A three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable

Abstract

This invention relates to the field of cable technology and discloses a three-core T-shaped fully shielded anti-discharge cross-linked polyethylene power cable, comprising a conductor connection part, a conductor shielding wrapping layer, a main insulation wrapping layer, a T-shaped protective shell, and a cross-linking heating assembly. The cross-linking heating assembly is installed inside the T-shaped protective shell to directly perform in-situ heating and cross-linking of the conductor shielding wrapping layer and the main insulation wrapping layer. Heating melts and solidifies the wrapping layer material, eliminating micro-layer gaps and pores between layers, thus physically blocking gas ionization channels and significantly improving the partial discharge protection capability and overall insulation life. The T-shaped protective shell is fastened to the outside of the main insulation wrapping layer and forms a closed cavity, effectively isolating external moisture and impurities.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable. Background Technology

[0002] Three-core cross-linked polyethylene (XLPE) power cables are widely used in medium- and high-voltage power transmission scenarios such as municipal power grids and industrial power distribution due to their excellent insulation performance, good heat resistance, and large transmission capacity. In complex power transmission and distribution networks, it is often necessary to branch the cable trunk line midway to divert current, thus forming power cables with T-shaped branch structures. The insulation continuity, shielding integrity, and overall anti-discharge capability of the stripped and reconstructed areas of such cables with branch nodes directly determine the operational safety and service life of the entire line. In existing cable branching construction technologies, the electrical performance at the branch point is usually restored by in-situ stripping and reconnection followed by layer-by-layer wrapping of insulation material. For example, patent document CN203774007U - A novel YJV type cross-linked polyethylene insulated power cable discloses a traditional three-core power cable main structure, which is mainly composed of multi-strand stranded conductive cores, an inner semi-conductive shielding layer, a cross-linked polyethylene main insulation layer, and an outer protective sheath layer by layer. This structure can meet the insulation, protection, and conductivity requirements of conventional straight-line power transmission and is suitable for most standardized laying scenarios.

[0003] However, these traditional branched power cables still have obvious structural defects in practical applications and long-term operation: the geometry of the T-shaped branch area is complex (especially the cross-sectional change at the conductor joint). Currently, strip insulation and shielding materials are generally wrapped layer by layer. Due to the limitations of manual construction accuracy and the physical bonding characteristics of the strip itself, tiny interlayers and pores are easily generated between the wrapping layers and between turns. Under the continuous action of the alternating high voltage electric field, gas ionization is very likely to occur inside these micropores, which can induce partial discharge. Long-term action can lead to insulation dendration or even breakdown. Summary of the Invention

[0004] The main objective of this invention is to provide a three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable to solve the technical problems of traditional T-type cables, where micropore defects easily occur in the insulation and shielding wrapping layers, leading to partial discharge, and the lack of in-situ heating and curing methods makes it impossible to completely eliminate the pores.

[0005] To achieve the above objectives, the present invention provides a three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable, comprising a conductor connection portion, a conductor shielding wrapping layer, a main insulation wrapping layer, a T-type protective shell, and a cross-linked heating assembly; The conductor connection part is formed by hot-melt welding of the exposed conductive cores of three cross-linked polyethylene power cables to form a T-shaped structure; A conductor shielding wrapping layer is tightly wrapped around the outside of the conductive core and the conductor connection; A main insulation wrapping layer is tightly wrapped around the outside of the conductor shielding wrapping layer; A T-shaped protective shell is fastened and covered on the outside of the main insulation wrapping layer, and a closed cavity is formed between the inner wall of the T-shaped protective shell and the outer wall of the main insulation wrapping layer; A cross-linking heating component is installed inside the T-shaped protective housing to heat and cure the conductor shielding wrapping layer and the main insulation wrapping layer to eliminate micropore defects between the wrapping layers.

[0006] Preferably, the T-shaped protective shell is a T-shaped tubular structure formed by detachably connecting an upper and lower splicing shell.

[0007] Preferably, the cross-linking heating assembly includes multiple heating elements, which are attached to the inner wall of the T-shaped protective housing.

