Cable outdoor terminal

Abstract

The invention relates to a cable outdoor terminal. The cable outdoor terminal comprises a sleeve, an upper shielding case, a stress cone, a stress cone support and a lower shielding case, the upper shielding case is fixed at the upper end of the sleeve through an upper fitting, the lower shielding case is fixed at the lower end of the sleeve through a lower fitting, the upper fitting, the lower fitting and the sleeve define a sealed cavity, and the sealed cavity is filled with an insulating agent; the stress cone is arranged at the inner bottom of the sleeve in a supporting mode through the stress cone support, the stress cone support is fixed to the lower hardware fitting, the cross section of a semi-conductive layer of the stress cone after being cut in the axial direction is in a bilateral protruding petal shape, the petal-shaped concave-convex structure can disperse electric field concentration points, and electric field distortion at the edge of a traditional conical cross section is avoided. The gradient morphology of the petals can form gradient transition of electric field intensity, reduce abrupt change of an interface between the insulating layer and the semi-conductive layer, and inhibit partial discharge.

Description

Technical Field

[0001] This application relates to the field of high-voltage cable transmission technology, and in particular to an outdoor cable terminal. Background Technology

[0002] With the rapid development of my country's power industry, the power grid scale continues to expand, and the demand for transmission capacity is constantly increasing. High voltage and large power grids have become an inevitable trend in power system development. High-voltage cable transmission systems have advantages such as small footprint, high reliability, immunity to weather interference, and good electromagnetic compatibility, making them particularly suitable for power transmission in urban power grids, special geographical environments (such as mountainous areas and river crossings), and high load density areas. As a key component connecting cables to overhead lines or transformers, outdoor cable terminals must withstand extremely high electrical, mechanical, and thermal stresses. Their insulation performance, sealing properties, and long-term reliability directly determine the safety of the entire transmission system.

[0003] The stress cone in cable user outdoor terminals is a critical component, mainly used to control the electric field distribution at the cable terminal and avoid insulation breakdown or partial discharge caused by electric field concentration. However, the traditional stress cone design for cable user outdoor terminals generally adopts an axisymmetric tapered cross-section, which easily leads to electric field concentration at the insulation-semiconductive layer interface, especially in the region of abrupt curvature change at the end of the cone, resulting in uneven electric field distribution. Summary of the Invention

[0004] Therefore, it is necessary to provide an outdoor cable terminal that enables a more uniform electric field distribution.

[0005] An outdoor cable terminal includes: a sleeve, an upper shielding cover, a stress cone, a stress cone support, and a lower shielding cover;

[0006] The upper shield is fixed to the upper end of the sleeve by an upper hardware, and the lower shield is fixed to the lower end of the sleeve by a lower hardware. The upper hardware, the lower hardware and the sleeve together form a sealed cavity, and the sealed cavity is filled with an insulating agent.

[0007] The stress cone is supported by the stress cone holder at the inner bottom of the sleeve. The stress cone holder is fixed to the lower hardware. The cross-section of the semiconductive layer of the stress cone after being cut along the axial direction is a double-sided convex petal shape.

[0008] In one embodiment, the insulating layer of the stress cone is designed to be cylindrical and coaxially arranged with the sleeve.

[0009] In one embodiment, the stress cone support is a hollow design with openings in the sidewalls.

[0010] In one embodiment, the stress cone is made of polytetrafluoroethylene.

[0011] In one embodiment, a sealing ring is provided at the connection between the stress cone support and the lower hardware.

[0012] In one embodiment, a shielding ring is also included, which is fixed to the upper end of the sleeve by the upper fitting.

[0013] In one embodiment, the shielding ring includes a small ring structure and a large ring structure, the small ring structure being disposed on the side away from the sleeve, and the large ring structure being disposed on the side closer to the sleeve.

[0014] In one embodiment, the outer wall of the sleeve is provided with an umbrella-shaped structure of alternating sizes, and the umbrella-shaped structure is made of composite material or ceramic material.

