Tower collapse risk assessment method for icing tower line system under strong wind effect

Abstract

The invention discloses a tower collapse risk assessment method for an ice-coated tower line system under the action of strong wind, and the method comprises the steps: firstly defining a displacement drift ratio and a compression-tensile yield ratio to correspond to the state of a power transmission tower, and then obtaining the structure, design and meteorological parameters of an operation environment of a power transmission line from a practical project; a tower-line coupling system finite element model of the power transmission line is established based on the actual parameters, and the safety state of the tower-line coupling system is determined according to the horizontal initial tension. According to dynamic response characteristic analysis of the icing tower line system under the action of strong wind, numerical simulation analysis is carried out on tower top representative node displacement of a power transmission tower and the maximum equivalent stress borne by a tower body, states corresponding to relevant parameters are set and correspond to simulation results, and the running state of the tower line system at the moment is analyzed. The method can be applied to power transmission line safety state assessment in scenes of different power transmission tower models, different icing thicknesses, different wind speeds and the like, and a scientific basis is provided for risk assessment and early warning work.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and more specifically, relates to a tower collapse risk assessment method for an ice-covered tower line system under strong winds. Background Art

[0002] Wind load and ice load are important natural disasters that threaten the safe operation of power transmission lines. In actual projects, the transmission tower line system often suffers from lateral instability damage due to wind load, which will cause large-scale power outages and seriously affect the normal production and life of society and people. At the same time, ice on the conductors and towers will increase the possibility of such damage.

[0003] When the tower-line system is subjected to wind load and ice load, the top of the tower-line system will be displaced, and the maximum equivalent stress on the tower body will also change. The risk status judgment of the tower-line system when it is subjected to wind and ice response is conducive to timely warning of the collapse of the transmission tower. There are two forms of failure of the transmission tower. The first form of failure is that the internal force of the rod exceeds the maximum resistance of the rod material, resulting in partial or overall damage to the structure. This form of failure is called strength yield failure. The second form of failure is that although the internal force of the rod is within the allowable range, the structure has an uncontrollable and unrecoverable deformation, and the structure cannot maintain a stable state under this action. This form of failure is called loss of stability failure. Summary of the invention

[0004] In view of the above-mentioned existing problems, the present invention proposes a tower collapse risk assessment method for an ice-covered tower line system under strong winds, the purpose of which is to provide timely warning for the tower collapse risk of the transmission tower line system, so as to adopt countermeasures in advance to avoid accidents.

[0005] The specific technical solution adopted by the present invention is: a tower collapse risk assessment method for an ice-covered tower line system under strong wind, comprising the following steps:

[0006] Step 1: Use the displacement drift ratio and the compression-tensile yield ratio as two ways to determine whether the transmission tower collapses, and determine the correspondence between the displacement drift ratio interval and the compression-tensile yield ratio interval and the transmission tower status.

[0007] Furthermore, the transmission tower representative node displacement is extracted and defined as u; the transmission tower height is defined as u h ; The displacement drift ratio η can be defined as: The correspondence between the displacement drift ratio interval and the state of the transmission tower is:

[0008]

[0009] Furthermore, the maximum equivalent stress on the tower body is extracted and defined as σ, α is the strength reduction factor of the angle steel member connected by a single leg, which can be uniformly taken as 0.85, and the yield strength of the tower body member steel is σ s , the compression-tension yield ratio can be defined as: The correspondence between the compression-tension yield ratio interval and the state of the transmission tower is:

[0010]

[0011] Step 2: Collect information such as the structure and design parameters of each part of the transmission line, the operating environmental meteorological conditions, etc., determine the structure of each part of the transmission line tower-line system based on the collected information, and select the simulation unit type; establish an overall coordinate system, with the direction parallel to the main circuit tower line as the x direction, the direction perpendicular to the main circuit tower line as the z direction, and the y-axis direction as the vertical; set unit nodes, connect each node through line commands, and set the material parameters of each part; perform conductor form-finding work, apply 4 fixed constraints at the bottom of the tower, and set the two ends of the insulator string as hinged connections to obtain the finite element model of the tower-line system of the transmission line; use the node force method to add the equivalent of ice to the tower-line system of the transmission line to obtain the tower-line coupling system of the iced transmission line.

