Method and system for evaluating conductivity uniformity of high-voltage cable buffer layer material
By applying constant current source current on the high-voltage cable buffer layer and using infrared cameras to collect temperature distribution maps, the problem of difficulty in evaluating the conductivity uniformity of the buffer layer in the prior art is solved, and the intuitive reflection of the conductive performance distribution and ablation risk are achieved. accurate judgment.
Patent Information
- Application Number
- CN202411541639.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-18
AI Technical Summary
The prior art is difficult to intuitively and effectively evaluate the conductivity uniformity of the high-voltage cable buffer layer, resulting in the inability to accurately judge the risk of ablation.
The constant current source provides a change in the surface temperature of the buffer layer. The infrared camera collects the temperature distribution map and analyzes the temperature distribution map to calculate the percentage of the surface overheating area to the total area, thereby determining the degree of conductivity uniformity.
It realizes an intuitive reflection of the conductive performance distribution of the buffer layer, can accurately locate local conductive performance problems, and improves the ability to judge the ablation risk of high-voltage cable buffer layer.
Smart Images
Figure CN119470547A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of electrical testing technology, and in particular to a method and system for evaluating the conductive uniformity of a high-voltage cable buffer layer material. Background Art
[0002] The buffer layer is an important component of the high-voltage cable structure. It is located between the cable insulation layer and the corrugated aluminum sheath and has the functions of conducting electricity, buffering mechanical damage and longitudinal water blocking. However, in recent years, in some large cities in China, such as Beijing, Shanghai, and Guangzhou, high-voltage cable body breakdown accidents have frequently occurred due to insufficient water blocking performance of the buffer layer. These accidents are structural defects of the cable, causing huge economic losses, and are increasing year by year. Therefore, reliably evaluating the risk of ablation defects in the high-voltage cable buffer layer has important engineering significance and economic value.
[0003] The conductive non-uniformity of the buffer layer is one of the main factors leading to the ablation defect of the buffer layer of high-voltage cables. The porous mesh structure of the buffer layer material gives it non-uniform semi-conductive properties. In addition, the pressure on the buffer layer causes its effective conductive path to change, thereby changing the distribution of volume resistivity. When the cable buffer layer is subjected to excessive pressure locally, the local volume resistivity will drop sharply, resulting in increased conductive non-uniformity of the buffer layer. This will lead to local current density concentration in the buffer layer, which will in turn cause overheating and ablation defects in the buffer layer, which is one of the main causes of ablation defects in the buffer layer of high-voltage cables. Therefore, accurately evaluating the non-uniformity of the conductive capacity of the buffer layer material is of great significance for judging the ablation risk of the high-voltage cable buffer layer.
[0004] At present, the relevant standards for buffer layers at home and abroad only stipulate the characterization method of the average volume resistivity of the buffer layer within a certain area. However, since the average volume resistivity can only provide the average value of the overall conductive performance, it cannot intuitively reflect the distribution and unevenness of the conductive performance. Therefore, there is currently a lack of intuitive and effective methods to evaluate the conductive uniformity of the buffer layer, which seriously limits the judgment of the ablation risk of the high-voltage cable buffer layer. Summary of the invention
[0005] The embodiments of the present invention provide a method and system for evaluating the conductivity uniformity of a buffer layer material of a high-voltage cable, which can intuitively reflect the distribution of the conductivity performance of the buffer layer material.
[0006] An embodiment of the present invention provides a method for evaluating the conductive uniformity of a high-voltage cable buffer layer material, comprising:
[0007] Obtaining a temperature distribution diagram of the buffer layer to be evaluated; wherein, after the current emitted by the constant current source passes through the buffer layer to be evaluated, the surface temperature of the buffer layer changes;
[0008] Analyze and extract the temperature distribution map of the buffer layer to be evaluated to obtain the area below the preset overheating temperature range, the area within the preset overheating temperature range, and the area above the preset overheating temperature range;
[0009] Calculate the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range;
[0010] The degree of conductivity uniformity of the buffer layer to be evaluated is determined according to the numerical range of the percentage.
[0011] Furthermore, before the buffer layer to be evaluated passes through the current emitted by the constant current source, the buffer layer to be evaluated has been dried.
