Non-invasive nuclear power suspension cable stress measurement method

Abstract

The present application relates to the technical field of cable, especially to a non-invasive nuclear power suspension cable stress measurement method.The method comprises the following steps: scanning the nuclear power suspension cable by using a laser scanner to draw a three-dimensional point cloud map; processing the three-dimensional point cloud map of the nuclear power suspension cable to form a two-dimensional point cloud map of the nuclear power suspension cable; based on the two-dimensional point cloud map, a catenary equation based on a terrain coordinate system is established by means of supplementing displacement variables; the catenary equation is linearized to convert the linear equation into a matrix form, and the horizontal tension of the nuclear power suspension cable is calculated by using the established matrix equation.The present application combines laser scanning technology and catenary theory, analyzes the shape of the nuclear power suspension cable to obtain the actual stress of the cable, and realizes remote and non-invasive measurement of the stress of the nuclear power suspension cable.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and more particularly to a non-invasive method for measuring the stress on suspended cables in nuclear power plants. Background Technology

[0002] Nuclear power cables are a crucial component of nuclear power plants, primarily laid on cable trays. The cables dangle between two cable trays, subjecting them to continuous loads. Monitoring the stress on these dangling cables is essential for assessing their availability and lifespan. Currently, force gauges or accelerometers are often attached to the cable ends to measure the stress, but both techniques require additional equipment and are somewhat invasive.

[0003] Attaching a force gauge to the end of a cable allows for real-time measurement of the cable's stress. This technology offers the advantage of directly measuring cable stress with high accuracy, but it is highly invasive and can easily affect cable operation.

[0004] Attaching an accelerometer to the end of a cable allows for the measurement of cable vibration, from which the stress on the cable can be calculated. This technology reduces the intrusion of the measuring equipment into the cable by using an indirect measurement method, but it still requires attaching the equipment to the cable end and cannot achieve remote measurement. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a non-invasive method for measuring the stress on nuclear power plant suspension cables. By combining laser scanning technology and catenary theory, the actual stress on the cable is obtained by analyzing the shape of the nuclear power plant suspension cable, thereby realizing remote, non-invasive measurement of the stress on the nuclear power plant suspension cable.

[0006] This invention provides a non-invasive method for measuring the stress on a nuclear power plant suspension cable, comprising the following steps:

[0007] Step 1: Use a laser scanner to scan the nuclear power plant's suspended cables and create a 3D point cloud map;

[0008] Step 2: Process the 3D point cloud map of the nuclear power plant suspension cable to form a 2D point cloud map of the nuclear power plant suspension cable;

[0009] Step 3: Based on the two-dimensional point cloud map, establish the catenary equation based on the terrain coordinate system by supplementing displacement variables;

[0010] The catenary equation is linearized, transforming it into a matrix form. The established matrix equation is then used to calculate the horizontal tension of the nuclear power plant's suspension cable.

[0011] In a specific embodiment of the present invention, step 1 specifically includes:

[0012] Step 1-1: Secure the laser scanner directly in front of the nuclear power plant's suspension cable, ensuring its stability; turn on the laser scanner, set the scanning parameters, and begin scanning;

[0013] After the laser beam is emitted, the time difference from emission to reflection and then to reception is recorded, and the spatial coordinates of the surface of the nuclear power plant suspension cable are calculated.

[0014] Steps 1-2: After the scan is completed, the acquired raw data is transferred to the computer and converted into a 3D point cloud map.

[0015] In a specific embodiment of the present invention, step 2 specifically includes:

[0016] Step 2-1: Import the generated 3D point cloud image file of the nuclear power plant suspension cable into the 3D point cloud processing software; Step 2-2: Perform point cloud simplification processing to remove duplicate point clouds;

[0017] Steps 2-3: Perform noise reduction on the point cloud;

[0018] Steps 2-4: Perform geometric segmentation on the 3D point cloud, extracting only the portion of the nuclear power plant's suspended cable;

[0019] Steps 2-5: Select a two-dimensional coordinate system and project the three-dimensional cable point cloud into the two-dimensional coordinate system;

[0020] Steps 2-6: Export the two-dimensional point cloud map of the nuclear power plant suspension cable.

