Analysis method of electric field distribution of 10kV overhead insulated conductor at different swing positions

Abstract

The present invention relates to a method for analyzing the electric field distribution of a 10kV overhead insulated conductor at different swinging positions. By determining the position and electrical load of the overhead insulated conductor, a simulation model of the 10kV overhead insulated conductor is established, and the constructed simulation model is meshed and solved. The solved data is processed to obtain the electric field distribution of the insulated conductor when it is at different swinging positions. The present invention couples the structure of the insulated conductor with the electric field, so when analyzing the electric field distribution of conductors at different positions, there is no need to modify the model, and it is more consistent with reality. At the same time, the present invention uses finite element simulation to analyze the electric field distribution at the connection between the 10kV overhead insulated conductor and the support insulator, and obtains the electric field distribution cloud map and the electric field vector distribution cloud map on the surface and inside of the insulated conductor at the connection, which provides theoretical support for the analysis of the galloping fault mechanism of the 10kV overhead insulated conductor.

Description

Technical Field

[0001] The invention belongs to the technical field of power distribution analysis, in particular to a method for analyzing electric field distribution at different swing positions of a 10kV overhead insulated conductor. Background Art

[0002] 10kV distribution network overhead line is one of the core components of the distribution network and an important part of the entire power system. In recent years, the dancing of 10kV overhead lines has occurred in areas including Tianjin, Hebei, Jilin, etc., which has brought challenges to the safe and reliable operation of the distribution network. In the past, people's attention to the dancing of overhead lines was mainly focused on lines with voltage levels of 110kV and above, but with the continuous improvement of people's requirements for quality of life, this has put forward high requirements for the safe and stable operation of distribution network lines. It is crucial to minimize or even avoid the occurrence of fault accidents.

[0003] In order to improve the safety and reliability of operation, the country has transformed the 10kV distribution network overhead lines, and the insulated conductors have gradually eliminated the traditional bare conductors, which to a certain extent avoids insulation failures caused by conductor dancing. However, under the action of mechanical and electric fields, the insulation layer will still be damaged, causing insulation failure of the conductor. According to the investigation results of actual fault conditions, it is found that insulation damage is prone to occur at the connection between the conductor and the insulator, so it is necessary to study the electric field distribution here.

[0004] The study of electric field distribution of transmission lines uses numerical simulation methods, such as simulated charge method, finite element method and mathematical model method. The core of the simulated charge method is to replace the continuously distributed charge with a finite number of discrete charges outside the field, and use the superposition theorem to calculate the electric field strength and distribution; the mathematical model method is to establish a nonlinear mathematical model of the conductor electric field through formula derivation to analyze the electric field situation; the finite element method mainly uses various finite element software to analyze the electric field distribution of the conductor.

[0005] Traditional analysis of the electric field of wires is mainly focused on the impact of bare wires on surrounding hardware or the environment, rather than the analysis of the wire itself. At the same time, few people are interested in studying the electric field distribution of wires as their positions change during dancing. This requires that the analysis of the electric field during the dancing of wires should not only be an electric field analysis, but also a coupling analysis of the structure and the electric field. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art, and propose an electric field distribution analysis method for different swinging positions of 10kV overhead insulated conductors. On the basis of analyzing the conductor dancing process, different positions of the conductor are determined, and the electrical load of the conductor is determined according to the actual operating conditions. A conductive insulator model is established at a 1:1 ratio, and the electric field distribution at the connection between the conductor and the insulator when the conductor is in different swinging positions is analyzed. It is helpful to grasp the electric field change characteristics of 10kV overhead insulated conductors when they are dancing, and has a general reference value and theoretical significance for in-depth research on fault accidents of 10kV overhead insulated conductors.

[0007] The present invention solves the technical problem by adopting the following technical solutions:

[0008] The electric field distribution analysis method of 10kV overhead insulated conductor at different swing positions includes the following steps:

[0009] Step 1: Determine the location and electrical load of the overhead insulated conductor;

[0010] Step 2: Establish a 10kV overhead insulated conductor simulation model according to the position and electrical load of the overhead insulated conductor;

[0011] Step 3: Mesh the constructed simulation model;

[0012] Step 4, solving the simulation model after meshing;

[0013] Step 5: Process the solved results to obtain the variation law of the electric field strength at different swinging positions of the wire.

[0014] Moreover, the specific implementation method for determining the position of the overhead insulated conductor in step 1 is: determining the angle between the center of the conductor after swinging and the center of the conductor in the original position and the angle between the line connecting the center of the conductor cross section after swinging and the center of the conductor in the original position and the vertical direction.

