Cable fault online positioning method, device and system

Abstract

The invention provides a cable fault online positioning method, device and system. The method comprises the following steps: acquiring an incident signal and a reflected signal; the incident signal is a signal injected into a to-be-detected cable, and the reflected signal is a signal generated by reflection at a fault point in the to-be-detected cable; the to-be-detected cable is in an online state; fourier decomposition is carried out according to the incident signal and the reflection signal, and a reflection coefficient test spectrum of the cable fault point is obtained; and carrying out online positioning on a cable fault point according to the reflection coefficient test spectrum. According to the invention, online, efficient and accurate fault point positioning of the cable can be realized, and the safety and stability of the cable are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and in particular to a method, device and system for online positioning of cable faults. Background Art

[0002] With the rapid development of urbanization in my country, a large number of power cables are widely used in power transmission and distribution systems. As an important power transmission line in the power transmission and distribution system, the stable operation of power cables is crucial to power transmission. However, in actual applications, due to the influence of manufacturing process and external environment, cables may have problems such as local insulation aging and breakage. If local defects occur in the cable and the defects cannot be located in time, it is very easy to induce electrical breakdown or even regional power outages, posing a serious threat to personal safety and grid stability. Therefore, accurate positioning of cable faults has a decisive impact on ensuring the safe and reliable operation of the power system. The existing cable fault positioning method is to perform offline monitoring during cable maintenance, which is inefficient and takes a long time to test. Summary of the invention

[0003] In order to solve the technical problems existing in the prior art, the present invention provides a cable fault online positioning method, device and system, which can realize efficient and accurate positioning of the fault point of the cable in the online state, thereby improving the safety and stability of the cable.

[0004] The present invention provides a method for online positioning of cable faults, comprising: obtaining an incident signal and a reflected signal; the incident signal is a signal injected into a cable to be detected, and the reflected signal is a signal generated by reflection of a fault point in the cable to be detected; the cable to be detected is in an online state; Fourier decomposition is performed according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of a cable fault point; and online positioning of the cable fault point is performed according to the reflection coefficient test spectrum.

[0005] According to a cable fault online location method provided by the present invention, the objective function of the reflection coefficient test spectrum is: ; in, is the objective function of the reflection coefficient test spectrum, A n is the amplitude of the incident signal, B n is the amplitude of the reflected signal, n is a non-negative integer, is the angular frequency, t For time, is the phase of the incident signal, is the phase of the reflected signal, f nis the independent variable of the reflectance test spectrum.

[0006] According to a cable fault online positioning method provided by the present invention, the cable fault point is positioned online according to the reflection coefficient test spectrum, including: using a P-order Prony algorithm to determine a reflection coefficient fitting spectrum; the reflection coefficient fitting spectrum and the reflection coefficient test spectrum satisfy the square error and minimum principle; according to the period of the reflection coefficient fitting spectrum and the propagation speed of the reflection signal, the cable fault online positioning distance is obtained.

[0007] According to a cable fault online location method provided by the present invention, the square error and minimum principle satisfies the formula: ; The objective function of the reflection coefficient fitting spectrum is: ; ; ; in, is the objective function of the reflection coefficient fitting spectrum, is the objective function of the reflection coefficient test spectrum, is the sum of squared errors, For The minimum value of the N for n The maximum value of n is a non-negative integer, p for m The maximum value of m is a positive integer, a m and z m are all intermediate variables. C m is the amplitude of the reflection coefficient fitted spectrum, is the phase of the reflection coefficient fitting spectrum, is the attenuation factor, T m is the period of the reflection coefficient fitting spectrum, is the sampling interval of the reflection coefficient fitting spectrum, Im is the imaginary part of the complex number, and Re is the real part of the complex number.

[0008] According to a cable fault online positioning method provided by the present invention, the cable fault online positioning distance satisfies the formula: ; ; ; in, X 1 is the online location distance of the cable fault without considering the cable material properties, v 1 is the propagation speed of the reflected signal without considering the cable material properties, is the phase shift constant, R is the distributed resistance of the cable, L is the distributed inductance of the cable, G is the distributed conductance of the cable, C is the distributed capacitance of the cable, is the angular frequency, f 1. f 2 are the independent variables of the reflection coefficient test spectrum f n The minimum and maximum values ​​of .

