A single-phase ground fault detection method based on the integral ratio of the d-axis current multiple fundamental frequency component

Abstract

The present invention belongs to the technical field of relay protection of power system distribution network, and provides a single-phase ground fault detection method based on the integral ratio of d-axis current multiple fundamental frequency component, step 1: obtain the three-phase current #imgabs0# of each feeder; step 2: calculate the positive and negative sequence components #imgabs1# of the three-phase current of each feeder; step 3: calculate the d-axis current #imgabs2# of each feeder; step 4: extract the d-axis current i dn The components #imgabs3# and #imgabs4# at 50 Hz and 100 Hz are integrated; step 5: calculating the integral ratio #imgabs5#; the present invention collects three-phase current data of each feeder, calculates its positive and negative sequence components, and uses double dq transformation to obtain the d-axis current, and then extracts the components of the d-axis current at 50 Hz and 100 Hz for integration. By comparing the integral ratio of these two frequency components, it is determined whether a single-phase grounding fault occurs in the feeder. The present invention has the effect of effectively detecting faults in the steady-state range and under high transition resistance conditions, and improving the accuracy and reliability of fault detection.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of power system distribution network, in particular to a single-phase grounding fault detection method based on the integral ratio of a d-axis current multiplied by a fundamental frequency component. Background Art

[0002] The distribution network is a vital public infrastructure, playing a crucial role in ensuring power supply, supporting economic and social development, and improving people's livelihoods. Currently, low-current grounding (ungrounded or grounded via arc suppression coils) is the predominant neutral point operation mode in distribution networks, accounting for over 75%. In my country, the majority of power outages are caused by distribution network faults, of which single-phase grounding faults account for 70% to 80%. When the fault transition resistance is high, the fault current signature is weak. Arc suppression coils compensate for the capacitive current, making fault information extraction more difficult. In the steady-state range, when the system operates in an overcompensated state, the zero-sequence currents of all lines are in phase. The amplitudes of the fault line and the non-fault line are easily affected by line parameters, making it difficult to distinguish. Failure to promptly remove the fault line can further expand the fault range, potentially leading to serious 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 d-axis current times the fundamental frequency component to solve the problem raised in the background art. Summary of the Invention

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

[0005] In a first aspect, the present invention provides a single-phase ground fault detection method based on the integral ratio of the d-axis current multiple fundamental frequency component, comprising the following steps:

[0006] Step 1: Obtain the three-phase current of each feeder ;

[0007] Step 2: Calculate the positive and negative sequence components of the three-phase current of each feeder , ; When is the positive sequence component, When is negative sequence component;

[0008] Step 3: Calculate the d-axis current of each feeder ;

[0009] Step 4: Extract d-axis current Components at 50Hz and 100Hz 、 , calculate its integral;

[0010] Step 5: Calculate the integral ratio , When it is determined to be a faulty feeder, The feeder is judged to be healthy.

[0011] Preferably, the process of obtaining the three-phase current of each feeder in step 1 is as follows: a current detection device is installed on each line of the distribution network to collect the three-phase current signals respectively. ,in, , n is the number of each feeder, and the time of fault occurrence is s, the sampling start time is s, the end time is s, and a three-phase current signal with a data window length of 10 power frequency cycles is obtained.

[0012] Preferably, the specific process of step 2 is:

[0013] Step 2.1: Use Fourier transform to extract the fundamental frequency component of the three-phase current of each feeder ,in, is the three-phase fundamental frequency current The amplitude of is the initial phase, , f The power frequency is 50Hz;

[0014] Step 2.2: The vector form of , according to the symmetric component method:

[0015] ;

[0016] Where, , For feeder n The zero sequence current, 、 is the vector form of the positive and negative sequence current of phase A of each feeder, and for phases B and C, it is as follows:

[0017] ;

[0018] Where, is the vector form of the positive and negative sequence current of phase B, is the vector form of the positive and negative sequence current of phase C;

[0019] The three-phase positive and negative sequence current vectors of each feeder can be expressed as:

[0020] ;

[0021] Where, and are the amplitude and initial phase of the positive and negative sequence currents of the three phases of each feeder, respectively. As follows:

[0022] .