[0021] In a specific embodiment of the present invention, step 3 specifically includes:

[0022] Step 3-1: Use the two-dimensional point cloud map of the nuclear power plant suspension cable obtained by laser scanning to establish the nuclear power plant suspension cable curve in a two-dimensional coordinate system according to the catenary theory;

[0023] Step 3-2: Add displacement variables and establish the modified catenary equation;

[0024] Step 3-3: Linearize the nonlinear form of the catenary equation using the Maclaurin series to obtain the processed equation;

[0025] Steps 3-4: Fit the catenary equation using the least squares method, and perform theoretical regression analysis using the measurement point set to determine the best fit;

[0026] Steps 3-5: Transform the linear equation into matrix form;

[0027] Steps 3-6: Determine any three points on the cable, and solve for the initial values ​​a0, u0, t0 in the equation based on the matrix equation; then solve for the catenary parameter a.

[0028] Steps 3-7: Calculate the horizontal tension based on the catenary parameter a;

[0029] H = aw;

[0030] In the formula, H is the horizontal tension of the nuclear power plant suspension cable, a is the catenary parameter, and w is the weight per unit length of the nuclear power plant suspension cable.

[0031] In a specific embodiment of the present invention, in step 3-1, the equation of the catenary is expressed as shown in equation (1):

[0032]

[0033] In the formula, y is the position of the cable in the vertical direction along the catenary coordinate system, x is the position of the cable in the horizontal direction along the catenary coordinate system, and a is the catenary parameter.

[0034] In a specific embodiment of the present invention, in step 3-2, the modified expression of the catenary equation is shown in equation (3):

[0035]

[0036] In the formula, u and t are offset parameters describing the shift from the terrain coordinate system to the catenary coordinate system.

[0037] In a specific embodiment of the present invention, in step 3-3, the processed equation is shown in equation (4):

[0038]

[0039] In a specific embodiment of the present invention, in steps 3-4, the fitted linear equation is:

[0040]

[0041] In a specific embodiment of the present invention, in steps 3-5, the matrix form is v = AX + L;

[0042] Specifically

[0043]

[0044]

[0045] In a specific embodiment of the present invention, in steps 3-6, the coordinates of three known points on the cable in the terrain coordinate system are substituted into the transformed equation (7) of the catenary equation to establish a system of equations to solve for the initial values ​​a0, u0, t0.

[0046] After calculating the unknowns a0, u0, and t0, a, u, and t can be calculated using equation (9):

[0047]

[0048] Compared with the prior art, the non-invasive method for measuring the force on nuclear power plant suspension cables of the present invention has the following advantages:

[0049] (1) High-precision three-dimensional data of nuclear power plant suspension cables were obtained by using laser scanning technology; the data were effectively extracted and optimized by processing three-dimensional point cloud processing software; and then the catenary theory was used to fit the processed data, realizing remote, non-invasive and accurate analysis of the stress state of nuclear power plant suspension cables.

[0050] (2) The present invention adopts remote operation, which does not require contact with cables, thus ensuring the safe operation of nuclear power; and it can also achieve live operation without affecting the normal power supply of the power plant.

[0051] (3) High measurement accuracy, fast analysis speed, and adaptability to extreme environments. Attached Figure Description

[0052] Figure 1 A flowchart illustrating a non-invasive method for measuring the stress on suspended cables in nuclear power plants;

[0053] Figure 2 This represents a schematic diagram of a laser scanner.

[0054] Figure 3 This shows the layout of the laser scanner;

[0055] Figure 4 This diagram illustrates the steps involved in 3D point cloud processing software.

[0056] Figure 5 This represents a two-dimensional point cloud diagram of a nuclear power plant's suspended cable.

