CN117092453B

CN117092453B - Fault positioning method, device and equipment for three-core cable and storage medium

Info

Publication number: CN117092453B
Application number: CN202311352631.5A
Authority: CN
Inventors: 余俊贤; 王瑛; 戴栋; 黄伟校
Original assignee: Shanghai Haineng Xianyuan Technology Co ltd; South China University of Technology SCUT
Current assignee: Shanghai Haineng Xianyuan Technology Co ltd; South China University of Technology SCUT
Priority date: 2023-10-19
Filing date: 2023-10-19
Publication date: 2023-12-19
Anticipated expiration: 2043-10-19
Also published as: CN117092453A

Abstract

The invention discloses a fault locating method, device and equipment for a three-core cable and a storage medium. The method comprises the following steps: establishing a wave equation of the fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and acquiring a first general solution of the wave equation; determining a second pass solution of the wave equation according to the first pass solution and the reflection coefficient matrix of the fault-free three-core cable at the end impedance mismatch point; acquiring a head-end fault reflection coefficient function of each conductor in the three-core cable to be detected; determining a head-end fault-free reflection coefficient function of each conductor according to the second pass solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function; processing each fault information function to obtain fault positioning waveforms of all conductors in the three-core cable to be detected; and determining the fault position of the three-core cable to be detected according to the fault positioning waveform, so that the fault positioning of the three-core cable is realized.

Description

Fault positioning method, device and equipment for three-core cable and storage medium

Technical Field

The present invention relates to the field of fault locating technologies, and in particular, to a fault locating method, device, equipment and storage medium for a three-core cable.

Background

Because the overhead line with complex offshore topography is difficult to lay, in order to ensure safe and stable transmission of electric energy, submarine cables are generally used for power transmission. The commonly used submarine cable comprises a three-phase single-core cable and a three-phase three-core cable, and compared with the three-phase single-core high-voltage cable, the three-phase three-core high-voltage cable has the advantages of smaller electric energy loss, larger transmission capacity, smaller occupied area, lower transportation and installation cost and wide application.

After the three-core submarine cable is affected by a plurality of adverse factors and metal sheath circulation, the electrical performance can be gradually deteriorated, and defects such as damage, aging and the like can be changed into faults slowly, so that the service life of the three-core cable is greatly shortened. The existing fault positioning method for the cable is only limited to a wire core conductor, but the cable does not only have one wire core conductor, and the high-voltage three-core submarine cable comprises a plurality of conductors, such as wire cores and metal sleeves of three coaxial cables in a pipeline, armor in the pipeline and the like. There is a complex electromagnetic coupling relationship between these conductors, and a infinitesimal circuit model built based only on the core conductors cannot correctly locate the fault of the cable.

Disclosure of Invention

The invention provides a fault positioning method, device and equipment for a three-core cable and a storage medium, which are used for solving the problem that a complex electromagnetic coupling relation exists among a plurality of conductors in the three-core cable, and the fault position of the three-core cable cannot be accurately determined.

According to an aspect of the present invention, there is provided a fault locating method for a three-core cable, including:

establishing a wave equation of a fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and acquiring a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable;

determining a second general solution of the wave equation under the condition of terminal impedance mismatch according to the first general solution and a reflection coefficient matrix of the fault-free three-core cable at the terminal impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable;

sending sweep frequency signals with different frequencies to each conductor in the three-core cable to be detected, and obtaining a head end fault reflection coefficient function of each conductor in the three-core cable to be detected;

determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second general solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function;

Processing each fault information function to obtain fault locating waveforms of all conductors in the three-core cable to be detected; and determining the fault position of the three-core cable to be detected according to the fault positioning waveform.

According to another aspect of the present invention, there is provided a fault locating device for a three-core cable, comprising:

the first general solution determining module is used for establishing a wave equation of the fault-free three-core cable based on a multi-conductor electromagnetic coupling theory and acquiring a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable;

the second general solution determining module is used for determining a second general solution of the wave equation under the condition of terminal impedance mismatch according to the first general solution and a reflection coefficient matrix of the fault-free three-core cable at the terminal impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable;

the frequency sweep module is used for sending frequency sweep signals with different frequencies to each conductor in the three-core cable to be detected and obtaining a head end fault reflection coefficient function of each conductor in the three-core cable to be detected;

The information function determining module is used for determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second general solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function;

the fault locating module is used for processing each fault information function to obtain fault locating waveforms of all conductors in the three-core cable to be detected; and determining the fault position of the three-core cable to be detected according to the fault positioning waveform.

According to another aspect of the present invention, there is provided an electronic apparatus including:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

the memory stores a computer program executable by the at least one processor to enable the at least one processor to perform the method of fault localization of a three-core cable according to any of the embodiments of the present invention.

According to another aspect of the present invention, there is provided a computer readable storage medium storing computer instructions for causing a processor to implement the fault locating method of the three-core cable according to any one of the embodiments of the present invention when executed.

According to the technical scheme, a wave equation of the fault-free three-core cable is established based on a multi-conductor electromagnetic coupling theory, and a first general solution of the wave equation is obtained; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable; determining a second general solution of the wave equation under the condition of terminal impedance mismatch according to the first general solution and the reflection coefficient matrix of the fault-free three-core cable at the terminal impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable; sending sweep frequency signals with different frequencies to each conductor in the three-core cable to be detected, and obtaining a head end fault reflection coefficient function of each conductor in the three-core cable to be detected; determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second pass solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function; processing each fault information function to obtain fault positioning waveforms of all conductors in the three-core cable to be detected; the fault location waveform is determined according to the fault location waveform, and the fault location waveform is determined by adopting a frequency domain reflection technology and a multi-conductor electromagnetic coupling theory, so that the fault location of the three-core cable is accurately located, and the problem that the fault location of the three-core cable cannot be accurately located due to the complex electromagnetic coupling relation among a plurality of conductors in the three-core cable is solved.

