Generator stator winding single-phase earth fault positioning method and system

Abstract

The invention discloses a generator stator winding single-phase earth fault positioning method and system, and the method comprises the steps: obtaining voltage and current signals, and carrying out the preprocessing, and obtaining a first voltage signal and a first current signal; based on the analysis result of the first voltage signal, processing the first current signal within a set time range by using a signal analysis method to obtain a plurality of modulus maxima or unique modulus maxima at equal or unequal time intervals; if a plurality of modulus maxima or unique modulus maxima at equal time intervals are obtained, performing first calculation to obtain a fault position; and if a plurality of modulus maxima at unequal time intervals are obtained, second calculation is carried out to obtain a fault position, so that the reliability of fault positioning is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection design for power systems, and particularly to a method and system for locating single-phase grounding faults in generator stator windings. Background Art

[0002] Single-phase grounding faults in generator stator windings are one of the common fault types in power systems. Especially in the case of high-resistance grounding faults, due to the weak fault characteristics, fault location becomes particularly difficult. Traditional fault location methods usually rely on the analysis of fault current. However, in the case of high fault resistance, the fault current is extremely weak, resulting in inaccurate or even failed location. Therefore, a method for accurately locating faults in high-resistance grounding of generator stator windings has become a technical problem in power equipment maintenance.

[0003] Currently, the methods for locating generator stator winding grounding faults are mainly divided into on-line fault location methods and off-line fault location methods. The on-line fault location method is based on the fault characteristics of the stator winding, but accurate generator parameters are required. The off-line fault location method is difficult to detect due to weak fault characteristics in high-resistance faults, and there are also large errors. Therefore, developing a new method that can accurately and effectively locate faults in generator stator windings under high-resistance grounding fault conditions has important practical significance and application value. Summary of the Invention

[0004] In view of the above existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides a method and system for locating single-phase grounding faults in generator stator windings to solve the problems existing in the existing methods for locating single-phase grounding faults in generator stator windings, such as the need for accurate generator parameters and the failure of location under high-resistance faults.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a method for locating single-phase grounding faults in generator stator windings, including:

[0008] Obtain voltage and current signals, and perform preprocessing to obtain a first voltage signal and a first current signal;

[0009] Based on the result of the analysis of the first voltage signal, process the first current signal using signal analysis methods within a set time range to obtain multiple modulus maxima or a unique modulus maximum at equal or unequal time intervals;

[0010] If multiple modulus maxima or a unique modulus maximum at equal time intervals are obtained, perform a first calculation to obtain the fault location;

[0011] If multiple modulus maxima with unequal time intervals are obtained, a second calculation is performed to obtain the fault location.

[0012] As a preferred embodiment of the single-phase grounding fault location method for the generator stator winding described in the present invention, wherein: the preprocessing includes:

[0013] Construct a signal information matrix from the discrete signal points of the voltage and current signals;

[0014] Decompose the signal information matrix to obtain a matrix and the corresponding eigenvector matrix;

[0015] Set the values in the matrix with amplitudes less than the first threshold to 0, and reconstruct the signal information matrix using the eigenvector matrix to obtain the first voltage signal and the first current signal.

[0016] As a preferred embodiment of the single-phase grounding fault location method for the generator stator winding described in the present invention, wherein: the multiple modulus maxima at equal time intervals include:

[0017] The absolute value of the result of subtracting the difference between the occurrence time of the post modulus maximum and the occurrence time of the current modulus maximum from the difference between the occurrence time of the pre modulus maximum and the occurrence time of the current modulus maximum is less than or equal to 1 sampling interval.

[0018] As a preferred embodiment of the single-phase grounding fault location method for the generator stator winding described in the present invention, wherein: the first calculation includes:

[0019] For multiple modulus maxima at equal time intervals or a unique modulus maximum, record the occurrence time of the first modulus maximum as the arrival time of the fault point reflection wave;

[0020] Subtract the time when the signal is injected from the head end from the time when the fault point reflection wave arrives at the head end to obtain the first time interval, subtract the time when the signal is injected from the head end from the time when the signal injected from the head end arrives at the end and is received at the end to obtain the second time interval, and multiply the ratio of the first time interval to the second time interval by half of the total length of the fault branch to obtain the fault location.

