Cable insulation layer structure, cable and preparation method thereof

Abstract

The invention relates to the field of cables, and discloses a cable insulation layer structure, a cable and a preparation method thereof.The cable insulation layer structure sequentially comprises a high-resistance polyethylene core insulation layer, an ion purification interface layer containing an ion trapping agent and an intelligent composite protection layer from inside to outside; the ion purification interface layer is used for capturing invaded corrosive ions, the intelligent composite protection layer is made of a composite material, and a microsensor network associated with the piezoelectric functional filler is further embedded in the insulation layer structure and used for collecting damage signals. According to the invention, through multi-mechanism cooperation, erosion of moisture and harmful ions to the core insulating layer is effectively inhibited, and the reliability of long-term operation of the cable is improved; meanwhile, self-sensing and early warning of mechanical damage are realized, and the safety of a cable system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cables, in particular to a cable insulation layer structure, a cable and a preparation method thereof. BACKGROUND

[0002] Cables, especially those used for medium and high voltage power transmission, are indispensable key components in modern power systems. The reliability and service life of long-term operation largely depend on the performance stability of the insulation layer, which is the core component. Currently, cross-linked polyethylene (XLPE) and other polymer materials are widely used as insulation materials for cables due to their excellent electrical and mechanical properties.

[0003] However, in practical applications, especially in humid environments such as oceans, coasts, or underground direct burial, the polymer insulation layer inevitably faces the problem of water intrusion. When water penetrates into the polymer insulation under the continuous action of an electric field, it will trigger a tree-like degradation phenomenon known as "water treeing". The growth of water trees will gradually reduce the dielectric strength of the insulation material, forming an electric stress concentration point, and eventually may lead to insulation breakdown, causing cable failure, and seriously affecting the safety and stability of the power supply system.

[0004] In some harsh application scenarios, the invading water often contains corrosive inorganic ions such as chloride ions. The presence of these ions will significantly accelerate the initiation and growth of water trees, and produce electrochemical corrosion on the insulation material, making the insulation performance degradation process more rapid and complex. To address this problem, existing technologies usually use methods such as developing water tree-resistant resins (TR-XLPE) or increasing the thickness of the outer sheath of the insulation layer. However, although water tree-resistant resins can delay the growth of water trees to some extent, they cannot fundamentally prevent their formation during long-term service, especially in high-concentration ion environments, their protective effect will be limited. Simply increasing the thickness of the sheath and other physical barrier methods have limited effect on water barrier improvement, and cannot solve the continuous damage of harmful ions that have already invaded.

[0005] In addition, cables may be subjected to external mechanical impact, excessive bending or extrusion during laying, transportation and operation, which will produce micro-cracks in the insulation structure. These microscopic defects can also become the starting point of electric stress concentration, inducing electrical faults. Currently, the detection of such internal structural damage mainly relies on offline high-voltage testing and other regular maintenance methods, which not only need to interrupt the operation of the cable, but also often fail to effectively find small defects in the early stages, lacking real-time warning capability for damage events.

[0006] Therefore, the prior art still has deficiencies in providing a comprehensive solution capable of simultaneously effectively inhibiting insulation deterioration under combined action of water and corrosive ions and capable of real-time online monitoring of mechanical damage state of the insulation structure. SUMMARY

[0007] The technical problem to be solved by the present application is that the insulation layer of the existing cable, especially the cable applied in harsh environments such as the sea, is prone to cause insulation performance degradation due to the invasion of water and corrosive ions during long-term service, form water trees, and ultimately affect the operation reliability and service life of the cable. In addition, there is a lack of real-time and effective online monitoring means for external mechanical damage or internal micro-cracks of the cable.

[0008] To solve the above technical problems, the present application provides a cable insulation layer structure, a cable comprising the structure and a preparation method thereof.

