Nondestructive testing device and method for insulation defects of submarine cable and molded joint of submarine cable

Abstract

The invention discloses an insulation defect nondestructive testing device and method for a submarine cable and a molded joint of the submarine cable, and relates to the field of defect detection, and the device comprises a signal transmitting module which is used for transmitting a sine frequency sweeping signal; the data acquisition module is respectively connected with the signal transmitting module, a conductor of the detected submarine cable and a metal shielding layer of the detected submarine cable, and is used for transmitting the sine sweep frequency signal to the conductor of the detected submarine cable as an incident signal and receiving a reflected signal generated by the detected submarine cable; the data processing module is used for determining reflection coefficient spectrum test data of the tested submarine cable according to the incident signal and the reflection signal; and the control module is used for setting frequency parameters of the sine sweep frequency signals, controlling the working state of each module, drawing an oscillogram according to the reflection coefficient spectrum test data, and carrying out defect detection and positioning on the detected submarine cable based on the oscillogram. According to the invention, nondestructive testing and positioning can be carried out on insulation defects of a large-length submarine cable and a molded joint thereof.

Description

Technical Field

[0001] The present application relates to the field of defect detection, and in particular to a device and method for nondestructive detection of insulation defects of submarine cables and molded joints thereof. Background Art

[0002] High-voltage submarine cables are essential for high-capacity, low-loss, and long-distance cross-sea power transmission. Limited by the production process, the length of a single submarine cable often cannot meet the actual distance requirements of cross-sea connections. Molded joints can connect multiple submarine cables that do not meet the length requirements. The main insulation and recovery insulation of the molded joint are made of the same insulating material, but due to the difference in the preparation process of the two, an interface is inevitably formed between the two. Interface defects are potential weaknesses that cause damage to the submarine cable system.

[0003] As the operating life of submarine cables increases, the actual operating life of submarine cables is much shorter than the expected life. In order to ensure the normal operation of the power system, it is necessary to detect and accurately locate the faults of submarine cables and their molded joints in a timely manner. It is difficult to directly observe the insulation defects of actual long-length submarine cables. If large-scale offshore excavation work is carried out to find insulation defects, it will not only greatly increase the time and labor costs, but also seriously affect the quality of submarine cables and the stability of the power system.

[0004] Therefore, considering a nondestructive detection scheme for insulation defects of 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 the present application is to provide a device and method for nondestructive detection of insulation defects of submarine cables and their molded joints, which can perform nondestructive detection and positioning of insulation defects of long-length submarine cables and their molded joints.

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

[0007] In a first aspect, the present application provides a submarine cable and a molded joint insulation defect nondestructive detection device thereof, wherein the submarine cable comprises a plurality of submarine cable bodies, the plurality of submarine cable bodies are fixedly connected by a molded joint, the submarine cable bodies and the molded joint both comprise a conductor and a metal shielding layer, and the submarine cable and the molded joint insulation defect nondestructive detection device thereof comprises:

[0008] A signal transmitting module, used for transmitting a sine frequency sweep signal;

[0009] 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, respectively, for transmitting the sinusoidal frequency sweep signal as an incident signal to the conductor of the submarine cable under test, and receiving a reflected signal generated by the submarine cable under test;

[0010] A data processing module, connected to the data acquisition module, for determining the reflection coefficient spectrum test data of the submarine cable under test according to the incident signal and the reflected signal;

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

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

[0013] The control module determines the frequency step of the sinusoidal swept frequency signal according to 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 swept frequency signal according to the length of the reaction force cone area of ​​a single molded joint and the signal propagation speed inside the insulation.

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

[0015]

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

[0017]

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

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

[0020] Furthermore, the process of the control module drawing a waveform diagram according to the reflection coefficient spectrum test data includes:

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

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

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

[0024] Determine a final reflection coefficient real part time domain signal according to the real part of the transformed compensation function and the preliminary reflection coefficient real part time domain signal;

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

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

[0027]

[0028] Wherein, Re(Γ(l)) is the real part of the headend reflection coefficient, C(n) is the time domain signal of the real part of the preliminary reflection coefficient, N is the number of frequency sweep points, e is a 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 an imaginary unit.

