A non-destructive testing device and method for insulation defects in submarine cables and their molded joints.

Abstract

This application discloses a non-destructive testing device and method for insulation defects in submarine cables and their molded joints, relating to the field of defect detection. The device includes: a signal transmitting module for transmitting a sinusoidal sweep frequency signal; a data acquisition module connected to the signal transmitting module, the conductor of the submarine cable under test, and the metal shielding layer of the submarine cable under test, for transmitting the sinusoidal sweep frequency signal as an incident signal to the conductor of the submarine cable under test and receiving the reflected signal generated by the submarine cable under test; a data processing module for determining the reflection coefficient spectrum test data of the submarine cable under test based on the incident and reflected signals; and a control module for setting the frequency parameters of the sinusoidal sweep frequency signal, controlling the working state of each module, and plotting a waveform diagram based on the reflection coefficient spectrum test data, and performing defect detection and location on the submarine cable under test based on the waveform diagram. This application can perform non-destructive testing and location of insulation defects in long-length submarine cables and their molded joints.

Description

Technical Field

[0001] This application relates to the field of defect detection, and in particular to a non-destructive testing device and method for insulation defects in submarine cables and their molded joints. Background Technology

[0002] High-voltage submarine cables are crucial for high-capacity, low-loss, and long-distance transoceanic power transmission. Due to manufacturing limitations, the length of a single submarine cable often cannot meet the actual distance requirements for transoceanic connections. Molded joints can connect multiple submarine cables that do not meet the length requirements. While the body insulation and restoring insulation of a molded joint are made of the same insulating material, differences in their manufacturing processes inevitably lead to an interface between them. Interface defects are a potential weakness that can cause damage to the submarine cable system.

[0003] As submarine cables age, their actual service life is far shorter than expected. To ensure the normal operation of the power system, timely detection and accurate location of faults in submarine cables and their molded joints are necessary. However, it is difficult to directly observe insulation defects in long-length submarine cables. Conducting large-scale offshore excavation to find insulation defects would not only significantly increase time and manpower costs but also seriously affect the quality of the submarine cables and the stability of the power system.

[0004] Therefore, developing a non-destructive testing scheme for insulation defects in long-length submarine cables and their molded joints will play an important role in the safe operation of power systems. Summary of the Invention

[0005] The purpose of this application is to provide a non-destructive testing device and method for insulation defects in submarine cables and their molded joints, which can perform non-destructive testing and location of insulation defects in long-length submarine cables and their molded joints.

[0006] To achieve the above objectives, this application provides the following solution:

[0007] In a first aspect, this application provides a non-destructive testing device for insulation defects in submarine cables and their molded joints. The submarine cable includes multiple cable bodies, which are fixedly connected by molded joints. Both the cable bodies and the molded joints include conductors and metal shielding layers. The non-destructive testing device for insulation defects in submarine cables and their molded joints includes:

[0008] The signal transmission module is used to transmit sinusoidal sweep signals;

[0009] The data acquisition module is connected to the signal transmission module, the conductor of the submarine cable under test, and the metal shielding layer of the submarine cable under test, respectively. It is used to transmit the sinusoidal sweep frequency signal as the incident signal to the conductor of the submarine cable under test, and to receive the reflected signal generated by the submarine cable under test.

[0010] A data processing module, connected to the data acquisition module, is used to determine the reflection coefficient spectrum test data of the submarine cable under test based on the incident signal and the reflected signal.

[0011] The control module is connected to the signal transmission module, the data acquisition module, and the data processing module, respectively. It is used to set the frequency parameters of the sinusoidal sweep signal, control the working status of the signal transmission module, the data acquisition module, and the data processing module, and draw a waveform diagram based on the reflection coefficient spectrum test data. Based on the waveform diagram, it performs defect detection and location on the tested submarine cable.

[0012] Furthermore, the frequency parameters of the sinusoidal sweep signal include the frequency step size and the frequency bandwidth;

[0013] The control module determines the frequency step size of the sinusoidal sweep signal based on the total length of the submarine cable under test and the signal propagation speed inside the insulation; and determines the frequency bandwidth of the sinusoidal sweep signal based on the length of the reactive force cone region of a single molded joint and the signal propagation speed inside the insulation.