It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a flowchart of a fault locating method for a three-core cable according to a first embodiment of the present invention;

FIG. 2 is a schematic view of the layered structure of a three-core cable;

FIG. 3 is a schematic illustration of the manner in which a three-core cable is grounded;

fig. 4 is a flowchart of a fault locating method of a three-core cable according to a second embodiment of the present invention;

FIG. 5 is a schematic diagram of a trace impedance circuit model of a fault-free three-core cable;

FIG. 6 is a schematic diagram of a infinitesimal admittance circuit model of a non-faulty three-core cable;

fig. 7 is a schematic structural diagram of a fault locating device for a three-core cable according to a third embodiment of the present invention;

Fig. 8 is a schematic structural diagram of an electronic device implementing a fault locating method of a three-core cable according to an embodiment of the present invention.

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The frequency domain reflection technology (Frequency Domain Reflectometer, FDR) is an effective method for realizing fault location according to the reflection coefficient of the head end of the cable, but the traditional method for fault location of the cable FDR generally builds a calculation model aiming at the coaxial cable, and the three-core cable comprises a plurality of conductors, and a complex electromagnetic coupling relation exists among the plurality of conductors. The single conductor calculation model using coaxial cable cannot correctly reflect the positioning result of the three-core cable under the FDR method. Meanwhile, the same fault can cause different conductor positioning waveforms to change to different degrees, and the existing fault positioning method only measures the positioning waveforms of the wire core conductors, so that the fault far away from the wire core conductors is difficult to detect, and the fault position of the three-core cable is difficult to position. Aiming at the problems, the three-core cable FDR fault positioning method based on the multi-conductor electromagnetic coupling theory can more accurately give out the positioning waveforms of the plurality of conductors of the three-core cable under the FDR method, and determine the position of the defect or fault of the cable and the structure of the cable according to the positioning waveforms.

Example 1

Fig. 1 is a flowchart of a fault locating method for a three-core cable according to an embodiment of the present invention, where the fault locating method is applicable to a case of fault locating for a three-core cable with multiple conductors, and the method may be performed by a fault locating device for a three-core cable, where the fault locating device for a three-core cable may be implemented in a form of hardware and/or software, and the fault locating device for a three-core cable may be configured in an electronic device. As shown in fig. 1, the method includes:

S110, establishing a wave equation of a fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and acquiring a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable.

The ABC three-phase coaxial cable in the three-core cable is in close contact with each other in the pipeline, so that except for the electromagnetic coupling relationship between the wire cores in the same phase and the metal sheath, the electromagnetic coupling relationship between the metal sheath and the metal sheath in different phases is also present. These conductors together form a multi-conductor system of a three-core cable, with complex electromagnetic coupling relationships between them. Illustratively, fig. 2 is a schematic diagram of the layered structure of a three-core cable. As shown in fig. 2, the three-core cable sequentially comprises, from the outer layer to the inner layer: an outer sheath layer 12, armors 11, an inner cushion layer 10, a wrapping belt 9, a filling 8 and an ABC three-phase coaxial cable; the coaxial cable of each phase comprises from the outer layer to the inner layer in sequence: the cable comprises a nonmetal sheath 7, a metal sheath 6, a semiconductive water-resistant belt 5, an outer semiconductive shielding layer 4, an insulating layer 3, an inner semiconductive shielding layer 2 and a cable core 1. Fig. 3 is a schematic diagram of a grounding mode of the three-core cable, as shown in fig. 3, a head end of the three-core cable is opened, a tail end wire core is normally connected with a load, and a metal sheath and an armor are normally grounded. The three-core cable generally comprises 7 conductors, namely a core 1 and a metal sheath 6 of the three coaxial cables and an outermost armor 11.

The wave equation of the three-core cable without faults is an equation which is established for a multi-conductor micro-element circuit model (such as the relation among the impedance, admittance, voltage and current of each conductor) of the three-core cable without faults and can represent the fluctuation condition of the voltage and the current of each conductor in the three-core cable without faults.

In the embodiment, the multi-conductor electromagnetic coupling theory is applied to theoretical analysis of the reflection coefficient of the head end of the cable, and the wave equation of the three-core cable in the fault-free state is constructed according to the loop formed between adjacent conductors of the cable and the electromagnetic coupling relation. And further solving a first general solution of the wave equation of the fault-free three-core cable according to the unit impedance matrix and the unit admittance matrix. The first general solution includes: voltage modulus and current modulus of each conductor in the fault-free three-core cable at any place.

S120, determining a second general solution of the wave equation under the condition of terminal impedance mismatch according to the first general solution and the reflection coefficient matrix of the fault-free three-core cable at the terminal impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable.

Wherein, the three-core cable can cause travelling wave refraction and reflection under the condition of impedance mismatch, thereby generating corresponding reflection coefficient. Therefore, a second pass solution of the wave equation in the case of end impedance mismatch needs to be further determined according to the reflection coefficient matrix generated by the traveling wave refraction-reflection principle.

In the embodiment, the reflection coefficient matrix of the fault-free three-core cable at the end impedance mismatch point can be calculated according to the travelling wave refraction and reflection principle; the first general solution of the wave equation is rewritten according to the reflection coefficient matrix, and the second general solution of the wave equation in consideration of the terminal impedance mismatch can be obtained.

S130, sending sweep frequency signals with different frequencies to each conductor in the three-core cable to be detected, and obtaining a head end fault reflection coefficient function of each conductor in the three-core cable to be detected.

