A high voltage cable buffer water-blocking tape for preventing electrical arcing

Abstract

The application discloses a high-voltage cable buffer water-blocking belt capable of preventing electric ablation, and relates to the field of high-voltage cable structures. The application comprises, from top to bottom, 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, wherein the first fluffy cotton layer and the second fluffy cotton layer are of the same structure, and the first fluffy cotton layer and the second fluffy cotton layer are both provided with copper films and tin-plated aluminum films on the inner and outer sides. The application can not only ensure better water-blocking performance, but also obviously prevent electric ablation.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable structures, and more particularly to a high-voltage cable buffer water-blocking strip to prevent electro-erosion. Background Technology

[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. By adding conductive carbon black to the non-woven fabric and fluffy cotton, its conductivity is increased. Due to its relatively simple process, it has been favored by the industry. However, high-voltage cable buffer water-blocking tape ablation accidents occur frequently, which has seriously threatened the safety of the power transmission system. Scholars have analyzed the ablation mechanism and believe that the reasons for the ablation of the existing buffer water-blocking tape include: (1) After the buffer water-blocking tape gets 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 performance 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 insulating shield, resulting in insufficient elasticity of the fluffy cotton, which cannot guarantee the electrical contact between the insulating shield and the aluminum sheath. (3) The water-blocking powder is weakly alkaline when it comes into contact with water. Once it comes into contact with the aluminum sheath, it will react and corrode the aluminum sheath, which cannot guarantee the electrical contact between the buffer water-blocking tape and the aluminum sheath. (4) In order to ensure electrical tightness between fluffy cotton and non-woven fabric, less water-blocking powder is added, resulting in poor water-blocking effect. (5) Water-blocking powder is an insulating material. After the water-blocking powder expands when it comes into contact with water, fluffy cotton and non-woven fabric will have an electrical shielding phenomenon.

[0003] Therefore, there is an urgent need for a buffer water-blocking strip that can solve the above-mentioned 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 strip to prevent electro-erosion, comprising, from top to bottom, 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. The first fluffy cotton layer and the second fluffy cotton layer have the same structure. The inner and outer surfaces of the first fluffy cotton layer are respectively provided with a copper film layer and a tin-plated aluminum film layer. The inner and outer surfaces of the second fluffy cotton layer are respectively provided with a copper film layer and a tin-plated aluminum film layer.

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

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

[0007] Furthermore, the first and second filter cotton layers are activated carbon filter cotton that has been treated with acetic acid vapor fumigation.

[0008] Furthermore, conductive polymer fibers are added to the first and second nonwoven fabric layers.

[0009] Furthermore, the water-blocking powder added to the water-blocking layers 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 to the fluffy surface and the non-woven fabric. On the one hand, it can isolate the water-blocking powder and prevent the water-blocking powder from precipitating on the surface of the fluffy cotton after absorbing water, thus reducing the electrical contact between the buffer layer and the aluminum sheath. On the other hand, the water-blocking powder becomes weakly alkaline when it gets damp, which will corrode the non-woven fabric-buffering tape and even the aluminum sheath. Adding a filter cotton treated with acetic acid vapor can neutralize the alkalinity and protect the buffer layer and the aluminum sheath.

[0012] The buffer water-blocking tape of this invention features copper and aluminum films sprayed onto both the inner and outer sides of the fluffy cotton, respectively. Compared to traditional buffer water-blocking tapes that require an external copper wire shielding strip, the integrated structure, combined with the full-area aluminum film, provides better electrical contact than spaced copper wires. The aluminum film contacts the aluminum sheath, ensuring that no electrochemical reaction occurs under normal circumstances. Furthermore, the lightweight and integrated design of the aluminum film, without the constraint of a metal shielding strip, better preserves the elasticity of the fluffy cotton, resulting in strong electrical contact between the buffer layer and the aluminum sheath. Adding a copper film to the inner side of the fluffy cotton improves the situation where moisture absorption of the water-blocking powder and uneven carbon black distribution cause electric field concentration, leading to buffer layer ablation.