[0015] In one embodiment, the outer edges of the upper shield and the lower shield are rounded rectangles.

[0016] In one embodiment, a tail tube is also included, which is fixed to the lower end of the sleeve by the lower fitting.

[0017] The aforementioned outdoor cable terminal includes a sleeve, an upper shield, a stress cone, a stress cone support, and a lower shield. The upper shield is fixed to the upper end of the sleeve by an upper fitting, and the lower shield is fixed to the lower end of the sleeve by a lower fitting. The upper and lower fittings and the sleeve together form a sealed cavity, which is filled with insulating agent. The stress cone is supported by a stress cone support at the bottom of the inner part of the sleeve. The stress cone support is fixed to the lower fitting. The cross-section of the semiconductive layer of the stress cone after axial cutting is a double-sided convex petal shape. The petal-shaped concave and convex structure can disperse the electric field concentration point and avoid the electric field distortion at the edge of the traditional conical cross-section. The gradual deformation of the petals can form a gradient transition of electric field intensity, reduce the abrupt change at the interface between the insulation layer and the semiconductive layer, and suppress partial discharge. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an outdoor cable terminal in one embodiment;

[0020] Figure 2 This is a detailed schematic diagram of the sleeve in one embodiment;

[0021] Figure 3This is a schematic diagram of the stress cone structure in one embodiment;

[0022] Figure 4 This is a schematic diagram of the stress cone support structure in one embodiment;

[0023] Figure 5 This is a schematic diagram of the shielding ring in one embodiment;

[0024] Figure 6 This is a schematic diagram of the upper shielding cover in one embodiment;

[0025] Figure 7 This is a schematic diagram of the structure of the lower shield in one embodiment;

[0026] Figure 8 This is a schematic diagram of the electric field line distribution of an outdoor cable terminal in one embodiment. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. The accompanying drawings illustrate embodiments of this application; however, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of this application more thorough and complete. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0029] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0030] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0031] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] In an exemplary embodiment, Figure 1 As shown, an outdoor cable terminal is provided, comprising: a sleeve 1, an upper shield 2, a stress cone 3, a stress cone support 4, and a lower shield 5. The upper shield 2 is fixed to the upper end of the sleeve 1 by an upper fitting 6, and the lower shield 5 is fixed to the lower end of the sleeve 1 by a lower fitting 7. The upper fitting 6, the lower fitting 7, and the sleeve 1 together form a sealed cavity, which is filled with an insulating agent. The stress cone 3 is supported at the inner bottom of the sleeve 1 by the stress cone support 4, and the stress cone support 4 is fixed to the lower fitting 7. The cross-section of the semiconductive layer of the stress cone 3 after axial cutting is a double-sided convex petal shape.

[0034] Among them, bushing 1 is a key component for connecting high-voltage power cables to overhead lines or electrical equipment, and must meet requirements for insulation, sealing, and weather resistance. Bushing 1 can be made of high-strength inorganic ceramic material, with a brown appearance and excellent weather resistance, anti-leakage, and water-repellent properties. Bushing 1 can also be made of silicone rubber or glass fiber impregnated with epoxy resin composite material, weighing less than 50% of that of ceramic bushings, and possessing both flexibility and explosion-proof performance.

[0035] For example, referring to Figure 2 The outer wall of the bushing 1 is provided with alternating umbrella-shaped skirt structures 11 of varying sizes. The umbrella-shaped skirt structures 11 can be made of composite materials or ceramic materials. Among them, the umbrella-shaped skirt structures 11 made of silicone rubber can provide excellent resistance to flashover, UV resistance, and aging resistance. For the above-mentioned umbrella-shaped skirt structures 11, the creepage distance is required to be greater than 35000mm, and the power frequency withstand voltage is required to be greater than 870kV.

