Test sample for testing electrical performance of cable insulation-shielding composite material and preparation method of test sample

Abstract

The invention provides a test sample for testing the electrical performance of a cable insulation-shielding composite material and a preparation method thereof.The test sample comprises a slice of the cable insulation-shielding composite material and an insulation coating layer, and the slice comprises an insulation layer and a shielding layer which are stacked in sequence; an insulating coating layer covers the surface of the side, where the shielding layer is located, of the slice; the insulating coating layer comprises at least one concave part, and the concave part penetrates from the surface, relatively away from the slice, of the insulating coating layer to the surface, adjacent to the insulating coating layer, of the shielding layer in the thickness direction of the insulating coating layer. According to the test sample provided by the invention, the electrical performance test of the insulation-shielding composite cable can be completed, and the insulation-shielding matching problem in the actual cable can be reflected, so that the performance of the composite cable can be better evaluated and represented.

Description

Technical Field

[0001] The present application relates to the field of electrical technology, and in particular to a test specimen for electrical properties of a cable insulation-shielding composite material and a preparation method thereof. Background Art

[0002] With the rapid development of the power transmission industry, the three-layer co-extrusion production process of cross-linked polyethylene cables has become more mature, making the research and use of insulation-shielded composite cables more mature. In order to meet the requirements of high-voltage transmission lines, the current cable material research should pay more attention to the matching of insulation-shielding in composite cables, and the performance test of the insulation layer itself should also consider the impact of the matching shielding layer. The existing insulation-shielding composite specimens used to test the electrical properties of composite cables mainly include insulation-shielding contact specimens and shielding-insulation-shielding sandwich structure specimens. However, both of these specimens combine separate insulation materials and shielding materials together, which makes it difficult to reflect the matching problem of insulation-shielding in actual cables. Summary of the invention

[0003] Based on this, the present application provides a test specimen for the electrical properties of a cable insulation-shielding composite material and a preparation method thereof, which can complete the electrical performance test of the insulation-shielding composite cable and reflect the insulation-shielding matching problem in the actual cable, thereby better evaluating and characterizing the performance of the composite cable.

[0004] The first aspect of the present application provides a test specimen for the electrical properties of a cable insulation-shielding composite material, comprising a slice and an insulating coating layer of the cable insulation-shielding composite material, the slice comprising an insulating layer and a shielding layer stacked in sequence, the insulating coating layer covering the surface of the slice on the side where the shielding layer is located; the insulating coating layer comprises at least one recess, the recess extending along the thickness direction of the insulating coating layer, from the surface of the insulating coating layer relatively far from the slice to the surface of the shielding layer adjacent to the insulating coating layer.

[0005] In some embodiments of the present application, one or more of the following conditions are met:

[0006] (1) The insulating coating layer contains insulating material and curing agent;

[0007] Optionally, the insulating material includes one or more of epoxy resin, silicone rubber and polyester resin;

[0008] Optionally, the curing agent includes at least one of an amine curing agent and an acid anhydride curing agent;

[0009] (2) The thickness of the insulating coating layer is 0.2 mm to 0.3 mm;

[0010] (3) The length of the slice is 95 mm to 105 mm, the width of the slice is 76 mm to 84 mm, and the thickness of the slice is 0.35 mm to 0.45 mm.

[0011] In some embodiments of the present application, the insulating coating layer comprises one said recess;

[0012] Optionally, the center point of the concave portion coincides with the center point of the slice;

[0013] Optionally, the orthographic projection of the recess along the thickness direction of the insulating coating layer is a rectangle.

[0014] In some embodiments of the present application, the length of the rectangle is 8 mm to 12 mm, and the width of the rectangle is 8 mm to 12 mm.