[0015] Moreover, the angle between the center of the swung conductor and the center of the original conductor is in the range of 0-90°, and the angle between the line connecting the center of the cross section of the swung conductor and the center of the original conductor and the vertical direction is in the range of 0-180°.

[0016] Moreover, the electrical load of the overhead insulated conductor in step 1 is the maximum value U of the single-phase line operating voltage. m :

[0017]

[0018] Among them, the maximum allowable operating voltage of 10kV lines in the power system is 11kV.

[0019] Moreover, the specific implementation method of step 2 is:

[0020] The overhead insulated conductor is equivalent to a finite length line charge, and the electric field strength E(x′) at the right side x' is calculated as:

[0021]

[0022] Will Substituting cosθ=x' / R into the electric field strength E(x'), we get:

[0023]

[0024] Where y' is half of the charge of the finite length line, ε is the dielectric constant, and e x is the unit vector along the x-axis direction, R is the distance between any charge element dq on the wire and point A, θ is the angle between the partial electric field direction and the total electric field direction, and a three-dimensional simulation model is established for the wire of the post insulator part at a ratio of 1:1. The wire and the post insulator are connected by contact.

[0025] Moreover, the specific implementation method of step 3 is: the support insulator model of the overhead insulated conductor is divided by using a large grid, and the rest is divided by using a small grid.

[0026] Furthermore, the step 4 includes a structure solution and an electric field solution.

[0027] Moreover, the specific implementation method of the structural solution is: by applying a physical load to the wire in Static Structural, the wire is displaced, and the result of this part is used as the initial condition for solving the next part.

[0028] Moreover, the specific implementation method of the electric field solution is: the electric field is equivalent to an electrostatic field or an electric quasistatic field:

[0029]

[0030]

[0031]

[0032]

[0033] Among them, D = εE in an isotropic linear dielectric, D is the electric flux density, also known as electric displacement; S represents an arbitrary closed surface in an infinite vacuum electrostatic field; V is the volume defined by the surface S; ρ is the polarization charge density in the dielectric; E is the electric field intensity; l represents a closed path in the electrostatic field; ▽ represents the gradient operator; ε represents the dielectric constant;

[0034] For a uniform dielectric, the electric field distribution satisfies the potential Poisson's equation:

[0035]

[0036] When the free charge density is 0, the electric field distribution satisfies the potential Laplace equation for:

[0037]

[0038] in, is the Laplace operator, is the potential, and The methods for determining the given boundary conditions are Dirichlet conditions and Neumann conditions.

[0039] Moreover, the specific implementation method of step 5 is: after the calculation is completed, the electric field distribution cloud map and the electric field vector distribution cloud map at the connection between the insulated conductor and the support insulator are obtained, the model is cut to obtain the electric field distribution cloud map and the electric field vector distribution cloud map inside the conductor insulation layer, and a specific point in the model is selected to obtain a specific electric field strength value and then obtain the change law of the electric field strength when the conductor is in different positions.

[0040] The advantages and positive effects of the present invention are:

[0041] 1. The present invention determines the position and electrical load of the overhead insulated conductor, establishes a 10kV overhead insulated conductor simulation model, meshes and solves the constructed simulation model, and processes the solved data to obtain the electric field distribution when the insulated conductor is at different swing positions. The present invention couples the structure of the insulated conductor with the electric field, so when analyzing the electric field distribution of conductors at different positions, there is no need to modify the model, and it is more consistent with reality.

[0042] 2. The present invention uses finite element simulation to analyze the electric field distribution at the connection between the 10kV overhead insulated conductor and the support insulator, and obtains the electric field distribution cloud map and electric field vector distribution cloud map on the surface and inside of the insulated conductor at the connection, which provides theoretical support for the analysis of the galloping fault mechanism of the 10kV overhead insulated conductor.

[0043] 3. The present invention uses Static Structural-Electric to build a model and apply loads, effectively avoiding the problem of difficult setting of wire positions and extremely difficult observation of test phenomena when building a physical model. During the simulation process, the results can be visualized and the model can be accurately set. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of determining the position of the conductor when it dances with the wind;

[0045] Figure 2 This is a schematic diagram of the electric field strength calculation of the present invention;

[0046] Figure 3 It is a three-dimensional finite element model diagram of the present invention;

[0047] Figure 4 The mesh division of the simulation model of the present invention;

[0048] Figure 5 The electric field and electric field vector distribution at the connection between the conductor and the support insulator when θ=0.9° in the present invention;

[0049] Figure 6 This is a schematic diagram of the electric field strength value points of the present invention;

[0050] Figure 7 The electric field intensity variation when the conductor α=90° is located at different θ in the present invention;

[0051] Figure 8 The electric field intensity variation when the conductor θ=1.35° is located at different α in the present invention;

[0052] Fig. 9 The change of the electric field strength inside the conductor when the conductor α=90° is located at different θ;

[0053] Fig.10 The figure shows the change of the electric field strength inside the conductor when the conductor with angle θ=1.35° is located at different angles α. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below with reference to the accompanying drawings.

