Quality detection method applied to cable production

Abstract

The invention discloses a quality detection method applied to cable production, and particularly relates to the technical field of cable detection. A high-precision detection device is used for carrying out grading detection and analysis on a high-potential area with static electricity accumulation on the surface of a cable, high-potential points are preliminarily identified from a current dense area, charge density distribution and breakdown strength stability are accurately measured, the risk of static electricity accumulation is evaluated, the area is divided into a high risk area, a medium risk area and a low risk area based on an analysis result, and the risk of static electricity accumulation is evaluated. And further electrostatic suppression measures and equipment protection are taken in the medium-risk area, so that the safety and accuracy of cable quality detection are improved, and the stability and reliability of the detection equipment and the cable in a high-voltage electrostatic environment are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of cable detection, and in particular to a quality detection method applied to cable production. Background Art

[0002] The quality inspection of cable production refers to the evaluation of various properties and parameters of cables during the manufacturing process to ensure the safety, reliability and compliance with relevant standards of the cables. These inspections cover all stages from the entry of raw materials into the factory to the exit of finished products, mainly including tests on the conductor resistance, insulation performance, withstand voltage, mechanical strength and flame retardancy of the cables. Through systematic inspections, defects or hidden dangers that may occur in the production process can be discovered in a timely manner to ensure that the quality of the finished cables is stable and meets the use requirements.

[0003] Specifically, cable quality inspection includes testing the conductivity of the conductor to ensure that the cable has a suitable resistance value when current passes through it, thereby reducing energy consumption. However, in the case of high conductor resistance and uneven conductor surface, static electricity may accumulate inside the cable. When the cable carries high current, due to uneven resistance or poor insulation performance, a high potential area will be formed at the static electricity accumulation point. If static electricity accumulates to a certain extent, static electricity discharge will occur in an instant, and this discharge may penetrate the insulation layer and form a high-temperature arc. Static electricity discharge will not only damage the insulation material of the cable, but may also further induce arc discharge, and in severe cases even cause fire or explosion. At the same time, the high-temperature arc discharge caused by static electricity accumulation may affect the quality inspection equipment connected or in contact with the cable. The instantaneous high temperature and high voltage generated by the discharge will damage the electronic components of the inspection equipment, especially the resistance tester, insulation tester and breakdown voltage inspection equipment, and may even cause the inspection equipment to short-circuit or malfunction. Summary of the invention

[0004] The purpose of the present invention is to provide a quality detection method applied to cable production to solve the shortcomings of the background technology.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a quality detection method applied to cable production, comprising the following steps: S1: Cut a test cable of standard length from the produced cables, use a high-precision infrared thermal imager to perform a preliminary scan, locate the current-intensive area, and preliminarily identify the target high-potential point; S2: Connect each target high potential point on the cable surface to a high-sensitivity potentiometer, and apply a test current value to the cable to measure the voltage value of each target high potential point, and draw a potential distribution diagram based on the potential difference to locate the high potential area; S3: For the located high potential area, use a highly sensitive electrostatic potentiometer to measure the electrostatic charge on the cable surface in the high potential area. Measure the surface potential at different positions on the surface of the high potential area in a grid-like manner, convert it into surface charge density, and analyze the surface charge density distribution to evaluate the abnormal degree of charge accumulation on the cable surface in the high potential area. S4: If the abnormal degree of charge accumulation is high, a high voltage breakdown tester is used to test the breakdown strength of the insulation layer in the high potential area, and the breakdown voltage of the insulation layer under gradually increasing voltage is measured. By analyzing the variation range of the breakdown voltage, the stability of the dielectric breakdown strength in the high potential area is evaluated; S5: Comprehensively analyze the abnormal degree of charge accumulation on the cable surface in the high potential area and the stability of the dielectric breakdown strength in the high potential area, and determine the risk of static electricity accumulation in the high potential area based on the analysis results; S6: According to the risk of static electricity accumulation in high potential areas, the high potential areas are divided into high risk areas, medium risk areas and low risk areas. The risk of static electricity accumulation in high potential areas on the surface of cables in medium risk areas within a fixed time period is further analyzed, and corresponding static electricity suppression and detection equipment protection measures are taken according to the analysis results.

[0006] Preferably, in S3, the charge density distribution anomaly index is generated after analyzing the distribution of the measured charge density data, and the method for obtaining the charge density distribution anomaly index is: Define the neighborhood parameter k, for each data point p, calculate the Euclidean distance between it and all points in the data set, and find the kth nearest point, denoted as k-distance, marked as , used to define the k-neighborhood of p, i.e., the distance from p is no more than The set of all points of ; For each point p and its neighboring point o∈ , defines the reachable distance from p to o for: ;in, is the distance from point o to its kth nearest neighbor, called the k-distance of o. is the actual Euclidean distance between p and o, for and The maximum value in ; The local reachability density of each point p By calculating the average of the inverse of the reachable distances of all neighboring points of p, we can get: ; In the formula, represents the number of points in the k-neighborhood of p. For each point p, its local anomaly factor is calculated by the ratio of its neighbors’ local reachability density to its own local reachability density. , the expression is: ; In the formula, for The local reachable density of each point is calculated based on The charge density distribution anomaly index is obtained by performing weighted average calculation on the values.

