High-voltage cable buffering water-blocking tape capable of preventing electric ablation

Abstract

The invention discloses a high-voltage cable buffer water-blocking tape for preventing electric ablation, and relates to the field of high-voltage cable structures. The water-blocking fabric comprises a first fluffy cotton layer, a first filter cotton layer, a non-woven fabric layer, a water-blocking powder layer, a second non-woven fabric layer, a second filter cotton layer and a second fluffy cotton layer which are sequentially arranged from top to bottom, the first fluffy cotton layer and the second fluffy cotton layer are the same in structure, and copper films and tin-plated aluminum films are arranged on the inner sides and the outer sides of the first fluffy cotton layer and the second fluffy cotton layer. According to the invention, better water-blocking performance can be ensured, and electric ablation can be obviously prevented at the same time.

Description

Technical Field

[0001] The invention relates to the field of high-voltage cable structures, and in particular to a high-voltage cable buffer water-blocking tape for preventing electrical ablation. Background Art

[0002] The existing high-voltage cable buffer water-blocking tape consists of a three-layer structure of non-woven fabric, water-blocking powder, and fluffy cotton. The conductivity is increased by adding conductive carbon black to the non-woven fabric and fluffy cotton. Due to its relatively simple process, it has been favored by the industry. However, the frequent ablation accidents of high-voltage cable buffer water-blocking tapes have seriously threatened the safety of the power transmission system. Scholars have analyzed the ablation mechanism and believe that the causes of ablation of the existing buffer water-blocking tape include: (1) After the buffer water-blocking tape is damp, the water-blocking powder precipitates on the surface of the water-blocking tape and the carbon black is unevenly distributed, which affects the electrical properties of the buffer water-blocking tape. (2) The fluffy cotton structure in the buffer water-blocking tape is repeatedly squeezed by the aluminum sheath and the insulation shield, resulting in insufficient elasticity of the fluffy cotton, which cannot ensure the electrical contact between the insulation shield and the aluminum sheath. (3) The water-blocking powder will become weakly alkaline when it comes into contact with water. Once it encounters the aluminum sheath, it will react and corrode the aluminum sheath, and the electrical contact between the buffer water-blocking tape and the aluminum sheath cannot be guaranteed. (4) In order to ensure the electrical closeness between the fluffy cotton and the non-woven fabric, the amount of water-blocking powder added is small, resulting in poor water-blocking effect. (5) The water-blocking powder is an insulating material. After the water-blocking powder expands when it comes into contact with water, there is an electrical shielding phenomenon between the fluffy cotton and the non-woven fabric.

[0003] Therefore, there is an urgent need for a buffer water-blocking tape that can solve the above ablation defects. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a high-voltage cable buffer water-blocking tape for preventing electrical ablation, comprising a first fluffy cotton layer, a first filter cotton layer, a non-woven fabric layer, a water-blocking powder layer, a second non-woven fabric layer, a second filter cotton layer, and a second fluffy cotton layer, which are arranged in sequence from top to bottom. The first fluffy cotton layer and the second fluffy cotton layer have the same structure, and a copper film layer and a tin-plated aluminum film layer are respectively provided on the inner and outer sides of the fluffy cotton layer.

[0005] Furthermore, carbonized graphite fibers are added to the first fluffy cotton layer and the second fluffy cotton layer.

[0006] Furthermore, the first filter cotton layer and the second filter cotton layer are activated carbon filter cotton.

[0007] Furthermore, the first filter cotton layer and the second filter cotton layer are activated carbon filter cottons that have been fumigated with acetic acid vapor.

[0008] Furthermore, polymer conductive fibers are added to the first non-woven fabric layer and the second non-woven fabric layer.

[0009] Furthermore, the water-blocking powder added to the water-blocking layer contains tungsten carbide highly conductive powder and / or chromium carbide highly conductive powder.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The buffer water-blocking tape of the present invention adds a filter layer treated with acetic acid vapor between the fluffy surface and the non-woven fabric. On the one hand, the water-blocking powder can be isolated to prevent the water-blocking powder from precipitating on the fluffy cotton surface after absorbing water, thereby reducing the electrical contact ability between the buffer layer and the aluminum sheath. On the other hand, the water-blocking powder becomes a weak base after being damp, which will corrode the non-woven fabric-buffer tape and even the aluminum sheath. Adding a layer of filter cotton treated with acetic acid vapor can play a neutralizing role and protect the buffer layer and the aluminum sheath.