[0015] The second aspect of the present application provides a method for preparing a test specimen for the electrical properties of a cable insulation-shielding composite material, comprising:

[0016] Circular cutting the insulation-shielding composite cable comprising the cable insulation-shielding composite material to prepare slices of the cable insulation-shielding composite material, wherein the slices include an insulation layer and a shielding layer stacked in sequence;

[0017] According to the shielding distribution state of the shielding layer, a plurality of layers of high temperature tape are applied to the surface of the shielding layer side of the slice to form one or more coating areas distributed at intervals, and an insulating slurry is applied to the remaining area of ​​the surface of the shielding layer side of the slice except the coating area;

[0018] After the insulating slurry is cured, the high-temperature tape is removed to form an insulating coating layer to prepare the test sample, wherein the insulating coating layer covers the surface of the slice on the side where the shielding layer is located; the insulating coating layer includes at least one recess, and the recess extends along the thickness direction of the insulating coating layer, from the surface of the insulating coating layer relatively far away from the slice to the surface of the shielding layer adjacent to the insulating coating layer.

[0019] In some embodiments of the present application, one or more of the following conditions are met:

[0020] (1) The insulating paste comprises an insulating material and a curing agent;

[0021] Optionally, the insulating material includes one or more of epoxy resin, silicone rubber and polyester resin;

[0022] Optionally, the curing agent includes at least one of an amine curing agent and an acid anhydride curing agent.

[0023] (2) The thickness of the coating area is 0.2 mm to 0.3 mm;

[0024] (3) The length of the slice is 95 mm to 105 mm, the width of the slice is 76 mm to 84 mm, and the thickness of the slice is 0.35 mm to 0.45 mm.

[0025] In some embodiments of the present application, the coating area is one;

[0026] Optionally, the center point of the coated area coincides with the center point of the slice;

[0027] Optionally, the orthographic projection of the coating area along the thickness direction of the insulating coating layer is a rectangle.

[0028] In some embodiments of the present application, the length of the rectangle is 8 mm to 12 mm, and the width of the rectangle is 8 mm to 12 mm.

[0029] In some embodiments of the present application, the insulated-shielded composite cable includes one or both of a cross-linked polyethylene-shielded composite cable and a polypropylene-shielded composite cable.

[0030] In some embodiments of the present application, the curing temperature is 25°C to 35°C or 80°C to 140°C.

[0031] This application directly uses slices of cable insulation-shielding composite materials to form test specimens. Compared with the previous method of combining separate insulation materials and shielding materials to obtain insulation-shielding composite specimens, it can better evaluate the interface state between actual cable insulation and shielding, study the matching problem of the interface, and then improve the cable performance for different insulation materials, and improve the cable three-layer co-extrusion production process. In the insulating coating layer of the test specimen, the concave portion can be used as a test area for electrical properties, such as breakdown performance, and other areas except the concave portion can avoid the surface flashover phenomenon that occurs when the slice is subjected to a breakdown performance test, so that the breakdown test voltage can be successfully applied, ensuring the smooth progress of the experiment, and better evaluating the electrical performance of the processed and prepared cable, or testing the electrical performance of the cable that has been in service for a period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic diagram of the front view of a test specimen for testing the electrical properties of a cable insulation-shielding composite material according to an embodiment of the present application.

[0033] FIG2 is a schematic diagram of the top view of a test specimen for testing the electrical properties of a cable insulation-shielding composite material according to an embodiment of the present application.

[0034] FIG3 is a schematic diagram of ring cutting of an insulated-shielded composite cable according to an embodiment of the present application.

[0035] FIG4 is a flow chart of the preparation of a test sample for the electrical properties of a cable insulation-shielding composite material according to an embodiment of the present application.

[0036] FIG5 is a schematic diagram of an apparatus for testing AC breakdown performance according to an embodiment of the present application.

[0037] 6 is a diagram of the ablation channel of a test sample of the electrical performance of the cable insulation-shielding composite material according to an embodiment of the present application after a breakdown test.

[0038] Reference numerals: 10 slice of cable insulation-shielding composite material; 20 insulation coating layer; 100 insulation layer; 110 shielding layer; 200 recess. DETAILED DESCRIPTION

[0039] In order to facilitate understanding of the present application, the present application will be described more comprehensively below. 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.

