Method and device for judging tidal current direction, electronic equipment and readable medium

Abstract

The invention discloses a tidal current direction judgment method and device, electronic equipment and a readable medium. The determination method (100) comprises: when any circuit breaker in all circuit breakers in a loop circuit detects a circuit fault, determining a fault type (101); and when the fault type is a two-phase short-circuit fault, determining the tidal current direction of the second circuit breaker according to whether the phase angle of the instantaneous value of the positive-sequence current of the second circuit breaker in all circuit breakers in the loop circuit is greater than 90 degrees after the two-phase short-circuit fault occurs (102).

Description

Method, device, electronic device and readable medium for determining tidal direction Technical Field

[0001] The embodiments of the present application mainly relate to the field of electric power, and in particular to a method, device, electronic device and readable medium for determining the direction of a current. Background Art

[0002] Low-voltage power grids typically have a hierarchical structure. However, with the increasing use of renewable energy, ring or mesh structures will become more prevalent in the future. Directional short-time delay protection devices for low-voltage circuit breakers are already widely used in the electronic trip units of air circuit breakers and molded case circuit breakers to maintain selectivity in multi-source low-voltage power grids. Selective protection can reduce the impact of faults on power systems and improve the continuity and reliability of power supply. However, in ring-shaped low-voltage power grids, the direction of power flow during a fault is difficult to detect, resulting in the inability of directional short-time delay protection devices to maintain selectivity.

[0003] Summary of the Invention

[0004] Embodiments of the present application provide a method, device, electronic device, and readable medium for determining the direction of a power flow, which are used to quickly and accurately determine the direction of a power flow passing through a related circuit breaker when a short circuit fault occurs in a ring-shaped low-voltage power grid.

[0005] In a first aspect, a method for determining a power flow direction is provided, comprising: determining the type of fault when any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault; and determining the power flow direction of a second circuit breaker among all circuit breakers in the ring circuit based on whether a phase angle of an instantaneous value of a positive sequence current of the second circuit breaker after the two-phase short circuit fault occurs is greater than 90° when the fault type is a two-phase short circuit fault.

[0006] In a second aspect, a device for determining the direction of a tidal current is provided, comprising components for executing each step of the method provided in the first aspect.

[0007] In a third aspect, an electronic device is provided, comprising: at least one memory configured to store computer-readable code; and at least one processor configured to call the computer-readable code and execute each step of the method provided in the first aspect.

[0008] In a fourth aspect, a computer-readable medium is provided, on which computer-readable instructions are stored. When the computer-readable instructions are executed by a processor, the processor executes each step in the method provided in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following figures are intended only to illustrate and explain the embodiments of the present application and are not intended to limit the scope of the embodiments of the present application.

[0010] FIG1 is a flow chart of a method for determining a tidal current direction according to an embodiment of the present application;

[0011] FIG2 is a schematic diagram of a device for determining a tidal current direction according to an embodiment of the present application;

[0012] FIG3 is a schematic diagram of an electronic device according to an embodiment of the present application.

[0013] Description of Reference Numerals

[0014] 100: Method for determining the direction of the tide 101-102: Method and steps

[0015] 20: Tidal current direction determination device 21: First determination module 22: Second determination module

[0016] 300: Electronic device 301: Memory 302: Processor DETAILED DESCRIPTION

[0017] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that discussing these embodiments is merely to enable those 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 examples set forth in the claims. The functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the embodiments of the present application. Various examples may omit, replace, or add various processes or components as needed. For example, the described method may be performed in an order different from the described order, and various steps may be added, omitted, or combined. In addition, the features described relative to some examples may also be combined in other examples.

[0018] As used herein, the term "including" and its variations are open terms meaning "including but not limited to". The term "based on" means "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0019] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0020] FIG1 is a flow chart of a method for determining a tidal current direction according to an embodiment of the present application. As shown in FIG1 , the method 100 for determining a tidal current direction includes:

[0021] Step 101: When any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault, the fault type is determined.

[0022] Optionally, before determining the fault type, the instantaneous value of the positive sequence current and the instantaneous value of the negative sequence current of each circuit breaker in all circuit breakers in the ring circuit are calculated.

[0023] Optionally, calculate the instantaneous value of the positive sequence current I positive It can be calculated by the following formula:

[0024] Among them, I A is the instantaneous A-phase current value detected by the relevant circuit breaker after removing the harmonic current, I B is the instantaneous B-phase current value detected by the relevant circuit breaker after removing the harmonic current, I C It is the instantaneous C-phase current value detected by the relevant circuit breaker after removing the harmonic current.

[0025] Calculate the instantaneous value of negative sequence current I negative It can be calculated by the following formula:

[0026] Among them, I A is the instantaneous A-phase current value detected by the relevant circuit breaker after removing the harmonic current, I B is the instantaneous B-phase current value detected by the relevant circuit breaker after removing the harmonic current, I C It is the instantaneous C-phase current value detected by the relevant circuit breaker after removing the harmonic current.