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

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

[0031] Wherein, 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 frequency 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 uses the following formula to perform a discrete Fourier inverse transform on the signal attenuation compensation function:

[0033]

[0034] Wherein, 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 final reflection coefficient real part time domain signal is:

[0036] C'(n)=Re(D(0,2L(m)))·*C(n);

[0037] Among them, C'(n) is the real part time domain signal 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 real part time domain signal of the preliminary reflection coefficient, Re(D(0,2L(m))) and C(n) are both matrices with 1 row and n columns, and .* indicates the element-by-element multiplication of the two matrices.

[0038] In a second aspect, the present application provides a method for nondestructive detection of insulation defects of a submarine cable and a molded joint thereof, using the above-mentioned nondestructive detection device for insulation defects of a submarine cable and a molded joint thereof, and the method for nondestructive detection of insulation defects of a submarine cable and a molded joint thereof comprises:

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

[0040] generating a sine sweep signal based on a frequency parameter;

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

[0042] Determining reflection coefficient spectrum test data of the submarine cable under test according to the incident signal and the reflected signal;

[0043] A waveform diagram is drawn according to the reflection coefficient spectrum test data, and defect detection and positioning 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] The present application provides a device and method for nondestructive detection of insulation defects of submarine cables and molded joints thereof, which transmits a sinusoidal frequency sweep signal to the conductor of the submarine cable under test and receives a reflection signal generated by the submarine cable under test, determines reflection coefficient spectrum test data of the submarine cable under test according to the incident signal and the reflection signal, and further draws a waveform diagram according to the reflection coefficient spectrum test data, thereby realizing nondestructive detection and positioning of insulation defects of long-length submarine cables and molded joints thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 A schematic diagram of the structure of a long length submarine cable including a multi-molded plastic connector;

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

[0049] Figure 3 A schematic diagram of a nondestructive detection device for insulation defects of a submarine cable and its molded joint provided in one embodiment of the present application;

[0050] Figure 4 A schematic flow chart of a method for nondestructive testing insulation defects of a submarine cable and its molded joint provided in one embodiment of the present application;

[0051] Figure 5 A schematic diagram of a process for drawing a submarine cable insulation defect detection and positioning waveform diagram in one embodiment of the present application;

[0052] Figure 6 The schematic diagram of the reaction force cone structure and dimensions of the ±500kV high voltage DC submarine cable molded joint;

[0053] Figure 7 This is a diagram showing the results of defect detection and positioning in one embodiment of the present application.

[0054] Figure numerals: 101-submarine cable body, 102-molded joint, 103-conductor, 104-conductor shielding layer, 105-body insulation layer, 106-insulation shielding layer, 107-metal shielding layer, 108-outer sheath, 201-insulation interface, 202-insulation recovery area, 203-reaction force cone, 204-reaction force cone area, 301-signal transmission module, 302-data acquisition module, 303-data processing module, 304-control module. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0056] The preventive tests carried out on cables on a regular basis mainly include measuring insulation resistance, measuring power frequency or extremely low frequency dielectric loss, measuring AC leakage current and AC / DC withstand voltage tests, but these methods have certain limitations: on the one hand, frequent preventive tests with high electric fields may cause irreversible insulation damage to the cable; on the other hand, preventive tests can only determine whether there is an insulation fault problem in the cable, but cannot determine the location of the insulation defect. The purpose of this application is to provide a non-destructive detection device and method for insulation defects of submarine cables and their molded joints, so as to realize the detection and positioning of insulation defects of long-length submarine cables and their molded joints.

[0057] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0058] In an exemplary embodiment, Figure 1 As shown, the submarine cable includes a plurality of submarine cable bodies 101, and the plurality of submarine cable bodies 101 are fixedly connected by a molded joint 102. The submarine cable body 101 and the molded joint 102 both include a conductor 103 and a metal shielding layer 107. From the inside to the outside, the submarine cable body 101 includes a conductor 103, a conductor shielding layer 104, a body insulation layer 105, an insulation shielding layer 106, a metal shielding layer 107 and an outer sheath 108. Figure 2 As shown, the molded joint 102 has an insulating interface 201 , an insulating recovery region 202 , a reaction force cone 203 , and a reaction force cone region 204 .