[0014] Furthermore, the value of the frequency step size satisfies the following formula:

[0015]

[0016] The value of the frequency bandwidth satisfies the following formula:

[0017]

[0018] Where Δf is the frequency step size, l is the total length of the submarine cable under test, v is the signal propagation speed inside the insulation, and f b For frequency bandwidth, l m The length of the reactive force cone region of a single molded joint.

[0019] Furthermore, the reflection coefficient spectrum test data is the real part of the reflection coefficient at the beginning of the submarine cable under test.

[0020] Furthermore, the process by which the control module plots a waveform based on the reflection coefficient spectrum test data includes:

[0021] Perform a discrete inverse Fourier transform on the real part of the first-end reflection coefficient to obtain the time-domain signal of the real part of the preliminary reflection coefficient;

[0022] Establish a frequency domain vector and a distance vector, and determine a signal attenuation compensation function based on the frequency domain vector and the distance vector;

[0023] Perform a discrete inverse Fourier transform on the signal attenuation compensation function to obtain the transformed compensation function;

[0024] The final reflection coefficient real part time domain signal is determined based on the real part of the transformed compensation function and the time domain signal of the real part of the preliminary reflection coefficient.

[0025] A waveform diagram is plotted with the distance vector as the horizontal axis and the amplitude of the real part of the time-domain signal of the final reflection coefficient as the vertical axis.

[0026] Furthermore, the control module performs a discrete inverse Fourier transform on the real part of the head-end reflection coefficient using the following formula:

[0027]

[0028] Where Re(Γ(l)) is the real part of the first-end reflection coefficient, C(n) is the time-domain signal of the real part of the initial reflection coefficient, N is the number of sweep points, e is the natural constant, k is the frequency domain index, k = 0, 1, ..., N-1, n is the time domain index, n = 0, 1, ..., N-1, and j is the imaginary unit.

[0029] Furthermore, the signal attenuation compensation function is:

[0030] d(F(k),2L(m))=e 2α(F(k))2L(m) ;

[0031] Where d(F(k),2L(m)) is the signal attenuation compensation function, F(k) is the frequency domain vector, k is the frequency domain index, k=0,1,…,N-1, N is the number of sweep points, L(m) is the distance vector, m is the distance index, m=0,1,…,N-1, and α is the attenuation coefficient of the submarine cable under test.

[0032] Furthermore, the control module performs a discrete inverse Fourier transform on the signal attenuation compensation function using the following formula:

[0033]

[0034] Where D(n,2L(m)) is the transformed compensation function, n is the time domain index, n=0,1,…,N-1, j is the imaginary unit, e is the natural constant, and j is the imaginary unit.

[0035] Furthermore, the time-domain signal of the real part of the final reflection coefficient is:

[0036] C'(n)=Re(D(0,2L(m)))·*C(n);

[0037] Where C'(n) is the time-domain signal of the real part of the final reflection coefficient, Re(D(0,2L(m))) is the real part of the compensation function when n=0 after transformation, C(n) is the time-domain signal of the real part of the initial reflection coefficient, Re(D(0,2L(m))) and C(n) are both 1-row n-column matrices, and .* indicates that the two matrices are multiplied element by element.

[0038] Secondly, this application provides a non-destructive testing method for insulation defects in submarine cables and their molded joints, using the aforementioned non-destructive testing device for insulation defects in submarine cables and their molded joints. The non-destructive testing method for insulation defects in submarine cables and their molded joints includes:

[0039] Set the frequency parameters of the sinusoidal sweep signal;

[0040] Generate a sinusoidal sweep frequency signal based on frequency parameters;

[0041] The sinusoidal sweep frequency signal is transmitted as an incident signal to the conductor of the submarine cable under test, and the reflected signal generated by the submarine cable under test is received.

[0042] Based on the incident signal and the reflected signal, determine the reflection coefficient spectrum test data of the submarine cable under test;

[0043] A waveform diagram is plotted based on the reflection coefficient spectrum test data, and the defect detection and location of the tested submarine cable are performed based on the waveform diagram.