[0009] The present application provides a cable insulation layer structure in a first aspect, which is used to coat the conductor core of the cable. The structure comprises, from inside to outside, in order:

[0010] A high-resistance polyethylene core insulation layer;

[0011] An ion purification interface layer coated outside the high-resistance polyethylene core insulation layer. The ion capture agent is dispersed in the layer. The ion capture agent has a specific pore structure or functional group, which is used to selectively capture and fix inorganic ions such as chloride ions in water by physical adsorption or ion exchange when a small amount of water invades, so as to prevent harmful ions from migrating to the core insulation layer and inhibit the occurrence of electrochemical corrosion.

[0012] An intelligent composite protective layer coated outside the ion purification interface layer. The layer is made of a specific composite material, and the components of the composite material include, by total mass percentage:

[0013] Polyethylene matrix resin: 45-55wt%;

[0014] Aluminum hydroxide filler: 40-50wt%. The filler acts as a physical barrier, and its high filling amount increases the tortuosity of the penetration path of water molecules in the polymer matrix, thereby reducing the diffusion rate of water molecules.

[0015] Nano-inorganic filler: 1.5-3.5 wt%. The nano-inorganic filler has different dielectric constant and conductivity from the polyethylene matrix resin. Under the working electric field formed by the power-on of the cable, according to Maxwell-Wagner theory, interfacial polarization occurs at the interface between the nano-filler and the matrix resin, forming a micro electric field. This micro electric field produces dielectrophoresis force on water molecules with polarity, which shows repulsion, thereby actively pushing water molecules out of the composite protective layer.

[0016] Piezoelectric functional filler: 2.0-4.0 wt%. The filler is a material with piezoelectric effect. When the intelligent composite protective layer is subjected to external mechanical stress (such as impact, extrusion, bending) or internal micro-cracks, the filler undergoes mechanical deformation, and the positive and negative charge centers in it move relative to each other, thereby generating a polarization charge on its surface, forming a measurable voltage or current signal.

[0017] Micro-sensor network embedded in the insulation layer structure. The network is laid out to establish signal acquisition association with the piezoelectric functional filler, for real-time acquisition of the voltage or current signal generated by the piezoelectric functional filler, and through a signal processing system to analyze the amplitude, frequency and source location of the signal to determine the occurrence of damage events.

[0018] In a preferred embodiment, the ion capturing agent is a 4A molecular sieve or a hydrotalcite.

[0019] In a preferred embodiment, the nano-inorganic filler is nano-titanium dioxide or nano-zinc oxide surface modified with stearic acid or silane coupling agent. The piezoelectric functional filler is piezoelectric grade polyvinylidene fluoride.

[0020] The second aspect of the present application provides a cable, comprising: a conductor core; and an insulation layer structure as described in any one of the preceding first aspects, wrapped around the conductor core.

[0021] In a preferred embodiment, the cable further comprises a metal braided armor layer wrapped around the cable insulation layer structure, for providing macroscopic mechanical protection.

[0022] The third aspect of the present application provides a method for preparing a cable, comprising the following steps:

[0023] S1, preparing a composite material:

[0024] a) melt-blending the base resin for forming the ion purification interface layer with the ion capturing agent, granulating to obtain the ion purification interface layer composite material;

[0025] b) melt blending, granulating polyethylene matrix resin, aluminum hydroxide filler, nano-inorganic filler and piezoelectric functional filler to prepare the smart composite protective layer composite material, wherein the components of the smart composite protective layer composite material are 45-55wt% of polyethylene matrix resin, 40-50wt% of aluminum hydroxide filler, 1.5-3.5wt% of nano-inorganic filler, and 2.0-4.0wt% of piezoelectric functional filler in total mass percentage;

[0026] S2, extrusion molding the cable core:

[0027] Using a multi-layer co-extrusion process, a high-resistance polyethylene core insulation layer, an ion-purified interface layer using the composite material obtained in step S1a), and a smart composite protective layer using the composite material obtained in step S1b) are sequentially extruded and formed on the conductor core wire to form a cable core;

[0028] S3, cabling:

[0029] A micro-sensor network is arranged outside the smart composite protective layer of the cable core, and then a metal armor layer and / or an outer sheath is coated outside the micro-sensor network to obtain a finished cable.

