Transparent silicone rubber reinforced stress cone cable middle insulation joint and assembly method

Abstract

The invention relates to the technical field of conductive connection, in particular to a transparent silicone rubber reinforced stress cone cable middle insulation joint and an assembling method.The insulation joint comprises an insulation part body integrally prefabricated by liquid silicone rubber, a stress cone and a conductor connecting pipe are arranged in the insulation part body, and a protective shell is arranged outside the insulation part body; a non-uniformly wound fiber reinforced framework is compounded in an insulator of the stress cone, the fiber winding angle of the fiber reinforced framework gradually changes from the axial center to the two ends, the winding angle of the central area is 53-57 degrees, the winding angles of the two end areas are 43-47 degrees, and the fiber reinforced framework is used for providing gradient constraint rigidity during radial expansion. Uniform and high-retention-rate retraction stress is generated during axial retraction; a closed compensation cavity is formed between the protective shell and the outer surface of the insulating part body; the cable has a good interface pressure self-maintaining function, and safe and stable operation of a cable system can be effectively guaranteed.

Description

Technical Field

[0001] This invention relates to the field of cable connection technology, specifically to a transparent silicone rubber reinforced stress cone cable intermediate insulation joint and assembly method. Background Technology

[0002] High-voltage cables are key carriers of electrical energy transmission, and their safe and stable operation is crucial to ensuring the electricity supply for social production and daily life. As a core component in high-voltage cable lines, insulation joints are responsible for connecting cable conductors and achieving reliable electrical insulation. Their performance directly affects the overall lifespan and operational safety of the cable system.

[0003] Utility model patent CN206322868U discloses a straight-through insulating joint with an integral prefabricated silicone rubber insulator, comprising: a prefabricated silicone rubber body, a metal protective shell, a fiberglass outer protective shell, a terminal block, and a core body. One end of the core body is provided with a terminal block, and the other end is provided with the prefabricated silicone rubber body. The core body and the prefabricated silicone rubber body are located inside the metal protective shell. The two ends of the metal protective shell are metal tail tubes of different lengths. A tubular insulating ring extends from the surface of the metal protective shell. The outer wall of the metal protective shell is provided with a fiberglass outer protective shell, and the space between the metal protective shell and the fiberglass outer protective shell is filled with waterproof sealant. Through this method, the integral prefabricated silicone rubber insulator straight-through insulating joint of this utility model features a compact structure and small size. The straight-through and insulating joints share the same prefabricated component. It adopts an advanced on-site dual-machine expansion installation: one machine expands while the other retracts onto the connected two cables, greatly improving installation efficiency and reducing the labor intensity of installers.

[0004] Invention patent CN111585063B discloses a method for manufacturing an integral prefabricated intermediate joint, specifically relating to the field of insulated power cable accessory manufacturing technology. The method includes four steps: preparing a stress cone, preparing a high-voltage shield, preparing an outer insulating shield, assembling components, and preparing an insulating filler layer. This method allows for rapid production of the integral prefabricated intermediate joint, facilitating manufacturing, and providing a clear hierarchical structure. The coordinated use of each structural layer enhances the joint's bending resistance and extends its service life. This invention sequentially molds the stress cone, high-voltage shield, outer insulating shield, and insulating filler layer, using different vulcanization processes to ensure the coordinated structure and improve the overall mechanical properties of the intermediate joint body. The resulting intermediate joint exhibits good elasticity and high hardness, which is beneficial for its use. It eliminates mold seams in the insulation and solves the problem caused by a thin shielding layer, thus ensuring better insulation performance.

[0005] Existing high-voltage cable insulation joints have several shortcomings in practical applications. Firstly, during installation, traditional insulation joints suffer from significant localized stress concentration due to the interference fit between the insulation component and the cable core. This can easily lead to fatigue damage and interface debonding of the insulation material during long-term operation. Conventional fiber-reinforced structures, using a uniform winding method, cannot effectively adapt to the stress distribution differences during insulation deformation, making it difficult to balance the mechanical performance requirements of radial expansion and axial contraction. This results in excessively rapid interface pressure decay, severely threatening insulation performance. Secondly, during long-term cable operation, fluctuations in ambient temperature and changes in current load cause thermal expansion and contraction of the insulation component, leading to interface pressure relaxation. Existing compensation measures often use ordinary sealant, whose coefficient of thermal expansion is incompatible with the insulation material, failing to achieve dynamic stress compensation. The pressure compensation effect is particularly weak when silicone rubber softens under high-temperature conditions, greatly increasing the risk of partial discharge and insulation breakdown.

[0006] Furthermore, traditional insulated joints lack effective real-time monitoring methods for interface pressure, making it difficult for maintenance personnel to grasp the joint's operating status. Fault early warning relies on manual inspections and experience-based judgment, which carries the risks of lag and missed detections, failing to meet the needs of smart grids for equipment status awareness and proactive maintenance. These shortcomings result in insufficient reliability and high maintenance costs for existing cable insulated joints during long-term operation, becoming a key technical obstacle restricting the intelligent and efficient development of high-voltage cable systems. Summary of the Invention

[0007] The purpose of this invention is to provide a transparent silicone rubber reinforced stress cone cable intermediate insulation joint, which has a good interface pressure self-maintaining function, realizes technical improvements from multiple dimensions of materials, structure and monitoring system, and can effectively ensure the safe and stable operation of cable system.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A transparent silicone rubber reinforced stress cone cable intermediate insulation joint includes an insulation body prefabricated from liquid silicone rubber. The insulation body has a stress cone and a conductor connecting tube inside, and a protective shell on the outside. The insulation body of the stress cone is compounded with a non-uniformly wound fiber-reinforced skeleton. The fiber winding angle of the fiber-reinforced skeleton gradually changes from its axial center to both ends. The winding angle in the central region is 53°~57°, and the winding angle in the two end regions is 43°~47°. It is used to provide gradient constraint stiffness during radial expansion and generate uniform and high retention rate retraction stress during axial retraction.

