A method and system for locating multiple faults in distribution network cable lines

Abstract

The present invention discloses a method and system for multi-fault location of distribution network cable lines, belonging to the field of distribution network cable fault location; the method includes: S1 calculating a global differential scattering matrix; S2 calculating a differential time reversal operator, performing eigenvector decomposition on the differential time reversal operator, and selecting the eigenvector x with the largest eigenvalue; S3 reconstructing the time-domain inversion waveform by using the eigenvector x and the Fourier spectrum of the pulse waveform; S4 simulating to obtain the time-domain response voltage waveforms at each detection point; S5 calculating the energy values at each location of the line, drawing an energy map, and finding the strongest fault point fx; S6 adding a fault at the fault point fx in the fault-free simulation model, and measuring its differential scattering matrix #imgabs0#S7 calculating the differential scattering matrix coefficient α i and the differential scattering matrix S corresponding to the real fault i ; S8 updating the global differential scattering matrix; S9 repeating S2-S8 until no new fault locations can be located in the updated global differential scattering matrix.

Description

Technical Field

[0001] The invention belongs to the field of distribution network cable fault positioning, and in particular relates to a distribution network cable line multi-fault positioning method and system. Background Art

[0002] In the distribution network, cable lines have become one of the important components of distribution lines due to their many advantages such as stable and reliable power supply and durability. Although the power supply reliability of power cables is very high, they are generally buried directly underground and the line structure is relatively complex. When a fault occurs, it is not easy to directly find the fault location and eliminate the fault in time. Therefore, it is necessary to use fault location methods to troubleshoot faults. In recent years, time reversal technology has the characteristics of forming time and space focusing at the fault point, avoiding the difficulty of extracting wave head features, and solving the problems of easy misjudgment of the arrival time of traveling waves. It has the advantages of broad application prospects for line fault location. However, this method will be affected by the line topology and the back-and-forth reflection and scattering of each endpoint. Therefore, it is necessary to know the refraction and reflection relationship between each port of the line. The scattering matrix in microwave theory can characterize the refraction and reflection relationship between each port of the network itself and between each port, contains all the refraction and reflection information of the multi-port network, and can implicitly characterize the topology of the line. Therefore, the scattering matrix and time reversal technology can be combined to achieve accurate positioning of line faults. However, when there are multiple faults in the network at the same time, the above method cannot completely locate all faults. For example, if this method is used to locate multiple faults in the distribution network cable, it is necessary to measure the fault scattering matrix of the network again after each fault is located, and repeat this cycle until no obvious fault characteristics can be located. The workload will increase exponentially, and the need for rapid fault location cannot be guaranteed. The power outage time will increase, causing greater economic losses. Summary of the invention

[0003] In view of the deficiencies in the prior art, an object of the present invention is to provide a method and system for locating multiple faults in a distribution network cable line.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for locating multiple faults in a distribution network cable line comprises the following steps:

[0006] S1, measure and calculate the frequency domain scattering matrix of the distribution network cable line in the fault state and the fault-free state, and then calculate the global differential scattering matrix;

[0007] S2, based on the global differential scattering matrix, calculating the differential time reversal operator, and performing eigenvector decomposition on the differential time reversal operator, and selecting the eigenvector x with the largest eigenvalue;

[0008] S3, for any network port in the network, reconstructing a time domain inversion waveform using the characteristic vector x and the Fourier spectrum of the pulse waveform;

[0009] S4, establishing a fault-free simulation model according to the proportionality of the line parameters, connecting matching impedances at each port of the network and correspondingly injecting the time domain inversion waveform, setting a number of detection points on each line, and simulating and obtaining the time domain response voltage waveform at each detection point;

[0010] S5, according to the time domain response voltage waveform, calculate the energy value of each line, and draw an energy spectrum. The line position corresponding to the maximum value point is the fault point fx with the strongest fault characteristics among multiple faults;

[0011] S6, adding a fault at the fault point fx in the fault-free simulation model and measuring its differential scattering matrix

[0012] S7, according to the differential scattering matrix Calculate the effective eigenvalues ​​and their corresponding eigenvectors, and then calculate the differential scattering matrix coefficient α by the decomposition method of the differential scattering matrix i The differential scattering matrix S corresponding to the real fault i ;

[0013] S8, based on the differential scattering matrix coefficient α i The differential scattering matrix S corresponding to the real fault i , the differential scattering matrix S that eliminates the contribution of the i-th fault from the global differential scattering matrix i , to complete the update;

[0014] S9, repeat S2-S8 until there is no new fault position to be located in the updated global differential scattering matrix, and then stop locating.

