High-temperature-resistant control cable for transformer

Abstract

The invention relates to the technical field of wires and cables, and particularly discloses a high-temperature-resistant control cable for a transformer. A high-temperature-resistant control cable for a transformer comprises conductor wire cores, a polyimide insulating layer, an aerogel heat insulation layer and a sheath. The polyimide insulating layer comprises the following raw materials: polyimide, graphene oxide, potassium titanate whiskers, an ultraviolet light absorber, a silane coupling agent and an antioxidant; the aerogel heat insulation layer is prepared from the following raw materials: silicon dioxide aerogel, basalt fiber, stearic acid, silica sol, magnesium hydroxide, hexagonal boron nitride and a silane coupling agent. After the control cable is subjected to a high-temperature resistance test, the absolute values of the tensile strength change rate and the elongation at break change rate are 13.9 and 14.3 at least, the high-temperature resistance of the control cable is improved, and the service life of the control cable in a high-temperature environment is prolonged.

Description

Technical Field

[0001] This application relates to the field of wire and cable technology, and more specifically, it relates to a high-temperature resistant control cable for transformers. Background Technology

[0002] In power systems, transformers, as core equipment for power transmission and distribution, are widely used in power plants, substations, industrial plants, and high-rise buildings. With the continuous growth in electricity demand, the capacity of individual transformers is constantly increasing. During operation, the internal core losses, winding copper losses, and leakage flux losses generate a large amount of heat, causing a significant increase in the temperature of the tank and surrounding environment. The hot spot temperature of the transformer windings can reach 90-110℃, and during overload or short-term faults, the temperature can even exceed 150℃. Furthermore, under high-temperature environments, the insulation layer of traditional cables is prone to softening and cracking, leading to a decline in the electrical performance of the cables, a shortened service life, and increased maintenance costs and safety hazards in the power system.

[0003] In related technologies, silicone rubber and fluoroplastics are used to replace traditional polyvinyl chloride to improve the high temperature resistance of control cables. However, silicone rubber has low mechanical strength, making the cables susceptible to damage from external forces. Furthermore, the siloxane main chain is prone to breakage after contact with transformer oil mist, making it difficult to meet actual usage requirements. Summary of the Invention

[0004] To improve the high temperature resistance of control cables, this application provides a high temperature resistant control cable for transformers.

[0005] Firstly, this application provides a high-temperature resistant control cable for transformers, which adopts the following technical solution: A high-temperature resistant control cable for transformers includes a conductor core, a polyimide insulation layer, an aerogel insulation layer, and a sheath; the polyimide insulation layer comprises the following raw materials in parts by weight: 50-70 parts polyimide, 0.5-1 parts graphene oxide, 3-8 parts potassium titanate whiskers, 0.5-1 parts ultraviolet absorber, 1-2 parts silane coupling agent, and 1-3 parts antioxidant; The aerogel insulation layer comprises the following raw materials in parts by weight: 80-90 parts silica aerogel, 5-15 parts basalt fiber, 1-3 parts stearic acid, 1-3 parts silica sol, 5-10 parts magnesium hydroxide, 3-8 parts hexagonal boron nitride, and 0.5-1.5 parts silane coupling agent.

[0006] By adopting the above technical solution, copper alloy conductor cores are selected for the conductor core, which have good electrical and thermal conductivity, thus improving the overall high temperature resistance of the control cable from the conductor end.

[0007] The polyimide insulating layer uses polyimide as the main raw material. Polyimide has high temperature resistance. Potassium titanate whiskers are one-dimensional needle-like rigid structures that can be interspersed between the two-dimensional sheets of graphene oxide, restricting the slippage and creep of polyimide molecular chains at high temperatures. At the same time, it prevents the graphene oxide sheets from stacking and agglomerating due to thermal motion. In addition, graphene oxide can prevent potassium titanate whiskers from agglomerating in the polyimide insulating layer system. The two enhance each other's dispersibility and ensure the uniformity of heat resistance performance at high temperatures.

