Pumped storage power station 500kV high-voltage cable buffer layer structure mechanical performance optimization method, cable buffer layer and cable

Abstract

The invention discloses a mechanical property optimization method for a 500kV high-voltage cable buffer layer structure of a pumped storage power station, a cable buffer layer and a cable. The method comprises the following steps: S1, optimizing the size matching design of an aluminum sheath and the cable buffer layer: controlling the rolling depth of a trough of the aluminum sheath into the cable buffer layer to be within a set range; s2, improving the compression performance of the cable buffer layer: optimizing the structure and material of the cable buffer layer; s3, based on the axial force when the temperature of the cable changes, the friction performance between the buffer strip and the aluminum sheath is optimized; s4, optimizing the ductility of the cable buffer layer according to the radial expansion amount of the cable during full-load operation; and S5, optimizing the pitch and trough form of the aluminum sheath, and improving the contact area between the cable buffer layer and the aluminum sheath. By means of the method, the mechanical performance of the 500kV pumped storage cable buffer layer can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage cable product design technology. Specifically, it relates to a method for optimizing the mechanical properties of a buffer layer structure for a 500kV high-voltage cable in a pumped storage power station, as well as the cable buffer layer and the cable itself. Background Technology

[0002] In the main electrical circuit of a pumped-storage power station, power cables are key equipment for achieving bidirectional power transmission. They primarily use 500kV cross-linked polyethylene (XLPE) insulated cables to connect the generators in the underground powerhouse to the main transformer on the ground. During generator operation, they transmit enormous amounts of electricity to the power grid, while during pumping operation, they draw power from the grid to drive the generator units. Because their installation methods are mainly divided into vertical shafts and inclined tunnels, both face mechanical stress from significant elevation differences, humid environments, and stringent fire prevention requirements.

[0003] Currently, high-voltage cables in 500kV pumped-storage substations commonly employ cable buffer layers with gold-coated fabric structures. These layers are prone to various mechanical performance problems under conditions of high elevation differences, serpentine laying, and fluctuating operating loads. Under fluctuating load conditions, the cable core undergoes periodic thermal expansion and contraction due to temperature changes, repeatedly compressing and frictionally slipping the metal braided layer of the cable buffer. This causes fatigue fracture or loosening of the braided copper wires, weakening the stress homogenization and support capacity of the cable buffer layer. Over time, these mechanical damages can lead to structural loosening, interface peeling, and sheath deformation, reducing the overall mechanical stability and fatigue resistance of the cable, thus creating potential hazards for insulation aging and subsequent electrical faults. Summary of the Invention

[0004] The primary objective of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a method for optimizing the mechanical properties of the buffer layer structure of a 500kV high-voltage cable in a pumped storage power station. The method of this invention can significantly improve the mechanical properties of the buffer layer of the 500kV pumped storage cable.

[0005] A second objective of the present invention is to provide a cable buffer layer.

[0006] A third objective of this invention is to provide a cable.

[0007] The objective of this invention is achieved through the following technical solution: a method for optimizing the mechanical properties of a 500kV high-voltage cable buffer layer structure in a pumped storage power station, comprising the following steps: S1. Optimize the size matching design between the aluminum sheath and the cable buffer layer: control the depth of the aluminum sheath troughs into the cable buffer layer within the set range; S2. Improve the compression performance of the cable buffer layer: Optimize the structure and materials of the cable buffer layer, and perform full stress-strain curve calculation and testing on the cable buffer layer materials; S3. Optimize the friction performance between the buffer strip and the aluminum sheath: Based on the axial force when the cable temperature changes, calculate the friction coefficient between the aluminum sheath and the cable buffer layer, and select the cable buffer layer material according to the friction coefficient. S4. Optimize the elongation performance of the cable buffer layer: Based on the radial expansion of the cable during full-load operation, obtain the compression performance index of the cable buffer layer, and select the cable buffer layer material according to the compression performance index. S5. Improve the contact area between the cable buffer layer and the aluminum sheath: Optimize the pitch and trough shape of the aluminum sheath to increase the contact area.