[0007] Preferably, in S4, a breakdown voltage fluctuation index is generated after analyzing the variation range of the breakdown voltage value between various measurement points. The method for obtaining the breakdown voltage fluctuation index is: Define the size of the sliding window w, that is, the number of measurement points included in each calculation of the standard deviation. After determining the window size w, traverse the entire breakdown voltage data set in a sliding manner. For each sliding window starting from the first point in the data set, calculate the standard deviation of the breakdown voltage value in the window, where the breakdown voltage data is , the data in the i-th window is ; In each sliding window, calculate the mean breakdown voltage and standard deviation ; Traverse the data set by sliding window and calculate the standard deviation of each window Summarize to form a set of standard deviation data ; Use the aggregated standard deviation data to calculate the overall fluctuation index, and take the mean of the standard deviations of all windows as the final breakdown voltage fluctuation index, expressed as: ; Where SD is the breakdown voltage fluctuation index.

[0008] Preferably, in S5, the charge density distribution anomaly index and the breakdown voltage fluctuation index are converted into feature vectors, and the feature vectors are used as inputs of the machine learning model. The machine learning model predicts the risk value label of electrostatic accumulation in high potential areas for each group of feature vectors as a prediction target, and minimizes the sum of prediction errors of the risk value labels of electrostatic accumulation in all high potential areas as a training target. The machine learning model is trained until the sum of prediction errors converges, and the model training is stopped. The risk value of electrostatic accumulation in high potential areas is determined according to the model output results, wherein the machine learning model is a polynomial regression model.

[0009] Preferably, in S6, the high potential area is divided into a high risk area, a medium risk area and a low risk area according to the risk of electrostatic accumulation in the high potential area, specifically: The obtained risk value of electrostatic accumulation in the high potential area is compared with the gradient standard threshold, the gradient standard threshold includes a first standard threshold and a second standard threshold, and the first standard threshold is less than the second standard threshold, and the risk value of electrostatic accumulation in the high potential area is compared with the first standard threshold and the second standard threshold respectively; If the risk value of electrostatic accumulation in the high potential area is greater than the second standard threshold, it means that the risk of electrostatic accumulation in the high potential area is high, and a first-level warning signal is generated, and the high potential area on the cable surface is divided into a high-risk area; If the risk value of electrostatic accumulation in the high potential area is greater than or equal to the first standard threshold and less than or equal to the second standard threshold, it means that the risk of electrostatic accumulation in the high potential area is medium, and a secondary warning signal is generated, and the high potential area on the cable surface is divided into a medium risk area; If the risk value of static electricity accumulation in the high potential area is less than the first standard threshold, it means that the risk of static electricity accumulation in the high potential area is low. At this time, a third-level warning signal is generated, and the high potential area on the cable surface is divided into a low-risk area.

[0010] Preferably, in S6, the risk of electrostatic accumulation in the high potential area on the surface of the cable in the medium risk area within a fixed time period is further analyzed, and corresponding electrostatic suppression and detection equipment protection measures are taken according to the analysis results, specifically: The charge density σ(t) and potential V(t) on the cable surface are analyzed to identify the trend of electrostatic accumulation in high potential areas. The charge density change rate is defined as: ;in, represents the rate of change of charge density, if If the change rate exceeds the preset threshold value Δσthreshold, it means that the speed of charge accumulation increases. At this time, the potential change rate of the high potential area is analyzed. The calculation expression of the potential change rate of the high potential area is: ; When ΔV is greater than the set potential change rate ΔVthreshold, it means that the potential accumulation is accelerating, and emergency electrostatic suppression measures should be taken immediately.

[0011] Preferably, the charge is dispersed by coating the cable surface with a conductive coating so that the charge density is kept within a safe range and the coating resistance is satisfy: ;in, is the maximum potential threshold of the high potential region, is the desired charge discharge current, drain current satisfy: ; where A is the surface area of ​​the high potential region, is the ground resistance; by optimizing and A, control the drainage rate to ensure that the charge is discharged within a safe range; install a transient voltage suppressor TVS at the input end of the detection equipment to prevent the equipment from being damaged under instantaneous high voltage, and the TVS trigger voltage satisfy: ; Where Vthreshold is the device's withstand voltage threshold.

