Power cable semi-conductive shielding material strip surface protrusion form detection method

Abstract

The invention discloses a method for detecting the shape of a bulge on the surface of a power cable semi-conductive shielding material strip, and the method comprises the following steps: carrying out the physical modification of the surface of a to-be-detected power cable semi-conductive shielding material strip through a modifying substance, and preparing a modified to-be-detected substance; detecting the surface of the modified to-be-detected object by using a super depth-of-field microscope, and determining the size of a surface bulge of the to-be-detected power cable semi-conductive shielding material strip; the modified substance comprises one or two of polyethylene glycol and paraffin. The surface of the power cable semi-conductive shielding material strip is physically modified, so that pits in the surface of the strip are effectively filled, the roughness of the surface of the strip is reduced, flaw sites are filtered and eliminated, the real 3D form of protrusions on the surface of a cable semi-conductive shielding layer can be effectively observed by adopting a super-depth-of-field microscope, the size precision is higher, and the service life is prolonged. Based on optical detection and a Z-axis depth image synthesis technology, the real shape and size of the surface bulge can be more accurately restored, and meanwhile, the method is simple to operate and high in reproducibility.

Description

Technical Field

[0001] The invention relates to the field of detection, and in particular to a method for detecting the morphology of protrusions on the surface of a semi-conductive shielding material strip of a power cable. Background Art

[0002] In the construction of modern urban power grids and the layout of offshore wind power, high-voltage cables and even ultra-high-voltage cables play an indispensable role. The demand for high-voltage and ultra-high-voltage cables has grown rapidly, driving the market demand for domestic ultra-smooth high-voltage semi-conductive shielding materials.

[0003] The semi-conductive shielding layer of the cable is mainly made of base resin, conductive carbon black and dispersant through melt blending and extrusion. It plays an important role in eliminating the air gap between the metal core and the insulation layer and evenly distributing the interface electric field in the cable structure. The service life and safety of high-voltage cables are closely related to the performance of their semi-conductive shielding layer. Key performance indicators such as the mechanical properties, electrical properties and surface finish of the shielding layer determine the upper limit of the voltage level that the high-voltage cable can withstand.

[0004] Since the semi-conductive shielding layer contains tiny carbon black particles, surface protrusions may be formed during the manufacturing process, affecting the interface coordination between the insulating layer and the semi-conductive shielding layer. According to the Mason equation, the surface protrusions will cause the electric field distortion at the interface between the insulating layer and the shielding layer, thereby shortening the service life of the high-voltage cable. According to my country's standard GB / T18890.2-2015, the semi-conductive shielding layer should be evenly coated on the insulating layer and tightly bonded to it. Therefore, the higher the voltage level of the cable, the higher the requirements for the surface finish of the semi-conductive shielding layer, and the stricter the size control of the surface protrusions to ensure that it can effectively and evenly distribute the electric field.

[0005] The traditional surface finish evaluation method is mainly based on sampling and testing the extruded strip with an industrial optical microscope, recording whether the size of the protrusions on the surface of the shielding layer within a certain length or a certain observation area meets the product's use standards. However, the industrial optical microscope can only reflect the 2D shape and size of the protrusions, and cannot truly reflect the true shape and size of the protrusions. For the shielding layer of high-voltage and ultra-high-voltage cables, the surface finish requirements are higher, and the number and size of the surface protrusions are smaller. At this time, the characterization accuracy of the industrial optical microscope is even more difficult to meet the needs. Summary of the invention

[0006] Based on this, it is necessary to provide a method for detecting the morphology of protrusions on the surface of semi-conductive shielding material strips of power cables with higher characterization accuracy.

[0007] The present application provides a method for detecting the morphology of protrusions on the surface of a semi-conductive shielding material strip of a power cable.

[0008] The following steps are involved:

[0009] Using a modified substance to physically modify the surface of a semi-conductive shielding material strip of a power cable to be tested, so as to prepare a modified object to be tested;

[0010] Using an ultra-depth-of-field microscope to detect the surface of the modified object to be tested, and determining the size of the surface protrusions of the semi-conductive shielding material strip of the power cable to be tested;

[0011] The modifying substance includes one or both of polyethylene glycol and paraffin.

[0012] In one embodiment, the step of physical modification includes: immersing the semi-conductive shielding material tape of the power cable to be tested into a modifying substance, and physically coating the surface of the semi-conductive shielding material tape of the power cable to be tested.

