A cross-line phase sequential fault detection method based on zero sequence capacitance variation characteristics

Abstract

The application belongs to the technical field of power system distribution network relay protection, and provides a cross-line phase successive fault detection method based on zero sequence capacitance variation characteristics. The method collects bus zero sequence voltage and each feeder zero sequence current in real time, monitors zero sequence voltage starting protection device by using sliding window technology, then uses extended Prony algorithm to perform high-precision fitting on fault transient signal, extracts frequency point information in the signal, and further calculates zero sequence capacitance of each feeder first and secondary fault in complex frequency domain. Finally, based on the polarity and standard deviation variation characteristics of the zero sequence capacitance, a detection criterion is constructed to realize accurate detection and differentiation of the cross-line phase successive fault. The application avoids the filtering requirement and zero sequence CT polarity limitation in the traditional method, improves the accuracy, reliability and response speed of fault detection, and reduces the misjudgment and missed judgment risk caused by manual operation.

Description

Technical Field

[0001] This invention belongs to the field of relay protection technology for power system distribution networks, specifically a method for detecting cross-line successive faults based on the characteristics of zero-sequence capacitance changes. Background Technology

[0002] In my country's medium- and low-voltage distribution network systems, single-phase grounding faults are a frequent type of electrical fault. During a single-phase grounding fault, the voltage of the faulty phase drops significantly, while the voltage of the non-faulty phases rises to the line voltage level. This voltage change can easily cause other equipment in the power grid to break down at weak points in their insulation, leading to more serious electrical accidents. In particular, when a single-point fault is not dealt with in a timely manner, it may trigger subsequent multi-point faults, causing the fault range to expand further. This process of a single-point fault gradually evolving into a multi-point fault is called a successive fault.

[0003] With the increasing complexity of distribution network structures and the continuous improvement of cable coverage, the probability of secondary faults is showing a gradual upward trend. However, most existing distribution network protection devices only have the ability to detect the initial fault line and lack continuous fault location functionality. This means that after the protection device trips and disconnects the initial fault line, if zero-sequence voltage still exists in the system, it indicates that a secondary fault may have occurred. However, existing fault location devices cannot make further accurate judgments on this, leading to a heavy reliance on manual circuit breaking for secondary fault detection. This is not only time-consuming and labor-intensive but also increases the risks and uncertainties in fault handling.

[0004] According to statistics from the Shaanxi Electric Power Research Institute, the probability of cascading faults occurring in single-phase grounding faults is approximately 2.81%. If such cascading faults are not handled promptly, they will pose a serious threat to the economic operation of the power grid and personal safety. Therefore, developing a method for accurately and quickly detecting cross-line cascading faults is of great significance for improving the operational reliability and safety of distribution networks. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a cross-line successive fault detection method based on the characteristics of zero-sequence capacitance changes. This method solves the problem that in the prior art, if zero-sequence voltage still exists in the system after the protection device trips and disconnects the first faulty line, it indicates that a secondary fault may have occurred. However, existing line selection devices cannot make further accurate judgments on this, leading to a heavy reliance on manual circuit breaking operations for secondary fault detection. This is not only time-consuming and labor-intensive, but also increases the risks and uncertainties in fault handling.

[0006] In a first aspect, the present invention provides a method for detecting cross-line successive faults based on the characteristics of zero-sequence capacitance changes, comprising the following steps:

[0007] Step 1: Collect the bus zero-sequence voltage U0 and the zero-sequence current I of each feeder. 0i And slide window U0 and denote it as U h , if U h >U th Activate the protection device; among which, U th The preset threshold;

[0008] Step 2: Select 1 / 2 period as the data window, and use the extended Prony algorithm to analyze the transient zero-sequence voltage U0 and zero-sequence current I of the first fault and the subsequent fault, respectively. 0i The fitting process yields the amplitude, phase, attenuation factor, and frequency parameters, where i is the feeder number.

[0009] Step 3: Using the parameters obtained in Step 2, calculate the zero-sequence capacitance C of each feeder for the initial fault and the subsequent fault in the complex frequency domain. 0i(I) and C 0i(II) ;

[0010] Step 4: Construct detection criteria: using C 0i(I) The polarity is used as the detection criterion for the first fault; the standard deviation S is used. i Characterization C 0i(I) With C 0i(II) Based on the differences in variation, construct a criterion for secondary fault detection.

