Crosslinked polyethylene insulated corrosion resistant power cable

Abstract

The application belongs to the technical field of electric wire and cable, and discloses a cross-linked polyethylene insulation corrosion-resistant power cable, aiming at solving the defects that the existing cable outer sheath is easy to cause internal metal corrosion after being damaged and lacks active repair. The cable comprises a conductor core, an insulation layer, an inner and outer semi-conductive shielding layer, a metal shielding layer, a metal armor layer and a self-repairing outer sheath. The self-repairing outer sheath is radially provided with a first repair sublayer and a second repair sublayer, and contains a base polymer, first repair microcapsules, second repair microcapsules and an nm container of corrosion inhibitor. A catalyst primer coating is arranged between the metal armor layer and the self-repairing outer sheath. The application can realize instant response to damage, structure self-healing and active corrosion inhibition, and significantly improve the long-term service reliability of the cable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric wires and cables, and particularly relates to a cross-linked polyethylene insulated corrosion-resistant power cable. BACKGROUND

[0002] As an indispensable key component in modern power systems, power cables bear the core function of power transmission and distribution, and the stability and reliability of their performance are directly related to the normal operation of the entire national economy and the energy security of social life. In the overall structure of power cables, there are usually a conductor core, an insulation layer, a metal shielding layer or an armored layer, and an outermost protective jacket.

[0003] Among them, cross-linked polyethylene is widely used as the core insulation material for high-voltage and medium-voltage power cables due to its excellent electrical insulation performance, heat resistance and chemical stability. In order to protect the internal precise insulation structure and the metal shielding or armored layer from the erosion and mechanical damage of the external environment, the cable is usually covered with a solid outer jacket, which constitutes the first and most important physical barrier against the external environment.

[0004] Specifically, the outer jacket material of the power cable in the prior art generally uses high-density polyethylene, polyvinyl chloride (PVC) and other high molecular polymers. The original intention of these materials is to provide excellent mechanical strength, wear resistance and isolation ability against common corrosive media such as water and chemicals. Under ideal working conditions, an intact outer jacket can effectively isolate the internal structure of the cable from the external harsh environment, thereby ensuring the safe and stable operation of the cable within the designed service life.

[0005] This protection strategy based on the core concept of "passive isolation" has indeed successfully solved the main problems faced at a certain stage of the development of cable technology, greatly improving the reliability and service life of power cables, and has become a standard technical solution widely adopted and applied in the industry. The logical basis of this solution is to maximize the physical and chemical inertness and mechanical toughness of the outer jacket material itself to resist foreseeable external stress and maintain its integrity as a static physical barrier.

[0006] However, with the continuous development of related technologies and the increasingly stringent requirements for performance indicators in application scenarios, especially in extreme environments such as marine engineering, chemical parks, coastal high-salt areas, and direct burial under complex geological conditions, some inherent characteristics of the above-mentioned technical solution based on the core concept of "passive isolation" at the principle level have gradually revealed its fundamental limitations in dealing with new challenges.

[0007] The reason is that the effectiveness of the protection system is completely based on the premise that the outer sheath must maintain absolute, flawless physical integrity throughout the service life. But in the actual construction, transportation and long-term service process, the cable will inevitably be subjected to dragging, friction, bending, impact or extrusion of sharp objects, and long-term stress caused by soil settlement, thermal expansion and contraction. These factors make it almost inevitable that small, even invisible scratches, cracks or pinhole defects will occur on the surface of the outer sheath. Once such microscopic defects are formed, they become a fatal breach of the entire "passive isolation" protection system.

[0008] Corrosive media such as moisture, dissolved oxygen, chloride ions, etc. will quickly penetrate and diffuse along the defect to the interface between the outer sheath and the inner metal armor layer or shielding layer by capillary action. In this interface area, a local corrosion environment that is relatively isolated from the outside but continuously moistened is formed, i.e. the so-called occluded corrosion cell, causing the corrosion process of the metal layer to proceed at a rate far exceeding expectations. More dangerously, this internal corrosion, which begins with a microscopic defect, is completely undetectable from the outside at the initial stage, with a high degree of concealment.

[0009] When corrosion expands to a certain extent, causing the armor layer to lose mechanical strength or the shielding layer to deteriorate in electrical performance, ultimately leading to cable failure, the internal damage is often very serious and completely irreversible. This chain of catastrophic and irreparable deterioration triggered by a trivial initial damage exposes the deep-seated contradictions in the traditional protection concept: a static barrier designed for "sturdiness" itself shows extreme vulnerability to "minor damage" and lacks any form of fault tolerance or dynamic response mechanism after damage.

[0010] Therefore, the core problem of the prior art is not just the mechanical strength of the outer sheath material, but the fundamental shortcoming of the "passive protection" design philosophy. This design philosophy views damage as an end event that needs to be absolutely avoided, rather than a certain process that needs to be dynamically managed and responded to throughout the life cycle. All technical inputs are focused on raising the threshold for damage occurrence, completely ignoring the consequences of damage once it occurs.

[0011] Therefore, how to break through this traditional, static protection mindset and give the cable outer sheath the ability to actively respond and self-repair after suffering microscopic damage, thereby immediately blocking the invasion path of corrosive media at the initial stage of damage and fundamentally eliminating the chain degradation reaction caused by minor physical damage, has become a key challenge and technical problem to be solved for those skilled in the art. SUMMARY

[0012] The technical problem to be solved by the present application is to overcome the fundamental defect that the outer sheath of the power cable lacks active repair ability after suffering from micro-damage, resulting in hidden and disastrous corrosion of the internal metal components. The protection concept of the prior art completely relies on passive physical isolation of the outer sheath. Once the physical barrier is slightly damaged, it provides an irreversible channel for the invasion of corrosive media, thereby triggering a chain of deterioration reactions, seriously threatening the long-term service safety and reliability of the cable.