[0015] Furthermore, the step of calculating the global differential scattering matrix includes:

[0016] S11, for an N-port network, multiple groups of 2×2×Tn dimensional scattering matrices are measured by injecting pulses to measure responses, and then the frequency domain scattering matrix of the N×N×Tn dimensional network under fault conditions is reconstructed;

[0017] S12, geometric modeling fault-free simulation model, by injecting pulses at each port and connecting the remaining ports to matching impedance, the response of each port is measured, and then the frequency domain scattering matrix of the network with N×N×Tn dimensions in the fault-free state is calculated;

[0018] S13, subtracting the frequency domain scattering matrix under the fault state from the frequency domain scattering matrix under the non-fault state to obtain a global differential scattering matrix.

[0019] Furthermore, the calculation formula of the differential time reversal operator is:

[0020] H(ω)=S G ·S G *

[0021] Where H(ω) is the differential time inversion operator, S G is the global differential scattering matrix, and * represents the conjugate transpose operation.

[0022] Furthermore, the calculation formula of the time domain inversion waveform is:

[0023] g i (t) = ∫x i (w)F(ω)e jωt dω

[0024] In the formula, g i (t) is the time domain inversion waveform, F(ω) is the Fourier spectrum of the pulse waveform f(t); i (ω) is a vector of Tn×1 dimension in the feature vector x, j is an imaginary unit, ω is a frequency domain parameter, and t is time.

[0025] Furthermore, the energy value calculation formula at each point of the line is:

[0026]

[0027] Where E(x) is the energy at x, u(x,t) is the time domain response voltage waveform, Z is the cable wave impedance, and t is time.

[0028] Furthermore, the differential scattering matrix The calculation steps include:

[0029] S61, by adding a virtual fault at the fault point fx in the fault-free simulation model, selecting the unmatched impedance as the transition impedance, and starting from the definition of the scattering matrix, measuring the fault scattering matrix of the network;

[0030] S62, perform difference processing on the fault scattering matrix obtained in S61 and the frequency domain scattering matrix in the fault-free state obtained in S12, so as to calculate the differential scattering matrix

[0031] Further, the differential scattering matrix coefficient α is calculated as i The differential scattering matrix S corresponding to the real fault i The steps include:

[0032] S71, according to the differential scattering matrix Calculate its unique valid eigenvalue vi The corresponding eigenvector w i ;

[0033] S72, the differential scattering matrices of different fault types at the same fault point have a multiple relationship, namely:

[0034]

[0035] In the formula, μ i for The corresponding main eigenvalue, T is the transposition operation, α i is the differential scattering matrix coefficient, then the global differential scattering matrix S G It can be expressed as:

[0036]

[0037] Where N is the number of all faults in the line.

[0038] Then the differential scattering matrix coefficient α i The approximate calculation formula is as follows:

[0039]

[0040] Based on this, the differential scattering matrix coefficient α is calculated i The differential scattering matrix S corresponding to the real fault i .

[0041] Furthermore, the update expression of the global differential scattering matrix is:

[0042]

[0043] In the formula, is the updated global differential scattering matrix, is the global differential scattering matrix before updating.

[0044] A distribution network cable line multi-fault locating system, comprising:

[0045] Global differential scattering matrix calculation module: measures and calculates the frequency domain scattering matrix of the distribution network cable line in fault state and fault-free state, and then calculates the global differential scattering matrix;

[0046] Eigenvector solving module: based on the global differential scattering matrix, calculating the differential time reversal operator, and performing eigenvector decomposition on the differential time reversal operator, and selecting the eigenvector x with the largest eigenvalue;

[0047] Time domain inversion waveform construction module: for any network port in the network, the time domain inversion waveform is reconstructed using the characteristic vector x and the Fourier spectrum of the pulse waveform;

[0048] Time domain response voltage waveform construction module: establish a fault-free simulation model according to the line parameters in equal proportion, connect matching impedance to each port of the network and inject the time domain inversion waveform accordingly, set several detection points on each line, and simulate and obtain the time domain response voltage waveform at each detection point;

[0049] Energy spectrum drawing module: Calculate the energy value at each point of the line according to the time domain response voltage waveform, and draw the energy spectrum. The line position corresponding to the maximum value point is the fault point fx with the strongest fault characteristics among multiple faults.