[0030] In one specific embodiment, in step S3, the process of preparing the material of the smart composite protective layer includes: melt blending polyethylene matrix resin, nano-inorganic filler and piezoelectric functional filler to prepare a functional master batch, and then melt blending the functional master batch with aluminum hydroxide filler and the remaining polyethylene matrix resin.

[0031] In one specific embodiment, in step S2, the ion-purified interface layer is formed by extruding a polymer composite material containing molecular sieves or hydrotalcite outside the core insulation layer.

[0032] In one specific embodiment, in step S3, the micro-sensor network is an optical fiber grating sensor array arranged along the axial direction of the cable.

[0033] In summary, the present application has the following at least one beneficial technical effect:

[0034] 1. The cable insulation layer structure of the present application sets an ion-purified interface layer, uses ion capture agents to selectively fix harmful inorganic ions in invading moisture, and chemically prevents the initiation of electrochemical degradation; at the same time, the high filling amount of aluminum hydroxide filler in the outer coated smart composite protective layer constructs a tortuous physical penetration path, which physically delays the diffusion of water molecules. This synergistic protection system combining chemical filtration and physical barrier can effectively maintain the dielectric performance stability of the core insulation layer in a long-term humid heat stress environment.

[0035] 2. The smart composite protective layer of the present application, by introducing nano-inorganic fillers with specific dielectric properties into the polymer matrix, generates an interfacial polarization effect at the interface between the filler and the matrix under the working electric field of the cable. This effect forms a microscopic electric field gradient that exerts a continuous repulsive force on polar water molecules, constituting an active mechanism for repelling water molecules. The introduction of this mechanism enables the insulation structure to maintain a lower saturated water absorption level, enhancing its protective ability in a humid environment.

[0036] 3. The structure of the present application integrates piezoelectric functional fillers in the smart composite protective layer and deploys a micro-sensor network associated with signal acquisition, transforming the originally passive protective layer into a sensing system that can respond to external mechanical stress. When the structure is impacted or deformed, the piezoelectric fillers convert mechanical energy into measurable signals, which are captured and transmitted by the micro-sensor network. This design enables immediate response to structural damage events, providing a technical means for monitoring the operational status of the cable.

[0037] 4. The overall design of the present application highly integrates various protective and monitoring functions in a compact multi-layer structure. In particular, different functional fillers for physical barrier, active water repulsion, and damage perception are uniformly compounded in a single smart composite protective layer through specific preparation processes. This integrated structural design ensures that the functional mechanisms work together, ensuring the realization of protection and monitoring functions, while also ensuring the process feasibility and compactness of the overall cable structure. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0039] The main raw materials and reagents used in the following examples are as follows, and the reagents not specifically described are commercially available analytical pure or higher grade products.

[0040] Low-density polyethylene (LDPE) resin: grade LD200BW, Saudi Basic Industries Corporation (SABIC), CAS No.: 9002-88-4.

[0041] Ethylene-vinyl acetate copolymer (EVA): grade Elvax265, DuPont, VA content 28%, CAS No.: 24937-78-8.

[0042] 4A molecular sieve: powder, average particle size 3-5 microns, pore size 4Å, Shanghai Hengye Molecular Sieve Co., Ltd., CAS No.: 1318-02-1.

[0043] Hydrotalcite: grade DHT-4A, Kyowa Chemical Industry Co., Ltd., CAS No.: 11097-59-9.

[0044] Aluminum hydroxide (ATH): grade H-42M, silane surface treated, Showa Denko K.K., CAS No.: 21645-51-2.

[0045] Nano titanium dioxide (TiO2): rutile type, average particle size 30 nm, surface modified with silane coupling agent KH-570, Xuancheng Jingrui New Material Co., Ltd., CAS No.: 13463-67-7.

[0046] Nano zinc oxide (ZnO): average particle size 50 nm, surface treated with stearic acid, Jiangsu Xianfeng Nanometer Material Technology Co., Ltd., CAS No.: 1314-13-2.

[0047] Polyvinylidene fluoride (PVDF): piezoelectric grade powder, grade Solef 6010, Solvay, CAS No.: 24937-79-9.

[0048] Conductor core wire: 19-strand bundle tinned copper wire, cross-sectional area 10 mm 2 .