[0059] In an exemplary embodiment, Figure 3 As shown, a nondestructive detection device for insulation defects of submarine cables and molded joints thereof is provided, comprising: a signal transmitting module 301, a data acquisition module 302, a data processing module 303 and a control module 304. The connection relationship and function of each module are respectively introduced below.

[0060] (1) The signal transmitting module 301 is used to transmit a sine frequency sweep signal.

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

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

[0063] In an exemplary embodiment, the data acquisition module 302 receives the sine frequency sweep signal from the signal transmission module 301, and transmits the sine frequency sweep signal as an incident signal to the conductor 103 of the submarine cable under test; at the same time, 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, which separates the received incident signal and the reflected signal, and transmits the separated incident signal and the reflected signal to the data processing module 303.

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

[0065] In an exemplary embodiment, the data processing module 303 includes an amplitude and 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 is the real part of the head end reflection coefficient of the submarine cable under test. The real part of the head end reflection coefficient can be calculated by the amplitude and phase of the head end reflection coefficient obtained by the test.

[0067] The ratio of the reflected voltage to the incident voltage is defined as the reflection coefficient. Considering the open-circuit operation state at the end of the submarine cable, the incident signal is totally reflected at the end of the submarine cable. When there are multiple faults in the cable, the incident signal is reflected at each fault point, and the reflected signals are transmitted to the head end of the cable, forming a head end reflection coefficient spectrum containing the operation status information of the entire cable. Since the real and imaginary parts of the head end reflection coefficient Γ(l) are in the same form, with only a 90° phase difference, they can both reflect the transmission characteristics of the cable transmission line, so only the real part Re(Γ(l)) of the head end 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 frequency sweep signal, control the working states of the signal transmission module 301, the data acquisition module 302 and the data processing module 303, draw a waveform diagram according to the reflection coefficient spectrum test data, and perform defect detection and positioning on the submarine cable under test based on the waveform diagram.

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

[0070] The control module 304 determines the frequency step of the sinusoidal swept frequency signal according to 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 swept frequency signal according to the length of the reaction force cone area 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 is the actual measurable length, l is the total length of the submarine cable being measured, v is the propagation speed of the signal inside the insulation, that is, the wave speed of the electromagnetic wave signal in the submarine cable being measured, c 0 is the speed of electromagnetic waves in vacuum, μ r is the relative magnetic permeability of submarine cable insulation, ε r is the relative dielectric constant of submarine cable insulation.

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

[0075]

[0076] The actual measurement accuracy is calculated by calculating the number of sampling points within the total length l of the submarine cable being measured (the number of effective points N s ) indicates. s It can represent the number of measurement points on the entire line of the submarine cable. The time resolution Δt represents the minimum time interval that can be distinguished on the time axis. The time resolution multiplied by the propagation speed v of the signal inside the insulation is the spatial resolution of the local defect location of the submarine cable, that is:

[0077] According to the time resolution Δt and frequency bandwidth f b Relationship: Determine the number of valid points N s for

[0078] According to the number of valid points N s Determine the measurement accuracy, measurement accuracy and frequency bandwidth f b According to the specific number of test points required for the reaction force cone area of ​​the molded joint, the frequency bandwidth f can be determined b range, thereby determining the overall accuracy.

[0079] On this basis, in order to ensure the accuracy of the internal defect detection of the molded joint 102, there are at least two detection points in the reaction force cone area of ​​the molded joint.m , then the time resolution satisfies:

[0080] It can be concluded that the frequency bandwidth range is: Valid points N s The range is:

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

[0082] In an exemplary embodiment, the process of the control module 304 drawing a waveform diagram according to the reflection coefficient spectrum test data includes the following steps 201 to 205 .