[0008] Preferably, in step S1, the formula for calculating the depth of the aluminum sheath trough rolled into the cable buffer layer is: Δ1 = Δ·λ, Equation (1). Where Δ is the natural thickness of the cable buffer layer, λ is the corrugation coefficient, the inner diameter of the uncorrugated aluminum sheath D2=D1+2Δ, the inner diameter of the corrugated aluminum sheath trough D3=D1+2λΔ, D1 is the outer diameter of the insulated wire core, and the depth Δ1 of the aluminum sheath trough into the cable buffer layer is controlled between 1.0mm and 2.0mm.

[0009] Preferably, in step S2, the optimized structure and materials of the cable buffer layer specifically include: The cable buffer layer consists of an inner water-blocking tape, a second outer water-blocking tape, and an outer water-blocking tape, wound sequentially from the inside out. The total thickness of the cable buffer layer is 3.0mm to 3.5mm. The materials used for the cable buffer layer are polyester non-woven fabric, conductive carbon black, and superabsorbent polymer.

[0010] Preferably, in step S3, the formula for calculating the axial force when the cable temperature changes is: F a1 =+8EI / (B+n) 2 ·(αt) / 2, Equation (2), F a2 =-8EI / B 2 ·(αt) / 2, Equation (3), Equation (4) Among them, F a1 and F a2 These represent the axial force of the cable insulation core in the serpentine arc when the temperature rises and falls, respectively, in N; EI represents the bending resistance of the cable insulation core; B represents the width of the serpentine arc, in mm. n α represents the slippage in the serpentine arc direction, in mm; α is the coefficient of linear expansion of the cable insulation core, in 1 / K. t Temperature rise is measured in Kelvin (K); L represents the fixture installation spacing in mm.

[0011] Preferably, the formula for calculating the coefficient of friction is: μ=F / mgx, Equation (5) Where μ is the coefficient of friction between the aluminum sheath and the cable buffer layer; F is the magnitude of the axial force in N; mg is the weight per unit length of the cable in N / mm; and x is the cable length in mm.

[0012] Preferably, in step S4, the formula for calculating the radial expansion is: ΔS = S1 - S0, Equation (6). Where ΔS is the maximum radial expansion, S0 and S1 are the outer diameters of the cable insulation core before and after the temperature change, respectively, and the formula for calculating S1 is: Equation (7) Where d is the outer diameter of the conductor, in mm; t is the temperature rise, in K.

[0013] Preferably, in step S5, optimizing the pitch and trough shape of the aluminum sheath specifically includes increasing the pitch of the aluminum sheath and using an arc-shaped trough, so that the contact mode between the cable buffer layer and the aluminum sheath changes from line contact to surface contact.

[0014] A cable buffer layer is prepared using the method described above. The cable buffer layer does not contain a gold-coated fabric structure. The cable buffer layer is wrapped with an inner water-blocking tape, a second outer water-blocking tape, and an outer water-blocking tape from the inside out. The total thickness of the cable buffer layer is 3.0 mm to 3.5 mm.

[0015] A cable includes the cable buffer layer described above, and an aluminum sheath, wherein the troughs of the aluminum sheath are arc-shaped, and the pitch of the aluminum sheath is configured to enable surface contact between the cable buffer layer and the aluminum sheath.

[0016] The present invention has the following advantages and effects compared with the prior art: This invention ensures the mechanical stability of the cable buffer layer during long-term operation through precise structural dimension matching and friction and wear control, avoiding insulation damage caused by stress concentration, structural deformation, or wear. Optimized buffer layer structure and material selection ensure good resilience and support capacity during long-term operation, effectively coping with radial stress. Friction coefficient control based on axial force calculation effectively suppresses relative slippage of the conductor during axial expansion, improving the overall stress coordination and fatigue resistance of the cable. By designing arc-shaped troughs and increasing the pitch of the aluminum sheath, the contact method is changed from line contact to surface contact, significantly reducing the risk of localized stress concentration and wear. The method of this invention can significantly improve the mechanical properties of the 500kV pumped-storage cable buffer layer, comprehensively improving the mechanical adaptability of pumped-storage cables under high drop, long distance, and complex laying conditions, and significantly enhancing the structural stability and operational reliability of the cable. Attached Figure Description

[0017] Figure 1 This is an optimization flowchart of the mechanical performance optimization method for the buffer layer structure of a 500kV high-voltage cable in a pumped storage power station according to the present invention.