[0021] As a preferred embodiment of the single-phase grounding fault location method for the generator stator winding described in the present invention, wherein: the multiple modulus maxima with unequal time intervals include:

[0022] Use all the modulus maximum times to perform a first calculation on the fault location to obtain a first fault location;

[0023] The time when the signal injected from the head end is propagated to the end and collected at the head end of the line is the first time, and the occurrence times of multiple modulus maxima extracted after injecting the signal from the end are the second times;

[0024] Convert the second time and perform a second calculation to obtain a second fault location;

[0025] Compare the first fault location and the second fault location, take the nearest point to calculate the average value, and obtain the fault location.

[0026] As a preferred solution of the single-phase grounding fault location method for the generator stator winding described in the present invention, wherein: the transformation of the second moment includes:

[0027] The obtained moment after transformation is the moment of injecting the signal from the head end minus the second moment plus twice the first moment minus the moment of injecting the signal from the end of the fault branch.

[0028] As a preferred solution of the single-phase grounding fault location method for the generator stator winding described in the present invention, wherein: the second calculation includes:

[0029] Denote the moment obtained after transformation minus the moment of injecting the signal from the head end as the third time interval, denote the moment when the signal injected from the head end reaches the end minus the moment of injecting the signal from the head end as the second time interval, multiply the ratio of the third time interval to the second time interval by half of the total length of the fault branch, and obtain the fault location.

[0030] In a second aspect, the present invention provides a single-phase grounding fault location system for a generator stator winding, including:

[0031] A preprocessing module, which acquires voltage and current signals, and performs preprocessing to obtain a first voltage signal and a first current signal;

[0032] A processing module, which is used to process the first current signal by using signal analysis methods within a set time range based on the result of analyzing the first voltage signal, and obtain multiple modulus maxima or a unique modulus maximum at equal time intervals or unequal time intervals;

[0033] A first calculation module, which is used to perform a first calculation to obtain the fault location if multiple modulus maxima or a unique modulus maximum at equal time intervals are obtained;

[0034] A second calculation module, which is used to perform a second calculation to obtain the fault location if multiple modulus maxima at unequal time intervals are obtained.

[0035] In a third aspect, the present invention provides a computing device, including:

[0036] A memory and a processor;

[0037] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the single-phase grounding fault location method for the generator stator winding are implemented.

[0038] Fourthly, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for locating single-phase grounding faults in the generator stator winding.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses the singular value decomposition method (SVD) to denoise the collected voltage and current signals, improving the clarity of the signals. By using wavelet transform to analyze the denoised signals, the mutation points in the signals, namely the modulus maxima, can be effectively extracted. These modulus maxima correspond to the arrival time of the traveling wave and are the key information for fault location. By injecting signals from the head and end of the fault branch respectively and analyzing, the reliability of fault location is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 It is a schematic diagram of the overall process logic of the method for locating single-phase grounding faults in the generator stator winding according to an embodiment of the present invention;

[0042] Figure 2 It is the current signal at the injection end and the voltage signal at the non-injection end when the transition resistance is 1000Ω in the method for locating single-phase grounding faults in the generator stator winding according to an embodiment of the present invention;

[0043] Figure 3 It is the current signal at the injection end and the voltage signal at the non-injection end when the transition resistance is 3000Ω in the method for locating single-phase grounding faults in the generator stator winding according to an embodiment of the present invention;

[0044] Figure 4 It is the waveform reflection process when injecting a signal at the M end in the method for locating single-phase grounding faults in the generator stator winding according to an embodiment of the present invention;

[0045] Figure 5 It is the waveform reflection process when injecting a signal at the N end in the method for locating single-phase grounding faults in the generator stator winding according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0047] Embodiment 1

[0048] Referring to Figure 1 , an embodiment of the present invention provides a method for locating a single-phase grounding fault in a generator stator winding, including:

