Simulation method of high-voltage cable buffer layer repair effect based on graphite powder injection

Abstract

The present invention relates to a simulation method for the repair effect of a high-voltage cable buffer layer based on graphite powder injection. A three-dimensional simulation model of a 220KV high-voltage cable corrugated aluminum sheath is established according to the structure and parameters of the 220KV high-voltage cable corrugated aluminum sheath, and the required injection pressure and graphite powder particle size simulation setting parameters are brought into the established three-dimensional simulation model; according to the standard k-ε turbulence equation and the graphite powder force equation, a graphite powder diffusion control equation is established to obtain the graphite powder diffusion and adhesion effect under different injection pressures and different particle sizes. The present invention can evaluate the diffusion uniformity and diffusion distance of the graphite powder in the buffer layer after repair by simulating the diffusion process of the graphite powder in the actual cable buffer layer repair process, which is of great significance to the cable repair work, and can guide the injection process of the engineering site through simulation means to improve the repair effect.

Description

Technical Field

[0001] The invention belongs to the field of high voltage electricity technology, and in particular to a method for simulating the repair effect of a buffer layer of a high voltage cable based on graphite powder injection. Background Art

[0002] In the urban power supply system, the safe, reliable and reasonable operation of important high-voltage lines is crucial to ensure the safe production of the power grid. 110KV and 220KV high-voltage cables are important trunk lines of the urban power transmission network. Ensuring their safety and reliability has always been an important task for power production and operation units. Once the above lines fail, it will cause power outages, cause major economic losses, and cause social public order chaos, seriously affecting the safety and stability of the city. At present, there are common electrical performance defects in the buffer layer in the city's operating high-voltage cable lines. Under complex operating conditions, they may cause discharge, ablation and other phenomena, causing insulation shielding damage, and in severe cases, they may develop into breakdown failures. In order to eliminate the "stock" defect hazards of the buffer layer of the operating cable, researchers have proposed to improve the contact effect between the cable buffer layer and the aluminum sheath based on the injection of graphite powder, and improve the conductivity between the two to avoid the occurrence of cable buffer ablation failures. However, the technology for this repair method is not yet mature, and there is a lack of guidance for the selection of injection parameters including injection pressure and graphite powder particle size. At the same time, the diffusion law of graphite powder between the buffer layer and the aluminum sheath is still unclear. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a simulation method for the repair effect of a high-voltage cable buffer layer based on graphite powder injection. The method can evaluate the diffusion uniformity and diffusion distance of the graphite powder in the buffer layer after repair, which is of great significance to the cable repair work. At the same time, the injection process at the engineering site can be guided by simulation to improve the repair effect.

[0004] The present invention solves the technical problem by adopting the following technical solutions:

[0005] The simulation method of the repair effect of the buffer layer of a high-voltage cable based on graphite powder injection includes the following steps:

[0006] Step 1, establishing a three-dimensional simulation model of the 220KV high-voltage cable corrugated aluminum sheath according to the structure and parameters of the 220KV high-voltage cable corrugated aluminum sheath;

[0007] Step 2, setting injection pressure and graphite powder particle size simulation parameters;

[0008] Step 3: According to the standard k-ε turbulence equation and the graphite powder force equation, the graphite powder diffusion control equation is established, the simulation parameters set in step 2 are substituted into the volume diffusion control equation, and the three-dimensional model of step 1 is used as the calculation domain for iterative solution to obtain the graphite powder diffusion and adhesion effects under different injection pressures and different particle sizes.

[0009] Moreover, the structure and parameters of the corrugated aluminum sheath of the 220KV high-voltage cable in step 1 include: the corrugated aluminum sheath has a spiral structure, has a regular intercept and corrugation depth, its profile is a sinusoidal waveform when viewed from the axial section, the corrugation peak spacing is 3cm, and the corrugation depth is 5mm.

[0010] Moreover, the step 1 of establishing the three-dimensional simulation model of the corrugated aluminum sheath of the 220KV high-voltage cable comprises the following steps:

[0011] Step 1.1, draw the reference line of corrugation depth and total length of corrugated aluminum sheath;

[0012] Step 1.2, rotate the corrugation depth reference line around the total length reference line drawn on the corrugated aluminum sheath to form a spiral surface, and the rotation interval is 3 cm;

[0013] Step 1.3, obtain the parametric spiral line of the spiral surface in step 1.2, and draw a circle with a diameter of 102 mm at the starting point of the spiral line;

[0014] Step 1.4: Use the circle drawn in step 1.3 as the scanning entity of the spiral surface, draw the total length reference line of the corrugated aluminum sheath as the scanning direction, and use the parameterized spiral line of the surface as the scanning path to obtain a three-dimensional simulation model of the corrugated aluminum sheath model.

