Method for determining single-phase grounding fault feeder in high voltage plant grounding system

Abstract

The present application proposes a method for determining a single-phase grounding fault feeder of a high-voltage plant grounding system, which relates to the field of relay protection of power systems. The present application uses wavelet modulus maximum and correlation coefficient transformation matrix feature quantities to select a small current grounding fault line. First, the fault is identified and the fault time is determined based on the modulus maximum algorithm; secondly, the bus fault or feeder fault can be identified by using the constraint relationship between the incoming line zero-sequence current and the sum of the zero-sequence currents of each feeder; finally, if it is a feeder fault, the correlation coefficient change matrix is ​​constructed based on the correlation coefficient transformation matrix method between zero-sequence mutation quantities, and a line selection vector is formed according to the characteristics of the correlation coefficient transformation matrix, and the minimum element corresponding to the line selection vector is the faulty feeder. This method has a stronger anti-interference ability and is not affected by factors such as transition resistance, noise, and abnormal data.

Description

Technical Field

[0001] The present application relates to the field of relay protection for electric power systems, and in particular to a method for determining a single-phase grounding fault feeder in a high-voltage plant grounding system. Background Art

[0002] The reliability of power supply of hydropower stations is related to the vital interests of users and the safety of electricity use. When a single-phase grounding fault occurs in a small current grounding system, the fault signal is weak and the fault characteristics are complex, making detection difficult. Some hydropower stations are affected by the neutral point grounding method, and the zero-sequence current of the single-phase grounding fault becomes smaller, making the fault characteristics more difficult to identify. Single-phase grounding faults account for about 80% of the total faults. If they are not eliminated early, they are likely to develop into serious phase-to-phase short-circuit faults. Therefore, quickly and accurately selecting the faulty feeder is conducive to rapid isolation and troubleshooting, reducing the scope of power outages and economic losses.

[0003] The existing technology uses the fault line selection algorithm based on real-time information collection, which is mainly based on the fault zero-sequence current characteristics, and uses advanced information processing methods to explore the differences between the amplitude of the fault feeder and the non-fault feeder. The traditional method is to identify the fault feeder by using the significant difference between the steady-state zero-sequence current and the transient zero-sequence current of the fault feeder and the non-fault feeder. However, the traditional fault moment confirmation uses the amplitude of the zero-sequence voltage for fault identification, which is easily affected by the transition resistance and the neutral point grounding method; directly analyzing the transient zero-sequence current waveform of the fault feeder, due to the small zero-sequence current characteristic quantity, it is easily disturbed by the load current, which affects the smooth implementation of the fault line selection method based on the zero-sequence current difference judgment basis. Summary of the invention

[0004] The present application aims to at least to some extent solve the problems in the related art that the fault line selection through the original zero-sequence current signal characteristics is susceptible to interference from load current noise, the neutral point compensation method affects the wrong selection, and the accuracy of fault moment identification.

[0005] To this end, one purpose of the present application is to propose a method for determining a single-phase grounding fault feeder in a high-voltage plant grounding system, comprising: in response to monitoring a single-phase grounding fault in the high-voltage plant grounding system, obtaining an original zero-sequence voltage instantaneous signal corresponding to a bus PT at a bus incoming line end of the high-voltage plant grounding system, wherein the high-voltage plant grounding system is provided with k feeders, the first sections of the k feeders are all equipped with zero-sequence current transformers, and the bus incoming line end of the high-voltage plant grounding system is provided with a three-phase current transformer; performing wavelet algorithm decomposition on the zero-sequence voltage instantaneous signal, extracting the zero-sequence voltage wave head according to the wavelet modulus maximum value, so as to perform fault identification and determine the fault time; obtaining the zero-sequence current instantaneous signal corresponding to each of the k feeders in a preset data window at the fault time and the incoming line zero-sequence current instantaneous signal corresponding to the bus incoming line end, and based on the preset data window, the zero-sequence current instantaneous signal is obtained. The constraint relationship between the zero-sequence current instantaneous signal corresponding to each of the k feeders and the zero-sequence current instantaneous signal of the incoming line is assumed to distinguish between bus fault and feeder fault; in response to the judgment result being a feeder fault, the zero-sequence current mutation amount of each of the k feeders in the preset data window at the fault moment is obtained; according to the characteristic relationship between the zero-sequence current mutation amounts of each of the k feeders, a correlation coefficient matrix is ​​determined, the correlation coefficient matrix is ​​normalized, and a correlation coefficient transformation matrix is ​​constructed, and column summation and normalization are performed based on the correlation coefficient transformation matrix to form a line selection vector with a dimension of k, and the feeder corresponding to the minimum element in the line selection vector is taken as the fault feeder, wherein each element in the correlation coefficient matrix is ​​used to reflect the correlation between the zero-sequence current mutation amount of the feeder corresponding to the row where the element is located and the zero-sequence current mutation amount of the feeder corresponding to the column where the element is located.