[0012] In the above technical solution, the technical effects and advantages provided by the present invention are: 1. The present invention comprehensively analyzes and suppresses the risk of electrostatic accumulation in high-potential areas of cables through high-precision detection and graded risk management. In the specific detection process, infrared thermal imaging and high-sensitivity potential difference measurement are used to preliminarily identify the current-dense areas on the cable surface, and the charge accumulation and dielectric strength stability in high-potential areas are evaluated in combination with the charge density anomaly index and breakdown voltage fluctuation index. Based on the comprehensive analysis results, the risk of electrostatic accumulation is predicted through a machine learning model and graded processing is performed to ensure that the risk of electrostatic discharge is effectively controlled.

[0013] 2. The present invention not only effectively reduces the damage of electrostatic discharge to the cable insulation layer and quality inspection equipment. Especially for medium-risk areas with strong electrostatic accumulation tendency, further electrostatic suppression measures such as conductive coating to disperse charge, grounding drainage to control discharge, potential change rate monitoring, etc. are adopted, and transient voltage suppressor (TVS) is installed at the port of the detection equipment for equipment protection, so as to ensure the stability and safety of cable detection, which can not only significantly improve the accuracy of cable quality detection and equipment durability, but also reduce the risk of equipment failure and safety accidents caused by static electricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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 recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0015] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] For examples, see Figure 1 As shown, the quality inspection method applied to cable production described in this embodiment includes the following steps: S1: Cut a test cable of standard length from the produced cables, use a high-precision infrared thermal imager to perform a preliminary scan, locate the current-intensive area, and preliminarily identify the target high-potential point; S2: Connect each target high potential point on the cable surface to a high-sensitivity potentiometer, and apply a test current value to the cable to measure the voltage value of each target high potential point, and draw a potential distribution diagram based on the potential difference to locate the high potential area; S3: For the located high potential area, use a highly sensitive electrostatic potentiometer to measure the electrostatic charge on the cable surface in the high potential area. Measure the surface potential at different positions on the surface of the high potential area in a grid-like manner, convert it into surface charge density, and analyze the surface charge density distribution to evaluate the abnormal degree of charge accumulation on the cable surface in the high potential area. S4: If the abnormal degree of charge accumulation is high, a high voltage breakdown tester is used to test the breakdown strength of the insulation layer in the high potential area, and the breakdown voltage of the insulation layer under gradually increasing voltage is measured. By analyzing the variation range of the breakdown voltage, the stability of the dielectric breakdown strength in the high potential area is evaluated; S5: Comprehensively analyze the abnormal degree of charge accumulation on the cable surface in the high potential area and the stability of the dielectric breakdown strength in the high potential area, and determine the risk of static electricity accumulation in the high potential area based on the analysis results; S6: According to the risk of static electricity accumulation in high potential areas, the high potential areas are divided into high risk areas, medium risk areas and low risk areas. The risk of static electricity accumulation in high potential areas on the surface of cables in medium risk areas within a fixed time period is further analyzed, and corresponding static electricity suppression and detection equipment protection measures are taken according to the analysis results.

[0018] Among them, in S1, a test cable of standard length is cut from the produced cable, and a high-precision infrared thermal imager is used for preliminary scanning to locate the current-intensive area to preliminarily identify the target high-potential point, specifically: Randomly cut samples of standard length from the produced cable batch to ensure that the samples are representative and can reflect the quality of the entire batch of cables. Clean the surface of the test sample to avoid dust, dirt and other factors that interfere with the accuracy of thermal imaging detection.

[0019] Place the test sample in a temperature-controlled environment to reach the standard test temperature (usually about 20°C) to ensure that the external ambient temperature does not affect the accuracy of infrared thermal imaging detection. Confirm that the sample insulation layer is intact to avoid insulation layer defects affecting the stability of current distribution.

[0020] Use a high-precision infrared thermal imager and set it to a temperature sensitivity range suitable for the cable material to ensure that the slight temperature differences on the cable surface can be clearly captured. Adjust the resolution of the thermal imager to the highest level to ensure that the slight temperature changes on the cable surface can be accurately detected.

[0021] Apply a certain stable DC current to the test cable sample to simulate its operating state under normal working current conditions. Wait for a period of time (usually several minutes) to ensure that the current is evenly distributed in the sample and reaches a stable state, so that the resistance and current distribution of the cable more accurately reflect the high potential point.

[0022] Use a thermal imager to scan the cable surface, focusing on areas with higher cable surface temperatures. Since areas with higher resistance generate more heat when current passes through them, these areas often correspond to areas of high potential with dense current. Record and take thermal imaging images, marking all areas of abnormal temperature on the sample for further analysis.