[0008] The aerogel insulation layer uses silica aerogel as the main raw material. Its high porosity effectively blocks external heat transfer to the polyimide insulation layer, reducing internal temperature rise and improving the cable's heat resistance limit. Basalt fiber, acting as a rigid skeleton, is interspersed within the aerogel pores, inhibiting skeleton collapse at high temperatures and enhancing the high-temperature mechanical stability of the aerogel insulation layer. This prevents insulation layer damage due to mechanical stress during cable laying or at high temperatures, maintaining insulation integrity. Stearic acid improves the interfacial bonding between silica aerogel and basalt fiber, preventing delamination at high temperatures and ensuring the long-lasting effectiveness of the aerogel insulation layer. Magnesium hydroxide decomposes and absorbs heat at high temperatures, reducing internal temperature rise and releasing water vapor to dilute oxygen, inhibiting thermal oxidative degradation of the aerogel insulation layer. The layered structure of hexagonal boron nitride complements the porous structure of silica aerogel, forming a thermal insulation network that prevents aging of the aerogel insulation layer caused by localized heat accumulation. Furthermore, hexagonal boron nitride effectively blocks infrared thermal radiation at high temperatures, further reducing the heat absorption of the aerogel insulation layer. Silane coupling agents eliminate interfacial gaps at high temperatures, reduce microcracks caused by thermal stress, improve the uniformity of dispersion of various raw materials in the aerogel insulation layer matrix, prevent increased thermal conductivity due to localized filler agglomeration, ensure the consistency of the high-temperature resistance of the insulation layer, and enhance the interfacial bonding force of various raw materials. This prevents delamination due to differences in thermal expansion under high-temperature conditions, maintaining the long-term stability of the aerogel insulation layer.

[0009] Preferably, the sheath comprises the following raw materials in parts by weight: 85-95 parts polytetrafluoroethylene, 2-5 parts fluororubber, 0.1-0.5 parts antioxidant, 5-15 parts glass fiber, 10-20 parts magnesium hydroxide, and 1-3 parts compatibilizer.

[0010] By employing the above technical solutions, the CF bond energy in the polytetrafluoroethylene (PTFE) molecular chain is extremely high, making it resistant to breakage and decomposition at high temperatures, thus providing a basic high-temperature resistant skeleton for the sheath. Furthermore, PTFE does not melt or soften at high temperatures and is chemically inert, not reacting with oxygen, acids, or alkalis, preventing the sheath from degrading and failing in high-temperature environments. Fluororubber improves the brittleness of PTFE, enhancing the flexibility and impact resistance of the sheath at high temperatures, preventing cracking under thermal cycling or mechanical stress, and extending the high-temperature life of the sheath. Glass fiber inhibits creep and thermal deformation of the sheath at high temperatures, improving its high-temperature mechanical strength, assisting in blocking heat conduction, and reducing heat accumulation inside the sheath. Magnesium hydroxide reduces the internal temperature rise of the sheath while releasing water vapor to dilute oxygen, inhibiting combustion reactions at high temperatures. It can form a ceramic protective layer on the sheath surface, blocking heat and oxygen intrusion, increasing the sheath's high-temperature resistance time in fires, preventing combustion failure at high temperatures, and protecting the cable's internal structure. The compatibilizer eliminates interfacial gaps at high temperatures, avoids interfacial cracking caused by differences in thermal expansion, and improves the uniformity of dispersion of each raw material in the sheath matrix. It also prevents stress concentration at high temperatures caused by local filler agglomeration, ensuring the consistency of the sheath's high-temperature resistance performance.

[0011] Preferably, the weight ratio of graphene oxide to potassium titanate whiskers is 1:(4-8).

[0012] By adopting the above technical solution and adjusting the weight ratio of graphene oxide to potassium titanate whiskers, it is more conducive to improving the dispersion of the two in the polyimide insulation layer system, thereby further improving the high temperature resistance of the control cable.

[0013] Preferably, the fluororubber is obtained through modification, specifically: S1. Add nano-cerium oxide to anhydrous ethanol and disperse by ultrasonication to obtain nano-cerium oxide suspension; add trifluoropropyltrimethoxysilane to nano-cerium oxide suspension, adjust pH to 4-5, heat to 60-65℃ and stir reaction, centrifuge, wash, dry and set aside. S2. Soften and plasticize the fluororubber, mix it, add the nano-cerium oxide obtained in S1, mix it, add the peroxide vulcanizing agent and crosslinking agent, mix it, mature it, vulcanize it, and obtain the modified fluororubber.