[0011] Preferably, in step 1, the real-time monitoring of the bus zero-sequence voltage U0, and its sliding window recording as U... h , if U h >U th The protection device is activated, and the zero-sequence current I of each feeder is simultaneously collected. 0i The system sampling frequency is 10kHz.

[0012] Preferably, in step 2, the discrete-time function form of the Prony algorithm is:

[0013]

[0014] In the formula, It is the estimated value of the nth sampling point of y(n), where P is the modal order, a complex number. Δt is the sampling interval; the amplitude A of each modal signal can be solved through a series of transformations. k Initial phase θ k Attenuation factor α k and oscillation frequency f k for:

[0015]

[0016] Preferably, step 3 calculates the initial fault zero-sequence capacitance C in the complex frequency domain.0i(I) and the zero-sequence capacitance C of the secondary fault 0i(II) The process is as follows:

[0017] Step 3.1: Substitute s=α+jω into the current-voltage relationship U(s)=I(s)[(R0+sL0+2 / sC0) / / (2 / sC0)] in the complex frequency domain of each feeder, where R0, L0 and C0 represent the zero-sequence resistance, inductance and capacitance of the line, respectively; let the real and imaginary parts of the voltage and current in the complex frequency domain be U R U I I R I I The complex frequency domain equation can be obtained as follows:

[0018]

[0019]

[0020] Step 3.2: Obtain the computation matrix A = By for the frequency domain equations at n frequency points using the extended Prony algorithm. Solving this matrix yields the parameter C. 0i(I) and C 0i(II) ,in:

[0021]

[0022] Preferably, step 4 specifically includes the following steps:

[0023] Step 4.1: Initial Fault Detection Criteria: If one of the feeders C 0i(I) If <0, then line i is the first faulty feeder, and the rest are healthy feeders; if all feeders C 0i(I) If the value is less than 0, it is considered a busbar fault;

[0024] Step 4.2: Secondary Fault Detection Criteria: The system bus is connected to i feeders, using the standard deviation S i Characterization C 0i(I) With C 0i(II) The difference in variation, μ=(C 0i(Ι) +C 0i(Ⅱ) ) / 2, set the threshold S set If S i >S set If it is, then it is a feeder with a secondary fault; otherwise, it is a healthy feeder; S i and S set The expression is:

[0025]

[0026] Secondly, the present invention provides a cross-line successive fault detection system based on zero-sequence capacitance change characteristics, applicable to the aforementioned cross-line successive fault detection method based on zero-sequence capacitance change characteristics, the system comprising:

[0027] The data acquisition module is used to acquire the bus zero-sequence voltage U0 and the zero-sequence current I of each feeder in real time. 0i And by performing a sliding window process on the zero-sequence voltage U0 of the bus, U is obtained. h ; when U h Greater than the preset threshold U th When this happens, the protection device will be activated;

[0028] The signal processing module, connected to the data acquisition module, is used to select a 1 / 2 period as the data window and utilize the extended Prony algorithm to process the transient zero-sequence voltage U0 and zero-sequence current I during the initial fault and subsequent fault periods, respectively. 0i By fitting the data, the amplitude, initial phase, attenuation factor, and oscillation frequency parameters of each modal signal are obtained.

[0029] The zero-sequence capacitance calculation module, connected to the signal processing module, is used to calculate the zero-sequence capacitance C of each feeder for the initial and subsequent faults in the complex frequency domain, based on the parameters obtained from the signal processing module. 0i(I) and C 0i(II) ;

[0030] The fault detection criterion construction module, connected to the zero-sequence capacitance calculation module, is used to construct detection criteria based on the results of the zero-sequence capacitance calculation module. It utilizes C... 0i(I) The polarity is used as the detection criterion for the first fault, utilizing the standard deviation S. i Characterization C 0i(I) With C 0i(II) Based on the differences in variation, construct a criterion for secondary fault detection.

[0031] Thirdly, the present invention provides a computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method.

