A method and apparatus for detecting series arc faults in a power distribution network based on boundary elements

Abstract

The application discloses a kind of based on boundary element's distribution network series arc fault detection method and device, it is related to electric power engineering technical field.When the derivative of the voltage drop of boundary element on distribution network is detected to be greater than the first preset threshold value for many times in succession, then enter series arc fault detection stage;In series arc fault detection stage, real-time calculation full-cycle fault component, and according to full-cycle fault component, the instantaneous energy of full-cycle fault component is calculated;Then with half-cycle as a unit, when the maximum instantaneous energy in half-cycle exists is greater than the second preset threshold value, determine that half-cycle occurs series arc fault;When the number of half-wave of series arc fault that distribution network occurs in preset duration is greater than or equal to preset quantity threshold value, determine that distribution network occurs series arc fault, and send alarm signal or trip.The method can improve the detection efficiency of distribution network series arc fault.

Description

Technical Field

[0001] This invention relates to the field of power engineering technology, and in particular to a method and device for detecting series arc faults in distribution networks based on boundary elements. Background Technology

[0002] Currently, electrical fires pose a significant threat to people's lives and property. Extensive research data indicates that series arcing in low-voltage power distribution lines is one of the main causes of electrical fires. However, the characteristics of series arcing faults are weak, making it difficult for existing relay protection devices in low-voltage power distribution systems to detect and isolate them. For series arcing fault detection, commonly used methods include detection based on single-ended and double-ended electrical quantities. However, detection based on single-ended electrical quantities is only applicable when the series arcing fault occurs on the main branch of the line; when a single branch fault occurs across multiple loads, the fault characteristics are overwhelmed by the load current. Detection based on double-ended electrical quantities relies on communication and requires monitoring points at each load location, resulting in poor economic efficiency.

[0003] In response, existing technologies propose a series arc detection method for constructing line boundaries. This method solves the problem of poor selectivity in traditional single-ended quantity detection and can, to some extent, offset harmonic interference and avoid malfunctions caused by load plugging and unplugging. However, it still has the following core pain points: it relies on complex time-frequency algorithms and has a large computational load. Summary of the Invention

[0004] Therefore, it is necessary to provide a method and device for detecting series arc faults in power distribution networks based on boundary elements, in order to address the above-mentioned technical problems.

[0005] The present invention adopts the following technical solution: This invention provides a method for detecting series arc faults in distribution networks based on boundary elements, comprising: Real-time detection of voltage drop at the upper boundary components of the distribution network; the boundary components are located at the installation positions of the third-level residual current protection of the distribution network; When the derivative of the voltage drop of the boundary element is detected to be greater than the first preset threshold multiple times in a row, the series arc fault detection stage is entered. During the series arc fault detection stage, the full-cycle fault component is calculated in real time, and the instantaneous energy of the full-cycle fault component is calculated based on the full-cycle fault component. Using half-cycles as units, when the maximum instantaneous energy within a half-cycle exceeds a second preset threshold, it is determined that a series arc fault has occurred in that half-cycle. When the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset threshold, it is determined that a series arc fault has occurred in the distribution network.

[0006] Optionally, the derivative of the voltage drop of the boundary element is calculated using the following formula: ; in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point For boundary elements in the first Voltage drop at each sampling point The time interval between two adjacent sampling points.

[0007] Optionally, "multiple times" means three consecutive times, that is, the derivative of the voltage drop of the boundary element is greater than the first preset threshold for three consecutive times, expressed by the formula: ; in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point The derivative, This is the first preset threshold.

[0008] Optionally, the first The formula for calculating the full-cycle fault component corresponding to each sampling point is: ; in, For the first The full-cycle fault component corresponding to each sampling point For boundary elements in the first Voltage drop at each sampling point The number of sampling points per power frequency cycle. For boundary elements in the previous week wave Voltage drop at each sampling point.

[0009] Optionally, the first The formula for calculating the instantaneous energy of the full-cycle fault component corresponding to each sampling point is: ; in, For the first The instantaneous energy of the full-cycle fault component corresponding to each sampling point; For the first The full-cycle fault component at each sampling point.