[0012] Furthermore, the temperature distribution diagram of the buffer layer to be evaluated is analyzed and extracted to obtain the area below the preset overheating temperature range, the area within the preset overheating temperature range, and the area above the preset overheating temperature range, including:
[0013] De-noising, smoothing and contrast enhancement are performed on the temperature distribution map of the buffer layer to be evaluated to obtain a pre-processed temperature distribution map;
[0014] According to the preset overheating temperature range, the different temperature areas in the preprocessed temperature distribution map are segmented by an image segmentation algorithm to obtain areas below the preset overheating temperature range, areas within the preset overheating temperature range, and areas above the preset overheating temperature range;
[0015] By means of the pixel counting method, the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range and the area of the region above the preset overheating temperature range are obtained.
[0016] Further, according to the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, the percentage of the overheating area of the buffer layer to be evaluated to the total area is calculated, including:
[0017] The percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated by the following formula:
[0018]
[0019] Among them, δ represents the percentage of the overheated area of the buffer layer to be evaluated to the total area, p 1 Indicates the area below the preset overheat temperature range, p 2Represents the area of the region within the preset superheat temperature range, p 3 represents the area of the region above the preset overheating temperature range, S represents the total area of the buffer layer, ξ 1 , 2 and 3 represent the weight coefficient below the preset overheating temperature range, the weight coefficient within the preset overheating temperature range, and the weight coefficient above the preset overheating temperature range, respectively, and ξ 1 <ξ 2 <ξ 3 .
[0020] Further, according to the numerical range of the percentage, the degree of conductivity uniformity of the buffer layer to be evaluated is determined, including:
[0021] If the percentage is greater than 0 and does not exceed 20%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is good;
[0022] If the percentage is greater than 20% and less than 40%, it is determined that the degree of conductivity uniformity of the buffer layer to be evaluated is degraded;
[0023] If the percentage is greater than 40% and less than 60%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is significantly damaged;
[0024] If the percentage is greater than 60%, it is determined that the conductivity uniformity of the buffer layer to be evaluated has lost its conductivity and current-sharing capability.
[0025] Based on the above method embodiment, the present invention provides a system for evaluating the conductive uniformity of a high-voltage cable buffer layer material, including: a host computer, an infrared camera, conductive glass, a buffer layer to be evaluated, a wire clamp, a constant current source, and a protective resistor;
[0026] The two wire clamps respectively clamp two pieces of conductive glass, and the wire of one wire clamp is connected to the positive electrode of the constant current source, and the wire of the other wire clamp is connected to one end of the protective resistor; wherein the other end of the protective resistor is connected to the negative electrode of the constant current source;
[0027] The buffer layer to be evaluated is between two pieces of conductive glass; wherein both the upper and lower surfaces of the buffer layer to be evaluated are in contact with the conductive glass without any gap;
[0028] The infrared camera is placed directly above the buffer layer to be evaluated and the two conductive glasses, so that the infrared camera can collect the temperature distribution diagram of the buffer layer to be evaluated; wherein, after the current emitted by the constant current source passes through the buffer layer to be evaluated, the surface temperature of the buffer layer changes;
[0029] The host computer is used to obtain the temperature distribution map of the buffer layer to be evaluated transmitted by the infrared camera;
[0030] Analyze and extract the temperature distribution map of the buffer layer to be evaluated to obtain the area below the preset overheating temperature range, the area within the preset overheating temperature range, and the area above the preset overheating temperature range;
[0031] Calculate the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range;
[0032] The degree of conductivity uniformity of the buffer layer to be evaluated is determined according to the numerical range of the percentage.
[0033] Furthermore, the system for evaluating the conductivity uniformity of the high-voltage cable buffer layer material further includes: a drying box;
[0034] The drying box is used to dry the buffer layer to be evaluated before the buffer layer to be evaluated passes through the current emitted by the constant current source.
[0035] Furthermore, the host computer analyzes and extracts the temperature distribution map of the buffer layer to be evaluated, and obtains the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, including:
[0036] De-noising, smoothing and contrast enhancement are performed on the temperature distribution map of the buffer layer to be evaluated to obtain a pre-processed temperature distribution map;
[0037] According to the preset overheating temperature range, the different temperature areas in the preprocessed temperature distribution map are segmented by an image segmentation algorithm to obtain areas below the preset overheating temperature range, areas within the preset overheating temperature range, and areas above the preset overheating temperature range;
[0038] By means of the pixel counting method, the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range and the area of the region above the preset overheating temperature range are obtained.
