A method and device for locating and imaging soft faults in a transmission line

Abstract

The present invention discloses a method and device for soft fault location and imaging of a transmission line. The method includes: obtaining a reflection signal and a transmission signal; calculating a reflection coefficient R t and a transmission coefficient T t , and performing a fast Fourier transform on the two coefficients to obtain R k and T k ; converting R k and T k into the wavenumber domain for calculation to obtain a first-order velocity perturbation distribution V1(2k) in the wavenumber domain; performing an inverse fast Fourier transform on the first-order velocity perturbation distribution V1(2k) in the wavenumber domain to obtain V1(x); solving the distribution of the next-order V j (x) through the relationship between different order numbers from V1(x), V2(x)... V j+1 (x), and obtaining V j+1 (x) through an inverse fast Fourier transform in the wavenumber domain; after multiple calculations, an accurate velocity perturbation distribution is obtained to achieve the location and imaging of soft faults on the transmission line. The present invention realizes more accurate soft fault location, helps the power fault monitoring system to obtain more comprehensive information about the soft faults on the line, and can be widely applied to the field of cable soft fault location.

Description

Technical Field

[0001] The present invention relates to the field of cable soft fault positioning, and in particular to a transmission line soft fault positioning and imaging method and device. Background Art

[0002] With the development of modern science and technology, electric energy has become an indispensable and important energy source in human life. As the main carrier of electric energy transmission, power lines are distributed in every corner of modern systems, providing energy transmission for various complex systems and also transmitting control signals. For modern systems, it is like the blood vessels and nerve networks of the human body, playing an extremely important role.

[0003] However, during the operation of the transmission line, it will be affected by external factors, resulting in soft faults such as line aging, insulation damage, cable breakdown, etc. The continued deterioration of these phenomena will lead to hard faults (ie, short circuit, open circuit) in the original transmission line and even cause serious consequences such as fire. If the location and characteristics of soft faults can be accurately determined, serious economic losses caused by hard faults in the line can be avoided, so monitoring soft faults is more valuable than monitoring hard faults.

[0004] Existing monitoring solutions are mainly based on a variety of sensor devices, such as smoke alarms, infrared alarms, etc., to monitor the lines in real time. However, since power transmission lines are often buried underground or in walls, it is difficult to implement solutions that rely on sensor monitoring. In addition, due to the complex spatial distribution of power in modern systems, such as the length of wires in civil aircraft is close to 400 kilometers, it is difficult to complete line fault detection using handheld infrared equipment.

[0005] In recent years, domestic and foreign scholars have proposed a variety of non-invasive transmission line soft fault detection schemes. Among them, when a soft fault occurs in the cable, the reflected wave of the fault is easily submerged in the reflection of the branch based on the reflected wave measurement scheme, and when multiple soft faults occur at the same time, a "pseudo fault point" will appear. Although the power soft fault location scheme based on electromagnetic time reversal can achieve accurate point fault location, the distance of the soft fault cannot be ignored in actual situations. At the same time, the scheme requires accurate line topology information and global time synchronization, which also makes the scheme difficult to use in soft fault location and imaging. In addition, the existing schemes focus on the accurate location of the fault and cannot realize the calculation of key fault features (such as dielectric constant), which makes the power fault perception not comprehensive enough and fire warning difficult. Therefore, soft fault location and imaging in actual situations have become difficult problems in real-time monitoring of power transmission lines. Summary of the invention

[0006] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the present invention aims to provide a method and device for locating and imaging soft faults in a transmission line.

[0007] The technical solution adopted by the present invention is:

[0008] A method for locating and imaging soft faults in a transmission line comprises the following steps:

[0009] S1. A receiver and a transmitter are set at both ends of the transmission line. The transmitter transmits a detection signal f(x, t). The receiver and the transmitter respectively record the discrete reflection signal R within a preset time length. t (x, t) and the transmission signal T t (x,t);

[0010] S2, according to the reflected signal R t (x, t) and the transmission signal T t (x, t) respectively calculate the reflection coefficient R t and the transmission coefficient T t , and perform fast Fourier transform on the two coefficients to get R k and T k ;

[0011] S3, R k and T k Convert to the wave number domain for calculation and find the first-order velocity disturbance distribution V in the wave number domain 1 (2k);

[0012] S4, for the first-order velocity disturbance distribution V 1 (2k) performs high-frequency filtering to the first-order velocity disturbance distribution V 1 (2k) Perform inverse fast Fourier transform in the wave number domain to obtain V 1 (x);

[0013] S5, V 1 (x), V 2 (x)…V j (x) Solve the next level V through the relationship between different levels j+1 (2k), and V is obtained by inverse fast Fourier transform in the wave number domain j+1 (x), where j represents different orders;

[0014] S6. After multiple calculations in step S5, accurate velocity disturbance distribution is obtained to achieve the location and imaging of soft faults in the transmission line.