[0010] Optionally, the method further includes: When a series arc fault is detected in the distribution network, an alarm signal is issued or the circuit breaker is tripped.

[0011] This invention provides a boundary element-based distribution network series arc fault detection device, comprising: The detection start-up module is used to detect the voltage drop of the upper boundary element of the distribution network in real time. The boundary element is arranged at the installation position of the third-level residual current protection of the distribution network. When the derivative of the voltage drop of the boundary element is detected to be greater than the first preset threshold multiple times in a row, the series arc fault detection stage is entered. The fault detection module is used to calculate the full-cycle fault component in real time during the series arc fault detection stage, and to calculate the instantaneous energy of the full-cycle fault component based on the full-cycle fault component; taking half-cycle as the unit, when the maximum instantaneous energy in a half-cycle is greater than a second preset threshold, it is determined that a series arc fault has occurred in that half-cycle; when the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset number threshold, it is determined that a series arc fault has occurred in the distribution network.

[0012] The present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for detecting series arc faults in power distribution networks based on boundary elements.

[0013] The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the above-described method for detecting series arc faults in power distribution networks based on boundary elements.

[0014] The above-mentioned at least one technical solution adopted in this invention can achieve the following beneficial effects: In this invention, boundary elements are installed at the installation locations of the third-level residual current protection in the distribution network. During the operation of the distribution network, it is only necessary to monitor the voltage drop of the boundary elements and the magnitude of the first preset threshold in real time. This computational load is much smaller than that of full-cycle energy analysis. Only when the derivative of the voltage drop is greater than the first preset threshold multiple times consecutively does the series arc fault detection stage begin, avoiding continuous high-load calculations. Furthermore, in the series arc fault detection stage, it is only necessary to calculate the instantaneous energy of the full-cycle fault component, using half-cycles as units, to locate whether a series arc fault has occurred in a half-cycle. When the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset number threshold, it is determined that a series arc fault has occurred in the distribution network. This invention improves the efficiency of series arc fault detection in the distribution network by judging whether a series arc fault has occurred through the instantaneous energy of the full-cycle fault component. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0016] Figure 1 A schematic flowchart of a distribution network series arc fault detection method based on boundary elements provided by the present invention; Figure 2 This invention provides a structural diagram of a series arc fault distribution network system with installed boundary elements; Figure 3 This invention provides an instantaneous energy waveform diagram of a full-cycle fault component under normal conditions. Figure 4 This invention provides an instantaneous energy waveform diagram of the full-cycle fault component under fault conditions within the fault occurrence zone; Figure 5 This invention provides an instantaneous energy waveform diagram of the full-cycle fault component under the condition of an external fault occurrence. Figure 6 This invention provides a schematic diagram of a computer device for implementing a method for detecting series arc faults in a power distribution network based on boundary elements. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0018] This invention proposes a series arc fault detection method for low-voltage distribution networks with established boundaries, based on boundary elements. This method extracts fault features by using the difference between adjacent full-cycle values ​​and uses instantaneous energy features to detect series arc faults, thereby improving the selectivity and reliability of series arc fault detection. The method is simple in principle, highly reliable, and computationally efficient, and it is selective without the need for coordination between upper and lower level protection.

[0019] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram of a method for detecting series arc faults in a distribution network based on boundary elements, as described in this invention. The method specifically includes the following steps: S101 is used to detect the voltage drop of the upper boundary elements of the distribution network in real time; the boundary elements are arranged at the installation positions of the third-level residual current protection of the distribution network.

[0021] According to the principle of three-level residual current protection, boundary elements and series arc fault detection devices for the distribution network are configured at the three-level residual current protection installation locations of the distribution network line ("main-middle-end") to ensure the selectivity of series arc detection. Specifically, boundary elements and series arc fault detection devices for the distribution network are installed at the main incoming line, the branch line incoming line, and the load point of the distribution network system.