[0023] Analyze the differences in temperature distribution in the image and identify "hot spots" with higher temperatures, which are usually current-intensive areas. Based on the temperature distribution map, mark the hot spots as preliminarily identified high-potential points to provide a reference for subsequent tests.

[0024] Mark the confirmed high-temperature area as the target high-potential point, and record its location, surface temperature, area and other parameters in detail so that it can be further accurately measured using a potentiometer. Record the test conditions (such as test current value, ambient temperature, test time, etc.) to ensure the repeatability of subsequent tests and the traceability of results.

[0025] S2: Connect each target high potential point on the cable surface to a high-sensitivity potentiometer, and apply a test current value to the cable to measure the voltage value of each target high potential point, and draw a potential distribution diagram based on the potential difference to locate the high potential area.

[0026] Select measurement points: At the high potential point position marked on the cable surface, determine multiple measurement points to accurately measure the voltage value of each high potential point. Connect each target high potential point of the cable to a high-sensitivity potentiometer (usually a four-wire connection) to ensure accurate voltage measurement at each point and reduce the interference of the wire's own resistance on the measurement.

[0027] Connect the cable to a constant current power supply and apply the specified test current value to simulate the current distribution of the cable under actual working conditions. Maintain a constant current and wait for a few minutes to allow the current distribution in the cable to stabilize before measuring the voltage to avoid measurement errors caused by current fluctuations.

[0028] Use a potentiometer to measure the voltage value of each high potential point in turn to ensure that the actual potential value of each target point is accurately captured. Record the voltage value of each measurement point, paying special attention to the potential difference with the initial zero potential point. Repeat the measurement several times to reduce accidental errors and ensure that the recorded voltage data is reliable and stable.

[0029] The voltage value of each high potential point is organized into a data table, including the voltage value, location coordinates, and relative potential difference. Use drawing software (such as Matlab, Origin, or Matplotlib in Python) to draw a potential distribution diagram to show the potential difference at different points on the cable surface. According to the potential distribution diagram, the area with higher and concentrated voltage is located and marked as a high potential area for further analysis of the possibility of static electricity accumulation.

[0030] S3: For the located high potential areas, use a highly sensitive electrostatic potentiometer to perform electrostatic measurement on the cable surface in the high potential area. Measure the surface potential at different positions on the surface of the high potential area in a grid manner, convert it into surface charge density, and evaluate the abnormal degree of charge accumulation on the cable surface in the high potential area by analyzing the surface charge density distribution.

[0031] On the cable surface in the high potential area, a uniform grid of measurement points is divided. The grid density depends on the area size and accuracy requirements, and a 1cm×1cm or finer grid is usually selected. A highly sensitive electrostatic potentiometer is installed above the grid, and its sensitivity and range are adjusted to ensure that it can measure tiny surface potential differences.

[0032] Measure the surface potential value at each point of the grid in turn, making sure to record the electrostatic potential at each point. In order to obtain high-precision data, you can repeat the measurement at each point and take the average value. During the measurement process, record the potential value and position coordinates of each measurement point in detail, and record the data in a table for subsequent analysis.

[0033] According to Coulomb's law, the surface potential value is converted into surface charge density (σ), in, is the vacuum dielectric constant, E is the measured electric field strength (calculated by the potential gradient), and the potential value of each grid point is converted into the corresponding surface charge density value to generate a surface charge density distribution map of the entire high potential area.

[0034] The surface charge density values ​​are plotted to form a charge density distribution map, which allows you to visually observe the degree of charge accumulation in high potential areas. Areas with darker colors or higher values ​​indicate more severe charge accumulation. Identify abnormal accumulation points in the map where the charge density is significantly higher than the surrounding areas. Abnormal accumulation points indicate areas where static electricity is more likely to accumulate and are potential discharge risk points.

[0035] After analyzing the distribution of the measured charge density data, the charge density distribution anomaly index is generated. The method for obtaining the charge density distribution anomaly index is as follows: Define the neighborhood parameter k, usually 10 to 20, for each data point p, calculate the Euclidean distance between it and all points in the data set, and find the kth nearest point, denoted as k-distance, marked as , used to define the k-neighborhood of p, i.e., the distance from p is no more than The set of all points of ; For each point p and its neighboring point o∈ , defines the reachable distance from p to o for: ;in, is the distance from point o to its kth nearest neighbor, called the k-distance of o. is the actual Euclidean distance between p and o, for and The maximum value in ; The local reachability density of each point p By calculating the average of the inverse of the reachable distances of all neighboring points of p, we can get: ; In the formula, Represents the number of points in the k-neighborhood of p. A lower LRD value means that the density near the point is lower, which may be an outlier. For each point p, its local outlier factor is calculated by the ratio of its neighbor's local reachable density to its own local reachable density. , the expression is: ; In the formula, for The local reachable density of the point is calculated based on the The charge density distribution anomaly index is obtained by performing weighted average calculation on the values.