[0049] S100: Obtain voltage and current signals, and perform preprocessing to obtain a first voltage signal and a first current signal;

[0050] S200: Based on the result of analyzing the first voltage signal, process the first current signal using signal analysis methods within a set time range to obtain multiple modulus maxima or a unique modulus maximum at equal or unequal time intervals;

[0051] In an alternative embodiment, the signal analysis method may include empirical mode decomposition. Through empirical mode decomposition, multiple IMFs are obtained, and each IMF corresponds to a specific frequency band of the signal. Select the IMFs related to the fault characteristics for further analysis to determine the arrival time of the traveling wave; it may also include Hilbert-Huang transform. The arrival time of the traveling wave is associated with the mutation points identified by the instantaneous frequency and amplitude changes obtained through Hilbert-Huang transform;

[0052] In an alternative embodiment, the signal analysis method may further include mathematical morphology. By operations such as erosion, dilation, opening operation, and closing operation of mathematical morphology, the mutation points in the signal are highlighted to assist in determining the arrival time of the traveling wave;

[0053] In the embodiments of the present application, the signal analysis method includes wavelet transform;

[0054] Perform wavelet transform on the denoised voltage signal, and record the time when the modulus maximum first appears in the wavelet transform result as t2;

[0055] Perform wavelet transform on the denoised current signal. The current signal includes at least one modulus maximum between the times t0 and 2t2 within the set time range. Record the time when the i-th modulus maximum appears as t ai , where i is a natural number other than 0;

[0056] Wavelet transform is a digital signal processing method, and its calculation method can be implemented in MATLAB. In MATLAB, the function modwt is used to implement the wavelet transform of a signal, and the modulus maximum value of the first-level detail coefficients is extracted. The specific programming method is as follows: use waveletType = 'db1'; level = 4; W = modwt(I, waveletType, level); perform wavelet transform on the signal I, where the mother wave waveletType used is db1 and the decomposition level level is 4 levels. Subsequently, use the function cd1 = W(1, :); extract the first-level detail coefficients, and finally obtain the modulus maximum value according to the first-level detail coefficients to achieve the detection of the arrival time of the traveling wave. The moment when the modulus maximum value first appears in the wavelet transform result is denoted as t2;

[0057] Specifically, the modulus maximum value of wavelet transform is defined as: W s f(x) is defined as the wavelet transform of the function f(x). Under the condition of a certain scale S and in a certain neighborhood of x0, for all x ∈ (x - σ, x + σ), there is |W s f(x)| ≤ |W s f(x0)|, where W s f(x0) is the modulus maximum value, and x0 is the modulus maximum value point of the wavelet transform;

[0058] Performing wavelet transform on the denoised voltage signal is an algorithm for extracting signal mutation points. Since the arrival of the traveling wave will cause the signal to mutate, the result of wavelet transform will show an obvious modulus maximum value when the original signal mutates. The arrival time of the traveling wave can be determined by the moment when the modulus maximum value point appears.

[0059] It should be noted that wavelet transform can effectively separate the signal from the noise, reduce the interference of the noise, improve the clarity and reliability of the signal, and more accurately analyze the local characteristics of the signal, especially the transient response during the occurrence of a fault.

[0060] S300: If multiple modulus maximum values at equal time intervals or a unique modulus maximum value are obtained, then perform the first calculation to obtain the fault location;

[0061] S400: If multiple modulus maximum values at unequal time intervals are obtained, then perform the second calculation to obtain the fault location.

[0062] Specifically, after the generator shuts down due to a single-phase grounding fault and the fault phase and fault branch have been determined, the two ends of the fault branch are respectively defined as the head end and the tail end. At the moment t0, a DC voltage is injected into the head end of the fault branch, and the current signal at the head end and the voltage signal at the tail end are collected;

[0063] It should be noted that by using singular value decomposition (SVD) for denoising and wavelet transform to extract signal mutation points, the arrival time of the reflected wave at the fault point can be identified more accurately, thereby improving the accuracy of fault location. Compared with traditional online fault location methods, it reduces the dependence on parameters, making fault location more independent and reliable. By injecting signals and analyzing the reflected waves of the signals to locate faults, the fault location can be determined more quickly, improving the efficiency of fault handling.

