Insulator surface dirt adhesion process modeling method and device based on electrothermal coupling characteristics

Abstract

The invention discloses an insulator surface dirt adhesion process modeling method and device based on electrothermal coupling characteristics. The modeling method comprises the following steps: giving the height, the radius, the number of umbrella skirts and the radius of the umbrella skirts of an insulator body, and giving the voltage grade of the insulator; determining boundary conditions of electric field calculation, and calculating electric field distribution around the insulator; determining the wind speed of the area where the insulator is located, and calculating the air flow field distribution around the insulator; calculating the motion characteristics of the dirt particles according to the air velocity; calculating the leakage current density of the surface of the insulator through the electric field distribution characteristics, and calculating the temperature distribution of the surface of the insulator; calculating the water content of the surface of the insulator according to the temperature distribution of the surface of the insulator; and calculating the adhesion characteristics of the dirt particles according to the insulator surface water content. Factors of an electric field, leakage current, a temperature field and the surface water content of the insulator are introduced, and the gradual evaporation process of a water film on the surface of the insulator, the non-uniform distribution phenomenon of the water film and the influence of electric heating coupling on the surface of the insulator on the adhesion effect of dirt particles are considered.

Description

Technical Field

[0001] The present invention relates to a method and device for modeling the contamination adhesion process on the surface of an insulator based on electrothermal coupling characteristics, belonging to the technical field of analyzing the contamination deposition characteristics of insulators under contaminated conditions. The calculation method is applicable to a three-dimensional model of the complete insulator shape. Background Art

[0002] Insulators are critical components of power transmission systems, providing insulation and support for transmission lines. In polluted environments, contaminants gradually adhere to the insulator surface, increasing the probability of insulator flashover or breakdown, threatening the stable operation of the power system. Contaminants exhibit varying adhesion characteristics at different locations on the insulator surface, leading to uneven contamination accumulation and, ultimately, varying failure probabilities at different locations. The adhesion characteristics of contaminants are related to the moisture content, electric field distribution, temperature field distribution, and air flow field distribution on the insulator surface. Measuring the contamination characteristics on the insulator surface requires calculating these physical fields and the moisture content on the insulator surface. In engineering practice, measuring the contamination characteristics on the insulator surface under polluted conditions is crucial for detecting and predicting insulator failures, helping to determine insulator cleaning strategies and prioritize cleaning areas prone to contamination. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem of measuring the contamination accumulation characteristics of the insulator surface under contaminated conditions described in the background technology part, and proposes a method and device for modeling the contamination adhesion process on the insulator surface based on electrothermal coupling characteristics.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] A modeling method for the contamination adhesion process on the insulator surface based on electrothermal coupling characteristics includes the following steps:

[0006] S1: Given the height and radius of the insulator body, the number of sheds and the shed radius of the insulator, and the voltage level of the insulator;

[0007] S2: Determine the boundary conditions of the electric field and calculate the electric field distribution around the insulator based on the boundary conditions of the electric field;

[0008] S3: Determine the wind speed in the area where the insulator is located and calculate the air flow field distribution around the insulator;

[0009] S4: Calculate the motion characteristics of the dirt particles based on the air flow rate;

[0010] S5: Calculate the leakage current density on the insulator surface based on the electric field distribution characteristics, and calculate the temperature distribution on the insulator surface;

[0011] S6: Calculate the water content on the insulator surface based on the temperature distribution on the insulator surface;

[0012] S7: Calculate the adhesion characteristics of contaminant particles based on the moisture content on the insulator surface.

[0013] Furthermore, the boundary conditions for the electric field calculation in step S2 are specifically in the following form:

[0014] (1) The electric potential at infinity is zero boundary condition

[0015]

[0016] (2) The potential of the insulator high-voltage electrode and the grounding electrode are known.

[0017]

[0018] Where, is the potential of the high voltage electrode, Γ HV and Γ GND They are the surfaces of the insulator high voltage electrode and the grounding electrode respectively.

[0019] The electric field distribution around the insulator is calculated using the Laplace equation, which is expressed as follows:

[0020]

[0021] Where, is the electric potential, ε is the dielectric constant, is the electric field intensity, and grad is the gradient operator.