[0036] The larger the charge density distribution anomaly index is, the higher the degree of abnormal charge accumulation on the cable surface in the high-potential area is. Specifically, a higher anomaly index means that the charge density at that point deviates significantly from its neighborhood density, and there may be significant charge accumulation. Excessive accumulation of static electricity can easily lead to an increased risk of local discharge, which may in turn cause insulation breakdown and arc discharge on the cable surface. Areas with larger anomaly indices are generally charge-dense hotspots, which means that the area is more likely to accumulate static electricity and reach the discharge threshold, posing a hidden danger to the safe operation of the cable.

[0037] On the contrary, if the charge density distribution anomaly index is small, or even close to 1, it means that the charge density in the high potential area is relatively uniform, and there is no significant difference from the density of its surrounding areas. This indicates that the charge accumulation in this area is low, the static electricity distribution is relatively uniform, and it is unlikely to have local discharge or breakdown problems. The area with a lower anomaly index is usually not a risk point for static electricity accumulation, and the cable has a smaller static electricity burden in this area. Relatively speaking, the threat to the cable's insulation layer and overall safe operation is relatively low.

[0038] S4: If the abnormal degree of charge accumulation is high, use a high-voltage breakdown tester to test the breakdown strength of the insulation layer in the high-potential area, measure the breakdown voltage of the insulation layer under gradually increasing voltage, and evaluate the stability of the dielectric breakdown strength in the high-potential area by analyzing the variation amplitude of the breakdown voltage.

[0039] Ensure that the high voltage breakdown tester is in normal working condition, calibrate its voltage rise rate and range, and adapt it to the voltage range and insulation characteristics of the cable. Generally, a standard voltage rise rate (such as 500V / s or lower) is set to ensure that the voltage rises steadily and gradually during the test so as to accurately determine the breakdown voltage.

[0040] Expose the high potential area of ​​the test cable sample between the two electrodes of the high voltage breakdown tester, ensure that the insulation layer of the test point is intact, and the test part is clean and free of dirt or oxides to avoid affecting the test results. Use a fixed fixture to stabilize the test sample to ensure that the insulation layer is evenly stressed to avoid measurement errors caused by poor contact.

[0041] The voltage is gradually increased on the high voltage breakdown tester, starting from the initial voltage (such as 0V) until the insulation layer breaks down. When the insulation layer breaks down (usually accompanied by a sharp increase in current), the voltage value is immediately recorded, which is called the breakdown voltage.

[0042] Select multiple test points in the same high potential area, repeatedly apply a gradually increasing voltage and record the breakdown voltage value each time to obtain a set of data. This step ensures the reliability of the data and can evaluate the uniformity of the dielectric strength in the area. For the breakdown voltage values ​​of different test points, record their values ​​and the corresponding voltage rise rate for subsequent analysis.

[0043] The difference between the maximum and minimum breakdown voltage is defined as the breakdown voltage variation. The smaller the variation, the more stable the dielectric strength of the insulation layer; if the variation is large, it indicates that the dielectric strength is unevenly distributed and there may be local weak points.

[0044] The breakdown voltage fluctuation index is generated by analyzing the variation range of the breakdown voltage value between each measurement point. The method for obtaining the breakdown voltage fluctuation index is: Define the size w (window width) of the sliding window, i.e. the number of measurement points included in each calculation of the standard deviation. The window size can be selected based on the distribution characteristics of the data. Usually smaller windows (such as w=3 or w=5) are suitable for fine detection of local fluctuations, while larger windows are suitable for overall trend analysis. After determining the window size w, traverse the entire breakdown voltage data set in a sliding manner.

[0045] For each sliding window starting from the first point in the data set, the standard deviation of the breakdown voltage value in the window is calculated, where the breakdown voltage data is , the data in the i-th window is ; In each sliding window, calculate the mean breakdown voltage and standard deviation ; Traverse the data set by sliding window and calculate the standard deviation of each window Summarize to form a set of standard deviation data ; Use the aggregated standard deviation data to calculate the overall fluctuation index, and take the mean of the standard deviations of all windows as the final breakdown voltage fluctuation index, expressed as: ; Where SD is the breakdown voltage fluctuation index.

[0046] The larger the breakdown voltage fluctuation index, the more unstable the dielectric breakdown strength distribution in the high potential area. Specifically, a higher fluctuation index reflects the significant variation of the breakdown voltage between different measurement points, which means that there is local inhomogeneity in the dielectric properties of the insulation layer and there may be weak points. Areas with large voltage fluctuations are prone to local breakdown and discharge at high potential, increasing the risk of insulation failure. This instability makes the insulation layer more prone to accidental breakdown in a long-term high voltage environment, posing a potential threat to the reliability and safety of the cable.

