X-ray detection method and equipment for cable

Abstract

The invention discloses an X-ray detection method and X-ray detection equipment for a cable. According to the method, excitation current is connected to two ends of the cable, and the time of partial discharge current flowing through the two ends of the cable is detected to quickly and accurately position the damage position. Meanwhile, the sensing unit generates induced electromotive force according to the change of the partial discharge current, and the specific position of the internal damaged wire unit is accurately obtained according to the proportional relation of the induced electromotive force. And arranging a damage detector at the damaged part to carry out transmission scanning on the damaged part, reconstructing a cable section image at the damaged part and calculating defect data. According to the method, the position of the damaged part in the cable can be rapidly and accurately positioned, the coordinate of the damaged wire can be obtained, meanwhile, the cross section image of the damaged part of the cable can be obtained, and the damage condition can be accurately evaluated by calculating defect data.

Description

Technical Field

[0001] The present invention relates to the technical field of cable status detection, and in particular to an X-ray detection method and device for cables. Background Art

[0002] Cables play a vital role in modern power and communication infrastructure. As cable applications become more widespread and complex, ensuring their long-term reliability and safety becomes particularly important. However, in actual operation, cables often age, deteriorate, or even become damaged due to operating conditions, environmental factors, and human factors, leading to frequent power failures and causing serious impacts on social production and life.

[0003] In the existing cable detection technology, the temperature detection method has been used to detect the cable damage. For example, the method of detecting cable damage based on cable temperature disclosed in Chinese patent application number CN202211035840.2, by installing a temperature detection device on the surface of the cable, converting the temperature signal of the working cable into a voltage signal, and designing a voltage threshold to determine whether the cable is damaged. This method can only be found after the cable has been damaged and a major fault has formed, and it is impossible to achieve early damage diagnosis inside the cable. Therefore, the prior art has developed a pulse signal detection method to achieve early diagnosis of the cable. Chinese patent application with publication number CN114460500A discloses a continuous detection device for cable joints, which transmits a pulse fundamental wave signal through a detector. If the cable in the detection area is in a bad connection state, it can receive the fundamental wave signal and reflect the pulse harmonic signal. The detector receives the pulse harmonic signal to determine the position and damage of the cable. Due to the influence of the working current and environment inside the cable, this method has a large error and cannot accurately determine the location of the cable damage. The detection of damage is too single, and it is impossible to go deep into the internal situation of the cable for detection, and it is difficult to determine the specific damage of the cable. Therefore, the prior art needs to be further improved. Summary of the invention

[0004] In order to solve the defects of the above-mentioned prior art, the present invention proposes an X-ray detection method and equipment for cables, which can quickly determine the internally damaged conductors and the location of the damage, and accurately obtain the defect data of the damaged parts.

[0005] The technical solution of the present invention is achieved in this way: A method for X-ray detection of cables comprises the following steps: Step 1: The cable to be tested has a plurality of conductor units, and two ends of the cable to be tested are connected to a first wiring terminal and a second wiring terminal, wherein one of the conductor units is damaged; Step 2: Connect an excitation current between the first terminal and the second terminal to generate a partial discharge current at the damaged part, the first terminal receiving the partial discharge current at a first discharge time t1, and the second terminal receiving the partial discharge current at a second discharge time t2; Step 3: Determine the axial position s of the damaged part according to the first discharge time t1 and the second discharge time t2; Step 4: symmetrically arrange the three groups of sensing units around the first terminal or the second terminal, construct a reference coordinate system based on the first terminal or the second terminal, and construct a deflection coordinate system based on the damaged wire unit; Step 5: The partial discharge current flows through the cable, and the three groups of sensor units at the first terminal or the second terminal generate electromagnetic induction, and the induced voltage amplitudes U1, U2, and U3 of the three groups of sensor units are detected respectively; Step 6: Determine the reference coordinate system by clockwise rotation to obtain the deflection angle β of the deflection coordinate system and the offset k between the damaged conductor unit and the origin of the deflection coordinate system according to the induced electromotive force; Step 7: Arrange a damage detector at the axis position s, and generate a cable transmission image at the axis position every time the rotation angle of the damage detector increases by θ; Step 8: Reconstruct the cross-sectional image at the axial position s according to the 2π / θ group of transmission images, and generate defect data at the damaged part according to the cross-sectional image; Step 9: Generate position data based on the axial position s, deflection angle β, and offset k, and output the position data of the damaged area and defect data.