[0022] Furthermore, the wind speed in the area where the insulator is located in step S3 is defined as the wind speed at infinity:

[0023] u i (x,y,z)| ∞ =v 0.i (6)

[0024] Where, v 0.i is the velocity component of the wind speed in the area where the insulator is located.

[0025] The air flow field is described by the turbulence equation, which is in the following form:

[0026]

[0027] Where ρ is the air density, k is the turbulent kinetic energy, t is the time, and ε TD is the turbulent dissipation rate, μ is the viscosity coefficient, μ t is the turbulent viscosity, σ k is the Prandtl number of turbulent kinetic energy, G k is the turbulent energy term, σk is the Prandtl number of turbulent dissipation rate; x i is the spatial position (i=1, 2, 3, representing the X, Y, and Z axis directions respectively), u i is the velocity component. C 1ε is the turbulent kinetic energy correction coefficient, C 2ε is the turbulence dissipation correction factor, C μ is the turbulent viscosity correction factor.

[0028] Furthermore, the motion characteristics of the pollution particles in step S4 are described by the kinetic equation of particle motion, which is specifically described as follows:

[0029]

[0030]

[0031] Where m p is the mass of the particle, v p is the particle velocity, F g and F f are the gravity and air flow drag on the particles, g is the acceleration due to gravity, and ρ is the p and ρ are the densities of the particle and air, respectively, and d is the particle diameter.

[0032] Furthermore, the specific calculation method of the leakage current density on the insulator surface in step S5 is as follows:

[0033] J=γE (13)

[0034] Where J is the leakage current density and γ is the conductivity of the insulator surface.

[0035] Furthermore, in step S5, the temperature distribution on the surface of the insulator is calculated using the heat conduction equation, which is specifically expressed as follows:

[0036]

[0037] Φ=JE (15)

[0038] Where T is temperature, t is time, ρ is density, c is specific heat, λ is thermal conductivity, and Φ is the heat source.

[0039] Furthermore, the water content of the insulator is calculated according to the temperature distribution on the surface of the insulator in step S6, specifically in the following form:

[0040]

[0041] Where, σ RHis the mass of water per unit area on the insulator surface, M is the molar mass of water, ΔH is the phase change enthalpy of water from liquid to gas, R is the universal gas constant, and T0 is the ambient temperature.

[0042] Furthermore, the adhesion characteristics of the dirt particles in step S7 are specifically as follows:

[0043] The criteria for determining whether dirt particles can adhere to the surface of the insulator are:

[0044]

[0045] Where, is the reduced mass of the pollution particle, m p is the mass of the dirt particle, v' is the incident velocity, ΔE h1 is the kinetic energy loss of the particles when they first contact the insulator surface, ΔE h2 is the kinetic energy loss due to viscous dissipation.

[0046] A device for modeling the contamination adhesion process on an insulator surface based on electrothermal coupling characteristics, comprising: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, the instructions being used for the processor to execute any of the aforementioned methods for modeling the contamination adhesion process on an insulator surface based on electrothermal coupling characteristics.

[0047] This paper uses electrothermal coupling to calculate the contamination adhesion characteristics of insulators under contaminated conditions. By calculating the electric field distribution on the insulator, the leakage current density at different locations on the insulator surface is derived. Based on the thermal effect of the leakage current, the surface temperature distribution and water film evaporation rate are calculated, which in turn provides the water content at different locations on the insulator surface. This allows the adhesion characteristics of contaminant particles to be calculated at these locations.

[0048] Compared with the calculation method of the existing technology which mainly considers the influence of the air flow field on the adhesion of dirt particles, the present invention introduces the factors of electric field, leakage current, temperature field and moisture content on the insulator surface, and takes into account the gradual evaporation process of the water film on the insulator surface and the uneven distribution of the water film, thereby better judging the influence of the electrothermal coupling of the insulator surface on the adhesion of dirt particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a flow chart of the modeling method;

[0050] Figure 2 Schematic diagram of the calculation area; the figure includes a cube-shaped calculation area-100, an insulator and its electrode-200, a calculation area boundary-101, and the insulator and its electrode parts include an insulator body-201, a high-voltage electrode-202, and a grounding electrode-203.

[0051] Figure 3 Schematic diagram of insulator size parameters; size parameters include insulator body height h insul , insulator radius r insul , skirt radius r shed 、Number of sheds n shed .