[0023] Preferably, the specific process of step 3 is:

[0024] Step 3.1: Take the phase of the positive sequence current of phase A of each feeder as the double dq transformation angle ;

[0025] Step 3.2: Through double dq transformation, the three-phase fundamental frequency positive and negative sequence currents of each feeder are converted to They are all projected onto the coordinate axis that rotates at the same angular velocity as the positive sequence component. The positive sequence transformation process is as follows:

[0026] ;

[0027] Where, 、 are the d and q axis components of the positive sequence current;

[0028] The negative sequence transformation is as follows:

[0029] ;

[0030] Where, 、 are the d and q axis components of the negative sequence current;

[0031] Step 3.3: Calculate the d-axis current of each feeder , the calculation formula is as follows:

[0032] .

[0033] Preferably, the specific process of step 4 is:

[0034] 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 expressed as 、 ;

[0035] Step 4.2: Select 10 power frequency cycles after the fault moment and calculate the 50Hz current component. Integrate and calculate the area enclosed by the absolute value of the waveform and the time axis , as follows:

[0036] ;

[0037] Where, is the time when the fault occurs, ;

[0038] Step 4.3: 100Hz current component Integrate and calculate the area enclosed by the absolute value of the waveform and the time axis , as follows:

[0039] .

[0040] Preferably, the specific process of step 5 is:

[0041] Step 5.1: and Ratio, we get , as follows:

[0042] ;

[0043] Step 5.2: If , it is determined that the feeder has a fault; if , no fault has occurred.

[0044] In a second aspect, the present invention provides a single-phase ground fault detection device based on the integral ratio of the d-axis current times the fundamental frequency component, which is applied to the above-mentioned single-phase ground fault detection method based on the integral ratio of the d-axis current times the fundamental frequency component, comprising:

[0045] Data acquisition module, used to obtain three-phase current data of each feeder;

[0046] Symmetrical component calculation module, used to calculate the positive and negative sequence components of the three-phase current of each feeder;

[0047] Dual dq conversion module, used to calculate the d-axis current of each feeder;

[0048] Current component extraction and integration module, used to extract and integrate the components of the d-axis current at 50Hz and 100Hz;

[0049] The fault detection criterion module is used to determine whether a feeder fault occurs based on the integral ratio.

[0050] 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 d-axis current times the fundamental frequency component.

[0051] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned single-phase grounding fault detection method based on the integral ratio of the d-axis current times the fundamental frequency component.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. This method collects three-phase current data from each feeder and uses the symmetrical component method and double dq transformation technology to accurately extract the d-axis current components at 50Hz and 100Hz. It then determines whether a single-phase ground fault has occurred in the feeder by comparing the integral ratio of these two frequency components. This method effectively avoids the misjudgment or missed detection caused by traditional methods due to the in-phase zero-sequence current in the steady-state interval or the weak fault characteristics under high transition resistance, significantly improving the accuracy of fault detection.

[0054] 2. The data window length used in this invention is 10 power frequency cycles (0.2s) after the fault occurs, ensuring sufficient data length to capture fault characteristics. Furthermore, by integrating specific frequency components, the fault characteristics are amplified, resulting in a significant difference in the integral ratio between the faulty line and the healthy line, further enhancing the reliability of fault detection.

[0055] 3. In distribution networks with an ungrounded neutral point or grounded via an arc suppression coil, when a single-phase ground fault occurs and the transition resistance is high, the fault current characteristics are weak, making it difficult to effectively detect with traditional methods. However, by extracting the characteristic frequency component of the d-axis current and calculating the integral ratio, the present invention can effectively identify single-phase ground faults in high transition resistance conditions, thereby improving the system's fault tolerance.

[0056] 4. Through a series of mathematical transformations and calculations, the present invention transforms complex three-phase current data into a concise integral ratio criterion, simplifying the fault detection process and improving detection efficiency. Furthermore, the method is easily automated and intelligent, and can be widely applied in distribution network relay protection systems.

