Non-uniform deicing jump dynamic characteristic analysis method for transmission conductor under non-uniform ice coating

Abstract

The invention relates to the field of power distribution, and relates to a power transmission conductor non-uniform deicing jump dynamic characteristic analysis method under non-uniform icing, which comprises the following steps: S1, designing a conductor non-uniform icing form, and establishing a conductor-insulator chain system finite element analysis model; s2, shape finding analysis is carried out, and the initial shape of the wire under the action of the self-weight load is determined; s3, simulating wire icing by using an equivalent load method, and loading the obtained equivalent force to each node of the wire; s4, transient dynamic analysis is carried out, and conductor deicing is simulated by using a method of suddenly unloading concentrated loads; and S5, exporting a calculation result, and analyzing the influence of different parameters on the power transmission conductor deicing jump dynamic characteristics. The method is used for solving the problems that an existing simulation method is not comprehensive enough when the deicing dynamic characteristics are analyzed, and the requirement for analyzing the non-uniform deicing dynamic characteristics of the transmission conductor under non-uniform ice coating cannot be met.

Description

Technical Field

[0001] The invention relates to the field of power distribution, and in particular to a method for analyzing dynamic characteristics of non-uniform ice shedding and jumping of power transmission lines under non-uniform ice coverage. Background Art

[0002] Line icing refers to the phenomenon that raindrops condense on transmission lines after contacting cold air, causing the wires to be frozen on a large scale. Lines are prone to ice in low-temperature and humid natural environments, especially in micro-topography and micro-meteorological areas, where uneven ice is easily formed. Line icing seriously threatens the safe operation of the power grid. my country has a vast territory and diverse climate changes, and is one of the regions with the most serious icing of transmission lines in the world. Under the influence of rising temperatures, natural wind or external forces, the ice on the line will fall off, causing the line to oscillate greatly, resulting in insufficient safety clearance of the transmission line, and it is very easy to cause safety accidents such as flashover and tripping; the shedding of line icing will also increase the unbalanced tension between gears, damage the insulator strings and hardware on the line, and in extreme cases may even cause accidents such as line breakage and tower collapse, causing large-scale power outages on the line and affecting the safe operation of the power system. Therefore, in order to ensure the safe operation of the power system, it is necessary to study the dynamic characteristics of the transmission line after deicing, and explore the influence of different parameters on the dynamic characteristics of deicing jump.

[0003] Defects and shortcomings of the existing technology: Domestic and foreign scholars have conducted a lot of research on the dynamic characteristics of ice shedding and jump of transmission lines, but there are still some shortcomings. Most of the current research focuses on the non-uniform ice shedding characteristics under uniform ice coverage of the conductor or the uniform ice shedding characteristics under non-uniform ice coverage, and lacks research on the dynamic characteristics of non-uniform ice shedding under non-uniform ice coverage of the transmission line. However, the existing simulation methods cannot meet the needs of analyzing the dynamic characteristics of non-uniform ice shedding under non-uniform ice coverage. In addition, most of the current research on ice shedding jump focuses on the jump height in the center of the conductor span, but when considering non-uniform ice coverage and non-uniform ice shedding, the location where the maximum height of the conductor ice shedding jump occurs is not necessarily located in the center of the span, and the design of the tower head size and the reasonable arrangement of the position of each phase conductor need to determine the maximum height of the conductor ice shedding jump and its occurrence location. Therefore, in order to provide a reference for the anti-icing design of the transmission line and the formulation of the deicing plan, and to ensure the safe operation of the transmission line, a method for analyzing the dynamic characteristics of non-uniform ice shedding of the transmission line under non-uniform ice coverage is needed, so as to conduct a more in-depth study on the dynamic characteristics of ice shedding of the transmission line and explore the law of the location of the maximum conductor ice shedding jump height. Summary of the invention

[0004] The purpose of the present invention is to provide a method for analyzing the dynamic characteristics of non-uniform ice shedding jump of transmission lines under non-uniform ice covering, so as to solve the problem that the existing simulation methods are not comprehensive enough in analyzing the dynamic characteristics of ice shedding and cannot meet the needs of analyzing the dynamic characteristics of non-uniform ice shedding of transmission lines under non-uniform ice covering.