[0014] By adopting the above technical solution, nano-cerium oxide, as a rare earth oxide, possesses excellent oxygen capture ability and thermal stability. Modifying fluororubber with nano-cerium oxide can alleviate molecular chain breakage, reduce the erosion of molecular chains by oxidation products, inhibit thermal creep and rearrangement of molecular chains at high temperatures, maintain the cross-linked network structure of fluororubber, reduce high-temperature deformation of fluororubber, and further improve the high-temperature resistance of fluororubber. Before modification, nano-cerium oxide is pretreated. Nano-cerium oxide treated with trifluoropropyltrimethoxysilane has better compatibility with fluororubber, reduces agglomeration, and improves the effect of nano-cerium oxide-modified fluororubber. Subsequently, nano-cerium oxide, a peroxide vulcanizing agent, and a cross-linking agent are added. The peroxide vulcanizing agent initiates cross-linking of fluororubber molecular chains by generating free radicals, while the cross-linking agent increases the cross-linking density. Finally, the network structure is cured through curing and vulcanization, thereby improving the high-temperature resistance and mechanical properties of fluororubber.

[0015] Preferably, the amount of nano-cerium oxide used is 3%-5% of the mass of the fluororubber.

[0016] By adopting the above technical solution and adjusting the amount of nano-cerium oxide, the modification effect of fluororubber can be improved, thereby further enhancing the high temperature resistance of fluororubber.

[0017] Preferably, the sheath material also includes nano-tungsten trioxide.

[0018] By adopting the above technical solution, magnesium hydroxide exhibits poor interfacial compatibility in polytetrafluoroethylene (PTFE). Adding nano-tungsten trioxide, with its low surface energy, can improve this interfacial compatibility and reduce stress concentration at the interface under high temperatures, thus preventing sheath cracking. Furthermore, magnesium hydroxide lowers the internal temperature of the sheath, hindering the conduction of oxygen and heat to the matrix and delaying thermal oxidation reactions, while nano-tungsten trioxide enhances the density of the insulation layer, further improving the sheath's high-temperature resistance.

[0019] Preferably, the weight ratio of the nano-tungsten trioxide to magnesium hydroxide is 1:(8-12).

[0020] By adopting the above technical solution and adjusting the weight ratio of nano-tungsten trioxide to magnesium hydroxide, it is more conducive to improving the high temperature resistance of the sheath, thereby improving the high temperature resistance of the cable.

[0021] In summary, this application includes at least one of the following beneficial technical effects: (1) In this application, the conductor core is first wrapped in a polyimide insulation layer, then an aerogel insulation layer is tightly bonded to the outside, and then a sheath is covered on the outside. The types and dosages of the raw materials of the conductor core, polyimide insulation layer, aerogel insulation layer and sheath are controlled so that after the control cable is heat-aged at 150℃ for 336h, the absolute values ​​of the change rate of tensile strength and the change rate of elongation at break are 15.7-16.0 and 16.8-17.1, respectively, which has high high temperature resistance.

[0022] (2) This application modifies the fluororubber in the sheath material and controls the amount of nano-cerium oxide, so that after the control cable is heat-aged at 150℃ for 336h, the absolute values ​​of the change rate of tensile strength and the change rate of elongation at break are 14.9-15.2 and 15.5-16.0, respectively, which further improves the high temperature resistance of the control cable.

[0023] (3) This application improves the high temperature resistance of the control cable by adding nano tungsten trioxide to the sheath material and controlling the weight ratio of nano tungsten trioxide to magnesium hydroxide. After the high temperature resistance test of the control cable is carried out at 150℃ for 336h, the absolute values ​​of the change rate of tensile strength and the change rate of elongation at break are 13.9-14.3 and 14.3-14.6, respectively. Detailed Implementation

[0024] The present application will be further described in detail below with reference to specific embodiments.