[0010] A sealed compensation chamber is formed between the protective shell and the outer surface of the insulating component body;

[0011] The compensation chamber is filled with a thermal expansion type sealing composite material, and the ratio of the volume expansion coefficient of the thermal expansion type sealing composite material to the volume expansion coefficient of the silicone rubber material of the insulating component body is in the range of 0.9~1.1.

[0012] The protective shell also integrates a pressure sensing module. The probe of the pressure sensing module extends into the compensation chamber and abuts against the outer surface of the insulating body, for real-time monitoring of interface pressure data.

[0013] In one embodiment of the present invention, the fiber of the fiber-reinforced skeleton is a para-aramid fiber that has been surface-modified with a silane coupling agent. The silane coupling agent used for surface modification is vinyltris-(2-methoxyethoxy)silane. The fineness of the para-aramid fiber is 1500 denier, and the tensile strength is not less than 3000 MPa.

[0014] In one embodiment of the present invention, the thermally expandable sealing composite material uses a two-component polyurethane as the matrix and uniformly disperses a microcapsule foaming agent that has undergone surface coating treatment. The core of the microcapsule foaming agent is azodicarbonamide, and the capsule wall is a gelatin-gum arabic composite wall material. Its thermal decomposition temperature is 110℃±5℃. The thermally expandable sealing composite material is triggered to expand at the thermal decomposition temperature, and the resulting expansion stress is 0.07MPa~0.12MPa.

[0015] In one embodiment of the present invention, the amount of the microcapsule foaming agent added is 3% to 5% of the total weight of the thermal expansion sealing composite material.

[0016] In one embodiment of the present invention, the pressure sensing module further includes a wireless transmission unit and a built-in power supply. The wireless transmission unit is used to transmit the interface pressure data to the outside. The pressure sensing module as a whole is sealed and encapsulated in a preset installation chamber inside the protective shell using epoxy resin potting compound.

[0017] In one embodiment of the present invention, the protective shell is a combined structure consisting of an inner shell made of T2 pure copper and an outer shell made of epoxy glass fiber composite material, which are detachably connected by bolts. The cavity between the inner shell and the outer shell constitutes the compensation chamber.

[0018] In one embodiment of the present invention, the wireless transmission unit is connected to a controller, and the controller is configured as follows:

[0019] Receive interface pressure time series data P(t) sent back by the wireless transmission unit; calculate the interface pressure decay rate V=|dP(t) / dt|;

[0020] Establish an early warning mechanism: when V continuously exceeds the first threshold V1 for 24 hours, a level 1 early warning signal is issued; when V continuously exceeds the second threshold V2 for 2 hours, where V2>V1, a level 2 alarm signal is issued and planned maintenance is recommended.

[0021] Establish an emergency response mechanism: If the received pressure data P(t) drops by more than 30% of its rated value within 60 seconds, an emergency short-circuit trip recommendation command will be generated immediately.

[0022] In addition, this invention also discloses a method for assembling a transparent silicone rubber reinforced stress cone cable intermediate insulation joint, comprising the following steps:

[0023] Includes the following steps:

[0024] S1, Cable end pretreatment:

[0025] a. Using the cable stripping positioning tool, precisely strip the cable outer sheath, metal sheath, and semi-conductive layer in sequence to expose the insulation layer and conductor of a specified length;

[0026] b. Use a precision non-woven cloth soaked in anhydrous ethanol to thoroughly clean all exposed cable layer interfaces and conductor surfaces to ensure that there are no contaminants.

[0027] S2, Preheating of the insulating component body:

[0028] c. Place the insulating component body in the constant temperature heating device and preheat it at 40±5℃ for at least 30 minutes to optimize its elastic properties;

[0029] S3, Controllable expansion and positioning of the insulating component body:

[0030] d. Place the preheated insulating body onto the expansion mandrel of the hydraulic pre-expansion device;

[0031] e. Key control point: Activate the hydraulic pre-expansion device and control its expansion mandrel to expand radially at a uniform speed. The tension closed-loop control system of this device monitors the expansion force in real time and ensures that its maximum value never exceeds 75% of the yield strength of the insulating component material.

[0032] f. Once expanded to the target diameter, the insulation body in the expanded state is translated to the pre-treated cable end so that its stress cone is precisely aligned with the semi-conductive break in the cable insulation.

[0033] g. Control the expansion mandrel of the hydraulic pre-expansion device to retract at a uniform speed with a time of not less than 10 seconds, so that the insulating body retracts evenly and tightly wraps around the cable insulation layer;

[0034] S4, Conductor connection and protective housing assembly:

[0035] h. Install the conductor connecting pipe and use a hydraulic crimping tool to complete the conductor crimping according to the specified process;

[0036] i. Assemble the inner shell and outer shell of the protective shell in sequence, and detachably connect and fasten them with connecting bolts to a specified torque, thereby forming the compensation chamber between the outer surface of the protective shell and the outer surface of the insulating component;

[0037] S5, Vacuum infusion of thermal expansion type sealing composite material:

[0038] j. Mix components A and B of the thermal expansion sealing composite material according to claim 3 in a certain proportion and preheat to (40±2)℃ to reduce its viscosity;

[0039] k. Connect the glue injection pipe of the vacuum injection equipment to the glue injection valve on the protective shell, and connect the air extraction pipe to the exhaust valve;

[0040] 1. Start the vacuum injection equipment, evacuate the compensation chamber to below -0.095MPa, and maintain this vacuum level for at least 15 minutes;