[0013] In one of the embodiments, the semi-conductive shielding material tape of the power cable to be tested is immersed in the modified substance for a time period of 1 min to 10 min.

[0014] In one of the embodiments, the semiconductive shielding material tape of the power cable to be tested is immersed in the modifying substance at a temperature greater than the melting point of the modifying substance.

[0015] In one of the embodiments, the temperature at which the semi-conductive shielding material tape of the power cable to be tested is immersed in the modified substance is 50°C to 70°C.

[0016] In one embodiment, the physical modification further includes polishing and cleaning steps to prepare the modified analyte.

[0017] In one embodiment, the cleaning agent in the cleaning step is an organic solvent.

[0018] In one embodiment, the organic solvent includes one or more of ethanol, ether, acetone, toluene, xylene, chloroform and gasoline.

[0019] In one embodiment, the thickness of the modified object to be tested is 0.8 mm to 1.2 mm.

[0020] In one embodiment, the step of determining the size of the surface protrusions of the semi-conductive shielding material strip of the power cable to be tested includes: using the white balance mode of the ultra-depth of field microscope to detect the surface of the modified test object.

[0021] The present application can effectively fill the surface pits of the semi-conductive shielding material strip of the power cable by physically modifying the surface of the semi-conductive shielding material strip of the power cable, reduce the roughness of the material surface and filter out defective sites, and further use the ultra-depth of field microscope to effectively observe the true 3D shape of the protrusions on the surface of the cable semi-conductive shielding layer with higher dimensional accuracy. Based on optical detection and Z-axis depth image synthesis technology, the true shape and size of the surface protrusions can be restored more accurately and realistically. At the same time, this method is simple to operate and has strong reproducibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The observation results of the surface defects of the same power cable semi-conductive shielding material strip under traditional industrial optical microscope and super depth of field microscope are compared.

[0024] Figure 2 The ultra-depth-of-field microscopy characterization results of typical protrusions of the semiconductive shielding material tape 1 for power cables.

[0025] Figure 3 The ultra-depth-of-field microscopy characterization results of typical protrusions of the semiconductive shielding material tape 2 for power cables.

[0026] Figure 4 These are the ultra-depth-of-field microscopy characterization results of typical protrusions of the power cable semiconductive shielding material tape 3 before and after surface modification with polyethylene glycol.

[0027] Figure 5 These are the characterization results of the traditional industrial optical microscope on the surface of the power cable semiconductive shielding material tape 3 after being modified with tetradecanol. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0030] The term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" includes three parallel solutions: A, B, and "a combination of A and B".

[0031] In this article, unless otherwise specified, "one or more" means any one of the listed items or any combination of the listed items. Similarly, "one or more" and other expressions that mean "one or more" are also understood in the same way unless otherwise specified.

[0032] In this document, "further", "further", "particularly", "for example", "such as", "example", "for example", etc. are used for descriptive purposes, indicating that the previous and subsequent technical solutions are related in terms of the content covered, but should not be understood as limiting the previous technical solution, nor can they be understood as limiting the scope of protection of this document. In this document, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0033] Herein, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If multiple "optional" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" item is independent of each other. In this application, descriptions such as "optionally contain", "optionally include", etc. mean "contain or not contain". "Optional component X" means that component X exists or does not exist, or means that component X is contained or not contained.

[0034] In this document, the terms "first", "second", "third", "fourth", etc. in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0035] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0036] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0037] Herein, the term "room temperature" or "normal temperature" generally refers to 4°C~35°C, for example, 20°C±5°C. In some embodiments herein, "room temperature" or "normal temperature" refers to 10°C~30°C. In some embodiments herein, "room temperature" or "normal temperature" refers to 20°C~30°C.

[0038] In this article, if there are multiple steps involved in the method flow, unless there is a clear different description in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders than described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0039] The present application provides a method for detecting the morphology of protrusions on the surface of a semi-conductive shielding material strip of a power cable, comprising the following steps:

[0040] Using a modified substance to physically modify the surface of a semi-conductive shielding material strip of a power cable to be tested, so as to prepare a modified object to be tested;

[0041] The surface of the modified object to be tested is inspected using an ultra-depth-of-field microscope to determine the size of the surface protrusions of the semi-conductive shielding material strip of the power cable to be tested;

[0042] The modifying substance includes one or both of polyethylene glycol and paraffin wax.

[0043] Furthermore, the modified substance is polyethylene glycol with a weight average molecular weight of 5000-8000, polyethylene glycol with a melting point of 40°C-60°C, and paraffin with a melting point of 52°C-57°C.