[0055] The electric field distribution analysis method of 10kV overhead insulated conductor at different swing positions includes the following steps:

[0056] Step 1: Determine the location and electrical load of the overhead insulated conductors.

[0057] When the conductor swings with the wind, its position changes in three-dimensional space, and the support insulator can be regarded as stationary. Therefore, the swing position of the conductor is characterized by two angles, such as Figure 1 (a), that is, the angle between the center of the wire after swinging and the center of the wire in the original position, and Figure 1 As shown in (b), the angle between the line connecting the center of the conductor cross section after swinging and the center of the conductor in the original position and the vertical direction. Figure 1 In (a), the angle θ between the center of the wire after swinging and the center of the wire in the original position ranges from 0 to 90°. Figure 1 In (b), the angle α between the center of the conductor cross section after the swing and the line connecting the center of the conductor in the original position and the vertical direction ranges from 0 to 180°.

[0058] The present invention mainly studies the electric field at the connection between the support insulator and the conductor when the conductor is placed in different positions, so only a single conductor is modeled. According to the national standard of my country, the maximum allowable operating voltage of a 10kV line in the power system is 11kV. The maximum operating voltage of a single line is obtained by calculation. m for:

[0059]

[0060] Step 2: Establish a 10kV overhead insulated conductor simulation model based on the location and electrical load of the overhead insulated conductor.

[0061] The overhead insulated conductor is equivalent to a finite length line charge and is placed in Figure 2 In the coordinate system shown, the electric field strength E(x′) at point A on the right side of the wire is calculated as:

[0062]

[0063] Depend on Figure 2 get, Substituting cosθ=x' / R into the electric field strength E(x'), we get:

[0064]

[0065] Where y' is half of the charge of the finite length line, ε is the dielectric constant, and e x is the unit vector along the x-axis, R is the distance between any charge element dq on the wire and point A, and θ is the angle between the partial electric field direction and the total electric field direction.

[0066] The electric field strength at a certain point is related to the length of the wire. In addition, the actual structure of the transmission line is large and cannot be fully reproduced through modeling. Therefore, there are more or less errors in the simulation results, but the phenomena and change laws reflected in the experiment are not affected. Therefore, the present invention only establishes a three-dimensional simulation model of the wire of the support insulator part at a ratio of 1:1. The wire and the support insulator are connected by contact. The specific model is as follows Figure 3 The outer diameter of the conductor is 20 mm, the thickness of the insulation layer is 3.4 mm, and the diameter of the post insulator rod is 40 mm.

[0067] Step 3: Mesh the constructed simulation model.

[0068] like Figure 4 The figure shows the specific mesh division of the simulation model. Since the contact surface between the insulated conductor and the post insulator is actually small, the model needs to be meshed finer. And because the main research is the electric field distribution of the insulating layer of the insulated conductor, the mesh of the post insulator model can be slightly coarser.

[0069] Step 4: Perform structural and electric field solutions on the meshed simulation model.

[0070] The purpose of solving the structure of the simulation model is to make the wires in different spatial positions: by applying physical loads to the wires in StaticStructural, the wires are displaced. The results of this part are then used as the initial conditions for solving the next part.

[0071] When conducting electric field analysis on the external insulation of a power system, the electric field is equivalent to an electrostatic field or an electroquasistatic field:

[0072]

[0073]

[0074]

[0075]

[0076] Among them, D = εE in an isotropic linear dielectric, D is the electric flux density, also known as electric displacement; S represents an arbitrary closed surface in an infinite vacuum electrostatic field; V is the volume defined by the surface S; ρ is the polarization charge density in the dielectric; E is the electric field intensity; l represents a closed path in the electrostatic field; ▽ represents the gradient operator; ε represents the dielectric constant;

[0077] For a uniform dielectric, the electric field distribution satisfies the potential Poisson's equation:

[0078]

[0079] When the free charge density is 0, the electric field distribution satisfies the potential Laplace equation for:

[0080]

[0081] in, is the Laplace operator, is the potential, and Poisson's equation and Laplace's equation express the universal relationship between the spatial variation of the potential at each point in the field and the free charge density at that point. The solution to the electrostatic field can be regarded as the solution to Poisson's equation or Laplace's equation under certain conditions. In the solution process, the boundary conditions of the electrostatic field and the properties of the potential are also required to determine the solution of the electrostatic field. There are two main ways to give boundary conditions, namely Dirichlet conditions and Neumann conditions, that is, the potential value of each point on the boundary surface of the known field and the potential normal derivative value of each point.