[0012] The buffer water-blocking tape of the present invention sprays copper film and aluminum film on both sides of the inside and outside of the fluffy cotton respectively. Compared with the traditional buffer water-blocking tape that needs to be wrapped with copper wire shielding tape, the integrated structure and the full-area aluminum film are better than the intermittent copper wire in ensuring electrical contact ability. The aluminum film is in contact with the aluminum sheath, ensuring that no electrochemical reaction occurs in most cases. In addition, the aluminum film is light in weight and has an integrated design without the constraints of the metal shielding tape, which can better ensure the elasticity of the fluffy cotton and make the buffer layer and the aluminum sheath have strong electrical contact ability. Adding copper film on the inside of the fluffy cotton can improve the situation where the water-blocking powder is damp and the uneven distribution of carbon black causes electric field concentration and causes ablation of the buffer layer.

[0013] The buffer water-blocking tape of the present invention adopts the same structure with good electrical performance on both sides, which can ensure the electrical contact ability between the insulation shield and the aluminum sheath. Due to the completely symmetrical structure, it can not only ensure high efficiency during production, but also can be flipped during use, that is, the first fluffy cotton layer can be used as the inner layer, or the second fluffy surface layer can be used as the inner layer. The double-sided fluffy surface structure can ensure that the elastic performance of the buffer water-blocking tape is better than the single-sided fluffy surface structure of the traditional buffer water-blocking tape, improve the electrical contact ability between the buffer water-blocking tape and the aluminum sheath, and significantly reduce the problem of buffer layer ablation. And the positions of the first non-woven fabric layer and the second non-woven fabric layer can be interchanged as needed, which can improve the efficiency during wrapping and greatly improve production efficiency.

[0014] The buffer water-blocking tape of the present invention has a seven-layer structure instead of a three-layer structure in the prior art. Each layer cooperates with each other, which can not only ensure better water-blocking performance, but also significantly prevent electrical ablation. In addition, the present application does not require multiple layers (four or six layers) of winding during use, and only needs to be simply wound with one or two layers to achieve the ideal effect. The present invention has excellent effects of water blocking, electrical conductivity and anti-ablation.

[0015] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a buffer water blocking tape according to a specific embodiment of the present invention;

[0017] Figure 2 This is a process flow chart of adding graphite fiber to fluffy cotton according to a specific embodiment of the present invention;

[0018] Figure 3 This is a specific process flow chart of the interweaving and blending method of a specific embodiment of the present invention;

[0019] Figure 4 In a specific embodiment of the present invention, the electric field distribution of the new buffer water-blocking tape after being dampened;

[0020] Figure 5 It is the electric field distribution of the traditional buffer water-blocking tape after being damp in a specific embodiment of the present invention.

[0021] In the figure, 1-first fluffy cotton layer, 2-first filter cotton layer, 3-first non-woven fabric layer, 4-water-blocking powder layer, 5-second non-woven fabric layer, 6-second filter cotton layer, 7-second fluffy cotton layer, 8-tin-plated aluminum film layer, 9-copper film layer, 10-copper film layer, 11-tin-plated aluminum film layer. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0023] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present invention in a schematic manner, and thus the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0024] While some exemplary embodiments of the present invention have been described for the purpose of illustration, it should be understood that the present invention may be implemented in other ways not specifically shown in the drawings.

[0025] like Figure 1As shown, a high-voltage cable buffer water-blocking tape for preventing electrical ablation includes a first fluffy cotton layer 1, a first filter cotton layer 2, a first non-woven fabric layer 3, a water-blocking powder layer 4, a second non-woven fabric layer 5, a second filter cotton layer 6 and a second fluffy cotton layer 7, which are arranged in sequence from top to bottom.

[0026] The first fluffy cotton layer 1 and the second fluffy cotton layer 7 can ensure that the buffer water-blocking belt has better buffering elasticity. The fluffy cotton layer and the filter cotton layer, and the filter surface layer and the non-woven fabric layer are fixedly connected by a conductive epoxy resin glue layer, and the non-woven fabric layer and the water-blocking powder layer are fixedly connected by a nickel-coated conductive glue. The conductive epoxy resin glue is mainly composed of a polyurethane curing agent and an epoxy resin, which has good chemical stability and wear resistance, and is conducive to ensuring the stability of the structure of the buffer water-blocking belt. The nickel-coated conductive glue has good electrical conductivity and high temperature performance. Since the water-blocking powder has poor thermal conductivity and is prone to temperature concentration, the use of a nickel-coated conductive glue can ensure the water-blocking effect of blocking moisture.