[0064] In the embodiment of the present application, the above step S100 includes the following sub-steps A1 - A3;

[0065] In A1: Construct a signal information matrix from the discrete signal points of the voltage and current signals;

[0066] In A2: Decompose the signal information matrix to obtain a matrix and the corresponding eigenvector matrix;

[0067] In A3: Set the values in the matrix with amplitudes less than the first threshold to 0, and reconstruct the signal information matrix using the eigenvector matrix to obtain the first voltage signal and the first current signal.

[0068] Specifically, the first voltage signal and the first current signal are the denoised voltage signal and current signal;

[0069] In an alternative embodiment, the signal denoising technique may include wavelet denoising. The voltage signal is decomposed into approximation coefficients and detail coefficients using wavelet decomposition. The approximation coefficients mainly contain the low-frequency part of the signal, while the detail coefficients contain the high-frequency part of the signal. By selecting an appropriate threshold to perform soft thresholding or hard thresholding on the detail coefficients, noise can be effectively removed, and the denoised signal can be obtained through wavelet reconstruction; the signal denoising technique may also include wavelet packet denoising. By performing multi-level wavelet packet decomposition on the signal, the noise components in the signal can be more accurately located. After wavelet packet decomposition, the coefficients are thresholded, and the wavelet packet coefficients less than the threshold are set to 0, while the coefficients higher than the threshold are retained, thereby achieving the purpose of denoising. The processed wavelet packet coefficients are inversely transformed through wavelet packet to obtain the denoised signal;

[0070] The signal denoising technique may also include singular value decomposition denoising. By constructing the signal into a matrix and performing SVD decomposition, singular values and the corresponding singular vectors are obtained. After SVD decomposition, the singular values are thresholded. Usually, the larger singular values are retained and the smaller singular values are suppressed. By reconstructing the signal matrix, the denoised signal can be obtained;

[0071] In the embodiment of the present application, the signal denoising technique includes the singular value decomposition method;

[0072] Use the singular value decomposition method to construct a signal information matrix from the collected discrete signal points E(1), E(1)…E(t), which is expressed as:

[0073]

[0074] Perform singular value decomposition on the signal information matrix to obtain a singular value matrix and the corresponding eigenvector matrix. The singular values with smaller amplitudes in the singular value matrix are set to 0, and the signal information matrix is reconstructed using the eigenvector matrix to obtain the denoised discrete signals E’(1), E’(2),…E’(t). After the above steps, the denoising of the collected voltage and current signals is completed.

[0075] It should be noted that through the singular value decomposition method, signals and noise can be effectively separated, the signal-to-noise ratio of the signal can be improved, the characteristics of the signal can be made more obvious, which is convenient for subsequent fault analysis and location. It can identify and retain the main characteristics of the signal, and at the same time remove those small singular values corresponding to noise, and important information of the signal can be retained while denoising.

[0076] In the embodiment of the present application, the above step S300 includes the following sub-steps B1 - B3;

[0077] In B1: Take the absolute value of the result of subtracting the difference between the occurrence time of the post-mode maximum and the occurrence time of the current-mode maximum from the difference between the occurrence time of the pre-mode maximum and the occurrence time of the current-mode maximum, which is less than or equal to 1 sampling interval.

[0078] In B2: For multiple mode maxima or a unique mode maximum at equal time intervals, record the occurrence time of the first mode maximum as the arrival time of the fault point reflection wave;

[0079] In B3: Denote the time when the fault point reflection wave reaches the head end minus the time when the signal is injected from the head end as the first time interval, and denote the time when the signal injected from the head end reaches the end end minus the time when the signal is injected from the head end as the second time interval. Multiply the ratio of the first time interval to the second time interval by half of the total length of the fault branch to obtain the fault location.