[0015] Moreover, the graphite powder diffusion control equation established in step 3 is divided into a continuous phase control equation and a discrete phase control equation.

[0016] Moreover, the continuous phase governing equation is:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022] Where ρ is the fluid density, u is the velocity, k is the turbulent kinetic energy, l is the characteristic length of the pipe, F is the volume force, g is the gravitational acceleration, ε is the turbulent dissipation rate, μ is the fluid dynamic viscosity, is the gradient operator symbol, u T is the turbulent dynamic viscosity, is the velocity gradient, σ k is the residual of turbulent kinetic energy variance, p k is the turbulent kinetic energy term, σ ε is the residual of the turbulence dissipation rate variance, is the turbulent dissipation rate gradient, C ε1 For and C ε2 is the linear source term coefficient of the equation.

[0023] Moreover, the discrete phase governing equation is:

[0024]

[0025]

[0026]

[0027]

[0028] Among them, m p is, v is, F d is the drag force between the particle and the fluid, F g is the gravitational force on the particle, F d It is related to the relative velocity between the particle phase and the fluid phase and the windward area of ​​the particles, m p is the mass of powder, u' is the velocity vector of graphite particles, τ p is the particle velocity response time, v represents the flow field velocity vector, d p Powder particle size, μ is the fluid dynamic viscosity, k is the turbulent kinetic energy, ξ is the uncorrelated unit variance Gaussian number vector, ρ p is the particle density.

[0029] Moreover, in step 3, the three-dimensional simulation model is used as the calculation domain and iterative solutions are performed based on the above equations to obtain the diffusion and adhesion effects of graphite powder in the calculation domain under different injection pressures and different particle sizes, including the following steps:

[0030] Step 3.1, importing the three-dimensional simulation model established in step 1 into the simulation software;

[0031] Step 3.2, setting the simulation parameters of the three-dimensional simulation model according to the pressure and parameters in step 2;

[0032] Step 3.3, select the turbulence k-ε module of the simulation software for the flow field velocity distribution calculation, and bring the calculation results into the fluid flow particle tracking module of the simulation software to calculate the motion trajectory of the split particles;

[0033] Step 3.4, setting the simulation boundary conditions of the three-dimensional simulation model;

[0034] Step 3.5, meshing the three-dimensional simulation model;

[0035] Step 3.6: The diffusion and adhesion effects of graphite powder under different injection pressures and different particle sizes are calculated by iteratively solving the three-dimensional simulation model.

[0036] The advantages and positive effects of the present invention are:

[0037] The present invention establishes a three-dimensional simulation model of a 220KV high-voltage cable corrugated aluminum sheath according to the structure and parameters of the 220KV high-voltage cable corrugated aluminum sheath, and brings the required injection pressure and graphite powder particle size simulation setting parameters into the established three-dimensional simulation model; according to the standard k-ε turbulence equation and the graphite powder force equation, a graphite powder diffusion control equation is established to obtain the graphite powder diffusion and adhesion effect under different injection pressures and different particle sizes. The present invention can evaluate the diffusion uniformity and diffusion distance of the graphite powder in the repaired buffer layer by simulating the diffusion process of the graphite powder in the actual cable buffer layer repair process, which is of great significance to the cable repair work, and can guide the injection process on the engineering site through simulation means to improve the repair effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of 220KV high voltage cable structure

[0039] Figure 2 A schematic diagram of a reference baseline of corrugation depth and total length of a corrugated aluminum sheath is drawn for the present invention;

[0040] Figure 3 Generate a helical surface schematic diagram for the present invention;

[0041] Figure 4 It is a schematic diagram of the parameterized spiral line of the spiral surface of the present invention;

[0042] Figure 5 A schematic diagram of a circle with a diameter of 102 mm drawn at the starting point of the parametric spiral line of the spiral surface of the present invention;

[0043] Figure 6 This is a schematic diagram of a three-dimensional simulation model of a corrugated aluminum sheath according to the present invention;

[0044] Figure 7 This is a schematic diagram of the simulation results of graphite powder diffusion during the cable repair process of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below with reference to the accompanying drawings.

[0046] The simulation method of the repair effect of the buffer layer of a high-voltage cable based on graphite powder injection includes the following steps:

[0047] Step 1: Establish a three-dimensional simulation model of the 220KV high-voltage cable corrugated aluminum sheath according to the structure and parameters of the 220KV high-voltage cable corrugated aluminum sheath.

