An ANSYS numerical simulation method for de-icing galloping of ice-covered conductors based on beam elements

Abstract

The present invention discloses an ANSYS numerical simulation method for de-icing jump of ice-covered conductors based on beam elements, which is characterized by the following steps: S1: Determine the steel frame structure of the transmission tower and the number of conductor splits, and select the type of beam element; establish the overall coordinate system, with the tower height as the y-axis direction, the cross-arm wire suspension as the z-axis direction, and the outer projection direction of the cross-arm as the x-axis direction to establish the transmission tower model; S2: Conduct the self-weight sag finding of the transmission conductors to determine the initial displacement form of the transmission conductors when they reach the equilibrium state under the action of self-weight; S3: Determine the ice load, conduct the static calculation of ice-covered self-weight, determine the displacement of the transmission conductors when they reach the equilibrium state under the ice-covered self-weight, that is, the ice-covered static equilibrium position, and the difference between the maximum value of the conductor amplitude and the ice-covered static equilibrium position is the jump height; S4: Use the method of changing density to simulate the ice-covered and de-icing processes of the transmission conductors; simulate the uniform ice-covered condition on each section of the transmission line conductor unit by changing the material density of all elements.

Description

Technical Field

[0001] The invention relates to the technical field of power transmission lines, in particular to an ANSYS numerical simulation method for ice shedding jumping of ice-covered conductors based on beam units. Background Art

[0002] With the development of my country's economy and society, the demand for electric energy is increasing day by day. Many transmission lines inevitably cross heavy ice areas with severe meteorological conditions such as high altitude, low temperature, strong wind, etc., which brings challenges to the construction of power grids. In areas where my country's power grids are severely covered with ice, the most frequent and most serious transmission line accidents in the ice disasters over the years are mechanical and electrical failures caused by ice shedding and jumping after ice covering. Ice shedding and jumping after ice covering are one of the main causes of safe operation accidents in Yunnan power grid. Ice shedding and jumping after ice covering are inevitable, but due to the different conditions of transmission line conductor models, spans, split forms, tower types, and terrains crossed, the transmission lines are often affected by natural conditions during operation, and various problems such as ice shedding and jumping, wake-induced galloping and dancing often occur, which seriously endanger the safe operation of the lines. Ice shedding and jumping of transmission lines refers to the up and down vibration of the conductors caused by the melting and falling of ice covering the transmission lines in the ice area under natural conditions such as temperature increase, mechanical ice breaking, sublimation ice melting, etc., which is called ice jumping in engineering. During ice jumping, the gaps between the phase conductors and the ground conductors may be smaller than the corresponding insulation gaps, leading to electrical accidents such as flashover, burns, or even wire burnout. Therefore, studying the formation mechanism, maximum ice jump height, and methods to prevent ice jumping of transmission lines is of great significance for the insulation design of transmission lines. Summary of the invention

[0003] The present invention provides an ANSYS numerical simulation method for ice-shedding jumping of ice-covered conductors based on beam units, establishes a refined model of the coupling of transmission towers and conductor insulators, improves the degree of freedom of all nodes on the transmission line, and adopts a density change method to simulate the icing and deicing process of the transmission line in establishing the transmission line icing model, introduces a Rayleigh damping model, and calculates the vibration process of the transmission line after deicing.

[0004] In order to achieve the above results, the specific technical solution adopted by the present invention is as follows: an ANSYS numerical simulation method for ice-shedding jumping of ice-covered conductors based on beam elements, comprising the following steps:

[0005] S1: Determine the static model of the transmission line: The transmission tower is a spatial rigid frame structure. In the ANSYS spatial coordinates, the transmission tower model is established with the tower height as the y-axis direction, the crossarm hanging wire as the z-axis direction, and the crossarm cantilever direction as the x-axis direction. Beam188 is a beam unit with two nodes, which is suitable for analyzing slender beam structures considering shear deformation. The transmission tower rods are all simulated using beam188 units.

[0006] When simulating transmission lines, considering the uneven icing of transmission lines and the torsional of conductors caused by de-icing, beam188 with three-dimensional beam elements is used in this paper for simulation. The insulator string can be regarded as a rigid body rotating around a fixed axis, hinged at one end to the cross arm of the transmission tower and at the other end to the transmission line. Beam188 elements are used for simulation, and one element is divided for each insulator string.