[0052] Figure 4 Schematic diagram of electric field boundary conditions.

[0053] Figure 5 Schematic diagram of wind speed in the air flow field; the figure includes an air inflow boundary 101a and an air outflow boundary 101b.

[0054] Figure 6 Schematic diagram of the contamination particle adhesion process; the figure includes the insulator surface 201a, the water film 300, and the contamination particle 400. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further introduced below in conjunction with specific implementation methods.

[0056] The overall technical solution of the present invention is as follows: first, a calculation model of the electric field and air flow field in the area around the insulator is established; then, the electric field calculation model is used to calculate the electric field distribution; the air flow velocity in the area near the insulator is calculated using the air flow field model; the movement characteristics of the contamination particles are calculated using the air flow velocity; the leakage current of the insulator is calculated using the electric field distribution, and the temperature distribution on the insulator surface is calculated; the moisture content on the insulator surface is calculated using the temperature distribution on the insulator surface; finally, the adhesion characteristics of the contamination particles are calculated based on the movement characteristics of the contamination particles and the moisture content on the insulator surface.

[0057] like Figure 2 As shown, the computational region surrounding the insulator and its electrode 200 is a finite-volume cubic space 100, with the insulator and electrode positioned at the center of the computational region. The computational region is set to a finite-volume space because, when using finite element software to calculate electric or flow field distributions, the software cannot directly handle field calculations in infinite space. Therefore, the space must be truncated, and the computational region is set to a cubic space.

[0058] The modeling of the contamination adhesion process on the insulator surface includes calculating the electric field, air flow field and temperature field in the calculation area where the insulator is located, such as Figure 1 The specific steps are as follows:

[0059] S1: Given the insulator size parameters, the voltage level of the insulator is given.

[0060] Insulator size parameters such as Figure 3As shown, including the height h of the body insul and radius r insul , given the number of sheds n of the insulator shed and skirt radius r shed .

[0061] S2: Determine the boundary conditions for electric field calculation and calculate the electric field distribution around the insulator.

[0062] like Figure 4 As shown, the boundary conditions include:

[0063] (1) The electric potential at infinity is zero boundary condition

[0064]

[0065] However, when using finite element calculation software to calculate the electric field distribution, the software cannot handle the boundary conditions at infinity. Therefore, the boundary conditions at infinity are approximated and the boundary potential 101 of the calculation area is set to 0.

[0066] (2) The potentials of the insulator high-voltage electrode 202 and the ground electrode 203 are known.

[0067]

[0068] Where, is the potential of the high voltage electrode, The value of is equal to the voltage level of the insulator in step S1, Γ HV and Γ GND They are the surfaces of the insulator high voltage electrode and the grounding electrode respectively.

[0069] The electric field is calculated using Laplace's equation:

[0070]

[0071] Where, is the electric potential, ε is the dielectric constant, is the electric field intensity, and grad is the gradient operator.

[0072] S3: Determine the wind speed in the area where the insulator is located and calculate the air flow field distribution around the insulator.

[0073] Wind speed and direction Figure 5 Theoretically, the wind speed in the area where the insulator is located is the wind speed at infinity:

[0074] u i (x,y,z)| ∞ =v 0.i (6)

[0075] Where, v 0.iis the velocity component of the wind speed in the insulator area. However, the finite element software cannot handle the boundary conditions at infinity, so Figure 5 The approximate air velocity boundary conditions are shown: two opposite boundary surfaces of the calculation area are selected as the air inlet boundary 101a and the air outlet boundary 101b, respectively. The wind speed on these two boundaries is perpendicular to the boundary surface itself, and the flow velocity is v0.

[0076] The air flow field is described by the turbulence equations, including the ε equation and the k equation. The k equation is:

[0077]

[0078] The ε equation is:

[0079]

[0080] μ t Calculated as:

[0081]

[0082] Where ρ is the air density, k is the turbulent kinetic energy, t is the time, and ε TD is the turbulent dissipation rate, μ is the viscosity coefficient, μ t is the turbulent viscosity, σ k is the Prandtl number of turbulent kinetic energy, G k is the turbulent energy term, σ k is the Prandtl number of turbulent dissipation rate; x i is the spatial position, u i is the velocity component. C 1ε is the turbulent kinetic energy correction coefficient, C 2ε is the turbulence dissipation correction factor, C μ are the turbulent viscosity correction coefficients. These three correction coefficients are empirical coefficients, and their values are 1.42, 1.68, and 0.09 respectively based on experimental experience.