The three-core cable to be detected is a cable needing fault positioning. The reflection coefficient of the head end without faults is the reflection coefficient corresponding to the travelling wave refraction and reflection generated by the head end of the three-core cable without faults under the condition that the impedance of the tail end is not matched. In the embodiment, a sweep signal with preset frequency is sent to one conductor in the three-core cable without faults through a sweep generator each time, and the head end fault reflection coefficient of the conductor in the three-core cable without faults is measured; and determining a head-end fault reflection coefficient function of the conductor according to the head-end fault reflection coefficients obtained by the sweep signals with different frequencies.

And S140, determining a head-end fault-free reflection coefficient function of each conductor in the three-core cable to be detected according to the second pass solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function.

The first-end fault reflection coefficient refers to a reflection coefficient corresponding to traveling wave refraction and reflection generated by the first end of the three-core cable to be detected under the condition that the terminal impedance is not matched. The fault information function can reflect the waveform difference presented on the line refraction and reflection of the three-core cable to be detected and the three-core cable without fault under the condition that the terminal impedance is not matched.

In this embodiment, for each conductor in the three-core cable to be detected, a head-end non-fault reflection coefficient function of the conductor is determined according to the second pass solution and the sweep signal, and a fault information function is determined according to the head-end non-fault reflection coefficient function and the head-end fault reflection coefficient.

S150, processing each fault information function to obtain fault positioning waveforms of all conductors in the three-core cable to be detected; and determining the fault position of the three-core cable to be detected according to the fault positioning waveform.

Wherein, the fault location of the three-core cable to be detected may include: the fault of the three-core cable in the cross section (which may include, for example, a conductor fault in the three-core cable or a structural layer fault between conductors) or the fault position of the three-core cable in the length direction is located.

In the embodiment, the fault locating waveforms of the conductors in the three-core cable to be detected can be obtained by carrying out denoising, time domain locating and other treatments on the fault information function; and analyzing fault locating waveforms of the conductors according to a preset fault locating strategy, and determining the fault position of the three-core cable to be detected.

In an alternative embodiment, the method for fault location of the three-core cable to be detected in the length direction may be: and determining according to fault locating waveforms of any one conductor in the three-core cable to be detected. If abnormal peaks appear in the fault locating waveform of the conductor, determining the position of the peak as the fault position of the three-core cable to be detected in the length direction.

In another alternative implementation. The fault positioning method of the three-core cable to be detected on the cross section can be as follows: acquiring the number of fault conductors; the fault conductor may be a conductor that exhibits an abnormal spike in the corresponding fault localization waveform; and positioning the barrier layer of the three-core cable to be detected according to the number of the fault conductors and the position relation of each fault conductor.

According to the technical scheme, a wave equation of the fault-free three-core cable is established based on a multi-conductor electromagnetic coupling theory, and a first general solution of the wave equation is obtained; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable; determining a second general solution of the wave equation under the condition of terminal impedance mismatch according to the first general solution and the reflection coefficient matrix of the fault-free three-core cable at the terminal impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable; sending sweep frequency signals with different frequencies to each conductor in the three-core cable to be detected, and obtaining a head end fault reflection coefficient function of each conductor in the three-core cable to be detected; determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second pass solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function; processing each fault information function to obtain fault positioning waveforms of all conductors in the three-core cable to be detected; and determining the fault position of the three-core cable to be detected according to the fault positioning waveform. The fault location waveform is determined by adopting a frequency domain reflection technology and a multi-conductor electromagnetic coupling theory, so that the fault position of the three-core cable is accurately located, and the problem that the fault position of the three-core cable cannot be accurately located due to the complex electromagnetic coupling relation among a plurality of conductors in the three-core cable is solved.

Example two

Fig. 4 is a flowchart of a fault locating method for a three-core cable according to a second embodiment of the present invention, where the determining manner of the fault information function of each conductor in the foregoing embodiment is further defined. As shown in fig. 4, the method includes:

s210, establishing a wave equation of a fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and acquiring a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable.

In an alternative embodiment of the present embodiment, establishing a wave equation of a fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and obtaining a first general solution of the wave equation includes:

s211, establishing a unit impedance matrix of the three-core cable without faults, a first differential equation between the current and the voltage of each conductor and a second differential equation between the unit admittance matrix of the three-core cable without faults and the current and the voltage of each conductor according to a micro-element circuit model of the three-core cable without faults;

s212, determining a wave equation of the fault-free three-core cable according to the first differential equation and the second differential equation based on a multi-conductor electromagnetic coupling theory;

S213, calculating a first general solution of the wave equation by using a phase-mode transformation calculation method.

FIG. 5 is a schematic diagram of a trace impedance circuit model of a fault-free three-core cable; fig. 6 is a schematic diagram of a infinitesimal admittance circuit model of a non-faulty three-core cable. In the present embodimentIn the step S211, the specific steps may be: (1) Carrying out infinitesimal division on the fault-free three-core cable, and marking the length of each section as infinite smallThe method comprises the steps of carrying out a first treatment on the surface of the (2) Establishing a first differential equation between the unity impedance matrix of the three-core cable and the current and voltage of each conductor based on a model of a micro-element impedance circuit as shown in FIG. 5, e.g

Equation 1:；

equation 2:

equation 3:；

equation 4:；

equation 5:

equation 6:；/>；

equation 7:。

wherein,voltage of three-phase core of three-core cable without fault, c represents core, < ->Three-core cable indicating no faultA, B and C phases of (b); />Representing the voltage of a three-phase metal sheath of a fault-free three-core cable, and s represents the metal sheath; />The voltage of armor of the outermost layer of the three-core cable; />Representing the current of the three-phase core of the fault-free three-core cable; />Representing the current of the three-phase metal sheath of the three-core cable without faults; />Representing the current of the armor of the outermost layer of the three-core cable without failure. Unit impedance matrix- >Is a symmetrical matrix; />Representing the self-impedance of the three-phase core and the metal sheath of a fault-free three-core cable, +.>；Representing the self-impedance of the armor of the barrier three-core cable; />Representing the mutual impedance between the in-phase core and the metal sheath of a fault-free three-core cable, +.>，/>And->；/>Representing the mutual impedance between the armor of the three-core cable without faults and the three-phase wire core and the three-phase metal sheath.