[0057] 5. The present invention sets a clear integral ratio threshold (W n >1 is determined as a faulty feeder, W n <1, the feeder is considered healthy), providing an intuitive and easy-to-use basis for fault detection. This basis not only facilitates engineering implementation but also helps improve the timeliness and effectiveness of fault handling. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 : Fault detection flow chart of the present invention;

[0059] Figure 2 : The positive and negative sequence double dq transformation coordinate system of the present invention;

[0060] Figure 3 : 10kV resonant grounding system model of the present invention;

[0061] Figure 4: The d-axis current waveform of each feeder of the present invention;

[0062] Figure 5 : 50Hz and 100Hz current waveforms of each feeder of the present invention. DETAILED DESCRIPTION

[0063] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0064] The present invention provides a single-phase ground fault detection method based on the integral ratio of the d-axis current multiple fundamental frequency component, such as Figure 1 As shown, the following steps are included:

[0065] Step 1: Obtain the three-phase current of each feeder ;

[0066] Step 2: Calculate the positive and negative sequence components of the three-phase current of each feeder , ; When is the positive sequence component, When is negative sequence component;

[0067] Step 3: Calculate the d-axis current of each feeder ;

[0068] Step 4: Extract d-axis current Components at 50Hz and 100Hz 、 , calculate its integral;

[0069] Step 5: Calculate the integral ratio , When it is determined to be a faulty feeder, The feeder is judged to be healthy.

[0070] From the above, it can be seen that this method collects the three-phase current of each feeder, calculates its positive and negative sequence components, obtains the d-axis current through double dq transformation, and extracts the 50Hz and 100Hz components for integral comparison. It can effectively identify single-phase grounding fault feeders, especially in the steady-state range and high transition resistance conditions. 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.

[0071] Specifically, the process of obtaining the three-phase current of each feeder in step 1 is as follows: a current detection device is installed on each line of the distribution network to collect the three-phase current signals ,in, , n is the number of each feeder, and the time of fault occurrence is s, the sampling start time is s, the end time is s, and a three-phase current signal with a data window length of 10 power frequency cycles is obtained.

[0072] Specifically, the specific process of step 2 is:

[0073] Step 2.1: Use Fourier transform to extract the fundamental frequency component of the three-phase current of each feeder ,in, is the three-phase fundamental frequency current The amplitude of is the initial phase, , f The power frequency is 50Hz;

[0074] Step 2.2: The vector form of , according to the symmetric component method:

[0075] ;

[0076] Where, , For feeder n The zero sequence current, 、 is the vector form of the positive and negative sequence current of phase A of each feeder, and for phases B and C, it is as follows:

[0077] ;

[0078] Where, is the vector form of the positive and negative sequence current of phase B, is the vector form of the positive and negative sequence current of phase C;

[0079] The three-phase positive and negative sequence current vectors of each feeder can be expressed as:

[0080] ;

[0081] Where, and are the amplitude and initial phase of the positive and negative sequence currents of the three phases of each feeder, respectively. As follows:

[0082] .

[0083] From the above, it can be seen that by using Fourier transform to accurately extract the fundamental frequency component of the three-phase current of each feeder, and combining it with the symmetrical component method to decompose the three-phase current into positive-sequence and negative-sequence components, this process effectively simplifies the complex three-phase current data, so that the subsequent double dq transform and fault detection criteria can 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 range and under high transition resistance conditions.

[0084] Specifically, the specific process of step 3 is:

[0085] Step 3.1: Take the phase of the positive sequence current of phase A of each feeder as the double dq transformation angle ;

[0086] Step 3.2: Through double dq transformation, the three-phase fundamental frequency positive and negative sequence currents of each feeder are converted to They are all projected onto the coordinate axis that rotates at the same angular velocity as the positive sequence component. The positive sequence transformation process is as follows:

[0087] ;

[0088] Where, 、 are the d and q axis components of the positive sequence current;

[0089] The negative sequence transformation is as follows:

[0090] ;

[0091] Where, 、 are the d and q axis components of the negative sequence current;

[0092] Step 3.3: Calculate the d-axis current of each feeder , the calculation formula is as follows:

[0093] ;

[0094] As can be seen from the above, using the phase of each feeder's A-phase positive-sequence current as the dq transformation angle and combining it with a double dq transformation to project each feeder's three-phase fundamental frequency positive and negative-sequence currents onto coordinate axes rotating at the same angular velocity as the positive-sequence component effectively separates the positive and negative-sequence components in the current, allowing accurate calculation of each feeder's d-axis current. This not only simplifies the complexity of current data processing but also improves the accuracy of current component analysis. This provides a reliable data foundation for subsequent fault detection criteria based on the integral ratio of the d-axis current times the fundamental frequency component, significantly improving the accuracy and efficiency of single-phase ground fault detection.