[0013] To achieve the above-mentioned application purposes, the present application provides a cross-linked polyethylene insulated corrosion-resistant power cable, the core of which is to construct a self-repairing outer sheath system with multi-stage response, multiple repair mechanisms and synergistic protection functions. The system upgrades the traditional passive protection mode to a dynamic intelligent protection system that can actively respond at the initial stage of damage, physically block and chemically repair in stages, and actively inhibit corrosion at key interfaces, thereby fundamentally eliminating the evolution path from a small physical defect to a disastrous cable failure.

[0014] To achieve the above-mentioned technical solutions, the present application provides a cross-linked polyethylene insulated corrosion-resistant power cable, which comprises, in order from the inside out along the radial direction, a conductor core, an insulation layer, an inner semiconductive shielding layer, an outer semiconductive shielding layer, a metal shielding layer, a metal armor layer, and a self-repairing outer sheath.

[0015] The conductor core is composed of multiple strands of tightly pressed circular annealed copper wire or aluminum wire.

[0016] The insulation layer is a cross-linked polyethylene material prepared by peroxide cross-linking or silane cross-linking process, and has a volume resistivity of not less than 1x10 14 Ω·m and a power frequency breakdown field strength of not less than 20 kV / mm.

[0017] The inner semiconductive shielding layer and the outer semiconductive shielding layer are both cross-linked semiconductive polymer materials, which form a close contact with the conductor core and the insulation layer to homogenize the electric field distribution.

[0018] The metal shielding layer adopts a copper tape wrapping or copper wire weaving structure, and its main function is to shield the electric field and provide a fault current path.

[0019] The metal armor layer is provided outside the metal shielding layer and adopts a double-layer galvanized steel belt gap wrapping structure to provide mechanical protection for the cable.

[0020] The self-repairing outer sheath is the core technology of the present application, which is coated on the outermost part of the metal armor layer. The self-repairing outer sheath is not a single homogeneous material layer, but a composite structure with a functional gradient distribution designed precisely. Specifically, the self-repairing outer sheath comprises a base polymer and first repair microcapsules, second repair microcapsules and corrosion inhibitor nano-containers dispersed in the base polymer.

[0021] The base polymer is a blend of high-density polyethylene and maleic anhydride grafted high-density polyethylene. Among them, the density of high-density polyethylene is 0.955-0.965 g / cm 3 , and the melt index is 0.4-0.6 g / 10 min; the grafting rate of maleic anhydride in maleic anhydride grafted high-density polyethylene is 0.8%-1.2%, and the mass percentage in the blend is 5%-10%, which is used to improve the interfacial compatibility and bonding strength between the base polymer and the microcapsules and nano-containers. Rice

[0022] Further, to realize the multi-level response repair function, the self-repairing outer sheath is provided with a layered structure with different functional emphases along its radial thickness direction, and is sequentially provided with a first repair sublayer and a second repair sublayer from the outside to the inside.

[0023] The first repair sublayer, i.e. the outer layer part of the self-repairing outer sheath, has a thickness of 30%-40% of the total thickness of the outer sheath. The main function of this layer is to respond quickly and seal immediately to surface micro scratches or initial cracks. To this end, the first repair sublayer mainly disperses the first repair microcapsules in the base polymer thereof.

[0024] The first repair microcapsule has a small particle size and a low breaking threshold. Its average particle size is controlled at 10-30 μm, and the capsule wall thickness is 150-300 nm. The capsule wall material of the first repair microcapsule is a polyurethane-urea copolymer prepared by interfacial polymerization, which has a certain brittleness to ensure that it can break under a small strain. Its capsule core material is a low-viscosity, moisture-cured one-component polyurethane prepolymer repair agent.

[0025] The polyurethane prepolymer is prepared by reacting toluene diisocyanate with polyether polyol under strict anhydrous conditions, and the content of terminal isocyanate group (-NCO) is controlled at 2.8%-4.0%. The viscosity of the repair agent is less than 200 mPa·s at 25°C, so as to ensure that it can rapidly penetrate and fill the micro cracks by capillary force after being released from the broken microcapsule. The mass percentage of the first repair microcapsule in the first repair sublayer is 10%-20%.

[0026] ​The second repair sublayer, which is the inner layer of the self-healing outer sheath, accounts for 60%-70% of the total thickness of the outer sheath and is in direct contact with the internal catalyst primer coating. The main function of this layer is to provide high-strength structural repair and active chemical corrosion inhibition after the rapid sealing effect of the first repair sublayer, or in the event of more severe and deeper crack damage. To this end, the second repair sublayer primarily disperses the second repair microcapsules and the corrosion inhibitor nm container within its matrix polymer.

[0027] The second repair microcapsule has a larger particle size and a higher rupture threshold to respond to more severe mechanical damage. Its average particle size is controlled at 100-180 μm, and it has a bilayered capsule wall structure. The inner capsule wall is made of polyvinylbenzene with a thickness of 500-800 nm, providing the main mechanical strength and chemical stability; the outer capsule wall is made of polymethyl methacrylate-acrylic acid copolymer with a thickness of 100-200 nm, and its surface contains carboxyl functional groups to enhance the chemical bonding with maleic anhydride-grafted high-density polyethylene in the matrix polymer.

[0028] The core material of the second repair microcapsule is component A of a two-component epoxy resin system, namely a liquid epoxy resin prepolymer. Specifically, it is a mixture of bisphenol A diglycidyl ether and 1,4-butanediol diglycidyl ether reactive diluent at a ratio of 85:15 (mass ratio), with a viscosity of 600-900 mPa·s at 25°C. The second repair microcapsule constitutes 20%-30% of the second repair sublayer by mass.

[0029] The corrosion inhibitor nanocontainer is a layered double hydroxide (LDH) nanocontainer. Rice The film is specifically a zinc-aluminum layered double hydroxide. Its layer diameter is 150-300 nm, and its thickness is 10-25 nm. The interlayer anion in the double hydroxide is a corrosion inhibitor anion, specifically benzotriazole (BTA). - ).