[0006] According to an embodiment of the present application, a zero-sequence voltage instantaneous signal is decomposed by a wavelet algorithm, and the zero-sequence voltage wave head is extracted according to the wavelet modulus maximum value to perform fault identification and determine the fault moment, including: performing a wavelet algorithm decomposition on the zero-sequence voltage instantaneous signal to obtain 4 layers of sub-signals of different scales generated after the decomposition; performing singular point detection and feature extraction on each sub-signal to obtain related singular point signals, and optimizing each sub-signal according to the wavelet modulus maximum value to determine the zero-sequence voltage wave head; performing multi-scale analysis on the singular point signal and combining it with the zero-sequence voltage wave head to perform fault identification and determine the fault moment.

[0007] According to one embodiment of the present application, when determining the wavelet modulus maximum, let A(t) be a smooth function and wavelet P(t) be its first-order derivative, that is, Then the wavelet transform formula of signal f at scale s and position u is:

[0008]

[0009] That is, the modulus maximum |Wf(s,u)| of the wavelet transform is the maximum of the first-order derivative of the function after the signal f is smoothed by A(t), corresponding to the mutation point of the signal f.

[0010] According to an embodiment of the present application, based on the constraint relationship between the instantaneous zero-sequence current signals corresponding to the preset k feeders and the instantaneous zero-sequence current signals of the incoming lines, the bus fault and the feeder fault are distinguished, including:

[0011] Discretization processing is performed on the instantaneous zero-sequence current signals corresponding to the k feeders and the instantaneous zero-sequence current signals of the incoming lines in the preset data window at the time of the fault;

[0012] Responding to Satisfaction

[0013]

[0014] It is determined that a busbar fault has occurred in the high-voltage plant grounding system;

[0015] Responding to Satisfaction

[0016]

[0017] It is determined that a feeder fault has occurred in the high-voltage plant grounding system;

[0018] In the above formula, k represents the total number of feeders, M represents the number of discrete points in the preset data window, n represents the independent variable of the discrete points in the preset data window, and i represents the total number of feeders in the preset data window. 00 Represents the instantaneous signal of the incoming zero-sequence current corresponding to the bus incoming terminal. Representative The instantaneous signal of zero-sequence current of the feeder, The value ranges from 1 to k.

[0019] According to an embodiment of the present application, in response to the determination result that the feeder is faulty, the zero-sequence current mutation amount of each of the k feeders in the preset data window at the fault time is obtained, and the calculation formula of the zero-sequence current mutation amount is:

[0020]

[0021] In the above formula, Representative The zero-sequence current mutation of a feeder at a certain moment, The value ranges from 1 to k. Representative The instantaneous signal of zero-sequence current of feeder, t s represents the fault moment, T represents one cycle of the power frequency, and n is a positive integer.

[0022] According to an embodiment of the present application, a correlation coefficient matrix is ​​determined according to a characteristic relationship between the zero-sequence current mutation quantities of k feeders, including:

[0023] The correlation calculation is performed on the sequences corresponding to the zero-sequence current mutations of each of the two feeders. The correlation calculation formula is:

[0024]

[0025] In the above formula, ρ xy represents the correlation of the discrete signal sequences of the zero-sequence current mutation quantities of the two feeders, x(n) represents the discrete signal sequence of the zero-sequence current mutation quantity of one of the two feeders, y(n) represents the discrete signal sequence of the zero-sequence current mutation quantity of the other feeder, and N represents the number of zero-sequence current mutation quantities corresponding to each feeder.