[0049] Fiber Bragg grating (FBG) sensor: single-mode optical fiber (G.652.D), center wavelength 1550 nm ± 1.0 nm.

[0050] Armored metal wire: diameter 0.2 mm tinned copper wire.

[0051] Example 1: Preparation of a cable insulation layer structure, a cable and a preparation method thereof

[0052] This example provides a cable, and the preparation process is as follows:

[0053] Step one: preparation of ion-purified interface layer composite

[0054] 100 parts by mass of ethylene-vinyl acetate copolymer (EVA) particles and 5 parts by mass of 4A molecular sieve powder (dried in a vacuum oven at 120°C for 4 hours before use) were placed in a high-speed mixer and physically premixed at a rotation speed of 800 rpm for 10 minutes. The uniformly mixed material was fed into a 35 mm diameter twin-screw extruder, and the temperature of each zone of the extruder was set to 150°C, 165°C, 170°C, 175°C, and 170°C, and the screw rotation speed was set to 200 rpm. The extruded strip was cooled in water, dried by blowing, and then granulated to obtain ion-purification interface layer composite material A.

[0055] Step two: preparation of intelligent composite protective layer material

[0056] This step was prepared by a two-step method. First, 10% low-density polyethylene (LDPE) resin, 2.5% nano-titanium dioxide (TiO2) powder, and 2.5% polyvinylidene fluoride (PVDF) powder were weighed according to the mass percentage, and a functional masterbatch was prepared by a high-shear twin-screw extruder. The temperature of each zone of the extruder was set to 180°C, 195°C, 210°C, 210°C, and 200°C, and the screw rotation speed was 300 rpm. The blend was extruded and granulated to obtain functional masterbatch A.

[0057] Subsequently, 45% aluminum hydroxide (ATH) filler, 40% low-density polyethylene (LDPE) resin, and 15% functional masterbatch A were weighed according to the total mass percentage of the final product, and the three were fed into another twin-screw extruder for secondary melt blending. The temperature of each zone of the extruder was set to 160°C, 175°C, 185°C, and 180°C, and the screw rotation speed was 150 rpm. After the extruded strip was cooled and granulated, intelligent composite protective layer material A was obtained. The mass percentage of each component in the final composite material is: LDPE 50wt%, ATH 45wt%, nano-TiO2 2.5wt%, and PVDF 2.5wt%.

[0058] Step three: extrusion molding of cable multi-layer structure

[0059] A three-layer co-extrusion cable extrusion production line was used, and 19 strands of tinned copper wire were used as the conductor core. Low-density polyethylene (LDPE) resin was used in the first layer extruder to extrude a high-resistance polyethylene core insulation layer with a thickness of 3.0 mm outside the conductor core. The second layer extruder used ion-purification interface layer composite material A prepared in step one to extrude an ion-purification interface layer with a thickness of 0.5 mm outside the core insulation layer. The third layer extruder used intelligent composite protective layer material A prepared in step two to extrude an intelligent composite protective layer with a thickness of 2.0 mm outside the ion-purification interface layer.

[0060] Step four: sensor network layout and armor layer preparation

[0061] A fiber containing multiple fiber Bragg grating sensors is laid along the axial direction of the cable in a spiral manner outside the extruded cable semi-product. Subsequently, a planetary armoring machine is used to uniformly weave the 0.2 mm diameter tinned copper wire outside the smart composite protective layer at a weaving angle of 55 degrees, forming a metal woven armored layer with a coverage rate of not less than 92%, and finally obtaining the cable product of Example 1.

[0062] Example 2: Preparation of another cable insulation layer structure, cable and method for preparing the same

[0063] The preparation method of this example is basically the same as that of Example 1, with the difference being that:

[0064] In the preparation of the ion purification interface layer composite material, 5 parts by mass of hydrotalcite is used instead of 4A molecular sieve.