[0018] Figure 2 This is a schematic diagram of the cable buffer layer structure of a conventional 500kV cable in Embodiment 1 of the present invention.

[0019] Figure 3 This is a schematic diagram of the optimized 500kV cable buffer layer structure in Embodiment 1 of the present invention.

[0020] Figure 4 This is a schematic diagram comparing the corrugation depth of traditional and optimized aluminum sheaths in Embodiment 1 of the present invention, where (a) is the traditional aluminum sheath model and (b) is the optimized aluminum sheath model.

[0021] in: Figure 2 In the middle section: 1 is conductor; 2 is conductor shield; 3 is insulation layer; 4 is insulation shield layer; 5 is cable buffer layer; 5-1 is water-blocking tape; 5-2 is gold-infused cloth water-blocking tape; 5-3 is water-blocking tape; 6 is corrugated aluminum sheath; 7 is outer sheath. Figure 3 In the diagram: 01 is conductor; 02 is conductor shield; 03 is insulation layer; 04 is insulation shield layer; 05 is cable buffer layer; 501 is outer water-blocking tape; 502 is secondary outer water-blocking tape; 503 is inner water-blocking tape; 06 is corrugated aluminum sheath; 07 is polyethylene sheath; 08 is flame-retardant polyethylene sheath. Figure 4 middle: 3 is the insulation layer; 4 is the insulation shielding layer; 5 is the cable buffer layer; 6 is the corrugated aluminum sheath. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0023] Example 1 like Figure 1 The diagram shows an optimization flowchart for a method to optimize the mechanical properties of a 500kV high-voltage cable buffer layer structure in a pumped storage power station, including the following steps: S1. Optimize the size matching design between the aluminum sheath and the cable buffer layer: control the depth of the aluminum sheath troughs into the cable buffer layer within the set range; S2. Improve the compression performance of the cable buffer layer: Optimize the structure and materials of the cable buffer layer, and perform full stress-strain curve calculation and testing on the cable buffer layer materials; S3. Optimize the friction performance between the buffer strip and the aluminum sheath: Based on the axial force when the cable temperature changes, calculate the friction coefficient between the aluminum sheath and the cable buffer layer, and select the cable buffer layer material according to the friction coefficient. S4. Optimize the elongation performance of the cable buffer layer: Based on the radial expansion of the cable during full-load operation, obtain the compression performance index of the cable buffer layer, and select the cable buffer layer material according to the compression performance index. S5. Improve the contact area between the cable buffer layer and the aluminum sheath: Optimize the pitch and trough shape of the aluminum sheath to increase the contact area.

[0024] Specifically, 500kV pumped-storage cables differ from other high-voltage cables due to their unique operating and laying conditions, requiring optimization of the buffer layer structure for this specific voltage level. This invention, through systematic multi-dimensional collaborative design, aims to improve the mechanical performance of the 500kV pumped-storage cable buffer layer. Specifically: Step S1 forms the basis for optimization. By precisely controlling the depth of the aluminum sheath's insertion into the cable buffer layer, sufficient contact pressure is ensured to form a stable electrical connection and suppress partial discharge. Secondly, excessive insertion avoids excessive pressure on the internal insulation shielding layer, preventing mechanical damage. Step S2 aims to improve the performance of the cable buffer layer under radial pressure. After optimizing the structure and selecting materials, full stress-strain curve calculations and tests accurately determine key parameters such as the elastic modulus, yield strength, and compression set of the selected material during compression. This ensures that the cable buffer layer effectively absorbs and buffers stress while maintaining sufficient support during long-term cable operation and under cyclic radial forces, preventing structural collapse and functional failure due to excessive compression or deformation. Step S3 addresses the axial movement of the cable caused by thermal expansion and contraction due to load changes. Friction coefficient control based on axial force calculations effectively suppresses relative slippage of the conductor during axial expansion. Step S4 considers the buffer layer's ability to cope with radial thermal expansion of the cable insulation conductor. By calculating the maximum radial expansion of the cable after full-load temperature rise, quantitative indicators (compression performance indicators) are provided to guide material selection, considering the required expansion space and deformation energy of the buffer layer. Traditionally, the corrugated aluminum sheath and buffer layer are mostly in line contact, resulting in extremely high contact pressure, easily leading to localized wear and stress concentration. Step S5 aims to reduce the interface stress along the buffer layer by improving the contact area between the cable buffer layer and the aluminum sheath.

