CN113156262B - High-voltage cable fault positioning method and system based on impedance spectrum - Google Patents
High-voltage cable fault positioning method and system based on impedance spectrum Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/58—Testing of lines, cables or conductors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention discloses a high-voltage cable fault positioning method and system based on impedance spectroscopy, and belongs to the technical field of cable fault positioning. The method comprises the steps of forming an electromagnetic loop of an impedance spectrum signal by utilizing the electromagnetic coupling effect of a wire core and a metal sheath of the medium-voltage cable which are used for cross interconnection of different phases of metal sheaths in the high-voltage cable to be tested; measuring an impedance spectrum of the electromagnetic circuit of the impedance spectrum signal; selecting cables with any length and the same type as the tested high-voltage cable, testing impedance spectrums of tail end open circuits and tail end short circuits of the cables, and calculating parameters of the cables; using generalized orthogonality of impedance spectra, with ej2βxAnd performing integral transformation on the impedance spectrum for a kernel function to obtain a fault positioning curve of the measured high-voltage cable. The invention can quickly, accurately and nondestructively position the fault of the high-voltage cable by forming a new loop to measure the impedance spectrum of the cross interconnection cable and obtaining the fault position in the cross interconnection cable by an integral conversion method, and has important significance for the safe and stable operation of a power system.
Description
Technical Field
The invention belongs to the technical field of cable fault positioning, and particularly relates to a high-voltage cable fault positioning method and system based on impedance spectroscopy.
Background
With the development of the power industry in China, the operation and maintenance length of the high-voltage cable is longer and longer. The quick and accurate positioning of the cable fault has important significance for the safe and stable operation of the line. The impedance spectrum technology is a novel cable fault positioning method, high voltage does not need to be applied, discharging does not need to be carried out, a measuring circuit is simple, no damage is caused to a cable, and the method has a good application prospect in cable fault positioning. At present, an impedance spectrum technology is applied to fault diagnosis of medium and low voltage cables and obtains a good effect, a measurement mode of a cable impedance spectrum is generally shown in fig. 1, firstly, a sweep frequency signal is input at one end of a cable, (a) a loop is formed in a single-phase coaxial cable through a wire core and a metal sheath, and (b) a loop is formed in a multi-phase cable through a two-phase wire core. The cable impedance is obtained through the ratio of voltage to current, and the cable impedance spectrum is obtained through measuring the impedance of the cable under different frequencies.
The high-voltage cable is usually a single-core coaxial cable, and impedance spectrum measurement can be performed in a conventional manner, but because single-phase alternating current flows through a core of the high-voltage cable, induced electromotive force is generated in a corresponding metal sheath, and induced current is further generated. In order to reduce the power frequency induced voltage, the metal sheaths of the cables are generally interconnected in a cross-connection manner. However, due to the existence of the connection mode of the metal sheath cross-connection in the high-voltage cable, the impedance spectrum of the cross-connection cable cannot be measured at present, and the fault location of the cross-connection cable cannot be performed through the impedance spectrum, so that the impedance spectrum method cannot be applied to the fault diagnosis of the high-voltage cable.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a high-voltage cable fault positioning method and system based on impedance spectrums, and aims to solve the problem of measuring the impedance spectrums of cross-connected high-voltage cables.
In order to achieve the purpose, the invention provides a high-voltage cable fault positioning method based on impedance spectroscopy, which comprises the following steps:
s1, forming an electromagnetic loop of an impedance spectrum signal by utilizing an electromagnetic coupling effect of a wire core and a metal sheath of a medium-voltage cable which is used for cross interconnection of different phase metal sheaths in a tested high-voltage cable;
s2, connecting an impedance analyzer between the phase wire core and the metal protective layer, and measuring the impedance spectrum of the electromagnetic loop of the impedance spectrum signal in the step S1;
s3, selecting a cable with any length and the same model as the tested high-voltage cable, testing the impedance spectrum of the tail end open circuit and the tail end short circuit, and calculating the propagation constant gamma, the attenuation coefficient alpha and the phase shift coefficient beta of the cable;
s4, utilizing the generalized orthogonality of the impedance spectrum measured in S2, and calculating parameters according to S3 by using ej2βxPerforming integral transformation on the impedance spectrum for a kernel function to obtain a fault location curve of the cable and a fault point positionAnd (3) placing the position of an abrupt peak corresponding to the positioning function, wherein x is the variable of the axial direction of the measured high-voltage cable.