[0041] m. Under vacuum conditions, the preheated thermal expansion sealing composite material is injected into the compensation chamber at a low and uniform speed through the injection valve until a continuous flow of adhesive liquid comes out of the exhaust valve;

[0042] n. Close the exhaust valve and the glue injection valve in sequence, and let it stand and cure for 24 hours at 25±5℃;

[0043] S6, Installation and sealing of the pressure sensing module:

[0044] o. Install the pressure sensing module into the preset mounting compartment on the protective shell, ensuring that its probe extends into the compensation chamber and makes good contact with the outer surface of the insulating body;

[0045] p. Use epoxy resin potting compound to completely seal the gaps around the pressure sensing module inside the installation chamber;

[0046] q. Secure the hatch cover plate to complete the assembly work.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention achieves both active and passive maintenance of interfacial pressure, fundamentally ensuring the long-term electrical reliability of the joint. The fiber-reinforced skeleton, through its specific configuration of non-uniform winding, provides non-linearly increasing constraint stiffness during radial expansion during installation, greatly suppressing the irreversible plastic deformation of the polymer network of the insulating component. This allows the stress cone to release highly uniform axial retraction stress close to the initial design value after installation, providing strong and stable initial pressure to the interface and laying the foundation for pressure maintenance from a passive perspective. Simultaneously, the thermally expandable sealing composite material, due to its expansion coefficient matching that of silicone rubber, can deform collaboratively with the insulating component during thermal cycling, avoiding additional stress caused by differences in thermal expansion.

[0049] More importantly, in this invention, when the joint experiences a temperature rise due to load or short-circuit current, it generates continuous expansion stress. This stress acts directly on the outer surface of the insulation component through the compensation chamber, actively compensating for potential internal stress relaxation and forming a dynamic pressure maintenance mechanism. The direct benefit of the pressure sensing module is the realization of real-time monitoring of the interface pressure. This transforms the joint's state from an unknown "black box" to a real-time perceptible "white box," providing the crucial data foundation for predictive maintenance and fundamentally changing the traditional operation and maintenance model. Through the synergistic effect of the fiber-reinforced skeleton, the thermally expandable sealing composite material, and the pressure sensing module, a complete system for sensing, maintaining, and monitoring interface pressure is formed, ultimately ensuring the ultimate safety and long service life of the high-voltage cable connection point. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0051] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0052] Figure 2 For the present invention Figure 1 A magnified view of a portion of point A in the middle.

[0053] Figure 3 This is a control flowchart of the controller of the present invention.

[0054] Figure label:

[0055] 101 Insulating body, 102 Stress cone, 103 Conductor connecting tube, 104 Protective shell, 105 Compensation chamber, 106 Thermal expansion type sealing composite material, 107 Semi-conductive tape, 108 Tin-plated shielding mesh, 109 Insulating self-adhesive tape, 110 PVC tape, 111 Inner shielding tube, 112 Outer shielding tube, 113 Cable core. Detailed Implementation

[0056] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0057] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0058] Example 1:

[0059] See Figure 1 and Figure 2 This embodiment discloses a transparent silicone rubber reinforced stress cone 102 cable intermediate insulation joint, including an insulation body 101 prefabricated from liquid silicone rubber. The insulation body 101 has a stress cone 102 and a conductor connecting tube 103 inside, and a protective shell 104 outside. The insulation body of the stress cone 102 is composite with a non-uniformly wound fiber-reinforced skeleton. The fiber winding angle of the fiber-reinforced skeleton gradually changes from its axial center to both ends. The winding angle in the central region is 53°~57°, and the winding angle in the two end regions is 43°~47°. It is used to provide gradient constraint stiffness when expanding radially and to generate uniform and high retention rate retraction stress when retracting axially.

[0060] A sealed compensation chamber 105 is formed between the protective shell 104 and the outer surface of the insulating body 101;

[0061] The compensation chamber 105 is filled with a thermal expansion type sealing composite material 106, and the ratio of the volume expansion coefficient of the thermal expansion type sealing composite material 106 to the volume expansion coefficient of the silicone rubber material of the insulating body 101 is in the range of 0.9 to 1.1.

[0062] The protective shell 104 also integrates a pressure sensing module. The probe of the pressure sensing module extends into the compensation chamber 105 and abuts against the outer surface of the insulating body 101, for real-time monitoring of interface pressure data. The conductor connecting tube 103 is used to connect the cable cores 113.

[0063] In some embodiments, preferably, the angle gradually changes from 56° at the axial center to 46° at both ends.

[0064] Furthermore, in practical use, a semi-conductive strip 107, a tin-plated shielding mesh 108, an insulating self-adhesive tape 109, and a PVC tape 110 are sequentially arranged on the outer side of the insulating component body 101. An outer shielding tube 112 is arranged between the insulating component body 101 and the semi-conductive strip 107, and an inner shielding tube 111 is built into the insulating component body 101.

[0065] In practical applications, the primary cause of cable joint failure is partial discharge resulting from interface pressure relaxation. Interface pressure Due to the shrinkage force of silicone rubber Provide, and This stems from the entropic elasticity of the polymer network. During the installation and expansion of traditional joints, the polymer chains undergo slippage, orientation, and even breakage, leading to irreversible plastic deformation; that is, the retraction force decreases exponentially with time t. ;

[0066] in, The initial retraction force, It is the attenuation coefficient. It's time.

[0067] This invention utilizes a built-in, non-uniformly wound fiber-reinforced skeleton with a gradually increasing winding angle of 54°-60°. This provides non-linearly increasing constraint stiffness during radial expansion, significantly suppressing irreversible movement of the polymer chains and controlling the permanent deformation rate after installation to below 2%. This also reduces the initial shrinkage force. The loss is minimal. By reducing the attenuation coefficient k in the force attenuation formula to almost zero, This achieves long-term self-sustaining of interface pressure, fundamentally eliminating insulation failure caused by pressure decay.

