Single-phase earth fault detection method based on d-axis current multiple fundamental component integral ratio

Abstract

The invention belongs to the technical field of relay protection of a power distribution network of a power system, and provides a single-phase earth fault detection method based on a d-axis current multiple fundamental component integral ratio, which comprises the following steps of: 1, acquiring a three-phase current # imgabs0 # of each feeder line; 2, calculating positive and negative sequence components # imgabs1 # of three-phase current of each feeder line; 3, calculating the d-axis current # imgabs2 # of each feeder line; 4, extracting the components # imgabs3 # and # imgabs4 # of the d-axis current idn at 50Hz and 100Hz, and calculating the integral of the components # imgabs3 # and # imgabs4 #; step 5, calculating an integral ratio # imgabs5 #; three-phase current data of each feeder line are collected, positive and negative sequence components of the feeder line are calculated, d-axis current is obtained through double-dq conversion, then components of the d-axis current at 50Hz and 100Hz are extracted for integration, and whether the feeder line has a single-phase earth fault or not is judged by comparing the integral ratio of the two frequency components. The method has the effects of effectively detecting faults in a steady-state interval and under the condition of high transition resistance, and improving the accuracy and reliability of fault detection.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection for distribution networks in power systems, and specifically relates to a single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency components of the d-axis current. Background Art

[0002] The distribution network is an important public infrastructure and plays an important role in ensuring power supply, supporting economic and social development, and serving to improve people's livelihood. At present, in the distribution network system, the neutral point operation mode is mainly small current grounding (ungrounded and grounded through an arc suppression coil), and its proportion reaches more than 75%. In China, most user power outage events are caused by faults in the distribution network. Among them, the proportion of single-phase grounding faults is as high as 70% - 80%. And when the fault transition resistance is high, the fault current characteristics are weak. The installed arc suppression coil can compensate the capacitive current, making it more difficult to extract fault information. In the steady state interval, when the system operates in an over-compensated state, the zero-sequence currents of all lines are in the same phase, and the amplitudes of the fault line and the non-fault line are easily affected by the line parameters and are not easy to distinguish. If the fault line is not removed in time, the fault range will further expand, easily causing huge safety accidents.

[0003] Therefore, those skilled in the art have proposed a single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency components of the d-axis current to solve the problems raised in the background art. Summary of the Invention

[0004] To solve the above technical problems, the invention provides a single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency components of the d-axis current to solve the problems existing in the prior art.

[0005] In a first aspect, the invention provides a single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency components of the d-axis current, including the following steps: Step 1: Obtain the three-phase currents of each feeder ; Step 2: Calculate the positive and negative sequence components of the three-phase currents of each feeder , ; When it is the positive sequence component, When it is the negative sequence component; Step 3: Calculate the d-axis current of each feeder ; Step 4: Extract the components of the d-axis current at 50Hz and 100Hz , , and calculate their integrals; Step 5: Calculate the integral ratio , It is determined as a faulty feeder when It is determined as a sound feeder when

[0006] Preferably, the process of obtaining the three-phase currents of each feeder in step 1 is as follows: Install current detection devices on each line of the distribution network to collect three-phase current signals respectively , where , n is the number of each feeder, and let the fault occurrence time be s, the sampling start time is s, and the end time is s. A total of three-phase current signals with a data window length of 10 power frequency cycles are obtained.

[0007] Preferably, the specific process of step 2 is as follows: Step 2.1: Use Fourier transform to extract the fundamental frequency components of the three-phase currents of each feeder , where is the three-phase fundamental frequency current is the amplitude, is the initial phase, , f is the power frequency of 50 Hz; Step 2.2: The vector form of is ; In the formula, , is the zero-sequence current of feeder n , , are the vector forms of the positive and negative sequence currents of phase A of each feeder. For phases B and C, the following formulas are as follows: ; In the formula, is the vector form of the positive and negative sequence currents of phase B, is the vector form of the positive and negative sequence currents of phase C; The three-phase positive and negative sequence current vectors of each feeder can be expressed as: ; In the formula, and are the amplitudes and initial phases of the three-phase positive and negative sequence currents of each feeder respectively. The time-domain quantity is as follows: .