[0044] According to the specific embodiments provided in this application, this application has the following technical effects:

[0045] This application provides a non-destructive testing device and method for insulation defects in submarine cables and their molded joints. By transmitting a sinusoidal sweep frequency signal to the conductor of the submarine cable under test and receiving the reflected signal generated by the submarine cable under test, the reflection coefficient spectrum test data of the submarine cable under test is determined based on the incident signal and the reflected signal. Furthermore, a waveform diagram is plotted based on the reflection coefficient spectrum test data, thereby realizing non-destructive testing and location of insulation defects in long-length submarine cables and their molded joints. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A schematic diagram of a long submarine cable containing multiple molded joints;

[0048] Figure 2This is a schematic diagram of the structure of a molded joint;

[0049] Figure 3 A schematic diagram of a non-destructive testing device for insulation defects of submarine cables and their molded joints provided in an embodiment of this application;

[0050] Figure 4 A flowchart illustrating a non-destructive testing method for insulation defects in submarine cables and their molded joints, provided as an embodiment of this application;

[0051] Figure 5 This is a flowchart illustrating the process of drawing waveforms for detecting and locating insulation defects in submarine cables, as shown in one embodiment of this application.

[0052] Figure 6 A schematic diagram showing the structure and dimensions of the reactive force cone of a ±500kV high-voltage DC submarine cable molded joint.

[0053] Figure 7 This is a diagram showing the result of defect detection and location in one embodiment of this application.

[0054] Reference numerals: 101-Submarine cable body, 102-Molded connector, 103-Conductor, 104-Conductor shielding layer, 105-Body insulation layer, 106-Insulation shielding layer, 107-Metallic shielding layer, 108-Outer sheath, 201-Insulation interface, 202-Restored insulation area, 203-Reactive force cone, 204-Reactive force cone area, 301-Signal transmission module, 302-Data acquisition module, 303-Data processing module, 304-Control module. Detailed Implementation

[0055] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0056] Regular preventative testing of cables mainly involves measuring insulation resistance, measuring dielectric loss at power frequency or very low frequency, measuring AC leakage current, and performing AC / DC withstand voltage tests. However, these methods have certain limitations: on the one hand, frequent high-electric-field preventative testing may cause irreversible insulation damage to the cable; on the other hand, preventative testing can only determine whether the cable has insulation faults, but cannot determine the location of the insulation defects. The purpose of this application is to provide a non-destructive testing device and method for insulation defects in submarine cables and their molded joints, enabling the detection and location of insulation defects in long-length submarine cables and their molded joints.

[0057] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] In one exemplary embodiment, such as Figure 1 As shown, the submarine cable includes multiple cable bodies 101, which are fixedly connected by molded connectors 102. Both the cable body 101 and the molded connector 102 include a conductor 103 and a metallic shielding layer 107. From the inside out, the cable body 101 consists of a conductor 103, a conductor shielding layer 104, a body insulation layer 105, an insulation shielding layer 106, a metallic shielding layer 107, and an outer sheath 108. Figure 2 As shown, the molded joint 102 has an insulating interface 201, a restoring insulation region 202, a reactive force cone 203, and a reactive force cone region 204.

[0059] In one exemplary embodiment, such as Figure 3 As shown, a non-destructive testing device for insulation defects in submarine cables and their molded joints is provided, comprising: a signal transmission module 301, a data acquisition module 302, a data processing module 303, and a control module 304. The connection relationships and functions of each module are described below.

[0060] (1) Signal transmission module 301 is used to transmit sinusoidal sweep frequency signals.

[0061] In one exemplary embodiment, the signal transmitting module 301 is a sweep frequency signal generator, which is directly connected to the data acquisition module 302 and transmits a sinusoidal sweep frequency signal.

[0062] (2) The data acquisition module 302 is connected to the signal transmission module 301, the conductor 103 of the submarine cable under test and the metal shielding layer 107 of the submarine cable under test respectively. The data acquisition module 302 is used to transmit the sinusoidal sweep frequency signal as the incident signal to the conductor 103 of the submarine cable under test, and to receive the reflected signal generated by the submarine cable under test.

[0063] In an exemplary embodiment, the data acquisition module 302 receives a sinusoidal sweep frequency signal from the signal transmission module 301 and transmits the sinusoidal sweep frequency signal as an incident signal to the conductor 103 of the submarine cable under test; simultaneously, the data acquisition module 302 receives the reflected signal generated after entering the submarine cable under test. The data acquisition module 302 includes a coupler that separates the received incident signal and reflected signal, and transmits the separated incident signal and reflected signal to the data processing module 303.