[0044] In a specific example, the step of physical modification includes: immersing the semi-conductive shielding material tape of the power cable to be tested into a modifying substance, and physically coating the surface of the semi-conductive shielding material tape of the power cable to be tested.

[0045] In a specific example, the semi-conductive shielding material tape of the power cable to be tested is immersed in the modified substance for 1 min to 10 min. Further, the time for the semi-conductive shielding material tape of the power cable to be tested to be immersed in the modified substance can be, but is not limited to, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.

[0046] In a specific example, the semiconductive shielding material tape of the power cable to be tested is immersed in the modifying substance at a temperature greater than the melting point of the modifying substance.

[0047] Further, the temperature at which the semi-conductive shielding material tape of the power cable to be tested is immersed in the modified substance is 50° C. to 70° C. Specifically, the temperature may be, but is not limited to, 50° C., 52° C., 54° C., 56° C., 58° C., 60° C., 62° C., 64° C., 66° C., 68° C. or 70° C.

[0048] In a specific example, the physical modification further includes polishing and cleaning steps to prepare the modified object to be tested.

[0049] It can be understood that the polishing method may be, but is not limited to, grinding.

[0050] In a specific example, the surface of the semi-conductive shielding material strip of the power cable to be tested is physically modified by using an abrasive body with a mesh size of 300-600 meshes and then polished. Furthermore, the polishing times are at least three times.

[0051] Furthermore, the cleaning step includes: using an organic solvent to polish the surface of the modified object to be tested and then cleaning it.

[0052] Furthermore, the organic solvent can be but is not limited to one or more of ethanol, ether, acetone, toluene, xylene, chloroform and gasoline. The above organic solvents are used to clean impurities on the surface of the semi-conductive shielding material strip, mainly including screen residue impurities accumulated inside the screw during the extrusion process and fine burnt particles, etc., to reduce the impact of the above impurities on actual observation.

[0053] In a specific example, after polishing and cleaning the surface of the modified object to be tested and before preparing the sample, a coating step is further included.

[0054] In a specific example, the coating step includes polishing the modified object to be tested with a high temperature resistant tape and then coating it after cleaning. This can avoid scratches that affect the experimental results when touching the sample with gloves or placing the sample on the sample table with tweezers; it can also avoid contamination by factors such as dust in the air adsorbed on the surface of the semi-conductive shielding material of the power cable to be tested. It can be understood that the above coating only plays a protective role, and the surface of the modified object to be tested does not contain high temperature resistant tape.

[0055] In a specific example, the thickness of the modified object to be tested is 0.8 mm to 1.2 mm. Further, the thickness of the modified object to be tested may be, but is not limited to, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm or 1.2 mm.

[0056] In a specific example, the step of determining the size of the surface protrusions of the semi-conductive shielding material strip of the power cable to be tested includes: using the white balance mode of the ultra-depth of field microscope to detect the surface of the modified test object. Further, the analysis site is further screened to ensure that it is a circular protrusion on the surface and other defects caused during the processing. The depth of field synthesis is determined according to the actual situation. The mode adopts white balance, adjusts the contrast, adjusts the saturation, and adjusts the multiple. The specific value is determined according to the actual situation of the protrusion. In principle, it is ensured that the protrusion is exactly within the observation range, and the three-dimensional size of the protrusion on the surface of the semi-conductive shielding material strip is determined within the appropriate exposure range.

[0057] The present application can effectively fill the surface pits of the semi-conductive shielding material strip of the power cable by physically modifying the surface of the semi-conductive shielding material strip of the power cable, reduce the roughness of the material surface and filter out defective sites, and further use the ultra-depth of field microscope to effectively observe the true 3D shape of the protrusions on the surface of the cable semi-conductive shielding layer with higher dimensional accuracy. Based on optical detection and Z-axis depth image synthesis technology, the true shape and size of the surface protrusions can be restored more accurately and realistically. At the same time, this method is simple to operate and has strong reproducibility.

[0058] Compared with traditional industrial optical microscopes, the ultra-depth of field microscope has higher accuracy in characterizing the size of surface protrusions. It can effectively observe the true morphology of surface defect sites and distinguish whether they are surface defects. At the same time, it adopts a simple and universal surface modification method to effectively filter and eliminate defect points on the surface of the strip, ensuring the high characterization accuracy of the ultra-depth of field microscope, and can better meet the characterization requirements of the surface finish of high-voltage or ultra-high-voltage shielding layers.