[0068] Meanwhile, this invention, through its built-in non-uniformly wound fiber-reinforced skeleton with a gradually increasing winding angle of 54°-60°, provides non-linearly increasing constraint stiffness during radial expansion, greatly suppressing the irreversible movement of polymer chains and controlling the permanent deformation rate after installation to below 2%. This means that the initial retraction force... The loss is minimal. By reducing the attenuation coefficient k in the force attenuation formula to near zero, This achieves long-term self-sustaining of interface pressure, fundamentally eliminating insulation failure caused by pressure decay.

[0069] In one embodiment of the present invention, the fiber of the fiber-reinforced skeleton is a para-aramid fiber that has been surface-modified with a silane coupling agent. The silane coupling agent used for surface modification is vinyltris-(2-methoxyethoxy)silane. The fineness of the para-aramid fiber is 1500 denier, and the tensile strength is not less than 3000 MPa.

[0070] In one embodiment of the present invention, the thermally expandable sealing composite material 106 uses a two-component polyurethane as a matrix and uniformly disperses a microcapsule foaming agent that has undergone surface coating treatment. The core of the microcapsule foaming agent is azodicarbonamide, and the capsule wall is a gelatin-gum arabic composite wall material. Its thermal decomposition temperature is 110℃±5℃. The thermally expandable sealing composite material 106 is triggered to expand at the thermal decomposition temperature, and the resulting expansion stress is 0.07MPa~0.12MPa.

[0071] In practical applications, the microcapsule foaming agent is prepared using a complex coagulation method: gelatin and gum arabic are dissolved in an aqueous phase at a 1:1 mass ratio, azodicarbonamide is added as the core, and the pH is adjusted to 4.0-4.5 to allow the composite colloid to coagulate and encapsulate the core. After crosslinking, washing, and drying, microcapsules are obtained with a particle size range of 20-50 μm and an encapsulation rate ≥90%. The microcapsules are dispersed in a polyurethane matrix using a vacuum planetary mixer at 40°C and 200 rpm for 30 minutes to ensure uniform dispersion without agglomeration.

[0072] In one embodiment of the present invention, the amount of the microcapsule foaming agent added is 3% to 5% of the total weight of the thermal expansion sealing composite material 106.

[0073] Because cables generate Joule heat during load fluctuations or short circuits, their temperature rises. The elastic modulus of silicone rubber decreases with increasing temperature, further weakening the retraction force. In this invention, the compensation chamber 105 is filled with a microencapsulated sealing composite material with a matching coefficient of thermal expansion. When the joint temperature rises to the microcapsule trigger temperature (110℃±5℃) due to overload or short circuit, the core material decomposes and generates gas, producing an expansion stress of 0.07MPa~0.12MPa. This stress precisely compensates for the interfacial pressure loss due to the decrease in the silicone rubber modulus. Based on the material's chemical properties, this autonomous, passive intelligent feedback mechanism maintains dynamic balance of interfacial pressure at critical moments without external energy input, greatly improving the safety margin and reliability of the joint.

[0074] In one embodiment of the present invention, the pressure sensing module further includes a wireless transmission unit and a built-in power supply. The wireless transmission unit is used to transmit the interface pressure data to the outside. The entire pressure sensing module is sealed and encapsulated in a pre-set installation chamber inside the protective shell 104 using epoxy resin potting compound.

[0075] In one embodiment of the present invention, the protective shell 104 is a combined structure consisting of an inner shell made of T2 pure copper and an outer shell made of epoxy glass fiber composite material, which are detachably connected by bolts. The cavity between the inner shell and the outer shell constitutes the compensation chamber 105.

[0076] The introduction of fiber-reinforced skeleton not only improves the elasticity of stress cone 102 but also greatly enhances its overall mechanical strength and tear resistance, enabling the joint to better withstand short-circuit electrodynamic impacts. Simultaneously, the T2 pure copper inner shell provides an excellent thermal stability path for short-circuit current, while the epoxy fiberglass outer shell offers extremely high mechanical strength and protection level. This composite structural design gives the joint extremely high overall mechanical reliability, making it suitable for various harsh laying environments such as direct burial and conduit installations.

[0077] In practical use, the mounting compartment of the pressure sensing module is located on the outer shell. The probe rod (probe) passes sequentially through pre-set through holes in the outer shell, the compensation chamber area, and the inner shell, ultimately allowing the probe head to directly contact the outer surface of the insulating component. Fluororubber O-rings are installed at each location where the probe rod passes through the shell to achieve a reliable seal and ensure the airtightness of the compensation chamber.

[0078] See Figure 3 In one embodiment of the present invention, the wireless transmission unit is connected to a controller, and the controller is configured as follows:

[0079] S101: Receive the interface pressure time series data P(t) sent back by the wireless transmission unit; calculate the interface pressure decay rate V=|dP(t) / dt|; where P(t) is the interface pressure value at time t, in MPa, measured by the pressure sensing module, and V is the interface pressure decay rate.

[0080] S102: Establish an early warning mechanism: When V continuously exceeds the first threshold V1 for 24 hours, issue a first-level early warning signal; when V continuously exceeds the second threshold V2 for 2 hours, where V2>V1, issue a second-level alarm signal and recommend planned maintenance.

[0081] S103: Establish an emergency response mechanism: When the received pressure data P(t) drops by more than 30% of its rated value within 60 seconds, an emergency short-circuit trip recommendation command is immediately generated.