[0006] In the present invention, in step 2, the instantaneous current of the first terminal is detected, and the excitation current and the partial discharge current are decomposed from the instantaneous current.

[0007] In the present invention, in step 3, the axial position s=Lt1 / (t1+t2), where L is the total length of the cable to be tested.

[0008] In the present invention, in step 6, the induced electromotive forces generated by the partial discharge current in the three groups of sensor units are e1, e2, and e3, and e1:e2:e3= U1:U2:U3. The deflection angle β and the offset k are calculated based on e1:e2= U1:U2 and e2:e3= U2:U3.

[0009] In the present invention, in step 7, the damage detector includes a ray generating unit and a ray receiving unit.

[0010] In the present invention, in step 8, the projection intensity of each pixel of the transmission image is measured according to the initial intensity of the X-ray, the intensity attenuation logarithm of the pixel is calculated, the attenuation coefficient of the cross-sectional point mapped by the pixel is inversely solved according to the intensity attenuation logarithm of multiple pixel positions, and the cross-sectional image is reconstructed according to the attenuation coefficient of each cross-sectional point.

[0011] In the present invention, the ray projection distance of each cross-sectional point of the cable cross-sectional image is determined according to the position of the ray generating unit and the position of the ray receiving unit, and then the pixel position mapped by the cross-sectional point is determined.

[0012] In the present invention, in step 9, the position data includes the axis coordinate s and the polar coordinate (-β, k) of the injury site.

[0013] A device for implementing the X-ray detection method of the cable, comprising: a first terminal, a second terminal, an excitation power supply, a current detection unit, three sets of sensor units, a voltage detection unit, a first processing unit, a second processing unit, a ray generating unit, a ray receiving unit, a third processing unit, and an output unit, wherein: The first terminal is configured to be connected to one end of a cable to be tested; The second terminal is configured to be connected to the other end of the cable under test; The excitation power supply is configured to connect an excitation current between the first terminal and the second terminal; The current detection unit is configured to detect a first discharge moment when the first terminal receives the partial discharge current and a second discharge moment when the second terminal receives the partial discharge current; The three groups of sensing units are configured to be arranged at the first terminal or the second terminal; The voltage detection unit is configured to detect the induced voltage amplitude of the sensing unit; The first processing unit is configured to determine the axial position of the lesion according to the first discharge moment and the second discharge moment; The second processing unit is configured to determine the deflection angle and the deflection distance according to the induced voltage amplitude; The ray generating unit is configured to emit X-rays at the axial position; The ray receiving unit is configured to receive the transmitted X-rays and generate a transmission image; The third processing unit is configured to reconstruct the cross-sectional image and generate defect data of the damaged portion; The output unit is configured to generate position data according to the axial position, the deflection angle, and the offset, and output the position data and the defect data.

[0014] In the present invention, the device also includes a damage detector, a walking unit and a rotating unit. The damage detector is used to carry a ray generating unit and a ray receiving unit to perform X-ray detection on the cable. The walking unit is used to control the damage detector to move along the cable to an axial position s, and the rotating unit is used to control the damage detector to rotate around the cable.

[0015] The X-ray detection method and device for the cable of the present invention have the following beneficial effects: the excitation current is connected to both ends of the cable to generate partial discharge current at the damaged part, and the present invention quickly and accurately locates the position of the damaged part in the cable by detecting the flow time of the partial discharge current. The present invention calculates the polar coordinates of the damaged conductor in the cross section based on the induced electromotive force generated by the partial discharge current in the sensing unit, and accurately locates the position of the damaged conductor in the cable. The present invention arranges a damage detector at the damaged part of the cable to perform transmission scanning on the damaged part, reconstructs the cable cross-sectional image and calculates the defect data, thereby realizing accurate detection of the damage in the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of the X-ray detection method for cables of the present invention; Figure 2 This is a schematic diagram of the distribution of conductor units in the cable of the present invention; Figure 3 A schematic diagram of partial discharge current generated at a damaged part of the present invention; Figure 4 This is a schematic diagram of the distribution of three sensing units of the present invention; Figure 5 Schematic diagram of the reference coordinate system of the present invention; Figure 6 A schematic diagram of the position of a damaged conductor unit in a reference coordinate system of the present invention; Figure 7 It is a schematic diagram of the deflection coordinate system of the present invention; Figure 8 This is a schematic diagram of the X-ray transmission cable emitted by the ray generating unit of the present invention; Fig. 9 The diagram is a schematic diagram of the distribution of pixel positions on the ray receiving unit of the present invention and the received X-rays; Fig.10 It is a schematic diagram of the equipment of the X-ray method of the cable of the present invention; Fig.11 This is a schematic diagram of the interior of the damage detector, the walking unit and the rotating unit of the present invention; Fig.12 This is a block diagram of the equipment operation of the X-ray method for cables of the present invention. DETAILED DESCRIPTION