[0005] In order to solve the above problems, the technical solution of the present invention is: The method for analyzing the dynamic characteristics of non-uniform ice shedding and jumping of transmission lines under non-uniform ice covering includes the following steps: S1: designing the non-uniform ice covering form of the conductor and establishing a finite element analysis model of the conductor-insulator string system; S2: Perform form-finding analysis to determine the initial shape of the conductor under the deadweight load; S3: Use the equivalent load method to simulate the icing of the conductor, and load the obtained equivalent force to each node of the conductor; S4: Perform transient dynamic analysis and simulate the conductor shedding by suddenly unloading concentrated loads; S5: Export the calculation results and analyze the influence of different parameters on the dynamic characteristics of ice shedding of transmission lines.

[0006] In step S1, the method for establishing a finite element analysis model of a conductor-insulator string system comprises the following steps: S1.1: Investigate and collect relevant information, including conductor parameters, insulator string parameters, hardware parameters and meteorological conditions; S1.2: According to meteorological parameters and icing characteristics, design different non-uniform icing forms to simulate non-uniform icing of conductors; S1.3: According to the parameters of each part structure, establish the conductor-insulator string point line model; S1.4: Define the unit type, use LINK10 units to simulate the conductor, use BEAM188 units to simulate the insulator string, wire clamp and spacer, and set the material properties of each part; S1.5: Divide the grid into units, divide the insulator string, wire clamp and spacer into one unit, and divide the conductor into one unit every 1m; S1.6: Set boundary conditions. Fixed constraints are used at both ends of the conductor. The suspension insulator string constrains the translational freedom of its suspension point and releases its rotational freedom.

[0007] In step S2, the method for determining the initial shape of the conductor under the action of its own weight load includes: applying an initial strain and elastic modulus to it, performing a nonlinear solution under the action of its own weight load, and updating the coordinates after the solution; on this basis, restoring the actual elastic modulus value of the conductor for nonlinear iteration, with the horizontal tension of the conductor as the convergence condition, and the final result after convergence is the initial shape of the conductor under the action of its own weight load.

[0008] In step S3, the method of loading the obtained equivalent force to each node of the conductor includes: assuming that the entire conductor is non-uniformly iced, dividing the de-icing section into several sections, and calculating the equivalent concentrated force of each section; for the convenience of calculation, the actual ice is equivalent to an ideal ice with the same circular cross-section and uniform thickness, and the size of the equivalent concentrated load F applied to each node of each section can be calculated according to the following formula: F = ρπb (D + b) Lg / n; Where: ρ is the ice density, which is 900 kg / m 3 ; g is the acceleration due to gravity, which is 9.8m / s 2 ; b is the ice thickness (m); D is the outer diameter of the overhead line (m); L is the conductor length (m); n is the number of nodes; The equivalent concentrated load of each node is calculated using the above formula and applied to the corresponding node of the finite element model to simulate different forms of non-uniform icing.

[0009] In step S4, the method of simulating conductor deicing by suddenly unloading concentrated loads includes: setting the solution type to transient dynamic analysis, using the complete method for solving, simulating deicing by unloading the concentrated load applied at the deicing section node in a very short time, and the vibration amplitude of the conductor after deicing will gradually decrease due to the existence of damping and eventually tend to be stable; since the damping of the transmission line is difficult to determine, the Rayleigh damping model is used in the analysis, as shown in the following formula: [C] = α[M] + β[K]; Where: C is the damping matrix; M is the mass matrix; K is the stiffness matrix; α is the mass damping coefficient; β is the stiffness damping coefficient; ω1 and ω2 are the first-order and second-order vibration frequencies of the conductor, respectively; ξ is the damping ratio, which is 10% for iced conductors and 2% for un-iced conductors.