[0027] The first fluffy cotton layer 1 and the second fluffy cotton layer 7 have the same structure. The upper and lower sides of the first fluffy cotton layer 1 are respectively covered with a tin-plated aluminum film layer 8 and a copper film layer 9. The upper and lower sides of the second fluffy cotton layer 7 are respectively covered with a copper film layer 10 and a tin-plated aluminum film layer 11. The thickness range of the copper film layer and the copper film layer is 0.12mm±0.05mm. The copper film layer has excellent electrical properties, which can play a role in homogenizing the electric field and making up for the electrical properties of other structures in the inner layer of the buffer water-blocking tape; the price and density of the aluminum film layer are relatively low, which can ensure the inherent fluffiness of the fluffy cotton while ensuring the electrical properties. In actual production, the wrapping buffer water-blocking tape will be compressed, so the interval between the bimetallic films is very small; and because the acidity of acetic acid is weak and copper is not a very active metal, there will be no chemical reaction between them. Even at high temperatures, it involves complex reaction conditions. Therefore, in the present invention, the copper film is sprayed on the inside of the fluffy cotton, which can reduce the corrosion of acetic acid vapor to the fluffy cotton and increase the resistivity of the buffer layer. At the same time, based on the characteristic of copper being easily oxidized, the use of copper film can, on the one hand, absorb possible oxygen in the fluffy cotton, react to form copper oxide, which can reduce the degree of ablation. At the same time, copper oxide can also absorb moisture in the fluffy cotton to form an electrolyte, enhance conductivity, and further improve the electrical properties of the fluffy cotton layer, achieving multiple effects at one stroke.

[0028] In order to ensure the electrical properties while not affecting the fluffiness of the fluffy cotton layer, in a specific embodiment, a copper film layer and an aluminum film layer are coated on both sides of the fluffy cotton layer using a double-spraying method of "copper inside and aluminum outside", which is equivalent to adding a layer of metal protective film on each side of the fluffy cotton, which is not only beneficial to the uniform electric field distribution of the buffer water-blocking belt, but also can improve the conductivity and strength of the buffer layer. Compared with the metal wire shielding structure, it can not only save metal raw materials, but also because of the larger coverage area, the water-blocking belt has better electrical properties. During spraying, in order to achieve full coverage of the metal film on both sides of the fluffy cotton, a longitudinal spray-transverse blowing process is adopted to ensure that the copper-aluminum metal film is 0.12mm±0.05mm.

[0029] The way the corrugated aluminum sheath contacts the aluminum film can avoid chemical corrosion of the aluminum sheath and improve the stability of the cable structure.

[0030] In order to ensure the conductivity, heat resistance and chemical corrosion resistance of the fluffy cotton layer while reducing the thermal shrinkage ability, carbonized graphite fibers are added to the first fluffy cotton layer 1 and the second fluffy cotton layer 7, so that the fluffy cotton shrinks mainly as a mechanical force, thereby increasing the service life of the buffer water-blocking belt.

[0031] In a specific embodiment, the graphite fiber is added by wet spinning, which firmly combines the fluffy cotton and the graphite fiber together, so that the overall fabric has better strength and durability and a longer service life. The mass ratio of the fluffy cotton to the graphite fiber is 5:1. The process of the wet spinning method is as follows Figure 2 As shown, fluffy cotton and graphite fiber are mixed in a mass ratio of 5:1, the raw silk is coagulated, and the graphite fiber is added to the fluffy cotton through processes such as drawing.

[0032] The first filter cotton layer and the second filter cotton layer are activated carbon filter cotton, which are filled with an appropriate amount of graphite fibers, which can not only play a conductive role, but also absorb water and impurities in the water to prevent chemical corrosion. In addition, the water-blocking powder will expand rapidly when it comes into contact with water, and the activated carbon filter cotton can ensure that fewer water-blocking powder particles penetrate into the surface of the buffer layer to affect its electrical and thermal performance.

[0033] The water-blocking powder is prevented from being precipitated on the fluffy cotton layer, thereby improving the electrical contact ability between the buffer water-blocking belt and the aluminum sheath. The first filter cotton layer and the second filter cotton layer are used to prevent the water-blocking powder from being precipitated.

