A method and system for detecting a through-line fault section based on cable core sheath electrical quantity

Abstract

The application discloses a through-line fault detection section method and system based on cable core sheath electrical quantity, and belongs to the field of railway power through-line relay protection. Specifically, after a fault occurs in a high-speed railway cable through line, firstly, a sheath current sensor arranged in a cable direct grounding box is used to acquire metal sheath current data of each section cable through line, a cable core voltage sensor arranged in a box transformer is used to acquire three-phase voltage data of each section cable core and construct cable core zero sequence voltage; then, wavelet transform and reconstruction are performed on the data, metal sheath current and zero sequence voltage fault characteristic bands of each section are determined, wavelet reconstruction coefficients of the metal sheath current and the zero sequence voltage in the fault characteristic bands are subjected to correlation analysis, and a correlation coefficient is calculated; finally, a fault section is detected according to the size of the correlation coefficient. Theoretical analysis and simulation results show that the method does not need data transmission of each section, has fast fault section discrimination response speed, and the result is accurate and reliable.

Description

TECHNICAL FIELD

[0001] The application relates to a through-line fault detection section method and system based on cable core sheath electrical quantity, and belongs to the field of railway power through-line relay protection. BACKGROUND

[0002] In order to improve the reliability of power supply of through-line, 10kV comprehensive power through-line and primary load power through-line are both supplied by three-phase single-core power cable in newly-built high-speed railway. Cable through-line fault seriously affects the safety and reliability of high-speed railway transportation. Research on cable through-line fault section detection technology and its application can greatly reduce the time for fault finding and fault repair. Therefore, it is of great practical significance to invent a method or monitoring system for quickly realizing cable through-line fault section detection for ensuring railway operation safety.

[0003] At present, after the fault of railway cable through-line occurs and power is cut off, the dispatch personnel manually analyze and try to put the load switch to judge the fault section, so that the fault positioning speed is slow and the power supply time of the non-fault section is long. Some power through-lines are installed with fault positioning devices based on impedance ranging. When single-phase grounding fault occurs in the line, if the transition resistance is large, the fault section cannot be given, and the fault checking time is long. Some through-lines are installed with traveling wave ranging devices at the station end. However, since the cable through-line is long and the attenuation of the traveling wave in the cable through-line is serious when the fault traveling wave reaches the station end monitoring device from the fault point, the traveling wave signal has been almost attenuated, which brings difficulties to the traveling wave signal monitoring and the calibration of the wave head arrival time. Therefore, the traveling wave method is directly applied to the cable through-line, and the effect is poor.

[0004] In summary, when the impedance method and the traveling wave method are applied to the cable through-line, there are some problems, which are difficult to meet the requirements of the development of high-speed railway in China. Therefore, it is necessary to explore methods other than the impedance method and the traveling wave method to realize the fault section finding of high-speed railway cable through-line. SUMMARY

[0005] The application aims to solve the problem of high-speed railway through-line fault section detection, and provides a through-line fault detection section method and system based on cable core sheath electrical quantity, which can effectively overcome the defects of the impedance method and the traveling wave method, and realize the effective detection of high-speed railway through-line fault section.

[0006] In order to achieve the above object, the application adopts the following scheme: a through line fault detection section method and system based on cable core sheath electrical quantity, belonging to the field of railway power through line relay protection. Specifically, after the fault of the high-speed railway cable through line, first, the metal sheath current data of each section of the cable through line is obtained through the sheath current sensor arranged in the cable direct grounding box, the three-phase voltage data of the cable core of each section of the cable is obtained through the cable core voltage sensor arranged in the box transformer, and the cable core zero sequence voltage is constructed; then, wavelet transform and reconstruction are performed on the same, the fault characteristic frequency band of the metal sheath current and the zero sequence voltage of each section is determined, the wavelet reconstruction coefficients of the metal sheath current and the zero sequence voltage in the fault characteristic frequency band are analyzed in correlation, and the correlation coefficient is calculated; finally, the fault section is detected according to the size of the correlation coefficient.

[0007] The application provides a through line fault detection section method based on cable core sheath electrical quantity, and specifically includes the following steps.