[0032] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention utilizes the extended Prony algorithm to perform high-precision fitting of zero-sequence current and zero-sequence voltage, effectively extracting frequency information from the signal and avoiding leakage errors that may be introduced by traditional discrete Fourier transform. Furthermore, by using full-frequency information in the complex frequency domain to calculate the equivalent zero-sequence capacitance to ground, no additional filtering is required, thus improving the accuracy and efficiency of signal processing.

[0035] 2. This invention achieves accurate detection of successive faults across lines by constructing a detection criterion based on the characteristics of zero-sequence capacitance changes. For a healthy line, its equivalent zero-sequence capacitance always remains its own capacitance to ground; however, for a line with a secondary fault, its equivalent zero-sequence capacitance will change significantly due to the redistribution of zero-sequence current. This invention utilizes this characteristic, characterizing the difference in zero-sequence capacitance changes by calculating the standard deviation, thereby constructing a secondary fault detection criterion. This criterion does not involve polarity judgment, thus eliminating the limitation of zero-sequence CT (current transformer) polarity and improving the reliability and accuracy of fault detection.

[0036] 3. The method of this invention can quickly activate the protection device after a fault occurs, and rapidly determine the fault type by real-time monitoring and calculation of changes in zero-sequence capacitance, thereby achieving a rapid response to successive faults across lines. Furthermore, since this method does not rely on manual operation, it reduces misjudgments and missed judgments caused by human factors, further improving the reliability and safety of fault detection. Attached Figure Description

[0037] Figure 1 This is a flowchart of the fault detection process of the present invention;

[0038] Figure 2 This is a model diagram of the 10kV resonant grounding system of the present invention;

[0039] Figure 3 This is a frequency point diagram of the zero-sequence current fitting for each feeder in this invention;

[0040] Figure 4 This is a diagram showing the changes in zero-sequence capacitance during the initial and subsequent faults of each feeder in this invention.

[0041] Figure 5 This is a schematic diagram of the simulation results of the fault detection criterion of the present invention. Detailed Implementation

[0042] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0043] Example: This invention provides a method for detecting successive cross-line faults based on the characteristics of zero-sequence capacitance changes, such as... Figure 1 As shown, it includes the following steps:

[0044] Step 1: Collect the bus zero-sequence voltage U0 and the zero-sequence current I of each feeder. 0i And slide window U0 and denote it as U h , if U h >U th Activate the protection device;

[0045] Specifically, in step 1, the real-time monitoring of the bus zero-sequence voltage U0 is recorded as U using a sliding window. h , if U h >U th The protection device is activated, and the zero-sequence current I of each feeder is simultaneously collected. 0i The system sampling frequency is 10kHz;

[0046] First, the device presets a threshold value U. th Then, by real-time monitoring of the bus zero-sequence voltage U0, and recording it as U using sliding window technology. h , when U h Exceeding the preset threshold U th Immediately activate the protection device and simultaneously collect the zero-sequence current I of each feeder at a system sampling frequency of 10kHz. 0i ;

[0047] The effect of the above process is that it can respond quickly to fault signals, ensure that the protection mechanism is activated in time when a fault occurs, and at the same time, the high-frequency sampling ensures the accuracy and real-time nature of the data, providing a reliable basis for subsequent fault detection.

[0048] Step 2: Select 1 / 2 period as the data window, and use the extended Prony algorithm to analyze the transient zero-sequence voltage U0 and zero-sequence current I of the first fault and the subsequent fault, respectively. 0i The fitting process yields the amplitude, phase, attenuation factor, and frequency parameters, where i is the feeder number.

[0049] Specifically, in step 2, the discrete-time function of the Prony algorithm is as follows:

[0050]

[0051] In the formula, It is the estimated value of the nth sampling point of y(n), where P is the modal order, a complex number. Δt is the sampling interval; the amplitude A of each modal signal can be solved through a series of transformations. k Initial phase θ k Attenuation factor α k and oscillation frequency f k for:

[0052]

[0053] By selecting half a period after the fault occurrence as the data window, the extended Prony algorithm is applied to analyze the transient zero-sequence voltage U0 and zero-sequence current I during the initial and subsequent faults. 0i Fitting is performed, and the estimated value of each sampling point is calculated using the discrete-time function form of the algorithm. Further transformations are then used to obtain the amplitude A of each modal signal. k Initial phase θ k Attenuation factor α k and oscillation frequency f k Key parameters, etc.