[0025] The above five steps, considered from different dimensions, are parallel and form a systematic buffer layer performance solution, which significantly improves the mechanical performance of the 500kV pumped storage cable buffer layer, comprehensively improves the mechanical adaptability of the pumped storage cable under high drop, long distance and complex laying conditions, and significantly enhances the structural stability and operational reliability of the cable.

[0026] In step S1, the formula for calculating the depth of the aluminum sheath trough rolled into the cable buffer layer is: Δ1 = Δ·λ, Equation (1). Where Δ is the natural thickness of the cable buffer layer, λ is the corrugation coefficient, the inner diameter of the uncorrugated aluminum sheath D2=D1+2Δ, the inner diameter of the corrugated aluminum sheath trough (excluding the aluminum sheath thickness) D3=D1+2λΔ, D1 is the outer diameter of the insulated core, and the depth Δ1 of the aluminum sheath trough into the cable buffer layer is controlled between 1.0mm and 2.0mm.

[0027] Specifically, precisely controlling the depth Δ1 within the range of 1.0mm to 2.0mm can maximize the protection of the insulation system while providing the necessary electrical performance and distributing the contact stress within a reasonable range.

[0028] In step S2, the optimized structure and materials of the cable buffer layer specifically include: The cable buffer layer consists of an inner water-blocking tape, a second outer water-blocking tape, and an outer water-blocking tape, wound sequentially from the inside out. The total thickness of the cable buffer layer is 3.0mm to 3.5mm. The materials used for the cable buffer layer are polyester non-woven fabric, conductive carbon black, and superabsorbent polymer.

[0029] Specifically, Figure 2 and Figure 3 These are schematic diagrams of the cable buffer layer structure for traditional and optimized 500kV cables, respectively. Through optimized buffer layer structure and material selection, good resilience and support capacity are ensured during long-term operation, effectively coping with radial stress.

[0030] In step S3, the formula for calculating the axial force when the cable temperature changes is: F a1 =+8EI / (B+n) 2 ·(αt) / 2, Equation (2), F a2 =-8EI / B 2 ·(αt) / 2, Equation (3), Equation (4) Among them, F a1 and F a2 These represent the axial force of the cable insulation core in the serpentine arc when the temperature rises and falls, respectively, in N; EI represents the bending resistance of the cable insulation core; B represents the width of the serpentine arc, in mm. n α represents the slippage in the serpentine arc direction, in mm; α is the coefficient of linear expansion of the cable insulation core, in 1 / K. t Temperature rise is measured in Kelvin (K); L represents the fixture installation spacing in mm.

[0031] The formula for calculating the coefficient of friction is: μ=F / mgx, Equation (5) Where μ is the coefficient of friction between the aluminum sheath and the cable buffer layer; F is the magnitude of the axial force in N; mg is the weight per unit length of the cable in N / mm; and x is the cable length in mm.

[0032] Specifically, by establishing a mathematical model of axial force under cable temperature changes as shown in formulas (2)-(4), the axial force generated by the cable core in the serpentine laying state can be quantitatively analyzed. Then, the required ideal friction coefficient μ is derived from the axial force (formula 5). This step transforms the macroscopic mechanical requirements (suppressing slip) into microscopic material selection criteria (friction coefficient). Based on the calculated target friction coefficient, high-strength polyester and other materials with matching surface properties can be selected so that the static friction between the buffer layer and the aluminum sheath interface is sufficient to resist most of the axial thermal stress, thereby significantly reducing or even eliminating relative slip, and fundamentally avoiding buffer layer damage and metal fatigue caused by fretting wear.

[0033] In step S4, the formula for calculating the radial expansion is: ΔS = S1 - S0, Equation (6). Where ΔS is the maximum radial expansion, S0 and S1 are the outer diameters of the cable insulation core before and after the temperature change, respectively, and the formula for calculating S1 is: Equation (7) Where d is the outer diameter of the conductor, which is approximately constant and is in mm; t is the temperature rise, in K.