[0065] In the preparation of the smart composite protective layer material, 2.0 wt% of nano-zinc oxide (ZnO) is used instead of nano-titanium dioxide, and 3.0 wt% of polyvinylidene fluoride (PVDF) is used. To ensure that the total mass percentage is 100%, the amount of low-density polyethylene (LDPE) resin is adjusted to 48 wt%, and the amount of aluminum hydroxide (ATH) is adjusted to 47 wt%.

[0066] The subsequent cable extrusion, sensor layout and armored layer preparation steps are the same as those described in Example 1.

[0067] Comparative Example:

[0068] Comparative Example 1:

[0069] A cable with a conventional structure is prepared, which has the same conductor core as Example 1, a high-resistance polyethylene insulation layer with a thickness of 3.0 mm, and a common low-density polyethylene sheath layer with a thickness of 2.5 mm. The cable does not contain an ion purification interface layer, a smart composite protective layer, and a micro-sensor network.

[0070] Comparative Example 2:

[0071] The difference compared with Example 1 is that the ion purification interface layer is not prepared, and the smart composite protective layer material A is directly extruded outside the high-resistance polyethylene core insulation layer in the cable multi-layer structure extrusion step. The remaining preparation steps and materials used are the same.

[0072] Comparative Example 3:

[0073] The difference compared with Example 1 is that: in the process of preparing the smart composite protective layer material A, the polyvinylidene fluoride (PVDF) powder in its formula is not included, and its 2.5wt% mass is replaced by low-density polyethylene (LDPE) resin; and in the subsequent step, the fiber Bragg grating sensor network is not laid. The rest of the preparation steps and the materials used are the same.

[0074] Comparative Example 4:

[0075] The difference compared with Example 1 is that: in the process of preparing the smart composite protective layer material A, the polyvinylidene fluoride (PVDF) powder in its formula is not included, and its 2.5wt% mass is replaced by low-density polyethylene (LDPE) resin; and in the subsequent step, the fiber Bragg grating sensor network is not laid. The rest of the preparation steps and the materials used are the same.

[0076] Comparative Example 5:

[0077] The difference compared with Example 1 is that: in the final step, the fiber Bragg grating sensor network is not laid. All the rest of the preparation steps and the materials used are exactly the same.

[0078] Test Example:

[0079] Test Example 1: Long-term insulation performance stability test

[0080] The purpose of this test example is to evaluate the insulation performance retention ability of different cable samples in a humid heat electrical aging environment.

[0081] Test Steps:

[0082] Take 5 sections of 5 meters long respectively from the cable products prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2. Use epoxy resin to waterproof and seal the two ends of each cable sample, and make the samples to be tested.

[0083] For the 1 sample in each group that has not been aged, according to the GB / T3048.8-2007 standard, use power frequency alternating voltage to uniformly increase the voltage at a rate of 2kV / s until the sample breaks down, and record the initial breakdown voltage value.

[0084] Place the remaining 4 samples horizontally in a 2m³ stainless steel saltwater tank, ensuring that the middle 3 meters of the sample are completely submerged. Add a 3.5wt% NaCl solution to the tank and heat it to 70℃±2℃. Apply a 10kV alternating voltage to all samples and continue the accelerated humid heat electrical aging test for 1000 hours.

[0085] After the aging test is completed, take out the samples, rinse their surfaces with deionized water and dry them. Perform a power frequency breakdown voltage test on each aged sample, following the test method in step 2. Calculate the arithmetic mean of the breakdown voltages of each group after aging.

[0086] The breakdown voltage retention rate of each group of samples was calculated according to the average of the measured initial breakdown voltage and the breakdown voltage after aging. The calculation formula was: breakdown voltage retention rate (%) = (breakdown voltage after aging / initial breakdown voltage) x 100%.

[0087] The test results are recorded in the following table:

[0088] Table 1: Breakdown voltage and retention rate before and after accelerated electrical aging test

[0089] Sample No. Initial breakdown voltage (kV) Breakdown voltage after aging (kV) Breakdown voltage retention rate (%) Example 1 124.6 113.8 91.3 Example 2 121.9 109.1 89.5 Comparative Example 1 95.3 32.7 34.3 Comparative Example 2 123.8 75.2 60.7

[0090] Test result analysis:

[0091] From the test data in Table 1, it can be seen that after 1000 hours of humid heat electrical aging test, the breakdown voltage retention rates of the samples of Example 1 and Example 2 are significantly higher than those of Comparative Example 1 and Comparative Example 2. Specifically, the breakdown voltage retention rates of Example 1 and Example 2 are 91.3% and 89.5%, respectively, while those of Comparative Example 1 and Comparative Example 2 are only 34.3% and 60.7%, respectively.