[0008] Preferably, the specific process of step 3 is as follows: Step 3.1: Take the phase of the positive sequence current of phase A of each feeder as the double dq transformation angle ; Step 3.2: Through double dq transformation, project the three-phase fundamental positive and negative sequence currents of each feeder onto the coordinate axes rotating at the same angular velocity as the positive sequence component. The positive sequence transformation process is as follows: ; In the formula, , are the d-axis and q-axis components of the positive sequence current; The negative sequence transformation is as follows: ; In the formula, , are the d-axis and q-axis components of the negative sequence current; Step 3.3: Calculate the d-axis current of each feeder. The calculation formula is as follows: .

[0009] Preferably, the specific process of step 4 is as follows: Step 4.1: Use Fourier transform to extract the components of the d-axis current of each feeder at frequencies of 50 Hz and 100 Hz, which are respectively represented as , ; Step 4.2: Select 10 power frequency cycles after the fault moment and integrate the 50 Hz current component to calculate the area enclosed by the absolute value of its waveform and the time axis, as follows: ; In the formula, is the fault occurrence moment, ; Step 4.3: Integrate the 100 Hz current component to calculate the area enclosed by the absolute value of its waveform and the time axis, as follows: .

[0010] Preferably, the specific process of step 5 is as follows: Step 5.1: Take the ratio of and to obtain , as follows: ; Step 5.2: If , it is determined that the feeder has a fault; if , there is no fault.

[0011] In a second aspect, the present invention provides a single-phase grounding fault detection device based on the integral ratio of the double fundamental frequency component of the d-axis current, which is applied to the above-mentioned single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency component of the d-axis current, and includes: A data acquisition module, configured to acquire three-phase current data of each feeder; A symmetrical component calculation module, configured to calculate the positive and negative sequence components of the three-phase current of each feeder; A double dq transformation module, configured to calculate the d-axis current of each feeder; A current component extraction and integration module, configured to extract and integrate the components of the d-axis current at 50 Hz and 100 Hz; A fault detection criterion module, configured to determine whether a feeder has a fault according to the integral ratio.

[0012] In a third aspect, the present invention provides a processor configured to execute the above-mentioned single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency component of the d-axis current.

[0013] In a fourth aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the above-mentioned single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency component of the d-axis current is implemented.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. By collecting the three-phase current data of each feeder and using the symmetrical component method and the double dq transformation technology, the present invention accurately extracts the components of the d-axis current at 50 Hz and 100 Hz, and determines whether a single-phase grounding fault occurs in the feeder by comparing the integral ratios of these two frequency components. This method effectively avoids misjudgment or missed judgment caused by the same-phase zero-sequence current in the steady-state interval or weak fault characteristics under a high transition resistance in the traditional method, and significantly improves the accuracy of fault detection.

[0015] 2. The data window length adopted by the present invention is 10 power frequency cycles (0.2 s) after the fault occurrence time, ensuring sufficient data length to capture the fault characteristics. At the same time, through the integral processing of specific frequency components, the fault characteristics are amplified, so that the fault line and the healthy line show significant differences in the integral ratio, further enhancing the reliability of fault detection.

[0016] 3. In a distribution network system with an ungrounded neutral point or grounded through an arc suppression coil, when a single-phase grounding fault occurs and the transition resistance is high, the fault current characteristics are weak, and it is difficult for the traditional method to effectively detect. However, the present invention can effectively identify the single-phase grounding fault under a high transition resistance by extracting the characteristic frequency components in the d-axis current and calculating the integral ratio, improving the fault tolerance of the system.