[0034] Specifically, by calculating the maximum radial expansion, this method determines that the traditional metal braided fabric (golden cloth) structure should be eliminated to improve ductility, as metal braids have limited ductility and are prone to fatigue. By eliminating the gold cloth structure and instead selecting high-strength polyester or non-woven fabric with higher elongation at break, the buffer layer can readily adapt to radial dimensional changes during cable operation, maintaining a tight fit with the insulation shielding layer at all times. It will not detach from the internal structure due to insufficient ductility, thus ensuring the continuity of the stress buffering effect.

[0035] In step S5, optimizing the pitch and trough shape of the aluminum sheath specifically includes increasing the pitch of the aluminum sheath and using an arc-shaped trough to change the contact mode between the cable buffer layer and the aluminum sheath from line contact to surface contact.

[0036] Specifically, this invention changes the contact method from line contact to surface contact by increasing the pitch of the aluminum sheath and adopting an arc-shaped trough design. This improvement allows mechanical and thermal stresses to be evenly distributed over a larger contact area, significantly reducing the pressure per unit area, improving interface stability and stress transmission uniformity, and further enhancing the cable's fatigue resistance.

[0037] Taking a 500kV, 1600mm² cross-section pumped storage cable as an example, the optimized design method of this invention is specifically implemented as follows: S1. Optimized size matching design between aluminum sheath and buffer layer: Optimized dimensional matching was achieved through thermo-mechanical coupling simulation analysis and precision manufacturing tolerance control. The design incorporates a 290 / 500kV, 1×1600mm... 2 The cable's insulated core outer diameter D1 = 122.0 mm, the corrugated aluminum sheath's trough inner diameter is D3 = 125.0 mm, and the crest outer diameter is 141.0 mm. The corrugation coefficient λ is taken as 0.43. Calculations show: the uncorrugated aluminum sheath inner diameter D2 = 128.9 mm; the cable buffer layer's natural thickness Δ = 3.45 mm under no-pressure conditions; and the depth of the aluminum sheath trough into the buffer layer calculated using the formula Δ1 = Δ·λ = 1.48 mm.

[0038] The buffer layer structure was designed with a target Δ1 range of 1.0mm to 2.0mm. The calculated Δ1 value for the cable sample was 3.45mm, and the depth Δ1 of the aluminum sheath trough embedded in the buffer layer was 1.48mm. This matching design significantly increases the contact area between the aluminum sheath trough and the buffer layer, effectively reducing pressure under the same conditions, preventing mechanical damage to the insulation shield, ensuring a stable electrical connection to suppress partial discharge, and ultimately improving the overall mechanical safety of the cable.

[0039] S2. Improve the compression performance of the buffer layer: The cable buffer layer (semi-conductive cable buffer layer) consists of three layers: an inner water-blocking strip, a second outer water-blocking strip, and an outer water-blocking strip. The inner water-blocking strip comprises three layers of 0.38×80mm semi-conductive water-blocking strips, wound to the right; the second outer water-blocking strip comprises two layers of 0.8×80mm semi-conductive buffer water-blocking strips, wound to the left; and the outer water-blocking strip comprises two layers of 0.38×80mm semi-conductive water-blocking strips, wound to the right. The total thickness of the cable buffer layer is 3*0.38 + 2*0.80 + 1*0.38 = 3.12 mm, requiring stable support at this thickness. Specifically, for this thickness, the inner and outer water-blocking strips are made of polyester non-woven fabric filled with conductive carbon black. Full stress-strain curve testing is performed on the materials to ensure that the compression set meets the requirements.

[0040] S3. Optimize the friction performance between the buffer strip and the aluminum sheath: Theoretical calculations were performed using cable structure data and serpentine laying parameters. The cable unit weight (mg) was taken as 0.5 N / mm², and the cable insulation core bending strength (EI) was taken as 1.3 × 10⁻⁶. 10 N·mm 2 The coefficient of linear expansion α of the cable insulation core is taken as 2 × 10⁻⁶. - 5 1 / K; temperature rise t is 65K; clamp installation spacing L = 3000mm; total cable length is approximately twice the clamp installation spacing, x is taken as 6000mm; serpentine arc width B = 300mm. The calculated slippage n = 29.72mm; the calculated axial force Fa1 =621.8N; F a2 =-751.1N; the friction coefficient was calculated to be μ=0.25 based on the maximum axial force (absolute value). Therefore, high-strength polyester was selected as the material for the cable buffer layer.