[0007] S2: Shape finding of the transmission line under its own weight: When performing de-icing dynamic analysis, it is necessary to first determine the initial displacement form of the transmission line when it reaches the equilibrium state under its own weight, that is, the shape finding of the transmission line under its own weight. Only by correct shape finding can the accuracy of the next modal analysis, de-icing transient analysis and other analyses be ensured. During the shape finding process, the non-linear influence of the transmission line needs to be considered. The final equilibrium position of the transmission conductor under its own weight is the initial configuration position. In this project, the iterative method is used to perform shape finding analysis on the transmission line. The main idea is that under the action of the conductor gravity, the geometric shape of the conductor is repeatedly updated until the error between the horizontal tension of the conductor and the known stringing tension is within the allowable range, and then the initial configuration of the conductor can be obtained.

[0008] S3: Simulation of the icing load on the transmission conductor: The icing load on the transmission line can be regarded as a uniformly distributed load. Since the stiffness of the ice is much smaller than that of the transmission conductor itself and has little influence on the de-icing response, the ice stiffness is not considered, and the distributed lumped mass method is used to simulate the icing load on the transmission conductor. During the calculation process, the ice on the transmission conductor is equivalent to lumped masses one by one and simulated with Mass21 elements. After performing a static analysis on the self-weight of the tower and the line, the material density of the second icing condition is set to the conductor body density plus the mass of ice per unit length divided by the cross-sectional area of the conductor, becoming a uniformly iced condition.

[0009] S4: Simulation of the de-icing process of the transmission line: Conductors or cables are generally simulated with LINK10 elements, but when the vibration amplitude of the conductor is large, it may cause the conductor to lose stiffness under compression and lead to convergence difficulties. Therefore, beam elements (BEAM188) are used for simulation. Although the flexural stiffness of the conductor is considered, due to the very small flexural stiffness, the behavior of the extremely flexible beam is the same as that of the cable. The MPCHG command is used to change the material density of all elements to simulate the uniformly iced condition on each section of the transmission line conductor unit. Each span of the conductor is divided into 100 elements. The ESEL command is used to select the de-icing elements of the conductor. By repeatedly using the MPCHG command in the load step, the material density of the de-icing condition is set to the conductor body density plus the mass of ice per unit length that decreases cyclically with the load step time divided by the cross-sectional area of the conductor. Different de-icing speeds are achieved by changing the number of substeps of the load step.

[0010] S5: Static analysis under the self-weight of the conductor: In the first load step, the shape and sag of the transmission conductor under the known self-weight of the conductor will be obtained. Using the trial calculation method of the skew parabola formula, first create a model with a parabola close to the sag, then apply the self-weight load of the conductor. If "the vertical coordinate at the mid-span + the vertical displacement at the mid-span" is equal to the sag, the analysis of this load step is completed; otherwise, adjust the sag during modeling until the requirements are met.

[0011] S6: After the end of step S5, in the second load step, the static analysis after icing is increased. Here, the icing load is directly applied without considering the icing process, and the dynamic effect of the icing load is not considered. That is, under the state of the self-weight of the conductor, the self-weight of the ice covering is applied again, and the equivalent ice covering body density is applied to the body density of the transmission conductor through the MPCHG command to complete the analysis of this load step.

[0012] S7: The third and subsequent load steps are for the analysis of the ice shedding process. At this time, the time integration effect is turned on, and it is assumed that the ice is shed uniformly within a certain time (ramp load, non-uniform load). The method of modifying the material properties (density) is used to achieve ice shedding between load steps, that is, the MPCHG command is used to modify the element material number. If the method of applying load is used to simulate the ice shedding process, the change of the system mass cannot be considered.

[0013] S8: The fourth load step is the vibration process after complete ice shedding. The end time of the calculation can be determined as needed. From the calculation results, it can be seen that the conductor not only vibrates up and down but also longitudinally. The time history curve of the vertical displacement at the mid-span is basically centered on the self-weight displacement. When considering damping, it finally decays to the self-weight displacement.

[0014] S9: On the basis of the above, a finite element model of tower-line ice shedding jump is established to analyze the variation law of the ice jump height of the transmission line under different ice covering thicknesses, ice shedding rates, "zipper-type" ice shedding and other factors.