[0047] On the contrary, if the breakdown voltage fluctuation index is small, it means that the dielectric breakdown strength in the high potential area is relatively stable, and the breakdown voltage value varies less between each measurement point. A low fluctuation index means that the dielectric properties of the insulation layer are evenly distributed, without significant weak points, and can more effectively withstand voltage shocks under high potential. This stable dielectric breakdown strength enhances the insulation layer's ability to resist breakdown, making the cable safer and more reliable in high voltage environments, and has a positive effect on the cable life and performance stability.

[0048] S5: Comprehensively analyze the abnormal degree of charge accumulation on the cable surface in the high potential area and the stability of the dielectric breakdown strength in the high potential area, and determine the risk of static electricity accumulation in the high potential area based on the analysis results.

[0049] The charge density distribution anomaly index and the breakdown voltage fluctuation index are converted into feature vectors, and the feature vectors are used as inputs of the machine learning model. The machine learning model predicts the risk value label of electrostatic accumulation in high potential areas for each group of feature vectors as the prediction target, and minimizes the sum of prediction errors of all risk value labels of electrostatic accumulation in high potential areas as the training target. The machine learning model is trained until the sum of prediction errors converges, and the model training is stopped. The risk value of electrostatic accumulation in high potential areas is determined according to the model output results, wherein the machine learning model is a polynomial regression model.

[0050] The method for obtaining the risk value of electrostatic accumulation in high potential areas is to obtain the corresponding function expression from the feature vector training data of the trained machine learning model: ; In the formula, is the output function of the model, is the charge density distribution anomaly index, is the breakdown voltage fluctuation index, It is the risk value of static electricity accumulation in high potential areas.

[0051] S6: According to the risk of static electricity accumulation in high potential areas, the high potential areas are divided into high risk areas, medium risk areas and low risk areas. The risk of static electricity accumulation in high potential areas on the surface of cables in medium risk areas within a fixed time period is further analyzed, and corresponding static electricity suppression and detection equipment protection measures are taken according to the analysis results.

[0052] The obtained risk value of electrostatic accumulation in the high potential area is compared with the gradient standard threshold, the gradient standard threshold includes a first standard threshold and a second standard threshold, and the first standard threshold is less than the second standard threshold, and the risk value of electrostatic accumulation in the high potential area is compared with the first standard threshold and the second standard threshold respectively; If the risk value of electrostatic accumulation in the high potential area is greater than the second standard threshold, it means that the risk of electrostatic accumulation in the high potential area is high, and a first-level warning signal is generated, and the high potential area on the cable surface is divided into a high-risk area; If the risk value of electrostatic accumulation in the high potential area is greater than or equal to the first standard threshold and less than or equal to the second standard threshold, it means that the risk of electrostatic accumulation in the high potential area is medium, and a secondary warning signal is generated, and the high potential area on the cable surface is divided into a medium risk area; If the risk value of static electricity accumulation in the high potential area is less than the first standard threshold, it means that the risk of static electricity accumulation in the high potential area is low. At this time, a third-level warning signal is generated, and the high potential area on the cable surface is divided into a low-risk area.

[0053] It should be noted here that the importance of the first-level warning signal is greater than that of the second-level warning signal, and the importance of the second-level warning signal is greater than that of the third-level warning signal. Relevant personnel can take corresponding handling measures according to different warning signal levels.

[0054] Further analyze the risk of electrostatic accumulation in high-potential areas on the cable surface in medium-risk areas within a fixed time period, and take corresponding electrostatic suppression and detection equipment protection measures based on the analysis results, specifically: The charge density σ(t) and potential V(t) on the cable surface are analyzed to identify the trend of electrostatic accumulation in high potential areas. The charge density change rate is defined as: ;in, represents the rate of change of charge density. If If the preset rate of change threshold Δσthreshold is exceeded, it means that the speed of charge accumulation increases, which may cause the potential to rise rapidly. At this time, the rate of change of the potential in the high potential area is analyzed, and the calculation expression of the rate of change of the potential in the high potential area is: ; When ΔV is greater than the set potential change rate ΔVthreshold, it means that the potential accumulation is accelerated, which may trigger local electrostatic discharge. It is recommended to take emergency electrostatic suppression measures.

[0055] Static electricity suppression measures include: applying a conductive coating on the cable surface to disperse the charge so that the charge density remains within a safe range. Should meet: ;in, is the maximum potential threshold of the high potential region, Is the desired charge discharge current. This condition ensures that the coating can disperse the charge when the critical potential is reached to avoid static electricity accumulation. Set up a charge discharge channel to allow static electricity to be discharged through the ground path to reduce static electricity accumulation. Drainage current Should meet: ; where A is the surface area of ​​the high potential region, is the grounding resistance. and A, can control the drainage rate to ensure that the charge is discharged within a safe range.