[0039] Further, the host computer calculates the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range, including:
[0040] The percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated by the following formula:
[0041]
[0042] Among them, δ represents the percentage of the overheated area of the buffer layer to be evaluated to the total area, p 1 Indicates the area below the preset overheat temperature range, p 2 Represents the area of the region within the preset superheat temperature range, p 3 represents the area of the region above the preset overheating temperature range, S represents the total area of the buffer layer, ξ 1 , 2 and 3 represent the weight coefficient below the preset overheating temperature range, the weight coefficient within the preset overheating temperature range, and the weight coefficient above the preset overheating temperature range, respectively, and ξ 1 <ξ 2 <ξ 3 .
[0043] Furthermore, the host computer determines the degree of conductivity uniformity of the buffer layer to be evaluated according to the numerical range of the percentage, including:
[0044] If the percentage is greater than 0 and does not exceed 20%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is good;
[0045] If the percentage is greater than 20% and less than 40%, it is determined that the degree of conductivity uniformity of the buffer layer to be evaluated is degraded;
[0046] If the percentage is greater than 40% and less than 60%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is significantly damaged;
[0047] If the percentage is greater than 60%, it is determined that the conductivity uniformity of the buffer layer to be evaluated has lost its conductivity and current-sharing capability.
[0048] Compared with the prior art, the beneficial effects of the embodiment of this solution are:
[0049] The present invention provides current through a constant current source so that the surface temperature of the buffer layer to be evaluated changes after the current is passed through it, and then the surface temperature distribution of the buffer layer to be evaluated is collected by an infrared camera to generate a temperature distribution map of the buffer layer to be evaluated. The temperature distribution map can intuitively show which areas are seriously heated by the color of the temperature. These seriously heated areas indicate areas with poor conductivity, high impedance or local faults, which helps to locate local conductivity problems; then, the temperature distribution map of the buffer layer to be evaluated is analyzed and extracted to determine the area below a preset overheating temperature range, the area within a preset overheating temperature range, and the area above a preset overheating temperature range, and then calculate the percentage of the surface overheating area of the buffer layer to be evaluated to the total area. According to the numerical range of this percentage, the degree of conductivity uniformity of the buffer layer to be evaluated can be determined.
[0050] In summary, after the buffer layer is heated by a constant current source, the surface temperature distribution diagram of the buffer layer is collected by an infrared camera, and the distribution of the conductive properties is intuitively reflected by different temperature colors, which helps to locate local conductive properties problems. BRIEF DESCRIPTION OF THE DRAWINGS
[0051] Figure 1 It is a schematic flow chart of a method for evaluating the conductive uniformity of a high-voltage cable buffer layer material provided by an embodiment of the present invention;
[0052] Figure 2 It is a structural schematic diagram of an evaluation system for the conductive uniformity of a high-voltage cable buffer layer material provided by an embodiment of the present invention; wherein, 1 is a host computer, 2 is an infrared camera, 3 is a first conductive glass, 4 is a second conductive glass, 5 is a buffer layer to be evaluated, 6 is a first wire clamp, 7 is a second wire clamp, 8 is a constant current source, and 9 is a protective resistor. DETAILED DESCRIPTION
[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.
[0054] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.
[0055] like Figure 1 As shown, an embodiment of the present invention provides a method for evaluating the conductive uniformity of a high-voltage cable buffer layer material, the method comprising at least the following steps:
[0056] Step S1: obtaining a temperature distribution diagram of the buffer layer to be evaluated; wherein, after the buffer layer to be evaluated passes through the current emitted by the constant current source, the surface temperature of the buffer layer changes;
[0057] In a preferred embodiment, the buffer layer to be evaluated has been dried before the current emitted by the constant current source passes through the buffer layer to be evaluated.
[0058] For step S1, first, the original buffer layer to be evaluated is placed in a drying box for drying in advance. During the drying process, the drying temperature range is set between 60°C and 100°C, and the drying time is set between 6h and 24h to remove moisture from the buffer layer to be evaluated, so as to avoid the influence of moisture on the measurement of thermal radiation and surface temperature distribution in the subsequent evaluation process.
[0059] Next, the dried buffer layer to be evaluated is used as the evaluation material, and the constant current source is turned on to apply a constant current to the buffer layer to be evaluated. The constant current range is between 50mA and 800mA, and it lasts for a period of time. The constant current duration of this embodiment is between 30s and 60min. When the constant current flows through the buffer layer to be evaluated, it will cause the surface temperature of the buffer layer to be evaluated to change. The buffer layer to be evaluated is photographed using a high-precision infrared camera. The infrared camera will capture the thermal radiation on the surface of the buffer layer to be evaluated and convert it into a thermal image, thereby obtaining a temperature distribution map of the buffer layer to be evaluated. In order to ensure accuracy, it is necessary to avoid obstructions during the shooting process and keep the camera stable to avoid image blur or jitter.