[0027] Step 102: When the fault type is a two-phase short circuit fault, the power flow direction of the second circuit breaker is determined based on whether the phase angle of the instantaneous positive sequence current of the second circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is greater than 90°.

[0028] Alternatively, the second circuit breaker may be each circuit breaker among all the circuit breakers, or may be any one of them.

[0029] Optionally, the fault type is determined based on the instantaneous value of the positive-sequence current and the instantaneous value of the negative-sequence current of the first circuit breaker in which the fault is detected. Optionally, when the instantaneous value of the positive-sequence current of the first circuit breaker exceeds 50% of the rated current and the instantaneous value of the negative-sequence current exceeds 50% of the rated current, the fault type is determined to be a two-phase short circuit fault.

[0030] Optionally, when the phase angle of the instantaneous positive sequence current of the second circuit breaker in the ring circuit after the two-phase short circuit fault occurs is greater than 90°, the power flow direction of the second circuit breaker is determined to be negative. When the phase angle of the instantaneous positive sequence current of the second circuit breaker in all circuit breakers in the ring circuit after the two-phase short circuit fault occurs is less than or equal to 90°, the power flow direction of the second circuit breaker is determined to be positive.

[0031] Optionally, when it is determined that the flow direction of the first circuit breaker is positive / negative, the corresponding information is notified to the directional short-time delay protection device in the first circuit breaker, so that the directional short-time delay protection device determines the corresponding protection threshold. The protection threshold may specifically include a positive short-time delay tripping current setting and a negative short-time delay tripping current setting, as well as a positive tripping time setting and a negative tripping time setting.

[0032] In the embodiment of the present application, when any circuit breaker in a ring circuit detects a circuit fault, it is first determined whether the fault type is a two-phase short-circuit fault. This is because according to relevant simulation results, a two-phase short-circuit fault will cause the controller of the circuit breaker to detect both the forward and reverse currents, while this problem does not exist in the case of a single-phase / three-phase short-circuit fault. Optionally, the relevant simulation results can be obtained by building a circuit model based on actual parameters in a simulation tool, and then assuming test scenarios and conditions. When the fault type is a two-phase short-circuit fault, the current direction of the second circuit breaker is determined based on whether the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker in all the circuit breakers in the ring circuit after the two-phase short-circuit fault occurs is greater than 90°.

[0033] The embodiments of the present application can quickly and accurately determine the direction of power flow through the relevant circuit breakers, allowing the directional short-time delay protection device to determine the corresponding protection threshold, thereby improving the power supply continuity and reliability of the entire ring-shaped low-voltage power grid system. The embodiments of the present application also do not require additional hardware, and the related computing costs are low and can be easily processed by a common single-chip microcomputer.

[0034] In one embodiment, when the instantaneous value of the positive-sequence current of the first circuit breaker exceeds 50% of the rated current, and the instantaneous value of the negative-sequence current does not exceed 50% of the rated current, the relevant fault type is determined to be a single-phase short circuit fault / three-phase short circuit fault. Optionally, when the fault type is determined to be a single-phase short circuit fault / three-phase short circuit fault, a determination is made as to whether the power flow of the third circuit breaker among all circuit breakers is oscillating. If the power flow of the third circuit breaker is oscillating, the power flow direction of the third circuit breaker is determined after a preset delay. Optionally, the third circuit breaker can be all circuit breakers, or any one of them.

[0035] Alternatively, the rate of change ζ can be calculated based on the maximum and minimum current values ​​of the third circuit breaker within a specified time range. Based on the rate of change ζ, it is determined whether the power flow of the third circuit breaker among all circuit breakers is oscillating. Alternatively, the rate of change ζ can be calculated using the following formula:

[0036] Among them, I max Refers to the maximum current of the third circuit breaker within a specified time range, I min It refers to the minimum current of the third circuit breaker within a specified time range.

[0037] Optionally, when the change rate is greater than a preset threshold, such as 50%, it is determined that the power flow of the first circuit breaker where the fault is detected has oscillation.

[0038] The embodiment of the present application can solve the power oscillation problem caused by the drastic change of the fault current by delaying the determination of the power flow direction of the third circuit breaker, thereby avoiding the problem of erroneous tripping of the circuit breaker controller.

[0039] FIG2 is a schematic diagram of a tidal current direction determination device 20 according to an embodiment of the present application. As shown in FIG2 , the tidal current direction determination device 20 includes:

[0040] The first determination module 21 is configured to determine the type of fault when any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault.

[0041] The second judgment module 22 is configured to: when the fault type is a two-phase short circuit fault, determine the power flow direction of the second circuit breaker according to whether the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is greater than 90°.

[0042] Through the embodiments of the present application, the direction of the power flow passing through the relevant circuit breaker can be quickly and accurately determined, so that the directional short-time delay protection device can determine the corresponding protection threshold, thereby improving the power supply continuity and reliability of the entire ring low-voltage power grid system.

