A method for evaluating the risk of tower collapse of an iced tower line system under strong wind action

Abstract

The application discloses a method for evaluating the risk of tower collapse of an iced tower-line system under strong wind action, which firstly defines displacement drift ratio and compression-tension yield ratio to correspond to the state of the power transmission tower, and secondly obtains the structure, design and meteorological parameters of the power transmission line from the actual project, and establishes a tower-line coupling system finite element model of the power transmission line based on the actual parameters, and determines the safety state of the tower-line coupling system according to the horizontal initial tension. The application is aimed at the dynamic response characteristic analysis of the iced tower-line system under strong wind action, and the representative node displacement at the top of the power transmission tower and the maximum equivalent stress suffered by the tower body are analyzed by numerical simulation, the state corresponding to the set relevant parameters is set, and the running state of the tower-line system at the time is analyzed by corresponding to the simulation result. The method of the application can be applied to the safety state evaluation of the power transmission line in different power transmission tower models, different icing thicknesses and different wind speeds, and can provide a scientific basis for risk evaluation and early warning work.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power systems, and more particularly relates to a tower collapse risk assessment method for an iced tower-line system under strong wind action. BACKGROUND

[0002] Wind load and icing load are important natural disasters threatening the safe operation of power transmission lines. In actual engineering, the power transmission tower-line system often experiences lateral instability failure under wind load, which can cause large-scale power outages and seriously affect the normal production and life of society and people. Meanwhile, conductor icing and tower icing can increase the possibility of such damage.

[0003] When the tower-line system is subjected to wind load and icing load, displacement will occur at the top of the tower-line system, and the maximum equivalent stress on the tower body will also change. Therefore, risk assessment of the tower-line system under wind and icing response is beneficial to the timely warning of power transmission tower collapse accidents. The power transmission tower has two failure modes. The first failure mode is that the internal force of the member exceeds the maximum resistance capacity of the member material, resulting in local or overall failure of the structure. This failure mode is called strength yield failure. The second failure mode is that the internal force of the member is within the allowable range, but the structure produces uncontrollable deformation that cannot be recovered, and the structure cannot maintain a stable state under such action. This failure mode is called loss of stability failure. SUMMARY

[0004] In view of the above-mentioned existing problems, the present application provides a tower collapse risk assessment method for an iced tower-line system under strong wind action, which aims to timely warn the tower collapse risk of the power transmission tower-line system, so as to take measures in advance to avoid accidents.

[0005] The specific technical scheme adopted by the present application is as follows: a tower collapse risk assessment method for an iced tower-line system under strong wind action, comprising the following steps:

[0006] Step 1: taking displacement drift ratio and compression-tension yield ratio as two determination methods for determining whether the power transmission tower collapses, determining the corresponding relationship between the displacement drift ratio interval, the compression-tension yield ratio interval and the state of the power transmission tower.

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

[0008]

[0009] Furthermore, the maximum equivalent stress on the tower body is extracted and defined as σ, α is the strength reduction factor for the angle steel member with a single connection, which can be uniformly taken as 0.85, and the yield strength of the steel members of the tower body is σ. s The compressive-tensile yield ratio can be defined as: The correspondence between the compressive / tensile yield ratio range and the state of the transmission tower is as follows:

[0010]

[0011] Step 2: Collect information on the structure and design parameters of each part of the transmission line, as well as the environmental meteorological conditions during operation. Based on the collected information, determine the structure of each part of the transmission line tower-line system and select the simulation element 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 as the vertical direction. Set element nodes, connect each node using the line command, and set the material parameters for each part. Perform conductor shape finding, apply four 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 nodal force application method to apply the equivalent icing effect to the tower-line system of the transmission line to obtain the tower-line coupled system of the iced transmission line.

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

[0014] Furthermore, the two determination methods set in step 1 address two types of transmission tower damage. In particular, when the tower condition corresponding to the section determined by one of the two determination methods is dangerous, measures should be taken immediately to prevent further damage to the transmission tower. Attached Figure Description

[0015] Figure 1 This is a flowchart of the present invention;

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

[0017] Figure 3A schematic diagram of the wind direction angle under wind load on the tower-line system;

[0018] Figure 4 This is a partially enlarged schematic diagram of the wind load and ice load on the tower line system using the nodal force application method. Specific implementation methods

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] like Figure 1 As shown, a method for assessing the collapse risk of an ice-covered tower line system under strong winds includes the following steps:

[0021] Step 1: According to national standards, displacement drift ratio and compressive-tensile yield ratio are used as two deterministic methods to determine whether a transmission tower has collapsed. Determine the correspondence between the displacement drift ratio range and the compressive-tensile yield ratio range and the state of the transmission tower.