[0030] The corrosion inhibitors were loaded onto the interlayer of the double hydroxides via ion exchange at a loading rate of 25%-35% (mass percentage). These corrosion inhibitor nanocapsules were uniformly dispersed in the matrix polymer of the second repair sublayer at a mass percentage of 2%-5%.

[0031] One key technical feature of the present application is that a catalyst primer coating is provided between the outer surface of the metal armor layer and the inner surface of the self-repairing outer sheath. This coating is the key to achieving efficient curing of the epoxy resin in the second repair microcapsule. The catalyst primer coating is 15-25 μm thick and consists of two parts: one part is a polyurethane-based film-forming resin as an adhesive and carrier; the other part is a latent curing agent for the B component of a two-component epoxy resin system, which is uniformly dispersed in the form of micron-sized solid powder in the film-forming resin.

[0032] The latent curing agent is a modified fatty amine adduct with a melting point of 55-65°C and an average particle size of less than 8 μm. The curing agent is solid at room temperature and does not react with the polyurethane carrier and is not soluble therein, but when it comes into contact with the liquid epoxy resin prepolymer released from the second repair microcapsule, it can quickly dissolve therein and initiate an irreversible cross-linking and curing reaction.

[0033] The working mechanism and synergistic process of the self-repairing outer sheath system constructed by the present application are as follows:

[0034] In the first stage, rapid plugging response. When the cable outer sheath is scratched or slightly impacted by external objects during transportation, laying or service, and microcracks are generated in the first repair sublayer on the surface thereof, stress concentration on the crack propagation path will first cause the first repair microcapsule with smaller particle size and more brittle capsule wall to rupture. The low-viscosity, moisture-cured polyurethane prepolymer repair agent in the capsule core is released and quickly fills into the crack.

[0035] After the repair agent comes into contact with moisture in the trace amount of water vapor or air that has penetrated along the crack from the outside, the -NCO groups at the ends of the repair agent chemically react with water molecules to generate unstable carbamic acid, which further decomposes to release carbon dioxide gas and form amine groups.

[0036] The amine groups will continue to react with the remaining -NCO groups to form urea bonds, thereby achieving cross-linking and curing of the entire system. This process is completed within a few minutes at room temperature, forming a dense polyurethane-urea polymer barrier that physically plugs the crack channel and prevents further intrusion of corrosive media.

[0037] In the second stage, structural repair and interface curing. When the cable is subjected to more severe extrusion, bending or impact, causing the crack to propagate and penetrate the first repair sublayer and reach the second repair sublayer, the greater stress and strain on the crack path will cause the second repair microcapsule with higher mechanical strength to rupture. The high-viscosity epoxy resin prepolymer in the capsule core is released and fills into the wider and deeper crack cavity.

[0038] Due to gravity and fluidity, the liquid epoxy resin will flow to the deepest part of the crack, i.e. the interface with the metal armor layer. At this point, the liquid epoxy resin comes into contact with the catalyst primer coating pre-coated on the surface of the metal armor layer. The dispersed solid modified fatty amine adduct curing agent particles in the coating dissolve rapidly in the epoxy resin and undergo ring-opening addition polymerization with the epoxy groups. This reaction, which does not require external heating, can be completed in a few hours at room temperature, forming a cross-linked network structure with extremely high mechanical strength and excellent adhesion properties.

[0039] The cured product not only completely fills the crack cavity, restoring the structural integrity and mechanical strength of the outer sheath, but more importantly, it forms a solid, dense chemical bonding layer between the self-repairing outer sheath and the metal armor layer, completely eliminating any interfacial debonding and potential corrosion channels.

[0040] Third stage, active chemical corrosion inhibition. At the same time as the above-mentioned physical plugging and structural repair process occurs, or within a short time window when the repair is not yet complete, the corrosive medium (especially moisture containing chloride ions) that has invaded along the crack path will react with the corrosion inhibitor nm container in the second repair sublayer.

[0041] On the one hand, the invading chloride ions will displace the benzotriazole anion root corrosion inhibitor between the double hydroxide layers through ion exchange; on the other hand, at the initial stage of metal corrosion, the metal surface at the crack tip will exhibit a local slightly acidic environment due to anodic reaction, which will promote the local dissolution of the zinc-aluminum layered double hydroxide structure, further accelerating the release of BTA corrosion inhibitor molecules.

[0042] The released BTA molecules will quickly migrate to the surface of the metal armor layer at the crack tip, forming a stable coordination complex protective film with the metal atoms through the nitrogen atoms on the triazole ring, effectively inhibiting the anodic dissolution and cathodic reduction processes of the metal, thereby actively and targetedly inhibiting the occurrence of corrosion reactions at the chemical level.

[0043] The manufacturing method of the present application specifically includes the following steps:

[0044] Step one, preparation of first and second repair microcapsules. First and second repair microcapsules with core materials of moisture-cured polyurethane prepolymers and epoxy resin prepolymers, respectively, are prepared by using the interface polymerization method and the double-layer wall construction method known in the art, respectively, and are dried and sieved.

[0045] Step two, preparation of corrosion inhibitor nanometer container. Zinc-aluminum layered double hydroxide precursor is synthesized by co-precipitation method, and then benzotriazole is loaded into the interlayer by ion exchange method to obtain BTA-LDH nm powder.

[0046] Step three, preparation of the first repair sub-layer and the second repair sub-layer blend. After high-density polyethylene and maleic anhydride grafted high-density polyethylene are uniformly melt blended in a torque rheometer at 170°C, a predetermined amount of the first repair microcapsule and the mixture of the second repair microcapsule and BTA-LDH are added, respectively, and continue to blend at a lower shear rate for 5-10 min to ensure uniform dispersion and not to damage the capsule structure, and then cool and granulate to obtain two different outer sheath special materials.

[0047] Step four, preparation of the catalyst primer coating. Polyurethane film-forming resin is dissolved in a mixed solvent of ethyl acetate and butanone, then a micronized modified aliphatic amine adduct curing agent is added and stirred uniformly in a high-speed disperser to obtain a coating.