[0022] Boundary elements refer to electrical equipment primarily used to isolate faults in different areas of a power distribution network. Optionally, boundary elements can be a combination of magnetic rings and capacitors. Boundary elements are required to have low power frequency impedance to avoid affecting the normal operation of the system, and high impedance at high frequencies to amplify the high-frequency characteristics of series arc fault currents and avoid installing broadband current transformers.

[0023] Optionally, the voltage drop of the upper boundary element of the distribution network can be detected in real time by a voltage transformer, with the primary side of the voltage transformer connected to both sides of the boundary element.

[0024] S102, when the derivative of the voltage drop of the boundary element is detected to be greater than the first preset threshold multiple times in a row, the series arc fault detection stage is entered.

[0025] After detecting the voltage drop of the boundary element, the derivative of the voltage drop can be calculated to represent the voltage drop at the first... Taking the voltage drop at a single sampling point as an example, the formula for calculating the derivative of the voltage drop of a boundary element is as follows: (1); in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point For boundary elements in the first Voltage drop at each sampling point The time interval between two adjacent sampling points.

[0026] After obtaining the derivative of the voltage drop, it can be compared with a first preset threshold. This is repeated three times consecutively (i.e., the derivative of the voltage drop of the boundary element is greater than the first preset threshold for three consecutive times). The formula is as follows: (2); in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point The derivative, This is the first preset threshold.

[0027] If formula (2) is satisfied, then the series arc fault detection stage is entered.

[0028] Optionally, the first preset threshold is a set value, which can be set according to the maximum value of the time derivative at any point in the waveform during normal operation.

[0029] S103 calculates the full-cycle fault component in real time during the series arc fault detection stage, and calculates the instantaneous energy of the full-cycle fault component based on the full-cycle fault component.

[0030] No. The formula for calculating the full-cycle fault component corresponding to each sampling point is: (3); in, For the first The full-cycle fault component corresponding to each sampling point For boundary elements in the first Voltage drop at each sampling point The number of sampling points per power frequency cycle. For the boundary element in the previous cycle of the first wave Voltage drop at each sampling point.

[0031] Optionally, the boundary element in the first , and When the derivative of the voltage drop at each sampling point is greater than the first preset threshold, the series arc fault detection stage begins. During the series arc fault detection stage, the voltage drop at each sampling point can be calculated according to formula (3). The sampling point and the full-cycle fault component corresponding to any subsequent sampling point.

[0032] Based on the full-cycle fault component at each sampling point, the instantaneous energy of the full-cycle fault component corresponding to each sampling point is calculated, including: for any sampling point, the square of the full-cycle fault component at the sampling point is determined as the instantaneous energy of the full-cycle fault component corresponding to the sampling point, as shown in formula (4). The formula for calculating the instantaneous energy of the full-cycle fault component corresponding to each sampling point is: (4); in, For the first The instantaneous energy of the full-cycle fault component corresponding to each sampling point; For the first The full-cycle fault component at each sampling point.

[0033] S104, taking half-cycles as units, when the maximum instantaneous energy within a half-cycle is greater than the second preset threshold, it is determined that a series arc fault has occurred in that half-cycle.

[0034] The instantaneous energy at each sampling point of the full cycle can be determined based on formula (4). A series arc fault criterion is established, with half-cycles as the unit. When the maximum instantaneous energy within a half-cycle is greater than the second preset threshold, a series arc fault is determined to have occurred in the corresponding half-cycle. Optionally, the second preset threshold is a setting value, which is set according to the maximum instantaneous energy of the fault component detected when avoiding faults outside the fault zone.

[0035] S105, when the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset number threshold, it is determined that a series arc fault has occurred in the distribution network.

[0036] Optionally, the preset duration can be 1 second, and the preset quantity threshold can be 14.

[0037] Arc fault alarm or tripping criteria. According to the current standard GB14287.4-2014 for series arc detection, when the number of fault arc half-waves occurring in the protected line of the distribution network reaches 14 or more within 1 second, a series arc fault is determined to have occurred in the distribution network, and when a series arc fault is determined to have occurred in the distribution network, an alarm signal or tripping is issued.