[0043] The present application also provides an electronic device 300. FIG3 is a schematic diagram of electronic device 300 according to an embodiment of the present application. As shown in FIG3 , electronic device 300 includes a processor 302 and a memory 301. Memory 301 stores instructions, wherein the instructions, when executed by processor 302, implement method 100 as described above.

[0044] Among them, at least one processor 302 may include a microprocessor, an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a state machine, etc. Embodiments of computer-readable media include, but are not limited to, floppy disks, CD-ROMs, magnetic disks, memory chips, ROMs, RAMs, ASICs, configured processors, all-optical media, all tapes or other magnetic media, or any other medium from which a computer processor can read instructions. In addition, various other forms of computer-readable media can send or carry instructions to a computer, including routers, private or public networks, or other wired and wireless transmission devices or channels. Instructions may include code in any computer programming language, including C, C++, C language, Visual Basic, Java, and JavaScript.

[0045] In addition, the embodiments of the present application further provide a computer-readable medium having computer-readable instructions stored thereon, and when the computer-readable instructions are executed by the processor, the processor executes the aforementioned method for determining the direction of the trend. Embodiments of computer-readable media include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROMs, CD-Rs, CD-RWs, DVD-ROMs, DVD-RAMs, DVD-RWs, DVD+RWs), magnetic tapes, non-volatile memory cards, and ROMs. Optionally, computer-readable instructions can be downloaded from a server computer or a cloud via a communication network.

[0046] It should be noted that not all steps and modules in the above processes and system structure diagrams are required, and certain steps or modules can be omitted according to actual needs. The execution order of each step is not fixed and can be adjusted as needed. The system structure described in the above embodiments can be a physical structure or a logical structure, that is, some modules may be implemented by the same physical entity, or some modules may be implemented by multiple physical entities, or may be implemented by certain components in multiple independent devices.

Claims

1. A method for determining the direction of a tidal current, comprising: -When any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault, determining (101) the type of the fault; -When the fault type is a two-phase short circuit fault, judging (102) the flow direction of the second circuit breaker according to whether the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is greater than 90°.

2. The method according to claim 1, characterized in that Before determining (101) the fault type, the method further includes: - calculating the instantaneous value of the positive sequence current and the instantaneous value of the negative sequence current for each of all the circuit breakers in the ring circuit.

3. The method according to claim 2, characterized in that The determining (101) of the fault type includes: - judging the fault type according to the instantaneous value of the positive sequence current and the instantaneous value of the negative sequence current of the first circuit breaker where the fault is detected.

4. The method according to claim 1, characterized in that: The determining (102) of the flow direction of the first circuit breaker according to whether the phase angle of the instantaneous value of the positive sequence current of the first circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is greater than 90° comprises: - when the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is greater than 90°, it is determined that the power flow direction of the second circuit breaker is negative; -When the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is less than or equal to 90°, it is determined that the power flow direction of the second circuit breaker is forward.

5. The method according to claim 3, characterized in that: When the fault type is a two-phase short circuit fault, the method includes: -When the instantaneous value of the positive sequence current of the first circuit breaker exceeds 50% of the rated current, and the instantaneous value of the negative sequence current exceeds 50% of the rated current, the fault type is determined to be a two-phase short circuit fault.

6. The method according to claim 1, characterized in that After determining (101) the fault type, the method further includes: -When the fault type is a single-phase short circuit fault / three-phase short circuit fault, determining whether the power flow of the third circuit breaker among all the circuit breakers is oscillating; -When the third circuit breaker has power flow oscillation, determine the power flow direction of the third circuit breaker after a preset delay.

7. The method according to claim 6, characterized in that The determining whether the power flow of the third circuit breaker among all the circuit breakers is oscillating comprises: - calculating the rate of change according to the maximum and minimum values ​​of the current of the third circuit breaker within a specified time range; - According to the change rate, it is determined whether the power flow of the third circuit breaker among all the circuit breakers has oscillation.

8. A device for determining the direction of a tidal current, comprising: - A first judgment module (21), configured to: -When any circuit breaker among all circuit breakers in a ring circuit detects a circuit fault, determining the type of the fault; - A second judgment module (22), configured to: -When the fault type is a two-phase short circuit fault, the flow direction of the second circuit breaker is determined based on whether the phase angle of the instantaneous value of the positive sequence current of the second circuit breaker among all the circuit breakers in the ring circuit after the two-phase short circuit fault occurs is greater than 90°.

9. An electronic device, characterized in that: include: at least one memory (301) configured to store computer readable code; At least one processor (302) is configured to call the computer-readable code to execute the steps in the method according to any one of claims 1 to 7.

10. A computer-readable medium, characterized in that The computer-readable medium stores computer-readable instructions, and when the computer-readable instructions are executed by a processor, the processor executes the steps in the method according to any one of claims 1 to 7.

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