[0009] According to a cable fault online positioning method provided by the present invention, the cable fault online positioning distance satisfies the formula: ; ; ; in, X 2 is the online location distance of the cable fault considering the cable material properties, v 2 is the propagation speed of the reflected signal taking into account the cable material properties, c 0 is the speed of light 3x10 8 m / s is the propagation speed of electromagnetic waves in vacuum; Relative magnetic permeability, which is the ratio of the magnetic permeability of the insulating medium to the magnetic permeability of the vacuum; Relative dielectric constant, that is, the ratio of the dielectric constant of the insulating medium to the dielectric constant of vacuum, is the phase shift constant, R is the distributed resistance of the cable, L is the distributed inductance of the cable, G is the distributed conductance of the cable, C is the distributed capacitance of the cable, is the angular frequency, f 1. f 2 are the independent variables of the reflection coefficient test spectrum f n The minimum and maximum values ​​of .

[0010] According to a cable fault online location method provided by the present invention, the incident signal is an underdamped oscillation signal generated by an RLC circuit; the underdamped oscillation signal is used for single injection into the cable to be detected.

[0011] According to a cable fault online locating method provided by the present invention, the frequency range of the reflection coefficient test spectrum is 100 kHz to 500 kHz.

[0012] The present invention also provides an online cable fault positioning device, comprising: an acquisition module, used to acquire an incident signal and a reflected signal; the incident signal is a signal injected into a cable to be detected, and the reflected signal is a signal generated by reflection of a fault point in the cable to be detected; the cable to be detected is in an online state; a Fourier transform calculation module, used to perform Fourier decomposition according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; and a positioning module, used to perform online positioning of the cable fault point according to the reflection coefficient test spectrum.

[0013] The present invention also provides a cable fault online positioning system, comprising a signal generating device, a signal injection device, a signal acquisition device, a signal transmission device and the above-mentioned cable fault online positioning device; the signal generating device is used to generate the incident signal; the signal injection device is used to inject the incident signal into the cable to be detected; the signal acquisition device is used to acquire the incident signal and the reflected signal; the signal transmission device is used to transmit the incident signal and the reflected signal to the cable fault online positioning device; the cable fault online positioning device is used to execute the steps of the above-mentioned cable fault online positioning method.

[0014] The present invention provides a method, device and system for online positioning of cable faults, the method comprising: obtaining an incident signal and a reflected signal; the incident signal is a signal injected into a cable to be detected, and the reflected signal is a signal generated by reflection at a fault point in the cable to be detected; the cable to be detected is in an online state; Fourier decomposition is performed according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; and the cable fault point is positioned online according to the reflection coefficient test spectrum. The present invention can realize efficient and accurate positioning of the fault point of the cable in an online state, and improves the safety and stability of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 The present invention is a schematic diagram of a process of an online cable fault location method.

[0017] Figure 2The present invention is a schematic diagram of the principle of a cable fault online positioning method provided by the present invention.

[0018] Figure 3 It is a curve diagram of the incident signal and the reflected signal provided by the present invention.

[0019] Figure 4 It is a curve diagram of the reflection coefficient test spectrum provided by the present invention.

[0020] Figure 5 It is a schematic diagram of the RLC circuit provided by the present invention.

[0021] Figure 6 It is a structural schematic diagram of a cable fault online locating device provided by the present invention.

[0022] Figure 7 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0024] Please refer to Figure 1 , Figure 1 A schematic flow chart of a method for online cable fault location provided by the present invention.

[0025] Please refer to Figure 2 , Figure 2 A schematic diagram of the principle of a cable fault online locating method provided by the present invention.

[0026] The present invention provides a method for online positioning of cable faults, comprising: 101: Acquire an incident signal and a reflected signal; the incident signal is a signal injected into the cable to be detected, and the reflected signal is a signal generated by reflection at a fault point in the cable to be detected; the cable to be detected is in an online state; 102: Perform Fourier decomposition according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; 103: Online location of cable fault points based on reflection coefficient test spectrum.