[0036] Specifically, both the upper fitting 6 and the lower fitting 7 can be flange structures. The upper shield 2 is fixed to the upper end of the sleeve 1 via the upper flange, and the lower shield 5 is fixed to the lower end of the sleeve 1 via the lower flange. The upper flange, lower flange, and sleeve together form a sealed cavity, which is filled with an insulating agent. The insulating agent can be low-temperature resistant silicone oil, which meets the requirements for insulating oil use in extremely cold weather (-50°C), thus improving the electrical performance of the outdoor cable terminal.

[0037] Furthermore, the stress cone 3 is supported at the inner bottom of the sleeve 1 by a stress cone holder 4, and the stress cone holder 4 is fixed to the lower hardware 7 to ensure the long-term stable operation of the stress cone. In one example, the distance between the stress cone 3 and the lower hardware 7 is 1000-2000 mm. Based on this installation distance, the axial electric field gradient of the stress cone can be ensured to transition smoothly, avoiding the formation of an electric field concentration area between the lower hardware 7 and the end of the stress cone 3.

[0038] This can be understood as follows: the cable passes through the sleeve 1, and the stress cone support 4 acts as an intermediate component, precisely positioning the stress cone 3 at the bottom of the sleeve 1, ensuring that the stress cone 3 and the stress cone support 4 are coaxially arranged with the sleeve 1 and with the cable conductor.

[0039] Among them, reference Figure 3 The cross-section of the semiconductive layer 31 of the stress cone 3, after being cut along the axial direction, is shaped like a double-sided raised petal. The raised structure effectively disperses the electric field concentration point, avoiding the electric field distortion at the edge of the traditional conical cross-section. The two sides of the "petal" are equivalent to increasing the local radius of curvature, reducing the surface electric field intensity. The gradient morphology can form a gradient transition of electric field intensity, reduce the abrupt change at the interface between the insulating layer and the semiconductive layer, and suppress partial discharge.

[0040] For example, the semiconductive layer 31 of the stress cone 3 can have a large arc radius of R150 to R250 and a small arc radius of R10 to R20.

[0041] Specifically, the semiconductive large arc is a large-radius transition arc between the semiconductive layer 31 and the main insulation of the cable, as shown in the reference. Figure 3 The arc at position A. By setting the semiconducting large arc to a large radius of curvature, the electric field is smoothly dispersed, avoiding electric field concentration at the break in the metal shielding layer (where the field strength is highest), reducing the tangential electric field component, and preventing surface discharge.

[0042] The semiconductive small arc is a small-radius transition arc that gradually tapers towards the end of the semiconductive layer 31, as shown in the reference. Figure 3 The arc at position B. By setting the semiconductive small arc to a small radius of curvature, it can be used to mitigate the difference in dielectric constant between the semiconductive layer 31 and the insulating layer, reduce the distortion of the electric field at the end, and avoid partial discharge caused by abrupt shape changes at the end of the stress cone.

[0043] For example, the semiconductive layer 31 of the stress cone 3 is made of EPDM rubber, which has advantages such as large clamping force, good heat dissipation and high breakdown strength compared with silicone rubber stress cone. Furthermore, since its molecular distribution is similar to that of XLPE insulation of cable, it has good compatibility and higher safety.

[0044] The aforementioned outdoor cable terminal includes a sleeve, an upper shield, a stress cone, a stress cone support, and a lower shield. The upper shield is fixed to the upper end of the sleeve by an upper fitting, and the lower shield is fixed to the lower end of the sleeve by a lower fitting. The upper and lower fittings and the sleeve together form a sealed cavity, which is filled with insulating agent. The stress cone is supported by a stress cone support at the bottom of the inner part of the sleeve. The stress cone support is fixed to the lower fitting. The cross-section of the semiconductive layer of the stress cone after axial cutting is a double-sided convex petal shape. The petal-shaped concave and convex structure can disperse the electric field concentration point and avoid the electric field distortion at the edge of the traditional conical cross-section. The gradual deformation of the petals can form a gradient transition of electric field intensity, reduce the abrupt change at the interface between the insulation layer and the semiconductive layer, and suppress partial discharge.