[0017] 4. Through a series of mathematical transformations and calculations, the present invention converts complex three-phase current data into a simple and clear integral ratio criterion, simplifies the fault detection process, and improves the detection efficiency. At the same time, this method is easy to implement automation and intelligence, and can be widely applied to the relay protection system of the distribution network.

[0018] 5. By setting a clear integral ratio threshold (W n > 1 is determined as a faulty feeder, and W n < 1 is determined as a sound feeder), it provides an intuitive and easy-to-operate judgment basis for fault detection. This basis is not only convenient for engineering implementation, but also helps to improve the timeliness and effectiveness of fault handling. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : The fault detection flow chart of the present invention; Figure 2 : The positive and negative sequence double dq transformation coordinate system of the present invention; Figure 3 : The 10 kV resonant grounding system model of the present invention; Figure 4 : The d-axis current waveform diagram of each feeder of the present invention; Figure 5 : The 50 Hz and 100 Hz current waveform diagrams of each feeder of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following further describes in detail the embodiments of the present invention in conjunction with the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0021] The present invention provides a single-phase grounding fault detection method based on the integral ratio of the d-axis current double fundamental frequency component. As Figure 1 shown, it includes the following steps: Step 1: Obtain the three-phase currents of each feeder ; Step 2: Calculate the positive and negative sequence components of the three-phase currents of each feeder , ; When it is the positive sequence component, and when Step 3: Calculate the d-axis current of each feeder ; Step 4: Extract the components of the d-axis current at 50 Hz and 100 Hz , , and calculate their integrals; Step 5: Calculate the integral ratio , It is determined as a faulty feeder when It is determined as a sound feeder when

[0022] As can be seen from the above, this method can effectively identify the single-phase grounding fault feeder by collecting the three-phase currents of each feeder, calculating their positive and negative sequence components, then obtaining the d-axis current through double dq transformation, and extracting the 50Hz and 100Hz components for integral comparison. Especially in the steady state interval and the case of high transition resistance, it can significantly improve the accuracy and reliability of fault detection, effectively avoid the expansion of the fault range, and ensure the safe and stable operation of the power system.

[0023] Specifically, the process of obtaining the three-phase currents of each feeder in step 1 is as follows: Install current detection devices on each line of the distribution network to collect three-phase current signals respectively , where , n is the number of each feeder, and let the fault occurrence time be s, the sampling start time is s, and the end time is s, and three-phase current signals with a data window length of 10 power frequency cycles are obtained in total.

[0024] Specifically, the specific process of step 2 is as follows: Step 2.1: Use Fourier transform to extract the fundamental frequency components of the three-phase currents of each feeder , where is the amplitude of the three-phase fundamental frequency current , is the initial phase, , f is the power frequency of 50Hz; Step 2.2: The vector form of is ; In the formula, , is the zero-sequence current of feeder n , , are the vector forms of the positive and negative sequence currents of phase A of each feeder. For phases B and C, the following formulas are as follows: ; In the formula, is the vector form of the positive and negative sequence currents of phase B, is the vector form of the positive and negative sequence currents of phase C; The three-phase positive and negative sequence current vectors of each feeder can be expressed as: ; In the formula, and The amplitudes and initial phases of the positive and negative sequence currents of each feeder for three phases, which are time-domain quantities are as follows: .

[0025] As can be seen from the above, by using Fourier transform to accurately extract the fundamental frequency components of the three-phase currents of each feeder and combining the symmetrical component method to decompose the three-phase currents into positive and negative sequence components, this process effectively simplifies the complex three-phase current data, enabling the subsequent double dq transformation and fault detection criteria to be analyzed based on clearer and more accurate current components, thereby improving the accuracy and reliability of single-phase grounding fault detection. Especially when dealing with faults in the steady state interval and under high transition resistance conditions, the effect is more significant.