[0027] In order to solve the problems of low efficiency and long test time of traditional cable offline detection, the present invention provides a cable fault online positioning method. The cable fault online positioning device 5 first obtains the incident signal V 1(t ) and reflected signal V 2( t ). Due to the non-periodicity of the incident and reflected signals, it is necessary to extend the signal period to infinity and then perform Fourier decomposition into a series of trigonometric functions with different amplitudes and phases. , The amplitude and phase parameters of the linear combination are A 0. A n , B 0. B n , , are all constants, n 0,1,2,3,4... N . According to the Fourier decomposition results of the incident signal and the Fourier decomposition results of the reflected signal, the reflection coefficient test spectrum of the cable fault point can be calculated. Finally, the cable fault point can be located online according to the reflection coefficient test spectrum. For example, the fault point location can be calculated by using the period of the reflection coefficient test spectrum and the propagation speed of the signal in the cable, or by using the period of the reflection coefficient fitting spectrum and the propagation speed of the signal in the cable.

[0028] Among them, the incident signal can be a pulse signal generated by the signal generating device 1 composed of an RLC circuit through under-damped oscillation, and the amplitude of the incident signal can be optimized and selected according to the detection distance of the cable. The signal generating device 1 is connected to the signal injection device 2, and the signal generating device 1 injects the incident signal into the cable to be detected through the signal injection device 2 to locate the fault point. The reflected signal is a signal reflected when the incident signal encounters the fault point. Based on the fact that any signal satisfies the Dirichlet condition, the signal can be expressed as a linear combination of a set of sinusoidal functions. The signal acquisition device 3 sends the collected incident signal and reflected signal to the signal transmission device 4. The signal transmission device 4 is used to transmit the incident signal and the reflected signal to the cable fault online positioning device 5.

[0029] The cable to be detected may be a 10 kV power cable, and the present invention does not make any special limitation thereto.

[0030] In summary, the cable fault online location method of the present invention can save the test time of cable fault online location. Through regular online detection, potential problems of the cable can be discovered early, some unnecessary power outage accidents can be reduced, and the safety and stability of the cable can be improved.

[0031] Please refer to Figure 3 , Figure 3 This is a graph of the incident signal and the reflected signal provided by the present invention.

[0032] Please refer to Figure 4 , Figure 4 This is a curve chart of the reflection coefficient test spectrum provided by the present invention.

[0033] As a preferred embodiment, the objective function of the reflection coefficient test spectrum is: ; in, is the objective function of the reflection coefficient test spectrum, A n is the amplitude of the incident signal, B n is the amplitude of the reflected signal, n is a non-negative integer, is the angular frequency, t For time, is the phase of the incident signal, is the phase of the reflected signal, f n is the independent variable of the reflection coefficient test spectrum.

[0034] In this embodiment, by V 1( t ) and reflected signal V 2( t ) is decomposed by Fourier to obtain a series of cosine functions of different frequencies, and then substituted into The reflection coefficient test spectrum of the cable fault point can be obtained by calculation.

[0035] As a preferred embodiment, the cable fault point is located online according to the reflection coefficient test spectrum, including: using the P-order Prony algorithm to determine the reflection coefficient fitting spectrum; the reflection coefficient fitting spectrum and the reflection coefficient test spectrum meet the square error and minimum principle; according to the period of the reflection coefficient fitting spectrum and the propagation speed of the reflected signal, the cable fault online positioning distance is obtained.

[0036] As a preferred embodiment, the square error and minimum principle satisfy the formula: ; The objective function of the reflection coefficient fitting spectrum is: ; ; ; in, is the objective function of the reflection coefficient fitting spectrum, is the objective function of the reflection coefficient test spectrum, is the sum of squared errors, For The minimum value of theN for n The maximum value of n is a non-negative integer, p for m The maximum value of m is a positive integer, a m and z m are all intermediate variables. C m is the amplitude of the reflection coefficient fitting spectrum, is the phase of the reflection coefficient fitting spectrum, is the attenuation factor, T m is the period of the reflection coefficient fitting spectrum, is the sampling interval of the reflection coefficient fitting spectrum, Im is the imaginary part of the complex number, and Re is the real part of the complex number.