[0017] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0018] Embodiment 1

[0019] like Figure 1 As shown, an X-ray detection method for a cable in this embodiment includes the following steps: Step 1: The cable to be tested has multiple conductor units. The two ends of the cable to be tested are connected to a first terminal and a second terminal. One of the conductor units is damaged. The conductor units in the cable to be tested are distributed as follows: Figure 2 shown.

[0020] Step 2: Connect an excitation current between the first terminal and the second terminal, and a partial discharge current is generated at the damaged part. The first terminal receives the partial discharge current at the first discharge time t1, and the second terminal receives the partial discharge current at the second discharge time t2. When the conductor unit is not damaged, the insulating material that wraps the conductor is good, and the excitation current connected to both sides of the cable will flow evenly throughout the cable. When the conductor unit is damaged, its insulating material is destroyed. Therefore, when the excitation current is connected, the damaged part will output partial discharge current to both ends of the cable due to excessive local current. A specific excitation current such as a sine wave or a square wave can be preset, and the instantaneous current of the first terminal and the second terminal can be detected. The preset excitation current is decomposed from the instantaneous current to obtain the partial discharge current. The peak position of the partial discharge current received by the first terminal is the first discharge time t1 of the partial discharge current, and the peak position of the partial discharge current received by the second terminal is the second discharge time t2 of the partial discharge current.

[0021] Step 3: Determine the axial position s of the damaged part according to the first discharge time t1 and the second discharge time t2. Figure 3 As shown, partial discharge current is generated at the damaged part and emitted to the first terminal and the second terminal. According to the time when the partial discharge current reaches the first terminal and the second terminal, the axial position s of the damaged part from the first terminal can be obtained, s=Lt1 / (t1+t2), where L is the total length of the cable to be tested.

[0022] Step 4: Arrange the three groups of sensing units symmetrically around the first terminal or the second terminal, construct a reference coordinate system based on the first terminal or the second terminal, and construct a deflection coordinate system based on the damaged wire unit. Figure 4 As shown, three groups of sensing units, i.e., three coil groups with equal arc lengths, are symmetrically arranged around the first terminal or the second terminal. The arc length of the coil groups is 2π / 3, and the arc radius is r. The current changes at both ends of the cable can be received to generate induced electromotive force. The three coil groups form a cylindrical sensing component. Figure 5 As shown, a reference coordinate system with the center of the cylindrical sensing component as the origin is constructed at the terminal where the coil group is installed. The present invention does not limit the specific pointing directions of the x and y axes of the reference coordinate system. For the convenience of calculation, the present embodiment adjusts the x and y axes so that the arc coordinate ranges of the three coil groups in the reference coordinate system are as follows: Figure 5 As shown in (0,2π / 3), (2π / 3,4π / 3), (4π / 3,2π). Figure 6As shown in , the polar coordinates of the damaged conductor unit in the reference coordinate system are assumed to be (-β, k), and the deflected coordinate system is obtained by rotating the reference coordinate system clockwise around the origin by β. Figure 7 As shown, in the deflection coordinate system, the polar coordinates of the damaged unit are (0, k), and the radian coordinate ranges of the three coil groups are (β, β+2π / 3), (β+2π / 3, β+4π / 3), and (β+4π / 3, β+2π).

[0023] Step 5: The partial discharge current flows through the cable, and the three groups of sensor units at the first terminal or the second terminal generate electromagnetic induction, and the induced voltage amplitudes U1, U2, and U3 of the three groups of sensor units are detected respectively. When the partial discharge current flows through the first terminal and the second terminal of the cable, the three coil groups at the first terminal or the second terminal can sense the current change in the cable and generate an induced electromotive force, and the voltage signals of the three coil groups are detected respectively by the voltage detection unit. The voltage signal is a cosine wave-like signal that suddenly increases and gradually decays. In order to ensure the reference of the signal, the extreme value of the wave signal is selected as the voltage amplitude in this embodiment, so the voltage amplitudes of the three coil groups are U1, U2, and U3 respectively. It should be noted that since the excitation current will also generate electromagnetic induction, the electric induction voltage corresponding to the excitation current satisfies the preset waveform. The induced voltage referred to in the present invention refers to the induced voltage after the induced voltage generated by the excitation current is eliminated.