[0048] like Figure 1 As shown, the structure and parameters of the corrugated aluminum sheath of the 220KV high-voltage cable include: the corrugated aluminum sheath is a spiral structure with regular intercept and corrugation depth. Its profile is a sine wave when viewed from the axial section, the corrugation peak spacing is 3cm, and the corrugation depth is 5mm.

[0049] like Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown in the figure, establishing a 3D simulation model of a 220KV high voltage cable corrugated aluminum sheath includes the following steps:

[0050] Step 1.1, draw the reference line of corrugation depth and total length of corrugated aluminum sheath;

[0051] Step 1.2, rotate the corrugation depth reference line around the total length reference line drawn on the corrugated aluminum sheath to form a spiral surface, and the rotation interval is 3 cm to represent the corrugation pitch of the corrugated aluminum sheath;

[0052] Step 1.3, obtain the parametric spiral line of the spiral surface in step 1.2, and draw a circle with a diameter of 102 mm at the starting point of the spiral line, which represents the inner wall of the longitudinal section of the aluminum sheath wrinkle;

[0053] Step 1.4: Use the circle drawn in step 1.3 as the scanning entity of the spiral surface, draw the total length reference line of the corrugated aluminum sheath as the scanning direction, and use the parameterized spiral line of the surface as the scanning path to obtain a three-dimensional simulation model of the corrugated aluminum sheath model.

[0054] Step 2: Set the injection pressure and graphite powder particle size simulation parameters.

[0055] Step 3: According to the standard k-ε turbulence equation and the graphite powder force equation, the graphite powder diffusion control equation is established, the simulation parameters set in step 2 are substituted into the volume diffusion control equation, and the three-dimensional model of step 1 is used as the calculation domain for iterative solution to obtain the graphite powder diffusion and adhesion effects under different injection pressures and different particle sizes.

[0056] The established graphite powder diffusion control equation is divided into the continuous phase (fluid) control equation and the discrete phase (graphite powder) control equation. Among them, the continuous phase control equation is:

[0057]

[0058]

[0059]

[0060]

[0061]

[0062] Where ρ is the fluid density, u is the velocity, k is the turbulent kinetic energy, l is the characteristic length of the pipe, F is the volume force, g is the gravitational acceleration, ε is the turbulent dissipation rate, μ is the fluid dynamic viscosity, is the gradient operator symbol, μ T is the turbulent dynamic viscosity, is the velocity gradient, σ k is the residual of turbulent kinetic energy variance, p k is the turbulent kinetic energy term, σ ε is the residual of the turbulence dissipation rate variance, is the turbulent dissipation rate gradient, C ε1 For and C ε2 is the linear source term coefficient of the equation.

[0063] The discrete phase governing equation is:

[0064]

[0065]

[0066]

[0067]

[0068] Among them, m p is, v is, F d is the drag force between the particle and the fluid, F g is the gravitational force on the particle, F d It is related to the relative velocity between the particle phase and the fluid phase and the windward area of ​​the particles, m p is the mass of powder, u' is the velocity vector of graphite particles, τ p is the particle velocity response time, v represents the flow field velocity vector, d p Powder particle size, μ is the fluid dynamic viscosity, k is the turbulent kinetic energy, ξ is the uncorrelated unit variance Gaussian number vector, ρ p is the particle density.

[0069] The three-dimensional simulation model is used as the calculation domain and iteratively solved based on the above equation to obtain the diffusion and adhesion effect of graphite powder in the calculation domain under different injection pressures and different particle sizes, including the following steps:

[0070] Step 3.1, importing the three-dimensional simulation model established in step 1 into the simulation software;

[0071] Step 3.2, setting the simulation parameters of the three-dimensional simulation model according to the pressure and parameters in step 2;

[0072] Step 3.3, select the turbulence k-ε module of the simulation software for the flow field velocity distribution calculation, and bring the calculation results into the fluid flow particle tracking module of the simulation software to calculate the motion trajectory of the split particles;

[0073] Step 3.4, setting the simulation boundary conditions of the three-dimensional simulation model;

[0074] Step 3.5, meshing the three-dimensional simulation model;

[0075] Step 3.6: The diffusion and adhesion effects of graphite powder under different injection pressures and different particle sizes are calculated by iteratively solving the three-dimensional simulation model.

[0076] like Figure 7 As shown, a schematic diagram of the simulation results of graphite powder diffusion during cable repair is obtained. By simulating the diffusion process of graphite powder during the actual cable buffer layer repair process, the diffusion uniformity and diffusion distance of the graphite powder in the buffer layer after repair can be evaluated, which is of great significance for guiding the cable repair work.