[0040] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. It should be noted that, unless otherwise specified, the term "and / or" used herein includes any and all combinations of one or more related listed items, and "above" and "below" are inclusive of the number, and the meaning of "multiple" in "one or more" is more than two.

[0042] 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.

[0043] 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.

[0044] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0045] During the research process, the inventor found that for insulated-shielded composite cables, in order to better evaluate the interface state between insulation and shielding and study the matching problem of the interface, samples can be taken from the insulated-shielded composite cables to study the performance of the cable insulation-shielding materials. Currently common sampling methods include ring cutting cable sampling, slicing parallel to the cable axis, and slicing perpendicular to the cable axis. For the electrical performance of composite cables, especially the breakdown performance test, the ring cutting method of the cable in the above sampling method can obtain a larger area of ​​insulated-shielded composite slices. However, the inventor found that the shielding area in the composite slice obtained by this slicing method is large and continuous. Therefore, when conducting a breakdown performance test of the composite slice, due to the conductive performance of the shielding and its continuous distribution state, surface flashover is prone to occur when the breakdown test is performed directly, resulting in the inability to apply the test voltage and the inability to carry out the breakdown performance test. In order to solve the above-mentioned technical problems, the inventor proposed the following technical solution of this application.

[0046] In the first aspect, referring to Figures 1 and 2, the present application provides a test specimen for the electrical properties of a cable insulation-shielding composite material, which includes a slice 10 and an insulating coating layer 20 of the cable insulation-shielding composite material, wherein the slice includes an insulating layer 100 and a shielding layer 110 stacked in sequence, and the insulating coating layer 20 covers the surface of the slice 10 on the side where the shielding layer 110 is located; the insulating coating layer 20 includes at least one recess 200, and the recess 200 extends along the thickness direction of the insulating coating layer 20, from the surface of the insulating coating layer 20 relatively away from the slice 10 to the surface of the shielding layer 110 adjacent to the insulating coating layer 20.

[0047] This application directly uses slices of cable insulation-shielding composite materials to form test specimens. Compared with the previous method of combining separate insulation materials and shielding materials to obtain insulation-shielding composite specimens, it can better evaluate the interface state between actual cable insulation and shielding, study the matching problem of the interface, and then improve the cable performance for different insulation materials, and improve the cable three-layer co-extrusion production process. In the insulating coating layer of the test specimen, the concave portion can be used as a test area for electrical properties, such as breakdown performance, and other areas except the concave portion can avoid the surface flashover phenomenon that occurs when the slice is subjected to a breakdown performance test, so that the breakdown test voltage can be successfully applied, ensuring the smooth progress of the experiment, and better evaluating the electrical performance of the processed and prepared cable, or testing the electrical performance of the cable that has been in service for a period of time.

[0048] In other words, the test specimen provided by the present application, since the slices of the cable insulation-shielding composite material are directly sampled from the insulation-shielding composite cable, the specimen structure can better meet the research on the cable insulation-shielding matching performance. Among them, the size and number of the recesses used as the breakdown performance test area can be determined according to the distribution state of the shielding in the slice. The diameter of the ball-ball electrode used for the breakdown test can be determined according to the size of the recess. When the test specimen is subjected to a breakdown test, due to the conductivity of the shielding layer, the applied field strength can be evenly distributed in the test area.

[0049] In some embodiments, the insulating coating layer comprises an insulating material and a curing agent.

[0050] In some embodiments, the insulating material includes one or more of epoxy resin, silicone rubber and polyester resin.

[0051] In some embodiments, the curing agent includes at least one of an amine curing agent and an acid anhydride curing agent.

[0052] In some embodiments, the thickness of the insulating coating layer is 0.2 mm to 0.3 mm.