[0008] Step 1: After the fault of the high-speed railway power through line, the transient data of the current of the metal sheath of each section of the cable is obtained through the sheath current sensor arranged in the direct grounding box, the three-phase voltage transient data of the cable core of each section of the cable is obtained through the voltage sensor arranged in the box transformer, and the cable core zero sequence voltage is constructed;

[0009] Step 2: The transient data of the current of the metal sheath of each section of the cable is subjected to wavelet transform and reconstruction, the energy of the transient current of the sheath of each section of the cable in each frequency band is calculated, and the fault characteristic frequency band of the current is determined according to the maximum energy principle , wherein x represents the section of the through line.

[0010] Step 3: The transient data of the zero sequence voltage of the cable core of each section of the cable is subjected to wavelet transform and reconstruction, the energy of the zero sequence voltage of the cable core of each section of the cable in each frequency band is calculated, and the fault characteristic frequency band of the voltage is determined according to the maximum energy principle , wherein x represents the section of the through line.

[0011] Step 4: The wavelet reconstruction coefficients of the transient data of the metal sheath current and the zero sequence voltage of the cable core of each section of the cable in the respective fault characteristic frequency band are analyzed in correlation, and the correlation coefficient of each section of the cable is calculated , wherein x represents the section of the through line.

[0012] Step 5: According to the correlation coefficient , the section is determined to be faulty, wherein x represents the section of the through line.

[0013] Further, in Step 1,

[0014] Step1.1: The transient data of the sheath current of each section is obtained by the sheath current sensor arranged in the direct grounding box.

[0015] Step1.2: The cable core zero sequence voltage is constructed by the three-phase voltage in the box transformer substation: Ux= U a + U b + U c ;

[0016] Step1.3: The time window of the transient current data and the voltage data is 2 ms before the fault and 8 ms after the fault.

[0017] Further, in Step2:

[0018] Step2.1: The calculation method of the energy of the transient current of the sheath of each section of the cable is as follows:

[0019]

[0020] wherein, is the wavelet reconstruction coefficient of the transient current of the metal sheath of each section of the cable, k is the kth data, there are m data in total, and j is the frequency band of the sheath transient current;

[0021] Step2.2: The frequency band corresponding to the maximum energy is the fault characteristic frequency band of the sheath current .

[0022] Further, in Step3:

[0023] Step3.1: The calculation method of the energy of the cable core zero sequence voltage of each section is as follows:

[0024]

[0025] wherein, is the wavelet reconstruction coefficient of the transient current of the metal sheath of each section of the cable, k is the kth data, there are m data in total, and j is the frequency band of the sheath transient current;

[0026] Step3.2: The frequency band corresponding to the maximum energy is the fault characteristic frequency band of the zero sequence voltage .

[0027] Further, in Step4: The calculation method of the correlation analysis is as follows:

[0028] p x = ∑ k = 1 m [ Id I α x ( k ) × Ud U α x ( k ) ] × [ ∑ k = 1 m Id I α x 2 ( k ) ∑ k = 1 m Ud U α x 2 ( k ) ] − 1 / 2

[0029] wherein, x is the xth section of the cable through line, a correlation coefficient of a wavelet reconstruction coefficient of the metal sheath current of the xth section in a fault characteristic frequency band, a wavelet reconstruction coefficient of the metal sheath current of the xth section in a fault characteristic frequency band, a wavelet reconstruction coefficient of the metal sheath current of the xth section in a fault characteristic frequency band, a wavelet reconstruction coefficient of the metal sheath current of the xth section in a fault characteristic frequency band, a wavelet reconstruction coefficient of the metal sheath current of the xth section in a fault characteristic frequency band.

[0030] Further, in Step 5, the method for judging the fault section is: if the correlation coefficient is greater than 0, the section is a non-fault section; if the correlation coefficient is less than 0, the section is a fault section.

[0031] Another aspect of the present application provides a through-line fault section detection system based on cable core sheath electrical quantities, which specifically comprises:

[0032] a data acquisition module: acquiring transient current data of metal sheaths of railway through-line cable sections and three-phase voltage data of cable cores;

[0033] a data processing module: constructing three-phase voltage of the through-line cable core into zero sequence voltage, wavelet decomposing and reconstructing the metal sheath current data of each section cable and the zero sequence voltage data of the cable core, calculating a correlation coefficient of a wavelet reconstruction coefficient of the metal sheath current of the xth section in a fault characteristic frequency band,

[0034] a fault judging module: detecting the fault section according to the data processing result and outputting the result.