[0037] In order to further improve the accuracy of fault point location, in this embodiment, the P-order Prony algorithm can be used to determine the reflection coefficient fitting spectrum and calculate the period of the reflection coefficient fitting spectrum, and then the online location distance of the cable fault can be calculated. Among them, the reflection coefficient fitting spectrum and the reflection coefficient test spectrum meet the minimum square error and minimum principle. In this embodiment, the characteristics of the curve amplitude attenuation (attenuation factor ), so the accuracy of fault point location is higher.

[0038] As a preferred embodiment, the cable fault online location distance satisfies the formula: ; ; ; in, X 1 is the online location distance of cable fault without considering the cable material properties, v 1 is the propagation speed of the reflected signal without considering the cable material properties, is the phase shift constant, R is the distributed resistance of the cable, L is the distributed inductance of the cable, G is the distributed conductance of the cable, C is the distributed capacitance of the cable, is the angular frequency, f 1. f 2 are the independent variables of the reflection coefficient test spectrum f n The minimum and maximum values ​​of .

[0039] In this embodiment, according to the period of the reflection coefficient fitting spectrum, without considering the influence of the cable insulation material properties on the signal propagation speed, the average speed is obtained by integration. v 1. Then, calculate the distance of the cable fault online location according to the distance calculation formula. X 1.

[0040] As a preferred embodiment, the cable fault online location distance satisfies the formula: ; ; ; in, X 2 is the online location distance of cable faults considering the cable material properties, v 2 is the propagation speed of the reflected signal taking into account the cable material properties, c 0 is the speed of light 3x10 8 m / s is the propagation speed of electromagnetic waves in vacuum; Relative magnetic permeability, which is the ratio of the magnetic permeability of the insulating medium to the magnetic permeability of the vacuum; Relative dielectric constant, that is, the ratio of the dielectric constant of the insulating medium to the dielectric constant of vacuum, is the phase shift constant, R is the distributed resistance of the cable, L is the distributed inductance of the cable, G is the distributed conductance of the cable, C is the distributed capacitance of the cable, is the angular frequency, f 1. f 2 are the independent variables of the reflection coefficient test spectrum f n The minimum and maximum values ​​of .

[0041] In order to further improve the accuracy of online cable fault location, in this embodiment, according to the period of the reflection coefficient fitting spectrum, the influence of the cable insulation material properties on the signal propagation speed is considered, and the average speed is obtained by integration, and then the actual material properties of the defective cable are introduced. Relative magnetic permeability, The relative dielectric constant is used to correct the geometric mean of the signal propagation speed, and then the online location distance of the cable fault is obtained. X 2. The online positioning accuracy of cable fault points is higher.

[0042] As a preferred embodiment, the incident signal is an underdamped oscillation signal generated by an RLC circuit; the underdamped oscillation signal is used for single injection into the cable to be detected.

[0043] Please refer to Figure 5 , Figure 5 The schematic diagram of the RLC circuit provided by the present invention.

[0044] In this embodiment, the incident signal is generated by the RLC circuit of the signal generating device 1. Specifically, the capacitor is charged by controlling the switch KF1, and then KF1 is disconnected and KF2 is closed to generate an underdamped oscillation signal as the incident signal. The underdamped oscillation signal can be injected into the cable to be tested once, which can save the test time of the reflection coefficient test spectrum.

[0045] In signal processing, underdamped oscillations can be described as the natural decay of the signal amplitude over time, which can be exponential or polynomial.

[0046] As a preferred embodiment, the frequency range of the reflection coefficient test spectrum is 100 kHz to 500 kHz.

[0047] In this embodiment, the objective function of the reflection coefficient test spectrum is middle f n is the independent variable, unit is Hz, f n The range is that this embodiment extracts the frequency band components in the interval of 100kHz-500kHz in the decomposed signal to calculate the reflection coefficient spectrum of the cable fault point to ensure accurate extraction of the fault characteristics.