[0015] Furthermore, the expression of the fast Fourier transform in step S2 is as follows:

[0016]

[0017]

[0018] Among them, xs represents the coordinates of the emission source, x R and x T They represent the reflected wave receiver position and the transmitted wave receiver position respectively.

[0019] Further, in step S3, R k and T k Convert to the wave number domain to solve the first-order velocity perturbation distribution V 1 The calculation formula for (2k) is:

[0020]

[0021] Where k = ω / v 0 , ω is the angular frequency, v 0 is the phase velocity of electromagnetic wave propagation in the reference transmission line.

[0022] Furthermore, the first-order velocity disturbance distribution V 1 (2k) performs high frequency filtering, including:

[0023] Exponential filtering, Hamming window filtering or low-pass filtering is used to filter the first-order velocity disturbance distribution V 1 (2k) performs high frequency filtering.

[0024] Furthermore, step S4 also includes the following steps:

[0025] When k=0 in step S3, V 1 (2k) There is no solution to the problem, so the approximate solution of taking adjacent wave numbers is used for compensation.

[0026] Furthermore, in step S4, the first-order velocity disturbance distribution V 1 (2k) Perform inverse fast Fourier transform in the wave number domain to obtain V 1 (x), the corresponding inverse Fourier transform calculation formula is:

[0027]

[0028] Where k = ω / v 0 , ω is the angular frequency.

[0029] Furthermore, the expression of the relationship between the different class numbers in step S5 is:

[0030]

[0031] Among them, ∈ is an additionally defined order operator, V j and V j′ denote the j-th and j′-th order velocity disturbance distributions, respectively, x′ denotes the coordinates along the transmission line, U 0is the transfer function after removing the transmitting source signal, New Green's function constructed after Volterra reformulation.

[0032] Furthermore, after multiple calculations in step S5, an accurate velocity disturbance distribution is obtained, including:

[0033] Each iteration calculation requires that V obtained in step S5 of the jth iteration be j (x) and V j (2k) are all brought into step S5 of the j+1th order to obtain the next-order V j+1 (2k), until j = N, the current iteration is completed, through Output the velocity perturbation results of the Nth-order inverse scattering fit.

[0034] Furthermore, the output of the velocity disturbance result of the N-order inverse scattering fitting includes:

[0035] pass The premise is that the magnetic permeability of the soft fault area remains unchanged, and it is converted into the distribution result of the dielectric constant ε(x) along the transmission line. By analyzing the amplitude change of the dielectric constant distribution, the soft fault of the transmission line can be accurately located, the fault area and the dielectric constant imaging of the fault can be achieved.

[0036] Another technical solution adopted by the present invention is:

[0037] A transmission line soft fault location and imaging device, comprising:

[0038] at least one processor;

[0039] at least one memory for storing at least one program;

[0040] When the at least one program is executed by the at least one processor, the at least one processor implements the above method.

[0041] The beneficial effects of the present invention are as follows: the present invention realizes more accurate soft fault positioning, and accurately calculates important characteristics of the current line (such as dielectric constant) by calculating the transmission phase velocity of the electromagnetic signal, which can help the power fault monitoring system obtain more comprehensive information on line soft faults and achieve more accurate fire warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 1 is a schematic diagram of the steps of a method for locating and imaging soft faults of a transmission line in an embodiment of the present invention;

[0044] Figure 2 is an experimental simulation scene diagram in an embodiment of the present invention;

[0045] Figure 3 It is a velocity disturbance result diagram after fitting a transmission line soft fault location and imaging method based on inverse scattering series expansion in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The embodiments of the present invention 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 only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0047] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to 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 invention.