[0038] This invention provides a method for detecting series arc faults in distribution networks based on boundary elements. The method extracts fault features by using the difference between adjacent full-cycle values ​​and uses instantaneous energy features for series arc fault detection. The method is simple in principle, requires no communication, and can achieve absolute selectivity without additional voltage transformers. Boundary elements and instantaneous energy both have a methodological effect on transient current features, thus resulting in high sensitivity. In addition, the difference between adjacent full-cycle values ​​is used to offset load fluctuations and harmonic interference, while the boundary provides shielding.

[0039] In one embodiment, such as Figure 2 As shown, Figure 2 This is a structural diagram of a series arc fault distribution network system with installed boundary elements. l A1 This is the main power line for this household. l A2 For branch lines, l A3 For load lines, l B For other households' main lines, M A M B For the series arc fault detection device of this household and other households, a boundary element is installed on each line; arc faults are set at the main line of this household and the main line of other households.

[0040] The simulation sampling frequency is 1.25MHz. Five sampling points are taken after the fault. The instantaneous energy of the full-cycle fault component under normal conditions, arc fault within the fault zone, and arc fault outside the fault zone are as follows: Figure 3 , Figure 4 and Figure 5 As shown, Figure 3 This is the instantaneous energy waveform of the full-cycle fault component under normal conditions. Figure 4 This is a waveform diagram of the instantaneous energy of the full-cycle fault component under fault conditions within the fault zone. Figure 5 The image shows the instantaneous energy waveform of the full-cycle fault component under the condition of an external fault. The maximum value of the half-cycle represents the maximum instantaneous energy within the half-cycle. It can be seen that the instantaneous energy of the fault component is very different in the three cases, making them easy to distinguish.

[0041] The method provided by this invention is used to determine whether a line fault has occurred under different load conditions. 0.5 is used as the instantaneous energy setting value (second preset threshold) in the series arc fault detection device of the household distribution network. The simulation parameters are shown in Table 1, and the test results under normal operating conditions are shown in Table 2. A fault occurs within the designated area, i.e., in... The detection results under the condition of series arc fault are shown in Table 3. When an external fault occurs, that is, in The test results under the condition of series arc fault are shown in Table 4.

[0042] Table 1. Circuit parameters used in each simulation group Table 2. Maximum instantaneous half-wave energy under different loads under normal conditions Table 3. Detection results for different loads under fault conditions within the fault zone. Table 4. Detection results for different loads under the condition of an external fault. The above test results show that the method provided by the present invention has strong reliability and selectivity in detecting series arc faults.

[0043] When applying the boundary element-based distribution network series arc fault detection method provided by this invention, it is not necessary to consider... Figure 1 The steps shown are executed in sequence. The specific execution order of each step can be determined as needed, and this invention does not impose any restrictions on it.

[0044] The above describes a method for detecting series arc faults in distribution networks based on boundary elements, provided by one or more embodiments of the present invention. Based on the same idea, the present invention also provides a corresponding device for detecting series arc faults in distribution networks based on boundary elements, the device comprising: The detection start-up module is used to detect the voltage drop of the upper boundary element of the distribution network in real time. The boundary element is arranged at the installation position of the third-level residual current protection of the distribution network. When the derivative of the voltage drop of the boundary element is detected to be greater than the first preset threshold multiple times in a row, the series arc fault detection stage is entered. The fault detection module is used to calculate the full-cycle fault component in real time during the series arc fault detection stage, and to calculate the instantaneous energy of the full-cycle fault component based on the full-cycle fault component; taking half-cycle as the unit, when the maximum instantaneous energy in a half-cycle is greater than a second preset threshold, it is determined that a series arc fault has occurred in that half-cycle; when the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset number threshold, it is determined that a series arc fault has occurred in the distribution network.

[0045] Specific limitations regarding the boundary element-based distribution network series arc fault detection device can be found in the limitations of the boundary element-based distribution network series arc fault detection method described above, and will not be repeated here. Each module in the aforementioned boundary element-based distribution network series arc fault detection device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0046] The present invention also provides a computer-readable storage medium storing a computer program that can be used to execute the above-described... Figure 1 A method for detecting series arc faults in distribution networks based on boundary elements is provided.