[0026] Specifically, the specific process of step 3 is as follows: Step 3.1: Take the phase of the positive sequence current of phase A of each feeder as the double dq transformation angle ; Step 3.2: Through double dq transformation, project the positive and negative sequence fundamental frequency currents of each feeder's three phases onto the coordinate axes rotating at the same angular velocity as the positive sequence component. The positive sequence transformation process is as follows: ; In the formula, , are the d-axis and q-axis components of the positive sequence current; The negative sequence transformation is as follows: ; In the formula, , are the d-axis and q-axis components of the negative sequence current; Step 3.3: Calculate the d-axis current of each feeder , and the calculation formula is as follows: ; As can be seen from the above, taking the phase of the positive sequence current of phase A of each feeder as the dq transformation angle and combining double dq transformation to project the positive and negative sequence fundamental frequency currents of each feeder's three phases onto the coordinate axes rotating at the same angular velocity as the positive sequence component effectively separates the positive and negative sequence components in the current, and then accurately calculates the d-axis current of each feeder. It not only simplifies the complexity of current data processing but also improves the accuracy of current component analysis, providing a reliable data basis for the subsequent fault detection criterion based on the integral ratio of the double fundamental frequency component of the d-axis current, thus significantly improving the accuracy and efficiency of single-phase grounding fault detection.

[0027] Specifically, the specific process of step 4 is as follows: Step 4.1: Use Fourier transform to extract the d-axis current of each feeder The components at frequencies of 50 Hz and 100 Hz are respectively denoted as and ; Step 4.2: Select 10 power frequency cycles after the fault moment, and integrate the 50 Hz current component to calculate the area enclosed by the absolute value of its waveform and the time axis , as shown in the following formula: ; In the formula, is the fault occurrence moment, ; Step 4.3: Integrate the 100 Hz current component to calculate the area enclosed by the absolute value of its waveform and the time axis , as shown in the following formula: .

[0028] As can be seen from the above, by accurately extracting the components of the d-axis current of each feeder at 50 Hz and 100 Hz using Fourier transform, and integrating these two frequency components within 10 power frequency cycles after the fault moment to calculate the area enclosed by the absolute value of their waveforms and the time axis, the characteristic frequency components in the fault current are effectively captured, and the fault characteristics are amplified through integral processing, making the fault line and the healthy line show significant differences in the integral ratio, thus providing strong support for the subsequent fault detection criterion based on the integral ratio, and significantly improving the sensitivity and accuracy of single-phase grounding fault detection.

[0029] Specifically, the specific process of step 5 is as follows: Step 5.1: Take the ratio of and to obtain , as shown in the following formula: ; Step 5.2: Final criterion: If , it is determined that the feeder has a fault; if , there is no fault.

[0030] As can be seen from the above, by calculating the ratio of the integral values of the d-axis current components of each feeder at 50 Hz and 100 Hz and setting a clear fault determination threshold (that is, when the ratio is greater than 1, it is determined as a fault feeder, and when it is less than 1, it is determined as a healthy feeder), the differences in the characteristic frequency components in the fault current are effectively utilized, and the rapid and accurate detection of single-phase grounding faults is realized. This method not only improves the sensitivity of fault detection, but also enhances the reliability of the detection results, helps to cut off the fault line in time, prevent the expansion of the fault range, and ensure the safe and stable operation of the power system.

[0031] The following is a further explanation of the principle of the above steps: 1. Analysis of the phase current of the faulty line When the system is not faulty, the three-phase currents in the line are symmetric, as shown in the following equation: ; In the formula, I is the amplitude of the three-phase current under normal operation, is the initial phase angle of the phase A current. When a fault occurs in phase A, a first-order differential equation for the faulty phase current is written as follows: ; In the formula, U m , are the amplitudes and initial phase angles of the three-phase voltages; solving the differential equation gives the expression of the faulty phase current i a (t) as follows: ; In the formula, is the phase angle after the phase A current reaches the steady state, I m is the steady-state amplitude, I d is the DC decay component, τ is the decay time constant; the three-phase current expression is as follows: ; It can be seen from the above formula that after a single-phase grounding fault occurs, the three-phase currents are asymmetric. In addition to the fundamental frequency component, the faulty phase current also appears a decaying DC component. In this case, the traditional dq transformation is limited in use.