[0048] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0049] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0050] like Figure 1As shown, this embodiment provides a method for locating and imaging soft faults of transmission lines. This method can not only locate and image soft faults of a certain length, but also can realize accurate imaging of multiple soft fault characteristics by using inverse scattering series expansion when multiple soft faults coexist. This method overcomes the premise that the existing scheme requires global time synchronization and accurate topology information, and helps the existing power line monitoring system to obtain more comprehensive line soft fault feature information. The method specifically includes the following steps:

[0051] S101. A receiver and a transmitter are set at both ends of the transmission line. The transmitter transmits a detection signal f(x, t). The receiver and the transmitter respectively record a discrete reflection signal R within a preset time length. t (x, t) and the transmission signal T t (x,t).

[0052] In step S101, the receiver and the transmitter respectively record the signal for a period of time. During the recording process, the receiver and the transmitter do not need to be time synchronized, and the receiver can start recording after receiving the signal. In addition, the cable length does not need to be known during the measurement process, and the reference transmission speed v of the cable 0 The magnetic permeability μ at the port 0 and dielectric constant ε 0 Decide.

[0053] S102, according to the reflected signal R t (x, t) and the transmission signal T t (x, t) respectively calculate the reflection coefficient R t and the transmission coefficient T t , and perform fast Fourier transform on the two coefficients to get R k and T k .

[0054] The fast Fourier transform in step S102 can be expressed as follows:

[0055]

[0056]

[0057] where x s represents the coordinates of the emission source, x R and x T Represent the reflected wave receiver position and the transmitted wave receiver position respectively. It should be noted that since this scheme does not require global time synchronization, and the transmitter generally also plays the role of the reflected wave receiver, the above T t (x T,t) does not need to be synchronized with the detection signal f(x,t). It only needs to keep the duration consistent during calculation (0-padding can be used).

[0058] S103, R k and T k Convert to the wave number domain for calculation and find the first-order velocity disturbance distribution V in the wave number domain 1 (2k).

[0059] In step S103, R k and T k Convert to the wave number domain to solve the first-order velocity perturbation distribution V 1 The calculation formula for (2k) is as follows:

[0060]

[0061] where k = ω / v 0 , ω is the angular frequency, v 0 is the phase velocity of electromagnetic wave propagation in the reference transmission line. 0 The selection of is generally based on the permeability μ and dielectric constant ε obtained after impedance matching at the transmitting end of the transmission line. Perform calculations.

[0062] S104, for the first-order velocity disturbance distribution V 1 (2k) performs high-frequency filtering to the first-order velocity disturbance distribution V 1 (2k) Perform inverse fast Fourier transform in the wave number domain to obtain V 1 (x).

[0063] The first-order velocity disturbance distribution V in step S103 1 (2k) performs high frequency filtering to overcome the Gibbs artifact phenomenon that will occur in the subsequent step S105. At the same time, when k=0 in step S103, V 1 (2k) There is no solution to the problem. The approximate solution of the adjacent wave number is used to compensate for V 1 (2k) Perform inverse fast Fourier transform in the wave number domain to obtain V 1 (x).

[0064] As an optional implementation, the high-frequency filtering in step S104 may adopt existing commonly used exponential filtering, Hamming window filtering or low-pass filtering solutions.

[0065] In addition, in step S104, the first-order velocity disturbance distribution V 1 (2k) The compensation is performed by using the approximate scheme of adjacent wavenumber values. Here, the approximate scheme of adjacent wavenumber values ​​can be replaced by adjacent frequency points (i.e., taking the wavenumber response value H(k) closest to the wavenumber 0). 1) as a substitute for k = 0), frequency difference compensation (i.e., the difference in subsequent wave number responses ΔH = |H(k 2 )-H(k 1 )|accumulated at the wave number response closest to wave number 0 H(k 1 ) as an alternative when k=0) and other solutions.

[0066] In step S104, V 1 (2k) Perform inverse fast Fourier transform in the wave number domain to obtain V 1 (x), its corresponding inverse Fourier transform can be written as the following calculation formula:

[0067]

[0068] S105, V 1 (x), V 2 (x)…V j (x) Solve the next level V through the relationship between different levels j+1 (2k), and V is obtained by inverse fast Fourier transform in the wave number domain j+1 (x), where j represents different orders.