[0008] Preferably, the three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable further includes a plastic sealing layer, which is tightly wrapped around the conductor connection and located between the conductor shielding wrapping layer and the main insulation wrapping layer.

[0009] Preferably, each of the three ends of the T-shaped protective shell has an external threaded connection part along the outer circumference, and a locking nut is threaded onto the external threaded connection part. One end of the locking nut is integrally formed with an inwardly extending radial limiting retaining ring. A pressure equalizing and tightening sleeve is embedded in each of the three ports of the T-shaped protective shell. The pressure equalizing and tightening sleeve is sleeved on the outside of the main insulation wrapping layer. The inner wall of the radial limiting ring abuts against the outer end face of the pressure equalizing and tightening sleeve to apply radial clamping force to the main insulation wrapping layer.

[0010] Preferably, each port segment of the T-shaped protective housing has two annular inner conical surfaces spaced circumferentially on its inner wall; The equalizing and tightening sleeve consists of two mirror-symmetrical and fixedly connected mating pressure tubes, with the outer wall of each mating pressure tube slidingly fitting against the corresponding annular inner conical surface.

[0011] Preferably, the pressure-applying pipe includes, in sequence, a coaxial docking section, a wedge-shaped conical section, a flexible pressure-applying section, and a force-transmitting flange ring; The reduced diameter end of the wedge-shaped conical section is coaxially connected to one end of the coaxial mating section, the expanded diameter end of the wedge-shaped conical section is coaxially connected to the outer ring of the force transmission flange ring, and the inner ring of the force transmission flange ring is fixedly connected to the outer wall of the flexible pressure application section. The two coaxial sections belonging to the same pressure equalizing and tightening sleeve are coaxially connected. The outer wall of the wedge-shaped conical section fits against the inner conical surface of the ring, and the radial limiting retaining ring of the locking screw sleeve abuts against the end face of the force transmission flange ring. Multiple axial deformation grooves are formed along the circumferential direction on the pressure-applying pipe, penetrating the pipe wall. These grooves extend sequentially through the flexible pressure-applying section, the force-transmitting flange ring, and the wedge-shaped cone section. The coaxial docking section has multiple axial blind slots along the circumferential direction at the end away from the wedge-shaped cone section. The multiple axial blind slots correspond one-to-one with the multiple axial deformation slots and are interconnected with each other. The flexible pressure section includes multiple arc-shaped crimping petals arranged in a circular array along the circumference. The arc-shaped crimping petals extend toward the conductor connection part, and their ends leave a gap with the conductor connection part. The end face of the arc-shaped crimping flap near the conductor connection part is provided with multiple guide blind holes spaced apart along its arc trajectory. An elastic element is arranged in the guide blind hole, and a guide push rod is connected to each elastic element. The end of the guide push rod away from the elastic element extends out of the guide blind hole and is fixedly connected to an adaptive compensation pressure block.

[0012] Preferably, the junction between the conductor connection portion and the conductive core is formed with three stepped sections. Multiple adaptive compensation blocks located at the end of the flexible pressure section on the same side cooperate with the corresponding stepped section and abut against and fit against the transition corner of the stepped section under the elastic force of the elastic element.

[0013] Preferably, the side wall of the T-shaped protective housing has an injection port for injecting insulating filler.

[0014] The beneficial effects of the above scheme are: A cross-linking heating component is installed inside the T-shaped protective shell to directly heat and cross-link the conductor shielding wrapping layer and the main insulation wrapping layer in situ. Heating melts and solidifies the wrapping material, eliminating tiny interlayer gaps and pores between layers, thus physically blocking gas ionization channels and significantly improving partial discharge protection and overall insulation life. The T-shaped protective shell is fastened to the outside of the main insulation wrapping layer, forming a closed cavity that effectively isolates external moisture and impurities. Attached Figure Description

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 This is a schematic diagram of the existing conductor connection part and conductive wire core; Figure 2 This is a schematic diagram of the three-dimensional structure of a portion of the present invention; Figure 3 yes Figure 2 Cross-sectional structural diagram; Figure 4 yes Figure 3 Enlarged structural diagram of region A in the middle; Figure 5 yes Figure 3 A magnified structural diagram of region B in the middle; Figure 6 yes Figure 5 A magnified structural diagram of region C in the middle; Figure 7 yes Figure 3 Front view structural diagram; Figure 8 This is a partial cross-sectional structural diagram of the present invention; Figure 9 This is a three-dimensional structural diagram of the pressure equalization and tightening sleeve of the present invention.