[0026] Based on the correlation of the discrete signal sequences of the zero-sequence current mutation of each two feeders, a correlation coefficient matrix is ​​constructed. The correlation coefficient matrix is ​​expressed as:

[0027]

[0028] Each element a in the correlation coefficient matrix ij =a ji (i≠j) is used to reflect the correlation between the discrete signal sequence of the zero-sequence current mutation amount of the feeder corresponding to the i-th row where the element is located and the discrete signal sequence of the zero-sequence current mutation amount of the feeder corresponding to the j-th column where the element is located; the diagonal elements of the correlation coefficient matrix reflect the correlation of the discrete signal sequences of each feeder itself, and the value of the diagonal elements is 1.

[0029] According to an embodiment of the present application, the correlation coefficient matrix is ​​normalized to construct a correlation coefficient transformation matrix, including:

[0030] Each element in the correlation coefficient matrix is ​​judged, elements greater than zero are set to 1, elements less than zero are set to 0, and elements equal to zero are maintained as 0 to obtain the correlation coefficient transformation matrix, which is expressed as:

[0031]

[0032] The element b of the correlation coefficient transformation matrix B ij It is composed of 0 or 1.

[0033] According to an embodiment of the present application, summing up the columns and normalizing the correlation coefficient transformation matrix to form a line selection vector with a dimension of k, summing up the columns and normalizing the correlation coefficient transformation matrix to form a line selection vector with a dimension of k, and taking the feeder corresponding to the minimum element in the line selection vector as the fault feeder, including:

[0034] The jth column of the correlation coefficient transformation matrix B is transformed according to Calculate and form a line vector P with dimension k, where P = [P 1 P 2 … P k ], the feeder corresponding to the minimum element in the line selection vector P is taken as the fault feeder.

[0035] According to one embodiment of the present application, the method for determining a single-phase grounding fault feeder in a high-voltage plant grounding system further includes: in response to a judgment result that the busbar fault is present, directly determining that the cause of the single-phase grounding fault in the high-voltage plant grounding system is a busbar fault.

[0036] The present application achieves at least the following beneficial effects: the present application adopts a wavelet algorithm for fault identification, and can extract the zero-sequence voltage wave head, thereby determining the fault moment; at the same time, according to the preset constraint relationship, the bus fault and the feeder fault can be distinguished, further improving the accuracy of fault identification, based on the correlation of the zero-sequence current mutation amount of each feeder, by constructing a correlation coefficient matrix, normalization processing and correlation coefficient transformation and other methods, a line selection vector with a dimension of k can be calculated, and the faulty feeder can be determined. Compared with the traditional manual maintenance method, this scheme can achieve more accurate and rapid fault location. This scheme requires the use of professional monitoring instruments and data processing software, and can realize automated fault detection and location, reduce manual intervention and the risk of misjudgment, and improve work efficiency and reliability. The use of this scheme can effectively shorten the fault handling cycle, reduce system downtime and maintenance costs, and improve the stability and economic benefits of the power system. Compared with related technologies, this scheme has stronger anti-interference ability, is not affected by factors such as transition resistance, noise, and abnormal data, and achieves more robust fault line selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0038] Figure 1 It is an exemplary schematic diagram of a method for determining a single-phase grounding fault feeder of a high-voltage plant grounding system shown in the present application.

[0039] Figure 2 It is an overall flow chart of a method for determining a single-phase grounding fault feeder of a high-voltage plant grounding system shown in the present application.

[0040] Figure 3 This is a schematic diagram of a high-voltage plant system grounding fault line selection model shown in this application.

[0041] Figure 4 A waveform for fault identification based on wavelet transform modulus maximum is shown in this application.

[0042] FIG5( a ) is a waveform diagram of the sum of zero-sequence currents of each feeder and the zero-sequence current of the incoming line when a feeder fault is simulated as shown in the present application.

[0043] FIG5( b ) is a waveform diagram of the sum of the zero-sequence currents of the feeders and the zero-sequence current of the incoming line when simulating a bus fault as shown in the present application.

[0044] Figure 6 Schematic diagram of zero-sequence current waveforms of feeders when a feeder L3 simulates a single-phase grounding fault shown in the present application.