[0045] In one exemplary embodiment, continuing with reference to Figure 3 The insulating layer 32 of the stress cone 3 is designed to be cylindrical and is coaxial with the sleeve 1.

[0046] Specifically, the semiconductive layer 31 of the stress cone 3 is fitted inside the insulating layer 32, and both are fitted onto the cable inside the sleeve 1. The insulating layer 32 is designed as a cylinder, with an inner diameter ranging from φ70 to 90 mm and an outer diameter ranging from φ400 to 500 mm. The insulating layer 32 can be formed by vacuum casting of epoxy resin material or by molding and vulcanizing silicone rubber.

[0047] It is understandable that designing the insulation layer 32 of the stress cone 3 as a cylinder can provide an axisymmetric electric field distribution, avoiding electric field concentration caused by sharp corners or abrupt changes, and further improving the non-uniform electric field distribution of the stress cone. The large outer diameter (φ400~500mm) provides sufficient axial transition space for the semi-conductive layer 31 of the stress cone 3, achieving a smooth attenuation of the electric field intensity from the conductor to ground. The uniform circumferential stress distribution of the cylindrical structure allows for smaller deformation and avoids cracking when subjected to internal cable thermal expansion or external bushing assembly pressure. The thick-walled design absorbs mechanical vibration energy, reducing the risk of micro-slippage at the stress cone interface. The inner diameter of the cylinder (φ70~90mm) provides sufficient clearance to allow the cable insulation layer to thermally expand without compressing the stress cone.

[0048] Furthermore, the cross-section of the semiconductive layer 31 is shaped like two protruding lobes, which increases the contact area between the semiconductive layer 31 and the insulating layer 32, producing a physical anchoring effect similar to "gear meshing", improving the bonding strength, reducing the risk of delamination caused by thermal expansion and contraction or mechanical vibration, and further preventing interface slippage.

[0049] In one exemplary embodiment, refer to Figure 4 The stress cone support 4 is a hollow design with openings in the side wall.

[0050] Specifically, the stress cone support 4 needs to withstand the axial preload and thermal expansion stress of the stress cone. Therefore, the main body of the stress cone support 4 is designed as an annular or cylindrical cavity, which can reduce the overall weight of the stress cone support 4 while ensuring rigidity and ensuring stable support of the stress cone.

[0051] Furthermore, the sidewall of the stress cone support 4 has multiple through holes symmetrically distributed; these can be circular holes or, for example, holes like... Figure 4 The elongated groove shown allows the insulating agent within the sealed cavity of sleeve 1 to flow, enabling active heat exchange in the stress cone region and improving heat dissipation efficiency. Simultaneously, if the stress cone support 4 is made of metal, the perforated structure can interrupt the continuous conductive path of the metal bracket, suppressing eddy currents and reducing local field strength. Furthermore, the aforementioned hollow structure facilitates tool insertion for adjusting the stress cone position, reducing assembly time.

[0052] In one exemplary embodiment, the stress cone is made of polytetrafluoroethylene (PTFE), with an inner diameter of φ150-200mm and an outer diameter of φ300-400mm.

[0053] Specifically, based on the superior electrical properties of polytetrafluoroethylene (PTFE), such as its dielectric strength far exceeding that of epoxy resin, the risk of insulation breakdown can be significantly reduced, and the eddy current loss problem commonly found in metal brackets can be avoided. Furthermore, its hydrophobic surface prevents condensation from causing surface discharge (especially suitable for humid environments). In addition, PTFE exhibits outstanding thermal stability, with a temperature range of -200℃ to +260℃, making it suitable for the thermal cycling of cables during operation. Its low thermal conductivity, combined with the hollow design of the stress cone bracket, achieves thermal isolation, significantly reducing the temperature gradient of the stress cone. Moreover, PTFE is resistant to acids and alkalis, and SF6 decomposition products, with a lifespan of over 30 years (metal brackets typically need replacement every 15-20 years).