[0059] The weight proportions of the components of the semi-conductive shielding material of power cables are as follows: 50 to 70 parts of base resin, 20 to 40 parts of conductive carbon black, 0 to 2 parts of dispersant, 1 to 6 parts of functional additives and 0.9 to 2 parts of cross-linking agent. The functional additives include 0 to 2 parts of coupling agent, 1 to 3 parts of lubricant and 0.6 to 1 part of antioxidant.

[0060] It is understood that the base resin may be, but is not limited to, ethylene butyl acrylate copolymer (EBA). The conductive carbon black is a high-purity conductive carbon black with a DBP absorption value of 130ml / 100g~150ml / 100g and an ash content of <0.1%. The dispersant may be, but is not limited to, one or both of ethylene bis stearamide (EBS) and oleamide.

[0061] Furthermore, the coupling agent is silane coupling agent KH550; the lubricant is zinc stearate; and the antioxidant is one or more of antioxidant 1010, antioxidant 168 and antioxidant 300.

[0062] Furthermore, the components of the power cable semi-conductive shielding material tape are mixed, melt-blended, and then melt-extruded to prepare the power cable semi-conductive shielding material tape.

[0063] The present application is further described in detail below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance given in the present application, and can also be based on the experimental manuals or conventional conditions in the art, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0064] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed. "Normal temperature" refers to 25°C; "normal pressure" refers to 100KPa or 101KPa.

[0065] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The composition of the power cable semi-conductive shielding material tape 1 is 63 parts of ethylene bisstearamide EBA, 34 parts of conductive carbon black, 0 parts of dispersant, 0.5 parts of coupling agent, 1 part of lubricant, 1 part of cross-linking agent and 0.5 parts of antioxidant.

[0067] The composition of the power cable semi-conductive shielding material tape 2 is 62 parts of ethylene bisstearamide EBA, 34 parts of conductive carbon black, 1 part of dispersant, 0.5 part of coupling agent, 1 part of lubricant, 1 part of cross-linking agent and 0.5 part of antioxidant.

[0068] The composition of the power cable semi-conductive shielding material tape 3 is 61 parts of ethylene bisstearamide EBA, 34 parts of conductive carbon black, 2 parts of dispersant, 0.5 parts of coupling agent, 1 part of lubricant, 1 part of cross-linking agent and 0.5 parts of antioxidant.

[0069] The power cable semi-conductive shielding material strip 1, the power cable semi-conductive shielding material strip 2 and the power cable semi-conductive shielding material strip 3 are prepared respectively, and the specific steps are as follows:

[0070] Step 1: Prepare the components of the power cable semi-conductive shielding material tape with different dispersant contents, mix the base resin, conductive carbon black, dispersant and functional additives evenly after a series of pre-treatments according to the weight ratio, and melt-blend them to obtain a masterbatch, which is then placed in a constant temperature box at 60°C to fully absorb the cross-linking agent to obtain a power cable semi-conductive shielding material tape masterbatch, with a melt blending temperature of 160°C and a rotation speed of 60rpm;

[0071] Step 2: melt-extrude the power cable semi-conductive shielding material tape obtained in step (1) to prepare a cable semi-conductive shielding layer tape for analysis, with a melt extrusion temperature of 130°C, a rotation speed of 100 rpm, and a tape extrusion rate of 1 cm / s.

[0072] The surface of the power cable semi-conductive shielding material strip 3 is modified by using a modifier polyethylene glycol and a modifier tetradecanol, respectively, and the specific steps are as follows:

[0073] The semi-conductive shielding material strip 3 of the power cable is subjected to physical coating surface modification. The modified material adopts polyethylene glycol (Mw=5000~8000; Tm≈53.6℃) or tetradecanol. The strip is fully immersed in polyethylene glycol melt in a 60℃ environment or in tetradecanol melt in a 40℃ environment for 3 minutes, then taken out and naturally cooled. The surface of the strip is polished at room temperature with a ceramic grinding wheel, mesh number: 400, and the polishing is repeated more than 3 times.