[0053] In some embodiments, the length of the slice is 95 mm to 105 mm, the width of the slice is 76 mm to 84 mm, and the thickness of the slice is 0.35 mm to 0.45 mm.

[0054] In some embodiments, the insulating coating layer includes one recessed portion.

[0055] In some embodiments, a center point of the recess coincides with a center point of the slice.

[0056] It should be noted that the "center point of the recess" mentioned in the present application refers to the center point of the orthographic projection of the recess along the thickness direction of the insulating coating layer; the "center point of the slice" refers to the center point of the cross-section of the slice perpendicular to the thickness direction; the "center point of the coating area" refers to the center point of the orthographic projection of the coating area along the thickness direction of the slice.

[0057] In some embodiments, the orthographic projection of the recess along the thickness direction of the insulating coating layer is a rectangle.

[0058] In some embodiments, the length of the rectangle is 8 mm to 12 mm, and the width of the rectangle is 8 mm to 12 mm.

[0059] In a second aspect, the present application provides a method for preparing a test specimen for electrical properties of a cable insulation-shielding composite material, which can be used to prepare the test specimen of the first aspect of the present application, and may include the following steps:

[0060] S1. Circular cutting the insulation-shielding composite cable comprising the cable insulation-shielding composite material to prepare slices of the cable insulation-shielding composite material, wherein the slices include an insulation layer and a shielding layer stacked in sequence;

[0061] S2. According to the shielding distribution state of the shielding layer, a plurality of layers of high temperature tape are applied to the surface of the shielding layer side of the slice to form one or more spaced coating areas, and an insulating slurry is applied to the remaining area of ​​the surface of the shielding layer side of the slice except the coating area;

[0062] S3. After the insulating slurry is cured, the high-temperature tape is removed to form an insulating coating layer, and the test sample is prepared. The insulating coating layer covers the surface of the slice on the side where the shielding layer is located; the insulating coating layer includes at least one recess, and the recess extends along the thickness direction of the insulating coating layer, from the surface of the insulating coating layer relatively far away from the slice to the surface of the shielding layer adjacent to the insulating coating layer.

[0063] It should be noted that in step S1, since the cable insulation-shielding composite material is sliced ​​by ring cutting, the shielding will be distributed on the insulation in an irregular distribution state on the slice. In order to ensure the safety and accuracy of the electrical performance test, the following conditions need to be met when selecting the breakdown test area (i.e., the coating area):

[0064] (1) There should be a large insulation area around the breakdown test area;

[0065] (2) A certain distance should be maintained between multiple breakdown test areas to avoid mutual influence between the test areas.

[0066] After the above steps S2~S3, a recess can be formed after removing the coating area of ​​the high-temperature tape. Therefore, the present application can directly obtain a slice of the cable insulation-shielding composite material from the insulation-shielding composite cable (i.e., the finished cable) by ring cutting the insulation-shielding composite cable. Compared with the previous method of combining separate insulating materials and shielding materials to obtain an insulation-shielding composite specimen, the test specimen obtained by the preparation method of the present application can better evaluate the interface state between the actual cable insulation and the shielding, study the matching problem of the interface, and then improve the cable performance for different insulating materials and improve the cable three-layer co-extrusion production process.

[0067] In addition, by forming an insulating coating layer on the surface of the slice on the side where the shielding layer is located, while the slice is subjected to a breakdown performance test, the surface flashover phenomenon that occurs during the breakdown performance test can be avoided, so that the breakdown test voltage can be successfully applied, ensuring the smooth progress of the experiment, and better evaluating the electrical performance of the processed and prepared cable, or testing the electrical performance of the cable that has been in service for a period of time.

[0068] In some embodiments, the insulating paste includes an insulating material and a curing agent.

[0069] In some embodiments, the insulating material includes one or more of epoxy resin, silicone rubber and polyester resin.

[0070] In some embodiments, the curing agent includes at least one of an amine curing agent and an acid anhydride curing agent.

[0071] In some embodiments, the amine curing agent includes one or more of polyetheramine, ethylenediamine, diethylenetriamine and metaphenylenediamine.