[0054] The effect of the above steps is that they can extract frequency information from the signal with high precision, avoid leakage errors that may be introduced by traditional discrete Fourier transform, and provide a reliable data foundation for subsequent accurate calculation of zero-sequence capacitance and construction of fault detection criteria.

[0055] Step 3: Using the parameters obtained in Step 2, calculate the zero-sequence capacitance C of each feeder for the initial fault and the subsequent fault in the complex frequency domain. 0i(I) and C 0i(II) ;

[0056] Specifically, step 3 calculates the initial fault zero-sequence capacitance C in the complex frequency domain. 0i(I) and the zero-sequence capacitance C of the secondary fault 0i(II) The process is as follows:

[0057] Step 3.1: Substitute s=α+jω into the current-voltage relationship U(s)=I(s)[(R0+sL0+2 / sC0) / / (2 / sC0)] in the complex frequency domain of each feeder, where R0, L0 and C0 represent the zero-sequence resistance, inductance and capacitance of the line, respectively; let the real and imaginary parts of the voltage and current in the complex frequency domain be U R U I I R I I The complex frequency domain equation can be obtained as follows:

[0058]

[0059] Step 3.2: Obtain the computation matrix A = By for the frequency domain equations at n frequency points using the extended Prony algorithm. Solving this matrix yields the parameter C. 0i(I) and C 0i(II) ,in:

[0060]

[0061] First, the modal signal parameters obtained in step 2 are substituted into the current-voltage relationship in the complex frequency domain of each feeder to construct a complex frequency domain equation containing zero-sequence resistance R0, inductance L0, and capacitance C0. Then, the calculation matrix A = By is formed using n sets of frequency point data obtained through the extended Prony algorithm to create the frequency domain equation set. By solving this matrix, the zero-sequence capacitance C of each feeder under the initial fault and secondary fault conditions is obtained. 0i(I) and C 0i(II) ;

[0062] The effect of the above steps is that they can accurately calculate the change in zero-sequence capacitance before and after the fault, providing key data support for the subsequent construction of fault detection criteria based on the characteristics of zero-sequence capacitance change, and improving the accuracy and reliability of fault detection.

[0063] Step 4: Construct detection criteria: using C 0i(I) The polarity is used as the detection criterion for the first fault; the standard deviation S is used. i Characterization C 0i(I) With C 0i(II) Based on the differences in variation, construct a criterion for secondary fault detection;

[0064] Specifically, step 4 involves the following steps:

[0065] Step 4.1: Initial Fault Detection Criteria: If one of the feeders C 0i(I) If <0, then line i is the first faulty feeder, and the rest are healthy feeders; if all feeders C 0i(I) If the value is less than 0, it is considered a busbar fault;

[0066] Step 4.2: Secondary Fault Detection Criteria: The system bus is connected to i feeders, using the standard deviation S i Characterization C 0i(I) With C 0i(II) The difference in variation, μ=(C 0i(Ι) +C 0i(Ⅱ) ) / 2, set the threshold S set If S i >S set If it is, then it is a feeder with a secondary fault; otherwise, it is a healthy feeder; S i and S set The expression is:

[0067]

[0068] First, based on the initial fault detection criteria, check the zero-sequence capacitance C of each feeder. 0i(I) If the C of a certain feeder 0i(I) If the value is less than 0, the feeder is determined to be the first faulty line; otherwise, it is considered a healthy line. If all feeders C 0i(I) If all values ​​are less than 0, it is determined to be a busbar fault;

[0069] Next, based on the secondary fault detection criteria, the zero-sequence capacitance C of each feeder is calculated. 0i(I) With C 0i(II) Standard deviation S i and with the preset threshold S set Comparison, if S i Greater than S set If the fault is found, the feeder is determined to be a secondary fault line; otherwise, it is considered a healthy line.