[0095] Specifically, the specific process of step 4 is:

[0096] 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 expressed as 、 ;

[0097] Step 4.2: Select 10 power frequency cycles after the fault moment and calculate the 50Hz current component. Integrate and calculate the area enclosed by the absolute value of the waveform and the time axis , as follows:

[0098] ;

[0099] Where, is the time when the fault occurs, ;

[0100] Step 4.3: 100Hz current component Integrate and calculate the area enclosed by the absolute value of the waveform and the time axis , as follows:

[0101] .

[0102] From the above, it can be seen that by using Fourier transform to accurately extract the 50Hz and 100Hz components of the d-axis current of each feeder, and integrating these two frequency components within 10 power frequency cycles after the fault moment, the area enclosed by the absolute value of their waveform and the time axis is calculated, thereby effectively capturing the characteristic frequency components in the fault current, and amplifying the fault characteristics through integration processing, so that the fault line and the sound line show a significant difference in the integral ratio, which provides strong support for the subsequent fault detection criterion based on the integral ratio and significantly improves the sensitivity and accuracy of single-phase grounding fault detection.

[0103] Specifically, the specific process of step 5 is:

[0104] Step 5.1: and Ratio, we get , as follows:

[0105] ;

[0106] Step 5.2: Final judgment: If , it is determined that the feeder has a fault; if , no fault has occurred.

[0107] As can be seen from the above, by calculating the ratio of the integrated values ​​of the 50Hz and 100Hz components of each feeder's d-axis current and setting a clear fault determination threshold (i.e., a feeder is identified as faulty when the ratio is greater than 1, and as healthy when it is less than 1), this method effectively utilizes the differences in the characteristic frequency components of the fault current to achieve rapid and accurate detection of single-phase grounding faults. This method not only improves the sensitivity of fault detection but also enhances the reliability of the detection results, helping to promptly remove the faulty line, prevent the fault from expanding, and ensure the safe and stable operation of the power system.

[0108] The following is a further explanation of the principles of the above steps:

[0109] 1. Fault line phase current analysis

[0110] When there is no fault in the system, the three-phase current in the line is symmetrical, as shown in the following formula:

[0111] ;

[0112] Where, I is the three-phase current amplitude under normal operation, is the initial phase angle of the current in phase A. When a fault occurs in phase A, the first-order differential equation for the fault phase current is written as follows:

[0113] ;

[0114] Where, U m 、 is the amplitude and initial phase angle of the three-phase voltage; solve the differential equation to get the fault phase current i a The expression of (t) is as follows:

[0115] ;

[0116] Where, is the phase angle after the A phase current reaches steady state, I m is the steady-state amplitude, I d is the DC attenuation component, τ is the decay time constant; the three-phase current expression is as follows:

[0117] ;

[0118] 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 fault phase current also has an attenuated DC component. In this case, the use of traditional dq transformation is limited.

[0119] 2. Double DQ conversion

[0120] After a single-phase grounding fault occurs in the distribution network system, the three-phase current in the line becomes asymmetric. Therefore, the positive and negative sequence components of the three-phase fundamental frequency current are extracted using the symmetrical component method, and then converted to an angular velocity of In the positive sequence synchronous rotating coordinate system, Figure 2 As shown, the transformation matrix is ​​as follows:

[0121] ;

[0122] The d-axis component of the positive sequence current is , the negative sequence current and the positive sequence current have the same angular velocity but opposite direction, so 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 primarily consists of a fundamental frequency component and a double frequency component. Analysis shows that the double frequency component is primarily caused by the negative-sequence current in the line. This negative-sequence component primarily exists in the faulty line, while the negative-sequence current in the intact line is minimal. Therefore, the double frequency component of the d-axis current of the three-phase current in the intact line in the positive-sequence synchronous rotating coordinate system is very small. This characteristic can be exploited to detect the faulty line.

[0123] 3. Detection criteria

[0124] Select a time window of 0.2s, that is , At the time of fault occurrence, extract the 50Hz and 100Hz components of the d-axis current of each line 、 , and integrate its absolute value:

[0125] ;

[0126] That is, calculate the absolute value of the waveform and the area enclosed by the time axis, and take the ratio of the two:

[0127] ;

[0128] Compared with the sound line, the fault line contains a large number of double frequency components, and the amplitude is significantly larger than the fundamental frequency component. Therefore, for the fault line, there is , on the contrary, for a sound line, . Example

[0129] Build as Figure 3 The simulation model of the resonant grounding system is shown. Set up 4 feeders , for overhead, cable and overhead-cable mixed lines. The first section of the line is equipped with a current transformer, and a single-phase ground fault is set to occur at 0.6s. At 3 km, the fault resistance is 2000Ω. The overcompensation degree is 5%, and the arc suppression coil inductance is calculated. , series resistance ;Line parameters are shown in Table 1;

[0130]

[0131] In order to observe its characteristics conveniently, the calculated d-axis current of each feeder is filtered out of the DC component, as shown in Figure 4 shown by Figure 4 It can be seen that after the fault occurs, the d-axis current of the faulty feeder undergoes a sudden change, the amplitude increases significantly, and the frequency changes, which is significantly different from that of the healthy feeder.