[0010] In step S5, the maximum jump height of the wire in the entire time history analysis, the time when the maximum jump height occurs and the corresponding position are obtained, including the following steps: S5.1: define two arrays, the dimensions of which are the same as the number of de-icing file nodes, for storing the maximum value of each node in the entire time history analysis and the time point corresponding to the maximum value; S5.2: Enter the time history postprocessor, use the loop and Nsol and Get commands to obtain the maximum value of the calculation results of each node and the time point corresponding to the maximum value, and store them in the array defined in the previous step; S5.3: Use loops and judgments to obtain the maximum value of the data in the array, and record the time point and node number corresponding to the maximum value. This is the maximum jump height of the wire in the entire time history analysis, the time when the maximum jump height occurs, and the corresponding position.

[0011] The beneficial effects of the present invention are: (1) The present invention provides a method for analyzing the dynamic characteristics of non-uniform ice shedding and jump of transmission lines under non-uniform ice covering. The method solves the problem that the existing simulation methods are not comprehensive enough in analyzing the dynamic characteristics of ice shedding and cannot meet the needs of analyzing the dynamic characteristics of non-uniform ice shedding of transmission lines under non-uniform ice covering.

[0012] (2) The method of the present invention is simple, convenient and efficient. It can obtain the maximum height of the conductor jumping due to ice shedding and its occurrence location with one click, thereby providing a basis for the design of the tower head size and the reasonable arrangement of the positions of the conductors of each phase, thereby ensuring the safe operation of the transmission line.

[0013] (3) This method uses ANSYS APDL language for parametric modeling and has good general analysis capabilities. It can change the corresponding parameters according to different working conditions to perform numerical simulation on the dynamic response of the transmission line to remove ice, thereby analyzing the influence of different parameters on the dynamic characteristics of the transmission line to remove ice. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 The figure is an overall flow chart of the method of the present invention.

[0015] Figure 2 Schematic diagram of the non-uniform ice coating designed for an embodiment of the present invention.

[0016] Figure 3 It is a schematic diagram of a finite element model of a conductor-insulator string system according to an embodiment of the present invention.

[0017] Figure 4 Flow chart of the shape-finding method in an embodiment of the present invention.

[0018] Figure 5 Schematic diagram of the non-uniform deicing form designed for an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, a method for analyzing the dynamic characteristics of non-uniform ice shedding jump of a transmission line is implemented in the following steps: S1: Investigate and collect relevant information, design the non-uniform icing form of the conductor, and establish a finite element analysis model of the conductor-insulator string system; in this embodiment, considering the icing characteristics of micro-topography and micro-meteorological areas, two different non-uniform icing forms, namely step icing and central concentrated icing, are designed, such as Figure 2 As shown; this embodiment uses ANSYS software APDL language to model, and the conductor-insulator string system finite element model is as follows Figure 3 As shown, the specific process includes: S1.1: Investigate and collect relevant information, including conductor parameters, insulator string parameters, hardware parameters and meteorological conditions; S1.2: According to meteorological parameters and icing characteristics, design different non-uniform icing forms to simulate non-uniform icing of conductors; S1.3: Based on the collected structural parameters of each part, the key points of the conductor-insulator string system are generated using the K command, and then the point-line model of the conductor-insulator string system is established by connecting these key points using the L command; S1.4: Define the unit type. In the modeling process, use LINK10 units to simulate the conductors, use BEAM188 units to simulate the insulator strings, wire clamps and spacers, and set the material properties of each part through the attribute definition command MP, such as density, elastic modulus, Poisson's ratio, etc.; S1.5: Divide the mesh units. When performing finite element analysis, the density of the mesh directly affects the accuracy of the results. Considering the calculation time and the accuracy of the calculation results, use the mesh division related commands to divide the insulator string, wire clamp, and spacer into 1 unit, and divide the conductor into a unit every 1m; S1.6: Set boundary conditions. Fixed constraints are used at both ends of the conductor. The suspension insulator string constrains the translational freedom of its suspension point and releases its rotational freedom to ensure that the suspension string can rotate around the suspension point. The connection between the conductor and the suspension insulator string, wire clamp, and spacer rod is node coupling.