[0060] It should be noted that the buffer layer material of the present invention is a part of the material in the high-voltage cable, located between the cable insulation shielding layer and the corrugated aluminum sheath, and plays the role of providing a conductive path, buffering mechanical damage, and longitudinal water blocking.
[0061] Step S2: Analyze and extract the temperature distribution diagram of the buffer layer to be evaluated, and obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range;
[0062] In a preferred embodiment, the temperature distribution diagram of the buffer layer to be evaluated is analyzed and extracted to obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, including:
[0063] De-noising, smoothing and contrast enhancement are performed on the temperature distribution map of the buffer layer to be evaluated to obtain a pre-processed temperature distribution map;
[0064] According to the preset overheating temperature range, the different temperature areas in the preprocessed temperature distribution map are segmented by an image segmentation algorithm to obtain areas below the preset overheating temperature range, areas within the preset overheating temperature range, and areas above the preset overheating temperature range;
[0065] By means of the pixel counting method, the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range and the area of the region above the preset overheating temperature range are obtained.
[0066] For step S2, the temperature distribution map of the buffer layer to be evaluated is collected by a high-precision infrared camera and transmitted to the host computer through a wired or wireless transmission method. On the host computer, first, the temperature distribution map is preprocessed: the temperature distribution map is denoised by using image filtering technology, such as median filtering or Gaussian filtering, to eliminate noise interference in the image and improve image quality; the denoised temperature distribution map is smoothed by a smoothing filter to eliminate discontinuities and detail noise in the temperature distribution map, so that the contour of the temperature distribution map is smoother; in order to enhance the visualization effect of the image, the temperature distribution map is processed by enhancing the contrast to make different temperature areas more obvious and clear, which is helpful for subsequent image segmentation and analysis.
[0067] Secondly, an image segmentation algorithm, such as threshold segmentation or a segmentation method based on edge detection, is used to segment the preprocessed temperature distribution map into different temperature regions, each region representing a different temperature range. In this embodiment, the overheating temperature range is set to 50°C to 200°C, and the temperature distribution map is divided into three regions, namely, a region below the overheating temperature range (the temperature of this region is <50°C), a region processing the overheating temperature range (50°C≤the temperature of this region≤200°C), and a region above the overheating temperature range (the temperature of this region is >200°C).
[0068] For each temperature zone, traverse each pixel of the temperature distribution map and count it according to the temperature zone to which the pixel belongs. When a pixel belongs to a certain temperature zone, the pixel count of the corresponding zone increases. According to the pixel count, calculate the area of each temperature zone, where the size of each pixel can be determined according to the resolution of the infrared camera. Multiply the pixel count by the size of each pixel to get the area of each temperature zone, that is, the area p of the area below the preset overheating temperature range. 1 , the area p of the region within the preset overheating temperature range 2 And the area p above the preset overheat temperature range 3 .
[0069] Step S3: Calculate the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range;
[0070] In a preferred embodiment, the percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated based on the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range, including:
[0071] The percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated by the following formula:
[0072]
[0073] Among them, δ represents the percentage of the overheated area of the buffer layer to be evaluated to the total area, p 1 Indicates the area below the preset overheat temperature range, p 2 Represents the area of the region within the preset superheat temperature range, p 3 represents the area of the region above the preset overheating temperature range, S represents the total area of the buffer layer, ξ 1 , 2 and 3 represent the weight coefficient below the preset overheating temperature range, the weight coefficient within the preset overheating temperature range, and the weight coefficient above the preset overheating temperature range, respectively, and ξ 1 <ξ 2 <ξ 3 .
[0074] For step S3, the percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated by the formula Considering the area contribution and weight coefficient of different temperature zones, the proportion of the overheated area on the buffer layer surface to the total area of the buffer layer is comprehensively evaluated. By calculating the percentage δ of the overheated area on the buffer layer surface to be evaluated to the total area, the severity of the overheating problem can be understood more accurately.