[0070] The effect of the above steps is to accurately distinguish between initial and subsequent faults, and to improve the accuracy and reliability of cross-line successive fault detection.

[0071] As can be seen from the above, this invention monitors the zero-sequence voltage of the bus in real time and activates the protection device. It uses the extended Prony algorithm to fit the fault transient signal with high precision, extracts key parameters, calculates the change of zero-sequence capacitance in the complex frequency domain, and then constructs a detection criterion based on the polarity and standard deviation of zero-sequence capacitance. This enables accurate identification of the first and subsequent faults in cross-line successive faults, thereby avoiding the filtering requirements and zero-sequence CT polarity limitations in traditional methods. This improves the accuracy, reliability, and response speed of fault detection and reduces the risk of misjudgment and missed judgment caused by manual operation.

[0072] Working principle: This method collects the zero-sequence voltage of the bus and the zero-sequence current of each feeder in real time, uses sliding window technology to monitor the zero-sequence voltage and activate the protection device, and then uses the extended Prony algorithm to perform high-precision fitting on the fault transient signal, extracts the frequency information in the signal, and then calculates the zero-sequence capacitance of the first and subsequent faults of each feeder in the complex frequency domain. Finally, based on the polarity and standard deviation variation characteristics of the zero-sequence capacitance, a detection criterion is constructed to achieve accurate detection and differentiation of successive faults across lines.

[0073] Application example: Building a system using PSCAD / EMTDC, such as... Figure 2 The 10kV resonant grounding system model shown uses a frequency-dependent phase domain model for the distribution lines. This model considers the influence of distributed parameters and the frequency correlation of components, resulting in extremely high accuracy. Specific line parameters are shown in Table 1. The system sampling frequency is 10kHz, and the arc suppression coil uses a 10% overcompensation. p =0.2155H.

[0074] Table 1 Line Parameter Settings

[0075]

[0076]

[0077] The feeders for the initial and subsequent faults were set as L2 and L1, respectively, with fault distances of 10km and 9km, transition resistances of 1200Ω and 300Ω, respectively, both faulted by phase A, and a fault time interval of 20ms. The zero-sequence current fitting frequency, zero-sequence capacitance variation, and fault detection results for each feeder are listed below. Figure 3 , Figure 4 and Figure 5 .

[0078] exist Figure 4 In the initial fault, the zero-sequence capacitance of L2 is negative, while the zero-sequence capacitances of the other feeders are all positive. Based on the detection data, L2 is determined to be the initially faulty line. After a secondary fault, the zero-sequence current redistributes under the full response state of the system, causing changes in the fault loop and thus altering the zero-sequence capacitance of the faulty line. After excluding the initially faulty feeder, Figure 5 Standard deviation S of the remaining feeders i =[3.68,——,0.15,0.20],S set =0.80, while S1 = 3.68 > S set L1 was determined to be a secondary fault line. The detection results were consistent with the simulation preset conditions, verifying the effectiveness of the invention.

[0079] As described above, this invention presents a method for detecting successive cross-line faults based on the characteristics of zero-sequence capacitance changes. First, the zero-sequence voltage of the bus and the zero-sequence current data of each feeder are collected. Second, the extended Prony algorithm is used to fit the zero-sequence current and zero-sequence voltage to obtain the amplitude, initial phase, attenuation factor, and oscillation frequency parameters of each mode signal. Third, the zero-sequence capacitance of the first and subsequent faults of each feeder is calculated in the complex frequency domain. Finally, a detection criterion is constructed based on the two-stage zero-sequence capacitance change characteristics. This method eliminates the need for filtering, overcomes the limitation of zero-sequence CT polarity, and improves the accuracy and reliability of detecting successive cross-line faults.

[0080] In summary, the present invention has the following effects:

[0081] 1. Fault signal processing: This invention utilizes the extended Prony algorithm to achieve high-precision extraction of signal frequency information, avoiding leakage errors and other information introduced by the traditional discrete Fourier transform. On this basis, the equivalent zero-sequence capacitance to ground is calculated using full-frequency information in the complex frequency domain without the need for filtering.