[0050] Differential scattering matrix measurement module: Add a fault at the fault point fx in the fault-free simulation model and measure its differential scattering matrix

[0051] Coefficient solution module: According to the differential scattering matrix Calculate the effective eigenvalues ​​and their corresponding eigenvectors, and then calculate the differential scattering matrix coefficient α by the decomposition method of the differential scattering matrix i The differential scattering matrix S corresponding to the real fault i ;

[0052] Matrix update module: based on the differential scattering matrix coefficient α i The differential scattering matrix S corresponding to the real fault i , the differential scattering matrix S that eliminates the contribution of the i-th fault from the global differential scattering matrix i , to complete the update;

[0053] And, positioning module: repeatedly use the time domain inversion waveform construction module to the matrix update module until there is no new fault position to be located in the updated global differential scattering matrix, and then stop positioning.

[0054] A computer storage medium stores a readable program, and when the program is run, the positioning method is executed.

[0055] Beneficial effects of the present invention:

[0056] 1. The present invention combines the frequency domain scattering matrix with the time inversion technology. The scattering matrix is ​​used to characterize the refraction and reflection information of the line topology and its branch points. The differential scattering matrix is ​​then used to eliminate the influence of the line branch points and endpoints on the signal scattering. The spatial focusing of the time inversion energy spectrum is used to locate the fault position with the most obvious fault characteristics among multiple faults.

[0057] 2. The present invention updates the global differential scattering matrix according to the global differential scattering moment decomposition algorithm, and then locates each fault in turn, without measuring the fault scattering matrix for each location, thereby improving the efficiency of fault location. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0059] Figure 1 is a flow chart of the method of the present invention;

[0060] Figure 2 This is a 13-node line diagram of a distribution network in an embodiment of the present invention;

[0061] Figure 3 It is the first fault location diagram in the embodiment of the present invention;

[0062] Figure 4 is the second fault location diagram in the embodiment of the present invention;

[0063] Figure 5 is the third fault location diagram in the embodiment of the present invention;

[0064] Figure 6 This is the fourth fault location diagram in the embodiment of the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] like Figure 1 As shown, a method for locating multiple faults in a distribution network cable line comprises the following steps:

[0067] S1, measure and calculate the frequency domain scattering matrix S1(ω) of the distribution network cable line in the fault state and the frequency domain scattering matrix S2(ω) in the fault-free state, and then calculate the global differential scattering matrix S G ;

[0068] The specific steps include:

[0069] S11, starting from the definition of frequency domain scattering matrix, for an N-port network, multiple groups of 2×2×Tn (Tn is the number of sampling points) scattering matrices are measured by injecting pulses to measure responses, and then the frequency domain scattering matrix S1(ω) of the N×N×Tn dimensional network under fault condition is reconstructed;

[0070] S12, geometric modeling fault-free simulation model, injects pulses at each port and connects the remaining ports to matching impedance to measure the response of each port, and then calculates the frequency domain scattering matrix S2(ω) of the network with N×N×Tn dimensions in the fault-free state.

[0071] S13, the frequency domain scattering matrix S1(ω) under the fault state is processed differently from the frequency domain scattering matrix S2(ω) under the fault-free state to obtain the global differential scattering matrix S G , that is, S G =S1(ω)-S2(ω).

[0072] S2, based on the global differential scattering matrix obtained in S1, calculates the differential time reversal operator H(ω), and performs eigenvector decomposition on the differential time reversal operator H(ω), and selects the eigenvector x with the largest eigenvalue therefrom, which specifically includes the following steps:

[0073] S21, calculate the differential time reversal operator; the calculation formula is:

[0074] H(ω)=S G ·S G * ;

[0075] Where H(ω) is the differential time inversion operator, S G is the global differential scattering matrix, * represents the conjugate transpose operation;

[0076] S22, perform eigenvector decomposition on the time reversal operator H(ω), and select the eigenvector x=[x1(ω),x2(ω),…,x N (ω)] T , each value corresponds to a port, x i (ω) is a vector of dimension Tn×1.

[0077] S3, for any network port in the network, uses the feature vector x obtained in S2 and the Fourier spectrum F(ω) of the pulse waveform f(t) to reconstruct the time domain inversion waveform g i (t):

[0078] g i (t) = ∫x i (w)F(ω)e jωt dω

[0079] In the formula, g i (t) is the time domain inversion waveform, F(ω) is the Fourier spectrum of the pulse waveform f(t); i (ω) is a vector of Tn×1 dimension in the feature vector x, j is an imaginary unit, ω is a frequency domain parameter, and t is time.