[0077] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. A simulation method for repairing the buffer layer of a high-voltage cable based on graphite powder injection, characterized in that: The following steps are involved: Step 1, establishing a three-dimensional simulation model of the 220KV high-voltage cable corrugated aluminum sheath according to the structure and parameters of the 220KV high-voltage cable corrugated aluminum sheath; Step 2, setting injection pressure and graphite powder particle size simulation parameters; Step 3: According to the standard k-ε turbulence equation and the graphite powder force equation, the graphite powder diffusion control equation is established, the simulation parameters set in step 2 are brought into the volume diffusion control equation, and the three-dimensional model of step 1 is used as the calculation domain for iterative solution to obtain the graphite powder diffusion and adhesion effects under different injection pressures and different particle sizes; The established graphite powder diffusion control equation is divided into continuous phase control equation and discrete phase control equation; The continuous phase governing equation is: Where ρ is the fluid density, u is the velocity, k is the turbulent kinetic energy, l is the characteristic length of the pipe, F is the volume force, g is the gravitational acceleration, ε is the turbulent dissipation rate, μ is the fluid dynamic viscosity, is the gradient operator symbol, u T is the turbulent dynamic viscosity, is the velocity gradient, σ k is the residual of turbulent kinetic energy variance, p k is the turbulent kinetic energy term, σ ε is the residual of the turbulence dissipation rate variance, is the turbulent dissipation rate gradient, C ε1 For and C ε2 is the linear source term coefficient of the equation; The discrete phase governing equation is: Among them, F d is the drag force between the particle and the fluid, F g is the gravitational force on the particle, F d It is related to the relative velocity between the particle phase and the fluid phase and the windward area of ​​the particles, m p is the mass of the powder, u' is the velocity vector of the graphite particles, τ p is the particle velocity response time, v represents the flow field velocity vector, d p Powder particle size, μ is the fluid dynamic viscosity, k is the turbulent kinetic energy, ξ is the uncorrelated unit variance Gaussian number vector, ρ p is the particle density.

2. The method for simulating the repair effect of a high-voltage cable buffer layer based on graphite powder injection according to claim 1 is characterized in that: The structure and parameters of the corrugated aluminum sheath of the 220KV high-voltage cable in step 1 include: the corrugated aluminum sheath is a spiral structure with regular intercept and corrugation depth, its profile is a sine wave when viewed from the axial section, the corrugation peak spacing is 3cm, and the corrugation depth is 5mm.

3. The method for simulating the repair effect of a high-voltage cable buffer layer based on graphite powder injection according to claim 1 or 2, characterized in that: The step 1 of establishing a 3D simulation model of a 220KV high voltage cable corrugated aluminum sheath comprises the following steps: Step 1.1, draw the reference line of corrugation depth and total length of corrugated aluminum sheath; Step 1.2, rotate the corrugation depth reference line around the total length reference line drawn on the corrugated aluminum sheath to form a spiral surface, and the rotation interval is 3 cm; Step 1.3, obtain the parametric spiral line of the spiral surface in step 1.2, and draw a circle with a diameter of 102 mm at the starting point of the spiral line; Step 1.4: Use the circle drawn in step 1.3 as the scanning entity of the spiral surface, draw the total length reference line of the corrugated aluminum sheath as the scanning direction, and use the parameterized spiral line of the surface as the scanning path to obtain a three-dimensional simulation model of the corrugated aluminum sheath model.

4. The method for simulating the repair effect of a high-voltage cable buffer layer based on graphite powder injection according to claim 1 is characterized in that: In step 3, the three-dimensional simulation model is used as the calculation domain and iterative solutions are performed based on the above equations to obtain the diffusion and adhesion effects of graphite powder in the calculation domain under different injection pressures and different particle sizes, including the following steps: Step 3.1, importing the three-dimensional simulation model established in step 1 into the simulation software; Step 3.2, setting the simulation parameters of the three-dimensional simulation model according to the pressure and parameters in step 2; Step 3.3, select the turbulence k-ε module of the simulation software for the flow field velocity distribution calculation, and bring the calculation results into the fluid flow particle tracking module of the simulation software to calculate the motion trajectory of the split particles; Step 3.4, setting the simulation boundary conditions of the three-dimensional simulation model; Step 3.5, meshing the three-dimensional simulation model; Step 3.6: The diffusion and adhesion effects of graphite powder under different injection pressures and different particle sizes are calculated by iteratively solving the three-dimensional simulation model.

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