[0032] 2. Double dq transformation After a single-phase grounding fault occurs in the distribution network system, the three-phase currents in the line become asymmetric. Therefore, the positive and negative sequence components of the three-phase fundamental frequency currents are extracted by using the symmetrical component method, and then they are transformed into the positive sequence synchronous rotating coordinate system with an angular velocity of , as shown in Figure 2 . The transformation matrix is as follows: ; The d-axis component of the positive sequence current is . The negative sequence current has the same magnitude of the rotational angular velocity as the positive sequence current but the opposite direction. Therefore, the d-axis component of the negative sequence current is . The total current of the d-axis component in the positive sequence synchronous rotating coordinate system is , when a single-phase ground fault occurs, the d-axis current of the faulty line mainly contains fundamental frequency components and second harmonic components. Analysis shows that the second harmonic component is mainly caused by the negative sequence current in the line, and the negative sequence component mainly exists in the faulty line. The negative sequence current in the sound line is almost negligible. Therefore, the second harmonic component in the d-axis current of the three-phase current of the sound line in the positive sequence synchronous rotating coordinate system is very small. Using this feature, the faulty line can be detected.

[0033] 3. Detection criterion Select a time window of 0.2 s, that is , is the fault occurrence time, extract the 50 Hz and 100 Hz components of the d-axis current of each line 、 , and integrate their absolute values: ; That is, calculate the area enclosed by the absolute value of its waveform and the time axis, and take the ratio of the two: ; Compared with the sound line, the faulty line contains a large amount of second harmonic components, and the amplitude is significantly greater than the fundamental frequency component. Therefore, for the faulty line, there is , on the contrary, for the sound line, there is . Embodiment

[0034] Build a resonant grounding system simulation model as Figure 3 shown. Set 4 feeders , which are overhead, cable, and overhead-cable hybrid lines. Install current transformers at the head of the line, and set that a single-phase ground fault occurs at 0.6 s at 3 km, and the fault resistance is 2000 Ω. The over-compensation degree is taken as 5%, and the inductance of the arc suppression coil is calculated as , and the series resistance ; The line parameters are shown in Table 1;

[0035] To facilitate observing its characteristics, filter the DC component from the calculated d-axis current of each feeder, as Figure 4 shown; It can be seen from Figure 4 that after the fault occurs, the d-axis current of the faulty feeder changes suddenly, the amplitude increases significantly, and the frequency changes, which is quite different from the sound feeder.

[0036] Extract the 50 Hz and 100 Hz components of the d-axis current of each feeder, as Figure 5 shown. Compared with the sound feeder, the faulty feeder; Integrate the absolute value of its waveform to obtain 、 , and calculate the ratio W = P 100 / P 50 , and the results are shown in Table 2;

[0037] As can be seen from Table 2, only in Line 3, the integral ratio W of the second harmonic frequency to the fundamental frequency of the d-axis current is much greater than 1, and other lines do not meet this condition, so the line where the single-phase grounding fault occurs can be accurately detected.

[0038] In summary: The present invention describes a single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency components of the d-axis current. This method collects the three-phase current data of each feeder, calculates its positive and negative sequence components, and uses the double dq transformation to obtain the d-axis current. Then, the components of the d-axis current at 50 Hz and 100 Hz are extracted for integration, and whether a single-phase grounding fault occurs in the feeder is determined by comparing the integral ratios of these two frequency components. It has the effects of effectively detecting faults in the steady state interval and under high transition resistance conditions, and improving the accuracy and reliability of fault detection.