[0075] In this embodiment, the weight coefficient ξ 1 , 2 and 3 The values are 0.1, 0.5 and 1 respectively, where the area above the preset overheating temperature range contributes the most to the percentage, and the area below the preset overheating temperature range contributes the least to the percentage. This setting can reflect the importance of the high temperature area to the overheating problem. It should be noted that according to the conditions of different materials, the weight coefficient can be adjusted to flexibly control the influence of different temperature areas on the overheating percentage.
[0076] Step S4: Determine the degree of conductivity uniformity of the buffer layer to be evaluated according to the numerical range of the percentage.
[0077] In a preferred embodiment, determining the degree of conductivity uniformity of the buffer layer to be evaluated according to the numerical range of the percentage includes:
[0078] If the percentage is greater than 0 and does not exceed 20%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is good;
[0079] If the percentage is greater than 20% and less than 40%, it is determined that the degree of conductivity uniformity of the buffer layer to be evaluated is degraded;
[0080] If the percentage is greater than 40% and less than 60%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is significantly damaged;
[0081] If the percentage is greater than 60%, it is determined that the conductivity uniformity of the buffer layer to be evaluated has lost its conductivity and current-sharing capability.
[0082] For step S4, the degree of conductive uniformity of the buffer layer to be evaluated is judged according to the percentage of the overheated area of the buffer layer to be evaluated calculated in step S3 to the total area. If the percentage is greater than 0 and not more than 20%, this means that the percentage of the overheated area of the buffer layer to be evaluated to the total area is small, indicating that the conductive uniformity of the buffer layer is good, and the conductive uniformity of the buffer layer to be evaluated is judged to be good; if the percentage is greater than 20% and not more than 40%, this means that the percentage of the overheated area of the buffer layer to be evaluated to the total area is large, indicating that the conductive uniformity of the buffer layer has deteriorated, and the conductive uniformity of the buffer layer to be evaluated is judged to be deteriorated; if the percentage is greater than 40% and not more than 60%, this means that the percentage of the overheated area of the buffer layer to be evaluated to the total area has increased significantly, indicating that the conductive uniformity of the buffer layer has been significantly damaged, and the conductive uniformity of the buffer layer to be evaluated is judged to be significantly damaged; if the percentage is greater than 60%, this means that the percentage of the overheated area of the buffer layer to be evaluated to the total area is very large, exceeding the threshold of 60%. This means that the conductive uniformity of the buffer layer has been severely damaged and cannot provide normal conductive current sharing capability. The conductive uniformity of the buffer layer to be evaluated is judged to have lost its conductive current sharing capability.
[0083] Based on the percentage of hot spot area on the buffer layer surface to be evaluated to the total area, the conductive uniformity of the buffer layer can be quantitatively evaluated, thereby gaining a more comprehensive understanding of the data support for the buffer layer material in high-voltage cables, which helps ensure the stable operation of high-voltage cables and extend their service life.
[0084] It should be noted that compared with the buffer layer volume resistivity test method specified in the industry standard, this method calculates the volume resistivity value by measuring the current and voltage difference to evaluate the conductivity of the buffer layer. The volume resistivity value reflects the overall conductivity of the buffer layer. The lower the volume resistivity value, the better the conductivity of the buffer layer. The current can pass through the entire buffer layer more evenly, thereby reducing the risk of local overheating and burning. However, this test method cannot intuitively understand the distribution of the conductivity inside the buffer layer.
[0085] Therefore, the present invention proposes a method for evaluating the conductive uniformity of the above-mentioned high-voltage cable buffer layer material. The surface temperature of the buffer layer is collected by an infrared camera, and the percentage of the overheated surface area of the buffer layer to the total area can be quantitatively calculated by analyzing the infrared image. This can provide a more comprehensive and intuitive understanding of the conductive performance and distribution of the buffer layer, and help to discover and locate areas with poor conductive performance, thereby providing more targeted data support for formulating repairs, improvements and material selections, and helping to ensure the stable operation of the high-voltage cable and extend its service life.