[0015] The beneficial effects of the present invention are as follows:

[0016] An ANSYS numerical simulation method for ice shedding jump of ice-covered conductors based on beam elements proposed by the above scheme realizes the ice shedding process and simulation of a specific transmission line, conducts a form-finding analysis of the equilibrium position and stress distribution of the line system under the action of self-weight or ice covering load, and uses this as the initial state for subsequent dynamic analysis of the structural system. Determine the ice shedding simulation method, use ANSYS software to perform numerical simulation calculations of ice shedding jump of transmission towers, conductors (ground wires) and insulators, analyze the variation law of the bounce height of the transmission line, and provide a reference for ice shedding fault warning and line operation and maintenance of overhead lines.

[0017] Furthermore, the ice shedding jump height of the transmission conductor can be obtained for checking the minimum phase-to-phase clearance, and a correction formula for determining the minimum phase-to-phase clearance of the conductor can be obtained.

[0018] Furthermore, the correction formula can be used to calculate the phase interval gaps in batches and obtain the ice jump height warning line diagram, based on which the maximum span and ice coating thickness can be determined, which can be used for the minimum clearance check and early warning, and has high engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of a refined model of a transmission tower;

[0020] Figure 2 is a schematic diagram of the initial configuration of a transmission line;

[0021] Figure 3 is a schematic diagram of a uniformly ice-coated unit of a transmission line;

[0022] Figures 4-1 to 4-6 is a schematic diagram of the ice shedding mode of an overhead line. Among them, Figure 4-1 is the uniform ice shedding in the middle span; Figure 4-2 is the uniform ice shedding at the side span; Figure 4-3 is the uniform ice shedding; Figure 4-4 is the ice shedding from the middle to both sides; Figure 4-5 is the ice shedding from both sides to the mid-span; Figure 4-6 is the ice shedding from the left to the right;

[0023] Figure 5 is a schematic diagram of the conductor configuration under the application of self-weight load;

[0024] Figure 6 is for a 20 mm ice coating thickness and 0.49 g / cm 3 time history diagram of conductor displacement under the self-weight of ice coating density;

[0025] Figure 7 is the time history diagram of ice jump displacement of the tower-line system with a 20 mm ice coating thickness;

[0026] Figure 8 is the time history diagram of ice jump displacement of the tower-line system with a 20 mm ice coating thickness and a 50% ice shedding rate;

[0027] Figure 9 is the time history diagram of ice jump displacement of the tower-line system with a 20 mm ice coating thickness, a 50% ice shedding rate, and ice shedding from left to right. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following describes the specific embodiments of the present invention in conjunction with the drawings and embodiments:

[0029] As Figures 1 to 9 shown, it shows the specific embodiments of the present invention. As shown in the figure, a method for ANSYS numerical simulation of ice shedding jump of ice-coated conductors based on beam elements disclosed by the present invention includes the following steps:

[0030] S1: Determine the static model of the transmission line: The transmission tower is a spatial rigid frame structure. In the ANSYS spatial coordinate system, the tower height is taken as the y-axis direction, the cross-arm wire suspension is taken as the z-axis direction, and the outer projection direction of the cross-arm is taken as the x-axis direction to establish the transmission tower model. Beam188 is a beam element with two nodes, suitable for analyzing slender beam structures considering shear deformation. All members of the transmission tower are simulated using beam188 elements, as Figure 1 shown.

[0031] S2: Shape finding of the transmission line under its own weight: When performing de-icing dynamic analysis, it is necessary to first determine the initial displacement shape of the transmission line when it reaches the equilibrium state under its own weight, that is, the shape finding of the transmission line under its own weight. Only by correct shape finding can the accuracy of the next modal analysis, de-icing transient analysis and other analyses be ensured. During the shape finding process, the nonlinear influence of the transmission line needs to be considered. The final equilibrium position of the transmission line under its own weight is the initial configuration position. In this project, the iterative method is used to perform shape finding analysis on the transmission line. The main idea is that under the action of the wire gravity, the geometric shape of the wire is repeatedly updated until the error between the horizontal tension of the wire and the known stringing tension is within the allowable range, that is, the initial configuration of the wire can be obtained, as Figure 2 shown.