[0083] S4: Calculate the motion characteristics of the dirt particles based on the air flow rate.

[0084] The motion characteristics of the dirt particles are described by the kinetic equation of their particle motion:

[0085]

[0086] Where m p is the mass of the particle, v p is the particle velocity, F g and F f are the gravity and air drag on the particles respectively. g and F f They are

[0087]

[0088] Where m p is the mass of the particle, v is the particle velocity, F g and F f are the gravity and air flow drag on the particles, g is the acceleration due to gravity, and ρ is the p and ρ are the densities of the particle and air, respectively, and d is the particle diameter.

[0089] S5: Calculate the leakage current density on the insulator surface based on the electric field distribution characteristics, and calculate the temperature distribution on the insulator surface.

[0090] J=γE (13)

[0091] Where J is the leakage current density and γ is the conductivity of the insulator surface. Leakage current on the insulator surface generates Joule heating, causing the insulator surface temperature to rise. The temperature distribution on the insulator surface is calculated using the heat conduction equation, as follows:

[0092]

[0093] Φ=JE (15)

[0094] Where T is temperature, t is time, ρ is density, c is specific heat capacity, λ is thermal conductivity, and Φ is the Joule heat power per unit volume of leakage current.

[0095] S6: Calculate the water content on the insulator surface based on the temperature distribution on the insulator surface.

[0096] The moisture on the surface of the insulator gradually evaporates due to leakage current, and the change in moisture content over time is:

[0097]

[0098] Where, σ RH is the mass of water per unit area on the insulator surface, M is the molar mass of water, ΔH is the phase change enthalpy of water from liquid to gas, R is the universal gas constant, and T0 is the ambient temperature.

[0099] S7: Calculate the adhesion characteristics of contaminant particles based on the moisture content on the insulator surface.

[0100] like Figure 6 As shown, the dirt particle 400 collides with the insulator surface 201a containing the water film 300 at a speed of v'. The conditions for determining whether the dirt particle can adhere to the insulator surface are:

[0101]

[0102] Where, is the reduced mass of the pollution particle, m p is the mass of the dirt particle, v' is the incident velocity, ΔE h1 is the kinetic energy loss of the particles when they first contact the insulator surface, ΔE h2 is the kinetic energy loss due to viscous dissipation.

[0103] if The dirt particles will not adhere to the surface of the insulator, but will rebound at a speed of v":

[0104]

[0105] ΔE h1 for:

[0106]

[0107] Where Δv h1 is the velocity of the particles colliding with the insulator surface, E s is the surface energy, r is the particle radius, E p0 is the initial kinetic energy of the particle at the time of incidence.

[0108] ΔE h2 for:

[0109]

[0110] α=1.2728-4.2783e+11.087e 2 (27)

[0111] Where, δ gap is the minimum contact distance between the particle and the surface, a is the contact surface radius, α is the dissipation coefficient, and e is the restitution coefficient.

[0112] According to another aspect of the present invention, there is also provided a device for modeling the contamination adhesion process on the surface of an insulator based on electrothermal coupling characteristics, comprising: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement the aforementioned method for modeling the contamination adhesion process on the surface of an insulator based on electrothermal coupling characteristics.

[0113] In addition to the above embodiments, the present invention may also have other implementation methods. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A modeling method for the contamination adhesion process on the insulator surface based on electrothermal coupling characteristics, characterized in that: The following steps are involved: S1: Given the height and radius of the insulator body, the number of sheds and the shed radius of the insulator, and the voltage level of the insulator; S2: Determine the boundary conditions of the electric field and calculate the electric field distribution around the insulator based on the boundary conditions of the electric field; S3: Determine the wind speed in the area where the insulator is located and calculate the air flow field distribution around the insulator; S4: Calculate the motion characteristics of the dirt particles based on the air flow rate; S5: Calculate the leakage current density on the insulator surface based on the electric field distribution characteristics, calculate the heating power on the insulator surface based on the leakage current density, and calculate the temperature distribution on the insulator surface; S6: Calculate the water content on the insulator surface based on the temperature distribution on the insulator surface; S7: Calculate the adhesion characteristics of contaminant particles based on the moisture content on the insulator surface.