[0048] Step five, cable core processing and coating construction. After the cable core wrapped with the metal armor layer is cleaned and subjected to corona treatment, the catalyst primer coating prepared in the previous step is uniformly coated on the outer surface of the galvanized steel tape armor layer by immersion coating or spraying, and then dried and cured through an infrared heating channel to form a firm primer layer.

[0049] Step six, co-extrusion molding of the self-repairing outer sheath. The cable core coated with the catalyst primer coating is sent to a double-layer co-extrusion head. Two extruders are used to supply the first repair sub-layer and the second repair sub-layer special materials to the inner and outer channels of the co-extrusion head, respectively. Through precise design of the mold, the self-repairing outer sheath with an inner and outer double-layer structure is extruded and molded at high temperature and high pressure in one step, and the inner wall of the second repair sub-layer is ensured to be tightly fused with the catalyst primer coating on the cable core.

[0050] Step seven, cooling and finished product inspection. After the extruded cable is cooled and shaped in a circulating water tank, spark test, size measurement and performance detection are carried out, and finally the identification is sprayed and the cable is wound.

[0051] The present application successfully constructs a self-repairing system by designing a gradient functional outer sheath containing a first repair sub-layer and a second repair sub-layer, and combining a catalyst primer coating preset at the key interface. Compared with the prior art, the present application has the following beneficial effects:

[0052] Instantaneous response and rapid plugging of damage are achieved: by millisecond-level perception and min-level repair of micro-cracks, the initial path of corrosion medium intrusion is effectively blocked.

[0053] High-strength structural self-healing is achieved: by deep repair of severe damage, the mechanical integrity and protection function of the outer sheath are restored, and the repair efficiency is more than 90%.

[0054] The targeted repair and reinforced bonding at the critical interface are realized: through the design of the catalyst primer coating, it is ensured that the repair reaction occurs precisely at the sheath-armor interface where corrosion is most likely to occur, and a chemical bond far exceeding the physical bonding strength is formed, thus eliminating the hidden danger of interface corrosion.

[0055] The synergy of physical barrier and chemical protection is realized: the macro crack filling and micro corrosion inhibition are combined to build a double-insurance protection system, which significantly improves the long-term reliability and service life of the cable in harsh corrosive environments.

[0056] Therefore, the present application completely changes the passive protection mode of traditional power cables, and endows the cable outer sheath with unprecedented intelligent response and self-maintenance capability, which is a fundamental breakthrough in the field of power cable protection technology. DETAILED DESCRIPTION

[0057] In order to make the objects, 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 skilled in the art without creative labor fall within the scope of protection of the present application.

[0058] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the usual placement state, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation to the present application.

[0059] In order to more clearly set forth the technical core of the present application, hereinafter, with a specific implementation form of a cross-linked polyethylene insulated corrosion-resistant power cable as a carrier, the structural composition, preparation process of each part, synergistic working mechanism and the final technical effects achieved will be systematically and engineeringly described in detail.

[0060] In one specific embodiment, the cross-linked polyethylene insulated corrosion-resistant power cable provided by the present application has a nominal voltage grade of 8.7 / 15kV, and a conductor cross-sectional area of 240mm 2 The overall structure is radially from inside to outside, in turn, the conductor core, the insulation layer, the inner semiconductive shielding layer, the outer semiconductive shielding layer, the metal shielding layer, the metal armor layer and the self-repairing outer sheath as the core technology carrier of the present application.

[0061] The conductor core is the main body to carry current, which is selected to be the tight-pressed circular annealed copper conductor in accordance with the second provision in the national standard GB / T 3956-2008. Specifically, the conductor is tightly twisted in a concentric layer manner by a plurality of circular annealed copper single wires with a diameter of 2.21 mm, and the nominal cross-sectional area after twisting reaches 240 mm 2 , the twisting pitch ratio is controlled to be between 15 and 18, and the structure is compact by the tight-pressing process, and the tight-pressing coefficient is not less than 0.92, so as to effectively reduce the outer diameter and the alternating current resistance of the conductor.

[0062] The insulating layer is tightly wrapped on the outer side of the conductor core. The material selected for the insulating layer is high-purity and super-clean cross-linked polyethylene. The cross-linked polyethylene material is prepared by using the peroxide cross-linking process in the chemical cross-linking method, and is specifically completed on a catenary continuous vulcanization production line. The density of the base polyethylene resin is 0.922 g / cm 3 , and the melt index is 2.0 g / 10 min. Before extrusion, the polyethylene base material is mixed with a cross-linking agent master batch containing dicumyl peroxide under strictly controlled conditions. The extrusion thickness of the insulating layer is accurately controlled to be 4.5 mm.

[0063] After extrusion molding, the cable core immediately enters the high-temperature and high-pressure cross-linking pipeline, and under the protection of nitrogen atmosphere, the continuous cross-linking reaction is carried out at a temperature interval of 180°C to 200°C and a pressure of 1.5 to 2.0 MPa. After the completion of the cross-linking and curing, the cross-linking degree of the insulating layer is not less than 85%, the elongation is less than 100% in the hot extension test at 90°C, and the permanent deformation rate is less than 5%. The finally formed insulating layer has excellent electrical properties, the volume resistivity at room temperature is higher than 5×10 15 Ω·m, and the measured value of the power frequency breakdown field strength at 20°C is stable at more than 25 kV / mm, which ensures the electrical reliability of the long-term operation of the cable.

[0064] The inner semi-conductive shielding layer and the outer semi-conductive shielding layer jointly constitute the core electrical structure of the high-voltage cable. Both layers are made of cross-linked semi-conductive polymer materials, which have good compatibility and interface bonding force with the insulating layer material. Specifically, the inner semi-conductive shielding layer is directly extruded on the outer side of the conductor core, which functions to eliminate the electric field distortion caused by the uneven twisting of the conductor surface, and forms a smooth equipotential surface.