[0047] The present invention also provides Figure 6 The schematic diagram of the computer device shown is as follows: Figure 6 As shown, at the hardware level, this computer device includes a processor, internal bus, network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then executes it to achieve the above. Figure 1 A method for detecting series arc faults in distribution networks based on boundary elements is provided.

[0048] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this invention.

Claims

1. A method for detecting series arc faults in a distribution network based on boundary elements, characterized in that, include: Real-time detection of voltage drop at the upper boundary of the power distribution network; Boundary elements are located at the installation positions of the third-level residual current protection in the distribution network. When the derivative of the voltage drop of the boundary element is detected to be greater than the first preset threshold multiple times in a row, the series arc fault detection stage is entered. During the series arc fault detection stage, the full-cycle fault component is calculated in real time, and the instantaneous energy of the full-cycle fault component is calculated based on the full-cycle fault component. Using half-cycles as units, when the maximum instantaneous energy within a half-cycle exceeds a second preset threshold, it is determined that a series arc fault has occurred in that half-cycle. When the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset number threshold, it is determined that a series arc fault has occurred in the distribution network. The formula for calculating the derivative of the voltage drop across the boundary element is: ； in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point For boundary elements in the first Voltage drop at each sampling point The time interval between two adjacent sampling points; No. The formula for calculating the full-cycle fault component corresponding to each sampling point is: ； in, For the first The full-cycle fault component corresponding to each sampling point For boundary elements in the first Voltage drop at each sampling point The number of sampling points per power frequency cycle. For boundary elements in the previous week wave Voltage drop at each sampling point; No. The formula for calculating the instantaneous energy of the full-cycle fault component corresponding to each sampling point is: ； in, For the first The instantaneous energy of the full-cycle fault component corresponding to each sampling point; For the first The full-cycle fault component at each sampling point.

2. The method according to claim 1, characterized in that, Three consecutive times means the derivative of the voltage drop across the boundary element is greater than the first preset threshold for three consecutive times. This is expressed by the formula: ； in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point The derivative, This is the first preset threshold.

3. The method according to claim 1, characterized in that, The method further includes: When a series arc fault is detected in the distribution network, an alarm signal is issued or the circuit breaker is tripped.

4. A distribution network series arc fault detection device based on boundary elements, characterized in that, The device includes: The detection start-up module is used to detect the voltage drop of the upper boundary element of the distribution network in real time. The boundary element is arranged at the installation position of the third-level residual current protection of the distribution network. When the derivative of the voltage drop of the boundary element is detected to be greater than the first preset threshold multiple times in a row, the series arc fault detection stage is entered. The fault detection module is used to calculate the full-cycle fault component in real time during the series arc fault detection stage, and to calculate the instantaneous energy of the full-cycle fault component based on the full-cycle fault component; taking half-cycle as the unit, when the maximum instantaneous energy in a half-cycle is greater than a second preset threshold, it is determined that a series arc fault has occurred in that half-cycle; when the number of half-cycles of series arc faults occurring in the distribution network within a preset time period is greater than or equal to a preset number threshold, it is determined that a series arc fault has occurred in the distribution network. The formula for calculating the derivative of the voltage drop across the boundary element is: ； in, For boundary elements in the first Voltage drop at each sampling point The derivative, For boundary elements in the first Voltage drop at each sampling point For boundary elements in the first Voltage drop at each sampling point The time interval between two adjacent sampling points; No. The formula for calculating the full-cycle fault component corresponding to each sampling point is: ； in, For the first The full-cycle fault component corresponding to each sampling point For boundary elements in the first Voltage drop at each sampling point The number of sampling points per power frequency cycle. For boundary elements in the previous week wave Voltage drop at each sampling point; No. The formula for calculating the instantaneous energy of the full-cycle fault component corresponding to each sampling point is: ； in, For the first The instantaneous energy of the full-cycle fault component corresponding to each sampling point; For the first The full-cycle fault component at each sampling point.

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