[0069] The relationship between the different class numbers described in step S105 can be expressed as follows:

[0070]

[0071] where ∈ is an additionally defined order operator, V j represents the j-th order velocity disturbance distribution, U 0 The transfer function after removing the emission source signal can be expressed as e ikx express, The new Green's function constructed after Volterra reformulation, the new Green's function from x' to x It can be expressed as:

[0072]

[0073] Where H(x'-x) is the Heaviside function. Through the above relationship between different orders, ∈ of the same power order can be expressed as an equation, as shown below:

[0074] ∈:

[0075] ∈ 2 :

[0076] ∈ 3 :

[0077] …

[0078] From the above formula, we can find that the expansion of higher-order series requires the use of the values ​​of all previous series, so the solution needs to be solved iteratively.

[0079] S106. After multiple calculations in step S105, an accurate velocity disturbance distribution is obtained to achieve the location and imaging of the soft fault of the transmission line.

[0080] In order to obtain accurate transmission line fault location and imaging, multiple iterations of step S105 are required. Each iteration requires the V obtained in the jth iteration step S105 to be converted into j (x) and V j (2k) are all brought into step S105 of the j+1th step to obtain the next-order V j+1 (2k). When j = N, the current iteration is completed, through Output the velocity perturbation results of the Nth-order inverse scattering fit.

[0081] Among them, the velocity perturbation result of the output N-order inverse scattering fitting can be obtained by The premise is that the magnetic permeability of the soft fault area remains unchanged, and it is converted into the distribution result of the dielectric constant ε(x) along the transmission line. By analyzing the amplitude change of the dielectric constant distribution, such as the increase or decrease of the amplitude of the aging part, the soft fault of the transmission line can be accurately located. The fault area and the dielectric constant imaging of the fault can be achieved.

[0082] The above method is explained in detail below in conjunction with specific embodiments.

[0083] See also Figure 1 This example provides a method for locating and imaging soft faults of a transmission line based on inverse scattering series expansion. In this embodiment, the third-order inverse scattering series is used for positioning and imaging. The total length of the transmission line to be tested is 510 meters, of which 180 meters are aged, and the magnetic permeability of the aged part remains unchanged, and the dielectric constant is 1.2 times that of the normal transmission line. Figure 2 This step includes the following steps:

[0084] S201. A receiver and a transmitter are respectively set at the A and B ports at both ends of the transmission line. The transmitter emits a Gaussian modulated pulse with a center frequency of 5 MHz and a voltage amplitude of 1 V. The receiver and the transmitter respectively record the reflected signal R of 10 μs. t (x, t) and the transmission signal T t (x,t).

[0085] S202, through R t and T t Calculate the reflection coefficient R t and the transmission coefficient Tt , and perform fast Fourier transform on the two coefficients to get R k and T k .

[0086] S203, the R obtained in step S202 k and T k By converting to the wave number domain for calculation, the first-order velocity disturbance distribution V in the wave number domain can be obtained. 1 (2k).

[0087] In step S203, R k and T k Convert to the wave number domain to solve the first-order velocity perturbation distribution V 1 The calculation formula for (2k) is as follows:

[0088]

[0089] where k = ω / v 0 , ω is the angular frequency, v 0 is the phase velocity of electromagnetic wave propagation in the reference transmission line. 0 The selection of is generally based on the magnetic permeability μ obtained after impedance matching at the transmitting end of the transmission line. 0 and dielectric constant ε 0 pass Perform calculations.

[0090] S204: the first-order velocity disturbance distribution V in step S203 1 (2k) performs high frequency filtering to overcome the Gibbs artifact phenomenon that will be generated in the subsequent step S205. At the same time, when k=0 in step S203, V 1 (2k) There is no solution to the problem. The approximate solution of the adjacent wave number is used to compensate for V 1 (2k) Perform inverse fast Fourier transform to obtain V 1 (x).

[0091] In this embodiment, high frequency filtering adopts an exponential filtering scheme, which can be expressed as follows:

[0092]

[0093] Here p is set to 4 and α is set to 32.

[0094] In step S204, the first-order velocity disturbance distribution V 1 (2k) The compensation is performed by using the scheme of approximating the adjacent wave number value. The adjacent wave number value of this embodiment can be approximated by using adjacent frequency points, that is, taking the wave number response value H(k) closest to the wave number 0 1 ) as an alternative when k=0.