[0074] Use an optical industrial optical microscope and an ultra-depth-of-field microscope to detect the protrusions on the surface of the semi-conductive shielding material of the power cable, and follow the following steps:

[0075] Step 1: Select a self-made semi-conductive shielding material extrusion strip, use a magnifying glass to mark the protrusions on the cable shielding layer surface, cut the strip to ensure that the marked site is located in the middle area of ​​the sample, repeatedly clean the sample surface with ethanol and then cover the marked point with PTFE tape. The sample is 1mm thick, 10mm wide and 10mm long;

[0076] Step 2: Transfer the sample obtained in step (1) to a super-depth-of-field three-dimensional stereo microscope for morphological observation, and determine the three-dimensional size of the surface protrusions. Further screen the analysis sites to ensure that they are circular protrusions on the surface and other defects caused during the processing. The depth of field synthesis is determined according to the actual situation. The mode uses white balance, contrast +5, saturation +10, and the magnification is determined according to the actual situation of the protrusions. In principle, it is ensured that the protrusions are exactly within the observation range and the exposure is appropriate.

[0077] It can be understood that the surface protrusions of the semi-conductive shielding material strip of the power cable are detected using a conventional optical industrial optical microscope, and the observation equipment in step 2 is changed to a conventional industrial optical microscope and the observation mode is appropriately adjusted.

[0078] The surface finish characterization test results of the power cable semi-conductive shielding material strip 1, the power cable semi-conductive shielding material strip 2 and the power cable semi-conductive shielding material strip 3 are respectively performed using a traditional industrial optical microscope and an ultra-depth of field microscope as shown in Tables 1 and 2.

[0079] Table 1 Surface finish characterization results based on traditional industrial optical microscope

[0080]

[0081] Table 2 Surface finish characterization results based on ultra-depth of field microscopy

[0082]

[0083] Results Analysis

[0084] Based on the comparison of the results in Table 1 and Table 2 and the actual observation results, it is found that the resolution and characteristics of traditional industrial optical microscopes determine that the accuracy of the morphology and size analysis of surface protrusions is not high, and it is impossible to distinguish defects such as "island-like" protrusions embedded with impurities, "mountain-like" protrusions and "pits" covered by the outer layer of resin matrix. Figure 1 This is a comparison of the observation results of the surface defects of the same power cable semi-conductive shielding material strip under traditional industrial optical microscope and ultra-depth of field microscope. It is difficult to accurately distinguish the true morphology of the surface defects of the shielding layer under traditional industrial optical microscope. It can only determine that the 2D outer diameter of the defect site is about 52µm. Under the ultra-depth of field microscope, it can be observed that the defect site is an obvious pit with a 2D outer diameter of about 55.95µm. In the 3D morphology diagram, it can be clearly observed that the depth of the pit is about 11.99µm. This proves that the ultra-depth of field microscope has better accuracy and characterization effect. Figure 2 , Figure 3 as well as Figure 4As shown, the ultra-depth-of-field microscopy characterization results of the protrusions of power cable semi-conductive shielding material strip 1, power cable semi-conductive shielding material strip 2 and power cable semi-conductive shielding material strip 3 are respectively. For power cable semi-conductive shielding material strip 3, the modification method of physically coating the surface of the strip with polyethylene glycol can effectively fill the pits on the surface of the power cable semi-conductive shielding material strip, reduce the roughness of the surface of the strip and filter out defective sites. Specifically, the defective sites are effectively filled and the color distribution of the height chromatogram of the protrusion site area after modification is more uniform. At the same time, due to the recalibration of the horizontal baseline, the protrusion height is reduced from 14.71µm to 13.66µm, a reduction of 7.1%, avoiding defective sites such as pits that have a large impact on the protrusion size detection, effectively improving the characterization accuracy of the ultra-depth-of-field microscopy size analysis, which is of great significance for the detection of the protrusion size of semi-conductive shielding material strips in the actual production process. Figure 5 Shown are optical microscope digital photos of the surface of the strip before and after physical coating with tetradecanol, which has a melting point of 35°C~39°C and has similar properties to polyethylene glycol. The results show that based on the good fluidity of tetradecanol and its excellent interfacial compatibility with the EBA resin matrix, it also has a good effect on the coating modification of the strip. However, due to its low melting point, it may melt into droplets due to local friction heat during the grinding process of the ceramic grinding wheel. It is impossible to effectively distinguish whether the protrusions on the surface of the strip are droplets formed by the modifier tetradecanol, which affects the actual observation effect. As a result, even under an optical microscope, it is impossible to effectively observe the morphology of the surface protrusions of the power cable semi-conductive shielding material strip.