[0024] Step 6: Determine the deflection angle β of the deflection coordinate system obtained by clockwise rotation of the reference coordinate system and the offset k between the damaged conductor unit and the origin of the deflection coordinate system based on the induced electromotive force. The induced electromotive force generated by the coil assembly is related to the position coordinates of the damaged conductor unit in the reference coordinate system, and can be numerically equivalent to the deflection angle β of the deflection coordinate system obtained by clockwise rotation of the reference coordinate system and the offset k between the damaged conductor unit and the origin of the deflection coordinate system.

[0025] When the discharge current passes through the cable, an induced magnetic field is generated in the coil group. In the deflection coordinate system, the induced magnetic field component of any point in the coil group perpendicular to the cable plane with polar coordinates (α, r) is , where i is the partial discharge current flowing through the cable unit, μ is the vacuum permeability and μ=4π×10 -7 H / m. Therefore, the induced electromotive force of the coil group can be obtained by integrating the induced magnetic field component at any point of the coil group: According to the position coordinates of the three coil groups, the induced electromotive forces of the three coil groups can be obtained as follows: , , .

[0026] Since the voltage amplitudes of different coil groups are related to the induced electromotive force of the coil groups, for coils of the same size and number of turns, the greater the induced electromotive force, the greater the voltage amplitude. Therefore, in this embodiment, e1:e2:e3=U1:U2:U3, from which e1:e2= U1:U2 and e2:e3= U2:U3 are extracted, and these two equations are combined to form an equation group. There are only two unknowns in the equation group, namely the deflection angle β and the offset distance k, so the values ​​of β and k can be obtained.

[0027] Step 7: Arrange a damage detector at the axis position s, and generate a cable transmission image at the axis position every time the rotation angle of the damage detector increases by θ. The damage detector includes a ray generating unit and a ray receiving unit. The ray generating unit is controlled to emit X-rays with an initial intensity of E. The ray receiving unit receives X-rays that pass through the cable to be tested to generate a transmission image and calculate the projection intensity E' of each pixel. Then, the damage detector is rotated around the cable by θ, and the above operation is repeated to generate a transmission image until the damage detector is rotated around the cable by 2π.

[0028] Step 8: Reconstruct the cross-sectional image at the axial position s based on the 2π / θ group of transmission images, and generate defect data at the damaged location based on the cross-sectional image. The transmission image is a strip image at the axial position s, with multiple pixels, and each pixel corresponds to an X-ray. Figure 8 As shown, a plane rectangular coordinate system is established with the cable center as the origin. At a certain rotation angle, the coordinates of the ray generating unit (x0, y0) are taken. For any section point coordinate A (x, y) on the cross section, d1 and d2 are determined according to the positions of the ray generating unit and the ray receiving unit in the coordinate system. The ray projection distance d3 = [(y0-y) / (x0-x)-y0 / x0] × (d1+d2) of the X-ray passing through point A is determined according to the coordinates of point A (x, y), the coordinates of the ray generating unit (x0, y0), d1, and d2. Then, the pixel position mapped to the section point is determined according to the ray projection distance. The positive and negative signs of the result indicate the direction of the pixel position in the ray receiving unit and the middle pixel position.

[0029] At a certain rotation angle, the intensity attenuation logarithm σ=ln(E / E') of the X-ray at each pixel is calculated based on the initial X-ray intensity E and the projection intensity E' of each pixel. The intensity attenuation logarithm of each pixel is composed of the attenuation coefficients of all cross-sectional points on the cable cross-section through which the corresponding X-ray passes.