2. The method for modeling the contamination adhesion process on the insulator surface based on the electrothermal coupling characteristics according to claim 1 is characterized in that: In step S2, the boundary conditions for electric field calculation are as follows: (1) The electric potential at infinity is zero boundary condition (2) The potential of the insulator high-voltage electrode and the grounding electrode are known. Where, is the potential of the high voltage electrode, Γ HV and Γ GND They are the surfaces of the insulator high voltage electrode and the grounding electrode respectively; The method for calculating the electric field distribution using the Laplace equation is as follows: Where, is the electric potential, ε is the dielectric constant, is the electric field intensity, x, y, z are the coordinates in three-dimensional space, and grad is the gradient operator.

3. The method for modeling the contamination adhesion process on the insulator surface based on the electrothermal coupling characteristics according to claim 1 is characterized in that: In step S3, the wind speed in the area where the insulator is located is defined as the wind speed at infinity: u i (x,y,z)| ∞ =v 0.i (6) Where, v 0.i is the velocity component of the wind speed in the area where the insulator is located; The air flow field is described by the turbulence equation, which is in the following form: Where ρ is the air density, k is the turbulent kinetic energy, t is the time, and ε TD is the turbulent dissipation rate, μ is the viscosity coefficient, μ t is the turbulent viscosity, σ k is the Prandtl number of turbulent kinetic energy, G k is the turbulent energy term, σ k is the Prandtl number of turbulent dissipation rate; x i is the spatial position, u i is the velocity component, C 1ε is the turbulent kinetic energy correction coefficient, C 2ε is the turbulence dissipation correction factor, C μ is the turbulent viscosity correction factor.

4. The method for modeling the contamination adhesion process on the insulator surface based on the electrothermal coupling characteristics according to claim 1 is characterized in that: In step S4, the motion characteristics of the dirt particles are described by the kinetic equation of their particle motion, which is specifically described as follows: Where m p is the mass of the particle, v p is the particle velocity, F g and F f are the gravity and air flow drag on the particles, g is the acceleration due to gravity, and ρ is the p and ρ are the densities of the particle and air, respectively, and d is the particle diameter.

5. The method for modeling the contamination adhesion process on the insulator surface based on the electrothermal coupling characteristics according to claim 1 is characterized in that: In step S5, the calculation method of the leakage current density on the insulator surface is as follows: J=γE (13) Where J is the leakage current density and γ is the conductivity of the insulator surface.

6. The method for modeling the contamination adhesion process on the insulator surface based on electrothermal coupling characteristics according to claim 1 is characterized in that: In step S5, the temperature distribution on the surface of the insulator is calculated using the heat conduction equation, which is specifically in the following form: Φ=JE (15) Where T is temperature, t is time, ρ is density, c is specific heat, λ is thermal conductivity, and Φ is the heat source.

7. The method for modeling the contamination adhesion process on the insulator surface based on electrothermal coupling characteristics according to claim 1 is characterized in that: In step S6, the moisture content of the insulator is calculated based on the temperature distribution on the surface of the insulator. The specific form is as follows: Where σ RH is the mass of water per unit area on the insulator surface, M is the molar mass of water, ΔH is the phase change enthalpy of water from liquid to gas, R is the universal gas constant, and T0 is the ambient temperature.

8. The method for modeling the contamination adhesion process on the insulator surface based on electrothermal coupling characteristics according to claim 1 is characterized by: In step S7, the specific form of the adhesion characteristics of the dirt particles is as follows: The criteria for determining whether dirt particles can adhere to the surface of the insulator are: Where, is the reduced mass of the pollution particle, m p is the mass of the dirt particle, v' is the incident velocity, ΔE h1 is the kinetic energy loss of the particles when they first contact the insulator surface, ΔE h2 is the kinetic energy loss due to viscous dissipation.

9. A device for modeling the contamination adhesion process on the surface of an insulator based on electrothermal coupling characteristics, characterized in that: include: at least one processor; And, a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement the method for modeling the contamination adhesion process on the surface of an insulator based on the electrothermal coupling characteristics as described in any one of claims 1 to 8.

Images