Preferably, a kernel function e is takenj2βxForming an integral positioning function
Wherein f is1、f2The upper and lower limits of the impedance spectrum measurement frequency, and z (f) the measured impedance spectrum of the crossed interconnection cable.
Preferably, a complete cross-connection section comprises three sections of cables, wherein a1, B1 and C1 are respectively the tail part of the metal sheath of the first section of A, B, C three-phase cable, a2, B2 and C2 are respectively the head part of the metal sheath of the second section of A, B, C three-phase cable, a1 and B2 are respectively connected with the core wire and the metal sheath of the medium-voltage cable, and the electromagnetic coupling of the core wire and the metal sheath of the medium-voltage cable is utilized to form electrical connection, so that the electrical connection between the first section and the second section is formed; an electrical connection between the second and third segments is similarly constructed.
Preferably, the impedance of the cross-connect cable is:
wherein l is the length of the cable, gamma is the propagation constant of the A-phase cable, gamma isLIs the reflection coefficient, x, of the end of the high-voltage cable under test2，x3The distance Z between two cross interconnection joints in a complete cross interconnection interval and the tail end of the measured high-voltage cable0Is the characteristic impedance, Z, of the high-voltage cable under testmIs the equivalent impedance of the medium voltage cable.
Preferably, the propagation constant γ of the cable is formulated as:
wherein，ZscAs short-circuit impedance, ZopFor open-circuit impedance, the attenuation coefficient α is the real part of the propagation constant γ, and the phase shift coefficient β is the imaginary part of the propagation constant γ.
Another aspect of the present invention provides a system for locating a fault in a high voltage cable based on impedance spectroscopy, comprising:
the electromagnetic loop building module is used for forming an electromagnetic loop of an impedance spectrum signal by utilizing the electromagnetic coupling effect of a wire core and a metal protective layer of a medium-voltage cable which are used for cross interconnection among different phases of metal protective layers in the tested high-voltage cable;
the impedance spectrum measuring module is used for connecting the impedance analyzer between the measuring phase wire core and the metal protective layer and measuring the impedance spectrum of the electromagnetic loop of the impedance spectrum signal;
the parameter testing module is used for selecting a cable with any length and the same type as the tested high-voltage cable, testing the impedance spectrum of the tail end open circuit and the tail end short circuit, and calculating the propagation constant gamma, the attenuation coefficient alpha and the phase shift coefficient beta of the cable;
a fault positioning module for utilizing the generalized orthogonality of the impedance spectrum and measuring the obtained parameters by the parameter measuring module according to ej2βxAnd performing integral transformation on the impedance spectrum for a kernel function to obtain a fault location curve of the measured high-voltage cable, wherein the position of a fault point corresponds to the position of a sudden change peak of the location function, and x is a variable in the axial direction of the measured high-voltage cable.
Compared with the prior art, the cable fault positioning method for the impedance spectrum of the cross interconnection cable is provided by the technical scheme, the impedance spectrum of the cross interconnection cable is measured by forming a new loop, the fault position in the cross interconnection cable is obtained by an integral conversion method, the fault of the high-voltage cable can be quickly, accurately and nondestructively positioned, and the method has important significance for safe and stable operation of a power system.