[0030] like Fig. 9As shown, due to the limitation of the number of pixel bits of the ray receiving unit, X-rays can only be received at the midpoint of the pixel bit, so it cannot be ensured that each X-ray passing through the cross-sectional point can receive the corresponding projection intensity and calculate its intensity attenuation logarithm. For X-rays whose intensity attenuation logarithm cannot be directly calculated, this embodiment supplements the intensity attenuation logarithm of such X-rays. Assume that the X-rays that can directly receive the projection intensity through the ray receiving unit to calculate the intensity attenuation logarithm are known X-rays, and the X-rays that cannot directly receive the projection intensity through the ray receiving unit to calculate the intensity attenuation logarithm are unknown X-rays. The linear interpolation method is used to calculate the intensity attenuation logarithm of the unknown X-ray: σ(u)=(1-ξ)σ(u-1)+ξσ(u+1), where σ(u) represents the intensity attenuation logarithm of the unknown X-ray, σ(u-1) and σ(u+1) represent the intensity attenuation logarithms of the next and previous known X-rays adjacent to the unknown X-ray, respectively, and ξ is the ratio of the difference in ray projection distances between the unknown X-ray and the next known X-ray adjacent to it at the pixel position to the width of a single pixel position.

[0031] The attenuation logarithm of the intensity of each pixel of the transmission image and the attenuation coefficient of the corresponding multiple cross-section points form an equation. The transmission images at 2π / θ angles are combined to form a system of equations, which can be solved to obtain the attenuation coefficient of each cross-section point. To ensure that the system of equations is solvable, the product of the number of transmission images and the number of pixels in each transmission image should be greater than the number of cross-section points. Since the attenuation coefficient of the cross-section point can determine the damage of the point, the pixel value of the corresponding pixel point can be calculated based on the attenuation coefficient of the cross-section point to reflect the damage. The attenuation coefficient of the cross-section point is used as the pixel proposed value of the point, and the pixel proposed values ​​of all cross-section points are normalized to the interval [0,255] to obtain the pixel value of each pixel point, and reconstruct the cross-section image of the cable.

[0032] The reconstructed cable cross-sectional image is then subjected to median filtering, histogram equalization, and sharpening processing in sequence to optimize the cross-sectional image to obtain a corrected image. The specific optimization process is described in Example 2. The defect data of the damaged area is then calculated based on the corrected image. The present invention does not limit the specific calculation method of the defect data. This embodiment uses the area of ​​the damaged area in the corrected image as the defect data.

[0033] Step 9: Generate position data based on the axial position s, deflection angle β, and offset distance k, and output the position data and defect data of the damaged part. Determine the position of the damaged part on the cable based on the axial position s, and then generate polar coordinates (-β, k) through the deflection angle β and offset distance k to determine the position of the damaged conductor unit in the cable to obtain the position data of the damaged part.

[0034] Embodiment 2 This embodiment further discloses the image optimization processing method of the present invention.

[0035] First, perform median filtering on the cross-sectional image B. Let (p, j) be the coordinates of the pixel block in the image. Set an M×M sliding window, let M=2m+1, and m be a positive integer. Let the sliding window slide on the image in sequence to obtain the M pixels in the window at a certain moment. 2 The sample pixel values ​​of M pixels are f(pm,jm),...,f(p,j),...,f(p+m,j+m). 2 The pixel values ​​are sorted in order of size, and the middle value is taken as the new pixel value z(p,j) of the pixel block (p,j). The sliding window is traversed to the entire image to obtain the new pixel values ​​of each pixel block, and the median filtered image C is obtained according to the new pixel values.

[0036] Next, perform histogram equalization on image C. Count the number of occurrences of each pixel value q in image C. q , the probability density function PDF(q) of each pixel value is calculated according to the number of pixel blocks of each pixel value = n q / T 2 , T is the number of pixel blocks of the cross-sectional image side length, and then calculate the cumulative distribution function of the pixel value q , and then map the cumulative distribution function to [0,255], that is, F(q)=255CDF(q). Through this step, the pixels with pixel value q in image C can be replaced by F(q). According to F(q), the histogram-equalized image D can be constructed.

[0037] Finally, the image D is sharpened to obtain the corrected image. Assume that the pixel value of the pixel block in the image D is g(p,j), and the gradient at any pixel block (pj) in the image D is grad(p,j)=[g p 'g j '], where g p ' represents the partial derivative of the pixel function with respect to p, g j ' represents the partial derivative of the pixel function with respect to j. Since g(p,j) is a discrete function, the partial derivative can be expressed as g p =g(p+1,j)-g(p,j), g j '=g(p,j+1)-g(p,j), to simplify the calculation, grad(p,j)=|g p '|+|g j'| replaces the gradient value. After the gradient is determined, a threshold λ is set. On the pixel block (p,j), if grad(p,j)≥λ, the original pixel value is replaced by the gradient, that is, g"(p,j)= grad(p,j); if grad(p,j)<λ, the original pixel value is kept, that is, g"(p,j)= g(p,j). Traverse each pixel point in the image in turn to obtain a new pixel value g"(p,j), and recreate the sharpened corrected image based on g"(p,j). The corrected image can more clearly show the outline and details of the damaged area in the cross-sectional image at the axial position s of the cable, which is convenient for accurate calculation of defect data.