[0080] Specifically, if multiple mode maxima at equal time intervals or a unique mode maximum are obtained, then record the occurrence time t a1 of the first mode maximum as the arrival time of the fault point reflection wave, and use the first calculation to obtain the fault location to complete the fault location;

[0081] The satisfaction condition of the mode maxima at equal time intervals is expressed as:

[0082] |(t a(i+1) - t a(i) ) - (t a(i) - t a(i-1) )| ≤ 1 sampling interval

[0083] Among them, t a(i+1) is the moment when the maximum value of the front mold appears, and t a(i) is the moment when the maximum value of the current mold appears, and t a(i-1) is the moment when the maximum value of the back mold appears;

[0084] Specifically, if there are multiple mold maxima with equal intervals, then the moment t ai when the maximum value of the current mold appears and the moments t a(i+1) , t a(i-1) when the maximum values of the front and back molds appear are almost equal, that is, (t a(i+1) -t a(i) ) = (t a(i) -t a(i-1) ). Therefore, the criterion used is:

[0085] |(t a(i+1) -t a(i) )-(t a(i) -t a(i-1) )| ≤ 1 sampling interval.

[0086] It should be noted that by accurately identifying the mold maxima with equal time intervals, the moment when the reflected wave of the fault point arrives can be determined more accurately, the accuracy of fault location can be improved, the location error can be reduced, the characteristics of the fault signal can be effectively identified, and the robustness of signal processing can be enhanced. By setting a clear criterion (that is, the time interval difference between the mold maxima does not exceed 1 sampling interval), the fault diagnosis process is simplified, making the fault location process more efficient and automated.

[0087] In the embodiment of the present application, when determining multiple mold maxima with equal time intervals, the first calculation is expressed as:

[0088]

[0089] Among them, t1 is the moment when the reflected wave of the fault point arrives, t0 is the moment when the signal is injected from the head end, t2 is the moment when the signal injected from the head end reaches the end, and L is the total length of the fault branch;

[0090] Specifically, all signal mutation moments t ai are used to calculate the corresponding fault positions x a1 , x a2 , x a3 …;

[0091] It should be noted that by considering the propagation time of the signal from the head end to the end and from the end to the head end, the position of the fault point can be accurately calculated, depending on the time difference of signal propagation rather than the absolute value of the signal. Therefore, it is not sensitive to small changes in the signal, enhancing the robustness of the fault location method.

[0092] In the embodiment of the present application, the above step S400 includes the following sub-steps C1 - C4;

[0093] In C1: Using all the modulus maximum moments, perform a first calculation on the fault location to obtain a first fault location;

[0094] In C2: The time when the signal injected at the end propagates to the end after being collected at the head of the line is the first time, and the times when multiple modulus maxima appear after injecting the signal from the end are the second times;

[0095] In C3: Convert the second time and perform a second calculation to obtain a second fault location;

[0096] In C4: Compare the first fault location and the second fault location, take the closest points and calculate the average value to obtain the fault location.

[0097] Specifically, when obtaining multiple modulus maxima with unequal time intervals, use all the modulus maximum moments \(t_i\) ai , where \(i\) is a natural number not including 0, and use the first calculation to calculate the fault locations \(x_i\) ai , where \(i\) is a natural number not including 0;

[0098] Inject a voltage signal from the end of the fault branch at time \(T_0\), repeat S100 and S200, extract the time \(T_2\) corresponding to the first occurrence of the modulus maximum point from the head voltage signal, and extract the time \(T_i\) corresponding to one or more modulus maximum points of the head current signal between \(T_0\) and \(2T_2\) ai , where \(i\) is a natural number not including 0.

[0099] In the embodiment of the present application, after completing steps C1 - C4 in the above step S400, the following step C5 is further included;

[0100] In C5: The converted time is the time when the signal is injected from the head minus the second time plus twice the first time minus the time when the signal is injected from the end of the fault branch.

[0101] Specifically, through time conversion, convert \(T_i\) ai into \(t_i\) in sequence ′ ai , where \(i\) is a natural number not including 0;

[0102] \(t_i\) ′ ai = \(t_0 - T_i\) ai + 2T2 - T0

[0103] where \(t_0\) is the time when the signal is injected from the head, \(T_i\) aiIt is the second moment, that is, the moments when multiple modulus maxima are extracted after injecting a signal from the end. T2 is the first moment, that is, the moment when the signal injected from the end is collected at the head end of the line and propagates to the end. T0 is the moment when a signal is injected from the end of the faulty branch.