[0013] The buffer water-blocking tape of this invention employs the same electrically efficient structure on both sides, ensuring electrical contact between the insulating shield and the aluminum sheath. Due to its completely symmetrical structure, it guarantees high production efficiency and can be flipped during use, allowing either the first or second fluffy cotton layer to be used as the inner layer. This double-sided fluffy structure, compared to the traditional single-sided fluffy structure of buffer water-blocking tapes, ensures better elasticity, improves electrical contact between the tape and the aluminum sheath, and significantly reduces the risk of buffer layer erosion. Furthermore, the positions of the first and second non-woven fabric layers can be interchanged as needed, improving wrapping efficiency and significantly increasing production efficiency.

[0014] The buffer water-blocking tape of this invention has a seven-layer structure, replacing the three-layer structure of the prior art. Each layer works together to ensure better water-blocking performance while significantly preventing electro-erosion. Furthermore, this application eliminates the need for multiple layers (four or six layers) of winding during use; simply winding one or two layers is sufficient to achieve the desired effect. This invention offers excellent water-blocking, electrical conductivity, and ablation prevention properties.

[0015] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a buffer water-blocking strip according to a specific embodiment of the present invention;

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

[0018] Figure 3 This is a detailed process flow diagram of the interlacing and blending method according to a specific embodiment of the present invention;

[0019] Figure 4 This is a specific embodiment of the present invention, showing the electric field distribution of the novel buffer water-blocking strip after it becomes damp;

[0020] Figure 5 This is a specific embodiment of the present invention, showing the electric field distribution of a traditional water-blocking buffer strip after it becomes damp.

[0021] In the diagram, 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 Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0023] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] Some exemplary embodiments of the invention have been described for illustrative purposes. It should be understood that the invention may be implemented in other ways not specifically shown in the accompanying drawings.

[0025] like Figure 1As shown, a high-voltage cable buffer water-blocking strip for preventing electro-erosion includes, from top to bottom, 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.

[0026] The first fluffy cotton layer 1 and the second fluffy cotton layer 7 ensure that the buffer water-blocking tape has better cushioning elasticity. The fluffy cotton layer and the filter cotton layer, as well as the filter surface layer and the non-woven fabric layer, are fixedly connected by conductive epoxy resin adhesive layers. The non-woven fabric layer and the water-blocking powder layer are fixedly connected by nickel-coated conductive adhesive. The conductive epoxy resin adhesive is mainly composed of polyurethane curing agent and epoxy resin, and has good chemical stability and wear resistance, which helps to ensure the structural stability of the buffer water-blocking tape. The nickel-coated conductive adhesive has good electrical conductivity and high-temperature performance. Because the water-blocking powder has poor thermal conductivity and is prone to temperature concentration, the use of nickel-coated conductive adhesive can ensure the water-blocking effect.

[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 of both the copper film layer and the copper film layer ranges from 0.12mm ± 0.05mm. The copper film layer has excellent electrical properties, which can homogenize the electric field and compensate for the electrical properties of other structures in the inner layer of the buffer water-blocking strip. The aluminum film layer has a lower price and density, ensuring both electrical performance and the inherent fluffiness of the fluffy cotton. In actual production, the buffer water-blocking strip is wrapped using a tight compression method, resulting in a very small gap between the bimetallic films. Furthermore, since acetic acid is a weak acid and copper is a relatively inert metal, they do not react chemically. Even at high temperatures, complex reaction conditions are involved. Therefore, in this invention, spraying a copper film on the inner side of the fluffy cotton can reduce the corrosion of the fluffy cotton by acetic acid vapor and increase the resistivity of the buffer layer. Meanwhile, given the characteristic that copper is easily oxidized, using a copper film can absorb any oxygen that may be present in the fluffy cotton, reacting to form copper oxide, which can reduce the degree of ablation. At the same time, copper oxide can also absorb moisture from the fluffy cotton, forming an electrolyte and enhancing conductivity, further improving the electrical performance of the fluffy cotton layer, achieving multiple benefits in one fell swoop.