[0082] The controller can be implemented using an industrially common embedded microprocessor (such as the ARM Cortex-M series) or a programmable logic controller (PLC). It communicates with the wireless transmission unit of the pressure sensing module via a built-in LoRa receiver module to acquire pressure data P(t).

[0083] The controller runs a built-in algorithm program that uses the difference method or least squares method to fit and calculate the pressure decay rate V=|dP(t) / dt|, and compares the V value with preset thresholds V1 and V2 to make a judgment.

[0084] The thresholds V1 and V2 can be determined based on engineering experience or by formula: After calculating a baseline value, the result is determined through experiments.

[0085] in, , Correction factor, , , .

[0086] The controller samples pressure data at a frequency of 1 Hz and smooths it using a first-order low-pass filter (cutoff frequency 0.1 Hz). The first threshold V1 is set to 0.05 MPa / day, and the second threshold V2 is set to 0.15 MPa / day. These values ​​are based on engineering experience and the minimum interface pressure formula. The calculation yielded a value of k, which ranged from 1.2 to 1.5, and this was verified through accelerated aging tests.

[0087] In practical applications, traditional joints operate as black boxes, requiring maintenance based on periodic inspections or post-failure repairs, resulting in high costs and low efficiency. This embodiment's pressure sensing module provides the ability to directly measure interface pressure. Its beneficial effect is the realization of predictive maintenance based on first principles. This is achieved by monitoring pressure data. And calculate its decay rate. This allows for accurate assessment of the aging condition of the connector. When Exceeding the electric field strength and the dielectric constant of the material When the calculated threshold is The system can issue early warnings. This changes the operation and maintenance mode from the traditional "scheduled maintenance" to "on-demand maintenance," avoiding resource waste and unexpected power outages.

[0088] To facilitate understanding by those skilled in the art, the present invention will be further described below in conjunction with specific applications.

[0089] A transparent silicone rubber reinforced stress cone cable intermediate insulation joint, the components are manufactured as follows:

[0090] Preparation of the insulating body and fiber-reinforced skeleton: Imported high-strength liquid silicone rubber (LSR) with a Shore A hardness of 45 and a tear strength of 28kN / m was selected as the substrate.

[0091] Para-aramid fiber with a linear density of 1500 denier and a tensile strength of 3200 MPa was selected as the reinforcing material. It was placed in a plasma treatment device and treated with a mixture of argon and vinyltris-(2-methoxyethoxy)silane (A-172) vapor (volume ratio 95:5) at 800 W for 6 minutes to achieve surface grafting modification of the silane coupling agent.

[0092] The treated aramid fibers were wound on a mandrel at a gradually changing angle using a precision winding machine: from 56° at the axial center of stress cone 102 to 46° at both ends. During the winding process, a coupling agent solution of vinyltris-(2-methoxyethoxy)silane (A-172) at a concentration of 1 wt% was sprayed simultaneously.

[0093] Using a transfer molding process, LSR is injected into a mold with a pre-wound fiber-reinforced skeleton, and vulcanized at 120°C and 10MPa for 15 minutes to obtain the insulating body with the built-in fiber-reinforced skeleton. The internal stress cone 102 structure is formed in one step.

[0094] Preparation of thermal expansion type sealing composite material 106:

[0095] Take a two-component polyurethane prepolymer, wherein component A is a prepolymer based on diphenylmethane diisocyanate (MDI) (NCO content 23% ± 1%), and component B is a mixture of polyether polyol (functionality 3, hydroxyl value 350 mg KOH / g) and catalyst. Weigh components A and B in a ratio of NCO:OH = 1.05:1, and mix them in the same ratio.

[0096] A microcapsule foaming agent, accounting for 4% of the total weight, is added to the microcapsules. The microcapsules use gelatin-gum arabic as the composite wall material and azodicarbonamide as the core material, with a thermal decomposition temperature of 110°C.

[0097] The mixture was homogenized at 40°C in a vacuum planetary mixer, degassed, and discharged to obtain the thermal expansion type sealing composite material 106, whose expansion coefficient was tested to be 3.0×10−4 / K.

[0098] In some preferred embodiments, the selected liquid silicone rubber (LSR) substrate has a coefficient of volume expansion of approximately 3.2 × 10⁻⁻⁻⁶. 4 / K. The thermal expansion sealing composite material configured has a volume expansion coefficient (including microcapsules) of approximately 3.0 × 10⁻ 4 / K.

[0099] Protective housing 104 and pressure sensing module:

[0100] The protective shell 104 consists of an inner shell formed by cold stretching of T2 pure copper and an outer shell formed by winding epoxy glass fiber. The two are connected by bolts, and injection holes and vent holes are machined on it.

[0101] Purchase a MEMS piezoresistive pressure sensing module, which includes a probe, a wireless transmission unit (based on a wireless communication protocol), and a built-in power supply.

[0102] The specific assembly method is as follows:

[0103] The assembly method of the high-voltage cable insulation joint includes the following steps:

[0104] S1, Cable end pretreatment:

[0105] a. Using a special positioning tool for cable stripping, precisely strip the outer sheath, metal sheath, and semi-conductive layer of the cable in sequence to expose the insulation layer and conductor of the specified length;

[0106] b. Use a precision non-woven cloth soaked in anhydrous ethanol to thoroughly clean all exposed cable layer interfaces and conductor surfaces to ensure that there are no contaminants.

[0107] S2, Preheating of the insulating component body 101:

[0108] c. Place the insulating component body in a constant temperature heating device and preheat it at 40±5℃ for at least 30 minutes to optimize its elastic properties;

[0109] S3, Controllable expansion and positioning of the insulating component body 101:

[0110] d. Place the preheated insulating body onto the expansion mandrel of the hydraulic pre-expansion device;

[0111] e. Key control point: Activate the hydraulic pre-expansion device and control its expansion mandrel to expand radially at a uniform speed. The tension closed-loop control system of this device monitors the expansion force in real time and ensures that its maximum value never exceeds 75% of the yield strength of the insulating component material.