[0064] (3) The data processing module 303 is connected to the data acquisition module 302. The data processing module 303 is used to determine the reflection coefficient spectrum test data of the submarine cable under test based on the incident signal and the reflected signal.

[0065] In an exemplary embodiment, the data processing module 303 includes an amplitude-phase receiver, which calculates the reflection coefficient spectrum test data of the submarine cable under test by reading the incident signal and the reflected signal, and converts the analog signal of the reflection coefficient spectrum test data into a digital signal through an analog-to-digital converter, and then transmits the reflection coefficient spectrum test data of the submarine cable under test to the control module 304.

[0066] The reflection coefficient spectrum test data represents the real part of the reflection coefficient at the beginning of the submarine cable under test. The real part of the reflection coefficient at the beginning can be calculated from the amplitude and phase of the reflection coefficient at the beginning obtained from the test.

[0067] The ratio of reflected voltage to incident voltage is defined as the reflection coefficient. Considering the open-circuit operation at the end of the submarine cable, the incident signal undergoes total reflection at the end of the submarine cable. When multiple faults exist in the cable, the incident signal is reflected at each fault point, and the reflected signals are all transmitted to the cable head, forming a head reflection coefficient spectrum containing information about the entire cable's operating status. Since the real and imaginary parts of the head reflection coefficient Γ(l) have the same form, differing only by 90° in phase, and both can reflect the transmission characteristics of the cable transmission line, only the real part Re(Γ(l)) of the head reflection coefficient needs to be analyzed.

[0068] (4) The control module 304 is connected to the signal transmission module 301, the data acquisition module 302 and the data processing module 303 respectively. The control module 304 is used to set the frequency parameters of the sinusoidal sweep signal, control the working status of the signal transmission module 301, the data acquisition module 302 and the data processing module 303, and draw a waveform diagram based on the reflection coefficient spectrum test data. Based on the waveform diagram, the test submarine cable is used for defect detection and location.

[0069] In one exemplary embodiment, the controller is a computer. The frequency parameters of the sinusoidal sweep signal include the frequency step size and the frequency bandwidth. The amplitude of the sinusoidal sweep signal does not exceed 10V. The frequency bandwidth f b =f max -f min f max For the highest frequency, f min For the lowest frequency, f max =f min +(N-1)×Δf, where N is the number of sweep points. Frequency bandwidth f b The determination of the frequency step size Δf needs to take into account the actual measurable length and the measurement accuracy.

[0070] The control module 304 determines the frequency step size of the sinusoidal sweep signal based on the total length of the submarine cable under test and the signal propagation speed inside the insulation; and determines the frequency bandwidth of the sinusoidal sweep signal based on the length of the reactive force cone region of a single molded joint and the signal propagation speed inside the insulation.

[0071] The actual measurable length must be greater than or equal to the total length of the submarine cable being measured.

[0072]

[0073] Among them, S real Where l is the actual measurable length, v is the total length of the submarine cable being measured, and ν is the signal propagation speed inside the insulation, i.e., the wave speed of the electromagnetic signal in the submarine cable being measured. c0 is the wave speed of electromagnetic waves in vacuum, μ r ε is the relative permeability of the insulation of the submarine cable. r is the relative permittivity of the submarine cable insulation.

[0074] That is, the value of the frequency step size satisfies the following formula:

[0075]

[0076] The actual measurement accuracy is determined by calculating the number of sampling points (N effective points) within the total length l of the submarine cable being measured. s ) indicates. N s This can represent the number of measurement points along the entire submarine cable line. The time resolution Δt represents the smallest distinguishable time interval on the time axis. Multiplying the time resolution by the signal propagation speed v inside the insulation gives the spatial resolution for locating local defects in the submarine cable, i.e.:

[0077] Furthermore, based on the time resolution Δt and frequency bandwidth f b Relationship: Determine the number of valid points N s for

[0078] Based on the number of valid points N s Determine the measurement accuracy; measurement accuracy is related to frequency bandwidth f. b Based on the specific number of detection points required in the reactive force cone region of the molded joint, the frequency bandwidth f can be determined. b The range is determined, thereby determining the overall accuracy.