[0012] Step 3: On the finite element model of step 2, the additional load method is used to simulate the ice load and wind load on the transmission tower and the conductor (ground) line. The self-damping model is introduced to simulate the vibration process of the transmission line in the actual project. Numerical simulation is performed to obtain the representative node displacement of each part of the ice-covered tower-line system at the top of the tower and the maximum equivalent stress on the tower body under strong wind, and the simulation results of the transmission tower-line system under wind load and ice load are obtained.

[0013] Step 4: Extract the displacement parameters of the representative node at the top of the tower and the maximum equivalent stress parameters of the tower body, and compare them with the displacement drift ratio and compression-tension yield ratio defined in step 1 to obtain the operating status of the transmission tower at this time. When the parameters exceed the stable and safe state, it is determined that there is a risk in the tower-line coupling system and a timely warning is issued.

[0014] Furthermore, the two determination methods set in step 1 are for two forms of transmission tower damage. In particular, when the tower state corresponding to the interval of one of the two determination methods is dangerous, measures should be taken immediately to prevent the transmission tower from further damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the present invention;

[0016] Figure 2 It is a finite element model of tower-line system based on actual engineering;

[0017] Figure 3Schematic diagram of wind direction angle of wind load on tower-line system;

[0018] Figure 4 This is a locally enlarged schematic diagram of the tower-line system subjected to wind loads and ice loads using the node force addition method. Specific implementation methods

[0020] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] like Figure 1 As shown, a tower collapse risk assessment method for an ice-covered tower line system under strong winds comprises the following steps:

[0022] Step 1: According to national standards, the displacement drift ratio and the compression-tensile yield ratio are used as two methods to determine whether the transmission tower has collapsed, and the correspondence between the displacement drift ratio interval and the compression-tensile yield ratio interval and the transmission tower status is determined.

[0023] Furthermore, the transmission tower representative node displacement is extracted and defined as u; the transmission tower height is defined as u h ; The displacement drift ratio η can be defined as: The correspondence between the displacement drift ratio interval and the state of the transmission tower is:

[0024]

[0025] Furthermore, the maximum equivalent stress on the tower body is extracted and defined as σ, α is the strength reduction factor of the angle steel member connected by a single leg, which can be uniformly taken as 0.85, and the yield strength of the tower body member steel is σ s , the compression-tension yield ratio can be defined as: The correspondence between the compression-tension yield ratio interval and the state of the transmission tower is:

[0026]

[0027] Step 2: Collect information such as the structure and design parameters of each part of the transmission line, the operating environment and meteorological conditions, determine the structure of each part of the transmission line tower-line system based on the collected information, and select the simulation unit type; establish an overall coordinate system, with the direction parallel to the main circuit tower line as the x direction, the direction perpendicular to the main circuit tower line as the z direction, and the y-axis direction as the vertical direction; set unit nodes, connect each node through line commands, and set the material parameters of each part; perform conductor shape finding, apply 4 fixed constraints at the bottom of the tower, and set the two ends of the insulator string as hinged connections to obtain the finite element model of the tower-line system of the transmission line; use the node force method to add the equivalent of ice to the tower-line system of the transmission line to obtain the tower-line coupling system of the ice-covered transmission line; such as Figure 2 shown.

[0028] Step 3: On the finite element model of the tower-line coupling system, combined with the wind speed, wind direction angle and ice thickness parameters, the additional load method is used to simulate the ice load and wind load on the transmission line. The self-damping model is introduced to simulate the vibration process of the transmission line in the actual project. Numerical simulation is performed to obtain the representative node displacement of each part of the ice-covered tower-line system at the top of the tower and the maximum equivalent stress on the tower body under the action of strong wind, and the simulation results of the transmission tower-line system under the action of wind load and ice load are obtained;

[0029] Step 4: Extract the displacement parameters of the representative node at the top of the tower and the maximum equivalent stress parameters of the tower body, and compare them with the displacement drift ratio and compression-tension yield ratio defined in step 1 to obtain the operating status of the transmission tower at this time. When the parameters exceed the stable and safe state, it is determined that there is a risk in the tower-line coupling system and a timely warning is issued.

[0030] Furthermore, when the tower state corresponding to a certain interval of the displacement drift ratio and the compression-tension yield ratio is dangerous, measures should be taken immediately to prevent the transmission tower from further damage.

[0031] In summary, the present invention can change the material structure parameters of the tower-line system through a numerical simulation method, realize the risk assessment and early warning of tower collapse of the ice-covered tower-line system under strong wind, and has high engineering use value. The method of the present invention can be applied to the safety status assessment of transmission lines in scenarios with different transmission tower models, spans, height differences, conductor (ground) wire models, different ice thicknesses and different wind speeds, and provide a scientific basis for risk assessment and early warning work.