[0104] In the embodiment of the present application, after completing step C5 in the above step S400, the following step C6 is further included;

[0105] In C6: Denote the third time interval as the time obtained after transformation minus the time when a signal is injected from the head end. Denote the second time interval as the time when the end receives the signal injected from the head end and reaches the end minus the time when the signal is injected from the head end. Multiply the ratio of the third time interval to the second time interval by half of the total length of the faulty branch to obtain the fault location.

[0106] Specifically, denote the transformed t ′ ai Calculate the corresponding fault location x in sequence ′ ai , where i is a natural number not including 0, and the second calculation is expressed as:

[0107]

[0108] where, t ′ ai is the time obtained after transformation;

[0109] Compare the fault location x ai (x a1, x a2, x a3… ) with the fault location x ′ ai (x ′ a1 , x ′ a2 , x ′ a3 ), take the two closest points and calculate the average value, that is, determine the fault location.

[0110] It should be noted that by comprehensively considering multiple modulus maximum moments and the time characteristics of signal propagation, the fault point can be located more accurately, reducing the error that may be brought by judging at a single moment. Calculating using multiple modulus maximum moments increases the robustness of the method, reduces the influence of accidental errors, and makes the fault location result more reliable.

[0111]

[0112] ​The above is a schematic solution of a method for locating single-phase grounding faults in the stator winding of a generator. It should be noted that the technical solution of the single-phase grounding fault location system for the stator winding of the generator belongs to the same concept as the technical solution of the above-mentioned method for locating single-phase grounding faults in the stator winding of the generator. For the details not described in detail in the technical solution of the single-phase grounding fault location system for the stator winding of the generator in this embodiment, reference can be made to the description of the technical solution of the above-mentioned method for locating single-phase grounding faults in the stator winding of the generator.

[0113] In this embodiment, the single-phase grounding fault location system for the stator winding of a generator includes:

[0114] A preprocessing module that acquires voltage and current signals and performs preprocessing to obtain a first voltage signal and a first current signal;

[0115] A processing module that, based on the result of analyzing the first voltage signal, processes the first current signal using a signal analysis method within a set time range to obtain multiple modulus maxima at equal time intervals or unequal time intervals or a unique modulus maximum;

[0116] A first calculation module that, if multiple modulus maxima at equal time intervals or a unique modulus maximum are obtained, performs a first calculation to obtain the fault location;

[0117] A second calculation module that, if multiple modulus maxima at unequal time intervals are obtained, performs a second calculation to obtain the fault location.

[0118] This embodiment also provides a computing device applicable to the situation of locating single-phase grounding faults in the stator winding of a generator, including:

[0119] A memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the method for locating single-phase grounding faults in the stator winding of a generator as proposed in the above embodiment.

[0120] This embodiment also provides a storage medium on which a computer program is stored, and when the program is executed by a processor, it implements the method for locating single-phase grounding faults in the stator winding of a generator as proposed in the above embodiment.

[0121] The storage medium proposed in this embodiment and the method for locating single-phase grounding faults in the stator winding of a generator proposed in the above embodiment belong to the same inventive concept. For the technical details not described in detail in this embodiment, reference can be made to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0122] From the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software and necessary general-purpose hardware, and of course, it can also be implemented by hardware. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a floppy disk, read-only memory (ROM), random access memory (RAM), flash memory (FLASH), hard disk, or optical disc of a computer, etc., including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods of various embodiments of the present invention.

[0123] Embodiment 2

[0124] As shown in Table 1, Figures 2 - 5 a method for locating a single-phase grounding fault of a generator stator winding is provided. To verify the beneficial effects of the present invention, an electromagnetic simulation software PSCAD was used to establish a circuit model of a generator stator winding based on the Bergeron model.