[0045] Figure 7 Schematic diagram of the waveform of the zero-sequence current mutation of each feeder when a feeder L3 simulates a single-phase grounding fault shown in the present application. DETAILED DESCRIPTION

[0046] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0047] Figure 1 is an exemplary schematic diagram of a method for determining a single-phase grounding fault feeder of a high-voltage plant grounding system shown in the present application, such as Figure 1 As shown, the method for determining the single-phase grounding fault feeder of the high-voltage plant grounding system includes the following steps:

[0048] S101, in response to monitoring a single-phase grounding fault in a high-voltage plant grounding system, obtain the original zero-sequence voltage instantaneous signal corresponding to the bus PT at the bus incoming line end of the high-voltage plant grounding system, wherein the high-voltage plant grounding system is provided with k feeders, the first sections of the k feeders are all equipped with zero-sequence current transformers, and the bus incoming line end of the high-voltage plant grounding system is provided with a three-phase current transformer.

[0049] S102, decomposing the zero-sequence voltage instantaneous signal using a wavelet algorithm, extracting the zero-sequence voltage wave head according to the wavelet modulus maximum value, so as to perform fault identification and determine the fault moment.

[0050] When a single-phase grounding occurs in the high-voltage plant grounding system, the transient signal generated by the fault contains irregular mutation signals, which are usually called singular point signals. The singular point signal contains rich transient information, one of which is fault identification information. In this application, the zero-sequence voltage transient signal u 0Wavelet algorithm decomposition is performed to obtain 4 layers of sub-signals of different scales generated after decomposition; singular point detection and feature extraction are performed on each sub-signal to obtain relevant singular point signals, and each sub-signal is optimized according to the wavelet modulus maximum to determine the zero-sequence voltage wave head; multi-scale analysis is performed on the singular point signal to amplify the local characteristics of the fault signal, and combined with the zero-sequence voltage wave head, fault identification is performed and the fault moment is determined.

[0051] Among them, when determining the maximum value of the wavelet modulus, let A(t) be a smooth function and wavelet P(t) be its first-order derivative, that is, Then the wavelet transform formula of signal f at scale s and position u is:

[0052]

[0053] That is, the modulus maximum |Wf(s,u)| of the wavelet transform is the maximum of the first-order derivative of the function after the signal f is smoothed by A(t), corresponding to the mutation point of the signal f.

[0054] S103, obtaining the zero-sequence current instantaneous signals corresponding to the k feeders and the incoming zero-sequence current instantaneous signals corresponding to the bus incoming end in the preset data window at the time of the fault, and distinguishing the bus fault from the feeder fault based on the constraint relationship between the preset zero-sequence current instantaneous signals corresponding to the k feeders and the incoming zero-sequence current instantaneous signals.

[0055] Discretization processing is performed on the zero-sequence current instantaneous signals corresponding to the k feeders and the zero-sequence current instantaneous signals of the incoming lines in the preset data window at the fault moment.

[0056] In response to satisfying the following equation:

[0057]

[0058] It is determined that a busbar fault has occurred in the high-voltage plant grounding system;

[0059] In response to satisfying the following equation:

[0060]

[0061] It is determined that a feeder fault has occurred in the high-voltage plant grounding system;

[0062] In the above formula, k represents the total number of feeders, M represents the number of discrete points in the preset data window, n represents the independent variable of the discrete points in the preset data window, and i represents the total number of feeders in the preset data window. 00 Represents the instantaneous signal of the incoming zero-sequence current corresponding to the bus incoming terminal. Representative The instantaneous signal of zero-sequence current of the feeder, The value ranges from 1 to k.

[0063] S104, in response to the determination result that the feeder is faulty, obtaining the zero-sequence current mutation amount of each of the k feeders in the preset data window at the time of the fault.

[0064] If there is a feeder fault, in order to further identify the faulty feeder, the zero-sequence current mutation of each feeder is first obtained. The method is to obtain the zero-sequence current mutation after the fault minus the zero-sequence current before the fault occurs within a fixed period. The calculation formula of the zero-sequence current mutation is:

[0065]

[0066] In the above formula, Representative The zero-sequence current mutation of a feeder at a certain moment, The value ranges from 1 to k. Representative The instantaneous signal of zero-sequence current of feeder, t s represents the fault moment, T represents one cycle of the power frequency, and n is a positive integer.