[0035] The present application has the following advantages:

[0036] 1. The present application uses transient data of cable through-line section sheath current and three-phase voltage of the cable core to realize the judgment of the fault section, and since the transient data is used, the inherent defects of the power frequency quantity method that is greatly affected by the transition resistance and the traveling wave method that is prone to misjudgment caused by missed detection can be avoided;

[0037] 2. The present application uses transient data of each section to judge whether there is a fault or not, without the need for data transmission and clock synchronization equipment, and the method is low in implementation cost;

[0038] 3. The voltage transient data is obtained through the voltage sensor in the PT cabinet of the box transformer, and the current traveling wave data is obtained through the current sensor installed on the grounding wire of the direct grounding box, so that only one sensor is needed to monitor the three-phase cable of the through-line, and the influence on the existing equipment is small, and the method is easy to implement.

[0039] ​​In summary, this invention, by combining the characteristics of each section of a cable through-line being directly grounded at one end and protected grounded at the other end, creatively extracts and utilizes the fault characteristics of the zero-sequence transient voltage of the cable core and the transient current of the sheath, and proposes a method and system for detecting fault sections in through-line based on the electrical quantities of the cable core and sheath, thus saving the time for fault finding in through-line. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings of the present invention are as follows:

[0041] Figure 1 This is a typical wiring diagram of the high-speed railway cable through-line of the present invention;

[0042] Figure 2 This diagram illustrates the method for obtaining the sheath current and core voltage of the high-speed railway cable through-line according to the present invention.

[0043] Figure 3 This is a flowchart of the high-speed railway cable through-line fault section detection method of the present invention;

[0044] Figure 4 This is a block diagram of the high-speed railway cable through-line fault section detection system of the present invention;

[0045] Figure 5 This is a wavelet coefficient diagram of the sheath current energy spectrum and its characteristic frequency band in the non-faulty section (section 2) when the cable through section 5 is faulty in Embodiment 1 of the present invention.

[0046] Figure 6 This is a diagram showing the zero-sequence voltage energy spectrum and wavelet coefficients in the non-faulty section (section 2) when a fault occurs in section 5 of the cable through-line in Embodiment 1 of the present invention.

[0047] Figure 7 This is a wavelet coefficient diagram of the sheath current energy spectrum and its characteristic frequency band when a fault occurs in section 5 of the cable through-line in Embodiment 1 of the present invention.

[0048] Figure 8 This is a diagram of the zero-sequence voltage energy spectrum and wavelet coefficients in the characteristic frequency band of the faulty section (section 5) when a fault occurs in section 5 of the cable through-line in Embodiment 1 of the present invention.

[0049] Figure 9This is a wavelet coefficient diagram of the sheath current energy spectrum and its characteristic frequency band in the non-faulty section (section 7) when the cable through section 5 is faulty in Embodiment 1 of the present invention.

[0050] Figure 10 This is a diagram showing the zero-sequence voltage energy spectrum and wavelet coefficients in the non-faulty section (section 7) when a fault occurs in section 5 of the cable through-line in Embodiment 1 of the present invention.

[0051] Figure 11 This is a wavelet coefficient diagram of the sheath current energy spectrum and its characteristic frequency band in the non-faulty section (section 2) when the cable through section 4 is faulty in Embodiment 2 of the present invention.

[0052] Figure 12 This is a diagram showing the zero-sequence voltage energy spectrum and wavelet coefficients in the non-faulty section (section 2) when a fault occurs in section 4 of the cable through-line in Embodiment 2 of the present invention.

[0053] Figure 13 This is a wavelet coefficient diagram of the sheath current energy spectrum and its characteristic frequency band when a fault occurs in section 4 of the cable through-line in Embodiment 2 of the present invention.

[0054] Figure 14 This is a diagram of the zero-sequence voltage energy spectrum and wavelet coefficients in the characteristic frequency band of the faulty section (section 4) when a fault occurs in section 4 of the cable through-line in Embodiment 2 of the present invention.