[0072] In some embodiments, the anhydride curing agent includes at least one of methyltetrahydrophthalic anhydride, maleic anhydride, and phthalic anhydride.

[0073] In some embodiments, the coating area has a thickness of 0.2 mm to 0.3 mm.

[0074] In some embodiments, the length of the slice is 95 mm to 105 mm, the width of the slice is 76 mm to 84 mm, and the thickness of the slice is 0.35 mm to 0.45 mm.

[0075] In some embodiments, the number of the coated regions is one.

[0076] In some embodiments, the center point of the coated area coincides with the center point of the slice.

[0077] In some embodiments, the orthographic projection of the coating area along the thickness direction of the insulating coating layer is a rectangle.

[0078] In some embodiments, the length of the rectangle is 8 mm to 12 mm, and the width of the rectangle is 8 mm to 12 mm.

[0079] In some embodiments, the insulation-shielded composite cable includes one or both of a cross-linked polyethylene-shielded composite cable and a polypropylene-shielded composite cable.

[0080] In some embodiments, the curing temperature is 25°C to 35°C or 80°C to 140°C.

[0081] In some embodiments, the insulated-shielded composite cable used for circumcision is a cross-linked polyethylene-shielded composite cable, the insulating material is epoxy resin, and the curing temperature is 25°C~35°C.

[0082] In some embodiments, the insulated-shielded composite cable is a polypropylene-shielded composite cable, the insulating material is epoxy resin, and the curing temperature is 25°C to 35°C.

[0083] In some embodiments, the insulated-shielded composite cable is a polypropylene-shielded composite cable, the insulating material is epoxy resin, and the curing temperature is 80° C. to 140° C. (high temperature curing).

[0084] In some embodiments, the insulated-shielded composite cable is a cross-linked polyethylene-shielded composite cable, the insulating material is vulcanized silicone rubber, and the curing temperature is 25°C to 35°C.

[0085] In some embodiments, the method of obtaining slices by ring cutting of the insulated-shielded composite cable is as follows: Referring to FIG3, the insulated-shielded composite cable includes a conductor 30, an inner shielding layer 40, an insulating layer 50, and an outer shielding layer 60 from the inside to the outside; when performing ring cutting, the ring cutting thickness can be controlled to be 0.4 mm and the blade width can be 80 mm. Then, the structure containing both insulation and shielding is selected from the samples obtained by ring cutting and cut into slices with a length of 100 mm, and the test specimens are prepared on this basis.

[0086] In some embodiments, the preparation process of the test sample for the electrical properties of the cable insulation-shielding composite material can be seen in Figure 4: first, take a slice of the cable insulation-shielding composite material, and determine that the breakdown test area is the square area in the center of the slice shielding layer according to the distribution state of the shielding in the slice, and this area is coated with high-temperature tape, and the remaining area is coated with insulating slurry; after the insulating slurry is cured, the high-temperature tape is removed to obtain a test sample.

[0087] In some embodiments, the size and number of the recesses serving as the breakdown test regions may be determined according to the distribution state of the shielding in the slice.

[0088] In some embodiments, an example of a method for preparing a test specimen for the electrical properties of a cable insulation-shielding composite material is as follows:

[0089] S10, using a cable ring cutting device to ring cut the insulation-shielding composite cable to obtain slices of the cable insulation-shielding composite material;

[0090] S20, coating a 10 mm × 10 mm area in the center of one side of the slice shielding layer with multiple layers of tape as an electrical performance test area;

[0091] S30, applying the insulating slurry to the remaining area on one side of the surface of the sliced ​​shielding layer, and after the insulating slurry is cured, removing the multiple layers of tape to obtain a test sample of the electrical properties of the cable insulation-shielding composite material.