[0080] S4, establish a fault-free simulation model based on the line parameters, connect matching impedances to each port of the network and inject the time domain inversion waveform g obtained in S3 accordingly i (t), a fixed number of detection points are set on each line, and the time domain response voltage waveform u(x,t) at each detection point is obtained by simulation.

[0081] S5, according to the time domain response voltage waveform obtained in S4, the energy value of each part of the line is calculated, and an energy spectrum is drawn. The line position corresponding to the maximum value point is the fault point fx with the strongest fault characteristic among the multiple faults;

[0082] Among them, the calculation expression of the energy value E(x) at each point of the line is:

[0083]

[0084] Where E(x) is the energy at x, u(x,t) is the time domain response voltage waveform, Z is the cable wave impedance, and t is the time;

[0085] Afterwards, an energy spectrum is drawn according to the calculated energy value E(x), wherein the line position corresponding to the maximum value point is the fault point fx with the strongest fault characteristic among the multiple faults.

[0086] S6, add an arbitrary type of fault at the fault point fx located by S5 in the fault-free simulation model and measure its differential scattering matrix The specific steps include:

[0087] S61, by adding a virtual fault at the fault point fx located by S5 in the fault-free simulation model, selecting the unmatched impedance as the transition impedance, and starting from the definition of the scattering matrix, measuring the fault scattering matrix of the network;

[0088] S62, perform difference processing on the fault scattering matrix obtained in S61 and the frequency domain scattering matrix in the fault-free state obtained in S12, so as to calculate its differential scattering matrix

[0089] S7, the differential scattering matrix obtained from S6 Calculate its unique effective eigenvalue and its corresponding eigenvector, and then calculate the differential scattering matrix coefficient α by the decomposition method of the differential scattering matrix i The differential scattering matrix S corresponding to the real fault i ;

[0090] The specific steps include:

[0091] S71, the differential scattering matrix obtained from S6 Calculate the unique valid eigenvalue v by using the matrix eigenvalue and eigenvector solution methodi (main eigenvalue) and its corresponding eigenvector w i ;

[0092] S72, the differential scattering matrices of different fault types at the same fault point have a multiple relationship, namely:

[0093]

[0094] In the formula, μ i for The corresponding main eigenvalue, T is the transposition operation, α i is the differential scattering matrix coefficient, then S G It can be expressed as:

[0095]

[0096] In the formula, S G is the global differential scattering matrix, N is the number of all faults in the line, then α i The approximate calculation formula is as follows:

[0097]

[0098] Based on this, the differential scattering matrix coefficient α is calculated i The differential scattering matrix S corresponding to the real fault i .

[0099] S8, differential scattering matrix coefficient α calculated based on S7 i The differential scattering matrix S corresponding to the real fault i , the differential scattering matrix S that eliminates the contribution of the i-th fault from the global differential scattering matrix i , to complete the update, the expression is:

[0100]

[0101] In the formula, is the updated global differential scattering matrix, is the global differential scattering matrix before updating.

[0102] S9, repeat S2-S8 until there is no new fault position to be located in the updated global differential scattering matrix, that is, stop locating when the positioning result coincides with the previous result.

[0103] Example:

[0104] This embodiment uses Figure 2The distribution network 13-node line shown in the figure performs multi-fault location analysis. There are four faults in total, located at 1km of AB line, 1.5km of ADE line, 1.4km of ADF line, and 1.8km of ADGI line. The specific steps include:

[0105] S1, measure and calculate the frequency domain scattering matrix S1(ω) of the distribution network cable line in the fault state and the frequency domain scattering matrix S2(ω) in the fault-free state, and then calculate the global differential scattering matrix S G ;

[0106] S2, calculate the differential time reversal operator H(ω) based on the differential scattering matrix obtained in S1, perform eigenvector decomposition on H(ω), and select the eigenvector x with the largest eigenvalue;

[0107] S3, for any network port in the network, uses the eigenvector obtained in S2 and the Fourier spectrum F(ω) of the pulse waveform f(t) to reconstruct the time domain inversion waveform g i (t);

[0108] S4, construct a simulation model of the fault-free distribution network cable line, and convert the time domain inversion waveform g obtained in S3 i (t) are injected into each port of the line respectively, detection points are set in the constructed simulation model, and the time domain response voltage waveform u(x,t) at each detection point of the line is obtained;