[0021] S2: Perform form-finding analysis to determine the initial shape of the conductor under the action of its own weight load. The specific process is as follows: Figure 4 As shown in Figure 1, after the model is established according to the steps described in S1, a larger initial strain (the initial strain is 0.8 to 1, such as 0.9) and a smaller elastic modulus (10 of the original elastic modulus) are applied to it. -3 Up to 10 -4 times, such as 7.6×10 7Pa), and use the ACEL command to apply the self-weight load for nonlinear solution, and update the coordinates of each node after the solution; on this basis, restore the actual elastic modulus value of the wire for nonlinear iteration, and take the error of the horizontal tension of the wire not exceeding 2% (the error is determined according to the actual situation) as the convergence condition. The final result after convergence is the initial shape of the wire under the action of the self-weight load, and then compare the obtained initial shape with the calculation result of the catenary formula to determine whether the model meets the requirements.

[0022] S3: Use the equivalent load method to simulate the icing of the conductor and load the equivalent concentrated force to each node of the conductor. The specific method is as follows: For the convenience of calculation, the actual icing is equivalent to an ideal icing with the same circular cross-section and uniform thickness. The equivalent concentrated load F applied to each node can be calculated according to the following formula: F = ρπb(D+b)Lg / n; Where: ρ is the ice density, which is 900 kg / m 3 ; g is the acceleration due to gravity, which is 9.8m / s 2 ; b is the ice thickness (m); D is the outer diameter of the overhead line (m); L is the conductor length (m); n is the number of nodes.

[0023] In this embodiment, the conductor is non-uniformly iced in the entire section. The de-icing conductor is divided into several sections. The equivalent concentrated load of the nodes of each section of the conductor is calculated using the above formula, and the equivalent concentrated load is applied to the corresponding nodes of the finite element model using the F command, thereby simulating non-uniform ice coverage.

[0024] S4: Perform transient dynamic analysis and simulate conductor deicing by suddenly unloading concentrated loads. The specific method is: use the / SOLU command to enter the solution mode, set the solution type to transient dynamic analysis, and use the complete method to solve; use the TIMINT command to turn on the time integration effect during deicing, and simulate deicing by unloading the concentrated load applied at the deicing section node in a very short time. After deicing, the vibration amplitude of the conductor will gradually decrease due to the existence of damping and eventually stabilize. This embodiment designs four different non-uniform deicing forms: middle deicing, two-side deicing, high-side deicing, and low-side deicing. Figure 5 shown.

[0025] Damping is an important parameter in structural dynamics analysis and is the main indicator for evaluating the dynamic characteristics of the system. The form and size of damping directly affect the dynamic performance of the system. Since the damping of the transmission line is difficult to determine, the Rayleigh damping model is used in the analysis, as shown in the following formula: [C] = α[M] + β[K]; Where: C is the damping matrix; M is the mass matrix; K is the stiffness matrix; α is the mass damping coefficient; β is the stiffness damping coefficient; ω1 and ω2 are the first-order and second-order vibration frequencies of the conductor, respectively; ξ is the damping ratio, which is 10% for iced conductors and 2% for un-iced conductors.

[0026] S5: Export the calculation results and analyze the influence of different parameters on the dynamic characteristics of ice-shedding jump of transmission line. The specific process is as follows: After the solution is completed, the time history postprocessor can be entered using the / POST26 command to export the time history curves of node displacement, insulator string tension, conductor tension and other results, but the maximum height of the conductor ice-shedding jump and its occurrence location cannot be determined.