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

[0084]

[0085] Wherein, C(n) is the real time domain signal of the preliminary reflection coefficient, e is a natural constant, k is a frequency domain index, k=0,1,…,N-1, n is a time domain index, n=0,1,…,N-1, and j is an 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 the frequency domain vector F(k), time vector T(n) and 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] There is a phenomenon of signal attenuation during the transmission of electromagnetic wave signals inside the insulation of submarine cables, especially for long-length submarine cable lines spanning hundreds of kilometers; the degree of signal attenuation increases with the increase of transmission distance; the attenuation coefficient α increases with the increase of frequency f; by measuring the attenuation coefficient α, and fitting the function α(f) of the attenuation coefficient α changing with the 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] Wherein, 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, performing a discrete Fourier inverse transform on the signal attenuation compensation function to obtain a transformed compensation function:

[0096]

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

[0098] Step 204: determine a final reflection coefficient real part time domain signal according to the real part of the transformed compensation function and the preliminary reflection coefficient real part time domain signal.

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

[0100] C'(n)=Re(D(0,2L(m)))·*C(n);

[0101] Among them, C'(n) is the real part time domain signal 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 real part time domain signal of the preliminary reflection coefficient, Re(D(0,2L(m))) and C(n) are both matrices with 1 row and n columns, and .* indicates the element-by-element multiplication of the two matrices.

[0102] Step 205 , drawing a waveform graph with the distance vector as the horizontal coordinate and the amplitude of the real part time domain signal of the final reflection coefficient as the vertical coordinate.

[0103] Further, according to the waveform diagram, when a peak appears at the horizontal coordinate x in the time domain spectrum, it indicates that an insulation defect occurs at the position x of the submarine cable under test; when no peak appears at the horizontal coordinate x in the time domain spectrum, no insulation defect occurs in the submarine cable under test.

[0104] In another exemplary embodiment, based on the above-mentioned nondestructive detection device for insulation defects of submarine cables and molded joints thereof, a nondestructive detection method for insulation defects of submarine cables and molded joints thereof is provided, such as Figure 4As shown, the process includes the following steps 401 to 405.

[0105] Step 401, setting the frequency parameters of the sine frequency sweep signal. The frequency parameters of the sine frequency sweep signal are set by the control module 304. Then, the signal transmission module 301, the data acquisition module 302 and the data processing module 303 are turned on.

[0106] Step 402: Generate a sine frequency sweep signal based on a frequency parameter.

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

[0108] Step 404, based on the incident signal and the reflected signal, the reflection coefficient spectrum test data of the submarine cable under test is determined. The incident signal and the reflected signal are read by the data processing module 303 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: Draw a waveform diagram according to the reflection coefficient spectrum test data, and perform defect detection and positioning on the submarine cable under test based on the waveform diagram. The control module 304 calculates the reflection coefficient spectrum test data and draws a waveform diagram for detecting and positioning submarine cable insulation defects. The specific process is as follows: Figure 5 As shown,

[0110] A specific example is provided below:

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

[0112] The signal propagation speed v inside the insulation is 1.695×10 8 m / s; According to the length limit 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 reaction force cone region 204 of the molded joint 102 b≥2260MHz; measure the attenuation coefficient α and fit the function of the attenuation coefficient α changing with the frequency f α(f)=k·f, where k is 2.5×10 -11 .

[0113] The incident signal is a sine sweep signal with a maximum frequency of f max =2261MHz, minimum frequency f min =1MHz, frequency step Δf=1.5×10 3 Hz, frequency bandwidth f b =2260MHz, meets the requirements.

[0114] The frequency domain data of the reflection coefficient are inversely transformed by Fourier transform to obtain the time domain data, including calculating the real part of the reflection coefficient, performing discrete Fourier inverse transform on the real part of the reflection coefficient and signal attenuation compensation; the final result is as follows Figure 7 As shown, analysis shows that there is a significant defect at both molded joints 102 of the measured circuit.

[0115] The above examples verify the effectiveness of the incident signal parameter setting basis and the reflection coefficient frequency domain data processing method 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, stored data, displayed data, 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 relevant data must comply with relevant regulations.

[0117] In this application, all actions to obtain signals, information or data are carried out in compliance with the relevant data protection laws and policies of the country where they are located and with the authorization given by the owner of the corresponding device.