[0022] Furthermore, the representative node displacement of the transmission tower is extracted and defined as u; the height of the transmission tower is defined as u. h The displacement drift ratio η can be defined as: The correspondence between the displacement drift ratio range and the transmission tower status is as follows:

[0023]

[0024] Furthermore, the maximum equivalent stress on the tower body is extracted and defined as σ, α is the strength reduction factor for the angle steel member with a single connection, which can be uniformly taken as 0.85, and the yield strength of the steel members of the tower body is σ. s The compressive-tensile yield ratio can be defined as: The correspondence between the compressive / tensile yield ratio range and the state of the transmission tower is as follows:

[0025]

[0026] Step 2: Collect information on the structure and design parameters of each part of the transmission line, as well as the environmental meteorological conditions during operation. Based on the collected information, determine the structure of each part of the transmission line tower-line system and select the simulation element 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 as the vertical direction; set element nodes, connect each node using line commands, and set the material parameters for each part; perform conductor shape finding, apply four fixed constraints at the tower base, and set the two ends of the insulator string as hinged connections to obtain the finite element model of the transmission line tower-line system; use the nodal force application method to apply the equivalent icing effect to the transmission line tower-line system, obtaining the tower-line coupled system of the iced transmission line; for example... Figure 2 As shown.

[0027] Step 3: On the finite element model of the tower-line coupled system, combined with 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 carried out to obtain the displacement of the representative node at the top of the tower and the maximum equivalent stress on the tower body of each part of the ice-covered tower-line system under strong wind. The simulation results of the transmission tower-line system under wind load and ice load are obtained.

[0028] 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 compressive-tensile 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 an early warning is issued in time.

[0029] Furthermore, if the tower condition corresponding to a certain range of displacement drift ratio and compressive-tensile yield ratio is dangerous, measures should be taken immediately to prevent further damage to the transmission tower.

[0030] In summary, this invention can modify the material and structural parameters of the tower-line system through numerical simulation, enabling risk assessment and early warning of tower collapse under strong winds caused by icing. This method has high engineering value. Furthermore, the method can be applied to the safety status assessment of transmission lines in scenarios involving different tower types, spans, elevation differences, conductor (ground) wire types, varying icing thicknesses, and different wind speeds, providing a scientific basis for risk assessment and early warning.

Claims

1. A method for assessing the collapse risk of an ice-covered tower line system under strong winds, characterized in that, First, the displacement drift ratio and compressive-tensile yield ratio are defined to correspond to the state of the transmission tower. Second, the structural, design and meteorological parameters of the transmission line and its operating environment are obtained from actual engineering projects. Based on these actual parameters, a finite element model of the tower-line coupling system of the transmission line is established, and the safety state of the tower-line coupling system is determined according to the initial horizontal tension. It includes the following steps: Step 1: According to national standards, displacement drift ratio and compressive-tensile yield ratio are used as two deterministic methods to determine whether a transmission tower has collapsed. Determine the correspondence between the displacement drift ratio range and the compressive-tensile yield ratio range and the state of the transmission tower. Step 2: Collect information on the structural and design parameters of each part of the transmission line, as well as the environmental meteorological conditions during operation. Based on the collected information, determine the structure of each part of the transmission line tower-line system and select the simulation element 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 as the vertical direction. Set element nodes, connect each node using the line command, and set the material parameters for each part. Perform conductor shape finding, apply four 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 nodal force application method to apply the equivalent icing effect to the tower-line system of the transmission line to obtain the tower-line coupled system of the iced transmission line. Step 3: On the finite element model of the tower-line coupled 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 carried out to obtain the displacement of the representative node at the top of the tower and the maximum equivalent stress on the tower body of each part of the ice-covered tower-line system under strong wind. The simulation results of the transmission tower-line system under 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 compressive-tensile 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 an early warning is issued in time.

2. The method for assessing the risk of tower collapse under strong winds in an ice-covered tower line system according to claim 1, characterized in that, The specific method for defining the correspondence between the displacement drift ratio and the displacement drift ratio range and the transmission tower state in step 1 is as follows: Extracting the representative node displacement of the transmission tower, defined as The height of a transmission tower is defined as follows: The displacement drift ratio η is defined as: η = ; The correspondence between the displacement drift ratio range and the transmission tower status is as follows: When η < 1 / 200, the transmission tower is in normal operation. When 1 / 100 < η < 1 / 200, the transmission tower is in a state of minor damage; When 1 / 50 < η < 1 / 100, the transmission tower is in a severely damaged state. When η>1 / 50, the transmission tower is in the state of member failure.

3. The method for assessing the risk of tower collapse under strong winds in an ice-covered tower line system according to claim 1, characterized in that... The specific method for defining the correspondence between the compressive yield ratio and the compressive yield ratio range and the transmission tower condition in step 1 is as follows: The maximum equivalent stress on the tower body is defined as follows: , The strength reduction factor for angle steel members with single-limb connections is uniformly taken as 0.

85. The yield strength of the steel members in the tower structure is given by the compressive-tensile yield ratio, which is defined as: ; The correspondence between the compressive / tensile yield ratio range and the state of the transmission tower is as follows: when The transmission tower structure is safe; when The transmission tower is highly susceptible to instability and requires reinforcement. when The tower structure has become unstable and the tower members need to be replaced.

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

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