[0112] f. After expanding to the target diameter, the insulation body in the expanded state is translated to the pre-treated cable end so that its stress cone 102 is precisely aligned with the semi-conductive break of the cable insulation.

[0113] g. Control the expansion mandrel of the hydraulic pre-expansion device to retract at a uniform speed with a time of not less than 10 seconds, so that the insulating body retracts evenly and tightly wraps around the cable insulation layer;

[0114] S4, Conductor connection and protective housing 104 assembly:

[0115] h. Install conductor connecting pipe 103 and use hydraulic crimping tools to complete conductor crimping according to the specified process;

[0116] i. The inner shell and outer shell of the protective shell 104 are assembled in sequence, and they are detachably connected and fastened with connecting bolts to a specified torque, thereby forming the compensation chamber 105 between the protective shell 104 and the outer surface of the insulating component body;

[0117] S5, Vacuum infusion of thermal expansion type sealing composite material 106:

[0118] j. Mix components A and B of the thermal expansion type sealing composite material 106 in proportion and preheat to (40±2)℃ to reduce its viscosity;

[0119] k. Connect the injection pipe of the vacuum injection equipment to the injection valve on the protective shell 104, and connect the air extraction pipe to the exhaust valve;

[0120] 1. Start the vacuum injection equipment, evacuate the compensation chamber 105 to below -0.095MPa, and maintain this vacuum level for at least 15 minutes;

[0121] m. Under the condition of maintaining vacuum, the preheated thermal expansion type sealing composite material 106 is injected into the compensation chamber 105 at a low speed and uniform speed through the injection valve until a continuous flow of adhesive liquid is seen from the exhaust valve.

[0122] n. Close the exhaust valve and the glue injection valve in sequence, and let it stand and cure for 24 hours at 25±5℃; S6, Installation and sealing of the pressure sensing module:

[0123] o. Install the pressure sensing module into the preset mounting compartment on the protective shell 104, ensuring that its probe extends into the compensation chamber 105 and makes good contact with the outer surface of the insulating body;

[0124] In actual use, the probe of the pressure sensing module is passed through the pre-set sealing hole on the protective shell to ensure that its probe head directly abuts the outer surface of the integral prefabricated silicone rubber insulator, and the O-rings of each sealing position are installed in sequence; the probe head is a MEMS piezoresistive pressure sensor, and its measuring surface is in direct contact with the outer surface of the insulator body, and zero-point calibration and temperature compensation are performed before installation.

[0125] p. Use epoxy resin potting compound to completely seal the gaps around the pressure sensing module inside the installation chamber;

[0126] q. Secure the hatch cover plate to complete the assembly work.

[0127] After completion, performance testing and results were performed.

[0128] Interface pressure after installation: The initial average interface pressure read by the pressure sensing module is 0.85 MPa.

[0129] Thermal cycling test: 100 thermal cycles were conducted from -40℃ to 80℃ according to the standard. After the test, the interface pressure was measured to be 0.82 MPa, with a pressure retention rate as high as 96.5%.

[0130] Short circuit test: Apply a short circuit current of 40kA / 2s.

[0131] During the test, the joint temperature rose to 115°C, and the microcapsules in the thermally expanding sealing composite material 106 successfully decomposed to produce gas, generating additional pressure. Sensor data showed that the interface pressure not only did not decrease during the short circuit, but instead briefly increased to 0.89 MPa, effectively compensating for the thermal softening effect of the silicone rubber. After the test, the joint remained intact.

[0132] Long-term aging: A 1000-hour long-term electrothermal aging test was conducted at 90℃. During this period, pressure data was continuously monitored through the wireless transmission unit. The calculated pressure decay rate ν was consistently lower than the first-level warning threshold ν1, and the system did not issue any alarms, indicating that the joint condition was extremely stable.

[0133] Comparative Example 1:

[0134] The comparative example uses a traditional fiber-reinforced high-voltage cable connector. The structure of the traditional fiber-reinforced high-voltage cable connector is similar to that of the present invention, but there are key differences:

[0135] Fiber reinforcement: Aramid fibers are also embedded in its stress cone 102, but the fibers are not treated with plasma and silane coupling agent, and are wound in a uniform manner with a constant 55° angle, rather than a gradually changing angle.

[0136] Sealant: The compensation chamber 105 is filled with ordinary two-component polyurethane sealant with an expansion coefficient of 4.5×10−4 / K, which is incompatible with silicone rubber and does not contain microencapsulated foaming agent.

[0137] No sensing function: It does not have a pressure sensing module.

[0138] After installation and testing using the same process, the results are as follows:

[0139] Interface pressure after installation: Initial pressure is 0.80 MPa.

[0140] After the thermal cycling test: the interface pressure dropped to 0.68 MPa, and the pressure retention rate was only 85%.

[0141] Short-circuit test: After applying a short-circuit current of 40kA / 2s, the joint temperature rose to 115℃. Because ordinary sealant could not provide compensation pressure, the interface pressure plummeted to below 0.60MPa. Post-test dissection revealed a microscopic gap visible to the naked eye at the interface between stress cone 102 and the cable insulation, accompanied by slight traces of partial discharge.

[0142] Long-term aging: After 1000 hours of aging at 90℃, the interface pressure decreased to 0.55MPa, and the rate of decrease far exceeded the safety threshold.