、/>、/>、/>The intermediate variable is defined for describing the unit impedance matrix of the three-core cable conveniently, and specific calculation formulas are shown in formulas 2 to 7. Wherein (1)>Representing the unit impedance of the inner surface of a conductor of a three-phase wire core and a metal sheath of the three-core cable; />Representing the unit impedance of the outer surface of the three-phase wire core and the metal sheath of the three-core cable; />Representing the internal and external surface transimpedance of a three-phase metal sheath of a three-core cable; />、/>、/>The unit impedance of the inner surface and the unit transimpedance of the outer armor of the three-core cable are respectively represented; />The unit insulation impedance formed by insulation among a three-phase wire core, a metal sheath and armor in the three-core cable is represented; />The unit insulation impedance formed by insulation between the armor of the outermost layer of the three-core cable and the ground is represented;indicate->Phase metal sheath and->Unit impedance between phase metal jackets. / >Is the ground unit impedance.

(3) Establishing a second differential equation between the unit admittance matrix of the fault-free three-core cable and the current and voltage of each conductor according to the infinitesimal admittance circuit model as shown in FIG. 6, e.g

Equation 8:；

equation 9:；

equation 10:；

equation 11:；

equation 12:

equation 13:；

equation 14:；

wherein the unit admittance matrix Y is referred to as a matrix.Representing the self admittance of the ABC three-phase wire core of the fault-free three-core cable and the metal sheath; />Is the self-admittance of the armor of a fault-free three-core cable. />Indicating the admittance between the metallic sheaths of the different phases of the three-core cable without faults. />Representing the transadmittance between the armor of the fault-free three-core cable and the ABC three-phase metal sheath.

、/>、/>、/>The intermediate variables are defined for convenience in describing the unit admittance matrix of the three-core cable, and specific calculation formulas are shown in formulas 9 to 14. Wherein (1)>Representing admittance between a wire core and a metal sheath in a three-phase cable of a three-core cable; />Representation threeAdmittance between the metal sheath and the armor in the three phases of the core cable; />Representing admittance between the three-core cable armor and ground; />Indicating the admittance between adjacent phase metallic jackets in a three-core cable.

The specific steps of S212 may be: the conductor voltage variable matrix in the first differential equation and the second differential equation is marked as U, the conductor current matrix is marked as I, the unit impedance matrix is marked as Z, and the unit admittance matrix is marked as Y; the differential equation for a fault-free three-core cable that takes into account the electromagnetic coupling between multiple conductors can be abbreviated as follows:

Equation 15:

equation 16:

then, according to formulas 1 to 2 and formulas 15 to 16, the wave equation of the trouble-free three-core cable can be changed to:

equation 17:

equation 18:

the specific steps of S213 may be: the phase-mode transformation needs to be represented by the following relation:

equation 19:

equation 20:；/>。

wherein,representing a conductor voltage phasor transformation matrix; />Representing a conductor current phasor transformation matrix; />Representing diagonal matrix +.>Representing the conductor voltage modulus; />Representing the conductor current modulus.

From equations 17 to 20, the wave equation of the fault-free three-core cable after the phase-mode transformation can be obtained as follows:

equation 21:

equation 22:

solving a wave equation of the fault-free three-core cable after phase mode transformation to obtain a first general solution as follows:

equation 23:

equation 24:

wherein,representing the modulus transmission coefficient of the cable, < >>Representing modulus characteristic impedance, +.>Andrepresenting the forward voltage wave and the reverse voltage wave of the head end of the three-core cable without faults respectively, the values of which are given by boundary conditions.

S220, determining a second general solution of the wave equation under the condition of terminal impedance mismatch according to the first general solution and the reflection coefficient matrix of the fault-free three-core cable at the terminal impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable.

In an alternative embodiment of the present invention, determining the second solution of the wave equation in the case of the end impedance mismatch according to the first solution and the reflection coefficient matrix of the non-faulty three-core cable at the end impedance mismatch point includes:

s221, establishing a circuit model of the fault-free three-core cable under the condition that the tail ends of the fault-free three-core cable are not matched with impedance;

s222, determining a terminal reflection coefficient matrix and a head-end reflection coefficient matrix of the fault-free three-core cable according to the circuit model based on a travelling wave refraction and reflection principle;

s223, substituting the tail end reflection coefficient matrix and the head end reflection coefficient matrix into the first complete solution to obtain a second complete solution of the wave equation under the condition that the tail end impedance is not matched.

In this embodiment, the specific steps of S221 may be: establishing a circuit model of a section of uniform fault-free three-core cable and unmatched impedance of the tail end, setting the cable length as l, and setting the impedance of the tail end asAnd satisfies a first general solution of the wave equation of the three-core cable. Thus, according to the principle of travelling wave refraction and reflection, a multi-conductor voltage at the end of the cable at end x=l can be obtained>And current->Such as:

equation 25: ；

Equation 26:

wherein, and->Respectively representing forward wave voltage and backward wave voltage of the tail end of the fault-free three-core cable.

The specific steps of S222 may be:

as is known from ohm's law, the voltage at the end of a three-core cable without faultAnd current->The method meets the following conditions:

equation 27:the method comprises the steps of carrying out a first treatment on the surface of the Wherein (1)>An impedance matrix representing the load of the end-connected, non-faulty three-core cable.