[0041] S4. Optimize the stretchability of the buffer layer: Calculate the radial expansion of a 500kV, 1600mm² cable under full load operation, assuming the conductor outer diameter is... d =50.93mm, outer diameter of insulated wire core S 0 =119.1mm, temperature rise during full load operation t= 65 K Calculate the outer diameter of the insulated wire core after temperature change, and calculate the maximum radial expansion. ΔS The thickness is approximately 2.15mm. Based on this, the gold-coated structure was abandoned and a high-strength polyester or non-woven fabric was chosen as the material for the buffer layer. Its elongation at break is 20%, which is better than the gold-coated structure.

[0042] S5. Improve the contact area between the aluminum sheath and the buffer layer: like Figure 4 This diagram illustrates the comparison of the creasing depth of traditional and optimized wrinkled aluminum sheaths. (a) shows the traditional aluminum sheath model, and (b) shows the optimized aluminum sheath model. Specifically, the increased contact area is achieved by optimizing the creasing morphology of the aluminum sheath. The aluminum sheath was designed with an inner diameter of 125.0 mm for the troughs and an outer diameter of 141.0 mm for the peaks. The pitch between the wrinkled aluminum sheaths was improved to increase the contact area. Based on the above data, the wrinkle profile was optimized, the pitch distance was appropriately increased, and an arc-shaped trough was adopted. The arc-shaped trough provides a smooth, continuous surface, allowing the buffer layer to deform and conform more uniformly. The contact area is a strip-shaped region, changing the contact method from line contact to surface contact.

[0043] Through the above systematic optimization design, the mechanical performance of 500kV pumped storage cables has been significantly improved, especially their adaptability and operational reliability under conditions of high drop and long distance laying.

[0044] Example 2 A cable buffer layer is prepared using the method described in Example 1. The cable buffer layer does not contain a gold-coated fabric structure. The cable buffer layer is wrapped with an inner water-blocking tape, a second outer water-blocking tape, and an outer water-blocking tape from the inside out. The total thickness of the cable buffer layer is 3.0 mm to 3.5 mm.

[0045] Specifically, by eliminating the metal braided fabric structure, the problem of buffer layer failure caused by fatigue fracture and loosening of the metal braided wires is fundamentally avoided, thus improving the long-term stability of the structure. An inner layer, a secondary outer layer, and an outer layer of water-blocking tape are wound sequentially from the inside out, and combined with a total thickness of 3.0mm~3.5mm, to form a stable elastic network that effectively absorbs radial expansion and provides uniform support, preventing localized collapse.

[0046] Example 3 A cable includes a cable buffer layer as described in Example 2, and an aluminum sheath, the troughs of which are arc-shaped, and the pitch of the aluminum sheath is configured to allow surface contact between the cable buffer layer and the aluminum sheath.

[0047] Specifically, by combining the aluminum sheath with its arc-shaped troughs with the buffer layer of specific structure in Example 2, a transition from line contact to surface contact is achieved. This design allows mechanical and thermal stresses to be evenly distributed over a larger contact area, greatly suppressing local stress concentration and fretting wear. This cable structure design is highly adaptable to the operating conditions of pumped storage power stations with high elevation differences, serpentine laying, and large load fluctuations.

[0048] The above embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any changes or other equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. A method for optimizing the mechanical properties of the buffer layer structure of a pumped storage power plant 500 kV high voltage cable, characterized by, The method comprises the steps of: S1, optimizing the size matching design of the aluminum sheath and the cable buffer layer: controlling the depth of the aluminum sheath trough rolled into the cable buffer layer within a set range; S2, improving the compression performance of the cable buffer layer: optimizing the structure and material of the cable buffer layer, and performing full stress-strain curve calculation and testing on the cable buffer layer material; S3, optimizing the friction performance between the buffer belt and the aluminum sheath: based on the axial force when the cable temperature changes, calculating the friction coefficient between the aluminum sheath and the cable buffer layer, and selecting the cable buffer layer material according to the friction coefficient; S4, optimizing the ductility performance of the cable buffer layer: according to the radial expansion amount of the cable under full load operation, obtaining the compression performance index of the cable buffer layer, and selecting the cable buffer layer material according to the compression performance index; S5, improving the contact area between the cable buffer layer and the aluminum sheath: optimizing the pitch and trough shape of the aluminum sheath to increase the contact area.