[0055] Figure 15 This is a wavelet coefficient diagram of the sheath current energy spectrum and its characteristic frequency band in the non-faulty section (section 7) when the cable through section 4 is faulty in Embodiment 2 of the present invention.

[0056] Figure 16 This is a diagram showing the zero-sequence voltage energy spectrum and wavelet coefficients of the non-faulty section (section 7) under its characteristic frequency band when a fault occurs in section 4 of the cable through-line in Embodiment 2 of the present invention. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] The purpose of this invention is to provide a method and system for detecting fault sections in through-cable cables based on the electrical quantities of the cable core sheath, aiming to solve the problem of fault section detection in through-cable cables. The invention will be further described below with reference to specific embodiments.

[0059] Example 1: This example is based on...Figure 1 The structural diagram shown illustrates a simulation model of a railway cable through-line built using PSCAD electromagnetic transient simulation software. The through-line between substations M and N is 45km long, entirely composed of cables, and divided into 9 segments, each 5km long. The grounding method of the cable through-line sheath and the installation locations of the current sensors are as follows. Figure 2 As shown. The fault is set to occur in section 5, the fault type is a single-phase ground fault of phase A, the transition resistance is 10Ω, and the simulation sampling rate is 20kHz.

[0060] According to such Figure 3 and Figure 4 The method and system for detecting faults in through-line sections based on the electrical quantities of the cable core sheath, as shown, include the following specific steps:

[0061] Step 1: After a fault occurs in the high-speed railway power transmission line, the transient current data of the cable metal sheath in each section is obtained by the sheath current sensor installed in the direct grounding box, and the transient three-phase voltage data of the cable core in each section is obtained by the voltage sensor installed in the transformer box, and the zero-sequence voltage of the cable core is constructed. The data acquisition time window is from 2ms before the fault to 8ms after the fault.

[0062] Step 2: Perform wavelet transform and reconstruction on the transient data of the cable's metallic sheath current (Ix) in each section, calculate the energy of the transient current of the cable sheath in each frequency band, and determine the characteristic frequency band of the current fault according to the principle of maximizing energy. Where x represents the through-line section. In this embodiment, the transient current signal of the cable's metallic sheath in each section is divided into 7 frequency bands, and the energy of the transient current of the cable sheath in each section of the through-line in each frequency band is calculated. (10-5kHz) (5-2.5kHz) (2.5-1.25kHz) (1.25-0.625kHz) (625-312.5Hz) (312.5-156.25Hz) (156.25-78.125Hz). Figure 5 , 7 9 represent the energy spectrum diagrams of the transient currents I2, I5, and I7 of the metal sheath of cables in sections 2, 5, and 7 in each frequency band, and their wavelet reconstruction coefficient waveform diagrams in the fault characteristic frequency band (E6).

[0063] Step 3: Perform wavelet transform and reconstruction on the transient data of zero-sequence voltage (Ux) of cable cores in each section, calculate the energy of zero-sequence voltage of cable cores in each section in each frequency band, and determine the characteristic frequency band of voltage fault according to the principle of maximizing energy. Where x represents the through-line section. In this embodiment, the transient voltage signal of the cable core in each section is divided into 7 frequency bands, and the energy of the transient voltage of the cable core in each section of the through-line in each frequency band is calculated. (10-5kHz) (5-2.5kHz) (2.5-1.25kHz) (1.25-0.625kHz) (625-312.5Hz) (312.5-156.25Hz) (156.25-78.125Hz). Figure 6 , 8 10 represents the energy spectrum of the transient zero-sequence voltages U2, U5, and U7 of the cable core in sections 2, 5, and 7 in each frequency band, and the waveform of their wavelet reconstruction coefficients in the fault characteristic frequency band (E6), respectively.

[0064] Step 4: Perform correlation analysis on the wavelet reconstruction coefficients of the transient data of the cable's metallic sheath current and zero-sequence voltage in each section within their respective fault characteristic frequency bands, and calculate the comprehensive correlation coefficient of the cable in each section. , where x represents the through section. In this embodiment, , , .

[0065] Step 5: Based on the calculation results and the criteria of this invention: Section 2 is a non-faulty section; Section 5 is the faulty section; Section 7 is a non-faulty section. Furthermore, calculations show that: , , , , , According to the criteria provided by this invention, sections 1, 3, 4, 6, 8, and 9 are non-faulty sections. The test results are correct.