[0017] Explanation of reference numerals in the attached figures 1. Conductor connection part; 11. Stepped section; 12. Conductive core; 2. Conductor shielding wrapping layer; 3. Main insulation wrapping layer; 4. T-shaped protective shell; 41. Upper assembled shell; 42. Lower assembled shell; 43. External threaded connection part; 44. Locking sleeving; 441. Radial limiting retaining ring; 45. Pressure equalizing and tightening sleeve; 46. Annular inner conical surface; 47. Butt joint pressure tube; 471. Coaxial butt joint section; 472. Wedge-shaped conical section; 473. Flexible pressure section; 4731. Arc-shaped crimping flap; 4732. Guide blind hole; 4734. Guide push rod; 4735. Adaptive compensation pressure block; 474. Force transmission flange ring; 475. Axial deformation groove; 476. Axial blind groove. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Example

[0019] See Figure 2 , Figure 3 and Figure 7 This embodiment provides a three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable, mainly including a conductor connection part 1, a conductor shielding wrapping layer 2, a main insulation wrapping layer 3, a T-type protective shell 4, and a cross-linking heating assembly (not shown). See also Figure 1 and Figure 3Three cross-linked polyethylene power cables have their sheaths, outer semiconductive layers, main insulation, and inner semiconductive layers stripped from their ends, exposing a certain length of the internal conductive cores 12. Two cables have their conductive cores 12 arranged coaxially as the main conductor cores, while the third cable has its conductive core 12 arranged perpendicular to the main conductor cores as a branch conductor core. The ends of the three cables are overlapped and then fused together by thermofusion welding (such as exothermic welding or induction welding) to form a conductor connection 1 with a "T"-shaped cross-section. Thermofusion welding allows the metal of the three conductor cores to fully melt and resolidify at the joint. Compared to traditional mechanical crimping, this results in lower contact resistance, stronger current carrying capacity, and avoids the crimped interface from heating up due to oxidation under long-term current flow. Since the cross-section of the conductive core 12 is usually smaller than the cross-section of the welded accumulation area of ​​the conductor connection 1, see [reference needed]. Figure 1 At the junction of the conductor connection 1 and each conductive core 12, three stepped sections 11 are naturally formed, which are annular steps transitioning from the outer diameter of the welded expansion portion of the core. This stepped section 11 is not only a transition area for the conductor geometry, but also the mating positioning surface of the adaptive compensation block 4735 described later.

[0020] See Figure 3 and Figure 6 The conductor shielding wrapping layer 2 is made of semi-conductive tape (such as semi-conductive self-adhesive tape or semi-conductive heat-shrinkable tape) tightly wrapped around the outside of the conductive core 12 and the conductor connection part 1 in an overlapping wrapping manner, so that the outer surface of the entire T-shaped conductor forms a continuous, equipotential semi-conductive shielding surface, thereby homogenizing the electric field on the conductor surface and eliminating the risk of tip discharge in the welding area. The main insulation wrapping layer 3 is made of cross-linked polyethylene insulation tape (or cross-linkable insulation tape such as ethylene propylene rubber) tightly wrapped around the outside of the conductor shielding wrapping layer 2 in a multi-layer overlapping wrapping manner. During wrapping, there is a certain amount of overlap between each layer and between each turn to ensure the continuity of the insulation thickness. It should be noted that the conductor shielding wrapping layer 2 and the main insulation wrapping layer 3 are generally formed by wrapping strip materials layer by layer. Due to the limitations of manual construction accuracy and tape bonding characteristics, micro-pore defects such as micro-layers and gaps are very easy to occur between wrapping layers and between turns. As demonstrated in existing Chinese patent literature (e.g., CN224304396U - A novel fusion-bonded polyethylene cable Y-type seamless cross-linking structure, or CN107064759A - A method for judging the type of insulation defects in ultra-high voltage equipment, or CN114825195A - A method for connecting cross-linked polyethylene insulated cables), under the continuous action of an alternating high-voltage electric field, gas ionization occurs inside these micropores, inducing partial discharge. Long-term effects will lead to dendration or even breakdown (i.e., induced electrical treeing). This is precisely the core target that the subsequent cross-linking heating component and the clamping structure in this embodiment need to work together to eliminate.