[0025] The following raw materials used in this application are all commercially available products and are intended to fully disclose the raw materials used in this application. They should not be construed as limiting the source of the raw materials. Specifically, they are: conductor core, copper alloy core; polyimide, brand AURUM (Mitsui, Japan), grade K-20; graphene oxide, particle size 500 mesh; potassium titanate whiskers, diameter 0.1-0.3μm, length 5-15μm, model YC-083; ultraviolet absorber, model UV-312; silane coupling agent, model KH-570; antioxidant, model MIANOX300; silica aerogel, powder particles; basalt fiber, monofilament 11μm; stearic acid, active ingredient content 99%; silica sol, active ingredient content 40%. Magnesium hydroxide, with an effective ingredient content of 99%; hexagonal boron nitride, with a particle size of 100nm; polytetrafluoroethylene, brand: Daikin Japan, model: F-104C; glass fiber, monofilament 11μm; compatibilizer, brand: Dow Chemical, type: PTW; nano-cerium oxide, with a particle size of 50nm; trifluoropropyltrimethoxysilane, with an effective substance content of 98%; peroxide vulcanizing agent, di-tert-butyl peroxide, with an effective ingredient content of 99%; crosslinking agent, powder crosslinking agent TAIC, with an effective ingredient content of 99.8%; nano-tungsten trioxide, with a particle size of 30nm.

[0026] The following are examples of the preparation of modified fluororubber: Preparation Example 1 The modified fluororubber of Example 1 was prepared by the following steps: S1. Add 100g of nano-cerium oxide to 500mL of anhydrous ethanol, disperse by ultrasonication to obtain nano-cerium oxide suspension; add 10g of trifluoropropyltrimethoxysilane to nano-cerium oxide suspension, adjust pH to 4, heat to 60℃ and stir reaction, centrifuge, wash, dry and set aside. S2. 1 kg of fluororubber is plasticized and softened, mixed, 20 g of nano-cerium oxide obtained from S1 is added, mixed, 1.5 g of peroxide vulcanizing agent and 1.5 g of crosslinking agent are added, mixed, cured, and vulcanized to obtain modified fluororubber.

[0027] Preparation Examples 2-5 The preparation methods of the modified fluororubber in Preparation Examples 2-5 are the same as those in Preparation Example 1, except that the amount of nano-cerium oxide used is different, namely 30g, 40g, 50g and 60g, respectively. The other types and amounts of raw materials are the same as those in Preparation Example 1.

[0028] Example 1 The high-temperature resistant control cable for transformers in Example 1 was prepared by the following method: According to the dosage in Table 1, the raw materials of polyimide insulation layer are mixed at 120℃ for 15 min, extruded (zone 1 temperature is 150℃, zone 2 temperature is 170℃, zone 3 temperature is 160℃), and vulcanized at 140℃ for 10 min to obtain polyimide insulation layer material. According to the dosage in Table 2, the raw materials of the aerogel insulation layer are mixed at 120℃ for 15 minutes, extruded (zone 1 temperature is 150℃, zone 2 temperature is 170℃, zone 3 temperature is 160℃), and vulcanized at 140℃ for 10 minutes to obtain the aerogel insulation layer material. According to the dosage in Table 3, the raw materials for the sheath are mixed at 120℃ for 15 minutes, extruded (zone 1 temperature is 150℃, zone 2 temperature is 170℃, zone 3 temperature is 160℃), and vulcanized at 140℃ for 10 minutes to obtain the sheath material. Copper alloy wires are stranded to form a conductor core. A polyimide insulation layer is extruded over the conductor, an aerogel insulation layer is extruded over the polyimide insulation layer, and a sheath is extruded over the aerogel insulation layer to obtain a high-temperature control cable for transformers.

[0029] Examples 2-5 The high-temperature control cable for transformers in Examples 2-5 differs from that in Example 1 in that the amount of graphene oxide and potassium titanate whiskers in the polyimide insulation layer is different.