[0067] S105, determine the correlation coefficient matrix according to the characteristic relationship between the zero-sequence current mutations of the k feeders, normalize the correlation coefficient matrix, construct a correlation coefficient transformation matrix, perform column summing and normalization based on the correlation coefficient transformation matrix to form a line selection vector with a dimension of k, and take the feeder corresponding to the minimum element in the line selection vector as the fault feeder, wherein each element in the correlation coefficient matrix is ​​used to reflect the correlation between the zero-sequence current mutation of the feeder corresponding to the row where the element is located and the zero-sequence current mutation of the feeder corresponding to the column where the element is located.

[0068] Since the zero-sequence current mutation waveforms of the faulty feeder and the non-faulty feeder are quite different, and the zero-sequence current mutation waveforms between the non-faulty feeders are similar, in order to make the result of the correlation operation truly reflect the correlation between the two signals and eliminate the influence of the signal amplitude on it, based on this feature, according to the characteristic relationship between the zero-sequence current mutations of the k feeders, the correlation coefficient method is introduced to calculate the correlation of the discrete signal sequences corresponding to the zero-sequence current mutations of each two feeders. The general calculation formula for the correlation is:

[0069]

[0070] In the above formula, ρ xy represents the correlation of the discrete signal sequences of the zero-sequence current mutation quantities of the two feeders, x(n) represents the discrete signal sequence of the zero-sequence current mutation quantity of one of the two feeders, y(n) represents the discrete signal sequence of the zero-sequence current mutation quantity of the other feeder, and N represents the number of zero-sequence current mutation quantities corresponding to each feeder.

[0071] Among them, the value of the correlation coefficient ρ is between -1 and 1. When the change trends of the two characteristic sequences X and Y are the same, ρ>0, where ρ=1 means that X and Y are completely positively correlated. When the change trends of the two characteristic sequences X and Y are opposite, ρ<0, where ρ=-1 means that X and Y are completely negatively correlated. When the change rules of X and Y are quite different, ρ approaches 0, where ρ=0 means that X and Y have no correlation. The correlation coefficient measures the similarity relationship between the two data sets by sorting the original data, and greatly reduces the interference of load current and abnormal data with mutation data.

[0072] Based on the correlation of the discrete signal sequences of the zero-sequence current mutation of each two feeders, a correlation coefficient matrix is ​​constructed. The correlation coefficient matrix A is expressed as:

[0073]

[0074] Each element a in the correlation coefficient matrix ij =a ji (i≠j) is used to reflect the correlation between the discrete signal sequence of the zero-sequence current mutation of the feeder corresponding to the i-th row where the element is located and the discrete signal sequence of the zero-sequence current mutation of the feeder corresponding to the j-th column where the element is located; the diagonal elements of the correlation coefficient matrix reflect the correlation of the discrete signal sequences of each feeder. The value of the diagonal element is 1. According to the symmetry of the matrix, there exists a ij =a ji (i≠j).

[0075] Since the elements in matrix A are both positive and negative, considering the anti-interference of data processing, the correlation coefficient matrix is ​​normalized, that is, each element in the correlation coefficient matrix is ​​judged, the elements greater than zero are set to 1, the elements less than zero are set to 0, and the elements equal to zero are maintained as 0 to obtain the correlation coefficient transformation matrix, which is expressed as:

[0076]

[0077] The element b of the correlation coefficient transformation matrix B ij It is composed of 0 or 1.

[0078] The jth column of the correlation coefficient transformation matrix B is transformed according to Calculate and form a line vector P with dimension k, where P = [P 1 P 2 … P k ], the feeder corresponding to the minimum element in the line selection vector P is taken as the fault feeder.

[0079] Further, in response to the determination result being a busbar fault, it is directly determined that the cause of the single-phase grounding fault occurring in the high-voltage plant grounding system is the busbar fault.

[0080] The present application adopts wavelet algorithm for fault identification, which can extract the zero-sequence voltage wave head and thus determine the fault moment; at the same time, according to the preset constraint relationship, bus faults and feeder faults can be distinguished, further improving the accuracy of fault identification, and based on the correlation of the zero-sequence current mutation of each feeder, by constructing a correlation coefficient matrix, normalization processing and correlation coefficient transformation and other methods, a line selection vector with a dimension of k can be calculated, and the faulty feeder can be determined. Compared with the traditional manual maintenance method, this scheme can achieve more accurate and rapid fault location. This scheme requires the use of professional monitoring instruments and data processing software, which can realize automated fault detection and location, reduce the risk of manual intervention and misjudgment, and improve work efficiency and reliability. The scheme can effectively shorten the fault handling cycle, reduce system downtime and maintenance costs, and improve the stability and economic benefits of the power system. Compared with related technologies, this scheme has stronger anti-interference ability, is not affected by factors such as transition resistance, noise, and abnormal data, and achieves more robust fault line selection.