[0054] In one exemplary embodiment, continuing with reference to Figure 1 A sealing ring 8 is provided at the connection between the stress cone support 4 and the lower hardware 7.

[0055] Specifically, the sealing ring 8 is used to prevent the insulation inside the sealed cavity from leaking out, and can be implemented using an oil seal. In one example, the material of the sealing ring 8 can be fluororubber (FKM) or hydrogenated nitrile rubber (HNBR), and the lip structure can be a double-lip type (main sealing lip + dustproof lip), which can simultaneously prevent the leakage of insulating oil and the intrusion of dust.

[0056] In one exemplary embodiment, continuing with reference to Figure 1 The aforementioned outdoor cable terminal also includes a shielding ring 9 fixed to the upper end of the sleeve 1 via an upper fitting 6.

[0057] The shielding ring 9 can be made of either aluminum alloy or copper alloy, and its structure can be circular or spherical. Specifically, the shielding ring 9 can be fixed to the upper flange to secure it to the upper end of the sleeve 1. It can be understood that the shielding ring 9 serves to shield the electric field, uniformly distribute the electric field lines, and improve the power frequency withstand voltage and lightning impulse voltage.

[0058] In one exemplary embodiment, please refer to Figure 5 The shielding ring 9 includes a small ring structure 91 and a large ring structure 92. The small ring structure 91 is located on the side away from the sleeve, and the large ring structure 92 is located on the side closer to the sleeve.

[0059] Specifically, the diameter of the small ring structure 91 can be set to φ300~400mm, the diameter of the large ring structure 92 can be set to φ600~800mm, the distance between the small ring structure 91 and the large ring structure 92 can be set to 300~800mm, and the overall outer diameter of the shielding ring 9 can be set to φ3000~4000mm.

[0060] It is understandable that the smaller ring structure 91, with a smaller diameter, is positioned closer to the cable conductor side to match the high electric field intensity region on the conductor surface, precisely controlling the electric field attenuation gradient of the conductor shielding layer and avoiding abrupt changes in the electric field. Conversely, the larger ring structure 92, with a larger diameter, is positioned closer to the bushing side (grounding end), in a low-field region. Increasing its diameter expands the equipotential distribution range and reduces the axial field intensity gradient at the bushing inlet. The combined double-ring structure forms a stepped capacitive coupling, making the radial electric field transition from the conductor to ground smoother.

[0061] In one example, the shielding ring 9 is a hollow ring structure. The shielding ring 9 is connected to the bushing 1 through a single-through pipe and the upper hardware 6, realizing the self-adjustment function of the insulating oil level in the sealed cavity. When the insulating oil in the bushing 1 is heated and expands, causing the internal pressure to increase, the insulating oil can enter the shielding ring 9 through the upper hardware 6 and the single-through pipe, thereby avoiding the problem of damage to the outdoor cable terminal and leakage of insulating oil due to excessive internal pressure.

[0062] In one exemplary embodiment, please refer to Figure 6 and Figure 7 The outer edges of the upper shield 2 and the lower shield 5 are rounded rectangles.

[0063] Specifically, the upper shield 2 and the lower shield 5 can be made of either aluminum alloy or copper alloy, and their outer edges can be set to be rounded rectangles to shield the electric field and distribute the electric field lines evenly.

[0064] This design, compared to the traditional sharp rectangular design, increases the radius of curvature and effectively suppresses the maximum electric field. The rounded corners make the distribution of equipotential lines smoother, avoiding surface charge accumulation caused by abrupt changes.

[0065] In one exemplary embodiment, please refer to Figure 1 The aforementioned outdoor cable terminal also includes a tail pipe 10 fixed to the lower end of the sleeve 1 via a lower fitting 7.

[0066] Specifically, the tail tube 10 is typically a hollow metal tube (such as stainless steel or aluminum alloy) that serves as a transitional sealing cavity between the cable insulation layer and the sleeve 1. The tail tube 10 must be secured to ensure axial load transfer and radial sealing. The lower fitting 7 can also provide axial preload to the tail tube 10 via a bolt assembly to prevent it from loosening.