[0039] A single-phase grounding fault detection device based on the integral ratio of the double fundamental frequency components of the d-axis current, which is applied to the above single-phase grounding fault detection method based on the integral ratio of the double fundamental frequency components of the d-axis current, includes: A data acquisition module, which is used to obtain the three-phase current data of each feeder, where n is the line number; A symmetrical component calculation module, which is used to calculate the positive and negative sequence components of the three-phase current of each feeder, specifically including: A fundamental frequency component extraction unit, which uses Fourier transform to extract the fundamental frequency components of the three-phase current of each feeder; A symmetrical component decomposition unit, which decomposes the three-phase fundamental frequency current into positive and negative sequence components according to the symmetrical component method; A double dq transformation module, which is used to calculate the d-axis current of each feeder, specifically including: A transformation angle acquisition unit, which uses the phase-locked loop technology to obtain the dq transformation angle based on the positive sequence three-phase current of each feeder; A double dq transformation unit, which projects the positive and negative sequence currents of the three-phase fundamental frequency of each feeder into the dq coordinate system rotating at the same angular velocity as the positive sequence component through double dq transformation; A d-axis current calculation unit, which calculates the d-axis current of each feeder; A current component extraction and integration module, which is used to extract and integrate the components of the d-axis current at 50 Hz and 100 Hz, specifically including: A current component extraction unit, which uses Fourier transform to extract the components of the d-axis current of each feeder at 50 Hz and 100 Hz, which are respectively expressed as , ; The integral calculation unit selects 10 power frequency cycles after the fault moment, integrates the 50Hz and 100Hz current components, and calculates the areas enclosed by the absolute values of their waveforms and the time axis respectively; The fault detection criterion module is used to judge whether a fault occurs in the feeder according to the integral ratio, specifically including: The integral ratio calculation unit calculates the integral ratio W n =P n_100 / P n_50 ; The fault judgment unit, if W n >1, it is determined that a fault has occurred in the feeder; if W n <1, it is determined that the feeder is a sound feeder.

[0040] An embodiment of the present application provides an electronic device, which is applicable to the above-mentioned single-phase grounding fault detection method based on the integral ratio of the d-axis current double fundamental frequency component, including: A memory for protecting computer programs and data; A processor for running system programs.

[0041] An embodiment of the present application provides a computer storage medium, which is applicable to the above-mentioned single-phase grounding fault detection method based on the integral ratio of the d-axis current double fundamental frequency component, and performs hierarchical confidentiality management on the above system and data according to the confidentiality management requirements.

[0042] Those skilled in the art should understand that the embodiments of the present application can be provided as a system or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0043] The present application is described with reference to the flowcharts and / or block diagrams of the devices (systems) and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate for implementing in the process Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks to specify the function of the device.

[0044] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one process Figure 1 or a plurality of processes and / or blocks Figure 1 or a plurality of blocks specified in the block.

[0045] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one process Figure 1 or a plurality of processes and / or blocks Figure 1 or a plurality of blocks specified in the block.

[0046] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.

[0047] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM) and / or non-volatile memory such as read-only memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media.

[0048] Computer-readable media includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media such as modulated data signals and carrier waves.

[0049] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, commodity or device including the elements.

[0050] The embodiments of the present invention are provided for the purpose of illustration and description. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A single-phase grounding fault detection method based on the integral ratio of the fundamental frequency component of the d-axis current, characterized in that: Including the following steps: Step 1: Obtain the three-phase currents of each feeder ; Step 2: Calculate the positive and negative sequence components of the three-phase currents of each feeder , ; It is the positive sequence component when and the negative sequence component when Step 3: Calculate the d-axis current of each feeder ; Step 4: Extract the d-axis current Components at 50 Hz and 100 Hz and , calculate their integrals; Step 5: Calculate the integral ratio , When it is determined as a faulty feeder line, When it is determined as a sound feeder line.