[0034] The double-sided fluffy cotton buffer water-blocking tape designed by the present invention can ensure greater elasticity. Compared with the traditional buffer water-blocking tape with an elasticity of ±0.35mm, the buffer water-blocking tape mentioned in the present invention can reach ±0.65mm, which effectively avoids damage to the buffer water-blocking tape caused by thermal expansion and contraction and mechanical pressure, and has excellent electrical contact ability.

[0035] During use, since the main component of water-blocking powder is sodium polyacrylate (CH3NaO2) n Once the traditional water-blocking tape is damp, the following reactions will occur:

[0036] Na + +CO2+OH - →Na2CO3 / NaHCO3;

[0037] Al+OH - +H2O→AlO2 - ;

[0038] AlO2 - +CO2+H2O→Al(OH)3;

[0039] It can be seen that once water penetrates into the water-blocking powder in the traditional water-blocking tape, the water-blocking powder will become weakly alkaline when it meets water, and will corrode the copper sheath for a long time. In order to solve this problem, the first filter cotton layer and the second filter cotton layer in this embodiment are activated carbon filter cotton fumigated with acetic acid vapor. In the presence of acetic acid vapor, the first step reaction above has a neutralization reaction: OH - +H + →H2O, that is, the weak alkalinity of the water-blocking powder when it meets water, neutralizes with acetic acid and cannot undergo further reactions, thus achieving a neutralization effect and making the water-blocking tape a neutral environment, thereby preventing corrosion of the aluminum sheath and accelerating the ablation of the buffer layer. Moreover, due to the good volatility of acetic acid, it can carry away part of the water vapor. Furthermore, the acetate ions produced by the hydrolysis of acetic acid can achieve the effect of enhancing the conductive properties.

[0040] In order to better ensure the electrical performance, the non-woven fabric layer is added with polymer conductive fibers, the mass ratio of the non-woven fabric fibers to the polymer conductive fibers is 3:1, and the non-woven fabric layer is prepared by an interweaving blending method, and the two fibers are interwoven together through a loom to form a blended fiber material. The specific process steps of the interweaving blending method are as follows Figure 3 shown.

[0041] In a specific embodiment, the water-blocking powder added to the water-blocking powder layer contains tungsten carbide strong conductive powder and / or chromium carbide strong conductive powder. The structure contains carbides with better conductivity than graphite, etc., which can ensure that the water-blocking powder still has excellent electrical properties even after expansion. The electrical conductivity of the tungsten carbide and chromium carbide is required to be greater than 5×10 6 s / m, the mass addition ratio is: tungsten carbide: chromium carbide: water-blocking powder = 3:3:20; the main component of the water-blocking powder in this application is sodium polyacrylate, and the addition of carbide is to increase the electrical properties of the water-blocking powder.

[0042] By redesigning the structure of the buffer water-blocking tape, the electrical ablation of the buffer water-blocking tape of the high-voltage cable can be significantly reduced, especially for some special fields, such as aerospace and military industries, which can highly ensure the safety of the power system. The thickness of each layer inside the buffer water-blocking tape can be adjusted according to the actual application conditions and scenarios to ensure that the overall thickness of the buffer water-blocking tape is less than 3.35mm, and less than 2.5mm after compression.

[0043] In order to further illustrate the effect of the present invention, in a specific embodiment, the water blocking tape of the present application is compared with the water blocking tape in the prior art.

[0044] The thickness of each layer of the water-blocking tape in the present application is as follows: in a specific embodiment, the thickness of the first fluffy cotton layer 1 and the second fluffy cotton layer 7 is 1 mm; the thickness of the first filter cotton layer 2 and the second filter cotton layer 6 is 0.15 mm; the thickness of the first non-woven fabric layer 3 and the second non-woven fabric layer 5 is 0.25 mm; the thickness of the first water-blocking powder layer and the second water-blocking powder layer is 0.3 mm; the thickness deviation of each layer is 0.1mm.

[0045] The novel buffer water-blocking tape of the present invention has a thickness range of 3±0.25 mm and a unit area weight of 300±8 g / m 2 , longitudinal tensile strength ≥ 65N / cm, longitudinal elongation ≥ 20%, expansion rate ≥ 30mm / min. Overall, the surface resistance of the new buffer water-blocking tape is less than 300Ω, and the volume resistivity is less than 1×10 2 Ω•m.