[0067] In one specific embodiment, an outdoor cable terminal suitable for cable systems with voltage levels of 750kV and above is provided.

[0068] Currently, in Northwest my country, the development and utilization of abundant energy resources (such as wind power and photovoltaics) have rendered the existing 330kV voltage level cable transmission system unable to meet the stability requirements of power transmission and future development needs of the region. Therefore, upgrading the voltage level to 750kV and above has become a key technological direction for solving the problem of large-capacity, long-distance power transmission. Currently, 750kV and higher voltage level transmission lines are mainly overhead lines, but overhead lines have the following significant disadvantages: 1. Large land occupation: Overhead lines require the erection of towers and the creation of line corridors, which is difficult to implement in areas with scarce land resources or environmentally sensitive areas; 2. Susceptibility to weather conditions: Severe weather such as lightning strikes, snow, and strong winds may cause line tripping or disconnection, threatening the safe and stable operation of the power grid; 3. Limited transmission quality: Electromagnetic environment problems (such as corona loss and radio interference) and high line impedance of overhead lines affect the efficiency and quality of power transmission.

[0069] In contrast, high-voltage cable transmission systems offer advantages such as smaller footprint, higher reliability, immunity to weather interference, and better electromagnetic compatibility, making them particularly suitable for urban power grids, special geographical environments (such as mountainous areas and river crossings), and high-load-density areas. However, the core technological challenge for 750kV and above voltage level cable systems lies in the development of supporting accessories (such as outdoor terminals). As a crucial component connecting cables to overhead lines or transformers, outdoor cable terminals must withstand extremely high electrical, mechanical, and thermal stresses. Their insulation performance, sealing properties, and long-term reliability directly determine the safety of the entire transmission system. Therefore, developing outdoor cable terminals for 750kV and above voltage levels is a key step in overcoming the technological bottlenecks of high-voltage cable transmission and promoting the high-quality development of the power industry, possessing significant technological value.

[0070] Based on this, this embodiment addresses the current gap in the technology of power cable accessories for 750kV and above by providing an outdoor cable terminal suitable for cable systems with voltage levels of 750kV and above.

[0071] Reference Figure 1 The outdoor cable terminal provided in this embodiment includes a sleeve 1, an upper shield 2, a stress cone 3, a stress cone support 4, a lower shield 5, an upper hardware 6, a lower hardware 7, a sealing ring 8, a shielding ring 9, and a tail tube 10.

[0072] Specifically, the upper shield 2 is fixed to the upper end of the sleeve 1 by the upper hardware 6, and the lower shield 5 is fixed to the lower end of the sleeve 1 by the lower hardware 7. The upper hardware 6, the lower hardware 7, and the sleeve 1 together form a sealed cavity, which is filled with insulating agent. The stress cone 3 is supported by the stress cone support 4 at the inner bottom of the sleeve 1. The stress cone support 4 is fixed to the lower hardware 7. The cross-section of the semiconductive layer of the stress cone 3 after axial cutting is double-sided convex petal-shaped. A sealing ring 8 is provided at the connection between the stress cone support 4 and the lower hardware 7. The shielding ring 9 is fixed to the upper end of the sleeve 1 by the upper hardware 6, and the tail tube 10 is fixed to the lower end of the sleeve 1 by the lower hardware 7.

[0073] For bushing 1, the outer wall is provided with an umbrella skirt structure 11 of alternating sizes. The umbrella skirt structure 11 can also be made of composite material or ceramic material. The creepage distance is required to be greater than 35000mm and the power frequency withstand voltage is required to be greater than 870kV.

[0074] For the stress cone 3, the distance between the stress cone 3 and the lower fitting 7 is 1000–2000 mm. The semi-conductive layer 31 of the stress cone 3 can have a large arc radius of R150–R250 and a small arc radius of R10–R20. The insulating layer 32 of the stress cone 3 is designed as a cylinder and is coaxially arranged with the sleeve 1. The insulating layer 32 is designed as a cylinder, with an inner diameter ranging from φ70–90 mm and an outer diameter ranging from φ400–500 mm.