[0079] Based on this, to ensure the accuracy of internal defect detection in the molded joint 102, at least two detection points are present in the reactive force cone region of the molded joint. The detection points are determined according to the length l of the reactive force cone region of a single molded joint. mThen the time resolution satisfies:

[0080] The frequency bandwidth range can be determined as follows: Valid points N s The scope is:

[0081] In addition, the control module 304 can further control the operating status of the signal transmission module 301, the data acquisition module 302, and the data processing module 303.

[0082] In an exemplary embodiment, the process by which the control module 304 plots a waveform based on the reflection coefficient spectrum test data includes the following steps 201 to 205.

[0083] Step 201: Perform a discrete inverse Fourier transform on the real part of the first-end reflection coefficient to obtain the time-domain signal of the preliminary real part of the reflection coefficient.

[0084]

[0085] Where C(n) is the time-domain signal of the real part of the initial reflection coefficient, e is the natural constant, k is the frequency domain index, k = 0, 1, ..., N-1, n is the time domain index, n = 0, 1, ..., N-1, and j is the imaginary unit.

[0086] Step 202: Establish a frequency domain vector and a distance vector, and determine a signal attenuation compensation function based on the frequency domain vector and the distance vector.

[0087] This application establishes a frequency domain vector F(k), a time vector T(n), and a distance vector L(m):

[0088] F(k)=[f min ,f min +Δf,...,f min +(N-1)Δf].

[0089] T(n)=[0,Δt,...,(N-1)Δt].

[0090] L(m)=[0,0.5·vΔt,...,0.5·(N-1)vΔt].

[0091] Electromagnetic wave signals experience signal attenuation during transmission within the insulation of submarine cables, especially for long submarine cable lines spanning hundreds of kilometers. The degree of signal attenuation increases with the transmission distance. The attenuation coefficient α increases with the frequency f. By measuring the attenuation coefficient α, a function α(f) is fitted to show the change of the attenuation coefficient α with frequency f.

[0092] Define the signal attenuation compensation function d(F(k),2L(m)):

[0093] d(F(k),2L(m))=e 2α(F(k))2L(m) ;

[0094] Where k is the frequency domain index, k = 0, 1, ..., N-1, L(m) is the distance vector, m is the distance index, m = 0, 1, ..., N-1, and α is the attenuation coefficient of the submarine cable under test.

[0095] Step 203: Perform a discrete inverse Fourier transform on the signal attenuation compensation function to obtain the transformed compensation function:

[0096]

[0097] Where D(n,2L(m)) is the transformed compensation function, n is the time-domain index, n=0,1,…,N-1, and e is the natural constant.

[0098] Step 204: Determine the time-domain signal of the real part of the final reflection coefficient based on the real part of the transformed compensation function and the time-domain signal of the real part of the preliminary reflection coefficient.

[0099] Taking n = 0, the real part Re(D(0,2L(m))) of the transformed compensation function is combined with the time-domain signal C(n) of the real part of the initial reflection coefficient to obtain the time-domain signal of the real part of the final reflection coefficient:

[0100] C'(n)=Re(D(0,2L(m)))·*C(n);

[0101] Where C'(n) is the time-domain signal of the real part of the final reflection coefficient, Re(D(0,2L(m))) is the real part of the compensation function when n=0 after transformation, C(n) is the time-domain signal of the real part of the initial reflection coefficient, Re(D(0,2L(m))) and C(n) are both 1-row n-column matrices, and .* indicates that the two matrices are multiplied element by element.

[0102] Step 205: Plot a waveform diagram with the distance vector as the horizontal axis and the amplitude of the real part of the time-domain signal of the final reflection coefficient as the vertical axis.

[0103] Furthermore, according to the waveform diagram, when a peak appears at the x-axis in the time domain spectrum, it indicates that an insulation defect has occurred at the x-axis of the submarine cable under test; when no peak appears in the time domain spectrum, it indicates that no insulation defect has occurred in the submarine cable under test.

[0104] In another exemplary embodiment, based on the above-described non-destructive testing device for insulation defects in submarine cables and their molded joints, a method for non-destructive testing of insulation defects in submarine cables and their molded joints is provided, such as... Figure 4As shown, the process includes steps 401 to 405.

[0105] Step 401: Set the frequency parameters of the sinusoidal sweep signal. The frequency parameters of the sinusoidal sweep signal are set via control module 304. Then, the signal transmission module 301, data acquisition module 302, and data processing module 303 are activated.

[0106] Step 402: Generate a sinusoidal sweep signal based on the frequency parameters.