[0143] A comparison of Example 1 and Comparative Example 1 clearly demonstrates that the fiber-reinforced skeleton, with its specific surface treatment and gradual winding, fundamentally optimizes mechanical properties and suppresses installation deformation. The intelligent sealing composite material with a matched coefficient of thermal expansion and containing microcapsules introduces an active pressure compensation mechanism, responding to abnormal operating conditions. The integrated pressure sensing module enables real-time awareness and predictability of the status. These three elements work together to solve the fundamental problem of reliably maintaining interfacial pressure over the long term. The comparative example proves that the absence of any one of these features leads to a significant decrease in performance.

[0144] This embodiment details the entire process from component preparation to final assembly. Key control parameters in the assembly method, such as the expansion force control at 75% yield strength, a retraction time of no less than 10 seconds, a vacuum degree of -0.095 MPa, and an injection temperature of (40±2) °C, are indispensable process guarantees for ensuring that the fiber-reinforced skeleton and the thermally expandable sealing composite material 106 fulfill their design functions and ultimately achieve the invention's objective of self-sustaining interfacial pressure.

[0145] Example 2:

[0146] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the insulating layer of the stress cone 102 has a gradient dielectric constant structure. From the axial center of the stress cone 102 to both ends, the dielectric constant is continuously decreasing. The dielectric constant of the central region is 4.5~5.0, and the dielectric constant of the two end regions is 2.8~3.2. The gradient dielectric constant structure is achieved by gradient dispersion of barium titanate nanoparticles in a liquid silicone rubber matrix. The volume fraction of the barium titanate nanoparticles continuously decreases from 15%~18% in the central region to 5%~8% in the two end regions.

[0147] Furthermore, the barium titanate nanoparticles are cubic phase nanoparticles modified with γ-aminopropyltriethoxysilane (KH550), with a particle size of 50~80nm and a dielectric constant ≥3000; the gradient dispersion is achieved by a step-by-step injection molding process, during which the feeding rate of the nanoparticles is controlled to decrease linearly from the center to both ends as the injection position changes, with the feeding rate varying from 8~2g / min.

[0148] In practical applications, the prefabrication method for gradient dielectric constant stress cones is as follows:

[0149] Material preparation: Liquid silicone rubber (LSR) with a Shore A hardness of 45 was selected as the matrix. Cubic phase barium titanate nanoparticles with a particle size of 60 nm and a dielectric constant of 3200 were used. These nanoparticles were modified with KH550. The modification process involved placing the nanoparticles in an ethanol solution, adding 1.5 wt% KH550, stirring at 60°C for 2 hours, and then vacuum drying before use. The dielectric constant was measured using a broadband dielectric spectrometer (such as the Alpha-A Analyzer) at a frequency of 1 kHz.

[0150] Gradient dispersion process: A twin-screw step-by-step injection molding machine is used, with the mold corresponding to the stress cone 102 forming cavity. The injection molding process involves controlling the nanoparticle feeding rate in three stages.

[0151] The first segment, the central region of the stress cone, accounts for 1 / 3 of the total length: feeding rate 8 g / min, nanoparticle volume fraction 16%, dielectric constant 4.8;

[0152] The second section, the intermediate transition region, accounts for 1 / 3 of the total length: feeding rate 5 g / min, nanoparticle volume fraction 11%, dielectric constant 3.9;

[0153] The third segment, the two ends, accounts for 1 / 3 of the total length: feeding rate 2 g / min, nanoparticle volume fraction 6%, dielectric constant 3.0;

[0154] Vulcanization molding: After injection molding, vulcanization is carried out at 125℃ and 12MPa for 20 minutes to obtain gradient dielectric constant stress cone 102. The dielectric constant distribution is verified by a broadband dielectric spectrometer to ensure continuous decrease without abrupt changes.

[0155] Compared with Example 1, the assembly process is adjusted as follows:

[0156] Following the assembly steps S1 to S6 in Example 1, the expansion force parameters are adjusted only during the controllable expansion and positioning of the insulating component body in S3: due to the local mechanical property differences of the gradient dielectric structure, the maximum expansion force is controlled to 70% of the yield strength of the insulating component body material to avoid cracks in the nanoparticle enrichment area; the expansion rate is reduced to 0.5 mm / s to ensure the morphological stability of the gradient structure during the expansion process.

[0157] Performance tests and results comparison are shown in Table 1 below:

[0158] Table 1:

[0159] Test Project Example 1 Example 2 range of change Maximum electric field strength (kV / mm) 4.2 2.8 33.3% Partial discharge quantity (pC) ≤5 ≤2 60% Dielectric loss after 100 thermal cycles (%) 0.08 0.04 50% Insulation integrity rate after short circuit impact 95% 100% 5.3%

[0160] Traditional stress cones use uniform dielectric materials, leading to electric field concentration at both ends (electric field strength often exceeding 5kV / mm), which can easily cause partial discharge and insulation breakdown during long-term operation. This embodiment, through a gradient dielectric constant design, utilizes the inverse relationship between dielectric constant and electric field strength to achieve a uniform electric field distribution within the stress cone, fundamentally solving the electric field concentration problem. Simultaneously, the gradient structure, together with the fiber-reinforced skeleton and thermally expanding sealing material of the original application, forms a synergistic system for electric field regulation, mechanical support, and pressure compensation: the fiber skeleton ensures the mechanical stability of the gradient structure, and the thermally expanding material prevents dielectric interface debonding caused by temperature changes. Together, these three elements improve the long-term insulation reliability of the joint, meeting the latest requirements of smart grids for low field strength, low loss, and high stability in high-voltage equipment.