[0125] Voltage and current data at both ends of the winding were obtained through an oscilloscope. The length of the generator stator winding was set to 360 meters, with a unit resistance of 0.000848 Ω / m, a unit inductance of 0.70233 μH / m, and a unit capacitance of 15.820 pF / m. A 100V DC voltage was applied at the M end with a rise time of 10 nanoseconds, and a simple fault was set at a distance of 150 meters from the injection end. An oscilloscope with a sampling rate of 100 MHz was used to capture the voltage and current signals between the fault point and the injection end, and the signal white noise was set to 30 dB. Considering that the reflected wave reflected back from the fault point to the injection end must arrive earlier than the reflected wave at the non-injection end, a 5-microsecond data window was selected, and the expected arrival time was before 2.4 microseconds.

[0126] For stator winding grounding faults with transient resistances of 1000 Ω, 1500 Ω, 2000 Ω, 2500 Ω, and 3000 Ω, the fault location method was verified;

[0127] As Figure 2 and Figure 3As shown, the current signal (Im) at the head end (injection end) and the voltage signal (En) at the tail end (non-injection end) are respectively shown under fault resistances of 1000Ω and 3000Ω. The x-axis corresponds to the number of sampling points, and the y-axis represents the voltage and current signal amplitudes. These charts also show the noisy signal, the denoised signal, the wavelet transform result, and the arrival time of the traveling wave marked on the original signal. Table 1 summarizes the calculated fault distances and the wavelet thresholds (maximum value normalized to 1) used to detect signal mutations.

[0128] Table 1 Fault location results under different transition resistances

[0129] Fault resistance / Ω Wavelet threshold / pu Fault location / m Error / % 1000 Ω 0.13 152.801 0.78％ 1500 Ω 0.08 151.980 0.55％ 2000 Ω 0.08 151.322 0.37％ 2500 Ω 0.07 152.801 0.78％ 3000 Ω 0.062 152.801 0.78％

[0130] As can be seen from Table 1, when the fault resistance reaches about 3000Ω, if multiple modulus maxima with equal time intervals or a unique modulus maximum are obtained after denoising and wavelet transform of the current signal collected at the head end, then the moment t a1 when the first modulus maximum appears is recorded as the arrival moment t1 of the reflected wave at the fault point, and the fault location is calculated using the first calculation to complete the fault location.

[0131] As Figure 4 shown, as the fault resistance increases, for example, when the fault resistance is 5000Ω, multiple modulus maxima with unequal time intervals are obtained. Inject signals from the M end and extract the reflected wave signals. Multiple suspected arrival times of the traveling wave are obtained through denoising and wavelet transform, and the corresponding fault locations are 25.671m, 109.1m, 145.467m, 152.801m, and 277.487m respectively;

[0132] As Figure 5 shown, inject signals from the N end and extract the reflected signals. Multiple suspected arrival times of the traveling wave are obtained, and the corresponding fault locations are 196.884m, 161.909m, 154.372m, and 150.452m respectively. The fault distance of 152.801m measured from the M end is the closest to the fault distance of 154.372m measured from the N end. The average value of the fault locations determined by this method is 153.586m;

[0133] Table 2 Fault location results for a 4000Ω grounding transition resistance

[0134] Fault location (m) Fault location (m) Error (%) 30 30.45 -0.13％ 70 68.06 0.54％ 110 109.37 0.17％ 170 168.34 0.46％ 250 248.70 0.36％ 310 308.57 0.40％

[0135] Table 3 Fault location results for a 5000Ω grounding transition resistance

[0136] Fault location (m) Fault location (m) Error (%) 30 29.60 0.11％ 70 68.54 0.41％ 110 109.25 0.21％ 170 170.43 -0.12％ 250 249.73 0.08％ 310 309.68 0.09％

[0137] As shown in Table 2 and Table 3, the fault location results for different fault positions at fault resistances of 4000Ω and 5000Ω are summarized. At different fault positions and fault resistances, the maximum fault location error is only 0.54%, achieving high-precision fault location.