[0132] Extract the 50Hz and 100Hz components of the d-axis current of each feeder, such as Figure 5 As shown, compared with the healthy feeder, the fault feeder; integrating the absolute value of its waveform, we get 、 , and make the ratio W=P 100 / P 50 , the results are shown in Table 2;

[0133]

[0134] As shown in Table 2, only the integral ratio W of the d-axis current double frequency to the fundamental frequency in line 3 is much greater than 1. The other lines do not meet this condition, and the line where the single-phase grounding fault is located can be accurately detected.

[0135] In summary: The present invention describes a single-phase grounding fault detection method based on the integral ratio of the d-axis current times the fundamental frequency component. The method collects the three-phase current data of each feeder, calculates its positive and negative sequence components, and uses double dq transformation to obtain the d-axis current, and then extracts the components of the d-axis current at 50Hz and 100Hz for integration. By comparing the integral ratio of these two frequency components, it is determined whether a single-phase grounding fault has occurred in the feeder. The method has the effect of effectively detecting faults in the steady-state range and under high transition resistance conditions, and improving the accuracy and reliability of fault detection.

[0136] A single-phase grounding fault detection device based on the integral ratio of the d-axis current multiple of the fundamental frequency component is applied to the above-mentioned single-phase grounding fault detection method based on the integral ratio of the d-axis current multiple of the fundamental frequency component, comprising:

[0137] The data acquisition module is used to obtain the three-phase current data of each feeder, including n Number the line;

[0138] The symmetrical component calculation module is used to calculate the positive and negative sequence components of the three-phase current of each feeder, specifically including:

[0139] A fundamental frequency component extraction unit extracts the fundamental frequency components of the three-phase currents of each feeder using Fourier transform;

[0140] The symmetrical component decomposition unit decomposes the three-phase fundamental frequency current into positive sequence components and negative sequence components according to the symmetrical component method;

[0141] The dual dq conversion module is used to calculate the d-axis current of each feeder, specifically including:

[0142] The transformation angle acquisition unit uses phase-locked loop technology to obtain the dq transformation angle based on the positive sequence three-phase current of each feeder;

[0143] The double dq transformation unit projects the three-phase fundamental frequency positive and negative sequence currents of each feeder into a dq coordinate system that rotates at the same angular velocity as the positive sequence component through double dq transformation;

[0144] A d-axis current calculation unit, for calculating the d-axis current of each feeder;

[0145] The current component extraction and integration module is used to extract and integrate the components of the d-axis current at 50Hz and 100Hz. Specifically, it includes:

[0146] The current component extraction unit uses Fourier transform to extract the components of the d-axis current of each feeder at 50Hz and 100Hz, which are expressed as 、 ;

[0147] The integral calculation unit selects 10 power frequency cycles after the fault moment, integrates the 50Hz and 100Hz current components, and calculates the area enclosed by the absolute value of their waveforms and the time axis respectively;

[0148] The fault detection criterion module is used to determine whether a feeder fault occurs based on the integral ratio. Specifically, it includes:

[0149] Integral ratio calculation unit, calculates the integral ratio W n =P n_100 / P n_50 ;

[0150] Fault judgment unit, if W n >1, the feeder is judged to be faulty; if W n <1, the feeder is judged to be a healthy feeder.

[0151] An embodiment of the present application provides an electronic device applicable to the above-mentioned single-phase grounding fault detection method based on the integral ratio of the d-axis current multiple fundamental frequency component, including:

[0152] Memory, used to protect computer programs and data;

[0153] Processor, used to run system programs.

[0154] 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 multiple fundamental frequency component, and performs hierarchical confidentiality management on the above-mentioned system and data in accordance with confidentiality management requirements.