[0056] To protect testing equipment (such as resistance testers, insulation testers, and breakdown voltage test equipment) from arc discharge, take the following protective measures: Install a transient voltage suppressor TVS at the input end of the detection equipment to prevent the equipment from being damaged under transient high voltage. The following conditions should be met: ; Among them, Vthreshold is the withstand voltage threshold of the equipment, which ensures that at the moment of arc discharge, TVS can quickly limit the voltage to a safe range. Electromagnetic shielding materials are added to the detection equipment to prevent high-frequency electromagnetic waves generated by electrostatic discharge from interfering with the detection signal. The electromagnetic shielding effectiveness is calculated, and the electromagnetic shielding effectiveness S is expressed as: ;in, is the electric field strength without shielding, It is the electric field strength after shielding. Improving the shielding effectiveness S can significantly reduce electromagnetic interference and make the detection equipment run more stably.

[0057] In this embodiment, during the cable detection process, a test sample of standard length is cut from the production cable, and a high-precision infrared thermal imager is first used for preliminary scanning to locate the current-intensive area to identify potential high-potential points. Then, each high-potential point is connected to a high-sensitivity potentiometer, and a test current is applied to measure the voltage value and draw a potential distribution diagram to determine the high-potential area. Next, an electrostatic potentiometer is used to perform grid-like electrostatic measurement on the surface of the cable in the high-potential area, and the surface potential is converted into charge density, and the abnormal degree of charge accumulation is analyzed. For areas with a high degree of abnormal charge accumulation, a high-voltage breakdown tester is used to gradually increase the voltage, measure the breakdown strength of the insulating layer in the area, and analyze its stability. Subsequently, the risk of electrostatic accumulation in the high-potential area is determined in combination with the abnormal degree of charge accumulation and the stability of the breakdown strength, and the area is divided into high-risk, medium-risk or low-risk areas accordingly. For medium-risk areas, the risk of electrostatic accumulation is further analyzed regularly, and electrostatic suppression and detection equipment protection measures are implemented according to the results to ensure the safety and accuracy of cable detection.

[0058] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A quality inspection method for cable production, characterized in that: The steps include: S1: Cut a test cable of standard length from the produced cables, use a high-precision infrared thermal imager to perform a preliminary scan, locate the current-intensive area, and preliminarily identify the target high-potential point; S2: Connect each target high potential point on the cable surface to a high-sensitivity potentiometer, and apply a test current value to the cable to measure the voltage value of each target high potential point, and draw a potential distribution diagram based on the potential difference to locate the high potential area; S3: For the located high potential area, use a highly sensitive electrostatic potentiometer to measure the electrostatic charge on the cable surface in the high potential area. Measure the surface potential at different positions on the surface of the high potential area in a grid-like manner, convert it into surface charge density, and analyze the surface charge density distribution to evaluate the abnormal degree of charge accumulation on the cable surface in the high potential area. S4: If the abnormal degree of charge accumulation is high, a high voltage breakdown tester is used to test the breakdown strength of the insulation layer in the high potential area, and the breakdown voltage of the insulation layer under gradually increasing voltage is measured. By analyzing the variation range of the breakdown voltage, the stability of the dielectric breakdown strength in the high potential area is evaluated; S5: Comprehensively analyze the abnormal degree of charge accumulation on the cable surface in the high potential area and the stability of the dielectric breakdown strength in the high potential area, and determine the risk of static electricity accumulation in the high potential area based on the analysis results; S6: According to the risk of static electricity accumulation in high potential areas, the high potential areas are divided into high risk areas, medium risk areas and low risk areas. The risk of static electricity accumulation in high potential areas on the surface of cables in medium risk areas within a fixed time period is further analyzed, and corresponding static electricity suppression and detection equipment protection measures are taken according to the analysis results.

2. A quality inspection method for cable production according to claim 1, characterized in that: In S3, the distribution of the measured charge density data is analyzed to generate a charge density distribution anomaly index. The method for obtaining the charge density distribution anomaly index is: Define the neighborhood parameter k, for each data point p, calculate the Euclidean distance between it and all points in the data set, and find the kth nearest point, denoted as k-distance, marked as , used to define the k-neighborhood of p, i.e., the distance from p is no more than The set of all points of ; For each point p and its neighboring point o∈ , defines the reachable distance from p to o for: ;in, is the distance from point o to its kth nearest neighbor, called the k-distance of o. is the actual Euclidean distance between p and o, for and The maximum value in ; The local reachability density of each point p By calculating the average of the inverse of the reachable distances of all neighboring points of p, we can get: ; In the formula, represents the number of points in the k-neighborhood of p. For each point p, its local anomaly factor is calculated by the ratio of its neighbors’ local reachability density to its own local reachability density. , the expression is: ; In the formula, for The local reachable density of the point is calculated based on the The charge density distribution anomaly index is obtained by performing weighted average calculation on the values.