[0048] The cable fault online locating device 5 provided by the present invention is described below. The cable fault online locating device 5 described below and the cable fault online locating method described above can be referred to each other.

[0049] Please refer to Figure 6 , Figure 6 A schematic structural diagram of a cable fault online locating device provided by the present invention.

[0050] The present invention also provides an online cable fault positioning device 5, comprising: an acquisition module 601, used to acquire an incident signal and a reflected signal; the incident signal is a signal injected into the cable to be detected, and the reflected signal is a signal generated by reflection at the fault point in the cable to be detected; the cable to be detected is in an online state; a Fourier transform calculation module 602, used to perform Fourier decomposition according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; a positioning module 603, used to perform online positioning of the cable fault point according to the reflection coefficient test spectrum.

[0051] The cable fault online locating system provided by the present invention is described below. The cable fault online locating system described below and the cable fault online locating method described above can be referred to each other.

[0052] The present invention also provides a cable fault online positioning system, comprising a signal generating device 1, a signal injection device 2, a signal acquisition device 3, a signal transmission device 4 and the above-mentioned cable fault online positioning device 5; the signal generating device 1 is used to generate an incident signal; the signal injection device 2 is used to inject the incident signal into the cable to be detected; the signal acquisition device 3 is used to collect the incident signal and the reflected signal; the signal transmission device 4 is used to transmit the incident signal and the reflected signal to the cable fault online positioning device 5; the cable fault online positioning device 5 is used to execute the steps of the above-mentioned cable fault online positioning method.

[0053] Figure 7 An example of a structural diagram of an electronic device is shown in FIG. Figure 7 As shown, the electronic device may include: a processor 710, a communications interface 720, a memory 730 and a communication bus 740, wherein the processor 710, the communications interface 720 and the memory 730 communicate with each other through the communication bus 740. The processor 710 may call the logic instructions in the memory 730 to execute the cable fault online location method, the method comprising: obtaining an incident signal and a reflection signal; the incident signal is a signal injected into the cable to be detected, and the reflection signal is a signal generated by reflection at the fault point in the cable to be detected; the cable to be detected is in an online state; Fourier decomposition is performed according to the incident signal and the reflection signal to obtain a reflection coefficient test spectrum of the cable fault point; and the cable fault point is located online according to the reflection coefficient test spectrum.

[0054] In addition, the logic instructions in the above-mentioned memory 730 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable 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 method 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. Various media that can store program codes.

[0055] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the online cable fault positioning method provided by the above-mentioned methods, and the method includes: obtaining an incident signal and a reflected signal; the incident signal is a signal injected into the cable to be detected, and the reflected signal is a signal generated by reflection at the fault point in the cable to be detected; the cable to be detected is in an online state; Fourier decomposition is performed according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; and the cable fault point is positioned online according to the reflection coefficient test spectrum.

[0056] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the cable fault online positioning method provided by the above-mentioned methods, the method comprising: obtaining an incident signal and a reflected signal; the incident signal is a signal injected into the cable to be detected, and the reflected signal is a signal generated by reflection at the fault point in the cable to be detected; the cable to be detected is in an online state; Fourier decomposition is performed based on the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; and the cable fault point is positioned online based on the reflection coefficient test spectrum.

[0057] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0058] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cable fault online location method, characterized in that: include: Acquire an incident signal and a reflected signal; the incident signal is a signal injected into the cable to be detected, and the reflected signal is a signal generated by reflection at a fault point in the cable to be detected; the cable to be detected is in an online state; Perform Fourier decomposition on the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; The cable fault point is located online according to the reflection coefficient test spectrum.

2. The cable fault online location method according to claim 1, characterized in that: The objective function of the reflection coefficient test spectrum is: ； in, is the objective function of the reflection coefficient test spectrum, A n is the amplitude of the incident signal, B n is the amplitude of the reflected signal, n is a non-negative integer, is the angular frequency, t For time, is the phase of the incident signal, is the phase of the reflected signal, f n is the independent variable of the reflectance test spectrum.