Drawings
FIG. 1 is a cable impedance spectrum measurement circuit of the prior art, (a) is a wiring diagram for measuring the impedance spectrum of a single-phase coaxial cable, and (b) is a wiring diagram for measuring the impedance spectrum of a multi-phase cable;
FIG. 2 is a schematic diagram of a cross-connect wiring;
FIG. 3 is an impedance spectroscopy measurement loop of a complete cross-interconnect segment;
FIG. 4 is an impedance measurement circuit in a cross-connect cable, (a) for an actual circuit and (b) for a simplified circuit;
FIG. 5 is a schematic view of a test cross-connect cable;
FIG. 6 is a cross-connect cable fault location experimental measured impedance spectrum;
fig. 7 is a cross-connect cable fault location experimental location curve.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a high-voltage cable fault positioning method based on impedance spectroscopy, which comprises the following steps:
s1, forming an electromagnetic loop of an impedance spectrum signal by utilizing an electromagnetic coupling effect of a wire core and a metal sheath of a medium-voltage cable which is used for cross interconnection of different phase metal sheaths in a tested high-voltage cable;
s2, connecting an impedance analyzer between the phase wire core and the metal protective layer, and measuring the impedance spectrum of the electromagnetic loop of the impedance spectrum signal in the step S1;
s3, selecting a cable with any length and the same model as the tested high-voltage cable, testing the impedance spectrum of the tail end open circuit and the tail end short circuit, and calculating the propagation constant gamma, the attenuation coefficient alpha and the phase shift coefficient beta of the cable;
s4, utilizing the generalized orthogonality of the impedance spectrum measured in S2, and calculating parameters according to S3 by using ej2βxPerforming integral transformation on the impedance spectrum for a kernel function to obtain a fault location curve of the cable, wherein the position of a fault point corresponds to the position of a sudden change peak of the location function, and x is the axial direction of the measured high-voltage cableThe variation of the direction.
Firstly, a cross interconnection wiring mode of the metal protective layer in the high-voltage cable is explained:
because the cables with the voltage class of 110kV and above are single-phase coaxial cables, the single-phase alternating current flows through the wire cores, and induced electromotive force is generated in the corresponding metal protective layer, so that induced current is generated. And the longer the cable, the greater the induced electromotive force and the greater the induced current. In order to reduce the power frequency induced voltage, the metal sheaths of the cables are generally interconnected in a cross manner when the cables are longer.
The wiring diagram of cross-connection is shown in fig. 2, and sheath cross-connection means that the whole cable is divided into 3N sections (N is a positive integer), an insulating joint is arranged between every two sections, and three phases of sheaths at the insulating joint are connected by coaxial cables. As shown in fig. 2, the cable is divided into three sections, a1, B1 and C1 are respectively the tail of the metal sheath of the first section of A, B, C three-phase cable, a2, B2 and C2 are respectively the head of the metal sheath of the second section of A, B, C three-phase cable, and a1 and B2, B1 and C2, and C1 and a2 are connected to form the cross-connection of the metal sheaths of the high-voltage cable. The second and third sections of the cable are also cross-interconnected in the same manner by insulated joints. Because the phase difference of the current of the three-phase wire core is approximately 120 degrees, the phase difference of the induced voltage of the three-phase metal protective layer is also approximately 120 degrees. Three sections of metal protective layers of different phases are connected in series in a cross interconnection grounding mode, and the aim of reducing the power frequency induction voltage is fulfilled by utilizing the offset effect of different-phase induction voltages.
Therefore, due to the cross interconnection wiring mode of the metal protective layers in the high-voltage cable, the A-phase metal protective layer is disconnected at the cross interconnection position, and an impedance spectrum measurement loop cannot be formed between the A, B, C three-phase cable single-phase wire core and the metal protective layer, so that the cable fault positioning technology based on the impedance spectrum cannot be applied to the high-voltage cable all the time.