[0057] Figure 6 This diagram shows the relationship between the catenary coordinate system and the topographic coordinate system. Detailed Implementation

[0058] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0059] An embodiment of the present invention discloses a non-invasive method for measuring the stress on a nuclear power plant suspension cable, comprising the following steps:

[0060] Step 1: Use a laser scanner to scan the nuclear power plant's suspended cables and create a 3D point cloud map;

[0061] A laser scanner is positioned directly in front of the cable, emitting a beam of laser light that travels at high speed and illuminates the nuclear power plant's suspension cable. When the laser beam touches the cable surface, a portion is reflected back to the scanner. By measuring the time difference between the laser's emission, reflection, and return, the scanner calculates the distance the laser beam has traveled, thus determining the cable's surface coordinates. Simultaneously, the laser scanner converts the physical nuclear power plant suspension cable into a tangible and computationally calculable three-dimensional point cloud representing its spatial coordinates.

[0062] Step 2: Process the 3D point cloud map of the nuclear power plant suspension cable to form a 2D point cloud map of the nuclear power plant suspension cable;

[0063] Specifically, it includes:

[0064] Step 2-1: Import the 3D point cloud image of the nuclear power plant's suspended cable into the 3D point cloud processing software;

[0065] Step 2-2: Perform point cloud simplification processing to remove duplicate point clouds;

[0066] Steps 2-3: Perform noise reduction on the point cloud;

[0067] Steps 2-4: Perform geometric segmentation on the 3D point cloud, extracting only the portion of the nuclear power plant's suspended cable;

[0068] Steps 2-5: Select a two-dimensional coordinate system and project the three-dimensional cable point cloud into the two-dimensional coordinate system;

[0069] Steps 2-6: Export the two-dimensional point cloud map of the nuclear power plant's suspension cable;

[0070] Step 3: Analyze the two-dimensional point cloud diagram of the nuclear power plant's suspended cable based on the catenary theory to obtain the tension on the cable;

[0071] Specifically:

[0072] The equation for the catenary is shown in equation (1):

[0073]

[0074] In the formula, y is the position of the cable in the vertical direction along the catenary coordinate system, x is the position of the cable in the horizontal direction along the catenary coordinate system, and a is the catenary parameter, the expression of which is shown in formula (2):

[0075]

[0076] In the formula, H is the horizontal tension of the nuclear power plant suspension cable, a is the catenary parameter, and w is the weight per unit length of the nuclear power plant suspension cable.

[0077] Given the two-dimensional curve of the nuclear power plant suspension cable, the catenary parameter a can be calculated using equation (1). Given the weight w per unit length of the cable, the horizontal tension H of the cable can be calculated using equation (2).

[0078] Since the nuclear power cable curve, after being scanned and processed by a laser scanner, is located in a topographic coordinate system, there is a certain coordinate deviation between it and the theoretical catenary coordinate system. By supplementing displacement variables, a catenary equation based on the topographic coordinate system is established. The modified expression of the catenary equation is shown in equation (3):

[0079]

[0080] In the formula, u and t are offset parameters describing the shift from the terrain coordinate system to the catenary coordinate system.

[0081] Since the catenary equation in equation (3) is nonlinear, it needs to be linearized using the Maclaurin series for easier subsequent calculations and analysis. The linearized equation is shown in equation (4):

[0082]

[0083] Since the cable must be parallel to the OX axis of the defined terrain coordinate system, the catenary equation is determined based on a set of measurement points using the least squares method. The theoretical regression analysis used to determine the best-fit catenary equation for the dataset is based on… Implementation involves minimizing the sum of squared residuals. The expression for v is shown in equation (5):

[0084]

[0085] Its linear form is shown in equation (6):

[0086]

[0087]

[0088] a0, u0, t0 are the initial estimates, and da, du, dt are the correction values;

[0089] Equation (6) can be expressed in matrix form as equations (7) to (8):

[0090]

[0091] Matrix form: v = AX + L(8)

[0092] Design matrix A to include partial derivative terms, X = [da, du, dt] T L is a constant term vector.

[0093] After determining the above equations, the coordinates of three known points on the cable in the terrain coordinate system are substituted into the catenary equation to establish a system of equations to solve for the initial values ​​a0, u0, t0.

[0094] After calculating the unknowns a0, u0, t0, use the least squares linear equation system to update the parameters and repeat the iteration until convergence, until da, du, dt are less than the preset threshold.