[0095] In step S204, V 1 (2k) Perform inverse fast Fourier transform in the wave number domain to obtain V 1 (x), its corresponding inverse Fourier transform can be written as the following calculation formula:

[0096]

[0097] S205, V 1 (x), V 2 (x)…V j (x) Solve the next level V through the relationship between different levels j+1 (2k), and V is obtained by inverse fast Fourier transform in the wave number domain j+1 (x).

[0098] The relationship between the different class numbers described in step S205 can be expressed as follows:

[0099]

[0100] where ∈ is an additionally defined order operator, V j represents the j-th order velocity disturbance distribution, U 0 The transfer function after removing the emission source signal can be expressed as e ikx express, The new Green's function constructed after Volterra reformulation, the new Green's function from x' to x It can be expressed as:

[0101]

[0102] Where H(x'-x) is the Heaviside function. Through the above relationship between different order numbers, ∈ of the same power order can be expressed as an equation. Since this embodiment uses the third-order inverse scattering series for fitting, the first three-order relationship is as follows:

[0103] ∈:

[0104] ∈ 2 :

[0105] ∈ 3 :

[0106] From the above formula, we can find that the expansion of higher-order series requires the use of the values ​​of all previous series, so the solution needs to be solved iteratively.

[0107] S206, after multiple calculations in step S205, finally through Get accurate velocity disturbance distribution. The fact that the magnetic permeability μ of the transmission line changes very little makes it possible to locate and image the soft faults of the transmission line.

[0108] In order to obtain accurate transmission line fault location and imaging in step S206, it is necessary to perform multiple iterations of step S205. Each iteration requires the V obtained in the jth iteration step S205 to be j (x) and V j (2k) are all brought into step S205 of the j+1th step to obtain the next-order V j+1 (2k). When j=3, the current iteration is completed, through Output the velocity perturbation results of the third-order inverse scattering fit.

[0109] The velocity perturbation results of the first three-order inverse scattering fitting are as follows: Figure 3 As shown, it can be The premise is that the magnetic permeability of the soft fault area remains unchanged, and it is converted into the distribution result of the dielectric constant ε(x) along the transmission line. By analyzing the amplitude change of the dielectric constant distribution, the soft fault of the transmission line can be accurately located, the fault area and the dielectric constant imaging of the fault can be achieved.

[0110] In summary, the present invention has the following advantages and beneficial effects compared with the prior art:

[0111] (1) The present invention solves the problem of locating and imaging soft faults in power lines of a certain length. Such soft faults are more common in real life. For example, the aging of power line insulation is usually the aging of an entire section. Solving such problems is more practical.

[0112] (2) The present invention does not require time synchronization between the transmitter and the receiver, which solves the positioning position offset problem caused by clock asynchrony between sensors on the edge of the power network. At the same time, since the monitored power line system terminals often appear in basements or meter boxes, communications are severely obstructed, and high-precision clock synchronization is a challenge. The present invention is easier to implement in a power fault monitoring system.

[0113] (3) The present invention does not need to know the line topology of the system in advance during implementation. In actual power systems, power transmission lines are often buried inside walls, which makes it difficult to obtain important topological information such as length in advance. The present invention does not need to obtain information such as topological length in advance. It can be calculated by using relevant information at the access end, which greatly reduces the difficulty of deploying the power fault monitoring system.

[0114] (4) The present invention not only realizes more accurate soft fault location, but also can accurately calculate important characteristics of the current line (such as dielectric constant) by calculating the transmission phase velocity of the electromagnetic signal, which can help the power fault monitoring system obtain more comprehensive information on line soft faults and achieve more accurate fire warning.

[0115] This embodiment also provides a transmission line soft fault location and imaging device, including:

[0116] at least one processor;

[0117] at least one memory for storing at least one program;

[0118] When the at least one program is executed by the at least one processor, the at least one processor implements Figure 1 The method shown.

[0119] A transmission line soft fault location and imaging device of this embodiment can execute a transmission line soft fault location and imaging method provided by the method embodiment of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0120] The present application also discloses a computer program product or a computer program, which includes a computer instruction stored in a computer-readable storage medium. A processor of a computer device can read the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes Figure 1 The method shown.

[0121] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.

[0122] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise specified, one or more of the functions and / or features described may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in separate physical devices or software modules. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the present invention. More specifically, in view of the properties, functions, and internal relationships of the various functional modules in the device disclosed herein, the actual implementation of the module will be understood within the conventional skills of the engineer. Therefore, those skilled in the art can implement the present invention set forth in the claims without excessive experimentation using ordinary techniques. It is also understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.