[0028] To ensure electrical performance without compromising the fluffiness of the cotton layer, in one specific embodiment, a "copper inside, aluminum outside" dual-blowing method is used to coat both sides of the cotton layer with copper and aluminum film layers. This is equivalent to adding a metal protective film to each side of the cotton layer, which not only helps to homogenize the electric field distribution of the water-blocking band but also improves the conductivity and strength of the buffer layer. Compared with a metal wire shielding structure, this method not only saves metal raw materials but also provides better electrical performance due to the larger coverage area. During the blowing process, to ensure that the metal film fully covers both sides of the cotton layer, a longitudinal spraying followed by a transverse blowing process is used, ensuring that the copper and aluminum metal film thickness is 0.12mm ± 0.05mm.

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

[0030] To ensure the electrical conductivity, heat resistance, and chemical corrosion resistance of the fluffy cotton layer while reducing its thermal shrinkage capacity, carbonized graphite fibers are added to the first fluffy cotton layer 1 and the second fluffy cotton layer 7. This allows the fluffy cotton to primarily shrink under mechanical force, thereby increasing the service life of the buffer water-blocking strip.

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

[0032] The first and second filter cotton layers are activated carbon filter cotton, filled with an appropriate amount of graphite fiber. This fiber serves both to conduct electricity and to adsorb water and impurities, preventing chemical corrosion. Furthermore, the water-blocking powder expands rapidly upon contact with water, and the activated carbon filter cotton ensures that minimal water-blocking powder particles penetrate the buffer layer surface, affecting its electrothermal performance.

[0033] The first and second filter cotton layers prevent the water-blocking powder from precipitating onto the fluffy cotton layer, thereby improving the electrical contact between the buffer water-blocking tape and the aluminum sheath.

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

[0035] During use, the main component of the water-blocking powder is sodium polyacrylate (CH3NaO2). n Traditional water-blocking strips will react as follows once they get damp:

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

[0037] Al+OH - +H₂O→AlO₂ - ;

[0038] AlO2 - +CO2+H2O→Al(OH)3;

[0039] It is known that in traditional water-blocking tapes, once water seeps into the water-blocking powder, the powder becomes weakly alkaline upon contact with water, which will corrode the copper sheath over time. To solve this problem, in this embodiment, the first and second filter cotton layers are activated carbon filter cotton treated with acetic acid vapor fumigation. In the presence of acetic acid vapor, the above-mentioned first step reaction undergoes a neutralization reaction: OH - +H + →H2O, the weak alkalinity of the water-blocking powder when it comes into contact with water, neutralizes the acetic acid, preventing further reactions and achieving a neutralization effect. This creates a neutral environment for the water-blocking tape, preventing corrosion of the aluminum sheath and accelerating the ablation of the buffer layer. Furthermore, due to the high volatility of acetic acid, some moisture can be carried away. In addition, the acetate ions produced by the hydrolysis of acetic acid can enhance the conductivity.

[0040] To better ensure electrical performance, conductive polymer fibers are added to the nonwoven fabric layer. The mass ratio of nonwoven fabric fibers to conductive polymer fibers is 3:1. The material is prepared using an interlacing blending method, where the two types of fibers are interwoven together on a loom to form a blended fiber material. The specific process steps of the interlacing blending method are as follows: Figure 3 As shown.

[0041] In one specific embodiment, the water-blocking powder layer contains tungsten carbide and / or chromium carbide powder, which are highly conductive. This structure incorporates carbides with superior conductivity compared to graphite, ensuring excellent electrical performance even after the water-blocking powder expands. The conductivity of the tungsten carbide and chromium carbide is required to be greater than 5 × 10⁻⁶. 6 The mass addition ratio of s / m 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 carbides is to increase the electrical properties of the water-blocking powder.

[0042] By redesigning the structure of the buffer water-blocking strip, the electro-erosion of the high-voltage cable buffer water-blocking strip can be significantly reduced. This is particularly beneficial in specialized fields such as aerospace and military, ensuring a high level of power system safety. The thickness of each layer within the buffer water-blocking strip can be adjusted according to the actual application and scenario, ensuring that the overall thickness of the buffer water-blocking strip is less than 3.35mm, and less than 2.5mm after compression.

[0043] To further illustrate the effects of the present invention, in a specific embodiment, the water-blocking tape of this application is compared with the water-blocking tape in the prior art.

[0044] The thickness of each layer of the water-blocking tape in this 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; and the thickness deviation of each layer is ±0.1 mm.