[0095] When updating parameters, a, u, and t can be calculated using equation (9):

[0096]

[0097] The final horizontal tension of the nuclear power plant's suspension cable can be calculated using equation (10):

[0098] H = aw (10)

[0099] To further understand the present invention, the non-invasive nuclear power plant suspension cable stress measurement method provided by the present invention will be described in detail below with reference to embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0100] Example 1

[0101] 3D point cloud mapping of nuclear power plant suspension cables

[0102] 1) Equipment Preparation: Select a suitable laser scanner, ensuring it has millimeter-level measurement accuracy and a sufficient scanning range. Prepare necessary auxiliary equipment, such as tripods, data storage devices, and computers.

[0103] 2) Site Survey: Before conducting laser scanning, a site survey of the nuclear power plant cable trays and suspended cables is conducted to ensure the safety of the scanning area. The optimal placement of the laser scanner is determined, typically in front of the suspended cables to ensure complete coverage of the cable geometry.

[0104] 3) Laser Scanning: Fix the laser scanner in the predetermined position, ensuring its stability. Start the laser scanner, set appropriate scanning parameters, and begin the scanning process. After the laser beam is emitted, the scanner will record the time difference between the laser beam's emission, reflection, and reception, thereby calculating the spatial coordinates of the nuclear power plant's suspension cable surface.

[0105] 4) Data Processing: After scanning, the acquired raw data is transferred to a computer. Specialized software is used to process the laser scan data, converting the raw data into a 3D point cloud map.

[0106] 2. Drawing of two-dimensional point cloud diagrams for nuclear power plant suspension cables

[0107] 1) Import data: Import the generated 3D point cloud image file of the nuclear power plant suspension cable into the 3D point cloud processing software, ensuring that the software can read the data format.

[0108] 2) Point Cloud Simplification: Inspect the 3D point cloud in the software to identify any duplicate point clouds. Use simplification tools to process the point cloud to reduce the computational burden and improve the efficiency of subsequent processing.

[0109] 3) Noise processing: For noise points caused by environmental or operational factors, noise reduction tools are used to filter the point cloud. This ensures that valid data is retained while removing unnecessary noise points, thereby improving data accuracy.

[0110] 4) Geometric segmentation: The processed 3D point cloud is geometrically segmented, focusing on extracting the suspended cable portion of the nuclear power plant. Modeling tools are used to select and separate cable areas to ensure data integrity.

[0111] 5) Coordinate Transformation: Select a two-dimensional coordinate system suitable for catenary theory analysis. Project the extracted three-dimensional cable point cloud data to convert it into a position in the two-dimensional coordinate system.

[0112] 6) Export 2D point cloud map: After completing the above steps, export the 2D point cloud map of the nuclear power plant's suspension cable. Ensure the exported file format meets the requirements.

[0113] 3. Stress Analysis of Suspension Cables in Nuclear Power Plants

[0114] 1) Curve equation establishment: Using the two-dimensional point cloud map of the nuclear power plant suspension cable obtained by laser scanning, the curve of the nuclear power plant suspension cable in the two-dimensional coordinate system is established according to the catenary theory.

[0115] 2) Coordinate system deviation handling: The cable curve is located in the terrain coordinate system, which differs from the theoretical coordinate system of the catenary. Displacement variables are added, and the modified catenary equation is established.

[0116] 3) Equation linearization: The nonlinear form of the catenary equation is linearized using the Maclaurin series to obtain the processed equation.

[0117] 4) Data fitting: The least squares method is used to fit the catenary equation, and theoretical regression analysis is performed using the measurement point set to determine the best fit.

[0118] 5) Matrix Form Conversion: Transform the linear equation into matrix form to facilitate subsequent solution.

[0119] 6) Solve for unknowns: Determine any three points on the cable, and establish three linear equations based on the above equations to solve for the unknowns.

[0120] 7) Calculation results: The horizontal tension of the nuclear power plant suspension cable was calculated as the result of the stress analysis.