[0085] In addition, the size of the protrusions on the surface of a series of shielding layer samples was evaluated on a three-dimensional scale based on the ultra-depth of field microscope. The results show that with the increase of the EBS dispersant content, the number and size of the protrusions on the surface of the shielding layer, including the size and height of the protrusions, will decrease significantly. For example, the average height of the protrusions of the power cable semi-conductive shielding material strip 1 is about 77.4µm, and the average height of the protrusions of the power cable semi-conductive shielding material strip 2 and the power cable semi-conductive shielding material strip 3 are about 42.6µm and 16.2µm, respectively.

[0086] In the actual production process of the semi-conductive shielding layer, the quality of the surface finish of the shielding layer, such as the size and number of protrusions on the surface of the shielding layer, is closely related to the dispersion and processing of carbon black. This is because the cause of the protrusions on the surface of the shielding layer is mainly due to the agglomeration of carbon black. With the increase of EBS content, the dispersion of carbon black is higher, the probability of agglomeration is lower or the size of the formed carbon black agglomerates is smaller. Since the density of the carbon black agglomerates themselves is lower than the normal dispersion area of ​​carbon black, dot-shaped protrusions will form above the carbon black agglomerate site, i.e., on the surface of the shielding layer, and the size of the protrusion point, such as the 2D outer diameter and height, is closely related to the dispersion of carbon black or the size of the carbon black agglomerates. Semi-conductive shielding layers with higher voltage levels require extremely excellent surface finish. Therefore, a more accurate and convenient surface finish evaluation method is of great guiding significance for the regulation of raw material ratios and processing conditions in actual production.

[0087] In summary, compared with traditional industrial optical microscopes, appropriate surface modification and ultra-depth of field microscopes can analyze the protrusions on the surface of the shielding layer with higher accuracy, and the morphological characteristics and size can be reflected more accurately and realistically, which can effectively restore the true size of the protrusions on the shielding layer. When evaluating cables with higher requirements for surface finish, such as the semi-conductive shielding layer of high-voltage and ultra-high-voltage cables, the ultra-depth of field microscope has better adaptability and can effectively identify and distinguish the morphology of defects on the surface of the shielding layer, which is of great significance for the characterization of the surface finish of the semi-conductive shielding layer of the cable.

[0088] The above embodiments only express several implementation methods of the present invention, which is convenient for understanding the technical solution of the present invention in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solution provided by the present invention are all within the protection scope of the claims attached to the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the content of the attached claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A method for detecting the morphology of protrusions on the surface of a semi-conductive shielding material strip of a power cable, characterized in that: The following steps are involved: Using a modified substance to physically modify the surface of a semi-conductive shielding material strip of a power cable to be tested, to prepare a modified object to be tested; Using an ultra-depth-of-field microscope to detect the surface of the modified object to be tested, and determining the size of the surface protrusions of the semi-conductive shielding material strip of the power cable to be tested; The modifying substance includes one or both of polyethylene glycol and paraffin.

2. The detection method according to claim 1, characterized in that The physical modification step includes: immersing the semi-conductive shielding material strip of the power cable to be tested into a modified substance, and physically coating the surface of the semi-conductive shielding material strip of the power cable to be tested.

3. The detection method according to claim 2, characterized in that The time for immersing the semi-conductive shielding material strip of the power cable to be tested in the modified substance is 1 min to 10 min.

4. The detection method according to any one of claims 1 to 3, characterized in that The semiconductive shielding material tape of the power cable to be tested is immersed in the modifying substance at a temperature greater than the melting point of the modifying substance.

5. The detection method according to claim 4, characterized in that: The temperature at which the semi-conductive shielding material strip of the power cable to be tested is immersed in the modified substance is 50° C. to 70° C.

6. The detection method according to any one of claims 1 to 3, characterized in that: The physical modification also includes polishing and cleaning steps to prepare the modified test object.

7. The detection method according to claim 6, characterized in that The cleaning agent in the cleaning step is an organic solvent.

8. The detection method according to claim 7, characterized in that The organic solvent includes one or more of ethanol, ether, acetone, toluene, xylene, chloroform and gasoline.

9. The detection method according to any one of claims 1 to 3, characterized in that: The thickness of the modified object to be tested is 0.8 mm to 1.2 mm.

10. The detection method according to any one of claims 1 to 3, characterized in that: The step of determining the size of the surface protrusions of the semi-conductive shielding material strip of the power cable to be tested comprises: using the white balance mode of the ultra-depth-of-field microscope to detect the surface of the modified object to be tested.

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