[0065] The outer semi-conductive shielding layer is tightly extruded on the outer side of the insulating layer, which functions to form a smooth transition between the insulating layer and the grounded metal shielding layer, and avoid the electric field concentration on the insulating surface.

[0066] In this embodiment, the inner and outer semiconductive shielding layers and the insulating layer are formed by one-time extrusion molding through a three-layer co-extrusion process, ensuring perfect interface bonding between the three layers without air gap or impurities. The volume resistivity of the semiconductive material is controlled to be below 500 Ω·m at 90°C. The thickness of the inner semiconductive shielding layer is 0.8 mm, and the thickness of the outer semiconductive shielding layer is 0.7 mm.

[0067] In addition to the three-layer co-extruded core, there is a metal shielding layer wrapped around. This layer uses a soft annealed copper strip with a thickness of 0.12 mm and a width of 25 mm, wrapped in an interstitial manner. The overlap rate of the wrapping is controlled between 15% and 20%, ensuring electrical continuity. The main function of the metal shielding layer is to shield the electric field outside the insulating layer during normal operation, preventing electromagnetic interference to the outside, and providing a low-impedance path for fault current when the system experiences grounding or short-circuit faults, with an effective cross-sectional area meeting the requirements of the system short-circuit capacity.

[0068] To give the cable enough ability to resist external mechanical damage, a metal armor layer is provided outside the metal shielding layer. The metal armor layer in this embodiment uses a double-layer interstitial wrapping structure of galvanized steel strips. The thickness of the galvanized steel strip used is 0.5 mm, and the width is 40 mm.

[0069] The two layers of steel strips are wrapped in opposite directions, and the wrapping trajectory of the second layer of steel strips exactly covers the interstitial gap of the first layer of steel strips, forming a complete mechanical protection cylinder. This structure can effectively resist radial extrusion force and a certain degree of impact force, protecting the internal cable structure from damage during installation and operation.

[0070] The outermost part of the entire cable structure is the self-repairing outer sheath, which is the core innovation of the technical solution of the present application. The self-repairing outer sheath is not a single homogeneous polymer layer in the traditional sense, but a complex structure layer with gradient functional distribution designed with precision and functionality. Its total thickness is 3.2 mm, and it is composed of a base polymer as a continuous phase, and a first repair microcapsule, a second repair microcapsule, and a corrosion inhibitor nano container as dispersed phases carrying different repair functions.

[0071] The base polymer is the structural basis of the entire self-repairing outer sheath, which is prepared by melt blending of high-density polyethylene and maleic anhydride grafted high-density polyethylene. The selected high-density polyethylene has a melt index of 0.45 g / 10 min at 190°C under a load of 2.16 kg, with excellent environmental stress cracking resistance and mechanical strength. The selected maleic anhydride grafted high-density polyethylene has a base high-density polyethylene with similar properties to the above-mentioned grade, and the grafting rate of maleic anhydride is precisely controlled at 1.0%.

[0072] The mass percentage of the maleic anhydride grafted high-density polyethylene in the blend is 8%. The maleic anhydride grafted high-density polyethylene is introduced to act as an interfacial compatibilizer. Its polyethylene segment has natural compatibility with the matrix high-density polyethylene, while its polar maleic anhydride group can chemically react with or form hydrogen bonds with the functional groups on the surface of the subsequently added microcapsule wall or nanocapsule, thereby significantly enhancing the interfacial bonding force between the matrix and the functional filler, preventing interfacial debonding during extrusion processing or cable bending, and ensuring uniform and stable dispersion of the functional components.

[0073] Further, to achieve multi-level response and phased repair for different degrees of damage, the self-repairing outer sheath is constructed into a layered structure with clear functional division along its radial thickness direction, and is sequentially provided with a first repair sublayer and a second repair sublayer from the outside to the inside.

[0074] The first repair sublayer is the part of the self-repairing outer sheath directly exposed to the external environment, and its thickness is designed to be 1.0 mm, accounting for about 31% of the total thickness of the outer sheath. The core mission of this layer is to respond quickly and seal immediately to slight damage such as micro-scratches and initial cracks on the surface, and to kill potential corrosion channels in the cradle. To achieve this purpose, the first repair microcapsules are dispersed in the matrix polymer of this layer at a mass percentage of 15%. The first repair microcapsules have a smaller particle size and a lower mechanical rupture threshold. The preparation process is as follows: first, the capsule wall is prepared by interfacial polymerization.

[0075] The aqueous solution containing polyether polyol is used as the dispersed phase, and the cyclohexane organic phase containing toluene diisocyanate is subjected to high-speed shearing emulsification to form an O / W emulsion. At the emulsion interface, toluene diisocyanate reacts with water to form an amine, which then polymerizes with toluene diisocyanate, and toluene diisocyanate also reacts with polyether polyol to form a polyurethane-urea copolymer capsule wall. By accurately adjusting the amount of emulsifier, stirring rate and reaction temperature, the average particle size of the microcapsules is controlled to be 25±5 μm, and the capsule wall thickness is controlled to be 200±50 nm. The capsule wall material has moderate brittleness, which ensures that it can break under a small stress strain (about 1%). The capsule core material is a low-viscosity, moisture-cured one-component polyurethane prepolymer repair agent.

[0076] The repair agent was prepared by reacting toluene diisocyanate with polyether polyol in strictly anhydrous toluene solvent at 60 °C for 4 hours. The content of active isocyanate group (-NCO) at the end of the product was precisely controlled at 3.5% by controlling the molar ratio of toluene diisocyanate to polyol at 2:1. The viscosity of the repair agent at 25 °C was measured as 180 mPa-s, which low viscosity property ensured its rapid penetration and complete filling of the micro-cracks with width of only tens of μm by means of capillary force after its release from the ruptured microcapsules.