[0082] 2. Fault Detection Criteria: This invention utilizes changes in zero-sequence capacitance to characterize the redistribution of zero-sequence current under secondary faults. For a healthy circuit, the equivalent zero-sequence capacitance is always its own capacitance to ground; however, for a circuit with a secondary fault, the equivalent zero-sequence capacitance changes significantly compared to a healthy circuit. Using standard deviation as the detection criterion eliminates polarity judgment, thus overcoming the limitation of zero-sequence CT polarity and resulting in high reliability.

[0083] A cross-line successive fault detection system based on zero-sequence capacitance change characteristics, applicable to the aforementioned cross-line successive fault detection method based on zero-sequence capacitance change characteristics, the system comprising:

[0084] The data acquisition module is used to acquire the bus zero-sequence voltage U0 and the zero-sequence current I of each feeder in real time. 0i And by performing a sliding window process on the zero-sequence voltage U0 of the bus, U is obtained. h ; when U h Greater than the preset threshold U th When this happens, the protection device will be activated;

[0085] The signal processing module, connected to the data acquisition module, is used to select a 1 / 2 period as the data window and utilize the extended Prony algorithm to process the transient zero-sequence voltage U0 and zero-sequence current I during the initial fault and subsequent fault periods, respectively. 0i By fitting the data, the amplitude, initial phase, attenuation factor, and oscillation frequency parameters of each modal signal are obtained.

[0086] The zero-sequence capacitance calculation module, connected to the signal processing module, is used to calculate the zero-sequence capacitance C of each feeder for the initial and subsequent faults in the complex frequency domain, based on the parameters obtained from the signal processing module. 0i(I) and C 0i(II) ;

[0087] The fault detection criterion construction module, connected to the zero-sequence capacitance calculation module, is used to construct detection criteria based on the results of the zero-sequence capacitance calculation module. It utilizes C... 0i(I) The polarity is used as the detection criterion for the first fault, utilizing the standard deviation S. i Characterization C 0i(I) With C 0i(II) Based on the differences in variation, construct a criterion for secondary fault detection.

[0088] As can be seen from the above, this cross-line successive fault detection system based on the zero-sequence capacitance change characteristics acquires electrical quantities in real time and accurately and activates protection through the data acquisition module, extracts fault feature parameters with high precision using the extended Prony algorithm through the signal processing module, accurately calculates the zero-sequence capacitance change before and after the fault in the complex frequency domain through the zero-sequence capacitance calculation module, and constructs a criterion based on the difference in capacitance polarity and standard deviation through the fault detection criterion construction module. This system achieves rapid and accurate detection of cross-line successive faults, gets rid of the limitation of zero-sequence CT polarity, improves the reliability and response speed of fault detection, and reduces human error and missed detection.

[0089] This application provides an electronic device applicable to the above-described cross-line successive fault detection method based on zero-sequence capacitance change characteristics, including:

[0090] Memory is used to protect computer programs and data;

[0091] A processor is used to run system programs.

[0092] This application provides a computer storage medium applicable to the above-mentioned cross-line successive fault detection method based on zero-sequence capacitance change characteristics, and performs hierarchical confidentiality management of the above-mentioned system and data in accordance with confidentiality management requirements.

[0093] Those skilled in the art will understand that embodiments of this application can be provided as a system or a computer program product. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this 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.