Claims

1. A method for locating a single-phase grounding fault of a generator stator winding, characterized in that: include: Acquire voltage and current signals, and perform preprocessing to obtain a first voltage signal and a first current signal; Based on the result of analyzing the first voltage signal, the first current signal is processed by a signal analysis method within a set time range to obtain a plurality of modulus maxima or a unique modulus maximum at equal or unequal time intervals; If multiple modulus maxima or a unique modulus maximum with equal time intervals are obtained, a first calculation is performed to obtain the fault location; If multiple modulus maxima with unequal time intervals are obtained, a second calculation is performed to obtain the fault location.

2. The method for locating a single-phase grounding fault of a generator stator winding according to claim 1, characterized in that: Preprocessing includes: Construct a signal information matrix from discrete signal points of voltage and current signals; Decomposing the signal information matrix to obtain a matrix and a corresponding eigenvector matrix; The values ​​in the matrix whose amplitudes are less than the first threshold are reset to 0, and the signal information matrix is ​​reconstructed using the eigenvector matrix to obtain the first voltage signal and the first current signal.

3. The method for locating a single-phase grounding fault of a generator stator winding according to claim 2, characterized in that: Multiple modulus maxima with equal time intervals include: The absolute value of the difference between the time when the previous modulus maximum value appears and the time when the current modulus maximum value appears minus the difference between the time when the current modulus maximum value appears and the time when the next modulus maximum value appears is less than or equal to 1 sampling interval.

4. The method for locating a single-phase grounding fault of a generator stator winding according to claim 3, characterized in that: The first calculation includes: For multiple modulus maxima or a unique modulus maximum at equal time intervals, the time when the first modulus maximum appears is recorded as the arrival time of the reflected wave at the fault point; The moment when the reflected wave from the fault point reaches the head end minus the moment when the signal is injected from the head end is recorded as the first time interval, and the moment when the end receives the signal injected from the head end minus the moment when the signal arrives at the end is recorded as the second time interval. The ratio of the first time interval to the second time interval is multiplied by half of the total length of the fault branch to obtain the fault location.

5. The method for locating a single-phase grounding fault of a generator stator winding according to claim 1 or 4, characterized in that: Multiple modulus maxima at unequal time intervals include: Using all the modulus maximum moments, a first calculation is performed on the fault position to obtain a first fault position; The time when the signal injected from the end of the line is collected from the head end is propagated to the end end as the first time, and the time when multiple modulus maxima extracted from the end injection signal appear is the second time; Convert the second moment and perform a second calculation to obtain a second fault position; Compare the first fault location with the second fault location, take the nearest point and find the average value to get the fault location.

6. The method for locating a single-phase grounding fault of a generator stator winding according to claim 5, characterized in that: Transforming the second moment includes: The time obtained after conversion is the time when the signal is injected from the head end minus the second time plus twice the first time minus the time when the signal is injected from the end of the fault branch.

7. The method for locating a single-phase grounding fault of a generator stator winding according to claim 5, characterized in that: The second calculation includes: The time obtained after conversion minus the time when the signal is injected from the head end is recorded as the third time interval, and the time when the signal injected from the head end is received by the end minus the time when the signal is injected from the head end is recorded as the second time interval. The ratio of the third time interval to the second time interval is multiplied by half of the total length of the fault branch to obtain the fault location.

8. A system using the method for locating a single-phase ground fault of a generator stator winding according to any one of claims 1 to 7, characterized in that: include: A preprocessing module, which acquires the voltage and current signals and performs preprocessing to obtain a first voltage signal and a first current signal; A processing module, configured to process the first current signal by using a signal analysis method within a set time range based on the result of analyzing the first voltage signal, to obtain a plurality of modulus maxima or a unique modulus maximum at equal or unequal time intervals; A first calculation module, configured to perform a first calculation to obtain a fault location if multiple modulus maxima or a unique modulus maximum at equal time intervals are obtained; The second calculation module is used to perform a second calculation to obtain the fault location if a plurality of modulus maxima with unequal time intervals are obtained.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the method for locating a single-phase grounding fault of a generator stator winding are implemented as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for locating a single-phase grounding fault of a stator winding of a generator as claimed in any one of claims 1 to 7.

Images