[0082] Step 5: Process the solved results.

[0083] After the calculation is completed, the electric field distribution cloud map and the electric field vector distribution cloud map at the connection between the insulated conductor and the support insulator are obtained. The model is cut to obtain the electric field distribution cloud map and the electric field vector distribution cloud map inside the conductor insulation layer. The specific point in the model is selected to obtain the specific electric field strength value and then the change law of the electric field strength when the conductor is in different positions is obtained.

[0084] According to the above-mentioned electric field distribution analysis method of 10kV overhead insulated conductor at different swing positions, the correctness of the present invention is verified by analyzing the electric field distribution of 10kV overhead insulated conductor and support insulator. The specific steps are:

[0085] Step 1: Determine the location and electrical load of the overhead insulated conductors.

[0086] The selected θ are 0.45°, 0.9°, 1.35°, 1.8° and 2.25° respectively; the selected α are 0°, 30°, 60°, 90°, 120°, 150° and 180° respectively. The load is adjusted in Static Structural to make the wire in the above position.

[0087] In Electric, a voltage load of 8.98 kV is applied to the insulated wire core.

[0088] Step 2: Establish a 10kV overhead insulated conductor simulation model based on the location and electrical load of the overhead insulated conductor.

[0089] The medium in the simulation model includes the post insulator and the insulated wire. Since the present invention performs structure-electric field coupling analysis, the model must bear both mechanical load and electrical load. The material parameter settings of different parts in the simulation model are shown in Table 1. The outer diameter of the wire is 20 mm, the thickness of the insulation layer is 3.4 mm, and the diameter of the post insulator rod is 40 mm. The specific model is as follows Figure 3 shown.

[0090] Table 1 Simulation model material parameters

[0091]

[0092] Step 3: Mesh the constructed simulation model.

[0093] Since the contact surface between the insulated conductor and the post insulator is actually small, the model needs to be meshed finer. And because the main research is the electric field distribution of the insulating layer of the insulated conductor, the mesh of the post insulator model can be slightly coarser. The specific meshing of the simulation model is as follows Figure 4 shown.

[0094] Step 4: Solve the simulation model after meshing.

[0095] Structure solving:

[0096] The purpose of the structural solution is to place the insulated wire in different positions, in order to simulate the position of the wire during the wire dancing process. Figure 1 According to the rules given in , through structural solution, θ is obtained to be 0.45°, 0.9°, 1.35°, 1.8° and 2.25°, and the α corresponding to each θ value is 0°, 30°, 60°, 90°, 120°, 150° and 180°.

[0097] Power plant solution:

[0098] By simulating and analyzing the electric field characteristics of the conductor at different positions, the electric field distribution at the connection between the conductor and the support insulator when the conductor is moved to different positions is obtained.

[0099] When θ = 0.9°, the electric field and electric field vector distribution at the connection between the conductor and the support insulator are as follows: Figure 5 As shown in the figure. From the electric field distribution diagram, it can be seen that no matter what the value of α is, the field strength on the contact surface boundary is greater than the field strength inside the contact surface; in the vector diagram, the electric field vector distribution on the contact surface boundary is dense, while the electric field vector distribution in other parts is sparse. As α changes, the distribution of the electric field on the contact surface also changes; in the vector diagram, it can be found that not only the density of the electric field vector changes, but also the direction of the electric field vector changes. The swing of the wire changes both the magnitude of the electric field and the direction of the electric field vector.

[0100] Step 5: Process the solved results to obtain the variation law of the electric field strength at different swinging positions of the wire.

[0101] Since the electric field strength at the contact surface boundary between the conductor and the support insulator is relatively large, in order to further analyze the electric field changes at the connection between the conductor and the support insulator, Figure 6 (a) shows the electric field at six points on the boundary of the connection and the Figure 6 As shown in (b), the electric field at five points on the cross section of the connection is analyzed.

[0102] like Figure 7 As shown in the figure, the electric field strength changes at six points of the selected connection under different θ conditions when α = 90°; Figure 8As shown in the figure, the change of electric field strength at the six points of the selected connection under different α conditions when θ=1.35°. When α is a constant, the change law of the electric field strength at the six points A to F is not exactly the same, but θ=0.9° and θ=1.80° are the maximum points of the electric field strength change curve of these six points, and the change of the electric field strength at the six points under different θ conditions is very obvious. When θ is a constant, the change law of the electric field strength at the six points A to F is basically the same, with only certain differences in numerical values. When α=120°, the electric field strength at the six points all reaches the maximum, and the gap between the maximum and minimum values ​​is significant.