[0081] Figure 2 This is a general flow chart of a method for determining a single-phase grounding fault feeder of a high-voltage plant grounding system shown in the present application, such as Figure 2 As shown, if a single-phase grounding fault is detected in the high-voltage plant grounding system, the original zero-sequence voltage instantaneous signal corresponding to the bus PT at the bus incoming line end of the high-voltage plant grounding system is obtained, wherein the high-voltage plant grounding system is provided with k feeders, and the first sections of the k feeders are all equipped with zero-sequence current transformers, and the bus incoming line end of the high-voltage plant grounding system is provided with a three-phase current transformer.

[0082] The zero-sequence voltage instantaneous signal is decomposed by wavelet algorithm, and the zero-sequence voltage wave head is extracted according to the wavelet modulus maximum value. If a zero-sequence voltage wave head exists, fault identification is performed and the fault moment is determined.

[0083] The instantaneous zero-sequence current signals corresponding to the k feeders and the instantaneous zero-sequence current signals corresponding to the busbar incoming line end are obtained in the preset data window at the fault moment, and based on the constraint relationship between the preset instantaneous zero-sequence current signals corresponding to the k feeders and the instantaneous zero-sequence current signals of the incoming line, the busbar fault and the feeder fault are distinguished.

[0084] In response to the determination result that the feeder is faulty, the zero-sequence current mutation amount of each of the k feeders in the preset data window at the time of the fault is obtained.

[0085] According to the characteristic relationship between the zero-sequence current mutations of the k feeders, a correlation coefficient matrix is ​​determined, the correlation coefficient matrix is ​​normalized, and a correlation coefficient transformation matrix is ​​constructed. Based on the correlation coefficient transformation matrix, column summation and normalization are performed to form a line selection vector with a dimension of k. The feeder corresponding to the minimum element in the line selection vector is taken as the fault feeder, and the other feeders are taken as non-fault feeders. Each element in the correlation coefficient matrix is ​​used to reflect the correlation between the zero-sequence current mutation of the feeder corresponding to the row where the element is located and the zero-sequence current mutation of the feeder corresponding to the column where the element is located.

[0086] In response to the determination result being a busbar fault, it is directly determined that the cause of the single-phase grounding fault occurring in the high-voltage plant grounding system is the busbar fault.

[0087] The following introduces the simulation experiments and related data of this scheme. Figure 3 This is a schematic diagram of a high-voltage plant system grounding fault line selection model shown in this application, such as Figure 3 As shown in the figure, a 10kV high-voltage plant grounding system is built using MATLAB / Simulink. The 10kV high-voltage plant grounding system contains 4 feeders L1, L2, L3, and L4. The parameters of the transformer are: rated capacity is 4.5MV·A; no-load loss is 7.5kW; short-circuit loss is 32kW, the first section zero-sequence current transformer of the feeder is TAk (k=1, 2, 3, 4), the incoming three-phase current transformer is TA0, the simulation time is 0.2s, the fault time is 0.04s, and the sampling frequency of each cycle is 200 / 0.02s.

[0088] During the simulation experiment, a single-phase grounding fault was simulated based on feeder L3. Figure 4 This application shows a waveform based on wavelet transform modulus maximum fault identification, such as Figure 4 As shown in the figure, since the simulated fault time is 0.04s, the corresponding sampling point is N = 400. Figure 4 The corresponding N=395 is shown in Table 1, and the maximum error is only 1.25. The maximum values ​​of zero-sequence voltage modulus for different grounding resistances are shown in Table 1.

[0089] Table 1 Fault identification results based on wavelet transform modulus maximum algorithm

[0090]

[0091] FIG5( a ) is a waveform diagram of the sum of the zero-sequence currents of each feeder and the zero-sequence current of the incoming line when a feeder fault is simulated as shown in the present application. As shown in FIG5( a ), the sum of the zero-sequence currents of each feeder is the same as the zero-sequence current of the incoming line.