Voltage at the endForward wave voltage +.>And counter-wave voltage>The travelling wave refraction and reflection principle is satisfied, and the specific expression is as follows:

28：the method comprises the steps of carrying out a first treatment on the surface of the Wherein F represents the end reflection coefficient matrix of the three-core cable without faults.

According to formulas 25 to 28, the end reflection coefficient matrix of the fault-free three-core cable is obtained as follows:

equation 29:

at head-end x=0, the head-end voltage of the fault-free three-core cableAnd head-end current->The method meets the following conditions:

equation 30:

equation 31:

head end voltageForward wave voltage +.>And counter-wave voltage>The inter-satisfied traveling wave refraction-reflection principle can be expressed as:

equation 32:wherein K is a head-end reflection coefficient matrix representing the three-core cable without faults.

From equations 28, 30 and 32, the head-end reflection coefficient matrix K can be obtained as:

equation 33:

equation 30 may be further rewritten as follows according to equation 32:

Equation 34:wherein E is an n-order identity matrix, and n corresponds to the number of conductors in the three-core cable without faults.

The specific steps of S223 may be: determining a second voltage modulus and a second current modulus of the wave equation under the condition of mismatching of the terminal impedance according to a first general solution of the wave equation of the fault-free three-core cable, such as:

equation 35:

equation 36:

s230, sending sweep frequency signals with different frequencies to each conductor in the three-core cable to be detected, and obtaining a head end fault reflection coefficient function of each conductor in the three-core cable to be detected.

In this embodiment, sweep signals with different frequencies are sent to each conductor in the three-core cable to be detected through the sweep generator, and a head-end fault reflection coefficient function is determined according to head-end fault reflection coefficients formed by the obtained sweep signals with different frequencies in each conductor in the three-core cable to be detected。

S240, calculating reflection signals generated by each sweep frequency signal on each conductor in the fault-free three-core cable.

In this embodiment, the swept signal from the swept signal source (e.g., a scanner) is recorded as e, and the swept signal source has an internal impedance. Because the sweep frequency signal source respectively sends sweep frequency signals with different frequencies to each conductor, and only one conductor in the fault-free three-core cable is swept at a time, the signal and the internal impedance exist only on the conductor irradiated by the sweep frequency signal, and the other parameters are all 0. For example, the amplitude of the signal sent by the sweep frequency signal source is 10V, the initial frequency is 1MHz, the cut-off frequency is 100MHz, and the total sampling point is 10001.

In the present embodiment, the head-end current of the trouble-free three-core cable is further determined according to the formulas 31 and 32And forward wave voltage->The relation between them can be expressed as:

equation 37:；

by means of head-end voltageAnd head-end current->Determining a head-end input impedance matrix for a fault-free three-core cable in the event of a terminal mismatch>Can be expressed as:

equation 38:。

recording the signal sent by the sweep frequency signal source as e, and sweeping at the same timeThe frequency signal source has internal impedance. Because only one conductor of the three-core cable is driven with the sweep frequency signal at a time, the signal and the internal impedance exist only at the conductor driven with the signal, and the other parameters are all 0. In the process of scanning the fault-free three-core cable by adopting the scanning signal source, the impedance in the scanning signal source and the cable are in series connection, thereby meeting ohm law, and the voltage of the scanning signal e and the fault-free three-core cable can be deduced by combining the formula 30>The relationship between them is expressed as:

equation 39:；

taking into account the voltage of each conductor of the cable of the swept source signal eAnd current->Can be expressed as:

equation 40:

equation 41:

according to the head-end voltage of the fault-free three-core cableHead-end current->Impedance in signal source- >Calculating the inverse received by the sweep frequency signal sourceRadio signal->Can be expressed as:

equation 42:。

s250, determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to each reflection signal and the second interpretation; the head-end failsafe reflection coefficient function is a function of the head-end failsafe reflection coefficient as a function of frequency.

In this embodiment, the transmission signal received by the swept source isCan be divided into forward wave voltage->Reverse wave voltage->Can be expressed as:

equation 43:。

based on the internal impedance of the swept sourceInput impedance +.>Calculating reflection coefficient->Can be expressed as:

equation 44:；

the transmitting signal received by the sweep frequency signal source is forward wave voltageAnd counter-wave voltage->The relation between the forward wave voltage and the backward wave voltage satisfies the traveling wave refraction and reflection principle, and can be expressed as follows:

equation 45:；

substituting the formulas 43 to 45 into the formula 42, and calculating to obtain the forward waveAnd counter-traveling wave->Specifically, the method can be expressed as:

equation 46:；

equation 47:；

due toAnd->Are modulus parameters, which are converted according to the formula 20 to obtain the actual forward waveAnd counter-traveling wave->Specifically, the method can be expressed as:

Equation 48:；

equation 49:；

since the swept signal sweeps only one conductor at a time in the three-core cable without fault, the conductor being swept is taken as the target conductor. Target conductor forward waveIs a matrix->The%>The corresponding elements of the target conductors, the target conductors counter-traveling waveIs a matrix->Is the->And the corresponding elements of the target conductors. Therefore, the head-end reflection coefficient of the target conductor in the trouble-free three-core cable +.>Can be expressed as:

equation 50:。

frequency sweep signal e and initial frequency of selected frequency sweep signal sourceAnd cut-off frequency->And the number N of the frequency test points, circularly executing the frequency sweeping signals with different frequencies respectively sent to each conductor in the fault-free three-core cable through the frequency sweeping signal source, and according to the frequency sweeping signals of the frequency sweeping signal sourceCalculating a reflected signal received by a sweep frequency signal source; determining the head-end reflection coefficient of each conductor in the fault-free three-core cable according to the reflected signals and the second general solution, and finally obtaining the head-end reflection coefficient of each conductor in the fault-free three-core cable under different preset frequencies>Function as a function of frequency->。

And S260, for each conductor in the three-core cable to be detected, determining the difference between the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function as a fault information function of the conductor.