[0092] Comparing the data of Example 1 and Comparative Example 2, the difference between their initial structures is whether there is an ion purification interface layer. The insulation performance of Comparative Example 2 significantly decreases after aging, which is because the inrush of water carrying NaCl dissociated inorganic ions directly acts on the interface of the core insulation layer, inducing an irreversible electrochemical degradation process under the action of the electric field. In the structure of Example 1, the ion purification interface layer is set to fix the inrush of harmful ions through the physical adsorption and ion exchange of the ion capture agent inside, preventing their migration to the core insulation layer, thereby effectively inhibiting the initiation and growth of water trees and maintaining the dielectric properties of the core insulation layer material.

[0093] Comparing the data of Example 1 and Comparative Example 1, the difference in performance between the two reflects the effectiveness of the overall structural design of the present application. Comparative Example 1, as a conventional cable, has limited barrier ability to water and ions due to its single polyethylene sheath layer, resulting in rapid degradation of its insulation performance in harsh environments. The structure provided by the present application forms a multi-dimensional and synergistic protection system through the chemical filtering effect of the ion purification interface layer and the tortuous physical barrier path formed by the high filling amount of aluminum hydroxide in the intelligent composite protective layer. This system delays and inhibits the erosion of external harmful species to the core insulation layer from both chemical and physical aspects, thus showing higher long-term operation reliability.

[0094] Test Example 2: Water absorption rate test

[0095] This test example aims to evaluate the anti-water absorption performance of the outer protective structure of different cable samples.

[0096] Test procedure:

[0097] From the cable products prepared in Example 1, Comparative Example 1 and Comparative Example 3, the outer protective structure (for Example 1 and Comparative Example 3, it is the intelligent composite protective layer; for Comparative Example 1, it is the ordinary polyethylene sheath layer) was stripped respectively, and was prepared into sheet-shaped samples with the size of 50 mm x 50 mm x 2 mm, 3 pieces were prepared for each group.

[0098] All samples were placed in a vacuum drying oven at 80℃ for 24 hours until constant weight. After taking out, cool to room temperature in the desiccator, weigh the initial dry weight using an analytical balance with a precision of 0.1 mg, and record it as W dry .

[0099] All samples were immersed in deionized water at 70℃±2℃ for 720 hours of continuous immersion.

[0100] After the end of immersion, the samples were taken out of the water, the surface adhering water was quickly absorbed with filter paper, and the weighing was completed within 1 minute, the wet weight was recorded, and recorded as W wet .

[0101] According to the measured dry weight and wet weight, the saturated water absorption rate of each group of samples was calculated. The calculation formula is: saturated water absorption rate (%) = [(W wet -W dry ) / W dry ] x 100%. The arithmetic mean value of 3 samples in each group was taken as the final result.

[0102] The test results are recorded in the following table:

[0103] Table 2: Saturated water absorption test results

[0104] Sample No. Saturation water absorption rate (%) Example 1 0.18 Comparative Example 1 1.52 Comparative Example 3 0.73

[0105] Test result analysis:

[0106] From the test data in Table 2, the saturated water absorption rate of the sample of Example 1 is the lowest, which is 0.18%, which is significantly lower than that of Comparative Example 1 and Comparative Example 3. The saturated water absorption rate of Comparative Example 3 is 0.73%, and the saturated water absorption rate of Comparative Example 1 is the highest, reaching 1.52%. The data shows that the intelligent composite protective layer structure provided by the present application has excellent water permeability resistance.