[0045] The novel water-blocking buffer strip of this invention has a thickness ranging from 3±0.25mm and a unit area weight of 300±8g / m². 2 The longitudinal tensile strength is ≥65 N / cm, the longitudinal elongation is ≥20%, and the expansion rate is ≥30 mm / min. Overall, the surface resistivity of the new type of buffer water-blocking tape is less than 300 Ω, and the volume resistivity is less than 1×10⁻⁶. 2 Ω•m.

[0046] The specific experimental steps are as follows:

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

[0048] Expansion rate: Take a 5×5cm sample with a thickness of d1, inject 3 ml of water into each of the two fluffy surfaces, and measure the thickness again after 1 min to get d2. The expansion rate is calculated as [(d2-d1) / d1].

[0049] Surface resistance: The prepared new type of buffer water-blocking tape (250mm*250mm) was placed on an insulating rubber pad (300mm*300mm). Two copper electrodes (two copper rod electrodes, T-shaped, each with a measurement area of ​​200mm*1mm) were placed parallel to each other on the semiconductive sample and made in close contact with the semiconductive sample. A DC voltage of 4.5V was applied between the two copper electrodes. After charging for 1 minute, the resistance was read with a multimeter.

[0050] Volume resistivity: A two-electrode system was used. The upper electrode was a brass rod electrode, weighing 2 kg and with a diameter of 50 mm, therefore the sample diameter was selected as 60 mm. The lower electrode was a brass plate electrode, 100 mm * 100 mm * 10 mm. The sample was placed on the copper plate electrode, and then the copper rod electrode was pressed onto the sample. The experimental voltage was set to 4.5 V DC voltage. After charging for 1 minute, the volume resistivity value was read using a multimeter.

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

[0052] A comparison of parameters of two types of buffer layer materials when exposed to moisture was conducted. The moisture test procedure was as follows: Two newly prepared buffer layers, each 105 mm thick, were injected with 10 ml of water from the side using a syringe. After standing for 4.5 hours, the material parameters were measured.

[0053] The data comparison in the experiment shows that the density of each layer of the new buffer water-blocking tape is similar, but its electrical conductivity and thermal conductivity are better than those of the traditional buffer water-blocking tape. This is of great significance in avoiding electrical ablation and thermal ablation.

[0054] Based on the parameters of the two types of water-blocking tapes mentioned above, simulations were conducted under the same conditions. After the buffer water-blocking tape became damp, the suspended voltage on the insulating shield was 30V. The electric field distribution of the two types of buffer water-blocking tapes is as follows: Figure 4 and Figure 5 As shown.

[0055] As can be seen from the comparison, considering only the electric field distribution after the buffer layer becomes damp, the maximum electric field strength of the novel water-blocking buffer strip of this invention is only 0.268kV / mm, which is much smaller than 1.02kV / mm, showing a significant advantage compared with traditional water-blocking strips.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A high-voltage cable buffer water-blocking strip to prevent electro-erosion, characterized in that, It includes, from top to bottom, a first fluffy cotton layer, a first filter cotton layer, a first 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. The first fluffy cotton layer and the second fluffy cotton layer have the same structure. The inner and outer surfaces of the first fluffy cotton layer are respectively provided with a copper film layer and a tin-plated aluminum film layer. The inner and outer surfaces of the second fluffy cotton layer are respectively provided with a copper film layer and a tin-plated aluminum film layer. The first and second fluffy cotton layers are incorporating carbonized graphite fibers, with a mass ratio of fluffy cotton to graphite fibers of 5:

1. The fluffy cotton and graphite fibers are then firmly bonded together using a wet spinning method. The first and second filter cotton layers are activated carbon filter cotton that has been treated with acetic acid vapor fumigation.

2. The high-voltage cable buffer water-blocking strip for preventing electro-erosion according to claim 1, characterized in that, High molecular conductive fibers are added to the first nonwoven fabric layer and the second nonwoven fabric layer.

3. A high-voltage cable buffer water-blocking strip for preventing electro-erosion according to claim 1, characterized in that, The water-blocking powder layer contains tungsten carbide and / or chromium carbide highly conductive powders, the latter having a conductivity greater than 5 × 10⁻⁶. 6 s / m.

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