Claims

1. A method for assessing the risk of tower collapse of an ice-covered tower line system under strong winds, characterized in that: Firstly, the displacement drift ratio and compression-tension yield ratio are defined to correspond to the state of the transmission tower. Secondly, the structure, design and meteorological parameters of the transmission line operation environment are obtained from actual projects. Based on these actual parameters, the tower-line coupling system finite element model of the transmission line is established, and the safety state of the tower-line coupling system is determined according to the horizontal initial tension. It includes the following steps: Step 1: According to national standards, the displacement drift ratio and the compression-tension yield ratio are used as two ways to determine whether the transmission tower collapses, and the correspondence between the displacement drift ratio interval and the compression-tension yield ratio interval and the transmission tower status is determined; Step 2: Collect information such as the structure and design parameters of each part of the transmission line, the operating environment and meteorological conditions, determine the structure of each part of the tower-line system of the transmission line based on the collected information, and select the type of simulation unit; establish an overall coordinate system, with the direction parallel to the main circuit tower line as the x direction, the direction perpendicular to the main circuit tower line as the z direction, and the y-axis direction as the vertical direction; set unit nodes, connect each node through line commands, and set the material parameters of each part; perform conductor shape finding, apply 4 fixed constraints at the bottom of the tower, and set the two ends of the insulator string as hinged connections to obtain the finite element model of the tower-line system of the transmission line; use the node force method to add the equivalent of ice to the tower-line system of the transmission line to obtain the tower-line coupling system of the iced transmission line; Step 3: On the finite element model of the tower-line coupling system, combined with the wind speed, wind direction angle and ice thickness parameters in the actual project, the additional load method is used to simulate the ice load and wind load on the transmission line. The self-damping model is introduced to simulate the vibration process of the transmission line in the actual project. Numerical simulation is performed to obtain the representative node displacement of each part of the ice-covered tower-line system at the top of the tower and the maximum equivalent stress on the tower body under the action of strong wind, and the simulation results of the transmission tower-line system under the action of wind load and ice load are obtained; Step 4: Extract the displacement parameters of the representative node at the top of the tower and the maximum equivalent stress parameters of the tower body, and compare them with the displacement drift ratio and compression-tension yield ratio defined in step 1 to obtain the operating status of the transmission tower at this time. When the parameters exceed the stable and safe state, it is determined that there is a risk in the tower-line coupling system and a timely warning is issued.

2. The method for assessing the risk of tower collapse of an ice-covered tower line system under strong wind according to claim 1, characterized in that: The specific method of defining the correspondence between the displacement drift ratio and the displacement drift ratio interval and the state of the transmission tower in step 1 is: Extract the transmission tower representative node displacement, defined as u; the transmission tower height is defined as u h ; The displacement drift ratio η can be defined as: The correspondence between the displacement drift ratio interval and the state of the transmission tower is: When η<1 / 200, the transmission tower is in normal operation; When 1 / 100<η<1 / 200, the transmission tower is slightly damaged; When 1 / 50<η<1 / 100, the transmission tower is in serious damage; When η>1 / 50, the state of the transmission tower is rod failure.

3. The method for assessing the risk of tower collapse of an ice-covered tower line system under strong wind according to claim 1, characterized in that The specific method of defining the correspondence between the compression-tension yield ratio and the compression-tension yield ratio interval and the state of the transmission tower in step 1 is: The maximum equivalent stress on the tower body is extracted and defined as σ. α is the strength reduction factor of the angle steel member connected with a single leg, which can be uniformly taken as 0.

85. σ s is the yield strength of the tower member steel, and the compression-tension yield ratio can be defined as: The correspondence between the compression-tension yield ratio interval and the state of the transmission tower is: When λ≤0.5, the transmission tower is safe; When 0.5<λ<0.7, the transmission tower is more likely to become unstable and needs to be reinforced; When λ≥0.7, the transmission tower body has become unstable and the poles need to be replaced.

4. The method for assessing the risk of tower collapse of an ice-covered tower line system under strong wind according to claim 1, characterized in that: The wind speed, wind direction angle and ice thickness set in step 3 are response parameters; the tower top representative node displacement and the maximum equivalent stress on the tower body are result parameters.

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