[0107] Comparing the data of Example 1 and Comparative Example 3, the difference between their material formulations is the presence or absence of nano-inorganic fillers. In the electric field environment of the cable under power, the Maxwell-Wagner interfacial polarization occurs between the nano-titanium dioxide fillers and the polyethylene matrix in the smart composite protective layer of Example 1 due to the difference in dielectric constant. This polarization effect generates a microscopic electric field gradient in the material, which exerts a dielectrophoretic force on water molecules with polarity, which acts as a continuous repulsive force to actively inhibit the intrusion and aggregation of water molecules. The material of Comparative Example 3 does not contain such nano-fillers, so it does not have this active water-repelling mechanism, and its water absorption rate is much higher than that of Example 1.

[0108] Comparing the data of Comparative Example 3 and Comparative Example 1, the water absorption rate of Comparative Example 3 is also significantly lower than that of Comparative Example 1. The reason is that although the protective layer of Comparative Example 3 lacks an active water-repelling component, it still contains a high filling amount of aluminum hydroxide fillers. These fillers form a complex and tortuous physical penetration path in the polymer matrix, prolonging the time and distance of water molecules diffusing into the material, and playing a passive barrier role. The ordinary polyethylene sheath layer of Comparative Example 1 lacks such a physical barrier structure, so its water permeation resistance is the weakest. This set of comparison data further confirms that the present application realizes more effective inhibition of water intrusion through the combination of physical barrier and active water-repelling mechanism.

[0109] Test Example 3: Damage signal response test

[0110] This test example aims to evaluate the ability of the cable structure to generate measurable signals when subjected to external mechanical impact.

[0111] Test steps:

[0112] Cut a length of 2 meters from each of the cable products prepared by Example 1, Comparative Example 4 and Comparative Example 5, respectively. Securely fix each sample on a horizontal test platform.

[0113] For the sample of Example 1, connect the fiber Bragg grating sensors laid inside it to a high-frequency fiber Bragg grating demodulator, which is used to monitor the change in reflection wavelength of the grating in real time.

[0114] Use a drop hammer impact testing machine to raise a 0.2 kg hammer to a height of 1 meter and let it fall freely, applying an impact of 1.96 J of energy at a distance of 10 cm from the midpoint of the sample.

[0115] Record the maximum shift in reflection wavelength collected by the fiber Bragg grating demodulator at the instant of impact.

[0116] Repeat the impact test of Step 3 for the samples of Comparative Example 4 and Comparative Example 5. Since neither Comparative Example 4 nor 5 has laid a network of fiber Bragg grating sensors, record their signal response as "no signal output".

[0117] The impact test was repeated 3 times for each sample, the wavelength shift of each time was recorded, and the average value was calculated.

[0118] The test results are recorded as shown in the following table:

[0119] Table 3 Mechanical impact response test results

[0120] Sample No. Impact energy (J) First wavelength shift (pm) Second wavelength shift (pm) Third wavelength shift (pm) Average maximum wavelength shift (pm) Example 1 1.96 35.7 34.2 36.1 35.3 Comparative Example 4 1.96 - - - No signal output Comparative Example 5 1.96 - - - No signal output

[0121] Test result analysis:

[0122] From the test data in Table 3, it can be seen that after being subjected to standardized mechanical impact, only the sample of Example 1 produced a signal output that could be stably detected by the instrument, with an average maximum wavelength shift of 35.3 pm. In contrast, the samples of Comparative Examples 4 and 5 had no signal output under the same impact conditions. This result shows that the specific structure provided by the present application can effectively convert external mechanical energy into a measurable signal.

[0123] The mechanism of this phenomenon is that in the intelligent composite protective layer of Example 1, the dispersed piezoelectric functional filler undergoes mechanical deformation under the stress generated by the drop hammer impact. According to the piezoelectric effect, this deformation causes the relative displacement of positive and negative charge centers inside the filler, thereby generating a local electric field and stress field around the filler. The transient change of this local field acts on the immediately adjacent fiber Bragg grating sensor, causing a slight change in the grating period, which ultimately manifests as a measurable wavelength shift on the fiber Bragg grating demodulator.