2. The method for optimizing mechanical performance of the buffer layer structure of a pumped storage power station 500 kV high-voltage cable according to claim 1, characterized in that, In step S1, the calculation formula of the depth of the aluminum sheath trough rolled into the cable buffer layer is: Δ1=Δ·λ, formula (1), Wherein, Δ is the natural thickness of the cable buffer layer, λ is the corrugation coefficient, the inner diameter of the uncorrugated aluminum sheath D2=D1+2Δ, the inner diameter of the corrugated aluminum sheath D3=D1+2λΔ, D1 is the outer diameter of the insulated core, and the depth Δ1 of the aluminum sheath trough rolled into the cable buffer layer is controlled within 1.0mm~2.0mm.

3. The method for optimizing mechanical performance of the buffer layer structure of a pumped storage power station 500 kV high voltage cable according to claim 1, characterized in that, In step S2, the optimization of the structure and material of the cable buffer layer specifically includes: The cable buffer layer is wound with an inner water barrier belt, an outer water barrier belt and an outer water barrier belt from inside to outside, and the total thickness of the cable buffer layer is 3.0mm~3.5mm, and the material of the cable buffer layer is selected from polyester non-woven fabric.

4. The method for optimizing mechanical performance of the buffer layer structure of a pumped storage power station 500 kV high voltage cable according to claim 1, characterized in that, In step S3, the calculation formula of the axial force when the cable temperature changes is: F a1 =+8EI / (B+n) 2 ·(αt) / 2, equation (2), F a2 = -8EI / B 2 • (αt) / 2, equation (3), , formula (4), Wherein, F a1 and F a2 respectively are the axial force of the cable insulation core serpentine arc when the temperature rises and the temperature drops, the unit is N; EI is the bending resistance of the cable insulation core; B is the amplitude width of the serpentine arc, the unit is mm; n is the slip amount in the direction of the amplitude of the serpentine arc, the unit is mm; α is the linear expansion coefficient of the cable insulation core, the unit is 1 / K; t is the temperature rise, the unit is K; L is the installation spacing of the clamp, the unit is mm.

5. The method for optimizing the mechanical performance of the buffer layer structure of a pumped storage power station 500 kV high voltage cable according to claim 4, characterized in that, The calculation formula of the friction coefficient is: μ=F / mgx, formula (5), Wherein, μ is the friction coefficient between the aluminum sheath and the cable buffer layer; F is the size of the axial force, unit: N; mg is the unit length weight of the cable, unit: N / mm; x is the length of the cable, unit: mm.

6. The method for optimizing the mechanical performance of the buffer layer structure of a pumped storage power station 500 kV high voltage cable according to claim 1, characterized in that, In step S4, the calculation formula of the radial expansion amount is: ΔS=S1-S0, formula (6), Wherein, ΔS is the maximum radial expansion amount, S0 and S1 are the outer diameters of the cable insulated core before and after temperature change respectively, and the calculation formula of S1 is: , formula (7), Wherein, d is the outer diameter of the conductor, unit: mm; t is the temperature rise, unit: K.

7. The method for optimizing the mechanical performance of the buffer layer structure of a pumped storage power station 500 kV high voltage cable according to claim 1, characterized in that, In step S5, the pitch and trough shape of the aluminum sheath are optimized, specifically including changing the contact mode between the cable buffer layer and the aluminum sheath from linear contact to surface contact by increasing the pitch of the aluminum sheath and adopting circular arc trough.

8. A cable buffer layer prepared by the method of any one of claims 1 to 7, characterized by, The cable buffer layer does not contain gold cloth structure, and the cable buffer layer is wound with an inner water barrier belt, an outer water barrier belt and an outer water barrier belt from inside to outside, and the total thickness of the cable buffer layer is 3.0mm~3.5mm.

9. A cable, characterized by It comprises the cable buffer layer according to claim 8, and the aluminum sheath, the trough of the aluminum sheath is circular arc, and the pitch of the aluminum sheath is configured to form surface contact between the cable buffer layer and the aluminum sheath.

Images