[0092] FIG5( b ) is a waveform diagram of the sum of the zero-sequence currents of each feeder and the zero-sequence current of the incoming line when a busbar fault is simulated as shown in the present application. As shown in FIG5( b ), the sum of the zero-sequence currents of each feeder and the zero-sequence current of the incoming line are quite different.

[0093] Among them, the bus fault and feeder fault simulation data are shown in Table 2.

[0094] Table 2 Busbar fault and feeder fault identification results

[0095]

[0096] Figure 6 Schematic diagram of zero-sequence current waveform of each feeder when a feeder L3 simulates a single-phase grounding fault shown in this application, Figure 7 FIG. 1 is a schematic diagram of the waveform of the zero-sequence current mutation of each feeder when a feeder L3 simulates a single-phase grounding fault shown in the present application, as shown in FIG. Figure 7 As shown in the figure, the zero-sequence current mutations between non-fault feeders are relatively similar, and the waveforms of zero-sequence current mutations between fault feeders and non-fault feeders are quite different.

[0097] During the simulation of a single-phase grounding fault on feeder L3, the correlation coefficient matrix calculated based on the zero-sequence current mutation is as follows.

[0098]

[0099] The correlation coefficient transformation matrix B is formed as follows

[0100]

[0101] It can be seen from the correlation coefficient matrix A that the correlation coefficients between the faulty feeder and the non-faulty feeder are negatively correlated, and the correlation coefficients between the non-faulty feeders are positively correlated. The line selection vector P can be formed according to the change matrix B:

[0102] P = [0.75 0.75 0.25 0.75]

[0103] The value corresponding to feeder L3 in the line selection vector P is the smallest, that is, it corresponds to a simulated single-phase grounding fault of feeder L3.

[0104] Under the same working conditions, the single-phase grounding faults of different feeders are simulated, and the fault results of different grounding resistances are shown in Table 3.

[0105] Table 3 Feeder single-phase grounding fault identification results

[0106]

[0107] This application verifies the applicability of a single-phase grounding fault line selection method for a high-voltage plant system of a hydropower station through different grounding resistances and grounding positions.

[0108] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0109] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0110] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0111] Although the embodiments of the present application 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 application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for determining a single-phase grounding fault feeder in a high-voltage plant grounding system, characterized in that: include: In response to monitoring a single-phase grounding fault in a high-voltage plant grounding system, an original zero-sequence voltage instantaneous signal corresponding to a bus PT at a bus inlet end of the high-voltage plant grounding system is obtained, wherein the high-voltage plant grounding system is provided with k feeders, the first sections of the k feeders are all equipped with zero-sequence current transformers, and the bus inlet end of the high-voltage plant grounding system is provided with a three-phase current transformer; Decomposing the zero-sequence voltage instantaneous signal using a wavelet algorithm to obtain four layers of sub-signals of different scales generated after the decomposition; Performing singular point detection and feature extraction on each of the sub-signals to obtain related singular point signals, and optimizing each sub-signal according to the wavelet modulus maximum to determine the zero-sequence voltage wave head; Perform multi-scale analysis on the singular point signal and combine it with the zero-sequence voltage wave head to identify the fault and determine the fault time; Obtaining the zero-sequence current instantaneous signals corresponding to the k feeders and the incoming zero-sequence current instantaneous signals corresponding to the bus incoming end in the preset data window at the fault moment, and distinguishing between bus fault and feeder fault based on the preset constraint relationship between the zero-sequence current instantaneous signals corresponding to the k feeders and the incoming zero-sequence current instantaneous signals; In response to the determination result that the feeder is faulty, obtaining the zero-sequence current mutation amount of each of the k feeders in a preset data window at the time of the fault; According to the characteristic relationship between the zero-sequence current mutations of k feeders, a correlation coefficient matrix is ​​determined, the correlation coefficient matrix is ​​normalized, and a correlation coefficient transformation matrix is ​​constructed. Column summation and normalization are performed based on the correlation coefficient transformation matrix to form a line selection vector with a dimension of k, and the feeder corresponding to the minimum element in the line selection vector is taken as the fault feeder, wherein each element in the correlation coefficient matrix is ​​used to reflect the correlation between the zero-sequence current mutation of the feeder corresponding to the row where the element is located and the zero-sequence current mutation of the feeder corresponding to the column where the element is located.