[0038] Embodiment 3 like Figures 10 to 12 As shown, this embodiment discloses a device for implementing the X-ray detection method of the cable, including: a first terminal, a second terminal, an excitation power supply, a current detection unit, three groups of sensing units, a voltage detection unit, a first processing unit, a second processing unit, a ray generating unit, a ray receiving unit, a third processing unit, and an output unit. The first terminal is configured to be connected to one end of the cable to be tested. The second terminal is configured to be connected to the other end of the cable to be tested. The excitation power supply is configured to connect an excitation current between the first terminal and the second terminal. The current detection unit is configured to detect a first discharge moment when the first terminal receives a partial discharge current and a second discharge moment when the second terminal receives a partial discharge current. The three groups of sensing units are composed of three coil groups and are configured to be arranged at the first terminal or the second terminal. The voltage detection unit is configured to detect the induced voltage amplitude of the sensing unit. The first processing unit is configured to determine the axial position of the damage according to the first discharge moment and the second discharge moment. The second processing unit is configured to determine the deflection angle and the offset distance according to the induced voltage amplitude. The ray generating unit is configured to emit X-rays at the axial position. The ray receiving unit is configured to receive the transmitted X-rays and generate a transmission image. The third processing unit is configured to reconstruct the cross-sectional image and generate defect data of the damaged part. The output unit is configured to generate position data according to the axial position, deflection angle, and offset, and output the position data and defect data. Fig.11 The device also includes a damage detector, a walking unit and a rotating unit. The damage detector is used to carry a ray generating unit and a ray receiving unit to perform X-ray detection on the cable. The walking unit is used to control the damage detector to move along the cable to an axial position s, and the rotating unit is used to control the damage detector to rotate around the cable.

[0039] Reference Fig.12The present invention first connects the two ends of the conductor unit in the cable to the first terminal and the second terminal, then connects an excitation power supply between the first terminal and the second terminal to generate an excitation current, and the current excitation causes the damaged part in the cable to emit a partial discharge current, and then measures the time when the partial discharge current flows to the first terminal and the second terminal through the current detection unit, and calculates the position of the damaged part in the cable through the first discharge moment, the second discharge moment, and the total length of the cable. When the discharge current flows through the first terminal and the second terminal, a group of sensor units are placed at the first terminal or the second terminal, and the sensor units generate induced electromotive force and induced voltage through the change of the partial discharge current at the first terminal or the second terminal. The reference coordinate system is determined by calculating the induced electromotive force to obtain the deflection angle β of the deflection coordinate system and the offset k between the conductor unit with damage and the origin of the deflection coordinate system, thereby obtaining the polar coordinates of the position of the conductor unit with damage in the cable. A damage detector is then arranged at the location of the damage, and multiple transmission images of the cable cross section are obtained through the ray generating unit, the ray receiving unit and the rotating unit. The cross-sectional image of the cable is reconstructed and optimized to obtain a corrected image through the third processing unit, and the defect data of the damage site is calculated. Finally, the output unit outputs the position data consisting of the axial position of the damage site, the polar coordinates of the damaged conductor unit, and the defect data consisting of the damaged area of ​​the cable cross-sectional image.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cable X-ray detection method, characterized in that: The following steps are involved: Step 1: The cable to be tested has a plurality of conductor units, and two ends of the cable to be tested are connected to a first wiring terminal and a second wiring terminal, wherein one of the conductor units is damaged; Step 2: Connect an excitation current between the first terminal and the second terminal to generate a partial discharge current at the damaged part, the first terminal receiving the partial discharge current at a first discharge time t1, and the second terminal receiving the partial discharge current at a second discharge time t2; Step 3: Determine the axial position s of the damaged part according to the first discharge time t1 and the second discharge time t2; Step 4: symmetrically arrange the three groups of sensing units around the first terminal or the second terminal, construct a reference coordinate system based on the first terminal or the second terminal, and construct a deflection coordinate system based on the damaged wire unit; Step 5: The partial discharge current flows through the cable, and the three groups of sensor units at the first terminal or the second terminal generate electromagnetic induction, and the induced voltage amplitudes U1, U2, and U3 of the three groups of sensor units are detected respectively; Step 6: Determine the reference coordinate system by clockwise rotation to obtain the deflection angle β of the deflection coordinate system and the offset k between the damaged conductor unit and the origin of the deflection coordinate system according to the induced electromotive force; Step 7: Arrange a damage detector at the axis position s, and generate a cable transmission image at the axis position every time the rotation angle of the damage detector increases by θ; Step 8: Reconstruct the cross-sectional image at the axial position s according to the 2π / θ group of transmission images, and generate defect data at the damaged part according to the cross-sectional image; Step 9: Generate position data based on the axial position s, deflection angle β, and offset k, and output the position data of the damaged area and defect data.