[0094] This application is described with reference to flowchart illustrations and / or block diagrams of apparatus (systems) and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0095] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0096] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0097] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0098] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0099] Computer-readable media include both permanent and non-permanent, removable and non-removable media, which can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, 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, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0100] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0101] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for detecting successive faults of cross-line phases based on zero sequence capacitance variation characteristics, characterized in that, The method comprises the following steps: Step 1: Collect bus zero sequence voltage U0 and each feeder zero sequence current I 0i And make a sliding window record of U0 as U h If U h > U th , start the protection device; Step 2: The first and second fault transient zero-sequence voltage U0and zero-sequence current I0are fitted by using the extended Prony algorithm with 1 / 2 cycle as the data window, and the amplitude, phase, damping factor and frequency parameters are obtained, i is the feeder number. 0i Step 2: The first and second fault transient zero-sequence voltage U0and zero-sequence current I0are fitted by using the extended Prony algorithm with 1 / 2 cycle as the data window, and the amplitude, phase, damping factor and frequency parameters are obtained, i is the feeder number. Step 3: With the parameters obtained in Step 2, calculate the zero sequence capacitance C of each feeder primary fault and secondary fault in the complex frequency domain respectively 0i(I) and C 0i(II) ; Step 4: Constructing detection criterion: using C 0i(I) polarity as the detection criterion of the initial failure; using the standard deviation S i to represent the change difference of C 0i(I) and C 0i(II) , constructing the detection criterion of secondary failure; In step 1, the bus zero sequence voltage U0 is monitored in real time, and a sliding window is recorded as U h If U h > U th , the protection device is started, and the zero sequence current I 0i of each feeder is collected, and the system sampling frequency is 10 kHz; In step 2, the function form of the Prony algorithm in discrete time is: ； wherein is the estimated value of the n-th sample point of the m-th mode, P is the modal order, the complex number , Δt is the sampling interval; through a series of transformations, the modal signal amplitude A k , the initial phase θ k , the attenuation factor α k , and the oscillation frequency f k can be solved as follows: ； Step 3: Calculate the primary fault zero sequence capacitance C in the complex frequency domain 0i(I) and the secondary fault zero sequence capacitance C 0i(II) The process is as follows: Step 3.1: The current-voltage relationship of each feeder in the complex frequency domain is given by where R0, L0, and C0represent the line zero-sequence resistance, inductance, and capacitance, respectively; and where R0, L0, and C0represent the line zero-sequence resistance, inductance, and capacitance, respectively; and The real and imaginary parts of the voltage and current in the complex frequency domain are respectively R , I , R , I The complex frequency domain equation can be obtained as ； ； Step 3.2: Get the calculation matrix A = By of the frequency domain equation group under n groups of frequency points by extending the Prony algorithm, and solve the matrix to get the parameter C 0i(I) and C 0i(II) wherein: ； The specific steps of step 4 are: Step 4.1: Initial fault detection criterion: If one of the feeders C 0i(I) <0, then line i is the initial fault feeder and the rest are healthy feeders; if all feeders C 0i(I) <0, then it is considered as bus fault; Step 4.2: Secondary fault detection criterion: the system bus is connected with i feeders, using the standard deviation S i Characterization C 0i(I) The difference of change with C 0i(II) , μ = (C 0i(Ι) + C 0i(Ⅱ) ) / 2, set threshold S set ; if S i > S set , it is a secondary fault feeder; otherwise, it is a healthy feeder; S i and S set The expression is: 。 2. A cross-line phase sequential fault detection system based on zero sequence capacitance variation characteristics, characterized in that: The system suitable for the cross-line phase sequential fault detection method based on zero sequence capacitance variation characteristics as claimed in claim 1 comprises: A data acquisition module is configured to acquire the bus zero sequence voltage U0 and the zero sequence current I of each feeder in real time. 0i The bus zero sequence voltage U0 is processed by a sliding window to obtain U h When U h is greater than a preset threshold U th , the protection device is started. The signal processing module is connected with the data acquisition module, and is used for selecting 1 / 2 cycle as a data window, and using an extended Prony algorithm to respectively fit transient zero sequence voltage U0 and zero sequence current I0 during a primary fault and a secondary fault 0i and obtaining amplitude, initial phase, attenuation factor and oscillation frequency parameters of each modal signal. The zero sequence capacitance calculation module is connected with the signal processing module, and is configured to calculate zero sequence capacitances C of the primary faults and the secondary faults of the feeders in the complex frequency domain according to parameters obtained by the signal processing module 0i(I) and C 0i(II) ; The fault detection criterion construction module is connected with the zero sequence capacitance calculation module, and is used for constructing detection criteria according to the results of the zero sequence capacitance calculation module: using the polarity of C 0i(I) as the detection criterion of the first fault, using the standard deviation S i to represent the difference of the change of C 0i(I) and C 0i(II) , and constructing the detection criterion of the secondary fault.

3. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that, The processor executes the computer program to realize the method of claim 1.

4. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the method of claim 1.

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