[0021] This embodiment may also include a molding compound layer. This molding compound layer is tightly wrapped around the conductor connection portion 1 and is located between the conductor shielding wrapping layer 2 and the main insulation wrapping layer 3. The molding compound layer can be made of a highly fluid, fusible insulating tape or filler adhesive, which preferentially melts and fills irregular areas where T-shaped or other wrapping tapes are difficult to adhere properly when heated. See also... Figure 2 and Figure 3 The T-shaped protective outer shell 4 is fastened and covers the outside of the main insulation wrapping layer 3, forming a closed cavity between its inner wall and the outer wall of the main insulation wrapping layer 3. This closed cavity serves two purposes: firstly, it isolates external moisture, dust, and impurities, preventing moisture discharge at the interface during operation; secondly, it acts as a barrier during heating and cross-linking. (See also...) Figure 3 The T-shaped protective housing 4 is a T-shaped tubular structure formed by detachably connecting an upper assembly housing 41 and a lower assembly housing 42. The two assembly housings are joined together along the axial split surfaces, avoiding the problem of the integral tubular housing not being able to fit into the pre-formed assembly. Sealing strips can be provided on the mating surfaces of the two assembly housings to ensure cavity sealing. The cross-linking heating assembly includes multiple heating elements, which are attached to the inner wall of the T-shaped protective housing 4 and distributed along the three arms of the T to cover the entire length of the conductor shielding wrapping layer 2 and the main insulation wrapping layer 3. The heating elements can be PTC heating elements, resistance heating films, or silicone rubber heating strips, and their leads are led out through sealed wire holes on the housing wall and connected to the temperature control power supply. During operation, the temperature control power supply is turned on, and the heat generated by the heating elements is transferred through the closed cavity to the main insulation wrapping layer 3 and the conductor shielding wrapping layer 2, causing the cross-linked polyethylene material therein to heat up to the cross-linking reaction temperature. Under heating, the wrapping tape melts, flows, and cross-links to solidify, fusing and filling the tiny interlayers and pores between layers and turns, thereby eliminating micropore defects from a physical source and blocking gas ionization channels. After heating is complete and it cools naturally, a dense, micropore-free shielding and insulation integrated structure is obtained, significantly improving the ability to prevent partial discharge and the insulation life.

[0022] See Figures 3-5 The T-shaped protective housing 4 has three ends with an externally threaded connection 43 along its outer circumference. A locking sleeve 44 is threaded onto the externally threaded connection 43. One end of the locking sleeve 44 has an integrally formed radially extending retaining ring 441. A pressure equalizing sleeve 45 is embedded in each of the three ends of the T-shaped protective housing 4, and is fitted over the main insulating wrapping layer 3. When the locking sleeve 44 is tightened, the inner wall of the radially limiting retaining ring 441 abuts against the outer end face of the pressure equalizing sleeve 45 and pushes the pressure equalizing sleeve 45 axially into the housing. This axial thrust is then converted into radial pressure on the main insulating wrapping layer 3 through the following conical surface fit, ensuring uniform compaction of the main insulating wrapping layer 3 at the ends. This seals the ends and cavities, eliminates air gaps at the end interfaces, and equalizes the electric field. (See also...) Figure 3 , Figure 5 and Figure 9Each port segment of the T-shaped protective housing 4 has two annular inner conical surfaces 46 spaced circumferentially on its inner wall (the two annular inner conical surfaces are arranged facing each other axially). The pressure equalizing and tightening sleeve 45 consists of two mirror-symmetrical and fixedly connected mating pressure tubes 47, the outer wall of each mating pressure tube 47 slidingly fitting against the corresponding annular inner conical surface 46.