[0027] To obtain the maximum jump height of the wire in the entire time history analysis, the time when the maximum jump height occurs and the corresponding position, follow the steps below: S5.1: define two arrays, the dimensions of which are the same as the number of de-icing file nodes, for storing the maximum value of each node in the entire time history analysis and the time point corresponding to the maximum value; S5.2: Enter the time history postprocessor, use the loop and Nsol and Get commands to obtain the maximum value of the calculation results of each node and the time point corresponding to the maximum value, and store them in the array defined in the previous step; S5.3: Use loops and judgments to obtain the maximum value of the data in the array, and record the time point and node number corresponding to the maximum value. This is the maximum jump height of the wire in the entire time history analysis, the time when the maximum jump height occurs, and the corresponding position.

[0028] In this embodiment, the deicing step spacing is 400 meters, the height difference is 40 meters, the ice covering forms are two non-uniform ice covering forms: step ice covering and central concentrated ice covering, the equivalent ice covering thickness is 12.5 mm, the deicing method is non-uniform deicing, and the deicing section length is 50%. According to the above steps, after the calculation is completed, the maximum jump height of the conductor in the entire time history analysis, the time when the maximum jump height occurs and the corresponding position can be extracted with one click, which is simple, convenient and efficient, as shown in Table 1. In the table: H max is the maximum jump height; L max is the distance from the maximum jump height to the low suspension point; L max The ratio to the gear distance L.

[0029] Table 1 Maximum ice shedding jump height and position of transmission lines under different working conditions

[0030] As shown in Table 1, the position of the maximum jump height of the transmission line after deicing is significantly affected by the deicing form. When the middle part is deicing, the maximum jump height point is located near the mid-span; when the high side and low side are deicing, the maximum jump height point moves to the high and low suspension points respectively; when the two sides are deicing, the jump height is relatively small, and the position of the maximum jump height point is not fixed, which is greatly affected by the ice covering form. In general, the maximum jump height point during non-uniform deicing is mainly distributed in the range of 0.39 to 0.62 times the span. Therefore, when deicing is non-uniform, attention should be paid to whether the safety clearance within the span range of the line meets the requirements.

[0031] After the analysis is completed, according to the above steps S1-S5, the corresponding procedures are changed to perform numerical simulation on the de-icing dynamic response of the transmission line under different ice thickness, de-icing rate, span, height difference, and number of spans, so as to analyze the influence of different parameters on the de-icing dynamic characteristics of the transmission line.

[0032] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A method for analyzing the dynamic characteristics of non-uniform ice shedding jump of transmission lines under non-uniform ice coverage, characterized in that: The following steps are involved: S1: Design the non-uniform ice coating form of the conductor and establish the finite element analysis model of the conductor-insulator string system; S2: Perform form-finding analysis to determine the initial shape of the conductor under the deadweight load; S3: Use the equivalent load method to simulate the icing of the conductor, and load the obtained equivalent force to each node of the conductor; S4: Perform transient dynamic analysis and simulate the conductor shedding by suddenly unloading concentrated loads; S5: Export the calculation results and analyze the influence of different parameters on the dynamic characteristics of ice shedding of transmission lines.

2. The method for analyzing the dynamic characteristics of non-uniform ice shedding jump of power transmission lines under non-uniform ice coverage according to claim 1 is characterized in that: In step S1, the method for establishing a finite element analysis model of a conductor-insulator string system comprises the following steps: S1.1: Investigate and collect relevant information, including conductor parameters, insulator string parameters, hardware parameters and meteorological conditions; S1.2: According to meteorological parameters and icing characteristics, design different non-uniform icing forms to simulate non-uniform icing of conductors; S1.3: According to the parameters of each part structure, establish the conductor-insulator string point line model; S1.4: Define the unit type, use LINK10 units to simulate the conductor, use BEAM188 units to simulate the insulator string, wire clamp and spacer, and set the material properties of each part; S1.5: Divide the grid into units, divide the insulator string, wire clamp and spacer into one unit, and divide the conductor into one unit every 1m; S1.6: Set boundary conditions. Fixed constraints are used at both ends of the conductor. The suspension insulator string constrains the translational freedom of its suspension point and releases its rotational freedom.