[0066] Example 2: This example is based on... Figure 1 The structural diagram shown illustrates a simulation model of a railway cable through-line built using PSCAD electromagnetic transient simulation software. The through-line between substations M and N is 45km long, entirely composed of cables, and divided into 9 segments, each 5km long. The grounding method of the cable through-line sheath and the installation locations of the current sensors are as follows. Figure 2As shown. The fault is set to occur in section 4, the fault type is a single-phase ground fault of phase A, the transition resistance is 1kΩ, and the simulation sampling rate is 20kHz.

[0067] According to such Figure 3 and Figure 4 The method and system for detecting faults in through-line sections based on the electrical quantities of the cable core sheath, as shown, include the following specific steps:

[0068] Step 1: After a fault occurs in the high-speed railway power transmission line, the transient current data of the cable metal sheath in each section is obtained by the sheath current sensor installed in the direct grounding box, and the transient three-phase voltage data of the cable core in each section is obtained by the voltage sensor installed in the transformer box, and the zero-sequence voltage of the cable core is constructed. The data acquisition time window is from 2ms before the fault to 8ms after the fault.

[0069] Step 2: Perform wavelet transform and reconstruction on the transient data of the cable's metallic sheath current (Ix) in each section, calculate the energy of the transient current of the cable sheath in each frequency band, and determine the characteristic frequency band of the current fault according to the principle of maximizing energy. Where x represents the through-line section. In this embodiment, the transient current signal of the cable's metallic sheath in each section is divided into 7 frequency bands, and the energy of the transient current of the cable sheath in each section of the through-line in each frequency band is calculated. (10-5kHz) (5-2.5kHz) (2.5-1.25kHz) (1.25-0.625kHz) (625-312.5Hz) (312.5-156.25Hz) (156.25-78.125Hz). Figure 11 , 13 15 represents the energy spectrum of the transient currents I2, I4, and I7 of the metal sheath of the cable in sections 2, 4, and 7 in each frequency band, and the waveform of the wavelet reconstruction coefficients in the fault characteristic frequency band (E6).

[0070] Step 3: Perform wavelet transform and reconstruction on the transient data of zero-sequence voltage (Ux) of cable cores in each section, calculate the energy of zero-sequence voltage of cable cores in each section in each frequency band, and determine the characteristic frequency band of voltage fault according to the principle of maximizing energy. Where x represents the through-line section. In this embodiment, the transient voltage signal of the cable core in each section is divided into 7 frequency bands, and the energy of the transient voltage of the cable core in each section of the through-line in each frequency band is calculated. (10-5kHz) (5-2.5kHz) (2.5-1.25kHz) (1.25-0.625kHz) (625-312.5Hz) (312.5-156.25Hz) (156.25-78.125Hz). Figure 12 , 14 16 represents the energy spectrum of the transient zero-sequence voltages U2, U5, and U7 of the cable core in sections 2, 4, and 7 in each frequency band, and the waveform of their wavelet reconstruction coefficients in the fault characteristic frequency band (E6), respectively.

[0071] Step 4: Perform correlation analysis on the wavelet reconstruction coefficients of the transient data of the cable's metallic sheath current and zero-sequence voltage in each section within their respective fault characteristic frequency bands, and calculate the comprehensive correlation coefficient of the cable in each section. , where x represents the through section. In this embodiment, , , .

[0072] Step 5: Based on the calculation results and the criteria of this invention: Section 2 is a non-faulty section; Section 4 is the faulty section; Section 7 is a non-faulty section. Furthermore, calculations show that: , , , , , According to the criteria provided by this invention, sections 1, 3, 5, 6, 8, and 9 are non-faulty sections. The test result is correct.