[0032] S3: Simulation of the ice coating load on the transmission wire: The ice coating load on the transmission line can be considered as a uniformly distributed load. Since the stiffness of the ice coating is much smaller than that of the transmission wire itself and has little influence on the de-icing response, the ice coating stiffness is not considered. The distributed lumped mass method is used to simulate the ice coating load on the transmission wire. During the calculation process, the ice coating on the transmission wire is equivalent to lumped masses one by one and simulated using Mass21 elements. After performing a static analysis on the self-weight of the tower and wire, the material density of the second ice coating condition is set to the wire body density plus the mass of the ice coating per unit length divided by the cross-sectional area of the wire, becoming a uniform ice coating condition, as Figure 3 shown, which shows the rod element simulating the transmission wire and the Mass21 element simulating the ice coating.

[0033] S4: Simulation of the de-icing process of the transmission line: Wires or cables are generally simulated using LINK10 elements, but when the vibration amplitude of the wire is large, it may cause the wire to be compressed and lose its stiffness, resulting in convergence difficulties. Therefore, beam elements (BEAM188) are used for simulation. Although the bending stiffness of the wire is considered, due to the very small bending stiffness, the behavior of the extremely flexible beam is the same as that of the cable. The MPCHG command is used to change the material density of all elements to simulate the uniform ice coating condition on each section of the transmission line wire element. Each span of the wire is divided into 100 elements. The ESEL command is used to select the de-icing elements of the wire. By repeatedly using the MPCHG command in the load step, the material density of the de-icing condition is set to the wire body density plus the mass of the ice coating per unit length that decreases cyclically with the load step time divided by the cross-sectional area of the wire. Different de-icing forms are achieved by changing the number of substeps of the load step, as shown in Figure 4.

[0034] S5: Static analysis under the self-weight of the conductor: In the first load step, the shape and sag of the transmission conductor under the known self-weight of the conductor will be obtained. Using the trial calculation method of the skew parabola formula, first create a model with a parabola close to the sag, and then apply the self-weight load of the conductor. If the "vertical coordinate at the mid-span + vertical displacement at the mid-span" is equal to the sag, the analysis of this load step is completed; otherwise, adjust the sag during modeling until the requirement is met, as shown in Figure 5 shown.

[0035] S6: After the end of step S5, in the second load step, the static analysis after icing is increased. Here, the icing load is directly applied without considering the icing process, and the dynamic effect of the icing load is not considered. That is, under the state of the self-weight of the conductor, the self-weight of the ice is applied again, and the equivalent ice density is applied to the density of the transmission conductor body to complete the analysis of this load step. At this time, the total density of the iced conductor is: L δ = L D + L ice , L D is the linear density of the conductor, and L ice is the linear density of the ice.

[0036] S7: The third and subsequent load steps are for the analysis of the ice shedding process. At this time, the time integration effect is turned on, and it is assumed that the ice is shed uniformly within a certain time (ramp load, non-uniform load). The method of modifying the material properties (density) is used to achieve ice shedding between load steps, that is, the MPCHG command is used to modify the element material number. If the method of applying load is used to simulate the ice shedding process, the change of the system mass cannot be considered.

[0037] S8: The fourth load step is for the vibration process after complete ice shedding, and the end time of the calculation can be determined as needed. From the calculation results, it can be seen that the conductor not only has up and down vibrations but also longitudinal vibrations. The time history curve of the vertical displacement at the mid-span is basically centered on the self-weight displacement. When considering damping, it finally decays to the self-weight displacement, as shown in Figure 6 shown

[0038] S9: On the basis of the above, a finite element model of tower-line ice-shedding jump is established to analyze the variation law of the ice-jump height of the transmission line under different ice thicknesses, ice-shedding rates, "zipper-type" ice shedding and other factors, as shown in Figures 7 to 9 shown.

[0039] Adopt a kind of icing measurement device and its measurement method based on the ice layer capacitance effect proposed by the above scheme to realize the measurement of the natural icing and its electrical parameters of atmospheric structures.

[0040] Furthermore, the obtained ice-shedding jump height of the transmission conductor can be used to check the minimum phase-to-phase clearance, and a correction formula for determining the minimum phase-to-phase clearance of the conductor can be obtained.