[0030] Table 1. Raw material dosage (kg) for polyimide insulating layers in Examples 1-5 Example 1 Example 2 Example 3 Example 4 Example 5 polyimide 60 60 60 60 60 Graphene oxide 1 0.8 0.7 0.6 0.5 Potassium titanate whiskers 3 3.2 4.2 4.8 5 UV absorber 0.8 0.8 0.8 0.8 0.8 Silane coupling agent 1.5 1.5 1.5 1.5 1.5 antioxidants 2 2 2 2 2 Table 2. Raw material dosage (kg) for aerogel insulation layers in Examples 1-5 Examples 1-5 Silica aerogel 85 Basalt fiber 10 stearic acid 2 silica sol 2 Magnesium hydroxide 8 Hexagonal boron nitride 5 Silane coupling agent 1 Table 3. Raw material dosage (kg) for sheaths in Examples 1-5 Examples 1-5 polytetrafluoroethylene 90 Fluororubber 3 antioxidants 0.3 Fiberglass 10 Magnesium hydroxide 15 compatibilizer 2 Examples 6-10 The high-temperature control cables for transformers in Examples 6-10 are the same as those in Example 3, except that the fluororubber in the sheath material is the modified fluororubber prepared in Examples 1-5, while the types and amounts of other raw materials are the same as in Example 3.

[0031] Examples 11-15 The high-temperature control cables for transformers in Examples 11-15 are the same as those in Example 8, except that the sheath material also includes nano-tungsten trioxide, with specific amounts of 2.5 kg, 1.88 kg, 1.5 kg, 1.25 kg and 1 kg. The other types and amounts of raw materials are the same as those in Example 8.

[0032] Comparative Example 1 The high-temperature control cable for the transformer in Comparative Example 1 is the same as that in Example 1, except that the potassium titanate whiskers of the polyimide insulation layer are replaced with graphene oxide in equal amounts, while the other raw materials and dosages are the same as in Example 1.

[0033] Comparative Example 2 The high-temperature control cable for the transformer in Comparative Example 2 is the same as that in Example 1, except that the graphene oxide in the polyimide insulation layer is replaced with potassium titanate whiskers in equal amounts, while the other raw materials and dosages are the same as in Example 1.

[0034] Performance Testing (Part 1) The performance of the high-temperature resistant control cables for transformers obtained in different Examples 1-15 and Comparative Examples 1-2 was tested. The test results are detailed in Table 4.

[0035] Tensile strength change rate: The high temperature resistance performance of the control cable was tested according to JB / T10437. The cable was heat-aged at 150℃ for 336 hours, and the tensile strength change rate was detected.

[0036] Change rate of elongation at break: The high temperature resistance performance of the control cable was tested according to JB / T10437. The cable was heat-aged at 150℃ for 336 hours, and the change rate of elongation at break was detected.

[0037] Dielectric strength: The dielectric strength of the control cable is tested in accordance with GB / T1408.1-2016 "Test methods for electrical strength of insulating materials - Part 1: Test at power frequency".

[0038] Table 4 Performance test results of high-temperature resistant control cables for different transformers The test results in Table 4 show that the high-temperature resistant control cable for transformers obtained in this application, after undergoing a high-temperature performance test at 150℃ for 336 hours, exhibits the lowest absolute values ​​of tensile strength change rate and elongation at break change rate at 13.9 and 14.3, respectively. This improves the high-temperature resistance of the control cable. Furthermore, the control cable has a dielectric strength of up to 38kV / mm, demonstrating excellent electrical performance. This significantly enhances the stability and safety of power transmission in the control cable, extends its service life in high-temperature environments, and substantially reduces its maintenance costs.

[0039] Based on the performance test data of the high-temperature resistant control cables for transformers in Examples 1-5, it can be seen that after the high-temperature performance test of the control cables in Examples 2-4 at 150℃ for 336 hours, the absolute values ​​of the change rate of tensile strength and the change rate of elongation at break are 15.7-16.0 and 16.8-17.1, respectively, which are lower than those in Examples 1 and 5. This indicates that when the weight ratio of graphene oxide to potassium titanate whiskers in the polyimide insulation layer is 1:(4-8), the high-temperature resistance of the control cable can be improved.