[0073] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for detecting fault sections in a through-line based on electrical quantities of the cable core sheath, characterized in that: Step 1: After a fault occurs in the high-speed railway power transmission line, the sheath current sensor installed in the direct grounding box is used to obtain the transient current data of the metal sheath of the cable in each section, and the voltage sensor installed in the transformer box is used to obtain the transient three-phase voltage data of the cable core in each section and construct the zero-sequence voltage of the cable core. Step 2: Perform wavelet transform and reconstruction on the transient data of the cable's metallic sheath current (Ix) in each section, calculate the energy of the transient current of the cable sheath in each frequency band, and determine the characteristic frequency band α of the current fault according to the principle of maximizing energy. Ix , where x represents the section of the through line; Step 3: Perform wavelet transform and reconstruction on the transient data of zero-sequence voltage (Ux) of cable cores in each section, calculate the energy of zero-sequence voltage of cable cores in each section in each frequency band, and determine the voltage fault characteristic frequency band α according to the principle of maximizing energy. Ux , where x represents the section of the through line; Step 4: Perform correlation analysis on the wavelet reconstruction coefficients of the transient data of the cable's metallic sheath current and zero-sequence voltage in each section within their respective fault characteristic frequency bands, and calculate the correlation coefficient ρ of each cable section. x The calculation method is as follows: Where x is the x-th segment of the cable connection, ρ x Id is the correlation coefficient between the wavelet coefficients of the characteristic frequency band of the cable's metallic sheath current and the wavelet coefficients of the zero-sequence voltage of the cable core in section x. Iαx For the sheath current in section x in the fault characteristic frequency band α I Wavelet reconstruction coefficients within, Ud Uαx The zero-sequence voltage of the cable core in section x is in the fault characteristic frequency band α. U The wavelet reconstruction coefficients within the range, where k is the kth data point, and there are a total of m data points; Step 5: Based on the correlation coefficient ρ x The size determines whether the section is faulty. The determination method is: if ρ x If ρ > 0, then the section is a non-faulty section; if ρ x If the value is less than 0, then the section is a faulty section.

2. The method for detecting fault sections in a through-line based on electrical quantities of the cable core sheath according to claim 1, characterized in that: In Step 1, the sheath current of the three-phase single-core cable flows into the ground through the grounding wire of the grounding box. The cable metal sheath current sensor is installed on the grounding wire of the direct grounding box. Only one sensor is needed to monitor the three-phase cable of the through-line. The zero-sequence voltage of the cable core is constructed from the three-phase voltage in the transformer substation PT cabinet: Ux = U a +U b +U c The time window for sheath current traveling wave and core voltage transient data is from 2ms before the fault to 8ms after the fault.

3. The method for detecting fault sections in a through-line based on electrical quantities of the cable core sheath according to claim 1, characterized in that: In Step 2, the calculation method for the transient current energy of each frequency band of the cable metal sheath in each section is as follows: Where Id(k) is the wavelet reconstruction coefficient of the transient current of the cable metal sheath in each section, k is the kth data point, there are a total of m data points, and j is the frequency band of the sheath transient current. The frequency band corresponding to the maximum energy is the characteristic frequency band α of the sheath current fault. I .

4. The method for detecting fault sections in a through-line based on the electrical quantities of the cable core sheath according to claim 1, characterized in that: In Step 3, the calculation method for the zero-sequence voltage energy of each frequency band of the cable core in each section is as follows: Where Ud(k) is the wavelet reconstruction coefficient of the transient voltage of the cable core in each section, k is the kth data point, there are m data points in total, and j is the frequency band of the sheath transient current. The frequency band corresponding to the maximum energy is the zero-sequence voltage fault characteristic frequency band α. U .

5. A through-line fault detection section system based on electrical quantities of the cable core sheath, characterized in that... The method for detecting fault sections in a through-line based on the electrical quantities of the cable core sheath, as described in any one of claims 1-4, specifically includes: Data acquisition module: Collects transient current data of the metal sheath of cables and three-phase voltage data of the cable core in each section of the railway line; Data processing module: Constructs the three-phase voltage of the cable core of the through-line cable into the zero-sequence voltage of the cable core, performs wavelet decomposition and reconstruction on the metal sheath current data and the zero-sequence voltage data of the cable core in each section, and calculates the correlation coefficient of the wavelet coefficient of the characteristic frequency band of the metal sheath current and the characteristic frequency band of the zero-sequence voltage of the cable core in each section of the through-line cable. It includes a zero-sequence voltage construction unit, a wavelet processing unit, a fault characteristic frequency band judgment unit, and a correlation coefficient calculation unit. Fault Section Detection Module: Based on the data processing results, detects the fault section and outputs the results.

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