3. The method for analyzing the dynamic characteristics of non-uniform ice shedding jump of power transmission lines under non-uniform ice coverage according to claim 1 is characterized in that: In step S2, the method for determining the initial shape of the conductor under the action of its own weight load includes: applying an initial strain and elastic modulus to it, performing a nonlinear solution under the action of its own weight load, and updating the coordinates after the solution; on this basis, restoring the actual elastic modulus value of the conductor for nonlinear iteration, with the horizontal tension of the conductor as the convergence condition, and the final result after convergence is the initial shape of the conductor under the action of its own weight load.

4. The method for analyzing the dynamic characteristics of non-uniform ice shedding jump of power transmission lines under non-uniform ice coverage according to claim 1 is characterized in that: In step S3, the method of applying the obtained equivalent force to each node of the conductor includes: assuming that the entire conductor is non-uniformly iced, dividing the de-icing section into several sections, and calculating the equivalent concentrated force of each section; for the convenience of calculation, the actual ice is equivalent to an ideal ice with the same circular cross-section and uniform thickness, and the size of the equivalent concentrated load F applied to each node of each section can be calculated according to the following formula: F = ρπb(D+b)Lg / n; Where: ρ is the ice density, which is 900 kg / m 3 ; g is the acceleration due to gravity, which is 9.8m / s 2 ; b is the ice thickness (m); D is the outer diameter of the overhead line (m); L is the conductor length (m); n is the number of nodes; The equivalent concentrated load of each node is calculated using the above formula and applied to the corresponding node of the finite element model to simulate different forms of non-uniform icing.

5. The method for analyzing the dynamic characteristics of non-uniform ice shedding jump of power transmission lines under non-uniform ice coverage according to claim 1 is characterized in that: In step S4, the method of simulating conductor deicing by suddenly unloading concentrated loads includes: setting the solution type to transient dynamic analysis, using the complete method for solving, simulating deicing by unloading the concentrated load applied at the deicing section node in a very short time, and the vibration amplitude of the conductor after deicing will gradually decrease due to the existence of damping and eventually tend to be stable; since the damping of the transmission line is difficult to determine, the Rayleigh damping model is used in the analysis, as shown in the following formula: [C] = α[M] + β[K]; Where: C is the damping matrix; M is the mass matrix; K is the stiffness matrix; α is the mass damping coefficient; β is the stiffness damping coefficient; ω1 and ω2 are the first-order and second-order vibration frequencies of the conductor, respectively; ξ is the damping ratio, which is 10% for iced conductors and 2% for un-iced conductors.

6. The method for analyzing the dynamic characteristics of non-uniform ice shedding jump of power transmission lines under non-uniform ice coverage according to claim 1 is characterized in that: In step S5, the maximum jump height of the wire in the entire time history analysis, the time when the maximum jump height occurs and the corresponding position are obtained, including the following steps: S5.1: define two arrays with the same dimension as the number of de-icing nodes, which are used to store the maximum value of each node in the entire time history analysis and the time point corresponding to the maximum value; S5.2: Enter the time history postprocessor, use the loop and Nsol and Get commands to obtain the maximum value of the calculation results of each node and the time point corresponding to the maximum value, and store them in the array defined in the previous step; S5.3: Use loops and judgments to obtain the maximum value of the data in the array, and record the time point and node number corresponding to the maximum value. This is the maximum jump height of the wire in the entire time history analysis, the time when the maximum jump height occurs, and the corresponding position.

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