[0092] In some embodiments, the test sample can be subjected to an AC breakdown performance test. For an example of the test equipment, see FIG5 . The size of the test sample used for the test is 100 mm × 80 mm × 0.4 mm. According to the size of the test area of ​​about 10 mm × 10 mm, the diameter of the ball-to-ball electrode used is 20 mm. The voltage rise rate is 1 kV / s. In the test sample, only the recessed portion as the test area can be subjected to a breakdown test. Each test area can only be subjected to one breakdown test, and the number of tests for each test sample is the same as the number of recessed portions in the sample as the test area. The insulating coating layer in the test sample can effectively prevent surface flashover during the test. During the test, the measuring electrode and the test sample are immersed in the transformer oil. When the test sample is subjected to a breakdown test, due to the conductivity of the shielding, the applied field strength is a uniform field strength applied to the test area. The diameter of the ball-to-ball electrode used for the breakdown test can be determined according to the size of the test area.

[0093] In order to accurately calculate the breakdown field strength of the cable insulation, according to the calculation formula of the breakdown field strength, in addition to the breakdown voltage obtained by the test, it is also necessary to know the thickness of the insulating layer at the breakdown point. In the test sample, since the thickness of the slices of the cable insulation-shielding composite material obtained by ring cutting is uneven, and the concave portion serving as the breakdown test area is the insulation-shielding composite layer, the thickness of the insulating layer at the breakdown point cannot be directly obtained by measurement. Therefore, in a third aspect, the present application provides a test method that can be used to evaluate the thickness of the insulating layer in the test sample of the first aspect of the present application, which may include the following steps:

[0094] S1', cutting the sample after the breakdown test to make a narrow strip sample centered at the breakdown point, and performing low-temperature brittle fracture on the sample;

[0095] S2', observe the breakdown point of the sample after brittle fracture by SEM (scanning electron microscope) and calculate the thickness of the insulation layer at the breakdown point.

[0096] In some embodiments, examples of the above test methods are as follows:

[0097] S10', cut the sample after the breakdown test into a narrow strip sample centered at the breakdown point, fix the sample and place it in liquid nitrogen for 30 minutes and brittle fracture. Since the breakdown point is the weak point area of ​​the sample, the brittle fracture is likely to occur at the breakdown point.

[0098] S20', after drying the sample, observe it under a scanning electron microscope. After spraying gold on the fracture of the sample, stick it on the sample table with conductive tape for observation. By adjusting the magnification, find the breakdown channel, as shown in Figure 6. According to the electron microscope photo of the sample, find the insulation shielding interface, and estimate the thickness of the insulation layer at the breakdown point by the average thickness of the insulation around the breakdown point, and then calculate the breakdown field strength.

[0099] Example

[0100] The following are specific examples, which more specifically describe the contents disclosed in this application, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0101] Example 1

[0102] (1) Use cable ring cutting equipment to ring cut the cross-linked polyethylene insulated-shielded composite cable to obtain slices. Coat the area of ​​about 10 mm × 10 mm in the center of the surface of the side where the shield layer is located with multiple layers of tape as the breakdown test area.

[0103] (2) Place the epoxy resin in a vacuum oven at 80°C for 30 minutes to make it flowable, spray the sample mold with a release agent and place it in an oven at 80°C for 60 minutes, then weigh the amine curing agent polyetheramine and the epoxy resin in a mass ratio of 3:10 and mix them. Use a degassing mixer, first set the mixer speed to 2000r / min, stir for 15 minutes; then set the speed to 2200r / min, degas for 15 minutes, and fully mix the ethylenediamine and epoxy resin to obtain an insulating slurry.

[0104] (3) Apply the insulating slurry to the remaining area of ​​the surface of the shielding layer in the slice, place it in a mold for fixation, and demold it after curing at 25°C for 48 hours; finally, remove the high-temperature tape to obtain a test sample.

[0105] Example 2

[0106] (1) Use cable ring cutting equipment to ring cut the polypropylene insulated-shielded composite cable to obtain slices. Coat the area of ​​about 10 mm × 10 mm in the center of the surface of the side where the shield layer is located with multiple layers of tape as the breakdown test area.