[0077] The second repair sub-layer is the inner part of the self-repairing outer sheath, with a thickness of 2.2 mm, accounting for about 69% of the total thickness of the outer sheath. This layer is in close contact with the catalyst primer coating inside the cable. Its function is to provide high-strength structural repair for more serious and deeper crack damage after the rapid plugging by the first repair sub-layer, and at the same time release corrosion inhibitor at the metal interface of the damaged area to provide active chemical corrosion inhibition. To this end, the second repair sub-layer has dispersed in its base polymer two functional components: second repair microcapsules and corrosion inhibitor nanocapsules.

[0078] The second repair microcapsules, with the design target of responding to more serious mechanical damage, therefore have larger particle size and higher mechanical strength. The mass percentage of the second repair microcapsules in the second repair sub-layer is 25%. The preparation of the microcapsules adopts a more complex double-wall construction technology. First, a hard poly(styrene-divinylbenzene) inner capsule wall is formed by suspension polymerization with divinylbenzene as crosslinking monomer and styrene as co-monomer under the action of oil-soluble initiator. Then, with this as core, a second-step seed emulsion polymerization is carried out. Methyl methacrylate and acrylic acid are used as co-monomers to polymerize in aqueous phase, so that a poly(methyl methacrylate-acrylic acid) copolymer outer capsule wall is coated on the surface of the core particle.

[0079] By this method, the prepared microcapsules have an average particle size of 150 ± 20 μm. The thickness of the inner capsule wall is about 650 nm, which provides the main mechanical strength and chemical stability, so that the rupture strain threshold is increased to about 5%; the thickness of the outer capsule wall is about 150 nm, and the carboxyl functional groups rich on it can esterify with the maleic anhydride groups in the base polymer or form strong hydrogen bonds, thereby greatly strengthening the interface anchoring of the microcapsules with the base. The core material of the second repair microcapsules is component A in a two-component epoxy resin system. The specific formulation is: 85 parts by mass of bisphenol A diglycidyl ether epoxy resin mixed with 15 parts by mass of 1,4-butanediol diglycidyl ether active diluent.

[0080] The addition of the diluent adjusts the viscosity of the core material to 750 mPa-s at 25°C, ensuring that it can effectively flow to fill cracks upon release, without running off due to being too low in viscosity.

[0081] The corrosion inhibitor nm container functions to intelligently release corrosion inhibitor molecules to protect the metal armor layer when the corrosion medium invades. The mass percentage of the corrosion inhibitor nm container in the second repair sublayer is 3%. In this embodiment, zinc-aluminum layered double hydroxide is used as the nm container carrier. The preparation thereof uses a coprecipitation method: a mixed salt solution containing Zn(NO3)2·6H2O and Al(NO3)3·9H2O (molar ratio Zn:Al = 3:1) is added dropwise into deionized water under nitrogen protection and vigorous stirring, and a basic solution containing NaOH and Na2CO3 is added dropwise into the deionized water under nitrogen protection and vigorous stirring at the same time, and the pH value is controlled to be constant at 9.5 in real time by using a dilute NaOH solution. The reaction is carried out at 65°C for 4 hours, and then the reaction product is aged for 24 hours to obtain an LDH-CO3 precursor. Subsequently, ion exchange is performed, and the LDH-CO3 powder is dispersed in a 0.2 mol / L benzotriazole sodium salt (Na-BTA) solution, and stirring is performed at 60°C for 48 hours.

[0082] In this process, BTA - Anions replace CO3 2- Anions in the interlayer of the LDH. After washing, centrifugation and vacuum drying, the corrosion inhibitor nm container loaded with benzotriazole (BTA) (BTA-LDH) is obtained. The loading amount of BTA is 30% (mass percentage) as determined by thermogravimetric analysis. Transmission electron microscopy observation shows that the prepared BTA-LDH has a hexagonal nm sheet structure, and the average diameter of the sheet layer is 200 nm, and the thickness is about 15 nm. Such a structure endows it with a very high specific surface area, which is beneficial to rapid ion exchange and pH response with the surrounding environment.

[0083] One of the key components in the technical solution of the present application is a catalyst primer coating layer that is pre-provided between the outer surface of the metal armor layer and the inner surface of the self-repairing outer sheath. The coating layer is the key to realizing efficient and targeted curing of the epoxy resin in the second repair microcapsule.

[0084] The coating layer is applied by dip coating, and the thickness after curing is controlled to be 20 μm. The coating layer is composed of two parts: one part is an oil-based polyurethane prepolymer that serves as a film-forming resin and a carrier; and the other part is a latent curing agent that serves as component B in a two-component epoxy resin system. The curing agent uses a modified aliphatic amine adduct micro powder that has been subjected to surface sealing treatment, and the melting point thereof is about 60°C, and the average particle size is controlled to be less than 5 μm.

[0085] In the preparation of the coating, the curing agent micro-powder is uniformly dispersed in the ethyl acetate / butanone solution of the polyurethane resin. Since the curing agent is an inert solid at room temperature and is insoluble in the solvent system, no chemical reaction will occur during the storage and application of the coating. However, once the liquid epoxy resin prepolymer (released from the broken second repair microcapsule) comes into contact with it, the surface sealing layer of the curing agent micro-powder will be quickly dissolved by the epoxy resin, exposing the active amine group, thus immediately initiating the cross-linking and curing reaction with the epoxy group, without the need for any external heating or catalysis.

[0086] The manufacturing method of the present application specifically comprises the following series of interlinked engineering steps:

[0087] Step one, preparation of functional fillers. The first and second repair microcapsules with core materials of moisture-curable polyurethane prepolymer and epoxy resin prepolymer, respectively, are prepared by the interfacial polymerization method and the double-layer wall construction method described in detail above, and are treated by filtration, washing and vacuum drying at 40°C for 24 hours, and finally sieved through a 200-mesh sieve to ensure no agglomerates. At the same time, BTA-LDH nm powder is prepared by co-precipitation and ion exchange methods and is also subjected to the same drying treatment.