[0121] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0122] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A non-invasive method for measuring the force on a nuclear power plant suspension cable, characterized in that, Includes the following steps: Step 1: Use a laser scanner to scan the nuclear power plant's suspended cables and create a 3D point cloud map; Step 2: Process the 3D point cloud map of the nuclear power plant suspension cable to form a 2D point cloud map of the nuclear power plant suspension cable; Step 3: Based on the two-dimensional point cloud map, establish the catenary equation based on the terrain coordinate system by supplementing displacement variables; The catenary equation is linearized and transformed into matrix form. The horizontal tension of the nuclear power plant suspension cable is then calculated using the established matrix equation. Step 3 specifically includes: Step 3-1: Use the two-dimensional point cloud map of the nuclear power plant suspension cable obtained by laser scanning to establish the nuclear power plant suspension cable curve in a two-dimensional coordinate system according to the catenary theory; The equation for the catenary is shown in equation (1): （1）； In the formula y It is the position of the cable along the vertical direction of the catenary coordinate system. x It is the position of the cable along the horizontal direction of the catenary coordinate system. a These are the parameters of the catenary; Step 3-2: Add displacement variables and establish the modified catenary equation; The modified equation for the catenary is shown in equation (3): （3）； In the formula u and t It is a parameter describing the offset from the terrain coordinate system to the catenary coordinate system; Step 3-3: Linearize the nonlinear form of the catenary equation using the Maclaurin series to obtain the processed equation; Steps 3-4: Fit the catenary equation using the least squares method, and perform theoretical regression analysis using the measurement point set to determine the best fit; The fitted linear equation is: （6）； a0, u0, t0 are the initial estimates, and da, du, dt are the correction values; Steps 3-5: Transform the linear equation into matrix form; Steps 3-6: Determine any three points on the cable and solve for the initial values ​​in the equation based on the matrix equation. , , Then, the catenary parameters are solved. a ; Steps 3-7: Based on catenary parameters a Calculate the horizontal tension; ； In the formula H For the horizontal tension of the nuclear power plant suspension cable, a For catenary parameters, w Weight per unit length of nuclear power plant suspension cable.

2. The non-invasive method for measuring the force on a nuclear power plant suspension cable according to claim 1, characterized in that, Step 1 specifically includes: Step 1-1: Secure the laser scanner directly in front of the nuclear power plant's suspension cable, ensuring its stability; turn on the laser scanner, set the scanning parameters, and begin scanning; After the laser beam is emitted, the time difference from emission to reflection and then to reception is recorded, and the spatial coordinates of the surface of the nuclear power plant suspension cable are calculated. Steps 1-2: After the scan is completed, the acquired raw data is transferred to the computer and converted into a 3D point cloud map.

3. The non-invasive method for measuring the force on a nuclear power plant suspension cable according to claim 1, characterized in that, Step 2 specifically includes: Step 2-1: Import the generated 3D point cloud image file of the nuclear power plant suspension cable into the 3D point cloud processing software; Step 2-2: Perform point cloud simplification processing to remove duplicate point clouds; Steps 2-3: Perform noise reduction on the point cloud; Steps 2-4: Perform geometric segmentation on the 3D point cloud, extracting only the portion of the nuclear power plant's suspended cable; Step 2-5: Select a two-dimensional coordinate system and project the three-dimensional cable point cloud into the two-dimensional coordinate system; Step 2-6: Export the two-dimensional point cloud map of the nuclear power plant suspension cable.

4. The non-invasive method for measuring the force on a nuclear power plant suspension cable according to claim 1, characterized in that, In step 3-3, the processed equation is shown in equation (4): （4）。 5. The non-invasive method for measuring the force on a nuclear power plant suspension cable according to claim 1, characterized in that, In steps 3-5, the matrix form is as follows: ; Specifically （7） 。 6. The non-invasive method for measuring the force on a nuclear power plant suspension cable according to claim 5, characterized in that, In steps 3-6, the coordinates of three known points on the cable in the terrain coordinate system are substituted into the transformed equation (7) of the catenary equation to establish a system of equations and solve for the initial values. , , ; Calculate the unknown quantity , , Then, it can be calculated using equation (9). a , u , t : （9）。

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