[0086] like Figure 2 As shown, based on the above method embodiment, a corresponding system embodiment is provided;
[0087] An embodiment of the present invention provides a system for evaluating the conductivity uniformity of a high-voltage cable buffer layer material, comprising: a host computer 1, an infrared camera 2, a first conductive glass 3, a second conductive glass 4, a buffer layer to be evaluated 5, a first wire clamp 6, a second wire clamp 7, a constant current source 8, and a protective resistor 9;
[0088] The first wire clamp 6 clamps the first conductive glass 3, and the wire of the first wire clamp 6 is connected to the positive electrode of the constant current source 8. The second wire clamp 7 clamps the second conductive glass 4, and the wire of the second wire clamp 7 is connected to one end of the protection resistor 9; wherein the other end of the protection resistor 9 is connected to the negative electrode of the constant current source 8;
[0089] The buffer layer 5 to be evaluated is between the first conductive glass 3 and the second conductive glass 4; wherein the upper and lower surfaces of the buffer layer 5 to be evaluated are in contact with the conductive glass without any gap;
[0090] The infrared camera 2 is placed directly above the buffer layer 5 to be evaluated and the two conductive glasses, so that the infrared camera 2 can collect the temperature distribution diagram of the buffer layer 5 to be evaluated; wherein, after the buffer layer 5 to be evaluated passes through the current emitted by the constant current source 8, the surface temperature of the buffer layer changes;
[0091] The host computer 1 is used to obtain the temperature distribution diagram of the buffer layer 5 to be evaluated transmitted by the infrared camera 2;
[0092] Analyze and extract the temperature distribution diagram of the buffer layer 5 to be evaluated, and obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range;
[0093] Calculate the percentage of the surface overheating area of the buffer layer 5 to be evaluated to the total area according to the area of the area below the preset overheating temperature range, the area within the preset overheating temperature range, and the area above the preset overheating temperature range;
[0094] According to the numerical range of the percentage, the degree of conductivity uniformity of the buffer layer 5 to be evaluated is determined.
[0095] In the above system, the buffer layer 5 to be evaluated is a rectangular parallelepiped with dimensions of 15 cm×15 cm×5 cm. In comparison, the dimensions of the first conductive glass 3 and the second conductive glass 4 are A cm×15 cm×5 cm, wherein A>15, i.e., the length (A) of the first conductive glass 3 and the second conductive glass 4 is longer than that of the buffer layer 5 to be evaluated, so as to ensure that they completely cover both sides of the buffer layer 5 to be evaluated, so as to achieve good contact and heat conduction effects.
[0096] After the constant current source 8 is turned on, a constant current is generated from the positive electrode of the constant current source 8, and the current intensity range is between 50mA and 800mA. The current is transmitted to the first wire clamp 6 along the wire, and the first wire clamp 6 clamps the second conductive glass 4, so that the current is transmitted to the second conductive glass 4. Then, the current is transmitted to the first conductive glass 3 and the second wire clamp 7 through contact with the buffer layer 5 to be evaluated. Finally, the current is transmitted back to the negative electrode of the constant current source 8 through the wire. It should be noted that the duration of the emitted current should be between 30s and 60min. If the current duration is too short, the surface temperature distribution diagram of the buffer layer 5 to be evaluated may not reflect the conductivity uniformity, and if the current duration is too long, the buffer layer 5 to be evaluated may be damaged.
[0097] In a preferred embodiment, the system for evaluating the conductivity uniformity of the high-voltage cable buffer layer material further includes: a drying box;
[0098] The drying box is used to dry the buffer layer 5 to be evaluated before the buffer layer 5 to be evaluated passes through the current emitted by the constant current source 8 .
[0099] In one embodiment of the present invention, the drying box is mainly used in the evaluation system of the conductive uniformity of the high-voltage cable buffer layer material to dry the buffer layer 5 to be evaluated, and remove the moisture or other volatile substances in the buffer layer 5 to be evaluated. The presence of moisture or other volatile substances will affect the conductive performance of the buffer layer 5 to be evaluated, so it is necessary to ensure that the surface of the material is dry to provide a reliable benchmark for the subsequent conductive performance evaluation.
[0100] In a preferred embodiment, the host computer 1 analyzes and extracts the temperature distribution diagram of the buffer layer 5 to be evaluated, and obtains the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, including:
[0101] De-noising, smoothing and contrast enhancement are performed on the temperature distribution map of the buffer layer 5 to be evaluated, so as to obtain a pre-processed temperature distribution map;
[0102] According to the preset overheating temperature range, the different temperature areas in the preprocessed temperature distribution map are segmented by an image segmentation algorithm to obtain areas below the preset overheating temperature range, areas within the preset overheating temperature range, and areas above the preset overheating temperature range;
[0103] By means of the pixel counting method, the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range and the area of the region above the preset overheating temperature range are obtained.