[0109] S5, calculate the energy value E(x) at each point of the line according to S4, draw the corresponding energy spectrum, and determine the fault location fx with the strongest fault feature among the multiple faults that have not yet been located;

[0110] S6, add an arbitrary type of fault at the fault point fx located by S5 in the fault-free simulation model and measure its differential scattering matrix

[0111] S7, based on S6 Calculate its unique effective eigenvalue and its corresponding eigenvector, and then calculate α by decomposing the differential scattering matrix i The differential scattering matrix S corresponding to the real fault i ;

[0112] S8, update the global differential scattering matrix;

[0113] S9, repeat the process of S2-S8 until there is no new fault position to be located in the updated global differential scattering matrix, that is, stop locating when the positioning result coincides with the previous result.

[0114] The four fault location energy spectra of this embodiment are respectively as follows: Figure 3 , Figure 4 , Figure 5 as well as Figure 6 The first fault location result is as shown in Figure 3 As shown in the figure, the ADF line achieved the maximum focus at 1.4 km, and the error was 0; the second positioning result is as follows Figure 4 As shown in the figure, accurate focusing is achieved and the maximum value is reached at 1.8 km of the ADGI line, and the error is 0; the third positioning result is as follows Figure 5 As shown in the figure, focusing is achieved at 0.98 km on the AB line with a small error. The positioning error can be reduced by changing the detection interval. The fourth positioning result is shown in Figure 6 As shown, the focusing reaches the maximum value at 1.516 km of the ADE line, with a small error, which can meet the positioning requirements. At this point, all faults have been located. If the global scattering matrix is ​​updated again and positioned, the positioning result will coincide with the above positioning result, that is, there are no other fault positions to be located, and the positioning cycle can be ended accordingly.

[0115] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", 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 invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0116] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for locating multiple faults in a distribution network cable line, characterized in that: The following steps are involved: S1, measure and calculate the frequency domain scattering matrix of the distribution network cable line in the fault state and the fault-free state, and then calculate the global differential scattering matrix; S2, based on the global differential scattering matrix, calculating the differential time reversal operator, and performing eigenvector decomposition on the differential time reversal operator, and selecting the eigenvector x with the largest eigenvalue; S3, for any network port in the network, reconstructing a time domain inversion waveform using the characteristic vector x and the Fourier spectrum of the pulse waveform; S4, establishing a fault-free simulation model according to the proportionality of the line parameters, connecting matching impedances at each port of the network and correspondingly injecting the time domain inversion waveform, setting a number of detection points on each line, and simulating and obtaining the time domain response voltage waveform at each detection point; S5, according to the time domain response voltage waveform, calculate the energy value of each line, and draw an energy spectrum. The line position corresponding to the maximum value point is the fault point fx with the strongest fault characteristics among multiple faults; S6, adding a fault at the fault point fx in the fault-free simulation model and measuring its differential scattering matrix S7, according to the differential scattering matrix Calculate the effective eigenvalues ​​and their corresponding eigenvectors, and then calculate the differential scattering matrix coefficient α by the decomposition method of the differential scattering matrix i The differential scattering matrix S corresponding to the real fault i ; S8, based on the differential scattering matrix coefficient α i The differential scattering matrix S corresponding to the real fault i , the differential scattering matrix S that eliminates the contribution of the i-th fault from the global differential scattering matrix i , to complete the update; S9, repeat S2-S8 until there is no new fault position to be located in the updated global differential scattering matrix, and then stop locating.

2. A method for locating multiple faults in a distribution network cable line according to claim 1, characterized in that: The calculation steps of the global differential scattering matrix include: S11, for an N-port network, multiple groups of 2×2×Tn dimensional scattering matrices are measured by injecting pulses to measure responses, and then the frequency domain scattering matrix of the N×N×Tn dimensional network under fault conditions is reconstructed; S12, geometric modeling fault-free simulation model, by injecting pulses at each port and connecting the remaining ports to matching impedance, the response of each port is measured, and then the frequency domain scattering matrix of the network with N×N×Tn dimensions in the fault-free state is calculated; S13, subtracting the frequency domain scattering matrix under the fault state from the frequency domain scattering matrix under the non-fault state to obtain a global differential scattering matrix.