[0123] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0124] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0125] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0126] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0127] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / 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 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 may be combined in any one or more embodiments or examples in a suitable manner.

[0128] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0129] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for locating and imaging soft faults in a transmission line, characterized in that: The following steps are involved: S1. A receiver and a transmitter are set at both ends of the transmission line. The transmitter transmits a detection signal f(x, t). The receiver and the transmitter respectively record the discrete reflection signal R within a preset time length. t (x, t) and the transmission signal T t (x,t); S2, according to the reflected signal R t (x, t) and the transmission signal T t (x, t) respectively calculate the reflection coefficient R t and the transmission coefficient T t , and perform fast Fourier transform on the two coefficients to get R k and T k , the expression is: Among them, x s represents the coordinates of the emission source, x R and x T denote the reflected wave receiver position and the transmitted wave receiver position respectively; S3, R k and T k Convert to the wave number domain for calculation and find the first-order velocity disturbance distribution V1(2k) in the wave number domain. The calculation formula is: Where, k = ω / v0, ω is the angular frequency, v0 is the phase velocity of electromagnetic wave propagation in the reference transmission line; S4, performing high-frequency filtering on the first-order velocity disturbance distribution V1(2k), and performing inverse fast Fourier transform in the wave number domain on the first-order velocity disturbance distribution V1(2k) to obtain V1(x); S5, V1(x), V2(x)…V j (x) Solve the next level V through the relationship between different levels j+1 (2k), and V is obtained by inverse fast Fourier transform in the wave number domain j+1 (x), where j represents different orders; the expression of the relationship between the different order numbers is: Among them, ∈ is an additionally defined order operator, V j and V j′ denote the j-th and j′-th order velocity disturbance distributions respectively, x′ denotes the coordinates along the transmission line; U0 is the transfer function after removing the emission source signal, and e ikx express; The new Green's function constructed after Volterra reformulation, the new Green's function from x' to x It is expressed as: Where H(x'-x) is the Heaviside function; S6. After multiple iterations of step S5, Get accurate velocity disturbance distribution, combined with On the premise that the magnetic permeability of the soft fault area remains unchanged, the distribution of the dielectric constant ε(x) along the transmission line is obtained to achieve the positioning and imaging of the soft fault of the transmission line; where μ0 is the magnetic permeability at the port.

2. A transmission line soft fault location and imaging method according to claim 1, characterized in that: The high-frequency filtering of the first-order velocity disturbance distribution V1(2k) in step S4 includes: Exponential filtering, Hamming window filtering or low-pass filtering is used to perform high-frequency filtering on the first-order velocity disturbance distribution V1(2k).

3. A transmission line soft fault location and imaging method according to claim 1, characterized in that: Step S4 also includes the following steps: In order to solve the problem that V1(2k) has no solution when k=0 in step S3, adjacent frequency point replacement or frequency point difference compensation is adopted to compensate.

4. A transmission line soft fault location and imaging method according to claim 1, characterized in that: In step S4, the first-order velocity disturbance distribution V1(2k) is subjected to a wave number domain fast Fourier inverse transform to obtain V1(x). The corresponding calculation formula of the inverse Fourier transform is: Wherein, k = ω / v0, ω is the angular frequency.

5. A transmission line soft fault location and imaging method according to claim 4, characterized in that: After multiple iterations of step S5, Obtain accurate velocity disturbance distribution, including: Each iteration calculation requires that V obtained in step S5 of the jth iteration be j (x) and V j (2k) are all brought into step S5 of the j+1th order to obtain the next-order V j+1 (2k), until j = N, the current iteration is completed, through Output the velocity perturbation result of N-order inverse scattering fitting.

6. A transmission line soft fault location and imaging method according to claim 5, characterized in that: The output of the velocity disturbance result of the N-order inverse scattering fitting includes: pass The premise is that the magnetic permeability of the soft fault area remains unchanged, and it is converted into the distribution result of the dielectric constant ε(x) along the transmission line. By analyzing the amplitude change of the dielectric constant distribution, the soft fault of the transmission line can be accurately located, the fault area and the dielectric constant imaging of the fault can be achieved.

7. A transmission line soft fault location and imaging device, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method according to any one of claims 1 to 6.

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