The impedance spectrum measuring loop of the high-voltage cable is shown in figure 3. Fig. 3 shows a complete cross-connection section of A, B, C three-phase single-core coaxial cross-connection cable, wherein A, B, C three-phase cable is divided into three sections, which pass through a1 and a2 respectively; b1, B2; c1, C2 intermediate linkers, within which，a1a2The metal sheath of the segment cable is connected with the core wire of the medium voltage cable M1, b3b4The metal sheath of the section cable is connected with the metal sheath of the M2 cable, the core of the M1 cable is connected with the metal sheath of the M2 cable at the grounding resistance, and therefore a is connected1a2Metal sheath of cable segment and b3b4The metal sheaths of the cable sections are connected to form a cross-connect. a is3a4The metal sheath of the cable section is connected with the metal sheath of the M1 cable, and a is an electromagnetic coupling between the M1 cable core and the metal sheath1a2Segment metal sheath and a3a4The metal sheath is electrically connected through a cable M1. And measuring the impedance spectrum of the A-phase cable, wherein the measurement loop is shown as a thick solid line in fig. 3, and the A-phase core and the A-phase metal sheath, the M1 cable core and the sheath, and the M2 cable core and the sheath form the impedance spectrum measurement loop together.
Converting the loop into a distributed parameter circuit can result in a circuit as shown in fig. 4, in (a) the medium voltage cable between the sheaths is also equivalent to a distributed parameter model. Because of I2＝I3＝I4The medium voltage cable between the A-phase sheaths can be equivalent to an impedance Zm。
The voltage and current of the impedance measurement loop in S2 can be obtained as:
Ix1and Ix2Are respectively the position x1And x2Current of (V)+And V-Respectively a forward voltage and a reverse voltage in the cable, gamma is the propagation constant of the A-phase cable, gamma isLX is the reflection coefficient of the cable end and x is the distance from the cable end.
When x ═ l, the head end impedance spectrum of the cable can be found to be:
so that the head end impedance spectrum of the cross-connect cable is e-2γl，
As a function of (c).
When there is a fault on the cross-connect cable, assume the fault data head end distance is x3Then the impedance spectrum of the head end of the cross-connect cable is e-2γl，
As a function of (c). Due to x1，x2Is a distance from the end, then l-x1，l-x2Respectively the distance from the head end to the two cross-connect connectors.
Step S3 determines the phase shift coefficient of the cable by a method based on the input impedance of the cable. When the cable end is open, the load reflection coefficient is 1, and the cable input impedance is recorded as open-circuit impedance Zop(ii) a When the end of the cable is short-circuited, the load reflection coefficient is-1, and the input impedance of the cable is recorded as short-circuit impedance Zsc. The open circuit impedance and the short circuit impedance of the healthy cable head end are as follows:
thereby obtaining the characteristic impedance Z of the cableCAnd propagation constant gamma
Here, the phase shift coefficient β is an imaginary part of the propagation constant γ, so that the phase shift coefficient β can be obtained from the propagation constant of the cable.
Explaining the method for cable fault location in S4:
when the integral of the product of two functions has a significant difference in the values of the two cases, mathematically called the orthogonal function system, for a function system { f }i… i is 1,2 … n, if any two functions are in a certain closed interval [ a, b ]]The integral of the product above satisfies the following relation:
then call { fi… i is 1,2 … n is an orthogonal function system.
The trigonometric function system is a widely used orthogonal function system, and has the following form:
{1,cosx,sinx,sin2x,sin2x,......cosnx,sinnx}
the functions are orthogonal in [ -pi, pi ], i.e., where the product of any two functions over [ -pi, pi ] is zero and the product integral of two identical functions is not zero.
And because of
e-2γl＝e-2αl(-sin2βl+jcos2βl) (8)
If taking the kernel function ej2βxAnd forming an integral positioning function, wherein the integral positioning function is as follows:
f (x) is an integral localization function, f1、f2The upper and lower limits of the impedance spectrum measurement frequency, and z (f) the measured impedance spectrum of the crossed interconnection cable.
Due to the orthogonality of the trigonometric functions, one can obtain:
thus, the integral transform positioning function is at x3，l-x1，l-x2Abrupt peaks appear at the cable fault points, namely abrupt peaks appear at the fault points and the positions of the cross interconnections, so that the cable fault points can be located.