[0155] Those skilled in the art will appreciate that the embodiments of the present application may be provided as a system or a computer program product. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0156] 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, as well as 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 a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0157] These computer program instructions may 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, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0158] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0159] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0160] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0161] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology for information storage. 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 technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed 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.

[0162] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, commodity, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, commodity, or apparatus comprising the element.

[0163] 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 on 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 ground fault detection method based on the integral ratio of the d-axis current multiple fundamental frequency component, characterized by: The following steps are involved: Step 1: Obtain the three-phase current of each feeder ; Step 2: Calculate the positive and negative sequence components of the three-phase current of each feeder , ; When is the positive sequence component, When is negative sequence component; Step 3: Calculate the d-axis current of each feeder ; Step 4: Extract d-axis current Components at 50Hz and 100Hz 、 , calculate its integral; Step 5: Calculate the integral ratio , When it is determined to be a faulty feeder, It is determined to be a healthy feeder; 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 expressed as 、 ; Step 4.2: Select 10 power frequency cycles after the fault moment and calculate the 50Hz current component. Integrate and calculate the area enclosed by the absolute value of the waveform and the time axis , as follows: ； Where, is the time when the fault occurs, ; Step 4.3: 100Hz current component Integrate and calculate the area enclosed by the absolute value of the waveform and the time axis , as follows: ； The specific process of step 5 is as follows: Step 5.1: and Ratio, we get , as follows: ； Step 5.2: If , it is determined that the feeder has a fault; if , no fault has occurred.

2. A single-phase ground fault detection method based on the integral ratio of the d-axis current multiple fundamental frequency component as claimed in claim 1, characterized in that: The process of obtaining the three-phase current of each feeder in step 1 is as follows: a current detection device is installed on each line of the distribution network to collect the three-phase current signals respectively. ,in, , n is the number of each feeder, and the time of fault occurrence is s, the sampling start time is s, the end time is s, and a three-phase current signal with a data window length of 10 power frequency cycles is obtained.

3. The single-phase ground fault detection method based on the integral ratio of the d-axis current multiplied by the fundamental frequency component according to claim 1, characterized in that: The specific process of step 2 is: Step 2.1: Use Fourier transform to extract the fundamental frequency component of the three-phase current of each feeder ,in, is the three-phase fundamental frequency current The amplitude of is the initial phase, , f The power frequency is 50Hz; Step 2.2: The vector form of , according to the symmetric component method: ； Where, , For feeder n The zero sequence current, 、 is the vector form of the positive and negative sequence current of phase A of each feeder, and for phases B and C, it is as follows: ； Where, is the vector form of the positive and negative sequence current of phase B, is the vector form of the positive and negative sequence current of phase C; The three-phase positive and negative sequence current vectors of each feeder can be expressed as: ； Where, and are the amplitude and initial phase of the positive and negative sequence currents of the three phases of each feeder, respectively. As follows: 。 4. The single-phase ground fault detection method based on the integral ratio of the d-axis current multiplied by the fundamental frequency component according to claim 1, characterized in that: The specific process of step 3 is: 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, the three-phase fundamental frequency positive and negative sequence currents of each feeder are converted to They are all projected onto the coordinate axis that rotates at the same angular velocity as the positive sequence component. The positive sequence transformation process is as follows: ； Where, 、 are the d and q axis components of the positive sequence current; The negative sequence transformation is as follows: ； Where, 、 are the d 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: 。 5. A single-phase ground fault detection device based on the integral ratio of the d-axis current multiple fundamental frequency component, characterized in that: A single-phase ground fault detection method based on the integral ratio of the d-axis current times the fundamental frequency component as described in any one of claims 1 to 4, comprising: Data acquisition module, used to obtain three-phase current data of each feeder; Symmetrical component calculation module, used to calculate the positive and negative sequence components of the three-phase current of each feeder; Dual dq conversion module, used to calculate the d-axis current of each feeder; Current component extraction and integration module, used to extract and integrate the components of the d-axis current at 50Hz and 100Hz; The fault detection criterion module is used to determine whether a feeder fault occurs based on the integral ratio.

6. A processor, characterized in that: The method is configured to execute a single-phase ground fault detection method based on an integral ratio of a d-axis current times a fundamental frequency component according to any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor, a single-phase grounding fault detection method based on the integral ratio of the d-axis current times the fundamental frequency component according to any one of claims 1 to 4 is implemented.

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