[0075] The stress cone support 4 is made of polytetrafluoroethylene (PTFE), with an inner diameter of φ150~200mm and an outer diameter of φ300~400mm.

[0076] The shielding ring 9 includes a small ring structure 91 and a large ring structure 92. The diameter of the small ring structure 91 can be set to φ300~400mm, the diameter of the large ring structure 92 can be set to φ600~800mm, the distance between the small ring structure 91 and the large ring structure 92 can be set to 300~800mm, and the overall outer diameter of the shielding ring 9 can be set to φ3000~4000mm.

[0077] In this embodiment, to optimize the electric field line distribution and improve the power frequency withstand voltage and lightning impulse voltage, the structure, size, and relative position of each component of the aforementioned outdoor cable terminal were specially designed to form an organic whole, such as... Figure 8 The diagram shows the distribution of its electric field lines.

[0078] The outdoor cable terminal provided in the above embodiment passes the following parameters for the 750kV type: (① Partial discharge test: rise to 760kV and hold for 10s, then drop to 652.5kV, sensitivity ≤5pC, no detectable discharge; ② Power frequency voltage test: rise to 870kV and hold for 15min, no insulation breakdown or flashover occurs; ③ Thermal cycling voltage test: 20 times; conductor temperature 95~100℃, voltage 870kV, no insulation breakdown or flashover occurs; ④ Switching impact test: conductor temperature 95~100℃, ±1550kV 10 times each, no insulation breakdown or flashover occurs; ⑤ Lightning impact test: conductor temperature 95~100℃, ±2100kV 10 times each, no insulation breakdown or flashover occurs).

[0079] Therefore, it can be understood that the outdoor cable terminal provided in this application embodiment can be effectively applied to cable systems with voltage levels of 750kV and above.

[0080] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0081] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An outdoor cable terminal, characterized in that, include: Sleeve, upper shielding cover, stress cone, stress cone support and lower shielding cover; The upper shield is fixed to the upper end of the sleeve by an upper hardware, and the lower shield is fixed to the lower end of the sleeve by a lower hardware. The upper hardware, the lower hardware and the sleeve together form a sealed cavity, and the sealed cavity is filled with an insulating agent. The stress cone is supported by the stress cone holder at the inner bottom of the sleeve. The stress cone holder is fixed to the lower hardware. The cross-section of the semiconductive layer of the stress cone after being cut along the axial direction is a double-sided convex petal shape.

2. The outdoor cable terminal according to claim 1, characterized in that, The insulating layer of the stress cone is designed to be cylindrical and is coaxially arranged with the sleeve.

3. The outdoor cable terminal according to claim 1, characterized in that, The stress cone support is a hollow design with openings in the sidewalls.

4. The outdoor cable terminal according to claim 3, characterized in that, The stress cone is made of polytetrafluoroethylene.

5. The outdoor cable terminal according to claim 1, characterized in that, A sealing ring is provided at the connection between the stress cone support and the lower hardware.

6. The outdoor cable terminal according to claim 1, characterized in that, It also includes a shielding ring that is fixed to the upper end of the sleeve by the upper fitting.

7. The outdoor cable terminal according to claim 6, characterized in that, The shielding ring includes a small ring structure and a large ring structure. The small ring structure is located on the side away from the sleeve, and the large ring structure is located on the side closer to the sleeve.

8. The outdoor cable terminal according to claim 1, characterized in that, The outer wall of the sleeve is provided with an umbrella skirt structure of alternating sizes, and the umbrella skirt structure is made of composite material or ceramic material.

9. The outdoor cable terminal according to claim 1, characterized in that, The outer edges of the upper shield and the lower shield are rounded rectangles.

10. The outdoor cable terminal according to claim 1, characterized in that, It also includes a tail tube that is fixed to the lower end of the sleeve by the lower fitting.

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