And (4) obtaining the fault position and the position of the cross-linked interconnection point by the positioning curve in S4, and eliminating the cable intermediate joint through a cable drawing in step S5 to finish the fault positioning of the cross-linked high-voltage cable.
Examples
The method provided by the invention is applied to a fault location experiment of a high-voltage cross-connection cable, and a field fault location experiment is carried out on a 110kV high-voltage cable in a cable trench, wherein the cable is a cross-linked polyethylene insulated single-core cable. The cable model is YJLW-64/110kV-1 × 630, the diameter of the copper core is 30mm, and the area is 630m2. The main insulation thickness is 18mm, the semiconductor layer thickness is 1mm, the aluminum sheath thickness is 3mm, the length is 3838m, according to the construction drawing, the three-phase cable is arranged in a delta shape, and the cable has an open circuit fault at a position 1492.2m away from the cable measuring end. There are two connections between the measurement terminal and the open circuit fault. The No. 1 joint is an insulating joint which is 509.5 meters away from the measuring end, the metal protective layers of the three-phase cable are crossed and interconnected in the No. 1 joint, and the No. 2 joint is a through joint which is 1006.1 meters away from the measuring end. The insulated joint is grounded through the protector.
A phase cable is taken as an experimental cable, a circuit is formed by the phase A cable core wire, the metal protective layer and the cross-interconnected medium-voltage cable, and the impedance and the phase of the cable are tested by a WK6500B precision impedance analyzer. The measurement frequency ranges from 1MHz to 120 MHz. The experiment is shown in FIG. 5. The test cable comprises a cross-interconnected insulated connector and a through connector.
The measured impedance spectrum is shown in fig. 6 according to steps S1, S2. Integral transformation of the measured impedance spectrum according to step S4 may result in a localization curve as shown in fig. 7. The localization results shown in fig. 7 indicate that the localization function curve has distinct local mutation peaks at 523m, 994.2m and 1510.6 m. And the cross-connect joint is much taller than the straight-through joint alignment spike. The positioning error of the joint is 13.5m, the positioning error of a fault point is 18.4m, the error is caused by the fact that the distance between the joint position and the joint, which is given in a drawing, is only a design value, and due to construction reasons, the actual cable length is not completely equal to the drawing length, so that the cable length given in the drawing and the cable length in an actual cable trench have errors, and the positioning error is controlled within 2% of the cable length. Therefore, the method provided by the invention achieves a good positioning effect in the high-voltage cross interconnection cable.
It will be understood by those skilled in the art that the foregoing is only an exemplary embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, since various modifications, substitutions and improvements within the spirit and scope of the invention are possible and within the scope of the appended claims.
Claims (6)
1. A high-voltage cable fault positioning method based on impedance spectroscopy is characterized in that different phase metal guard layers in a high-voltage cable are cross-interconnected through a medium-voltage cable, and the method comprises the following steps:
s1, forming an electromagnetic loop of an impedance spectrum signal by utilizing an electromagnetic coupling effect of a wire core of a medium-voltage cable and a metal protective layer; a complete cross-connection section comprises three sections of cables, wherein A1, B1 and C1 are respectively the tail part of a metal sheath of a first section of A, B, C three-phase cables, A2, B2 and C2 are respectively the head part of a metal sheath of a second section of A, B, C three-phase cables, A1 and B2 are respectively connected with a core wire and the metal sheath of a medium-voltage cable, and the core wire and the metal sheath of the medium-voltage cable are electromagnetically coupled to form electrical connection, so that the electrical connection between the first section and the second section is formed; establishing an electrical connection between the second section and the third section in the same way; the impedance of the cross-connect cable is:
wherein l is the length of the cable, gamma is the propagation constant of the A-phase cable, gamma isLIs the reflection coefficient, x, of the end of the high-voltage cable under test2，x3The distance Z between two cross interconnection joints in a complete cross interconnection interval and the tail end of the measured high-voltage cable0Is the characteristic impedance, Z, of the high-voltage cable under testmIs the equivalent impedance of the medium voltage cable;
s2, measuring an impedance spectrum of the electromagnetic circuit in the step S1;
s3, selecting a cable with any length and the same model as the tested high-voltage cable, testing the impedance spectrum of the tail end open circuit and the tail end short circuit, and calculating the propagation constant gamma, the attenuation coefficient alpha and the phase shift coefficient beta of the cable;
s4, utilizing the generalized orthogonality of the impedance spectrum measured in S2, and calculating parameters according to S3 by using ej2βxAnd performing integral transformation on the impedance spectrum for a kernel function to obtain a fault location curve of the measured high-voltage cable, wherein the fault point corresponds to a sudden change peak of the fault location curve, and x is a variable in the axial direction of the measured high-voltage cable.