[0104] In a preferred embodiment, the host computer 1 calculates the percentage of the overheated area of the surface of the buffer layer 5 to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range, including:
[0105] The percentage of the overheated surface area of the buffer layer 5 to be evaluated to the total area is calculated by the following formula:
[0106]
[0107] Wherein, δ represents the percentage of the overheated area of the buffer layer 5 to be evaluated to the total area, p 1 Indicates the area below the preset overheat temperature range, p 2 Represents the area of the region within the preset superheat temperature range, p 3 represents the area of the region above the preset overheating temperature range, S represents the total area of the buffer layer, ξ 1 , 2 and 3 represent the weight coefficient below the preset overheating temperature range, the weight coefficient within the preset overheating temperature range, and the weight coefficient above the preset overheating temperature range, respectively, and ξ 1 <ξ 2 <ξ 3 .
[0108] In a preferred embodiment, the host computer 1 determines the degree of conductivity uniformity of the buffer layer 5 to be evaluated according to the numerical range of the percentage, including:
[0109] If the percentage is greater than 0 and does not exceed 20%, it is determined that the degree of conductive uniformity of the buffer layer 5 to be evaluated is good;
[0110] If the percentage is greater than 20% and not more than 40%, it is determined that the degree of conductivity uniformity of the buffer layer 5 to be evaluated is degraded;
[0111] If the percentage is greater than 40% and less than 60%, it is determined that the degree of conductive uniformity of the buffer layer 5 to be evaluated is significantly damaged;
[0112] If the percentage is greater than 60%, it is determined that the conductivity uniformity of the buffer layer 5 to be evaluated has lost its conductivity and current-sharing capability.
[0113] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.
Claims
1. A method for evaluating the conductive uniformity of a high-voltage cable buffer layer material, characterized in that: include: Acquire a temperature distribution diagram of the buffer layer to be evaluated; wherein, after the buffer layer to be evaluated passes through the current emitted by the constant current source, the surface temperature of the buffer layer changes; Analyze and extract the temperature distribution map of the buffer layer to be evaluated to obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range; Calculate the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area within the preset overheated temperature range, and the area above the preset overheated temperature range; The degree of conductivity uniformity of the buffer layer to be evaluated is determined according to the numerical range of the percentage.
2. The method for evaluating the conductive uniformity of a high-voltage cable buffer layer material according to claim 1, characterized in that: Before the buffer layer to be evaluated is subjected to the current emitted by the constant current source, the buffer layer to be evaluated has been dried.
3. The method for evaluating the conductivity uniformity of a high-voltage cable buffer layer material according to claim 1, characterized in that: The temperature distribution diagram of the buffer layer to be evaluated is analyzed and extracted to obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, including: De-noising, smoothing and contrast enhancement are performed on the temperature distribution map of the buffer layer to be evaluated to obtain a pre-processed temperature distribution map; According to the preset overheating temperature range, the different temperature regions in the preprocessed temperature distribution map are segmented by an image segmentation algorithm to obtain regions below the preset overheating temperature range, regions within the preset overheating temperature range, and regions above the preset overheating temperature range; By means of the pixel counting method, the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range and the area of the region above the preset overheating temperature range are obtained.
4. The method for evaluating the conductive uniformity of a high-voltage cable buffer layer material according to claim 1, characterized in that: According to the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, the percentage of the overheating area of the buffer layer to be evaluated to the total area is calculated, including: The percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated by the following formula: Among them, δ represents the percentage of the overheated area of the buffer layer to be evaluated to the total area, p1 represents the area of the region below the preset overheated temperature range, p2 represents the area of the region within the preset overheated temperature range, p3 represents the area of the region above the preset overheated temperature range, S represents the total area of the buffer layer, ξ1, ξ2 and ξ3 represent the weight coefficient below the preset overheated temperature range, the weight coefficient within the preset overheated temperature range and the weight coefficient above the preset overheated temperature range, respectively, and ξ1<ξ2<ξ3.
5. The method for evaluating the conductive uniformity of a high-voltage cable buffer layer material according to claim 1, characterized in that: Determining the degree of conductivity uniformity of the buffer layer to be evaluated according to the numerical range of the percentage includes: If the percentage is greater than 0 and not more than 20%, it is determined that the conductivity uniformity of the buffer layer to be evaluated is good; If the percentage is greater than 20% and less than 40%, it is determined that the degree of conductivity uniformity of the buffer layer to be evaluated is degraded; If the percentage is greater than 40% and less than 60%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is significantly damaged; If the percentage is greater than 60%, it is determined that the conductivity uniformity of the buffer layer to be evaluated has lost its conductivity and current balancing capability.