[0103] like Fig. 9 As shown in the figure, the electric field strength changes at five points of the wire cross section at the selected connection when the wire is located at different θ conditions when α = 90°; Fig.10 As shown in the figure, the change of electric field strength at five points of the wire cross section at the selected connection under different α conditions when the wire is located at θ=1.35°. Compared with the change of the electric field on the surface of the connection, the change of the electric field in the insulation layer inside the wire is more irregular. When the wire is in the same position, the electric field strength of each point is quite different, and there is a big difference in the electric field strength at the same point at different positions. At the same time, there is also a phenomenon that the change law of the electric field strength at points a and c is similar, and the change law of the electric field strength at points d and e is similar. It can be seen that the change law of the electric field is related to the location of the electric field.

[0104] 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. The electric field distribution analysis method of 10kV overhead insulated conductor at different swing positions is characterized by: The following steps are involved: Step 1: Determine the location and electrical load of the overhead insulated conductor; The specific implementation method for determining the position of the overhead insulated conductor is: determining the angle between the center of the conductor after the swing and the center of the conductor at the original position and the angle between the line connecting the center of the conductor cross section after the swing and the center of the conductor at the original position and the vertical direction; The angle between the center of the conductor after swinging and the center of the conductor in the original position is in the range of 0 to 90°, and the angle between the line connecting the center of the conductor cross section after swinging and the center of the conductor in the original position and the vertical direction is in the range of 0 to 180°; Step 2: Establish a 10kV overhead insulated conductor simulation model according to the position and electrical load of the overhead insulated conductor; The overhead insulated conductor is equivalent to a finite length line charge, and the electric field strength E(x′) at the right side x' is calculated as: Will Substituting cosθ=x' / R into the electric field strength E(x'), we get: Where y' is half of the charge of the finite length line, ε is the dielectric constant, and e x is a unit vector along the x-axis direction, R is the distance between any charge element dq on the conductor and point A, θ is the angle between the direction of the partial electric field and the direction of the total electric field, and a three-dimensional simulation model is established for the conductor of the post insulator part at a ratio of 1:

1. The conductor and the post insulator are connected by contact; Step 3: Mesh the constructed simulation model; Step 4, solving the simulation model after meshing, including structural solution and electric field solution; The specific implementation method of structural solution is: apply physical load to the wire in StaticStructural to make the wire displace, and use the result of this part as the initial condition for the next part of the solution; The specific implementation method of solving the electric field is to equate the electric field to an electrostatic field or an electric quasistatic field: ∮ S D·dS=∫ V ρdV ∮ l E·dl=0 Among them, D = εE in an isotropic linear dielectric, D is the electric flux density, also known as electric displacement; S represents any closed surface in an infinite vacuum electrostatic field; V is the volume defined by the surface S; ρ is the polarization charge density in the dielectric; E is the electric field intensity; l represents a closed path in the electrostatic field; represents the gradient operator; ε represents the dielectric constant; For a uniform dielectric, the electric field distribution satisfies the potential Poisson's equation: When the free charge density is 0, the electric field distribution satisfies the potential Laplace equation for: in, is the Laplace operator, is the potential, and The given boundary conditions are determined by the Dirichlet condition and the Neumann condition. Step 5: Process the solved results to obtain the variation law of the electric field strength at different swinging positions of the wire.

2. The electric field distribution analysis method for different swing positions of a 10kV overhead insulated conductor according to claim 1 is characterized in that: The electrical load of the overhead insulated conductor in step 1 is the maximum value of the single-phase line operating voltage U m : Among them, the maximum allowable operating voltage of 10kV lines in the power system is 11kV.

3. The electric field distribution analysis method for different swing positions of a 10kV overhead insulated conductor according to claim 1 is characterized in that: The specific implementation method of step 3 is: the support insulator model of the overhead insulated conductor is divided by a large grid, and the rest is divided by a small grid.

4. The electric field distribution analysis method for different swing positions of a 10kV overhead insulated conductor according to claim 1 is characterized in that: The specific implementation method of step 5 is: after the calculation is completed, the electric field distribution cloud map and the electric field vector distribution cloud map at the connection between the insulated conductor and the support insulator are obtained, the model is cut to obtain the electric field distribution cloud map and the electric field vector distribution cloud map inside the conductor insulation layer, and a specific point in the model is selected to obtain a specific electric field strength value and then obtain the change law of the electric field strength when the conductor is at different positions.

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