2. The method of fault localization according to claim 1, wherein a kernel function e is takenj2βxAnd forming an integral positioning function:
wherein f is1、f2The upper and lower limits of the impedance spectrum measurement frequency, and z (f) the measured impedance spectrum of the crossed interconnection cable.
3. A method for fault localization according to claim 1, wherein the propagation constant γ of the cable is formulated as:
wherein Z isscAs short-circuit impedance, ZopFor open-circuit impedance, the attenuation coefficient α is the real part of the propagation constant γ, and the phase shift coefficient β is the imaginary part of the propagation constant γ.
4. A high-voltage cable fault location system based on impedance spectroscopy, wherein different phase metal guard layers in a high-voltage cable are cross-interconnected through a medium-voltage cable, the system comprises:
the electromagnetic circuit building module is used for forming an electromagnetic circuit of an impedance spectrum signal by utilizing the electromagnetic coupling effect of a wire core of the medium-voltage cable and the metal protective layer; a complete cross-connection section comprises three sections of cables, wherein A1, B1 and C1 are respectively the tail part of a metal sheath of a first section of A, B, C three-phase cables, A2, B2 and C2 are respectively the head part of a metal sheath of a second section of A, B, C three-phase cables, A1 and B2 are respectively connected with a core wire and the metal sheath of a medium-voltage cable, and the core wire and the metal sheath of the medium-voltage cable are electromagnetically coupled to form electrical connection, so that the electrical connection between the first section and the second section is formed; establishing an electrical connection between the second section and the third section in the same way; the impedance of the cross-connect cable is:
wherein l is the length of the cable, gamma is the propagation constant of the A-phase cable, gamma isLIs the reflection coefficient, x, of the end of the high-voltage cable under test2，x3The distance Z between two cross interconnection joints in a complete cross interconnection interval and the tail end of the measured high-voltage cable0Is the characteristic impedance, Z, of the high-voltage cable under testmIs the equivalent impedance of the medium voltage cable;
the impedance spectrum measuring module is used for measuring the impedance spectrum of the electromagnetic loop of the impedance spectrum signal;
the parameter testing module is used for selecting a cable with any length and the same type as the tested high-voltage cable, testing the impedance spectrum of the tail end open circuit and the tail end short circuit, and calculating the propagation constant gamma, the attenuation coefficient alpha and the phase shift coefficient beta of the cable;
a fault positioning module for utilizing the generalized orthogonality of the impedance spectrum and measuring the obtained parameters by the parameter measuring module according to ej2 βxAnd performing integral transformation on the impedance spectrum for a kernel function to obtain a fault location curve of the measured high-voltage cable, wherein the fault point corresponds to a sudden change peak of the fault location function, and x is a variable in the axial direction of the measured high-voltage cable.
5. The fault location system of claim 4, wherein a kernel function e is takenj2βxForming an integral positioning function
Wherein f is1、f2The upper and lower limits of the impedance spectrum measurement frequency, and z (f) the measured impedance spectrum of the crossed interconnection cable.
6. The fault location system of claim 4, wherein the propagation constant γ of the cable is formulated as:
wherein Z isscAs short-circuit impedance, ZopFor open-circuit impedance, the attenuation coefficient α is the real part of the propagation constant γ, and the phase shift coefficient β is the imaginary part of the propagation constant γ.
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