3. A method for locating multiple faults in a distribution network cable line according to claim 1, characterized in that: The calculation formula of the differential time reversal operator is: H(ω)=S G ·S G * Where H(ω) is the differential time inversion operator, S G is the global differential scattering matrix, and * represents the conjugate transpose operation.

4. A method for locating multiple faults in a distribution network cable line according to claim 1, characterized in that: The calculation formula of the time domain inversion waveform is: g i (t)=∫x i (w)F(ω)e jωt dω In the formula, g i (t) is the time domain inversion waveform, F(ω) is the Fourier spectrum of the pulse waveform f(t), x i (ω) is a vector of Tn×1 dimension in the feature vector x, j is an imaginary unit, ω is a frequency domain parameter, and t is time.

5. A method for locating multiple faults in a distribution network cable line according to claim 1, characterized in that: The energy value calculation formula at each point of the line is: Where E(x) is the energy at x, u(x,t) is the time domain response voltage waveform, Z is the cable wave impedance, and t is time.

6. A method for locating multiple faults in a distribution network cable line according to claim 2, characterized in that: The differential scattering matrix The calculation steps include: S61, by adding a virtual fault at the fault point fx in the fault-free simulation model, selecting the unmatched impedance as the transition impedance, and starting from the definition of the scattering matrix, measuring the fault scattering matrix of the network; S62, perform difference processing on the fault scattering matrix obtained in S61 and the frequency domain scattering matrix in the fault-free state obtained in S12, so as to calculate the differential scattering matrix 7. A method for locating multiple faults in a distribution network cable line according to claim 1, characterized in that: As described above, the differential scattering matrix coefficient α is calculated i The differential scattering matrix S corresponding to the real fault i The steps include: S71, according to the differential scattering matrix Calculate its unique valid eigenvalue v i The corresponding eigenvector w i ; S72, the differential scattering matrices of different fault types at the same fault point have a multiple relationship, namely: In the formula, μ i for The corresponding main eigenvalue, T is the transposition operation, α i is the differential scattering matrix coefficient; Then the global differential scattering matrix S G It can be expressed as: Where N is the number of all faults in the line; Then the differential scattering matrix coefficient α i The approximate calculation formula is as follows: Based on this, the differential scattering matrix coefficient α is calculated i The differential scattering matrix S corresponding to the real fault i .

8. A method for locating multiple faults in a distribution network cable line according to claim 1, characterized in that: The update expression of the global differential scattering matrix is: In the formula, is the updated global differential scattering matrix, is the global differential scattering matrix before updating.

9. A distribution network cable line multi-fault location system, characterized in that: include: Global differential scattering matrix calculation module: measures and calculates the frequency domain scattering matrix of the distribution network cable line in fault state and fault-free state, and then calculates the global differential scattering matrix; Eigenvector solving module: based on the global differential scattering matrix, calculating the differential time reversal operator, and performing eigenvector decomposition on the differential time reversal operator, and selecting the eigenvector x with the largest eigenvalue; Time domain inversion waveform construction module: for any network port in the network, the time domain inversion waveform is reconstructed using the characteristic vector x and the Fourier spectrum of the pulse waveform; Time domain response voltage waveform construction module: establish a fault-free simulation model according to the line parameters in equal proportion, connect matching impedance to each port of the network and inject the time domain inversion waveform accordingly, set several detection points on each line, and simulate and obtain the time domain response voltage waveform at each detection point; Energy spectrum drawing module: Calculate the energy value at each point of the line according to the time domain response voltage waveform, and draw the energy spectrum. The line position corresponding to the maximum value point is the fault point fx with the strongest fault characteristics among multiple faults. Differential scattering matrix measurement module: Add a fault at the fault point fx in the fault-free simulation model and measure its differential scattering matrix Coefficient solution module: According to the differential scattering matrix Calculate the effective eigenvalues ​​and their corresponding eigenvectors, and then calculate the differential scattering matrix coefficient α by the decomposition method of the differential scattering matrix i The differential scattering matrix S corresponding to the real fault i ; Matrix update module: based on the differential scattering matrix coefficient α i The differential scattering matrix S corresponding to the real fault i , the differential scattering matrix S that eliminates the contribution of the i-th fault from the global differential scattering matrix i , to complete the update; And, positioning module: repeatedly use the time domain inversion waveform construction module to the matrix update module until there is no new fault position to be located in the updated global differential scattering matrix, and then stop positioning.

10. A computer storage medium storing a readable program, characterized in that: When the program is running, the positioning method described in any one of claims 1 to 8 is executed.

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