[0107] (2) Place the epoxy resin in a vacuum oven at 80°C for 30 minutes to make it flowable, spray the sample mold with a release agent and place it in an oven at 80°C for 60 minutes, then weigh the amine curing agent ethylenediamine and the epoxy resin in a mass ratio of 3:10 and mix them. Use a degassing mixer, first set the mixer speed to 2000r / min, stir for 15 minutes; then set the speed to 2200r / min, degas for 15 minutes, and fully mix the ethylenediamine and epoxy resin to obtain an insulating slurry.

[0108] (3) Apply the insulating slurry to the remaining area of ​​the surface of the shielding layer in the slice, place it in a mold for fixation, and demold it after curing at 25°C for 48 hours; finally, remove the high-temperature tape to obtain a test sample.

[0109] Example 3

[0110] (1) Use cable ring cutting equipment to ring cut the polypropylene insulated-shielded composite cable to obtain slices. Coat the area of ​​about 10 mm × 10 mm in the center of the surface of the side where the shield layer is located with multiple layers of tape as the breakdown test area.

[0111] (2) Place the epoxy resin in a vacuum oven at 80°C for 30 minutes to make it flowable, spray the sample mold with a release agent and place it in an oven at 100°C for 30 minutes, then weigh the epoxy resin anhydride curing agent methyltetrahydrophthalic anhydride and the accelerator N,N-dimethylbenzylamine and mix them according to the ratio of 100:x:0.6 (x=EV×166×0.9, EV is the epoxy value of the epoxy resin, that is, the number of moles of epoxy groups contained in every 100g of epoxy resin, in mol / (100g)). Use a degassing mixer, first set the mixer speed to 2000r / min, stir for 15 minutes; then set the speed to 2200r / min, degas for 15 minutes, and fully mix the anhydride curing agent, accelerator and epoxy resin to obtain an insulating slurry.

[0112] (3) Apply the insulating slurry to the remaining area of ​​the surface of the shielding layer in the slice, place it in the mold, and then put the mold into a vacuum blast electric heating drying oven, evacuate at room temperature, and continue degassing for 10 minutes to remove bubbles in the sample. Then turn on the oven air inlet knob and perform high-temperature curing at normal pressure. The high-temperature curing procedure is to cure at 80°C for 2 hours, then increase the temperature to 140°C, and cure at 140°C for 12 hours to complete the curing of the sample; finally, remove the high-temperature tape to obtain the test sample.

[0113] Example 4

[0114] (1) Use cable ring cutting equipment to ring cut the cross-linked polyethylene insulated-shielded composite cable to obtain slices. Coat the area of ​​about 10 mm × 10 mm in the center of the surface of the side where the shield layer is located with multiple layers of tape as the breakdown test area.

[0115] (2) Stir the component A of the two-component condensation room temperature vulcanized silicone rubber (RTV-2 glue) appropriately to disperse the filler that sinks to the bottom into the glue liquid. Shake the component B curing agent up and down in a sealed state to fully mix the components of different densities to avoid affecting the curing effect. Then weigh the component A and the component B curing agent in a mass ratio of 10:1 and mix them; use manual or mechanical stirring to fully mix the component A and the component B curing agent. When mixing, avoid high-speed and long-term stirring to generate high temperatures (not higher than 38°C) to prepare the insulating slurry.

[0116] (4) Apply the insulating slurry to the remaining area of ​​the surface of the shielding layer in the slice, place it in the mold, and then put the mold into a vacuum blast electric heating drying oven, evacuate at room temperature, and continue degassing for 10 minutes to remove bubbles in the sample. Then turn on the oven air inlet knob and cure at normal pressure. There are two curing procedures: the first is to demold after curing at 25°C for 24 hours; the second is to cure at 25°C for 5 hours, then heat to 50°C and cure at 50°C for 12 hours to complete the curing of the sample; finally, remove the high-temperature tape to obtain the test sample.