[0023] See Figure 9 Each pressure-applying pipe 47 comprises, axially, a coaxial docking section 471, a wedge-shaped conical section 472, a flexible pressure-applying section 473, and a force-transmitting flange ring 474. The reduced-diameter end of the wedge-shaped conical section 472 is coaxially connected to one end of the coaxial docking section 471, and the expanded-diameter end of the wedge-shaped conical section 472 is coaxially connected to the outer ring of the force-transmitting flange ring 474. The inner ring of the force-transmitting flange ring 474 is fixedly connected to the outer wall of the flexible pressure-applying section 473. During assembly, the two coaxial docking sections 471 belonging to the same pressure-equalizing sleeve 45 are coaxially docked, so that the two pressure-applying pipes 47 are assembled into a complete sleeve; the outer walls of the two wedge-shaped conical sections 472 on both sides are respectively in contact with the two annular inner conical surfaces 46; the radial limiting retaining ring 441 of the locking nut 44 abuts against the end face of the force-transmitting flange ring 474. When the locking nut 44 is tightened, the radial limiting retaining ring 441 transmits the axial force to the mating pressure tube 47 via the force transmission flange ring 474, forcing the wedge-shaped conical segment 472 to slide along the annular inner conical surface 46. Due to the guiding effect of the conical surface, the wedge-shaped conical segment 472 is radially contracted, thereby driving the flexible pressure section 473 to radially close, applying a uniform circumferential pressing force to the main insulation wrapping layer 3; thereby enabling the arc-shaped crimping petal 4731 at the end of the flexible pressure section 473 to perform a precise pressing action on the main insulation wrapping layer 3 located on one side of the conductor connection portion 1. This pressing action, by providing continuous radial mechanical stress, can forcefully squeeze out the residual air between the insulation layers and at the interface, thereby physically eliminating the air gap. Combined with the above-mentioned heating cross-linking process, it blocks the gas ionization path inside the micropores. To enable the pressure-applying pipe 47 to possess the aforementioned elastic deformation capability for radial contraction, multiple axial deformation grooves 475 are formed along the circumferential direction on the pressure-applying pipe 47, penetrating the pipe wall. These axial deformation grooves 475 extend sequentially through the flexible pressure-applying section 473, the force-transmitting flange ring 474, and the wedge-shaped conical section 472, thereby dividing the pipe wall into multiple independently radially deflectable fan-shaped lobes, allowing for smooth radial contraction under conical pressure. At the end of the coaxial docking section 471 away from the wedge-shaped conical section 472, multiple axial blind grooves 476 are formed along the circumferential direction. These axial blind grooves 476 correspond one-to-one with and are interconnected with the multiple axial deformation grooves 475, extending the effective deformation length of the deformation grooves, reducing the clamping force required for contraction, and preserving the complete ring at the end of the coaxial docking section 471 to ensure the docking positioning of the two pipes.

[0024] See Figure 6The flexible pressure section 473 includes multiple arc-shaped crimping flaps 4731 arranged in a circular array along the circumference. The arc-shaped crimping flaps 4731 extend towards the conductor connection portion 1, with a gap between their ends and the conductor connection portion 1 to prevent the crimping flaps from directly and rigidly pressing against the conductor and damaging the cladding. Multiple guide blind holes 4732 are spaced apart along the arc trajectory of the end face of the arc-shaped crimping flaps 4731 near the conductor connection portion 1. An elastic element (such as a compression coil spring) is disposed within each guide blind hole 4732. A guide push rod 4734 is connected to each elastic element. The end of the guide push rod 4734 away from the elastic element extends out of the guide blind hole 4732 and is fixedly connected to an adaptive compensation pressure block 4735. The guide blind hole 4732 and the guide push rod 4734 form a sliding guide pair, while the elastic element provides axial elastic preload.