6. A system for evaluating the conductivity uniformity of a high-voltage cable buffer layer material, characterized in that: include: Host computer, infrared camera, conductive glass, buffer layer to be evaluated, wire clamp, constant current source and protective resistor; The two wire clamps respectively clamp the two conductive glasses, and the wire of one wire clamp is connected to the positive electrode of the constant current source, and the wire of the other wire clamp is connected to one end of the protective resistor; wherein the other end of the protective resistor is connected to the negative electrode of the constant current source; The buffer layer to be evaluated is between the two pieces of conductive glass; wherein the upper and lower surfaces of the buffer layer to be evaluated are in full contact with the conductive glass without any gap; The infrared camera is placed directly above the buffer layer to be evaluated and the two conductive glasses, so that the infrared camera collects a temperature distribution diagram of the buffer layer to be evaluated; wherein, after the current emitted by the constant current source passes through the buffer layer to be evaluated, the surface temperature of the buffer layer changes; The host computer is used to obtain the temperature distribution map of the buffer layer to be evaluated transmitted by the infrared camera; Analyze and extract the temperature distribution map of the buffer layer to be evaluated to obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range; Calculate the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area within the preset overheated temperature range, and the area above the preset overheated temperature range; The degree of conductivity uniformity of the buffer layer to be evaluated is determined according to the numerical range of the percentage.
7. The evaluation system for the conductive uniformity of the high-voltage cable buffer layer material according to claim 6, characterized in that: Also includes: Drying box; The drying box is used to dry the buffer layer to be evaluated before the buffer layer to be evaluated passes through the current emitted by the constant current source.
8. The system for evaluating the conductivity uniformity of the high-voltage cable buffer layer material according to claim 6, characterized in that: The host computer analyzes and extracts the temperature distribution map of the buffer layer to be evaluated to obtain the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range, and the area of the region above the preset overheating temperature range, including: De-noising, smoothing and contrast enhancement are performed on the temperature distribution map of the buffer layer to be evaluated to obtain a pre-processed temperature distribution map; According to the preset overheating temperature range, the different temperature regions in the preprocessed temperature distribution map are segmented by an image segmentation algorithm to obtain regions below the preset overheating temperature range, regions within the preset overheating temperature range, and regions above the preset overheating temperature range; By means of the pixel counting method, the area of the region below the preset overheating temperature range, the area of the region within the preset overheating temperature range and the area of the region above the preset overheating temperature range are obtained.
9. The system for evaluating the conductivity uniformity of the high-voltage cable buffer layer material according to claim 6, characterized in that: The host computer calculates the percentage of the overheated area of the buffer layer to be evaluated to the total area according to the area of the area below the preset overheated temperature range, the area of the area within the preset overheated temperature range, and the area of the area above the preset overheated temperature range, including: The percentage of the overheated area of the buffer layer to be evaluated to the total area is calculated by the following formula: Among them, δ represents the percentage of the overheated area of the buffer layer to be evaluated to the total area, p1 represents the area of the region below the preset overheated temperature range, p2 represents the area of the region within the preset overheated temperature range, p3 represents the area of the region above the preset overheated temperature range, S represents the total area of the buffer layer, ξ1, ξ2 and ξ3 represent the weight coefficient below the preset overheated temperature range, the weight coefficient within the preset overheated temperature range and the weight coefficient above the preset overheated temperature range, respectively, and ξ1<ξ2<ξ3.
10. The system for evaluating the conductivity uniformity of the high-voltage cable buffer layer material according to claim 6, characterized in that: The host computer determines the degree of conductivity uniformity of the buffer layer to be evaluated according to the numerical range of the percentage, including: If the percentage is greater than 0 and not more than 20%, it is determined that the conductivity uniformity of the buffer layer to be evaluated is good; If the percentage is greater than 20% and less than 40%, it is determined that the degree of conductivity uniformity of the buffer layer to be evaluated is degraded; If the percentage is greater than 40% and less than 60%, it is determined that the degree of conductive uniformity of the buffer layer to be evaluated is significantly damaged; If the percentage is greater than 60%, it is determined that the conductivity uniformity of the buffer layer to be evaluated has lost its conductivity and current balancing capability.