[0161] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0162] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A transparent silicone rubber reinforced stress cone cable intermediate insulation joint, comprising an insulation body prefabricated from liquid silicone rubber, wherein the insulation body contains a stress cone and a conductor connecting tube, and is provided with a protective shell on the outside, characterized in that: The insulator of the stress cone is insulated with a non-uniformly wound fiber-reinforced skeleton. The fiber winding angle of the fiber-reinforced skeleton gradually changes from its axial center to both ends. The winding angle in the central region is 53°~57°, and the winding angle in the two end regions is 43°~47°. It is used to provide gradient constraint stiffness during radial expansion and to generate uniform and high retention rate retraction stress during axial retraction. A sealed compensation chamber is formed between the protective shell and the outer surface of the insulating component body; The compensation chamber is filled with a thermally expanding sealing composite material; The protective shell also integrates a pressure sensing module. The probe of the pressure sensing module extends into the compensation chamber and abuts against the outer surface of the insulating body, for real-time monitoring of interface pressure data.

2. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 1, characterized in that: The fiber reinforcing skeleton is a para-aramid fiber that has been surface-modified with a silane coupling agent, and the silane coupling agent used for surface modification is vinyltris-(2-methoxyethoxy)silane.

3. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 1, characterized in that: The thermal expansion type sealing composite material uses a two-component polyurethane as the matrix and uniformly disperses microcapsule foaming agent that has undergone surface coating treatment.

4. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 3, characterized in that: The amount of the microcapsule foaming agent added is 3% to 5% of the total weight of the thermal expansion sealing composite material.

5. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 1, characterized in that: The pressure sensing module also includes a wireless transmission unit and a built-in power supply. The wireless transmission unit is used to transmit the interface pressure data to the outside. The entire pressure sensing module is sealed and encapsulated in a pre-set installation chamber inside the protective shell using epoxy resin potting compound.

6. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 1, characterized in that: The protective shell is a combination structure consisting of an inner shell made of T2 pure copper and an outer shell made of epoxy glass fiber composite material, which are detachably connected by bolts. The cavity between the inner shell and the outer shell constitutes the compensation chamber.

7. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 5, characterized in that: The wireless transmission unit is connected to a controller, which is configured as follows: Receive interface pressure time series data P(t) sent back by the wireless transmission unit; calculate the interface pressure decay rate V=|dP(t) / dt|; Establish an early warning mechanism: when V continuously exceeds the first threshold V1 for 24 hours, a level 1 early warning signal is issued; when V continuously exceeds the second threshold V2 for 2 hours, where V2>V1, a level 2 alarm signal is issued and planned maintenance is recommended. Establish an emergency response mechanism: If the received pressure data P(t) drops by more than 30% of its rated value within 60 seconds, an emergency short-circuit trip recommendation command will be generated immediately.

8. The transparent silicone rubber reinforced stress cone cable intermediate insulation joint according to claim 1, characterized in that: The insulating layer of the stress cone has a gradient dielectric constant structure, with the dielectric constant decreasing continuously from the center of the stress cone to both ends.

9. A method for assembling a transparent silicone rubber reinforced stress cone cable intermediate insulation joint as described in any one of claims 1-7, characterized in that, Includes the following steps: S1, Cable end pretreatment: a. Using the cable stripping positioning tool, precisely strip the cable outer sheath, metal sheath, and semi-conductive layer in sequence to expose the insulation layer and conductor of a specified length; b. Use a precision non-woven cloth soaked in anhydrous ethanol to thoroughly clean all exposed cable layer interfaces and conductor surfaces to ensure that there are no contaminants. S2, Preheating of the insulating component body: c. Place the insulating component body in the constant temperature heating device and preheat it at 40±5℃ for at least 30 minutes to optimize its elastic properties; S3, Controllable expansion and positioning of the insulating component body: d. Place the preheated insulating body onto the expansion mandrel of the hydraulic pre-expansion device; e. Key control point: Activate the hydraulic pre-expansion device and control its expansion mandrel to expand radially at a uniform speed. The tension closed-loop control system of this device monitors the expansion force in real time and ensures that its maximum value never exceeds 75% of the yield strength of the insulating component material. f. Once expanded to the target diameter, the insulation body in the expanded state is translated to the pre-treated cable end so that its stress cone is precisely aligned with the semi-conductive break in the cable insulation. g. Control the expansion mandrel of the hydraulic pre-expansion device to retract at a uniform speed with a time of not less than 10 seconds, so that the insulating body retracts evenly and tightly wraps around the cable insulation layer; S4, Conductor connection and protective housing assembly: h. Install the conductor connecting pipe and use a hydraulic crimping tool to complete the conductor crimping according to the specified process; i. Assemble the inner shell and outer shell of the protective shell in sequence, and detachably connect and fasten them with connecting bolts to a specified torque, thereby forming the compensation chamber between the outer surface of the protective shell and the outer surface of the insulating component; S5, Vacuum infusion of thermal expansion type sealing composite material: j. Mix components A and B of the thermal expansion sealing composite material according to claim 3 in a certain proportion and preheat to 40±2℃ to reduce its viscosity; k. Connect the glue injection pipe of the vacuum injection equipment to the glue injection valve on the protective shell, and connect the air extraction pipe to the exhaust valve; 1. Start the vacuum injection equipment, evacuate the compensation chamber to below -0.095MPa, and maintain this vacuum level for at least 15 minutes; m. Under vacuum conditions, the preheated thermal expansion sealing composite material is injected into the compensation chamber at a low and uniform speed through the injection valve until a continuous flow of adhesive liquid comes out of the exhaust valve; n. Close the exhaust valve and the glue injection valve in sequence, and let it stand and cure for 24 hours at 25±5℃; S6, Installation and sealing of the pressure sensing module: o. Install the pressure sensing module into the preset mounting compartment on the protective shell, ensuring that its probe extends into the compensation chamber and makes good contact with the outer surface of the insulating body; p. Use epoxy resin potting compound to completely seal the gaps around the pressure sensing module inside the installation chamber; q. Secure the hatch cover plate to complete the assembly work.

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