[0107] Step 403: The sinusoidal sweep frequency signal is transmitted as an incident signal to the conductor 103 of the submarine cable under test, and the reflected signal generated by the submarine cable under test is received. The data acquisition module 302 separates the received incident signal and reflected signal through a coupler, and transmits the separated incident signal and reflected signal to the data processing module 303.

[0108] Step 404: Determine the reflection coefficient spectrum test data of the submarine cable under test based on the incident signal and the reflected signal. The data processing module 303 reads the incident signal and the reflected signal to obtain the reflection coefficient test data corresponding to different frequency points within a wide frequency band; then the data processing module 303 transmits the reflection coefficient spectrum test data of the submarine cable under test to the control module 304.

[0109] Step 405: A waveform diagram is plotted based on the reflection coefficient spectrum test data, and defect detection and location are performed on the tested submarine cable based on the waveform diagram. The control module 304 calculates the reflection coefficient spectrum test data and plots the waveform diagram for submarine cable insulation defect detection and location. The specific process is as follows: Figure 5 As shown,

[0110] The following is a specific example:

[0111] Taking a 500kV high-voltage submarine cable line as an example, with a length of l = 25km, the length of the reaction cone region 204 of the molded joint 102 is l. m =150mm, the overall length of the molded connector 102 insulation is 600mm, the structure and dimensions are as follows Figure 6 As shown. It is known that the location of the molded joint 102 is approximately 10 km and 16 km away.

[0112] The signal propagation speed v inside the insulation is 1.695 × 10⁻⁶. 8 m / s; Due to the length limitation of the submarine cable line, the frequency step Δf ≤ 1.695 × 10 3 Hz; The frequency bandwidth f is calculated based on the length of the reactive force cone region 204 of the molded joint 102. b≥2260MHz; Measure the attenuation coefficient α and fit a function α(f)=k·f for the attenuation coefficient α as a function of frequency f, where k is 2.5×10 -11 .

[0113] The incident signal is a sinusoidal swept-frequency signal with a maximum frequency f. max =2261MHz, lowest frequency f min =1MHz, frequency step size Δf =1.5×10 3 Hz, frequency bandwidth f b =2260MHz, which meets the requirements.

[0114] The inverse Fourier transform of the frequency domain data of the reflection coefficient yields the time domain data, including calculating the real part of the reflection coefficient, performing a discrete inverse Fourier transform on the real part of the reflection coefficient, and signal attenuation compensation; the final result is as follows. Figure 7 As shown. Analysis reveals a significant defect in both molded connectors 102 of the measured circuit.

[0115] The above examples have verified the effectiveness of the incident signal parameter setting basis and the frequency domain data processing method for reflection coefficient proposed in this application.

[0116] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0117] In this application, all actions to acquire signals, information, or data are carried out in compliance with the relevant data protection laws and policies of the country where the location is situated, and with the authorization granted by the owner of the relevant device.

[0118] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0119] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0120] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0121] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A non-destructive testing device for insulation defects in submarine cables and their molded joints, wherein the submarine cable comprises multiple cable bodies, which are fixedly connected by molded joints, and both the cable bodies and the molded joints include a conductor and a metal shielding layer, characterized in that... The non-destructive testing device for insulation defects in submarine cables and their molded joints includes: The signal transmission module is used to transmit sinusoidal sweep signals; The data acquisition module is connected to the signal transmission module, the conductor of the submarine cable under test, and the metal shielding layer of the submarine cable under test, respectively. It is used to transmit the sinusoidal sweep frequency signal as the incident signal to the conductor of the submarine cable under test, and to receive the reflected signal generated by the submarine cable under test. A data processing module, connected to the data acquisition module, is used to determine the reflection coefficient spectrum test data of the submarine cable under test based on the incident signal and the reflected signal. A control module, connected to the signal transmission module, the data acquisition module, and the data processing module, is used to set the frequency parameters of the sinusoidal sweep signal, control the working states of the signal transmission module, the data acquisition module, and the data processing module, and plot a waveform based on the reflection coefficient spectrum test data. Based on the waveform, defects in the tested submarine cable are detected and located. The reflection coefficient spectrum test data represents the real part of the reflection coefficient at the beginning of the tested submarine cable. The process by which the control module plots a waveform based on the reflection coefficient spectrum test data includes: Perform a discrete inverse Fourier transform on the real part of the first-end reflection coefficient to obtain the time-domain signal of the real part of the preliminary reflection coefficient; Establish a frequency domain vector and a distance vector, and determine the signal attenuation compensation function based on the frequency domain vector and the distance vector: d(F(k),2L(m))=e 2α (F(k)) 2L(m) Where d(F(k),2L(m)) is the signal attenuation compensation function, F(k) is the frequency domain vector, k is the frequency domain index, k = 0, 1, ..., N-1, N is the number of sweep points, L(m) is the distance vector, m is the distance index, m = 0, 1, ..., N-1, and α is the attenuation coefficient of the submarine cable under test. The signal attenuation compensation function is subjected to a discrete inverse Fourier transform to obtain the transformed compensation function. The final reflection coefficient real part time domain signal is determined based on the real part of the transformed compensation function and the time domain signal of the real part of the preliminary reflection coefficient. A waveform diagram is plotted with the distance vector as the horizontal axis and the amplitude of the real part of the time-domain signal of the final reflection coefficient as the vertical axis.