3. A quality inspection method for cable production according to claim 2, characterized in that: In S4, the breakdown voltage fluctuation index is generated after analyzing the variation range of the breakdown voltage value between each measurement point. The method for obtaining the breakdown voltage fluctuation index is: Define the size of the sliding window w, that is, the number of measurement points included in each calculation of the standard deviation. After determining the window size w, traverse the entire breakdown voltage data set in a sliding manner. For each sliding window starting from the first point in the data set, calculate the standard deviation of the breakdown voltage value in the window, where the breakdown voltage data is , the data in the i-th window is ; In each sliding window, calculate the mean breakdown voltage and standard deviation ; Traverse the data set by sliding window and calculate the standard deviation of each window Summarize to form a set of standard deviation data ; Use the aggregated standard deviation data to calculate the overall fluctuation index, and take the mean of the standard deviations of all windows as the final breakdown voltage fluctuation index, expressed as: ; Where SD is the breakdown voltage fluctuation index.

4. A quality inspection method for cable production according to claim 3, characterized in that: In S5, the charge density distribution anomaly index and the breakdown voltage fluctuation index are converted into feature vectors, and the feature vectors are used as inputs of the machine learning model. The machine learning model predicts the risk value label of electrostatic accumulation in high potential areas for each group of feature vectors as a prediction target, and minimizes the sum of prediction errors of risk value labels of electrostatic accumulation in all high potential areas as a training target. The machine learning model is trained until the sum of prediction errors converges, and the model training is stopped. The risk value of electrostatic accumulation in high potential areas is determined according to the model output results, wherein the machine learning model is a polynomial regression model.

5. A quality inspection method for cable production according to claim 4, characterized in that: In S6, according to the risk of electrostatic accumulation in the high potential area, the high potential area is divided into high risk area, medium risk area and low risk area, specifically: The obtained risk value of electrostatic accumulation in the high potential area is compared with the gradient standard threshold, the gradient standard threshold includes a first standard threshold and a second standard threshold, and the first standard threshold is less than the second standard threshold, and the risk value of electrostatic accumulation in the high potential area is compared with the first standard threshold and the second standard threshold respectively; If the risk value of electrostatic accumulation in the high potential area is greater than the second standard threshold, it means that the risk of electrostatic accumulation in the high potential area is high, and a first-level warning signal is generated, and the high potential area on the cable surface is divided into a high-risk area; If the risk value of electrostatic accumulation in the high potential area is greater than or equal to the first standard threshold and less than or equal to the second standard threshold, it means that the risk of electrostatic accumulation in the high potential area is medium, and a secondary warning signal is generated, and the high potential area on the cable surface is divided into a medium risk area; If the risk value of static electricity accumulation in the high potential area is less than the first standard threshold, it means that the risk of static electricity accumulation in the high potential area is low. At this time, a third-level warning signal is generated, and the high potential area on the cable surface is divided into a low-risk area.

6. A quality inspection method for cable production according to claim 5, characterized in that: In S6, the risk of electrostatic accumulation in the high potential area on the cable surface in the medium risk area within a fixed time period is further analyzed, and corresponding electrostatic suppression and detection equipment protection measures are taken according to the analysis results, specifically: The charge density σ(t) and potential V(t) on the cable surface are analyzed to identify the electrostatic accumulation trend in high potential areas. The charge density change rate is defined as: ;in, represents the rate of change of charge density, if If the change rate exceeds the preset threshold value Δσthreshold, it means that the speed of charge accumulation increases. At this time, the potential change rate of the high potential area is analyzed. The calculation expression of the potential change rate of the high potential area is: ; When ΔV is greater than the set potential change rate ΔVthreshold, it means that the potential accumulation is accelerating, and emergency electrostatic suppression measures should be taken immediately.

7. A quality inspection method for cable production according to claim 6, characterized in that: By applying a conductive coating on the cable surface to disperse the charge, the charge density is kept within a safe range and the coating resistance is satisfy: ;in, is the maximum potential threshold of the high potential region, is the desired charge discharge current, drain current satisfy: ; where A is the surface area of ​​the high potential region, is the ground resistance; by optimizing and A, control the drainage rate to ensure that the charge is discharged within a safe range; install a transient voltage suppressor TVS at the input end of the detection equipment to prevent the equipment from being damaged under instantaneous high voltage, and the TVS trigger voltage satisfy: ; Where Vthreshold is the device's withstand voltage threshold.

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