In the present embodiment, the head-end fault reflection coefficient functionAnd head-end fault-free reflection coefficient functionIs determined as a function of the fault information>Can be expressed as: />

Equation 51:。

s270, for each conductor, windowing a fault information function of the conductor; and carrying out inverse Fourier transform processing on the windowed fault information function to obtain a fault information time domain positioning function.

In this embodiment, the chebyshev window may be selected to process the real part of the original fault information function, and the processed real part of the fault information function is the real functionCan be expressed as:

equation 52:；

where real represents the real part of the data taken from brackets, chebwin represents the chebyshev window function,representing multiplication with scale matrix corresponding elements.

Processing the windowed real part function of fault information by inverse discrete Fourier transformFault information time Domain positioning function->Can be expressed as:

equation 53:

wherein N representsLength of real part function array of fault information, +.>Variable representing data in the real function array of fault information, < ->Is +.>And cut-off frequency->Related time array and satisfies，/>，/>；/>For time resolution, +.>Total time for round trip of sweep signal, +. >For the total length of the three-core cable to be tested, +.>The wave speed of the sweep frequency signal in the three-core cable to be detected is obtained.

S280, converting the fault information time domain locating function into a space domain to obtain a fault locating waveform of the conductor.

In the embodiment, according to the relation between the wave speed of the sweep frequency signal and the time and distance, the fault information time domain positioning function is converted into a space domain, and the positioning waveforms of all conductors in the three-core cable to be detected are obtained.

Distance travelled by the swept frequency signalWave speed->Time->The relationship between them can be expressed as:

equation 54:。

because the swept frequency signal source receives a signal that makes a round trip in the cable, the signal actually travels twice the total length of the cable. Accordingly, a time array is calculatedCorresponding toSpace array->As shown below, the function of the space array is to correlate each time-domain positioning information with a specific position, the space array +.>Can be expressed as:

equation 55:；

using space arraysReplacement time array->Finally, the fault information space domain function of all conductors of the three-core cable to be detected can be obtained>The function is the positioning waveform.

S290, obtaining the number of fault conductors; and positioning the barrier layer of the three-core cable to be detected according to the number of the fault conductors and the position relation of each fault conductor.

Wherein the faulty conductor is a conductor in which an abnormal spike occurs in the corresponding fault localization waveform.

In this embodiment, from analyzing the locating waveform peaks of all conductors, researching the relationship among the locating waveforms of the core conductor, the metal sheath conductor and the armoured conductor to obtain the position and the structure of the fault in the three-core cable to be detected, the specific steps include:

(1) The number of faulty conductors in which abnormal spikes in the locating waveform occur is determined. The failure of the three-core cable to be detected can cause the locating waveform of the conductor to appear as a peak different from a normal state. And detecting the locating waveform peak values of the wire core conductor, the metal sheath conductor and the armored conductor, and considering that the three-core cable to be detected at a certain position has faults as long as the peak number at the position is more than or equal to 1.

(2) The barrier layer is determined based on the positional relationship between the faulty conductors.

If there is only one faulty conductor, then the faulty conductor is a barrier layer.

If two fault conductors exist, when the two fault conductors are not adjacent, the faults are independently generated on the two fault conductors; when two conductors are adjacent, a fault occurs on both the faulty conductor and the structural layer between the faulty conductors.

If three fault conductors exist, when all the three fault conductors are not adjacent, faults respectively occur on the wire cores of the ABC three phases; when two fault conductors have adjacent relation, the fault occurs on the first, the second adjacent conductors and the structure layer sandwiched between them, and the fault exists on the third fault conductor alone; when there is an adjacent relationship between the three faulty conductors, the fault occurs on the structural layer that extends through the three faulty conductors and the middle thereof.

If four fault conductors exist, when the four fault conductors are not adjacent, faults respectively occur on the wire core and armor of the ABC three-phase cable; when adjacent relation exists between two fault conductors, faults occur on the first adjacent fault conductor, the second adjacent fault conductor and the structural layer sandwiched between the first adjacent fault conductor and the second adjacent fault conductor, and defects or faults exist on the third fault conductor and the fourth fault conductor independently; when there is a continuous adjacent relationship between the three fault conductors, the fault occurs on the first, second, and third continuous adjacent fault conductors and the structural layer sandwiched therebetween, and the fourth fault conductor has a defect or fault alone; when there is a continuous adjacent relationship between the four fault conductors, the fault occurs on the structural layer that extends through the four fault conductors and the middle thereof;

If five fault conductors exist, at least three fault conductors have continuous adjacent relation due to the limitation of the cable structure, when the continuous adjacent relation exists among the three conductors, the faults occur on the first, second and third continuous adjacent fault conductors and the structure clamped between the first, second and third continuous adjacent fault conductors, and the fourth and fifth fault conductors have defects or faults independently; when adjacent relations exist among the four fault conductors, faults occur on the first, second, third and fourth continuous adjacent fault conductors and the structural layers sandwiched between the first, second, third and fourth continuous adjacent fault conductors, and defects or faults exist on the fifth fault conductor independently; when there is a continuous adjacent relationship between the five faulty conductors, the fault occurs on the structural layer that extends through the five faulty conductors and the middle thereof;

if six fault conductors exist, at least five fault conductors have continuous adjacent relation due to the limitation of the cable structure, and the faults occur on the first to five continuous adjacent fault conductors and the structure sandwiched between the first to five continuous adjacent fault conductors, and the sixth fault conductor has faults alone; when there is a continuous adjacent relationship between the six fault conductors, the fault occurs throughout the six fault conductors and the structural layers therebetween;

If there are seven faulty conductors, there must be a continuous adjacent relationship between each of the seven conductors due to the cable structural constraints, the fault occurring throughout the seven faulty conductors and the structural layers therebetween.