[0118] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present 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 may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0119] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0120] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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 article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A nondestructive detection device for insulation defects of a submarine cable and its molded joint, wherein the submarine cable comprises a plurality of submarine cable bodies, the plurality of submarine cable bodies are fixedly connected by a molded joint, the submarine cable bodies and the molded joint both comprise a conductor and a metal shielding layer, and the device is characterized in that: The nondestructive detection device for insulation defects of submarine cables and molded joints thereof comprises: A signal transmitting module, used for transmitting a sine frequency sweep 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, respectively, for transmitting the sinusoidal frequency sweep signal as an incident signal to the conductor of the submarine cable under test, and receiving a reflected signal generated by the submarine cable under test; A data processing module, connected to the data acquisition module, for determining the reflection coefficient spectrum test data of the submarine cable under test according to the incident signal and the reflected signal; The control module is connected to the signal transmission module, the data acquisition module and the data processing module respectively, and is used to set the frequency parameters of the sinusoidal frequency sweep signal, control the working states of the signal transmission module, the data acquisition module and the data processing module, draw a waveform diagram according to the reflection coefficient spectrum test data, and perform defect detection and positioning on the tested submarine cable based on the waveform diagram.

2. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 1 is characterized in that: The frequency parameters of the sine frequency sweep signal include frequency step length and frequency bandwidth; The control module determines the frequency step of the sinusoidal swept frequency signal according to 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 swept frequency signal according to the length of the reaction force cone area of ​​a single molded joint and the signal propagation speed inside the insulation.

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

4. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 1, characterized in that: The reflection coefficient spectrum test data is the real part of the reflection coefficient of the head end of the submarine cable under test.

5. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 4 is characterized in that: The process of the control module drawing a waveform diagram according to the reflection coefficient spectrum test data includes: Performing a discrete Fourier inverse transform on the real part of the head-end reflection coefficient to obtain a preliminary real part time domain signal of the reflection coefficient; Establishing a frequency domain vector and a distance vector, and determining a signal attenuation compensation function based on the frequency domain vector and the distance vector; Performing a discrete Fourier inverse transform on the signal attenuation compensation function to obtain a transformed compensation function; Determine a final reflection coefficient real part time domain signal according to the real part of the transformed compensation function and the preliminary reflection coefficient real part time domain signal; A waveform diagram is drawn with the distance vector as the horizontal coordinate and the amplitude of the real part time domain signal of the final reflection coefficient as the vertical coordinate.

6. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 5, characterized in that: The control module performs a discrete Fourier inverse transform on the real part of the head-end reflection coefficient using the following formula: Wherein, Re(Γ(l)) is the real part of the headend reflection coefficient, C(n) is the time domain signal of the real part of the preliminary reflection coefficient, N is the number of frequency sweep points, e is a 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 an imaginary unit.

7. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 5, characterized in that: The signal attenuation compensation function is: d(F(k),2L(m))=e 2α (F(k)) 2L(m) ; Wherein, 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 frequency 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.

8. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 7, characterized in that: The control module uses the following formula to perform a discrete Fourier inverse transform on the signal attenuation compensation function: Wherein, 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.

9. The nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to claim 8, characterized in that: The final reflection coefficient real part time domain signal is: C'(n)=Re(D(0,2L(m)))·*C(n); Among them, C'(n) is the real part time domain signal 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 real part time domain signal of the preliminary reflection coefficient, Re(D(0,2L(m))) and C(n) are both matrices with 1 row and n columns, and .* indicates the element-by-element multiplication of the two matrices.

10. A method for nondestructive testing insulation defects of submarine cables and molded joints thereof, using the nondestructive testing device for insulation defects of submarine cables and molded joints thereof according to any one of claims 1 to 9, characterized in that: The nondestructive detection method for insulation defects of submarine cables and molded joints thereof comprises: Set the frequency parameters of the sine sweep signal; generating a sine sweep signal based on a frequency parameter; The sinusoidal swept frequency signal is transmitted as an incident signal to the conductor of the submarine cable under test, and a reflected signal generated by the submarine cable under test is received; Determining reflection coefficient spectrum test data of the submarine cable under test according to the incident signal and the reflected signal; A waveform diagram is drawn according to the reflection coefficient spectrum test data, and defect detection and positioning of the tested submarine cable are performed based on the waveform diagram.

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