[0124] Through comparison with the comparative examples, it can be further confirmed that the implementation conditions of this function. Comparative Example 4 does not contain piezoelectric functional fillers in its protective layer, so it cannot generate an initial piezoelectric signal under impact, resulting in no signal output. More critically, Comparative Example 5 contains fillers that can generate a piezoelectric effect, but due to the absence of a microsensor network for signal collection and transmission in its structure, the local and transient physical field changes cannot be captured and converted into signals that can be analyzed by external equipment. Therefore, the test results confirm that the combination of piezoelectric functional fillers and microsensor networks is a necessary structure for converting mechanical damage events into measurable warning signals.

[0125] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application.

Claims

1. A cable insulation layer structure, characterized in that, The structure, from the inside out, includes the following: High-resistivity polyethylene core insulation layer; An ion purification interface layer is wrapped around the high-resistivity polyethylene core insulation layer, and an ion scavenging agent for selectively capturing inorganic ions is dispersed in the ion purification interface layer. A smart composite protective layer covering the ion purification interface layer, the smart composite protective layer being made of a composite material, the components of which, by total mass percentage, include: Polyethylene matrix resin: 45-55 wt%; Aluminum hydroxide filler for physical barrier: 40-50 wt% Nano-inorganic fillers that can generate interfacial polarization effects under the action of an electric field to repel water molecules: 1.5-3.5 wt%; Piezoelectric functional fillers that can generate measurable piezoelectric signals when subjected to mechanical stress: 2.0-4.0 wt% And a microsensor network embedded in the insulating layer structure, the microsensor network establishing a signal acquisition association with the piezoelectric functional filler, for real-time acquisition and analysis of the piezoelectric signal.

2. The cable insulation layer structure according to claim 1, characterized in that, The ion scavenger is a type 4A molecular sieve or hydrotalcite.

3. The cable insulation layer structure according to claim 1, characterized in that, The nano-inorganic filler is surface-modified nano-titanium dioxide or nano-zinc oxide, and the piezoelectric functional filler is piezoelectric grade polyvinylidene fluoride.

4. A cable, characterized in that, include: Conductor core wire; as well as The cable insulation layer structure that covers the conductor core.

5. The cable according to claim 4, characterized in that, It also includes a metal braided armor layer covering the cable insulation structure.

6. A method for manufacturing the cable as described in claim 4, characterized in that, Includes the following steps: S1. Preparation of composite materials: a) The matrix resin used to form the ion purification interface layer is melt-blended with the ion capture agent, granulated, and the ion purification interface layer composite material is prepared. b) A smart composite protective layer composite material is prepared by melt blending polyethylene matrix resin, aluminum hydroxide filler, nano-inorganic filler, and piezoelectric functional filler, followed by granulation. The components of the smart composite protective layer composite material, by total mass percentage, are: polyethylene matrix resin 45-55 wt%, aluminum hydroxide filler 40-50 wt%, nano-inorganic filler 1.5-3.5 wt%, and piezoelectric functional filler 2.0-4.0 wt%. S2, Extruded cable core: A multi-layer co-extrusion process is used to sequentially extrude a high-resistance polyethylene core insulation layer, an ion-purified interface layer using the composite material obtained in step S1a), and an intelligent composite protective layer using the composite material obtained in step S1b) to form a cable core. S3, Cable Assembly: A micro-sensor network is deployed outside the intelligent composite protective layer of the cable core, and then a metal armor layer and / or an outer sheath are wrapped around the micro-sensor network to obtain the finished cable.

7. The preparation method according to claim 6, characterized in that, In step S3, the process of preparing the material for the intelligent composite protective layer includes: firstly, melting and blending polyethylene matrix resin, nano-inorganic filler and piezoelectric functional filler to form a functional masterbatch, and then melting and blending the functional masterbatch with aluminum hydroxide filler and the remaining polyethylene matrix resin a second time.

8. The preparation method according to claim 6, characterized in that, In step S2, the ion purification interface layer is formed by extruding a polymer composite containing molecular sieves or hydrotalcite onto the outside of the core insulating layer.

9. The preparation method according to claim 6, characterized in that, In step S3, the micro-sensor network is a fiber optic grating sensor array arranged along the cable axis.