[0046] The specific test steps are as follows:

[0047] Mechanical properties: Longitudinal tensile strength / longitudinal elongation measurement, test specimen width is 20mm±0.5mm, gauge length is 100mm, tensile rate is 100mm / min, the experiment is carried out, longitudinal tensile strength is ≥65N / cm, longitudinal elongation is ≥20%.

[0048] Expansion rate: Sampling 5 5cm, thickness is d1, 3 ml of water is injected into the fluffy surfaces on both sides, and the thickness is remeasured after 1 minute, which is d2. The expansion rate is [(d2-d1) / d1].

[0049] Surface resistance: Place the prepared new buffer water-blocking tape (250mm*250mm) on an insulating rubber pad (300mm*300mm), place two copper electrodes (two copper rod electrodes in a T shape, each with a measuring area of ​​200mm*1mm) in parallel on the semi-conductive sample and in close contact with the semi-conductive sample, apply a 4.5V DC voltage between the two copper electrodes, and read the resistance with a multimeter after charging for 1 minute.

[0050] Volume resistance: A two-electrode system is used, with the upper electrode being a brass rod electrode, weighing 2kg and having a diameter of 50mm, so the sample diameter is 60mm, and the lower electrode being a brass plate electrode, 100mm*100mm*10mm. The sample is placed on the copper plate electrode, and then the copper rod electrode is pressed on the sample. The experimental voltage is set to 4.5V DC voltage, and after charging for 1min, the measured volume resistance value is read with a multimeter.

[0051] In contrast, the traditional water-blocking tape is composed of a fluffy cotton layer, a non-woven fabric layer and a water-blocking powder layer arranged in sequence. Take a domestic manufacturer's 2.0mm×80mm traditional water-blocking tape as an example: the thickness of the fluffy cotton is 1.5mm, the thickness of the non-woven fabric is 0.3mm, and the water-blocking powder layer is 0.2mm.

[0052] Comparison of parameters of two buffer layer materials when exposed to moisture. The process of moisture test: Take two newly made buffer layers, each 105mm, inject 10ml of water from the side with a syringe, let it stand for 4.5h, and then measure the material parameters respectively:

[0053] From the comparison of experimental data, it can be seen that the density of each layer of the new buffer water-blocking tape is similar, but the electrical conductivity and thermal conductivity are better than those of the traditional buffer water-blocking tape, which is of great significance in avoiding electrical ablation and thermal ablation.

[0054] Based on the parameters of the above two types of water-blocking tapes, the suspension voltage on the insulation shield is 30V after the buffer water-blocking tape is damp under the same simulation conditions. The electric field distribution of the two types of buffer water-blocking tapes is as follows: Figure 4 and Figure 5 shown.

[0055] By comparison, it can be seen that only from the electric field distribution after the buffer layer is damp, the maximum electric field strength of the new buffer water-blocking tape of the present invention is only 0.268 kV / mm, which is much smaller than 1.02 kV / mm, and has obvious advantages over traditional water-blocking tape.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A high-voltage cable buffer water-blocking tape for preventing electrical ablation, characterized in that: It includes a first fluffy cotton layer, a first filter cotton layer, a non-woven fabric layer, a water-blocking powder layer, a second non-woven fabric layer, a second filter cotton layer and a second fluffy cotton layer, which are arranged in sequence from top to bottom. The first fluffy cotton layer and the second fluffy cotton layer have the same structure, and a copper film layer and a tin-plated aluminum film layer are respectively provided on the inner and outer sides of the fluffy cotton layer.

2. The high-voltage cable buffer water-blocking tape for preventing electrical ablation according to claim 1 is characterized in that: The first fluffy cotton layer and the second fluffy cotton layer are added with carbonized graphite fibers.

3. The high-voltage cable buffer water-blocking tape for preventing electrical ablation according to claim 1 is characterized in that: The first filter cotton layer and the second filter cotton layer are activated carbon filter cotton.

4. The high-voltage cable buffer water-blocking tape for preventing electrical ablation according to claim 3 is characterized in that: The first filter cotton layer and the second filter cotton layer are activated carbon filter cottons that have been fumigated with acetic acid steam.

5. The high-voltage cable buffer water-blocking tape for preventing electrical ablation according to claim 1 is characterized in that: The non-woven fabric layer is added with high molecular conductive fibers.

6. The high-voltage cable buffer water-blocking tape for preventing electrical ablation according to claim 1 is characterized in that: The water-blocking powder added to the water-blocking layer contains tungsten carbide highly conductive powder and / or chromium carbide highly conductive powder.

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