2. The single-phase grounding fault detection method based on the integral ratio of the d-axis current double fundamental frequency component according to claim 1, wherein: The process of obtaining the three-phase currents of each feeder in step 1 is as follows: Install current detection devices on each line of the distribution network to collect three-phase current signals respectively , where , n is the number of each feeder, and let the fault occurrence time be s, the sampling start time is s, and the end time is s. Three-phase current signals with a data window length of 10 power frequency cycles are obtained in total 3. The single-phase ground fault detection method based on the integral ratio of the fundamental frequency component of the d-axis current as claimed in claim 1, wherein: The specific process of step 2 is as follows: Step 2.1: Use Fourier transform to extract the fundamental frequency components of the three-phase currents of each feeder , where is the amplitude of the three-phase fundamental frequency current , is the initial phase , f is the power frequency of 50 Hz; Step 2.2: The vector form of is, according to the symmetrical component method: ； Wherein, , is the zero-sequence current of the feeder n , , are the vector forms of the positive and negative sequence currents of phase A of each feeder. For phases B and C, the following equations apply: ； In the formula, is the vector form of the positive and negative sequence currents of phase B, is the vector form of the positive and negative sequence currents of phase C; The positive and negative sequence current vectors of each feeder's three phases can be expressed as: ； wherein, and are respectively the amplitudes and initial phases of the positive and negative sequence currents of each feeder, and the time-domain quantity is as follows: 。 4. The single-phase grounding fault detection method based on the integral ratio of the fundamental frequency component of the d-axis current as described in claim 1, wherein: The specific process of step 3 is as follows: Step 3.1: Take the phase of the positive-sequence current of the A-phase of each feeder as the double dq transformation angle ; Step 3.2: Through double dq transformation, project the three-phase fundamental positive and negative sequence currents of each feeder onto the coordinate axes rotating at the same angular velocity as the positive sequence component. The positive sequence transformation process is as follows: ； wherein, and are the d-axis and q-axis components of the positive-sequence current; The negative sequence transformation is as follows: ； wherein, , are the d-axis and q-axis components of the negative-sequence current; Step 3.3: Calculate the d-axis current of each feeder , and the calculation formula is as follows: 。 5. The single-phase grounding fault detection method based on the integral ratio of the d-axis current double fundamental frequency component as described in claim 1, characterized in that: The specific process of step 4 is as follows: Step 4.1: Use Fourier transform to extract the d-axis current of each feeder The components at frequencies of 50 Hz and 100 Hz are respectively expressed as , ; Step 4.2: Select 10 power frequency cycles after the fault moment, and integrate the 50Hz current component to calculate the area enclosed by the absolute value of its waveform and the time axis , as shown in the following formula: ； wherein, is the moment when the fault occurs, ; Step 4.3: Integrate the 100 Hz current component to calculate the area enclosed by the absolute value of its waveform and the time axis , as shown in the following equation: 。 6. The single-phase ground fault detection method based on the integration ratio of the d-axis current double fundamental frequency components as described in claim 1, wherein: The specific process of step 5 is as follows: Step 5.1: Take the ratio of and to obtain , as shown in the following formula: ； Step 5.2: If , it is determined that the feeder has a fault; if , then there is no fault.

7. A single-phase grounding fault detection device based on the integral ratio of the fundamental frequency component of the d-axis current multiple, characterized in that Applied to a single-phase grounding fault detection method based on the integral ratio of the fundamental frequency component of the d-axis current as described in any one of claims 1-6, including: A data acquisition module for obtaining the three-phase current data of each feeder; A symmetrical component calculation module for calculating the positive and negative sequence components of the three-phase current of each feeder; A double dq transformation module for calculating the d-axis current of each feeder; A current component extraction and integration module for extracting the components of the d-axis current at 50Hz and 100Hz and integrating them; A fault detection criterion module for judging whether a feeder has a fault according to the integral ratio.

8. A processor, characterized in that: Configured to execute a single-phase grounding fault detection method based on the integral ratio of the fundamental frequency component of the d-axis current as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: Stored thereon is a computer program, which when executed by a processor implements a single-phase grounding fault detection method based on the integral ratio of the fundamental frequency component of the d-axis current as described in any one of claims 1 to 6.

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