[0117] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0118] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A test specimen for electrical properties of a cable insulation-shielding composite material, characterized in that: The invention comprises a slice of the cable insulation-shielding composite material and an insulating coating layer, wherein the slice comprises an insulating layer and a shielding layer stacked in sequence, and the insulating coating layer covers the surface of the slice on the side where the shielding layer is located; The insulating coating layer includes at least one recessed portion, which penetrates along a thickness direction of the insulating coating layer from a surface of the insulating coating layer relatively far from the slice to a surface of the shielding layer adjacent to the insulating coating layer.

2. The test specimen according to claim 1, characterized in that: Meet one or more of the following conditions: (1) The insulating coating layer contains insulating material and curing agent; Optionally, the insulating material includes one or more of epoxy resin, silicone rubber and polyester resin; Optionally, the curing agent includes at least one of an amine curing agent and an acid anhydride curing agent; (2) The thickness of the insulating coating layer is 0.2 mm to 0.3 mm; (3) The length of the slice is 95 mm to 105 mm, the width of the slice is 76 mm to 84 mm, and the thickness of the slice is 0.35 mm to 0.45 mm.

3. The test specimen according to claim 1 or 2, characterized in that: The insulating coating layer includes a recessed portion; Optionally, the center point of the concave portion coincides with the center point of the slice; Optionally, the orthographic projection of the recess along the thickness direction of the insulating coating layer is a rectangle.

4. The test specimen according to claim 3, characterized in that: The length of the rectangle is 8 mm to 12 mm, and the width of the rectangle is 8 mm to 12 mm.

5. A method for preparing a test sample for the electrical performance of a cable insulation-shielding composite material, characterized in that: include: Circular cutting the insulation-shielding composite cable comprising the cable insulation-shielding composite material to prepare slices of the cable insulation-shielding composite material, wherein the slices include an insulation layer and a shielding layer stacked in sequence; According to the shielding distribution state of the shielding layer, a plurality of layers of high temperature tape are applied to the surface of the shielding layer side of the slice to form one or more coating areas distributed at intervals, and an insulating paste is applied to the remaining area of ​​the surface of the shielding layer side of the slice except the coating area; After the insulating slurry is cured, the high-temperature tape is removed to form an insulating coating layer to prepare the test sample, wherein the insulating coating layer covers the surface of the slice on the side where the shielding layer is located; the insulating coating layer includes at least one recess, and the recess extends along the thickness direction of the insulating coating layer, from the surface of the insulating coating layer relatively far away from the slice to the surface of the shielding layer adjacent to the insulating coating layer.

6. The preparation method according to claim 5, characterized in that: Meet one or more of the following conditions: (1) The insulating paste comprises an insulating material and a curing agent; Optionally, the insulating material includes one or more of epoxy resin, silicone rubber and polyester resin; Optionally, the curing agent includes at least one of an amine curing agent and an acid anhydride curing agent; (2) The thickness of the coating area is 0.2 mm to 0.3 mm; (3) The length of the slice is 95 mm to 105 mm, the width of the slice is 76 mm to 84 mm, and the thickness of the slice is 0.35 mm to 0.45 mm.

7. The preparation method according to claim 5 or 6, characterized in that: The coating area is one; Optionally, the center point of the coated area coincides with the center point of the slice; Optionally, the orthographic projection of the coating area along the thickness direction of the insulating coating layer is a rectangle.

8. The preparation method according to claim 7, characterized in that: The length of the rectangle is 8 mm to 12 mm, and the width of the rectangle is 8 mm to 12 mm.

9. The preparation method according to claim 5 or 6, characterized in that: The insulated-shielded composite cable includes one or both of a cross-linked polyethylene-shielded composite cable and a polypropylene-shielded composite cable.

10. The preparation method according to claim 5 or 6, characterized in that: The curing temperature is 25°C to 35°C or 80°C to 140°C.

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