Example III

Fig. 7 is a schematic structural diagram of a fault locating device for a three-core cable according to a third embodiment of the present invention. As shown in fig. 7, the apparatus includes: a first interpretation module 310, a second interpretation module 320, a sweep module 330, an information function determination module 340, and a fault location module 350; wherein,

a first general solution determining module 310, configured to establish a wave equation of a fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and obtain a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable;

a second solution determining module 320, configured to determine a second solution of the wave equation in the case of end impedance mismatch according to the first solution and a reflection coefficient matrix of the fault-free three-core cable at the end impedance mismatch point; the second solution includes: a second voltage modulus and a second current modulus for each conductor in the fault-free three-core cable;

The sweep frequency module 330 is configured to send sweep frequency signals with different frequencies to each conductor in the three-core cable to be detected, and obtain a head end fault reflection coefficient function of each conductor in the three-core cable to be detected;

an information function determining module 340, configured to determine a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second solution and the sweep signal, and determine a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function;

the fault locating module 350 is configured to process each fault information function to obtain fault locating waveforms of all conductors in the three-core cable to be detected; and determining the fault position of the three-core cable to be detected according to the fault positioning waveform.

Optionally, the first general solution determining module is specifically configured to:

establishing a unit impedance matrix of the three-core cable without faults, a first differential equation between the current and the voltage of each conductor and a second differential equation between the unit admittance matrix of the three-core cable without faults and the current and the voltage of each conductor according to a micro-element circuit model of the three-core cable without faults;

Determining a wave equation of the fault-free three-core cable according to the first differential equation and the second differential equation based on a multi-conductor electromagnetic coupling theory;

a first general solution of the wave equation is calculated using a phase-model transformation calculation method.

Optionally, the second solution determining module is specifically configured to:

establishing a circuit model of the fault-free three-core cable under the condition that the tail ends of the fault-free three-core cable are not matched with impedance;

based on a travelling wave refraction and reflection principle, determining a tail end reflection coefficient matrix and a head end reflection coefficient matrix of the fault-free three-core cable according to the circuit model;

substituting the tail end reflection coefficient matrix and the head end reflection coefficient matrix into the first complete solution to obtain a second complete solution of the wave equation under the condition that the tail end impedance is not matched.

Optionally, the information function determining module is specifically configured to:

calculating reflection signals generated by each sweep frequency signal on each conductor in the fault-free three-core cable;

determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to each reflected signal and the second solution; the head-end fault-free reflection coefficient function is a function of the head-end fault-free reflection coefficient changing with frequency;

And for each conductor in the three-core cable to be detected, determining the difference between the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function as a fault information function of the conductor.

Optionally, the fault locating module is specifically configured to:

for each conductor, windowing a fault information function of the conductor;

performing inverse Fourier transform processing on the windowed fault information function to obtain a fault information time domain positioning function;

and converting the fault information time domain locating function into a space domain to obtain a fault locating waveform of the conductor.

Optionally, the fault location module is further configured to:

acquiring the number of fault conductors; the fault conductor is a conductor with abnormal peaks in the corresponding fault locating waveforms;

and positioning the barrier layers of the three-core cable to be detected according to the number of the fault conductors and the position relation of each fault conductor.

The fault locating device for the three-core cable provided by the embodiment of the invention can execute the fault locating method for the three-core cable provided by any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the executing method.

Example IV

Fig. 8 shows a schematic diagram of the structure of an electronic device 10 that may be used to implement an embodiment of the invention. Electronic devices are intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. Electronic equipment may also represent various forms of mobile devices, such as personal digital processing, cellular telephones, smartphones, wearable devices (e.g., helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be exemplary only, and are not meant to limit implementations of the inventions described and/or claimed herein.

As shown in fig. 8, the electronic device 10 includes at least one processor 11, and a memory, such as a Read Only Memory (ROM) 12, a Random Access Memory (RAM) 13, etc., communicatively connected to the at least one processor 11, in which the memory stores a computer program executable by the at least one processor, and the processor 11 may perform various appropriate actions and processes according to the computer program stored in the Read Only Memory (ROM) 12 or the computer program loaded from the storage unit 18 into the Random Access Memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 may also be stored. The processor 11, the ROM 12 and the RAM 13 are connected to each other via a bus 14. An input/output (I/O) interface 15 is also connected to bus 14.

Various components in the electronic device 10 are connected to the I/O interface 15, including: an input unit 16 such as a keyboard, a mouse, etc.; an output unit 17 such as various types of displays, speakers, and the like; a storage unit 18 such as a magnetic disk, an optical disk, or the like; and a communication unit 19 such as a network card, modem, wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information/data with other devices via a computer network, such as the internet, and/or various telecommunication networks.

The processor 11 may be a variety of general and/or special purpose processing components having processing and computing capabilities. Some examples of processor 11 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various specialized Artificial Intelligence (AI) computing chips, various processors running machine learning model algorithms, digital Signal Processors (DSPs), and any suitable processor, controller, microcontroller, etc. The processor 11 performs the various methods and processes described above, such as the fault locating method of a three-core cable.

In some embodiments, the fault localization method of the three-wire cable may be implemented as a computer program tangibly embodied on a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program may be loaded and/or installed onto the electronic device 10 via the ROM 12 and/or the communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11, one or more steps of the three-wire cable fault locating method described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to perform the fault localization method of the three-core cable by any other suitable means (e.g., by means of firmware).