2. The method according to claim 1, characterized in that When determining the maximum value of the wavelet modulus, let A(t) be a smooth function and the wavelet function P(t) be its first-order derivative, that is, Then the wavelet transform formula of signal f at scale s and position u is: Among them, the modulus maximum value |Wf(s,u)| of the wavelet transform is the maximum value of the first-order derivative of the function after the signal f is smoothed by A(t), corresponding to the mutation point of the signal f.

3. The method according to claim 2, characterized in that The discrimination between bus fault and feeder fault based on the constraint relationship between the instantaneous zero-sequence current signals corresponding to the preset k feeders and the instantaneous zero-sequence current signals of the incoming lines comprises: Discretization processing is performed on the instantaneous zero-sequence current signals corresponding to the k feeders and the instantaneous zero-sequence current signals of the incoming lines in the preset data window at the time of the fault; Responding to Satisfaction It is determined that a busbar fault occurs in the high-voltage plant grounding system; in response to the It is determined that a feeder fault has occurred in the high-voltage plant grounding system; In the above formula, k represents the total number of feeders, M represents the number of discrete points in the preset data window, n represents the independent variable of the discrete points in the preset data window, and i represents the total number of feeders in the preset data window. 00 Represents the instantaneous signal of the incoming zero-sequence current corresponding to the bus incoming terminal. Representative The instantaneous signal of zero-sequence current of the feeder, The value ranges from 1 to k.

4. The method according to any one of claims 1 to 3, characterized in that In response to the judgment result being a feeder fault, the zero-sequence current mutation amount of each of the k feeders in the preset data window at the fault moment is obtained, and the calculation formula of the zero-sequence current mutation amount is: In the above formula, Representative The zero-sequence current mutation of the feeder, The value ranges from 1 to k. Representative The instantaneous signal of zero-sequence current of feeder, t s represents the fault moment, T represents one cycle of the power frequency, and n1 is a positive integer.

5. The method according to claim 4, characterized in that Determining the correlation coefficient matrix according to the characteristic relationship between the zero-sequence current mutation quantities of the k feeders comprises: The correlation calculation is performed on the discrete signal sequences corresponding to the zero-sequence current mutations of each of the two feeders. The general calculation formula for the correlation is: In the above formula, ρ xy represents the correlation of the discrete signal sequences of the zero-sequence current mutations of the two feeders, x(n) represents the discrete signal sequence of the zero-sequence current mutation of one of the two feeders, y(n) represents the discrete signal sequence of the zero-sequence current mutation of the other feeder, and N represents the number of zero-sequence current mutations corresponding to each feeder; Based on the correlation of the discrete signal sequences of the zero-sequence current mutation of each two feeders, a correlation coefficient matrix is ​​constructed. The correlation coefficient matrix is ​​expressed as: Each element a in the correlation coefficient matrix A ij =a ji , i≠j, is used to reflect the correlation between the discrete signal sequence of the zero-sequence current mutation amount of the feeder corresponding to the i-th row where the element is located and the discrete signal sequence of the zero-sequence current mutation amount of the feeder corresponding to the j-th column where the element is located; the diagonal elements of the correlation coefficient matrix reflect the correlation of the discrete signal sequences of each feeder itself, and the value of the diagonal elements is 1.

6. The method according to claim 5, characterized in that The normalizing the correlation coefficient matrix to construct a correlation coefficient transformation matrix includes: Each element in the correlation coefficient matrix is ​​judged, elements greater than zero are set to 1, elements less than zero are set to 0, and elements equal to zero are maintained as 0 to obtain the correlation coefficient transformation matrix, and the correlation coefficient transformation matrix is ​​expressed as: The element b of the correlation coefficient transformation matrix B ij It is composed of 0 or 1.

7. The method according to claim 6, characterized in that The step of performing column summing and normalization based on the correlation coefficient transformation matrix to form a line selection vector with a dimension of k, and taking a feeder corresponding to a minimum element in the line selection vector as a faulty feeder, comprises: The j column of the correlation coefficient transformation matrix B is transformed according to Calculate and form a line vector P with dimension k, where P = [P1 P2 … P k ], k represents the total number of feeders, and the feeder corresponding to the minimum element in the line selection vector P is taken as the fault feeder.

8. The method according to claim 1, characterized in that The method further comprises: In response to the determination result being a busbar fault, it is directly determined that the cause of the single-phase grounding fault occurring in the high-voltage plant grounding system is the busbar fault.

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