[0040] Based on the performance test data of the high-temperature resistant control cables for transformers in Examples 6-10, it can be seen that after the high-temperature performance test of the control cables in Examples 7-9 at 150℃ for 336 hours, the absolute values ​​of the change rate of tensile strength and the change rate of elongation at break are 14.9-15.2 and 15.5-16.0, respectively, which are lower than those in Examples 6 and 10. This indicates that modifying the fluororubber in the sheath material and controlling the amount of nano-cerium oxide can further improve the high-temperature resistance of the control cables.

[0041] Based on the performance test data of the high-temperature resistant control cables for transformers in Examples 11-15, it can be seen that after the high-temperature performance test of the control cables in Examples 12-14, which underwent heat aging at 150℃ for 336 hours, the absolute values ​​of the change rate of tensile strength and the change rate of elongation at break were 13.9-14.3 and 14.3-14.6, respectively, which were lower than those in Examples 11 and 15. This indicates that adding nano-tungsten trioxide to the sheath material and controlling the weight ratio of nano-tungsten trioxide to magnesium hydroxide can further improve the high-temperature resistance of the control cables.

[0042] Furthermore, based on the performance test data of the high-temperature resistant control cable for transformers in Comparative Examples 1-2 and Example 1, it was found that adding graphene oxide and potassium titanate whiskers to the polyimide insulation layer can improve the high-temperature resistance of the control cable to varying degrees.

[0043] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-temperature resistant control cable for transformers, characterized in that, It includes a conductor core, a polyimide insulation layer, an aerogel insulation layer, and a sheath; the conductor core is made of copper alloy. The polyimide insulating layer comprises the following raw materials in parts by weight: 50-70 parts polyimide, 0.5-1 parts graphene oxide, 3-5 parts potassium titanate whiskers, 0.5-1 parts ultraviolet absorber, 1-2 parts silane coupling agent, and 1-3 parts antioxidant. The aerogel insulation layer comprises the following raw materials in parts by weight: 80-90 parts silica aerogel, 5-15 parts basalt fiber, 1-3 parts stearic acid, 1-3 parts silica sol, 5-10 parts magnesium hydroxide, 3-8 parts hexagonal boron nitride, and 0.5-1.5 parts silane coupling agent.

2. The high-temperature resistant control cable for transformers according to claim 1, characterized in that, The sheath comprises the following raw materials in parts by weight: 85-95 parts polytetrafluoroethylene, 2-5 parts fluororubber, 0.1-0.5 parts antioxidant, 5-15 parts glass fiber, 10-20 parts magnesium hydroxide, and 1-3 parts compatibilizer.

3. The high-temperature resistant control cable for transformers according to claim 1, characterized in that, The weight ratio of graphene oxide to potassium titanate whiskers is 1:(4-8).

4. The high-temperature resistant control cable for transformers according to claim 2, characterized in that, The fluororubber is obtained through modification, specifically: S1. Add nano-cerium oxide to anhydrous ethanol and disperse by ultrasonication to obtain nano-cerium oxide suspension; add trifluoropropyltrimethoxysilane to nano-cerium oxide suspension, adjust pH to 4-5, heat to 60-65℃ and stir reaction, centrifuge, wash, dry and set aside. S2. Soften and plasticize the fluororubber, mix it, add the nano-cerium oxide obtained in S1, mix it, add the peroxide vulcanizing agent and crosslinking agent, mix it, mature it, vulcanize it, and obtain the modified fluororubber.

5. The high-temperature resistant control cable for transformers according to claim 4, characterized in that, The amount of nano-cerium oxide used is 3%-5% of the mass of fluororubber.

6. The high-temperature resistant control cable for transformers according to claim 2, characterized in that: The sheath material also includes nano-tungsten trioxide.

7. The high-temperature resistant control cable for transformers according to claim 6, characterized in that: The weight ratio of the nano-tungsten trioxide to magnesium hydroxide is 1:(8-12).

8. A method for preparing a high-temperature resistant control cable for a transformer according to any one of claims 1-7, characterized in that, The process includes the following steps: stranding copper alloy wires to form a conductor core, extruding a polyimide insulation layer over the conductor, extruding an aerogel insulation layer over the polyimide insulation layer, and extruding a sheath over the aerogel insulation layer to obtain a high-temperature resistant control cable for transformers.

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