Various implementations of the systems and techniques described here above may be implemented in digital electronic circuitry, integrated circuit systems, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standard Products (ASSPs), systems On Chip (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs, the one or more computer programs may be executed and/or interpreted on a programmable system including at least one programmable processor, which may be a special purpose or general-purpose programmable processor, that may receive data and instructions from, and transmit data and instructions to, a storage system, at least one input device, and at least one output device.

A computer program for carrying out methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the computer programs, when executed by the processor, cause the functions/acts specified in the flowchart and/or block diagram block or blocks to be implemented. The computer program may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present invention, a computer-readable storage medium may be a tangible medium that can contain, or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer readable storage medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, the computer readable storage medium may be a machine readable signal medium. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

To provide for interaction with a user, the systems and techniques described here can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to a user; and a keyboard and a pointing device (e.g., a mouse or a trackball) through which a user can provide input to the electronic device. Other kinds of devices may also be used to provide for interaction with a user; for example, feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form, including acoustic input, speech input, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a background component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such background, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), wide Area Networks (WANs), blockchain networks, and the internet.

The computing system may include clients and servers. The client and server are typically remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also called a cloud computing server or a cloud host, and is a host product in a cloud computing service system, so that the defects of high management difficulty and weak service expansibility in the traditional physical hosts and VPS service are overcome.

It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present invention may be performed in parallel, sequentially, or in a different order, so long as the desired results of the technical solution of the present invention are achieved, and the present invention is not limited herein.

The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims

1. A method for locating a fault in a three-core cable, comprising:

establishing a wave equation of a fault-free three-core cable based on a multi-conductor electromagnetic coupling theory, and acquiring a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable; wherein, the multiconductor of three-core cable includes: the cable comprises a cable core, a metal sheath and armors of three coaxial cables;

determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second general solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function; the first-end fault reflection coefficient refers to a reflection coefficient corresponding to travelling wave refraction and reflection generated by the first end of the three-core cable to be detected under the condition that the impedance of the tail end is not matched; the head-end fault reflection coefficient function is a function of the head-end fault reflection coefficient changing along with frequency; the reflection coefficient of the head end without faults is the reflection coefficient corresponding to the travelling wave refraction and reflection generated by the head end under the condition that the impedance of the tail end of the three-core cable without faults is not matched; the head-end fault-free reflection coefficient function is a function of the head-end fault-free reflection coefficient changing with frequency; the fault information function can reflect the waveform difference presented on the line refraction and reflection of the three-core cable to be detected and the three-core cable without fault under the condition that the terminal impedance is not matched;

Processing each fault information function to obtain fault locating waveforms of all conductors in the three-core cable to be detected; determining the fault position of the three-core cable to be detected according to the fault positioning waveform;

wherein said determining a second pass solution of said wave equation in case of end impedance mismatch from said first pass solution and a reflection coefficient matrix of said fault-free three-core cable at end impedance mismatch points comprises:

2. The method of claim 1, wherein the establishing a wave equation for a fault-free three-core cable based on multi-conductor electromagnetic coupling theory and obtaining a first general solution for the wave equation comprises:

3. The method of claim 1, wherein said determining a head-end fault-free reflection coefficient function for each conductor in said fault-free three-core cable from said second pass solution and said swept signal comprises:

and determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to each reflected signal and the second interpretation.

4. A method according to claim 3, wherein said determining a fault information function from said head-end fault reflection coefficient and said head-end fault free reflection coefficient comprises:

5. The method according to claim 1, wherein said processing each of said fault information functions to obtain fault location waveforms for all conductors in said three-core cable to be tested comprises:

For each conductor, windowing a fault information function of the conductor;

6. The method according to claim 1 or 5, wherein said determining a fault location of the three-core cable to be detected from the fault location waveform comprises:

7. A fault locating device for a three-core cable, comprising:

the first general solution determining module is used for establishing a wave equation of the fault-free three-core cable based on a multi-conductor electromagnetic coupling theory and acquiring a first general solution of the wave equation; the first general solution includes: a first voltage modulus and a first current modulus for each conductor in the fault-free three-core cable; wherein, the multiconductor of three-core cable includes: the cable comprises a cable core, a metal sheath and armors of three coaxial cables;

the information function determining module is used for determining a head-end fault-free reflection coefficient function of each conductor in the fault-free three-core cable according to the second general solution and the sweep frequency signal, and determining a fault information function according to the head-end fault reflection coefficient function and the head-end fault-free reflection coefficient function; the first-end fault reflection coefficient refers to a reflection coefficient corresponding to travelling wave refraction and reflection generated by the first end of the three-core cable to be detected under the condition that the impedance of the tail end is not matched; the head-end fault reflection coefficient function is a function of the head-end fault reflection coefficient changing along with frequency; the reflection coefficient of the head end without faults is the reflection coefficient corresponding to the travelling wave refraction and reflection generated by the head end under the condition that the impedance of the tail end of the three-core cable without faults is not matched; the head-end fault-free reflection coefficient function is a function of the head-end fault-free reflection coefficient changing with frequency; the fault information function can reflect the waveform difference presented on the line refraction and reflection of the three-core cable to be detected and the three-core cable without fault under the condition that the terminal impedance is not matched;

The fault locating module is used for processing each fault information function to obtain fault locating waveforms of all conductors in the three-core cable to be detected; determining the fault position of the three-core cable to be detected according to the fault positioning waveform;

the second solution determining module is specifically configured to:

8. An electronic device, the electronic device comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

the memory stores a computer program executable by the at least one processor to enable the at least one processor to perform the fault localization method of the three-wire cable of any one of claims 1-6.

9. A computer readable storage medium storing computer instructions for causing a processor to perform the method of fault localization of a three-core cable according to any one of claims 1-6.