[0025] See Figure 6 The aforementioned stepped section 11 is located at the junction of the conductor connection 1 and the conductive core 12, and is in the shape of an annular step. Multiple adaptive compensation blocks 4735 located at the end of the flexible pressure section 473 on the same side cooperate with the corresponding stepped section 11 and, under the elastic force of the elastic element, abut against and adhere to the transition corner of the stepped section 11. The function of this structure is that there is a sudden change in diameter between the welded expansion of the conductor connection 1 and the conductive core 12, and this stepped transition corner is precisely the weakest area where shielding and insulation wrapping are most difficult to adhere firmly and where the electric field is most easily distorted. The adaptive compensation block 4735 adheres to the corner under the continuous elastic force of the elastic element, and can continuously apply compensation pressure to the wrapping layer at that location during the heating and softening stage, compacting and filling any air gaps that may exist at the corner. At the same time, the elastic element allows the guide push rod 4734 to adaptively expand and contract with the thermal expansion and cooling of the wrapping layer, ensuring that a stable fitting pressure is maintained throughout the entire heating-heating-cooling process, thereby eliminating the risk of partial discharge at the corner of the stepped section 11.

[0026] See Figure 2 The T-shaped protective shell 4 has an injection port on its side wall for injecting insulating filler. After heat cross-linking or assembly sealing, a flowable insulating filler (such as insulating potting silicone rubber, epoxy potting compound, etc.) can be injected into the closed cavity through the injection port. After the filler cures, it fills the remaining cavity between the shell and the main insulating wrapping layer 3, further eliminating residual air, improving the overall insulation strength and mechanical protection performance, and also providing a moisture-proof sealing effect. The injection port can be sealed after injection.

[0027] First, the three cable cores are stripped, butt-jointed, and hot-melt welded to form the conductor connection 1. Then, the conductor shielding layer 2, (and, if necessary, a plastic sealing layer), and the main insulation layer 3 are wrapped around it sequentially. The upper and lower composite shells 41 and 42 are radially closed and fastened to the outside of the main insulation layer 3, forming a closed cavity. At each of the three ports, equalizing and tightening sleeves 45 are inserted and the locking screws 44 are tightened, causing the flexible pressure section 473 to radially tighten and the adaptive compensation pressure block 4735 to conform to the stepped section 11. The arc-shaped pressing flap 4731 presses and eliminates air gaps inside the wrapping layer, completing port sealing and interface compaction. The cross-linking heating component is then connected to heat and cross-link the wrapping layer in situ, eliminating interlayer micropore defects. After cooling, insulating filler is injected through the injection port and sealed. This yields a dense, fully shielded, and highly effective three-core T-type cross-linked polyethylene power cable with excellent anti-discharge performance.

[0028] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable, characterized in that, include: A conductor connection part (1) is formed by hot-melt welding of the exposed conductive cores (12) of three cross-linked polyethylene power cables. A conductor shielding wrapping layer (2) is tightly wrapped around the outside of the conductive core (12) and the conductor connection part (1); A main insulating wrapping layer (3) is tightly wrapped around the outside of the conductor shielding wrapping layer (2); A T-shaped protective shell (4) is fastened and covered on the outside of the main insulating wrapping layer (3), and a closed cavity is formed between the inner wall of the T-shaped protective shell (4) and the outer wall of the main insulating wrapping layer (3); A cross-linking heating component is disposed inside the T-shaped protective shell (4) for heating and curing the conductor shielding wrapping layer (2) and the main insulation wrapping layer (3) to eliminate micropore defects between the wrapping layers.

2. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 1, characterized in that, The T-shaped protective shell (4) is a T-shaped tubular structure formed by detachably connecting an upper splicing shell (41) and a lower splicing shell (42).

3. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 1, characterized in that, The cross-linking heating assembly includes multiple heating elements, which are attached to the inner wall of the T-shaped protective shell (4).

4. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 1, characterized in that, It also includes a molding compound that tightly covers the outer periphery of the conductor connection (1) and is sandwiched between the conductor shielding wrapping layer (2) and the main insulation wrapping layer (3).

5. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to any one of claims 1-4, characterized in that, The three ends of the T-shaped protective shell (4) are each provided with an external threaded connection (43) along the outer circumference. A locking sleeve (44) is threaded onto the external threaded connection (43). One end of the locking sleeve (44) is integrally formed with an inwardly extending radial limiting ring (441). A pressure equalizing and tightening sleeve (45) is embedded in each of the three ports of the T-shaped protective shell (4). The pressure equalizing and tightening sleeve (45) is sleeved on the outside of the main insulation wrapping layer (3). The inner wall of the radial limiting ring (441) abuts against the outer end face of the pressure equalizing and tightening sleeve (45) to apply radial clamping force to the main insulation wrapping layer (3).

6. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 5, characterized in that, Each port segment of the T-shaped protective shell (4) has two annular inner cone surfaces (46) spaced out along the circumference. The equalizing and tightening sleeve (45) consists of two mirror-symmetrical and fixedly connected mating pressure tubes (47); The outer walls of the two docking pressure tubes (47) are respectively slidably attached to the annular inner conical surfaces (46) on both sides of the inner wall of the port.

7. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 6, characterized in that, The pressure-applying pipe (47) includes, in sequence, a coaxial docking section (471), a wedge-shaped conical section (472), a flexible pressure-applying section (473), and a force-transmitting flange ring (474). The reduced diameter end of the wedge-shaped conical segment (472) is coaxially connected to one end of the coaxial docking segment (471), the expanded diameter end of the wedge-shaped conical segment (472) is coaxially connected to the outer ring of the force transmission flange ring (474), and the inner ring of the force transmission flange ring (474) is fixedly connected to the outer wall of the flexible pressure application segment (473). The two coaxial mating sections (471) belonging to the same pressure equalizing sleeve (45) are coaxially mated, the outer wall of the wedge-shaped cone section (472) is in contact with the annular inner cone surface (46), and the radial limiting retaining ring (441) of the locking screw sleeve (44) abuts against the end face of the force transmission flange ring (474). The pressure-applying pipe (47) has multiple axial deformation grooves (475) that penetrate the pipe wall along the circumferential direction. The multiple axial deformation grooves (475) extend sequentially through the flexible pressure-applying section (473), the force-transmitting flange ring (474), and the wedge-shaped cone section (472). The coaxial docking section (471) away from the wedge-shaped cone section (472) has a plurality of axial blind grooves (476) along the circumferential direction. The plurality of axial blind grooves (476) correspond one-to-one with the plurality of axial deformation grooves (475) and are interconnected. The flexible pressure section (473) includes a plurality of arc-shaped crimping petals (4731) arranged in a circular array along the circumferential direction. The arc-shaped crimping petals (4731) extend toward the conductor connection part (1) and their ends are separated from the conductor connection part (1). The arc-shaped crimping flap (4731) has multiple guide blind holes (4732) spaced apart along its arc trajectory on the end face near the conductor connection part (1). An elastic element is disposed in the guide blind hole (4732), and a guide push rod (4734) is connected to each elastic element. The end of the guide push rod (4734) away from the elastic element extends out of the guide blind hole (4732) and is fixedly connected to an adaptive compensation pressure block (4735).

8. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 7, characterized in that, The junction of the conductor connection part (1) and the conductive wire core (12) has three cross-sectional stepped parts (11). Multiple adaptive compensation blocks (4735) located at the end of the flexible pressure section (473) on the same side cooperate with the corresponding cross-sectional stepped portion (11) and abut against and adhere to the transition corner of the cross-sectional stepped portion (11) under the elastic force of the elastic element.

9. The three-core T-type fully shielded anti-discharge cross-linked polyethylene power cable according to claim 1, characterized in that, The side wall of the T-shaped protective shell (4) is connected to an injection port for injecting insulating filler.

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