[0041] Furthermore, the correction formula can be used to calculate the phase-to-phase clearance in batches and obtain the ice-jump height warning line diagram, based on which the maximum span and ice coating thickness can be determined, which can be used for the minimum clearance check and early warning, and has high engineering practical value.

[0042] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention. These changes involve related technologies well-known to those skilled in the art, and all of these fall within the protection scope of the present invention's patent.

[0043] Many other changes and modifications can be made without departing from the concept and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A numerical simulation method for de-icing jump of ice-covered conductors based on beam elements in ANSYS, characterized in that , it includes the following steps: S1: Determine the steel frame structure of the transmission tower and the number of conductor splits, and select the type of beam element; establish the global coordinate system, with the tower height as the y-axis direction, the cross-arm wire suspension as the z-axis direction, and the outward extension direction of the cross-arm as the x-axis direction to establish the transmission tower model; obtain the conductor parameters, insulator string parameters, icing parameters, and conductor-insulator string constraint parameters in the transmission line, and establish the conductor-insulator string static model; connect the conductor-insulator string static model with the transmission tower model to obtain the overall static model of the transmission line; S2: Conduct the self-weight sag shaping of the transmission conductor to determine the initial displacement form of the transmission conductor when it reaches the equilibrium state under its own weight; S3: Determine the icing load, conduct the static calculation of self-weight with ice, and determine the displacement of the transmission conductor when it reaches the equilibrium state under the self-weight with ice, that is, the static equilibrium position with ice. The difference between the maximum value of the conductor amplitude and the static equilibrium position with ice is the jump height; S4: Use the method of changing density to simulate the icing and de-icing processes of the transmission conductor; simulate the uniform icing condition on each section of the transmission line conductor unit by changing the material density of all elements; after conducting the static analysis of the tower-line self-weight, set the material density of the second icing condition to the conductor body density plus the mass of ice per unit length divided by the cross-sectional area of the conductor to become the uniform icing condition; S5: The sag of the transmission conductor determined by step S2; adopt the trial calculation method of the inclined parabola formula. First, create a model with a parabola close to the sag, and then apply the self-weight load of the conductor. If the "vertical coordinate at the mid-span + vertical displacement at the mid-span" is equal to the sag, then complete the analysis of this load step, otherwise adjust the sag during modeling; S6: Conduct the static analysis after adding ice, directly apply the icing load without considering the icing process, and do not consider the dynamic effect of the icing load; S7: Turn on the time integration effect and assume uniform de-icing within a certain time; realize de-icing by modifying the material properties between load steps; S8: Determine the vibration process after complete de-icing and determine the end time of the calculation as needed; S9: Establish a finite element model for tower-line de-icing jump, and simulate the variation law of the ice jump height of the transmission line under different icing thicknesses, de-icing rates, and "zipper-type" de-icing factors.

2. A numerical simulation method for de-icing jump of ice-covered conductors based on beam elements in ANSYS according to claim 1, characterized in that: In step S2, under the action of the conductor gravity, the geometric shape of the conductor is repeatedly updated until the error between the horizontal tension of the conductor and the known stringing tension is within the allowable range, and then the initial configuration of the conductor can be obtained; In step S7, de-icing is realized by modifying the material density between load steps, that is, using commands to modify the element material number.

3. A numerical simulation method for de-icing jump of ice-covered conductors based on beam elements in ANSYS according to claim 1, characterized in that: After obtaining the de-icing jump height of the transmission line conductor in step S9, the minimum phase-to-phase clearance is verified to obtain a correction formula for determining the minimum phase-to-phase clearance of the conductor. The correction formula is used to perform batch calculations of the phase-to-phase clearance and obtain an ice jump height warning line diagram. Based on this, the maximum span and ice thickness are determined, and the minimum clearance is checked and warned.

4. A numerical simulation method for de-icing jump of ice-covered conductors based on beam elements according to claim 1, characterized in that: In step S3, during the calculation process, the ice covering of the transmission line conductor is equivalent to a series of concentrated masses and simulated by the Mass21 element. After performing a static analysis of the self-weight of the tower and the conductor, the material density of the second ice-covered condition is set to the conductor body density plus the mass of ice per unit length divided by the cross-sectional area of the conductor, becoming a uniform ice-covered condition.

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