[0088] Step two, preparation of self-repairing sheath blend. A co-rotating twin-screw extruder is used, with nine temperature zones set from the feeding port to the die, and the temperature profile is 140-155-170-175-180-180-175-170-170°C. First, high-density polyethylene chips and maleic anhydride grafted high-density polyethylene chips are added from the main feeding port through a loss-in-weight feeder at a mass ratio of 92:8 for melt blending. A side feeding port is set in the middle of the screw, and the second repair microcapsules and BTA-LDH powder (mass ratio about 25:3) that have been mixed uniformly are added to the molten matrix polymer through another loss-in-weight feeder. The configuration of this section of the screw uses low-shear kneading blocks to ensure uniform dispersion of the functional fillers while minimizing damage to the microcapsule structure. After degassing, cooling, and strand pulling, the second repair sub-layer special material is prepared. Using the same method, in another extruder, high-density polyethylene and maleic anhydride grafted high-density polyethylene are blended at a ratio of 92:8, and then 15% of the first repair microcapsules by mass are added from the side feeding port to prepare the first repair sub-layer special material.

[0089] Step three, the construction of the catalyst primer coating. The cable core of the completed double-layer galvanized steel tape armored cable is first subjected to solvent cleaning and high-frequency corona treatment to enable the surface to reach a surface energy of 42 mN / m or more, so as to improve the adhesion of the coating. Subsequently, the cable core is passed through an immersion coating tank at a speed of 10 m / min, and the tank is filled with a catalyst primer coating prepared in advance. After leaving the coating tank, the coating thickness is precisely controlled by means of an air knife, and then the cable core is immediately introduced into a three-stage infrared heating tunnel to volatilize the solvent and cure the coating into a film.

[0090] Step four, co-extrusion molding of the self-repairing outer sheath. The cable core coated with the catalyst primer coating is fed into a specially designed double-layer co-extrusion crosshead. Two extruders (the main machine for the second repair sublayer and the auxiliary machine for the first repair sublayer) melt and pump the corresponding special materials into the inner and outer flow channels of the co-extrusion head, respectively. The temperature of the extruders is set to 170-185°C, and the temperature of the head is controlled at 185°C. Through the precise design of the mold flow channel, the two material flows are combined at the die orifice in a molten state to cover the cable core in one pass, forming an inner and outer double-layer structure with a clear interface. In this process, the high-temperature second repair sublayer inner wall melts with the catalyst primer coating on the cable core, forming a firm physical bond.

[0091] Step five, cooling and product processing. The extruded cable is immediately introduced into a circulating water tank with a length of 60 m for sufficient cooling and setting through stepwise cooling. The cooled cable is then successively subjected to an on-line spark test bench and a laser diameter measuring instrument to ensure electrical insulation and dimensional accuracy. Finally, the cable is wound into a qualified product after being printed with model specifications and other marks by a code jet printer.

[0092] The present application aims to solve the problem of lack of active repair capability of traditional power cable outer sheath after damage, which leads to internal metal corrosion. A self-repairing outer sheath system with three-level synergy of "rapid plugging-structure repair-active corrosion inhibition" is constructed. To verify the performance of the system, five groups of examples are designed by changing the key parameters (repair microcapsule content, corrosion inhibitor loading, catalyst performance, etc.), and the self-repairing efficiency, corrosion resistance and long-term reliability are compared and analyzed.

[0093] Example parameter design:

[0094] Example 1 (basic control group):

[0095] Self-repairing outer sheath structure: total thickness 3.0 mm, first repair sublayer thickness 1.0 mm (33%), second repair sublayer thickness 2.0 mm (67%).

[0096] First repair sub-layer: matrix is high density polyethylene blended with maleic anhydride grafted high density polyethylene (grafting rate 1.0%) at 92:8, first repair microcapsule (particle size 20 μm, capsule wall polyurethane-urea) content 15%, capsule core is moisture-cured polyurethane prepolymer (-NCO content 3.5%, 25℃ viscosity 180 mPa•s).

[0097] Second repair sub-layer: second repair microcapsule (particle size 150 μm, double-layer capsule wall) content 25%, capsule core is epoxy resin prepolymer (25℃ viscosity 750 mPa•s); corrosion inhibitor nm container (zinc-aluminum LDH, flake size 200 nm) content 3%, benzotriazole (BTA) loading 30%.

[0098] Catalyst primer coating: thickness 20 μm, containing modified fatty amine adduct (melting point 60℃, particle size 5 μm).

[0099] Example 2 (first repair microcapsule content optimization group):

[0100] Difference from Example 1: the mass percentage of first repair microcapsule in the first repair sub-layer is adjusted to 20% (other parameters are the same).

[0101] Example 3 (second repair microcapsule content optimization group):

[0102] Difference from Example 1: the mass percentage of second repair microcapsule in the second repair sub-layer is adjusted to 30% (other parameters are the same).

[0103] Example 4 (corrosion inhibitor loading optimization group):

[0104] Difference from Example 1: the BTA loading in the corrosion inhibitor nm container is increased to 35% (other parameters are the same).

[0105] Example 5 (catalyst activity optimization group):

[0106] Difference from Example 1: the melting point of modified fatty amine adduct in the catalyst primer coating is reduced to 55℃, and the particle size is 3 μm (other parameters are the same).

[0107] III. Performance test method

[0108] Self-repairing efficiency test: a 0.5mm deep scratch is pre-prepared with a blade, and the tensile strength recovery rate after 1 hour (first stage) and 24 hours (second stage) of repair is tested respectively (based on the undamaged sample).

[0109] Corrosion resistance test: the pre-prepared scratch cable sample is immersed in 5% NaCl solution for 30 days, and the corrosion rate of the metal armor layer (μm / year) is tested by electrochemical workstation.

[0110] Long-term reliability test: repeat the above self-repair efficiency and corrosion rate test after 1000 hours of thermal aging (90°C).

