker exceeds 50% of the rated current and that the instantaneous value of its negative sequence current also exceeds 50% of the rated current. Optionally, if the fault type is assessed as a single-phase or three-phase short-circuit fault, it is then assessed whether oscillating current flows are present at a third circuit breaker among all the circuit breakers. If oscillating current flows are present at the third circuit breaker, the current flow direction of the third circuit breaker is assessed after a preset delay period.Optionally, the third circuit breaker can be either any circuit breaker among all the circuit breakers or any circuit breaker.
[0027] Optionally, a rate of change ζ can be calculated based on the maximum and minimum current values at the third circuit breaker within the specified time interval. Based on the rate of change ζ, it is assessed whether oscillating current flows are present at the third circuit breaker among all circuit breakers. Optionally, the rate of change ζ can be calculated using the following formula: ζ=Imax−IminImax
[0028] This stands for I max for the maximum value of the current at the third circuit breaker within the specified time interval, and stands I min for the minimum current value at the third circuit breaker within the specified time interval.
[0029] If the rate of change is greater than a preset threshold, for example 50%, it is optionally assessed that oscillating current flows are present at the first circuit breaker that detected the fault.
[0030] By delaying the assessment of the current flow direction of the third circuit breaker, the present embodiments of the present application can solve the problem of power fluctuations caused by abrupt changes in the fault current, thereby preventing a faulty tripping of the circuit breaker control.
[0031] Fig. Figure 2 shows a schematic view of a device for assessing the direction of current flow 20 according to an embodiment of the present application. As in Fig. As shown in 2, the device for assessing the direction of current flow comprises 20: a first assessment module 21, which is configured to assess the type of fault when any protective device among all protective devices in a ring circuit detects a circuit fault; and a second assessment module 22, which is configured to assess a current flow direction of a second protective device in the case that the type of fault is a two-phase short-circuit fault, depending on whether the phase angle of an instantaneous value of the positive sequence current of the second protective device among all protective devices in the ring circuit after the occurrence of the two-phase short-circuit fault exceeds 90°.
[0032] Using the embodiments of the present application, the direction of current flow through a relevant circuit breaker can be assessed quickly and accurately in order to determine the corresponding protection thresholds by the directed short-time delayed protection device and thus improve the continuity and reliability of the power supply in the entire ring-shaped low-voltage power network system.
[0033] In the embodiments of the present application, an electronic device 300 is provided. Fig. Figure 3 shows a schematic view of an electronic device 300 according to an embodiment of the present application. As in Fig. As shown in Figure 3, the electronic device 300 comprises a processor 302 and a memory 301. Instructions are stored in the memory 301, and when the instructions are executed by the processor 302, the procedure 100 described above is implemented.
[0034] In this context, at least one processor 302 may comprise a microprocessor, an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), or a state machine, etc. An embodiment of the computer-readable medium includes: a floppy disk, CD-ROM, a magnetic disk, a memory chip, ROM, RAM, ASIC, a configured processor, a purely optical medium, any magnetic tape or other magnetic media, or any other media from which a computer processor can read instructions without being limited thereto. Furthermore, various computer-readable media in other forms may transmit or carry the instructions to the computer, including routers, private or public networks, or other wired and wireless transmission devices or channels.The instructions can contain code in any computer programming language, including C, C++, C programming language, Visual Basic, Java, and JavaScript.
[0035] Furthermore, the embodiments of the present application provide a computer-readable medium on which computer-readable instructions are stored, wherein, when executed by a processor, the computer-readable instructions cause the processor to perform the method described above for determining the direction of current flow. One embodiment of the computer-readable medium comprises a floppy disk, a hard disk, a magneto-optical disk, an optical disk (e.g., CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, and DVD+RW), a magnetic tape, a non-volatile memory card, and ROM. Optionally, the computer-readable instructions can be downloaded from a server computer or from the cloud via a communication network.
[0036] It should be noted that not all steps and modules are necessary in the preceding processes or structural views of the system, and some steps or modules can be ignored depending on practical requirements. The order in which the individual steps are executed is not fixed and can be adjusted as needed. The system structures described in the preceding individual embodiments can be physical or logical structures. That is, some modules can be implemented by the same physical entity; alternatively, some modules can be implemented by multiple physical entities, or they can be implemented jointly by some components in several independent devices.
Claims
[1] Methods for assessing the direction of current flow, which include: - Assess (101) the nature of a fault when any circuit breaker among all the circuit breakers in a ring circuit detects a circuit fault; - Assess (102) the current flow direction of a second protective switch in the event that the fault is a two-phase short-circuit fault, depending on whether the phase angle of an instantaneous value of the positive sequence current of the second protective switch exceeds 90° among all protective switches in the ring circuit after the occurrence of the two-phase short-circuit fault. [2] Method according to claim 1, characterized by , that the procedure includes, prior to the step of assessing (101) the nature of the fault: - Calculating the instantaneous value of a positive sequence current and the instantaneous value of a negative sequence current of each circuit breaker among all circuit breakers in the ring circuit. [3] Method according to claim 2, characterized by , that the assessment (101) of the nature of the fault includes: - Assessing the nature of a fault based on the instantaneous values of a positive sequence current and a negative sequence current of a first circuit breaker through which the fault is detected. [4] Method according to claim 1, characterized by , that the assessment (102) of a current flow direction of the first circuit breaker depending on whether the phase angle of an instantaneous value of the positive sequence current of the first circuit breaker exceeds 90° among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault includes: - Assessing the current flow direction of the second circuit breaker as negative if the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker is greater than 90° among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault; - Assessing a current flow direction of the second circuit breaker as positive if the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker among all circuit breakers in the ring circuit after the occurrence of the two-phase short-circuit fault is less than or equal to 90°. [5] Method according to claim 3, characterized by , that the case where the type of fault is a two-phase short-circuit fault includes: - Assess the nature of the fault as a two-phase short-circuit fault if the instantaneous value of the positive sequence current of the first circuit breaker exceeds 50% of the rated current and the instantaneous value of its negative sequence current also exceeds 50% of the rated current. [6] Method according to claim 1, characterized by , that the procedure after the step of assessing (101) the nature of the fault includes: - Assess whether oscillating current flows are present at a third circuit breaker among all circuit breakers when the fault type is a single-phase or three-phase short-circuit fault; - Assessing the current flow direction of the third circuit breaker after a preset delay period if oscillating current flows are present at the third circuit breaker. [7] Method according to claim 6, characterized by, that assessing whether oscillating current flows are present at the third circuit breaker among all circuit breakers includes: - Calculating a rate of change based on the maximum and minimum values of the current at the third circuit breaker within the specified time interval; - Assess whether oscillating current flows are present at the third circuit breaker among all circuit breakers, based on the rate of change. [8] Device for assessing the direction of current flow, comprising: - a first assessment module (21) which is set up to, - to assess the type of fault when any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault; - a second assessment module (22) which is set up to, - to assess the current flow direction of a second protective switch in the event that the type of fault is a two-phase short-circuit fault, depending on whether the phase angle of an instantaneous value of the positive sequence current of the second protective switch exceeds 90° among all protective switches in the ring circuit after the occurrence of the two-phase short-circuit fault. [9] Electronic device, characterized by , that it includes: at least one memory (301) configured to store a computer-readable code; at least one processor (302) configured to call the computer-readable code to execute the steps of the method according to any one of claims 1 to 7. [10] Computer-readable medium, characterized bythat computer-readable instructions are stored on the computer-readable medium, wherein the computer-readable instructions, when executed by a processor, cause that processor to perform the steps of the method according to any one of claims 1 to 7.