2. The non-destructive testing device for insulation defects of submarine cables and their molded joints according to claim 1, characterized in that, The frequency parameters of the sinusoidal sweep signal include the frequency step size and the frequency bandwidth. The control module determines the frequency step size of the sinusoidal sweep signal based on the total length of the submarine cable under test and the signal propagation speed inside the insulation; and determines the frequency bandwidth of the sinusoidal sweep signal based on the length of the reactive force cone region of a single molded joint and the signal propagation speed inside the insulation.

3. The non-destructive testing device for insulation defects of submarine cables and their molded joints according to claim 2, characterized in that, The value of the frequency step size satisfies the following formula: The value of the frequency bandwidth satisfies the following formula: Where Δf is the frequency step size, l is the total length of the submarine cable under test, v is the signal propagation speed inside the insulation, and f b For frequency bandwidth, l m The length of the reactive force cone region of a single molded joint.

4. The non-destructive testing device for insulation defects of submarine cables and their molded joints according to claim 1, characterized in that, The control module uses the following formula to perform a discrete inverse Fourier transform on the real part of the head reflection coefficient: Where Re(Γ(l)) is the real part of the first-end reflection coefficient, C(n) is the time-domain signal of the real part of the initial reflection coefficient, N is the number of sweep points, e is the natural constant, k is the frequency domain index, k = 0, 1, ..., N-1, n is the time domain index, n = 0, 1, ..., N-1, and j is the imaginary unit.

5. The non-destructive testing device for insulation defects of submarine cables and their molded joints according to claim 1, characterized in that, The control module uses the following formula to perform a discrete inverse Fourier transform on the signal attenuation compensation function: Where D(n,2L(m)) is the transformed compensation function, n is the time domain index, n=0,1,…,N-1, j is the imaginary unit, e is the natural constant, and j is the imaginary unit.

6. The non-destructive testing device for insulation defects of submarine cables and their molded joints according to claim 5, characterized in that, The time-domain signal of the real part of the final reflection coefficient is: C'(n)=Re(D(0,2L(m)))·*C(n); Where C'(n) is the time-domain signal of the real part of the final reflection coefficient, Re(D(0,2L(m))) is the real part of the compensation function when n=0 after transformation, C(n) is the time-domain signal of the real part of the initial reflection coefficient, Re(D(0,2L(m))) and C(n) are both 1-row n-column matrices, and .* indicates that the two matrices are multiplied element by element.

7. A method for non-destructive testing of insulation defects in submarine cables and their molded joints, using the non-destructive testing device for insulation defects in submarine cables and their molded joints as described in any one of claims 1-6, characterized in that, The non-destructive testing method for insulation defects in submarine cables and their molded joints includes: Set the frequency parameters of the sinusoidal sweep signal; Generate a sinusoidal sweep frequency signal based on frequency parameters; The sinusoidal sweep frequency signal is transmitted as an incident signal to the conductor of the submarine cable under test, and the reflected signal generated by the submarine cable under test is received. Based on the incident signal and the reflected signal, determine the reflection coefficient spectrum test data of the submarine cable under test; A waveform diagram is plotted based on the reflection coefficient spectrum test data, and the defect detection and location of the tested submarine cable are performed based on the waveform diagram.

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