[0111] Data comparison results:

[0112]

[0113] Conclusion analysis:

[0114] The influence of the first repair microcapsule content: Example 2 (20% content) has a 26% increase in 1-hour recovery rate compared to Example 1 (15%), indicating that increasing the first repair microcapsule content can significantly improve the initial rapid plugging effect. This is because more microcapsules rupture to release repair agents, quickly filling small cracks and reducing the invasion of corrosive media into the channel.

[0115] The influence of the second repair microcapsule content: Example 3 (30% content) has a 24-hour recovery rate of 97%, which is 5% higher than Example 1, and the performance remains stable after thermal aging. This shows that increasing the second repair microcapsule content can enhance the structural repair strength, and the double-layer capsule wall design cooperates with the epoxy resin curing system to effectively restore the mechanical integrity of the outer sheath.

[0116] The influence of the corrosion inhibitor load: Example 4 (35% load) has a 37.5% reduction in corrosion rate compared to Example 1, and still maintains the lowest corrosion rate (0.7 μm / year) after thermal aging. This is because a higher load of BTA forms a protective film on the metal surface through ion exchange and pH response mechanisms, more effectively inhibiting anodic dissolution.

[0117] The influence of catalyst performance: Example 5 (low melting point, small particle size catalyst) has a 24-hour recovery rate of 98%, which is the highest among all groups. This shows that reducing the melting point and particle size of the catalyst can accelerate its reaction rate with the epoxy resin, shorten the curing time, strengthen the interface bonding, and reduce the risk of interface corrosion.

[0118] Optimal solution: Example 3 (second microcapsule optimization) and Example 5 (catalyst optimization) perform best in structural repair efficiency, and Example 4 has a significant advantage in corrosion resistance. In practical applications, the combination of high second microcapsule content and high corrosion inhibitor load can be preferred to balance structural repair and corrosion inhibition.

[0119] In summary, the application upgrades the traditional passive physical isolation protection concept to a dynamic intelligent protection system which can actively respond, repair and inhibit corrosion after damage by systematic innovation design of cable sheath material and structure. The system fundamentally solves the inherent problem that micro physical defects inevitably lead to catastrophic cable failure, greatly improving the long-term service safety and reliability of power cables in complex and harsh environments. The implementation of the application has great technical value and practical significance for ensuring the stable operation of critical infrastructure.

[0120] The above is only a preferred embodiment of the application, and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A cross-linked polyethylene insulated corrosion-resistant power cable, characterized in that, Its structure, from the inside to the outside along the radial direction, includes: conductor core, insulation layer, inner semiconducting shielding layer, outer semiconducting shielding layer, metal shielding layer, metal armor layer, catalyst primer coating, and self-healing outer sheath. The self-healing outer sheath is configured as a first repair sub-layer and a second repair sub-layer from the outside to the inside along its radial thickness direction. Both layers are based on a blend of high-density polyethylene and maleic anhydride-grafted high-density polyethylene as the matrix polymer. The high-density polyethylene has a density of 0.955 to 0.965 g / cm³. 3 The melt flow index is 0.4 to 0.6 g / 10min; the grafting rate of maleic anhydride in the maleic anhydride-grafted high-density polyethylene is 0.8% to 1.2%, and the mass percentage of maleic anhydride in the blend is 5% to 10%. The thickness of the first repair sublayer accounts for 30% to 40% of the total thickness of the self-healing outer sheath, and 10% to 20% by mass of the first repair microcapsules are dispersed in its matrix polymer; the average particle size of the first repair microcapsules is 10 to 30 μm, the capsule wall is a polyurethane-urea copolymer material with a capsule wall thickness of 150 to 300 nm, and the core material is a moisture-cured single-component polyurethane prepolymer repair agent, which is prepared by reacting toluene diisocyanate with polyether polyol, the content of its terminal isocyanate groups is 2.8% to 4.0%, and the viscosity at 25°C is less than 200 mPa·s; The thickness of the second repair sublayer accounts for 60% to 70% of the total thickness of the self-healing outer sheath. Its matrix polymer disperses 20% to 30% by mass of the second repair microcapsules and 2% to 5% by mass of corrosion inhibitor nanocapsules. The average particle size of the second repair microcapsules is 100 to 180 μm, and they have a double-layered capsule wall. The inner capsule wall is made of polyvinylbenzene with a thickness of 500 to 800 nm, and the outer capsule wall is made of polymethyl methacrylate-acrylic acid copolymer with a thickness of 100 to 200 nm. The outer surface of the outer capsule wall contains carboxyl functional groups. The core material is a liquid epoxy resin prepolymer, which is a mixture of bisphenol A diglycidyl ether and 1,4-butanediol diglycidyl ether reactive diluent, with a viscosity of 600 to 900 mPa·s at 25°C.

2. The cross-linked polyethylene insulated corrosion-resistant power cable according to claim 1, characterized in that, The corrosion inhibitor nm container is a zinc-aluminum layered double hydroxide nm sheet with a sheet diameter of 150 to 300 nm and a thickness of 10 to 25 nm; the interlayer anion of the zinc-aluminum layered double hydroxide is a benzotriazole corrosion inhibitor anion, and the loading of the corrosion inhibitor anion is 25% to 35% by mass.

3. The cross-linked polyethylene insulated corrosion-resistant power cable according to claim 1, characterized in that, The catalyst primer coating has a thickness of 15 to 25 μm and is composed of a polyurethane-based film-forming resin and a μm-level solid powder as a latent curing agent, wherein the latent curing agent exists in a dispersed form in the film-forming resin. The latent curing agent is a modified fatty amine adduct with a melting point of 55 to 65°C and an average particle size of less than 8 μm. The curing agent is solid at room temperature and can dissolve in the liquid epoxy resin prepolymer released from the second repair microcapsule and initiate a cross-linking curing reaction.

4. The cross-linked polyethylene insulated corrosion-resistant power cable according to claim 1, characterized in that, The insulating layer is a cross-linked polyethylene material, prepared by peroxide cross-linking or silane cross-linking processes; Its volume resistivity is not less than 1×10 14 Ω·m, power frequency breakdown field strength not less than 20 kV / mm.

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