2. The X-ray detection method of a cable according to claim 1, characterized in that: In step 2, the instantaneous current of the first terminal is detected, and the excitation current and the partial discharge current are decomposed from the instantaneous current.

3. The X-ray detection method of a cable according to claim 1, characterized in that: In step 3, the axial position s=Lt1 / (t1+t2), where L is the total length of the cable to be tested.

4. The X-ray detection method for cables according to claim 1, characterized in that: In step 6, the induced electromotive forces generated by the partial discharge current in the three groups of sensor units are e1, e2, and e3, and e1:e2:e3= U1:U2:U3. The deflection angle β and the offset distance k are calculated based on e1:e2= U1:U2 and e2:e3= U2:U3.

5. The X-ray detection method of a cable according to claim 1, characterized in that: In step 7, the damage detector includes a ray generating unit and a ray receiving unit.

6. The X-ray detection method of a cable according to claim 1, characterized in that: In step 8, based on the initial intensity of the X-ray, the projection intensity of each pixel of the transmission image is measured, the intensity attenuation logarithm of the pixel is calculated, the attenuation coefficient of the cross-sectional point mapped by the pixel is inversely solved based on the intensity attenuation logarithms of multiple pixel bits, and the cross-sectional image is reconstructed based on the attenuation coefficient of each cross-sectional point.

7. The X-ray detection method of a cable according to claim 6, characterized in that: The ray projection distance of each cross-sectional point of the cable cross-sectional image is determined according to the position of the ray generating unit and the position of the ray receiving unit, and then the pixel position mapped by the cross-sectional point is determined.

8. The X-ray detection method of a cable according to claim 1, characterized in that: In step 9, the position data includes the axis coordinate s and polar coordinates (-β, k) of the injury site.

9. A detection device for implementing the X-ray detection method of the cable according to claim 1, characterized in that: include: A first wiring terminal, a second wiring terminal, an excitation power supply, a current detection unit, three sets of sensor units, a voltage detection unit, a first processing unit, a second processing unit, a ray generating unit, a ray receiving unit, a third processing unit, and an output unit, wherein: The first terminal is configured to be connected to one end of a cable to be tested; The second terminal is configured to be connected to the other end of the cable under test; The excitation power supply is configured to connect an excitation current between the first terminal and the second terminal; The current detection unit is configured to detect a first discharge moment when the first terminal receives the partial discharge current and a second discharge moment when the second terminal receives the partial discharge current; The three groups of sensing units are configured to be arranged at the first terminal or the second terminal; The voltage detection unit is configured to detect the induced voltage amplitude of the sensing unit; The first processing unit is configured to determine the axial position of the lesion according to the first discharge moment and the second discharge moment; The second processing unit is configured to determine the deflection angle and the deflection distance according to the induced voltage amplitude; The ray generating unit is configured to emit X-rays at the axial position; The ray receiving unit is configured to receive the transmitted X-rays and generate a transmission image; The third processing unit is configured to reconstruct the cross-sectional image and generate defect data of the damaged portion; The output unit is configured to generate position data according to the axial position, the deflection angle, and the offset, and output the position data and the defect data.

10. The detection device for implementing the X-ray detection method of cables according to claim 9, characterized in that: The device also includes a damage detector, a walking unit and a rotating unit. The damage detector is used to carry a ray generating unit and a ray receiving unit to perform X-ray detection on the cable. The walking unit is used to control the damage detector to walk along the cable to an axial position s. The rotating unit is used to control the damage detector to rotate around the cable.

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