3. The cable fault online location method according to claim 1, characterized in that: The online positioning of the cable fault point according to the reflection coefficient test spectrum includes: The reflection coefficient fitting spectrum is determined by using a P-order Prony algorithm; the reflection coefficient fitting spectrum and the reflection coefficient test spectrum satisfy the square error and minimum principle; The online location distance of the cable fault is obtained according to the period of the reflection coefficient fitting spectrum and the propagation speed of the reflection signal.

4. The cable fault online location method according to claim 3, characterized in that: The square error and minimum principle satisfy the formula: ； The objective function of the reflection coefficient fitting spectrum is: ； ； ； in, is the objective function of the reflection coefficient fitting spectrum, is the objective function of the reflection coefficient test spectrum, is the sum of squared errors, For The minimum value of the N for n The maximum value of n is a non-negative integer, p for m The maximum value of m is a positive integer, a m and z m are all intermediate variables. C m is the amplitude of the reflection coefficient fitted spectrum, is the phase of the reflection coefficient fitting spectrum, is the attenuation factor, T m is the period of the reflection coefficient fitting spectrum, is the sampling interval of the reflection coefficient fitting spectrum, Im is the imaginary part of the complex number, and Re is the real part of the complex number.

5. The cable fault online location method according to claim 4, characterized in that: The cable fault online positioning distance satisfies the formula: ； ； ； in, X 1 is the online location distance of the cable fault without considering the cable material properties, v 1 is the propagation speed of the reflected signal without considering the cable material properties, is the phase shift constant, R is the distributed resistance of the cable, L is the distributed inductance of the cable, G is the distributed conductance of the cable, C is the distributed capacitance of the cable, is the angular frequency, f 1. f 2 are the independent variables of the reflection coefficient test spectrum f n The minimum and maximum values ​​of .

6. The cable fault online location method according to claim 4, characterized in that: The cable fault online positioning distance satisfies the formula: ； ； ； in, X 2 is the online location distance of the cable fault considering the cable material properties, v 2 is the propagation speed of the reflected signal taking into account the cable material properties, c 0 is the speed of light 3x10 8 m / s is the propagation speed of electromagnetic waves in vacuum; Relative magnetic permeability, which is the ratio of the magnetic permeability of the insulating medium to the magnetic permeability of the vacuum; Relative dielectric constant, that is, the ratio of the dielectric constant of the insulating medium to the dielectric constant of vacuum, is the phase shift constant, R is the distributed resistance of the cable, L is the distributed inductance of the cable, G is the distributed conductance of the cable, C is the distributed capacitance of the cable, is the angular frequency, f 1. f 2 are the independent variables of the reflection coefficient test spectrum f n The minimum and maximum values ​​of .

7. The cable fault online location method according to claim 1, characterized in that: The incident signal is an underdamped oscillation signal generated by an RLC circuit; the underdamped oscillation signal is used for single injection into the cable to be detected.

8. The cable fault online location method according to any one of claims 1 to 7, characterized in that: The frequency range of the reflection coefficient test spectrum is 100 kHz to 500 kHz.

9. A cable fault online positioning device, characterized in that: include: An acquisition module is used to acquire an incident signal and a reflected signal; the incident signal is a signal injected into the cable to be detected, and the reflected signal is a signal generated by reflection at a fault point in the cable to be detected; the cable to be detected is in an online state; A Fourier transform calculation module, used for performing Fourier decomposition according to the incident signal and the reflected signal to obtain a reflection coefficient test spectrum of the cable fault point; A positioning module is used to locate the cable fault point online according to the reflection coefficient test spectrum.

10. A cable fault online positioning system, characterized in that: It comprises a signal generating device, a signal injecting device, a signal collecting device, a signal transmitting device and the cable fault online locating device according to claim 9; The signal generating device is used to generate the incident signal; The signal injection device is used to inject the incident signal into the cable to be detected; The signal acquisition device is used to acquire the incident signal and the reflected signal; The signal transmission device is used to transmit the incident signal and the reflected signal to the cable fault online positioning device; The cable fault online locating device is used to execute the steps of the cable fault online locating method according to any one of claims 1 to 8.

Images